JPH0864337A - Corona discharge device - Google Patents

Abstract

PURPOSE: To make surface potential uniform in the later half in a charged region to obtain a uniform charging property by generating such corona discharge voltage that the distance between a corona discharge electrode and a shield side surface on an upstream process becomes smaller than the distance between the corona discharge electrode and a shield side surface in a downstream process. CONSTITUTION: In an experimental device having a shield case 2c and a grid 2f, for example, the height of the case 2 is made 16mm, length 230mm, the thickness of an insulating board 2a is made 1.6mm, the diameter of a photosensitive body 1 is made 50mm, and the distance between the tip of a discharge electrode 2b in the (n) direction and the edge of the shield case 2c is made 7mm. By arranging the discharge electrode 2b in an upstream process, a uniform charge property can be obtained. By arranging the discharge electrode 2b in the position moved 1-2mm to the upstream process, the most preferable charge property can be obtained. Such corona discharge voltage that the distance between the corona discharge electrode 2b and a shield side surface in the upstream process becomes smaller than the distance between the corona discharge electrode 2b and a shield side surface in a downstream process is generated.

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 for applying an electric charge to an object to be charged by utilizing a corona discharge phenomenon.

[0002]

2. Description of the Related Art In an image forming apparatus for forming an image by electrophotography, a high voltage of 5 to 10 kV is applied to a tungsten wire having a diameter of 50 to 100 .mu.m as a charging device for supplying a predetermined charging potential to the surface of an image forming body. There is known a corona discharge device that applies and moves ions generated by the discharge on the wire to the surface of the image forming body for charging. In this method, when used for negative discharge, the discharge points are randomly positioned on the wire depending on the state of the wire surface, and the discharge is uneven with respect to the surface to be charged. In addition, a shield case as an auxiliary electrode and a grid for potential control are used. This type is called the scorotron type.

In recent years, for example, Japanese Patent Laid-Open No. 63-1527.
As disclosed in Japanese Patent Laid-Open No. 2 (1994), a corona discharge device using a sawtooth discharge electrode instead of a tungsten wire has been proposed. In this type of corona discharge device, the discharge points are regularly located at the saw-teeth tip, so that the discharge is more uniform with respect to the surface to be charged, and due to its operational advantage, the discharge required for uniform charging compared to the wire. Since the current is small and the discharge current is small, the amount of ozone generated can be suppressed.

However, since the discharge point is specified, it is easily affected by damage to the tooth tips of the sawtooth discharge electrode, adherence of floating matter to the electrode tip, and tilting (bending) of the electrode,
In that case, the discharge itself becomes unstable and the variation becomes large.
Therefore, in order to stabilize the discharge, a shield case as an auxiliary electrode and a grid for potential control are also used, which requires a considerable discharge current. Therefore, the amount of ozone generated also increases.

The shield case is usually connected to the ground potential, or to an appropriate potential having the same polarity as the voltage applied to the discharge electrode in order to increase the charging efficiency.
It is floating. The grid usually has the same polarity as the desired charging potential, and the absolute value is 20 to 20 in absolute value.
It is connected to a potential higher by 60V.

However, in the conventional scorotron type discharge device, it is easily affected by dirt, and due to the oxidation and spatter of the discharge electrode and the grid, the adhesion and growth of foreign matter,
The discharge state fluctuates, and the charging uniformity decreases. Further, the image forming body applied to the image forming apparatus does not rise to the desired potential on the surface of the image forming body with the initially set discharge amount due to the change over time and the abrasion due to use. Furthermore, the value of the charging potential is not constant due to changes in the discharge environment such as temperature and humidity.

Conventionally, in order to deal with such a problem, the potential of the photoconductor (image forming body) before charging and the potential of the photoconductor after charging are substituted into a predetermined functional expression, and the grid is calculated based on the result. Control the voltage.

The surface potential of the photoconductor is detected, and the developing bias voltage is controlled based on the result.

