JP2010020118A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which allows only deteriorated toner to be surely discharged from a developing device without causing lowering of throughput. <P>SOLUTION: When printing processing is started, toner residual amount in a developing part is always monitored by a toner presence/absence sensor (S1) and (S2). When the absence of toner is detected, a CPU interrupts printing operation (S3), sets a predetermined time in a time counter (S4), and sets discharge mode bias so that a direction of potential between a supply roller 44 and a developing roller 13 may be reverse to that when ordinary printing (S5). Then, the CPU performs idling of an image forming part (solid development with the deteriorated toner only by bias voltage having no image data, and removal of the deteriorated toner in the solid development on a photoreceptor drum 7 by a cleaner 8) (S6), displays an instruction to exchange toner on a display device (S8) when the time counter counts up (Y in S7), and stops a motor to stop the operation of the device (S9), whereby processing is finished. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus having a developing unit in which a toner cartridge containing non-magnetic one-component toner is replaceable with a developing tank.

  2. Description of the Related Art Conventionally, there is an image recording apparatus that prints a monochrome or color image (hereinafter also referred to as printing) by using an electrophotographic method using toner. In printing using toner, a toner image is developed on a photosensitive member by toner in a developing unit in an image forming unit, the developed toner image is transferred to a sheet, and the transferred toner image is heated and pressured in a fixing device. To form a toner image.

  When the toner stored in the developing device is consumed by printing and the remaining amount of toner in the developing device falls below a certain level, the remaining amount detecting device is activated to notify the user that there is no toner and the operation of the device is stopped. The user removes the toner cartridge that has run out of toner from the developing device, replaces it with a new toner cartridge, and continues the printing operation.

  By repeating such an operation, a printed image can be obtained repeatedly. By the way, the external additive added to the toner by repeating the printing process is embedded in the toner or detached from the toner, so that the toner deteriorates.

  Further, toner to be crushed is also generated due to shear (peeling off) by the doctor blade and contact pressure between the photosensitive drum and the developing roller, which becomes deteriorated toner. Such toner deterioration is repeated over time, and when the toner in the toner cartridge runs out, deteriorated toner and a weakly reverse external additive accumulate around the supply roller.

  In particular, in an image forming apparatus of a type in which the toner cartridge is replaced and used, the deteriorated toner increases in the developing unit composed of the supply roller and the developing roller each time the toner cartridge is replaced.

  Since the deteriorated toner is not normally charged, its polarity does not have a normal polarity and is charged to the opposite polarity or has almost no charged charge. These deteriorated and reverse polarity toners and external additives with weak reverse polarity separated from the toner are easily pressed against the supply roller side by the action of the electric field between the developing roller and the supply roller. .

  Therefore, it becomes difficult for normal toner to be supplied from the supply roller to the developing roller, and therefore, the printed image is disturbed and a high-quality image cannot be obtained.

  In view of this, various image forming apparatuses have been proposed in which such deteriorated toner in the developing device is discharged to the outside (transferred from the developing device onto the photosensitive member) and toner having good chargeability is used.

  For example, as a method of discharging reverse toner that has deteriorated to have a reverse polarity, the developer bias voltage of the developer carrying member is set positively with respect to the potential of the photosensitive member so that the potential difference from the photosensitive member can be increased. A method for discharging the reversal toner has been proposed.

  In this method, the time for the reverse toner discharge mode is increased as the amount of toner consumption since the previous toner discharge is increased, as the cumulative number of rotations of the developer carrier increases, or as the number of images formed increases. (For example, refer to Patent Document 1).

  In the case of an image forming apparatus using a two-component developer, a predetermined bias voltage is applied to the developing roller and the photosensitive drum, and the deteriorated toner in the developing device is transferred to the surface of the photosensitive drum. Has been proposed.

