JPH0376464B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a toner removing device for an electronic copying machine.

Generally, in an electronic copying machine, a photosensitive drum is charged, light reflected from a document is sent to the surface of the photosensitive drum, and toner is applied to an electrostatic latent image formed on the surface of the photosensitive drum depending on the intensity of the sent light. is attached and then transferred to the paper surface as the photosensitive drum rotates.

In such dry-type electronic copying machines, the transfer rate (rate of adhesion to the paper surface during transfer) is about 70 to 80%, so toner remains on the surface of the photosensitive drum after transfer, and this residual toner is transferred to the photosensitive drum. The toner is removed by a toner removal device installed near the drum. This toner removal device uses a so-called blade method in which a blade made of an elastic material is pressed against the surface of the photosensitive drum to scrape off the residual toner after transfer as the photosensitive drum rotates, and a roller that removes the residual toner in the opposite direction. There are various methods such as the so-called roller method that transfers and collects residual toner by applying a polar potential, but since the transfer is performed using toner with a large particle size, it is difficult to maintain the average particle size distribution of the residual toner after transfer. When the diameter is 10 to 15 .mu.m, a large number of fine toners of several .mu.m or less remain in the residual toner, and these fine toners cannot be sufficiently removed by any of the conventional methods.

The present invention was made in view of the above-mentioned circumstances, and its purpose is to provide a charging section that periodically applies a potential of opposite polarity to the residual toner, and a charging section to charge the residual toner. A cleaning section is provided to scrape off the residual toner, and the scraped off residual toner is aggregated with each other by electrostatic adsorption to form coarse particles, so that even minute toner can be reliably and effectively removed. An object of the present invention is to provide a toner removing device for an electronic copying machine.

Hereinafter, the present invention will be specifically described based on an embodiment shown in the drawings. FIG. 1 shows a schematic configuration diagram of a dry type electronic copying machine using a dry type developer (toner), in which a photosensitive drum 1 is a cylindrical conductive drum 1a.
The photosensitive layer 1b is formed on the surface of the photosensitive layer 1b. The electronic copying machine of this embodiment is capable of sequentially performing charging, exposure, development, transfer, etc. while the photosensitive drum 1 rotates in the direction of arrow X (counterclockwise). That is, the photosensitive drum 1 is charged with a single polar charge in the charging section 2, and then exposed with light in the exposing section 3 to form an electrostatic latent image, and this electrostatic latent image is changed to a single polar charge in the developing section 4. The toner image is visualized by adhering the toner, and the toner image is transferred onto the paper surface in the transfer section 5. In this case, in this embodiment, the photosensitive drum 1 is positively charged, and the toner is a negatively charged frictionally charged toner.

Further, after the transfer, the toner remaining on the photosensitive drum 1 is conveyed to a toner charging section 6 installed near the photosensitive drum 1. The toner charging unit 6 is configured by, for example, a corona discharger, and is applied with the output voltage of the DC high-voltage power supply 7 so that the toner has a potential opposite to that of the toner (in this embodiment, the toner potential is is negative, so a positive potential) is applied periodically. The DC voltage power supply 7 generates a positive high voltage at predetermined intervals according to the output of the control circuit 8, and the voltage applied to the toner charging section 6 is a rectangular pulsating voltage.

Then, the toner charged by the toner charging section 6 is conveyed to a static elimination lamp 9 installed near the photosensitive drum 1. The static elimination lamp 9 is used to optically eliminate the excess charge on the photosensitive drum 1 when it is turned on, and is designed to eliminate only the electric charge on the photosensitive drum 1 without removing the charge on the toner. .

Further, the toner that has passed through the static elimination lamp 9 is transferred to a cleaning section 10 installed near the photosensitive drum 1.
transported to. The cleaning section 10 is housed inside an outer case 11, and includes an elastic blade 12 that comes into pressure contact with the surface of the photosensitive drum 1 and scrapes off residual toner as the photosensitive drum 1 rotates, and an elastic blade 12 that scrapes off residual toner as the photosensitive drum 1 rotates.
1, and a toner receiving portion 13 for receiving scraped toner.

Figure 2a shows the voltage waveform applied to the toner charging unit 6, in which the DC high voltage power supply 7 is ON for t ₁ hour and is ON for t ₂ hours.
By being controlled by the control circuit 8 such as OFF, the voltage waveform applied to the toner charging section 6 becomes as shown in FIG. This time t ₁ is the time at which the toner is kept being charged until it can be recharged to a positive polarity of the opposite polarity. In order to obtain a desired amount of reverse polarity charging during a half period of the voltage waveform applied to the toner charging unit 6, as shown in FIG. 2b,
If the linear velocity of the photosensitive drum 1 is v, the corona discharge area by the toner charging section 6 is l, and the period of the voltage waveform applied to the toner charging section 6 is T, then until the area l completely passes through the toner charging section 6. , the toner charging section 6
Since a constant discharge needs to occur, the condition T≧2l/v is required. Furthermore, if the charging time in the charging section 2 in one copying process is tc, the toner in the area developed within the tc time needs to be converted to the opposite polarity at least once, so tc Must be ≧T. Therefore, the cycle of the voltage waveform applied to the toner charging section 6 has its own limitations, and it is desirable that tc≧T≧2l/v.

