JPH06202487A - Transfer material transferring and separating method for image forming device - Google Patents

Abstract

PURPOSE:To eliminate the need of applying an excessive current so that discharge may be stabilized in the case of separation and to simplify the constitution of a separating means by impressing a high frequency AC voltage lower than the discharge start voltage of all the members other than an image carrier ground electrode as separation bias. CONSTITUTION:When a transfer material reaches a separation part where an image carrier is opposed to a separation electrode, the separation bias having interpeak voltage 6kV and obtained by superposing DC on AC is impressed on the electrode by an AC power source and a DC power source. The positive charge of the transfer material is neutralized and destaticized, and the transfer material is separated from the image carrier by elasticity and stiffness of its own and carried to a fixing part. Relation between the frequency of the AC power source and a separation difference current is as shown by figure. Namely, it is known that faulty separation occurs when destaticization is too weak and toner is retransferred when it is too strong, but a range where such a failure does not occur, is widened by making the frequency high. In the case of impressing 6kV on the electrode, discharge is performed only toward the image carrier, and a discharge wire in an exposed state is used.

Description

Detailed Description of the Invention

[0001]

[Object of the Invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrostatic transfer process such as an electrostatic copying machine and a printer, and more particularly to a method of transferring and separating a transfer material.

2. Description of the Related Art In a known image forming apparatus including a step of electrostatically transferring a toner image electrostatically formed on the surface of an image carrier to a transfer material such as paper Since the transfer material tends to be attracted to the image carrier due to the electric charge applied to the transfer material, it is necessary to positively separate the transfer material from the image carrier immediately after the transfer.

Various types of separating means have been proposed in the past, but a corona discharger for separation arranged at a position after transfer causes an electric charge having a polarity opposite to that at the time of transfer to transfer material. It is well known that the electrostatic separation means for imparting and neutralizing and removing the electric charge acquired by the transfer material at the time of transfer has been put into practical use and has a certain effect.

The corona discharger used for the above purpose is generally said to have a very low discharge efficiency, which will be briefly described with reference to FIG.

Image carrier 10 extending in the direction perpendicular to the plane of the drawing.
1 travels in the direction of the arrow in the figure, and a corona discharger 102 is arranged in parallel with this as a charger for transfer or separation.

The corona discharger includes a charging line 102 "and a shield member 10 which surrounds the charging line 102" and is open only on the image carrier side.
2 ′, a voltage is applied to the charging line by the power supply 103, and at the same time, a discharge current flows between the charging line and the image carrier to form an electric field for performing transfer.

[0006] However, current contributing I ₂ actually transferred to the separation flows in the direction of the inner image carrier current I ₀ flowing into the charging wire 102 "is the current I ₁ flowing through the shield member 102 'direction Compared to this, it is overwhelmingly less efficient.

However, as a practical problem, it has been said that it is unavoidable to prevent discharge unevenness caused by minute irregularities existing on the charging line, contamination by floating toner, etc., and maintain a stable charging function. A decline in function due to long-term use was unavoidable.

First, in order to maintain the charging function, the object to be charged, which generally performs the transfer and separation actions during image formation of this kind, is an insulator or a high resistance material, and therefore it is difficult to discharge it directly. For this reason, it is necessary to place a conductive member such as a shield member or wire near the discharge electrode to cause a discharge between the conductive member and this, and to maintain this discharge thereafter. Since the characteristics are quadratic functions and difficult to control, the input current to the discharge line (the above-mentioned I
_{Since the} current I ₂ that contributes to the charging for ₁ ) is made small and fine adjustment is possible, the inefficiency described above has been unavoidable.

[0009] By the way, as for the discharge device for separation, it is often the case that an AC separation bias is applied to the electrodes during separation. In this case, the peak-to-peak voltage Vpp is increased to improve the static elimination function. Is widely used, and although this has the effect of increasing the speed at which the average potential of the object to be discharged is lowered, it is used as a separation charger to lower the potential on the back surface of the transfer material that carries the toner image with charged toner. When weakening the adsorption force between the image carrier and the image carrier, even if Vpp is increased or the distance to the image carrier is decreased to increase the average potential lowering speed, the instantaneous potential fluctuation is large. As a result of experiments, it has been found as a result that defective separation and retransfer of toner to the image bearing member occur, and the potential fluctuations in which such a situation is likely to occur are about ± 500 to 1000V.

