JP5962064B2 - Image forming apparatus - Google Patents

Description

  The invention disclosed in this specification relates to a technique for collecting toner in an image forming apparatus that forms an image using toner.

  2. Description of the Related Art Conventionally, in an image forming apparatus that forms an image on paper or the like using toner, a technique for collecting toner remaining on an image carrier after forming an image is known (for example, Patent Document 1). In this technique, the toner remaining on the image carrier is removed using a cleaning roller charged to a potential opposite to that of the toner, and then the cleaning roller is charged to a potential having the same polarity as that of the toner, and the toner deposited on the cleaning roller is removed. The toner is returned to the image carrier, and the toner returned to the image carrier is collected using a developing device. In the image forming apparatus, a charging roller may be disposed between the cleaning roller and the developing device. When the toner returned to the image carrier passes through a position facing the charging roller, the toner is transferred to the charging roller. If attached, the image carrier cannot be charged uniformly using the charging roller. In the prior art, when the toner returned to the image carrier passes through the vicinity of the charging roller, the charging roller is charged to the same polarity as the toner, thereby preventing the toner from adhering to the charging roller. Techniques to do this are disclosed.

JP-A-7-56407

  However, since the image carrier is a dielectric, when the toner is returned from the cleaning roller to the image carrier, the toner on the image carrier is returned by a potential having the same polarity as the toner charged by the cleaning roller. The toner may be charged to the same polarity as the toner. Therefore, even if the charging roller is charged to the same polarity as that of the toner when the portion passes the position facing the charging roller, the absolute value of the potential of the portion is larger than the absolute value of the charging roller potential. If it is large, it is not possible to prevent toner from adhering to the charging roller.

  The invention disclosed in this specification discloses a technique for suppressing toner from adhering to a charging portion in an image forming apparatus that forms an image using toner.

  An image forming apparatus disclosed in this specification includes a carrier that carries toner that rotates around an axis and is charged to a predetermined polarity, a charging unit that contacts the carrier and charges the carrier, and the carrier A collection unit that contacts the body and collects the toner from the carrier, an adjustment unit that adjusts the potential of the collection unit and the charging unit, and a control unit, and the control unit is provided in the collection unit. A discharge process for applying a potential having the same polarity as the polarity of the toner to release the toner from the recovery unit to the carrier, and an attachment part on the carrier to which the discharged toner adheres are attached to the charging unit. When passing through the facing position, a potential that is the same polarity as the polarity of the toner and that is greater than the absolute value of the potential of the recovery portion when discharging the toner from the recovery portion to the attachment portion is charged. Application processing to be applied to the part , To the execution.

  In this image forming apparatus, in the application process, the control unit has a potential of the same polarity as that of the toner on the charging unit, and the adhering unit to which the toner returned from the recovery unit adheres passes a position facing the charging unit. A potential is applied so that the absolute value of the potential of the charging portion is equal to or greater than the absolute value of the potential of the collecting portion when returning the toner from the collecting portion to the attaching portion. Therefore, when the toner is returned from the recovery unit to the carrier, the adhesion portion charged to near the potential of the recovery unit at that time is moved to a position facing the charging unit by the rotation of the carrier, so that the toner and the charging unit Repels electrically. Therefore, it is possible to suppress the toner returned to the carrier from the collection unit from adhering to the charging unit.

  In the image forming apparatus, the control unit may be configured such that, in the application process, the counter unit is charged when the counter unit of the carrier facing the charging unit passes a position facing the recovery unit. A potential larger than the absolute value of the potential of the charging unit when facing the unit may be applied to the recovery unit.

  In this image forming apparatus, in the application process, the control unit causes the recovery unit to detect the absolute value of the potential of the recovery unit when the counter unit passes the position where the counter unit opposes the recovery unit. A potential larger than the absolute value of the potential of the charged portion is applied. Therefore, even when the counter part charged to near the potential of the charging part at that time moves to a position facing the recovery part by the rotation of the carrying part, the toner and the counter part are electrically Attract each other. Therefore, it is possible to easily release the toner from the collection unit to the carrier.

  In the above image forming apparatus, the carrier is rotated in a predetermined rotation direction, the charging unit is rotated in accordance with the rotation of the carrier, and the collecting unit is in contact with the carrier. The outer peripheral distance from the position of contact with the charging unit to the position of contact with the recovery unit in the rotation direction of the support is shorter than the total outer peripheral distance of the recovery unit. It is good also as a structure.

  In this image forming apparatus, in the application process, the counter part on the carrier charged to the vicinity of the potential of the charging part at that time is brought into contact with the recovery part by the rotation of the carrier. First, the collection unit contacts the carrier over the entire circumference, and the collection unit finishes returning the toner to the carrier. According to this image forming apparatus, even when the absolute value of the potential of the facing portion is higher than the absolute value of the potential of the collecting portion, the event of returning the toner from the collecting portion to the facing portion does not occur. Therefore, it is possible to easily release the toner from the collection unit to the carrier.

  In the image forming apparatus, the control unit maintains a constant potential difference between the charging unit and the recovery unit in the application process, and the potentials of the charging unit and the recovery unit with time. It is good also as a structure which raises the absolute value of.

  According to this image forming apparatus, the control unit maintains a constant potential difference between the charging unit and the recovery unit in the application process, so that the processing burden on the control unit in the application process can be reduced. In addition, since the control unit increases the absolute value of the potential of the charging unit and the recovery unit with time in the application process, even if the potential difference between the charging unit and the recovery unit is kept constant, the control unit The absolute value of the potential of the charging unit when the adhering part to which the returned toner has adhered passes through the position facing the charging unit is greater than or equal to the absolute value of the electric potential of the collecting unit when returning the toner from the collecting unit to the adhering part. can do.

