Image forming system and head moving method

Abstract

To provide an image forming system capable of moving a head to each of a plurality of image forming positions quickly and accurately.SOLUTION: An image forming system includes: a head; a head moving mechanism having a carriage, a stepping motor, a power transmission mechanism, a first sensor, and a second sensor; and a controller. The controller rotates the stepping motor by the number of steps S1 and moves the head to a first position from a time point when the head reaches a first preliminary position, rotates the stepping motor by the number of steps S2 and moves the head to a second position from a time point when the head reaches a second preliminary position, and rotates the stepping motor by the number of steps S3 and moves the head to a third position from a time point when the head reaches a third preliminary position.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to an image forming system and a head moving method. [Background technology]

[0002] Image forming systems are used that form images on a medium (such as paper) by ejecting ink from a head having nozzles onto the medium. Some such image forming systems are configured to move the head between an image forming position for forming an image on the medium and a position (e.g., a maintenance position) spaced apart from the image forming position.

[0003] Patent document 1 discloses a sheet digital printing press that includes a head holding unit equipped with a nozzle head and a guide member that guides the nozzle head of the head holding unit between a first position inside the printing press and a second position outside the printing press. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-241002 Summary of the Invention [Problem to be solved by the invention]

[0005] Some image forming systems have multiple image forming positions. The multiple image forming positions include, for example, a main image forming position and a sub-image forming position. The main image forming position is a position that is mainly used for image formation by the image forming system. Specifically, the sub-image forming position is used, for example, when adjusting the heads or when a malfunction occurs in one of the heads.

[0006] However, with the configuration disclosed in the sheet digital printing machine of Patent Document 1, it is not easy to suitably move the head to each of the multiple image forming positions.

[0007] SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming system and a head moving method that can quickly and accurately move a head to each of a plurality of image forming positions. [Means for solving the problem]

[0008] According to a first aspect of the present invention, a head that ejects liquid to form an image on a medium; a head moving mechanism that moves the head along a head moving direction between an image forming area on one end side of the head moving direction and a retreat area on the other end side of the head moving direction, a carriage supporting the head; A stepping motor; a power transmission mechanism connected to the carriage and the stepping motor and configured to transmit power of the stepping motor to the carriage; a first sensor and a second sensor that detect that the head is positioned in the image forming area, the first sensor and the second sensor each being turned off when the head is positioned in the evacuation area; a head moving mechanism including: a controller electrically connected to the stepping motor, the first sensor, and the second sensor; The controller When moving the head from the retraction area to a first position in the image forming area, the stepping motor is rotated in one direction to move the head toward the one end at a first speed up to a first preliminary position where the first sensor changes from an off state to an on state, and from the point where the head reaches the first preliminary position, the stepping motor is rotated in the one direction by a number of steps S1 to move the head to the first position at a second speed that is lower than the first speed, When moving the head from the retraction area to a second position in the image forming area that is different from the first position, the stepping motor is rotated in the one direction to move the head toward the one end at the first speed up to a second preliminary position where the second sensor changes from an off state to an on state, and from the point where the head reaches the second preliminary position, the stepping motor is rotated in the one direction by a number of steps S2 to move the head to the second position at the second speed, When the head is moved from the retraction area to a third position in the image forming area that is different from the first and second positions, the stepping motor is rotated in the one direction to move the head toward the one end at the first speed up to the third preliminary position where the first sensor, which has turned on as the head reaches the first preliminary position, changes to the off state again, and from the point where the head reaches the third preliminary position, the stepping motor is rotated in the one direction by the number of steps S3 to move the head to the third position at the second speed.

[0009] According to a second aspect of the present invention, a head that ejects liquid to form an image on a medium; a head moving mechanism that moves the head along a head moving direction between an image forming area on one end side of the head moving direction and a retreat area on the other end side of the head moving direction, a carriage supporting the head; A stepping motor; a power transmission mechanism connected to the carriage and the stepping motor and configured to transmit power of the stepping motor to the carriage; a first sensor and a second sensor that detect that the head is positioned in the image forming area, the first sensor and the second sensor each being turned off when the head is positioned in the evacuation area; a head moving mechanism including: a controller electrically connected to the stepping motor, the first sensor, and the second sensor, The controller: When moving the head from the retraction area to a first position in the image forming area, the stepping motor is rotated in one direction to move the head toward the one end at a first speed up to a first preliminary position where the first sensor changes from an off state to an on state, and once the head reaches the first preliminary position, the stepping motor is rotated in the one direction by a number of steps S1 to move the head to the first position at a second speed lower than the first speed; When moving the head from the retraction area to a second position in the image forming area that is different from the first position, the stepping motor is rotated in the one direction to move the head toward the one end at the first speed up to a second preliminary position where the second sensor changes from an off state to an on state, and from the point where the head reaches the second preliminary position, the stepping motor is rotated in the one direction by a number of steps S2 to move the head to the second position at the second speed. When moving the head from the retraction area to a third position in the image forming area that is different from the first position and the second position, the stepping motor is rotated in the one direction to move the head toward the one end at the first speed up to the third preliminary position where the first sensor, which has turned on as the head reaches the first preliminary position, changes to the off state again, and from the point where the head reaches the third preliminary position, the stepping motor is rotated in the one direction by the number of steps S3 to move the head to the third position at the second speed. [Effects of the Invention]

[0010] According to the image forming system and head moving method of the present invention, a user of the system and method can quickly and accurately move the head to each of a plurality of image forming positions. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of the printer. [Figure 2] FIG. 2 is a schematic diagram of the printer as viewed in the medium width direction. [Figure 3] Figure 3(a) is a perspective view of the head assembly, and Figure 3(b) is a top view of the head assembly. [Figure 4] 4 is a schematic diagram showing the relative positions of the head unit, platen, and maintenance unit in the medium width direction. Note that only the head on the upstream side in the transport direction is shown, and only the wiper and nozzle cap corresponding to that head are shown. [Figure 5] 5 is a schematic side view of the movement mechanism as seen from the left in the medium width direction, in which the curvature of the carriage along the transport direction is omitted. [Figure 6] Figures 6(a) and 6(b) are explanatory diagrams showing the movement mechanism as viewed from downstream in the transport direction. Figure 6(a) shows the head unit in the printing position, and Figure 6(b) shows the head unit in the maintenance position. For ease of explanation, the stepping motor shaft, the pinion gear attached to the shaft, and the rack gear that meshes with the pinion gear are also shown in the figures, but these are not visible when the movement mechanism is viewed from downstream in the transport direction. [Figure 7] FIG. 7 is a functional block diagram showing the electrical configuration of the printer. [Figure 8] These are top views showing the relationship between the head assembly and the medium placement area at each of the three printing positions. The top view shows the relationship between the head assembly and the medium placement area at the right printing position. The middle view shows the relationship between the head assembly and the medium placement area at the center printing position. The bottom view shows the relationship between the head assembly and the medium placement area at the left printing position. [Figure 9]9(a) to 9(f) are explanatory diagrams showing the positional relationship in the medium width direction between the detection plate fixed to the carriage and the left and right sensors fixed to the housing. FIG. 9(a) shows the positional relationship when the head assembly is in the right sensor light-blocking position, and FIG. 9(b) shows the positional relationship when the head assembly is in the right printing position. FIG. 9(c) shows the positional relationship when the head assembly is in the left sensor light-blocking position, and FIG. 9(d) shows the positional relationship when the head assembly is in the center printing position. FIG. 9(e) shows the positional relationship when the head assembly is in the right sensor light-receiving position, and FIG. 9(f) shows the positional relationship when the head assembly is in the left printing position. In each figure, a black circle indicates that the sensor is in a light-blocking state, and a white circle indicates that the sensor is in a light-receiving state. [Figure 10] Figure 10 is an explanatory diagram showing the positional relationship between the right printing position, center printing position, left printing position, right sensor light-shielding position, left sensor light-shielding position, and right sensor light-receiving position, as well as the movement speed when moving the head assembly to each of the right printing position, center printing position, and left printing position. [Figure 11] FIG. 11 is a flowchart showing the procedure for initial adjustment of the printer. [Figure 12] Fig. 12 is a side view showing a comparative example of a moving mechanism as seen from downstream in the conveying direction. As in Fig. 6(a), the stepping motor shaft, the pinion gear attached to the shaft, and the rack gear meshing with the pinion gear are also shown in the figure, but these are not visible when the moving mechanism is seen from downstream in the conveying direction. [Figure 13]Figures 13(a) to 13(f) are explanatory diagrams showing the positional relationship in the medium width direction between the detection plate fixed to the carriage and the left and right sensors fixed to the housing. Figure 13(a) shows the positional relationship when the head assembly is in the right sensor light-blocking position, and Figure 13(b) shows the positional relationship when the head assembly is in the right printing position. Figure 13(c) shows the positional relationship when the head assembly is in the right sensor light-receiving position, and Figure 13(d) shows the positional relationship when the head assembly is in the center printing position. Figure 13(e) shows the positional relationship when the head assembly is in the left sensor light-blocking position, and Figure 13(f) shows the positional relationship when the head assembly is in the left printing position. In each figure, a black circle indicates that the sensor is in a light-blocking state, and a white circle indicates that the sensor is in a light-receiving state. [Figure 14] Figure 14 is an explanatory diagram showing the positional relationships between the right printing position, central printing position, left printing position, right sensor light-shielding position, right sensor light-receiving position, and left sensor light-shielding position, as well as the movement speed when moving the head assembly to each of the right printing position, central printing position, and left printing position. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Embodiment> A printer (image forming system) 100 according to an embodiment of the present invention will be described with reference to FIGS.

[0013] [Printer 100] As shown in Figures 1 and 2, the printer 100 mainly comprises a head unit 10, a platen 20, a feed shaft 31, a take-up shaft 32, a pair of transport rollers 41, 42, an ink tank 50, a maintenance unit 60, a movement mechanism 70, a controller 80, and a housing 90 that houses these components.

[0014] In the following description, the direction in which the transport roller pairs 41, 42 are aligned, i.e., the direction in which the medium PM is transported during image formation, is referred to as the transport direction of the printer 100. With regard to the transport direction, the upstream and downstream of the direction in which the medium PM is transported are referred to as the upstream and downstream of the transport direction, respectively. Furthermore, the direction perpendicular to the transport direction in a horizontal plane, i.e., the direction in which the rotation axes of the transport roller pairs 41, 42 extend, is referred to as the medium width direction. With regard to the medium width direction, the left and right when viewed from downstream to upstream in the transport direction are referred to as the left and right of the medium width direction, respectively. The medium width direction is an example of the "head movement direction" in the present invention.

[0015] The head unit 10 includes a first head unit 11 and a second head unit 12. The second head unit 12 is located downstream of the first head unit 11 in the transport direction.