In this method, it is specified that the refresh process is executed before toner replenishment with an average printing rate determined in advance, or the refresh process is executed by performing the aging operation of the developer after toner replenishment. ing. Here, the aging operation refers to stirring the toner in the developing device and the replenished unused toner for a predetermined time (see, for example, Patent Document 2).
JP 2006-119309 A JP 2007-034051 A

  By the way, in each of the conventional methods for discharging the deteriorated toner, the relationship between the voltage applied to the developing roller and the potential of the photosensitive member is specified, but there is no explanation about the state inside the developing tank. It raised the question that the effect was not clear.

  In Patent Document 1 or 2, the toner discharge process is set at the end of image formation or every predetermined number of sheets. Therefore, when a print signal is received during the toner discharge process, the toner discharge is performed. When the process is interrupted and the printing process is started, the printing must be resumed while the discharge of the deteriorated toner is insufficient, so that the image quality is deteriorated.

  On the other hand, when the printing process is started after the toner discharging process is finished, there is a problem that the throughput is substantially reduced.

  In addition, in the case of an image forming apparatus using a one-component developer, the aging operation of the developer after toner replenishment and the refreshing process are performed may be performed in the case of an image forming apparatus using a two-component developer. In this case, the regular toner is discharged together with the deteriorated toner having a weak polarity, so that the effect that only the deteriorated toner is ejected to the developing roller side cannot be expected.

  In view of the above-described conventional situation, an object of the present invention is to provide an image forming apparatus that reliably removes only deteriorated toner from a developing device without causing a decrease in throughput.

  The image forming apparatus according to the present invention includes a developing roller that carries at least a non-magnetic one-component toner and develops a toner image on the latent image on the electrostatic latent image carrier, and supplies the toner to the developing roller and develops the toner. An image forming apparatus having a developing device including a supply roller for forming a toner layer on a roller and a developing tank having a doctor blade for charging the toner on the developing roller and forming a thin layer. A toner cartridge configured separately from the developing tank and detachable from the developing tank and containing the toner to be supplied to the developing tank; and the toner contained in the toner cartridge is consumed and remains. Cartridge toner detecting means for detecting that there is no amount, and the toner remaining in the toner cartridge is detected by the cartridge toner detecting means. A developer tank toner detecting means for detecting that the remaining amount of the toner in the developing tank is equal to or less than a predetermined value; and A reverse polarity bias voltage applying means for applying a bias voltage having a reverse polarity to that in the case where a normal toner layer is formed on the supply roller, and the reverse polarity by the reverse polarity bias voltage applying means. A notification means for notifying the toner cartridge to be replaced with a new toner cartridge after the deteriorated toner remaining in the developing tank is discharged by the application of the bias voltage, and a notification of toner cartridge replacement by the notification means. And a drive stopping means for stopping the driving of the developing device in synchronism with each other.

  According to the present invention, it is possible to provide an image forming apparatus that reliably excludes only deteriorated toner from a developing device without causing a decrease in throughput.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
FIG. 1 is a cross-sectional view illustrating an internal configuration of a color image forming apparatus (hereinafter simply referred to as a printer) including a developing device that uses a non-magnetic one-component toner according to Embodiment 1 of the present invention.

  A printer 1 shown in FIG. 1 is an electrophotographic secondary transfer tandem color image forming apparatus, and includes an image forming unit 2, an intermediate transfer belt unit 3, a paper feeding unit 4, and a duplex printing conveyance unit 5. It consists of

  The image forming unit 2 has a configuration in which four image forming units 6 (6M, 6C, 6Y, and 6K) are arranged in a multistage manner from right to left in FIG.

  Of the four image forming units 6, three image forming units 6M, 6C and 6Y on the upstream side (the right side in the figure) are magenta (M), cyan (C) and yellow (subtractive three primary colors, respectively). A mono-color image is formed with the color toner of Y), and the image forming unit 6K forms a monochrome image with black (K) toner mainly used for dark portions of characters and images.

