JP5412852B2 - Image forming device toner recycling mechanism - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, or a composite machine of these, and particularly relates to control of a toner recycling mechanism for returning untransferred toner to a developing chamber.

In an electrophotographic image forming apparatus, there are a one-component developing method mainly composed of toner and a two-component developing method mainly composed of toner and carrier.
In either method, after the latent image on the image carrier is developed to form a visible image, the image is transferred onto a recording medium (hereinafter referred to as paper) or an intermediate transfer belt. Transfer residual toner remains.

  Also, the timing error of applying the charging potential to the image carrier at the start and end of the printing operation and the application of the developing bias to the developing unit, the region where the charging potential of the image carrier is unstable until the rise is stable, or the charging unstable Excess toner may exist on the image carrier in addition to the original image-formed / transferred toner, such as adhesion of the toner to the background of the image carrier.

  The cleaning unit collects these toners. In many image forming apparatuses, individually collected toner is accumulated as waste toner in a waste toner tank and collected and discarded during maintenance. On the other hand, waste toner is used from the viewpoint of reducing running costs and environmental considerations. There is also an image forming apparatus having a toner recycling system in which the transfer residual toner collected in the cleaning unit without being discharged is returned to the developing chamber and reused.

  After transfer of fresh toner from the toner bottle, the transfer residual toner is also subjected to stress at each stage, such as stirring in the developing device, forming a visible image by developing on the image carrier, passing through the transfer site, and collecting at the cleaning unit. ing. In addition, the cleaning unit is structurally downstream of the image forming operation after transfer, and may be disposed relatively close to a fixing device located downstream of the transfer as well. For this reason, it may be exposed to heat, and wax contained in the collected toner or deposited on the surface will melt, and fluidity is likely to be lowered or aggregated.

  If this state is repeated or left for a long time, the toner functions and characteristic values will be deteriorated, and the quality of the printed image will be deteriorated. The solidification of the toner on the toner conveyance path causes toner conveyance failure and conveyance mechanism lock, and causes internal contamination due to a phenomenon such as toner dropping, toner overflow, and toner spillage.

  Until now, as disclosed in Patent Document 1, some toner recycling systems have a waste toner tank and are provided with a mechanism for switching between recycling and disposal so as not to be 100% recycled. . In those having this mechanism, as in Patent Document 2 and Patent Document 3, the discard / recycle ratio is also changed depending on the paper type in consideration of the influence of paper dust. Further, some having the same mechanism increase the amount of discarded toner as in Patent Document 4.

  However, if it depends on the type of paper, the brand of the paper is unlimited, and it depends strongly on the operator who actually operates, so there is a risk of setting errors. Too much fear of such an operator error, if the toner disposal ratio is increased to give a margin to the paper dust mixing rate, the end of the toner recycling system will end in the end. In this case, it can be said that it is better to provide a paper dust collecting mechanism on the paper conveyance path before transfer if a margin for the paper type is provided.

  There is Patent Document 5 as an example of an attempt to establish a toner recycling system without a waste toner tank. In this system, a mechanism for supplying and supplying fresh toner to the cleaning unit is provided, and the collected toner and fresh toner are mixed in the cleaning unit and then supplied to the developing chamber. However, in this regard, there is a drawback that even the fresh toner deteriorates due to circumstances such as conveyance to a cleaning unit that is easily affected by external temperature and mixing with the collected toner.

  There is also a patent document 6 that proposes that a new charger is provided and the charge is recovered by the cleaning unit after manipulating the charge polarity. However, the charging of the toner before recovery is performed afterwards in the recovery / conveyance / development chamber. -It is unclear whether the effect can be maintained until a step such as re-development.

