Liquid droplet ejection device

Abstract

To provide a liquid droplet discharge device which can determine an optimal discharge timing even when a discharge gap changes curvedly.SOLUTION: A liquid droplet discharge device includes: a carriage which reciprocates a recording head, which has a plurality of nozzles for discharging a liquid droplet to a recording medium supported by platen, in a predetermined direction; and a control part which controls a discharge timing of the liquid droplet so as to adhere to the recording medium in a plurality of positions in a reciprocation direction of the carriage. The control part includes: height measuring means which measures a height of a plurality of positions; change rate calculation means which calculates a height change rate corresponding to each of the plurality of positions on the basis of the height; an optimal position setting means which sets an optimal position for each of the plurality of positions of which the height is measured on the basis of the height change rate; and optimal discharge timing determination means which measures the height in the optimal position by the height measuring means, and determines an optimal discharge timing as an optimal discharge timing of the liquid droplet on the basis of the height in the optimal position.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a droplet ejection device. [Background technology]

[0002] Among devices that eject liquid ink in the form of droplets, there is known a droplet ejection device that ejects droplets toward a medium while moving a droplet ejection head back and forth in the width direction of the medium, which is a direction perpendicular to the transport direction of the medium. The droplet ejection head is mounted on a carriage that performs a main scan of the medium by moving back and forth in the width direction of the medium, and ejects droplets at a predetermined timing while performing a main scan by moving the carriage toward the medium transported over a platen. By attaching these droplets to the medium, an image (dots) is recorded on the medium and an image is formed.

[0003] Conventionally, in droplet ejection devices, the ejection gap, which is the relative distance between the platen and the carriage, can vary depending on the position in the main scanning direction due to the influence of carriage assembly errors and wear of the carriage sliding bearings over time.

[0004] If the ejection gap varies depending on the position in the main scanning direction, even if the recording head ejects droplets at the right timing for image formation, the ink will adhere to a position different from the ideal position for the droplets (ideal position), which will have a negative effect on stable high-quality image formation.

[0005] In addition to changes in the carriage over time, variations (fluctuations) in the ejection gap can also occur due to the effects of assembly errors in the platen, changes over time, etc. For example, variations in the ejection gap occur when the platen is tilted in the main scanning direction due to changes over time, or when the platen is configured by connecting multiple plate-like members in the main scanning direction and the inclination of each plate-like member in the main scanning direction differs.

[0006] As a technique for addressing the above-mentioned problem, a control technique is known that corrects the timing of droplet ejection from a print head according to the state of the ejection gap. For example, a control technique is known in which any position in the main scanning direction or the medium transport direction is set as a detection position for determining the optimal ejection timing, and the ejection timing at each detection position is corrected to be optimal (see Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0007] The technology disclosed in Patent Document 1 can correct variations (changes) in the ejection gap if they are linear, but to apply this technology to ejection gaps that change in a curved manner, it is not possible to determine the detection position for determining the ejection timing.

[0008] The present invention has been made in consideration of the above circumstances, and has an object to provide a droplet ejection device that can determine optimal ejection timing even if the ejection gap changes in a curved manner. [Means for solving the problem]

[0009] In order to solve the above technical problems, one aspect of the present invention relates to a droplet ejection device comprising: a carriage for reciprocating in a predetermined direction a recording head having a plurality of nozzles that eject droplets onto a recording medium supported by a platen; and a control unit for controlling the ejection timing of the droplets so that the droplets adhere to the recording medium at a plurality of positions in the reciprocating movement direction of the carriage, wherein the control unit comprises: a height measurement means for measuring height at the plurality of positions; a change rate calculation means for calculating a height change rate corresponding to each of the plurality of positions based on the height; an optimal position setting means for setting an optimal position for each of the plurality of positions where the height is measured based on the height change rate; and an optimal ejection timing determination means for measuring the height at the optimal position using the height measurement means, and determining an optimal ejection timing, which is the optimal ejection timing of the droplets, based on the height at the optimal position. Effect of the Invention

[0010] According to the present invention, even if the ejection gap changes in a curved manner, the optimal ejection timing can be determined. [Brief description of the drawings]

[0011] [Figure 1] 1 is a perspective view showing the overall configuration of an inkjet printer that is an embodiment of a droplet ejection device according to the present invention. [Diagram 2] FIG. 2 is a plan view showing a mechanism of the inkjet printer. [Diagram 3] 3A and 3B are plan views illustrating the operation of a recording head provided in the inkjet printer. [Figure 4] 5A to 5C are side views illustrating the operation of a recording head provided in the inkjet printer. [Diagram 5] FIG. 4 is an explanatory diagram showing an example of a test pattern formed by the inkjet printer. [Figure 6] FIG. 2 is an explanatory diagram showing a reading sensor included in the inkjet printer. [Figure 7] FIG. 2 is a block diagram showing the configuration of a control unit included in the inkjet printer. [Figure 8] 5A to 5C are diagrams showing examples of the shape of a platen according to the embodiment. [Figure 9] 6 is a flowchart showing the flow of a process for optimizing ejection timing executed by a control unit included in the inkjet printer. [Figure 10] 6 is a flowchart showing the flow of a process for optimizing ejection timing executed by a control unit included in the inkjet printer. [Figure 11] 10A and 10B are diagrams showing an example of setting a reference position in the optimization process. [Figure 12] 6A to 6C are diagrams showing examples of ejection timing at the reference position. [Figure 13] 11A and 11B are diagrams showing an example of a movement position set in the optimization process. [Figure 14]6A to 6C are diagrams showing examples of ejection timing at the above movement positions. [Figure 15] 13 is a diagram illustrating a state in which a gap fluctuation calculated based on the ejection timing related to the reference position and the movement position occurs locally. FIG. [Figure 16] 13A and 13B are diagrams illustrating examples of information of local changes identified based on optimized ejection timings related to the reference position and the movement position. [Figure 17] FIG. 13 is a diagram showing an example in which the gap variation of the reference position set in the optimization process is small. [Figure 18] 6A and 6B are diagrams showing an example of setting an optimal formation position in the optimization process. [Figure 19] 10A and 10B are diagrams showing an example of setting of formation positions that are set based on ejection timings optimized in the optimization process. [Figure 20] 8A to 8C are diagrams showing an example of settings of ejection timing optimized in the optimization process. [Figure 21] 8A to 8C are diagrams showing an example of settings of ejection timing optimized in the optimization process. [Figure 22] 8A to 8C are diagrams showing an example of settings of ejection timing optimized in the optimization process. [Figure 23] 10A to 10C are diagrams showing an example of setting of formation positions that are set based on ejection timings optimized in the optimization process. [Figure 24] 10A and 10B are diagrams showing an example of setting an optimized formation position in another embodiment of the inkjet printer. [Diagram 25] FIG. 10 is a diagram showing an example of setting an optimized formation position in still another embodiment of the inkjet printer. [Figure 26] FIG. 2 is a block diagram showing a detailed configuration of a control unit included in the inkjet printer. [Figure 27] FIG. 11 is a perspective view showing the overall configuration of an inkjet printer that is another embodiment of a droplet ejection device according to the present invention. [Figure 28] FIG. 2 is a block diagram showing the configuration of a control unit included in the inkjet printer. [Figure 29]FIG. 2 is a block diagram showing a detailed configuration of a control unit included in the inkjet printer. [Diagram 30] 6 is a flowchart showing a flow of a discharge timing optimization process and an air volume adjustment process executed by a control unit of the inkjet printer. [Diagram 31] 6 is a flowchart showing a flow of a discharge timing optimization process and an air volume adjustment process executed by a control unit of the inkjet printer. [Diagram 32] 6 is a flowchart showing a flow of a discharge timing optimization process and an air volume adjustment process executed by a control unit of the inkjet printer. [Diagram 33] 10A to 10C are diagrams showing an example of a formation position that is set based on the ejection timing optimized in the optimization process, and an example of an air volume adjustment mode. [Diagram 34] 13A and 13B are diagrams showing an example of a formation position that is set based on the ejection timing optimized in the optimization process, and another example of a mode of air volume adjustment. [Diagram 35] 13A and 13B are diagrams showing an example of a formation position that is set based on the ejection timing optimized in the optimization process, and another example of a mode of air volume adjustment. [Diagram 36] 4A to 4C are diagrams illustrating a platen gap and air volume adjustment in the inkjet printer. [Figure 37] 13A and 13B are diagrams showing an example of a formation position that is set based on the ejection timing optimized in the optimization process, and another example of a mode of air volume adjustment. [Figure 38] 13A and 13B are diagrams showing an example of a formation position that is set based on the ejection timing optimized in the optimization process, and another example of a mode of air volume adjustment. [Figure 39] 13A and 13B are diagrams showing an example of a formation position that is set based on the ejection timing optimized in the optimization process, and another example of a mode of air volume adjustment. [Diagram 40] 13A and 13B are diagrams showing an example of a formation position that is set based on the ejection timing optimized in the optimization process, and another example of a mode of air volume adjustment. [Diagram 41]13A and 13B are diagrams showing an example of a formation position that is set based on the ejection timing optimized in the optimization process, and another example of a mode of air volume adjustment. [Diagram 42] 5A and 5B are diagrams illustrating the influence of the platen gap and the air volume in the inkjet printer. [Diagram 43] 5A and 5B are diagrams illustrating the influence of the platen gap and the air volume in the inkjet printer. [Diagram 44] 5A and 5B are diagrams illustrating the influence of the platen gap and the air volume in the inkjet printer. [Diagram 45] 5A and 5B are diagrams illustrating the influence of the platen gap and the air volume in the inkjet printer. [Diagram 46] 13A and 13B are diagrams showing an example of a formation position that is set based on the ejection timing optimized in the optimization process, and another example of a mode of air volume adjustment. [Figure 47] 13A and 13B are diagrams showing an example of a formation position that is set based on the ejection timing optimized in the optimization process, and another example of a mode of air volume adjustment. [Figure 48] 13A and 13B are diagrams showing an example of a formation position that is set based on the ejection timing optimized in the optimization process, and another example of a mode of air volume adjustment. [Figure 49] 13A and 13B are diagrams showing an example of a formation position that is set based on the ejection timing optimized in the optimization process, and another example of a mode of air volume adjustment. [Figure 50] 13A and 13B are diagrams showing an example of a formation position that is set based on the ejection timing optimized in the optimization process, and another example of a mode of air volume adjustment. [Figure 51] 13A and 13B are diagrams showing an example of a formation position that is set based on the ejection timing optimized in the optimization process, and another example of a mode of air volume adjustment. [Figure 52] 13A and 13B are diagrams showing an example of a formation position that is set based on the ejection timing optimized in the optimization process, and another example of a mode of air volume adjustment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] [Basic configuration example of a droplet ejection device] Hereinafter, an embodiment of the liquid droplet ejection device according to the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an overall image of an inkjet printer 100 according to this embodiment. FIG. 2 is a plan view showing an example of the configuration of a mechanism. As shown in FIG. 1, the inkjet printer 100 is configured to form dots (images) by ejecting liquid ink while conveying a recording medium 16 to a main body supported by a main body frame 70. The direction of the arrow X in FIG. 1 corresponds to the "main scanning direction". The direction of the arrow Y corresponds to the "sub-scanning direction". The main scanning direction is the reciprocating movement direction of the carriage 5 carrying the recording head 6, as described later. The sub-scanning direction is a direction perpendicular to the main scanning direction and corresponds to the conveying direction of the recording medium 16. In the following description, a mechanism for supplying the recording medium 16 to the inkjet printer 100 is omitted. For example, as a media supply mechanism applicable to the inkjet printer 100, a media conveying configuration can be used in which a continuous length of the recording medium 16, which has been sent out from a rolled media and turned into a sheet, is supplied to a position where the recording head 6 moves in the main scanning direction, and is wound up downstream in the conveying direction.

