JPS63286876A - Transfer material separating device for image forming device - Google Patents

Abstract

PURPOSE:To reduce occurrence of dangers, such as spark discharge, creeping discharge, and to make a image forming device adaptable to a high speed and miniaturization, by making the positive- and negative-side peak values of an AC voltage waveform applied to a separating electrifier almost equal to each other and relatively changing the positive- and negative-side waveform areas. CONSTITUTION:This separating device is constituted in such a way that the positive- and negative-side peak values of the AC voltage waveform applied to a separating electrifier 7 are made almost equivalent to each other and the positive- and negative- side waveform areas are relatively changed. In other words, a square-wave high-voltage power source 3 and corona current detecting circuit 4 are connected with the charging line of the electrifier 7 and a square-wave duty ratio controlling circuit 5 controls the duty ratio of square waves so that a corona discharging current becomes a prescribed value by using the signal of the corona current detecting circuit 4. Therefore, the p-p value of the applied voltage is lowered and this image forming device can be made adaptable to a high speed and miniaturization. Moreover, occurrence of dangers of abnormal discharge can be reduced sharply.

Description

Detailed Description of the Invention (1) Purpose of the Invention (Field of Industrial Application) This invention relates to image forming apparatuses that utilize an electrostatic recording process, such as electrostatic copying machines and printers, and particularly to transfer material separation devices thereof. It is related to.

(Prior art and issue 8 to be solved) A sheet-like transfer material such as paper is brought close to a transferable toner image formed on the surface of an image carrier, and a transfer charger electrostatically charges the toner image onto the transfer material. In a well-known image forming apparatus configured to transfer images, the transfer material tends to be attracted to the image carrier due to the electric charge applied to the transfer material by the transfer charger. In order to neutralize and eliminate the charge on the transfer material, a device equipped with a separate charger for imparting a charge of opposite polarity to that of the transfer charger has been put into practical use.

In this type of separation charger, the charge on the transfer material is normally removed by AC corona discharge applied with a high AC voltage with a DC bias, and the charger's charge removal function is based on the peak - t.

-It depends on the peak value (p-p value), and the higher this value is, the greater the static elimination ability is.

Given the recent trend towards higher speeds in this type of equipment, in order to rapidly and reliably eliminate static electricity after transfer, it is necessary to
-It is desirable to increase the p value, but on the other hand, increasing this value inevitably increases the risk of spark discharge and creeping discharge.On the other hand, in this type of image formation It is also true that smaller devices are becoming more and more popular, and from this perspective, it is possible to obtain the desired separation characteristics with the lowest possible p-p value. desirable.

In addition, the charging wire of such a separation charger is easily contaminated by fine paper dust generated from the paper used as the transfer material, floating toner inside the device, etc., and the peak value becomes high due to the superimposition of direct current on alternating current. From this point of view, the risk of abnormal discharge occurring cannot be avoided.

The present invention has been made to deal with such a situation, and reduces the risk of spark discharge and creeping discharge without causing an increase in the peak value of the peak value or the superimposed AC/DC waveform. However, it is an object of the present invention to provide a transfer material separation device that is suitable for speeding up and downsizing image forming apparatuses.

(2) Structure of the invention (technical means for solving the problem and its operation) In order to achieve the above object, the present invention utilizes a transfer charger to transfer a transferable toner image formed on an image bearing member. and transfer it to the transfer material,
Then, in an image forming apparatus configured to separate the transfer material from the image carrier by a separation charger, the positive and negative peak values of the AC high voltage waveform applied to the separation charger are approximately equal, and the waveforms on both the positive and negative sides are It is characterized by being configured so that the area changes relatively.

With this configuration, the p-p value of the applied voltage can be lowered, thereby easily adapting to higher speed and smaller size of the image forming apparatus, and greatly reducing the risk of abnormal discharge occurrence. Can be done.

(Description of an Embodiment) FIG. 1 is a side view of a main part showing an embodiment in which the present invention is applied to a copying machine equipped with a rotating cylindrical photoreceptor.
A transfer charger ri2 and a separation charger 7 are disposed on the photoreceptor l rotating in the direction, and the toner image formed on the surface of the photoreceptor l is transferred to a transfer material (not shown) supplied by a conveyance path 6. It is assumed that the toner image reaches the transfer site where the transfer charger exists at the same timing, and the toner image is transferred to the transfer material at this site.

It should be noted that, as is well known, there are, of course, disposed around the photoconductor the members necessary for image formation, such as a charger, an image signal applying means, a developing device, and a cleaning device.
Since they are not directly related to the present invention, they are all omitted.

After the transfer, the transfer material further advances to the left in the figure and reaches the position of the separation charger 7, where it is neutralized by a corona discharge with a polarity opposite to that at the time of transfer, is separated from the photoreceptor, and is sent to a fixing site (not shown). shall be carried out.

In such a thing, in the present invention.

A rectangular wave high voltage power supply 3 and a corona current detection circuit 4 are connected to the charging wire of the separation charger, and a signal from the corona current detection circuit causes a rectangular wave duty ratio control circuit 5 to control the corona discharge current to a predetermined value. The structure is such that the duty ratio of the rectangular wave is controlled so that

FIG. 2 is a graph showing a comparison between the case where the discharge current of the separation charger is controlled according to the present invention and the case where a known AC/DC superimposed waveform is applied.

