JP2016210566A - Sheet conveyance device, printer and driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve accurate sheet conveyance even if there are variations in output torque characteristics of a variable output torque clutch for transmitting a driving force to a roll, in a device for conveying a sheet by using the roll taking up the sheet.SOLUTION: A sheet conveyance device comprises: a rotor 31 which can rotate for taking up a sheet or for delivering the taken-up sheet; a drive source 34 which generates the driving force for rotating the rotor; and a variable output torque clutch 34 which defines the driving force for rotating the rotor 31 with output torque. The output torque defining the driving force for rotating the rotor 31 by the variable output torque clutch 34 is defined in accordance with a sheet taking-up amount of the rotor 31.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a sheet conveying apparatus, a printing apparatus, and a roll driving method, and more particularly to control of output torque when a roll around which a sheet is wound is driven via a variable output torque clutch.

  Some mechanisms for conveying a continuous sheet in a printer or the like control the driving of a roll by using a clutch such as a powder clutch that makes output torque variable when driving a roll around which a continuous sheet is wound. By this torque control, it is possible to drive the roll according to the amount of the sheet wound on the roll, and as a result, for example, an appropriate tension is applied to the sheet to maintain the accuracy of sheet conveyance. Can do.

  Japanese Patent Application Laid-Open No. H10-260260 describes that an appropriate tension is applied by controlling the driving of the roll via the brake function of the powder clutch by feeding back the tension acting on the sheet. In this control, brake torque (output torque) by the clutch is determined according to torque characteristic data prepared in advance.

JP 2014-87131 A

  However, in Patent Document 1, when there is a variation in output torque characteristics due to individual differences in variable output torque clutches or changes with time, it is possible that torque characteristic data prepared in advance may not match. In this case, it is impossible to drive the roll corresponding to the amount of sheets wound around the roll. As a result, for example, it is not possible to apply an appropriate tension to the sheet, resulting in a problem such as a decrease in accuracy such as sheet conveyance.

  The present invention solves the above-described problem, and provides a sheet conveying apparatus, a printing apparatus, and a roll driving method capable of conveying a sheet with high accuracy even if the output torque characteristics of a variable output torque clutch vary. The purpose is to do.

  Therefore, in the present invention, in the sheet conveying apparatus, a rotating body capable of rotating to wind the sheet or rotating to wind the wound sheet, and a driving source for generating a driving force for rotating the rotating body. And a variable output torque clutch that determines a driving force for rotating the rotating body by an output torque, and an output torque that determines a driving force for rotating the rotating body by the variable output torque clutch. And a control means determined according to the amount of winding of the body sheet.

  According to the above configuration, in a device that conveys a sheet using a roll on which the sheet is wound, even if there is variation in the output torque characteristics of the variable output torque clutch for transmitting the driving force to the roll, the accurate sheet Can be transported.

1 is a cross-sectional view schematically illustrating an internal configuration of a printing apparatus according to an embodiment of the present invention. It is a block diagram which shows the structure of the control part shown in FIG. It is a figure explaining operation | movement of the single-sided printing mode by the printing apparatus of one Embodiment of this invention. It is a figure explaining the operation | movement in the double-sided printing mode by the printing apparatus of this embodiment. It is a perspective view which mainly shows a drive structure of the winding roll in the sheet supply part which concerns on one Embodiment of this invention. It is a figure explaining the output torque characteristic of the powder clutch which concerns on this embodiment. It is a flowchart which shows the correction process of the output torque characteristic of the powder clutch which concerns on one Embodiment of this invention. It is a figure explaining the output torque curve after correction | amendment by the process shown in FIG. 7 of a powder clutch. It is a figure explaining the rotation angle measurement part of this embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  A printing apparatus according to an embodiment of the present invention uses a long and continuous sheet (a continuous sheet longer than the length of a repeated print unit (one page or unit image) in the conveyance direction), and simplex printing and duplex printing. This is a line printer that supports both printing. Here, the unit image means one print unit (one page) when a plurality of pages are sequentially printed on a continuous sheet. The length of the unit image varies depending on the image size to be printed. For example, the length in the sheet conveyance direction is 135 mm for the L size photograph, and the length in the sheet conveyance direction is 297 mm for the A4 size.

  It should be noted that the application of the present invention is not limited to the printing apparatus shown in the present embodiment, but is also applied to a printing apparatus such as a printer complex machine, a copying machine, a facsimile machine, and various device manufacturing apparatuses. be able to. The printing process may be any printing system such as an inkjet system, an electrophotographic system, a thermal transfer system, a dot impact system, and a liquid development system. The present invention is not limited to print processing, and can be applied to a sheet processing apparatus that performs various processing (recording, processing, coating, irradiation, reading, inspection, etc.) on a roll sheet.

  FIG. 1 is a cross-sectional view schematically showing the internal configuration of the printing apparatus according to the present embodiment. The printing apparatus according to the present embodiment generally includes a sheet supply unit 1, a decurling unit 2, a skew correction unit 3, a printing unit 4, an inspection unit 5, a cutter unit 6, an information recording unit 7, a drying unit 8, a reversing unit 9, Each unit includes a discharge conveyance unit 10, a sorter unit 11, a discharge unit 12, a humidification unit 20, and a control unit 13. A sheet as a print medium is conveyed by a conveyance mechanism including a roller pair and a belt along a sheet conveyance path indicated by a solid line in the drawing, and each unit performs each process. In this specification, at an arbitrary position in the sheet conveyance path, the side close to the sheet supply unit 1 is referred to as “upstream” and the opposite side is referred to as “downstream”.

  The sheet supply unit 1 holds and supplies a continuous sheet wound in a roll shape. The sheet supply unit 1 can store two rolls R1 and R2, and is configured to selectively feed and supply the sheet, and to wind the sheet. Each of the rolls R1 and R2 includes a rotating body, a driving source for rotating the rotating body, and a powder clutch disposed between the driving source and the rotating body, as will be described later with reference to FIG. Then, by controlling the transmission torque (output torque) of the powder clutch, it is possible to perform roll driving according to the amount of sheets wound up by the roll. As a result, when winding and unwinding the sheet, the rolls can be rotated at a predetermined rotational speed, respectively, and an appropriate tension can be applied to the sheet with a transport mechanism such as another roller pair. In addition, the inversion part 9 mentioned later is also provided with the same structure.

  The decurling unit 2 reduces curling (warping) of the sheet supplied from the sheet supply unit 1. The decurling unit 2 uses two pinch rollers for one driving roller, curls the sheet in a direction (predetermined direction) that gives a curl in the opposite direction of curling, and applies a decurling force to curl. Reduce. The decurling unit 2 can adjust the decurling force. The skew correction unit 3 corrects the skew (inclination with respect to the original traveling direction) of the sheet that has passed through the decurling unit 2. The sheet skew is corrected by pressing the sheet end on the reference side against the guide member.

  The print unit 4 forms an image by performing print processing on the conveyed sheet from above with the print head 14. The print head 14 has a line type print head in which an inkjet nozzle row is formed in a range that covers the maximum width of a sheet that is supposed to be used. The print head 14 has a plurality of print heads arranged in parallel along the transport direction. In this example, there are seven print heads corresponding to seven colors of C (cyan), M (magenta), Y (yellow), LC (light cyan), LM (light magenta), G (gray), and K (black). . The number of colors and the number of print heads are not limited to seven. As the inkjet method, a method using a heating element, a method using a piezo element, a method using an electrostatic element, a method using a MEMS element, or the like can be adopted. Each color ink is supplied from the ink tank to the print head 14 via an ink tube. As will be described later, in the printing unit 4, the print head 14 is movable in a direction to retract from the sheet. Thereby, the interval of the print head 14 with respect to the sheet is adjusted.

  The inspection unit 5 optically reads the inspection pattern or image printed on the sheet by the printing unit 4 using a scanner, and inspects the nozzle state of the print head, the sheet conveyance state, the image position, etc., and the image is printed correctly. It is determined. The cutter unit 6 includes a mechanical cutter that cuts a printed sheet into a predetermined length. The information recording unit 7 records print information (unique information) such as a print serial number and date in a non-print area of the cut sheet. In this recording, characters and codes are printed by an inkjet method, a thermal transfer method, or the like. A sensor 23 for detecting the leading edge of the cut sheet is provided on the upstream side of the information recording unit 7 and the downstream side of the cutter unit 6. That is, the sensor 23 detects the edge of the sheet between the recording position by the cutter unit 6 and the information recording unit 7, and the timing at which the information recording unit 7 records information is controlled based on the detection timing of the sensor 23. . The drying unit 8 heats the sheet printed by the printing unit 4 and dries the applied ink.

  The sheet conveyance path from the sheet supply unit 1 to the drying unit 8 is referred to as a first path. The first path has a U-turn shape between the printing unit 4 and the drying unit 8, and the cutter unit 6 is located in the middle of the U-turn shape.

  The reversing unit 9 is used when performing double-sided printing, and is a unit for temporarily winding a continuous sheet that has been printed on the front surface and reversing the front and back. The reversing unit 9 is a path (loop path) (referred to as a second path) from the drying unit 8 through the decurling unit 2 to the printing unit 4 for supplying the sheet that has passed through the drying unit 8 to the printing unit 4 again. It is provided on the way. The reversing unit 9 includes a rotating body (drum) that rotates to wind up the sheet. The continuous sheet that has been printed on the front surface and has not been cut is temporarily wound around a rotating body. When the winding is finished, the rotating body rotates reversely, and the wound sheet is sent to the printing unit 4 via the decurling unit 2. Since this sheet is turned upside down, the printing unit 4 can print on the back side.

  The discharge conveyance unit 10 conveys the sheet cut by the cutter unit 6 and dried by the drying unit 8 and conveys the sheet to the sorter unit 11. The discharge conveyance unit 10 is provided in a route (referred to as a third route) different from the second route in which the reversing unit 9 is provided. In order to selectively guide the sheet conveyed on the first path to one of the second path and the third path, a path switching mechanism having a movable flapper is provided at a branch position of the path. The sorter unit 11 and the discharge unit 12 are provided on the side of the sheet supply unit 1 and at the end of the third path. The sorter unit 11 sorts printed sheets for each group as necessary. The sorted sheets are discharged to the discharge unit 12 including a plurality of trays. As described above, the third path is arranged to pass under the sheet supply unit 1 and discharge the sheet on the opposite side of the printing unit 4 and the drying unit 8 with the sheet supply unit 1 interposed therebetween.

  As described above, the sheet supply unit 1 to the drying unit 8 are sequentially provided in the first path. The tip of the drying unit 8 is branched into a second route and a third route, the reversing unit 9 is provided in the middle of the second route, and the tip of the reversing unit 9 joins the first route. A discharge part 12 is provided at the end of the third path.

  The humidifying unit 20 generates humidified gas (air) and supplies it between the print head 14 of the print unit 4 and the sheet. Thereby, the ink drying of the nozzle of the print head 14 is suppressed. The humidifying unit 20 and the printing unit 4 are connected by a first duct 21, and the humidifying unit 20 and the drying unit 8 are further connected by a second duct 22. The drying unit 8 generates a humid and high-temperature gas when the sheet is dried. This gas is introduced into the humidifying unit 20 through the second duct 22 and used as auxiliary energy for generating a humidified gas in the humidifying unit 20. The humidified gas generated in the humidifying unit 20 is introduced into the print unit through the first duct 21.

  The control unit 13 executes control of each unit of the entire printing apparatus. FIG. 2 is a block diagram illustrating a configuration of the control unit 13. The control unit 13 includes a CPU, a storage device, a controller including various control units, an external interface, and an operation unit 15 that is input and output by a user. The operation of the printing apparatus is controlled based on a command from a host device 16 such as a controller or a host computer connected to the controller via an external interface.

  A controller (range enclosed by a broken line) included in the control unit 13 includes a CPU 201, a ROM 202, a RAM 203, an HDD 204, an image processing unit 207, an engine control unit 208, and an individual unit control unit 209. The CPU 201 controls the operation of each unit of the printing apparatus in an integrated manner. The ROM 202 stores programs to be executed by the CPU 201 such as control described later in FIG. 7 and fixed data necessary for various operations of the printing apparatus. The RAM 203 is used as a work area for the CPU 201, used as a temporary storage area for various received data, and stores various setting data. The HDD 204 (hard disk) can store and read programs executed by the CPU 201, print data, and setting information necessary for various operations of the printing apparatus. The operation unit 15 is an input / output interface with a user, and includes an input unit such as a hard key and a touch panel, and an output unit such as a display for presenting information and a sound generator.

  An image processing unit 207 performs image processing of print data handled by the printing apparatus. The color space (for example, YCbCr) of the input image data is converted into a standard RGB color space (for example, sRGB). Various image processing such as resolution conversion, image analysis, and image correction is performed on the image data as necessary. The engine control unit 208 performs drive control of the print head 14 of the print unit 4 according to print data based on a control command received from the CPU 201 or the like. The engine control unit 208 also controls the transport mechanism of each unit in the printing apparatus. The individual unit control unit 209 includes a sheet supply unit 1, a decurling unit 2, a skew correction unit 3, an inspection unit 5, a cutter unit 6, an information recording unit 7, a drying unit 8, a reversing unit 9, a discharge conveyance unit 10, and a sorter unit. 11, a sub-controller for individually controlling each unit of the discharge unit 12 and the humidification unit 20. The individual unit control unit 209 controls the operation of each unit based on a command from the CPU 201. The external interface 205 is an interface (I / F) for connecting the controller to the host device 16 and is a local I / F or a network I / F. The above components are connected by the system bus 210. The host device 16 is a device serving as a supply source of image data for causing the printing apparatus to perform printing.

  Next, the basic operation during printing will be described. Since the printing operation differs between the single-sided printing mode and the double-sided printing mode, each will be described.

  FIG. 3 is a diagram for explaining the operation in the single-sided printing mode by the printing apparatus according to the present embodiment. The conveyance path from the printing of the sheet supplied from the sheet supply unit 1 to the discharge unit 12 is indicated by a bold line. Show. The sheet supplied from the sheet supply unit 1 and processed by the decurling unit 2 and the skew feeding correction unit 3 is printed on the front surface (first surface) by the printing unit 4. An image (unit image) having a predetermined unit length in the transport direction is sequentially printed on a long continuous sheet, and a plurality of images are printed side by side. The printed sheet passes through the inspection unit 5 and is cut for each unit image in the cutter unit 6. The cut sheet is recorded with print information on the back side of the sheet by the information recording unit 7 as necessary. Then, the cut sheets are conveyed one by one to the drying unit 8 and dried. Thereafter, the sheet is sequentially discharged and stacked on the discharge unit 12 of the sorter unit 11 via the discharge conveyance unit 10. On the other hand, the sheet left on the print unit 4 side by cutting the last unit image is sent back to the sheet supply unit 1, and the sheet is wound up by the roll R1 or R2. At the time of feeding back, the decurling force at the decurling unit 2 is adjusted to be small, and the print head 14 is retracted from the sheet.

  FIG. 4 is a diagram for explaining the operation in the duplex printing mode by the printing apparatus of the present embodiment. In double-sided printing, a back side (second side) printing operation is executed after a front side (first side) printing operation. In the first front surface print sequence, the operation in each unit from the sheet supply unit 1 to the inspection unit 5 is the same as the single-sided printing operation described above. The cutter unit 6 is conveyed to the drying unit 8 as a continuous sheet without performing a cutting operation. After the surface ink is dried by the drying unit 8, the sheet is guided not to the path on the discharge conveyance unit 10 (third path) but to the path on the reversing unit 9 (second path). In the second path, the sheet is wound around the rotating body of the reversing unit 9 that rotates in the forward direction (counterclockwise direction in the drawing). When all of the scheduled printing on the surface is completed in the printing unit 4, the trailing edge of the print area of the continuous sheet is cut by the cutter unit 6. With reference to the cutting position, the continuous sheet on the downstream side (printed side) in the conveying direction is wound up to the rear end (cutting position) of the sheet by the reversing unit 9 through the drying unit 8. On the other hand, at the same time as the winding by the reversing unit 9, the continuous sheet left on the upstream side in the conveyance direction (the printing unit 4 side) with respect to the cutting position does not leave the sheet tip (cutting position) in the decurling unit 2. Then, the sheet is fed back to the sheet supply unit 1, and the sheet is wound on the roll R1 or R2. By this feed back (back feed), collision with a sheet supplied again in the following back surface printing sequence is avoided. At the time of feeding back, the decurling force at the decurling unit 2 is adjusted to be small, and the print head 14 is retracted from the sheet.

  After the above-described front surface print sequence, the back surface print sequence is switched. The rotating body of the reversing unit 9 rotates in the opposite direction (clockwise direction in the drawing) to that during winding. The end of the wound sheet (the trailing edge of the sheet at the time of winding becomes the leading edge of the sheet at the time of feeding) is fed into the decurling unit 2 along the path of the broken line in the figure. The decurling unit 2 corrects the curl imparted by the rotating body. The sheet whose front and back sides are reversed is sent to the printing unit 4 through the skew correction unit 3 and printed on the back side of the sheet. The printed sheet passes through the inspection unit 5 and is cut into predetermined unit lengths set in advance in the cutter unit 6. Since the cut sheet is printed on both sides, recording by the information recording unit 7 is not performed. Cut sheets are conveyed one by one to the drying unit 8, and sequentially discharged and stacked on the discharge unit 12 of the sorter unit 11 via the discharge conveyance unit 10.

  FIG. 5 is a perspective view mainly showing a driving configuration of each of the rolls R <b> 1 and R <b> 2 in the sheet supply unit 1. As shown in FIG. 5, each of the rolls R <b> 1 and R <b> 2 includes a rotating body 31 that winds up the sheet S and feeds the wound sheet S, and a driving unit 30 that drives and rotates the rotating body. Configured. The rotating body 31 is configured to be rotatable in both the direction in which the sheet S is wound up and the direction in which the opposite sheet S is fed out. The drive unit 30 includes a drive source 33 such as a motor, a powder clutch 34 as a variable output torque clutch interposed between the drive source 33 and the rotating body 31, and other transmission mechanisms. The

  The powder clutch 34 of the drive unit 30 transmits the driving force of the drive source 33 to the rotating body 31 when the transmission torque reaches a torque commensurate with the amount of sheets wound around the rotating body 31. As a result, the predetermined rotational speed of the drive source 33 can be transmitted to the rotating body 31 regardless of the amount of the sheet wound by the rotating body 31. The powder clutch 34 of the present embodiment outputs a torque according to the supplied current value according to the current value-output torque characteristic corrected by the process described later with reference to FIG. As a result, even when there are variations in characteristics due to individual differences or changes over time, it is possible to output a transmission torque commensurate with the amount of sheets wound around the rotating body 31, and to appropriately transmit the driving force of the driving source 33. And can be shut off.

  FIG. 6 is a diagram illustrating an output torque characteristic that is a relationship between a current value to be supplied and an output torque of the powder clutch according to the present embodiment. In FIG. 6, the horizontal axis represents the current value, and the vertical axis represents the output torque value. The solid line 40 is a characteristic curve provided by the manufacturer of the powder clutch 34 according to the present embodiment. For example, the user of the powder clutch 34 can read and use the numerical value from the curve according to the purpose. The broken line 41 and the broken line 42 show two examples in which the characteristics of the output torque vary due to individual differences of the powder clutch 34, changes with time, and the like.

  FIG. 7 is a flowchart showing a correction process of the output torque characteristic of the powder clutch according to the embodiment of the present invention. The correction process of this embodiment is started when the winding operations of the rolls R1 and R2 are completed. As a result, the output characteristics can be corrected in accordance with the sheet winding amount at that time. In addition, by repeating this process every time the winding operation is finished, the output characteristic data as shown in FIG. 6 is obtained by using a plurality of correction values (with different winding amounts) acquired thereby. Can be created.

  When the roll R1 or R2 detects the end of sheet winding (step 50), the current supplied to the powder clutch 34 is turned off (step 51). As a result, the tension of the sheet S acting on the rotating body 31 is released. While the current is off, the motor of the drive source 33 is rotated in the direction opposite to the winding direction, that is, in the direction in which the sheet is loosened (step 52). After the rotational speed of the motor of the drive source 33 reaches a constant speed, the current value of the powder clutch 34 is gradually increased to increase the output torque (step 53).

  When the output torque of the powder clutch 34 reaches the transmission torque for rotating the rotator 31, and the rotator 31 starts to rotate, this is detected by the rotation angle measurement unit 54 (step 55). The current value when rotation is detected by the rotation angle measurement unit 54 is stored in the RAM 203 (FIG. 2), and the set current value obtained from the characteristic curve 40 shown in FIG. 6 and the detected current value are stored. The correction value is calculated by comparison, and is stored in the RAM 203 together with the winding amount information at that time (step 57). Moreover, when the rotation angle measurement part 54 detects rotation of the rotary body 31, the drive of the rotary body 31 by the drive source 33 is stopped (step 58). Further, the current value of the powder clutch 34 corresponding to the winding amount at that time is set to a corrected value (step 59). Finally, the operation after the winding operation, for example, the supply of the sheet from the rotating body 31 is started (step 60).

  In the above description, the correction process of the output torque characteristic of the powder clutch is performed every time the winding operation is completed, but the timing of implementation is not limited to this form. For example, the operating time of the apparatus, the print amount, and the like can be used as conditions. Further, it may be performed at the time of installation, shipment, maintenance, or the like of the apparatus.

  FIG. 8 is a diagram for explaining the corrected output torque curve of the powder clutch 34, and particularly shows an enlarged low torque region. By executing the process described above with reference to FIG. 7 for each of a plurality of different winding amounts, the corrected output torque characteristic data indicated by the curve 61 is obtained. For example, when the output torque required for a certain winding amount X1 is T1, the set current value of standard characteristic data prepared in advance is A1. On the other hand, the current value is calculated as A2 by performing the processing of FIG. As a result, the current value is corrected to A2 with respect to the winding amount X1. That is, by setting the required output torque at the winding amount at the time when the winding is completed, it is possible to set the current value according to the state of the powder clutch and the load state of the device each time.

  FIG. 9 is a diagram illustrating the rotation angle measurement unit 54 of the present embodiment. In the drive unit 30 configured in the sheet supply unit 1, the rotation angle measurement unit 54 includes an encoder 62, and the encoder 62 is disposed on the axis of the rotating body 31. By using the encoder 62, the current value of the powder clutch 34 can be increased smoothly. The encoder 62 can be replaced by a shielding flag 54. For example, in the reversing unit 9, a shielding flag 63 is used for the rotation angle measuring unit 54, and the shielding flag 63 is a part of the circumferential portion on the axis of the rotating body 31. Placed in. When the shielding flag 63 is used, it is necessary to set the current value increase to a staircase setting in order to determine whether or not the rotating body 31 has rotated once.

(Other embodiments)
In the embodiment described above, the present invention is applied to the powder clutch for transmitting the driving force of the driving source to the rotating body and for blocking, but the application of the present invention is not limited to this form. Of course. For example, the present invention can be applied to the brake function of a powder clutch described in Patent Document 1. That is, according to the tension information fed back, it is possible to set a torque that serves as a brake for setting and outputting a current value according to the characteristic curve shown in FIG. And it correct | amends according to the sheet | seat winding amount of a roll, and can finally obtain a characteristic as shown in FIG.

  Moreover, although the above-mentioned embodiment is related with the sheet winding apparatus in the printing apparatus, it can be similarly applied to an apparatus that includes a winding roll and supplies sheets of paper or other materials.

DESCRIPTION OF SYMBOLS 1 Sheet supply part 9 Inversion part 13 Control part 30 Drive part 31 Rotating body 33 Drive source 34 Powder clutch (variable output torque clutch)
62 Encoder 63 Shield flag

Claims (7)

A rotating body capable of rotating for winding or unwinding the sheet;
A driving source for generating a driving force for rotating the rotating body;
A variable output torque clutch that determines a driving force for rotating the rotating body by an output torque;
Control means for determining an output torque of the variable output torque clutch according to a winding amount of a sheet of the rotating body;
A sheet conveying apparatus comprising:   The control means determines the output torque according to a predetermined characteristic data indicating a relationship between the current value and the output torque, the characteristic data is corrected according to a winding amount of the sheet of the rotating body, The sheet conveying apparatus according to claim 1, wherein the output torque is determined by a current value according to the corrected characteristic data.   The characteristic data is corrected by a plurality of output torques corresponding to a plurality of winding amounts of the sheet of the rotating body and a plurality of current values corresponding to the plurality of output torques. The sheet conveying apparatus according to the description.   The variable output torque clutch is a clutch that transmits and interrupts the driving force of the driving source to the rotating body, and the output torque determined by the control means is transmitted by the driving force of the driving source. The sheet conveying apparatus according to any one of claims 1 to 3, wherein the torque is a torque at which the rotating body starts to rotate.   The sheet conveying apparatus according to claim 4, wherein the variable output torque clutch is a powder clutch. A sheet conveying device according to any one of claims 1 to 5,
A printing apparatus comprising printing means for printing on a conveyed sheet. A rotating body capable of rotating for winding or unwinding a sheet, a driving source for generating a driving force for rotating the rotating body, and a torque for outputting the driving force for rotating the rotating body A variable output torque clutch that defines a driving method in a device comprising:
A driving method characterized in that an output torque of the variable output torque clutch is determined according to a winding amount of a sheet of the rotating body.

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