JPH10254224A - Noncontact electrifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely remove dust and residual toner stuck to the surface of an electrifying roller, and to uniformly electrify it, in a noncontact electrifier. SOLUTION: In the noncontact electrifier constituted in such a manner that the electrifying roller 20 and a photoreceptor drum 10 are arranged to face each other with a very small gap between the electrified surface of the electrifying roller 20 and the surface of the photoreceptor drum 10, an air flow generator 30A for making an air flow is provided in the vicinity of a position where the photoreceptor drum 10 is nearest to the electrifying roller 20. The air flow generator 30A is of a hollow case provided to cover the entire effective width of the electrifying roller 20 along its axis line and provided with an opening part 31 formed in the position facing the proximity part T of the roller 20 and the drum 10. Air A is blown out through a hose 32 and the opening part 31, so that the air flow is generated in the vicinity of the proximity part T.

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 in an electrophotographic image forming apparatus such as a copying machine, a laser printer, and a facsimile, and more particularly, to applying a voltage to a charging roller which is not in contact with a moving photosensitive member. And a non-contact charging device for charging the surface of the photoreceptor.

[0002]

2. Description of the Related Art In the above-mentioned non-contact charging device, a charging surface of a charging roller is arranged in a non-contact state with a photoreceptor with a small gap secured between the charging roller and a surface of a photoreceptor (for example, a photoreceptor drum). By applying a charging voltage to the photosensitive member, the surface of the photosensitive member is charged to a predetermined potential via the minute gap.

In this non-contact charging device, the amount of ozone generated is smaller than that of a corona charger using airborne corona discharge, and a contact charger for charging by contacting a charging roller or a charging blade with a photosensitive member. There are advantages such as less damage to the surface of the photoreceptor as compared with.

[0004]

However, in the above-mentioned non-contact charging device, the same air discharge as the corona charger is used in principle. Therefore, although not as much as the corona charger, the discharge generation such as ozone is not performed. Things occur.
When the discharge products gradually adhere to and accumulate on the photoreceptor surface, image blurring and image deletion may occur.

[0005] Further, if additives such as silica contained in the transfer residual toner and components such as a filling amount contained in the transfer paper are electrically or mechanically adhered and deposited on the surface of the charging roller due to long-term use, There is a problem that image unevenness occurs. In order to remove these deposits, the surface of the charging roller may be cleaned with a cleaning member such as a brush.In this case, if the brush is rotated at a high speed to increase the cleaning efficiency or the rigidity of the brush is increased. In addition, there is a problem that the wear of the surface of the charging roller is advanced and the life thereof is shortened.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide a non-contact method capable of uniformly removing dust and residual toner attached to the surface of a charging roller and uniformly charging the charging roller. An object of the present invention is to provide a charging device so that a high-quality image can be stably obtained in an image forming apparatus for a long period of time.

[0007]

According to a first aspect of the present invention, there is provided a non-contact charging device for applying a voltage to a charging roller which does not contact a moving photosensitive member to charge the surface of the photosensitive member. Wherein air flow generating means for generating an air flow is provided near a position where the photosensitive member and the charging roller are closest to each other. In this non-contact charging device, dust and residual toner attached to the charging roller are removed by the air flow, and a uniform charging potential is formed on the charging roller.

According to a second aspect of the present invention, there is provided a non-contact charging device according to the first aspect, wherein the airflow generating means includes an opening opposed to a position where the photosensitive member and the charging roller are closest to each other. It is characterized in that air with a positive pressure is blown out through the opening or air is sucked with a negative pressure. In this non-contact charging device, the above configuration ensures that an airflow is generated near the position where the photosensitive member and the charging roller are closest to each other.

According to a third aspect of the present invention, there is provided the non-contact charging device according to the second aspect, wherein the flow rate of the air flow generated by the air flow generation means in the vicinity of the opening is adjusted by moving the surface of the photosensitive member. The speed is set within a range of 1/100 to 1000 times the speed. In this non-contact charging device, a uniform charging potential is formed on the charging roller more effectively than the device of the second aspect by the above configuration.

According to a fourth aspect of the present invention, there is provided a non-contact charging device according to the first aspect, wherein the air flow generating means is a member fixed near a position where the photosensitive member and the charging roller are closest to each other. The air flow is generated in the vicinity of these closest parts by movement of the photoconductor or rotation of the charging roller. With this configuration, the airflow can be generated near the position where the photosensitive member and the charging roller are closest to each other, without using any special power source.

The non-contact charging device according to claim 5, wherein a voltage is applied to a charging roller that is not in contact with the moving photosensitive member to charge the surface of the photosensitive member.
An air flow generating means for generating an air flow around the charging roller is provided around the charging roller. In this non-contact charging device, since an air flow is generated around the charging roller by the air flow generating means, the air flow is formed over a wide area of the charging roller surface. For this reason, the effect of removing dust and residual toner attached to the charging roller and the effect of uniformly charging the charging roller are significantly enhanced.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. First Embodiment FIG. 1 is a side view of a non-contact charging device, and FIG. 2 is an elevation thereof. FIGS. 3A, 3B and 4 are side views showing different application examples of the charging roller. The non-contact charging device 1 shown in FIG. 1 covers the charging roller 20 approaching the photoconductor drum 10 whose surface is covered by the photoconductor 10a, and covers the entire effective width thereof along the axis of the charging roller 20. And an air flow generating device 30A as an air flow generating means.

FIG. 3A shows the charging roller 20.
(B) and charging rollers 20A, 20 as shown in FIG.
B, 20C apply. FIG. 4A is a side view,
(B) is an elevation view. Charging roller 2 shown in FIG.
0A has an elastic layer 23 made of a conductor (including a resistor) around a metal core 22 having a shaft portion (also called a journal portion) 21. The surface of the elastic layer 23
A thin surface layer 24, also made of a conductor, is covered. On the other hand, in the charging roller 20B shown in FIG. 3B, the periphery of the similar core metal 22 is formed by a surface elastic layer 25 made of a conductor.
Covered by The charging roller 20C shown in FIG. 4 is a metal cylinder.

Each of the charging rollers 20A to 20C is urged to approach the photosensitive member 10a by a spring (not shown) abutting on the side surface of the shaft portion 21 of the cored bar 22, and is illustrated via this spring. No voltage is applied from the high voltage power supply. Then, the voltage applied to the core metal 22 reaches the surface via the elastic layer 23, the surface layer 24 or the surface elastic layer 25 made of a conductor, respectively, and charges the surface of the photoreceptor 10a at an approach portion (not shown). .

In FIG. 1, the photosensitive drum 10 is
When connected to ground, it rotates clockwise as indicated by the arrow. The charging roller 20 approaching the photosensitive drum 10 by its own weight and a spring (not shown) is rotated clockwise or counterclockwise by a driving system different from the rotation of the photosensitive drum 10, and is supplied from a high-voltage power supply (not shown). The surface of the photoconductor 10a is charged according to the applied voltage (−600 V to −5 kV).

As shown in FIG. 1, an air flow generator 30A
Is a hollow box provided along the charging roller 20 so as to cover the entire effective width thereof, and is attached to the right side of the charging roller 20. This air flow generator 30A
Is located at a position facing the approaching portion T between the charging roller 20 and the photosensitive drum 10, for example, a length (axial direction of the charging roller) 2
It has a rectangular opening 31 of 1 cm and a width (dimension in a direction perpendicular to the axis) of 5 mm. Then, the airflow generator 30
On the upper part of A, a hose 3 for feeding air from the opening 31
2 are connected. Thus, the air A from the hose 32 is blown out from the opening tool 31 toward the approaching portion T, thereby generating an airflow near the approaching portion T.

The flow velocity of the air A is set within a range of 1/100 to 1000 times the moving speed of the photosensitive drum 10. Here, the reason for setting the above range will be described. For example, assuming that 20 images are formed per minute on A4 size paper fed to the image forming apparatus in the long side direction, the moving speed of the photoconductor 10a, that is, the peripheral speed of the photoconductor drum 10 and the charging roller 20 Vs is
It is approximately 29.7 cm × 20 sheets / min = 594 cm / min.

