JPS60232576A - Electrostatic recording apparatus - Google Patents

Abstract

PURPOSE:To secure stable bias voltage by feeding the bias voltage from corona discharger for electrostatic charging and image transfer, etc. CONSTITUTION:A scorotron type corona discharger 5 is a charging electrode for uniformly charging a photosensitive drum 4, a developing device 6 develops the electrostatic latent image of an original formed on said drum 4, and the inside of the device 6 is provided with a developing sleeve 6a rotating near the drum 4. Each prescribed high voltage is applied to the charging electrode 5, the transfer electrode 7, and a separating electrode 9, respectively from high voltage sources 13-15, and the voltage VA of the grid 5a of the charging electrode 5 is divided in voltage with resistors R1, R2 and the obtained bias voltage VB is applied to the developing sleeve 6a of the device 6. This bias voltage VB thus obtained is stable because it is obtained by dividing the stable grid voltage VA. In addition, the bias voltage VB may be changed over in accordance with the density of the original.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to electrostatic recording devices such as laser printers and electrophotographic copying machines, and particularly to improvements in the application of developing bias in this type of recording device.

(b) Prior Art Recently, a recording apparatus such as a laser printer that records an image by scanning a photoreceptor with a laser beam or an electron beam and then obtains the image by electrophotographic processing has been developed and put into practical use.

This type of recording apparatus uses a developing device that develops a latent image formed on a photoreceptor.

Generally, magnetic brush type developing devices are widely used. In a recording device using a magnetic brush type developing device, a bias voltage is applied to the magnetic sleeve in order to adjust the density of the recorded image and eliminate so-called fog to improve the quality of the image.

Conventionally, a bias power source was created and a voltage of 50V to 500V was applied. In addition, the recording apparatus is provided with separate power supplies for applying high voltages to charging, transfer, and separation electrodes, respectively. That is, since the shapes and sizes of the electrodes differ from electrode to electrode, there are voltage application conditions that match the electrode conditions, making it impossible to use a common power source.

However, there are charging electrodes and transfer electrodes that uniformly charge the photoreceptor, and electrodes that generate a voltage suitable for obtaining a developing bias. For example, an electrode type called the scorotron method is usually used for charging electrodes, and when a high voltage is applied to the electrode wire of this type of electrode, a discharge is generated between the electrode wire and the back plate, and at this time, about 5oov is applied to the bridge. Voltage is generated. The present invention has been made by focusing on this point and the fact that the developing bias is lower than the voltage applied to the electrodes.

(c) Object and Structure of the Invention In view of the above points, the present invention aims to obtain a stable bias voltage without providing an independent power supply, and in order to achieve this object.

The structure is such that a bias voltage is supplied from a corona discharger for use in transfer, etc.

) Example The present invention will be explained below based on the drawings.

FIG. 1 shows a schematic configuration of an electrophotographic copying machine using a developing device according to the present invention, in which 1 is an optical system for copying composed of mirrors, lenses, etc., 4 is a photosensitive drum that rotates in the direction of the arrow; 5 is a charging electrode that uniformly charges the photoreceptor drum 4, and is a scorotron type corona discharger; 6 is a developing device that develops the electrostatic latent image of the document formed on the photoreceptor drum 4; A developing sleeve 6 rotating close to the drum 4
A is provided. Reference numeral 7 designates a transfer electrode that transfers the developed original image onto the recording paper P fed from the paper cassette 8; 9 a separation electrode that separates the transferred recording paper P from the photoreceptor drum 4; and 10 a photoreceptor. A cleaning device removes the developer remaining on the drum 4, a conveying device 11 conveys the separated recording paper, and a fixing device 12.

Charged electrode5. The transfer electrode 71 separation electrode 9 is connected to the high voltage power source 13,1
4.15, predetermined high voltages are applied to the developing stage IJ-Proa of the developing device 6, and the voltage VA generated on the grid 5a of the charging electrode '5 is divided by resistors R1 and R2. A bias voltage VB is applied. The bias voltage VB obtained in this manner is stable because it is obtained by dividing the stable grid voltage vA.

Note that the bias voltage VB may be switched depending on the density of the original.

The bias voltage VB is thus applied to the charged electrode 5 during discharge.
In addition to dividing the grid voltage VA, as shown in FIG. 2, the back plate 5b of the charging electrode 5 may be used as an electrode, and the voltage drop across the resistors R4 and R5 due to a constant current flowing from this electrode to the ground may be utilized. The bias voltage obtained in this way also becomes a stable voltage.

(e) Detailed Description of the Invention As described above, in the present invention, the bias voltage is supplied by the voltage applied to the charged electrode, so that a stable bias voltage can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of an embodiment of an electrophotographic copying machine using a developing device according to the present invention. FIG. 2 is a schematic diagram showing the main parts of another embodiment of the developing device according to the present invention. l... Reciprocating document table 2... Exposure lamp 3...
Optical system 4... Photosensitive drum 5... Corona discharger
5a... Grid 6... Developing device 6a... Developing sleeve 7... Transfer electrode 8... Paper feed cassette 9...
... Separation electrode 10 ... Cleaning device 11 ...
Conveying device 12... Fixing device 13, 14.15...
High-voltage power supply patent applicant Hiroo Tsuchi Suzuki, attorney for Konishiroku Photo Industry Co., Ltd.

Claims (1)

[Claims] An electrostatic recording device characterized in that a developing bias voltage is supplied from an electrode of a corona discharger in the electrostatic recording device.