JP5195850B2 - Printer - Google Patents

Description

  The present invention relates to a printer capable of duplex printing on a printing medium.

  2. Description of the Related Art Conventionally, double-sided printers that can print characters and images on both sides of a printing medium such as printing paper are known. Among them, for example, as in the printer described in Patent Document 1, after printing one surface (front surface) of the printing paper with the print head, the print paper is again printed with the print head after the front and back are reversed by the switchback mechanism. It is widely known that the printer is configured to print the other side (back side) of the printing paper.

  Also, there is a configuration in which the front and back of the print medium are reversed using a drum that rotates while holding the print medium. For example, the printer described in Patent Document 2 includes two vacuum drums each configured to be rotatable, and two inkjet heads disposed so as to face the two vacuum drums. Each vacuum drum is provided with a configuration for adsorbing printing paper (printing medium). Specifically, a plurality of holes are provided on the outer peripheral surface of each vacuum drum, and the plurality of holes communicate with a plurality of air chambers provided inside the drum. The plurality of air chambers are provided with a plurality of valves for switching between communication / blocking states with the suction source. In this configuration, the printing paper can be adsorbed to a predetermined region on the outer peripheral surface of the vacuum drum by generating a vacuum state independently in the plurality of air chambers by using the plurality of valves.

  The printer of Patent Document 2 first rotates one of the printing papers by one inkjet head facing the drum while rotating the vacuum drum in a state where the printing paper is sucked and held on one vacuum drum. Print the surface (surface). Next, the printing paper on which the front surface has been printed is transferred to the other vacuum drum with its front and back reversed. Then, while the printing paper is sucked and held on the other vacuum drum, the other surface of the printing paper is rotated by the other inkjet head facing the drum while rotating the other drum in the same manner as the above surface printing. (Back side) is printed.

JP 2001-31309 A JP-T-2001-514107 (FIG. 1)

  In a printer that reverses the front and back of a print medium by a switchback mechanism, such as the printer of Patent Document 1, the print medium is warped and jammed at the time of switchback when the print medium is momentarily unconstrained (jam). There is a problem that is likely to occur. In particular, when the print head is an ink-jet head, the print medium is likely to warp greatly during the period from when the ink is jetted onto only one side of the print medium until the ink is completely dried. Is likely to occur.

  On the other hand, the printer of Patent Document 2 conveys a print medium while being sucked and held on a vacuum drum, and the binding force of the print medium when the print medium is reversed while delivering the print medium between the two drums is the switchback type. Higher than For this reason, problems such as clogging of the print medium due to warping are unlikely to occur. However, in the printer of Patent Document 2, it is necessary to dispose two inkjet heads for printing the front surface and the back surface of the print medium, respectively, facing the two vacuum drums. Therefore, the number of parts increases, leading to an increase in cost, and it becomes difficult to reduce the size of the printer.

  An object of the present invention is to provide a printer capable of double-sided printing and capable of suppressing warping of a print medium with a simpler configuration than the conventional one.

According to a first aspect of the present invention, there is provided a printer according to a first aspect of the present invention, a first drum configured to be rotatable, a first rotation driving unit that rotationally drives the first drum, and a first suction that sucks a print medium onto the outer peripheral surface of the first drum. Means, an inkjet head for performing printing by ejecting ink onto the print medium adsorbed on the outer peripheral surface of the first drum so as to face the outer peripheral surface of the first drum, and the first drum in the radial direction A second drum arranged adjacently and configured to be rotatable, a second rotation driving means for rotating the second drum, and a second suction for adsorbing the print medium to the outer peripheral surface of the second drum Means, a transfer means for transferring the print medium between the first drum and the second drum, and printing on the surface by the inkjet head in a state of being adsorbed to the outer peripheral surface of the first drum The first rotation driving means and the second rotation means are arranged so that the printing medium is delivered to the second drum by the delivery means, and the printing medium is turned upside down and then returned to the first drum again by the delivery means. A conveyance control unit that controls the rotation driving unit, and a holding unit that holds the print medium that is transferred between the first drum and the second drum on a common outer tangent line of the first drum and the second drum. And the delivery means controls the first suction means and the second suction means so as to weaken the suction force of the transfer source drum and to increase the suction force of the transfer destination drum, The printing medium is transferred between the first drum and the second drum .

  First, ink is ejected from the inkjet head onto the surface of the print medium sucked and held on the first drum by the first sucking means to print the surface of the print medium. Then, in a state where the print medium with the surface printed is sucked and held by the first drum, the first drum is rotated by the first rotation driving means to convey the print medium, and the print medium is transferred to the second drum by the delivery means. hand over.

  Next, in a state where the print medium is sucked and held on the second drum by the second suction means, the second drum is rotated by the second rotation driving means to convey the print medium, and the print medium is transferred to the first drum by the delivery means. Return again. Here, when the print medium is transferred between the first drum and the second drum, the front and back sides of the print medium are reversed, and the first drum has a surface (back surface) opposite to the previously printed surface. Is exposed from the second drum. Then, ink is ejected from the inkjet head onto the print medium to print the back surface of the print medium.

As described above, according to the present invention, the front and back of the print medium are reversed while the print medium is adsorbed and restrained by the first drum and the second drum, so that it is possible to suppress warping during conveyance and reverse of the front and back. Furthermore, the print medium on which the surface is printed on the first drum is turned upside down by transfer to and from the second drum, and returned to the first drum facing the ink jet head, whereby the ink jet facing the first drum. Both the front surface and the back surface of the print medium can be printed by the head. Accordingly, it is possible to perform double-sided printing while suppressing warping of the printing medium with a relatively simple configuration. Furthermore, when the print medium is delivered on the common outer tangent line of the first drum and the second drum, the print medium is instantaneously separated from the drum, so that the restraining force is reduced and warpage is likely to occur. Therefore, in the present invention, by holding the print medium by the holding unit on the common outer tangent, the warp can be suppressed by restraining the print medium when delivering on the common outer tangent.
In addition, according to this configuration, the print medium can be delivered simply by controlling the first suction means and the second suction means and changing the suction force of the two drums, respectively. No member is required.

  In the printer of the second invention according to the first invention, the conveyance control means uses the print medium printed on the surface as a closest point between the first drum and the second drum, and the first drum. The first rotation driving means and the second rotation driving means are controlled to be transferred between the first drum and the second drum by the transfer means on a common circumscribing line extending over the first drum and the second drum. It is characterized by this.

  When the two drums are transferred at the closest point (the closest position), the front and back of the print medium are reversed. On the other hand, when the two drums are transferred on the common tangent (common outer tangent), the front and back of the print medium are not reversed. In this way, by performing the transfer at the two positions between the first drum and the second drum, the print medium having the surface printed on the first drum is once transferred to the second drum and the front and back sides thereof are transferred. After reversing, it is possible to return to the first drum again.

The printer according to a third aspect is the printing medium according to the second aspect, wherein the transport control means first prints on the surface while rotating the first drum and the second drum in the same direction. Passing from the first drum to the second drum on one of the two common circumscribing lines,
Next, by rotating the first drum in the opposite direction to the second drum, the print medium is reversed from the second drum to the first drum while reversing the front and back of the print medium at the closest point. The first rotation driving means and the second rotation driving means are controlled so as to pass.

  When the transport path as described above is adopted, the print medium printed on the front surface is first transferred from the first drum to the second drum on the common outer tangent line, so the print medium is not reversed immediately. It is possible to prevent the printing medium from being turned upside down when the surface is not completely dry.

A printer according to a fourth invention is the printer according to any one of the first to third inventions, wherein the holding means has a plurality of protrusions arranged in the circumferential direction, and is disposed outside the common circumscribing line. And a cylindrical second roller disposed inside the common circumscribing line so as to face the first roller across the common circumscribing line.

  According to this configuration, the print medium can be reliably held by the first roller and the second roller facing each other. In addition, when the print medium printed by the inkjet head is transferred from the first drum to the second drum without being reversed upside down on the common outer tangent, the surface printed just before the transfer is the common outer tangent. It faces the outside (on the opposite side of the drum). In addition, in the present invention, the first roller having a plurality of protrusions is disposed outside the common circumscribing line. That is, of the first roller and the second roller of the holding unit, the first roller having a small contact area with the printing medium comes into contact with the surface immediately after printing. Therefore, it is possible to transport the print medium without making the printed surface as dirty as possible.

  A printer of a fifth invention is the printer according to any one of the first to fourth inventions, wherein the transport control means performs the printing of the back surface after reversing the print medium printed on the front surface. In addition, the double-sided printing mode for controlling the first rotation driving means and the second rotation driving means and the printing medium printed on the surface are discharged without being sent to the inkjet head so as to be sent again to the inkjet head. Thus, the one-sided printing mode for controlling the first rotation driving means and the second rotation driving means can be selectively executed.

  According to this configuration, not only can the double-sided printing mode be selected to perform double-sided printing of the printing medium, but also the single-sided printing mode can be selected to perform printing on only one side of the printing medium (single-sided printing). is there.

  The printer according to a sixth aspect is the printer according to the fifth aspect, wherein the conveyance control unit is configured to perform the conveyance of the first drum and the second drum during the conveyance in the double-sided printing mode and the single-sided printing mode. Controlling the first rotation driving means and the second rotation driving means so that the print medium is bent in two directions, ie, a direction in which the print medium is convex on one side and a direction in which the print medium is convex on the other side. It is a feature.

  According to this configuration, since the print medium is bent in two directions not only during double-sided printing but also during single-sided printing, warping of the print medium can be suppressed.

According to a seventh invention, in any one of the first to sixth inventions, a plurality of through holes arranged in the circumferential direction are formed on the outer peripheral surfaces of the first drum and the second drum, respectively. And
The first adsorbing means and the second adsorbing means respectively include a columnar fixed body disposed inside the corresponding drum with a gap from the inner surface of the drum, and an inner peripheral surface of the drum or the fixed body. And a plurality of partition walls provided at intervals in the circumferential direction, and a space between the fixed body and the drum is formed by dividing the plurality of partition walls in the circumferential direction. A plurality of decompression chambers and decompression means capable of decompressing each of the plurality of decompression chambers independently, wherein each of the decompression chambers communicates with the plurality of through holes. Is.

  According to this configuration, by independently depressurizing the plurality of decompression chambers, it is possible to switch between adsorption and desorption (separation) of the print medium for each partial region in the circumferential direction of the outer peripheral surface of the drum. Smooth transfer between the drum and the second drum is possible. On the other hand, since a plurality of through-holes communicate with one decompression chamber, the print medium can be adsorbed simultaneously in the plurality of through-holes by the decompression of one decompression chamber, and the holding of the print medium is ensured. It can be done. In addition, there is an advantage that the configuration is simplified compared to the case where one decompression chamber is associated with one through hole and a large number of through holes are independently controlled.

According to an eighth aspect of the invention, in the seventh aspect , the through hole is not provided in a partial region of the drum, and the circumferential length of the partial region in which the through hole is not provided. Is equal to or longer than the circumferential length of the drum corresponding to one of the decompression chambers, and further comprises position detecting means for detecting the position of the tip of the printing medium,
The transport control means uses the detection result of the position detection means so that the leading end of the print medium is adsorbed by the through hole closest to the partial area in a direction opposite to the rotation direction of the drum. Based on this, the first rotation driving means and the second rotation driving means are controlled.

  As described above, a plurality of through holes communicate with one decompression chamber. In addition, when the front end of the print medium is adsorbed by a through hole and closes the through hole, the print medium is blocked by the print medium adjacent to the rotation direction side of the drum from the closed through hole. If there is another open hole in the open state that is not peeled off, the through hole blocked by the printing medium and the open through hole can be connected to the same decompression chamber. Become. At this time, even if an attempt is made to depressurize the decompression chamber, the atmosphere flows into the decompression chamber from the open through hole, so that the decompression chamber is not easily decompressed, and the suction force at the tip portion is reduced.

  Therefore, in the present invention, in the outer peripheral area of the drum, a through hole is not provided in a part of the drum having a length equal to or longer than the circumferential length of the drum corresponding to one decompression chamber. And the conveyance control means detects the position of the front end of the print medium based on the detection result of the position detection means by the through hole closest to the partial area in the direction opposite to the rotation direction of the drum. The rotation of the drum is controlled so that the tip of the drum is adsorbed. As a result, it is possible to avoid a state in which the through hole blocked by the front end portion of the print medium and another through hole in the open state communicate with the same decompression chamber, and it is possible to prevent a decrease in the adsorption power of the front end portion. .

  According to the present invention, since the front and back of the print medium are reversed while adsorbing and restraining the print medium to the first drum and the second drum, it is possible to suppress warping during conveyance and when the front and back are reversed. Further, the print medium on which the surface is printed on the first drum is turned upside down by transfer to and from the second drum, and returned to the first drum that faces the ink jet head, so that the ink jet head faces the first drum. Can print both the front and back sides of the print medium. Accordingly, it is possible to perform double-sided printing while suppressing warping of the printing medium with a relatively simple configuration. Furthermore, when the print medium is delivered on the common outer tangent line of the first drum and the second drum, the print medium is instantaneously separated from the drum, so that the restraining force is reduced and warpage is likely to occur. Therefore, in the present invention, by holding the print medium by the holding unit on the common outer tangent, the warp can be suppressed by restraining the print medium when delivering on the common outer tangent.