  The image forming apparatus further includes a transfer unit that transfers the toner carried on the carrier to a transfer target, the adjustment unit adjusts the potential of the transfer unit, and the control unit A recovery process of applying a potential opposite to the polarity of the toner to the recovery unit and recovering the toner from the carrier to the recovery unit. In the recovery process, A reverse polarity potential is applied, a specified potential having the same polarity as that of the toner is applied to the charging unit, the toner is transferred to the transfer object, and in the applying process, the specified potential is applied to the charging unit. It is good also as a structure which applies the electric potential below the absolute value of this.

  In this image forming apparatus, in the application process, the control unit causes the charging unit to apply a potential whose absolute value is equal to or less than the absolute value of the specified potential used for toner transfer onto the transfer target. Therefore, it is possible to prevent the absolute value of the potential of the charging unit from exceeding the specified absolute value during the application process and damage to the carrier passing through the position facing the charging unit during the application process. be able to.

  The image forming apparatus further includes a transfer unit that transfers the toner carried on the carrier to a transfer target, the adjustment unit adjusts the potential of the transfer unit, and the control unit A recovery process of applying a potential opposite to the polarity of the toner to the recovery unit and recovering the toner from the carrier to the recovery unit. In the recovery process, A reverse polarity potential is applied, a specified potential having the same polarity as that of the toner is applied to the charging unit, the toner is transferred to the transfer object, and in the applying process, the specified potential is applied to the charging unit. It is good also as a structure to apply.

  In this image forming apparatus, in the application process, the control unit causes the charging unit to apply a potential whose absolute value is equal to a specified potential used for toner transfer onto the transfer target. For this reason, it is possible to prevent the absolute value of the potential of the charging unit from exceeding the specified absolute value during the application process, and damage to the carrier passing through the position facing the charging unit during the application process. In addition, it is not necessary to adjust the potential of the charging unit to a potential different from the potential of the charging unit in the recovery process in the application process, and the processing burden on the control unit in the application process can be reduced.

  According to the image forming apparatus disclosed in this specification, it is possible to suppress toner from adhering to the charging unit.

Cross section of printer Enlarged view of the periphery of the photoconductor of Embodiment 1 Enlarged view of the periphery of the photoconductor of Embodiment 1 Printer block diagram Flow chart showing print processing Flow chart showing cleaning process and potential application process Time chart showing potential application timing of Embodiment 1 Enlarged view of the periphery of the photoconductor of Embodiment 2. The flowchart which shows the electric potential application process of Embodiment 2. Time chart showing potential application timing of embodiment 2

<Embodiment 1>
The first embodiment will be described with reference to FIGS.

1. FIG. 1 is a side sectional view showing a schematic configuration of a printer 10 according to the present embodiment. As shown in FIG. 1, the printer 10 is a direct transfer laser printer that forms a monochrome image using a single color toner, and is configured in a casing 12. The printer 10 is an example of an image forming apparatus.

  A supply tray 14 is provided on the inner bottom of the casing 12, and a sheet material 16 such as paper is stacked on the supply tray 14. The supply tray 14 is configured to be openable and closable with respect to the casing 12. When the sheet material 16 is supplied to the supply tray 14 by the user and stored in the casing 12, the sheet material 16 is pressed against the pickup roller 20 by the pressing plate 18. When the pickup roller 20 rotates, the sheet material 16 is conveyed to the supply roller 22 and the registration roller 24 along the conveyance path 28. The sheet material 16 is conveyed to the image forming unit 30 after skew correction is performed by the registration roller 24.

  The image forming unit 30 includes a pair of support rollers 32 and 34, a belt 36, and a transfer roller 37. The belt 36 is provided between the support rollers 32 and 34 and has a ring shape. The transfer roller 37 is disposed inside the ring-shaped belt 36. The support rollers 32 and 34 rotate counterclockwise, and the belt 36 moves accordingly. The transfer roller 37 is an example of a transfer unit.

  An image forming unit 40 is provided on the upper side of the belt 36. The image forming unit 40 includes a scanner unit 42 and a process unit 44. The process unit 44 includes a developing device 46, a photoreceptor 48, a drum cleaner 52, a charging roller 54, and the like. The developing device 46 is filled with toner and is provided with a developing roller 56, and supplies positively charged toner to the photoconductor 48 via the developing roller 56. The photoconductor 48 is an example of a carrier, the drum cleaner 52 is an example of a recovery unit, and the charging roller 54 is an example of a charging unit.

  2 and 3 show an enlarged structure around the photoconductor 48. The photoconductor 48 has a cylindrical shape and rotates about an axis 48A as indicated by an arrow 59. In the photoconductor 48, the periphery of the conductive shaft 48A is covered with a dielectric 48B, and a ground potential is applied to the shaft 48A. The charging roller 54 contacts the photoconductor 48 at the charging position P <b> 1, and is rotated by the rotation of the photoconductor 48. The charging roller 54 is applied with a positive potential, and charges the surface of the photoconductor 48 to a constant positive potential at the charging position P1. The developing roller 56 contacts the photoconductor 48 at a supply position P2 different from the charging position P1 in the circumferential direction of the photoconductor 48, and is rotated along with the rotation of the photoconductor 48.

  The drum cleaner 52 is different from the charging position P1 and the supply position P2 in the circumferential direction of the photoconductor 48, and in the recovery position P3 that is not located between the charge position P1 and the supply position P2 in the rotation direction of the photoconductor 48. Is rotated by the rotation of the photoconductor 48. When a negative potential is applied, the drum cleaner 52 collects the toner supplied to the photoconductor 48 at the collection position P3. Further, when a positive potential is applied, the drum cleaner 52 releases the collected toner to the photoconductor 48.

