JPH1152668A - Electrifying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrifying device which prevents the occurrence of unevenness in the electrification of a photosensitive body to improve an image quality. SOLUTION: This is an electrifying device composed of a photosensitive drum 1 and an electrifying roller 2 which comes into pressure contact with the drum 1 to rotate together. A gas flow generating device 3A to generate a gas flow opposite to the drum 1 is provided. In this formation, an air is blasted toward the electrified part of the drum 1 being about to enter an electrifying area or sucked from there to uniformly extend powder stains or ion stains on the surface of the drum 1 for facilitating uniform electrification, and the unevenness of electrification due to the irregularity of the film thickness on the drum 1 can be prevented through the movement of charge and ion caused by a gas stream occurring on the surface of the drum 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device used for an electrophotographic apparatus such as a PPC copying machine, a facsimile, a printer, and the like.

[0002]

2. Description of the Related Art An electrostatic latent image is formed by exposing an image on a photoreceptor having a charged surface, and the electrostatic latent image is developed and converted into a toner image. As an image forming apparatus for transferring and fixing on paper, for example, a copying machine and a laser printer are widely used. In such an image forming apparatus, a charging device is used to charge the surface of the photoconductor.

Conventionally, a charging device charges a photoreceptor in a non-contact manner by using a corona discharge charger such as a corotron or a scorotron. The charging charger by corona discharge is excellent in that the photoconductor is uniformly charged, but requires a special high-voltage power supply using a flyback transformer or the like because the applied voltage is as high as 5 KV to 8 KV. Further, in the charger using corona discharge, the loss of the discharge current is large and only a part of the charge is effective for charging the photosensitive member. Therefore, the discharge current is large, for example, several hundred μA to several mA.

[0004] Therefore, there is a problem that a large amount of ozone is generated in the charging charger by corona discharge. In particular, when a negatively charged organic photoconductor was frequently used for the photoreceptor, the generation of ozone increased because a negative high voltage was applied to the charged charger. For this reason,
-55572, a charging charger as shown in
In other words, there has been a proposal for efficiently forcibly exhausting a large amount of ozone generated in the vicinity of the photoconductor using a cooling fan.

[0005] However, when a large amount of ozone is exhausted into a room, not only an unpleasant odor is caused but also an environmental problem occurs that impairs human health in the room. For this reason, while the image forming apparatus is on standby, measures such as stopping corona discharge are taken to reduce the amount of generated ozone, or adsorption treatment using activated carbon or the like is performed before discharging the ozone. There were management inconveniences such as forgetting the time.

Therefore, instead of the non-contact charging method using corona discharge, contact charging is performed in which a charging roller made of a conductor or a resistor and to which a voltage for charging is applied is brought into contact with the surface of the photosensitive member to charge the surface. A charging device of the system has been used. In the contact charging method, for example, the applied voltage is as low as 600 V to 2 KV and there is no loss of the discharge current as in the charging charger by the corona discharge described above. As described above, in the charging device of the contact charging type, since both the applied voltage and the charging current can be reduced, a small-sized power supply device can be used, and ozone is not generated in principle.

As a practical problem, most of the charging of the photoreceptor surface is performed by the contact of the charging roller, but a minute arc discharge starts at a slight interval just before the contact, so that generation of ions such as ozone is indispensable. Although it cannot be said, the amount of generation is so small that it does not cause environmental problems.

To ensure that the charging roller is in close contact with the surface of the photoreceptor, a force is generally applied in the direction of contact with the surface of the photoreceptor by a spring or the like. Therefore, the charging roller tends to slightly deform the center of the charging roller. Therefore, the conductor or resistor itself on the surface of the charging roller, or the inside thereof is formed of an elastic body,
The generation of voids is prevented.

However, due to the lifting of the central portion and the unevenness of the thickness of the surface layer, the contact pressure partially decreases,
It is not possible to completely suppress the occurrence of floating around the periphery due to dust or residual toner. For this reason, when charging unevenness occurs, the influence appears on the formed electrostatic latent image.

In the case of minute gaps, charging is also performed by arc discharge, corona discharge, etc., but the applied voltage is lower than charging by non-contact corona discharge using a corotron, scorotron, etc. The tendency to do so is inevitable. In addition, even if the amount of ions generated by arc discharge, corona discharge, and the like is very small, it can not be said that there is no risk of promoting uneven charging because the ion concentration locally increases.

