JPH01315782A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain an image of high quality over a long period of time by detecting the change in a transfer and separating current, miniaturizing and simplifying the constitution, and surely evading the damage to a photosensitive body by instantaneously interrupting high voltage. CONSTITUTION:A protecting member 6, consisting of an insulating material, is placed in a position on the high voltage feeding side within a sealed case but off the part which faces the photosensitive body, connected to an ampere meter through a terminal 8. A separating electrifying device is constituted in the same way as this transfer electrifying device. Then the change in monitor current from the terminal 8 is processed comparatively at 50hz, and when the change exceeds a certain set value, the output of a high voltage transformer is cut off. Therefore, damage to the photosensitive body by abnormal discharging in the transfer and separating parts can be eliminated as much as possible, extending its life, obtaining a high quality image over a long period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus using an electrostatic transfer process, such as an electrostatic copying machine and a printer.

(Prior art and problems to be solved) In a well-known image forming apparatus configured to form a toner image on a photoreceptor on the surface of an image carrier and transfer it to a transfer material such as paper, an amorphous silicon photosensitive member is used as the photoreceptor. The body has a high surface hardness (Vickers hardness of 1000 or more), so it has great mechanical strength and is resistant to repeated electrostatic charges.
It has high durability with almost no potential fluctuations due to exposure, background fogging, or crystallization phenomena, so it can produce stable, high-quality images over a long period of time at low running costs. 1+
Because of this, they are increasingly being used in high-speed copying machines and laser beam printers that print continuously for long periods of time.

However, on the other hand, when manufacturing this photoreceptor, a method is used in which silane gas is decomposed and deposited on the surface of the image carrier base material, so the manufacturing cost is high and image defects may occur due to local abnormal film formation. Therefore, from the viewpoint of reducing the price of the photoreceptor and preventing abnormal film formation, the thickness of the photoreceptor is currently limited to about 20 to 304 trr.

By the way, the electric field strength per unit 11 thickness of the hydrogenated amorphous silicon photoreceptor used as this type of photoreceptor is 6.
Since the voltage is 0 to 90 V/pm, the insulation resistance when such a product is used in an image forming apparatus using an electrostatic method is approximately +2.0 to 2.4 KV/-0.8 to 1.4 KV/-0. OKV, smaller than other photoreceptors.

For this reason, in image forming apparatuses using amorphous silicon photoreceptors, abnormal discharge is likely to occur, and if this reaches the photoreceptor and causes dielectric breakdown, the photoreceptor will be damaged by
In some cases, pinholes with a diameter of approximately 0.00 km may occur, resulting in image defects and affecting the life of the photoreceptor.

In this type of image forming apparatus, during transfer, a transfer charger applies a transfer bias to transfer the toner image on the photoreceptor to the transfer material, and then a separation charger applies a separation bias to remove the transfer material from the photoreceptor. In well-known image forming apparatuses that have a separation process, during transfer, the charging wire of the charger is contaminated by toner scattering near the transfer charger and fine paper dust from the paper used as the transfer material, resulting in abnormal discharge. Moreover, since high-voltage alternating current is applied to the one-separation charger, the charging wire is likely to vibrate, which is likely to cause abnormal discharge.

Of course, in order to deal with this situation, a method has been proposed in which the current change in the transformer that applies high voltage to each charger is detected and the high voltage application is cut off, but as mentioned above,
Amorphous silicon photoreceptors have low insulation resistance, and it is necessary to detect and respond to smaller current changes. Therefore, adequately responding to this is difficult in terms of space and cost within the image forming device. It is actually difficult to do so, and it has been considered unavoidable to have a discharge destruction capacity of 3 to 10 pieces and a length of 2 to 10 mm.

The present invention has been made to deal with this current situation, and has a small and simple configuration that quickly and accurately detects changes in corona current and instantaneously cuts off high voltage to ensure damage to the photoreceptor. It is an object of the present invention to provide an image forming apparatus that avoids this problem and can obtain high-quality images over a long period of time.

(2) Structure of the Invention (Technical Means for Solving Problems and Its Effects) In order to achieve the object described above, the present invention provides a method for bringing a transfer material into contact with a toner image on the surface of an amorphous silicon photoreceptor, and transferring the toner image to the surface of an amorphous silicon photoreceptor. In an image forming apparatus that applies a charge to transfer the toner image to a transfer material, and then applies a separation charge to separate the transfer material from the photoreceptor, in the transfer and/or separation band-loaded goo L stage, The present invention is characterized in that a means for detecting changes in the rotation 9j and/or separation current is provided at the f-stage.

With this configuration, it is possible to detect current changes in the charger with high precision and effectively prevent the occurrence of image defects due to dielectric breakdown of the amorphous silicon photoreceptor due to abnormal discharge. becomes.

(Description of Examples) FIGS. 1A and 1B are cross-sectional views of a transfer charger to which the present invention is applied in the longitudinal direction and in the direction orthogonal thereto,
As shown in the figure, a charging wire 1a is stretched in a shield case l having a rectangular cross section, and its open side faces the surface of a photoreceptor (not shown) with a small gap. A transfer material (also not shown) is passed through the gap,
At this time, a transfer bias is applied to the +iri charge Vjla to transfer the toner image on the surface of the photoreceptor to the transfer material.

