JPH0831545A - Corona discharge device - Google Patents

Abstract

PURPOSE:To provide a corona discharge device whose discharge quantity is little, applying voltage to the discharge electrode is low, and discharge stability, charge efficiency and charge uniformity are excellent by setting an auxiliary electrode on the side face of a discharge electrode. CONSTITUTION:A common electrode 13a is formed on an insulation board 1a, and a discharge electrode portion composed of plural serrate from discharge electrodes 2a are provided on the board 1a separated from the electrode 13a by a fixed space (d). The electrode 13a and respective electrodes 2a are connected to each other via plural stabilizing resistors 16a. The tips of the electrode 2a are bonded to the board 1a so as to extrude out of the edge portion of the board 1a toward a photoreceptor 4 side separated therefrom by a distance (g). First auxiliary electrode 18a is fitted to the board 1a via a spacer 3a, and second auxiliary electrode 19a is bonded to the back face of the board 1a. The electrode 13a is connected to a voltage source 5 so as to apply a drive voltage to the electrodes 2a to discharge. The electrodes 18a, 19a are connected to a power source 6 so that a lower voltage than the apply voltage to the electrodes 2a is applied to the electrodes 18a, 19a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corona discharge device which applies a corona discharge phenomenon to uniformly charge an object to be charged,
In particular, the present invention relates to a corona discharge device capable of downsizing the discharge device, stabilizing the discharge current, and lowering the driving voltage.

[0002]

2. Description of the Related Art Heretofore, there has been proposed a corona discharge device using a discharge electrode formed in a pin shape or a sawtooth shape as disclosed in, for example, Japanese Patent Laid-Open No. 60-80870. Fig. 17 (a) is a block diagram of this type of corona discharge device.
Shown in This device configuration includes a grid electrode 11, a shield case 12 having a U-shaped cross section, an insulating substrate 14 supported by the shield case 12, and a stainless steel plate (thickness: 0.1 mm) provided on the insulating substrate 14. ) And the sawtooth discharge electrode section 15).

The shield case 12 is provided for the purpose of preventing discharge from reaching other parts of the apparatus, stabilizing discharge, reducing driving voltage, and the like. Moreover, although the discharge can be stabilized to some extent only with the shield case 12,
In order to obtain further sufficient charging uniformity, the grid electrode is located in the opening of the shield case.

A voltage slightly higher than the charging potential of the photoconductor is applied to the grid electrode 11, and when the discharge amount is larger than the desired charging potential, the large amount is absorbed by the grid electrode 11 to cause charging. Uniformity can be achieved.

FIG. 1B is a front view of the sawtooth discharge electrode portion 15. When the pitch p between the tooth portions of each discharge electrode is 2 mm, the tooth tips of the saw-toothed discharge electrodes 15 are made of the insulating substrate 1.
2mm from the edge of 4 to the side of the photoconductor 4
It is provided on the insulating substrate 14 so as to come to the protruding position. The sawtooth discharge electrode 15 is connected to the high voltage power supply 9. By applying a high voltage (for example, -4.5 kV) to the saw-tooth discharge electrode 15 by the high-voltage power supply 9, corona discharge is stably generated from the tip of the tooth, and the surface of the photoconductor 4 is charged.

A grid electrode 11 to which a voltage (for example, -620 V) smaller than the voltage applied to the sawtooth discharge electrode 9 is applied by a high voltage power supply 10 is provided between the discharge electrode 15 and the photosensitive member 4. . The grid electrode 11 controls the charging potential of the photoconductor 4 to a predetermined potential.

[0007]

FIG. 18 is a model diagram (a) of a corona discharge device using the conventional sawtooth discharge electrode shown in FIG. 17, a graph (b) showing its discharge characteristics, and an equivalent circuit diagram. (C) is shown. A high-voltage power supply 21 is connected between the discharge electrode 17 corresponding to the saw-tooth discharge electrode 15 and the discharge target 20 corresponding to the photoconductor 4 in FIG. 17A, and the discharge electrode 17 and the discharge target 20 are connected to each other. Corona discharge occurs in the gap g between them.

A certain driving voltage is a constant voltage (discharge starting voltage V
th), corona discharge starts, and if the drive voltage E and the discharge current I after the start of discharge are limited to the actual use range (discharge current 0.4 A or more per pin of discharge current), a nearly linear relationship is obtained. Can be considered to have. Therefore, from the figure (c), the discharge current I is expressed by I = (E-Vth) / Rg (Rg: void impedance corresponding to void).

The discharge start voltage Vth is substantially constant between the respective discharge electrodes, but the void impedance Rg is about ± 30 between the respective discharge electrodes 15 due to variations in the shape of the electrode tips and the effects of deposits on the tips. It has a variation of%. If the air gap impedance varies by ± 30% between the discharge electrodes 15,
The discharge current also fluctuated at a rate of ± 30%, and uneven charging occurred.

Further, in the conventional corona discharge device, the shield case is provided so as to cover the discharge electrode, and the grid electrode is provided on the opening surface of the shield case, so that it is necessary to apply a high voltage to the discharge electrode. In order to secure leak resistance and safety to the photoconductor, the shield case, and the grid electrode, a distance of 5 to 10 mm is provided between the discharge electrode and the photoconductor, the shield case, and the grid electrode. In addition, the apparatus becomes large, and in order to charge the photoconductor to a predetermined voltage, it is necessary to increase the drive voltage of the discharge electrode and discharge more than necessary to the grid electrode and the shield case.

Further, as described above, since the discharge amount of the discharge electrode is large, there are problems that the discharge stability, charging efficiency, and charging uniformity are poor, and the amount of ozone generated due to the discharge amount is large.

In view of the above problems, the present invention provides a corona discharge device which has a smaller discharge amount, a smaller voltage applied to a discharge electrode, and is excellent in discharge stability, charging efficiency, and charging uniformity as compared with the prior art. To aim.

[0013]

The structure of the corona discharge device of the present application has a discharge electrode for discharging a photoconductor and an auxiliary electrode to which a voltage smaller than a voltage applied to the discharge electrode is applied. The auxiliary electrode is provided on both sides of the discharge electrode, and the discharge electrode is connected to a voltage power supply via a resistor having a predetermined resistance value.

It is preferable that the discharge electrode is composed of a plurality of needle-shaped electrodes arranged at regular intervals. Regarding the distance between the discharge electrode and the auxiliary electrode, the voltage applied to the discharge electrode is E (kV) and the voltage applied to the auxiliary electrode is V _S (k
V), the distance between the discharge part of the discharge electrode and the auxiliary electrode is d (m
m), it is preferable to satisfy d ≦ | E−Vs |.

The smaller the distance between the discharge electrode and the object to be discharged, the more the driving voltage can be reduced, and the discharge current from each discharge electrode can be made uniform. However, when the distance becomes less than the discharge electrode pitch. Discharge electrode Dispersion of charge occurs due to the discharge electrode pitch.

Therefore, by setting the distance between the discharge electrode and the object to be discharged as small as possible within the range of the discharge electrode pitch or more, it is possible to suppress the occurrence of charging variations due to the discharge electrode pitch and to improve the charging uniformity. This is preferable because it can be improved and the driving voltage can be reduced.

Further, in this structure, as a method of controlling the voltage applied to the discharge electrode and the auxiliary electrode, either one of the discharge electrode and the auxiliary electrode is subjected to constant current control, and the other electrode is subjected to constant voltage control. Alternatively, during rotation before the actual charging of the photoconductor, the discharge electrode and the auxiliary electrode are subjected to constant current control so that the discharge current to the photoconductor becomes a constant magnitude, and the discharge electrode and the auxiliary electrode generated at that time are controlled. The applied voltage is held or stored, and the discharge electrode and the auxiliary electrode are subjected to constant voltage control according to the applied voltage value that is held or stored during actual charging. As a result, the charging current value can always be controlled to be constant regardless of environmental conditions, and excellent charge controllability can be obtained.

