JPH01292377A - Transfer material separating device for image forming device - Google Patents

Abstract

PURPOSE:To reduce the disorder of a waveform, to lower a peak-to-peak voltage, and to reduce the size and weight of the device by superposing 1st and 2nd sine waveforms and the voltage applying to a separation electrostatic discharger and using the obtained voltage. CONSTITUTION:First and second sine wave high-voltage power sources 3 and 4 and a DC voltage power source 5 are connected to the discharge wire of the separation electrostatic discharger 8 in series and the power source 5 is driven by a corona current control circuit 7 with the signal of a corona current detecting circuit 6 to control the quantity of corona discharge. Further, the frequency of the power source 4 is set three times as high as that of the power source 3 and the powers of both power sources are superposed on over the other so that the voltage waveform of the former lowers the peak value of the voltage waveform of the latter. A toner image formed on the surface of a photosensitive body 1 reaches the transfer position where a transfer charger 2 is present while timed with the transfer supplied by the circuit 6 and the toner image on the photosensitive body 1 is transferred at this position to a transfer material. Then the transfer material is separated from the photosensitive body 1 by the corona discharging of a discharger 8 having the opposite polarity from in the transfer and further conveyed to a fixation position.

Description

Detailed Description of the Invention (1) Purpose of the Invention (Field of Industrial Application) This invention relates to an image forming apparatus that uses an electrostatic transfer process in an electrostatic copying machine, a printer, etc., and particularly to a transfer material separation device thereof. It is related to.

(Prior art and issues to be solved) A sheet-like transfer material such as paper is brought into contact with a transferable toner image formed on the surface of an image carrier, and the toner image is electrostatically transferred to the transfer material by a transfer charger. In well-known image forming apparatuses that include a step of transferring, the charge acquired by the transfer material during transfer tends to stick to the image carrier even after transfer, so it is necessary to actively separate this from the image carrier. There is.

As a separation means for this purpose, a separation static eliminator is placed at the post-transfer position, and this applies a charge of opposite polarity to the transfer material during transfer to neutralize and eliminate the charge obtained during transfer. are already in widespread use.

A commonly used separation static eliminator is one that is configured to apply a corona discharge from the back side of the transfer material using a voltage of alternating current and direct current, and its static eliminator function depends on the peak-to-peak voltage of the applied voltage. However, the larger this value, the higher the static elimination ability.

Therefore, considering the recent trend toward faster operation in this type of image forming apparatus, it is desirable to increase the peak-to-peak value of the voltage applied to the separation static eliminator in order to quickly separate the transfer material. However, on the other hand, if this value is increased, abnormal discharges such as spark discharge and creeping discharge are likely to occur, so it cannot be made thicker without limit.

In addition, the discharge wire of this cleaning device is easily contaminated by fine paper dust generated from the paper used as the transfer material, floating toner inside the device, etc., and if the peak-to-peak voltage is increased, abnormal discharge may occur from this point as well. This is not preferable as it makes it easier.

Furthermore, given the recent trend toward smaller and lighter image forming apparatuses of this type, which allow more users without special expertise to easily use them, it is preferable to use as low a peak-to-peak voltage as possible. It is desirable to have a material that provides good separability.

Particularly in image carriers that use amorphous silicon photoreceptors, excessive charge tends to accumulate due to abnormal discharge, which causes pinholes to occur in the photoreceptor due to dielectric breakdown, shortening its lifespan. There is.

As a means to effectively obtain an output equivalent to the sine waveform of the applied voltage without increasing the peak-to-peak voltage, JP-A-52
As seen in Publication No. 42218, No. 52-42219, and Japanese Unexamined Patent Publication No. 54-139736, a square wave is used, or a waveform made flat by flattening the peak part of the sine waveform with a limiter is used. However, these naturally contain high-order harmonics, and in high-pressure discharge devices such as separation static eliminators,
Since the leakage current of harmonic components increases, problems arise such as the need to increase the power supply capacity and noise countermeasures due to leakage.

Furthermore, even if an ideal rectangular wave or a sine waveform with a flattened peak is input, in an actual charger corona discharge, a high voltage waveform similar to the input waveform cannot be obtained due to the relationship between space capacitance and leakage current. Usually, the desired peak-to-peak voltage cannot be obtained due to waveform distortion.

The present invention has been made in order to cope with such a situation, and reduces the risk of abnormal discharge without increasing the peak-to-peak voltage of the voltage applied to the separation static eliminator, and increases the speed of this type of image forming apparatus. It is an object of the present invention to provide a transfer material separation device that is suitable for downsizing and has an excellent separation function.

(2) Structure of the invention (technical means for solving the problem, its effect) In order to achieve the above object, the present invention provides a method for bringing a transfer material into contact with a transferable toner image on the surface of an image carrier to In an image forming apparatus that electrostatically transfers the image to a transfer material and then electrostatically separates the transfer material from the image carrier by the action of a separation static eliminator,
A transfer material separating device characterized in that the voltage waveform applied to the separation static eliminator is a voltage waveform formed by superimposing a first sine waveform and a second sine waveform having a frequency three times that of the first sine waveform. be.

With this configuration, disturbances in the voltage waveform applied to the separation static eliminator can be minimized to lower its peak value, and the separable range can be expanded.

(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 amorphous silicon photoreceptor, which extends perpendicularly to the paper surface. , a transfer charger 29 and a separation static eliminator 8 are arranged close to each other in parallel with the photoreceptor 1 rotating in the direction of the arrow.The toner image formed on the surface of the photoreceptor 1 is transferred to the transfer ( (not shown), the toner image on the photoreceptor is transferred to the transfer material at this location.

After the transfer, the transfer material is charge-eliminated by a separation charge eliminator 8 by a corona discharge having a polarity opposite to that at the time of transfer, separated from the photoreceptor, and further conveyed to a fixing site (not shown).

Needless to say, a latent image forming means, a developing device, a cleaning device, and other members necessary for forming fine images are arranged around the photoreceptor 1, but these are not directly related to the present invention. Since there is no such thing, I have omitted everything.

In the above device, according to the present invention, a first sine wave high voltage power source 3. Second
4. Sine wave high voltage power supply. Connect the DC voltage power supplies 5 in series,
The corona current control circuit 7 drives the DC voltage power supply in response to the signal from the corona current detection circuit 6 to control the amount of corona discharge. The voltage waveform of the former is assumed to be three times as large as the voltage waveform of the latter, and the two are superimposed so that the peak value of the voltage waveform of the latter decreases.

The results of the experiment will be explained below. As described above, amorphous silicon is used for the photoreceptor, negative polarity toner is used as the developer, and positive polarity is used for the transfer current.

FIG. 2 shows the voltage waveform of the above-mentioned device exchange, where the chain line A is the sine wave waveform generated by the power supply 3, the peak-to-peak voltage is 13.6 kV, and the frequency f = 500 Hz, and the dotted line B is a sine wave waveform generated by the power source 4, the peak-to-peak voltage was 2.4 kV, and f=1500 Hz.

The relationship between A and B is that in peak-to-peak voltage, B is 0.1 of A.
The frequency is 0.33 to 0.33 times, preferably 0.15 to 0.25 times, but in this case it is 0.18 times, and the frequency B is 3 times that of A, and the peak of one polarity of A is the peak of the other polarity of B. The two were superimposed so that the peak of A was lowered to match the polarity peak of A.

Solid line C is a composite waveform of A and H, and the peak-to-peak voltage is 1.
The voltage will be 1.8kV and the frequency will be 500Hz.

To explain the effect of such applied voltage, the conventionally used waveform A (peak-to-peak voltage 13.6k)
The corona current value when only V) is applied to the static eliminator 8 is the sum of positive and negative blue components, and is 550 ILA, and when waveform C (peak-to-peak voltage 11.8 kV) is applied, it is 525 ILA, which is almost the same corona current. A current was obtained. This current value is A
The waveform corresponds to a peak-to-peak voltage of 13.4 kV, and it was found that the peak-to-peak voltage can be lowered by 1.6 kV in the C waveform than in the A waveform to obtain the same corona current.

The discharge starting voltage of the separation static eliminator 8 is approximately 13.
5kV, so looking at the positive electrode side, the discharge electric field is (13,4/2)-3°5 = 3,2kV in the case of A waveform.
For C waveform, (11,8/2)-3,5=2.4k
V, and the discharge electric field in the case of the C waveform is 75% of that in the case of the A waveform.

Next, a peak-to-peak voltage of 13.4 kV is applied to the A waveform, and 11.8 kV is applied to the C waveform, and the ratio of positive and negative corona discharge is changed by the DC power supply 5, that is, the difference current is changed to 1
The extent of separable, retranscriptional occurrence was investigated.

In the A waveform, the separation is -10, which is more negative than A, and the retransfer occurs at more negative than -100gA, so the tolerance range is -10 to -100gA, that is,
It was 90 ruA.

This is θ~-120ILA in the C waveform, and the allowable range is 120 pots A.

In this way, the range of good separation can be expanded.

FIG. 3 shows an embodiment in which a grid electrode is used in the separation static eliminator. Parts corresponding to those in the previous embodiment are designated by the same reference numerals, and special attention will be given to them. Omit explanations unless necessary.

In the illustrated device, two separate static eliminators are used, and a grid electrode 9 is disposed only in the latter half (downstream side in the direction of movement of the transfer material) of the separate static eliminator on the transfer charger side.
A resistance element indicated by O is connected. Note that, of course, a bias power supply, a nonlinear element, etc. can be used instead of the resistor.

The reason for using a grid electrode is that in addition to stabilizing the separation discharge, the balance between separation and retransferability can be changed by adjusting the discharge current distribution.
For example, by connecting a resistance element to the grid electrode, a self-biasing effect can be provided, and the grid potential can be made to follow the transfer material potential, thereby improving the static elimination efficiency.

In the above device, the waveform applied to the discharge wire of the separation static eliminator corresponds to the one shown in Figure 2 C. Looking at the discharge current 1 separation retransferability between this and the case of A waveform, the A waveform has a peak. The sum of the positive and negative components of the corona discharge current when the peak-to-peak voltage was 13.4 to 1 was 1080 gAte, and when the peak-to-peak voltage was 11.8 kV in the C waveform, the sum was 1040 #LA, which gave almost the same discharge current.

Also, the allowable range for separating and retransferring human waveforms is +30 to -15
At 0 gA, the allowable width is 1801 LA, and for the C waveform, this is +50 to -180 gA, and the allowable width is 23
It was 0JLA.

It can thus be seen that the separation and retransferability is improved even in the separation apparatus using the grid electrode.

A disadvantage of using grid electrodes is that dirt on the grid electrodes may cause abnormal discharge between the discharge wire of the static eliminator and the grid electrodes. Sparks (abnormal discharge) occurred after 50,000 sheets were passed, but C waveform, peak-to-peak voltage 11
．． In the case of 8 kV, no sparks were generated even after approximately 100,000 sheets were passed.

(3) As described in detail, according to the present invention, in a transfer material separation device employing an electrostatic separation method, the first and second sine waveforms are superimposed on the voltage applied to the separation static eliminator. Since voltage is used, waveform disturbance is small, peak-to-peak voltage is reduced, and the range in which good transfer materials can be separated can be expanded, so the separation function can be stably maintained over a long period of time, and the image forming device This is effective in making it suitable for miniaturization and weight reduction.

[Brief explanation of the drawing]

Fig. 1 is a side view of the main parts of a copying machine showing an embodiment of the present invention, Fig. 2 is a diagram showing the waveform of the voltage applied to the separation static eliminator, and Fig. 3 is a main part showing another embodiment of the invention. FIG. 1φ: Photoreceptor, 2: Transfer charger, 3.4: AC bias power supply, 5: DC high voltage power supply, 8: Separation static eliminator, 9: Grid electrode. Figure 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) After the transfer material is brought into contact with the transferable toner image on the surface of the image carrier and the toner image is electrostatically transferred to the transfer material, the transfer material is separated from the image carrier by the action of a static eliminator. In an image forming apparatus that electrically separates the voltage waveforms applied to the separation static eliminator, a first sine waveform and a second sine waveform having a frequency three times that of the first sine waveform are combined. A transfer material separation device that uses a voltage waveform that is superimposed to lower the peak value of a first sine waveform. (2) The transfer material separation device according to claim 1, wherein the peak-to-peak voltage of the second sine waveform is 1/10 to 1/3 of that of the first sine waveform.