Image forming apparatus

Abstract

Provided is an image forming apparatus capable of suppressing a decrease in durability of a fixing section when a sheet is cut by a cutter. The control unit (101) rotates the heating rotating body (51) or the pressing rotating body (52) to convey the sheet, rotates the discharge rollers (36, 37) to convey the sheet that has passed through the nip portion (N), stops the discharge rollers when the cutting position in the sheet reaches the disposition position (B) of the cutter, and, after stopping the discharge rollers, rotates the heating rotating body or the pressing rotating body to convey the sheet. The cutting of the sheet by the cutter (10) is started.

Description

Technical Field

[0001] The present invention 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 transport direction. In addition, the leading end of the paper discharged from the fixing unit is detected by a discharge switch, and after a predetermined time has elapsed, the discharge roller for discharging the paper stops. When the discharge roller stops, the boundary line between the first image and the second image on the paper is in a state located at the cutting position of the cutter, and the cutter is driven to cut the paper along this boundary line.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2002-362823 Summary of the Invention

[0006] Technical Problem to be Solved by the Invention

[0007] In the image forming apparatus disclosed in Patent Document 1, when the paper is cut by the cutter, the discharge roller stops, so that the cut portion of the paper is in a state located at the cutting position of the cutter. As the discharge roller stops, when the pair of rollers in the fixing unit also stop, heat is applied to the nip portion between the pair of rollers, and the pair of rollers are locally heated. As a result, the durability of the fixing unit may be reduced. An object of the present invention is to suppress a decrease in the durability of the fixing unit.

[0008] Technical Means for Solving the Technical Problem

[0009] In order to solve the above technical problems, an image forming apparatus according to the present invention includes: a processing unit that forms an image on a sheet; a fixing unit that has a heating rotating body, a heater, and a pressure applying rotating body, the heater heats the heating rotating body, a nip portion is formed between the pressure applying rotating body and the heating rotating body, and the fixing unit fixes the image on the sheet; a discharge roller that is disposed downstream of the fixing unit in the sheet conveying direction and is used to discharge the sheet; a main motor that transmits driving force to at least the heating rotating body or the pressure applying rotating body; a cutter that is disposed downstream of the fixing unit in the conveying direction and cuts the sheet; and a control unit that controls the heater so that the temperature of the fixing unit becomes a first temperature at which the image is fixed on the sheet, the control unit controls the main motor to rotate the heating rotating body or the pressure applying rotating body to convey the sheet, the control unit stops the discharge roller when the cutting position in the sheet reaches the position where the cutter is disposed, and then controls the cutter to cut the sheet, and at the time point when the cutting of the sheet by the cutter starts, the control unit sets the target value of the temperature of the fixing unit to a second temperature lower than the first temperature and controls the heater, or the control unit drives the main motor and controls the main motor to rotate the heating rotating body or the pressure applying rotating body.

[0010] The control unit performs the following control: at the time point when the cutting of the sheet by the cutter starts, in a state where the main motor is driven to rotate the heating rotating body or the pressure applying rotating body, or the target value of the temperature of the fixing unit is set to a second temperature lower than the first temperature. Thereby, local temperature rise of the heating rotating body and the pressure applying rotating body can be suppressed. Therefore, a decrease in the durability of the fixing unit can be suppressed.

[0011] In the image forming apparatus according to the present invention, it may also be that a discharge motor is further included, the discharge motor transmits driving force to the discharge roller, the control unit controls the discharge motor to rotate the discharge roller to convey the sheet that has passed through the nip portion, stops the discharge roller when the cutting position in the sheet reaches the position where the cutter is disposed, and after the control unit stops the discharge roller, starts the cutting of the sheet by the cutter in a state where the main motor is driven to rotate the heating rotating body or the pressure applying rotating body. Thereby, even after the sheet passes through the nip portion and the discharge roller stops, the heating rotating body and the pressure applying rotating body are in a rotating state, so that local temperature rise of the heating rotating body and the pressure applying rotating body can be suppressed. Therefore, a decrease in the durability of the fixing unit can be suppressed.

[0012] In the image forming apparatus of the present invention, it is also possible that the processing unit has a photosensitive drum, and the image forming apparatus includes: a registration roller that is disposed upstream of the photosensitive drum in the conveying direction and is the conveying roller closest to the photosensitive drum among a plurality of conveying rollers for conveying a sheet; a first sheet sensor that is disposed between the photosensitive drum and the registration roller in the conveying direction and is capable of detecting the passage of the sheet, and the control unit controls the discharge motor based on the time point when the first sheet sensor detects the sheet.

[0013] The first sheet sensor is disposed between the photosensitive drum and the registration roller. In addition, the registration roller is the conveying roller closest to the discharge roller in the conveying direction among a plurality of conveying rollers disposed upstream of the photosensitive drum. Therefore, the first sheet sensor is disposed at a position as close as possible to the discharge roller on the upstream side of the photosensitive drum.

[0014] 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 time point when the first sheet sensor detects the sheet, and thus can start the driving of the discharge motor at an appropriate moment and start the rotational driving of the discharge roller.

[0015] In the image forming apparatus of the present invention, it is also possible that the fixing unit has a second sheet sensor that is disposed downstream of the nip portion in the conveying direction and is capable of detecting the passage of the sheet, and the control unit controls the discharge motor based on the time point when the second sheet sensor detects the sheet.

[0016] Since the second sheet sensor is disposed downstream of the nip portion in the conveying direction, it is disposed at a position closer to the discharge roller than the fixing unit. In addition, after the second sheet sensor detects the sheet, the sheet reaches the discharge roller. Therefore, the control unit controls the discharge motor based on the time point when the second sheet sensor detects the sheet, and thus can start the driving of the discharge motor at an appropriate moment and start the rotational driving of the discharge roller.

[0017] In the image forming apparatus of the present invention, it is also possible that when a predetermined time has elapsed since the start of the driving of the discharge motor, the control unit stops the discharge motor to stop the sheet. The control unit can appropriately control the discharge roller so that the cutting position in the sheet reaches the position where the cutter is disposed.

[0018] In the image forming apparatus of the present invention, in the case of performing continuous printing in which a plurality of sheets are continuously printed, the control unit may set the driving duration of the main motor according to the number of printed sheets. When the driving duration is equal to or longer than a threshold time, after the sheet is cut by the cutter while the main motor is continuously driven, the control unit controls the discharge motor to rotate the discharge roller, discharges the cut sheet, and starts supplying the next sheet to be discharged through the discharge roller.

[0019] The control unit continuously drives the main motor in order to cope with the printing of the next sheet, thereby being able to suppress local temperature rise of the heating rotating body and the pressure rotating body. In addition, since the control unit continuously drives the main motor, the time from the start of printing of the sheet to the end of printing can be shortened compared with the case where the driving of the main motor is stopped.

[0020] In the image forming apparatus of the present invention, the fixing unit may have a second sheet sensor that is disposed downstream of the nip portion in the conveying direction and can detect the passage of the sheet, and the control unit sets the driving duration based on the time point when the second sheet sensor detects the sheet.

[0021] The second sheet sensor is disposed downstream of the nip portion in the conveying direction. Therefore, after the sheet reaches the nip portion, the second sheet sensor detects the sheet. Therefore, the control unit sets the driving duration based on the time point when the second sheet sensor detects the sheet, and thus can stop the driving of the main motor at an appropriate time to stop the heating rotating body.

[0022] In the image forming apparatus of the present invention, the control unit may control the heater to make the temperature of the fixing unit a second temperature lower than the first temperature based on the time point when the second sheet sensor detects the completion of the passage of the sheet.

[0023] When the second sheet sensor detects the passage of the sheet, since the sheet has passed through the nip portion, it is preferable to lower the temperature of the fixing unit. In this case, since the control unit controls the heater to make the temperature of the fixing unit a second temperature lower than the first temperature, local temperature rise of the heating rotating body and the pressure rotating body can be suppressed.

[0024] In the image forming apparatus of the present invention, it is also possible that the processing unit includes a photosensitive drum, and the image forming apparatus includes: a registration roller that is disposed upstream of the photosensitive drum in the conveying direction and is the conveying roller closest to the photosensitive drum among a plurality of conveying rollers for conveying a sheet; and a first sheet sensor that is disposed between the photosensitive drum and the registration roller in the conveying direction and is capable of detecting the passage of a sheet, and the control unit sets the driving duration based on the time point when the first sheet sensor detects the sheet.

[0025] The first sheet sensor is disposed between the photosensitive drum and the registration roller. In addition, the registration roller is the conveying roller closest to the nip portion in the conveying direction among the plurality of conveying rollers disposed upstream of the photosensitive drum. Therefore, the first sheet sensor is disposed on the upstream side of the photosensitive drum at a position as close as possible to the nip portion.

[0026] Furthermore, after the first sheet sensor detects the sheet, the sheet reaches the nip portion. Therefore, the control unit sets the driving duration based on the time point when the first sheet sensor detects the sheet, and thus can stop the driving of the main motor at an appropriate time to stop the heating rotating body.

[0027] In the image forming apparatus of the present invention, it is also possible that the control unit controls the heater based on the time point when the first sheet sensor detects the completion of the passage of the sheet, so that the temperature of the fixing unit becomes a second temperature lower than the first temperature.

[0028] Since the sheet passes through the nip portion after a predetermined time has elapsed after the first sheet sensor detects the passage of the sheet, it is preferable to lower the temperature of the fixing unit based on the time point when the first sheet sensor detects the passage of the sheet. In this case, since the control unit controls the heater so that the temperature of the fixing unit becomes a second temperature lower than the first temperature, local temperature rise of the heating rotating body and the pressure rotating body can be suppressed.

[0029] In the image forming apparatus of the present invention, it is also possible that after the sheet is cut by the cutter, the control unit controls the discharge motor to rotate the discharge roller to discharge the cut sheet, and in the case of performing continuous printing in which a plurality of sheets are continuously printed, after discharging the cut sheet, the control unit controls the heater to reach the first temperature. Since the temperature of the fixing unit is appropriately controlled in order to cope with the printing of the next sheet, the image can be sufficiently fixed on the next sheet.

[0030] In the image forming apparatus of the present invention, it is also possible that, when starting the supply of the next sheet in a state where the main motor is continuously driven, the control unit controls the heater so that the temperature of the fixing unit becomes a third temperature higher than the first temperature. Since the heat required for fixing can be ensured for the heating rotating body when printing on the next sheet, the image can be sufficiently fixed on the next sheet.

[0031] In the image forming apparatus of the present invention, it is also possible that, after the sheet is cut by the cutter, the control unit controls the discharge motor to rotate the discharge roller to discharge the cut sheet, and after discharging the cut sheet, the control unit stops the discharge roller. By stopping the discharge roller when it is not necessary to drive the discharge roller, the noise generated by the discharge roller can be suppressed.

[0032] In the image forming apparatus of the present invention, it is also possible that the processing unit includes a photosensitive drum, a developing roller, and a transfer unit. The developing roller supplies toner to the photosensitive drum, and the transfer unit transfers the toner supplied to the photosensitive drum to the sheet. The photosensitive drum and the developing roller rotate by receiving driving force transmitted from the main motor. Since the main motor transmits driving force to the photosensitive drum and the developing roller, the photosensitive drum and the developing roller can be centrally driven by the main motor.

[0033] In the image forming apparatus of the present invention, it is also possible to include: a supply tray on which sheets are placed; a pickup roller that conveys sheets from the supply tray to the processing unit by receiving driving force transmitted from the main motor; and 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. When the temperature of the fixing unit reaches a specified temperature, which is a temperature higher than the standby temperature waiting for printing on the sheet, the control unit sets it to the transmission state through the clutch and conveys the sheet from the supply tray.

[0034] When the temperature of the fixing unit reaches a specified temperature, which is a temperature higher than the standby temperature, the control unit enters a state where driving force is transmitted from the main motor to the pickup roller and conveys the sheet from the supply tray. Therefore, in a state where the heat required for fixing is ensured for the heating rotating body, the image can be sufficiently fixed on the sheet.

[0035] The image forming apparatus of the present invention may also include a discharge motor that transmits a driving force to the discharge roller, and a control unit that controls the discharge motor to rotate the discharge roller to convey a sheet that has passed through the nip portion, and stops the discharge roller when the cutting position in the sheet reaches the position where the cutter is disposed. Before the heating rotating body or the pressing rotating body starts rotating and before the discharge roller stops, the control unit controls the heater so that the target value of the temperature of the fixing unit becomes a second temperature lower than the first temperature. After the discharge roller stops, the cutting of the sheet by the cutter is started. In the case of performing continuous printing in which a plurality of sheets are continuously printed, before the cutting of the sheet by the cutter is completed, the control unit controls the heater so that the temperature of the fixing unit becomes the first temperature.

[0036] According to the above structure, before the cutting of the sheet by the cutter is completed, the control unit drives the main motor and controls the heater that controls the temperature of the fixing unit to the second temperature so that the temperature of the fixing unit becomes the first temperature. Therefore, it is possible to equalize the temperature of the nip portion of the fixing unit during sheet cutting and accelerate the start of conveyance of the next sheet. As a result, it is possible to reduce the decrease in the printing speed during continuous printing. That is, in the prior art, when cutting a sheet using a cutter, the discharge roller and a pair of rollers of the fixing unit are stopped before the cutting of the sheet. When performing the next printing for continuous printing, in order to equalize the temperature of the pair of rollers of the fixing unit, the discharge roller and the pair of rollers of the fixing unit are driven after the cutting of the sheet is completed. Therefore, sometimes the time from the start of printing to the end of printing during continuous printing becomes long. An object of the present invention is to shorten the time from the start of printing to the end of printing during continuous printing compared to the prior art. According to one aspect of the present invention, it is possible to shorten the time from the start of printing to the end of printing during continuous printing.

[0037] In the image forming apparatus of the present invention, the processing unit may include a photosensitive drum, and the image forming apparatus may include: a registration roller that is disposed upstream of the photosensitive drum in the conveying direction and is the conveying roller closest to the photosensitive drum among a plurality of conveying rollers that convey a sheet; and a first sheet sensor that is disposed between the photosensitive drum and the registration roller in the conveying direction and is capable of detecting the passage of a sheet, and the control unit controls the discharge motor based on the time point when the first sheet sensor detects the sheet.

[0038] The first sheet sensor is disposed between the photosensitive drum and the registration roller. In addition, the registration roller is the conveying roller closest to the discharge roller in the conveying direction among a plurality of conveying rollers disposed upstream of the photosensitive drum. Therefore, the first sheet sensor is disposed as close as possible to the discharge roller on the upstream side of the photosensitive drum.

[0039] 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 time point when the first sheet sensor detects the sheet, and thus can start driving the discharge motor at an appropriate moment and start the rotational drive of the discharge roller.

[0040] In the image forming apparatus of the present invention, it may also be that the fixing unit has a second sheet sensor, which is disposed downstream of the nip portion in the conveying direction and can detect the passage of the sheet, and the control unit controls the discharge motor based on the time point when the second sheet sensor detects the sheet.

[0041] Since the second sheet sensor is disposed downstream of the nip portion in the conveying direction, it is disposed closer to the discharge roller than the fixing unit. In addition, after the second sheet sensor detects the sheet, the sheet reaches the discharge roller. Therefore, the control unit controls the discharge motor based on the time point when the second sheet sensor detects the sheet, and thus can start driving the discharge motor at an appropriate moment and start the rotational drive of the discharge roller.

[0042] In the image forming apparatus of the present invention, it may also be that when a predetermined time has elapsed since the start of driving of the discharge motor, the control unit stops the discharge motor to stop the sheet. The control unit can appropriately control the discharge roller so that the cutting position in the sheet reaches the position where the cutter is disposed.

[0043] In the image forming apparatus of the present invention, it may also be that the fixing unit has a second sheet sensor, which is disposed downstream of the nip portion in the conveying direction and can detect the passage of the sheet, and the control unit controls the heater based on the time point when the second sheet sensor detects the completion of the passage of the sheet so that the target value of the temperature of the fixing unit becomes the second temperature.

[0044] After passing through the second sheet sensor, the heater is controlled so that the temperature of the fixing unit becomes a second temperature lower than the first temperature. Therefore, before the start of cutting the sheet by the cutter, the temperature of the fixing unit can be lowered. Thereby, local temperature rise of the heating rotating body and the pressing rotating body can be suppressed.

[0045] In the image forming apparatus of the present invention, it is also possible that the processing unit has a photosensitive drum, and the image forming apparatus includes: a registration roller that is disposed upstream of the photosensitive drum in the conveying direction and is the conveying roller closest to the photosensitive drum among a plurality of conveying rollers for conveying a sheet; and a first sheet sensor that is disposed between the photosensitive drum and the registration roller in the conveying direction and is capable of detecting the passage of a sheet. The control unit controls the heater based on the time point when the first sheet sensor detects the completion of the passage of the sheet so that the target value of the temperature of the fixing unit becomes the second temperature.

[0046] After passing through the first sheet sensor, the heater is controlled so that the temperature of the fixing unit becomes a second temperature lower than the first temperature. Therefore, before the start of cutting the sheet by the cutter, the temperature of the fixing unit can be reduced. Thereby, local heating of the nip portion of the fixing unit can be suppressed.

[0047] In the image forming apparatus of the present invention, it is also possible that, in the case of performing continuous printing, the control unit sets the driving duration of the main motor according to the number of printed sheets of the sheet. When the driving duration is equal to or longer than a threshold time, after the sheet is cut by the cutter while the main motor is continuously driven, the control unit controls the discharge motor to rotate the discharge roller, discharges the cut sheet, and starts supplying the next sheet to be discharged through the discharge roller. The control unit continuously drives the main motor in order to cope with the printing of the next sheet, thereby being able to suppress local heating of the heating rotating body and the pressing rotating body.

[0048] In the image forming apparatus of the present invention, it is also possible that the fixing unit has a second sheet sensor that is disposed downstream of the nip portion in the conveying direction and is capable of detecting the passage of a sheet. The control unit sets the driving duration based on the time point when the second sheet sensor detects the sheet.

[0049] The second sheet sensor is disposed downstream of the nip portion in the conveying direction. Therefore, after the sheet reaches the nip portion, the second sheet sensor detects the sheet. Therefore, the control unit sets the driving duration based on the time point when the second sheet sensor detects the sheet, and thus can stop the driving of the main motor at an appropriate moment to stop the heating rotating body.

