Paper powder discharge method and image forming apparatus

Abstract

To provide a technique with which paper powder can be discharged from a paper powder recovery box without disassembling a drum unit.SOLUTION: The electric potential of a first cleaning roller 40 is increased compared with the electric potential of a first cleaning shaft 50. Paper powder can thus be moved from a paper powder recovery box 60 to the first cleaning roller 40 through the first cleaning shaft 50. Consequently, paper powder can be discharged from the paper powder recovery box 60 without disassembling a drum unit.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to a paper dust removal method and an image forming apparatus. [Background technology]

[0002] Electrophotographic image forming devices such as laser printers and LED printers are well known. These image forming devices have a drum unit that is detachable from the main body. The drum unit includes a photosensitive drum, a cleaning roller, a cleaning shaft, and a paper dust collection box. Paper dust adhering to the outer peripheral surface of the photosensitive drum is collected in the paper dust collection box via the cleaning roller and the cleaning shaft.

[0003] A conventional drum unit including such a cleaning roller, a cleaning shaft, and a paper dust collection box is described in, for example, Patent Document 1. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-165000 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventionally, in order to discharge the paper dust collected in the paper dust collection box from the paper dust collection box to the outside, it has been necessary to disassemble the drum unit.

[0006] An object of the present disclosure is to provide a technique that allows paper dust to be discharged from a paper dust collection box without disassembling the drum unit. [Means for solving the problem]

[0007] A first disclosure of the present application is a drum unit that, during normal use, collects paper dust on a photosensitive drum using a first cleaning roller in contact with the photosensitive drum, and collects the paper dust on the first cleaning roller onto the first cleaning shaft by making the potential of a first cleaning shaft in contact with the first cleaning roller higher than the potential of the first cleaning roller, and collects the paper dust on the cleaning shaft into a paper dust collection box using a sponge in contact with the first cleaning shaft.The paper dust discharge method discharges paper dust from the paper dust collection box while the photosensitive drum, the first cleaning roller, the first cleaning shaft, and the paper dust collection box are assembled to a drum frame of the drum unit, and is characterized by having a paper dust discharge step of rotating the first cleaning roller and the first cleaning shaft while making the potential of the first cleaning roller higher than the potential of the first cleaning shaft.

[0008] A second disclosure of the present application is the paper dust discharge method of the first disclosure, characterized in that in the paper dust discharge process, the photosensitive drum, the first cleaning roller, and the first cleaning shaft are rotated while a charger makes the potential of the photosensitive drum higher than the potential of the first cleaning roller.

[0009] A third disclosure of the present application is the paper dust discharge method of the second disclosure, characterized in that in the paper dust discharge step, the drum unit is attached to an image forming device having a circular transfer belt, a portion of the transfer belt is sandwiched between the photosensitive drum and a transfer roller, and the transfer belt is rotated with the potential of the transfer roller set higher than the potential of the photosensitive drum.

[0010] A fourth disclosure of the present application is the paper dust discharging method of the third disclosure, characterized in that in the paper dust discharging step, another portion of the transfer belt is sandwiched between a second cleaning roller and a backup roller, and the transfer belt is rotated with the potential of the second cleaning roller set higher than the potential of the backup roller.

[0011] A fifth disclosure of the present application is the paper dust discharge method of the second disclosure, characterized in that in the paper dust discharge step, the photosensitive drum and a second cleaning roller are brought into contact with each other, and the photosensitive drum and the second cleaning roller are rotated while the potential of the second cleaning roller is set higher than the potential of the photosensitive drum.

[0012] A sixth disclosure of the present application is the paper dust discharging method of the fourth or fifth disclosure, characterized in that in the paper dust discharging step, a second cleaning shaft is brought into contact with the second cleaning roller, and the second cleaning roller and the second cleaning shaft are rotated in a state in which the potential of the second cleaning shaft is made higher than the potential of the cleaning roller.

[0013] A seventh disclosure of the present application is the paper dust discharging method of the sixth disclosure, characterized in that the paper dust adhering to the outer surface of the second cleaning shaft is scraped off into a paper dust discharge box.

[0014] An eighth disclosure of the present application is a paper dust discharge method according to any one of the first to seventh disclosures, characterized in that the paper dust discharge process is carried out with the drum unit positioned so that the opening of the paper dust collection box faces downward.

