JP2008026739A - Charging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging device capable of suppressing soil on an electrode to a predetermined allowable level or below even when the integral value of the number of printing sheets is increased. <P>SOLUTION: The charging device 1 includes the long needle electrode 2, a cleaning roller 5, a motor 62, and a controller 71. The needle electrode 2 is disposed opposite the surface of a photoreceptor drum 31 that holds a developer image printed on paper. The cleaning roller 5 is freely moved in contact with the needle electrode 2 along the lengthwise direction of the needle electrode 2. The motor 62 moves the cleaning roller 5. The controller 71 assumes, as a unit area, a print area calculated by multiplying the area of paper and a print proportion, that is, a print area obtained when printing is carried out on paper of a predetermined size at a predetermined proportion. The controller 71 obtains the accumulated value of a multiple of a print area relative to unit area per paper, and performs a cleaning process by moving a cleaning roller 5 when the accumulated value reaches a set value. The set value is set so that an interval from a cleaning process to the subsequent cleaning process decreases as an accumulated value increases. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a charging device that charges the surface of a photoreceptor of an image forming apparatus that performs electrophotographic image formation to a uniform potential.

  An electrophotographic image forming apparatus is equipped with a charging device that charges the surface of the photoreceptor to a uniform potential. As the charging device, there is a non-contact type charging device that does not contact the surface of the photoreceptor. The non-contact charging device charges the surface of the photoreceptor by discharging from an electrode to which a high voltage power source is applied. Surrounding dust is adsorbed on a portion of the electrode that generates a high-voltage electric field, and the electrode becomes dirty. If the electrode is left dirty, proper discharge from the electrode cannot be performed.

A conventional charging device includes a needle electrode having a plurality of needles arranged in a direction orthogonal to the moving direction of the surface of the photoreceptor, and a pair of pad members facing each other across the needle electrode needle (For example, refer to Patent Document 1). In this conventional charging device, the pad member is moved along the arrangement direction of the plurality of needles, so that the pad member is sequentially brought into contact with the surfaces of the plurality of needles to remove dirt attached to the needles.
JP 11-338265 A

  However, even if a cleaning process for removing dirt attached to the electrode is performed, dirt remains in a portion of the electrode where the cleaning member does not contact. In the conventional charging device, the cleaning process is performed every predetermined number of printed sheets. For this reason, as the integrated value of the number of printed sheets increases, dirt remaining on the electrode accumulates, and the dirt on the electrode may exceed a predetermined allowable level before the next cleaning process is performed.

  An object of the present invention is to provide a charging device capable of suppressing electrode contamination to a predetermined allowable level or less even when the integrated value of the number of printed sheets increases.

  The charging device of the present invention is configured as follows in order to solve the above-described problems.

  (1) The charging device of the present invention includes a long electrode, a cleaning member, a drive source, and a control device. The electrode is disposed to face the surface of the photoconductor that carries the developer image printed on the recording medium. The cleaning member is made movable while contacting the electrode along the longitudinal direction of the electrode. The drive source moves the cleaning member. The control device is a printing area calculated by multiplying the area of the recording medium by a printing ratio, and a unit area for each recording medium, where the printing area when printing on a recording medium of a predetermined size at a predetermined ratio is a unit area A cumulative value of a multiple of the printing area for the print area is acquired, and when the cumulative value reaches a predetermined set value, a cleaning process is performed by moving the cleaning member. The set value is set so that the interval from the previous cleaning process to the next cleaning process becomes shorter as the cumulative value increases.

  In this configuration, the print area calculated by multiplying the area of the recording medium by the printing ratio of the developer image is acquired for each recording medium that is a multiple of a predetermined unit area, and the cumulative value of the multiple is acquired. Is done. Since the interval at which the cleaning process is performed is set based on the area where the developer image is printed, the cleaning process is performed at an interval according to the accumulated amount of dirt remaining on the electrode. As the cumulative value increases, the setting value is set so that the interval from the previous cleaning process to the next cleaning process is shortened. Before the level rises, the electrode is cleaned.

  (2) In the charging device of the present invention, when acquiring the multiple, the size of the recording medium is the size corresponding to the above-mentioned predetermined size of the A size and the B size, and the larger size Can be converted to

  In this configuration, it is not necessary to perform complicated calculations by converting the size of the A size and the B size to the size corresponding to the predetermined size. Moreover, since it converts into the size of the larger side, the timing which performs a cleaning process is advanced.

  (3) In the charging device of the present invention, when maintenance work is performed, the cumulative value can be set to a set value that is scheduled to be subjected to the next cleaning process.

  In this configuration, when the charging device maintenance work is performed between the cleaning processes, it is assumed that the next cleaning process has been performed, and the subsequent cleaning process interval is set. For this reason, the interval at which the cleaning process is performed is set so as not to be longer than the original interval when the maintenance operation is not performed.

  (4) In the charging device of the present invention, the accumulated value can be initialized when the electrode is replaced.

  In this configuration, when the electrode is exchanged, the dirt accumulated in the electrode disappears. Therefore, by initializing the accumulated value, the accumulated value becomes a value corresponding to the degree of contamination of the electrode.

  (5) The charging device of the present invention further includes a support that rotatably supports the cleaning member, the electrode is a needle electrode having a plurality of needles arranged in one direction, and the support is a plurality of needles. The tips of the plurality of needles are sequentially buried from the surface of the cleaning member to the inside of the cleaning member and then exposed from the inside of the cleaning member when the support is moved. .

  In a conventional charging device using a pad member made of felt or the like as a cleaning member, the pad member cannot be provided with sufficient elasticity, and the needle tip of the needle electrode is likely to be deformed. Also, the felt fibers cut by contact with the needle adhere to the surface of the needle and contaminate the needle electrode. Furthermore, since the pad member contacts the side surface parallel to the needle arrangement direction on the surface of the needle, it is impossible to reliably clean the entire front end portion of the needle to which dust is most likely to adhere due to the generation of a high-voltage electric field.

  On the other hand, in the structure of this invention, the cleaning member moves together with the support so that the tip portions of the plurality of needles of the needle electrode are sequentially inserted into and removed from the cleaning member. When the tip of each needle is immersed in and removed from the cleaning member, the entire tip of each needle contacts the cleaning member, and the tip of each needle is contacted by the cleaning member. The entire surface of is cleaned.

  According to the present invention, the following effects can be obtained.

  (1) By setting the interval for performing the cleaning process based on the area where the developer image is printed, the cleaning process can be performed at an interval corresponding to the accumulated amount of dirt remaining on the electrode. By setting the setting value so that the interval from the previous cleaning process to the next cleaning process becomes shorter as the cumulative value increases, even if the integrated value of the number of printed sheets increases, the contamination of the electrode is below a predetermined allowable level. Can be suppressed.

  (2) By converting the size of the recording medium to the larger size corresponding to the above-mentioned predetermined size of the A size and B size, the complicated processing is eliminated and the cleaning process is performed. The process of setting the interval can be simplified, and the timing of performing the cleaning process can be advanced so that the contamination of the electrodes can be suppressed to a predetermined allowable level or less.

  (3) When the maintenance work is performed, the cumulative value is set to a setting value that is scheduled to be the next cleaning process, so that the interval of the cleaning process performed after the maintenance work is performed is It is possible to prevent the maintenance interval from becoming longer than the original interval and to suppress the degree of contamination of the electrodes to a predetermined allowable level or less.

  (4) By initializing the accumulated value when the electrode is replaced, the accumulated value can be set to a value corresponding to the degree of contamination of the electrode. For this reason, by performing the cleaning process when the cumulative value reaches the set value, the degree of contamination of the electrodes can be more accurately suppressed to a predetermined allowable level or less.

  (5) The tip of each needle of the needle electrode is inserted into and removed from the cleaning member in order, so that the entire tip of each needle is brought into contact with the cleaning member, and the needle is deformed and fibers are adhered. The entire tip of the needle can be cleaned without any occurrence.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a configuration of an image forming apparatus 100 to which a charging device 1 according to an embodiment of the present invention is applied. The image forming apparatus 100 forms an image on a sheet (including a recording medium such as an OHP) in any one of the copier mode, the printer mode, and the FAX mode. Each mode is selected by the user. The image forming apparatus 100 can perform double-sided printing.

  The image forming apparatus 100 includes a document reading unit 10, a paper feeding unit 20, an image forming unit 30, a paper discharge unit 40, an operation panel unit (not shown), and the like. The document reading unit 10 is disposed on the upper part of the apparatus main body, and includes a platen glass 11, a document placing tray 12, a scanner optical system 13, and the like. The scanner optical system 13 includes a light source 14, reflection mirrors 15 </ b> A to 15 </ b> C, an optical lens 16, and a CCD (Charge Coupled Device) 17. The light source 14 irradiates light on a document placed on the platen glass 11 or a document transported on the document transport path R from the document placing tray 12. The reflection mirrors 15 </ b> A to 15 </ b> C reflect the reflected light from the document and guide it to the optical lens 16. The optical lens 16 focuses the reflected light guided by the reflection mirrors 15 </ b> A to 15 </ b> C on the CCD 17. The CCD 17 outputs an electrical signal corresponding to the reflected light.

  The paper feed unit 20 is disposed at the lower part of the apparatus main body and includes a paper feed tray 21 and a pickup roller 22. The paper feed tray 21 stores paper to be fed to the paper transport path S1 during image formation. The pickup roller 22 rotates to feed the paper placed on the paper feed tray 21 to the paper transport path S1.

  The image forming unit 30 is disposed on the manual feed tray side below the document reading unit 10. The image forming unit 30 includes a laser scanning unit (hereinafter referred to as LSU) 37, a photosensitive drum 31, and a fixing device 36. Around the photosensitive drum 31, the charging device 1, the developing device 33, the transfer device 34, and the cleaner unit 35 are arranged in this order along the direction of the arrow shown in FIG. Yes.

  The paper discharge unit 40 is disposed above the paper feed tray 21 and includes a paper discharge roller 41 and a paper discharge tray 42. The paper discharge roller 41 discharges the paper transported on the paper transport path S <b> 1 to the paper discharge tray 42. The paper discharge roller 41 is capable of reversible rotation. When image formation is performed on both sides of the paper, the paper is held in a state where the paper on which the image formation on the front surface that has been transported on the paper transport path S1 has been sandwiched is sandwiched. The paper rotates in the direction opposite to the discharging direction and is conveyed to the paper conveyance path S2. As a result, the front and back sides of the sheet are reversed, the back side faces the photosensitive drum 31, and the toner image is transferred to the back side. The paper discharge tray 42 stacks and stores the paper discharged from the paper discharge rollers 41.

  When a start key provided on the operation panel unit is pressed, the image forming apparatus 100 rotates the pickup roller 22 to feed a sheet to the sheet conveyance path S1. The fed paper is conveyed to a registration roller 51 provided on the paper conveyance path S1.

  The registration roller 51 stops rotating when the leading edge of the sheet arrives. The registration roller 51 starts to rotate at a timing when the leading edge of the sheet coincides with the leading edge of the toner image formed on the photosensitive drum 31 between the photosensitive drum 31 and the transfer device 34.

  The image data read by the document reading unit 10 is subjected to image processing under the conditions input from the operation panel unit, and then transmitted to the LSU 37 as print data. The LSU 37 forms an electrostatic latent image by irradiating the surface of the photosensitive drum 31 charged to a predetermined potential by the charger 32 with laser light based on the image data via a polygon mirror and various lenses (not shown). To do. Thereafter, the toner attached to the surface of the MG roller 33A provided in the developing device 33 is attracted and attached to the surface of the photosensitive drum 31 according to the potential gap on the surface of the photosensitive drum 31, and electrostatic The latent image is visualized as a toner image (developer image).

  The toner image on the surface of the photosensitive drum 31 is transferred to the surface of the paper by the transfer device 34. The toner remaining on the surface of the photosensitive drum 31 after the transfer process is collected by the cleaner unit 35.

  The sheet that has completed the transfer process passes through the fixing device 36 to be applied with heat and pressure, and the toner image is melted and fixed, and is discharged to the discharge tray 42 by the discharge roller 41.

  2A is a front sectional view of the charging device 1, and FIG. 2B is a right side view of the main part of the charging device 1. FIG. The charging device 1 includes a needle electrode 2, a holder 3, a support 4, a cleaning roller 5, a screw screw 61, a motor 62, and a case 7. The charging device 1 is disposed above the photosensitive drum 31. Needle electrode 2 corresponds to an electrode of the present invention.

  The needle electrode 2 is made of a thin band-shaped metal material, and a plurality of needles 2A extend downward from the lower end at regular intervals over the entire length. The plurality of needles 2 </ b> A are arranged along the arrangement direction X parallel to the longitudinal direction of the needle electrode 2. The charging device 1 is arranged with the longitudinal direction of the needle electrode 2 parallel to the axial direction of the photosensitive drum 31. Therefore, the arrangement direction X is parallel to the rotation axis of the photosensitive drum 31. The length of the needle electrode 2 is longer than the axial length of the peripheral surface of the photosensitive drum 31.

  The holder 3 is made of an insulating material such as resin, and includes a holding portion 3A and a terminal portion 3B. The holding unit 3 </ b> A holds the needle electrode 2. The length of the holding portion 3 </ b> A is longer than the arrangement range of the plurality of needles 2 </ b> A in the needle electrode 2. 3 A of holding | maintenance parts exhibit a fixed cross-sectional shape shown by hatching in FIG. 2 (A) within the plane orthogonal to the arrangement direction X. The terminal portion 3B houses a terminal (not shown). The terminal connects a high voltage power source (not shown) and the needle electrode 2.

  The support 4 has an open bottom surface and is attached to the outside of the holding portion 3A from above. Projections 4A and 4B are formed on the inner surface of the support 4. The support 4 sandwiches the holding portion 3A in the vertical direction between the inner upper surface and the protrusions 4A and 4B, and sandwiches the holding portion 3A in the left-right direction on the inner side surface. Therefore, the support 4 is restricted from moving including rotation in a plane orthogonal to the arrangement direction X. A hole 4C is formed in the upper part of the support body 4, and a female screw part is formed in the hole 4C.

  The cleaning roller 5 is a cleaning member of the present invention, and is rotatably supported by the lower end portion of the support 4. As an example, the cleaning roller 5 is an elastic body containing an abrasive. The hardness of the abrasive is set lower than the material of the needle electrode 2 and higher than dust such as toner. From the peripheral surface of the cleaning roller 5, the tip of the needle 2A is buried inside.

  As the elastic body constituting the cleaning roller 5, a suitable material is experimentally selected from known rubber materials and resin materials on the condition that the needle 2 </ b> A is elastically deformed without being easily cut by the insertion and removal of the needle 2 </ b> A. Can be selected. The abrasive can be appropriately selected from known materials and used on the condition that toner and dust can be removed from the surface of the needle 2A without damaging the surface of the needle 2A. It can be included.

  The end of the screw screw 61 on the back side is screwed into the hole 4 </ b> C of the support 4. The front end (not shown) of the screw screw 61 protrudes from the front surface of the holder 3.

  The case 7 is attached to the outside of the support 4 over the entire length of the holder 3. Case 7 shields needle electrode 2.

  When a high voltage power supply is applied to the needle electrode 2 via the terminal housed in the terminal portion 3B, the applied electric field concentrates at the tip of each of the plurality of needles 2A of the needle electrode 2 and discharge occurs in this portion. It becomes easy. As a result, a discharge is generated on the surface of the photosensitive drum 31 from each of the plurality of needles 2A. By this discharge, the surface of the photosensitive drum 31 is charged to a predetermined potential.

  The holding portion 3A has a constant cross-sectional shape perpendicular to the arrangement direction X at least within the arrangement range of the plurality of needles 2A. As described above, the support body 4 is attached to the outside of the holding portion 3 </ b> A and is restricted from moving including rotation in a plane orthogonal to the arrangement direction X. Therefore, the support 4 is guided by the holding portion 3A and is reciprocally movable in the arrangement direction X within at least the arrangement range of the plurality of needles 2A.

  FIG. 3 is a diagram illustrating a cleaning operation of the cleaning roller 5. The tip of the needle 2A is buried in the peripheral surface of the cleaning roller 5 that is rotatably supported by the support 4. When the support 4 moves along the arrangement direction X, the cleaning roller 5 also moves together with the support 4. At this time, each of the plurality of needles 2 </ b> A is sequentially buried in the peripheral surface of the cleaning roller 5. The cleaning roller 5 moves along the arrangement direction X while rotating by the resistance acting on the peripheral surface from the plurality of needles 2A.

  The cleaning roller 5 is disposed between the needle electrode 2 and the peripheral surface of the photosensitive drum 31. The diameter of the cleaning roller 5 is made as large as possible without contacting the peripheral surface of the photosensitive drum 31. When the cleaning roller 5 moves in the arrangement direction X, the tip of at least one needle 2 </ b> A is always buried in the peripheral surface of the cleaning roller 5. For this reason, the cleaning roller 5 rotates reliably when moving in the arrangement direction X, and the peripheral surface of the cleaning roller 5 is damaged by the tip of the needle 2A and the needle 2A is deformed by the peripheral surface of the cleaning roller 5. Minimized.

  The support position of the cleaning roller 5 on the support body 4 is set so that the tip portion having a length of about 0.5 mm from the tip of the needle 2 </ b> A is buried in the peripheral surface of the cleaning roller 5. When the cleaning roller 5 moves along with the support body 4 along the arrangement direction X, the distal end portion of the needle 2A gradually immerses into the cleaning roller 5 from the distal end, and then is gradually withdrawn. During this time, the entire surface of the tip of the needle 2A comes into contact with the elastic body constituting the cleaning roller 5, and is polished by the abrasive contained in the elastic body. Since the cleaning roller 5 rotates while the plurality of needles 2 </ b> A are sequentially inserted and removed, at least the adjacent needles 2 </ b> A are embedded at different positions on the circumferential surface of the cleaning roller 5. Thereby, the entire surface of the tip of the needle 2A is cleaned.

  FIG. 4 is a right side view of the charging device 1. The charging device 1 includes a screw screw 61 on the upper surface side. The screw screw 61 has a length comparable to the substantially entire length of the holder 3. An end portion on the back side of the screw screw 61 is screwed into the hole 4 </ b> C of the support 4. A mounting portion 9 is formed at the front end portion of the holder 3. The mounting portion 9 has substantially the same outer shape as the terminal portion 3B. A bearing 9 </ b> A is formed on the upper surface of the mounting portion 9. An end portion on the front side of the screw screw 61 is supported by the bearing 9 </ b> A of the mounting portion 9.

  In a state where the charging device 1 is mounted in the image forming apparatus 100, the terminal portion 3 </ b> B and the mounting portion 9 are located in a range outside the image forming region W on the surface of the photosensitive drum 31. Further, the support 4 is positioned at a home position set within a range outside the image forming area W on the surface of the photosensitive drum 31 in a standby state where cleaning is not performed. Therefore, the support 4, the terminal portion 3 </ b> B, and the mounting portion 9 do not become an obstacle to image formation on the surface of the photosensitive drum 31.

  The rotation of the motor 62 is transmitted to the screw screw 61. The motor 62 rotates in both forward and reverse directions. The motor 62 corresponds to the drive source of the present invention.

  The support 4 is restricted from moving in the plane orthogonal to the arrangement direction X with respect to the holder 3 and does not rotate around the axis in the arrangement direction X. The rotational force of the screw screw 61 is converted into a moving force in the axial direction of the screw screw 61 and transmitted to the support 4. By supplying rotation in both forward and reverse directions from the motor 62 to the screw screw 61, the support 4 is guided by the holding portion 3A of the holder 3 and reciprocates along the arrangement direction X. At this time, the plurality of needles 2A of the needle electrode 2 are sequentially buried in the surface while the cleaning roller 5 supported by the support body 4 rotates. By driving the motor 62 at a predetermined timing, the needle electrode 2 can be automatically cleaned. The driving of the motor 62 is controlled by the control device 71 via a driver.

  A memory 72 and a forced execution button 73 are connected to the control device 71. The forced execution button 73 accepts forced execution of the cleaning process.

  When the tip portions of the plurality of needles 2A of the needle electrode 2 are sequentially inserted into and removed from the cleaning roller 5, the entire surface of the tip portion of each needle 2A comes into contact with the cleaning roller 5, and deformation of the needle 2A and adhesion of fibers The entire surface of the distal end portion of the needle 2A is cleaned without causing the. However, when the tip of the needle 2A is inserted into and removed from the cleaning roller 5, a part of the dirt adhering to the tip of the needle 2A is part of the needle 2A that is inserted into the cleaning roller 5. And always remain in the vicinity of the boundary between the non-immersed part.

  FIG. 5 is a diagram illustrating a relationship between the integrated value of the number of printed sheets and the degree of contamination of the needle electrode 2. In the charging device 1, a cumulative value of a multiple of the printing area with respect to the unit area for each sheet is obtained with a printing area of a predetermined ratio of a predetermined size of paper as a unit area. When the accumulated value reaches a predetermined set value, a cleaning process is performed by moving the cleaning roller 5.

  The print area is the area of the toner image printed on the paper, and is calculated by multiplying the paper size by the print ratio. Since the interval at which the cleaning process is performed is set based on the printing area, the cleaning process is performed at an interval corresponding to the accumulated amount of dirt remaining on the needle electrode 2.

  In the charging device 1 according to this embodiment, a multiple of the printing area with respect to the unit area is counted as the number of printed sheets. Therefore, the cumulative value of the multiple of the printing area with respect to the unit area for each sheet of paper is expressed as an integrated value of the number of printed sheets.

  In the charging device 1, as an example, the printing area when printing on A4 size paper at a printing ratio of 10% is defined as a unit area, and the number of printed sheets is counted as one.

  When the printing ratio is the same, A3 size sheets are counted as two sheets, and A5 size sheets are counted as 0.5 sheets.

  When counting the number of printed sheets, the paper size is the size corresponding to the paper size (A4 size here), which is the basis for determining the unit area, of A size and B size (here A size). And it is converted to the size of the larger side. In this embodiment, B size paper is counted as A size paper on the large size side. Specifically, when the printing ratio is the same, one B5 size sheet is converted to one A4 size sheet, and one B4 size sheet is one A3 size sheet (two A4 size sheets). ). This eliminates the need for complicated calculations, simplifies the process of setting the interval of the cleaning process, and suppresses the contamination of the needle electrode 2 below a predetermined allowable level by advancing the timing of the cleaning process. .

  As an example, the print ratio is rounded up at 10% intervals. When the paper sizes are the same, for example, when the printing ratio is twice (20%) with respect to the printing ratio (10% here) used as the basis for determining the unit area, the number of printed sheets is two. When the printing ratio is 0.5 times (5%), the number of printed sheets is rounded up and counted as one sheet.

  In FIG. 5, a solid line diagram 81 shows a relationship between the integrated value of the number of printed sheets and the degree of contamination of the needle electrode 2 when the cleaning process interval is shortened as the integrated value of the number of printed sheets increases. The broken line diagram 82 shows the relationship between the integrated value of the number of printed sheets and the degree of contamination of the needle electrode 2 when the interval for performing the cleaning process is made equal regardless of the integrated value of the number of printed sheets.

  As shown in broken line FIG. 82, in the conventional charging device, the cleaning process is performed every predetermined number of sheets regardless of the integrated value of the number of printed sheets. Even if the cleaning process is performed, dirt remaining on the needle electrode 2 is present, and therefore, the dirt accumulated in the needle electrode 2 increases as the integrated value of the number of printed sheets increases. For this reason, when the integrated value of the number of printed sheets increases, the degree of contamination of the needle electrode 2 becomes higher than a predetermined allowable level indicated by a one-dot chain line 83. When the contamination level of the needle electrode 2 is higher than a predetermined allowable level, the quality of the image formed by the image forming apparatus 100 is degraded.

  In the charging device 1, as shown in the solid line diagram 81, the cleaning process interval is shortened as the integrated value of the number of printed sheets increases. In the charging device 1, as an example, the integrated value of the number of printed sheets is 1000 sheets, 1900 sheets, 2700 sheets, 3400 sheets, so that the cleaning processing interval decreases by 100 sheets as the integrated value of the printed sheets increases. The set value is set so that the cleaning process is performed at 4000 sheets, 4500 sheets,.

  The integrated value of the number of printed sheets and the timing (setting value) at which the cleaning process should be performed are stored in the memory 72. As an example, the memory 72 stores the number of printed sheets at the interval at which the cleaning process is performed and the number of cleaning processes after the previous replacement of the needle electrode 2 in association with each other. As a timing at which the cleaning process should be performed, a value obtained by adding the number of printed sheets at an interval corresponding to the number of cleaning processes to the integrated value of the number of printed sheets when the previous cleaning process is performed is set. In this embodiment, the control device 71 states that the first cleaning process is 1000 printed at intervals, the second cleaning process is 900 printed at intervals, the third cleaning process is 800 printed at intervals, and so on. As shown in FIG.

  As an example, the needle electrode 2 is replaced when the integrated value of the number of printed sheets becomes a preset value among 60,000 to 100,000. The integrated value of the number of printed sheets is initialized when the needle electrode 2 is replaced. When the needle electrode 2 is replaced, the newly installed needle electrode 2 is not soiled. Therefore, the integrated value of the number of printed sheets corresponds to the degree of contamination of the needle electrode 2 by initializing the accumulated number of printed sheets. It becomes the value.

  When the maintenance of the image forming apparatus 100 is performed, the charging apparatus 1 is also maintained, and at this time, the needle electrode 2 is temporarily cleaned. When the maintenance operation of the charging device 1 is performed between the previous cleaning process and the next cleaning process, the subsequent cleaning process interval is adjusted assuming that the next cleaning process has been performed. In this embodiment, for example, when the maintenance work is performed when the integrated value of the number of printed sheets is 3000 sheets, the next cleaning process is performed assuming that the cleaning process that should have been performed when the accumulated number is 3400 sheets is performed. The next cleaning process is performed when the integrated value of the number of printed sheets is 3600 sheets. In this way, the timing of performing the cleaning process is controlled so that the cleaning process is not performed longer than the original interval.

  FIG. 6 is a flowchart showing a part of the processing procedure of the control device 71. When there is a print request (S1), the control device 71 obtains an added value M3 of the integrated value M1 of the number of prints before the current print request and the number of prints M2 to be printed in the current print request job. Calculate (S2).

  The control device 71 compares the integrated value M4 of the number of printed sheets at the timing at which the cleaning process should be performed with the added value M3 (S3), and if M4> M3, prints on the paper (S4). The control device 71 defines an added value M3 as the integrated value M1 of the number of printed sheets (S5).

  The user can press the cleaning process forcible execution button 73 when it is determined that the stain caused by the charging device 1 has occurred by looking at the print result. When the forced execution button 73 is pressed (S6), the control device 71 forcibly executes the cleaning process regardless of the integrated value of the number of printed sheets (S7). The user can perform the cleaning process of the needle electrode 2 at a desired timing by pressing the forced execution button 73.

  If M4> M3 is not satisfied in S3, the control device 71 performs a cleaning process for the needle electrode 2 (S7). The controller 71 adds a value obtained by adding the number of printed sheets at an interval corresponding to the number of times of the next cleaning process to the integrated value M5 of the number of printed sheets at the time of the cleaning process, as an integrated value M4 of the timing at which the next cleaning process should be performed. Define (S8). At this time, the integrated value M4 of the timing at which the next cleaning process should be performed is set so that the cleaning process interval becomes shorter as the integrated value M1 of the number of printed sheets increases. Thereby, even when the integrated value M1 of the number of printed sheets is increased, the degree of contamination of the needle electrode 2 is suppressed to a predetermined allowable level 83 or less.

  In place of the needle electrode 2, a corona charger electrode can be used.

  Finally, the description of the above-described embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

1 is a cross-sectional view illustrating a configuration of an image forming apparatus 100 to which a charging device 1 according to an embodiment of the present invention is applied. (A) is a front sectional view of the charging device 1, and (B) is a right side view of a main part of the charging device 1. It is a figure which shows the cleaning operation | movement of the cleaning roller. 2 is a right side view of the charging device 1. FIG. It is a figure which shows the relationship between the integrated value of the number of printed sheets, and the contamination degree of the needle electrode. 7 is a flowchart showing a part of the processing procedure of the control device 71.

Explanation of symbols

1, 1A, 1B, 1C, 1D Charging device 2 Needle electrode 2A Needle 3 Holder 3A Holding part 4 Support body 5 Cleaning roller (cleaning member)
31 Photosensitive drum 61 Screw screw 71 Controller 72 Memory 100 Image forming apparatus X Array direction

Claims (5)

An elongated electrode disposed opposite to the surface of the photoreceptor carrying the developer image printed on the recording medium;
A cleaning member that is movable while contacting the electrode along the longitudinal direction of the electrode;
A drive source for moving the cleaning member;
Printing area calculated by multiplying the area of the recording medium by the printing ratio, and the printing area when printing on a recording medium of a predetermined size at a predetermined ratio as a unit area, the printing area for the unit area for each recording medium And a control device that performs a cleaning process by moving the cleaning member when the cumulative value reaches a predetermined set value.
The charging device is characterized in that the set value is set such that the interval from the previous cleaning process to the next cleaning process becomes shorter as the cumulative value increases.   When obtaining the multiple, the size of the recording medium is a size corresponding to the predetermined size of A size and B size, and is converted to a larger size. Item 2. The charging device according to Item 1.   3. The charging device according to claim 1, wherein the cumulative value is set to a setting value at which a next cleaning process is scheduled to be performed when a maintenance operation is performed.   4. The charging device according to claim 1, wherein the cumulative value is initialized when the electrode is replaced. 5. And further comprising a support for rotatably supporting the cleaning member,
The electrode is a needle electrode having a plurality of needles arranged in one direction,
The support is arranged movably along the arrangement direction of the plurality of needles,
5. The tip of each of the plurality of needles is exposed from the inside of the cleaning member after being sequentially buried from the surface of the cleaning member when the support is moved. The charging device described.

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