JPH04237083A - Controller for destaticizer for peeling of image forming device - Google Patents

Abstract

PURPOSE:To obviate the generation of retransfer and finger marks by constituting the above device in such a manner that the destaticizing capacity of a destaticizer for peeling can be changed over and that the destaticizing capacity of the destaticizer for peeling is increased at the time of operating a pretransfer destaticizer. CONSTITUTION:This controller is so constituted that the destaticizing capacity of the destaticizer 18 for peeling can be changed over and that the destaticizing capacity of the destaticizer 18 for peeling is increased at the time of operating the pretransfer destaticizer 25. The retransfer of the toner images transferred onto paper to the photosensitive body and the generation of voids are prevented even in either of the case thin and less stiff paper is to be used as paper and the case the paper curls at the time of the 2nd copying in double-side copying, multiple copying, synthetic copying, etc. The appearance of finger marks for peeling by the insufficient destaticizing capacity of the destaticizer 18 for peeling is obviated. The images having good quality are formed in this way.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to image forming apparatuses such as electrophotographic copying machines, facsimile machines, printers, etc., which develop an electrostatic latent image formed on a photoreceptor with toner and transfer the toner image to paper. The present invention relates to a control device that controls the operation of a stripping static eliminator that strips paper onto which a toner image has been transferred from a photoreceptor.

0002

[Prior Art] Conventionally, when an electrostatic latent image formed on a photoreceptor is developed to form a toner image and the toner image is transferred to paper, static eliminating light is applied to the photoreceptor before the transfer. The pre-transfer static elimination lamp is well known as a pre-transfer static elimination lamp that eliminates static electricity from a photoreceptor and facilitates the transfer of a toner image onto a sheet of paper by a transfer corotron. In particular, when the paper is thin and stiff, or when the paper is curled during the second copy in double-sided copying, multiple copying, composite copying, etc., the pre-transfer static elimination lamp is used to transfer the photoreceptor. Eliminating the charge beforehand is effective in preventing transfer defects such as white spots caused by retransfer of the toner image once transferred onto the paper onto the photoreceptor. Furthermore, instead of the pre-transfer static elimination lamp as mentioned above, an AC+
It is also known that substantially the same effect can be achieved using a pre-transfer static elimination corotron using DC discharge.

By the way, if the static eliminator for peeling off the paper on which the toner image has been transferred is increased too much, the transferred toner image will be retransferred. Conventionally, the charge removal ability of the stripping static eliminator has been moderately suppressed, because paper can be forcibly peeled off using a peeling finger provided downstream of the stripping static eliminator even if the paper is not removed.

0004

[Problems to be Solved by the Invention] As described above, it is known that the pre-transfer static eliminator is used alone to suit the environmental conditions and usage conditions, but it is also known that the pre-transfer static eliminator is used to eliminate the possibility of peeling. The static eliminator's static eliminator was used at a constant level without increasing its ability much. Therefore, even if the photoreceptor is neutralized before transfer using the pre-transfer static eliminator, the static eliminator's ability to eliminate static electricity is not improved, so the paper is not necessarily peeled off by the peeling static eliminator, and the paper is forcibly removed using the peeling finger. Since the toner was peeled off, finger marks caused by this forced peeling appeared on the copies, and it was not possible to obtain good copies.

[0005] The present invention has been made in view of the above situation, and an object of the present invention is to remove electricity downstream of the transfer charger when attempting to obtain a copy without retransfer using a pre-transfer static eliminator. It is an object of the present invention to provide a control device for a stripping static eliminator that can improve the static eliminating ability of a disposed stripping static eliminator and obtain copies free of finger marks.

