JP3235381B2 - Corona discharge device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a copying machine, a printer,
The present invention relates to a scorotron type corona discharge device used in an electrophotographic image forming apparatus such as a reader printer and a facsimile, and more particularly to a corona discharge device having a protruding electrode.

[0002]

2. Description of the Related Art Conventionally, a corona discharge device used in an electrophotographic image forming apparatus includes a wire discharge method using a wire electrode and a pin using a protruding electrode such as a needle electrode or a sawtooth electrode. A discharge method is used. It is known that the amount of ozone generated by the pin discharge method is as small as about 1/4 as compared with the wire discharge method, and it is widely used in recent years.

[0003] In this pin discharge method, electric charges are emitted from a tip portion of an electrode with a spread angle, and the discharge is concentrated in a direction toward the tip. For this reason, when a discharge is caused from a conductive plate on which a plurality of projecting electrodes are arranged, there is a problem that a portion of the member to be charged closer to the projecting electrodes has a high surface potential and a portion far from the projecting electrodes has a low surface potential. . (Less than,
A phenomenon in which the surface potential of the member to be charged is distributed between a high portion and a low portion is referred to as discharge unevenness. Conventionally, in order to reduce the discharge unevenness, a scorotron discharge method in which a grid electrode controlled at a constant voltage is arranged between the tip of the protruding electrode and the photoconductor has been adopted.

[0004]

However, in the pin discharge method, since the discharge direction is concentrated in the direction toward the member to be charged, ozone and nitrogen oxides (hereinafter referred to as NOx) generated by corona discharge. Are concentrated and adhere to the member to be charged. Ozone is a factor that degrades the electrical characteristics of the photosensitive member that is the member to be charged. Further, it is known that sucking a large amount of ozone for a long period of time has an adverse effect on the human body.
Therefore, ozone is removed using an ozone filter. However, as the amount of ozone removed increases, the removal performance decreases and the amount of ozone discharged outside the machine increases. NOx
Is a substance having a hygroscopic property, and adheres to the photoreceptor, so that the adhered portion may dew. For example, when this pin discharge method is used in an electrophotographic image forming apparatus, if NOx adheres to the photoreceptor and dew condensation occurs, the surface resistance of the photoreceptor decreases, and the charge of the unexposed charge holding unit is reduced. May move to a portion having no exposed charge, and the edge portion of the latent image may be blurred or the image may be erased. (This phenomenon is hereinafter referred to as image flow.) When NOx adheres to the tip of the protruding electrode, N
Ox reacts with moisture in the air to generate nitric acid, and the nitric acid erodes the tip portion, and the tip portion becomes round due to long-term use of the protruding electrode. ) Adheres and grows, causing uneven discharge.

The present invention has been made in view of the above problems, and can reduce the amount of ozone and NOx generated. As a result, even after long-term use of a corona discharge device, uneven discharge and image leakage occur. It is an object of the present invention to provide a corona discharge device in which no corona occurs.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an electrode member having a plurality of protruding electrodes arranged toward a photoreceptor, and an electrode member disposed on the opposite side of the electrode member from the photoreceptor. Charging current flowing to the substrate of the photoconductor in a scorotron discharge type corona discharge device having a shield plate and a grid electrode having a plurality of grid lines disposed between the electrode member and the photoconductor. The relation between Ip and the grid electrode current Ig flowing through the grid electrode is 1.5 ≦ Ig /
A corona discharge device characterized by satisfying a conditional expression of Ip ≦ 4.

[0007]

In the corona discharge device according to the present invention, as described above, in the corona discharge device of the scorotron discharge type provided with the protruding electrodes, the relationship between the photosensitive member charging current Ip and the grid electrode current Ig is 1.5 ≦. By being configured so as to satisfy the condition of Ig / Ip ≦ 4, the generation amount of ozone and nitrogen oxide is suppressed, and the surface potential of the photoconductor does not decrease even after long-term use of the photoconductor. .