[0013] Next, the configuration of the mechanical parts of the inkjet printer 100 will be described in detail with reference to Fig. 2. In the inkjet printer 100, a main support guide rod 3 and a secondary support guide rod 4 are horizontally supported in a substantially horizontal positional relationship between a first side plate 1 and a second side plate 2 that constitute both side plates of the main body. A carriage 5 is supported by the main support guide rod 3 and the secondary support guide rod 4 so as to be slidable back and forth in the main scanning direction.

[0014] The carriage 5 carries four recording heads 6 (6y, 6m, 6c, 6k) as droplet ejection heads that eject yellow (Y) ink, magenta (M) ink, cyan (C) ink, and black (Bk) ink. The recording heads 6 are mounted on the carriage 5 with their respective ejection surfaces (nozzle surfaces) facing downward. The carriage 5, main support guide rod 3, and secondary support guide rod 4 form a movement mechanism that moves the recording heads 6 back and forth in the main scanning direction.

[0015] In addition, the recording head 6 is equipped with an ink cartridge 7 that holds liquid ink of each color at the top. In the following description, the symbol "6" means any one of "6y, 6m, 6c, 6k" or a general term. In addition, the expression "ink cartridge 7" means any one of "7y, 7m, 7c, 7k" or a general term corresponding to each ink cartridge (6y, 6m, 6c, 6k). The ink cartridge 7 is replaceably mounted on the four recording heads 6 and is an ink supply body for supplying ink of each color. In addition, the ink cartridge 7 is not limited to a replaceable form, and may be refilled with ink from an ink tank 60 (see FIG. 1).

[0016] The carriage 5 is connected to a timing belt 11 that is stretched between a drive pulley (drive timing pulley) 9 rotated by a main scanning motor 8, and a driven pulley (idler pulley) 10. A control unit 107, which will be described later, drives and controls the main scanning motor 8, thereby controlling the movement of the carriage 5 in the main scanning direction.

[0017] The carriage 5 is also provided with an encoder sensor 41, which detects a "mark" provided on the encoder sheet 40 during movement in the main scanning direction. Based on the output (encoder value) from the encoder sensor 41 that detects the mark, the control unit 107 (described later) controls the drive of the main scanning motor 8, moves the recording head 6 to a predetermined position at a predetermined timing, and controls the ejection timing based on the encoder value.

[0018] In addition, in the inkjet printer 100, a first sub-frame 13 and a second sub-frame 14 are erected on a bottom plate 12 connecting the first side plate 1 and the second side plate 2. A transport roller 15 is rotatably held between the first sub-frame 13 and the second sub-frame 14. A sub-scanning motor 17 is disposed on the second sub-frame 14 side. Rotation of the sub-scanning motor 17 is transmitted to the transport roller 15. A gear 18 fixed to the rotation shaft of the sub-scanning motor 17 and a gear 19 fixed to the shaft of the transport roller 15 serve as a mechanism for transmitting this rotation. As the transport roller 15 rotates, the recording medium 16 moves in the sub-scanning direction on a platen 200.

[0019] In addition, a subsystem 21 is disposed between the first side plate 1 and the first subframe 13 as a reliability maintenance and recovery mechanism for the recording head 6. The subsystem 21 is configured such that four capping means 22 for capping the ejection surface of the recording head 6 are held by a holder 23, and the holder 23 is held by a link member 24 so as to be swingable.

[0020] When the carriage 5 moves in the main scanning direction and comes into contact with an engagement portion 25 provided on the holder 23, the holder 23 is lifted up and the ejection surface of the recording head 6 is capped by the capping means 22. When the carriage 5 moves to an image forming area (above the recording medium 16), the holder 23 is lifted down and the capping means 22 moves away from the ejection surface of the recording head 6.

[0021] The capping means 22 is connected to a suction pump 27 via a suction tube 26, and is configured to form an air release port and communicate with the atmosphere via the air release tube and an air release valve. The suction pump 27 is configured to discharge waste liquid (waste ink) sucked in when the capping means 22 is in contact with the ejection surface into a waste liquid storage tank. By using the capping means 22 and the suction pump 27, liquid ink adhering to the periphery of the ejection surface and inappropriate liquid ink that is causing clogging in the nozzles can be removed as waste liquid, and the ejection state of the liquid ink can be maintained in an optimal state.

[0022] A wiper blade 32 for wiping the ejection surface of the recording head 6 is attached to a blade arm 31 and installed on the side of the holder 23. The blade arm 31 is pivotally supported and held to be swingable by the rotation of a cam that is rotated by a driving means.

[0023] [Example of droplet ejection device operation] Next, an overview of basic operations involving processing performed to determine optimal ejection timing for the recording head 6 in an inkjet printer 100 that is an embodiment of a droplet ejection device will be described with reference to Figures 3 to 5. Figure 3 is a top view of the carriage 5. Figure 4 is a side view of the carriage 5. Figure 5 is a diagram showing an example of the configuration of a platen 200 and a test pattern 101.

[0024] As already explained, in the inkjet printer 100 according to this embodiment, the ejection control mechanism that ejects liquid ink as droplets onto the recording medium 16 includes the carriage 5, the main support guide rod 3, the encoder sheet 40, and the platen 200. The carriage 5 is also equipped with a recording head 6 and an encoder sensor 41. The drive control of the carriage 5 in the main scanning direction and the ejection operation of the recording head 6 are configured to be performed by a control unit 107 (described later) based on an output value (encoder value) from the encoder sensor 41.

