Inkjet head drive control method and inkjet recording apparatus

Abstract

Provided are a method for controlling driving of an inkjet head, and an inkjet recording apparatus, with which ink can be discharged in a more stable manner. A method for controlling driving of an inkjet head comprising a nozzle that discharges ink, a supply flow channel that supplies the ink to the nozzle, an ejection flow channel through which the ink in the supply flow channel is ejected, and a drive element that performs an action for inducing pressure fluctuation in the ink within the supply flow channel in accordance with an applied drive signal, wherein: the method includes a non-discharge driving step for performing non-discharge driving in which a drive signal that does not cause ink to be discharged from the nozzle is applied to the drive element; and in the signal waveform of the drive signal relating to non-discharge driving, the average ink level position in the nozzle after the drive signal has been applied is farther from the open surface of the nozzle than the ink level position in the nozzle before the drive signal is applied.

Description

[Technical field]

[0001] The present invention relates to an inkjet head drive control method and an inkjet recording apparatus. [Background technology]

[0002] In an inkjet recording device that ejects ink from a nozzle to record an image, if unejected ink accumulates near the nozzle, problems can occur such as separation of components and evaporation of water from the nozzle opening, causing deviations from appropriate ink ejection conditions, making it impossible to obtain the desired image quality or causing poor ink ejection.

[0003] In response to this, there is a technology that provides a recovery flow path for recovering ink supplied to an inkjet head, and circulates the ink at an appropriate flow rate to prevent the ink from stagnating for a long period of time. Patent Document 1 discloses a technology that applies negative pressure to the ink in the nozzle during standby when no ink ejection operation is being performed, and draws and maintains the ink surface position (meniscus) close to the circulation flow path, so that the ink near the nozzle opening that is out of the ink circulation flow path can be more easily recovered and circulated. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-107403 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the meniscus is brought closer to the circulation flow path, the meniscus becomes more likely to be disturbed by the influence of the ink flow, which may cause ink to not be ejected normally the next time.

[0006] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide an inkjet head drive control method and an inkjet recording apparatus that are capable of ejecting ink more stably. [Means for solving the problem]

[0007] In order to achieve the above object, the invention described in claim 1 comprises: A drive control method for an inkjet head including a nozzle that ejects ink, a supply flow path that supplies ink to the nozzle, a discharge flow path that discharges the ink in the supply flow path, and a drive element that operates to generate pressure fluctuations in the ink in the supply flow path in response to an applied drive signal, comprising: a non-ejection driving step of performing non-ejection driving by applying the drive signal to the drive element so as not to eject ink from the nozzle; The signal wave of the drive signal related to the non-ejection drive The shape is , The rising portion of the voltage, the portion that is maintained at the voltage after the rising, and the falling portion that returns to the initial voltage from the rising voltage are all connected together. Contains Rarely, The voltage rise reduces the pressure of the ink; The fall time is longer than the rise time, before message In the signal waveform, The above The average ink level position in the nozzle after the drive signal is applied is farther from the nozzle opening surface than the average ink level position in the nozzle before the drive signal is applied.

[0009] In addition, claims 2 The invention described is as follows: 1 In the inkjet head drive control method described above, The fall time is longer than the rise time by at least 0.3 times the resonance period associated with the pressure vibration of the ink inside the nozzle.

[0010] In addition, claims 3 The invention described is as follows: 2 In the inkjet head drive control method described above, The fall time is longer than the rise time by 0.35 times the resonance period or more, and the rise time is 0.2 times the resonance period or less.

[0011] Also, claims 4 The invention described herein is as follows: 3 2. The inkjet head drive control method according to claim 1 , The inkjet head ejects ceramic ink or white ink.

[0012] Also, claims 5 The invention described herein is as follows: 4 2. The inkjet head drive control method according to claim 1 , The non-ejection driving step is performed in each recording cycle of each pixel in which ink is not ejected during recording of an image.

