JP2015093756A - Printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid an enlargement of a head unit due to mounting of star wheels thereto, and further to maintain a constant positional relation of the star wheels with respect to a platen.SOLUTION: A printer 1 comprises a platen upper unit 20 fixed to an upper portion of a platen unit 8. The platen upper unit 20 comprises first star wheels 25A and second star wheels 25B which are separated from the platen unit 8 and are mounted to horizontal frame portions 22a through 22e extending parallel to a direction perpendicular to a sheet transportation direction in an upper portion of a platen surface 8a. Hereby, lifting of a continuous sheet P transported along the platen surface 8a is suppressed. When a head unit 7 is moved to a printing execution position 7A, head leading end portions 76 formed with ink nozzle surfaces 77a through 77d are positioned in spaces surrounded by the horizontal frame portions 22a through 22e and the first star wheels 25A, and the head leading end portions 76 can enter the spaces.

Description

  The present invention relates to a support structure for a star wheel that prevents a sheet-like medium from floating from a platen surface.

  Some inkjet printers use a star wheel in which protrusions are formed on the outer peripheral edge at a constant pitch in order to prevent the sheet-like medium conveyed along the platen surface from floating from the platen surface. Patent Documents 1 and 2 disclose this type of printer. The printer (inkjet recording apparatus) of Patent Document 1 includes a spur (star wheel) mounted on a head unit on which a head group is mounted, and the spur (star wheel) regulates the medium from being lifted from the conveyor belt. . Moreover, the printer of patent document 2 mounts a spur (star wheel) in the housing of the head unit. The medium is transported along a support member (platen) that faces the head unit. The roller surface of the driving roller is exposed on the surface of the support member, and the spur (star wheel) is disposed to face the driving roller. The medium is conveyed while being pressed against the driving roller by a spur (star wheel).

Japanese Patent No. 4274180 JP 2009-262544 A

  Here, in a line head type printer that has a large print head that exceeds the width of the recording paper and prints the print head while stopped on the recording paper, the head unit with the print head mounted on the carriage is originally large. is there. If a star wheel is further mounted on a large head unit, the head unit is further increased in size, and the structure of the carriage that supports the print head becomes complicated. In addition, an increase in the size of the head unit necessitates an increase in the output of a carriage motor that drives the carriage, which increases the cost. In addition, when a star wheel is mounted on the head unit, the star wheel moves together when the head unit is withdrawn from the platen. For this reason, there is a possibility that the position of the star wheel cannot always be kept constant.

  SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a printer that can avoid the adverse effects associated with an increase in the size of a head unit due to a star wheel that regulates the lifting of a medium, and can maintain a constant positional relationship of the star wheel with respect to the platen. Is to propose.

  In order to solve the above-described problems, a printer of the present invention includes a platen unit including a platen surface that supports a sheet-like medium, and a print head that prints on the medium, and the print head is mounted on the platen surface. A print execution position opposite to the print execution position, a head unit that can move to the retreat position in which the print head is retreated from the print execution position, and a print unit that is disposed so as to overlap the platen surface and separated from the platen unit. The platen upper unit is equipped with a star wheel.

  In this way, the printer of the present invention is mounted on the platen upper unit separated from the platen unit, so that the star wheel that regulates the lifting of the medium from the platen surface is not mounted on the head unit, but is placed on the platen surface. doing. Thus, by separating the star wheel from the head unit, it is possible to avoid a decrease in the positional accuracy of the star wheel with respect to the platen surface due to the operation of moving the head unit between the print execution position and the retracted position. In addition, since it is possible to avoid an increase in the size of the head unit due to the star wheel and its support member, it is possible to avoid the complexity of the support structure of the head unit, and it is possible to avoid an increase in cost due to a higher output of the carriage motor that drives the head unit.

  In the present invention, the platen upper unit includes a plurality of support frames that support the star wheel, and when the head unit is positioned at the print execution position, the ink nozzle surface of the print head is supported by the plurality of support frames. It is desirable that the gap surrounded by the frame and the star wheel is positioned at a position overlapping in a direction perpendicular to the platen surface. As described above, by providing a plurality of support frames, the star wheel can be disposed over the entire platen surface, and the lift of the medium can be suppressed over the entire platen surface. Further, the ink discharge to the medium is not hindered by the star wheel and its support frame.

  Further, in the present invention, the head unit includes a print head lifting mechanism that moves the print head closer to and away from the platen surface, and the print head includes a head tip portion on which the ink nozzle surface is formed, When the print head elevating mechanism lowers the print head to a platen gap holding position where the print head and the platen surface maintain a predetermined gap, a gap surrounded by the plurality of support frames and the star wheel is formed. It is desirable that the head tip portion enters. In this way, the platen gap can be adjusted without causing the platen upper unit and the head unit to interfere with each other. Further, when the head unit is moved to the retracted position, the head unit can be raised to avoid interference with the platen upper unit.

  In this case, it is desirable that the star wheels are attached to the plurality of support frames at positions that do not overlap when viewed in the medium transport direction. If it does in this way, when a medium is conveyed, it can avoid that the same position on a medium is continuously pressed by a plurality of starwheels. Therefore, it is possible to avoid a star wheel mark on the medium.

  Here, in the present invention, a protrusion is formed on the outer peripheral edge of the star wheel, and the platen upper unit has a wheel cleaner that contacts the tip when the tip of the protrusion on the star wheel is separated from the medium. Is desirable. In this way, it is possible to remove the stain on the star wheel due to ink or the like adhering to the medium immediately after printing. Accordingly, it is possible to avoid contamination of the medium due to ink or the like adhering to the star wheel.

  In the present invention, the wheel cleaner is a rotating body having a cylindrical outer peripheral surface, and the rotating body is disposed so that the outer peripheral surface is in contact with a tip of the protrusion, and the rotation of the star wheel is performed. It is desirable to be supported so as to be driven and rotated. If it does in this way, it can control that rotation of a star wheel is prevented by cleaning. Further, the outer peripheral surface of the rotating body can be used as a cleaning surface over the entire periphery.

  In this case, the platen upper unit is provided with a biasing member that biases the star wheel toward the platen surface, and the rotating body moves the star wheel in a biasing direction by the biasing member. When it does, it is desirable to be supported so that it may move following the movement of the star wheel. If it does in this way, the state which pressed down the medium with the star wheel can be maintained. Further, it is possible to maintain a state in which the wheel cleaner (rotating body) is always in contact with the tip of the star wheel protrusion.

