Image forming device

Abstract

To provide an image forming apparatus that can prevent a reduction in the life of a photoconductor drum in warming-up processing.SOLUTION: An image forming apparatus 1 comprises: a registration roller pair 34; a photoconductor drum 54; a fuser 60; a paper ejection tray 72; a pre-registration sensor 81; a drum clutch 96; and a control unit 9. In warming-up processing of driving the registration roller pair 34 and the fuser 60, when the pre-registration sensor 81 detects a sheet S within a first time T1 for driving the photoconductor drum 54, the control unit 9 continues the drive of the photoconductor drum 54 after the lapse of the first time T1 to eject the detected sheet S to the paper ejection tray 72, and when the pre-registration sensor 81 does not detect the sheet S within the first time T1, can execute first mode processing of stopping the drive of the photoconductor drum 54 at the time point when the first time T1 elapses, and driving the registration roller pair 34 and the fuser 60 while stopping the drive of the photoconductor drum 54 to complete the warming-up processing.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] In the past, image forming devices have had cases where residual sheets remained in the device due to the power being turned off during printing or a jammed sheet remaining in the device without being removed. If printing is performed with residual sheets remaining in the device, newly fed sheets may collide with the residual sheets, preventing normal printing.

[0003] Furthermore, in an image forming apparatus, a warm-up process is performed to drive the fixing unit, photosensitive drum, sheet conveying rollers, etc. when the power is turned on, when recovering from an error, when recovering from sleep mode, etc. The image forming apparatus described in Patent Document 1 is configured to automatically discharge remaining sheets in parallel with the warm-up process. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-286586 Summary of the Invention [Problem to be solved by the invention]

[0005] However, because the residual sheets are located either near or far from the sheet discharge section within the device, automatic sheet discharge requires the photosensitive drum, transport rollers, etc. to be driven for a long period of time. Furthermore, when driving the photosensitive drum, high pressure must be applied to the photosensitive drum and the developing roller to prevent toner from adhering to the photosensitive drum from the developing roller.

[0006] In this way, when automatic paper discharge is performed in the warm-up process, the photosensitive drums and the like are driven for a long period of time, thereby shortening the life of the photosensitive drums and the like.

[0007] Therefore, the present invention provides an image forming apparatus that can prevent the shortening of the life of the photosensitive drum and the like caused by performing automatic paper discharge during the warm-up process. [Means for solving the problem]

[0008] The image forming apparatus that solves the above problem has the following features.

[0009] That is, the image forming apparatus includes a transport roller for transporting a sheet, a photosensitive drum on which a toner image to be transferred to the sheet is formed, a fuser for fixing the transferred toner image to the sheet, an output tray, a detection sensor arranged upstream of the transport roller in the sheet transport direction and detecting the sheet, a switching unit for switching between driving and stopping the photosensitive drum, and a control unit, and the control unit is capable of executing a first mode process in which, during a warm-up process in which the transport roller and the fuser are driven, the photosensitive drum is driven for a predetermined time, and if the detection sensor detects a sheet within the predetermined time, the switching unit continues to drive the photosensitive drum even after the predetermined time has elapsed, and the detected sheet is discharged to the output tray, and if the detection sensor does not detect a sheet within the predetermined time, the switching unit stops the drive of the photosensitive drum when the predetermined time has elapsed, and the transport roller and the fuser are driven while the drive of the photosensitive drum is stopped, thereby completing the warm-up process.

[0010] In this way, by stopping the driving of the photosensitive drum if the detection sensor does not detect a sheet within a predetermined time during the warm-up process, the driving time of the photosensitive drum can be reduced and the shortening of the life of the photosensitive drum can be suppressed. Also, if the detection sensor detects a sheet before the predetermined time has elapsed, the driving of the photosensitive drum continues and the remaining sheets in the device are automatically discharged, so that the remaining sheets can be automatically discharged while reducing the driving time of the photosensitive drum.

[0011] The predetermined time is equal to or longer than the time required for the photosensitive drum to rotate at least three times.

[0012] This makes it possible to prevent toner from adhering to the photosensitive drum during the warm-up process, and to reduce the driving time of the photosensitive drum.

[0013] In addition, if the detection sensor detects a sheet after the specified time has elapsed during the warm-up process, the control unit determines that a jam has occurred in the sheet, stops the warm-up process, and issues a notification urging the user to remove the jammed sheet.

[0014] As a result, even if the detection sensor detects a sheet after the lapse of a predetermined time, the photosensitive drum is not driven again, so that the driving time of the photosensitive drum can be reduced.

[0015] The sheet transport device also includes a sheet transport path that runs from upstream of the transport roller in the sheet transport direction through the transport roller, the photosensitive drum, and the fixing unit, a re-transport path that guides the sheet that has passed through the fixing unit to the transport path upstream of the transport roller in the sheet transport direction, and a junction point that is located upstream of the transport roller in the sheet transport direction and where the transport path and the initial transport path merge, and the detection sensor is located downstream of the junction point in the sheet transport direction, and if the detection sensor detects a sheet at the start of the warm-up process, the control unit determines that a jam has occurred in the sheet, stops the warm-up process, and issues a notification urging the user to remove the jammed sheet.

[0016] The sheet detected by the detection sensor at the start of the warm-up process may be a residual sheet that was left behind immediately after being fed from the sheet feed unit. If the residual sheet is automatically discharged, the sheet will be damaged by the heat of the fixing unit, etc. However, if the sheet detected by the detection sensor is a residual sheet that was left behind immediately after being fed, it can be removed without being automatically discharged, and the residual sheet will not be damaged by the fixing unit and can be reused.

[0017] The device also includes a paper discharge section located downstream of the fixing device in the sheet transport direction and discharging the sheet, and a paper discharge sensor located between the fixing device and the paper discharge section and detecting the sheet, and if the paper discharge sensor detects a sheet after starting the warm-up process, the control section determines that a jam has occurred in the sheet, stops the warm-up process, and issues a notification urging the user to remove the jammed sheet.

[0018] If a sheet detected by a paper discharge sensor located near the fixing unit is, for example, a jammed sheet, automatic paper discharge may cause the sheet to wrap around the fixing unit, damaging it. Therefore, if a sheet remaining in the device is detected by the paper discharge sensor, the device determines that the sheet is jammed and prompts the user to remove the sheet without automatically discharging it, thereby preventing damage to the fixing unit.

[0019] In addition, the control unit can execute a second mode process in the warm-up process, which constantly drives the photosensitive drum while the warm-up process is being performed, and can selectively set either a first mode in which the first mode process is executed, or a second mode in which the second mode process is executed.

[0020] As a result, when there is little need to execute the first mode processing, such as when the image forming device is used infrequently, the second mode can be selected and the second mode processing can be executed, thereby increasing the remaining position patterns of remaining sheets that can be automatically discharged.

[0021] The device also includes a common drive source that drives the conveying roller, the photosensitive drum, and the fixing device, and the switching unit is an electromagnetic clutch that switches between a transmission state in which the drive force from the drive source is transmitted to the photosensitive drum and a cut-off state in which the drive force from the drive source is not transmitted to the photosensitive drum.

[0022] This allows for lower costs and space savings compared to, for example, providing a drive source for driving the photosensitive drum separately from a drive source for driving a fixing device, etc., or using a clutch type that is turned on / off by a motor as a switching unit for switching the drive of the photosensitive drum. [Effects of the Invention]

[0023] According to the present invention, it is possible to suppress the shortening of the life of the photosensitive drum by reducing the driving time of the photosensitive drum, and also possible to automatically discharge remaining sheets while reducing the driving time of the photosensitive drum. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 2 is a central cross-sectional view showing the image forming apparatus. [Figure 2] FIG. 2 is a block diagram relating to sheet conveyance in the image forming apparatus. [Figure 3] 10 is a central cross-sectional view showing the remaining position of the remaining sheet in the housing. FIG. [Figure 4] FIG. 10 is a diagram showing a flow of a warm-up process when a first mode process is executed. [Figure 5] FIG. 10 is a timing chart showing a case where the pre-register sensor does not detect a sheet during the first time period from when the main motor starts to be driven during the warm-up process. [Figure 6] FIG. 10 is a timing chart showing a case in which the pre-register sensor detects a sheet during the first time period from when the main motor starts to be driven until the first time period has elapsed during the warm-up process. [Figure 7] 10 is a timing chart showing a case in which the pre-register sensor detects the sheet S after the first time has elapsed since the main motor started to be driven in the warm-up process. FIG. [Figure 8] FIG. 10 is a diagram showing a flow of a warm-up process when a second mode process is executed. DETAILED DESCRIPTION OF THE INVENTION

[0025] Next, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0026] [Image forming device] An image forming apparatus 1 shown in FIG. 1 is one embodiment of the image forming apparatus according to the present invention, and is a laser printer that forms an image on a sheet S by electrophotography.

[0027] In the following description, the right side in Fig. 1 is defined as the front side of the image forming apparatus 1, the left side in Fig. 1 is defined as the rear side of the image forming apparatus 1, the front side of the paper in Fig. 1 is defined as the left side of the image forming apparatus 1, and the back side of the paper in Fig. 1 is defined as the right side of the image forming apparatus 1. In addition, the upper and lower sides in Fig. 1 are defined as the upper and lower sides of the image forming apparatus 1, respectively.

[0028] The image forming apparatus 1 is one embodiment of the image forming apparatus according to the present invention, and includes a housing 2, a paper feed section 3, an image forming section 5, and a paper discharge section .

[0029] The housing 2 houses a paper feed unit 3, an image forming unit 5, and a paper discharge unit 7. The paper feed unit 3 is located at the bottom of the housing 2 and transports a sheet S supported on a paper feed tray 30 to the image forming unit 5. The image forming unit 5 is located downstream of the paper feed unit 3 in the sheet transport direction and forms an image on the sheet S transported from the paper feed unit 3. The paper discharge unit 7 is located downstream of the image forming unit 5 in the sheet transport direction and discharges the sheet S on which an image has been formed in the image forming unit 5 to the outside of the image forming apparatus 1, or transports the sheet S again toward the image forming unit 5.

[0030] The paper feed unit 3 includes a paper feed tray 30 that supports the sheet S, a paper feed mechanism 32, a conveying roller pair 33, and a registration roller pair 34. The image forming apparatus 1 has a conveying path P1 for the sheet S that runs from the paper feed unit 3 to the paper discharge unit 7 via the image forming unit 5.

[0031] The sheet feed tray 30 has a pressure plate 31 and a pressing plate 311. The pressure plate 31 is a plate-shaped member that supports the sheets S from below. The pressure plate 31 is rotatable around a rotation fulcrum 31a at its rear end, and by rotating around the rotation fulcrum 31a, it can be raised and lowered between a lowered position and an upper position. The pressing plate 311 is located below the pressure plate 31, and can raise and lower the pressure plate 31 between the lowered position and the upper position.

[0032] The paper feed mechanism 32 includes a paper feed roller 32a, a separation roller 32b, and a separation pad 32c. The paper feed roller 32a is a roller for sending the sheet S supported in the paper feed tray 30 toward the separation roller 32b. The separation roller 32b is disposed downstream of the paper feed roller 32a in the sheet conveying direction, and the separation pad 32c is disposed opposite the separation roller 32b and is biased toward the separation roller 32b.

[0033] The sheets S sent by the paper feed roller 32a toward the separation roller 32b are separated one by one between the separation roller 32b and the separation pad 32c. The separated sheets S are sent to the conveying path P1.

[0034] The sheet S sent to the conveying path P is conveyed toward the image forming unit 5 by a conveying roller pair 33 and a registration roller pair 34. The registration roller pair 34 regulates the movement of the leading edge of the sheet S being conveyed, stops the sheet S temporarily, and then conveys the sheet S toward the image forming unit 5 at a predetermined timing. The registration roller pair 34 is an example of a conveying roller that conveys a sheet.

[0035] A pre-registration sensor 81 is arranged upstream of the registration roller pair 34 in the sheet conveying direction, and a post-registration sensor 82 is arranged downstream of the registration roller pair 34 in the sheet conveying direction. The pre-registration sensor 81 is an example of a detection sensor that detects a sheet.

[0036] The pre-registration sensor 81 and the post-registration sensor 82 are sensors for detecting the sheet S. When the leading edge in the conveying direction of the sheet S conveyed along the conveying path P1 reaches the position of the pre-registration sensor 81, the pre-registration sensor 81 is turned on to detect the sheet S, and when the trailing edge in the conveying direction of the sheet S conveyed along the conveying path P1 passes the position of the pre-registration sensor 81, the pre-registration sensor 81 is turned off to no longer detect the sheet S.

[0037] In addition, when the leading edge of the sheet S in the conveying direction being conveyed along the conveying path P1 reaches the position of the post-registration sensor 82, the post-registration sensor 82 is turned on to detect the sheet S, and when the trailing edge of the sheet S in the conveying direction being conveyed along the conveying path P1 passes the position of the post-registration sensor 82, the post-registration sensor 82 is turned off to no longer detect the sheet S.

[0038] During printing, the pair of registration rollers 34 starts rotating when the leading edge of the sheet S in the transport direction being transported along the transport path P1 reaches the position of the pre-registration sensor 81 and a predetermined time has elapsed since the pre-registration sensor 81 is turned on, and stops rotating when the trailing edge of the sheet S in the transport direction reaches the position of the post-registration sensor 82 and a predetermined time has elapsed since the post-registration sensor 82 is turned off.

[0039] The image forming section 5 includes a process cartridge 50 that transfers an image onto the surface of the sheet S transported from the paper feed section 3, an exposure unit 56 that exposes the surface of the photosensitive drum 54 in the process cartridge 50, and a fixing device 60 that fixes the image transferred onto the sheet S by the process cartridge 50.

[0040] The process cartridge 50 is disposed above the paper feed unit 3 within the housing 2, and includes a developer storage chamber 51, a supply roller 52, a developing roller 53, a photosensitive drum 54, a transfer roller 55, and the like.

[0041] The exposure unit 56 is equipped with a laser diode, a polygon mirror, a lens, a reflecting mirror, etc., and exposes the surface of the photosensitive drum 54 by irradiating the photosensitive drum 54 with laser light based on image data input to the image forming apparatus 1.

[0042] Toner that will become the developer is stored in the developer storage chamber 51. The toner stored in the developer storage chamber 51 is stirred by a stirring member (not shown) and sent to the supply roller 52. The supply roller 52 further supplies the toner sent from the developer storage chamber 51 to the developing roller 53.

[0043] The developing roller 53 is disposed in close contact with the supply roller 52, and carries toner supplied from the supply roller 52 and positively charged by a sliding contact member (not shown). A developing bias is applied to the developing roller 53 by a bias application means (not shown).

[0044] The photosensitive drum 54 is disposed adjacent to the developing roller 53. The surface of the photosensitive drum 54 is uniformly charged by a charger (not shown) and then exposed by the exposure unit 56. The exposed portion of the photosensitive drum 54 has a lower potential than the other portions, and an electrostatic latent image based on the image data is formed on the photosensitive drum 54. Then, positively charged toner is supplied from the developing roller 53 to the surface of the photosensitive drum 54 on which the electrostatic latent image has been formed, thereby visualizing the electrostatic latent image into a toner image.

[0045] The transfer roller 55 is disposed opposite the photosensitive drum 54, and a transfer bias is applied to it by a bias application means (not shown). With the transfer bias applied to the surface of the transfer roller 55, the toner image formed on the surface of the photosensitive drum 54 is transferred to the surface of the sheet S by conveying the sheet S while sandwiching it between the photosensitive drum 54 on which the toner image has been formed and the transfer roller 55. In other words, the toner image to be transferred to the sheet S is formed on the photosensitive drum 54.

[0046] The sheet S onto which the toner image has been transferred is transported to a fixing device 60. The fixing device 60 includes a heating roller 61 and a pressure roller 62 that is in pressure contact with the heating roller 61, and the toner image on the sheet S transported to the fixing device 60 is thermally fixed while the sheet S passes between the heating roller 61 and the pressure roller 62. In other words, the fixing device 60 fixes the transferred toner image onto the sheet.

[0047] The paper discharge section 7 is located downstream of the fixing unit 60 in the sheet transport direction, and includes a paper discharge roller pair 71 and a paper discharge tray 72. The paper discharge roller pair 71 is configured to be able to discharge the sheet S, which has been transported from the fixing unit 60 along the transport path P1, towards the outside of the housing 2. The paper discharge tray 72 is formed on the top surface of the housing 2, and supports the sheet S discharged to the outside of the housing 2 by the paper discharge roller pair 71. A paper discharge sensor 83 is disposed between the fixing unit 60 and the paper discharge roller pair 71 in the sheet transport direction. The paper discharge sensor 83 is a sensor for detecting the sheet S.

[0048] The pair of discharge rollers 71 are configured to be rotatable in a discharge direction, which is a rotation direction when conveying the sheet S toward the discharge tray 72, and in a re-conveyance direction, which is a rotation direction opposite to the discharge direction. The image forming apparatus 1 has a re-conveyance path P2 that guides the sheet S, which has been conveyed along the conveyance path P1 and passed through the fixing device 60, to the conveyance path P1 upstream of the pair of registration rollers 34 in the sheet conveyance direction.

[0049] The re-conveying path P2 branches off from the conveying path P1 at a branching point Pb located between the fixing unit 60 and the pair of discharge rollers 71, then extends forward between the image forming unit 5 and the paper feed tray 30, and merges with the conveying path P1 at a junction point Pa located between the pair of conveying rollers 33 and the pair of registration rollers 34.

[0050] The sheet S conveyed from the fixing device 60 to the paper discharge unit 7 can be conveyed again to the image forming unit 5 via a re-conveyance path P2 by rotating the paper discharge roller pair 71 in the re-conveyance direction. The sheet S conveyed to the re-conveyance path P2 by the paper discharge roller pair 71 is conveyed toward the image forming unit 5 by a first re-conveyance roller pair 35 and a second re-conveyance roller pair 36 provided on the re-conveyance path P2.

[0051] The image forming apparatus 1 is capable of double-sided printing, in which a sheet S, on one side of which an image has been formed in the image forming unit 5, is transported again to the image forming unit 5 via a re-transport path P2, and an image is formed on the other side of the sheet S.

[0052] In the image forming apparatus 1, the conveying path P1 passes through the registration roller pair 34, the photosensitive drum 54, and the fixing unit from the upstream side in the sheet conveying direction of the registration roller pair 34. The re-conveying path P2 guides the sheet S that has passed through the fixing unit 60 to the conveying path P1, which is upstream in the sheet conveying direction of the registration roller pair 34. A junction Pa of the conveying path P1 and the re-conveying path P2 is located upstream in the sheet conveying direction of the registration roller pair 34, and the pre-registration sensor 81 is located downstream in the sheet conveying direction of the junction Pa.

[0053] 2, the image forming apparatus 1 includes a control unit 9, a main motor 91, a paper discharge motor 92, a paper feed clutch 93, a registration clutch 94, a developing clutch 95, and a drum clutch 96. The main motor 91, the paper discharge motor 92, the paper feed clutch 93, the registration clutch 94, the developing clutch 95, and the drum clutch 96 are connected to the control unit 9, and their operations are controlled by the control unit 9.

[0054] The main motor 91 is connected to the paper feed roller 32a, the separation roller 32b, the conveying roller pair 33, the registration roller pair 34, the first re-conveying roller pair, the second re-conveying roller pair 36, the developing roller 53, the photosensitive drum 54, and the heating roller 61 of the fixing unit 60. The paper feed roller 32a, the separation roller 32b, the conveying roller pair 33, the registration roller pair 34, the first re-conveying roller pair, the second re-conveying roller pair 36, the developing roller 53, the photosensitive drum 54, and the heating roller 61 are driven by the main motor 91. The main motor 91 is an example of a common drive source that drives the conveying rollers, the photosensitive drum, and the fixing unit.

[0055] In this way, in the image forming apparatus 1, the pair of registration rollers 34, the photosensitive drum 54, the heating roller 61 of the fixing unit 60, etc. are driven by a common main motor 91. This makes it possible to reduce costs and save space compared to, for example, providing a drive source for driving the photosensitive drum 54 separately from a drive source for driving the fixing unit 60, etc., or using a clutch of a type that is turned on / off by a motor as a switching unit for switching the drive of the photosensitive drum 54.

[0056] The paper feed roller 32a is connected to the main motor 91 via a paper feed clutch 93. The paper feed clutch 93 is configured, for example, by an electromagnetic clutch, and can be switched between a transmission state in which the driving force from the main motor 91 is transmitted to the paper feed roller 32a and a cut-off state in which the driving force from the main motor 91 is not transmitted to the paper feed roller 32a.

[0057] The registration roller pair 34 is connected to the main motor 91 via a registration clutch 94. The registration clutch 94 is configured, for example, by an electromagnetic clutch, and can be switched between a transmission state in which the driving force from the main motor 91 is transmitted to the registration roller pair 34 and a cut-off state in which the driving force from the main motor 91 is not transmitted to the registration roller pair 34.

[0058] The developing roller 53 is connected to the main motor 91 via a developing clutch 95. The developing clutch 95 is configured, for example, by an electromagnetic clutch, and is switchable between a transmission state in which the driving force from the main motor 91 is transmitted to the developing roller 53 and a cut-off state in which the driving force from the main motor 91 is not transmitted to the developing roller 53.

[0059] The photosensitive drum 54 is connected to the main motor 91 via a drum clutch 96. The drum clutch 96 is configured by, for example, an electromagnetic clutch, and is switchable between a transmission state in which the driving force from the main motor 91 is transmitted to the photosensitive drum 54 and a cut-off state in which the driving force from the main motor 91 is not transmitted to the photosensitive drum 54. The drum clutch 96 is an example of a switching unit that switches between driving and stopping the photosensitive drum.

[0060] The main motor 91 is connected to the pressure plate 311, and the pressure plate 311 is driven by the main motor 91. When the pressure plate 311 is driven by the main motor 91, the pressure plate 311 is raised and lowered.

[0061] The paper discharge motor 92 is connected to the paper discharge roller pair 71, and the paper discharge roller pair 71 is driven by the paper discharge motor 92. When driven by the paper discharge motor 92, the paper discharge roller pair 71 rotates in the paper discharge direction or the re-conveyance direction.

[0062] The pre-registration sensor 81, the post-registration sensor 82, and the paper discharge sensor 83 are connected to the control unit 9, and the control unit 9 receives detection information from the pre-registration sensor 81, the post-registration sensor 82, and the paper discharge sensor 83.

[0063] [Warming up process] In the image forming apparatus 1, a warm-up process is executed by the control unit 9 when the power is turned on, when recovering from an error such as a jam of the sheet S, when recovering from a sleep mode, etc. The warm-up process is a process that drives the registration roller pair 34, the process cartridge 50 including the developing roller 53 and the photosensitive drum 54, the fixing unit 60, the main motor 91, etc., to heat the heating roller 61 in the fixing unit 60, clean the photosensitive drum 54, and check the state of the process cartridge 50, etc.

[0064] During the warm-up process, if the power is turned off during printing or a jammed sheet S remains inside the housing 2, an automatic paper discharge process is executed to automatically discharge the remaining sheets.

[0065] 3, there are a first remaining position S1, a second remaining position S2, a third remaining position S3, a fourth remaining position S4, and a fifth remaining position S5 as remaining position patterns for the remaining sheet in the housing 2. The first remaining position S1 is a remaining position where the sheet S is located between the post-registration sensor 82 and the paper discharge sensor 83. The second remaining position S2 is a remaining position where the leading edge of the conveyed sheet S is located at a position where it is detected by the pre-registration sensor 81.

[0066] The third remaining position S3 is a remaining position where the leading edge of the sheet S transported along the re-conveying path P2 is located upstream of the pre-registration sensor 81 in the sheet transport direction, and the trailing edge of the sheet S transported along the re-conveying path P2 is located downstream of the discharge roller pair 71 in the sheet transport direction. The fourth remaining position S4 is a remaining position where the trailing edge of the sheet S transported along the re-conveying path P2 is sandwiched between the discharge roller pair 71 when the discharge roller pair 71 is rotating in the re-conveying direction. The fifth remaining position S5 is a remaining position where the leading edge of the sheet S is sandwiched between the discharge roller pair 71 when the discharge roller pair 71 is rotating in the re-conveying direction.

[0067] The control unit 9 can selectively execute a first mode process, which reduces the operating time of the photosensitive drum 54, etc., and thereby suppresses a reduction in the lifespan of the photosensitive drum 54, etc., as a warm-up process including an automatic paper discharge process, and a second mode process, which can increase the remaining position patterns of remaining sheets that can be automatically discharged.

[0068] The control unit 9 can selectively set either a first mode in which a first mode process is executed or a second mode in which a second mode process is executed. The first mode or the second mode can be set by, for example, a user inputting information into an input unit or the like provided in the image forming apparatus 1.

[0069] (Warm-up process when executing first mode process) The warm-up process when the first mode process is executed will be described.

[0070] 4, when the warm-up process starts, the control unit 9 determines whether the pre-registration sensor 81 detects the sheet S (step S01). If the control unit 9 determines in step S01 that the pre-registration sensor 81 does not detect the sheet S (step S01: N), it starts driving the main motor 91 (step S02). When the control unit 9 starts driving the main motor 91, the control unit 9 switches the paper feed clutch 93, the registration clutch 94, the development clutch 95, and the drum clutch 96 to a transmission state.

[0071] When the main motor 91 starts to drive, the main motor 91 drives the registration roller pair 34, the photosensitive drum 54, the developing roller 53, the fixing unit 60, etc. (step S03). A high voltage is also applied to the photosensitive drum 54 and the developing roller 53. Furthermore, the main motor 91 drives the pressure plate 311 of the paper feed tray 30, and the pressure plate 31 starts to rise (step S03).

[0072] After starting to drive the main motor 91, the control unit 9 determines whether the pre-registration sensor 81 has detected the sheet S (step S04). If the control unit 9 determines in step S04 that the pre-registration sensor 81 has not detected the sheet S (step S04: N), the control unit 9 determines whether a first time T1 has elapsed since the main motor 91 started to drive (step S05). The first time T1 is an example of a predetermined time for driving the photosensitive drum in the warm-up process.

[0073] If the control unit 9 determines in step S05 that the first time T1 has not elapsed (step S05: N), it executes step S04 again. If the pre-register sensor 81 does not detect the sheet S in step S04, the control unit 9 repeatedly executes step S04 until the first time T1 has elapsed.

[0074] If the first time T1 has elapsed without the pre-registration sensor 81 detecting the sheet S in step S04 (step S05: Y), the control unit 9 switches the developing clutch 95 and the drum clutch 96 to a disconnected state, and stops the developing roller 53 and the photosensitive drum 54 (step S06). In this case, the developing roller 53 and the photosensitive drum 54 remain stopped, and the registration roller pair 34 and the fixing unit 60 continue to be driven.

[0075] In addition, when driving the photosensitive drum 54 and the developing roller 53 during the warm-up process, in order to prevent toner from the developing roller 53 from adhering to the photosensitive drum 54, it is necessary to drive the photosensitive drum 54 and the developing roller 53 under high pressure for at least the time required for the photosensitive drum 54 to rotate three times.

[0076] Therefore, in the warm-up process, the first time T1 from when the main motor 91 starts to drive until the photosensitive drum 54 and the developing roller 53 are stopped is set to a time that is at least equal to the time required for the photosensitive drum 54 to rotate three times. By setting the first time T1 to a time that is at least equal to the time required for the photosensitive drum 54 to rotate three times in this way, it is possible to reduce the drive time of the photosensitive drum 54 and the developing roller 53 while preventing toner from adhering to the photosensitive drum 54 during the warm-up process.

[0077] After stopping the developing roller 53 and the photosensitive drum 54 in step S06, the control unit 9 determines whether the warm-up process is complete (step S07). If the control unit 9 determines in step S07 that the warm-up process is not complete (step S07: N), it determines whether the pre-registration sensor 81 has detected the sheet S (step S08). If the control unit 9 determines in step S08 that the pre-registration sensor 81 has not detected the sheet S (step S08: N), it executes step S07 again.

[0078] The control unit 9 can determine whether the warm-up process in step S07 is complete by, for example, determining whether a second time T2 has elapsed since the start of driving the main motor 91. The second time T2 can be set to a time sufficient to complete each of the processes in the warm-up process, such as heating the heating roller 61 in the fixing device 60, cleaning the photosensitive drum 54, and checking the state of the process cartridge 50.

[0079] When the control unit 9 determines in step S07 that the warm-up process is complete (step S07: Y), it stops driving the main motor 91 (step S09) and ends the warm-up process. Note that when the warm-up process is complete, that is, when the second time T2 has elapsed since the main motor 91 started to be driven, the lifting of the pressure plate 31 of the paper feed tray 30 has been completed.

[0080] Furthermore, after the registration roller pair 34, the photosensitive drum 54, the fixing unit 60, etc. are driven in step S03, the control unit 9 determines whether the sheet discharge sensor 83 has detected the sheet S (step S11). If the control unit 9 determines in step S11 that the sheet discharge sensor 83 has not detected the sheet S (step S11: N), it determines whether the warm-up process has been completed (step S12).

[0081] If the control unit 9 determines in step S12 that the warm-up process is not complete (step S12: N), it executes step S11 again. If the control unit 9 determines in step S12 that the warm-up process is complete (step S12: Y), it stops driving the main motor 91 (step S09) and ends the warm-up process.

[0082] In this way, if the pre-register sensor 81 does not detect the sheet S between the start of driving of the main motor 91 and the first time T1 has elapsed, and if the pre-register sensor 81 does not detect the sheet S between the end of the first time T1 and the completion of the warm-up process, and if the paper discharge sensor 83 does not detect the sheet S between the start of driving of the main motor 91 and the completion of the warm-up process, then there are no remaining sheets at the first remaining position S1, the second remaining position S2, the third remaining position S3, and the fourth remaining position S4.

[0083] In such a case, as shown in FIG. 5, when a first time T1 has elapsed since the start of driving of the main motor 91, the drum clutch 96 and the development clutch 95 are switched to a disconnected state to stop the driving of the photosensitive drum 54 and the development roller 53, and then when a second time T2 has elapsed, it is determined that the warm-up process is complete, the driving of the main motor 91 is stopped, and the warm-up process is terminated.

[0084] During the warm-up process, if the pre-registration sensor 81 does not detect the sheet S when the first time T1 has elapsed since the main motor 91 started to be driven, the drive of the photosensitive drum 54 and the developing roller 53 is stopped, thereby reducing the drive time of the photosensitive drum 54 and the developing roller 53. This makes it possible to prevent the shortening of the lifespan of the photosensitive drum 54 and the developing roller 53.

[0085] When the control unit 9 determines in step S04 that the pre-registration sensor 81 has detected the sheet S (step S04: Y), that is, when the pre-registration sensor 81 detects the sheet S between the start of driving of the main motor 91 and the elapse of the first time T1, the control unit 9 maintains the transmission state of the drum clutch 96 even after the elapse of the first time T1, and continues driving the photosensitive drum 54 and the developing roller 53 (step S21).

[0086] If the pre-registration sensor 81 detects a sheet S between the start of driving of the main motor 91 and the first time T1 has elapsed, this means that a residual sheet was present in a position near the pre-registration sensor 81 at the third residual position S3 before the start of the warm-up process.

[0087] In this case, the control unit 9 continues to drive the photosensitive drum 54 even after the first time T1 has elapsed, and transports the sheet S along the transport path P1 and automatically discharges it (step S22). When automatically discharging the sheet S, the control unit 9 drives the discharge motor 92 to rotate the pair of discharge rollers 71, and discharges the sheet S transported to the discharge unit 7 onto the discharge tray 72.

[0088] After starting automatic discharge of the sheet S in step S22, the control unit 9 determines whether discharge is complete (step S23). Whether discharge is complete can be determined, for example, by determining whether a predetermined time has elapsed since the trailing edge of the discharged sheet S passed the discharge sensor 83. The control unit 9 repeatedly executes step S23 until it determines that discharge is complete (step S23: N).

[0089] When the control unit 9 determines in step S23 that paper ejection is complete (step S23: Y), it determines whether the warm-up process is complete (step S24). Whether the warm-up process is complete can be determined, as in step S07, by determining whether the second time T2 has elapsed since the main motor 91 started to be driven. The control unit 9 repeatedly executes step S24 until it determines that the warm-up process is complete (step S24: N).

[0090] When the control unit 9 determines in step S24 that the warm-up process has been completed (step S24: Y), it stops driving the main motor 91 (step S09) and ends the warm-up process.

[0091] If the pre-registration sensor 81 does not detect a sheet S between the start of driving of the main motor 91 and the elapse of the first time T1, the control unit 9 stops driving the photosensitive drum 54 and the developing roller 53. On the other hand, if a remaining sheet is present near the pre-registration sensor 81 at the third remaining position S3 and the pre-registration sensor 81 detects a sheet S between the start of driving of the main motor 91 and the elapse of the first time T1, the control unit 9 continues driving the photosensitive drum 54 and the developing roller 53 and executes automatic discharge of the sheet S detected by the pre-registration sensor 81. This makes it possible to execute automatic discharge of the remaining sheet while reducing the drive time of the photosensitive drum 54 and the developing roller 53.

[0092] 6, the control unit 9 starts control to stop the main motor 91 after determining that paper discharge is complete, but there are cases where the second time T2 has elapsed at the time when control to stop the main motor 91 is started. In this case, the main motor 91 is actually stopped after the third time T3 has elapsed since control to stop the main motor 91 was started, so the time required for the warm-up process is longer than the second time T2 plus the third time T3, i.e., longer than the second time T2.

[0093] When the control unit 9 determines in step S08 that the pre-registration sensor 81 has detected the sheet S (step S08: Y), that is, when the pre-registration sensor 81 detects the sheet S after the first time T1 has elapsed since the main motor 91 started to drive, it determines that a jam has occurred in the sheet S (step S31).

[0094] After determining that a jam has occurred in the sheet S, the control unit 9 stops the main motor 91 and stops the warm-up process (step S32). The control unit 9 then issues a notification urging the user to remove the jammed sheet S (step S33). The notification urging the user to remove the jammed sheet S can be made, for example, by displaying a message on a display unit provided in the image forming apparatus 1 or by emitting a sound from the image forming apparatus 1.

[0095] When the notification urging the user to remove the sheet S is sent in step S33, the image forming apparatus 1 enters an error state in which a jam has occurred, but the image forming apparatus 1 recovers from the error state when the user who has received the notification urging the user to remove the sheet S removes the sheet S from the image forming apparatus 1. When the image forming apparatus 1 recovers from the error state, the control unit 9 can execute the warm-up process again.

[0096] In this way, when the pre-registration sensor 81 detects the sheet S after the first time T1 has elapsed since the main motor 91 started to be driven, this means that a remaining sheet exists at a position at the third remaining position S3 that is a predetermined distance away from the pre-registration sensor 81, or at the fourth remaining position S4. When a remaining sheet exists at a position at the third remaining position S3 that is a predetermined distance away from the pre-registration sensor 81, or at the fourth remaining position S4, the sheet S transported along the re-transport path P2 does not reach the pre-registration sensor 81 until the first time T1 has elapsed since the main motor 91 started to be driven. Therefore, the sheet S is detected by the pre-registration sensor 81 after the first time T1 has elapsed since the main motor 91 started to be driven.

[0097] 7, if the pre-registration sensor 81 detects a sheet S after the first time T1 has elapsed since the start of driving of the main motor 91, the control unit 9 performs a jam determination (step S31), stops the main motor 91 (step S32), and stops the warm-up process. In this way, by stopping the warm-up process when the pre-registration sensor 81 detects a sheet S after the first time T1 has elapsed, the photosensitive drum 54 and the developing roller 53 will not be driven again even if the pre-registration sensor 81 detects a sheet S, and the drive time of the photosensitive drum 54 and the developing roller 53 can be reduced.

[0098] If the control unit 9 determines in step S01 that the pre-register sensor 81 has detected the sheet S (step S01: Y), that is, if the pre-register sensor 81 had already detected the sheet S before starting to drive the main motor 91, it determines that a jam has occurred in the sheet S (step S31).

[0099] After determining that a jam has occurred in the sheet S, the control unit 9 stops the main motor 91 to stop the warm-up process (step S32). The control unit 9 then issues a notification to prompt the user to remove the jammed sheet S (step S33).

[0100] In this way, when the warm-up process starts, if the pre-register sensor 81 detects the sheet S before the main motor 91 is driven, it means that a remaining sheet exists at the second remaining position S2.

[0101] The sheet S at the second remaining position S2 at the start of the warm-up process may be a remaining sheet that has just been fed from the paper feed mechanism 32. If the remaining sheet is automatically discharged, the sheet S will be damaged by the heat of the fixing unit 60, etc. However, if the sheet S detected by the pre-register sensor 81 is a remaining sheet that has just been fed, it can be removed without being automatically discharged, and the remaining sheet will not be damaged by the fixing unit 60 and can be reused.

[0102] When the control unit 9 determines in step S11 that the paper discharge sensor 83 has detected the sheet S (step S11: Y), that is, when the paper discharge sensor 83 detects the sheet S after starting the warm-up process, it determines that a jam has occurred in the sheet S (step S41).

[0103] After determining that a jam has occurred in the sheet S, the control unit 9 stops the main motor 91 to stop the warm-up process (step S42). The control unit 9 then issues a notification to prompt the user to remove the jammed sheet S (step S43). The notification in step S43 can be the same as the notification issued in step S33.

[0104] In this way, when the paper discharge sensor 83 detects the sheet S after the start of the warm-up process, it means that there is a remaining sheet at the first remaining position S1. If the sheet S detected by the paper discharge sensor 83 located near the fixing unit 60 is, for example, a jammed sheet, automatic paper discharge may cause the sheet S to wrap around the fixing unit 60, damaging the fixing unit 60. Therefore, when the paper discharge sensor 83 detects the sheet S remaining at the first remaining position S1, it determines that the sheet S is jammed without automatic paper discharge and prompts the removal of the sheet S, thereby preventing damage to the fixing unit 60.

[0105] In the image forming apparatus 1, the discharge motor 92 is not driven during the warm-up process except when automatic discharge of the sheet S is performed in step S22. Therefore, if automatic discharge is not performed when a remaining sheet is present at the fifth remaining position S5, the sheet S located at the fifth remaining position S5 will not be discharged during the warm-up process. In this case, the sheet S located at the fifth remaining position S5 will be discharged in the printing operation after the warm-up process is completed.

[0106] (Warming-up process when executing second mode process) Next, the warm-up process when the second mode process is executed will be described.

[0107] 8, when the warm-up process starts, the control unit 9 determines whether the pre-registration sensor 81 detects the sheet S (step S51). If the control unit 9 determines in step S51 that the pre-registration sensor 81 does not detect the sheet S (step S51: N), it starts driving the main motor 91 (step S52). When starting to drive the main motor 91, the control unit 9 switches the paper feed clutch 93, the registration clutch 94, the development clutch 95, and the drum clutch 96 to a transmission state.

[0108] When the main motor 91 starts to drive, the main motor 91 drives the registration roller pair 34, the photosensitive drum 54, the developing roller 53, the fixing unit 60, etc. (step S53). The main motor 91 also drives the pressure plate 311 of the paper feed tray 30, and the pressure plate 31 starts to rise (step S53).

[0109] If a remaining sheet is present at the third remaining position S3 or the fourth remaining position S4, the control unit 9 starts driving the main motor 91 and then automatically discharges the remaining sheet (step S54). The control unit 9 can detect the presence of a remaining sheet at the third remaining position S3 or the fourth remaining position S4, for example, by determining whether the pre-register sensor 81 detects the sheet S within a predetermined time after starting to drive the main motor 91. When automatically discharging the sheet S, the control unit 9 drives the discharge motor 92 to rotate the pair of discharge rollers 71, and discharges the sheet S conveyed to the discharge unit 7 onto the discharge tray 72.

[0110] After starting to drive the main motor 91, the control unit 9 determines whether the sheet discharge sensor 83 has detected the sheet S (step S55). If the control unit 9 determines in step S55 that the sheet discharge sensor 83 has not detected the sheet S (step S55: N), the control unit 9 determines whether a fourth time T4 has elapsed since the main motor 91 started to drive (step S56).

[0111] If the control unit 9 determines in step S57 that the fourth time T4 has not elapsed (step S56: N), it executes step S55 again. If the sheet discharge sensor 83 has not detected the sheet S in step S55, the control unit 9 repeatedly executes step S55 until the fourth time T4 has elapsed. The fourth time T4 can be set to the longest time it takes for a remaining sheet to reach the sheet discharge sensor 83 when there is a remaining sheet at the first remaining position S1, for example.

[0112] If the fourth time T4 has elapsed without the sheet discharge sensor 83 detecting the sheet S in step S56 (step S56: Y), the control unit 9 determines whether or not the automatic discharge of the sheet S has been completed (step S57). The determination of whether or not the discharge has been completed can be made, for example, by determining whether or not a predetermined time has elapsed since the trailing edge of the discharged sheet S passed the sheet discharge sensor 83. The control unit 9 repeatedly executes step S58 until it determines that the discharge has been completed (step S57: N).

[0113] When the control unit 9 determines in step S57 that paper ejection is complete (step S57: Y), it determines whether the warm-up process is complete (step S58). Whether the warm-up process is complete can be determined, as in step S07, by determining whether the second time T2 has elapsed since the main motor 91 started to be driven. The control unit 9 repeatedly executes step S58 until it determines that the warm-up process is complete (step S58: N).

[0114] When the control unit 9 determines in step S58 that the warm-up process is complete (step S58: Y), it stops driving the main motor 91 (step S59) and ends the warm-up process. Note that when the warm-up process is complete, that is, when the second time T2 has elapsed since the main motor 91 started to be driven, the lifting of the pressure plate 31 of the paper feed tray 30 has been completed.

[0115] In the warm-up process when the second mode process is executed, the control unit 9 constantly drives the photosensitive drum 54 and the developing roller 53 from the start to the end of the warm-up process.

[0116] If the control unit 9 determines in step S51 that the pre-register sensor 81 has detected the sheet S (step S51: Y), that is, if the pre-register sensor 81 had already detected the sheet S before starting to drive the main motor 91, it determines that a jam has occurred in the sheet S (step S61).

[0117] After determining that a jam has occurred in the sheet S, the control unit 9 stops the main motor 91 to stop the warm-up process (step S62). The control unit 9 then issues a notification to prompt the user to remove the jammed sheet S (step S63). The notification in step S63 may be the same as the notification issued in step S33.

[0118] Even in the warm-up process when the second mode processing is executed, if the pre-register sensor 81 detects the sheet S before the main motor 91 is driven at the start of the warm-up process, this means that a residual sheet is present at the second residual position S2.

[0119] When the control unit 9 determines in step S55 that the paper discharge sensor 83 has detected the sheet S (step S55: Y), that is, when the paper discharge sensor 83 detects the sheet S after starting the warm-up process, it determines that a jam has occurred in the sheet S (step S61).

[0120] After determining that a jam has occurred in the sheet S, the control unit 9 stops the main motor 91 to stop the warm-up process (step S62). The control unit 9 then issues a notification to prompt the user to remove the jammed sheet S (step S63).

[0121] In the warm-up process when the second mode process is executed, if the sheet discharge sensor 83 detects the sheet S after the start of the warm-up process, it means that a remaining sheet exists at the first remaining position S1.

[0122] In this way, during the warm-up process when the second mode process is executed, the photosensitive drum 54 and the developing roller 53 are constantly driven while the warm-up process is being performed, and if a remaining sheet is present at the third remaining position S3 or the fourth remaining position S4, the sheet S is automatically discharged.

[0123] In the second mode process, the photosensitive drum 54 and the developing roller 53 are constantly driven while the warm-up process is being performed, which results in a longer drive time for the photosensitive drum 54 and the developing roller 53 compared to the first mode process. However, when there is little need to perform the first mode process, such as when the image forming apparatus 1 is used infrequently, the second mode can be selected and the second mode process executed, thereby increasing the remaining position patterns of remaining sheets that can be automatically discharged.

[0124] In the image forming apparatus 1, the discharge motor 92 is not driven during the warm-up process except when automatic discharge of the sheet S is performed in step S54. Therefore, if automatic discharge is not performed when a remaining sheet is present at the fifth remaining position S5, the sheet S located at the fifth remaining position S5 will not be discharged during the warm-up process. In this case, the sheet S located at the fifth remaining position S5 will be discharged in the printing operation after the warm-up process is completed. [Explanation of symbols]

[0125] 1. Image forming device 7 Paper output section 34 Registration roller pair 54 Photosensitive drum 60 Fixing unit 71 Paper ejection roller pair 81 Front of cash register sensor 83 Paper ejection sensor 91 Main motor 96 Drum clutch P1 transport route P2 Re-transportation route Pa confluence S seat T1 1st Hour

Claims

1. a conveying roller for conveying a sheet; a photosensitive drum on which a toner image to be transferred to a sheet is formed; a fixing device that fixes the transferred toner image onto a sheet; A paper output tray, a detection sensor disposed upstream of the conveying roller in a sheet conveying direction, the detection sensor detecting the sheet; a switching unit for switching between driving and stopping of the photosensitive drum; A control unit; Equipped with The control unit In the warm-up process for driving the conveying roller and the fixing unit, the photosensitive drum is driven for a predetermined time, and when the detection sensor detects a sheet within the predetermined time, the driving of the photosensitive drum is continued by the switching unit even after the predetermined time has elapsed, and the detected sheet is discharged to the discharge tray; An image forming apparatus characterized in that, if the detection sensor does not detect a sheet within the specified time, the switching unit stops driving the photosensitive drum when the specified time has elapsed, and the conveying roller and the fixing unit are driven while the driving of the photosensitive drum is stopped, thereby executing a first mode process to complete the warm-up process.

2. 2. The image forming apparatus according to claim 1, wherein the predetermined time is equal to or longer than the time required for the photosensitive drum to rotate at least three times.

3. The control unit 3. The image forming apparatus according to claim 1, wherein if the detection sensor detects a sheet after the predetermined time has elapsed during the warm-up process, it determines that a jam has occurred in the sheet, stops the warm-up process, and issues a notification urging the user to remove the jammed sheet.

4. a sheet conveyance path extending from an upstream side of the conveyance roller in a sheet conveyance direction via the conveyance roller, the photosensitive drum, and the fixing unit; a re-conveyance path that guides the sheet that has passed through the fixing unit to the conveyance path that is upstream of the conveyance roller in the sheet conveyance direction; a junction point located upstream of the conveying roller in the sheet conveying direction, where the conveying path and the re-conveying path join together; Equipped with the detection sensor is disposed downstream of the junction in a sheet conveying direction, The control unit An image forming apparatus as described in any one of claims 1 to 3, wherein if the detection sensor detects a sheet at the start of the warm-up process, it determines that a jam has occurred in the sheet, stops the warm-up process, and issues a notification urging the user to remove the jammed sheet.

5. a sheet discharge unit located downstream of the fixing unit in a sheet conveying direction, the sheet discharge unit discharging the sheet; a sheet discharge sensor disposed between the fixing unit and the sheet discharge unit, the sheet discharge sensor detecting the sheet; Equipped with The control unit An image forming apparatus as described in any one of claims 1 to 4, wherein if the paper discharge sensor detects a sheet after starting the warm-up process, it determines that a jam has occurred in the sheet, stops the warm-up process, and issues a notification urging the user to remove the jammed sheet.

6. The control unit In the warm-up process, a second mode process can be executed in which the photosensitive drum is constantly driven while the warm-up process is being performed, 6. The image forming apparatus according to claim 1, wherein one of a first mode in which the first mode processing is performed and a second mode in which the second mode processing is performed can be selectively set.

7. a common drive source for driving the conveying roller, the photosensitive drum, and the fixing unit; The image forming apparatus according to any one of claims 1 to 6, wherein the switching unit is an electromagnetic clutch that switches between a transmission state in which the driving force from the driving source is transmitted to the photosensitive drum and a cut-off state in which the driving force from the driving source is not transmitted to the photosensitive drum.

Images