As described above, in order to obtain a stable corona discharge, it can be said that the charging efficiency is inevitably deteriorated, but this means that an excessive current-voltage input to the electrodes is required. However, there are problems such as cost increase due to complication of the apparatus, leakage accident, generation of ozone, and the like, and further, separation failure due to large potential fluctuation at the time of separation of the transfer material from the image carrier, and retransfer are likely to occur. there were.

The present invention has been made to cope with such a situation, and in the separating means constituted so that an AC corona current for separation is passed through the separation charger, the image carrier and the transfer material are supplied to this current. A high-frequency corona current that can also flow to the target is used to directly discharge the object to be charged, and it is possible to reduce the input current voltage to the discharge electrode, which reduces costs and promotes the reduction of ozone generation. There is almost no need for a shield plate as the above, and the amount of charge applied to the charged object at one time (half a cycle of alternating current) is reduced to cause separation defects and retransfer due to excessive potential rise of the charged object. It is an object of the present invention to provide a separation method capable of preventing the above.

[0012]

[Constitution of the invention]

In order to achieve the above object, the present invention brings a transfer material into contact with a transferable toner image formed on the surface of an image carrier and applies a transfer bias to the back surface of the transfer material. Then, the separation bias is applied to the back surface of the transfer material by a separation electrode to apply a separation bias having the opposite polarity to that of the transfer material to separate the transfer material from the image carrier. As
High-frequency alternating current in which the discharge start voltage between the separation electrode and the image carrier ground sandwiching the transfer material and the image carrier is lower than the discharge start voltage of all members other than the image carrier ground electrode in the vicinity of the separation electrode. This is a transfer separation method in which a voltage is applied.

With this structure, it is possible to simplify the structure of the separating means without the need to pass an excessive current in order to stabilize the discharge and transfer during the transfer and separation of the image forming apparatus. In addition, the amount of charge applied to the transfer material at one time (AC half cycle) can be reduced to prevent the occurrence of separation failure or retransfer due to an excessive increase in potential.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS "FIG. 1" shows an embodiment of the present invention and shows only the vicinity of a transfer and separation portion of an image forming apparatus.

An image carrier 1 having an amorphous silicon photoconductor having a positive charging property on the surface of an aluminum substrate runs at a peripheral speed of 480 mm / sec in the direction of arrow A in the figure, and the toner image formed on the surface of the image carrier is After the negatively charged toner T is formed by the action of a primary charging device (not shown), an image signal applying means, a developing device, etc., the negatively charged toner T reaches the transfer part and the separation part as the image carrier 1 travels. .

When a toner image arrives at a transfer site where the image carrier 1 and the transfer charger 2 face each other, the transfer material P is supplied to the transfer site in synchronism with this, and at the same time, the DC power supply 3 causes the charger 2 to be charged. A transfer bias is applied to the transfer material P to give a positive charge to the back surface of the transfer material P, and the negatively charged toner T on the image carrier side is transferred to the transfer material P.

After that, when the transfer material P reaches a separation site where the image carrier 1 and the separation electrode 4 face each other, a peak-to-peak voltage Vpp = a DC voltage is superposed on the electrode 4 by an AC power supply 5 and a DC power supply 6. A separation bias of 6 Kv is applied, and the positive charges of the transfer material P are neutralized and removed. After that, the transfer material itself is separated from the image carrier 1 by its elasticity and elasticity, and is not shown. It shall be transported to the fixing site.

The separating electrode is made of a gold-plated tungsten wire having a diameter of 60.phi. And is arranged at a distance d1 = 3 mm from the image carrier 1 and a distance d2 = 4 mm from the shield plate 2'of the transfer charger as shown. It has been done.

Further, the separation differential current Is (= | I ⁺ |-| I
^- |) Is adjusted by changing the output of the AC high-voltage power supply 5 and the DC power supply 6 arranged in series.

The relationship between the frequency of the AC power supply 5 and the separation difference current Is was examined by using the apparatus having such a configuration.

Electrodes with the image carrier 1 and the transfer material P stopped
Frequency and total current I when AC high voltage is input to
_T (= | I⁺ │ + │I Looking at the relationship of ~ |), it is 50
It was about 20 μA up to 0 Hz, but 1 to 5 KHz
100 μA or more, 300 K to 400 μ at 10 KHz
It was observed that the corona discharge was rapidly activated with A. This
The corona current at is the total current I_T Of the transfer material
P and the photosensitive layer 1 ″ are sandwiched and flow to the photoconductor earth electric electrode 17
Current I_T "(= | I⁺ "| + | I ~" |) is 90%
The shield plate 2'of the transfer charger 2 occupies the above.
Almost no flow, ie I_T (= | I⁺ ’| + |
I ~ '|) was almost zero.

