JP2022026561A - Control method for liquid discharge device, and liquid discharge device - Google Patents

Abstract

To suppress discharge failure of a liquid discharge device.SOLUTION: Provided is a control method of a liquid discharge device having a discharge unit for discharging liquid in a pressure chamber from a nozzle according to drive of a piezoelectric element. The method of controlling the liquid discharge device comprises: a detection step of detecting residual vibration generated in the discharge unit according to drive of the piezoelectric element; and a setting step of setting a circulation flow amount of liquid circulating from a supply channel for supplying the liquid to the pressure chamber into a recovery channel for recovering the liquid in the pressure chamber based on a detection result of the residual vibration.SELECTED DRAWING: Figure 1

Description

The present invention relates to a control method for a liquid discharge device and a liquid discharge device.

A liquid ejection device such as an inkjet printer drives a piezoelectric element provided in the ejection section of the liquid ejection device to eject a liquid such as ink filled in a pressure chamber provided in the ejection section to a medium. Form an image. The image quality of the image formed by such a liquid discharge device is affected by the viscosity of the liquid in the discharge portion. Therefore, for example, in Patent Document 1, the liquid in the discharge portion is thickened by circulating the liquid from the supply flow path for supplying the liquid to the pressure chamber to the recovery flow path for collecting the liquid in the pressure chamber. A technique for suppressing a defective discharge is disclosed.

Japanese Unexamined Patent Publication No. 2020-001315

However, in the liquid discharge device described in Patent Document 1, even if the liquid is circulated from the supply flow path to the recovery flow path, if the flow rate of the circulated liquid is not appropriate, a discharge failure may occur. be.

In order to solve the above problems, the control method of the liquid discharge device according to the preferred embodiment of the present invention is to control the liquid discharge device having a discharge unit for discharging the liquid in the pressure chamber from the nozzle according to the drive of the piezoelectric element. The method is a detection step of detecting residual vibration generated in the discharge portion according to the drive of the piezoelectric element, and a supply flow path for supplying a liquid to the pressure chamber based on the detection result of the residual vibration. It is provided with a setting step of setting the circulation flow rate of the liquid circulating in the recovery flow path for collecting the liquid in the pressure chamber.

In order to solve the above problems, the liquid discharge device according to the preferred embodiment of the present invention has a discharge unit that discharges the liquid in the pressure chamber from the nozzle according to the drive of the piezoelectric element, and the liquid discharge device according to the drive of the piezoelectric element. From the detection unit that detects the residual vibration generated in the discharge unit and the supply flow path that supplies the liquid to the pressure chamber to the recovery flow path that collects the liquid in the pressure chamber based on the detection result of the residual vibration. It is provided with a setting unit for setting the circulating flow rate of the circulating liquid.

It is a functional block diagram which shows the structural example of the liquid discharge apparatus which concerns on this invention. It is a perspective view which shows the internal structure of a liquid discharge device schematically. It is sectional drawing which shows the structural example of a recording head. It is a top view which shows the arrangement example of the nozzle in a head module. It is a block diagram which shows an example of the structure of a head unit. It is a timing chart for showing the operation of a liquid discharge device. It is explanatory drawing for demonstrating the relationship between the individual designation signal and the connection state designation signal. It is a block diagram which shows the structural example of the amplitude specific circuit. It is a figure for demonstrating a residual vibration signal. It is a flowchart which shows an example of the operation of the liquid discharge device which concerns on this embodiment. It is a flowchart which shows an example of the operation of the liquid discharge apparatus which concerns on 2nd Embodiment. It is explanatory drawing which shows the relationship between the flow rate set for the nth time, and the change amount calculated in the process when the process shown in FIG. 11 is executed.

Hereinafter, suitable embodiments for carrying out the present invention will be described with reference to the drawings. The dimensions and scale of each element in each drawing referred to in the following description are appropriately different from the actual product.

In this embodiment, as an example of a liquid ejection device, an inkjet printer that ejects ink and prints an image on a medium will be described. The "ink" in the following description is an example of a liquid.

<1. Overview of liquid discharge device>
FIG. 1 is a functional block diagram showing a configuration example of the liquid discharge device 1. As shown in FIG. 1, print data Img is supplied to the liquid discharge device 1. The print data Img is data showing an image formed by the liquid ejection device 1 supplied from a host computer such as a personal computer or a digital camera. The liquid ejection device 1 executes a printing process of forming an image based on the print data Img on the medium P.

