JPH05158324A - Electrifier - Google Patents

Abstract

PURPOSE:To prevent the environmental influence of temperature, humidity, etc., and the mechanical influence of a vibration, etc., in an electrifier electrifying a photosensitive body. CONSTITUTION:A voltage fluctuated in the same polarity by a voltage generator 22, is applied to an electrifier 10 opposite to the photosensitive body 14. Thus, a potential difference is imparted between a high resistor 20 and the photosensitive body 14, corona discharging occurs, and a molecule existing between the high resistor 20 and the photosensitive body 14 is ionized. The generated negative ion is sent on the side of a photosensitive drum 16, so that the photosensitive body 14 is electrified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charger used in an electrophotographic image forming apparatus or the like and used to charge a charge receptor such as a photoconductor.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus or the like, a corotron charger 80 as shown in FIG. 3 is used, and the corotron charger 80 covers a discharge wire 82 with a shield case 84, Photoconductor 86 and conductor 8
8 is configured to face the photosensitive drum 89. Then, by applying a high voltage to the discharge wire 82, a corona discharge is generated between the discharge wire 82 and the photoconductor 86, and the discharge wire 8 is caused by this corona discharge.
The molecules existing between 2 and the photoconductor 86 are ionized.
The generated ions flow to the photoconductor 86 to charge the photoconductor 86.

On the other hand, a proximity type charger 90 as shown in FIG. 4 has also been proposed for the purpose of reducing the amount of ozone generated by further downsizing the charger. In this proximity type charger 90, a high electric resistance body 92 is attached to an electrode 91, and the high electric resistance body 92 is arranged close to a photosensitive drum 98 composed of a photosensitive body 94 and a conductor 96. Then, by applying a high voltage to the high electric resistance body 92, corona discharge is generated between the high electric resistance body 92 and the photoconductor 94, and the high electric resistance body 9 is generated by this corona discharge.
The molecules existing between 2 and the photoconductor 94 are ionized.
The generated ions flow to the photoconductor 94 to charge the photoconductor 94.

[0004]

However, in the former corotron charger 80, since the distance between the charger 80 and the photoconductor 86 is large, the ions generated at the bending angle also flow to other parts than the photoconductor 86. So it was not used effectively. Therefore, in order to charge the photoconductor 86, it is necessary to apply a high voltage to the discharge wire 82 in order to generate many ions, and accordingly, the amount of harmful ozone is increased. There is.

In the latter proximity type charger 90, the amount of harmful ozone is reduced, but if the resistance value of the high electric resistance 92 is lowered to increase the charge amount, the influence of temperature, humidity, etc. May cause spark discharge. And
If a spark discharge occurs, it takes time for the voltage of the charger 90 to rise again, so until the voltage of the charger 90 rises to a voltage sufficient to cause a discharge,
The discharge is stopped and an uncharged portion is generated on the photoconductor 94. Further, when the direct current voltage applied to the high electric resistance 92 is increased in order to increase the charge amount, the ions are excessively concentrated on the photoconductor 94, and the so-called streamer mode, which is generated by the repulsion of the ions of the same polarity, is entered. As a result, there arises a problem that the charging of the photosensitive member 94 has an island-shaped distribution.

Therefore, in the proximity type charger 90,
There are contradictory factors between the stable discharge and the increase in the amount of charge, and there is a narrow tolerance for environmental and mechanical influences to achieve uniform and stable charge. However, there is a drawback that it is difficult to design the structure.

The present invention has been made to solve the above-mentioned problems, and has a simple structure and is less susceptible to environmental influences such as temperature and humidity and mechanical influences such as vibration,
It is an object of the present invention to provide a charging device capable of stable operation.

[0008]

In order to achieve this object, the charger of the present invention comprises an ion generating means for ionizing molecules existing between electrodes by giving a potential difference between the electrodes and causing a discharge. The charge acceptor is charged by sending the ions generated by the ion generating means to the charge acceptor, and the control means is provided for changing the potential difference applied between the electrodes with the same polarity.

The control means may periodically change the voltage between the electrodes.

Further, the ion generating means may be arranged such that the high resistance body is arranged in the vicinity of the charge acceptor and a potential difference is applied between the high resistance body and the charge acceptor.

[0011]

The ion generating means in the charger of the present invention having the above-mentioned structure causes the control means to apply a potential difference that changes with the same polarity between the electrodes to cause a discharge and ionize the molecules existing between the electrodes. The ionized molecules are attracted to and charge the charge acceptor. At this time, even if the average potential difference is set large, the charge acceptor can be uniformly and stably charged without shifting to the streamer mode.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the charger of the present invention will be described below with reference to the drawings.