The uneven charging of the electrostatic latent image appears as uneven density of the finally obtained toner image. In particular, it is noticeable in the intermediate density portion, but in some cases, it is also recognized in the high density portion, that is, in the solid black portion, which is a cause of image quality deterioration.

Further, in a charging roller having a surface layer coated on an elastic layer, charging unevenness occurs corresponding to the film thickness unevenness of the surface layer. Then, in the case of halftone copying, the charging unevenness directly becomes the unevenness of the image density. Further, at the time of continuous copying, the ambient temperature and the surface temperature of the charging roller change with the number of sheets passed (mainly, temperature rise), and the charging potential fluctuates accordingly.

Further, when continuous copying is performed by halftone copying, white streaks or black streaks corresponding to the pitch of one rotation of the photosensitive drum may occur on the first to fifth sheets or the first to twentieth sheets. is there.

The present inventor has previously proposed Japanese Patent Application No. 7-241443 in order to solve the problems in the contact charging device. Although the above problem could be solved by this proposal, there is room for further improvement.

[0015]

For example, recently, as shown in FIG. 13, a function-separated type laminated photoreceptor is used as a photosensitive layer of an OPC photoreceptor (organic photoreceptor). The charge carrier generation layer (CGL) 14 formed on the conductive support 11 and the charge carrier transfer layer (C)
TL) 15, so-called CTL upper layer system (laminated type)
Is used. In this CTL upper layer system, the charge carrier transfer layer was thick, and if there was a variation in the film thickness, the charge potential varied in proportion to the film thickness, and charge unevenness was likely to occur. SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to provide a charging device that prevents the occurrence of uneven charging of a photoconductor and improves image quality.

[0016]

According to a first aspect of the present invention, there is provided a charging device comprising a photosensitive drum and a charging roller which is pressed against the photosensitive drum and rotates with the photosensitive drum. A gas flow generating device for generating a gas flow is provided facing the body drum. In this configuration, by blowing or sucking air on the charged portion of the photoconductor drum that is going to enter the charging area, powder dirt and ionic dirt on the surface of the photoconductor drum are uniformly spread to enable uniform charging. At the same time, uneven charging due to variations in the thickness of the photosensitive drum
This can be prevented by moving charges and ions by the gas flow generated on the surface of the photosensitive drum.

According to a second aspect of the present invention, in the charging device according to the first aspect, the flow velocity of the gas flow generated by the gas flow generator is one of the moving speed of the photosensitive drum.
It is characterized by being within the range of / 1000 times to 1000 times. In this configuration, a gas flow having a flow rate within a range of 1/1000 to 1000 times the moving speed of the photosensitive drum surface is generated on the photosensitive drum surface.

According to a third aspect of the present invention, there is provided the charging device according to the first aspect, wherein the gas flow is generated by spraying. In this configuration, a gas flow can be generated by spraying.

According to a fourth aspect of the present invention, in the charging device according to the first aspect, the gas flow is caused by suction. With this configuration, a gas flow can be generated by suction.

According to a fifth aspect of the present invention, in the charging device according to the first aspect, the gas flow generating device is disposed upstream of a contact portion between the charging roller and the photosensitive drum. It is characterized by. With this configuration, the gas flow generated by the gas flow generation device can prevent the powder contamination and the ionic contamination on the upstream side before charging.

According to a sixth aspect of the present invention, in the charging device according to the first aspect, the gas flow generating device is disposed downstream of a contact portion between the charging roller and the photosensitive drum. It is characterized by. With this configuration, charges and ions can be moved downstream by the gas flow generated by the gas flow generation device to prevent charging unevenness.

According to a seventh aspect of the present invention, in the charging device according to the first aspect, the gas flow generating device is provided on both the upstream side and the downstream side of a contact portion between the charging roller and the photosensitive drum. It is characterized by being arranged in. In this configuration, it is possible to prevent charging of the powder and ionic contamination on the upstream side by the upstream gas flow generation device and then charge the battery, and to charge and ion by the gas flow on the downstream side by the downstream gas flow generation device. Can be moved to prevent charging unevenness.

According to another aspect of the present invention, there is provided a charging device comprising: a photosensitive drum connected to a driving source; and a charging roller which presses and rotates with the photosensitive drum.
A gas flow generating member for generating a gas flow is provided facing the photosensitive drum. In this configuration, the gas is generated from the surface of the photosensitive drum connected to the driving source by the gas flow generating member, and a gas flow is generated by laminar flow or turbulent flow.

According to a ninth aspect of the present invention, in the charging device of the eighth aspect, the gas flow generating member comprises a wedge-shaped member. In this configuration, the air is stripped from the surface of the photosensitive drum connected to the drive source by the wedge-shaped member, and a gas flow due to laminar flow or turbulent flow is generated on the surface of the photosensitive drum.

Further, the charging device according to the tenth aspect provides the charging device according to the eighth aspect.
Wherein the gas flow generating member is a flat member. In this configuration,
Air is stripped from the surface of the photosensitive drum connected to the drive source by the flat member, and a gas flow due to laminar flow or turbulent flow is generated on the surface of the photosensitive drum.

Further, the charging device of claim 11 is the charging device of claim 8
Wherein the gas flow generating member is disposed upstream of a contact portion between the charging roller and the photosensitive drum. With this configuration, the gas flow generated by the gas flow generating member can prevent the powder contamination and the ionic contamination on the upstream side before charging.

Further, the charging device of claim 12 is the charging device of claim 8.
Wherein the gas flow generating member is disposed downstream of a contact portion between the charging roller and the photosensitive drum. With this configuration, charges and ions can be moved downstream by the gas flow generated by the gas flow generation device to prevent charging unevenness.

Further, the charging device of claim 13 is the charging device of claim 8.
Wherein the gas flow generating member is disposed on both the upstream side and the downstream side of the contact portion between the charging roller and the photosensitive drum.
In this configuration, the upstream gas flow generating member can prevent powder contamination and ion contamination on the upstream side and then be charged, and the downstream gas flow generation member can charge and ion by the gas flow on the downstream side. Can be moved to prevent charging unevenness.

Further, the charging device of claim 14 is a charging device of claim 8.
Wherein the gas flow generating member is at least a part of an upper cover case of the cleaning unit. In this configuration, claim 1
As in the case of the operation of 0, air is stripped from the surface of the photosensitive drum connected to the drive source, and a gas flow due to laminar flow or turbulent flow is generated on the surface of the photosensitive drum.

Further, the charging device of claim 15 is the charging device of claim 8.
Wherein the gas flow generating member is at least a part of an upper cover case of the developing unit. In this configuration, similarly to the operation of the fourteenth aspect, air is stripped from the surface of the photosensitive drum connected to the drive source, and a gas flow due to laminar flow or turbulent flow is generated on the surface of the photosensitive drum.

[0031]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a side view of a contact charging device according to a first embodiment of the present invention, and FIG. 2 is an elevation view thereof. In the first embodiment, the air flow generating device 3A, which is a gas flow generating device, is attached to the photosensitive drum 1 side of the charging section of a copying machine capable of copying A4 size paper at 20 sheets / min.

The contact charging device 100 shown in FIG. 1 covers a charging roller 2 in contact with a photosensitive drum 1 whose surface is covered with a photosensitive member, and covers the entire effective width along the charging roller 2. And an air flow generating device 3A provided in the above.

The charging roller 2 has, for example, an elastic layer made of a conductor around a metal core 21 having a shaft, and a thin surface layer made of a conductor is formed on the surface of the elastic layer. Coated. The charging roller 2 includes a core 2
1 may be covered by a surface elastic layer made of a conductor.

The charging roller 2 is urged by a spring (not shown) in contact with the shaft of the metal core 21 so as to come into contact with the photoreceptor, and a voltage is supplied from a high-voltage power supply (not shown) via the spring. Has been applied. Then, the voltage applied to the core metal 21 reaches the surface via the elastic layer, the surface layer, or the surface elastic layer made of a conductor, respectively, and at a contact portion (not shown), the surface of the photosensitive member 12 of the photosensitive drum 1 Is charged.

In FIG. 1, the photoconductor 12 of the photoconductor drum 1 is made of an OPC photoconductor.
Among these OPC photoconductors, a function-separated type photoconductor is used. The photoconductor drum 1 includes a drum base 11 made of aluminum and a stacked photoconductor 12 stacked on the drum base 11. As shown in FIG. 13, the laminated photoreceptor 12 has an undercoat layer (UCL) 13 formed on the drum base 11 and a film thickness 1 on the undercoat layer 13.
Charge carrier generation layer (CGL) 14 having a thickness of less than μm
And the film thickness 1 formed on the charge carrier generation layer 14.
A charge carrier transfer layer (CTL) 15 having a thickness of 5 to 40 μm. The charge carrier generation layer 14 includes a charge carrier generation material (CG) in a state of pigment fine particles in a resin binder.
It is a pigment dispersion layer in which M) is dispersed. The charge carrier transport layer 15 is a layer in which a charge carrier transport material (CTM) is dispersed and dissolved in a resin binder. Since an electron-donating charge carrier transport material having high hole mobility is used,
The photoreceptor is of a negative charging type.

The photosensitive drum 1 rotates clockwise as shown by the arrow while connected to the ground.
The charging roller 2, which is in contact with the photosensitive drum 1 by its own weight and a spring (not shown), rotates counterclockwise as shown by an arrow following the rotation of the photosensitive drum 1, and applies an applied voltage from a high-voltage power supply (not shown). The surface of the photoreceptor is charged according to (−600 V to −2 KV).

The air flow generator 3A includes a hollow box provided along the charging roller 2 so as to cover the entire effective width of the charging roller 2, and an inlet side of a contact portion between the charging roller 2 and the photosensitive drum 1; That is, it is mounted on the upstream side of rotation. The airflow generating device 3A has, for example, a length (axial direction of the charging roller 2) 21 at a position facing the photosensitive drum 1.
cm, rectangular opening 32A having a width (direction orthogonal to the axis) of 5 mm
have. And on the upper part of the air flow generator 3A,
A hose 31A for feeding air from the opening 32A is connected.

Thus, by blowing air from the hose 31A toward the center of the photosensitive drum 1 from the opening 32A, an air flow is generated on the surface of the photosensitive drum 1. The flow velocity of the air is set in a range of 1/1000 to 1000 times the moving speed of the photosensitive drum 1.

Next, the reason for setting this range will be described. For example, assuming that 20 images are formed per minute on A4 size paper fed in the long side direction, the moving speed of the photoconductor, that is, the peripheral speed of the photoconductor drum 1 and the charging roller 2 is approximately Vs = 29. 0.7 cm × 20 sheets / min = 59
4 cm / min.

On the other hand, 6.2 liters / h
Assuming that air is supplied for a minute, the area of the opening 32A is 21 cm × 0.5 cm = 10.5 square cm.
The flow velocity of the air at the opening 32A is Vair = 620.
0 ml / min ÷ 10.5 square cm = 5900 cm
/ Min. Therefore, the flow rate of air and the photosensitive drum 1
Is Vair / Vs = 0.99, which is almost equal to 1.

When an image was formed under the above conditions, density unevenness was not recognized even after a considerably strict inspection. Therefore, the flow velocity is almost proportional to the flow rate of the air, and the opening 3
Since it is almost inversely proportional to the width of 2A, the experiment was conducted by changing these settings and changing the ratio Vair / Vs.

FIG. 3 shows Vair / V obtained by the experiment.
FIG. 4 is a graph showing the correlation between the s and the potential distribution ratio, FIG. 4 is a graph showing the distribution of the charging potential of the photosensitive drum 1 when the potential distribution ratio is 0.96, and FIG. FIG. 6 is a diagram showing the distribution of the charged potential of the photosensitive drum 1 when is 0.85.

As shown in FIG. 4, the value of the potential distribution ratio is set to 0.
When it is 96 or more, the distribution of the charged potential with respect to the position of the photosensitive drum 1 is almost constant, and there is almost no uneven charging. On the other hand, as shown in FIG.
If it is smaller than 95, the distribution of the charged potential of the photosensitive drum 1 is reduced at the end, and uneven charging occurs. Therefore, Vair /
It is necessary to set Vs.

According to the results of the experiment, as shown in FIG.
When Vair / Vs is in the range of 1/1000 to 1000,
It was confirmed that the value of the potential distribution ratio was 0.96 or more. Therefore, in the present embodiment, the flow velocity of the air A is set to 1/1000 of the moving speed of the photosensitive drum 1 to 10 times.
It was set within the range of 00 times.

The blowing flow rate Vair depends on the opening 3
Although it is inversely proportional to the short dimension of 2A, in this experiment, the opening 3
Practical size 0.05cm-0.5c for short dimension of 2A
m.

The hose 31A of the air flow generator 3A
Not only when supplying air from and blowing out air,
Similar results were obtained when air was sucked into the hose 31A under a negative pressure.