  Further, as shown in FIG. 1, the scanner unit 42 is arranged on the upper part of the photoconductor 48 of the process unit 44. The scanner unit 42 is based on image data sent from a RAM 66 (see FIG. 4) by a central processing unit (see FIG. 4, hereinafter referred to as CPU) 62, which will be described later, from the charging position P1 to the supply position P2 in the rotation direction of the photoconductor 48. The laser beam L is irradiated to the photosensitive member 48 between the two. As a result, the surface potential of the photoconductor 48 charged to a constant positive potential by the charging roller 54 is partially lowered, and an electrostatic latent image corresponding to the image to be formed on the surface of the photoconductor 48 is formed due to the decrease in the potential. Is done. By supplying positively charged toner to the electrostatic latent image, the photoconductor 48 carries the toner by electrostatic force, and a toner image is formed on the surface of the photoconductor 48 (see FIG. 2).

  The toner image formed on the surface of the photoconductor 48 faces the belt 36 and passes through a transfer position P4 (see FIG. 2) located between the supply position P2 and the collection position P3 in the rotation direction of the photoconductor 48. At this time, a negative transfer bias is applied to the transfer roller 37, and the toner image on the photoconductor 48 is transferred onto the sheet material 16. As a result, an image is formed on the sheet material 16. The image formed on the sheet material 16 is sent to the fixing device 50, and after the image formed on the sheet material 16 is fixed, the image is conveyed to the discharge tray 38 by the conveyance roller 26. In other words, the pickup roller 20, the supply roller 22, the registration roller 24, and the conveyance roller 26 form a conveyance unit 29 that conveys the sheet material 16 placed on the supply tray 14 to the discharge tray 38 along the conveyance path 28. ing.

  On the other hand, the toner remaining on the photoreceptor 48 without being transferred onto the sheet material 16 at the transfer position P4 is recovered by the drum cleaner 52 to which a negative potential is applied at the recovery position P3. The drum cleaner 52 is applied with a positive potential in a non-image forming period in which image formation on the sheet material 16 is completed and image formation is not performed on the sheet material 16, and contacts the photoconductor 48 over the entire circumference. Then, the collected toner is discharged again to the photoreceptor 48 (see FIG. 3). The toner discharged to the photoconductor 48 is conveyed to the supply position P2 via the charging position P1 and returned to the developing device.

  As described above, in the photoreceptor 48, the dielectric 48B covers the periphery of the conductive shaft 48A. Therefore, in the non-image forming period, when the drum 48 is in contact with the drum cleaner 52 to which the positive potential is applied at the collection position P3, the dielectric 48B is polarized between the shaft 48A to which the ground potential is applied. As a result, the portion of the photoconductor 48 that contacts the drum cleaner 52, that is, the adhering portion 48 D to which the toner released from the drum cleaner 52 adheres has a positive potential equivalent to that of the drum cleaner 52. Therefore, when the adhering portion 48D having a positive potential comes into contact with the charging roller 54 by the rotation of the photoconductor 48 and the toner adhering to the adhering portion 48D adheres to the charging roller 54, the photosensitive member 48 is used by using the charging roller 54. Cannot be charged to a constant positive potential.

  The printer 10 according to this embodiment includes a potential adjustment circuit 58 (see FIG. 1) that adjusts the potential applied to the transfer roller 37, the drum cleaner 52, and the charging roller 54. As will be described later, the drum cleaner 52 and the charging roller 54 are included. By adjusting the potential applied to the toner, the toner is prevented from adhering to the charging roller 54. The potential adjustment circuit 58 is an example of an adjustment unit.

  In the printer 10 of this embodiment, as shown in FIG. 3, the outer peripheral distance L1 from the charging position P1 to the recovery position P3 in the rotation direction of the photoconductor 48 is longer than the total outer peripheral distance L2 of the drum cleaner 52. Is set. Therefore, in the non-image forming period, the drum cleaner 52 is in contact with the charging roller 54 of the photoconductor 48 before the contact portion 48E having a positive potential reaches the collection position P3 due to the rotation of the photoconductor 48. 48 is brought into contact with the entire circumference of the drum 48, and the release of the toner from the drum cleaner 52 to the photosensitive member 48 is completed. Therefore, in the printer 10 of this embodiment, toner is not released from the drum cleaner 52 to the contact portion 48E. The contact part 48E is an example of an opposing part.

2. FIG. 4 is a block diagram schematically showing the electrical configuration of the printer 10. As shown in FIG. 4, the printer 10 includes an ASIC (Application Specific Integrated Circuit) 60 that controls each part of the printer 10. The ASIC 60 includes a CPU 62, a ROM 64, a RAM 66, and a drive circuit 68. Via the bus 70, in addition to the transport unit 29, the scanner unit 42, and the potential adjustment circuit 58, a power switch, various setting buttons, and a communication line are used. It is connected to the input part 71 which receives the operation command from a user, and the output part 72 which consists of LED and displays the condition of the printer 10. A range 74 obtained by combining the CPU 62 and the ROM 64 indicated by a dotted line in FIG. 4 is an example of the control unit.

  The ROM 64 stores various programs for controlling the operation of the printer 10, and the CPU 62 controls each unit according to the program read from the ROM 64. Specifically, the CPU 62 controls the potential adjustment circuit 58, and the potential adjustment circuit 58 adjusts the potential applied to the transfer roller 37, the drum cleaner 52, and the charging roller 54 based on the control from the CPU 62. The RAM 66 stores image data to be transmitted to the scanner unit 42 at the time of image formation.

