Liquid droplet ejection apparatus

Abstract

To provide a droplet discharge device capable of more accurately detecting a discharge failure of a droplet from a nozzle.SOLUTION: In the droplet discharge device 100, at a predetermined first time point, one or more droplets are located in a first section P1 of the flight path, the first section S1 being a section that extends in the second direction from the light emitter 61 and crosses a direct optical path LA, the direct optical path LA being an optical path of a light flux that directly enters the light receiver 62 through the light-reception-side opening 68. In addition, the discharge timing and the number of discharges of droplets from the nozzle 41 are adjusted and droplets are discharged so that one or more droplets are positioned in the second section S2, which is a section of the flying path that crosses the reflected light path, which is the optical path of the light beam that is incident on the light receiver 62 through the light reception-side opening 68 after being reflected by the nozzle surface 40, and a discharge failure of droplets from the nozzle 41 is detected based on the light reception signal.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] BACKGROUND ART Conventionally, an inkjet recording apparatus such as that shown in Patent Document 1 has been known (see Patent Document 1, for example).

[0003] This inkjet recording device has a recording head that ejects ink droplets from nozzles to record an image, and a light-emitting element and a light-receiving element that are arranged opposite each other near the ejection port surface of the recording head where the ink ejection ports of the nozzles are located.It drives the nozzles and detects whether or not ink droplets are being ejected from the nozzles based on whether or not there is a change in the detection signal of the light-receiving element due to light blocking. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-168001 Summary of the Invention [Problem to be solved by the invention]

[0005] However, because the droplets ejected from the nozzles are very small, the signal change caused by the light blocking ejected from the light receiving element is small, and in an environment with high signal noise, the signal change is buried in the noise, making it difficult to detect the droplets. [Means for solving the problem]

[0006] In order to solve the above problem, a droplet ejection device according to one aspect of the present invention comprises: an ejection head having a nozzle surface formed with nozzles capable of ejecting droplets in a first direction; and a head drive unit that ejects the droplets from the nozzles; a light-emitting element; a light-receiving element positioned opposite the light-emitting element in a second direction intersecting the first direction and on which a light beam emitted from the light-emitting element and crossing a flight path of the droplets ejected from the nozzles is incident; a light-receiving-side cover that covers the light-receiving element and has a light-receiving-side opening through which the light beam passes, and which outputs a light-receiving signal corresponding to the amount of light received by the light-receiving element; and a controller that controls the head drive unit, wherein the controller detects at a predetermined first point in time The timing and number of droplets ejected from the nozzle are adjusted so that one or more droplets are positioned in a first section of the flight path, which is a section that extends from the light-emitting element in the second direction and crosses a direct optical path, which is the optical path of the light beam that passes through the light-receiving side opening and is directly incident on the light-receiving element, and one or more droplets are positioned in a second section of the flight path, which is a section that extends from the light-emitting element in a direction that intersects the second direction and crosses a reflected optical path, which is the optical path of the light beam that passes through the light-receiving side opening after being reflected by the nozzle surface and is incident on the light-receiving element, and poor ejection of the droplets from the nozzle is detected based on the light-receiving signal.

[0007] According to this configuration, the S / N ratio of the received light signal can be improved, and defective ejection of droplets from the nozzles can be detected more accurately. [Effects of the Invention]