On the other hand, if 6.2 liter / min of air is supplied from the hose 32, the area of the opening 31 is 21
cm × 0.5 cm = 10.5 cm ² , the flow rate of air at the opening 31 is Vair = (6200 ml /
Min) ÷ (10.5 cm ² ) = 590 cm / min. Therefore, the ratio of the flow rate of air to the peripheral speed of the photosensitive drum 10, Vair / Vs, is 0.99, which is almost equal to 1.
When an image was formed under the above conditions, no image density unevenness was observed even after a considerably strict inspection. Therefore, the flow velocity of the air is substantially proportional to the flow rate, and substantially inversely proportional to the width of the opening 31.
The experiment was performed while changing air / Vs.

FIG. 5A shows Vair obtained by the experiment.
FIG. 4 is a diagram showing a relationship between / Vs and a potential distribution ratio. FIG.
(B) shows the charging roller 20 when the potential distribution ratio is 0.96.
FIG. 5C is a diagram showing the distribution of the charging potential of the charging roller 20 when the potential distribution ratio is 0.85.

As shown in FIG. 5B, when the potential distribution ratio is 0.95 or more, the distribution of the charging potential with respect to the position of the charging roller 20 becomes almost constant, and charging unevenness is almost eliminated. On the other hand, as shown in FIG. 5C, when the potential distribution ratio is smaller than 0.95, the distribution of the charging potential of the charging roller 20 decreases in the axial center portion, and charging unevenness occurs. I do. Therefore, it is necessary to set Vair / Vs so that the potential distribution ratio becomes 0.95 or more.

According to the results of the experiment, as shown in FIG. 5A, it was confirmed that the potential distribution ratio was 0.95 or more when Vair / Vs was in the range of 1/100 to 1000. Therefore, in the present embodiment, the flow velocity V of the air A
The air was set within a range of 1/100 to 1000 times the moving speed of the photosensitive drum 10. The above Vair
Is inversely proportional to the short dimension of the opening 31, but in this experiment, the short dimension of the opening 31 was set to a practical size of 0.05 cm.
０．５0.5 cm. Also, the air flow generator 30A
Similar results were obtained not only in the case where air was supplied from the hose 32 and the air A was blown out, but also when the air in the hose 32 was suctioned with a negative pressure.

Since the non-contact charging device 1 of the present embodiment has the above-described configuration, dust and residual toner adhere to the surface of the photosensitive drum 10 rotating clockwise in FIG. If these are present, these deposits
Side, or moves to the right side in the drawing of the approaching portion T while being attached to the photosensitive drum 10. At this time, air A having a flow velocity in a range of 1/100 to 1000 times the moving speed of the photosensitive drum 10 is blown out from the opening 31 of the air flow generating device 30A.
The dust and the residual toner attached to the charging roller 20 and the photosensitive drum 10 are removed, and the charging potential of the charging roller 20 becomes substantially constant as shown in FIG. As a result, a favorable charging action by the charging roller 20 becomes possible, and the image quality is improved by the non-contact charging device 1.

In the case of non-contact charging using a charging roller (or the like), the surface of the charging roller 20 is
As the surface of a approaches, the arc discharge occurs when the absolute value of the applied voltage is relatively low (600 V), and the discharge to which corona discharge is further applied when the absolute value of the applied voltage is relatively high (5 kV).
Each of them starts as described above. Therefore, even if a slight lifting occurs due to dust or the like at the center of the charging roller 20, charging is performed. that time,
Even if the absolute amount is small, ions such as ozone are generated by the discharge, but the concentration is not negligible from a local viewpoint. For this reason, ions of different polarities may recombine and disappear, and ions of the same polarity will repel each other strongly, causing a complex phenomenon with positive and negative factors, resulting in uneven charging. Appear.

