JPH02273763A - Corona discharging device - Google Patents

Abstract

PURPOSE:To prevent a strong ion wind from flowing toward a photosensitive body and to improve electrostatic discharging stability by covering a wire for corona discharging, providing shield plates which form an opening for electrostatic discharging and openings for ozone discharging and making an electric field in the vicinity of the openings for ozone discharging intenser than an electric field in the vicinity of the opening for electrostatic charging. CONSTITUTION:The corona discharging device is constituted of the corona discharging wire 1, a back plate 2 and side plates 3 and 4 which are arranged around the wire, and the electric field in the vicinity the openings 8 and 9 for ozone discharging is made intenser than the electric field in the vicinity of the opening 7 for electrostatic discharging. Namely, a proper bias voltage having the same polarity with an ion flow is applied to the side plates 3 and 4 and the potential differences between the wire 1 and side plates 3 and 4 are set smaller than the potential difference between the wire 1 and back plate 2; and an electric field produced between the wire 1 and back plate 2 is made intense and an electric field which is produced between the wire 1 and side plates 3 and 4 is made weak. Consequently, the corona discharging is stabilized and the strong ion wind is prevented from flowing toward the surface of the photosensitive body 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a corona discharge device used in electrophotographic copying machines and the like.

(Prior Art) A corona discharge device is used, for example, in an electrophotographic copying machine, as a charger for uniformly charging a photoreceptor, a transfer device for transferring a toner image onto paper, or for removing electric charge on the photoreceptor. Used in static eliminators, etc.

A corona discharge device is equipped with a wire for applying high voltage and a shield plate (stability &) that surrounds the wire and stabilizes the discharge.For example, when used as a charger, the distance between the wire and the surface of the photoreceptor is It is installed parallel to the axis so that it is constant. When a high voltage is applied between the wire and the surface of the photoreceptor in this state, corona discharge starts near the wire, and a current due to the generated ions flows between the wire and the surface of the photoreceptor, creating an electric charge on the surface of the photoreceptor. Accumulated.

(Problems to be Solved by the Invention) When corona discharge is performed, ozone is generated accordingly. Since ozone has the property of acting on the surface of the photoreceptor and deteriorating the photoreceptor, it is necessary to take measures to prevent ozone from having an adverse effect on the photoreceptor.

In the corona discharge device described in Japanese Patent Laid-Open No. 51-10785, ozone generated by corona discharge is discharged to the side opposite to the photoreceptor through a discharge opening provided in a shield plate.

However, in the device disclosed in the above publication, the shield plate is grounded, and most of the current due to corona discharge flows through the shield plate, resulting in a large amount of power being wasted.
Not only is it uneconomical, but in order to obtain a high charging capacity, a high voltage and high output power source is required, which increases the cost. Moreover, a large amount of ozone is generated due to the large amount of overall cost discharge, and even if ozone is efficiently discharged, the effect on the human body cannot be ignored.

To prevent large amounts of current from flowing to the shield plate,
A corona discharge device has been proposed in which a bias voltage of the same polarity as the voltage applied to the wire is applied to the shield plate, so that most of the current due to discharge flows between the wire and the photoreceptor (see Figure 5). In this case, the voltage applied to the wire may be relatively low, but since an ion flow occurs from the wire toward the photoreceptor during discharge, the wind generated by this ion flow (ion wind) is transferred from the periphery of the wire to the photoreceptor. The ozone flows toward the surface of the body, and all the ozone generated by the discharge is carried to the surface of the photoreceptor, degrading the photoreceptor.

Furthermore, it has been proposed that an insulating layer is provided on the inner surface of the shield plate to block the ion current to the shield plate (see FIG. 8, which will be explained later).

), it has the same drawbacks as the above method of applying a bias voltage to the shield plate, and in addition, the insulating layer is charged, and while the discharge body is stopped, surrounding foreign objects and dust are attracted to the insulating layer, causing uneven charging during discharge. There is a problem with inviting people.