  Rather, as proposed in Patent Document 7, at the start of the image forming sequence, exposure by the image exposure unit is started at the same time as or earlier than the start of application of the charging voltage of the charging unit, and the charging unit is started at the start of application of the charging voltage. The exposure of the image exposure unit is stopped at the same time or after the most upstream part of the region on the image forming body facing the image exposure position of the image exposure unit, and the development bias voltage of the development unit Is applied at the same time as the part on the image forming body that was at the exposure position at the moment of exposure stop reaching the development position or within a predetermined range before that, to reduce wasteful movement with high accuracy and as much as possible. It is better to reduce the stress on the toner and reduce the untransferred residual toner. However, it is extremely difficult to raise the accuracy as mentioned in Patent Document 7, and various types of mounted devices and parts are also expensive in implementation.

  As a comparatively good example, the configuration disclosed in Patent Document 8 is different from its original purpose, but all the collected toner on the conveyance path including the inside of the cleaning unit is conveyed into the developing chamber at the end of the printing operation. After the operation is finished, there is no external heat stress in the cleaning unit or on the transport path, and there is no toner supply from the recycle path in the development chamber at the start of the next printing operation. Is possible. However, every time the printing operation is completed, the operation is extended for transporting the collected toner. Even if the condition of the toner and the developer can be maintained, the wear of the image carrier and the cleaning blade is accelerated. The exchange cycle will be shortened. Also, continuing the operation for a long time after the end of printing causes anxiety to the apparatus user above all.

  As long as the apparatus is operating, the transfer residual toner collected to the cleaning unit is intermittently returned to the developing chamber through the recycle conveyance path, and stirred as a developer and used for development. Normally, after printing is completed, post-processing operations such as cleaning and static elimination are performed, and then the drive system of the apparatus is stopped. However, the time is short, and the collected toner remains in the cleaning unit or recycling transport path. It stops in the state. Although the operation stops, in the heat fixing method used for toner fixing in many electrophotographic image forming apparatuses, the residual heat remains in the apparatus, and the temperature in the apparatus does not decrease immediately. Furthermore, in recent years, from the viewpoint of energy saving, it is often designed and set not only to stop the drive system after the printing operation but also to stop the operation of the fan installed and operated for the purpose of exhausting heat from the machine. The in-flight temperature is more difficult to drop. In addition, the cleaning unit is structurally downstream of the image forming operation after transfer, and is also disposed relatively close to the fixing device after transfer, and the toner that is collected and remains in the cleaning unit and the recycling transport path is also present. As a result, it is exposed to heat.

  In recent years, due to the progress of low-temperature fixing, the in-machine temperature is lower than in the past, but this low-temperature fixing itself is largely due to toner, and the collected toner is also easily affected by external heat. Further, regarding the toner, the particle size is also being reduced, but this not only increases the surface area per volume and is easily affected by the external temperature, but also causes a decrease in fluidity.

  When toner aggregates and solidifies due to the influence of external temperature in the cleaning unit and on the recycling path, print quality problems such as adhesion of the aggregated toner to the image initially occur, and the situation further deteriorates. If a conveyance failure occurs, the toner conveyance mechanism will be locked, causing problems such as toner dropping, toner overflow, and toner spillage.In addition to contamination inside the machine, the toner will also flow out of the machine, causing the operator's hands, clothes, There may be a problem that the carpets, desks, etc. are soiled.

  In addition, the toner transport mechanism lock may cause damage to the mechanism, and it is not necessary to clean the same as in-machine contamination due to toner scattering, so that the apparatus can be operated normally unless the unit or parts are replaced. It may not be possible to recover. If such a situation is reached, the situation in which the apparatus cannot be used will take a long time, which may cause a great loss to the user's business.

  For these reasons, in a recent image forming apparatus, the state in which the toner collected in the cleaning unit and on the transport path from the unit remains or stagnates is repeated even if there is no problem temporarily. It is inconvenient if the possibility is not solved.

  In this regard, although various proposals have been made in the past as described above, in view of the fact that the present invention is not sufficiently satisfactory, the present invention provides a large-scale new mechanism in an image forming apparatus having a toner recycling system. In addition, the present invention provides a configuration that minimizes toner deterioration in the collected toner conveyance path including the inside of the cleaning unit without adding any expensive parts / functions and without burdening other parts of the apparatus. This is the issue.

