Liquid dispensing device

Abstract

To reduce discharge failures.SOLUTION: A liquid discharge device includes: a pressure chamber; a first flow path for supplying liquid to the pressure chamber; a second flow path for discharging liquid from the pressure chamber; a nozzle branching from the second pass and discharging liquid; a driving element; a driving signal generation unit which generates a driving signal; and a control unit for controlling supply of driving signals to the driving element based on printing data. The driving signal includes a discharge pulse and a non-discharge pulse. When a time length equal to or greater than an integer multiple of 1 / 2 of a natural oscillation period of meniscus of the liquid in the nozzle is defined as a prescribed time length, the control unit supplies a discharge pulse to the driving element when a period of interest is a non-discharge period, does not supply a non-discharge pulse to the driving element when the period of interest is a non-discharge period and a lapsed time length from the most recent discharge period to the period of interest is less than the prescribed time length, and supplies a non-discharge pulse to the driving element when the period of interest is a non-discharge period and the lapsed time length is equal to or greater than the prescribed time length.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present disclosure relates to a liquid ejection device. [Background technology]

[0002] Liquid ejection devices, such as inkjet printers, generally have a liquid ejection head that ejects liquid such as ink. As disclosed in Patent Document 1, for example, the liquid ejection head includes a pressure chamber, a first flow path that supplies liquid to the pressure chamber, a second flow path that discharges the liquid from the pressure chamber, a nozzle that ejects the liquid from the second flow path, and a drive element that applies pressure fluctuations to the liquid in the pressure chamber in response to a drive signal.

[0003] Patent Document 1 discloses a configuration for circulating liquid in a flow path including a pressure chamber, a first flow path, and a second flow path. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-103602 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, a drive signal is not supplied to a drive element corresponding to a nozzle during periods when the nozzle is not ejecting liquid. Furthermore, the nozzle branches off from the second flow path and extends in a direction different from the second flow path. Therefore, even if the liquid is circulated as described above, the liquid tends to stagnate in the nozzle during periods when the nozzle is not ejecting liquid. As a result, nozzles that do not eject liquid for long periods of time may experience ejection problems due to thickening of the liquid, etc. [Means for solving the problem]

[0006] In order to solve the above problems, a liquid ejection device according to a preferred aspect of the present disclosure includes a pressure chamber, a first flow path that supplies liquid to the pressure chamber, a second flow path that discharges liquid from the pressure chamber, a nozzle that branches off from the second flow path and ejects liquid, a drive element that applies pressure fluctuations to the liquid in the pressure chamber in response to a drive signal, a drive signal generation unit that generates the drive signal, and a control unit that controls supply of the drive signal to the drive element based on print data so that, for each unit period of a predetermined cycle, a target period becomes either an ejection period in which liquid is ejected from the nozzle or a non-ejection period in which liquid is not ejected from the nozzle, and a non-ejection pulse that drives the drive element to generate a pressure fluctuation in the pressure chamber that is strong enough to prevent liquid from being ejected from the nozzle, and when a time length that is equal to or greater than q times (q is an integer equal to or greater than 1) half the natural vibration period of a meniscus of the liquid in the nozzle is set as a predetermined time length, the control unit supplies the ejection pulse to the drive element when the target period is the ejection period, does not supply either the ejection pulse or the non-ejection pulse to the drive element when the target period is the non-ejection period and the elapsed time length from the ejection period immediately preceding the target period is less than the predetermined time length, and supplies the non-ejection pulse without supplying the ejection pulse to the drive element when the target period is the non-ejection period and the elapsed time length is equal to or greater than the predetermined time length. [Brief explanation of the drawings]

[0007] [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] FIG. 2 is a diagram showing the electrical configuration of the liquid ejection device according to the first embodiment. [Figure 3] FIG. 2 is a schematic diagram illustrating a circulation flow path of the liquid ejection head. [Figure 4] FIG. 4 is a cross-sectional view taken along the line A1-A1 in FIG. 3. [Figure 5] FIG. 2 is an enlarged cross-sectional view of the nozzle. [Figure 6] FIG. 2 is a diagram for explaining a switching circuit. [Figure 7] FIG. 4 is a diagram for explaining a drive signal. [Figure 8] FIG. 4 is a diagram for explaining an output signal from a switching circuit. [Figure 9] FIG. 10 is a diagram for explaining a period during which a non-ejection pulse is used. [Figure 10] 10 is a graph showing the change over time in the amount of the meniscus of the liquid coming out of the nozzle after an ejection pulse is supplied to the drive element. [Figure 11] 10A and 10B are diagrams for explaining vibration of the meniscus of the liquid in the nozzle due to supply of a non-ejection pulse to the drive element. [Figure 12] FIG. 10 is a diagram showing the electrical configuration of a liquid ejection device according to a second embodiment. [Figure 13] 10 is a graph showing the change over time in the amount of the meniscus of the liquid coming out of the nozzle after the supply of an ejection pulse to the drive element when the damping coefficient of the second flow path is changed. [Figure 14] FIG. 10 is a schematic diagram illustrating a circulation flow path of a liquid ejection head according to a third embodiment. [Figure 15] 15 is a cross-sectional view taken along the line A2-A2 in FIG. 14. DETAILED DESCRIPTION OF THE INVENTION

[0008] Preferred embodiments of the present disclosure will be described below with reference to the accompanying drawings. Note that the dimensions and scale of each part in the drawings may differ from the actual dimensions and are shown schematically to facilitate understanding. Furthermore, the scope of the present disclosure is not limited to these embodiments unless otherwise specified in the following description to the effect that the present disclosure is limited.

[0009] In the following description, the mutually intersecting X-axis, Y-axis, and Z-axis will be used as appropriate. In the following description, one direction along the X-axis is the X1 direction, and the direction opposite the X1 direction is the X2 direction. Similarly, the opposite directions along the Y-axis are the Y1 direction and the Y2 direction. The opposite directions along the Z-axis are the Z1 direction and the Z2 direction.

[0010] Typically, the Z axis is a vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. However, the Z axis does not have to be a vertical axis. Furthermore, the X axis, Y axis, and Z axis are typically perpendicular to each other, but are not limited to this. For example, they may intersect at an angle between 80° and 100°.

[0011] A: First embodiment A1: Overall configuration of the liquid ejection device 1 is a schematic diagram showing an example of the configuration of a liquid ejection device 100 according to a first embodiment. The liquid ejection device 100 is an inkjet printing device that ejects liquid such as ink as droplets onto a medium M. The medium M is, for example, printing paper. Note that the medium M is not limited to printing paper, and may be a printing target made of any material, such as a resin film or fabric.

[0012] As shown in FIG. 1, the liquid ejection device 100 includes a liquid container 10, a control unit 20, a transport mechanism 30, a moving mechanism 40, a liquid ejection head 50, and a circulation mechanism 60.

[0013] The liquid container 10 stores ink. Specific examples of the liquid container 10 include a cartridge that is detachable from the liquid ejection device 100, a bag-shaped ink pack made of flexible film, and an ink tank that can be refilled with ink. The type of ink stored in the liquid container 10 is arbitrary.

[0014] The control unit 20 controls the operation of each element of the liquid ejection device 100. The control unit 20 includes, for example, one or more processing circuits such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array), and one or more storage circuits such as a semiconductor memory. The detailed configuration of the control unit 20 will be described later with reference to FIG. 2.

[0015] The transport mechanism 30 transports the medium M in the Y1 direction under the control of the control unit 20. The movement mechanism 40 reciprocates the liquid ejection head 50 along the X axis under the control of the control unit 20. The movement mechanism 40 has a substantially box-shaped carriage 41 that houses the liquid ejection head 50, and an endless transport belt 42 to which the carriage 41 is fixed. Note that the number of liquid ejection heads 50 mounted on the carriage 41 is not limited to one, and may be multiple. In addition to the liquid ejection head 50, the carriage 41 may also be equipped with the aforementioned liquid container 10.

[0016] Under the control of the control unit 20, the liquid ejection head 50 ejects ink supplied from the liquid container 10 from each of a plurality of nozzles onto the medium M. This ejection is performed in parallel with the transport of the medium M by the transport mechanism 30 and the reciprocating movement of the liquid ejection head 50 by the movement mechanism 40, thereby forming an ink image on the surface of the medium M.

[0017] The liquid container 10 is connected to the liquid ejection head 50 via a circulation mechanism 60. The circulation mechanism 60 is a mechanism that supplies ink to the liquid ejection head 50 and recovers ink discharged from the liquid ejection head 50 for resupply to the liquid ejection head 50 under the control of the control unit 20. The operation of the circulation mechanism 60 can suppress an increase in the viscosity of the ink and reduce the accumulation of air bubbles in the ink. The detailed configuration of the circulation mechanism 60 will be described later with reference to FIG. 3.

[0018] A2: Electrical configuration of the liquid ejection device 2 is a diagram showing the electrical configuration of the liquid ejection device 100 according to the first embodiment. The control unit 20 will be described below with reference to FIG. 2, but prior to this, the liquid ejection head 50 will be briefly described.

[0019] As shown in FIG. 2, the liquid ejection head 50 includes a head chip 51 and a switching circuit 52.

[0020] The head chip 51 has a plurality of drive elements 51e, and ink is ejected from the nozzles by appropriately driving the plurality of drive elements 51e. Here, each drive element 51e applies pressure to the ink upon receiving a supply signal Vin. Details of the head chip 51 will be described later with reference to Figures 3 to 5.

[0021] Under the control of control unit 20, switching circuit 52 switches whether or not to supply drive signal Com output from control unit 20 as supply signal Vin to each of multiple drive elements 51e of head chip 51. Details of switching circuit 52 will be described later with reference to Figures 6 to 8.

[0022] 2, the liquid ejection head 50 has one head chip 51, but this is not limited thereto, and the liquid ejection head 50 may have two or more head chips 51. Hereinafter, when the number of nozzles N in the head chip 51 is M, in order to distinguish between the M or M sets of drive elements 51e corresponding to the M nozzles, the drive elements 51e may be written as drive elements 51e[m] using the subscript [m], where M is a natural number greater than or equal to 1, and m is a natural number greater than or equal to 1 and less than or equal to M. Furthermore, the subscript [m] may be used to indicate the correspondence between the M other components or signals corresponding to the nozzle N or drive element 51e in the liquid ejection device 100 and the nozzle N or drive element 51e and the nozzle N or drive element 51e[m].