  In the present invention, it is desirable that the platen upper unit is fixed to a printer main body frame. In this way, the platen upper unit can be held at a fixed position.

  According to the present invention, since the star wheel that regulates the lifting of the medium from the platen surface is mounted not on the head unit but on the platen upper unit, the head unit is moved between the print execution position and the retracted position. It is possible to avoid a decrease in the positional accuracy of the star wheel with respect to the platen surface. In addition, since it is possible to avoid an increase in the size of the head unit due to the star wheel and its support member, it is possible to avoid the complexity of the support structure of the head unit, and it is possible to avoid an increase in cost due to a higher output of the carriage motor that drives the head unit.

1 is an external perspective view of a line inkjet printer according to an embodiment of the present invention. It is a schematic longitudinal cross-sectional view which shows the internal mechanism of the line inkjet printer of FIG. It is explanatory drawing which shows a medium conveyance mechanism typically. It is a perspective view of a platen unit. It is a perspective view of the platen unit which removed the conveyance belt. It is explanatory drawing of the platen unit which removed the conveyance belt. It is a perspective view which shows the state which has arrange | positioned the platen upper unit on the platen unit. It is explanatory drawing of the state which has arrange | positioned the platen upper unit on the platen unit. It is explanatory drawing of an upper unit main-body part. It is a perspective view of a head unit. It is the bottom view which looked at the head unit from the platen unit side. It is operation | movement explanatory drawing of a head unit. It is sectional drawing which cut | disconnected the upper unit main-body part in the printer width direction. It is explanatory drawing of the attachment structure of a 2nd star wheel. It is explanatory drawing of the attachment structure of a 1st star wheel.

  Embodiments of a printer to which the present invention is applied will be described below with reference to the drawings. In the following embodiments, the present invention is applied to a printer that loads and prints roll paper, but is also applicable to a printer that prints on other forms of media.

(overall structure)
FIG. 1 is an external perspective view of a line inkjet printer according to an embodiment of the present invention, and FIG. 2 is a schematic longitudinal sectional view showing an internal mechanism thereof. As shown in FIG. 1, a line inkjet printer 1 (hereinafter simply referred to as “printer 1”) includes a printer housing 2 having a rectangular parallelepiped shape as a whole. On the front surface 2a of the printer housing 2, an operation unit 3 is provided on one side in the width direction, and a paper discharge port 4 is formed on the other side. A maintenance opening / closing lid 5 is provided below the paper discharge port 4. Hereinafter, in the present specification, the front-rear direction of the printer is indicated by X, and the width direction of the printer is indicated by Y. Further, the front of the printer is denoted by reference numeral X1, and the rear of the printer is denoted by reference numeral X2.

  As shown in FIG. 2, a roll paper storage unit 6 is formed inside the printer housing 2 on the printer rear X2 side. In addition, a head unit 7 is disposed on the upper portion of the printer front X1 side, and a platen unit 8 is disposed on the lower side thereof. The head unit 7 includes a print head 71 that is a line-type inkjet head. The print head 71 is formed with an ink nozzle row that ejects ink droplets. The ink nozzle row is formed over a length including the maximum width of the continuous paper P fed from the roll paper 9 loaded in the roll paper storage unit 6. Further, the platen unit 8 includes a horizontal platen surface 8 a facing the nozzle surface of the print head 71. The platen surface 8a is constituted by a horizontal belt portion 81a of a conveyance belt 81 described later.

  Inside the printer housing 2, the continuous paper P drawn from the roll paper 9 of the roll paper storage unit 6 passes through the print position by the print head 71 along the medium conveyance path 10 indicated by the one-dot chain line, and the printer The paper is conveyed toward the paper discharge port 4 that opens in the front surface 2 a of the housing 2, and is discharged from the paper discharge port 4. The medium conveyance path 10 is gently lowered until the first path portion 10a extending obliquely upward toward the printer rear X2 side and the direction from the upper end of the first path portion 10a to the printer front X1 and reaching the platen surface 8a. And a third path portion 10c extending horizontally from the end of the platen surface 8a on the printer rear X2 side toward the printer front X1 side. The printing position by the print head 71 is provided in the middle of the third path portion 10c.

  A medium supply roller 11 is disposed at the bottom of the roll paper storage unit 6. The medium supply roller 11 is always held in contact with the roll paper 9 attached to the roll paper storage unit 6 from below. The medium supply roller 11 is driven to rotate by a supply motor (not shown), thereby feeding the continuous paper P from the roll paper 9 to the first path portion 10a. The continuous paper P can be fed out by attaching the roll paper 9 to the rotary shaft and rotationally driving the rotary shaft by a supply motor.

  A tension lever 12 that applies a back tension to the continuous paper P is disposed at a position where the direction of the medium path 10 is changed from the first path portion 10a to the second path portion 10b. An arc-shaped outer peripheral surface is formed at the tip of the tension lever 12, and the continuous paper P is stretched over this. The tension lever 12 is attached so as to be rotatable around a predetermined rotation center 13. A spring member (not shown) is attached to the tension lever 12 at a position away from the rotation center 13. The spring member is supported by the printer housing frame, and urges the tension lever 12 toward the printer rear X2. That is, the tension lever 12 is urged in a direction to increase the tension of the continuous paper P. A slide type tension lever can be used instead of the rotary type tension lever 12.

  A rotary encoder 14 is disposed at the rotation center 13 of the tension lever 12. The rotary encoder 14 can detect the rotation position of the tension lever 12 steplessly or in multiple steps. For example, an optical sensor such as an optical potentiometer or various sensors such as a magnetic sensor is used. Can do. By detecting the rotational position of the tension lever 12 by the rotary encoder 14, the tension fluctuation of the continuous paper P can be monitored and the conveyance control can be performed so as to keep the tension at an appropriate value.

  A paper guide 15 is arranged along the second path portion 10b on the printer front X1 side of the tension lever 12. The paper guide 15 has a shape that gently descends toward the front X1 of the printer, and guides the continuous paper P from the tension lever 12 toward the platen surface 8a.

  A belt-type medium transport mechanism 16 is provided in the medium transport path 10 along the third path portion 10c. FIG. 3 is an explanatory diagram schematically showing the medium transport mechanism 16. The medium transport mechanism 16 drives the transport belt 81, which is an endless belt disposed below the third path portion 10c, a plurality of guide rollers 82a to 82e around which the transport belt 81 is bridged, and the transport belt 81. A belt driving roller 82f that rotates, and a conveyance motor (not shown) that rotates the belt driving roller 82f. The conveyor belt 81 is pressed against the belt driving roller 82f by a guide roller 82a. By rotating the belt driving roller 82f, the conveyance belt 81 moves along a route passing through the guide rollers 82a to 82e. An encoder (not shown) for detecting the rotation amount is attached to the rotation shaft of the belt driving roller 82f.

