JPS60216361A - Brush electrostatic charging and transferring device - Google Patents

Abstract

PURPOSE:To improve transfer efficiency by bringing a conductive brush into contact with a photosensitive body, and impressing an AC superposed DC voltage which is generated by superposing an AC voltage upon a DC voltage by >=20% and is + or -200-+ or -2,000V to the conductive brush. CONSTITUTION:A contactor 12 contacts the reverse surface of a transfer material 8 gently during transfer as shown in the figure to charge electrostatically the reverse surface of the transfer material 8 uniformly, so a visible image (toner) on a photosensitive body 2 is transferred to the surface of the transfer material 8 by electrostatic attraction. Then when a DC voltage lower than 200V is impressed to the conductive brush 13, the electrostatic attraction of the toner is weakened because the transfer material has a low potential, so the toner is not transferred sufficiently. When the impressed voltage is >=2,000V, on the other hand, discharge is caused between the transfer material and toner particles or among toner particles to decrease the electrostatic charge quantity of toner or invert the polarity, thereby lowering the transfer efficiency. For the purpose, the impressed voltage is set to + or -200-+ or -2,000V, and then electrostatic charge uniformity is improved and the transfer efficiency is made superior.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a charging/transfer device that charges a photoreceptor in a copying machine and transfers a visible image formed on the photoreceptor to a transfer material. The present invention relates to a brush charging/transfer device K that charges and transfers electricity by contacting a photoreceptor with a photoreceptor.

As disclosed in Japanese Patent Application Laid-Open No. 56-147160, a conductive brush is provided in contact with a photoreceptor, and a voltage is applied to uniformly charge the surface of the photoreceptor as a brush charging device. Separately from the brush charging device, a conductive brush is provided facing the photoconductor, and a brush transfer device applies voltage to transfer the visible image (toner image) formed on the photoconductor to a transfer material. It has been known.

Such brush charging devices and transfer devices have the advantage that they do not generate ozone and do not require adjustment or replacement of parts, unlike charging devices and transfer devices that use a corona discharger.

However, the above-mentioned structure requires dedicated conductive brushes for each of the charging device and the transfer device, resulting in an increase in the number of parts and wiring, resulting in high costs.

In order to solve this problem, charging and transfer can be performed using one conductive brush, but the conductive brush of the brush charging device has a DC voltage of 2° to improve charging uniformity. Since an AC voltage of more than 100% is being applied, if more than necessary AC voltage is applied, the maximum and minimum values of the voltage waveform will be outside the optimal applied voltage range during transfer, and the conductive brush of the brush charging device will be damaged. When transferring by applying the same voltage as during charging, the transfer efficiency decreases, so it is practically impossible to perform charging and transfer using one conductive brush as described above.

Note that the above-mentioned problem can be solved by completely switching the applied voltage between charging and transfer.

In this case, a means for switching the applied voltage is required, which increases the cost, and the voltage must be switched at the same time as charging and transfer, making the control troublesome. .

OBJECTS OF THE INVENTION It is an object of the invention to be able to perform charging and transfer using a single conductive brush, and to improve uniform charging properties and transfer efficiency without changing the applied voltage. .

Structure of the invention An AC voltage of 20% or more of the DC voltage is superimposed on the conductive roll, and the minimum and maximum values of the voltage waveform are ±200 to ±2.
000 V AC/DC superimposed DC voltage is applied.

Embodiment FIG. 1 is a schematic explanatory diagram of a copying machine, in which a photoreceptor 2 is rotatably supported within a main body 1 of the copying machine.

Around the photoreceptor 2 there is a charging device, a transfer device 3. Cleaning device 4
．． Exposure device5. Developing devices 6 and the like are arranged in sequence, and the photoreceptor 2 is charged while it rotates twice.

After the exposure, development, transfer, and cleaning steps are performed, a visible image is transferred to the transfer material ε sent from the paper feeder 7, and then transferred to the fixing device 9.
It is fixed and becomes a copy.

That is, at the start of copying, the photoreceptor 2 is uniformly charged by the charging and transferring device 3, the exposure device 5 exposes the document image to form a latent image, and the developing device 6 converts the latent image into a visible image ( toner image). Then, the photoreceptor 2 rotates once and the visible image is charged, and when it reaches the transfer device 3, the back side of the transfer material 8 fed by the paper feeder 7 is charged, and due to the electrostatic attraction force with the visible image. Transfer the visible image to transfer material g.

When the photoreceptor 2 further rotates, the remaining donor is cleaned by the cleaning device 4, and the series of copying operations is completed.

The charging and transferring device 3 is as shown in FIG.

A roller-type conductive brush 13 is provided in which a large number of conductive contacts 12 are implanted on the circumferential surface of a conductor core 11.

The contactor 2 is arranged so as to lightly contact the surface of the photoreceptor 2, and rotated at a circumferential speed of 1 to 5 times the circumferential speed of the photoreceptor 2 rotating in the direction of the arrow.

Furthermore, a DC power source 14 and an AC power source 15 are connected to the conductor core 11, and an AC superimposed DC voltage (the maximum voltage waveform value.

The minimum value is 200 to 2000 V) is applied.

The contact 12 is made of, for example, nylon fiber mixed with a conductor such as carbon, and is electrically conductive. - Because of this, when charging, the surface of the photoreceptor 12 is uniformly charged by contact when the contactor 12 comes into contact with the photoreceptor 2, and an AC voltage of 20% or more of the DC voltage is not applied. Uniform charging properties can be improved.

Furthermore, during transfer, the contactor 12 lightly contacts the back surface of the transfer material ε as shown in FIG. 3, and the back surface of the transfer material 8 is uniformly charged by contact. ) The visible image is transferred to the surface of the transfer material g by the electrostatic attraction force between the transfer material g and the transfer material g. -Here, when the transfer efficiency was measured by applying only a DC voltage ξ to the conductive brush +3, the results shown in FIG. 4 were obtained.

From this, it is clear that applying a voltage of 200 V to 2000 V provides excellent transfer efficiency.

This is because in a region where the applied voltage is lower than 200'V, the transfer material has only a low potential, and therefore the electrostatic attraction force with the toner is weak and cannot be sufficiently applied.

When the applied voltage is 2000V or more, between the transfer material and the toner,
Alternatively, a discharge occurs between toner and toner.

It is thought that the amount of charge on the toner decreases or the polarity reverses, resulting in a decrease in transfer efficiency.

Further, the transfer efficiency and charging uniformity were measured by applying a DC voltage of +500 V to the conductive brush 13 and varying the voltage of a superimposed AC voltage, and the results shown in FIG. 5 were obtained.

As a result, it has been found that charging uniformity improves when an AC voltage of 300 V or more is fully superimposed, and transfer efficiency decreases when an AC voltage of 500 V or more is superimposed.

From the above, if an AC voltage of 20% or more of the DC voltage is superimposed, the charging uniformity will improve, and the total voltage of the DC voltage and AC voltage (that is, the maximum and minimum values of the ! pressure waveform) will be 20%.
If the voltage is within the range of 0 to 2000 V, the transfer efficiency will not decrease.

Note that the above explanation applies to a positively charged system.

In the case of a negative charging system, a voltage in the range of -200 to -2000V may be applied.

In addition, the conductive brush is as shown in FIG.

Fixed qv with contact 12 implanted in flat conductor core I+
It may also be used as a conductive brush for rats.

Effects of the Invention Charging and transfer can be performed with one conductive brush 13, and since an AC voltage of 20 or more times the DC voltage is superimposed and a friend AC superimposed DC voltage is applied, charging uniformity can be improved. The range of the minimum and maximum values of the voltage waveform of the AC superimposed DC voltage is ±200 to ±2000V, so the transfer efficiency is not reduced, and charging uniformity can be maintained without changing the applied voltage between charging and transfer. improve or
Transfer efficiency can be improved.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a schematic illustration of a copying machine, FIG. 2 is an illustration of charging operation, FIG. 3 is an illustration of transfer operation, and FIG. 4 is a diagram showing applied voltage to the conductive brush and transfer. Figure 5 shows the charging uniformity and transfer efficiency when the DC voltage is constant and the AC voltage is changed. Figure 6 shows the relationship between the conductive brush and the efficiency. It is an explanatory diagram. 2 is a photoreceptor, and 13 is a conductive brush.

Claims (1)

[Claims] The conductive brush 13 is brought into contact with the photoreceptor 2, and an alternating current voltage of 20% or more of the direct current voltage is superimposed on the conductive brush +3, and the minimum and maximum values of the voltage waveform are between ±200 and ±2.
A brush charging/transfer device characterized in that an AC superimposed DC voltage in the range of 2000 V is applied.