JPH11143325A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image of high quality without surface fogging, etc., even after a stop is made during the operation of a printing period by temporarily recovering toner remaining after a transfer and then, discharging this toner onto an image forming body in a nonimage region and recovering the toner with a developing means. SOLUTION: One cleaning cycle consists of the recovery and discharge of the toner on a photoreceptor drum which are executed by the application of a toner recovering bias V1 to a cleaning roller during one or more rotations of the photoreceptor drum, and the application of a toner discharge bias V2 to the cleaning roller during one or more rotations of the photoreceptor drum respectively. One or several cycles are executed. When one or several cycles are completed, the rotations of the photoreceptor drum are stopped and it becomes a standby state for forming the next image. Thus, a large amount of toner which is formed on the photoreceptor drum and in a sticking state, without being transferred, is removed and an excellent printed image can be obtained at the time of executing reworking.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, etc., which forms an image by arranging a charging means, an image exposing means, a developing means and the like around an image forming body. The present invention relates to an image forming apparatus of the type.

[0002]

2. Description of the Related Art Conventionally, as one type of an electrophotographic image forming apparatus, a charging means, an image exposing means and a developing means are arranged around an image forming body, and the charging of the image forming body by the charging means and image exposure are performed. Image forming apparatus for forming a latent image on an image forming body by means of an image exposing means, forming an image of the latent image by contact reversal development by a developing means, and then transferring the image to a transfer material by a transferring means Is used.

On the other hand, in order to make effective use of the toner, after the image is formed, the transfer residual toner remaining on the image forming body is cleaned by a cleaning means, and the cleaning toner is conveyed to a developing means using a screw pipe or the like. A toner recycling method for reuse in the process is generally used. However, since the toner recycling method of transporting the cleaning toner using the screw pipe has a complicated mechanism, a roller-shaped member is used as the cleaning means, and a bias is applied to transfer the residual toner of the image portion on the image carrier. Is temporarily recovered (moved) from the image forming body to the roller-shaped cleaning means, and a bias having a further opposite polarity is applied to the non-image portion to discharge (adhere) the toner on the cleaning means to the image forming body again and to the developing means. Carry,
Japanese Patent Application Laid-Open No. 8-166750 discloses a method in which toner on an image forming body is collected into a developing unit by a developing unit and reused.
It is proposed in JP-A-8-152832, JP-A-8-6454, JP-A-6-51672 and the like.

On the other hand, a transfer means for transferring a toner image on an image forming body by applying a bias to a roller-shaped member is used.

[0005]

The cleaning means using such a roller-shaped member is excellent in toner recycling, but has disadvantages. When a large amount of untransferred toner adheres to the image forming body, a conventional cleaning means using a cleaning blade that slides can clean it all at once. It is difficult to clean them all at once by using a cleaning means using. When the amount of the collected toner increases, it takes time to discharge the once collected toner and recycle the toner. If the printer is stopped forcibly due to a paper jam during the printing operation, or if the power is turned off during the printing operation, a large amount of untransferred toner is attached to the image forming body, and the printer is restarted. In such a case, there is a problem that sufficient cleaning is not performed by a cleaning unit using a roller-shaped member, and a high-quality image cannot be obtained for a while thereafter.

[0006] It is a first object of the present invention to provide an image forming apparatus which uses a roller-shaped member as a cleaning means for recycling, whereby a high-quality image can be continuously obtained even after the forced stop.

Further, if the toner adhered to the image forming body continues to adhere to the image forming body for a while, the adhesion of the toner to the image forming body increases, and there is a problem that cleaning becomes difficult.
A second object of the present invention is to sufficiently clean residual toner already adhered on an image forming body during image formation, or to sufficiently remove residual toner from an image formed body after image formation. A second object of the present invention is to provide an image forming apparatus which can always obtain a good quality image and which uses a roller-shaped member as a cleaning means for recycling.

[0008]

SUMMARY OF THE INVENTION A first object of the present invention is to:
Toner recycling means for once recovering the transfer residual toner formed by the developing means on the rotating image forming body and remaining without being transferred, and then discharging the untransferred toner onto the image forming body in the non-image area and collecting it by the developing means Wherein, when the image forming apparatus is forcibly stopped and restarted, the toner recycling unit controls to perform a collecting operation and a discharging operation while the image forming body is rotated. Image forming apparatus.

A second object of the present invention is to collect a transfer residual toner formed on a rotating image forming body by a developing means and remaining without being transferred, and then collect it on the image forming body in a non-image area. In an image forming apparatus having a toner recycling unit that discharges and collects the toner to the developing unit, the toner recycling unit rotates the image forming body before, after, or before or after a printing operation. The operation is achieved by an image forming apparatus characterized by performing control.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of the present invention, the present invention is applied. An image forming apparatus having a toner recycling unit that discharges the toner onto the image forming body in the area and collects the toner in the developing unit will be described.

FIG. 1 is a sectional view of a laser printer showing an embodiment of an image forming apparatus for performing such toner recycling. FIG. 2 is a main part view of FIG.
7 is an operation timing chart of bias application to the transfer unit and the cleaning unit.

In FIG. 1 or FIG. 2, a photosensitive drum 10 as an image forming body has a peripheral speed (linear speed) of 150 m, for example.
At a speed of m / sec, it is driven and rotated in the direction indicated by the arrow in FIG. After being charged to -700 V, image exposure based on an image signal is performed by an exposure optical system 12 as an image exposure unit. As a result, the minimum potential of the photoreceptor subjected to image exposure becomes about -50V.

The exposure optical system 12 rotationally scans a laser beam emitted from a laser light source (not shown) by a rotary polygon mirror 12b to form a latent image on the photosensitive drum 10 via an fθ lens 12c, a reflection mirror 12d, and the like. You.

A developing device 13 is provided as developing means for developing with a one-component developer or a two-component developer composed of toner or toner and carrier, and develops a latent image formed on the photosensitive drum 10. Is performed by the developing sleeve 13a that carries the developer. The development is performed between the developing sleeve 13a and the photosensitive drum 10 between the developing sleeve 13a and the photosensitive drum 10 by the developing unit bias E3 applied between the developing sleeve 13a and the toner having the same polarity (minus polarity in the present embodiment) as −400 to −−. This is performed by reversal development using a contact method to which a development bias V5 of 600 V is applied. As the toner used for the developer, a spherical toner having high recovery efficiency of the transfer residual toner described later is preferably used.

Recording paper P, which is a transfer material, is sent out by a feed roller 15a from a paper feed cassette 15 which is a transfer material storage means, fed by a feed roller 15b, and conveyed to a timing roller 15c.

The recording paper P is provided in contact with the photosensitive drum 10 in synchronization with the toner image formed on the photosensitive drum 10 by driving the timing roller 15c, and is provided at the contact portion. Photoreceptor drum 1 of transfer roller 14a as transfer means rotating in the same direction as
The toner is fed to a nip portion (transfer area) 14b formed between the toner and the toner, and has a reverse polarity (plus polarity in this embodiment) of 300 to 1500 V with respect to the toner indicated by the solid line in FIG. The negative polarity toner image on the peripheral surface of the photosensitive drum 10 is collectively transferred onto the recording paper P by the transfer roller 14a to which the transfer bias V3 is applied.

When the transfer bias V3 is applied to the transfer roller 14a by the transfer roller bias E2, the toner image on the photosensitive drum 10 is completely transferred to the image forming area as shown in the timing chart of FIG. Is set larger than the image forming area.

When a corona transfer device directly facing the image forming member is used as the transfer means, the toner polarity is inverted by corona discharge with respect to the toner in the absence of the transfer material or the toner outside the transfer material even if the transfer material is present. (The positive polarity in the present embodiment), and the transfer residue on the image forming body by the cleaning unit to which the toner collecting bias V1 having the opposite polarity (positive polarity in the present embodiment) to the toner described later is applied. It makes it difficult to collect toner. In the above-described transfer roller or transfer belt, the transfer roller or the transfer belt is preferable because the toner outside the transfer material is transferred to the transfer unit side with the negative polarity without reversing the polarity, and the load on the cleaning unit is reduced. Used.