[0006]

[Means for Solving the Problems] A control device for a stripping static eliminator of an image forming apparatus according to the present invention that achieves the above object includes at least a latent image carrier and an electrostatic potential formed on the latent image carrier. A developing device that develops the image with toner, and a transfer charging device that charges the surface of the copy paper opposite to the transfer surface with an electric charge of the same polarity as the latent image in order to transfer the developed toner image onto the copy paper. a discharging device, a stripping static eliminator that removes charges on the surface opposite to the transfer surface of the copy paper in order to separate the copy paper from the latent image carrier after the transfer process, and a latent image formed with a toner image before transfer. In a control device for a stripping static eliminator in an image forming apparatus having a pre-transfer static eliminator that neutralizes a carrier, the static eliminator's static eliminator is configured to be switchable, and when the pre-transfer static eliminator is operated, the stripping static eliminator is configured to be switchable. The present invention is characterized in that the static eliminator is configured to increase its ability to remove static electricity.

In this case, the stripping static eliminator is configured with an AC corona discharger containing a DC bias current, and by increasing the DC bias current to the opposite polarity to the charging polarity by the transfer charger, the stripping static eliminator is The most typical method is to enhance the static elimination ability, and a static elimination lamp or a static elimination corona discharger is used as the pre-transfer static eliminator.

[0008]

[Operation] In the present invention, the static eliminator's static eliminator is configured to be switchable, and when the pre-transfer static eliminator is operated, the static eliminator's static eliminator is increased. When using thin paper with no stiffness,
Also, if the paper is curled during the second copy in double-sided copying, multiple copying, composite copying, etc., the toner image transferred onto the paper may be retransferred onto the photoreceptor. In addition to preventing white spots, it also eliminates the appearance of finger marks on copies due to the paper being forcibly peeled off by the peeling finger due to the lack of static eliminating ability of the peeling static eliminator, allowing for higher quality image formation. can.

[0009]

EMBODIMENTS Prior to describing the embodiments of the present invention, the functions of the pre-transfer static eliminator lamp and the peeling static eliminator will be briefly explained. As shown in FIG. 5, for example, when a negatively charged electrostatic latent image formed on a drum-shaped photoreceptor is developed with positively charged toner, in state (2) after development,
The photoreceptor reaches the transfer position (2) on the transfer charger with the + toner electrostatically attached to the -charge on the surface of the photoreceptor. Here, the back surface of the paper receives a negative charge from a transfer charger, and the electrostatic force of this charge transfers the positively charged toner on the photoreceptor to the surface of the paper. Next, at position (3) of the stripping static eliminator, most of the - transferred charges on the back side of the paper are removed, but as the paper moves away from the surface of the photoreceptor, some amount of - remains due to the separation distance. Due to the electrostatic force of the transferred charge, the toner transferred to the paper surface remains on the paper surface even after the transferred charge is removed.
Transcription is complete.

However, as shown in FIG. 6, when the paper is not stiff or curls upward, the paper does not separate from the surface of the photoreceptor when the stripping static eliminator is at position (3). As the paper follows this, the charge on the back side of the paper is removed more rapidly (as is clear from the figure, as the paper follows the photoreceptor, the charge removal width becomes wider, so the charge is removed more quickly), and almost no charge is left. Moreover, since the paper is close to the surface of the photoreceptor, the toner once transferred to the paper is electrostatically attracted by the charge on the photoreceptor, and after the transferred charge is removed, it is transferred to the photoreceptor again. (retransfer, retransfer), resulting in white spots on the paper due to poor transfer.

On the other hand, as shown in FIG. 7, if a pre-transfer static elimination lamp is placed in front of the transfer position and the static elimination light is irradiated through the developed toner image, the negative charge on the photoreceptor surface is reduced. Since a considerable part of the static electricity is removed by the static electricity removal light that enters between the toners, at the position from ■ to ■,
There is not much negative charge remaining on the surface of the photoreceptor, and even if the paper is not stiff or curls upward, toner will not be retransferred at positions (1) and (2). By the way, if such a pre-transfer static elimination lamp is used to constantly perform optical static elimination, it will cause optical fatigue on the photoreceptor, which is undesirable. Therefore, the pre-transfer static eliminator lamp should be turned on only when using thin paper with low stiffness, or when the paper has curled after passing through the heat fixing device, such as when duplexing or multiple copying. It is desirable to do so.

