JPS6350709B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording paper static eliminator in an electronic copying machine.

FIG. 1 is a schematic diagram for explaining the operation of an electronic copying machine, in which 1 is a photoconductor (photosensitive drum), 2 is a charging corotron, 3 is an exposure device, 4 is a transfer corotron, and 5 is a paper static eliminator ( Corotron for Detack),
6 is a corotron for drum static elimination (pre-cleaning), 7 is a high-voltage power supply, and 8 is recording paper.

As is well known, as the photosensitive drum 1 is rotated in the direction of the arrow, uniform charging, exposure (electrostatic latent image formation), and development (toner image formation) are performed.
The toner image on the photosensitive drum 1 is transferred to a corotron 4 for transfer.
The image is transferred onto the recording paper 8 by. The recording paper 8 on which the toner image has been transferred is charge-eliminated by the paper charge-eliminating corotron 5, and then peeled off from the photosensitive drum 1, and the toner image is fixed. On the other hand, the photosensitive drum is neutralized by a drum neutralizing corotron, and is prepared for the next copying cycle.

By causing an electric discharge to occur between the corotron 5 for eliminating paper charge and the photosensitive drum 1 and neutralizing the charge on the paper 8, the paper 8 can be easily peeled off from the drum 1. At this time, the way the paper 8 is separated from the drum 1 changes depending on the physical conditions such as the electric charge on the paper 8 and the strain of the paper, and it is difficult to always maintain the best state of paper separation. For example, if the paper has a large amount of charge before being neutralized and there is no stiffness on the paper, the alternating current component of the static eliminating output must be increased.

In order to control the voltage applied to the high-voltage power supply for neutralizing the recording paper in the conventional electronic copying machine as described above, that is, the corotron 5 for eliminating static electricity from the paper shown in FIG. ) or constant current control that keeps the alternating current flowing through the discharge body constant.

In constant current detection type control, the average value or effective value of the discharge current that flows when an AC voltage is applied to the discharge wire (discharge body) is detected, but in this case,
Due to dirt on the discharge wire, etc., the negative current component contained in the alternating current fluctuates more than the positive current component, and the static elimination effect sometimes deteriorates.

According to the inventor's experiments, compared to this alternating current, the effect on charge removal from recording paper is as follows:
It was found that the negative direct current component (average value of AC) contained in alternating current is many times larger. In particular, it has been found that when the high voltage power supply includes a bias circuit for setting the negative current to be larger than the positive current, the fluctuation in the negative current component becomes even larger. If the static elimination effect is reduced due to fluctuations in the negative current component, there is a drawback that it becomes difficult to separate the recording paper from the photoconductor. If the discharge voltage is increased in order to eliminate this drawback, a retransfer phenomenon occurs in which the toner transferred to the paper adheres to the photoconductor again, resulting in a new drawback that the copied image is disturbed. As described above, since the permissible range of voltage and current values for obtaining appropriate paper peeling characteristics is narrow, adjustment and maintenance have conventionally been difficult.

This invention is an electronic copying machine that detects the negative current, which is important for making it easier to separate the paper from the photoconductor, out of the discharge current for paper static elimination, and keeps this current constant to realize stable paper separation. The present invention provides a static eliminator for machines.

FIG. 2 is a circuit diagram of one embodiment of the present invention.
E ₁ and E ₂ are low-voltage power supplies, and the high voltage induced in the secondary winding L ₂ of the high-voltage transformer T is applied to the corotron 5 for paper static elimination. _L2 is a phase correction winding. The positive direction current i ₊ flowing from the discharge wire of the corotron 5 to the photosensitive drum 1 flows through the winding L ₂ , the varistor V, the variable resistor R, the discharge wire of the corotron 5,
It flows through the photosensitive drum 1, ground and diode _D1 . On the other hand, from photosensitive drum 1 to corotron 5
The negative current i _- flowing towards the diode D ₃ ,
Winding L ₂ , capacitor C ₁ , ground, photosensitive drum 1,
and flows through the discharge wire of corotron 5. By this, the negative direction current i _- becomes the positive direction current i ₊
can be made larger than.

Since the negative current i _- flows through the above path, it charges the capacitor C ₁ . The charging voltage of capacitor C ₁ is applied to the base of transistor T ₁ ,
It is compared with the reference voltage of the zener diode ZD, which is connected to the base of the transistor T ₂ . The signal resulting from said comparison is amplified by transistor _T3 and controls the internal impedance of transistor _T4 .

When the charging voltage of the capacitor C ₁ due to the negative current i _- is smaller than the reference value, the collector voltage of the transistor T ₂ will be low, so that the transistor
The collector voltage of T ₃ becomes higher. As a result, the internal impedance of transistor T ₄ becomes small,
Since the current supplied to the primary winding _L1 of the high voltage transformer T increases, the negative direction current _i- also increases. On the other hand, when the charging voltage of the capacitor _C1 due to the negative direction current _i- is larger than the reference value, the collector voltage of the transistor _T2 increases and the collector voltage of the transistor _T3 decreases. As a result, transistor T ₄
The internal impedance of becomes large, the excitation current of the primary winding decreases, and the negative direction current i _- decreases. In this way, the negative current i _- is held at a predetermined constant value. Note that the current value in this case may be an average value or an effective value.

As described above, according to the present invention, it is possible to maintain (the average value or effective value of) the negative current of the corotron for paper static elimination at a predetermined constant value, and it is possible to realize stable paper peeling. I can do it.

In the above, a case has been described in which the photosensitive drum 1 is uniformly charged positively, exposed to light, developed with negatively charged toner, and a toner image is transferred to recording paper by a transfer corotron with positive polarity. When uniform charging, exposure, development with positively charged toner, and transfer of a toner image onto recording paper using a transfer corotron with negative polarity are performed, it is necessary to maintain the positive current of the corotron for paper static elimination at a constant value. It will be clear that similar effects can be achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an electronic copying machine, and FIG. 2 is a circuit diagram of an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Photoconductor (photosensitive drum), 2... Corotron for charging, 3... Exposure device, 4... Corotron for transfer, 5... Corotron for paper static elimination, 6... Corotron for drum static elimination, 7... High voltage power supply, 8...
Recording sheet.

Claims (1)

[Claims] 1 Transfer the toner image on the photoconductor to recording paper,
A paper static eliminator for electronic copying machines that generates a discharge between the corotron for paper static neutralization installed on the back of the recording paper and the photoconductor to eliminate static from the paper, then peels the recording paper from the photoconductor and fixes it. a power supply means for generating an alternating current voltage to be applied to the corotron for paper static elimination, and a half-wave of the discharge current between the paper static elimination corotron and the photoconductor in a direction that neutralizes the charge on the recording paper; An electronic device characterized by comprising means for detecting and holding a current value, and means for feedback controlling the power supply means in a direction to suppress the fluctuation when the half-wave current value detected by the means fluctuates. Paper static eliminator for copying machines.