JPH01154184A - Electrostatic separating device for transfer type image recording device - Google Patents

Abstract

PURPOSE:To make a secure separation without reference to original image density by detecting the image density of an original between original exposure scanning and development and controlling AC electric power supplied to a separation electrode according to the detected quantity. CONSTITUTION:A density detecting means 25 detects the image density of the original between the original exposure scanning process and developing process. The density detected quantity is made into a signal, which is inputted to a central processing unit (CPU) 28. Then the proper value of electric power supplied to the separation electrode 15 controlled according to a program set in the CPU 28 previously is calculated from the input value and the CPU 28 outputs a control signal for controlling the current control means of a power unit according to the calculated value, thereby supplying proper electric power corresponding to the original image density to the separation electrode 15. Consequently, an original image having any original image density can securely be separated.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an electrostatic separation device for separating transfer sheets used in transfer type image recording devices such as electrophotographic copying machines and laser printers.

[Background of the invention]

Transfer-type image recording devices such as electrophotographic copying machines and laser printers use a rotating drum-type photoreceptor having a photoconductive photosensitive layer on the outer circumferential surface, and as the photoreceptor drum is rotated, electrostatic charges are applied to the photosensitive layer. A latent image is formed and developed with toner,
The obtained toner image is transferred to a transfer paper or the like to obtain a desired recorded matter. The transfer paper remains in contact with the surface of the photoreceptor during transfer, and the toner image is transferred to the surface of the transfer paper by a corona discharge of opposite polarity to the toner applied from the back of the transfer paper, completing the transfer. In order to promote separation from the surface of the photoreceptor, the transfer paper after the transfer is subjected to a method such as applying AC corona discharge from the back side of the transfer paper using a separation electrode to eliminate static electricity. However, in this separation using separation electrodes, the charging characteristics of the transfer paper on which the transferred image is formed differ due to the original image density, etc., and stable separation performance cannot always be obtained. If the separation of the transfer paper is incomplete, the transfer paper may collide with the lower part of the cleaning device or enter the cleaning device, causing a paper jam, which not only hinders the formation of copied images, but also This will damage the photosensitive layer of the photosensitive drum and cause the cleaning device to malfunction.

[Problems to be solved by the invention]

The density of original images ranges over a wide range, for example from plain white paper to solid black paper, and the charging characteristics of the transfer paper onto which the toner images of these original images are transferred have large variations depending on the density difference of the original images. There is. Therefore, the AC power supplied to the separation electrodes with a DC component superimposed also has an appropriate value depending on the density characteristics of the original image. FIG. 8 is a characteristic diagram showing the relationship between the original image density and the DC component of the power supplied to the separation electrodes. The vertical axis direction is the document image density, and the horizontal axis direction is the current value of the DC component. As is clear from the figure, the appropriate current value range for the DC component of the supplied power is different between the solid black original image and the blank original image. (Usually, the image density of an original falls between the above two.) Therefore, the optimum value for each original image density also takes different values. Conventionally, since there is a common area in the current value range that both of these can take, a current value that exists in this common area is selected,
It was permanently adopted. However, this method does not necessarily work with all types of transfer paper, and paper jams may occur due to poor separation.
A solution to solve this problem is desired.

[Means to solve the problem]

The present invention has been made in order to solve the above-mentioned problems, and the present invention has been made to provide a transfer paper separation method for a transfer type image recording device that can improve the separation characteristics regardless of the original image density. The purpose is to provide a device. The above purpose is an electrostatic separation device for a transfer type image recording device, which supplies high-voltage AC power with a DC component superimposed to a separation electrode, and uses this separation electrode to separate transfer paper that is in close contact with the surface of a photoreceptor. , a detection means for detecting the image density of the original during the period from the original exposure scanning process to the development process, and a DC component supplied to the separation electrode is superimposed according to the detection amount detected by the detection means. A control means for controlling high-voltage AC power is provided, and the separation performance of the separation electrode is configured to be controllable according to the original image density. .