  Each of the image forming units 6 has the same configuration except for the color of the toner stored in the toner container (toner cartridge). Accordingly, the configuration of the black (K) image forming unit 6K will be described below as an example.

  The image forming unit 6 includes a photosensitive drum 7 at the bottom. The peripheral surface of the photosensitive drum 7 is made of, for example, an organic photoconductive material. A cleaner 8, a charging roller 9, an optical writing head 11, and a developing roller 13 of the developing device 12 are arranged around the periphery of the photosensitive drum 7.

  The developing device 12 puts one of magenta (M), cyan (C), yellow (Y), and black (K) toners in the upper toner container as indicated by M, C, Y, and K in the drawing. An intermediate portion is provided with a toner replenishing mechanism for the lower portion.

  In addition, the developing roller 13 is provided in the lower portion of the developing device 12 at the side opening, and includes a toner stirring member, a toner supply roller for supplying toner to the developing roller 13, and a toner layer on the developing roller 13 as a fixed layer. It has a doctor blade that regulates the thickness.

  The intermediate transfer belt unit 3 has an endless transfer belt 14 extending in a flat loop shape from substantially the left and right sides of the figure at the approximate center of the main unit, and the transfer belt 14 is stretched over the transfer belt 14. A driving roller 15 and a driven roller 16 are provided to circulate and move the belt 14 counterclockwise in the drawing.

  The transfer belt 14 transfers the toner image directly onto the belt surface (primary transfer) and conveys the toner image to the transfer position to the paper for further transfer (secondary transfer). The whole is called an intermediate transfer belt unit.

  The intermediate transfer belt unit 3 includes a belt position control mechanism 17 in the loop of the flat loop-shaped transfer belt 14. The belt position control mechanism 17 includes a primary transfer roller 18 made of a conductive foam sponge that presses against the lower peripheral surface of the photosensitive drum 7 via the transfer belt 14.

  The belt position control mechanism 17 has three primary transfer rollers 18 corresponding to the three image forming units 6M, 6C, and 6Y of magenta (M), cyan (C), and yellow (Y) as vertical support shafts. Rotate to the center with the same period.

  Then, the belt position control mechanism 17 rotates and moves one primary transfer roller 18 corresponding to the black (K) image forming unit 6K at a rotational movement cycle different from the cycle of the three primary transfer rollers 18. The belt 14 is moved away from the photosensitive drum 7.

  That is, the belt position control mechanism 17 moves the position of the transfer belt 14 of the intermediate transfer belt unit 3 to full color mode (all four primary transfer rollers 18 are in contact with the transfer belt 14), monochrome mode (to the image forming unit 6K). Only the corresponding primary transfer roller 18 is in contact with the transfer belt 14) and all non-transfer modes (all four primary transfer rollers 18 are separated from the transfer belt 14).

  In the intermediate transfer belt unit 3, a belt cleaner unit is disposed further upstream of the uppermost image forming unit 6M on the upstream side in the belt movement direction, and is flat and thin so as to be substantially along the entire lower surface. The waste toner collection container 19 is detachably disposed.

  The paper feed unit 4 includes two paper feed cassettes 21 arranged in two upper and lower stages, and in the vicinity of the paper feed opening (right side in the figure) of the two paper feed cassettes 21, respectively, A feeding roller 23, a separating roller 24, and a standby conveying roller pair 25 are disposed.

  In the paper conveyance direction (vertical upward direction in the figure) of the standby conveyance roller pair 25, a secondary transfer roller 26 that is in pressure contact with the driven roller 16 via the transfer belt 14 is disposed, and the secondary transfer portion to the paper is arranged. Forming.

  A belt-type heat fixing device 27 is disposed downstream (upward in the drawing) of the secondary transfer portion, and the sheet after fixing is fixed to the belt-type heat fixing device 27 further downstream of the belt-type heat fixing device 27. A pair of carry-out rollers 28 for carrying out the paper and a pair of paper discharge rollers 31 for discharging the carried paper to a paper discharge tray 29 formed on the upper surface of the apparatus are disposed.

