JP2987034B2 - Corona discharge device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a corona discharge device for uniformly charging an object to be charged by applying a corona discharge phenomenon used in, for example, an electrophotographic apparatus.

[0002]

2. Description of the Related Art FIG. 9 is a block diagram of an electronic copying machine which is an electrophotographic apparatus having a corona discharge device. The electronic copying machine is provided with a photosensitive drum 1 on which an outer peripheral surface is exposed to light L reflected from a document by optical scanning. The photoconductor drum 1 has a drum-shaped base made of a conductive material such as aluminum as a base and is rotatably supported on the drum. A photoconductive layer made of, for example, an organic photoconductor is formed on the surface of the base. Is driven to rotate in the direction of arrow A. When the above-mentioned reflected light L is exposed to the uniformly charged outer peripheral surface of the photosensitive drum 1, the electrostatic latent image corresponding to the image pattern of the document is formed on the outer peripheral surface. ing. Around the photosensitive drum 1, a charging charger 2 for charging the outer peripheral surface of the rotary drum 1 to a predetermined potential, and a photosensitive drum 1
A developing unit 3 for visualizing the electrostatic latent image formed on the photosensitive drum 1 as a toner image with a toner T, a transfer charger 4 for transferring the toner image formed on the photosensitive drum 1 to transfer paper P, and a photosensitive drum 1 A cleaner unit 5 for collecting the toner T remaining on the photosensitive drum 1 and a charge removing lamp 6 for removing the charge remaining on the photosensitive drum 1 are provided respectively. Further, as described above, the photosensitive drum 1 and the transfer charger 4
Transfer direction of transfer paper P conveyed between (direction of arrow B)
A fixing unit 7 for fixing the transferred toner image on the transfer paper P is provided on the downstream side. The charging charger 2 and the transfer charger 4 are each constituted by a corona discharge device.

[0003] The present invention relates to an improvement of this corona discharge device. The charging charger 2 has a configuration in which, for example, a corona discharge device 2c shown in FIG. 10 described later is supported by the shield case 2a and disposed in a U-shaped shield case 2a. Corona discharge device 2
The common electrode 10c is connected to a high voltage power supply + Vcc, and a high voltage of -3.5 kV is applied from the high voltage power supply + Vcc. A discharge is generated to charge the outer peripheral surface of the photosensitive drum 1.

The grid electrode 2b provided on the photosensitive drum 1 side of the shield case 2a controls the discharge current from the discharge electrode 9 by applying a voltage of -620 V from a high voltage power supply + Vcc, and The charging potential on the outer peripheral surface of the drum 1 is set and controlled to a predetermined potential of -600V.

On the other hand, the transfer charger 4 is configured similarly to the charging charger 2 except for the grid electrode 2b, and includes a shield case 4a having a U-shaped cross section and a shield case 4a.
A corona discharge device 4c shown in FIG. 10 is supported in a, and a high voltage power supply + Vcc is connected to the corona discharge device 4c.

When a high voltage is applied to the corona discharge device 4c from the high voltage power supply + Vcc, the transfer charger 4 generates a corona discharge from the tip of each discharge electrode to charge the back surface of the transfer paper P. The toner image formed on the outer peripheral surface of the photosensitive drum 1 is transferred onto the transfer paper P.

Conventionally, as a corona discharge device used for a charger, a transfer charger and the like in an electrophotographic process such as the above-mentioned electronic copying machine and printer, a diameter of 50 to 10 is used.
There is known a system in which a high voltage of 5 to 10 kV is applied to a 0 μm tungsten wire, and ions generated by the application of the high voltage are transferred to the surface of a photoreceptor to perform charging. However, in this method, in order to stabilize the discharge, a shield case is arranged at a certain distance from the tungsten wire, and further, a grid electrode is provided as a control electrode in order to make charging on the photoconductor uniform. Some are. Due to the unnecessary discharge from the tungsten wire to the shield case and the grid electrode, a large amount of ozone is generated, and there is a problem that an image is deteriorated or a human body is adversely affected.