However, due to the presence of the air flow, the ion concentration is locally reduced, the one having a negative factor is removed, and the one having a positive factor remains. Alternatively, the next new discharge is smoothly performed by the decrease in the ion concentration. It is considered that such a phenomenon acts in the positive direction to perform charging uniformly and eliminate charging unevenness. In this embodiment, if the air flow rate or the air flow rate is set large, it is possible to prevent the temperature of the charging roller 20 and the photosensitive drum 10 from rising, and to prevent not only the charging condition but also the development and transfer conditions from changing. Also becomes possible.

Second Embodiment FIG. 6 is a side view of a non-contact charging device. In the non-contact charging device 2, an air flow generating device 30B having the same structure as the air flow generating device 30A is mounted on the left side of the charging roller 20, and the opening 31 of the air flow generating device 30B is connected to the charging roller 20 and the photosensitive drum 10 The configuration is directed toward the approaching portion T.

With such a configuration, when dust or residual toner adhering to the surface of the photosensitive drum 10 rotating clockwise reaches the vicinity of the approaching portion T, the dust and residual toner are removed by the airflow generator 3.
By the airflow from OB, it is removed just before the approaching portion T. That is, in the non-contact charging device 2 of the present embodiment,
The dust and the residual toner are removed before adhering to the charging roller 20, and the dust and the residual toner adhering to the charging roller 20 are also removed in front of the approaching portion T, so that a further removing effect is obtained. be able to. The other configuration, operation, and effect of the non-contact charging device 2 are the same as those of the first embodiment, and the description thereof is omitted.

Third Embodiment FIG. 7 is a side view of a non-contact charging device. In the non-contact charging device 3, the air flow generating device 3 is provided on both sides of the charging roller 20.
0A and 30B are attached, and an air flow generator 30C is attached on the upper surface side of the charging roller 20.

In such a configuration, dust and residual toner are removed just before the approaching portion T between the charging roller 20 and the photosensitive drum 10 by the airflow generating device 30B on the left side. The dust and residual toner that have moved to the right side can be removed by the airflow generator 30A on the right side. Then, dust and residual toner that have passed through the right airflow generator 30A are reliably removed by the airflow generator 30C and the left airflow generator 30B.

As described above, according to the non-contact charging device of the present embodiment, the three-contact charging device
With three air flow generators 30A, 30B, 30C,
Dust and residual toner attached to the charging roller 20 can be completely removed. Further, since the air flow is generated over substantially the entire charging roller 20, the charging roller 20
In addition, a more uniform charging potential can be formed.
As a result, the operation reliability of the non-contact charging device 3 can be improved. Other configurations of the non-contact charging device 3,
The operation and effect are the same as those of the first and second embodiments, and the description thereof will be omitted.

By the way, in order to facilitate understanding,
Although the first to third embodiments have been described as typical embodiments of the non-contact charging device using the airflow generation device, the present invention is not limited to these embodiments. That is, various forms can be adopted as shown in the following [Table 1] to [Table 3] within the scope of the gist of the present invention, and
As a result, the same effects as those of the first to third embodiments can be obtained.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

Fourth Embodiment FIG. 8 is a side view of a non-contact charging device. The non-contact charging device 4 includes a photoconductor drum 10, a charging roller 20 approaching the photoconductor drum 10, and a pull-out fitting 40 as an air flow generating device.
A. The pull-out fitting 40A is fixed to the right side of the charging roller 20 so as to cover the entire effective width thereof along the charging roller 20 and to face the charging roller 20 except for a slight gap B.

In such a configuration, when the charging roller 20 rotates counterclockwise, the charging roller 20 and the pull-out fitting 4 are rotated.
The air in the gap B portion between 0A and the surface of the charging roller 20 is peeled off, and an air flow (laminar flow or turbulent flow) blown toward the approaching portion T from between the extraction fitting 40A and the photosensitive drum 10 is generated. Occur. Further, an airflow due to the air passing through the gap of the pull-out fitting 40A is generated at the outlet side of the gap.

Thus, the same effects as those of the non-contact charging device 1 can be obtained. However, in the non-contact charging device 4 according to the present embodiment, unlike the non-contact charging device 1, there is no need to provide a fan or a pump that requires power to generate an air flow, and the arrangement space is small. Help me.
For this reason, it is possible to reduce the size of the non-contact charging device and reduce the manufacturing cost.