Further, in a corona discharge device of a scorotron discharge type having a protruding electrode, the charging current I
By configuring the relationship between p, the grid electrode current Ig, and the shield plate current Ish to satisfy the condition of 1 ≦ (Ig + Ip) / Ish, the amount of ozone and nitrogen oxides generated is further reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a pin discharge type corona discharge device according to the present invention will be described below with reference to the drawings. The present inventors have developed a scorotron discharge type corona discharge device equipped with a protruding electrode, which accurately controls the surface potential of the photoreceptor even during long-term use, and prevents image flow and discharge unevenness. The aim of the present invention was to invent a corona discharge device capable of reducing the generation of NOx, which causes the generation of NOx. Specifically, each element (hereinafter, referred to as a parameter) constituting the corona discharge device, that is, an electrode plate,
Experiments were carried out while variously changing the setting conditions of the grid electrode and the shield plate, and desired setting conditions of each parameter were obtained.

These experiments are performed using an electrophotographic copying machine 100 shown in FIG. 1. In the charging charger 1 of the copying machine 100, copying is performed by changing the setting conditions of the above-described parameters in various ways. The setting conditions of each parameter capable of suppressing the generation amount of NOx while maintaining the charging performance were investigated. The setting conditions of the investigated parameters are the setting conditions capable of maintaining the charging performance as described above. Not only the suppression of the generation amount of NOx but also the discharge unevenness and the start of use of the photoconductor due to causes other than the adhesion of NOx. Potential difference ΔV between the surface potential Vo at the time of use and the surface potential Vo ′ after long-term use
Setting conditions that can keep o small are obtained. This is because the image density decreases when the potential difference ΔVo between the surface potential Vo at the start of use of the photoconductor and the surface potential Vo ′ after long-term use increases.

First, the configuration and image forming operation of the electrophotographic copying machine 100 used in the experiment will be described. The electrophotographic copying machine 100 is an example of an image forming apparatus including a corona discharge device to which the present invention described below is applied. FIG.
FIG. 2 is a sectional view of a main part showing an image forming unit of the electrophotographic copying machine 100.

The image forming section of the electrophotographic copying machine 100 includes a photosensitive member 2 rotating in a direction indicated by an arrow h, and a charger 1, an eraser lamp 3, an optical developing device 5 (not shown), and a transfer member arranged around the photosensitive member 2. It includes a charger 6, a separation charger 7, a cleaning device 8, and the like. The photoreceptor 2 is a negatively-charged OPC photoreceptor having a diameter of 100 mm, and has a charge generation layer on the peripheral surface of an aluminum substrate.
And a charge transfer layer composed of a polycarbonate resin and a hydrazone-based compound.

After the photosensitive member 2 is neutralized by the eraser lamp 3, it is uniformly charged by the charging charger 1. Further, exposure is performed by image light 4 emitted from an optical system (not shown), and an electrostatic latent image is formed on the photoconductor 2. Thereafter, the electrostatic latent image is developed by the developing device 5 containing the toner to form a toner image. The toner image developed by the above-described developing device 5 onto a transfer material (not shown) is transferred from the photoconductor 2 by the transfer charger 6. The transfer material onto which the toner image has been transferred has its electrostatic attraction reduced by the AC output of the separation charger 7 and is separated from the photoconductor 2. Thereafter, the toner remaining on the photoreceptor 2 is collected by the cleaning device 8, and the transfer material is sent to a fixing device (not shown), where the image is fixed. You.

Next, the configuration of the charging charger 1 will be described. FIG. 2 is a schematic diagram showing the charging charger 1. FIG. 3 is a side view showing the electrode plate 11 provided on the charging charger 1, and FIG.
FIG. 3 is a front view showing a grid electrode 12 provided in the first embodiment.

As described above, the charger 1 is a corona discharge device of a pin discharge type and a scorotron discharge type, and is an electrode plate 1 on which a plurality of sawtooth electrodes 111 are arranged.
1, a grid electrode 12 disposed between the photosensitive member 2 on the tip side of the sawtooth electrode 111, and the electrode plate 11 so as to surround the electrode plate 11 in a substantially U-shape from three directions excluding the tip direction of the sawtooth electrode 111. The shield plate 13 and the like are arranged.

The electrode plate 11 discharges electric charges from the sawtooth electrode 111 toward the photoreceptor 2 and has a plurality of sawtooth electrodes 111 arranged at a predetermined pitch P. This sawtooth electrode 1
11 is obtained by, for example, etching the electrode plate 11 or rolling and pressing. The electrode is not limited to a sawtooth electrode. For example, as shown in FIGS. 5A to 5C, a razor-shaped electrode 1 having a rectangular parallelepiped with a tip shaped like a mountain.
12, a wire-shaped electrode 113 such as a wire or a wire, a wire-shaped electrode 113 having a columnar shape, a needle-shaped electrode 114 having a shape having a sharpened cylindrical end, or a projecting electrode having another shape.
The electrode plate 11 is connected to a high voltage power supply 14a and is maintained at a constant current Vp. The high voltage power supply 14a may be a constant voltage power supply, but constant current control is preferable in order to obtain a more stable discharge current.