[0050] In the image forming apparatus of the present invention, it may also be that the processing unit has a photosensitive drum, and the image forming apparatus includes: a registration roller that is disposed upstream of the photosensitive drum in the conveying direction and is the conveying roller closest to the photosensitive drum among a plurality of conveying rollers for conveying a sheet; and a first sheet sensor that is disposed between the photosensitive drum and the registration roller in the conveying direction and is capable of detecting the passage of the sheet, and the control unit sets the driving duration based on the time point when the first sheet sensor detects the sheet.

[0051] The first sheet sensor is disposed between the photosensitive drum and the registration roller. In addition, the registration roller is the conveying roller closest to the nip portion in the conveying direction among the plurality of conveying 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.

[0052] Furthermore, after the first sheet sensor detects the sheet, the sheet reaches the nip portion. Therefore, the control unit sets the driving duration based on the time point when the first sheet sensor detects the sheet, and thus can stop the driving of the main motor at an appropriate moment to stop the heating rotating body.

[0053] In the image forming apparatus of the present invention, it may also be that when performing the continuous printing, after the start of cutting of the sheet by the cutter, the control unit controls the heater so that the temperature of the fixing unit becomes the first temperature.

[0054] The heater that is controlled to be the second temperature before the discharge motor is driven is controlled to become the first temperature after the start of cutting of the sheet by the cutter. Thereby, the temperature of the fixing unit can be appropriately controlled for printing the next sheet. In addition, the time from the completion of sheet cutting to the heater becoming the first temperature can be shortened. Thereby, the decrease in the printing speed can be alleviated.

[0055] In the image forming apparatus of the present invention, it may also be that after the sheet is cut by the cutter, the control unit controls the discharge motor to rotate the discharge roller to discharge the cut sheet, and after discharging the cut sheet, the control unit stops the discharge roller. When the discharge roller does not need to be driven, by stopping the discharge roller, the noise generated by the discharge roller can be suppressed.

[0056] In the image forming apparatus of the present invention, it is also possible that the processing unit includes a photosensitive drum, a developing roller, and a transfer unit. The developing roller supplies toner to the photosensitive drum, and the transfer unit transfers the toner supplied to the photosensitive drum onto a sheet. The photosensitive drum and the developing roller rotate by receiving driving force transmitted from the main motor. Since the main motor transmits driving force to the photosensitive drum and the developing roller, the photosensitive drum and the developing roller can be centrally driven by the main motor.

[0057] The image forming apparatus of the present invention may also include: a supply tray for placing a sheet; a pickup roller for conveying the sheet from the supply tray to the processing unit by receiving driving force transmitted from the main motor; and a clutch capable of switching 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. When the temperature of the fixing unit reaches a specified temperature, the control unit sets the clutch to the transmission state through the clutch and conveys the sheet from the supply tray. The specified temperature is higher than the standby temperature waiting for printing on the sheet.

[0058] When the temperature of the fixing unit reaches a specified temperature, which is higher than the standby temperature, the control unit becomes a state in which driving force is transmitted from the main motor to the pickup roller, and conveys the sheet from the supply tray. Therefore, in a state where sufficient heat for fixing is ensured for the heating rotating body, the image can be sufficiently fixed on the sheet.

[0059] The image forming apparatus of the present invention may also be such that, before the rear end of the sheet passes through the nip portion, the control unit sets a target value of the temperature of the fixing unit to a second temperature lower than the first temperature and controls the heater. The control unit rotates the discharge roller to convey the sheet that has passed through the nip portion, and stops the discharge roller when the cutting position in the sheet reaches the position where the cutter is disposed, and then cuts the sheet through the cutter.

[0060] When cutting the sheet through the cutter, the control unit sets the target value of the temperature of the fixing unit to a second temperature lower than the first temperature (printing temperature) for fixing the image on the sheet and controls the heater before the rear end of the sheet passes through the nip portion. Then, the cutting position of the sheet that has passed through the nip portion is stopped at the position where the cutter is disposed. Thus, when cutting the sheet through the cutter, since the temperature of the fixing unit becomes lower than the first temperature, local heating of the heating rotating body and the pressure rotating body can be suppressed, and a decrease in the durability of the fixing unit can be suppressed.

[0061] In the image forming apparatus of the present invention, it is also possible that after the rear end of the sheet passes through the nip portion, the control unit stops driving the main motor. By stopping the driving of the main motor when the driving of the main motor is not required, the durability of the fixing unit and the like driven by the main motor can be improved.

[0062] In the image forming apparatus of the present invention, it is also possible that the processing unit has a photosensitive drum, and the image forming apparatus includes: a registration roller that is disposed upstream of the photosensitive drum in the conveying direction and is the conveying roller closest to the photosensitive drum among the plurality of conveying rollers for conveying the sheet; and a first sheet sensor that is disposed between the photosensitive drum and the registration roller in the conveying direction and can detect the passage of the sheet. When a first time has elapsed since the time point when the first sheet sensor detects the sheet, the control unit sets the target value of the temperature of the fixing unit to the second temperature and controls the heater.

[0063] When a first time has elapsed since the time point when the first sheet sensor detects the sheet, the control unit sets the target value of the temperature of the fixing unit to a second temperature lower than the first temperature (printing temperature) and controls the heater. Thereby, when the sheet is cut by the cutter, since the temperature of the fixing unit becomes lower than the first temperature, local temperature rise of the heating rotating body and the pressure rotating body can be suppressed.

[0064] In the image forming apparatus of the present invention, it is also possible that the fixing unit has a second sheet sensor that is disposed downstream of the nip portion in the conveying direction and can detect the passage of the sheet. When a second time has elapsed since the time point when the second sheet sensor detects the sheet, the control unit sets the target value of the temperature of the fixing unit to the second temperature and controls the heater.

[0065] When a second time has elapsed since the time point when the second sheet sensor detects the sheet, the control unit sets the target value of the temperature of the fixing unit to a second temperature lower than the first temperature (printing temperature) and controls the heater. Thereby, when the sheet is cut by the cutter, since the temperature of the fixing unit becomes lower than the first temperature, local temperature rise of the heating rotating body and the pressure rotating body can be suppressed.

[0066] In the image forming apparatus of the present invention, it is also possible that the control unit stops driving the main motor based on the time point when the second sheet sensor detects the completion of the passage of the sheet. By stopping the driving of the main motor when the driving of the main motor is not required, the durability of the components driven by the main motor can be improved.

[0067] In the image forming apparatus of the present invention, it may also be provided with a discharge motor that transmits a driving force to the discharge roller. The discharge roller can be independently controlled by the discharge motor.

[0068] In the image forming apparatus of the present invention, it may also be that the processing unit has a photosensitive drum, and the image forming apparatus includes: a registration roller that is disposed upstream of the photosensitive drum in the conveying direction and is the conveying roller closest to the photosensitive drum among the plurality of conveying rollers for conveying a sheet; and a first sheet sensor that is disposed between the photosensitive drum and the registration roller in the conveying direction and can detect the passage of the sheet. The control unit starts driving of the discharge motor based on the time point when the first sheet sensor detects the sheet. The control unit can start driving of the discharge motor based on the time point when the first sheet sensor detects the sheet.

[0069] In the image forming apparatus of the present invention, it may also be that when a third time has elapsed since the start of driving of the discharge motor, the control unit stops the discharge motor to stop the sheet. The discharge roller can be appropriately driven and controlled so that the cutting position in the sheet reaches the position where the cutter is disposed and stops.

[0070] In the image forming apparatus of the present invention, it may also be that the fixing unit has a second sheet sensor that is disposed downstream of the nip portion in the conveying direction and can detect the passage of the sheet. The control unit stops the discharge motor to stop the sheet based on the time point when the second sheet sensor detects the completion of the passage of the sheet. The discharge roller can be appropriately driven and controlled so that the cutting position in the sheet reaches the position where the cutter is disposed and stops.

[0071] In the image forming apparatus of the present invention, it may also be that after the sheet is cut by the cutter, the control unit controls the discharge motor to rotate the discharge roller to discharge the cut sheet. In the case of performing continuous printing in which a plurality of sheets are continuously printed, after the cut sheet is discharged, the control unit drives the main motor, and the control unit controls the heater so that the temperature of the fixing unit becomes the first temperature. The temperature of the fixing unit can be appropriately controlled to cope with printing of the next sheet.

[0072] In the image forming apparatus of the present invention, it is also possible that after the sheet is cut by the cutter, the control unit controls the discharge motor to rotate the discharge roller to discharge the cut sheet. In the case of performing continuous printing in which a plurality of sheets are continuously printed, the control unit drives the main motor simultaneously with the start of driving of the discharge motor, and the control unit controls the heater so that the temperature of the fixing unit becomes the first temperature. The temperature of the fixing unit can be appropriately controlled to cope with the printing of the next sheet. In addition, since the main motor is driven simultaneously with the start of driving of the discharge motor, the start time point of conveying the next sheet can be advanced, and the speed of printing can be achieved.

[0073] In the image forming apparatus of the present invention, it is also possible that after the sheet is cut by the cutter, the control unit controls the discharge motor to rotate the discharge roller to discharge the cut sheet, and after discharging the sheet, the control unit stops the discharge motor to stop the discharge roller. By stopping the discharge motor when the driving of the discharge roller is not required, noise can be suppressed.

[0074] In the image forming apparatus of the present invention, it is also possible that the processing unit includes: a photosensitive drum; a developing roller that supplies toner to the photosensitive drum; and a transfer unit that transfers the toner supplied to the photosensitive drum to a sheet, and the photosensitive drum and the developing roller rotate by the driving force of the main motor. The photosensitive drum and the developing roller rotate by the driving force from the main motor. Thus, the photosensitive drum and the developing roller can be rotated synchronously, and toner can be carried on the photosensitive drum.

[0075] In the image forming apparatus of the present invention, it is also possible that it includes: a supply tray on which sheets are placed; a pickup roller that conveys the sheets from the supply tray to the processing unit by being transmitted with the driving force of the main motor; and a clutch that can be switched to 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. When the temperature of the fixing unit reaches a sheet supply temperature higher than the second temperature, the control unit switches the clutch to the transmission state, transmits the driving force from the main motor to the pickup roller, and the control unit conveys the sheets from the supply tray to the processing unit.

[0076] When the temperature of the fixing unit reaches a temperature higher than the second temperature, that is, the sheet supply temperature (paper supply temperature or printing temperature), the control unit transmits the driving force from the main motor to the pickup roller through the clutch, and conveys the sheets from the supply tray to the processing unit. Thus, when the sheet on which the toner is transferred reaches the fixing unit, the temperature of the fixing unit can be reliably made to reach the first temperature at which the image is fixed on the sheet.

[0077] In the image forming apparatus of the present invention, it is also possible that, in the sheet, at the moment when the sheet passes through the nip portion after passing a position that is one perimeter distance away from the heating rotating body on the downstream side in the conveying direction from the rear end of the sheet and before the rear end of the sheet passes through the nip portion, the control unit sets the target value of the temperature of the fixing unit to the second temperature and controls the heater.

[0078] Before the rear end of the sheet passes through the nip portion, the target value of the temperature of the fixing unit 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 fixing unit becomes lower than the first temperature, local temperature rise of the heating rotating body and the pressure rotating body can be suppressed, and deterioration of the durability of the fixing unit can be suppressed.

[0079] Effects of the Invention

[0080] According to one aspect of the present invention, deterioration of the durability of the fixing unit can be suppressed when the sheet is cut by the cutter. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 It is a diagram showing an example of the schematic configuration of the image forming apparatus according to Embodiment 1.

[0082] Figure 2 It shows Figure 1 a block diagram of the electrical configuration of the image forming apparatus shown.

[0083] Figure 3 It is shown by Figure 1 an example of a flowchart showing the printing control process performed by the CPU of the image forming apparatus shown.

[0084] Figure 4 It shows Figure 3 a sub-flowchart of an example of the process of the printing cut-off process of.

[0085] Figure 5 It is a timing chart showing an example of the relationship between the driving times of the respective driving units and the temperature of the fixing device.

[0086] Figure 6 It is a diagram for explaining the cutting of the sheet passing through the nip portion.

[0087] Figure 7 It is a timing chart showing an example of the relationship between the driving times of the respective driving units and the temperature of the fixing device in Modification 1 of the image forming apparatus according to Embodiment 1.

[0088] Figure 8This is a sub - flowchart showing an example of the process of print cutting in the image forming apparatus according to Embodiment 2.

[0089] Figure 9 This is a timing chart showing an example of the relationship between the driving times of respective driving units and the temperature of the fuser in the image forming apparatus according to Embodiment 2.

[0090] Figure 10 This is a sub - flowchart showing an example of the process of print cutting in the image forming apparatus according to Embodiment 3.

[0091] Figure 11 This is a timing chart showing an example of the relationship between the driving times of respective driving units and the temperature of the fixing unit.

[0092] Figure 12 This is a diagram for explaining the cutting of a sheet through the nip portion.

[0093] Figure 13 This is a diagram for explaining the cutting of paper by a cutter.

[0094] Figure 14 This is a timing chart showing an example of the relationship between the driving times of respective driving units and the temperature of the fuser in Modification 1 of the image forming apparatus according to Embodiment 3.

[0095] Figure 15 This is a sub - flowchart showing an example of the process of print cutting in the image forming apparatus according to Embodiment 4.

[0096] Figure 16 This is a timing chart showing an example of the relationship between the driving times of respective driving units and the temperature of the fixing unit.

[0097] Figure 17 This is a diagram for explaining the relationship between the sheet passing through the nip portion and the driving of the heater. Detailed Embodiments

[0098] (Embodiment 1)

[0099] [Overall Structure of Image Forming Apparatus 1]

[0100] Based on Figure 1 The schematic structure of the image forming apparatus 1 will be described. Figure 1 This is a diagram showing an example of the schematic structure of the image forming apparatus 1 according to Embodiment 1. As Figure 1 shown, the image forming apparatus 1 is a monochrome laser printer and includes a device main body 2, a conveying unit 3, an image forming unit 4, a fuser 5, a cutter 10, and an operation panel 120. Hereinafter, for convenience of explanation, as Figure 1As indicated by the arrows, the up-down direction and the front-back direction of the image forming apparatus 1 are defined.

[0101] The apparatus main body 2 has a front cover 20, a supply tray 21, a discharge tray 22, a conveyance path 201, and a branch path 200. The apparatus main body 2 has an openable and closable front cover 20 on its front surface.

[0102] The apparatus main body 2 has a detachable supply tray 21 at its lower part. A sheet P is placed on the supply tray 21. The sheet P is a standard-sized sheet such as A4 size. The sheet P is, for example, a paper medium such as plain paper or thick paper. The apparatus main body 2 has a discharge tray 22 at its upper part. The sheet P on which an image has been formed is placed on the discharge tray 22.

[0103] The conveyance path 201 is for conveying the sheet P placed on the supply tray 21 to the cutter 10 via the image forming unit 4, and for conveying 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 path different from the conveyance path 201 for conveying the sheet P not cut by the cutter 10 toward the discharge tray 22.

[0104] The start point of conveyance of the sheet P in the branch path 200 is the confluence position C with the conveyance path 201. The confluence position C is located upstream of the first discharge roller 36 and the third discharge roller 40 in the conveyance direction of the sheet P, and is provided downstream of the fixing unit 5. The conveyance direction of the sheet P is the direction from the supply tray 21 toward the discharge tray 22 along the conveyance path 201, or the direction from the supply tray 21 toward the discharge tray 22 along the conveyance path 201 and the branch path 200. Hereinafter, the conveyance direction of the sheet P will be simply referred to as the conveyance direction.

[0105] In addition, the branch path 200 is disposed below the conveyance path 201. In addition, a flapper 8 for distributing the sheet P to the conveyance path 201 or the branch path 200 is provided near the confluence position C. When the flapper 8 is in the first position, the sheet P is distributed to the branch path 200. In addition, when the flapper 8 is in the second position, the sheet P is distributed to the conveyance path 201. The flapper 8 is configured to operate by the driving force from a driving motor (not shown).

[0106] The conveyance unit 3 has a pickup roller 31, a separation roller 32, a paper dust removing 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. In addition, the conveyance unit 3 has an electromagnetic clutch 107, a main motor 108, and a discharge motor 140 (see Figure 2 ).

[0107] By transmitting the driving force from the main motor 108, the pickup roller 31 picks up the sheet P in the supply tray 21 lifted upward by the sheet pressing plate 21A. Further, the pickup roller 31 conveys the sheet P toward the conveyance path 201 and conveys the sheet 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 anti-paper dust roller 33 removes the paper dust on the surface of the sheet P.

[0108] The registration roller 34 is disposed upstream of the photosensitive drum 61 (described later) of the image forming unit 4 in the conveyance path 201, and is the conveyance roller closest to the photosensitive drum 61 among the plurality of conveyance rollers that convey the sheet P. The registration roller 34 is the conveyance roller that is located upstream of the image forming unit 4 and closest to the photosensitive drum 61 in the conveyance path 201. The plurality of conveyance rollers refers to, for example, the pickup roller 31, the separation roller 32, and the anti-paper dust roller 33. After aligning the direction of the top end of the sheet P, the registration roller 34 conveys the sheet P toward the image forming unit 4. The roller 35 conveys the sheet P after passing through the fixing unit 5 toward the first discharge roller 36 side.

[0109] The first discharge roller 36 and the second discharge roller 37 are disposed downstream of the merging position C in the conveyance path 201. The first discharge roller 36 and the second discharge roller 37 are disposed at an upstream position and a downstream position with respect to the arrangement position B of the cutter 10 with the cutter 10 interposed therebetween.

[0110] The third discharge roller 40 is disposed downstream of the merging position C in the branch path 200. The first discharge roller 36, the second discharge roller 37, and the third discharge roller 40 discharge the sheet P from the inside of the apparatus main body 2 to the outside of the apparatus main body 2.

[0111] The image forming unit 4 is an example of a processing unit that forms an image on the sheet P and is housed in the apparatus main body 2. The image forming unit 4 includes a drum cartridge 6 and a laser unit 7. The drum cartridge 6 includes a photosensitive drum 61, a toner storage section 62, a supply roller 63, a developing roller 64, a charger 65, a transfer roller TR, and a pinch roller 66.

[0112] By opening the front cover 20, the drum cartridge 6 can be detached from the apparatus main body 2. The pinch roller 66 of the drum cartridge 6 is disposed opposite to the registration roller 34. The pinch roller 66 rotates following the rotation of the registration roller 34 and conveys the sheet P together with the registration roller 34.