The recording paper P after the transfer is separated from the photosensitive drum 10 by a curvature, and is conveyed by a conveying belt 16 to a heating fixing roller 17 having a heater inside at least one of the rollers.
a and a pressure roller 17b, the toner is conveyed to the fixing device 17 and heat and pressure are applied between the heating fixing roller 17a and the pressure roller 17b to fix the toner adhered on the recording paper P. The sheet is discharged to the outside of the apparatus by a discharge roller 18.

The toner remaining in the untransferred toner area on the peripheral surface of the photoreceptor drum 10 after the transfer of the image forming area where the toner image is to be formed is, for example, an optical static eliminator 19 as a static eliminator using an LED. Accordingly, the latent image at the edge portion of the image having particularly strong toner adhesion is smoothed by uniform light elimination, and the potential level of the photosensitive drum 10 is reduced to substantially zero over the entire surface. FIG. 2 shows the cleaning bias E1 for the cleaning roller.
A toner collection bias V1 of 300 to 1500 V having a polarity opposite to that of the toner indicated by the solid line (positive polarity in the present embodiment) is applied, and comes into contact with the photosensitive drum 10 in the same direction as the photosensitive drum 10 at the contact portion. The toner is collected on the outer peripheral surface of the cleaning roller 110 by the cleaning roller 110 as a rotating cleaning unit. As described above, in order to completely recover the transfer residual toner in the transfer residual toner region, the toner recovery bias application region is formed slightly longer on both sides than the image forming region as shown in FIG.

The potential level of the photosensitive drum 10 is made substantially zero by the light neutralization of the light neutralizer 19, the electrostatic attraction of the transfer residual toner to the photosensitive drum 10 is weakened, and the transfer residual toner is easily moved. In addition, the transfer to the cleaning roller 110 to which the toner collection bias V1 of the opposite polarity (positive polarity) to the transfer residual toner is applied is facilitated, and the collection efficiency is improved.

Also, a speed difference is provided between the rotation speed of the cleaning roller 110 and the rotation speed of the photosensitive drum 10 so that the cleaning roller 110 is deviated from the photosensitive drum 10 and is forcibly driven to rotate to remove residual toner on the photosensitive drum 10. The adhesive force is mechanically weakened to facilitate the movement of the toner. The speed difference of the cleaning roller 110 with respect to the photosensitive drum 10 is preferably 1 to 10%, and if it is less than 1%, the effect of weakening the adhesive force is not sufficient, and if it exceeds 10%, the speed difference is too large and toner is scattered. Also, toner filming on the image forming body easily occurs, which is not preferable. When the rotation speed of the cleaning roller 110 is higher than the rotation speed of the photosensitive drum 10 by 1 to 10%, the cleaning roller 110 bites into the photosensitive drum 10 to remove toner, and the toner on the photosensitive drum 10 is removed. Preferred without spilling.

The collected toner adhered to the cleaning roller 110 is made uniform by a toner leveling plate 111 having elasticity as a toner leveling member attached to a cleaning casing 112 of the cleaning device 100. The toner leveling member is selected to have a triboelectric charging characteristic that does not change the toner polarity. Since the toner layer is made uniform by the toner leveling plate 111, the toner is efficiently collected by the cleaning roller 110. When the toner locally adheres to the cleaning roller 110, a bias is not sufficiently applied due to the charge of the toner, and the frictional force with the image forming body also decreases. For this reason, it is desirable to make the toner layer uniform. Further, it also facilitates the discharge of toner from the cleaning roller 110 described below to the photosensitive drum 10. As the toner leveling plate 111, a resin film, Mylar, or the like is used.