[0016] The first head unit 11 has two head assemblies HDA and a carriage 111 that holds the two head assemblies HDA. The two head assemblies HDA have the same structure. The two head assemblies HDA are aligned in the transport direction and held together by the carriage 111.

[0017] Each of the two head assemblies HDA is a so-called line-type head (head bar). Each of the two head assemblies HDA is box-shaped (Fig. 3(a)) and has ten heads HD located on its underside HDAb (Fig. 3(b)). The ten heads HD have the same structure.

[0018] The ten heads HD are positioned in a staggered (zigzag) pattern along the medium width direction. Specifically, the ten heads HD include five heads HD arranged in the medium width direction to form a first row L1, and five heads HD arranged in the medium width direction to form a second row L2. The second row L2 is located downstream of the first row L1 in the transport direction. The heads HD that make up the second row L2 are shifted to the right in the medium width direction relative to the heads HD that make up the first row L1.

[0019] Inside each of the two head assemblies HDA, a flow path (not shown) is formed that supplies ink supplied from the ink tank 50 to each of the ten heads HD.

[0020] The underside of each of the ten heads HD is a nozzle surface NZS on which multiple nozzles NZ are formed. Each of the multiple nozzles NZ is a minute opening that ejects ink toward the medium PM. For convenience of explanation, it is assumed that each head HD in this embodiment has 36 nozzles NZ formed therein. The 36 nozzles form four nozzle rows aligned in the transport direction, and each nozzle row includes nine nozzles NZ aligned in the width direction of the medium. The image formation resolution per nozzle row is 150 dpi, and the image formation resolution of a head HD having four nozzle rows is 600 dpi. Note that the number of nozzles NZ in a head HD may be more than 36, and the number of nozzle rows may be more than four. The image formation resolution of a head HD may also be greater than 600 dpi. For example, the image formation resolution of a head HD may be increased by increasing the number of nozzle rows in the head HD while reducing the resolution of each nozzle row to less than 150 dpi.

[0021] A plurality of individual flow paths (not shown) are formed inside each of the ten heads HD. Ink flowing from the head assembly HDA to the head HD flows through the plurality of individual flow paths to each of the plurality of nozzles NZ. Each of the plurality of individual flow paths has a pressure chamber (not shown) near the nozzle NZ. A drive element DE (FIG. 7) is located above each pressure chamber, and each drive element DE is connected to the controller 80 via a driver IC 85 (FIG. 7).

[0022] 2, the carriage 111 is a plate-like member curved along the transport direction. Each of the two head assemblies HDA is held by the carriage 111 with an area near the bottom end of the head assembly HDA fitting into an opening (not shown) formed in the carriage 111.

[0023] The carriage 111 holds the two head assemblies HDA so that their up-down directions (i.e., the directions in which each head assembly HDA ejects ink) are different from each other. Therefore, each of the two head assemblies HDA ejects ink droplets perpendicular to the medium PM being transported within a transport path CR (described in detail below) that curves along the medium width direction.

[0024] The second head unit 12 (FIG. 1) has six head assemblies HDA and a carriage 121 that holds the six head assemblies HDA. Each of the six head assemblies HDA has the same structure as the head assembly HDA held by the first head unit 11. The six head assemblies HDA are lined up in the transport direction and held together by the carriage 121.

[0025] 2, the carriage 121 is a plate-like member curved along the transport direction. Each of the six head assemblies HDA is held by the carriage 121 with an area near the bottom end of the head assembly HDA fitting into an opening (not shown) formed in the carriage 121.

[0026] The carriage 121 holds the six head assemblies HDA so that the up-down direction of each of the six head assemblies HDA (i.e., the direction in which each head assembly HDA ejects ink) is slightly different from one another. Therefore, each of the six head assemblies HDA ejects ink droplets perpendicular to the medium PM being transported within a transport path CR (described in detail below) that curves along the medium width direction.

[0027] In this embodiment, the carriage 111 and two head assemblies HDA of the first head unit 11 can be moved up and down by an elevator mechanism (not shown). The carriage 121 and six head assemblies HDA of the second head unit 12 can be moved up and down by an elevator mechanism (not shown). That is, the height of the nozzle surfaces NZS of the eight head assemblies HDA relative to the conveyance surface CS (FIG. 2; described in detail later) can be changed. The elevator mechanism that moves the eight head assemblies HDA up and down can be, for example, the movement mechanism described in JP 2022-142275 A.

[0028] The platen 20 supports the medium PM from below when the first head unit 11 and the second head unit 12 of the head unit 10 eject ink toward the medium PM. As shown in FIG. 2 , the platen 20 has an arch frame 21 and a plurality of rollers 22 rotatably held by the arch frame 21.

[0029] As shown in FIG. 4, the arch frame 21 has a bottom portion 21B and a pair of wall portions 21W extending upward from both ends of the bottom portion 21B in the medium width direction.

[0030] The rollers 22 have the same shape and dimensions. The rollers 22 are held in a line in the conveying direction by the arch frame 21, with their respective rotation axes (not shown) aligned with the medium width direction. In this embodiment, the rollers 22 are held by the arch frame 21 so that the upper end of each roller 22 is positioned on a curved surface that curves along the conveying direction. The upper ends of the rollers 22 define a conveying surface CS (FIG. 2) that curves along the conveying direction.

[0031] 2, the head unit 10 and the platen 20 are positioned so that the lower surface HDAb of the head assembly HDA faces the transport surface CS. A transport path CR curved along the transport direction is defined between the lower surface HDAb of the head assembly HDA and the transport surface CS.

[0032] The feed shaft 31 is connected to the feed motor M 31(Fig. 7), and the winding shaft 32 is a rotating shaft rotated by the winding motor M 32 (FIG. 7) is a shaft that rotates. A feed roll PM1 (FIG. 2) on which the medium PM before image formation is wound in a roll is attached to the feed shaft 31. A take-up roll PM2 (FIG. 2) on which the medium PM after image formation is wound in a roll is attached to the take-up shaft 32.

[0033] The medium PM sent out from the feed roll PM1 is wound up by the take-up roll PM2 after an image is formed on it by the head unit 10. As the medium PM, for example, roll paper can be used.

[0034] The pair of transport rollers 41, 42 (FIG. 1) are positioned on either side of the platen 20 in the transport direction. The pair of transport rollers 41, 42 are each rotated by a driving force transmitted from a transport motor M4 (FIG. 7). The pair of transport rollers 41, 42 send the medium PM downstream in the transport direction when the head unit 10 forms an image on the medium PM.

[0035] The ink tank 50 (FIG. 1) is divided into seven sections so that it can contain seven colors (seven types) of ink. The seven colors of ink are sent to a reservoir 52 through a conduit 51. The conduit 51 and the reservoir 52 are also divided into seven sections so that they can circulate and contain the seven colors of ink. Each color of ink sent to the reservoir 52 is circulated between the reservoir 52 and one of the eight head assemblies HDA via a conduit and a pump (not shown).

[0036] In this embodiment, white ink is sent to the two head assemblies HDA of the first head unit 11. Six color inks are sent to the six head assemblies HDA of the second head unit 12. The six color inks are, for example, black ink, cyan ink, magenta ink, yellow ink, orange ink, and violet ink.

[0037] The maintenance unit 60 (FIG. 1) is a mechanism for performing maintenance on the head unit 10. Specifically, maintenance of the head unit 10 can include, for example, wiping the head HD, flushing in which ink is ejected from the nozzles NZ to remove foreign matter (air bubbles, particles, etc.), and purging in which ink is sucked from the nozzles NZ to remove foreign matter, etc.

[0038] The maintenance unit 60 is positioned alongside the platen 20 in the medium width direction. In this embodiment, the maintenance unit 60 is positioned to the right of the platen 20.

[0039] The maintenance unit 60 has a first maintenance pan 611, a second maintenance pan 612, eight wiper units 62, and 80 nozzle caps 63.

[0040] The first maintenance pan 611 and the second maintenance pan 612 are respectively flat-plate-shaped members that receive ink that drops from the first head unit 11 and the second head unit 12. The first maintenance pan 611 and the second maintenance pan 612 each have a bottom 61B, a peripheral wall 61W that stands upright from the periphery of the bottom 61B, and a separation wall 61P that extends in the medium width direction and connects one side of the peripheral wall 61W to the other side.

[0041] The bottom 61B of the first maintenance pan 611 is rectangular in plan view and is divided into two areas A1 and A2 by one separation wall 61P. The bottom 61B of the second maintenance pan 612 is rectangular in plan view and is divided into six areas A3 to A8 by five separation walls 61P.

[0042] The eight wiper units 62 each wipe the heads HD of the eight head assemblies HDA of the head unit 10. The eight wiper units 62 are located one each in areas A1 to A8 of the bottom 61B of the first maintenance pan 611 and the second maintenance pan 612. The eight wiper units 62 have the same structure.

[0043] Each of the eight wiper units 62 has a base 620 and a first wiper 621 and a second wiper 622 supported by the base 620.

[0044] The base 620 is a platform-shaped structure located near the left end in the medium width direction in each of the areas A1 and A2 of the bottom 61B of the first maintenance pan 611 and the areas A3 to A8 of the bottom 61B of the second maintenance pan 612.

[0045] The first wiper 621 is a wiper that wipes the nozzle surfaces NZS of the heads HD in the first row L1 of the corresponding head assembly HDA. The second wiper 622 is a wiper that wipes the nozzle surfaces NZS of the heads HD in the second row L2 of the corresponding head assembly HDA. The second wiper 622 is located downstream in the transport direction and to the right in the medium width direction of the first wiper 621. The first wiper 621 and the second wiper 622 are each formed from a flexible material (rubber, for example). The first wiper 621 and the second wiper 622 have the same shape.

[0046] The 80 nozzle caps 63 cover the 80 heads HD of the head unit 10, respectively, to prevent the ink from drying out, etc. The 80 nozzle caps 63 have the same structure. The 80 nozzle caps 63 are located on the bottoms 61B of the first maintenance pan 611 and the second maintenance pan 612. Specifically, 10 nozzle caps 63 are located in a staggered pattern along the medium width direction to the right of the wiper unit 62 in each of areas A1 to A8.

[0047] When the first head unit 11 is positioned above the first maintenance pan 611, or when the second head unit 12 is positioned above the second maintenance pan 612 (FIG. 4), each nozzle cap 63 is positioned directly below the corresponding head HD. In this state, an elevation mechanism (not shown) moves the two head assemblies HDA of the first head unit 11 or the six head assemblies HDA of the second head unit 12 up and down, and the nozzle caps 63 are displaced between a covering state in which they abut against the heads HD and cover the nozzles NZ of the heads HD, and a non-covering state in which the nozzle caps 63 are separated from the heads HD.

