JPS61270773A - Developing device - Google Patents

Abstract

PURPOSE:To stabilize the electric potential of a developing electrode at any time and to obtain a proper image by turning the developing electrode to a higher impedance state than an earth as DC. CONSTITUTION:An AC power supply 3 of which one electrode is connected to the earth is connected to a sleeve 2 which is the developing electrode, and when a photosensitive drum 1 is rotated and an electrostatic latent image on the drum 1 reaches the sleeve 2, electrically charged toner held on the surface of the sleeve 2 is reciprocally fried between the sleeve 2 an the drum 1 to develop the electrostatic latent image. In this case, the sleeve 2 is turned to the higher impedance state than the earth and the sleeve 2 is set up to a floating state from the earth as DC by a capacitor 4 connected between the AC power supply 3 and the eath. Consequently, the change of the developing state of the sleeve 2 is loosened and developing can be attained always under approximately proper state.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a developing device used in an image forming apparatus such as a copying machine or a laser beam printer, and particularly relates to a developing device that applies an alternating current voltage to a developing electrode.

(Prior Art) Conventionally, this type of developing device applies an alternating current voltage to a developing sleeve that is rotatably arranged to face a photosensitive drum, and the electrostatic latent image on the photosensitive drum is held on the developing sleeve. Some devices develop the electrostatic latent image by causing charged toner to fly back and forth between the developing sleeve and the photosensitive drum.

One electrode of the AC power source that applies an AC voltage to the developing sleeve is directly connected to ground, and the developing sleeve is in a low DC impedance state.

(Problems to be Solved by the Invention) However, in the case of such conventional technology, since the developing sleeve as a developing electrode is in a low DC impedance state, the developing sleeve is susceptible to changes in the charged potential of the photosensitive drum, etc. There is a problem in that the developing conditions determined by the potential difference between the developing sleeve and the photoreceptor drum are not constant, and a desired image cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and its purpose is to make it possible to always stabilize the potential of the developing electrode and obtain a proper image. An object of the present invention is to provide a developing device.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a developing device that develops an electrostatic latent image on a photoreceptor by applying at least an alternating current voltage to a developing electrode. The developing electrode is configured to be in a high impedance state with respect to ground.

(Example) The present invention will be explained below based on the illustrated example. 1st
In the figure, 1 is a photosensitive drum on whose surface an electrostatic latent image corresponding to image information is formed, and the photosensitive drum 1 is a cylindrical body made of metal such as aluminum whose surface is coated with a photoconductive material. Yes, the metal cylinder is connected to ground. Reference numeral 2 denotes a developing sleeve as a developing electrode, and an AC power source 3 is connected to the developing sleeve 2, one electrode of which is connected to ground. When the photosensitive drum 1 rotates and the electrostatic latent image on the photosensitive drum 1 reaches the developing sleeve 2, the developing sleeve 2 is applied with an alternating current voltage by the AC power supply 3. Charged toner (not shown) held on the surface of the photosensitive drum 1 flies back and forth between the photosensitive drum 1 and the electrostatic latent image is developed.

In the present invention, in order to bring the developing sleeve 2 into a high impedance state with respect to the ground, a capacitor 4 is connected between the AC power supply 3 and the ground, and the developing sleeve 2 is placed in a DC floating state with respect to the ground. It has become.

Therefore, the potential of the electrostatic latent image on the photosensitive drum 1 may be affected by changes in the charging characteristics of the linear photosensitive drum 1 itself, changes in the potential when charging the photosensitive drum 1, environmental changes such as humidity, etc. When there is a corresponding change, the potential fluctuation of the electrostatic latent image is divided between the photosensitive drum 1 and the capacitor 4 because the developing sleeve 2 is in a DC 70-ting state. Therefore, changes in the developing state of the developing sleeve 2 are alleviated, and development can always be performed in a state close to proper.

FIG. 2 shows a second embodiment of the developing device according to the present invention. In this embodiment, a DC power source 5 is inserted between the AC power source 3 and the capacitor 4, and the potential of the developing sleeve 2 is corrected. The other configurations and functions are the same as those of the first embodiment.

FIG. 3 shows a third embodiment of the developing device according to the present invention. In this embodiment, a resistor 6 is connected in parallel with the capacitor 4 of the first embodiment to maintain the developing sleeve 2 in a high impedance state. It is something. Besides being able to control the DC impedance of the developing sleeve 2 by setting the value of this resistor 6, its structure and operation are as follows.
This is the same as the embodiment.

FIG. 4 shows a fourth embodiment of the developing device according to the present invention. In this embodiment, a constant voltage element 7 such as a Zener diode is connected in parallel with the capacitor 4 of the first embodiment. It is in a high impedance state up to the operating point of the element 7, and when it exceeds that point, it becomes a low impedance state, and the limiter operation of the impedance state of the developing sleeve 2 is performed.

In both the embodiments shown in FIGS. 3 and 4, a DC power source may be connected to the circuit as necessary in order to correct the developing voltage as shown in FIG.

(Effect of the invention) The present invention consists of the above configuration and operation.

Since the developing electrode is in a high DC impedance state with respect to the ground, even if the surface potential of the photoreceptor fluctuates for some reason, or even if the surface potential changes due to various originals, the developing electrode will not be affected by the fluctuation. Therefore, it is possible to always perform proper development.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a first embodiment of a developing device according to the present invention, FIG. 2 is a schematic diagram showing a second embodiment of the present invention, and FIG. 3 is a schematic diagram showing a third embodiment of the present invention. FIG. 4 is a schematic diagram showing a fourth embodiment of the present invention. Explanation of symbols

Claims (1)

[Claims] 1. A developing device for developing an electrostatic latent image on a photoreceptor by applying at least an alternating current voltage to a developing electrode, the developing device being characterized in that the developing electrode is placed in a DC high impedance state with respect to ground.