[0015] A ninth disclosure of the present application is an image forming apparatus comprising a main body housing and a drum unit attachable to the main body housing, the drum unit having a photosensitive drum, a first cleaning roller in contact with the photosensitive drum, a first cleaning shaft in contact with the first cleaning roller, a paper dust collection box with an opening in which the first cleaning shaft is positioned, and a sponge in contact with the first cleaning shaft, characterized in that the image forming apparatus is capable of performing a normal operation in which a first potential is applied to the first cleaning roller and a second potential higher than the first potential is applied to the first cleaning shaft, and a paper dust discharge operation in which a third potential is applied to the first cleaning roller and a fourth potential lower than the third potential is applied to the first cleaning shaft. [Effects of the Invention]

[0016] According to the first to eighth disclosures, in the paper dust discharging step, the potential of the first cleaning roller is set higher than the potential of the first cleaning shaft. This allows paper dust to be transferred from the paper dust collection box to the first cleaning roller via the first cleaning shaft. Therefore, paper dust can be discharged from the paper dust collection box without disassembling the drum unit.

[0017] Furthermore, according to the second disclosure, the paper dust can be moved from the paper dust collection box to the photosensitive drum via the first cleaning shaft and the first cleaning roller.

[0018] Furthermore, according to the third disclosure, paper dust can be transferred from the paper dust collection box to the transfer belt via the first cleaning shaft, the first cleaning roller, and the photosensitive drum.

[0019] Furthermore, according to the fourth disclosure, paper dust can be moved from the paper dust collection box to the second cleaning roller via the first cleaning shaft, the first cleaning roller, the photosensitive drum, and the transfer belt.

[0020] Furthermore, according to the fifth disclosure, the paper dust can be moved from the paper dust collection box to the second cleaning roller via the first cleaning shaft, the first cleaning roller, and the photosensitive drum.

[0021] Furthermore, according to the sixth disclosure, paper dust can be moved from the second cleaning roller to the second cleaning shaft.

[0022] Furthermore, according to the seventh disclosure, it is possible to move paper dust from the paper dust collection box to the paper dust discharge box.

[0023] Furthermore, according to the eighth disclosure, paper dust can be discharged more efficiently from the paper dust collection box.

[0024] According to the ninth disclosure, during the paper dust discharge operation, the potential of the first cleaning roller is set higher than the potential of the first cleaning shaft. This allows paper dust to be transferred from the paper dust collection box to the first cleaning roller via the first cleaning shaft. Therefore, paper dust can be discharged from the paper dust collection box without disassembling the drum unit. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic diagram of an image forming apparatus. [Figure 2] FIG. 2 is a perspective view of the drum unit. [Figure 3] FIG. 2 is a partial cross-sectional view of the drum unit. [Figure 4] FIG. [Figure 5] FIG. 4 is a cross-sectional view of the drum unit taken along line AA in FIG. 3. [Figure 6] FIG. 10 is a diagram showing how paper dust is discharged. [Figure 7] 10A and 10B are diagrams illustrating the state of paper dust discharge in a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following, a direction parallel to the rotation axis of the photosensitive drum 30 will be referred to as a "first direction."

[0027] <1. Configuration of image forming device> FIG. 1 is a schematic diagram of an image forming apparatus 100. The image forming apparatus 100 is an electrophotographic printer. Specifically, the image forming apparatus 100 is a laser printer or an LED printer. As shown in FIG. 1, the image forming apparatus 100 includes a main body housing 101, a control unit 102, a belt unit 3, a drum unit 2, and four developing cartridges 1.

[0028] The belt unit 3 can be attached to the main body housing 101. The four developer cartridges 1 can be attached to the drum unit 2. Furthermore, the drum unit 2 with the four developer cartridges 1 attached can be attached to the main body housing 101.

[0029] Toner, which is a developer, is accommodated inside the developer cartridge 1. The four developer cartridges 1 accommodate toner of different colors. Each developer cartridge 1 has a developer roller 10. The developer roller 10 is rotatably supported on the housing of the developer cartridge 1. The developer roller 10 has a cylindrical outer circumferential surface extending in a first direction. The toner accommodated inside the developer cartridge 1 is carried on the outer circumferential surface of the developer roller 10.

[0030] 2 is a perspective view of the drum unit 2. As shown in FIGS.