  In the conveyor belt 81, a portion that is stretched between the guide rollers 82b and 82c is a horizontal belt portion 81a that extends horizontally along the third path portion 10c. Pinch rollers 17a and 17b are pressed from the same side as the head unit 7 to the upstream end and the downstream end of the horizontal belt portion 81a in the transport direction (that is, the front-rear direction X of the printer). The medium transport mechanism 16 transports the continuous paper P sandwiched between the pinch rollers 17a and 17b and the horizontal belt portion 81a.

  The platen unit 8 is equipped with a paper detector 18 that detects the continuous paper P conveyed along the platen surface 8a. The detection position by the paper detector 18 is provided upstream of the printing position by the print head 71 (that is, the printer rear X2 side) in the third path portion 10c. As shown in FIG. 2, the continuous paper P is drawn from the roll paper 9 loaded in the roll paper storage unit 6 along the first path portion 10 a of the medium transport path 10, and is stretched around the tension lever 12. The tip is set to extend along the second path portion 10b. In this state, a supply operation by the medium supply roller 11 is performed, and further, a transport operation by the medium transport mechanism 16 is performed, and a cueing operation is performed in which the top of the continuous paper P reaches the print position by the print head 71. Thereafter, the medium transport mechanism 16 performs a transport operation of continuously transporting at a constant speed in the forward feed direction from the printing position toward the paper discharge port 4. The print head 71 is driven in synchronism with this conveying operation to print on the surface of the continuous paper P passing through the printing position.

(Platen unit)
4 is a perspective view of the platen unit 8, and FIG. 5 is a perspective view of the platen unit 8 with the conveyor belt 81 removed. FIG. 6 is an explanatory view of the platen unit 8 with the conveyor belt removed. FIG. 6 (a) is a plan view, and FIGS. 6 (b) and 6 (c) are viewed from one side and the other side in the printer width direction Y. FIG. 6D is a side view of the printer as viewed from the front side of the printer. As shown in FIG. 4, in the platen unit 8, horizontal belt portions 81 a of four transport belts 81 are stretched in the front-rear direction X of the printer on the upper surface facing the head unit 7. The horizontal belt portion 81a spans between a guide roller 82b disposed at the end of the platen unit 8 on the printer front X1 side and a guide roller 82c disposed near the end of the platen unit 8 on the printer rear X2 side. This is a portion of the conveyed belt 81. Further, a guide roller 82d is disposed further to the back X2 side of the printer than the guide roller 82c. The conveyance belt 81 is stretched between the guide rollers 82c and 82d so as to be inclined from the upstream end of the horizontal belt portion 81a toward the printer lower side.

  The platen unit 8 includes a unit main body 83 that is configured by a sheet metal member or the like. The unit main body 83 includes side frames 83 a and 83 b that constitute one side surface and the other side surface of the platen unit 8 in the printer width direction Y. The side frames 83a and 83b support both ends of guide rollers 82a to 82e around which the conveyor belt 81 is stretched and a belt driving roller 82f (see FIG. 3) that drives the conveyor belt 81. In addition, a transport motor is mounted inside the unit main body 83.

  A first side plate 84a and a second side plate 84b are attached in parallel to the upper end edges of the side frames 83a and 83. The first side plate 84a and the second side plate 84b are rectangular sheet metal members that extend horizontally in the longitudinal direction X of the printer. The first side plate 84a is screwed to the side frame 83a by fixing screws 88 at two positions on both ends in the longitudinal direction (that is, the front-rear direction X of the printer). On the other hand, the second side plate 84b is attached so as to swing around a support shaft 83c provided in the unit main body 83, and is positioned in a posture parallel to the first side plate 84a. The screw is fixed to the side frame 83b by a fixing screw 88 at a location.

  As shown in FIGS. 5 and 6, the first side plate 84 a and the second side plate 84 b support both ends of five support rollers 85 a to 85 e that extend parallel to the printer width direction Y. Each of the five support rollers 85a to 85e and the guide rollers 82b, 82c, and 82d includes a roller body 86b that supports the conveyance belt 81 and a support shaft 86a to which the roller body 86b is rotatably attached. . On the upper surface of the platen unit 8, four rows in which a plurality of roller bodies 86b are arranged in a row in the longitudinal direction X of the printer are formed, and a horizontal belt portion 81a is stretched over each row. On the upper surface of the platen unit 8, a holder 87 is disposed in a gap where the support shaft 86a and the roller body 86b are not disposed.

  Among the four horizontal belt portions 81a, a gap is provided between the horizontal belt portion 81a disposed closest to the first side plate 84a and the adjacent horizontal belt portion 81a. The detection portion of the paper detector 18 described above is exposed at a position near X2. As the paper detector 18, an optical sensor or the like can be used. The paper detector 18 detects the continuous paper P from the gap between the horizontal belt portions 81a.

(Formation of platen gap)
Here, three spheres 19 (see FIGS. 7 and 8) are disposed between the platen unit 8 and the head unit 7. The platen unit 8 comes into contact with the spherical body 19 from the lower side and the head unit 7 comes into contact from the upper side, so that the gap (platen gap) between the nozzle surface of the print head 71 and the platen surface 8a is maintained at a constant size. ing. On the platen unit 8 side, the contact portion with the sphere 19 is formed on the first side plate 84a and the second side plate 84b. That is, as shown in FIGS. 4 to 6, platen side abutting portions 89 a and 89 b are formed on the upper end edge of the first side plate 84 a at two locations on both ends in the longitudinal direction. The platen side abutting portions 89a and 89b are horizontal plates that are bent substantially perpendicularly from the upper end edge of the first side plate 84a and extend toward the center in the width direction of the platen surface 8a. In addition, a platen side contact portion 89c is formed at one central position in the longitudinal direction of the upper end edge of the second side plate 84b. The platen side abutting portion 89c is a horizontal plate that is bent at a substantially right angle from the upper end edge of the second side plate 84b and extends outward in the width direction of the platen surface 8a. The three spheres 19 come into contact with the platen side contact portions 89a, 89b, 89c one by one from the upper side.

