JPH05107876A - Electrostatic charging device fitted to be used in image forming device - Google Patents

Abstract

PURPOSE:To lower hum noise and leakage current caused by high frequency discharge while a merit by the high-frequency discharge is kept by providing plural discharge electrodes and impressing plural kinds of voltage whose phase and (or) waveform is different on the respective electrodes. CONSTITUTION:A primary electrostatic charger 2 is disposed close to an image carrier 1. The surf ace of the image carrier 1 is uniformly electrostatically charged by electrostatic charging bias impressed by the primary electrostatic charger 2. The discharge electrodes 2-1 and 2-2 connected to power sources V1 and V2 are disposed in the primary electrostatic charger 2. The discharge electrodes 2-1 and 2-2 are electrostatic charge wires or needle electrodes. In the respective power sources V1 and V2, a low-frequency pulse wave is outputted according to a control signal C in a state where the phase thereof is shifted by 1/2 cycle. Therefore, the frequency of a discharge current from the aperture part of the charger 2 becomes the sum of the frequencies of respective pulse waves, that is, twofold frequency. Thus, high-frequency output is obtained on the electrostatic charging surface of the image carrier 1 by inputting the bias of comparatively low frequency.

Description

Detailed Description of the Invention

[0001]

[Object of the Invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device suitable for use in a copying machine, a printer or the like which uses an electrostatic transfer process.

[0002]

2. Description of the Related Art In a known image forming apparatus including a step of electrostatically forming a toner image on a charged surface of an image carrier and electrostatically transferring the toner image to a transfer material such as paper. , When initially charging the photosensitive layer on the surface of the image carrier, transferring the toner image to the transfer material, and then separating the transfer material from the image carrier, a corona discharger (hereinafter referred to as a charging device) is used. It is widely practiced to impart a charge to a charged surface or to neutralize and remove the charge.

The charging device will be briefly described below.
For example, it is common to apply a DC voltage mainly to a primary charger that uniformly charges the surface of the image bearing member, a transfer charger that is used for transfer, etc., and it is only to secure a uniform charged state. It is difficult to use a grid because it is difficult, but in any case, the charging efficiency against the supplied current is low, and the discharge current is large, so ozone is easily generated, and the charger is easily contaminated. In order to avoid such a point, there has been proposed a method in which pulse charging, AC charging, and particularly application of a high frequency bias is used to obtain charging uniformity.

Further, it has been proposed to apply an AC separation bias to a separation charger that promotes separation of the transfer material from the image carrier after the transfer. In this case, in order to enhance the charge removal effect of the transfer material, an applied bias is applied. Peak-to-peak voltage V
It has been found that increasing the frequency of the applied bias is effective for preventing the occurrence of separation failure and retransfer caused by increasing pp.

By the way, applying a high frequency bias to the charging device inevitably causes problems such as corona hum noise and increased leakage current.

The present invention has been made in order to cope with such a situation, and in the corona discharger (charging device) as described above, a plurality of charging lines are provided inside and the phase and the waveform are respectively formed. It is an object of the present invention to provide a charging device in which a low frequency voltage outside the audible range, which is different from the above, is applied, and a high frequency corona discharge current is finally obtained from the discharger.

[0007]

[Constitution of the invention]

In order to achieve the above object, the present invention provides a charging device which uses corona AC discharge or pulse discharge to charge a surface to be charged.
A plurality of discharge electrodes are provided, a plurality of voltages having different phases and / or waveforms are applied to each electrode, and the charging device outputs a discharge having a frequency to which the plurality of voltages are applied. It is a thing.

With such a structure, a high frequency output can be obtained on the charging surface by inputting a bias having a relatively low frequency. Therefore, while maintaining the advantage of the high frequency discharge, hum and leakage associated therewith can be obtained. The current can be reduced.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [FIG. 1] FIG. 1 is a schematic side view of a primary charging portion showing an embodiment of the present invention, in which a primary charger 2 is disposed in the vicinity of an image carrier 1 traveling in a direction of an arrow shown in the drawing. Yes,
It is assumed that the surface of the image carrier 1 is uniformly charged by the charging bias applied by this, and the imagewise exposure E is applied to the charged surface to form an electrostatic latent image. Image carrier 1
Needless to say, a developing portion, a transfer portion, a cleaning portion, and the like are further provided in the vicinity of, but they are omitted because they are not directly related to the present invention (in the embodiments below. The same applies to the case).