As shown in FIG. 1, the liquid discharge device 1 includes a control unit 2, a head unit HU, a drive signal generation circuit 4, a storage unit 5, an amplitude specifying circuit 6, a circulation mechanism 26, and a transfer mechanism 7. Have.

The control unit 2 includes a CPU. However, the control unit 2 may be configured to have a programmable logic device such as an FPGA in place of the CPU or in addition to the CPU. CPU is an abbreviation for Central Processing Unit, and FPGA is an abbreviation for Field-programmable gate array.

The control unit 2 serves as a circulation control unit 21, a print control unit 22, a flow rate determination unit 23, an attenuation factor calculation unit 24, and a change amount calculation unit 25 by operating the CPU according to a control program stored in the storage unit 5. Function.

Although the details will be described later, the circulation mechanism 26 circulates the ink from the supply flow path 133 to the recovery flow path 134 via the pressure chamber C. The flow rate determining unit 23 determines the flow rate of the ink circulating from the supply flow path 133 to the recovery flow path 134 via the pressure chamber C. The flow rate determination unit 23 is an example of a “setting unit”. The circulation control unit 21 controls the circulation mechanism 26 so that the flow rate of the ink circulating from the supply flow path 133 to the recovery flow path 134 via the pressure chamber C is the flow rate determined by the flow rate determination unit 23. do. The details of the supply flow path 133, the pressure chamber C, and the recovery flow path 134 will be described later. The print control unit 22 generates a print signal SI for controlling the head unit HU, a waveform designation signal dCom for controlling the drive signal generation circuit 4, and a signal for controlling the transport mechanism 7.

The waveform designation signal dCom is a signal that defines the waveform of the drive signal Com. The drive signal Com is an analog signal for driving the discharge unit D, which will be described later. The drive signal generation circuit 4 includes a DA conversion circuit and generates a drive signal Com having a waveform defined by the waveform designation signal dCom. The drive signal Com of the present embodiment includes a drive signal Com-A and a drive signal Com-B. The print signal SI is a digital signal for designating the type of operation of the ejection unit D. Specifically, the print signal SI is a signal that specifies the type of operation of the discharge unit D by designating the head unit HU whether or not to supply the drive signal Com to the discharge unit D.

The damping rate calculation unit 24 calculates the damping rate of the residual vibration detected from the discharge unit D. The change amount calculation unit 25 calculates the change amount of the damping rate of the residual vibration detected from the discharge unit D at a predetermined time interval. The flow rate determination unit 23 determines the flow rate of the ink circulating from the supply flow path 133 to the recovery flow path 134 via the pressure chamber C based on the calculation result of the change amount calculation unit 25. The damping rate of the residual vibration and the amount of change in the damping rate of the residual vibration will be described later.

As shown in FIG. 1, the head unit HU has a switch circuit 31, a recording head 32, and a detection circuit 33.

The recording head 32 includes M ejection portions D. The value M is a natural number satisfying "M ≧ 1". In the following description, among the M ejection portions D provided on the recording head 32, the m-th ejection portion D will be referred to as a ejection unit D [m]. The variable m is a natural number satisfying "1 ≦ m ≦ M". Further, in the following description, when the component or signal of the liquid discharge device 1 corresponds to the discharge unit D [m] among the M discharge units D, the component or signal is to be represented. A subscript [m] is added to the code.

The switch circuit 31 switches whether or not to supply the drive signal Com to the discharge unit D [m] based on the print signal SI. In the following, among the drive signal Com, the drive signal Com supplied to the discharge unit D [m] may be referred to as a supply drive signal Vin [m]. Further, the switch circuit 31 detects a detection potential signal Vout [m] indicating the potential of the upper electrode Zu [m] of the piezoelectric element PZ [m] possessed by the ejection portion D [m] based on the print signal SI. It switches whether to supply to 33. The piezoelectric element PZ [m] and the upper electrode Zu [m] will be described later.

The detection circuit 33 generates a residual vibration signal Vd [m] based on the detection potential signal Vout [m]. The residual vibration signal Vd [m] shows the waveform of the residual vibration which is the vibration remaining in the discharge unit D [m] after the discharge unit D [m] is driven by the supply drive signal Vin [m]. The detection circuit 33 is an example of a “detection unit”.