In this embodiment, the pull-out fitting 40A is used.
Is used, but when this is composed of a conductor,
In order to prevent the discharge, it is necessary to apply the same voltage as that of the charging roller 20, and hold the pull-out fitting 40A with an insulator. However, if an insulator having the same shape is used instead of the pull-out fitting 40A, the holding thereof is simplified. Further, it is not always necessary to have the same shape as the illustrated pull-out fitting 40 </ b> A, and the same effect can be obtained even if it is provided opposite to the photosensitive drum 10 instead of the charging roller 20. The other configuration, operation, and effect of the non-contact charging device 4 are the same as those of the first embodiment (the non-contact charging device 1), and thus description thereof will be omitted.

Fifth Embodiment FIG. 9 is a side view of a non-contact charging device. This non-contact charging device 5 has a pull-out fitting 40B having the same structure as the pull-out fitting 40A.
Is mounted on the left side of the charging roller 20 so as to cover the entire effective width thereof along the charging roller 20 and to face the charging roller 20 except for a slight gap B. Thereby, the same effect as in the second embodiment (non-contact charging device 2) can be obtained. However, in the non-contact charging device 5, unlike the non-contact charging device 2, the size of the device can be reduced and the manufacturing cost can be reduced. The other configuration, operation and effect of the non-contact charging device 5 are the same as those of the non-contact charging device 2, and therefore the description thereof is omitted.

Sixth Embodiment FIG. 10 is a side view of a non-contact charging device. In this non-contact charging device 6, pull-out fittings 40 are provided on both sides of the charging roller 20.
A and 40B are attached, and a pull-out fitting 40C is attached to the upper surface side of the charging roller 20. Thereby, the same effect as in the third embodiment (non-contact charging device 3) can be obtained. However, this non-contact charging device 6
Thus, unlike the non-contact charging device 3, the size of the device can be reduced and the manufacturing cost can be reduced. Other configurations, functions and effects of the non-contact charging device 6 are the same as those of the non-contact charging device 3, and therefore, the description thereof is omitted.

Seventh Embodiment FIG. 11 is a side view of a non-contact charging device. In this non-contact charging device 7, on both sides and the upper surface side of the charging roller 20,
It has a configuration in which square members 50 to 52 having a rectangular cross section are attached. Even in such a configuration, the sixth embodiment is used.
The same effect as (Non-contact charging device 6) was obtained. Accordingly, in the non-contact charging device 7, unlike the non-contact charging device 6, the square member 50 having a simple cross-sectional shape that does not require cross-section processing.
Since the same effect as that of the non-contact charging device 6 can be obtained in the case of ５２52, the manufacturing cost of the device can be further reduced.
The other configuration, operation and effect of the non-contact charging device 7 are the same as those of the non-contact charging device 6, and the description thereof will be omitted.

By the way, the above-described fourth to seventh embodiments have been described as typical embodiments of the non-contact charging device using members such as the pull-out fitting 40A, but the present invention is not limited to these embodiments. Not something. That is, various forms can be adopted as shown in the following [Table 4] within the scope of the gist of the present invention, and the same effects as those of Embodiments 4 to 7 can be obtained by these.

[0042]

[Table 4]

Eighth Embodiment FIG. 12 is a side view of a non-contact charging device. In the non-contact charging device 8, a plate member 53 having a U-shaped cross section is attached to the charging roller 20.
Is covered. In such a configuration, the same effects as those of the non-contact charging devices 6 and 7 of the sixth and seventh embodiments were obtained. Therefore, in the non-contact charging device 8, unlike the non-contact charging devices 6 and 7, a large number of members are not used, and the same effect as the non-contact charging devices 6 and 7 can be obtained with one plate member 53. The device manufacturing cost can be further reduced. Other configurations and operational effects of the non-contact charging device 8 are the same as those of the non-contact charging devices 6 and 7, and the description thereof is omitted.