The primary charger 2 is provided with discharge electrodes 2-1 and 2-2 connected to power sources V ₁ and V ₂ , respectively, and their outputs are shown in FIG. 2 by a control signal C. As described above, the low-frequency pulse waves are output with their phases shifted by 1/2 cycle.

As a result, the discharge current from the opening of the charger 2 has a frequency twice that of each pulse wave. In this case, two pulses having the same waveform were used, but it goes without saying that the number of pulses is not limited to this. In the above example, the same-wave output from the two power supplies is phase-shifted by the control signal, but the invention is not limited to such a method.
For example, take multiple outputs from one power supply
It is also possible to interpose a capacitor between the output source below and the charger and shift the phase.

With this configuration, the input side is composed of a plurality of low frequencies regardless of the high frequency on the output side. Therefore, while maintaining the effect of applying the high frequency, corona hum and Leakage current can be reduced.

FIGS. 3A, 3B, 4A and 4B show another embodiment, in which a needle electrode is used as the electrode of the charger, and the tip of the electrode connected to the power sources V ₁ and V ₂ is used. Is "Fig. 4
As shown in "B", they are arranged alternately,
These are arranged linearly in the charger 2 as shown in FIG. 4A. The mode of use is arranged as shown in FIG. 3, and by applying the same bias as that of the above-mentioned embodiment to each electrode, it is possible to obtain the discharge current of double frequency. By configuring in this way,
It is possible to narrow the charging range of the surface to be charged, as compared with the case of using the charging line.

FIG. 5 is a schematic side view showing a case where the present invention is applied to a transfer device. When the toner T supplied at the developing site (not shown) arrives at the transfer site where the image carrier 1 and the transfer charger 3 face each other, the transfer material P is supplied to the transfer site at a timing corresponding to the transfer site. A transfer bias is applied by the charger 3, the toner T on the image carrier side is transferred to the transfer material by the action of the electric field formed by the charging device 3, and then the transfer material is separated from the image carrier 1 by the action of the separation charger 4.
Furthermore, it shall be conveyed to a fixing part (not shown).

In such a structure, three charging lines 3-1, 3-2, 3-3 are provided inside the transfer charger 3 and the phases thereof are shifted by 1/3. Three biases were applied as shown in FIG. 7 by V ₃ , V ₂ and V ₁ .

In order to measure the corona discharge current obtained by the transfer charger having such a structure, as shown in FIG. 6, the charging lines 3-1, 3-2, 3-3 of the charger are turned on. Then, the current I ₂ 'flowing into the conductive plate 5 was observed with an oscilloscope using a resistor R. As a result, a waveform as shown by I ₂ ' in FIG. 7 was confirmed, and the corona of the frequency 3f was confirmed by the bias of the frequency f. A discharge could be generated.

FIG. 8 is a schematic side view showing an embodiment in which the present invention is applied to a separation charger, in which the toner T adhering to the surface of the image carrier 1 traveling in the direction of the arrow in FIG. When the body 1 and the transfer charger 2 arrive at a transfer site where they face each other, a transfer bias is applied to the transfer charger 2 by a power source 2 ′, and the toner is transferred to the transfer material.

A separation charging device 3 is disposed downstream of the transfer charging device 2 as viewed in the running direction of the image carrier, and when the transfer material arrives at this position, the separation charging device shows the transfer charging condition. By applying a separation bias of opposite polarity, the transfer material neutralizes and removes the charge obtained during transfer, and the transfer material separates from the image carrier due to its elasticity and stiffness, and proceeds to a fixing part (not shown). To do.

In such a device, three charging lines 3-1, 3-2, 3-3 are provided inside the separation charger 3 and the phase relationship of the output voltages is controlled by the controller C. Separation bias is applied by the adjusted power supplies V ₁ , V ₂ , and V ₃ .

A pulse voltage as indicated by the same reference numeral in FIG. 9 is applied to each of the charging lines 3-1, 3-2, 3-3, the same as shown in FIG. 6 above. The voltage V ₄ due to the corona current I and the resistance R (preferably about 10 ⁸ Ω) obtained by using the above device was observed with an oscilloscope to confirm the waveform as shown in the lower part of FIG. That is, discharge of frequency 3f could be generated by three power sources of frequency f.

"FIG. 10", "FIG. 11" and "FIG. 12",
Each of "Fig. 13" shows another actual state,
"0" and "Fig. 12" schematically show the structure of the separation portion in which the separation charging device is arranged in close proximity to the image carrier. The former has two charging lines and the latter has four charging lines. FIG. 11 and FIG. 13 show the respective separate chargers 3.
The output discharge current obtained from the above is shown. In each configuration, the portions corresponding to those of the device of the above-described embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. From these, in the former case, the discharge current of frequency 2f is generated by the two power sources of frequency f, and in the latter case, the frequency f is used.
It can be seen that a discharge current having a frequency of 4f can be obtained by the four power supplies.

Although not shown, also in the case of the above-described separate charger, a charger using a needle-shaped electrode as shown in the above-mentioned "FIG. 3", "FIG. 4A", and "FIG. 4" is used. You can immediately see that you can use.

FIG. 14 shows another embodiment, and FIG.
FIG. 3 is an explanatory view showing the arrangement of the needle-shaped electrodes. As can be readily understood from the figure, the charger 3 is provided with three sets of electrodes, two of which have the electrode arrangement as shown in FIG. One electrode is arranged independently, and a bias is applied by _three power sources V ₁ , V ₂ and V ₃ .

[0024]

As described above, according to the present invention, in a charging device for applying a high-voltage AC bias to charge a surface to be charged, a plurality of relatively low-frequency biases are appropriately changed in phase and waveform. Since it is configured such that a high frequency bias is applied to the charging surface by changing the application, it is possible to prevent the generation of noise and the increase of the leakage current due to the application of the high frequency bias. It has a remarkable effect when applied to a charging device.

[Brief description of drawings]

FIG. 1 is a side view schematically showing a configuration when the present invention is applied to a primary charger of an image forming apparatus.

FIG. 2 is a diagram showing a relationship between an input waveform and an output waveform of the above.

FIG. 3 is a schematic side view of a primary charger showing another embodiment.

FIG. 4A and

FIG. 4B is a plan view showing the configuration and arrangement of electrodes of the charger and a perspective view of the electrodes.

FIG. 5 is a schematic side view showing a configuration when the present invention is applied to a transfer charger.

FIG. 6 is a block diagram of an apparatus for inspecting the relationship between the input and output of the same as above.

FIG. 7 is a waveform diagram showing an input waveform and an output waveform of the same device.

FIG. 8 is a side view of a charging device showing a case where the present invention is applied to a separation charging device.

FIG. 9 is a waveform diagram showing the relationship between the input waveform and the output waveform of the same as above.

FIG. 10 and

FIG. 12 is a schematic side view showing another embodiment in which the present invention is applied to a separation charger.

FIG. 11 and

FIG. 13 is a waveform diagram showing the relationship between the input waveform and the output waveform, respectively, which are the same as above.

FIG. 14 is a schematic side view showing still another embodiment in which the present invention is applied to a separation charger.

FIG. 15 is a plan view showing the electrode arrangement of the charger as above.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier 2 Primary charger 2-1, 2-2, 2-3 Charging line 3 Separation charger 3-1, 3-2, 3-3 Charging line 5 Conductor plate 6 Transfer charger

Claims (6)

[Claims] 1. A charging device using corona discharge current or pulse discharge to charge a surface to be charged, wherein a plurality of discharge electrodes are provided and a plurality of voltages having different phases and / or different waveforms are applied to each electrode. The charging device is suitable for use in an image forming apparatus that outputs a discharge having a frequency to which a plurality of voltages are applied from the charging device. 2. The charging device according to claim 1, wherein the charging device is a primary charger of the image forming apparatus. 3. The charging device according to claim 1, wherein the charging device is a transfer charging device of an image forming apparatus. 4. The charging device according to claim 1, wherein the charging device is a separate charging device of the image forming apparatus. 5. The charging device according to claim 1, wherein the electrode is a charging wire. 6. The electrode according to claim 1, wherein the electrodes are a plurality of needle-like electrodes arranged so as to alternately apply voltages having different phases and / or different waveforms. Charging device.