Image forming apparatus

Abstract

To provide an image forming apparatus that, when cutting a sheet with a cutter, can prevent a reduction in the durability of a fixing unit.SOLUTION: A control unit (101) controls a heater (53) so that a temperature of a heating rotating body (51) becomes a first temperature for fixing an image to a sheet (P), controls a main motor (108) to rotate the heating rotating body or a pressure rotating body (52), thereby conveying the sheet, sets a target value of the temperature of the heating rotating body to a second temperature lower than the first temperature before a sheet rear end (PL) of the sheet passes through a nip part (N) and controls the heater, rotates ejection rollers (36, 37) to convey the sheet having passed through the nip part, stops the ejection rollers when a cut position of the sheet reaches an arrangement position (B) of a cutter (10), and subsequently cuts the sheet with the cutter.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This disclosure relates to an image forming apparatus.

Background Art

[0002] In the image forming apparatus described in Patent Document 1, a discharge unit is provided above the fixing unit to discharge the paper that has passed through the fixing unit. A cutter is provided between the fixing unit and the discharge unit, and the sheet is cut in a direction perpendicular to the conveyance direction by a horizontal cutter that constitutes the cutter. After the leading end of the paper discharged from the fixing unit is detected by a discharge switch, the pair of discharge rollers stop after a predetermined time has elapsed. As a result, the boundary line between the first image and the second image on the paper is positioned at the cutting position of the horizontal cutter. Then, the horizontal cutter is driven so that the paper is cut along the boundary line between the first image and the second image.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the image forming apparatus described in Patent Document 1, when the paper is cut by the horizontal cutter, the cutting position of the paper is positioned at the cutting position of the horizontal cutter by stopping the pair of discharge rollers. Along with the stop of the pair of discharge rollers, the pair of rollers of the fixing unit also stop. In this case, heat is applied to the nip portion between the pair of rollers, and the pair of rollers locally heats up. As a result, the durability of the fixing unit may decrease.

[0005] This disclosure is made to solve the above-mentioned problems and aims to provide an image forming apparatus that can suppress the decrease in durability of the fixing part when the sheet is cut with a cutter. [Means for solving the problem]

[0006] To solve the above-mentioned problems, the present invention provides an image forming apparatus comprising: a process unit for forming an image on a sheet; a fixing unit for fixing an image on a sheet, having a heating rotating body, a heater for heating the heating rotating body, and a pressurizing rotating body that forms a nip portion between itself and the heating rotating body; a discharge roller for discharging the sheet, which is located downstream of the fixing unit in the sheet transport direction; a main motor for transmitting driving force to at least the heating rotating body or the pressurizing rotating body; a cutter for cutting the sheet, which is located downstream of the fixing unit in the transport direction; and a control unit, wherein the control unit controls the processing The heater is controlled so that the temperature of the heating rotating body reaches a first temperature for fixing an image onto the sheet, the main motor is controlled to rotate the heating rotating body or the pressurizing rotating body to transport the sheet, the heater is controlled to set the target temperature of the heating rotating body to a second temperature lower than the first temperature before the rear end of the sheet passes the nip portion, the discharge roller is rotated to transport the sheet that has passed the nip portion, the discharge roller is stopped when the cutting position on the sheet reaches the position where the cutter is positioned, and then the sheet is cut by the cutter.

[0007] When cutting the sheet with a cutter, the control unit controls the heater by setting the target temperature of the heating rotating body to a second temperature, which is lower than the first temperature (printing temperature) at which the image is fixed to the sheet, before the trailing edge of the sheet passes through the nip. The cutting position of the sheet after it has passed through the nip is then stopped at the cutter's position. As a result, when the sheet is cut with the cutter, the temperature of the heating rotating body is lower than the first temperature, which suppresses localized heating of the heating rotating body and the pressurizing rotating body, thereby suppressing a decrease in the durability of the fixing part.

[0008] In the image forming apparatus of this disclosure, the control unit may stop driving the main motor after the rear end of the sheet has passed the nip portion. By stopping the driving of the main motor when it is not necessary to drive the main motor, the durability of the fixing unit and other components driven by the main motor can be improved.

[0009] In the image forming apparatus of the present disclosure, the process unit has a photosensitive drum, and in the transport direction, it is arranged on the upstream side of the process unit and includes a registration roller which is the transport roller closest to the photosensitive drum among a plurality of transport rollers that transport a sheet, and a first sheet sensor which is arranged between the photosensitive drum and the registration roller in the transport direction and is capable of detecting the passage of a sheet, and the control unit may set the target value of the temperature of the heating rotating body to the second temperature and control the heater when a first time has elapsed from the time the first sheet sensor detects the sheet.

[0010] The control unit controls the heater by setting the target temperature of the heating rotating body to a second temperature, which is lower than the first temperature (printing temperature), after one hour has elapsed since the first sheet sensor detected the sheet. As a result, when the sheet is cut by the cutter, the temperature of the heating rotating body is lower than the first temperature, which suppresses localized temperature increases in the heating rotating body and the pressurizing rotating body.

[0011] In the image forming apparatus of the present disclosure, the fixing unit has a second sheet sensor located downstream of the nip unit in the transport direction and capable of detecting the passage of a sheet, and the control unit may set the target value of the temperature of the heating rotating body to the second temperature and control the heater when a second time has elapsed from the time the second sheet sensor detects the sheet.

[0012] The control unit controls the heater by setting the target temperature of the heating rotating body to a second temperature, which is lower than the first temperature (printing temperature), two hours after the second sheet sensor detects the sheet. As a result, when the sheet is cut by the cutter, the temperature of the heating rotating body is lower than the first temperature, which suppresses localized temperature increases in the heating rotating body and the pressurizing rotating body.

[0013] In the image forming apparatus of this disclosure, the control unit may stop driving the main motor based on the time when the second sheet sensor detects the completion of the sheet's passage. By stopping the driving of the main motor when it is not necessary, the durability of the components driven by the main motor can be improved.

[0014] The image forming apparatus of this disclosure may be equipped with a discharge motor that transmits driving force to the discharge roller. The discharge roller can be controlled independently by the discharge motor.

[0015] The image forming apparatus of the present disclosure includes a process unit having a photosensitive drum, a registration roller which is the closest transport roller to the photosensitive drum among a plurality of transport rollers that transport a sheet and is located upstream of the photosensitive drum in the transport direction, and a first sheet sensor which is located between the photosensitive drum and the registration roller in the transport direction and is capable of detecting the passage of a sheet, and the control unit may start driving the discharge motor based on the time when the first sheet sensor detects the sheet. The control unit can start driving the discharge motor based on the time when the first sheet sensor detects the sheet.

[0016] In the image forming apparatus of this disclosure, the control unit may stop the discharge motor and stop the sheet after a third time has elapsed since the start of driving the discharge motor. The discharge roller can be appropriately driven and controlled so that the cutting position on the sheet reaches the position where the cutter is positioned and stops.

[0017] In the image forming apparatus of this disclosure, the fixing unit has a second sheet sensor located downstream of the nip unit in the transport direction and capable of detecting the passage of the sheet, and the control unit may stop the discharge motor and stop the sheet based on the time when the second sheet sensor detects the completion of the sheet's passage. The discharge roller can be appropriately driven and controlled so that the cutting position on the sheet reaches the position where the cutter is located and stops.

[0018] In the image forming apparatus of this disclosure, after the cutter cuts the sheet, the control unit controls the discharge motor to rotate the discharge roller and discharge the cut sheet. When performing continuous printing in which multiple sheets are printed in succession, after the cut sheet is discharged, the control unit may drive the main motor and control the heater so that the temperature of the heating rotating body reaches the first temperature. The temperature of the heating rotating body can be appropriately controlled for printing the next sheet.

[0019] In the image forming apparatus of this disclosure, after the cutter cuts the sheet, the control unit controls the discharge motor to rotate the discharge roller and discharge the cut sheet. When performing continuous printing in which multiple sheets are printed in succession, the control unit may drive the main motor at the same time as the discharge motor is started and control the heater so that the temperature of the heating rotating body reaches the first temperature. The temperature of the heating rotating body can be appropriately controlled for printing the next sheet. Furthermore, since the main motor is driven at the same time as the discharge motor is started, the start time for transporting the next sheet can be advanced, and printing can be expedited.

[0020] In the image forming apparatus of this disclosure, the control unit may, after cutting the sheet with the cutter, control the discharge motor to rotate the discharge roller to discharge the cut sheet, and after discharging the sheet, stop the discharge motor and stop the discharge roller. Noise can be suppressed by stopping the discharge motor when it is not necessary to drive the discharge roller.

[0021] In the image forming apparatus of this disclosure, the process unit includes a photosensitive drum, a developing roller that supplies toner to the photosensitive drum, and a transfer unit that transfers the toner supplied on the photosensitive drum to a sheet. The photosensitive drum and the developing roller may be rotated by the driving force of the main motor. The photosensitive drum and the developing roller rotate by the driving force from the main motor. This allows the photosensitive drum and the developing roller to rotate in sync, and toner to be carried on the photosensitive drum.

[0022] The image forming apparatus of the present disclosure includes a supply tray on which a sheet is placed, a pickup roller that transports the sheet from the supply tray to the process section by transmitting the driving force of the main motor, and a clutch that can be switched between a transmission state in which the driving force is transmitted from the main motor to the pickup roller and a non-transmission state in which the driving force is not transmitted from the main motor to the pickup roller. The control unit may switch the clutch to the transmission state when the temperature of the heating rotating body reaches a sheet supply temperature higher than the second temperature, thereby transmitting the driving force from the main motor to the pickup roller and transporting the sheet from the supply tray to the process section.

[0023] When the temperature of the heating rotating body reaches the sheet supply temperature (paper feeding temperature or printing temperature), which is higher than the second temperature, the control unit transmits the driving force from the main motor to the pickup roller via a clutch and transports the sheet from the supply tray to the process unit. This ensures that when the sheet with the transferred toner reaches the fuser unit, the temperature of the heating rotating body reaches the first temperature required to fix the image to the sheet.

[0024] In the image forming apparatus of the present disclosure, the control unit may set the target temperature of the heating rotating body to the second temperature and control the heater at a timing between the point downstream of the sheet by a distance equivalent to one rotation of the heating rotating body from the rear end of the sheet passing the nip portion and the point before the rear end of the sheet passes the nip portion.

[0025] Before the rear end of the sheet passes through the nip portion, the target value of the temperature of the heating rotator is set to a second temperature lower than the first temperature (printing temperature), and the heater is controlled. As a result, when the sheet is cut by the cutter, since the temperature of the heating rotator is lower than the first temperature, it is possible to suppress the local temperature rise of the heating rotator and the pressure rotator, and it is possible to suppress the deterioration of the durability of the fixing portion.

Advantages of the Invention

[0026] According to one aspect of the present disclosure, when cutting a sheet with a cutter, it is possible to suppress the deterioration of the durability of the fixing portion.

Brief Description of the Drawings

[0027] [Figure 1] It is a diagram showing an example of the schematic configuration of the image forming apparatus according to the present embodiment. [Figure 2] It is a block diagram showing the electrical configuration of the image forming apparatus shown in FIG. 1. [Figure 3] It is a main flowchart showing an example of the flow of print control by the CPU of the image forming apparatus shown in FIG. 1. [Figure 4] It is a sub flowchart showing an example of the flow of the printing and cutting process of FIG. 3. [Figure 5] It is a timing chart showing an example of the relationship between the drive timing of each drive unit and the temperature of the fixing portion. [Figure 6] It is a diagram for explaining the relationship between the sheet passing through the nip portion and the heater drive.

Modes for Carrying Out the Invention

[0028] 〔Embodiment 1〕 [Overall Configuration of Image Forming Apparatus 1] The schematic configuration of the image forming apparatus 1 will be described based on Figure 1. Figure 1 is a diagram showing an example of the schematic configuration of the image forming apparatus 1 according to this embodiment. As shown in Figure 1, the image forming apparatus 1 is a monochrome laser printer and comprises a main body 2, a transport unit 3, an image forming unit 4, a fuser 5, a cutter 10, and an operation panel 120. For the sake of convenience in the following explanation, the vertical and horizontal directions of the image forming apparatus 1 will be defined as indicated by the arrows in Figure 1.

[0029] The device body 2 includes a front cover 20, a supply tray 21, a discharge tray 22, a transport path 201, and a branch path 200. The device body 2 has an openable and closable front cover 20 on its front surface.

[0030] The main body of the device 2 has a removable supply tray 21 at its lower part. Sheets P are placed on the supply tray 21. Sheets P are standard-sized sheets such as A4 size. Sheets P are paper media such as plain paper or cardboard. The main body of the device 2 has an output tray 22 at its upper part. Sheets P on which images have been formed are placed on the output tray 22.

[0031] The transport path 201 is a path for transporting the sheet P placed on the supply tray 21 to the cutter 10 via the image forming unit 4, and then transporting the first sheet P1 and the second sheet P2 (see Figure 6) cut by the cutter 10 toward the discharge tray 22. The branch path 200 is a separate path from the transport path 201 for transporting the sheet P that has not been cut by the cutter 10 toward the discharge tray 22.

[0032] The starting point for conveying sheet P in the branching path 200 is the junction point C with the conveying path 201. The junction point C is located upstream in the conveying direction from the first discharge roller 36 and the third discharge roller 40. The branching path 200 is located below the conveying path 201. A flapper 8 is provided near the junction point C to distribute sheet P to either the conveying path 201 or the branching path 200. When the flapper 8 is in the first position, it distributes sheet P to the branching path 200. When the flapper 8 is in the second position, it distributes sheet P to the conveying path 201. The flapper 8 is configured to operate using driving force from a drive motor (not shown).

[0033] The conveying unit 3 includes a pickup roller 31, a separation roller 32, a paper dust removal roller 33, a registration roller 34, a roller 35, a first discharge roller 36, a second discharge roller 37, and a third discharge roller 40. The conveying unit 3 also includes a main motor 108 and a discharge motor 140 (see Figure 2).

[0034] The pickup roller 31 picks up the sheets P in the supply tray 21 that have been pushed upward by the sheet pressing plate 21A, and transports the sheets P toward the transport path 201. The separation roller 32 separates the sheets P picked up by the pickup roller 31 one by one. The paper dust removal roller 33 removes paper dust and other debris from the surface of the sheets P.

[0035] In the transport path 201, upstream of the image forming unit 4, is the registration roller 34, which is the transport roller closest to the photosensitive drum 61. The registration roller 34 aligns the direction of the leading edge of the sheet P and then transports the sheet P toward the image forming unit 4. Roller 35 transports the sheet P, after it has passed through the fuser 5, toward the first discharge roller 36.

[0036] In the transport path 201, the first discharge roller 36 and the second discharge roller 37 are positioned downstream of the merging point C. The first discharge roller 36 and the second discharge roller 37 are positioned upstream and downstream of the cutter 10's position B.

[0037] A third discharge roller 40 is positioned downstream of the merging point C in the branching path 200. The first discharge roller 36 and the second discharge roller 37 rotate to discharge the sheet P into the discharge tray 22.

[0038] The image forming unit 4 is an example of a process unit that forms an image on a sheet P, and is housed within the main body 2 of the apparatus. The image forming unit 4 has a drum cartridge 6 and a laser unit 7. The drum cartridge 6 has a photosensitive drum 61, a toner storage unit 62, a supply roller 63, a developing roller 64, a charger 65, a transfer roller TR, and a pinch roller 66. The drum cartridge 6 can be removed from the main body 2 of the apparatus by opening the front cover 20. The pinch roller 66 of the drum cartridge 6 is positioned opposite the registration roller 34. The pinch roller 66 rotates in conjunction with the rotation of the registration roller 34, and together with the registration roller 34, it transports the sheet P.

[0039] The photosensitive drum 61 rotates clockwise by the driving force transmitted from the main motor 108 (see Figure 2), thereby transporting the sheet P in the transport direction. The toner storage section 62 contains toner. The supply roller 63 supplies the toner from the toner storage section 62 to the developing roller 64. The charger 65 is a Scorotron-type charger that uniformly charges the surface of the photosensitive drum 61. The charger 65 may also be a charging roller.

[0040] A transfer roller TR is positioned opposite the photosensitive drum 61. The transfer roller TR is an example of a transfer member and forms a transfer nip TN between itself and the photosensitive drum 61 in the transport path 201. A transfer belt may be used instead of the transfer roller TR.

[0041] The main body of the device 2 has a laser unit 7 at its upper interior. The laser unit 7 includes a polygon mirror 131, a laser light-emitting unit 132 (see Figure 2), lenses and reflectors (not shown), etc. The laser unit 7 exposes the surface of the photosensitive drum 61 by rapidly scanning the surface of the photosensitive drum 61 with laser light (see dashed line) based on image data emitted from the laser light-emitting unit 132.

[0042] The surface of the photosensitive drum 61 is exposed by the laser unit 7, forming an electrostatic latent image based on the image data. The developing roller 64 supplies toner to the electrostatic latent image formed on the surface of the photosensitive drum 61, thereby forming a toner image on the surface of the photosensitive drum 61.

[0043] A transfer voltage is applied to the transfer roller TR by a voltage application unit (not shown). The transfer roller TR transports the sheet P between itself and the photosensitive drum 61, thereby transferring the toner image formed on the surface of the photosensitive drum 61 to the sheet P as it passes through the transfer nip TN. In this way, an image is formed on the sheet P.

[0044] A fuser 5 is located downstream of the image forming unit 4 in the transport path 201. The fuser 5 is an example of a fuser unit. The fuser 5 includes a heating roller 51, a pressure roller 52, a heater 53, a temperature sensor 54, and a paper discharge sensor 112. The heating roller 51 is an example of a heating rotating body and heats the sheet P. The pressure roller 52 is an example of a pressure rotating body and forms a nip N with the heating roller 51 to pressurize the sheet P. The pressure roller 52 rotates counterclockwise due to the driving force of the main motor 108. The heating roller 51 rotates clockwise, following the pressure roller 52.

[0045] Alternatively, the heating roller 51 may be configured to rotate clockwise due to the driving force of the main motor 108, and the pressure roller 52 may be configured to rotate counterclockwise following the heating roller 51. Or, the driving force of the main motor 108 may be transmitted to both the heating roller 51 and the pressure roller 52, so that the heating roller 51 rotates clockwise and the pressure roller 52 rotates counterclockwise.

[0046] The heater 53 is, for example, a halogen heater, and heats the heating roller 51. The temperature sensor 54 is installed inside the fuser unit 5 and detects the temperature of the heating roller 51. The temperature sensor 54 outputs a signal corresponding to the detected temperature to the CPU 101 (see Figure 2).

[0047] The fuser 5 heats the sheet P with the heating roller 51 and rotates the pressure roller 52, thereby conveying the sheet P while applying pressure with the heating roller 51 and the pressure roller 52, and fixing the image formed on the sheet P by the image forming unit 4 to the sheet P.

[0048] The fuser 5 is configured to include a heating roller 51, a pressure roller 52, and a heater 53, but is not limited to this configuration. For example, the fuser 5 may have a heater, a nip plate that receives radiant heat from the heater, a heating belt that rotates around the nip plate, and a pressure roller. In this case, the heating belt is an example of a heating rotating body.

[0049] Furthermore, the fuser 5 may have a substrate on which a heating pattern is formed, a belt that rotates around the substrate, and a pressure roller, and the substrate and the belt may be in contact with each other. In this case, the belt is an example of a heating rotating body. Alternatively, the fuser 5 may have a heating roller, a heater, and a pressure belt. In this case, the pressure belt is an example of a pressure rotating body.

[0050] In the transport path 201, a cutter 10 is positioned at position B, which is downstream of the fuser 5 and the merging position C. The cutter 10 is a well-known cutter mechanism capable of cutting the sheet P. The cutter 10 is composed of, for example, a blade 75 (see Figure 2), a fixed blade, a cutter carriage, and a cutting motor 106 (see Figure 2). The cutter 10 may also have a pair of upper and lower blades 75.

[0051] The blade 75 is, for example, a rotatable round blade, which is held in the cutter carriage. The fixed blade is fixed to a frame that extends horizontally within the device body 2. The cutter carriage is configured to reciprocate in the width direction of the sheet P along rails that extend horizontally within the device body 2, driven by the cutting motor 106.

[0052] When the sheet P is in position B of the cutter 10, the cutter carriage moves along the width direction of the sheet P, causing the sheet P to be cut by being sandwiched between the blade 75 and the fixed blade.

[0053] [Electrical configuration of image forming apparatus 1] Next, the electrical configuration of the image forming apparatus 1 will be explained with reference to Figure 2. Figure 2 is a block diagram showing the electrical configuration of the image forming apparatus 1. As shown in Figure 2, the image forming apparatus 1 further includes an ASIC (Application Specific Integrated Circuit) 105, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, an NVRAM (Non-Volatile Random Access Memory) 104, a pre-cash sensor 110, a post-cash sensor 111, a paper ejection sensor 112, a temperature and humidity sensor 113, and a communication interface (I / F) 130.

[0054] The ASIC105 is equipped with a CPU (Central Processing Unit) 101. The CPU 101 is an example of a control unit and performs overall control of each part of the image forming apparatus 1. The ASIC105 is electrically connected to the ROM 102, RAM 103, NVRAM 104, cutting motor 106, electromagnetic clutch 107, main motor 108, and ejection motor 140. The ASIC105 is also electrically connected to the pre-cash register sensor 110, post-cash register sensor 111, paper ejection sensor 112, temperature and humidity sensor 113, operation panel 120, communication I / F 130, fuser 5, and laser unit 7.

[0055] ROM102 is an example of a memory unit. ROM102 stores various control programs and settings for controlling the image forming apparatus 1. Specifically, ROM102 stores information on the printing temperature of the heating roller 51 and pressure roller 52 when fixing an image onto the sheet P. The printing temperature is an example of a first temperature. It also stores information on the standby temperature of the heating roller 51 and pressure roller 52 while waiting for the sheet P to be transported. The standby temperature is an example of a second temperature. Furthermore, it stores information such as the feedable temperature of the heating roller 51 and pressure roller 52 when transporting the sheet P from the supply tray 21. The feedable temperature is an example of a sheet supply temperature.

[0056] RAM 103 is used as a work area from which various control programs are read, and as a storage area for temporarily storing image data included in the print job. The CPU 101 controls each part of the image forming apparatus 1 while storing the processing results in RAM 103 or NVRAM 104 according to the control programs read from ROM 102 and signals output from various sensors.

[0057] The cutting motor 106 is an example of a drive source for the cutter. The CPU 101 drives the cutting motor 106 to move the cutter carriage, thereby moving the blade 75 in the width direction of the sheet P and cutting the sheet P.

[0058] The main motor 108 transmits driving force to the transport unit 3, the pressure roller 52, and the drum cartridge 6. When the CPU 101 drives the main motor 108 in the forward direction, driving force is transmitted to the pressure roller 52, the photosensitive drum 61, the developing roller 64, the pickup roller 31, and the registration roller 34. The pressure roller 52, the photosensitive drum 61, the developing roller 64, the pickup roller 31, and the registration roller 34 then rotate in a direction that transports the sheet P in the transport direction.

[0059] On the other hand, even if the CPU 101 drives the main motor 108 in reverse, the drive force is not transmitted to the pressure roller 52, drum cartridge 6, pickup roller 31, and registration roller 34.

[0060] The electromagnetic clutch 107 is an example of a clutch and is controlled by the CPU 101. By turning on the electromagnetic clutch 107, the CPU 101 enables the driving force of the main motor 108 to be transmitted to the pickup roller 31. Conversely, by turning off the electromagnetic clutch 107, the CPU 101 prevents the driving force of the main motor 108 from being transmitted to the pickup roller 31. When the image forming apparatus 1 is started up, the CPU 101 sets the electromagnetic clutch 107 to off.

[0061] The discharge motor 140 transmits driving force to the first discharge roller 36, the second discharge roller 37, and the third discharge roller 40. The CPU 101 transmits driving force to the first discharge roller 36, the second discharge roller 37, and the third discharge roller 40 by driving the discharge motor 140 in the forward direction. As a result, the first discharge roller 36, the second discharge roller 37, and the third discharge roller 40 rotate in a direction that conveys the sheet P in the conveying direction.

[0062] The pre-register sensor 110 is positioned upstream of the registration roller 34 in the transport path 201 and is a sensor that detects when the sheet P passes. The pre-register sensor 110 can be a sensor with an actuator that swings when the sheet P comes into contact with it, or an optical sensor, etc. The pre-register sensor 110 outputs an ON signal when the sheet P is passing and an OFF signal when the sheet P is not passing. The detection signal from the pre-register sensor 110 is output to the CPU 101.

[0063] The post-register sensor 111 is an example of a first sheet sensor, and is positioned upstream of the fuser 5 in the transport path 201, specifically between the photosensitive drum 61 and the registration roller 34, to detect when the sheet P passes through. The post-register sensor 111 has the same configuration as the pre-register sensor 110. The detection signal from the post-register sensor 111 is output to the CPU 101.

[0064] The paper discharge sensor 112 is an example of a second sheet sensor and is located in the transport path 201 between the heating roller 51 and roller 35 of the fuser 5, that is, downstream of the nip section N, to detect when a sheet P passes through. The paper discharge sensor 112 has the same configuration as the pre-cash register sensor 110. The detection signal from the paper discharge sensor 112 is output to the CPU 101. The paper discharge sensor 112 outputs an OFF signal before the sheet P passes through the paper discharge sensor 112, and outputs an ON signal while the sheet P, having passed through the nip section N, is passing through the paper discharge sensor 112. In other words, the paper discharge sensor 112 turns ON when the leading edge of the sheet P in the transport direction enters the paper discharge sensor 112, and then turns OFF when the trailing edge of the sheet P leaves the paper discharge sensor 112.

[0065] The temperature and humidity sensor 113 is a sensor that detects the temperature and humidity outside the main body of the device 2. The temperature and humidity sensor 113 is located, for example, on the side of the main body of the device 2. The temperature and humidity sensor 113 outputs a signal to the CPU 101 corresponding to the detected temperature and humidity. Alternatively, instead of the temperature and humidity sensor 113, a temperature sensor that detects the temperature outside the main body of the device 2 and a humidity sensor that detects the humidity outside the main body of the device 2 may be placed on the main body of the device 2.

[0066] The control panel 120 is located on the top surface of the main body 2 of the device. The control panel 120 has, for example, a touch panel in which a touchpad and display are integrally formed, and a key button section. The control panel 120 receives user input and outputs the received information to the CPU 101. The user can, for example, set whether or not to cut sheet P by operating the control panel 120.

[0067] The communication interface 130 is connected to a network such as a LAN and enables connection to external devices such as a PC that have a driver for the image forming apparatus 1 installed. The CPU 101 can receive print jobs via the communication interface 130. A print job contains various information necessary for forming an image on the sheet P, such as image data for image formation and the size and type of sheet P used for image formation.

[0068] [Print control flow by CPU101] Next, an example of the print control flow by the CPU 101 of the image forming apparatus 1 will be explained based on Figures 3 to 6. Figure 3 is the main flowchart showing an example of the print control flow by the CPU 101 of the image forming apparatus 1. In the following explanation, we will use as an example the case in which, after printing on one side of an A4 size sheet P, the sheet P is cut to divide it into two A5 size sheets, a first sheet P1 and a second sheet P2 (see Figure 6).

[0069] As shown in Figure 3, in S11, the CPU 101 determines whether it has received a print job via the communication interface 130. If the CPU 101 determines that it has received a print job via the communication interface 130 (S11: YES), it proceeds to the process in S13 described below.

[0070] On the other hand, if the CPU 101 determines that it has not received a print job via the communication interface 130 (S11:NO), it proceeds to process S12. In S12, the CPU 101 determines whether it has received a print command input via the operation panel 120. If it determines that it has not received a print command input via the operation panel 120 (S12:NO), the CPU 101 executes process S11 again.

[0071] On the other hand, if the CPU 101 determines that it has received a print command input via the operation panel 120 (S12: YES), it proceeds to process S13. In S13, the CPU 101 starts driving the heater 53. For example, as shown in Figure 5, the CPU 101 starts driving the heater 53 at time T1. That is, it starts supplying power to the heater 53.

[0072] After power is supplied to the heater 53, in S14 the CPU 101 determines whether or not to cut sheet P. That is, if the input print job instructs that sheet P needs to be cut, the CPU 101 determines to cut sheet P (S14: YES) and proceeds to process S17. On the other hand, if sheet P does not need to be cut (S14: NO), the CPU 101 proceeds to process S15.

[0073] In S15, the CPU 101 moves the flapper 8 to the first position and proceeds to the process in S16. When the flapper 8 moves to the first position, sheet P is distributed to branch path 200. If the flapper 8 is already in the first position at the start of S15, the CPU 101 maintains the state in which the flapper 8 is in the first position and proceeds to the process in S16.

[0074] In S16, the CPU 101 performs a printing process that does not involve cutting the sheet P, and then terminates the process. A detailed explanation of the printing process that does not involve cutting the sheet P is omitted, but the sheet P on which the toner image has been formed and fixed is guided by the flapper 8 to a branch path 200 having a third discharge roller 40. The sheet P guided to the branch path 200 is discharged onto the discharge tray 22 by the rotation of the third discharge roller 40.

[0075] In S17, the CPU 101 determines the cutting position A for dividing the sheet P into two equal parts and stores it in the RAM 103. Specifically, as shown in Figure 6, the CPU 101 determines the cutting position A for dividing the A4-sized sheet P into two equal parts, a first sheet P1 and a second sheet P2, which have equal lengths in the transport direction, at a position L2 from the leading edge in the transport direction and stores it in the RAM 103. The length L2 is calculated, for example, based on the amount of sheet P transported by the encoder (not shown) from the time the post-register sensor 111 detects the leading edge of sheet P until the post-register sensor 111 detects the trailing edge of sheet P.

[0076] In S18, the CPU 101 reads the printing temperatures of the heating roller 51 and pressure roller 52 used to fix the image onto the sheet P from the ROM 102. Then, the CPU 101 sets the temperature of the heating roller 51 to reach the printing temperature, for example, approximately 190°C, starts controlling the voltage applied to the heater 53, and then proceeds to the process in S19.

[0077] In S19, the CPU 101 drives the main motor 108 in the forward direction and then proceeds to the process in S20. As a result, the pressure roller 52, photosensitive drum 61, developing roller 64, and registration roller 34 rotate in a direction that transports the sheet P in the transport direction. Consequently, for example, as shown in Figure 5, if the pressure roller 52 or heating roller 51 of the fuser 5 is driven to rotate at time T2, the rate of temperature rise of the fixing temperature between the heating roller 51 and the pressure roller 52, that is, at the nip section N, becomes slightly slower.

[0078] In S20, the CPU 101 determines, via the temperature sensor 54, whether the temperature of the heating roller 51 and the pressure roller 52 has reached the paper-feeding temperature. The paper-feeding temperature is the temperature at which the driving force of the main motor 108 can be transmitted to the pickup roller 31, for example, 170°C. If the CPU 101 determines, via the temperature sensor 54, that the temperature of the heating roller 51 and the pressure roller 52 has not reached the paper-feeding temperature (S20: NO), it executes the process of S20 again.

[0079] On the other hand, if the CPU 101 determines via the temperature sensor 54 that the temperature of the heating roller 51 and the pressure roller 52 has reached the paper feeding temperature (S20: YES), it proceeds to the process in S21. In S21, the CPU 101 executes a sub-process for print cutting and then terminates the process.

[0080] [Sub-processing for printing and cutting] Next, an example of the print cutting process performed by the CPU 101 in S21 will be explained based on Figure 4. Figure 4 is a subflowchart showing an example of the print cutting process. As shown in Figure 4, in S111, the CPU 101 drives a drive motor (not shown) to move the flapper 8 to the second position and proceeds to the process in S112. As the flapper 8 moves to the second position, the sheet P is distributed to the transport path 201. If the flapper 8 is already in the second position at the start of S111, the CPU 101 maintains the flapper 8 in the second position and proceeds to the process in S112.

[0081] In S112, the CPU 101 executes a pickup command to pick up the sheet P in the supply tray 21 using the pickup roller 31. Specifically, the CPU 101 turns on the electromagnetic clutch 107 to set the system so that the driving force of the main motor 108 is transmitted to the pickup roller 31. The process then proceeds to S113.

[0082] In S113, if the discharge motor 140 is running, the CPU 101 stops the discharge motor 140 after a predetermined time has elapsed, for example, after about 2 to 3 seconds, and proceeds to the process in S114. This ensures that sheet P is discharged reliably. If the discharge motor 140 is not running, the CPU 101 proceeds to the process in S114 after S112 without executing S113.

[0083] In S114, the CPU 101 determines whether the detection signal input from the post-cash register sensor 111 has changed from "off" to "on". Specifically, the CPU 101 determines that the detection signal has turned "on" by detecting the leading edge of the conveyed sheet P with the post-cash register sensor 111 and acquiring the detection signal sent from the post-cash register sensor 111.

[0084] Then, if the detection signal input from the post-cash register sensor 111 has not changed from "off" to "on" (S114: NO), the CPU 101 executes process S114 again. On the other hand, if the detection signal input from the post-cash register sensor 111 has changed from "off" to "on" (S114: YES), the CPU 101 proceeds to process S115.

[0085] In S115, the CPU 101 starts measuring the elapsed time from the moment the detection signal input from the post-register sensor 111 changes from "off" to "on," and proceeds to the process in S116. In S116, the CPU 101 starts image formation on the sheet P by the image forming unit 4. Specifically, the CPU 101 controls the photosensitive drum 61 and the transfer roller TR to form an image on the sheet P based on the image data. That is, the CPU 101 uses the transfer roller TR to transfer the toner image formed on the photosensitive drum 61 to the sheet P. Then, the fuser 5 fixes the image formed on the sheet P to the sheet P.

[0086] Next, in S117, the CPU 101 starts forward rotation of the discharge motor 140 to rotate the first discharge roller 36 and the second discharge roller 37, and proceeds to the process in S118. As a result, for example, as shown in Figure 5, the paper discharge drive that rotates the first discharge roller 36 and the second discharge roller 37 is started at time T2.

[0087] In S118, the CPU 101 determines whether the detection signal input from the paper ejection sensor 112 has changed from "off" to "on". Specifically, the CPU 101 determines that the detection signal has turned "on" by detecting the leading edge of the sheet P being transported by the paper ejection sensor 112 and acquiring the detection signal sent from the paper ejection sensor 112. If the detection signal input from the paper ejection sensor 112 has not changed from "off" to "on" (S118: NO), the CPU 101 executes the process in S118 again. On the other hand, if the detection signal input from the paper ejection sensor 112 has changed from "off" to "on" (S118: YES), the CPU 101 proceeds to the process in S119.

[0088] In S119, the CPU 101 determines whether the elapsed time since the detection signal of the post-register sensor 111, which was started to be measured in S115, changed from "off" to "on," has reached a predetermined time, that is, whether a predetermined time has elapsed. This predetermined time is an example of the "first time." For example, the predetermined time is the elapsed time from time T2 to time T3, as shown in Figure 5.

[0089] Then, if the CPU 101 determines that the elapsed time since the detection signal of the post-cash register sensor 111 changed from "off" to "on" has not reached a predetermined time, that is, the predetermined time has not elapsed (S119: NO), it executes the process of S119 again. On the other hand, if the CPU 101 determines that the elapsed time since the detection signal of the post-cash register sensor 111 changed from "off" to "on" has reached a predetermined time, that is, the predetermined time has elapsed (S119: YES), it proceeds to the process of S120.

[0090] In S120, the CPU 101 reads the standby temperatures of the heating roller 51 and pressure roller 52 from the ROM 102 while waiting for the sheet P to be transported. Then, the CPU 101 sets the temperature of the heating roller 51 to the standby temperature, for example, about 130°C, starts controlling the voltage applied to the heater 53, and then proceeds to the process in S121.

[0091] For example, as shown in Figure 5, the CPU 101 stops driving the heater 53 at time T3. Here, as shown in Figure 5, the driving of the heater 53 is stopped at time T3, but at time T3, the sheet P has not yet completed passing between the heating roller 51 and the pressure roller 52, that is, the nip portion N. Specifically, for example, the timing at which the driving of the heater 53 is stopped is when the sheet P at position A2 shown in Figure 6 passes the nip portion N. Position A2 is a length L1 from the rear end PL of the sheet in the forward direction of transport. This length L1 is preferably less than or equal to the circumference of one rotation of the heating roller 51 in order to ensure that the image is fixed to the sheet P.

[0092] In S121, the CPU 101 determines whether the detection signal input from the paper ejection sensor 112 has changed from "on" to "off". Specifically, the CPU 101 determines that the detection signal has turned "off" because, after the paper ejection sensor 112 detects the leading edge of the sheet P being transported, it can no longer receive the detection signal sent from the paper ejection sensor 112 once the sheet P has passed the trailing edge.

[0093] Then, if the detection signal input from the paper output sensor 112 has not changed from "on" to "off" (S121:NO), the CPU 101 executes the process of S121 again. On the other hand, if the detection signal input from the paper output sensor 112 has changed from "on" to "off" (S121:YES), the CPU 101 determines that the paper output sensor 112 has detected the completion of sheet P's passage and proceeds to the process of S122.

[0094] For example, as shown in Figure 5, if the detection signal input from the paper ejection sensor 112 changes from "on" to "off" at time T4, the CPU 101 determines that the paper ejection sensor 112 has detected that the sheet P has completed its passage. In other words, the CPU 101 determines that the trailing edge PL of the sheet P has passed the nip portion N. Therefore, the CPU 101 can stop driving the heater 53 by (time T4 - time T3) earlier than the time (time T4) when the trailing edge PL of the sheet P has passed the nip portion N.

[0095] In S122, the CPU 101 starts measuring the elapsed time from the moment the detection signal input from the paper ejection sensor 112 changes from "on" to "off". Subsequently, the CPU 101 determines whether the elapsed time from the moment the detection signal input from the paper ejection sensor 112 changes from "on" to "off" has reached a predetermined stop time, that is, whether the predetermined stop time has elapsed. The predetermined stop time is the elapsed time from the moment the detection signal input from the paper ejection sensor 112 changes from "on" to "off" until the cutting position A (see Figure 6) of the sheet P reaches the position B (see Figure 1) of the cutter 10. The predetermined stop time is stored in the ROM 102 in advance. For example, the predetermined stop time is the elapsed time from time T4 to time T5, as shown in Figure 5.

[0096] Then, if the CPU 101 determines that the elapsed time since the detection signal input from the paper output sensor 112 changed from "on" to "off" has not reached a predetermined stop time (S122: NO), it executes the process in S122 again. On the other hand, if the CPU 101 determines that the elapsed time since the detection signal input from the paper output sensor 112 changed from "on" to "off" has reached a predetermined stop time (S122: YES), it proceeds to the process in S123.

[0097] In S123, the CPU 101 stops the main motor 108 and then proceeds to the process in S124. For example, as shown in Figure 5, at time T5, the main motor 108 is stopped, the heating roller 51 and pressure roller 52 of the fuser 5 are stopped, and the fuser drive is stopped. By stopping the main motor 108 when it is not needed, the durability of the heating roller 51 and pressure roller 52 of the fuser 5, which are driven by the main motor 108, can be improved.

[0098] In S124, the CPU 101 stops the discharge motor 140 and then proceeds to the process in S125. For example, as shown in Figure 5, at time T5, the discharge motor 140 is stopped, and the paper discharge drive is stopped. As a result, the first discharge roller 36 and the second discharge roller 37 stop with the sheet P gripped, so that the sheet P stops with the cutting position A (see Figure 6) at the position B (see Figure 1) of the cutter 10.

[0099] In S125, the CPU 101 drives the cutting motor 106 to move the blade 75 held in the cutter carriage back and forth in the width direction of the sheet P, and then proceeds to the process in S126. For example, as shown in Figure 5, the cutter drive is started by starting the cutting motor 106 at time T5, and the cutting motor 106 is stopped at time T6. As a result, the sheet P is cut into two equal parts: the first sheet P1 and the second sheet P2.

[0100] Here, an example of the fixing temperature of the nip portion N of the heating roller 51 and pressure roller 52 during sheet P cutting will be explained based on Figure 5. The dashed graph 71 shows the change in the fixing temperature of the nip portion N when the heater 53 is set to a standby temperature, for example, approximately 130°C, at time T4 when the rear end PL (see Figure 6) of sheet P has passed the nip portion N. The solid graph 72 shows the change in the fixing temperature of the nip portion N when the heater 53 is set to a standby temperature, for example, approximately 130°C, at time T3 when the position A2 (see Figure 6) of sheet P has passed the nip portion N.

[0101] As shown in the dashed graph 71, when the heater 53 is set to the standby temperature at time T4 and the heater 53 is stopped, the fixing temperature at the nip section N at time T5, when the main motor 108 is stopped, is temperature Q1. Then, at time T5, after the main motor 108 is stopped, the fixing temperature at the nip section N rises to temperature Q2 while the sheet P is being cut by the cutter 10.

[0102] On the other hand, as shown in the solid line graph 72, when the heater 53 is set to the standby temperature at time T3 and the heater 53 is stopped, the fixing temperature at the nip portion N at time T5 when the main motor 108 is stopped is a temperature R1 which is lower than temperature Q1. Then, at time T5, after the main motor 108 is stopped, the fixing temperature at the nip portion N during cutting of the sheet P by the cutter 10 rises to a temperature R2 which is lower than temperature Q2.

[0103] Therefore, at time T3, when position A2 (see Figure 6), which is a length L1 forward from the rear end PL of the sheet P in the conveying direction, has passed the nip section N, the set temperature of the heater 53 is set to the standby temperature. This makes it possible to keep the rise in the fixing temperature of the nip section N during cutting of the sheet P by the cutter 10 at a temperature R2 that is lower than temperature Q2. As a result, it is possible to suppress the localized temperature rise of the nip section N of the heating roller 51 and pressure roller 52 during cutting of the sheet P, and to suppress a decrease in the durability of the heating roller 51 and pressure roller 52 of the fuser 5.

[0104] Returning to Figure 4, in S126, the CPU 101 determines whether the currently running print job contains image data to be printed for the next sheet P. If the CPU 101 determines that the currently running print job does not contain image data to be printed for the next sheet P (S126: NO), it proceeds to process S127. In S127, the CPU 101 restarts the discharge motor 140 to rotate the first discharge roller 36 and the second discharge roller 37 to discharge the cut first sheet P1 and second sheet P2, and then proceeds to process S128.

[0105] In S128, the CPU 101 stops the operation of the discharge motor 140, terminates the flow shown in Figure 4, and returns to the main flowchart.

[0106] On the other hand, in S126, if the CPU 101 determines that there is image data to be printed for the next sheet P in the currently running print job (S126: YES), the process proceeds to S129. In S129, the CPU 101 restarts the discharge motor 140 to rotate the first discharge roller 36 and the second discharge roller 37, discharges the cut first sheet P1 and the second sheet P2, and then proceeds to S130. In S130, the CPU 101 restarts the main motor 108 to rotate the heating roller 51 and the pressure roller 52, etc., and then proceeds to S131.

[0107] For example, as shown in Figure 5, at time T6, the CPU 101 stops the cutting motor 106. The CPU 101 also restarts the discharge motor 140 to rotate the first discharge roller 36 and the second discharge roller 37, and discharges the cut first sheet P1 and the second sheet P2. At time T6, simultaneously with the start of the discharge motor 140, the CPU 101 also starts the main motor 108 to restart the rotation of the heating roller 51 and the pressure roller 52, etc.

[0108] In S131, the CPU 101 reads the printing temperatures of the heating roller 51 and pressure roller 52 used to fix the image onto the sheet P from the ROM 102. Then, the CPU 101 sets the temperature of the heating roller 51 to rise to the printing temperature, for example, approximately 190°C, and starts controlling the voltage applied to the heater 53 before proceeding to the process in S132. For example, as shown in Figure 5, at time T7, the CPU 101 sets the temperature of the heating roller 51 to rise to the printing temperature and starts controlling the voltage applied to the heater 53.

[0109] In S132, the CPU 101 determines, via the temperature sensor 54, whether the temperature of the heating roller 51 and the pressure roller 52 has reached the paper-feeding temperature. If the CPU 101 determines that the temperature of the heating roller 51 and the pressure roller 52 has not reached the paper-feeding temperature (S132: NO), it executes the process in S132 again.

[0110] On the other hand, if the CPU 101 determines that the temperature of the heating roller 51 and the pressure roller 52 has reached the paper-feeding temperature (S132: YES), it executes the process in S112 again.

[0111] As a result, when the temperature of the heating roller 51 and the pressure roller 52 reaches a paper-feedable temperature higher than the standby temperature, the sheet P is transported from the supply tray 21 to the image forming unit 4. Consequently, when the sheet P, onto which toner has been transferred via the photosensitive drum 61, reaches the nip section N, the temperature of the heating roller 51 and the pressure roller 52 can be reliably set to the printing temperature at which the image is fixed to the sheet P. For example, as shown in Figure 5, at time T8, when the leading edge of the sheet P reaches the nip section N, the fixing temperature of the nip section N can be reliably set to the printing temperature, for example, approximately 190°C.

[0112] [Various variations] [Example 1] In the embodiment described above, in S119 shown in Figure 4, the CPU 101 determines whether a predetermined time has elapsed since the detection signal from the post-cash sensor 111 changed from "off" to "on," but it is not limited to this. For example, the CPU 101 may determine whether a predetermined time has elapsed since the detection signal input from the paper output sensor 112 changed from "off" to "on." This predetermined time is an example of a "second time."

[0113] Then, if the CPU 101 determines that the elapsed time since the detection signal of the paper output sensor 112 changed from "off" to "on" has not reached a predetermined second time, that is, that the predetermined second time has not elapsed (S119: NO), it executes the process of S119 again. On the other hand, if the CPU 101 determines that the elapsed time since the detection signal of the paper output sensor 112 changed from "off" to "on" has reached a predetermined second time, that is, that the predetermined second time has elapsed (S119: YES), it may proceed to the process of S120.

[0114] As a result, when the sheet P is cut by the cutter 10, the temperature of the heating roller 51 is lower than the printing temperature at which the image is fixed to the sheet P. Therefore, it is possible to suppress the localized heating of the nip portion N where the pressure roller 52 contacts the heating roller 51. Consequently, it is possible to suppress a decrease in the durability of the heating roller 51 and pressure roller 52 of the fuser unit 5.

[0115] [Differentiation 2] In the embodiment described above, in steps S129 to S130 shown in Figure 4, the CPU 101 starts driving the main motor 108 at the same time as starting to drive the discharge motor 140, but it is not limited to this. For example, in step S129, the CPU 101 restarts driving the discharge motor 140 to rotate the first discharge roller 36 and the second discharge roller 37, and discharges the cut first sheet P1 and the second sheet P2. Then, in step S130, the CPU 101 may restart driving the main motor 108 after the discharge motor 140 has been restarted and the cut first sheet P1 and the second sheet P2 have been discharged. This allows the temperature of the heating roller 51 to be appropriately controlled for printing on the next sheet P.

[0116] [Difference 3] Although the image forming apparatus 1 of the above embodiment is described as a monochrome laser printer, it is not limited to this and may be a color laser printer.

[0117] [Differentiation Example 4] The image forming apparatus 1 of the above embodiment was described in the case where the sheet P is cut into two equal parts, but it is not limited to this, and for example the sheet P may be cut into three equal parts, and the cutting position A of the sheet P can be changed as appropriate.

[0118] [Difference 5] The image forming apparatus 1 of the above embodiment receives print jobs via a communication I / F 130, but is not limited to this; for example, print jobs may be received via a USB interface.

[0119] [Additional Notes] This disclosure is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of this disclosure. [Explanation of Symbols]

[0120] 1. Image forming apparatus 4 Image forming unit 5. Fuser 10 cutters 31 Pickup Roller 34 Registration Roller 36 First discharge roller 37 Second discharge roller 51 Heating roller 52 Pressure rollers 53 Heater 61 Photosensitive drum 64 Developing Roller 101 CPU 106 Cutting motor 107 Electromagnetic clutch 108 Main motor 111 Post-checkout sensor 112 Paper output sensor 140 Discharge motor TR Transfer Roller

Claims

1. A process unit for forming an image on a sheet, The fixing unit comprises a heating rotating body, a heater for heating the heating rotating body, and a pressurizing rotating body that forms a nip portion between itself and the heating rotating body, and a fixing unit for fixing an image to a sheet. A discharge roller for discharging the sheet is located downstream of the fixing section in the sheet transport direction, At least a main motor that transmits driving force to the heating rotating body or the pressurizing rotating body, A cutter for cutting the sheet is positioned downstream of the fixing section in the aforementioned transport direction, It comprises a control unit and, The control unit, The heater is controlled so that the temperature of the heating rotating body reaches a first temperature for fixing the image onto the sheet. The main motor is controlled to rotate the heating rotating body or the pressurizing rotating body to transport the sheet. Before the rear end of the sheet passes the nip portion, the heater is controlled by setting the target temperature of the heating rotating body to a second temperature lower than the first temperature. An image forming apparatus characterized by rotating the discharge roller to transport the sheet that has passed through the nip portion, stopping the discharge roller when the cutting position on the sheet reaches the position where the cutter is positioned, and then cutting the sheet with the cutter.

2. The image forming apparatus according to claim 1, characterized in that the control unit stops driving the main motor after the rear end of the sheet has passed the nip portion.

3. The process unit has a photosensitive drum, In the aforementioned transport direction, the registration roller is located upstream of the process section and is the transport roller closest to the photosensitive drum among a plurality of transport rollers that transport the sheet, In the aforementioned transport direction, a first sheet sensor is positioned between the photosensitive drum and the registration roller, and is capable of detecting the passage of a sheet. Equipped with, The control unit, The image forming apparatus according to claim 1, characterized in that, after a first time has elapsed since the first sheet sensor detected the sheet, the heater is controlled by setting the target value of the temperature of the heating rotating body to the second temperature.

4. The fixing unit is positioned downstream of the nip unit in the transport direction and has a second sheet sensor capable of detecting the passage of the sheet. The image forming apparatus according to claim 1, characterized in that the control unit controls the heater by setting the target value of the temperature of the heating rotating body to the second temperature when a second time has elapsed since the second sheet sensor detected the sheet.

5. The image forming apparatus according to claim 4, characterized in that the control unit stops driving the main motor based on the time when the second sheet sensor detects the completion of the sheet's passage.

6. The image forming apparatus according to claim 1, characterized in that it is further equipped with a discharge motor that transmits driving force to the discharge roller.

7. The process unit has a photosensitive drum, In the aforementioned transport direction, the registration roller is located upstream of the photosensitive drum and is the transport roller closest to the photosensitive drum among a plurality of transport rollers that transport the sheet, In the aforementioned transport direction, a first sheet sensor is positioned between the photosensitive drum and the registration roller, and is capable of detecting the passage of a sheet. Equipped with, The control unit, The image forming apparatus according to claim 6, characterized in that the discharge motor is started to drive based on the time when the first sheet sensor detects the sheet.

8. The image forming apparatus according to claim 7, characterized in that the control unit stops the discharge motor and stops the sheet after a third time has elapsed since the start of driving the discharge motor.

9. The fixing unit is positioned downstream of the nip unit in the transport direction and has a second sheet sensor capable of detecting the passage of the sheet. The image forming apparatus according to claim 7, characterized in that the control unit stops the discharge motor and stops the sheet based on the time when the second sheet sensor detects that the sheet has completed passing.

10. The control unit, After the sheet is cut by the cutter, the discharge motor is controlled to rotate the discharge roller and discharge the cut sheet. When performing continuous printing in which multiple sheets are printed in succession, after the sheets have been cut and ejected, the main motor is driven. The image forming apparatus according to claim 6, characterized in that the heater is controlled so that the temperature of the heating rotating body reaches the first temperature.

11. The control unit, After the sheet is cut by the cutter, the discharge motor is controlled to rotate the discharge roller and discharge the cut sheet. When performing continuous printing in which multiple sheets are printed in succession, the main motor is driven at the same time as the discharge motor is started to drive. The image forming apparatus according to claim 6, characterized in that the heater is controlled so that the temperature of the heating rotating body reaches the first temperature.

12. The control unit, After the sheet is cut by the cutter, the discharge motor is controlled to rotate the discharge roller and discharge the cut sheet. The image forming apparatus according to claim 6, characterized in that the discharge motor is stopped and the discharge roller is stopped after the sheet has been discharged.

13. The aforementioned process unit is Photosensitive drum and A developing roller that supplies toner to the photosensitive drum, It has a transfer unit that transfers the toner supplied onto the photosensitive drum to a sheet, The image forming apparatus according to claim 1, characterized in that the photosensitive drum and the developing roller are rotated by the driving force of the main motor.

14. A supply tray on which the sheet is placed, A pickup roller, which is driven by the main motor, transports the sheet from the supply tray to the process section. A clutch that can switch between a transmission state in which driving force is transmitted from the main motor to the pickup roller and a non-transmission state in which driving force is not transmitted from the main motor to the pickup roller, Equipped with, The control unit, When the temperature of the heating rotating body reaches a sheet supply temperature higher than the second temperature, the clutch is switched to the transmission state to transmit the driving force from the main motor to the pickup roller. The image forming apparatus according to claim 1, characterized in that a sheet is transported from the supply tray to the process section.

15. The control unit, The image forming apparatus according to claim 1, characterized in that, in the sheet, after the position downstream in the conveying direction, by a distance equivalent to one rotation of the heating rotating body from the rear end of the sheet, has passed the nip portion, and before the rear end of the sheet has passed the nip portion, the heater is controlled by setting the target value of the temperature of the heating rotating body to the second temperature.

Images