JP4975122B2 - Printing apparatus and sheet processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To implement a compact de-curling mechanism that can de-curl sheets led in from different directions. <P>SOLUTION: In obverse printing, a sheet supplied from a sheet supply part (1) is led to a nip position between a first pinch roller (31) and a de-curling roller (20) from a first direction and is delivered under de-curling force applied by the de-curling roller (20). In reverse printing, on the other hand, the sheet supplied from a reverse part is led to the nip position from a second direction opposite to the first direction and is delivered under de-curling force applied by the de-curling roller (20). <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a printing apparatus that prints on a sheet.

  Patent Document 1 discloses a printing apparatus that performs double-sided printing on the front and back of a sheet by an inkjet method using a long continuous sheet wound in a roll shape.

JP 2008-126530 A

  The rolled sheet has curls. When the sheet is supplied to the printing unit while holding the curl, the leading end of the sheet and the print head may come into contact with each other. Therefore, it is desired that the sheet pulled out from the roll is decurled (curled) before printing by the printing unit.

  In the apparatus of Patent Document 1, in double-sided printing, after printing on a sheet front (front) surface, the sheet is once wound around a winding shaft, and the front and back are reversed and printing is performed on the back surface of the sheet. Even when the sheet is wound around the winding shaft, curling is newly applied in the winding direction. Therefore, it is desirable to decal before printing the front side as well as before inverting the sheet and printing the back side. This is a new problem in double-sided printing. However, the device of Patent Document 1 does not consider any decals.

  The present invention has been made based on recognition of the above problems. An object of the present invention is to provide a printing apparatus capable of performing decurling by a decurling mechanism common to both front surface printing and back surface printing in double-sided printing. Another object of the present invention is to provide a sheet processing apparatus having a compact decurling mechanism capable of decurling a sheet introduced from different directions.

The present invention is a printing apparatus capable of performing double-sided printing on a first surface and a second surface of a sheet, a sheet supply unit for holding and supplying a sheet wound in a roll shape, and the sheet A decurling unit for decurling the sheet supplied from the supplying unit, a printing unit for printing on the sheet that has passed through the decurling unit, and a reversing unit for winding up the sheet printed by the printing unit and inverting the front and back of the sheet has, in the duplex printing, the sheet supplied from the sheet supply section printed on the first surface in the decal in the decurling unit the printed portion is wound around the reversing portion being performed, then the control of such a sheet fed from the reverse unit again being decal by the decurling unit printed on the second surface before SL in the printing unit is performed ,
The decurling unit decurl roller and, disposed around the decurling roller capable of forming a nip state between each of the decurling roller, on both sides of the first pinch roller and the first pinch roller second has a pinch roller and a third pinch roller, the sheet supplied from the sheet supply section, wherein is introduced from the first direction between the first pinch roller and the decurling roller, said at least from the first pinch roller The sheet decurled by being conveyed in a state where the sheet is wound around a part of the decurling roller in the range up to the second pinch roller, sent toward the printing unit, and supplied from the reversing unit, the the first direction between the first pinch roller and the decurling roller is introduced from a second direction opposite, at least the first Some of the decurling roller in the range from the pinch roller to said third pinch roller being decal by being conveyed in a state where the sheet is wound around, characterized in that it is directed to the print unit.

  According to the present invention, it is possible to realize a printing apparatus capable of performing decurling by a decurling mechanism common to both front surface printing and back surface printing in double-sided printing. For this reason, high-quality double-sided printing is possible. In addition, a sheet processing apparatus including a compact decurling mechanism that can decur a sheet introduced from different directions is realized.

Schematic showing the internal configuration of the printing device Block diagram of control unit Diagram for explaining the operation in single-sided print mode and double-sided print mode Flow chart showing the sequence of decal operation Diagram for explaining decaling operation in front side printing Diagram for explaining decaling operation in front side printing Diagram for explaining decaling operation in front side printing Diagram for explaining the decurling operation in back side printing Diagram for explaining the decurling operation in back side printing The figure which shows the structure of the adjustment mechanism of decal force Conceptual diagram showing the configuration of a modified example of the decurling unit

  Hereinafter, an embodiment of a printing apparatus using an inkjet method will be described. The printing apparatus of this example uses a long and continuous sheet (a continuous sheet longer than the length of a repeated printing unit (referred to as one page or unit image) in the conveyance direction), and is used for both single-sided printing and double-sided printing. It is a compatible high-speed line printer. For example, it is suitable for the field of printing a large number of sheets in a print laboratory or the like. In this specification, even if a plurality of small images, characters, and blanks are mixed in the area of one print unit (one page), what is included in the area is collectively referred to as one unit image. . That is, 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.

