JPS63137282A - Destaticizing method for electrophotographic sensitive material - Google Patents

Abstract

PURPOSE:To effectively destaticize a photosensitive body by superposing a DC voltage having a polarity opposite to that of the photosensitive body to an AC voltage and applying them to a separating charger and increasing the DC voltage if a transfer paper does not exist between the photosensitive body and the separating charger. CONSTITUTION:The AC voltage is applied from a terminal 11 to a separating charger 5 simultaneously with start of a main motor, and a terminal 13 is turned off to superpose 100V DC bias voltage to the AC voltage because a transfer paper P does not exist between the separating charger 5 and a drum 1. When printing is started, a roll 14 feeds the transfer paper P at a proper time and is detected by a sensor 15, and a timer turns on the terminal 13 after a prescribed time and a relay 23 is switched to reduce the DC bias to 500V. After the transfer paper P passes, the timer turns off the terminal 13 after a prescribed time to switch the relay 23, and 100V is superposed again. By this constitution, the conventional separating charger is used to effectively destaticize the photosensitive body, and reduction of lives of the photosensitive body and a cleaning blade is prevented.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for eliminating static electricity from a photoreceptor for electrophotography, and is a method for effectively eliminating static electricity from photoreceptors in copiers, laser printers, etc. that have an electrophotographic process. used to do.

(Prior art) Generally, an electronic copying machine corona-charges the surface of a drum-shaped photoreceptor during charging to form a uniform static charge distribution, and then erases the static charge with a reflected light beam corresponding to the information. An electrostatic latent image is formed, developed with toner, transferred to transfer paper, and fixed by a heating roller. To transfer onto the transfer paper, a high voltage of several KV is applied to the transfer charger to charge the back side of the transfer paper, and to separate the transfer paper from the photoreceptor, an AC voltage of several KV is applied to the separation charger. It is designed to be applied.

However, in such a copying machine, when copies are made to many papers (transfer paper) of the same size and then to a larger size paper, fog occurs in the size range of the previous many papers. There is a problem in that a so-called paper size memory phenomenon or a filming phenomenon occurs. This is thought to be because deposits such as talc contained in the paper adhere to the photoreceptor, reducing the ability of this portion to eliminate static electricity using light. As a countermeasure for this, it is possible to eliminate static electricity from the photoreceptor using a separate static elimination charger, and then use a cleaner blade to remove the residual toner (f). It is very difficult to store it in the narrow space around the photoreceptor, and it also requires a new dedicated power source, which results in a large amount of equipment being used. It is also possible to increase the pressure of the cleaner blade on the photoreceptor to remove the deposits along with the remaining toner, but this method has many problems such as shortening the lifespan of the cleaner blade and the photoreceptor. .

(Means for Solving the Problems) The present invention solves the above-mentioned circumstances, eliminates the need to provide a dedicated static elimination charger, and does not shorten the life of the photoreceptor or cleaner blade (such as paper size memory phenomenon). The purpose of this invention is to provide a method for removing static electricity from a photoconductor that can prevent this, and the technical means for this purpose is to remove the static charge on the photoconductor 1 by using a separation charger 5 for separating the transfer paper P from the photoconductor 1 after transfer. For electrophotography, a DC voltage of opposite polarity is applied superimposed on an AC voltage, and the DC voltage is increased when there is no transfer paper P between the photoreceptor 1 and the separate charger 5. This is a method for removing static electricity from a photoreceptor.

(Example) The present invention will be explained below based on illustrated embodiments.

In FIG. 1, around the rotationally driven photoreceptor drum 1, there is an electrostatic charge +2, a developing device! 3, a transfer charger 4, a separation charger 5, and a cleaning blade 6 are provided. During charging 2, transfer charger 4 and during separation charging 5, a high voltage power supply device 7.
High voltages from 8.9 and 11.9 are applied to each terminal, and the on/off switching thereof is performed by controlling the respective remote terminals 10, 11.12 to turn on and off. Note that a DC voltage is applied to the charging charger 2 and the transfer charger 4, and an AC voltage containing a DC bias component is applied to the separation charger 5. The switching terminal 13 provided in the high voltage power supply device 8 is connected to the AC voltage applied to the separation charger 5 to I! This is for switching the magnitude of the DC bias component to be multiplied by i.

