JP5309829B2 - Inkjet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet printer A comprising: a platen 23 having a suction hole for sucking a recording sheet of paper; a sucking device 36 for sucking the recording paper being carried on the platen 23 via the suction hole to suckingly hold it on the platen 23; and an ink head H opposed to the platen 23 for discharging ink to the recording paper being carried on the platen 23 to print images, wherein the recording sheet on the surface side of which printing is finished is reversed upside down, and printing is made on the reverse side for actualizing both side printing while preventing such a suction error that the recording sheet with its front end floating from the platen 23 is carried during reverse-side printing. <P>SOLUTION: A changing mechanism 100 is provided for changing the curving characteristics of the recording sheet on the surface side of which printing is finished, or eliminating the curve thereof so that, when the recording sheet enters onto the platen 23 during reverse-side printing, its front end abuts on the surface of the platen 23. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention belongs to a technical field related to an ink jet printer that prints an image on a recording paper by ejecting ink from the print head onto the recording paper.

  In this type of ink jet printer, it is necessary to keep the distance between the print head and the recording paper constant (set distance) in order to improve the print quality of the recording paper. In a printer, a plurality of suction holes are provided in a platen for supporting a recording sheet disposed opposite to a print head, and a recording fan conveyed on the platen is disposed on a lower side of the platen. So as to be sucked and held on the surface.

In addition, in recent years, in the inkjet printer, in addition to the need for higher image quality of printed images, there is an increasing need for customers who want to print on both sides of recording paper. In the ink jet printer shown in FIG. 2, a print head is disposed on one side of the recording paper, and after printing on one side of the recording paper, the recording paper is turned upside down and re-supplied to the printing unit. Is printed on both sides of the recording paper.
JP 2007-33155A JP 2006-192838 A

  By the way, in the ink jet printer that performs double-sided printing shown in Patent Document 2, it is conceivable to adopt the recording paper suction structure shown in Patent Document 1 in order to improve the print quality of each surface.

  However, in the ink jet printer, generally, by performing a printing process on one side of the recording paper, the recording paper has an intermediate portion in the transport direction at both ends (leading edge and trailing edge). On the other hand, a curve characteristic protruding toward the printed surface side occurs. For this reason, when the recording paper enters the platen when the recording paper is turned upside down to perform printing on the other side of the recording paper, the leading edge of the recording paper (the downstream edge in the transport direction) is the other side. Warps up and floats up from the platen. As a result, the suction force of the suction fan cannot be sufficiently applied to the leading end of the recording paper, and the conveyance is continued while the leading end of the recording paper is lifted, and the print quality is improved due to rubbing between the recording paper and the print head. There is a problem that the recording head is lowered or the leading end of the recording paper collides with the print head to cause a printing error.

  The present invention has been made in view of such points, and an object of the present invention is to provide a platen having a suction hole for sucking a recording paper and a recording paper conveyed on the platen through the suction hole. A suction means for sucking and holding on the platen, and an ink head disposed opposite to the platen and ejecting ink onto a recording paper transported on the platen to print an image, Ink jet printers that can be printed on both sides by reversing the front and back of the recording paper that has been printed on one side and printing on the other side. Is intended to prevent a printing error by preventing a suction error caused by the leading edge of the recording paper floating from the platen, and to improve the printing quality of the recording paper.

In order to achieve the above object, according to the present invention, in an ink jet printer configured to be capable of double-sided printing of recording paper, the recording paper after printing on the one side surface re-supplied to the printing unit is provided. bending properties by performing characteristic changing process to change the (the conveyance direction intermediate portion of the recording paper characteristics projecting the one side is already printed surface side of the both end portions) having, again to the printing unit the downstream side end portion when the recording paper supplied enters on the platen includes a changing mechanism for Hoboto contact to the platen surface, the change mechanism, after printing of the to one side surface As the length of the recording paper is longer, a stronger bending force is applied to the recording paper, thereby giving a bending characteristic opposite to the bending characteristic along the conveying direction of the recording paper. I made it.

  Specifically, in the first aspect of the invention, a printing unit that prints on one side of the recording paper by ejecting ink from the print head, a recording paper supply unit that supplies the recording paper to the printing unit, and the printing And a platen that is disposed to face the print head and supports the recording paper supplied from the recording paper supply unit and has a suction hole for sucking the recording paper, and is provided in the printing unit. A suction unit that sucks and holds the recording paper supplied from the recording paper supply unit on the platen by sucking the recording paper through the suction hole; and the printing unit. A printing conveyance unit that conveys the recording sheet to the side opposite to the recording paper supply unit while being adsorbed by the platen, and the recording sheet printed on one side by the printing unit is reversed and is then returned to the printing unit. A recording paper refeeding unit for feeding, and the printing In, by printing on the other side surface of the re-supplied recording paper from the recording paper resupply portion directed to an inkjet printer for printing on both sides of the recording paper.

Then, the provided recording paper resupply unit, the printing unit to re-supplied is printed after completion of the recording paper that characteristic changes to change the curvature characteristics along the conveying direction with the said the one side surface A change mechanism for performing processing, wherein the change mechanism is configured so that when the recording paper re-supplied to the printing unit enters the platen, the leading end thereof substantially contacts the platen surface. The curve characteristic of the recording paper after the printing on the one side of the printing sheet along the conveyance direction is such that the intermediate portion in the conveyance direction of the recording paper is already printed on both ends. A characteristic that protrudes to the one side that is the surface side, and the characteristic changing process is a bending characteristic that is opposite to the bending characteristic along the conveyance direction of the recording paper after the printing on the one side surface is completed. And the change mechanism further includes the one side. As the length of the recording paper after printing on the surface is longer, a stronger bending force is applied to the recording paper, which is opposite to the bending characteristics of the recording paper along the conveying direction. Suppose that it is comprised so that a curve characteristic may be provided.

  According to the above configuration, the changing mechanism changes the bending characteristic (that is, the bending characteristic generated by printing on the one side surface) of the recording paper after the printing on the one side surface re-supplied to the printing unit. In addition, by performing the characteristic changing process for removing the curvature, when the recording paper enters the platen, the leading end (the downstream end in the transport direction) is brought into substantially contact with the platen surface.

  Accordingly, when printing on the other side of the recording paper in the printing unit, when the leading end of the recording paper enters the platen, the suction force by the suction means is sufficiently applied to the leading end of the recording paper. Can act.

  For this reason, it is possible to prevent a suction error by the suction means and reliably hold the leading end portion of the recording paper on the platen surface. Accordingly, it is possible to surely prevent the printing quality of the recording paper from being deteriorated due to rubbing between the recording paper front end portion and the print head, and the printing error due to the recording paper front end portion colliding with the print head.

  Further, if the recording paper leading edge can be adsorbed to the platen surface as described above, the entire range from the leading edge to the trailing edge of the recording paper is sequentially applied as the recording paper subsequently enters the platen. It can be reliably adsorbed and held on the platen surface. Therefore, the print quality of the recording paper can be improved by maintaining the distance between the print head and the recording paper constant (to ensure the flatness of the recording paper).

Further, the curve characteristic of the recording paper after printing on the one side surface (curvature characteristic generated on the recording paper by printing on one side surface of the recording paper) is such that the intermediate portion in the transport direction of the recording paper has both ends. A characteristic of projecting to the one side which is the printed surface side with respect to the portion, and having a characteristic that the front end of the recording paper is easily lifted off the platen when printing on the other side (when the recording paper is reversed) Even if it is a thing, the adsorption | suction mistake at the time of back surface printing can be prevented by providing a change mechanism as mentioned above.

Then, when the characteristic changing process is executed by the changing mechanism, the recording paper is given a bending characteristic opposite to the bending characteristic generated by the printing of the one side surface.

Accordingly, the curved characteristic that a recording paper after printing of the to one side surface has found conveying direction intermediate portion of the as recording paper Tsu der having a characteristic which projects finished print surface side (one side) also, by the shape characteristic changing process by changing mechanism thereafter is performed, the inflection characteristic of the recording paper, that the conveying direction intermediate portion is changed to the characteristic protruding unprinted side (the other side) It becomes. For this reason, when printing on the other side of the recording paper, the leading edge of the recording paper can be brought into contact with the platen surface to prevent its lifting. Therefore, as possible out to be reliably attracted holding the recording paper tip platen surface.