This is the distance d1 = 3 mm, d2 = 10 mm
Therefore, when high frequency high voltage is applied to the electrode 4, the discharge start voltage in the image carrier 1 direction is Vpp = 5.4 KV and the discharge start voltage in the transfer charger 2 direction is Vpp = 7.2 KV. When Vpp = 6 KV is applied, the image carrier 1
This is because the discharge is performed only in the direction. No DC discharge was generated in this configuration.

Next, the separation difference current was changed to examine the separation state of the transfer material from the image carrier 1 and the occurrence of transfer omission due to retransfer. The results are shown in FIG.

Referring to the figure, the vertical axis represents the AC frequency Hz, and the horizontal axis represents the differential current Is. In this case, since the transfer bias is of positive polarity, the static elimination action is stronger as Is moves to the right in the figure. Is shown.

As is well known, if the charge removal is too weak, separation failure will occur, and if it is too strong, retransfer will occur, but as shown in the figure, there is a usable range in which such inconvenience does not occur as the frequency increases. spread. This is because the discharge current amount is increased by increasing the frequency to improve the charge removal capability and the potential fluctuation on the back surface of the transfer material is reduced.

When a separating charger having a shield plate as a separating means as shown in FIG. 7 is used, a large amount of current I1 that does not flow toward the image carrier is unavoidable. In order to obtain the same effect as that of the above embodiment by using such a device, the applied voltage Vpp should be 13
And ~14KV, total current ^{(| I + | + | I} - |)
Also requires 5 to 10 times more output. Further, if a corona discharge of 1 KV or more is performed, a corona hum noise is generated, which causes noise, which is not practically possible, but the present invention is also suitable from this point.

With the same configuration as in FIG.
0φ and d1 = 2.5 mm. With such a configuration, the discharge starting voltage could be set to 4.0 KV. Further, Vpp for achieving the same effect as that of the above-mentioned embodiment was improved by 4.8 KV.

Further, in the case of the present invention, as shown in FIG. 1, since the exposed discharge line can be used as the separating electrode, the maintenance, repair and replacement thereof are extremely easy. Furthermore, it has become possible to use a static elimination needle as a bias applying member for separation. When a high voltage is applied to the static elimination needle as a separating means, the edge of the static elimination material on the transfer material side is formed into a serrated shape, so white spots may occur due to re-transfer due to excessive static elimination. Therefore, it was used only for low- and medium-speed equipment, and not for high-speed machines that need to positively remove electricity.

According to the present invention, since the frequency is high and the amount of electric charge discharged from the static elimination needle once is small (half cycle), overcharge is not eliminated, so that retransfer can be prevented and the static elimination needle can be effectively used. .

Next, in the apparatus as shown in FIG. 1, only the separating means uses the separating charger as shown in FIG. 7,
The results of the endurance test with the one using an exposed discharge line as shown in FIG. 1 are shown.

In the former case, the discharge line 102 ″ and the image carrier 101
Is 8.0 mm, the distance between the discharge line and the shield plate 102 'is 8.0 mm, the applied voltage is 500 Hz, and the peak-to-peak voltage Vpp is a sine wave.

When the usable range shown in FIG. 2 was measured with this product, it was found that the initial width was 0 to -100 μA and the width was about 100 μA, but after passing 200,000 sheets, it was -2.
It decreased to 5 to -50 μA and 25 μA.

On the other hand, in the latter case, the frequency is 5 kHz.
When a sine wave with a z and a peak-to-peak voltage of 6 kV was applied, the usable range was +25 to -100 μA in the initial stage, and approximately 12
The width was 5 μA, which was almost the same as the initial stage even after passing 200,000 sheets.

Further, comparing the surface states of the discharge lines after passing the paper, in the former case, blackening was caused by oxidation, the shield plate was contaminated with the toner, and the accumulation of paper powder was observed at the bottom. This is considered to be because in the former case, the total current is overwhelmingly larger than in the latter case, so that the oxidation due to the generation of ions and the toner adhesion are promoted.

In the latter case, since the total amount of current is small, the oxidation and the adhesion of toner are small, and since the shield plate is not attached, naturally no paper dust is accumulated. In the latter case, even if the surface of the discharge line is oxidized, it is 1 kHz.
The above conditions are advantageous because they can be discharged without any trouble.