  The drive circuit 68 is connected to the motor M and transmits a pulse signal to the motor M based on a command from the CPU 62. When the motor M rotates in accordance with the pulse signal input from the drive circuit 68, the transport unit 29 is driven in accordance with this, and the sheet material 16 is step-conveyed along the transport path 28. That is, when conveying the sheet material 16, the CPU 62 transmits a pulse signal to the motor M via the drive circuit 68, and the conveyance unit 29 conveys the sheet material 16 accordingly.

3. Printing Process Next, the printing process of the printer 10 will be described with reference to FIGS. FIG. 5 shows a flowchart of a printing process executed by the CPU 62 in accordance with a predetermined program. FIG. 7 shows a printing process in which the potential adjustment circuit 58 performs the transfer roller 37, the drum cleaner 52, the charging, based on the control from the CPU 62. 3 is a time chart of the potential applied to the roller. In FIG. 7, Vtr means a potential applied to the transfer roller 37, Vcl means a potential applied to the drum cleaner 52, and Vch denotes a potential applied to the charging roller 54.

  FIG. 7 shows Vdm1, which is the potential of the photoconductor 48, together with the potential. Vdm <b> 1 indicates a potential before the contact with the charging roller 54 of the photosensitive member 48 in a portion in contact with the charging roller 54 out of the potential of the photosensitive member 48.

  In FIG. 7 and the following description, a period required for the photoconductor 48 to rotate from the position PA to the position PB is referred to as a period TAB. For example, a period required for the photoconductor 48 to rotate from the charging position P1 to the transfer position P4 is described as a period T14, and a period required for the photoconductor 48 to rotate from the collection position P3 to the charging position P1 is T31. The period required for the photoreceptor 48 to rotate from the charging position P1 to the collection position P3 is described as T31, and the period required for the photoreceptor 48 to rotate from the collection position P3 to the supply position P2 is represented as T31. Describe.

  When starting the process, the CPU 62 first executes an image forming process. In the image forming process, the CPU 62 first controls the potential adjustment circuit 58 to apply +1500 V to the charging roller 54 at the elapsed time t1 (S2, FIG. 7LE1), and also controls the scanner unit 42 so that the charging roller 54 keeps constant. An electrostatic latent image is formed by irradiating the surface of the photoconductor 48 charged to the potential of the laser beam L with a laser beam L. As a result, toner image formation is started on the surface of the photoreceptor 48 after a period T12 from the elapsed time t1 (see FIG. 2). The image forming process includes a collecting process.

  The CPU 62 applies −1000 V to the transfer roller 37 at the elapsed time t2 when the period T14 has elapsed from the elapsed time t1 (S4, FIG. 7LE2), and matches the toner image formed on the surface of the photoreceptor 48 with the elapsed time t2. Then, the image is transferred to the sheet material 16 conveyed to the transfer position P4, and an image is formed on the sheet material 16. Further, the CPU 62 applies −800V to the drum cleaner 52 at the elapsed time t3 after the elapsed time t1 from the elapsed time t1 (S6, FIG. 7LE3), and removes the toner remaining on the photoconductor 48 without being transferred to the sheet material 16. Electrically attracted and collected from the photoreceptor 48 to the drum cleaner 52 (see FIG. 2). Hereinafter, the toner collected by the drum cleaner 52 is referred to as residual toner.

  The CPU 62 waits for completion of image formation on the sheet material 16 (S8: NO), and forms an image on the sheet material 16 using various sensors (not shown) disposed along the conveyance path 28. Is detected (S8: YES), the potential of the charging roller 54 is returned to the ground potential at the elapsed time t4. The CPU 62 returns the potential of the transfer roller 37 to the ground potential after the lapse of the period T14 from the elapsed time t4, and returns the potential of the drum cleaner 52 to the ground potential after the lapse of the period T13 from the elapsed time t4 (S10). The CPU 62 ends the image forming process at an elapsed time t5 when a period longer than the period T13 has elapsed from the elapsed time t4. Thus, at the end of the image forming process, the potential Vdm1 of the photoconductor 48 becomes the ground potential.

  At the end of the image forming process, the CPU 62 executes a cleaning process and a potential application process (S12). The cleaning process period and the potential application process period correspond to a non-image formation period. FIG. 6 shows a flowchart of the cleaning process and the potential application process executed by the CPU 62 according to a predetermined program. The cleaning process and the potential application process are independently executed by the same CPU 62. In the following description, the CPU 62 that performs the cleaning process is formally referred to as CPU 62A, and the CPU 62 that performs the potential application process is formally referred to as CPU 62B. The cleaning process and the potential application process include a discharge process and an application process.

  In the cleaning process and the potential application process, the CPU 62B first sets the potential of the charging roller 54 to +1500 V, which is the same as the image forming process period, at the elapsed time t5 (S22), and sets the potential of the drum cleaner 52 to the polarity of the image forming process period. A different + 800V is set (S24), and the potential of the transfer roller 37 is set to + 1000V having a polarity different from that of the image forming process period (S25). When these potential setting processes are completed, the CPU 62B turns on the cleaning flag set in the RAM 66 (S26).

  The CPU 62A waits for the cleaning flag to turn on (S42: NO). When the cleaning flag is turned on (S42: YES), the rotation of the photoconductor 48 is started (S44). When the rotation of the photoconductor 48 is started, the drum cleaner 52, the charging roller 54, and the transfer roller 37 that are in contact with the photoconductor 48 start to rotate. The CPU 62A monitors the rotation speed of the photoconductor 48, and when the rotation speed of the photoconductor 48 reaches a specified speed, the CPU 62A turns on the drive flag (S46).