The impedance on the output side of the high-voltage power supply that applies a voltage to the corona discharge electrode of the discharge device is detected, and the output of the bias power supply applied to the high-voltage power supply and the grid is operated based on the discharge impedance calculated from this. Control before start.

In order to determine the discharge current for obtaining a predetermined potential according to the deterioration condition, a corona discharge is performed by constant current control before the operation is started, and a necessary discharge is performed by a detection signal converted into a voltage value corresponding to the discharge current. The voltage is determined, and constant voltage control is performed with the determined discharge voltage during operation.

A potential detection sensor for detecting the surface potential of the photoconductor is provided, and the detection signal is signal-processed and then fed back to the high-voltage power source to adjust the voltage applied to the grid or to control the constant current. To maintain a uniform discharge.

A complicated detection circuit that accurately captures subtle changes in the photoconductor current due to aging and environmental changes is provided, and the photoconductor current is controlled to a predetermined value.

The grid current, the shield case current, or both currents are detected and fed back to the high voltage power source to control the grid voltage and the voltage applied to the discharge electrode.

And the like, to make the charging potential of the photosensitive member and the image quality uniform,
Various measures for stabilization have been proposed.

Further, in order to improve the charging efficiency and obtain a uniform and stable charging property with a smaller discharge current, (1) of the edges of the U-shaped shield plate, the edge of the shield plate on the upstream side in the photoconductor rotating direction. The distance between the photoconductor and the photoconductor is set larger than the distance between the photoconductor and the edge of the shield plate on the downstream side in the photoconductor rotation direction.

(2) A grid is provided at a position downstream of the center of the U-shaped ends of the shield plate in the direction of rotation of the photoconductor.

(3) The opening area of the grid holes of the grid is configured to become narrower toward the downstream side in the moving direction of the photosensitive member.

Various countermeasures such as the above have been proposed.

[0019]

However, these measures require high-precision circuit elements, sensors, and complicated circuits, which makes the device expensive. In addition, the manufacturing method and mounting become complicated, and high accuracy is required. And, there are still problems in the uniformity and stability of the charging property obtained in this way, and further improvement is required, and there is a problem that sufficient effects cannot be obtained only by changing the shape of the shield or grid. is there.

The present invention was devised in view of such circumstances, and the surface potential of the body to be charged can be reduced with a smaller discharge current without causing the apparatus to be complicated, large, and expensive. It is an object of the present invention to provide a corona discharge device capable of uniformly and stably setting a desired potential over a long period of time.

[0021]

A corona discharge device according to a first aspect of the present invention is a corona discharge device for applying an electric charge to a surface of an object to be charged, the bottom surface and both side surfaces of the corona discharge electrode being made of a conductive material. The corona discharge electrode is provided so that the distance between the corona discharge electrode and the shield side surface on the process upstream side is smaller than the distance between the corona discharge electrode and the shield side surface on the process downstream side. It is characterized by having done.

A corona discharge device according to a second aspect of the present invention is a corona discharge device for applying an electric charge to the surface of an object to be charged, comprising shield means made of a conductive material on the bottom surface and both side surfaces of the corona discharge electrode. The voltage | Vc _U | applied to the shield on the process upstream side is smaller than the voltage | Vc _D | applied to the shield on the process downstream side.

A corona discharge device according to a third aspect of the present invention is a corona discharge device for applying an electric charge to the surface of an object to be charged,
In a scorotron type discharge device having a shield means made of a conductive material on the bottom surface and both side surfaces of the corona discharge electrode, a grid for potential control is provided between the corona discharge electrode and the charged body, The grid is disposed on the process downstream side of the opening of the shield.

A corona discharge device according to a fourth aspect of the present invention is a corona discharge device for applying an electric charge to the surface of an object to be charged,
In a scorotron type discharge device having a shield means made of a conductive material on the bottom surface and both side surfaces of the corona discharge electrode, a grid for potential control is provided between the corona discharge electrode and the charged body, Potential of the grid |
Vg | is set so that the upstream side of the process is large and the downstream side of the process is small.