The grid electrode 12 is, as shown in FIG.
A plurality of grid lines are arranged at predetermined intervals. The width of the grid line is L in the direction along the electrode plate 11, and the interval between the grid lines is D. The grid electrode 12 is connected to a power source 14b for controlling the voltage to a constant voltage Vg.
It is connected to the. Note that a constant voltage element such as a varistor may be connected to the grid electrode 12 instead of the power supply 14b.

The shield plate 13 is disposed so as to surround the electrode plate 11 in a U-shape from three directions excluding the tip direction of the sawtooth electrode 111. The shield plate 13 is formed of a conductive material, and is provided with a power supply 14 for controlling the voltage to a constant voltage Vsh.
c, and may be grounded via a resistor, or may be directly grounded. Further, there is an opening 13a in a direction opposite to the tip direction of the sawtooth electrode 111, and N
In order to prevent Ox and ozone from staying between the saw-toothed electrode 111 and the photoconductor 2, the air is exhausted by a fan (not shown) through the opening 13a. It should be noted that if the configuration is such that NOx and ozone hardly stay between the saw-toothed electrode 111 and the photoconductor 2, there is no need to particularly provide the opening 13a.

As a result of examining each parameter as described above, it was found that each parameter had the following tendency. (1) Electrode plate 11 (see FIGS. 2 and 3) When the pitch P of the sawtooth electrode 111 is small, electric fields of two adjacent electrodes interfere with each other, so that discharge unevenness is likely to occur. When the pitch P is increased, the amount of ozone generated is reduced, but the gap between the electrodes is increased, so that discharge unevenness is likely to occur. Therefore, it is desirable that the pitch P of the sawtooth electrode 111 is 1 mm to 4 mm.

Further, as the tooth angle θ of the saw-tooth electrode 111 decreases, the amount of ozone and NOx generated tends to decrease, but at the same time, the strength of the tip of the saw-tooth electrode 111 becomes insufficient and the tip is easily broken or bent. Become. Conversely, when the tooth angle θ of the sawtooth electrode 111 increases, ozone and NO
The amount of generation of x tends to increase. Therefore, it is desirable that the tooth angle θ of the sawtooth electrode 111 is 5 ° to 30 °.

Further, as the thickness t of the electrode plate 11 decreases, the amount of generated ozone tends to decrease. However, when the thickness t is excessively small, the mechanical strength of the electrode plate 11 decreases, which is not desirable. Also, as the thickness t increases, the amount of generated ozone tends to increase. Therefore, the thickness t of the electrode plate 11 is set to be 0.
It is desirable that the thickness be from 0.05 mm to 0.1 mm.

(2) Grid electrode 12 (see FIG. 4) The relationship between the grid line interval D and grid line width L of the grid electrode 12 and the pitch P of the sawtooth electrode 111 satisfies the relationship defined by the following equation. Is desirable. P
/ (D + L) = n (where n is an integer) or n + 0.9 ≦ P / (D + L) ≦ n + 1.1 The relationship defined by the above equation between the grid line interval D, the grid line width L, and the pitch P. If satisfied, sawtooth electrode 1
Even if the tip of the saw-tooth electrode 111 is eroded by nitric acid (especially occurs in a high-temperature and high-humidity environment), or a deposit such as Si adheres to the tip of the saw-tooth electrode 111, the discharge unevenness from the saw-tooth electrode 111 is induced This discharge unevenness can be reduced.

The distance dpc from the tip of the sawtooth electrode 111 to the photosensitive member 2 and the pitch P of the sawtooth electrode 111
Grid line interval D and grid line width L of grid electrode 12
It is desirable that the relationship with satisfies the condition defined by the following equation. 2 ≦ dpc (D + L) / P ≦ 8 If dpc (D + L) / P is set in this range, discharge unevenness tends to be reduced. Specifically, the sawtooth electrode 1
If the distance dpc from the tip of the photoconductor 11 to the photoconductor 2 is too large, uneven discharge is likely to occur. Conversely, if the distance dpc from the tip of the saw-toothed electrode 111 to the photoconductor 2 becomes too small, the amount of electric charge that reaches the photoconductor by slipping from the electrode plate 11 to the grid and between the grids increases, causing discharge unevenness.