  The duplex printing conveyance unit 5 includes a start return path 32a that branches from the intermediate conveyance path between the carry-out roller pair 28 and the discharge roller pair 31 to the right lateral direction in the drawing, and then an intermediate return path 32b that bends downward. A terminal return path 32c that bends in the left lateral direction opposite to the above and eventually reverses the return sheet, and four return roller pairs 33a, 33b, 33c, and 33d arranged in the middle of these return paths are provided. ing.

  The exit of the end return path 32 c communicates with a conveyance path to the pair of standby conveyance rollers 25 corresponding to the sheet feeding cassette 21 below the sheet feeding unit 4. In this example, a cleaning unit 35 and a take-in roller 36 are disposed on the upper surface of the intermediate transfer belt unit 3.

  The cleaning unit 35 comes into contact with the upper surface of the transfer belt 14 and scrapes and removes the waste toner. The take-in roller 36 takes over the waste toner removed by the cleaning unit 35 and is not shown in the drawing, and is temporarily stored in the belt cleaner unit. The accumulated waste toner is conveyed to the upper part in the dropping cylinder by a conveying screw and sent to the waste toner collecting container 19 through the dropping cylinder.

  Further, in order to bring the cleaning unit 35 into pressure contact with the transfer belt 14 with an appropriate pressure, a pressure roller 37 is provided on the intermediate transfer belt unit 3 side to press the transfer belt 14 toward the cleaning unit 35 from below. ing.

  As shown in FIG. 1, the image forming apparatus 1 does not directly transfer a toner image onto a conventional sheet, but an intermediate transfer belt on a sheet that is vertically conveyed to a secondary transfer unit by a standby conveyance roller pair 25. 14 is a method of transferring a toner image through the image forming apparatus 14.

  Therefore, it is possible to cope with a maintenance process for recovering from a problem such as a paper jam occurring in the paper transport path by simply opening the right side of FIG.

  In addition, since troubles such as paper jam do not occur in the arrangement section of the kits, the operation for attaching and detaching consumables such as the kits concentrated on the left side of FIG. 1 may be a small space that can be replaced in the longitudinal direction. It is configured as follows.

  Thereby, the dimension between kits is reduced as much as possible, and size reduction of the whole apparatus main body is achieved. Further, the optical writing head itself is also miniaturized and is configured closer to the photosensitive drum.

  FIG. 2 is a cross-sectional view showing the image forming unit 6. As shown in FIG. 2, the developing device 12 shown in FIG. 1 includes a toner cartridge 41 including an upper toner hopper A38 and a lower toner hopper B39, and a developing portion 43 including an exterior frame.

  FIG. 3 is a perspective view showing a state where the toner cartridge 41 and the developing drum unit 58 of the image forming unit 6 are combined.

  FIG. 4 is a diagram showing a configuration in which the toner cartridge 41 can be inserted into and removed from the developing drum unit 58 in the image forming unit 6 in a direction perpendicular to the sheet conveyance direction of the apparatus main body.

  2 and 3, the developing unit 43 includes, in addition to the developing roller 13 described above, a supply roller 44 that supplies toner to the developing roller 13 and a layer of toner supplied onto the developing roller 13. A doctor blade 45 that regulates the toner to a certain thickness, a stirring member 46 that stirs the toner of the developing unit 43, and the like.

  Further, the photosensitive drum 7, the cleaner 8, and the charging roller 9 are integrally incorporated with the developing device 12 inside the exterior frame 42 as a drum unit portion 57. The drum unit 57 and the developing unit 43 of the developing device 12 form a developing drum unit 58.

  The photosensitive drum 7 is usually formed by uniformly depositing an organic photoconductor on the surface of a conductive metal roller, and the metal roller portion is grounded.