A corona discharge device according to a fifth aspect of the present invention is a corona discharge device for applying an electric charge to the surface of an object to be charged,
In a scorotron type discharge device having a shield means made of a conductive material on the bottom surface and both side surfaces of the corona discharge electrode, a grid for potential control is provided between the corona discharge electrode and the charged body, The grid is arranged such that the distance g between the grid and the body to be charged is 0.5 mm ≦ g ≦ 1.0 mm.

A corona discharge device according to a sixth aspect of the present invention is a corona discharge device for applying an electric charge to the surface of an object to be charged,
In a scorotron type discharge device having a shield means made of a conductive material on the bottom surface and both side surfaces of the corona discharge electrode, a grid for potential control is provided between the corona discharge electrode and the charged body, The relationship between the predetermined charging potential Vs of the body to be charged and the grid voltage Vg is | Vg | ≦ |
The grid voltage is set so as to be Vs |.

[0027]

In the corona discharge device according to the first aspect, by displacing the position of the corona discharge electrode toward the process upstream side,
The center of the discharge distribution is moved to the upstream side of the process, and the current easily flows through the charged body.In the initial stage of charging, high-density corona ions are sent to the charged body to roughly charge the charged body, and then the surface is charged in the latter half of the charging area. By uniformizing the potential, uniform charging property can be obtained with a smaller discharge current.

In the corona discharge device of the second aspect, the shield voltage is made smaller on the process upstream side than on the process downstream side, thereby moving the center of the discharge distribution to the process upstream side, and in the same manner as described above, a smaller discharge current is obtained. It is possible to obtain uniform chargeability.

In the corona discharge device of the third aspect, the grid is removed within a range not exceeding the desired surface potential so that as much current as possible is flown to the charged body and the charged body is first roughly charged. By homogenizing the surface potential in the latter half of the charging area, uniform charging property can be obtained with a smaller discharge current.

In the corona discharge device of claim 4, the grid voltage is set to a large value on the upstream side of the process and is set to a value close to the desired surface potential on the downstream side of the process, so that the body to be charged is first roughly charged and charged. By uniformizing the surface potential in the latter half of the region, uniform charging property can be obtained with a smaller discharge current.

In the corona discharge device of the fifth aspect, by setting the distance between the grid and the member to be charged sufficiently small, more current is made to flow to the member to be charged during the charging time, and charging with good charging efficiency is performed. As a result, uniform chargeability can be obtained with a smaller discharge current.

In the corona discharge device of the sixth aspect, the grid voltage is set so that a region in which the charging potential is sufficiently saturated can be used, so that the potential variation in the charging region and the discharge electrode and the body to be charged are caused. It is possible to suppress changes in the charging potential of the member to be charged due to an increase in the number of times of use and changes in the charging potential due to the discharge environment, and as a result, it is possible to obtain uniform charging properties with a smaller discharge current.

[0033]

Embodiments of the corona discharge device according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows the construction of an electrophotographic apparatus such as a copying machine or a laser printer using the corona discharge device according to the embodiment. The photoreceptor 1 having an axis in a direction perpendicular to the paper surface is an image forming body, that is, a body to be charged, and rotatably supports a drum-shaped base body made of a conductive material such as aluminum.
A photoconductive layer made of OPC (organic photosensitive conductor: organic photoconductor) or the like is formed on the peripheral surface of a substrate. This photoconductor 1 is shown by the arrow W
It is configured to be driven and rotated in the direction of. A corona discharge device (charger) 2 and a corona discharge device (transfer device) 2 ′ are closely opposed to the photoreceptor 1.