By the way, as shown in FIG. 7, when the surface of the photoreceptor before transfer is neutralized using a pre-transfer static elimination lamp or a pre-transfer static elimination corotron, not much charge remains on the surface of the photoreceptor. Therefore, in such a case, it is conceivable to increase the static elimination ability of the peeling static eliminator to make it easier to peel the paper. Therefore, by taking the DC bias current of the stripping static eliminator as a variable, we investigated the occurrence of retransfer that occurs at the leading edge of the paper when the pre-transfer static eliminator lamp is turned on and off, and the retransfer phenomenon that occurs at the leading edge of the paper when the pre-transfer static eliminator lamp is turned on. When the appearance of marks was graded, the results shown in FIG. 8 were obtained. Note that the paper used was thin paper without stiffness, and the toner used was red. Further, the current applied to the transfer corotron was -550 μA, and the alternating current voltage applied to the peeling corotron was 4.2 kV and the frequency was 600 Hz. In FIG. 8, as the DC bias current of the peeling corotron on the horizontal axis increases toward the positive side, it means that the ability to remove static electricity from the back surface of the paper increases. As is clear from this figure, when the pre-transfer static elimination lamp is turned on to prevent retransfer of the toner image, the static elimination ability is increased rather than keeping the DC bias current of the stripping corotron at its normal state. This means that by shifting the image in the opposite direction, the generation of finger marks can be suppressed while preventing retransfer.

From the above results, when used in an electrophotographic copying machine equipped with a pre-transfer static elimination lamp or a pre-transfer static elimination corotron, capable of manual feeding mode, double-sided copying and image composition functions, from the viewpoint of preventing retransfer, it is necessary to It is desirable to operate the pre-transfer static eliminator lamp or pre-transfer static eliminator corotron during the paper feed mode and manual feed mode (because thin and stiff paper is normally used as the paper in the manual feed mode), Accordingly, it is desirable to simultaneously increase the direct current bias current of the stripping corotron in a direction that enhances the static elimination ability, from the viewpoint of suppressing the generation of finger marks.

Based on the above knowledge, the present invention will be explained based on examples. FIG. 1 is a diagram showing the configuration of an electrophotographic copying machine capable of manual feeding mode, an automatic document feeder, double-sided copying, and image composition functions, in which a control device according to the present invention is applied.

In the figure, reference numeral 11 denotes a latent image carrier such as a photosensitive drum, 12 a pre-charger such as a corotron, which charges the surface of the latent image carrier 11 in advance, and 13 a latent image on the latent image carrier 11. An inter-image lamp 14 that lights up in areas other than the forming area forms an exposure lamp 14a that irradiates illumination light onto the original 21 on the platen 22, and an optical path that guides reflected light from the original 21 to the latent image carrier 11. multiple mirrors 1
4b and an exposure optical system 1 comprising an imaging lens 14c that forms an optical image from the original 21 onto the position of the latent image carrier 11;
5 is a developing device that develops the latent image on the latent image carrier 11 with toner;
Reference numeral 25 denotes a pre-transfer static elimination lamp; 26, a chute that maintains the thrusting posture of the copy paper 16 with respect to the latent image carrier 11 and corrects deformation of the copy paper 16; and 17, the toner image on the latent image carrier 11 is transferred to the copy paper 16. A transfer charger such as a corotron 18 transfers the copy paper 16 to the latent image carrier 11 after the transfer process.
A stripping static eliminator 19 is a DC-biased AC corotron that removes charges on the copy paper 16 in order to remove it from the latent image carrier 11 when the stripping static eliminator 18 is incompletely stripping the copy paper 16 from the latent image carrier 11. A peeling finger 20 forcibly peels off the copy paper 16, a cleaner 20 that removes residual toner on the latent image carrier 11, and a fixing device 23 that fixes the toner image on the copy paper 16 after the transfer process.