[0023] As shown in FIG. 2, the control unit 20 includes a control circuit 21, a memory circuit 22, a power supply circuit 23, and a drive signal generation circuit 24.

[0024] The control circuit 21 has a function to control the operation of each part of the liquid ejection device 100 and a function to process various data. The control circuit 21 includes, for example, one or more processors such as a CPU (Central Processing Unit). Note that the control circuit 21 may include a programmable logic device such as an FPGA (Field-Programmable Gate Array) instead of or in addition to a CPU. Furthermore, when the control circuit 21 is made up of multiple processors, the multiple processors may be mounted on different boards or the like.

[0025] The memory circuit 22 stores various programs executed by the control circuit 21 and various data such as print data Img processed by the control circuit 21. The memory circuit 22 includes, for example, one or both of semiconductor memories: a volatile memory such as RAM (Random Access Memory) and a non-volatile memory such as ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), or PROM (Programmable ROM). The print data Img is supplied from an external device 200 such as a personal computer or digital camera. The memory circuit 22 may be configured as part of the control circuit 21.

[0026] The power supply circuit 23 receives power from a commercial power supply (not shown) and generates various predetermined potentials. The generated potentials are supplied to various parts of the liquid ejection device 100 as appropriate. For example, the power supply circuit 23 generates a power supply potential VHV and an offset potential VBS. The offset potential VBS is supplied to the liquid ejection head 50. The power supply potential VHV is also supplied to the drive signal generation circuit 24.

[0027] The drive signal generation circuit 24 is a circuit that generates a drive signal Com for driving each drive element 51e. Specifically, the drive signal generation circuit 24 includes, for example, a DA conversion circuit and an amplifier circuit. In the drive signal generation circuit 24, the DA conversion circuit converts the waveform designation signal dCom from the control circuit 21 from a digital signal to an analog signal, and the amplifier circuit amplifies the analog signal using the power supply potential VHV from the power supply circuit 23 to generate the drive signal Com. Here, of the waveforms included in the drive signal Com, the signal with the waveform that is actually supplied to the drive element 51e is the aforementioned supply signal Vin. The waveform designation signal dCom is a digital signal that defines the waveform of the drive signal Com.

[0028] The control circuit 21 executes a program stored in the memory circuit 22 to control the operation of each part of the liquid ejection device 100. Here, by executing the program, the control circuit 21 generates control signals Sk1 and Sk2, a print data signal SI, a waveform designation signal dCom, a latch signal LAT, a change signal CNG, and a clock signal CLK as signals for controlling the operation of each part of the liquid ejection device 100.

[0029] The control signal Sk1 is a signal for controlling the driving of the transport mechanism 30. The control signal Sk2 is a signal for controlling the driving of the movement mechanism 40. The print data signal SI is a digital signal for specifying the operating state of the drive element 51e. The latch signal LAT and the change signal CNG are used in conjunction with the print data signal SI and are timing signals that determine the timing of ink ejection from each nozzle of the head chip 51. These timing signals are generated, for example, based on the output of an encoder that detects the position of the carriage 41 mentioned above.

[0030] A3: Flow path of liquid ejection head Fig. 3 is a schematic diagram illustrating the circulation flow path of the liquid ejection head 50. As shown in Fig. 3, the liquid ejection head 50 is provided with a plurality of nozzles N, a plurality of individual flow paths IP, a first common liquid chamber R1, and a second common liquid chamber R2, and a circulation mechanism 60 is connected to the first common liquid chamber R1 and the second common liquid chamber R2.

[0031] The plurality of nozzles N are arranged along the Y axis. Each of the plurality of nozzles N ejects ink in the Z2 direction. A group of the plurality of nozzles N constitutes a nozzle row L. The plurality of nozzles N are also arranged at equal intervals.

[0032] An individual flow path IP communicates with each of the plurality of nozzles N. Each of the plurality of individual flow paths IP extends along the X axis and communicates with a different nozzle N. Furthermore, the plurality of individual flow paths IP are arranged along the Y axis.

[0033] As shown in FIG. 3, each individual flow path IP has a pressure chamber Ca, a pressure chamber Cb, a communicating flow path Nf which is an example of a "second flow path", an individual supply flow path Ra1 which is an example of a "first flow path", and an individual discharge flow path Ra2.

[0034] Each of the pressure chambers Ca and pressure chambers Cb in each individual flow path IP extends along the X-axis and is a space that stores ink ejected from a nozzle N that is connected to the individual flow path IP. In the example shown in FIG. 3, the multiple pressure chambers Ca are arranged along the Y-axis. Similarly, the multiple pressure chambers Cb are arranged along the Y-axis. In each individual flow path IP, the positions of the pressure chambers Ca and pressure chambers Cb in the direction along the Y-axis are the same in the example shown in FIG. 3, but they may be different. In the following, when there is no need to particularly distinguish between the pressure chambers Ca and pressure chambers Cb, they will simply be referred to as "pressure chambers C." In addition, as will be described later, a drive element 51e is provided corresponding to each of the pressure chambers Ca and Cb, and in this embodiment, M sets of drive elements 51e, each consisting of two drive elements 51e, are used.

[0035] A communication flow path Nf is arranged between the pressure chamber Ca and the pressure chamber Cb in each individual flow path IP. In each individual flow path IP, the communication flow path Nf is a flow path that connects the pressure chamber Ca and the pressure chamber Cb. Furthermore, the multiple communication flow paths Nf are arranged along the Y axis at intervals from one another. A nozzle N is provided in each communication flow path Nf. In each communication flow path Nf, ink is ejected from the nozzle N due to pressure fluctuations within the pressure chamber Ca and the pressure chamber Cb described above.

[0036] Each individual flow path IP is provided with an individual supply flow path Ra1 that is located between the pressure chamber Ca and the first common liquid chamber R1. The individual supply flow path Ra1 is a flow path that connects the pressure chamber Ca and the first common liquid chamber R1. Similarly, each individual flow path IP is provided with an individual discharge flow path Ra2 that is located between the pressure chamber Cb and the second common liquid chamber R2. The individual discharge flow path Ra2 is a flow path that connects the pressure chamber Cb and the second common liquid chamber R2.

[0037] The individual flow paths IP are commonly connected to a first common liquid chamber R1 and a second common liquid chamber R2. Each of the first common liquid chamber R1 and the second common liquid chamber R2 is a space extending along the Y axis over the entire area in which the nozzles N are distributed. When viewed in the Z axis direction, the individual flow paths IP are located between the first common liquid chamber R1 and the second common liquid chamber R2.

[0038] Here, the first common liquid chamber R1 is connected to the end E1 of each individual flow path IP in the X2 direction. The first common liquid chamber R1 stores ink to be supplied to each individual flow path IP. Meanwhile, the second common liquid chamber R2 is connected to the end E2 of each individual flow path IP in the X1 direction. The second common liquid chamber R2 stores ink that is not used for ejection and is discharged from each individual flow path IP.

[0039] A circulation mechanism 60 is connected to the first common liquid chamber R1 and the second common liquid chamber R2. The circulation mechanism 60 supplies ink to the first common liquid chamber R1 and recovers ink discharged from the second common liquid chamber R2 for resupply to the first common liquid chamber R1. The circulation mechanism 60 has a first supply pump 61, a second supply pump 62, a storage container 63, a recovery flow path 64, and a supply flow path 65.

[0040] The first supply pump 61 is a pump that supplies ink stored in the liquid container 10 to the storage container 63. The storage container 63 is a sub-tank that temporarily stores ink supplied from the liquid container 10. The recovery flow path 64 connects the second common liquid chamber R2 to the storage container 63 and is a flow path for recovering ink from the second common liquid chamber R2 to the storage container 63. Ink stored in the liquid container 10 is supplied to the storage container 63 from the first supply pump 61, and ink discharged from each individual flow path IP to the second common liquid chamber R2 is also supplied via the recovery flow path 64. The second supply pump 62 is a pump that sends out ink stored in the storage container 63. The supply flow path 65 connects the first common liquid chamber R1 to the storage container 63 and is a flow path for supplying ink from the storage container 63 to the first common liquid chamber R1.

[0041] A4: Specific structure of the head chip Fig. 4 is a cross-sectional view taken along line A1-A1 in Fig. 3. Fig. 4 shows a cross section of head chip 51 cut along a plane perpendicular to the Y axis along individual flow channels IP. As shown in Fig. 4, head chip 51 has a nozzle substrate 51a, a flow channel substrate 51b, a pressure chamber substrate 51c, a vibration plate 51d, a plurality of drive elements 51e, a case 51f, a protection plate 51g, and a wiring substrate 51h.

[0042] The nozzle substrate 51a, flow path substrate 51b, pressure chamber substrate 51c, and diaphragm 51d are stacked in this order in the Z1 direction. Each of these components extends along the Y axis and is manufactured, for example, by processing a silicon single crystal substrate using semiconductor processing technology. These components are bonded to each other with an adhesive or the like. Note that another layer, such as an adhesive layer, or a substrate may be appropriately interposed between two adjacent components of these components.

[0043] The nozzle substrate 51a is provided with a plurality of nozzles N. Each of the plurality of nozzles N extends along the Z axis and penetrates the nozzle substrate 51a, and is a through-hole that allows ink to pass through.

[0044] The flow path substrate 51b is provided with the portions of the individual flow paths IP excluding the pressure chambers Ca and Cb, a liquid chamber R1a that is a part of the first common liquid chamber R1, and a liquid chamber R2a that is a part of the second common liquid chamber R2. That is, the flow path substrate 51b is provided with the communication flow path Nf, the individual supply flow path Ra1, the individual discharge flow path Ra2, the liquid chamber R1a, and the liquid chamber R2a.

[0045] Each of the liquid chambers R1a and R2a is a space that penetrates the flow path substrate 51b. A vibration absorber 51i that closes the opening of the space is provided on the surface of the flow path substrate 51b facing the Z2 direction.

[0046] The vibration absorber 51i is a layered member made of an elastic material. The vibration absorber 51i forms part of the wall surfaces of the first common liquid chamber R1 and the second common liquid chamber R2, and absorbs pressure fluctuations in the first common liquid chamber R1 and the second common liquid chamber R2.