[0048] The movement mechanism 70 (FIG. 1) is a mechanism that displaces the head unit 10 between a printing position for performing printing and a maintenance position for performing maintenance. The head unit 10 (first head unit 11 and second head unit 12) in the printing position is shown by dashed lines in FIG. 4. The head unit 10 in the maintenance position is shown by solid lines in FIG. 4.

[0049] As shown in FIG. 1, the movement mechanism 70 has a first movement mechanism 71 that moves the first head unit 11 and a second movement mechanism 72 that moves the second head unit 12.

[0050] As shown in Figures 5, 6(a), and 6(b), the first moving mechanism 71 mainly includes a rack gear 701, a pair of guided portions 702, a pair of guide rails 703, a stepping motor 704, a pinion gear 705, a left sensor 706l, a right sensor 706r, and a maintenance position sensor 707. The rack gear 701 and the pinion gear 705 are an example of a "power transmission mechanism." The left sensor 706l is an example of a "second sensor," and the right sensor 706r is an example of a "first sensor." The maintenance position sensor is an example of a "third sensor."

[0051] 5, the rack gear 701 is located at the upstream end in the transport direction of the lower surface 111b of the carriage 111 of the first head unit 11. The gear teeth of the rack gear 701 are aligned in the medium width direction.

[0052] The pair of guided portions 702 are located on the lower surface 111b of the carriage 111 of the first head unit 11. One guided portion 702 is located near the upstream end of the lower surface 111b in the transport direction, and the other guided portion 702 is located near the downstream end of the lower surface 111b in the transport direction. Each of the pair of guided portions 702 is an elongated member, and its cross section perpendicular to the longitudinal direction is generally C-shaped with a recess 702R. Each of the pair of guided portions 702 is located so that its longitudinal direction is parallel to the medium width direction.

[0053] The pair of guide rails 703 are positioned below the first head unit 11. One guide rail 703 is positioned near the upstream end of the first head unit 11 in the transport direction, and the other guide rail 703 is positioned near the downstream end of the first head unit 11 in the transport direction. Each of the pair of guide rails 703 is a long member, and its cross section perpendicular to the longitudinal direction has a base 703B and a T-shaped convex portion 703P. Each of the pair of guide rails 703 is positioned so that the long dimension is parallel to the medium width direction.

[0054] The pair of guided portions 702 and the pair of guide rails 703 are each positioned and engaged with the convex portions 703P of the guide rails 703 in the concave portions 702R of the guided portions 702.

[0055] A stepping motor 704 is located upstream in the transport direction of the first head unit 11. As shown in Figures 6(a) and 6(b), the stepping motor 704 is located in the approximate center, in the medium width direction, of the movable range MR1 of the first head unit 11 that moves between the printing position and the maintenance position.

[0056] The pinion gear 705 is fixed to the rotation shaft of the stepping motor 704. The pinion gear 705 is engaged with a rack gear 701 that the carriage 111 has.

[0057] When the pinion gear 705 is rotated by the drive of the stepping motor 704, the first head unit 11 moves along the medium width direction due to the engagement between the pinion gear 705 and the rack gear 701. The first head unit 11 moves in the medium width direction with the guided portion 702 supported and guided by the guide rail 703.

[0058] The left sensor 706l and the right sensor 706r (FIGS. 6(a) and 6(b)) are sensors for aligning the carriage 111 to one of three printing positions (i.e., right printing position, center printing position, and left printing position; details will be described later). The left sensor 706l is located near the left end of the movable range MR1 of the carriage 111, and the right sensor 706r is located to the right of the left sensor 706l. The left sensor 706l and the right sensor 706r are each located on a frame (not shown) fixed to the housing 90.

[0059] Each of the left sensor 706l and the right sensor 706r is an optical sensor having a light-emitting element EM that emits light and a light-receiving element RC that receives the light from the light-emitting element EM. In this embodiment, the light-emitting element EM and the light-receiving element RC face each other in the conveyance direction, and the light-emitting element EM emits light along the conveyance direction.

[0060] The maintenance position sensor 707 is a sensor for aligning the carriage 111 to the maintenance position. The maintenance position sensor 707 is located near the right end of the movable range MR1 of the carriage 111. The maintenance position sensor 707 is located on a frame (not shown) fixed to the housing 90.

[0061] Like the left sensor 706l and the right sensor 706r, the maintenance position sensor 707 is an optical sensor having a light-emitting element EM that emits light and a light-receiving element RC that receives light from the light-emitting element EM. In this embodiment, the light-emitting element EM and the light-receiving element RC face each other in the conveyance direction, and the light-emitting element EM emits light along the conveyance direction.

[0062] The first movement mechanism 71 further has a detection plate PT that is detected by a left sensor 706l and a right sensor 706r, and a detection plate pt that is detected by a maintenance position sensor 707 (FIGS. 6(a) and 6(b)). The detection plate PT and the detection plate pt are each flat plates that are fixed to the end face of the carriage 111 on the downstream side in the transport direction and extend in a plane perpendicular to the transport direction. The detection plate PT is fixed to the carriage 111 at the left end in the medium width direction. The detection plate pt is fixed to the carriage 111 at the right end in the medium width direction.

[0063] The left sensor 706l and the right sensor 706r each detect the position of the carriage 111 based on the detection target plate PT blocking the light from the light-emitting unit EM. The maintenance position sensor 707 detects the position of the carriage 111 based on the detection target plate pt blocking the light from the light-emitting unit EM.

[0064] The second movement mechanism 72 has the same configuration as the first movement mechanism 71, except that the object to be moved is the carriage 121 of the second head unit 12, rather than the carriage 111 of the first head unit 11.

[0065] 5, in the second movement mechanism 72, the rack gear 701 is located at the upstream end in the transport direction of the lower surface 121b of the carriage 121 of the second head unit 12. A stepping motor 704 of the second movement mechanism 72 is located upstream in the transport direction of the second head unit 12. A pair of guided portions 702 of the second movement mechanism 72 are located on the lower surface 121b of the carriage 121 of the second head unit 12. One guided portion 702 is located near the upstream end in the transport direction of the lower surface 121b, and the other guided portion 702 is located near the downstream end in the transport direction of the lower surface 121b.

[0066] The left sensor 706l and right sensor 706r (FIGS. 6(a) and 6(b)) of the second movement mechanism 72 are sensors for aligning the carriage 121 with one of three printing positions. The left sensor 706l is located near the left end of the movable range MR2 of the carriage 121, and the right sensor 706r is located to the right of the left sensor 706l.

[0067] The maintenance position sensor 707 of the second moving mechanism 72 is a sensor for aligning the carriage 121 at the maintenance position. The maintenance position sensor 707 is located near the right end of the movable range MR2 of the carriage 121.

[0068] The detection plate PT and detection plate pt of the second moving mechanism 72 are each flat plates that are fixed to the end face of the carriage 121 on the downstream side in the transport direction and extend in a plane perpendicular to the transport direction. The detection plate PT is fixed to the carriage 121 at the left end in the medium width direction. The detection plate pt is fixed to the carriage 121 at the right end in the medium width direction.

[0069] The controller 80 (FIG. 7) performs overall control of each part of the printer 100. The controller 80 is connected to an external device (not shown) such as a PC so as to be able to communicate data, and controls each part of the printer 100 based on print data sent from the external device, thereby forming an image on the medium PM according to the print data.

[0070] The controller 80 has a CPU 81, a ROM 82, a RAM 83, and an EEPROM (registered trademark) 84. The ROM 82 stores various data necessary for the operation of the controller 80. The RAM 83 is a working memory for the CPU 81. The EEPROM 84 stores control programs executed by the CPU 81, etc.

[0071] The controller 80 controls the driver IC 85 of the head HD and the feed motor M via an ASIC (not shown). 31 , winding motor M 32, the conveying motor M4, the stepping motor 704 of the first moving mechanism 71, and the stepping motor 704 of the second moving mechanism 72. The controller 80 is further connected to the left sensor 706l, the right sensor 706r, and the maintenance position sensor 707 of each of the first moving mechanism 71 and the second moving mechanism 72.

[0072] [Printing method] Printing (image formation) on the medium PM using the printer 100 is performed as follows.

[0073] When the printer 100 prints on the medium PM, the controller 80 controls each part of the printer 100 to cause the printer 100 to perform a transport process of transporting the medium PM in the transport direction and an ejection process of ejecting ink from the head unit 10 onto the medium PM.

[0074] In the conveying process, the controller 80 controls the feeding motor M 31 , winding motor M 32 , and conveyance motor M4 are driven to rotate feed shaft 31, take-up shaft 32, and conveyance roller pairs 41 and 42, thereby sending medium PM downstream in the conveyance direction.

[0075] In the ejection process, the controller 80 drives the drive elements DE in a manner corresponding to the print data received from an external device such as a PC, causing ink droplets to be ejected from the head HD toward the medium PM supported by the transport surface CS in the transport path CR. When the ink droplets land on the medium PM, an image corresponding to the print data is formed on the medium PM.

[0076] The controller 80 causes the printer 100 to execute the transport process and the ejection process in parallel, thereby forming an image on the medium PM.

[0077] [Move the head assembly HDA to the printing position] The printer 100 of this embodiment uses three print positions as the positions of the head assembly HDA when printing on the medium PM (i.e., the positions of the head assembly HDA when performing the ejection process to form an image on the medium PM). The three print positions are a right print position, a center print position, and a left print position.

[0078] When the head assembly HDA is in the right printing position (upper row in Figure 8), the area to the right of the medium placement area MA (i.e., the area on the transport surface CS where the medium PM can be placed) of the rightmost head HD in the first row L1, and the entire rightmost head HD in the second row L2, are located outside the right of the medium placement area MA. Note that the dimension of the medium placement area MA in the medium width direction is the maximum dimension in the medium width direction of the medium PM that can be transported via the transport path CR.

[0079] When the head assembly HDA is in the central printing position (middle row in Figure 8), the area to the left of the medium placement area MA of the leftmost head HD in the first row L1 and the area to the right of the medium placement area MA of the rightmost head HD in the second row L2 are located outside the medium placement area MA. When the head assembly HDA is in the central printing position, the center position of the head assembly HDA in the medium width direction (the center position of the area spanning from the leftmost nozzle NZ of the leftmost head HD to the rightmost nozzle NZ of the rightmost head HD) coincides with the center position of the medium width direction of the medium placement area MA.

[0080] When the head assembly HDA is in the left printing position (lower row in FIG. 8), the entire head HD at the left end of the first row L1 and the portion of the head HD at the left end of the second row L2 that is to the left of the medium placement area MA are located outside the medium placement area MA. Note that in this embodiment, for heads HD that are only partially located outside the medium placement area MA at each printing position, an area that is half the length of the head HD in the medium width direction is located outside the medium placement area MA.