An object of the present invention is to provide a corona discharge device that stabilizes the discharge, reduces the amount of unnecessary ion flow, and directs the ion wind away from the discharge target.

(Means for Solving the Problems) A corona discharge device according to the present invention includes a corona discharge wire and a shield plate that surrounds the corona discharge wire from the periphery and is provided with a discharge opening and an ozone discharge opening. The shield plate is characterized by having a structure in which the electric field near the ozone discharge opening is stronger than the electric field near the discharge opening (effect) When a high voltage is applied to the corona discharge wire, the corona discharge A corona discharge is generated by the discharge wire toward the shield plate and the discharge target, but the discharge to the portion of the shield plate near the discharge opening is small, and the discharge to the portion near the ozone discharge opening is relatively large.

(Example) Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 schematically shows the configuration of an example of a corona discharger according to the present invention. This corona discharger is a charger that charges the surface of the photoreceptor drum, and it uses a corona discharge wire! , a stabilizer plate (consisting of three parts, back plate 2 and side plate 3.4) arranged around it, and a discharge amount lower defined by the lower edge of side plate 3.4. flow control grid 5
This constitutes a so-called scorotron type corona discharge device.

In this example, the ion flow control grid 5 and the back plate 2 are in opposing positions with respect to the corona discharge wire. Further, the ion flow control grid 5 is arranged near the photoreceptor drum 6.

The photoreceptor drum 6 is provided with a photoreceptor layer on its surface.
The substrate of the photoreceptor layer is grounded.

The back plate 2 is grounded, and the side plates 3, 4 are connected to bias power supplies 11, 12, respectively. The corona discharge wire 1 is also connected to a high voltage power source I3 to generate a strong electric field for corona discharge. Furthermore, the ion flow control grid 5 is connected to a grid power supply I4 for generating control voltage;
A varistor or the like may also be used. (The power supplies 13 and 14 are omitted from subsequent figures for simplicity.) As a result,
A potential approximately equal to the potential at which the surface of the photoreceptor on the photoreceptor drum 6 should be charged is generated in the ion flow control grid 5 .

FIG. 2 shows a perspective view of the corona discharger shown in FIG. However, in this example, unlike the example in Figure 1, the two side plates 3 and 4 are electrically coupled to form one side plate 3', but electrically the configurations in both figures are essentially the same. It is common to

When this corona discharger is used as a charger,
The photoreceptor on the surface of the rotationally driven photoreceptor drum 6 is irradiated with an eraser (not shown) in advance, and is subjected to the action of corona discharge without any residual charge on the surface, and becomes negatively charged.

In corona discharge, by applying an appropriate bias voltage with the same polarity as the ion flow to the side plates 3 and 4, the potential difference between the wire 1 and each side plate 3 and 4 is changed to the potential difference between the wire 1 and the back plate 2. Since the electric field generated between the wire 1 and each side plate 3.4 can be set smaller, the electric field generated between the wire 1 and the back plate 2 can be made stronger, and the electric field generated between the wire 1 and each side plate 3.4 can be made smaller. The flow can be controlled so that it mainly directs toward the back plate 2 and photoreceptor drum 6. With this structure, the ion flow toward the side plates 3.4, which are part of the stabilizer plates, is almost eliminated, so the amount of current flowing into the public stabilizer plates 2 to 4 can be reduced, and the overall amount of discharge is reduced. Therefore, the amount of ozone generated can be reduced and the transformer power can be reduced.