The characteristic curve diagram in FIG. 3 shows the charging characteristics of the toner by the toner charging section 6, and the horizontal axis is the amount of ions discharged from the toner charging section 6 flowing to the photosensitive drum 1, that is, the drum current (μA). The vertical axis represents the tendency of the toner having an initial triboelectric charge amount of A to be charged to the opposite polarity due to the discharge, as the toner layer potential (V). Accordingly, from FIG. 3, the drum current value B required to recharge the toner potential (1 Vt) to the opposite polarity can be read. Therefore, the current value of B is set in the toner charging section 6.

The use of the above embodiment will now be described with reference to FIGS. 4a to 4e. FIGS. 4a to 4e are schematic diagrams of each process in which residual toner is processed after transfer while being sequentially conveyed to the toner charging section 6, the static eliminating lamp 9, and the cleaning section 10. FIGS. That is, first, FIG. 4a shows the state before the residual toner enters the toner charging section 6, and the surface of the photosensitive drum 1 (the surface of the photosensitive layer 1b), which is positively charged, The residual toner charged on the toner is conveyed to the toner charging section 6 while being attached thereto. During the time period from t=0 to t= _t1 in which the residual toner passes through the toner charging section 6, the residual toner is subjected to positive corona discharge by the toner charging section 6. As a result, the corona ions discharged from the toner charging section 6 positively charge the negatively charged residual toner until it becomes approximately the same as the initial frictional charge amount, and also have a charging effect on the photosensitive drum 1. As a result, positive corona ions adhere to the surface of the photosensitive drum 1, as shown in FIG. 4b. Then, during the period from time t= _t1 to t= _t1 + _t2 , the DC high voltage power supply 7 is turned off under the control of the control circuit 8. As a result, the residual toner is not subjected to discharge from the toner charging section 6, so that
As shown, it remains negatively charged.
Therefore, in the process of the residual toner passing through the toner charging section 6, the charge area of the residual toner is sequentially divided into a positive charge area and a negative charge area.

The residual toner that has passed through the toner charging section 6 is conveyed to the static elimination lamp 9. In the process of passing through the charge eliminating lamp 9, the excess charge on the photosensitive drum 1 is removed without causing any change in the amount of charge of the residual toner, resulting in a state as shown in FIG. 4d.

Then, the residual toner passes through the toner receiving section 13 of the cleaning section 10 and is sent to the elastic blade 12 that is in pressure contact with the surface of the photosensitive drum 1. In this case, the residual toner is periodically charged with positive and negative polarities, but since the excess charge on the photosensitive drum 1 has been removed, the residual toner on the photosensitive drum 1 is
The toner is in a state of weak electrostatic adsorption between its own charge and the so-called mirror image force induced in the photosensitive drum 1. When the residual toner is sent to the blade 12, the fine toner particles are aggregated together by electrostatic adsorption and become coarse particles in a snowdrop pattern, as shown in FIG. 4e. . In this case, the more the particles become coarse, the total amount of coarse particles becomes
As the amount of positive and negative charges gradually becomes neutralized,
The electrostatic adsorption force to the photosensitive drum 1 becomes smaller, and the relative physical forces of the toner's own rotation, stirring, and gravitational action become larger than the mirror image force of the photosensitive drum 1. At this time, while sliding or rotating on the surface of the photosensitive drum 1, the toner gradually falls naturally toward the toner receiving portion 13 side. At this time, it has the effect of electrostatically adsorbing the fine toner particles that have climbed toward the blade 12 while adhering to the photosensitive drum 1, and in the process of falling, the coarse particles further head toward neutralization, and the toner is recovered. It also has a self-cleaning function that facilitates cleaning.

Note that although the above embodiment uses a static elimination lamp, a configuration may also be adopted in which static elimination is performed using an Ac corona discharger.

Further, in the above embodiment, an elastic blade was used to scrape off the residual toner, but a rubber roll, a magnetic roll, or the like may be used as long as it scrapes off the toner.

As described in detail above, the present invention includes a drum to which residual toner is attached, a charging unit that periodically applies a potential of opposite polarity to the residual toner, and a charging unit that scrapes the charged residual toner. It has a cleaning part that removes residual toner, and is configured so that the scraped residual toner aggregates with each other and becomes coarse particles by electrostatic adsorption, so the toner removal effect is significantly improved compared to conventional ones. In addition, even minute toner particles can be removed reliably and well.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a schematic configuration diagram of an electronic copying machine, FIG. 2a is a diagram showing the voltage waveform applied to the toner charging section, and FIG. Figure 3 shows the charging area; Figure 3 is a charging characteristic curve diagram of the toner charging section; Figures 4a to 4e show the residual toner being sequentially conveyed to the toner charging section, static elimination lamp, and cleaning section after transfer. FIG. 1... Photosensitive drum, 6... Toner charging section, 10
...Cleaning department.

Claims (1)

[Claims] 1. A drum to which residual toner is attached, a charging section that periodically applies a potential of opposite polarity to that of the residual toner, and a cleaning section that scrapes off the residual toner charged by the charging section. A toner removing device for an electronic copying machine, characterized in that residual toner is aggregated together in a cleaning section by electrostatic adsorption.