The charger 2 is provided with a sawtooth discharge electrode 2b made of stainless steel (thickness 0.1 mm) prepared by etching, laser processing or the like on an insulating substrate 2a, and has a U-shaped cross section. It is supported inside the case 2c.
The sawtooth discharge electrode 2b is connected to the high voltage power supply 2d,
By applying a high voltage from the high-voltage power supply 2d, corona discharge is generated from the tooth tips and the surface of the photoconductor 1 is charged. A grid 2f to which a voltage of −600V is applied by a high voltage power supply 2e is arranged between the discharge electrode 2b and the photoconductor 1, and the charging potential of the photoconductor 1 is a predetermined potential (−600V).
V).

After the surface of the photoconductor 1 is charged to a predetermined potential by the charging device 2, an electrostatic latent image is formed on the surface of the photoconductor 1 by exposure 3, and the electrostatic latent image is developed by the developing device 4. To form a toner image. Next, when this toner image reaches the transfer portion where the transfer device 2'and the photoconductor 1 face each other, the transfer material 5 is supplied to the transfer portion at the same timing (the arrow Z direction in the drawing). The back surface of the transfer material 5 is charged by a transfer device 2'having substantially the same configuration as the charging device 2 except that there is no grid at the transfer site, and the toner image on the photoconductor 1 is transferred to the transfer material 5. Thereafter, the transfer material 5 carrying the toner image is conveyed to the fixing device 6, while the toner remaining on the photoconductor 1 is cleaned by the cleaner 7
After being collected in step 1, the residual charges on the photoconductor 1 are removed by the discharge lamp 8 and the process proceeds to the next step.

FIG. 2 is an enlarged view of a main part of the sawtooth discharge electrode 2b in FIG. The number of teeth of the sawtooth discharge electrode 2b is 107.
The pitch p of each tooth is 2 mm, and the tooth tip is bonded onto the insulating substrate 2a so that the tooth tip is located at a position protruding from the edge of the insulating substrate 2a toward the photoconductor 1 (d = 2 mm). ing. The common electrode 2g, which is connected to the discharge electrode 2b through a resistor (not shown), is connected to the high-voltage power supply 2d. By applying a high voltage from the high-voltage power supply 2d, corona discharge is generated from the tooth tips, and the photoconductor 1 Charge the surface of.

FIG. 3 shows the distribution of the discharge intensity for one tooth tip of the sawtooth discharge electrode 2b.

FIG. 4 shows the photoconductor 1 with respect to the potential of the photoconductor 1.
The relationship of the discharge current (drum current) flowing in the is shown. In the initial stage of discharge when the potential of the photoconductor 1 is low, more discharge current flows.

FIG. 5 shows the experimental apparatus (the viewing direction is from the side opposite to that in FIG. 1). In this experimental apparatus, the position of the saw-tooth discharge electrode 2b is displaceable in the direction perpendicular to the line n extending from the center of the charger 2 in parallel with the charging direction, and the position of the grid 2f is set as described above. It can be displaced in the direction of the line n and in the direction perpendicular to the line n. In FIG. 5, 2c is a shield case and 2f is a grid. The height of the shield case 2c is 16 mm,
The length is 230 mm and the thickness of the insulating substrate 2a is 1.6 m.
m, the diameter of the photoconductor 1 is 50 mm, and the dimension between the tip of the discharge electrode 2b and the end of the shield case 2c along the n direction is 7 mm.

(1) In the experimental apparatus shown in FIG. 5, when the discharge electrode 2b is vertically moved to the upstream side of the process by 0 to 3.0 mm to charge the photosensitive member 1, the uneven charging in the axial direction of the photosensitive member 1 occurs. The results are shown in FIG. According to this result, a more uniform charging property can be obtained by disposing the discharge electrode 2b on the upstream side of the process. It is preferable to dispose the discharge electrode 2b at a position moved by 1 to 2 mm on the upstream side of the process to obtain the best charging property.