[0113] The photosensitive drum 61 rotates clockwise by the driving force transmitted from the main motor 108 (refer to Figure 2 ) and conveys the sheet P in the conveyance direction. The toner storage section 62 stores toner. The supply roller 63 supplies the toner in the toner storage section 62 to the developing roller 64. The charger 65 is a vacuum tube type charger that uniformly charges the surface of the photosensitive drum 61. Further, the charger 65 may be a charging roller.

[0114] A transfer roller TR is disposed at a position opposite to the photosensitive drum 61. The transfer roller TR is an example of a transfer unit, and a transfer nip TN is formed between the transfer roller TR and the photosensitive drum 61 in the conveyance path 201. In addition, a transfer belt may be used instead of the transfer roller TR as an example of the transfer unit.

[0115] The apparatus main body 2 has a laser unit 7 in the upper part of its interior. The laser unit 7 includes a polygon mirror 131, a laser light emitting unit 132 (refer to Figure 2 ), a lens, a mirror, etc. not shown. The laser unit 7 exposes the surface of the photosensitive drum 61 by scanning the surface of the photosensitive drum 61 at high speed with a laser (refer to the double-dot chain line) based on image data emitted from the laser light emitting unit 132.

[0116] The surface of the photosensitive drum 61 is exposed by the laser unit 7, thereby forming an electrostatic latent image based on the image data. The developing roller 64 forms a toner image on the surface of the photosensitive drum 61 by supplying toner to the electrostatic latent image formed on the surface of the photosensitive drum 61.

[0117] A transfer voltage is applied to the transfer roller TR by a voltage application unit not shown. The transfer roller TR transfers the toner image formed on the surface of the photosensitive drum 61 to the sheet P passing through the transfer nip TN by conveying the sheet P between the transfer roller TR and the photosensitive drum 61. In other words, the transfer roller TR transfers the toner supplied to the photosensitive drum 61 to the sheet P. In this way, image formation on the sheet P is performed.

[0118] A fixing device 5 is disposed on the downstream side of the image forming unit 4 in the conveyance path 201. The fixing device 5 is an example of a fixing unit. The fixing device 5 includes a heating roller 51, a pressure roller 52, a heater 53, a temperature sensor 54, and a paper discharge sensor 112.

[0119] 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 a nip portion N is formed between the heating roller 51 and the pressure roller 52 to press the sheet P. The pressure roller 52 rotates counterclockwise by the driving force of the main motor 108. The heating roller 51 rotates clockwise following the pressure roller 52.

[0120] Alternatively, it may be configured such that the heating roller 51 rotates clockwise by the driving force of the main motor 108, and the pressure roller 52 rotates counterclockwise following the heating roller 51. Or, it may be configured such that the driving force of the main motor 108 is transmitted to both the heating roller 51 and the pressure roller 52, the heating roller 51 rotates clockwise, and the pressure roller 52 rotates counterclockwise.

[0121] The heater 53 is, for example, a halogen heater that heats the heating roller 51. The temperature sensor 54 is disposed in the fixing 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 ).

[0122] The fixing unit 5 heats the sheet P by the heating roller 51 and rotates the pressure roller 52, so that the sheet P is conveyed while being pressed between the heating roller 51 and the pressure roller 52, and the image formed on the sheet P by the image forming unit 4 is fixed on the sheet P.

[0123] In addition, the fixing unit 5 has a structure including the heating roller 51, the pressure roller 52, and the heater 53, but is not limited thereto. For example, the fixing unit 5 may have a structure including a heater, a clamping plate that receives radiant heat from the heater, a heating belt that rotates around the clamping plate, and a pressure roller. In this case, the heating belt is an example of a heating rotating body.

[0124] Alternatively, the fixing unit 5 may have a structure including a substrate formed with a heat generating pattern, a belt that rotates around the substrate, and a pressure roller, and the substrate and the belt are in contact with each other. In this case, the belt is an example of a heating rotating body. Alternatively, the fixing unit 5 may have a structure including a heating roller, a heater, and a pressure belt. In this case, the pressure belt is an example of a pressing rotating body.

[0125] The cutter 10 is disposed at a position B in the conveyance path 201 on the downstream side of the fixing unit 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 to include, for example, a blade 75 (see Figure 2 ), a fixed blade, a cutter carriage 11 (see Figure 7 ), and a cutting motor 106 (see Figure 2 ). In addition, the cutter 10 may have a pair of upper and lower blades 75.

[0126] The blade 75 is, for example, a rotatable circular blade and is held by the cutter carriage 11. The fixed blade is fixed to a frame provided in the apparatus main body 2 so as to extend in the left-right direction. The cutter carriage 11 is configured to be able to reciprocate in the width direction of the sheet P along a rail 12 (see Figure 7 ) by the driving force of the cutting motor 106, and the rail 12 is provided in the apparatus main body 2 so as to extend in the left-right direction.

[0127] When the sheet P is at the position B where the cutter 10 is disposed, the cutter carriage 11 moves in the width direction of the sheet P, so that the sheet P is clamped by the blade 75 and the fixed blade and is cut.

[0128] [Electrical Structure of the Image Forming Apparatus 1]

[0129] Next, with reference to Figure 2 the electrical structure of the image forming apparatus 1 will be described. Figure 2 FIG. is a block diagram showing the electrical structure of the image forming apparatus 1. As Figure 2 shown, 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-alignment sensor 110, an after-alignment sensor 111, a paper discharge sensor 112, a temperature and humidity sensor 113, and a communication interface (I / F) 130.

[0130] A CPU (Central Processing Unit) 101 is mounted on the ASIC 105. The CPU 101 is an example of a control unit and performs overall control of each part of the image forming apparatus 1. The ASIC 105 is electrically connected to the ROM 102, the RAM 103, the NVRAM 104, a cut-off motor 106, an electromagnetic clutch 107, a main motor 108, and a discharge motor 140. In addition, the ASIC 105 is electrically connected to the pre-alignment sensor 110, the after-alignment sensor 111, the paper discharge sensor 112, the temperature and humidity sensor 113, an operation panel 120, a communication I / F 130, a fixing unit 5, and a laser unit 7.

[0131] The ROM 102 is an example of a storage unit. The ROM 102 stores various control programs, various settings, etc. for controlling the image forming apparatus 1. Specifically, information on the printing temperatures of the heating roller 51 and the pressure roller 52 when the image is fixed on the sheet P is stored in the ROM 102. The printing temperature is an example of a first temperature. That is, in the present embodiment, the temperature of the fixing unit is the temperature of the heating roller 51 and the pressure roller 52. However, it may be only the temperature of the heating roller 51, and the control unit may be configured to control the temperature of the entire fixing unit or the temperature of a part of the fixing unit (for example, the nip N) by controlling the temperature of the heating roller 51.

[0132] In addition, information on the standby temperatures of the heating roller 51 and the pressure roller 52 when waiting to convey the sheet P is stored in the ROM 102. The standby temperature is an example of a second temperature. Further, information on the paper feedable temperatures of the heating roller 51 and the pressure roller 52 when conveying the sheet P from the supply tray 21 is stored in the ROM 102. The paper feedable temperature is an example of a sheet supply temperature. In addition, information such as a high temperature is stored in the ROM 102. The high temperature is an example of a third temperature.

[0133] The RAM 103 is used as a work area for reading various control programs and a storage area for temporarily storing image data included in a printing job. The CPU 101 controls each part of the image forming apparatus 1 while storing its processing results in the RAM 103 or the NVRAM 104 according to the control program read from the ROM 102 and signals output from various sensors.

[0134] The cutting motor 106 is an example of a driving source for a cutter. The CPU 101 drives the cutting motor 106 to move the cutter carriage 11, so that the blade 75 moves in the width direction of the sheet P to cut the sheet P.

[0135] The main motor 108 transmits driving force to the conveying unit 3, the pressure roller 52, and the drum cartridge 6. When the CPU 101 drives the main motor 108 to rotate forward, 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.

[0136] Then, the pressure roller 52, the photosensitive drum 61, the developing roller 64, the pickup roller 31, and the registration roller 34 rotate in the direction of conveying the sheet P along the conveying direction. Since the main motor 108 transmits driving force to the photosensitive drum 61, the developing roller 64, etc., the photosensitive drum 61, the developing roller 64, etc. can be centrally driven by the main motor 108.

[0137] On the other hand, there is a structure in which driving force is not transmitted to the pressure roller 52, the drum cartridge 6, the pickup roller 31, and the registration roller 34 even when the CPU 101 drives the main motor 108 to rotate reversely. Alternatively, the CPU 101 may control the main motor 108 to rotate at least one of the heating roller 51 and the pressure roller 52 to convey the sheet P.

[0138] 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.

[0139] Specifically, the CPU 101 sets the transmission state in which the driving force of the main motor 108 is transmitted to the pickup roller 31 by turning on the electromagnetic clutch 107. On the other hand, the CPU 101 sets the non - transmission state in which the driving force of the main motor 108 is not transmitted to the pickup roller 31 by turning off the electromagnetic clutch 107. At the start of the image forming apparatus 1, the CPU 101 sets the electromagnetic clutch 107 to the off state.

[0140] 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 to rotate forward. Then, the first discharge roller 36, the second discharge roller 37, and the third discharge roller 40 rotate in the direction of conveying the sheet P along the conveying direction.

[0141] The pre-registration sensor 110 is a sensor that is disposed upstream of the registration roller 34 in the conveying path 201 and detects the passage of the sheet P. The pre-registration sensor 110 can use a sensor having an actuator that swings by contacting the sheet P, a light sensor, or the like. The pre-registration sensor 110 outputs an ON signal in a state where the sheet P is passing through, and outputs an OFF signal in a state where the sheet P is not passing through. The detection signal of the pre-registration sensor 110 is output to the CPU 101.

[0142] The post-registration sensor 111 is an example of a first sheet sensor, and is a sensor that is disposed upstream of the fixing device 5 in the conveying path 201. Specifically, it is disposed between the photosensitive drum 61 and the registration roller 34 in the conveying direction and can detect the passage of the sheet P. The post-registration sensor 111 has the same structure as the pre-registration sensor 110. The detection signal of the post-registration sensor 111 is output to the CPU 101.

[0143] The paper discharge sensor 112 is an example of a second sheet sensor, and is a sensor that is disposed between the heating roller 51 of the fixing device 5 and the roller 35 in the conveying path 201, that is, on the downstream side of the nip portion N, and can detect the passage of the sheet P. The paper discharge sensor 112 has the same structure as the pre-registration sensor 110.

[0144] The detection signal of 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 during the process in which the sheet P after passing through the nip portion N passes through the paper discharge sensor 112. That is, when the leading end of the sheet P in the conveying direction enters the paper discharge sensor 112, the paper discharge sensor 112 turns on. Subsequently, when the rear end PL of the sheet P (refer to Figure 6 ) passes through the paper discharge sensor 112, the paper discharge sensor 112 turns off.

[0145] The temperature and humidity sensor 113 is a sensor that detects the temperature and humidity outside the main body 2 of the detection device. The temperature and humidity sensor 113 is arranged, for example, on the side surface of the device main body 2. The temperature and humidity sensor 113 outputs a signal corresponding to the detected temperature and humidity to the CPU 101. In addition, instead of the temperature and humidity sensor 113, a temperature sensor that detects the temperature outside the main body 2 of the detection device and a humidity sensor that detects the humidity outside the main body 2 of the detection device may be arranged on the device main body 2.

[0146] The operation panel 120 is arranged on the upper surface of the device main body 2. The operation panel 120 has, for example, a touch panel in which a touchpad and a display are integrally formed and a button section. The operation panel 120 receives the operation of the user and outputs the received information to the CPU 101. The user can, for example, set whether to cut the sheet P by operating the operation panel 120.

[0147] The communication I / F 130 is connected to a network such as a LAN and can be connected to an external device such as a PC equipped with a driver for the image forming apparatus 1. The CPU 101 can receive a printing job via the communication I / F 130. The printing job includes image data for image formation, the size and type of the sheet P for image formation, and various information required for forming an image on the sheet P.

[0148] [Flow of printing control by the CPU 101]

[0149] Next, based on Figures 3 to 6 An example of the flow of printing control performed by the CPU 101 of the image forming apparatus 1 will be described. Figure 3 is a main flow chart showing an example of the flow of printing control performed by the CPU 101 of the image forming apparatus 1. In the following description, an example is illustrated and described in which after single-sided printing on a sheet P of A4 size, a cutting process is performed on the sheet P to divide it into two first sheets P1 and second sheets P2 of A5 size (see Figure 6 ).

[0150] As Figure 3 shown, in S11, the CPU 101 determines whether a printing job is received via the communication I / F 130. Then, when the CPU 101 determines that a printing job is received via the communication I / F 130 (S11: Yes), it proceeds to the process of S13 described later.

[0151] On the other hand, when the CPU 101 determines that a printing job has not been received via the communication I / F 130 (S11: No), it proceeds to the process of S12. In S12, the CPU 101 determines whether a print command has been input via the operation panel 120. Then, when it is determined that a print command has not been received via the operation panel 120 (S12: No), the CPU 101 executes the process of S11 again.

[0152] On the other hand, when the CPU 101 determines that a print command has been input via the operation panel 120 (S12: Yes), it proceeds to the process of S13. In S13, the CPU 101 starts driving the heater 53. For example, as Figure 5 shown, the CPU 101 starts driving the heater 53 at time T1. That is, power supply to the heater 53 is started.

[0153] After starting the power supply to the heater 53, in S14, the CPU 101 determines whether to cut the sheet P. That is, when the input printing job indicates that the sheet P needs to be cut, it is determined to cut the sheet P (S14: Yes), and the process proceeds to S17. On the other hand, when the CPU 101 does not need to cut the sheet P (S14: No), it proceeds to the process of S15.

[0154] In S15, the CPU 101 moves the shutter 8 to the first position and proceeds to the process of S16. By moving the shutter 8 to the first position, the sheet P is distributed to the branch path 200. In addition, when the shutter 8 is already in the first position at the start time of step S15, the CPU 101 maintains the state where the shutter 8 is in the first position and proceeds to the process of S16.

[0155] In S16, the CPU 101 performs a printing process without cutting the sheet P. For the printing process without cutting the sheet P, detailed description is omitted, but the top end of the sheet on which the toner image has been formed and fixed is guided to the branch path 200 having the third discharge roller 40 by the shutter 8. The sheet guided to the branch path 200 is discharged onto the discharge tray 22 by the rotation of the third discharge roller 40.

[0156] In S17, the CPU 101 determines the cutting position A for bisecting the sheet P and stores it in the RAM 103. Specifically, as Figure 6 shown, the CPU 101 determines the cutting position A where the A4 - sized sheet P is bisected into the first sheet P1 and the second sheet P2 having equal lengths in the conveying direction as the position of length L2 from the top end in the conveying direction and stores it in the RAM 103.

[0157] The length L2 is calculated, for example, based on the conveyance amount of the sheet P detected by an encoder (not shown) from when the front end of the sheet P is detected by the post-alignment sensor 111 to when the rear end PL of the sheet P is detected by the post-alignment sensor 111 after alignment.

[0158] In S18, the CPU 101 reads from the ROM 102 the printing temperatures of the heating roller 51 and the pressure roller 52 when an image is fixed on the sheet P. Then, the CPU 101 sets the temperature of the heating roller 51 to reach the printing temperature, for example, about 190°C, and after starting the control of the voltage applied to the heater 53, enters the process of S19.

[0159] In S19, after the CPU 101 drives the main motor 108 to rotate forward, it enters the process of S20. As a result, the pressure roller 52, the photosensitive drum 61, the developing roller 64, and the registration roller 34 rotate in the direction of conveying the sheet P along the conveying direction. As a result, for example, as Figure 5 shown, when the pressure roller 52 or the heating roller 51 in the fixing unit 5 is driven to rotate at time T2, the temperature rising speed of the fixing temperature in the nip portion N between the heating roller 51 and the pressure roller 52 slightly slows down.

[0160] In S20, 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 available temperature. The paper-feeding available temperature is the temperature at which the driving force of the main motor 108 can be transmitted to the pickup roller 31, and is, for example, 170°C. Then, when the CPU 101 determines via the temperature sensor 54 that the temperatures of the heating roller 51 and the pressure roller 52 have not reached the paper-feeding available temperature (S20: No), it executes the process of S20 again.

[0161] On the other hand, when the CPU 101 determines via the temperature sensor 54 that the temperatures of the heating roller 51 and the pressure roller 52 have reached the paper-feeding available temperature (S20: Yes), it enters the process of S21. In S21, the CPU 101 ends this process after executing a sub-process of the printing cut-off process.

[0162] [Sub-process of the printing cut-off process]

[0163] Next, based on Figures 4 to 6 , an example of the flow of the printing cut-off process executed by the CPU 101 in the above S21 will be described. Figure 4 is a sub-flowchart showing an example of the flow of the printing cut-off process. Figure 5 is a timing chart showing an example of the relationship between the driving times of the respective driving units and the temperature of the fixing unit 5. Figure 6 is a diagram for explaining the cutting of the sheet P passing through the nip portion N.

[0164] As Figure 4As shown, in S111, the CPU 101 drives a drive motor (not shown) to move the shutter 8 to the second position, and proceeds to the process of S112. By moving the shutter 8 to the second position, the sheet P is distributed to the conveyance path 201. In addition, when the shutter 8 is already in the second position at the start time of step S111, the CPU 101 maintains the state where the shutter 8 is in the second position, and proceeds to the process of S112.

[0165] In S112, the CPU 101 executes a pickup command to pick up the sheet P in the supply tray 21 by the pickup roller 31. Specifically, the CPU 101 turns on the electromagnetic clutch 107 and sets the transmission state in which the driving force of the main motor 108 is transmitted to the pickup roller 31. Subsequently, the process proceeds to S113.

[0166] In S113, the CPU 101 determines whether the detection signal input from the post-alignment sensor 111 changes from "off" to "on". Specifically, the CPU 101 detects the top end of the conveyed sheet P by the post-alignment sensor 111, obtains the detection signal sent from the post-alignment sensor 111, and thus determines that the detection signal has become "on".

[0167] Then, when the detection signal input from the post-alignment sensor 111 does not change from "off" to "on" (S113: No), the CPU 101 executes the process of S113 again. On the other hand, when the detection signal input from the post-alignment sensor 111 changes from "off" to "on" (S113: Yes), the process proceeds to S114.

[0168] In S114, the CPU 101 starts image formation of 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 based on the image data on the sheet P. That is, the CPU 101 transfers the toner image formed on the photosensitive drum 61 to the sheet P through the transfer roller TR. Then, through the fuser 5, the image formed on the sheet P is fixed to the sheet P.