An object of the present invention is to provide an image forming apparatus having a toner recycling system that cleans and collects transfer residual toner remaining on the image carrier after the image forming process and conveys the toner again to the developing device. A cleaning blade including a cleaning blade that cleans and collects transfer residual toner remaining on the toner, and a recycled toner conveying screw provided along a longitudinal direction of the cleaning blade, and is disposed below the cleaning device in the vertical direction. A first conveying screw that conveys toner from one end side to the other end side in the axial direction of the image bearing member on the image bearing member side, and a toner that is provided in parallel with the first conveying screw and that is disposed from the other end side to the one end side. A developing device including a second conveying screw for conveying, and the cleaning device. Anda dropping conveying path for dropping the toner by its own weight to the other end of the toner supply port of the developing device from the other end, the developing device, detects the toner density in the lower portion of the second conveying screw includes a toner density sensor for the recycle toner conveying screw, said image bearing member driving system, and the the drive system of the developing device which is driven by an independent drive system, when the printing operation ends, The toner transport speed by the recycled toner transport screw is set to be higher than that during the printing operation, and the transfer device also uses the cleaning device after the operation of the image carrier and the developing device is stopped when the printing operation is finished. the recovered to continue again faster than during the printing operation the conveying operation of the toner recycling system for transporting to the developing device, further printing operation The time from the timing when the image carrier part positioned at the rear end of the latent image passes through the cleaning device to the stop of the operation of the toner recycling system at a high speed from the end on one end side of the cleaning device More than the time required for the transfer residual toner to be transported to the toner replenishing port of the developing device, and after the operation of the toner recycling system at a high speed is stopped, the toner density sensor causes the fresh toner to be supplied to the developing device. It is solved by determining whether or not replenishment is necessary .

The time from the timing when the image bearing member site located latent image rear end during printing operation ends passes through the cleaning device to the stop of the operation of the transport operation that is faster the toner recycling system, one end side of the cleaning device It is effective to set the time longer than the time required for the transfer residual toner to be conveyed from the end portion to the toner replenishing port of the developing device .

According to the present invention, in an image forming apparatus having a toner recycling system that cleans and collects transfer residual toner remaining on an image carrier after image forming processing and transports the toner to a developing device again, the recycled toner is used at the end of the printing operation. The toner conveying speed by the conveying screw is set to be higher than that during the printing operation, and after the operation of the image carrier and the developing device is stopped at the end of the printing operation, the transfer residual toner is collected by the cleaning device and again the developing device. Since the toner recycling system that transports the toner to the printer continues at a higher speed than the printing operation , no large new mechanism or expensive parts / functions are added, and the image carrier, cleaning device, and each slide It is possible to reduce the residual toner on the recycling route in a short time without causing excessive operation that causes fatigue and wear of the part, Toner can be prevented from lowering and toner scattering, toner dropping toner overflow problems such image quality deterioration, aggregation and solidification in the cycle path.

At the end of the printing operation, the time from the timing at which the image carrier portion located at the rear end of the latent image passes through the cleaning device to the stop of the operation of the toner recycling system at a high speed is defined as one end of the cleaning device. By setting the time longer than the time required for the transfer residual toner to be conveyed from the image forming unit to the toner replenishing port of the developing device, it is possible to prevent deterioration in image quality due to toner degradation, toner aggregation and toner solidification on the recycling path. It is possible to make necessary and sufficient additional operations for preventing problems such as scattering inside, outside of the apparatus due to scattering, toner dropping, and toner overflow.

1 is a schematic configuration diagram of a copying machine. FIG. 3 is a partial configuration diagram of a region from a cleaning device to a developing device around an image carrier for understanding the concept of collecting recycled toner. FIG. 3 is a conceptual perspective view for explaining a toner recycling path.