[0025] The platen 200 is for supporting the recording medium 16 when liquid ink is ejected onto the recording medium 16. Since the inkjet printer 100 is a wide machine with a long scanning movement distance in the main scanning direction, the platen 200 is configured by connecting a plurality of plate-like members 300 in the main scanning direction (carriage movement direction), as exemplified in Figs. 4 and 5. By configuring the platen 200 as described above, it is possible to avoid a decrease in surface accuracy of the platen 200, mainly in the main scanning direction, compared to a case in which the platen 200 is configured from a single large part. Also, to configure the platen 200 from a single part of the same size, a large "mold" is required in the manufacturing process, which increases the mold cost and increases the manufacturing cost, but this has the effect of avoiding this.

[0026] 5 shows a case where the platen 200 is configured by connecting five plate-like members 300. The configuration of the platen 200 is not limited to this, and the number of plate-like members 300 may be increased (reduced) to configure a platen 200 of a predetermined size. Also, the number of plate-like members 300 configuring the platen 200 may be increased (reduced) by changing the individual size of the plate-like members 300. Furthermore, if the accuracy can be improved to the extent that surface accuracy and manufacturing costs do not become issues, and the cost can be reduced, the platen 200 may be configured from a single member.

[0027] The recording head 6 has a plurality of nozzle rows, and ejects liquid ink as droplets onto the recording medium 16 transported onto the platen 200, to record a test pattern 101 consisting of an image (dots) on the recording medium 16. The test pattern 101 is a specific image pattern formed on the recording medium 16 in order to detect a change in the distance between the ejection surface of the recording head 6 mounted on the carriage 5 and the recording medium 16 on the platen 200. As will be described later, by reading the test pattern 101, it is possible to calculate the difference (amount of deviation) between the position (attachment position) of the droplets attached to the recording medium 16 and the ideal position, and it is possible to correct the ejection timing of the recording head 6 so as to correct the amount of deviation.

[0028] 3, a reading sensor 30 is mounted on the carriage 5 of the inkjet printer 100. The reading sensor 30 optically reads the test pattern 101 by irradiating the test pattern 101 with light and receiving the light reflected from the test pattern 101 to obtain a sensor output value of the test pattern 101.

[0029] The reading sensor 30 is, for example, a reflective optical sensor, and includes a light emitting section 301 and a light receiving section 302 as shown in FIG.

[0030] The configuration of the reading sensor 30 and its detection method are not particularly limited as long as they are capable of detecting the test pattern 101 recorded on the recording medium 16, and any configuration or detection method can be applied. Similarly, the position of the reading sensor 30 is not particularly limited as long as they are capable of detecting the test pattern 101 recorded on the recording medium 16, and the reading sensor 30 can be disposed at any position. For example, the reading sensor 30 may be disposed integrally with the carriage 5, or may be disposed separately from the carriage 5.

[0031] [Example of the configuration of the control mechanism of the droplet ejection device] Next, the control mechanism of the inkjet printer 100 will be described with reference to Fig. 7. As shown in Fig. 7, the control mechanism of the inkjet printer 100 includes a control unit 107, a ROM 118, a RAM 119, a storage unit 120, an operation unit 121, a carriage 5, a main scanning driver 109, a recording head 6, a recording head driver 111, an encoder sensor 41, a reading sensor 30, a paper transport unit 112, and a sub-scanning driver 113.

[0032] The control unit 107 supplies print data and drive control signals (pulse signals) to the storage unit 120 and each driver, and controls the entire printing apparatus. The control unit 107 controls the drive of the carriage 5 in the main scanning direction via a main scanning driver 109. The control unit 107 also controls the timing of ink ejection by the print head 6 via a print head driver 111. The control unit 107 also controls the drive of the paper transport unit 112 (transport belt, etc.) in the sub-scanning direction via a sub-scanning driver 113.

[0033] The control unit 107 also measures the "height" of a predetermined position in the moving direction of the carriage 5 corresponding to the formation position of the test pattern 101 read by the reading sensor 30, which corresponds to a plurality of positions in the main scanning direction of the platen 200. Here, the "height" will be explained. In this specification, the "height" corresponds to the distance in the vertical direction (Z direction) from the recording medium 16 on the platen 200 to the ejection surface of the recording head 6, and represents the so-called "ejection gap." The process of measuring the "height" as the platen gap based on the reading result of the test pattern 101 corresponds to the "height measurement process." In other words, the control unit 107 constitutes a height measurement means. Therefore, as described later, the height measurement means measures the platen gap for each of "a plurality of positions (plural positions)" that the carriage 5 can take in the main scanning direction of the platen 200, and calculates the height.

[0034] "Height calculation" means calculating data indicating the ejection gap in order to calculate data (correction value) necessary for correction to optimize the ejection timing at which the recording head 6 ejects ink at any position in the main scanning direction. In other words, "height calculation" is part of a process for optimizing the ejection timing of droplets at each of multiple positions in the main scanning direction based on the height (platen gap) measured at each of multiple positions. This ejection timing optimization process can improve the accuracy of the landing position of droplets on the recording medium 16 at any position in the main scanning direction.

[0035] This makes it possible to calculate a "correction value" as control data for "accelerating" or "delaying" the droplet ejection timing at any position in the main scanning direction compared to a default value in order to land droplets at ideal positions on the recording medium 16 while the recording head 6 moves in the main scanning direction. That is, in order to optimize the droplet ejection timing, the position in the main scanning direction is set taking into account local and nonlinear changes in the platen gap, and the ejection timing is optimized at that set position.

[0036] The control unit 107 also constitutes a change rate calculation means for calculating a change rate of "height" measured corresponding to a plurality of positions in the main scanning direction of the platen 200. The change rate of height means the degree of change from the height of other positions adjacent to each other when the heights of the plurality of positions are used as a reference. The control unit 107 has a processing function for setting optimal positions corresponding to the plurality of positions based on the height change rate corresponding to each of the plurality of positions, and for determining the optimal ejection timing (optimum ejection timing) for the recording head 6 based on the optimal positions. Therefore, the control unit 107 also constitutes an optimal position setting means and an optimal ejection timing determination means.

[0037] 26, the control unit 107 has various functional blocks through cooperation between an internal calculation processing function and a control program stored in the storage unit 120, and executes the processes described below using these functional blocks. The control unit 107 has, for example, a height measurement means 151, a change rate calculation means 152, an optimal position setting means 153, and an optimal ejection timing determination means 154.

[0038] The operation unit 121 sets the optimal test pattern 101 selected by the user. That is, the inkjet printer 100 can also set the optimal test pattern 101 by the user. Here, the optimal test pattern 101 can be set for each test pattern recorded in the main scanning direction (carriage movement direction). This allows the control unit 107 to obtain an optimal ink ejection timing correction value at each position where the test pattern 101 is recorded in the main scanning direction. That is, the user can set the position where the test pattern 101 is formed as a measurement target via the operation unit 121, so that the position in the main scanning direction of the platen 200 for measuring the height can be arbitrarily set. The control unit 107 can determine the optimal ink ejection timing correction value by measuring the height at each set position, calculating the height change rate, and setting the optimal position. Then, the control unit 107 can adjust the ejection timing of the ink ejected from the recording head 6 based on the set correction value.

[0039] The encoder sensor 41 detects the marks on the encoder sheet 40 and outputs an encoder value obtained by the detection to the control unit 107. The control unit 107 controls the driving of the carriage 5 in the main scanning direction via a main scanning driver 109 based on the encoder value.

[0040] The ROM 118 stores necessary information, for example, programs such as processing procedures to be executed by the control unit 107. The RAM 119 is used as a working memory or the like.

[0041] The reading sensor 30 is configured as a reflective optical sensor that detects the position where the test pattern 101 is formed, and includes a light-emitting unit 301 and a light-receiving unit 302, as shown in Fig. 6. The light-emitting unit 301 emits light, and the light emitted from the light-emitting unit 301 is reflected by the surface of the test pattern 101. The light-receiving unit 302 detects the reflected light (reflected light intensity) reflected by the surface of the test pattern 101, and obtains a sensor output value of the test pattern 101.

[0042] The reading sensor 30 outputs the sensor output value of the test pattern 101 acquired by the light receiving unit 302 to the control unit 107. The inkjet printer 100 forms the test pattern 101 at any preset position (L1 to L6 in FIG. 5), for example, as illustrated in FIG. 5. The control unit 107 calculates the reading result of the test pattern 101 based on the sensor output value when the reading sensor 30 reads the test pattern 101 at each position and the encoder value from the encoder sensor 41, and calculates the difference (deviation amount) from the ideal position. The control unit 107 determines a correction value for the optimal ejection timing of the liquid ink based on the calculated difference (deviation amount).

