Image forming device

Abstract

To provide an image forming apparatus that has better print quality than before.SOLUTION: An image forming apparatus comprises photoconductor drums (52), developing units (60), electrifying units (53), recovery devices (54, 61, 91), and a control unit (100). The control unit (100) executes recovery operation determination processing when executing a print job, and executes recovery operation before executing image forming processing.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an image forming apparatus. [Background technology]

[0002] Conventionally, there have been image forming apparatuses equipped with a developer cartridge that can be attached to and detached from the image forming apparatus main body. For example, the image forming apparatus described in Patent Document 1 determines whether a developer cartridge is new when it is attached to the image forming apparatus main body. If it is determined that the developer cartridge is new, it activates a new developer start-up mode and performs idle rotation for the time required to homogenize the developer and charge the toner. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-056601 Summary of the Invention [Problem to be solved by the invention]

[0004] However, because the idle rotation required to charge the toner is not limited to when a new developer cartridge is installed, the image forming apparatus described in Patent Document 1 may start image formation with the toner in an insufficiently charged state. In this case, the toner with insufficient charge moves to the photosensitive member via the developing roller, and the toner may fall onto the paper instead of being carried by the photosensitive member. This may result in a decrease in print quality.

[0005] The present disclosure aims to provide an image forming apparatus that provides better print quality than conventional ones. [Means for solving the problem]

[0006] In order to solve the above problem, the image forming apparatus of the present disclosure includes a photosensitive drum, a developing unit having a developing roller and a toner storage unit that stores toner, a charger that charges the photosensitive drum, a recovery device that recovers toner adhering to the surface of the photosensitive drum, and a control unit. When a print job is executed, the control unit executes a recovery operation determination process whose execution condition is that the amount of operation of the developing unit since its unused state is less than a predetermined value and the elapsed time since the image formation process based on the previous print job is greater than or equal to a predetermined time. The control unit is also configured to execute recovery operations including a charging process that charges the photosensitive drum using the charger if the execution condition is met before executing the image formation process based on the print job, an idling process that rotates the developing roller before the start of the image formation process, and rotates the developing roller for a time longer than the rotation time of the developing roller when the execution condition is not met, and a toner recovery process that recovers toner adhering to the surface of the photosensitive drum using the recovery device.

[0007] According to the above configuration, a collection operation determination process is executed before an image forming process is executed. If the collection operation determination process determines that the conditions for executing the collection operation are met, the charging process, the idle rotation process, and the toner collection process are executed. As a result, even if toner with insufficient charge adheres to the surface of the photosensitive drum via the developing roller during the idle rotation process, the toner can be collected during the toner collection process. More specifically, the idle rotation process rotates the developing roller for a longer period of time than when the conditions for executing the collection operation determination process are not met, thereby increasing the charge on the toner. Furthermore, the toner that adheres to the surface of the photosensitive drum can be collected during the process of increasing the charge on the toner. This reduces the risk of toner not being carried by the photosensitive drum and falling onto the sheet due to insufficient charge on the toner, thereby providing an image forming apparatus with better print quality than conventional apparatuses.

[0008] In the image forming device according to the present disclosure, the execution conditions for the recovery operation determination process may further include a case where the amount of operation of the developing device since its unused state is less than a predetermined value and the elapsed time since the image forming process based on the previous print job cannot be obtained.

[0009] According to the above configuration, even if the elapsed time since the previous image forming process cannot be obtained, the recovery operation can be performed, and thus the charge amount of the toner can be increased even if the elapsed time since the previous image forming process cannot be obtained.

[0010] In the image forming apparatus according to the present disclosure, the operation amount may be a cumulative number of rotations of the developing roller.

[0011] According to the above configuration, the cumulative number of rotations of the developing roller can be used as the amount of operation of the developing unit.

[0012] In the image forming apparatus according to the present disclosure, the recovery device may have a cleaning roller that rotates in contact with the surface of the photosensitive drum to recover toner adhering to the photosensitive drum, and the control unit may apply a first cleaning bias to the cleaning roller during the toner recovery process, the first cleaning bias being a bias that is smaller than the surface potential of the photosensitive drum or a bias of opposite polarity to the surface potential of the photosensitive drum.

[0013] According to the above configuration, the toner adhering to the surface of the photosensitive drum can be collected by the cleaning roller.

[0014] The image forming apparatus according to the present disclosure may further include a belt in contact with the surface of the photosensitive drum and a transfer roller arranged to sandwich the belt between the belt and the photosensitive drum, wherein the recovery device has a belt cleaner that recovers toner adhering to the belt, and the control unit may apply a second cleaning bias, which is a bias of opposite polarity to the surface potential of the photosensitive drum, to the transfer roller in the toner recovery process in order to transfer the toner adhering to the surface of the photosensitive drum to the belt, and recover the toner transferred to the belt by the belt cleaner while rotating the belt.

[0015] According to the above configuration, the toner adhering to the surface of the photosensitive drum is transferred to the belt, and the toner transferred to the belt can be collected by the belt cleaner.

[0016] The image forming apparatus according to the present disclosure may further include a contact / separation mechanism that can switch between a contact state in which the photosensitive drum and the developing roller are in contact with each other and a separated state in which the photosensitive drum and the developing roller are separated from each other, and the control unit may be configured to bring the photosensitive drum and the developing roller into the contact state during the idling process.

[0017] According to the above configuration, the photosensitive drum and the developing roller are in contact with each other during the idle rotation process, so that the toner can be transferred from the developing roller to the photosensitive drum while preventing the toner from scattering during the idle rotation process.

[0018] In the image forming apparatus according to the present disclosure, the developing device may further include a memory for storing information regarding the amount of operation, and the control unit may determine whether the amount of operation is less than a predetermined value based on the information regarding the amount of operation stored in the memory.

[0019] According to the above configuration, it is determined whether the operation amount of the developing unit is less than a predetermined value based on the information about the operation amount of the developing unit stored in the memory, and therefore it is possible to determine whether the idling process and the toner recovery process are necessary even if the developing unit has been replaced from another image forming apparatus.

[0020] The image forming device according to the present disclosure may be configured such that the memory includes information regarding the charging characteristics of the toner contained in the toner storage unit, and the control unit executes the recovery operation determination process when it determines, based on the information regarding the charging characteristics, that the toner contained in the toner storage unit has low charging efficiency.

[0021] According to the above configuration, when the toner charging efficiency is low, for example, in the case of a developer in which black toner is stored in the toner storage section, the recovery operation determination process is executed, but when the developer in which toner other than black is stored in the toner storage section, the recovery operation determination process is not executed.

[0022] Therefore, the recovery operation is performed only on the developing device of a specific color with low toner charging efficiency, so that the recovery operation can be prevented from lengthening the time until printing is completed. [Effects of the Invention]

[0023] According to one aspect of the present disclosure, it is possible to provide an image forming apparatus that has better print quality than conventional ones. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a diagram showing a schematic configuration of a color printer according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is a diagram showing a color printer with the front cover open and the drawer pulled out. [Figure 3] FIG. 2 is a diagram illustrating functional blocks of a color printer. [Figure 4]1A and 1B are diagrams showing an example of a contact / separation mechanism, in which (A) shows a color mode, (B) shows a monochrome mode, and (C) shows a separation mode. [Figure 5] FIG. 4 is a diagram showing an example of developing device information stored in a developing device memory. [Figure 6] 10 is a flowchart illustrating an example of the operation of a color printer. [Figure 7] 10 is a timing chart relating to a collection operation. DETAILED DESCRIPTION OF THE INVENTION

[0025] An embodiment of the present disclosure will be described in detail below.

[0026] <Outline of color printer configuration> FIG. 1 is a diagram showing a schematic configuration of a color printer 1 according to an embodiment of the present disclosure. FIG. 2 is a diagram showing the color printer 1 with the front cover 11 open and the drawer 51 pulled out. The color printer 1, which is an example of an image forming apparatus, is a laser printer that prints an image on a sheet S using an electrophotographic method. In the following description, the directions of the color printer 1 shown in each drawing will be referred to as follows: the "right side" facing the paper surface of each drawing will be referred to as the "front side," the "left side" facing the paper surface of each drawing will be referred to as the "rear side," and the "upper side" and "lower side" facing the paper surface of each drawing will be referred to as the "upper side" and "lower side," respectively. The directions from the front side to the back side will sometimes be referred to as the front-to-rear direction.

[0027] As shown in FIG. 1, the color printer 1 includes a main body 10, a conveying section 20 disposed inside the main body 10, an image forming section 30, a cleaning unit 90, and a control section 100.

[0028] 2, color printer 1 has an opening 10A at the front of main body 10 for attaching and detaching process unit 50 (described later), and a front cover 11. Front cover 11 is an openable cover for closing opening 10A. Front cover 11 is provided on main body 10 so as to be rotatable around its lower end.

[0029] The conveying unit 20 is provided in the lower part of the main body 10, and includes a sheet tray 21 that stores sheets S, a pressure plate 22, and a feeding mechanism 23. The conveying unit 20 conveys the sheets S to the image forming unit 30 by the feeding mechanism 23.

[0030] The image forming section 30 includes an exposure unit 40, a process unit 50, a transfer unit 70, and a fixing unit 80.

[0031] The exposure unit 40 is provided in the upper part of the main body 10. The exposure unit 40 exposes the surface of the photosensitive drum 52 with laser light (see the dashed line in FIG. 1) emitted from the exposure unit 40 based on image data.

[0032] The process unit 50 is disposed between the sheet tray 21 and the exposure unit 40, and includes a drawer 51, four photosensitive drums 52 arranged in the front-to-rear direction, a charger 53 provided for each photosensitive drum 52, a cleaning roller 54, and a developing unit 60.

[0033] The drawer 51 is a member that holds the photosensitive drum 52 and the like. The drawer 51 is configured to be detachable from the main body 10. This allows the members held in the drawer 51, such as the photosensitive drum 52 and the developing unit 60, to be individually replaced while pulled out from the main body 10. In other words, the drawer 51, the photosensitive drum 52, and the developing unit 60 are configured to be separable from each other.

[0034] The photosensitive drum 52 is a member in which a photosensitive layer is formed on the outer peripheral surface of a cylindrical drum body having electrical conductivity, and is provided so as to be rotatable in the direction of the arrow shown on the photosensitive drum 52 in FIG.

[0035] The charger 53 includes a charging wire, a grid electrode, and the like, the reference numerals of which are omitted, and is configured to uniformly charge the surface of the photosensitive drum 52 .

[0036] The cleaning roller 54 is a member in which a metal rotating shaft is covered with a roller body made of a conductive elastic foam. The cleaning roller 54 collects toner adhering to the surface of the photosensitive drum 52 while rotating in contact with the surface of the photosensitive drum 52.

[0037] The photosensitive drum 52, the charger 53, and the cleaning roller 54 may be provided individually to the main body 10, or may be provided as a drum unit that is detachable from the main body 10.

[0038] The developing device 60 includes a developing roller 61, a supply roller 62, a layer thickness regulating blade 63, a toner storage section 64 configured to store toner, and an agitator 65 as an example of an agitating member. The developing roller 61 is a roller configured to be able to supply toner to the photosensitive drum 52, and the agitator 65 is configured to agitate the toner stored in the toner storage section 64 by rotating.

[0039] The toner storage section 64 of each developing device 60 stores toner of each color, yellow, magenta, cyan, and black, in that order from the front to the rear of the main body 10. Hereinafter, in this specification and drawings, when identifying a developing device 60 or a photosensitive drum 52 corresponding to a toner color, the symbols Y, M, C, and K will be appropriately assigned to correspond to yellow, magenta, cyan, and black, respectively.

[0040] The toner contained in the toner container 64 is supplied from the supply roller 62 to the developing roller 61, and is regulated to a certain thickness between the developing roller 61 and the layer thickness regulating blade 63 before being carried on the surface of the developing roller 61.

[0041] The transfer unit 70 is provided between the sheet tray 21 and the process unit 50, and includes a drive roller 71, a driven roller 72, a conveyor belt 73 which is an example of a belt, and a transfer roller 74. The conveyor belt 73 is an endless belt stretched between the drive roller 71 and the driven roller 72, and is disposed opposite the photosensitive drum 52. Four transfer rollers 74 are provided corresponding to the photosensitive drums 52, and are disposed so as to sandwich the conveyor belt 73 between the corresponding photosensitive drum 52.

[0042] The fixing unit 80 is provided at the rear side of the process unit 50 and the transfer unit 70, and includes a heating roller 81 and a pressure roller 82.

[0043] In the image forming section 30 configured as above, the surface of each photosensitive drum 52 is uniformly charged by the charger 53 and exposed by the exposure unit 40. As a result, an electrostatic latent image based on image data is formed on the surface of the photosensitive drum 52.

[0044] Furthermore, the toner carried by the developing roller 61 is supplied to the electrostatic latent image formed on the surface of the photosensitive drum 52, thereby making the electrostatic latent image visible and forming a toner image on the surface of the photosensitive drum 52. Then, the sheet S, which has been transported from the transport unit 20 onto the transport belt 73, passes between each transfer roller 74, which is arranged to sandwich the transport belt 73 between itself and the photosensitive drum 52, thereby sequentially transferring the toner images formed on each photosensitive drum 52 onto the sheet S. The sheet S, onto which the toner image has been transferred, is transported between a heating roller 81 and a pressure roller 82, whereby the toner image is thermally fixed. The sheet S, onto which the toner image has been thermally fixed, is discharged onto the discharge tray 12 by transport rollers 18 and discharge rollers 19.

[0045] In this embodiment, the conveying belt 73 conveys the sheet S onto which the toner image is transferred, but it may also be an intermediate transfer belt in which the toner image is transferred onto the belt itself, and the toner image transferred onto the belt is further transferred onto the sheet S.

[0046] The cleaning unit 90 is disposed below the conveyor belt 73. The cleaning unit 90 includes a belt cleaner 91, a collection roller 92, a scraping blade 93, a storage section 94, and a backup roller 95 that holds the conveyor belt 73 between the cleaning unit 90 and the belt cleaner 91.

[0047] The cleaning unit 90 is configured to collect toner adhering to the surface of the conveyor belt 73 using a belt cleaner 91 , and to collect the toner in a reservoir 94 via a collection roller 92 and a scraping blade 93 .

[0048] Instead of the belt cleaner 91, a cleaning blade or a cleaning brush may be brought into contact with the conveyor belt 73 to collect the toner adhering to the surface of the conveyor belt 73.

[0049] <Color printer functional configuration> 3 is a diagram showing the functional blocks of color printer 1. In addition to the above-mentioned components, color printer 1 also includes control unit 100, drive unit 13, main body memory 14, connector 15, and connection / disconnection mechanism 16. Furthermore, developing unit 60, which is detachably attached to color printer 1, includes developing unit memory 67.

[0050] (control unit 100) The control unit 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, and a RAM (Random Access Memory) 103.

[0051] CPU 101 performs processing in accordance with programs read from ROM 102 and stores the results of that processing in RAM 103 while controlling each part of color printer 1. ROM 102 stores various programs, including, for example, programs for controlling each part of color printer 1. RAM 103 is used as a working area when CPU 101 executes the various programs and as a temporary storage area for data.

[0052] (Driver 13) The drive device 13 inputs a driving force to the developing device 60. Here, the description will be made with reference to FIG. 2 as needed. As shown in FIG. 2, the drive device 13 includes four joints 13A that input a driving force to an input gear (not shown), a motor (not shown), and a gear train that transmits the driving force of the motor to the joints 13A. The joints 13A are configured to move forward and backward relative to the developing device 60 in conjunction with the opening and closing of the front cover 11, for example, and engage with the input gear when the developing device 60 is attached to the main body 10 and the front cover 11 is closed. The joints 13A are also configured to be able to input a driving force even when the developing device 60 is displaced by switching between a contact state and a separation state between the photosensitive drum 52 and the developing roller 61 using a contact / separation mechanism 16 (described later).

[0053] (Main memory 14) Returning to FIG. 3, the main memory 14 is a memory from which information can be read and written. The type of the main memory 14 is not particularly limited. For example, the main memory 14 is a volatile memory or a non-volatile memory. The main memory 14 stores developer information 140, which is various information related to the developer 60. The developer information 140 will be described in detail later.

[0054] (Connector 15) The connector 15 is electrically connected to a developer memory 67 provided in the developer 60. When the connector 15 and the developer memory 67 are electrically connected, the control unit 100 becomes able to communicate with the developer memory 67. In other words, the control unit 100 becomes able to write information to the developer memory 67, rewrite information, and read information from the developer memory 67.

[0055] (Approach / separate mechanism 16) The contact / separation mechanism 16 is configured to switch between a contact state in which the photosensitive drum 52 and the developing roller 61 are in contact with each other, and a separation state in which the photosensitive drum 52 and the developing roller 61 are separated from each other. The developing roller 61 is biased by a spring (not shown) in a direction from the developing roller 61 toward the photosensitive drum 52, and the contact / separation mechanism 16 is configured to move the developing roller 61 in a direction opposite to the direction from the developing roller 61 toward the photosensitive drum 52. Details of the contact / separation mechanism 16 will be described with reference to FIG. 4.

[0056] 4A and 4B are diagrams showing an example of the contact / separation mechanism 16, where (A) shows the color mode, (B) shows the monochrome mode, and (C) shows the separation mode. As shown in Fig. 4, the contact / separation mechanism 16 includes, for example, a linear cam 200 and a cam drive mechanism 300.

[0057] The linear cam 200 is a generally plate-shaped member that is long in the front-rear direction and is provided to the side of the process unit 50, and is supported so as to be movable in the front-rear direction relative to the main body 10. The upper surface of the linear cam 200 is provided with one recess 201 that can be engaged with the rotation shaft KS of the developing roller 61K, three recesses 202 that can be engaged with the rotation shafts CS, MS, and YS that correspond to the developing rollers 61C, 61M, and 61Y, respectively, and an inclined surface 203 that slopes upward from the rear to the front toward the upper surface of the linear cam 200 on the front side of the bottom surfaces of the recesses 201 and 202. The recess 201 is formed to be longer in the front-rear direction than the recess 202.

[0058] The cam drive mechanism 300 is a mechanism for transmitting the driving force of the drive unit 13 to the linear cam 200. As shown in Fig. 4, the cam drive mechanism 300 includes a plurality of gears including a cam gear 301, and a lower surface gear 302 provided on the lower surface of the linear cam 200 so as to mesh with the tooth tips of the cam gear 301. The cam drive mechanism 300 transmits the driving force to the linear cam 200 through the meshing of the cam gear 301 and the lower surface gear 302. When the cam gear 301 rotates clockwise as indicated by the dashed arrow in Fig. 4, the linear cam 200 moves rearward, and when the cam gear 301 rotates counterclockwise as indicated by the solid arrow in Fig. 4, the linear cam 200 moves frontward.

[0059] When the cam gear 301 rotates clockwise, of the rotation axes KS, CS, MS, and YS of the four developing rollers 61 that were engaged with the recesses 201 and 202, the rotation axes CS, MS, and YS move upward along the inclined surface 203. As a result, the developing rollers 61Y, 61M, and 61C are separated from the photosensitive drums 52Y, 52M, and 52C, as shown in FIG. 4(B). When the cam gear 301 stops in this state, the monochrome mode is entered, in which only the photosensitive drum 52K and the developing roller 61K are in contact with each other.

[0060] When the cam gear 301 further rotates clockwise from the state shown in FIG. 4(B), the linear cam 200 moves further rearward. When the linear cam 200 moves rearward, the rotation shaft KS moves upward along the inclined surface 203, as shown in FIG. 4(C). This separates the developing roller 61K from the photosensitive drum 52K. When the developing roller 61K is separated, the state becomes a separation mode in which all the developing rollers 61 are separated from the photosensitive drum 52K.

[0061] When the cam gear 301 rotates counterclockwise from the separation mode, the linear cam 200 moves forward. As a result, of the rotation axes KS, CS, MS, and YS of the four developing rollers 61 supported on the upper surface of the linear cam 200, the rotation axis KS moves downward along the inclined surface 203. This brings the rotation axis KS into contact with the photosensitive drum 52K. When the cam gear 301 stops in this state, the monochrome mode is entered. When the cam gear 301 further rotates counterclockwise from the state shown in FIG. 4B, the linear cam 200 moves further forward. When the linear cam 200 moves forward, the rotation axes CS, MS, and YS move downward along the inclined surface 203 as shown in FIG. 4A. This brings the photosensitive drums 52Y, 52M, and 52C into contact with the developing rollers 61Y, 61M, and 61C, entering the color mode.

[0062] Although the linear cam 200 is described as having recesses 201 and 202 that can engage with the rotation axes YS, MS, CS, and KS of the developing rollers 61Y, 61M, 61C, and 61K, the linear cam 200 is not limited to this configuration. For example, the linear cam 200 may be configured such that the rotation axes YS, MS, CS, and KS engage with portions other than the recesses 201 and 202 to move the developing devices 60. In this case, the linear cam 200 does not need to have the recesses 201 and 202. In other words, the linear cam 200 only needs to have a structure that can move the rotation axes YS, MS, CS, and KS up and down. Furthermore, the contact / separation mechanism 16 may have a structure such as a cam provided for each developing device 60, instead of the linear cam 200. In other words, each of the developing devices 60Y, 60M, 60C and 60K may be configured to have a cam that is configured to switch between a contact state in which the photosensitive drum 52 and the developing roller 61 are in contact with each other and a separated state in which the photosensitive drum 52 and the developing roller 61 are separated from each other.

[0063] (Developer memory 67) 3, the developer memory 67 is a memory from which information can be read and written. There are no particular limitations on the type of developer memory 67, as long as it is a non-volatile memory. The developer memory 67 stores developer information 670, which is various information related to the developers 60, distinguishing between each developer 60.

[0064] (Developer information 670) 5 is a diagram showing an example of developer information 670 stored in developer memory 67. The developer information 670 includes, for example, color information 671, a cumulative number of developing roller rotations 672, and capacity information 673. In this embodiment, the developer information 140 stored in the main body memory 14 has the same data structure as the developer information 670, and therefore a detailed description of the developer information 140 will be omitted.

[0065] (Color information 671) The color information 671 is information indicating the color of the toner contained in the toner container 64. In the present embodiment, as an example, the toner container 64 contains four colors: C, M, Y, and K. The color information 671 indicates one of the above colors.

[0066] (Cumulative number of rotations of the developing roller: 672) The cumulative number of developing roller rotations 672 is an example of the amount of operation of the developing device 60. The cumulative number of developing roller rotations 672 is information indicating the number of rotations of the developing roller 61 in the developing device 60 that have occurred in conjunction with the execution of image formation processing based on a print job since the developing device 60 was first installed in the color printer 1. In other words, the cumulative number of developing roller rotations 672 is the cumulative value of the number of rotations of the developing roller 61 from when the developing device 60 was unused.

[0067] (Capacity information 673) The capacity information 673 is information indicating the capacity of toner in the toner storage unit 64. For example, the capacity information 673 is information indicating the amount of toner filled in the toner storage unit 64 when it is new. The capacity information 673 is also information indicating the amount of toner remaining after the toner filled in the toner storage unit 64 is consumed by executing an image forming process. The capacity information 673 may be composed of values ​​corresponding to a plurality of stages from full to empty, for example. For example, the capacity information 673 may be a character string such as "FULL" to "EMPTY," or a numerical value such as "100%" to "0%," or a combination of a character string and a numerical value. The information may be configured to be displayed on a display (not shown) provided on the main body.

[0068] The initial value of the capacity information 673 corresponds to the maximum amount that can be stored in the toner storage unit 64. As an example, the control unit 100 may calculate the amount of toner consumed in printing based on the print data. The control unit 100 may subtract the amount of toner obtained by this calculation from the capacity information 673, and write a value corresponding to the remaining amount of toner into the developing unit memory 67 as new capacity information 673.

[0069] Note that the amount of toner consumed in printing is not limited to being calculated based on print data, and for example, when toner is consumed as the developing device 60 is used, a value corresponding to the remaining amount of toner may be obtained by a sensor (not shown) optically measuring the toner in the toner storage unit 64. The control unit 100 may write the value corresponding to the remaining amount of toner obtained by this measurement into the developing device memory 67 as capacity information 673.

[0070] Note that the above-described various types of information in the developer information 670 are merely examples of information that may be included in the developer information 670. The developer information 670 may also include information other than the above-described various types of information. Furthermore, some of the above-described various types of information in the developer information 670 may be omitted as appropriate.

[0071] <Collecting operation determination process> Next, a flow chart will be described with reference to the flow of the collection operation determination process executed by the control unit 100 of the color printer 1. Fig. 6 is a flowchart for explaining an example of the operation of the color printer 1.

[0072] The collection operation determination process is a process for determining whether or not a collection operation is necessary based on the execution conditions of the collection operation. Specifically, when a print job is executed, if the amount of operation of the developing device 60 since its unused state is less than a predetermined value and the elapsed time since the image formation process based on the previous print job is equal to or longer than a predetermined time, the control unit 100 determines to execute the collection operation.

[0073] The condition for executing the collection operation is not limited to when the elapsed time since the image forming process based on the previous print job is equal to or greater than a predetermined time. Specifically, the condition for executing the collection operation may be when the amount of operation of the developing device 60 since its unused state is less than a predetermined value when a print job is executed, and when the elapsed time since the image forming process based on the previous print job cannot be obtained. This is because when the elapsed time since the previous image forming process cannot be obtained, the charge amount of the toner may have decreased.

[0074] When the control unit 100 receives a print command, in step S1, the control unit 100 acquires the developing unit information 670 stored in the developing unit memory 67. Note that the control unit 100 may acquire the developing unit information 140 stored in the main body memory 14.

[0075] In step S2, upon acquiring the developing device information 670, the control unit 100 determines whether the operation amount of the developing device 60 is less than a predetermined value. The operation amount of the developing device 60 is the operation amount of the developing device 60 from an unused state, which in this embodiment is the cumulative number of rotations of the developing roller 672. The cumulative number of rotations of the developing roller 672 is stored in the developing device memory 67. The cumulative number of rotations of the developing roller 61 newly acquired through image formation processing is added to the cumulative number of rotations of the developing roller 672 read from the developing device memory 67. The cumulative number of rotations of the developing roller 61 newly acquired through image formation processing is then added to the cumulative number of rotations of the developing roller 672 read from the developing device memory 67, thereby rewriting the cumulative number of rotations of the developing roller 672 and updating it to the latest information.

[0076] The predetermined value of the cumulative number of rotations of the developing roller 672 is determined in advance for each developing roller 61 depending on the type, specifications, etc. of the developing roller 61. The predetermined value of the cumulative number of rotations of the developing roller 61 is a threshold value calculated from the total number of rotations allowed for the developing roller 61, for example, less than 5% of the total number of rotations. In other words, upon acquiring the developing device information 670, the control unit 100 determines whether the amount of operation of the developing device 60 is less than the predetermined value based on whether the cumulative number of rotations of the developing roller 672 is less than 5% of the total number of rotations. The cumulative number of rotations of the developing roller 672 may be stored in the main body memory 14.

[0077] If the control unit 100 determines that the cumulative number of rotations of the developing roller 672 is not less than the predetermined value (S2: NO), the control unit 100 executes image forming processing based on the print job in step S3, and ends the flow.

[0078] On the other hand, if the control unit 100 determines that the cumulative number of developing roller rotations 672 is less than the predetermined value (S2: YES), then in step S4, the control unit 100 acquires the time that has elapsed since the image forming process based on the previous print job. The time that has elapsed since the image forming process based on the previous print job is stored in the developing unit memory 67. That is, the control unit 100 acquires the time that has elapsed since the previous image forming process that is stored in the developing unit memory 67. Note that the time that has elapsed since the previous image forming process may also be stored in the main body memory 14. Furthermore, the time that has elapsed since the previous image forming process may also be acquired from a timing mechanism for measuring time, instead of from the developing unit memory 67, for example.

[0079] In step S5, the control unit 100 determines whether or not the elapsed time since the previous image forming process has been acquired from the developing unit memory 67. The case where the elapsed time since the previous image forming process cannot be acquired occurs, for example, when the developing unit memory 67 is a volatile memory and the first image forming process has not been performed since the color printer 1 was turned off and then turned back on. Also, this occurs when the developing unit 60 is a brand new unit that has never been installed in the color printer 1 since being shipped from the factory, and no image forming process has ever been performed with the brand new developing unit 60. Also, this occurs when the developing unit 60 is not a brand new unit, but is removed from the color printer 1 and then re-installed in the color printer 1. If the control unit 100 cannot acquire the elapsed time since the previous image forming process from the developing unit memory 67 (S5: NO), the control unit 100 executes a recovery operation in step S6. The recovery operation will be described in detail later.

[0080] On the other hand, if the control unit 100 can acquire the elapsed time since the previous image forming process from the developing unit memory 67 (S5: YES), the control unit 100 determines in step S7 whether the acquired elapsed time since the previous image forming process is equal to or greater than a predetermined time. The predetermined time is stored in the developing unit memory 67. The predetermined time is determined in advance for each developing unit 60 depending on the type, specifications, etc. of the developing unit 60. The predetermined time is, for example, a time determined between 2 hours and 12 hours. In other words, the control unit 100 determines whether the elapsed time since the previous image forming process is equal to or greater than the predetermined time based on whether the elapsed time since the previous image forming process is equal to or greater than the predetermined time stored in the developing unit memory 67. The predetermined time may be stored in the developing unit memory 67.

[0081] If the control unit 100 determines that the elapsed time since the acquired previous image forming process is less than a predetermined time (S7: NO), the control unit 100 executes the image forming process based on the print job and ends the flow in step S3. On the other hand, if the control unit 100 determines that the elapsed time since the acquired previous image forming process is equal to or greater than a predetermined time (S7: YES), the control unit 100 executes the collection operation in step S6.

[0082] <Details of collection operation> As explained above, when the control unit 100 determines in the collection operation determination process that the collection operation should be performed before the image forming process based on the print job is performed, the control unit 100 performs the charging process, the idling process, and the toner collection process. Here, the explanation will be given with reference to FIG. 7 as needed. FIG. 7 is a timing chart related to the collection operation.

[0083] (Charging treatment) The charging process is a process in which the photosensitive drum 52 is charged by the charger 53. When the color printer 1 is powered on, the control unit 100 applies a charging bias to the charger 53, as shown at time t1. This charges the surface of the photosensitive drum 52 to the same polarity as the charging bias. At this time, the surface potential of the photosensitive drum 52 becomes approximately the same potential as the potential applied as the charging bias. In addition, the control unit 100 starts driving the developing roller 61, transfer roller 74, cleaning roller 54, and belt cleaner 91 at the timing (time t1) when the charging bias is applied.

[0084] (Idle rotation processing) The control unit 100 starts the idling process at the timing indicated by time t1. The idling process is a process of rotating the developing roller 61 before the start of the image forming process. In the idling process, the control unit 100 rotates the developing roller 61 for a time period longer than the rotation time of the developing roller 61 when the execution conditions for the collection operation are not satisfied. For example, the control unit 100 rotates the developing roller 61 for a second time period longer than the first time period, which is the time period for rotating the developing roller 61 for the image forming process.

[0085] After starting the idling process, the control unit 100 drives the contact / separation mechanism 16 at the timing shown as time t2 to bring the photosensitive drum 52 into contact with the developing roller 61. Note that this contact state may be in either the color mode or the monochrome mode.

[0086] The control unit 100 rotates the developing roller 61 while keeping the photosensitive drum 52 and the developing roller 61 in contact with each other until the second time has elapsed. Note that, during the idle rotation process, the control unit 100 does not apply the bias that is applied when performing the image forming process to the developing roller 61. This makes it possible to suppress the supply of toner from the developing roller 61 to the photosensitive drum 52.

[0087] The second time is the time indicated by time T2, and is determined in advance for each developing device 60 depending on the type and specifications of the developing device 60. The second time is a time determined, for example, between 5 and 30 seconds. At the timing indicated by time t3, the control unit 100 drives the contact / separation mechanism 16 to separate the photosensitive drum 52 and the developing roller 61. Thereafter, when time T2 has elapsed, that is, at the timing indicated by time t4, the rotation of the developing roller 61 is stopped. This ends the idling process.

[0088] The timing at which the driving of the contact / separation mechanism 16 is completed is set to a timing before the lapse of time T2. More specifically, the driving of the contact / separation mechanism 16 may be set to be completed between time t3 and time t4.

[0089] (Toner recovery process) In the recovery operation, the control unit 100 executes a toner recovery process in which the toner adhering to the surface of the photosensitive drum 52 is recovered by the cleaning roller 54, which is an example of a recovery device. The recovery device may be configured to include a belt cleaner 91 in addition to the cleaning roller 54. Also, the recovery device may be configured to use the developing roller 61. In other words, the recovery device may be configured to use the cleaning roller 54, the belt cleaner 91, and the developing roller 61 simultaneously, or any of them may be omitted.

[0090] The control unit 100 performs the toner recovery process from the time when the control unit 100 starts driving the cleaning roller 54, the belt cleaner 91, and the transfer roller 74 at the timing shown as time t1 until the control unit 100 stops driving the cleaning roller 54, the belt cleaner 91, and the transfer roller 74 at the timing shown as time t4.

[0091] (Toner collection by cleaning roller 54) The cleaning roller 54 is configured to be able to clean the surface of the photosensitive drum 52 by coming into contact with the surface of the photosensitive drum 52. In other words, the cleaning roller 54 is configured to be able to collect toner adhering to the surface of the photosensitive drum 52 by cleaning the surface of the photosensitive drum 52.

[0092] The toner is, for example, positively charged and is positively charged during operation of the color printer 1. The cleaning roller 54 is configured to perform a collection operation to clean the surface of the photosensitive drum 52 in accordance with instructions from the control unit 100.

[0093] The recovery operation here refers to an operation that includes returning the toner on the surface of the cleaning roller 54 from the surface of the cleaning roller 54 to the surface of the photosensitive drum 52, and recovering the toner from the surface of the photosensitive drum 52 to the surface of the cleaning roller 54.

[0094] In an operation of returning the toner on the surface of the cleaning roller 54 from the surface of the cleaning roller 54 to the surface of the photosensitive drum 52, a bias having the same polarity as the surface potential of the photosensitive drum 52 but a potential with a larger absolute value than the surface potential of the photosensitive drum 52 is applied to the cleaning roller 54 as a bias for returning the toner to the surface of the photosensitive drum 52. In an operation of recovering the toner from the surface of the photosensitive drum 52 to the surface of the cleaning roller 54, a bias having the same polarity as the surface potential of the photosensitive drum 52 but a potential with a smaller absolute value than the surface potential of the photosensitive drum 52, or a first cleaning bias which is a bias with a polarity opposite to the surface potential of the photosensitive drum 52, is applied to the cleaning roller 54. In this embodiment, the polarity opposite to the polarity of the charge by the charger 53 is negative polarity.

[0095] (Toner collection by belt cleaner 91) The belt cleaner 91 is configured to clean the surface of the conveyor belt 73. Specifically, the control unit 100 returns the toner on the surface of the cleaning roller 54 from the surface of the cleaning roller 54 to the surface of the photosensitive drum 52. Then, in order to transfer the toner adhering to the surface of the photosensitive drum 52 to the conveyor belt 73, a second cleaning bias having a polarity opposite to the polarity of the charge by the charger 53 is applied to the transfer roller 74. As a result, the toner adhering to the surface of the photosensitive drum 52 adheres to the surface of the conveyor belt 73. Then, while the conveyor belt 73 is being rotated, the belt cleaner 91 collects the toner transferred to the conveyor belt 73. The toner collected by the belt cleaner 91 is collected into a storage unit 94 via a collection roller 92 and a scraping blade 93.

[0096] (Toner collection by developing roller 61) The developing roller 61 is configured to be able to clean the surface of the photosensitive drum 52. Specifically, it is configured to return the toner adhering to the surface of the photosensitive drum 52 to a toner storage section 64 provided in the developing device 60 so that the recovered toner can be reused. When recovering the toner adhering to the surface of the photosensitive drum 52, the control section 100 charges the surface of the photosensitive drum 52 with the charger 53, making the potential of the surface of the photosensitive drum 52 higher than the potential of the developing roller 61. As a result, the positively charged toner adhering to the surface of the photosensitive drum 52 moves to the developing roller 61 and is returned to the toner storage section 64.

[0097] <Effects of this embodiment> According to the above configuration, a collection operation determination process is executed before the image formation process is executed. If the collection operation determination process determines that the conditions for executing the collection operation are met, the collection operation is executed by performing the charging process, the idle rotation process, and the toner collection process. As a result, even if toner with insufficient charge adheres to the surface of the photosensitive drum 52 via the developing roller 61 during the idle rotation process, the toner can be collected by the toner collection process. More specifically, the developing roller 61 is rotated for a time longer than the rotation time of the developing roller when the conditions for executing the collection operation determination process are not met during the idle rotation process, thereby increasing the charge on the toner. Furthermore, toner adhering to the surface of the photosensitive drum 52 can be collected during the process of increasing the charge on the toner. This reduces the possibility of toner falling onto the sheet S without being carried by the photosensitive drum 52 due to an insufficient charge on the toner, thereby providing a color printer 1 with better print quality than conventional color printers.

[0098] Furthermore, with the above configuration, even if the elapsed time since the previous image forming process cannot be obtained, the recovery operation can be performed, thereby increasing the charge amount of the toner even if the elapsed time since the previous image forming process cannot be obtained.

[0099] Furthermore, with the above configuration, the cumulative number of rotations of the developing roller 672 can be used as the amount of operation of the developing device 60.

[0100] Furthermore, with the above configuration, the toner adhering to the surface of the photosensitive drum 52 can be collected by the cleaning roller 54.

[0101] Furthermore, with the above configuration, the toner adhering to the surface of the photosensitive drum 52 is transferred onto the conveyor belt 73. Furthermore, the toner transferred onto the conveyor belt 73 can be collected by the belt cleaner 91.

[0102] Furthermore, with the above configuration, the photosensitive drum 52 and the developing roller 61 are in contact with each other during the idle rotation process. Therefore, the toner can be transferred from the developing roller 61 to the photosensitive drum 52 while suppressing toner scattering during the idle rotation process.

[0103] Furthermore, with the above configuration, it is determined whether the amount of operation of the developer 60 is less than a predetermined value based on the developer information 670, which is information relating to the amount of operation of the developer 60 stored in the developer memory 67. Therefore, even if the developer 60 has been replaced from another color printer, it is possible to determine whether the idling process and the toner recovery process are necessary.

[0104] (Variation 1) In addition to the developing device information 670 of the embodiment, the developing device information 670 may include information regarding charging characteristics. In detail, between step S1 and step S2, the control unit 100 acquires information regarding charging characteristics, and when it determines that the toner contained in the toner container 64 has low charging efficiency based on the information regarding charging characteristics, it executes a collection operation determination process.

[0105] The information regarding the charging characteristics is, for example, a flag indicating that the collection operation determination process needs to be executed. For example, the value of the flag indicating that the collection operation determination process needs to be executed may be set to "0," and the value of the flag indicating that the collection operation determination process does not need to be executed may be set to "1." The information regarding the charging characteristics may also be, for example, color information 671. In this case, the control unit 100 may be configured to acquire the color information 671, and if the acquired color information 671 indicates K, to execute the collection operation determination process.

[0106] Furthermore, the information relating to the charging characteristics may be, for example, capacity information 673. In this case, the control unit 100 may be configured to acquire the capacity information 673, and if the acquired capacity information 673 is "information indicating that the toner capacity is large," to execute the collection operation determination process. The toner capacity here refers to information indicating the total amount of toner that the toner storage unit 64 can store; for example, the total amount of toner that the toner storage unit 64 can store is larger for a toner storage unit 64 that stores K toner than for a toner storage unit 64 that stores C toner.

[0107] According to the above configuration, when the toner charging efficiency is low, for example, when the developing device 60 contains K toner in the toner storage section 64, the recovery operation determination process is executed, and when the developing device 60 contains toner other than K in the toner storage section 64, the recovery operation determination process is not executed.

[0108] Therefore, the recovery operation is performed only on the developing device 60 of a specific color with low toner charging efficiency, so that the recovery operation can be prevented from lengthening the time until the image forming process is completed.

[0109] (Variation 2) In this embodiment, it is determined whether the amount of operation of the developing device 60 from an unused state is less than a predetermined value based on the developing device information 670 stored in the developing device memory 67. However, it may also be determined whether the amount of operation of the developing device 60 from an unused state is less than a predetermined value without using the developing device information 670 stored in the developing device memory 67.

[0110] For example, the control unit 100 executes a new product detection process to determine whether the developing unit 60 is new or an old product, based on information transmitted by an information transmission gear that transmits predetermined information. If the control unit 100 determines that the developing unit 60 is new through the new product detection process, it executes a collection operation determination process. After determining that the developing unit 60 is new through the new product detection process, the control unit 100 stores information regarding the amount of operation of the developing unit 60 in the developing unit memory 67. Alternatively, the information transmitted by the information transmission gear may be stored in the developing unit memory 67 or the developing unit memory 67. This allows for control such that the collection operation determination process is executed when the developing unit 60 is determined to be new, and the collection operation determination process is not executed when the developing unit 60 is determined not to be new. Therefore, the collection operation is executed only when the developing unit 60 is new, thereby preventing the time required to complete printing from being extended by executing the collection operation.

[0111] (Variation 3) In this embodiment, during the idle rotation process, the bias that is applied when the image formation process is performed is not applied to the developing roller 61, but it is also possible to apply a bias that is the same polarity as the bias that is applied when the image formation process is performed, but has a smaller absolute value than when the image formation process is performed.

[0112] (Variation 4) In the embodiment, the operation amount of the developing device 60 is determined based on the cumulative number of rotations of the developing roller 672, but it may also be determined based on the capacity information 673. In this case, in step S2, upon acquiring the developing device information 670, the control unit 100 determines whether the operation amount of the developing device 60 is less than a predetermined value based on the capacity information 673. For example, if the toner capacity indicated as the capacity information 673 is between 100% and 80%, it is determined that the operation amount is less than the predetermined value (S2: YES).

[0113] (Variation 5) Furthermore, color printer 1 may be an MFP (Multi-Function Printer) that also has other functions such as a scanner or a facsimile. Even when color printer 1 is an MFP, color printer 1 may execute the various processes described in the embodiment in the same manner as color printer 1 of the embodiment.

[0114] (Software implementation example) The functions of color printer 1 can be realized by a program that causes a computer to function as color printer 1, and by a program that causes a computer to function as each control block of color printer 1, particularly control unit 100.

[0115] In this case, color printer 1 includes a computer having at least one control device, such as a processor, and at least one storage device, such as a memory, as hardware for executing the above-mentioned programs. By executing the above-mentioned programs using the above-mentioned control device and storage device, each of the functions described in the above-mentioned embodiments is realized.

[0116] The program may be stored non-transitoryly on one or more computer-readable storage media. The storage media may or may not be included in the color printer 1. In the latter case, the program may be supplied to the color printer 1 via any wired or wireless transmission medium.

[0117] In addition, some or all of the functions of the control blocks described above can be realized by logic circuits. For example, an integrated circuit in which a logic circuit functioning as the control block described above is formed is also included in the scope of the present disclosure. In addition, the functions of the control blocks described above can also be realized by, for example, a quantum computer.

[0118] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Configurations obtained by appropriately combining different technical means disclosed in the respective embodiments are also included in the technical scope of the present disclosure. [Explanation of symbols]

[0119] 1 color printer 52 Photosensitive drum 53 Charger 54 Cleaning roller 60 Developer 61 Developing roller 64 Toner storage compartment 91 Belt cleaner 100 control section

Claims

1. A photosensitive drum; a developing unit including a developing roller and a toner storage unit that stores toner; a charger that charges the photosensitive drum; a recovery device that recovers toner adhering to the surface of the photosensitive drum; a contact / separation mechanism that can switch between a contact state in which the photosensitive drum and the developing roller are in contact with each other and a separation state in which the photosensitive drum and the developing roller are separated from each other; a control unit, The control unit When you run a print job, executes a collection operation determination process whose execution condition is that the amount of operation of the developing device since the unused state is less than a predetermined value and the elapsed time from the image forming process based on the previous print job is equal to or longer than a predetermined time; If the execution condition is satisfied before the image forming process based on the print job is executed, a charging process for charging the photosensitive drum by the charger; an idling process of rotating the developing roller before the start of the image forming process, the idling process being to rotate the developing roller for a time longer than the rotation time of the developing roller when the execution condition is not satisfied; a toner recovery process for recovering the toner adhering to the surface of the photosensitive drum by the recovery device; In the idling process, the photosensitive drum and the developing roller are brought into contact with each other.

2. 2. The image forming apparatus according to claim 1, wherein the execution conditions for the recovery operation determination process further include a case where the amount of operation of the developing device since its unused state is less than a predetermined value, and the elapsed time since the image forming process based on the previous print job cannot be obtained.

3. 3. The image forming apparatus according to claim 1, wherein the operation amount is the cumulative number of rotations of the developing roller.

4. the recovery device has a cleaning roller that recovers toner adhering to the photosensitive drum while rotating in contact with the surface of the photosensitive drum, The control unit 4. An image forming apparatus according to claim 1, wherein in the toner recovery process, a first cleaning bias is applied to the cleaning roller, the first cleaning bias being a bias smaller than the surface potential of the photosensitive drum or a bias having an opposite polarity to the surface potential of the photosensitive drum.

5. a belt in contact with the surface of the photosensitive drum; a transfer roller disposed between the photosensitive drum and the belt, the recovery device has a belt cleaner that recovers toner adhering to the belt, The control unit In the toner recovery process, a second cleaning bias, which is a bias having a polarity opposite to that of the surface potential of the photosensitive drum, is applied to the transfer roller in order to transfer the toner adhering to the surface of the photosensitive drum to the belt; 5. The image forming apparatus according to claim 1, wherein the toner transferred onto the belt is collected by the belt cleaner while the belt is being rotated.

6. The developing device further includes a memory that stores information about the operation amount, and the control unit 6. The image forming apparatus according to claim 1, wherein it is determined whether the amount of movement is less than a predetermined value based on the information about the amount of movement stored in the memory.

7. the memory includes information regarding the charging characteristics of the toner contained in the toner container; The control unit 7. The image forming apparatus according to claim 6, wherein the recovery operation determination process is executed when it is determined that the toner contained in the toner container has low charging efficiency based on the information regarding the charging characteristics.

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