When the grid line width L becomes too small, the mechanical strength of the grid electrode 12 becomes weak. Conversely, when the grid line width L increases, the current Ig flowing from the electrode plate 11 to the grid electrode 12 increases. At this time,
The charge passing between the grids decreases,
The charged potential of the photoconductor 2 becomes lower than the potential of the grid electrode 12, or uneven discharge occurs. Therefore, the grid line width L is desirably 0.05 mm to 0.2 mm.

Further, when the grid line interval D becomes smaller,
The current Ig flowing from the electrode plate 11 to the grid electrode 12 increases. Under such conditions, at the start of charging, the electric charge discharged from the electrode plate 11 hardly reaches the photoconductor 2 by passing between the grid lines, so that a predetermined photoconductor potential Vo is obtained. In this case, it is necessary to increase the potential difference between the grid voltage Vg and the photoconductor surface potential Vo.
On the other hand, when the grid line interval D becomes large, when the potential difference between the photoreceptor surface potential Vo and the grid voltage Vg becomes small after the start of charging, the electrode plate 11 discharges electricity, and passes through between grid lines to expose the photosensitive body. Since the electric charge reaching the body 2 increases, discharge unevenness occurs. To obtain a predetermined photoconductor surface potential Vo, the grid voltage Vg must be lower than the photoconductor surface potential Vo. Therefore, it is desirable that the grid line interval D is 0.5 mm to 1.8 mm.

Further, when the distance X between the grid electrode 12 and the photosensitive member 2 is reduced, the discharge from the electrode plate 11 increases, and the amount of electric charge that passes through the grid lines and reaches the photosensitive member 2 increases, resulting in discharge unevenness. Is easy to occur. Further, in the grid electrode 12, when the electrode plate 11 discharges, an electrostatic force acts in a direction in which the grid electrode 12 separates from the photoconductor 2 and approaches the electrode plate 11, and when the electrode plate 11 does not discharge, the grid line is applied to the photoconductor. The force acts in the direction attracted to 2, and the grid electrode 12 vibrates. Therefore, when the distance X between the grid electrode 12 and the photoconductor 2 is small, the grid electrode 12 comes into contact with the surface of the photoconductor 2 due to the vibration of the grid electrode 12, and the photoconductor 2 is easily damaged. When the distance X between the grid electrode 12 and the photoconductor 2 is reduced, the potential difference between the grid voltage Vg and the photoconductor surface potential Vo can be reduced, and the predetermined photoconductor surface potential can be reduced by controlling the grid voltage Vg. Vo can be obtained. On the other hand, when the distance X between the grid electrode 12 and the photoconductor 2 increases, the amount of electric charge that reaches the photoconductor 2 from the electrode plate 11 through the space between the grid lines tends to decrease. To obtain a predetermined photoconductor surface potential Vo, the grid voltage Vg needs to be higher than Vo, and the potential difference between the photoconductor surface potential Vo and the grid voltage Vg increases. For this reason, the distance X between the grid electrode 12 and the photoconductor 2 is set to 0.
It is desirable to be 5 mm to 1.8 mm.

(3) Shield plate 13 When the distance Y from the tip of the electrode plate 11 to the shield plate 13 is reduced, the amount of electric charge traveling from the electrode plate 11 to the shield plate 13 increases, and the charged object such as the photosensitive member 2 is removed. The predetermined charge Vo cannot be obtained because the charge to be charged decreases. High voltage power supply 1
4a must be increased, and the amount of ozone and NOx generated increases. Therefore, the setting conditions of the shield plate 13 may be determined in consideration of these tendencies.

While conducting the various experiments described above for each parameter, the present inventors determined that the photosensitive member charging current Ip
It has been found that the ratio of the current amount such as the grid electrode current Ig and the like affects the occurrence of image blur. Needless to say, this is because the generation amount of NOx and the adhesion amount to the photoconductor 2 are different. Then, the present inventors investigated the optimal setting conditions of the photoconductor charging current Ip and the grid electrode current Ig which can suppress the generation amount of NOx and prevent the image deletion and the discharge unevenness. Specifically, in the copying machine 100 described above with reference to FIGS. 1 to 5, each parameter is set as in setting condition 1 described below, and the photoconductor charging current Ip and the grid electrode current Ig are changed to perform copying. Was carried out, and the presence or absence of image flow and discharge unevenness was confirmed.

