JPH01287588A - Transfer material separating device for image forming device - Google Patents

Abstract

PURPOSE:To speed up and adapt an image forming device to a tendency to size reduction by without entailing the danger of abnormal discharge by applying a distorted AC voltage to an electrostatic separating discharger so that crest values nearby a positive and a negative peak value are decreased. CONSTITUTION:The electrostatic separating discharger 7 is provided on the downstream side of an electrostatic transfer discharging electrode 2 and applies a transfer material with a bias having the opposite polarity from that in transfer to neutralized charges of the transfer material and discharge the transfer material electrostatically, thereby separating the transfer material from a photosensitive body. Then a high voltage power source 3 which generates an alternating current distorted so that the current is flat nearby its positive and negative peaks, a corona current detecting circuit 4, and a duty ratio control circuit 5 which controls the duty ratio of the alternating current with the signal of the circuit 4 so that a corona discharging current has a specific value are connected to the discharge wire of the separating discharger 7. The voltage between peaks of the AC voltage applied to the separating discharger 7 is lowered and abnormal discharge is evaded to separate the transfer material stably. Consequently, the image forming device is easily speeded up and reduced in size.

Description

Detailed Description of the Invention (1) Purpose of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus that utilizes an electrostatic transfer process, such as an electrostatic copying machine or a printer, and particularly to a transfer material separation device thereof. It is.

(Prior art and problems to be solved) In a well-known image forming apparatus that includes a process of electrostatically transferring a transferable toner image formed on the surface of an image carrier onto a sheet-like transfer material such as paper, Because of the electric charge imparted to the transfer material, it tends to be electrostatically attracted to the image carrier after transfer, so it is necessary to actively separate the transfer material from the image carrier using an appropriate separation means. .

Conventionally, as transfer material separation means for this purpose, a separation static eliminator placed at a post-transfer position applies a charge of opposite polarity to the transfer material during transfer, and neutralizes and eliminates the charge during transfer. It is well known that an electrostatic separation means constructed to reduce the adsorption effect on the image carrier has been proposed and implemented, and has achieved certain effects.

In this type of separation static eliminator, it is common to first eliminate static electricity by corona discharge by applying a voltage that is a combination of AC and DC voltage, and the static elimination function depends on the peak-to-peak voltage value of the applied AC voltage. There is a tendency that the larger this value is, the greater the static elimination ability is.

However, on the other hand, if this value is increased, spark discharge,
It is difficult to make it extremely large because there is a risk of abnormal discharge such as creeping discharge occurring.

Incidentally, in recent years, in this type of image forming apparatus, various materials such as selenium and other inorganic photoconductive materials, organic semiconductors (OPC), and amorphous silicon semiconductors have been used as photosensitive layer materials for forming latent images, depending on the intended purpose. Since amorphous silicon has high sensitivity and high durability, it is also compatible with the recent trend toward higher speeds for this type of equipment, so it is gradually being used. .

On the other hand, looking at the withstand voltage characteristics, the OPC photoreceptor has a voltage resistance of about 20 pm.
c7) 5kV or more in layer thickness (250V/4rn)
, Se-Te, and 5e-As have a voltage of 3 kV (60 V/ILi) or more at a layer thickness of approximately 50 lm, whereas amorphous silicon has a voltage of approximately 2 kV at a layer thickness of 25 lm.

For this reason, as mentioned above, amorphous silicon is exposed to high voltage corona for a long time like in a high-speed machine,
In addition, in the case of devices that require long maintenance intervals and are likely to be used with dirty charging wires, abnormal discharge is likely to occur, increasing the risk of pinholes occurring and resulting deterioration of image quality. become.

In addition, the dielectric εS of the amorphous silicon photoreceptor is approximately 10, which is larger than that of OPC and Se-based materials, which is approximately 3.6, and the amount of corona discharge required to obtain the same photoreceptor potential is large. , it is necessary to increase the pressure of corona discharge, which also promotes the occurrence of abnormal discharge.

Of course, by increasing the layer thickness, it is possible to raise the withstand voltage limit and avoid the above-mentioned drawbacks to some extent, but in the case of amorphous silicon, the film formation characteristics may deteriorate or the film formation may take a long time. Therefore, it is not practical in terms of productivity and cost.

