JP2015069105A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of suppressing the movement of developer from a development roller to a photoreceptor drum when abnormality occurs in a charging wire for charging the photoreceptor drum.SOLUTION: An image forming apparatus includes a control device 100 configured to execute image formation control for forming an image on a sheet. The control device 100 is configured to execute charging bias stop control to control a bias application device 200 to stop to apply a charging bias to a charging wire 52A when the abnormality of the charging wire 52A is detected during the image formation control, development roller separation control to control a contact/separation mechanism 300 to separate a photoreceptor drum 51 from a development roller 54 during the charging bias stop control and sheet ejection control to control a conveyance mechanism for conveying a sheet to eject the sheet during the image formation from the device main body during the development roller separation control.

Description

  The present invention relates to an electrophotographic image forming apparatus such as a laser printer or a copying machine.

  As an electrophotographic image forming apparatus, Patent Document 1 discloses that when abnormal discharge occurs in a charger during an image forming operation, the value of the charging voltage is reduced, and the occurrence of abnormal discharge is stopped by the reduction. An apparatus configured to discharge a sheet during image formation is disclosed. According to such an image forming apparatus, it is possible to reduce time and effort for the user to remove the paper on which image formation was being performed, and therefore, it is possible to reduce the countermeasures to be taken when abnormal discharge occurs.

JP 2010-14817 A

  By the way, in the prior art, when an abnormal discharge occurs, the value of the charging voltage is reduced to such an extent that the developer does not adhere to the unexposed portion of the photoconductor, but from the developer carrier such as a developing roller to the photoconductor. The transfer of the developer was not considered.

  The present invention has been made in view of the above background, and can suppress the movement of the developer from the developer carrying member to the photosensitive member when an abnormality occurs in the charging member that charges the photosensitive member. An object is to provide a forming apparatus.

In order to achieve the above object, an image forming apparatus of the present invention includes a photosensitive member, a charging member that charges the photosensitive member by applying a charging bias, and a developer carrying member that supplies the developer to the photosensitive member in contact with the photosensitive member. An image forming unit having a body, a bias applying device for applying a charging bias, a contact / separation mechanism for contacting or separating the photosensitive member and the developer carrier, and a transport mechanism for transporting a recording sheet, And a control device configured to execute image formation control for forming an image on a recording sheet by controlling an image forming unit, a bias applying device, and a conveyance mechanism.
When the control device detects an abnormality of the charging member during the image formation control, the control device controls the bias applying device to stop the application of the charging bias to the charging member, and the contact and separation during the charging bias stop control. Developer movement suppression control for controlling the mechanism to separate the photosensitive member from the developer carrying member, and sheet discharge for discharging the recording sheet during image formation from the apparatus main body by controlling the conveyance mechanism during developer movement suppression control The control is configured to be executable.

  According to such a configuration, when the application of the charging bias to the charging member is stopped, the photosensitive member and the developer carrying member are separated from each other, so that the movement of the developer from the developer carrying member to the photosensitive member is suppressed. can do. Thereby, wasteful consumption of the developer and contamination of the photosensitive member due to the adhesion of the developer can be suppressed.

In order to achieve the above-described object, the image forming apparatus of the present invention includes a photosensitive member, a charging member that charges the photosensitive member by applying a charging bias, and a developer carrying member that supplies the developer to the photosensitive member by applying a developing bias. An image forming unit having a body, a bias applying device for applying a charging bias and a developing bias, a conveying mechanism for conveying a recording sheet, and a recording sheet by controlling the image forming unit, the bias applying device, and the conveying mechanism And a control device configured to execute image formation control for forming an image.
The control device controls the bias applying device to stop the application of the charging bias to the charging member when an abnormality of the charging member is detected during the image formation control, and the bias application during the charging bias stop control. During the developer movement suppression control, and the developer movement suppression control in which the developing bias is applied so that the potential difference between the photosensitive member and the developer carrier is smaller than during the image formation control on the developer carrier by controlling the apparatus. And a sheet discharge control for discharging a recording sheet during image formation from the apparatus main body by controlling the conveyance mechanism.

  According to such a configuration, when the application of the charging bias to the charging member is stopped, the potential difference between the photosensitive member and the developer carrying member becomes small, so that the developer from the developer carrying member to the photosensitive member can be reduced. Movement can be suppressed. Thereby, wasteful consumption of the developer and contamination of the photosensitive member due to the adhesion of the developer can be suppressed.

  The image forming apparatus described above includes a notifying unit for notifying abnormality of the charging member, and the control device is configured to notify the abnormality of the charging member by controlling the notifying unit after starting the charging bias stop control. be able to.

  In the above-described image forming apparatus, the control device can be configured to resume the image forming control when detecting that the abnormality of the charging member has been resolved.

  The image forming apparatus described above includes a cleaning member for removing the developer attached to the photoreceptor, and the control device detects that the abnormality of the charging member has been resolved and then restarts the image forming control. The first cleaning control for removing the developer attached to the photosensitive member by the cleaning member can be configured to be executable.

  According to this, since the image formation control can be resumed after the photosensitive member is cleaned, it is possible to suppress deterioration in image quality due to the developer on the photosensitive member adhering to the recording sheet.

  In the above-described image forming apparatus, the image forming unit includes a transfer member that transfers the developer on the photosensitive member to the recording sheet by applying a transfer bias, and the bias applying apparatus is configured to apply the transfer bias and control the transfer member. The apparatus controls the bias application device during the developer movement suppression control, applies a transfer bias to the transfer member, and performs a second cleaning control for transferring the developer on the photosensitive member to the recording sheet discharged by the sheet discharge control. It can be configured to be executable.

  According to this, the photoconductor can be cleaned without providing a dedicated member for cleaning the photoconductor. Further, in a configuration including a dedicated member for cleaning the photoconductor, the cleaning performance can be improved.

  The above-described image forming apparatus is provided with a cleaning member for removing the developer attached to the photosensitive member, and the control device is photosensitive by the cleaning member until the recording sheet is discharged from the apparatus main body by sheet discharge control. The third cleaning control for removing the developer attached to the body can be executed.

  According to this, it is possible to shorten the time until the image formation control is restarted as compared with the case where the photosensitive member is cleaned after the recording sheet during image formation is discharged.

  The image forming apparatus described above includes a sheet setting unit for setting a recording sheet before image formation, and the control device develops on the condition that the recording sheet is sent from the sheet setting unit toward the image forming unit. It can be set as the structure which performs agent movement suppression control and sheet | seat discharge control.

  According to the present invention, it is possible to suppress the movement of the developer from the developer carrying member to the photosensitive member when an abnormality occurs in the charging member that charges the photosensitive member.

1 is a diagram illustrating an overall configuration of a color printer as an example of an image forming apparatus. FIG. 2 is a diagram illustrating a configuration of a main part of a color printer. FIG. 2 is a diagram illustrating a configuration of a main part of a color printer in a state where a photosensitive drum and a developing roller are separated from each other. It is a flowchart which shows the control in a control apparatus. It is a flowchart of wire abnormality response control of a 1st embodiment. It is a flowchart of wire abnormality response control of 2nd Embodiment. It is a flowchart of wire abnormality response control of 3rd Embodiment. It is a flowchart of wire abnormality response control of 4th Embodiment.

[First Embodiment]
Next, the first embodiment will be described in detail with reference to the drawings as appropriate. In the following, first, the overall configuration of the color printer 1 as an example of the image forming apparatus will be briefly described, and then the detailed configuration of the color printer 1 according to the characteristic part of the invention will be described. In the following description, the direction will be described with reference to the user who uses the color printer 1. Specifically, the left side of FIG. 1 as viewed from the user is “front”, the right side of FIG. 1 as viewed from the user is “rear”, and the front side of FIG. 1 is “right”. ”, The left side of the page is“ left ”. Further, the vertical direction in FIG.

<Overall configuration of color printer>
As shown in FIG. 1, the color printer 1 mainly includes a paper feeding unit 20, an image forming unit 30, and a collecting unit 90 in a main body housing 10 as an example of an apparatus main body. On the upper side of the main body housing 10 is provided an upper cover 12 configured such that the front side can be opened and closed up and down with the rear side as a rotation center.

  The sheet feeding unit 20 is provided at a lower portion in the main body housing 10 and mainly includes a sheet feeding tray 21 as an example of a sheet setting unit and a sheet feeding mechanism 22. The paper feed tray 21 is a member for setting paper S as an example of a recording sheet before image formation, and is detachable from the main body housing 10. The paper feed mechanism 22 sends out the paper S from the paper feed tray 21 toward the image forming unit 30 and supplies the paper S to the image forming unit 30 one by one.

  The image forming unit 30 mainly includes four exposure units 40, four process cartridges 50, a transfer unit 70, and a fixing unit 80.

  The exposure unit 40 includes a plurality of light emitting diodes (LEDs) (not shown) that are arranged to face the photosensitive drum 51 and are arranged in the left-right direction at the tip thereof. The exposure unit 40 causes the LED to blink based on the image data, thereby exposing the surface of the charged photosensitive drum 51 to form an electrostatic latent image on the photosensitive drum 51. The exposure unit 40 is held by the upper cover 12 through the holding unit 14 and is separated from the photosensitive drum 51 by opening the upper cover 12.

  The process cartridges 50 are arranged in the front-rear direction between the upper cover 12 and the paper feed tray 21, and each can be attached to and detached from the main body housing 10 (replaceable) when the upper cover 12 is opened. It has become. Each process cartridge 50 mainly includes a photosensitive drum 51 as an example of a photosensitive member, a charger 52, a developing unit 53, and a cleaning roller 57 as an example of a cleaning member.

  The photosensitive drum 51 is a member in which a photosensitive layer is formed on the outer peripheral surface of a cylindrical drum body having conductivity, and a shaft that is connected to the drum body is grounded, and rotates in a direction indicated by an arrow in FIG. To drive.

  The charger 52 includes a charging wire 52 </ b> A as an example of a charging member, a grid electrode that is omitted from the reference numeral, and the like, and is disposed to face the upper rear of the photosensitive drum 51. The charging wire 52A generates a corona discharge by applying a positive charging bias to uniformly positively charge the surface of the photosensitive drum 51.

  The developing unit 53 includes a developing roller 54 as an example of a developer carrying member, a supply roller with reference numerals omitted, a layer thickness regulating blade, a toner storage unit that stores positively charged toner as an example of a developer, and the like. And is disposed opposite to the front upper side of the photosensitive drum 51. The developing roller 54 is configured to be able to carry toner, and supplies toner to the photosensitive drum 51 by applying a positive developing bias in a state where the developing roller 54 is in contact with the photosensitive drum 51.

  The cleaning roller 57 is a member in which a metal rotating shaft is covered with a roller body made of a conductive foamed elastic body, and is disposed facing the back of the photosensitive drum 51. The cleaning roller 57 removes and temporarily holds the toner adhering to the photosensitive drum 51 after transfer by applying a negative cleaning bias during image formation control, which will be described later, and also performs cleaning during collection control, which will be described later. The toner held by applying a positive bias (hereinafter referred to as an ejection bias) having a polarity opposite to that of the bias is moved onto the photosensitive drum 51.

  The transfer unit 70 is provided between the paper feeding unit 20 and the process cartridge 50, and includes a driving roller 71, a driven roller 72, an endless conveyance belt 73, and a transfer roller 74 as an example of four transfer members. It is mainly equipped with. The conveyor belt 73 is stretched between the driving roller 71 and the driven roller 72, and the respective photosensitive drums 51 are arranged on the upper side of the outer peripheral surface so as to face each other. The transfer roller 74 is disposed to face the lower side of the photoconductive drum 51 via the conveyance belt 73, and onto the photoconductive drum 51 on the sheet S conveyed between the photoconductive drum 51 by application of a negative transfer bias. The toner image is transferred.

  The fixing unit 80 is provided behind the process cartridge 50 and the transfer unit 70, and mainly 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.

  The collection unit 90 is provided below the conveyance belt 73 and conveys between the first collection roller 91, the second collection roller 92, the scraping blade 93, the toner storage unit 94, and the first collection roller 91. A backup roller 95 that sandwiches the belt 73 is mainly provided. The collection unit 90 collects toner and the like attached on the conveyance belt 73 in the toner storage unit 94.

<Detailed configuration of color printer>
As shown in FIG. 2, the color printer 1 includes a control device 100, a bias applying device 200, a contact / separation mechanism 300, and a display device 400 as an example of a notification unit.

  The bias applying device 200 is a device for applying a charging bias, a developing bias, a transfer bias, a cleaning bias, and a discharge bias, and is connected to the charging wire 52A, the developing roller 54, the transfer roller 74, and the cleaning roller 57. Since such a bias application device 200 can employ a known configuration, a detailed description thereof will be omitted in this specification. In FIG. 2, for the sake of convenience, a configuration in which a bias is applied to the charging wire 52A, the developing roller 54, the cleaning roller 57, and the transfer roller 74 by one bias applying device 200 is illustrated, but the present invention is not limited thereto. For example, the bias applying device may be provided individually corresponding to the charging wire 52 </ b> A, the developing roller 54, the cleaning roller 57, and the transfer roller 74.

  The contact / separation mechanism 300 is a mechanism for bringing the photosensitive drum 51 and the developing roller 54 into contact with or apart from each other (see FIG. 3). In the present embodiment, the contact / separation mechanism 300 is configured to move the developing unit 53 relative to the photosensitive drum 51 to bring the developing roller 54 into contact with or separate from the photosensitive drum 51. Since such a contact / separation mechanism 300 can employ a known configuration, detailed description thereof is omitted in this specification.

  The display device 400 is a device for notifying the abnormality of the charging wire 52 </ b> A, and is specifically configured as a liquid crystal display or an organic EL display provided in the main body housing 10. In order to notify the abnormality of the charging wire 52A, the display device 400 displays a message such as “Please clean the charging wire” or a message “Please replace the cartridge”, for example.

  Here, the abnormality of the charging wire 52A refers to a state in which corona discharge due to the application of a charging bias may not be performed normally. Specifically, for example, the electrical resistance of the charging wire 52A increases due to adhesion of silica, which is an external additive of the toner, to the charging wire 52A, and a current flowing through the charging wire 52A when a charging bias is applied is predetermined. It is in a state where it is below the value.

  The control device 100 is a device that controls the operation of the color printer 1 by controlling each part of the color printer 1. The control device 100 includes a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), an input / output interface, and the like (not shown), and the detection results of various sensors and preset programs. Control is performed by performing each arithmetic processing based on the above.

In the present embodiment, the control device 100 is mainly configured to be able to execute image formation control, collection control, and wire abnormality response control.
Details of each control will be described below.

(Image formation control)
The image formation control is mainly control for executing an operation of forming an image on the paper S by controlling the image forming unit 30, the bias applying device 200, and the transport mechanism. Here, the transport mechanism is a mechanism for transporting the paper S in the direction from the inside of the paper feed tray 21 toward the paper discharge tray 13 (outside the main body housing 10). In this embodiment, the paper feed mechanism is mainly used. The mechanism 22, the photosensitive drum 51, the transfer unit 70, the fixing unit 80, the transport roller 15, and the discharge roller 16 are configured.

  The control device 100 executes image formation control when a print job including an image formation instruction and image data is input from a personal computer (not shown).

  More specifically, in image formation control, the image forming unit 30 is driven, the surface of the rotating photosensitive drum 51 is positively charged by the charger 52 to which a charging bias is applied, and exposed by the exposure unit 40. Then, an electrostatic latent image based on the image data is formed on the photosensitive drum 51. Then, toner is supplied from a developing roller 54 to which a developing bias is applied to the photosensitive drum 51, whereby the electrostatic latent image is visualized and a toner image is formed on the photosensitive drum 51.

  At an appropriate timing so far, the control device 100 drives the paper feed mechanism 22 (conveyance mechanism) and supplies the paper S stored in the paper feed tray 21 to the image forming unit 30. Then, the toner image on the photosensitive drum 51 is transferred onto the paper S by conveying the paper S supplied from the paper supply unit 20 between the photosensitive drum 51 and the transfer roller 74 to which a transfer bias is applied. To do. Thereafter, the sheet S on which the toner image is transferred is conveyed between the heating roller 81 and the pressure roller 82 to thermally fix the toner image. Then, the sheet S on which the toner image is thermally fixed is discharged out of the main body housing 10 (on the sheet discharge tray 13) by the transport roller 15 and the discharge roller 16.

  In the series of operations so far, the control device 100 drives the cleaning roller 57 while applying a cleaning bias, and collects the toner remaining on the surface of the photosensitive drum 51 after the transfer on the cleaning roller 57.

(Recovery control)
The collection control mainly controls the process cartridge 50, the transfer unit 70, the collection unit 90, and the bias applying device 200, and the toner adhering to the cleaning roller 57, the photosensitive drum 51, and the conveyance belt 73 is transferred to the toner storage unit 94. This is control for executing the collecting operation.
The control device 100 executes collection control, for example, after the image formation control is finished.

  More specifically, in the collection control, a discharge bias is applied to the cleaning roller 57 to discharge the toner attached to the cleaning roller 57 and move it onto the photosensitive drum 51. Further, a transfer bias is applied to the transfer roller 74 to move the toner adhering to the photosensitive drum 51 onto the transport belt 73. Then, the toner collected on the conveyance belt 73 is collected in the toner storage unit 94 by the first collection roller 91, the second collection roller 92, and the scraping blade 93.

  After executing the collection control for a predetermined time, the control device 100 ends and puts the color printer 1 into a standby state for the next print job input.

(Wire abnormality control)
The wire abnormality handling control is a control executed when the control device 100 detects an abnormality of the charging wire 52A during the image formation control. In the present embodiment, the control device 100 monitors the current flowing through the charging wire 52A when the charging bias is applied, and if the current flowing through the charging wire 52A becomes equal to or less than a predetermined value, the charging wire 52A is abnormal. Is determined to have occurred.

  When the control device 100 detects an abnormality in the charging wire 52A during the image formation control, specifically, an abnormality has occurred in the charging wire 52A because the current flowing through the charging wire 52A has become a predetermined value or less. In principle, charging bias stop control, abnormality notification control, developer roller separation control as an example of developer movement suppression control, paper discharge control as sheet discharge control, and operation stop control can be executed. It is configured.

  In addition, when the control device 100 detects that the abnormality of the charging wire 52A has been resolved after executing the operation stop control, specifically, the current flowing through the charging wire 52A exceeds a predetermined value and the charging wire 52A When it is determined that the abnormality has been resolved, the first cleaning control and the image formation resumption control can be executed.

  The charging bias stop control is a control for controlling the bias applying device 200 to execute an operation for stopping the application of the charging bias to the charging wire 52A.

  The abnormality notification control is control for executing an operation of controlling the display device 400 to notify the abnormality of the charging wire 52A after starting the charging bias stop control. Specifically, after starting the charging bias stop control, the control device 100 controls the display device 400 at an appropriate timing, and instructs the display device 400 to “clean the charging wire”, for example. Display a message.

  The developing roller separation control is a control for executing the operation of separating the photosensitive drum 51 and the developing roller 54 by controlling the contact / separation mechanism 300 during the charging bias stop control. As a result, the photosensitive drum 51 and the developing roller 54 shown in FIG. 2 are brought into contact with each other, and the photosensitive drum 51 and the developing roller 54 shown in FIG. Will be cut off.

  The paper discharge control is a control for executing an operation of discharging the paper S during image formation from the main body housing 10 by controlling the transport mechanism during the developing roller separation control. Here, during the developing roller separation control, not only during the operation of separating the photosensitive drum 51 and the developing roller 54 but also during maintaining the separated state of the photosensitive drum 51 and the developing roller 54. It is out. Further, the sheet S during image formation is a conveyance path of the sheet S before being fed from the sheet feed tray 21 by the sheet feed mechanism 22 and discharged from the main body housing 10 onto the sheet discharge tray 13. It is the sheet S existing above.

  The operation stop control is performed after the paper S is discharged from the main body housing 10 onto the paper discharge tray 13 by executing the paper discharge control, or when the paper discharge control is not executed as will be described later. Is executed mainly to control the transport mechanism to stop the transport operation of the paper S and the like. The control device 100 continues to execute the operation stop control until it is detected that the abnormality of the charging wire 52A has been resolved.

  In this embodiment, when the control device 100 detects an abnormality in the charging wire 52A during image formation control, the sheet S is sent from the sheet feed tray 21 toward the image forming unit 30 by the sheet feed mechanism 22 ( The above-described developing roller separation control and paper discharge control are executed on the condition that the paper is fed and is not discharged from the main body casing 10 onto the paper discharge tray 13 (not discharged). It is configured. In other words, when the control device 100 detects an abnormality in the charging wire 52A during image formation control, the sheet S is not sent out from the paper feed tray 21 toward the image forming unit 30 by the paper feed mechanism 22. When the sheet S does not exist on the conveyance path of the sheet S, the above-described developing roller separation control and sheet discharge control are not executed.

  Whether or not the sheet S is sent from the sheet feeding tray 21 toward the image forming unit 30 is determined by, for example, a first sheet detection sensor (not shown) provided near the sheet feeding mechanism 22 on the sheet S conveyance path. can do. Whether or not the paper S is discharged from the main body housing 10 onto the paper discharge tray 13 is determined by, for example, a second paper detection (not shown) provided on the downstream side of the fixing unit 80 on the transport path of the paper S. It can be determined by a sensor.

  The reason why the sheet discharge control is not executed when the sheet S is not sent from the sheet feed tray 21 toward the image forming unit 30 is that in this case, between the sheet feed tray 21 and the sheet discharge tray 13. This is because there is no sheet S to be discharged on the conveyance path of the sheet S, so that it is not necessary to drive the conveyance mechanism in order to discharge the sheet S from the main body housing 10.

  The first cleaning control is mainly control for controlling the process cartridge 50 and executing the operation of removing the toner adhering to the photosensitive drum 51 by the cleaning roller 57 to which the cleaning bias is applied. After detecting that the abnormality has been resolved, it is executed before resuming image formation control. The operation executed by the first cleaning control is the same as the operation for collecting the toner remaining on the surface of the photosensitive drum 51 after the transfer onto the cleaning roller 57, which is executed during the image forming control.

  The image formation restart control is control for restarting image formation control by controlling the image forming unit 30, the bias applying device 200, the contact / separation mechanism 300, and the transport mechanism. Specifically, in the image formation resumption control, the contact / separation mechanism 300 is controlled so that the photosensitive drum 51 and the developing roller 54 shown in FIG. Then, an operation of shifting to image formation control is executed. As a result, the color printer 1 executes an operation of forming the image that was being formed when the abnormality of the charging wire 52A was detected on the paper S.

Next, the flow of control in the control device 100 will be described.
As shown in FIG. 4, when a print job is input to the color printer 1 in the standby state, the control device 100 executes image formation control to form an image on the paper S (S101). During image formation control, the control device 100 determines whether or not each charging wire 52A is abnormal while forming an image on the paper S (S103).

  If no abnormality is detected in all the charging wires 52A during the image formation control (S103, No), the processing of the input print job is completed and the image formation on the paper S is completed (S105, Yes). The apparatus 100 executes collection control to collect the toner attached to the cleaning roller 57, the photosensitive drum 51, and the conveyance belt 73 in the toner storage unit 94 (S107), and waits for the color printer 1 after the collection control is completed. State.

  On the other hand, when at least one abnormality among the four charging wires 52A is detected during the image formation control (S103, Yes), the control device 100 executes wire abnormality response control (S200).

  As shown in FIG. 5, in the wire abnormality response control S200, the control device 100 executes the charging bias stop control to stop the application of the charging bias to the charging wire 52A (S201), and executes the abnormality notification control. For example, a message such as “Please clean the charging wire” is displayed on the display device 400 to notify the abnormality of the charging wire 52A (S203). The display device 400 may be configured to be able to notify the charging wire 52A in which an abnormality has occurred individually (for each color).

  Next, the control device 100 determines whether or not the paper S is sent out from the paper feed tray 21 toward the image forming unit 30 (whether or not it is fed) (S205). When the paper S has been sent out (when it has been fed) (S205, Yes), the control device 100 determines whether or not the sent paper S is discharged from the main body housing 10 onto the paper discharge tray 13. It is determined (whether or not the paper has been discharged) (S206).

  When the sheet S has not been discharged (when it has not been discharged) (S206, No), the control device 100 executes the developing roller separation control to separate the photosensitive drum 51 and the developing roller 54 (S207). Then, the paper S that has been sent out by executing the paper discharge control is discharged from the inside of the main body housing 10 onto the paper discharge tray 13 (S209). Thereafter, the control device 100 executes operation stop control to stop the transport operation of the paper S (S211). Further, when the sheet S is not sent out at step S205 (when it is not fed) (No), or when the sheet S is discharged at step S206 (when it is discharged) (Yes). The control device 100 executes the operation stop control without executing the developing roller separation control and the paper discharge control to stop the transport operation of the paper S (S211).

  After stopping the operation of the color printer 1, the control device 100 determines whether or not the abnormality of the charging wire 52A has been resolved (S213). When the user cleans the charging wire 52A or replaces the charging wire 52A (process cartridge 50) and the abnormality of the charging wire 52A is resolved (S213, Yes), the control device 100 performs the first cleaning control. And the toner adhering to the photosensitive drum 51 is removed by the cleaning roller 57 (drum cleaning is executed) (S215).

  After executing the first cleaning control, the control device 100 executes image formation resumption control to bring the photosensitive drum 51 and the developing roller 54 into contact with each other, and proceeds to image formation control (S217). Thereafter, as shown in FIG. 4, the control device 100 executes image formation control to form an image on the paper S (S101), determines whether the charging wire 52A is abnormal (S103), and the paper S When the image formation is completed (S105, Yes), the collection control is executed (S107), and after the collection control is completed, the color printer 1 is set in a standby state.

  According to the present embodiment described above, when an abnormality of the charging wire 52A is detected during image formation control, the sheet S during image formation is discharged from the main body housing 10, and thus the user has to remove the sheet S. It can be omitted. Then, when the application of the charging bias to the charging wire 52A is stopped, the photosensitive drum 51 and the developing roller 54 are separated from each other, so that toner movement from the developing roller 54 to the photosensitive drum 51 can be suppressed. . Thereby, wasteful consumption of toner and contamination of the photosensitive drum 51 due to toner adhesion can be suppressed.

  In the present embodiment, the first cleaning control for removing the toner adhering to the photosensitive drum 51 is executed after detecting that the abnormality of the charging wire 52A has been resolved and before restarting the image forming control. Image formation control can be resumed after the photosensitive drum 51 is cleaned. As a result, it is possible to suppress deterioration in image quality due to the toner on the photosensitive drum 51 adhering to the paper S supplied after resuming image formation control.

  In the present embodiment, the first cleaning control is executed before the image forming control is resumed after detecting that the abnormality of the charging wire 52A has been resolved. However, the present invention is not limited to this. It is not a thing. For example, instead of the first cleaning control, the recovery control may be executed.

  In this embodiment, when the paper S is not sent from the paper feed tray 21 toward the image forming unit 30, the development roller separation control and the paper discharge control are not executed. It is not limited to. For example, when the paper S is not sent from the paper feed tray 21 toward the image forming unit 30, the developing roller separation control may be executed without executing only the paper discharge control.

[Second Embodiment]
Next, a second embodiment will be described. In the embodiments described below including this embodiment, the same components and control processes as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 6, in this embodiment, the control device 100 executes the second cleaning control (see step S221) instead of the first cleaning control (step S215 in FIG. 5) described in the first embodiment. It is configured to be possible.

  In the second cleaning control, the bias applying device 200 is controlled to apply the transfer bias to the transfer roller 74 during the developing roller separation control, and the toner on the photosensitive drum 51 is transferred to the paper S discharged by the paper discharge control. This is a control to execute the operation. During the developing roller separation control here, the photosensitive drum 51 and the developing roller 54 may be in the middle of separation, or may be after the photosensitive drum 51 and the developing roller 54 are separated. .

  Specifically, in the present embodiment, in the wire abnormality handling control S200 shown in FIG. 6, the control device 100 controls the bias applying device 200 while the developing roller 54 is being separated or after the developing roller 54 is separated (S207). Then, a transfer bias is applied to the transfer roller 74 (S221). Thereafter, the paper discharge control is executed by driving the transport mechanism, whereby the toner on the photoconductive drum 51 is transferred to the paper S transported between the photoconductive drum 51 and the transfer roller 74, thereby The toner adhering to the body drum 51 is removed.

  In the present embodiment, the developing roller separation control and the paper discharge control are executed regardless of whether or not the paper S is sent out from the paper feed tray 21 toward the image forming unit 30. Supplementally, in the paper discharge control of this embodiment, the toner on the photosensitive drum 51 is transferred to the paper S to clean the photosensitive drum 51, so that the paper S is directed from the paper feed tray 21 toward the image forming unit 30. If it is not sent out, the carrying mechanism is controlled to send out one sheet S from the paper feed tray 21 and carry it toward the outside of the main body housing 10 (the paper discharge tray 13).

  According to the present embodiment described above, the photosensitive drum 51 can be cleaned without providing a dedicated member for cleaning the photosensitive drum 51 such as the cleaning roller 57. Thereby, the configuration of the color printer 1 can be simplified and the cost can be reduced.

  In the present embodiment, the second cleaning control is executed instead of the first cleaning control. However, the present invention is not limited to this. For example, both the first cleaning control (step S215 in FIG. 5) and the second cleaning control (step S221 in FIG. 6) may be executed. According to this, the cleaning performance of the photosensitive drum 51 can be enhanced.

[Third Embodiment]
Next, a third embodiment will be described.
As shown in FIG. 7, in the present embodiment, the control device 100 performs a third cleaning control (see step S231) that performs the same operation as the first cleaning control described in the first embodiment on the paper discharge control. It is configured to be executable until S is discharged from the main body casing 10.

  Specifically, in the present embodiment, after executing the developing roller separation control in the wire abnormality handling control S200 shown in FIG. 7 (S207), the control device 100 executes the paper discharge control and removes the paper S from the main body housing. While discharging from the inside 10 onto the paper discharge tray 13, the third cleaning control is executed to remove the toner adhering to the photosensitive drum 51 by the cleaning roller 57 (drum cleaning is executed) (S231).

  In the present embodiment, when the abnormality of the charging wire 52A is resolved (S213, Yes), the control device 100 determines whether or not the sheet discharge control is executed (S233). When the paper discharge control is executed (S233, Yes), since the drum cleaning is executed at the same time (see step S231), the control device 100 executes the image formation resumption control (S217). On the other hand, when the sheet discharge control is not executed (S233, No), since the drum cleaning is not executed, the control device 100 executes the control (drum cleaning) for performing the same operation as the third cleaning control. Thereafter, image formation resumption control is executed (S217).

  According to the present embodiment described above, in particular, when the third cleaning control for executing drum cleaning during discharge of the paper S is executed, it is compared with the case where drum cleaning is executed after the paper S is discharged. Thus, the time until the image forming control is restarted can be shortened.

[Fourth Embodiment]
Next, a fourth embodiment will be described.
In this embodiment, the color printer 1 does not include the contact / separation mechanism 300 as shown in FIG. Further, as shown in FIG. 8, the control device 100 reduces the developing bias as another example of the developer movement suppression control instead of the developing roller separation control (step S207 in FIG. 5) described in the first embodiment. Control (step S241) can be executed.

  In developing bias reduction control, the bias applying device 200 is controlled during charging bias stop control, and a developing bias is applied to the developing roller 54 such that the potential difference between the photosensitive drum 51 and the developing roller 54 becomes smaller than during image formation control. It is control to execute the operation to perform. In the present embodiment, the application of the developing bias to the developing roller 54 is stopped as the developing bias reduction control.

  According to this embodiment, when the application of the charging bias to the charging wire 52 </ b> A is stopped, the application of the developing bias to the developing roller 54 is stopped to stop the photosensitive drum 51 than during image formation control. Since the potential difference between the developing roller 54 and the developing roller 54 is small, toner movement from the developing roller 54 to the photosensitive drum 51 can be suppressed. Thereby, wasteful consumption of toner and contamination of the photosensitive drum 51 due to toner adhesion can be suppressed.

  In this embodiment, the control for stopping the application of the developing bias to the developing roller 54 is exemplified as the developing bias reduction control. However, the present invention is not limited to this. For example, the development bias reduction control may be control for applying a development bias having a smaller absolute value than during image formation control.

  In this embodiment, when the paper S is not sent from the paper feed tray 21 toward the image forming unit 30, the development roller separation control and the paper discharge control are not executed. It is not limited to. For example, when the paper S is not sent from the paper feed tray 21 toward the image forming unit 30, the development bias reduction control may be executed without executing only the paper discharge control.

  In the present embodiment, the developing roller separation control (step S207 in FIG. 5) in the first embodiment is replaced with the developing bias reduction control (step S241 in FIG. 8). However, the present embodiment is not limited to this. is not. For example, the developing roller separation control (step S207 in FIGS. 6 and 7) in the second embodiment and the third embodiment can be applied to the development bias reduction control.

  Although the embodiment has been described above, the present invention is not limited to the embodiment. About a concrete structure, it can change suitably in the range which does not deviate from the meaning of invention as follows.

  In the embodiment, the display device 400 that notifies the abnormality of the charging wire 52 </ b> A by displaying a message is exemplified as the notification unit, but the notification unit is not limited thereto. For example, the notification unit may be a lamp that notifies the abnormality of the charging wire 52A by turning on or off, or a speaker that notifies the abnormality of the charging wire 52A by sound such as sound. Further, the notification unit may be configured by combining a display device, a lamp, a speaker, and the like.

  In the embodiment, the color printer 1 includes the collection unit 90 and is configured to execute the collection control after the image formation control. However, the present invention is not limited to this. For example, the color printer 1 may be configured to store the toner collected by the cleaning roller 57 in each process cartridge 50 without including the collection unit 90.

  In the above embodiment, the cleaning roller 57 is exemplified as the cleaning member, but the present invention is not limited to this. For example, the cleaning member may be a brush roller having a conductive fiber layer on the surface. The cleaning member may be a developing roller. In this case, referring to FIG. 1, the toner on the photosensitive drum 51 is removed from the photosensitive drum 51 by the developing roller 54 and is collected in the toner storage portion of the developing unit 53. The cleaning member may be a cleaning blade that scrapes off the developer on the photosensitive member, a cleaning brush, or the like. The application of the cleaning bias to the cleaning member is arbitrary. For example, when a cleaning blade is used as the cleaning member, the cleaning bias may not be applied.

  In the above-described embodiment, the scorotron charger 52 having the grid electrode has been exemplified. However, the present invention is not limited to this. For example, a corotron charger may be used. In the above-described embodiment, the charging wire 52A is exemplified as the charging member. However, the charging member is not limited to this. For example, the charging member may be an array of needle-shaped electrodes, a charging roller, or the like.

  In the embodiment, the photosensitive drum 51 is exemplified as the photosensitive member. However, the photosensitive drum 51 is not limited thereto. For example, the photosensitive member may be a photosensitive belt.

  In the above-described embodiment, the transfer roller 74 is exemplified as the transfer member. However, the transfer roller 74 is not limited thereto. For example, the transfer member may be a transfer charger having substantially the same configuration as the charger 52.

  In the above-described embodiment, the sheet feeding tray 21 is exemplified as the sheet setting unit. However, the present invention is not limited to this. For example, the sheet setting unit may be a so-called manual feed tray.

  In the embodiment, the color printer 1 that includes a plurality of photoreceptors, charging members, developer carriers, and the like and can form a color image is exemplified as the image forming apparatus. However, the present invention is not limited to this. For example, the image forming apparatus may be a printer that includes one photoconductor, one charging member, one developer carrier, and the like and can form only a monochrome image. The image forming apparatus is not limited to a printer, and may be, for example, a copier or a multi-function machine including a document reading apparatus such as a flat bed scanner.

  In the above embodiment, an example in which the present invention is applied to an image forming apparatus using a positively charged toner has been described, but the present invention is not limited to this. That is, the present invention can also be applied to an image forming apparatus that uses a negatively charged toner (developer). In this case, the polarity of the bias is opposite to that in the above embodiment.

DESCRIPTION OF SYMBOLS 1 Color printer 10 Main body housing | casing 15 Conveyance roller 16 Discharge roller 21 Paper feed tray 22 Paper feed mechanism 30 Image formation part 51 Photoconductor drum 52A Charging wire 54 Developing roller 57 Cleaning roller 70 Transfer unit 74 Transfer roller 80 Fixing unit 100 Control apparatus 200 Bias Application Device 300 Contact / Separation Mechanism 400 Display Device S Paper

Claims (8)

An image forming unit comprising: a photoconductor; a charging member that charges the photoconductor by applying a charging bias; and a developer carrier that supplies the developer to the photoconductor while being in contact with the photoconductor.
A bias applying device for applying a charging bias;
A contacting / separating mechanism for contacting or separating the photosensitive member and the developer carrying member;
A transport mechanism for transporting the recording sheet;
A control device configured to execute image formation control for controlling the image forming unit, the bias applying device, and the transport mechanism to form an image on a recording sheet;
When the control device detects an abnormality of the charging member during the image formation control,
Charging bias stop control for controlling the bias applying device to stop the application of the charging bias to the charging member;
Developer movement suppression control for controlling the contact / separation mechanism during the charging bias stop control to separate the photosensitive member from the developer carrier;
An image forming apparatus configured to execute sheet discharge control for controlling the transport mechanism to discharge a recording sheet during image formation from the apparatus main body during the developer movement suppression control. An image forming unit comprising: a photoconductor; a charging member that charges the photoconductor by applying a charging bias; and a developer carrier that supplies the developer to the photoconductor by applying a developing bias;
A bias applying device for applying a charging bias and a developing bias;
A transport mechanism for transporting the recording sheet;
A control device configured to execute image formation control for controlling the image forming unit, the bias applying device, and the transport mechanism to form an image on a recording sheet;
When the control device detects an abnormality of the charging member during the image formation control,
Charging bias stop control for controlling the bias applying device to stop the application of the charging bias to the charging member;
During the charging bias stop control, the bias applying device is controlled so that a developing bias is applied to the developer carrier so that the potential difference between the photosensitive member and the developer carrier is smaller than during the image formation control. Developer movement suppression control;
An image forming apparatus configured to execute sheet discharge control for controlling the transport mechanism to discharge a recording sheet during image formation from the apparatus main body during the developer movement suppression control. An informing unit for informing about the abnormality of the charging member;
The image forming apparatus according to claim 1, wherein the control device notifies the abnormality of the charging member by controlling the notification unit after starting the charging bias stop control.   4. The image forming apparatus according to claim 1, wherein the control device restarts the image forming control when detecting that the abnormality of the charging member is resolved. 5. A cleaning member for removing the developer attached to the photoreceptor;
The control device performs first cleaning control for removing the developer attached to the photosensitive member by the cleaning member after detecting that the abnormality of the charging member has been resolved and before restarting the image forming control. The image forming apparatus according to claim 4, wherein the image forming apparatus is configured to be possible. The image forming unit includes a transfer member that transfers the developer on the photoconductor to a recording sheet by applying a transfer bias,
The bias applying device is configured to apply a transfer bias;
The control device controls the bias application device during the developer movement suppression control to apply a transfer bias to the transfer member, and the developer on the photosensitive member is discharged onto the recording sheet discharged by the sheet discharge control. The image forming apparatus according to claim 1, wherein the second cleaning control for transferring is executable. A cleaning member for removing the developer attached to the photoreceptor;
The control device is configured to be able to execute a third cleaning control for removing the developer attached to the photosensitive member by the cleaning member until the recording sheet is discharged from the apparatus main body by the sheet discharge control. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. It has a sheet set part for setting the recording sheet before image formation,
The control device performs the developer movement suppression control and the sheet discharge control on the condition that a recording sheet is sent from the sheet setting unit toward the image forming unit. The image forming apparatus according to claim 7.

Images