Since the contact charging device according to the present embodiment has the above-described configuration, even if the charge potential varies due to the film thickness variation in the charge carrier moving layer 15 of the photosensitive drum 1, the photosensitive member can be used. Air A having a flow rate in the range of 1/1000 to 1000 times the moving speed of the photosensitive drum 1 is supplied from the opening 32A of the air flow generating device 3A attached to the upstream side of the rotation of the drum 1. Is blown toward the center of the
The movement of ions was possible, and the unevenness of the charged potential was eliminated. As a result, the image quality can be improved by the contact charging device 100.

The presence of the air flow locally reduces the ion concentration, and those having a negative factor are removed while those having a positive factor remain. Alternatively, the next new discharge is smoothly performed by the decrease in the ion concentration. It is considered that such a decrease acts in the positive direction to perform charging uniformly and eliminate uneven charging.

In this embodiment, if the flow velocity or air flow is set to be large, the temperature of the photosensitive drum 1 can be prevented from rising, and the temperature of the charging roller 2 in contact with the photosensitive drum 1 can be prevented. In addition, it is possible to keep the development and transfer conditions unchanged.

(Second Embodiment) FIG. 6 is a side view of a contact charging device according to a second embodiment of the present invention. In the contact charging device 200 of the present embodiment, an air flow generating device 3B having the same structure as the air flow generating device of FIG. 1 is attached to the right side of the contact portion between the charging roller 2 and the photosensitive drum 1, that is, downstream of rotation. The opening 32 </ b> B of the airflow generating device 3 </ b> B is configured to face the center O of the photosensitive drum 1.

In this configuration, even if the charge carrier moving layer 15 (CTL) of the photosensitive drum 1 has a variation in the charging potential due to a variation in the film thickness, the air flow attached to the downstream side of the rotation of the photosensitive drum 1 Opening 32 of generator 3B
From B, air A having a flow rate in the range of 1/1000 to 1000 times the moving speed of the photosensitive drum 1 is blown toward the center of the photosensitive drum 1, and the air flow causes the charge / ion Movement was possible, and unevenness of the charged potential was eliminated. As a result, the image quality can be improved by the contact charging device 200. Note that the other configuration, operation, and effect are the same as those in the first embodiment, and thus description thereof is omitted.

(Third Embodiment) FIG. 7 is a side view of a contact charging device according to a third embodiment of the present invention. In the contact charging device 300 of the present embodiment, the airflow generating device 3 of FIG.
A. The air flow generators 3A and 3B having the same
Attached to both sides of the contact portion between the photoconductor drum 1 and the upstream side and the downstream side of the rotation, the respective air flow generating devices 3
The openings 32A and 32B of A and 3B face the center O of the photosensitive drum 1.

In this configuration, even if the charge carrier moving layer 15 (CTL) of the photosensitive drum 1 has a variation in charging potential due to a variation in film thickness, the charge carrier moving layer 15 (CTL) is mounted on the upstream and downstream sides of the rotation of the photosensitive drum 1. Air flow generator 3
A, 3B, through the openings 32A, 32B, the photosensitive drum 1
The air A having a flow rate in the range of 1/1000 to 1000 times the moving speed of the air is blown toward the center of the photosensitive drum 1, so that the air flow can move charges and ions and charge. The non-uniformity of the potential was eliminated more than in the first and second embodiments. As a result, the image quality can be further improved by the contact charging device.

The other structure, operation and effect are the same as those of the first embodiment.
The description is omitted because it is the same as the embodiment. Combinations of blowing and suctioning are shown in the following table, but all combinations were effective.

[0055]

[Table 1]

(Fourth Embodiment) FIG. 8 is a side view of a contact charging device according to a fourth embodiment of the present invention. In the contact charging device 400 of the present embodiment, the wedge-shaped member 4A, which is an airflow generating member, is attached to the left side of the contact portion between the charging roller 2 and the photosensitive drum 1, that is, upstream of rotation, and the wedge-shaped member 4A is attached. The structure is directed toward the center of the photosensitive drum 1. The wedge-shaped member 4A is arranged along the photoconductor drum 1 so as to cover the entire effective width thereof, and is opposed to the photoconductor drum 1 except for a slight gap.

In this configuration, even if the charge carrier moving layer 15 of the photosensitive drum 1 has a variation in the charging potential due to the variation in the film thickness, the air flow generating member attached to the upstream side of the rotation of the photosensitive drum 1 can be used. The laminar flow or the turbulent flow is generated by stripping off the air on the surface of the photosensitive drum 1 caused by the rotation of the photosensitive drum 1 and the charging roller 2 without using the air blowing power source or the suction power source. Thus, the same operation and effect as those of the first embodiment can be obtained. The shape of the wedge-shaped member is an example, and various other shapes are possible. Note that the other configuration, operation, and effect are the same as those in the first embodiment, and thus description thereof is omitted.