[0169] Next, in S115, the CPU 101 starts the forward rotation drive of the discharge motor 140 to rotate the first discharge roller 36 and the second discharge roller 37, and proceeds to the process of S116. Thereby, for example, as Figure 5 shown, the paper discharge drive for rotating the first discharge roller 36 and the second discharge roller 37 starts at time T2.

[0170] Therefore, like the processes of S113 and S115, the CPU 101 controls the discharge motor 140 based on the time point when the post-alignment sensor 111 detects the sheet P. The post-alignment sensor 111 is disposed between the photosensitive drum 61 and the registration roller 34. In addition, the registration roller 34 is the conveyance roller among the plurality of conveyance rollers disposed on the upstream side of the photosensitive drum 61 that is closest to the first discharge roller 36 and the second discharge roller 37 in the conveyance direction. Therefore, the post-alignment sensor 111 is disposed on the upstream side of the photosensitive drum 61 at a position as close as possible to the first discharge roller 36 and the second discharge roller 37.

[0171] Furthermore, after the post-alignment sensor 111 detects the sheet P, the sheet P reaches the first discharge roller 36. Therefore, since the CPU 101 controls the discharge motor 140 based on the time point when the post-alignment sensor 111 detects the sheet P, it is possible to start driving the discharge motor 140 at an appropriate moment and start the rotational driving of the first discharge roller 36 and the second discharge roller 37.

[0172] In S116, the CPU 101 determines whether the detection signal input from the paper discharge sensor 112 changes from "off" to "on". Specifically, the CPU 101 detects the top end of the conveyed sheet P through the paper discharge sensor 112, obtains the detection signal sent from the paper discharge sensor 112, and thus determines that the detection signal has changed to "on".

[0173] For example, as Figure 5 shown, the CPU 101 determines at time T3 that the detection signal input from the paper discharge sensor 112 changes from "off" to "on". At this time, the CPU 101 controls the discharge motor 140 to rotate the first discharge roller 36 and the second discharge roller 37 to convey the sheet P that has passed through the nip portion N.

[0174] Then, when the detection signal input from the paper discharge sensor 112 does not change from "off" to "on" (S116: No), the CPU 101 executes the process of S116 again. On the other hand, when the detection signal input from the paper discharge sensor 112 changes from "off" to "on" (S116: Yes), the CPU 101 proceeds to the process of S117.

[0175] In S117, the CPU 101 determines whether the driving duration of the main motor 108 based on the number of consecutive printed sheets of the printing job is equal to or longer than the threshold time. The number of consecutive printed sheets is counted, for example, based on the number of sheets P after the sensor position of the pre-alignment sensor 110 or the like. In addition, the number of consecutive printed sheets may be the number of printed sheets specified for one printing job, or the total number of printed sheets when the sheet P is continuously printed in multiple printing jobs. Further, the number of consecutive printed sheets may also be the number of printed sheets when the interval between printing jobs is within a specified time even if there is a printing interruption between printing jobs. The driving duration of the main motor 108 based on the number of consecutive printed sheets corresponds as shown in Table 1 below.

[0176] [Table 1]

[0177] Number of consecutive printed sheets Drive duration More than 60 sheets 30 seconds 30 to 59 sheets 20 seconds 10 to 29 sheets 15 seconds Less than 10 sheets 3 seconds

[0178] When the number of consecutive printed sheets is 60 sheets or more, the driving duration of the main motor 108 is 30 seconds. When the number of consecutive printed sheets is 30 to 59 sheets, the driving duration of the main motor 108 is 20 seconds. When the number of consecutive printed sheets is 10 to 29 sheets, the driving duration of the main motor 108 is 15 seconds. When the number of consecutive printed sheets is less than 10 sheets, the driving duration of the main motor 108 is 3 seconds.

[0179] Thus, when the CPU 101 performs continuous printing in which multiple sheets P are continuously printed, the driving duration of the main motor 108 is set according to the number of printed sheets of the sheet P. In addition, when the heating roller 51 and the pressure roller 52 have a layer made of rubber, the driving duration is preferably longer than when the heating roller 51 and the pressure roller 52 do not have such a layer and the surface is coated.

[0180] The threshold time is, for example, 20 seconds. Then, when the CPU 101 determines that the driving duration of the main motor 108 based on the number of consecutive printed sheets of the printing job is equal to or longer than the threshold time (S117: Yes), it proceeds to the process of S119 described later.

[0181] On the other hand, when the CPU 101 determines that the driving duration of the main motor 108 based on the number of consecutive printed sheets of the printing job is less than the threshold time (S117: No), it proceeds to the process of S118. In S118, the CPU 101 determines to perform a process of stopping the main motor 108 after the driving duration of the main motor 108 has elapsed, and proceeds to the process of S119.

[0182] Through the process of S117, in order to determine whether to execute the process of S118, the CPU 101 sets the driving duration of the main motor 108 at the time point when the sheet P is detected by the paper discharge sensor 112 in S116.

[0183] The paper discharge sensor 112 is arranged on the downstream side of the nip portion N in the conveying direction. Therefore, after the sheet P reaches the nip portion N, the paper discharge sensor 112 detects the sheet P. Thus, the CPU 101 sets the driving duration of the main motor 108 based on the time point when the paper discharge sensor 112 detects the sheet P, and thus can stop the driving of the main motor 108 at an appropriate moment to stop the heating roller 51.

[0184] In S119, the CPU 101 determines whether the detection signal input from the paper discharge sensor 112 changes from "ON" to "OFF". Specifically, after the CPU 101 detects the leading end of the conveyed sheet P by the paper discharge sensor 112, since the rear end of the sheet P passes through and the detection signal sent from the paper discharge sensor 112 cannot be obtained, it is determined that the detection signal changes to "OFF".

[0185] Then, when the detection signal input from the paper discharge sensor 112 does not change from "ON" to "OFF" (S119: NO), the CPU 101 executes the process of S119 again. On the other hand, when the detection signal input from the paper discharge sensor 112 changes from "ON" to "OFF" (S119: YES), the CPU 101 determines that the paper discharge sensor 112 has detected the completion of the passage of the sheet P and enters the process of S120.

[0186] For example, as Figure 5 shown, when the detection signal input from the paper discharge sensor 112 changes from "ON" to "OFF" at time T4, the CPU 101 determines that the paper discharge sensor 112 has detected the completion of the passage of the sheet P. That is, the CPU 101 determines that the rear end PL of the sheet P has passed through the nip portion N.

[0187] In S120, the CPU 101 reads the standby temperatures of the heating roller 51 and the pressure roller 52 when waiting for the sheet P to be conveyed from the ROM 102. Then, the CPU 101 sets the temperature of the heating roller 51 to be reduced to the standby temperature, for example, about 130 °C, and after starting the control of the voltage applied to the heater 53, enters the process of S121. The standby temperature is a temperature lower than the printing temperature. For example, as Figure 5 shown, the CPU 101 stops the driving of the heater 53 at time T5. At the moment of time T5, the sheet P has completed passing between the heating roller 51 and the pressure roller 52, that is, the nip portion N.

[0188] Through the processing of S120, the CPU 101 controls the heater 53 based on the time point when the sheet P is detected to have passed through by the paper discharge sensor 112, so that the temperature of the heating roller 51 becomes a standby temperature lower than the printing temperature. When the paper discharge sensor 112 detects the passing of the sheet P, the sheet P has passed through the nip portion N. Therefore, it is preferable to lower the temperature of the heating roller 51. In this case, the CPU 101 controls the heater 53 so that the temperature of the heating roller 51 becomes a standby temperature lower than the printing temperature, thereby being able to suppress the local temperature rise of the heating roller 51 and the pressure roller 52.

[0189] In S121, the CPU 101 starts measuring the elapsed time from the time point when the forward rotation drive of the discharge motor 140 starts. Then, the CPU 101 determines whether the elapsed time from the time point when the forward rotation drive of the discharge motor 140 starts has reached a specified stop time, that is, determines whether the specified stop time has elapsed. In addition, the specified stop time is the elapsed time from the time point when the forward rotation drive of the discharge motor 140 starts until the cutting position A of the sheet P (refer to Figure 6 ) reaches the arranged position B of the cutter 10 (refer to Figure 1 ). The specified stop time is stored in the ROM 102 in advance. For example, the specified stop time is the elapsed time from time T2 to time T6 as shown in Figure 5 .

[0190] Then, when the CPU 101 determines that the elapsed time from the time point when the forward rotation drive of the discharge motor 140 starts has not reached the specified stop time (S121: No), it executes the processing of S121 again. On the other hand, when the CPU 101 determines that the elapsed time from the time point when the forward rotation drive of the discharge motor 140 starts has reached the specified stop time (S121: Yes), it proceeds to the processing of S122.

[0191] In S122, after the CPU 101 stops the discharge motor 140, it proceeds to the processing of S123. For example, as shown in Figure 5 , the CPU 101 stops the discharge motor 140 at time T6 and stops the paper discharge drive. Thus, since the first discharge roller 36 and the second discharge roller 37 stop while clamping the sheet P, the sheet P stops in a state where the cutting position A is at the arranged position B of the cutter 10. That is, the CPU 101 stops the first discharge roller 36 and the second discharge roller 37 when the cutting position A of the sheet P reaches the arranged position B of the cutter 10.

[0192] Through the processing of S121 and S122, when the CPU 101 has passed a specified time since the start of driving the discharge motor 140, it stops the discharge motor 140 to stop the sheet P. Thus, the CPU 101 can appropriately control the first discharge roller 36 and the second discharge roller 37 so that the cutting position A of the sheet P reaches the arrangement position B of the cutter 10.

[0193] In S123, the CPU 101 drives the cutting motor 106 to reciprocate the cutting blade 75 held by the cutter carriage 11 in the width direction of the sheet P. After starting to drive the cutting motor 106, the CPU 101 enters the processing of S1240. For example, as Figure 5 shown, the CPU 101 starts the cutter drive by starting to drive the cutting motor 106 at time T6 and stops the cutting motor 106 at time T7.

[0194] Therefore, the sheet P is bisected into a first sheet P1 and a second sheet P2. Here, after the CPU 101 stops the first discharge roller 36 and the second discharge roller 37, in a state where the main motor 108 is driven to rotate the heating roller 51 or the pressure roller 52, the cutter 10 starts cutting the sheet P.

[0195] Here, based on Figure 5 An example of the fixing temperature of the nip portion N of the heating roller 51 and the pressure roller 52 will be described. In addition, the curve 71 represents the change in the fixing temperature of the nip portion N of the heating roller 51 and the pressure roller 52. The CPU 101 sets the temperature of the heater 53 to the standby temperature at time T5. When the drive of the heater 53 is stopped, as shown by the curve 71, the fixing temperature of the nip portion N starts to decrease from time T5.

[0196] And the CPU 101 is in a state where the main motor 108 is driven to rotate the heating roller 51 or the pressure roller 52 at the time point of driving the cutting motor 106 at time T6. Therefore, the fixing temperature of the nip portion N at time T6 is lower than the fixing temperature of the nip portion N at time T5.

[0197] Therefore, it becomes a state where the sheet P passes through the nip portion N at time T4 and the heating roller 51 and the pressure roller 52 also rotate after the first discharge roller 36 and the second discharge roller 37 stop at time T6. Therefore, it is possible to suppress local temperature rise of the heating roller 51 and the pressure roller 52 at time T6. Therefore, it is possible to suppress a decrease in the durability of the fixing device 5.

[0198] In S1240, the CPU 101 determines whether to stop the main motor 108 after the driving duration of the main motor 108 has elapsed by determining whether the process of S118 has been executed. When the CPU 101 has executed the process of S118 (S1240: Yes), the CPU 101 stops the main motor 108 at the time point when the set driving duration of the main motor 108 has elapsed (S124), and then proceeds to the process of S125.

[0199] For example, as Figure 5 shown, the CPU 101 stops driving the main motor 108 at time T7, stops the heating roller 51 and the pressure roller 52 of the fixing unit 5, and stops the fixing drive. Thereby, when the driving of the main motor 108 is not required, by stopping the driving of the main motor 108, the durability of the heating roller 51, the pressure roller 52, etc. of the fixing unit 5 driven by the main motor 108 can be improved.

[0200] In addition, in S1240, when the CPU 101 has not executed the process of S118 (S1240: No), the CPU 101 does not stop the main motor 108, continuously drives the main motor 108, and proceeds to the process of S125. That is, when the CPU 101 determines that the driving duration of the main motor 108 is equal to or longer than the threshold time, after starting to cut off the driving of the motor 106, the main motor 108 is in a continuously driven state.

[0201] In S125, the CPU 101 restarts the driving of the discharge motor 140, rotates the first discharge roller 36 and the second discharge roller 37, and after discharging the first sheet P1 and the second sheet P2 whose discharge has been cut off, proceeds to the process of S126. For example, as Figure 5 shown, at time T7, the paper discharge drive for rotating the first discharge roller 36 and the second discharge roller 37 is restarted.

[0202] In S126, after the CPU 101 stops the driving of the discharge motor 140, the CPU 101 proceeds to the process of S127. For example, as Figure 5 shown, the CPU 101 stops the discharge motor 140 at time T8 and stops the paper discharge drive.

[0203] Through the processes of S123 to S126, after the CPU 101 cuts the sheet P using the cutter 10, the CPU 101 controls the discharge motor 140 to rotate the first discharge roller 36 and the second discharge roller 37 to discharge the cut sheet P. Then, after the CPU 101 discharges the cut sheet P, the CPU 101 stops the first discharge roller 36 and the second discharge roller 37. Thereby, when the driving of the first discharge roller 36 and the second discharge roller 37 is not required, the first discharge roller 36 and the second discharge roller 37 are stopped, so that the noise generated by the first discharge roller 36 and the second discharge roller 37 can be suppressed.

[0204] In S127, the CPU 101 determines whether there is image data for printing the next sheet P in the printing job being executed. Then, when the CPU 101 determines that there is no image data for printing the next sheet P in the printing job being executed (S127: No), it proceeds to the process of S128. The next sheet P refers to the sheet P picked up from within 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.

[0205] In S128, if the main motor 108 is in operation, the CPU 101 stops the main motor 108 after a predetermined time, for example, after about 2 to 3 seconds or so, and ends Figure 4 the process shown, and returns to the main flowchart. Additionally, if the main motor 108 is not in operation, the CPU 101 ends Figure 4 the process shown and returns to the main flowchart. Moreover, the moment "after a predetermined time" is also the moment "after the driving duration". On the other hand, when the CPU 101 determines that there is image data for printing the next sheet P in the printing job being executed (S127: Yes), it proceeds to the process of S129.

[0206] In S129, the CPU 101 reads from the ROM 102 the printing temperatures of the heating roller 51 and the pressure roller 52 when fixing the image on the sheet P. Then, the CPU 101 sets the temperature of the heating roller 51 to rise to the printing temperature, and after starting the control of the voltage applied to the heater 53, it proceeds to the process of S130. For example, as Figure 5 shown, the CPU 101 sets the temperature of the heating roller 51 to rise to the printing temperature at time T8 and starts the control of the voltage applied to the heater 53.

[0207] Through the process of S129, when the CPU 101 performs continuous printing, after discharging the cut sheet P, it controls the heater 53 to reach the printing temperature. Thus, since the temperature of the heating roller 51 can be appropriately controlled to cope with the printing of the next sheet P, the image can be sufficiently fixed on the next sheet P.

[0208] In S130, if the main motor 108 is stopped, the CPU 101 restarts the driving of the main motor 108, and after rotating the heating roller 51, the pressure roller 52, etc., it proceeds to the process of S131. For example, as Figure 5 shown, at time T9, the fixing drive for rotating the pressure roller 52 and the heating roller 51 of the fixing unit 5 is restarted.

[0209] In S131, 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 feedable temperature. The paper feedable temperature is a temperature higher than the standby temperature. Then, when the CPU 101 determines that the temperature of the heating roller 51 has not reached the paper feedable temperature (S131: No), the process of S131 is executed again.

[0210] On the other hand, when the CPU 101 determines that the temperatures of the heating roller 51 and the pressure roller 52 have reached the paper feedable temperature (S131: Yes), the process of S112 is executed again. Thereafter, for example, in the time period from T10 to T16, the CPU 101 executes the same process as that executed in the time period from T2 to T8. When the next sheet P is picked up by the pickup roller 31, if the main motor 108 is in operation in S128, the main motor 108 is stopped at time T17 after a predetermined time has elapsed.

[0211] Here, when the CPU 101 determines in S117 that the driving duration of the main motor 108 is equal to or longer than the threshold time, the sheet P is cut by the cutter 10 in S123 while the main motor 108 is continuously driven. In addition, after the sheet P is cut while the main motor 108 is continuously driven, the discharge motor 140 is controlled in S125 to rotate the first discharge roller 36 and the second discharge roller 37, and the cut sheet P is discharged.

[0212] Then, the CPU 101 considers the case where the image data for printing the next sheet P is included in the printing job being executed in S127, and the case where the temperatures of the heating roller 51 and the pressure roller 52 are the paper feedable temperature in S131. In this case, while continuously driving the main motor 108, the CPU 101 starts to supply the next sheet P of the sheet P discharged by the first discharge roller 36 and the second discharge roller 37.

[0213] By continuously driving the main motor 108 to cope with the printing of the next sheet P, the CPU 101 can suppress local temperature rise of the heating roller 51 and the pressure roller 52. In addition, since the CPU 101 continuously drives the main motor 108, the time from the start of printing on the sheet P to the end of printing can be shortened compared with the case where the driving of the main motor 108 is stopped.

[0214] In S131, when the temperatures of the heating roller 51 and the pressure roller 52 reach the paper feedable temperature higher than the standby temperature, the CPU 101 conveys the sheet P from the supply tray 21 to the image forming unit 4. As a result, when the sheet P on which the toner has been transferred via the photosensitive drum 61 reaches the nip portion N, the temperature of the heating roller 51 can reliably reach the printing temperature at which the image is fixed on the sheet P. For example, as Figure 5As shown, at time T11, when the top of the sheet P reaches the nip portion N, the fixing temperature of the nip portion N can be reliably set to the printing temperature.

[0215] [Modification Example 1-1]

[0216] Figure 7 is a timing chart showing an example of the relationship between the driving times of the respective driving units and the temperature of the fixing unit 5 in Modification Example 1 of the image forming apparatus 1 according to Embodiment 1. As Figure 7 shown, the CPU 101 may also drive the main motor 108 to rotate forward at time T2 and then stop the main motor 108 at time T17. That is, the CPU 101 may continuously drive the main motor 108 from time T2 to time T17.