Further, as the length of the recording paper after printing on the one side surface is longer, a stronger bending force is applied to the recording paper, whereby the recording paper has a curve along its transport direction. Since a bending characteristic opposite to the characteristic is given, an appropriate bending force according to the strength of the bending characteristic of the recording sheet at the end of printing on one side surface can be applied to the recording sheet.

According to a second aspect of the present invention, in the first aspect of the invention, a drying process is performed by blowing warm air on the printing surface of the recording paper on which printing has been performed at the printing unit downstream of the printing unit in the transport direction. A drying unit is provided for the recording paper immediately after the drying unit is disposed on the downstream side in the transport direction with respect to the drying unit. It is assumed that the characteristic changing process is executed.

According to this configuration, it is possible to execute the characteristic changing process by the changing mechanism for the recording paper that is easily deformed by being heated by the dry air (warm air), thereby easily making the curved characteristic of the recording paper. it is strange puff Rukoto to. Therefore, it is possible to more reliably prevent an adsorption error during printing on the other side of the recording paper.

As described above, according to the ink jet printer of the present invention, in the ink jet printer that performs double-sided printing of the recording paper, the curve characteristic of the recording paper after the printing on the one side surface that is re-supplied to the printing unit has by performing the characteristic change process to change a variable recording paper to be resupplied to the printing unit for Ru its downstream side end portion is Hoboto contact to the platen surface when entering on the platen A change mechanism, and the change mechanism adds a stronger bending force to the recording paper as the length of the recording paper after the printing on the one side ends is increased. Since the curve characteristic opposite to the curve characteristic along the transport direction is provided, the adsorption error due to the leading edge of the recording paper floating from the platen when printing on the other side of the recording paper is prevented. Times printing error To together, it is possible to improve the print quality of the recording sheet, it may be added an appropriate curvature force corresponding to the intensity of the bending characteristics of the print end time of the recording sheet on one side of the surface on the recording paper.

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

  FIG. 1 shows an external appearance of an inkjet printer A according to an embodiment of the present invention, and FIG. 2 schematically shows an internal configuration of the inkjet printer A. The ink jet printer A is used in a photographic print system. For example, the ink jet printer A is a recording paper based on image data transmitted via a communication cable from a reception block that acquires image data and performs necessary correction processing and the like. Printing is performed on P (see FIGS. 3 and 6). The recording paper P is a cut sheet of a predetermined size, and a plurality of types of sizes are preset as the sizes (the length of the recording paper P and the length of the recording paper P are set according to the size of the recording paper P). Width is decided).

  The ink jet printer A includes a printer main body 1 having a casing 2 with a caster 3 provided on the lower surface thereof, and a detachably attached upper portion of one side of the casing 2 of the printer main body 1 and a plurality of recordings. A cassette 5 that can store paper P in the thickness direction and a duplex printing unit 7 that is detachably attached to the upper surface of the housing 2 are provided. In the present embodiment, the side on which the cassette 5 is attached (left side in FIG. 2) is referred to as the printer front side, and the opposite side (right side in FIG. 2) is referred to as the printer rear side. Also, the direction perpendicular to the paper surface of FIG. 2 is the left-right direction of the printer, and coincides with the width direction of the recording paper P accommodated in the cassette 5 and conveyed in the printer main body 1 and the duplex printing unit 7. .

  As shown in FIG. 2, in a state where the double-sided printing unit 7 is attached to the printer main body 1, it is possible to print on both the front and back sides of the recording paper P as will be described in detail later. On the other hand, when printing is performed only on one side of the recording paper P and double-sided printing is not necessary, the double-sided printing unit 7 is usually removed from the printer body 1 (see FIG. 13). However, even when the duplex printing unit 7 is attached to the printer main body 1, it is possible to print on only one side of the recording paper P. By bundling a plurality of recording papers P printed on both sides, a photo album or a photo book can be produced.

  The cassette 5 differs depending on the size of the recording paper P. When the cassette 5 is attached to the printer main body 1, the operator selects the size (length and length) of the recording paper P corresponding to the cassette 5. Width) is input by an operation switch (not shown). Further, the width regulating members 84 and 85 (see FIG. 10) of the correction mechanism 81 (described later) are aligned to a position corresponding to the width of the recording paper P by operating an operation member (not shown). For example, an IC chip is provided in the cassette 5, and the size of the recording paper P is stored in the IC chip. When the cassette 5 is attached, the printer main body 1 stores the IC chip. The contents may be read. This eliminates the need for the operator's input work. Further, the positioning of the width regulating members 84 and 85 of the correction mechanism 81 may be automatically performed by a motor in accordance with the result of the input by the operator's operation switch or the result of reading the stored contents of the IC chip.

  As shown in detail in FIG. 3, a set tray 11 for setting the recording paper P in a state of being stacked in the thickness direction is disposed in the cassette 5. The set tray 11 is supported in the cassette 5 so as to be rotatable about a shaft 11a extending in the left-right direction of the printer at a substantially center of the set tray 11 in the front-rear direction of the printer. The set tray 11 is biased by a spring so that the rear end of the printer rotates to the ascending side. As a result, the uppermost recording paper P among the plurality of recording papers P set on the set tray 11 comes into contact with the feeding roller 14 disposed at the upper part of the rear end of the printer in the cassette 5. It will be.

  The feeding roller 14 is driven in a counterclockwise direction in FIG. 3 by a motor (not shown) disposed on the printer main body 1 side, and the feeding roller 14 is rotationally driven by this motor. As a result, only one uppermost recording sheet P is moved to the rear side of the printer and fed out of the cassette 5. At this time, in order to prevent the recording sheet P positioned below the uppermost recording sheet P from being dragged by the uppermost recording sheet P and simultaneously feeding a plurality of recording sheets P to the outside of the cassette 5. When the feed roller 14 is rotated by a predetermined amount, the tray pressing mechanism 16 lowers the rear end of the set tray 11 on the printer.

  The tray pressing mechanism 16 includes a tray pressing lever 17 supported on the printer body 1 so as to be rotatable about a shaft 17a extending in the left-right direction of the printer, and the tray pressing lever 16 is rotated around the shaft 17a. And a lever rotating cam 18 for moving the lever. The lever rotating cam 18 is rotated around a shaft 18a by a motor (not shown). One end of the tray push-down lever 17 enters the cassette 5 so as to be positioned above the rear end of the printer on the set tray 11 when the cassette 5 is attached to the printer main body 1. On the other hand, the other end of the tray pressing lever 17 is in contact with the cam surface of the lever rotating cam 18. In order to always maintain this contact state, the tray pressing lever 17 is urged by a spring so that the other end portion moves toward the lever rotating cam 18 (that is, one end portion moves upward). Has been.

  When the feed roller 14 is rotated by a predetermined amount, the lever rotating cam 18 is rotated so that the one end portion of the tray pressing lever 17 comes into contact with the rear end portion of the set tray 11 on the printer side. Press this down. As a result, the recording paper P positioned below the uppermost recording paper P is prevented from being dragged by the uppermost recording paper P, and a plurality of recording papers P are not simultaneously fed out of the cassette 5. When the lever rotating cam 18 is rotated halfway, the one end portion of the tray pressing lever 17 starts to rise, and accordingly, the rear end of the printer of the set tray 11 is raised by the spring, and then the most The upper recording paper P contacts the feed roller 14. When the lever rotation cam 18 makes one rotation, the rotation of the lever rotation cam 18 stops and the tray pressing lever 17 returns to the initial state.

  The recording paper P delivered to the outside of the cassette 5 by the delivery roller 14 is supplied to a printing unit 21 described later in the printer body 1. Thus, the feed roller 14 of the cassette 5 constitutes a recording paper supply unit that supplies the recording paper P to the printing unit 21.

  A printing unit 21 that performs printing based on the image data is provided in the vicinity of the mounting portion of the cassette 5 in the upper part of the housing 2 of the printer main body 1. As shown in detail in FIGS. 4 and 5, the printing unit 21 includes a print head H that prints on one side surface (upper side surface) of the recording paper P and the recording paper P supplied from the feeding roller 14. A printing transport unit 22 that transports the recording paper P to the opposite side (the rear side of the printer) when printing on the recording paper P, and a platen 23 that supports the recording paper P transported from the printing transport unit 22. I have.

  A crimp-type upstream roller pair 24 is disposed at the upstream end (printer front end) of the print transport unit 22, and a crimp-type upstream roller pair 24 is disposed at the downstream end (printer rear end) of the print transport unit 22. A downstream roller pair 25 is provided. Drive rollers 24a and 25a located below the upstream roller pair 24 and the downstream roller pair 25 are driven by the same motor (not shown). Further, the driven rollers 24b and 25b positioned above the upstream roller pair 24 and the downstream roller pair 25 are pressed against the corresponding lower driving rollers 24a and 25a, and the pressing is released. It is possible to switch between states.

  First and second sensors 27 and 28 (both of a light projecting part and a light receiving part) for detecting the recording paper P are disposed on the upstream side and the downstream side of the upstream roller pair 24, respectively. ing. The first sensor 27 detects that the leading edge of the recording paper P has entered the casing 2 of the printer main body 1 from the cassette 5 or the duplex printing unit 7, and by this detection, the upstream roller pair 24 drive rollers 24a are driven. The second sensor 28 detects the leading edge of the recording paper P delivered from the upstream roller pair 24, and from this detection of the leading edge of the recording paper P by the second sensor 28, the print start portion of the recording paper P is printed. When the recording paper P is conveyed by the upstream roller pair 24 by an amount that reaches the lower position of the head H, printing on the recording paper P is started. Further, from the detection of the leading edge of the recording paper P by the second sensor 28, when the recording paper P is conveyed by the upstream roller pair 24 by an amount such that the leading edge of the recording paper P reaches the downstream roller pair 25, The upstream roller pair 24 is changed from the pressure-bonded state to the pressure-released state, and the downstream roller pair 25 is changed from the pressure-released state to the pressure-bonded state, and this time, the recording paper P is conveyed by the downstream roller pair 25.

  The print head H is movable along two guide rails 31 extending in the main scanning direction X (see FIG. 5) that coincides with the width direction of the recording paper P (left and right direction of the printer) at the upper position of the recording paper P. It is configured. Further, the print head H has two head units 32 arranged in the sub-scanning direction Y (see FIG. 5) that is perpendicular to the main scanning direction X and coincides with the moving direction of the recording paper P (the front-rear direction of the printer). In addition, a plurality of colors of ink are ejected downward from a large number of ink ejection nozzles (not shown) provided on the lower surfaces of these two head units 32, whereby a predetermined amount is applied to the upper surface of the recording paper P. The image of can be printed. In this embodiment, the head units 32 are arranged in two stages in the sub-scanning direction Y. However, the head units 32 do not have to be two stages, and may be one stage or three stages or more.

  Both the head units 32 have the same configuration, and each has a plurality of nozzle arrays arranged in the main scanning direction X for ejecting ink of each color. In each nozzle array, the ink discharge nozzles are arranged in a row in the sub-scanning direction Y. Thus, each head unit 32 is configured to be able to form a color image by itself. Then, the recording paper P is transported intermittently (stepwise) in the sub-scanning direction Y by a fixed unit transport amount by the upstream roller pair 24 or the downstream roller pair 25, and the recording paper P at the time of this intermittent transport. When the printing head H is stopped, the print head H is scanned one time in the main scanning direction X (one-way operation or one-time operation). During this scanning, ink ejection of each color of each head unit 32 is performed at each position in the main scanning direction X. Ink is simultaneously ejected from the nozzles onto the upper surface of the recording paper P. That is, after one scan of the print head H, the recording paper P is transported by the unit transport amount, and then the print head H is scanned once again, and this operation is repeated to print a desired image. .

  Here, as a configuration for ink discharge of the print head H in the present embodiment, ink is discharged from an ink discharge nozzle communicating with the pressure chamber by changing the volume of the pressure chamber filled with ink by a piezo element. The general piezo type is used.

  The platen 23 is made of a plate-like member, and the upper surface thereof is a support surface 23 a that supports the recording paper P. The platen 23 is provided with a number of suction holes 23b (see FIG. 5) penetrating in the thickness direction (vertical direction) and opening to the support surface 23a. A case body 35 that forms a space with the platen 23 is disposed below the platen 23, and a suction device 36 including a fan and the like is disposed below the case body 35. The suction hole 23 b communicates with a space in the case body 35, and this space communicates with a suction port of the suction device 36, and the platen is opened via the suction hole 23 b by the operation of the suction device 36. A negative pressure is generated on the support surface 23 a side of the recording medium 23, so that the recording paper P is sucked and held on the support surface 23 a of the platen 23. Thereby, it becomes possible to ensure the flatness of the recording paper P at the time of printing and to improve the printing quality.

  Further, the support surface 23a of the platen 23 is formed with a recess 23c (see FIG. 5) extending in the sub-scanning direction Y for accommodating the ink absorbing material 38. The ink absorbing member 38 allows a part of the ink ejected from the print head H (head unit 32) to be printed on the recording paper P on the support surface 23a when performing borderless printing for printing an image on the entire recording paper P. This is provided in order to prevent the support surface 23a of the platen 23 from being soiled by the ink that has come off from the outer edge of the width direction. For this reason, the concave portion 23c is located at a position corresponding to the width direction edge of the recording paper P on the support surface 23a and a position corresponding to the print head H in the sub-scanning direction Y on the support surface 23a. (Ie, extending in the sub-scanning direction Y). In the example of FIG. 5, a total of ten recesses 23 c are provided, five on each side, so as to be compatible with recording paper P of five different widths. The ink absorbing material 38 is preferably made of, for example, a sponge having excellent ink absorbability.

  Here, when performing borderless printing, ink is ejected to the edge of the recording paper P in the width direction, and ink protruding from the edge is absorbed by the ink absorber 38. Printing is performed with a predetermined amount (for example, 2 mm) of blank space without ejecting ink at the very front and back edges of the recording paper P. Then, the margin is finished by cutting the margin with a cutter 40 described later. This is because, when ink is ejected toward the leading edge or the trailing edge of the recording paper P, the ink is drawn into the suction hole 23b by the suction action by the suction hole 23b, and the print quality is deteriorated. This is because the support surface 23a is stained with ink.

  On the downstream side of the print transport unit 22 in the upper part of the casing 2 of the printer main body 1, the recording paper P fed from the downstream end (downstream roller pair 25) of the print transport unit 22 is placed on the front and back sides. A U-turn portion 45 is provided for making a U-turn so as to be reversed and the conveyance direction is reversed.

  Between the U-turn part 45 and the print transport part 22, a cutter 40 for cutting the margins at the leading edge and the trailing edge of the recording paper P when the borderless printing is performed is disposed. The cutter 40 is disposed on the upper side of the conveyance path of the recording paper P and the lower side of the conveyance path of the recording paper P, and is vertically moved with respect to the fixed blade 40a by a motor (not shown). The movable blade 40b is moved, and the movable blade 40b moves from the lower side to the upper side of the recording paper P to cut the recording paper P. Chips resulting from this cutting fall and are stored in a waste box 41 (see FIG. 2) disposed in the lower part of the housing 2. When printing on both sides of the recording paper P, the margin is cut by the cutter 40 after printing on both sides.

  The U-turn portion 45 is disposed in the upstream portion of the U-turn portion 45 and sandwiches the recording paper P from the print conveying portion 22 and discharges it to the rear side (downstream side) of the printer. 21, a change mechanism 100 including a conveyance roller pair 44 that performs a process (hereinafter referred to as a characteristic change process) for changing the curve characteristic of the recording paper P re-supplied to the paper 21, and is discharged from the change mechanism 100. A pair of pressure-conveying conveyance rollers 46 that sandwich the recording paper P and further convey it to the rear side of the printer, and a first direction changing member that changes the conveyance direction of the recording paper P conveyed by the conveyance roller pair 46 upward. 47, two pairs of pressure-feeding conveyance rollers 48 that are disposed downstream of the first direction changing member 47 and sandwich the recording paper P and convey the recording paper P upward, and are conveyed by the conveyance roller pair 48. Direction of transported recording paper P A second orientation changing member 49 that changes to the front side of the printer, a pressure-conveying pair of conveyance rollers 50 that are disposed at the downstream end of the U-turn portion 45 and sandwich the recording paper P and discharge from the U-turn portion 45; A third sensor 51 (consisting of a light projecting part and a light receiving part) is provided that is disposed in the vicinity of the pair of transport rollers 50 and detects that the recording paper P is in the position. A pair of guide plates 52 for guiding the leading end of the recording paper P fed from the lower conveyance roller pair 48 to the upper conveyance roller pair 48 is provided between the two conveyance roller pairs 48. It is arrange | positioned so that it may be pinched | interposed.

  In the upstream portion of the change mechanism 100 between the conveying roller pair 46 and the change mechanism 100 in the upstream portion of the U-turn portion 45, the ink attached to the upper side surface of the recording paper P in the printing portion 21 is dried. Is provided with a drying device 53 that blows dry air (warm air) W on the upper surface of the recording paper P. The drying device 53 has a suction fan 54 for taking air into the drying device 53, a heater 55 for heating the air taken in by the suction fan 54, and an opening at the lower end of the drying device 53. An exhaust nozzle unit 56 that blows air heated by the heater 55 on the upper surface of the recording paper P as dry air W, and a safety thermo 57 that detects the temperature in the drying device 53 and stops the heater 55 in an emergency manner. Yes. A fifth sensor 193 that detects the leading end of the recording paper P (also referred to as the downstream end in the transport direction and also referred to as the front end) is provided below the drying device 53 and upstream of the change mechanism 100. ) Is arranged.

  Among all the transport roller pairs 44, 46, 48, 50 of the U-turn section 45, the rollers that contact the surface of the recording paper P opposite to the printing surface by the printing section 21 (the transport roller pair 44 in the upstream portion, 46 is a lower roller, two downstream transport roller pairs 48 are printer rear rollers, and the upper transport roller pair 50 is an upper roller). 48a and 50a, which are in contact with the printing surface (the upper roller in the transport roller pair 44 and 46, the front roller in the transport roller pair 48, and the lower roller in the transport roller pair 50) Are provided as driven rollers 44b, 46b, 48b and 50b, respectively. These driven rollers 44b, 46b, 48b, 50b are made of a softer material than the drive rollers 44a, 46a, 48a, 50a. For example, the drive rollers 44a, 46a, 48a and 50a are made of polypropylene, and the driven rollers 44b, 46b, 48b and 50b are made of urethane foam. In this way, by allowing the driven rollers 44b, 46b, 48b, and 50b in contact with the printing surface to be soft, it is possible to increase the permissible speed of the recording paper P. Further, by making the drive rollers 44a, 46a, 48a, and 50a in contact with the surface opposite to the printing surface hard, it is possible to ensure the conveyance accuracy of the recording paper P and to prevent the occurrence of meandering and the like. .

  All the drive rollers 44a, 46a, 48a, 50a are driven by the same motor (not shown). The rotational speed of the drive rollers 44a, 46a, 48a, 50a, that is, the transport speed of the recording paper P by the transport roller pairs 44, 46, 48, 50 is configured to be variable. That is, the degree of drying of the ink by the drying device 53 changes according to the environmental conditions (temperature, humidity, etc.) in which the ink jet printer A is installed, so the transport speed is changed accordingly. Further, when the duplex printing unit 7 is attached to the printer main body 1, the ink may be dried while the recording paper P is conveyed by the duplex printing unit 7. Set to a relatively fast speed so that the ink does not dry completely. On the other hand, when the duplex printing unit 7 is not attached to the printer main body 1 (see FIG. 13), the recording paper P discharged from the U-turn portion 45 by the conveying roller pair 50 is directly outside the casing 2. The ink is discharged and placed on the upper surface of the housing 2, and for this reason, a slow speed is set so that the ink is almost completely dried by the drying device 53.

  The third sensor 51 detects the trailing edge of the recording paper P and detects the discharge of the recording paper P from the U-turn portion 45. When the duplex printing unit 7 is not attached to the printer main body 1, the discharge of the recording paper P to the outside of the housing 2 is detected. On the other hand, when the duplex printing unit 7 is attached to the printer main body 1, when the recording paper P is transported by an amount in which the trailing edge deviates from the transport roller pair 50 from detection of the trailing edge of the recording paper P. In addition, the conveyance speed of the recording paper P in the duplex printing unit 7 is changed (up).

  The duplex printing unit 7 has a two-part structure of a first unit 8 that covers the upper surface of the housing 2 and a second unit 9 that is located above the cassette 5. Only the first unit 8 can be detached from the housing 2 in a state where the duplex printing unit 7 is attached to the printer main body 1. With the first unit 8 removed, maintenance work is performed on the printing unit 21 (especially the print head H, etc.) through a maintenance opening (normally closed with a lid) provided on the top surface of the housing 2. be able to. Therefore, even after the duplex printing unit 7 is attached to the printer main body 1, the maintenance work of the printing unit 21 can be easily performed.

  In the first unit 8 of the double-sided printing unit 7, the recording paper P sent out from the U-turn unit 45 passes the printing unit 21 to the cassette 5 side (the printer front side with respect to the printing unit 21). A reverse transport unit 61 is provided for transporting to the front. The reverse conveyance unit 61 includes three pairs of pressure-conveying conveyance rollers 62 that sandwich the recording paper P and convey the recording paper P to the front side of the printer, and a downstream end of the reverse conveyance unit 61 (the front end of the first unit 8 on the printer). And a fourth sensor 63 (consisting of a light projecting part and a light receiving part) for detecting that the recording paper P is in the position.

  The transport path in the reverse transport unit 61 is a straight path slightly inclined downward toward the front side of the printer. The reason for this inclination is as follows. That is, the height position of the conveying roller pair 50 of the U-turn portion 45 is sufficient on the upper surface of the housing 2 on which the recording paper P is placed when the duplex printing unit 7 is not attached to the printer main body portion 1. It is necessary to be at a height position where the number of recording sheets P can be placed. On the other hand, in a switchback unit 66 (described later) in the second unit 9, the number of supply roller pairs 69 (described later) that supplies the switched back recording paper P to the upstream end of the print transport unit 22 is set to the minimum of the recording paper P. It is desirable to reduce as much as possible in consideration of the relationship with the length, and for this purpose, the switchback unit 66 needs to be at a height position close to the print conveyance unit 22. For this reason, the conveyance path in the reverse conveyance unit 61 that connects the U-turn unit 45 and the switchback unit 66 is inclined as described above.

  In the entire transport roller pair 62 of the reverse transport unit 61, a roller (upper roller) that contacts the surface of the recording paper P opposite to the print surface of the print unit 21 is a drive roller 62a, and the print surface The roller (lower roller) in contact with is a driven roller 62b. Similar to the conveying roller pair 44, 46, 48, 50 of the U-turn portion 45, the driven roller 62b is made of a softer material than the driving roller 62a.

  All the driving rollers 62a are driven by the same motor (not shown). The rotational speed of the drive roller 62a, that is, the transport speed of the recording paper P by the transport roller pair 62 is determined by the drive rollers 44a, 46a, 48a, 50a of the transport roller pairs 44, 46, 48, 50 of the U-turn section 45. Similarly to the above, it is configured to be variable. As described above, from the detection of the trailing edge of the recording sheet P by the third sensor 51, the conveying speed is increased when the recording sheet P is conveyed by an amount by which the trailing edge deviates from the conveying roller pair 50. That is, since the conveyance path is curved in the U-turn portion 45, it is necessary to set a speed at which the printing surface can be stably conveyed without damaging the printing surface, and the trailing edge of the recording paper P is upstream of the conveyance roller pair 50. In this state, the conveyance speed of the recording paper P by the conveyance roller pair 62 needs to be the same as the conveyance speed in the U-turn unit 45, but if the trailing edge of the recording paper P is separated from the conveyance roller pair 50, Since the recording paper P is transported along the straight transport path, the allowable speed is increased and the transport speed is increased. However, the transport speed is adjusted according to the status (the number of existing sheets and the existing position) of the recording paper P existing on the downstream side.

  In the second unit 9, the recording paper P transported from the reverse transport unit 61 is switched back and supplied from the rear end side of the recording paper P to the upstream end of the printing transport unit 22. A switchback portion 66 is provided. The switchback portion 66 is provided with a pressure-sensitive switchback roller pair 67 composed of a lower driving roller 67 a and an upper driven roller 67 b, and a conveyance path on the upstream side of the switchback roller pair 67. The pair of first guide members 68 that guide the recording paper P conveyed from the reverse conveying unit 61 to the switchback roller pair 67 and the switched back recording paper P are supplied to the upstream end of the printing conveying unit 22. A pair of pressure-feeding supply rollers 69, a pair of switchback rollers 67, and a pair of supply rollers 69, and a pair of second guides that guide the switched back recording paper P to the supply roller pair 69. A guide member 70 is provided.

  The drive roller 67a of the switchback roller pair 67 is driven forward by a motor (not shown) sandwiching the recording paper P and transported to the front side of the printer, and reversely rotated by sandwiching the recording paper P and transported to the rear side of the printer. Is configured to be possible.

  The switchback roller pair 67 and the first guide member 68 can be integrally rotated around the rotation axis of the drive roller 67a of the switchback roller pair 67 by a motor (not shown). A driven roller 67b of the roller pair 67 is positioned at a first position (see FIG. 6) substantially directly above the driving roller 67a, and a second position is positioned at the rear side of the printer with respect to the driving roller 67a (see FIG. 6). 7). Further, when the driven roller 67b is in the first position, the first guide member 68 is positioned on the extension of the transport path in the reverse transport unit 61 (see FIG. 6), and the driven roller 67b is in the second position. Sometimes, it is located on the extension of the second guide member 70 (see FIG. 7).

  Here, a method of switching back the recording paper P conveyed from the reverse conveyance unit 61 will be described. When the switchback roller pair 67 receives the recording paper P conveyed from the reverse conveying unit 61, the driving roller 67a is rotating forward and the driven roller 67b is in the first position. Then, after the fourth sensor 63 detects the trailing edge of the recording paper P, the recording paper P is conveyed to the front side of the printer by the switchback roller pair 67 by such an amount that the trailing edge is positioned on the first guide member 68. Then (see FIG. 6), the forward rotation of the drive roller 67a is stopped. At this time, at least the front end portion (tip portion) of the recording paper P is positioned on a loading tray 74 described later.

  Subsequently, the switchback roller pair 67 and the first guide member 68 are rotated clockwise in FIG. 6 to switch the driven roller 67b from the first position to the second position. As a result, the leading end side (front side of the printer) of the recording paper P is lifted and curved in a state of being in contact with the two auxiliary rollers 72 disposed on the upper side of the switchback roller pair 67 and on the front side of the printer ( (See FIG. 7).

  Thereafter, the drive roller 67a is rotated in the reverse direction, and the recording paper P is conveyed from the rear end side toward the supply roller pair 69 side. At this time, the auxiliary roller 72 rotates as the recording paper P is transported, so that the rear end side portion of the recording paper P to be switched back (corresponding to the front end side portion when the drive roller 67a is rotated forward) is smooth. While moving, the inner wall surface of the second unit 9 is not rubbed and scratched. The recording paper P to be switched back by the switchback roller pair 67 reaches the supply roller pair 69 through the first guide member 68 and the second guide member 70 (see FIG. 8).

  The supply roller pair 69 includes a driving roller 69a driven by a motor (not shown) and a driven roller 69b pressed against the driving roller 69a. The pressure-bonded state of the driven roller 69b to the drive roller 69a can be released as will be described later (the same applies to the driven roller 67b of the switchback roller pair 67).

  Below the supply roller pair 69, a pair of third guide members 73 provided on the upper part of the front side of the printer in the casing 2 of the printer main body 1 are disposed so as to sandwich the conveyance path. The recording paper P is supplied to the upstream end portion of the print transport unit 22 through the third guide member 73. In this way, the upper side of the recording paper P supplied to the print transport unit 22 via the duplex printing unit 7 is the side first printed on the recording paper P by the printing unit 21 (hereinafter referred to as the front side). This is the surface (back side surface) on the side opposite to the surface (front side surface) (hereinafter referred to as the back side) and is not yet printed. And it prints on both surfaces of the said recording paper P by printing on a back side surface similarly to the time of the first printing.

  The switchback roller pair 67 also serves to discharge the recording paper P conveyed from the reverse conveyance unit 61 to the outside of the second unit 9 without switching back. That is, when discharging the recording paper P to the outside of the second unit 9, the switchback roller pair 67 continues to rotate without stopping the forward rotation of the driving roller 67a. On the front side of the printer on the outer wall of the second unit 9, there is provided a loading tray 74 for receiving and loading the recording paper P sent out by the switchback roller pair 67. The recording paper P printed on both sides as described above and the recording paper P that can be printed only on the front side are discharged to the outside of the second unit 9 by the switchback roller pair 67 and placed on the placement tray 74. Will be.

  A cover member 75 for preventing dust and the like from adhering to the recording paper P placed on the placement tray 74 is placed on the upper side of the placement tray 74 on the front side of the printer on the outer wall of the second unit 9. A cantilever is supported so as to cover the upper side of the placing tray 74. The cover member 75 is supported at the base end portion (the rear end portion of the printer) so as to be rotatable about a shaft 75a extending in the left-right direction of the printer, and the cover member 75 is rotated about the shaft 75a. It is also possible to make it stand up so as to extend upward from the base end.

  In the vicinity of the switchback roller pair 67 on the upper surface of the outer wall of the second unit 9, a manual insertion opening 77 through which the recording paper P can be manually inserted is formed. In the manual insertion opening 77, a pair of manual insertion guide members 78 are disposed so as to sandwich the manually inserted recording paper P in the thickness direction, and the manual insertion guide member 78 allows manual recording. The leading edge of the paper P is guided to the switchback roller pair 67 side. Further, the manual insertion opening 77 is covered with a lid member 79 (see FIG. 1), and when the operator manually inserts the recording paper P, the operator opens the lid member 79 and a mode (not shown). Operate the switch to switch to manual feed mode. As a result, as shown in FIG. 9, the driven roller 67b of the switchback roller pair 67 is switched to the second position, and the drive roller 67a rotates in the reverse direction. Then, the operator inserts the recording paper P from the manual insertion opening 77. At this time, if the cover member 75 is in an upright state, the cover member 75 serves as a tray for supporting the recording paper P, and insertion of the recording paper P becomes easy. When the recording paper P is inserted through the manual insertion opening 77 in this way, the recording paper P is conveyed toward the supply roller pair 69 by the switchback roller pair 67, and is the same as the recording paper P which is switched back and conveyed. In addition, the supply roller pair 69 supplies the print conveyance unit 22 (printing unit 21).

  As shown in FIG. 10, a correction mechanism 81 that corrects the position in the width direction of the recording paper P supplied to the print transport unit 22 is provided on both the left and right sides of the second guide member 70 in the switchback unit 66. ing. The correction mechanism 81 includes a pair of left and right upper release levers 82 that bring the driven roller 67b of the switchback roller pair 67 into a pressure release state, and a pair of left and right lower release levers that bring the driven roller 69b of the supply roller pair 69 into a pressure release state. It has a side release lever 83 and a pair of left and right width regulating members 84 and 85 that come into contact with both lateral ends of the recording paper P.

  As shown in FIG. 11, the upper release levers 82 and the lower release levers 83 are rotatable around shafts 82a and 83a extending in the left-right direction of the printer. One end portion of each upper release lever 82 is located in the vicinity of the shaft end portion of the driven roller 67b in the press-bonded state at the second position in the switchback roller pair 67, while the other end portion of each upper release lever 82 is Abuts against the cam surface of the release cam 86 supported by a shaft 86a extending in the left-right direction of the printer. One end portion of each lower release lever 83 is connected to the shaft end portion of the driven roller 69 b of the supply roller pair 69, while the other end portion of each lower release lever 83 is connected to the release cam 86. It is in contact with the cam surface.

  The release cam 86 is rotated by a motor (not shown) together with its shaft 86a. When the release cam 86 is rotated by 90 °, each upper release lever 82 is rotated around the shaft 82a as shown in FIG. In this figure, the follower roller 67b of the switchback roller pair 67 is released from the pressure-bonding release state, and each lower release lever 83 rotates around the shaft 83a in the counterclockwise direction in FIG. The driven roller 69b of the supply roller pair 69 is brought into a pressure released state. When the release cam 86 is further rotated by 90 °, the driven rollers 67b and 69b of the switchback roller pair 67 and the supply roller pair 69 are brought into a pressure-bonded state.

  As described above, the width regulating members 84 and 85 are located at positions corresponding to the width of the recording paper P to be printed by the operation of the operator. That is, the width restricting members 84 and 85 are located at positions where they abut on both ends in the width direction of the recording paper P to be printed. These width restricting members 84 and 85 are bent so that rectangular grooves that open on the opposing surfaces are formed, and the bottom surfaces of these grooves are in contact with both side edges of the recording paper P in the width direction. The upstream portion of the bottom surface of the groove portion is inclined outward in the width direction of the transport path toward the upstream side so that the recording paper P is guided into the groove portion.

  The one (left side in FIG. 10) width regulating member 84 is configured to be movable in the width direction of the recording paper P by a predetermined amount across the position positioned by the operator's operation, and the other (in FIG. 10). It is urged by a spring so as to approach the width regulating member 85 on the right side). The width regulating member 85 is fixed at a position positioned by an operator's operation. The recording paper P is pushed toward the width regulating member 85 by the urging of the width regulating member 84, and the end of the recording paper P on the width regulating member 85 side comes into contact with the width regulating member 85. The width regulating member 85 is arranged so that the position of the recording paper P at this time becomes the reference position in the width direction of the transport path.

  However, the urging force of the width regulating member 84 is relatively weak. Therefore, when the recording paper P is conveyed by the switchback roller pair 67 or the switchback roller pair 67 and the supply roller pair 69, The width regulating member 84 can not push the recording paper P toward the width regulating member 85 by losing the conveying force by the roller pairs 67 and 69. That is, the urging force of the width regulating member 84 moves the recording paper P in the width direction when the switchback roller pair 67 and the driven rollers 67b and 69b of the supply roller pair 69 are switched to the pressure released state by the switching mechanism. It is set to a possible value. For this reason, the width regulating member 84 cannot correct the position in the width direction of the recording paper P during conveyance of the recording paper P, and moves in the width direction of the recording paper P as the recording paper P meanders. . As a result, the recording paper P tends to shift to the left in FIG. 10 from the reference position.

  Accordingly, the correction mechanism 81 switches the driven rollers 67b and 69b of the switchback roller pair 67 and the supply roller pair 69 to the pressure-released state so that the recording paper P is moved to the width regulating member 85 side by the urging of the width regulating member 84. The position of the recording paper P in the width direction with respect to the conveyance path is corrected. Specifically, when the leading edge of the recording paper P reaches a predetermined position (for example, slightly downstream of the supply roller pair 69), the conveyance of the recording paper P by the switchback roller pair 67 and the supply roller pair 69 is stopped, Thereafter, the switchback roller pair 67 and the driven rollers 67b and 69b of the supply roller pair 69 are brought into the pressure-release state by the switching mechanism. As a result, the recording paper P is in a free state, and is moved toward the width regulating member 85 by the biasing of the width regulating member 84, so that the recording paper P is accurately aligned with the reference position in the width direction of the transport path. In this way, the position of the recording paper P in the width direction with respect to the transport path is corrected, and the posture (tilt) of the recording paper P with respect to the transport path is also corrected to a normal posture. Then, when a predetermined time (the time from when the recording paper P is moved by the urging of the width regulating member 84 to complete the correction) has passed since the release of the pressure bonding, the driven rollers of the switchback roller pair 67 and the supply roller pair 69 67b and 69b are brought into a pressure-bonded state by the switching mechanism, and the conveyance of the recording paper P by the switchback roller pair 67 and the supply roller pair 69 is resumed.

  The correction operation is executed once or a plurality of times for the same recording paper P. When the correction operation is executed a plurality of times, when the recording paper P is conveyed by a predetermined amount from the resumption of the conveyance. Then, the conveyance is stopped again, and the same operation as described above is repeated. The number of executions of the correction operation is determined according to the characteristics of the recording paper P (dimensional characteristics such as length and thickness, and material characteristics such as hardness and surface quality (gloss and matte)). For example, the number of executions is increased as the length of the recording paper P (the size of the recording paper P input by the operator as described above) is increased, and the position in the width direction over the entire length of the recording paper P is increased. Perform the correction. Further, since the recording paper P is difficult to move in the width direction due to a large thickness or hardness of the recording paper P (input by an operator or stored in an IC chip and reading it), the recording paper P becomes difficult to move in the width direction. Increase the number of executions by as much. It is preferable to change the position (that is, the predetermined position and the predetermined amount) at which the recording paper P is stopped when the correction operation is performed according to the number of times of execution.

  In this way, the recording paper P is supplied to the printing conveyance unit 22 (printing unit 21) in a state where it is accurately aligned with the reference position in the width direction of the conveyance path. In this way, printing is performed stably, and the print quality is improved.

  The U-turn section 45, the reverse transport section 61, and the switchback section 66 connect the downstream end and the upstream end of the print transport section 22 and surround the print head H together with the print transport section 22. The recording paper P printed on the front side surface, which is formed from the downstream end of the print transport unit 22 and forms a circular transport path, is reversed and fed to the upstream end of the print transport unit 22. The recording paper resupply unit 88 is configured. By this recording paper refeeding unit 88, the recording paper P printed on the front side can be reversed and fed back to the printing unit 21, and printing can also be performed by printing on the back side of the recording paper P. Printing can be performed on both sides of the paper P.

  The recording paper P printed on the back side is switched by the U-turn unit 45 and the reverse transport unit 61 in the same way as when transported after printing on the front side (during the first transport of the recording paper P). It is conveyed to the back part 66. At this time, the switchback roller pair 67 of the switchback unit 66 continues to rotate normally, and the recording paper P is discharged onto the loading tray 74. When the recording paper P printed on the back side is transported by the U-turn unit 45 and the reverse transport unit 61, the drive rollers 44a, 46a, 48a, 50a, 62a of the transport roller pairs 44, 46, 48, 50, 62 are provided. 62a comes into contact with the front side surface of the recording paper P. At this point, the ink adhering to the front side surface is already completely dried, so the recording paper P is transported at the same speed as the first transporting. There is no problem. However, in order to further improve the print quality, it is possible to make the conveyance speed at the second conveyance slower than at the first conveyance.

  The recording paper resupply unit 88 is capable of holding at least one recording paper P printed before the recording paper P while the printing unit 21 is printing on one recording paper P. It is set to length. As a result, the period from printing on the front side of one recording sheet P to printing on the back side can be used for printing at least one subsequent recording sheet P.

  For example, when performing double-sided printing on the smallest recording paper P among the plurality of sizes, the first to fourth recording paper P is continuously supplied from the cassette 5 to the printing unit 21. The printing unit 21 continuously prints on the front side of the recording paper P. When printing is performed on the fourth recording sheet P, the three recording sheets P that have been printed first are located in any part of the recording sheet resupply unit 88 (usually, The first recording paper P is located in the switchback unit 66, the second recording paper P is located in the reverse conveyance unit 61, and the third recording paper P is located in the U-turn unit 45). When the printing on the fourth recording paper P is completed, the first recording paper P printed on the front side is supplied to the printing unit 21 and the back side of the first recording paper P Printing is performed on the front side, and then printing is continuously performed on the back side of the second to fourth recording sheets P. When printing is performed on the back side surface of the fourth recording sheet P, the first recording sheet P is discharged onto the loading tray 74 by the switchback roller pair 67, and the second and third sheets. The recording paper P is located in the reverse conveyance unit 61 and the U-turn unit 45, respectively.

  When printing on the back side surface of the fourth recording sheet P is completed, the fifth to eighth recording sheets P are continuously supplied from the cassette 5 to the printing unit 21, and are supplied to the printing unit 21. Then, printing is continuously performed on the front side of the recording paper P. In this way, printing is sequentially performed on the front side surface and the back side surface of the recording paper P as a set of four recording papers P. In addition, it is also possible to interpose a set for performing single-sided printing between two sets for performing double-sided printing.

  Therefore, in this embodiment, when performing double-sided printing on only one recording sheet P, the recording sheet P printed on the front side passes through the long conveyance path of the recording sheet refeeding unit 88, and then Since printing is performed on the back side of the recording paper P, the processing time becomes long. However, when double-sided printing is performed on a predetermined number or more of recording paper for business use or the like, at least one sheet is supplied by the recording paper refeeding unit 88. The other recording paper P can be printed while the recording paper P is being conveyed, and the printing processing capability can be improved. In addition, the ink attached to the front side of the recording paper P in the printing unit 21 can be sufficiently dried before printing on the back side, and printing is performed by printing on the back side in this dry state. Both sides of the paper P are not wetted with ink at the same time, and it is possible to reliably prevent the occurrence of show-through due to ink penetration. Further, curling and undulation phenomena are less likely to occur on the recording paper P. Therefore, it is possible to prevent the print quality of the recording paper P from being deteriorated.

  As described above, the changing mechanism 100 functions as a transport roller for transporting the recording paper P, and is re-supplied to the printing unit 21 (the recording paper P that has been printed on the front side). When the sheet enters the platen 23, the characteristic changing process is executed such that the downstream end thereof substantially contacts the surface of the platen 23.

  Specifically, as shown in FIG. 14, the changing mechanism 100 determines the relative positions of the driving roller 44a, the driven roller 44b that sandwiches the recording paper P together with the driving roller 44a, and the driven roller 44b with respect to the driving roller 44a. A position changing roller 183 to be changed and a free roller 180 that is arranged on the upstream side of the drive roller 44a and rotates in conjunction with the movement of the conveyed recording paper P are provided.

  The drive roller 44a includes a roller shaft 181a (see FIG. 17) extending in the width direction of the recording paper P and a plurality of roller portions 181b, 181b,... Arranged at intervals in the axial direction of the roller shaft 181a. It consists of and.

  The driven roller 44b has an outer diameter smaller than that of the driving roller 44a and continuously extends in the width direction of the recording paper P, and is provided around the driving roller 44a so as to be moved substantially along the roller surface. .

  Specifically, the shaft end portion of the driven roller 44b is rotatably attached to the lever portion 184. The lever portion 184 includes a substantially U-shaped attachment portion 184a (see FIG. 14) having a tip portion branched into two toward the downstream side in a side view, and an obliquely extending downward from the lower portion on the upstream side of the attachment portion 184a. And a contact portion 184b. A follower roller 44b is rotatably attached to the substantially U-shaped upper end portion of the attachment portion 184a, and a lever shaft 185 is attached to the lower end portion. The lever portion is centered on the lever shaft 185. By rotating 184, the driven roller 44b is configured to move substantially along the roller surface of the drive roller 44a.

  Further, a biasing spring 186 (see FIG. 14) is attached to the lever portion 184 so as to straddle between the contact portion 184b and the mounting bracket 191 disposed on the upstream side of the free roller 180. The lever portion 184 is urged in the clockwise direction in FIG. 14, and the driven roller 44b is positioned at a pressure release position described later.

  On the upstream side of the lever portion 184, a position changing roller 183 is disposed that rotates while pressing against the abutting portion 184b to rotate the lever portion 184 counterclockwise against the urging force of the urging spring 186. Has been. The position changing roller 183 includes a main body 183a that is rotatable about a rotation axis extending in the width direction, and a roller 183b that is rotatably attached to the upper end of the main body 183a and abuts against the abutment 184b. The main body 183a is rotated around the rotation axis by a pulse motor (not shown).

  Then, while the roller portion 183b of the position change roller 183 is in contact with the contact portion 184b of the lever portion 184, the rotation angle of the position change roller 183 is changed and pressed, so that the driven roller 44b with respect to the drive roller 44a is pressed. The relative position is changed.

  Specifically, as shown in FIG. 14, when the roller portion 183 b of the position changing roller 183 is not brought into contact with the contact portion 184 b of the lever portion 184, the lever portion 184 is most affected by the biasing force of the biasing spring 186. It is positioned at the crimp release position that is the left end position. At this pressure-bonding release position, a predetermined gap H is provided between the driving roller 44a and the driven roller 44b, and the pressure-bonding of the recording paper P is released. The detection piece 187 is attached to the main body 183a of the position change roller 183, and when the detection piece 187 is disengaged leftward from the transmission sensor 188, the driven roller 44b is positioned at the pressure release position. It is said.

  Next, as shown in FIG. 15, the transmission sensor 188 detects while rotating the main body 183a of the position changing roller 183 in the clockwise direction so that the roller 183b contacts the contact 184b of the lever 184. By pressing until the piece 187 is detected, the lever portion 184 is rotated counterclockwise against the urging force of the urging spring 186, so that the recording paper P is not changed in its curvature characteristic (recording paper). The driven roller 44b is positioned at the transport position for transport (without executing the characteristic changing process for P). At this transport position, the driven roller 44b is disposed upstream of the driving roller 44a. In this way, a gap can be provided between the rollers 44a and 44b as compared with the case where the driving roller 44a and the driven roller 44b are arranged in a direction perpendicular to the recording paper conveyance direction. It is possible to reduce the load applied to the recording paper P by weakening the pressing force between 44b.

  The main body 183a of the position change roller 183 is further rotated in the clockwise direction (see FIG. 16), and the roller 183b is moved to the right from the transmission sensor 188 until the detection piece 187 is not detected. By pressing the contact portion 184b, the recording paper P is positioned at the shape characteristic change position where the characteristic change process is executed.

  When the leading end of the recording paper P is detected by the fifth sensor 193 (see FIG. 4) disposed on the upstream side of the changing mechanism 100, the driven roller 44b is positioned at the pressure-release release position. When the recording paper P detected by the sensor 193 is the recording paper P after the double-sided printing is completed, the leading end of the recording paper P passes between the rollers 44a and 44b, and at the same time, the driven roller 44b is conveyed from the pressure release position. On the other hand, when the recording paper P has been printed only on the front side, the leading end of the recording paper P passes between the rollers 44a and 44b, and at the same time, the driven roller 44b is changed from the pressure release position to the shape characteristic change. Switch to position.

  In the state where the driven roller 44b is switched from the pressure release position to the shape characteristic changing position, the driven roller 44b is applied to the recording paper P straddling the driving roller 44a and the free roller 180 as shown in FIG. It is pressed from the front side (printed side) and a bending load is applied to the recording paper P (characteristic changing process is executed). As a result, the recording sheet P after passing through both the transport rollers 44a and 44b is given a curve characteristic in which the middle portion in the length direction protrudes to the back side (unprinted surface side) with respect to both end portions. It becomes. Here, the recording paper P that has been printed on the front side (the recording paper P before passing through both the transport rollers 44a and 44b) is recorded due to the influence of the printing (the influence of the ink adhering to the printing surface). The characteristic change process is applied to the recording paper P after the printing of the front side is finished, because a curved characteristic occurs in which the middle portion in the length direction of the paper P protrudes to the front side (already printed side) with respect to both ends. On the other hand, it can be said that this is a process of imparting (having) a curve characteristic opposite to the curve characteristic in the length direction of the recording paper.

  By executing such a characteristic changing process, it is possible to prevent a printing error at the time of printing on the back side of the recording paper P, and to improve the printing quality of the recording paper P. That is, when this characteristic changing process is not executed, when the recording paper P is turned upside down so as to perform the back side printing, the curving characteristics of the recording paper P (the intermediate portion in the transport direction is relative to both ends). The leading edge (and the trailing edge) of the recording paper is warped and floats up from the platen 23 due to the characteristic of protruding to the printed surface side). There is a problem that adsorption cannot be performed (an adsorption error occurs).

  On the other hand, in the present embodiment, the recording paper P after the printing on the front side surface is given a curved characteristic opposite to the curved characteristic, so that the recording paper P has a reverse side surface. During printing, the leading end portion of the recording paper P can be securely brought into contact with the surface of the platen 23 and can be sucked and held on the surface of the platen 23 by the suction device 36 (a suction mistake can be prevented). Thus, it is possible to reliably prevent printing image rubbing caused by continuing conveyance of the recording paper P while the leading edge of the recording paper P is lifted, and printing errors in which the recording paper leading edge collides with the front side of the printer of the print head H. Can do.

  If the recording paper leading end can be reliably adsorbed on the surface of the platen 23, the recording paper P subsequently enters the platen 23, and the entire recording paper P reaches the rear end. The range can be successively and securely held on the surface of the platen 23. Therefore, the distance between the print head H and the recording paper P can always be kept constant (set distance), and the printing quality of the recording paper P (particularly the printing quality on the back side of the recording paper) can be improved.

  Note that, if the bending characteristic of the reverse direction is too strong, the transportability of the recording paper P deteriorates, the damage of the recording paper P increases, and the product quality deteriorates, or the back side surface printing ends. Since a decurling process (curving removal process) for removing the curvature later becomes necessary and problems such as a further increase in damage to the recording paper P occur, the degree of curvature is so small that such a problem does not occur. Preferably.

  The shape characteristic changing position is set at a plurality of locations (represented by phantom lines in FIG. 16) substantially along the roller surface of the drive roller 44a. In the example shown in FIG. 16, the driven roller 44b indicated by a solid line is provided. As a reference shape characteristic change position, a position where the follower roller 44b is rotated counterclockwise from this position and a strong bending force applied to the recording paper is stronger, and a clockwise direction than the reference shape characteristic change position. A weak position where the bending force is weakened by rotating the driven roller 44b and a weakest position where the driven roller 44b is rotated further in the clockwise direction than the weak position are set. The position changing roller 183 adjusts the strength of the bending force applied to the recording paper P by moving the driven roller 44b between the weakest position and the strong position.

  By doing so, it is possible to apply an appropriate bending force to the recording paper P according to the strength of the bending characteristics of the recording paper when the front side printing is finished.

In other words, the longer the length of the recording paper P is, the easier it is to bend, and the bending characteristics at the end of front side printing become stronger. From this, in this embodiment, it is determined whether the length of the recording paper P belongs to any of the three ranges of preset length / medium / short, and the longer the length of the recording paper P, The position of the driven roller 44b is sequentially changed to the strong position side to increase the bending force applied to the recording paper P. Since the length of the recording paper P corresponds to the size of the recording paper P as described above, the length of the recording paper P may be determined from the input result by the operator's operation switch or the reading result of the stored contents of the IC chip. . As a reference form, the bending force applied to the recording paper P may be adjusted according to the material of the recording paper P. In other words, an appropriate bending force is applied to the recording paper P in order to obtain a target bending characteristic, for example, by setting the bending force to be strong for a stiff and hard recording paper P. Also good.

  Further, the changing mechanism 100 is disposed in the vicinity of the downstream side with respect to the drying device 53 as described above, and the characteristic changing process is performed on the recording paper P immediately after drying by the drying device 53. It has become.

  In this way, it is possible to execute the characteristic changing process on the recording paper P that is easily deformed by being heated by the dry air (warm air). It is possible to change to a target characteristic without fail. Accordingly, it is possible to more reliably prevent an adsorption error during printing on the back side surface of the recording paper P.

(Other embodiments)
The configuration of the present invention is not limited to the above embodiment, but includes various other configurations. That is, in the prior SL embodiment, the tip portion of the recording sheet P front surface printing is completed, the shape characteristic change both the transport roller 44a of the change mechanism 100, at the same time the position of the driven roller 44b passes through the inter-44b from pinch release position However, the present invention is not limited to this. For example, the rear end portion of the recording paper P (the front end portion of the recording paper P after being switched back by the switchback roller pair 67 and when printing on the back side The position of the driven roller 44b may be the transport position until the leading edge of the recording paper P) passes between the transport rollers 44a and 44b, and the position may be switched to the shape characteristic changing position simultaneously with the passage .

  In the embodiment, after the printing on the back side of the recording paper P is completed, the characteristic changing process by the changing mechanism 100 is not performed on the recording paper P (the driven roller 44b is positioned at the transport position). However, the present invention is not limited to this, and by performing the characteristic changing process on the recording paper P after the back side printing is finished, the curvature of the recording paper P along the transport direction is removed (decal processing). May be performed). In this way, even when the recording paper P after the back surface printing has a relatively strong bending characteristic, it can be removed.

  Further, in the embodiment, the change mechanism 100 is disposed on the upstream side with respect to the switchback unit 66 in the recording paper refeeding unit 88, but may be disposed on the downstream side. In other words, it may be disposed anywhere in the recording paper resupply unit 88.

  In the above embodiment, the recording paper resupply unit 88 forms a circular conveyance path that surrounds the print head H together with the print conveyance unit 22, but it is not always necessary to form a circular conveyance path. For example, the recording paper P that has been printed on the front side may be moved forward so as to start the back side printing after being reversed (backed) to the upstream end of the printing unit 21 after being reversed.

  The present invention is useful for an ink jet printer that performs printing on both sides of a recording paper, and is particularly useful when performing double-sided printing using a cut sheet of cut roll paper.

1 is a perspective view illustrating an appearance of an ink jet printer according to an embodiment of the present invention. It is the schematic seen from the side which shows the internal structure of an inkjet printer. It is sectional drawing which shows the detail of the inside of a cassette. It is a side view which shows the detail of a printing part and a U-turn part. It is a top view which shows the detail of a printing part. FIG. 6 is a schematic diagram illustrating a state in which a switchback roller pair of a switchback unit receives a recording sheet conveyed from a reverse conveyance unit. FIG. 7 is a view corresponding to FIG. 6 showing a state in which the driven rollers of the switchback roller pair are switched to the second position. FIG. 7 is a view corresponding to FIG. 6 illustrating a state in which the switchback roller pair switches back the recording paper to the supply roller pair. FIG. 7 is a view corresponding to FIG. 6 showing a state in which the recording paper is manually inserted from the manual insertion opening. It is a perspective view which shows the detail of a switchback part. It is a C direction arrow figure of FIG. FIG. 12 is a view corresponding to FIG. 11 showing a state where the switchback roller pair and the driven roller of the supply roller pair are in a pressure release state. FIG. 3 is a view corresponding to FIG. 2 showing a state in which the duplex printing unit is removed from the printer body. It is a side view when the driven roller of the change mechanism is positioned at the pressure release position. It is a side view when the driven roller of the changing mechanism is positioned at the transport position. It is a side view when the driven roller of the changing mechanism is positioned at the shape characteristic changing position. It is the front view which looked at the change mechanism from the downstream.

A Inkjet printer H Print head P Recording paper 14 Feeding roller (recording paper supply unit)
21 Printing unit 23 Platen 23b Suction hole 36 Suction device (suction means)
45 U-turn section (recording paper refeed section)
53 Drying equipment (drying section)
61 Reverse transport unit (recording paper resupply unit)
66 Switchback unit (recording paper resupply unit)
88 Recording Paper Refeed Unit 100 Changing Mechanism

Claims (2)

A printing unit that discharges ink from the print head to perform printing on one side of the recording paper, a recording paper supply unit that supplies the recording paper to the printing unit, and a printing unit that faces the print head. And a platen that supports the recording paper supplied from the recording paper supply unit and has a suction hole for sucking the recording paper, and the recording paper provided in the printing unit and supplied from the recording paper supply unit Is sucked through the suction hole to be sucked and held on the platen, and is supplied to the printing unit, and the recording paper is supplied to the platen while being sucked by the platen at the time of printing. A printing conveyance unit that conveys the recording sheet to the opposite side of the printing unit, and a recording sheet refeeding unit that reverses the recording sheet printed on one side of the printing unit and re-supplies the printing sheet to the printing unit, In the printing section, from the recording paper resupply section By printing on the other side of the supplied recording sheet, an ink jet printer for printing on both sides of the recording paper,
Wherein provided in the recording paper resupply unit, the printing unit again supplied by the one-side printing after the end of the recording sheet whose conveyance direction bending characteristics to change the characteristics change processing along with to the plane of the Further comprising a change mechanism to perform,
The changing mechanism is configured to perform the characteristic changing process so that a leading end portion of the recording paper re-supplied to the printing unit approaches the platen surface when the recording paper enters the platen .
The curve characteristic of the recording paper after the printing on the one side surface along the conveyance direction is such that the intermediate portion in the conveyance direction of the recording paper is on the printed surface side with respect to both ends. A prominent characteristic,
The characteristic changing process is a process of imparting a bending characteristic opposite to the bending characteristic along the transport direction of the recording paper after the printing on the one side surface is completed,
Further, the changing mechanism applies a stronger bending force to the recording paper as the length of the recording paper after the printing on the one side is finished, so that the conveying direction of the recording paper is increased. An ink jet printer configured to impart a curve characteristic opposite to the curve characteristic along the line . The inkjet printer according to claim 1 , wherein
A drying unit is provided on the downstream side in the transport direction from the printing unit to perform a drying process by blowing warm air on the printing surface of the recording paper on which printing has been performed in the printing unit,
The changing mechanism is disposed downstream of the drying unit in the transport direction, and is configured to execute the characteristic changing process on a recording sheet immediately after the drying process is performed in the drying unit. An ink jet printer characterized by being made.

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