Furthermore, when amorphous silicon is used as a photoconductor, a surface protective layer, a photosensitive layer, a charge injection blocking layer, and a substrate are laminated. It has been found that down occurs first and causes pinholes throughout the photosensitive layer.

Furthermore, with the recent progress in miniaturization of this type of image forming apparatus, it has become possible for even people who are said to be ``mechanically weak'' to be able to use this type of apparatus freely and safely. Although it is strongly required, from this point of view, it goes without saying that it is desirable to obtain good separation characteristics with as low a peak-to-peak voltage as possible.

The present invention has been made in order to cope with the above-mentioned situation, and in particular, in an image forming apparatus using an amorphous silicon photoreceptor, it is possible to prevent the increase in the peak-to-peak voltage of the voltage applied to the separation static eliminator and the risk of occurrence of abnormal discharge. The object of the present invention is to provide a transfer material separation device that is well suited to the trend toward higher speeds and smaller size image forming apparatuses without causing any problems.

(2) Structure of the invention (technical means for solving the problem and its effect) In order to achieve the above object, the present invention provides a transfer material in which a toner image formed on the surface of an amorphous silicon photoreceptor is brought into contact with the toner image. In the image forming apparatus, the transfer material is transferred by a transfer charger, and then a one-separation static eliminator applies a charge of a polarity opposite to that at the time of transfer to the transfer material to separate it from the image carrier. The present invention is characterized in that the separation static eliminator is provided with means for applying an alternating current voltage that is distorted so as to reduce the peak value near the peak value on the positive and negative sides.

With this configuration, it is possible to perform good separation of the transfer material with a lower bias than in the conventional one.

(Description of an Embodiment) FIG. 1 shows the main part of an embodiment in which the present invention is applied to a copying machine equipped with a cylindrical photoreceptor that extends perpendicular to the plane of the paper and rotates in the direction of arrow A. be.

It is assumed that an amorphous silicon photosensitive layer is formed on the photoreceptor 1, and a transfer charger 2 and a separation static eliminator 7 are disposed adjacent to this, and the toner image formed on the surface of the photoreceptor 1 is In synchronization with the transfer material (not shown) supplied by the conveyance path 6, the transfer charger 2 reaches the transfer site facing the photoconductor 1, and at this site, the transfer charger 2 receives a transfer bias. , the toner image is transferred from the photoreceptor to a transfer material.

At this time, due to the transfer bias applied to the transfer material, the transfer material tends to be attracted to the photoreceptor. A bias having a polarity opposite to that during transfer is applied to the transfer material to neutralize and eliminate the charge on the transfer material, separating it from the photoreceptor, and further conveying this transfer material to a fixing site (not shown). do.

Needless to say, members necessary for forming fine images such as an electrostatic latent image forming means, a developing device, and a cleaning device are arranged around the photoreceptor 1, but these are not directly related to the present invention. Therefore, all are omitted.

In the above-described device, one aspect of the present invention includes a high-voltage power source 3. which generates an alternating current distorted so that the vicinity of the positive and negative peaks are flat, as shown in the figure, in the discharge wire of the separation static eliminator 7.
Corona current detection circuit 4: According to the signal from this circuit, the duty of the alternating current is adjusted so that the corona discharge current reaches a predetermined value.
A duty ratio control circuit 5 for controlling the ratio is connected.

Figure 2 is a graph comparing the case where the discharge current of the separation static eliminator is controlled according to the present invention (curve b in the figure) and the case where a known superimposed voltage of alternating current and direct current is applied (curve a in the figure). be.

In this graph, the horizontal axis shows the peak-to-peak value of the applied voltage, and the vertical axis shows the separation static eliminator when the transfer material for a white original begins to separate and can be separated without retransferring for a black original. The permissible width of the DC component (I5) of the corona discharge current (
ΔIs) is shown.

As can be seen from the figure, for example, the allowable width Δwork $ = 30
In order to obtain 0 JLA, approximately 14
kV is required, whereas in the present invention, approximately 12 kV is required.
By applying the present invention,
The lower peak-to-peak voltage greatly reduces the risk of abnormal discharge, pinhole formation, etc.