[0217] In addition, the CPU 101 may also restart the driving of the discharge motor 140 at time T7 and then stop the discharge motor 140 at time T14 to stop the paper discharge driving. That is, the CPU 101 may continuously drive the discharge motor 140 from time T7 to time T14.

[0218] Here, based on Figure 7 an example of the fixing temperature of the nip portion N of the heating roller 51 and the pressure roller 52 will be described. In addition, the curve 72 represents the change in the fixing temperature of the nip portion N of the heating roller 51 and the pressure roller 52 in Modification Example 1.

[0219] As described above, the CPU 101 continuously drives the main motor 108 from time T2 to time T17. Thus, during the period from time T6 to time T7, even when the discharge motor 140 is stopped, the main motor 108 is driven to rotate the heating roller 51 or the pressure roller 52. Therefore, the fixing temperature of the nip portion N between time T6 and time T7 is lower than the fixing temperature of the nip portion N at time T5.

[0220] Therefore, during the period when the first discharge roller 36 and the second discharge roller 37 are stopped, the heating roller 51 and the pressure roller 52 are in a rotating state. Therefore, it is possible to suppress local temperature rise of the heating roller 51 and the pressure roller 52 between time T6 and time T7. Therefore, it is possible to suppress a decrease in the durability of the fixing unit 5.

[0221] [Modification Example 1-2]

[0222] The CPU 101 may also execute between the process of S116 and the process of S117 Figure 4Processing of S115 as shown. That is, the CPU 101 can also start the forward rotation drive of the discharge motor 140 when the detection signal input from the paper discharge sensor 112 changes from "off" to "on" (S116: Yes), and enter the processing of S117. In this way, the CPU 101 controls the discharge motor 140 based on the time point when the paper discharge sensor 112 detects the sheet P.

[0223] In the processing of S121 and S122, when a predetermined time has elapsed since the start of the drive of the discharge motor 140, the CPU 101 stops the discharge motor 140 to stop the sheet P, but can also stop the discharge motor 140 based on the detection signal input from the alignment post-sensor 111 or the paper discharge sensor 112.

[0224] The paper discharge sensor 112 is arranged on the downstream side of the nip portion N in the conveying direction, so it is arranged at a position closer to the first discharge roller 36 and the second discharge roller 37 than the fixing device 5. In addition, after the paper discharge sensor 112 detects the sheet, the sheet P reaches the first discharge roller 36. Therefore, the CPU 101 controls the discharge motor 140 based on the time point when the paper discharge sensor 112 detects the sheet P, so that the drive of the discharge motor 140 can be started at an appropriate moment, and the rotation drive of the first discharge roller 36 and the second discharge roller 37 can be started.

[0225] [Modification Examples 1-3]

[0226] The CPU 101 can also execute between the processing of S114 and the processing of S115 Figure 4 The processing of S117 as shown. That is, after the CPU 101 starts the image formation of the sheet P by the image forming unit 4 in S114, it can determine whether the drive duration of the main motor 108 based on the number of consecutive printed sheets of the printing job is equal to or longer than the threshold time. In addition, in this case, when the CPU 101 determines "yes" in S117, it enters the processing of S115, and when it determines "no" in S117, after executing the processing of S118, it enters the processing of S115.

[0227] Therefore, after the processing of S114, in order to determine whether to execute the processing of S118, the CPU 101 sets the drive duration of the main motor 108 based on the time point when the alignment post-sensor 111 detects the sheet P in S113.

[0228] The alignment post-sensor 111 is arranged between the photosensitive drum 61 and the registration roller 34. In addition, the registration roller 34 is the conveying roller among the plurality of conveying rollers arranged on the upstream side of the photosensitive drum 61 that is closest to the nip portion N in the conveying direction. Therefore, the alignment post-sensor 111 is arranged on the upstream side of the photosensitive drum 61 as close as possible to the nip portion N.

[0229] Furthermore, after the alignment sensor 111 detects the sheet P after alignment, the sheet P reaches the nip portion N. Therefore, the CPU 101 sets the driving duration of the main motor 108 based on the time point when the alignment sensor 111 detects the sheet P, and thus can stop the driving of the main motor 108 at an appropriate time to stop the heating roller 51.

[0230] [Modification Example 1-4]

[0231] The CPU 101 can also perform the process of determining whether the detection signal input from the alignment sensor 111 changes from "ON" to "OFF" instead of Figure 4 the process of S119 shown. The CPU 101 can also execute this process again when the detection signal input from the alignment sensor 111 does not change from "ON" to "OFF". On the other hand, when the detection signal input from the alignment sensor 111 changes from "ON" to "OFF", the CPU 101 can determine that the passage of the sheet P detected by the alignment sensor 111 is completed and enter the process of S120.

[0232] In this way, the CPU 101 can also control the heater 53 in S120 to make the temperature of the heating roller 51 the standby temperature based on the time point when the alignment sensor 111 detects the completion of the passage of the sheet P.

[0233] After a predetermined time has elapsed since the alignment sensor 111 detects the passage of the sheet P, the sheet P passes through the nip portion N. Therefore, it is preferable to lower the temperature of the heating roller 51 based on the time point when the alignment sensor 111 detects the passage of the sheet P. In this case, the CPU 101 controls the heater 53 to make the temperature of the heating roller 51 the standby temperature lower than the printing temperature, and thus can suppress the local temperature rise of the heating roller 51 and the pressure roller 52.

[0234] [Modification Example 1-5]

[0235] The CPU 101 can also perform the process of determining whether the temperatures of the heating roller 51 and the pressure roller 52 reach the printing temperature via the temperature sensor 54 in Figure 3 S20 shown. The CPU 101 can also execute the above process again when it is determined via the temperature sensor 54 that the temperatures of the heating roller 51 and the pressure roller 52 do not reach the printing temperature. On the other hand, when it is determined via the temperature sensor 54 that the temperatures of the heating roller 51 and the pressure roller 52 reach the printing temperature, the CPU 101 can enter the process of S21.

[0236] Therefore, when the temperature of the heating roller 51 reaches a specified temperature which is higher than the standby temperature for waiting to print on the sheet P, the CPU 101 can also set the electromagnetic clutch 107 to the above-mentioned transmission state in S112 and convey the sheet P from the supply tray 21. This specified temperature is the printing temperature or the allowable paper feeding temperature.

[0237] When the temperature of the heating roller 51 reaches a specified temperature which is higher than the standby temperature, the CPU 101 becomes a state of transmitting the driving force from the main motor 108 to the pickup roller 31 and conveys the sheet P from the supply tray 21. Therefore, in a state where the heat required for fixing is ensured for the heating roller 51, the image can be sufficiently fixed on the sheet P.

[0238] (Embodiment 2)

[0239] Embodiment 2 of the present invention will be described below. In addition, for convenience of description, components having the same functions as those described in Embodiment 1 are denoted by the same reference numerals, and the description thereof will not be repeated.

[0240] Figure 8 It is a sub-flowchart showing an example of the process flow of the print cut-off process in the image forming apparatus according to Embodiment 2. Figure 9 It is a timing chart showing an example of the relationship between the driving timing of each driving unit and the temperature of the fixing unit 5 in the image forming apparatus according to Embodiment 2. In Figure 8 for the process same as the process shown in Figure 4 the same reference numerals as those shown in Figure 4 are added. In addition, the curve 73 represents the change in the fixing temperature of the nip portion N of the heating roller 51 and the pressure roller 52 in Embodiment 2.

[0241] In Embodiment 2, the CPU 101 can also execute, in S21, the sub-process of the print cut-off process shown in Figure 4 instead of the sub-process of the print cut-off process shown in Figure 8 shown. Figure 8 The print cut-off process shown in Figure 4 differs from the print cut-off process shown in

[0242] in that the process of S120 is changed to the process of S211, the processes of S212 and S213 are added, and the process of S129 is changed to the process of S214. Figure 8As shown, after the CPU 101 executes the process of S119, in S211, if the set temperature is a high temperature, the CPU 101 reads from the ROM 102 the printing temperature of the heating roller 51 and the pressure roller 52 when fixing an image on the sheet P. Then, the CPU 101 sets the temperature of the heating roller 51 to be reduced to the printing temperature, and after starting the control of the voltage applied to the heater 53, enters the process of S121.

[0243] For example, as Figure 9 shown, the CPU 101 sets the temperature of the heating roller 51 to be reduced to the printing temperature at time T22, and starts the control of the voltage applied to the heater 53. Time T22 is a time after time T12 and before time T14.

[0244] In addition, when the CPU 101 determines that there is no image data for printing the next sheet P in the printing job being executed (S127: No), it enters the process of S212. In S212, the CPU 101 reads the standby temperature from the ROM 102. Then, the CPU 101 sets the temperature of the heating roller 51 to be reduced to the standby temperature, and after starting the control of the voltage applied to the heater 53, enters the process of S128.

[0245] Furthermore, when the CPU 101 determines that there is image data for printing the next sheet P in the printing job being executed (S127: Yes), it enters the process of S213. In S213, the CPU 101 determines whether it is the temperature rising time based on the pickup time. The pickup time is the time when the CPU 101 turns on the electromagnetic clutch 107 in S112 and sets the driving force of the main motor 108 to be transmitted to the pickup roller 31. The temperature rising time is the time after a specified time from the pickup time and is an example of the start time of sheet P supply.

[0246] When the CPU 101 determines that it is not the temperature rising time based on the pickup time (S213: No), it executes the process of S213 again. On the other hand, when the CPU 101 determines that it is the temperature rising time based on the pickup time (S213: Yes), it enters the process of S214.

[0247] In S214, the CPU 101 reads from the ROM 102 a high temperature higher than the printing temperature. Then, the CPU 101 sets the temperature of the heating roller 51 to rise to the high temperature, and after starting the control of the voltage applied to the heater 53, enters the process of S130. For example, as Figure 9 shown, the CPU 101 sets the temperature of the heating roller 51 to rise to the high temperature at time T21, and starts the control of the voltage applied to the heater 53. Time T21 is a time after time T8 and before time T9.

[0248] As described above, when the CPU 101 starts supplying the next sheet P in a state where the main motor 108 is continuously driven, based on the temperature rise time, the heater 53 is controlled so that the temperature of the heating roller 51 becomes a high temperature higher than the printing temperature. Thereby, when printing on the next sheet P, the heat required for fixing to the heating roller 51 can be ensured, so that the image can be sufficiently fixed to the next sheet P.

[0249] (Embodiment 3)

[0250] [Flow of printing control performed by CPU 101]

[0251] In Embodiment 1 and this embodiment, Figure 3 the processing in the main flowchart showing an example of the flow of printing control performed by the CPU 101 of the image forming apparatus 1 is substantially the same, and the differences will be described. In S13, the CPU 101 starts driving the heater 53. For example, as Figure 11 shown, the CPU 101 starts driving the heater 53 at time T101. That is, the power supply to the heater 53 is started.

[0252] In S17, the CPU 101 determines the cutting position A for bisecting and cutting the sheet P, and stores it in the RAM 103. Specifically, as Figure 12 shown, the CPU 101 determines the cutting position A where the A4-sized sheet P is bisected into the first sheet P1 and the second sheet P2 having equal lengths in the conveying direction as the position of the length L from the top end in the conveying direction, and stores it in the RAM 103.

[0253] The length L is calculated, for example, based on the conveyance amount of the sheet P detected by an encoder (not shown) from when the top end of the sheet P is detected by the post-alignment sensor 111 to when the rear end PL of the sheet P is detected by the post-alignment sensor 111.

[0254] In addition, in S19, after the CPU 101 drives the main motor 108 to rotate forward, the process proceeds to S20. As a result, the pressure roller 52, the photosensitive drum 61, the developing roller 64, and the registration roller 34 rotate in the direction of conveying the sheet P in the conveying direction. As a result, for example, as Figure 11 shown, when the pressure roller 52 or the heating roller 51 in the fuser 5 is rotationally driven at time T102, the temperature rise rate of the fixing temperature in the nip portion N, that is, between the heating roller 51 and the pressure roller 52, becomes slightly slower. Since the processing other than the above processing is the same as the processing in the main flowchart of Embodiment 1, the description thereof is omitted.

[0255] [Sub-process of printing and cutting process]

[0256] Next, based on Figure 10 , an example of the process of the printing and cutting process executed by the CPU 101 in S21, which is a sub-process of the printing and cutting process different from that in Embodiment 1 in this embodiment, will be described. Figure 10 It is a sub-flowchart showing an example of the process of the printing and cutting process. Figure 11 It is a timing chart showing an example of the relationship between the driving time of each driving unit and the temperature of the fixing unit 5. Figure 12 It is a diagram for explaining the cutting of the sheet P through the nip portion N. Figure 13 It is a diagram for explaining the cutting of the paper P by the cutter 10. In addition, Figure 11 The case where the driving duration of the main motor 108 is longer than a threshold time described later is illustrated.

[0257] As Figure 10 shown, in S111, the CPU 101 drives a driving motor (not shown) to move the shutter 8 to the second position and enters the process of S1112. By moving the shutter 8 to the second position, the sheet P is allocated to the conveyance path 201. In addition, when the shutter 8 is already in the second position at the start time of step S1111, the CPU 101 maintains the state where the shutter 8 is in the second position and enters the process of S1112.

[0258] In S1112, the CPU 101 executes a pickup command to pickup the sheet P in the supply tray 21 by the pickup roller 31. Specifically, the CPU 101 turns on the electromagnetic clutch 107 and sets the transmission state in which the driving force of the main motor 108 is transmitted to the pickup roller 31. Subsequently, it enters the process of S1113.

[0259] In S1113, if the discharge motor 140 is in driving, the CPU 101 stops the discharge motor 140 after a predetermined time and enters the process of S1114. Thereby, the sheet P can be reliably discharged. In addition, if the discharge motor 140 is not in driving, the CPU 101 does not execute S1113 after S1112 and enters the process of S1114.

[0260] In S1114, the CPU 101 determines whether the detection signal input from the post-alignment sensor 111 changes from "off" to "on". Specifically, the CPU 101 detects the top end of the conveyed sheet P through the post-alignment sensor 111, obtains the detection signal sent from the post-alignment sensor 111, and thus determines that the detection signal becomes "on".

[0261] Then, when the detection signal input from the post-alignment sensor 111 does not change from "off" to "on" (S1114: No), the CPU 101 executes the process of S1114 again. On the other hand, when the detection signal input from the post-alignment sensor 111 changes from "off" to "on" (S1114: Yes), the CPU 101 determines that the sheet P has passed and proceeds to the process of S1115.

[0262] In S1115, the CPU 101 starts the image formation of 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 based on the image data on the sheet P. That is, the CPU 101 transfers the toner image formed on the photosensitive drum 61 to the sheet P through the transfer roller TR. Then, through the fixing unit 5, the image formed on the sheet P is fixed to the sheet P.

[0263] Next, in S1116, the CPU 101 determines whether the detection signal input from the paper discharge sensor 112 changes from "off" to "on". Specifically, the CPU 101 detects the top end of the conveyed sheet P through the paper discharge sensor 112, obtains the detection signal sent from the paper discharge sensor 112, and thus determines that the detection signal is "on". For example, as Figure 11 shown, the CPU 101 determines that the detection signal input from the paper discharge sensor 112 changes from "off" to "on" at time T103.

[0264] Then, when the detection signal input from the paper discharge sensor 112 does not change from "off" to "on" (S1116: No), the CPU 101 executes the process of S1116 again. On the other hand, when the detection signal input from the paper discharge sensor 112 changes from "off" to "on" (S1116: Yes), the CPU 101 proceeds to the process of S1117.

[0265] In S1117, the CPU 101 determines whether the driving duration of the main motor 108 based on the continuous printing sheet number of the printing job is equal to or greater than the threshold time. The continuous printing sheet number is counted based on, for example, the number of sheets P at the sensor positions such as through the pre-alignment sensor 110. In addition, the continuous printing sheet number can be either the number of printed sheets specified for one printing job or the total number of printed sheets when the sheets P are continuously printed in multiple printing jobs. Furthermore, the continuous printing sheet number can also be the number of printed sheets when the interval between printing jobs is within the specified time even if the printing is interrupted between printing jobs. The driving duration of the main motor 108 based on the continuous printing sheet number corresponds as shown in Table 1 below.

[0266] [Table 2]

[0267] Number of consecutive printed sheets Drive duration More than 60 sheets 30 seconds 30 to 59 sheets 20 seconds 10 to 29 sheets 15 seconds Less than 10 sheets 3 seconds

[0268] When the number of continuously printed sheets is more than 60, the driving duration of the main motor 108 is 30 seconds. When the number of continuously printed sheets is from 30 to 59, the driving duration of the main motor 108 is 20 seconds. When the number of continuously printed sheets is from 10 to 29, the driving duration of the main motor 108 is 15 seconds. When the number of continuously printed sheets is less than 10, the driving duration of the main motor 108 is 3 seconds.

[0269] Thus, when the CPU 101 executes continuous printing in which a plurality of sheets P are continuously printed, the driving duration of the main motor 108 is set according to the number of printed sheets of the sheet P. In addition, the driving duration in the case where the heating roller 51 and the pressure roller 52 have a layer made of rubber is preferably longer than the driving duration in the case where the heating roller 51 and the pressure roller 52 do not have such a layer and the surface is coated.

[0270] The threshold time is, for example, 20 seconds. Then, when it is determined that the driving duration of the main motor 108 based on the number of continuously printed sheets of the printing job is equal to or more than the threshold time (S1117: Yes), the process proceeds to S1119 described later.

[0271] On the other hand, when it is determined that the driving duration of the main motor 108 based on the number of continuously printed sheets of the printing job is less than the threshold time (S1117: No), the process proceeds to the process of S1118. In S1118, the CPU 101 determines to execute the process of stopping the main motor 108 after the driving duration of the main motor 108 has elapsed, and proceeds to the process of S1119. That is, in S1118, the CPU 101 sets the actual driving duration of the main motor 108 to the time set in S16 or S17.

[0272] Through the process of S1117, the CPU 101 sets the driving duration of the main motor 108 at the time point when the sheet P is detected by the paper discharge sensor 112 in order to determine whether to execute the process of S1118.