1 is a schematic configuration diagram of a printer according to an embodiment. FIG. 2 is a block diagram schematically illustrating an electrical configuration of a printer. It is an enlarged view of the outer peripheral part of a drum, (a) shows the case where there is a through hole in the entire drum periphery, and (b) shows the case where no through hole is provided in a partial region of the drum outer peripheral surface. It is a figure which shows the operation | movement (paper feeding and front surface printing) of the printer at the time of duplex printing mode selection. It is a figure which shows the operation | movement (delivery on the common external tangent just after front surface printing) at the time of duplex printing mode selection. It is a figure which shows operation | movement (delivery at the nearest point) of the printer at the time of duplex printing mode selection. It is a figure which shows the operation | movement (back surface printing) of the printer at the time of duplex printing mode selection. It is a figure which shows the operation | movement (delivery on the common external tangent immediately after back surface printing) at the time of duplex printing mode selection. FIG. 7 is a diagram illustrating an operation (paper discharge) of a printer when a duplex printing mode is selected. It is a figure which shows the operation | movement (paper feeding and surface printing) of the printer at the time of single-sided printing mode selection. It is a figure which shows operation | movement (delivery at the nearest point) of the printer at the time of single-sided printing mode selection. FIG. 7 is a diagram illustrating an operation (paper discharge) of a printer when a single-sided printing mode is selected. It is a figure which shows the operation | movement (paper feeding and surface printing) of the printer at the time of double-sided printing mode selection based on the change form. It is a figure which shows the operation | movement (delivery by the nearest point) of the printer at the time of double-sided printing mode selection based on the change form. It is a figure which shows the operation | movement (delivery on a common external tangent, and back surface printing) at the time of double-sided printing mode selection concerning the change form. It is a figure which shows the operation | movement (paper discharge) of the printer at the time of double-sided printing mode selection concerning the change form.

  Next, an embodiment of the present invention will be described. FIG. 1 is a schematic configuration diagram of the printer according to the present embodiment, and FIG. 2 is a block diagram schematically showing an electrical configuration of the printer of FIG.

  As shown in FIGS. 1 and 2, the printer 100 according to the present embodiment rotates two drums (first drum 1 and second drum 2) and two drums 1 and 2, which are each configured to be rotatable. Two drum drive motors 11 and 12 (first and second rotational drive means) to be driven and two drums 1 and 2 are provided respectively, and printing paper P (print medium) is provided on the outer peripheral surface of the drums 1 and 2. Two suction mechanisms 3 (first and second suction means) to be sucked, four ink jet heads 4 facing the outer peripheral surface of the first drum 1 and performing printing by jetting ink onto the printing paper P, and first A sheet feeding mechanism 5 that supplies printing paper P to one drum 1, a paper discharge mechanism 6 that discharges printing paper P from the second drum 2, and a control device 7 that controls the entire printer 100 are provided.

  The printer 100 conveys the printing paper P between the first drum 1 and the second drum 2 and reverses the front and back of the printing paper P on the conveyance path 10 indicated by a two-dot chain line in FIG. By doing so, both sides of the printing paper P can be printed by the inkjet head 4 facing the first drum 1. That is, of the two drums 1 and 2, the first drum 1 has the function of a platen that supports the printing paper P on which an image or the like is printed by the inkjet head 4. On the other hand, the second drum 2 functions as a reversing drum for reversing the printing paper P printed on the first drum 1 from the front to the back. In addition, single-sided printing is possible in which the front surface of the printing paper P is printed by the inkjet head 4 and then discharged as it is without printing the back surface. Hereinafter, a specific configuration of the printer 100 that realizes the above-described operation will be described in detail in order.

  As shown in FIG. 1, the two drums (first drum 1 and second drum 2) are each formed in a cylindrical shape, and are arranged close to each other in the radial direction. In the present embodiment, the diameters of the two drums 1 and 2 are the same. The drums 1 and 2 are configured to be rotatable in two forward and reverse directions, and can be driven to rotate in both directions by corresponding drum drive motors 11 and 12. Each drum has a large number of through holes 13 arranged in the circumferential direction, and the inner spaces of the drums 1 and 2 communicate with the atmosphere through the large number of through holes 13. A suction mechanism 3 described later is provided in the inner space of the drums 1 and 2. The drums 1 and 2 rotate in a state where the printing paper P is sucked to the outer peripheral surface by the suction mechanism 3, whereby the printing paper P is conveyed in the circumferential direction of the drums 1 and 2.

  An ink receiving member 14 is provided on a part of the outer peripheral surface of the first drum 1 to receive ink ejected from the nozzles when flushing the nozzles of the inkjet head 4 described later.

  A paper feeding mechanism 5 that supplies the printing paper P toward the first drum 1 is provided at a predetermined position on the tangent line of the first drum 1 of the two drums 1 and 2. The sheet feeding mechanism 5 includes a sheet feeding roller 20, a nip roller 21 disposed opposite to the sheet feeding roller 20 with the printing paper P interposed therebetween, and a sheet feeding motor 22 that rotationally drives the sheet feeding roller 20 (see FIG. 2). ), And the paper feed guides 23 and 24 and the like, and the printing paper P sandwiched between the paper feed roller 20 and the nip roller 21 is supplied to the first drum 1 through the paper feed guides 23 and 24. A paper detection sensor 25 that detects that the printing paper P has been supplied is provided at a paper feeding position (position A in FIG. 1) where the printing paper P is supplied from the paper supply mechanism 5 to the first drum 1. It has been.

  In addition, a paper discharge mechanism 6 that discharges the printing paper P conveyed by the second drum 2 is provided at a predetermined position on the tangent line of the second drum 2. The paper discharge mechanism 6 includes a paper discharge roller 26, a nip roller 27 arranged to face the paper discharge roller 26 with the printing paper P interposed therebetween, and a paper discharge motor 28 that rotationally drives the paper discharge roller 26 (see FIG. 2). ) And a paper discharge guide 29 and the like, and the print paper P sent from the second drum 2 through the paper discharge guide 29 is nipped by the paper discharge roller 26 and the nip roller 27 and discharged.

  As shown in FIG. 1, a paper feed position A (supply position) where the printing paper P is supplied by the paper feeding mechanism 5 and a paper discharge position B (discharge position) where the printing paper P is discharged by the paper discharge mechanism 6. ) Is point-symmetric with respect to the closest point C between the first drum 1 and the second drum 2. The feeding direction of the printing paper P to the first drum 1 by the paper feeding mechanism 5 and the discharging direction of the printing paper P from the second drum 2 by the paper ejection mechanism 6 are drum tangential directions, and The direction is the same (upper direction in FIG. 1). By adopting such a layout, the two drums 1 and 2, the paper feeding mechanism 5 and the paper discharging mechanism 6 can be arranged in a compact manner.

  On two common outer tangent lines 35 and 36 extending across the first drum 1 and the second drum 2, there are two holding the printing paper P transferred between the first drum 1 and the second drum 2. Each holding mechanism 8 (holding means) is provided. The two holding mechanisms 8 have the same configuration. That is, each holding mechanism 8 includes a first transport roller 30 (first roller) having a plurality of protrusions arranged in the circumferential direction, and a cylindrical second transport that faces the first transport roller 30 with the printing paper P interposed therebetween. The conveyance direction (left-right direction in FIG. 1) of the roller 31 (second roller), the conveyance motor 32 that rotationally drives the second conveyance roller 31, and the roller pair including the first conveyance roller 30 and the second conveyance roller 31 Paper transport guides 33 and 34 are provided on both sides, respectively.

  When the printing paper P is delivered on the common outer tangent lines 35 and 36 of the first drum 1 and the second drum 2, the binding force is reduced because the printing paper P is instantaneously separated from the drums 1 and 2. Then, the printing paper P tends to be warped. Therefore, the holding mechanism 8 restrains the printing paper P between the first conveyance roller 30 and the second conveyance roller 31 when the printing paper P is transferred between the first drum 1 and the second drum 2. Hold securely.

  When the printing paper P printed by the inkjet head 4 is transferred from the first drum 1 to the second drum 2 on the common outer tangent lines 35 and 36, the surface printed immediately before the transfer is 2 It faces outward (on the opposite side to the drums 1 and 2) with respect to the common outer tangent lines 35 and 36 of the book. In the present embodiment, among the first transport roller 30 and the second transport roller 31 of the holding mechanism 8, the first transport roller 30 having a plurality of protrusions is disposed outside the common outer tangent lines 35 and 36. . That is, of the first transport roller 30 and the second transport roller 31, the first transport roller 30 having a small contact area with the printing paper P comes into contact with the surface immediately after printing, and the printed surface is made as much as possible. The printing paper P can be conveyed without being soiled.

  The four inkjet heads 4 face the outer peripheral surface of the first drum 1 and eject inks of four colors (yellow, magenta, cyan, and black) onto the printing paper P conveyed by the first drum 1. The inkjet head 4 is not limited to one having a specific configuration. For example, a so-called line that has a large number of nozzles arranged over substantially the entire width direction of the printing paper P (the vertical direction in FIG. 1), and performs printing by ejecting ink from the large number of nozzles while being positioned and fixed. It may be a mold head. Alternatively, a so-called serial head that performs printing by ejecting ink from nozzles while reciprocating in the width direction of the printing paper P may be used.

  Since the two suction mechanisms 3 (first suction means and second suction means) provided on the first drum 1 and the second drum 2 have the same configuration, the suction mechanisms provided on the first drum 1 will be described below. 3 will be described.

  The suction mechanism 3 includes a columnar fixed body 40 disposed inside the first drum 1 with a gap from the inner surface of the first drum 1. The fixed body 40 is fixed to a frame of the printer 100 (not shown) so as not to move, and the first drum 1 located outside the fixed body 40 rotates relative to the fixed body 40.

  Four partition walls 41 are provided on the outer peripheral surface of the fixed body 40 at regular intervals (90 ° angular intervals) in the circumferential direction, and the tip of each partition wall 41 is connected to the inner surface of the first drum 1. It comes in sliding contact. The space between the first drum 1 and the fixed body 40 is divided into four in the circumferential direction by the four partition walls 41, so that four decompression chambers 42 (42a) formed in a quarter arc shape. To 42d) are formed. 1 shows an example in which the four partition walls 41 are formed integrally with the fixed body 40. However, the partition wall 41 is formed of a member different from the fixed body 40, and the fixed body It may be fixed to the outer peripheral surface of 40.

  The four decompression chambers 42 are connected to a suction pump 43 (a decompression unit: see FIG. 2) as a suction source. Further, between the four decompression chambers 42 and the suction pump 43, there are provided four switching valves 44 (for example, solenoid valves, etc.) for switching the communication state and the cutoff state independently. By switching the communication / blocking of the four decompression chambers 42 and the suction pump 43 independently by the four switching valves 44, the suction pump 43 can decompress the four decompression chambers 42 independently. Become.

  By the way, as mentioned earlier, as shown in FIG. 1, the first drum 1 (second drum 2) is formed with a plurality of through holes 13 arranged at intervals in the circumferential direction. In the first drum 1, two or more through-holes 13 are arranged in the circumferential direction in a region between the two points in contact with the two partition walls 41 (¼ arc region). That is, the plurality of through holes 13 communicate with one decompression chamber 42 partitioned by the two partition walls 41. As a result, in the situation where the printing paper P is present on the outer peripheral surfaces of the drums 1 and 2, when the decompression (suction) of a certain decompression chamber 42 is performed by the suction pump 43, a plurality of communication with the decompression chamber 42 is performed. The printing paper P is adsorbed in each of the through holes 13. As described above, since the plurality of through holes 13 communicate with one decompression chamber 42, the printing paper P can be simultaneously adsorbed by the plurality of through holes 13 due to the decompression of the one decompression chamber 42. P can be held securely. Further, one decompression chamber 42 corresponds to one through-hole 13 on a one-to-one basis, and there is an advantage that the configuration is simplified compared to the case where a large number of through-holes 13 are controlled independently.

  By rotating the drums 1 and 2 while the printing paper P is sucked by the suction mechanism 3, the printing paper P can be conveyed along the circumferential direction of the drums 1 and 2 while the printing paper P is restrained. It is possible to suppress warping of the printing paper P being conveyed. In addition, by independently switching the decompression states of the four decompression chambers 42, it is possible to select in which region of the outer peripheral surfaces of the drums 1 and 2 the suction of the printing paper P is performed. Accordingly, the printing paper P can be transferred between the first drum 1 and the second drum 2 by appropriately selecting the decompression chamber 42 for decompressing the first drum 1 and the second drum 2. It becomes like this. The delivery of the printing paper P between the two drums 1 and 2 will be specifically described later.

  As shown in FIG. 1, a partial region 50 where the through hole 13 is not provided exists on the outer peripheral surface of the first drum 1 (second drum 2), and the circumferential length of the partial region 50 is present. The length is equal to or larger than the circumferential length of the drums 1 and 2 corresponding to one decompression chamber 42 (circular arc region having a central angle of 90 ° in FIG. 1). This configuration prevents a decrease in the suction force of the leading end when the through hole 13 that is blocked by the leading end of the printing paper P and another through hole 13 that is in an open state communicate with the same decompression chamber 42. The details will be described later. In the first drum 1, the ink receiving member 14 that receives ink ejected when the nozzles of the inkjet head 4 are flushed is provided in the partial region 50 where the through-hole 13 is not provided. Is provided.

Next, the electrical configuration of the printer 100 centering on the control device 7 will be described with reference to FIG. 2 includes, for example, a central processing unit (CPU) that is a central processing unit, and a ROM (Read Only Memory) in which various programs and data for controlling the overall operation of the printer 100 are stored. And a RAM (Random Access Memory) that temporarily stores data processed by the CPU, etc., and a program stored in the ROM is executed by the CPU to perform various controls as described below. It may be performed in software. Alternatively, it may be realized by hardware in which various circuits including an arithmetic circuit are combined.

  The control device 7 includes a head control unit 61, a conveyance control unit 62 (conveyance control unit), a suction control unit 63, and a position detection unit 64 (position detection unit). The head controller 61 controls the inkjet head 4 based on print data input from an input device 55 such as a PC to eject ink toward the print paper P, and prints a desired image or the like on the print paper P. Let The conveyance control unit 62 also includes a first drum driving motor 11 and a second drum driving motor 12 that rotate and drive the first drum 1 and the second drum 2, a paper feeding motor 22 of the paper feeding mechanism 5, and a paper discharging mechanism 6. The paper discharge motor 28, the conveyance motor 32 of the two holding mechanisms 8 and the like are controlled to cause the first drum 1 and the second drum 2 to convey the printing paper P. Specific conveyance control by the conveyance control unit 62 will be described in detail later.

  The suction control unit 63 controls the suction pump 43 and the switching valve 44 of the two suction mechanisms 3 so that the suction mechanism 3 sucks the printing paper P onto the first drum 1 or the second drum 2 and the first drum. The printing paper P is transferred between the first drum 2 and the second drum 2.

  Here, supplementary description will be given of the transfer of the printing paper P between the two drums 1 and 2 under the control of the suction mechanism 3. At the time of delivery, the suction control unit 63 weakens the suction force of the transfer source drum to peel the print paper P from the drum, and increases the suction force of the transfer destination drum to remove the transfer source drum from the transfer source drum. The peeled printing paper P is adsorbed.

  More specifically, it corresponds to the area where the leading end of the printing paper P is peeled out of the four decompression chambers 42a to 42d provided on the transfer source drum while the two drums 1 and 2 are rotating together. The communication between the decompression chamber 42 and the suction pump 43 is blocked by the switching valve 44, the decompression state of the decompression chamber is released, and the leading end portion of the printing paper P is peeled off from the transfer source drum. At the same time, in the delivery destination drum, the decompression chamber 42 corresponding to the region that receives the leading end of the printing paper P is communicated with the suction pump 43 by the switching valve 44, and the decompression chamber 42 is brought into a decompressed state, The front end of the printing paper P peeled off from the drum is adsorbed. As a result, the printing paper P is delivered to the delivery destination drum.

  That is, in this embodiment, the suction control unit 63 that independently controls the two suction mechanisms 3 corresponds to the delivery means of the present application. According to this configuration, since the printing paper P can be delivered simply by controlling the two suction mechanisms 3 and changing the suction forces of the two drums 1 and 2, respectively, a special member for delivery is not required. Thus, the configuration becomes simple. The suction mechanism 3 has four decompression chambers 42a to 42d divided in the circumferential direction of the drums 1 and 2 and four switching valves 44 corresponding to the four decompression chambers 42a to 42d. Since the two decompression chambers 42a to 42d can be decompressed independently, the printing paper P is sucked and released (separated) for each partial region in the circumferential direction of the outer peripheral surface of the drums 1 and 2. Since switching is possible, smooth delivery between the first drum 1 and the second drum 2 is possible.

  The position detection unit 64 conveys the printing paper P detected by the paper detection sensor 25 based on the paper feed timing at which the printing paper P is supplied to the first drum 1 and information on the rotation speeds of the first drum 1 and the second drum 2. The leading end position of the printing paper P inside is detected. As described above, grasping the leading end position of the printing paper P is indispensable for performing printing by the ink jet head 4, but in the present embodiment, the detection result of the position detecting unit 64 for the following purposes in addition to printing. Is used.

  FIG. 3 is a partially enlarged view of the outer peripheral portion of the first drum 1. Hereinafter, the first drum 1 will be described as an example, but the same applies to the second drum 2. As described above, the plurality of through holes 13 communicate with one decompression chamber 42. Then, as shown in FIG. 3A, when the through hole 13 (13 a) having the leading end portion of the printing paper P is sucked to block the through hole 13, the blocked through hole 13 is blocked. If there is another open hole 13b in an open state that is not blocked by the printing paper P, adjacent to the rotation direction (arrow direction) side of the drum 1, the printing paper P is blocked. The through hole 13a and the open through hole 13b can communicate with the same decompression chamber 42a. At this time, even if the decompression chamber 42a is to be decompressed, the atmosphere flows into the decompression chamber 42a from the open through-hole 13b. Therefore, the decompression chamber 42a is not easily decompressed, and the suction force at the front end of the printing paper P is increased. Will be reduced.

  Therefore, in the present embodiment, in order to solve the above problem, first, as shown in FIG. 1, the through hole 13 is not provided in the outer peripheral surface of the first drum 1 (second drum 2). A partial region 50 exists, and the circumferential length of the partial region 50 is equal to or more than the circumferential length of the drum 1 corresponding to one decompression chamber 42 (arc region having a central angle of 90 °). Is also getting bigger. Then, as shown in FIG. 3 (b), with respect to the direction opposite to the rotation direction of the drum 1, the position so that the front end portion of the printing paper P is adsorbed by the through hole 13a closest to the partial region 50. The drum drive motor 11 is controlled based on the leading end position of the printing paper P detected by the detection unit 64. As a result, it is possible to avoid a state in which the through hole 13a closed by the leading end portion of the printing paper P and another through hole 13 in the open state communicate with the same decompression chamber 42, and the leading edge of the printing paper P It is possible to prevent a decrease in the adsorption power of the part.

  By the way, the printer 100 of the present embodiment performs printing on one side (front surface) of the printing paper P by the inkjet head 4, and then reverses the front and back surfaces to the other side (back side) of the printing paper P. Selectively execute double-sided printing mode in which printing is performed by the inkjet head 4 and single-sided printing mode in which printing is performed on the front surface of the printing paper P by the inkjet head 4 and then printing is performed without performing printing on the back side. It is possible to do. Hereinafter, a series of controls of the printer 100 in each of the double-sided printing mode and the single-sided printing mode will be described focusing on the conveyance control of the printing paper P.

(Duplex printing mode)
The duplex printing mode will be described with reference to FIGS. As shown in FIG. 4, first, when the printing paper P supplied from the paper feeding mechanism 5 is detected by the paper detection sensor 25, the suction mechanism 3 executes the pressure reduction in the decompression chambers 42 a and 42 b, and the printing paper P The tip is adsorbed to the first drum 1. At this time, the other decompression chambers 42c and 42d are not decompressed. As shown in FIG. 4, the decompression chamber 42 in the decompressed state is hatched (the same applies to the following description).

  At this time, the conveyance control unit 62 prints in the through hole 13a closest to the rotation direction (direction of arrow a) in the region 50 where the through hole 13 of the first drum 1 is not formed. Based on the leading edge position of the printing paper P detected by the position detector 64 so that the leading edge of the paper P is attracted, the first drum 1 is rotated (rotation driven by the first drum driving motor 11). To control. Note that the control for adsorbing the leading end of the printing paper P to a predetermined position is performed in order to maintain the attracting force of the leading end of the printing paper P (whichever of the first drum 1 and the second drum 2). Is also always performed when the printing paper P is received, and description of the above control will be omitted as appropriate.

  Thereafter, the conveyance control unit 62 controls the first drum drive motor 11 to move the first drum 1 in the counterclockwise direction (the direction of the arrow a) in a state where the printing paper P is attracted to the first drum 1. The printing paper P is transported to a position facing the inkjet head 4 by rotating. At this time, printing is performed on one surface (front surface) of the printing paper P by the inkjet head 4.

  Next, in this state, while continuing the rotation of the first drum 1 in the direction of arrow a, the second drum drive motor 12 is controlled to move the second drum 2 in the same direction as the first drum 1 (arrow a direction). Rotate. Then, as shown in FIG. 5, the printing paper P peels from the first drum 1 on the outer peripheral surface of the first drum 1 corresponding to the decompression chamber 42d where decompression is not performed, and further, the first drum 1 and the second drum 1 While being held by the holding mechanism 8 (the first conveyance roller 30 and the second conveyance roller 31) positioned on one (upper) common outer tangent line between the drums 2, the drum 2 is sent to the second drum 2. At the same time, the suction mechanism 3 of the second drum 2 is caused to decompress the decompression chambers 42b, 42c, and 42d. As a result, the leading end portion of the printing paper P peeled off from the first drum 1 is adsorbed to a region corresponding to the decompression chamber 42d of the second drum 2, and the first drum 1 to the second drum 2 at the common outer tangent line. The printing paper P is handed over.

  It should be noted that the front and back of the printing paper P are not reversed during delivery on the common outer tangent. That is, the printing paper P is delivered to the second drum 2 with the surface printed immediately before being exposed. Therefore, the printing paper P is not reversed immediately after printing on the front surface, but the printing paper P is reversed when the surface is not completely dry, preventing the printed image from being stained. Is done.

  Next, as shown in FIG. 6, the second drum driving motor 12 rotates the second drum 2 in the direction a while the printing paper P is attracted to the second drum 2, and the printing paper P is moved in the direction a. The leading end of the printing paper P is moved to the closest point C between the first drum 1 and the second drum 2. Further, the decompression chamber 42d of the first drum 1 is switched to a decompressed state, and the first drum drive motor 11 rotates the first drum 1 in the direction opposite to the second drum 2 (arrow b direction). Then, the printing paper P peels from the second drum 2 in the region corresponding to the decompression chamber 42 a where the decompression is not performed on the second drum 2, and the peeled printing paper P is decompressed by the first drum 1. The printing paper P is transferred from the second drum 2 to the first drum 1 at the closest point C. At the time of delivery at the nearest contact point C, the front and back sides of the printing paper P are reversed, and the printing paper P is attracted to the first drum 1 so that the non-printed surface (back surface) is exposed.

  Then, as shown in FIG. 7, the first drum 1 is rotated in the b direction with the printing paper P adsorbed while the decompression chambers 42 a, 42 b, 42 d are maintained in a decompressed state. The printed printing paper P is conveyed to the inkjet head 4 again. At this time, printing is performed on the back surface of the printing paper P by the inkjet head 4.

  Next, as shown in FIG. 8, while the second drum 2 is rotated in the same direction (b direction) as the first drum 1, the printing paper P on which the back surface is printed is changed to the first drum 1 and the second drum 2. On the other (lower) common outer tangent line, the second mechanism 2 passes the second drum 2 while being held by the holding mechanism 8. At this time, the operation of switching the decompression state of the decompression chamber 42 and the like is the same as the delivery described with reference to FIG.

  Finally, as shown in FIG. 9, after the printing paper P is transported to the vicinity of the paper discharge mechanism 6 (paper discharge position B) by the rotation of the second drum 2, it corresponds to the pressure reduction chamber 42 d where no pressure reduction is performed. In the region, the printing paper P is peeled from the second drum 2, and the printing paper P on which both sides are printed is discharged from the second drum 2 by the paper discharge mechanism 6.

  By the way, when the transport path of the printing paper P as described above is adopted, during the transportation, the two directions of bending acting on the printing paper P (bending in a direction protruding toward one surface (front surface) side, Bending in a direction that is convex toward the surface (back surface) side) is evenly applied. That is, the bending in the convex direction acting on the printing paper P before turning the front and back is 1/4 rotation on the first drum 1 (corresponding to the decompression chamber 42a, as can be seen from FIGS. 4 to 6). Area), and acts on the second drum 2 during a total of one quarter rotation (area corresponding to the decompression chambers 42b, 42c, and 42d). On the other hand, as shown in FIGS. 6 to 9, the bending in the direction of convexing on the back side that acts on the printing paper P after the front and back are reversed is 3/4 rotations (decompression chambers 42 a and 42 b). , 42 d), and 1/4 rotation on the second drum 2 (region corresponding to the decompression chamber 42 c). Thus, the bending of the printing paper P can be suppressed by the bending of the printing paper P evenly in two directions.

(Single-sided printing mode)
Next, the single-sided printing mode will be described with reference to FIGS. First, as shown in FIG. 10, the decompression chambers 42 a, 42 b and 42 d are decompressed in the first drum 1, and the printing paper P supplied from the paper feeding mechanism 5 is adsorbed to the first drum 1, while the first drum 1 Is rotated in the direction of arrow a, and the printing paper P is conveyed. Further, printing is performed on one surface (front surface) of the printing paper P by the inkjet head 4.

  Next, as shown in FIG. 11, in the first drum 1, the decompression chamber 42 d close to the nearest contact C is in a decompressed state, so that the printing paper P is brought into the nearest contact with the rotation of the first drum 1. It is conveyed to C. On the other hand, in the second drum 2, the decompression chambers 42b and 42c are brought into a decompressed state, and the second drum 2 is rotated in the direction opposite to the first drum 1 (direction of arrow b). As a result, the printing paper P is transferred from the first drum 1 to the second drum 2 at the closest point C. At this time, the front and back of the printing paper P are reversed.

  Then, as shown in FIG. 12, after the second drum 2 is rotated in the b direction with the printing paper P adsorbed, the printing paper P is conveyed to the paper discharge mechanism 6 and then the area corresponding to the decompression chamber 42d. Then, the printing paper P is peeled from the second drum 2, and the printing paper P on which only one side (front surface) is printed is discharged from the second drum 2 by the paper discharge mechanism 6.

  In the single-sided printing mode, there is no need to print the back side, and therefore it is not always necessary to reverse the front and back after the front side is printed as shown in FIG. Therefore, if the paper feed position and the paper discharge position are appropriately set, the printing paper P is conveyed on the path outside the first drum 1 and the second drum 2 (the path not passing through the closest point C), and the front and back sides are reversed. It is also possible to discharge the sheet without doing so. However, in such a path, the printing paper P is transported with its surface always exposed, and only bending that protrudes to the front side acts on the printing paper P, so that a large warp tends to occur. Therefore, from the viewpoint of suppressing warpage, as shown in FIGS. 10 to 12, the printing paper P is conveyed in an S shape and the front and back are intentionally reversed so that the printing paper P is bent in two directions. preferable.

  According to the printer 100 of the present embodiment described above, the printing paper P is attracted to and restrained by the first drum 1 and the second drum 2 while being transferred between the first drum 1 and the second drum 2. In addition, since the front and back sides of the printing paper P are reversed, it is possible to suppress warping of the printing paper P during conveyance and when the front and back are reversed. Further, the printing paper P that has been turned upside down is returned to the first drum 1 facing the ink jet head 4, whereby both the front and back surfaces of the printing paper P are printed by the ink jet head 4 facing the first drum 1. Can do. Accordingly, it is possible to perform printing on both sides of the printing paper P with a relatively simple configuration while suppressing warping of the printing paper P. Further, when the double-sided printing mode is selected, the printing paper P is conveyed so that the two-direction bending acting on the printing paper P is uniform, so that the warpage of the printing paper P can be further suppressed.

  In addition to the double-sided printing mode, a single-sided printing mode in which the printing paper P is not returned to the inkjet head 4 after printing on one side can be selected, and printing on only one side can also be performed. Further, even when the single-sided printing mode is selected, the printing paper P is conveyed so that bending in two directions acts, so that the warping of the printing paper P can be suppressed.

  Since the holding mechanism 8 that holds the printing paper P is provided on the common outer tangent lines 35 and 36 of the first drum 1 and the second drum 2, the printing paper P is instantaneously separated from the drums 1 and 2. It is possible to reliably hold the printing paper P during delivery on the outer tangent lines 35 and 36 and suppress warping.

  Next, modified embodiments in which various modifications are made to the embodiment will be described. However, components having the same configuration as in the above embodiment are given the same reference numerals and description thereof is omitted as appropriate.

1] The conveyance path of the printing paper P at the time of double-sided printing is not limited to the path of the above-described embodiment, and for example, paths as shown in FIGS. 13 to 16 may be adopted. That is, first, as shown in FIG. 13, the inkjet head 4 is caused to print the surface of the printing paper P adsorbed by the first drum 1. Next, as shown in FIG. 14, at the closest point C between the first drum 1 and the second drum 2, the printing paper P is transferred while being reversed. After that, as shown in FIG. 15, the printing paper P is placed on the common outer tangent line of the first drum 1 and the second drum 2 (upper side) from the second drum 2 to the first drum 1 without reversing the front and back. 1 passes to the drum 1 and causes the inkjet head 4 to print the back surface of the printing paper P. Finally, the printing paper P is transferred from the first drum 1 to the second drum 2 on the other (lower) common outer tangent line, and is discharged from the second drum 2 by the paper discharge mechanism 6.

  Also in the above-described path, the printing paper P on which the front surface is printed on the first drum 1 is turned upside down at the time of delivery to and from the second drum 2 and then returned to the first drum 1 to print the back side. Is possible. However, in this path, the front and back are reversed at the closest point C immediately after the surface is printed by the first drum 1. For this reason, from the viewpoint of preventing the printed surface of the printing paper P from becoming dirty at the time of reversal, the front and back are not reversed by handing over the common outer tangent line of the drums 1 and 2 immediately after the surface is printed. The path of the above embodiment (FIGS. 4 to 9), in which the surface is dried while being adsorbed to the two drums 2, and then reversed when the closest point C is transferred to the first drum 1 is reversed. preferable.

2] The suction mechanism that sucks the printing paper P onto the drum is not limited to the configuration of the above-described embodiment, and can be changed as appropriate. For example, a plurality of suction pumps 43 may be connected to the plurality of decompression chambers 42 in a one-to-one correspondence. In this case, the decompression of each decompression chamber 42 can be performed by controlling the suction force of the corresponding suction pump 43 or controlling ON / OFF of the suction pump 43.

  The partition wall 41 that partitions the decompression chamber 42 may be provided not on the outer peripheral surface of the fixed body 40 but on the inner surfaces of the drums 1 and 2. Further, a plurality of decompression chambers 42 corresponding to the plurality of through holes 13 formed in the drums 1 and 2 may be formed between the drums 1 and 2 and the fixed body 40.

  Further, the suction mechanism is not limited to the one based on the decompression (suction) of the decompression chamber 42 as in the embodiment. For example, a so-called electrostatic adsorption type adsorption mechanism in which static electricity is generated on the outer peripheral surfaces of the drums 1 and 2 to adsorb the printing paper P may be used.

3] In the above embodiment, as the transfer means for transferring the printing paper P between the first drum 1 and the second drum 2, the suction force of the suction mechanism 3 of the first drum 1 and the second drum 2 is changed. Although the delivery configuration is illustrated, the delivery means is not limited to such a configuration. For example, it is composed of rollers, paper guides, and the like in contact with the outer peripheral surfaces of the drums 1 and 2, and the printing paper P is forcibly applied from the outer peripheral surfaces of the drums 1 and 2 by directly applying a peeling force to the printing paper P The structure which peels off may be sufficient.

4] In the above-described embodiment, the printing paper P is conveyed while only the two drums 1 and 2 are reversed, but a member other than the two drums 1 and 2 (another drum, an auxiliary roller, etc.) is added. Then, the printing paper P including front and back inversion may be transported.

5] In the above-described embodiment, the printing paper P is transferred between the first drum 1 and the second drum 2 without inverting the front and back on the common outer tangent line of the two drums 1 and 2. However, it is not always necessary to perform delivery on the common outer tangent, and delivery may be performed without reversing the front and back at a position slightly shifted from the common outer tangent to the drum side or the opposite side of the drum. .

6] In the above embodiment, the diameters of the two drums 1 and 2 are the same, but the diameters of the two drums 1 and 2 may be different.

  For example, if the diameter of the second drum 2 is made larger than that of the first drum 1, the time during which the printing paper P is conveyed in the circumferential direction while being attracted to the second drum 2 becomes longer than that of the first drum 1. . Therefore, as in the above-described embodiment, immediately after the surface of the printing paper P is printed on the first drum 1, the printing paper P is passed from the first drum 1 to the second drum 2 without being turned upside down. While the printing paper P is conveyed in the circumferential direction by the second drum 2, the ink on the surface is reliably dried.

  Further, if the diameter of the second drum 2 is sufficiently larger than the first drum 1 (for example, about several times), a plurality of printing sheets P can be adsorbed simultaneously on the outer peripheral surface of the second drum 2. It becomes. As a result, a plurality of printing sheets P adsorbed by the second drum 2 are continuously supplied to the first drum 1, whereby a plurality of printing sheets P are continuously printed on the first drum 1. Can do.

7] The paper feed position for supplying the print paper P to the first drum 1 and the paper discharge position for discharging the print paper P from the second drum 2 are not limited to the positional relationship of the above-described embodiment. It can be changed in consideration of the above.

DESCRIPTION OF SYMBOLS 1 1st drum 2 2nd drum 3 Adsorption mechanism 4 Inkjet head 7 Control apparatus 8 Holding mechanism 11 1st drum drive motor 12 2nd drum drive motor 13 Through-hole 30 1st conveyance roller 31 2nd conveyance roller 35,36 Common circumscribing Line 40 Fixed body 41 Bulkhead part 42 Decompression chamber 43 Suction pump 62 Transport control part 63 Adsorption control part 64 Position detection part 100 Printer A Paper feed position B Paper discharge position C Nearest point P Printing paper

Claims (8)

A first drum configured to be rotatable;
First rotational drive means for rotationally driving the first drum;
First adsorbing means for adsorbing a print medium on the outer peripheral surface of the first drum;
An inkjet head that performs printing by ejecting ink onto the print medium that is attracted to the outer peripheral surface of the first drum, facing the outer peripheral surface of the first drum;
A second drum arranged in the vicinity of the first drum in the radial direction and configured to be rotatable;
Second rotation driving means for rotating the second drum;
Second adsorbing means for adsorbing the print medium on the outer peripheral surface of the second drum;
Delivery means for delivering the print medium between the first drum and the second drum;
The print medium printed on the surface by the inkjet head while being adsorbed to the outer peripheral surface of the first drum is transferred to the second drum by the transfer means, and further, the front and back of the print medium are reversed. A conveyance control means for controlling the first rotation driving means and the second rotation driving means so as to return the first drum to the first drum again by the delivery means;
Holding means for holding the print medium delivered between the first drum and the second drum on a common outer tangent line of the first drum and the second drum;
Equipped with a,
The delivery means is
The first suction means and the second suction means are controlled so as to weaken the suction force of the transfer source drum and increase the suction force of the transfer destination drum. A printer characterized in that the print medium is transferred between the printers. The transport control means includes
The first medium and the second drum are printed on the surface of the print medium, and the first medium and the second drum are arranged on a common outer tangent line extending over the first drum and the second drum. The printer according to claim 1, wherein the first rotation driving unit and the second rotation driving unit are controlled so as to be transferred between the drum and the second drum. The transport control means includes
First, while rotating the first drum and the second drum in the same direction, the print medium printed on the surface is transferred from the first drum to the second drum, out of the two common outer tangent lines. Pass on one of the
Next, by rotating the first drum in the opposite direction to the second drum, the print medium is reversed from the second drum to the first drum while reversing the front and back of the print medium at the closest point. 3. The printer according to claim 2, wherein the first rotation driving unit and the second rotation driving unit are controlled so as to pass. The holding means is
A first roller having a plurality of protrusions arranged in a circumferential direction and disposed outside the common circumscribing line, and disposed so as to face the first roller with the common circumscribing line sandwiched inside the common circumscribing line The printer according to claim 1, further comprising a cylindrical second roller. The transport control means includes
Double-sided printing for controlling the first rotation driving means and the second rotation driving means so that the printing medium printed on the front surface is turned upside down and then sent back to the inkjet head for printing on the back surface. Mode,
The single-sided printing mode for controlling the first rotation driving means and the second rotation driving means can be selectively executed so that the print medium printed on the surface is discharged without being sent to the inkjet head. The printer according to claim 1, wherein the printer is provided. The transport control means includes
In both of the duplex printing mode and the simplex printing mode, the printing medium is convex on one side and convex on the other side during conveyance by the first drum and the second drum. 6. The printer according to claim 5, wherein the first rotation driving unit and the second rotation driving unit are controlled so as to be bent in two directions. A large number of through holes arranged in the circumferential direction are formed on the outer peripheral surfaces of the first drum and the second drum, respectively.
The first adsorption means and the second adsorption means are respectively
A columnar fixed body disposed inside the corresponding drum with a gap from the inner surface of the drum,
A plurality of partition walls provided on the inner peripheral surface of the drum or the outer peripheral surface of the fixed body at intervals in the circumferential direction;
A plurality of decompression chambers formed by dividing the space between the fixed body and the drum in the circumferential direction by the plurality of partition walls;
A decompression means capable of decompressing each of the plurality of decompression chambers independently,
Each the decompression chamber, the printer according to any one of claims 1 to 6 in which a plurality of the through holes is equal to or in communication. The through hole is not provided in a partial region of the drum, and the circumferential length of the partial region where the through hole is not provided is the circumferential direction of the drum corresponding to one decompression chamber More than length,
Furthermore, it comprises a position detection means for detecting the position of the tip of the printing medium,
The transport control means includes
Based on the detection result of the position detection means, the first rotation is performed so that the front end of the print medium is adsorbed by the through hole closest to the partial region in the direction opposite to the rotation direction of the drum. 8. The printer according to claim 7 , wherein the printer controls the driving means and the second rotation driving means.

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