Ninth Embodiment FIG. 13 is a side view of a non-contact charging device. In this non-contact charging device 9, a plate member 54 having an arc-shaped cross section is
In this configuration, the same effect as in the non-contact charging device 8 of the eighth embodiment can be obtained. The other configuration, operation and effect of the non-contact charging device 9 are the same as those of the non-contact charging device 8, and the description thereof will be omitted.

[0045]

As described above, according to the non-contact charging device according to the first aspect, the dust and the residual toner attached to the charging roller are removed by the air flow generated by the air flow generating means to reduce the uneven charging. Generation can be prevented, and a uniform charging potential can be formed on the charging roller.

According to the second aspect of the present invention, the position where the photosensitive member and the charging roller come closest to each other by blowing out or sucking in air through the opening of the air flow generating means. , An air flow is reliably generated in the vicinity of the charging roller, so that the effect of removing dust and residual toner from the charging roller and the effect of forming a uniform charging potential of the charging roller can be enhanced.

According to the non-contact charging device of the third aspect, with a predetermined configuration, a uniform charging potential can be formed on the charging roller more effectively than the device of the second aspect.

According to the fourth aspect of the present invention, the airflow is generated in the vicinity of the position where the photosensitive member and the charging roller are closest to each other without using any special power source. Can be. Therefore, a non-contact charging device can be provided at low cost.

According to the non-contact charging device of the fifth aspect, since a plurality of air flow generating means are used, the effect of removing dust and residual toner from the charging roller is remarkably enhanced, and it is ensured. A uniform charging potential can be formed on the charging roller. Therefore, the operation reliability of the non-contact charging device is improved.

[Brief description of the drawings]

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

FIG. 2 is an elevation view of FIG.

FIG. 3 is a side view showing an application example of a charging roller;
(A) shows a first application example, and (b) shows a second application example.

FIG. 4 shows a third application example of the charging roller.
(A) is a side view, (b) is an elevation view.

FIG. 5 is a diagram showing a potential distribution, in which (a) shows Vair /
4 shows a relationship between Vs and a potential distribution ratio. (B) shows the distribution of the charging potential of the charging roller when the potential distribution ratio is 0.96.
(C) shows the distribution of the charging potential of the charging roller when the potential distribution ratio is 0.85.

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

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

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

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

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

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

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

FIG. 13 is a side view of a non-contact charging device according to a ninth embodiment of the present invention.

[Explanation of symbols]

 1-9 Non-contact charging device 10 Photoreceptor drum 10a Photoreceptor 20, 20A-20C Charging roller 30A-30C Air flow generator 31 Opening 32 Hose 40A-40C Pull-out fitting 50-52 Square material 53,54 Plate material A Air B gap T approaching part

Claims (5)

[Claims] In a non-contact charging device for charging a surface of a photosensitive member by applying a voltage to a charging roller which is not in contact with a moving photosensitive member, an air flow is provided near a position where the photosensitive member and the charging roller are closest to each other. A non-contact charging device provided with an air flow generating means for generating the pressure. 2. The non-contact charging device according to claim 1, wherein the airflow generating means includes an opening facing a position where the photosensitive member and the charging roller are closest to each other, and through the opening,
A non-contact charging device which blows out air at a positive pressure or sucks air at a negative pressure. 3. The non-contact charging device according to claim 2, wherein the flow velocity of the air flow generated by the air flow generation means in the vicinity of the opening is 1/10 of the moving speed of the photosensitive member surface.
A non-contact charging device characterized by being set within a range of 0 to 1000 times. 4. The non-contact charging device according to claim 1, wherein the air flow generating means comprises a member fixed near a position where the photosensitive member and the charging roller are closest to each other, and moves the photosensitive member or adjusts the charging roller. A non-contact charging device characterized in that an air flow is generated near these closest parts by rotation. 5. A non-contact charging device for applying a voltage to a charging roller which is not in contact with a moving photosensitive member to charge a surface of the photosensitive member, wherein an air flow generating means for generating an air flow around the charging roller. Is disposed around the charging roller.