[0273] The paper discharge sensor 112 is arranged on the downstream side of the nip portion N in the conveying direction. Therefore, after the sheet P reaches the nip portion N, the paper discharge sensor 112 detects the sheet P. Therefore, the CPU 101 sets the driving duration of the main motor 108 based on the time point when the paper discharge sensor 112 detects the sheet P, and thus can stop the driving of the main motor 108 at an appropriate moment to stop the heating roller 51.

[0274] In S1119, the CPU 101 determines whether the detection signal input from the paper discharge sensor 112 changes from "ON" to "OFF". Specifically, after the paper discharge sensor 112 detects the top end of the conveyed sheet P, the CPU 101 cannot obtain the detection signal sent from the paper discharge sensor 112 because the rear end of the sheet P passes through, and thus determines that the detection signal has changed to "OFF".

[0275] Then, when the detection signal input from the paper discharge sensor 112 does not change from "ON" to "OFF" (S1119: NO), the CPU 101 executes the process of S1119 again. On the other hand, when the detection signal input from the paper discharge sensor 112 changes from "ON" to "OFF" (S1119: YES), the CPU 101 determines that the paper discharge sensor 112 has detected the completion of the passage of the sheet P and proceeds to the process of S1120.

[0276] For example, as Figure 11 shown, when the detection signal input from the paper discharge sensor 112 changes from "ON" to "OFF" at time T104, the CPU 101 determines that the paper discharge sensor 112 has detected the completion of the passage of the sheet P. That is, the CPU 101 determines that the rear end PL of the sheet P has passed through the nip portion N.

[0277] In S1120, the CPU 101 reads from the ROM 102 the standby temperatures of the heating roller 51 and the pressure roller 52 when waiting for the sheet P to be conveyed. Then, the CPU 101 sets the temperature of the heating roller 51 to be reduced to the standby temperature, for example, about 130°C, and after starting the control of the voltage applied to the heater 53, proceeds to the process of S1121. The standby temperature is a temperature lower than the printing temperature. For example, as Figure 11 shown, the CPU 101 stops the drive of the heater 53 at time T5. At the moment of time T105, the sheet P has completed passing between the heating roller 51 and the pressure roller 52, that is, through the nip portion N.

[0278] Through the process of S1120, the CPU 101 controls the heater 53 based on the time point when the paper discharge sensor 112 detects the completion of the passage of the sheet P so that the temperature of the heating roller 51 becomes the standby temperature lower than the printing temperature. After the sheet P has passed through the paper discharge sensor 112, the heater 53 is controlled so that the temperature of the heating roller 51 becomes the standby temperature lower than the printing temperature. Therefore, before the start of cutting the sheet P by the cutter 10, the temperature of the heating roller 51 can be reduced. Thereby, local heating of the heating roller 51 and the pressure roller 52 can be suppressed.

[0279] In S1121, the CPU 101 starts the forward rotation drive of the motor 140 to rotate the first discharge roller 36 and the second discharge roller 37, and enters the process of S1122. Thus, the first discharge roller 36 and the second discharge roller 37 rotate in the direction of conveying the sheet P along the conveying direction. In S1121, the CPU 101 starts the drive of the motor 140 based on the time point when the sheet P is detected by the post-alignment sensor 111. For example, as Figure 11 shown, the CPU 101 rotates the discharge motor 140 at time T106 to start the paper discharge drive.

[0280] Therefore, as in the processes of S1114 and S1121, the CPU 101 controls the discharge motor 140 based on the time point when the post-alignment sensor 111 detects the sheet P. The post-alignment sensor 111 is disposed between the photosensitive drum 61 and the registration roller 34. In addition, the registration roller 34 is the conveying roller among the plurality of conveying rollers disposed on the upstream side of the image forming unit 4 that is closest to the first discharge roller 36 and the second discharge roller 37 in the conveying direction. Therefore, the post-alignment sensor 111 is disposed on the upstream side of the image forming unit 4 as close as possible to the first discharge roller 36 and the second discharge roller 37.

[0281] Furthermore, after the post-alignment 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 point when the post-alignment sensor 111 detects the sheet P, so that the drive of the discharge motor 140 can be started at an appropriate moment, and the rotation drive of the first discharge roller 36 and the second discharge roller 37 can be started.

[0282] In S1122, the CPU 101 starts measuring the elapsed time from the time point when the forward rotation drive of the discharge motor 140 starts. Then, the CPU 101 determines whether the elapsed time from the time point when the forward rotation drive of the discharge motor 140 starts has reached a specified stop time, that is, determines whether a specified stop time has elapsed. In addition, the specified stop time is the elapsed time from the time point when the forward rotation drive of the discharge motor 140 starts until the cutting position A of the sheet P (refer to Figure 12 ) reaches the configuration position B of the cutter 10 (refer to Figure 1 ). The specified stop time is stored in the ROM 102 in advance. For example, the specified stop time is the elapsed time from time T106 to time T107 as shown in Figure 11 .

[0283] Then, when the CPU 101 determines that the elapsed time from the start of the forward rotation drive of the discharge motor 140 has not reached the specified stop time (S1122: No), the process of S1122 is executed again. On the other hand, when the CPU 101 determines that the elapsed time from the start of the forward rotation drive of the discharge motor 140 has reached the specified stop time (S1122: Yes), the process proceeds to S1123.

[0284] In S1123, after the CPU 101 stops the discharge motor 140, the process proceeds to S1124. For example, as Figure 11 shown, the CPU 101 stops the discharge motor 140 at time T107 and stops the paper discharge drive. As a result, since the first discharge roller 36 and the second discharge roller 37 stop while clamping the sheet P, the sheet P stops in a state where the cutting position A is located at the configuration position B of the cutter 10. That is, the CPU 101 stops the first discharge roller 36 and the second discharge roller 37 when the cutting position A of the sheet P reaches the configuration position B of the cutter 10.

[0285] Through the processes of S1122 and S1123, when the specified time has elapsed since the start of the drive of the discharge motor 140, the CPU 101 stops the discharge motor 140 to stop the sheet P. Thus, the CPU 101 can appropriately control the first discharge roller 36 and the second discharge roller 37 so that the cutting position A of the sheet P reaches the configuration position B of the cutter 10.

[0286] In S1124, the CPU 101 drives the cutting motor 106 to reciprocate the blade 75 held by the cutter carriage 11 in the width direction of the sheet P. After the CPU 101 starts driving the cutting motor 106, the process proceeds to S1125. For example, as Figure 11 shown, the CPU 101 starts the cutter drive by starting the drive of the cutting motor 106 at time T107 and stops the cutting motor 106 at time T109. As a result, the sheet P is bisected into a first sheet P1 and a second sheet P2.

[0287] In S1125, the CPU 101 determines whether there is image data for printing the next sheet P in the printing job being executed. The next sheet P refers to the sheet P 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. When the CPU 101 determines that there is image data for printing the next sheet P in the printing job being executed (S1125: Yes), the process proceeds to S1126.

[0288] In S1126, the CPU 101 reads the printing temperatures of the heating roller 51 and the pressure roller 52 when fixing an image on the sheet P from the ROM 102. Then, the CPU 101 sets to raise the temperature of the heating roller 51 to the printing temperature, and after starting the control of the voltage applied to the heater 53, enters the process of S1127. For example, as Figure 11 shown, the CPU 101 sets to raise the temperature of the heating roller 51 to the printing temperature at time T108 and starts the control of the voltage applied to the heater 53.

[0289] The CPU 101 performs the process of S1126 before the cutting of the sheet by the cutter is completed. Here, with reference to Figure 13 , the cutting of the sheet by the cutter will be described. Figure 13 The cutter 10 located at the standby position SP in the standby state without the cutting paper is shown. When the CPU 101 drives the cutting motor 106 to rotate forward, the cutter carriage 11 moves in the forward direction D1, and thus the sheet P is cut. Subsequently, the CPU 101 drives the cutting motor 106 to perform reverse rotation opposite to the forward rotation, moves the cutter carriage 11 in the return direction D2, and positions the cutter carriage 11 at the standby position SP. Then, the CPU 101 stops the cutting motor 106, and the cutting of the sheet P is completed.

[0290] In addition, the CPU 101 may also be structured as follows: after moving the cutter carriage 11 in the forward direction D1 to cut the sheet P, the cutting motor 106 is stopped, and after moving the cutter carriage 11 in the return direction D2 to cut the subsequently conveyed sheet P, the cutting motor 106 is stopped to complete the cutting.

[0291] Here, an example of the fixing temperature of the nip portion N of the heating roller 51 and the pressure roller 52 will be described based on Figure 11 . In addition, the curve 711 represents the change in the fixing temperature of the nip portion N of the heating roller 51 and the pressure roller 52. When the CPU 101 sets the temperature of the heater 53 to the standby temperature at time T105 and stops the driving of the heater 53, as shown by the curve 711, the fixing temperature of the nip portion N starts to drop from time T105.

[0292] Then, the CPU 101 is in a state of driving the main motor 108 to rotate the heating roller 51 or the pressure roller 52 from time T106 to time T108. Therefore, the fixing temperature of the nip portion N from time T106 to time T108 is lower than the fixing temperature of the nip portion N at time T105.

[0293] Before the cutting of the sheet P by the cutter 10 is completed, the CPU 101 drives the main motor 108 and controls the heater 53, which is for controlling the temperature of the heating roller 51 to the standby temperature, so that the temperature of the heating roller 51 is controlled to the printing temperature. Therefore, the temperature of the nip portion N can be made uniform during the cutting of the sheet P, and the conveyance start of the next sheet can be accelerated. Thereby, the decrease in the printing speed during continuous printing can be alleviated.

[0294] In addition, according to the structure in which the CPU 101 executes S1126 after S1124, the heater 53, which is controlled to the standby temperature before the driving of the discharge motor 140, is controlled so as to become the printing temperature after the start of the cutting of the sheet P by the cutter 10. Thereby, the temperature of the heating roller 51 can be appropriately controlled in response to the printing of the next sheet P. In addition, the time from the completion of the cutting of the sheet P to the heater 53 becoming the printing temperature can be accelerated. Thereby, the decrease in the printing speed can be alleviated.

[0295] In S1127, if the main motor 108 is stopped, the CPU 101 restarts the driving of the main motor 108, and after rotating the heating roller 51, the pressure roller 52, etc., enters the process of S1128. In addition, if the main motor 108 is not stopped, the CPU 101 does not execute S1127 after S1126 and enters the process of S1128.

[0296] In S1128, the CPU 101 restarts the driving of the discharge motor 140, rotates the first discharge roller 36 and the second discharge roller 37, and after discharging the cut first sheet P1 and second sheet P2, enters the process of S1129. For example, as Figure 11 shown, at time T109, the paper discharge drive for restarting the rotation of the first discharge roller 36 and the second discharge roller 37 is performed.

[0297] In S1129, 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 supply temperature. The paper supply temperature is a temperature higher than the standby temperature. Then, when the CPU 101 determines that the temperature of the heating roller 51 has not reached the paper supply temperature (S1129: No), the process of S1129 is executed again.

[0298] On the other hand, when the CPU 101 determines that the temperatures of the heating roller 51 and the pressure roller 52 have reached the paper supply temperature (S1129: Yes), the process of S1112 is executed again. In addition, in the process of S1113 executed again, the CPU 101 stops the discharge motor 140, which was driven in the process of S1128, after a predetermined time. For example, as Figure 11As shown, at time T110 after a specified time, the discharge motor 140 is stopped to stop the paper discharge drive. Thereafter, for example, at times T111 to T115, the CPU 101 executes the same processing as that executed at times T103 to T107.

[0299] Here, when the CPU 101 determines in S1117 that the drive duration of the main motor 108 is equal to or longer than the threshold time, while continuously driving the main motor 108, the sheet P is cut by the cutter 10 in S1124. Further, after cutting the sheet P while continuously driving the main motor 108, the CPU 101 controls the discharge motor 140 to rotate the first discharge roller 36 and the second discharge roller 37 in S1128 to discharge the cut sheet P.

[0300] Then, the CPU 101 considers the case where there is image data for printing the next sheet P in the printing job being executed in S1125, and determines in S1129 that the temperatures of the heating roller 51 and the pressure roller 52 are at the paper feedable temperature. In this case, while continuously driving the main motor 108, the CPU 101 starts the supply of the next sheet P of the sheet P discharged by the first discharge roller 36 and the second discharge roller 37. Thereby, the CPU 101 continuously drives the main motor 108 in response to the printing of the next sheet, and thus can suppress the local temperature rise of the heating roller 51 and the pressure roller 52.

[0301] Then, when the CPU 101 determines that there is no image data for printing the next sheet P in the printing job being executed (S1125: No), the process proceeds to the process of S1130. In S1130, the CPU 101 restarts the drive of the discharge motor 140 to rotate the first discharge roller 36 and the second discharge roller 37, and after discharging the cut first sheet P1 and second sheet P2, the process proceeds to the process of S1131. For example, as Figure 11 shown, at time T116, the paper discharge drive for rotating the first discharge roller 36 and the second discharge roller 37 is restarted.

[0302] In S1131, after the CPU 101 stops the drive of the discharge motor 140, the process proceeds to the process of S1132. For example, as Figure 11 shown, the CPU 101 stops the discharge motor 140 at time T117 to stop the paper discharge drive.

[0303] Through the processing of S1124, S1128, S1130, and S1131, after the CPU 101 cuts the sheet P using the cutter 10, it controls the discharge motor 140 to rotate the first discharge roller 36 and the second discharge roller 37 to discharge the cut sheet P. Then, after discharging the cut sheet P, the CPU 101 stops the first discharge roller 36 and the second discharge roller 37. Thus, without the need to drive the first discharge roller 36 and the second discharge roller 37, the first discharge roller 36 and the second discharge roller 37 are stopped, thereby suppressing the noise generated by the first discharge roller 36 and the second discharge roller 37.

[0304] In S1132, if the main motor 108 is in operation, the CPU 101 stops the main motor 108 after a specified time, for example, after about 2 to 3 seconds. For example, as Figure 11 shown, the CPU 101 stops driving the main motor 108 at time T118, stops the heating roller 51 and the pressure roller 52 of the fuser 5, and stops the fusing drive. After S1128, the CPU 101 ends Figure 10 the process shown, and the main flowchart also ends. In addition, the moment of "after a specified time" is also the moment of "after the drive duration".

[0305] [Variant Example 3-1]

[0306] Figure 14 is a timing chart showing an example of the relationship between the driving times of each drive unit and the temperature of the fuser 5 in Variant Example 1 of the image forming apparatus 1 according to Embodiment 3. Figure 14 An example is illustrated where the drive duration of the main motor 108 is shorter than a threshold time described later. In addition, the curve 721 represents the change in the fusing temperature at the nip portion N of the heating roller 51 and the pressure roller 52.

[0307] As Figure 14 shown, the CPU 101 can also stop the main motor 108 after the sheet discharge sensor 112 detects the completion of the passage of the sheet P at time T104 and before raising the temperature of the heating roller 51 to the printing temperature at time T108. That is, the CPU 101 can stop the main motor 108 between time T104 and time T108.

[0308] Specifically, in Figure 10In S1117, when the CPU 101 determines that the driving duration of the main motor 108 is less than the threshold time based on the continuous number of printed sheets of the printing job (S1117: No), it proceeds to the process of S1118. The CPU 101 decides in S1118 to stop the main motor 108 after the driving duration of the main motor 108 has elapsed. According to the decision in S1118, the CPU 101 stops the main motor 108 before the temperature of the heating roller 51 rises to the printing temperature in S1126. For example, as Figure 14 shown, the CPU 101 stops the main motor 108 at time T121 between time T104 and time T108.

[0309] In Figure 10 the S1127 shown, the CPU 101 restarts the driving of the stopped main motor 108, rotates the heating roller 51, the pressure roller 52, etc., and then proceeds to the process of S1128. For example, as Figure 14 shown, the CPU 101 drives the main motor 108 at time T122.

[0310] As described above, the CPU 101 stops the driving of the main motor 108 between time T104 and time T108. Thus, during the period from time T104 to time T108, that is, during the period from when the heater 53 is stopped to when the driving of the heater 53 is restarted, the main motor 108 is stopped. For example, in the case of a small number of printed sheets, even if the driving duration is shortened, the temperature of the nip portion N can be made lower than the fixing temperature at time T105.

[0311] [Modification Example 3-2]

[0312] The CPU 101 may also execute the process of S1121 shown Figure 10 between the process of S1116 and the process of S1117. That is, the CPU 101 may start the forward driving of the discharge motor 140 when the detection signal input from the paper discharge sensor 112 changes from "off" to "on" (S1116: Yes), and then proceed to the process of S1117. In this way, the CPU 101 controls the discharge motor 140 based on the time point when the sheet P is detected by the paper discharge sensor 112.

[0313] In the processes of S1121 and S1122, the CPU 101 stops the discharge motor 140 to stop the sheet P when a predetermined time has elapsed since the start of the driving of the discharge motor 140, but it may also stop the discharge motor 140 based on the detection signal input from the alignment post-sensor 111 or the paper discharge sensor 112.

[0314] The paper discharge sensor 112 is arranged on the downstream side of the nip portion N in the conveying direction, and thus is arranged at a position closer to the first discharge roller 36 and the second discharge roller 37 than the fixing unit 5. In addition, after the paper discharge sensor 112 detects the sheet, the sheet P reaches the first discharge roller 36. Therefore, the CPU 101 controls the discharge motor 140 based on the time point when the paper discharge sensor 112 detects the sheet P, and thus can start the drive of the discharge motor 140 at an appropriate time and start the rotational drive of the first discharge roller 36 and the second discharge roller 37.

[0315] [Modification Example 3-3]

[0316] The CPU 101 may also execute Figure 10 the process of S1117 shown. That is, the CPU 101 may also determine whether the drive duration of the main motor 108 based on the number of consecutive printed sheets of the printing job is equal to or longer than the threshold time after starting the image formation of the sheet P by the image forming unit 4 in S1114. In addition, in this case, when the CPU 101 determines "yes" in S1117, it proceeds to the process of S1115, and when it determines "no" in S1117, after executing the process of S1118, it proceeds to the process of S1115.

[0317] Therefore, after the process of S1114, the CPU 101 sets the drive duration of the main motor 108 based on the time point when the alignment sensor 111 detects the sheet P in S1113 in order to determine whether to execute the process of S1118.

[0318] The alignment sensor 111 is arranged between the photosensitive drum 61 and the registration roller 34. In addition, the registration roller 34 is the conveying roller among the plurality of conveying rollers arranged on the upstream side of the image forming unit 4 that is closest to the nip portion N in the conveying direction. Therefore, the alignment sensor 111 is arranged on the upstream side of the image forming unit 4 at a position as close as possible to the nip portion N.