  In addition, the charging roller 9 has a white printing state charging potential (a uniformly applied initializing potential, a method of applying a positive polarity and a method of applying a negative polarity, and a negative polarity in this example. High voltage) is applied to the photosensitive drum 7.

  By this application, the photosensitive layer on the peripheral surface of the photosensitive drum 7 is uniformly charged to a minus high potential of, for example, “−500 V (volt)”.

  The optical writing head 11 shown in FIG. 1 includes a laser light source or an LED light source, and selectively exposes the peripheral surface of the photosensitive drum 7 charged to a minus high potential according to image information.

  By this exposure, a negative low potential portion whose potential is attenuated to about “−50 V” is formed on the surface of the photosensitive drum 7, and the low potential portion of “−50 V” and the high potential of “−500 V” charged in advance are formed. An electrostatic latent image is formed by the portion.

  The developing device 12 contains non-magnetic one-component toner. The developing roller 13 is applied with a developing bias of, for example, “−300 V” from the high voltage power supply 47. The supply roller 44 is applied with a supply bias of “−500 V” from another high-voltage power supply 48. The doctor blade 45 is further applied with a doctor bias of “−300 V” from another high-voltage power supply 49.

  An electric field between the supply roller 44 and the developing roller 13 acts from the developing roller 13 to the supply roller 44. The negatively charged toner receives a force in the direction of the developing roller 13 from the supply roller 44, moves in the direction of the developing roller 13, and adheres to the surface of the developing roller 13.

  The toner adhering to the surface of the developing roller 13 is regulated to a constant layer thickness by the doctor blade 45 and is about −5 to −25 μq / g by a minus high voltage potential applied from the high voltage power supply 48 via the doctor blade 45. It is charged to a relatively weak negative potential with a charge.

  The developing roller 13 conveys the toner layer to a portion facing the photosensitive drum 7 while rotating. At the facing portion between the developing roller 13 and the photosensitive drum 7, a potential difference of “−250 V” is formed between the low potential portion of the “−50 V” electrostatic latent image and the developing roller 13. That is, the low potential portion of the electrostatic latent image forms a positive polarity potential relative to the developing roller 13.

  Due to the electric field due to this potential difference, the non-magnetic toner charged to the negative polarity is transferred to the positive potential electrostatic latent image low potential portion of the photosensitive drum 7 to form a toner image. This toner image is conveyed to the facing portion between the photosensitive drum 7 and the primary transfer roller 18 shown in FIG. 1 by the rotation of the photosensitive drum 7.

  The primary transfer roller 18 faces the photosensitive drum 7 and presses against the photosensitive drum 7 via the transfer belt 14 to form a transfer portion. The primary transfer roller 18 is formed of, for example, a conductive sponge and connected to a positive high voltage power source (not shown). The primary transfer roller 18 applies a positive transfer bias to the transfer belt 14.

  A negative toner image on the photosensitive drum 7 that is rotated and conveyed to the transfer portion is transferred to the transfer belt 14 that has become a positive potential due to this voltage application. Similarly, the transfer belt 14 onto which four toner images of magenta (M), cyan (C), yellow (Y), and black (K) are transferred by the four image forming units 6 is transferred to the transfer belt 14. The toner image is conveyed to a secondary transfer portion where the driven roller 16 and the secondary transfer roller 26 are in pressure contact with each other.

  Then, the toner image is transferred to the paper in the secondary transfer unit. The toner image transferred onto the paper is fixed on the paper surface by heat and pressure by the belt-type heat fixing device 27 and is discharged onto the paper discharge tray 29 by the pair of carry-out rollers 28 and the paper discharge tray 29.

  Returning to FIG. 2, the cleaner 8 is provided with a cleaning blade 51 that contacts the peripheral surface of the photosensitive drum 7 and a conveying screw 52.

