Liquid discharge device and defective nozzle determination method

Abstract

To enable the improvement for efficiently executing processing for determining presence / absence of defects of a nozzle.SOLUTION: A liquid discharge device includes: a liquid discharge head having a plurality of nozzles; a carriage mounted with the liquid discharge head and alternately executing first movement as movement in a first direction and second movement as movement in a second direction opposite to the first direction; and a control part for controlling the liquid discharge head and the carriage, wherein the control part can determine whether or not the nozzle is a defective nozzle on the basis of vibration generated by applying a driving signal having a specific waveform different from a driving signal for discharging a liquid from the nozzle to a piezoelectric element, and applies the driving signal having the specific waveform in a deceleration / acceleration period astride a first moving deceleration period until the carriage during the first movement is decelerated and stopped from a state of constant movement, and a second moving acceleration period which is a period later than the first moving deceleration period and until the carriage becomes in the state of constant movement after being accelerated from the stop state and starting second movement.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a liquid ejection apparatus and a method for determining a defective nozzle. [Background technology]

[0002] Inkjet printers eject liquid such as ink from each nozzle of the head while moving a carriage carrying a head having multiple nozzles back and forth along a predetermined main scanning direction to print on a medium such as paper. In such inkjet printers, solidified ink or debris can clog the nozzles, causing problems with ejecting liquid from the nozzles. A nozzle in which a defect has occurred is called a defective nozzle. Defective can also be referred to as abnormal. Conventionally, a process has been performed to determine whether or not a nozzle is defective (see Patent Document 1).

[0003] Patent document 1 discloses a method of supplying a drive signal to a piezoelectric element provided corresponding to each nozzle and determining whether or not a nozzle is defective based on the so-called residual vibration that occurs after the piezoelectric element is driven in response to the drive signal. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-149551 A Summary of the Invention [Problem to be solved by the invention]

[0005] The movement of the carriage consists of an acceleration period in which it accelerates from a stopped state to a predetermined speed, a constant speed period in which it moves at a constant speed at the predetermined speed, and a deceleration period in which it decelerates from the constant speed state to a stop. Such acceleration periods, constant speed periods, and deceleration periods exist for both outward movement and return movement along the main scanning direction. Printing on the medium is performed mainly during the constant speed period in which the carriage passes over the medium. Meanwhile, at the beginning of the acceleration period and the end of the deceleration period, the carriage is positioned outside the medium. For this reason, conventional inkjet printers have determined the presence or absence of nozzle defects based on the above-mentioned residual vibrations by using either the acceleration period or the deceleration period of the carriage in association with carriage movement control.

[0006] In the inkjet printer, for a nozzle determined to be defective, the missing dots on the medium can be compensated for in subsequent printing by ejecting liquid using a nozzle located in a position that can substitute for the defective nozzle, such as a nozzle adjacent to the defective nozzle. However, the head has many nozzles. In the inkjet printer, there is a limit to the processing capacity for generating residual vibrations and determining whether a nozzle is defective based on the residual vibrations, so that the determination can only be made for some of the nozzles during one movement of the carriage. If a nozzle is defective but is not subject to the determination as to whether it is defective, the missing dots caused by that nozzle will not be compensated for in subsequent printing performed until it becomes subject to the determination as to whether it is defective, which causes a decrease in print quality. In view of this situation, there is a need for improvements to efficiently execute the process of determining whether or not a nozzle is defective. [Means for solving the problem]

[0007] The liquid ejection device is capable of generating pressure fluctuations in a pressure chamber by driving a piezoelectric element, thereby ejecting liquid filled in the pressure chamber from a nozzle, and comprises a liquid ejection head having a plurality of nozzles, a carriage mounted with the liquid ejection head and alternately performing a first movement, which is movement in a first direction, and a second movement, which is movement in a second direction opposite to the first direction, and a control unit for controlling the liquid ejection head and the carriage, wherein the control unit is capable of executing a defective nozzle determination process for each of the plurality of nozzles, which determines whether the nozzle is a defective nozzle based on vibrations generated by applying to the piezoelectric element a drive signal of a specific waveform different from a drive signal applied to the piezoelectric element to eject liquid from the nozzle, and applies the drive signal of the specific waveform during a deceleration / acceleration period, which is a period spanning a first movement deceleration period, which is a period during which the carriage during the first movement decelerates from a predetermined constant speed movement state to a stop, and a second movement acceleration period, which is a period after the first movement deceleration period and is a period during which the carriage accelerates from a stopped state to start the second movement and reach the constant speed movement state.

