JP2019098614A - Liquid ejection device - Google Patents

Abstract

To independently carry out liquid circulation and vibration of a liquid meniscus formed in a nozzle.SOLUTION: An individual channel comprises: a nozzle; a pressure chamber; a descender channel for connecting the nozzle and the pressure chamber; a diaphragm channel for connecting the pressure chamber and a manifold; and a circulation channel for connecting the descender channel and the manifold channel. To vibrate an ink meniscus formed in the nozzle, a piezoelectric actuator that applies pressure to ink in the pressure channel is driven at a first resonance frequency F1 that resonates the pressure chamber and the piezoelectric actuator. To circulate ink between the individual channel and the manifold channel, the piezoelectric actuator is driven at a second resonance frequency F2 that resonates the descender channel.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a liquid ejection apparatus that ejects liquid from a nozzle.

  In the recording head described in Patent Document 1, when the piezoelectric element is driven, the ink in the pressure generation chamber is discharged from the nozzle, and at the same time, a part of the ink is returned to the reservoir via the circulation passage. That is, ink can circulate between the reservoir and the pressure generation chamber.

JP 2012-71485 A

  Therefore, for example, when sedimentation occurs in the ink, the circulation of the ink can eliminate the sedimentation. Further, when the piezoelectric element is driven to such an extent that the ink is not ejected, the meniscus of the ink vibrates at the nozzle. Therefore, when the thickening of the ink is occurring, the thickening can also be canceled by the vibration.

  However, in the recording head of Patent Document 1, when the piezoelectric element is driven, circulation of the ink and vibration of the meniscus occur simultaneously. Therefore, for example, when the ink is circulated to eliminate the settling of the ink, the meniscus of the ink formed in the nozzle continues to vibrate. At this time, the elimination of sedimentation often requires more time than the elimination of thickening. While the thickened ink is diluted with fresh ink on the ink side across the meniscus, volatile components of the ink are released from the meniscus on the air side. As a result, thickening of the ink progresses throughout the entire print head, and there is a possibility that the ejection characteristics may change.

  An object of the present invention is to provide a liquid discharge apparatus capable of independently performing circulation of liquid and oscillation of a meniscus formed on a nozzle.

  A liquid discharge apparatus according to a first aspect of the present invention comprises a plurality of individual flow paths and a common flow path to which the plurality of individual flow paths are connected, each individual flow path comprising a nozzle, a pressure chamber, and A descender channel connecting the nozzle and the pressure chamber, a throttle channel connecting the pressure chamber and the common channel, and a circulation channel connecting the descender channel and the common channel; An actuator for applying pressure to the liquid in the pressure chamber, a drive unit for driving the actuator, and a control unit for controlling the drive unit, the control unit being formed on the nozzle When vibrating the meniscus of the liquid, the driving device is driven at a first resonance frequency at which the pressure chamber to which the actuator is added in the individual flow paths resonates, and the pressure chamber and the circulation flow Through when circulating the liquid to the drive device, serial drives the actuator at a second resonant frequency, wherein the descender passage resonates among individual channels.

  In the present invention, by selectively driving the actuator at either the first resonance frequency or the second resonance frequency, the oscillation of the meniscus of the liquid formed in the nozzle and the circulation of the liquid are performed independently. Can. By selectively using the resonance frequency, two effects of thickening elimination in the vicinity of the nozzle and settling elimination in the flow path can be obtained in an effective state.

  A liquid discharge apparatus according to a second aspect of the present invention is the liquid discharge apparatus according to the first aspect, wherein the sum of the compliance of the pressure chamber and the compliance of the actuator is the compliance of the throttling channel, and the descender flow. The first resonance frequency is a resonance frequency corresponding to the sum of the compliance of the pressure chamber and the compliance of the actuator, which is larger than the compliance of the path and smaller than the compliance of the meniscus of the liquid in the nozzle.

  If the sum of the compliance of the pressure chamber and the compliance of the piezoelectric actuator is greater than the compliance of the throttling channel, the compliance of the descender channel and less than the compliance of the meniscus of the liquid in the nozzle, The resonance frequency can be set according to the sum of the compliance of the pressure chamber and the compliance of the piezoelectric actuator.

  A liquid discharge apparatus according to a third aspect of the invention is the liquid discharge apparatus according to the first or second aspect, wherein the compliance of the descender channel is larger than the compliance of the circulation channel, and the second resonance frequency is And the frequency according to the compliance of the descender channel.

  In the case where the compliance of the descender channel is larger than the compliance of the circulation channel, the second resonance frequency can be set as the resonance frequency corresponding to the compliance of the descender channel.

  A liquid discharge apparatus according to a fourth invention is the liquid discharge apparatus according to any one of the first to third inventions, wherein the compliance of the descender channel is the sum of the compliance of the pressure chamber and the compliance of the actuator. Also, the second resonant frequency is higher than the first resonant frequency.

  In general, the lower the compliance, the higher the resonant frequency. In the present invention, since the compliance of the descender channel is smaller than the sum of the compliance of the pressure chamber and the compliance of the actuator, the second resonance frequency can be made higher than the first resonance frequency. In addition, driving at the second resonance frequency, which has a high frequency, can accelerate the flow of the liquid when circulating the liquid, and can efficiently eliminate sedimentation of the liquid (when the second resonance frequency is low, the liquid The flow of the liquid when it is circulated may be delayed, and the sedimentation of the liquid may not be eliminated).

  A liquid discharge apparatus according to a fifth aspect of the invention is the liquid discharge apparatus according to any of the first to fourth aspects, wherein the control device is configured to drive the meniscus when vibrating the liquid meniscus formed in the nozzle. The device is driven at the first resonant frequency after driving the actuator at the second resonant frequency.

  When the actuator is driven at the second resonance frequency, the liquid circulates, but the circulation continues for a while even if the drive is stopped. Therefore, in the present invention, the actuator is driven at the first resonant frequency after being driven at the second resonant frequency. In the nozzle, the thickened liquid is agitated by the vibration of the meniscus. Since the circulation continues even after the driving is stopped, the stirred liquid is diffused on the liquid flow by the circulation. Thereby, the liquid in the nozzle can quickly eliminate the thickening.

  A liquid discharge apparatus according to a sixth aspect of the invention is the liquid discharge apparatus according to the fifth aspect, wherein the control device causes the drive device to generate the second meniscus when vibrating the liquid meniscus formed in the nozzle. The actuator is driven at the first resonance frequency while the circulation after driving at the resonance frequency is sustained.

  In the present invention, while the circulation after driving the actuator at the second resonant frequency is continued, the actuator is driven at the first resonant frequency to vibrate the meniscus, whereby the liquid stirred by the meniscus oscillation is generated. , It can be diffused on the flow of liquid by circulation.

  A liquid discharge apparatus according to a seventh invention is the liquid discharge apparatus according to the fifth or sixth invention, wherein the control device causes the drive device to vibrate the meniscus of the liquid formed in the nozzle, Driving of the actuator at the second resonant frequency and driving of the actuator at the first resonant frequency are alternately and repeatedly performed.

  In the present invention, when vibrating the meniscus of the liquid formed in the nozzle, the liquid in the nozzle is thickened by repeating the driving at the first resonance frequency following the driving of the actuator at the second resonance frequency. It can be resolved quickly.

  A liquid discharge apparatus according to an eighth invention is the liquid discharge apparatus according to any one of the first to seventh inventions, wherein the control device operates the drive device when vibrating the meniscus of the liquid formed in the nozzle. When driving the actuator at the first resonance frequency using a rectangular wave and circulating the liquid in the pressure chamber through the circulation flow path, the second resonance frequency using a trapezoidal wave in the driving device Drive the actuator.

  When vibrating the meniscus of the liquid formed on the nozzle, a rectangular wave is used to drive the actuator at the first resonance frequency. When circulating the liquid, the trapezoidal wave is used to drive the actuator at the second resonant frequency. The trapezoidal wave of the second resonant frequency has a smaller frequency component of sine waves other than the second resonant frequency as compared with the rectangular wave of the second resonant frequency, and therefore the meniscus of the liquid formed in the nozzle Unnecessary vibration can be prevented.

  A liquid discharge apparatus according to a ninth aspect of the present invention is the liquid discharge apparatus according to any of the first to eighth aspects, wherein the circulation flow path has a larger inertance than the nozzle.

  In the present invention, since the inertance of the circulation channel is larger than the inertance of the nozzle, when the actuator is driven to discharge the liquid from the nozzle, the pressure generated in the pressure chamber can be efficiently transmitted to the nozzle .

  A liquid discharge apparatus according to a tenth aspect of the present invention is the liquid discharge apparatus according to any of the first to ninth aspects, wherein the flow path for circulation is a value obtained by dividing the flow path resistance by the inertance than the nozzle. Some damping factors are small.