(2) As shown in FIG. 7A, with respect to the voltage of the shield case 2c, the case voltage | Vc _U | on the process upstream side is changed to the case voltage | Vc _D on the process downstream side.
Set smaller than |. For example, Vc _U = -500
V and Vc _D = -1500V. By doing so, as shown in FIG. 7B, the discharge density distribution is in a state in which its center is deviated to the process upstream side. As a result, more uniform chargeability can be obtained as in the case of (1).

(3) In the experimental apparatus shown in FIG. 8, the grid 2f is connected to the downstream side of the process with respect to the line m in which the side surface on the upstream side of the process in the shield case 2c is extended to the photoconductor 1 side.
When the photosensitive member 1 is displaced by mm, the uneven charging in the axial direction of the photosensitive member 1 has the result shown in FIG. From this,
It can be seen that if the grid 2f is arranged so as to be offset toward the downstream side of the process, a more uniform charging property can be obtained. Furthermore, when the discharge electrode 2b is arranged so as to be displaced toward the upstream side of the process, a more uniform charging property can be obtained.

Here, some attention must be paid to the arrangement position of the grid 2f. This is because if the portion (space portion) where the grid 2f is not arranged is too large in the charging area, the desired surface potential of the photoconductor is exceeded in this space portion, or even if it is not exceeded, it is not sufficiently uniformized in the charging area. Because. When the charge amount of only the space portion was measured by the experimental apparatus shown in FIG. 8, the result shown in FIG. 10 was obtained.
If the space portion is 5.5 mm or more, the charging potential in the space portion exceeds the desired surface potential −600 V, which is not suitable. Judging from the uniformity of charging, the maximum value of the space portion is 5 mm.

(4) In the configuration shown in FIG. 5, the distribution ratio Id / of the photoconductor current Id with respect to the increase of the grid voltage | Vg |
Since It tends to increase, as shown in FIG. 11, in the first half of the charging area on the process upstream side, the grid potential is, for example, −
Electrification is efficiently performed by setting 700V and the surface potential of the photoconductor to a high value within a range not exceeding the desired surface potential, and in the latter half of the charging area of the photoconductor 1, the grid voltage is set to a voltage at which the desired surface potential is obtained, for example, -600V. Set and charge accurately.

As shown in FIG. 12, the grid voltage may be gradually reduced from the process upstream side to the process downstream side. By doing so, uniform charging property can be obtained more efficiently.

(5) In the experimental apparatus shown in FIG. 5, a charging test was conducted using the distance g between the grid 2f and the photoconductor 1 as a parameter, and the results shown in FIG. 13 were obtained.
It can be seen that the smaller the distance g, the better the charging efficiency.
Further, as shown in the figure, the smaller the distance g, the smaller the uneven charging. From the above, it is preferable to make the distance g between the grid 2f and the photoconductor 1 as small as possible. Grid 2f
Considering the mounting accuracy and abnormal discharge of the
Is preferably 0.5 mm ≦ g ≦ 1.0 mm.

(6) Table 1 in the experimental apparatus shown in FIG.
When the charging test was performed under the conditions of 6 patterns shown in
FIG. 14 shows the relationship between the voltage applied to the discharge electrode 2b and the surface potential of the photoconductor 1. In the figure, L, C, and R indicate measured values on the left side, the center, and the right side of the photoconductor 1 in the axial direction, respectively. The surface potential on the Y axis is the average value of the charged potential of the photoconductor in the circumferential direction.

[0049]

[Table 1]

There are large variations in charging characteristics due to differences in discharge electrodes (different electrodes, presence / absence of discharge history, discharge environment) and differences in photoconductor (charge position, presence / absence of charge history). FIG.
No. 4 shows such a large variation. This difference in charge amount causes variations in surface potential or deviation from the desired charge potential.