Next, for the non-image forming area between the image forming areas after passing through the transfer residual toner area, the charged non-image forming area on the photosensitive drum 10 is used by using the light neutralizer 19 as an exposure device. To form an electric pattern of, for example, a mesh-like latent image having an electrostatic edge portion for facilitating toner adhesion. In the non-image forming area where the latent image of the mesh-like electric pattern is formed, the cleaning bias E1 for the cleaning roller is set to the same polarity as the toner indicated by the dotted line in FIG.
Is switched to the toner discharge bias V2 to which −300 to −1500 V is applied to discharge (attach) the collected toner on the cleaning roller 110 onto the photosensitive drum 10. Since the toner on the cleaning roller 110 is more strongly attracted to the edge portion by the stronger electric field at the edge portion of the latent image of the mesh-like electric pattern than the portion removed by the exposure,
Good discharge (adhesion) from the cleaning roller 110 to the photosensitive drum 10 is performed. At this time, as shown in FIG. 3, the toner discharge bias application area is between the toner recovery bias application areas and is set slightly shorter than the image formation area (non-image formation area).
Is set shorter than the toner discharge bias application region so that all the collected toner on the cleaning roller 110 is discharged (adhered) onto the photosensitive drum 10.

Similarly to the toner discharge by the cleaning roller 110, the toner adhering to the transfer roller 14a is also discharged to the photosensitive drum 10. That is, for example, L is applied to the charged non-image forming area on the photosensitive drum 10.
Exposure is performed by the pre-transfer exposure device 14c using the ED to form an electric pattern of a mesh-like latent image as described above, and a non-image forming area in which a latent image of the mesh-like electric pattern is formed. At this time, the transfer roller bias E2 is switched to the transfer toner discharge bias V4 to which -300 to -1500 V of the same polarity (minus polarity in this embodiment) as the toner indicated by the dotted line in FIG. Then, the toner on the transfer roller 14a is discharged (adhered).

The negative polarity toner on the transfer roller 14a to which the transfer toner discharge bias V4 is applied is repelled by the negative polarity transfer toner discharge bias V4 and moves onto the photosensitive drum 10, thereby causing the transfer roller 14a to move. Will be cleaned. At this time, as shown in FIG. 3, the transfer toner discharge bias application area is between the toner recovery bias application areas and is set to be slightly shorter than the image formation area (non-image formation area). (Length for one round) is set shorter than the toner discharge bias application area so that all the toner adhering to the transfer roller 14a is discharged (adhered) to the photosensitive drum 10.

The photosensitive drum 1 whose potential level has been made substantially zero by discharging toner by the cleaning roller 110.
0, a toner layer is formed. The attached toner is attached to the photosensitive drum 10 with a negative polarity by the toner discharge bias V2, and the potential level of the toner layer is substantially -50.
About V.

Subsequently, the surface potential of the photosensitive drum 10 is applied to the photosensitive drum 10 to which the discharged toner is adhered by a scorotron charger 11 as a charging means by using a DC voltage having the same polarity as that of the toner (minus polarity in this embodiment). But-
When recharging is performed at 750 V, the potential level on the surface of the photosensitive drum 10 is charged to, for example, about -650 V, and the potential level of the attached toner layer slightly increases to about -100 V due to the recharging.

In this state, the discharged toner which has been recharged and adhered to the photosensitive drum 10 reaches the developing unit 13, and the developing unit bias E3 applied to the developing unit 13 described with reference to FIG.
Is switched from a developing bias V5 of -400 to -600 V to a developing recovery bias V6 shown by a dotted line in FIG. 2, and a developing bias V5 of, for example, -500V lower than the photoconductor potential.
Is rubbed by the developer on the developing sleeve 13a of the developing device 13 to which a developing recovery bias V6 of, for example, -200 V, which is lower than the developing bias V5 and has the same polarity as the toner (in the present embodiment, minus polarity), is applied. The toner is cleaned (collected) from the drum 10 to the developing device 13. Further, the value of the development recovery bias V6 is determined by subtracting the value of the development bias V5 used for reversal development during image formation from −400 to 600V.
200-400V (both have negative polarity)
By setting a lower value of -200 to -300 V, the toner can be favorably attracted to the developing sleeve 13a. Further, the value of the development recovery bias V6 is set to a value of -200 to -300 V which is lower than the potential level of the surface of the photosensitive drum 10 due to recharging by about -650 V by 300 to 500 V (both have negative polarity). Thus, the toner can be favorably attracted to the developing sleeve 13a.