[0047] The communication flow path Nf has a first communication flow path Na1, a second communication flow path Na2, and a nozzle flow path Nfa. The first communication flow path Na1 and the second communication flow path Na2 are each a space that penetrates the flow path substrate 51b. The first communication flow path Na1 and the second communication flow path Na2 are connected to each other via the nozzle flow path Nfa. The first communication flow path Na1 connects the pressure chamber Ca to the nozzle flow path Nfa. The second communication flow path Na2 connects the pressure chamber Cb to the nozzle flow path Nfa. The nozzle flow path Nfa is a space within a groove provided on the surface of the flow path substrate 51b facing the Z2 direction, and extends along the X axis. Here, the nozzle substrate 51a forms a part of the wall surface of the nozzle flow path Nfa.

[0048] The individual supply flow path Ra1 and the individual discharge flow path Ra2 are each spaces that penetrate the flow path substrate 51b. The individual supply flow path Ra1 connects the first common liquid chamber R1 to the pressure chamber Ca, and supplies ink from the first common liquid chamber R1 to the pressure chamber Ca. One end of the individual supply flow path Ra1 opens to the surface of the flow path substrate 51b facing the Z1 direction. The other end of the individual supply flow path Ra1 is the upstream end of the individual flow path IP, and opens to the wall surface of the first common liquid chamber R1 in the flow path substrate 51b. In contrast, the individual discharge flow path Ra2 connects the second common liquid chamber R2 to the pressure chamber Cb, and discharges ink from the pressure chamber Cb to the second common liquid chamber R2. One end of the individual discharge flow path Ra2 opens to the surface of the flow path substrate 51b facing the Z1 direction. On the other hand, the other end of the individual discharge flow path Ra2 is the downstream end of the individual flow path IP, and opens into the wall surface of the second common liquid chamber R2 in the flow path substrate 51b.

[0049] The pressure chamber substrate 51c is provided with pressure chambers Ca and pressure chambers Cb of a plurality of individual channels IP. Each of the pressure chambers Ca and Cb penetrates the pressure chamber substrate 51c and is a gap between the channel substrate 51b and the diaphragm 51d.

[0050] The diaphragm 51d is a plate-like member that can vibrate elastically. The diaphragm 51d is a laminate including, for example, a first layer made of silicon oxide (SiO2) and a second layer made of zirconium oxide (ZrO2). Here, another layer such as a metal oxide may be interposed between the first and second layers. Part or all of the diaphragm 51d may be integrally formed with the pressure chamber substrate 51c using the same material. For example, the diaphragm 51d and the pressure chamber substrate 51c can be integrally formed by selectively removing a portion in the thickness direction of a plate-like member of a predetermined thickness in an area corresponding to the pressure chamber C. Alternatively, the diaphragm 51d may be formed from a layer of a single material.

[0051] A plurality of drive elements 51e corresponding to different pressure chambers C are provided on the surface of the vibration plate 51d facing the Z1 direction. Each drive element 51e is configured, for example, by laminating a first electrode and a second electrode facing each other with a piezoelectric layer disposed between the electrodes. Each drive element 51e changes the pressure of the ink in the pressure chamber C, thereby causing the ink in the pressure chamber C to be ejected from the nozzle N. When a drive signal Com is supplied, the drive element 51e deforms, causing the vibration plate 51d to vibrate. This vibration causes the pressure chamber C to expand and contract, thereby changing the pressure of the ink in the pressure chamber C.

[0052] The case 51f is a case for storing ink. The case 51f is provided with a liquid chamber R1b (a portion of the first common liquid chamber R1 other than the liquid chamber R1a), a liquid chamber R2b (a portion of the second common liquid chamber R2 other than the liquid chamber R2a), an inlet port P1, and an outlet port P2. The liquid chamber R1b and the liquid chamber R2b are each recessed portions provided in the surface of the case 51f facing the Z2 direction. The inlet port P1 is a through-hole whose inner surface extends from the surface of the case 51f facing the Z1 direction to the wall surface of the liquid chamber R1b. The inlet port P1 is connected to the supply flow path 65 of the circulation mechanism 60 described above. The outlet port P2 is a through-hole whose inner surface extends from the surface of the case 51f facing the Z1 direction to the wall surface of the liquid chamber R2b. The outlet port P2 is connected to the recovery flow path 64 of the circulation mechanism 60 described above.

[0053] The protective plate 51g is a plate-like member placed on the surface of the diaphragm 51d facing the Z1 direction, and protects the multiple drive elements 51e and reinforces the mechanical strength of the diaphragm 51d. A space for accommodating the multiple drive elements 51e is formed between the protective plate 51g and the diaphragm 51d.

[0054] The wiring board 51h is mounted on the surface of the diaphragm 51d facing the Z1 direction, and is a mounting component for electrically connecting the control unit 20 and the head chip 51. For example, a flexible wiring board 51h such as an FPC (Flexible Printed Circuit) or an FFC (Flexible Flat Cable) is preferably used. The above-mentioned switching circuit 52 is mounted on the wiring board 51h.

[0055] In the head chip 51 having the above-described configuration, the operation of the circulation mechanism 60 described above causes ink to flow through the first common liquid chamber R1, the individual supply flow path Ra1, the pressure chamber Ca, the communicating flow path Nf, the pressure chamber Cb, the individual discharge flow path Ra2, and the second common liquid chamber R2 in this order.

[0056] In addition, the supply signal Vin from the switching circuit 52 simultaneously drives the drive elements 51e corresponding to both the pressure chamber Ca and the pressure chamber Cb, thereby fluctuating the pressure in the pressure chamber Ca and the pressure chamber Cb, and ink is ejected from the nozzle N in accordance with this pressure fluctuation.

[0057] A5: Nozzle Fig. 5 is an enlarged cross-sectional view of the nozzle N. Fig. 5 shows a cross section of a portion of the nozzle flow path Nfa and the nozzle N, perpendicular to the Y-axis. As shown in Fig. 5, the nozzle N branches off from the nozzle flow path Nfa and extends in a direction different from the nozzle flow path Nfa. Here, the nozzle flow path Nfa extends in the direction along the X-axis, while the nozzle N extends in the direction along the Z-axis.

[0058] 5, the nozzle N has a first portion NP1 and a second portion NP2. These are arranged in the Z1 direction in the order of first portion NP1, second portion NP2. In other words, the second portion NP2 is provided between the nozzle flow path Nfa and the first portion NP1. The nozzle flow path Nfa and the first portion NP1 communicate with each other via the second portion NP2.

[0059] The first portion NP1 opens on a surface of the nozzle substrate 51a facing the Z2 direction and extends along the Z axis. The second portion NP2 opens on a surface of the nozzle substrate 51a facing the Z1 direction and extends in a direction along the Z axis. The first portion NP1 and the second portion NP2 are arranged coaxially. However, the width W1 of the first portion NP1 is smaller than the width W2 of the second portion NP2. In other words, the width W2 of the second portion NP2 is larger than the width W1 of the first portion NP1. In this way, the nozzle N has a shape whose width gradually decreases in the Z2 direction. Note that the width W1 is the length of the first portion NP1 in a direction perpendicular to the Z axis. The width W2 is the length of the second portion NP2 in a direction perpendicular to the Z axis.

[0060] The specific width W1 of the first portion NP1 is not particularly limited, but is determined appropriately depending on, for example, the characteristics such as the ink ejection amount or ejection speed required for the nozzle N. In addition, the length L1 of the first portion NP1 in the direction along the Z axis is also not particularly limited, but is determined appropriately depending on the characteristics such as the ink ejection amount or ejection speed required for the nozzle N.

[0061] The width W2 of the second portion NP2 may be larger than the width W1 of the first portion NP1, but is preferably smaller than the width of the nozzle flow path Nfa in the direction along the Y axis. In this case, crosstalk between two second portions NP2 adjacent to each other in the direction along the Y axis can be reduced. Furthermore, the length L2 of the second portion NP2 in the direction along the Z axis is determined appropriately depending on the width W2 of the second portion NP2 or the thickness of the nozzle substrate 51a, etc.

[0062] As described above, the nozzle N extends in a direction intersecting the extension direction of the nozzle flow path Nfa. Therefore, even if the circulation mechanism 60 described above is operated, the circulating flow of ink generated in the nozzle flow path Nfa by the operation does not easily reach the nozzle N. In particular, in a nozzle N having the first portion NP1 and the second portion NP2 described above, it is necessary to ensure a certain length in the Z-axis direction for each of the first portion NP1 and the second portion NP2, so the circulating flow does not easily reach the first portion NP1 compared to a nozzle with a fixed width. For this reason, ink is likely to stagnate in the nozzle N during periods when the drive element 51e is not operated. Therefore, if this period continues for a long period of time, it may lead to an increase in the viscosity of the ink in the nozzle N.

[0063] Therefore, in the liquid ejection device 100, even during periods when ink is not being ejected from the nozzle N, the drive element 51e is driven to vibrate the meniscus MN for a predetermined period of time to an extent that ink is not ejected from the nozzle N. This vibration of the meniscus MN agitates the ink in the nozzle N, and combined with the action of the ink circulating flow by the circulation mechanism 60, ink replacement is carried out smoothly between the nozzle N and the nozzle flow path Nfa. This prevents the ink in the nozzle N from thickening, etc.

[0064] Here, even during a period when ink is not being ejected from the nozzle N, the drive element 51e for vibrating the meniscus MN described above is not driven in the nozzle N for a predetermined period immediately after the ink is ejected. In the nozzle N for a predetermined period immediately after the ink is ejected, the ink meniscus MN vibrates due to residual vibration, and the ink is agitated. Therefore, even if the drive element 51e for vibrating the meniscus MN is not separately driven, the ink in the nozzle N is prevented from thickening. This point will be explained later with reference to Figures 9 and 10.

[0065] In this way, by not driving the drive element 51e for vibrating the meniscus MN for the nozzle N for a predetermined period immediately after ink ejection, it is possible to reduce heat generation due to excessive driving of the drive element 51e.

