JPS6339915B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a static eliminator that eliminates static electricity by electrically neutralizing an electrostatic latent image formed on a dielectric material with a charge having a polarity opposite to that of the latent image charge.

FIG. 1 is a schematic diagram of an electrostatic transfer type recording device used in conventional facsimile machines, copying machines, and the like. The drum 1 is rotatably provided in the direction of arrow A, and as the drum 1 rotates, an electrostatic latent image charge is first applied by the recording head 4 to the dielectric 2 which has been neutralized in the vicinity of OV. be done. Next, the toner in the developing device 5 adheres to the latent image on the dielectric material 2 by Coulomb force and is visualized. The transfer device 8 transfers the toner 6 on the dielectric material 2 developed by the Coulomb force of the generated corona onto the transfer paper 7.
The transfer paper 7 is fed out in the direction of arrow B from the transfer paper stacking table 13 by a feeding means 14 such as a feeding roller,
It is in contact with the dielectric 2 at the location where the transfer device 8 is provided. The transfer paper 7 on which the transfer has been completed is peeled off from the dielectric 2 by corona generated by the peeler 9.
Thereafter, the sheet is further fed out in the direction of arrow B by the feeding means 14 and fixed by the fixing device 11. This means that the transfer to the transfer paper 7 is complete,
After the transfer, the dielectric 2 on the drum 1 is fully charged with the same polarity as the electrostatic latent image by the pre-charger 10, and after the surface potential of the dielectric 2 is made almost uniform, it is cleaned. Residual toner is removed by device 12. The dielectric 2 that has been cleaned is charged to the opposite polarity to the latent image charge by the static eliminator 3 for reuse, and the surface charge is neutralized.

By the way, as the static eliminator 3 conventionally used, a corona charger as shown in FIG. 2 has been used. The configuration of the corona charger is roughly divided into a corotron shown in FIG. 2A, which consists of a shield plate 15 and a corona wire 16, and a scorotron, shown in FIG. be done. The corotron of A is made by applying a DC high voltage of opposite polarity to the latent image charge, which is usually around 7 Kv, to the corona wire 16, so that the corona wire 16 has a voltage of about 1.5 kW.
A corona discharge is caused between the shield plate 15, which is located cm away, and charged particles (ozone O _3, etc.) are converted into corona beams.
The dielectric material 2 is sprayed and charged at a distance of 1.6 to 1.7 cm. However, in static elimination using a corotron, it has been difficult to uniformly eliminate static electricity at a set potential because the distribution of the electrostatic latent image is not uniform and the amount of discharge increases when humidity is high.

The scorotron shown in FIG. 2B is used to eliminate static electricity more uniformly than the corotron. Static elimination using the scorotron first involves parallel line grid 1.
When a DC voltage is applied to 7, a corona current flows through the dielectric 2 and the parallel wire grid 17. When the surface potential of the dielectric 2 exceeds the grid potential, all corona current flows to the parallel grid 17, and no further discharge occurs. Usually parallel grid 1
7 voltage is set to OV. However, static elimination using a scorotron has the disadvantage that most of the corona current flows through the parallel wire grid 17, resulting in extremely poor static elimination efficiency and slow static elimination speed.

In general, when removing charges using a corona charger, it is desirable to keep the potential difference between the latent image area and the non-latent image area below a certain value in order to prevent uneven charge removal. In addition to the need for precharging with a charger, the first
Second, corona discharge generates a large amount of ozone _O3 , which causes a bad odor and is harmful to the human body.Secondly, high voltage switching is required to turn on and off the corona charger that discharges. Therefore, there were problems such as this causing noise generation.

The present invention has been made in view of the conventional problems, and provides a static eliminator that does not require precharging, can completely eliminate latent image charges at low voltage, and does not generate ozone or noise. The purpose is to provide.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A static eliminator according to an embodiment of the present invention will be described below with reference to the drawings.

First, the principle of the present application is to use a main electrode 18 connected to a power supply 19 with a polarity opposite to that of the latent image charge 20 as shown in FIG. In this method, a direct discharge is caused, and the latent image charge 20 is electrically neutralized by the generated ions, thereby eliminating the charge.

FIG. 4 schematically shows this static elimination method. In the figure, A indicates the start of discharge, and positive ions 23 are generated. B is
This shows that the positive ions 23 that have reached the dielectric 21 are electrically neutralized with the negative latent image charges 20. The surface potential of the dielectric 21 after neutralization has shifted to the positive side. This discharge continues until the discharge critical potential falls below the discharge critical potential according to the Patsien curve according to Patsien's law, which will be described later. At this time, since the non-latent image portion also does not rise above the discharge critical potential, the surface potential of the dielectric 21 is uniformly removed.