[0008] A faulty nozzle determination method executed by a liquid ejection device, the liquid ejection device being capable of generating pressure fluctuations in a pressure chamber by driving a piezoelectric element, thereby ejecting liquid filled in the pressure chamber from a nozzle, the liquid ejection device comprising: a liquid ejection head having a plurality of the nozzles; and a carriage mounted with the liquid ejection head, which alternately performs a first movement, which is movement in a first direction, and a second movement, which is movement in a second direction opposite to the first direction, the liquid ejection head being capable of executing a faulty nozzle determination process for each of the plurality of nozzles, which determines whether or not the nozzle is a faulty nozzle based on vibrations generated by applying to the piezoelectric element a drive signal of a specific waveform different from a drive signal applied to the piezoelectric element to eject liquid from the nozzle, the drive signal of the specific waveform being applied during the first movement, the carriage decelerating from a predetermined constant speed movement state during the first movement to a stop, and a second movement acceleration period, which is a period after the first movement deceleration period and is a period during which the carriage accelerates from a stopped state to start the second movement and reach the constant speed movement state. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a simplified device configuration. [Diagram 2] FIG. 4 is a diagram showing the relationship between the medium and the liquid ejection head as viewed from above. [Diagram 3] FIG. 4 is a cross-sectional view showing a simplified structure including one nozzle and a piezoelectric element corresponding to the nozzle. [Figure 4] 3A and 3B are diagrams simply illustrating various drive signals applied to each piezoelectric element in the embodiment. [Diagram 5] 5A and 5B are diagrams each simply illustrating a conventional technique to be compared with this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the drawings are merely examples for explaining the present embodiment. Since the drawings are examples, the shapes may not be accurate, the drawings may not match each other, and some parts may be omitted.

[0011] 1 shows a simplified configuration of a liquid ejection device 10 according to this embodiment. The liquid ejection device 10 includes a control unit 11, a display unit 13, an operation reception unit 14, a communication IF 15, a storage unit 16, a transport unit 17, a carriage 18, a liquid ejection head 19, a drive circuit 21, and the like. IF stands for interface. The control unit 11 includes one or more ICs having a CPU 11a as a processor, a ROM 11b, a RAM 11c, and the like, and other non-volatile memories, and the like.

[0012] In the control unit 11, a processor, i.e., a CPU 11a, executes arithmetic processing according to one or more programs 12 stored in a ROM 11b or other memory, using a RAM 11c or the like as a work area, thereby controlling the liquid ejection device 10. Note that the processor is not limited to a single CPU, and may be configured to perform processing using multiple CPUs or a hardware circuit such as an ASIC, or may be configured to perform processing in cooperation with a CPU and a hardware circuit.

[0013] The display unit 13 is a means for displaying visual information, and is configured, for example, by a liquid crystal display, an organic EL display, or the like. The display unit 13 may be configured to include a display and a drive circuit for driving the display. The operation reception unit 14 is a means for receiving operations by a user, and is realized, for example, by a physical button, a touch panel, a mouse, a keyboard, or the like. Of course, the touch panel may be realized as one function of the display unit 13.

[0014] The communication IF 15 is a collective term for one or more IFs for connecting the liquid ejection device 10 to an external device via a wired or wireless connection in compliance with a predetermined communication protocol including a known communication standard. The external device is, for example, various communication devices such as a personal computer, a server, a smartphone, or a tablet terminal.

[0015] The storage unit 16 is configured with a storage device such as a hard disk drive or a solid state drive. The storage unit 16 may be a part of the memory of the control unit 11. The storage unit 16 may also be understood as a part of the control unit 11. The storage unit 16 stores various information necessary for controlling the liquid ejection device 10.

[0016] The transport unit 17 is a means for transporting the medium in a predetermined transport direction, and includes a rotating roller and a motor for rotating the roller, etc. The upstream and downstream of the transport are simply referred to as upstream and downstream below. The medium is typically paper, but other than paper, various materials that can be the subject of printing or recording with liquid, such as fabric and film, can be used as the medium. The transport direction is also called the sub-scanning direction. The transport unit 17 may be a mechanism for transporting the medium on a belt or pallet.

[0017] The carriage 18 is a mechanism capable of reciprocating along a predetermined main scanning direction by receiving power from a carriage motor (not shown). The main scanning direction and the transport direction intersect. The intersection of the main scanning direction and the transport direction may be interpreted as being perpendicular or nearly perpendicular. The carriage 18 is equipped with a liquid ejection head 19. Therefore, the liquid ejection head 19 moves back and forth along the main scanning direction together with the carriage 18. The movement of the liquid ejection head 19 and the movement of the carriage 18 are synonymous.