  The cleaning blade 51 removes the waste toner remaining on the peripheral surface of the photosensitive drum 7, and the transport screw 52 passes the removed waste toner through the transport screw 52 b disposed on the upper left exterior frame 42 a of the exterior frame 42. Then, the toner is sent to the waste toner collection bag 54 via the conveying screw 52c in the waste toner storage pipe 53 disposed in the upper toner hopper A38.

  The lower toner hopper B39 is provided with an agitator 55 for agitating the internal toner at the center, and a seal member 56 is interposed between the lower opening and the opening of the developing unit 43. Has been. The internal toner is supplied to the developing unit 43 through the opening of the lower partition wall by the rotation of the agitator 55.

  An outline of the toner supply will be briefly described. The toner cartridge 41 includes an outer case and an inner case, and a toner agitator 55 for sending toner into the developing unit 43 is disposed in the inner case in a rotatable structure. Initially, the outer case is filled with toner, and no toner enters the inner case.

  The toner cartridge 41 is mounted on the developing unit 43 as shown in FIG. 2, and a lock lever (not shown) for fixing the toner cartridge 41 is moved, whereby the claw (not shown) arranged on the toner cartridge 41 also has a claw (not shown). At the same time, the inner case rotates, the toner enters from the outer case, and the toner is replenished from the inner case to the developing unit 43 by the rotation of the agitator 55.

  Thus, the toner is sequentially consumed from the image forming unit by a supply flow of outer case → inner case → developing unit → supply roller → developing roller → photosensitive drum.

  The toner is consumed by the image formation. First, the absence of toner in the inner case (lower toner hopper B39) is detected by the rotation period of the agitator 55, and a “no hot partner” signal is notified to the control device.

  The rotating shaft of the agitator 55 is connected to a one-way gear. When the toner hopper B39 has a sufficient amount of toner, the rotation is constant, so that the presence of toner is detected. It detects the absence of toner by falling and rotating with its own weight.

  Thereafter, when the toner finally runs out in the developing unit 43, the toner presence / absence sensor composed of a pressure sensor using a piezoelectric element or the like detects that the pressure from the toner has become a predetermined value or less, "No toner" signal.

  In this example, the specification is such that the detection of the toner in the developing unit is output when the remaining toner amount in the developing unit 43 is 10 g. Then, when the detection of the absence of toner is activated to prevent the occurrence of an image defect or a hardware failure, after the discharged toner is discharged as will be described later, a toner cartridge replacement instruction is issued, the apparatus is stopped, and the forced Printing is forbidden.

  Knowing the notification of the toner cartridge replacement instruction, the user removes the tonerless cartridge from the developing drum unit 58 and replaces it with a new toner cartridge 41 as shown in FIG.

  The lifetime of the image forming unit 6 is set at a rotation time of the photosensitive drum 7 of 425,000 seconds, and there is no restriction on how many toner cartridges 41 are used during that time.

  The image forming unit 6 is provided with a fuse. When a new image forming unit 6 is mounted on the main body of the printer 1, an electric current is supplied to the fuse to cut the fuse. Thereafter, the fuse breakage is detected. Thus, it is determined whether the image forming unit 6 is new or old.

  Then, the rotation time of the photosensitive drum 7 is measured from the time when a new image forming unit 6 is detected. Accordingly, the remaining life can be displayed by simply subtracting from the set life time of 425,000 seconds.

  By the way, as described above, the detection of the toner in the developing unit in this example is considered that the developing unit has no toner when the remaining amount of toner in the developing unit 43 reaches approximately 10 g. A toner-less detection signal is output to the control unit.

  At this time, about 10 g of the toner remaining in the developing portion is mostly deteriorated toner having a reverse polarity or being crushed. Therefore, in this example, the reverse toner (deteriorated toner) is removed using the print processing interruption time period for replacing and mounting a new toner cartridge 41.