Further, there are first and second discharge electrode rows composed of a plurality of discharge electrodes on both sides of the insulating substrate, and the discharge electrodes are connected to a voltage power source via resistors having a predetermined resistance value. In the corona discharge device, a voltage having an oscillating waveform is applied to the first and second discharge electrode rows, and either one of the first and second discharge electrode rows serves as an auxiliary electrode. Therefore, it is characterized in that the voltages are applied to the respective discharge electrodes with their phases shifted. It is most preferable that the phase shift is 180 °.

Further, in this configuration, when the discharge electrode pitch p of the first discharge electrode array and the discharge electrode pitch p of the second discharge electrode array are arranged so as to be offset from each other by 1/2 of the discharge electrode pitch p, the discharge is apparent. Since the electrode pitch is small and becomes p / 2, the distance between the discharge electrode and the discharge target can be reduced,
Further, it is preferable that the driving voltage can be reduced and the charging uniformity can be improved.

[0020]

In the corona discharge device of the present application, the auxiliary electrode is provided on the side surface of the discharge electrode, and a resistor having a predetermined resistance value is connected between the discharge electrode and the driving voltage source, whereby the discharge electrode and the auxiliary electrode are connected. Therefore, it is not necessary to perform unnecessary discharge to other parts as in the conventional case, and the shield case, the grid electrode, etc. are not required, so that the device can be downsized. In addition, the drive voltage of the discharge electrode can be made lower than before, the distance between the tip of the discharge electrode and the photoconductor can be shortened, discharge stability and charging uniformity are excellent, and charging efficiency is high. It is possible to realize a corona discharge device that generates a small amount of ozone.

The voltage applied to the discharge electrode is E (k
V), V _S (kV voltage applied to the auxiliary electrode), when the discharge portion of the discharge electrode distance between the auxiliary electrode was d (mm),
It is more effective if the condition of d ≦ | E−Vs | is satisfied.

In the corona discharge device according to the second aspect, the applied voltage waveforms of the first discharge electrode array and the second discharge electrode array are oscillating waveforms, and the phase of the applied voltage waveform to the first discharge electrode array and the If the waveform of the applied voltage to the two discharge electrode rows is out of phase by 180 °, for example, the oscillation waveform of the applied voltage is a rectangular wave of 0 V (grounded state) and the driving voltage that causes the discharge. When the driving voltage is applied to the column and the column is in the discharge state, the second discharge electrode column is 0 V (ground state)
Therefore, the first discharge electrode array acts as an auxiliary electrode of the first discharge electrode array, and conversely, when the second discharge electrode array is in a discharge state, the first discharge electrode array acts as an auxiliary electrode. Since the discharge from the discharge electrode is stabilized, the grid electrode and the shield case are not required, the device can be downsized, high charging efficiency can be obtained, and the amount of ozone generated can be reduced.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. 1 is a schematic configuration diagram of the corona discharge device of the present application, FIG.
3A is a perspective view of a discharge / auxiliary electrode portion in the corona discharge device of the present application, FIG. 3B is a front view of the discharge electrode portion, and FIG. 3 is a sectional view of portion X in FIG. 3B is a cross-sectional view taken along line Y and Y of FIG.

A common electrode 13a is formed on the insulating substrate 1a, and a plurality of (107 in this embodiment) discharge electrodes 2a are formed on the insulating substrate 1a at a constant distance d from the common electrode 13a. Section is provided.

The discharge electrode 2a is made of stainless steel having a thickness of 0.1 mm, and is formed in a sawtooth shape by etching. The common electrode 13a and each discharge electrode 2a have about 50
It is electrically connected by a plurality of stabilizing resistors 16a (hereinafter referred to as chip resistors) having a resistance value of 0 MΩ. The number of the discharge electrodes 2a is 107, the pitch P between the discharge electrodes 2a is 2 mm, and the tip of the discharge electrodes 2a is positioned so as to project 2 mm from the edge portion of the insulating substrate 1a toward the photoconductor 4 side. Is bonded to the insulating substrate 1a.

The distance g from the tip of the discharge electrode 2a to the surface of the photosensitive drum 4 (hereinafter referred to as the discharge gap g) is 3 mm. The first auxiliary electrode 18a is made of stainless steel and has a thickness of 0.5 mm, and is attached to the insulating substrate 1a via the spacer 3a.