[0043] [First embodiment of ejection timing correction] Hereinafter, an embodiment of the process for correcting the ejection timing (determining the optimal ejection timing) executed in the inkjet printer 100 will be described with reference to the flowcharts in Figs. 9 and 10 and other drawings. The optimization process according to this embodiment is executed by the control unit 107 illustrated in Figs. 7 and 26. In this embodiment, it is assumed that the position of the surface of the platen 200 facing the print head 6 varies in the main scanning direction as shown in Fig. 8. That is, the platen 200 according to this embodiment has an ejection gap that varies in the main scanning direction, and the state of the variation (state of the ejection gap variation) is not uniform but also includes a curved variation.

[0044] In an inkjet printer 100 equipped with a platen 200 as shown in FIG. 8, in order to optimize the ejection timing of the recording head 6 and to perform processing to offset variations in droplet deposition positions due to fluctuations in the ejection gap, the user first sets an arbitrary position via the operation unit 121 as shown in FIG. 11. This setting is referred to as "setting A." In setting A, the gaps between each of the multiple positions (A1 to A10) are set to be equal based on the width dimension of the platen 200 in the main scanning direction. In this embodiment, ten positions are set as predetermined positions. In this embodiment, each of the positions (A1 to A10) included in setting A becomes a reference position.

[0045] 5, a test pattern 101 is formed for each position (A1 to A10) of setting A, and each test pattern 101 is read by the reading sensor 30. As a result, as shown in FIG. 12, the ejection timing for each position (A1 to A10) related to setting A is determined and stored in the memory unit 120 (S901).

[0046] Fig. 12(a) is a graph showing the difference between the "height" of each position (A1 to A10) of setting A and the ideal state for the positions in the main scanning direction of the platen 200 shown in Fig. 11. The origin "0" of the vertical axis represents the height in the ideal state. Fig. 12(b) is a table showing the correction values ​​of the ejection timing for the heights at each position (A1 to A10) shown in Fig. 12(a).

[0047] Next, the control unit 107 forms a test pattern 101 for each position (B1 to B10) of setting B as shown in FIG. 5, by setting B, which is a setting shifted to a position equivalent to half the distance (section distance) between each position (A1 to A10) of setting A. Then, as a result of reading each test pattern 101 by the reading sensor 30, the ejection timing for each position (B1 to B10) of setting B is determined as shown in FIG. 14, and stored in the storage unit 120 (S902). Note that in S902, the amount (movement amount) by which each position (B1 to B10) of setting B is shifted from each position (A1 to A10) of setting A may be a preset amount, or may be arbitrarily set by the user via the operation unit 121. Therefore, each position (B1 to B10) of setting B is set as a movement position using a predetermined movement amount with respect to each position (A1 to A10) of setting A, which is a reference position.

[0048] Fig. 14(a) is a graph showing the difference between the "height" of each position (B1 to B10) of setting B and the ideal state for the positions in the main scanning direction of the platen 200 shown in Fig. 13. The origin "0" of the vertical axis represents the height in the ideal state. Fig. 14(b) is a table showing the correction values ​​of the ejection timing for the heights at each position (B1 to B10) shown in Fig. 14(a).

[0049] Next, the "presence or absence of a local change" of the platen 200 is detected based on the calculated height in each of the settings A and B. In the following description, the "presence or absence of a local change" does not mean the height in each position of the platen 200 in the main scanning direction set based on a predetermined rule such as in the settings A and B, but means whether the height in a position other than these positions deviates from the ideal height. That is, in the following process, based on the ejection timing calculated in S901 and S902, the deviation amount of the height of the platen 200 in the main scanning direction that is not measured in the settings A and B is calculated, and it is determined that "there is a local change" at a position where the deviation amount is greater than a predetermined threshold. In addition, among the changes in the height of the platen 200 in the main scanning direction, a curved change also corresponds to a local change when viewed in detail. Therefore, the "local change" in this embodiment includes the "curved change".

[0050] In determining whether the change corresponds to a local change, the first linear threshold value is read from the storage unit 120, and the corrected ejection timing is calculated by correcting the ejection timing at the midpoint between the positions A1 and A2 based on the corrected ejection timing after the ejection timing at the position A1 in the setting A is corrected by the value shown in FIG. 12 and the corrected ejection timing after the ejection timing at the position A2 in the setting A is corrected by the value shown in FIG. 12. The difference between the calculated corrected ejection timing (the midpoint between the positions A1 and A2) and the corrected ejection timing after the ejection timing at the position B2 in the setting B is corrected by the value shown in FIG. 14 is calculated. That is, the height of the midpoint between the positions A1 and A2 in the setting A can be calculated on the assumption of linearity from the heights calculated based on the ejection timings of the positions A1 and A2, that is, the heights calculated at the positions adjacent to each other. However, in reality, the height of the midpoint does not necessarily match a linear change. Therefore, the height of the midpoint is determined using the difference between the value calculated based on the setting A and the value calculated from the detection result of the test pattern 101 formed at the midpoint. Then, these calculated differences are compared with a first linear threshold value (S903).

[0051] Here, the first linear threshold is "0.5". In this case, as illustrated in FIG. 15, the ejection timing for the midpoint between positions A1 and A2 in setting A based on the ejection timings therebetween (see FIG. 12) is "-1". On the other hand, the corrected ejection timing for position B1 in setting B is "+1". That is, as illustrated in FIG. 15, the calculation in S903 is "first linear threshold 0.5<2 (=(+1)-(-1))" (S903:Y). Therefore, when the comparison process in S903 is "Y", it indicates that a local change exists.

[0052] When it is determined in S903 that a local change exists, the result (local change information) is stored in the storage unit 120 (S904). The first linear threshold used in S903 is pre-stored in the storage unit 120. Also, the user can set the first linear threshold via the operation unit 121.

[0053] In the comparison calculation in S903, if the first linear threshold is larger (S903: N), or after S904, it is determined whether the determination process in S903 has been completed for all positions set in setting A and setting B (S905). If the determination process has not been completed for all positions (S905 / N), the process returns to S903.

[0054] In this case, for example, similar to the case of positions A1 and A2, the ejection timing of the midpoint between positions A2 and A3 is calculated from the corrected ejection timing of position A2 in setting A and the corrected ejection timing of position A3. Then, the difference between the result and the corrected ejection timing of position B3 in setting B is compared with a first linear threshold. If the comparison result is greater than the first linear threshold, the result (local change information) is associated with the judgment position and stored in the memory unit 120. The same process is performed for positions A3 and onwards to judge whether there is a local change. When the above process is performed for all sections up to position A10, the local change information stored in the memory unit 120 is as shown in FIG. 16.

[0055] In S905, if the determination process for all positions has been completed (S905 / Y), the process proceeds to the process shown in Fig. 10. Next, in the process of S905, it is determined whether or not there is one or more pieces of information indicating that a local change is "present" (one or more positions where a local change is occurring) in the local change information stored in the storage unit 120 (S1001). As already explained, for example, in the result shown in Fig. 16, there are three "present" positions (S1001 / Y), so the process proceeds to S1002.

[0056] If the number of local changes is zero (S1001 / N), it is determined whether or not the number of sections can be reduced in setting A. In this embodiment, the number of sections (N) is "10", but a process is performed to reduce the number of sections to less than this (S1008).

[0057] The process of S1008 will be described in detail below. First, the section setting threshold is read from the storage unit 120, and the magnitude of the difference in ejection timing between each section related to setting A and each section related to setting B is compared with the section setting threshold.

[0058] For example, as shown in Fig. 17(a), if there is no local change in the height calculated in setting A, and the section between positions A4 and A5 is the section in which the change in height at each adjacent position in setting A exceeds the section setting value, the comparison result will be as shown in Fig. 17(b). Note that the local change will be as shown in Fig. 17(c).

[0059] In the comparison result, sections smaller than the section setting threshold are not set as positions for calculating the correction value of the ejection timing, and since the change in height is large in the section between positions A4 and A5, only this position is set as a position for correcting the ejection timing. This setting is set as setting D, and is stored in the storage unit 120 together with information about the position related to setting D shown in Fig. 18. As described above, by reducing the number of sections, it is possible to reduce the amount of work required for readjustment when operating the inkjet printer 100 for the first time.

[0060] Return to S1001. If the number of local changes is greater than 1 (S1001 / Y), the positions with the larger values ​​of the local change information (Rn) stored in the memory unit 120 in S904 are preferentially set as positions for calculating the correction value of the ejection timing. This setting is stored in the memory unit 120 as setting C (S1002). An example of setting C is shown in FIG. 19. Position C1 of setting C is set to a position where local changes are likely to be detected, such as between position B2 of setting B and position A2 of setting A. Position C2 of setting C is also set to a position where local changes are likely to be detected, such as between position A2 of setting A and position B3 of setting B.