  FIG. 5 is a flowchart for explaining the process for removing the deteriorated toner. This process is performed by, for example, a CPU (central processing unit) of the control unit based on a program built in a memory of a control unit (not shown).

  As shown in FIG. 5, when the printing process of the printer 1 is started, first, the toner presence / absence sensor is driven (step S1). Thereby, during the printing process, the presence or absence of toner in the developing unit 43 is continuously detected, and the detection result is notified to the CPU.

  The CPU determines the presence / absence of toner in the developing unit 43 based on the notified detection result (step S2). If the detection result notified to the CPU is “toner present” (N in S2), the presence / absence detection of toner is continued. During this time, the printing process is continued.

  When the toner consumption progresses and eventually the remaining amount of toner in the developing unit 43 becomes less than a predetermined amount, that is, 10 g or less is detected by the toner presence sensor (S2 is Y), the CPU interrupts the printing operation. (Step S3).

  Then, a predetermined time is set in the time counter built in the CPU, and time measurement is started (step S4).

  Here, the predetermined time set in the time counter is a period of time until the deteriorated toner is completely developed on the photosensitive drum 7 and removed by the cleaner 8 until the deteriorated toner is completely discharged until approximately 10 g of the deteriorated toner disappears. This is the idling time (the photosensitive drum 7 is rotated without actually printing an image).

  Following the above, the CPU sets the ejection mode bias (step S5). In this process, the same bias voltage as that during the printing operation is applied to the charging roller 9, and the same developing bias of “−300 V” as that during the printing operation is also applied to the developing roller 13.

  A bias voltage of “−200 V” different from that during the printing operation is applied to the supply roller 44. As a result, the direction of the electric field between the developing roller 13 and the supply roller 44 is opposite to that during normal printing operation. The setting of each bias voltage becomes a setting value of the bias voltage in the discharge mode.

  Subsequently, the CPU starts an idling operation (step S6). As described above, the direction of the electric field between the developing roller 13 and the supply roller 44 is opposite to that during the normal printing operation, so that the deteriorated toner whose polarity is reversed from that during the normal printing operation. Then, the toner is efficiently supplied from the supply roller 44 to the developing roller 13.

  The deteriorated toner on the developing roller 13 is solid-developed on the idly rotating photosensitive drum 7 and removed by the cleaner 8.

  Then, the CPU determines whether or not the time counter set in step S4 has been counted up (step S7). If the time counter has not yet been counted up (S7 is N), the process returns to step S5, and step S5 is performed. Repeat the process of ~ S7.

  By repeating the processing in steps S5 to S7 in this manner, the deteriorated toner remaining in the developing unit 43 is sequentially discharged from the developing roller 13 to the photosensitive drum 7 and from the photosensitive drum 7 to the cleaner 8. To go.

  When the CPU determines that the time counter has been counted up (S7 is Y), the CPU determines that all of the deteriorated toner in the developing unit 43 has been discharged, and displays the toner cartridge 41 on the operation panel (not shown). An exchange instruction is displayed (step S8). Thereby, the user is notified of the replacement instruction of the toner cartridge 41.

  Further, the CPU stops the rotation of the motor in parallel with the above display process (step S9). As a result, the idling of the photosensitive drum 7 and the operation of the other drive parts are stopped, and the new toner cartridge 41 is replaced by the user.

  As described above, in the present exemplary embodiment, when the absence of toner in the developing unit 43 is detected, the bias voltage applied to the supply roller 44 is changed so that the deteriorated toner whose polarity is reversed is easily discharged. Then, the deteriorated toner is discharged.

  Further, since the deteriorated toner is discharged when the toner cartridge 41 is replaced, the deteriorated toner can be discharged without reducing the normal throughput.

  Further, since the discharging process is performed when the deteriorated toner density before the new toner is replenished in the developing unit 43, the deteriorated toner can be discharged efficiently and the new toner and the deteriorated toner are not mixed. Therefore, a good image without image degradation can be obtained forever.