Note that the DC component of the corona discharge current in the embodiment of FIG. 1 is calculated by applying the difference between the currents divided by the diodes 8 and 9 and flowing to the ammeter as shown in FIG. - By the ratio control circuit 5, a in the voltage waveform applied to the static eliminator 7 shown in FIG. 4, ! -b ratio (duty ratio) was controlled.

FIG. 5 shows another embodiment of the present invention, in which the discharge wire of the separation static eliminator 7 disposed downstream of the transfer charger 2 disposed close to the amorphous silicon photoreceptor 1 has the same structure as that shown in FIG. A DC power supply 13 is connected to a high voltage power supply 12 that generates a similar AC wave distorted so as to reduce the peak value near the positive and negative peaks.
are superimposed, and the corona current is controlled by the corona current control circuit 14.
shall be controlled by.

FIG. 6 shows the voltage waveform applied to the separation static eliminator 7 in the above embodiment, where the symbol a indicates the DC voltage level.

FIG. 7 shows an example in which the same branching idea as the present invention is applied to other means, and parts corresponding to those shown in FIG. 5 are given the same reference numerals. There are, and explanations about them will be omitted.

In this device, in order to improve transfer efficiency, a post charger 15 that applies a corona discharge of the same polarity as the toner after development generates an alternating current wave that is distorted so as to reduce the wave height near the peak. A power source 12° for controlling the corona current, a DC power source 13′ superposed thereon for controlling the corona current, and a corona control circuit 14′ for controlling this are provided.

With this configuration, the voltage applied by the power supply at 12° can be reduced to approximately 8 kV, whereas a normal sine waveform AC high voltage power supply requires approximately 9.5 kV (peak-to-peak voltage). A similar effect can be obtained by lowering the discharge voltage, and the risk of abnormal discharge can be avoided.

(3) As described in detail, according to the present invention, transcription (tf'
Separation and removal is performed in a transfer material separation device that electrostatically transfers a toner image on the surface of an image carrier onto a transfer material using an electric device, and then electrostatically separates the transfer material from the image carrier using a separation static eliminator. Since it is possible to reduce the peak-to-peak voltage of the AC voltage applied to the electric appliance, it is possible to avoid abnormal discharge in image forming apparatuses that use amorphous silicon photoreceptors, and to enable stable separation of the transfer material. It is possible to obtain a transfer material separation device that prevents photoreceptor deterioration and image defects caused by image formation, and that is easily adapted to speeding up and downsizing image forming apparatuses.

[Brief explanation of the drawing]

FIG. 1 is a side view of essential parts of an image forming apparatus showing an embodiment of the present invention; 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 a known device; 3 shows the current measurement circuit of the device shown in FIG. 1, FIG. 4 shows the output waveform of the static eliminator in the device shown in FIG. 1, and FIG. 5 shows the current measurement circuit of the device shown in FIG. 1. Main part side view. FIG. 6 is a graph showing the output waveform of the above-mentioned separation static eliminator, and FIG. 7 is an application example in which the same technical concept as the present invention is applied to a post charger. 1... Photoreceptor, 2 fists/Φ transfer charger, 3.13.13
°...AC high voltage power supply, 4.14 and 14° pots...DC high voltage power supply, 6...Transfer material conveyance path, 7...separation static eliminator. Fig. 1 Fig. 2 Fig. -719.

Claims (3)

[Claims] (1) After the toner image formed on the amorphous silicon photoconductor is transferred to the transfer material that is in contact with it by a transfer charger, the transfer material is electrostatically separated from the image carrier by a separation static eliminator. In the image forming apparatus, the transfer material separating device is provided with means for applying a distorted alternating current voltage to the separation static eliminator so as to reduce a wave height value near the peak value on the positive and negative sides. (2) The positive and negative peak values of the AC voltage applied to the separation static eliminator are substantially the same, and the relative change in the waveform area on the positive and negative sides is performed by changing the duty ratio. Transfer material separation device. (3) The transfer material separation device according to claim 1 or 2, wherein the voltage applied to the separation static eliminator is alternating current and direct current superimposed.