  FIG. 7 is a perspective view showing a state in which the platen upper unit is disposed on the platen unit 8. 8 is an explanatory view showing a state in which the platen upper unit is disposed on the platen unit 8. FIG. 8A is a plan view, and FIGS. 8B and 8C are one side in the printer width direction Y. The side view seen from the other side, FIG.8 (d) is ZZ sectional drawing (sectional drawing of a spherical body holding | maintenance part) of Fig.8 (a). FIG. 9 is an explanatory view of the upper unit main body portion in the platen upper unit, FIG. 9A is a perspective view, and FIG. 9B is a bottom view as seen from the platen unit 8 side. As shown in FIG. 2, a platen upper unit 20 is disposed between the platen unit 8 and the head unit 7. The spherical body 19 is held by the platen upper unit 20.

  As shown in FIGS. 7 to 9, the platen upper unit 20 has a substantially rectangular planar shape as a whole. The platen upper unit 20 includes a thin upper unit main body 20A that overlaps the upper surface of the platen unit 8, and a fixed frame 20B attached to the end of the upper unit main body 20A on the printer rear X2 side. The platen upper unit 20 is fixed to an apparatus main body frame (printer main body frame) of the printer 1 via a fixed frame 20B.

  The upper unit main body 20A includes a pair of vertical frame portions 21a and 21b extending in parallel with the front-rear direction X of the printer along the side frames 83a and 83b of the platen unit 8, and five support rollers 85a provided on the platen unit 8. 5 horizontal frame parts 22a-22e (support frame) arranged so that it may overlap with -85e. The horizontal frame portions 22a to 22e extend in parallel to the printer width direction Y that intersects the conveyance direction of the continuous paper P, and both ends thereof are connected to the vertical frame portions 21a and 21b. As shown in FIG. 9, the end portions of the vertical frame portions 21a and 21b on the printer rear X2 side protrude further to the printer rear X2 side than the horizontal frame portion 22e positioned closest to the printer rear X2 side, and are fixed here. A frame 20B is attached.

  In the upper unit main body 20A, three sphere holding portions 23a to 23c for holding the three spheres 19 are formed. The spherical body holding portions 23a to 23c are formed at positions overlapping the above-described platen side contact portions 89a to 89c, and the spherical body holding portions 23a and 23b are formed at two locations along the vertical frame portion 21a. A spherical body holding portion 23c is formed at one place on 21b. As shown in FIG. 8D, the sphere holding part 23a is attached so as to rotatably support the penetrating part 24a penetrating the vertical frame part 21b in the vertical direction of the printer and the sphere 19 arranged in the penetrating part 24a. And a support member 24b made of wire. The structures of the sphere holding portions 23b and 23c are the same as this.

  FIG. 10 is a perspective view of the head unit, and FIG. 11 is a bottom view of the head unit 7 viewed from the platen unit 8 side. As shown in FIGS. 2 and 10, the head unit 7 includes a print head 71, an inner carriage 72 on which the print head 71 is mounted, and an outer carriage 73 that holds the inner carriage 72 in a state in which the inner carriage 72 can be moved in the vertical direction of the printer. I have. Two carriage shafts 74 a and 74 b extending in the printer width direction Y are arranged on the printer unit X1 side and the printer rear X2 side of the head unit 7. The outer carriage 73 is slidably mounted on the two carriage shafts 74a and 74b.

  As shown in FIG. 2, a pressing mechanism 79 </ b> A that presses and lowers the inner carriage 72 toward the platen surface 8 a is provided at the top of the head unit 7. The pressing mechanism 79A is driven by a pressing motor (not shown). In FIG. 10, the pressing mechanism 79A is not shown. On the other hand, as shown in FIG. 10, four coil springs 79B are provided between the outer carriage 73 and the inner carriage 72 to urge the inner carriage 72 upward (in a direction away from the platen surface 8a). When the pressing state by the pressing mechanism 79A is released, the inner carriage 72 is pulled upward by the biasing force of the coil spring 79B. That is, the press mechanism 79A and the coil spring 79B constitute a print head lifting mechanism 79 that moves the print head 71 closer to and away from the platen surface 8a.

  12A and 12B are diagrams for explaining the operation of the head unit 7. FIG. 12A shows a state in which the head unit 7 is at the retracted position 7B, and FIGS. 12B and 12C show a state in which the head unit 7 is at the print execution position 7A. Is shown. The head unit 7 is configured to be movable between a print execution position 7A where the print head 71 is opposed to the platen surface 8a and a retreat position 7B where the print head 71 is retreated from above the platen unit 8. In this embodiment, since the platen upper unit 20 is disposed on the platen unit 8, the movement between the print execution position 7A and the retreat position 7B is performed as shown in FIG. This is performed in a state where the inner carriage 72 and the print head 71 are raised to a position where they do not interfere with the unit 20. Further, when printing is performed by ejecting ink from the print head 71, as shown in FIG. 12C, the inner carriage 72 and the print head 71 are lowered and the inner carriage 72 is moved to the sphere 19 held by the platen upper unit 20. The test is performed in a state in which 72 is in contact.

  The outer carriage 73 is movable along the carriage shafts 74a and 74b by a driving force of a carriage motor (not shown), and a first position 73A (see FIGS. 12B and 12C) facing the platen unit 8 and the platen. It moves between the second position 73B (see FIG. 12A) withdrawn from the unit 8 above. Further, the inner carriage 72 on which the print head 71 is mounted moves the sphere 19 to the platen side contact portions 89a and 89b by moving in the vertical direction of the printer with respect to the outer carriage 73 when the outer carriage 73 is at the first position 73A. , 89c pressed against the platen gap holding position 72A (see FIG. 12C), and the raised position 72B where the print head 71 and the inner carriage 72 do not interfere with the upper unit main body 20A (see FIGS. 12A and 12B). It is possible to move between.

  As shown in FIG. 11, the print head 71 includes four heads: a first head 71a, a second head 71b, a third head 71c, and a fourth head 71d. Each head is formed with an ink nozzle that ejects one of four colors of CMYK ink. Head-side contact portions 75a, 75b, and 75c are formed on the lower end surface of the inner carriage 72 on which the print head 71 (the first head 71a to the fourth head 71d) is mounted. The head side contact portions 75a, 75b, and 75c are moved in the upper unit main body 20A when the outer carriage 73 moves to the first position 73A facing the platen unit 8 and the head unit 7 moves to the print execution position 7A. It is formed in three places which overlap with the spherical body holding parts 23a-23c.