(Fifth Embodiment) FIG. 9 is a side view of a contact charging device according to a fifth embodiment of the present invention. In the contact charging device 500 of the present embodiment, a wedge-shaped member 4B having a substantially wedge-shaped cross section, which is an airflow generating member, is attached to the right side of the contact portion between the charging roller 2 and the photosensitive drum 1, that is, downstream of rotation. The wedge-shaped member is structured so as to face the center of the photosensitive drum 1.

With this configuration, even if the charge carrier moving layer 15 of the photosensitive drum 1 has a variation in the charging potential due to a variation in the film thickness, the air flow generating member attached downstream of the rotation of the photosensitive drum 1 can be used. The laminar flow or the turbulent flow is generated by stripping off the air on the surface of the photosensitive drum 1 caused by the rotation of the photosensitive drum 1 and the charging roller 2 without using the air blowing power source or the suction power source. As a result, the same operation and effect as in the second embodiment can be obtained. The shape of the wedge-shaped member is an example, and various other shapes are possible. Note that the other configuration, operation and effect are the same as those of the second embodiment, and thus description thereof is omitted.

(Sixth Embodiment) FIG. 10 shows a sixth embodiment of the present invention.
FIG. 2 is a side view of the contact charging device according to the embodiment. In the contact charging device 600 of the present embodiment, wedge-shaped members 4A and 4B which are air flow generating members having the same structure as the air flow generating member of FIG.
Are mounted on both sides of the contact portion between the charging roller 2 and the photosensitive drum 1, that is, on the upstream and downstream sides of the rotation, and the respective airflow generating members are directed toward the center O of the photosensitive drum 1.

In this configuration, even if the charge carrier moving layer 15 of the photosensitive drum 1 has a variation in the charging potential due to a variation in the film thickness, the air flow attached to the upstream and downstream sides of the rotation of the photosensitive drum 1 The generation member removes air on the surface of the photoreceptor drum 1 generated by rotation of the photoreceptor drum 1 and the charging roller 2 without using an air blowing power source or a suction power source, thereby forming a laminar flow or a turbulent flow. Can be generated, and the charging unevenness can be eliminated more than the fourth and fifth embodiments. As a result, the image quality can be further improved by the contact charging device. The shape of the wedge-shaped member is an example, and various other shapes are possible. Note that the other configuration, operation, and effect are the same as those of the fourth embodiment, and thus description thereof is omitted.

(Seventh Embodiment) FIG. 11 shows a seventh embodiment of the present invention.
FIG. 2 is a side view of the contact charging device according to the embodiment. In the contact charging device 700 of the present embodiment, the long flat plate member 5 is replaced with the long flat plate member instead of the wedge-shaped air flow generating member shown in FIG.
A and 5B are mounted on both sides of the contact portion between the charging roller 2 and the photosensitive drum 1, that is, on the upstream and downstream sides of the rotation, and each air flow generating member is directed toward the center of the photosensitive drum 1. I have.

In this configuration, even if the charge carrier moving layer 15 of the photosensitive drum 1 has a variation in the charging potential due to a variation in the film thickness, the long carrier attached to the upstream and downstream sides of the rotation of the photosensitive drum 1 can be used. The flat member removes air on the surface of the photosensitive drum 1 generated by the rotation of the photosensitive drum 1 and the charging roller 2 without using a power source for blowing air or a power source for suctioning the air, thereby causing laminar flow or turbulence. A flow was generated, and uneven charging was eliminated as in the tenth embodiment. As a result, the image quality can be improved by the contact charging device. The shape of the long flat plate member is an example, and various other shapes are possible. Note that the other configuration, operation, and effect are the same as those in the sixth embodiment, and thus description thereof is omitted.

(Eighth Embodiment) FIG. 12 shows an eighth embodiment of the present invention.
FIG. 2 is a side view of the contact charging device according to the embodiment. In the contact charging device 800 of the present embodiment, the upper cover 61 of the cleaning unit 6 is used instead of the long flat plate-shaped member of FIG.
The upper cover 71 of the developing unit 7 is used as a device for improving the potential distribution ratio, and each upper cover is directed toward the center of the photosensitive drum 1.

