JP2018146864A - Image forming apparatus and method for controlling the same, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately determine an increase in frictional force generated between a photoreceptor and a slide-contact member.SOLUTION: A control device 100 executes determination processing of determining whether or not the difference between a charging current based on a detection signal received from a first detection part 250 and a transfer current based on a detection signal received from a second detection part 260 is equal to or more than a predetermined threshold, and when determining that the difference is equal to or more than the predetermined threshold in the determination processing, executes friction reduction processing of supplying lubricant to a slide-contact member (cleaning blade 57).SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus including a photoconductor, a control method thereof, and a program.

  In the photosensitive layer cleaning that removes foreign matter on the photosensitive layer by sliding the blade in contact with the photosensitive layer of the photosensitive member, the function can be maintained if there is no lubricant in the contact portion between the photosensitive layer and the blade. Can not. If the amount of lubricant is small, the frictional force increases and the blade tip may move. In this case, a decrease in cleaning performance and an increase in driving torque of the photosensitive member become problems.

  On the other hand, in Patent Document 1, when a driving torque of a motor for driving a photosensitive member is detected and the detected driving torque exceeds a certain value, toner is placed on the photosensitive member as a lubricant, The method of supplying to the tip is taken.

JP 2012-194513 A

  However, as in the prior art, when the frictional force is predicted by the driving torque of the motor and it is determined whether the toner can be supplied or not, it is applied not only to the frictional force of the blade but also to the mechanism that transmits power from the motor to the photosensitive member. Torque detection varies because it is affected by the environmental dependency of grease (change in viscosity due to temperature and humidity). As a result, the lubricant (toner) may not be supplied to the blade at an appropriate timing, and the toner on the blade may be exhausted or the toner may be supplied excessively.

  SUMMARY An advantage of some aspects of the invention is that it appropriately determines an increase in frictional force generated between a photosensitive member and a sliding contact member.

In order to solve the above problems, an image forming apparatus according to the present invention includes a photosensitive member having a photosensitive layer, a charger that charges the surface of the photosensitive member, and a charging voltage application circuit that applies a charging voltage to the charger. , An exposure device that exposes the surface of the photoconductor, a developing device that supplies a developer to the photoconductor, a transfer member that transfers the developer on the surface of the photoconductor to a transfer medium, and a transfer to the transfer member A transfer voltage applying circuit for applying a voltage; a sliding contact member that is in sliding contact with the surface of the photosensitive member; a first detection unit that detects a charging current flowing through the charger; and a first detecting unit that detects a transfer current flowing through the transfer member. 2 detection units, and a control device that receives detection signals from the first detection unit and the second detection unit.
The control device determines whether a difference between a charging current based on the detection signal received from the first detection unit and a transfer current based on the detection signal received from the second detection unit is equal to or greater than a predetermined threshold. When the determination process determines that the difference is greater than or equal to a predetermined threshold value, a friction reduction process for supplying a lubricant to the sliding contact member is performed.

  The control method according to the present invention includes a photosensitive member having a photosensitive layer, a charger that charges the surface of the photosensitive member, a charging voltage application circuit that applies a charging voltage to the charger, and a surface of the photosensitive member. An exposure apparatus for exposing the photosensitive member, a developing device for supplying a developer to the photosensitive member, a transfer member for transferring the developer on the surface of the photosensitive member to a transfer medium, and a transfer voltage for applying a transfer voltage to the transfer member. An application circuit; a sliding contact member that is in sliding contact with the surface of the photosensitive member; a first detection unit that detects a charging current flowing through the charger; a second detection unit that detects a transfer current flowing through the transfer member; And a control device that receives detection signals from the first detection unit and the second detection unit, and a control method by the control device in the image forming apparatus, based on the detection signal received from the first detection unit Charging current and the second detection A step of determining whether or not a difference from a transfer current based on a detection signal received from a predetermined threshold is greater than or equal to a predetermined threshold, and a lubricant applied to the sliding contact member when it is determined that the difference is greater than or equal to a predetermined threshold And a step of supplying.

  A program according to the present invention includes a photosensitive member having a photosensitive layer, a charger for charging the surface of the photosensitive member, a charging voltage application circuit for applying a charging voltage to the charger, and a surface of the photosensitive member. An exposure device for exposing, a developing device for supplying a developer to the photoconductor, a transfer member for transferring the developer on the surface of the photoconductor to a transfer medium, and a transfer voltage application for applying a transfer voltage to the transfer member A circuit, a sliding member that is in sliding contact with the surface of the photoconductor, a first detection unit that detects a charging current flowing through the charger, a second detection unit that detects a transfer current flowing through the transfer member, And a control device that receives a detection signal from the second detection unit. A program for operating the control device, wherein the control device is connected to the first detection unit from the first detection unit. Based on the received detection signal Means for executing a determination process for determining whether or not a difference between the charging current and a transfer current based on the detection signal received from the second detection unit is equal to or greater than a predetermined threshold; When it is determined that the value is equal to or greater than a predetermined threshold value, it functions as means for executing a friction reduction process for supplying a lubricant to the sliding contact member.

  When the difference between the charging current and the transfer current is greater than or equal to a predetermined threshold value, the frictional force between the photoconductor and the sliding contact member is increased, and there is a high possibility that charges are generated in the photosensitive layer due to the frictional force. Therefore, in the image forming apparatus or the control method thereof described above, it is possible to appropriately determine the increase in frictional force by determining whether or not the difference between the charging current and the transfer current is equal to or greater than a predetermined threshold. . Further, when it is determined that the difference between the charging current and the transfer current is equal to or greater than a predetermined threshold value, the friction reducing process is executed, so that the lubricant can be supplied to the sliding contact member at an appropriate timing, and the photosensitive member An increase in frictional force generated between the body and the sliding contact member can be satisfactorily suppressed.

Further, an image forming apparatus according to the present invention includes a photosensitive member having a photosensitive layer, a charger that charges the surface of the photosensitive member, a charging voltage application circuit that applies a charging voltage to the charger, An exposure device that exposes the surface, a developing device that supplies a developer to the photoreceptor, a transfer member that transfers the developer on the surface of the photoreceptor to a transfer medium, and a transfer that applies a transfer voltage to the transfer member A voltage application circuit; a sliding member that is in sliding contact with the surface of the photoreceptor; a first detection unit that detects a charging current flowing through the charger; and a second detection unit that detects a transfer current flowing through the transfer member; A control device that receives detection signals from the first detection unit and the second detection unit.
The control device determines whether a difference between a charging current based on the detection signal received from the first detection unit and a transfer current based on the detection signal received from the second detection unit is equal to or greater than a predetermined threshold. When the determination process determines that the difference is greater than or equal to a predetermined threshold value, the notification process for notifying the abnormality by the notification device is performed.

  According to this configuration, it is possible to appropriately determine the increase in the frictional force by determining whether or not the difference between the charging current and the transfer current is greater than or equal to a predetermined threshold value. In addition, when it is determined that the difference between the charging current and the transfer current is equal to or greater than a predetermined threshold, that is, when the frictional force is increased, an abnormality is notified, and for example, the user is prompted to replace the sliding member. Thus, an increase in frictional force generated between the photosensitive member and the sliding contact member can be satisfactorily suppressed.

  According to the present invention, it is possible to appropriately determine an increase in frictional force generated between the photoconductor and the sliding contact member.

1 is a cross-sectional view illustrating a color printer according to an embodiment of the present invention. FIG. 6 is a diagram illustrating the separation between a photosensitive drum and a developing roller. It is a figure which shows structures, such as a control apparatus. It is a figure which shows the arrangement | positioning relationship of the member around a photoconductor drum. FIGS. 3A and 3B are diagrams showing the principle that residual charges are generated inside a photosensitive layer. FIGS. It is figure (a)-(e) which shows the principle from which a residual charge is removed. It is a flowchart which shows operation | movement of a control apparatus. It is a flowchart which shows a residual charge removal process. It is a flowchart which shows a friction reduction process. It is a time chart which shows operation | movement of a control apparatus. It is a flowchart which shows operation | movement of the control apparatus which concerns on the modification 1 of this invention. It is a flowchart which shows operation | movement of the control apparatus which concerns on the modification 2 of this invention.

  Next, a first embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, first, the overall configuration of a color printer as an example of an image forming apparatus will be described, and then the features of the present invention will be described in detail.

  In the following description, the direction of the color printer is defined as “front side” on the left side toward the paper surface of FIG. 1, “rear side” on the right side toward the paper surface, “left side” on the back side toward the paper surface, and toward the paper surface. Let the near side be the “right side”. In addition, the vertical direction toward the page is defined as the “vertical direction”.

  As shown in FIG. 1, the color printer 1 includes a paper feeding unit 20 that supplies a sheet P as an example of a transfer medium in a main body housing 10 and an image forming unit that forms an image on the fed paper P. 30 and a paper discharge unit 90 for discharging the paper P on which an image is formed.

  The paper feed unit 20 includes a paper feed tray 21 that stores the paper P, and a paper transport device 22 that transports the paper P in the paper feed tray 21 to the image forming unit 30.

  The image forming unit 30 mainly includes a scanner 40 as an example of an exposure apparatus, a plurality of process units 50, a transfer unit 70, a cleaning device 60, and a fixing unit 80.

  The scanner 40 is disposed on the upper side of the plurality of process units 50, and includes a laser light emitting unit (not shown), a polygon mirror, a lens, a reflecting mirror, and the like that are not shown. In the scanner 40, the laser beam is emitted after being reflected by a polygon mirror or a reflecting mirror or passing through a lens, and irradiated on the surface of a photosensitive drum 51 as an example of a photosensitive member by high-speed scanning. .

  The plurality of process units 50 are arranged side by side in the front-rear direction. The process unit 50 includes a drum unit 510 and a developing device 520 that can be attached to and detached from the drum unit 510.

  The drum unit 510 includes a photosensitive drum 51, a charging roller 52 as an example of a charger, and a cleaning blade 57 as an example of a sliding contact member. The developing device 520 includes a developing roller 54, a supply roller 55, and a toner storage chamber 56 for storing toner as an example of a developer.

  In the process unit 50, those indicated by reference numerals 50K, 50Y, 50M, and 50C containing toners of black, yellow, magenta, and cyan are arranged in this order from the upstream side in the conveyance direction of the paper P. In the present specification and drawings, when the photosensitive drum 51 and the developing roller 54 corresponding to the color of the toner are specified, K, Y, M are associated with black, yellow, magenta, and cyan, respectively. , C is attached.

  As shown in FIG. 3, the photosensitive drum 51 includes a cylindrical element tube 51A and a photosensitive layer 51B formed on the outer peripheral surface of the element tube 51A. The elementary tube 51A is made of a conductive member such as metal. The photosensitive layer 51B is formed of a positively chargeable organic photosensitive layer in which a charge generation material, an electron transport material, and a hole transport material are dispersed in a resin. The elementary tube 51 </ b> A is connected to the ground potential of the color printer 1.

  The charging roller 52 is a roller that charges the surface of the photosensitive drum 51. The charging roller 52 is in contact with the surface of the photosensitive drum 51. A positive charging voltage is applied to the charging roller 52 during charging.

  The developing roller 54 contacts the photosensitive drum 51 and supplies toner to the electrostatic latent image on the photosensitive drum 51 to develop the electrostatic latent image with toner. In this embodiment, when the toner is supplied from the developing roller 54 to the photosensitive drum 51, the toner is positively charged by the sliding contact between the developing roller 54 and the supply roller 55. It has come to be.

  As shown in FIG. 2, the developing roller 54 can be moved toward and away from the photosensitive drum 51 by controlling the contact / separation mechanism TM with the control device 100. Specifically, in the color mode, all the developing rollers 54K, 54Y, 54M, and 54C come into contact with the corresponding photosensitive drums 51K, 51Y, 51M, and 51C, and the respective photosensitive drums 51K, 51Y, 51M, and 51C are in contact with each other. Toner is supplied to the printer. In the monochrome mode, only the black developing roller 54K contacts the photosensitive drum 51K, and the other three color developing rollers 54Y, 54M, and 54C are separated from the corresponding photosensitive drums 51Y, 51M, and 51C. It is like that. Further, in the residual charge removal process described later, all the developing rollers 54K, 54Y, 54M, and 54C are separated from the corresponding photosensitive drums 51K, 51Y, 51M, and 51C, respectively.

  As shown in FIG. 1, the cleaning blade 57 is a member that collects foreign matters such as toner adhering to the surface of the photosensitive drum 51. The cleaning blade 57 is in sliding contact with the surface of the photosensitive drum 51.

  The transfer unit 70 is provided between the paper feeding unit 20 and each process unit 50, and includes a driving roller 71, a driven roller 72, a conveying belt 73, a transfer roller 74 as an example of an electric field forming member and a transfer member. It has.

  The driving roller 71 and the driven roller 72 are arranged in parallel in a spaced manner in the front-rear direction, and a conveyance belt 73 formed of an endless belt is stretched between them. The outer surface of the conveyance belt 73 is in contact with each photosensitive drum 51. In addition, four transfer rollers 74 that sandwich the conveyor belt 73 with the respective photosensitive drums 51 are arranged inside the conveyor belt 73 so as to face the respective photosensitive drums 51. A negative transfer voltage is applied to the transfer roller 74 during transfer.

  The charging roller 52, the developing roller 54, the transfer roller 74, and the cleaning blade 57 provided around the photosensitive drum 51 are arranged in this order in the rotation direction of the photosensitive drum 51.

  The cleaning device 60 is a device that slidably contacts the conveyance belt 73 and collects toner or the like adhering to the conveyance belt 73, and is disposed facing the lower side of the conveyance belt 73.

  The fixing unit 80 is disposed on the rear side of each process unit 50 and the transfer unit 70, and includes a heating roller 81 and a pressure roller 82 that is disposed to face the heating roller 81 and presses the heating roller 81.

  In the image forming unit 30 configured as described above, first, the surface of each photosensitive drum 51 is uniformly charged positively by the charging roller 52 and then exposed by the scanner 40. As a result, positive and negative charges are generated inside the photosensitive layer 51B (see FIG. 3), and the negative charges are transported to the surface, so that the positive charges charged on the surface are canceled by the negative charges. An electrostatic latent image is formed. Thereafter, the toner in the developing device 520 is supplied to the electrostatic latent image on the photosensitive drum 51 by the developing roller 54, so that the toner image is carried on the photosensitive drum 51.

  Next, the paper P supplied on the conveyor belt 73 passes between each photosensitive drum 51 and each transfer roller 74, so that the toner image carried on each photosensitive drum 51 is on the paper P. Transcribed. Then, as the paper P passes between the heating roller 81 and the pressure roller 82, the toner image transferred onto the paper P is thermally fixed.

  The paper discharge unit 90 mainly includes a plurality of transport rollers 91 that transport the paper P. The sheet P on which the toner image has been transferred and heat-fixed is transported by the transport roller 91 and discharged outside the main body housing 10.

  As shown in FIG. 3, the color printer 1 includes a control device 100, a charging voltage application circuit 210, a drum driving mechanism 220, a development voltage application circuit 230, a transfer voltage application circuit 240, and a first detection unit 250. The 2nd detection part 260 is provided.

  The charging voltage application circuit 210 is a circuit that applies a positive charging voltage to each charging roller 52. The drum drive mechanism 220 is a mechanism for rotating the photosensitive drum 51 and includes a motor, a gear, a clutch, and the like.

  The development voltage application circuit 230 is a circuit that applies a positive development bias to each development roller 54. The developing bias at the time of printing is set to a value lower than the charging voltage and higher than the surface potential of the exposed portion of the photosensitive drum 51. The transfer voltage application circuit 240 is a circuit that applies a negative transfer voltage to each transfer roller 74.

  The first detector 250 is a detector that detects a charging current flowing through the charging roller 52. When detecting the charging current, the first detection unit 250 outputs a first detection signal, which is a detection signal corresponding to the charging current, to the control device 100.

  The second detector 260 is a detector that detects a transfer current flowing through the transfer roller 74. When detecting the transfer current, the second detection unit 260 outputs a second detection signal, which is a detection signal corresponding to the transfer current, to the control device 100.

  The control device 100 includes a CPU, a ROM, a RAM, and the like, and according to the reception of the first detection signal, the second detection signal, the print command, and the like according to a program prepared in advance, The forming unit 30 and the paper discharge unit 90 are controlled. The control device 100 performs a determination process for determining whether or not the frictional force between the photosensitive drum 51 and the cleaning blade 57 has increased, and a friction reduction process for supplying toner as an example of a lubricant to the cleaning blade 57. Can be executed. The control device 100 can execute an image forming process for forming a toner image on the paper P and a residual charge removing process for removing residual charges remaining in the photosensitive layer 51B of the photosensitive drum 51. The control device 100 rotates the photosensitive drum 51 and the like via the drum driving mechanism 220 when performing each process.

  Here, when the photosensitive drum 51 slides on the cleaning blade 57 or the like, positive and negative charges are generated in the photosensitive layer 51B. Normally, this charge is removed from the photosensitive layer 51B at a predetermined rate by the action of the first electric field E1 generated between the charging roller 52 and the elementary tube 51A when passing through the charging roller 52. May remain in the photosensitive layer 51B. As shown in FIGS. 5A and 5B, the charges remaining in the photosensitive layer 51B become residual charges C1 and C2 that are not easily affected by the electric field, and the photosensitive drum 51 is cleaned by the cleaning blade 57. It gradually increases every time it touches. Since these residual charges C1 and C2 are charges that are difficult to move freely, even if an electric field is applied during charging, the residual charges C1 and C2 are unlikely to move from the place and are considered to accumulate near the surface of the photosensitive layer 51B. Yes.

  The control device 100 executes a charging voltage application process and a transfer voltage application process before executing the determination process. In addition, the control device 100 performs a first charging process, a first exposure process, a development process, and a transfer process in the image forming process, and a second charging process and a second exposure in the residual charge removal process. A process, a stop process, and a second electric field generation process are executed. In other words, the control device 100 functions as means for executing each process described above by operating based on a program. Moreover, the control method by the control apparatus 100 includes a step of executing each process described above.

  The charging voltage application process is a process of applying a third charging voltage to the charging roller 52. In the present embodiment, the third charging voltage is set to the same value as the first charging voltage applied in the first charging process described later. Note that the third charging voltage may be larger or smaller than the first charging voltage. The control device 100 starts the charging voltage application process when the power of the color printer 1 is turned on or when a print command is received. Then, the control device 100 applies the third charging voltage to the charging roller 52 via the charging voltage application circuit 210 in the charging voltage application process.

  In the transfer voltage application process, while the portion of the photosensitive drum 51 charged by the charge voltage application process passes through a position facing the transfer roller 74, the transfer voltage application circuit 240 is used to transfer the transfer voltage to the transfer roller 74. The third transfer voltage having the same polarity as the first transfer voltage is applied.

Here, as shown in FIG. 4, the first position P1 facing the charging roller 52 on the surface of the photosensitive drum 51 is more sensitive than the fourth position P4 facing the transfer roller 74 on the surface of the photosensitive drum 51. It is located upstream of the body drum 51 in the rotational direction. Further, the first position P1 is separated from the fourth position P4 in the circumferential direction of the photosensitive drum 51 by a first distance D1 on the upstream side in the rotation direction. Therefore, the first time T1 until the portion charged by the charging roller 52 reaches the fourth position P4 can be expressed by the following equation (1).
T1 = D1 / S (1)
D1: A portion of the surface of the photosensitive drum 51 that includes the first position P1 and the fourth position P4 and is downstream of the first position P1 and upstream of the fourth position P4. Long S: peripheral speed of the photosensitive drum 51

  The control device 100 starts the transfer voltage application process after elapse of the first time T1 from the start of the charging voltage application process.

  In the determination process, a difference between the charging current based on the first detection signal and the transfer current based on the second detection signal is detected as an excess current Ie, and it is determined whether or not the excess current Ie is equal to or greater than a predetermined threshold value Ith. It is processing. Here, the threshold value Ith can be appropriately set by experiment, simulation, or the like. Specifically, the control device 100 acquires a transfer current based on the second detection signal received from the second detection unit 260 as the first current while executing the transfer voltage application process. Further, the control device 100 is based on the first detection signal received from the first detection unit 250 while the part of the photosensitive drum 51 whose surface potential has been lowered by the transfer voltage application process passes through the charging roller 52. The charging current is acquired as the second current. And the control apparatus 100 is using the 1st electric current and 2nd electric current which were acquired at such timing for the calculation of the difference in a judgment process, ie, the calculation of the excess electric current Ie.

  Note that the order of obtaining the first current and the second current can be determined as appropriate. For example, the first current may be acquired before the second current, the first current and the second current may be acquired simultaneously, or the second current may be acquired before the first current. Also good. In addition, the number of acquisitions of the first current and the second current may be one time or may be a plurality of times. When each current is acquired a plurality of times, for example, the difference between the average values of the respective currents may be calculated as the excess current Ie.

  More specifically, the control device 100 starts the transfer voltage application process after the first time T1 described above from the start of the charging voltage application process, and then acquires the first current. Further, the control device 100 acquires the second current after the elapse of the second time T2 from the start of the transfer voltage application process, and starts the determination process based on the acquired first current and second current. Here, the second time T2 can be expressed by the following equation (2).

T2 = D2 / S (2)
D2: A portion of the surface of the photosensitive drum 51 that includes the fourth position P4 and the first position P1, and that is downstream of the fourth position P4 and upstream of the first position P1. Long S: peripheral speed of the photosensitive drum 51

  When determining that the excess current Ie is equal to or greater than the threshold value Ith in the determination process, the control device 100 executes a residual charge removal process or a friction reduction process described later. Specifically, when the control device 100 determines that Ie ≧ Ith in the determination processing first executed after receiving the print command, first, residual charge removal processing is executed. Then, the control device 100 executes the determination process again after executing the residual charge removal process, and executes the friction reduction process when it is determined that Ie ≧ Ith as a result of the determination in this determination process.

  In addition, when determining that the excess current Ie is less than the threshold value Ith in the determination process, the control device 100 executes a print standby process or an image forming process. Specifically, the control device 100 executes determination processing with the color printer 1 being turned on as a trigger, and when it is determined that Ie <Ith, it executes print standby processing. Here, a known process can be employed as the print standby process. For example, in the print standby process, the control device 100 stops the rotation of the photosensitive drum 51 and the like, and turns off each voltage.

  In addition, the control device 100 executes determination processing with the reception of the print command as a trigger, and executes image forming processing when determining that Ie <Ith. Hereinafter, each process executed by the control device 100 in the image forming process will be described.

  The first charging process is a process of charging the surface of the photosensitive drum 51 by the charging roller 52. Specifically, the first charging process is a process for executing a first exposure process based on image data to be described later. That is, the first charging process is a process for charging a portion of the photosensitive drum 51 facing the scanner 40 to an appropriate surface potential from the start to the end of the first exposure process. In the present embodiment, the first charging voltage is set to a predetermined value V1. The predetermined value V1 is set to 1500 V, for example.

  The controller 100 applies the first charging voltage to the charging roller 52 via the charging voltage application circuit 210 in the first charging process. More specifically, the control device 100 outputs a control signal corresponding to the first charging voltage to the charging voltage application circuit 210 based on reception of the print command. The charging voltage application circuit 210 applies a first charging voltage to the charging roller 52 in accordance with a control signal output from the control device 100.

  The first exposure process is a process in which the surface of the photosensitive drum 51 charged by the first charging process is exposed by the scanner 40 to form an electrostatic latent image on the surface. The control device 100 forms an electrostatic latent image on the surface of the photosensitive drum 51 by blinking the scanner 40 based on image data corresponding to the print command in the first exposure process. The execution time of the first exposure process varies depending on the amount of image data. Further, the execution time of the first charging process described above also varies in accordance with the variation in the execution time of the first exposure process.

  The development process is a process for forming a toner image on the surface of the photosensitive drum 51 by supplying toner to the electrostatic latent image by the developing roller 54. In the development process, the control device 100 applies a development voltage to the development roller 54 via the development voltage application circuit 230. The development voltage is set to 300 V, for example.

  The transfer process is a process for transferring the toner image onto the paper P. The control device 100 applies the first transfer voltage to the transfer roller 74 via the transfer voltage application circuit 240 in the transfer process.

Next, each process executed by the control device 100 in the residual charge removal process will be described.
The second charging process is a process in which the surface of the photosensitive drum 51 is charged by the charging roller 52 while the photosensitive drum 51 rotates once in a period different from the execution period of the first charging process and the charging voltage application process. . Specifically, the control device 100 performs the second charging process only for a specified time TD required for the photosensitive drum 51 to make one rotation. In the present embodiment, the control device 100 continuously executes the second charging process after the charging voltage application process ends. Further, the control device 100 applies the second charging voltage to the charging roller 52 via the charging voltage application circuit 210 in the second charging process. In the present embodiment, the second charging voltage is set to the same value as the first charging voltage, that is, the predetermined value V1. However, the present invention is not limited to this, and the second charging voltage may be smaller or larger than the first charging voltage.

  In the second exposure process, the photosensitive drum 51 rotates once during the period in which the portion of the photosensitive drum 51 charged by the second charging process passes through the second position P2 (see FIG. 4) facing the scanner 40. During this process, the surface of the photosensitive drum 51 is exposed by the scanner 40. Specifically, the control device 100 starts the second exposure process after the third time T3 has elapsed since the start of the second charging process. Here, the third time T3 can be expressed by the following equation (3).

T3 = D3 / S (3)
D3: a part of the surface of the photosensitive drum 51 that includes the second position P2 and the first position P1, and is located upstream of the second position P2 and downstream of the part of the first position P1. Long S: peripheral speed of the photosensitive drum 51

  In addition, the control device 100 ends the second exposure process after the lapse of the specified time TD required for the photosensitive drum 51 to make one rotation after starting the second exposure process.

  In the second exposure process, the control device 100 controls the scanner 40 so that the entire width of the image forming area of the photosensitive drum 51 is exposed. Here, the width of the image forming area refers to the width of the image forming area in the axial direction of the photosensitive drum 51.

  In the second exposure process, it is sufficient that most of the image forming area is exposed. For example, in the second exposure process, about 90% of the width of the entire image forming area may be exposed, about 80% of the width may be exposed, or about 70% of the width may be exposed. May be.

  The stop process is performed from the developing roller 54 to the photosensitive drum 51 during a period in which the portion of the photosensitive drum 51 exposed by the second exposure process passes the third position P3 (see FIG. 4) facing the developing roller 54. In this process, the supply of toner to the printer is stopped. Specifically, the control device 100 separates the developing roller 54 from the photosensitive drum 51 by controlling the contact / separation mechanism TM in the stop process. In the present embodiment, the control device 100 starts a stop process after the end of the image forming process, and ends the stop process when starting a friction reducing process described later or starting the next image forming process.

  In the second electric field generation process, the photosensitive drum 51 rotates once during the period in which the portion of the photosensitive drum 51 exposed by the second exposure process passes through the fourth position P4 facing the transfer roller 74. This is a process for generating a second electric field E2 between the tube 51A of the photosensitive drum 51 and the transfer roller 74. Here, the second electric field E2 is an electric field opposite to the first electric field E1 (see FIG. 6A) generated in the photosensitive layer 51B during charging.

The control device 100 starts the second electric field generation process after the fourth time T4 has elapsed since the start of the second exposure process. Here, the fourth time T4 can be expressed by the following equation (4).
T4 = D4 / S (4)
D4: a portion including the second position P2 and the fourth position P4 (see FIG. 4) facing the transfer roller 74 on the surface of the photoconductive drum 51, and downstream of the second position P2, and Peripheral length of the part upstream from the fourth position P4 S: Peripheral speed of the photosensitive drum 51

  In addition, the control device 100 ends the second electric field generation process after the lapse of the specified time TD required for the photosensitive drum 51 to make one rotation after starting the second electric field generation process. That is, in the present embodiment, the time for executing the second charging process, the time for executing the second exposure process, and the time for executing the second electric field generation process are set to the same length.

  In the second electric field generating process, the control device 100 applies a second transfer voltage having the same polarity as the first transfer voltage to the transfer roller 74 via the transfer voltage application circuit 240. In the present embodiment, as the transfer voltage control, for example, constant current control is adopted such that the transfer current flowing through the transfer roller 74 becomes a constant target value.

  In the constant current control, the control device 100 monitors the value of the current flowing through the transfer roller 74, and determines the transfer voltage applied from the transfer voltage application circuit 240 to the transfer roller 74 so that the transfer current becomes a constant target value. Then, a control signal is output to the transfer voltage application circuit 240 based on the determined transfer voltage. Note that the voltage value of the transfer voltage when executing the constant current control varies depending on the paper type, environmental conditions (temperature and humidity), the presence or absence of the paper, etc., but in the present embodiment, for convenience, the first transfer voltage, The values of the second transfer voltage and the third transfer voltage will be described using the same value (−V2: FIG. 10).

  Note that the target value of the transfer current in the transfer process, the transfer voltage application process, and the second electric field generation process may be the same or different. The transfer voltage control is not limited to constant current control, and may be constant voltage control in which a constant transfer voltage is applied to the transfer roller 74. In this case, the first transfer voltage, the second transfer voltage, and the third transfer voltage may be the same value or different values.

Finally, the friction reduction process will be described.
In the friction reduction process, the control device 100 brings the developing roller 54 into contact with the photosensitive drum 51 by terminating the stop process, and executes the third exposure process.

  The third exposure process is a process of exposing the surface of the photosensitive drum 51 by the scanner 40 for a predetermined time. Here, the predetermined time can be appropriately set to a time corresponding to the amount of toner supplied to the cleaning blade 57. In the present embodiment, the predetermined time is defined as a specified time TD required for the photosensitive drum 51 to make one rotation.

  In the third exposure process, the control device 100 controls the scanner 40 so that the entire width of the image forming area of the photosensitive drum 51 is exposed. Here, the width of the image forming area refers to the width of the image forming area in the axial direction of the photosensitive drum 51.

  In the third exposure process, most of the image forming area only needs to be exposed. For example, in the second exposure process, about 90% of the width of the entire image forming area may be exposed, about 80% of the width may be exposed, or about 70% of the width may be exposed. May be.

  When starting the friction reduction process, the control device 100 performs the end of the stop process and the start of the third exposure process substantially simultaneously. Note that the end timing of the stop process and the start timing of the third exposure process are not limited to this. For example, the stop process may be ended before the start of the third exposure process or after the start of the third exposure process.

In addition, when ending the friction reduction process, the control device 100 first ends the third exposure process, and then starts the stop process after the sixth time T6 has elapsed. Here, the sixth time T6 can be expressed by the following equation (5).
T6 = D6 / S (5)
D6: a portion including the second position P2 and the third position P3 (see FIG. 4) facing the developing roller 54 on the surface of the photosensitive drum 51, and is downstream of the second position P2, and Peripheral length of the part upstream from the third position P3 S: Peripheral speed of the photosensitive drum 51

  The end timing of the third exposure process and the start timing of the stop process are not limited to this. For example, the stop process may be started after a time different from the sixth time T6 from the end of the third exposure process or before the end of the third exposure process. However, by stopping the stop process until the time equal to or longer than the sixth time T6 has elapsed since the end of the third exposure process, the toner can be satisfactorily improved up to the last exposed part in the third exposure process. Can be supplied. Note that when the friction reduction process is executed with the reception of the print command as a trigger, the stop process is ended, and the next image formation is performed while the developing roller 54 is in contact with the photosensitive drum 51. Processing may be executed.

Next, the principle of removing the residual charges C1 and C2 will be described with reference to FIG.
As shown in FIG. 6A, when the second charging process is executed, positive charges are accumulated on the surface of the photosensitive drum 51, and the surface potential of the photosensitive layer 51B becomes a positive potential. Therefore, when the second charging process is executed, a first electric field E1 is generated from the surface of the photosensitive layer 51B toward the grounded tube 51A. Note that the residual charges C1 and C2 are not easily moved from the place even if the first electric field E1 is applied, and remain.

  As shown in FIG. 6B, when the second exposure process is executed after the second charging process, positive and negative charges C11 and C12 are generated inside the photosensitive layer 51B. Further, the charges C11 and C12 generated by exposure are easily moved by the action of an electric field.

  Of the charges C11 and C12 generated by the exposure, the negative charge C12 moves toward the surface of the photosensitive layer 51B by the action of the first electric field E1. The moved negative charge C12 is canceled with the positive charge charged on the surface of the photosensitive layer 51B, and is canceled with the positive residual charge C1 remaining on the surface layer of the photosensitive layer 51B. As a result, as shown in FIG. 6C, a negative residual charge C2 and a positive charge C11 remain in the photosensitive layer 51B.

  Thereafter, as shown in FIG. 6D, when the second electric field generation process is executed, a second electric field E2 is generated in the photosensitive layer 51B. The positive charge C11 in the photosensitive layer 51B moves toward the surface of the photosensitive layer 51B by the action of the second electric field E2. The moved positive charge C11 is offset with the negative residual charge C2 remaining on the surface layer of the photosensitive layer 51B. Thereby, as shown in FIG. 6E, the residual charges C1 and C2 in the photosensitive layer 51B are substantially removed.

  Next, the operation of the control device 100 will be described with reference to FIG. 7, FIG. 8, and FIG. In the state immediately after the color printer 1 is turned on or before the control device 100 receives a print command, the stop process is being executed and the developing roller 54 is separated from the photosensitive drum 51.

  As shown in FIG. 7, when the power is turned on or a print command is received (START), the control device 100 first starts a charging voltage application process (S1). When the first time T1 elapses from the start of the charging voltage application process, the control device 100 starts the transfer voltage application process (S2).

  When the second time T2 has elapsed from the start of the transfer voltage application process, the control device 100 detects an excess current Ie (S3). After step S3, control device 100 determines whether or not excess current Ie is greater than or equal to threshold value Ith (S4).

  If it is determined in step S4 that Ie ≧ Ith (Yes), the control device 100 determines whether or not the flag F is 0 (S5). Here, the flag F is a flag indicating whether or not the residual charge removal process has been executed. When the flag F is 0, it indicates that the residual charge removal process has not been executed yet. It shows that the charge removal processing has been executed.

  If it is determined in step S5 that F = 0 (Yes), the control device 100 ends the charging voltage application process (S6). After step S6, the control device 100 executes a residual charge removal process (S7). The residual charge removal process will be described in detail later.

  After step S7, that is, after executing the residual charge removal process, the control device 100 sets the flag F to 1 (S8) and executes the processes of steps S1 to S4 again. If it is determined that Ie ≧ Ith in the second process of step S4 (Yes), the control device 100 determines that F = 0 is not satisfied in step S5 (No), and executes the friction reduction process (S9). ). The friction reduction process will be described later in detail.

  After step S9, the control device 100 returns the flag F to 0 and ends this control. If it is determined in step S4 that Ie <Ith (No), the control device 100 ends the transfer voltage application process (S11) and ends the charging voltage application process (S12). And after step S12, the control apparatus 100 returns the flag F to 0, and complete | finishes this control. Note that after the completion of this control, the control device 100 executes the above-described print standby process or image forming process.

Next, the residual charge removal process will be described.
As shown in FIG. 8, in the residual charge removal process, the control device 100 first starts the second charging process (S21). Here, step S21 is a process that is continuously performed immediately after step S6 described above, and therefore the second charging process is started immediately after the end of the charging voltage application process. In the present embodiment, since the third charging voltage in the charging voltage application process and the second charging voltage in the second charging process are set to the same predetermined value V1, the actual processing includes steps S6 and 21. The charging voltage of the predetermined value V1 is continuously applied without the charging voltage being turned off. When the third charging voltage and the second charging voltage are different from each other, the third charging voltage may be switched to the second charging voltage in step S21.

  When the third time T3 has elapsed from the start of the second charging process, the control device 100 starts the second exposure process (S22). When the fourth time T4 has elapsed from the start of the second exposure process, the control device 100 ends the transfer voltage application process and starts the second electric field generation process (S23). In this embodiment, since the target value of the transfer current is constant in each process, the third transfer voltage in the transfer voltage application process and the second transfer voltage in the second electric field generation process are approximately the same value (− Therefore, as an actual process, a transfer voltage having substantially the same value is continuously applied without turning off the transfer voltage. When the target value of the transfer current in the transfer voltage application process and the second electric field generation process is set to a different value, the third transfer voltage may be switched to the second transfer voltage in step S23.

  Thereafter, the control device 100 ends the second charging process when the specified time TD has elapsed from the start of the second charging process, that is, when the photosensitive drum 51 makes one revolution (S24). Next, when the specified time TD has elapsed from the start of the second exposure process, the control device 100 ends the second exposure process (S25). In addition, when the specified time TD has elapsed from the start of the second electric field generation process, the control device 100 ends the second electric field generation process (S26) and ends the residual charge removal process.

Next, the friction reduction process will be described.
As shown in FIG. 9, in the friction reduction process, the control device 100 first ends the transfer voltage application process (S31). After step S31, the control device 100 brings the developing roller 54 into contact with the photosensitive drum 51 (S32) and executes a third exposure process (S33).

  Specifically, in step S <b> 32, the control device 100 finishes the stop process and makes it possible to supply toner from the developing roller 54 to the photosensitive drum 51. In Step S33, control device 100 performs the 3rd exposure processing for regulation time TD.

  When the sixth time T6 has elapsed from the end of the third exposure process, the control device 100 starts the stop process, thereby separating the developing roller 54 from the photosensitive drum 51 (S34). When this control is executed with the reception of the print command as a trigger, the process of step S34 need not be executed.

Next, when the seventh time T7 has elapsed from the end of the third exposure process, the control device 100 ends the charging voltage application process (S35) and ends this control. Here, the seventh time T7 can be expressed by the following equation (6).
T7 = D7 / S (5)
D7: a portion including the second position P2 and the fifth position P5 (see FIG. 4) in contact with the cleaning blade 57 on the surface of the photosensitive drum 51, the downstream side from the second position P2, and Peripheral length of the part upstream from the fifth position P5 S: Peripheral speed of the photosensitive drum 51

  By completing the charging voltage application process after the elapse of the seventh time T7, the portion exposed at the end of the third exposure process is supplied with toner by the developing roller 54 and then reaches the tip of the cleaning blade 57. Then, the charging voltage application process can be finished. That is, the charging voltage application process can be ended after all the toners on all the parts exposed in the third exposure process are supplied to the cleaning blade 57. For this reason, it is possible to suppress the useless application of the charging voltage. When this control is executed with the reception of the print command as a trigger, the process of step S35 need not be executed.

Next, an example of the operation of the control device 100 will be described with reference to FIG.
As shown in FIG. 9, when the power of the color printer 1 is turned on (time t1), the control device 100 first executes a charging voltage application process. At this time, the developing roller 54 is separated from the photosensitive drum 51.

  When the first time T1 elapses from the time t1 when the charging voltage application process is started, the control device 100 starts the transfer voltage application process (time t2). When the second time T2 has elapsed from the time t2 when the transfer voltage application process is started, the control device 100 detects the excess current Ie and determines whether or not the detected excess current Ie is equal to or greater than the threshold value Ith. Is executed (time t3).

  When determining that Ie ≧ Ith in the determination processing, the control device 100 ends the charging voltage application processing and starts the second charging processing in the residual charge removal processing (time t4). When the third time T3 elapses from the time t4 when the second charging process is started, the control device 100 starts the second exposure control (time t5).

  When the fourth time T4 elapses from the time t5 when the second exposure control is started, the control device 100 ends the transfer voltage application process and starts the second electric field generation process (time t6). When the specified time TD elapses from time t4 when the second charging process is started, the control device 100 ends the second charging process (time t7).

  When the specified time TD elapses from time t5 when the second exposure control is started, the control device 100 ends the second exposure control (time t8). When the specified time TD elapses from time t6 when the second electric field generation process is started, the control device 100 ends the second electric field generation process and ends the residual charge removal process (time t9).

  After finishing the residual charge removal process, the control device 100 starts the charging voltage application process again (time t10). Thereafter, the transfer voltage application process and the determination process are started at the same timing as described above (time t11, t12).

  If it is determined again that Ie ≧ Ith in the determination process, the control device 100 starts the friction reduction process (time t13). In the friction reduction process, the control device 100 starts the end of the transfer voltage application process, the end of the stop process, and the third exposure process almost simultaneously.

  When the specified time TD elapses from time t13, the control device 100 ends the third exposure process (time t14). When the sixth time T6 has elapsed from time t14 when the third exposure process is completed, the control device 100 starts a stop process (time t15). When the seventh time T7 elapses from time t14 when the third exposure process ends, the control device 100 ends the charging voltage application process (time t16).

According to the above, the following effects can be obtained in the present embodiment.
When the excess current Ie is equal to or greater than the threshold value Ith, there is a high possibility that the frictional force between the photosensitive drum 51 and the cleaning blade 57 is increased, and charge is generated in the photosensitive layer 51B due to the frictional force. Therefore, by determining whether or not the excess current Ie is equal to or greater than the threshold value Ith, it is possible to appropriately determine whether or not an electric charge resulting from the friction force has occurred, that is, whether or not the friction force has increased. . In addition, when it is determined that the excess current Ie is equal to or greater than the threshold value Ith, the friction reduction process is executed, so that the toner can be supplied to the cleaning blade 57 at an appropriate timing, and the photosensitive drum 51 and the cleaning blade 57 can be supplied. It is possible to satisfactorily suppress an increase in frictional force generated between the two.

  Since the transfer voltage application process is started after the first time T1 has elapsed since the start of the charging voltage application process, for example, the transfer voltage application process is started before the first time T1 has elapsed since the start of the charge voltage application process. Compared to the embodiment, it is possible to suppress the useless application of the third transfer voltage, and it is possible to suppress power consumption.

  Since the determination process is started when the second time T2 has elapsed since the start of the transfer voltage application process, for example, the determination process is started after elapse of a time longer than the second time T2 from the start of the transfer voltage application process. In comparison, the time from the start of the charging voltage application process to the determination process can be shortened.

  If it is determined in the first determination process that Ie ≧ Ith, the residual charge removal process is executed, so that it is possible to suppress an erroneous determination in the determination process due to the influence of the residual charges C1 and C2. Can do.

  By performing the second charging process and the second exposure process for one rotation of the photosensitive drum 51, the first electric field E1 and the charges C11 and C12 generated by the exposure are generated over the photosensitive layer 51B of the entire circumference of the photosensitive drum 51. Can be made. Therefore, the positive residual charge C1 corresponding to the first electric field E1 out of the residual charges C1 and C2 can be removed by the action of the negative charge C12 generated by the exposure and the first electric field E1. Further, by performing the second electric field generation process for one rotation of the photosensitive drum 51, the second electric field E2 opposite to the first electric field E1 is generated over the photosensitive layer 51B of the entire circumference of the photosensitive drum 51. it can. Therefore, the negative residual charge C2 corresponding to the second electric field E2 can be removed by the action of the positive charge C11 generated by the exposure and the second electric field E2.

  Since the second electric field generation process is performed by applying a second transfer voltage having the same polarity as the first transfer voltage to the transfer roller 74, for example, a member for generating the second electric field is provided separately from the transfer roller 74. In comparison, the residual charges C1 and C2 can be removed with a simple configuration.

  Since the second electric field generation process is started after the elapse of the fourth time T4 from the start of the second exposure process, for example, the second electric field generation process is started before the fourth time T4 elapses from the start of the second exposure process. Compared with the form to perform, it can suppress performing a 2nd electric field generation process wastefully, and can suppress power consumption.

  Since the second exposure process is started after the elapse of the third time T3 from the start of the second charge process, for example, the second exposure process is started before the third time T3 elapses from the start of the second charge process. Compared to the above, it is possible to suppress the second exposure process from being performed wastefully and to suppress power consumption.

  In the stop process, the developing roller 54 is separated from the photosensitive drum 51, so that the toner can be satisfactorily stopped from moving from the developing roller 54 to the photosensitive drum 51.

  Since the time for executing the second charging process, the time for executing the second exposure process, and the time for executing the second electric field generation process are set to the same length, it is possible to suppress performing each process wastefully. be able to.

  In addition, this invention is not limited to the said embodiment, It can utilize with various forms so that it may illustrate below. In the following description, the same reference numerals are given to members having substantially the same structure as in the above embodiment, and the description thereof is omitted.

  In the above-described embodiment, the determination process or the like is executed before the image forming process. However, the present invention is not limited to this, and the determination process or the like may be executed after the image forming process. Further, the residual charge removal process in the embodiment is not necessarily required. Specifically, the control device 100 may be configured to perform control according to the flowchart shown in FIG.

  In the form shown in FIG. 11, when the image forming process is finished, that is, when printing for the number of sheets based on the print command is finished (START), the control device 100 executes the processes of steps S1 to S4 similar to the above embodiment. To do. If it is determined in step S4 that Ie ≧ Ith (Yes), the control device 100 executes a friction reduction process (S9) similar to that in the above-described embodiment, and ends this control.

  When it is determined in step S4 that Ie <Ith (No), the control device 100 executes the processes of steps S11 and S12 similar to those in the above embodiment. Even in this embodiment, when Ie ≧ Ith, the friction reducing process is executed, so that the same effect as in the above embodiment can be obtained.

  In addition, in the form of FIG. 11, you may provide the alerting | reporting process which alert | reports abnormality to a user with an alerting | reporting apparatus instead of step S9. That is, the control device 100 may be configured to execute a notification process for notifying the abnormality by the notification device when it is determined in the determination process that the excess current Ie is equal to or greater than the threshold value Ith. Here, the notification device may be a display panel, a lamp, a buzzer, or the like provided in the color printer 1, or may be an external device such as a computer connected to the color printer 1 wirelessly or by wire.

  According to this, when it is determined that the excess current Ie is equal to or greater than the threshold value Ith, an abnormality is notified, so that, for example, the user can be prompted to replace the worn member, and the photosensitive drum 51, the cleaning blade 57, and the like. The increase in the frictional force generated during

  Moreover, as shown in FIG. 12, the control apparatus 100 may be comprised so that both a friction reduction process and an alerting | reporting process may be performed. Specifically, in the form shown in FIG. 12, the notification process is executed when the value of the excess current Ie does not become smaller than the threshold value Ith even if the friction reduction process is executed.

  Here, the flowchart shown in FIG. 12 includes steps S1 to S4, S9, S11, and S12 similar to the flowchart shown in FIG. In the flowchart shown in FIG. 12, new steps S41 to S44 are provided.

  Specifically, when it is determined that Ie ≧ Ith in Step S4 (Yes), the control device 100 determines whether or not the flag F2 is 0 (S41). Here, the flag F2 is a flag indicating whether or not the friction reduction process has been executed. When the flag F2 is 0, it indicates that the friction reduction process has not yet been executed. When the flag F2 is 1, the friction reduction process is performed. Indicates that

  If it is determined in step S41 that F2 = 0 (Yes), the control device 100 executes a friction reduction process (S9). After step S9, the control device 100 sets the flag F2 to 1 (S42) and ends this control.

  If it is determined in step S41 that F2 = 0 is not satisfied (No), the control device 100 executes notification processing (S43). After step S43 or after step S12, the control device 100 returns the flag F2 to 0 (S44) and ends this control.

Next, an example of operation | movement of the control apparatus 100 which concerns on this form is demonstrated.
When receiving the first print command, the control device 100 executes an image forming process. After the image forming process is finished, the control device 100 executes the processes of steps S1 to S4.

  If it is determined in step S4 that Ie ≧ Ith, the controller 100 executes the friction reduction process (S9), sets the flag F2 to 1 (S42), and ends this control. Next, when receiving the second print command, the control device 100 sequentially executes an image forming process and steps S1 to S4.

  If it is determined again in step S4 that Ie ≧ Ith, that is, if the excess current Ie does not become smaller than the threshold value Ith despite the previous friction reduction processing (Yes), the control device 100 determines in step S41. It judges that it is No and performs information processing (S43). That is, when the excess current Ie is equal to or greater than the threshold value Ith in the first determination process performed after the friction reduction process is performed, the control device 100 performs an abnormality by the notification device without performing the friction reduction process. An informing process for informing is executed.

  According to this aspect, when the excess current Ie exceeds the threshold value Ith in the determination process at the time of the next printing after the friction reducing operation is performed, there is a high possibility that the apparatus has an abnormality. It is possible to promptly notify the abnormality without doing so.

  In this embodiment, the notification process is performed when it is determined that Ie ≧ Ith in the determination process that is first performed after the friction reduction process is performed, but the present invention is not limited to this. For example, when it is determined that Ie ≧ Ith in any one of a plurality of determination processes performed after a predetermined time elapses or a print command is received a plurality of times after the friction reduction process is executed A notification process may be executed.

  In the above-described embodiment, the second charging voltage application process is performed after the second electric field generation process is finished. However, the present invention is not limited to this. A second charging voltage application process may be performed. In this case, the charging voltage application process may be continuously performed after the second charging process.

Alternatively, the second transfer voltage application process may be started after the fifth time T5 has elapsed since the second exposure process was completed. Here, the fifth time T5 can be expressed by the following equation (6).
T5 = D5 / S (6)
D5: a portion including the second position P2 and the fourth position P4 (see FIG. 4) facing the transfer roller 74 on the surface of the photoconductive drum 51, and downstream of the second position P2, and Peripheral length of the part upstream from the fourth position P4 S: Peripheral speed of the photosensitive drum 51

  In the embodiment, since the transfer roller 74 is used as the electric field forming member, the distance D4 described above is the same distance as the distance D5, and the fourth time T4 is the same time as the fifth time T5. ing. However, for example, when a member different from the transfer roller 74 is used as the electric field forming member, the distance D4 is different from the distance D5, and the fourth time T4 is different from the fifth time T5. Become.

  As described above, the second transfer voltage application process is started after the elapse of the fifth time T5 from the end of the second exposure process. For example, the second transfer voltage application process is performed after the second electric field generation process. Can be done continuously. For this reason, useless transfer voltage ON / OFF can be eliminated, and the control can be simplified.

  In the above embodiment, the paper P is exemplified as the transfer medium. However, the present invention is not limited to this, and the transfer medium may be, for example, an OHP sheet.

  In the above embodiment, the cleaning blade 57 is exemplified as the sliding contact member. However, the present invention is not limited to this, and the sliding contact member may be, for example, a cleaning roller or a charging roller.

  In the embodiment, the toner is exemplified as the lubricant. However, the present invention is not limited to this, and other lubricants such as grease may be used. In this case, for example, in the friction reduction process, a process may be performed in which the sponge impregnated with grease is moved from a position away from the photosensitive member and brought into contact with the photosensitive member.

  The timing at which the developing roller 54 is separated, that is, the timing at which the stop process is started may be any time as long as the last exposed portion by the first exposure process based on the image data has reached the developing roller 54. Similarly, the end timing of the stop process may be any time after the portion charged by the charging roller 52 has reached the position facing the developing roller 54.

  The start timing and execution time of the second charging process, the second exposure process, and the second electric field generation process are not limited to the above embodiments, and can be set as appropriate. For example, the start timing of the second charging process, the second exposure process, and the second electric field generation process may be performed simultaneously. When the start timing of the second electric field generation process is set earlier than that in the embodiment shown in FIG. 10, a portion where the surface potential of the photosensitive drum 51 becomes negative is generated, and this portion causes the charging roller 52 to There is a possibility that the surface potential of this portion does not rise to a preferable potential only after passing once. Therefore, in this case, the time for the second charging process may be adjusted until the negatively charged portion rises to a preferable surface potential.

  Each process may be performed continuously in each embodiment, or may be performed separately.

  The developer is not limited to a positively charged toner, and may be a negatively charged toner. In the case of using negatively charged toner, the polarity of each voltage described above may be changed to the opposite polarity.

  The photoreceptor is not limited to the photoreceptor drum 51, and may be, for example, a belt-like photoreceptor.

  The charger is not limited to the charging roller 52, and may be, for example, a corona discharge type charger provided at a position away from the photoreceptor. That is, the charger may include a charging wire and a grid electrode.

  The exposure apparatus is not limited to the scanner 40, and may be, for example, an LED unit that exposes the photosensitive member with an LED or a static eliminator that neutralizes the surface of the photosensitive member.

  The developing device is not limited to the developing device 520 provided with the developing roller 54 that is in contact with the photosensitive drum 51, and may be a non-contact type developing device that is disposed away from the photosensitive member, for example.

  The transfer member is not limited to the transfer roller 74, and may be, for example, a non-contact type transfer member that is disposed apart from the photosensitive drum.

  The electric field forming member is not limited to the transfer roller 74 or the photosensitive drum 51, and may be, for example, the cleaning blade 57 or the non-contact transfer member described above.

  The stop process is not limited to the process performed by the contact / separation of the developing roller 54, and for example, the developing voltage applied to the developing roller is switched to a voltage smaller than the surface potential of the exposed portion of the photosensitive drum. The supply of toner from the roller to the photosensitive drum may be stopped.

  The image forming apparatus is not limited to the color printer 1 and may be, for example, a monochrome printer, a copying machine, or a multifunction machine.

  The transfer medium is not limited to the paper P. For example, in an intermediate transfer type printer, a belt that contacts the photosensitive drum may be used.

  Moreover, you may implement combining each element demonstrated by above-described embodiment and modification arbitrarily.

DESCRIPTION OF SYMBOLS 1 Color printer 40 Scanner 51 Photosensitive drum 51B Photosensitive layer 54 Developing roller 57 Cleaning blade 74 Transfer roller 100 Control apparatus 210 Charging voltage application circuit 240 Transfer voltage application circuit 250 1st detection part 260 2nd detection part 520 Developer

Claims (13)

A photoreceptor having a photosensitive layer;
A charger for charging the surface of the photoreceptor;
A charging voltage application circuit for applying a charging voltage to the charger;
An exposure apparatus for exposing the surface of the photoreceptor;
A developer for supplying a developer to the photoreceptor;
A transfer member that transfers the developer on the surface of the photoreceptor to a transfer medium;
A transfer voltage application circuit for applying a transfer voltage to the transfer member;
A sliding contact member in sliding contact with the surface of the photoreceptor;
A first detector for detecting a charging current flowing through the charger;
A second detection unit for detecting a transfer current flowing through the transfer member;
A control device that receives detection signals from the first detection unit and the second detection unit, and
The control device includes:
A determination process is performed to determine whether a difference between the charging current based on the detection signal received from the first detection unit and the transfer current based on the detection signal received from the second detection unit is equal to or greater than a predetermined threshold. And
An image forming apparatus, wherein a friction reduction process for supplying a lubricant to the sliding contact member is executed when it is determined in the determination process that the difference is equal to or greater than a predetermined threshold value. The control device includes:
A charging voltage application process for applying a charging voltage to the charger via the charging voltage application circuit;
Transfer voltage application for applying a transfer voltage to the transfer member via the transfer voltage application circuit while the portion of the photoconductor charged by the charging voltage application process passes through a position facing the transfer member. Process, and
During the execution of the transfer voltage application process, a transfer current based on the detection signal received from the second detection unit is acquired as a first current,
While the portion of the photoconductor whose surface potential has been lowered by the transfer voltage application process passes through a position facing the charger, the charging current based on the detection signal received from the first detection unit is second. Get as current
The image forming apparatus according to claim 1, wherein the acquired second current and the first current are used for calculating the difference in the determination process. The control device starts the transfer voltage application process after a lapse of a first time T1 from the start of the charging voltage application process,
The first time T1 is set such that the distance from the position facing the charger on the surface of the photoconductor to the position facing the transfer member is D1, and the peripheral speed of the photoconductor is S.
T1 = D1 / S
The image forming apparatus according to claim 2, wherein: The control device starts acquiring the second current after elapse of a second time T2 from the start of the transfer voltage application process,
The second time T2 is a distance from a position facing the transfer member to a position facing the charger on the surface of the photoconductor D2 and a peripheral speed S of the photoconductor.
T2 = D2 / S
The image forming apparatus according to claim 3, wherein: The control device includes:
A residual charge removal process for removing residual charges generated in the photosensitive layer can be performed;
In the determination process, if the difference between the charging current and the transfer current is greater than or equal to the threshold value, the residual charge removal process is executed,
After finishing the residual charge removal process, the determination process is executed again,
5. The image forming apparatus according to claim 1, wherein the friction reduction process is executed when the difference is equal to or greater than the threshold as a result of re-determination in the determination process. 6. . An electric field forming member for generating a second electric field in the photosensitive layer opposite to the first electric field generated in the photosensitive layer during charging;
The control device includes:
A first charging process for charging the surface of the photoreceptor with the charger;
A first exposure process for exposing the surface of the photoreceptor charged by the first charging process by the exposure device to form an electrostatic latent image on the surface;
A developing process for supplying a developer to the electrostatic latent image by the developing unit to form a developer image on the surface of the photoreceptor;
A transfer process for transferring the developer image to a transfer medium;
A second charging process for charging the surface of the photoconductor by the charger during at least one rotation of the photoconductor in a period different from the execution period of the first charging process;
During the period in which the portion of the photoconductor charged by the second charging process passes through a position facing the exposure apparatus, the surface of the photoconductor is made to move by the exposure apparatus during at least one rotation of the photoconductor. A second exposure process for exposing;
A stop process for stopping the supply of the developer from the developing unit to the photoconductor during a period in which the portion of the photoconductor exposed by the second exposure process passes through a position facing the developing unit;
In a period in which the portion of the photoconductor exposed by the second exposure process passes through a position facing the electric field forming member, at least during the rotation of the photoconductor, the photoconductor and the electric field forming member A second electric field generation process for generating the second electric field between
6. The image forming apparatus according to claim 5, wherein in the residual charge removal process, the second charging process, the second exposure process, the stop process, and the second electric field generation process are executed. The control device starts the second exposure process after elapse of a third time T3 from the start of the second charging process,
In the third time T3, when the distance from the position facing the charger on the surface of the photoconductor to the position facing the exposure device is D3, and the peripheral speed of the photoconductor is S,
T3 = D3 / S
The image forming apparatus according to claim 6, wherein: The control device starts the second electric field generation process after elapse of a fourth time T4 from the start of the second exposure process,
In the fourth time T4, when the distance from the position facing the exposure device on the surface of the photoconductor to the position facing the electric field forming member is D4, and the peripheral speed of the photoconductor is S,
T4 = D4 / S
The image forming apparatus according to claim 7, wherein: The control device starts the transfer voltage application process after elapse of a fifth time T5 from the end of the second exposure process,
In the fifth time T5, when the distance from the position facing the exposure device on the surface of the photoconductor to the position facing the transfer member is D5 and the peripheral speed of the photoconductor is S,
T5 = D5 / S
The image forming apparatus according to claim 7, wherein:   The control device executes the friction reduction process when the difference between the charging current and the transfer current is equal to or greater than the threshold value in the determination process executed first after the friction reduction process is executed. The image forming apparatus according to any one of claims 1 to 9, wherein a notification process for notifying abnormality is performed by the notification device. A photoreceptor having a photosensitive layer;
A charger for charging the surface of the photoreceptor;
A charging voltage application circuit for applying a charging voltage to the charger;
An exposure apparatus for exposing the surface of the photoreceptor;
A developer for supplying a developer to the photoreceptor;
A transfer member that transfers the developer on the surface of the photoreceptor to a transfer medium;
A transfer voltage application circuit for applying a transfer voltage to the transfer member;
A sliding contact member in sliding contact with the surface of the photoreceptor;
A first detector for detecting a charging current flowing through the charger;
A second detection unit for detecting a transfer current flowing through the transfer member;
An informing unit for informing the abnormality;
A control device that receives detection signals from the first detection unit and the second detection unit, and
The control device includes:
A determination process is performed to determine whether a difference between the charging current based on the detection signal received from the first detection unit and the transfer current based on the detection signal received from the second detection unit is equal to or greater than a predetermined threshold. And
An image forming apparatus comprising: performing a notification process for notifying an abnormality by a notification device when it is determined in the determination process that the difference is equal to or greater than a predetermined threshold value. A photoreceptor having a photosensitive layer;
A charger for charging the surface of the photoreceptor;
A charging voltage application circuit for applying a charging voltage to the charger;
An exposure apparatus for exposing the surface of the photoreceptor;
A developer for supplying a developer to the photoreceptor;
A transfer member that transfers the developer on the surface of the photoreceptor to a transfer medium;
A transfer voltage application circuit for applying a transfer voltage to the transfer member;
A sliding contact member in sliding contact with the surface of the photoreceptor;
A first detector for detecting a charging current flowing through the charger;
A second detection unit for detecting a transfer current flowing through the transfer member;
A control device for receiving a detection signal from the first detection unit and the second detection unit, and a control method by the control device in an image forming apparatus comprising:
Determining whether the difference between the charging current based on the detection signal received from the first detection unit and the transfer current based on the detection signal received from the second detection unit is equal to or greater than a predetermined threshold;
And a step of supplying a lubricant to the sliding contact member when it is determined that the difference is equal to or greater than a predetermined threshold value. A photoreceptor having a photosensitive layer;
A charger for charging the surface of the photoreceptor;
A charging voltage application circuit for applying a charging voltage to the charger;
An exposure apparatus for exposing the surface of the photoreceptor;
A developer for supplying a developer to the photoreceptor;
A transfer member that transfers the developer on the surface of the photoreceptor to a transfer medium;
A transfer voltage application circuit for applying a transfer voltage to the transfer member;
A sliding contact member in sliding contact with the surface of the photoreceptor;
A first detector for detecting a charging current flowing through the charger;
A second detection unit for detecting a transfer current flowing through the transfer member;
A control device that receives detection signals from the first detection unit and the second detection unit, and a program for operating the control device.
The control device;
A determination process is performed to determine whether a difference between the charging current based on the detection signal received from the first detection unit and the transfer current based on the detection signal received from the second detection unit is equal to or greater than a predetermined threshold. Means to
A program for causing a friction reducing process to supply a lubricant to the sliding contact member when the difference is determined to be equal to or greater than a predetermined threshold in the determination process.

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