  As shown in FIG. 12C, when the head unit 7 is positioned at the print execution position 7A and the inner carriage 72 is lowered to the platen gap holding position 72A by the pressing mechanism 79A of the print head lifting mechanism 79, three positions are obtained. The head side abutting portions 75a, 75b, and 75c abut against the three spheres 19 held by the upper unit main body portion 20A from above, and press these spheres 19 against the platen side abutting portions 89a, 89b, and 89c. As a result, the distance (platen gap) between the nozzle surface (ink nozzle surfaces 77 a to 77 d described later) of the print head 71 and the platen surface 8 a is maintained at a predetermined dimension according to the diameter of the sphere 19. As will be described later, the head unit 7 and the platen upper unit 20 can lower the inner carriage 72 and the print head 71 mounted thereon to the platen gap holding position 72A without interfering with each other. Yes.

(Star wheel)
In addition to the sphere 19, the upper unit main body 20 </ b> A of the platen upper unit 20 is mounted with a star wheel that regulates the floating of the continuous paper P from the platen surface 8 a. As shown in FIG. 9, the upper unit main body 20A has a first star wheel 25A attached as a star wheel so as to protrude from the horizontal frame portions 22a to 22e toward the printer front X1 side or the printer rear X2 side, Two types of second star wheels 25B are mounted so as to protrude from the horizontal frame portions 22a to 22e directly below.

  The first star wheel 25A includes four horizontal belt portions in each of the three horizontal frame portions 22b to 22d except for two at both ends of the five horizontal frame portions 22a to 22e in the upper unit main body portion 20A. It is attached to four places which overlap with 81a. The four first star wheels 25A are attached in two postures, a posture protruding toward the printer front X1 side and a posture protruding toward the printer rear X2 side, and the first star wheel 25A attached in these two postures. The star wheels 25A are alternately arranged in the printer width direction Y. On the other hand, first star wheels 25A are respectively attached to the two horizontal frame portions 22a and 22e at both ends. That is, the first star wheel 25A in a posture protruding toward the printer rear X2 side is attached to the horizontal frame portion 22a positioned closest to the printer front X1 side at two locations. Also, the first star wheel 25A in a posture protruding toward the printer front X1 side is attached to the horizontal frame portion 22e positioned closest to the printer rear X2 side at two locations.

  On the other hand, five second star wheels 25B are attached to each of the five horizontal frame portions 22a to 22e in the upper unit main body portion 20A. That is, in each of the three horizontal frame portions 22b to 22d, one second star wheel 25B is attached at one location adjacent to the first star wheel 25A closest to the vertical frame portion 21b, and the remaining three first star wheels are attached. Two second star wheels 25B are attached between the wheels 25A. Also, five second star wheels 25B are attached to the two horizontal frame portions 22a and 22e at both ends, respectively.

  In the upper unit main body 20A, a large number of first star wheels 25A and second star wheels 25B are mounted in a range overlapping with the platen surface 8a as described above. These first star wheels 25A and second star wheels 25B are mounted. As a result, the floating of the entire platen surface 8a is restricted. The attachment positions of the first star wheels 25A in the horizontal frame portions 22a to 22e are set so as not to overlap when viewed in the front-rear direction X of the printer (conveying direction of the continuous paper P). That is, in FIG. 9B, the first star wheels 25A at first glance appear to be arranged in four rows in a straight line at regular intervals in the front-rear direction X of the printer. Slightly shifted in direction Y. Similarly, the mounting positions of the second star wheels 25B in the horizontal frame portions 22a to 22e are set so as not to overlap when viewed in the front-rear direction X of the printer (conveying direction of the continuous paper P). That is, in FIG. 9B, the first star wheels 25A at first glance appear to be linearly arranged in five rows at regular intervals in the longitudinal direction X of the printer. Slightly shifted in direction Y. If it does in this way, when the continuous paper P is conveyed, it can avoid that the same position on the continuous paper P is continuously pressed by the some 1st star wheel 25A and the 2nd star wheel 25B. Therefore, it is possible to avoid the marks of the first star wheel 25A and the second star wheel 25B on the continuous paper P.

(Star wheel mounting structure)
FIG. 13 is a cross-sectional view (Z1-Z1 cross-sectional view in FIG. 9A) of the upper unit main body 20A cut in the printer width direction Y. FIG. 14 is an explanatory view of the mounting structure of the second star wheel 25B. FIG. 14A is a cross-sectional view cut in the printer width direction Y (partially enlarged view of region B in FIG. 13), FIG. ) Is a cross-sectional view (Z2-Z2 cross-sectional view of FIG. 9A) cut in the front-rear direction X of the printer. FIG. 15 is an explanatory view of the mounting structure of the first star wheel 25A. FIG. 15A is a cross-sectional view cut in the printer width direction Y (partial enlarged view of region A in FIG. 13), FIG. ) Is a cross-sectional view (Z3-Z3 cross-sectional view of FIG. 9A) cut in the longitudinal direction X of the printer.

  As shown in FIGS. 9A and 13, in the horizontal frame portion 22b, first attachment portions 26 are formed at four locations, which are attachment positions of the first star wheel 25A. The first attachment portion 26 is a recess that opens to the side from which the first star wheel 25A protrudes. Moreover, the 2nd attaching part 27 is formed in the horizontal frame part 22b at five places which are the attachment positions of the 2nd star wheel 25B. The second attachment portion 27 is a through-hole having a substantially rectangular cross section that penetrates the horizontal frame portion 22b in the vertical direction of the printer (that is, the direction perpendicular to the platen surface 8a). In the other horizontal frame portions 22a and c to 22e, the first mounting portion 26 and the second mounting portion 27 are similarly formed at the mounting positions of the first star wheel 25A and the second star wheel 25B.

  Here, with reference to Fig.9 (a), FIG.13, FIG.14 etc., the attachment structure to the 2nd attachment part 27 of the 2nd star wheel 25B is demonstrated. One end (lower end) of the second mounting portion 27 is opened facing the platen surface 8a, and the second star wheel 25B is disposed so that a part of the second mounting portion 27 protrudes toward the platen surface 8a. The second star wheel 25 </ b> B includes a circular main body portion 41 having a predetermined thickness and a thin plate portion 42 that protrudes radially outward from the outer peripheral surface of the main body portion 41. As shown in FIG. 14B, protrusions 43 are formed on the outer peripheral edge of the thin plate portion 42 at regular angular intervals in the circumferential direction. The tip 43a of the protrusion 43 has a pointed shape, and protrudes radially outward in the radial direction at the outer peripheral edge of the second star wheel 25B. As shown in FIG. 9A, groove-shaped notches extending upward from the opening edge on the lower side (platen surface 8a side) of the second attachment portion 27 are provided on both sides of the horizontal frame portion 22b in the front-rear direction X of the printer. A portion 27a is formed. The second star wheel 25B is attached in a state in which the outer peripheral edge is inserted into the notch 27a.

  As shown in FIG. 14A, the second star wheel 25B is formed with a center hole 41a that penetrates the center of the main body 41 in the printer width direction Y in the printer width direction Y. The center hole 41a extends in the printer width direction Y. An extending coil spring 44 is mounted. Both ends of the coil spring 44 are engaged with an opening edge on the side facing the platen surface 8 a of the second mounting portion 27, and the second star wheel 25 </ b> B is supported by the coil spring 44. The second star wheel 25B is urged toward the platen surface 8a by the urging force of a torsion spring 45 (urging member) attached to the coil spring. For this reason, the state where the tip 43a of the protrusion 43 of the second star wheel 25B is in elastic contact with the continuous paper P on the platen surface 8a is maintained.

  In the second mounting portion 27, a wheel cleaner 50B is disposed above the second star wheel 25B (the side opposite to the platen surface 8a). The wheel cleaner 50 </ b> B includes a rotation shaft 51 extending in the printer width direction Y, a cylindrical support body 52 that is coaxially attached to the rotation shaft 51, and a recess formed in the axial center portion of the outer peripheral surface of the support body 52. A cleaning member 53 having a predetermined thickness attached to the entire circumference of 52a is provided. As the cleaning member 53, an elastic material such as foamed resin is used. The rotating shaft 51, the support body 52, and the cleaning member 53 are integrally assembled, and the wheel cleaner 50B constitutes a rotating body that rotates integrally around the rotating shaft 51.

  A pair of inner wall surfaces facing the printer width direction Y are provided on the upper part of the second mounting portion 27, and both ends of the rotating shaft 51 can be moved in the vertical direction on the inner wall surface and are rotatable. A pair of groove portions 27b that are supported in a simple state are formed. The wheel cleaner 50B is disposed so that both ends of the rotating shaft 51 are inserted into the groove 27b and placed on the second star wheel 25B. Therefore, the outer peripheral surface 53a of the cleaning member 53 is pressed against the tip 43a of the protrusion 43 of the second star wheel 25B by the weight of the wheel cleaner 50B.

  In this state, when the second star wheel 25B is driven and rotated by the continuous paper P conveyed along the platen surface 8a, the wheel cleaner 50B pressed against the tip 43a of the protrusion 43 is driven and rotated. As a result, the tip 43a of the protrusion 43 after contacting the continuous paper P sequentially contacts the outer peripheral surface 53a of the cleaning member 53, and the dirt such as ink adhering to the tip 43a of the protrusion 43 is removed. The second star wheel 25B is supported by the urging force of the torsion spring 45 so as to move up and down in accordance with the unevenness of the continuous paper P. Even if the second star wheel 25B moves in the urging direction of the torsion spring 45, The wheel cleaner 50B can move following the movement of the second star wheel 25B by its own weight. Accordingly, the state in which the cleaning member 53 is pressed against the tip 43a of the protrusion 43 is maintained, and cleaning can always be performed.

  Next, with reference to FIG. 9A, FIG. 13, FIG. 15, etc., the attachment structure of the first star wheel 25A to the first attachment portion 26 will be described. As shown in FIG. 9A, the first attachment portion 26 is a groove-like recess that is recessed toward the printer front X1 side or the printer rear X2 side. As shown in FIG. A wheel support member 46 is attached. The star wheel support member 46 includes a first arm portion 46a extending along the recess bottom surface 26a of the first attachment portion 26, and a lower end (end portion on the platen surface 8a side) of the first arm portion 46a opposite to the recess bottom surface 26a. And a support shaft 46c for connecting the two bent members in a state in which the two bent members are arranged at a predetermined interval in the printer width direction Y. A pair of inner wall surfaces facing the printer width direction Y are provided at the end of the first mounting portion 26 on the platen surface 8a side, and a support shaft 46c extending in the printer width direction Y is rotatably spanned therebetween. Yes.

  The star wheel support member 46 is arranged such that the two second arm portions 46b protrude from the first mounting portion 26, and the first wheel support member 46 is provided between the two second arm portions 46b by a support shaft (not shown). A star wheel 25A is rotatably attached. The first star wheel 25A has the same configuration as the second star wheel 25B, includes the main body 41 and the thin plate portion 42 described above, and has protrusions 43 that protrude radially outward in the outer peripheral edge. . A coil spring 47 (biasing member) is disposed between the upper end of the first arm portion 46a and the recess bottom surface 26a. The star wheel support member 46 swings about the support shaft 46c by the biasing force of the coil spring 47, and the first star wheel 25A attached to the tip of the second arm portion 46b is biased toward the platen surface 8a. . For this reason, the state where the tip 43a of the projection 43 of the first star wheel 25A is in elastic contact with the continuous paper P on the platen surface 8a is maintained.

  A wheel cleaner 50A is disposed on the first mounting portion 26 obliquely above the first star wheel 25A. The wheel cleaner 50 </ b> A includes a cylindrical cleaning member 54 made of the same material as the cleaning member 53 of the wheel cleaner 50 </ b> B described above, and a support 55 attached to a central hole formed at the radial center of the cleaning member 54. Yes. The support body 55 is provided with rotating shafts 55a that protrude on both sides in the printer width direction Y. The star wheel support member 46 is formed with a recess 48 on which the rotation shaft 55a is placed at a corner where the first arm portion 46a and the second arm portion 46b are connected. The bottom surface of the recess 48 is an inclined surface that descends toward the platen surface 8a toward the first star wheel 25A. In the wheel cleaner 50A, the rotation shaft 55a is disposed on the bottom surface of the recess 48, so that the cleaning member 54 is attached to the tip 43a of the projection 43 of the first star wheel 25A by its own weight obliquely upward from the first star wheel 25A. The outer peripheral surface 54a is pressed.

  In this state, when the first star wheel 25A is driven and rotated by the continuous paper P conveyed along the platen surface 8a, the wheel cleaner 50A pressed against the tip 43a of the protrusion 43 is rotated. As a result, the tip 43a of the protrusion 43 after contacting the continuous paper P sequentially contacts the outer peripheral surface 54a of the cleaning member 54, and dirt such as ink adhering to the tip 43a of the protrusion 43 is removed. The first star wheel 25 </ b> A is supported by the urging force of the coil spring 47 so as to move up and down according to the unevenness of the continuous paper P. Even if the first star wheel 25 </ b> A moves in the urging direction by the coil spring 47. The wheel cleaner 50 </ b> A can move in the direction along the bottom surface of the recess 48 by following the movement of the first star wheel 25 </ b> A by its own weight. Therefore, the state in which the cleaning member 54 is pressed against the tip 43a of the protrusion 43 by its own weight is maintained.

(Head tip shape)
As shown in FIG. 11, the head end of the print head 71 (the first head 71a to the fourth head 71d) is located in a rectangular area surrounded by the inner carriage 72 on the surface facing the platen surface 8a of the head unit 7. Four sections 76 are arranged at regular intervals in the longitudinal direction X of the printer. These four head tip portions 76 have the same shape and are elongated in the printer width direction Y. Each head tip 76 is formed with four sets of ink nozzle surfaces 77a to 77d forming an ink nozzle row. Each of the four sets of ink nozzle surfaces 77a to 77d has an elongated shape extending in parallel with the printer width direction Y. More specifically, in each head front end portion 76, the ink nozzle surfaces 77a and 77c are arranged in one row with a predetermined gap in the printer width direction Y, so that this row and the printer longitudinal direction X are adjacent to each other. The ink nozzle surfaces 77b and 77d are arranged in a line with a predetermined gap in the printer width direction Y. The ink nozzle surfaces 77a to 77d are arranged in the order of the ink nozzle surfaces 77a, 77b, 77c, and 77d by a certain amount in the printer width direction Y when viewed in the longitudinal direction X of the printer, In 76, the ink nozzles are arranged over the entire range including the maximum width of the continuous paper P. Concave portions 76a are formed at two positions in the gap where the ink nozzle surfaces 77a and 77c are not arranged on the side surface of the head front end portion 76 on the printer front X1 side. In addition, on the side surface of the head front end portion 76 on the printer rear X2 side, concave portions 76a are formed at two places in the gap where the ink nozzle surfaces 77b and 77d are not arranged.

  When the head unit 7 is positioned at the print execution position 7A facing the platen unit 8, the four head tips 76 in the print head 71 (the first head 71a to the fourth head 71d) are 1 in FIG. As indicated by the dotted line, the positioning is performed at a position overlapping with the gap surrounded by the horizontal frame portions 22a to 22e. Further, in the gap between the horizontal frame portions 22a to 22e, the position where the first star wheel 25A protrudes is positioned so that the concave portion 76a formed in the head front end portion 76 overlaps. That is, the four head end portions 76 are perpendicular to the platen surface 8a with respect to the gaps surrounded by the horizontal frame portions 22a to 22e and the first star wheel 25A (in other words, the conveying direction of the continuous paper P and It is positioned at a position overlapping with the continuous paper P in the direction orthogonal to the width direction of the continuous paper P, and positioned so as to face the continuous paper P on the platen surface 8a.

  When the head unit 7 lowers the inner carriage 72 and the print head 71 to the platen gap holding position 72A at the print execution position 7A, the head unit 7 has four gaps surrounded by the horizontal frame portions 22a to 22e and the first star wheel 25A. The head tip 76 enters without interference. At this time, since the second star wheel 25B is disposed directly below the horizontal frame portions 22a to 22e, the second star wheel 25B does not interfere with the head tip portion 76. Therefore, the print head 71 and the inner carriage 72 can be lowered and the platen gap can be kept constant without causing the platen upper unit 29 and the head unit 7 to interfere with each other. Then, each of the four color inks can be ejected from the four head end portions 76 to the entire range including the maximum width of the continuous paper P, and printing can be performed on the entire area of the continuous paper P. Further, when the head unit 7 is moved to the retracted position 7B, the head unit 7 can be raised while avoiding interference with the platen upper unit 20.

(Main effects of this embodiment)
As described above, the printer 1 according to this embodiment includes the print execution position 7A in which the print head 71 is opposed to the platen surface 8a and the head unit that can move to the retreat position 7B in which the print head 71 is retreated from the print execution position 7A. 7 and a platen upper unit 20 that is arranged so as to overlap the platen surface 8 a and is separated from the platen unit 8. Then, the first star wheel 25A and the second star wheel 25B are mounted on the platen upper unit 20, and the floating of the continuous paper P from the platen surface 8a is restricted. Thus, by separating the first star wheel 25A and the second star wheel 25B from the head unit 7, the first star wheel is moved by moving the head unit 7 between the print execution position 7A and the retreat position 7B. It can avoid that the position accuracy with respect to the platen surface 8a of 25A and the 2nd star wheel 25B falls. Further, since it is possible to avoid an increase in the size of the head unit 7 by being integrated with the platen upper unit 20 on which the first star wheel 25A and the second star wheel 25B are mounted, it is possible to avoid the complexity of the support structure of the head unit 7. Further, it is possible to avoid an increase in cost due to a higher output of the carriage motor that drives the head unit 7.

  In this embodiment, the platen upper unit 20 is equipped with the wheel cleaners 50A and 50B that come into contact with the tips 43a of the projections 43 of the first star wheel 25A and the second star wheel 25B. The stains on the first star wheel 25A and the second star wheel 25B due to the ink adhering to the ink can be removed, and the stain on the continuous paper P due to the ink adhering to the first star wheel 25A and the second star wheel 25B can be avoided.

  Furthermore, in this embodiment, the wheel cleaners 50A and 50B are rotating bodies including cylindrical outer peripheral surfaces 53a and 54a, and are disposed so that the outer peripheral surfaces 53a and 54a are in contact with the tip 43a of the protrusion 43, and the first star wheel. 25A and the second star wheel 25B rotate along with the rotation. Therefore, it can suppress that rotation of the 1st star wheel 25A and the 2nd star wheel 25B is prevented by cleaning operation. Further, the outer peripheral surfaces 53a and 54a of the wheel cleaners 50A and 50B can be used as cleaning surfaces over the entire periphery.

  Further, in this embodiment, the first star wheel 25A and the second star wheel 25B are urged toward the platen surface 8a. However, the wheel cleaners 50A and 50B have the first star wheel 25A and the second star wheel by their own weight. It is supported in a movable state following the movement of 25B. Therefore, the tip 43a of the protrusion 43 and the cleaning surface can always be kept in contact with each other.

  In addition, in this embodiment, the platen upper unit 20 on which the sphere 19, the first star wheel 25A, the second star wheel 25B, and the like are mounted is also separated from the platen unit 8, so that paper jam removal work, maintenance, etc. In addition, it is possible to easily perform an operation of opening the opening / closing lid 5 on the front side of the printer and pulling the platen unit 8 forward of the printer. Accordingly, it is possible to easily remove the continuous paper P jammed on the platen surface 8a.

(Other embodiments)
In the above embodiment, the first star wheel 25A and the second star wheel 25B are arranged so as not to overlap when viewed in the front-rear direction X of the printer, but one of the first star wheel 25A and the second star wheel 25B. If only the parts are viewed in the longitudinal direction X of the printer, they may be arranged so as not to overlap. For example, you may arrange | position so that the attachment position of the 1st star wheel 25A and the 2nd star wheel 25B in an adjacent horizontal frame part may not overlap among five horizontal frame parts 22a-22e.

  In the above embodiment, two types of star wheels, the first star wheel 25A and the second star wheel 25B, are mounted, but only one of them may be used. In addition, the configuration of the star wheel is not limited to such a configuration, and a star wheel having another configuration may be mounted on the upper unit main body 20A.

  The above-described form is the printer 1 having a form in which the platen gap is maintained by contact with the sphere 19, but the present invention can also be applied to a printer having a form in which the platen gap is maintained by other methods.

DESCRIPTION OF SYMBOLS 1 ... Line inkjet printer (printer), 2 ... Printer housing, 2a ... Front surface, 3 ... Operation part, 4 ... Paper discharge port, 5 ... Opening / closing lid, 6 ... Roll paper storage part, 7 ... Head unit, 7A ... Printing Execution position, 7B ... retracted position, 8 ... platen unit, 8a ... platen surface, 9 ... roll paper, 10 ... medium transport path, 10a ... first path part, 10b ... second path part, 10c ... third path part, DESCRIPTION OF SYMBOLS 11 ... Medium supply roller, 12 ... Tension lever, 13 ... Center of rotation, 14 ... Rotary encoder, 15 ... Paper guide, 16 ... Medium conveyance mechanism, 17a, 17b ... Pinch roller, 18 ... Paper detector, 19 ... Sphere ( Platen gap forming member), 20 ... platen upper unit, 20A ... upper unit main body, 20B ... fixed frame, 21a, 21b ... vertical frame, 22a-22 ... Horizontal frame part (support frame), 23a-23c ... Sphere holding part, 24a ... Penetration part, 24b ... Support member, 25A ... First star wheel, 25B ... Second star wheel, 26 ... First attachment part, 26a ... Recess bottom surface, 27 ... second mounting portion, 27a ... notch portion, 27b ... groove portion, 41 ... main body portion, 41a ... center hole, 42 ... thin plate portion, 43 ... projection, 43a ... tip, 44 ... coil spring, 45 ... Torsion spring (biasing member), 46 ... star wheel support member, 46a ... first arm, 46b ... second arm, 46c ... support shaft, 47 ... coil spring (biasing member), 48 ... concave, 50A ... Wheel cleaner (rotating body), 50B ... Wheel cleaner (rotating body), 51 ... Rotating shaft, 52 ... Supporting body, 52a ... Recess, 53 ... Cleaning member, 53a ... Outer peripheral surface, 54 ... Cleaning member, 4a ... outer peripheral surface, 55 ... support, 55a ... rotating shaft, 71 ... print head, 71a ... first head, 71b ... second head, 71c ... third head, 71d ... fourth head, 72 ... inner carriage, 72A Platen gap holding position, 72B ... Ascending position, 73 ... Outer carriage, 73A ... First position, 73B ... Second position, 74a, 74b ... Carriage shaft, 75a-75c ... Head side abutting part, 76 ... Head end part , 76a ... recess, 77a-77d ... ink nozzle surface, 79 ... print head lifting mechanism, 79A ... pressing mechanism, 79B ... coil spring, 81 ... transport belt, 81a ... horizontal belt portion, 82a-82e ... guide roller, 82f ... Belt drive roller, 83... Unit body, 83a, 83b ... side frame, 83c ... support shaft, 84a ... first side plate, 84b ... second side plate , 85a to 85e ... support roller, 86a ... support shaft, 86b ... roller body, 87 ... holder, 88 ... fixing screw, 89a to 89c ... platen side contact portion, P ... continuous paper (medium)

Claims (8)

A platen unit having a platen surface for supporting a sheet-like medium;
A head unit which is mounted with a print head for printing on the medium, and which can be moved to a print execution position where the print head is opposed to the platen surface, and a retreat position where the print head is retreated from the print execution position When,
A platen upper unit arranged to overlap the platen surface and separated from the platen unit;
A printer characterized in that a star wheel is mounted on the platen upper unit. The platen upper unit includes a plurality of support frames that support the star wheel,
When the head unit is positioned at the printing execution position, the ink nozzle surface of the print head is in a direction perpendicular to the platen surface with respect to the gap surrounded by the plurality of support frames and the star wheel. The printer according to claim 1, wherein the printer is positioned at an overlapping position. The head unit includes a print head lifting mechanism that moves the print head closer to and away from the platen surface,
The print head includes a head tip portion on which the ink nozzle surface is formed,
When the print head elevating mechanism lowers the print head to a platen gap holding position where the print head and the platen surface maintain a predetermined gap, a gap surrounded by the plurality of support frames and the star wheel The printer according to claim 2, wherein the head tip portion is inserted into the printer.   4. The printer according to claim 2, wherein the star wheels are attached to the plurality of support frames at positions that do not overlap when viewed in the medium conveyance direction. 5. A protrusion is formed on the outer periphery of the star wheel,
The wheel cleaner that contacts the tip when the tip of the projection of the star wheel is separated from the medium is mounted on the platen upper unit. Printer. The wheel cleaner is a rotating body having a cylindrical outer peripheral surface,
The printer according to claim 5, wherein the rotating body is disposed so that the outer peripheral surface is in contact with a tip of the protrusion, and is supported so as to be driven to rotate as the star wheel rotates. . The platen upper unit is provided with a biasing member that biases the star wheel toward the platen surface,
The said rotary body is supported so that it may move following the movement of the said star wheel, when the said star wheel moves in the urging | biasing direction by the said urging | biasing member. printer. The printer according to claim 1, wherein the platen upper unit is fixed to a printer main body frame.

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