In this configuration, even if there is a variation in the charging potential due to a variation in the film thickness of the charge carrier moving layer 15 of the photosensitive drum 1, the upper cover attached to the upstream and downstream sides of the rotation of the photosensitive drum 1. 61 and 71, the air on the surface of the photosensitive drum 1 generated by the rotation of the photosensitive drum 1 and the charging roller 2 is peeled off without using a power source for blowing air or a power source for suctioning the air, thereby causing laminar flow or turbulence. A flow was generated, and the charging unevenness was eliminated as in the seventh embodiment. As a result, the image quality can be improved by the contact charging device. The shape of the upper cover is an example, and various other shapes are possible. Note that the other configuration, operation, and effect are the same as those of the seventh embodiment, and thus description thereof is omitted.

[0066]

As described above, according to the charging device of the first aspect, in the charging device including the photosensitive drum and the charging roller that comes into pressure contact with the photosensitive drum and follows the photosensitive drum, the charging device includes the photosensitive drum. A gas flow generator that generates a gas flow toward the center of the photoconductor drum is provided, so that powder dirt and ionic dirt on the surface of the photoconductor drum can be spread evenly to enable uniform charging, and the thickness of the photoconductor drum The charge unevenness due to the above-mentioned variation can be prevented by moving charges and ions by the gas flow generated on the photosensitive drum surface.

According to the charging device of the present invention, the flow velocity of the gas flow generated by the gas flow generation device is in the range of 1/1000 to 1000 times the moving speed of the photosensitive drum, so that the potential The distribution ratio can be 0.96 or more.

Further, according to the charging device of the third aspect, since the gas flow is by blowing, the same effect as in the first aspect can be obtained by the gas flow generated by the blowing.

According to the charging device of the fourth aspect, since the gas flow is by suction, the same effect as in the first aspect can be obtained by the gas flow generated by the suction.

According to the charging device of the present invention, since the gas flow generating device is disposed upstream of the contact portion between the charging roller and the photosensitive drum, the gas flow generating device generates the gas flow. By the gas flow, charging can be performed after preventing powder contamination and ionic contamination on the upstream side, and charging unevenness can be prevented.

According to the charging device of the present invention, since the gas flow generating device is disposed downstream of the contact portion between the charging roller and the photosensitive drum, the gas flow generated by the gas flow generating device is reduced. Accordingly, charges and ions can be moved on the downstream side to prevent charging unevenness.

According to the charging device of the present invention, the gas flow generating device is disposed on both the upstream side and the downstream side of the contact portion between the charging roller and the photosensitive drum. The gas flow generator prevents charging of powder and ionic dirt on the upstream side before charging, and the gas flow generator on the downstream side charges and charges by the gas flow on the downstream side.
By moving the ions, charging unevenness can be prevented.

According to another aspect of the present invention, there is provided a charging device comprising a photosensitive drum connected to a driving source and a charging roller which comes into pressure contact with the photosensitive drum and rotates with the photosensitive drum. Since a gas flow generating member for generating a gas flow is provided to face the air, the air is stripped from the surface of the photosensitive drum connected to the driving source by the gas flow generating member, and the air is generated by laminar flow or turbulent flow. Flow occurs.

According to the charging device of the ninth aspect, since the gas flow generating member is a wedge-shaped member, the air is stripped from the surface of the photosensitive drum connected to the driving source by the wedge-shaped member. Air flow due to laminar flow or turbulent flow is generated on the surface of the photoreceptor drum, and uneven charging can be prevented.

Further, according to the charging device of the tenth aspect, since the gas flow generating member is a flat member, air is stripped from the surface of the photosensitive drum connected to the driving source by the flat member. Air flow due to laminar flow or turbulent flow is generated on the surface of the photoreceptor drum, and uneven charging can be prevented.

According to the eleventh aspect of the present invention, since the gas flow generating member is disposed upstream of a contact portion between the charging roller and the photosensitive drum, the gas flow generated by the gas flow generating member is provided. Thereby, charging can be performed after preventing powder contamination and ion contamination on the upstream side.

According to the charging device of the twelfth aspect, since the gas flow generating member is disposed downstream of the contact portion between the charging roller and the photosensitive drum, the gas flow generated by the gas flow generating device is provided. Accordingly, charges and ions can be moved on the downstream side to prevent charging unevenness.