The setting condition 1 was set as follows, taking into account the tendency of each of the above-described parameters, as a setting condition in which image leakage and discharge unevenness hardly occur. Setting condition 1: Pitch of electrode 111 P: 2 mm Thickness of electrode plate 11 t: 0.05 mm Tooth angle of electrode 111 θ: 10 ° Grid line width L: 0.1 mm Grid line interval D: 0.9 mm Tip of electrode plate 11 Dpc: 10 mm dpc (D + L) / P = 5 Distance between grid electrode 12 and photoconductor 2 X: 1 mm Distance between electrode plate 11 and shield plate 13 Y: 2 mm And this setting condition 1 In the experiment below, the photoconductor charging current Ip without image leakage and discharge unevenness was generated.
And the optimum conditions of the grid current Ig were determined.

As shown in FIG. 2, for the purpose of the experiment, ammeters 15a to 15c are connected to the grid electrode 12, the substrate of the photosensitive member 2, and the shield plate 13, respectively. Then, the photosensitive member 2 was charged by changing the setting of each current value of the ammeters 15a to 15c, and an image was formed on the photosensitive member 2. At this time, the presence or absence of discharge unevenness and image flow was confirmed.

Specifically, the ammeter 15b is changed by changing the current flowing through the electrode plate 11 or the peripheral speed of the photosensitive member 2.
The value of the photoconductor charging current Ip shown in FIG.
Change to 0μA, 200μA, 250μA,
The experiment was performed by further changing the value of the grid current Ig for each value of Ip. At the time of the experiment, the ammeters 15a to 1
Various combinations of the energizing current of the electrode plate 11 and the peripheral speed of the photoconductor 2 were changed so that each current value (Ip, Ig, Ish) of 5c became an experimental value. Note that the value of the current supplied to the electrode plate 11 was changed by changing the output of the high-voltage power supply 14a.

Further, the presence or absence of image leakage is checked by the electrode plate 1
After the formation of a visible image on the photoreceptor 2 was repeated 100,000 times by setting the voltage Vp applied to 1 to -800 V, it was left for 12 hours in an environment of high temperature and high humidity and then copied. Was. While only the latent image is formed on the photoconductor 2, the developing device 5 is replaced with a surface voltmeter (not shown) to measure the surface potential Vo of the photoconductor 2, and Vo-Vg (the control voltage of the grid electrode 12). Represents the difference between the charged potential of the photoconductor 2 and the value near 0, and △ Vo = Vo−Vo ′ (between the surface potential Vo at the start of use of the photoconductor 2 and the surface potential Vo ′ after long-term use). (Potential difference). When actually performing copying, the developing device 5 was attached again, and the latent image formed on the photoconductor 2 was converted into a toner image. Vo−Vg and ΔVo were determined in order to confirm whether or not good charging performance was maintained. That is, when Vo−Vg increases, the ability to control the photoconductor surface potential by the grid voltage decreases, and when ΔVo increases, the image density decreases. The reason why the copy was performed in an environment of high temperature and high humidity was that NOx adhered to the photoreceptor 2 and this adhered NOx
This is because a copy is taken in a state where dew has formed on the image to confirm the presence or absence of image flow.

The results of this experiment will be described below. FIG.
Means Ig / I when the copying speed is 460 mm / s.
It is the graph which showed the relationship between p and Vo-Vg. In this graph, the horizontal axis indicates the value of Ig / Ip, and the vertical axis indicates Vo-Vg.
The value of is taken. As can be seen from the graph of FIG.
In the case of g / Ip = 0.5, the value of Vo−Vg becomes extremely large, and the surface potential Vo of the photoconductor 2 is reduced to the grid voltage V.
This is not preferable for controlling with g precisely. In addition, Ig /
When Ip = 0.5, discharge unevenness occurs and the surface potential V
A portion where o is extremely low occurs, and in the copy, a portion where the image density is low appears in a streak shape. Therefore, at least 1.0 ≦
It is necessary to make Ig / Ip.

Table 3 shows the results of an experiment for confirming the presence or absence of image flow by setting the setting condition 1 when 1.0 ≦ Ig / Ip.