The illustrated electric appliance has a reciprocating movement in its longitudinal direction.
A cleaning member 2 equipped with a cleaning pad 2a is disposed so as to sandwich the charging wire 1a, and is threaded onto a threaded rod 5 connected to a motor 3 via a joint 4 to move within the charger. It is designed to clean the charged wire.

In such a charger, the one shown in the figure has a protective member 6 formed of a brush or the like made of an insulating material on the high-voltage supply side inside the shield case at a position away from the part facing the photoreceptor. A standard shield member 7 is provided on the outside of the standard shield member 7, and this is connected to an ammeter (not shown) via a terminal 8.

Although the above is a transfer charger, the separation charger also has a similar configuration.

FIG. 2 is a flowchart showing the high voltage cutoff sequence according to the present invention, in which changes in the monitor current from the terminal 8 are compared at 50 Hz.

If the change exceeds a constant value (leI), the output of the high voltage transformer is cut off.

Experimental Example As a photoreceptor, a cylindrical aluminum substrate with a diameter of 108 g+- was coated with a charge injection blocking layer of 3 layers, a photoconductive layer of 25 layers, and a photoconductive layer of 0.5 g. An amorphous silicon photoreceptor was used in which a surface protective layer (SiC) was formed in this order by plasma glow discharge.

This photoreceptor was rotated at 440 ■■/sec, AC 7.8 KV (peak-to-peak voltage) was applied as a transfer bias, AC 14 KV (peak-to-peak voltage) and DC +2 as a separation bias.
．． A superimposed voltage of 4KV is applied, and a mixture of paper powder collected from the paper feed section, stainless steel chips and conductive resin thread cut into 2 to 3 mm pieces is applied to the grid line of the shield case or separation charger. Shomaro was there to pass the paper.

First, when the device was activated (high voltage was applied to the charger) with the sequence function stopped as shown in Figure 2, spark discharge occurred with a high probability.

Next, in order to activate the function shown in Fig. 2, paper was passed as usual while applying the above-mentioned mixture each time, and after the transfer material was discharged, the paper was cleaned with a cleaning member and the first paper was passed. .

The paper was passed 50 times, and spark discharge was confirmed by sound and sparks in 29 of those times, and the high voltage was shut off in 18 of those times.

Image status for 29 times when discharge was confirmed.

Table 1 below shows the presence or absence of discharge destruction marks on the surface of the photoreceptor, the number of them, and so on.

Table 1 In the above table, the number of destruction marks judged from the 1 image in which the detection device was activated is 1, and the image quality is judged as O1Δ.
, indicated by ×, and the shape is determined by the reflection WJ microscope (X100).
The depth was determined.

The device does not work because: ■ The discharge is a positive discharge and the current change is small and does not reach the detection level. ■ The discharge is weak and does not reach the photoreceptor and stops at the opening edge of the grid or shield case. There may be cases.

In any case, as seen from the above table, the damage in the case where the detection was not detected was small and was not fatal to the image quality.

When the detection device was activated, the destructive power was limited to only one, and although the depth was large, it was small, so there was no immediate fatal damage in terms of image quality.

l In the biped experiment setup, stop the photoreceptor.

While irradiating the transfer/separation charger portion with light, monitor the current flowing through the standard shield member (1) and the current I2 flowing into the photoreceptor for both positive and negative polarity.
Figure 3A shows the results of measuring the current change when spark discharge occurs.
It is shown in Figure 3B.

This figure shows that negative discharges with large current changes are easier to detect and cause more damage.

In order to compare with the experimental results described in Comparative Example, paper was passed under similar conditions without the detection device functioning, and the results shown in Table 2 were obtained.

Table 2 The same evaluation as in the above experiment was performed, but the image quality deteriorated significantly, regardless of the number, shape, etc. of discharge destruction ability.

Is that the transcription? Although the case of iF electric appliances has been described, it has been confirmed that the same tendency as in the above case occurs even when a similar abnormal discharge detection means is applied to a separation charger.

(3) Effects of the Invention 1: As explained above, according to the present invention, in an image forming apparatus using an amorphous silicon photoreceptor, a small, low-cost device can be used to transfer a portion that is difficult to transfer in one minute. This greatly contributes to eliminating damage to the photoreceptor due to abnormal discharge as much as possible, extending its life, and obtaining high-quality images over a long period of time.

[Brief explanation of the drawing]

FIG. 1A and FIG. 1B are sectional views taken in the longitudinal direction and a direction perpendicular to the longitudinal direction of the transfer charger that can be used in the present invention, respectively, and FIG. 2 is a flowchart showing the operation of the same. FIGS. 3A and 3B are graphs showing changes in the monitor current and the current flowing into the photoreceptor when a spark discharge occurs in positive and negative cases, respectively. l・ψφshield case, 2・kai・'172 kRfi
R material, 5... Screw, 6... Protective member, 7... Mark shield member, 8... Terminal. Figure 2 Figure 3A

Claims (1)

[Scope of Claims] A transfer material is brought into contact with the toner image on the surface of the amorphous silicon photoreceptor, and a transfer charge is applied to transfer the toner image to the transfer material, and a separation charge is then applied to the transfer material. An image forming apparatus for separating a material from a photoreceptor, characterized in that the transfer and/or separation charge imparting means is provided with means for detecting changes in the transfer and/or separation current within the means. Forming device.