JPS6250857A - Electrostatic charging device - Google Patents

Abstract

PURPOSE:To reduce the size of a device and to perform constant electrostatic charging by obtaining an AC and a DC voltage by a single transformer means. CONSTITUTION:An electrostatic discharging member 1 is composed of an induction electrode put in a dielectric 4 and a linear discharging element 3 and a member 5 to be charged electrostatically is formed of an insulator or photoconductor on a conductive base 6 and moves horizontally. When the AC voltage of the winding 14 of a transformer 12 is applied, the electrode 3 generate positive and negative ions and the member 5 to be charged is charged electrostatically by extracting necessary ions with the bias voltage generated by rectifying the AC voltage of the winding 15. Thus, the AC and DC voltages are obtained by the single transformer means to reduce the size of the electrostatic charging device.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a charging device that can be used in electrostatic recording, electrophotographic devices, and the like.

11 Ai Traditionally, in electrostatic recording and electrophotographic equipment, wire diameter 0
．． Corona charging devices that perform corona discharge by applying a high voltage to a wire of about 1 mm are widely used. However, such a corona charging device has the disadvantage that the wire is thin and easily damaged, and furthermore, dirt on the wire causes uneven discharge, resulting in non-uniform charging of the charged object.

Furthermore, it is necessary to maintain a certain distance between the wire and the conductive shield member surrounding the wire, which limits the miniaturization of the corona charging device.

On the other hand, as another charging device, an alternating current voltage is applied between electrodes that sandwich a dielectric material, thereby generating positive and negative ions at the junction between the end face of one electrode and the dielectric material, and applying an external electric field. to extract ions of desired polarity (Unexamined Japanese Patent Publication No. 5
Publication No. 4-53537, patent application filed by the applicant in 1982
No. 187399).

FIG. 1 shows the basic configuration of this type of device, in which a discharge member 1
is arranged with respect to the charged member 5 and has a dielectric 4, an induction electrode 2, and a discharge electrode 3. Induction electrode 2 and discharge electrode 3
During this period, alternating voltages are applied by the alternating voltage applying means 7, while the charged member 5, which moves in the direction of arrow A relative to the discharge member 1, is an insulator or photoconductive member on a conductor base 6. A bias voltage is applied between the conductor base 6 and the discharge electrode 3 by a bias voltage applying means 7. By applying an alternating voltage between the induction electrode 2 and the discharge electrode 3, a discharge is caused from around the discharge electrode 3,
After generating sufficient positive and negative ions, the charged member 5 is charged by selectively extracting the above pressure or negative ions using an electric field caused by a bias voltage applied between the discharge electrode 3 and the conductive substrate 6. It is something that makes you

In such a device, the thickness of the 1M electric body 4 is reduced (
For example, the thickness is 500 pm or less, preferably 20 to 2
0 OILm), stable discharge can be obtained with a lower applied voltage (for example, about 1.5 to 2.5 KV peak-to-peak) than in conventional corona charging devices. Furthermore, the charging device can be made smaller than the conventional corona charging device.

This is because by reducing the thickness of the dielectric 4, the electric field strength between the two electrodes can be increased even if the alternating voltage applied between the two electrodes sandwiching the dielectric 4 is low. For this reason, if the electric field strength at the edge of one electrode (discharge electrode) is high enough to cause a discharge, discharge is possible, and a creeping discharge occurs along the surface of the dielectric 4 in contact with this electrode.

In this charging device, airborne particles adhere to the wire of a conventional corona charging device. It is said that it is suitable for uniform charging because it is difficult for the discharge electrode to become contaminated, such as so-called wire contamination.

However, this charging device has the disadvantage of requiring both an alternating voltage power supply and a bias power supply, thus increasing the size and cost of the device. moreover,
When actually charging with this charging device, in order to obtain uniform charging, the environment near the discharge electrode cannot be ignored.
In particular, it varies greatly depending on humidity, and uniform and stable discharge cannot be obtained under relatively high humidity (for example, relative humidity of 40% or more).

11 The present invention therefore provides a charging device of the above type, comprising:
The primary objective is to provide something small and inexpensive.

Another object of the invention is to provide a charging device capable of constant charging despite changes in the environment.

11 and 1 According to the present invention, a dielectric body, an induction electrode and a discharge electrode extending between the dielectric body, and a voltage applied alternately between the induction electrode and the discharge electrode to generate the discharge electrode. It has transformer means for applying both an alternating voltage that generates ions in the vicinity and an external electric field that acts between the discharge electrode and the charged object to extract the ions and charge the charged object to a specific polarity. Since a charging device characterized by the following is provided, the entire charging device can be made small and inexpensive.

real jl example Embodiments of the present invention will be described below based on the drawings.