A timing roller 14 feeds the transfer paper P, and a sensor 15 detects that the paper is being fed.

Figure 2 is a high voltage power supply! ! 8 circuit diagram is shown.

The outputs of the oscillation circuit 24 and the power circuit 25 that operate with low DC voltage are input to the negative winding 20 of the step-up transformer TR+, and the secondary winding 2 for AC is boosted to AC5KV.
One output end of the is connected to the separate charger 5 via the protective resistor 26, and the other end is connected to the DC voltage of 500 V by the contact 23a of the relay 23, which operates by turning the switching terminal 13 on and off.
or 1000V. This DC voltage (DC bias) has a polarity opposite to that of the DC voltage applied to 4 during transfer charging. The oscillation circuit 2 is activated by turning on and off the remote terminal 11.
The oscillation operation of 4 is controlled, and the high voltage output is turned on and off. In addition, 22 is the tertiary winding for DC, 27.28.29
is a resistor for voltage division, 30.31 is a diode for rectification,
32 is a constant voltage varistor, and 33 and 34 are capacitors.

FIG. 3 is a time chart showing the relationship between the output of the sensor 15 that detects the transfer paper P and the DC bias voltage applied to the separate charger 5, and FIG. 4 shows the waveform of the voltage applied to the separate charger 5. It is a diagram. Figures 1 to 4
In the figure, a photoreceptor drum 1 is corona-charged by a charging medium 2, and is electrostatically charged by being subjected to image exposure. An II image is formed, developed with toner by the developing device Wi3, and then transferred to the transfer paper P fed by the timing roller 14. At this time, a DC voltage is applied to the transfer charger 4 to charge the back surface of the transfer paper, and the toner on the photosensitive drum l is transferred to the transfer paper P by an electric field based on the charged charge.

Now, during separation charging 5, the main motor (not shown) is driven, the remote terminal 11 is turned on, and AC voltage is applied at the same time, and at this time, the transfer paper P is connected to the separation charger 5 and the photoreceptor drum l. Therefore, the switching terminal 13 is turned off (the switching terminal 13 is not connected to the ground terminal G), and a DC bias voltage of 1000 V is superimposed and applied (the waveform shown in Figure 4). voltage), when printing is started, the timing roller 14 rotates at an appropriate timing and the transfer paper P is sent forward. When the transfer paper P is detected by the sensor 15, the transfer paper P reaches between the separation charger 5 and the photosensitive drum 1 and the switching terminal 13 is turned on after a time t1 according to the timer. 23 is activated, its contact 23a is switched, and the DC bias component of the voltage applied to the separation charger 5 is 100 O.
V to 500V (Fig. 4) When the transfer paper P passes the sensor 15, after the time t2 set by the timer, the switching terminal 13 is switched on, assuming that the transfer paper P has passed between the separation charger 5 and the photosensitive storage drum 1. This causes the relay 23 to return and the contact 23a to switch, and the DC bias to the separate charger 5 increases again to 1000 V (Fig. 4b), the low voltage value of the DC bias (50 V).
0V) is low enough to prevent scattering of the toner on the transfer paper P and reverse transfer of the toner on the transfer paper P onto the photoreceptor drum 1, and an optimum value that does not cause poor separation of the transfer paper P. value is selected. When the transfer paper P is not between the separation charger 5 and the photoreceptor drum L, the DC bias is set to high voltage (
By setting the voltage to 100 OV), the effect of eliminating static electricity from the photoreceptor drum 1 is enhanced, and the paper size memory phenomenon is prevented from occurring. The above-mentioned time 11 is 0 time (2 means
The time is set to be longer than the time required for the transfer paper P to pass from the position of the sensor 15 to the position of the separation charger.

