Patent Publication Number: US-10787009-B2

Title: Printing apparatus

Description:
The present application is based on, and claims priority from JP Application Serial Number 2018-145668, filed Aug. 2, 2018, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a printing apparatus. 
     2. Related Art 
     Typically, a recording device provided with a sheet storage mechanism that stores a sheet discharged from a discharge port is known (for example, see JP-A-2012-176821). 
     However, in the recording device described above, there is a problem that, when the sheet is stored in the sheet storage mechanism in a state where a portion of the sheet on which an image is formed is not sufficiently dried, due to a deformation of the sheet or the like, the portion of the sheet on which the image is formed is rubbed and the image quality is decreased. 
     SUMMARY 
     The printing apparatus according to the present application includes a first roller pair configured to sandwich and convey a continuous medium, a printing head that is located downstream of the first roller pair in a conveying direction of the continuous medium and that is configured to perform printing on the continuous medium, a cutting unit that is located downstream of the printing head in the conveying direction of the continuous medium and that is configured to cut the continuous medium, a second roller pair that is located downstream of the cutting unit in the conveying direction of the continuous medium and that is configured to sandwich and convey the continuous medium, a common driving source configured to apply driving force to the first roller pair and the second roller pair, and a clutch mechanism configured to cut power from the driving source to the second roller pair, wherein the clutch mechanism is an electromagnetic mechanism that releases transmission of the power by electromagnetism. 
     The printing apparatus described above may further include a medium detector that is located between the first roller pair and the printing head and that is configured to detect presence or absence of the continuous medium, and a control unit that is configured to, after the continuous medium is cut, convey, in a reverse direction, the continuous medium located at a supply side, and that is configured to, after an end portion at the downstream side of the continuous medium is detected by the medium detector, convey the continuous medium in a forward direction and temporarily stop the continuous medium at a predetermined position. The control unit controls the clutch mechanism to, when the continuous medium is conveyed in the reverse direction, cut the power from the driving source to the second roller pair and, when the continuous medium is conveyed in the forward direction after being temporarily stopped at the predetermined position, couple the power from the driving source to the second roller pair, and then, when a distance between the second roller pair and an end portion at the upstream side in the conveying direction of the continuous medium that is sandwiched by the second roller pair is 2 mm±1 mm, cut the power from the driving source to the second roller pair. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating a configuration of a printing apparatus. 
         FIG. 2  is a schematic view illustrating the configuration of the printing apparatus. 
         FIG. 3  is a block diagram illustrating a control configuration of the printing apparatus. 
         FIG. 4A  is a schematic view illustrating a control method of the printing apparatus. 
         FIG. 4B  is a schematic view illustrating the control method of the printing apparatus. 
         FIG. 4C  is a schematic view illustrating the control method of the printing apparatus. 
         FIG. 4D  is a schematic view illustrating the control method of the printing apparatus. 
         FIG. 4E  is a schematic view illustrating the control method of the printing apparatus. 
         FIG. 4F  is a schematic view illustrating the control method of the printing apparatus. 
         FIG. 4G  is a schematic view illustrating the control method of the printing apparatus. 
         FIG. 4H  is a schematic view illustrating the control method of the printing apparatus. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, embodiments of the present disclosure will be described below with reference to the figures. Note that, in each of the figures below, to illustrate each of members and the like in a recognizable size, each of the members and the like is illustrated to a scale different from an actual scale. 
     First, a configuration of a printing apparatus  1  will be described.  FIG. 1  is a perspective view illustrating the configuration of the printing apparatus  1 . Note that in the following description, assuming that the printing apparatus  1  illustrated in  FIG. 1  is placed on a horizontal surface, a direction along the upward and downward directions (vertical direction) is illustrated as a Z axis direction, and a direction along the horizontal surface is illustrated as an X axis direction and a Y axis direction. That is, when the printing apparatus  1  is viewed from the front, the X axis direction that is the width direction, the Y axis direction that is the depth direction, and the Z axis direction that is the height direction are different directions and are orthogonal to each other. 
     As illustrated in  FIG. 1 , for example, the printing apparatus  1  is an ink jet printer capable of forming an image with respect to a sheet S (roll paper) as a continuous medium with a relatively large size, such as an A0 size or B0 size of the JIS standard. The printing apparatus  1  includes a main body  2  and a discharged sheet receiving unit  3 . The main body  2  is disposed on the upper portion of a prop  8  that is erected on a base  9 . The discharged sheet receiving unit  3  has a stacker  4 . The stacker  4  is disposed below the main body  2  and receives the sheet S discharged from the main body  2  side. 
     The printing apparatus  1  includes a substantially rectangular parallelepiped housing  12 . On the top surface of the housing  12 , a sheet feed cover  13  located on the rear side and a maintenance cover  14  located on the front side are provided to be openable and closable. An operation panel  15  for performing various operations of the printing apparatus  1  is disposed at a position adjacent to the maintenance cover  14  in the X axis direction on the upper surface of the housing  12 . Then, a discharge port  16  that allows discharging of the sheet S on which the image is formed in the housing  12  is disposed on the front surface of the housing  12  on the +Y direction side in the Y axis direction. In the present embodiment, the +Y direction in the Y axis direction coincides with the discharge direction of the sheet S. 
       FIG. 2  is a schematic view illustrating the configuration of the printing apparatus  1 . As illustrated in  FIG. 2 , the housing  12  of the printing apparatus  1  includes a recording unit  20  that records an image of character, photographs, and the like on the sheet S, and a first support member  31  and a second support member  32  that support the sheet S. In addition, the housing  12  of the printing apparatus  1  includes a conveying unit  40  that conveys the sheet S, and a cutting unit  50  that cuts the sheet S recorded by the recording unit  20 . Then, a control unit  18  that controls each of the components of the printing apparatus  1  is provided. 
     A roll body R in which the sheet S is wound in a roll shape is disposed in the housing  12 . The roll body R is disposed rearward in the housing  12  in  FIG. 2 . The roll body R is rotatably supported by a shaft  23  provided to extend in the width direction (X axis direction) of the sheet S. According to the present embodiment, the sheet S is conveyed out from the roll body R by rotating the shaft  23  in the counterclockwise direction in  FIG. 2 . The conveyed out sheet S is conveyed by the conveying unit  40  and is discharged from the housing  12  to the outside of the housing  12  through the discharge port  16  that opens to the front surface of the housing  12 . That is, according to the present embodiment, a direction from the rear to the front of the housing  12  is a conveying direction D of the sheet S conveyed by the conveying unit  40 . 
     The recording unit  20  includes a printing head  21  (for example, an ink jet head) that ejects ink as a liquid toward the sheet S and prints on the sheet S, and a carriage  22  on which the printing head  21  is mounted. The carriage  22  is supported by a frame  19  disposed in the housing  12  and a guide shaft  17  attached to the frame  19 . The guide shaft  17  extends in the width direction (X axis direction) of the sheet S. The carriage  22  is movable along the guide shaft  17  by the power of a motor (not illustrated). That is, the carriage  22  reciprocates in a direction (X axis direction) that intersects the conveying direction D of the sheet S. The printing head  21  can eject ink on the sheet S across the X axis direction (width direction) by moving the carriage  22  along the guide shaft  17 . 
     The first and second support members  31  and  32  are configured by plate-shaped members. The first support member  31  is disposed upstream of the second support member  32  in the conveying direction D of the sheet S, and guides the sheet S conveyed out from the roll body R toward the recording unit  20 . The second support member  32  is disposed to face the printing head  21  of the recording unit  20 . At the ejected position E where the second support member  32  and the printing head  21  face each other, ink is ejected from the printing head  21  onto the sheet S. 
     The conveying unit  40  conveys the sheet S conveyed out from the roll body R toward the discharge port  16  from within the housing  12  along the first and second support members  31  and  32  while sandwiching the sheet S. In the conveying unit  40  of the present embodiment, a first roller pair  41  is disposed on the most upstream side in the conveying direction D, and the second roller pair  42  is disposed on the most downstream side in the conveying direction D. 
     The first roller pair  41  is disposed upstream of the printing head  21  in the conveying direction D and is disposed between the first support member  31  and the second support member  32 . The first roller pair  41  sandwiches and conveys the sheet S and includes a first driving roller  41   a  and a driven roller  41   b  which is capable of being driven to rotate with respect to the rotation of the first driving roller  41   a . The second roller pair  42  includes a second driving roller  42   a  and a driven roller  42   b  which is capable of driven rotation with respect to the rotation of the second driving roller  42   a.    