"FIG. 3" shows the structure of the separation part showing another embodiment, and the structure of the other parts is the same as that of "FIG. 1".

As shown in the figure, in this apparatus, as shown by reference numerals 4, 4 ', and 4 ", three discharge lines serving as separating means are provided in the traveling direction of the transfer material so as to enlarge the charging area. As shown in the above-mentioned "Fig. 1", if the discharge line is brought close to the transfer material, the charging area becomes narrow, and in the case of a high speed machine, there is a possibility that a charge removal failure occurs unless the voltage and frequency are increased. is there. However, it is practically impossible to raise the voltage indefinitely. Therefore, with the configuration of this embodiment, it is possible to expand the charging region and increase the total amount of current to obtain the desired static elimination effect. it can.

FIG. 4 shows a separating means showing still another embodiment, in which the discharge line is denoted by reference numeral 4,
Two pieces are arranged as shown by 4 ', and the distances d1 and d2 from the respective transfer materials P are made different. With such a configuration, it is possible to form the charging area, the amount of current, and the distribution on the back surface of the transfer material P in the optimum state as much as possible.

In this case, the possibility of adjusting the amount of current and its distribution is further improved by changing not only the distance of the transfer material space of each discharge line, but also their diameters, and combining this with the aforementioned distance change. Increase. Further, although the one shown in the drawing has two discharge lines, it is needless to say that the present invention is not limited to this.

Further, as shown in FIG. 5, the impedance Z is added to the auxiliary discharge line arranged near the main discharge line 4.
_{By connecting 1} and Z ₂ (resistor, varistor, diode, etc.), it is possible to stabilize the discharge and control the polarity.

Furthermore, as shown in FIG. 6, a grid-shaped discharge line 4'is arranged between the main discharge line 4 and the transfer material P, and an impedance Z ₃ is connected to this to discharge the charge. You can control.

When a plurality of discharge lines as described above are used, for example, in FIG. 5, the discharge start voltage between the discharge line 4 and the image carrier 1 is V _B1 , and the discharge start voltage is the same as that of the discharge line 4. 4 ', the discharge start voltage between the discharge lines 4 and 4 "is V _B2, and the high frequency high voltage applied to the discharge line 4 is Vp (peak-to-peak voltage)," Vp / 2> V _{B2 "} By setting the voltage so that the relationship of> V _B1 ″ is maintained, the current flowing in the direction of the image carrier 1 is made much larger than the current flowing into the discharge lines 4 ′, 4 ″, and good charge removal is achieved. Can get the action.

[0043]

As described above, after the toner image on the image carrier side is electrostatically transferred to the transfer material such as paper which is in contact with the toner image, the transfer material is electrostatically transferred from the image carrier. In the image forming apparatus to be separated, it is possible to directly discharge the image carrier and the transfer material by applying a high frequency and high voltage to the discharge line serving as the separation electrode, so that the discharge like a well-known separation charger is stabilized. Therefore, it is not necessary to pass an excessive current, so the corona current can be reduced, and therefore, a shield material or the like for maintaining discharge is not required. Therefore, the input current voltage to the discharge line can be reduced and the device It has a remarkable effect on the simplification and cost reduction, and the prevention of ozone and noise.

[Brief description of drawings]

FIG. 1 is a side view schematically illustrating a configuration near a transfer / separation portion of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a graph showing the effect of the present invention.

FIG. 3

FIG. 6 is a schematic side view of essential parts, each showing another embodiment of the present invention.

FIG. 7 is a schematic side view showing a configuration of a separation charger of a known image forming apparatus.

[Explanation of symbols]

 1 image carrier 2 transfer charger 4 discharge line for separation

Claims (2)

[Claims] 1. A transfer material is brought into contact with a transferable toner image formed on the surface of an image carrier, and a transfer bias is applied to the back surface of the transfer material to perform transfer. Then, a separation electrode has a polarity opposite to that at the time of transfer. In the transfer material transfer / separation method of the image forming apparatus for applying the separation bias to the back surface of the transfer material to separate the transfer material from the image carrier, the separation electrode and the image sandwiching the transfer material and the image carrier are used as the separation bias. A transfer separation method in which a high-frequency AC voltage whose discharge start voltage between the carrier grounds is lower than the discharge start voltage of all members near the separation electrode other than the image carrier ground electrode is applied. 2. The transfer separation method for a transfer material according to claim 1, wherein the frequency of the separation bias is 1 kHz or more.