  After turning on the cleaning flag, the CPU 62B waits for the drive flag set in the RAM 66 to be turned on (S28: NO). When the drive flag is turned on (S28: YES), the elapsed time t5 has elapsed. At time t6, the potential set in S22, S24, and S25 is applied to the charging roller 54, the drum cleaner 52, and the transfer roller 37 (S30, FIGS. 7LE4 to 6). As a result, the residual toner collected by the drum cleaner 52 is electrically repelled from the drum cleaner 52, and the residual toner is discharged to the photoreceptor 48 (see FIG. 3).

  Further, the potential of the adhering portion 48 </ b> D where the discharged residual toner adheres in the photoreceptor 48 rises to a potential equivalent to that of the drum cleaner 52. Then, at an elapsed time t7 after a lapse of a period T31 from the elapsed time t6, the attaching portion 48D passes through the charging position P1, and as shown by an arrow 76 in FIG. 7, the potential increases to the same potential as the charging roller 54 and the drum cleaner 52. Adhering part 48D (refer FIG. 7LE7) contacts.

  In the present embodiment, since a higher potential than the drum cleaner 52 is applied to the charging roller 54 in the cleaning process and the potential application process, the potential of the charging roller 54 is higher than the potential of the adhesion portion 48D. Therefore, the residual toner attached to the attachment portion 48D is electrically repelled from the charging roller 54, and the state where the residual toner is attached to the attachment portion 48D is maintained. The residual toner adhering to the adhering portion 48D reaches the supply position P2 after passing through the charging position P1, and is collected by the developing unit 46 at the supply position P2.

  The drum cleaner 52 finishes releasing the residual toner to the photosensitive member 48 at an elapsed time t8 when a period T3 required for one rotation of the drum cleaner 52 has elapsed from the elapsed time t6. The developing device 46 finishes collecting the residual toner at an elapsed time t9 after a period T32 has elapsed from the elapsed time t8. The residual toner that cannot be collected by the developing device 46 passes through the transfer position P4 by the rotation of the photoconductor 48, but a positive potential having the same polarity as the toner is applied to the transfer roller 37. Therefore, the residual toner is suppressed from adhering to the belt 36.

  The CPU 62A waits for the total period of the period T3 and the period T32 to elapse from the elapsed time t6 (S48: NO), and when the total period elapses (S48: YES), the drive flag at the elapsed time t8. Is turned off (S50). The CPU 62A stops the rotation of the photoconductor 48 (S52) and ends the cleaning process. As a result, the rotation of the drum cleaner 52 and the charging roller 54 in contact with the photoconductor 48 is also stopped.

  The CPU 62B waits for the drive flag to turn off after applying the set potential to the charging roller 54 and the drum cleaner 52 (S32: NO), and when the drive flag is turned off (S32: YES), at the elapsed time t8. The potentials of the charging roller 54 and the drum cleaner 52 are returned to the ground potential (S34). The CPU 62B turns off the cleaning flag (S36) and ends the voltage application process.

4). Effects of the present embodiment (1) In the printer 10 of the present embodiment, the CPU 62B applies a positive potential having the same polarity as that of the toner and higher than that of the drum cleaner 52 to the charging roller 54 in the voltage application process. . The adhesion portion 48 </ b> D of the photoconductor 48 in contact with the drum cleaner 52 does not become higher than the potential applied to the drum cleaner 52, and rises only to a potential equivalent to the potential applied to the drum cleaner 52. Therefore, even when the adhesion portion 48D comes into contact with the charging roller 54 at the charging position P1, the potential of the charging roller 54 can be reliably set higher than the potential of the adhesion portion 48D, and the residual toner is electrically connected to the charging roller 54. To repel. Therefore, in the printer 10, it is possible to suppress the residual toner attached to the attaching portion 48 </ b> D from attaching to the charging roller 54.

(2) In the printer 10 of the present embodiment, the outer peripheral distance L1 from the charging position P1 to the recovery position P3 in the rotation direction of the photoconductor 48 is set longer than the total outer peripheral distance L2 of the drum cleaner 52. Therefore, in the cleaning process and the potential application process period, the photosensitive member 48 contacts the charging roller 54 and before the contact portion 48E that has risen to a potential equivalent to the potential applied to the charging roller 54 reaches the recovery position P3. The drum cleaner 52 rotates once, and the discharge of residual toner from the drum cleaner 52 to the photoconductor 48 is completed. Therefore, in the printer 10, toner is not discharged from the drum cleaner 52 to the contact portion 48E, and the drum cleaner 52 is transferred from the drum cleaner 52 to the photosensitive member 48 regardless of the level relationship between the potential of the drum cleaner 52 and the potential of the contact portion 48E. Residual toner can be easily released.

(3) In the printer 10 of the present embodiment, the CPU 62B applies the same potential as the potential in the image forming process to the charging roller 54 in the potential application process. Therefore, the potential applied to the charging roller 54 in the cleaning process and the potential application process period becomes higher than the potential applied to the charging roller 54 in the image forming process, and the photosensitive member 48 passing through the charging position P1 in the potential application process period. It is possible to suppress damage. Further, it is not necessary to adjust the potential applied to the charging roller 54 to a potential different from the potential in the image forming process during the potential application process period, and the processing burden on the CPU 62B can be reduced.

(4) In the printer 10 of the present embodiment, the CPU 62B applies a positive potential having the same polarity as the toner to the transfer roller 37 in the voltage application process. Therefore, it is possible to suppress the residual toner from adhering to the belt 36 when the residual toner that has not been collected by the developing device 46 and remains in the adhering portion 48D passes through the transfer position P4.