  The present invention can be widely applied to printing apparatuses such as printers, multifunction printers, copiers, facsimile machines, and various device manufacturing apparatuses. The printing process may be any system such as an inkjet system, an electrophotographic system, a thermal transfer system, a dot impact system, or 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 continuous sheet.

  FIG. 1 is a schematic cross-sectional view showing the internal configuration of the printing apparatus. The printing apparatus according to the present embodiment is capable of duplex printing on the first surface of the sheet and the second surface on the back side of the first surface, using the sheet wound in a roll shape. Inside the printing apparatus, there are roughly 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, and a discharge unit. Each unit includes a transport unit 10, a sorter unit 11, a discharge unit 12, and a control unit 13. A sheet 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 is processed in each unit. Note that 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 is a unit for holding and supplying a continuous sheet wound in a roll shape. The sheet supply unit 1 can store two rolls R <b> 1 and R <b> 2, and is configured to selectively pull out and supply a sheet. The number of rolls that can be stored is not limited to two, and one or three or more rolls may be stored.

  The decurling unit 2 is a unit that 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, and curls the sheet by curving and passing the sheet so as to give the curl in the opposite direction, thereby reducing the curl.

  The skew correction unit 3 is a unit that corrects 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 printing unit 4 is a sheet processing unit that forms an image by performing a printing process on the conveyed sheet from above with the print head 14. That is, the print unit 4 is a processing unit that performs a predetermined process on the sheet. The printing unit 4 also includes a plurality of conveyance rollers that convey the sheet. 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.

  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. This is a unit for determining whether or not. The scanner has a CCD image sensor and a CMOS image sensor.

  The cutter unit 6 is a unit including a mechanical cutter that cuts a printed sheet into a predetermined length. The cutter unit 6 also includes a plurality of conveyance rollers for sending out the sheet to the next process.

  The information recording unit 7 is a unit that records print information (unique information) such as a print serial number and date in a non-print area of the cut sheet. Recording is performed by printing characters and codes using an inkjet method, a thermal transfer method, or the like. A sensor 17 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 17 detects the edge of the sheet between the cutter unit 6 and the recording position of the information recording unit 7, and the information recording unit 7 controls the timing of information recording based on the detection timing of the sensor 17.

  The drying unit 8 is a unit for heating the sheet printed by the printing unit 4 and drying the applied ink in a short time. Inside the drying unit 8, hot air is applied at least from the lower surface side to the passing sheet to dry the ink application surface. The drying method is not limited to the method of applying hot air, and may be a method of irradiating the sheet surface with electromagnetic waves (such as ultraviolet rays and infrared rays).

  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 a unit for temporarily winding a continuous sheet on which front surface printing has been completed when performing double-sided printing, 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 winding rotary body (drum) that rotates to wind the sheet. The continuous sheet that has been printed on the surface and has not been cut is temporarily wound around the winding rotary member. When the winding is completed, the winding rotary member rotates in the reverse direction, and the wound sheet is fed out in the reverse order to the winding and supplied to the decurling unit 2 and sent to the printing unit 4. Since this sheet is turned upside down, the printing unit 4 can print on the back side. More specific operation of duplex printing will be described later.

  The discharge conveyance unit 10 is a unit for conveying the sheet cut by the cutter unit 6 and dried by the drying unit 8 and delivering 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 is a unit for sorting printed sheets for each group as necessary. The sorted sheets are discharged to the discharge unit 12 including a plurality of trays. In this way, the third path has a layout that passes below the sheet supply unit 1 and discharges the sheet to the opposite side of the printing unit 4 and the drying unit 8 across the sheet supply unit 1.

  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 control unit 13 is a unit that controls each unit of the entire printing apparatus. 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.

  FIG. 2 is a block diagram showing the concept of the control unit 13. 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. A CPU 201 (central processing unit) controls the operation of each unit of the printing apparatus in an integrated manner. The ROM 202 stores programs executed by the CPU 201 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.