[0081] In this embodiment, the distance (shift amount) in the medium width direction between the head assembly HDA at the right printing position and the head assembly HDA at the center printing position, and the distance (shift amount) in the medium width direction between the head assembly HDA at the center printing position and the head assembly HDA at the left printing position, are each equal to the length of the head HD in the medium width direction. In this specification and the present invention, the "head length in the medium width direction" refers to the distance along the medium width direction from the nozzle at one end of the head in the medium width direction to the nozzle at the other end of the head in the medium width direction. Note that the distance (shift amount) in the medium width direction between the head assembly HDA at the right printing position and the head assembly HDA at the center printing position, and the distance (shift amount) in the medium width direction between the head assembly HDA at the center printing position and the head assembly HDA at the left printing position, are not limited to the above and may be any value, and may even be different from each other. The right printing position, center printing position, and left printing position can be set so that all of the nozzles NZ of the head assembly HDA are positioned within the medium placement area MA at at least three printing positions.

[0082] Note that the printer 100 of this embodiment uses the center printing position in normal printing processes, and uses the right and left printing positions in initial settings (described in detail below). This is because in the initial settings, it becomes necessary to eject ink from nozzles NZ located outside the medium placement area MA at the center printing position. Alternatively, the printer 100 of this embodiment may use the right and left printing positions in normal printing processes. For example, if a problem such as poor ejection occurs with some of the nozzles used at the center printing position, the problem can be resolved or mitigated by using the right and left printing positions.

[0083] The following describes the movement of the head assembly HDA from the maintenance position to each of the right printing position, the center printing position, and the left printing position, and the movement of the head assembly HDA from one of the right printing position, the center printing position, and the left printing position to the maintenance position. The description will be given using an example in which the controller 80 controls the first movement mechanism 71 to move the head assembly HDA of the first head unit 11. The controller 80 also controls the second movement mechanism 72 to move the head assembly HDA of the second head unit 12 in the same procedure as described below. The controller 80 may control the first movement mechanism 71 to move the head assembly HDA of the first head unit 11 and the second movement mechanism 72 to move the head assembly HDA of the second head unit 12 at the same timing, or may perform these movements independently at different timings.

[0084] (1) Move to the right printing position When moving the head assembly HDA of the first head unit 11 from the maintenance position to the right printing position (upper part of FIG. 8), the controller 80 first rotates the stepping motor 704 of the first movement mechanism 71 in the forward direction to move the carriage 111 (and thus the head assembly HDA) leftward in the medium width direction. The controller 80 moves the carriage 111 leftward in the medium width direction at a first speed V1 to a position (FIG. 9(a)) where the detection target plate PT fixed to the carriage 111 blocks light from the light-emitting element EM of the right sensor 706r and the right sensor 706r changes from a light-receiving state to a light-blocking state. The light-receiving state of the sensors 706r and 706l is a state in which the light-receiving elements RC of the sensors 706r and 706l receive light from the light-emitting element EM, and is an example of an "off state." The light-blocking state of the sensors 706r and 706l is a state in which the light-receiving elements RC of the sensors 706r and 706l do not receive light from the light-emitting elements EM, and is an example of an "on state." Hereinafter, the position at which the right sensor 706r changes from the light-receiving state to the light-blocking state will be referred to as the right sensor light-blocking position (FIG. 10). The controller 80 can determine that the carriage 111 has reached the right sensor light-blocking position based on the change in the signal from the right sensor 706r from a light-receiving signal to a light-blocking signal.

[0085] The controller 80 may move the carriage 111 at a constant speed over the entire range from the maintenance position to the right sensor light-shielding position. Alternatively, the controller 80 may change the speed of the carriage 111 as it moves from the maintenance position to the right sensor light-shielding position. For example, the controller 80 may accelerate the carriage 111, which starts moving leftward from the maintenance position, to a maximum speed and then decelerate it to reach the right sensor light-shielding position. If the speed of the carriage 111 (head assembly HDA) is constant over the entire range from the maintenance position to the right sensor light-shielding position, the constant speed is the first speed V1. If the speed of the carriage 111 (head assembly HDA) changes over the range from the maintenance position to the right sensor light-shielding position, the average speed from the maintenance position to the right sensor light-shielding position is the first speed V1.

[0086] Next, from the point when the carriage 111 reaches the right sensor light-blocking position, the controller 80 rotates the stepping motor 704 in the forward direction by the number of steps S1 at a rotational speed at which the carriage 111 moves at a second speed V2 that is slower than the first speed V1. As a result, the carriage 111 moves to the left in the medium width direction at the second speed V2 that is slower than the first speed V1, and reaches the right printing position. When the carriage 111 is in the right printing position, the left end of the detection target plate PT is located between the left sensor 706l and the right sensor 706r, and the right end of the detection target plate PT is located to the right of the right sensor 706r. Therefore, the left sensor 706l is in a light-receiving state, and the right sensor 706r is in a light-blocking state (FIG. 9(b)).

[0087] (2) Move to the central printing position When moving the head assembly HDA of the first head unit 11 from the maintenance position to the central printing position (middle row in FIG. 8), the controller 80 first rotates the stepping motor 704 of the first movement mechanism 71 in the forward direction to move the carriage 111 (and thus the head assembly HDA) leftward in the medium width direction. The controller 80 moves the carriage 111 leftward in the medium width direction at a first speed V1 to a position (FIG. 9(c)) where the detection target plate PT fixed to the carriage 111 blocks light from the light-emitting element EM of the left sensor 706l and the left sensor 706l changes from a light-receiving state to a light-blocking state. Hereinafter, the position where the left sensor 706l changes from a light-receiving state to a light-blocking state is referred to as the left sensor light-blocking position (FIG. 10). The controller 80 can determine that the carriage 111 has reached the left sensor light-blocking position based on the change in the signal from the left sensor 706l from a light-receiving signal to a light-blocking signal. In this embodiment, the dimension of the detection plate PT in the medium width direction is greater than the separation distance in the medium width direction between the right sensor 706r and the left sensor 706l. Therefore, when the carriage 111 reaches the left sensor light-blocking position, the right sensor 706r is also in a light-blocking state.

[0088] The controller 80 may move the carriage 111 at a constant speed over the entire range from the maintenance position to the left sensor light-shielding position. Alternatively, the controller 80 may change the speed of the carriage 111 in the process from the maintenance position to the left sensor light-shielding position. If the speed of the carriage 111 (head assembly HDA) is constant over the entire range from the maintenance position to the left sensor light-shielding position, the constant speed is the first speed V1. If the speed of the carriage 111 (head assembly HDA) changes over the process from the maintenance position to the left sensor light-shielding position, the average speed from the maintenance position to the left sensor light-shielding position is the first speed V1.

[0089] Next, from the point when the carriage 111 reaches the left sensor light-shielding position, the controller 80 rotates the stepping motor 704 in the forward direction by the number of steps S2 at a rotational speed at which the carriage 111 moves at a second speed V2 that is slower than the first speed V1. As a result, the carriage 111 moves leftward in the medium width direction at the second speed V2 that is slower than the first speed V1, and reaches the center printing position. When the carriage 111 is in the center printing position, the left end of the detection target plate PT is located to the left of the left sensor 706l, and the right end of the detection target plate PT is located to the right of the right sensor 706r. Therefore, both the left sensor 706l and the right sensor 706r are in a light-shielding state (FIG. 9(d)).

[0090] (3) Move to left printing position When moving the head assembly HDA of the first head unit 11 from the maintenance position to the left printing position (lower part of FIG. 8), the controller 80 first rotates the stepping motor 704 of the first movement mechanism 71 in the forward direction to move the carriage 111 (and thus the head assembly HDA) leftward in the medium width direction. The controller 80 moves the carriage 111 leftward in the medium width direction at a first speed V1 to a position (FIG. 9(e)) where the detection target plate PT fixed to the carriage 111 passes the light-emitting portion EM of the right sensor 706r, causing the right sensor 706r to change from a light-receiving state to a light-blocking state and then to return to the light-receiving state. Hereinafter, the position where the right sensor 706r changes from a light-receiving state to a light-blocking state and then to the light-receiving state again is referred to as the right sensor light-receiving position (FIG. 10). The controller 80 can determine that the carriage 111 has reached the right sensor light-receiving position based on the signal from the right sensor 706r changing from a light-receiving signal to a light-blocking signal and then changing back to a light-receiving signal. In this embodiment, the left sensor 706l is in a light-blocking state when the carriage 111 reaches the right sensor light-receiving position.

[0091] The controller 80 may move the carriage 111 at a constant speed over the entire range from the maintenance position to the right sensor re-light-receiving position. Alternatively, the controller 80 may change the speed of the carriage 111 in the process from the maintenance position to the right sensor re-light-receiving position. If the speed of the carriage 111 (head assembly HDA) is constant over the entire range from the maintenance position to the right sensor re-light-receiving position, the constant speed is the first speed V1. If the speed of the carriage 111 (head assembly HDA) changes over the process from the maintenance position to the right sensor re-light-receiving position, the average speed from the maintenance position to the right sensor re-light-receiving position is the first speed V1.

[0092] Next, from the point when the carriage 111 reaches the right sensor light-receiving position, the controller 80 rotates the stepping motor 704 in the forward direction by step number S3 at a rotational speed at which the carriage 111 moves at a second speed V2 that is slower than the first speed V1. As a result, the carriage 111 moves leftward in the medium width direction at the second speed V2 that is slower than the first speed V1, and reaches the left printing position. When the carriage 111 is in the left printing position, the left end of the detection target plate PT is located to the left of the left sensor 706l, and the right end of the detection target plate PT is located between the left sensor 706l and the right sensor 706r (FIG. 9(f)). Therefore, the left sensor 706l is in a light-blocking state, and the right sensor 706r is in a light-receiving state.

[0093] The movement of the head assembly HDA described above will be summarized with reference to FIG. 10. When the head assembly HDA is moved from the maintenance position to the right printing position, as shown in the upper part of FIG. 10, it moves to the right sensor light-blocking position at a first speed V1, and then rotates the stepping motor 704 by the number of steps S1 to move it to the right printing position at a second speed V2. When the head assembly HDA is moved from the maintenance position to the center printing position, as shown in the middle part of FIG. 10, it moves to the left sensor light-blocking position at the first speed V1, and then rotates the stepping motor 704 by the number of steps S2 to move it to the center printing position at the second speed V2. When the head assembly HDA is moved from the maintenance position to the left printing position, as shown in the lower part of FIG. 10, it moves to the right sensor light-receiving position at the first speed V1, and then rotates the stepping motor 704 by the number of steps S3 to move it to the left printing position at the second speed V2.

