JPH037114B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for stopping an electrophotographic printer used as a terminal printer that outputs characters and graphics at high speed.

Electrophotographic printers such as those mentioned above generally use a so-called reversal development method, in which toner is attached to the uncharged portion of the photoreceptor, which is the opposite of a normal copying machine due to the lifespan of the light source and power consumption. However, since the toner remaining on the photoreceptor after development transfer is collected by a cleaning section and used again in the developing device, the sequence for stopping the printing operation is simple.

However, recently with the above electrophotographic printers,
In order to improve image quality and extend the life of the photoconductor, once used toner is no longer collected and reused, there is a need to use toner efficiently and avoid wasteful consumption. It has become like that. In order to meet this requirement, conventionally, when the printing operation is stopped, the high-voltage power supply for primary charging is turned off, and then the bias power supply is turned on until the primarily charged portion of the photoreceptor passes in front of the developing device, thereby reducing the surface charge. When the unused portion reaches the front of the developing device, the bias power source is turned off to prevent toner not directly related to recorded data from adhering to the photoreceptor.

However, in reality, even if printing is stopped in the above sequence, when the high-voltage power source for primary charging is turned off, the surface of the photoreceptor facing the primary charger will move away from the primary charger as shown in Figure 1. Therefore, since the potential distribution exhibits an irregular potential distribution with a boundary where the potential decreases, if the developing bias power is turned off at the same time as the part A in FIG. Toner adheres to the surface of the photoreceptor during regular development, and when the bias power is turned off at the same time as the part B in Figure 1 reaches the front of the developer, reverse development occurs on the surface of the photoreceptor that had previously passed in front of the developer. Toner adheres to the surface.

An object of the present invention is to prevent toner from being wastefully attached to a photoreceptor when the printing operation is stopped, as described above, and to efficiently consume toner.

For this purpose, in an electrophotographic printer using a reversal development method, the present invention irradiates the surface of a photoreceptor with a light source for writing print data at the same time as the high-voltage power supply for primary charging is cut off when the printing operation is stopped, thereby eliminating the surface charge. The developing bias power supply is turned off as soon as the exposed portion reaches the developing device.

The present invention will be explained below with reference to the drawings.

FIG. 2 shows the mechanism of the electrophotographic printer of the present invention, in which 1 is a photosensitive drum having a photosensitive member on its surface and rotates in the direction of the arrow in the figure; 2 is a photosensitive drum that rotates in the direction of the arrow in the figure; The primary charger that charges electricity, 3
An optical writing head consists of a light source consisting of an LED array and an imaging element, etc.; 4 a developing device that attaches toner to the electrostatic latent image on the photoreceptor 1 and develops the image; 5 promotes transfer by corona discharge. A transfer charger 6 is an erasing lamp that exposes the entire surface of the photosensitive drum 1 to release surface charge; 7 is a cleaning unit that removes residual toner on the photosensitive drum 1; 8 is a primary charger connected to the primary charger 2; 9 is a high voltage power source for developing bias, and 10 is a printing paper.

In the above configuration, printing is performed using a so-called electrophotographic method. First, the surface of the photosensitive drum is uniformly and positively charged by the primary charger 2, and then print data is written onto the photosensitive drum 1 by the optical writing head 3.
Writing of print data is done in the optical writing head 3.
This is done by selectively emitting light from an LED according to the print data, and focusing the image using a focusing rod lens or the like. When print data is written on the photosensitive drum 1, a surface charge disappears in a dot pattern, forming an electrostatic latent image of the print data. This electrostatic latent image is visualized by the developer 4 when toner adheres to the area where the surface charge has disappeared. The toner attached to the photosensitive drum 1 is transferred to the printing paper 1 in the transfer section.
The residual toner is transferred to zero and the remaining toner is removed by the cleaning unit 7. The transferred image on the printing paper 10 is fixed by a fixing device (not shown).

In an electrophotographic printer that prints using such a process, the sequence for stopping the printing operation will be explained with reference to Figure 3. First, when a printing stop command is issued, the primary charging At the same time as the high voltage source 8 is turned off, the LDEs of the optical writing head 3 are made to emit light all at once. The light emission from the optical writing head 3 is at least equal to the time required for the portion of the surface of the photosensitive drum 1 located near the primary charger, where the surface potential is 0 V, to pass through the optical writing head 3 when the high-voltage power source 8 for primary charging is disconnected. T ₁
Just keep going. Therefore, after the primary charging high-voltage power supply 8 is turned off, the surface of the photosensitive drum 1 passing through the optical writing head 3 has no charge. Next, as shown in FIG. 3c, the time after the start of light emission of the optical writing head 3
After T ₂ has elapsed, the high voltage power supply 9 for developing bias is turned off. The time _T2 is the time required for the photosensitive drum 1 to rotate from the optical writing head 3 to the position of the developing device 4. Therefore, the time when the high-voltage power supply 9 for developing bias is turned off coincides with the time when the first part of the photosensitive drum 1 that has been exposed to the entire surface of the optical writing head 3 passes through the developing device 4, and the high-voltage power supply 9 for developing bias is turned off. After that, the surface potential of photosensitive drum 1 is 0V.
Only that part passes through. Therefore, at the same time as the developing bias power source 9 for the developing device 4 is cut off, the surface potential of the photosensitive drum 1 is switched from V ₃ to 0 V as shown in FIG. 3d. Therefore, no electrostatic force is generated to cause toner to adhere to the photosensitive drum 1, and neither normal development nor reverse development is performed.

The command to stop the rotation of the photosensitive drum 1 and the extinguishing of the erasing lamp 6 are issued after the above-mentioned time (T ₁ +T ₂ ) has elapsed, as shown in FIGS. 3b and 3c.

In this way, according to the above print stop sequence,
Since the surface potential distribution of the photosensitive drum 1 passing through the developing unit 4 switches from V ₃ to 0 V with a sharp boundary, the developing bias power supply is turned off at the same time as the boundary passes through the developing unit 4. For example, an electric field for transferring toner is not generated between the photosensitive drum 1 and the developing device 4, and neither normal development nor reverse development is performed.

As explained above, according to the present invention, the toner in the developing device is not wasted when the printing operation is stopped, and the toner usage efficiency is improved in an electrophotographic printer that does not reuse the collected toner. be.

In the above embodiment, the light source of the optical writing head is
Although LED is used, OFT is used as the light source for optical writing.
Even if the present invention is applied to an electrophotographic printer using a laser beam or a laser beam, the same effects as described above can be obtained.

[Brief explanation of the drawing]

Figure 1 is a diagram used to explain the conventional problems, Figure 2
The figure is a schematic configuration diagram of an electrophotographic printer embodying the present invention, and FIG. 3 is a time chart illustrating a printing operation stop sequence in an embodiment of the present invention. 1...Photosensitive drum, 2...Primary charger, 3...
Optical writing bed, 4...Developer, 8...High voltage power supply for primary charging, 9...High voltage power supply for developing bias.

Claims (1)

[Claims] 1. A photosensitive drum that rotates in a predetermined direction, a high voltage source that drives a charger that charges the photosensitive drum,
A method for stopping an electrophotographic printer of a reversal development type that has a light source for writing print data that selectively eliminates the charge on the photosensitive drum and a developing bias power source that drives a developing device that develops the photosensitive drum. While the drum is being rotated, the charging high-voltage power source is turned off, and at the same time, the entire surface of the photosensitive drum is exposed to light by the print data writing light source to start dissipating the surface charge on the photosensitive drum. and a second step of cutting off the developing bias power supply at the timing when the beginning of the portion where the surface charge of the photosensitive drum disappears due to the entire surface exposure reaches the developing device. How to stop.