Liquid discharge device and control method of liquid discharge device

Abstract

To provide a liquid discharge device capable of preventing discharge failure while suppressing thickening of liquid.SOLUTION: A controller 7 of a liquid discharge device 100 repeatedly executes a printing process in which a discharge head 4 and a recording medium 110 are moved relative to each other such that a nozzle 41 passes through a printing region P and a non-printing region Q, and a drive signal is output. When it is determined that a duty ratio being a ratio of a liquid amount discharged from the nozzle 41 by a discharge waveform to a maximum liquid amount that can be discharged from the nozzle 41 in one printing process is equal to or greater than a first threshold, a next first non-discharge waveform of the discharge waveform is set to a waveform that vibrates liquid in a pressure chamber 45 more weakly than a first non-discharge waveform in a case where the duty ratio is less than the first threshold.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection apparatus and a method for controlling the liquid ejection apparatus. [Background technology]

[0002] A liquid ejection device has been known for some time (see, for example, Patent Document 1). The control means of this liquid ejection device executes micro-vibration drive within the non-ejection period when the length of the non-ejection period from the end point of a first drive cycle in which ejection drive is executed to the start point of a second drive cycle in which ejection drive is executed immediately after the first drive cycle is longer than a threshold value. This makes it possible to suppress thickening of the liquid. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-171308 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when printing is performed in a printing area with a high duty ratio, which is the ratio of the number of times the ejection head ejects liquid to the maximum number of times the ejection head can eject liquid, such as solid printing, and then micro-vibration driving is performed, there is a problem in that ejection defects are likely to occur in the high duty ratio printing of the next pass after the micro-vibration driving is performed. [Means for solving the problem]

[0005] In order to solve the above problem, a liquid ejection device according to one aspect of the present disclosure includes an ejection head having a nozzle capable of ejecting liquid toward a recording medium, a pressure chamber communicating with the nozzle, and an actuator that changes the volume of the pressure chamber in response to a drive signal; a movement mechanism that relatively moves the ejection head and the recording medium so that the nozzle passes through a print area that is an area to be printed on the recording medium and a non-print area; and a controller that generates and outputs the drive signal having an ejection waveform that is a waveform that drives the actuator to eject the liquid from the nozzle located in the print area, and a first non-ejection waveform that is a waveform that drives the actuator to vibrate the liquid in the pressure chamber of the nozzle located in the non-print area without ejecting it, and the controller moves the ejection head and the recording medium so that the nozzle passes through the print area and the non-print area. A printing process is repeatedly executed in which the drive signal is output while moving the nozzle relative to the nozzle, and when it is determined that the duty ratio, which is the ratio of the amount of liquid ejected from the nozzle by the ejection waveform to the maximum amount of liquid that can be ejected from the nozzle in one printing process, is equal to or greater than a first threshold value, the first non-ejection waveform following the ejection waveform is set to a waveform that vibrates the liquid in the pressure chamber more weakly than the first non-ejection waveform when the duty ratio is less than the first threshold value.

[0006] According to this configuration, it is possible to prevent ejection defects while suppressing the increase in viscosity of the liquid. [Effects of the Invention]

[0007] The present disclosure provides an effect of being able to prevent ejection defects while suppressing thickening of the liquid. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram illustrating an example of the configuration of a liquid ejection device according to a first embodiment. [Figure 2] 2 is a cross-sectional view showing an example of the configuration of a discharge head of the liquid discharge device of FIG. 1. FIG. [Figure 3] 2 is a block diagram showing an example of a functional configuration of the liquid ejection device of FIG. 1. FIG. [Figure 4] 2 is a plan view schematically showing the relationship between the ejection head of the liquid ejection device of FIG. 1 and the print area and non-print area. FIG. [Figure 5] 2 is a diagram showing an example of a non-ejection waveform of a drive signal output by a controller of the liquid ejection device of FIG. 1. FIG. [Figure 6] 2 is a flowchart showing an example of the operation of the liquid ejection device of FIG. [Figure 7] FIG. 10 is a diagram showing another example of a non-ejection waveform of a drive signal output by a controller of the liquid ejection device. [Figure 8] FIG. 10 is a diagram showing yet another example of a non-ejection waveform of a drive signal output by a controller of the liquid ejection device. [Figure 9] FIG. 10 is a diagram showing yet another example of a non-ejection waveform of a drive signal output by a controller of the liquid ejection device. [Figure 10] FIG. 10 is a block diagram showing another example of the functional configuration of the liquid ejection device. [Figure 11] 11 is a flowchart showing an example of the operation of the liquid ejection device of FIG. [Figure 12] 10 is a plan view schematically showing another relationship between the ejection head of the liquid ejection device and the printing area and non-printing area. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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.

[0010] The functions of the elements disclosed herein can be performed using circuits or processing circuits, including general-purpose processors, special-purpose processors, integrated circuits, application-specific integrated circuits (ASICs), 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.