[0066] If the drive element 51e for vibrating the meniscus MN of the nozzle N for a predetermined period immediately after ink ejection were driven, the meniscus MN would vibrate excessively. As a result, the meniscus MN would be affected by the circulating flow of ink in the nozzle flow channel Nfa and would vibrate in the direction of the circulating flow. If the drive element 51e for ejecting ink from the nozzle N were driven in this state, the ink ejection from the nozzle N would become unstable, potentially resulting in a deterioration in image quality. In contrast, by not driving the drive element 51e for vibrating the meniscus MN of the nozzle N for a predetermined period immediately after ink ejection, it is possible to reduce the deterioration in image quality caused by excessive vibration of the meniscus MN. The driving of the drive element 51e is described in detail below.

[0067] A6: Driving the driving element 51e Fig. 6 is a diagram for explaining the switching circuit 52. The driving element 51e is driven by a supply signal Vin from the switching circuit 52. The switching circuit 52 will be explained below with reference to Fig. 6. In the example shown in Fig. 6, a driving signal Com-A and a driving signal Com-B are used as the driving signal Com.

[0068] As shown in FIG. 6, wirings LHa and LHb are connected to the switching circuit 52. The wiring LHa is a signal line that transmits the drive signal Com-A. The wiring LHb is a signal line that transmits the drive signal Com-B. Note that in FIG. 6, one of the first electrode and second electrode of the drive element 51e described above is shown as electrode Zd[m], and the other is shown as electrode Zu[m]. The wiring LHd is connected to the electrode Zd[m]. The wiring LHd is a power supply line to which an offset potential VBS is supplied.

[0069] The switching circuit 52 has M switches SWa (SWa[1]] to SWa[M]), M switches SWb (SWb[1]] to SWb[M]), and a connection state designation circuit 52a that designates the connection states of these switches.

[0070] The switch SWa[m] is a switch that switches between conduction (ON) and non-conduction (OFF) between the wiring LHa for transmitting the drive signal Com-A and the electrode Zu[m] of the drive element 51e[m]. The switch SWb[m] is a switch that switches between conduction (ON) and non-conduction (OFF) between the wiring LHb for transmitting the drive signal Com-B and the electrode Zu[m] of the drive element 51e[m]. Each of these switches is, for example, a transmission gate.

[0071] The connection state designation circuit 52a generates connection state designation signals SLa[1] to SLa[M] that designate the on / off states of the switches SWa[1] to SWa[M], and connection state designation signals SLb[1] to SLb[M] that designate the on / off states of the switches SWb[1] to SWb[M], based on the clock signal CLK, print data signal SI, latch signal LAT, and change signal CNG supplied from the control circuit 21.

[0072] For example, although not shown, the connection state designation circuit 52a includes multiple transfer circuits, multiple latch circuits, and multiple decoders in one-to-one correspondence with the drive elements 51e[1] to 51e[M]. Of these, the transfer circuit receives a print data signal SI. The print data signal SI includes an individual designation signal for each drive element 51e. The individual designation signals are serially supplied and transferred sequentially to the multiple transfer circuits in synchronization with a clock signal CLK. The latch circuit latches the individual designation signal supplied to the transfer circuit based on a latch signal LAT. The decoder generates connection state designation signals SLa[m] and SLb[m] based on the individual designation signal, the latch signal LAT, and the change signal CNG.

[0073] The switch SWa[m] is switched on and off according to the connection state designation signal SLa[m] generated as described above. For example, the switch SWa[m] is in an on state when the connection state designation signal SLa[m] is at a high level, and in an off state when the connection state designation signal SLa[m] is at a low level. As described above, the switching circuit 52 supplies part or all of the waveform included in the drive signal Com-A as the supply signal Vin to one or more drive elements 51e selected from the multiple drive elements 51e.

[0074] Similarly, the switch SWb[m] is switched on and off in response to the connection state designation signal SLb[m]. For example, the switch SWb[m] is turned on when the connection state designation signal SLb[m] is at a high level, and turned off when the connection state designation signal SLb[m] is at a low level. As described above, the switching circuit 52 supplies part or all of the waveform included in the drive signal Com-B as the supply signal Vin to one or more drive elements 51e selected from the plurality of drive elements 51e.

[0075] A7: Drive signal FIG. 7 is a diagram illustrating the drive signal Com. As shown in FIG. 7, the latch signal LAT includes a pulse PlsL for defining a unit period Tu. The unit period Tu corresponds to a printing cycle for forming dots of ink from the nozzle N on the medium M. The unit period Tu is defined, for example, as the period from the rising edge of a pulse PlsL to the rising edge of the next pulse PlsL. The change signal CNG also includes a pulse PlsC for dividing the unit period Tu into a preceding control period Tu1 and a succeeding control period Tu2. The control period Tu1 is, for example, the period from the rising edge of the pulse PlsL to the rising edge of the pulse PlsC. The control period Tu2 is, for example, the period from the rising edge of the pulse PlsC to the rising edge of the pulse PlsL.

[0076] The drive signal Com-A has an ejection pulse PA1 provided in the control period Tu1 and an ejection pulse PA2 provided in the control period Tu2. Each of the ejection pulses PA1 and PA2 is a potential pulse that drives the drive element 51e to generate a pressure fluctuation in the pressure chamber C strong enough to eject ink from the nozzle N. When the ejection pulse PA1 is supplied to the drive element 51e, a small amount of ink is ejected from the nozzle N as an ink droplet. When the ejection pulse PA2 is supplied to the drive element 51e, a medium amount of ink is ejected from the nozzle N as an ink droplet.

[0077] 7, each of the ejection pulses PA1 and PA2 has a waveform that drops from a reference potential to a potential lower than the reference potential, then rises to a potential higher than the reference potential, and then returns to the reference potential. The potential difference between the highest and lowest potentials of the ejection pulse PA1 is smaller than the potential difference between the highest and lowest potentials of the ejection pulse PA2. The reference potential is, for example, a potential higher than the offset potential VBS.

[0078] The drive signal Com-B has a non-ejection pulse PB1 provided in the control period Tu1 and an ejection pulse PB2 provided in the control period Tu2. The non-ejection pulse PB1 is a potential pulse that drives the drive element 51e to generate pressure fluctuations in the pressure chamber C that are strong enough to prevent ink from being ejected from the nozzle N. When the non-ejection pulse PB1 is supplied to the drive element 51e, the ink meniscus MN in the nozzle N is slightly vibrated without causing ink to be ejected from the nozzle N. The ejection pulse PB2 is a potential pulse that drives the drive element 51e to generate pressure fluctuations in the pressure chamber C that are strong enough to eject ink from the nozzle N. When the ejection pulse PB2 is supplied to the drive element 51e, a small amount of ink is ejected from the nozzle N as an ink droplet.

[0079] 7, the non-ejection pulse PB1 has a waveform that drops from a reference potential to a potential lower than the reference potential and then returns to the reference potential. Similarly to the aforementioned ejection pulses PA1 and PA2, the ejection pulse PB2 has a waveform that drops from a reference potential to a potential lower than the reference potential, then rises to a potential higher than the reference potential, and then returns to the reference potential. Furthermore, the minimum potential of the ejection pulse PB2 is lower than the minimum potential of the non-ejection pulse PB1. Furthermore, the potential difference between the maximum and minimum potentials of the ejection pulse PA2 is equal to the potential difference between the maximum and minimum potentials of the ejection pulse PA1.

[0080] The potential difference between the maximum and minimum potentials of the ejection pulse PA2 may be different from the potential difference between the maximum and minimum potentials of the ejection pulse PA1. The minimum potential of the ejection pulse PB2 may be equal to or greater than the minimum potential of the non-ejection pulse PB1.

[0081] The above ejection pulses PA1, PA2, PB1, and PB2 are appropriately selected and used as the supply signal Vin, which makes it possible to adjust the amount of ink ejected from the nozzle N, or to slightly vibrate the ink in the nozzle N without ejecting ink from the nozzle N.

[0082] A8: Discharge period and non-discharge period Fig. 8 is a diagram for explaining the supply signal Vin from the switching circuit 52. Fig. 8 shows waveforms of the supply signal Vin for forming small dots, medium dots, and large dots on the medium M, for slightly vibrating the ink in the nozzle N without ejecting ink from the nozzle N, and for not ejecting ink from the nozzle N without slightly vibrating the ink in the nozzle N.

[0083] When forming a large dot on the medium M, the supply signal Vin within the unit period Tu has a waveform that includes an ejection pulse PA1 in the control period Tu1 and an ejection pulse PA2 in the control period Tu2. By supplying such a supply signal Vin to the drive element 51e, small-volume ink droplets and medium-volume ink droplets are ejected consecutively in this order from the nozzle N. As a result, these ink droplets land on the medium M in a combined state, forming a large dot on the medium M.

[0084] When a medium dot is formed on the medium M, the supply signal Vin within the unit period Tu has a waveform that includes an ejection pulse PA1 in the control period Tu1 and an ejection pulse PB2 in the control period Tu2. When this supply signal Vin is supplied to the drive element 51e, a small amount of ink droplet is ejected twice in succession from the nozzle N. As a result, these ink droplets are combined and land on the medium M, forming a medium dot on the medium M.

[0085] When forming a small dot on the medium M, the supply signal Vin within the unit period Tu has a waveform that includes an ejection pulse PA1 during the control period Tu1 and is at the reference potential throughout the control period Tu2. When this supply signal Vin is supplied to the drive element 51e, a small amount of ink droplet is ejected once from the nozzle N. As a result, when this ink droplet lands on the medium M, a small dot is formed on the medium M.

[0086] When slightly vibrating the ink meniscus MN in the nozzle N without ejecting ink from the nozzle N, the supply signal Vin within the unit period Tu has a waveform that includes a non-ejection pulse PB1 during the control period Tu1 and is at the reference potential throughout the control period Tu2. By supplying such a supply signal Vin to the drive element 51e, the ink in the nozzle is slightly vibrated without ejecting ink droplets from the nozzle N. In this case, no dots are formed on the medium M.

[0087] When ink is not ejected from the nozzle N without causing the meniscus MN of the ink in the nozzle N to vibrate slightly, the supply signal Vin within the unit period Tu has a waveform that maintains the reference potential over the control periods Tu1 and Tu2. By supplying such a supply signal Vin to the drive element 51e, ink in the nozzle N is not vibrated slightly and ink is not ejected from the nozzle N. In this case, no dots are formed on the medium M either.

