Image forming apparatus

Abstract

To provide a technique that can cut a sheet at a desired cut position even if the sheet shrinks due to heat of a fuser applied to the sheet.SOLUTION: A CPU 101 executes: conveying processing (S218, S220) for conveying a sheet S along a conveyance path 201 by using a plurality of conveying rollers 35, 36, 85 to 87, correcting an amount of rotation of a first ejection roller 85 and a second ejection roller 86 for an ideal cut position CP of the sheet S passing through a part of the conveyance path 201 to reach a cutter position B, based on results of detection performed by a sheet detection sensor SE4 and an ejection sensor SE3, rotating the first ejection roller 85 and the second ejection roller 86 by the corrected amount of rotation, and subsequently stopping the first ejection roller 85 and the second ejection roller 86; and cutting processing (S222) for, after the conveying processing, cutting the sheet S in a cutting direction by using a cutter 10.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] This application relates to an image forming apparatus that cuts an image-formed sheet with a cutter.

Background Art

[0002] Patent Document 1 describes an image forming apparatus that conveys a sheet sent out from an image forming unit to the position of a cutter and cuts the sheet in a direction orthogonal to the conveyance direction at the central portion in the conveyance direction of the sheet. This image forming apparatus includes a sheet detection unit that controls a branch guide in response to detecting the sheet and discharges the cut sheet separately to a first discharge tray and a second discharge tray.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in an image forming apparatus configured to pass a sheet on which an image is formed by an image forming unit through a fixing device to fix the image on the sheet, the sheet may shrink due to the heat applied to the sheet by the fixing device. In the image forming apparatus described in Patent Document 1, the shrinkage of the sheet due to the heat applied to the sheet by the fixing device is not considered, so there is a possibility that the sheet cannot be accurately cut at the central portion in the conveyance direction of the sheet.

[0005] An object of this application is to provide a technique that enables the sheet to be cut at a desired cutting position even when the sheet shrinks due to the heat applied to the sheet by the fixing device.

Means for Solving the Problems

[0006] To achieve the above objective, the present invention provides an image forming apparatus comprising: an apparatus body having a sheet transport path; a heating rotating body; a pressurizing rotating body that forms a nip between itself and the heating rotating body; a fixer for fixing an image formed on a sheet to the sheet; a plurality of transport rollers having a first discharge roller located downstream of the fixer in the sheet transport direction along the transport path and transporting the sheet, and a second discharge roller located downstream of the first discharge roller in the transport direction and discharging the sheet transported by the first discharge roller to the outside of the apparatus body; a cutter located at a cutter position between the first discharge roller and the second discharge roller in the transport direction and capable of cutting the sheet in a cutting direction intersecting the transport direction; and between the first discharge roller and the second discharge roller in the transport direction The system comprises a first sensor that detects whether or not a sheet is present at a first detection position, a second sensor that detects whether or not a sheet is present at a second detection position between a first discharge roller and a fuser in the transport direction, and a control unit. The control unit, in a transport process in which a sheet is transported along a transport path using a plurality of transport rollers, corrects the amount of rotation of the first and second discharge rollers so that the ideal cutting position of the sheet passing through a part of the transport path reaches the cutter position, based on the detection results of the first and second sensors, and after rotating the first and second discharge rollers by the corrected amount of rotation, it performs a transport process in which the first and second discharge rollers are stopped, and after the transport process, it performs a cutting process in which the sheet is cut in the cutting direction using a cutter.

[0007] According to the image forming apparatus of the present invention, the amount of rotation of the first discharge roller and the second discharge roller for the ideal sheet cutting position to reach the cutter position is determined by the detection of the first sensor and the second sensor. Based on the results, the rotation is corrected, and after the first and second discharge rollers rotate by the corrected amount, they stop and the sheet is cut at that stopping position. Therefore, even if the sheet shrinks due to the heat applied to it by the fuser, it is possible to cut the sheet at the desired cutting position.

[0008] Furthermore, the control unit is characterized in that, during the transport process, it acquires a first timing when the front end of the sheet reaches a first detection position based on the detection result of the first sensor, and a second timing when the rear end of the sheet reaches a second detection position based on the detection result of the second sensor, and corrects the amount of rotation of the first discharge roller and the second discharge roller based on the acquired first and second timings.

[0009] This allows the sheet length to be measured precisely, making it possible to cut the sheet at the desired cutting position even if the sheet shrinks due to the heat applied by the fuser.

[0010] Furthermore, the image forming apparatus of the present invention further comprises a main motor that rotates either a heating rotating body or a pressurizing rotating body included in the fuser, and an discharge motor that rotates a first discharge roller and a second discharge roller, and the control unit controls the main motor and the discharge motor so that the rotation speed of the discharge motor is faster than the rotation speed of the main motor.

[0011] As a result, even if the sheet flexes while passing through the fuser, the first and second discharge rollers increase the sheet's transport speed, making it possible to eliminate the flexing of the sheet.

[0012] Furthermore, the image forming apparatus of the present invention further comprises a memory, in which the amount of rotation of the first discharge roller and the second discharge roller required to transport the sheet from the second detection position of the second sensor to the first detection position of the first sensor is pre-stored as the first rotation amount. The control unit, in the transport process, acquires the amount of rotation of the first discharge roller and the second discharge roller required from the first timing to the second timing as the second rotation amount, acquires the sheet length in the transport direction of the sheet after passing through the fuser based on the first rotation amount and the second rotation amount, determines the cutting position on the sheet from the acquired sheet length, and stops the rotational drive of the discharge motor.

[0013] This eliminates the need to measure predetermined fixed values, making it possible to obtain the sheet length in the sheet's transport direction more accurately.

[0014] Furthermore, the control unit is characterized in that, after acquiring the second timing, it controls the discharge motor to rotate until the determined cutting position on the sheet reaches the cutter position.

[0015] This allows the sheet to be stopped when the determined cutting position on the sheet reaches the cutter position.

[0016] Furthermore, the discharge motor is a stepping motor, and the control unit controls the stopping timing of the discharge motor based on the number of steps of the stepping motor.

[0017] This makes it possible to control the stopping timing of the discharge motor by simply counting the number of steps of the stepping motor.

[0018] Furthermore, the first sensor is located upstream of the cutter position in the transport direction, the first rotation amount is indicated by the number of steps of the stepping motor, and the memory contains the rotation amounts of the first and second discharge rollers required to transport the sheet from the first detection position of the first sensor to the cutter position, with the rotation amount indicated by the number of steps of the stepping motor being the third rotation amount. It is stored in advance, and in the transport process, the control unit acquires the second rotation amount as the number of steps of the stepping motor, and after acquiring the second timing, The discharge motor is controlled to rotate for a duration of {first rotation - (first rotation + second rotation) / 2 + third rotation}.

[0019] This makes it possible to accurately cut the sheet in the center of the conveying direction by simply counting the number of steps of the stepping motor, even if the sheet shrinks due to the heat applied by the fuser.

[0020] Further, the first sensor is located on the downstream side in the conveyance direction from the cutter position, the first rotation amount is indicated by the number of steps of the stepping motor, and in the memory, the first discharge roller and the second discharge roller required to convey the sheet from the cutter position to the first detection position of the first sensor The rotation amount, which is the rotation amount indicated by the number of steps of the stepping motor, is stored in advance as the third rotation amount. In the conveyance process, the control unit acquires the second rotation amount as the number of steps of the stepping motor, and after acquiring the second timing, { First rotation amount - (First rotation amount + Second rotation amount) / 2 - Third rotation amount}, control is performed to rotationally drive the discharge motor.

[0021] Thereby, even if the sheet shrinks due to the heat applied to the sheet by the fixing device, it is possible to accurately cut at the center in the conveyance direction of the sheet by a simple method of counting the number of steps of the stepping motor.