This will be specifically explained using FIGS. 5 to 10.
FIG. 5 is an external view of a static eliminator according to an embodiment of the present invention, in which plate-shaped auxiliary electrodes are arranged on both sides of the plate-shaped main electrode 18 provided on the insulator 27 so as to be sandwiched therebetween. 28 are integrally arranged.
Therefore, the main electrode 18 and the sub-electrode 28 are separated,
Compared to a configuration in which the dielectric material 21 is sandwiched between the main electrode 18 and the sub-electrode 28, there are advantages such as easier adjustment between the two electrodes. Furthermore, as a device that can achieve substantially the same effect as this, it is also possible to have a plate-shaped sub-electrode 28 integrally arranged adjacent to the plate-shaped main electrode 18 and only on one of the electrodes. In either case, manufacturing is extremely easy using electrostatic recording head manufacturing technology.

Next, the operation of the static eliminator having the above-described structure will be explained below.

FIG. 6 is a block diagram of a control circuit of the static eliminator shown in FIG. 5, and FIG. 7 is an operating waveform diagram thereof. Whether the latent image charge 20 is positive or negative, it simply reverses the polarity of the voltage applied to the main electrode 18 and the sub-electrode 28, and only the case where the latent image charge 20 is negative will be described here. The synchronization signal generation circuit 31 outputs a one-line synchronization signal a. The period of the synchronization signal a is T, and the dielectric 21
During that time, the image is sent by one scan in the sub-scanning direction. The application number setting switch 29 is set to one period T of the synchronization signal a.
During this period, the number of pulses to be applied to the main electrode 18 and the sub-electrode 28 is set, and in this embodiment, it is set to four times. The application timing control circuit 30 generates a timing pulse b based on the line synchronization signal a from the synchronization signal generation circuit 31 and the signal from the application number setting switch 29. The main electrode drive circuit 32 and the sub-electrode drive circuit 33 are
When the timing pulse b from the application timing control circuit 30 is input, application pulses c and d whose voltage levels have been converted are outputted. The positive applied pulse c is applied to the main electrode 18, and the negative applied pulse d is applied to the sub-electrode 28. However, as described below, since a discharge is caused by the potential difference between the voltages of both electrodes, the dielectric 21 is grounded. Compared to the case where control is performed using a single main electrode, static electricity can be removed with a lower voltage applied to the main electrode.

The main electrode 18 and the sub-electrode 28 are capacitively coupled via the dielectric 21 and the conductor 22, and the opposing area of the main electrode 18 with respect to the dielectric 21 is the area of the sub-electrode 28.
If the resistance value of the conductor 22 is appropriate, the pulse voltage value applied to the main electrode 18 is sufficiently small compared to the facing area of
A difference between V _P and the pulse voltage value V _F applied to the sub-electrode 28 is applied between the main electrode 18 and the dielectric 21, and when this potential difference (V _P −V _F ) exceeds the critical potential for discharge, a discharge occurs. The critical potential of this discharge can be determined by the Patsien curve according to Patsien's law shown in FIG. In other words, the Patsien curve shown in FIG. 8 shows the relationship between the gap length between the main electrode 18 and the dielectric 21 and the discharge voltage required to cause a discharge. The setting indicates that discharge can be performed at the lowest voltage. Therefore, the gap length between the main electrode 18 and the dielectric 21 in the present invention is C(μ), which is the minimum value of the discharge voltage on the Passien curve.
is the most preferable, but there is no limitation thereto, and the designer may determine a preferable gap length according to the Patsien curve. As a result of experiments, the upper limit of this gap length is about 30μ, and good results can be obtained with a gap length of 8 to 14μ. When a discharge occurs, the surface potential of the dielectric 21 reaches a predetermined potential (saturation potential Va to be described later) through the process shown in FIG. 4, and when this potential is reached, the discharge stops. This principle is explained in the 9th
This will be explained with reference to the figures and FIG. 9th
The figure shows a main electrode 18, a sub-electrode 28, and a dielectric 21.
The potential difference (V _P −V _F ) between the applied pulse voltage value V _P of the main electrode 18 and the applied pulse voltage value V _F of the auxiliary electrode 28 when the distance between them is constant, and the dielectric 2 after static electricity removal.
1 shows the relationship between the surface potentials of No. 1. That is, when the distance between the main electrode 18 and the dielectric 21 is kept constant, the threshold of the potential difference that causes a discharge is V _T , the surface potential of the dielectric 21 before discharge is V _S , and the saturation potential of the dielectric 21 after discharge Let V _a be (V _P −V _F )−V _S
Discharge occurs at V _P −V _F satisfying >V _T and stops when the surface potential V _S of the dielectric 21 reaches (V _P −V _F )−V _S =V _T. At this time, V _S =V _a . The number of applications from the start of this discharge and the dielectric 2
FIG. 10 shows the relationship between the surface potentials of No. 1. When the distance between the main electrode 18 and the sub-electrode 28 and the dielectric 21 is kept constant, the surface potential of the dielectric 21 is
It can be seen that as the number of times the discharge is applied increases, the latent image charge is neutralized and V _{S is finally saturated with V S =} V _a , and does not rise above a constant value Va. Therefore, if V _P +V _F is selected so that Va is close to OV, the latent image charge on the dielectric 21 will be removed by discharge. As is clear from Figure 10, the saturation potential Va is approximately OV, but this is because Va is not set to a very large value so as not to affect the re-formation of the image by the recording head after charge removal. be. In addition, the polarity of Va is set to be opposite to the electrostatic latent image, but this is due to the slight difference in the unevenness of the dielectric surface between the main electrode 18 and the dielectric 2.
Generally, the gap length between
This is to prevent the occurrence of a portion where discharge does not occur in the recessed portion and where static electricity cannot be removed, and to ensure static electricity removal.