Further, in this embodiment, an automatic document feeder (hereinafter abbreviated as ADF) 30 is provided at the top of the copying machine, and this ADF 30 has a document set tray 31 disposed near the platen 22. , a document feed roll 32 that feeds the set document 21 in the document set tray 31 to the platen 22 side according to the timing of each copy cycle; The original 21 sent to the side is conveyed to the registration position of the platen 22, and after the copying cycle is completed, the original 21 is transferred to the platen 22.
a conveyor belt 33 for discharging and conveying from the registration position of No. 2;
The document storage tray 34 is formed integrally with the platen cover 24 and stores the document 21 discharged by the conveyance belt 33.

Furthermore, in this embodiment, copy paper 1
The paper transport system 40 that transports the paper 6 is configured to be capable of manual feeding mode, multiple composite copying, and double-sided copying operations. That is, the paper conveyance system 40 includes paper feed cassettes 41 and 42 that each accommodate copy paper 16 of a plurality of sizes, for example;
An intermediate tray 43 that temporarily stores the copy paper 16 after the first copy cycle during multiple composite copying and double-sided copying, and a feed roll 44 that sends out the copy paper 16 from the paper feed cassettes 41, 42 and the intermediate tray 43. 46
and a supply side conveyance path 47 for guiding the copy paper 16 from the paper feed cassettes 41, 42 and the intermediate tray 43 to the transfer site.
and disposed near the transfer site in this supply conveyance path 47,
Feed roll 57 from supply side conveyance path 47 or manual feed port 56
A registration gate 48 consisting of a registration roll that once positions the copy paper 16 supplied from the paper supply path 58 inserted through the paper supply path 58 and then sends it to a transfer site at a predetermined timing, and a copy paper that has completed a series of copying operations. an ejection tray 49 for ejecting and accommodating the copy paper 16, an ejection side transport path 50 for guiding the copy paper 16 that has passed through the transfer site to the ejection tray 49 side after passing through the fixing device 23; U that guides the paper 16 to the intermediate tray 43 side
A turn conveyance path 51, a first switching gate 52 disposed at the intersection of the discharge side conveyance path 50 and the U-turn conveyance path 51 to select either of the conveyance paths, and an intermediate between the U-turn conveyance path 51. Copy paper 16 is provided near the tray 43.
and the reversing conveyance path 53 used when reversing the U
A second switching gate 5 disposed at the intersection of the turn conveyance path 51 and the reversal conveyance path 53 to select either of the conveyance paths.
4. In the figure, reference numeral 55 is a transport roll that transports the copy paper 16 within each transport path, and 56 is a transport roll that transports the copy paper 1.
6. This is a conveyor belt for conveyance.

Furthermore, a start switch 61 for starting the copying operation is provided on the console panel at the top of the copying machine.
In addition to this, there is also a parallel compositing mode switch 62 that is pressed when compositing multiple images onto a single copy sheet 16 in parallel, and a double-sided copying mode switch 63 that is pressed when duplexing.
, manual feed mode switch 64 that is turned on when in manual feed mode
Various switches such as the following are arranged, and input signals from each switch are input to the control unit 70.

In this embodiment, the control unit 7
0 is realized as a microcomputer system as shown in FIG.

In the figure, a start switch 61, a parallel composition mode switch 62, and a double-sided copying mode switch 6 are shown.
3 and the manual feed mode switch 64 are input to the CPU 72 via an input interface 71. This CPU 72 executes various programs including a parallel synthesis mode program stored in advance in the ROM 73 based on input data.
Data is exchanged with the RAM 74. The CPU 72 outputs various operation signals via the output interface 75, and outputs various operation signals to the main motor power source 83, ADF 30, and optical system 14 for rotating the magnification change section 81, the cassette selection section 82, and the latent image carrier 11. System 1
4 exposure lamp 14a, pre-charger 12, pre-transfer static eliminator lamp 25, transfer device 17, stripping static eliminator 18, inter-image lamp 13, developer movement control system 85, and paper transport system 4
0 is controlled.