  When the liquid is continuously discharged from the nozzle, after the discharge of the liquid, the vibration of the meniscus of the liquid formed on the nozzle is sufficiently damped to discharge the next liquid in order to stabilize the discharge characteristics. Is preferred. In the present invention, since the damping coefficient of the nozzle is large, the vibration of the meniscus is rapidly damped when the liquid is discharged from the nozzle. Thereby, the time interval which discharges a liquid from a nozzle can be shortened. In addition, since the damping coefficient of the circulation channel is small, when the liquid is circulated, the pressure of the liquid in the circulation channel is unlikely to be attenuated, and the circulation of the liquid can be efficiently maintained.

  In the present invention, the oscillation of the meniscus of the liquid formed in the nozzle and the circulation of the liquid can be performed independently.

FIG. 1 is a schematic configuration diagram of a printer according to an embodiment of the present invention. It is a top view of the ink jet head of FIG. (A) is an enlarged view of a region surrounded by an alternate long and short dash line shown in FIG. 2, (b) is a cross-sectional view taken along the line B-B of (a), (c) is an enlarged view of a nozzle portion of (b) FIG. FIG. 2 is a block diagram showing the electrical configuration of the printer of the first embodiment. It is an equivalent circuit of an individual flow path and a piezoelectric actuator. It is a figure which shows the relationship between the drive frequency of a piezoelectric actuator calculated using the equivalent circuit, and the gain in the meniscus of a nozzle, and the flow path for circulation. (A) is a figure showing a drive signal given to an individual electrode when discharging ink from a nozzle, (b) is a signal showing a drive signal given to an individual electrode when vibrating a meniscus, (c 2.) is a diagram showing drive signals applied to the individual electrodes when the ink is circulated. FIG. 17 is a flowchart showing a flow of processing for eliminating thickening of the ink in the nozzle in Modification Example 1. FIG. FIG. 18 is a flowchart showing a flow of processing for eliminating thickening of the ink in the nozzle in the modification 2; FIG.

  Hereinafter, preferred embodiments of the present invention will be described.

  As shown in FIG. 1, the printer 1 according to the present embodiment (the “liquid discharge device” of the present invention) includes a carriage 2, an inkjet head 3, a platen 4, and transport rollers 5 and 6. .

  The carriage 2 is supported by two guide rails 7 and 8 extending in the scanning direction. The carriage 2 is connected to a carriage motor 56 (see FIG. 4) via a gear or the like (not shown). When the carriage motor 56 is driven, the carriage 2 moves in the scanning direction along the guide rails 7 and 8. In the following, as shown in FIG. 1, the description will be made by defining the right and left sides in the scanning direction.

  The inkjet head 3 is mounted on the carriage 2 and moves in the scanning direction together with the carriage 2. The inkjet head 3 is a so-called serial head. The lower surface of the inkjet head 3 is a discharge surface 3 a, and a plurality of nozzles 15 are formed. The plurality of nozzles 15 form a nozzle row 9 side by side in the transport direction orthogonal to the scanning direction. Four nozzle rows 9 are arranged in the scanning direction on the ejection surface 3a. The nozzle rows 9 correspond to black, yellow, cyan, and magenta pigment inks from the rightmost side to the left in the scanning direction.

  The platen 4 faces the ejection surface 3 a and supports the entire recording sheet P in the scanning direction from below. The transport rollers 5 and 6 are both roller pairs, and are disposed so as to sandwich the inkjet head 3 and the platen 4 in the transport direction. The conveyance rollers 5 and 6 are connected to a conveyance motor 57 (see FIG. 4) via a gear or the like (not shown). When the conveyance motor 57 is driven, the conveyance rollers 5 and 6 rotate to convey the recording sheet P in the conveyance direction.

<Inkjet head>
Next, the inkjet head 3 will be described. As shown in FIGS. 3A and 3B, the ink jet head 3 has a pressure applied to the ink in the pressure chamber 10 and the flow path unit 21 in which the ink flow path including the nozzle 15, the pressure chamber 10, etc. is formed. And a piezoelectric actuator 22 to be applied. FIG. 3A is an enlarged view of a region surrounded by an alternate long and short dash line shown in FIG.

  The flow path unit 21 is a stack of six plates 31 to 36. A plurality of individual channels 20 and four manifold channels 11 are formed inside.

  The plurality of individual flow channels 20 are arranged in the transport direction to constitute an individual flow channel array 19. Here, four individual flow path rows 19 are arranged along the scanning direction. Each individual flow passage 20 has a circulation flow passage 16 in addition to the nozzle 15, the pressure chamber 10, the throttle flow passage 12, and the descender flow passage 14.