FIG. 5 shows another embodiment, and parts similar to those in the embodiment shown in FIG. 1 are given the same numbers and their explanation will be omitted. During charging 16, a scorotron is used to prevent the potential of the photoreceptor drum 1 from changing, and a DC high-voltage power supply 17 used commonly for the charger 16 and the transfer charger 4 is turned on and off. In addition to the remote terminal 18 for control, a switching terminal 19 for switching the DC output voltage is provided. This switching terminal 19 is connected to the switching terminal 13 of the high-voltage power supply device 8 for the separation charging mode 5, and the DC voltage applied to the transfer charger 4 can be switched by inputting this switching terminal 19. In other words, referring also to FIG. 6, when the aforementioned sensor 15 or the like detects that the transfer paper P is not on the transfer charger 4 or the separation charger 5, the DC bias of the high voltage power supply device 8 is 1000 V. When the transfer paper P is present, the DC bias returns to a low voltage of 500 cm, and the output of the high voltage power supply 17 decreases to 5KV.
7's output also increases to 5.5KV. By lowering the applied voltage when there is no transfer paper P on the transfer sheet 4 during transfer charging in this way, the size memory phenomenon can be more effectively prevented.

FIG. 7 shows still another embodiment, in which an AC high-voltage power supply 41 for the separate charger 5 is provided with only a remote terminal 43 for on/off control, and a switching terminal 45 is used to switch the DC bias. DC high voltage power supply device 2 with
1, a two-step DC voltage of high and low polarity opposite to the charging polarity of the photosensitive drum 1 is applied to the stabilizer plate 5a of the separate charger 5. When the transfer paper P is not on the separation charger 5, the DC bias voltage applied to the stabilizing plate 5a is increased by the input to the switching terminal 45, thereby increasing the static elimination effect of the photoreceptor drum l, thereby preventing the size memory phenomenon. It can be prevented.

(Effects of the Invention) According to the present invention, a DC voltage having a polarity opposite to that of the photoreceptor is superimposed and applied to the separation charger, and when there is no transfer paper between the photoreceptor and the separation charger, this DC voltage is applied to the separation charger. Since the bias voltage is increased, the conventionally used separate charger can be used, and there is no need for a dedicated static electricity removal charge, so the configuration around the photoreceptor can be changed from the conventional one. There is no need,
It can be made compact. Further, the life of the photoreceptor and the cleaner blade is not shortened, and the photoreceptor can be effectively neutralized to prevent the so-called Baber size memory phenomenon.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention, with FIG. 1 schematically showing a photoreceptor and its surroundings, and FIG. 2 showing a high-voltage power supply device i.
! 8 is a circuit diagram, FIG. 3 is a time chart showing changes in the DC bias voltage applied to the separate charger 5, and FIG. 4 is a diagram showing the waveform of the voltage applied to the separate charger 5.
FIG. 5 is a diagram similar to FIG. 1 showing another embodiment, FIG. 6 is a time chart showing changes in the voltage applied in the embodiment of FIG. 5, and FIG. 7 is a still another embodiment. FIG. 1 is a diagram similar to FIG. l... Photosensitive drum (photosensitive body), 5... Separation charger, 5a... Stabilizer, 8.20.42... High voltage power supply device, 11, 43.44... Remote terminal, 13 ．．
45...Switching terminal, 15...Sensor, P...Transfer paper. Applicant Minolta Camera Co., Ltd. Figure 3 Atsushi 4 Figure 6 Figure 7

Claims (1)

[Claims] A DC voltage with a polarity opposite to that of the photoconductor is applied superimposed on an AC voltage to a separation charger for separating the transfer paper from the photoconductor after transfer, and the transfer is carried out between the photoconductor and the separation charger. A method for eliminating static from an electrophotographic photoreceptor, comprising increasing the DC voltage when no paper is present.