[0094] The right printing position is an example of the "first position," the center printing position is an example of the "second position," and the left printing position is an example of the "third position." Also, the right sensor light-blocking position is an example of the "first reserve position," the left sensor light-blocking position is an example of the "second reserve position," and the right sensor light-receiving position is an example of the "third reserve position."

[0095] (4) Move to the maintenance position When moving the head assembly HDA of the first head unit 11 to the maintenance position, the controller 80 first rotates the stepping motor 704 of the first movement mechanism 71 in the reverse direction to move the carriage 111 to the right in the medium width direction at a first speed V1. The controller 80 continues moving the carriage 111 to the right in the medium width direction at the first speed V1 until the output signal of the maintenance position sensor 707 becomes a light-blocking signal. After that, after the output signal of the maintenance position sensor 707 changes to a light-blocking signal, the controller 80 rotates the stepping motor 704 in the reverse direction a predetermined number of steps from that point onward so that the carriage 111 is decelerated and moves at a third speed V3. As a result, the carriage 111 moves to the right in the medium width direction at a third speed V3 that is slower than the first speed V1 and reaches the maintenance position. The third speed V3 may be the same as the second speed V2 or may be different from the second speed V2.

[0096] [Initial adjustment of Printer 100] The following describes the initial adjustments that are performed when starting operation of the printer 100. The initial adjustments are performed after the printer 100 is installed and before printing of a desired image onto a medium PM using the printer 100 is started.

[0097] As shown in the flowchart of FIG. 11, the initial adjustment of the printer 100 includes a print position setting step S1, an alignment step S2, and an image quality adjustment step S3.

[0098] In the print position setting step S1, the controller 80 sets three print positions (i.e., right print position, center print position, and left print position) for each of the carriage 111 of the first head unit 11 and the carriage 121 of the second head unit 12 to appropriate positions.

[0099] In the printer 100 of this embodiment, the left sensor 706l and the right sensor 706r of each of the first moving mechanism 71 and the second moving mechanism 72 are fixed to the housing 90. The detected plate PT of the first moving mechanism 71 is fixed to the carriage 111 of the first head unit 11, and the detected plate PT of the second moving mechanism 72 is fixed to the carriage 121 of the second head unit 12. Therefore, the right sensor light-blocking position (FIG. 9(a)), left sensor light-blocking position (FIG. 9(c)), and right sensor light-receiving position (FIG. 9(e)) of each of the carriages 111 and 121 are determined based on the physical configuration of the printer 100 (i.e., the positions of each sensor and detected plate).

[0100] On the other hand, the right printing position (FIG. 9(b)) is the position of the carriages 111, 121 after the stepping motor 704 has rotated forward by step number S1 from the point at which the carriages 111, 121 reached the right sensor light-shielding position. Similarly, the central printing position (FIG. 9(d)) is the position of the carriages 111, 121 after the stepping motor 704 has rotated forward by step number S2 from the point at which the carriages 111, 121 reached the left sensor light-shielding position. Similarly, the left printing position (FIG. 9(f)) is the position of the carriages 111, 121 after the stepping motor 704 has rotated forward by step number S3 from the point at which the carriages 111, 121 reached the right sensor light-receiving position. Therefore, by appropriately setting the values of step numbers S1, S2, and S3 used by the controller 80 to control the stepping motor 704, the right printing position, central printing position, and left printing position can be set to appropriate positions.

[0101] The specific procedure for setting the print position will be described using as an example a case where the controller 80 sets the number of steps S1, S2, and S3 used to control the first movement mechanism 71. The controller 80 also sets the number of steps S1, S2, and S3 used to control the second movement mechanism 72 using a similar procedure.

[0102] First, the controller 80 rotates the stepping motor 704 of the first moving mechanism 71 in the forward direction to move the carriage 111 to the left. At this time, the controller 80 calculates the number of steps of the stepping motor 704 required to move the carriage 111 from the right sensor light-shielding position to the left sensor light-shielding position (measurement step number MS 12 10). Furthermore, the controller 80 calculates the number of steps of the stepping motor 705 required for the carriage 111 to move from the left sensor light-shielding position to the right sensor light-receiving position based on the number of output pulses output from the stepping motor 704 (measurement step number MS 23 ) is measured.

[0103] Next, the controller 80 determines the number of measurement steps MS 12 , the number of steps S2, and the number of steps required to move from the right printing position to the center printing position (design number of steps DS 12 ) and calculate the number of steps S1 using (Equation 1). S1 = S2 + (MS 12 -DS 12 )...(Formula 1)

[0104] Here, the number of design steps DS 12 is a value stored as a design value, for example, in ROM 82. The right print position, the center print position, and the distance between them are determined by design, and the number of steps required to move from the right print position to the center print position is also a fixed value determined based on the design. The number of steps S2 is input, for example, by an operator. The operator may input the design value for the number of steps S2 as is, or may input the design value after correcting it so that the center print position is the design position.

[0105] Next, the controller 80 determines the number of measurement steps MS 23 , the number of steps S2, and the number of steps required to move from the center printing position to the left printing position (design number of steps DS 23 ) and calculate the number of steps S3 using (Equation 2). S3 = S2 + (DS23 -MS 23 )...(Formula 2)

[0106] Here, the number of design steps DS 23 is a design value stored, for example, in ROM 82. The center print position, left print position, and the distance between them are determined by design, and the number of steps required to move from the center print position to the left print position is also a fixed value determined based on the design.

[0107] The controller 80 stores the calculated step numbers S1 and S3 together with the step number S2 used in the calculation in the ROM 82. The controller 80 also sets the calculated step numbers S1 and S3 and the step number S2 used in the calculation as the step numbers S1, S2, and S3 used in controlling the first moving mechanism 71.

[0108] In the above method, the step numbers S1 and S3 are calculated based on the actual measured step number MS 12 , M.S. 23 and the design value of the number of steps S2 and the design number of steps DS 12 , D.S. 23 Therefore, even if at least one of the right sensor light-blocking position, left sensor light-blocking position, and right sensor light-receiving position is shifted from the designed position due to the influence of an assembly error between the components that make up the printer 100, the influence of the shift can be suppressed and the interval between each printing position can be set appropriately.

[0109] In the alignment step S2, an operator aligns the position of the image formed on the medium PM by the head assembly HDA of the first head unit 11 with the position of the image formed on the medium PM by the head assembly HDA of the second head unit 12.

[0110] The alignment step S2 is performed with both the head assembly HDA of the first head unit 11 and the head assembly HDA of the second head unit 12 positioned at either the right print position, the center print position, or the left print position. The print position setting step S1 described above has appropriately set the positional relationship between the three print positions in each of the first head unit 11 and the second head unit 12. Therefore, once alignment is performed for any one of the three print positions, alignment is also completed for the remaining two print positions.

[0111] In the alignment step S2, the worker first forms a test pattern image using the head assembly HDA of the first head unit 11, and forms a test pattern image using the head assembly HDA of the second head unit 12, via the controller 80. Next, the worker scans and captures each of the formed images, and inputs the acquired image data into the controller 80. Based on the input image data, the controller 80 calculates the amount of misalignment in the medium width direction between the reference nozzles of the first head unit 11 and the reference nozzles of the second head unit 12, i.e., the amount of positional misalignment in the medium width direction between the image formed by the head assembly HDA of the first head unit 11 and the image formed by the head assembly HDA of the second head unit 12.

[0112] Thereafter, based on the calculated amount of misalignment, the controller 80 selects the nozzles NZ to be used for image formation for each of the head assemblies HDA of the first head unit 11 and the head assemblies HDA of the second head unit 12. For example, the controller 80 selects the nozzles to be used for image formation so that the nozzles NZ to be used for image formation among the multiple nozzles NZ in the head assembly HDA of the first head unit 11 and the nozzles NZ to be used for image formation among the multiple nozzles NZ in the head assembly HDA of the second head unit 12 are positioned within the same region in the medium width direction. This aligns the position of the image formed on the medium PM by the head assembly HDA of the first head unit 11 with the position of the image formed on the medium PM by the head assembly HDA of the second head unit 12. In addition, the controller 80 may align the position of the image formed on the medium PM by the head assembly HDA of the first head unit 11 with the position of the image formed on the medium PM by the head assembly HDA of the second head unit 12 by adjusting the number of steps S1 to S3 used to move the first head unit 11 and / or the number of steps S1 to S3 used to move the second head unit 12 based on the calculated amount of positional deviation.

[0113] In the image quality adjustment step S3, the controller 80 adjusts the image quality of the image formed by the head assembly HDA of the first head unit 11, and adjusts the image quality of the image formed by the head assembly HDA of the second head unit 12.

[0114] The specific procedure of the image quality adjustment step S3 will be described using as an example a case where the controller 80 adjusts the image quality of the first head unit 11. The controller 80 also adjusts the image quality of the second head unit 12 in the same manner as below.

[0115] The controller 80 moves the head assembly HDA of the first head unit 11 from the maintenance position to the right printing position, and forms a test image on the medium PM using the head assembly HDA at the right printing position. Next, the controller 80 moves the head assembly HDA of the first head unit 11 to the maintenance position, and then moves it from the maintenance position to the center printing position. Then, the controller 80 forms a test image on the medium PM using the head assembly HDA at the center printing position. Next, the controller 80 moves the head assembly HDA of the first head unit 11 to the maintenance position, and then moves it from the maintenance position to the left printing position. Then, the controller 80 forms a test image on the medium PM using the head assembly HDA at the left printing position. Thereafter, the controller 80 adjusts the image quality of the image formed by the head assembly HDA of the first head unit 11 based on the three formed test images (specifically, for example, setting the voltage input to the drive elements DE). In this way, by forming a test image at each of the three printing positions and adjusting the image quality based on this, ink is ejected from all of the nozzles NZ of the head assembly HDA, allowing for better image quality adjustment.

[0116] The advantageous effects of the printer 100 of this embodiment and the method of moving the head unit 10 executed by the controller 80 in the printer 100 are summarized below.

[0117] In the printer 100 and movement method of this embodiment, two sensors (a right sensor 706r and a left sensor 706l) are used to move the head assembly HDA to three printing positions. The stepping motor 704 is rotated forward to move the head assembly HDA at a first speed V1 until the head assembly HDA reaches the light-blocking position or the light-receiving position of either of the two sensors. From the light-blocking position or the light-receiving position of either of the two sensors, the stepping motor 704 is rotated forward a predetermined number of steps to move the head assembly HDA at a second speed V2 (< the first speed V1).