  The nozzle 15 is formed through the plate 36. The lower surface of the plate 36 is a discharge surface 3 a of the ink jet head 3 in which all the nozzles are opened. The pressure chamber 10 is formed through the plate 31. The pressure chamber 10 has a substantially rectangular planar shape whose longitudinal direction is the scanning direction, and vertically overlaps the nozzle 15 at the right end portion in the scanning direction.

  The throttle channel 12 is formed across the two plates 32 and 33. In the scanning direction, the throttle channel 12 extends along the upper surface of the plate 33, and one end is connected to the left end of the pressure chamber 10. The other end is connected to a manifold channel 11 (described later). The descender channel 14 is formed through the plates 32-35. The descender channel 14 connects the right end portion of the pressure chamber 10 in the scanning direction to the nozzle 15 vertically. The circulation channel 16 is formed in the plate 35 and extends in the scanning direction along its lower surface. The circulation channel 16 connects the lower end of the descender channel 14 to the manifold channel 11 (described later).

  Four manifold channels 11 are formed through the two plates 34, 35. One manifold channel 11 corresponds to one individual channel row 19. Each extends along the individual flow path row 19 and is aligned in the scanning direction. In the scanning direction, each manifold channel 11 is located on the left side of the corresponding nozzle 15 and the circulation channel 16 and vertically overlaps with the left half of the pressure chamber 10 and the throttle channel 12. At this time, the manifold channel 11 is connected to the left end of the corresponding throttle channel 12 at the left end, and the right end is connected to the left end of the circulation channel 16. Further, in each manifold channel 11, the upstream end in the transport direction extends vertically through the four plates 31 to 35. The opening at the upper end is the ink supply port 11a.

  An ink cartridge (not shown) is connected to the ink supply port 11a via an external pipe (for example, a tube or the like). Thus, the ink stored in the ink cartridge is supplied to the manifold channel 11 from the ink supply port 11 a. The four ink supply ports 11a are arranged in the scanning direction to constitute one supply port array.

  The piezoelectric actuator 22 has two piezoelectric layers 41 and 42, one common electrode 43, and a plurality of individual electrodes 44, as shown in FIG. The piezoelectric layers 41 and 42 are piezoelectric materials whose main component is lead zirconate titanate. The piezoelectric layer 41 is fixed to the upper surface of the flow path unit 21 (plate 31), and seals the opening of the pressure chamber 10. That is, the piezoelectric layer 41 constitutes the side wall of the plurality of pressure chambers 10.

  The common electrode 43 is sandwiched between the two piezoelectric layers 41 and 42. The individual electrodes 44 are formed on the upper surface of the piezoelectric layer 42 and are arranged in a 1: 1 positional relationship with the pressure chamber 10.

  The control device 50 controls the driver IC 58 ("drive device" in the present invention, see Fig. 4) based on the print command. In the standby state before the start of printing, both electrodes 43 and 44 have a ground potential.

  At the time of ink ejection, a drive signal is applied between the two electrodes 43 and 44 from the driver IC 58. At this time, the individual electrode 44 selectively takes one of the ground potential GND and the drive potential Va. The common electrode 43 is always at the ground potential GND. The piezoelectric layer 42 between the two electrodes 43 and 44 is a polarized active portion, and contracts in the surface direction when an electric field is applied in the thickness direction (polarization direction). The piezoelectric layer 41 does not displace spontaneously.

  Therefore, when the individual electrode 44 takes the driving potential Va (when an electric field is applied), the unit actuator (portion overlapping the pressure chamber 10 of the piezoelectric layers 41 and 42 including the electrode) is deformed to be convex toward the pressure chamber 10 side. Do. The volume of the pressure chamber 10 decreases rapidly, and the ink inside is pressurized. The pressure wave reaches the nozzle 15 with vibration of each part of the flow path. The ink is ejected from the nozzle 15. Subsequently, the individual electrode 44 takes a ground potential. Thereby, the unit actuator returns to the state before deformation. Based on the image data, this convex deformation and its recovery are repeated to perform printing.

<Control device>
Next, the control device 50 that controls the printer 1 will be described. As shown in FIG. 4, the control device 50 includes a central processing unit (CPU) 51, a read only memory (ROM) 52, a random access memory (RAM) 53, a flash memory 54, and an application specified integrated circuit (ASIC) 55. And controls operations of the carriage motor 56, the conveyance motor 57, the driver IC 58, and the like.

