JPS6122302B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in electrophotographic copying machines.

Conventionally, an electrophotographic copying machine that automatically forms different copy images on both the front and back sides of transfer paper is known from US Pat. No. 3,869,202.
However, in this electrophotographic copying machine, when obtaining a large number of copies, the copying operation to obtain one copy is repeated multiple times, so vibrations and noise caused by the movement of the optical system or document table in the exposure device, etc. This occurs every time a copying operation is performed, increases power consumption, slows down the copying speed, and makes it impossible to copy images on the front and back sides of the same document. On the other hand, an electrophotographic copying machine that forms one electrostatic latent image on a photoreceptor and produces many copies from this electrostatic latent image was developed in the 1970s.
This method is known from publications such as No. 17298 and US Pat. No. 3,045,587. According to this electrophotographic copying machine, a large number of copies are obtained from one electrostatic latent image, so the number of times that electrostatic latent images are formed on the photoreceptor is reduced, and the optical system of the exposure device or the document table is moved. Although the vibration and noise caused by the transfer paper are significantly reduced, power consumption is saved, and copying can be performed at high speed, it is not possible to form copied images on both sides of the transfer paper. Therefore, by utilizing the features of both of the electrophotographic copying machines mentioned above, two electrostatic latent images of different original images are simultaneously formed on the photoreceptor, and then a copy image is formed on both sides of the transfer paper using these two electrostatic latent images. It is also possible to repeat the action. However, with this method, it is not possible to form a copy image on the other side of the transfer paper until the copy image formed on one side of the transfer paper is sufficiently fixed, and it takes time to obtain one copy. This increases the time it takes to obtain a large number of copies.

The present invention eliminates the above-mentioned drawbacks, reduces vibration and noise caused by the exposure device, consumes less power, and can copy images on both sides of a transfer paper at high speed.Furthermore, images on both sides of the same document can be copied. The purpose of the present invention is to provide a new electrophotographic copying machine that can.

An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIGS. 1 and 2, an original is placed on an original table 1, and the number P of copies of this original is set in a preset counter 2. In this case, as shown in Fig. 3, the original platen 1 is divided into left and right halves by a central boundary line 3, and during single-sided copying, in which copies are made only on one side of the transfer paper, the original is placed on the right side ₁ . During double-sided copying, in which copies are made on both sides of the transfer paper, the original is placed on the right side 1 ₁ with the left edge aligned, and at the same time the left side 1 ₂
Another document is placed on top with its right end aligned with the boundary line 3. For example, if the document is B5 size, it is placed as shown by the dotted line in the figure, and if it is A4 or B4 size, it is placed as shown by the dashed line or chain double dotted line in the figure. Also, when duplexing images of both the front and back sides of the same original, the original is first placed on the right side ₁₁ ,
Thereafter, at a time to be described later, the document is turned over and placed on the left side portion ₁₂ . The exposure device 4 is a slit exposure device consisting of a document table 1, a lamp 5, mirrors 6 to 8, an in-mirror lens 9, a shutter 48, and an aperture member 49. The document on the document table 1 is illuminated by the lamp 5. The reflected light from mirror 6~
The lamp 5 and mirrors 6 and 7 scan the original by moving in the direction of the arrow shown in the figure in synchronization with the rotation of the photoreceptor 10. When the document table 1 is in the illustrated position, the right side portion ₁₁ of the document is exposed, and when the document table 1 moves to the right, the left side portion ₁₂ is exposed. A copy size setting piece 11 is installed on the side of the document table 1.
Switches 12 and 13 are arranged in a row below the copy size setting piece 11 and switches 12 and 1.
3 is moved in the left and right direction according to the copy size. Further, a driving piece 14 is fixed to the lower side of the boundary line 3 on the document table 1, and a driving piece 15 is fixed to the lower side of the mirror 6, and switches 16 and 17 are installed below the normal position of the driving pieces 14 and 15. Placed. Therefore, the switches 16 and 17 are driven by the driving pieces 14 and 15 to detect when the document table 1, the lamp 5, and the mirrors 6 and 7 are in their normal positions, and the switches 12 and 13 respectively detect when the document table 1, lamp 5, and mirrors 6 and 7 are in their normal positions. 1 unit
When the lamp 5 and the mirrors 6 and 7 move by a distance corresponding to the copy size, they are driven by the drive pieces 14 and 15 and this is detected. The control device 18 controls the moving distance of the document table 1, the moving distance of the lamp 5, and the mirrors 6, 7 according to the copy size based on signals from these switches 12, 13, 16, and 17. On the other hand, the storage device 19 stores the lower limit setting level of the copy image density, and the lower limit setting level can be arbitrarily rewritten. The end-of-life detection device 20 detects that the life of the electrostatic latent image on the photoreceptor 10 has ended by receiving the output signal from the storage device 19 and detecting that the density of the copied image has decreased to the lower limit setting level. For example, it may be configured such that a counter counts the number of copies and generates an output signal when the counted number becomes an integral multiple of the number set in the storage device 19. The end-of-life detection device 20 may be configured to detect when the surface potential of the image portion of the photoreceptor 10, the density of the toner image, or the image density of the copy has decreased to a lower limit setting level, or a timer may be used to detect the electrostatic It may be set at the time of forming the latent image, and the operating time may be set depending on the life of the electrostatic latent image. The control device 18 includes a life end detection device 20, a preset counter 2, switches 12, 13, 16, 17,
Each device in the electronic copying machine is controlled to perform the following operations based on signals from a single-sided copy switch, a double-sided copy switch, etc.