[0013] Also, claims 6 The invention described is an inkjet head including a nozzle for ejecting ink, a supply flow path for supplying ink to the nozzle, a discharge flow path for discharging the ink in the supply flow path, and a drive element for performing an operation to generate a pressure fluctuation in the ink in the supply flow path in response to an applied drive signal; A control unit; Equipped with the control unit performs non-ejection driving by applying the drive signal to the drive element so as not to eject ink from the nozzle; The signal wave of the drive signal related to the non-ejection drive The shape is , The rising portion of the voltage, the portion that is maintained at the voltage after the rising, and the falling portion that returns to the initial voltage from the rising voltage are all connected together. Contains Rarely, The voltage rise reduces the pressure of the ink; The fall time is longer than the rise time, before message In the signal waveform, The above The average ink level position in the nozzle after the drive signal is applied is farther from the nozzle opening surface than the average ink level position in the nozzle before the drive signal is applied. An inkjet recording device. Effect of the Invention

[0014] According to the present invention, there is an effect that the ink can be ejected more stably in the ink-jet head. [Brief description of the drawings]

[0015] [Figure 1] 1 is a block diagram showing a functional configuration of an inkjet printing apparatus according to an embodiment of the present invention; [Diagram 2] 5 is a cross-sectional view illustrating a flow path structure of ink in the vicinity of a nozzle. FIG. [Figure 3A] FIG. 4 is a diagram illustrating an example of an output drive signal. [Figure 3B] FIG. 4 is a diagram illustrating an example of an output drive signal. [Figure 4A] FIG. 2 is a diagram for explaining the state of an ink surface; [Figure 4B] FIG. 2 is a diagram for explaining the state of an ink surface; [Diagram 5] 11 is a chart showing an example of the recession state of the ink liquid level position according to the relationship between the rise time and the fall time. [Figure 6] 11 is a graph showing the degree of effect of ink replacement within a nozzle relative to the ink circulation flow speed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the functional configuration of an inkjet recording apparatus 1 according to this embodiment.

[0017] The inkjet recording device 1 is configured such that a control unit 40, a transport drive unit 41, a recording operation unit 42, a memory unit 44, a communication unit 51, a display unit 52, an operation reception unit 53, a liquid delivery pump 54, etc. are connected to a bus 49 and are capable of sending and receiving signals between them.

[0018] The control unit 40 includes a CPU 401 (Central Processing Unit), a ROM 402 (Read Only Memory), and a RAM 403 (Random Access Memory). The CPU 401 performs various calculation processes. The CPU 401 receives measurement signals and status signals from each part, and transmits control signals to each part to cause it to perform appropriate operations. The ROM 402 stores setting data, programs, and the like. The RAM 403 provides a working memory space for the CPU 401 and stores temporary data. The temporary data may include image data to be recorded, as well as the setting data and processing data thereof.

[0019] The transport drive unit 41 operates a transport unit that transports and moves a recording medium on which an image to be recorded is recorded based on a control signal from the control unit 40. The transport unit has, for example, an endless belt on which the recording medium is placed and a rotating drum, and the transport drive unit 41 moves the endless belt around at a predetermined speed and rotates the rotating drum. The transport drive unit 41 has, for example, a rotary motor.

[0020] The recording operation unit 42 performs an operation of ejecting ink onto a recording medium to record an image. The recording operation unit 42 has an inkjet head 420. The inkjet head 420 has a plurality of nozzles N, piezoelectric elements 421 (drive elements), and head drive units 422. The nozzles N eject ink. The piezoelectric elements 421 are positioned along an ink supply path communicating with the nozzles N, and deform when a drive voltage is applied. The piezoelectric elements 421 cause pressure fluctuations in the ink in the ink supply path according to a drive signal indicating a change pattern of the drive voltage by a deformation operation according to the drive signal. The head drive unit 422 outputs a drive signal to a selected piezoelectric element 421. The recording operation unit 42 may have a plurality of inkjet heads 420. The type of ink ejected is not particularly limited, but may be, for example, a ceramic ink. The ink may also include a white ink. Many of these inks are more likely to separate into components than other inks.