[0088] As described above, the ejection pulses PA1, PA2, and PB2 are used appropriately during the ejection period when ink is ejected from the nozzle N. Furthermore, during the non-ejection period when ink is not ejected from the nozzle N, the non-ejection pulse PB1 is used without the ejection pulses PA1, PA2, and PB2, or none of the ejection pulses PA1, PA2, and PB2 and the non-ejection pulse PB1 is used. Note that during the ejection period, any of the ejection pulses PA1, PA2, and PB2 may be used in combination with the non-ejection pulse PB1.

[0089] FIG. 9 is a diagram illustrating the use period of the non-ejection pulse PB1. FIG. 9 shows a case in which k consecutive non-ejection periods, each of which is a unit period Tu during which ink is not ejected, follow an ejection period, each of which is a unit period Tu during which ink is ejected, in the nozzle N[m] based on the print data Img. The unit periods Tu corresponding to the k non-ejection periods are shown as unit periods Tu_1 to Tu_k. Also shown are the elapsed time lengths t_k-2 to t_k from the ejection period to the unit periods Tu_k-2 to Tu_k. In the example shown in FIG. 9, k is an integer greater than or equal to 4. Hereinafter, the elapsed time lengths t_k-2 to t_k may be referred to as elapsed time t without distinction.

[0090] The target period is a unit period Tu that is used to determine which supply signal Vin to supply to the drive element 51e[m]. If the target period is a non-ejection period and the elapsed time t from the most recent ejection period of the target period is less than a predetermined time Th, none of the ejection pulses PA1, PA2, PB2 nor the non-ejection pulse PB1 is supplied to the drive element 51e[m]. Here, the predetermined time Th, which will be described later with reference to FIG. 10, is a time length that is equal to or greater than q times half the natural vibration period Tm of the ink meniscus MN in the nozzle N (q is an integer greater than or equal to 1).

[0091] 9, when the unit period Tu_k-2 is the target period, the elapsed time t_k-2 from the ejection period immediately preceding the unit period Tu_k-2 is less than the predetermined time Th. Therefore, during the unit period Tu_k-2, none of the ejection pulses PA1, PA2, PB2 and the non-ejection pulse PB1 is supplied to the drive element 51e.

[0092] On the other hand, if the target period is a non-ejection period and the elapsed time length t is equal to or greater than the predetermined time length Th, the non-ejection pulse PB1 is supplied to the drive element 51e without supplying the ejection pulses PA1, PA2, and PB2.

[0093] 9, when the unit period Tu_k-1 is the target period, the elapsed time t_k-1 from the ejection period immediately preceding the unit period Tu_k-1 is equal to or longer than the predetermined time Th. Therefore, during the unit period Tu_k-1, the ejection pulses PA1, PA2, and PB2 are not supplied to the drive element 51e, and only the non-ejection pulse PB1 is supplied.

[0094] Furthermore, when the unit period Tu_k is the target period, the length of time t_k that has elapsed since the ejection period immediately preceding the unit period Tu_k is equal to or longer than the predetermined length of time Th. Therefore, the ejection pulses PA1, PA2, and PB2 are not supplied to the drive element 51e, and only the non-ejection pulse PB1 is supplied.

[0095] The determination of whether the elapsed time length t is equal to or greater than the predetermined time length Th can also be made by, for example, determining whether or not a discharge period exists within a determination period that is n times the cycle of the unit period Tu (n is an integer equal to or greater than 1) and that corresponds to the predetermined time length Th. That is, if a discharge period exists within the determination period, the elapsed time length t is determined to be less than the predetermined time length Th. On the other hand, if no discharge period exists within the determination period, the elapsed time length t is determined to be equal to or greater than the predetermined time length Th. Note that the length of the determination period is approximately the same as the predetermined time length t.

[0096] After determining that the elapsed time length t is equal to or greater than the predetermined time length Th, the elapsed time length t remains equal to or greater than the predetermined time length Th until the target period, which is the target unit period Tu, becomes the ejection period. Therefore, if the target period is a non-ejection period, the unit period Tu immediately preceding the target period is a non-ejection period, and a non-ejection pulse PB1 is supplied to the drive element 51e during the unit period Tu immediately preceding the target period, the elapsed time length t may be determined to be equal to or greater than the predetermined time length Th. In other words, if the target period is the unit period Tu immediately following the unit period Tu in which the non-ejection pulse PB1 is supplied to the drive element 51e[m], and ink is not ejected from the nozzle N[m] during the target period, the target period is determined to be a non-ejection period and the elapsed time length t is equal to or greater than the predetermined time length Th, and a non-ejection pulse PB1 is supplied to the drive element 51e.

[0097] 10 is a graph showing the change over time in the amount of ink meniscus MN emerging from nozzle N when ejection pulse PA1, ejection pulse PA2, or ejection pulse PB2 is supplied to the drive element 51e. This amount is the volume of the space enclosed by the meniscus MN and an imaginary plane that includes the entire outer edge of the tip of nozzle N. When the meniscus MN emerges from nozzle N, this amount is a positive value, and when the meniscus MN retracts into nozzle N, this amount is a negative value. Note that even if the position of the meniscus MN relative to the tip of nozzle N is used instead of this amount, a change over time similar to that shown in FIG. 10 is shown.

[0098] In the example shown in Figure 10, ink is ejected from nozzle N during the period from timing T0 to timing T1, and even after that period has elapsed, the meniscus MN vibrates at the natural vibration period Tm for a predetermined period. This is called residual vibration of the meniscus MN. Therefore, if the non-ejection pulse PB1 is used during that predetermined period, the residual vibration of the meniscus MN and the pressure change on the ink due to the non-ejection pulse PB1 will be combined, and there is a possibility that the meniscus MN will vibrate excessively. Therefore, the non-ejection pulse PB1 is used to avoid that predetermined period.

[0099] The length of this predetermined period corresponds to the aforementioned predetermined time length Th. Therefore, the aforementioned predetermined time length Th is a time length that is equal to or greater than q times (q is an integer equal to or greater than 1) half the natural vibration period of the ink meniscus MN in the nozzle N.

[0100] q is preferably 1 or more and 10 or less, more preferably 1 or more and 8 or less, and even more preferably 4 or more and 8 or less. If q is too small, the effect of reducing the undesired vibration of the meniscus MN described above tends to decrease depending on the waveforms of the ejection pulses PA1, PA2, and PB2. On the other hand, if q is too large, depending on the content of the print data Img, the period during which neither an ejection pulse nor a non-ejection pulse is supplied to the drive element 51e may become too long, which may result in thickening of the ink.

[0101] From the viewpoint of achieving both higher printing speed and higher image quality, the period (predetermined period) of the unit period Tu is preferably 8 μsec or more and 100 μsec or less. Meanwhile, the natural vibration period Tm of the ink meniscus MN in the nozzle N is generally equal to or greater than the period (predetermined period) of the unit period Tu, for example, 40 μsec or more and 120 μsec or less. Therefore, it is preferable that the predetermined time length Th be q times or more the time length equivalent to 1 / 2 the natural vibration period Tm of the meniscus MN, which is 20 μsec or more and 60 μsec or less.

[0102] FIG. 11 is a diagram for explaining the vibration of the meniscus MN of the ink in the nozzle N due to the supply of the non-ejection pulse PB1 to the drive element 51e. When the non-ejection pulse PB1 is supplied to the drive element 51e, the meniscus MN vibrates in the direction along the Z axis, that is, the direction in which the nozzle N extends. For this reason, the ink in the nozzle N is agitated. As a result, in combination with the action of the flow of the ink in the direction FL (circulation flow) in the nozzle flow path Nfa by the circulation mechanism 60, the replacement of the ink between the nozzle N and the nozzle flow path Nfa is smoothly performed.

[0103] Here, the vibration of the meniscus MN due to the supply of the non-ejection pulse PB1 to the drive element 51e is within a range where ink is not ejected from the nozzle N. That is, the non-ejection pulse PB1 causes a pressure fluctuation of a strength that does not eject ink from the nozzle N in the pressure chamber C by driving the drive element 51e.

[0104] Here, the position where the meniscus MN in the nozzle N is most drawn in by supplying the non-ejection pulse PB1 to the drive element 51e is preferably as close as possible to the nozzle flow path Nfa within a range where ink is not ejected from the nozzle N.

[0105] More specifically, when the length of the nozzle N is L and the distance between the position where the meniscus MN of the ink in the nozzle N is most drawn in and the tip of the nozzle N by supplying the non-ejection pulse PB1 to the drive element 51e is Lm, it is preferable to satisfy the relationship of Lm / L > 0.3, more preferably to satisfy the relationship of 0.3 < Lm / L < 1, and even more preferably to satisfy the relationship of 0.3 < Lm / L < 0.5. In this case, the replacement of the ink between the nozzle N and the nozzle flow path Nfa as described above is preferably performed. On the other hand, if Lm / L is too small, depending on the length and width of the first portion NP1 of the nozzle N, the replacement of the ink between the nozzle N and the nozzle flow path Nfa may be insufficient. On the other hand, if Lm / L is too large, there is a possibility of entrapping air bubbles in the nozzle N.

[0106] Furthermore, in a configuration in which the nozzle N has a first portion NP1 and a second portion NP2 as in this embodiment, it is preferable that the position at which the meniscus MN is pulled most deeply into the nozzle N by supplying the non-ejection pulse PB1 to the drive element 51e reaches the second portion NP2 of the nozzle N. In this case, ink replacement is preferably performed between the nozzle N and the nozzle flow path Nfa as described above.

[0107] If the non-ejection pulse PB1 set in this way is supplied to the drive element 51e at a timing less than the predetermined time length Th after the ejection pulse PA1, ejection pulse PA2, or ejection pulse PB2 is supplied to the drive element 51e, the residual vibration of the meniscus MN and the ink pressure fluctuation caused by the ejection pulse PB2 are combined, as described above, and the meniscus MN is significantly drawn in. As a result, the meniscus MN is affected by the circulating flow and vibrates in the direction of the circulating flow. If the ejection pulse PA1, ejection pulse PA2, or ejection pulse PB2 is supplied to the drive element 51e while the vibration of the meniscus MN is unstable, the ejection of ink from the nozzle N becomes unstable, which may result in a deterioration in image quality.