<Embodiment 2>
A second embodiment will be described with reference to FIGS. The present embodiment is different from the first embodiment in the relationship between the outer peripheral distance L1 and the outer peripheral distance L2, and the potential application process executed by the CPU 62B in the printing process. In the following description, the same description as that of the first embodiment will not be repeated.

1. FIG. 8 is an enlarged view of the structure around the photoconductor 48 of the present embodiment. In the printer 10 of the present embodiment, the outer peripheral distance L1 from the charging position P1 to the collection position P3 in the rotation direction of the photoconductor 48 is set shorter than the total outer peripheral distance L2 of the drum cleaner 52. Therefore, during the non-image forming period, the drum cleaner 52 contacts the photoconductor 48 over the entire circumference, and contacts the charging roller 54 of the photoconductor 48 before the release of the toner from the drum cleaner 52 to the photoconductor 48 is completed. Then, the contact portion 48E having a positive potential reaches the collection position P3 by the rotation of the photoconductor 48. That is, in the printer 10 of this embodiment, toner may be discharged from the drum cleaner 52 to the contact portion 48E.

  Therefore, when the contact portion 48E having a positive potential is higher than the potential applied to the drum cleaner 52, the toner cannot be discharged from the drum cleaner 52 to the contact portion 48E, and the toner is collected by the developing device 46. I can't. The printer 10 of this embodiment adjusts the potential applied to the drum cleaner 52 and the charging roller 54 as will be described later, thereby preventing the toner from adhering to the charging roller 54 and collecting the toner in the developing unit 46. Suppresses not being done.

2. Potential Application Processing Next, with reference to FIGS. 9 and 10, the potential application processing of the printing processing of the printer 10 will be described. FIG. 9 shows a flowchart of a potential application process executed by the CPU 62 in accordance with a predetermined program. FIG. 10 shows how the potential adjustment circuit 58 performs the transfer roller 37, the drum cleaner 52, and the like in the printing process based on the control from the CPU 62. 3 is a time chart of potentials applied to the charging roller 54. FIG. FIG. 10 shows Vdm1 and Vdm2 as the potential of the photoconductor 48 together with the above potential. Vdm <b> 2 indicates the potential before the contact with the charging roller 54 of the photosensitive member 48 in the portion of the potential of the photosensitive member 48 that contacts the drum cleaner 52.

  In the potential application process, the CPU 62B first sets the potential of the charging roller 54 to +500 V at the elapsed time t6 (S62), and sets the potential of the drum cleaner 52 to +300 V, which is different in polarity from the image forming process period (S64). The potential of the transfer roller 37 is set to +300 V, which is different in polarity from the image forming process period (S65). When the CPU 62B applies the potential set in S62, S64, and S65 to the charging roller 54, the drum cleaner 52, and the transfer roller 37 at the elapsed time t6 (S30, FIG. 7 LE4 to 6), the potential application time from the elapsed time t6. tv is measured.

  The CPU 62B waits for the potential application time tv to elapse for a predetermined time tk (S66: NO). When the predetermined time tk elapses (S66: YES), the charging roller 54, the drum cleaner 52, and the transfer The potential of the roller 37 is increased by 50 V, which is a unit potential (S68, S70, S71). When the potential of the charging roller 54 and the drum cleaner 52 is increased, the CPU 62B resets the potential application time tv and repeats the increase of the potential every time the potential application time tv elapses the specified time tk. As a result, the potentials of the charging roller 54 and the drum cleaner 52 continue to rise as time passes while the potential difference VS is maintained constant (FIGS. 9LE4 to 6).

  Next, the CPU 62B adjusts the potential difference VS between the charging roller 54 and the drum cleaner 52 (S72). The CPU 62B calculates a reference potential difference VK obtained by multiplying a unit potential by the number N of periods obtained by dividing the period T13 until the contact portion 48E reaches the collection position P3 by the specified time. The CPU 62B compares the potential difference VS with the reference potential difference VK. When the potential difference VS is equal to or less than the reference potential difference KV (S72: NO), the CPU 62B compares the potential difference VS with the unit potential (S74). When the potential difference VS is larger than the unit potential (S74: YES), the CPU 62B further increases only the potential of the drum cleaner 52 (S76) and adjusts the potential difference VS to be larger than the reference potential difference KV.

  During the potential application processing period, the potential of the contact portion 48E in contact with the charging roller 54 rises to a potential equivalent to that of the charging roller 54. Then, at the elapsed time t10 when the period T13 has elapsed from the elapsed time t6, the contact portion 48E passes to the recovery position P3, and as shown by the arrow 78 in FIG. 10, the drum cleaner 52 and the attachment portion 48D (see FIG. 7LE8) contact each other. To do. When the drum cleaner 52 and the attachment portion 48D come into contact with each other, residual toner is discharged from the drum cleaner 52 to the attachment portion 48D.

  In the present embodiment, the potential difference VS is adjusted to be larger than the reference potential difference KV in the potential application process. Therefore, even if the potential of the contact portion 48E is higher than the potential of the drum cleaner 52 when it comes into contact with the charging roller 54, the drum cleaner is in the period T13 during which the contact portion 48E moves from the charging position P1 to the recovery position P3. 52 repeats the unit potential increase N times, so that the drum cleaner 52 and the contact portion 48E come into contact with each other at a higher potential than the contact portion 48E. Therefore, the residual toner collected in the drum cleaner 52 is electrically attracted to the contact portion 48E, and the residual toner is discharged to the contact portion 48E.