[0035]

[Table 1]

As shown in Table 1, image leakage occurs when Ig / Ip = 13. This is because the amount of discharge from the electrode plate 11 increases and the amount of generated NOx increases.
As described above, if a large amount of NOx adheres to the surface of the photoreceptor 2, dew condensation occurs on the surface of the photoreceptor 2 in a high-temperature, high-humidity environment, and the electrical resistance on the surface of the photoreceptor 2 decreases. The charge of the image moves to the exposed portion to erase the image, or the edge portion of the image is blurred. on the other hand,
If 1 ≦ Ig / Ip ≦ 10, no image leakage occurred.

When Ig / Ip = 10 and 13, Ig / Ip
ΔVo is larger than Ip = 3. this is,
It is considered that a large amount of electric charges pass between the grid lines and reach the photoconductor 2. That is, the control ability of the scorotron is deteriorated, and the same movement as that at the time of corotron charging is performed by the amount of the slipped-through charges.

However, if .DELTA.Vo = about 20 V, the change in image density is extremely small as compared with when the photosensitive member 2 is started, and there is no problem in copy quality. As shown in Table 1, when the relationship between the photoconductor charging current Ip and the grid current Ig is 1.5 ≦ Ig / Ip ≦ 4, ΔVo can be suppressed to about 20 V or less.

Further, the photoconductor potential Vo is changed to the grid potential Vg.
It is desirable that Vo−Vg be small in order to control with high accuracy. As can be seen from FIG. 6, 1.5 ≦ Ig / Ip ≦ 4
Then, Vo−Vg is as small as about −20 V to +20 V, and the surface potential Vo of the photoconductor 2 can be controlled more accurately. Therefore, from the above results, 1.5 ≦ Ig / Ip ≦
It is desirable to set the photoconductor charging current Ip and the grid current Ig so that the value of Ig / Ip is included in the range of 4. In the case of Ig / Ip = 1.5, even if Vo-Vg was large, the photoconductor potential Vo could be accurately controlled by the grid potential Vg, and the reduction in image density was not a particular problem.

Next, experiments were conducted under the following set conditions 2 to 8, and the conclusions obtained from the above experimental results, that is, the optimum conditions of the photoconductor charging current Ip and the grid current Ig: 1.5 ≦
It was examined whether Ig / Ip ≦ 4 leads to similar conclusions under different setting conditions. More specifically, the setting conditions that are not so preferable, that is, the setting conditions in which image leakage is likely to occur, the setting conditions in which discharge unevenness is likely to occur, the surface potential Vo at the start of use of the photoconductor 2 and the surface potential Vo 'after long-term use are described. The test was performed under a setting condition in which the difference ΔVo between the grid voltage Vg and the grid voltage Vg and the photoconductor surface potential Vo tends to be large. The apparatus used for the experiment and the experiment method are the same as those in the case of the setting condition 1 described above.

Setting condition 2: Pitch of electrode 111 P: 2 mm Thickness of electrode plate 11: 0.1 mm Large tooth angle θ of electrode 111: 30 ° Large Grid line width L: 0.1 mm Grid line interval D: 0. 9 mm Distance between tip of electrode plate 11 and photoconductor 2 dpc: 14 mm dpc (D + L) / P = 7 Distance between grid electrode 12 and photoconductor 2 X: 1 mm Distance between electrode plate 11 and shield plate 13 Y: 0. In the setting condition 2 of 5 mm small, the thickness of the electrode plate 11 and the electrode tooth angle are set large, and the distance between the shield plate 13 and the electrode plate 11 is set small.

Setting condition 3: Pitch of electrode 111 P: 2 mm Thickness of electrode plate 11: 0.1 mm Large tooth angle θ of electrode 111: 30 ° Large Grid line width L: 0.1 mm Grid line interval D: 0. 9 mm Distance between tip of electrode plate 11 and photoconductor 2 dpc: 7 mm dpc (D + L) / P = 4 Distance between grid electrode 12 and photoconductor 2 X: 1 mm Distance between electrode plate 11 and shield plate 13 Y: 0. 5 mm small The setting condition 3 was different from the experimental condition 2 in that the photosensitive member 2 and the electrode plate 1 were different.
Ozone and NOx tend to adhere to the photoconductor 2 because the distance from the photoconductor 1 is short.