[0108] As described above, the liquid ejection device 100 includes a pressure chamber C, an individual supply flow path Ra1 which is an example of a "first flow path," a communicating flow path Nf which is an example of a "second flow path," a nozzle N, a drive element 51e, a drive signal generation circuit 24 which is an example of a "drive signal generation unit," and a control circuit 21 which is an example of a "control unit."

[0109] As described above, the individual supply flow path Ra1 supplies ink, which is an example of "liquid," to the pressure chamber C. The communication flow path Nf discharges ink from the pressure chamber C. The nozzle N branches off from the communication flow path Nf and ejects ink. The drive element 51e applies pressure fluctuations to the ink in the pressure chamber C in accordance with the drive signal Com. The drive signal generation circuit 24 generates the drive signal Com. Based on the print data Img, the control circuit 21 controls the supply of the drive signal Com to the drive element 51e so that, for each unit period Tu of a predetermined cycle, the target period is either an ejection period in which ink is ejected from the nozzle N or a non-ejection period in which ink is not ejected from the nozzle N.

[0110] As described above, the drive signal Com includes ejection pulses PA1, PA2, PB2 and a non-ejection pulse PB1. Each of the ejection pulses PA1, PA2, PB2 drives the drive element 51e to generate a pressure fluctuation in the pressure chamber C with a strength that causes ink to be ejected from the nozzle N. The non-ejection pulse PB1 drives the drive element 51e to generate a pressure fluctuation in the pressure chamber C with a strength that does not cause ink to be ejected from the nozzle N.

[0111] As described above, when the target period is an ejection period, the control circuit 21 supplies ejection pulses PA1, PA2, and PB2 to the drive element 51e. When the target period is a non-ejection period and the elapsed time t from the ejection period immediately preceding the target period is less than the predetermined time Th, the control circuit 21 does not supply any of the ejection pulses PA1, PA2, and PB2 or the non-ejection pulse PB1 to the drive element 51e. When the target period is a non-ejection period and the elapsed time t is equal to or greater than the predetermined time Th, the control circuit 21 does not supply the ejection pulses PA1, PA2, and PB2 to the drive element 51e, but supplies the non-ejection pulse PB1. Here, the predetermined time Th is equal to or greater than q times 1 / 2 the natural vibration period Tm of the ink meniscus MN in the nozzle N (q is an integer equal to or greater than 1).

[0112] In the liquid ejection device 100 described above, if the target period is a non-ejection period and the length of time t that has elapsed since the most recent ejection period of the target period is equal to or longer than the predetermined length of time Th, a non-ejection pulse PB1 is supplied to the drive element 51e, causing the meniscus MN of the liquid in the nozzle N to vibrate. Therefore, even if the nozzle N branches off from the communication flow path Nf, the ink in the nozzle N is agitated by the vibration, making it possible to reduce the accumulation of ink in the nozzle N during the non-ejection period. As a result, it is possible to reduce ejection defects due to thickening of the ink in the nozzle N, etc.

[0113] Furthermore, since the predetermined time length t is a time length equal to or greater than an integral multiple of the natural vibration period Tm1 / 2 of the ink meniscus MN in the nozzle N, it is possible to reduce undesired vibration of the ink meniscus MN in the nozzle N. As a result, it is also possible to reduce ejection defects caused by such vibration.

[0114] Furthermore, if the target period is a non-ejection period and the elapsed time t from the most recent ejection period of the target period is less than the predetermined time Th, the non-ejection pulse PB1 is not supplied to the drive element 51e. Therefore, the non-ejection pulse PB1 does not impart pressure fluctuations to the ink during the period in which the residual vibration of the meniscus MN, which vibrates after ink is ejected from the nozzle N, has not yet subsided. This prevents the vibration of the meniscus MN from becoming unstable, enabling stable ejection when ink is subsequently ejected from the nozzle N. Furthermore, because the vibration generated in the meniscus MN during the ejection period remains throughout the target period, the meniscus MN of the ink in the nozzle N can be vibrated even if the non-ejection pulse PB1 is not supplied to the drive element 51e. This effectively reduces ink retention in the nozzle N during the non-ejection period. This also prevents the drive element 51e from receiving an excessive non-ejection pulse PB1, reducing problems such as heat generation by the drive element 51e.

[0115] As described above, for example, if the target period is a non-ejection period and there is an ejection period within the judgment period, the control circuit 21 determines that the elapsed time length t is less than the predetermined time length Th. In this case, the non-ejection pulse PB1 is not supplied to the drive element 51e. On the other hand, if the target period is a non-ejection period and there is no ejection period within the judgment period, the control circuit 21 determines that the elapsed time length t is equal to or greater than the predetermined time length Th. In this case, the non-ejection pulse PB1 is supplied to the drive element 51e. Here, the judgment period is a period that is n times (n is an integer greater than or equal to 1) the predetermined cycle (the cycle of the unit period Tu) before the target period.

[0116] As described above, if the target period is a non-ejection period, the unit period Tu immediately preceding the target period is a non-ejection period, and a non-ejection pulse PB1 is supplied to the drive element 51e during the unit period Tu immediately preceding the target period, the control circuit 21 determines that the elapsed time length t is equal to or greater than the predetermined time length Th. In this case, the non-ejection pulse PB1 is supplied to the drive element 51e.

[0117] Furthermore, as described above, when the cycle (predetermined cycle) of the unit period Tu is 8 μsec or more and 100 μsec or less, the printing speed can be increased. Furthermore, with such a cycle of the unit period Tu, vibrations occurring in the meniscus MN during the ejection period tend to extend to the unit period Tu following the ejection period. Therefore, in such a case, the aforementioned effect can be significantly achieved by providing a period in which none of the ejection pulses PA1, PA2, PB2 and the non-ejection pulse PB1 is supplied to the drive element 51e.

[0118] Furthermore, as described above, when the natural vibration period Tm of the meniscus of ink in the nozzle N is 40 μsec or more and 120 μsec or less, the predetermined time length t is an integer multiple or more of a time length of 20 μsec or more and 60 μsec or less. By setting the predetermined time length t in this manner, the effect of reducing the undesired vibration of the meniscus MN described above can be obtained.

[0119] Furthermore, as described above, if the period (predetermined period) of the unit period Tu is equal to or shorter than the natural vibration period Tm of the meniscus MN of the ink in the nozzle N, the vibration generated in the meniscus MN during the ejection period continues to the unit period Tu that follows the ejection period. Therefore, in such a case, the aforementioned effect can be significantly obtained by providing a period in which none of the ejection pulses PA1, PA2, PB2 and the non-ejection pulse PB1 is supplied to the drive element 51e.

[0120] Furthermore, as described above, when the relationship Lm / L>0.3 is satisfied, supplying a non-ejection pulse PB1 to the drive element 51e can suitably agitate the ink in the nozzle N. Note that L is the length of the nozzle N, and Lm is the distance between the position of the ink meniscus MN that is drawn most deeply into the nozzle N by supplying the non-ejection pulse PB1 to the drive element 51e and the tip of the nozzle N.

[0121] As described above, the nozzle N has a first portion NP1 and a second portion NP2 provided between the first portion NP1 and the communication flow path Nf. The cross-sectional area of ​​the first portion NP1 is smaller than that of the second portion NP2. Furthermore, when none of the ejection pulses PA1, PA2, PB2 and the non-ejection pulse PB1 is supplied to the drive element 51e, the ink meniscus MN in the nozzle N is located within the first portion NP1. In contrast, when the non-ejection pulse PB1 is supplied to the drive element 51e, the ink meniscus MN in the nozzle N reaches the second portion NP2. Therefore, even when the nozzle N has a configuration including the first portion NP1 and the second portion NP2, the ink in the nozzle N can be suitably agitated by supplying the non-ejection pulse PB1 to the drive element 51e.

[0122] Furthermore, as described above, the nozzles N extend in a direction that intersects with the direction FL in which the ink flows through the communication flow path Nf. Therefore, if the non-ejection pulse PB1 is not used, the ink in the nozzles N is less likely to be affected by the flow of ink through the communication flow path Nf, and the ink in the nozzles N is likely to stagnate.

[0123] As described above, the liquid ejection device 100 includes a plurality of individual flow paths IP, a first common liquid chamber R1, and a second common liquid chamber R2. Each of the plurality of individual flow paths IP has a pressure chamber C, an individual supply flow path Ra1, and a nozzle N. The first common liquid chamber R1 is provided in common to the plurality of individual flow paths IP, and stores ink to be supplied to the individual supply flow path Ra1. The second common liquid chamber R2 is provided in common to the plurality of individual flow paths IP, and stores ink discharged from the communication flow path Nf.

[0124] As described above, the liquid ejection device 100 includes a circulation mechanism 60 that supplies ink to the first common liquid chamber R1 and collects ink from the second common liquid chamber R2. This allows the circulation mechanism 60 to generate a circulating flow of ink in each individual flow path IP. As a result, combined with this circulating flow, it is possible to effectively reduce ink stagnation in the nozzles N.

[0125] B: Second embodiment A second embodiment of the present disclosure will be described below. In the following exemplary embodiment, for elements whose actions and functions are similar to those of the first embodiment, the reference numerals used in the description of the first embodiment will be used, and detailed descriptions of each element will be omitted as appropriate.

[0126] 12 is a diagram showing the electrical configuration of a liquid ejection device 100A according to the second embodiment. The liquid ejection device 100A has the same configuration as the liquid ejection device 100 of the first embodiment described above, except that a sensor 70 is added and, accordingly, a control unit 20A is provided instead of the control unit 20.

[0127] The sensor 70 is a sensor that measures information related to the damping coefficient of the flow path from the nozzle N to the ends E1 and E2 of the individual flow path IP. When the resistance of the flow path from the nozzle N to the ends E1 and E2 of the individual flow path IP is R and the inertance of the flow path from the nozzle N to the ends E1 and E2 of the individual flow path IP is M, the damping coefficient is expressed as R / 2M. Here, the greater the viscosity of the ink in the flow path from the nozzle N to the ends E1 and E2 of the individual flow path IP, the greater the resistance R, and therefore the greater the damping coefficient. Therefore, information related to the damping coefficient may include, for example, information related to the viscosity of the ink in the flow path from the nozzle N to the ends E1 and E2 of the individual flow path IP. In other words, the sensor 70 is a sensor that outputs a signal corresponding to the viscosity of the ink in the flow path from the nozzle N to the ends E1 and E2 of the individual flow path IP.