[0031] The drum frame 20 is a frame that supports four photosensitive drums 30. Four developer cartridges 1 can be attached to the drum frame 20. The photosensitive drums 30 are cylindrical members that extend along a first direction. The photosensitive drums 30 are rotatable about a drum axis Ad (see FIG. 5) that extends in the first direction. The outer peripheral surfaces of the photosensitive drums 30 are covered with a photosensitive material.

[0032] When the developer cartridge 1 is mounted in the drum frame 20, the outer circumferential surface of the developer roller 10 comes into contact with the outer circumferential surface of the photosensitive drum 30. The toner in the developer cartridge 1 is supplied to the outer circumferential surface of the photosensitive drum 30 via the outer circumferential surface of the developer roller 10.

[0033] The belt unit 3 is a unit for transferring toner from the photosensitive drum 30 to printing paper. As shown in FIG. 1, the belt unit 3 has two pulleys 81, a transfer belt 82, and four transfer rollers 83. The transfer belt 82 is a circular flat belt. The transfer belt 82 is stretched between the two pulleys 81. The transfer rollers 83 come into contact with the inner surface of the transfer belt 82.

[0034] When the belt unit 3 is attached to the main body housing 101, the control unit 102 is electrically connected to the transfer roller 83. When the drum unit 2, which has the developer cartridge 1 attached, is attached to the main body housing 101 in which the belt unit 3 is attached, the photosensitive drum 30 comes into contact with the outer surface of the transfer belt 82. Then, a portion of the transfer belt 82 is sandwiched between the photosensitive drum 30 and the transfer roller 83.

[0035] When the image forming apparatus 100 is in use, the developing roller 10, the photosensitive drum 30, the two pulleys 81, and the transfer roller 83 all rotate. The toner in the developing cartridge 1 is supplied to the outer circumferential surface of the photosensitive drum 30 via the outer circumferential surface of the developing roller 10. The rotation of the two pulleys 81 also rotates the transfer belt 82. The printing paper moves together with the transfer belt 82 and is transported between the transfer belt 82 and the photosensitive drum 30. This causes the toner to be transferred from the photosensitive drum 30 to the printing paper.

[0036] The control unit 102 includes a processor and a memory, and controls the operation of each unit of the image forming apparatus 100 in accordance with a program stored in the memory.

[0037] <2. About the charger> 3 is a partial cross-sectional view of the drum unit 2. FIG. 3 shows a cross section perpendicular to the first direction. As shown in FIG. 3, the drum unit 2 has a charger 33. The charger 33 is a device that charges the outer peripheral surface of the photosensitive drum 30.

[0038] 3, the charger 33 includes a wire 31 and a grid 32. The wire 31 and the grid 32 are located near the outer circumferential surface of the photosensitive drum 30.

[0039] The wire 31 is a metal wire. The wire 31 extends in a first direction along the outer circumferential surface of the photosensitive drum 30. The wire 31 is disposed at a distance from the outer circumferential surface of the photosensitive drum 30. Both ends of the wire 31 in the first direction are supported by the drum frame 20.

[0040] The grid 32 is a metal plate with multiple holes. The grid 32 extends in the first direction along the outer circumferential surface of the photosensitive drum 30. The grid 32 is located between the outer circumferential surface of the photosensitive drum 30 and the wire 31. The grid 32 is supported by the drum frame 20.

[0041] 4 is a side view of the drum unit 2. As shown in FIG. 4, the drum unit 2 has a wire electrode 21 and a grid electrode 22. The wire electrode 21 is electrically connected to the wire 31 of the charger 33. The grid electrode 22 is electrically connected to the grid 32 of the charger 33. When the drum unit 2 with the developer cartridge 1 attached thereto is installed in the main body casing 101, the control unit 102 of the image forming apparatus 100 is electrically connected to the wire electrode 21 and the grid electrode 22.

[0042] During normal printing, the control unit 102 applies a wire voltage to the wire 31 via the wire electrode 21. Also, during normal printing, the control unit 102 applies a grid voltage to the grid 32 via the grid electrode 22. The grid voltage is a voltage different from the wire voltage. This causes a potential difference between the wire 31 and the grid 32 of the charger 33. This potential difference causes a corona discharge between the wire 31 and the grid 32. As a result, the outer peripheral surface of the photosensitive drum 30 is charged. The potential of the outer peripheral surface of the photosensitive drum 30 becomes the grid voltage.