  Although only one CPU 51 is illustrated in FIG. 4, the control device 50 may have one CPU 51, and the one CPU 51 may perform processing collectively, or a plurality of CPUs 51 are included. Alternatively, the plurality of CPUs 51 may share the processing. Further, although only one ASIC 55 is illustrated in FIG. 4, the control device 50 may include one ASIC 55, and the one ASIC 55 may perform processing collectively, or a plurality of ASICs 55 are included. The plurality of ASICs 55 may share processing.

<Equivalent Circuit of Individual Channel and Piezoelectric Actuator>
Next, the individual flow passage 20 and the piezoelectric actuator 22 will be described. These can be represented by an equivalent circuit 60 as shown in FIG. In the equivalent circuit 60, R _APA , R _DES , R _NOZ and R _CIR are the flow path resistances of the throttle flow path 12, the descender flow path 14, the nozzle 15 and the circulation flow path 16, respectively. Further, L _APA , L _DES , L _NOZ and L _CIR are the inertances of the throttle channel 12, the descender channel 14, the nozzle 15 and the circulation channel 16, respectively. C _APA , C _CAV , C _PZT , C _DES , C _CIR and C _NOZ respectively correspond to the throttle channel 12, the pressure chamber 10, the piezoelectric actuator 22, the descender channel 14, the circulation channel 16, and the nozzle 15. It is a compliance of the meniscus M (refer FIG.3 (c)) of the formed ink.

In addition, the flow path resistance of the pressure chamber 10 is negligibly small compared with R _APA , R _DES , R _NOZ and R _CIR . The inertances of the pressure chamber 10 and the piezoelectric actuator 22 are also negligibly small as compared with L _APA , L _DES , L _NOZ and L _CIR . Therefore, illustration of these is omitted in FIG.

Also, with regard to inertance, L _DES is greater than L _NOZ . For compliance, the sum of C _CAV and C _PZT [C _CAV + C _PZT ] is greater than C _APA and C _DES . Also, [C _CAV + C _PZT ] is smaller than C _NOZ . Furthermore, C _APA and C _CIR are sufficiently small compared to C _CAV , C _PZT and C _DES . Regarding the damping coefficient R / L, the damping coefficient R _CIR / L _CIR of the circulation flow path 16 is smaller than the damping coefficient R _NOZ / L _NOZ of the nozzle 15. The damping coefficient R / L represents the ease of damping of the applied vibration in a specific flow path portion.

  Here, using the equivalent circuit 60, the gain in the meniscus M of the nozzle 15 and the circulation flow path 16 was determined. The piezoelectric actuator 22 changed its drive frequency in the range of 10 kHz to 1 MHz. An example of the calculation result is shown in FIG. In this example, for the meniscus M, its frequency profile shows the highest gain around 100 kHz. The circulation channel 16 exhibits the highest gain near 750 kHz. The high frequency of the gain corresponds to the first resonance frequency of the pressure chamber 10 and the piezoelectric actuator 22 (the “first resonance frequency” of the present invention), and the latter corresponds to the first resonance frequency of the circulation channel 16 (the invention Corresponding to the “second resonant frequency” of

  The present embodiment is characterized in that when discharging ink, the piezoelectric actuator 22 is driven at a specific frequency. The control device 50 controls the driver IC 58 to apply a drive signal to the individual electrode 44 as shown in FIG. 7A. The drive signal is composed of a plurality of voltage pulses, the frequency of which is the first resonance frequency F1. The voltage pulse is a rectangular pulse, and the potential switches between the ground potential GND and the potential Va (≠ 0).

The first resonance frequency F1 is a frequency at which the pressure chamber 10 and the piezoelectric actuator 22 resonate. Here, the first resonance frequency F1 is a resonance frequency corresponding to [C _CAV + C _PZT ]. [ _C.sub.CAV + _C.sub.PZT ] has a large difference from _C.sub.APA and _C.sub.DES, and when driven at this frequency, the pressure chamber 10 and the piezoelectric actuator 22 will vibrate efficiently. At the same time, the ink is also efficiently ejected from the nozzles 15.

<Vibration of meniscus>
On the other hand, when the state in which the ink is not discharged continues, the ink is thickened in the nozzle 15. Thickening of the ink causes fluctuation of the ejection characteristics. Therefore, the meniscus M is vibrated to agitate the ink in the vicinity of the nozzle 15.