As described above, in order to prevent retransfer, it is desirable to turn on the pre-transfer static elimination lamp 25 on the second side of paper and in the manual feed mode. From the viewpoint of suppressing finger marks, it is desirable to shift the DC bias current in a direction that increases the static eliminating ability of the stripping static eliminator 18 at the same time as the pre-transfer static eliminator lamp 25 is turned on. Therefore, when the CPU 72 determines that the paper is on the second side or in the manual feed mode, the pre-transfer static eliminator lamp 25 is turned on, and the DC bias current of the peeling static eliminator 18 is controlled to be shifted in the direction of increasing the static removal ability. do. For this purpose, a pre-transfer static elimination lamp 25, a transfer device 1
7. The control system for the stripping static eliminator 18 is actually shown in Figure 3.
Configure as shown. The pre-transfer static elimination lamp 25 is a CPU
The discharge voltage including the DC bias current of the stripping static eliminator 18 is controlled by a high voltage source 86 whose output voltage is controlled by the CPU 72.

[0022] When the pre-transfer static elimination lamp 25 is turned on and
Control of the voltage applied to the stripping static eliminator 18 in conjunction with the light-off control is as follows:
For example, the procedure shown in FIG. 4 is used. That is, ST1
At , it is determined whether the image forming operation to be performed is double-sided copying or composite copying. If the image forming operation is double-sided copying or composite copying, it is determined in the next ST2 whether or not it is copying of the first side. In the case of the first side, it is not necessary to turn on the pre-transfer static eliminator lamp 25, so in ST3 the pre-transfer static eliminator lamp 25 is turned off, and in the next ST4, the DC bias current applied to the stripping static eliminator 18 is set to the normal nominal value. , especially the static elimination ability is not improved. On the other hand, if it is determined in ST2 that the second side is to be copied, it is necessary to turn on the pre-transfer static elimination lamp 25 to prevent retransfer, so in ST5, the pre-transfer static elimination lamp 25 is turned on.
In the next ST6, the DC bias current applied to the stripping static eliminator 18 is shifted from the normal nominal value to the positive side (
(See Figure 8) Improves static elimination ability and prevents finger marks from occurring due to poor peeling. If it is determined in ST1 that it is not double-sided copying or composite copying, the process proceeds to ST7, where it is determined whether manual feeding mode is selected. When it is determined that the manual feeding mode is selected, the pre-transfer static elimination lamp 25 is turned on in ST8, and the DC bias current applied to the stripping static eliminator 18 is shifted in the direction of increasing the static elimination capability in the next ST9. If it is determined in ST7 that the mode is not manual feed mode, it is not necessary to turn on the pre-transfer static eliminator lamp 25 because it is a single-sided copy of normal plain paper, and the pre-transfer static eliminator lamp 25 is turned on in ST10.
is turned off, and the DC bias current applied to the stripping static eliminator 18 is set to a normal nominal value in the next ST11, so that there is no need to particularly enhance the static eliminator ability.

In the above example, the pre-transfer static eliminator lamp 25 is used as the pre-transfer static eliminator, but a similar configuration can be achieved by using a pre-transfer static eliminator corona discharger instead. Further, although the pre-transfer static elimination lamp 25 is assumed to be automatically turned on when the second side of paper is being printed and when in the manual feed mode, it may be configured so that it can be forced to turn on manually during any copying. The stripping static eliminator 18 also shifts the applied DC bias current in the direction of increasing the static elimination ability as the pre-transfer static eliminator lamp 25 turns on.

Several embodiments of the control device for the stripping static eliminator of the image forming apparatus of the present invention have been described above.
It will be obvious that the present invention is not limited to these, and that various modifications can be made.

[0025]

As explained above, according to the control device for the stripping static eliminator of the image forming apparatus of the present invention, the static eliminating capacity of the stripping static eliminator is switchable, and when the pre-transfer static eliminator is operated, Since the static eliminator is configured to increase the static eliminating ability of the stripping static eliminator, it can be used when using thin paper with no stiffness, and when making the second copy in double-sided copying, multiple copying, composite copying, etc. In any case where the toner image is curled, it is possible to prevent the toner image transferred onto the paper from being re-transferred onto the photoreceptor and resulting in white spots, and also to prevent the toner image from becoming blank due to the lack of static elimination ability of the stripping static eliminator. Since the paper is forcibly peeled off by the peeling finger and finger marks do not appear on the copy, it is possible to form a higher quality image.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the configuration of an example of an electrophotographic copying apparatus using a control device for a stripping static eliminator according to the present invention.