  A dedicated processing unit is provided for units that require high-speed data processing. 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. Print data obtained by these image processes is stored in the RAM 203 or the HDD 204. 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 and a sub-controller for individually controlling each unit of the discharge unit 12. 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. The host device 16 may be a general-purpose or dedicated computer, or a dedicated image device such as an image capture having an image reader unit, a digital camera, or a photo storage. When the host device 16 is a computer, an OS, application software for generating image data, and a printer driver for the printing device are installed in a storage device included in the computer. Note that it is not essential to implement all of the above processing by software, and a part or all of the processing may be realized by hardware.

  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. 3A is a diagram for explaining the operation in the single-sided print mode. 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 conveyance direction is sequentially printed on a long continuous sheet to form a plurality of images 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 on the roll R1 or R2.

Thus, in single-sided printing, the sheet passes through the first path and the third path and is processed, and does not pass through the second path. In summary, in the single-sided print mode, the following sequences (1) to (6) are executed under the control of the control unit 13.
(1) A sheet is sent out from the sheet supply unit 1 and supplied to the printing unit 4;
(2) Repeat printing of unit images on the first side of the supplied sheet by the printing unit 4;
(3) Repeat cutting of the sheet by the cutter unit 6 for each unit image printed on the first surface;
(4) The sheets cut for each unit image are passed through the drying unit 8 one by one;
(5) The sheets that have passed through the drying unit 8 one by one are discharged to the discharge unit 12 through the third path;
(6) The last unit image is cut and the sheet left on the print unit 4 side is sent back to the sheet supply unit 1.

  FIG. 3B is a diagram for explaining the operation in the duplex printing mode. In double-sided printing, the back (second side) print sequence is executed after the front (front) side (first side) print sequence. 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 one-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 winding rotary 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, the continuous sheet remaining on the upstream side in the conveying direction (on the printing unit 4 side) with respect to the cutting position is not supplied to the decurling unit 2 at the sheet leading end (cutting position). 1 and the sheet is wound on roll R1 or R2. By this rewinding, collision with the sheet supplied again in the following back surface printing sequence is avoided.

  After the above-described front surface print sequence, the back surface print sequence is switched. The winding rotary 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. In the decurling unit 2, the curl imparted by the winding rotary member is corrected. That is, the decurling unit 2 is provided between the sheet supply unit 1 and the printing unit 4 in the first path and between the reversing unit 9 and the printing unit 4 in the second path, and functions as a decal in any path. It is a common unit. 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.

As described above, in duplex printing, a sheet passes through the first path, the second path, the first path, and the third path in this order. In summary, the following sequences (1) to (11) are executed under the control of the control unit 13 in the duplex printing mode.
(1) A sheet is sent out from the sheet supply unit 1 and supplied to the printing unit 4;
(2) Repeat printing of unit images on the first side of the supplied sheet by the printing unit 4;
(3) Pass the sheet printed on the first surface through the drying unit 8;
(4) The sheet that has passed through the drying unit 8 is guided to the second path and wound on the winding rotary body of the reversing unit 9;
(5) After repeated printing on the first surface, the sheet is cut by the cutter unit 6 behind the last printed unit image;
(6) The sheet is wound around the winding rotary body until the end of the cut sheet passes through the drying unit 8 and reaches the winding rotary body. At the same time, the sheet cut and left on the print unit 4 side is sent back to the sheet supply unit 1;
(7) When the winding is completed, the winding rotating body is rotated in the reverse direction, and the sheet is supplied again to the printing unit 4 from the second path;
(8) Repeat printing of unit images by the printing unit 4 on the second surface of the sheet supplied from the second path;
(9) Repeat cutting of the sheet by the cutter unit 6 for each unit image printed on the second surface;
(10) The sheets cut for each unit image are passed through the drying unit 8 one by one;
(11) The sheets that have passed through the drying unit 8 one by one are discharged to the discharge unit 12 through the third path.

  Next, the curl correction operation in the decurling unit 2 in the printing apparatus having the above-described configuration will be described in more detail.