Setting condition 4: Pitch of electrode 111 P: 4 mm large Thickness of electrode plate 11: 0.1 mm Tooth angle θ of electrode 111: 10 ° Grid line width L: 0.2 mm Large grid line interval D: 1. 6 mm Large Distance between tip of electrode plate 11 and photoconductor 2 dpc: 13 mm dpc (D + L) / P = 8 Distance between grid electrode 12 and photoconductor 2 X: 1 mm Distance between electrode plate 11 and shield plate 13 Y: 8 mm Large Setting condition 4 is that the electrode pitch P is large and the grid line width L
And the grid line interval D is large, and the distance between the photosensitive member 2 and the electrode plate 11 is large.

Setting condition 5: Pitch of electrode 111 P: 4 mm Large thickness of electrode plate 11 t: 0.1 mm Tooth angle θ of electrode 111: 10 ° Grid line width L: 0.1 mm Grid line interval D: 0.9 mm Distance between tip of electrode plate 11 and photoconductor 2 dpc: 8 mm dpc (D + L) / P = 2 Distance between grid electrode 12 and photoconductor 2 X: 1 mm Distance between electrode plate 11 and shield plate 13 Y: 6 mm Large setting Condition 5 is a configuration in which the electrode pitch P is large and the distance between the photoconductor 2 and the electrode plate 11 is small.

Setting condition 6: Pitch P of electrodes 111: 1 mm Small Thickness of electrode plate 11: 0.1 mm Tooth angle θ of electrodes 111: 10 ° Grid line width L: 0.2 mm Large grid line interval D: 1. 6 mm large Distance between tip of electrode plate 11 and photoconductor 2 dpc: 7 mm dpc (D + L) /P=5.4 Distance between grid electrode 12 and photoconductor 2 X: 1 mm Distance between electrode plate 11 and shield plate 13 Y : 4 mm In setting condition 6, the electrode pitch P is small and the grid line width L
And the grid line interval D is large, and the distance between the photoconductor 2 and the electrode plate 11 is small.

Setting condition 7: Pitch of electrode 111 P: 2 mm Thickness of electrode plate 11: 0.05 mm Teeth angle of electrode 111 θ: 10 ° Grid line width L: 0.1 mm Grid line interval D: 0.5 mm Small Distance between tip of electrode plate 11 and photoconductor 2 dpc: 12 mm dpc (D + L) /P=3.6 Distance between grid electrode 12 and photoconductor 2 X: 1.8 mm Large Distance between electrode plate 11 and shield plate 13 Y: 0.5 mm Setting condition 7 is a configuration in which the grid line interval D is small and the distance between the photoconductor 2 and the grid electrode 12 is large.

Setting condition 8, pitch P of electrodes 111: 2 mm Thickness of electrode plate 11: 0.05 mm Tooth angle θ of electrodes 111: 10 ° Grid line width L: 0.1 mm Grid line interval D: 1.6 mm Large Distance between tip of electrode plate 11 and photoconductor 2 dpc: 10 mm dpc (D + L) /P=8.5 Distance between grid electrode 12 and photoconductor 2 X: 1.0 mm Distance between electrode plate 11 and shield plate 13 Y : 2 mm Setting condition 8 is a configuration in which the grid line interval D is large.

As a result of the experiment under the setting conditions 2 to 8, in all cases, the result was almost the same as that of Table 1, that is, the setting condition 1. From this, the optimum condition of the photoconductor charging current Ip and the grid current Ig is 1.5 ≦
It was confirmed that Ig / Ip ≦ 4. Further, the three optimum conditions in consideration of the shield plate current Ish in addition to the photoconductor charging current Ip and the grid current Ig were considered. The apparatus used for the experiment is as described above.

FIG. 7 shows that (Ig + I) by keeping the copying speed constant at 460 mm / s and changing the current flowing through the electrode plate 11 and the distance Y between the electrode plate 11 and the shield plate 13.
By changing the value of (p) / Ish, (Ig + Ip) / Is
It shows the relationship between h and the ozone concentration. Vo-V
g / I and Ig / I to reduce discharge unevenness.
The value of the grid current Ig was varied with respect to the value of the photoconductor charging current Ip so that p = 2, 3, and 4.

Table 2 shows that, under the same conditions as in the above case, 10
This is a result of confirming whether or not there is an image flow when copying after copying for 10 hours and then allowing to stand for 12 hours in a high temperature / high humidity environment.