[0011] (Embodiment 1) FIG. 1 is a schematic diagram showing an example of the configuration of a liquid ejection device 100 according to the first embodiment.

[0012] The liquid ejection device 100 is a device that prints an image on a recording medium 110 using liquid ejected from an ejection head 4 based on image data. In the following, an inkjet printer that ejects ink will be described as the liquid ejection device 100.

[0013] The liquid ejection device 100 is a serial head type inkjet printer, and alternates between a step of ejecting ink to form an image on a recording medium 110 while the ejection head 4 moves (scans) in a main scanning direction, and a step of transporting the recording medium 110 in a sub-scanning direction. Note that, hereinafter, the direction in which the ejection head 4 moves back and forth is referred to as the first direction or main scanning direction, and a direction perpendicular to the first direction, which is the transport direction of the recording medium 110, is referred to as the second direction or sub-scanning direction. Furthermore, a direction perpendicular to both the first direction and the second direction is referred to as the third direction. The third direction is, for example, the up-down direction. In this way, the main scanning direction, the sub-scanning direction, and the third direction are perpendicular to each other, but this is not limited to this and they may intersect each other.

[0014] The ejection head 4 is housed in a housing 10 of the liquid ejection device 100. The ejection head 4 has a nozzle surface 40 in which a plurality of nozzles 41 capable of ejecting ink toward a recording medium 110 based on image data are formed. The nozzle surface 40 has a nozzle row in which the nozzles 41 are formed side by side in the sub-scanning direction, and the nozzle row is provided in a plurality of rows in the main scanning direction.

[0015] 2 is a cross-sectional view showing an example of the configuration of the ejection head 4. As shown in FIG. 2, the ejection head 4 is provided with a pressure chamber 45 and an actuator 42 for each nozzle 41. The pressure chamber 45 is a space in which ink is temporarily stored. The pressure chamber 45 communicates with the nozzle 41. The pressure chamber 45 is connected to an internal head flow path 62, which is an ink flow path provided within the head, and receives a supply of ink via the internal head flow path 62. The pressure chamber 45 has an opening 47.

[0016] The actuator 42 includes a driving element 46. The driving element 46 elastically deforms inward or outward of the pressure chamber 45 when driven. The driving element 46 is, for example, a piezoelectric element, and can be elastically deformed in a direction corresponding to the selected applied voltage by selectively increasing or decreasing the applied voltage relative to a reference voltage. When the driving element 46 elastically deforms outward of the pressure chamber 45, the volume of the pressure chamber 45 increases, generating negative pressure in the pressure chamber 45. When negative pressure is generated in the pressure chamber 45 due to the high flow resistance of the nozzle 41, ink flows in from the internal head flow path 62. When the driving element 46 elastically deforms inward of the pressure chamber 45, the volume of the pressure chamber 45 decreases, and the ink in the pressure chamber 45 is pressurized. After the driving element 46 elastically deforms outward of the pressure chamber 45, the driving element 46 subsequently elastically deforms inward, strongly pressurizing the ink stored in the pressure chamber 45, causing the ink to be ejected as ink droplets from the nozzle 41 communicating with the pressure chamber 45.

[0017] Furthermore, when the drive element 46 vibrates slightly due to its driving, the ink stored in the pressure chamber 45 and the nozzle 41 vibrates slightly without being ejected from the nozzle 41. This operation of vibrating the ink slightly will be referred to as non-ejection flushing below. If the state in which ink is not ejected from the nozzle 41 continues, the solvent will evaporate from the meniscus of the nozzle 41, causing a change in the state of the meniscus and an increase in the viscosity of the ink, which may result in problems such as difficulty in ejecting the ink from the nozzle 41. By performing non-ejection flushing, the ink inside the pressure chamber 45 and the nozzle 41 is agitated, the state of the meniscus can be maintained normal, and ejection defects can be prevented.

[0018] 1, the ejection head 4 is provided with an ink supply port 43 through which ink supplied from the outside flows in. The upstream end of the head internal flow path 62 is connected to the ink supply port 43.

[0019] The liquid ejection device 100 is equipped with 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.

[0020] Furthermore, the liquid ejection device 100 includes a transport unit 12 that transports the recording medium 110 on the platen 11 in the sub-scanning direction. The transport unit 12 includes, 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 the third direction, 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 rotary shaft of the transport motor via a reducer. Therefore, when the transport motor is driven, the two transport rollers 13 rotate about their axes, transporting the recording medium 110 on the platen 11 in the sub-scanning direction.