Since the difference in the charge amount becomes smaller as the charge potential becomes saturated with respect to the applied voltage, it is preferable to apply a voltage suitable for it to the discharge electrode 2b. However, if a voltage such that the relationship between the grid voltage Vg and the predetermined charging potential Vs applied to the photoconductor 1 is | Vg |> | Vs | is applied to the grid 2f as in the conventional case, the charging potential will greatly exceed the predetermined charging potential. become. It is conceivable to increase the distance between the grid 2f and the photoconductor 1 so that the surface potential of the photoconductor does not greatly exceed the predetermined charging potential.
As shown in, the charging efficiency is deteriorated, which is not suitable.

Therefore, by applying a voltage such that the relationship between the grid voltage Vg and the predetermined charging potential Vs is | Vg | ≦ | Vs | to the grid 2f, the predetermined charging potential can be obtained without impairing the charging efficiency. .

A more specific description will be given below. The predetermined charging potential Vs of the photoconductor will be described using the fact that Vs = Vg + V (It, g, s, e) due to the grid voltage Vg. In the above equation, V (It,
g, s, e) are constants determined by the discharge current, grid position, grid aperture, and other discharge environment.

FIG. 15 shows the charging characteristics under the conditions a and b in Table 1. The conditions are the same for a and b, but the objects themselves are different.

In the figure, the thick line is condition a and the thin line is condition b.
Is the case. Charging position (L, C, R) for condition a
The potential variation due to is relatively small, and under condition b, the potential variation is relatively large.

When the grid voltage Vg is set to -650V and the average surface potential Vs is set to -600V, an axial potential difference A shown in FIG.

On the other hand, the grid voltage Vg is set to -60.
When 0V and the average surface potential Vs are set to -600V,
The potential difference in the axial direction is B shown in FIG. 15, and it can be seen that the latter can suppress the potential variation due to the charging position.

Next, FIG. 16 shows the charging characteristics under the conditions a and c in Table 1, where the thick line is the condition a and the thin line is the condition c. It can be seen that the impedance of the discharge space rises due to the influence of the deposits deposited on the discharge electrode 2b due to the discharge, and the charging efficiency deteriorates.

When the grid voltage Vg is set to -650V and the average surface potential Vs is set to -600V, an axial potential difference of C shown in FIG. 16 occurs.

On the other hand, the grid voltage Vg is set to -60
When 0V and the average surface potential Vs are set to -600V,
The potential difference in the axial direction becomes D shown in FIG. 16, and the potential variation due to the charging position can be suppressed.

Next, FIG. 17 shows the charging characteristics under the conditions a and d in Table 1, where the thick line is the condition a and the thin line is the condition d. It can be seen that the amount of charge is reduced because the surface of the photoconductor 1 is worn and the electrostatic capacity is increased.

When the grid voltage Vg is set to -650V and the average surface potential Vs is set to -600V, an axial potential difference of E shown in FIG. 17 occurs.

On the other hand, the grid voltage Vg is set to -60.
When 0V and the average surface potential Vs are set to -600V,
The potential difference in the axial direction becomes F shown in FIG. 17, and the potential variation due to the charging position can be suppressed.

Next, FIG. 18 shows the charging characteristics under the conditions a, e and f in Table 1, where the thick line indicates the condition a,
The thick line represents the condition e and the thin line represents the condition f. It shows the difference in charging efficiency depending on the discharge environment. In this case, the same thing can be said as above.

Here, if the distance g between the grid 2f and the photoconductor 1 is large, the applied voltage and the discharge current required to obtain the predetermined charging potential Vs become considerably large, so the distance g is set to 0.5 mm. Set within the range of ≦ g ≦ 1.0 mm,
By setting the grid voltage Vg so that | Vg | ≦ | Vs |, a greater effect can be obtained.

The above experiment was conducted with an OPC of φ50 mm.
(Organic photoconductor), charger with opening width of 15 mm, discharge gap of 7 mm, process speed of 86 mm / s.