  5 to 7 are diagrams for explaining the configuration and operation of the decurling unit 2. The decurling unit 2 includes a decurling roller 20 for locally curving the sheet and applying a decurling force, and a first pinch roller 31 that faces the decurling roller 20 and can form a nip therebetween. The decurling unit 2 further includes a second pinch roller 41 and a third pinch roller 51 disposed on both sides so as to sandwich the first pinch roller around the decurling roller 20. The decurling roller 20 and the first pinch roller 31 form a first decurling roller pair 30, the decurling roller 20 and the second pinch roller 41 form a second decurling roller pair 40, and the decurling roller 20 and the third pinch roller 51 A third decal roller pair 50 is formed. In both cases, the decurling roller pair can independently form a nip state (can be separated and contacted).

  The decurling unit 2 is further supplied from a first introduction roller pair 21 that conveys and introduces a sheet supplied from the sheet supply unit 1 (first sheet supply unit), and a reversing unit 9 (second sheet supply unit). And a second introduction roller pair 22 for conveying and introducing the sheet. The decurling unit 2 further includes a discharge roller pair 23 that discharges the sheet from the decurling unit 2. The cam 32 and the pressing spring 33 form a drive mechanism for switching the nip state (separation and contact) by the first pinch roller 31. The cam 42 and the pressing spring 43 constitute a drive mechanism for switching the nip state by the second pinch roller 41. The cam 52 and the pressing spring 53 constitute a drive mechanism for switching the nip state by the third pinch roller 51.

  FIG. 4 is a flowchart showing the sequence of the decurling operation. The sequence differs depending on whether it is front side print (front side print in single-sided print mode and double-sided print mode) or back side print (back side print in double-sided print mode).

  In step S10, if the current print mode is front side printing, the process proceeds to step S11. If the current print mode is back side printing, the process proceeds to step S17.

  In step S11, the first decurling roller pair 30 is brought into the nip state, and the second decurling roller pair 40 and the third decurling roller pair 50 are brought into the separated state to release the nip. Specifically, the cam 32 rotates and the second pinch roller 41 and the third pinch roller 51 are lifted up from the pressure spring decurling roller 20 to be separated. Here, it is not essential that the third decurling roller pair 50 be released from the nip, and at least the second decurling roller pair 40 may be released from the nip.

  In step S12, the switch 24 for changing the traveling direction of the sheet in contact with the sheet is switched and set to a position as shown in FIG. In this state, with reference to the nip position of the first decurling roller pair 30, the switching device 24 enters the path on the side opposite to the sheet supply unit 1, and the switching device 24 moves from the path on the sheet supply unit 1 side. evacuate. Thus, the sheet S sent from the sheet supply unit 1 through the first introduction path toward the horizontal left direction (referred to as the first direction) in the drawing has passed the nip position of the first decurling roller pair 30. It abuts against the slope of the switch 24 and changes its direction of travel in the upper left direction of the figure. The direction in which the sheet S travels without being subjected to excessive stress can be changed.

  In step S <b> 13, the sheet supply from the sheet supply unit 1 is started. The leading end of the sheet S is nipped by the first introduction roller pair 21 in the first introduction path, nipped by the first decurling roller pair 30, and the direction of travel is changed by the switch 24, and the second decurling roller is released from the nip. Pass between pair 40. FIG. 5 shows a state where the second decurling roller pair 40 in the separated state has reached the position that has passed through the gap 25.

  In step S14, when the conveyance further proceeds from the state of FIG. 5 and the leading edge of the sheet S is nipped by the discharge roller pair 23, the sheet conveyance is temporarily stopped.

In step S15, the second pinch roller 41 is moved by the cam 32 and the pressing spring 33, and the sheet S is nipped by the second decurling roller pair 40. By this operation, the sheet S is wound around the decurling roller 20 and a decurling force is applied to the wound portion. The sheet S is bent at an angle (acute angle) smaller than 90 degrees with the decurling roller 20 at the apex, and is opposite to the winding direction of the sheet on the roll R1 of the sheet supply unit 1 .

  In step S16, the decurling roller 20 and the first introduction roller pair 21 are rotated in the reverse direction, and the sheet S is fed back in the reverse direction. FIG. 6 shows this state. The sheet S is fed back while being nipped by the first decurling roller pair 30 and the second decurling roller pair 40. The sheet S is conveyed while maintaining a state (a state in which a decurling force is applied) curved in the direction opposite to the sheet winding direction of the roll R1.