On the other hand, the flow of ions into the back plate 2, which is a part of the stabilizing plate, stabilizes the corona discharge and prevents the generation of a strong ion wind toward the surface of the photoreceptor. moreover,
The distance from the wire l to the back plate 2 is set shorter than the distance from the wire l to the photoreceptor 6, so that the electric field between the wire l and the back plate 2 is equal to the electric field between the wire l and the photoreceptor. By making it stronger than , the amount of ion flow into the back plate 2 becomes
The amount of water flowing into the photosensitive drum 6 can be controlled to be greater than the amount flowing into the photosensitive drum 6. In this way, if the amount of ion flow flowing into the back plate 2 is set to be larger than the amount flowing into the photoreceptor drum 6, the ion wind will flow as shown by the broken line arrow in FIG. , the ionic wind is generated from the side of the photoreceptor drum 6 toward the back plate 2, and is discharged to the outside through discharge openings 8.9 defined between each side plate 3.4 and the back plate 2, respectively. This prevents ozone generated due to corona discharge from directly acting on the photoreceptor, thereby reducing damage to the photoreceptor.

However, wire! Even if the distances between the back plate 2, the wire I, and the photoconductor are kept at the same level, if the surface of the photoconductor is even slightly charged, the potential difference between the wire I and the photoconductor decreases, so the distance between the wire I and the photoconductor decreases. The ion flow toward the photoreceptor surface is reduced. Therefore, as the surface of the photoreceptor is charged, an ion wind is generated from the photoreceptor drum 6 side toward the discharge opening 8.9.

Below, the results of electric field analysis for a corona discharger having the same configuration as the corona discharger shown in FIG. 1 will be explained using FIG. 3. In FIG. 3, a voltage of -5.5 kV is applied to the corona discharge wire 21. The back plate 22 is grounded, and the two side plates 23 and 24 are connected to a common bias power supply 31.
A voltage of -2 kV is applied. Further, a grid voltage of -0.67 kV is applied to the ion flow control grid 25. Note that the photoreceptor on the surface of the photoreceptor drum 26 is made free of residual charge by being irradiated with light.

Electric field lines obtained by performing electric field analysis in this state are shown in FIG. The electric lines of force connect the electric charges of each portion 21 to 26 and are distributed in a manner determined by the electric charge and the shape, arrangement, and potential of each portion 21 to 26. A high density of electric lines of force means that the electric field strength in the tangential direction of the lines of electric force at that portion is high. Ions generated by corona discharge move in the tangential direction of the lines of electric force. Therefore,
The ion stream flows in the direction of the photoreceptor drum 26 and in the direction of the back plate 22, but not in the direction of the side plates 23,24. Therefore, when the same amount of water flows into the photoreceptor, there is almost no wasteful flow into the side plates 23 and 24, so less power is required. Furthermore, the ion flow to the back plate 22 stabilizes the corona discharge. In addition, the back plate 22
Since there are more lines of electric force toward the photoreceptor than toward the photoreceptor, the ion wind flows toward the back plate 22. Therefore, ozone generated by the discharge is carried toward the back plate 22 and not toward the photoreceptor, thereby reducing damage to the photoreceptor.

When actually used as a charger, the photoreceptor approaches the charger with no residual charge due to light irradiation, and moves while accumulating charge on the surface due to the ion flow inside the charger.
When separated from the charger, it is charged to the same potential as the ion flow control grid 25. Therefore, as the photoreceptor is charged, the distribution of electric lines of force changes to become smaller.

At this time, the ion wind is directed further away from the photoreceptor, so damage to the photoreceptor is further reduced.

For comparison, FIG. 4 shows the results of electric field analysis in the conventional case where all the parts 22 to 24 of the stabilizer plate are grounded. All other points are the same as in Figure 3. As is clear from the figure, the ion stream flows into the photoreceptor and surrounding stabilizers 22-24, consuming a lot of power.

The example in FIG. 5 shows the electric field analysis results when the same bias voltage (-2 kV) is applied to each part 22 to 24 of the stabilizer plate. All other points are the same as in Figure 3. As the bias voltage increases, the stabilizers 22-24
The current flowing into the
In the case of , most of the ion wind is directed toward the photoreceptor. Therefore, the photoreceptor is seriously damaged. Furthermore, stabilizers 22 to 24
Since there is no discharge between the two, the discharge stability is lacking.

Next, a case will be described in which an insulating layer is attached to the surface of the stabilizing plate on the corona discharge wire side.

The corona discharger shown in FIG. 6 has the same structure as that shown in FIG.
Mylar plates 41 and 42, which are insulating layers, are attached to the entire surface of the first side, and all of the stabilizers 22 to 24 are grounded.

The same voltages as in FIG. 3 are applied to the corona discharge wire 21 and the ion flow control grid 25. Mylar board 41.
The potential on the surface of 42 becomes high and the flow of ions into the side plates 23.24 is prevented.

Further, as can be seen from the distribution of electric lines of force shown in the figure, the ion wind flows toward the back plate 22.

In the embodiment shown in FIG. 7, mylar plates 43, 44 are attached only to the half of the surface of the side plates 23, 24 on the photoreceptor side. In this case as well, the ion wind flows toward the back plate 22. However, in this embodiment, the current flows through the portions of the side plates 23 and 24 that are not covered with the mylar plates, so the waste of current is greater than in the embodiment shown in FIG. The ion flow flows into the upper half of the side plates 23 and 24, and the amount of ion flow is not reduced much.

In addition, in the comparative example shown in FIG.
．． 45 is attached. In this case, similar to the example in Figure 5,
Although the ion flow into the stabilizers 22 to 24 is reduced, the ion wind flows toward the photoreceptor, so damage to the photoreceptor due to the ion wind is not reduced. In addition, the stabilizer plate 22-2
Since there is no discharge with 4, the discharge is not stable. Furthermore, there is a lot of charge-up on the insulating layer, which causes surrounding foreign matter and dust to adhere while the discharge body is stopped, causing uneven charging.

As described above, the embodiments of the present invention (Fig. 3, Fig. 6, Fig. 7
In Figure), a potential difference is created between the side plates 23.24 and the back plate 22, causing the ion stream to flow into the back plate 22 while preventing it from flowing into the side plates 23.24.

Other means may be used to weaken the electric field near the discharge opening and strengthen it near the discharge opening.In the corona discharge device shown in FIG. 9, the wire l, the back plate 2. In the configuration consisting of the side plates 3, 4 and the photosensitive drum 6,
The back plate 2 is grounded, while the side plates 3.4 are grounded via respective resistance members 51, 52. The ion flow entering the side plate 3.4 causes a voltage drop across the resistive member 51.52, so that a potential difference occurs between the side plate 3.4 and the back plate 2.

Similarly to the margins below, in the examples shown in Figures 10(a) and (b),
A resistance member 53 connects the back plate 2 and the side plate 3.

Since the side plates 3 on both sides sandwiching the wire 1 are integral as shown in the top view of FIG. 10(b), this configuration forms a circuit electrically similar to the configuration of FIG. 9.

Further, in the corona discharger shown in FIG. 11, side plates 3" and 4" made of a resistive member are used, and each side plate 3'' is made of a resistive material.

4" is grounded. In this case as well, the circuit is electrically similar to the circuit shown in FIG.

A varistor, which is a special resistance element, can also be used instead of a resistor. FIG. 12 shows the resistor 51 in the configuration of FIG.
．． A corona discharger is shown in which a varistor 61,62 is used instead of 52. The ion flow to the side plate 3.4 is controlled by the varistor 61.6.
2, a potential difference is generated between the side plate 3.4 and the back plate 2, and the flow of ions into the side plate 3.4 is suppressed.

Furthermore, as shown in FIG. 13, the side plates 3.4 may be used as floating electrodes without being electrically connected to others. In this case, charges remain in the floating electrode due to the collision of ions, and the potential is higher than that of the grounded back plate 2, thereby suppressing the ion flow.

In the various corona dischargers described above, various means such as a bias power supply are used to create a potential difference between each part of the stabilizer plate and control the ion flow, but other means or a mixture of various means are used. may also be used.