A second auxiliary electrode 19a having the same shape and the same material as the first auxiliary electrode 18a is adhered to the back surface of the insulating substrate 1a. The common electrode 13a is connected to the voltage power supply 5, and a driving voltage (about −2.0 kV in this embodiment) is applied to the discharge electrode 2a by the voltage power supply 5, so that the photoconductor 4 and the auxiliary electrodes 18a and 19a. Discharge to.

The auxiliary electrodes 18a, 19a are connected to the voltage power supply 6, and the auxiliary electrodes 18a, 1a are connected by the voltage power supply 6.
By applying a voltage (about -500 V in this embodiment) smaller than the magnitude of the voltage applied to the discharge electrode 2a to 9a, the discharge current in the direction of the auxiliary electrode is reduced and the charging efficiency is improved. The magnitude of the applied voltage to the auxiliary electrodes 18a and 19a may be smaller than the magnitude of the applied voltage to the discharge electrode 2a.

The effect on the charging characteristics of the auxiliary electrode was confirmed by simulation and experiment. FIG. 4 is a model showing this corona discharge device by an equivalent electric circuit. Where Vg is the discharge start voltage for the photoreceptor,
Vs is the discharge start voltage for the auxiliary electrode, Rg is the void impedance between the discharge electrode 2a and the photoconductor, Rs is the void impedance between the discharge electrode 2a and the auxiliary electrodes 18a and 19a, Rc is the stabilizing resistance, and Ic is the discharge electrode 2a. Total discharge current discharged (hereinafter referred to as total current),
Ig is a discharge current in the direction of the photosensitive drum (hereinafter referred to as a charging current) in the total current, Is is a discharge current in the direction of the auxiliary electrode (hereinafter referred to as an auxiliary current) in the total current, and E is a driving voltage. . From this model, the charging current Ig is represented by the equation (1).

[0030]

[Equation 1]

The simulation conditions were set as follows. (1) Void impedance Rg by each discharge electrode 2a,
The fluctuation rates of Rs and Rs are constant regardless of the discharge gap g. (2) Void impedance Rg and R at each discharge electrode 2a
The volatility of s is equal. (3) The discharge starting voltages Vg and Vs are constant between the discharge electrodes 2a. (4) The discharge starting voltages Vg and Vs are equal. Based on the above simulation conditions, the case where the auxiliary electrode is provided on the side surface of the discharge electrode and the case where the auxiliary electrode is not provided (charging current Ig variation)-(void impedance Rg variation)
The characteristics are shown in FIG.

The variation of the charging current Ig is 107
When the maximum value of each of the charging currents Ig discharged from the individual discharge electrodes 2a is Igmax, the minimum value Igmin, and the average value is Igave, Igpp (%) = | Igmax-Igmin | / Iga
It is the variation represented by ve.

As shown in FIG. 5, when the auxiliary electrode is provided on the side surface of the discharge electrode, the variation in the charging current Ig between the discharge electrodes 2a is smaller than when the auxiliary electrode is not provided, and the auxiliary electrode 18 is provided.
It was confirmed that the charging current could be made uniform by using a and 19a.

FIG. 6 shows the result of an experiment in which the charging characteristics were examined with and without the auxiliary electrode provided on the side surface of the discharge electrode. The charging characteristics were evaluated by measuring the charging potential in the axial direction on the photoconductor drum and measuring the magnitude of the axial charging ripple (hereinafter referred to as charging variation). According to the measurement results shown in FIG. 6, the auxiliary electrode 18
It was confirmed that by providing a and 19a, the driving voltage was reduced and the charging uniformity was improved, that is, the charging variation was reduced.

Next, the auxiliary electrodes 18a and 19a and the discharge electrode 2
Similar to the above, the influence of the distance between a was examined by simulation and experiment. FIG. 7 shows the auxiliary electrode 18
The results of simulation of the relationship between the distances between the discharge electrodes 2a and 19a and the discharge electrode 2a and the variation of the charging current Ig.
The smaller the distance between 8a and 19a and the discharge electrode 2a, the smaller the variation in the charging current Ig.