  In step S <b> 17, the sheet conveyance is stopped by further returning from this state until the leading edge of the sheet S is pulled out from the nip position of the first decurling roller pair 30. In this way, a region having a predetermined length from the leading edge of the sheet S passes through the decurling roller 20 while curving in the direction opposite to the curling direction by the decurling roller 20, and the decurling force is applied by the “squeezing” operation at that time. Thus, the curl at the front end of the sheet S is corrected.

  In step S18, the nip of the second decurling roller pair 40 is released again.

  In step S19, the sheet is resumed in the forward direction again. Depending on the type of the sheet S to be used, the curl of the sheet drawn from the roll is very large, and there is a possibility that the desired correction cannot be performed by a single decurling operation. In such a case, the decurling operation at the leading end of the sheet by the above-described feeding back operation may be repeated a plurality of times (two or more times).

  When the leading edge of the sheet passes through the second decurling roller pair 40 and is nipped by the discharge roller pair 23, the second decurling roller pair 40 is switched to the nip state. Then, the sheet is continuously conveyed and discharged from the decurling unit 2.

  FIG. 7 shows a state where the sheet S passes through the decurling unit 2 and is sent to the printing unit 4 after the decurling operation at the leading end of the sheet. Also at this time, the sheet S is wound at an acute angle with respect to the decurling roller 20 and is curved, and the decurling force acts on all regions of the sheet S fed from the sheet feeding unit 1. By the above-described feeding back operation, the leading edge of the sheet repeatedly passes through the decurling roller 20 (total three times), so that a large amount of decurling force is applied to the leading edge of the sheet S that requires decurling.

  On the other hand, if it is determined in step S10 that the print is back side and the process proceeds to step S21, the following sequence is executed. 8 and 9 are diagrams for explaining the operation of the decurling unit 2 in the back side printing. As described above, in the back side printing, the sheet S is supplied from the reversing unit 9 (second sheet supply unit) to the decurling unit 2.

  In step S21, the first decurling roller pair 30 is brought into the nip state, and at least the third decurling roller pair 50 is brought into the separated state to release the nip.

  In step S22, the switch 24 is switched to a position as shown in FIG. In this state, on the basis of the nip position of the first decurling roller pair 30, the switcher 24 enters the path on the side of the sheet supply unit 1 (the side opposite to the reversing unit 9), and is opposite to the sheet supply unit 1. On the other side (the reversing unit 9 side), the switch 24 is retracted from the path. As a result, the sheet S sent from the reversing unit 9 through the second introduction path toward the horizontal right direction (referred to as the second direction) in the drawing is switched after the nip position of the first decurling roller pair 30 has passed. Abutting on the slope of the vessel 24, the traveling direction is changed to the upper right direction in the figure. The direction in which the sheet S travels without being subjected to excessive stress can be changed.

  In step S23, supply of the sheet from the reversing unit 9 is started. The leading edge of the sheet S is nipped by the second introduction roller pair 22 in the second introduction path, nipped by the first decurling roller pair 30, and the direction of travel is changed by the switch 24 so that the nip is released. Pass between pair 50. FIG. 8 shows a state in which the position has passed through the gap 26 of the third decurling roller pair 50 in the separated state.

  In step S24, when the conveyance further proceeds from the state of FIG. 8 and the leading edge of the sheet S is nipped by the discharge roller pair 23, the sheet conveyance is temporarily stopped.

In step S25, the third pinch roller 51 is moved by the cam 42 and the pressing spring 43, and the sheet S is nipped by the third decurling roller pair 50. By this operation, the sheet S is wound around the decurling roller 20 and a decurling force is applied to the wound portion. The sheet S is bent at an angle (acute angle) smaller than 90 degrees with the decurling roller 20 at the apex, and in a direction opposite to the sheet winding direction at the reversing unit 9.

  In step S26, the decurling roller 20 and the second introduction roller pair 22 are rotated in the reverse direction, and the sheet S is fed back in the reverse direction. The sheet S is fed back while being nipped by the first decurling roller pair 30 and the third decurling roller pair 50. The sheet S is conveyed while maintaining a state (a state in which the decurling force is applied) curved in the direction opposite to the sheet winding direction in the reversing unit 9.

  In step S27, the sheet conveyance is stopped from this state until the leading edge of the sheet S is further pulled out from the nip position of the first decurling roller pair 30, and the sheet conveyance is stopped. Thus, the curl at the leading edge of the sheet S is corrected by passing the decurling roller 20 while a region having a predetermined length from the leading edge of the sheet S is curved in the direction opposite to the curling direction by the decurling roller 20.

  In step S28, the nip of the third decurling roller pair 50 is released again. Next, in step S29, the sheet is resumed in the forward direction again. When the leading edge of the sheet passes through the third decal roller pair 50 and is nipped by the discharge roller pair 23, the third decal roller pair 50 is switched to the nip state. Then, the sheet is continuously conveyed and discharged from the decurling unit 2. FIG. 9 shows a state in which the sheet S passes through the decurling unit 2 and is sent to the printing unit 4 after the decurling operation at the leading end of the sheet. Also at this time, the sheet S is wound at an acute angle with respect to the decurling roller 20 and curved, and the decurling force also acts on all areas of the sheet S supplied from the reversing unit 9.

  As with the roll R1 or R2 of the sheet supply unit 1, the first surface of the sheet that has been printed on the first surface and wound around the winding rotary body of the reversing unit 9 is on the outer side (outer periphery). It is wound on. The introduction direction (first direction) of the sheet supply unit 1 (first sheet supply unit) from the reversing unit 9 (second sheet supply unit) to the nip position of the first decurling roller pair 30 of the decurling unit 2 is It is introduced from the opposite direction (second direction). Therefore, the sheet that has passed through the decurling unit 2 is turned upside down, and the second surface of the sheet faces the print head 14 in the printing unit 4.

  As described above, the common decurling unit 2 allows front side printing (sheet feeding from the sheet feeding unit 1 as the first sheet feeding unit) and backside printing (sheet from the reversing unit 9 as the second sheet feeding unit). The decurling operation is different from that of (supply).

  By the way, when the printing of the sheet S is continuously performed, the roll outer diameter (radius) of the roll R1 or R2 set in the sheet supply unit 1 becomes smaller as the sheet S is consumed. The smaller the rule radius, the greater the curl of the sheet at that portion. That is, as the sheet S is consumed, the necessary decurling force to be corrected increases. Further, the required decurling force varies depending on the type of sheet (rigidity, etc.). Therefore, the decurling unit 2 has a mechanism for adjusting the decurling force applied to the sheet, and can apply an appropriate decurling force according to the remaining amount (curled state) of the sheet.

  FIG. 10 is a configuration diagram of a decurling force adjusting mechanism in the decurling roller 20. The adjustment mechanism includes two types of adjustment means. The first adjusting means is a pressing mechanism having a cam 32 and a pressing spring 33. As the cam 32 rotates, the pressing force of the first pinch roller 31 against the decurling roller 20 by the pressing spring 33 changes continuously or stepwise, and the nip force of the first decurling roller pair 30 changes. As the nip force increases, the sheet rigidity is overcome and the winding amount of the sheet S around the decurling roller 20 increases, and the decurling force increases accordingly.

  The second adjusting means is a temperature adjusting mechanism including a heater 60 incorporated in the decurling roller 20. When the roller surface temperature of the decurling roller 20 is increased by the heater 60, the decurling force against the contacting sheet is increased. The higher the temperature, the greater the decal force. Therefore, the decurling force can be changed by adjusting the heat generation amount of the heater 60.

  In step S19 and step S29 described above, according to information on the remaining amount of the sheet wound around the roll R1 (R2) in the sheet supply unit 1 or the winding rotary body of the reversing unit 9, and / or information on the sheet type, The two adjusting means described above are controlled. As the remaining amount of roll decreases, the nip force of the first decurling roller pair 30 is increased and at the same time the temperature of the heater 60 is controlled to be increased so as to increase the decurling force. In order to acquire the remaining amount information of the roll, it is estimated by subtracting a decrease in the roll diameter corresponding to the consumed sheet length (number of continuous prints and idle feed amount) from the initial roll diameter. Alternatively, a dedicated sensor may be provided to directly detect the roll and obtain information on the remaining roll diameter. Alternatively, a sensor that directly measures the curl state of the sheet may be provided so that the required decurling force can be obtained more directly. The sheet type is acquired from information set by the user on the operation unit 15.

  Depending on the type of sheet used, there are some that do not require decurling. In that case, step S14 to step 18 and step S24 to step S28 in FIG. 4 may be skipped.

  FIG. 11 is a conceptual diagram showing a configuration of a modified example of the decurling unit 2. In the configuration described above, the decurling roller 20 is fixed, and the pinch rollers (the first pinch roller 31, the second pinch roller 41, and the third pinch roller 51) are moved so that the respective roller pairs are brought into contact with and separated from each other. On the other hand, in FIG. 11, the same function is realized by moving the decurling roller side.

  In FIG. 11, the decurling roller 101 can be selectively moved in two directions (D1, D2) indicated by arrows in the drawing by a driving mechanism. The switch 105 for switching the sheet path is switched between a position indicated by a solid line and a position indicated by a broken line in the drawing. In front side printing, the decurling roller 101 moves in the D1 direction. The decurling roller 101 and the first pinch roller 102 (first decurling roller pair) come into contact with each other to be in a nip state, and the decurling roller 101 and the second pinch roller 103 (second pair of decurling rollers) come into contact with each other to enter a nip state. At the same time, the switch 105 enters the position indicated by the solid line. In front-side printing, a sheet is introduced from the sheet supply unit 1 along the guide 106, nipped by the first decal roller pair and the second decal roller pair, and decurling force is applied including the feeding back operation as described above. The

  On the other hand, in the reverse side printing, the decurling roller 101 moves in the D2 direction. The decurling roller 101 and the first pinch roller 102 (first decal roller pair) abut and come into a nip state, and the decurling roller 101 and the third pinch roller 104 (third decurling roller pair) come into contact and enter a nip state. . At the same time, the switch 105 enters the position indicated by the broken line. In front side printing, a sheet is introduced from the reversing unit 9 along the guide 109, nipped by the first decal roller pair and the third decal roller pair, and the decurling force including the feeding back operation is applied as described above. .

  In the embodiment described above, the sheet supply unit 1 is regarded as a first sheet supply unit, and the reversing unit 9 is regarded as a second sheet supply unit, and the decurling unit 2 is common to sheets supplied from either one. Appropriate decal operation is performed. A printing apparatus having a compact decurling mechanism that can perform decurling twice in double-sided printing is realized. This enables high-quality double-sided printing.

  The present invention is not limited to this. Assuming that the reversing unit 9 supplies an unused roll R3, an unused sheet is supplied from one of the roll R1 (or R2) and the roll R3 and printed on one side. It can also be applied to such a system.

DESCRIPTION OF SYMBOLS 1 Sheet supply part 2 Decal part 4 Print part 13 Control part 14 Print head 20 Decal roller 21 1st introduction roller pair 22 2nd introduction roller pair 23 Discharge roller pair 24 Switcher 30 1st decurling roller pair 31 1st pinch roller 40 Second decal roller pair 41 Second pinch roller 50 Third decal roller pair 51 Third pinch roller 60 Heater

Claims (12)

A printing apparatus capable of performing double-sided printing on a first side and a second side of a sheet ,
A sheet supply unit for holding and supplying a rolled sheet,
A decurling unit for decurling the sheet fed from the sheet feeding unit;
A printing unit that prints on the sheet that has passed through the decurling unit;
A reversing unit that winds up the sheet printed by the printing unit and reverses the front and back of the sheet,
In duplex printing, the sheet supplied from the sheet supply section printed on the first surface in the decal in the decurling unit the printed portion is wound on the reversing section is made, then from the reversing portion the supplied sheet is controlled so printing is performed before Symbol second surface again being decal by the decurling unit the printing unit,
The decal part is
Decurling roller and, disposed around the decurling roller capable of forming a nip state between each of the decurling roller, the second pinch rollers and the third sides of the first pinch roller and the first pinch roller Having a pinch roller,
The sheet supplied from the sheet supply unit is introduced from the first direction between the first pinch roller and the decurling roller, and at least in the range from the first pinch roller to the second pinch roller , the decurling roller Is decurled by being conveyed in a state in which the sheet is wound around a part of the sheet , and sent to the print unit,
The sheet supplied from the reversing unit is introduced between the first pinch roller and the decurling roller from a second direction opposite to the first direction, and at least from the first pinch roller to the third pinch roller. A printing apparatus, wherein the sheet is decurled by being conveyed in a state where a sheet is wound around a part of the decurling roller in the range up to the above, and sent toward the printing unit.   The reversing unit includes a winding rotary member that winds up a sheet. In the double-sided printing, the sheet printed on the first surface is temporarily wound around the winding rotary member, and then the winding unit. The printing apparatus according to claim 1, wherein the rotary member rotates reversely and the temporarily wound sheet is introduced into the decurling unit from the second direction. A switch for switching a path, and when the sheet is supplied from the sheet supply unit, the switch is on the side opposite to the sheet supply unit with respect to the nip position of the first pinch roller and the decurling roller When the sheet is fed from the reversing unit, the switching unit moves on the side opposite to the reversing unit with respect to the nip position. The printing apparatus according to claim 1, wherein the printing apparatus changes the traveling direction of the sheet by entering the sheet. And having a discharge roller pair for feeding to the printing unit by nipping the sheet, printing apparatus according to any one of claims 1 to 3. Said sheet sheet supplied from the supply unit, the second pinch roller is spaced at state is sent et toward the printing unit passes through between the decurling roller and the second pinch roller, the sheet leading end is the It said second pinch roller if it is nipped by the discharge roller is switched to the nip state and then the sheet until at least the leading edge of the sheet is withdrawn from Knitting flop of the decurling roller and the first pinch roller is sent back in the opposite direction, then, The sheet is sent again to the print section ,
Sheet fed from the reversing unit passes between the third pinch rollers spaced above feed et al is in toward the printing unit in the state of the third pinch rollers and the decurling roller, the leading edge of the sheet the discharge switching the third pinch rollers When the nip to the nip state the roller, then the sheet until at least the leading edge of the sheet is withdrawn from Knitting flop of the decurling roller and the first pinch roller is sent back in the opposite direction, then the sheet The printing apparatus according to claim 4, wherein the printer is sent again to the printing unit.   The printing apparatus according to claim 1, further comprising an adjustment mechanism that adjusts a decurling force applied to the sheet by the decurling roller.   The printing apparatus according to claim 6, wherein the adjustment mechanism includes a mechanism that changes a force that presses the first pinch roller against the decurling roller.   The printing apparatus according to claim 6, wherein the adjustment mechanism includes a heater that is incorporated in the decurling roller to change a roller surface temperature.   It has means for acquiring information about the remaining amount of the sheet wound in a roll shape or information about the type of sheet, and the decurling force is adjusted by the adjusting mechanism based on the acquired information, The printing apparatus according to claim 6. The sheet held by the sheet supply unit is wound so that the leading edge of the sheet introduced from the first direction is curled in a direction away from the decurling roller, and the sheet wound by the reversing unit is 10. The printing apparatus according to claim 1, wherein the leading end of the sheet introduced from the second direction is wound so as to curl in a direction away from the decurling roller. An apparatus for processing sheets ,
A sheet processing unit;
The sheet to be subjected fed by decal anda decurling unit for feeding the sheet processing unit,
The decal part is
Decurling roller and, disposed around the decurling roller capable of forming a nip state between each of the decurling roller, the second pinch rollers and the third sides of the first pinch roller and the first pinch roller Having a pinch roller,
Sheet fed from the first direction, wherein the first pinch roller is introduced between the decurling roller, the sheet to a portion of the decurling roller in the range of from at least the first pinch roller to said second pinch roller are decal by is conveyed by winding with a state, it is directed to the sheet processing unit,
The sheet supplied from the second direction opposite to the first direction is introduced between the first pinch roller and the decurling roller, and at least in the range from the first pinch roller to the third pinch roller. A sheet processing apparatus, wherein the sheet is decurled by being conveyed in a state in which the sheet is wound around a part of the decurling roller , and is sent toward the sheet processing unit. Has a switching device for switching the path, the switching device is when the sheet is supplied from the first direction the sheet is fed from the first direction with respect to the nip position of the decurling roller and the first pinch roller that the side to change the traveling direction of the sheet enters the sheet conveying path on the opposite side to the said said switching device from the second direction when the sheet is supplied the second direction with respect to the nipping position and wherein the changing the traveling direction of the sheet enters the sheet conveying path on the opposite side to the side where the sheet is fed from the sheet processing apparatus according to claim 11, wherein.

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