  In the above example, the discharge mode bias voltage is changed so that only the bias voltage to the supply roller is different from that during normal printing. However, the potential of the photosensitive drum and the development bias voltage of the developing roller are changed. Also good.

  In short, it is only necessary that the direction of the electric field generated by the bias voltage is the same as that in the above-described embodiment, and it goes without saying that the voltage value to be applied as the bias voltage can be appropriately selected.

FIG. 2 is a cross-sectional view illustrating an internal configuration of a printer including a developing device that uses a non-magnetic one-component toner according to Embodiment 1. FIG. 2 is a cross-sectional view illustrating an image forming unit of the printer according to the first embodiment. FIG. 3 is a perspective view illustrating a state in which the toner cartridge and the developing drum unit of the image forming unit of the printer in Embodiment 1 are united. FIG. 2 is a diagram illustrating a configuration in which a toner cartridge can be inserted into and removed from a developing drum unit in a direction orthogonal to a paper transport direction of the apparatus main body in the image forming unit of the printer according to the first embodiment. 5 is a flowchart for explaining a process of removing deteriorated toner of the printer in the first embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 2 Image formation part 3 Intermediate transfer belt unit 4 Paper feed part 5 Duplex printing conveyance unit 6 (6M, 6C, 6Y, 6K) Image formation unit 7 (7m, 7c, 7y, 7k) Photosensitive drum 8 Cleaner 9 Charging roller 11 Optical writing head 12 Developer 13 Developing roller 14 Transfer belt 15 Drive roller 16 Driven roller 17 Belt position control mechanism 18 Primary transfer roller 19 Waste toner collection container 21 Paper feed cassette 22 Paper take-out roller 23 Feed roller 24 Roller 25 Standby transport roller pair 26 Secondary transfer roller 27 Belt type heat fixing device 28 Unloading roller pair 29 Paper discharge tray 31 Paper discharge roller pair 32a Start return path 32b Intermediate return path 32c End return path 33a, 33b, 33c, 33d Return Roller pair 35 Cleaning unit 36 Capture roller 7 the pressing roller 38 the toner hopper A
39 Toner Hopper B
41 toner cartridge 42 exterior frame 42a upper left exterior frame 43 developing unit 44 supply roller 45 doctor blade 46 stirring member 47, 48, 49 high voltage power supply 51 cleaning blade 52, 52b, 52c conveying screw 53 waste toner containing pipe 54 waste toner collecting bag 55 Agitator 56 Seal member 57 Drum unit 58 Developing drum unit

Claims (1)

A developing roller that carries at least a non-magnetic one-component toner and develops the toner image into a latent image on the electrostatic latent image carrier, and supplies the toner to the developing roller to form a toner layer on the developing roller. An image forming apparatus having a developing device including a supply roller and a developing tank having a doctor blade for charging the toner on the developing roller and forming a thin layer,
A toner cartridge configured separately from the developing tank, detachably attached to the developing tank, and containing the toner to be supplied to the developing tank;
Cartridge toner detection means for detecting that the toner contained in the toner cartridge is consumed and there is no remaining amount;
A developing tank toner detecting means for detecting that the remaining amount of the toner in the developing tank has become equal to or less than a predetermined level after the cartridge toner detecting means detects that the toner cartridge has no remaining toner;
When the developing tank toner detecting means detects that the remaining amount of toner in the developing tank is below a predetermined level, a bias voltage having a polarity opposite to that in the case of forming a normal toner layer on the supply roller is applied. Reverse polarity bias voltage applying means,
Notification means for informing the replacement of the toner cartridge with a new toner cartridge after the deteriorated toner remaining in the developing tank is discharged by the application of the reverse polarity bias voltage by the reverse polarity bias voltage application means; ,
Drive stop means for stopping the drive of at least the developing device in synchronization with notification of toner cartridge replacement by the notification means;
An image forming apparatus comprising: