JPS59104671A - Separating system of transfer material - Google Patents

Abstract

PURPOSE:To separate exactly a transfer machine by detecting an exposure quantity in case of image-exposing a picture of an original to a photosensitive body, and controlling a corona discharge quantity for an electrostatic separation in accordance with its detecting signal. CONSTITUTION:A separating discharger 15 for separating transfer paper 13 from a photosensitive body 1 is provided in parallel with a transfer discharger 14, and the charge charged to the transfer paper 13 is eliminated by executing a corona discharge of the opposite polarity. As for the copying paper 13 whose charge is eliminated, its adsorbing force to the photosensitive body 1 is weakened, separated from the photosensitive body 1 by its own weight and fed to the fixing part. On the other hand, the photosensitive body 1 is prepared for the following image forming process after the residual charge and toner are eliminated. Voltage applied to the separating discharger 15 is controlled in accordance with a picture of an original on an original placing plate 3, and in case of a white ground original, the applied voltage is made high, and in case of a black ground original, the applied voltage is made low. This control detects an exposure quantity of a reflected light from the original, and basing on its detection, voltage applied to the discharger 15 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to the separation of a transfer material from a photoreceptor in an electrophotographic copying machine, and particularly relates to a technique for electrostatically separating a transfer material.

<Prior art> After forming an electrostatic latent image on a photoreceptor, an electrophotographic copying machine
The latent image is developed and visualized as a toner image, and this toner image is electrostatically transferred to a transfer example (for example, plain paper) that is conveyed appropriately.After the transfer, the transfer material is separated from the photoreceptor, A transfer material is passed through a fixing section and the toner image is fixed on the transfer material to obtain a copy.When electrostatically transferring the above toner image, a transfer device that generates a corona discharge of opposite polarity to the toner from the back of the transfer material is used. It is widely used. At this time, since the transfer material charged by corona discharge is attracted to the photoreceptor by the Coulomb force and the π force acts, an appropriate means has been used to separate it from the photoreceptor.

As an example of the above separation mechanism, corona discharge from a separation corona discharger is used to remove the weekly charge on the transfer material, weaken the adhesion between the transfer material and the photoreceptor, and increase the rigidity (strength of the waist) of the transfer material. An electrostatic separation method is known in which the I8 tip is separated from the I8 tip by its own weight or weight.

By the way, the appropriate amount of discharge to separate the shading (depending on the shading and transfer) of the image of the original to be copied is different, as shown in Figure 1 (/?). This figure shows the image density of the original. The range of applied voltage is shown for each document a, b,
If the voltage baj is not applied within the shaded range relative to cK, it indicates that the transfer material can be separated. In FIG. 6, in the case of a white original a, Gτ is larger than the amount of charge applied to Q during transfer (A), and in order to remove this charge, the applied voltage applied to Gτ is increased, There are some prefectures where the number of corona discharges is greater than 1. Even in the character manuscript shown in K, it is about 1.1 equivalent to a. I'm very talented, C's black (that's the manuscript,
Even if the voltage applied to a and the like is lower than the voltage applied to the heel f dissipator π, separation is possible.

Conventionally, the voltage applied to the divider for UTP is fixed, but the voltage applied in the common QiIj range P that can be distributed is selected for all images, and the voltage corresponding to this range P is applied. There is. However, as shown in Figure 1, the common range P
Because π is very narrow, if environmental conditions, the type of transfer material, or other conditions change, the range that can be fractionated will shift significantly, and the drawback cannot be overcome unless stable separation is obtained.

Therefore, in order to eliminate the above-mentioned drawbacks, a method has been considered in which the surface potential of the photoreceptor is measured after image exposure is performed on the photoreceptor, and the amount of discharge by the separation discharger is controlled based on this measurement result. ing. However, when measuring the surface potential of a photoreceptor, only a partial measurement is possible, and it is almost difficult to measure the average value of the potential in the depth direction of the photoreceptor. Even if it could be realized, the device would not only be complicated but also expensive. Furthermore, it is difficult to perform stable and highly accurate measurements, which also makes it impossible to stably separate the transfer material.

OBJECT OF THE INVENTION The present invention performs electrostatic separation, and its purpose is to always enable stable separation of transfer materials regardless of the image on the original. In particular, the present invention is to control the amount of discharge of the discharger applied to the electrostatic charge #L to a constant value according to the image of the document.

<Embodiment> FIG. 2 is a block diagram showing an electrophotographic copying machine according to the present invention. In the figure, 1 is a photoreceptor formed of a drum-like Q, 2 is a charger for uniformly charging the photoreceptor 1, and 3 is an original table on which an original is placed. The document placed on the document table 3 is irradiated with light by the lamp 4 of the illumination device, and the reflected light is directed to the photoreceptor 1 by an optical system consisting of mirrors 5, 6, 7° 9, lens 8, and slit 10. An electrostatic latent image is formed on the surface. This electrostatic latent image is visualized as a toner image by the developing device 1 in the next step, and is brought into close contact with the photoreceptor surface 0 by a transfer paper 13 that is sent by a conveyor roller 12 in synchronization with the rotation of the photoreceptor 1. The image is then electrostatically transferred onto the transfer paper 13 by the transfer discharger 14 on the back side.

Fifteen separation discharge devices are arranged in parallel with the transfer discharge device 14 to separate the transfer paper 13 from the photoreceptor 1 according to the present invention. This separation discharger 15 is the transfer discharger 1
This is a corona discharge with a polarity opposite to that of transfer paper 1.
．． 3VC charged charge is removed. The copy paper 13 from which the charge has been removed in the separation discharger 15 has a weak adhesion force with the photoreceptor 1, and is separated from the photoreceptor 1 due to the rigidity and weight of the paper itself, and is transferred to the fixing section (Fig. (not shown).