[0018] The liquid ejection head 19 has a plurality of nozzles 20 capable of ejecting liquid. A drive circuit 21 that drives each nozzle 20 under the control of the control unit 11 is connected to the liquid ejection head 19. The nozzles 20 eject dots, which are droplets. The liquid ejection head 19 ejects liquid based on print data for printing an image. As is known, the control unit 11 controls the application of a drive signal to a piezoelectric element provided in each nozzle 20 through the drive circuit 21 according to the print data, thereby causing each nozzle 20 to eject or not eject dots, thereby printing an image on a medium. The drive circuit 21 may be regarded as a part of the control unit 11. The liquid ejection head 19 is capable of ejecting ink of various colors, such as cyan (C) ink, magenta (M) ink, yellow (Y) ink, and black (K) ink. Of course, the color of ink ejected by the liquid ejection head 19 is not limited to CMYK. The liquid ejection head 19 is also capable of ejecting various liquids, including ink and liquids that do not fall under the category of ink.

[0019] FIG. 2 shows a simplified relationship between the medium 30 and the liquid ejection head 19 from a top view. The carriage 18 carrying the liquid ejection head 19 alternates between a "first movement" in a first direction D1 and a "second movement" in a second direction D2 opposite to the first direction D1. In other words, the first direction D1 and the second direction D2 correspond to the main scanning direction. It does not matter whether the first movement or the second movement is regarded as the forward movement. For example, the first movement is regarded as the forward movement of the carriage 18, and the second movement is regarded as the return movement of the carriage 18. A direction D3 intersecting the first direction D1 and the second direction D2 is the conveying direction D3 of the medium 30 by the conveying unit 17.

[0020] 2 shows an example of an arrangement of nozzles 20 on a nozzle surface 23. The nozzle surface 23 is the lower surface of the liquid ejection head 19, and is the surface facing the medium 30. Each small circle in the nozzle surface 23 represents each nozzle 20. The liquid ejection head 19 is configured to receive ink of each color from liquid holding means (not shown) called an ink cartridge or ink tank, and eject the ink from the nozzles 20, and is provided with nozzle rows 24 for each ink color. FIG. 2 shows an example of a liquid ejection head 19 that ejects CMYK inks.

[0021] The nozzle row 24 consisting of the nozzles 20 that eject the C ink is the nozzle row 24C. Similarly, the nozzle row 24 consisting of the nozzles 20 that eject the M ink is the nozzle row 24M, the nozzle row 24 consisting of the nozzles 20 that eject the Y ink is the nozzle row 24Y, and the nozzle row 24 consisting of the nozzles 20 that eject the K ink is the nozzle row 24K. In the example of FIG. 2, the nozzle rows 24C, 24M, 24Y, and 24K are arranged along the directions D1 and D2. Furthermore, these multiple nozzle rows 24 for each color are arranged at the same position in the transport direction D3. One nozzle row 24 is composed of multiple nozzles 20 whose nozzle intervals, which are the intervals between the nozzles 20 in the transport direction D3, are constant or approximately constant.

[0022] The operation of the liquid ejection head 19 ejecting liquid together with the first and second movements of the carriage 18 is called a main scan or a pass. Also, the operation of the transport unit 17 transporting the medium 30 a determined distance from upstream to downstream between passes is called paper feed. The control unit 11 controls the liquid ejection head 19, the carriage 18, and the transport unit 17 to execute passes and paper feed, making it possible to print a two-dimensional image on the medium 30.

[0023] The liquid ejection device 10 has a maintenance box 22 that receives and stores waste liquid ejected by the liquid ejection head 19. The maintenance box 22 will be abbreviated as MTB 22 below. The MTB 22 is disposed within the range of movement of the liquid ejection head 19 by the carriage 18 and at a predetermined position outside the printing area through which the medium 30 passes. In the example of FIG. 2, the MTB 22 is disposed forward of the printing area corresponding to the medium 30 in the first direction D1. The control unit 11 causes the liquid ejection head 19 to perform so-called flushing when the liquid ejection head 19 is on the MTB 22.

[0024] Flushing is a type of maintenance for the liquid ejection head 19, and improves clogging of each nozzle 20 by forcibly causing each nozzle 20 to eject liquid. The liquid ejected by flushing is received by the MTB 22. In the example of FIG. 2, in order to prevent the device from becoming large, the width of the MTB 22 in the main scanning direction is designed to be smaller than the width of the liquid ejection head 19. Therefore, the liquid ejection head 19 flushes each nozzle row 24 at the timing when the nozzle row 24 passes over the MTB 22 while being moved by the carriage 18.