The photosensitive drum 10 from which the residual toner has been removed by the cleaning device 100, the scorotron charger 11 and the developing device 13 is uniformly charged again by the scorotron charger 11, and enters the next image forming cycle.

FIG. 4 is a side sectional view of the cleaning roller 110 as the cleaning means shown in FIG. 100a is a metal shaft, 100b is a conductive sponge, 110c is a sponge rubber, 110d is a conductive layer, and 100e is a resistance layer covering the outer peripheral surface of the conductive layer 100d. The cleaning roller 110 is configured.

As mechanical properties, the cleaning roller 1
In the relationship between the contact pressure with the image forming body of No. 10 and the collection efficiency,
In general, as the contact pressure increases, the collection efficiency increases and the collection variation also decreases. However, when the contact pressure becomes excessive, partial cleaning failure occurs in the image forming area or at the end. This phenomenon is due to the fact that the toner layer is pressed against the surface of the photoreceptor drum 10 and the untransferred toner aggregates, thereby increasing the mechanical adhesion. In particular, this is likely to occur when the pressure of the cleaning roller 110 is too high, when the toner layer is thick, or when the toner fluidity is poor. For this reason, the cleaning roller 110 serving as a cleaning unit is used.
Therefore, a characteristic having soft elasticity that does not cause aggregation of the transfer residual toner is required, and the total pressure of the cleaning roller 110 as a cleaning unit to the photosensitive drum 10 is maintained at 0.5 to 2 kg. Further, the roller resistance of the cleaning roller 110 as an electrical property is also
If the roller resistance is too low, abnormal discharge occurs at the contact portion between the photoconductor drum 10 and the cleaning roller 110, and the photoconductor drum 10 may be destroyed due to current concentration. If the roller resistance is low, the collection efficiency is significantly reduced in a high-temperature, high-humidity environment. This is because a low resistance roller tends to inject a reverse charge from the roller into the toner, and reduces the toner charge amount to weaken the electrostatic force. Conversely, in a high-resistance roller, the electric field applied to the toner is reduced, and the collection efficiency is reduced. The optimum volume resistance value range of the cleaning roller 110 is 10 ⁸ to 10 ¹² Ω · cm.

The resistance value of the cleaning roller 110 or the recording paper P as a transfer material changes by about two digits depending on the atmosphere, and the collection characteristic changes accordingly. For this reason, stable recovery cannot be performed by constant voltage control with respect to environmental fluctuations. On the other hand, in the constant current control, stable recovery is performed with high resistance to environmental fluctuations. Therefore, it is also possible to adopt a method of performing a constant voltage control by selecting an applied voltage stored in a ROM table, for example, as an arithmetic process from an appropriate current value of the cleaning roller 110 that enables good recovery.

The cleaning device 100 for recycling includes the cleaning roller 11 as described above.
In addition, toner particles are attached by attaching granular magnetic particles to the outer periphery of the rotating magnet roller, bringing the magnetic particles in the attached state into sliding contact with the photosensitive drum 10, and similarly switching the voltage applied to the magnet roller. It is also possible to use a cleaning device using a magnetic brush for collecting and discharging the toner.

(Embodiment 1) In the image forming apparatus of the present embodiment (the invention of claim 1), when the operation is stopped in the middle of the printing operation due to a jam or a power failure, the photosensitive drum 10 is restarted. The toner is recovered and discharged by the cleaning device 100 to remove a large amount of toner that has not been transferred and adhered to the photoreceptor, and a print waiting state is set. FIG. FIG. 6 is a timing chart of a toner collecting operation and a toner discharging operation in the present embodiment.