[0021] The drive waveform signal generating unit 43 generates a drive waveform signal to be included in the drive signal output by the head driving unit 422. Although not particularly limited, the drive waveform signal is generated by converting digital signal data indicating a plurality of types of drive waveforms into analog form, and outputting drive waveform signals with amplified voltage and current to the head driving unit 422. The head driving unit 422 selects one of the plurality of drive waveform signals, or combines a plurality of signals according to necessity or the driving method, and outputs the selected signal to each piezoelectric element 421 at an appropriate timing.

[0022] The control unit 40 outputs control signals to the transport drive unit 41 and the head drive unit 422 to operate them at appropriate timing, so that the recording medium faces the openings of the multiple nozzles N of the inkjet head 420 under appropriate conditions, and the ejected ink lands at an appropriate position on the recording medium. The specific ejection timing may be synchronized with a clock signal input from an oscillator circuit (not shown). The drive control signal specifies whether or not ink is ejected from each nozzle N in each ink ejection period, and the amount of ink ejected as necessary. The ink ejection period may be synchronized with the ink landing period (recording period) for each pixel, or multiple ink ejection periods may be set within a recording period. For example, an ejection signal or non-ejection signal is output at least once in the recording period for each pixel depending on whether or not ink is ejected to the pixel, and when the amount of ink ejected is large, the ejection signal may be output two or more times.

[0023] The storage unit 44 stores various data. The various data include image data acquired from the outside as a print job, data processed therefrom, various setting data related to image recording operations, etc. The various setting data may include initial setting data stored in the ROM 402 and update data for programs, etc.

[0024] The communication unit 51 controls communication between the inkjet recording device 1 and an external device. Print jobs and various control signals transmitted from the external device are received via the communication unit 51 and sent to the control unit 40. The control unit 40 performs various processes for the image recording operation according to the acquired print job. Note that image data analysis, rasterization, and other processes may be performed by an image processing CPU and memory provided separately from the control unit 40.

[0025] The display unit 52 performs various displays on the display screen based on a control signal input from the control unit 40. The display unit 52 may have, for example, a liquid crystal display screen and may be capable of displaying characters and images of menus, statuses, etc. The display unit 52 may also have other devices such as LED lamps.

[0026] The operation reception unit 53 has, for example, a touch panel positioned over the liquid crystal screen of the display unit 52, and receives input operations from the outside, such as from a user, and outputs the operations as input signals to the control unit 40. The control unit 40 outputs a display control signal to display statuses, menus, and the like on the liquid crystal screen. The operation reception unit 53 may also have a numeric keypad, push button switches, and / or rocker switches, etc.

[0027] The liquid feed pump 54 performs a liquid feed operation to feed ink from an ink tank (not shown) to the inkjet head 420. The operation of this liquid feed pump 54 supplies ink in an amount greater than the amount of ink ejected from the nozzle N, and ink that is not ejected is returned from the inkjet head 420 to the ink tank.

[0028] 2 is a cross-sectional view illustrating the ink flow path structure in the vicinity of the nozzle N of the inkjet head 420. This cross-sectional view includes one nozzle N. A plurality of nozzles N of the inkjet head 420 are arranged at least in a direction perpendicular to this cross section.

[0029] In the inkjet head 420, a nozzle substrate 110, a flow path substrate 120, a pressure chamber substrate 130, etc. are laminated. The nozzle substrate 110 is provided with a nozzle N.

[0030] The flow path substrate 120 has an ink flow path 121 that communicates with the nozzle N, and individual recovery flow paths 122 and 123 (discharge flow paths). The individual recovery flow paths 122 and 123 branch off from the ink flow path 121 at the bottom of the flow path substrate 120 in opposite directions to each other.