In the figure, the horizontal axis shows the peak-to-p of the applied voltage.
The eak value is taken, and the vertical axis shows the allowable width (I9) of the DC component (I9) of the corona discharge current of the separation charger during the time when the transfer material of the white original starts to separate and the black original can be separated without being retransferred. A
Ig).

Regarding the elements on the vertical axis, first of all, when the transfer material is a white background, static electricity can be removed with a DC component of the corona discharge current exceeding a certain value, and in the case of a black original, the DC component may be small, but If this is increased too much, a retransfer phenomenon will occur, so as mentioned above, the current range from the start of separation of a white original to the start of retransfer of a black original is set as an allowable range.

The curve (a) in FIG. 2 shows the relationship between the p-"p value and the current permissible range of a known AC/DC superimposed waveform, and the curve (b) shows a similar relationship according to the present invention.

As can be seen from this graph, by applying the present invention, it is possible to obtain the same tolerance range as the known one with a lower voltage (p-p value). For example, in order to obtain the tolerance range ΔIt=300 gA, the known method requires approximately 14 KV, but the present invention requires approximately 12 KV.

Note that the DC component of the corona discharge current is divided by a diode 8.9 and measured by an ammeter 10.9 as shown in FIG.
The difference in the current value flowing through the circuit 11 was applied to this, and the change was controlled by the duty ratio control circuit 5.

FIG. 4 shows another embodiment, in which a charging wire of a separation charger 7 disposed on the lower side of the transfer charger 2 disposed close to the photoreceptor l is connected to an AC high-voltage power supply 12 for corona current control. A DC high voltage power supply 13 is superimposed, and a varistor 15 is connected to the superimposed output side. Reference numeral 14 denotes a corona current control circuit, which controls the DC high voltage power supply 13.

FIG. 5 shows the voltage waveform applied to the charger 7.
In the figure, a indicates the DC voltage level, and b+ and b- indicate the rated values of the varistor.

Curve (C) in Fig. 2 is obtained by applying an AC voltage approximately IKV higher than the varistor's rated value (2 KV in P-P value) using the above device, and changing the varistor's rated value and DC voltage.
The static elimination current allowable range ΔI was measured.

Also in this case, compared to known ones, AIg =
It can be seen that in the case of 300 gA, it is possible to lower the IKVp-p value.

As explained above, according to the present invention, a transfer charger is used to transfer a toner image on an image bearing member to a transfer material, and then a separation charger is used to apply a charge of opposite polarity to the transfer material to the transfer material. In a separation device of an image forming apparatus configured to separate this from an image carrier, a rectangular wave voltage with a substantially constant peak value on the positive and negative sides is applied to a minute gi charger, and its duty ratio is The p of the applied AC voltage can be adjusted by changing the applied AC voltage, or by using an appropriate nonlinear element so that the peak values on the positive and negative sides of the AC waveform are almost constant, and by superimposing the DC voltage to obtain the desired static elimination current. - It becomes possible to lower the p value, and it is possible to reduce the abandonment of abnormal discharge due to high voltage or contamination of the charged wire.

(3) Effects of the Invention Since the present invention has the configuration described above, when the transfer material is electrostatically separated from the image carrier by the one-separation charger, the AC voltage applied to the separation charger is p
Since the eak-to-peak value can be lowered, it is possible to respond to higher speeds and smaller size image forming apparatuses. It is possible to reduce the occurrence of abnormal discharge due to contamination, etc., and perform stable and good separation at all times.

[Brief explanation of the drawing]

FIG. 1 is a side view of essential parts showing an embodiment in which the present invention is applied to a copying machine. FIG. 2 is a graph showing the relationship between the allowable range of static elimination current and the required applied voltage in the present invention and the known one. FIG. 3 is a current measuring circuit in the device shown in FIG. 1, and FIG. 4 is a side view of main parts showing another embodiment. FIG. 5 shows the output waveform of the separation charger same as above. DESCRIPTION OF SYMBOLS 1... Photoreceptor, 2... Cloud transfer charger, 3... Rectangular wave voltage power supply, 4... Fist corona current detection circuit, 5... Duty ratio control circuit, 7... Separation charger , 12・-・
AC voltage power supply, 13-Φψ DC voltage power supply, l-... corona current detection circuit, 15... varistor. Figure 1 Figure 2 P-P Direction Figure 3 Figure 4 Figure 5

Claims (3)

[Claims] (1) After the toner image formed on the image carrier is transferred to the transfer material that is in contact with it by a transfer charger, a charge with the opposite polarity to that during transfer is applied by a separation charger to cause the transfer material to carry the image. A separating device for an image forming apparatus configured to be separated from a human body is characterized in that the peak values on the positive and negative sides of the AC voltage waveform applied to the separation charger are made almost the same, and the waveform areas on the positive and negative sides are relatively changed. Transfer material separation device. (2) The transfer material separation device according to claim 1, wherein the AC voltage waveform applied to the separation charger is a rectangular wave, and the waveform is changed by changing the duty ratio. (3) The transfer material separation device according to claim 1, which has a limiter that limits the peak of the AC voltage applied to the separation charger, and the waveform change is made by superimposing the DC voltage.