  Also when vibrating the meniscus M, the piezoelectric actuator 22 is driven at the first resonance frequency F1. The control device 50 controls the driver IC 58 to apply a drive signal to the individual electrode 44 as shown in FIG. 7B. A rectangular voltage pulse constitutes a drive signal, and the potential switches between the ground potential GND and the potential Vb (<Va). Thereby, the meniscus M vibrates without discharging the ink. The ink in the vicinity of the nozzle 15 is agitated, and the thickening thereof is eliminated.

<Ink circulation>
Furthermore, when left for a long time, pigment particles in the ink settle out. Sedimentation of the ink component may lead to even non-ejection. On the other hand, in the present embodiment, the ink is circulated between the individual flow passage 20 and the manifold flow passage 11.

  When the ink is circulated, the piezoelectric actuator 22 is driven at the second resonant frequency F2. The control device 50 controls the driver IC 58 to apply a drive signal to the individual electrodes 44 as shown in FIG. 7C. A trapezoidal voltage pulse constitutes a drive signal, and its potential switches between ground potential GND and potential Vc. Thus, the ink in the manifold channel 11 flows from the throttle channel 12 into the pressure chamber 10 and the descender channel 14. The ink that has reached the descender channel 14 returns to the manifold channel 11 via the circulation channel 16. The circulation of the ink eliminates settling of the pigment particles.

In general, the lower the compliance, the higher the corresponding resonant frequency. In the present embodiment, C _DES is smaller than [C _CAV + C _PZT ]. Corresponding to this, the second resonance frequency F2 corresponding to C _DES is a resonance frequency higher than the first resonance frequency F1 corresponding to [C _CAV + C _PZT ]. Specifically, the first resonance frequency F1 is about 100 kHz, and the second resonance frequency F2 is about 750 kHz.

  Here, when the piezoelectric actuator 22 is driven at a certain frequency, if the frequency is the first resonance frequency F1, energy supplied from the outside is effectively used for the vibration of the pressure chamber 10 and the piezoelectric actuator 22. If the frequency is the second resonance frequency F2, the input energy is effectively used for the vibration of the descender channel 14. For frequencies other than this, the input energy is distributed to the vibrations of the various flow path parts.

  Usually, the time required for settling of the pigment particles is longer than the time required for the thickening of the ink. When the sedimentation (ink circulation) is performed at a frequency other than the second resonance frequency F2, the meniscus M is exposed to vibration for a long time more than necessary. On the contrary, in the entire inkjet head 3, there is a possibility that the thickening of the ink may be promoted.

  On the other hand, in the present embodiment, the piezoelectric actuator 22 is driven at the second resonance frequency F2. While the descender channel 14 resonates, the ink can be circulated in a state where the vibration of the meniscus M is suppressed as much as possible.

  Furthermore, by selectively using the drive frequency, it is possible to effectively eliminate the thickening in the vicinity of the nozzle 15 and the elimination of the sedimentation in the ink flow path.

  In addition, sedimentation elimination is affected by the flow velocity of the ink. The higher the driving frequency, the faster the flow velocity in circulation and the shorter the solution time. If the flow velocity is low, there is concern that the settling can not be resolved. On the other hand, in the present embodiment, the higher second resonance frequency F2 (> F1) is the circulation driving frequency of the ink, and the sedimentation can be canceled efficiently.

  Further, when circulating the ink, a trapezoidal wave is used as a drive signal. The drive signal has few frequency components of sine waves other than the included second resonance frequency F2. Therefore, when circulating the ink, the input energy is effectively used for the vibration of the descender channel 14.

Also, in general, as the inertance is larger, the liquid in the flow path is less likely to be displaced (position is likely to be maintained). In the present embodiment, L _CIR is larger than L _NOZ . Thereby, when it is desired to drive the piezoelectric actuator 22 to vibrate the meniscus M, the pressure generated in the pressure chamber 10 is efficiently transmitted to the nozzle 15. The circulation channel 16 also communicates with the descender channel 14, but this pressure is less _likely to be transmitted to the circulation channel 16 because of the relationship of L _CIR > L _NOZ . In particular, driving at the first resonance frequency F1 promotes this tendency because the input energy is likely to be used for the vibration of the pressure chamber 10 and the piezoelectric actuator 22.

Further, when ink is continuously ejected from the nozzle 15, it is preferable that the residual vibration of the meniscus M be sufficiently attenuated immediately before the ejection of the ink from the viewpoint of stable ejection of the ink. In the present embodiment, the damping coefficient R _NOZ / L _NOZ of the nozzle 15 is large. The residual vibration of the meniscus M attenuates quickly. Thus, the ink discharge interval can be shortened.

On the other hand, in the present embodiment, the attenuation coefficient R _CIR / L _CIR of the circulation channel 16 is small. When the ink is circulated, the force for displacing the ink is not easily attenuated, and the circulation of the ink can be efficiently maintained.

  As mentioned above, although the suitable embodiment of the present invention was described, the present invention is not limited to the above-mentioned embodiment, and various changes are possible within the limits of a claim.

  In the above embodiment, when the thickening of the ink is eliminated, the piezoelectric actuator 22 is simply driven at the first resonance frequency F1, but the invention is not limited thereto.

  For example, in the first modification, in order to eliminate the thickening of the ink, the operation procedure shown in FIG. 8 is followed. The control device 50 first drives the piezoelectric actuator 22 at the second resonance frequency F2. Thus, the ink circulates (S101). Subsequently, the piezoelectric actuator 22 is driven at the first resonance frequency F1 for a predetermined time T. Thereby, the meniscus M vibrates (S102).

  Here, even if the drive of S101 is stopped, the circulation of the ink continues for a while. Therefore, when the ink is circulated before the meniscus oscillation, the ink stirred by the oscillation of the meniscus M can be diffused on the remaining ink flow. Thus, in the vicinity of the nozzle 15, the thickened ink is quickly replaced with fresh ink.

  Further, in the first modification, the driving at the first resonance frequency F1 may be performed for a predetermined time T during which the circulation of the ink continues. Thereby, the meniscus M is vibrated while the circulation of the ink remains. Therefore, it is possible to place the stirred thickened ink on the remaining ink flow and diffuse it while effectively using the input energy for meniscus vibration.

  In the second modification, the circulation of ink and the vibration of the meniscus M are alternately repeated Na times. As shown in FIG. 9, the control device 50 first resets the number N to 0 (S201). Subsequently, as in S101 of Modified Example 1, the ink is circulated (S202). At this time, the piezoelectric actuator 22 is driven at the second resonance frequency F2. After the ink circulation continues for the predetermined time T1, the control device 50 switches the operation to the vibration of the meniscus M (S203), as in S102 of the first modification. The drive of the piezoelectric actuator 22 is performed at the first resonance frequency F1 and is continued for a predetermined time T2. When continuing for the predetermined time T2, the control device 50 increases the number N by 1 (update to [N + 1]) (S204), and when the number N is less than Na (S205: NO), returns to S202 and returns N When S reaches Na (S205: YES), the process ends.

  In the second modification, the ink circulation and the subsequent oscillation of the meniscus are repeated a plurality of times, so that the sedimentation and thickening of the ink can be reliably eliminated.

  In the first and second modifications, the ink is circulated before the meniscus vibration. At this time, meniscus oscillation is started while ink flow is remaining. The stop of the meniscus oscillation may be during the remaining of the ink flow or after this flow is interrupted. If the meniscus vibration is started immediately after stopping the circulation of the ink, it is possible to enjoy the quick replacement effect of the ink by the flow of the remaining ink.

  In the above-described embodiment, when the ink is circulated, the piezoelectric actuator 22 is driven by the trapezoidal wave drive signal, but the invention is not limited thereto. For example, a rectangular wave may be used as the drive signal.

In the above-described embodiment, the second resonance frequency F2 is set higher than the first resonance frequency F1 in response to C _DES being smaller than [C _CAV + C _PZT ], but the present invention is not limited thereto. If the first resonance frequency F1 is a frequency at which the pressure chamber 10 and the piezoelectric actuator 22 resonate, and the second resonance frequency F2 is a frequency at which the descender channel 14 resonates, the second resonance frequency F2 is higher than the first resonance frequency F1. It may also be low.

In the aforementioned embodiment, corresponding to C _DES is greater than C _CIR, but the second resonant frequency F2 and a frequency corresponding to the C _DES, is not limited thereto. The second resonance frequency F2 may be a frequency that is set regardless of C _{DES as} long as the second resonance frequency F2 causes the descender channel 14 to resonate.

In the embodiment described above, [C _CAV + C _PZT] is, C _APA, C _DES, corresponding to larger than C _NOZ, the first resonance frequency F1, the [C _CAV + C _PZT] According to the frequency, it is not limited to this. The first resonance frequency F1 may be a frequency that is set irrespective of [C _CAV + C _PZT ] as long as the pressure chamber 10 and the piezoelectric actuator 22 are resonated.

  Moreover, in the above-mentioned embodiment, although the inkjet head 3 produced the volume change of the pressure chamber 10 with the piezoelectric actuator 22, and applied pressure to ink, it is not restricted to this. For example, an actuator that applies pressure by expanding air bubbles into the pressure chamber by heating, an actuator that causes pressure change by causing a volume change of the pressure chamber 10 by electrostatic force, or the like may be used.

  Moreover, in the above-mentioned embodiment, although the inkjet head 3 discharges the pigment ink of 4 colors, it is not restricted to this. For example, only a part of ink may be pigment ink among the ink which the inkjet head 3 discharges, such as the inkjet head 3 discharging black pigment ink and color dye ink.

  Furthermore, although the example in which the present invention is applied to a printer provided with a so-called serial head has been described above, the present invention is not limited to this. It is also possible to apply the present invention to a printer provided with a so-called line head extending over the entire length of the recording sheet P in the scanning direction.

  Furthermore, although the example in which the present invention is applied to a printer that performs printing by discharging ink from the nozzles has been described above, the present invention is not limited thereto. For example, the present invention can be applied to a liquid discharge apparatus that discharges a liquid other than ink, such as a material of a wiring pattern of a wiring board.

DESCRIPTION OF SYMBOLS 1 printer 10 pressure chamber 12 throttling flow path 14 descender flow path 15 nozzle 16 circulation flow path 11 manifold flow path 20 individual flow path 22 piezoelectric actuator 58 driver IC
50 controller

Claims (10)

With multiple individual channels,
A common flow path to which the plurality of individual flow paths are connected,
Each individual channel is
A nozzle, a pressure chamber, a descender channel connecting the nozzle and the pressure chamber, a throttle channel connecting the pressure chamber and the common channel, the descender channel, and the common channel And a circulation flow path to be connected;
An actuator for applying pressure to liquid in the pressure chamber;
A drive device for driving the actuator;
And a control device for controlling the drive device,
The controller is
When vibrating the meniscus of the liquid formed in the nozzle, the driving device is driven at a first resonance frequency at which the pressure chamber to which the actuator is added in the individual flow paths resonates.
When the liquid is circulated through the pressure chamber and the circulation flow path, the drive device drives the actuator at a second resonance frequency at which the descender flow path of the individual flow paths resonates. Discharge device. The sum of the compliance of the pressure chamber and the compliance of the actuator is greater than the compliance of the throttling channel and the compliance of the descender channel, and less than the compliance of the meniscus of liquid in the nozzle,
The liquid discharge device according to claim 1, wherein the first resonance frequency is a resonance frequency corresponding to the sum of the compliance of the pressure chamber and the compliance of the actuator. The compliance of the descender channel is greater than the compliance of the circulation channel,
The liquid discharge device according to claim 1, wherein the second resonance frequency is a frequency according to the compliance of the descender channel. Compliance of the descender channel is less than the sum of the compliance of the pressure chamber and the compliance of the actuator,
The liquid discharge device according to any one of claims 1 to 3, wherein the second resonant frequency is higher than the first resonant frequency. The controller is
When vibrating the meniscus of the liquid formed in the nozzle, the driving device is driven at the first resonance frequency after driving the actuator at the second resonance frequency. The liquid discharge device according to any one of 4. The controller is
When vibrating the meniscus of the liquid formed on the nozzle, the driving device is driven at the first resonance frequency while the circulation after being driven at the second resonance frequency is maintained. The liquid discharge device according to claim 5, characterized in that The controller is
When vibrating the meniscus of the liquid formed in the nozzle, the drive device is caused to alternately and repeatedly drive the actuator at the second resonant frequency and drive the actuator at the first resonant frequency. The liquid discharge apparatus according to claim 5 or 6, wherein The controller is
When vibrating the meniscus of the liquid formed in the nozzle, the driving device drives the actuator at the first resonance frequency using a rectangular wave;
The liquid crystal device according to any one of claims 1 to 7, wherein when the liquid in the pressure chamber is circulated through the circulation flow path, the driving device drives the actuator at the second resonance frequency using a trapezoidal wave. The liquid ejection device according to claim 1.   The liquid discharge device according to any one of claims 1 to 8, wherein the circulation channel has a larger inertance than the nozzle.   The liquid discharge device according to any one of claims 1 to 9, wherein the circulation channel has a smaller attenuation coefficient, which is a value obtained by dividing channel resistance by inertance, than the nozzle.