First, the structure of the charger used in the electrophotographic image forming apparatus will be described with reference to FIG.

The charger 10 includes a conductor 1 as shown in FIG.
2 is disposed opposite to the photosensitive drum 16 coated with the photoconductor 14, and an electrode 18 for keeping the surface on the opposite side of the photoconductor 14 at an equal potential, and a high resistance body 20 attached to the electrode 18. It consists of and. The conductor 12 is grounded and the electrode 18 is connected to a voltage generator 22.

The high resistance element 20 has a surface resistance of 1
Titanium oxide or tantalum nitride having a film thickness of 0 ⁶ to 10 ⁸ Ω and a film thickness of 1 μm or less is preferably used, and the distance between the high resistance body 20 and the photoconductor 14 is a value between 0.3 mm and 1.0 mm. Are arranged as follows. Furthermore, this voltage generator 2
2 is connected to the waveform generator 24.

Next, the operation of the thus configured charger 10 will be described.

The waveform generated by the waveform generator 24 is amplified by the voltage generator 22. The amplified voltage has, for example, a waveform shape as shown in FIG. 2, and the voltage is between -1.6 kV and -1.4 kV so that the surface potential of the photoconductor 14 is about -700 V. Changes in a sine shape. Then, the voltage amplified by the voltage generator 22 is sent to the electrode 18.

When a voltage is applied to the electrode 18, the charger 1
Corona discharge is generated between 0 and the photosensitive drum 16, and the molecules existing between the high resistance body 20 and the photosensitive body 14 are ionized by this corona discharge. The negative ions generated here are attracted to the photoconductor 14 and charge the photoconductor 14. At this time, since the voltage as shown in FIG. 2 is applied to the electrode 18, even if the average voltage is set high in order to increase the potential of the photoconductor 14, the increased ions are intermittently exposed to light. Since the ions are attracted to the body 14 and the ions are not concentrated, stable charging can be performed without shifting to the streamer mode.

Then, the charged photoconductor 14 moves to the next exposure mechanism (not shown) as the photoconductor drum 16 rotates in the direction of the arrow. In the exposure mechanism, the photoconductor 14 is selectively irradiated with light from a light source (not shown), so that the photoconductor 1
The charges charged on the surface of No. 4 are selectively released, and the process proceeds to the next developing mechanism (not shown). In the developing mechanism, toner (not shown) is selectively attached to the photoconductor 14 depending on whether the surface of the photoconductor 14 is charged or not, and the toner is transferred to a recording sheet (not shown).

As a result, the photosensitive member 14 is uniformly charged, so that a uniform image can be formed on the recording paper.

The present invention is not limited to the embodiments described herein, and various modifications can be made without departing from the spirit of the invention. That is, in this embodiment, an example in which the present invention is applied to a proximity type charger is shown, but it goes without saying that a corotron charger, a scorotron charger, etc. are also effective.

Further, in this embodiment, the voltage generator and the waveform generator are shown separately, but equivalent functions may be integrated, and other waveforms such as a triangular wave and a rectangular wave may be used. As for the voltage, any value up to about -4 kV may be used.

In the present embodiment, the negative voltage was changed and supplied to the electrodes. However, the potential difference applied between the electrodes may be changed with the same polarity, and naturally the positive voltage is changed and supplied. You can

Further, in the present embodiment, the example of the photosensitive drum is shown as the charge acceptor, but the present invention is not limited to this, and a paper-like medium which is charged by ions may be used.

[0025]

As is apparent from the above description, the charger of the present invention stably charges the charge receptor without being affected by environmental influences such as temperature and humidity and mechanical influences such as vibration. Can be performed.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a charger embodying the present invention.

FIG. 2 is a timing diagram for explaining a voltage output from a voltage generator.

FIG. 3 is an explanatory diagram showing a configuration of a conventional corotron charger.

FIG. 4 is an explanatory diagram showing a configuration of a conventional proximity charger.

[Explanation of symbols]

 10 Charger 14 Photoreceptor 20 High Resistor 22 Voltage Generator 24 Waveform Generator

Claims (1)

[Claims] 1. An ion generating means for ionizing molecules existing between the electrodes by applying a potential difference between the electrodes to cause a discharge, and sending the ions generated by the ion generating means to a charge acceptor. A charger for charging a charge receptor, comprising a control means for changing a potential difference applied between the electrodes with the same polarity.