FIG. 2 is a schematic diagram illustrating an embodiment of the charging device according to the present invention. The discharge member l is the same as that in FIG. 1, and includes a dielectric material 4, an induction electrode 2. It has a discharge electrode 3 and is arranged with respect to a charged member 5 such as an electrophotographic photoreceptor. Discharge electrode 3
is linear, and is arranged substantially parallel to the center line in the width direction of the induction electrode 2.

Here, as the dielectric material 4, relatively hard inorganic materials such as ceramic, mica, and glass, and flexible organic polymer materials such as polyimide, tetrafluoroethylene, polyester, acrylic, vinyl chloride, and polyethylene are used. etc. are used.

The charged member 5, which moves in the direction of arrow A relative to the discharge member 1, is an insulator or photoconductor on a conductive substrate 6.

The charging method is to apply alternate voltages between the induction electrode 2 and the discharge electrode 3 to cause discharge from around the discharge electrode 3, generate enough positive and negative ions, and connect the discharge electrode 3 and the conductor. By selectively extracting the pressure or negative ions using an electric field caused by a bias voltage applied between the substrates 6, the insulator or photoconductor surface of the charged member 5 is made to have a specific polarity.
And it is charged to a desired value. - The voltage waveform applied between the induction electrode 2 and the discharge electrode 3 may be any of a sine wave, a rectangular wave, a pulsed waveform, etc.

In this embodiment, alternate voltage application between the induction electrode 2 and the discharge electrode 3° and bias voltage application between the conductor base 6 and the discharge electrode 3 are performed by voltage application means IO.

The voltage application means 10 has a step-up transformer 12, which includes an input winding 13, a first output winding 14 that generates an alternating voltage applied between an induction electrode and a discharge electrode, and a discharge electrode. The second output side winding 15 generates power for the bias voltage applied to the second output side winding 15. Second output winding 1
5 is connected to a rectifier circuit, which includes a rectifier diode 16, a flattening capacitor 17. It has a resistor 18. A varistor 21 is connected in parallel with the resistor 18, which keeps the DC potential constant. The voltage thus rectified is applied to the discharge electrode 3.

As described above, according to this embodiment, since the alternating voltage and DC voltage required by the discharge member 1 are supplied by a single transformer, the device can be made smaller and less expensive.

In this embodiment, a resistor 19 is provided between the charged member 6 and the rectifier circuit, and a smoothing capacitor 20 is further provided in parallel with the resistor 19.

Since all the charging current flowing through the charged object 5 passes through the resistor 19, the charging current can be detected by detecting the potential across the resistor 19. A signal indicating the detected charging current is input to the constant current control circuit 21, and a control signal for making the charging current equal to a preset current value is input to the AC oscillation circuit 22. An AC signal having an amplitude uniquely determined by the signal from the constant current control circuit is output from the AC oscillation circuit 22, and is input to the input winding of the step-up transformer via the power amplifier circuit 23.

FIG. 3 shows the waveforms of each part.

25 is a signal from the constant current control circuit 21, which is based on the charging current detected by the resistor 19 as described above.

The waveform 26 is an alternating voltage output generated from the first output winding 14 and applied to the discharge member 1, and the voltage amplitude is modulated according to the output of the constant current control circuit.

The waveform 27 is the output of the second output winding, and is the waveform after passing through a rectifier circuit and a varistor, and as shown in the figure, a constant voltage can be obtained.

The constant current control circuit described above provides a charging device that can provide a stable and constant amount of charge even when environmental changes such as temperature and humidity occur. Moreover, even if the external electric field changes for some reason, this change is detected by the current detection section, and by controlling the frequency of the alternating voltage, it is possible to maintain the charging current at a predetermined value.

11 Standal difference j As explained above, according to the present invention, since both the alternating voltage and the DC voltage required by the discharge member are supplied by a single transformer, the device can be made more compact and inexpensive.

[Brief explanation of the drawing]

FIG. 1 shows the basic configuration of a conventional charging device, FIG. 2 shows a charging device according to an embodiment of the present invention, and FIG. 3 shows voltage waveforms at various parts in FIG. Explanation of symbols 1 is a discharge member, 2 is an induction electrode, 3 is a discharge electrode, 4 is a dielectric, 5 is a charged object, 7 is an AC power source, 8 is a bias voltage application means, 1O is a transformer means, 13 is an input side winding, 14
15 is a first output side winding, and 15 is a second output side winding. Figure 1 Figure 3

Claims (1)

[Claims] A dielectric, an induction electrode and a discharge electrode extending between the dielectric, and ions generated near the discharge electrode by applying alternating voltages between the induction electrode and the discharge electrode. and transformer means for applying both an alternating voltage to cause the charged object to be charged and an external electric field that acts between the discharge electrode and the charged object to extract the ions and charge the charged object to a specific polarity. Device