[0061] Next, the control unit 107 forms the test pattern 101 as shown in Fig. 5 for each position (C1 to C8) of setting C. Then, as a result of reading each test pattern 101 by the reading sensor 30, the ejection timing for each position (C1 to C8) related to setting C is determined as shown in Fig. 20(a) and stored in the memory unit 120 (S1003). An example of information stored in the memory unit 120 in S1003 is shown in Fig. 20(b).

[0062] For comparison, FIG. 21 shows the ejection timing for setting A stored in memory unit 120 in S901, the ejection timing for setting B stored in memory unit 120 in S902, and the ejection timing for setting C stored in memory unit 120 in S1003.

[0063] Next, the presence or absence of a local change in height at each position of setting C calculated from the ejection timing related to setting C is determined. In determining whether or not it corresponds to a local change, the second linear threshold value is read from the storage unit 120, and the corrected ejection timing at the midpoint between positions B2 and A2 is calculated based on the corrected ejection timing at position B2 in setting B and the corrected ejection timing at position A2 in setting A. The difference between the calculated ejection timing (the midpoint between positions B2 and A2) and the corrected ejection timing at position C1 in setting C is calculated. Then, the calculated difference is compared with the second linear threshold value (S1004).

[0064] In S1004, when the second linear threshold is smaller (S1004: Y), a local change exists, so the result is stored in the storage unit 120 as S1 (Sn) (S1005). The second linear threshold used in S1004 is pre-stored in the storage unit 120. Also, the user can set the second linear threshold via the operation unit 121.

[0065] Next, the position C1 (Cn) where it is determined that a local change exists is stored in the storage unit 120 as a candidate to be included in the setting position related to the setting D in the subsequent processing (S1006).

[0066] In the comparison operation in S1004, when the second linear threshold is greater (S1004:N), or after S1006, the number of "Yes" local change information entries is subtracted (S1007), the process returns to S1001, and the processes of S1001, S1002, S1003, S1004, S1005, S1006, and S1007 are repeatedly executed until the number of "Yes" local change entries becomes zero.

[0067] Then, in S1001, if the number of "Yes" items in the local change information becomes zero (S1001:N), the process proceeds to S1008 as described above.

[0068] That is, similar processing is performed for position A2 of setting A, position B3 of setting B, and thereafter to determine the presence or absence of local changes, and the determination results are stored in storage unit 120. The results of determination for all sections up to position C8 of setting C are shown in FIG.

[0069] As a result of the above processing, setting D can be derived as the optimal position for forming the test pattern 101 based on the determination results of local changes related to settings A and B (see FIG. 16) and the determination results of local changes related to settings A, B, and C (see FIG. 22). FIG. 23 illustrates an example of the relationship between each position in setting D and each position of setting A, setting B, and setting C.

[0070] It is assumed that the result of deriving setting D will be that there are many local change points, and that the number of positions that can be set in the inkjet printer 100 will be exceeded. In that case, priority can be set based on the difference at the time of determining the local change, and the positions can be set in order of priority. In addition, the fact that the finite number of positions has been exceeded can be displayed on the operation unit 121 to prompt the user to change the number of positions related to setting A, etc. In addition, setting D and the corrected ejection timing at each position of setting D are stored in the memory unit 120 and used for subsequent ejection control.

[0071] [Second embodiment of ejection timing correction] Next, a description will be given of another embodiment of the process for correcting the ejection timing (determining the optimal ejection timing) described in the first embodiment. In the first embodiment, an example has been shown in which the user arbitrarily sets each position of setting A as the initial position for forming the test pattern 101.

[0072] Since the width of the recording medium 16 used in the inkjet printer 100 varies, it is possible that the width of the platen 200 differs from the width of the recording medium 16. In this case, the user may set the width of the recording medium 16 via the operation unit 121, and the positions related to setting A may be set automatically.

[0073] For example, if the width dimension of the recording medium 16 is shorter than the width dimension of the platen 200, the main scanning direction positions obtained by equally dividing the number of sections into 10 can be set at each position relative to the width dimension of the recording medium 16, as shown in Figure 24(a).

[0074] 24(b), the number of sections that can be set can be set while keeping the section width of the original setting A. In the case of FIG. 24(b), the number of sections in the original setting A, "10", is changed to "7". In either case, the control unit 107 stores the newly set number of sections in the storage unit 120 as the number of sections in setting A.

[0075] As described above, by performing the ejection timing correction process described as the first embodiment in accordance with the width dimension of the recording medium 16, the accuracy of ejection timing correction due to local changes in the platen 200 can be further improved.

[0076] [Third embodiment of ejection timing correction] Next, a description will be given of another embodiment of the process for correcting the ejection timing (determining the optimal ejection timing) described in the first embodiment. In the first embodiment, an example is shown in which the user arbitrarily sets each position of setting A as the initial position for forming the test pattern 101, and in the second embodiment, an example is shown in which the setting is based on the width dimension of the recording medium 16.

[0077] The width of an image (width of an image formation area) formed on recording medium 16 used in inkjet printer 100 is determined by image data related to the image to be formed. Therefore, it is conceivable that the image formation width may differ from the width dimension of platen 200 and the width dimension of recording medium 16. In this case, each position related to setting A may be automatically set based on the image formation width that can be calculated from the image data.

[0078] For example, when the image formation width is narrow relative to the width of the platen 200, as shown in FIG. 25(a), the number of sections can be set to 10, and the main scanning direction positions obtained by equally dividing the image formation width can be set to each position.

[0079] 25(b), the number of sections that can be set can be set while keeping the section width of the original setting A. In the case of FIG. 25(b), the number of sections in the original setting A, "10", is changed to "7". In either case, the control unit 107 stores the newly set number of sections in the storage unit 120 as the number of sections in setting A.

[0080] As described above, by performing the process of correcting the ejection timing described as the first embodiment in accordance with the image formation width as the droplet ejection range, the accuracy of the ejection timing correction due to local changes in the platen 200 can be further improved.

[0081] [Fourth embodiment of ejection timing correction] In a carriage scanning type inkjet printer such as the inkjet printer 100, after the ejection timing of the recording head 6 is corrected to an optimal one using the method shown in the first embodiment, factors that affect the optimality of the ejection timing may change (fluctuate), such as when the type of recording medium 16 is changed. Therefore, for example, when the type of recording medium 16 is changed, it becomes necessary to correct the ejection timing again.

[0082] In this case, if data relating to setting D is stored in memory unit 120, this setting D is used as the starting setting for the correction process, like setting A in S901, and then all or part of the same process as the detection process for the presence or absence of local changes performed using setting A, setting B, etc. is executed.

[0083] As described above, once the optimal ejection timing has been corrected, even if the conditions are changed, when the process for correcting the ejection timing to the optimal ejection timing is executed again, the optimal ejection timing can be newly corrected based on the ejection timing once acquired, rather than from the beginning (from setting A).

[0084] [Another example of a droplet ejection device] Next, another embodiment of the droplet ejection device according to the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an overall image of an inkjet printer 100A according to this embodiment. As shown in FIG. 1, the inkjet printer 100 is configured to form dots (images) by ejecting liquid ink while conveying a recording medium 16 to a main body supported by a main body frame 70. The direction of the arrow X in FIG. 27 corresponds to the "main scanning direction". The direction of the arrow Y corresponds to the "sub-scanning direction". The main scanning direction is the reciprocating movement direction of the carriage 5 carrying the recording head 6. The sub-scanning direction is a direction perpendicular to the main scanning direction and corresponds to the conveying direction of the recording medium 16. In the following description, a mechanism for supplying the recording medium 16 to the inkjet printer 100 is omitted. For example, as a media supply mechanism applicable to the inkjet printer 100, a media conveying configuration can be used in which a continuous length of the recording medium 16, which has been sent out from a rolled media and turned into a sheet, is supplied to a position where the recording head 6 moves in the main scanning direction, and is wound up downstream in the conveying direction.

[0085] Inside the inkjet printer 100A, a main support guide rod 3 and a secondary support guide rod 4 are hung between both side plates, and a carriage 5 is supported by the main support guide rod 3 and the secondary support guide rod 4 so as to be movable in the direction of arrow X (main scanning direction). A timing belt 11, which is hung between a drive pulley 9 and a pressure pulley 10, is connected to the carriage 5.

[0086] The carriage 5 is reciprocated in the main scanning direction by driving the timing belt 11 by a main scanning motor 8 via a drive pulley 9. Tension is applied to the timing belt 11 by a pressure pulley 10, so that the carriage 5 can be driven without slack.

[0087] When the recording medium 16 is set, the suction fan 400 is driven. By driving the suction fan 400, the recording medium 16 is attracted to the platen 200 that supports the recording medium 16. Therefore, the degree to which the recording medium 16 is attracted to the platen 200 (degree of suction) varies depending on the strength of the airflow of the suction fan 400. Furthermore, a plurality of suction fans 400 are arranged in the main scanning direction (X direction) which is the direction in which the carriage 5 reciprocates. Therefore, the degree of suction of the recording medium 16 can be adjusted in accordance with a local position in the main scanning direction depending on whether or not a suction fan 400 is operated and whether the airflow of a suction fan 400 is increased or decreased.

[0088] As already explained, the recording medium 16 is intermittently transported in the direction of the arrow Y (sub-scanning direction) below the carriage 5 which moves back and forth.

[0089] [Example of the configuration of the control mechanism of the droplet ejection device] Next, a control mechanism of the inkjet printer 100A will be described with reference to Fig. 28. The control configuration of the inkjet printer 100A shown in Fig. 28 has a similar configuration to the control mechanism of the inkjet printer 100 shown in Fig. 7.

[0090] That is, the control configuration of inkjet printer 100A includes control unit 107a, ROM 118, RAM 119, storage unit 120, operation unit 121, carriage 5, main scanning driver 109, recording head 6, recording head driver 111, encoder sensor 41, reading sensor 30, paper transport unit 112, and sub-scanning driver 113. Detailed description of components similar to those of control unit 107 will be omitted.

[0091] 28, the control configuration of inkjet printer 100A includes suction fan 400. The control unit 107a controls the driving of suction fan 400. That is, the control unit 107a adjusts the rotation speed and the like of suction fan 400 to adjust the air volume (fan air volume). The air volumes of the multiple suction fans 400 may be adjusted collectively or individually.

[0092] The control unit 107a supplies print data and drive control signals (pulse signals) to the storage unit 120 and each driver, and controls the entire printing apparatus. The control unit 107a controls the drive of the carriage 5 in the main scanning direction via a main scanning driver 109. It also controls the timing of ink ejection by the print head 6 via a print head driver 111. It also controls the drive of the paper transport unit 112 (transport belt, etc.) in the sub-scanning direction via a sub-scanning driver 113.

[0093] 28, the control unit 107a has various functional blocks through cooperation between an internal calculation processing function and a control program stored in the storage unit 120, and executes the processes described below using these functional blocks. The control unit 107a has, for example, a height measurement means 151, a change rate calculation means 152, an optimal position setting means 153, an optimal discharge timing determination means 154, and a fan air volume adjustment means 155.

[0094] The height measuring means 151, the rate of change calculating means 152, the optimum position setting means 153, and the optimum ejection timing determining means 154 are similar to those already described, and therefore detailed description thereof will be omitted.

[0095] The fan air volume adjustment means 155 also locally adjusts the air volume of the suction fan 400 so that optimal discharge timing can be controlled in response to local height changes in the platen 200 (local changes in the platen gap). The fan air volume adjustment means 155 is a means for locally adjusting the air volume of the suction fan 400 to adjust the degree of suction of the recording medium 16 to the platen 200. The fan air volume adjustment means 155 adjusts the air volume of each suction fan 400 so as to increase or decrease the suction force of a specific suction fan 400 that is disposed at a position corresponding to a position where the local change in the platen gap is large.

[0096] [First embodiment of ejection timing correction and air volume adjustment] Hereinafter, an embodiment of the ejection timing optimization process executed in the inkjet printer 100A and the air volume adjustment process that adjusts the air volume of the suction fan 400 accordingly will be described with reference to the flowcharts in Figures 30 to 32 and other drawings.

[0097] The process according to this embodiment is executed by the control unit 107a illustrated in Figures 28 and 29. In this embodiment as well, it is assumed that the position of the surface of the platen 200 facing the print head 6 varies in the main scanning direction as shown in Figure 8. That is, the platen 200 according to this embodiment has a discharge gap that varies locally in the main scanning direction, and the state of this variation (state of fluctuation of the discharge gap) is not uniform, but is localized and includes curved fluctuations.

[0098] In inkjet printer 100A equipped with platen 200 as shown in FIG. 8, when performing a process to enable offsetting of variations in droplet deposition positions due to fluctuations in the discharge gap, first, the user sets an arbitrary position via operation unit 121 as shown in FIG. 11. This setting is referred to as "setting A." In setting A, multiple positions are set so that the gaps between each of the positions (A1 to A10) are uniform based on the width dimension of platen 200 in the main scanning direction. In this embodiment, ten positions are set as predetermined positions. In this embodiment, each of the positions (A1 to A10) included in setting A becomes a reference position.

[0099] 5 for each position (A1 to A10) of setting A, and the reading sensor 30 reads each test pattern 101. As a result, as shown in FIG. 12, the ejection timing for each position (A1 to A10) of setting A is determined and stored in the memory unit 120 (S3001).

[0100] Thereafter, the processes from S3002 to S3004 are similar to the processes from S901 to S904, and therefore detailed explanations will be omitted.

[0101] Next, in S3005, which is a process similar to S905, if the determination process for all positions (10 positions as reference positions) is completed (S3005 / Y), the process proceeds to the process shown in FIG.

[0102] Next, it is determined whether or not there is one or more pieces of information indicating that a local change is "present" (one or more positions where a local change is occurring) in the local change information stored in storage unit 120 in the process of S3005 (S3101). That is, it is determined whether or not there is a local change at any of the preset reference positions (A1 to A10).

[0103] As already explained, for example, in the result shown in FIG. 16, there are three "Yes"s (S3101 / Y), so the process proceeds to S3102.

[0104] The processes from S3102 to S3107 are similar to the processes from S1002 to S1007 already described, and therefore detailed description thereof will be omitted.

[0105] In the judgment process of S3101, when it is judged that the number of local changes is zero (S31101 / N), the position setting is performed preferentially from the largest value of the local change amount Rh based on the local change judgment results for settings A and B (table in Figure 21) and the local change judgment results for settings A, B, and C (table in Figure 22).

[0106] Next, in S3201, it is determined whether the position related to the set setting D exceeds the finite number of set positions. If the setting D does not exceed the finite number of set positions (S3201 / Y), the same process as S1008 is performed (S3205). In the process in S3205, the position related to the set setting D is set as the set position for finally performing the optimization process of the ejection timing.

[0107] That is, as a result of the processing in S3001 to S3005 and S3101 to S3107, it is possible to derive a setting for setting D as the optimum setting position for forming the test pattern 101 based on the determination results of local changes for settings A and B (see FIG. 16) and the determination results of local changes for settings A, B, and C (see FIG. 22). FIG. 23 illustrates an example of the relationship between each position in setting D and each position of setting A, setting B, and setting C.

[0108] It is assumed that the result of deriving the positions related to setting D may be that there are many local change points, exceeding the finite number of positions that can be set in the inkjet printer 100A. In that case, a priority may be set based on the difference at the time of determining the local change, and the positions may be set in order of priority. In addition, the fact that the finite number of positions has been exceeded may be displayed on the operation unit 121 to prompt the user to change the number of positions related to setting A, etc. In addition, the positions related to setting D and the corrected ejection timing for each of the positions related to setting D are stored in the memory unit 120 and used for subsequent ejection control.

[0109] If the number of positions related to setting D exceeds the finite number of position settings (S3201 / N), it is determined whether or not the fan air volume of suction fan 400 has already been adjusted (S3202).

[0110] In the first discharge timing correction flow (S3201), if the number of position settings is exceeded (S3201 / N), the fan air volume adjustment process from S3203 onwards has already been executed. Therefore, the fan air volume adjustment should have been completed (S3202 / YES).

[0111] Even in this case, if the number of possible settings for setting D in S3201 is not below the threshold (S3201N), this corresponds to the number of position settings being exceeded again even after the fan airflow adjustment has been performed. In this case, it is expected that the adjustment will not end or will take an extremely long time. Therefore, if the fan airflow has already been adjusted in S3202 (S3202 / Y), the second fan airflow adjustment proceeds to S3205 to end the adjustment flow with the position setting set in S3201 as the final position setting.

[0112] As a result of the processing in S3205, based on the results of the determination of local changes related to settings A and B (see FIG. 16) and the results of the determination of local changes related to settings A, B, and C (see FIG. 22), setting D can be derived as information indicating the optimal setting position for forming test pattern 101, as shown in FIG. 23.

[0113] In S3202, when it is determined that the fan air volume setting has not been completed (S3202 / N), it is determined from the amount of local change Rh whether the local change in the platen 200 is a convex or concave shape. If it is a convex shape, adjusting (weakening) the fan air volume has almost no effect because the recording medium 16 basically conforms to the shape of the platen 200. If it is a concave shape, adjusting (weakening) the fan air volume can reduce the impact of the local change in the platen 200.

[0114] Therefore, in principle, the fan air volume of the suction fan 400 is adjusted according to the position of the local change in the platen 200 that is a convex shape. Whether or not the local change in the platen 200 is a convex shape is determined by whether or not the correction value derived by actually setting the position is smaller than a predetermined threshold value with respect to the value calculated by linear correction for each of settings A to C. Note that when the correction value is smaller than the threshold value, it is determined that the local change in the platen 200 at the position that is the subject of the determination is a convex shape. Through the above process, the position corresponding to the largest correction value and the largest value is extracted as a convex shape (S3203).

[0115] Following S3203, the air volume of the fan (closest fan) in the vicinity of the setting position where the local change in the convex shape is the best and largest is adjusted (S3204).

[0116] An example of fan air volume adjustment is shown in Fig. 33. Fig. 33 shows an example in which four suction fans 400 are arranged in the X direction of the platen 200 (the main scanning direction, the direction in which the carriage 5 reciprocates). The air volume of each suction fan 400 is indicated as "Fs" when the air volume is set to "strong". In the following description, the air volume is indicated as "Fm" when the air volume is set to "medium", and "Fw" when the air volume is set to "weak".

[0117] When the air volume of the suction fan 400 is set to "strong (Fs)", the recording medium 16 sucked by the suction fan 400 is sucked into the platen 200. When the air volume is set to "weak (Fw)", the degree to which the recording medium 16 in a position affected by the wind from the suction fan 400 is sucked into the platen 200 is weakened, and there is a possibility that the recording medium 16 may be lifted off the platen 200. When the air volume is set to "medium (Fm)", the degree of suction is assumed to be intermediate between the strong (Fs) and weak (Fw) settings.

[0118] 33, the airflow of the fan located between positions D1 and D2 and closer to position D2 is set to "high." This increases the airflow of the suction fan 400 at that position, and increases the degree to which the recording medium 16 is sucked onto the platen 200.

[0119] Also, as shown in FIG. 34, by adjusting (weakening) the fan airflow of the suction fan 400 and setting it to medium (Fm), the print medium is influenced by the suction fan 400 in that portion and floats slightly, making it less susceptible to the effects of sudden changes in the platen.

[0120] After the fan air volume is adjusted in S3204, the process returns to S3001.

[0121] It is not necessary to adjust the fan air volume near the location where the local change in the convex shape is greatest. For example, it is possible to adjust the fan air volume near the location where the slope changes from concave to convex as shown in Figure 35.

[0122] According to the first embodiment of the ejection timing optimization process and air volume adjustment process described above, by providing the control unit 107a that adjusts the air volume of the suction fan 400 individually or uniformly, it is possible to optimize the ejection timing in response to local changes in the platen 200 and optimize the adjustment of the air volume for suction. Furthermore, when there is no local change or only a small local change in the platen 200, the number of sections can be set to 10 or less to optimize the ejection timing.

[0123] In this case, the air volume of the suction fan 400 may remain at the standard (initial value). In this embodiment, the initial value of the suction fan 400 is set to "strong setting (Fs)" as shown in Fig. 36. Here, the fan air volume: strong is set as the initial value.

[0124] Note that if there are many positions (locations) where local changes occur on the platen 200, setting the number of sections to 10 will not be enough to handle all of the local changes. In this case, it is necessary to change the number of sections as shown in FIG.

[0125] To deal with this without changing the number of set sections, the air volume setting of the suction fan 400 arranged at the positions corresponding to these sections is set to "medium setting (Fm)" to smooth out the local change, as in section D3 to section D5 illustrated in Fig. 37. This makes it possible to perform correction processing for calculating the optimal timing without increasing the number of set sections (leaving the number at the initial setting of 10).

[0126] In this case, as shown in FIG. 38, the air volume setting of the suction fan 400 corresponding to the point D9 may be set to "medium setting (Fm)."

[0127] As described above, the inkjet printer 100A according to this embodiment can grasp the local change in the platen gap by actual measurement, and can adjust the position setting for adjusting the timing of droplet ejection and the degree to which the recording medium 16 is sucked into the platen 200. This makes it possible to set the optimal position for adjusting the timing of ejection over the entire main scanning direction of the recording medium 16.

[0128] [Second embodiment of ejection timing correction and air volume adjustment] Next, a description will be given of another embodiment of the ejection timing correction (optimum ejection timing determination) process described in the first embodiment and the corresponding air volume adjustment process of the suction fan 400. Note that the example in which the user arbitrarily sets each position of setting A as the initial position for forming the test pattern 101 is the same as in the previous embodiment.

[0129] For example, as shown in Fig. 39, assume that the number of sections set as described above increases from the initial setting when the number of positions in the main scanning direction is small under the platen 200. In this case, as shown in Fig. 40, it is also assumed that the number of positions cannot be reduced even if the air volume setting of the suction fan 400 is adjusted.

[0130] In this case, in the inkjet printer 100A according to this embodiment, the installation position of the suction fan 400 is moved in the main scanning direction as shown in Fig. 41. Then, by adjusting the fan air volume appropriately using the suction fan 400 after the movement, the number of set sections can be reduced.

[0131] As described above, according to the inkjet printer 100A of this embodiment, it is possible to set optimal positions for adjusting the ejection timing throughout the entire main scanning direction relative to the recording medium 16, thereby improving the image quality formed by the ejected droplets.

[0132] [Effect of moving the suction fan 400] Here, the suction effect by moving the suction fan 400 in the main scanning direction will be described. In general, the farther away from the installation position of the suction fan 400, the weaker the influence of the air volume of the suction fan 400. For example, when only one suction fan 400 is arranged in the main scanning direction of the platen 200, the influence of the suction force of the fan air volume on the recording medium 16 is as shown in FIG. 42. That is, when the suction fan 400 is arranged near the center of the platen 200 in the main scanning direction, the suction force at that position is the strongest. Then, the influence of the suction force becomes weaker toward the end in the main scanning direction.

[0133] When there is one suction fan 400, if the fan volume is reduced, the degree of suction of the recording medium 16 is as shown in Fig. 43. That is, the further away from the installation position of the suction fan 400, where the air volume setting is "weak (Fw)", the weaker the degree of suction becomes, and the recording medium 16 becomes floating above the platen 200.

[0134] Assume that three suction fans 400 are arranged in the main scanning direction of the platen 200, as shown in Fig. 44. In this arrangement, when the airflow setting of the suction fan 400 arranged near the center in the main scanning direction is set to "weak setting (Fw)", the degree of suction of the recording medium 16 becomes as shown in Fig. 45. That is, the recording medium 16 located closest to the central suction fan 400, which has its airflow setting set to "weak setting (Fw)", is raised the furthest from the platen 200.

[0135] In the example of FIG. 45, unlike the case where there is one suction fan 400, as the suction fans 400 approaching the ends in the main scanning direction are positioned such that the airflow is not weakened, and therefore the degree of suction of the recording medium 16 increases as the recording medium 16 approaches these suction fans 400 with the "strong setting (Fw)".

[0136] [Third embodiment of ejection timing correction and air volume adjustment] Next, a third embodiment will be described as another embodiment of the ejection timing correction (optimum ejection timing determination) process described in the first embodiment and the corresponding air volume adjustment process of the suction fan 400. Note that an example in which the user arbitrarily sets each position of setting A as the initial position for forming the test pattern 101 is the same as in the previous embodiment.

[0137] For example, as shown in FIG. 46, a suction fan 400 disposed below the platen 200 may be provided with a blocking mechanism 401 that partially blocks the suction between the recording medium 16 and the platen 200 .

[0138] In response to a local change in the platen gap, the blocking mechanism 401 partially blocks the airflow from the suction fan 400 in the main scanning direction by using the blocking mechanism 401, which is equipped with a shutter for blocking the airflow from the suction fan 400. This makes it possible to finely adjust the degree of suction of the recording medium 16 in the main scanning direction in conjunction with adjustment of the air volume setting of the suction fan 400.

[0139] 46, the blocking mechanism 401 is configured with an opening / closing shutter 402 and a duct 403 below the platen 200. The duct 403 is disposed below the platen 200, and, for example, eight opening / closing shutters 402 (#1 to #8) are arranged along the main scanning direction.

[0140] For example, by adjusting the opening / closing shutters 402 from #4 to #8 to weaken the suction force, the degree of suction of the recording medium 16 can be locally adjusted to move it away from the platen 200, thereby reducing variation in the posture of the recording medium 16.

[0141] As shown in FIG. 47, when the number of suction fans 400 is increased, the same effect can be obtained by performing the same process as described above.

[0142] At the ends in the main scanning direction, the influence of the strength of the airflow from the suction fan 400 is small, so the width of the duct 403 in the main scanning direction is made wide, and the width of the opening / closing shutter 402 is also made wide. Also, the width may be uniform in the main scanning direction.

[0143] As described above, according to the inkjet printer 100A of this embodiment, it is possible to set optimal positions for adjusting the ejection timing throughout the entire main scanning direction relative to the recording medium 16, thereby improving the image quality formed by the ejected droplets.

[0144] [Fourth embodiment of ejection timing correction and air volume adjustment] Next, a description will be given of another embodiment of the ejection timing correction (optimum ejection timing determination) process described in the first embodiment and the corresponding air volume adjustment process of the suction fan 400. Note that the example in which the user arbitrarily sets each position of setting A as the initial position for forming the test pattern 101 is the same as in the previous embodiment.

[0145] For example, the fan air volume adjustment means 155 included in the control unit 107a may adjust the fan air volume according to the type of recording medium 16. Since the thickness of the recording medium 16 varies depending on the type, the degree of change in the degree of suction relative to the strength of the fan air volume setting of the suction fan 400 will vary. In other words, since the degree of influence of the suction fan differs between thin and thick recording media 16, the influence of abrupt changes in the platen 200 can be weakened according to the recording medium 16 by adjusting the fan air volume according to the printing medium.

[0146] For example, when the fan air volume is adjusted as shown in Fig. 33, the fan air volume of the suction fan 400 located at a position corresponding to between D3 and D4 should be set to "medium setting (Fm)" as shown in Fig. 48. However, when the recording medium 16 is a thin type, the effect of adjusting the fan air volume is large. Therefore, as shown in Fig. 49, the fan air volume of the suction fan 400 located at a position corresponding to between D3 and D4 should be set to a setting (Fm+) that is stronger than the "medium setting (Fm)" and weaker than the "strong setting (Fs)".

[0147] The type of recording medium 16 may be set via the operation unit 121 and stored in the RAM 119, and the control unit 107a may read it out from the RAM 119 during processing.

[0148] 49, in the case of a thick type of recording medium 16, the effect of adjusting the fan air volume is less likely to occur. In this case, the fan air volume of the suction fan 400 disposed at a position corresponding to between D3 and D4 should be set to "weak setting (Fw)."

[0149] As described above, according to the inkjet printer 100A of this embodiment, it is possible to set optimal positions for adjusting the ejection timing throughout the entire main scanning direction for various recording media 16, thereby improving the image quality formed by the ejected droplets.

[0150] [Fifth embodiment of ejection timing correction and air volume adjustment] Next, a description will be given of another embodiment of the ejection timing correction (optimum ejection timing determination) process described in the first embodiment and the corresponding air volume adjustment process of the suction fan 400. Note that the example in which the user arbitrarily sets each position of setting A as the initial position for forming the test pattern 101 is the same as in the previous embodiment.

[0151] For example, the fan air volume adjustment means 155 included in the control unit 107a may adjust the fan air volume in accordance with the different widths depending on the type of recording medium 16. Note that the recording medium 16 may have different widths depending on the type. Therefore, the range of influence of the fan air volume of the suction fan 400 also differs depending on the width of the recording medium 16.

[0152] 51, if the width of the recording medium 16 is short, that is, if there is no recording medium 16 outside D4, the section setting can be narrowed according to the range of the width of the recording medium 16. If the local change in the platen 200 is outside the range of the width of the recording medium 16, there is no need to adjust the position setting and the fan air volume.

[0153] As described above, according to the inkjet printer 100A of this embodiment, the optimal position setting range for adjusting the ejection timing and the adjustment range of the fan air volume can be controlled in accordance with the dimensions of various recording media 16, thereby making the adjustment process more efficient.

[0154] [Sixth embodiment of ejection timing correction and air volume adjustment] Next, a description will be given of another embodiment of the ejection timing correction (optimum ejection timing determination) process described in the first embodiment and the corresponding air volume adjustment process of the suction fan 400. Note that the example in which the user arbitrarily sets each position of setting A as the initial position for forming the test pattern 101 is the same as in the previous embodiment.

[0155] For example, the fan air volume adjustment means 155 included in the control unit 107a may adjust the fan air volume in accordance with the width of the image formed on the recording medium 16 (image formation width 102).

[0156] 52, when the image formation width 102 for the recording medium 16 is narrow, that is, when an image is not formed outside D4, the section setting can be narrowed according to the range of the image formation width 102. If the local change in the platen 200 is outside the range of the image formation width 102, there is no need to adjust the position setting and the fan air volume.

[0157] As described above, according to the inkjet printer 100A of this embodiment, the optimal position setting range for adjusting the ejection timing and the adjustment range of the fan air volume can be controlled according to various image formation widths 102, thereby making the adjustment process more efficient.

[0158] The present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the technical gist of the present invention. The present invention covers all technical matters included in the technical ideas described in the claims. The above-described embodiments are preferred examples, but a person skilled in the art can realize various modifications from the disclosed contents. Such modifications are also included in the technical scope described in the claims.

[0159] For example, the present invention is not limited to devices that simply eject liquid to form an image on a medium, such as the inkjet printer 100 illustrated in each of the above embodiments, but can also be applied to multifunction peripherals (MFPs) that include an image reading unit in addition to an image forming unit. Furthermore, the type of liquid ink used in the test pattern 101 is not limited to four colors (CMYK). [Explanation of symbols]

[0160] 30: Reading sensor 100,100A: Inkjet printer 101: Test pattern 107,100Aa: Control section 109: Main scanning driver 111: Recording head driver 112: Paper transport section 113: Sub-scan driver 118: ROM 119:RAM 120: Storage section 121:Operation unit 200: Platen 300: Plate-shaped member 301: Light emitting part 302: Light receiving section [Prior art documents] [Patent documents]

[0161] [Patent Document 1] JP 2011-079296 A

Claims

1. a carriage for reciprocating a recording head having a plurality of nozzles for ejecting droplets onto a recording medium supported by a platen in a predetermined direction; a control unit that controls the ejection timing of the droplets onto the recording medium at a plurality of positions in a reciprocating movement direction of the carriage; Equipped with The control unit is a height measuring means for measuring heights at the plurality of positions; a change rate calculation means for calculating a height change rate corresponding to each of the plurality of positions based on the height; an optimum position setting means for setting the height at each of the plurality of positions where the height is measured based on the height change rate; an optimal ejection timing determination means for determining an optimal ejection timing for the droplets based on the height at the optimal position measured by the height measurement means; A droplet ejection device comprising:

2. the change rate calculation means calculates the height change rate based on the height measured at each of the plurality of positions and the height measured at another adjacent position; the optimum position setting means sets a position where the height change rate is greater than a predetermined threshold as the optimum position; The droplet ejection device according to claim 1 .

3. When there are a plurality of positions at which the height change rate is greater than a predetermined threshold value, the optimum position setting means sets the optimum positions in descending order of the height change rate. The droplet ejection device according to claim 2 .

4. the optimum position setting means varies the number of optimum positions to be set in accordance with a width dimension of the recording medium; The droplet ejection device according to claim 1 .

5. the optimum position setting means varies the number of optimum positions to be set in accordance with a width dimension of the image to be formed on the recording medium; The droplet ejection device according to claim 1 .

6. Equipped with an operation unit that can be operated by a user, the height measuring means sets the position to be measured based on a value set by the user via the operation unit, determining a movement amount from the position based on a value set by the user via the operation unit to set each of the plurality of positions; The droplet ejection device according to claim 1 .

7. a storage unit that stores the optimal position and the optimal ejection timing; the optimum position setting means sets a new optimum position based on the optimum position stored in the storage unit when the type of the recording medium is changed. The droplet ejection device according to claim 1 .

8. a plurality of suction fans for suctioning the recording medium on the rear side of the platen; The control unit further includes an air volume adjustment unit that adjusts the air volume of the suction fan individually or uniformly. The droplet ejection device according to claim 1 .

9. the air volume adjustment means adjusts the air volume of the suction fan in accordance with the optimal position. The droplet ejection device according to claim 8.

10. When the number of the optimal positions is greater than a predetermined number, the air volume adjustment means adjusts the air volume of the suction fan to be weaker than a default value in accordance with the optimal positions. The droplet ejection device according to claim 9 .

11. the suction fan is movable in a reciprocating direction of the carriage, the air volume adjustment means moves the position of the suction fan to a position corresponding to the optimal position; The droplet ejection device according to claim 8 .

12. the suction fan includes a blocking mechanism for individually blocking the flow of air toward the recording medium; The airflow adjusting means controls the blocking mechanisms individually. The droplet ejection device according to claim 8 .

13. the air volume adjustment unit adjusts the air volume of the suction fan in accordance with the type of the recording medium. The droplet ejection device according to claim 8 .

14. the air volume adjustment unit adjusts the air volume of the suction fan in accordance with the width of the recording medium in the reciprocating direction of the carriage. The droplet ejection device according to claim 8 .

15. the air volume adjustment unit adjusts the air volume of the suction fan in accordance with a width of a range in which droplets are discharged onto the recording medium in a reciprocating movement direction of the carriage. The droplet ejection device according to claim 8 .

Images