In the image forming apparatus of the present embodiment, a plurality of sensors are provided in the transfer path of the transfer sheet, and the print operation is started immediately when these sensors detect the occurrence of transfer sheet transfer failure (jam). Stop. When the jammed paper is removed, the printable state is restored. In this embodiment, when the jam detection signal returns to the printable state, the control unit calls the cleaning recycle mode program from the ROM by the signal to return to the printable state. The upper part performs cleaning and recycling of the toner in the attached state. Further, even when the printing operation is stopped due to a power failure or the like, when the power supply circuit is turned on and the restart signal is received, the control unit calls the cleaning recycle mode program from the ROM and is in a state of adhering on the photosensitive drum 10. Clean and recycle toner.

FIG. 6 is a timing chart of the cleaning / recycling process called and executed from the ROM. The timing of the toner collection bias V1 for the cleaning roller 110 during one or more rotations of the photosensitive drum 10 is shown. The cleaning is performed by applying the toner discharge bias V2 to the cleaning roller 110 during the one or more rotations of the photosensitive drum 10 and then collecting and discharging the toner on the photosensitive drum 10 during the subsequent rotation of the photosensitive drum 10. -One cycle or multiple cycles are performed as one cycle of recycling.
When the cleaning / recycling process is completed, the rotation of the photosensitive drum 10 is stopped, and the photosensitive drum 10 is in a standby state for the next image formation.

During the above-mentioned cleaning / recycling process, the scorotron charger 11 performs the same corona discharge as during image formation, and the developing device 13 applies the developing recovery bias V6 for recovering the toner. Further, a transfer toner discharge bias V4 is applied to the transfer roller 14a, and if toner adhered to the transfer roller 14a is present, the transfer roller 14a is also cleaned during this cleaning / recycling process. . Further, in the photo-eliminator 19, an exposure of an electric pattern of a mesh-like latent image is performed on the surface of the photoconductor on which the toner discharging process of the cleaning roller 110 is performed, so that the toner is easily discharged from the cleaning roller 110. Is exposed to the entire surface for static elimination.

By performing the cleaning / recycling process described above, a large amount of untransferred and adhered toner formed on the photosensitive drum 10 is also removed.
At the time of restart, a good print image is obtained.

(Embodiment 2) The image forming apparatus of this embodiment (the invention of claim 2) forms an image with the photosensitive drum 10 rotated before, after, or before or after a printing operation. The operation of collecting and discharging the toner by the cleaning device 100 is performed without performing the operation. FIG. 7 schematically illustrates a print operation according to the print program of the present invention. FIG. 7A shows a state when the print button is turned on. A print operation is performed with a predetermined recording paper size and the number of prints, but without forming an image prior to the print operation. Performs toner collection and discharge operations.
The recycling operation is set as a program to perform one cycle or a plurality of cycles. FIG. 7B shows a state in which after the printing operation for the set number of prints is completed, the toner collecting operation and the discharging operation are performed without performing image formation, and at the time when the collecting operation and the discharging operation are completed. The rotation of the photosensitive drum 10 is stopped to prepare for the next printing operation. Also in this case, the cleaning / recycling operation is set as a program so as to perform one cycle or a plurality of cycles, and the printing operation is performed according to the program.

FIG. 8 is a timing chart of the cleaning / recycling operation performed prior to the printing operation shown in FIG. When the print button is turned on, the photosensitive drum 10 starts rotating, and the same corona discharge as that at the time of image formation is performed by the scorotron charger 11, and the charging by the scorotron charger 11 continues to the printing operation. Done. cleaning·
Exposure by the exposure optical system 12 is not performed during recycling. Since the developing device 13 does not perform the developing operation using the latent image as the toner image during this time, the developing device 13 is applied with the developing recovery bias V6 for recovering the toner from the beginning. The transfer roller 14a comes into contact with the photosensitive surface without the recording paper interposed therebetween, and a transfer toner discharge bias V4 is applied.
If there is toner attached to the transfer roller 14a, the transfer roller 14a is also cleaned during this cleaning / recycling process.