Further, FIG. 8 shows the experimental results of examining the relationship between the distance between the auxiliary electrodes 18a and 19a and the discharge electrode 2a and the charging characteristic. Similar to the simulation result, it can be seen that the smaller the distance from the discharge electrode 2a is, the higher the charging uniformity is (the variation in charging is reduced) and the driving voltage is reduced.

In the conventional corona discharge device, the distance d (mm) between the discharge electrode 2a and the discharge target such as the grid electrode and the shield case is the voltage E applied to the discharge electrode 2a.
(KV), assuming that the applied voltage of the discharge target is Vs (kV), d> | E-Vs | is usually set to prevent the discharge from the discharge electrode 2a from shifting to spark discharge or arc discharge. Is. However, in the present invention, since the high resistance (500 MΩ) chip resistor 16a is provided between each discharge electrode and the voltage power source, there is no risk of shifting to spark discharge even if d ≦ | E−Vs |. Therefore, in the present invention, the distance between the discharge part of the discharge electrode and the auxiliary electrode can be set smaller, the corona discharge is stably maintained, the charging uniformity is improved, the driving voltage is reduced, and the device is further It can be made smaller and thinner.

According to the above result, the spacer 3 is used in this embodiment.
a and the insulating substrate 1a have a thickness of 1.5 mm, and the distance between the auxiliary electrodes 18a and 19a and the discharge electrode 2a is 1.
It was set to 5 mm.

Next, the relationship between the discharge gap g and the variation in charging current was examined by simulation and experiment. The graph shown in FIG. 9 is the result of the simulation. As can be seen from the simulation, it was confirmed that the smaller the discharge gap g, the smaller the variation in the charging current Ig.

FIG. 10 shows the experimental results of examining the relationship between the discharge gap g and the charging characteristics. As can be seen from the graph shown in FIG. 10, the smaller the discharge gap g, the smaller the driving voltage and the smaller the variation in charge, but when the discharge gap g is 2 mm or less, the variation in charge increases.

This is because when the discharge gap g becomes smaller than the discharge electrode 2a pitch p (2 mm), a component (discharge electrode 2) caused by the discharge electrode 2a pitch p in the charging variation.
This is because when the a pitch p is 2 mm, charging ripples of 2 mm cycle and 4 mm, 4 mm cycle) appear, and as the discharge gap g becomes smaller, the charge variation component due to the discharge electrode 2a pitch p increases.

FIG. 11 shows the result of theoretical analysis of the influence of the discharge electrode 2a pitch p on the charging characteristics by using the imaging method. The result of theoretical analysis shows that the discharge electrode 2a
The result obtained is that when the pitch / discharge gap becomes larger than 1, that is, when the discharge gap g becomes smaller than the electrode pitch p, the charging variation increases.

From these results, in the present embodiment, the discharge electrode 2
The pitch was set to 3 mm, which is slightly larger than the pitch p. As a result, it is possible to suppress the influence of variations in charging due to the pitch p of the discharge electrodes 2a, improve charging uniformity, and further downsize the device.

A method of controlling the voltage applied to the discharge electrode 2a and the auxiliary electrodes 18a and 19a in this embodiment will be described. As can be seen from the applied voltage-discharge current characteristics shown in FIG. 12A, in constant voltage control, environmental conditions (H in the figure).
(H: high temperature and high humidity, NN: normal temperature and normal humidity, LL: low temperature and low humidity) affects the discharge amount, and thus the charging potential varies. Therefore, if the auxiliary electrodes 18a and 19a and the discharge electrode 2a are controlled to a constant current and the charging current Ig in the drum direction is controlled to be constant at all times, there is no influence of the environment or the like. Will vary and therefore the discharge will become unstable.

Next, the relationship between the control method of the voltage applied to the discharge electrode and the auxiliary electrode and the charging property was examined by experiments in the following four cases. (1) Discharge electrode-constant voltage control, auxiliary electrode-constant voltage control (2) Discharge electrode-constant current control, auxiliary electrode-constant voltage control (3) Discharge electrode-constant voltage control, auxiliary electrode-constant current control (4) ) Discharge electrode-constant current control, auxiliary electrode-constant current control Fig. 12 (b) shows the experimental results. According to the experimental results,
The method (1) above is the most excellent in charging uniformity, but the charging potential fluctuates greatly due to environmental changes. On the contrary, in the control method of the above (4), the control of the charging current becomes unstable, so that the charging uniformity is poor.

Therefore, since the charging current can be constantly controlled, the stability of the charging potential with respect to the environment is excellent,
In terms of good charge uniformity, as in the method (2) or the method (3), either one of the discharge electrode and the auxiliary electrode is controlled by constant voltage to stabilize the discharge. Then, it was found that the other electrode may be subjected to constant current control in order to maintain the charging current constant.

In this embodiment, the charging current Ig required to charge the photoconductor 5 to the predetermined potential (-600V) is 20A. Therefore, when the method (2) is used, first, the auxiliary electrodes 18a and 19a are applied with a predetermined voltage (about −
The discharge electrode 2a is controlled so that the charging current Ig is always 20 A, that is, the total current It is | It−Is | = 20 (2). It is sufficient to control the drive voltage for the constant current.

When the control method (3) is used, first, the discharge electrode 2a is set to a predetermined voltage (about -2.0 k).
V), constant voltage control is performed, and the total current It is monitored so that the charging current Ig is always 20 A, that is, the auxiliary current Is satisfies the expression (2).
It suffices to control the voltage to 9a by constant current.

Discharge electrode-constant voltage control, auxiliary electrode-
The method of constant voltage control is the most excellent in charging uniformity, but the charging current fluctuates due to environmental changes, so that the charging potential fluctuates greatly due to the environment. Therefore, in order to improve the environmental characteristics while taking advantage of the excellent charging uniformity in this method, at the time of rotation before the actual charging of the photoreceptor,
The discharge electrode 2a and the auxiliary electrodes 18a and 19a are subjected to constant current control so that the discharge current to the photoconductor becomes constant.
Hold or store the voltage value generated at that time,
There is a method (5) of controlling the auxiliary electrodes 18a and 19a and the discharge electrode 2a by the voltage value held or stored at the time of actual charging.

As one embodiment of this method, the discharge electrode 2a and the auxiliary electrodes 18a and 19a are controlled to a constant current so that the total current It is 60 A and the auxiliary current Is is 40 A during the pre-rotation (charging current at this time). Ig is Ig = 60
-40 = 20A). The voltage applied to the discharge electrode 2a generated at this time (for example, -2.1 kV) and the auxiliary electrode 18
a, 19a, the applied voltage (for example, -550V) is held or stored, and the discharge electrode 2a is set to -2.
Constant voltage control of 1 kV and auxiliary electrodes 18a and 19a at -550V.

FIG. 9 (b) shows the result of measuring the charging characteristics by this method in the same manner as above. As shown in the figure,
It was confirmed that the control method improves the controllability of the charging potential with respect to the environment.

(Embodiment 2) FIG. 13 is a schematic diagram showing the construction of an embodiment of the corona discharge device according to claim 2 of the present application,
FIG. 14 is a perspective view (a) of the electrode portion and a front view (b) of the electrode portion.

The common electrode 13 is formed on the surface of the insulating substrate 1b.
b is formed, and a plurality of discharge electrodes 2b are formed on the surface of the insulating substrate 1b at a constant distance d from the common electrode 13b.
(Hereinafter referred to as a first discharge electrode array).

The discharge electrode 2b is made of stainless steel and has a thickness of about 0.1 mm, and is formed in a sawtooth shape by etching. The common electrode 13b and each discharge electrode 2b are about 500
It is electrically connected by a plurality of chip resistors 16b having a resistance value of MΩ.

The number of the discharge electrodes 2b is 107, the pitch p between the discharge electrodes 2b is 2 mm, and the tip of the discharge electrodes 2b is placed on the insulating substrate 1b so as to project 2 mm from the edge portion of the insulating substrate 1b. It is glued. Insulating substrate 1
A plurality of discharge electrodes 2b '(hereinafter referred to as a second discharge electrode array), a common electrode 13b' (not shown), and a chip resistor 16b 'are also arranged on the back surface of b in the same configuration as the front surface.
The common electrodes 13b and 13b 'are connected to the voltage power supplies 7 and 8, respectively.

As shown in FIG. 15, the voltage waveforms applied from the voltage power supplies 7 and 8 to the first and second discharge electrode arrays are binary values of a driving voltage (-2.5 kV) and 0 V (ground state). Is a rectangular wave having a duty of 50%, and has a form in which the phase is appropriately shifted (the case where it is shifted by 180 ° is most preferable).

That is, when a driving voltage (-2.5 kV) is applied to the first discharge electrode array and the second discharge electrode array adjacent to the first discharge electrode array is in the ground state, the second discharge electrode array is charged. It plays the same role as the auxiliary electrode in the invention of Item 1, the discharge of the first discharge electrode array is stabilized and uniformized, and the charging uniformity is improved, and
The driving voltage can be reduced.

Similarly, when a driving voltage is applied to the second discharge electrode array and the second discharge electrode array is in a discharge state, the discharge from the second discharge electrode array is stabilized because the first discharge electrode array serves as an auxiliary electrode. It is possible to make the charge uniform, improve the charge uniformity, and reduce the drive voltage. The voltage waveform is not limited to this, and may be any waveform having an oscillating waveform such as a sine wave or a pulse wave.

Further, as shown in FIG. 16, the first discharge electrode array and the second discharge electrode array are apparently attached to the insulating substrate 1b while being displaced by 1/2 of the discharge electrode pitch p. The discharge electrode pitch can be narrowed to p / 2 (1 mm), and the drive voltage can be further reduced and the charging uniformity can be improved.

[0060]

As described above, in the corona discharge device according to the first aspect of the present invention, by providing the auxiliary electrode on the side surface of the discharge electrode, the discharge from each discharge electrode can be stabilized and made uniform, and the charging can be performed. Uniformity is improved. Further, since the grid electrode and the shield case are not required, the device configuration can be simplified and the cost can be reduced. Also, since the amount of discharge is small, the drive voltage can be reduced, and high charging efficiency can be obtained.
Generation of ozone is also reduced.

Further, the distance d (m between the discharge electrode and the auxiliary electrode
m), when the applied voltage of the discharge electrode is E (kV) and the applied voltage of the auxiliary electrode is Vs (kV), by setting d ≦ | E−Vs |, the driving voltage can be further reduced and the charging can be made uniform. And the device can be made smaller and thinner.

Further, by setting the discharge gap as small as possible within the range of the discharge electrode pitch or more, it is possible to suppress the charging variation due to the discharge electrode pitch, improve the charging uniformity and reduce the drive voltage, and the device. Miniaturization is possible.

Further, by controlling the voltage applied to the discharge electrode with a constant current and controlling the voltage applied to the auxiliary electrode with a constant voltage, the charging current can be controlled to a constant value at all times, thus suppressing fluctuations in the charging potential due to environmental changes. You can

By controlling the voltage applied to the discharge electrode with a constant voltage and controlling the voltage applied to the auxiliary electrode with a constant current, the charging current can be controlled to a constant value at all times. be able to.

Further, during the rotation before the actual charging of the photoconductor, the discharge electrode and the auxiliary electrode are subjected to constant current control so that the discharge current (charging current) to the photoconductor becomes a constant magnitude. The voltage value to be held is stored or stored, and at the time of actual charging, by controlling the auxiliary electrode and the discharge electrode with a constant voltage according to the held or stored voltage value, the charging current value can be controlled to a constant value at all times. It is possible to suppress the fluctuation of the charging potential due to.

In the corona discharge device according to the second aspect of the invention, of the two discharge electrode arrays, the second discharge electrode array acts as an auxiliary electrode when the first discharge electrode array is in the discharge state, When the discharge electrode array of 1 is in the discharge state, the first discharge electrode array acts as an auxiliary electrode, so that the charging uniformity can be improved and the grid electrode and the shield case are not required, so that high charging efficiency can be obtained. The amount of ozone generated can be reduced, the device can be downsized, and the drive voltage can be reduced. Further, when the first auxiliary electrode array and the second auxiliary electrode array are attached in a state of being displaced from each other by ½ of the pitch, the apparent discharge electrode pitch is ½, so that the discharge gap is narrowed. Therefore, the driving voltage can be further reduced and the charging uniformity can be improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a corona discharge device according to an embodiment of the present invention.

FIG. 2 is a perspective view (a) of a discharge / auxiliary electrode portion and a front view (b) of a discharge electrode portion of the corona discharge device of the present application.

3 is an X sectional view (a) and a Y sectional view (b) in FIG. 2 (b).

FIG. 4 is an equivalent electric circuit diagram of a corona discharge device according to an embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between a charging characteristic and a void impedance depending on the presence or absence of an auxiliary electrode.

FIG. 6 is a diagram showing an experimental result of examining a charging characteristic depending on the presence or absence of an auxiliary electrode.

FIG. 7 is a diagram showing a relationship between a distance between an auxiliary electrode and a discharge electrode and a variation in charging current Ig.

FIG. 8 is a diagram showing a relationship between a distance between an auxiliary electrode and a discharge electrode and a charging characteristic.

FIG. 9 is a diagram showing a relationship between a discharge gap and variations in charging current.

FIG. 10 is a diagram showing a relationship between a discharge gap and charging characteristics.

FIG. 11 is a diagram showing a relationship between (discharge electrode pitch) / (discharge gap) and charging characteristics.

FIG. 12 is an explanatory view (a) and (b) of the relationship between the control method of the corona discharge device and the charging characteristic.

FIG. 13 is a schematic configuration diagram of a corona discharge device according to a second embodiment.

FIG. 14 is a perspective view (a) of an electrode portion and a front view (b) of the electrode portion of a corona discharge device according to a second embodiment.

FIG. 15 is a diagram showing voltage waveforms applied to the first and second discharge electrode arrays.

FIG. 16 is an explanatory diagram showing a state in which the first discharge electrode array and the second discharge electrode array are displaced by ½ of the discharge electrode pitch p.

FIG. 17 is a configuration diagram (a) of a conventional corona discharge device and an enlarged diagram (b) of a discharge electrode portion.

18 is a model diagram (a) of a corona discharge device using the conventional sawtooth discharge electrode shown in FIG. 17, a graph (b) showing discharge characteristics thereof, and an equivalent circuit diagram (c).

[Explanation of symbols]

 1a, 1b Insulating substrate 2a, 2b, 2b 'Discharge electrode 13a, 13b, Common electrode 16a, 16b, 16b' Chip resistor 18a, 19a Auxiliary electrode

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hiroyuki Sawai 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Prefecture Sharp Corporation (72) 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within the corporation

Claims (3)

[Claims] 1. A discharge electrode for discharging a photoconductor, and an auxiliary electrode to which a voltage smaller than a voltage applied to the discharge electrode is applied. The auxiliary electrode is provided on both sides of the discharge electrode. The discharge electrode is connected to a voltage power supply via a resistor having a predetermined resistance value. Wherein the voltage applied to the discharge electrodes _{E (kV), V S (} kV) voltage applied to the auxiliary electrode, when the discharge portion of the discharge electrode distance between the auxiliary electrode was d (mm), d ≦ | E
The corona discharge device according to claim 1, wherein -Vs | is satisfied. 3. An insulating substrate having first and second discharge electrode rows composed of a plurality of discharge electrodes on both sides thereof, wherein the discharge electrodes are connected to a voltage power source via resistors having a predetermined resistance value. In the corona discharge device, a voltage having an oscillating waveform is applied to the first and second discharge electrode arrays, and either one of the first and second discharge electrode arrays serves as an auxiliary electrode. Therefore, the corona discharge device is characterized in that the voltages are applied to the respective discharge electrode arrays with the phases thereof shifted.