JP2019109335A - Image forming apparatus, method for controlling image forming apparatus, and program for controlling image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus, a method for controlling the image forming apparatus, and a program for controlling the image forming apparatus that can improve accuracy in determining a life of charging rollers, while preventing an increase in size of an apparatus configuration.SOLUTION: An image forming apparatus comprises: photoreceptors 22; charging rollers 23 that charge the photoreceptors 22; a thickness calculation unit 62 that acquires a thickness of the photoreceptors 22; a reference current determination unit 63 that sets a reference current value on the basis of the acquired thickness; a DC current measuring unit 54 that measures a value of a DC component of a current flowing between the photoreceptors 22 and charging rollers 23 when a charging voltage in which an AC voltage is superimposed on a DC voltage is applied to the charging rollers 23; and a life information calculation unit 66 that performs determination as to a life of the charging rollers 23 on the basis of the reference current value and the measured value of the DC component.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus, a control method of the image forming apparatus, and a control program of the image forming apparatus. More particularly, the present invention relates to an image forming apparatus that makes a determination regarding the life of a charging roller, a control method of the image forming apparatus, and a control program of the image forming apparatus.

  The electrophotographic image forming apparatus includes an MFP (Multi Function Peripheral), a facsimile machine, a copier, a printer, etc. having a scanner function, a facsimile function, a copying function, a function as a printer, a data communication function, and a server function. is there.

  Generally, an image forming apparatus develops an electrostatic latent image formed on a photosensitive member by a developing device to form a toner image, transfers the toner image to a sheet, and then fixes the toner image to the sheet by a fixing unit. Forms an image on a sheet of paper. In the image forming apparatus, the electrostatic latent image on the surface of the photosensitive member is developed by the developing device to form a toner image, and the toner image is transferred to the intermediate transfer belt using the primary transfer roller. There also exist secondary transfer of a toner image on an intermediate transfer belt to a sheet using a transfer roller.

  The electrostatic latent image on the photosensitive member is formed by charging the surface of the photosensitive member and patterning the electrostatic latent image with an exposure device. The charging method of electrophotography includes a corona discharge method and a contact discharge method. Among them, in the contact discharge method, a charging roller, which is a roller-shaped semiconductive charging member, is disposed in contact with or in proximity to the surface of the photosensitive member, and a charging voltage is applied to the charging roller to perform proximity discharge. This is a charging method for charging the surface. The contact discharge method has the advantage of being able to reduce the generation of oxides (such as ozone) due to the flow of high-pressure current in air. The contact charging method has advantages such as a small amount of ozone generation, downsizing of the apparatus configuration, and reduction of charging current.

  Furthermore, in the contact charging method, a DC charging method using only a DC (direct current) voltage as a charging voltage applied to the charging roller and an AC (AC) component superimposed on a DC component as a charging voltage applied to the charging roller There is an AC charging method using a voltage.

  In the AC charging method, the discharge and the charge removal generated between the charging roller and the photosensitive member are forcibly repeated by the AC component. From this, the AC charging method has an advantage that the charging ability is high as compared with the DC charging method, and the uniformity of the potential on the surface of the photosensitive member after charging is high. The AC charging method also has an advantage that the uniformity of development can be improved.

  When the charging roller or the unit including the charging roller is used for a longer period of time than before, the charging performance of the charging roller tends to be lowered. That is, if the unit including the charging roller or the charging roller and the photosensitive member is extended in life, advantages such as reduction of downtime due to replacement, reduction of waste, and reduction of cost due to reduction of waste are obtained. Be On the other hand, the performance deterioration associated with long-term use of the charging roller becomes a problem. In the case where the photosensitive member is made of an organic photosensitive member, the film thickness is reduced due to the polishing of the photosensitive layer, and therefore the performance deterioration of the photosensitive member is also a problem.

  FIG. 17 is a view schematically showing the relationship between the cumulative rotation number of the charging roller and the surface potential of the photosensitive member when the charging voltage applied to the charging roller is constant.

  Referring to FIG. 17, the surface potential of the photosensitive member is lowered with the increase of the cumulative rotation number of the charge roller (the increase of the use period), and the charge performance is lowered. It is presumed that this is due to the following reason. When the use period of the charging roller is increased, trap sites for trapping the charge and portions for inhibiting the movement of the charge are formed inside or on the surface of the charging roller. When a charging voltage is applied to the charging roller, a part of the charge moving the charging roller due to the influence of the electric field formed by the charging voltage is captured by the trap site or the movement is inhibited. As a result, the charge moving on the charging roller is reduced, the discharge current flowing between the charging roller and the photosensitive member becomes difficult to flow, and the surface potential of the photosensitive member becomes lower than the target surface potential.

  The reduction in the charging performance of the charging roller described above is a problem particularly in long-life image forming apparatuses. Therefore, it has been necessary to accurately determine the life of the charging roller. The prior art which judges the lifetime of a charging roller is indicated by the following patent documents 1-3 etc., for example.

  Patent Document 1 below discloses a technique for detecting dirt on the surface of the charging roller by contacting the charging roller with the dirt detection roller unit and detecting the current flowing to the electrode roller of the dirt detection roller unit.

  Patent Document 2 below describes a technology for measuring the current value flowing through the charging roller with an ammeter by bringing the life detection member into contact with the charging roller, and determining the life of the charging roller based on the measured current value. It is disclosed.

  According to Patent Document 3 below, when the charging current (DC component) flowing at the time of strong exposure is less than a specified value, the charging member is increased in resistance due to the contamination of the charging member and the necessary charging current does not flow. Technology for notifying the service life of the charging member.

Japanese Patent Application Laid-Open No. 11-084829 JP 10-133456 A Japanese Patent Application Publication No. 08-152766

  However, in the techniques of Patent Documents 1 and 2, when the conductive member for measuring the current is kept in contact with the charging roller, when the charging voltage is applied to the charging roller, the current flows to the conductive member and the photosensitive member is It may happen that the required discharge current does not flow. In addition, an unnecessary current may flow to the photosensitive member when the life of the charging roller is detected, and the current flowing through the charging roller may not be accurately measured. In order to avoid these situations, depending on whether the photosensitive member is charged or the life is detected, between the state where the charging roller contacts the photosensitive body and the state where the charging roller separates from the photosensitive body Requires a mechanism to switch the state of the charging roller. Alternatively, a mechanism is required to switch the state of the conductive member between the state in which the conductive member is in contact with the charging roller and the state in which the conductive member is separated from the charging roller. As a result, the structure for detecting the life of the charging roller is complicated, and there is a problem that the size of the image forming apparatus is increased.

  Further, with regard to the technology of Patent Document 3, generally, an organic photosensitive member is used as a photosensitive member in an electrophotographic apparatus, but the organic photosensitive member is scraped with use and the film thickness decreases. The value of the charging current necessary for proper charging depends on the film thickness of the photoreceptor. For this reason, in a type of photosensitive member such as an organic photosensitive member whose film thickness is reduced due to use, the charging current value necessary for performing appropriate charging can not be accurately defined, and the life of the charging roller is determined. The accuracy was low.

  Specifically, when the photosensitive member is scraped and the film thickness is thin, the charging current value required to charge the surface of the photosensitive member to a predetermined surface potential is the film thickness as compared to the charging current value at the initial use. Increase in inverse proportion to For this reason, even if the charging current value is the same value as the initial use, the surface potential of the photosensitive member is lowered compared to the initial use. As a result, the charging roller which has already reached the end of its life will continue to be used, causing the occurrence of fogging which is a phenomenon in which the toner adheres to the non-image area and the density becomes high.

  When the film thickness of the photosensitive member changes, the amount of charge necessary to bring the surface potential to a predetermined potential fluctuates. Therefore, the reference current value needs to be determined based on the amount corresponding to the film thickness of the photosensitive member. The relationship between the reference current value and the film thickness of the photosensitive member is the same for both contact charging not depending on the charging method and non-contact charging such as scorotron.

  In addition, in the case of the DC charging method, even if the applied voltage is constant, the air gap voltage changes due to the change of the electrostatic capacity due to the change of the film thickness of the photosensitive member. Therefore, the charging potential increases as the film thickness of the photosensitive member decreases. That is, since the current increase due to the decrease of the film thickness and the current increase due to the increase of the surface potential are combined to increase the current, the reference current value can not be determined only by the DC current. In order to determine the reference current value, it is necessary to grasp the values corresponding to the surface potential and the film thickness of the photosensitive member.

  In the case of the AC charging method, the surface potential is substantially constant depending on Vdc regardless of the film thickness, so the surface potential can be grasped and the film thickness equivalent value can be grasped by the alternating current value, The reference current value can be determined. Further, the deviation from the reference current value of the charging current value necessary to charge the surface of the photosensitive member to a predetermined surface potential results in the decrease in the charging ability of the charging roller.

  The present invention is intended to solve the above-mentioned problems, and an object thereof is to control an image forming apparatus capable of improving the accuracy in determining the life of a charging roller while suppressing the enlargement of the apparatus configuration. A method, and a control program of an image forming apparatus.

  An image forming apparatus according to one aspect of the present invention is obtained by an image carrier, a charging roller for charging the image carrier, a film thickness acquisition unit for acquiring a film thickness of the image carrier, and a film thickness acquisition unit. Setting means for setting the reference current value based on the film thickness, and a direct current of the current flowing between the image carrier and the charging roller when the first charging voltage obtained by superimposing the alternating voltage on the direct current voltage is applied to the charging roller It comprises: a direct current measurement means for measuring the value of the component; and a determination means for making a judgment regarding the life of the charging roller based on the reference current value and the value of the direct current component measured by the direct current measurement means.

  Preferably, in the image forming apparatus, the determination means includes usage amount information which is information on the usage amount of the charging roller, and a shift current amount which is a difference between the reference current value and the value of the DC component measured by the DC measurement unit. And a life prediction unit that predicts the life of the charging roller when the amount of shift current reaches a predetermined threshold.

  Preferably, in the image forming apparatus, the usage information includes at least one of an accumulated traveling distance of the charging roller, an accumulated rotation number of the charging roller, an accumulated rotation time of the charging roller, and an accumulated number of printed sheets of the image forming apparatus. It is information that contains.

  Preferably, the image forming apparatus further includes state acquisition means for acquiring state information which is information related to the state of the image forming apparatus.

  Preferably, in the image forming apparatus, the state information is information including at least one of a temperature in the image forming apparatus, a humidity in the image forming apparatus, an operation history of the image forming apparatus, and a pause history of the image forming apparatus. .

  Preferably, in the image forming apparatus, storage is used to store history information which is information in which usage amount information, shift current amount, and state information are mutually associated when the life of the charging roller has been determined in the past by the determination means It further comprises a department.

  Preferably, in the image forming apparatus, the life prediction unit predicts the life of the charging roller based on the history information in which the state information satisfies the first condition among the history information stored in the storage unit.

  In the above image forming apparatus, preferably, the life prediction means is based on the history information in the group, and the classification means for dividing the history information stored in the storage unit into a plurality of groups based on the state information. And a life determining means for determining the life of the charging roller based on the life of each charging roller of the plurality of groups predicted by the group prediction means.

  In the above image forming apparatus, preferably, the life determining means is the shortest life of the charging roller among the life of the charging roller predicted by the group prediction means, or the life of the charging roller of the group having the largest amount of history information belonging to the group. Determined as the life of the charging roller.

  Preferably, in the above-described image forming apparatus, the film thickness acquiring unit is an AC component of the current flowing between the image carrier and the charging roller when a second charging voltage in which an AC voltage is superimposed on a DC voltage is applied to the charging roller. And a first film thickness calculating unit configured to calculate the film thickness of the image carrier based on the value of the AC component measured by the AC measuring unit.

  In the above image forming apparatus, preferably, the storage unit carries the usage amount information, the state information, and the image carrying capacity calculated by the first film thickness calculating unit when the life of the charging roller is determined by the judging unit in the past. The film thickness acquisition means further stores film thickness information which is information in which the film thickness of the body is associated with each other, and the film thickness acquisition means stores film thickness information in which state information satisfies the second condition among film thickness information stored in the storage unit. Based on the film thickness function, the film thickness function is used to set the film thickness function, which is a function indicating the relationship between the used volume information and the film thickness of the image carrier, and the film of the image carrier is used. If the second film thickness calculation means for calculating thickness and the state information acquired by the state acquisition means at the time of measurement by the alternating current measurement means satisfy the second condition, the calculation is performed by the first film thickness calculation means The film thickness is determined as the film thickness of the image carrier, and it is And a film thickness determining unit configured to determine the film thickness calculated by the second film thickness calculating unit as the film thickness of the image carrier when the state information acquired by the acquiring unit does not satisfy the second condition. .

  Preferably, in the above image forming apparatus, the image forming apparatus can communicate with an external apparatus, and transmits the use amount information, the amount of displacement current, and the state information to the external apparatus in association with each other; The life prediction means predicts the life of the charging roller based on the judgment result received by the result reception means.

  Preferably, in the above image forming apparatus, the image forming apparatus can communicate with the external apparatus, and receives function life information from the external apparatus that defines the relationship between usage amount information, shift current amount, and status information. Further, the life predicting means predicts the life of the charging roller using a life function based on the usage information, the amount of displacement current, and the state information.

  Preferably, the image forming apparatus further includes notification means for notifying the determination result by the determination means.

  A control method of an image forming apparatus according to another aspect of the present invention is a control method of an image forming apparatus including an image carrier and a charging roller for charging the image carrier, and acquires the film thickness of the image carrier. In the case where the first charging voltage in which the AC voltage is superimposed on the DC voltage is applied to the charging roller, and the setting step of setting the reference current value based on the film thickness acquired in the film thickness acquiring step The life of the charging roller based on the DC measurement step of measuring the value of the DC component of the current flowing between the image carrier and the charging roller, and the reference current value and the value of the DC component measured in the DC measurement step And a determination step of making a determination regarding

  A control program of an image forming apparatus according to still another aspect of the present invention is a control program of an image forming apparatus including an image carrier and a charging roller for charging the image carrier, and the film thickness of the image carrier The first charging voltage in which the AC voltage is superimposed on the DC voltage is applied to the charging roller. The setting step of setting the reference current value based on the film thickness acquisition step to be acquired and the film thickness acquired in the film thickness acquisition step In the case of the charging roller based on the DC measurement step of measuring the value of the DC component of the current flowing between the image carrier and the charging roller, and the reference current value and the DC component value measured in the DC measuring step. Allowing the computer to execute a determination step to make a determination regarding the lifespan.

  According to the present invention, it is possible to provide an image forming apparatus, a control method of the image forming apparatus, and a control program of the image forming apparatus, which can improve determination accuracy of the life of the charging roller while suppressing enlargement of the apparatus configuration. Can.

FIG. 1 is a cross-sectional view showing a configuration of an image forming apparatus 1 according to a first embodiment of the present invention. It is a block diagram which shows the control structure of the charging roller 23 in the 1st Embodiment of this invention. 5 is a flowchart showing a life detection operation of the charging roller 23 performed by the image forming apparatus 1 in the first embodiment of the present invention. 6 is a film thickness table showing the relationship between the AC current value and the film thickness of the photosensitive member 22 in the first embodiment of the present invention. It is a flowchart which shows lifetime estimation operation | movement of the charging roller 23 which the image forming apparatus 1 performs in 2nd Embodiment of this invention. It is a subroutine of the life prediction process (step S69 in FIG. 5) in the second embodiment of the present invention. It is a figure which shows typically the life prediction method in the 2nd Embodiment of this invention. It is a figure which shows typically the life prediction method in the 3rd Embodiment of this invention. It is a subroutine of the life prediction process (step S69 in FIG. 5) according to the third embodiment of the present invention. It is a subroutine of the life prediction process (step S69 in FIG. 5) in the fourth embodiment of the present invention. It is a figure which shows typically the life prediction method in the 4th Embodiment of this invention. It is a subroutine of the film thickness calculation process (step S63 in FIG. 5) in the fifth embodiment of the present invention. It is a figure which shows typically the film thickness calculation method in the 5th Embodiment of this invention. It is a figure which shows typically the usage aspect of the data center 2 in 6th Embodiment of this invention. It is a subroutine of the life prediction process (step S69 in FIG. 5) in the first example of the sixth embodiment of the present invention. It is a subroutine of the life prediction process (step S69 in FIG. 5) in the second example of the sixth embodiment of the present invention. FIG. 6 is a view schematically showing the relationship between the cumulative rotation number of the charging roller and the surface potential of the photosensitive member when the charging voltage applied to the charging roller is constant.

  Hereinafter, embodiments of the present invention will be described based on the drawings.

  In the following embodiment, the case where the image forming apparatus is an MFP will be described. The image forming apparatus may be a facsimile machine, a copier, a printer, or the like in addition to the MFP. The image forming apparatus may be any device that forms an image by an electrophotographic method, an electrostatic recording method, or the like.

  First Embodiment

  First, the configuration of the image forming apparatus in the present embodiment will be described.

  FIG. 1 is a cross-sectional view showing the configuration of an image forming apparatus 1 according to a first embodiment of the present invention.

  Referring to FIG. 1, the image forming apparatus 1 in the present embodiment is a tandem color image forming apparatus, and prints a full color image or a monochrome image on a sheet SH. The image forming apparatus 1 includes a sheet conveying unit 10, a toner image forming unit 20, a fixing device 40, an operation panel 41, a temperature and humidity sensor 42 (an example of a state acquiring unit), a bias power supply 50, and a control unit 60. And mainly.

  The sheet conveyance unit 10 includes a sheet feed tray 11, a sheet feed roller 12, a plurality of conveyance rollers 13, a sheet discharge roller 14, and a sheet discharge tray 15. The paper feed tray 11 accommodates a sheet SH for forming an image. The paper feed tray 11 may be plural. The paper feed roller 12 is provided between the paper feed tray 11 and the transport path TR. Each of the plurality of transport rollers 13 is provided along the transport path TR. The paper discharge roller 14 is provided at the most downstream part of the transport path TR. The discharge tray 15 is provided at the top of the image forming apparatus main body.

  The toner image forming unit 20 combines four color images of Y (yellow), M (magenta), C (cyan), and K (black) in a so-called tandem system, and transfers the toner image to a sheet. The toner image forming unit 20 includes image forming units 20 a, 20 b, 20 c and 20 d for Y, M, C, and K colors, an intermediate transfer member 21, a secondary transfer roller 29, and an intermediate transfer member cleaning device 30.

  The Y image forming unit 20a includes a photosensitive member 22a, a charging roller 23a, an exposure device 24a, a developing device 25a, a charge removing device 26a, a photosensitive member cleaning device 27a, and a primary transfer roller 28a.

  The photosensitive member 22a is rotationally driven in the direction indicated by the arrow α in FIG. Around the photosensitive member 22a, a charging roller 23a, an exposure device 24a, a developing device 25a, a primary transfer roller 28a, a charge removing device 26a, and a photosensitive member cleaning device 27a are disposed. The photosensitive member 22a is composed of a stacked organic photosensitive member including an Al (aluminum) tube, an undercoat layer sequentially stacked on the Al tube, a charge generation layer, and a charge transport layer having a thickness of about 30 μm. .

The charging roller 23a is a contact charging device and is in contact with the photosensitive member 22a. The charging roller 23a is driven to rotate as the photosensitive member 22a rotates. The charging roller 23a includes a cored bar made of metal and a conductive rubber layer formed on the cored bar. The charging roller 23a may have a multilayer structure in which a plurality of layers are formed as a conductive rubber layer. The charging roller 23a has an electrical resistance of 1 × 10 ⁴ Ω to 1 × 10 ⁸ Ω.

  The exposure device 24a is provided below the photosensitive member 22a. The charge removal device 26a is formed of an LED (Light Emitting Diode) or the like. The photoreceptor cleaning device 27a is always in pressure contact with the photoreceptor 22a.

  The M image forming unit 20b includes a photosensitive member 22b, a charging roller 23b, an exposure device 24b, a developing device 25b, a charge removing device 26b, a photosensitive member cleaning device 27b, and a primary transfer roller 28b. The C image forming unit 20c includes a photosensitive member 22c, a charging roller 23c, an exposure device 24c, a developing device 25c, a charge removing device 26c, a photosensitive member cleaning device 27c, and a primary transfer roller 28c. The K image forming unit 20d includes a photosensitive member 22d, a charging roller 23d, an exposing device 24d, a developing device 25d, a charge removing device 26d, a photosensitive member cleaning device 27d, and a primary transfer roller 28d. Each of the image forming units 20b, 20c, and 20d has the same configuration as that of the image forming unit 20a, and performs the same operation as that of the image forming unit 20a.

  The intermediate transfer member 21 is a belt, and is provided above the image forming units 20a, 20b, 20c, and 20d of Y, M, C, and K colors. The intermediate transfer body 21 is annular, and spans the rotating roller 21a. Intermediate transfer member 21 is rotationally driven in the direction indicated by arrow β in FIG. The intermediate transfer member 21 is made of a semiconductive material in which carbon is dispersed in a main raw material made of polycarbonate, PTFE (Polytetrafluoroethylene), or polyimide.

  Each of the primary transfer rollers 28a, 28b, 28c, and 28d is opposed to each of the photosensitive members 22a, 22b, 22c, and 22d with the intermediate transfer member 21 interposed therebetween. The secondary transfer roller 29 is in contact with the intermediate transfer member 21 in the transport path TR. The distance between the secondary transfer roller 29 and the intermediate transfer member 21 can be adjusted by a pressure separation mechanism (not shown). The intermediate transfer body cleaning device 30 is always in pressure contact with the intermediate transfer body 21.

  The fixing device 40 fixes the toner image on the sheet SH by conveying the sheet SH carrying the toner image along the conveyance path TR while gripping the sheet SH.

  The operation panel 41 displays various information and receives various operation inputs.

  The temperature and humidity sensor 42 detects the temperature and humidity in the image forming apparatus 1 and outputs the temperature and the humidity to the control unit 60.

  The bias power supply 50 supplies power to each member of the image forming apparatus 1 under the control of the control unit 60.

  Control unit 60 controls the overall operation of image forming apparatus 1. The control unit 60 includes a central processing unit (CPU) that executes a control program, a read only memory (ROM) that stores control programs and the like, and a random access memory (RAM) that configures a work area of the CPU. There is.

  The image forming apparatus 1 rotates the photosensitive member 22 a to uniformly charge the surface of the photosensitive member 22 a by the charging roller 23 a. The photosensitive member 22a is charged to, for example,-(minus) 600V. The image forming apparatus 1 applies a charging voltage to the core metal of the charging roller 23a to discharge between the photosensitive member 22a and the charging roller 23a, thereby charging the photosensitive member 22a. As the charging voltage, one obtained by superimposing an AC voltage on a DC voltage is used.

  The image forming apparatus 1 exposes the charged surface of the photosensitive member 22a according to the image forming information of Y by the exposure device 24a, and forms an electrostatic latent image of Y on the surface of the photosensitive member 22a.

  Next, the image forming apparatus 1 supplies toner from the developing device 25a to the photosensitive member 22a on which the electrostatic latent image is formed to perform development, thereby forming a Y toner image on the surface of the photosensitive member 22a. As a developer used for development, a two-component developer containing a toner and a carrier is used. Further, at the time of development, an AC voltage having a frequency of 1.5 kHz and a peak voltage Vpp of -400 V is superimposed on the sleeve of the developing device 25a with respect to a voltage value Vdc of a DC voltage of -400 V A development voltage is applied.

  Next, the image forming apparatus 1 uses the primary transfer roller 28a to transfer the Y toner image formed on the photosensitive member 22a onto the surface of the intermediate transfer member 21 (primary transfer). During transfer, a primary transfer bias is applied to the primary transfer roller 28 a, and the toner image is transferred to the intermediate transfer member 21 by the action of the transfer electric field formed thereby.

  In the image forming apparatus 1, after the primary transfer, the charge remaining on the photosensitive member 22a is removed using the charge removing device 26a, and the toner remaining on the photosensitive member 22a without being transferred to the intermediate transfer member 21 is removed by the photosensitive member cleaning device 27a. Remove. By removing the charge remaining on the photosensitive member 22a by the charge removal device 26a, the potential of the photosensitive member 22a can be uniformly lowered to about -10 V, and the uniformity of charging can be improved.

  Usually, the charge removal process by the charge removal apparatus 26a is performed after the cleaning process by the photosensitive member cleaning apparatus 27a and before the charging process by the charge roller 23a. However, in order to use the space effectively and to improve the cleaning performance, the static elimination step by the static elimination device 26a may be performed after the primary transfer and before the cleaning step by the photosensitive member cleaning device 27a. In this case, the charge removing device 26a may be disposed between the primary transfer roller 28a and the photosensitive member cleaning device 27a as shown in FIG.

  The image forming apparatus 1 sequentially transfers the MCK toner image onto the surface of the intermediate transfer member 21 using each of the image forming units 20b, 20c, and 20d in the same manner as the Y toner image. As each of the image forming units 20b, 20c, and 20d operates in synchronization with each other, a toner image in which toner images of Y, M, C, and K colors are combined is formed on the surface of the intermediate transfer member 21 in an overlapping manner.

  Subsequently, the image forming apparatus 1 conveys the toner image formed on the surface of the intermediate transfer member 21 to a position facing the secondary transfer roller 29 by the rotation roller 21 a.

  On the other hand, the image forming apparatus 1 feeds the sheet SH accommodated in the sheet feeding tray 11 by the sheet feeding roller 12 and the intermediate transfer member 21 and the secondary along the conveyance path TR by each of the plurality of conveyance rollers 13. It leads between the transfer roller 29. Then, the image forming apparatus 1 transfers the toner image formed on the surface of the intermediate transfer member 21 to the sheet SH by the secondary transfer roller 29. After the secondary transfer, the image forming apparatus 1 removes the toner remaining on the intermediate transfer member 21 without being transferred to the sheet SH by the intermediate transfer member cleaning device 30.

  The image forming apparatus 1 guides the sheet SH on which the toner image is transferred to the fixing device 40, and the fixing device 40 fixes the toner image on the sheet SH. Thereafter, the image forming apparatus 1 discharges the sheet SH on which the toner image is fixed to the sheet discharge tray 15 by the sheet discharge roller 14.

  Subsequently, a control configuration of the charging roller in any image forming unit among the image forming units 20a, 20b, 20c, and 20d will be described. In the following description, the photosensitive member and the charging roller in any image forming unit may be referred to as the photosensitive member 22 (an example of an image carrier) and the charging roller 23 (an example of a charging roller).

  FIG. 2 is a block diagram showing a control configuration of the charging roller 23 in the first embodiment of the present invention.

  Referring to FIG. 2, bias power supply 50 includes bias control unit 51, high voltage power supply 52, AC current measurement unit 53 (an example of alternating current measurement means), and DC current measurement unit 54 (an example of direct current measurement means). Contains.

  The bias control unit 51 controls the charging voltage applied by the high voltage power supply 52 under the control of the control unit 60.

  The high voltage power source 52 applies a charging voltage in which an AC voltage is superimposed on a DC voltage to the charging roller 23.

  AC current measurement unit 53 measures the value of an alternating current component of the discharge current flowing between photosensitive member 22 and charging roller 23 when the charging voltage is applied to charging roller 23 (hereinafter referred to as AC current value). Measure and output to the control unit 60.

  The DC current measurement unit 54 calculates the value of the DC component of the discharge current flowing between the photosensitive member 22 and the charging roller 23 when the charging voltage is applied to the charging roller 23 (hereinafter sometimes referred to as a DC current value). Measure and output to the control unit 60.

  The control unit 60 includes a main control unit 61, a film thickness calculation unit 62 (an example of a film thickness acquisition unit), a reference current determination unit 63 (an example of a setting unit), a reference current comparison unit 64, and usage amount information acquisition. Section 65, life information calculation section 66 (an example of determination means), sorting section 67, life information notification section 68 (an example of notification means), nonvolatile memory 69 (an example of a storage section), network interface 70 (an example Transmission means, result reception means, and function reception means).

  The main control unit 61 controls the overall operation of the image forming apparatus 1.

  The film thickness calculation unit 62 acquires (calculates) the film thickness of the photosensitive member 22.

  The reference current determination unit 63 determines a reference current value I 0 used for detecting the life of the charging roller 23 based on the film thickness acquired by the film thickness calculation unit 62.

  The reference current comparison unit 64 calculates the amount of shift current B by subtracting the DC power value measured by the DC current measurement unit 54 from the reference current value I0.

  The usage information acquisition unit 65 acquires usage information which is information on the usage of the charging roller 23. The used amount information is the cumulative rotation number of the charging roller 23 here, but the cumulative traveling distance of the charging roller 23, the cumulative rotation number of the charging roller 23, the cumulative rotation time of the charging roller 23, and the cumulative printing of the image forming apparatus 1 It is preferable that the information includes at least one of the number. In the following description, it is assumed that the usage information is the cumulative number of rotations of the charging roller.

  The life information calculation unit 66 determines the life of the charging roller 23 based on the reference current value and the DC current value measured by the DC current measurement unit 54.

  The sorting unit 67 sorts history information and film thickness information to be described later into groups.

  The life information notification unit 68 notifies the judgment result on the life of the charging roller 23 by the life information calculation unit 66.

  The non-volatile memory 69 stores various information.

  The network interface 70 communicates with an external device through a network.

  Subsequently, an operation (life detection operation) for detecting that the life of the charging roller 23 has reached in the image forming apparatus 1 according to the present embodiment will be described.

  FIG. 3 is a flowchart showing the life detection operation of the charging roller 23 performed by the image forming apparatus 1 in the first embodiment of the present invention. FIG. 4 is a film thickness table showing the relationship between the AC current value and the film thickness of the photosensitive member 22 in the first embodiment of the present invention.

  Referring to FIG. 3, control unit 60 executes the life detection mode of charge roller 23 at a predetermined timing (YES in S1). The predetermined timing includes, for example, the timing when the number of printed sheets of the image forming apparatus 1 reaches a predetermined number, the timing when the cumulative number of rotations of the charging roller 23 reaches a predetermined number of rotations, the timing when the power of the image forming apparatus 1 is turned on. Or, the timing at which the image forming apparatus 1 executes the image stabilization processing, the timing at which the image forming apparatus 1 controls the peak voltage of the AC component in the charging voltage, and the like.

  The control unit 60 starts rotational driving of the photosensitive member 22 (S3), applies a charging voltage obtained by superimposing AC voltage on DC voltage to the charging roller 23 (S5), and measures (acquires AC current value and DC current value) ) (S7). At the time of current measurement, it is necessary to apply a predetermined charging voltage. The charging bias conditions at the time of image formation are previously adjusted by processing for various image stabilization (density stabilization / Vpp adjustment). Since the current value changes when the condition of the charging voltage changes, the charging voltage applied at the time of current measurement needs to be a predetermined value. As an example of this predetermined value, the direct current component of the charging voltage applied to the charging roller 23 is, for example, -600 V, and the frequency of the alternating current component is, for example, 2 kHz. Note that each of the AC current value and the DC current value may be measured under conditions of different charging voltages.

  Subsequently, the control unit 60 calculates (acquires) the film thickness of the photosensitive member 22 using the film thickness calculation information stored in the non-volatile memory 69 based on the measured AC current value (S9). Generally, the film thickness of the photosensitive member 22 and the AC current value have a relationship as shown in FIG. 4, and as the film thickness of the photosensitive member 22 decreases, the AC current value also decreases. The control unit 60 may store, as film thickness calculation information, an approximate expression indicating the relationship between the film thickness of the photosensitive member 22 in FIG. 4 and the AC current value, or the film of the photosensitive member according to the AC current value. A table recording the thickness may be stored.

  The method of calculating the film thickness of the photosensitive member 22 is arbitrary, and in addition to the method using the above-mentioned AC current value, a method of detecting the film thickness based on the amount of change of the surface potential of the photosensitive member 22; A method of detecting from the displacement amount of the film thickness, or a method of detecting using the cumulative rotation number of the photosensitive member 22 may be used.

  Subsequently, the control unit 60 calculates (sets) a reference current value based on the calculated film thickness of the photosensitive member 22 (S11). The charging potential of the photosensitive member 22 does not depend on the film thickness of the photosensitive member 22 but depends on the direct current component of the charging voltage. The reference current value is a DC current value predicted in the case where the photosensitive member 22 is charged to a charging potential necessary for performing an appropriate image formation in a state where the charging roller 23 is unused. The reference current value I0 is calculated using the following equation (1) when the film thickness of the photosensitive member is film thickness d and the constant is constant K0.

  I0 = K0 / d (1)

  The constant K0 is a constant determined from the process speed, the dielectric constant of the photosensitive member 22, or the charging potential. The constant K0 is experimentally calculated in advance and stored in the non-volatile memory 69.

  Next, the control unit 60 makes a determination regarding the life of the charging roller 23 based on the reference current value and the measured DC current value. The control unit 60 calculates the amount of shift current B which is the difference between the reference current value I0 and the measured DC current value using the following equation (2) (S13).

  Deviation current amount B = reference current value I0−measured DC current value (2)

  The amount of displacement current B is an amount corresponding to the amount of current that the charging roller 23 can not supply with respect to the originally required charging current, and indicates the degree of deterioration of the charging performance (charge supply capability) of the charging roller 23 There is.

  Subsequently, the control unit 60 determines whether or not the charging roller 23 has reached the end of life by comparing the calculated amount of displacement current B with the threshold value BX (an example of a predetermined threshold value of the amount of displacement current). The control unit 60 determines whether the absolute value of the amount of deviation current B is less than or equal to the threshold BX (S15). The threshold value BX is experimentally calculated in advance and stored in the non-volatile memory 69.

  In step S15, when it is determined that the absolute value of the amount of displacement current B is equal to or less than the threshold BX (YES in S15), the control unit 60 determines that the charging roller 23 has not reached the life (S17), and step S1. Go to the process of

  When it is determined in step S15 that the absolute value of the amount of displacement current B is larger than the threshold BX (NO in S15), the control unit 60 determines that the charging roller 23 has reached the life (S19) and warns the operation panel 41. Is notified that the charging roller 23 has reached the end of its life (S21), and the process is ended.

  The control unit 60 may hold a plurality of threshold values BX, and may change the stage of warning to the user each time the amount of shift current B reaches each of the plurality of threshold values BX. Further, the control unit 60 instructs the user to use the charging roller 23, the remaining amount of the charging roller 23, the replacement of the charging roller 23, or charging the charging roller 23 according to the relationship between the shift current amount B and the threshold value BX. An instruction to replace the roller 23 may be notified. When it is determined that the charging roller 23 has reached the end of its life, the control unit 60 may stop the operation of the image forming apparatus 1 until the charging roller 23 is replaced.

  According to the present embodiment, the life of the charging roller 23 is determined by the value of the DC component of the discharge current flowing between the photosensitive member 22 and the charging roller 23 on the basis of the reference current value in consideration of the film thickness of the photosensitive member 22. Since the determination is made, the accuracy in determining the life of the charging roller can be improved. In addition, since the conductive member for measuring the current flowing through the charging roller 23 does not need to be brought into contact with the charging roller 23 in determining the life of the charging roller 23, a configuration for detecting the life of the charging roller 23 is used. This can be simplified, and the enlargement of the image forming apparatus can be suppressed.

  Second Embodiment

  In the present embodiment, an operation (life prediction operation) in which the image forming apparatus 1 predicts the life of the charging roller 23 based on the usage information (here, the cumulative number of rotations of the charging roller 23) and the shift current amount. explain.

  FIG. 5 is a flow chart showing a life prediction operation of the charging roller 23 performed by the image forming apparatus 1 in the second embodiment of the present invention.

  Referring to FIG. 5, control unit 60 sets variable n to 1 (S51), and executes the life prediction mode of charging roller 23 at a predetermined timing (YES in S53). The control unit 60 acquires the cumulative rotation number Rn of the charging roller 23 (S55). The cumulative rotation number Rn means the cumulative rotation number R of the charging roller 23 acquired at the n-th time. Next, the control unit 60 starts rotational driving of the photosensitive member 22 (S57), applies a predetermined charging voltage including a DC component and an AC component to the charging roller 23 (S59), and generates an AC current value and a DC value. The current value is measured (acquired) (S61).

  Subsequently, the control unit 60 calculates (acquires) the film thickness of the photosensitive member 22 using the film thickness calculation information stored in the non-volatile memory 69 based on the measured AC current value (S63). The reference current value is calculated (set) based on the film thickness of (S65). Next, the control unit 60 calculates a shift current amount Bn which is a difference between the reference current value and the measured DC current value (S67), and performs life prediction processing for predicting the life of the charging roller 23 (S69). The shift current amount Bn means the shift current amount B calculated at the n-th time. Subsequently, the control unit 60 notifies the user of the remaining life of the charging roller 23 by incrementing the variable n (S71) and displaying the remaining life on the operation panel 41 or the like (S73), and proceeds to the process of step S53. .

  FIG. 6 is a subroutine of the life prediction process (step S69 in FIG. 5) according to the second embodiment of the present invention. FIG. 7 is a view schematically showing a life prediction method in the second embodiment of the present invention.

  Referring to FIG. 6, in the life prediction process of step S69, control unit 60 associates the acquired cumulative number of revolutions Rn of charging roller 23 with the calculated amount of shift current Bn, and history information Mn (Rn, Bn). And stored in the non-volatile memory 69 (S101). In the non-volatile memory 69, history information M stored in the past is accumulated. The history information Mn means the history information M stored n-th time.

  Subsequently, the control unit 60 calculates constants K1 and K2 satisfying the following equation (3) based on the history information M1 to Mn stored in the non-volatile memory 69 (S103).

  B = K1 × R + K2 (3)

  In step S103, as shown in FIG. 7, the control unit 60 plots history information M1 to Mn on two-axis coordinates with the accumulated rotation number R of the charging roller 23 on the horizontal axis and the deviation current amount B on the vertical axis. The control unit 60 calculates constants K1 and K2 by deriving an approximate expression LN that approximates the relationship between the cumulative rotation number R of the charging roller 23 and the amount of shift current B using the least squares method or the like. The approximate expression for approximating the relationship between the cumulative rotation number R of the charging roller 23 and the amount of displacement current B does not have to be a linear expression, and may be any expression.

  Subsequently, the control unit 60 calculates the cumulative rotation number R of the charging roller 23 when the displacement current amount B reaches the threshold BX (an example of the threshold value of the displacement current amount) in the approximate expression LN, and the calculated cumulative rotation number R Is determined as the life revolution number RX, which is the cumulative number of revolutions that the charging roller 23 is expected to reach the life (S105). Next, the control unit 60 calculates the estimated remaining life of the charging roller 23 by calculating the difference between the life rotation number RX and the cumulative rotation number Rn of the charging roller 23 obtained in step S55 (S107) , To return.

  The control unit 60 may predict the life of the charging roller 23. In addition to the cumulative number of revolutions for the charging roller 23 to reach the life, the cumulative traveling distance for the charging roller 23 to reach the life and the charging roller 23 have a life The cumulative rotation time to reach and the cumulative number of printed sheets of the image forming apparatus 1 that the charging roller 23 reaches the end of life may be predicted.

  The control unit 60 may notify the user of the degree of wear of the charging roller 23, the remaining life of the charging roller 23, the replacement warning of the charging roller 23, and the like according to the calculated length of the remaining life. In addition, when the calculated remaining life is 0 or less, the control unit 60 may stop the operation of the image forming apparatus 1 until the charging roller 23 is replaced.

  The configuration and operation of image forming apparatus 1 other than those described above are similar to the configuration and operation of the image forming apparatus in the first and second embodiments, and therefore description thereof will not be repeated.

  According to the present embodiment, since it is possible to grasp the time when the charging roller 23 is expected to reach the end of its life, the convenience of the image forming apparatus can be improved.

  Third Embodiment

  Depending on the type of charging roller 23, the discharge current is affected by the state of the image forming apparatus 1 (temperature and humidity in the image forming apparatus 1, operation history of the image forming apparatus 1, and pause history of the image forming apparatus 1). The DC current value may fluctuate. In the present embodiment, attention is paid to the humidity in the image forming apparatus 1 as the state of the image forming apparatus 1.

  FIG. 8 is a diagram schematically showing a life prediction method in the third embodiment of the present invention.

Referring to FIG. 8, a group (black circles in FIG. 8) in which the humidity (state information E described later) of the image forming apparatus 1 satisfies condition A1 and a group (in FIG. 8) satisfying condition A2 It is divided into (white triangle). The condition A1 is a condition that the absolute humidity in the image forming apparatus 1 is in the range of 5 g / m ^{2 to} 15 g / m ² . The condition A2 is a condition that the absolute humidity in the image forming apparatus 1 is 20 g / m ² or more.

  In an environment of high humidity, a discharge current is likely to flow between the photosensitive member 22 and the charging roller 23, and therefore, the deterioration of the charging performance of the charging roller 23 is less likely to occur. Therefore, if the approximate expression is derived using both the plot belonging to the group of the condition A1 which is a normal condition and the plot belonging to the group which belongs to the condition A2 which is a high humidity condition, the accuracy of the approximate expression is lowered. As a result, the accuracy in predicting the remaining life of the charging roller 23 may be reduced.

  Therefore, in the image forming apparatus 1 according to the present embodiment, among the history information stored in the non-volatile memory 69, the charging roller is used based on the history information that indicates the condition of the image forming apparatus 1 as information. Predict the life of 23

  The image forming apparatus 1 according to the present embodiment performs the following operation in the life prediction process of FIG. 5 (step S69 of FIG. 5).

  FIG. 9 is a subroutine of the life prediction process (step S69 in FIG. 5) according to the third embodiment of the present invention.

  Referring to FIGS. 8 and 9, in the life prediction process of step S69, control unit 60 acquires state information En which is information indicating the state of image forming apparatus 1 (S121).

  The state information includes at least the temperature in the image forming apparatus 1, the humidity in the image forming apparatus 1 (in other words, the environment of the image forming apparatus 1), the operation history of the image forming apparatus 1, and the pause history of the image forming apparatus 1. It is preferable that it is information including one. The state information is typically the humidity in the image forming apparatus 1 detected by the temperature and humidity sensor 42. The state information En means the state information E stored n-th time.

  Subsequently, the control unit 60 associates the acquired state information En, the accumulated number of revolutions Rn of the charging roller 23 acquired, and the calculated amount of shift current Bn with each other as the history information Mn (En, Rn, Bn). It stores in the memory 69 (S123). In the non-volatile memory 69, history information M stored in the past is accumulated.

  Subsequently, the control unit 60 causes the history information M (in FIG. 8, for example) to satisfy a predetermined condition (for example, the above condition A1) (an example of the first condition) among the history information M1 to Mn stored in the non-volatile memory 69. The black circle) is extracted (S125). Next, based on the extracted history information M, the control unit 60 derives an approximate expression LN (FIG. 8) that approximates the relationship between the cumulative rotation number R of the charging roller 23 and the amount of shift current B to obtain Constants K1 and K2 satisfying 3) are calculated (S127).

  Next, the control unit 60 calculates the cumulative rotation number R of the charging roller 23 when the displacement current amount B becomes the threshold value BX in the approximate expression LN, and when the charging roller 23 reaches the end of the calculated cumulative rotation number R It is determined to be the life revolution number RX which is the predicted cumulative revolution number (S129). Next, the control unit 60 calculates the expected remaining life of the charging roller 23 by calculating the difference between the life rotation number RX and the cumulative rotation number Rn of the charging roller 23 obtained in step S55 (S131) , To return.

  The configuration and operation of image forming apparatus 1 other than those described above are similar to the configuration and operation of the image forming apparatus in the first and second embodiments, and therefore description thereof will not be repeated.

  According to the present embodiment, since the time when the charging roller 23 reaches the end of life is predicted based on the history information including appropriate environmental information, it is possible to improve the life prediction accuracy.

  Fourth Embodiment

  Image forming apparatus 1 according to the present embodiment divides the history information stored in nonvolatile memory 69 into a plurality of groups, and predicts the life of charging roller 23 based on the history information in each group. . The image forming apparatus 1 determines the life of the charging roller 23 based on the life of the charging roller 23 predicted for each of the plurality of groups.

  The image forming apparatus 1 according to the present embodiment performs the following operation in the life prediction process of FIG. 5 (step S69 of FIG. 5).

  FIG. 10 is a subroutine of the life prediction process (step S69 in FIG. 5) in the fourth embodiment of the present invention. FIG. 11 is a diagram schematically showing a life prediction method in the fourth embodiment of the present invention.

  10 and 11, in the life prediction process of step S69, control unit 60 acquires state information En which is information indicating the state of image forming apparatus 1 (S141). Subsequently, the control unit 60 associates the acquired state information En, the accumulated number of revolutions Rn of the charging roller 23 acquired, and the calculated amount of shift current Bn with each other as the history information Mn (En, Rn, Bn). It stores in the memory 69 (S143). In the non-volatile memory 69, history information M stored in the past is accumulated.

  Next, as shown in FIG. 11, the control unit 60, based on the status information E included in the history information M, stores the history information M stored in the non-volatile memory 69 into a plurality (four in this case) of groups GP1, It divides into GP2, GP3 and GP4 (S145). The group GP1 is a group of history information M in which the state information E satisfies the condition A1. The group GP2 is a group of history information M in which the state information E satisfies the condition A2. The group GP3 is a group of history information M in which the state information E satisfies the condition A3. The group GP4 is a group of history information M in which the state information E satisfies the condition A4. Each of the conditions A1, A2, A3 and A4 is different from one another.

  Subsequently, for each of the plurality of groups GP1, GP2, GP3 and GP4, the control unit 60 predicts the lifetime of the charging roller 23 based on the history information M in the group. The control unit 60 approximates, for each of the plurality of groups GP1, GP2, GP3 and GP4, the relationship between the cumulative number of revolutions R of the charging roller 23 and the amount of shift current B based on the history information M in the group. The constants K1 and K2 which satisfy the equation (3) are calculated by deriving each of the equations LN1, LN2, LN3 and LN4 (S147). The approximate expression LN1 is an approximate expression derived based on the history information M in the group GP1. The approximate expression LN2 is an approximate expression derived based on the history information M in the group GP2. The approximate expression LN3 is an approximate expression derived based on the history information M in the group GP3. The approximate expression LN4 is an approximate expression derived based on the history information M in the group GP4.

  Next, the control unit 60 calculates the cumulative rotation number R of the charging roller 23 when the amount of displacement current B becomes the threshold value BX in each of the approximate expressions LN1, LN2, LN3 and LN4 and calculates the calculated cumulative rotation number R The life rotation numbers RX1, RX2, RX3, and RX4 which are the cumulative rotation numbers that the charging roller 23 is predicted to reach the life are determined (S149). The life rotational speed RX1 is the life rotational speed of the group GP1 calculated from the approximate expression LN1. The life rotational speed RX2 is the life rotational speed of the group GP2 calculated from the approximate expression LN2. The life rotational speed RX3 is the life rotational speed of the group GP3 calculated from the approximate expression LN3. The life rotational speed RX4 is the life rotational speed of the group GP4 calculated from the approximate expression LN4.

  Subsequently, the control unit 60 controls the life rotation number RX of the charging roller 23 based on the life rotation numbers RX1, RX2, RX3 and RX4 of the charging roller 23 predicted for each of the plurality of groups GP1, GP2, GP3 and GP4. (S151).

  In step S151, control unit 60 may determine the shortest life rotation speed (life rotation speed RX4 in FIG. 11) among life rotation speeds RX1, RX2, RX3, and RX4 as life rotation speed RX.

  In step S151, control unit 60 may determine the life rotation speed (the life rotation speed RX1 in FIG. 11) of the group having the largest amount of history information belonging to the group as life rotation speed RX.

  In step S151, control unit 60 arranges groups GP1, GP2, GP3 and GP4 in the order in which the pieces of history information belonging to the group are large, and the arranged order is higher than the middle (group GP1 in FIG. 11). And GP2), and the shortest life rotation speed (life rotation speed RX1 in FIG. 11) among the life rotation speeds RX1 and RX2 of the extracted groups GP1 and GP2 may be determined as the life rotation speed RX.

  Further, in step S151, the control unit 60 excludes the history information belonging to the group which does not reach the predetermined number (group GP4 in FIG. 11), and the life rotation speed RX1, RX2 of the remaining groups GP1, GP2, and GP3. And RX3 may be determined as the life rotation speed RX, which is the shortest life rotation speed (life rotation speed RX1 in FIG. 11).

  Further, in step S151, control unit 60 is an approximate expression including approximations having a predetermined ratio or more of plots in which deviation from the approximate expression is a predetermined amount or more among approximate expressions LN1, LN2, LN3, and LN4 (an approximation in FIG. 11). The shortest life rotation number (life rotation number RX1 in FIG. 11) among the life rotation numbers RX1, RX2, and RX3 calculated from each of the remaining approximate expressions LN1, LN2, and LN3 excluding the expression LN4) is It may be determined as the life revolution number RX.

  Subsequently, the control unit 60 calculates the estimated remaining life of the charging roller 23 by calculating the difference between the determined life rotation number RX and the cumulative rotation number Rn of the charging roller 23 acquired in step S55 (see FIG. S153), return.

  The configuration and operation of image forming apparatus 1 other than those described above are similar to the configuration and operation of the image forming apparatus in the first and second embodiments, and therefore description thereof will not be repeated.

  According to the present embodiment, it is possible to avoid the situation in which the life prediction is performed by adopting the DC current value when the image forming apparatus 1 is in a rare state. As a result, it is possible to perform life prediction suitable for the state of the image forming apparatus 1, and it is possible to avoid a situation in which the life end of the charging roller 23 is predicted to be excessively short.

  Fifth Embodiment

  The AC current value used when calculating the film thickness of the photosensitive member 22 may be influenced by the state of the image forming apparatus 1 (in particular, the temperature and humidity of the image forming apparatus 1 (the environment of the image forming apparatus 1)). . Since the AC current value includes the induced current, the AC current value is more susceptible to the state of the image forming apparatus 1 than the DC current value.

  Here, the film thickness of the photosensitive member 22 is not influenced by the environment, and the amount of decrease does not change rapidly. On the other hand, it is desirable that the AC current value for detecting the film thickness of the photosensitive member 22 has little change due to the environment, and the shift current amount used for life prediction of the charging roller 23 is a condition that the change due to the usage amount of the charging roller 23 is large It is desirable to calculate

  In consideration of the above circumstances, in the image forming apparatus 1 according to the present embodiment, the film thickness calculated based on the AC current value is predicted to be inaccurate due to a change in the dielectric constant of the photosensitive member 22 or the like. In addition, the film thickness of the photosensitive member 22 calculated using the approximate expression calculated in advance based on the usage amount information is adopted.

  The image forming apparatus 1 of the present embodiment performs the following operation in the film thickness calculation process of FIG. 5 (step S63 of FIG. 5).

  FIG. 12 is a subroutine of the film thickness calculation process (step S63 in FIG. 5) according to the fifth embodiment of the present invention. FIG. 13 is a view schematically showing a film thickness calculation method in the fifth embodiment of the present invention.

  Referring to FIGS. 12 and 13, in the film thickness calculation process of step S63, control unit 60 obtains state information En (S201), and the film stored in nonvolatile memory 69 based on the measured AC current value. The film thickness dn of the photosensitive member 22 is calculated (acquired) using the thickness calculation information (S203). The film thickness dn means the film thickness d of the photosensitive member 22 calculated at the n-th time.

  Subsequently, the control unit 60 associates the acquired state information En, the acquired accumulated rotation number Rn of the charging roller 23, and the calculated film thickness dn with each other as the film thickness information Gn (En, Rn, dn). It stores in the memory 69 (S205). The non-volatile memory 69 stores film thickness information G stored in the past.

Subsequently, the control unit 60 selects, from the film thickness information G1 to Gn stored in the non-volatile memory 69, the film thickness information G (black circle in FIG. 13) satisfying the predetermined condition A11 (an example of the second condition). It extracts (S207). The condition A11 is preferably a condition in which the fluctuation of the AC current value caused by the state of the image forming apparatus 1 is small, such as the condition that the absolute humidity is 10 mg / m ² or more.

  Next, based on the extracted film thickness information G, the control unit 60 approximates the relationship between the cumulative rotation number R of the charging roller 23 and the film thickness d of the photosensitive member 22. Constants K3 and K4 which satisfy the following equation (4) are calculated by deriving one example of (1) (S209).

  d = K3 × R + K4 (4)

  Subsequently, the control unit 60 determines whether the acquired state information En satisfies the condition A11 (S211). The conditions used in step S211 may be different from the conditions used in step S209.

  When it is determined in step S211 that the acquired state information En satisfies the condition A11 (YES in S211), the control unit 60 determines that the film thickness dn calculated based on the AC current value is accurate. The control unit 60 adopts the film thickness dn calculated based on the AC current value (S213), and returns.

  If it is determined in step S211 that the acquired state information En does not satisfy the condition A11 (NO in S211), the control unit 60 determines that the film thickness dn calculated based on the AC current value is not accurate. The control unit 60 adopts the film thickness dnc calculated by the approximate expression LN11 using the cumulative rotation number Rn (S215), and returns.

  As another method of appropriately calculating the film thickness of the photosensitive member 22, the image forming apparatus 1 is configured to calculate the film thickness calculated based on the AC current value based on the AC current value when it is predicted to be inaccurate. A value obtained by multiplying the film thickness dn calculated as described above by a predetermined coefficient may be adopted as the film thickness of the photosensitive member 22.

  The configuration and operation of image forming apparatus 1 other than those described above are similar to the configuration and operation of the image forming apparatus in the first and second embodiments, and therefore description thereof will not be repeated.

  According to the present embodiment, even if it is predicted that the film thickness calculated based on the AC current value will be inaccurate, it is possible to use the film thickness of the photosensitive member 22 appropriately, and Since the life can be determined, the prediction accuracy of the life can be improved.

  Sixth Embodiment

  As in the third embodiment, when history information in which state information satisfies a predetermined condition is extracted and the life of the charging roller 23 is predicted based on the extracted history information, extraction is performed as the condition becomes stricter The number of historical information to be stored decreases and the error of the prediction result becomes large. When the history information is divided into groups to calculate the life of the charging roller 23 as in the fourth embodiment, the error due to the state of the image forming apparatus 1 decreases as the grouping is made finer, while The error of the prediction result due to the decrease in the number of pieces of history information to be assigned becomes large.

  Therefore, the image forming apparatus 1 according to the present embodiment determines the life of the charging roller 23 using the history information stored in the data center 2 (an example of an external device) connected by a network.

  FIG. 14 is a view schematically showing a use mode of the data center 2 in the sixth embodiment of the present invention. FIG. 14 (a) shows a first example of the usage mode, and FIG. 14 (b) shows a second example of the usage mode.

  The premise of the first and second examples will be described with reference to FIG. The image forming apparatus 1 can communicate with the data center 2. The data center 2 includes a CPU 2a that executes a control program, a ROM 2b that stores a control program, a RAM 2c that configures a work area of the CPU 2a, a network interface 2d that communicates via a network, and a storage unit 2e that stores various information. And so on.

  The data center 2 collects history information M (E, R, B) from a plurality of devices including the image forming apparatus 1 at a predetermined timing, and stores the collected history information M in the storage unit 2 e. The data center 2 calculates a function F (E, R, B) (an example of a life function) based on the collected history information M at a predetermined timing. The function F (E, R, B) is a function for calculating the amount of shift current B based on the state information E and the cumulative number of revolutions R. The data center 2 stores the function F (E, R, B) in the storage unit 2 e.

  The image forming apparatus 1 of the first example performs the following operation in the life prediction process of FIG. 5 (step S69 of FIG. 5).

  FIG. 15 is a subroutine of the life prediction process (step S69 in FIG. 5) in the first example of the sixth embodiment of the present invention.

  Referring to FIGS. 14A and 15, in the life prediction process of step S69, control unit 60 acquires state information En, which is information indicating the state of image forming apparatus 1 (S161). Next, the control unit 60 correlates the acquired state information En, the acquired accumulated rotation number Rn of the charging roller 23, and the calculated amount of shift current Bn with each other as history information Mn (Rn, Bn, Bn). It transmits to the center 2 (S163). The history information Mn transmitted in step S163 may further include information unique to the image forming apparatus 1, such as the installation place of the image forming apparatus 1. The amount of shift current Bn included in the history information Mn (Rn, Bn, Bn) transmitted in step S163 may be calculated using the film thickness dnc of the fifth embodiment.

  When the data center 2 receives the history information Mn, the data center 2 updates the function F (E, R, B) based on the received history information and the history information M already collected. The data center 2 calculates the life rotation speed RX using the function F (E, R, B) based on the history information Mn, and transmits the life rotation speed RX to the image forming apparatus 1. When the control unit 60 receives the life rotation number RX (S 165), the control unit 60 calculates the difference between the received life rotation number RX and the cumulative rotation number Rn of the charging roller 23 obtained in step S 55 to obtain The predicted remaining life is calculated (S167), and the process returns.

  The image forming apparatus 1 calculates the life rotation speed RX rather than the data center 2 calculating the life rotation speed RX as in the first example due to the process concentration on the data center 2 It can be efficient. In consideration of such a case, in the second example, the function F is transmitted in advance from the data center 2 to the image forming apparatus 1 at a necessary timing, and the image forming apparatus 1 holds the received function F. doing. The image forming apparatus 1 of the second example performs the following operation in the life prediction process of FIG. 5 (step S69 of FIG. 5).

  FIG. 16 is a subroutine of the life prediction process (step S69 in FIG. 5) in the second example of the sixth embodiment of the present invention.

  Referring to FIGS. 14B and 16, in the life prediction process of step S69, control unit 60 acquires state information En, which is information indicating the state of image forming apparatus 1 (S181). Next, the control unit 60 associates the acquired state information En, the acquired accumulated rotation number Rn of the charging roller 23, and the calculated amount of shift current Bn with each other as history information Mn, and based on the history information Mn, The life revolution number RX is calculated using the held function F (E, R, B) (S183). Subsequently, the control unit 60 calculates the expected remaining life of the charging roller 23 by calculating the difference between the calculated life rotation number RX and the cumulative rotation number Rn of the charging roller 23 obtained in step S55 (see FIG. S185), return.

  The configuration and operation of image forming apparatus 1 other than those described above are similar to the configuration and operation of the image forming apparatus in the first and second embodiments, and therefore description thereof will not be repeated.

  According to the present embodiment, since the life of the charging roller 23 is predicted based on a large number of pieces of history information collected by the data center 2, the prediction accuracy of the life can be improved.

  [Others]

  The embodiments described above can be combined with one another. As an example, the film thickness calculation process of the fifth embodiment may be adopted as the film thickness calculation process of the first embodiment.

  The processing in the above embodiment may be performed by software or may be performed using a hardware circuit. In addition, a program for executing the processing in the above-described embodiment can be provided, and the program is provided to the user by being recorded on a recording medium such as a CD-ROM, a flexible disk, a hard disk, a ROM, a RAM, and a memory card. You may decide to do it. The program is executed by a computer such as a CPU. Also, the program may be downloaded to the device via a communication line such as the Internet.

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

1 Image Forming Device 2 Data Center (Example of External Device)
2a CPU (Central Processing Unit)
2b ROM (Read Only Memory)
2c RAM (Random Access Memory)
2d, 70 network interface (example of transmission means, result reception means, and function reception means)
2e storage unit 10 sheet conveying unit 11 sheet feeding tray 12 sheet feeding roller 13 conveying roller 14 sheet discharging roller 15 sheet discharging tray 20 toner image forming unit 20a, 20b, 20c, 20d image forming unit 21 intermediate transfer member 21a rotating roller 22, 22a, 22b, 22c, 22d Photoreceptors (an example of an image carrier)
23, 23a, 23a, 23b, 23c, 23d Charging rollers 24a, 24b, 24c, 24d Exposure devices 25a, 25b, 25c, 25d Development devices 26a, 26b, 26c, 26d Charge removal devices 27a, 27b, 27c, 27d Photosensitive member cleaning Devices 28a, 28b, 28c, 28d Primary transfer roller 29 Secondary transfer roller 30 Intermediate transfer member cleaning device 40 Fixing device 41 Operation panel 42 Temperature and humidity sensor (an example of status acquisition means)
50 bias power supply 51 bias control unit 52 high voltage power supply 53 AC current measurement unit (an example of AC measurement means)
54 DC current measurement unit (an example of direct current measurement means)
60 control unit 61 main control unit 62 film thickness calculation unit (an example of film thickness acquisition means)
63 Reference current determination unit (an example of setting means)
64 Reference current comparison unit 65 Usage information acquisition unit 66 Life information calculation unit (an example of determination means)
67 classification unit 68 life information notification unit (an example of notification means)
69 Non-volatile memory (example of storage unit)
B Deviation current amount BX Deviation current threshold value d Photoconductor thickness E Status information F function (an example of life function)
G Film thickness information LN, LN1, LN2, LN3, LN4, approximate equation M Historical information R Cumulative rotation number RX, RX1, RX2, RX3, RX4 Life rotation number SH Paper TR transport path

Claims (16)

An image carrier,
A charging roller for charging the image carrier;
Film thickness acquisition means for acquiring the film thickness of the image carrier;
Setting means for setting a reference current value based on the film thickness acquired by the film thickness acquisition means;
DC measurement means for measuring the value of the DC component of the current flowing between the image carrier and the charging roller when a first charging voltage in which an AC voltage is superimposed on a DC voltage is applied to the charging roller;
An image forming apparatus comprising: determination means for determining the life of the charging roller based on the reference current value and a value of a direct current component measured by the direct current measurement means.   The determination means is based on usage amount information which is information on the usage amount of the charging roller, and a shift current amount which is a difference between the reference current value and the value of the DC component measured by the DC measurement unit. The image forming apparatus according to claim 1, further comprising a life prediction unit that predicts the life of the charging roller when the amount of shift current reaches a predetermined threshold.   The usage amount information is information including at least one of an accumulated traveling distance of the charging roller, an accumulated rotation number of the charging roller, an accumulated rotation time of the charging roller, and an accumulated number of printed sheets of the image forming apparatus. The image forming apparatus according to claim 2.   The image forming apparatus according to claim 2, further comprising a state acquisition unit that acquires state information that is information related to the state of the image forming apparatus.   3. The image forming apparatus according to claim 1, wherein the state information is information including at least one of a temperature in the image forming apparatus, a humidity in the image forming apparatus, an operation history of the image forming apparatus, and a stop history of the image forming apparatus. The image forming apparatus according to 4.   A storage unit for storing history information which is information in which the usage amount information, the amount of displacement current, and the state information are mutually associated when the life of the charging roller is determined in the past by the determination means; The image forming apparatus according to claim 4, comprising:   The image according to claim 6, wherein the life prediction means predicts the life of the charging roller based on the history information in which the state information satisfies a first condition among the history information stored in the storage unit. Forming device. The lifetime prediction means is
Sorting means for sorting the history information stored in the storage unit into a plurality of groups based on the state information;
Group prediction means for predicting the life of the charging roller based on the history information in each of the plurality of groups;
7. The image forming apparatus according to claim 6, further comprising: life determining means for determining the life of the charging roller based on the life of the charging roller of each of the plurality of groups predicted by the group prediction means.   The lifetime determining means charges the lifetime of the shortest charging roller among the lifetimes of the charging roller predicted by the group prediction means, or the lifetime of the charging roller of the group having the largest amount of history information belonging to the group, The image forming apparatus according to claim 8, which is determined as the lifetime of the roller. The film thickness acquisition means is
AC measurement means for measuring the value of the AC component of the current flowing between the image carrier and the charging roller when a second charging voltage obtained by superimposing an AC voltage on a DC voltage is applied to the charging roller;
The image formation according to any one of claims 6 to 9, further comprising: first film thickness calculation means for calculating the film thickness of the image carrier based on the value of the alternating current component measured by the alternating current measurement means. apparatus. The storage unit is configured to use the usage amount information, the state information, and the image carrier calculated by the first film thickness calculation unit when the life of the charging roller is determined by the determination unit in the past. Further store film thickness information which is information in which the film thicknesses of
The film thickness acquisition means is
Of the film thickness information stored in the storage unit, the function indicates the relationship between the usage amount information and the film thickness of the image carrier based on the film thickness information in which the state information satisfies the second condition. Function setting means for setting a certain film thickness function;
Second film thickness calculation means for calculating the film thickness of the image carrier using the film thickness function based on the usage amount information;
When the state information acquired by the state acquisition means satisfies the second condition at the time of measurement by the AC measurement means, the film thickness of the image carrier calculated by the first film thickness calculation means If the thickness is determined as the thickness and the state information acquired by the state acquiring means does not satisfy the second condition at the time of measurement by the AC measuring means, the film thickness calculated by the second film thickness calculating means is used. 11. The image forming apparatus according to claim 10, further comprising: a film thickness determining unit that determines the film thickness of the image bearing member. The image forming apparatus can communicate with an external device,
Transmitting means for associating the usage information, the amount of deviation current, and the state information with each other and transmitting the information to the external device;
A result receiving means for receiving from the external device the determination result on the life of the life roller;
The image forming apparatus according to claim 4, wherein the life predicting unit predicts the life of the charging roller based on the determination result received by the result receiving unit. The image forming apparatus can communicate with an external device,
The apparatus further comprises function receiving means for receiving from the external device a life function defining the relationship among the usage amount information, the amount of shift current, and the state information.
The image forming apparatus according to claim 4, wherein the life prediction unit predicts the life of the charging roller using the life function based on the usage information, the amount of shift current, and the state information. .   The image forming apparatus according to any one of claims 1 to 13, further comprising notification means for notifying a determination result by the determination means. A control method of an image forming apparatus, comprising: an image carrier; and a charging roller for charging the image carrier,
A film thickness acquisition step of acquiring a film thickness of the image carrier;
A setting step of setting a reference current value based on the film thickness acquired in the film thickness acquisition step;
A DC measurement step of measuring a value of a DC component of current flowing between the image carrier and the charging roller when a first charging voltage in which an AC voltage is superimposed on a DC voltage is applied to the charging roller;
A control method of an image forming apparatus, comprising: a determination step of determining the life of the charging roller based on the reference current value and a value of a direct current component measured in the direct current measurement step. A control program of an image forming apparatus comprising an image carrier and a charging roller for charging the image carrier,
A film thickness acquisition step of acquiring a film thickness of the image carrier;
A setting step of setting a reference current value based on the film thickness acquired in the film thickness acquisition step;
A DC measurement step of measuring a value of a DC component of current flowing between the image carrier and the charging roller when a first charging voltage in which an AC voltage is superimposed on a DC voltage is applied to the charging roller;
A control program of an image forming apparatus which causes a computer to execute a determination step of determining the life of the charging roller based on the reference current value and a value of a direct current component measured in the direct current measurement step.

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