[0008] The present invention has the effect of being able to more accurately detect defective ejection of droplets from the nozzles. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing an example of the configuration of a droplet ejection device according to a first embodiment. [Figure 2]1. FIG. 4 is a side view showing the light-emitting side cover and the light-receiving side cover of the discharge detection unit as viewed from a second direction of the droplet discharge device of FIG. [Figure 3] 1. FIG. 4 is a side view showing an example of the configuration of an optical path extending from a light-emitting element to a light-receiving element of the ejection detection unit of the droplet ejection device of FIG. 1, and shows a direct optical path. [Figure 4] 1. FIG. 4 is a side view showing an example of the configuration of an optical path extending from a light-emitting element to a light-receiving element of the ejection detection unit of the droplet ejection device of FIG. 1, and is a diagram showing a reflected optical path. [Figure 5] FIG. 5 is a view taken along the arrows AA in FIGS. 3 and 4. [Figure 6] FIG. 2 is a block diagram showing a functional configuration of the droplet ejection device of FIG. [Figure 7] 2A to 2C are diagrams illustrating an example of the operation of the droplet ejection device of FIG. [Figure 8] 4 is a graph showing the change over time in the amount of light received by a light receiving element during the nozzle state detection operation of the droplet ejection device of FIG. [Figure 9] FIG. 5 is a view taken along the arrows BB in FIGS. 3 and 4. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described with reference to the drawings. Note that the present invention is not limited to the following embodiments. In addition, the same or corresponding elements will be denoted by the same reference numerals throughout the drawings, and redundant description will be omitted.

[0011] The functions of the elements disclosed herein can be performed using circuits or processing circuits, including general-purpose processors, special-purpose processors, integrated circuits, ASICs (Application Specific Integrated Circuits), conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuitry. In this disclosure, a circuit, unit, or means is hardware that performs the recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed herein or other known hardware that is programmed or configured to perform the recited functions. Where the hardware is a processor, which is considered a type of circuit, the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and / or processor.

[0012] (Embodiment 1) FIG. 1 is a schematic diagram showing an example of the configuration of a droplet ejection device 100 according to the first embodiment.

[0013] The droplet ejection device 100 is a device that prints an image on a recording medium 110 using droplets ejected from an ejection head 4 based on image data. In the following, an inkjet printer that ejects ink as droplets will be described as the droplet ejection device 100.

[0014] The droplet ejection device 100 is a serial head type inkjet printer, and in the printing process, a step of ejecting droplets to form an image on the recording medium 110 while the ejection head 4 moves (scans) in the main scanning direction, and a step of transporting the recording medium 110 in the sub-scanning direction are alternately performed. Note that the droplet ejection device 100 is not limited to a serial head type inkjet printer.

[0015] The ejection head 4 is housed within the housing 10 of the droplet ejection device 100. The ejection head 4 has a nozzle surface 40 on which a plurality of nozzles 41 capable of ejecting droplets in a direction toward the recording medium 110 based on image data are formed. The nozzle surface 40 has a plurality of nozzle rows 42 in which the nozzles 41 are aligned in the sub-scanning direction. The plurality of nozzle rows 42 are aligned at predetermined intervals in the main scanning direction. The ejection head 4 is also provided with a head drive unit 45 (see FIG. 3). The head drive unit 45 has a drive element provided for each nozzle 41, and when driven, applies pressure to the liquid in the nozzle 41 to eject droplets from the corresponding nozzle 41, thereby ejecting droplets from the nozzle 41. Note that, hereinafter, the direction in which the ejection head 4 ejects droplets will be referred to as the first direction. The first direction is, for example, the up-and-down direction. The sub-scanning direction will sometimes be referred to as the second direction, and the main scanning direction will sometimes be referred to as the third direction. The first direction, the second direction, and the third direction are perpendicular to each other, but are not limited to this and may intersect with each other.

[0016] 1, the droplet ejection device 100 includes a platen 11 disposed opposite the ejection head 4. The platen 11 is positioned below the ejection head 4 at a predetermined distance, and has a flat upper surface. The upper surface of the platen 11 supports the recording medium 110 from below.

[0017] Furthermore, the droplet ejection device 100 is equipped with a transport unit 12 that transports the recording medium 110 on the platen 11 in the sub-scanning direction. The transport unit 12 has, for example, two transport rollers 13 and a transport motor. The two transport rollers 13 extend in the main scanning direction and, when viewed from above and below, are spaced apart in the sub-scanning direction so as to sandwich the platen 11 between them. Each transport roller 13 is connected to the rotating shaft of the transport motor via a reducer. Therefore, when driven by the transport motor, the two transport rollers 13 rotate about their axes, transporting the recording medium 110 on the platen 11 in the sub-scanning direction.

