JPS62254173A - Pre-cleaning electrostatic discharging device for electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To obtain excellent cleaning performance by switching the polarities and discharging current values inside and outside the transfer area on an image carrier and by making the cleaning condition of a photosensitive body constant after it passes through a pre-cleaning discharger regardless of whether or not discharging charges operate directly when a toner sticking pattern is formed outside the transfer area. CONSTITUTION:A photosensor 5 is provided, and the toner sticking pattern is formed outside the transfer area and detected optically to control toner density. Conditions inside and outside the transfer area becomes completely different according to whether or not transfer charges are received directly in a transfer process depending upon the presence or absence of transfer paper, and the DC component value of the discharge parameter of a pre-cleaning discharger 8 has effect very much. Consequently, the DC component value of the pre- cleaning charger 8 inside and outside the transfer area which determines whether or not a transfer discharger operates directly is switched accordingly to obtain excellent cleaning performance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a pre-cleaning discharge device for assisting in cleaning a photoreceptor of an electrophotographic copying machine.

(Prior Art) Conventionally, there is a method of providing a discharger before cleaning and performing alternating current discharge to control the amount of charge of toner input to cleaning and the potential of a photoreceptor. In this method, if the input conditions to the discharger are always constant, the output can be kept constant, and there is no problem if, for example, only the residual toner after transfer and the photoreceptor potential in that area are controlled. However, in recent years, devices have been put on the market that control, for example, toner density by optically detecting a toner adhesion pattern provided outside the transfer area. In this case, the input conditions may not be constant due to the difference between whether the charge from the transfer discharge device (or the charge in the case of a device with a separation discharge device) is directly received or not depending on the presence or absence of paper inside and outside the transfer area. Furthermore, it has become difficult to maintain constant output for both under the same conditions, resulting in a problem of poor cleaning.

(Purpose) The present invention improves cleaning conditions by keeping the cleaning conditions of the photoreceptor constant after passing through the discharger before cleaning, regardless of whether a discharge charge acts directly or not, when a toner adhesion pattern is formed outside the transfer area. The purpose is to obtain leaning performance.

(Structure) The present invention has been made in view of the above-mentioned problems, and uses a pre-cleaning discharge device in which the charge amount of the toner input for cleaning and the potential of the photoreceptor are controlled by a discharge device. The polarity of the discharge inside and outside the transfer area of the carrier
It is characterized by switching the discharge current value.

Hereinafter, a detailed explanation will be given based on the illustrated embodiment. 1
1 is a photosensitive drum, 2 is a charging/discharging device, 3 is a haze device, 4 is a developing device, 5 is a photosensor, 6 is a pre-transfer lamp, 7
8 is a transfer discharger, 8 is a pre-cleaning discharger, 9 is a cleaning blade, and 10 is a quenching lamp. The photo sensor 5 detects the toner adhesion pattern formed outside the transfer area and controls the toner density.

FIG. 1 shows the configuration of an electrophotographic apparatus used in experiments by the present inventor. As can be seen from the figure, this configuration consists of a photo sensor 5
The toner density is controlled by forming a toner adhesion pattern outside the transfer area and detecting it optically (in this case, the amount of reflected light).

FIG. 2 shows the transition of the photoreceptor potential and the amount of 1 to ner charge in each process of this apparatus. As is clear from the figure, the conditions inside and outside the transfer area are completely different depending on whether the transfer charge is directly received or not due to the presence or absence of transfer paper during the transfer process.

It is well known that it is very effective to remove especially the electrostatic adhesion between the photoreceptor and the adhesive 1 to 3 toner before cleaning when using the blade cleaning method. However, as mentioned above, since the input conditions are completely different inside and outside the transfer area, it has been found that it is not possible to achieve both using a constant discharge condition. Now, when the present invention conducted an experiment to supplement the above-mentioned input conditions, it was found that the DC component value of the discharge parameter of the pre-cleaning discharger 8 has a very effective effect.

Figure 3 shows the relationship between DC component value cleaning performance based on the experiment. The DC component value herein essentially means the difference between positive and negative discharge current values in AC discharge. Accordingly, by correspondingly switching the DC component value of the pre-cleaning discharger inside and outside the transfer area, which causes a difference between when the transfer discharger directly acts and when it does not, it is possible to have good leaning performance in both cases.

As a means for actually switching the DC component value, there is a method of switching the value of a DC voltage power source in which an AC high voltage DC is superimposed.

The following are experimental results using a device that only has a transfer discharge device, but there are also devices that use a separation discharge device in order to improve the separation of the transfer paper, and in this case as well, the The input conditions are different whether it acts directly or not, and it is necessary to switch the DC component value of the discharger before cleaning.

Furthermore, even if the cleaning method is not a blade, it is necessary to switch the cleaning method to suit each condition.

(Effects) 41 The present invention provides a pre-cleaning discharge device in which the amount of charge of toner input to cleaning and the potential of the photoconductor are controlled by a discharge device, in which the amount of charge on the toner input to cleaning and the potential of the photoreceptor are controlled inside and outside the transfer area of the image carrier. Since the discharge polarity and discharge current value are switched, if a toner adhesion pattern is formed outside the transfer area, the discharge charge will directly act on the photoreceptor after passing through the discharger before cleaning. Good cleaning performance can be obtained by keeping the cleaning conditions constant.

[Brief explanation of drawings]

Fig. 1 is a general schematic diagram of the electrophotographic copying machine according to the present invention, Fig. 2 is a diagram showing the relationship between the inside and outside of the transfer area, the photoreceptor potential, and the toner charge amount, and Fig. 3 is the discharge of the discharger before cleaning. FIG. 3 is a diagram showing current values and cleaning performance. 1...Photoreceptor 8...Discharger before cleaning 9...Cleaning blade Fig. 3

Claims (1)

[Claims] In a pre-cleaning discharge device in which the amount of toner charge input to cleaning and the potential of the photoreceptor are controlled by a discharger, the polarity of discharge and the discharge current value are switched inside and outside the transfer area on the image carrier. A pre-cleaning discharge device for an electrophotographic copying machine, characterized in that: