JP4797616B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and in particular, applies a voltage of a predetermined polarity to a transfer residual toner remaining on an image carrier after transferring a toner image to charge the transfer residual toner to a predetermined polarity, thereby performing a charged transfer. The present invention relates to an image forming apparatus including a cleaning device that adsorbs and collects residual toner.

  Conventionally, an image forming apparatus that forms an image using an electrophotographic system such as a laser printer or a digital copying machine is known. In this type of image forming apparatus, generally, a photosensitive member having a uniformly charged peripheral surface is driven to circulate, and a light beam is irradiated on the peripheral surface of the photosensitive member to form an electrostatic latent image. A toner image developed by attaching toner to the latent image is transferred to a recording medium to form an image.

  By the way, in this type of image forming apparatus, not all toner is transferred from the photoconductor to the recording medium, and there may be generated transfer residual toner remaining on the photoconductor, and this transfer residual toner is collected. Various cleaning mechanisms have been proposed.

  For example, in Patent Document 1, a voltage having a polarity opposite to the charging polarity of the toner for removing toner adhering to a traveling charged dielectric (corresponding to the above-described photoreceptor) is applied and traveling. A conductive rotating brush that contacts the dielectric, and is placed in contact with the dielectric surface on the upstream side of the traveling dielectric as viewed from the rotating brush, and the charge removal of the dielectric or the charged polarity of the dielectric is reversed. And a conductive fixed brush to which a voltage having a polarity to be converted is applied is disclosed.

  Further, Patent Document 2 discloses a first toner charge amount control means and a second toner charge amount control means (both conductive brushes) for charging transfer residual toner downstream of a transfer portion for transferring a toner image. The first toner charge amount control means is charged with the opposite polarity to the normal polarity, and the transfer residual toner on the charged photosensitive drum is normally treated by the second toner charge amount control means. An image forming apparatus is disclosed that employs a cleanerless system in which the electrode is charged and the transfer residual toner is collected by a developing device.

  By the way, in the image forming apparatuses disclosed in Patent Document 1 and Patent Document 2, a fixed brush, a first toner charge amount control unit, a second toner charge amount control unit, and the like as the usage time elapses. In some cases, the transfer residual toner is gradually deposited on the residual toner charging means for charging the transfer residual toner, and the deposited transfer residual toner is discharged onto the photoconductor to cause a cleaning failure.

Therefore, this type of image forming apparatus is periodically deposited on the residual toner charging unit by applying a voltage having a polarity opposite to that of the transfer residual toner to the residual toner charging unit in a state where the photosensitive member is driven in a circular manner. Some have a cleaning mode in which the residual toner charging means is refreshed by discharging the transfer residual toner to the photoreceptor.
JP-A-63-223681 JP 2002-99176 A

  However, even if a voltage having a polarity opposite to that of the transfer residual toner is applied to the residual toner charging unit, the transfer residual toner remains without being discharged sufficiently, and the residual toner charging unit may not be sufficiently refreshed. was there.

  The present invention has been made to solve the above-described problems, and provides an image forming apparatus capable of efficiently refreshing the residual toner charging unit by discharging more transfer residual toner from the residual toner charging unit. The purpose is to do.

In order to achieve the above object, the invention described in claim 1 is directed to a driving means for driving an image carrier on which a toner image is formed by electrophotography in a predetermined direction, and a toner image on the image carrier. A transfer means for transferring to the transfer body; and a contact means disposed on the peripheral surface of the image carrier downstream in the circumferential direction of the image carrier from the transfer position of the toner image, and a voltage of a predetermined polarity is applied, A residual toner charging means for charging the transfer residual toner remaining on the peripheral surface of the image carrier after the transfer to the predetermined polarity; and the image carrier on the downstream side in the circumferential direction from the residual toner charging means. A voltage which is disposed in contact with the peripheral surface and has a polarity opposite to the predetermined polarity with respect to the potential level of the peripheral surface of the image carrier is applied to adsorb the transfer residual toner charged to the predetermined polarity. To collect residual toner When the transfer residual toner deposited on the residual toner charging unit is collected, if the image carrier is driven in a circular manner, the circular drive of the image carrier is started after the circular drive is stopped. It is allowed when the predetermined polarity opposite the application of the residual toner voltage for cleaning as the polarity rows stomach, and voltage and opposite polarity for the remaining the residual toner cleaning the toner recovery unit to simultaneously said residual toner charging means become to control the application of voltage to the row Migihitsuji, the residual toner to said image bearing member of laps when initiates the circulation driving of the image bearing member when the drive is stopped at the same time the residual toner charging means and and control means for controlling row stomach, and the application of voltage and opposite polarity to become voltage for the residual toner cleaning to the residual toner recovery unit to the row Migihitsuji the application of voltage for cleaning .

  According to the first aspect of the present invention, the image bearing member on which the toner image is formed by the electrophotographic method is rotated in a predetermined direction by the driving unit, and the toner image on the image bearing member is transferred to the transfer target by the transfer unit. The toner image is transferred by applying a voltage of a predetermined polarity to the residual toner charging means disposed in contact with the peripheral surface of the image carrier downstream of the transfer direction of the image carrier from the transfer position of the toner image. Transfer toner remaining on the peripheral surface of the image carrier after the toner is transferred is charged to a predetermined polarity, and the residual toner disposed in contact with the peripheral surface of the image carrier downstream of the residual toner charging means in the circumferential direction A voltage having a polarity opposite to the predetermined polarity with respect to the potential level of the peripheral surface of the image carrier is applied to the collecting means, and the transfer residual toner charged to the predetermined polarity is adsorbed and collected. The transfer target may be, for example, a recording medium that finally records a toner image such as a recording sheet, or an intermediate transfer member that temporarily holds a toner image such as an intermediate transfer belt. Also good.

  According to the present invention, when the transfer residual toner deposited on the residual toner charging unit is collected by the control unit, if the image carrier is driven in a circular manner, the circular driving is stopped and then the rotational driving is stopped. When the circumferential driving of the image carrier is started and at the same time, a voltage having a polarity opposite to the predetermined polarity is applied to the residual toner charging means, and the circumferential driving of the image carrier is stopped. Control is performed so as to apply a voltage having a polarity opposite to a predetermined polarity to the residual toner charging means at the same time as the rotation of the image carrier is started.

  Thus, according to the first aspect of the present invention, when collecting the transfer residual toner deposited on the residual toner charging means, if the image carrier is driven in a circular manner, the circular drive is stopped, Since a voltage having a polarity opposite to the predetermined polarity is applied to the residual toner charging unit at the same time as the rotation of the image carrier is started, a large amount of transfer residual toner can be discharged from the residual toner charging unit. The residual toner charging means can be efficiently refreshed.

The present invention, as the invention of claim 2, wherein said control means intermittently orbiting drive of the image bearing member while being applied to the polarity and become the voltage of the opposite to the residual toner charging means Alternatively, control may be performed so as to temporarily stop.

In the present invention, as in the invention described in claim 3 , the residual toner charging means may be a brush or a non-woven fabric at least partly composed of conductive fibers.

  As described above, according to the present invention, when collecting the transfer residual toner deposited on the residual toner charging unit, if the image carrier is driven in a circular manner, the circular drive is stopped and the image carrier is stopped. Since a voltage having a polarity opposite to the predetermined polarity is applied to the residual toner charging unit at the same time when the body is started to rotate, a large amount of transfer residual toner can be discharged from the residual toner charging unit. It has an excellent effect that the toner charging means can be efficiently refreshed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, specific numerical values may be given for convenience of explanation, but the present invention is not limited to these numerical values.

[First Embodiment]
FIG. 1 shows a color laser printer 10 (hereinafter referred to as a printer) which is an example of an image forming apparatus according to an embodiment of the present invention. The printer 10 includes image forming units 12Y, 12M, 12C, and 12K that respectively form toner images of colors of yellow (Y), magenta (M), cyan (C), and black (K). A so-called tandem type full-color laser printer in which units 12Y, 12M, 12C, and 12K are arranged in parallel facing the intermediate transfer belt 14, and the toner images of four colors are superimposed while the intermediate transfer belt 14 makes one round. It is.

  The printer 10 includes a paper feed tray 16 at the bottom. A paper feed roll 18 is in contact with the leading end of the paper P set in the paper feed tray 16 in the transport direction, and the paper P is fed one sheet at a time by the paper feed roll 18 and a paper handling means (not shown). Paper is fed from the tray 16 to the downstream side in the transport direction. A pair of transport rolls 20 is arranged on the downstream side of the paper feed roll 18 in the transport direction, and the paper P is transported to the upper transfer unit 22 by the transport force from the transport roll 20.

  The transfer unit 22 is provided with a belt conveyance roll 24A around which the intermediate transfer belt 14 is wound, and a transfer roll 26 pressed against the belt conveyance roll 24A. The intermediate transfer belt 14 is sandwiched between the nip portion of the belt conveyance roll 24A and the transfer roll 26, and the toner image is transferred from the intermediate transfer belt 14 when the paper P passes through the nip portion.

  A fixing unit 28 is disposed downstream of the transfer unit 22 in the conveyance direction. The fixing unit 28 is provided with a heat roll 28A that becomes high temperature and a backup roll 28B that is pressed against the heat roll 28A, and the paper P passes through the nip portion between the heat roll 28A and the backup roll 28B. At this time, the toner is melted and solidified, fixed on the paper P, and discharged out of the apparatus.

  Here, the printing unit 11 in which the image forming units 12Y, 12M, 12C, and 12K superimpose the toner images on the intermediate transfer belt 14 will be described. Note that when distinguishing each color of yellow, magenta, cyan, and black, Y, M, C, and K are added after the code. However, if there is no need to distinguish each color, Y, M, C, and K are omitted.

  The intermediate transfer belt 14 includes the belt conveyance roll 24A described above, a belt conveyance roll 24B disposed on the left side of the belt conveyance roll 24A, and a belt conveyance roll 24C disposed obliquely below the belt conveyance roll 24A. , Is wrapped around. Image forming units 12Y, 12M, 12C, and 12K are sequentially arranged on the surface of the intermediate transfer belt 14 between the belt conveyance roll 24A and the belt conveyance roll 24B so as to face each other along the circumferential direction of the intermediate transfer belt 14. Thus, the toner images of the respective colors formed by the respective image forming units 12 are transferred so as to be superimposed on the intermediate transfer body belt 14.

  Next, a detailed configuration of the image forming unit 12 according to the first embodiment will be described with reference to FIG.

  The image forming unit 12 includes a cylindrical photosensitive drum 30 as an image carrier, and rotates in the direction of the arrow by the driving force of a motor 58 (see FIG. 4). Further, the intermediate transfer belt 14, the contact member 32, the cleaning device 34, the charging roll 36, and the developing device 38 are in contact with the photosensitive surface 30A of the photosensitive drum 30 in order along the rotation direction. Further, a light beam is scanned along the axial direction of the photosensitive drum 30 from the exposure device 40 on the photosensitive surface 30A between the charging roll 36 and the developing device 38.

  The charging roll 36 is applied with a predetermined bias voltage from a power source (not shown), and uniformly charges the abutting photosensitive surface 30A.

  The exposure device 40 uniformly scans the charged photosensitive surface 30A with a light beam based on image data. As a result, the potential of the region scanned by the light beam on the photosensitive surface 30A is lowered to form an electrostatic latent image.

  The developing device 38 includes a developing roll 38 </ b> A that can rotate about a rotation axis parallel to the photosensitive drum 30. The developing roller 38A is applied with a predetermined developing bias voltage from a power source (not shown) to charge the toner to a negative polarity, and rotates in the same direction as the rotation direction of the photosensitive drum 30 to transfer the charged toner to the photosensitive surface 30A. Supply. That is, the developing device 38 rotates the developing roll 38A in the reverse direction with respect to the photosensitive drum 30 at the nip portion that contacts the photosensitive surface 30A. It is increasing.

  A contact point (transfer position) with the intermediate transfer belt 14 is located downstream of the developing device 38 in the rotation direction, and the transfer roll 42 is sandwiched between the photosensitive drum 30 and the intermediate transfer belt 14. Is arranged. A positive transfer voltage having a polarity opposite to that of the toner is applied to the transfer roll 42 from a power source (not shown).

As shown in FIG. 3, the contact member 32 is a brush in which conductive nylon fibers 32B are planted on a rectangular column-shaped conductive base 32A made of metal or the like, and the thickness per brush hair is 2d. (Denier) (15.0 μm), the hair density of the brush is 430 kf / inch ² .

  The contact member 32 is connected to the first switch unit 53 via the connection line 47, and one of the two power sources of the first plus power source 60 and the first minus power source 62 is selected by the first switch unit 53 and brushed. A voltage is applied to. In the present embodiment, as an example, the first plus power source 60 is a DC power source having a voltage V = + 400V, and the first minus power source 62 is a DC power source having a voltage V = −800V.

  The cleaning device 34 has a rotating brush 34A that is rotatable about a rotation axis parallel to the photosensitive drum 30, and a rotating brush 34A that is in contact with the rotating brush 34A and is parallel to the rotating brush 34A. A recovery roll 34B that is driven and rotated, and a scraper 34C that contacts the peripheral surface of the recovery roll 34B are provided.

In the rotating brush 34A, conductive nylon fibers are planted around the shaft, the thickness per brush hair is 2d (denier) (15.0 μm), the brush hair density is 240 kf / inch ² , the shaft diameter Is 5 mm and the outer diameter is 12 mm. The rotating brush 34A is connected to the second switch unit 54 via the connection line 48, and one of the two power sources of the second plus power source 64 and the second minus power source 66 is selected by the second switch unit 54, A predetermined voltage is applied to the brush. In the present embodiment, as an example, the second positive power source 64 is a DC power source having a voltage V = + 50V, and the second negative power source 66 is a DC power source having a voltage V = −400V.

  Here, specifications of main members and main electric specifications constituting the image forming unit 12 according to the present embodiment will be described below.

Photosensitive drum 30: Organic photoconductor having a diameter of about 30.0 mm Charging roll 36: Semiconductive roll
DC + AC contact charging system
V _DC = −520v (DC component voltage value)
I _AC = 0.65 mA (AC component current value)
Frequency = 614Hz (AC component voltage waveform)
Exposure apparatus 40: Laser wavelength = 780 nm
Developing roll 38A: Diameter = 16.0 mm
Rotation speed = 208mm / sec
The direction of rotation is opposite to the direction of rotation of the photosensitive drum 30.
Development bias: V _DC = −400 V (DC component voltage value)
V _pp = 1500V (AC component voltage (Peak to Peak))
Frequency = 6 kHz (AC component voltage waveform)
Development system: Two-component development system Development gap (interval between the photosensitive drum 30 and the development roll 38A): about 0.3 mm
Intermediate transfer belt 14: made of polyimide, process speed: 104 mm / second, transfer roll 42: transfer bias + 500V to + 1000V
Transfer roll 26: Transfer bias + 1600V
The photosensitive drum 30 according to the present embodiment generates a discharge when the potential difference with other members in contact with the photosensitive drum 30 becomes 450V.

  FIG. 4 is a block diagram showing a functional configuration of a control system that controls the operation of the printer 10 according to the present embodiment.

  As shown in the figure, the printer 10 includes a control unit 50 that controls the operation of each device built in the printer 10 based on input image data and controls an image forming process for forming an image on paper P. A storage unit 52 for preliminarily storing various programs, various parameters, and the like, and temporarily storing image data indicating an image to be formed, and a drive control unit 56 for controlling the rotational drive of the motor 58 , Is provided.

  When an instruction signal for instructing the rotation of the photosensitive drum 30 is input, the drive control unit 56 supplies electric power to the motor 58 to rotate the motor 58 to rotate the photosensitive drum 30. When an instruction signal for instructing stoppage is input, power supply to the motor 58 is stopped and the photosensitive drum 30 is stopped.

  The control unit 50 is electrically connected to the storage unit 52, the drive control unit 56, the first switch unit 53, and the second switch unit 54. Therefore, the control unit 50 controls the rotation of the photosensitive drum 30 by accessing the storage unit 52, outputting an instruction signal for instructing the rotation or stop of the photosensitive drum 30 to the drive control unit 56, and the first switch. An instruction signal can be output to the unit 53 and the second switch unit 54 to control the voltage applied to the contact member 32 and the rotating brush 34A, respectively.

  Next, the operation of the printer 10 when image data is input and image forming processing is executed by the control unit 50 will be briefly described.

  When the image data is input, the control unit 50 outputs an instruction signal that instructs the drive control unit 56 to rotationally drive the photosensitive drum 30. The drive control unit 56 supplies electric power to the motor 58 and rotates the photosensitive drum 30 in the direction of the arrow in the drawing as shown in FIG.

  In addition, the control unit 50 outputs an instruction signal instructing switching to the first switch unit 53 so as to select the first negative power source 62 side, and selects the second positive power source 64 side to the second switch unit 54. An instruction signal for instructing switching is output.

  The first switch unit 53 electrically connects the contact member 32 and the first negative power source 62, and the second switch unit 54 electrically connects the rotary brush 34 </ b> A and the second positive power source 64. As a result, a voltage of −800 V is applied to the contact member 32 from the first negative power source 62, and a voltage of 50 V is applied to the rotating brush 34 </ b> A from the second positive power source 64.

  When the photosensitive drum 30 rotates in the direction of the arrow in the drawing, the photosensitive surface 30A is uniformly charged to a predetermined polarity potential by the charging roll 36. In the present embodiment, a bias voltage obtained by superimposing a DC voltage of −520 V and an AC voltage that generates an AC current of 0.65 mA is applied to the charging roll 36, and the photosensitive surface 30 </ b> A is charged to −500 V, for example. Is done.

  When the photosensitive drum 30 further rotates, the charged surface of the photosensitive surface 30A is scanned and exposed based on the image data by the exposure device 40, and the potential of the exposed portion of the charged surface decreases (for example, −200 V). An electrostatic latent image is formed. Thereafter, the toner charged negatively by the developing roll 38A to which a developing bias voltage in which a DC voltage of −400 V and an AC voltage having a peak-to-peak potential difference of 1500 V are superimposed is applied is exposed on the charged surface. By electrically adhering to the portion, the electrostatic latent image is developed (visualized) to form a toner image.

  Then, when the formed toner image passes through the transfer position as the photosensitive drum 30 rotates, the toner image is electrically attracted to the transfer roll 42 to which a transfer voltage of +500 V opposite in polarity to the toner is applied. Then, the image is transferred from the photosensitive drum 30 to the intermediate transfer belt 14.

  However, in the image forming unit 12, the toner transferred to the intermediate transfer belt 14 without being transferred to the intermediate transfer belt 14 or transferred to the intermediate transfer belt 14 on the upstream side is transferred to the downstream photosensitive drum 30. The transfer residual toner that is reversely transferred and remains on the photosensitive drum 30 is generated. The transfer residual toner includes toner having a reverse polarity in which the polarity is reversed to positive by the positive transfer voltage applied to the transfer roll 42 when passing through the transfer position.

  Therefore, the contact member 32 is discharged with the photosensitive drum 30 when a voltage of −800 V is applied, and the polarity of the residual transfer toner passing therethrough is unified to a negative polarity. The electric potential of the peripheral surface of the photosensitive drum 30 after passing through the contact member 32 becomes approximately −350 V due to discharge from the contact member 32. If the transfer residual toner cannot be made sufficiently negative in polarity by the contact member 32, a high negative voltage may be applied to the contact member 32. However, if the voltage is increased too much, the amount of discharge products generated by the discharge increases, and white spots of the image occur in a high-temperature and high-humidity environment. May be determined as appropriate.

  The cleaning device 34 rotates the rotating brush 34A to which a voltage of +50 V is applied, and adsorbs and collects (cleans) the transfer residual toner charged to a negative polarity. The collected transfer residual toner is transferred from the rotating brush 34A to the collecting roll 34B, and is removed and collected by the scraper 34C. The potential difference between the rotating brush 34A and the photosensitive drum 30 is 400V, which is smaller than 450V, which is the discharge start voltage, and no discharge occurs.

  By the way, since the contact member 32 is a brush in which the conductive nylon fibers 15B are flocked, transfer residual toner is gradually accumulated as the usage time elapses. In some cases, the photosensitive drum 30 is discharged. When a large amount of transfer residual toner is discharged from the contact member 32, the rotary brush 34A may not be able to sufficiently collect the transfer residual toner, and cleaning failure may occur.

  Therefore, the printer 10 according to the present embodiment is provided with a cleaning mode for discharging the transfer residual toner accumulated on the contact member 32.

  The control unit 50 executes a cleaning mode control process for controlling the cleaning mode before performing the next image forming process every time a certain number of sheets (for example, 100 sheets) are printed.

  Next, the operation of the printer 10 when executing the cleaning mode will be described with reference to FIG. FIG. 6 is a flowchart showing the flow of the cleaning mode control process executed by the control unit 50 of the printer 10 at this time. In addition, here, only control related to one contact member 32 will be described in order to avoid complications, but the control unit 50 performs similar processing on each contact member 32.

  In step 100 of FIG. 7, as indicated by t1 in FIG. The drive control unit 56 stops the supply of electric power to the motor 58 and stops the rotation of the photosensitive drum 30.

  In the next step 102, an instruction signal for instructing switching is output to the first switch unit 53 so as to select the first plus power source 60 side, and the second minus power source 66 side is selected to the second switch unit 54. An instruction signal for instructing switching is output, and an instruction signal for instructing the drive control unit 56 to rotationally drive the photosensitive drum 30 is output.

  The first switch portion 53 electrically connects the contact member 32 and the first plus power source 60, and the second switch portion 54 electrically connects the rotating brush 34A and the second minus power source 66.

  In addition, the drive control unit 56 supplies electric power to the motor 58 to rotate the photosensitive drum 30.

  As a result, as shown at t2 in FIG. 7, simultaneously with the start of rotation of the photosensitive drum 30 in the direction of the arrow in the drawing, a voltage of +400 V is applied to the contact member 32 from the first plus power source 60, and the rotating brush 34A is applied. A voltage of −400 V is applied from the second negative power source 66.

  As shown in FIG. 8, the contact member 32 discharges the deposited transfer residual toner onto the photosensitive drum 30 when a voltage of +400 V is applied. The discharged transfer residual toner is conveyed to the rotating brush 34A as the photosensitive drum 30 rotates, and is sucked and collected by the rotating brush 34A.

  In the next step 104, it is determined whether or not the predetermined period t3 has elapsed. If the determination is affirmative, the cleaning mode control process is terminated, the image forming process is continued, and if the determination is negative, the process is again performed. The process proceeds to step 104 and waits for the elapse of a predetermined period t3.

  During the predetermined period t3, after the photosensitive drum 30 starts to rotate, the transfer residual toner discharged from the contact member 32 passes through the rotating brush 34A at least once as the photosensitive drum 30 rotates. It is sufficient to determine the number of passages of the rotating brush 34A through an experiment or the like according to the amount of transfer residual toner to be discharged, and set the period appropriately in advance. For example, if the amount of discharged residual toner is very large and cannot be cleaned at once by the rotating brush 34A, the transfer voltage applied to the transfer roll 42 is set to a negative value and transferred to the intermediate transfer belt 14, for example. A method may be used in which the toner is collected by a cleaner on the transfer belt 14, or the photosensitive drum 30 is rotated twice and cleaned again by the rotating brush 34A.

  In the cleaning mode control process according to the present embodiment, the rotating photosensitive drum 30 is stopped in step 100, but the rotation of the drive control unit 56 is stopped when the cleaning mode control process is executed. In this case, step 102 and subsequent steps may be executed.

  Here, as a result of earnest research by the inventor, the contact member 32 has a voltage (a positive voltage in the present embodiment) that has a polarity opposite to the polarity of the transfer residual toner deposited when the photosensitive drum 30 starts to rotate. It has been found that a large amount of transfer residual toner is discharged when the voltage (2) is applied. This is considered to be because the bristle planted in the contact member 32 vibrates due to vibrations and changes in airflow caused by the photosensitive drum 30 starting to rotate.

In the experiments of the inventors, after printing 100 solid images, for example, the conventional cleaning mode shown in FIG. 9 is executed, and the voltage of +400 V is applied to the contact member 32 while the photosensitive drum 30 is driven to rotate. Is applied, immediately after the voltage is switched (t4 in FIG. 9), a transfer residual toner of about 0.5 g / m ² at maximum is discharged from the contact member 32, and then the amount gradually decreases. In the case of this conventional cleaning mode, although the life of the contact member 32 is increased, the amount of discharged toner is smaller than the accumulated amount, so that the transfer residual toner is finally accumulated on the contact member 32. As a result, a large amount of transfer residual toner may be suddenly discharged from the contact member 32 during image formation, resulting in poor cleaning.

On the other hand, after 100 solid images have been printed, the cleaning mode according to the present embodiment shown in FIG. 7 is executed to temporarily stop the rotational drive of the photosensitive drum 30, and then the rotational drive of the photosensitive drum 30. 2 and the application of a voltage having a reverse polarity to the contact member 32 are performed simultaneously, the transfer residual toner of about 12 g / m ² at maximum from the contact member 32 immediately after the photosensitive drum 30 is driven. The amount decreases rapidly afterwards.

  In the printer 10 according to the present embodiment, the cleaning mode according to the present embodiment is executed every time 100 sheets are printed, and a sheet passing test for 30,000 sheets of paper P is performed. A large amount of transfer residual toner was not suddenly discharged from the contact member 32, and no image quality defect such as black streak occurred on the print due to poor cleaning caused by the toner.

  As described above, according to the first embodiment, the image carrier (here, the photosensitive drum 30) on which the toner image is formed by the electrophotographic method is moved in a predetermined direction by the driving means (here, the motor 58). The toner image on the image carrier is transferred to the transfer target by the transfer means (here, the transfer roll 42), and the toner image on the downstream side in the circulation direction of the image carrier from the transfer position of the toner image is transferred. The peripheral surface of the image carrier after the toner image is transferred by applying a predetermined polarity (in this case, minus) voltage to the residual toner charging means (contact member 32) disposed in contact with the peripheral surface of the image carrier. The transfer residual toner remaining on the toner is charged to a predetermined polarity, and the potential level of the peripheral surface of the image carrier is applied to the residual toner collecting means disposed in contact with the peripheral surface of the image carrier downstream of the residual toner charging means. The polarity opposite to the specified polarity The composed voltage is applied, it is collected by suction transfer residual toner charged to a predetermined polarity.

  According to the present invention, when the transfer residual toner deposited on the residual toner charging unit is collected by the control unit (here, the control unit 50), when the image carrier is driven around, The rotation of the image carrier is controlled so that the rotation of the image carrier is started after the rotation is stopped, and at the same time, a voltage having a polarity opposite to a predetermined polarity is applied to the residual toner charging unit. Is stopped, the rotation of the image carrier is started, and at the same time, a voltage having a polarity opposite to the predetermined polarity is applied to the residual toner charging means. Since a large amount of transfer residual toner can be discharged from the contact member, the contact member can be efficiently refreshed.

  Further, according to the first embodiment, since the residual toner charging means is a brush at least partly composed of conductive fibers, the transfer residual toner can be charged efficiently.

  In the cleaning mode control process according to the present embodiment, a case where a negative voltage is applied to the contact member 32 simultaneously with the start of rotation of the photosensitive drum 30 as shown in FIG. 7 has been described. The present invention is not limited to this, and as shown in FIG. 10, after the negative voltage is applied to the contact member 32 (t2 in FIG. 10), the rotational driving of the photosensitive drum 30 is resumed (t5 in FIG. 10). ) Good. Also in this case, since a voltage having a polarity opposite to the polarity of the transfer residual toner accumulated when starting the rotation driving of the photosensitive drum 30 is applied, the timing at which the rotation driving of the photosensitive drum 30 is resumed. Since a large amount of transfer residual toner can be discharged, the same effects as in the present embodiment can be obtained.

  In addition, since the contact member 32 according to the present embodiment needs to be conductive in order to adjust the charge of the transfer residual toner to minus, when the brush in which the conductive fiber is planted as described above is used. However, the present invention is not limited to this, and even a brush in which conductive fibers and insulating fibers are mixed woven has conductivity, so that the charge of the transfer residual toner can be adjusted. Alternatively, a brush in which conductive fibers and insulating fibers are mixed may be used.

  Moreover, although the printer 10 according to the present embodiment has been described with respect to the case where a brush in which conductive fibers are planted is used as the contact member 32, the present invention is not limited to this, and a conductive fixed shape is used. For example, as shown in FIG. 11, a conductive urethane sponge 32C having a thickness of 3 mm is attached to a rectangular column-shaped conductive base 32A made of metal or the like, as shown in FIG. A non-woven fabric 32D having a thickness of 500 μm (0.5 mm) may be used as the contact member 32. The non-woven fabric is literally “a non-woven fabric” and is a sheet formed by laminating conductive fibers obtained by polymerizing conductive polymer polypyrrole on nylon and polyester having a diameter of about 5 μm. As a manufacturing method of a nonwoven fabric, there are a dry nonwoven fabric, a spun band, a wet nonwoven fabric and the like.

  Even when a non-woven fabric is used as the contact member 32 as described above, the transfer residual toner is gradually accumulated on the contact member 32 as the usage time elapses. By executing such a cleaning mode, a large amount of transfer residual toner can be discharged from the contact member 32, so that the same effect as in the present embodiment can be obtained.

  Further, the contact member 32 may be provided with an oscillation mechanism that slides in the axial direction in order to make the toner charge adjustment capability uniform in the axial direction.

  In addition, the cleaning device 34 according to the present embodiment includes the rotating brush 34A, the collection roll 34B, and the scraper 34C. However, in the printer 10 with a small amount of residual toner, only the flickering bar is provided. A simple configuration may be adopted.

[Second Embodiment]
In the second embodiment, a description will be given of an example in which the circumferential driving of the photosensitive drum 30 is temporarily stopped during the predetermined period t3.

  Since the configurations of the printer 10 and the image forming unit 12 according to the second embodiment are the same as those in FIGS. 1 and 2, a detailed description thereof is omitted here.

Here, in the experiments by the inventors, after 100 solid images are printed, if a cleaning mode in which the photosensitive drum 30 repeats driving and stopping is performed as in the present embodiment, immediately after the first driving. about a 12g ^{/ m} 2, 2 nd about 5g ^{/ m} 2, 3 round together with about 2 g / ^{m 2} to about 19 g / ^{m 2} things a large amount of transfer residual toner can be discharged to immediately drive.

  Therefore, in the cleaning mode control process according to the present embodiment, as shown in FIG. 12, the photosensitive drum 30 is repeatedly driven and stopped during a predetermined period t3.

  In the printer 10 according to the present embodiment, every time 100 sheets are printed, the cleaning mode in which the photosensitive drum 30 is repeatedly driven and stopped is executed as in the present embodiment to pass 30,000 sheets of paper P. As a result of the test, a large amount of transfer residual toner is not suddenly discharged from the contact member 32 during image formation until the end, and there is no image quality defect such as black streaks on the print due to poor cleaning due to the toner. It was outbreak.

  As described above, according to the second embodiment, the control unit temporarily stops the circumferential driving of the image carrier intermittently while a voltage having a reverse polarity is applied to the residual toner charging unit. Thus, since a larger amount of transfer residual toner can be discharged from the contact member and the contact member can be efficiently refreshed, the interval for executing the cleaning mode can be extended.

  In the first and second embodiments, the case where the photosensitive drum is cylindrical has been described. However, the present embodiment is not limited to this and, for example, wound around a plurality of rolls. It is good also as an endless belt hung. Also in this case, the same effect as in the present embodiment can be obtained.

  Further, the printer 10 according to the first and second embodiments is provided with a first switch portion 53 and a second switch portion 54 as means for controlling the voltage applied to the contact member 32 and the rotating brush 34A, and supplies power. Although the case where the voltage applied to the contact member 32 and the rotating brush 34A is changed by switching has been described, the present invention is not limited to this, and when the power source can change the applied voltage, The voltage applied to the contact member 32 and the rotating brush 34A may be changed by controlling the power source.

  Further, the configuration of the printer 10 described in the present embodiment (see FIG. 1) and the configuration of the image forming unit (see FIGS. 2, 5, and 8) are examples, and do not depart from the gist of the present invention. Needless to say, it can be appropriately changed within the range.

  Further, the applied voltage control processing (see FIG. 6) described in the present embodiment is also an example, and it is needless to say that it can be appropriately changed without departing from the gist of the present invention.

1 is a diagram illustrating an overall configuration of a printer according to a first embodiment. FIG. 2 is a diagram illustrating a detailed configuration of an image forming unit according to the first embodiment. It is a figure which shows the detailed structure of the contact member which concerns on 1st Embodiment. 2 is a block diagram illustrating a configuration of a control system of the printer according to the first embodiment. FIG. FIG. 4 is a diagram illustrating a toner flow during image formation in the image forming unit according to the first embodiment. It is a flowchart which shows the flow of the cleaning mode control process which concerns on 1st Embodiment. 6 is a timing chart showing the relationship between the driving timing of the photosensitive drum and the timing of voltage application to the contact member and the rotating brush according to the first embodiment. FIG. 4 is a diagram illustrating a toner flow in a cleaning mode in the image forming unit according to the first embodiment. It is a timing chart which shows the relationship between the drive timing of the photosensitive drum in the conventional cleaning mode, and the timing of the voltage application to a contact member and a rotating brush. 6 is a timing chart showing a modification of the driving timing of the photosensitive drum and the timing of voltage application to the contact member and the rotating brush according to the first embodiment. It is a figure which shows another structure of the contact member which concerns on 1st Embodiment. 10 is a timing chart showing the relationship between the drive timing of the photosensitive drum and the timing of voltage application to the contact member and the rotating brush according to the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Printer 14 Intermediate transfer belt 30 Photoconductor drum 32 Contact member 34A Rotating brush 42 Transfer roll 50 Control unit 53 First switch unit 54 Second switch unit 58 Motor

Claims (3)

Driving means for driving the image carrier on which the toner image is formed by electrophotography to rotate in a predetermined direction;
Transfer means for transferring the toner image of the image carrier to a transfer target;
The image carrier after being transferred by being placed in contact with the peripheral surface of the image carrier downstream of the image carrier from the transfer position of the toner image and applying a voltage of a predetermined polarity. Residual toner charging means for charging the transfer residual toner remaining on the peripheral surface to the predetermined polarity;
A voltage having a polarity opposite to the predetermined polarity with respect to the potential level of the peripheral surface of the image carrier is disposed in contact with the peripheral surface of the image carrier downstream of the residual toner charging unit in the circumferential direction. A residual toner recovery means for adsorbing and recovering the transfer residual toner applied to and charged to the predetermined polarity;
When collecting the transfer residual toner deposited on the residual toner charging means, if the image carrier is driven in a circular manner, the circular drive of the image carrier is started after the circular drive is stopped. It said residual toner to the charging unit becomes the predetermined polarity and the opposite polarity have residual row voltage application for toner cleaning and the voltage and opposite polarity for the residual toner cleaning to the residual toner collecting means at the same time and controlling the application of voltage to the row Migihitsuji, for the residual toner cleaning to the image bearing member simultaneously said residual toner charging means when starting the driving to rotate of the image bearing member when the orbiting drive is stopped in and control means for applying a row stomach voltage, and to control the application of the residual voltage and opposite polarity to become the voltage of the toner cleaning to the residual toner recovery unit to the row Migihitsuji,
An image forming apparatus. 2. The image formation according to claim 1, wherein the control unit performs control so as to temporarily stop the rotation of the image carrier intermittently while the voltage having the opposite polarity is applied to the residual toner charging unit. apparatus. The image forming apparatus according to claim 1, wherein the residual toner charging unit is a brush or a non-woven fabric at least a part of which is made of a conductive fiber.

Images