The bias voltage may also be related to the grid control voltage in a configuration similar to the corona discharger of FIG. 9, for example as shown in FIG. 14. In this case, the ion flow control grid 5 is grounded via the varistor 63 and the resistance member 54 is connected between the side plate 3.4 and the ion flow control grid 5.

Similarly, as shown in FIG. 15, the bias voltage may be related to the grid control voltage in the corona discharger configuration of FIG. 12 using a varistor instead of a resistor. In this case, the varistor 64 is connected between the side plate 3.4 and the ion flow control grid 5.

That's all for corona discharge wire! Although a case has been described in which the back plate is provided at the farthest position from the photoreceptor, the shape and position of the back plate may be different.

In the corona discharger shown in FIG. 16, a back plate 101 and side plates 102 are provided on the sides of the wire 1. The back plate 101 is provided farther from the side plate 102 with respect to the photoreceptor. The other side plate 103 is provided in a U-shape from above the wire l to the other side. Although the back plate +01 is grounded,
The side plates 102 and 103 respectively have bias power supplies 11.
12 applies a bias voltage having the same polarity as the ion flow, thereby reducing the inflow of the ion flow. Wire! and back plate 10
1, discharge mainly occurs and corona discharge is stabilized.

Furthermore, the ion wind generated by the ion flow flowing into the back plate 101 passes through between the back plate 101 and the side plates 102 and flows.

In the example shown in FIG. 17, a bias voltage of opposite polarity to the voltage applied to the wire I is applied to the back plate 101 by the bias power supply 11.
3. This bias voltage causes the back plate 10 to
The ion flow towards 1 is strengthened. For this reason, the side plate is 103°
Corona discharge is stable even if it is provided only on the sides.

The corona discharger shown in FIG. 18 differs from the corona discharger shown in FIG. 16 in that one side plate 103'' is provided diagonally to the right of the wire l.The back plate 101 is grounded; A bias voltage is applied to the side plate 102.

Furthermore, in the corona discharger shown in FIG. 19, the back plate consists of three parts 111.1-12, 113 and is provided above and to the sides of the wire 1.

On the other hand, the two side plates 114 and 115 are each provided on the lower side and connected to the bias power supplies 11 and 12, respectively. In the corona discharge, the ionic wind passes through the discharge openings between the sections 111, 112, 113.

Moreover, in the corona discharge device shown in FIG. 20, the wire! A side plate 121 is provided diagonally on the left side of , and another side plate in the shape of ] is provided upward from the right side! 22 is provided. Ground the side plate 12■, and the side plate!
22 is connected to bias power supply +23. The upper part of the side plate 121 is arranged closer to the wire l than the lower part. In this arrangement, the corona discharge is caused by the upper part of the side plate 121 and the wire 1.
occurs between. The entire side plate 121 has the same potential, but since its upper part is close to the wire 1, the electric field generated in the vicinity becomes stronger. On the other hand, since the lower part of the side plate 121 is far away from the wire 1, no corona discharge occurs. Therefore, the current flowing to the lower part of the side plate 121 and the side plate 122 is reduced.

In the corona discharger shown in FIG. 21, side plates 131. +32 is provided.

Each side plate 131, 132 is located close to the wire 1 at the top and away from the wire 1 at the bottom, and both are grounded. A corona discharge occurs between the wire I and the upper part of each side plate I31, 132, reducing the ion flow into the lower part of each side plate 131, 132.

In the corona discharger shown in FIGS. 20 and 21, the ion flow is lower than that of the stabilizer plate 121, 131, 1 than the surface of the photoreceptor.
32, and the ion wind flows in a direction away from the photoreceptor.

The above description has been made of the case where the present invention is applied to a charger, but FIG. 22 shows an example of the case where the present invention is applied to a transfer device.

Conventional transfer devices have, for example, provided a grounded stabilizer around the wire. In this embodiment, the corona discharge wire 20
11, a back plate 202 is provided on the side opposite to the photoreceptor drum, and side plates 203 and 204 are provided on both sides. The back plate 112 is grounded, and bias voltages are applied to the side plates 203 and 204 by bias power supplies 205 and 206, respectively.

In this configuration, the flow of ions into the side plates 203 and 204 is reduced. Further, corona discharge mainly occurs between the wire 201 and the back plate 202, and the ion wind flows in a direction away from the photoreceptor drum. Therefore, damage to the photoreceptor is reduced.

(Effects of the Invention) In the corona discharge device according to the present invention, since the electric field near the discharge opening is weak and the electric field near the discharge opening is strong, the ion current prevents a strong ion wind from flowing toward the photoreceptor,
Moreover, the amount of ions flowing into the stabilizer plate is reduced, the transpower can be reduced, and the cost can be reduced. Also,
Improves discharge stability. The amount of ozone generated is reduced, and since ozone is prevented from flowing toward the photoreceptor, damage to the photoreceptor is reduced.

The corona discharge device includes a corotron discharge device that controls discharge by applying voltage to the wire, and a screen grid (ion flow control grid) placed between the wire and the photoreceptor. A scorotron discharge device is included to control the potential of the scorotron. The invention applies to both.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a schematic configuration of a corona discharger. FIG. 2 is a perspective view of the corona discharger. FIG. 3 is a diagram of electric lines of force obtained as a result of electric field analysis in an example of a corona discharger. 4 and 5 are diagrams of electric lines of force of a comparative example of the corona discharger of FIG. 3, respectively. 6 and 7 are diagrams of electric lines of force obtained as a result of electric field analysis in modified examples of the corona discharger, respectively. FIG. 8 is a diagram of electric lines of force of a comparative example of the corona discharger of FIG. 6. FIG. 9 is a diagram showing a schematic configuration of a modified example of the corona discharger. 1O(a) and (b) are a sectional view and a top view, respectively, of a modification of the corona discharger of FIG. 9. FIG. 11 is a diagram showing a schematic configuration of another modification of the corona discharger of FIG. 9. FIG. 12 is a diagram showing a schematic configuration of a modified example of the corona discharger. FIG. 13 is a diagram showing a schematic configuration of another modification of the corona discharger. FIGS. 14 and 15 are diagrams each showing a schematic configuration of a modification in which the bias voltage is associated with the ion flow control voltage. FIG. 16, FIG. 17, and FIG. 18 are diagrams each showing a schematic configuration of a modified example in which the ion wind is flowed in an oblique direction. FIG. 19 is a diagram showing a schematic configuration of a modified example in which the back plate is divided. FIGS. 20 and 21 are diagrams each showing a schematic configuration of a modified embodiment in which the ion flow is controlled by the position of the stabilizer. FIG. 22 is a diagram showing a schematic configuration of a transfer device according to the present invention. 1... Corona discharge wire, 2... Back plate, 3.4...
- Side plate, 5... Ion flow control grid, 6... Photosensitive drum, 11-14... Power supply, 41.42... Mylar plate, 51.52... Resistance member, 61.62.・・・
Varistor, 101... Back plate, 102.103... Side plate, 113... Power supply, 121.122, 131, 13
2...Side plate. Figure 1 Patent Applicant Minolta Camera Co., Ltd. Agent Patent Attorney Aoyama Ao et al. Figure 3 Figure 5 Figure 6 Figure 7 Figure 8 Evening 1 o (b) Figure 12 Figure 13 Figure 14 Figure 15 Figure 19 Figure 16 Figure 17 Figure 20 Figure 21

Claims (1)

[Claims] (1) Consists of a corona discharge wire and a shield plate that surrounds the corona discharge wire and is formed with a discharge opening and an ozone discharge opening. A corona discharge device characterized by having a configuration in which the electric field is stronger than the electric field near the discharge opening.