JPS59148077A - Destaticization separating device for copy paper - Google Patents

Abstract

PURPOSE:To control the discharge of a corona discharger for destaticization and hold it in an inveriably accurate optimum state, and to obtain a clear image having no absence by detecting the variable density of an original image near an image forming lens by a detecting element. CONSTITUTION:The detecting element 18 which detects the density of the image of the original 1 is provided on the downstream side of a lens 8 on an optical path 4. The image is stopped down small at this position, so the variable density of an average original image is detected breadthwise. The corona discharge 17 for destaticization is provided closely to a corona discharger 15 for transfer. This discharger 17 destaticizes copy paper 16 from a reverse surface to separate the paper from a photosensitive body 10 by its nerve and own weight. The surface potential of the photosensitive body 10 is different depending upon the variable density of an original image and a nonimage part, so the variable density of this original image is detected by the element 18, amplified by an amplifying circuit, and delayed by a delay circuit to perform corresponding corona discharge by the discharger 17.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is used in transfer type electrostatic copying machines and printers to transfer a toner image on a photoreceptor onto copy paper, and then remove the copy paper from the photoreceptor. Related to the static eliminator and separator for copy paper used to neutralize paper: Conventionally, after a toner image corresponding to an original on a photoreceptor has been transferred to the copy paper, a corona for weight removal has been used as a means to separate the copy paper from the photoreceptor. By applying corona discharge from the back side of the copy paper after transfer using a discharge device, the electrostatic attraction between the photoreceptor and the copy paper is neutralized, and the copy paper is separated from the photoreceptor by the stiffness of the paper and its own weight. A configuration is used. However, it is preferable that the amount of corona discharge in this corona discharger is set to a value corresponding to the image of the document.

Otherwise, it will be difficult to completely peel off the copy paper onto which images of various original documents have been transferred.

In order to solve such problems, for example, a detection member, such as an electrode, for measuring the surface potential of the photoreceptor after exposure and before development is placed near the photoreceptor, and the output from this detection member is used to detect the downstream side of the transfer area. Some also change the discharge state of a static elimination corona discharger placed on the side. In such prior art, by providing one or several detection members, it is only possible to read the shading of the document at several locations in the width direction, which may result in incorrect detection results depending on the information on the document. Furthermore, with this detection method, the gap between the surface of the photoreceptor and the detection member must be set accurately, making it impossible to accurately detect the surface potential of the photoreceptor. It is difficult to accurately set the gap between the detection member and the photoreceptor because it depends on variations in the components. Another problem with this prior art is that toner adheres to the detection member and contaminates it, resulting in errors in surface potential measurements.

The purpose of the present invention is to solve all of the problems of the prior art at once, and it is possible to effectively use the entire surface of copy paper as a copying reservoir, and also to eliminate static electricity and peel off the copy paper. It is an object of the present invention to provide a static eliminator and separator for copy paper that can accurately set a corona discharge state and is easy to maintain.

FIG. 1 is a sectional view of a portion of a transfer type electrostatic copying machine according to an embodiment of the present invention. A transparent document table 2 on which a document 1 is placed moves horizontally for slit exposure. light source 3
The light is irradiated onto the original 1 via the mounting table 2, and the image of the original follows the path indicated by reference numeral 4, and passes through the reflecting mirror 5.
, 6 and 7, passes through a lens 8, is further reflected by a reflecting mirror 9, and is imaged onto a right cylindrical photoreceptor 10. Photoreceptor 10 is rotationally driven in the direction of arrow 11. The photoreceptor IO is charged by an exposure corona discharger 12,
An electrostatic latent image corresponding to the original image is formed in the exposure area 13. This electrostatic latent image is developed into a toner image by a magnetic brush developing device 14.

The toner image on the photoreceptor 10 is transferred by a transfer corona discharger 15 to a copy λ copy paper 1 that is conveyed in close contact with the photoreceptor 1o.
6. A static eliminating corona discharger 17 is arranged close to the transfer corona discharger 15 and on the downstream side in the conveyance direction of the copy paper I6. The charge-eliminating corona discharger 17 performs a function of discharging the transferred copy paper 16 from the back surface by applying a corona discharge to remove the charge, and peeling it off from the photoreceptor 1o by its elastic force and its own weight.

The surface potential on the photoreceptor 10 differs depending on the density of the original image and the portion where no image is formed. Therefore, in order to reliably separate the copy paper 16 from the photoreceptor 10 while maintaining good quality of the image transferred onto the copy paper, the corona discharger 17 for charge removal must perform optimal electrification. For example, if the discharge amount of the charge eliminating corona discharger 17 is too large, the toner will be attracted to the photoreceptor side and will not be transferred onto the copy paper, resulting in so-called missing images. -2, if the amount of discharge is too small, the copy paper will not be separated from the photoreceptor and will wrap around the photoreceptor, resulting in poor separation. According to the present invention, the discharge state of the charge eliminating corona discharger 17 is optimally determined, and as a result, the copy paper 16 is reliably peeled off from the photoreceptor 1°, and development such as image omission does not occur, resulting in clear copies. can be achieved.

FIG. 2 is a simplified diagram of the optical path 4 including the lens 8 for focusing the original image of the original onto the exposure area 13 of the photoreceptor 1o. A portion 1a of the original l is focused by a lens 8 and imaged at an exposure position 13 on a photoreceptor lo. In FIG. 2, the reflecting mirror 5°6.7.9 is omitted for convenience of illustration. On the downstream side of the lens 8 in the optical path 4, a detection element 18, such as a photodiode, for detecting the density of the original image is arranged. Nearer to the optical path 4 than the lens 8, the original image is narrowed down. Therefore, it is possible to detect the average density of the original image over a wide range in the width direction (direction perpendicular to the plane of the paper in FIG. 1) exposed by the detection element 18 having a relatively small shape. In this embodiment, since the exposure amount on the upstream side of the lens 8 with respect to the optical path 4 is not uniform due to the so-called COSθ law of the lens 8, the detection element 18 is disposed on the downstream side of the lens 8. It goes without saying that the upstream side may be used as long as the F stream side has a uniform exposure amount due to a correction plate or the like. Since the detection element [8] is located near the lens 8, the image quality will not deteriorate.

FIG. 3 is a block diagram related to the detection element 18 and the static eliminating corona discharger I7. Original 1 from detection element 18
An electrical signal representing the shade of the image is amplified by an amplifier circuit 20 and provided to a delay circuit 21. The delay circuit 21 is
It includes a low-pass filter 22, a packet brigade device 23, and a low-pass filter 24 to delay the electrical signal from the amplifier circuit 20. During this time, the exposed portion of the exposure area 13 of the photoconductor IO is marked by the arrow 11.
It may be the time W1 for the static elimination corona discharger 17 to move in the direction of static elimination and reach the static elimination position by the static elimination corona discharger 17, and in order to compensate for the operation delay W2 of the static elimination corona discharger 17 by this time W1, the time (Wl-W2) may be set. Delay circuit 21
The delayed signal from is given to the control circuit 25.

As a result, the discharge state of the static eliminating corona discharger 17 is changed. The static eliminating corona discharger 17 is energized by superimposing a DC voltage on a high-voltage AC voltage. In another embodiment of the present invention, the control circuit 25 is controlled to reduce the superimposed DC voltage as the original image becomes lighter in color. - The two-peak value may be changed to become larger.

As yet another embodiment of the present invention, not only the discharge state of the discharge corona discharge device 17 for static elimination is changed depending on the degree of density of the original image, but also the discharge state of the corona discharge device 15 for transfer is changed. You may also do so.

As described above, according to the present invention, the detection element is provided near the lens that forms the original image on the photoreceptor to detect the density of the original image. Averaged shading can be detected. A detection element provided near such a lens is advantageous because it does not adversely affect the original image formed on the photoreceptor.

This detection element is provided near the lens, so
There is no possibility of contamination due to adhesion of toner, etc., and therefore maintenance is easy, and the density of the original image can be accurately detected over a long period of time. Therefore, the discharge state of the static eliminating corona discharger is always maintained at an accurate optimum state. Therefore, the image transferred to the copy paper is clear and does not have image omissions.

Instead of the lens 8, a so-called in-mirror lens may be used, and the present invention can be practiced in connection with such a lens.

The present invention is not only practiced in connection with transfer-type electrostatic copying machines, but can also be widely practiced in connection with printers and other image forming devices.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a portion of a transfer type electrostatic copying machine according to an embodiment of the present invention, and FIG. 2 is a simplified diagram showing an optical path 4 through which a document image is formed on a photoreceptor 10. FIG. 3 is a block diagram related to the static eliminating corona discharger 17 and the detection element 18. 1... Original, 4... Optical path, 8... Lens, io
... Photoreceptor, 13... Exposure area, 14... Magnetic brush phenomenon device, 15... Corona discharger for transfer, 17.
...Corona discharger for weight removal, 18...Detection element, 20.
...Amplification circuit, 21...Delay circuit, 25...Control circuit Agent Patent attorney Kei Nishi

Claims (2)

[Claims] (1) Guide the original image to the photoreceptor through a lens to form an electrostatic latent image on the photoreceptor, visualize the electrostatic latent image as a toner image, and place the copy paper in close contact with the photoreceptor. In a copy paper static elimination/separation device that performs transfer using a transfer corona discharger, and then removes static electricity from the copy paper using a static elimination corona discharger to separate the copy paper from the photoreceptor, the copy paper is provided near the lens, a detection element that detects the density of the image, and a signal from this detection element until the position of the original image formed on the photoreceptor detected by the detection element reaches the position where static electricity is removed by the static elimination corona discharger. 1. A static eliminating and separating device for copy paper, comprising: a delay circuit that delays by a time related to time; and a control means that changes the discharge state of a static eliminating corona discharger in response to an output from the delay circuit. (2) The control means controls il'i! 2. The copying paper static elimination and separation device according to claim 1, wherein the discharge state of the transfer corona discharger is also changed in response to the output from the spreading circuit.