Charging system and image forming system

Abstract

A charging system includes: a charging member that rotates by being driven by a rotating image holding body and charges the image holding body; a removal member that, in a state of being disposed at a contact position in contact with the charging member, rotates by being driven by the rotating charging member, and removes deposits adhering to the charging member; a moving member that moves the removing member to a separated position separated from the charging member and the contact position; and at least one processor that, when the moving member is controlled to be predetermined, moves the removal member disposed at the separation position to the contact position, and removes attachments attached to the charging member by the removal member only for a removal time.

Description

Technical Field

[0001] The present invention relates to a charging system and an image forming system. Background Art

[0002] The image forming device described in Patent Document 1 comprises: an image carrier on which an image is formed; a charging roller for charging the image carrier; a first supporting member for supporting the charging roller; a cleaning member for cleaning the charging roller; a second supporting member for supporting the first supporting member; and a moving member for moving the second supporting member, wherein the second supporting member supports the first supporting member so that the charging roller is moved to a printing position in contact with the surface of the image carrier and a retreat position in contact with the surface of the image carrier by the movement of the second supporting member.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2007-193207

[0004] There is a removing member for removing the attached matter attached to the rotating charging member. The removing member is always in contact with the charging member and is driven by the rotating charging member to rotate, thereby removing the attached matter attached to the charging member.

[0005] However, the deposits that remain on the charging member without being removed by the removing member are pressed against the charging member by the removing member that rotates while in contact with the charging member, thereby sometimes forming a layer of the deposits on the charging member. Summary of the invention

[0006] An object of the present invention is to suppress the formation of a layer of deposits on a charging member, compared with a case where a removing member that rotates following the driving of a charging member is always in contact with the charging member.

[0007] The charging system involved in the first embodiment of the present invention is characterized in that it comprises: a charging component that rotates driven by a rotating image holding body and charges the image holding body; a removing component that rotates driven by the rotating charging component and removes attached matter attached to the charging component when it is arranged at a contact position in contact with the charging component; a moving component that moves the removing component to a separation position separated from the charging component and the contact position; and at least one processor that controls the moving component to move the removing component arranged at the separation position to the contact position when it is predetermined, and removes attached matter attached to the charging component only during a removal time.

[0008] The charging system involved in the second embodiment of the present invention is characterized in that in the charging system described in the first embodiment, the processor performs the following processing: after the number of images formed on the image holding body since the last removal of the attached matter reaches a predetermined number, the removal component arranged at the separation position is moved to the contact position, and the attached matter attached to the charging component is removed by the removal component only during the removal time.

[0009] The charging system involved in the third aspect of the present invention is characterized in that in the charging system described in the first or second aspect, the processor performs the following processing: after the number of images since the last removal of the attached matter reaches a predetermined number and when no image is formed, the removal component arranged at the separation position is moved to the contact position.

[0010] The charging system involved in the fourth aspect of the present invention is characterized in that in the charging system described in the first aspect, the processor performs the following processing: after the number of cycles of the image retaining body since the last removal of the attached matter reaches a predetermined number, the removal component arranged at the separation position is moved to the contact position, and the attached matter attached to the charging component is removed by the removal component only during the removal time.

[0011] The charging system involved in the 5th aspect of the present invention is characterized in that in the charging system described in the 1st or 4th aspect, the processor performs the following processing: after the number of cycles since the last removal of the attached matter reaches a predetermined number and when no image is formed, the removal component arranged at the separation position is moved to the contact position.

[0012] The charging system involved in the sixth aspect of the present invention is characterized in that, in the charging system described in the first aspect, it includes a detection unit, which detects the resistance between the charging component and the image retaining body, and the processor performs the following processing: after the resistance rises by a predetermined amount since the last removal of the attached matter, the removal component arranged at the separation position is moved to the contact position, and the attached matter attached to the charging component is removed by the removal component only during the removal time.

[0013] The charging system involved in the 7th aspect of the present invention is characterized in that in the charging system described in the 1st or 6th aspect, the processor performs the following processing: after the increase in the resistance since the last removal of the attached matter reaches a predetermined threshold and when no image is formed, the removal component arranged at the separation position is moved to the contact position.

[0014] The charging system involved in the 8th aspect of the present invention is characterized in that in the charging system described in the 6th or 7th aspect, the processor performs the following processing: deriving the difference in resistance before and after the removal of the attachment, when the difference in resistance is small, extending the next removal time compared to the case where the difference in resistance is large.

[0015] The image forming system involved in the 9th mode of the present invention is characterized in that it comprises: a charging system described in any one of the 1st to 8th modes; an image retaining body, which is charged by the charging system and an image is formed thereon; and a transfer device, which transfers the image formed on the image retaining body to a recording medium.

[0016] Effects of the Invention

[0017] According to the charging system of the first aspect of the present invention, compared with a case where the removing member that rotates following the charging member is always in contact with the charging member, it is possible to suppress the formation of a layer of deposits on the charging member.

[0018] According to the charging system of the second aspect of the present invention, compared with the case where the deposits are removed at predetermined intervals, it is possible to suppress the formation of a layer of deposits on the charging member.

[0019] According to the charging system of the third aspect of the present invention, it is possible to suppress a decrease in image quality compared to a case where the removing member disposed at the separated position is moved to the contact position during image formation.

[0020] According to the charging system of the fourth aspect of the present invention, compared with the case where the deposits are removed at predetermined intervals, it is possible to effectively suppress the formation of a layer of deposits on the charging member.

[0021] According to the charging system of the fifth aspect of the present invention, it is possible to suppress a decrease in image quality compared to a case where the removing member disposed at the separated position is moved to the contact position during image formation.

[0022] According to the charging system of the sixth aspect of the present invention, compared with the case where the deposits are removed at predetermined intervals, it is possible to effectively suppress the formation of a layer of deposits on the charging member.

[0023] According to the charging system of the seventh aspect of the present invention, it is possible to suppress a decrease in image quality compared to a case where the removing member disposed at the separated position is moved to the contact position during image formation.

[0024] According to the charging system of the eighth aspect of the present invention, it is possible to more effectively remove the adhering matter adhering to the charging member, compared with a case where the removal time is always the same.

[0025] According to the image forming system of the ninth aspect of the present invention, compared with a case where a charging system is provided in which the removing member is always in contact with the charging member, it is possible to suppress density unevenness of an output image. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Embodiments of the present invention will be described in detail with reference to the following drawings.

[0027] Figure 1 is a schematic structural diagram showing an image forming apparatus according to a first embodiment of the present invention;

[0028] Figure 2 is a structural diagram showing an image forming unit and a transfer device included in an image forming apparatus according to a first embodiment of the present invention;

[0029] Figure 3 is a structural diagram showing a charging device according to a first embodiment of the present invention;

[0030] Figure 4 is a perspective view showing an end portion of a removal member provided in a charging device according to a first embodiment of the present invention;

[0031] exist Figure 5 middle, Figure 5 (A) Figure 5 (B) is a diagram showing the charging device according to the first embodiment of the present invention, and is a state diagram showing a state where the removal member is arranged at the contact position and a state where the removal member is arranged at the separation position;

[0032] exist Figure 6 middle, Figure 6 (A) Figure 6 (B) is a diagram showing a hardware configuration and a functional configuration of a control unit provided in the charging device according to the first embodiment of the present invention;

[0033] Figure 7 is a flowchart showing a process of removing attached matter attached to a charging roller of a charging device according to a first embodiment of the present invention;

[0034] Figure 8 is a diagram showing evaluation results of examples and comparative examples according to the first embodiment of the present invention in a graphical form;

[0035] Fig. 9 1 is a diagram showing in a table the evaluation results of examples and comparative examples according to the first embodiment of the present invention;

[0036] exist Fig.10 middle, Fig.10 (A) Fig.10(B) is a diagram showing a hardware configuration and a functional configuration of a control unit provided in a charging device according to a second embodiment of the present invention;

[0037] Fig.11 is a flowchart showing a process of removing attached matter attached to a charging roller of a charging device according to a second embodiment of the present invention;

[0038] Fig.12 is a structural diagram showing a charging device according to a third embodiment of the present invention;

[0039] exist Fig.13 middle, Fig.13 (A) Fig.13 (B) is a diagram showing a hardware configuration and a functional configuration of a control unit provided in a charging device according to a third embodiment of the present invention;

[0040] Fig.14 This is a flowchart showing a process of removing adhering matter adhering to the charging roller of the charging device according to the third embodiment of the present invention.

[0041] Explanation of symbols

[0042] 10-image forming device (an example of an image forming system), 22-charging device (an example of a charging system), 72-removing component, 80-moving component, 91-CPU (an example of a processor), 122-charging device (an example of a charging system), 191-CPU (an example of a processor), 222-charging device (an example of a charging system), 224-resistance detector (an example of a detection unit), 291-CPU (an example of a processor). DETAILED DESCRIPTION

[0043] <First embodiment>

[0044] according to Figures 1 to 9 An example of a charging device and an image forming device according to the first embodiment of the present invention is described. In addition, arrow H shown in the figure indicates the vertical direction of the device (vertical direction), arrow W indicates the width direction of the device (horizontal direction), and arrow D indicates the back side direction of the device (horizontal direction).

[0045] (Image Forming Device 10)

[0046] like Figure 1 As shown, the image forming apparatus 10 includes a first housing 12, a second housing 14, an image forming unit 16, a media transfer unit 50, a post-processing unit 60, and a control unit 68. The control unit 68 controls each unit (such as each unit constituting the image forming unit 16) constituting the image forming apparatus 10. The image forming apparatus 10 is an example of an image forming system.

[0047] Furthermore, the first housing 12 and the second housing 14 are arranged side by side in the device width direction and are connected by a connection mechanism 44 .

[0048] [Image forming unit 16]

[0049] The image forming unit 16 is as follows Figure 1 As shown in FIG. 1 , the first frame 12 is configured inside the first frame 12, and as shown in FIG. Figure 2 As shown in the figure, the image forming unit 16 includes a toner image forming unit 20 for forming a toner image, and a transfer device 30 for transferring the image formed by the toner image forming unit 20 to a sheet member P as a recording medium. In addition, the image forming unit 16 includes a fixing device 40 for fixing the toner image transferred to the sheet member P to the sheet member P. In addition, the image forming unit 16 forms an image on the sheet member P by an electrophotographic system.

[0050] -Toner Image Forming Unit 20-

[0051] like Figure 2 As shown, the toner image forming unit 20 is configured to include an image holder 21, a charging device 22, an exposure device 23, and a developing device 24. A plurality of toner image forming units 20 are provided to form toner images for each color. In the present embodiment, toner image forming units 20 of four colors, namely yellow (Y), magenta (M), cyan (C), and black (K), are provided. Furthermore, the toner image forming units 20 of each color are provided with the same structure, and the toner image forming units 20 of each color are arranged in the order of yellow (Y), magenta (M), cyan (C), and black (K) from the upstream side in the circling direction of the transfer belt 31 provided in the transfer device 30. Furthermore, the image holder 21 of each color is in contact with the transfer belt 31. Furthermore, the toner image forming units 20 of each color are arranged in the device width direction. In addition, when it is not necessary to distinguish Y, M, C, and K for description, Y, M, C, and K are sometimes omitted.

[0052] The image holder 21 is formed in a cylindrical shape and is driven to rotate around its own axis by a driving member (not shown). As an example, a photosensitive layer having a negative charging polarity is formed on the outer peripheral surface of the image holder 21. Alternatively, an outer coating layer may be formed on the outer peripheral surface of the image holder 21.

[0053] The charging device 22 includes a charging roller 70 as an example of a charging member, and the charging roller 70 contacts the outer peripheral surface (photosensitive layer) of the image holder 21, rotates while being driven by the rotating image holder 21, and charges the outer peripheral surface of the image holder 21 to a negative polarity. The charging device 22 is an example of a charging system. The charging device 22 will be described in detail later.

[0054] The exposure device 23 forms an electrostatic latent image on the outer peripheral surface of the image holding body 21. Specifically, the exposure light L modulated according to the image data is irradiated onto the outer peripheral surface of the image holding body 21 charged by the charging device 22. Then, an electrostatic latent image is formed on the outer peripheral surface of the image holding body 21 by the irradiation of the exposure light L.

[0055] The developing device 24 develops the electrostatic latent image formed on the outer peripheral surface of the image holding body 21 into a toner image using a developer G containing a toner T (an example of powder) and a carrier CA, thereby forming a toner image on the outer peripheral surface of the image holding body 21. A toner cartridge 39 for replenishing the toner T to the developing device 24 is connected to the developing device 24 via a conveying path (not shown). The toner cartridges 39 of each color are arranged above the exposure device 23 in the device width direction, and are individually detachable (replaceable) from the first frame 12.

[0056] The transfer device 30 includes an endless transfer belt 31 for transferring the toner image of each color of the image holder 21, and the transfer belt 31 is wound around a plurality of rollers 32 to determine the posture. In the present embodiment, the transfer belt 31 is set to a posture of an inverted obtuse triangle shape that is long in the device width direction when viewed from the front side.

[0057] The roller 32d among the plurality of rollers 32 functions as a driving roller that causes the transfer belt 31 to revolve in the direction of arrow A. Furthermore, the roller 32t among the plurality of rollers 32 functions as a tension applying roller that applies tension to the transfer belt 31. The roller 32b among the plurality of rollers 32 functions as an opposing roller of a secondary transfer roller 34 described later.

[0058] Further, primary transfer rollers 33 for transferring the toner image formed on the outer peripheral surface of the image holder 21 to the transfer belt 31 are arranged on the opposite side of the image holder 21 of each color across the transfer belt 31 .

[0059] Moreover, a secondary transfer roller 34 that transfers the toner image transferred onto the transfer belt 31 onto the sheet member P contacts the top of the lower end side forming the obtuse angle of the transfer belt 31 , and a transfer nip NT is formed between the transfer belt 31 and the secondary transfer roller 34 .

[0060] The fixing device 40 fixes the toner image to the sheet member P to which the toner image is transferred by the transfer device 30. In the present embodiment, the fixing device 40 fixes the toner image to the sheet member P by heating and pressing the toner image in the fixing nip NF.

[0061] [Media transmission unit 50]

[0062] like Figure 1 As shown, the medium conveying section 50 is configured to include: a medium supplying section 52 for supplying the sheet member P to the image forming section 16; and a medium discharging section 54 for discharging the sheet member P on which the image is formed. In addition, the medium conveying section 50 is configured to include: a medium returning section 58 for use when forming an image on both surfaces of the sheet member P; and an intermediate conveying section 59 for conveying the sheet member P from the transfer device 30 to the fixing device 40.

[0063] The medium supply section 52 supplies the sheet member P one by one to the transfer nip NT of the image forming section 16 according to the transfer timing. In contrast, the medium discharge section 54 discharges the sheet member P to which the toner image is fixed by the fixing device 40 to the outside of the device. Furthermore, when an image is formed on the other surface of the sheet member P to which the toner image is fixed on one surface, the medium return section 58 reverses the front and back of the sheet member P and returns it to the image forming section 16 (the medium supply section 52).

[0064] [Post-processing unit 60]

[0065] like Figure 1 As shown, the post-processing unit 60 is arranged inside the second frame 14, and is configured to include: a medium cooling unit 62 for cooling the sheet member P with an image formed thereon; a correction device 64 for correcting the curvature of the sheet member P; and an image inspection unit 66 for inspecting the image.

[0066] The components constituting the post-processing unit 60 are disposed in the medium discharge unit 54 of the medium conveying unit 50 . The medium cooling unit 62 , the correction device 64 , and the image inspection unit 66 are disposed in this order from the upstream side in the discharge direction of the sheet member P.

[0067] (Function of Image Forming Apparatus 10)

[0068] Next, an overview of an image forming process and a post-processing process performed on the sheet member P by the image forming apparatus 10 will be described.

[0069] When an image is formed on the sheet member P, the image holder 21 and the developing roller (not shown) included in the developing device 24 rotate, and the transfer belt 31 revolves. Furthermore, the pressure roller 42 included in the fixing device 40 rotates, and the fixing belt (not shown) revolves.

[0070] The image holders 21 of each color are charged by the charging device 22 while rotating. The exposure devices 23 of each color emit exposure light L of each color according to image data to expose the charged image holders 21 of each color. An electrostatic latent image is formed on the outer peripheral surface of the image holders 21 of each color. The electrostatic latent image formed on the image holders 21 of each color is developed into a toner image with the developer G supplied from the developing device 24. Thus, a toner image of a corresponding color among yellow (Y), magenta (M), cyan (C), and black (K) is formed on the image holders 21 of each color.

[0071] Then, the toner images of the respective colors formed on the image holders 21 of the respective colors are sequentially transferred to the circulating transfer belt 31 by the primary transfer rollers 33 of the respective colors. Thus, a toner image in which the toner images of four colors are superimposed is formed on the transfer belt 31. The toner image is conveyed to the transfer nip NT by the circulation of the transfer belt 31. In the transfer nip NT, the toner image is transferred from the transfer belt 31 to the conveyed sheet member P.

[0072] The sheet member P to which the toner image is transferred is transported from the transfer nip NT of the transfer device 30 to the fixing nip NF of the fixing device 40 by the intermediate transport portion 59. The fixing device 40 applies heat and pressure (fixing energy) to the sheet member P passing through the fixing nip NF. Thus, the toner image transferred to the sheet member P is fixed to the sheet member P.

[0073] The sheet member P heated by the fixing device 40 is first cooled in the medium cooling unit 62. Then, the sheet member P is corrected for warping by the correction device 64. The toner image fixed on the sheet member P is inspected for the presence and extent of toner density defects, image defects, image position defects, etc. by the image inspection unit 66. The sheet member P is discharged to the outside of the second housing 14 by the medium discharge unit 54.

[0074] On the other hand, when an image is formed on the non-image surface (rear surface) of the sheet member P on which no image is formed (in the case of double-sided printing), the conveying path of the sheet member P that has passed through the image inspection section 66 is switched from the medium discharge section 54 to the medium return section 58. As a result, the sheet member P is reversed and fed to the medium supply section 52. An image is formed (fixed) on the rear surface of the sheet member P through the same process as the above process, and the sheet member P is discharged to the outside of the second housing 14 by the medium discharge section 54.

[0075] (Main structure)

[0076] Next, the charging device 22 will be described.

[0077] like Figure 3As shown in FIG. 1 , the charging device 22 is disposed above the image holding body 21 and includes: a charging roller 70 for charging the outer peripheral surface of the image holding body 21 to negative polarity; and a removing member 72 for removing attached matter from the surface of the charging roller 70. Furthermore, the charging device 22 includes: a moving member 80 for rotatably supporting the removing member 72 and moving the removing member 72 to a position separated from the charging roller 70 and a position contacting with the charging roller 70; and a control unit 90 for controlling each unit (refer to FIG. 1 ). Figure 6 ).

[0078] [Charging roller 70]

[0079] like Figure 3 As shown, the charging roller 70 includes a cylindrical shaft member 70a extending in the rear side direction of the device and a cylindrical roller portion 70b penetrating the shaft member 70a. The charging roller 70 is an example of a charging member.

[0080] Then, the roller portion 70 b comes into contact with the outer peripheral surface of the image holding member 21 from above the image holding member 21 .

[0081] In this structure, the charging roller 70 rotates driven by the rotating image holding member 21. Then, the charging roller 70 charges the outer peripheral surface of the image holding member 21 by applying a voltage from a power source to the charging roller 70 rotating driven by the image holding member 21.

[0082] [Removal of component 72]

[0083] like Figure 3 As shown, the removal member 72 includes a core material 74 formed in a cylindrical shape extending in the direction of the rear side of the device, and a removal material 76 spirally wound around the outer peripheral surface of the core material 74 .

[0084] The removal material 76 contacts the outer peripheral surface of the charging roller 70 from above the charging roller 70. The core material 74 of the removal member 72 is rotatably supported by a pair of support members 82 disposed at both ends of the removal member 72. In other words, the core material 74 is rotatably supported by the support members 82 around the axis of the core material 74.

[0085] As an example, the core material 74 is formed of a resin material (e.g., polyacetal resin, etc.). Also, as an example, the removal material 76 is formed by foaming a polyurethane resin, and is formed into a rectangular cross-section in a free state not wound around the outer peripheral surface of the core material 74. Furthermore, the removal material 76 is fixed to the outer peripheral surface of the core material 74 by using a double-sided tape (not shown).

[0086] like Figure 4 As shown, at both ends of the core material 74, holes 78 extending in the axial direction of the core material 74 are formed (at Figure 4Only one side is shown in the figure). In addition, both ends of the removed material 76 are compressed in the thickness direction and are embedded in the hole portion 78.

[0087] In this structure, the removal material 76 contacts the roller portion 70 b of the rotating charging roller 70 , and the removal member 72 is driven to rotate, so that the removal material 76 scrapes and removes the attached matter attached to the roller portion 70 b .

[0088] [Moving part 80]

[0089] like Figure 3 As shown, the moving members 80 are respectively arranged at both end portions of the removing member 72. Each moving member 80 includes: a supporting member 82 for rotatably supporting the removing member 72; a solenoid 84 for moving the supporting member 82 in a direction of approaching and separating from the charging roller 70; and a pressing member 86 for pressing the removing member 72 toward the charging roller 70.

[0090] The support member 82 is formed in a rectangular parallelepiped shape and supports the core material 74 of the removal member 72 via a bearing. The solenoid 84 is arranged above the support member 82. The pressing member 86 is a compression coil spring extending in the vertical direction and is arranged between the support member 82 and the solenoid 84.

[0091] In this structure, when the solenoid 84 is not energized, Figure 5 As shown in (B) of FIG. 8 , the moving member 80 moves the removal material 76 to a separation position from the charging roller 70. On the other hand, if the solenoid 84 is energized, as shown in FIG. Figure 5 As shown in (A), the moving member 80 moves the removal material 76 to a contact position with the charging roller 70. Then, the removal member 72 moved to the contact position is driven by the rotating charging roller 70 to rotate, and scrapes and removes the attached matter attached to the charging roller 70.

[0092] [Control unit 90]

[0093] -Hardware Structure of Control Unit 90-

[0094] like Figure 6 As shown in (A) of FIG. 1 , the control unit 90 includes a CPU (Central Processing Unit) 91, a ROM (Read Only Memory) 92, a RAM (Random Access Memory) 93, a memory 94, and a communication interface (I / F) 95. Each component is connected to each other so as to be communicable via a bus 99. The CPU 91 is an example of a processor.

[0095] The CPU 91 is a central processing unit and executes various programs or controls various parts. That is, the CPU 91 reads the program from the ROM 92 or the memory 94 and executes the program using the RAM 93 as a work area. The CPU 91 controls each structure and performs various calculations according to the program stored in the ROM 92 or the memory 94.

[0096] In the present embodiment, for example, a driving program for energizing the solenoid 84 according to the print job information is stored in the ROM 92 or the memory 94 .

[0097] The RAM 93 temporarily stores programs and data as a work area. The memory 94 is composed of a HDD (Hard Disk Drive) or an SSD (Solid State Drive), and stores various programs including an operating system and various data.

[0098] The communication interface 95 is an interface for communicating with the solenoid 84 and the like, and for example, a standard such as Ethernet (registered trademark), FDDI, or Wi-Fi (registered trademark) can be used.

[0099] When the above-mentioned driver program is executed, the control unit 90 uses the above-mentioned hardware resources to realize various functions. Next, the functional structure of the control unit 90 that realizes various functions by the control unit 90 will be described.

[0100] - Functional structure of control unit 90 -

[0101] like Figure 6 As shown in (B) of FIG. 1 , the control unit 90 includes a receiving unit 96, a determining unit 97, and an operating unit 98. Each functional configuration is realized by the CPU 91 reading and executing a driver program stored in the ROM 92 or the memory 94. In addition, the details of the control unit 90 will be described together with the functions described later.

[0102] (The function of the main structure)

[0103] Next, use Figure 7 The flowchart of FIG. 1 is used to explain a removal process of removing the attached matter attached to the charging roller 70 using the removal member 72. In an initial state before entering the removal process, the removal member 72 is arranged at the separated position.

[0104] When receiving unit 96 of control unit 90 receives print job information to be executed by image forming apparatus 10 from control unit 68 of image forming apparatus 10 , determination unit 97 of control unit 90 determines whether the number of images since the last removal has reached a threshold value based on the print job information in step S100 .

[0105] Specifically, if the received print job is executed after the removal member 72 moves to the contact position and removes the attached matter on the charging roller 70, the determination unit 97 determines whether the cumulative number of images has reached a threshold value. In the present embodiment, as an example, the threshold value of the number of images is set to 50,000. That is, if the received print job is executed after the removal member 72 moves to the contact position and removes the attached matter on the charging roller 70, the determination unit 97 determines whether the cumulative number of images has reached 50,000. If the number of images has reached the threshold value, the process proceeds to step S200. If the number of images has not reached the threshold value, the process of step S100 is performed again.

[0106] In step S200, the receiving unit 96 receives the operation information of the image forming apparatus 10 from the control unit 68 of the image forming apparatus 10, and the determining unit 97 determines whether the print job is completed. If the print job is completed, the process moves to step S300. If the print job is not completed, the process of step S200 is performed again.

[0107] In step S300, the operation unit 98 energizes the solenoid 84 to move the open position (reference Figure 5 (B)) on the removal member 72 to the contact position (reference Figure 5 (A)) moves only for a predetermined time. The removal member 72 moving to the contact position is driven by the rotating charging roller 70 to rotate, scraping and removing the attached matter attached to the charging roller 70. In this embodiment, as an example, the time for which the removal member 72 is in the contact position is set to 120 [sec]. That is, the removal time for removing the attached matter is set to 120 [sec]. If 120 [sec] has passed since the removal member 72 moved to the contact position, the operation unit 98 sets the solenoid 84 to a non-energized state, so that the contact position (reference Figure 5 (A)) on the removal member 72 moves to the separation position (reference Figure 5 (B)). If the removal member 72 moves to the separation position, the process proceeds to step S400.

[0108] In step S400, the receiving unit 96 receives information on the existence of a print job to be executed by the image forming apparatus 10 from the control unit 68 of the image forming apparatus 10. If there is a print job, the process returns to step S100 and the above process is performed. On the other hand, if there is no print job, the operation of one example ends.

[0109] -Actual machine test-

[0110] Here, the following actual machine test was conducted using DocuCentreVI C7771 manufactured by FUJIFILM Business Innovation Corp. The evaluation conditions, evaluation items, and evaluation results of the actual machine test will be described below.

[0111] (1) Embodiment 1

[0112] Evaluation conditions

[0113] An image having an image density (area coverage) of 80% was printed on 250,000 sheets of A4 size paper using black.

[0114] In Example 1, the threshold value of the number of images is set to 50,000 (50 kPV). That is, the removal member 72 is moved to the contact position every 50,000 (50 kPV). Moreover, the removal time is set to 120 [sec]. That is, the contact state of the removal member 72 is maintained during 120 [sec].

[0115] Evaluation items

[0116] The volume resistivity of the charging roller 70 was measured every 50,000 sheets (50 kPV). The target value of the volume resistivity of the charging roller 70 after printing 250,000 sheets was less than 10.5 [Ω·cm].

[0117] The volume resistivity was calculated by extracting a sheet-shaped measurement sample from the measurement object, and applying a voltage adjusted so that the electric field (applied voltage / composition sheet thickness) became 1000 V / cm for 30 seconds to the measurement sample using a measurement jig (R12702A / B resistivity test box: manufactured by ADVANTEST CORPORATION) and a high resistance measuring device (R8340A digital high resistance meter / micro ammeter: manufactured by ADVANTEST CORPORATION) in accordance with JIS K 6911 (1995). The current flowing therefrom was then calculated using the following formula.

[0118] Volume resistivity (Ω·cm) = (19.63×applied voltage (V)) / (current value (A)×measurement sample thickness (cm))

[0119] Furthermore, after printing 250,000 sheets (250 kPV), the change in volume resistivity of the charging roller 70 was derived. In addition, the target value of the change in volume resistivity after printing 250,000 sheets (250 kPV) was less than 2.0 [Ω·cm].

[0120] After printing 250,000 sheets (250 kPV), the thickness of the deposits (discharge products, external additives, etc.) accumulated on the charging roller 70 was measured by SEM observation. The target value of the thickness of the deposit layer after printing 250,000 sheets (250 kPV) was less than 2.0 [μm].

[0121] The level of density unevenness of the output image caused by the contamination of the charging roller 70 was evaluated in four stages: A, B, C, and D. The level of density unevenness was evaluated by visually observing the output image, with "A" indicating a level acceptable for commercial products, and "B", "C", and "D" indicating levels that were unacceptable for commercial products and in descending order of degree of unacceptability.

[0122] Evaluation results

[0123] The change in volume resistivity of the charging roller 70 of Example 1 is described in Figure 8 In the graph shown in FIG. The horizontal axis of the graph is the number of printed sheets (number of images), and the vertical axis is the volume resistivity. Moreover, the solid line in the graph represents the change in the volume resistivity of the charging roller 70 of Example 1. Moreover, regarding the dotted line in the graph, in Example 1, in order to understand the change in the volume resistivity before and after the removal of the attached matter, it represents the volume resistivity from the previous attached matter removal process to the volume resistivity before the next attached matter removal process.

[0124] As can be seen from the graph, in Example 1, the volume resistivity of the charging roller 70 after printing 250,000 sheets (250 kPV) was less than 10.5 [Ω·cm], which met the target.

[0125] Furthermore, in Example 1, the volume resistivity of the charging roller 70 after printing 250,000 sheets (250 kPV) is changed as shown in FIG. Fig. 9 As shown in the table, it was 0.1 [Ω·cm], which satisfied the target.

[0126] Furthermore, in Example 1, the thickness of the layer of the attached matter on the charging roller 70 after printing 250,000 sheets (250 kPV) is as follows: Fig. 9 As shown in the table, it is 0.0 [μm]. Thus, the thickness of the layer of the deposit is less than 2.0 [μm], which satisfies the target.

[0127] Furthermore, in Example 1, after printing 250,000 sheets (250 kPV), the level of density unevenness of the output image is as follows: Fig. 9 As described in the table, it is "A". That is, the density unevenness is at a level that is acceptable for commercial use.

[0128] (2) Embodiment 2

[0129] Evaluation conditions

[0130] In Example 2, the threshold value of the number of images is set to 5,000 (5kPV). That is, the removal member 72 is moved to the contact position every 5,000 (5kPV). In addition, the removal time is set to 60 [sec]. That is, the contact state of the removal member 72 is maintained during 60 [sec]. In addition, the other conditions are the same as those in Example 1.

[0131] Evaluation items

[0132] The evaluation items were the same as those in Example 1.

[0133] Evaluation results

[0134] The change in volume resistivity of the charging roller 70 of Example 2 is described in Figure 8 Specifically, the single-dot chain line in the graph represents the change in volume resistivity of the charging roller 70 of Example 2. As can be seen from the graph, in Example 2, the volume resistivity of the charging roller 70 after printing 250,000 sheets (250 kPV) is less than 10.5 [Ω·cm], which meets the target.

[0135] Furthermore, in Embodiment 2, the volume resistivity of the charging roller 70 after printing 250,000 sheets (250 kPV) is changed as shown in FIG. Fig. 9 As shown in the table, it was 0.5 [Ω·cm], which satisfied the target.

[0136] Furthermore, in Example 2, the thickness of the layer of the attached matter on the charging roller 70 after printing 250,000 sheets (250 kPV) is as follows: Fig. 9 As shown in the table, it is 0.5 [μm]. Thus, the thickness of the layer of the deposit is less than 2.0 [μm], which meets the target.

[0137] Furthermore, in Example 2, after printing 250,000 sheets (250 kPV), the level of density unevenness of the output image is as follows: Fig. 9 As described in the table, it is "A". That is, the density unevenness is at a level that is acceptable for commercial use.

[0138] (3) Embodiment 3

[0139] Evaluation conditions

[0140] In Example 3, the threshold value of the number of images is set to 100 images (100 PV). That is, the removal member 72 is moved to the contact position every 100 images (100 PV). In addition, the removal time is set to 10 [sec]. That is, the contact state of the removal member 72 is maintained during 10 [sec]. In addition, the other conditions are the same as those in Example 1.

[0141] Evaluation items

[0142] The evaluation items were the same as those in Example 1.

[0143] Evaluation results

[0144] The change in volume resistivity of the charging roller 70 of Example 3 is described in Figure 8 Specifically, the double-dashed line in the graph represents the change in volume resistivity of the charging roller 70 of Example 3. As can be seen from the graph, in Example 3, the volume resistivity of the charging roller 70 after printing 250,000 sheets (250 kPV) is less than 10.5 [Ω·cm], which meets the target.

[0145] Furthermore, in Embodiment 3, the volume resistivity of the charging roller 70 after printing 250,000 sheets (250 kPV) is changed as shown in FIG. Fig. 9 As shown in the table, it was 1.7 [Ω·cm], which satisfied the target.

[0146] Furthermore, in Example 3, the thickness of the layer of the attached matter on the charging roller 70 after printing 250,000 sheets (250 kPV) is as follows: Fig. 9 As shown in the table, it is 1.0 [μm]. Thus, the thickness of the layer of the deposit is less than 2.0 [μm], which satisfies the target.

[0147] Furthermore, in Example 3, after printing 250,000 sheets (250 kPV), the level of density unevenness of the output image is as follows: Fig. 9 As described in the table, it is "A". That is, the density unevenness is at a level that is acceptable for commercial use.

[0148] (4) Comparative Example

[0149] Evaluation conditions

[0150] In the comparative example, the removal member 72 is kept moved to the contact position. That is, the removal member 72 is kept in contact with the charging roller 70 at all times.

[0151] Evaluation items

[0152] The evaluation items were the same as those in Example 1.

[0153] Evaluation results

[0154] The change in volume resistivity of the charging roller 70 of the comparative example is described in Figure 8 Specifically, the dotted line in the graph represents the change in volume resistivity of the charging roller 70 of the comparative example. As can be seen from the graph, in the comparative example, the volume resistivity of the charging roller 70 after printing 250,000 sheets (250 kPV) was 10.5 [Ω·cm] or more, which did not meet the target.

[0155] Furthermore, in the comparative example, the volume resistivity of the charging roller 70 after printing 250,000 sheets (250 kPV) is changed as shown in FIG. Fig. 9 As shown in the table, it was 2.6 [Ω·cm], which did not meet the target.

[0156] In the comparative example, the thickness of the layer of the attached matter on the charging roller 70 after printing 250,000 sheets (250 kPV) is as follows: Fig. 9 As shown in the table, it is 2.0 [μm]. Thus, the thickness of the layer of the deposit is 2.0 [μm] or more, which does not meet the target.

[0157] In the comparative example, after printing 250,000 sheets (250 kPV), the level of density unevenness of the output image is as follows: Fig. 9 As shown in the table, it is "C". That is, the density unevenness is not at a level that can be tolerated in commercial products.

[0158] The following will examine the reasons why the thickness of the layer of the deposit on the charging roller 70 increases and the volume resistivity of the charging roller 70 increases in the comparative example.

[0159] The removal member 72 at the contact position is driven by the charging roller 70 and rotates, thereby removing the attached matter attached to the charging roller 70. However, since the removal member 72 is always arranged at the contact position, the attached matter that cannot be removed by the removal member 72 and remains on the charging roller 70 is pressed against the charging roller 70 by the removal member 72, and forms a layer on the surface of the charging roller 70 and is fixed, thereby forming a thin film. Therefore, it is considered that in the comparative example, the thickness of the attached matter on the charging roller 70 is thickened and the volume resistivity of the charging roller 70 is increased.

[0160] (Summarize)

[0161] As described above, in the charging device 22, the CPU 91 of the control unit 90 controls the moving member 80 to move the removal member 72 disposed at the separated position to the contact position at a predetermined time, and removes the attached matter attached to the charging roller 70 by the removal member 72 only during the removal time. Thus, compared with the case where the removal member driven by the charging roller and rotating is always in contact with the charging roller as in the comparative example, the formation of a layer of attached matter on the surface of the charging roller 70 is suppressed.

[0162] Furthermore, in the charging device 22, after the number of images from the last removal of the attached matter reaches a predetermined number, the removal member 72 disposed at the separation position is moved to the contact position, and the attached matter attached to the charging roller 70 is removed by the removal member 72 only during the removal time. Thus, compared with the case where the attached matter is removed at predetermined intervals, the formation of a layer of the attached matter on the surface of the charging roller 70 is effectively suppressed.

[0163] Furthermore, in the charging device 22, after the number of images since the last removal of the attached matter reaches a predetermined number and when no image is formed, the removal member 72 disposed at the separated position is moved to the contact position, and the attached matter attached to the charging roller 70 is removed by the removal member 72 only during the removal time. Thus, compared with the case where the removal member disposed at the separated position is moved to the contact position when forming an image, the rotation of the charging roller 70 when forming an image is stabilized, thereby suppressing the reduction in image quality. Here, when no image is formed is a state where a printing job is not performed.

[0164] Furthermore, in the image forming apparatus 10 , by providing the charging device 22 , density unevenness of the output image can be suppressed compared to the case where the charging device in which the removing member is always in contact with the charging roller is provided.

[0165] <Second embodiment>

[0166] Next, follow Fig.10 , Fig.11 An example of a charging device and an image forming apparatus according to a second embodiment will be described. The second embodiment will be described mainly focusing on the parts that are different from the first embodiment.

[0167] [Control unit 190]

[0168] -Hardware Configuration of Control Unit 190-

[0169] like Fig.10As shown in (A), the control unit 190 of the charging device 122 of the second embodiment includes a CPU (Central Processing Unit) 191, a ROM (Read Only Memory) 192, a RAM (Random Access Memory) 193, a memory 194, and a communication interface (I / F) 195. Moreover, each structure is connected to each other via a bus 199 so as to be communicable. The charging device 122 is an example of a charging system, and the CPU 191 is an example of a processor.

[0170] - Functional structure of control unit 190 -

[0171] like Fig.10 As shown in (B) of FIG. 1 , the control unit 190 includes a receiving unit 196, a determining unit 197, and an operating unit 198. Each functional configuration is implemented by the CPU 191 reading and executing a driver program stored in the ROM 192 or the memory 194. In addition, the details of the control unit 190 will be described together with the functions described later.

[0172] (The function of the main structure)

[0173] Next, use Fig.11 The flowchart of FIG. 1 is used to explain a removal process of removing the attached matter attached to the charging roller 70 using the removing member 72 .

[0174] If the receiving unit 196 of the control unit 190 receives the printing job information to be executed by the image forming device 10 in the future from the control unit 68 of the image forming device 10, then in step S1100, the determining unit 197 of the control unit 190 determines whether the number of cycles (rotation speed) of the image retaining body 21 since the last removal has reached a threshold value based on the printing job information.

[0175] Specifically, if the received print job is executed after the removal member 72 moves to the contact position and removes the attached matter on the charging roller 70, the determination unit 197 determines whether the number of cycles of the image holder 21 has reached the threshold value. In the present embodiment, as an example, the threshold value of the number of cycles of the image holder 21 is 200,000〔cycle〕. That is, if the received print job is executed after the removal member 72 moves to the contact position and removes the attached matter on the charging roller 70, the determination unit 197 determines whether the cumulative number of cycles of the image holder 21 has reached 200,000〔cycle〕 (200kcycle).

[0176] When the number of cycles of the image holding member 21 reaches 200,000 (200 kcycle), the process proceeds to step S1200. When the number of cycles of the image holding member 21 does not reach 200,000 (200 kcycle), the process of step S1100 is performed again.

[0177] In step S1200, receiving unit 196 receives operation information of image forming apparatus 10 from control unit 68 of image forming apparatus 10, and determining unit 197 determines whether the print job is completed. If the print job is completed, the process moves to step S1300. If the print job is not completed, the process of step S1200 is performed again.

[0178] In step S1300, the operation unit 198 energizes the solenoid 84 to move the open position (reference Figure 5 (B)) on the removal member 72 to the contact position (reference Figure 5 (A)) moves only for a predetermined time. The removal member 72 moving to the contact position is driven by the rotating charging roller 70 to rotate, scraping and removing the attached matter attached to the charging roller 70. In this embodiment, as an example, the predetermined time for the number of images is set to 120 [sec]. That is, the removal time for removing the attached matter is set to 120 [sec]. If 120 [sec] has passed since the removal member 72 moved to the contact position, the operation unit 198 sets the solenoid 84 to a non-energized state, so that the contact position (reference Figure 5 (A)) on the removal member 72 moves to the separation position (reference Figure 5 (B)). If the removal member 72 moves to the separation position, the process proceeds to step S1400.

[0179] In step S1400, receiving unit 196 receives information on the existence of a print job to be executed by image forming apparatus 10 from control unit 68 of image forming apparatus 10. If there is a print job, the process returns to step S1100 and the above process is performed. On the other hand, if there is no print job, the operation of one example ends.

[0180] -Actual machine test-

[0181] The following actual machine test was conducted using DocuCentreVI C7771 manufactured by FUJIFILM Business Innovation Corp. The conditions, evaluation items, and evaluation results of the actual machine test are described below.

[0182] (1) Embodiment 4

[0183] Evaluation conditions

[0184] In Example 4, the threshold value of the number of cycles of the image holding member 21 is set to 200,000 [cycle] (200 kcycle).

[0185] That is, the removing member 72 is moved to the contact position every 200,000 cycles (200 kcycles).

[0186] The removal time was set to 120 [sec]. That is, the contact state of the removal member 72 was maintained for 120 [sec]. Other conditions were the same as those of the first embodiment.

[0187] Evaluation items

[0188] The evaluation items were the same as those in Example 1.

[0189] Evaluation results

[0190] In Example 4, the volume resistivity of the charging roller 70 after printing 250,000 sheets (250 kPV) is changed as shown in FIG. Fig. 9 As shown in the table, it was 0.2 [Ω·cm], which satisfied the target.

[0191] Furthermore, in Embodiment 4, the thickness of the layer of the attached matter on the charging roller 70 after printing 250,000 sheets (250 kPV) is as follows: Fig. 9 As shown in the table, it is 0.2 [μm]. Thus, the thickness of the layer of the deposit is less than 2.0 [μm], which meets the target.

[0192] Furthermore, in Example 4, after printing 250,000 sheets (250 kPV), the level of density unevenness of the output image is as follows: Fig. 9 As described in the table, it is "A". That is, the density unevenness is at a level that is acceptable for commercial use.

[0193] (Summarize)

[0194] As described above, in the charging device 122, after the number of cycles of the image holding body 21 since the last removal of the attached matter reaches a predetermined number, the removal member 72 disposed at the separation position is moved to the contact position, and the attached matter attached to the charging roller 70 is removed by the removal member 72 only during the removal time. Thus, compared with the case where the attached matter is removed at predetermined intervals, the formation of a layer of the attached matter on the surface of the charging roller 70 is effectively suppressed.

[0195] Furthermore, in the charging device 122, after the number of cycles of the image holding body 21 since the last removal of the attached matter reaches a predetermined number and when no image is formed, the removal member 72 disposed at the separated position is moved to the contact position, and the attached matter attached to the charging roller 70 is removed by the removal member 72 only during the removal time. Thus, compared with the case where the removal member disposed at the separated position is moved to the contact position when forming an image, the rotation of the charging roller 70 is stabilized when forming an image, thereby suppressing the reduction of image quality.

[0196] <Third embodiment>

[0197] Next, follow Fig.12 , Fig.13 An example of a charging device and an image forming apparatus according to a third embodiment will be described. The third embodiment will be described mainly focusing on the parts that are different from the first embodiment.

[0198] like Fig.12 As shown, the charging device 222 according to the third embodiment includes a resistance detector 224 for detecting the resistance between the charging roller 70 and the image holding member 21. The charging device 222 is an example of a charging system, and the resistance detector 224 is an example of a detection unit.

[0199] [Control Unit 290]

[0200] -Hardware Configuration of Control Unit 290-

[0201] like Fig.13 As shown in (A) of FIG. 2 , the control unit 290 of the charging device 222 includes a CPU (Central Processing Unit) 291, a ROM (Read Only Memory) 292, a RAM (Random Access Memory) 293, a memory 294, and a communication interface (I / F) 295. The components are connected to each other so as to be communicable via a bus 299. The CPU 291 is an example of a processor.

[0202] - Functional structure of control unit 290 -

[0203] like Fig.13 As shown in (B) of FIG. 2 , the control unit 290 includes a receiving unit 296, a determining unit 297, and an operating unit 298. Each functional configuration is implemented by the CPU 291 reading and executing a driver program stored in the ROM 292 or the memory 294. In addition, the details of the control unit 290 will be described together with the functions described later.

[0204] (The function of the main structure)

[0205] Next, use Fig.14 The flowchart of FIG. 1 is used to explain a removal process of removing the attached matter attached to the charging roller 70 using the removing member 72 .

[0206] If the receiving unit 296 of the control unit 290 receives printing job information to be executed by the image forming device 10 in the future from the control unit 68 of the image forming device 10, and receives the resistance between the charging roller 70 and the image holder 21 after the last removal of the attachment from the resistance detector 224, then in step S2100, the receiving unit 296 monitors the resistance detected from the resistance detector 224 when the image is formed, and the determination unit 297 determines whether the resistance has increased by a predetermined amount since the last removal based on the monitored resistance.

[0207] Specifically, the determination unit 297 determines whether the amount of increase in resistance reaches a threshold value after the removal member 72 moves to the contact position and removes the deposits on the charging roller 70. In the present embodiment, as an example, the threshold value of the amount of increase in resistance is 1.0〔logΩ〕. That is, the determination unit 297 determines whether the amount of increase in resistance reaches 1.0〔logΩ〕 after the removal member 72 moves to the contact position and removes the deposits on the charging roller 70. If the amount of increase in resistance reaches 1.0〔logΩ〕, the process is transferred to step S2200. If the amount of increase in resistance does not reach 1.0〔logΩ〕, the process of step S2100 is performed again.

[0208] In step S2200, the receiving unit 296 receives the operation information of the image forming apparatus 10 from the control unit 68 of the image forming apparatus 10, and the determining unit 297 determines whether the print job is completed. If the print job is completed, the process moves to step S2300. If the print job is not completed, the process of step S2200 is performed again.

[0209] In step S2300, the operation unit 298 energizes the solenoid 84 to move the open position (reference Figure 5 (B)) on the removal member 72 to the contact position (reference Figure 5 (A)) moves only for a predetermined time. The removal member 72 moving to the contact position is driven by the rotating charging roller 70 to rotate, scraping and removing the attached matter attached to the charging roller 70. In this embodiment, as an example, the predetermined time for the number of images is set to 60 [sec]. That is, the removal time for removing the attached matter is set to 60 [sec]. If 60 [sec] has passed since the removal member 72 moved to the contact position, the operation unit 298 sets the solenoid 84 to a non-energized state, so that the contact position (reference Figure 5 (A)) on the removal member 72 moves to the separation position (reference Figure 5(B)). If the removal member 72 moves to the separation position, the process proceeds to step S2400.

[0210] In step S2400, the receiving unit 296 receives information on the existence of a print job to be executed by the image forming apparatus 10 from the control unit 68 of the image forming apparatus 10. If there is a print job, the process returns to step S2100 and the above process is performed. On the other hand, if there is no print job, the operation of one example ends.

[0211] In step S2300, the removal time is set to 60 [sec], but the control unit 290 may derive the difference in resistance before and after the removal of the attached matter, and when the difference in resistance is small, the next removal time may be extended compared to when the difference in resistance is large. In this way, the attached matter attached to the charging roller 70 can be removed more effectively than when the removal time is always the same.

[0212] -Actual machine test-

[0213] The following actual machine test was conducted using DocuCentreVI C7771 manufactured by FUJIFILM Business Innovation Corp. The specifications, evaluation items, and evaluation results of the actual machine test are described below.

[0214] (1) Embodiment 5

[0215] Evaluation conditions

[0216] In Example 5, the threshold value of the resistance increase is set to 1.0 [logΩ]. That is, every time the resistance increases by 1.0 [logΩ], the removal member 72 is moved to the contact position. In addition, the removal time is set to 60 [sec]. That is, the contact state of the removal member 72 is maintained during 60 [sec]. In addition, the other conditions are the same as those of Example 1.

[0217] Evaluation items

[0218] The evaluation items were the same as those in Example 1.

[0219] Evaluation results

[0220] In Example 5, the volume resistivity of the charging roller 70 after printing 250,000 sheets (250 kPV) is changed as shown in FIG. Fig. 9 As shown in the table, it was 0.4 [Ω·cm], which satisfied the target.

[0221] Furthermore, in Example 5, the thickness of the layer of the attached matter on the charging roller 70 after printing 250,000 sheets (250 kPV) is as follows: Fig. 9As shown in the table, it is 0.4 [μm]. Thus, the thickness of the layer of the deposit is less than 2.0 [μm], which meets the target.

[0222] Furthermore, in Example 5, after printing 250,000 sheets (250 kPV), the level of density unevenness of the output image is as follows: Fig. 9 As described in the table, it is "A". That is, the density unevenness is at a level that is acceptable for commercial use.

[0223] (Summarize)

[0224] As described above, in the charging device 222, after the resistance increases by a predetermined amount since the last removal of the attached matter, the removal member 72 disposed at the separated position is moved to the contact position, and the attached matter attached to the charging roller 70 is removed by the removal member 72 only during the removal time. Thus, compared with the case where the attached matter is removed at predetermined intervals, the formation of a layer of the attached matter on the surface of the charging roller 70 is effectively suppressed.

[0225] Furthermore, in the charging device 222, after the resistance has risen by a predetermined amount since the last removal of the attached matter and when an image is not formed, the removal member 72 disposed at the separated position is moved to the contact position, and the attached matter attached to the charging roller 70 is removed by the removal member 72 only during the removal time. Thus, compared with the case where the removal member disposed at the separated position is moved to the contact position when an image is formed, the rotation of the charging roller 70 is stabilized when an image is formed, thereby suppressing the reduction in image quality.

[0226] In addition, with respect to the present invention, a specific embodiment has been described in detail, but the present invention is not limited to the embodiment, and various other embodiments can be adopted within the scope of the present invention, which is clear to those skilled in the art. For example, in the above-mentioned embodiment, the removal action of removing the attached matter is performed when the image is not formed, but the removal action of removing the attached matter can also be performed when the image is formed. However, in this case, the effect exerted by removing the attached matter when the image is not formed is not exerted.

[0227] Furthermore, in the above embodiment, although not specifically described, the removal operation may be performed at predetermined intervals. However, in this case, the effect of performing the removal operation according to the number of images, the number of cycles of the image holder 21, or the amount of resistance increase is not achieved.

[0228] Furthermore, the threshold value of the number of images described in the first embodiment is just an example, and other threshold values ​​may be used.

[0229] Furthermore, the threshold value of the number of cycles of the image holding member 21 described in the second embodiment is an example, and other threshold values ​​may be used.

[0230] Furthermore, the threshold value of the amount of increase in resistance described in the third embodiment is an example, and other threshold values ​​may be used.

[0231] Furthermore, in the above-mentioned embodiment, the removal time is described as an example, but the actual removal time may be shorter or longer than the described removal time.

[0232] Furthermore, in the above embodiments, the control units 90 , 190 , 290 of the charging devices 22 , 122 , 222 are provided separately from the control unit 68 of the image forming apparatus 10 . However, the control unit of the charging device may constitute a part of the control unit 68 of the image forming apparatus 10 .

[0233] Furthermore, in the above-described embodiment, although not particularly described, the charging devices 22 , 122 , 222 and the image forming device 10 may be constituted by a single device or by a plurality of devices. (1)

[0235] A charging system comprising:

[0236] a charging member that rotates following the rotation of the image holding member and charges the image holding member;

[0237] a removing member which, when arranged at a contact position with the charging member, is driven by the rotating charging member to rotate and removes the attached matter attached to the charging member;

[0238] a moving member that moves the removing member to a separated position from the charging member and to the contact position; and

[0239] at least one processor,

[0240] The processor controls the moving member to move the removing member disposed at the separated position to the contact position at a predetermined time, and removes the attached matter attached to the charging member by the removing member only during a removal time. (2)

[0242] The charging system according to (1), wherein:

[0243] The processor performs the following processing:

[0244] After the number of images formed on the image holding body since the last removal of the attached matter reaches a predetermined number, the removal member arranged at the separation position is moved to the contact position, and the attached matter attached to the charging member is removed by the removal member only during the removal time. (3)

[0246] The charging system according to (1) or (2), wherein:

[0247] The processor performs the following processing:

[0248] After the number of images since the last removal of attached matter reaches a predetermined number and when no image is formed, the removal member disposed at the separated position is moved to the contact position. (4)

[0250] The charging system according to (1), wherein:

[0251] The processor performs the following processing:

[0252] After the number of cycles of the image holding body since the last removal of the attached matter reaches a predetermined number, the removal member arranged at the separation position is moved to the contact position, and the attached matter attached to the charging member is removed by the removal member only during the removal time. (5)

[0254] The charging system according to (1) or (4), wherein:

[0255] The processor performs the following processing:

[0256] After the number of cycles since the last removal of the attached matter reaches a predetermined number of times and when an image is not formed, the removal member disposed at the separated position is moved to the contact position. (6)

[0258] The charging system according to (1), comprising a detection unit configured to detect the electrical resistance between the charging member and the image holding member.

[0259] The processor performs the following processing:

[0260] After the resistance increases by a predetermined amount since the last removal of the attached matter, the removal member disposed at the separation position is moved to the contact position, and the attached matter attached to the charging member is removed by the removal member only during the removal time. (7)

[0262] The charging system according to (1) or (6), wherein:

[0263] The processor performs the following processing:

[0264] After the increase in the resistance since the last removal of the attached matter reaches a predetermined threshold value and when an image is not formed, the removal member disposed at the separated position is moved to the contact position. (8)

[0266] The charging system according to (6) or (7), wherein:

[0267] The processor performs the following processing:

[0268] The difference in resistance before and after the removal of the deposits is derived,

[0269] When the difference in resistance is small, the next removal time is extended compared to when the difference in resistance is large. (9)

[0271] An image forming system comprising:

[0272] The charging system as described in any one of (1) to (8);

[0273] an image holding body which is charged by the charging system and on which an image is formed; and

[0274] The transfer device transfers the image formed on the image holding member to a recording medium.

[0275] According to the charging system of (1), compared with a case where the removing member rotated by the charging member is always in contact with the charging member, it is possible to suppress the formation of a layer of deposits on the charging member.

[0276] According to the charging system of (2), compared with the case where the deposits are removed at predetermined intervals, it is possible to suppress the formation of a layer of deposits on the charging member.

[0277] According to the charging system of (3), it is possible to suppress a decrease in image quality compared to a case where the removing member disposed at the separated position is moved to the contact position during image formation.

[0278] According to the charging system of (4), compared with the case where the attached matter is removed at predetermined intervals, it is possible to effectively suppress the formation of a layer of the attached matter on the charging member.

[0279] According to the charging system of (5), it is possible to suppress a decrease in image quality compared to a case where the removing member disposed at the separated position is moved to the contact position during image formation.

[0280] According to the charging system of (6), compared with the case where the attached matter is removed at predetermined intervals, it is possible to effectively suppress the formation of a layer of the attached matter on the charging member.

[0281] According to the charging system of (7), it is possible to suppress a decrease in image quality compared to a case where the removing member disposed at the separated position is moved to the contact position during image formation.

[0282] According to the charging system of (8), compared with a case where the removal time is always the same, it is possible to effectively remove the attached matter attached to the charging member.

[0283] According to the image forming system of (9), compared with a case where a charging system is provided in which the removing member is always in contact with the charging member, it is possible to suppress density unevenness of an output image.

[0284] The above-mentioned embodiments of the present invention are provided for the purpose of illustration and description. In addition, the embodiments of the present invention do not fully and exhaustively include the present invention, and do not limit the present invention to the disclosed methods. Obviously, various modifications and changes are self-evident to those skilled in the art to which the present invention belongs. The present embodiment is selected and described in order to most easily understand the principles of the present invention and its application. Thus, other technicians in the art can understand the present invention through various variations optimized for specific uses assumed to be various embodiments. The scope of the present invention is defined by the above claims and their equivalents.

Claims

1. A charging system comprising: a charging member that rotates following the rotation of the image holding member and charges the image holding member; a removing member which, when arranged at a contact position with the charging member, is driven by the rotating charging member to rotate and removes the attached matter attached to the charging member; a moving member that moves the removing member to a separated position from the charging member and to the contact position; and at least one processor, The processor controls the moving member to move the removing member disposed at the separated position to the contact position at a predetermined time, and removes the attached matter attached to the charging member by the removing member only during a removal time.

2. The charging system according to claim 1, wherein: The processor performs the following processing: After the number of images formed on the image holding body since the last removal of the attached matter reaches a predetermined number, the removal member arranged at the separation position is moved to the contact position, and the attached matter attached to the charging member is removed by the removal member only during the removal time.

3. The charging system according to claim 1 or 2, wherein: The processor performs the following processing: After the number of images since the last removal of attached matter reaches a predetermined number and when no image is formed, the removal member disposed at the separated position is moved to the contact position.

4. The charging system according to claim 1, wherein: The processor performs the following processing: After the number of cycles of the image holding body since the last removal of the attached matter reaches a predetermined number, the removal member arranged at the separation position is moved to the contact position, and the attached matter attached to the charging member is removed by the removal member only during the removal time.

5. The charging system according to claim 1 or 4, wherein: The processor performs the following processing: After the number of cycles since the last removal of the attached matter reaches a predetermined number of times and when an image is not formed, the removal member disposed at the separated position is moved to the contact position.

6. The charging system according to claim 1, comprising a detection unit for detecting the resistance between the charging member and the image holding body. The processor performs the following processing: After the resistance increases by a predetermined amount since the last removal of the attached matter, the removal member disposed at the separation position is moved to the contact position, and the attached matter attached to the charging member is removed by the removal member only during the removal time.

7. The charging system according to claim 1 or 6, wherein: The processor performs the following processing: After the increase in the resistance since the last removal of the attached matter reaches a predetermined threshold value and when an image is not formed, the removal member disposed at the separated position is moved to the contact position.

8. The charging system according to claim 6 or 7, wherein: The processor performs the following processing: The difference in resistance before and after the removal of the deposits is derived, When the difference in resistance is small, the next removal time is extended compared to when the difference in resistance is large.

9. An image forming system comprising: The charging system according to any one of claims 1 to 8; an image holding body which is charged by the charging system and on which an image is formed; and The transfer device transfers the image formed on the image holding member to a recording medium.

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