[0018] The droplet ejection device 100 includes an ejection detection unit 6 located in a maintenance area A provided on one side of the platen 11 in the main scanning direction. The ejection detection unit 6 is a sensor that detects the ejection of droplets from the nozzles 41. The ejection detection unit 6 has a light-emitting element 61 and a light-receiving element 62. The light-emitting element 61 is, for example, an LED that emits infrared light. The light-receiving element 62 is, for example, a photodiode. The light-receiving element 62 is positioned opposite the light-emitting element 61 in the second direction. The light-emitting element 61 and the light-receiving element 62 are connected to a detection circuit 60 of the ejection detection unit 6. The detection circuit 60 outputs a light-receiving signal corresponding to the amount of light received by the light-receiving element 62.

[0019] The light-emitting element 61 and the light-receiving element 62 are covered by a light-emitting-side cover 65 and a light-receiving-side cover 67, respectively. This makes it possible to prevent mist generated when droplets are ejected from the nozzle 41 from adhering to the light-emitting element 61 and the light-receiving element 62. Figure 2 is a side view showing the light-emitting-side cover 65 and the light-receiving-side cover 67, as viewed from a second direction. As shown in Figure 2, the light-emitting-side cover 65 and the light-receiving-side cover 67 have a light-emitting-side opening 66 and a light-receiving-side opening 68 through which a light beam passes.

[0020] 3 and 4 are side views showing configuration examples of an optical path extending from the light-emitting element 61 toward the light-receiving element 62. In Fig. 4, the position of the distal end portion 68b in the first direction is indicated by a dashed dotted line. The light beam emitted from the light-emitting element 61 and incident on the light-receiving element 62 travels along a direct optical path P1 shown in Fig. 3 or a reflected optical path P2 shown in Fig. 4.

[0021] 3, the direct optical path P1 is the shortest path of the light beam emitted from the light-emitting element 61 and incident on the light-receiving element 62. The direct optical path P1 is the optical path of the light beam that extends from the light-emitting element 61 through the light-emitting side opening 66 in the second direction in which the nozzle rows 42 extend. The light beam that follows the direct optical path P1 further passes through the light-receiving side opening 68 and is directly incident on the light-receiving element 62. The direct optical path P1 also extends parallel to the nozzle face 40, with a gap of 2 to 3 mm between it and the nozzle face 40.

[0022] As shown in Figure 4, the reflected light path P2 is an optical path of the light beam that extends from the light-emitting element 61 through the light-emitting side opening 66 in a direction that intersects with the second direction, i.e., diagonally upward. The light beam that passes through the reflected light path P2 is further reflected by the nozzle surface 40, passes through the light-receiving side opening 68, and is incident on the light-receiving element 62. In this way, the reflected light path P2 passes above the direct light path P1. Therefore, as shown in Figures 3 and 4, droplets that are ejected from the nozzle 41 and fly cross the reflected light path P2 and the direct light path P1 in this order.

[0023] Fig. 5 is a view taken along the arrow AA in Fig. 3 and Fig. 4. As shown in Fig. 5, when viewed from the second direction, the region from the nozzle surface 40 to the distal end 68b is divided into multiple regions in the first direction at intervals v / f corresponding to the droplet velocity v and the ejection frequency f. From bottom to top in the first direction, the region is divided into, for example, four regions A1 to A4. The first region S1 in Fig. 5 is the section of the droplet flight path that crosses regions A1 and A2, through which the direct optical path P1 passes. The second region S2 in Fig. 5 is the section of the droplet flight path that crosses regions A3 and A4, which are above regions A1 and A2. The reflected optical path P2 passes through at least one of regions A3 and A4.