First, when performing single-sided copying, assuming that N copies can be obtained during the lifetime of the electrostatic latent image formed on the photoreceptor 10, when P<N, the single-sided copying switch is pressed. , the photoreceptor 10 is rotationally driven in the direction of the arrow in the figure. During the first rotation, the photoreceptor 10 is charged by the charging device 21, and the exposure device 4 exposes the original image to form an electrostatic latent image.
In this case, the original 1 remains in its normal position and the lamp 5 and mirrors 6 and 7 are moved by a distance corresponding to the copy size, so that the image of the original on the right side portion ₁₁ is exposed. Next, the photoreceptor 10 is transferred to a magnetic brush developing device 22.
The toner image is developed by the transfer device 24 and transferred onto the transfer paper from the first paper feed device 23. In order to extend the life of the latent image, consideration must be given to insulating the carrier when using a two-component developer consisting of a carrier and toner, or using a relatively high-resistance toner when using a single-component developer. be. Further, the developing method is not limited to the magnetic brush developing method, and for example, a powder cloud method, a touch-down developing method, etc. that can use the above developer can be used. Furthermore, regarding transfer devices, normal bias transfer rolls, corona transfer devices, etc. have an adverse effect on the life of latent images, so for example,
50-136033 etc. can be conveniently used. At this time, the first paper feeding device 23 is at the paper feeding position shown by the solid line in the figure, and the transfer paper is sent out by the paper feeding roller 25.
The second paper feed device 26 is located at the solid line position shown in the figure and is used as a paper discharge tray. The transfer device 24 is, for example, one that presses a transfer paper against the photoreceptor 10 using a transfer roller 27 to transfer the toner image. The transfer roller 27 is charged to a predetermined potential of the same polarity as the surface potential on the photoreceptor 10 by a charging device 28 in front of the transfer position in order to reduce attenuation of the electrostatic latent image on the photoreceptor 10 during transfer. At the rear side of the transfer position, the charge is removed by a corona charger 29 for charge removal. After the toner image is transferred, the end of the transfer paper is guided between a roller 31 and a belt 32 by a guide portion 30 . Rollers 31, 33-35, belt 32, guide member 3
0 constitutes a separating device 50, which peels off the transfer paper from the photoreceptor 10 using a roller 31 and a belt 32. This transfer paper has a belt 36 and rollers 37, 3.
After the toner is transported by a transport device 39 consisting of 8, and the toner is fixed by fixing rollers 40 and 41, it is discharged as a copy onto a paper discharge tray 44 by rollers 42 and 43. At this time, the corona charger 4 for charge removal
5 and the static eliminating lamp 46 are inactive, and the cleaning blade 47 in the magnetic brush developing device 22 is retracted from the surface of the photoreceptor 10. Next, after the second rotation of the photoconductor 10, the charging device 21 and the exposure device 4 become inactive, and the electrostatic latent image formation operation on the photoconductor 10 is no longer performed, and the shutter 48 closes, causing the photoconductor 10 to rotate once. A copy is obtained by the electrostatic latent image formed on the eye. That is, each time the photoreceptor 10 rotates once, the electrostatic latent image on the photoreceptor 10 is developed by the magnetic brush developing device 22, and the toner image is transferred by the transfer device 24 onto the transfer paper from the first paper feeder 23. The transfer paper is separated from the photoreceptor 10 by a separation device 50, transported by a transport device 39, heated by fixing rollers 40 and 41 to fix the toner, and discharged onto a paper discharge tray 44 by rollers 42 and 43. When the number of copies obtained in this way reaches the set number P, the output signal from the preset counter 2 to the control device 18 disappears, and the corona charger 45 and lamp 4
6 is operated to remove static electricity from the photoreceptor 10, and residual toner is removed from the photoreceptor 10 by a magnetic brush in the magnetic brush developing device 22. After the cleaning blade 47 is pressed against the photoreceptor 10 and removes the residual toner, The copy operation ends. According to the present invention, the number of times the cleaning operation is performed is very small compared to a normal cleaning operation, and therefore there is no point in providing the developing device and the cleaning device in separate locations.Therefore, the cleaning means is disposed within the developing device. Alternatively, if the developing device itself is energized for cleaning, the entire device can be made smaller, and the toner removed from the photoreceptor is collected within the developing device to be reused for development. It's convenient.