[0043] <3. Paper dust collection> Fig. 5 is a cross-sectional view of the drum unit 2 taken along the line AA in Fig. 3. As shown in Figs. 3 and 5, the drum unit 2 has a first cleaning roller 40 and a first cleaning shaft 50.

[0044] The first cleaning roller 40 is a roller for cleaning the outer peripheral surface of the photosensitive drum 30. The first cleaning roller 40 is rotatable about a first axis A1 extending in a first direction. The first cleaning roller 40 has a first cleaning roller shaft 41 and a first cleaning roller body 42.

[0045] The first cleaning roller shaft 41 is a cylindrical member extending along the first axis A1. The first cleaning roller shaft 41 is formed of metal or conductive resin. The first cleaning roller shaft 41 penetrates the first cleaning roller body 42 and extends in a first direction. The first cleaning roller shaft 41 is rotatably supported by the drum frame 20.

[0046] The first cleaning roller body 42 is a cylindrical member centered on the first axis A1. The first cleaning roller body 42 is made of elastically deformable rubber or sponge. The first cleaning roller body 42 is fixed to the periphery of the first cleaning roller shaft 41. The outer peripheral surface of the first cleaning roller body 42 contacts the outer peripheral surface of the photosensitive drum 30.

[0047] 4, the drum unit 2 has a first cleaning roller electrode 23. The first cleaning roller electrode 23 is electrically connected to a first cleaning roller shaft 41. When the drum unit 2 with the developer cartridge 1 attached thereto is attached to the main body casing 101, the control unit 102 of the image forming apparatus 100 is electrically connected to the first cleaning roller electrode 23.

[0048] During normal printing, the control unit 102 applies a first cleaning roller voltage to the first cleaning roller shaft 41 via the first cleaning roller electrode 23. The first cleaning roller voltage is lower than the grid voltage. In other words, the potential of the first cleaning roller 40 is lower than the potential of the outer circumferential surface of the photosensitive drum 30. Therefore, an electric field is formed between the photosensitive drum 30 and the first cleaning roller 40, directed from the photosensitive drum 30 to the first cleaning roller 40.

[0049] The toner is positively charged. Therefore, after the toner is transferred from the photosensitive drum 30 to the printing paper, the toner remaining on the outer circumferential surface of the photosensitive drum 30 is moved from the outer circumferential surface of the photosensitive drum 30 to the outer circumferential surface of the first cleaning roller 40 by the electric field generated between the photosensitive drum 30 and the first cleaning roller shaft 41. This removes the toner from the outer circumferential surface of the photosensitive drum 30.

[0050] Furthermore, the outer peripheral surface of the first cleaning roller 40 rotates at a different rotation speed relative to the outer peripheral surface of the photosensitive drum 30. As a result, paper dust adhering to the outer peripheral surface of the photosensitive drum 30 is scraped off and transferred to the outer peripheral surface of the first cleaning roller 40.

[0051] The first cleaning shaft 50 is a member for removing paper dust from the first cleaning roller 40. The first cleaning shaft 50 is rotatable about a second axis A2 extending in the first direction. The first cleaning shaft 50 has a cylindrical shape extending in the first direction. The first cleaning shaft 50 is formed from metal or conductive resin. The first cleaning shaft 50 is rotatably supported by the drum frame 20. The outer peripheral surface of the first cleaning shaft 50 contacts the outer peripheral surface of the first cleaning roller 40.

[0052] 4, the drum unit 2 has a first cleaning shaft electrode 24. The first cleaning shaft electrode 24 is electrically connected to the first cleaning shaft 50. When the drum unit 2 with the developer cartridge 1 attached thereto is attached to the main body casing 101, the control unit 102 of the image forming apparatus 100 is electrically connected to the first cleaning shaft electrode 24.

[0053] During normal printing, the control unit 102 applies a first cleaning shaft voltage to the first cleaning shaft 50 via the first cleaning shaft electrode 24. The first cleaning shaft voltage is a voltage higher than the first cleaning roller voltage. That is, the potential (second potential) of the first cleaning shaft 50 is higher than the potential (first potential) of the first cleaning roller 40. Therefore, an electric field is formed between the first cleaning roller 40 and the first cleaning shaft 50, directed from the first cleaning shaft 50 to the first cleaning roller 40.