【Example】

The first to third embodiments of the present invention are shown in FIGS. 1 to 7.
This will be explained in detail based on the figures. FIG. 3 is a configuration diagram of a transfer type image recording apparatus equipped with an electrostatic separation device. First, the general functions of the transfer type image recording apparatus will be explained with reference to FIG. The photosensitive drum IO is a drum-shaped image carrier in which a photoconductive substance is laminated to a certain thickness on a conductive metal substrate.
The photoconductive surface is rotatably configured to rotate as it passes sequentially through a plurality of processing stations. The photoreceptor drum IO is charged by a charger 7, and its surface holds a uniform charge. The photosensitive drum IO, whose photoconductive surface is uniformly charged, rotates and enters the exposure section 8. In the exposure section 8, a light image of the document on the document table glass l is reflected and guided by an exposure optical system A including mirrors 2, 3, 4, 6, a lens 5, etc., and is directed to the photoreceptor drum l. irradiated onto the photoconductive surface of the When the photoconductive layer of the irradiated part of the photosensitive drum 10 receives exposure light, the conductivity of the part that receives the light increases, and the electrical charge in that part escapes onto the conductive metal substrate, and the dark part is Positive charges remain depending on the degree of brightness and darkness, and as a result, an electrostatic latent image corresponding to the original image is formed on the surface of the photoconductive layer. The photoreceptor drum IO on which the electrostatic latent image has been formed rotates and enters the developing section B. In this developing section B, the electrostatic latent image is developed by a developer containing charged toner particles in a developing device 9,
It is visualized and becomes a toner image. On the other hand, the feed rollers lla to 11c are fed from the paper feed section C.
The transfer paper P sent out from the paper feed cassette is conveyed to the timing roller 13 by conveyance rollers 12a to 12c, and waits there. Then, the transfer paper P is sent out from the timing roller 13 to the photoreceptor drum 10 in synchronization so that the leading edge of the toner image area visualized on the photosensitive drum IO and the leading edge of the transfer paper P are aligned. The transfer paper P is a photosensitive drum l on which a toner image is formed.
The toner image is in close contact with the surface of the O drum, and in this state, the toner image is transferred to the transfer paper P by the discharge of the transfer pole 14. Transfer paper P onto which the toner image has been transferred by the transfer pole 14
Next, the photoreceptor drum 10 receives corona discharge of high-grade AC power with a DC component superimposed from the back side by the separator electrode 15.
separated from the surface. The cleaning device 20 removes residual toner from the photosensitive drum lO from which the transfer paper P has been separated, and the photosensitive drum lO returns to its original state. On the other hand, the transfer paper P separated from the photoreceptor drum IO is transported by the transport means 21 and reaches the fixing section E. In this fixing section E, heating roller 16 performs heat fixing. After the fixing is completed, the transfer paper P is discharged to the outside of the machine by a paper discharge roller 17. FIGS. 1A and 1B are configuration diagrams of a transfer type image recording apparatus showing a first and second embodiment of the present invention. Reference numerals 25A and 25B are reflected light reading type original image density detection means comprising a light emitting element and a light receiving element. The density detection means 25A, 25B scan the original image with a light emitting element, read the reflected light from the original image with a light receiving element, and detect the density of the original image. The detected density of the original image is converted into a signal and sent to a central processing unit (C
PU). Then, based on the input value, an appropriate power supply value to the separation electrode 15 is calculated, which is controlled according to a program set in advance in the central processing unit (CPU). Based on this calculated value, a control signal for controlling the current control means of the power supply device, which will be described later, is sent to the central processing unit (C
PU). In this way, appropriate power is supplied to the separation electrode 15 according to the original image density. The original image density detection means 25A and 25B are provided within the exposure optical system A. When the light emitting elements specific to the detection means 25A and 25B are made to emit light, a preliminary scan is performed immediately before the original image is scanned and exposed by the lamp L to detect the original image density. This preliminary scanning may be performed by a separately provided preliminary scanning mechanism, or may be performed by the original exposure scanning mechanism. When performing preliminary scanning, the document image density detection means 25A is provided at the position shown in FIG. 1(A), that is, within the exposure scanning mechanism. Further, when an exposure lamp L is used instead of the light emitting element specific to the detection means 25B, preliminary scanning is not performed and the reflected light of the original image irradiated by the exposure lamp L during scanning exposure of the original image is used in its optical path. The light is received by the light receiving element of the document image density detecting means 25 provided therein, and the density of the document image is detected (FIG. 1(B)). In this case, the detection means 25
The installation position of B may be any position in the optical path. In the second embodiment, it was provided at the position of the lens 5 shown in FIG. 1 (B). FIG. 2 is a block diagram of a transfer image recording apparatus showing a third embodiment of the present invention. Reference numeral 26 denotes potential detection means for detecting the surface potential of the photoreceptor after irradiating the exposure light of the original image. When the photoconductive layer of the irradiated part of the photosensitive drum IO receives exposure light, the conductivity of the part that receives the light increases, and the electrical charge in that part escapes onto the conductive metal substrate, and the dark part is Positive charges remain depending on the degree of brightness and darkness, and as a result, an electrostatic latent image corresponding to the original image is formed on the surface of the photoconductive layer. The potential detecting means 26 detects residual positive charges according to the degree of brightness and darkness described above. According to the measured potential output, the potential output value corresponding to the blank image mentioned above is approximately 100V.
The potential output value corresponding to a black solid image is approximately 800v.
Met. The detected amount by the potential output corresponding to the density of the detected original image is converted into a signal and sent to the central processing unit (cp), which will be described later.
s). Then, based on the input value, an appropriate power supply value to the separation electrode I5 is calculated, which is controlled according to a program set in advance in the central processing unit (CPU). Based on this calculated value, a control signal for controlling the current control means of the power supply device, which will be described later, is sent to the central processing unit (CP).
U). In this way, appropriate power is supplied to the separation electrode 15 according to the original image density. FIG. 4 shows a cross-sectional view of the transfer/separation section of the transfer type image recording device shown in FIGS. 1(A), (B) to FIG. Transfer pole 14,
The back surface of the separation electrode 15 is shielded by a shield member 23. The photoreceptor drum IO has a selenium (Se) photoreceptor deposited on the circumferential surface of the drum, and rotates in the direction of the arrow at a constant circumferential speed. The transfer pole 14 is a tungsten wire stretched at a constant distance from the surface of the photoreceptor drum 10, and a positive DC voltage is applied to the transfer pole 14 via a constant current controlled high voltage transformer. Since the selenium (Se) photoreceptor is a photoreceptor that is positively charged, it is positively charged by the charger 7 and forms a latent image by exposing the original light image. Therefore, in the developing section, the negatively charged toner adheres to the latent image area to form a toner image. In the transfer section, the transfer paper P is in close contact with the surface of the photoreceptor drum 10 and passes through it at a constant circumferential speed. The electrically attached toner is electrostatically attracted and transferred to the transfer paper P. The transfer current required to complete the transfer while the transfer paper that is in close contact with the photoreceptor drum IO moves to the separating section is 30
It is 0 to 350 μA. In the present invention, the original image density is a blank image (potential output 100V).
) or a black solid image (potential output 800V), this is an electrostatic separation device for a transfer type image recording apparatus that eliminates static electricity from any transfer paper and performs reliable separation. Separation electrode 15 is 1 stretched parallel to photoreceptor drum lO.
The separating wire 15a has a diameter of 0.
．． 08 mm tungsten wire is used. The distance between the surface of the photosensitive drum 10 and the separation wire 15a is Ba1m. A DC bias from a variable current power supply is applied to the separation wire 15a in accordance with the original image density. When the original image is blank, the DC bias is -80 μA and 8
The electric current is applied from behind the transfer paper P in a superimposed form on an AC voltage whose current is controlled to 00 μA, thereby eliminating static electricity. Also, when the original image is solid black, the DC bias is -20
The current is applied from behind the transfer paper P in a superimposed form on an AC voltage whose current is controlled to 800 μA at μA, thereby eliminating static electricity. The above-mentioned two cases are extreme cases, and a normal manuscript exists between the two. Therefore, the DC bias value mentioned above is
-20μ8 to -80μA may be changed continuously depending on the original image density, or it is preferable to divide a certain range and change stepwise. FIG. 5 is a characteristic diagram of the original image density and the corresponding current value of the DC component. In the figure, the horizontal axis represents the original image density (photoreceptor drum surface potential output after exposure light irradiation).
The vertical axis represents the current value of the DC component supplied to the separation pole. As mentioned above, in the case of a blank image (photoreceptor drum surface potential output after irradiation with exposure light: 100 V), the current value of the DC component supplied to the separation electrode is preferably -80 μA. Further, in the case of a black solid image (photosensitive drum surface potential output after irradiation with exposure light: 800 V), the current value of the DC component supplied to the separation electrode is preferably -20 μA. FIG. 6(A) is a wiring diagram of the separation electrode power supply device of this embodiment, and FIG. 6(B) is a current waveform of the power supplied from the power supply device. In the figure, 151 is an AC high voltage power supply, 152 is a DC high voltage power supply, 153 is a current control means, and b is a DC component that is variably controlled. As described above, the detected value of the original image density is once input to the central processing unit (CPU) and calculated according to a preset program, and a control signal for the current control means 153 is output. The DC component is determined by the output signal. The DC component is superimposed on the high-voltage AC power of the AC high-voltage power supply 151 and is supplied to the separation electrode 15 . FIG. 7 is a control block diagram of power supplied to the separation electrodes based on the original image density. The density of the original image is detected by the original image density detection means 25, and the detected amount is input to the central processing unit (CPU) 28. The central processing unit 28 calculates a control signal to be output to the power supply device 150 so as to supply the optimum supply power to the separation electrode 15 according to a preset program. The calculated control signal is input to a device 150 comprised of the central processing unit 28. In the power supply device 150, the power value supplied to the separation pole 15 is controlled by the control signal and converted to an appropriate value. In this way, the separation electrode 15 is supplied with AC power on which a DC component optimized according to the original image density is superimposed. Further, the potential detection means 26 detects the surface potential of the photosensitive drum after irradiating the original image with exposure light, and the detected amount is input to the central processing unit 28 . Then, through the same process as described above, the separation electrode 15 is supplied with AC power on which a DC component optimized according to the original image density (photoreceptor drum surface potential output after exposure light irradiation) is superimposed.

【Effect of the invention】

According to the present invention, it is possible to detect the density of the original, control the power value supplied to the separation electrodes according to the detected amount of density, and supply appropriate power to the separation electrodes in accordance with the density of the original image. It is now possible to provide an electrostatic separation device for a transfer type image recording device that can reliably separate document images of any document image density.

[Brief explanation of the drawing]

1A and 1B are block diagrams of a transfer type image recording apparatus equipped with a document image density detection means showing the first and second embodiments of the present invention, and FIG. 2 is a diagram showing a third embodiment of the present invention. A configuration diagram of a transfer type image recording device equipped with a potential detection means on the surface of a photoreceptor drum showing an example, FIG. 3 is a configuration diagram of a transfer type image recording device equipped with an electrostatic separation device, and FIG. 4 is a configuration diagram of a transfer type image recording device equipped with an electrostatic separation device. Cross-sectional view of the device, No. 5
Figure 8 and Figure 8 are characteristic diagrams showing the relationship between the original image density and the current value of the DC component of the power supplied to the separation electrodes, and Figure 6 (A
XB) is the wiring diagram of the power supply device that supplies power to the separation electrodes and the current waveform diagram of the power supplied from the power supply device, and Figure 7 shows the power supplied to the separation electrodes according to the original image density. It is a control block diagram of. lO...Photosensitive drum 15...Separation electrode 25...
- Original image density detection means 26...Potential detection means 28...Central processing unit (control means) 150...Power supply device A...Exposure optical system (original exposure scanning process) B...Development section ( Development process) P...Transfer paper

Claims (3)

[Claims] (1) In an electrostatic separation device for a transfer-type image recording device, in which high-voltage AC power with a DC component superimposed on a separation electrode is supplied, and the separation electrode separates transfer paper that is in close contact with the surface of a photoreceptor. , a detection means for detecting the image density of the document during the period from the document exposure scanning process to the development process; and a high voltage superimposed with a DC component supplied to the separation electrode according to the detection amount detected by the detection unit. 1. An electrostatic separator for a transfer type image recording apparatus, characterized in that the electrostatic separator for a transfer type image recording apparatus is provided with a control means for controlling alternating current power of the separator electrode, and the separation performance of the separator electrode is controllable according to the density of the original image. (2) The transfer type image recording apparatus according to claim 1, wherein the detection means is a reflected light reading type original image density detection means comprising a light emitting element and a light receiving element provided in the original exposure scanning process. Electrostatic separation device. (3) An electrostatic separation device for a transfer type image recording apparatus according to claim 1, wherein the detection means is a potential detection means for detecting a surface potential of a photoreceptor after being irradiated with exposure light of an original image.