In addition, when P≧N in single-sided copying, the operation is the same as when P<N in single-sided copying described above until the number of copies reaches N, but each time the number of copies reaches an integer multiple of N, the lifespan decreases. From the end detection device 20 to the control device 18
An output signal is added to the charge eliminating corona charger 45.
The static eliminating lamp 46 operates to eliminate static electricity from the photoconductor 10, and the cleaning blade 47 removes the static electricity from the photoconductor 1.
The residual toner on the photoreceptor is removed by the magnetic brush and the cleaning blade 47. Thereafter, the static eliminating corona charger 45 and the static eliminating lamp 46 become inoperative, and the cleaning blade 47 retreats from the photoreceptor 10. Then, the charging device 21 and the exposure device 4 operate to form an electrostatic latent image of the document on the right side portion 11 on the photoreceptor ₁₀ , and a copy is obtained from this electrostatic latent image in the same manner as described above. That is, the charging device 21 and the exposure device 4 become inoperative, and each time the photoreceptor 10 rotates, the electrostatic latent image on the photoreceptor 10 is developed by the magnetic brush developing device 22 and the electrostatic latent image is transferred from the first sheet feeding device 23. Transfer device 2 to transfer paper
4, the toner image is transferred. The transfer paper is separated from the photoreceptor 10 by a separation device 50, transported by a transport device 39, toner is fixed by fixing rollers 40 and 41, and discharged onto a paper discharge tray 44 by rollers 42 and 43. When the number of copies obtained in this way reaches the set number P, the output signal from the preset counter 2 to the control device 18 disappears, and the corona charger 45 and the lamp 46 are operated to remove the photoreceptor. 10 is neutralized, the cleaning blade 47 is brought into pressure contact with the photoreceptor 10, and the residual toner on the photoreceptor 10 is removed by the magnetic brush and the cleaning blade 47, and then the copying operation is completed.

In addition, when double-sided copying is performed, when the double-sided copying switch is pressed, the fixing roller 41 separates from the fixing roller 40 and comes into pressure contact with the fixing roller 51, and the conveying device 39 is moved between the separating device 50 and the fixing rollers 41, 51. Moving. Then, the original image on the right side ₁₁ of the document table 1 is copied onto one side of the set number of transfer sheets in almost the same way as in the case of single-sided copying, but the transfer sheet from the separation device 50 is transported by the transport device 39. After the toner is fixed by the fixing rollers 41 and 51, the charge is removed by the charge removing device 52 and the toner is fixed by the fixing rollers 53 and 54.
The paper is discharged to the second paper feeding device 26. This static eliminator uses a sheet with a toner image fixed on one side.
This device is necessary to eliminate negative effects such as multiple sheet feeding, jams, or poor speed performance due to static charges accumulated in the previous copying process when refeeding paper to form a toner image on the other side. be. As this static eliminator, a corona discharge device or a light current corona device, etc., to which a DC voltage of opposite polarity to the static charge on the sheet is applied, is used. In this case, the document table 1 moves rightward after completing the final exposure of the document image on the right side portion ₁₁ , and the document image on the left side portion ₁₂ comes to the exposure position. When you want to copy both sides of the same document, start moving the document table 1 and then copy the left side 1 _2.
The document on the right side portion ₁₁ may be turned over and placed on the left side portion ₁₂ before copying of the upper document image begins. When the output signal of the preset counter 2 disappears and the set number of sheets of transfer paper has been copied on one side, the first paper feeder 23 retreats from the paper feeding position and the second paper feeder 26 starts feeding as shown by the dotted line in the figure. When the paper is moved to the paper position, the fixing roller 41 is separated from the fixing roller 51 and comes into pressure contact with the fixing roller 40, and the conveying device 39
moves between the separating device 50 and the fixing rollers 40 and 41. This fixing device was developed by the applicant in the Showa era.
What is detailed in Japanese Patent Application No. 51-2651 dated January 12, 1951 can be used. Then, the original image is copied onto the transfer paper from the second paper feeder 26 in substantially the same manner as in the case of single-sided copying described above. In this case, since the original image on the left side portion ₁₂ of the original platen 1 is at the exposure position, this original image is copied. Further, the transfer paper in the second paper feeding device 26 is sent out by the paper feeding roller 25, and the toner image on the photoreceptor 10 is transferred to the back side by the transfer device 24, so that it is copied on both sides. The transfer paper separated from the photoreceptor 10 by the separation device 50 is transported by the transport device 39 to the fixing roller 40,
The toner is fixed in step 41 and discharged as a copy onto a paper discharge tray 44 by rollers 42 and 43. On the other hand, a paper detector (not shown) is provided to detect the presence of transfer paper in the second paper feeding device 26.
The output signal of this paper detector is applied to a control device 18. The control device 18 is a preset counter 2
After the output signal disappears, the copying operation is continued based on the output signal of this paper detector, and the copying operation is ended after copying is completed on the last transfer paper from the second paper feeder 26. The document table 1 is moved to its original position after the final exposure of the document image on the left side portion ₁₂ is completed.