[0118] The printer 100 and movement method of this embodiment use two sensors to move the head assembly HDA to each of the three printing positions, allowing it to move the head assembly HDA quickly and accurately to each of the three printing positions. For example, in a comparative example equipped with only the right sensor 706r, movement of the head assembly HDA to not only the right printing position but also the center printing position and left printing position is achieved by moving the head assembly HDA from the right sensor light-blocking position at a slower second speed V2. In this case, as shown in FIG. 10 , the distance between the right sensor light-blocking position and the center printing position or left printing position is large, making it difficult to quickly move the head assembly HDA to the center printing position or left printing position. It should be noted that, after the right sensor 706r enters a light-blocking state, it is possible to shorten the time required for movement by moving the head assembly HDA from the right sensor light-blocking position to the center printing position or left printing position at the first speed V1 partway. However, the faster the movement speed from the right sensor light-blocking position, the lower the accuracy of alignment to each printing position. In other words, from the viewpoint of ensuring the accuracy of alignment to each printing position, it is not desirable to move the head assembly HDA from the right sensor light blocking position at the first speed V1.

[0119] Furthermore, in a comparative example including only the left sensor 706l, the head assembly HDA is moved not only to the center printing position but also to the right and left printing positions by moving at a slow second speed V2 from the left sensor light-blocking position. However, because the distance between the left sensor light-blocking position and the right or left printing position is large, it is difficult to quickly move the head assembly HDA to the right or left printing position. It is possible to shorten the time required for movement by moving the head assembly HDA from the left sensor light-blocking position to the right or left printing position at the first speed V1 partway after the left sensor 706l enters the light-blocking state. However, the higher the movement speed from the left sensor light-blocking position, the lower the accuracy of alignment to each printing position, so it is not desirable to move the head assembly HDA from the left sensor light-blocking position at the first speed V1. Furthermore, when moving the head assembly HDA to the right printing position, the rotation direction (forward direction) of the stepping motor 704 when moving the head assembly HDA to the left sensor light-blocking position at the first speed V1 is different from the rotation direction of the stepping motor 704 when moving the head assembly HDA from the left sensor light-blocking position to the right printing position at the second speed V2. Therefore, the accuracy of aligning the head assembly HDA to the right printing position may decrease due to the influence of backlash between the rack gear 701 and the pinion gear 705.

[0120] 12, it is also possible to have a single optical sensor 706 and multiple detection plates PT1, PT2, and PT3. In this comparative embodiment, the head assembly HDA can be configured to move at a second speed V2 from a position where the optical sensor 706 is blocked for the first time (i.e., a position where the optical sensor is blocked by detection plate PT1) to the right printing position. In this configuration, the head assembly HDA can move at the second speed V2 from a position where the optical sensor 706 is blocked for the second and third times (i.e., a position where the optical sensor is blocked by detection plate PT2 and detection plate PT3) to the center printing position and the left printing position.

[0121] However, in this embodiment, the areas where the right sensor 706r, left sensor 706l, and detection plate PT are located are prone to ink mist generated by printing. If ink mist adheres to the sensor 706 or the detection plate PT, chattering may occur. Chattering is a phenomenon in which sensor output becomes unstable. For example, the optical sensor 706 repeatedly outputs an output indicating a light-blocking state and an output indicating a light-receiving state inaccurately. This phenomenon may be caused, for example, by ink mist adhering to the sensor. Therefore, in the configuration shown in FIG. 12, chattering is likely to cause erroneous detection of the position of the head assembly HDA. For example, if chattering occurs, the controller 80 may erroneously determine that the carriages 111 and 121 are located in a position where the optical sensor 706 is in the light-blocking state for the first time, even though the carriages 111 and 121 are located in a position where the optical sensor 706 is in the light-blocking state for the second and third times. Such problems caused by chattering can also occur when a comb-shaped detection material having a plurality of detection portions is used instead of a plurality of detection plates.

[0122] In contrast, the printer 100 and movement method of this embodiment use two sensors to move the head assembly HDA to the three printing positions, as described above, so there is no need to move the head assembly HDA over a long distance at the slow second speed V2, and there is no effect of backlash. Furthermore, because two sensors are used and control based on the sensor output is simple, the effects of chattering are also suppressed. Therefore, the printer 100 and movement method of this embodiment can quickly and accurately move the head assembly HDA to each of the three printing positions.

[0123] In the printer 100 and movement method of this embodiment, the detected material detected by the right sensor 706r and the detected material detected by the left sensor 706l (more specifically, the detected portion of the detected material that actually blocks light) are the same, and both are a single detected plate PT. In this way, by reducing the number of detected materials (and therefore the detected portions), the possibility of ink mist adhesion can be reduced, and the possibility of chattering can also be reduced.

[0124] In the printer 100 of this embodiment, the right sensor 706r and the left sensor 706l are fixed to the housing 90, not to the carriages 111 and 121. Therefore, there is no need to provide wiring for the right sensor 706r and the left sensor 706 between the housing 90, which is a fixed member, and the carriages 111 and 121, which are movable members. This is advantageous in that it does not require dealing with movement of the wiring that accompanies movement of the carriages 111 and 121, and the device configuration can be simplified.

[0125] In the printer 100 and movement method of this embodiment, the dimension of the detection plate PT in the medium width direction is greater than the separation distance in the medium width direction between the right sensor 706r and the left sensor 706l. When the head assembly HDA reaches the right sensor light re-receiving position, the left sensor 706l is in a light-blocking state. Therefore, when the right sensor 706r is in a light-receiving state, it is easy to determine whether the detection plate PT (and thus the head assembly HDA) is to the left or right of the right sensor 706r.

[0126] In the printer 100 and the movement method of this embodiment, the number of steps S2 and the number of design steps DS 12 , D.S. 23 and the number of measurement steps MS 12 , M.S. 23 The number of steps S1 and S3 is set based on the above. Therefore, the influence of assembly errors and the like can be suppressed, and the right print position, center print position, and left print position can be set accurately.

[0127] In the printer 100 and movement method of this embodiment, the print position is set not at the position where the right sensor 706r and the left sensor 706l respond, but at a position shifted by a distance corresponding to the steps S1 through S3 from the position where the right sensor 706r and the left sensor 706l respond. Therefore, by adjusting the steps S1 through S3, the print position can be fine-tuned without adjusting the physical positions of the right sensor 706r and the left sensor 706l. Furthermore, because the steps S1 and S3 are greater than the step S2, for example, even if the step S2 is adjusted to a smaller value, the step S1 and S3 do not become negative. If the step S1 or S3 were negative, it would be necessary to reverse the rotation direction of the stepping motor when moving from the right sensor light-blocking position to the right print position or from the right sensor light-receiving position to the left print position, which could result in backlash.

[0128] The printer 100 and movement method of this embodiment use three printing positions. Therefore, even though the dimension of the medium placement area MA in the medium width direction is shorter than the dimension of the head assembly HDA in the medium width direction, ink can be ejected from all of the nozzles NZ of the head assembly HDA to form an image. Note that the dimension of the head assembly HDA in the medium width direction is the distance in the medium width direction from the nozzle NZ located at one end of the head assembly HDA in the medium width direction to the nozzle NZ located at the other end in the medium width direction. In this way, being able to eject ink from all of the nozzles NZ is advantageous in that it can prevent clogging (ink solidification) in unused nozzles, changes in ink pressure propagation and ink droplets caused by such clogging, and ultimately a decrease in the quality of the formed image.

[0129] <Modification> The printer 100 and the movement method of this embodiment may also employ the following modifications.

[0130] In the printer 100 of the above embodiment, as shown in FIGS. 9(a) to 9(f), the length of the detection plate PT in the medium width direction is greater than the separation distance in the medium width direction between the left sensor 706l and the right sensor 706r. However, this is not limited to this. For example, as shown in FIGS. 13(a) to 13(f), the length of the detection plate PT in the medium width direction may be shorter than the separation distance in the medium width direction between the left sensor 706l and the right sensor 706r. The movement of the head assembly in this modified embodiment may be, for example, as shown in FIG. 14.

[0131] Specifically, when moving the head assembly HDA from the maintenance position to the right printing position, the controller 80 first moves the carriages 111 and 121 to the left in the medium width direction at a first speed V1 to the right sensor light-blocking position (FIG. 13(a)) where the right sensor 706r changes from a light-receiving state to a light-blocking state. The controller 80 then rotates the stepping motor 704 forward by the number of steps S1. This causes the carriage 111 to move to the left in the medium width direction at a second speed V2 that is slower than the first speed V1, and to reach the right printing position. When the carriages 111 and 121 are in the right printing position, the left end of the detection target plate PT is located between the left sensor 706l and the right sensor 706r, and the right end of the detection target plate PT is located to the right of the right sensor 706r. Therefore, the left sensor 706l is in the light-receiving state, and the right sensor 706r is in the light-blocking state (FIG. 13(b)).

[0132] When moving the head assembly HDA from the maintenance position to the central printing position, the controller 80 first moves the carriages 111 and 121 to the left in the medium width direction at a first speed V1 to the right sensor re-receiving position (FIG. 13(c)) where the right sensor 706r changes from a light-receiving state to a light-blocking state and then back to a light-receiving state. The controller 80 then rotates the stepping motor 704 forward by a number of steps S2. This causes the carriage 111 to move to the left in the medium width direction at a second speed V2 that is slower than the first speed V1, and to reach the central printing position. When the carriages 111 and 121 are in the central printing position, both the left and right ends of the detection target plate PT are located between the left sensor 706l and the right sensor 706r. Therefore, both the left sensor 706l and the right sensor 706r are in the light-receiving state (FIG. 13(d)).

[0133] When moving the head assembly HDA from the maintenance position to the center printing position, the controller 80 first moves the carriages 111 and 121 to the left in the medium width direction at a first speed V1 to the left sensor light-blocking position (FIG. 13(e)) where the left sensor 706l changes to a light-blocking state. The controller 80 then rotates the stepping motor 704 forward by a number of steps S3. This causes the carriage 111 to move to the left in the medium width direction at a second speed V2 that is slower than the first speed V1, and to reach the left printing position. When the carriages 111 and 121 are in the left printing position, the left edge of the detection target plate PT is located to the left of the left sensor 706l, and the right edge of the detection target plate PT is located between the left sensor 706l and the right sensor 706r. Therefore, the left sensor 706l is in a light-blocking state, and the right sensor 706r is in a light-receiving state (FIG. 13(f)).

[0134] In this modified embodiment, the right printing position is an example of the "first position," the center printing position is an example of the "third position," and the left printing position is an example of the "second position."

[0135] In the printer 100 of the above embodiment, the left sensor 706l and the right sensor 706r enter a light-blocking state (detection state) when the plate-shaped detection target plate PT blocks light from the light-emitting element EM. The maintenance position sensor 707 enters a light-blocking state (detection state) when the plate-shaped detection target plate PT blocks light from the light-emitting element EM. However, this is not limited to this. Instead of the plate-shaped detection target plates PT and pt, any detection target material, such as a block or pillar, can be used. Furthermore, the left sensor 706l, the right sensor 706r, and the maintenance position sensor 707 may each be configured to enter a detection state (an example of an "ON state") when the light-receiving unit RC receives light from the light-emitting element EM reflected by a mirror provided on the detection target material. Furthermore, the left sensor 706l, the right sensor 706r, and the maintenance position sensor 707 are not limited to optical sensors. For example, they may be contact-type sensors that enter a detection state (an example of an "ON state") when their contacts come into contact with the detection target material.

[0136] In the printer 100 of the above embodiment, the right sensor 706r, the left sensor 706l, and the maintenance position sensor 707 are fixed to a frame (not shown) fixed to the housing 90, and the detection plates PT and pt are fixed to the carriages 111 and 121, but this is not limiting. At least one of the right sensor 706r, the left sensor 706l, and the maintenance position sensor 707 may be fixed to the carriages 111 and 121, and the corresponding detection plates PT and pt may be fixed to a frame (not shown) fixed to the housing 90. When the detection plate PT moves together with the carriages 111 and 121, the path of its movement is an example of a "path along the head movement direction." When the detection plate PT is fixed to the housing 90, the path of relative movement of the detection plate PT as seen from the right sensor 706r and the left sensor 706l located on the carriages 111 and 121 is an example of a "path along the head movement direction."

[0137] In the printer 100 of the above embodiment, the dimension of the medium placement area in the medium width direction is shorter than the dimension of the head assembly HDA in the medium width direction (i.e., the distance in the medium width direction from the nozzle NZ located at one end in the medium width direction to the nozzle NZ located at the other end in the medium width direction). However, this is not limited to this. The dimension of the medium placement area in the medium width direction may be the same as the dimension of the head assembly HDA in the medium width direction, or may be longer than the dimension of the head assembly HDA in the medium width direction.

[0138] In the printer 100 of the above embodiment, the separation distance in the medium width direction between the right sensor 706r and the left sensor 706l and the width in the medium width direction of the detected material (e.g., the detected plate PT) can be set arbitrarily based on how the positional relationship between the right printing position, the center printing position, and the left printing position is designed. The separation distance in the medium width direction between the right sensor 706r and the left sensor 706l may be greater or smaller than the width in the medium width direction of the detected material. Furthermore, the detected material detected by the right sensor 706r and the detected material detected by the left sensor 706l may be different detected materials positioned apart in the medium width direction.

[0139] In the printer 100 of the above embodiment, the maintenance unit 60 does not have to have at least one of the maintenance pan 61 and the nozzle cap 63. Also, the printer 100 of the above embodiment does not have to have the maintenance unit 60. In a mode in which the maintenance unit 60 is not included, the movement mechanism 70 moves the head unit 10 between the printing position and a standby position to the right of the printing position. The area including the printing position is an example of an "image forming area," and the area including the maintenance position, standby position, etc. is an example of an "evacuation area."

[0140] In the printer 100 of the above embodiment, the direction in which the movement mechanism 70 moves the head unit 10 is the medium width direction, which is perpendicular to the transport direction, but this is not limited to this. The movement mechanism 70 may be configured to move the head unit 10 (and thus the head assembly HDA or head HD) between the image forming area and the retraction area, and the movement direction is arbitrary.

[0141] In the movement mechanism 70 of the printer 100 in the above embodiment, the driving force of the stepping motor 704 is transmitted to the carriages 111, 121 via the pinion gear 705 and the rack gear 701, but this is not limiting. The power transmission mechanism that transmits the driving force of the stepping motor 704 to the carriages 111, 121 may include any mechanism such as a gear, pulley, chain, or belt.

[0142] In the initial setting print position setting step S1 of the above embodiment, the design value is used as the number of steps S2, and the number of steps S1 and S3 is set to the actual measured value, the measured number of steps MS 12 , M.S. 23 and the design value of the number of steps S2 and the design number of steps DS 12 , D.S. 23 However, the calculation is not limited to this. A design value is used as one of the step numbers S1 to S3, and the remaining two are actual measurement values, that is, the measured step number MS 12 , M.S. 23 and one of the design step numbers S1 to S3 and the design step number DS 12 , D.S. 23 The calculation formula can be created appropriately based on the relationships shown in Figs. 10 and 14. Alternatively, the method for setting the number of steps S1 to S3 is arbitrary. For example, the number of measurement steps MS 12 , M.S. 23 The difference between these values and the design values (ideal values) (i.e., a value indicating the magnitude of the assembly error) may be calculated, and the design values (ideal values) of the step numbers S1 to S3 may be corrected based on the difference and used as the setting values for the step numbers S1 to S3.

[0143] In the above embodiment, the number of steps S2 is greater than the number of steps S1 and S3, but this is not limited to this. The magnitude relationship between the number of steps S1, S2, and S3 can be set arbitrarily. The number of steps S1 to S3 may be equal to one another.

[0144] The above has described the embodiment and modified examples using as an example a case where an image is formed on a medium PM by ejecting ink from the head unit 10. The head unit 10 may be a liquid ejection system that ejects any liquid for image formation, and the medium PM on which the image is formed may be, for example, paper, cloth, resin, etc.

[0145] The embodiments and modifications described herein are illustrative in all respects and should not be considered limiting. For example, the number and configuration of head assemblies HDA included in the head unit 10, and the number and configuration of heads HD included in the head assembly HDA, may be changed. If the head assembly HDA has a single head, descriptions regarding the position and dimensions of the head assembly HDA in the above embodiments and modifications may be read as descriptions regarding the position and dimensions of the head HD.

[0146] The number of colors that the printer 100 can print simultaneously is not limited, and the printer 100 may be configured to be capable of single-color printing only. The number and positions of the individual flow paths in the head HD, the number of nozzles NZ, and the number of nozzle rows may also be changed as appropriate. The resolution of the image formed by the head HD is also arbitrary, and may be, for example, 600 dpi or less or 1200 dpi or more.

[0147] The technical features described in each embodiment and modification can be combined with each other.

[0148] As long as the characteristics of the present invention are maintained, the present invention is not limited to the above-described embodiments, and other forms that can be conceived within the scope of the technical idea of the present invention are also included within the scope of the present invention.

[0149] (Addendum) It will be understood by those skilled in the art that the above embodiments and their modifications are specific examples of the following aspects.

[0150] (Item 1) a head that ejects liquid to form an image on a medium; a head moving mechanism that moves the head along a head moving direction between an image forming area on one end side of the head moving direction and a retreat area on the other end side of the head moving direction, a carriage supporting the head; A stepping motor; a power transmission mechanism connected to the carriage and the stepping motor and configured to transmit power of the stepping motor to the carriage; a first sensor and a second sensor that detect that the head is positioned in the image forming area, the first sensor and the second sensor each being turned off when the head is positioned in the evacuation area; a head moving mechanism including: a controller electrically connected to the stepping motor, the first sensor, and the second sensor; The controller When moving the head from the retraction area to a first position in the image forming area, the stepping motor is rotated in one direction to move the head toward the one end at a first speed up to a first preliminary position where the first sensor changes from an off state to an on state, and from the point where the head reaches the first preliminary position, the stepping motor is rotated in the one direction by a number of steps S1 to move the head to the first position at a second speed that is lower than the first speed, When moving the head from the retraction area to a second position in the image forming area that is different from the first position, the stepping motor is rotated in the one direction to move the head toward the one end at the first speed up to a second preliminary position where the second sensor changes from an off state to an on state, and from the point where the head reaches the second preliminary position, the stepping motor is rotated in the one direction by a number of steps S2 to move the head to the second position at the second speed, an image forming system in which, when moving the head from the retraction area to a third position in the image forming area that is different from the first position and the second position, the stepping motor is rotated in the one direction to move the head toward the one end at the first speed up to the third preliminary position where the first sensor, which has turned on when the head reaches the first preliminary position, changes to an off state again, and from the point where the head reaches the third preliminary position, the stepping motor is rotated in the one direction by step number S3 to move the head to the third position at the second speed.

[0151] (Item 2) Item 1. The image forming system according to item 1, wherein the distance between any two positions among the first position, the second position, and the third position that are adjacent to each other in the head movement direction is equal to the length of the head in the head movement direction.

[0152] (Item 3) a single detection object that moves relative to each of the first sensor and the second sensor on a path along the head movement direction; the first sensor is configured to switch between the on state and the off state based on a positional relationship with the detected material that moves relative to the first sensor on the path, 3. The image forming system according to item 1 or 2, wherein the second sensor is configured to switch between the on state and the off state based on a positional relationship with the detected material that moves relative to the second sensor on the path.

[0153] (Item 4) 4. The image forming system according to item 3, wherein the detection material is located on the carriage.

[0154] (Item 5) 5. The image forming system according to item 3 or 4, wherein the detection object is a plate-like member extending along the head movement direction.

[0155] (Item 6) the length of the plate-like member in the head movement direction is greater than the distance between the first sensor and the second sensor in the head movement direction, When the head is located at the second standby position, the first sensor is in an ON state, 6. The image forming system according to item 5, wherein the second standby position is located closer to the one end than the first standby position in the head movement direction, and the third standby position is located closer to the one end than the second standby position.

[0156] (Item 7) The controller The head is moved from the first preliminary position to the second preliminary position in the head movement direction, and the measured step number MS is the number of steps of the stepping motor required for this movement. 12 Measure the The head is moved from the second preliminary position to the third preliminary position in the head movement direction, and the measured step number MS is the number of steps of the stepping motor required for this movement. 23 Measure the the number of steps S2 and the number of measurement steps MS 12 The number of steps S1 is determined based on the number of steps S2 and the number of measurement steps MS 23 7. The image forming system according to item 6, wherein the number of steps S3 is determined based on the following.

[0157] (Item 8) The controller The number of steps S2 and the number of measurement steps MS 12 and a design step number DS, which is a design value of the number of steps of the stepping motor required to move the head from the first position to the second position. 12 Based on this, the number of steps S1 is determined by the following formula: S1 = S2 + (MS 12 -DS 12 ) The number of steps S2 and the number of measurement steps MS 23and the number of design steps, which is the design value of the number of steps of the stepping motor required to move the head from the second position to the third position, is designated as DS 23 Based on this, the number of steps S3 is determined by the following formula: S3 = S2 + (DS 23 -MS 23 ) Item 8. The imaging system according to item 7.

[0158] (Item 9) 9. The image forming system according to any one of items 6 to 8, wherein the number of steps S1 and / or the number of steps S3 is greater than the number of steps S2.

[0159] (Item 10) 10. The image forming system according to any one of items 1 to 9, wherein the length of a medium placement area in which the medium is placed during image formation in the head movement direction is shorter than the length of the head.

[0160] (Item 11) The controller moving the head from the retraction area to any one of the first position, the second position, and the third position to form an image on the medium; Next, the head is moved to the retract area, Next, the head is moved from the retraction area to any one of the first position, the second position, and the third position, and image formation is performed on the medium.

[0161] (Item 12) the heads include a first head and a second head; the head movement mechanism includes a first head movement mechanism that moves the first head in the head movement direction, and a second head movement mechanism that moves the second head in the head movement direction; The image forming system described in any one of items 1 to 11, wherein the controller is electrically connected to the first sensor, the second sensor, and the stepping motor of each of the first head moving mechanism and the second head moving mechanism.

[0162] (Item 13) Item 13. The image forming system according to item 12, wherein the controller detects the amount of deviation in the head movement direction between the reference nozzles of the first head and the reference nozzles of the second head, and determines the nozzles to be used for image formation by the first head and / or the nozzles to be used for image formation by the second head based on the amount of deviation.

[0163] (Item 14) 14. The image forming system according to any one of items 1 to 13, wherein the head moving mechanism further comprises a third sensor that detects that the head is positioned in the retraction area.

[0164] (Item 15) Item 15. The image forming system according to item 14, wherein the detected material used by the first sensor and the second sensor and the detected material used by the third sensor are positioned on the carriage, and the detected material used by the third sensor is positioned on the other end side of the head movement direction than the detected materials used by the first sensor and the second sensor.

[0165] (Item 16) a head that ejects liquid to form an image on a medium; a head moving mechanism that moves the head along a head moving direction between an image forming area on one end side of the head moving direction and a retreat area on the other end side of the head moving direction, a carriage supporting the head; A stepping motor; a power transmission mechanism connected to the carriage and the stepping motor and configured to transmit power of the stepping motor to the carriage; a first sensor and a second sensor that detect that the head is positioned in the image forming area, the first sensor and the second sensor each being turned off when the head is positioned in the evacuation area; a head moving mechanism including: a controller electrically connected to the stepping motor, the first sensor, and the second sensor, The controller: When moving the head from the retraction area to a first position in the image forming area, the stepping motor is rotated in one direction to move the head toward the one end at a first speed up to a first preliminary position where the first sensor changes from an off state to an on state, and once the head reaches the first preliminary position, the stepping motor is rotated in the one direction by a number of steps S1 to move the head to the first position at a second speed lower than the first speed; When moving the head from the retraction area to a second position in the image forming area that is different from the first position, the stepping motor is rotated in the one direction to move the head toward the one end at the first speed up to a second preliminary position where the second sensor changes from an off state to an on state, and from the point where the head reaches the second preliminary position, the stepping motor is rotated in the one direction by a number of steps S2 to move the head to the second position at the second speed. When moving the head from the retraction area to a third position in the image forming area that is different from the first position and the second position, the stepping motor is rotated in the one direction to move the head toward the one end at the first speed up to the third preliminary position where the first sensor, which has turned on when the head reaches the first preliminary position, changes to an off state again, and from the point where the head reaches the third preliminary position, the stepping motor is rotated in the one direction by step number S3 to move the head to the third position at the second speed. [Explanation of symbols]

[0166] 10 Head Unit 11 First head unit 12 Second head unit 111, 121 carriages 60 Maintenance Unit 70 Moving mechanism 71 1st movement mechanism 72 Second movement mechanism 701 Rack Gear 704 Stepping Motor 705 pinion gear 706r Right Sensor 706l Left sensor 707 Maintenance Position Sensor 80 Controller 100 printers HDA Head Assembly

Claims

1. a head that ejects liquid to form an image on a medium; a head moving mechanism that moves the head along a head moving direction between an image forming area on one end side of the head moving direction and a retreat area on the other end side of the head moving direction, a carriage supporting the head; A stepping motor; a power transmission mechanism connected to the carriage and the stepping motor and configured to transmit power of the stepping motor to the carriage; a first sensor and a second sensor that detect that the head is located in the image forming area, the first sensor and the second sensor each being turned off when the head is located in the evacuation area; a head moving mechanism including: a controller electrically connected to the stepping motor, the first sensor, and the second sensor; The controller When the head is moved from the retraction area to the first position in the image forming area, the stepping motor is rotated in one direction to move the head toward the one end at a first speed up to a first preliminary position where the first sensor changes from an off state to an on state, and from the point where the head reaches the first preliminary position, the stepping motor is rotated in one direction for a step number S １ and moving the head to the first position at a second speed that is slower than the first speed; When the head is moved from the retraction area to a second position in the image forming area that is different from the first position, the stepping motor is rotated in the one direction to move the head toward the one end at the first speed up to a second preliminary position where the second sensor changes from an off state to an on state, and from the point where the head reaches the second preliminary position, the stepping motor is rotated in the one direction for a step number S ２ rotate the head by a predetermined amount to move the head to the second position at the second speed; When the head is moved from the retraction area to a third position in the image forming area that is different from the first position and the second position, the stepping motor is rotated in the one direction to move the head toward the one end at the first speed up to the third preliminary position where the first sensor, which has been turned on as the head reaches the first preliminary position, changes to an off state again, and from the point where the head reaches the third preliminary position, the stepping motor is rotated in the one direction for a number of steps S ３ and rotate the head by only one rotation to move the head to the third position at the second speed.

2. 2. The image forming system according to claim 1, wherein the distance between any two adjacent positions among the first position, the second position, and the third position in the head movement direction is equal to the length of the head in the head movement direction.

3. a single detection object that moves relative to each of the first sensor and the second sensor on a path along the head movement direction; the first sensor is configured to switch between the on state and the off state based on a positional relationship with the detected material that moves relative to the first sensor on the path, 3. The image forming system according to claim 1, wherein the second sensor is configured to switch between the on state and the off state based on a positional relationship with the detected material that moves relative to the second sensor on the path.

4. 4. The image forming system according to claim 3, wherein the material to be detected is located on the carriage.

5. 4. The image forming system according to claim 3, wherein the detection material is a plate-like member extending along the head movement direction.

6. the length of the plate-like member in the head movement direction is greater than the distance between the first sensor and the second sensor in the head movement direction, When the head is located at the second standby position, the first sensor is in an ON state, 6. The image forming system according to claim 5, wherein the second standby position is located closer to the one end than the first standby position in the head movement direction, and the third standby position is located closer to the one end than the second standby position.

7. The controller The head is moved from the first preliminary position to the second preliminary position in the head movement direction, and the measured step number MS is the number of steps of the stepping motor required for the movement. １２ Measure the The head is moved from the second preliminary position to the third preliminary position in the head movement direction, and the measured step number MS is the number of steps of the stepping motor required for this movement. ２３ Measure the The number of steps S ２ and the number of measurement steps MS １２ Based on this, the number of steps S １ is determined, and the number of steps S ２ and the number of measurement steps MS ２３ Based on this, the number of steps S ３ 7. The image forming system according to claim 6, wherein the image forming system determines:

8. The controller The number of steps S ２ and the number of measurement steps MS １２ and a design step number DS, which is a design value of the number of steps of the stepping motor required to move the head from the first position to the second position. １２ Based on this, the number of steps S is calculated using the following formula: １ Determine S １ =S ２ +(MS １２ -DS １２ ) The number of steps S ２ and the number of measurement steps MS ２３ and DS is the number of design steps, which is the design value of the number of steps of the stepping motor required to move the head from the second position to the third position. ２３ Based on this, the number of steps S is calculated using the following formula: ３ Determine S ３ =S ２ +(DS ２３ -MS ２３ ) The image forming system according to claim 7 .

9. The number of steps S １ and / or the number of steps S ３ is the number of steps S ２ 7. The imaging system of claim 6, wherein the imaging system is larger than

10. 3. The image forming system according to claim 1, wherein a length of a medium placement area in which the medium is placed during image formation in the head movement direction is shorter than a length of the head.

11. The controller moving the head from the retraction area to any one of the first position, the second position, and the third position to form an image on the medium; Next, the head is moved to the retract area, 3. The image forming system according to claim 1, wherein the head is then moved from the retraction area to any other one of the first position, the second position, and the third position to form an image on the medium.

12. the heads include a first head and a second head; the head moving mechanism includes a first head moving mechanism that moves the first head in the head moving direction, and a second head moving mechanism that moves the second head in the head moving direction; 3. The image forming system according to claim 1, wherein the controller is electrically connected to the first sensor, the second sensor, and the stepping motor of each of the first head moving mechanism and the second head moving mechanism.

13. The image forming system of claim 12, wherein the controller detects the amount of deviation in the head movement direction between the reference nozzles of the first head and the reference nozzles of the second head, and determines the nozzles to be used for image formation by the first head and / or the nozzles to be used for image formation by the second head based on the amount of deviation.

14. 3. The image forming system according to claim 1, wherein the head moving mechanism further comprises a third sensor that detects that the head is positioned in the retraction area.

15. 15. An image forming system as described in claim 14, wherein the detected material used by the first sensor and the second sensor and the detected material used by the third sensor are positioned on the carriage, and the detected material used by the third sensor is positioned on the other end side of the head movement direction than the detected material used by the first sensor and the second sensor.

16. a head that ejects liquid to form an image on a medium; a head moving mechanism that moves the head along a head moving direction between an image forming area on one end side of the head moving direction and a retreat area on the other end side of the head moving direction, a carriage supporting the head; A stepping motor; a power transmission mechanism connected to the carriage and the stepping motor and configured to transmit power of the stepping motor to the carriage; a first sensor and a second sensor that detect that the head is located in the image forming area, the first sensor and the second sensor each being turned off when the head is located in the evacuation area; a head moving mechanism including: a head moving method used in an image forming system including the stepping motor, the first sensor, and a controller electrically connected to the second sensor, The controller: When the head is moved from the retraction area to the first position in the image forming area, the stepping motor is rotated in one direction to move the head toward the one end at a first speed up to a first preliminary position where the first sensor changes from an off state to an on state, and from the point where the head reaches the first preliminary position, the stepping motor is rotated in one direction for a step number S １ and moving the head to the first position at a second speed that is slower than the first speed. When the head is moved from the retraction area to a second position in the image forming area that is different from the first position, the stepping motor is rotated in the one direction to move the head toward the one end at the first speed up to a second preliminary position where the second sensor changes from an off state to an on state, and from the point where the head reaches the second preliminary position, the stepping motor is rotated in the one direction for a step number S ２ rotating the head by only a small amount to move the head to the second position at the second speed; When the head is moved from the retraction area to a third position in the image forming area that is different from the first position and the second position, the stepping motor is rotated in the one direction to move the head toward the one end at the first speed up to the third preliminary position where the first sensor, which has been turned on as the head reaches the first preliminary position, changes to an off state again, and from the point where the head reaches the third preliminary position, the stepping motor is rotated in the one direction for a number of steps S ３ and rotating the head by only one rotation to move the head to the third position at the second speed.

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