[0024] As shown in FIG. 2, the light-emitting side opening 66 of the light-emitting side cover 65 is formed, for example, in a rectangular shape. The opening area of ​​the light-emitting side opening 66 is formed larger than the opening area of ​​the light-receiving side opening 68. This allows the width of the optical path extending from the light-emitting element 61 to the light-receiving element 62 to be expanded. This prevents mist from adhering to the light-receiving element 62 and expands the area in which droplets can be detected. Furthermore, the dimension of the light-emitting side opening 66 in the first direction is smaller than the dimension in the third direction. This allows the light beam passing through the reflected light path P2 to be suppressed while expanding the area in which droplets can be detected, thereby preventing the light beam passing through the reflected light path P2 from being excessively incident on the light-receiving element 62. The light-receiving side opening 68 of the light-receiving side cover 67 is formed, for example, in a rectangular shape and has a proximal end 68a close to the nozzle face 40 and a distal end 68b far from the nozzle face 40. The distal end 68b defines the end of the direct optical path P1 on the side opposite to the side on which the nozzle face 40 is located in the first direction.

[0025] 1, the droplet discharge device 100 includes a movement mechanism 2 that moves the discharge head 4 back and forth in the main scanning direction. By moving the discharge head 4 with the movement mechanism 2, the discharge head 4 can be positioned in a maintenance area A. By moving the discharge head 4 in the main scanning direction in the maintenance area A with the movement mechanism 2, any one of the multiple nozzle rows 42 of the nozzles 41 can be positioned directly above the optical path P1, and a nozzle state detection operation, which will be described later, can be performed.

[0026] The movement mechanism 2 includes a carriage 21 that supports the ejection head 4 and moves back and forth in the main scanning direction together with the ejection head 4, and a carriage drive unit 22 that drives the carriage 21. The carriage drive unit 22 includes two guide rails 26, an endless belt 27, two pulleys 28, and a movement motor 29. When viewed from the first direction, the two guide rails 26 extend in the main scanning direction so as to pass through the platen 11 and the maintenance area A, and are spaced apart in the sub-scanning direction. The two guide rails 26 support the carriage 21 and guide it in the main scanning direction.

[0027] Two pulleys 28 are provided near both ends of one of the guide rails 26. An endless belt 27 is wound around the two pulleys 28. The carriage 21 is connected to a predetermined position on the endless belt 27. One of the pulleys 28 is connected to the rotation shaft of a movement motor 29 via a reducer. Therefore, when the movement motor 29 is driven, the endless belt 27 moves around the two pulleys 28, and the carriage 21 supporting the ejection head 4 moves in the main scanning direction along the guide rail 26. Furthermore, by controlling the rotation angle position of the rotation shaft of the movement motor 29, the carriage 21 and the ejection head 4 can be positioned within their reciprocating movement range at a position that corresponds to the rotation angle position of the rotation shaft of the movement motor 29.

[0028] In this embodiment, the ejection head 4 is configured to move, but the present invention is not limited to this. Instead, the platen 11 or the ejection detection unit 6 may be moved, and these and the ejection head 4 may move relatively.

[0029] The droplet ejection device 100 is equipped with a tank 3 that stores liquid to be supplied to the ejection head 4. The tank 3 is, for example, a cartridge-type tank, and is held at a predetermined position inside the housing 10. The tank 3 is covered by an openable and closable cover provided on the housing 10. The tank 3 can be attached to or detached from the droplet ejection device 100 by opening the cover. The liquid stored in the tank 3 is supplied to the nozzle 41 via a supply flow path 5.

[0030] Fig. 6 is a block diagram showing the functional configuration of the droplet ejection device 100. As shown in Fig. 6, the droplet ejection device 100 includes a controller 7. The controller 7 includes, as a functional configuration mainly made up of hardware, a control unit 71, a storage unit 72 connected to the control unit 71, and an interface 73. The control unit 71 is also connected to the head drive unit 45, transport unit 12, movement mechanism 2, and ejection detection unit 6 described above.