In the above embodiment, the discharge electrode 2b has been described as having a sawtooth shape, but it goes without saying that the same effect can be obtained with a comb tooth shape or a multi-needle electrode. Also, the optimum value etc. is determined by the balance of the opening width of the charger, the opening ratio of the grid, the discharge gap, the process speed, etc., so some changes are inevitable due to changes in conditions,
The same idea as described above can be applied. Furthermore, although the charging device of the electrophotographic apparatus has been particularly described in the above-described embodiments, the present invention is not limited to this, and may be applied to a corona discharge device such as a transfer device, a charge eliminating device or a peeling device of the electrophotographic device. It goes without saying that it can be applied.

[0068]

According to the corona discharge device of the first aspect, the corona discharge electrode and the shield side surface on the process upstream side have a distance smaller than the distance between the corona discharge electrode and the shield side surface on the process downstream side. By generating discharge electrodes, the center of the discharge distribution is moved to the process upstream side,
Electric current easily flows to the charged body High density corona ions are sent to the charged body at the initial stage of charging to roughly charge the charged body, and the surface potential is made uniform in the latter half of the charging area, resulting in a smaller discharge current. It is possible to obtain uniform chargeability.

According to the corona discharge device of the second aspect, the voltage | Vc _U | applied to the shield on the process upstream side is made smaller than the voltage | Vc _D | By moving the center of the distribution to the upstream side of the process, it is possible to obtain uniform chargeability with a smaller discharge current in the same manner as described above.

According to the corona discharge device of the third aspect, the grid is generated at the process downstream side of the opening of the shield so that as much current as possible is flown to the charged body, so that the charged body is roughly cleaned. By charging and uniformizing the surface potential in the latter half of the charging area, uniform charging property can be obtained with a smaller discharge current.

According to the corona discharge device of the fourth aspect, by setting the grid potential | Vg | so that the process upstream side is large and the process downstream side is small, the charged body is first roughly charged, and the latter half of the charging region is charged. By uniformizing the surface potential with, it is possible to obtain uniform chargeability with a smaller discharge current.

According to the corona discharge device of the fifth aspect, the distance g between the grid and the member to be charged is 0.5 mm ≦ g ≦ 1.0 m.
By arranging the grid so as to be m, more current is made to flow to the member to be charged during charging time, charging is performed with good charging efficiency, and as a result, uniform charging property can be obtained with less discharge current. it can.

According to the corona discharge device of claim 6, the grid voltage is set so that the relationship between the predetermined charging potential Vs of the member to be charged and the grid voltage Vg is | Vg | ≦ | Vs | It is possible to suppress variations in the potential in the area, changes in the charging potential of the charged body due to an increase in the number of times the discharge electrode or charged body is used, and changes in the charging potential due to the discharge environment, resulting in a smaller discharge current. It is possible to obtain uniform chargeability.

As described above, according to the present invention, charging with good charging efficiency is performed, and the surface potential of the body to be charged is reduced to a smaller discharge current without causing the apparatus to become complicated, large, and expensive. Therefore, it is possible to provide a corona discharge device capable of stably setting a desired potential over a long period of time while uniformly and therefore suppressing the amount of ozone generated.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an electrophotographic apparatus using a corona discharge device according to an exemplary embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of the sawtooth discharge electrode in FIG.

FIG. 3 is a diagram showing a distribution of discharge intensity from a sawtooth discharge electrode.

FIG. 4 is a diagram showing the relationship between the potential of the photoconductor and the discharge current of the photoconductor according to the experimental results.

FIG. 5 is a diagram showing an experimental apparatus used for an experiment according to the present invention.

FIG. 6 is a diagram showing the relationship between discharge electrode positions and uneven charging in the axial direction of the photosensitive member according to the present invention.

FIG. 7 is a diagram showing an embodiment of a corona discharge device according to the present invention and a discharge intensity distribution.

FIG. 8 is a diagram showing an experimental apparatus used for an experiment according to the present invention.