Specific experimental values are as follows. for example,
If the electrostatic latent image potential V _S is -100V, the gap length between the main electrode and the dielectric is 10μ, and the saturation potential Va is 10V, then the potential difference between the main electrode and the sub-electrode is approximately
Connect the main electrode to 360V (350V+10V...350V is the discharge starting voltage when the gap length is 10μ).
Good static elimination results can be obtained by applying a voltage of -150V to each of the 210V sub-electrodes. In other words, the potential difference between the electrostatic latent image on the static eliminator and the electrode was initially 460V (360V-(-
100V)), discharge starts and the latent image potential increases.
When the voltage rises to 10V, the potential difference between the electrostatic latent image and the electrode becomes
The discharge stops because the voltage reaches 350V. From this, the residual potential at the location where the electrostatic latent image exists forms part of the discharge voltage, and the above-mentioned discharge is mainly performed directly against the location where the electrostatic latent image exists. It can be understood that the voltage rises and converges to the saturation potential Va like the other parts.
As is clear from the above description, the present invention relates to a plate-shaped main electrode arranged close to the movable dielectric surface on which an electrostatic latent image is formed and perpendicular to the moving direction thereof, and a plate-shaped main electrode arranged parallel to and parallel to the main electrode. A plate-shaped sub-electrode arranged nearby is integrally provided, and a voltage of opposite polarity to the electrostatic latent image is applied to the main electrode, and a voltage of the same polarity as the electrostatic latent image is applied to the sub-electrode, respectively. Discharging means for directly discharging between the main electrode and the dielectric surface is disposed immediately before the electrostatic latent image is formed, and the applied voltage and the residual potential at the location where the electrostatic latent image exists A discharge voltage is obtained and discharge is started, and the discharge is stopped by neutralizing the residual charge due to the discharge to make the discharge voltage equal to or less than the discharge voltage threshold according to Patsien's law, and the dielectric material after discharge is The potential of the surface is of opposite polarity to the electrostatic latent image polarity and approximately
The distance between the electrode and the dielectric is set near the minimum value of the discharge voltage according to Patsien's law, which gives OV, and precharging is not required, ozone and noise are not generated, and the latent image charge is reduced. This has the effect that complete static elimination can be performed efficiently at low voltage. In addition, since the voltage is applied through the main electrode and the sub-electrode, it is possible to lower the voltage applied to the main electrode, and the manufacturing of the static eliminator itself is extremely simple, using the manufacturing technology of so-called electrostatic recording heads. It also has the advantage of being easy to perform.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of an electrostatic transfer type recording device used in conventional facsimile machines, copying machines, etc., Fig. 2 A and B are external views of a conventional static eliminator, and Fig. 3
4A, B, and C are diagrams showing the principle of static elimination according to the present invention, FIG. 5 is a perspective view of the static elimination device according to the present invention, and FIG. 6 is a block diagram of the control circuit of the static elimination device. 7a to d are operational waveform diagrams, FIG. 8 is a Patsien curve, FIG. 9 is a diagram showing the relationship between the voltage applied to the electrode of the static eliminator according to the present invention and the surface potential of the dielectric, and FIG. FIG. 10 is a diagram showing the relationship between the number of application pulses applied to the electrodes of the static eliminator according to the present invention and the surface potential of the dielectric. 1...Drum, 2, 21...Dielectric, 3...Static eliminator, 4...Recording head, 5...Developer, 7...
Transfer paper, 8...Transfer device, 9...Peeler, 10...
Pre-charger, 11... Fixing device, 12... Cleaning device, 18, 26... Main electrode, 22... Conductor, 24, 27... Insulator, 25, 28... Sub-electrode, 29... Application Number of times setting switch, 30... Application timing control circuit, 31... Periodic signal generation circuit, 32... Main electrode drive circuit, 33... Sub electrode drive circuit.

Claims (1)

[Claims] 1. A plate-shaped main electrode arranged close to the movable dielectric surface on which an electrostatic latent image is formed and perpendicular to its traveling direction, and a plate-shaped sub-electrode arranged parallel to and near this main electrode. are integrally provided, and a voltage of opposite polarity to the electrostatic latent image is applied to the main electrode, and a voltage of the same polarity as the electrostatic latent image is applied to the sub-electrode, so that the main electrode and the dielectric surface are connected to each other. A discharging means for directly discharging between the electrostatic latent images is placed immediately before the electrostatic latent image is formed, and a discharging voltage is obtained from the applied voltage and the residual potential at the location where the electrostatic latent image is present to start discharging. ,
The discharge is stopped by neutralizing the residual potential due to the discharge and making the discharge voltage below the discharge voltage threshold according to Patsien's law. A static eliminator characterized in that the distance between the electrode and the dielectric is set near the minimum value of the discharge voltage according to Patsien's law, which has opposite polarity and approximately OV.