[0021] The liquid ejection device 100 also includes a movement mechanism 2 that moves the ejection head 4 and the recording medium 110 relative to each other. FIG. 4 is a plan view schematically illustrating the relationship between the ejection head 4 and the printing region P and non-printing region Q. In this embodiment, the movement mechanism 2 moves the ejection head 4 and reciprocates the ejection head 4 in the main scanning direction within a predetermined movement range Z. As the ejection head 4 reciprocates, the nozzle 41 passes through the printing region P and the non-printing region Q, which is an area other than the area printed on the recording medium 110, as shown in FIG. 4. The printing region P is the area printed on the recording medium 110, and more specifically, the area where ink is ejected from the nozzle 41, spanning from the position where ink ejection from the nozzle 41 starts to the position where ink ejection ends. The printing region P includes an area where ink ejection from the nozzle 41 is temporarily suspended. In the movement range Z of the ejection head 4, in addition to the section C2 facing the recording medium 110 in the main scanning direction, the ejection head 4 also moves through a section adjacent to the area facing the recording medium 110. When ejecting ink from the nozzles 41, the ejection head 4 is usually controlled to move at a constant speed, so these adjacent sections C1 and C3 are used to accelerate the ejection head 4 to a constant speed or to decelerate the ejection head 4 after it has passed through the printing region P, and are included in the non-printing region Q.

[0022] 1, 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 third direction, the two guide rails 26 extend in the main scanning direction so as to cross the platen 11, 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.

[0023] The 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 along the guide rail 26 in the main scanning direction.

[0024] The liquid ejection device 100 also includes a tank 3 that stores ink 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 liquid ejection device 100 by opening the cover.

[0025] The liquid ejection device 100 also includes a conduit 61 that connects the tank 3 and the ink supply port 43 and supplies the ink stored in the tank 3 to the ink supply port 43 of the ejection head 4. The conduit 61 is, for example, a flexible resin tube, and when the distance between the carriage 21 and the tank 3 changes due to movement of the carriage 21, the conduit 61 bends and deforms, maintaining the connection between the tank 3 and the ejection head 4. The conduit 61 and the in-head flow path 62 form a supply flow path 5 that supplies liquid to the pressure chamber 45.

[0026] Fig. 3 is a block diagram showing an example of the functional configuration of the liquid ejection device 100. As shown in Fig. 3, the liquid 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 actuator 42, transport unit 12, and movement mechanism 2 described above.

[0027] 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 during 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 liquid ejection device 100 by executing the computer program while referencing the data stored in the storage unit 72.

[0028] The interface 73 is a connection device that connects the control unit 71 to devices external to the liquid ejection device 100. Examples of external devices include other computers, communication networks, recording media, displays, and other liquid ejection devices. The liquid 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.

[0029] The movement mechanism 2 has a movement drive circuit electrically connected to the movement motor 29 described above. 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, and to stop the carriage 21 at any position within its movable range. Therefore, the ejection head 4 mounted on the carriage 21 is moved back and forth in the main scanning direction (first direction) relative to the recording medium 110 by the movement mechanism 2. This causes the nozzles 41 to pass through the printing region P and the non-printing region Q.

[0030] The actuator 42 has a nozzle drive circuit electrically connected to each drive element 46 of the ejection head 4 and controls the operation of the drive elements 46 of each nozzle 41 based on instructions from the control unit 71. That is, the control unit 71 outputs a drive signal that drives the drive elements 46 to the nozzle drive circuit. The drive signal includes information on the voltage waveform to be applied to each drive element 46. The nozzle drive circuit generates a voltage waveform to be applied to each drive element 46 based on the input drive signal and outputs the generated voltage waveform to each drive element 46. The voltage waveform pattern included in the drive signal is first an ejection waveform. The ejection waveform is a waveform that drives each drive element 46 of the actuator 42 to eject liquid from the nozzles 41 located in the print area P. The ejection waveform is a pulse voltage waveform in which one or more waveform patterns selected from one or more ejection patterns stored in the memory unit 72 are arranged in chronological order.

[0031] FIG. 5 shows an example of a non-ejection waveform. Another waveform pattern of the drive signal generated by the control unit 71 is a non-ejection waveform. The non-ejection waveform is a waveform that drives each drive element 46 of the actuator 42 to perform non-ejection flushing, and is a pulse voltage waveform of a waveform pattern selected from one or more vibration patterns stored in the memory unit 72. Two predefined non-ejection waveform patterns are shown in FIG. 5: a strong waveform W1, shown by a solid line in FIG. 5, in which pulses P1 with a voltage peak value of V1 are arranged in chronological order; and a weak waveform W2, shown by a dashed-dotted line in FIG. 5, in which pulses P2 with a voltage peak value of V2, which is smaller than V1, are arranged in chronological order. Thus, the weak waveform W2 has a peak value that is positively correlated with the vibration intensity during non-ejection flushing, and is smaller than the strong waveform W1.

[0032] 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.

[0033] The controller 7 executes a pass printing process in which ink is ejected from the nozzles 41 in response to a drive signal while moving the carriage 21 in the main scanning direction using the movement mechanism 2, thereby forming an image on the recording medium 110 for each pass. That is, the liquid ejection device 100 transports the recording medium 110 using the transport unit 12 and stops it at a predetermined position on the platen 11, and then, while moving the ejection head 4 in one direction in the main scanning direction using the movement mechanism 2, ejects ink from the nozzles 41 in the printing region P and lands it on the recording medium 110. In this way, a partial image for one pass is formed on the stopped recording medium 110 by ink ejected while the ejection head 4 is moving.

[0034] Then, when the partial image for one pass has been formed, the conveying unit 12 again conveys the recording medium 110 a predetermined distance while the ejection head 4 is kept on standby. Then, when the conveying of the recording medium 110 has been completed, the movement mechanism 2 again moves the ejection head 4 in the other direction in the main scanning direction while ejecting ink from the nozzles 41 in the printing region P, thereby forming the next partial image for one pass. The liquid ejection device 100 alternately repeats this conveyance of the recording medium 110 and the ejection of ink while moving the carriage 21, thereby printing an entire image made up of one or more partial images on the recording medium 110.

[0035] 4, that is, the region of the non-printing region Q where the carriage 21 is accelerated toward the printing region P, and the region where the carriage 21 is decelerated after passing through the printing region P, the controller 7 performs non-ejection flushing to agitate the ink inside the pressure chambers 45 and the nozzles 41. The waveform of the drive signal generated by the controller 7 is a waveform in which, in a time series, non-ejection waveforms are positioned before and after an ejection waveform corresponding to a partial image for one pass. This non-ejection waveform is sometimes referred to as the first non-ejection waveform to distinguish it from other non-ejection waveforms.

[0036] In addition to the above, the liquid 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.

[0037] Incidentally, ink is supplied to the pressure chamber 45 by drawing ink from the supply channel 5 using negative pressure generated in the pressure chamber 45 by driving the drive element 46. However, if the amount of ink flowing into the pressure chamber 45 from the supply channel 5 is insufficient, the negative pressure in the pressure chamber 45 increases. In printing with a low duty ratio, the increase in negative pressure in the pressure chamber 45 causes more ink to flow into the pressure chamber 45, thereby decreasing the negative pressure in the pressure chamber 45. However, in pass printing with a high duty ratio, such as so-called solid printing, even if the negative pressure in the pressure chamber 45 increases, the flow channel resistance of the supply channel 5 may cause the ink supply to the pressure chamber 45 to remain insufficient. In this case, the negative pressure in the pressure chamber 45 further increases. In this way, if non-ejection flushing is performed, in which ink inside the nozzle 41 is vibrated without being ejected, when a large negative pressure is generated in the pressure chamber 45, ejection defects, in which ink is not ejected properly from the nozzle 41, may occur, resulting in reduced print quality. As shown in the following operational example, the liquid ejection device 100 operates to mitigate ejection defects caused by the influence of non-ejection flushing after executing a printing process with a high duty ratio.

[0038] [Example of operation] Next, a specific example of the operation of the printing process of the liquid ejection device 100 will be described. Fig. 6 is a flowchart showing an example of the operation of the liquid ejection device 100 according to the first embodiment.

[0039] First, the controller 7 starts the print process by receiving a print job input, for example, from the interface 73. The print job includes image data including RGB values, and the image data is stored in the storage unit 72 (step S1).

[0040] When the controller 7 receives a print job, it performs halftone processing on the image data containing RGB values. This halftone processing generates print data for ejecting ink from the ejection head 4. This print data is data that expresses the color of each pixel represented in the original image data using ink of predetermined colors, such as cyan, yellow, magenta, and black. This halftone processing can employ known data conversion methods, such as dithering and error diffusion. Then, pass print data is generated from the print data, in which pass print data for one pass corresponding to a partial image to be formed on the recording medium 110 by ejecting ink from the ejection head 4 while the ejection head 4 is moved in one direction of the main scanning direction is arranged in pass printing order (step S2). The pass print data is data that indicates the drive mode of the nozzles 41 for each position of the carriage 21 within the reciprocating movement range Z of the carriage 21, and includes the ejection waveform for each pass.

[0041] Next, the controller 7 calculates the duty ratio for each pass (step S4). The duty ratio is the ratio of the amount of liquid ejected from the nozzle 41 by the ejection waveform to the maximum amount of liquid that can be ejected from the nozzle 41.

[0042] Next, the controller 7 determines whether or not the duty ratio of each pass is equal to or greater than a first threshold value (step S5). The first threshold value is, for example, 80 percent, but is not limited to this.

[0043] Then, when the controller 7 determines that the duty ratio of the pass is less than the first threshold value (No in step S5), it sets the non-ejection waveform following the ejection waveform of the pass to the strong waveform W1. That is, the controller 7 sets the non-ejection waveform of the non-ejection flushing performed in the non-printing region Q in the section where the carriage 21 is decelerated after passing through the printing region P to the strong waveform W1 (step S6). Note that the non-ejection waveform of the non-ejection flushing performed in the non-printing region Q in the acceleration section of the next pass may also be set to the strong waveform W1.

[0044] Then, the controller 7 sets the time interval between one pass printing process and the pass printing process next to the first pass printing process, i.e., the waiting time of the ejection head 4 between pass printing processes, to T1 (step S7). The waiting time T1 is a time set according to, for example, the time required for the conveying unit 12 to convey the recording medium 110 in the sub-scanning direction for one pass.

[0045] On the other hand, if the controller 7 determines in step S5 that the duty ratio of the pass is equal to or greater than the first threshold value (Yes in step S5), it sets the non-ejection waveform following the ejection waveform of the pass to the weak waveform W2. That is, the controller 7 sets the non-ejection waveform of the non-ejection flushing performed in the non-printing region Q in the section where the carriage 21 is decelerated after passing through the printing region P to the weak waveform W2 (step S9). Note that in addition to the non-ejection waveform following the ejection waveform of the pass, the non-ejection waveform of the non-ejection flushing performed in the non-printing region Q in the acceleration section of the next pass may also be set to the weak waveform W2.

[0046] Then, the controller 7 further determines whether or not the duty ratio is equal to or greater than a second threshold value (step S10). The second threshold value is, for example, 90 percent, but is not limited to this.

[0047] Then, when the controller 7 determines that the duty ratio is less than the second threshold value (No in step S10), it sets the time interval to the next pass printing process, i.e., the waiting time of the ejection head 4 between pass printing processes, to T1 (step S7).

[0048] On the other hand, if the controller 7 determines that the duty ratio is equal to or greater than the second threshold value (Yes in step S10), it sets the time interval to the next pass printing process, i.e., the waiting time of the ejection head 4 between pass printing processes, to T2, which is longer than T1 (step S11).

[0049] Then, after step S7 or step S11, the controller 7 generates a drive signal for the actuator 42 based on the settings of the non-ejection waveform and standby time, and outputs it together with other signals such as a drive signal for the movement mechanism 2. This executes the printing process (step S8). In the printing process, the controller 7 repeatedly executes the pass printing process, thereby sequentially printing partial images for one pass, and completes the printing process.

[0050] In this way, when the duty ratio of the ejection waveform is less than the first threshold, the non-ejection waveform for the section in which the carriage 21 decelerates in the non-printing region Q after passing through the printing region P, i.e., the non-ejection waveform following the ejection waveform, is set to the strong waveform W1, and the wait time is set to T1. As a result, in a pass printing process with a low duty ratio, by setting the non-ejection waveform to the strong waveform W1, the ink inside the nozzle 41 is strongly vibrated without being ejected, and the state of the meniscus can be maintained normal. Furthermore, by shortening the wait time between printing passes, the time required for the printing process can be shortened.

[0051] Furthermore, when the duty ratio of the ejection waveform is equal to or greater than the first threshold and less than the second threshold, the non-ejection waveform for the section in which the carriage 21 decelerates in the non-printing region Q after passing through the printing region P is set to the weak waveform W2, and the standby time is set to T1. In this way, in a pass printing process with a high duty ratio, by setting the non-ejection waveform to the weak waveform W2, the ink in the nozzle 41 is vibrated weakly without being ejected, and it is possible to prevent negative pressure generated in the pressure chamber 45 from propagating to the nozzle 41. In addition, in a pass printing process with a high duty ratio, the meniscus is maintained normal by ejecting ink from the nozzle 41. Therefore, it is possible to prevent abnormalities in the meniscus by using the weak waveform W2, rather than the strong waveform W1. This makes it possible to prevent external air from being drawn into the nozzle 41, thereby suppressing ejection defects.

[0052] Furthermore, when the duty ratio of the ejection waveform is equal to or greater than the second threshold, the non-ejection waveform for the section in which the carriage 21 decelerates in the non-printing region Q after passing through the printing region P is set to a weak waveform W2, and the standby time is set to T2, which is longer than T1. As a result, in pass printing processes with an especially high duty ratio, by lengthening the standby time of the carriage 21 between pass printing processes, ink flows from the supply flow path 5 into the pressure chamber 45 during the extended time, and the excessive negative pressure generated in the pressure chamber 45 can be eliminated. This makes it possible to suppress ejection defects.

[0053] In this way, when the liquid ejection device 100 performs a printing process with a high duty ratio, the non-ejection waveform following the ejection waveform is a waveform that vibrates the liquid in the pressure chamber 45 more weakly than the waveform when performing a printing process with a low duty ratio, thereby preventing ejection defects while suppressing thickening of the liquid.

[0054] Furthermore, when the liquid ejection device 100 executes a printing process with a particularly high duty ratio, it lengthens the waiting time, which is the time interval between one pass printing process and the next pass printing process after the first pass printing process, thereby effectively eliminating the excessive negative pressure generated in the pressure chamber 45 and preventing ejection failures.

[0055] (Embodiment 2) The differences from the first embodiment will be explained.

[0056] In the first embodiment, the weak waveform W2 is a waveform that has a peak value that is positively correlated with the vibration intensity during non-ejection flushing and is smaller than that of the strong waveform W1.