[0319] Furthermore, after the alignment sensor 111 detects the sheet P, the sheet P reaches the nip portion N. Therefore, the CPU 101 sets the drive duration of the main motor 108 based on the time point when the alignment sensor 111 detects the sheet P, and thus can stop the drive of the main motor 108 at an appropriate time to stop the heating roller 51.

[0320] [Modification Example 3-4]

[0321] The CPU 101 may also replace Figure 10The CPU 101 executes a process of determining whether the detection signal input from the post-alignment sensor 111 changes from "ON" to "OFF" by means of the process of S1119 shown. The CPU 101 may also execute this process again when the detection signal input from the post-alignment sensor 111 does not change from "ON" to "OFF". On the other hand, when the detection signal input from the post-alignment sensor 111 changes from "ON" to "OFF", the CPU 101 may determine that the post-alignment sensor 111 has detected the completion of the passage of the sheet P and proceed to the process of S1120.

[0322] In this way, the CPU 101 can also control the heater 53 in S1120 based on the time point when the post-alignment sensor 111 detects the completion of the passage of the sheet P, so that the temperature of the heating roller 51 becomes the standby temperature.

[0323] By controlling the heater 53 based on the detection result of the post-alignment sensor 111, after passing the post-alignment sensor 111, the heater 53 is controlled so that the temperature of the heating roller 51 becomes a standby temperature lower than the printing temperature. Therefore, before the start of cutting the sheet P by the cutter 10, the temperature of the heating roller 51 can be reduced. Thereby, local temperature rise of the nip portion N can be suppressed.

[0324] [Modification Example 3-5]

[0325] The CPU 101 may also execute a process of determining whether the temperatures of the heating roller 51 and the pressure roller 52 reach the printing temperature via the temperature sensor 54 in Figure 3 S20 shown. The CPU 101 may also execute the above process again when it is determined via the temperature sensor 54 that the temperatures of the heating roller 51 and the pressure roller 52 do not reach the printing temperature. On the other hand, when it is determined via the temperature sensor 54 that the temperatures of the heating roller 51 and the pressure roller 52 reach the printing temperature, the CPU 101 may proceed to the process of S21.

[0326] Therefore, when the temperature of the heating roller 51 reaches a specified temperature which is higher than the standby temperature for waiting to print on the sheet P, that is, the printing temperature or the paper feed allowable temperature, the CPU 101 sets it to the above transmission state by the electromagnetic clutch 107 in S112 and conveys the sheet P from the supply tray 21.

[0327] When the temperature of the heating roller 51 reaches a specified temperature which is higher than the standby temperature, that is, the CPU 101 becomes a state of transmitting the driving force from the main motor 108 to the pickup roller 31 and conveys the sheet P from the supply tray 21. Therefore, in a state where the heat required for fixing is ensured for the heating roller 51, the image can be sufficiently fixed on the sheet P.

[0328] (Embodiment 4)

[0329] [Flow of printing control performed by CPU101]

[0330] In Embodiment 1 and the present embodiment, Figure 3 the processing in the main flowchart showing an example of the flow of printing control performed by the CPU101 of the image forming apparatus 1 is substantially the same, and the differences will be described. In S13, the CPU101 starts driving the heater 53. For example, as Figure 5 shown, the CPU101 starts driving the heater 53 at time T201. That is, the power supply to the heater 53 is started.

[0331] In S19, after the CPU101 drives the main motor 108 to rotate forward, it enters the processing of S20. As a result, the pressure roller 52, the photosensitive drum 61, the developing roller 64, and the registration roller 34 rotate in the direction of conveying the sheet P along the conveying direction. As a result, for example, as Figure 5 shown, when the pressure roller 52 or the heating roller 51 of the fixing device 5 is rotationally driven at time T202, the temperature rising speed of the fixing temperature in the nip portion N, that is, between the heating roller 51 and the pressure roller 52, becomes slightly slower. Since the processing other than the above-mentioned processing is the same as the processing of the main flowchart of Embodiment 1, the description thereof is omitted.

[0332] [Sub - processing of printing cut - off processing]

[0333] Next, based on Figure 15 , an example of the flow of the printing cut - off processing executed by the CPU101, which is a sub - processing of the printing cut - off processing different from Embodiment 1 in the present embodiment, will be described. Figure 15 is a sub - flowchart showing an example of the flow of the printing cut - off processing in the present embodiment. As Figure 15 shown, in S2111, the CPU101 drives a driving motor (not shown) to move the shutter 8 to the second position and enters the processing of S2112. By moving the shutter 8 to the second position, the sheet P is distributed to the conveying path 201. In addition, when the shutter 8 is already in the second position at the start time of step S2111, the CPU101 maintains the state where the shutter 8 is in the second position and enters the processing of S2112.

[0334] In S2112, the CPU101 executes a pickup command to pick up the sheet P in the supply tray 21 by the pickup roller 31. Specifically, the CPU101 turns on the electromagnetic clutch 107 and sets it to a state where the driving force of the main motor 108 is transmitted to the pickup roller 31. Subsequently, it enters the processing of S2113.

[0335] In S2113, if the discharge motor 140 is in drive, after a specified time has elapsed, for example, after about 2 to 3 seconds or so, the CPU 101 stops the discharge motor 140 and proceeds to the process of S2114. Thereby, the sheet P can be reliably discharged. Further, if the discharge motor 140 is not in drive, the CPU 101 does not execute S2113 after S2112 and proceeds to the process of S2114.

[0336] In S2114, the CPU 101 determines whether the detection signal input from the post-alignment sensor 111 has changed from "off" to "on". Specifically, the CPU 101 detects the top end of the conveyed sheet P through the post-alignment sensor 111, obtains the detection signal transmitted from the post-alignment sensor 111, and thereby determines that the detection signal has changed to "on".

[0337] Then, when the detection signal input from the post-alignment sensor 111 has not changed from "off" to "on" (S2114: No), the CPU 101 executes the process of S2114 again. On the other hand, when the detection signal input from the post-alignment sensor 111 has changed from "off" to "on" (S2114: Yes), the CPU 101 proceeds to the process of S2115.

[0338] In S2115, the CPU 101 starts measuring the elapsed time from the time point when the detection signal input from the post-alignment sensor 111 has changed from "off" to "on", and proceeds to the process of S2116. In S2116, the CPU 101 starts image formation of 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 based on the image data on the sheet P. That is, the CPU 101 transfers the toner image formed on the photosensitive drum 61 to the sheet P through the transfer roller TR. Then, through the fixing unit 5, the image formed on the sheet P is fixed to the sheet P.

[0339] Next, in S2117, the CPU 101 starts the forward rotation drive of the discharge motor 140 to rotate the first discharge roller 36 and the second discharge roller 37, and proceeds to the process of S2118. Thereby, for example, as Figure 16 shown, at time T202, the paper discharge drive for rotating the first discharge roller 36 and the second discharge roller 37 is started.

[0340] In S2118, the CPU 101 determines whether the detection signal input from the paper discharge sensor 112 changes from "off" to "on". Specifically, the CPU 101 detects the top end of the conveyed sheet P through the paper discharge sensor 112, obtains the detection signal sent from the paper discharge sensor 112, and thus determines that the detection signal is "on". Then, when the detection signal input from the paper discharge sensor 112 does not change from "off" to "on" (S2118: No), the CPU 101 executes the process of S2118 again. On the other hand, when the detection signal input from the paper discharge sensor 112 changes from "off" to "on" (S2118: Yes), the CPU 101 proceeds to the process of S2119.

[0341] In S2119, the CPU 101 determines whether the elapsed time since the detection signal of the alignment sensor 111, which started measurement in S2115 above, changed from "off" to "on" has reached a specified time, that is, whether the specified time has elapsed. This specified time is an example of the "first time". For example, the specified time is Figure 16 the elapsed time from time T202 to time T203 as shown.

[0342] Then, when the CPU 101 determines that the elapsed time since the detection signal of the alignment sensor 111 changed from "off" to "on" has not reached the specified time, that is, the specified time has not elapsed (S2119: No), the CPU 101 executes the process of S2119 again. On the other hand, when the CPU 101 determines that the elapsed time since the detection signal of the alignment sensor 111 changed from "off" to "on" has reached the specified time, that is, the specified time has elapsed (S2119: Yes), the CPU 101 proceeds to the process of S2120.

[0343] In S2120, the CPU 101 reads the standby temperatures of the heating roller 51 and the pressure roller 52 when waiting for the sheet P to be conveyed from the ROM 102. Then, the CPU 101 sets the temperature of the heating roller 51 to be reduced to the standby temperature, for example, about 130°C, and after starting the control of the voltage applied to the heater 53, proceeds to the process of S2121.

[0344] For example, as Figure 16 shown, the CPU 101 stops the drive of the heater 53 at time T203. Here, as Figure 16 shown, the drive of the heater 53 is stopped at the moment of time T203, but at the moment of time T203, the sheet P has not completed passing through between the heating roller 51 and the pressure roller 52, that is, the nip portion N. Specifically, for example, the moment when the drive of the heater 53 is stopped is Figure 17The moment when the position A2 of the sheet P shown passes through the nip portion N. The position A2 is the length L1 of the length from the rear end PL of the sheet toward the front side in the conveying direction. In order to reliably fix the image onto the sheet P, this length L1 is preferably equal to or less than the circumference of one rotation of the heating roller 51.

[0345] In S2121, the CPU 101 determines whether the detection signal input from the paper discharge sensor 112 changes from "ON" to "OFF". Specifically, after the CPU 101 detects the leading end of the conveyed sheet P by the paper discharge sensor 112, since the rear end of the sheet P passes through and the detection signal sent from the paper discharge sensor 112 cannot be obtained, it is determined that the detection signal has changed to "OFF".

[0346] Then, when the detection signal input from the paper discharge sensor 112 does not change from "ON" to "OFF" (S2121: NO), the CPU 101 executes the process of S2121 again. On the other hand, when the detection signal input from the paper discharge sensor 112 changes from "ON" to "OFF" (S2121: YES), the CPU 101 determines that the paper discharge sensor 112 has detected the completion of the passage of the sheet P and proceeds to the process of S2122.

[0347] For example, as Figure 16 shown, at time T204, when the detection signal input from the paper discharge sensor 112 changes from "ON" to "OFF", the CPU 101 determines that the paper discharge sensor 112 has detected the completion of the passage of the sheet P. That is, the CPU 101 determines that the rear end PL of the sheet P has passed through the nip portion N. Therefore, the CPU 101 can stop the driving of the heater 53 in advance by (time T204 - time T203) compared to the time point (time T204) when the rear end PL of the sheet P has passed through the nip portion N.

[0348] In S2122, the CPU 101 starts measuring the elapsed time from the time point when the detection signal input from the paper discharge sensor 112 changes from "ON" to "OFF". Then, the CPU 101 determines whether the elapsed time from the time point when the detection signal input from the paper discharge sensor 112 changes from "ON" to "OFF" has reached a specified stop time, that is, whether the specified stop time has elapsed. In addition, the specified stop time is the elapsed time from the time point when the detection signal input from the paper discharge sensor 112 changes from "ON" to "OFF" until the cutting position A of the sheet P (refer to Figure 17 ) reaches the configuration position B of the cutter 10 (refer to Figure 1 ). The specified stop time is stored in the ROM 102 in advance. For example, the specified stop time is Figure 16 the elapsed time from time T204 to time T205 as shown.

[0349] Then, when the CPU 101 determines that the time elapsed from the time point when the detection signal input from the paper discharge sensor 112 changes from "ON" to "OFF" has not reached the prescribed stop time (S2122: No), the CPU 101 executes the process of S2122 again. On the other hand, when the CPU 101 determines that the time elapsed from the time point when the detection signal input from the paper discharge sensor 112 changes from "ON" to "OFF" has reached the prescribed stop time (S2122: Yes), the CPU 101 proceeds to the process of S2123.

[0350] In S2123, CPU 101 stops main motor 108 and then proceeds to S2124. Figure 16 As shown, at time T205, the driving of the main motor 108 is stopped, the heating roller 51 and the pressure roller 52 of the fixing device 5 are stopped, and the fixing drive is stopped. Thus, when the driving of the main motor 108 is not needed, by stopping the driving of the main motor 108, the durability of the heating roller 51, the pressure roller 52, etc. of the fixing device 5 driven by the main motor 108 can be improved.

[0351] In S2124, the CPU 101 stops the discharge motor 140 and then proceeds to S2125. Figure 16 As shown, at time T205, the discharge motor 140 is stopped to stop the paper discharge drive. As a result, since the first discharge roller 36 and the second discharge roller 37 stop in a state of clamping the sheet P, the sheet P is at the cutting position A (refer to Figure 17 ) is located at the configuration position B of the cutter 10 (refer to Figure 1 ) state.

[0352] In S2125, the CPU 101 drives the cutting motor 106 to reciprocate the blade 75 held by the cutter carriage in the width direction of the sheet P, and proceeds to S2126. Figure 16 As shown, the cutter driving is started by starting the driving of the cutting motor 106 at time T205, and the cutting motor 106 is stopped at time T206. Thus, the sheet P is cut into two equal parts, namely, the first sheet P1 and the second sheet P2.

[0353] Here, based on Figure 16 An example of the fixing temperature of the nip portion N of the heating roller 51 and the pressure roller 52 when the sheet P is cut will be described. Figure 17 ) The change in the fixing temperature of the nip portion N when the setting temperature of the heater 53 is set to the standby temperature, for example, about 130° C. The solid line curve 72 represents the change in the fixing temperature of the nip portion N at the position A2 of the sheet P (refer to Figure 17)The time T203 when passing through the nip portion N, the set temperature of the heater 53 is set to the standby temperature, for example, the change in the fixing temperature of the nip portion N when set to about 130°C.

[0354] As shown by the dashed curve 71, when the temperature of the heater 53 is set to the standby temperature at time T204 and the driving of the heater 53 is stopped, the fixing temperature in the nip portion N at time T205 when the main motor 108 is stopped is temperature Q1. Then, after the main motor 108 is stopped at time T205, the fixing temperature in the nip portion N during the cutting of the sheet P by the cutter 10 rises to temperature Q2.

[0355] On the other hand, as shown by the solid curve 72, when the temperature of the heater 53 is set to the standby temperature at time T203 and the driving of the heater 53 is stopped, the fixing temperature in the nip portion N at time T205 when the main motor 108 is stopped is temperature R1 which is lower than temperature Q1. Then, after the main motor 108 is stopped at time T205, the fixing temperature in the nip portion N during the cutting of the sheet P by the cutter 10 rises to temperature R2 which is lower than temperature Q2.

[0356] Therefore, at time T203 when passing through the nip portion N at a position A2 which is at a distance L1 from the rear end PL of the sheet P in the front side of the conveying direction (refer to Figure 17 ), the set temperature of the heater 53 is set to the standby temperature. Thereby, it is possible to raise the fixing temperature in the nip portion N during the cutting of the sheet P by the cutter 10 to temperature R2 which is lower than temperature Q2. As a result, during the cutting of the sheet P, it is possible to suppress the local temperature rise of the nip portion N of the heating roller 51 and the pressure roller 52, and it is possible to suppress the deterioration of the durability of the heating roller 51, the pressure roller 52, etc. of the fixing device 5.

[0357] Return to Figure 15 , in S2126, the CPU 101 determines whether there is image data for printing the next sheet P in the printing job being executed. Then, when the CPU 101 determines that there is no image data for printing the next sheet P in the printing job being executed (S2126: No), it proceeds to the process of S2127. In S2127, the CPU 101 restarts the driving of the discharge motor 140 to rotate the first discharge roller 36 and the second discharge roller 37. After discharging the cut first sheet P1 and second sheet P2, it proceeds to the process of S2128.

[0358] In S2128, the CPU 101 stops the driving of the discharge motor 140, ends Figure 15 the flow shown, and returns to the main flow chart.

[0359] On the other hand, in the above S2126, when the CPU101 determines that there is image data for printing the next sheet P in the printing job being executed (S2126: Yes), it proceeds to the process of S2129. In S2129, the CPU101 restarts the drive of the discharge motor 140 to rotate the first discharge roller 36 and the second discharge roller 37. After discharging the cut first sheet P1 and second sheet P2, it proceeds to the process of S2130. In S2130, the CPU101 restarts the drive of the main motor 108 to rotate the heating roller 51, the pressure roller 52, etc., and then proceeds to the process of S2131.

[0360] For example, as Figure 16 shown, the CPU101 stops the cutting motor 106 at time T206. In addition, the CPU101 restarts the drive of 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 second sheet P2. In addition, at time T206, the CPU101 starts the drive of the main motor 108 simultaneously with the start of the drive of the discharge motor 140 to restart the rotation of the heating roller 51, the pressure roller 52, etc.

[0361] In S2131, the CPU101 reads from the ROM102 the printing temperatures of the heating roller 51 and the pressure roller 52 when fixing the image on the sheet P. Then, the CPU101 sets the temperature of the heating roller 51 to rise to the printing temperature, for example, about 190 °C. After starting the control of the voltage applied to the heater 53, it proceeds to the process of S2132. For example, as Figure 16 shown, the CPU101 sets the temperature of the heating roller 51 to rise to the printing temperature at time T207 and starts the control of the voltage applied to the heater 53.

[0362] In S2132, the CPU101 determines via the temperature sensor 54 whether the temperatures of the heating roller 51 and the pressure roller 52 have reached the paper feedable temperature. Then, when the CPU101 determines that the temperatures of the heating roller 51 and the pressure roller 52 have not reached the paper feedable temperature (S2132: No), it executes the process of S2132 again.

[0363] On the other hand, when the CPU101 determines that the temperatures of the heating roller 51 and the pressure roller 52 have reached the paper feedable temperature (S2132: Yes), it executes the process of S2112 again.

[0364] Thus, when the temperatures of the heating roller 51 and the pressure roller 52 reach the paper supply temperature higher than the standby temperature, the sheet P is conveyed from the supply tray 21 to the image forming unit 4. As a result, when the sheet P onto which the toner has been transferred via the photosensitive drum 61 reaches the nip portion N, the temperatures of the heating roller 51 and the pressure roller 52 can reliably reach the printing temperature at which the image is fixed to the sheet P. For example, as Figure 16 shown, at time T208, when the top end of the sheet P reaches the nip portion N, the fixing temperature of the nip portion N can be reliably set to the printing temperature, for example, about 190°C.

