JPS60133474A - Electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To compensate a lowering in the charge potential of a photosensitive body due to fatigue, etc., and maintain an invariably proper image by forming a reference visible image on the photosensitive body, detecting its reflection density by a photosensor, and controlling a high-voltage power source for electrostatic charging. CONSTITUTION:The photosensitive body 1 which is charged uniformly by a charger 2 is exposed to reflected light from a reference original 4 provided at an end part of contact glass 3 and an original 5 to form a reference electrostatic latent image and the electrostatic latent image of the original, and they are developed at a developing part 15 to form visible images. The reflection density of the reference visible image is detected by the photosensor 16, whose output is compared by a comparator 17 with a reference potential 18. The high-voltage power source 20 for electrostatic charging is brought under the feedback control of a control circuit 19 so that the photosensor output is equal to the reference potential all the time, namely, that the reference visible image density is invariably constant.

Description

[Detailed description of the invention] Industrial use! l[f.

The present invention-1 relates to an electrophotographic copying apparatus such as an electrostatic transfer type copying stone.

Conventional Structure and Problems In general, in a 711 secondary copying machine, the image quality is always low, either by uniformly charging the photoreceptor and transferring the formed 1-s powder image on the photoreceptor to transfer paper. It is important to be stable.

For this reason, it is important that the potential of the surface of the photoreceptor after uniform charging is always constant.

However, as the photoreceptor is used for an extended period of time, it deteriorates and its charging ability decreases, so that it may not be possible to obtain a suitable image. Furthermore, due to changes in environmental conditions, the charging ability may change and a normal 1E image may not be obtained.

E) It is also important that the developer or other pro-null conditions are stable, but they also deteriorate or their values fluctuate, making it difficult to maintain an optimal image. Ta.

OBJECT OF THE INVENTION The present invention aims to eliminate the drawbacks of the prior art as described in 2.
It is an object of the present invention to provide an electrophotographic copying apparatus that is equipped with means for maintaining stable and proper images at all times.

Structure of the invention - 5 # RI] rr se 1 - union - day 1 within pu - 2 *+;I
t#2, J'-W) Ifre$Ij; θ) At least a charging means, an exposure means, and a developing means are provided around the IMI.

comprising a transfer means and a cleaning means, a no-AI sensor is provided near the photoreceptor and between the developing means and the cleaning means, and a reference developed image is formed separately from the image area on the photoreceptor; The photo sensor is configured to detect the reflection density of the reference image, and control a high-voltage power source for charging in accordance with this detection output, thereby maintaining a stable/ζ optimum image at all times. be able to.

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

The figure is a block diagram schematically showing a copying apparatus to which the present invention is applicable.

In the figure, 1 is a photoreceptor, 2 is a charger, 3 is a contact glass, 4 is a reference original, 5 is a document, 6 is an illumination lamp, and a plurality of reflective mirrors 7° 8.9, 1○, 11
．． 12, 13 and lens 14 constitute an optical system.

16 is a developing section, 16 is a photosensor, 17 is a comparator, 1
8id reference potential, 19 is a control circuit for a high-voltage power supply, 2o is a high-voltage power supply for charging, 21 is a paper feed section, 22, 23, and 24 are chargers for transferring one sheet of paper and removing static electricity, and 25 is a cleaning section. .

The operation of this embodiment configured as above will be described below.

First, the photoreceptor 1, which is uniformly charged by the charger 2, is exposed to light reflected from the reference original 4 and the original 6 provided at the end of the contact glass 3, and a reference electrostatic latent image is formed on the surface of the original. forms an electrostatic latent image. Next, the electrostatic latent image of this document is developed in the developing section 15 to form a visible image.

The developed image formed on the photoreceptor is transferred by a transfer charger 22 onto paper fed from a paper feeding section 21 .

After the paper is separated using the separation charger 23, the potential on the photoreceptor is removed using the static eliminator 24, and finally, the remaining residue on the photoreceptor is removed using the cleaning section 25, thereby completing one process. .

In this series of steps, a photosensor 16 provided immediately after the developing section 16 and equipped with a light emitting circuit (variable circuit) and a light receiving amplification circuit detects the reflection density of the reference developed image formed on the photoreceptor. The output is detected by the photosensor and sent to the comparator 17.
The charging high-voltage power supply 20 is feedback-controlled by the control circuit 19 so that the photosensor output is always equal to the reference potential and the standard developed density is always constant. Note that the reference potential 18 is set in advance so as to provide an optimum image density.

In addition, according to the above embodiment, when the photo sensor detects the reflection density of the reference developed image and controls the high-voltage power supply for charging, the front part of the original has already been developed, so the front part of the image to be formed is different from the front part of the image. The image condition may be different between the rear part and the rear part. Therefore, in this embodiment, when only one sheet = 1 copy or before the first copy, a briscan is performed so that the irradiation lamp 6 irradiates only the reference original, and the reflection density of the reference image formed at this time is detected. to control the high-voltage power supply for charging the first copy. Next, the reflection density of the reference image formed at the same time as 77-stroke is determined by the width 1 J-h.
7 + gore 0 - the neighboring straw, thunder field, yiso, thunder fungus or cow 11 legs, and the same control is repeated thereafter.

Alternatively, even if the photosensor detects the reflection density of the reference image and controls the high-voltage power supply for charging, at that time V
Alternatively, the reference original may be provided at a position such that the portion of the photoreceptor where the original image is formed is in front of the charger.

As described above, according to this embodiment, a photosensor for detecting the reflection density of the reference developed image is provided between the developing means and the cleaning means, and the high-voltage power supply voltage for charging is controlled according to this detection output. This makes it possible to always maintain an optimal image.

Effects of the Invention As is clear from the explanation in Section 42, the present invention forms a reference developed image on a photoconductor separately from the image area, detects the reflection density of this reference developed image with a photosensor, Since the charging high-voltage power source is controlled in accordance with the output, it is possible to compensate for a decrease in the charging potential of the photoreceptor due to fatigue and the like and keep it constant, so that a proper image can always be maintained.

In addition, in the present invention, the reflection density of the reference developed image is detected and controlled after development, so even if image deterioration occurs due to developer deterioration or other process condition fluctuations, the charging high-voltage power source can be used in the same way. It is possible to control the image to maintain a proper image, and the effect is excellent.

[Brief explanation of the drawing]

The figure is a schematic configuration diagram showing one embodiment of the present invention. 1...Photoconductor, 2.Charger, 3.Contact glass, 4.Reference original, 5..Original, 6..Exposure lamp, 7, 8, 9, 1○, 11, 12゜13 Reflection mirror , 14...Lens, 15...Development section, 1
6-...Fumeto sensor, 17...Ratio axis device, 1
8-m--Reference potential, 19--Charging high-voltage power supply control circuit, 2O--Charging high-voltage power supply, 21...Paper feed γ<
1, 22...Transfer i;-Electric appliance, 23...Separation charger, 24.Electrostatic charger, 25...Cleaning section.

Claims (1)

[Claims] At least charging means and exposure means are provided around the photoreceptor. Equipped with a developing means, a transfer means, and a cleaning means,
(In the vicinity of the photoreceptor I and between the developing means and the cleaning means)) 1-A sensor is provided, and a reference developed image is formed separately from the image area of the photoreceptor-42, riiJ
Note! detecting the reflection density of the reference image with a sensor;
An electrophotographic copying apparatus characterized by: controlling a high-voltage power supply voltage for charging in accordance with this power.