  On the other hand, when the potential difference VS is equal to or less than the unit potential (S74: NO), the CPU 62B proceeds to the process of S32 without increasing the potential of the drum cleaner 52. Thereby, in the potential application process, a relationship in which the potential of the charging roller 54 is higher than the potential of the drum cleaner 52 is maintained, and the potential of the charging roller 54 when the charging roller 54 and the attaching portion 48D come into contact with each other is the potential of the attaching portion 48D. It is maintained higher than the potential. Therefore, also in the present embodiment, the residual toner attached to the attaching portion 48D is electrically repelled from the charging roller 54, and the residual toner does not adhere to the charging roller 54.

  The CPU 62B drives when the potential difference VS is larger than the reference potential difference KV (S72: YES) or when the potential difference VS is less than the reference potential difference KV and the potential difference VS is less than the unit potential (S72: NO, S74: NO). It is determined whether or not the flag is turned off (S32), and when it is determined that the drive flag is not turned off (S32: YES), the potential of the charging roller 54 is confirmed (S78). The CPU 62B confirms whether the potential of the charging roller 54 is +1450 V or less. If the potential of the charging roller 54 is +1450 V or less (S78: YES), the processing from S66 is repeated. On the other hand, when the potential of the charging roller 54 is higher than +1450 V (S78: NO), the processing from S32 is repeated, and the potentials of the charging roller 54 and the drum cleaner 52 are not increased. As a result, the potential of the charging roller 54 rises and is prevented from exceeding +1500 V, which is the potential during the image forming process period.

  The drum cleaner 52 finishes releasing the residual toner to the photosensitive member 48 at an elapsed time t8 after a period T3 has elapsed from the elapsed time t6. The developing device 46 finishes collecting the residual toner at an elapsed time t9 after a period T32 has elapsed from the elapsed time t8. The residual toner that cannot be collected by the developing unit 46 passes through the transfer position P4 due to the rotation of the photoconductor 48, and a positive potential having the same polarity as the toner is applied to the transfer roller 37. Since the potentials of the charging roller 54 and the drum cleaner 52 are increased as the potentials of the charging roller 54 and the drum cleaner 52 are increased, the residual toner is prevented from adhering to the belt 36.

3. Advantages of the present embodiment (1) In the printer 10 of the present embodiment, the CPU 62B causes the potential of the drum cleaner 52 when the drum cleaner 52 and the contact portion 48E are in contact with each other to be higher than the potential of the contact portion 48E. Also adjust it to be higher. Therefore, when the drum cleaner 52 and the contact portion 48E come into contact with each other, the residual toner attracts the contact portion 48E electrically. Therefore, it is possible to easily release the residual toner from the drum cleaner 52 to the contact portion 48E.

(2) In the printer 10 of the present embodiment, when the potential application time tv elapses the specified time tk in the potential application process, the CPU 62B raises the potentials of the charging roller 54 and the drum cleaner 52 both by unit potential. And the potential difference VS between the drum cleaner 52 and the drum cleaner 52 are kept constant. Therefore, it is not necessary to control the potentials of the charging roller 54 and the drum cleaner 52 independently, and the processing load on the CPU 62B in the voltage application processing can be reduced.

(3) In the printer 10 of this embodiment, the CPU 62B applies a potential lower than the potential in the image forming process to the charging roller 54 in the potential application process. Therefore, the potential applied to the charging roller 54 during the cleaning process and the potential application process period is higher than the potential applied to the charging roller 54 during the image forming process, and the photosensitive member passes through the charging position P1 during the cleaning process and the potential application process period. It is possible to suppress the body 48 from being damaged.

(4) In the printer 10 of the present embodiment, the CPU 62B applies a positive potential having the same polarity as that of the toner to the transfer roller 37 in the voltage application process, and adjusts the potentials of the charging roller 54 and the drum cleaner 52 to rise. To increase its potential. Therefore, it is possible to suppress the residual toner from adhering to the belt 36 when the residual toner that has not been collected by the developing device 46 and remains in the adhering portion 48D passes through the transfer position P4.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following various aspects are also included in the technical scope of the present invention.
(1) Although the above embodiment has been described using the printer 10 having a print function, the present invention is not limited to this. For example, it may be a multi-function machine that further includes at least one of a scanner function, a copy function, a facsimile function, and the like in addition to the print function. Further, it may be used in the printer 10 that forms a color image.

(2) In the above embodiment, the control unit has been described using an example in which the control unit is the range 74 that combines the CPU 62 and the ROM 64. However, the control unit is a CPU, ASIC, and a dedicated unit that executes various processes. You may comprise using an apparatus etc.

(3) In addition, the program executed by the CPU 62 is not necessarily stored in the ROM 64, and may be stored in the CPU 62 itself or in another storage device.

(4) In the above embodiment, an example in which the developing device 46 supplies positively charged toner to the photoconductor 48 and the image forming unit 30 forms an image on the sheet material 16 using the positively charged toner is used. However, the present invention is not limited to this. For example, when the developing device 46 supplies negatively charged toner to the photoconductor 48, the same effect as in the above embodiment can be obtained by reversing the polarity of the potential shown in the above embodiment. it can.

(5) In the above embodiment, in the potential application process, an example in which the application of the potential to the drum cleaner 52 and the charging roller 54 is started at the same time has been described. However, the application of the potential does not necessarily have to be started at the same time. The CPU 62B starts applying a potential to the drum cleaner 52 at the elapsed time t6, and starts charging the residual toner from the drum cleaner 52 to the adhesion portion 48D of the photoconductor 48, and then the charging roller 54 at the elapsed time t7 after a period T31 has elapsed. Application of a potential may be started.