[0031] The pressure chamber substrate 130 has an ink supply path 131, common recovery paths 132 and 133, an air chamber 134, etc. The ink supply path 131 communicates with the ink flow path 121, and together with the ink flow path 121, constitutes an individual ink supply path (supply path) to each nozzle N.

[0032] 2, and ink flowing out from the individual recovery channels 122, 123 related to the multiple nozzles N join together and flow, and is sent out of the inkjet head 420. That is, in this inkjet head 420, the ink flows through the individual supply channels to just above the nozzle N, a portion of the ink is ejected from the nozzle N, and the remainder is discharged from the individual supply channels through the individual recovery channels 122, 123 to the common recovery channels 132, 133. The discharged ink may be returned to an ink tank and sent again to the inkjet head 420. The individual supply channels and the individual recovery channels 122, 123 form a part of an ink circulation channel.

[0033] The pressure chamber substrate 130 is mainly made of a piezoelectric member. An electrode film (not shown) is provided on the wall surface of this piezoelectric member along the ink supply path 131, and the wall surface is deformed by applying a predetermined driving voltage via wiring connected to the electrode film. In response to this deformation, pressure fluctuations (vibrations) occur in the ink inside the ink supply path 131.

[0034] The air chamber 134 is a space for allowing deformation of the piezoelectric member, and also serves as a space for preventing the deformation from affecting each other between the ink supply paths 131 associated with other nozzles N aligned in the direction along the cross section.

[0035] Next, the driving operation of the inkjet recording apparatus 1 of this embodiment will be described. 3A and 3B are diagrams showing examples of driving signals outputted by the inkjet recording apparatus 1 of this embodiment.

[0036] In the inkjet recording device 1, as a plurality of drive signals, voltage signals of a trapezoidal wave (trapezoidal voltage change shape) are output, in which the drive voltage rises, is maintained, and then returns (falls) to the original voltage. The plurality of drive signals include at least an ejection signal that generates a pressure vibration (fluctuation) in the ink to eject ink, and a non-ejection signal that changes the position of the liquid surface inside the nozzle N without ejecting ink (performing non-ejection drive). As shown in FIG. 3A, the ejection signal has a trapezoidal wave shape including a maintenance period Ta1 of a first drive voltage Va1 changed from a reference voltage Vs, and a voltage rise period Tu1 and fall period Td1 that are shorter than the maintenance period Ta1 and have the same length as each other. The maintenance period Ta1 is about an acoustic resonance length (AL), which is half the resonance period related to the vibration of the ink in the individual supply flow path, but is not limited to being strictly 1AL, and may be appropriately adjusted. Here, as the voltage rises, the piezoelectric member deforms so that the individual supply flow paths expand, lowering the ink pressure, and as the voltage falls, the expansion of the individual supply flow paths is eliminated (they contract), increasing the ink pressure (pull-fire operation). That is to say, in the ejection signal, as the individual supply flow paths are suddenly deformed by the rise and fall of the applied voltage, not only does the ink surface (meniscus) in the nozzle N move due to a static pressure change, but vibration energy (kinetic energy) is also generated in the ink. As the applied voltage falls in line with the phase in which the vibrations generated by the rise of the applied voltage are outward (expanding), the ink further acquires momentum outward from the nozzle N, and the ink surface not only returns to its original position before the rise, but also protrudes from the nozzle opening, with a portion separating from the ink in the nozzle N and being ejected.

[0037] Note that, although the case is shown here where the first driving voltage Va1 is greater than the reference voltage Vs, the first driving voltage Va1 may be smaller than the reference voltage Vs (including the case where the voltage is a negative voltage) depending on the first driving voltage Va1 and the direction of the shape change of the piezoelectric element 421. In either case, a change in which the applied voltage deviates from the reference voltage Vs is defined as a rising edge, and a change in which the applied voltage returns to the reference voltage Vs is defined as a falling edge.

[0038] As shown in FIG. 3B, the non-ejection signal has a voltage difference between the reference voltage Vs and the second driving voltage Va2, i.e., a voltage amplitude, which is smaller than the voltage difference (voltage amplitude) between the reference voltage Vs and the first driving voltage Va1 in the ejection signal. Also, the fall time Td2 is longer than the rise time Tu2. Here, the sustain time Ta2 is set to 1AL, which is the same as the sustain time Ta1. Also, the rise time Tu2 is, for example, about 1 / 4AL, which is the same as the rise time Tu1 of the ejection signal, and the fall time Td2 is about 1AL, which is the same as the sustain time Ta2.

[0039] In this way, in the signal waveform of the non-ejection signal, the ink in the individual supply flow path is depressurized by the rise time Tu2, which is shorter than AL, and the ink surface (meniscus) in the nozzle N is drawn inward (toward the back) from the nozzle opening surface, and vibration energy is obtained due to the sudden pressure reduction. On the other hand, when the applied voltage is returned to the reference voltage Vs with the fall time Td2, which is significantly longer than the rise time Tu2, the ink pressure increases, but the vibration energy obtained by the pressure from the wall surface is small. In this case, the meniscus does not return to the position before the applied voltage rises (original position; here, for example, the average liquid surface position from the start of the ink ejection cycle to the start of the rise) at the same time as the end of the fall of the applied voltage. The position of the meniscus (here, the average liquid surface position for a predetermined time from the end of the fall) is further back (farther from the nozzle opening surface) than the original position. This state is not the final equilibrium state, and the meniscus slowly moves to the original position thereafter due to capillary action in the narrow nozzle N. This movement is sufficiently gentle compared to the period of the ink vibration occurring in response to the rise time Tu2 (a vibration component of about AL / 2 determined by the shape of the individual supply flow path, etc.).

[0040] As a result, immediately after the application of the non-ejection signal (after the driving signal has finished falling), most of the ink in the nozzle N has returned from the nozzle N into the ink flow path 121, and is collected by riding on the flow to the individual recovery flow paths 122 and 123. Thereafter, the meniscus in the nozzle N gradually moves away from the ink flow path 121 and returns, so that the meniscus does not remain near the flow of circulating ink for a long time. Therefore, the possibility that the meniscus will be disturbed and destroyed by the influence of this flow is reduced.

[0041] 4A and 4B are the same cross-sectional view as that shown in FIG. 4A, when the reference voltage Vs is applied, the position of the meniscus M is located closer to the opening side of the nozzle N. Therefore, the ink in the nozzle N is out of the ink circulation flow path indicated by the arrow, and remains there while the ink is not ejected.

[0042] As shown in FIG. 4B, when the second driving voltage Va2 is applied, the meniscus M is drawn from the opening of the nozzle N to the back due to the expansion and deformation of the ink supply path 131. At this time, most of the ink in the nozzle N is drawn back into the ink flow path 121. In this state, the meniscus M is very close to the circulating flow of ink, and the meniscus M is easily disturbed and destroyed by even a small disturbance in the flow. In order to replace the ink in the nozzle N, it is necessary that the ink that was originally in the nozzle N does not return when the meniscus M returns to its original position and the ink in the individual supply flow path again enters the nozzle N, so the state shown in FIG. 4B only needs to continue for the minimum time during which the ink drawn back from the nozzle N rides on the ink flow from the individual supply flow path to the individual recovery flow paths 122 and 123 and moves from the entrance of the nozzle N to the individual recovery flow paths 122 and 123.

[0043] In this way, by using an appropriate non-ejection signal, it is possible to appropriately control the meniscus position immediately after the non-ejection signal is applied. The conditions for obtaining such a meniscus position are determined according to the magnitudes of the rise time Tu2, the sustain time Ta2, and the fall time Td2 and their relationship, as described above. Here, a case where the sustain time Ta2 is fixed to 1AL will be described. Note that the actually required retraction length depends on the length of the nozzle N, etc., so the voltage amplitude according to the retraction length may be appropriately adjusted.

[0044] FIG. 5 is a chart showing an example of the retreat state of the ink level position according to the relationship between the rise time Tu2 and the fall time Td2.

[0045] From this result, when the fall time Td2 is short, particularly when it is 0.5AL or less, the liquid surface (meniscus) does not retreat after the application of the non-ejection signal (x). That is, vibration energy is given to the ink at the time of the fall, and the meniscus is not maintained at a position farther from the nozzle opening than the original position, which is the equilibrium position of the meniscus according to the size of the individual supply flow path after the fall. Also, even if the fall time Td2 is 0.7AL or more, if the rise time Tu2 is long, the meniscus is not likely to retreat. When the rise time Tu2 is 0.5AL or more, the meniscus does not retreat sufficiently to the boundary between the nozzle N and the ink flow path 121 due to the relationship with the fall time Td2. That is, when the rise time Tu2 is longer than the fall time Td2 by a certain amount, the vibration energy related to the pressure reduction of the ink is not obtained sufficiently, so that the force to draw the ink deep into the nozzle N does not remain sufficiently after the application of the non-ejection signal. Here, the meniscus can be retracted when the fall time Td2 is at least 0.6 AL (0.3 times the resonance period) longer than the rise time Tu2 (△). Also, when the rise time Tu2 is 0.4 AL or less (0.2 times the resonance period or less) and the fall time Td is 1.1 AL or more (i.e., 0.7 AL (0.35 times the resonance period) or more longer than the rise time Tu2), the meniscus retreats and the ink in the nozzle N flows out and circulates sufficiently effectively (◯).

[0046] 6 is a graph showing the degree of effect on maintaining normal ink ejection operation by the ink in the nozzle N with respect to the ink circulation flow speed. The ink flow speed here is the speed of the downward flow (toward the nozzle N) above the nozzle N in the ink flow path 121 when ink is not being ejected.

[0047] If the ink in the nozzle N remains without being properly replaced, problems with ink ejection will occur due to separation of the ink components and an increase in viscosity caused by evaporation of water. Such problems mainly include changes (reductions) in the ink ejection speed and ejection volume, and there may also be abnormalities in the ejection direction. Compared to when the ink flow speed is zero, if the ink flow speed is above a certain level, the above-mentioned ejection defects are suppressed, and it has been shown that the degree of this effect (progression of ejection defects) is sufficient regardless of the circulation speed as long as the flow speed is above the lower limit (here, about 3 mm / sec).

[0048] As described above, the driving method of the inkjet head 420 of this embodiment is a driving control method for the inkjet head 420 including the nozzle N for ejecting ink, the ink flow path 121 and the ink supply path 131 which are individual supply paths for supplying ink to the nozzle N, the individual recovery paths 122 and 123 for discharging the ink from the individual supply paths, and the piezoelectric element 421 which performs a deformation operation to cause a pressure fluctuation in the ink in the individual supply paths in response to an applied driving signal. This driving control method includes a non-ejection driving step in which the head driving unit 422 of the driving unit performs a non-ejection drive for applying a driving signal to the piezoelectric element 421 which does not eject ink from the nozzle N. In the signal waveform of the driving signal for the non-ejection drive, within each recording cycle, the average liquid level position of the ink in the nozzle N after the driving signal is applied is farther from the opening surface of the nozzle than the average liquid level position of the ink in the nozzle N before the driving signal is applied. In other words, by outputting a drive signal with a waveform that not only vibrates the meniscus but also temporarily retracts the meniscus at the end, the ink that flows out of the nozzle N during the temporary retraction can be recovered and circulated, and this state is not allowed to continue for long and is allowed to return to normal, easily reducing the possibility of the meniscus being disturbed or destroyed without the need for complex control.

[0049] In addition, the signal waveform of the drive signal for non-ejection drive includes a voltage rising portion, a portion that is maintained at the voltage after the rising portion, and a falling portion that returns from the voltage after the rising portion to the initial voltage, and the ink pressure is reduced by the rising portion of the voltage, and the falling portion has a longer time than the rising portion. This reduces the supply of kinetic energy to the ink that returns the meniscus to its original position compared to the retraction of the meniscus, thereby obtaining a drive waveform that is effective in recovering and replacing ink near the nozzle N.

[0050] Furthermore, the fall time Td2 is longer than the rise time Tu2 by at least 0.3 times the resonance period (2×AL) associated with the pressure vibration of the ink inside the nozzle N. As described above, by making the fall time Td2 appropriately longer than the rise time Tu2, it is possible to appropriately reduce the supply of kinetic energy for the ink meniscus to return to its original position, and it is possible to appropriately retract the meniscus close to the ink flow.

[0051] In addition, the fall time Td2 is longer than the rise time Tu2 by 0.7 times AL or more, and the rise time Tu2 is 0.4 times AL or less. By shortening the rise time Tu2 within an appropriate range and making the fall time Td2 longer than this, a more appropriate temporary retreat position of the meniscus can be obtained.

[0052] Furthermore, the inkjet head 420 ejects ceramic ink or white ink. These inks are prone to component separation and ejection abnormalities, so by making it possible to easily and appropriately circulate the ink in the nozzles N without destroying the meniscus as described above, it is possible to continue ejecting the ink more stably and normally.

[0053] The non-ejection driving step is performed in each recording cycle of each pixel that does not eject ink when recording an image. That is, while ink is not being ejected, the ink in the nozzles N is continuously replaced, and damage to the meniscus is sufficiently reduced, so that even during normal recording operation, the ink in the nozzles N with low ejection frequency can be kept in an appropriate state, and normal ink ejection can be performed immediately at the required timing.

[0054] In addition, the inkjet recording device 1 of this embodiment is equipped with an inkjet head 420 having a nozzle N that ejects ink, an ink flow path 121 and an ink supply path 131 as supply flow paths that supply ink to the nozzle N, individual recovery flow paths 122, 123 from which ink in the individual supply flow paths is discharged, and a piezoelectric element 421 that performs a deformation operation to cause pressure fluctuations in the ink in the individual supply flow path in response to an applied drive signal, and a control unit 40 (CPU 401). The control unit 40 (CPU 401) controls the head drive unit 422 to perform a non-ejection drive in which a drive signal that does not cause ink to be ejected from the nozzle N is applied to the piezoelectric element 421, and in the signal waveform of the drive signal related to the non-ejection drive, the average ink liquid level position after the drive signal is applied is farther from the opening surface of the nozzle N in each ink ejection period than the average ink liquid level position in the nozzle N before the drive signal is applied. This non-ejection drive not only simply vibrates the meniscus, but also outputs a drive signal with a waveform that temporarily retracts the meniscus at the end, allowing the ink to be returned from the nozzle N to the circulation flow path. The ink that flows out of the nozzle N is discharged, collected, and circulated by the circulating flow of ink, so that the ink in the nozzle N can be maintained in an appropriate state by the ink that flows into the nozzle N instead. On the other hand, because the meniscus does not remain in a retracted state for long and returns naturally, the possibility of the meniscus being disturbed or destroyed can be easily reduced without the need for complex control.

[0055] The present invention is not limited to the above-described embodiment, but may be modified in various ways. For example, in the above embodiment, the non-ejection drive is performed in every recording cycle of each pixel, but the meniscus does not necessarily have to be retracted as described above in every non-ink ejection recording cycle. The meniscus may be retracted only at a predetermined frequency or cycle.

[0056] Furthermore, in the above embodiment, the ceramic ink and the white ink are described as examples, but the present invention is not limited to these. Other types of ink may also be circulated in the nozzles N in the same manner.

[0057] In the above embodiment, the driving waveform is described as being a trapezoidal waveform, but strictly speaking, it is not limited to this as long as it is a trapezoidal waveform close to this. For example, the rise / fall of the driving waveform does not need to be a perfect straight line, and may be accompanied by a slight curved change, or the slope may change slightly along the way. Also, a well-known waveform that is smaller than the trapezoidal waveform related to stabilization of the vibration of the meniscus may be added. In addition, the specific configurations, contents and procedures of the processing operations, etc. shown in the above embodiments can be modified as appropriate without departing from the spirit of the present invention. The scope of the present invention includes the scope of the invention described in the claims and its equivalents. [Industrial Applicability]

[0058] The present invention can be utilized in an inkjet head drive control method and an inkjet recording apparatus. [Explanation of symbols]

[0059] 1 Inkjet recording device 40 Control section 401 CPU 402 ROM 403 RAM 41 Conveyor drive unit 42 Recording operation section 420 Inkjet Head 421 Piezoelectric element 422 Head drive unit 43 Drive waveform signal generator 44 Storage section 49 Bus 51 Communications Department 52 Display section 53 Operation reception section 54 Liquid delivery pump 110 Nozzle board 120 Flow Channel Substrate 121 Ink flow path 122, 123 Separate collection channels 130 Pressure chamber substrate 131 Ink supply path 132, 133 Common recovery flow path 134 Air chamber M Meniscus N Nozzle

Claims

1. A drive control method for an inkjet head including a nozzle that ejects ink, a supply flow path that supplies ink to the nozzle, a discharge flow path that discharges the ink in the supply flow path, and a drive element that operates to generate pressure fluctuations in the ink in the supply flow path in response to an applied drive signal, comprising: a non-ejection driving step of performing non-ejection driving by applying the drive signal to the drive element so as not to eject ink from the nozzle; The signal waveform of the drive signal related to the non-ejection drive is a voltage rising portion, a portion maintained at the voltage after the rising portion, and a falling portion returning from the voltage after the rising portion to the initial voltage are included in a continuous manner; The voltage rise reduces the pressure of the ink; The fall time is longer than the rise time, in the signal waveform, an average liquid level position of the ink in the nozzle after the drive signal is applied is farther from an opening surface of the nozzle than an average liquid level position of the ink in the nozzle before the drive signal is applied; A method for controlling the drive of an inkjet head.

2. 2. The method for controlling an ink jet head according to claim 1, wherein the fall time is longer than the rise time by at least 0.3 times a resonance period associated with pressure vibration of the ink in the nozzle.

3. 3. The method for controlling an ink jet head according to claim 2, wherein the fall time is longer than the rise time by 0.35 times the resonance period, and the rise time is not longer than 0.2 times the resonance period.

4. 4. The inkjet head drive control method according to claim 1, wherein the inkjet head ejects ceramic ink or white ink.

5. 5. The inkjet head drive control method according to claim 1, wherein the non-ejection driving step is performed in each recording cycle of each pixel for which ink is not ejected when recording an image.

6. an inkjet head including a nozzle for ejecting ink, a supply flow path for supplying ink to the nozzle, a discharge flow path for discharging the ink in the supply flow path, and a drive element for performing an operation to generate a pressure fluctuation in the ink in the supply flow path in response to an applied drive signal; A control unit; Equipped with the control unit performs non-ejection driving by applying the drive signal to the drive element so as not to eject ink from the nozzle; The signal waveform of the drive signal related to the non-ejection drive is a voltage rising portion, a portion maintained at the voltage after the rising portion, and a falling portion returning from the voltage after the rising portion to the initial voltage are included in a continuous manner; The voltage rise reduces the pressure of the ink; The fall time is longer than the rise time, in the signal waveform, an average liquid level position of the ink in the nozzle after the drive signal is applied is farther from an opening surface of the nozzle than an average liquid level position of the ink in the nozzle before the drive signal is applied; Inkjet recording device.

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