[0022] The apparatus main body includes a first discharge path that is a part of the conveyance path and discharges the sheet to the outside of the apparatus main body via the cutter position, and a second discharge path that is a part of the conveyance path and is different from the first discharge path and discharges the sheet to the outside of the apparatus main body. And a flapper that guides the sheet to either one of the first discharge path and the second discharge path. The control unit receives a print job including information on whether or not cutting of the sheet by the cutter is necessary, and when it is determined that cutting of the sheet is necessary based on the print job, the position of the flapper is moved to guide the sheet to the first discharge path. When it is determined that cutting of the sheet is not necessary based on the print job, the position of the flapper is moved to guide the sheet to the second discharge path.

[0023] Thereby, when cutting of the sheet is necessary, the flapper guides the sheet to the first discharge path, and when cutting of the sheet is not necessary, the flapper guides the sheet to the second discharge path, which is convenient. [[ID=十六]] [[ID=十七]]

Brief Description of the Drawings

[0024] [Figure 1] It is a cross-sectional view showing a schematic configuration of a monochrome laser printer according to the first embodiment of the present application. [Figure 2] It is a perspective view showing a schematic configuration of a cutter included in the monochrome laser printer of FIG. 1. [Figure 3] It is a block diagram showing a control configuration of the monochrome laser printer of FIG. 1. [Figure 4] It is a diagram for explaining problems that occur when cutting a shrunk sheet and countermeasures therefor. [Figure 5] It is a flowchart showing the procedure of printing processing in the monochrome laser printer of FIG. 1. [Figure 6] It is a flowchart showing the detailed procedure of sheet printing and cutting processing included in the printing processing of FIG. 5. [Figure 7] It is a flowchart showing the detailed procedure of sheet conveyance processing to the cutter position included in the printing processing of FIG. 5. [Figure 8] It is a flowchart showing the detailed procedure of sheet cutting processing included in the printing processing of FIG. 5. [Figure 9] It is a diagram for explaining the sheet conveyance processing to the cutter position of FIG. 7. [Figure 10] It is a diagram following FIG. 9 for explaining the sheet conveyance processing to the cutter position of FIG. 7. [Figure 11] It is a cross-sectional view showing a schematic configuration of a monochrome laser printer according to the second embodiment of the present application. [Figure 12] It is a flowchart showing the procedure of sheet conveyance processing to the cutter position in the monochrome laser printer of FIG. 11. [Figure 13] It is a diagram for explaining the sheet conveyance processing to the cutter position of FIG. 12.

Embodiments for Carrying out the Invention

[0025] Hereinafter, embodiments of the present application will be described in detail based on the drawings.

[0026] (First Embodiment) Figure 1 is a cross-sectional view showing the schematic configuration of a monochrome laser printer 1 according to the first embodiment of the present application. The monochrome laser printer 1 is an example of an image forming apparatus. Hereinafter, the monochrome laser printer 1 will be abbreviated as printer 1. Printer 1 comprises a main body 2, a transport unit 3, an image forming unit 4, a fuser 6, a cutter 10, and an operation panel PA. Hereinafter, for the sake of convenience of explanation, the vertical and horizontal directions of printer 1 will be defined as shown by the arrows in Figure 1. Also, the side of the paper facing you will be defined as left, and the side facing you will be defined as right.

[0027] The device body 2 includes a front cover 21, a supply tray 31, an output tray 22, a transport path 201, and a re-transport path 202. The front cover 21 is attached to the front of the device body 2 in a manner that allows it to be opened and closed. The supply tray 31 is attached to the bottom of the device body 2 in a manner that allows it to be attached and detached. A sheet S is placed on the supply tray 31. The sheet S is a standard-sized sheet, such as A4 size. The sheet S is a paper medium such as plain paper or cardboard, but is not limited to this, and may also be OHP film. The output tray 22 is provided on the top of the device body 2, and the sheet S on which the image is formed is placed on the output tray 22.

[0028] The transport path 201 is a path for transporting the sheet S placed on the supply tray 31 along the transport direction towards the discharge tray 22 via the image forming unit 4. The transport path 201 branches from the first branching position D1 into the first discharge path 201A and the second discharge path 201B. In other words, the sheet S transported via the image forming unit 4 is either discharged to the discharge tray 22 via the first discharge path 201A or discharged to the discharge tray 22 via the second discharge path 201B.

[0029] The re-transport path 202 is a path for transporting the sheet S, on which an image has been formed on one side, inverted and again toward the image forming unit 4. The re-transport path 202 branches off from the transport path 201 at the second branching position D2 and rejoins the transport path 201 at the merging position J on the upstream side of the transport direction of the pre-register sensor SE1.

[0030] The transport unit 3 includes a pickup roller 33, a separation roller 34, a registration roller 35, a roller 36, a first discharge roller 85, a second discharge roller 86, a third discharge roller 87, a flapper 88, re-transport rollers 38, 39, a main motor 108 (see Figure 3), and a discharge motor 109 (see Figure 3). The multiple transport rollers include a pickup roller 33, a separation roller 34, registration rollers 35, a roller 36, a first discharge roller 85, a second discharge roller 86, and a third discharge roller 87. The printer 1 uses these multiple transport rollers to transport the sheet S along the transport path 201.

[0031] The pickup roller 33 picks up the sheets S in the supply tray 31 that have been pushed upward by the sheet pressing plate 32 and transports them toward the transport path 201. The separation roller 34 separates the sheets S picked up by the pickup roller 33 one by one.

[0032] The registration roller 35 is positioned upstream of the image forming unit 4 in the transport path 201. After aligning the direction of the front end of the sheet S, the registration roller 35 transports the sheet S toward the image forming unit 4. The transport direction of the registration roller 35 is from front to back. The roller 36 transports the sheet S after it has passed through the fuser 6 toward the first discharge roller 85 or the third discharge roller 87. The transport direction of the fuser 6 and the roller 36 is from front to back and diagonally upward.

[0033] The first discharge roller 85 and the second discharge roller 86 are located in the first discharge path 201A. The first discharge roller 85 and the second discharge roller 86 are roller pairs consisting of a driven roller and a driven roller. The first discharge roller 85 is located upstream of the cutter position B where the cutter 10 is located, and the second discharge roller 86 is located downstream of the cutter position B.

[0034] The first discharge roller 85 and the second discharge roller 86 discharge the sheet S to the discharge tray 22 by rotating in the forward direction. Forward rotation is a rotation that transports the sheet S in the transport direction and corresponds to counterclockwise rotation with the left-right direction of the device body 2 as the axis. The transport direction in which the first discharge roller 85 transports the sheet S is from rear to front and upward. The transport direction in which the second discharge roller 86 transports the sheet S is from rear to front.

[0035] Meanwhile, the third discharge roller 87 is located in the second discharge path 201B. The third discharge roller 87 is also a roller pair consisting of a drive roller and a driven roller. The third discharge roller 87 discharges the sheet S to the discharge tray 22 by rotating in the forward direction. The third discharge roller 87 also transports the sheet S to the re-transport path 202 by rotating in the reverse direction, which is the opposite direction to the forward rotation. Reversing is a rotation that transports the sheet S in the opposite direction to the transport direction, and corresponds to a clockwise rotation with the left-right direction of the device body 2 as the axis. That is, the transport direction in which the sheet S is transported when the third discharge roller 87 rotates in the forward direction is from rear to front, and the direction in which the sheet S is transported when the third discharge roller 87 rotates in the reverse direction is from front to rear.

[0036] Retransport rollers 38 and 39 are arranged in the retransport path 202. The retransport rollers 38 and 39 transport the sheet S that has been transported in the retransport path 202 toward the image forming unit 4. By retransporting the sheet S, on which an image has been formed on one side, toward the image forming unit 4 via the retransport path 202 using the retransport rollers 38 and 39, it is possible to form an image on both sides of the sheet S. In other words, the transport direction in which the retransport rollers 38 and 39 transport the sheet is from rear to front.

[0037] The image forming unit 4 forms an image on the sheet S and is housed within the main body 2 of the device. The image forming unit 4 has a drum cartridge 5 and a laser unit 7. The drum cartridge 5 has a photoreceptor drum 51, a toner storage unit 57, a supply roller 56, a developer roller 55, a charger 52, a transfer roller 53, and a pinch roller 54. The drum cartridge 5 can be removed from the main body 2 of the device by opening the front cover 21. The pinch roller 54 of the drum cartridge 5 faces the registration roller 35. The pinch roller 54 rotates in accordance with the rotation of the registration roller 35 and transports the sheet S together with the registration roller 35.

[0038] The photoreceptor drum 51 is driven by the driving force transmitted from the main motor 108 (see Figure 3). By rotating clockwise, the sheet S is transported in the transport direction. In the photoreceptor drum 51, forward rotation, which is the rotation that transports the sheet S in the transport direction, is clockwise. The toner storage section 57 contains toner. The supply roller 56 supplies the toner from the toner storage section 57 to the developing roller 55. The charger 52 is a Scorotron type charger and uniformly charges the surface of the photoreceptor drum 51. Note that the charger 52 may also be a charging roller.

[0039] A transfer roller 53 is positioned opposite the photoreceptor drum 51. The transfer roller 53 forms a transfer nip TN between itself and the photoreceptor drum 51 in the transport path 201. A transfer belt may be used instead of the transfer roller 53.

[0040] The main body of the device 2 has a laser unit 7 at its upper interior. The laser unit 7 includes a polygon mirror 131 (see Figure 3), a laser light-emitting unit 132 (see Figure 3), lenses and reflectors (not shown), etc. The laser unit 7 exposes the surface of the photoreceptor drum 51 by rapidly scanning the surface of the photoreceptor drum 51 with laser light (see dashed line in Figure 1) based on image data emitted from the laser light-emitting unit 132.

[0041] The surface of the photoreceptor drum 51 is exposed by the laser unit 7, forming an electrostatic latent image based on the image data. The developing roller 55 supplies toner to the electrostatic latent image formed on the surface of the photoreceptor drum 51, thereby forming a toner image on the surface of the photoreceptor drum 51.

[0042] A transfer voltage is applied to the transfer roller 53 by a voltage application unit (not shown). The transfer roller 53 transports the sheet S between itself and the photoreceptor drum 51, thereby transferring the toner image formed on the surface of the photoreceptor drum 51 to the sheet S as it passes through the transfer nip TN. In this way, an image is formed on the sheet S.

[0043] A fuser 6 is located downstream of the image forming unit 4 in the transport path 201. The fuser 6 includes a heating roller 61, a pressure roller 62, a heater 63 (see Figure 3), and a temperature sensor 64 (see Figure 3). The heating roller 61 is an example of a heating rotating body and heats the sheet S. The pressure roller 62 is an example of a pressure rotating body and forms a nip N with the heating roller 61 to pressurize the sheet S. The pressure roller 62 rotates counterclockwise due to the driving force of the main motor 108. For the pressure roller 62, the forward rotation, which is the rotation that transports the sheet S in the transport direction, is counterclockwise. Thus, the pressure roller 62 is a driving roller and the heating roller 61 is a driven roller, but conversely, the heating roller 61 may be a driving roller that rotates clockwise due to the driving force of the main motor 108, and the pressure roller 62 may be a driven roller.

[0044] The heater 63 is, for example, a halogen heater, and heats the heating roller 61. The temperature sensor 64 is located near the heating roller 61 and detects the temperature of the heating roller 61. The temperature sensor 64 outputs a signal to the CPU 101 corresponding to the detected temperature.

[0045] The fuser 6 heats the sheet S with the heating roller 61 and rotates the pressure roller 62, thereby conveying the sheet S while applying pressure with the heating roller 61 and the pressure roller 62, and fixing the image formed on the sheet S by the image forming unit 4 to the sheet S.

[0046] The fuser 6 is configured to include a heating roller 61, a pressure roller 62, and a heater 63, but is not limited to these configurations. For example, the fuser 6 may have a heater, a nip plate that receives radiant heat from the heater, a heating belt that rotates around the nip plate, and a pressure roller. Alternatively, the fuser 6 may have a substrate on which a heating pattern is formed, a belt that rotates around the substrate, and a pressure roller, with the substrate and belt in contact. Furthermore, the fuser 6 may have a heating roller, a heater, and a pressure belt. .

[0047] In the first discharge path 201A, a cutter 10 is positioned at cutter position B between the first discharge roller 85 and the second discharge roller 86. As will be described later, the printer 1 stops the rotation of the first discharge roller 85 and the second discharge roller 86 so that the cutting position on the sheet S reaches cutter position B. With the rotation of the first discharge roller 85 and the second discharge roller 86 stopped, the printer 1 uses the cutter 10 to cut the sheet S at cutter position B.

[0048] Figure 2 shows a schematic configuration of the cutter 10. As shown in Figure 2, the cutter 10 includes a cutter frame 11, a slide rail 12, a fixed blade 13, a sheet passage section 14, a movable blade 15, a slide holder 16, and a cutting motor 106. The cutter frame 11 extends in the axial direction. The slide rail 12 is a rail extending in the axial direction formed on the cutter frame 11. The fixed blade 13 is a flat, plate-shaped blade extending in the axial direction and fixed to the cutter frame 11. The sheet passage section 14 is a space formed on the cutter frame 11 through which a sheet S passes. In this embodiment, the sheet passage section 14 is formed between the slide rail 12 and the fixed blade 13. The movable blade 15 is a disc-shaped blade and is rotatably fixed to the slide holder 16. The cutting motor 106 is, for example, a DC motor with an encoder, and the encoder (not shown) outputs a signal related to the rotation of the DC motor to the CPU 101.

[0049] The slide holder 16 engages with the slide rail 12 and is mounted on the cutter frame 11 so as to be slidable along the slide rail 12. When the cutting motor 106 is rotated forward, the slide holder 16 slides from one side to the other in the axial direction, and when the cutting motor 106 is rotated backward, the slide holder 16 slides from the other side to the one side in the axial direction. The slide holder 16 is movable from the initial position shown by the solid line in Figure 2 to the completed cutting position shown by the dashed line. When the sheet S is at cutter position B, and the slide holder 16 moves along the slide rail 12 to the completed cutting position, one sheet S is sandwiched between the fixed blade 13 and the movable blade 15 and cut into two sheets. The slide holder 16 is returned from the completed cutting position to the initial position. As will be described later, after the sheet S is cut, the printer 1 rotates the first discharge roller 85 and the second discharge roller 86 for a predetermined time to discharge the two sheets S into the discharge tray 22.

[0050] Printer 1 is configured to cut A4 and letter-sized sheets S at the center of the sheet in the transport direction using a cutter 10. In other words, the length of the transport path 201 from nip N to cutter position B in Figure 1 is designed to be longer than half the transport direction dimension (297 mm) of the A4-sized sheet S (148.5 mm). With this configuration, when cutting an A4 or letter-sized sheet S at cutter position B with the rotation of the first discharge roller 85 and second discharge roller 86 stopped, the rear end of the sheet S passes through nip N of the fuser 6. If the rotation of the first discharge roller 85 and second discharge roller 86 is stopped in order to cut the sheet S at cutter position B while the sheet S is held between the nip N of the fuser 6, the rotation of the pressure roller 62 must also be stopped. However, if the rotation of the pressure roller 62 is stopped while the sheet S is held between the nip N of the fuser 6, heat will be locally applied to the same location on the sheet S from the heating roller 61. Therefore, when cutting the sheet S at cutter position B with the rotation of the first discharge roller 85 and the second discharge roller 86 stopped, the rear end of the sheet S must pass through the nip N of the fuser 6.