  FIG. 1 is a diagram showing an outline of an image forming apparatus according to an embodiment of the present invention. An image reading apparatus 200 is mounted on the apparatus main body 100 of the copying machine as an image forming apparatus, and the apparatus main body 100 is simultaneously placed on the sheet bank 300. On the image reading apparatus 200, an automatic document feeder 400 that can be opened and closed up and down with the back side as a fulcrum as viewed in the figure is attached.

  The copying machine main body 100 is provided with a drum-shaped photoreceptor 10 as an image carrier. A charging device 11 is arranged on the left side of the periphery of the photoconductor 10, and a developing device 12, a transfer device 13, and a cleaning device 14 are arranged in order from the rotation direction (counterclockwise) A side of the photoconductor 10. .

  In the developing device 12, toner is attached by the developing roller, and the electrostatic latent image is visualized on the photoreceptor 10. In addition, the transfer device 13 is configured such that upper and lower rollers 15 and 16 are stretched over a transfer belt 17, and is pressed against and contacted with the peripheral surface of the photoconductor 10 at a transfer position B on the transfer belt 17. Yes. A toner replenishing device 20 is arranged on the left side of the charging device 11 and the cleaning device 14, and new toner is replenished to the developing device 12 by the toner replenishing device 20.

  Further, inside the copying machine main body 100, there is a sheet conveying device C that conveys the sheet S fed from the sheet cassette 61 in the sheet bank 300 from the lower side to the upper side through the transfer position B to the paper discharge stack unit 39. Is provided. The sheet conveying apparatus C includes a supply path R1, a manual feed path R2, and a sheet conveyance path R. In the sheet conveyance path R, a registration roller 21 is provided at an upstream position of the photoconductor 10. A thermal fixing device 22 is provided at a downstream position of the photoconductor 10. The thermal fixing device 22 includes a heating roller 30 and a pressure roller 32. Further, a paper discharge branch claw 34, a discharge roller 35, a first pressure roller 36, a second pressure roller 37, and a waist roller 38 are provided further downstream of the heat fixing device 22, and an image has been formed further ahead. A discharge stack unit 39 for stacking sheets is provided.

  Further, as shown in FIG. 1, the copier apparatus main body 100 is provided with a switchback device 42 on the apparatus main body surface on the right side in FIG. The switchback device 42 branches from the position of the discharge branch claw 34 in the sheet conveyance path R, and reverses the path R3 that guides the sheet to the switchback area 44 including the pair of switchback rollers 43, and the sheet conveyance from the switchback area 44 again. A sheet conveying apparatus D having a re-conveying path R4 that guides the sheet to the registration rollers 21 in the path R is provided. The sheet conveying apparatus D is provided with a plurality of sheet conveying rollers 66 for conveying the sheet.

  On the left side of the developing device 12 in the figure, a laser writing device 47 is provided. In addition to a laser light source (not shown), the laser writing device 47 includes a scanning rotary polygon mirror 48, a polygon motor 49, a scanning optical system 50 such as an fθ lens, and the like.

  The image reading apparatus 200 includes a light source 53, a plurality of mirrors 54, an imaging optical lens 55, an image sensor 56 such as a CCD, and the like. A contact glass 57 is provided on the upper surface. The automatic document feeder 400 on the contact glass 57 is provided with a document setting table (not shown) at the document placement position and a document stacking table (shown) at the discharge position. Further, a sheet conveying apparatus having an original conveying path (not shown) for conveying the original sheet from the original setting table to the original stack base through the reading position on the contact glass 57 of the image reading apparatus 200 is provided. This sheet conveying apparatus includes a plurality of sheet conveying rollers (not shown) for conveying a document sheet.

  Inside the sheet bank 300, sheet cassettes 61 that store sheets S as recording media, sheets S such as OHP films are provided in multiple stages. Each sheet cassette 61 is provided with a call roller 62, a supply roller 63, and a separation roller 64, respectively. A supply path R1 leading to the sheet conveyance path R of the copying machine main body 100 is formed on the right side of the sheet cassette 61 provided in multiple stages in the drawing.