[0025] 1 may be realized by a single printer, or may be realized by a plurality of devices connected to each other so as to be able to communicate with each other. In other words, the liquid ejection device 10 may actually be a liquid ejection system 10. The liquid ejection system 10 includes, for example, a control device that functions as a control unit 11, and a printer having a transport unit 17, a carriage 18, a liquid ejection head 19, a drive circuit 21, and the like. The liquid ejection device 10 or liquid ejection system 10 described above realizes a liquid ejection method and a defective nozzle determination method.

[0026] FIG. 3 is a simplified cross-sectional view of a part of the internal structure of the liquid ejection head 19, including one nozzle 20 and a piezoelectric element 25 corresponding to the nozzle 20. The structure is formed of multiple layers. Of course, various specific examples of the structure including the nozzle 20 and the piezoelectric element 25 corresponding to the nozzle 20 are known, so it is not necessary to be as shown in FIG. 3. The nozzle 20 opening on the nozzle surface 23 communicates with a pressure chamber 27 inside the liquid ejection head 19. Although not shown, the pressure chamber 27 is filled with a liquid such as ink. One of the walls surrounding the pressure chamber 27 is a vibration plate 26, and a piezoelectric element 25 is provided on the surface of the vibration plate 26 opposite the pressure chamber 27. The piezoelectric element 25 in FIG. 3 may be interpreted as an actuator including a piezoelectric element and an electrode attached to drive the piezoelectric element.

[0027] Under the control of the control unit 11, a drive signal is applied to the piezoelectric element 25 through the drive circuit 21 as described above, which causes the piezoelectric element 25 to deform and the vibration plate 26 to bend, generating a pressure fluctuation within the pressure chamber 27. In response to this pressure fluctuation, liquid is pushed out of the pressure chamber 27, and dots of liquid are ejected outside the nozzle face 23 through the nozzle 20.

[0028] The control unit 11 can execute a defective nozzle determination process for each of the multiple nozzles 20, which determines whether the nozzle 20 is a defective nozzle based on vibrations generated by applying a drive signal of a "specific waveform" different from the drive signal applied to the piezoelectric element 25 to eject liquid from the nozzle 20 to the piezoelectric element 25. The vibrations referred to here are so-called residual vibrations, and after applying a drive signal of a specific waveform to the piezoelectric element 25 to drive the piezoelectric element 25, for example, the vibration plate 26 vibrates. The control unit 11 determines whether the nozzle 20 is a defective nozzle by evaluating characteristics such as the frequency of the residual vibration signal generated in the piezoelectric element 25 in response to such residual vibrations based on a predetermined criterion. The method of determining whether a nozzle is a defective nozzle based on the residual vibrations is itself well known, so a detailed description will be omitted here.

[0029] In this embodiment, the control unit 11 applies a drive signal of a specific waveform to a "deceleration / acceleration period" which is a period spanning between a "first movement deceleration period", which is a period during which the carriage 18 during the first movement decelerates from a predetermined constant speed movement state to stop, and a "second movement acceleration period", which is a period after the first movement deceleration period, during which the carriage 18 accelerates from a stopped state to start the second movement and reach the constant speed movement state.

[0030] FIG. 4 is a diagram for explaining such features of the present embodiment, and shows in a simplified manner various drive signals applied from the drive circuit 21 to each piezoelectric element 25 under the control of the control unit 11. FIG. 4 shows a part of the period of the first movement of the carriage 18 and a part of the period of the second movement of the carriage 18 after the first movement. The period E between the first movement and the second movement is a stop period E during which the carriage 18 is stopped. After the carriage 18 finishes the first movement and before it starts the second movement, the speed of the carriage 18 always becomes 0. Therefore, even if the time during which the carriage 18 stops between the first movement and the second movement or between the second movement and the first movement is substantially 0 as perceived by the user, the stop period E does not strictly become 0.

[0031] The period A2 included in the first movement is a constant speed period A2 during which the carriage 18 moves at a constant speed. Of course, even if it is a constant speed, the speed is not necessarily constant in the strict sense, and there may be slight speed fluctuations. The last period A3 included in the first movement is a deceleration period A3 during which the carriage 18 decelerates from a constant speed movement state until it stops. In other words, the deceleration period A3 corresponds to the first movement deceleration period. The first period B1 included in the second movement is an acceleration period B1 during which the carriage 18 accelerates from a stopped state until it starts the second movement and moves at a constant speed. In other words, the acceleration period B1 corresponds to the second movement acceleration period. The period B2 included in the second movement is a constant speed period B2 during which the carriage 18 moves at a constant speed.