[0365] [Various Modification Examples]

[0366] [Modification Example 4-1]

[0367] In the above-described embodiment, in Figure 15 shown in S2119, the CPU 101 determines whether a predetermined time has elapsed since the detection signal from the alignment post-sensor 111 changed from "off" to "on", but it is not limited thereto. For example, the CPU 101 may also determine whether a predetermined time has elapsed since the detection signal input from the paper discharge sensor 112 changed from "off" to "on". This predetermined time is an example of the "second time".

[0368] Then, when the CPU 101 determines that the elapsed time since the detection signal from the paper discharge sensor 112 changed from "off" to "on" has not reached the predetermined second time, that is, when the predetermined second time has not elapsed (S2119: No), the CPU 101 executes the process of S2119 again. On the other hand, when the CPU 101 determines that the elapsed time since the detection signal from the paper discharge sensor 112 changed from "off" to "on" has reached the predetermined second time, that is, when the predetermined second time has elapsed (S2119: Yes), the CPU 101 proceeds to the process of S2120.

[0369] Thus, when the sheet P is cut by the cutter 10, the temperature of the heating roller 51 becomes lower than the printing temperature at which the image is fixed to the sheet P, so that local heating of the nip portion N where the pressure roller 52 abuts against the heating roller 51 can be suppressed. As a result, a decrease in the durability of the heating roller 51, the pressure roller 52, etc. of the fixing unit 5 can be suppressed.

[0370] [Modification Example 4-2]

[0371] In the above-described embodiment, in Figure 15In S2129 to S2130 shown, the CPU 101 starts driving the main motor 108 simultaneously with the start of driving the discharge motor 140, but it is not limited thereto. For example, in S2129, 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 second sheet P2. Then, in S2130, the CPU 101 may also restart driving the discharge motor 140, and after discharging the cut first sheet P1 and second sheet P2, start driving the main motor 108. Thus, for printing the next sheet P, the temperature of the heating roller 51 can be appropriately controlled.

[0372] [Modification Example]

[0373] The image forming apparatus 1 of the above-described embodiment is a monochrome laser printer, but it is not limited thereto, and it may also be a color laser printer.

[0374] [Modification Example]

[0375] The above-described embodiment of the image forming apparatus 1 has been described for the case where the sheet P is cut in half, but it is not limited thereto. For example, the sheet P may be cut into three equal parts, and the cutting position A of the sheet P can be appropriately changed.

[0376] [Modification Example]

[0377] The above-described embodiment of the image forming apparatus 1 receives a printing job through the communication I / F 130, but it is not limited thereto. For example, the printing job may also be received through a USB interface.

[0378] (Matters to be Noted)

[0379] The present invention is not limited to the above-described embodiments, and various changes can be made within the scope of the invention to be protected. Embodiments obtained by appropriately combining the technical means separately disclosed in different embodiments are also included in the technical scope of the present invention.

[0380] Reference Signs

[0381] 1 Image Forming Apparatus, 4 Image Forming Unit, 5 Fixer, 10 Cutter, 21 Supply Tray, 31 Pickup Roller, 34 Registration Roller, 36 First Discharge Roller, 37 Second Discharge Roller, 51 Heating Roller, 52 Pressing Roller, 53 Heater, 61 Photosensitive Drum, 64 Developing Roller, 65 Charger, 101 CPU, 107 Electromagnetic Clutch, 108 Main Motor, 111 Post-Alignment Sensor, 112 Paper Discharge Sensor, 140 Discharge Motor, A Cutting Position, B Arrangement Position of Cutter, N Roll Gap Portion, P Sheet, TR Transfer Roller.

Claims

1. An image forming apparatus, characterized in that, Comprising: A processing unit that forms an image on a sheet; A fixing unit having a heating rotator, a heater, and a pressing rotator, the heater heating the heating rotator, forming a nip portion between the pressing rotator and the heating rotator, and the fixing unit fixing the image on the sheet; A discharge roller disposed downstream of the fixing unit in the sheet conveyance direction and used to discharge the sheet; A main motor that transmits driving force to at least the heating rotator or the pressing rotator; A cutter disposed downstream of the fixing unit in the conveyance direction and cutting the sheet; And A control unit, The control unit controls the heater to make the temperature of the fixing unit the first temperature at which the image is fixed on the sheet, The control unit controls the main motor to rotate the heating rotator or the pressing rotator to convey the sheet, When the cutting position in the sheet reaches the position where the cutter is disposed, the control unit stops the discharge roller, and then controls the cutter to cut the sheet through the cutter, At the time point when the cutting of the sheet starts by the cutter, the control unit sets the target value of the temperature of the fixing unit to a second temperature lower than the first temperature and controls the heater, or the control unit drives the main motor and controls the main motor to rotate the heating rotator or the pressing rotator.

2. The image forming apparatus according to claim 1, wherein It further comprises a discharge motor that transmits driving force to the discharge roller, The control unit controls the discharge motor to rotate the discharge roller to convey the sheet that has passed through the nip portion, and stops the discharge roller when the cutting position in the sheet reaches the position where the cutter is disposed, After the control unit stops the discharge roller, in a state where the main motor is driven to rotate the heating rotator or the pressing rotator, the control unit starts the cutting of the sheet by the cutter.

3. The image forming apparatus according to claim 2, wherein The processing unit has a photosensitive drum, The image forming apparatus comprises: A registration roller disposed upstream of the photosensitive drum in the conveyance direction and being the conveyance roller closest to the photosensitive drum among the plurality of conveyance rollers for conveying the sheet; A first sheet sensor disposed between the photosensitive drum and the registration roller in the conveyance direction and capable of detecting the passage of the sheet, The control unit controls the discharge motor based on the time point when the first sheet sensor detects the sheet.

4. The image forming apparatus according to claim 2, wherein The fixing unit has a second sheet sensor disposed downstream of the nip portion in the conveyance direction and capable of detecting the passage of the sheet, The control unit controls the discharge motor based on the time point when the second sheet sensor detects the sheet.

5. The image forming apparatus according to claim 2, wherein When a predetermined time has elapsed since the start of driving of the discharge motor, the control unit stops the discharge motor to stop the sheet.

6. The image forming apparatus according to claim 2, wherein in the case of performing continuous printing in which a plurality of sheets are continuously printed, the control unit sets a driving duration of the main motor according to the number of printed sheets of the sheet, when the driving duration is equal to or longer than a threshold time, in a state where the main motor is continuously driven, after the sheet is cut by the cutter, the control unit controls the discharge motor to rotate the discharge roller, discharges the cut sheet, and starts supplying the next sheet of the sheet discharged through the discharge roller.

7. The image forming apparatus according to claim 6, wherein the fixing unit has a second sheet sensor that is disposed on the downstream side of the nip portion in the transport direction and can detect the passage of the sheet, the control unit sets the driving duration based on the time point when the second sheet sensor detects the passage of the sheet.

8. The image forming apparatus according to claim 7, wherein the control unit controls the heater so that the temperature of the fixing unit becomes a second temperature lower than the first temperature based on the time point when the second sheet sensor detects the completion of the passage of the sheet.

9. The image forming apparatus according to claim 6, wherein the processing unit has a photosensitive drum, the image forming apparatus includes: a registration roller that is disposed on the upstream side of the photosensitive drum in the transport direction and is the transport roller closest to the photosensitive drum among the plurality of transport rollers that transport the sheet; and a first sheet sensor that is disposed between the photosensitive drum and the registration roller in the transport direction and can detect the passage of the sheet, the control unit sets the driving duration based on the time point when the first sheet sensor detects the passage of the sheet.

10. The image forming apparatus according to claim 9, wherein the control unit controls the heater so that the temperature of the fixing unit becomes a second temperature lower than the first temperature based on the time point when the first sheet sensor detects the completion of the passage of the sheet.

11. The image forming apparatus according to claim 8, wherein after the sheet is cut by the cutter, the control unit controls the discharge motor to rotate the discharge roller and discharges the cut sheet, in the case of performing continuous printing in which a plurality of sheets are continuously printed, after discharging the cut sheet, the control unit controls the heater to become the first temperature.

12. The image forming apparatus according to claim 6, wherein when starting to supply the next sheet in a state where the main motor is continuously driven, the control unit controls the heater so that the temperature of the fixing unit becomes a third temperature higher than the first temperature based on the supply start time of the sheet.

13. The image forming apparatus according to claim 2, wherein After the sheet is cut by the cutter, the control unit controls the discharge motor to rotate the discharge roller and discharge the cut sheet. After discharging the cut sheet, the control unit stops the discharge roller.

14. The image forming apparatus according to claim 2, wherein: The processing unit includes a photosensitive drum, a developing roller, and a transfer unit. The developing roller supplies toner to the photosensitive drum, and the transfer unit transfers the toner supplied to the photosensitive drum to a sheet. The photosensitive drum and the developing roller are rotated by receiving driving force from the main motor.

15. The image forming apparatus according to claim 2, wherein Comprising: A supply tray on which a sheet is placed; A pickup roller that conveys the sheet from the supply tray to the processing unit by receiving driving force from the main motor; And 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. When the temperature of the fixing unit reaches a specified temperature, which is higher than the standby temperature for waiting to print on the sheet, the control unit sets the clutch to the transmission state and conveys the sheet from the supply tray.

16. The image forming apparatus according to claim 1, wherein: It further includes a discharge motor that transmits driving force to the discharge roller. The control unit controls the discharge motor to rotate the discharge roller to convey the sheet that has passed through the nip portion, and stops the discharge roller when the cutting position in the sheet reaches the position where the cutter is disposed. After the heating rotating body or the pressing rotating body starts to rotate and before stopping the discharge roller, the control unit controls the heater so that the target value of the temperature of the fixing unit becomes a second temperature lower than the first temperature. When performing continuous printing in which a plurality of sheets are continuously printed, before the cutting of the sheet by the cutter is completed, the control unit controls the heater so that the temperature of the fixing unit becomes the first temperature.

17. The image forming apparatus according to claim 16, wherein: The processing unit includes a photosensitive drum. The image forming apparatus includes: A registration roller that is disposed upstream of the photosensitive drum in the conveying direction and is the conveying roller closest to the photosensitive drum among the plurality of conveying rollers for conveying the sheet; And A first sheet sensor that is disposed between the photosensitive drum and the registration roller in the conveying direction and can detect the passage of the sheet. The control unit controls the discharge motor based on the time point when the first sheet sensor detects the sheet.

18. The image forming apparatus according to claim 16, wherein: The fixing unit includes a second sheet sensor that is disposed downstream of the nip portion in the conveying direction and can detect the passage of the sheet. The control unit controls the discharge motor based on the time point when the second sheet sensor detects the sheet.

19. The image forming apparatus according to claim 16, wherein: When a predetermined time has elapsed since the start of driving of the discharge motor, the control unit stops the discharge motor to stop the sheet.

20. The image forming apparatus according to claim 16, wherein the fixing unit has a second sheet sensor that is disposed downstream of the nip portion in the conveying direction and is capable of detecting the passage of a sheet, the control unit controls the heater based on the time point when the second sheet sensor detects the completion of the passage of the sheet so that the target value of the temperature of the fixing unit becomes the second temperature.

21. The image forming apparatus according to claim 16, wherein the processing unit has a photosensitive drum, the image forming apparatus includes: a registration roller that is disposed upstream of the photosensitive drum in the conveying direction and is the conveying roller closest to the photosensitive drum among the plurality of conveying rollers for conveying a sheet; and a first sheet sensor that is disposed between the photosensitive drum and the registration roller in the conveying direction and is capable of detecting the passage of a sheet, the control unit controls the heater based on the time point when the first sheet sensor detects the completion of the passage of the sheet so that the target value of the temperature of the fixing unit becomes the second temperature.

22. The image forming apparatus according to claim 16, wherein in the case of performing continuous printing, the control unit sets the driving duration of the main motor according to the number of printed sheets of the sheet, when the driving duration is equal to or longer than a threshold time, in a state where the main motor is continuously driven, after the sheet is cut by the cutter, the control unit controls the discharge motor to rotate the discharge roller, discharges the cut sheet, and starts supplying the next sheet of the sheet discharged through the discharge roller.

23. The image forming apparatus according to claim 22, wherein the fixing unit has a second sheet sensor that is disposed downstream of the nip portion in the conveying direction and is capable of detecting the passage of a sheet, the control unit sets the driving duration based on the time point when the second sheet sensor detects the sheet.

24. The image forming apparatus according to claim 22, wherein the processing unit has a photosensitive drum, the image forming apparatus includes: a registration roller that is disposed upstream of the photosensitive drum in the conveying direction and is the conveying roller closest to the photosensitive drum among the plurality of conveying rollers for conveying a sheet; and a first sheet sensor that is disposed between the photosensitive drum and the registration roller in the conveying direction and is capable of detecting the passage of a sheet, the control unit sets the driving duration based on the time point when the first sheet sensor detects the sheet.

25. The image forming apparatus according to claim 16, wherein in the case of performing continuous printing, after the start of cutting of the sheet by the cutter, the control unit controls the heater so that the temperature of the fixing unit becomes the first temperature.

26. The image forming apparatus according to claim 16, wherein: after the sheet is cut by the cutter, the control unit controls the discharge motor to rotate the discharge roller, and discharges the cut sheet; after discharging the cut sheet, the control unit stops the discharge roller.

27. The image forming apparatus according to claim 16, wherein: the processing unit includes a photosensitive drum, a developing roller, and a transfer unit, the developing roller supplies toner to the photosensitive drum, and the transfer unit transfers the toner supplied onto the photosensitive drum to a sheet; the photosensitive drum and the developing roller are rotated by receiving driving force transmitted from the main motor.

28. The image forming apparatus according to claim 16, wherein It includes: a supply tray for placing a sheet; a pickup roller that conveys the sheet from the supply tray to the processing unit by receiving driving force transmitted from the main motor; and 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; when the temperature of the fixing unit reaches a specified temperature, which is a temperature higher than the standby temperature waiting for printing on the sheet, the control unit sets the clutch to the transmission state and conveys the sheet from the supply tray.

29. The image forming apparatus according to claim 1, wherein: before the rear end of the sheet passes through the nip portion, the control unit sets the target value of the temperature of the fixing unit to a second temperature lower than the first temperature and controls the heater; the control unit rotates the discharge roller to convey the sheet that has passed through the nip portion, stops the discharge roller when the cutting position in the sheet reaches the position where the cutter is disposed, and then cuts the sheet by the cutter.

30. The image forming apparatus according to claim 29, wherein: after the rear end of the sheet passes through the nip portion, the control unit stops driving the main motor.

31. The image forming apparatus according to claim 29, wherein: the processing unit includes a photosensitive drum, the image forming apparatus includes: a registration roller that is disposed upstream of the photosensitive drum in the conveying direction and is the conveying roller closest to the photosensitive drum among the plurality of conveying rollers for conveying the sheet; and a first sheet sensor that is disposed between the photosensitive drum and the registration roller in the conveying direction and can detect the passage of the sheet; when a first time has elapsed since the time when the first sheet sensor detects the sheet, the control unit sets the target value of the temperature of the fixing unit to the second temperature and controls the heater.

32. The image forming apparatus according to claim 29, wherein: the fixing unit includes a second sheet sensor that is disposed downstream of the nip portion in the conveying direction and can detect the passage of the sheet. When a second time has elapsed since the time point when the sheet is detected by the second sheet sensor, the control unit sets the target value of the temperature of the fixing unit to the second temperature and controls the heater.

33. The image forming apparatus according to claim 32, wherein: The control unit stops driving the main motor based on the time point when the second sheet sensor detects the completion of the passage of the sheet.

34. The image forming apparatus according to claim 29, wherein: It includes a discharge motor that transmits driving force to the discharge roller.

35. The image forming apparatus according to claim 34, wherein: The processing unit has a photosensitive drum, The image forming apparatus includes: A registration roller that is disposed upstream of the photosensitive drum in the conveying direction and is the conveying roller closest to the photosensitive drum among the plurality of conveying rollers for conveying the sheet; And A first sheet sensor that is disposed between the photosensitive drum and the registration roller in the conveying direction and can detect the passage of the sheet, The control unit starts driving the discharge motor based on the time point when the first sheet sensor detects the sheet.

36. The image forming apparatus according to claim 35, wherein: When a third time has elapsed since the start of driving of the discharge motor, the control unit stops the discharge motor to stop the sheet.

37. The image forming apparatus according to claim 35, wherein: The fixing unit has a second sheet sensor that is disposed downstream of the nip portion in the conveying direction and can detect the passage of the sheet, The control unit stops the discharge motor to stop the sheet based on the time point when the second sheet sensor detects the completion of the passage of the sheet.

38. The image forming apparatus according to claim 34, wherein: After the sheet is cut by the cutter, the control unit controls the discharge motor to rotate the discharge roller to discharge the cut sheet, In the case of performing continuous printing in which a plurality of sheets are continuously printed, after discharging the cut sheet, the control unit drives the main motor, The control unit controls the heater so that the temperature of the fixing unit becomes the first temperature.

39. The image forming apparatus according to claim 34, wherein: After the sheet is cut by the cutter, the control unit controls the discharge motor to rotate the discharge roller to discharge the cut sheet, In the case of performing continuous printing in which a plurality of sheets are continuously printed, the control unit drives the main motor simultaneously with the start of driving of the discharge motor, The control unit controls the heater so that the temperature of the fixing unit becomes the first temperature.

40. The image forming apparatus according to claim 34, wherein: After the sheet is cut by the cutter, the control unit controls the discharge motor to rotate the discharge roller to discharge the cut sheet, After discharging the sheet, the control unit stops the discharge motor to stop the discharge roller.

41. The image forming apparatus according to claim 29, wherein the processing 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 rotate by the driving force of the main motor.

42. The image forming apparatus according to claim 29, wherein, It includes: a supply tray on which sheets are placed; a pickup roller that conveys the sheet from the supply tray to the processing unit by being transmitted 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, when the temperature of the fixing unit reaches the sheet supply temperature higher than the second temperature, the control unit switches the clutch to the transmission state and transmits the driving force from the main motor to the pickup roller, the control unit conveys the sheet from the supply tray to the processing unit.

43. The image forming apparatus according to claim 29, wherein when, in the sheet, at the moment when a position that is one perimeter distance away from the heating rotating body on the downstream side in the conveying direction from the rear end of the sheet passes through the nip portion and before the rear end of the sheet passes through the nip portion, the control unit sets the target value of the temperature of the fixing unit to the second temperature and controls the heater.

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