[0057] 7, in this embodiment, the weak waveform W22 is a waveform in which the wavelength that has a positive correlation with the vibration intensity during non-ejection flushing is smaller than the wavelength of the strong waveform W21. As a result, when performing a printing process with a high duty ratio, the liquid inside the pressure chamber 45 can be vibrated more weakly than when performing a printing process with a low duty ratio. This makes it possible to prevent ejection defects while suppressing thickening of the liquid.

[0058] (Embodiment 3) Differences from the first embodiment will now be described. In the first embodiment, the weak waveform W2 is a waveform in which the peak value, which is positively correlated with the vibration intensity during non-ejection flushing, is smaller than that of the strong waveform W1. In the present embodiment, as shown in FIG. 8, the weak waveform W32 shown by the dashed dotted line is a waveform in which the period A2, which is positively correlated with the frequency of vibration during non-ejection flushing, is longer than the period A1 of the strong waveform W31 shown by the solid line. This allows the liquid in the pressure chamber 45 to vibrate more weakly when a printing process with a high duty ratio is performed than when a printing process with a low duty ratio is performed. This makes it possible to prevent ejection defects while suppressing thickening of the liquid.

[0059] (Fourth embodiment) The differences from the first embodiment will now be described. In the first embodiment, the weak waveform W2 is a waveform in which the peak value, which has a positive correlation with the vibration intensity during non-ejection flushing, is smaller than that of the strong waveform W1. In the present embodiment, as shown in FIG. 9, the weak waveform W42 shown by the dashed dotted line is a waveform in which at least one of the rising slope and the falling slope is gentler than that of the strong waveform W41 shown by the solid line. This allows the liquid in the pressure chamber 45 to vibrate more weakly when a printing process with a high duty ratio is performed than when a printing process with a low duty ratio is performed. This makes it possible to prevent ejection defects while suppressing the viscosity of the liquid.

[0060] (Embodiment 5) Differences from the first embodiment will now be described. Fig. 10 is a block diagram showing an example of the functional configuration of a liquid ejection device 400 according to the fourth embodiment. In this embodiment, as shown in Fig. 10, a pressure sensor 8 that detects the pressure in the supply flow path 5 is provided in the supply flow path 5. More specifically, the pressure sensor 8 is provided in the ejection head 4 and detects the pressure in the in-head flow path 62. This allows the pressure sensor 8 to detect the pressure in the pressure chamber 45 that communicates with the supply flow path 5.

[0061] [Example of operation] Next, an example of the operation of the printing process of the liquid ejection device 400 will be specifically described.

[0062] FIG. 11 is a flowchart showing an example of the operation of the liquid ejection device 400.

[0063] First, the controller 7 of the liquid ejection device 400 acquires image data (step S501) and generates pass print data (step S502). Then, the controller 7 sets the non-ejection waveform following the pass ejection waveform to a strong waveform W1 (step S504), and sets the waiting time of the ejection head 4 between pass printing processes to T1 (step S505). Steps S501 to S505 are the same as steps S1, S2, S6, and S7 according to the first embodiment, respectively, and therefore their description will be omitted. Next, the controller 7 generates and outputs a drive signal. This executes the printing process (step S506). The drive signal is output sequentially as the printing process progresses.

[0064] Next, as the printing process progresses, it is determined whether the pressure in the supply flow path 5 detected by the pressure sensor 8 is equal to or greater than a predetermined third threshold value (step S507). The third threshold value is a pressure determined by, for example, measuring in advance the pressure in the supply flow path 5 that occurs when a printing process with a high duty ratio is executed. The third threshold value is set to a value equal to or less than the pressure in the supply flow path 5 at which poor ink ejection from the nozzles 41 is observed.

[0065] If the controller 7 determines that the pressure in the supply flow path 5 detected by the pressure sensor 8 is less than the third threshold value (No in step S507), it further determines whether printing has finished (step S508). If it determines that printing has not finished (No in step S508), it executes the determination in step S507 again. On the other hand, if it determines that printing has finished (No in step S508), it ends the printing process.

[0066] Thus, in each printing pass, when the carriage 21 passes through the printing region P of the pass while the maximum pressure in the supply flow path 5 is below the third threshold, the non-ejection waveform for the section in which the carriage 21 decelerates in the non-printing region Q, i.e., the non-ejection waveform following the ejection waveform, is set to the strong waveform W1. This causes the ink inside the nozzles 41 to vibrate strongly without ejecting, and the state of the meniscus can be maintained normal. In addition, the waiting time between printing passes is set to T1. This shortens the waiting time between printing passes, and shortens the time required for the printing process.

[0067] On the other hand, if the controller 7 determines in step S507 that the pressure in the supply flow path 5 detected by the pressure sensor 8 is equal to or greater than the third threshold (Yes in step S507), it changes the non-ejection waveform following the ejection waveform of the pass currently being printed to a weak waveform W2 and outputs it (step S509). Next, the controller 7 further determines whether the pressure in the supply flow path 5 detected by the pressure sensor 8 is equal to or greater than a fourth threshold (step S510). The fourth threshold is a pressure higher than the third threshold, and is a pressure determined, for example, by measuring in advance the high pressure in the supply flow path 5 that occurs when a printing process with an especially high duty ratio is executed.

[0068] Then, when the controller 7 determines that the pressure in the supply flow path 5 detected by the pressure sensor 8 is less than the fourth threshold value (No in step S510), it executes the determination in step S508 and the subsequent processes.

[0069] In this way, in each pass printing, when the maximum pressure in the supply flow path 5 is equal to or greater than the third threshold value and less than the fourth threshold value and the carriage 21 passes through the printing region P, the non-ejection waveform in the section where the carriage 21 is decelerated in the non-printing region Q is changed to the weak waveform W2. This makes it possible to suppress the negative pressure generated in the pressure chamber 45 from propagating to the nozzle 41, preventing external air from being drawn into the nozzle 41 and suppressing ejection defects.

[0070] On the other hand, if the controller 7 determines in step S510 that the pressure in the supply flow path 5 detected by the pressure sensor 8 is equal to or greater than the fourth threshold value (Yes in step S510), it changes the standby time of the ejection head 4 between pass printing processes to T2, which is longer than T1 (step S511), and then executes the determination in step S508 and the subsequent processes.

[0071] In this way, in each pass printing, when the maximum pressure of the supply flow path 5 is equal to or greater than the fourth threshold and the carriage 21 passes through the printing area P, not only is the non-ejection waveform changed to the weak waveform W2, but the standby time of the ejection head 4 between pass printing processes is also changed to T2, which is longer than T1. As a result, during the extended standby time, ink flows from the supply flow path 5 into the pressure chamber 45, and the excessive negative pressure generated in the pressure chamber 45 can be eliminated. This makes it possible to suppress ejection defects.

[0072] Then, the controller 7 repeatedly executes the pass printing process to sequentially print partial images for one pass, and completes the printing process.

[0073] In this way, when the pressure sensor 8 detects that high pressure is occurring in the supply flow path 5, the liquid ejection device 400 sets the non-ejection waveform to a waveform that vibrates the liquid in the pressure chamber 45 more weakly than the non-ejection waveform when performing a printing process with a low duty ratio, thereby preventing ejection failures while suppressing thickening of the liquid.

[0074] Furthermore, when the pressure sensor 8 detects that high pressure is occurring in the supply flow path 5, the liquid ejection device 100 lengthens the waiting time, which is the time interval between one pass printing process and the pass printing process next to the first pass printing process, thereby effectively eliminating the excessive negative pressure occurring in the pressure chamber 45 and preventing ejection failures.

[0075] (Sixth embodiment) The differences from the first embodiment will be explained.

[0076] In the first embodiment described above, the controller 7 performs non-ejection flushing in the non-printing region Q shown in Fig. 4. Then, when it is determined that the duty ratio of the pass is equal to or greater than the first threshold value (Yes in step S5), the controller 7 sets the non-ejection waveform following the ejection waveform of the pass to the weak waveform W2. That is, the controller 7 sets the non-ejection waveform of the non-ejection flushing performed in the non-printing region Q in the section where the carriage 21 is decelerated after passing through the printing region P to the weak waveform W2 (step S9).

[0077] FIG. 12 is a plan view schematically illustrating the relationship between the ejection head 4 of the liquid ejection device according to the sixth embodiment and the printing region P and non-printing region Q. In this embodiment, the controller 7 inserts a non-drive waveform into the drive signal to perform non-ejection flushing in the regions indicated by hatched lines in FIG. 12. That is, the controller 7 inserts a non-drive waveform into the drive signal to perform non-ejection flushing in regions of the printing region P where ink ejection from the nozzles 41 is temporarily suspended, in addition to the non-printing region Q. As a result, the drive signal output to the actuator 42 includes a first non-ejection waveform, which is a waveform that drives the actuator 42 to vibrate without ejecting liquid in the pressure chambers 45 of the nozzles 41 located in the non-printing region Q, and a second non-ejection waveform, which is a waveform that drives the actuator 42 to vibrate without ejecting liquid in the pressure chambers 45 of the nozzles 41 located in the printing region P.

[0078] Then, if the controller 7 determines in step S5 that the duty ratio of the pass is less than the first threshold value (No in step S5), it sets the second non-ejection waveform to the strong waveform W1 in addition to the first non-ejection waveform. On the other hand, if the controller 7 determines in step S5 that the duty ratio of the pass is equal to or greater than the first threshold value (Yes in step S5), it sets the second non-ejection waveform to the weak waveform W2 in addition to the first non-ejection waveform. This makes it possible to more appropriately suppress thickening of the liquid while preventing ejection defects.

[0079] 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]

[0080] P print area Q non-print area 2 Moving mechanism 4 Discharge head 7 Controller 41 nozzle 42 Actuator 45 Pressure Chamber 100 Liquid dispensing device 110 Recording medium

Claims

1. an ejection head having a nozzle capable of ejecting liquid toward a recording medium, a pressure chamber communicating with the nozzle, and an actuator that changes the volume of the pressure chamber in response to a drive signal; a movement mechanism that moves the ejection head and the recording medium relative to each other so that the nozzles pass through a printing area, which is an area to be printed on the recording medium, and a non-printing area; a controller that generates and outputs the drive signal having an ejection waveform, which is a waveform that drives the actuator to eject the liquid from the nozzle located in the printing area, and a first non-ejection waveform, which is a waveform that drives the actuator to vibrate the liquid in the pressure chamber of the nozzle located in the non-printing area without ejecting it; The controller a printing process of outputting the drive signal while moving the ejection head and the recording medium relative to each other so that the nozzles pass through the printing area and the non-printing area is repeatedly performed; When it is determined that the duty ratio, which is the ratio of the amount of liquid ejected from the nozzle by the ejection waveform to the maximum amount of liquid that can be ejected from the nozzle in the printing process of 1, is equal to or greater than a first threshold value, the liquid ejection device sets the first non-ejection waveform following the ejection waveform to a waveform that vibrates the liquid in the pressure chamber more weakly than the first non-ejection waveform when the duty ratio is less than the first threshold value.

2. the moving mechanism includes a carriage that supports the ejection head and moves back and forth in a first direction; The controller the printing process is a pass printing process in which the driving signal is output while the carriage is moved in the first direction, 2. A liquid ejection device as described in claim 1, wherein, when it is determined that the duty ratio in one pass printing process is equal to or greater than a second threshold value that is greater than the first threshold value, the waiting time, which is the time interval between the one pass printing process and the pass printing process next to the one pass printing process, is made longer than the waiting time when the duty ratio is less than the second threshold value.

3. 2. The liquid ejection device according to claim 1, wherein the first non-ejection waveform when the duty ratio is equal to or greater than the first threshold has a peak value or wavelength that is positively correlated with vibration intensity that is smaller than that of the first non-ejection waveform when the duty ratio is less than the first threshold.

4. 2. The liquid ejection device according to claim 1, wherein the first non-ejection waveform when the duty ratio is equal to or greater than the first threshold has a period that is positively correlated with the frequency of vibration that is longer than the first non-ejection waveform when the duty ratio is less than the first threshold.

5. 2. The liquid ejection device according to claim 1, wherein when the duty ratio is equal to or greater than the first threshold, at least one of the rising slope and the falling slope of the first non-ejection waveform is gentler than when the duty ratio is less than the first threshold.

6. The liquid ejection device of claim 1 , wherein the first threshold is 80 percent.

7. The liquid ejection device according to claim 2 , wherein the second threshold is 90 percent.

8. a supply flow channel that supplies the liquid to the pressure chamber; a pressure sensor that detects the pressure in the supply flow path; 2. The liquid ejection device according to claim 1, wherein, when the controller determines that the pressure detected by the pressure sensor is equal to or greater than a third threshold, the controller sets the first non-ejection waveform to a waveform that vibrates the liquid in the pressure chamber more weakly than the first non-ejection waveform when the pressure in the pressure chamber is less than the third threshold.

9. The liquid ejection device according to claim 1 , wherein the non-printing area is an area other than an area to be printed on the recording medium.

10. the drive signal has a second non-ejection waveform that is a waveform that drives the actuator to vibrate the liquid in the pressure chamber of the nozzle located in the printing area without ejecting the liquid, 2. The liquid ejection device according to claim 1, wherein when the controller determines that the duty ratio in one of the printing processes is equal to or greater than the first threshold value, the controller sets the second non-ejection waveform following the ejection waveform to a waveform that vibrates the liquid in the pressure chamber more weakly than the second non-ejection waveform when the duty ratio is less than the first threshold value.

11. an ejection head having a nozzle capable of ejecting liquid toward a recording medium, a pressure chamber communicating with the nozzle, and an actuator that changes the volume of the pressure chamber in response to a drive signal; a movement mechanism that moves the ejection head and the recording medium relative to each other so that the nozzles pass through a printing area, which is an area to be printed on the recording medium, and a non-printing area, the method comprising: a printing process in which the ejection head and the recording medium are moved relative to each other so that the nozzles pass through the printing area and the non-printing area, and the drive signal is output; In each of the printing processes, generating and outputting the drive signal having an ejection waveform, which is a waveform that drives the actuator to eject the liquid from the nozzle located in the printing area, and a first non-ejection waveform, which is a waveform that drives the actuator to vibrate the liquid in the pressure chamber of the nozzle located in the non-printing area without ejecting it, determining whether a duty ratio, which is a ratio of the amount of liquid ejected from the nozzle by the ejection waveform to the maximum amount of liquid that can be ejected from the nozzle in the printing process of 1, is equal to or greater than a first threshold value; A control method for a liquid ejection device, wherein, when it is determined that the duty ratio is equal to or greater than the first threshold, the first non-ejection waveform following the ejection waveform is set to a waveform that vibrates the liquid in the pressure chamber more weakly than the first non-ejection waveform when the duty ratio is less than the first threshold.

Images