  The copier apparatus main body 100 is further provided with a manual feed unit 68 on the right side in the drawing. The manual feed unit 68 is provided with a manual feed tray 67 that can be opened and closed, and a manual feed path R2 that guides a manual sheet set on the manual feed tray 67 to the sheet conveyance path R. Similarly, the manual feed tray 67 is provided with a calling roller 62, a supply roller 63, and a separation roller 64.

  When copying using the copying machine configured as described above, first, a main switch (not shown) is turned on, and a document is set on a document setting table of the automatic document feeder 400. In the case of a book document, the automatic document feeder 400 is opened, the document is set directly on the contact glass 57 of the image reading device 200, the automatic document feeder 400 is closed, and the document is pressed.

  When a start switch (not shown) is pressed, when the document is set on the automatic document conveying device 400, the image reading device 200 is driven after the document is moved by the sheet conveying roller onto the contact glass 57 through the document conveying path. The original content is read and discharged onto the original stack table. On the other hand, when the document is set directly on the contact glass 57, the image reading apparatus 200 is immediately driven.

  When the image reading apparatus 300 is driven, the image reading apparatus 200 moves the light source 53 along the contact glass 57, reflects light from the light source 53 on the document surface on the contact glass 57, and reflects the reflected light into a plurality of light. The light is reflected by the mirror 54, passed through the imaging optical lens 55, and put in the image sensor 56, and the image content is read by the image sensor 56. At the same time, the photoconductor 10 is rotated by a photoconductor drive motor (not shown), the surface of the photoconductor 10 is uniformly charged by the charging device 11 using a charging roller, and then read by the image reading device 200. A laser beam is irradiated in accordance with the content of the original and a writing process is executed using the laser writing device 47 to form an electrostatic latent image on the surface of the photoreceptor 10, and then toner is attached using the developing device 12. To visualize (develop) the electrostatic latent image.

  At the same time as the start switch is pressed, the sheet S selected from the multistage sheet cassette 61 in the sheet bank 300 is sent out by the calling roller 62, separated one by one by the supply roller 63 and the separation roller 64, and sent to the supply path R1. . The sheet S sent to the supply path R1 is transported by the sheet transport roller 66, guided to the sheet transport path R, abutted against the registration roller 21, stopped, and rotated with the visible toner image of the photoreceptor 10. At the same time, it is fed to the right side of the photoreceptor 10.

  Alternatively, when the manual sheet feeding unit 68 is used, the manual feed tray 67 is opened, and the sheet set on the opened manual feed tray 67 is sent out by the calling roller 62, and 1 by the supply roller 63 and the separation roller 64. Each sheet is separated and conveyed, guided from the manual feed path R2 to the sheet conveyance path R, and similarly sent by the registration rollers 21 to the right side of the photoreceptor 10 in time with the rotation of the photoreceptor 10. Visualized.

  Thereafter, the sheet S fed to the right side of the photoconductor 10 is transferred with the toner image on the photoconductor 10 by the transfer device 13 at the transfer position B. The residual toner on the photoconductor 10 after the image transfer is removed and cleaned by the cleaning device 14, and the residual potential on the photoconductor 10 from which the residual toner has been removed is removed by a static elimination device (not shown). In preparation for the next image formation starting from the charging device 11.

  On the other hand, the sheet S after the image transfer is conveyed by the transfer belt 17 and guided to the heat fixing device 22, passed between the heating roller 30 and the pressure roller 32, and conveyed to these rollers while being heated. Pressure is applied to fix the toner image. Thereafter, the sheet S on which the image has been fixed passes through the paper discharge roller 35, the first pressure roller 36, the second pressure roller 37, and the waist roller 38, so that the sheet S is placed on the paper discharge stack unit 39. Discharged and stacked.

  When images are transferred to both surfaces of the sheet S, the sheet having the toner image transferred on the surface by switching the discharge branch claw 34 is carried from the sheet conveying path R to the reversing path R3, and the switchback area 44 And is switched back by the switchback roller 43. The sheet S that has been switched back is guided to the re-conveying path R4, reversed, conveyed by the sheet conveying roller 66, and again guided to the sheet conveying path R, and then on the back surface of the sheet in the same manner as described above. The image will be transferred.