[0128] Changes in the viscosity of the ink in the flow path from the nozzle N to the ends E1 and E2 of the individual flow path IP can be measured, for example, based on the residual vibration of the pressure chamber Ca or the pressure chamber Cb, or the flight speed of the ink ejected from the nozzle N. Therefore, the sensor 70 outputs, for example, a signal based on the residual vibration of the ink in the pressure chamber Ca or the pressure chamber Cb, or a signal based on the flight speed of the ink ejected from the nozzle N, as a signal corresponding to the viscosity of the ink in the flow path from the nozzle N to the ends E1 and E2 of the individual flow path IP. The signal based on the residual vibration of the ink in the pressure chamber Ca or the pressure chamber Cb, and the signal based on the flight speed of the ink ejected from the nozzle N can be obtained using already known technology.

[0129] Furthermore, changes in the viscosity of the ink in the flow path from the nozzle N to the ends E1 and E2 of the individual flow path IP can be predicted depending on the temperature of the usage environment. Therefore, the sensor 70 may measure the temperature of the usage environment as information about the attenuation coefficient of the flow path from the nozzle N to the ends E1 and E2 of the individual flow path IP. In other words, the sensor 70 may be configured as a temperature sensor.

[0130] The control unit 20A is configured similarly to the control unit 20 of the first embodiment described above, except that it includes a control circuit 21A, which is an example of a "control unit," instead of the control circuit 21. The control circuit 21A is configured similarly to the control circuit 21, except that it changes the predetermined time length Th described above based on a signal from the sensor 70.

[0131] The control circuit 21A shortens the predetermined time length Th as the damping coefficient increases or as the viscosity of the ink in the flow path from the nozzle N to the ends E1 and E2 of the individual flow path IP increases. For example, when the relationship R / 2M≦7000 [1 / s] is satisfied, the control circuit 21A sets the predetermined time length Th to predetermined time length Th1, and when the relationship R / 2M>7000 [1 / s] is satisfied, the control circuit 21A sets the predetermined time length Th to predetermined time length Th2, which is shorter than predetermined time length Th1.

[0132] The higher the humidity of the usage environment, the more difficult it is for the ink in the nozzles N to dry, and the lower the humidity of the usage environment, the more easily the ink in the nozzles N will dry. In other words, the lower the humidity of the usage environment, the shorter the predetermined time length Th is preferable. Therefore, the predetermined time length Th can also be determined based on the damping coefficient or the viscosity of the ink and the humidity of the usage environment.

[0133] 13 is a graph showing the change over time in the amount of ink meniscus MN ejected from nozzle N after supplying any one of ejection pulses PA1, PA2, and PB2 to the drive element 51e when the attenuation coefficient of the flow path from nozzle N to ends E1 and E2 of individual flow paths IP is changed. In FIG. 13, the solid line indicates the case where the relationship R / 2M≦7000 [1 / s] is satisfied, and the dashed line indicates the case where R / 2M>7000 [1 / s].

[0134] In the example shown in FIG. 13, when the relationship R / 2M≦7000 [1 / s] is satisfied, the vibration of the meniscus MN settles down in a period of at least three times half the natural vibration period Tm. In contrast, when the relationship R / 2M>7000 [1 / s] is satisfied, the vibration of the meniscus MN settles down in a period of approximately one time half the natural vibration period Tm. In the example shown in FIG. 13, when the relationship R / 2M≦7000 [1 / s] is satisfied, the predetermined time length Th1 is set to a period of at least three times half the natural vibration period Tm. In contrast, when the relationship R / 2M>7000 [1 / s] is satisfied, the predetermined time length Th2 is set to at least one time half the natural vibration period Tm.

[0135] The second embodiment described above can also reduce ejection defects. In this embodiment, as described above, the control circuit 21A changes the predetermined time length Th in accordance with the damping coefficient of the flow path from the nozzle N to the ends E1 and E2 of the individual flow path IP. Therefore, even if the damping coefficient changes, the use period or non-use period of the non-ejection pulse PB1 can be appropriately set.

[0136] Furthermore, the control circuit 21A changes the predetermined time length Th based on information about the temperature of the usage environment. The temperature of the usage environment is correlated with the damping coefficient of the flow path from the nozzle N to the ends E1 and E2 of the individual flow paths IP. Therefore, it is possible to estimate a change in the damping coefficient of the communication flow path Nf based on information about the temperature of the usage environment. Therefore, it is possible to change the predetermined time length Th based on information about the temperature of the usage environment.

[0137] As described above, the liquid ejection device 100A includes a sensor 70 that outputs a signal corresponding to the viscosity of the ink in the flow path from the nozzle N to the ends E1 and E2 of the individual flow path IP. The control circuit 21A changes the predetermined time length Th based on the output result of the sensor 70. The viscosity of the ink in the flow path from the nozzle N to the ends E1 and E2 of the individual flow path IP is correlated with the damping coefficient of the flow path from the nozzle N to the ends E1 and E2 of the individual flow path IP. Therefore, it is possible to estimate a change in the damping coefficient based on the viscosity. Therefore, it is possible to change the predetermined time length Th based on the viscosity.

[0138] C: Third embodiment A third embodiment of the present disclosure will be described below. In the following exemplary embodiments, elements whose actions and functions are similar to those of the first embodiment will be designated by the same reference numerals as those used in the description of the first embodiment, and detailed descriptions thereof will be omitted where appropriate.

[0139] 14 is a schematic diagram illustrating the circulation flow path of a liquid ejection head 50B according to the third embodiment. The liquid ejection head 50B is similar to the liquid ejection head 50 of the first embodiment, except that it has a plurality of individual flow paths IPa and a plurality of individual flow paths IPb instead of the plurality of individual flow paths IP. That is, as shown in FIG. 14, the liquid ejection head 50B is provided with a plurality of nozzles N, a plurality of individual flow paths IPa, a plurality of individual flow paths IPb, a first common liquid chamber R1, and a second common liquid chamber R2, and is connected to a circulation mechanism 60.

[0140] More specifically, the liquid ejection head 50B is provided with a plurality of nozzles Na and a plurality of nozzles Nb. Each of these nozzles is configured similarly to the nozzle N in the above-described embodiment, and ejects ink in the Z2 direction. Note that, hereinafter, when there is no need to distinguish between the nozzles Na and Nb, they will simply be referred to as "nozzles N."

[0141] The plurality of nozzles Na are arranged along the Y axis, and a group of these constitutes a first nozzle row La. Similarly, the plurality of nozzles Nb are arranged along the Y axis, and a group of these constitutes a second nozzle row Lb.

[0142] The first nozzle row La and the second nozzle row Lb are aligned at a predetermined interval along the X-axis. Here, the arrangement pitch of the nozzles Na and the arrangement pitch of the nozzles Nb are equal to each other, but the nozzles Na and the nozzles Nb that are closest to each other are arranged so as to be offset from each other along the Y-axis.

[0143] An individual flow path IPa communicates with each of the multiple nozzles Na. Each of the multiple individual flow paths IPa extends along the X-axis and communicates with a different nozzle Na. Similarly, an individual flow path IPb communicates with each of the multiple nozzles Nb. Each of the multiple individual flow paths IPb extends along the X-axis and communicates with a different nozzle Nb. The individual flow paths IPa and IPb are alternately arranged along the Y-axis.

[0144] The individual flow paths IPa are similar to the individual flow paths IP of the above-described embodiment, except that the pressure chambers Cb are omitted. Specifically, the individual flow paths IPa include a first portion Pa1 and a second portion Pa2. The first portion Pa1 of each individual flow path IPa is a flow path between the upstream end E1 of the individual flow path IPa and the nozzle Na. The first portion Pa1 includes the pressure chamber Ca. On the other hand, the second portion Pa2 of each individual flow path IPa is a flow path between the downstream end E2 of the individual flow path IPa and the nozzle Na.

[0145] The individual flow paths IPb are similar to the individual flow paths IP of the above-described embodiment, except that the pressure chamber Ca is omitted. Specifically, the individual flow paths IPb include a third portion Pb1 and a fourth portion Pb2. The third portion Pb1 of each individual flow path IPb is a flow path between the upstream end E1 of the individual flow path IPb and the nozzle Nb. On the other hand, the fourth portion Pb2 of each individual flow path IPb is a flow path between the downstream end E2 of the individual flow path IPb and the nozzle Nb. The fourth portion Pb2 includes a pressure chamber Cb.

[0146] A first common liquid chamber R1 is connected to the upstream end E1 of each of the individual flow paths IPa and IPb, while a second common liquid chamber R2 is connected to the downstream end E2 of each of the individual flow paths IPa and IPb.

[0147] Fig. 15 is a cross-sectional view taken along line A2-A2 in Fig. 14. Fig. 15 shows a cross section of the liquid ejection head 50B cut along a plane parallel to the X-axis and Z-axis along the individual flow path IPa. The configuration relating to the individual flow path IPa will be described below as a representative example. Note that the individual flow path IPb is the same as the individual flow path IPa except that it is configured in a 180° different direction around the Z-axis, and therefore a description thereof will be omitted.

[0148] The individual flow paths IPa are the same as the individual flow paths IP of the first embodiment described above, except that the pressure chambers Cb are replaced with horizontal communicating flow paths Cq1. The liquid ejection head 50B is configured the same as the liquid ejection head 50 of the first embodiment described above, except that it includes a nozzle substrate 51aB, a flow path substrate 51bB, and a pressure chamber substrate 51cB instead of the nozzle substrate 51a, the flow path substrate 51b, and the pressure chamber substrate 51c. Note that in the individual flow paths IPa, the drive elements 51e corresponding to the pressure chambers Cb are omitted.

[0149] The nozzle substrate 51aB is provided with a plurality of nozzles Na. The nozzle substrate 51aB is configured in the same manner as the nozzle substrate 51a described above, except for the arrangement of the nozzles Na. When viewed in the direction along the Z axis, the nozzles Na overlap with the pressure chambers Ca.

[0150] The flow path substrate 51bB is provided with the above-mentioned individual flow paths IPa except for the pressure chambers Ca, the liquid chambers R1a and R2a.

[0151] 15, each individual flow path IPa has a communication flow path Nf, a horizontal communication flow path Cq1, an individual supply flow path Ra1, and an individual discharge flow path Ra2 in addition to the pressure chamber Ca. Of these, the communication flow path Nf, the horizontal communication flow path Cq1, the individual supply flow path Ra1, and the individual discharge flow path Ra2 are provided in the flow path substrate 51bB. Here, the first communication flow path Na1 of the communication flow path Nf overlaps with the nozzle Na when viewed in the direction along the Z axis. Furthermore, the nozzle Na branches off from the first communication flow path Na1 in a direction different from that of the nozzle flow path Nfa.

[0152] The horizontal communication channel Cq1 is a space extending along the X-axis. The horizontal communication channel Cq1 connects the second communication channel Na2 with the individual discharge channel Ra2, and guides ink from the second communication channel Na2 to the individual discharge channel Ra2.

[0153] The pressure chamber substrate 51cB is similar to the pressure chamber substrate 51c of the above-described embodiment, except that the pressure chamber Cb is omitted for the individual flow channel IPa.

[0154] According to the third embodiment, similarly to the first embodiment, ejection defects can be reduced by using a non-ejection pulse during the non-ejection period.

[0155] D: Modification The above-described embodiments can be modified in various ways. Specific modifications that can be applied to the above-described embodiments are exemplified below. Any of the following embodiments can be combined as desired within the scope of their mutual compatibility.

[0156] D1: Variation 1 In each of the above-described embodiments, the nozzle N has a first portion NP1 and a second portion NP2, but the nozzle N is not limited to this configuration. For example, the nozzle N may have a constant width or may have a shape with three or more steps.

[0157] D2: Variation 2 The driving element that changes the pressure of the ink in the pressure chamber C is not limited to the driving element 51e exemplified in the above-described embodiments. For example, a heating element that generates bubbles inside the pressure chamber C by heating to change the pressure of the ink may be used as the driving element.

[0158] D3: Variation 3 In each of the above-described embodiments, a serial-type liquid ejection device 100 in which a carriage 41 carrying a liquid ejection head 50 moves back and forth has been exemplified, but the present disclosure can also be applied to a line-type liquid ejection device in which multiple nozzles N are distributed across the entire width of the medium M.

[0159] D4: Variation 4 The liquid ejection device 100 exemplified in the above embodiment may be employed in various devices such as facsimile machines and copiers, in addition to devices dedicated to printing, and the applications of the present disclosure are not particularly limited. However, the applications of the liquid ejection device are not limited to printing. For example, a liquid ejection device that ejects a solution of a color material is used as a manufacturing device for forming color filters for display devices such as liquid crystal display panels. Furthermore, a liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device for forming wiring and electrodes on a wiring board. Furthermore, a liquid ejection device that ejects a solution of an organic substance related to a living body is used as a manufacturing device for manufacturing biochips, for example. [Explanation of symbols]

[0160] 10...liquid container, 20...control unit, 20A...control unit, 21...control circuit (control section), 21A...control circuit (control section), 22...memory circuit, 23...power supply circuit, 24...drive signal generation circuit, 30...transport mechanism, 40...movement mechanism, 41...carriage, 42...transport belt, 50...liquid ejection head, 50B...liquid ejection head, 51...head chip, 51a...nozzle substrate, 51aB...nozzle substrate, 51b...flow path substrate, 51bB...flow path substrate, 51c...pressure chamber substrate, 51cB...pressure chamber substrate, 51d...diaphragm, 51e...drive element, 51f...case, 51g...protective plate, 51h ...wiring board, 51i...vibration absorber, 52...switching circuit, 52a...connection state designation circuit, 60...circulation mechanism, 61...first supply pump, 62...second supply pump, 63...storage container, 64...recovery flow path, 65...supply flow path, 70...sensor, 100...liquid discharge device, 100A...liquid discharge device, 200...external device, C...pressure chamber, CLK...clock signal, CNG...change signal, Ca...pressure chamber, Cb...pressure chamber, Com...drive signal, Com-A...drive signal, Com-B...drive signal, Cq1...horizontal communication flow path, E1...end, E2...end, FL...direction, IP...individual flow path, IPa...individual flow path, I Pb...individual flow path, Img...print data, L...nozzle row, LAT...latch signal, LHa...wiring, LHb...wiring, LHd...wiring, La...first nozzle row, Lb...second nozzle row, M...medium, MN...meniscus, N...nozzle, NP1...first part, NP2...second part, Na...nozzle, Na1...first communicating flow path, Na2...second communicating flow path, Nb...nozzle, Nf...communicating flow path (second flow path), Nfa...nozzle flow path, P1...inlet, P2...outlet, PA1...ejection pulse, PA2...ejection pulse, PB1...non-ejection pulse, PB2...ejection pulse, Pa1...first part, Pa2...second part, P b1...third portion, Pb2...fourth portion, PlsC...pulse, PlsL...pulse, R1...first common liquid chamber, R1a...liquid chamber, R1b...liquid chamber, R2...second common liquid chamber, R2a...liquid chamber, R2b...liquid chamber, Ra1...individual supply flow path (first flow path), Ra2...individual discharge flow path, SI...print data signal, SLa...connection state designation signal, SLb...connection state designation signal, SWa...switch, SWb...switch, Sk1...control signal, Sk2...control signal, T0...timing, T1...timing, Tm...natural vibration period, Tu...unit period, Tu1...control period, Tu2...control period, Tu_1...unit period,Tu_k...unit period, Tu_k-1...unit period, Tu_k-2...unit period, VBS...offset potential, VHV...power supply potential, Vin...supply signal, Zd...electrode, Zu...electrode, dCom...waveform designation signal, t...elapsed time.

Claims

1. A pressure chamber; a first flow path that supplies liquid to the pressure chamber; a second flow path for discharging liquid from the pressure chamber; a nozzle branching from the second flow path and discharging a liquid; a driving element that applies a pressure fluctuation to the liquid in the pressure chamber in response to a driving signal; a drive signal generating unit that generates the drive signal for each unit period of a predetermined cycle; a control unit that controls supply of the drive signals to the drive elements based on print data so that the unit period is either an ejection period in which liquid is ejected from the nozzles or a non-ejection period in which liquid is not ejected from the nozzles, The drive signal is an ejection pulse that drives the drive element so as to generate a pressure fluctuation in the pressure chamber that is strong enough to eject liquid from the nozzle; a non-ejection pulse that drives the drive element so as to generate a pressure fluctuation in the pressure chamber that is strong enough to prevent liquid from being ejected from the nozzle, When a time length equal to or greater than q times (q is an integer equal to or greater than 1) half of the natural vibration period of the meniscus of the liquid in the nozzle is defined as a predetermined time length, The control unit supplying the ejection pulse to the drive element when a target period, which is a unit period that is a target of determining whether or not to supply the drive signal to the drive element, is the ejection period; When the target period is the non-ejection period, and the length of time that has elapsed from the ejection period immediately preceding the target period to the target period is less than the predetermined length of time, neither the ejection pulse nor the non-ejection pulse is supplied to the drive element, When the target period is the non-ejection period and the elapsed time length is equal to or longer than the predetermined time length, the non-ejection pulse is supplied to the driving element without supplying the ejection pulse. Liquid discharge device.

2. When a period that is n times (n is an integer equal to or greater than 1) the predetermined cycle before the target period is set as a determination period, The control unit If the target period is the non-ejection period and the ejection period is included in the determination period, it is determined that the elapsed time length is less than the predetermined time length; If the target period is the non-ejection period and the ejection period does not exist within the determination period, it is determined that the elapsed time length is equal to or longer than the predetermined time length. The liquid ejection device according to claim 1 .

3. the control unit determines that the elapsed time length is equal to or longer than the predetermined time length when the target period is the non-ejection period, the unit period immediately preceding the target period is the non-ejection period, and the non-ejection pulse is supplied to the drive element in the unit period immediately preceding the target period; The liquid ejection device according to claim 1 or 2.

4. The predetermined period is equal to or greater than 8 μsec and equal to or less than 100 μsec. The liquid ejection device according to claim 1 .

5. the natural vibration period of the meniscus of the liquid in the nozzle is 40 μsec or more and 120 μsec or less; The liquid ejection device according to claim 1 .

6. the predetermined period is equal to or less than the natural vibration period of the meniscus of the liquid in the nozzle; The liquid ejection device according to claim 1 .

7. When the length of the nozzle is L and the distance between the position of the meniscus of the liquid that is most drawn into the nozzle by the supply of the non-ejection pulse to the drive element and the tip of the nozzle is Lm, The relationship Lm / L>0.3 is satisfied. The liquid ejection device according to claim 1 .

8. the nozzle has a first portion and a second portion provided between the first portion and the second flow path, a cross-sectional area of ​​the first portion is smaller than a cross-sectional area of ​​the second portion; a meniscus of the liquid in the nozzle when neither the ejection pulse nor the non-ejection pulse is supplied to the drive element is located within the first portion; a meniscus of the liquid in the nozzle in a state in which the non-ejection pulse is supplied to the drive element reaches the second portion; The liquid ejection device according to claim 1 .

9. The nozzle extends in a direction intersecting a direction in which the liquid flows through the second flow path. The liquid ejection device according to claim 1 .

10. a plurality of individual flow paths each including the pressure chamber, the first flow path, the second flow path, and the nozzle; a first common liquid chamber provided in common to the plurality of individual flow paths and configured to store liquid to be supplied to the first flow paths; a second common liquid chamber provided in common to the plurality of individual flow paths and configured to store liquid discharged from the second flow path; The liquid ejection device according to claim 1 .

11. further comprising a circulation mechanism that supplies liquid to the first common liquid chamber and recovers liquid from the second common liquid chamber; The liquid ejection device according to claim 10.

12. The control unit changes the predetermined time length in accordance with a damping coefficient of the second flow path. The liquid ejection device according to claim 1 .

13. the control unit changes the predetermined time length based on information regarding one or both of the temperature and humidity of the usage environment. The liquid ejection device according to claim 1 .

14. a sensor that outputs a signal according to the viscosity of the liquid in the second flow path or the nozzle; The control unit changes the predetermined time length based on the output result of the sensor. The liquid ejection device according to claim 1 .

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