According to the charging device of the thirteenth aspect, since the gas flow generating member is disposed both on the upstream side and the downstream side of the contact portion between the charging roller and the photosensitive drum, the gas flow generating member is provided on the upstream side. The gas flow generating member prevents charging of powder and ionic contamination on the upstream side before charging, and the downstream gas flow generating member moves charges and ions by the gas flow on the downstream side to reduce charging unevenness. Can be prevented.

According to the charging device of the fourteenth aspect, the gas flow generating member is at least a part of the upper cover case of the cleaning unit. Air is stripped from the surface of the photoconductor drum, and an airflow due to laminar flow or turbulent flow is generated on the surface of the photoconductor drum.

According to the charging device of the fifteenth aspect, since the gas flow generating member is at least a part of the upper cover case of the developing unit, it is connected to the driving source similarly to the effect of the fourteenth aspect. Air is stripped from the surface of the photoconductor drum, and an airflow due to laminar flow or turbulent flow is generated on the surface of the photoconductor drum.

[Brief description of the drawings]

FIG. 1 is a side view of a contact charging device according to a first embodiment of the present invention.

FIG. 2 is a front view of the same.

FIG. 3 is a diagram showing a relationship between Vair / Vs and a potential distribution ratio.

FIG. 4 is a diagram illustrating a charging potential when a potential distribution ratio at a position on a photosensitive drum is 0.96.

FIG. 5 is a diagram illustrating a charging potential when a potential distribution ratio at a position on a photosensitive drum is 0.85.

FIG. 6 is a side view of a contact charging device according to a second embodiment of the present invention.

FIG. 7 is a side view of a contact charging device according to a third embodiment of the present invention.

FIG. 8 is a side view of a contact charging device according to a fourth embodiment of the present invention.

FIG. 9 is a side view of a contact charging device according to a fifth embodiment of the present invention.

FIG. 10 is a side view of a contact charging device according to a sixth embodiment of the present invention.

FIG. 11 is a side view of a contact charging device according to a seventh embodiment of the present invention.

FIG. 12 is a side view of a contact charging device according to an eighth embodiment of the present invention.

FIG. 13 is a diagram illustrating a photoconductor of a photoconductor drum.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 2 charging roller 3A air flow generator 3B air flow generator 4A wedge-shaped member 4B wedge-shaped member 5A long flat plate member 5B long flat plate member 6 cleaning unit 61 upper cover 7 developing unit 71 upper cover 12 Photoconductor

Claims (15)

[Claims] A charging device configured to generate a gas flow toward a center of the photosensitive drum, wherein the charging device includes a photosensitive drum and a charging roller that rotates while being pressed against the photosensitive drum. A charging device, comprising: 2. A flow rate of a gas flow generated by the gas flow generation device is 1/1000 of a moving speed of the photosensitive drum.
The charging device according to claim 1, wherein the charging time is in a range of 2 times to 1000 times. 3. The charging device according to claim 1, wherein the gas flow is generated by spraying. 4. The charging device according to claim 1, wherein the gas flow is by suction. 5. The charging device according to claim 1, wherein the gas flow generation device is disposed upstream of a contact portion between the charging roller and the photosensitive drum. 6. The charging device according to claim 1, wherein the gas flow generating device is disposed downstream of a contact portion between the charging roller and the photosensitive drum. 7. The charging device according to claim 1, wherein the gas flow generating device is disposed on both the upstream side and the downstream side of a contact portion between the charging roller and the photosensitive drum. . 8. A charging device comprising a photosensitive drum connected to a drive source and a charging roller which presses and rotates while being pressed against the photosensitive drum, for generating a gas flow facing the photosensitive drum. A charging device comprising a gas flow generating member. 9. The charging device according to claim 8, wherein the gas flow generating member is a wedge-shaped member. 10. The charging device according to claim 8, wherein the gas flow generating member is formed of a plate-like member. 11. The charging device according to claim 8, wherein the gas flow generating member is arranged upstream of a contact portion between the charging roller and the photosensitive drum. 12. The charging device according to claim 8, wherein the gas flow generating member is disposed downstream of a contact portion between the charging roller and the photosensitive drum. 13. The charging device according to claim 8, wherein the gas flow generating member is disposed on both the upstream side and the downstream side of a contact portion between the charging roller and the photosensitive drum. . 14. The charging device according to claim 8, wherein the gas flow generating member is at least a part of an upper cover case of a cleaning unit. 15. The charging device according to claim 8, wherein the gas flow generating member is at least a part of an upper cover case of the developing unit.