     The first and second driving rollers  41   a  and  42   a  are driven by a motor  46  as a common driving source. In the present embodiment, the first driving roller  41   a  of the first roller pair  41  and the motor  46  are coupled. The first driving roller  41   a  and the second driving roller  42   a  are coupled by a transmission gear. Then, the first and second driving rollers  41   a  and  42   a  are driven to rotate by the driving of the motor  46 . As a result, the first and second roller pairs  41  and  42  can rotate in a state in which the sheet S is sandwiched by the first and second driving rollers  41   a  and  42   a  and the driven roller  41   b  and  42   b , and can convey the sheet S along the conveying direction D. Here, it is conceivable that the driving source (motor) is disposed individually with respect to each of the first and second driving rollers  41   a  and  42   a , but in this case, there is a risk that the conveying amount of the sheet S is shifted and conveying accuracy is reduced due to the occurrence of dispersion in the conveying accuracy of the first and second driving rollers  41   a  and  42   a . Therefore, in the present embodiment, the conveying accuracy of the sheet S is improved by driving the first and second driving rollers  41   a  and  42   a  by the common driving source (motor  46 ). 
     In addition, a rotary encoder  47  as a measuring means is disposed on the motor  46 . The rotary encoder  47  is coupled to the control unit  18 . The rotary encoder  47  is a sensor that converts the amount of mechanical displacement of rotation into an electrical signal, and processes the signal to detect position, speed, and the like. According to the embodiment, the rotary encoder  47  is used to position the end portion Sa downstream of the sheet S described below. The rotary encoder  47  is configured by a slit disk fixed to a rotary shaft of the motor  46 , and a position detector disposed at a position where the peripheral edge of the slit disk passes. A plurality of position detection slits are formed at equal intervals throughout the entire circumference of the slit disk along the peripheral edge. Then, the position detector includes a light emitting unit configured by a light emitting diode, and a light receiving unit configured by a phototransistor so as to face each other via the peripheral edge of the slit disk. Then, the position detector is configured to output an electrical signal from the light receiving unit when light from the light emitting unit passes through the position detection slit of the slit disk and received by the light receiving unit. 
     The first and second driving rollers  41   a  and  42   a  are disposed to contact the sheet S from below. The driven roller  41   b  and  42   b  are disposed to contact the sheet S from above. The driven roller  42   b , when conveying the sheet S, contacts the surface of the sheet S on which the ink is ejected. Therefore, the driven roller  42   b  is configured by a star wheel having a small contact area with respect to the sheet S, or the like in order to reduce deterioration of the quality of the image recorded in the sheet S. Note that the configuration of the driven roller  41   b  is the same as that of the driven roller  42   b . A plurality of the first and second roller pairs  41  and  42  are disposed at predetermined intervals in the width direction. 
     The cutting unit  50  is disposed between the printing head  21  and the second roller pair  42  in the conveying direction D. The sheet S cut by the cutting unit  50  is discharged from the discharge port  16  via conveying by the second roller pair  42 . Note that the printing apparatus  1  according to the present embodiment is configured with a relatively small interval in the vertical direction Z in the opening of the discharge port  16  so that fingers of a user cannot be inserted into the housing  12  from the discharge port  16 . Therefore, by disposing the second roller pair  42  near the upstream side of the discharge port  16 , the sheet S can be smoothly conveyed toward the discharge port  16 , and sheet jam can be prevented from occurring. 
     The cutting unit  50  includes a cutting blade  51  for cutting the sheet S and a holding body  55  that holds the cutting blade  51 . The cutting blade  51  is configured by a disk-shaped driving blade  52  and a disk-shaped driven blade  53 . The driving blade  52  and the driven blade  53  are rotatably attached to the holding body  55 . The driving blade  52  and the driven blade  53  are disposed to be aligned in the vertical direction. The holding body  55  is capable of reciprocating along the X axis direction. The cutting unit  50  cuts the sheet S by the cutting blade  51  by moving the holding body  55  along the X axis direction. That is, the sheet S is cut by scanning the cutting unit  50  including the cutting blade  51  in the X axis direction that intersects the conveying direction D of the sheet S. 
     The cutting unit  50  includes a driving source such as a motor, to reciprocate the cutting unit  50  along the X axis direction by driving force of the motor. Note that the cutting unit  50  and the carriage  22  may be coupled, and the cutting unit  50  may reciprocate along the X axis direction by the power of the motor that moves the carriage  22 . 
     In addition, a medium detector  60  is disposed between the first roller pair  41  and the printing head  21  in the conveying direction D. The medium detector  60  is a sensor that detects the presence of the sheet S. The medium detector  60  is coupled to the control unit  18 , and the motor  46  is controlled based on detection data from the medium detector  60 . For example, the medium detector  60  is a photo-interrupter, and includes a light emitting unit that emits light and a light receiving unit that receives light emitted from the light emitting unit. For example, as a light emitting element of the light emitting unit, a Light Emitting Diode (LED) light emitting element, a laser light emitting element or the like are applied. In addition, the light receiving unit is configured by a phototransistor, a photo IC and the like. Then, a change in light receiving amount between the light emitting unit and the light receiving unit is converted into an electrical signal and output as detection data. The control unit  18  determines the presence of the sheet S based on the detection data, and controls the motor  46 . 
     Here, a clutch mechanism  43  configured to be able to cut the power from the motor  46  to the second roller pair  42  is disposed on the conveying unit  40 . That is, the clutch mechanism  43  is disposed between the motor  46  and the second driving roller  42   a . The clutch mechanism  43  is an electromagnetic clutch mechanism that can transmit or release the power from the motor  46  to the second driving roller  42   a  by electromagnetism. The clutch mechanism  43  is coupled to the control unit  18 . Then, based on a drive signal from the control unit  18 , when the clutch mechanism  43  is turned in an ON state, the power is transmitted from the motor  46  to the second driving roller  42   a . On the other hand, when the clutch mechanism  43  is turned in an OFF state, the power is released from the motor  46  to the second driving roller  42   a.    
     In addition, the conveying amount of the sheet S of the first roller pair  41  per predetermined driving amount of the motor  46  is smaller (lower) than the conveying amount of the sheet S of the second roller pair  42 . In other words, the second driving roller  42   a  is driven to accelerate with respect to the first driving roller  41   a . It is possible to drive the speed increasing by adjusting the diameter of the first driving roller  41   a  and the second driving roller  42   a , gear ratio, and the like. When the printing head  21  ejects ink onto the sheet S to form an image, in a case where the sheet S is extended due to the reception of ink, the sheet S bends and contacts the printing head  21 , and an ejection failure of the printing head  21  occurs. Accordingly, by making the conveying amount of the second driving roller  42   a  disposed downstream in the conveying direction D of the second support member  32  including the ejected position E larger than that of the first driving roller  41   a , tension can be applied to the sheet S, the occurrence of bending of the sheet S can be suppressed, and the occurrence of ejection failure can be prevented. 
     Next, the control configuration of the printing apparatus  1  will be described.  FIG. 3  is a block diagram illustrating the control configuration of the printing apparatus  1 . As illustrated in  FIG. 3 , the control unit  18  is coupled to the operation panel  15 , the printing head  21 , the carriage  22 , the conveying unit  40 , the cutting unit  50 , the medium detector  60 , and the rotary encoder  47 . Further, the control unit  18  is coupled to the clutch mechanism  43 . The control unit  18  includes a Central Processing Unit (CPU) for executing various programs, a Random Access Memory (RAM) for temporarily storing data, programs, and the like, a Read Only Memory (ROM) in which various data, various programs, and the like are recorded in advance in a non-volatile manner, and an interface. Then, the CPU processes various signals input via the interface based on data in the RAM and the ROM, and outputs control signals to each unit via the interface. The control unit  18  receives operation information of the user operation from the operation panel  15 , controls the carriage  22  (motor), the printing head  21 , the motor  46  of the conveying unit  40  and the cutting unit  50  (motor), and executes a printing operation (image forming process) and a cutting operation of the sheet S. In addition, the motor  46  is driven and controlled based on the detection data of the medium detector  60  and the rotary encoder  47 . In addition, the clutch mechanism  43  is turned ON/OFF to control the driving of the second driving roller  42   a.    
     Next, the control method of the printing apparatus  1  will be described.  FIG. 4A  to  FIG. 4H  are schematic views illustrating the control method of the printing apparatus  1 . In the control method of the printing apparatus  1  described below, each unit is driven and controlled based on a control signal of the control unit  18 . 
     As illustrated in  FIG. 4A , the control unit  18  drives the motor  46  of the conveying unit  40  to rotate in a forward direction to intermittently move the sheet S in the conveying direction D. Then, at each stop in the intermittent movement by the conveying unit  40 , the carriage  22  is moved in the X axis direction, and ink is ejected from the printing head  21  mounted on the carriage  22  toward the sheet S. As a result, a desired image is printed on the sheet S (image forming process). Note that during the process of image forming, the first and second driving rollers  41   a  and  42   a  are driven to rotate in the counterclockwise direction in  FIG. 4A . The sheet S on which the image is formed is conveyed in the conveying direction D by the conveying unit  40 , and is discharged from the discharge port  16  (see  FIG. 2 ). 
     Next, as illustrated in  FIG. 4B , after the predetermined recording operation is completed, that is, after the predetermined image is printed on the sheet S, the control unit  18  drives the cutting unit  50  to cut the sheet S. Specifically, the control unit  18  stops the conveying unit  40 , and stops the conveying of the sheet S. Thereafter, the control unit  18  moves the cutting unit  50  in the X axis direction. As a result, the sheet S is cut. The sheet S′ as a continuous medium cut by the cutting unit  50 , is held in a state of being nipped by the second roller pair  42 . 
     Next, as illustrated in  FIG. 4C , the control unit  18  conveys the sheet S located on the supply side (roll body R side) in the reverse direction. That is, the sheet S is conveyed in a direction opposite to the conveying direction D. Specifically, the control unit  18  drives the motor  46  to rotate in the reverse direction opposite to the forward direction. As a result, the first driving roller  41   a  rotates in the clockwise direction in  FIG. 4C . Then, the sheet S is conveyed in the direction opposite to the conveying direction D by the first roller pair  41 . In addition, when the sheet S on the supply side is conveyed in the reverse direction upstream in the conveying direction D, the control unit  18  cuts the power from the motor  46  to the second roller pair  42 . Specifically, the supply of current to the clutch mechanism  43  is stopped based on a control signal of the control unit  18 . As a result, the clutch mechanism  43  is turned in the OFF state and the power is released from the motor  46  to the second driving roller  42   a . Therefore, the second roller pair  42  including the second driving roller  42   a  is held in a state when the sheet S′ is cut. That is, the cut sheet S′ does not move upstream in the conveying direction D, and the sheet S′ does not conflict with the cutting unit  50  and the like. Then, the sheet S′ is held by the second roller pair  42 , and drying of the ink applied on the sheet S′ is promoted. 
     Next, as illustrated in  FIG. 4D , the control unit  18  stops the reverse conveying of the sheet S in a case where the end portion Sa on the downstream side of the sheet S conveyed in the reverse direction is detected by the medium detector  60 . Specifically, based on the detection data of the medium detector  60 , that is, based on the change data of the light receiving amount by the light receiving unit, when the end portion Sa on the downstream side of the sheet S passes through the medium detector  60 , the control unit  18  determines that the sheet S is not present, and stops driving the motor  46 . 
     Next, as illustrated in  FIG. 4E , the control unit  18  conveys the sheet S in the forward direction (conveys in the conveying direction D), and temporarily stops the end portion Sa on the downstream side of the sheet S at a predetermined position. Specifically, the control unit  18  drives the motor  46  to rotate in the forward direction. As a result, the first driving roller  41   a  rotates in the counterclockwise direction. Then, based on the detection data from the rotary encoder  47 , when the end portion Sa on the downstream side of the sheet S reaches the predetermined position, the drive of the motor  46  is stopped. In the control unit  18 , the detection data (output value) from the rotary encoder  47  corresponding to a distance from a position where the end portion Sa on the downstream side of the sheet S is detected by the medium detector  60  to the predetermined position is stored in advance. Note that the second roller pair  42  are in a state where the power from the motor  46  is cut off during the processes illustrated in  FIG. 4C  to  FIG. 4E . As a result, the state in which the sheet S′ is held by the second roller pair  42  is maintained, and drying of the ink applied on the sheet S′ is further promoted. 
     Next, as illustrated in  FIG. 4F , the control unit  18  conveys the sheet S and the sheet S′ in the forward direction toward the conveying direction D. Specifically, the motor  46  is driven to rotate in the forward direction. As a result, the first driving roller  41   a  rotates in the counterclockwise direction. Then, the sheet S is conveyed in the conveying direction D by the first roller pair  41 . In addition, the power from the motor  46  is transmitted to the second roller pair  42 . Specifically, current is supplied to the clutch mechanism  43  based on the control signal of the control unit  18 . As a result, the clutch mechanism  43  is turned in the ON state and the power is transmitted from the motor  46  to the second drive roller  42   a , and the second drive roller  42   a  rotates in the counterclockwise direction. As a result, the sheet S′ is conveyed in the conveying direction D by the second roller pair  42 . 
     Next, as illustrated in  FIG. 4G , the control unit  18  conveys the sheet S and the sheet S′ in the forward direction, and cuts (releases) the power from the motor  46  to the second roller pair  42  when the distance between the second roller pair  42  and the end portion S′b on the upstream side in the conveying direction of the sheet S′ which is sandwiched by the second roller pair  42  is a predetermined distance b. Note that the predetermined distance b of the present embodiment is 2 mm±1 mm. The control unit  18  drives the motor  46  to rotate in the forward direction and rotates the first driving roller  41   a  in the counterclockwise direction. As a result, the sheet S is conveyed in the conveying direction D by the first roller pair  41 . 
     On the other hand, based on the detection data of the rotary encoder  47  when the end portion S′b on the upstream side in the conveying direction of the sheet S′ reached the distance b, the power from the motor  46  to the second roller pair  42  is cut (released). Specifically, the supply of current to the clutch mechanism  43  is stopped based on the control signal of the control unit  18 . As a result, the clutch mechanism  43  is turned in the OFF state and the power is released from the motor  46  to the second driving roller  42   a . Therefore, the second roller pair  42  including the second driving roller  42   a  holds the sheet S′ in a state where the distance b between the second roller pair  42  and the end portion S′b on the upstream side in the conveying direction of the sheet S′ is 2 mm±1 mm. Specifically, the sheet S′ is held in a state where one end portion in the conveying direction D of the sheet S′ is held (nipped). Thus, the second roller pair  42  can nip a region other than the region of the sheet S′ where the image is formed, and can reduce contact between the driven roller  42   b  of the second roller pair  42  and the image formed on the sheet S′ and maintain the image quality. Note that in this state, the user may pull out the sheet S′ in the +Y direction. Since the second roller pair  42  nips one end portion of the sheet S′, the user can easily pull out the sheet S′ without loading from the second roller pair  42 . 
     In the control unit  18 , the time when the end portion Sa on the downstream side of the sheet S temporarily stops at the position moving a distance a from the medium detector  60  serves as a base point, and the detection data (output value) from the rotary encoder  47  corresponding to the distance b between the second roller pair  42  and the end portion S′b on the upstream side in the conveying direction of the sheet S′ is stored in advance. Note that the distance b can be set as the distance between the end portion S′b on the upstream side in the conveying direction of the sheet S′ and the center portion of the nip width in the conveying direction D of the second roller pair  42  when viewed from the Z direction. 
     Next, as illustrated in  FIG. 4H , the control unit  18  prints an image on the sheet S while conveying the sheet S by the first roller pair  41 . Specifically, the motor  46  is driven to rotate in the forward direction. As a result, the first driving roller  41   a  rotates in the counterclockwise direction. The sheet S is further conveyed in the conveying direction D In addition, the carriage  22  and the printing head  21  are driven, and ink is ejected from the printing head  21  to the sheet S at the ejected position E. As a result, an image is printed on the sheet S. 
     On the other hand, when the sheet S is conveyed in the conveying direction D and the end portion Sa on the downstream side of the sheet S reached the determined position, the control unit  18  conveys the sheet S′ in the conveying direction D by the second roller pair  42 . Here, the predetermined position is a position in which the end portion Sa on the downstream side of the sheet S and the end portion S′b on the upstream side of the sheet S′ are close to each other when viewed from the Z direction. For example, the predetermined position is the position in which the end portion Sa on the downstream side of the sheet S reached the intermediate position between the cutting unit  50  and the second roller pair  42 . More specifically, the predetermined position is the intermediate position between the end portion in +Z direction of the driving blade  52  of the cutting unit  50  and the center portion of the nip width in the conveying direction D of the second roller pair  42  when viewed from the Z direction. 
     At the predetermined position, in the control unit  18 , the time when the end portion Sa on the downstream side of the sheet S temporarily stops at the position moving a distance a from the medium detector  60  serves as a base point, and the detection data (output value) from the rotary encoder  47  corresponding to the position where the end portion Sa on the downstream side reached the intermediate position between the cutting unit  50  and the second roller pair  42  is stored in advance. Then, current is supplied to the clutch mechanism  43  based on the control signal of the control unit  18 . As a result, the clutch mechanism  43  is turned in the ON state and the power is transmitted from the motor  46  to the second drive roller  42   a . The second driving roller  42   a  rotates in a counterclockwise direction. The sheet S′ is conveyed in the conveying direction D. Then, when the sheet S′ is removed from the nip position of the second roller pair  42 , the sheet S′ falls and is stored in the stacker  4 . 
     That is, the sheet S′ is maintained in a state where the sheet S′ is nipped by the second roller pair  42  until the end portion Sa on the downstream side of the sheet S moves near the end portion S′b on the upstream side of the sheet S′. As a result, it is possible to ensure a longer time for drying the image printed on the sheet S′. Hereinafter,  FIG. 4A  to  FIG. 4H  are repeated. 
     According to the present embodiments, the following advantages can be obtained. 
     The sheet S on which the image is printed by the printing head  21  is conveyed in the conveying direction D by driving the first roller pair  41  and the second roller pair  42 . Thereafter, the sheet S conveyed in the conveying direction D is cut by the cutting unit  50 . Here, the sheet S on the supply side is conveyed in the reverse direction in the direction opposite to the conveying direction D for the next printing process. In this case, the sheet S is moved to the upstream side in the conveying direction D by driven the first roller pair  41  to rotate in the reverse direction (the clockwise direction in  FIG. 4C ). At this time, the transmission of the power of the second roller pair  42  is released by the electromagnetic clutch mechanism  43 . That is, the second roller pair  42  is held in a state where the cut sheet S′ is sandwiched (nipped) without rotating. As a result, sheet jam and the like can be prevented without the cut sheet S′ conflicting with the cutting unit  50 . In addition, drying of the image printing portion can be promoted in a state in which the sheet S′ is sandwiched by the second roller pair  42 . 
     In addition, after the sheet S on the supply side is detected by the medium detector  60 , the sheet S is conveyed in the forward direction toward the conveying direction D by the driving of the first roller pair  41 , and temporarily stopped at a predetermined position. At this time, the power is transmitted to the second roller pair  42 , and the cut sheet S′ is conveyed in the conveying direction D. Then, when the distance between the second roller pair  42  and the end portion S′b on the upstream side in the conveying direction D of the cut sheet S′ is 2 mm±1 mm, the power to the second roller pair  42  is released by the clutch mechanism  43 . As a result, the second roller pair  42  is held in a state in which one end portion of the sheet S′ is held (nipped) in the conveying direction D. Thus, the second roller pair  42  can nip a region other than the region of the sheet S′ where the image is formed, since the contact between the second roller pair  42  and the image formed on the sheet S′ is reduced, the image quality can be maintained. In addition, since the second roller pair  42  nip one end portion of the sheet S′, the user can easily pull out the sheet S′ in the +Y direction without loading from the second roller pair  42 . 
     Note that, the disclosure is not limited to the above-described exemplary embodiment, and various changes and improvements can be made to the above-described exemplary embodiment. Such modified examples are described below. 
     (Modified Example 1) In the above-described embodiment, as illustrated in  FIG. 4G , the rotary encoder  47  detected the distance b between the second roller pair  42  and the end portion S′b on the upstream side of the sheet S′ sandwiching by the second roller pair  42  in the conveying direction D by the second roller pair  42 , but it is not limited to this, for example, a light sensor such as a photo-interrupter may be disposed between the cutting unit  50  and the second roller pair  42 , which serves as the conveying path for the sheet S, and the distance b may be detected by the photo-interrupter. In addition, in the same manner as in  FIG. 4H , a predetermined position of the end portion Sa on the downstream side of the sheet S is detected by the rotary encoder  47 , but regardless of this, it may be detected by a photo-interrupter or the like in the same manner described above. Even with this configuration, similar advantages as described above can be obtained. 
     Contents derived from the embodiments will be described below. 
     The printing apparatus includes a first roller pair that sandwiches and sending conveys a continuous medium, a printing head that is located downstream of the first roller pair in a conveying direction of the continuous medium and that performs printing on the continuous medium, a cutting unit that is located downstream of the printing head in the conveying direction of the continuous medium and that cuts the continuous medium, a second roller pair that is located downstream of the cutting unit in the conveying direction of the continuous medium and that sandwiches and conveys the continuous medium, a common driving source that applies driving force to the first roller pair and the second roller pair, and a clutch mechanism configured to cut power from the driving source to the second roller pair, wherein the clutch mechanism is an electromagnetic mechanism that releases transmission of the power by electromagnetism. 
     According to this configuration, the continuous medium on which the image is printed by the printing head is conveyed in the conveying direction by driving the first roller pair and the second roller pair. The continuous medium conveyed in the conveying direction is cut by the cutting unit. Here, the continuous medium on the upstream side in the conveying direction of the cutting unit may be pulled back to a predetermined position in preparation for the next printing process. In this case, the first roller pair is driven in reverse rotation, and the continuous medium is moved in a direction opposite to the conveying direction. At this time, the power to the second roller pair can be released by the electromagnetic clutch mechanism. As a result, the second roller pair can remain in a state where the cut continuous medium is held (nipped) without rotating. Thus, the drying time after image printing of the cut continuous medium is ensured, and drying of the image printing portion can be promoted. 
     The printing apparatus described above may further includes a medium detector that is located between the first roller pair and the printing head and that detects the presence or absence of the continuous medium, and a control unit that, after the continuous medium is cut, conveys the continuous medium located on a supply side in a reverse direction, and that, after an end portion on the downstream side of the continuous medium is detected by the medium detector, conveys the continuous medium in a forward direction and temporarily stops the continuous medium at a predetermined position, wherein the control unit controls the clutch mechanism to, when the continuous medium is conveyed in the reverse direction, cut the power from the driving source to the second roller pair, and when the continuous medium is conveyed in the forward direction after being temporarily stopped at the predetermined position, couple the power from the driving source to the second roller pair, and then, when the distance between the second roller pair and an end portion on the upstream side in the conveying direction of the continuous medium that is sandwiched by the second roller pair is 2 mm±1 mm, cut the power from the driving source to the second roller pair. 
     According to this configuration, when the continuous medium is cut, the continuous medium on the supply side is conveyed in the reverse direction which is the reverse direction of the conveying direction for the next printing process. Note that, at this time, the transmission of the power to the second roller pair is released by the clutch mechanism, and the cut continuous medium is held in a state of sandwiching by the second roller pair. Thereafter, after the continuous medium on the supply side is detected by the medium detector, the continuous medium is conveyed in the forward direction in the conveying direction by the driving of the first roller pair, and temporarily stopped at the predetermined position. Thereafter, the continuous medium is conveyed in the forward direction in the conveying direction. At this time, the second roller pair is also driven by the power of the driving source, and the cut continuous medium is conveyed downstream in the conveying direction. Then, when the distance between the second roller pair and the end portion on the upstream side in the conveying direction of the cut continuous medium is 2 mm±1 mm, the power of the second roller pair is released by the electromagnetic clutch mechanism. As a result, the second roller pair is held in a state where the end portion of the continuous medium is held (nipped). Thus, the second roller pair can nip the region other than the region of the continuous medium where the image is formed, reduce the contact between the second roller pair and the image formed on the continuous medium, and the image quality can be maintained. In addition, since the second roller pair nips one end portion in the conveying direction of the continuous medium, the user can easily pull out the sheet in the conveying direction without loading from the second roller pair.