FIG. 9 is a diagram showing the relationship between the position of the discharge electrode according to the present invention and the uneven charging in the axial direction of the photoconductor.

FIG. 10 is a graph showing a charge amount in a grid space portion according to an experimental result.

FIG. 11 is a configuration diagram illustrating an embodiment of a corona discharge device according to the present invention.

FIG. 12 is a configuration diagram illustrating another embodiment of the corona discharge device according to the present invention.

FIG. 13 is a diagram showing the relationship between the grid position, uneven charging in the photosensitive member axial direction, and the surface potential according to the present invention.

FIG. 14 is a diagram showing charging characteristics of a corona discharge device according to experimental results.

FIG. 15 is a diagram showing charging characteristics (differences in discharge electrodes) for explaining an example of a corona discharge device according to the present invention.

FIG. 16 is a diagram showing another charging characteristic (difference in discharge history of discharge electrodes) for explaining an example of the corona discharge device according to the present invention.

FIG. 17 is a diagram showing another charging characteristic (difference in charging history of photoconductor) for explaining an example of the corona discharge device according to the present invention.

FIG. 18 is a diagram showing another charging characteristic (difference in discharge environment) for explaining an embodiment of the corona discharge device according to the present invention.

[Explanation of symbols]

 1 ... Photoreceptor 2 ... Corona discharge device (charger) 2a ... Insulating substrate 2b ... Sawtooth discharge electrode 2c ... Shield case 2d ... High voltage power supply 2e ... High voltage power supply 2f ... Grid 2g ... Common electrode 2 '... Corona discharge Device (transfer device) 3 ... exposure 4 ... developing device 5 ... transfer material 6 ... fixing device 7 ... cleaner 8 ... static elimination lamp

Claims (6)

[Claims] 1. A corona discharge device for applying an electric charge to the surface of an object to be charged, comprising shield means made of a conductive material on the bottom surface and both side surfaces of the corona discharge electrode, and the shield on the corona discharge electrode and the process upstream side. A corona discharge device, wherein the corona discharge electrode is arranged such that a distance from the side surface is smaller than a distance between the corona discharge electrode and the shield side surface on the process downstream side. 2. A corona discharge device for applying an electric charge to the surface of an object to be charged, comprising shield means made of a conductive material on the bottom surface and both side surfaces of a corona discharge electrode, and a voltage applied to the shield on the upstream side of the process. | Vc _U | is smaller than the voltage | Vc _D | applied to the shield on the process downstream side. 3. A corona discharge device for applying an electric charge to the surface of an object to be charged, comprising shield means made of a conductive material on the bottom surface and both side surfaces of the corona discharge electrode, and connecting the corona discharge electrode and the object to be charged. A scorotron type discharge device in which a grid for controlling potential is provided, wherein the grid is arranged on the process downstream side of the opening of the shield. 4. A corona discharge device for applying an electric charge to the surface of an object to be charged, comprising shield means made of a conductive material on the bottom surface and both side surfaces of the corona discharge electrode. In a scorotron type discharge device in which a grid for controlling potential is provided, a potential | Vg | of the grid is set so that the process upstream side is large and the process downstream side is small. 5. A corona discharge device for applying an electric charge to the surface of an object to be charged, comprising shield means made of a conductive material on the bottom surface and both side surfaces of the corona discharge electrode. In a scorotron type discharge device in which a grid for controlling potential is provided, a distance g between the grid and the charged body is 0.5 mm ≦ g ≦ 1.0.
A corona discharge device, wherein the grid is arranged so as to have a size of mm. 6. A corona discharge device for applying an electric charge to the surface of an object to be charged, comprising shield means made of a conductive material on the bottom surface and both side surfaces of the corona discharge electrode. In a scorotron type discharge device in which a grid for controlling potential is provided, the relationship between the predetermined charging potential Vs of the body to be charged and the grid voltage Vg is |
A corona discharge device, wherein the grid voltage is set so that Vg | ≦ | Vs |.