On the other hand, the photoreceptor 1 is cleaned of residual charges and toner, and is prepared for the next image formation.

In the copying machine configured as described above, the voltage applied to the separation discharger 15 of the present invention is controlled in accordance with the image of the document on the document table 3. As shown in Figure 1, in the case of a blank original,
The voltage applied to the separation discharger 15 is controlled to be high, and if the document is black, the applied voltage is controlled to be low. On the seventh day of execution of this control, the amount of exposure in the reflected light from the document is detected, and the voltage applied to the discharger 15 is controlled based on this detection. Hit 0. If there is a large amount of reflected light from the original, this means that the original is close to a blank original, and the applied voltage can be easily controlled.

- As a specific example, as shown in FIG. 2, a half mirror 16 is provided between the lens 8 and the reflecting mirror 9, and a part of the light is focused through the lens 17, and a photoelectric element 18 is used as a light amount detection means.
It is irradiating to. If the no-f mirror 16 is located close to the lens 8, it has the advantage that the mirror 16 can be made smaller. The signal from the photoelectric element 18 is amplified to an appropriate size by a photoelectric conversion circuit 19, and sent via a delay circuit 20 to a high voltage supply control circuit 21 that controls the high voltage applied to the separation discharger 15. . The delay circuit 20 is connected to the photoreceptor l.
1. The signal from the photoelectric conversion circuit 19 is supplied to the control circuit 21 with a delay of the time when the exposed portion rotates and reaches the position of the separation discharger 15.1. ing. In fact, the high voltage supply control circuit 21 controls and supplies the voltage according to the amount of light received by the photoelectric element 18.If the document is white as shown in FIG. The amount of light received also increases, and a higher voltage is applied to the discharge wire of the discharger 15. This control circuit 21 may be configured to control the applied voltage in proportion to the output signal Q of the photoelectric element 18, but it may compare the output signals and
If so, a configuration may be adopted in which each determined voltage is switched.

According to the above configuration, when a black original is placed, the amount of light received by the optical element 18 decreases as exposure starts. When this image-exposed position reaches the separation discharger 15, a voltage corresponding to the amount of light is applied to the control circuit 21.
The electric charge is applied to the discharge wire, and the charge on the transfer paper 13 is removed by the optimum amount of corona discharge, and the transfer paper 13 can be reliably separated from the photoreceptor.

Here, if there is a method for detecting the exposure amount as shown in FIG. 2, the total amount of light transmitted through the lens 8 can be measured. Moreover,
Since the slit exposure method is used, the exposed portion is a narrow strip-shaped range in the depth direction of the document. Therefore,
Since the measured amount of light is proportional to the average image density in the depth direction of the document, it is possible to apply an optimal voltage to the discharger 15.

Although an example of exposure amount detection is shown in FIG. 2, the invention is not limited to this, and the photoelectric element 18 may be placed in the middle of the light amount, for example, overlapping the lens 8.

In this case, the photoelectric element 18 has a small area and is not affected much by image formation. Further, as shown in FIG. 3, there are two photoelectric elements 18 on the left and right sides of the lens 8.

18-2, and the amount of light transmitted through the lens 8 is not detected, but the scattered light from the original is detected. As shown in the figure, there are photoelectric elements 18 on the left and right sides.

The reason for providing 18-2 is to correct the sensitivity to the position on the document.

It is clear that the present invention is applicable not only to an optical system using mirrors 5, 6° 7.9 and a lens 8 as shown in FIG. 2, but also to an optical system using a light condensing lens array. 3,
That is, the present invention can be implemented in any type of system that projects the image of the original onto the photoreceptor l.

<Effects of the Invention> According to the separation method of the electrophotographic copying machine of the present invention, when exposing the image of the document placed on the document table, the exposure 5'll
: The transfer material is separated from the photoreceptor by controlling the voltage applied to the corona discharger in order to detect l and control the amount of corona discharge for electrostatic charge H, based on this detection signal π. Because of this, the transfer material can be separated with an appropriate amount of discharge depending on the image of the original, and the separation can be ensured. In addition, it is relatively easy to detect the exposure amount,
The configuration for separation becomes extremely simple.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the relationship between the image density of the original and the voltage applied to the separable separation discharger, Fig. 2 is a block diagram showing the structure of an electrophotographic copying machine using the separation method of the present invention, and Fig. 3 FIG. 3 is a top view showing another specific example of the exposure amount detection according to the present invention. l: Photoreceptor, 3: Document table, 4: Illumination lamp,
5, 6, 7, 9: Reflection mirror, 8: Lens,
13: Transfer paper, 14: Transfer discharge device, 15: Separation discharge device, 16: Half mirror, 18 (18・-,,
18,): Photoelectric element, 19: Photoelectric conversion circuit,
20: Delay circuit, 21: High voltage supply control circuit.

Claims (1)

[Claims] 1. In order to perform electrostatic transfer of the toner image formed on the photoreceptor onto a transfer material that is appropriately fed by corona discharge, and to separate the attraction between the transfer hoop and the photoreceptor after this transfer, In a transfer material separation method in which a corona discharge of opposite polarity to the above corona discharge is performed to eliminate charges that are charged during transfer to the transfer material, and the transfer material is electrostatically separated from the photoreceptor, the original is transferred to the photoreceptor. Detect the exposure interval when imagewise exposing the image (elephant), and calculate the amount of corona discharge for electrostatic separation according to the exposure amount detection signal;
Transfer material separation method controlled by ilJ. 2. The transfer material separation method according to claim 1, wherein the voltage applied to the separation corona discharger is controlled as means for controlling the amount of corona discharge.