  Next, the toner supply operation will be described with reference to FIGS. The toner supplied from a toner supply port (not shown) is supplied onto the developer in the developing device 12. In the developing device 12, the developer composed of the carrier and the toner is fed in the depth direction of the paper surface in FIG. 2 while being stirred by the spiral conveying screw 2. The developer conveyance path is connected to the conveyance screw 1 on the back side, and is fed from the back side to the near side on the conveyance screw 1 side. Similarly, the conveyance path is connected to the conveyance screw 2 on the front side in FIG. 2, and the developer is circulated. The developer agitated with the toner is rotated clockwise from the conveying screw 1 and pumped up by a magnetic force to the developing roller 4 with a built-in magnet. A large amount of the developer adsorbed by the magnetic force on the surface of the developing roller is regulated to a constant amount by the developing doctor 70 and frictionally charged. The charged developer rises at the main pole of the maximum magnetic strength of the developing roller 4 and comes into contact with the photoreceptor 10. A bias voltage is applied to the developing roller 4, and the toner is selectively developed according to the electrostatic latent image on the photoreceptor 10. The toner concentration of the developer in the developing device is monitored by a toner concentration sensor 5 installed under the conveying screw 2. The toner concentration sensor 5 measures the toner concentration of the developer from the magnetic permeability of the developer. When the toner concentration is lowered, the magnetic carrier is concentrated, so that the magnetic permeability is increased. When the value measured by the toner density sensor 5 exceeds the target value (threshold value), toner is replenished from the toner replenishing device 20, and the toner density is controlled to a constant density. The target value is determined by measuring the reflection density of a pattern formed of toner on the photoconductor using a P sensor (pattern density sensor). Incidentally, in this example, since toner recycling is performed, the recycled toner is intermittently refluxed, and there is a possibility that toner concentration detection and supply control will become unstable. Accordingly, it is preferable that the toner density detection during the printing operation is performed at a timing at which it is expected that the toner density unevenness in the developing device has been eliminated, for example, after a predetermined time has elapsed after the end of the toner recycling operation. From the same point of view, it is expected that the determination of necessity of replenishment of fresh toner from the toner replenishing device will also eliminate the toner density unevenness in the developing device due to the recycling of the recycled toner after a predetermined time has elapsed after completion of the toner recycling operation. It is preferable to carry out at the timing.

  By such an operation, the control is performed so that the reference pattern density on the photosensitive member is kept constant. However, when the toner in the toner replenishing device 20 runs out, basically the density reduction cannot be suppressed. In such a situation, it is determined (or estimated) by means (not shown) that toner has run out from the output of the density sensor of the reference pattern and the toner density sensor.

  On the other hand, the toner remaining on the photoconductor after the transfer process is once recovered from the photoconductor and then returned to the developing device according to a recycling path. In this example, as shown in FIG. 3, the residual toner scraped off by the cleaning blade 141 is sent to the front side of the apparatus main body along the photosensitive body axial direction using the recycled toner conveying screw 142, and is not shown from the toner replenishing device. The fresh toner supplied through the toner replenishing port is merged and returned to the developing device 12 to be used in the developing process. In the recovery of the toner end, the developing roller and the agitating screw are rotated in order to mix the replenished toner and the developer well, and accordingly, the developer on the developing roller slides unevenly. In order to prevent the occurrence of this, the drive is applied to rotate the photosensitive member.

  In the conventional apparatus, the recycling unit is driven in synchronization with the photosensitive member drive system. In other words, since the driving of the recycling unit is intermittent because it synchronizes with the image forming operation, and the driving time is short, the recycled toner scraped off by the cleaning blade accumulates while gradually satisfying the recycling path, The recycle toner conveying screw is conveyed after being applied to the tooth surface, and returned to the developing device. At this time, the amount of recycled toner returned into the developing device varies depending on the image forming operation time.