[0051] Furthermore, the length of the transport path 201 from the nip of the roller 36 to the cutter position B in Figure 1 is designed to be longer than half the dimension (148.5 mm) of the A4 size sheet S in the transport direction (297 mm). This configuration allows the first discharge roller 85 and the When cutting the sheet S at cutter position B with the rotation of the second discharge roller 86 stopped, the rear end of the sheet S passes through the nip of roller 36. When cutting the sheet S at cutter position B with the rotation of the first discharge roller 85 and the second discharge roller 86 stopped, if the nip of roller 36 or pressure roller 62 rotates while gripping the sheet, there is a risk that the sheet S will bend into an accordion shape between the first discharge roller 85 and roller 36. Therefore, with the above configuration, it is possible to stop the sheet at the cutting position without bending into an accordion shape by only stopping the rotation of the first discharge roller 85 and the second discharge roller 86, without stopping the rotation of roller 36 or the fuser 6.

[0052] Furthermore, the length of the second discharge path 201B is designed to be shorter than the length of the first discharge path 201A. In other words, the second discharge roller 86 is located in front of the third discharge roller 87. This is to allow the sheet S to be quickly discharged to the outside of the device body 2 when the sheet S is not cut after image formation.

[0053] Next, the control configuration of printer 1 will be described with reference to Figure 3. As shown in Figure 3, printer 1 further includes an ASIC 105, a ROM 102, a RAM 103, an NVRAM 104, a post-cash sensor SE2, an ejection sensor SE3, a sheet detection sensor SE4, and a communication interface (I / F) 130.

[0054] The ASIC105 is equipped with a CPU101. The CPU101 is an example of a control unit and performs overall control of each part of the printer 1. The ASIC105 is electrically connected to the ROM102, RAM103, NVRAM104, cutting motor106, flapper88, electromagnetic clutch107, main motor108, ​​ejection motor109, pre-cash register sensor SE1, post-cash register sensor SE2, ejection sensor SE3, sheet detection sensor SE4, operation panel PA, communication I / F130, drum cartridge5, fuser6, and laser unit7.

[0055] ROM102 stores various control programs and settings for controlling printer 1. The printing process, described later using Figure 5, is included in the control program.

[0056] RAM103 is used as a work area from which various control programs are read, and as a storage area for temporarily storing image data included in the job. The CPU101 controls each part of the printer 1 while storing the processing results in RAM103 or NVRAM104 according to the control programs read from ROM102 and signals output from various sensors.

[0057] The CPU 101 drives the cutting motor 106 to move the slide holder 16, thereby moving the movable blade 15 in the width direction of the sheet S and cutting the sheet S.

[0058] The main motor 108 transmits driving force to the pickup roller 33, registration roller 35, roller 36, re-transport rollers 38 and 39, pressure roller 62, and drum cartridge 5. When the CPU 101 drives the main motor 108 in the forward direction, driving force is transmitted to the roller 36, pressure roller 62, photoreceptor drum 51, developing roller 55, pickup roller 33, and registration roller 35. Then, the roller 36, pressure roller 62, photoreceptor drum 51, developing roller 55, pickup roller 33, and registration roller 35 rotate in a direction that transports the sheet S in the transport direction.

[0059] Specifically, the roller 36 and pressure roller 62 rotate counterclockwise. The photoreceptor drum 51 rotates clockwise. The developing roller 55 rotates counterclockwise. The pickup roller 33 rotates counterclockwise. The registration roller 35 rotates counterclockwise.

[0060] On the other hand, even if the CPU 101 drives the main motor 108 in reverse, the drive force is not transmitted to the roller 36, pressure roller 62, drum cartridge 5, pickup roller 33, and registration roller 35.

[0061] The discharge motor 109 is, for example, a stepping motor, and transmits driving force to the first discharge roller 85, the second discharge roller 86, and the third discharge roller 87. When the CPU 101 drives the discharge motor 109 in the forward direction, the first discharge roller 85, the second discharge roller 86, and the third discharge roller 87 rotate counterclockwise. As a result, the sheet S is discharged to the discharge tray 22 via the first discharge path 201A or the second discharge path 201B. On the other hand, the CPU 101 drives the discharge motor 109 in the reverse direction, causing the first discharge roller 85, the second discharge roller 86, and the third discharge roller 87 to rotate clockwise. As a result, the sheet S being transported in the second discharge path 201B is transported in the opposite direction to the transport direction.

[0062] Furthermore, the CPU 101 rotates the re-transport rollers 38 and 39 clockwise by driving the discharge motor 109 in the forward direction. On the other hand, the CPU 101 rotates the re-transport rollers 38 and 39 clockwise by driving the discharge motor 109 in the reverse direction. As a result, the sheet S that has been transported in the reverse direction along the second discharge path 201B is transported towards the image forming unit 4 via the re-transport path 202.

[0063] The CPU 101 controls the electromagnetic clutch 107. By turning on the electromagnetic clutch 107, the CPU 101 enables the driving force of the main motor 108 to be transmitted to the pickup roller 33, while by turning off the electromagnetic clutch 107, the CPU 101 prevents the driving force of the main motor 108 from being transmitted to the pickup roller 33.

[0064] The CPU 101 controls the flapper 88. The CPU 101 can switch the position of the flapper 88 between a first position (position 88A, shown by a dashed line in Figure 1) and a second position (position 88B, shown by a solid line in Figure 1) by, for example, turning a flapper solenoid (not shown) on or off. The flapper 88 in the first position 88A guides the sheet S conveyed by the roller 36 to the first discharge path 201A. The flapper 88 in the second position 88B guides the sheet S conveyed by the roller 36 to the second discharge path 201B. The flapper 88 in the second position 88B also guides the sheet S in the second discharge path 201B to the re-conveyance path 202.

[0065] The pre-register sensor SE1 is positioned upstream of the registration roller 35 in the transport path 201 and is a sensor that detects when the sheet S passes. The pre-register sensor SE1 can be a sensor with an actuator that swings when the sheet S comes into contact with it, or an optical sensor, etc. The pre-register sensor SE1 outputs an ON signal when the sheet S is passing and an OFF signal when the sheet S is not passing. The detection signal from the pre-register sensor SE1 is output to the CPU 101.

[0066] The post-register sensor SE2 is positioned upstream of the fuser 6 in the transport path 201, specifically between the registration roller 35 and the transfer roller 53, and is a sensor that detects when the sheet S passes through. The post-register sensor SE2 has the same configuration as the pre-register sensor SE1. The detection signal from the post-register sensor SE2 is output to the CPU 101.

[0067] The discharge sensor SE3 is positioned between the fuser 6 and the roller 36 in the transport path 201 and detects when the sheet S passes through. The discharge sensor SE3 has the same configuration as the pre-cash register sensor SE1. The detection signal from the discharge sensor SE3 is output to the CPU 101.

[0068] The sheet detection sensor SE4 is positioned between the first discharge roller 85 and the cutter position B, and is a sensor that detects when a sheet S passes through. The sheet detection sensor SE4 has the same configuration as the pre-cash register sensor SE1. The detection signal from the sheet detection sensor SE4 is output to the CPU 101.

[0069] The control panel PA is located on the top surface of the main body 2 of the device. The control panel PA has, for example, a touch panel in which a touchpad and display are integrally formed, and a key button section. The control panel PA receives user input and outputs the received information to the CPU 101. The user can, for example, set whether or not to cut the sheet S by operating the control panel PA.

[0070] The communication interface 130 is connected to a network such as a LAN and enables connection to external devices such as a PC with a driver for printer 1 installed. The CPU 101 can receive print jobs via the communication interface 130. A print job includes various information necessary for forming an image on the sheet S, such as image data for image formation, the size and type of the sheet S used for image formation, and information on whether or not to cut the sheet S.

[0071] The control processes performed by printer 1, configured as described above, will be explained in detail below with reference to Figures 4 to 10.

[0072] Figure 4 illustrates the problems that arise when cutting a shrunk sheet Sa from a sheet S, and how to address them. Figure 4(a) shows the sheet S before it shrunk, and the dashed line in the figure indicates the cutting position CP for cutting the sheet S in the longitudinal direction, i.e., in the center of the transport direction. In contrast, Figure 4(b) shows the state in which a sheet S with a longitudinal length L has shrunk by a length Δ to become a sheet Sa with a length La. If this sheet Sa is cut at the cutting position CP for sheet S, the two resulting sheets will not be cut exactly in half because the length of the sheet on the downstream side in the transport direction, i.e., the sheet on the left in Figure 4, will be longer than the length of the sheet on the right. Therefore, the cutting position is shifted downstream by a length Δ / 2 from the cutting position CP to a cutting position CPa. By cutting at this cutting position CPa, as shown in Figure 4(c), sheet Sa can be cut into two sheets of length La / 2. The control process for cutting the shrunk sheet Sa exactly in half will be described below.

[0073] Figure 5 shows the steps of the printing process executed by the ASIC105, particularly the CPU101. This printing process is initiated when printer 1 is able to receive print jobs or print commands, for example, when printer 1 is powered on or when printer 1 is in standby mode. Hereafter, each step will be denoted by "S" in the description of each process.

[0074] In Figure 5, the CPU 101 first waits until it receives a print job via the communication interface 130 or a print command via the control panel PA (either S10 or S12: NO). Once it receives a print job or a print command (either S10 or S12: YES), the CPU 101 proceeds to S14.

[0075] In S14, the CPU 101 determines whether or not it is necessary to cut the sheet S to be printed. In this embodiment, this determination is made based on information included in the print job or print command regarding whether or not to cut the sheet S. In other words, if the user has set a mode that specifies cutting the sheet S when setting up the print job, or when setting up a print command via the operation panel PA, then the print job or print command will contain information that the sheet S should be cut. If cutting the sheet S is necessary (S14: YES), the CPU 101 proceeds to S16. On the other hand, if cutting the sheet S is not necessary (S14: NO), the CPU 101 proceeds to S20.

[0076] In S16, CPU 101 moves flapper 88 to the first position 88A. As described above, 88A transports the sheet S conveyed by the roller 36 to the first discharge path 201A This is the position to guide the user to. Next, CPU 101 executes the sheet printing and cutting process (S18), and then terminates the printing process.

[0077] Meanwhile, in S20, the CPU 101 moves the flapper 88 to the second position 88B. The second position 88B is the position that guides the sheet S, which has been conveyed by the roller 36, to the second discharge path 201B, as described above. Next, the CPU 101 performs normal printing (S22) and then terminates the printing process. In this embodiment, normal printing means printing an image onto the sheet S based on a print job or print command, and then discharging the sheet S to the discharge tray 22 without cutting it.

[0078] Figure 6 shows the detailed procedure for the sheet printing and cutting process in S18. In Figure 6, first the CPU 101 drives the main motor 108 in the forward direction (S200). At this time, the CPU 101 also turns on the heater 63.

[0079] Next, the CPU 101 executes a pickup command (S202). This causes the CPU 101 to turn on the electromagnetic clutch 107. When the electromagnetic clutch 107 is turned on, as described above, the driving force of the main motor 108 is transmitted to the pickup roller 33, so that the sheet S in the supply tray 31 is picked up and transported toward the transport path 201.

[0080] Next, the CPU 101 waits until the post-registration sensor SE2 switches from off to on (S204: NO). As described above, the post-registration sensor SE2 is positioned between the registration roller 35 and the transfer roller 53 in the transport path 201, and outputs an ON signal when the sheet S is passing through and an OFF signal when the sheet S is not passing through. Therefore, in S204, the CPU 101 waits until the post-registration sensor SE2 detects the front edge of the sheet S. Then, when the post-registration sensor SE2 detects the front edge of the sheet S (S204: YES), the CPU 101 starts image formation on the sheet S by the image forming unit 4 (S206).

[0081] Next, the CPU 101 waits until the discharge sensor SE3 switches from off to on (S208: NO). As described above, the discharge sensor SE3 is positioned between the fuser 6 and the roller 36 in the transport path 201, and outputs an ON signal when the sheet S is passing and an OFF signal when the sheet S is not passing. Therefore, in S208, the CPU 101 waits until the discharge sensor SE3 detects the front end of the sheet S. When the discharge sensor SE3 detects the front end of the sheet S (S208: YES), the CPU 101 drives the discharge motor 109 in the forward direction (S210). As a result, the first to third discharge rollers 85 to 87 begin to rotate. The CPU 101 controls the discharge motor 109 and the main motor 108 so that the rotation speed of the discharge motor 109 is faster than the rotation speed of the main motor 108. This is to eliminate the flexing of the sheet S when it is being transported in a flexed state between the roller 36 and the first discharge roller 85 or the third discharge roller 87. In other words, if the transport speed of the first discharge roller 85 and the third discharge roller 87 is faster than the transport speed of the roller 36, when the sheet S is transported by the first discharge roller 85 or the third discharge roller 87, the transport speed of the part of the sheet S that has passed the roller 36 will increase, and the flexed state will gradually be eliminated.

[0082] Next, the CPU 101 waits until the sheet detection sensor SE4 switches from off to on (S212:NO). As described above, the sheet detection sensor SE4 is positioned between the first discharge roller 85 and the cutter position B in the transport path 201, and detects when a sheet S is passing through. The CPU outputs an ON signal when the sheet S is on and an OFF signal when the sheet S has not yet passed. Therefore, in S210, the CPU 101 waits until the sheet detection sensor SE4 detects the front end of the sheet S. When the sheet detection sensor SE4 detects the front end of the sheet S (S210: YES), the CPU 101 starts measuring the number of steps of the discharge motor 109 (S214). As the discharge motor 109 is a stepping motor as described above, the CPU 101 can measure, or count, the number of steps while the discharge motor 109 is operating. The measurement result (count) can be stored, for example, in a STEP count area (not shown) reserved in a predetermined area of ​​RAM 103. Figure 9(a) shows the state when the front end of the sheet Sa has reached the detection position of the sheet detection sensor SE4.

[0083] Next, the CPU 101 waits until the discharge sensor SE3 switches from on to off (S216: NO). In other words, in S216, the CPU 101 waits until the discharge sensor SE3 detects the rear end of the sheet S. Then, when the discharge sensor SE3 detects the rear end of the sheet S (S216: YES), the CPU 101 executes the sheet transport process to the cutter position (S218). Figure 9(b) shows the state when the rear end of the sheet Sa has reached the detection position of the discharge sensor SE3.

[0084] Figure 7 shows the detailed procedure for the sheet transport process to the cutter position in S218. In Figure 7, the CPU 101 first determines the actual number of steps (S230). The actual number of steps (an example of the second rotation amount) is the number of steps from when the sheet detection sensor SE4 detects the front end of sheet Sa until when the discharge sensor SE3 detects the rear end of sheet Sa. The actual number of steps can be determined by reading the count value stored in the step count area at this time.

[0085] Next, the CPU 101 calculates the sheet length in steps of sheet S by adding a default value (length X: number of steps) and the measured number of steps (S232). Then, the CPU 101 calculates the number of steps from the cutting position CP to the cutter position B of sheet S in the transport path 201 including the first discharge path 201A using the following equation (1) (S234). Sheet length (number of steps) / 2 - Measured number of steps + Number of steps from sheet detection sensor SE4 to cutter position B ... (1)

[0086] Figure 10(a) is a diagram illustrating the processes in S232 and S234, showing the state where the rear end of sheet Sa has reached the detection position of discharge sensor SE3. At this time, the measured number of steps determined in S230 is 140 steps. The length X from discharge sensor SE3 to sheet detection sensor SE4 is a fixed default value of 200 steps, so the sheet length in steps in the conveying direction of sheet Sa can be calculated as 200 + 140 = 340 steps. The fixed default value of 200 steps for length X (an example of the first rotation amount) is stored in advance in NVRAM 104. The CPU 101 can read and use 200 steps for length X from NVRAM 104. Once the sheet length in steps is calculated in this way, the cutting position CPa is calculated as sheet length in steps / 2. Specifically, the cutting position CPa = 170 steps. Since the length X = 200 steps, the cutting position CPa is located 30 steps upstream (= 200 - 170) from the detection position of the sheet detection sensor SE4. Furthermore, the length Y from the detection position of the sheet detection sensor SE4 to the cutter position B is a fixed default value of 40 steps. Length Y The fixed default value of 40 steps (an example of the third rotation amount) is pre-stored in the NVRAM 104. Therefore, if the sheet Sa is transported downstream for 70 steps (=30+40) from the current position where the cutting position CPa is in the state where the discharge sensor SE3 is off, the cutting position CPa will reach the cutter position B. In other words, equation (1) represents the number of steps from when the rear end of the sheet S reaches the detection position of the discharge sensor SE3 until the cutting position CP of the sheet S reaches the cutter position B.

[0087] Returning to Figure 7, the CPU 101 then waits for the number of steps calculated in S234 until the discharge motor 109 is driven to rotate (S236: NO). Once the discharge motor 109 has rotated for that number of steps (S236: YES), the CPU 101 terminates the sheet transport process to the cutter position. After that, the CPU 101 proceeds to S220 in Figure 6.

[0088] In S220, the CPU 101 stops the discharge motor 109. Then, the CPU 101 performs the sheet cutting process (S222).

[0089] Figure 8 shows the detailed procedure for the sheet cutting process. In Figure 8, first the CPU 101 drives the cutting motor 106 in the forward direction (S240). The forward direction of the cutting motor 106 causes the movable blade 15 to start moving from the initial position toward the cutting completion position (the position shown by the dashed line in Figure 2). The CPU 101 then waits until the movable blade 15 of the cutter 10 reaches the cutting completion position (the position shown by the dashed line in Figure 2) (S242: NO), and when the movable blade 15 reaches the cutting completion position (S242: YES), the CPU 101 proceeds to S244. The CPU 101 can determine that the movable blade 15 has reached the cutting completion position from the initial position (the position shown by the solid line in Figure 2) by counting the rotation speed of the cutting motor 106 based on the output signal from the encoder attached to the cutting motor 106, and making a determination based on that count value.

[0090] In S244, the CPU 101 stops the cutting motor 106. Then, the CPU 101 reverses the drive of the cutting motor 106 (S246). The CPU 101 then waits until the moving blade 15 reaches its initial position (S248: NO), and once the moving blade 15 reaches its initial position (S248: YES), the CPU 101 terminates the sheet cutting process. After that, the CPU 101 proceeds to S224 in Figure 6.

[0091] When the CPU 101 executes the sheet cutting process, the sheet S is stopped with its cutting position CP reaching the cutter position B. Therefore, when the sheet cutting process is executed while the sheet S is stopped in this state, as shown in Figure 10(b), even if the sheet S has shrunk into sheet Sa, sheet Sa will be cut into two pieces at the center in the transport direction (cutting position CPa).

[0092] In step S224 of Figure 6, the CPU 101 drives the discharge motor 109 in the forward direction and stops the discharge motor 109 after a predetermined time has elapsed. As a result, the sheet S, which has been divided into two equal parts, is discharged to the discharge tray 22. Therefore, the "predetermined time" is the time it takes for the sheet on the upstream side in the transport direction of the divided sheet S to be discharged from the first discharge path 201A to the discharge tray 22.

[0093] Next, the CPU 101 determines whether or not the currently running job requires printing of the next sheet (S226). If the determination indicates that there is printing for the next sheet (S226: YES), the CPU 101 returns to processing S202 and continues processing from S202 onward. On the other hand, if there is no printing for the next sheet (S226: NO), the CPU 101 stops the main motor 108 (S228) and then terminates the sheet printing and cutting process.

[0094] As described above, the printer 1 of this embodiment includes a device body 2 having a sheet S transport path 201, a heating roller 61, a pressure roller 62 that forms a nip N between itself and the heating roller 61, a fuser 6 that fixes the image formed on the sheet S to the sheet S, a first discharge roller 85 located downstream of the fuser 6 in the transport direction of the sheet S along the transport path 201 and transporting the sheet S, and a second discharge roller located downstream of the first discharge roller 85 in the transport direction and discharging the sheet S transported by the first discharge roller 85 to the outside of the device body 2. The system includes a second discharge roller 86, a transport roller 35, 36, 85-87 having a cutter 10 located at cutter position B, which is between the first discharge roller 85 and the second discharge roller 86 in the transport direction, and capable of cutting the sheet S in a cutting direction intersecting the transport direction, a sheet detection sensor SE4 that detects whether or not a sheet S is present at a first detection position between the first discharge roller 85 and the second discharge roller 86 in the transport direction, a discharge sensor SE3 that detects whether or not a sheet S is present at a second detection position between the first discharge roller 85 and the fuser 6 in the transport direction, and a CPU 101.

[0095] Furthermore, the CPU 101, in a transport process in which the sheet S is transported along the transport path 201 using transport rollers 35, 36, 85~87, corrects the amount of rotation of the first discharge roller 85 and the second discharge roller 86 so that the ideal cutting position CP of the sheet S, which passes through a part of the transport path 201, reaches the cutter position B, based on the detection results of the sheet detection sensor SE4 and the discharge sensor SE3, and after rotating the first discharge roller 85 and the second discharge roller 86 by the corrected amount of rotation, performs a transport process (S218, S220) in which the first discharge roller 85 and the second discharge roller 86 are stopped, and after the transport process, performs a cutting process (S222) in which the sheet S is cut in the cutting direction using the cutter 10.

[0096] Thus, in the printer 1 of this embodiment, the amount of rotation of the first discharge roller 85 and the second discharge roller 86 required for the ideal cutting position CP of the sheet S to reach the cutter position B is corrected based on the detection results of the sheet detection sensor SE4 and the discharge sensor SE3. After the first discharge roller 85 and the second discharge roller 86 rotate by the corrected amount of rotation, they stop, and the sheet Sa is cut at that stopping position. Therefore, even if the sheet S shrinks due to the heat applied to the sheet S by the fuser 6, it is possible to cut the sheet Sa at the desired cutting position.

[0097] Incidentally, in this embodiment, the heating roller 61 is an example of a "heating rotating body". The pressure roller 62 is an example of a "pressure rotating body". The CPU 101 is an example of a "control unit". The sheet detection sensor SE4 is an example of a "first sensor". The discharge sensor SE3 is an example of a "second sensor".

[0098] Furthermore, the CPU 101 is characterized in that, during the conveying process, it acquires a first timing when the front end of the sheet S reaches a first detection position based on the detection result of the sheet detection sensor SE4 (S212), and a second timing when the rear end of the sheet S reaches a second detection position based on the detection result of the discharge sensor SE3 (S216), and corrects the amount of rotation of the first discharge roller 85 and the second discharge roller 86 based on the acquired first and second timings.

[0099] As a result, the sheet length of sheet S is measured, so even if sheet S shrinks due to the heat applied to sheet S by the fuser 6, it becomes possible to cut sheet Sa at the desired cutting position.

[0100] Furthermore, the printer 1 includes a main motor 108 that rotates either the heating roller 61 or the pressure roller 62 included in the fuser unit 6, and an ejection motor 109 that rotates the first ejection roller 85 and the second ejection roller 86. The CPU 101 controls the main motor 108 and the ejection motor 109 so that the rotational speed of the ejection motor 109 is faster than the rotational speed of the main motor 108.

[0101] As a result, even if the sheet S is deflected while passing through the fuser 6, the first discharge roller 85 and the second discharge roller 86 increase the conveying speed of the sheet S, making it possible to eliminate the deflection of the sheet S.

[0102] Printer 1 is further equipped with NVRAM 104. The NVRAM 104 stores in advance the amount of rotation of the first discharge roller 85 and the second discharge roller 86 required to transport the sheet S from the first detection position of the sheet detection sensor SE4 to the second detection position of the discharge sensor SE3 as the first rotation amount. The CPU 101 acquires the amount of rotation of the first discharge roller 85 and the second discharge roller 86 required from the first timing to the second timing as the second rotation amount during the transport process. Based on the first and second rotation amounts, it acquires the sheet length in the transport direction of the sheet Sa after passing through the fuser 6, determines the cutting position on the sheet S from the acquired sheet length, and stops the rotational drive of the discharge motor 109. Incidentally, NVRAM 104 is an example of "memory".

[0103] This eliminates the need to measure predetermined fixed values, making it possible to obtain the sheet length in the conveying direction of sheet Sa more accurately.

[0104] Furthermore, the CPU 101 controls the discharge motor 109 to rotate until the determined cutting position CPa on the sheet Sa reaches the cutter position B, after acquiring the second timing.

[0105] This allows the conveyance of the sheet Sa to be stopped when the determined cutting position CPa on the sheet Sa reaches the cutter position B.

[0106] Furthermore, the discharge motor 109 is a stepping motor, and the CPU 101 controls the stopping timing of the discharge motor 109 based on the number of steps of the stepping motor.

[0107] This makes it possible to control the stopping timing of the discharge motor 109 by simply counting the number of steps of the stepping motor.

[0108] Furthermore, the sheet detection sensor SE4 is located upstream of the cutter position B in the transport direction, the first rotation amount is indicated by the number of steps of the stepping motor, and the NVRAM 104 has in advance stored the rotation amount of the first discharge roller 85 and the second discharge roller 86 required to transport the sheet S from the first detection position of the sheet detection sensor SE4 to the cutter position B, which is indicated by the number of steps of the stepping motor, as the third rotation amount, and in the transport process, the CPU 101 acquires the second rotation amount by the number of steps of the stepping motor, and after acquiring the second timing, The discharge motor 109 is controlled to rotate for a duration of {first rotation amount - (first rotation amount + second rotation amount) / 2 + third rotation amount}.

[0109] As a result, even if the sheet S shrinks due to the heat applied by the fuser 6, it becomes possible to accurately cut the sheet Sa in the center of the transport direction by simply counting the number of steps of the stepping motor.

[0110] Furthermore, the device body 2 includes a first discharge path 201A which is part of the transport path 201 and discharges the sheet S to the outside of the device body 2 via cutter position B, a second discharge path 201B which is part of the transport path 201 and is a different path from the first discharge path 201A and discharges the sheet S to the outside of the device body 2, and a flapper 88 which guides the sheet S to either the first discharge path 201A or the second discharge path 201B. The CPU 101 receives a print job that includes information on whether or not cutting of the sheet by the cutter 10 is necessary. If it determines that cutting of the sheet is necessary based on the print job, it moves the position of the flapper 88 to guide the sheet S to the first discharge path 201A. If it determines that cutting of the sheet is unnecessary based on the print job, it guides the sheet S to the second discharge path 201B. A key feature is that the position of the flapper 88 is moved to guide the user.

[0111] This is convenient because, when cutting the sheet S is necessary, the flapper 88 guides the sheet S to the first discharge path 201A, and when cutting the sheet S is not necessary, the flapper 88 guides the sheet S to the second discharge path 201B.

[0112] (Second Embodiment) Next, a second embodiment of the present invention will be described. This embodiment is configured by changing the installation position of the sheet detection sensor SE4 described in the first embodiment, so the description will focus on the changed parts, and the description of other parts will be omitted as appropriate. The hardware of this embodiment will be almost the same as the hardware shown in Figures 1 to 3, but in order to clarify the installation position of the sheet detection sensor SE4a in this embodiment, the cross-sectional view in Figure 11 will be used instead of Figure 1. However, in Figure 11, the same reference numerals are used for the same components as in Figure 1.

[0113] While the sheet detection sensor SE4 in Figure 1 was installed between the first discharge roller 85 and cutter position B, the sheet detection sensor SE4a in Figure 11 is installed between cutter position B and the second discharge roller 86. Due to this difference in installation position, it is necessary to modify part of the sheet conveying process to the cutter position in Figure 7.

[0114] Figure 12 shows the detailed procedure for the sheet transport process to the cutter position performed by the CPU 101 of this embodiment. In Figure 12, the same steps as in Figure 7 are given the same step numbers, and explanations of those processes are omitted as appropriate.

[0115] In Figure 12, the CPU 101 calculates the number of steps from the cutting position CP to the cutter position B of the sheet S in the transport path 201 and the first discharge path 201A using the following equation (2) (S240). Sheet length (number of steps) / 2 - Measured number of steps - Number of steps from cutter position B to sheet detection sensor SE4 ... (2)

[0116] Figure 13 is a diagram illustrating the process in S240, showing the state where the rear end of sheet Sa has reached the detection position of discharge sensor SE3. At this time, the measured number of steps determined in S232 is 80 steps. In other words, the number of steps from when sheet detection sensor SE4 detects the front end of sheet Sa until when discharge sensor SE3 detects the rear end of sheet Sa is 80 steps. Since the length X1 from discharge sensor SE3 to sheet detection sensor SE4 is a fixed default value of 260 steps, the sheet length in steps in the conveying direction of sheet Sa can be calculated as 260 + 80 = 340 steps. Note that if the length X1 is pre-stored in NVRAM 104, for example, it can be read and used. Once the sheet length in steps is calculated in this way, the cutting position CPa is calculated as sheet length in steps / 2. Specifically, the cutting position CPa = 170 steps. Since the length X1 = 260 steps, the cutting position CPa is located 90 steps (= 260 - 170) upstream from the detection position of the sheet detection sensor SE4. Furthermore, the length Y1 from the cutter position B to the detection position of the sheet detection sensor SE4 is a fixed default value of 20 steps. Therefore, if the sheet Sa is transported so that the cutting position CPa moves 70 steps (= 90 - 20) downstream from its current position (= 170 steps), the cutting position CPa will reach the cutter position B. In other words, equation (2) represents the number of steps from when the rear end of the sheet Sa reaches the detection position of the discharge sensor SE3 until the cutting position CPa of the sheet Sa reaches the cutter position B.

[0117] As described above, in the printer 1 of this embodiment, the sheet detection sensor SE4a is located downstream of the cutter position B in the transport direction, and the first rotation amount is the stepping motion The NVRAM 104 stores in advance the third rotation amount, which is the amount of rotation of the first discharge roller 85 and the second discharge roller 86 required to transport the sheet S from cutter position B to the first detection position of the sheet detection sensor SE4a, and is indicated by the number of steps of the stepping motor. Then, in the transport process, the CPU 101 acquires the second rotation amount in terms of the number of steps of the stepping motor, and after acquiring the second timing, The discharge motor 109 is controlled to rotate for a duration of {first rotation amount - (first rotation amount + second rotation amount) / 2 - third rotation amount}. Incidentally, the sheet detection sensor SE4a is an example of the "first sensor".

[0118] As a result, even if the sheet S shrinks due to the heat applied by the fuser 6, it becomes possible to accurately cut the sheet Sa in the center of the transport direction by simply counting the number of steps of the stepping motor.

[0119] It should be noted that the present invention is not limited to the embodiments described herein, and various modifications are possible without departing from the spirit of the invention.

[0120] (1) In each embodiment, the detection positions where the pre-cash register sensor SE1, post-cash register sensor SE2, discharge sensor SE3, and sheet detection sensor SE4 detect the passage of the sheet S are approximately the same as the installation positions of the sensors. However, sensors may be used in which the installation position of the sensor and the detection position of the sheet S are far apart.

[0121] (2) In each embodiment, the control process of the present invention was described using the example of cutting sheet S into sheet Sa precisely in half when sheet S has shrunk, but even when sheet S has not shrunk, sheet S can be cut into half precisely by applying the control process of the present invention.

[0122] (3) In each embodiment, a monochrome laser printer 1 was described as an example of an image forming apparatus, but the apparatus is not limited to this, and a color laser printer may also be used.

[0123] (4) In each embodiment, the case in which sheet P is cut into two equal parts has been described, but the invention is not limited to this, and sheet P may be cut into, for example, three equal parts.

[0124] (5) In each embodiment, when a print job is received from outside the printer 1, it is received via the communication I / F 130, but the invention is not limited to this, and for example, the print job may be received via the USB interface.

[0125] (6) In each embodiment, the printer 1 was configured to be able to cut A4 size and letter size sheets S in the middle of the sheet, but for example, A4 size sheets may not be cut and only letter size sheets S may be cut. In that case, the length of the transport path 201 from the nip N to the cutter position B in Figure 1 and the length of the transport path 201 from the nip of the roller 36 to the cutter position B are half the dimension of the letter size in the transport direction (279.4 mm) It just needs to be designed to be longer than 139.7mm. Furthermore, it should be larger than A4 size. The large-sized sheets may be made cuttable.

[0126] (7) In each embodiment, the cutter 10 was composed of a movable blade 15 and a fixed blade 13, but its shape and type are not limited as long as it can cut the sheet S. For example, it may be a configuration in which the sheet is cut by dropping a blade that is long in the cutting direction onto the sheet S, or it may be scissors. [Explanation of symbols]

[0127] 1...Printer, 2...Main unit, 6...Fuser, 10...Cutter, 61...Heating roller, 62...Pressure roller, 85...First discharge roller, 86...Second discharge roller, 88...Flapper, 101...CPU, 102...ROM, 103...RAM, 104...NVRAM, 105...ASIC, 108...Main motor, 109...Discharge motor, 201...Conveyor path, 201A...First discharge path, 201B...Second discharge path, B...Cutter position, SE3...Discharge sensor, SE4, SE4a...Sheet detection sensor.

Claims

1. A device body having a sheet transport path, A fixing device comprising a heating rotating body and a pressurizing rotating body that forms a nip between itself and the heating rotating body, for fixing an image formed on the sheet to the sheet, A plurality of conveying rollers, each having: a first discharge roller located downstream of the fuser in the conveying direction of the sheet along the conveying path, for conveying the sheet; and a second discharge roller located downstream of the first discharge roller in the conveying direction, for discharging the sheet conveyed by the first discharge roller to the outside of the main body of the device. A cutter is positioned at a cutter position between the first discharge roller and the second discharge roller in the conveying direction, and is capable of cutting the sheet in a cutting direction intersecting the conveying direction. A first sensor for detecting whether or not the sheet is present at a first detection position between the first discharge roller and the second discharge roller in the conveying direction, A second sensor for detecting whether the sheet is present at a second detection position between the first discharge roller and the fuser in the transport direction, Control unit and Equipped with, The control unit, In a conveying process in which the sheet is conveyed along the conveying path using the plurality of conveying rollers, the amount of rotation of the first discharge roller and the second discharge roller so that the ideal cutting position of the sheet passing through a part of the conveying path reaches the cutter position is corrected based on the detection results of the first sensor and the second sensor, and after rotating the first discharge roller and the second discharge roller by the corrected amount of rotation, the conveying process stops the first discharge roller and the second discharge roller. After the conveying process, a cutting process is performed in which the sheet is cut in the cutting direction using the cutter, Execute An image forming apparatus characterized by the following:

2. The control unit, In the transport process, a first timing is obtained when the front end of the sheet reaches the first detection position based on the detection result of the first sensor, and a second timing is obtained when the rear end of the sheet reaches the second detection position based on the detection result of the second sensor, and the amount of rotation of the first discharge roller and the second discharge roller is corrected based on the obtained first and second timings. The image forming apparatus according to feature 1.

3. A main motor that rotates either the heating rotating body or the pressurizing rotating body included in the fuser, A discharge motor that rotates the first discharge roller and the second discharge roller, Furthermore, The control unit, The main motor and the discharge motor are controlled so that the rotational speed of the discharge motor is faster than the rotational speed of the main motor. The image forming apparatus according to feature 2.

4. memory, Furthermore, The memory contains the data from the second detection position of the second sensor to the first detection position of the first sensor. The amount of rotation of the first discharge roller and the second discharge roller necessary to transport the sheet to the discharge position is stored in advance as the first amount of rotation. The control unit, In the aforementioned transport process, The amount of rotation of the first discharge roller and the second discharge roller required from the first timing to the second timing is obtained as the second amount of rotation. Based on the first rotation amount and the second rotation amount, the sheet length of the sheet in the transport direction after passing through the fuser is obtained. The cutting position on the sheet is determined from the acquired sheet length, and the rotational drive of the discharge motor is stopped. The image forming apparatus according to feature 3.

5. The control unit, After acquiring the second timing, the discharge motor is controlled to rotate until the determined cutting position on the sheet reaches the cutter position. The image forming apparatus according to feature 4.

6. The aforementioned discharge motor is a stepping motor, The control unit, The stopping timing of the discharge motor is controlled by the number of steps of the stepping motor. The image forming apparatus according to feature 4.

7. The first sensor is located upstream of the cutter position in the transport direction, The first rotational amount is indicated by the number of steps of the stepping motor, The memory pre-stores, as a third rotation amount, the amount of rotation of the first discharge roller and the second discharge roller necessary to transport the sheet from the first detection position of the first sensor to the cutter position, which is indicated by the number of steps of the stepping motor. The control unit, In the aforementioned transport process, The second rotation amount is obtained by the number of steps of the stepping motor, After obtaining the second timing, The discharge motor is controlled to rotate for a duration of {first rotation - (first rotation + second rotation) / 2 + third rotation}. The image forming apparatus according to feature 6.

8. The first sensor is located downstream of the cutter position in the transport direction, The first rotational amount is indicated by the number of steps of the stepping motor, The memory pre-stores, as a third rotation amount, the amount of rotation of the first discharge roller and the second discharge roller necessary to transport the sheet from the cutter position to the first detection position of the first sensor, which is indicated by the number of steps of the stepping motor. The control unit, In the aforementioned transport process, The second rotation amount is obtained by the number of steps of the stepping motor, After obtaining the second timing, The discharge motor is controlled to rotate for a duration of {first rotation amount - (first rotation amount + second rotation amount) / 2 - third rotation amount}. The image forming apparatus according to feature 6.

9. The main body of the aforementioned device is A part of the transport path, a first discharge path for discharging the sheet to the outside of the device body via the cutter position, A second discharge route is part of the transport route, which is different from the first discharge route, and is for discharging the sheet to the outside of the main body of the device. A flapper that guides the sheet to either the first discharge path or the second discharge path, It has, The control unit, The system accepts a print job that includes information regarding whether or not the sheet needs to be cut by the aforementioned cutter. If it is determined that cutting of the sheet is necessary based on the print job, the position of the flapper is moved to guide the sheet to the first discharge path. If it is determined that cutting the sheet is unnecessary based on the print job, the position of the flapper is moved to guide the sheet to the second discharge path. The image forming apparatus according to feature 1.

Images