In recent years, for example, Japanese Patent Application Laid-Open No. 63-152
As disclosed in Japanese Patent Publication No. 72-72, etc., a corona discharge device using a plurality of needle-shaped electrodes or saw-tooth-shaped discharge electrodes instead of a tungsten wire has been proposed.
This type of corona discharge device has significant structural and operational advantages over the wire type, with relatively high structural strength and low required applied voltage.

However, the discharge between the electrodes is non-uniform due to variations in the shape of the discharge electrode tips, breakage, contamination, and the like. In order to obtain uniform charging, a discharge current must be flowed more than necessary. Although it is about 1/5 of the wire method, the amount of ozone generated is still large. One solution to this problem is to connect each of the discharge electrodes to a power supply via a separate resistor, as disclosed in Japanese Patent Application Laid-Open No. Hei 5-2314, to reduce the current flowing through each of the discharge electrodes. Techniques for controlling and stabilizing are known.

FIG. 10 is a plan view of an example of this type of corona discharge device. A common electrode 10 is formed on an insulating substrate 8, and a plurality of needle-shaped discharge electrodes 9 are arranged at a pitch p, for example, 2 mm at a certain interval from the common electrode 10. 1.5 GΩ between the common electrode 10 and each discharge electrode 9
It is electrically connected to a common electrode 10 by a plurality of control resistors 11 composed of a chip resistor having a resistance value of about the same and a resistance element such as a polymer organic material containing carbon or the like. The discharge current flowing through each discharge electrode 9 is stabilized by lowering the applied voltage by a constant voltage.

[0011]

However, in a corona discharge device using this control resistor, it is difficult to make the resistance of the control resistor connected to each discharge electrode uniform, and it is difficult to make the resistance uniform. In this case, the cost of the resistance element becomes very high. When a high-molecular-weight organic material containing carbon or the like is used as the resistance element, although it can be manufactured at low cost, the resistance variation between the resistance elements is large (a general resistance variation rate ± 50% or more). As a result, the discharge current of each discharge electrode fluctuates, causing uneven charging. Furthermore, it is difficult to connect a separate resistance element to each discharge electrode in terms of manufacturing, and there is a problem that the manufacturing cost increases. SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a corona discharge device capable of uniformizing a discharge current and uniformly charging even if the resistance value of a resistance element is somewhat non-uniform.

[0012]

According to a corona discharge device of the present invention, a plurality of discharge electrodes are electrically connected to a common electrode via a first resistance element, respectively. Are electrically connected to each other via the second resistance element. Note that the first resistance element and the second resistance element are formed by an integral resistor.

[0013]

A plurality of discharge electrodes are electrically connected to a common electrode via a first resistance element, and adjacent discharge electrodes are electrically connected to each other via a second resistance element. Therefore, even if the current flowing through the first resistance element varies due to the resistance variation of the first resistance element, the current variation is reduced by the second resistance element, and the discharge current from each discharge electrode is made uniform. . Furthermore, the first
When the above-mentioned resistance element and the second resistance element are formed by an integral type resistor, the resistor becomes inexpensive, the assembling of the corona discharge device becomes easy, and the manufacturing cost can be reduced.

[0014]

1 is a plan view of a corona discharge device according to the present invention.

A common electrode 10 is formed on the insulating substrate 8, and a plurality of needle-shaped discharge electrodes 9 are arranged on the insulating substrate 8 at a certain interval from the common electrode 10. I have. As a specific example, the discharge electrode 9 is manufactured by etching a stainless steel plate having a thickness of 0.1 mm, the number of electrodes is 107, the pitch p between each electrode is 2 mm, and the tip of the discharge electrode 9 is an insulating substrate. 8 is attached to the insulating substrate 8 so that the protruding amount d from the end to the photosensitive drum side is 2 mm. Each of the common electrode 10 and the 107 discharge electrodes 9 has 107 first electrodes having a resistance of about 1.5 GΩ.
Are electrically connected via control resistors 11, 11... Further, adjacent discharge electrodes 9 are electrically connected to each other through 106 bypass resistors 12, 12... Each having a resistance value of about 500 MΩ. These resistive elements may be inexpensive chip resistors that are generally used as electric circuit components, or polyethylene, polyester, polymethane, nylon, polyamide, polyimide, polycarbonate having a predetermined resistance value mixed with carbon black or metal powder. And other organic materials. The resistance variation of the 107 control resistors 11 is as follows.
5 GΩ ± 50%, and the resistance variation of the 106 bypass resistors is 500 MΩ ± 50%. The common electrode 10 is connected to a high voltage power supply, and generates a corona discharge from the tip of each discharge electrode when a high voltage is applied from the high voltage power supply.

Next, a description will be given of the results of a simulation study of the discharge characteristics of the corona discharge device according to the present invention.

FIGS. 2 (a) and 2 (b) show a conventional model using only control resistors Rc1 to Rcn without using a bypass resistor, and a bypass between adjacent discharge electrodes according to the present invention, respectively. Resistance Rb1-R
It is an equivalent circuit of a model in which b (n-1) is additionally inserted.

Here, the resistances Rg1 to Rgn are the gap impedance between each discharge electrode and the discharge target, and the potential Vth.
Is a discharge starting voltage, and I1 to In are discharge currents discharged from the respective discharge electrodes.

FIG. 3 shows the results of an experiment on the discharge characteristics of a corona discharge device having a plurality of discharge electrodes, which was separately conducted. The discharge characteristics (VI characteristics) have an applied voltage V with respect to the discharge current I. It has a certain threshold value (discharge start voltage Vth), and after the start of discharge, the applied voltage V and the discharge current I have a substantially linear relationship. Also, the discharge starting voltage (Vt) for each discharge electrode
h) are substantially equal, and the discharge characteristics after the start of the discharge fall within the range indicated by the broken line. Void impedance (Rg = (V−Vth)
/ I) was different (variation rate about ± 30%) between the respective discharge electrodes, and this result was adopted as the simulation condition. The resistance variation rate (resistance variation) of the bypass resistors Rb1 to Rb (n-1) is determined by the control resistance R at that time.
The calculation was performed by setting the resistance change rates of c1 to Rcn to be equal.

FIG. 4 shows the relationship between the resistance variation rate (resistance variation) of the control resistor Rc and the variation amount (standard deviation σ) of the discharge current I obtained by simulation. That is, when the control resistor Rc has a variation of ± 16% or more, the method according to the present invention in which the bypass resistor Rb is inserted has a smaller variation in the discharge current I, and as a result, a more uniform charging potential is obtained. It can be seen that it can be obtained.

Next, using the conventional corona discharge device shown in FIG. 10 and the corona discharge device of the present invention shown in FIG. It is shown in Table 1.

[0022]

[Table 1]

In the conventional corona discharge device, the charging variation on the photosensitive drum is 80 V, whereas in the corona discharging device according to the present invention, the charging variation is 40 V, which is about 1/2.
The charging uniformity effect by the bypass resistance was actually confirmed.

Hereinafter, another embodiment of the present invention will be described. FIG. 5 is a plan view of an embodiment in which the control resistor 11 and the bypass resistor 12 in FIG. 1 are configured as a ladder-shaped integrated resistor 13a. The integrated resistor 13a is formed by processing a sheet made of an organic material such as polycarbonate mixed with carbon or the like and having conductivity into a ladder shape by pressing or the like, and mounted on the insulating substrate 8. In this case, the resistance value and the size and shape are set so that the distance between the common electrode 10 and each discharge electrode 9 is about 1.5 GΩ, and the distance between adjacent discharge electrodes is about 500 MΩ. By thus forming the resistor in an integral shape, the cost of the resistor can be reduced as compared with the case where a separate resistor element is inserted into each discharge electrode as in the previous embodiment, and the corona discharge device can be used. Productivity also increases.

FIG. 6 is a plan view of an embodiment in which the resistor is formed as a comb-shaped integral resistor 13b as in the previous embodiment. Needless to say, the same effect as in the previous embodiment can be obtained even when the resistor is formed in such a shape.

FIG. 7 is a plan view of an embodiment in which the resistor is formed as a rectangular sheet-shaped integral resistor 13c. It goes without saying that even if the resistor is formed in such a shape, the effect of improving the variation in the discharge electrode due to the bypass resistance can be obtained. Further, as compared with the ladder-shaped or comb-shaped resistor of the previous embodiment, the shape of the resistor is further simplified, so that the resistor is more inexpensive. Further, reference holes 14a for positioning when the resistor 13c is mounted on the insulating substrate 8 are provided at both ends in the longitudinal direction of the resistor 13c. By configuring the resistor in such a shape, assembly is further facilitated and mounting accuracy is improved.

FIG. 8 is a perspective view for explaining a specific mounting method of the rectangular integrated resistor 13c. Electrical connection between the integrated resistor 13c and each of the discharge electrodes 9 and the common electrode 10 is made via an anisotropic conductive adhesive film 15.
The anisotropic conductive adhesive film 15 is generally used for connecting a high-definition circuit such as a liquid crystal panel, and has a thickness of 30 μm.
Has conductivity in the thickness direction (resistance in the thickness direction 0.5Ω),
It has insulating properties (plane resistance: 10 ¹⁰ Ω) in the plane direction.
Therefore, the integrated resistor 13c is connected to the reference hole 14a and the positioning pin 1 via the anisotropic conductive adhesive film 15 as shown in the figure.
After positioning by 4b, the integral resistor 13c can be easily fixed on the insulating substrate 8 by bonding by thermocompression bonding, and furthermore, the integral resistor 13c can be easily fixed by the conductivity of the anisotropic conductive adhesive film 15 in the thickness direction. Electrical connection between the common electrode 10 and each of the discharge electrodes 9 through the connection electrode 13c is reliably performed, and the insulation between each of the discharge electrodes and the common electrode is also made by the anisotropic conductive adhesive film 15.
Is ensured by the insulating property in the surface direction of

Using the electrophotographic apparatus shown in FIG. 9 having the charging charger and the transfer charger provided with the corona discharging device according to the present invention, the charging potential on the photosensitive drum 1 was measured. As a result, the conventional corona discharging device was used. It was confirmed that charging characteristics with less variation than the electrophotographic device could be obtained. In a copy test using a halftone original, it was confirmed that a copy sample with less unevenness than the conventional method could be obtained.

In this embodiment, a charging charger and a transfer charger of an electrophotographic apparatus have been particularly described. However, the present invention is not limited to this. For example, a corona discharge device such as a static eliminator or a peeling device of an electrophotographic apparatus may be used. It goes without saying that it also applies to.

[0030]

As described above, according to the present invention, the variation in the charging characteristics of the corona discharge device is reduced, and the assembling of the device is facilitated, so that the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a plan view of an embodiment of the present invention.

FIGS. 2A and 2B are equivalent circuit diagrams of a conventional example and a model according to the present invention, respectively.

FIG. 3 is a graph of discharge characteristics of a discharge electrode.

FIG. 4 is a graph of a calculation result by a simulation.

FIG. 5 is a plan view of another embodiment of the present invention.

FIG. 6 is a plan view of another embodiment of the present invention.

FIG. 7 is a plan view of another embodiment of the present invention.

FIG. 8 is an illustration of the assembly of the device of FIG. 7;

FIG. 9 is a configuration diagram of an electronic copying machine.

FIG. 10 is a plan view of a conventional corona discharge device.

[Description of Signs] 8 Insulating substrate 9 Discharge electrode 10 Common electrode 11 Control resistor 12 Bypass resistor 13a, 13b, 13c Integrated resistor

──────────────────────────────────────────────────続 き Continuing on the front page (72) Shogo Yokota, 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (72) Inventor Hiroyuki Sawai 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (56) References JP-A-63-15272 (JP, A) JP-A-5-2314 (JP, A) JP-A-63-109473 (JP, A) JP-A-5-45999 (JP, A) Japanese Patent Publication No. 3-1663 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/02 G03G 15/14 G03G 15/16 G03G 21/06 H01T 19/00

Claims (5)

(57) [Claims] A plurality of discharge electrodes are respectively connected to a common electrode via a first resistance element, and adjacent discharge electrodes of the discharge electrodes are electrically connected to each other via a second resistance element. A corona discharge device being connected. 2. The corona discharge device according to claim 1, wherein the first resistance element and the second resistance element are formed by an integral resistor. 3. The corona discharge device according to claim 2, wherein the integral resistor has a ladder shape. 4. The corona discharge device according to claim 2, wherein the integral resistor has a comb shape. 5. The corona discharge device according to claim 2, wherein the integral resistor is rectangular.