The amplitude specifying circuit 6 generates an amplitude information NSP indicating the amplitude of the residual vibration signal Vd [m] based on the residual vibration signal Vd [m]. In the following description, the discharge unit D [m] to be detected by the detection circuit 33 of the detection potential signal Vout [m] may be referred to as a detection target discharge unit Ds.

FIG. 2 is a perspective view schematically showing the internal structure of the liquid ejection device. As shown in FIG. 2, in the present embodiment, it is assumed that the liquid ejection device 1 is a serial type inkjet printer. Specifically, when executing the printing process, the liquid ejection device 1 conveys the medium P in the sub-scanning direction and reciprocates the head module 3 in the main scanning direction intersecting the sub-scanning direction while reciprocating the ejection unit. By ejecting ink from D, dots corresponding to the print data Img are formed on the medium P. In this embodiment, for convenience of explanation, as shown in FIG. 2, an X-axis extending in the sub-scanning direction, a Y-axis extending in the main scanning direction, and a Z-axis intersecting the X-axis and the Y-axis are used. Introduce a three-axis coordinate system with and. Then, in the present embodiment, it is assumed that the sub-scanning direction corresponds to the + X direction. In the following, the + X direction parallel to the X axis and the −X direction opposite to the + X direction are collectively referred to as the X axis direction, and the + Y direction parallel to the Y axis and the −Y opposite to the + Y direction are used. The direction may be collectively referred to as the Y-axis direction, and the + Z direction parallel to the Z-axis and the −Z direction opposite to the + Z direction may be collectively referred to as the Z-axis direction.

As shown in FIG. 2, the liquid ejection device 1 includes a housing 100, a carriage 300 that can reciprocate in the housing 100 in the Y-axis direction and mounts a head module 3, and a discharged ink receiving unit 400. Have. The discharged ink receiving unit 400 is a component for receiving the ink discharged from the head module 3. In the present embodiment, maintenance is a flushing process or a cleaning process in which ink is discharged from the head module 3 to the discharged ink receiving unit 400 based on the control of the control unit 2 before, during, and after the printing process. Processing is executed at predetermined time intervals.

As described above, the liquid discharge device 1 according to the present embodiment has a transfer mechanism 7. When the printing process is executed, the transport mechanism 7 reciprocates the carriage 300 in the Y-axis direction and transports the medium P in the + X direction to change the relative position of the medium P with respect to the head module 3. This makes it possible for the ink to land on the recording paper as a whole.

As shown in FIG. 1, the transport mechanism 7 has a carriage transport mechanism 71 for reciprocating the carriage 300 and a medium transport mechanism 72 for transporting the medium P. Further, as shown in FIG. 2, the transport mechanism 7 has a carriage guide shaft 760 that supports the carriage 300, and a timing belt 710 that is fixed to the carriage 300 and driven by the carriage transport mechanism 71. The carriage 300 is configured to be slidable on the outer peripheral surface of the carriage guide shaft 760 in the Y-axis direction. Therefore, the transport mechanism 7 can reciprocate the head module 3 together with the carriage 300 in the Y-axis direction along the carriage guide shaft 760. Further, the transport mechanism 7 includes a platen 750 provided in the −Z direction of the carriage 300 and a transport roller 730 that rotates in response to the drive of the medium transport mechanism 72 and transports the medium P on the platen 750 in the + X direction. Have.

In the present embodiment, as shown in FIG. 2, when the carriage 300 stores four ink cartridges 310 corresponding to one-to-one with four color inks of cyan, magenta, yellow, and black. Is assumed. Further, in the present embodiment, as an example, it is assumed that four ink cartridges 310 are provided in a one-to-one correspondence with four head units HU. Each ejection unit D receives ink from the ink cartridge 310 corresponding to the head unit HU to which the ejection unit D belongs. As a result, each ejection unit D can fill the inside with the supplied ink, and the filled ink can be ejected from the nozzle N. The ink cartridge 310 may be provided outside the carriage 300.