Further, the optical charge eliminator 19 performs overall exposure so that toner can be easily collected by the cleaning roller 110 in a range covering the image forming area, and removes toner from the cleaning roller 110 in a non-image forming area. Exposure of the electrical pattern of the mesh-like latent image is performed to facilitate ejection. In the cleaning roller 110, a toner collection bias V1 for collecting toner is applied to a range covering the image forming area, and a toner discharge bias V2 for discharging toner is applied to a non-image area. The toner discharged to and adhered to the non-image forming area on the photoconductor drum 10 is collected and recycled by the developing device 13 in a state where the above-mentioned developing and collecting bias V6 is applied.

In a general image forming apparatus, the relationship between the image forming area and the non-image forming area changes with a change in the size of the recording paper on which printing is performed. By performing the cleaning, a good print image can be obtained in a subsequent printing operation.

The same operation as that shown in FIG. 8 is performed in the cleaning / recycling operation following the printing operation. However, by adding such a process, the toner adheres to the photosensitive member surface for a long time. The continuation is prevented, and a good print image is always obtained.

[0045]

According to the first aspect of the present invention, even if the printing operation is stopped in the middle of a printing operation due to a jam or a power failure, a high-quality image free of ground fog or the like can be obtained. The transfer residual toner formed by the developing unit on the rotating image forming body and remaining without being transferred is once collected, then discharged onto the image forming body in a non-image area, and collected by the developing unit. An image forming apparatus having a toner recycling unit has been provided.

According to the second aspect of the present invention, printing is performed with the toner on the image forming body being cleaned, so that a high-quality printed image free from background fog or the like can be obtained.
Toner recycling means for once recovering the transfer residual toner formed by the developing means on the rotating image forming body and remaining without being transferred, and then discharging the untransferred toner onto the image forming body in the non-image area and collecting it by the developing means Is provided.

[Brief description of the drawings]

FIG. 1 is a sectional configuration diagram of a laser printer showing an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a main part diagram of FIG. 1 to which a charging unit is added.

FIG. 3 is an operation timing chart of bias application performed during printing.

FIG. 4 is a side sectional view showing an example of a cleaning unit.

FIG. 5 is a control block diagram according to the first embodiment.

FIG. 6 is an operation timing chart of bias application in cleaning / recycling of the first embodiment.

FIG. 7 is an explanatory diagram illustrating a relationship between a cleaning / recycling operation and a printing operation according to the second embodiment.

FIG. 8 is an operation timing chart of bias application in cleaning / recycling of the second embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 photoconductor drum 11 scorotron charger 12 exposure optical system 13 developing device 14 c pre-transfer exposure device 19 light eliminator (exposure device) 100 cleaning device 110 cleaning roller E1 cleaning roller cleaning bias E2 transfer roller bias E3 developer bias V1 toner Recovery bias V2 Toner discharge bias V3 Transfer bias V4 Transfer toner discharge bias V5 Development bias V6 Development recovery bias

Claims (2)

[Claims] An untransferred toner formed on a rotating image forming body by a developing unit and remaining without being transferred is once collected, discharged to a non-image area on the image forming body, and transferred to the developing unit. In an image forming apparatus having a toner recycling unit to be collected, when the image forming apparatus that has been forcibly stopped is restarted, the toner recycling unit is controlled to perform a collecting operation and a discharging operation with the image forming body rotated. An image forming apparatus. 2. A transfer residual toner formed by a developing unit on a rotating image forming body and remaining without being transferred is once recovered, discharged onto the image forming body in a non-image area, and transferred to the developing unit. In an image forming apparatus having a toner recycling unit to be collected, the toner recycling unit controls so as to perform a collecting operation and a discharging operation before or after or before or after a printing operation while the image forming body is rotated. An image forming apparatus comprising: