Image forming apparatus

Abstract

To reduce time from a printing start to a printing end in the case of continuous printing.SOLUTION: An image-forming device (1) includes a CPU (101). The CPU (101) controls a heater (53) such that a target value of temperature of a heating roller (51) becomes a second temperature lower than a first temperature after starting rotating the heating roller (51) and before stopping discharge rollers (36, 37, 40), drives a main motor (108) and rotates the heating roller (51) before completion of cutting of a sheet by a cutter (10) when executing continuous printing in which multiple sheets are printed continuously, and controls the heater (53) such that the temperature of the heating roller (51) becomes the first temperature.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] In the image forming apparatus disclosed in Patent Document 1, the paper that has passed through the fixing unit is discharged from a discharge unit provided above the fixing unit. A cutter provided between the fixing unit and the discharge unit cuts the paper in a direction orthogonal to the paper conveyance direction. Also, the leading end of the paper that has exited the fixing unit is detected by a discharge switch, and after a predetermined time has elapsed, the discharge roller that discharges the paper stops. When the discharge roller stops, the boundary line between the first image and the second image on the paper is positioned at the cutting position of the cutter, and the cutter is driven to cut the paper along the boundary line.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the image forming apparatus disclosed in Patent Document 1, when cutting the paper with a cutter, the discharge roller and a pair of rollers of the fixing unit are stopped before cutting the paper. When performing the next printing for continuous printing, in order to make the temperature of the pair of rollers of the fixing unit uniform, the discharge roller and the pair of rollers of the fixing unit are driven after the completion of cutting the paper. Therefore, the time from the start to the end of printing in the case of continuous printing may become long.

[0005] This disclosure has been made in view of the above problems, and an object thereof is to shorten the time from the start to the end of printing in the case of continuous printing compared to the conventional case.

Means for Solving the Problems

[0006] To solve the above 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 to 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, disposed 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, disposed downstream of the fixing unit in the transport direction; a discharge motor for transmitting driving force to the discharge roller; and a control unit, wherein the control unit controls the heater so that the temperature of the heating rotating body reaches a first temperature for fixing an image to the sheet, and controls the main motor to control the heating rotating body. The rolling body or the pressurized rotating body is rotated to transport the sheet, the discharge motor is controlled to rotate the discharge roller to transport the sheet that has passed through the nip section, the discharge roller is stopped when the cutting position on the sheet reaches the cutter position, the heater is controlled so that the target temperature of the heating rotating body is a second temperature lower than the first temperature after the heating rotating body starts rotating and before the discharge roller is stopped, the cutting of the sheet by the cutter is started after the discharge roller is stopped, and in the case of continuous printing in which multiple sheets are printed in succession, the main motor is driven to rotate the heating rotating body or the pressurized rotating body before the cutting of the sheet by the cutter is completed, and the heater is controlled so that the temperature of the heating rotating body is the first temperature.

[0007] According to the above configuration, the control unit drives the main motor before the cutter finishes cutting the sheet, and also controls the heater, which was previously controlled to raise the temperature of the heating rotating body to a second temperature, to raise the temperature of the heating rotating body to a first temperature. As a result, the temperature of the nip portion of the fixing unit can be made uniform during sheet cutting, and the start of transporting the next sheet can be accelerated. This reduces the decrease in printing speed during continuous printing.

[0008] In the image forming apparatus of the present disclosure, the process unit has a photosensitive drum, and 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 control the discharge motor based on the time when the first sheet sensor detects a sheet.

[0009] The first sheet sensor is positioned between the photosensitive drum and the registration roller. The registration roller is the transport roller closest to the discharge roller in the transport direction among the multiple transport rollers located upstream of the photosensitive drum. Therefore, the first sheet sensor is positioned as close as possible to the discharge roller on the upstream side of the photosensitive drum.

[0010] Furthermore, after the first sheet sensor detects the sheet, the sheet reaches the discharge roller. Therefore, the control unit controls the discharge motor based on the moment the first sheet sensor detects the sheet, so that the discharge motor can be started to drive at the appropriate timing and the rotation of the discharge roller can be started.

[0011] In the image forming apparatus of this disclosure, the fixing unit is located downstream of the nip unit in the transport direction and has a second sheet sensor capable of detecting the passage of a sheet, and the control unit may control the discharge motor based on the time when the second sheet sensor detects a sheet.

[0012] The second sheet sensor is positioned downstream of the nip section in the conveying direction, and is therefore closer to the discharge roller than the fixing section. Also, the sheet reaches the discharge roller after the second sheet sensor has detected it. Therefore, the control unit controls the discharge motor based on the moment the second sheet sensor detects the sheet, so that the discharge motor can be started to drive and the discharge roller can be started to rotate at the appropriate timing.

[0013] In the image forming apparatus of this disclosure, the control unit may stop the discharge motor and stop the sheet after a predetermined time has elapsed since the start of driving the discharge motor. The control unit can appropriately control the discharge roller so that the cutting position on the sheet reaches the position where the cutter is positioned.

[0014] In the image forming apparatus of the present disclosure, the fixing unit is located downstream of the nip unit in the transport direction and has a second sheet sensor capable of detecting the passage of a sheet, and the control unit may control the heater so that the target value of the temperature of the heating rotating body becomes the second temperature based on the time when the second sheet sensor detects the completion of the sheet's passage.

[0015] After passing through the second sheet sensor, the heater is controlled so that the temperature of the heating rotating body is lower than the first temperature. Therefore, the temperature of the heating rotating body can be lowered before the cutter starts cutting the sheet. This suppresses localized temperature increases in the heating rotating body and the pressurized rotating body.

[0016] In the image forming apparatus of the present disclosure, the process unit has a photosensitive drum, and 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 control the heater so that the target value of the temperature of the heating rotating body becomes the second temperature based on the time when the first sheet sensor detects the completion of the passage of the sheet.

[0017] After passing through the first sheet sensor, the heater is controlled so that the temperature of the heating rotating body becomes a second temperature, which is lower than the first temperature. Therefore, the temperature of the heating rotating body can be lowered before the cutter starts cutting the sheet. This suppresses localized heating of the nip portion of the fixing section.

[0018] In the image forming apparatus of the present disclosure, when performing continuous printing, the control unit sets the driving duration of the main motor according to the number of sheets to be printed, and if the driving duration is equal to or greater than a threshold time, the control unit may continue to drive the main motor, cut the sheet with the cutter, then control the discharge motor to rotate the discharge roller to discharge the cut sheet, and start supplying the next sheet after the sheet discharged by the discharge roller. By continuing to drive the main motor toward printing the next sheet, the control unit can suppress localized temperature rise of the heating rotating body and the pressurizing rotating body.

[0019] In the image forming apparatus of this disclosure, the fixing unit is located downstream of the nip unit in the transport direction and has a second sheet sensor capable of detecting the passage of a sheet, and the control unit may set the drive duration based on the time when the second sheet sensor detects a sheet.

[0020] The second sheet sensor is positioned downstream of the nip section in the conveying direction. Therefore, the second sheet sensor detects the sheet after it has reached the nip section. As a result, the control unit sets the drive duration based on the moment the second sheet sensor detects the sheet, allowing it to stop the main motor and the heating rotating body at the appropriate timing.

[0021] In the image forming apparatus of the present disclosure, the process unit has a photosensitive drum, and 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 set the drive duration based on the time when the first sheet sensor detects a sheet.

[0022] The first sheet sensor is disposed between the photosensitive drum and the registration roller. Further, the registration roller is the conveyance roller closest to the nip portion in the conveyance direction among a plurality of conveyance rollers disposed upstream of the photosensitive drum. Therefore, the first sheet sensor is disposed at a position as close as possible to the nip portion on the upstream side of the photosensitive drum.

[0023] Furthermore, after the first sheet sensor detects the sheet, the sheet reaches the nip portion. Therefore, the control unit sets the drive duration based on the time when the first sheet sensor detects the sheet, so that the drive of the main motor can be stopped at an appropriate timing to stop the heating rotator.

[0024] In the image forming apparatus of the present disclosure, when the control unit executes the continuous printing, the control unit may control the heater so that the temperature of the heating rotator becomes the first temperature after the start of cutting the sheet by the cutter.

[0025] The heater that was controlled to reach the second temperature before driving the discharge motor is controlled to reach the first temperature after the start of cutting the sheet by the cutter. Thereby, the temperature of the heating rotator can be appropriately controlled for printing the next sheet. Further, the time from the completion of cutting the sheet until the heater reaches the first temperature can be shortened. Thereby, a decrease in the printing speed can be reduced.

[0026] It is controlled to reach the first temperature after the start of cutting the sheet by the cutter. Thereby, the temperature of the heating rotator can be appropriately controlled for printing the next sheet. Further, the time from the completion of cutting the sheet until the heater reaches the first temperature can be shortened. Thereby, a decrease in the printing speed can be reduced. In the image forming apparatus of the present disclosure, after the control unit cuts the sheet by the cutter, the control unit controls the discharge motor to rotate the discharge roller, discharges the cut sheet, and after discharging the cut sheet, may stop the discharge roller. When the drive of the discharge roller is not necessary, noise by the discharge roller can be suppressed by stopping the discharge roller.

[0027] In the image forming apparatus of the present 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 onto the photosensitive drum to a sheet. The photosensitive drum and the developing roller may rotate by receiving a driving force from the main motor. Since the main motor transmits the driving force to the photosensitive drum and the developing roller, the main motor can drive the photosensitive drum and the developing roller together.

[0028] The image forming apparatus of the present disclosure includes a supply tray on which a sheet is placed, a pickup roller that conveys the sheet from the supply tray to the process unit by receiving a driving force from the main motor, a transmission state in which the driving force is transmitted from the main motor to the pickup roller, and a clutch that can switch between the transmission state and a non - transmission state in which the driving force is not transmitted from the main motor to the pickup roller. When the temperature of the heating rotating body reaches a predetermined temperature that is higher than the standby temperature for waiting for printing on the sheet, the control unit may set the clutch to the transmission state and convey the sheet from the supply tray.

[0029] When the temperature of the heating rotating body reaches a predetermined temperature that is higher than the standby temperature, the control unit sets the state in which the driving force is transmitted from the main motor to the pickup roller and conveys the sheet from the supply tray. Therefore, the image can be sufficiently fixed on the sheet in a state where the amount of heat required for fixing is ensured for the heating rotating body.

Advantages of the Invention

[0030] According to one aspect of the present disclosure, the time from the start to the end of printing in the case of continuous printing can be shortened.

Brief Description of the Drawings

[0031] [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] Figure 1 is a main flowchart showing an example of the print control flow by the CPU of the image forming apparatus. [Figure 4] Figure 3 is a subflowchart showing an example of the printing and cutting process. [Figure 5] This timing chart shows an example of the relationship between the drive timing of each drive unit and the temperature of the fixing unit. [Figure 6] This diagram illustrates the cutting of the sheet as it passes through the nip section. [Figure 7] This is a diagram illustrating the cutting of paper with a cutter. [Figure 8] This is a timing chart showing an example of the relationship between the drive timing of each drive unit and the temperature of the fuser in a modified example 1 of the image forming apparatus according to Embodiment 1. [Modes for carrying out the invention]

[0032] [Embodiment] [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 explanation, the vertical and horizontal directions of the image forming apparatus 1 will be defined below as indicated by the arrows in Figure 1.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] The starting point for conveying sheet P in branch route 200 is the junction point C with convey route 201. Junction point C is located upstream of the first discharge roller 36 and the third discharge roller 40 in the conveying direction of sheet P, and downstream of the fuser 5. The conveying direction of sheet P is either from the supply tray 21 to the discharge tray 22 along convey route 201, or from the supply tray 21 to the discharge tray 22 along convey route 201 and branch route 200. Hereinafter, the conveying direction of sheet P will simply be referred to as the conveying direction.

[0037] Furthermore, the branching path 200 is located below the transport path 201. Near the merging point C, a flapper 8 is provided for distributing the sheet P to either the transport path 201 or the branching path 200. When the flapper 8 is in the first position, it distributes the sheet P to the branching path 200. When the flapper 8 is in the second position, it distributes the sheet P to the transport path 201. The flapper 8 is configured to operate using driving force from a drive motor (not shown).

[0038] 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 an electromagnetic clutch 107, a main motor 108, and a discharge motor 140 (see Figure 2).

[0039] The pickup roller 31 receives driving force from the main motor 108 to pick up the sheets P in the supply tray 21 that have been pushed upward by the sheet pressing plate 21A. The pickup roller 31 then transports the sheets P toward the transport path 201, thereby transporting the sheets P to the image forming unit 4. 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.

[0040] The registration roller 34 is located upstream of the image forming unit 4 in the transport path 201 and is the transport roller closest to the photosensitive drum 61, which will be described later, among the multiple transport rollers that transport the sheet P. These multiple transport rollers include, for example, the pickup roller 31, the separation roller 32, and the paper dust removal roller 33. 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. The roller 35 transports the sheet P, after it has passed through the fuser 5, toward the first discharge roller 36.

[0041] 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.

[0042] In the branching path 200, a third discharge roller 40 is positioned downstream of the merging point C. The first discharge roller 36, the second discharge roller 37, and the third discharge roller 40 discharge the sheet P from inside the device body 2 to outside the device body 2.

[0043] 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.

[0044] The drum cartridge 6 can be removed from the main body 2 of the device 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 conveys the sheet P.

[0045] 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.

[0046] A transfer roller TR is positioned opposite the photosensitive drum 61. The transfer roller TR is an example of a transfer section and forms a transfer nip TN between itself and the photosensitive drum 61 in the transport path 201. Alternatively, a transfer belt may be used as an example of a transfer section instead of the transfer roller TR.

[0047] 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.

[0048] 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.

[0049] 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 other words, the transfer roller TR transfers the toner supplied onto the photosensitive drum 61 to the sheet P. In this way, an image is formed on the sheet P.

[0050] 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.

[0051] 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 portion 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.

[0052] 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.

[0053] 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).

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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 configured, for example, with a fixed blade, a blade 75 (see Figure 2), a cutting motor 106 (see Figure 2), and a cutter carriage 11 (see Figure 7). The cutter 10 may also have a pair of upper and lower blades 75.

[0058] The blade 75 is, for example, a rotatable round blade, which is held in the cutter carriage 11. The fixed blade is fixed to a frame that extends horizontally within the device body 2. The cutter carriage 11 is configured to reciprocate in the width direction of the sheet P along a rail 12 (see Figure 7) that extends horizontally within the device body 2, driven by the cutting motor 106.

[0059] When the sheet P is in position B of the cutter 10, the cutter carriage 11 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.

[0060] [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 register sensor 110, a post-cash register sensor 111, a paper ejection sensor 112, a temperature and humidity sensor 113, and a communication interface (I / F) 130.

[0061] 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.

[0062] 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 to the sheet P. The printing temperature is an example of a first temperature.

[0063] Furthermore, ROM 102 stores information about the standby temperatures 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. In addition, ROM 102 stores information about the paper-feedable temperature of the heating roller 51 and pressure roller 52 when transporting the sheet P from the supply tray 21. Moreover, ROM 102 stores information such as high temperatures. The high temperature is an example of a third temperature.

[0064] 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.

[0065] 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 11, thereby moving the blade 75 in the width direction of the sheet P and cutting the sheet P.

[0066] 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 from the main motor 108 to the pressure roller 52, the photosensitive drum 61, the developing roller 64, the pickup roller 31, and the registration roller 34.

[0067] The pressure roller 52, photosensitive drum 61, developing roller 64, pickup roller 31, and registration roller 34 rotate in a direction that transports the sheet P in the transport direction. Since the main motor 108 transmits driving force to the photosensitive drum 61 and developing roller 64, the main motor 108 can drive the photosensitive drum 61 and developing roller 64 together.

[0068] 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. The CPU 101 may also control the main motor 108 to rotate at least one of the heating roller 51 and the pressure roller 52 to transport the sheet P.

[0069] The electromagnetic clutch 107 is an example of a clutch and is controlled by the CPU 101. The electromagnetic clutch 107 can switch between a transmission state in which driving force is transmitted from the main motor 108 to the pickup roller 31 and a non-transmission state in which driving force is not transmitted from the main motor 108 to the pickup roller 31.

[0070] Specifically, the CPU 101 turns on the electromagnetic clutch 107, thereby enabling the driving force of the main motor 108 to be transmitted to the pickup roller 31. Conversely, the CPU 101 also turns off the electromagnetic clutch 107, thereby enabling the driving force of the main motor 108 to be transmitted to the pickup roller 31, thus enabling a non-transmission state. When the image forming apparatus 1 is started up, the CPU 101 sets the electromagnetic clutch 107 to the off state.

[0071] 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. The first discharge roller 36, the second discharge roller 37, and the third discharge roller 40 then rotate in a direction that conveys the sheet P in the conveying direction.

[0072] 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.

[0073] The post-register sensor 111 is an example of a first sheet sensor, positioned upstream of the fuser 5 in the transport path 201, specifically between the photosensitive drum 61 and the registration roller 34 in the transport direction, and capable of detecting the passage of the sheet P. 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.

[0074] 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 the roller 35 of the fuser 5, that is, downstream of the nip section N, and is a sensor capable of detecting the passage of the sheet P. The paper discharge sensor 112 has the same configuration as the pre-cash register sensor 110.

[0075] The detection signal from the paper ejection sensor 112 is output to the CPU 101. The paper ejection sensor 112 outputs an OFF signal before the sheet P passes through the sensor 112, and outputs an ON signal while the sheet P, having passed through the nip section N, is passing through the paper ejection sensor 112. In other words, the paper ejection sensor 112 turns ON when the leading edge of the sheet P in the transport direction enters the paper ejection sensor 112, and then turns OFF when the trailing edge PL (see Figure 8) of the sheet P passes through the paper ejection sensor 112.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] [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 7. 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, the first sheet P1 and the second sheet P2 (see Figure 6).

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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 S17. On the other hand, if sheet P does not need to be cut (S14: NO), the CPU 101 proceeds to S15.

[0084] In S15, the CPU 101 moves the flapper 8 to the first position and proceeds to S16. As the flapper 8 moves to the first position, the sheet P is distributed to the branching path 200. If the flapper 8 is already in the first position at the start of S15, the CPU 101 maintains the flapper 8 in the first position and proceeds to S16. In S16, the CPU 101 performs a printing process that does not involve cutting the sheet P. A detailed explanation of the printing process that does not involve cutting the sheet P is omitted, but the leading edge of the sheet, on which the toner image has been formed and fixed, is guided by the flapper 8 to the branching path 200 having the third discharge roller 40. The sheet guided to the branching path 200 is discharged onto the discharge tray 22 by the rotation of the third discharge roller 40.

[0085] 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 L in the transport direction from the tip, and stores it in the RAM 103.

[0086] The length L is calculated, for example, based on the amount of sheet P transported by an 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 PL of sheet P.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] [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. Figure 5 is a timing chart showing an example of the relationship between the drive timing of each drive unit and the temperature of the fuser 5. Figure 6 is a diagram illustrating the cutting of the sheet P as it passes through the nip section N. Figure 7 is a diagram illustrating the cutting of the paper P by the cutter 10. Note that Figure 5 illustrates the case where the drive duration of the main motor 108 is longer than the threshold time described later.

[0092] 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 along 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.

[0093] 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 transmission state so that the driving force of the main motor 108 is transmitted to the pickup roller 31. Then, the process proceeds to S113.

[0094] In S113, if the discharge motor 140 is running, the CPU 101 stops the discharge motor 140 after a predetermined time has elapsed 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.

[0095] 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.

[0096] 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 the process of 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 determines that sheet P has passed and proceeds to the process of S115.

[0097] In S115, 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.

[0098] Next, in S116, 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. For example, as shown in Figure 5, the CPU 101 determines at time T3 that the detection signal input from the paper ejection sensor 112 has changed from "off" to "on".

[0099] Then, if the detection signal input from the paper output sensor 112 has not changed from "off" to "on" (S116: NO), the CPU 101 executes process S116 again. On the other hand, if the detection signal input from the paper output sensor 112 has changed from "off" to "on" (S116: YES), the CPU 101 proceeds to process S117.

[0100] In S117, the CPU 101 determines whether the continuous operation time of the main motor 108, based on the number of consecutive printed sheets of a print job, is equal to or greater than a threshold time. The number of consecutive printed sheets is counted based on, for example, the number of sheets P that have passed the sensor position, such as the register sensor 110. The number of consecutive printed sheets may be the number of sheets specified for a single print job, or the total number of sheets printed when sheets P are printed continuously across multiple print jobs. Furthermore, the number of consecutive printed sheets may be the number of sheets printed even if printing is interrupted between print jobs, as long as the interval between print jobs is within a predetermined time. The continuous operation time of the main motor 108 based on the number of consecutive printed sheets is associated with the following table 1.

[0101] [Table 1] If the number of consecutive printed pages is 60 or more, the operating time of the main motor 108 is 30 seconds. If the number of consecutive printed pages is between 30 and 59, the operating time of the main motor 108 is 20 seconds. If the number of consecutive printed pages is between 10 and 29, the operating time of the main motor 108 is 15 seconds. If the number of consecutive printed pages is less than 10, the operating time of the main motor 108 is 3 seconds.

[0102] As a result, when the CPU 101 performs continuous printing in which multiple sheets P are printed in succession, it sets the drive duration of the main motor 108 according to the number of sheets P to be printed. Furthermore, it is preferable that the drive duration when the heating roller 51 and pressure roller 52 have a layer made of rubber is longer than the drive duration when the heating roller 51 and pressure roller 52 do not have such a layer and their surfaces are coated.

[0103] The threshold time is, for example, 20 seconds. If the CPU 101 determines that the continuous operation time of the main motor 108, based on the number of consecutive print jobs, is equal to or greater than the threshold time (S117: YES), it proceeds to the process in S119, which will be described later.

[0104] On the other hand, if the CPU 101 determines that the continuous operation time of the main motor 108, based on the number of consecutive print jobs, is less than the threshold time (S117: NO), it proceeds to process S118. In S118, the CPU 101 decides to execute a process to stop the main motor 108 after the continuous operation time has elapsed, and proceeds to process S119. In other words, in S118, the CPU 101 sets the actual continuous operation time of the main motor 108 to the time set in S16 or S17.

[0105] Based on the processing in S117, the CPU 101 determines whether or not to execute the processing in S118, and therefore sets the drive duration of the main motor 108 based on the time when the paper ejection sensor 112 detected the sheet P in S116.

[0106] The paper discharge sensor 112 is positioned downstream of the nip section N in the transport direction. Therefore, the paper discharge sensor 112 detects the sheet P after it has reached the nip section N. As a result, the CPU 101 sets the drive duration of the main motor 108 based on the time the paper discharge sensor 112 detects the sheet P, so that the drive of the main motor 108 can be stopped at the appropriate timing, thereby stopping the heating roller 51.

[0107] In S119, 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 as the sheet P passes the trailing edge.

[0108] Then, if the detection signal input from the paper output sensor 112 has not changed from "on" to "off" (S119: NO), the CPU 101 executes the process in S119 again. On the other hand, if the detection signal input from the paper output sensor 112 has changed from "on" to "off" (S119: 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 in S120.

[0109] 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.

[0110] 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. The standby temperature is lower than the printing temperature. For example, as shown in Figure 5, the CPU 101 stops driving the heater 53 at time T5. At time T5, the sheet P has completed passing between the heating roller 51 and the pressure roller 52, that is, through the nip section N.

[0111] In the process of S120, the CPU 101 controls the heater 53 so that the temperature of the heating roller 51 is lower than the printing temperature, based on the time when the paper ejection sensor 112 detects that the sheet P has finished passing. After the sheet P has passed the paper ejection sensor 112, the heater 53 is controlled so that the temperature of the heating roller 51 is lower than the printing temperature. Therefore, the temperature of the heating roller 51 can be lowered before the cutter 10 starts cutting the sheet P. This suppresses localized heating of the heating roller 51 and the pressure roller 52.

[0112] In S121, 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 S122. As a result, the first discharge roller 36 and the second discharge roller 37 rotate in a direction that conveys the sheet P in the conveying direction. In S121, the CPU 101 starts driving the discharge motor 140 based on the time when the post-register sensor 111 detects the sheet P. For example, as shown in Figure 5, at time T6, the CPU 101 rotates the discharge motor 140 to start the paper discharge drive.

[0113] Therefore, as in the processing of S114 and S121, the CPU 101 controls the discharge motor 140 based on the time when the post-registration sensor 111 detects the sheet P. The post-registration sensor 111 is located between the photosensitive drum 61 and the registration roller 34. The registration roller 34 is the transport roller that is closest to the first discharge roller 36 and the second discharge roller 37 in the transport direction among the multiple transport rollers located on the upstream side of the image forming unit 4. Therefore, the post-registration sensor 111 is located as close as possible to the first discharge roller 36 and the second discharge roller 37 on the upstream side of the image forming unit 4.

[0114] Furthermore, after the post-cash sensor 111 detects the sheet P, the sheet P reaches the first discharge roller 36. Therefore, the CPU 101 controls the discharge motor 140 based on the time the post-cash sensor 111 detects the sheet P, so that the discharge motor 140 can be started to drive at the appropriate timing, thereby starting the rotational drive of the first discharge roller 36 and the second discharge roller 37.

[0115] In S122, the CPU 101 starts measuring the elapsed time from the moment the forward rotation of the discharge motor 140 begins. Subsequently, the CPU 101 determines whether the elapsed time from the moment the forward rotation of the discharge motor 140 begins 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 forward rotation of the discharge motor 140 begins until the cutting position A of the sheet P (see Figure 6) reaches the position B of the cutter 10 (see Figure 1). The predetermined stop time is stored in the ROM 102 in advance. For example, the predetermined stop time is the elapsed time from time T6 to time T7, as shown in Figure 5.

[0116] Then, if the CPU 101 determines that the elapsed time since the start of forward rotation of the discharge motor 140 has not reached a predetermined stop time (S122: NO), it executes the process of S122 again. On the other hand, if the CPU 101 determines that the elapsed time since the start of forward rotation of the discharge motor 140 has reached a predetermined stop time (S122: YES), it proceeds to the process of S123.

[0117] In S123, the CPU 101 stops the discharge motor 140 and then proceeds to the process in S124. For example, as shown in Figure 5, at time T7, the CPU 101 stops the discharge motor 140 and stops the paper discharge drive. As a result, the first discharge roller 36 and the second discharge roller 37 stop with the sheet P gripped, so the sheet P stops with the cutting position A located at the cutter 10's position B. In other words, the CPU 101 stops the first discharge roller 36 and the second discharge roller 37 when the cutting position A on the sheet P reaches the cutter 10's position B.

[0118] As a result of the processing in S122 and S123, the CPU 101 stops the discharge motor 140 and stops the sheet P after a predetermined time has elapsed since the start of driving the discharge motor 140. This allows the CPU 101 to appropriately control the first discharge roller 36 and the second discharge roller 37 so that the cutting position A on the sheet P reaches the position B of the cutter 10.

[0119] In S124, the CPU 101 drives the cutting motor 106 to move the blade 75 held in the cutter carriage 11 back and forth in the width direction of the sheet P. After starting to drive the cutting motor 106, the CPU 101 proceeds to the process in S125. For example, as shown in Figure 5, the CPU 101 starts driving the cutter by starting to drive the cutting motor 106 at time T7, and stops the cutting motor 106 at time T9. As a result, the sheet P is cut in half into a first sheet P1 and a second sheet P2.

[0120] In S125, the CPU 101 determines whether the currently running print job contains image data to be printed for the next sheet P. The next sheet P is the sheet P that is picked up from the supply tray 21 by the pickup roller 31 after the sheet P discharged by the first discharge roller 36 and the second discharge roller 37. If the CPU 101 determines that the currently running print job contains image data to be printed for the next sheet P (S125: YES), the process proceeds to S126.

[0121] In S126, 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, starts controlling the voltage applied to the heater 53, and then proceeds to the process in S127. For example, as shown in Figure 5, at time T8, 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.

[0122] The CPU 101 performs the S126 process before the cutter completes cutting the sheet. Now, with reference to Figure 7, the cutting of the sheet by the cutter will be explained. Figure 7 shows the cutter 10 in standby position SP when it is in standby mode and has not yet cut any paper. When the CPU 101 drives the cutting motor 106 in the forward direction, the cutter carriage 11 moves in the forward direction D1, and the sheet P is cut. After that, the CPU 101 drives the cutting motor 106 in the reverse direction, opposite to the forward direction, to move the cutter carriage 11 in the return direction D2 and position the cutter carriage 11 at standby position SP. After that, the CPU 101 stops the cutting motor 106 and completes cutting the sheet P.

[0123] Alternatively, the CPU 101 may be configured to move the cutter carriage 11 in the forward direction D1 to cut the sheet P, then stop the cutting motor 106, and then move the cutter carriage 11 in the return direction D2 to cut the sheet P that is subsequently transported, then stop the cutting motor 106 to complete the cutting process.

[0124] Here, an example of the fixing temperature of the nip portion N of the heating roller 51 and the pressure roller 52 will be explained based on Figure 5. Note that Graph 71 shows the change in the fixing temperature of the nip portion N of the heating roller 51 and the pressure roller 52. If the CPU 101 sets the temperature of the heater 53 to the standby temperature at time T5 and stops driving the heater 53, the fixing temperature of the nip portion N will start to decrease from time T5, as shown in Graph 71.

[0125] During the period from time T6 to time T8, the CPU 101 drives the main motor 108 to rotate the heating roller 51 or the pressure roller 52. As a result, the fixing temperature of the nip portion N from time T6 to time T8 is lower than the fixing temperature of the nip portion N at time T5.

[0126] Before the cutter 10 completes cutting of the sheet P, the CPU 101 drives the main motor 108 and controls the heater 53, which was previously controlled to keep the temperature of the heating roller 51 at a standby temperature, to keep the temperature of the heating roller 51 at the printing temperature. As a result, the temperature of the nip section N can be made uniform during the cutting of the sheet P, and the start of transporting the next sheet can be accelerated. This reduces the decrease in printing speed during continuous printing.

[0127] Furthermore, in a configuration where the CPU 101 executes S126 after S124, the heater 53, which was controlled to be at a standby temperature before the discharge motor 140 is driven, is controlled to be at the printing temperature after the cutter 10 starts cutting the sheet P. This allows the temperature of the heating roller 51 to be appropriately controlled for printing on the next sheet P. In addition, the time from the completion of cutting the sheet P until the heater 53 reaches the printing temperature can be shortened. This reduces the decrease in printing speed.

[0128] In S127, if the main motor 108 is stopped, the CPU 101 restarts the main motor 108 to rotate the heating roller 51 and the pressure roller 52, etc., and then proceeds to the process in S128. If the main motor 108 is not stopped, the CPU 101 proceeds to the process in S128 after S126 without executing S127.

[0129] In S128, 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 the second sheet P2, and then proceeds to the process in S129. For example, as shown in Figure 5, at time T9, the paper discharge drive that rotates the first discharge roller 36 and the second discharge roller 37 is restarted.

[0130] In S129, the CPU 101 determines, via the temperature sensor 54, whether the temperatures of the heating roller 51 and the pressure roller 52 have reached the paper-feeding temperature. The paper-feeding temperature is higher than the standby temperature. If the CPU 101 determines that the temperature of the heating roller 51 has not reached the paper-feeding temperature (S129: NO), it executes the process in S129 again.

[0131] 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 (S129: YES), it executes the process in S112 again. In the process in S113, which is executed again, the CPU 101 stops the discharge motor 140, which was driven in the process in S128, after a predetermined time has elapsed. For example, as shown in Figure 5, at time T10, which is after the predetermined time has elapsed, the discharge motor 140 is stopped and the paper discharge drive is stopped. Thereafter, for example, at times T11 to T15, the CPU 101 executes the same process as the process executed at times T3 to T7.

[0132] Here, if the CPU 101 determines in S117 that the continuous operation time of the main motor 108 is equal to or greater than the threshold time, it continues to operate the main motor 108 and cuts the sheet P with the cutter 10 in S124. After cutting the sheet P with the main motor 108 still running, the CPU 101 controls the discharge motor 140 in S128 to rotate the first discharge roller 36 and the second discharge roller 37 to discharge the cut sheet P.

[0133] Next, consider the case where the CPU 101 determines in S125 that there is image data to be printed for the next sheet P in the print job currently in progress, and where in S129 it determines that the temperature of the heating roller 51 and the pressure roller 52 is at the paper feeding temperature. In this case, the CPU 101 continues to drive the main motor 108 and starts supplying the next sheet P after the sheet P discharged by the first discharge roller 36 and the second discharge roller 37. By doing so, the CPU 101 can suppress localized temperature increases of the heating roller 51 and the pressure roller 52 by continuing to drive the main motor 108 toward printing the next sheet P.

[0134] Then, if the CPU 101 determines that there is no image data to print for the next sheet P in the currently running print job (S125: NO), it proceeds to process S130. In S130, 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 the second sheet P2, and then proceeds to process S131. For example, as shown in Figure 5, at time T16, the paper discharge drive that rotates the first discharge roller 36 and the second discharge roller 37 is restarted.

[0135] In S131, the CPU 101 stops the operation of the ejection motor 140 and then proceeds to the process in S132. For example, as shown in Figure 5, the CPU 101 stops the ejection motor 140 at time T17 and stops the paper ejection drive.

[0136] In the processes of S124, S128, S130, and S131, the CPU 101 cuts the sheet P with the cutter 10, then controls the discharge motor 140 to rotate the first discharge roller 36 and the second discharge roller 37 to discharge the cut sheet P. After discharging the cut sheet P, the CPU 101 stops the first discharge roller 36 and the second discharge roller 37. This allows the CPU 101 to suppress noise from the first discharge roller 36 and the second discharge roller 37 by stopping them when they are not needed.

[0137] In S132, if the main motor 108 is running, the CPU 101 stops the main motor 108 after a predetermined time has elapsed, for example, after about 2 to 3 seconds. For example, as shown in Figure 5, at time T18, the CPU 101 stops the main motor 108, thereby stopping the heating roller 51 and pressure roller 52 of the fuser 5, and stopping the fuser drive. After S128, the CPU 101 terminates the flow shown in Figure 4, and the main flowchart also terminates. Note that the timing of "after the predetermined time has elapsed" is also the timing of "after the continuous drive time has elapsed".

[0138] [Example 1] Figure 8 is a timing chart showing an example of the relationship between the drive timing of each drive unit and the temperature of the fuser 5 in a modified example 1 of the image forming apparatus 1 according to Embodiment 1. Figure 8 illustrates a case where the driving duration of the main motor 108 is shorter than the threshold time described later.

[0139] As shown in Figure 8, the CPU 101 may stop the main motor 108 after the paper ejection sensor 112 detects the completion of sheet P's passage at time T4, but before raising the temperature of the heating roller 51 to the printing temperature at time T8. In other words, the CPU 101 may stop the main motor 108 between time T4 and time T8.

[0140] Specifically, in S117 of Figure 4, if the CPU 101 determines that the continuous operation time of the main motor 108, based on the number of consecutive print jobs, is less than the threshold time (S117: NO), it proceeds to process S118. In S118, the CPU 101 decides to execute a process to stop the main motor 108 after the continuous operation time has elapsed. In accordance with the decision in S118, the CPU 101 stops the main motor 108 in S126 before raising the temperature of the heating roller 51 to the printing temperature. For example, as shown in Figure 8, the CPU 101 stops the main motor 108 at time T21 between time T4 and time T8.

[0141] In S127 shown in Figure 4, the CPU 101 restarts the main motor 108, which was stopped, to rotate the heating roller 51 and the pressure roller 52, and then proceeds to the process in S128. For example, as shown in Figure 8, the CPU 101 drives the main motor 108 at time T22.

[0142] As described above, the CPU 101 stops driving the main motor 108 between time T4 and time T8. This stops the main motor 108 from time T4 to time T8, that is, during the period from when the heater 53 is stopped until the heater 53 is restarted. For example, if the number of printed pages is small, the temperature of the nip section N can be kept lower than the fixing temperature at time T5 even if the driving duration is shortened.

[0143] [Differentiation 2] The CPU 101 may perform the process shown in Figure 4, S121, between the processes of S116 and S117. In other words, if the detection signal input from the paper output sensor 112 changes from "off" to "on" (S116: YES), the CPU 101 may start forward rotation of the paper output motor 140 and proceed to the process of S117. In this way, the CPU 101 controls the paper output motor 140 based on the moment when the paper output sensor 112 detects the sheet P.

[0144] In the processing of S121 and S122, the CPU 101 stops the discharge motor 140 and stops the sheet P after a predetermined time has elapsed since the start of driving the discharge motor 140. Alternatively, the CPU 101 may stop the discharge motor 140 based on a detection signal input from the post-register sensor 111 or the paper output sensor 112.

[0145] The paper discharge sensor 112 is positioned downstream of the nip section N in the transport direction, and is therefore closer to the first discharge roller 36 and the second discharge roller 37 than to the fuser 5. Also, the sheet P reaches the first discharge roller 36 after the paper discharge sensor 112 detects the sheet. Therefore, the CPU 101 controls the discharge motor 140 based on the time the paper discharge sensor 112 detects the sheet P, so it can start driving the discharge motor 140 at the appropriate timing and start rotating the first discharge roller 36 and the second discharge roller 37.

[0146] [Difference 3] The CPU 101 may perform the process in S117 shown in Figure 4 between the processes in S114 and S115. In other words, after the image forming unit 4 starts forming an image on the sheet P in S114, the CPU 101 may determine whether the continuous driving time of the main motor 108, based on the number of consecutive print jobs, is equal to or greater than a threshold time. In this case, if the CPU 101 determines YES in S117, it proceeds to the process in S115, and if the CPU 101 determines NO in S117, it performs the process in S118 before proceeding to the process in S115.

[0147] Therefore, in order to determine whether or not to execute the process in S118 after the process in S114, the CPU 101 sets the drive duration of the main motor 108 based on the time when the post-register sensor 111 detects the seat P in S113.

[0148] The post-registration sensor 111 is positioned between the photosensitive drum 61 and the registration roller 34. The registration roller 34 is the transport roller closest to the nip section N in the transport direction among a plurality of transport rollers located upstream of the image forming unit 4. Therefore, the post-registration sensor 111 is positioned as close as possible to the nip section N on the upstream side of the image forming unit 4.

[0149] Furthermore, after the post-register sensor 111 detects the sheet P, the sheet P reaches the nip section N. Therefore, the CPU 101 sets the driving duration of the main motor 108 based on the time the post-register sensor 111 detects the sheet P, so that the driving of the main motor 108 can be stopped at the appropriate timing, thereby stopping the heating roller 51.

[0150] [Differentiation Example 4] The CPU 101 may, instead of performing the S119 process shown in Figure 4, execute a process to determine whether the detection signal input from the post-cash register sensor 111 has changed from "on" to "off". If the detection signal input from the post-cash register sensor 111 has not changed from "on" to "off", the CPU 101 may execute the process again. On the other hand, if the detection signal input from the post-cash register sensor 111 has changed from "on" to "off", the CPU 101 may determine that the post-cash register sensor 111 has detected the completion of passing through sheet P and proceed to the S120 process.

[0151] Thus, the CPU 101 may control the heater 53 in S120 so that the temperature of the heating roller 51 reaches the standby temperature, based on the time when the post-register sensor 111 detects that the sheet P has finished passing.

[0152] By controlling the heater 53 based on the detection result of the post-register sensor 111, the heater 53 is controlled so that after passing the post-register sensor 111, the temperature of the heating roller 51 becomes a standby temperature lower than the printing temperature. Therefore, the temperature of the heating roller 51 can be lowered before the cutter 10 starts cutting the sheet P. This suppresses localized heating of the nip portion N.

[0153] [Difference 5] In S20 shown in Figure 4, the CPU 101 may perform a process to determine, via the temperature sensor 54, whether the temperature of the heating roller 51 and the pressure roller 52 has reached the printing temperature. 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 printing temperature, it may perform the above process again. 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 printing temperature, it may proceed to the process in S21.

[0154] Therefore, if the temperature of the heating roller 51 reaches a predetermined temperature that is higher than the standby temperature for waiting to print on the sheet P, the CPU 101 may use the electromagnetic clutch 107 to enter the above transmission state in S112 and transport the sheet P from the supply tray 21. The predetermined temperature is the printing temperature or the paper feed permission temperature.

[0155] When the temperature of the heating roller 51 reaches a predetermined temperature higher than the standby temperature, the CPU 101 transmits driving force from the main motor 108 to the pickup roller 31 and transports the sheet P from the supply tray 21. Therefore, the image can be sufficiently fixed to the sheet P while ensuring that the heating roller 51 has enough heat to fix the image.

[0156] [Modification 6] 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.

[0157] [Difference 7] 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.

[0158] [Differentiation 8] 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.

[0159] 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]

[0160] 1 Image forming apparatus 4 Image forming section 5 fuser unit 10 cutter 21 Supply tray 31 Pickup roller 34 Registration roller 36 First discharge roller 37 Second discharge roller 51 Heating roller 52 Pressure roller 53 Heater 61 Photosensitive drum 64 Developing roller 65 Charger 101 CPU 107 Electromagnetic clutch 108 Main motor 111 Post-cash sensor 112 Paper output sensor 140 Discharge motor A Cutting position B Cutter placement position N Nip section P Sheet 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, A discharge motor that transmits driving force to the discharge roller, 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. The discharge motor is controlled to rotate the discharge roller and transport the sheet that has passed through the nip section, and the discharge roller is stopped when the cutting position on the sheet reaches the cutter position. After the heating rotating body starts rotating and before the discharge roller stops, the heater is controlled so that the target temperature of the heating rotating body becomes a second temperature, which is lower than the first temperature. After stopping the discharge roller, the cutter starts cutting the sheet. An image forming apparatus characterized in that, when performing continuous printing in which multiple sheets are printed in succession, the main motor is driven to rotate the heating rotating body or the pressurizing rotating body before the cutting of the sheets by the cutter is completed, and the heater is controlled so that the temperature of the heating rotating body reaches the first temperature.

2. The process unit has a photosensitive drum, In the aforementioned transport direction, the registration roller is positioned upstream of the photosensitive drum and is one of a plurality of transport rollers that transport the sheet, and is the transport roller closest to the photosensitive drum. The system includes a first sheet sensor positioned between the photosensitive drum and the registration roller in the aforementioned transport direction, which is capable of detecting the passage of a sheet. The image forming apparatus according to claim 1, characterized in that the control unit controls the discharge motor based on the time when the first sheet sensor detects a sheet.

3. 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 discharge motor based on the time when the second sheet sensor detects a sheet.

4. The image forming apparatus according to claim 1, characterized in that the control unit stops the discharge motor and stops the sheet after a predetermined time has elapsed since the start of driving the discharge motor.

5. 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 so that the target value of the temperature of the heating rotating body becomes the second temperature, based on the time when the second sheet sensor detects the completion of sheet passage.

6. The process unit has a photosensitive drum, In the aforementioned transport direction, the registration roller is positioned upstream of the photosensitive drum and is one of a plurality of transport rollers that transport the sheet, and is the transport roller closest to the photosensitive drum. The system includes a first sheet sensor positioned between the photosensitive drum and the registration roller in the aforementioned transport direction, which is capable of detecting the passage of a sheet. The control unit, The image forming apparatus according to claim 1, characterized in that the heater controls the heating rotating body so that the target temperature of the heating rotating body becomes the second temperature, based on the time when the first sheet sensor detects the completion of the sheet's passage.

7. The control unit, When performing the aforementioned continuous printing, the operating time of the main motor is set according to the number of sheets to be printed. The image forming apparatus according to claim 1, characterized in that, if the driving duration is equal to or greater than a threshold time, the main motor is kept running, the cutter cuts the sheet, the discharge motor is controlled to rotate the discharge roller to discharge the cut sheet, and the supply of the next sheet after the sheet discharged by the discharge roller is started.

8. 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 sets the driving duration based on the time when the second sheet sensor detects a sheet.

9. The process unit has a photosensitive drum, In the aforementioned transport direction, the registration roller is positioned upstream of the photosensitive drum and is one of a plurality of transport rollers that transport the sheet, and is the transport roller closest to the photosensitive drum. The system includes a first sheet sensor positioned between the photosensitive drum and the registration roller in the aforementioned transport direction, which is capable of detecting the passage of a sheet. The image forming apparatus according to claim 7, characterized in that the control unit sets the driving duration based on the time when the first sheet sensor detects a sheet.

10. The image forming apparatus according to claim 1, characterized in that, when the control unit performs continuous printing, it controls the heater so that the temperature of the heating rotating body reaches a first temperature after the cutting of the sheet by the cutter begins.

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. The image forming apparatus according to claim 1, characterized in that the discharge roller is stopped after the sheet has been discharged after cutting.

12. The process unit comprises 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 image forming apparatus according to claim 1, characterized in that the photosensitive drum and the developing roller rotate when a driving force is transmitted from the main motor.

13. A supply tray on which the sheet is placed, A pickup roller that transports a sheet from the supply tray to the process section by transmitting driving force from the main motor, The system includes 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. The image forming apparatus according to claim 1, characterized in that when the temperature of the heating rotating body reaches a predetermined temperature which is higher than the standby temperature for waiting to print on the sheet, the control unit uses the clutch to enter the transmission state and transports the sheet from the supply tray.

Images