JPS6173972A - Electrophotographic copying device - Google Patents

Abstract

PURPOSE:To reduce the cost and to improve the reliability by the simplification of the constitution of an electric accessory by turning on and off electrostatic charging, development, and transfer at the same timing and uniting respective power packs. CONSTITUTION:A high voltage is applied from a single power pack 12 to an electrostatic charger 2, developing roller 4a, and transfer charger 5. Therefore, a developing bias and transfer charger 5 are therefore turned on in an image forming cycle as the electrostatic charger 2 is turned on, and the electrostatic charging, development, and transfer are turned off for the 1st time after the transfer of a toner paper to transfer paper is finished. Secondary operation when they are turned off at the same timing is coped with by a means for cleaning, discharging, etc., and an erasing means and a transfer charger after electrostatic charging may be provided with a shutter for further perfection. Thus, the constitution of the electric accessory is simplified, so the cost is reduced and the reliability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an electrophotographic or copying apparatus having processes of charging, exposure, development, and transfer, and particularly relates to a high-voltage power supply thereof.

(Prior Art) FIG. 4 is a block diagram showing the image forming process means of a copying machine, which is the premise of the present invention.

In the figure, 1 is a photoreceptor unit, 2 is a charger,
3: optical system unit, 4: developing unit.

Reference numeral 5 indicates a transfer charger, 6 a paper feed cassette, and 7 a document table.

First, the original is irradiated with a linear light source (for example, a light lamp) in the optical system unit 3, and is then irradiated with light onto the photoreceptor 1 via the imaging element.
imaged on a surface. Before the photoreceptor 1 is irradiated with the reflected light image, it is uniformly charged by a charging jar 2.

Therefore, a static image corresponding to the original is formed on the photoreceptor 1 after passing through the imaging element. Since the photoreceptor 1 and the original move at the same speed, the electrostatic latent image is a projection K of the original at the same size. After a time sufficient for the rear end of the original to be projected, the charger 2 is turned off so as not to apply any excess charge to the photoreceptor 1.

On the other hand, as the latent image passes through the developing unit 4, toner is attached thereto and converted into a toner image. At this time, in order to maintain an appropriate amount of toner adhesion, a developing bias voltage is often applied to the developing roller 4a (shown in FIG. 5). A control circuit 11 (shown in FIG. 5) controls the transfer charger 5 to turn on when the leading edge of the toner image and the leading edge of the transfer paper supplied from the yarn feeding cassette 6 simultaneously enter the transfer section. The toner image on the photoreceptor 1 is transferred to the transfer paper by the transfer charger 5 applying a high voltage from the back side of the transfer paper. After the trailing edge of the toner image has been transferred, the transfer charger 5 is turned off. Thereafter, the transfer paper on which the toner image has been applied is fixed in a fixing section (not shown) to complete the copy, while the photoreceptor 1 is cleaned of residual toner remaining after the transfer by a cleaning means (not shown), and further The residual charge on the latent image is removed by a charge removing means (not shown) and the image is completely restored to its original state.

K in order to run the image forming cycle described above smoothly.

Conventionally, the configuration shown in FIG. 5 was used and the drive was performed with the timing shown in FIG. 6.

As shown in FIG. 5, the charger 2. developing row 24a,
Separate power backs 8 and 9 for each transfer charger 5
．． 10 was used, and the power backs 8, 9° 10 were driven by a timing command signal from a control circuit 11. The power backs 8, 9, and 10 apply a corona discharge voltage to the charging charger 2 and the transfer charger 5, and apply a bias voltage to the developing roller 4a.

In a normal copying machine, the developing bias remains on during the image forming period and there are no major side effects.However, in order to prevent the charger 2 from depositing excess toner' on the photoreceptor 1, the transfer charger 5 is applied to the photoreceptor 1. In order to prevent unnecessary charges from being applied, each of these devices is turned on only for a period corresponding to one copy. Moreover, since charging and transfer are often located at opposite sides of the photoreceptor, their driving timings deviate by a large amount as shown in the timing chart of FIG. In this way, the conventional configuration requires as many as three high voltage generation means (power backs) of the same circuit, and requires many connections from the timing signal and DC power supply, resulting in problems in terms of component configuration, equipment cost, and reliability. This is disadvantageous.Here, unnecessary toner on the photoreceptor can be removed by lJ = ng.Considering that unnecessary charges can also be removed by a static eliminating means, the timing shown in Figure @6 is not necessarily necessary.

(Objective) The present invention focuses on this point and aims to eliminate the drawbacks of the conventional example.

(Structure) For this purpose, the present invention is characterized in that each power back is integrated by turning on/off charging, developing bias, and transfer at the same timing.

An embodiment of the present invention will be described below based on FIGS. 1, 2, and 3.

Note that the same parts as in the conventional example are given the same reference numerals.

FIG. 1 is a high voltage "KA" circuit diagram according to the present invention.

A high voltage is applied from a single power back 12 to the charging charger 2°, the developing roller 4a, and the transfer charger 5.

Therefore, as shown in the timing chart of FIG.

In the image forming cycle, the developing bias and transfer charger 5 are also turned on when the charging charger 20 is turned on, and charging, development, and transfer are turned off only after the toner image has been transferred to the transfer paper. Since the counter pressure is at the same timing, it can be said that it can be supplied from one power back 12 as shown in FIG.

Figure 3 shows the circuit configuration of the power converter 2120. (a) A three-stage output section is provided on the secondary side of a transformer T in which a controlled oscillation circuit 13 is provided on the +21st order side, and each voltage applied section is provided with a three-stage output section. It is something that is connected. In addition, (b) shows the output winding divided by one KL''C resistor.

Naturally, with a power bag like this, the case can also be integrated.

For the above-mentioned integration, being able to drive at the same timing is of course a preferable condition, but it is not necessarily a necessary condition. In other words, even with a power back configuration as shown in Figure 3, a high voltage relay is installed on each secondary winding side.
It is also possible to turn on/off each at independent timing. The side effects of using the same timing can be dealt with by means such as cleaning and static elimination as described above, but in order to ensure completeness, it is possible to take measures such as providing a shutter on the erase means after charging or the erase means and the transfer charger using the exposure means. Measures can also be considered. Although these are not particularly shown in the drawings, sufficient pressure can be achieved using conventional techniques.

(Effects) The present invention is as described above.According to the present invention, it is possible to reduce costs and improve reliability by simplifying the configuration of electrical components, and by reducing the number of high-voltage components. It is also expected to improve safety and reduce side effects caused by noise.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a high-voltage electrical component according to the present invention, FIG. 2 is a diagram showing an example of its timing chart, and FIG. 3(a)
t(b) is a circuit diagram showing different types of power back structures, FIG. 4 is a block diagram showing the image forming process means of a copying machine to which the present invention is applied, and FIG. 5 is a diagram showing a conventional high-voltage power supply. The circuit diagram and FIG. 6 are its timing chart. 1... Photoreceptor, 2... Charger, 3... Optical system unit, 4... Developing unit, 5... Transfer charger , 12...
...Power back. Figure 1! Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Copy start transcription

Claims (1)

[Claims] A charging means for charging the photoreceptor, an exposure means for irradiating a reflected light image of the document onto the charged cold photoreceptor, and a developing means for visualizing the latent image created on the photoreceptor. An electrophotographic copying apparatus, comprising a transfer means for transferring the developed image onto paper, and at least the charging means and the transfer means are energized by one high voltage generating means.