It should be noted that the present invention is not limited to the above embodiments, and can be applied to, for example, an electrostatic latent image transfer method, a belt-shaped photoreceptor may be used, or double-sided copying of transfer paper can be set. The process may be performed for a certain number of copies instead of the number of copies, and may be modified as desired without changing the gist.

As described above, according to the electrophotographic copying machine according to the present invention, a plurality of copies are obtained from the electrostatic latent image formed on the photoreceptor, so the number of times the electrostatic latent image is formed on the photoreceptor is reduced, and the optical Vibration and noise caused by movement of the system or document table are significantly reduced, and power consumption is saved. Moreover, since copies are made continuously on one side of multiple sheets of transfer paper and then continuously copied on the other side, when copying on the other side of the transfer paper, the one-sided copy image is sufficiently fixed, and there is no need to wait, and the speed is extremely high. Copying can be performed, and images on both sides of the same original can be copied on both sides of transfer paper. In addition, when automatically copying the front and back sides of one original onto the front and back sides of a sheet, the number of exposure scans of the original is minimal compared to normal ones, so when it is displayed that the exposure scan process is not necessary again, Since the other side of the original can be set on the exposure scanning surface and preparations for the next exposure scanning can be made in advance, the above-mentioned copying, which has been difficult in the past, is also possible. In addition, the document table has two document placement sections, and after copying the document on one document placement section onto one side of the transfer paper, the document on the other document placement section is copied onto the other side of the transfer paper. Therefore, if you want to copy one side of two originals onto both sides of transfer paper, you only need to set the two originals on the two original placement areas of the original table; When copying on both sides of transfer paper, first set the original on one side of the document tray, make a one-sided copy, then turn the original over and place it on the other side while the exposure on one side of the original is completed and the one-sided copying continues. It is only necessary to set the document on the document placement area, and therefore, it is possible to reduce the loss time due to document setting and the risk of the document being set in such a manner.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view showing one embodiment of the present invention, FIG. 2 is a block diagram showing a part of the same embodiment,
FIG. 3 is a top view showing the document table of the same embodiment. 1...Original table, 2...Preset counter, 3
... Boundary line, 4 ... Exposure device, 5 ... Lamp, 6
~8...Mirror, 9...In-mirror lens, 10
... Photoreceptor, 11 ... Copy size setting piece, 12,
13... Switch, 14, 15... Drive piece, 1
6, 17...Switch, 18...Control device, 20
... Life end detection device, 21 ... Charging device, 22
...magnetic brush developing device, 23...first paper feeding device,
24...Transfer device, 26...Second paper feeding device, 39
...Transport device, 40, 41...Fixing roller, 44
... Paper ejection tray, 46 ... Static elimination lamp, 50 ...
... Separation device, 51 ... Fixing roller.

Claims (1)

[Claims] 1. A document table having two document placement portions on which original documents are placed, and a photoreceptor that is charged and an image of the document on one of the document placement portions of the document table is exposed to the photoreceptor. An electrostatic latent image is formed, and the development of the electrostatic latent image formed by one charging and image exposure on the photoreceptor and the transfer to one side of the transfer paper are continuously repeated to produce a large number of transfer papers. means for making one-sided copies;
After single-sided copying is performed on multiple sheets of transfer paper by this means, the photoreceptor is uniformly charged again and the image of the document on the other document placement portion of the document table is exposed onto the photoreceptor. By this, an electrostatic latent image is formed, and the development of the electrostatic latent image formed by one charging and image exposure on the photoreceptor and the transfer of the one-sided copy to the other side of the transfer paper are continuously repeated. means for obtaining a large number of copies by means of a method for obtaining a large number of copies, and a means for obtaining a copy image density at a lower limit when continuously repeating development and transfer of an electrostatic latent image formed by one charging and image exposure on the photoreceptor; The electrostatic latent image on the photoreceptor is detected by detecting that the electrostatic latent image has fallen to a set level, that the number of copies has become an integral multiple of the set number, or that a set time has elapsed since the formation of the electrostatic latent image. life end detection means for detecting the end of life; and control for forming a new electrostatic latent image by charging the photoreceptor and image exposure when the life end detection means detects the end of the life of the electrostatic latent image. An electrophotographic copying machine comprising means.