[0031] The control unit 71 is, for example, a computer, and includes a circuit such as a processor like an MPU or an integrated circuit like an ASIC. The storage unit 72 is a memory accessible from the control unit 71, and includes, for example, RAM and ROM. The RAM temporarily stores image data and various data used in calculations by the control unit 71. The ROM stores computer programs and data for various data processing operations. Therefore, the control unit 71 controls the operation of each unit of the droplet ejection device 100 by executing the computer program while referencing the data stored in the storage unit 72.

[0032] The interface 73 is a connection device that connects the control unit 71 to external devices of the droplet ejection device 100. Examples of external devices include other computers, communication networks, recording media, displays, and other droplet ejection devices. The droplet ejection device 100 acquires image data and print setting information from external devices, such as computers, via this interface 73. This image data includes raster data that indicates an image to be printed on the recording medium 110 and has RGB value gradation information.

[0033] The head drive unit 45 has a nozzle drive circuit electrically connected to each drive element of the ejection head 4, and controls the operation of the drive elements of each nozzle 41 based on instructions from the control unit 71. That is, the control unit 71 outputs a control signal to the nozzle drive circuit to drive the drive elements, and the nozzle drive circuit generates a drive signal based on the input control signal and outputs this drive signal to each drive element. As a result, each drive element is driven based on the corresponding drive signal and operates to apply a predetermined ejection pressure to the liquid in the nozzle 41 at a predetermined carriage position. Therefore, the ejection timing and size (volume) of the droplets ejected from each nozzle 41 can be controlled.

[0034] The transport unit 12 has a transport drive circuit electrically connected to the transport motor described above, and the operation of the transport motor is controlled by the control unit 71 via the transport drive circuit. This allows the transport unit 12 to transport the recording medium 110 on the platen 11 intermittently or continuously in the forward and backward directions, and also to stop and hold the recording medium 110 at a predetermined position on the platen 11.

[0035] The movement mechanism 2 has a movement drive circuit electrically connected to the movement motor 29 described above, and the operation of the movement motor 29 is controlled by the control unit 71 via the movement drive circuit. This allows the movement mechanism 2 to move the carriage 21 supporting the ejection head 4 in the main scanning direction at any speed. Furthermore, by controlling the rotational angle position of the movement motor 29, it is possible to position the carriage 21 supporting the ejection head 4. Therefore, the ejection head 4 mounted on the carriage 21 is moved back and forth in the main scanning direction relative to the recording medium 110 by the movement mechanism 2.

[0036] The droplet ejection device 100 ejects droplets while moving the ejection head 4 using the movement mechanism 2, thereby forming an image on the recording medium 110 for each pass. That is, the droplet ejection device 100 transports the recording medium 110 using the transport unit 12 and stops it at a predetermined position on the platen 11. Next, the movement mechanism 2 moves the ejection head 4 in one direction in the main scanning direction while ejecting droplets, causing them to land on the recording medium 110. In this way, a partial image for one pass is formed on the stopped recording medium 110 by droplets ejected while the ejection head 4 is moving. Then, after the partial image for one pass is formed, the recording medium 110 is transported again by the transport unit 12 a predetermined distance and stopped. Then, the movement mechanism 2 moves the ejection head 4 in the other direction in the main scanning direction while ejecting droplets, thereby forming a partial image for the next pass. The droplet ejection device 100 alternately repeats the transport of the recording medium 110 and the ejection of droplets in this manner, thereby printing an entire image consisting of one or more partial images on the recording medium 110.

[0037] In addition to the above, the droplet ejection device 100 may also include, as functional hardware components, output devices such as a display and a speaker that output various types of information to the outside, and input devices such as a touch panel and a physical switch that accept input of information from the outside.

[0038] [Example of operation] Below, we will explain an example of the nozzle state detection operation that detects whether the nozzle 41 is operating normally. Nozzle state detection is an operation that drives the head drive unit 45 and detects whether droplets are being ejected from the nozzle 41.

[0039] First, as shown in FIGS. 3 and 4, the control unit 71 positions the nozzle row 42 including the nozzle 41A for which nozzle state detection is to be performed above the direct light path P1 and the reflected light path P2.

[0040] Next, as shown in Figure 5, the control unit 71 ejects droplets from the nozzle 41A at a predetermined first point in time so that one or more droplets are located in each of the first section S1 and the second section S2 of the flight path of the droplets ejected from the nozzle 41A.

[0041] More specifically, the control unit 71 adjusts the ejection timing and number of droplets ejected from the nozzle 41A so that the droplets ejected from the nozzle 41A are aligned in a third section S3 as viewed from the second direction at the first time point. The third section S3 is a section extending from the nozzle face 40 to the distal end 68b of the light-receiving side opening 68, and includes a first section S1 that crosses the direct optical path P1 and a second section S2 that crosses the reflected optical path P2. That is, the control unit 7 adjusts the ejection timing and number of droplets ejected from the nozzle 41A so that, at the first time point, droplets ejected consecutively from the nozzle 41A with a number N of ejected droplets that satisfies the following formula (1) are positioned in the third section S3. This allows the droplets to be aligned over a length equal to or greater than the third section S3 of the droplet flight path at the first time point. In this embodiment, the length of the third section S3 in the first direction is set in advance as L in equation (1).

[0042]

number

[0043] Then, when the control unit 71 determines that there has been a decrease in the amount of received light based on the light reception signal at the first time point, it determines that droplets have been ejected from the nozzle 41A, and determines that the nozzle 41A is operating normally. On the other hand, when the control unit 71 determines that there has been no decrease in the amount of received light, it determines that there has been no ejection of droplets from the nozzle 41A, and determines that there has been a droplet ejection failure from the nozzle 41A. As described above, the S / N ratio of the light reception signal can be increased, and therefore it is possible to prevent the control unit 71 from making an erroneous determination when determining whether there has been a droplet ejection failure.

[0044] Fig. 7 is a diagram showing an example of operation of the droplet ejection device 100, illustrating the state of a droplet at a second point in time after the first point in time. In Fig. 7, the position of the distal end 68b in the first direction is indicated by a dashed line. Fig. 8 is a graph showing the change over time in the amount of light received by the light-receiving element 62 when a droplet is ejected from the nozzle 41A.

[0045] As shown in FIG. 7 , when viewed from the second direction, the light beam emitted from the light-emitting element 61 also passes through a region below the distal end 68b. This light beam is not directed toward the light-receiving element 62 and would not normally be incident on the light-receiving element 62. However, when multiple droplets ejected from the nozzle 41A pass through the third section S3 and are positioned in a region of the distal end 68b opposite the nozzle 41A at a second time point that is later than the first time point, the light beam passing through this region is disturbed by the droplets, and some of the light beam enters the light-receiving element 62. At this time, no droplets are positioned in the third section S3, and the light beam passing through the direct light path P1 and the reflected light path P2 enters the light-receiving element 62 without any obstruction, resulting in a normal state. Therefore, the light beam passing through the region of the distal end 68b opposite the nozzle 41 enters the light-receiving element 62, increasing the amount of light received compared to the amount received in the normal state.

[0046] Therefore, when droplets are ejected from the nozzle 41, the light-receiving element 62 detects a change in which the amount of received light decreases from the normal state at a first time point T1, and then increases from the normal state at a second time point T2, as shown in Fig. 8. The control unit 71 may determine whether the light-receiving element 62 detects this successive change, and detect droplets from the nozzle 41 based on this. This allows for more accurate detection of droplets being ejected from the nozzle 41.

[0047] As explained above, the controller 7 of the droplet ejection device 100 adjusts the ejection timing and number of droplets from the nozzle 41 so that, at a predetermined first point in time, one or more droplets are positioned in the first section S1 of the flight path of the droplets, which is the section that crosses the direct optical path P1, and one or more droplets are positioned in the second section S2 of the flight path, which is the section that crosses the reflected optical path P2, and detects any defective ejection of droplets from the nozzle 41 based on the received light signal. This makes it possible to improve the S / N ratio of the received light signal and more accurately detect any defective ejection of droplets from the nozzle 41.

[0048] Furthermore, the opening area of ​​the light-emitting side opening 66 is larger than the opening area of ​​the light-receiving side opening 68, and the dimension of the light-emitting side opening 66 in a first direction is smaller than the dimension in a third direction perpendicular to the first direction. This makes it possible to expand the area in which droplets can be detected, and to reduce the amount of light received by the light-receiving element 62 even when droplets ejected from the nozzle 41 pass through a position that is off the optical axis. Therefore, the droplet ejection device 100 can more accurately detect defective droplet ejection from the nozzle 41.

[0049] (Embodiment 2) The following describes the configuration and operation of the second embodiment, focusing on the differences from the first embodiment.

[0050] Instead of using equation (1) in the first embodiment, the control unit 71 may adjust the timing and number of droplets ejected from the nozzle 41 so that, at the first point in time, droplets having a number N of ejections that satisfies the following equation (2) are positioned in the third section S3:

[0051]

number

[0052] (Embodiment 3) The following describes the configuration and operation of embodiment 3, focusing on the differences from embodiment 1. In embodiment 1, the control unit 71 controls each nozzle 41 constituting the nozzle row 42 to eject droplets from the nozzle 41 by adjusting the ejection timing and number of droplets so that the droplets ejected from the nozzle 41 are aligned across the entire third section S3 at a predetermined first point in time.

[0053] In this embodiment, a first section S1 and a second section S2 are set individually for each nozzle 41, and information for identifying the relative positional relationship of the first section S1 and the second section S2 with respect to the nozzle 41 is pre-stored in the memory unit 72.

[0054] 4, the distance between the nozzle surface 40 and the reflected light path P2 varies depending on the nozzles 41 aligned in the second direction. For example, in the nozzle row 42, in the nozzle 41B located closer to the nozzle surface 40 than the outer nozzle 41A, the reflected light path P2 passes through a position closer to the nozzle surface 40, and the area through which the direct light path P1 passes and the area through which the reflected light path P2 passes are separated.

[0055] 9 is a view taken along the arrow BB in FIGS. 3 and 4. As shown in the view taken along the arrow BB, in the path taken by droplets ejected from nozzle 41B, a direct optical path P1 passes through regions A1 and A2, and a reflected optical path P2 passes through region A4. A first section S1 of nozzle 41B is set as a section of the flight path of droplets ejected from nozzle 41B that crosses regions A1 and A2. A second section S2 of nozzle 41B is set as a section that crosses region A4. In this way, in this embodiment, the first section S1 and second section S2 of nozzle 41B are set apart from each other.

[0056] 9, the control unit 71 ejects two droplets consecutively from the nozzle 41B at the maximum ejection frequency, and then ejects one more droplet after one cycle. As a result, at the first time point, droplets are positioned in each of the regions A1, A2, and A4, excluding the region A3. The droplets positioned in the regions A1 and A2 are positioned on the direct optical path P1 and block the light beam passing through the direct optical path P1. The droplets positioned in the region A4 are positioned on the reflected optical path P2 and block the light beam passing through the reflected optical path P2. As a result, the light beam passing through the direct optical path P1 and the reflected optical path P2 and incident on the light receiving element 62 can be appropriately reduced with a small number of droplets.

[0057] In this way, a first section S1, which is a section that crosses the direct optical path P1, and a second section S2, which is a section that crosses the reflected optical path P2, are individually set in the flight path of the droplets for each nozzle 41. Then, at a predetermined first point in time, the control unit 71 causes the nozzle 41B to eject droplets such that one or more droplets are positioned in each of the first section S1 and the second section S2 of the flight path of the droplets ejected from the nozzle 41B.

[0058] From the above description, many modifications and other embodiments of the present invention will be apparent to those skilled in the art. Therefore, the above description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode for carrying out the present invention. Details of the structure and / or function thereof may be substantially changed without departing from the spirit of the present invention. [Explanation of symbols]

[0059] P1 Direct optical path P2 reflected optical path S1 First Section S2 2nd Section S3 3rd Section 4 Discharge head 6 Discharge detection unit 7 Controller 40 Nozzle surface 41 nozzle 42 nozzle rows 45 Head drive unit 61 Light-emitting element 62 Photodetector 65 Light-emitting side cover 66 Light-emitting side opening 67 Light receiving cover 68 Light receiving side opening 68a Proximal end 68b Distal end 100 Droplet discharge device

Claims

1. a discharge head having a nozzle surface on which nozzles capable of discharging droplets in a first direction are formed, and a head driving unit for discharging the droplets from the nozzles; a light-emitting element; a light-receiving element positioned opposite the light-emitting element in a second direction intersecting the first direction, and on which a light beam emitted from the light-emitting element and crossing a flight path of the droplet ejected from the nozzle is incident; and a light-receiving-side cover covering the light-receiving element and having a light-receiving-side opening through which the light beam passes, and which outputs a light-receiving signal corresponding to the amount of light received by the light-receiving element; a controller for controlling the head driving unit, The controller the ejection timing and the number of ejections of the droplets from the nozzle are adjusted so that, at a predetermined first time point, one or more of the droplets are positioned in a first section of the flight path that is a section that extends from the light-emitting element in the second direction and crosses a direct optical path that is an optical path of the light beam that passes through the light-receiving side opening and is directly incident on the light-receiving element, and the one or more droplets are positioned in a second section of the flight path that is a section that extends from the light-emitting element in a direction intersecting the second direction and crosses a reflected optical path that is an optical path of the light beam that passes through the light-receiving side opening after being reflected on the nozzle surface and is incident on the light-receiving element, The droplet ejection device detects defective ejection of the droplets from the nozzle based on the light receiving signal.

2. the light-receiving side opening has a proximal end portion close to the nozzle face and a distal end portion far from the nozzle face in the first direction, a third section including the first section and the second section is a section extending from the nozzle surface to the distal end section when viewed from the second direction, The controller 2. The droplet ejection device according to claim 1, wherein the head drive unit is driven to eject the droplets from the nozzles at the first point in time so that the droplets ejected from the nozzles are aligned continuously in the third section at intervals according to an ejection frequency.

3. 3. The droplet ejection device according to claim 2, wherein the controller adjusts the ejection timing and number of ejections of the droplets from the nozzle so that, at the first point in time, the number N of droplets ejected continuously from the nozzle in the third section satisfies the following equation: [Equation 1]

4. The droplet ejection device according to claim 2 , wherein the ejection frequency is a maximum ejection frequency.

5. 3. The droplet ejection device according to claim 2, wherein the controller adjusts the ejection timing and number of ejections of the droplets from the nozzle so that, at the first point in time, the number N of droplets ejected continuously from the nozzle in the third section satisfies the following equation: [Equation 2]

6. the nozzle surface has a nozzle row in which a plurality of the nozzles are aligned in the second direction, The droplet ejection device according to claim 1 , wherein the first section and the second section are set for each of the nozzles.

7. The droplet ejection device according to claim 6 , wherein the first section and the second section of at least one of the plurality of nozzles are set to be spaced apart from each other.

8. the ejection detection unit further includes a light-emitting side cover that covers the light-emitting element and has a light-emitting side opening through which the light flux passes, The droplet ejection device according to claim 1 , wherein an opening area of ​​the light-emitting side opening is larger than an opening area of ​​the light-receiving side opening.

9. the ejection detection unit further includes a light-emitting side cover that covers the light-emitting element and has a light-emitting side opening through which the light flux passes, The droplet ejection device according to claim 1 , wherein the dimension of the light-emitting side opening in the first direction is smaller than the dimension in a third direction perpendicular to the first direction.

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