  In addition, there is a conventional device that extends the operation time so that the recycled toner collected in the recycling path is returned to the developing device each time when the image forming operation is completed, but the device operates even though the original printing operation is completed. If you want to perform a new printing operation next time, the so-called `` Please wait '' state will continue, leading to a decrease in productivity, and the operator will not be able to stop easily, so the operator will be anxious and distrustful It also becomes.

  In the present invention, after the printing operation is completed, the recycled toner transport screw is driven earlier so that the recycled toner can be returned to the developing device in a short time, and the image quality can be reduced and the toner can be reduced without lowering the productivity or anxiety / confidence of the operator. Prevents problems such as scattering, toner drop, and toner overflow.

  For example, when the length of the effective screw portion used for transporting recycled toner is 300 mm that can cover 297 mm of the short side of A3 paper, and the recycled toner transport screw with a screw pitch of 10 mm is rotated at 60 rpm, the transport screw It takes 30 seconds to feed the toner from one end to the other end, and from the upper right to the lower left in the perspective view of FIG. However, the speed of the conveying screw after printing is increased from 60 rpm to 120 rpm, which can be reduced to 15 seconds. Nevertheless, the recycling drive should be continued for 15 seconds or more in order to realize reliable recycled toner conveyance.

The driving of recycling the toner conveying screw, in separately provided Rukoto also the developing roller drive not only the photosensitive body driving system, is fast acting while extending only recycled toner conveying screw drive, by feeding the recycled toner into the developing device Prevents problems such as degradation of image quality, toner scattering, toner drop, and toner overflow without causing deterioration of the development system such as toner fixing to the developing sleeve or doctor blade, and photoconductor deterioration such as film abrasion or filming of the photoconductor. it can.

DESCRIPTION OF SYMBOLS 1, 2 Conveying screw 4 Developing roller 5 Toner density sensor 10 Photoconductor 12 Developing device 141 Cleaning blade 142 Recycle toner conveying screw

JP 2006-150016 A JP 2006-10880 A JP 2007-127983 A JP 2006-178421 A JP 2001-92323 A JP 2003-330340 A JP 2003-202790 A JP 2007-52051 A

Claims (1)

In an image forming apparatus having a toner recycling system that cleans and collects transfer residual toner remaining on an image carrier after image forming processing and conveys the toner to a developing device again.
The toner recycling system includes:
A cleaning device comprising: a cleaning blade for cleaning and recovering transfer residual toner remaining on the image carrier; and a recycled toner conveying screw provided along a longitudinal direction of the cleaning blade;
A first conveying screw that is disposed below the cleaning device in the vertical direction and conveys toner from one end side to the other end side in the image carrier axial direction on the image carrier side, and is provided in parallel with the first conveyance screw. A second conveying screw that conveys toner from the other end side to the one end side, and a developing device,
A dropping conveyance path for dropping toner by its own weight from the other end side of the cleaning device to a toner supply port on the other end side of the developing device;
Have
The developing device includes a toner concentration sensor that detects a toner concentration at a lower portion of the second conveying screw;
The recycled toner conveying screw, said image bearing member driving system, and the drive system of the developing device which is driven by an independent drive system,
At the end of the printing operation, the toner conveying speed by the recycled toner conveying screw is set to be higher than that during the printing operation, and after the operation of the image carrier and the developing device is stopped at the end of the printing operation, Continuing the transport operation of the toner recycling system that collects the transfer residual toner by the cleaning device and transports it again to the developing device at a higher speed than during the printing operation ;
Further, the time from the timing when the image carrier portion located at the rear end of the latent image passes through the cleaning device at the end of the printing operation to the stop of the high-speed transport operation of the toner recycling system is defined as one end of the cleaning device. More than the time required for the transfer residual toner to be conveyed from the side end to the toner supply port of the developing device,
An image forming apparatus comprising: determining whether or not replenishment of fresh toner to the developing device is necessary by the toner density sensor after the high-speed conveyance operation of the toner recycling system is stopped .

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