JPH0376463B2 - - 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 an original is sent to the surface of the photosensitive drum, and an electrostatic latent image is formed on the surface of the photosensitive drum depending on the intensity of the transmitted light. Toner is applied to the toner, 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 The toner is removed by a toner removing device installed near the photosensitive 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 and scrapes off the residual toner after transfer as the photosensitive drum rotates, and a method in which the residual toner is removed by a roller. There are various methods, such as the so-called roller method, which transfers and collects residual toner by applying a potential of opposite polarity.
Since the transfer is performed using toner with a large particle size, the particle size distribution of the residual toner after transfer should be adjusted to an average of 10 to 15 μm.
In this case, a large number of minute toners of several micrometers or less remain in the residual toner, and these minute toners cannot be sufficiently removed by any of the conventional methods.

The present invention has been made in view of the above-mentioned circumstances, and its objectives are to provide a charging section that alternately charges residual toner to a positive electrode and a negative electrode, and a cleaning device that scrapes off the residual toner charged with this charging section. A toner removal device for an electronic copying machine, which is provided with a section and which aggregates the scraped-off residual toner with each other to form coarse particles by electrostatic adsorption, thereby reliably and effectively removing even minute toner. Our goal is to provide the following.

Hereinafter, the present invention will be specifically described based on an embodiment shown in the drawings. FIG. 1 shows a schematic diagram of a dry electronic copying machine using a dry developing material (toner), and a photosensitive drum 1 has a structure in which a photosensitive layer 1b is formed on the surface of a cylindrical conductive drum 1a. .
The electronic copying machine of this embodiment has a photosensitive drum 1.
While rotating in the direction of arrow X (counterclockwise), charging, exposure, development, transfer, etc. can be sequentially performed. 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 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. This toner charging unit 6 is configured by, for example, a corona discharger, and when the output voltage of the positive and negative high voltage generator 7 is applied,
The positive and negative electrodes are alternately discharged at predetermined intervals. The positive and negative high voltage generator 7 alternately generates positive and negative high voltages at predetermined intervals according to the output of the control circuit 8, and the voltage applied to the toner charging unit 6 is a rectangular wave AC voltage. .

Then, the toner charged by the toner charging section 6 is conveyed to an Ac static elimination section 9 installed near the photosensitive drum 1. The Ac static eliminating unit 9 performs weak Ac discharge according to the output of the Ac high voltage generator 10 to eliminate excess positive and negative charges on the photosensitive drum 1, without discharging the toner charges. , only the charge on the photosensitive drum 1 is removed.

Furthermore, the toner that has passed through the Ac static eliminating section 9 is transferred to a cleaning section 11 disposed near the photosensitive drum 1.
transported to. This cleaning section 11 is housed inside an outer case 12, and includes an elastic blade 13 that is in 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 13 that is installed at the lower end of the outer case 12. A toner receiving portion 14 is provided to receive scraped toner.

FIG. 2 shows the voltage waveform applied to the toner charging unit 6, in which a positive voltage is applied to the toner charging unit 6 within time t ₁ , and within time t ₂ , a positive voltage is applied to the toner charging unit 6. A negative voltage is applied to. this time
t ₁ and t ₂ are the times during which electricity is continued to be applied at least until the toner can be recharged to the positive saturation amount of the positive electrode or the saturation amount of the negative polarity. As shown in FIG. 3, 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 the area l is Since it is necessary for a certain amount of discharge to occur in the toner charging section 6 before the toner completely passes through the toner charging section 6, the condition T≧2l/V is required. Furthermore, if the charging time in the charging unit 2 in one copying process is tc, then the toner in the area developed within the time tc is charged at least once or more in the positive,
Since it is necessary to convert to negative polarity, tc≧T must be satisfied. 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. 4 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 is the initial value A due to the discharge.
The toner layer potential (V) indicates the tendency of the toner having the amount of triboelectric charge to be charged to opposite polarities. Accordingly, the drum current values D and E required to recharge the toner to the saturation potentials B and C can be read from FIG. Therefore,
In the toner charging section 6, the current value is set to D, E or more.