[0032] The print waveform 40 indicated by the reference symbol 40 is the waveform of the drive signal applied to the piezoelectric element 25 to eject liquid from the nozzle 20, and application of such a print waveform 40 executes a pass by the first movement, i.e., printing on the medium 30. In the first movement, the period during which the print waveform 40 is applied to the piezoelectric element 25 is basically the constant speed period A2, but it continues to be applied for a while even after the constant speed period A2 has ended and the deceleration period A3 has begun.

[0033] The micro-vibration waveform 41 indicated by the reference symbol 41 is the waveform of a drive signal applied to the piezoelectric element 25 to generate a predetermined micro-vibration, and application of the micro-vibration waveform 41 generates micro-vibrations in the nozzle 20, the pressure chamber 27, etc., and suppresses thickening of the ink. The micro-vibration waveform 41 is not a waveform for ejecting liquid from the nozzle 20. In the first movement, the micro-vibration waveform 41 is applied within the deceleration period A3, after the period in which the printing waveform 40 is applied to the piezoelectric element 25.

[0034] The FL waveform 42 indicated by the reference symbol 42 is the waveform of a drive signal applied to the piezoelectric element 25 for flushing, and application of the FL waveform 42 executes flushing, which forcibly ejects liquid from the nozzle 20. In the first movement, the FL waveform 42 is applied within the deceleration period A3, after the period in which the micro-vibration waveform 41 is applied to the piezoelectric element 25. As can be seen from the explanation of FIG. 2, the FL waveform 42 is applied to the piezoelectric element 25 at the timing when the carriage 18 passes over the MTB 22, in the deceleration period A3 of the first movement.

[0035] The test waveform 43 indicated by the reference symbol 43 is the waveform of a drive signal applied to the piezoelectric element 25 to generate residual vibration, and corresponds to the above-mentioned "specific waveform." The test waveform 43 drives the piezoelectric element 25 to an extent that does not cause liquid to be ejected from the nozzle 20, generating residual vibration. The residual vibration waveform 44 indicated by the reference symbol 44 indicates the waveform of a residual vibration signal generated in the piezoelectric element 25 in response to the residual vibration generated after the application of the test waveform 43 to the piezoelectric element 25, and is used in the defective nozzle determination process as described above.

[0036] In the first movement, the test waveform 43 is applied during the deceleration period A3, after the period in which the FL waveform 42 is applied to the piezoelectric element 25. Furthermore, as shown in Fig. 4, the test waveform 43 is also applied continuously during the stop period E after the deceleration period A3 and during the acceleration period B1 of the second movement. A continuous period F spanning part of the deceleration period A3, the stop period E, and part of the acceleration period B1 is the deceleration / acceleration period F that straddles the deceleration period A3 and the acceleration period B1. In other words, in this embodiment, such a deceleration / acceleration period F is the application period of the test waveform 43, and therefore the control unit 11 can perform defective nozzle determination processing for the multiple nozzles 20 in response to this period.

[0037] In the acceleration period B1 of the second movement, after the deceleration / acceleration period F, the micro-vibration waveform 41 is applied to the piezoelectric element 25. The application of the micro-vibration waveform 41 at this timing can be considered a preparatory operation necessary to smoothly start the subsequent printing. After the application of the micro-vibration waveform 41, the application of the printing waveform 40 starts at the end of the acceleration period B1 of the second movement, and the constant speed period B2 of the second movement begins. In this way, the pass by the second movement, that is, printing on the medium 30, is performed. Needless to say, the waveforms and the number of waveforms shown in FIG. 4 are merely examples and are not necessarily the same as the actual ones.

[0038] Figures 5A and 5B each show a conventional technique, and show various drive signals applied to a piezoelectric element in a simplified manner. Figures 5A and 5B can be viewed in the same way as Figure 4, so explanations common to Figure 4 will be omitted. In conventional liquid ejection devices, the timing of flushing and the execution of the defective nozzle determination process was controlled in association with either the deceleration period A3 of the first movement or the acceleration period B1 of the second movement.

[0039] According to FIG. 5A, from the start of the acceleration period B1 of the second movement, the application of the micro vibration waveform 41, the application of the FL waveform 42, and the application of the test waveform 43 are executed in this order. Before the application of the print waveform 40 in the second movement, it is necessary to secure a period during which the micro vibration waveform 41 is applied as a preparation operation. Therefore, the period during the acceleration period B1 of the second movement during which the test waveform 43 can be applied to the piezoelectric element and the defective nozzle determination process can be executed is quite limited. Also, if the distance over which the carriage 18 accelerates is increased, the acceleration period B1 can be secured longer, and the period during which the test waveform 43 is applied can also be extended, but in that case, the problem of the device becoming larger will arise.

[0040] 5B, during the deceleration period A3 of the first movement, after printing is completed, the application of the micro vibration waveform 41, the application of the FL waveform 42, and the application of the test waveform 43 are executed in that order, and the application of the test waveform 43 also ends with the stopping of the carriage 18. Therefore, the period during which the test waveform 43 can be applied to the piezoelectric element to execute the defective nozzle determination process is limited even in the example of FIG.

[0041] According to this embodiment, the liquid ejection device 10 is capable of generating pressure fluctuations in the pressure chamber 27 by driving the piezoelectric element 25, and ejecting liquid filled in the pressure chamber 27 from the nozzle 20, and is equipped with a liquid ejection head 19 having a plurality of nozzles 20, a carriage 18 on which the liquid ejection head 19 is mounted and which alternately performs a first movement, which is a movement in a first direction, and a second movement, which is a movement in a second direction opposite to the first direction, and a control unit 11 which controls the liquid ejection head 19 and the carriage 18. The control unit 11 is capable of executing a faulty nozzle determination process for each of the multiple nozzles 20, which determines whether or not the nozzle 20 is a faulty nozzle based on vibrations generated by applying to the piezoelectric element 25 a drive signal of a specific waveform different from the drive signal applied to the piezoelectric element 25 to eject liquid from the nozzle 20, and applies a drive signal of a specific waveform during a deceleration / acceleration period F which is a period spanning a first movement deceleration period, which is a period during which the carriage 18 during its first movement decelerates from a predetermined constant speed movement state to a stop, and a second movement acceleration period, which is a period after the first movement deceleration period and is a period during which the carriage 18 accelerates from a stopped state to start a second movement and reaches the constant speed movement state.

[0042] According to this configuration, the control unit 11 can apply a drive signal of a specific waveform to the piezoelectric element 25 by utilizing the deceleration / acceleration period F that spans the first movement deceleration period and the second movement acceleration period of the carriage 18, and perform defective nozzle determination processing. In other words, printing is performed on the medium 30 by alternately repeating the first movement and the second movement of the carriage 18 carrying the liquid ejection head 19, and the number of nozzles that are the subject of defective nozzle determination processing per one first movement and one second movement can be increased compared to the conventional method, and the efficiency of determining whether the nozzle 20 is defective or not can be increased compared to the conventional method. As a result, the control unit 11 can recognize that the nozzle 20 is a defective nozzle as quickly as possible, and can improve the print quality by performing the above-mentioned complementation in the subsequent pass.

[0043] This embodiment will be further described. The control unit 11 may set the length of the period during which a drive signal of a specific waveform is applied during one second movement acceleration period based on the minimum value of the second movement acceleration period calculated in advance in accordance with the acceleration error of the carriage 18.

[0044] The first movement and the second movement of the carriage 18 are attempted to realize an ideal speed by the control unit 11 performing feedback control of the carriage motor based on a predetermined speed table. Therefore, the lengths of the acceleration period, constant speed period, and deceleration period in each of the first movement and the second movement are also determined by design. However, due to individual differences in the liquid ejection device 10, the installation location of the liquid ejection device 10, the inclination of the posture, etc., errors may occur in the acceleration and deceleration of the carriage 18. Therefore, the error that may occur in the acceleration of the carriage 18 is assumed based on various factors, and the minimum value of the second movement acceleration period is calculated according to the assumed error.

[0045] As an example, the length of the second movement acceleration period required to reach a predetermined speed of constant speed movement from a speed 0 state is designed to be 1.0 seconds, and the minimum value of the length of the second movement acceleration period calculated as described above is 0.8 seconds. In addition, the application of the micro vibration waveform 41 in the acceleration period B1 of the second movement shown in FIG. 4 must be performed, for example, 0.3 seconds before the acceleration period B1 ends. Then, if the length of the acceleration period B1 is 1.0 seconds, there is a 0.7 second margin before the application of the micro vibration waveform 41 starts. However, if the length of the acceleration period B1 is the minimum value of 0.8 seconds, there is only a 0.5 second margin before the application of the micro vibration waveform 41 starts. In the acceleration period B1, the application of the test waveform 43 must be completed before the application of the micro vibration waveform 41 starts.

[0046] In consideration of such circumstances, the control unit 11 sets the length of the period during which the drive signal of the test waveform 43 is applied during one acceleration period B1 to, for example, 0.5 seconds from the start of the acceleration period B1 based on the minimum value of the length of the acceleration period B1, for example, 0.8 seconds, and executes it exactly as set. With such a configuration, it is possible to avoid a situation in which the application period of the test waveform 43 in the acceleration period B1 of the second movement interferes with the application period of the micro-vibration waveform 41, making it impossible to properly secure the application period of the micro-vibration waveform 41.

[0047] The liquid ejection head 19 has n nozzle rows 24 in which a plurality of nozzles 20 are aligned in a third direction D3 intersecting the first direction D1 and the second direction D2. Each of n and m is an integer of 2 or more. n is 4 in the example of FIG. 2, but it does not have to be 4. When the control unit 11 is capable of applying a drive signal of a specific waveform to a plurality of piezoelectric elements 25 corresponding to a plurality of nozzles 20 of m nozzle rows 24 (which is less than n rows) during one deceleration / acceleration period F, the control unit 11 may make the frequency of applying the drive signal of a specific waveform to the piezoelectric elements 25 different between the nozzle row 24 for ejecting a first color ink as a liquid and the nozzle row 24 for ejecting a second color ink different from the first color.

[0048] As an example, let us assume that n=12 and m=5. Assuming that the liquid ejection head 19 has 12 nozzle rows 24, the 12 nozzle rows 24 may be configured to eject ink of different colors, or, for example, two nozzle rows 24 may be assigned to one color to eject ink of a total of six colors. The control unit 11, as a processing capability including the drive circuit 21, etc., can apply the test waveform 43 to the multiple piezoelectric elements 25 corresponding to the multiple nozzles 20 of the five nozzle rows 24 during one deceleration / acceleration period F.

[0049] In this specific example, three deceleration / acceleration periods F, or six passes in terms of the number of passes, are required to perform defective nozzle determination processing for all 12 nozzle rows 24. On the other hand, three deceleration / acceleration periods F allow defective nozzle determination processing for a maximum of 3×5=15 nozzle rows 24. Therefore, the control unit 11 applies the test waveform 43 to the piezoelectric element 25 more frequently for the nozzle row 24 ejecting the first color, for example, K ink, in which the impact of missing dots due to defective nozzles on image quality is relatively large, than for the nozzle row 24 ejecting the ink of the other color (second color). In other words, of the three deceleration / acceleration periods F, the nozzle row 24 ejecting the K ink is subject to application of the test waveform 43 to the piezoelectric element 25 during each of two of the deceleration / acceleration periods F, and the nozzle row 24 ejecting the ink of the other colors is subject to application of the test waveform 43 to the piezoelectric element 25 during any one of the three deceleration / acceleration periods F. According to this configuration, the control unit 11 can maintain print quality more appropriately by taking into account the characteristics of the ink, by varying the frequency at which a drive signal of a specific waveform is applied to the piezoelectric element 25 depending on the color of the ink.

[0050] The control unit 11 may apply a drive signal of a specific waveform more times during a stop period E in which the carriage 18 is stopped during the deceleration / acceleration period F when the stop period E has a second length that is longer than a first length than the number of times during which the drive signal of a specific waveform is applied during the stop period E when the stop period E has a first length.

[0051] The length of the stop period E varies depending on various conditions. As described above, the stop period E may be set to substantially 0 as perceived by the user. Alternatively, the stop period E may be set to several seconds or several tens of seconds, taking into account the time required by the user to dry the ink or to wait for the completion of paper feed. The setting of the stop period E also differs depending on the type of medium 30 used for printing. In any case, the control unit 11 acquires the setting of the stop period E in the printing process, and varies the number of times the test waveform 43 is applied during the stop period E, that is, the number of nozzles to be subjected to the defective nozzle determination process, depending on the length of the stop period E. Basically, the longer the stop period E, the more times the test waveform 43 is applied during the stop period E.

[0052] As can be seen from the above explanation, the length of the period during which test waveform 43 can be applied depends on the number of times test waveform 43 is applied, that is, the number of nozzles that are the target of the defective nozzle determination process. Although the claims describe only some of the combinations of claims, this embodiment naturally includes within its scope not only one-to-one combinations of independent claims and dependent claims, but also various combinations of multiple dependent claims. In addition to the liquid ejection device 10, this embodiment discloses inventions in various categories, such as a method based on processes or steps executed by the liquid ejection device 10, and a program 12 for implementing the method in cooperation with a processor.

[0053] For example, a method of determining a faulty nozzle is performed by a liquid ejection device 10, which is capable of generating pressure fluctuations in a pressure chamber 27 by driving a piezoelectric element 25, thereby ejecting liquid filled in the pressure chamber 27 from a nozzle 20, and is equipped with a liquid ejection head 19 having a plurality of nozzles 20, and a carriage 18 on which the liquid ejection head 19 is mounted, and which alternately performs a first movement, which is a movement in a first direction, and a second movement, which is a movement in a second direction opposite to the first direction. According to this method, a faulty nozzle determination process can be performed for each of the multiple nozzles 20, which determines whether or not the nozzle 20 is a faulty nozzle based on the vibration generated by applying to the piezoelectric element 25 a drive signal of a specific waveform different from the drive signal applied to the piezoelectric element 25 to eject liquid from the nozzle 20, and the drive signal of the specific waveform is applied during a deceleration / acceleration period F which is a period spanning a first movement deceleration period, which is the period during which the carriage 18 during the first movement decelerates from a predetermined constant speed movement state to stop, and a second movement acceleration period, which is the period after the first movement deceleration period and is the period during which the carriage 18 accelerates from a stopped state to start the second movement and reach the constant speed movement state. [Explanation of symbols]

[0054] 10...liquid ejection device, 11...control unit, 12...program, 17...transport unit, 18...carriage, 19...liquid ejection head, 20...nozzle, 21...drive circuit, 22...MTB, 23...nozzle surface, 24...nozzle row, 25...piezoelectric element, 26...vibration plate, 27...pressure chamber, 40...printing waveform, 41...micro-vibration waveform, 42...FL waveform, 43...test waveform, 44...residual vibration waveform

Claims

1. a liquid ejection head having a plurality of nozzles, the pressure chamber being capable of being driven by a piezoelectric element to generate a pressure fluctuation in the pressure chamber, and ejecting liquid filled in the pressure chamber from the nozzle; a carriage that carries the liquid ejection head and alternately performs a first movement that is a movement in a first direction and a second movement that is a movement in a second direction opposite to the first direction; a control unit that controls the liquid ejection head and the carriage, The control unit is a defective nozzle determination process can be executed for each of the plurality of nozzles, the process determining whether or not the nozzle is defective based on vibrations generated by applying to the piezoelectric element a drive signal having a specific waveform different from a drive signal applied to the piezoelectric element in order to eject liquid from the nozzle; A liquid ejection device characterized in that a drive signal of the specific waveform is applied during a deceleration / acceleration period that spans a first movement deceleration period, which is a period during which the carriage during the first movement decelerates from a predetermined constant speed movement state to stop, and a second movement acceleration period, which is a period after the first movement deceleration period, during which the carriage accelerates from a stopped state to start the second movement and reach the constant speed movement state.

2. The liquid ejection device according to claim 1, characterized in that the control unit sets the length of the period during which the drive signal of the specific waveform is applied during one second movement acceleration period based on a minimum value of the second movement acceleration period calculated in advance in accordance with an error in the acceleration of the carriage.

3. the liquid ejection head includes n nozzle rows in which a plurality of the nozzles are aligned in a third direction intersecting the first direction and the second direction; The liquid ejection device described in claim 1 or claim 2, characterized in that when the control unit is able to apply the drive signal of the specific waveform to a plurality of the piezoelectric elements corresponding to a plurality of the nozzles of a nozzle array of m arrays (which is less than the n arrays) during one deceleration / acceleration period, the control unit makes the frequency of applying the drive signal of the specific waveform to the piezoelectric elements different between the nozzle array for ejecting a first color of ink as a liquid and the nozzle array for ejecting a second color of ink different from the first color.

4. The liquid ejection device according to claim 1, characterized in that the control unit applies the drive signal of the specific waveform more times during a stop period in which the carriage is stopped during the deceleration / acceleration period when the stop period has a second length that is longer than the first length than the number of times the control unit applies the drive signal of the specific waveform during the stop period when the stop period has a first length.

5. A defective nozzle determination method executed by a liquid ejection device, comprising: The liquid ejection device is capable of generating pressure fluctuations in pressure chambers by driving piezoelectric elements to eject liquid filled in the pressure chambers from nozzles, and includes a liquid ejection head having a plurality of nozzles, and a carriage on which the liquid ejection head is mounted and which alternately performs a first movement which is a movement in a first direction and a second movement which is a movement in a second direction opposite to the first direction, a defective nozzle determination process can be executed for each of the plurality of nozzles, the process determining whether or not the nozzle is defective based on vibrations generated by applying to the piezoelectric element a drive signal having a specific waveform different from a drive signal applied to the piezoelectric element in order to eject liquid from the nozzle; a deceleration / acceleration period spanning a first movement deceleration period, during which the carriage during the first movement decelerates from a predetermined constant speed movement state to a stop, and a second movement acceleration period, a period following the first movement deceleration period, during which the carriage accelerates from a stopped state to begin the second movement and reach the constant speed movement state.

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