[0054] The paper dust is negatively charged. Therefore, the paper dust adhering to the outer peripheral surface of the first cleaning roller 40 moves from the outer peripheral surface of the first cleaning roller 40 to the outer peripheral surface of the first cleaning shaft 50 due to the electric field generated between the first cleaning roller 40 and the first cleaning shaft 50. This removes the paper dust from the outer peripheral surface of the first cleaning roller 40.

[0055] 3 and 5, the drum unit 2 also includes a paper dust collection box 60 and a sponge 61. The paper dust collection box 60 is a container that collects paper dust from the first cleaning shaft 50. The paper dust collection box 60 has an opening 62. The first cleaning shaft 50 is positioned in the opening 62.

[0056] The sponge 61 is attached to the edge of the opening 62 of the paper dust collection box 60. The sponge 61 is made of an elastic material such as urethane. The sponge 61 comes into contact with the outer circumferential surface of the first cleaning shaft 50. As a result, the paper dust adhering to the outer circumferential surface of the first cleaning shaft 50 is scraped off by the sponge 61 and collected in the paper dust collection box 60.

[0057] <4. Paper dust discharge> Next, a method for discharging paper dust from the paper dust collection box 60 will be described. Discharging paper dust is performed, for example, when recycling a used drum unit 2. In the following example, a case will be described in which paper dust is discharged from the paper dust collection box 60 in a state in which the drum unit 2 is attached to the main body housing 101 in which the belt unit 3 is attached.

[0058] Fig. 6 is a diagram showing how paper dust is discharged. As shown in Fig. 6, image forming apparatus 100 further includes a second cleaning roller 71, a second cleaning shaft 72, a paper dust discharge box 73, and a backup roller 74 in addition to the components described above.

[0059] The second cleaning roller 71 has a second cleaning roller shaft 711 and a second cleaning roller body 712. The second cleaning roller shaft 711 is cylindrical and extends in a first direction. The second cleaning roller shaft 711 is made of metal or conductive resin. The control unit 102 of the image forming apparatus 100 is electrically connected to the second cleaning roller shaft 711.

[0060] The second cleaning roller body 712 has a cylindrical shape extending in the first direction. The second cleaning roller body 712 is fixed to the periphery of the second cleaning roller shaft 711. The second cleaning roller body 712 is made of elastically deformable rubber or sponge. The outer peripheral surface of the second cleaning roller body 712 contacts the outer surface of the transfer belt 82.

[0061] The second cleaning shaft 72 is a member for removing paper dust from the second cleaning roller 71. The second cleaning shaft 72 is cylindrical and extends in the first direction. The second cleaning shaft 72 is formed of metal or conductive resin. The outer circumferential surface of the second cleaning shaft 72 contacts the outer circumferential surface of the second cleaning roller 71. The control unit 102 of the image forming apparatus 100 is electrically connected to the second cleaning shaft 72.

[0062] The paper dust discharge box 73 is a container that collects paper dust from the second cleaning shaft 72. The paper dust discharge box 73 has an opening 732. The second cleaning shaft 72 is positioned in the opening 732. The paper dust discharge box 73 also has a blade 731. The blade 731 is attached to the edge of the opening 732 of the paper dust discharge box 73. The blade 731 comes into contact with the outer circumferential surface of the second cleaning shaft 72. As a result, the paper dust adhering to the outer circumferential surface of the second cleaning shaft 72 is scraped off by the blade 731 and collected in the paper dust discharge box 73.

[0063] The backup roller 74 contacts the inner surface of the transfer belt 82. A portion of the transfer belt 82 is sandwiched between the second cleaning roller 71 and the backup roller 74. When the belt unit 3 is attached to the main body housing 101, the control unit 102 of the image forming apparatus 100 is electrically connected to the backup roller 74.

[0064] When paper dust is discharged from the paper dust collection box 60, the control unit 102 supplies voltage to the charger 33, the transfer roller 83, the first cleaning roller shaft 41, the first cleaning shaft 50, the second cleaning roller shaft 711, the second cleaning shaft 72, and the backup roller 74.

[0065] At this time, the potential of the first cleaning shaft 50 is set to a positive potential. Furthermore, the magnitude relationship between the potential of the first cleaning roller 40 and the potential of the first cleaning shaft 50 is reversed from that during normal printing. In other words, the potential of the first cleaning roller 40 is set higher than the potential of the first cleaning shaft 50.

[0066] Furthermore, the charger 33 makes the potential of the outer peripheral surface of the photosensitive drum 30 higher than the potential of the first cleaning roller 40. Furthermore, the potential of the transfer roller 83 is made higher than the potential of the outer peripheral surface of the photosensitive drum 30. Furthermore, the potential of the second cleaning roller 71 is made higher than the potential of the backup roller 74. Furthermore, the potential of the second cleaning shaft 72 is made higher than the potential of the second cleaning roller 71.

[0067] Then, while continuing to supply the above voltage, the control unit 102 rotates the photosensitive drum 30, the two pulleys 81, the transfer roller 83, the first cleaning roller 40, the first cleaning shaft 50, the second cleaning roller 71, the second cleaning shaft 72, and the backup roller 74.

[0068] The paper dust inside the paper dust collection box 60 is negatively charged. Therefore, the paper dust adheres to the outer peripheral surface of the first cleaning shaft 50, which is at a positive potential. Then, as the first cleaning shaft 50 rotates, the paper dust adhering to the outer peripheral surface of the first cleaning shaft 50 is transported between the first cleaning shaft 50 and the first cleaning roller 40.

[0069] Furthermore, the potential of the first cleaning roller 40 is higher than the potential of the first cleaning shaft 50. Therefore, an electric field is formed between the first cleaning shaft 50 and the first cleaning roller 40, directed from the first cleaning roller 40 to the first cleaning shaft 50. Therefore, the negatively charged paper dust moves from the outer circumferential surface of the first cleaning shaft 50 to the outer circumferential surface of the first cleaning roller 40. Then, the paper dust adhering to the outer circumferential surface of the first cleaning roller 40 is transported between the first cleaning roller 40 and the photosensitive drum 30 by the rotation of the first cleaning roller 40.

[0070] Furthermore, the potential of the outer peripheral surface of the photosensitive drum 30 is higher than the potential of the first cleaning roller 40. Therefore, an electric field is formed between the first cleaning roller 40 and the photosensitive drum 30, which is directed from the photosensitive drum 30 to the first cleaning roller 40. Therefore, the negatively charged paper dust moves from the outer peripheral surface of the first cleaning roller 40 to the outer peripheral surface of the photosensitive drum 30. Then, the paper dust adhering to the outer peripheral surface of the photosensitive drum 30 is transported between the photosensitive drum 30 and the transfer belt 82 by the rotation of the photosensitive drum 30.

[0071] Furthermore, the potential of transfer roller 83 is higher than the potential of the outer circumferential surface of photosensitive drum 30. Therefore, an electric field is formed between photosensitive drum 30 and transfer roller 83, directed from transfer roller 83 to photosensitive drum 30. Therefore, negatively charged paper dust moves from the outer circumferential surface of photosensitive drum 30 to the outer surface of transfer belt 82. Then, as transfer belt 82 rotates due to the rotation of two pulleys 81, paper dust adhering to transfer belt 82 is transported between second cleaning roller 71 and backup roller 74.

[0072] The potential of the second cleaning roller 71 is higher than the potential of the backup roller 74. Therefore, an electric field is formed between the backup roller 74 and the second cleaning roller 71, directed from the second cleaning roller 71 to the backup roller 74. Therefore, negatively charged paper dust moves from the outer surface of the transfer belt 82 to the outer circumferential surface of the second cleaning roller 71. Then, the paper dust adhering to the outer circumferential surface of the second cleaning roller 71 is transported between the second cleaning roller 71 and the second cleaning shaft 72 by the rotation of the second cleaning roller 71.

[0073] Furthermore, the potential of the second cleaning shaft 72 is higher than the potential of the second cleaning roller 71. Therefore, an electric field is formed between the second cleaning roller 71 and the second cleaning shaft 72, directed from the second cleaning shaft 72 to the second cleaning roller 71. Therefore, the negatively charged paper dust moves from the outer circumferential surface of the second cleaning roller 71 to the outer circumferential surface of the second cleaning shaft 72. Then, as the second cleaning shaft 72 rotates, the paper dust adhering to the outer circumferential surface of the second cleaning shaft 72 moves between the second cleaning shaft 72 and the blade 731.

[0074] The blade 731 scrapes off the paper dust adhering to the outer circumferential surface of the second cleaning shaft 72. As a result, the paper dust moves from the outer circumferential surface of the second cleaning shaft 72 into the paper dust discharge box 73.

[0075] As described above, in this embodiment, when paper dust is discharged from the paper dust collection box 60, the potential (third potential) of the first cleaning roller 40 is set higher than the potential (fourth potential) of the first cleaning shaft 50. This allows the paper dust to be moved from the paper dust collection box 60 to the first cleaning roller 40 via the first cleaning shaft 50. Therefore, the paper dust can be discharged from the paper dust collection box 60 without disassembling the drum unit 2. In other words, the paper dust can be discharged from the paper dust collection box 60 with the photosensitive drum 30, the first cleaning roller 40, the first cleaning shaft 50, and the paper dust collection box 60 still assembled to the drum frame 20.

[0076] In this embodiment, voltage is also supplied to the photosensitive drum 30, transfer roller 83, backup roller 74, second cleaning roller 71, and second cleaning shaft 72 as described above. This allows paper dust to be moved from the paper dust collection box 60 to the paper dust discharge box 73 via the first cleaning shaft 50, first cleaning roller 40, photosensitive drum 30, transfer belt 82, second cleaning roller 71, and second cleaning shaft 72. Therefore, paper dust can be discharged to the paper dust discharge box 73 without disassembling the drum unit 2.

[0077] <5. Variations> Although one embodiment has been described above, the present disclosure is not limited to the above embodiment.

[0078] <5-1. First modified example> In the above embodiment, the case where paper dust is discharged from paper dust collection box 60 with drum unit 2 attached to main body housing 101 has been described. However, paper dust may also be discharged from paper dust collection box 60 with drum unit 2 detached from main body housing 101.

[0079] In this case, a paper dust discharge device having a configuration equivalent to the two pulleys 81, transfer belt 82, transfer roller 83, second cleaning roller 71, second cleaning shaft 72, paper dust discharge box 73, and backup roller 74 described above may be connected to the drum unit 2. Then, similar to the above embodiment, the paper dust discharge device may supply voltage to each roller and rotate each roller to move paper dust from the paper dust collection box 60 to the paper dust discharge box 73.

[0080] <5-2. Second modified example> Furthermore, when paper dust is discharged from the paper dust collection box 60 with the drum unit 2 removed from the main body housing 101, a paper dust discharge device having only the second cleaning roller 71, the second cleaning shaft 72, and the paper dust discharge box 73 may be connected to the drum unit 2, as shown in FIG. 7.

[0081] In this case, the outer circumferential surface of the second cleaning roller 71 is brought into contact with the outer circumferential surface of the photosensitive drum 30. The paper dust discharge device supplies voltages to the charger 33, the first cleaning roller 40, the first cleaning shaft 50, the second cleaning roller 71, and the second cleaning shaft 72. At this time, the potential of the second cleaning roller 71 is made higher than the potential of the outer circumferential surface of the photosensitive drum 30. Then, while continuing to supply the voltages, the photosensitive drum 30, the first cleaning roller 40, the first cleaning shaft 50, the second cleaning roller 71, and the second cleaning shaft 72 are rotated.

[0082] <5-3.Third modified example> Furthermore, when paper dust is discharged from the paper dust collection box 60 with the drum unit 2 removed from the main body housing 101, the paper dust may be discharged with the drum unit 2 positioned so that the opening 62 of the paper dust collection box 60 faces downward. That is, the paper dust may be discharged with the opening 62 of the paper dust collection box 60 positioned lower in the direction of gravity than other parts of the paper dust collection box 60. In this way, the paper dust in the paper dust collection box 60 can be moved to the opening 62 by the action of gravity. This allows the paper dust in the paper dust collection box 60 to efficiently adhere to the first cleaning shaft 50. This allows the paper dust to be efficiently discharged from the paper dust collection box 60. <5-4. Other variations>

[0083] In the above embodiment, the drum unit 2 includes four photosensitive drums 30. However, the number of photosensitive drums 30 included in the drum unit 2 may be one to three, or may be five or more.

[0084] In the above embodiment, four developer cartridges 1 can be attached to the drum unit 2. However, the number of developer cartridges 1 that can be attached to the drum unit 2 may be one to three, or may be five or more.

[0085] For example, the drum unit 2 may include one photosensitive drum 30, one first cleaning roller 40, one first cleaning shaft 50, and one paper dust collection box 60. A plurality of drum units 2, each with one developer cartridge 1 attached, may be mountable in the main body casing 101.

[0086] Furthermore, the developing cartridge 1 does not necessarily have to have the developing roller 10. In that case, the drum unit 2 may have the developing roller 10.

[0087] Furthermore, the elements appearing in the above-described embodiment and modified examples may be combined as appropriate within the scope of not causing any contradiction. [Explanation of symbols]

[0088] 1: Developing cartridge 2: Drum unit 3: Belt unit 10: Developing roller 20: Drum frame 30: Photosensitive drum 33: Charger 40: First cleaning roller 50: First cleaning shaft 60: Paper dust collection box 61: Sponge 71: Second cleaning roller 72: Second cleaning shaft 73: Paper dust discharge box 74: Backup roller 82: Transfer belt 83: Transfer roller 100: Image forming device 101: Main body housing

Claims

1. During normal use, a first cleaning roller that contacts the photosensitive drum to collect paper dust on the photosensitive drum; a potential of a first cleaning shaft in contact with the first cleaning roller being set higher than a potential of the first cleaning roller, thereby collecting paper dust on the first cleaning roller onto the first cleaning shaft; A sponge in contact with the first cleaning shaft collects paper dust on the first cleaning shaft into a paper dust collection box. In the drum unit, a paper dust discharging method for discharging paper dust from the paper dust collection box in a state in which the photosensitive drum, the first cleaning roller, the first cleaning shaft, and the paper dust collection box are assembled to a drum frame of the drum unit, the method comprising: a paper dust discharging step of rotating the first cleaning roller and the first cleaning shaft while setting the potential of the first cleaning roller higher than the potential of the first cleaning shaft; A paper dust discharge method comprising the steps of:

2. The paper dust discharging method according to claim 1, The paper dust discharge method is characterized in that, in the paper dust discharge process, the photosensitive drum, the first cleaning roller, and the first cleaning shaft are rotated while a charger is used to make the potential of the photosensitive drum higher than the potential of the first cleaning roller.

3. The paper dust discharging method according to claim 2, The paper dust discharge method is characterized in that, in the paper dust discharge step, the drum unit is attached to an image forming device having a circular transfer belt, a portion of the transfer belt is sandwiched between the photosensitive drum and a transfer roller, and the transfer belt is rotated while the potential of the transfer roller is made higher than the potential of the photosensitive drum.

4. The paper dust discharging method according to claim 3, The paper dust discharge method is characterized in that, in the paper dust discharge step, another portion of the transfer belt is sandwiched between a second cleaning roller and a backup roller, and the transfer belt is rotated while the potential of the second cleaning roller is made higher than the potential of the backup roller.

5. The paper dust discharging method according to claim 2, The paper dust discharge method is characterized in that, in the paper dust discharge process, the photosensitive drum and a second cleaning roller are brought into contact with each other, and the photosensitive drum and the second cleaning roller are rotated while the potential of the second cleaning roller is set higher than the potential of the photosensitive drum.

6. The paper dust discharging method according to claim 4 or claim 5, The paper dust discharging method is characterized in that, in the paper dust discharging step, a second cleaning shaft is brought into contact with the second cleaning roller, and the second cleaning roller and the second cleaning shaft are rotated while the potential of the second cleaning shaft is made higher than the potential of the second cleaning roller.

7. The paper dust discharging method according to claim 6, The paper dust discharge method comprises scraping off paper dust adhering to the outer surface of the second cleaning shaft into a paper dust discharge box.

8. The paper dust discharging method according to any one of claims 1 to 5, The paper dust collection box has an opening, the first cleaning shaft is positioned in the opening, a paper dust discharging step of discharging the paper dust in a state in which the drum unit is positioned so that the opening of the paper dust collection box faces downward;

9. A main body housing; A drum unit that can be attached to the main body housing, A photosensitive drum; a first cleaning roller that contacts the photosensitive drum; a first cleaning shaft in contact with the first cleaning roller; a paper dust collection box having an opening in which the first cleaning shaft is positioned; a sponge in contact with the first cleaning shaft; a drum unit having An image forming apparatus comprising: a normal operation of applying a first potential to the first cleaning roller and applying a second potential higher than the first potential to the first cleaning shaft; a paper dust discharging operation in which a third potential is applied to the first cleaning roller and a fourth potential lower than the third potential is applied to the first cleaning shaft; An image forming apparatus characterized by being capable of executing the above.

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