Next, the operation of the above embodiment will be explained with reference to FIGS. 5a to 5e. 5a to 5e show that after the transfer, residual toner is removed from the toner charging section 6, the Ac static eliminating section 9,
FIG. 2 is a schematic diagram of a process performed while being sequentially conveyed to a cleaning section 11; That is, first, the fifth
Figure a shows the state before the residual toner enters the toner charging section 6, and the positively charged surface of the photosensitive drum 1 (the surface of the photosensitive layer 1b) has the negatively charged The toner is conveyed to the toner charging section 6 while being attached. In the process of this residual toner passing through the toner charging section 6, from time t=0 to t=
During the period t ₁ , 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 unit 6 positively charge the negatively charged residual toner to the charging saturation region, and also act on the photosensitive drum 1 to charge the surface of the photosensitive drum 1. Also, positive corona ions are attached, as shown in FIG. 5b. and,
During the period from time t=t ₁ to t=t ₁ +t ₂ , the residual toner is subjected to negative corona discharge by the toner charging section 6 . As a result, the corona ions discharged from the toner charging unit 6 further negatively charge the negatively charged residual toner to the charging saturation region, and neutralize the positive charges on the surface of the photosensitive drum 1. ,
Furthermore, since it is charged to a negative polarity, it becomes as shown in FIG. 5c. 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 Ac static eliminating section 9. This AC static eliminator 9
In the process of passing through the photosensitive drum 1, the surplus charge on the photosensitive drum 1 is removed by a weak Ac corona discharge with constant voltage property by the Ac static eliminating section 9, as shown in FIG. 5d.

The residual toner then passes through the toner receiving section 14 of the cleaning section 11 and is sent to the blade 13. 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 divided into the toner's own charge and the photosensitive drum. The conductive drum 1 is in a state of weak electrostatic adsorption with the mirror image charge induced on the conductive drum 1a. When the residual toner is sent to the blade 13 that is in pressure contact with the photosensitive drum 1, the fine toner particles are aggregated together by electrostatic adsorption and become coarse particles like a snowball. The result is as shown in Figure e. 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 is small, and the toner becomes coarse particles, and the overall physical force of its own rotation, stirring, and gravitational action is greater than the mirror image force of the photosensitive drum 1. At this time, the toner gradually falls naturally toward the toner receiving portion 14 while sliding or rotating on the surface of the photosensitive drum 1 . At this time, it has the effect of electrostatically adsorbing the minute toner particles that have climbed toward the blade 13 while adhering to the photosensitive drum 1, and in the process of falling, the coarse particles further head in the direction of neutralization, and the toner It also has a self-cleaning function that facilitates recovery.

Next, other embodiments of the present invention are shown in FIGS. 6a and 6b.
This will be explained with reference to FIG. In the device shown in FIG. 6a, the toner charging section 6 is configured with a grid-controlled corona discharger, and the output voltage of an Ac voltage generator 15 is applied to the corona wire, and a control circuit 16 is applied to the grid. The configuration is such that the output of a DC positive/negative generating power source 17 that generates DC positive/negative bias voltages with a controlled constant period is applied, and the shield electrode is further grounded. With this configuration, a drum current waveform as shown in FIG. 6b is obtained, and the remaining toner is alternately charged to the positive and negative electrodes as described in detail in the above embodiments, and the remaining toner is recharged and the excess on the photosensitive drum is removed. Charge removal becomes possible.

Further, FIG. 7 shows still another embodiment of the present invention, and the differences from the embodiment shown in FIG. 6a are as follows.
The output of the DC positive/negative generating power source 17 is applied to the shield electrode of the toner charging section 6, and the same effect as that of the embodiment shown in FIG. 6a is achieved.

Note that the present invention is not limited to the above-mentioned embodiments as long as the remaining toner can be recharged to positive and negative polarities at a predetermined period.

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 section that alternately charges the residual toner to a positive electrode and a load, and a cleaning section that scrapes off the residual toner charged by the charging section. It has a structure in which the scraped residual toner is aggregated with each other by electrostatic adsorption to form coarse particles, so the toner removal effect can be significantly enhanced compared to conventional methods, and the toner can be removed from microscopic particles. Even toner can be removed reliably and well.

[Brief explanation of drawings]

1 to 5 a to e show an embodiment of the present invention, and FIG. 1 is a schematic configuration diagram of an electronic copying machine;
Fig. 2 is a diagram showing the applied voltage waveform to the toner charging section, Fig. 3 is a diagram showing the charging area of the toner charging section, Fig. 4 is a charging characteristic curve diagram of the toner charging section, and Figs. 6e is a schematic diagram of each process in which the residual toner is sequentially transported to the toner charging section, the AC static eliminating section, and the cleaning section after transfer, and FIGS. 6a and 6b are other embodiments of the present invention. For example, FIG. 6a is a diagram showing the configuration of the main part, FIG. 6b is a diagram showing the drum current waveform, and FIG. 7 is a diagram showing the configuration of the main part showing still another embodiment of the present invention. 1... Photosensitive drum, 6... Toner charging section, 11
...Cleaning department.

Claims (1)

[Claims] 1. A drum to which residual toner is attached, a charging section to which the residual toner is alternately charged to a positive electrode and a negative electrode, and a cleaning section to scrape off the residual toner charged by the charging section. A toner removing device for an electronic copying machine, characterized in that toner particles are aggregated together in a cleaning section by electrostatic attraction.