[0051]

[Table 2]

As shown in FIG. 7, when the relationship between the photosensitive member charging current Ip, the grid current Ig, and the shield plate current Ish is defined by the relational expression of (Ig + Ip) / Ish, (Ig + Ip) / Ish = 1 To make (Ig
+ Ip) /Ish=0.5% of ozone generation was able to be reduced compared with the case of 0.5. Further, (Ig + Ip)
By setting / Ish = 3, (Ig + Ip) / Ish =
The ozone generation amount was reduced by 50% as compared with the case of 0.5. By increasing (Ig + Ip) / Ish in this manner, the amount of ozone generated can be reduced. Table 2
As shown in (1), when (Ig + Ip) /Ish=0.5, image flowing occurred. Therefore, it is desirable that the relationship among the photoconductor charging current Ip, the grid current Ig, and the shield plate current Ish be 1 ≦ (Ig + Ip) / Ish.

[0053]

According to the present invention as described above,
In a pin discharge type and scorotron type corona discharge device, the relationship between the photosensitive member charging current Ip and the grid current Ig is set in a range defined by a conditional expression: 1.5 ≦ Ig / Ip ≦ 4. As a result, the generation of ozone and nitrogen oxides was reduced, and the discharge from the protruding electrodes was stabilized. As a result, even when the photosensitive member is used for a long period of time, or in a high-temperature and high-humidity environment after the long-term use, or after the long-term use of the photosensitive member, uneven discharge is reduced, and image leakage can be prevented.

Further, since the potential difference between the photoconductor surface potential and the grid electrode potential is small, the photoconductor surface potential can be accurately controlled by the potential applied to the grid electrode.

Further, even after long-term use of the photoreceptor, the change in the surface potential of the photoreceptor is smaller than that at the start of use.
The surface potential can be accurately controlled, and the change in image density can be reduced.

Further, when the shield plate current Ish is taken into consideration, the relationship between the photosensitive member charging current Ip, the grid current Ig, and the shield plate current Ish is expressed by the following conditional expression: 1 ≦ (Ig + I
By setting the ratio in the range defined by p) / Ish, it is possible to eliminate image loss even after long-term use of the photoreceptor or in an environment of high temperature and high humidity after long-term use.

Further, by suppressing the amount of generated ozone, deterioration of the ozone filter can be suppressed, and the life of the ozone filter can be extended.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part showing an image forming unit of an electrophotographic copying machine 100.

FIG. 2 is a schematic diagram showing a configuration of a charging charger 1 and an experimental device.

FIG. 3 is a side view showing an electrode plate 11 provided in the charging charger 1;

FIG. 4 is a front view showing a grid electrode 12 provided in the charger 1;

FIG. 5 is a view showing a modification of the electrode plate 11;

FIG. 6 shows Ig when the copying speed is 460 mm / s.
4 is a graph showing the relationship between / Ip and Vo-Vg.

FIG. 7 is a graph showing the relationship between (Ig + Ip) / Ish and ozone concentration.

[Explanation of symbols]

 1: Charger 2: Photoreceptor 3: Eraser lamp 5: Developing device 6: Transfer charger 7: Separation charger 11: Electrode plate 12: Grit electrode 13 Shield plate 15a, 15b, 15c: Current monitor 100: Copy machine 111: Saw tooth Electrode

Continuation of the front page (56) References JP-A-6-11946 (JP, A) JP-A-6-301268 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15 / 02

Claims (2)

(57) [Claims] An electrode member having a plurality of protruding electrodes arranged toward a photoreceptor, a shield plate disposed on a side opposite to the photoreceptor with respect to the electrode member, and disposed between the electrode member and the photoreceptor. In a scorotron discharge type corona discharge device provided with a grid electrode having a plurality of grid lines, the relationship between the photoconductor charging current Ip flowing through the photoconductor substrate and the grid electrode current Ig flowing through the grid electrode is as follows: A corona discharge device characterized by satisfying a condition of 5 ≦ Ig / Ip ≦ 4. 2. The corona discharge device according to claim 1, wherein the photosensitive member charging current Ip, the grid electrode current Ig, and the
A corona discharge device characterized in that the relationship with a shield plate current Ish flowing through a shield plate satisfies a condition of 1 ≦ (Ig + Ip) / Ish.