(6) In the above embodiment, an example in which the residual toner discharged from the drum cleaner 52 to the photosensitive member 48 is returned to the developing device 46 has been described, but the present invention is not limited to this. The residual toner discharged to the photoreceptor 48 may be transported to the transfer position P4 after passing through the charging position P1 and the supply position P2, and further discharged to the belt 36. In this case, the residual toner discharged to the belt 36 is collected by a toner box (not shown) provided on a part of the belt 36 that is provided between the support rollers 32 and 34.

10: Printer, 37: Transfer roller, 46: Developer, 48: Photoconductor, 48D: Adhering portion, 48E: Contact portion, 52: Drum cleaner, 54: Charging roller, 56: Developing roller, 58: Potential adjustment circuit, 60: ASIC, 62: CPU, 64: ROM, 66: RAM, P1: charging position, P2: supply position, P3: collection position, P4: transfer position

Claims (5)

A carrier that rotates around an axis and carries toner charged to a predetermined polarity;
A charging unit that contacts the carrier and charges the carrier;
A collection unit that contacts the carrier and collects the toner from the carrier;
An adjustment unit for adjusting the potential of the recovery unit and the charging unit;
A control unit;
With
The controller is
A discharge process in which a potential having the same polarity as the polarity of the toner is applied to the recovery unit, and the toner is released from the recovery unit to the carrier;
When the attached portion on the carrier to which the discharged toner adheres passes through a position facing the charging portion, the potential is the same as the polarity of the toner, and the toner is transferred from the recovery portion to the attached portion. A potential that is greater than the absolute value of the potential of the recovery unit when the discharge unit is discharged is applied to the charging unit, and when the counter part of the carrier facing the charging unit passes through the position facing the recovery unit, An application process for causing the recovery unit to apply a potential that is greater than the absolute value of the potential of the charging unit when the facing unit faces the charging unit ;
An image forming apparatus that executes A carrier that rotates around a shaft in a predetermined rotation direction and carries toner charged to a predetermined polarity;
A charging unit that rotates in accordance with the rotation of the carrier, contacts the carrier and charges the carrier;
A collection unit that rotates in accordance with the rotation of the carrier, collects the toner from the carrier in contact with the carrier; and
An adjustment unit for adjusting the potential of the recovery unit and the charging unit;
A control unit;
With
The outer peripheral distance from the position in contact with the charging unit in the rotation direction of the carrier to the position in contact with the recovery unit is shorter than the total outer peripheral distance of the recovery unit,
The controller is
A discharge process in which a potential having the same polarity as the polarity of the toner is applied to the recovery unit, and the toner is released from the recovery unit to the carrier;
When the attached portion on the carrier to which the discharged toner adheres passes through a position facing the charging portion, the potential is the same as the polarity of the toner, and the toner is transferred from the recovery portion to the attached portion. An application process in which a potential that is greater than the absolute value of the potential of the recovery unit when discharging is applied to the charging unit;
An image forming apparatus that executes A carrier that rotates around an axis and carries toner charged to a predetermined polarity;
A charging unit that contacts the carrier and charges the carrier;
A collection unit that contacts the carrier and collects the toner from the carrier;
An adjustment unit for adjusting the potential of the recovery unit and the charging unit;
A control unit;
With
The controller is
A discharge process in which a potential having the same polarity as the polarity of the toner is applied to the recovery unit, and the toner is released from the recovery unit to the carrier;
When the attached portion on the carrier to which the discharged toner adheres passes through a position facing the charging portion, the potential is the same as the polarity of the toner, and the toner is transferred from the recovery portion to the attached portion. A potential larger than the absolute value of the potential of the recovery unit when the charging unit is discharged is applied to the charging unit to maintain a constant potential difference between the charging unit and the recovery unit, and the charging unit with time And an application process for increasing the absolute value of the potential of the recovery unit ;
An image forming apparatus that executes A carrier that rotates around an axis and carries toner charged to a predetermined polarity;
A charging unit that contacts the carrier and charges the carrier;
A collection unit that contacts the carrier and collects the toner from the carrier;
A transfer portion for transferring the toner carried on the carrier to a transfer object;
An adjustment unit for adjusting the potential of the transfer unit, the recovery unit, and the charging unit;
A control unit;
With
The controller is
A discharge process in which a potential having the same polarity as the polarity of the toner is applied to the recovery unit, and the toner is released from the recovery unit to the carrier;
When the attached portion on the carrier to which the discharged toner adheres passes through a position facing the charging portion, the potential is the same as the polarity of the toner, and the toner is transferred from the recovery portion to the attached portion. An application process in which a potential that is greater than the absolute value of the potential of the recovery unit when discharging is applied to the charging unit;
Was executed,
Applying a potential having a polarity opposite to that of the toner to the recovery unit, and further executing a recovery process of recovering the toner from the carrier to the recovery unit,
In the collection process, a potential having a polarity opposite to the polarity of the toner is applied to the transfer portion, and a specified potential having the same polarity as the polarity of the toner is applied to the charging portion, so that the toner is transferred to the transfer object. Let
An image forming apparatus that applies a potential less than an absolute value of the specified potential to the charging unit in the application process . The image forming apparatus according to claim 1 , wherein:
A transfer unit for transferring the toner carried on the carrier to a transfer object;
The adjustment unit adjusts the potential of the transfer unit,
The controller is
A recovery process of applying a potential having a polarity opposite to that of the toner to the recovery unit and recovering the toner from the carrier to the recovery unit;
In the collection process, a potential having a polarity opposite to the polarity of the toner is applied to the transfer portion, and a specified potential having the same polarity as the polarity of the toner is applied to the charging portion, so that the toner is transferred to the transfer object. Let
An image forming apparatus that applies the specified potential to the charging unit in the application process.

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