FIG. 2 is a block diagram showing a control system of the electrophotographic copying apparatus shown in FIG. 1;

FIG. 3 is a diagram showing the actual configuration of a control system for a pre-transfer static eliminator lamp, a transfer device, and a peeling static eliminator.

FIG. 4 is a flowchart showing a procedure for controlling a stripping static eliminator according to an embodiment of the present invention.

FIG. 5 is a diagram for explaining the mechanism of normal transfer and peeling.

FIG. 6 is a diagram illustrating how retransfer occurs when the paper is of weak stiffness.

FIG. 7 is a diagram for explaining the action of a pre-transfer static elimination lamp.

FIG. 8 is a diagram illustrating the results of grade evaluation of the occurrence of retransfer and the occurrence of finger marks at the leading edge of the paper with respect to the DC bias current of the stripping static eliminator.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11...Latent image carrier, 12...Pre-charger, 13...Interimage lamp, 14...Exposure optical system, 14a...Exposure lamp,
14b...mirror, 14c...imaging lens, 15...developing device,
16... Copy paper, 17... Transfer device, 18... Static eliminator for peeling,
19... paper peeling finger, 20... cleaner, 21... original, 22... platen, 23... fixing device, 24... platen cover, 25... pre-transfer static elimination lamp, 26... chute, 30
...Automatic document feeder, 31...Document set tray, 32...
Document feed roll, 33...Transport belt, 34...Document storage tray, 40...Paper transport system, 41, 42...Paper feed cassette,
43...Intermediate tray, 44, 45, 46...Feed roll, 4
7... Supply side conveyance path, 48... Registration gate, 49... Discharge tray, 50... Discharge side conveyance path, 51... U-turn conveyance path, 52
...first switching gate, 53...reversing conveyance path, 54...second switching gate, 55...conveyance roll, 56...conveyance belt,
56...Manual feed port, 57...Feed roll, 58...Manual feed paper supply path, 61...Start switch, 62...Parallel composition mode switch, 63...Double-sided copying mode switch, 64...Manual feed mode switch, 70...Control unit, 71...Input Interface, 72...CPU, 73...ROM, 74
...RAM, 75...Output interface, 81...Magnification variable section of optical system, 82...Cassette selection section, 83...Main motor power supply, 85...Developer drive control system, 86...High voltage source, 87...
low voltage source

Claims (4)

[Claims] Claim 1: At least a latent image carrier, a developer for developing an electrostatic latent image formed on the latent image carrier with toner, and a device for transferring the developed toner image onto copy paper. A transfer charger charges the surface of the copy paper opposite to the transfer surface with an electric charge of the same polarity as the latent image, and a transfer charger charges the surface of the copy paper opposite to the transfer surface to separate the copy paper from the latent image carrier after the transfer process. A control device for a stripping static eliminator in an image forming apparatus, which includes a stripping static eliminator that eliminates static charges on a surface of the image forming apparatus, and a pre-transfer static eliminator that neutralizes a latent image carrier on which a toner image is formed before transfer, A stripping static eliminator for an image forming apparatus, characterized in that the stripping static eliminator is configured to be switchable in its static eliminating capacity, and is configured to increase the static eliminating ability of the peeling static eliminator when operating a pre-transfer static eliminator. Control device. 2. The stripping static eliminator is an AC corona discharger that includes a DC bias current, and the DC bias current is increased to the polarity opposite to the charging polarity by the transfer charger. 2. A control device for a stripping static eliminator for an image forming apparatus according to claim 1, characterized in that the static eliminator is improved in static elimination ability. 3. The control device for a stripping static eliminator of an image forming apparatus according to claim 1, wherein a static eliminator is used as the pre-transfer static eliminator. 4. The control device for a stripping static eliminator of an image forming apparatus according to claim 1, wherein a static eliminator corona discharger is used as the pre-transfer static eliminator.