Here, an outline of the operation of the control unit 2 when the printing process is executed will be described.
When the print process is executed, the control unit 2 first stores the print data Img supplied from the host computer (not shown) in the storage unit 5. Next, the control unit 2 drives a signal for controlling the head unit HU such as a print signal SI and a waveform designation signal dCom or the like based on various data such as print data Img stored in the storage unit 5. A signal for controlling the signal generation circuit 4 and a signal for controlling the transport mechanism 7 are generated. Then, the control unit 2 controls the transport mechanism 7 so as to change the relative position of the medium P with respect to the head module 3 based on various signals such as the print signal SI and various data stored in the storage unit 5. At the same time, the drive signal generation circuit 4 and the switch circuit 31 are controlled so that the discharge unit D is driven. As a result, the control unit 2 adjusts the presence / absence of ink ejection from the ejection unit D, the ink ejection amount, the ink ejection timing, and the like, and forms an image corresponding to the print data Img on the medium P. Is executed, each part of the liquid discharge device 1 is controlled.

<2. Overview of recording head and discharge section>
Next, the recording head 32 and the discharge unit D provided on the recording head 32 will be described with reference to FIG.

FIG. 3 is a cross-sectional view showing a configuration example of the recording head 32. As shown in FIG. 3, the liquid discharge device 1 has a circulation mechanism 26. The circulation mechanism 26 is a mechanism for refluxing the ink discharged from the ink storage chamber 70a to the ink receiving chamber 60a. As shown in FIG. 3, the circulation mechanism 26 includes a first supply pump 261, a second supply pump 262, a storage container 263, an ink supply flow path 264, and an ink recovery flow path 265.

The first supply pump 261 is a pump that supplies the ink stored in the ink cartridge 310 to the storage container 263. The storage container 263 is a sub-tank for temporarily storing the ink supplied from the ink cartridge 310.

The ink stored in the ink cartridge 310 is supplied to the storage container 263 from the first supply pump 261, and the ink discharged from the ink storage chamber 70a is supplied to the storage container 263 via the ink recovery flow path 265. The ink recovery flow path 265 is a flow path that allows the ink storage chamber 70a and the storage container 263 to communicate with each other.

The ink supply flow path 264 is a flow path that allows the ink receiving chamber 60a and the storage container 263 to communicate with each other. The second supply pump 262 is a pump that delivers the ink stored in the storage container 263. The ink delivered from the second supply pump 262 is supplied to the ink receiving chamber 60a via the ink supply flow path 264.

As shown in FIG. 3, the recording head 32 has a pressure chamber plate 40, a protective substrate 50, a supply channel substrate 60, a channel forming substrate 30, and a recovery channel substrate 70.

The pressure chamber plate 40 is provided in the + Z direction of the flow path forming substrate 30. The protective substrate 50 is laminated on the pressure chamber plate 40. A pressure chamber C is formed in the pressure chamber plate 40. The pressure chamber plate 40 is manufactured by processing a silicon single crystal substrate, for example, according to a general processing method for manufacturing a semiconductor.

The protective substrate 50 is provided in the + Z direction of the pressure chamber plate 40 and covers the piezoelectric element PZ. The protective substrate 50 is a plate elongated in the X-axis direction. The protective substrate 50 is formed by, for example, injection molding a resin material or the like. The protective substrate 50 and the pressure chamber plate 40 are joined to each other by, for example, an adhesive.

The supply flow path substrate 60 is a plate long in the X-axis direction, and an ink receiving chamber 60a is provided inside. The ink receiving chamber 60a is a concave groove that opens in the −Z direction and extends along the X-axis direction, and receives the ink supplied from the ink cartridge 310 through the ink introduction port 62. The supply flow path substrate 60 is formed by, for example, injection molding a resin material or the like. The supply flow path substrate 60 and the flow path forming substrate 30 are joined to each other by, for example, an adhesive.

The flow path forming substrate 30 is a plate elongated in the X-axis direction. A supply flow path substrate 60 and a recovery flow path substrate 70 are provided in the + Z direction of the flow path forming substrate 30. A pressure chamber plate 40 and a protective substrate 50 are provided between the supply flow path substrate 60 and the recovery flow path substrate 70.

Further, a nozzle plate 52, a supply-side flexible plate 53, and a recovery-side flexible plate 54 are provided in the −Z direction of the flow path forming substrate 30. As a result, between the flow path forming substrate 30, the nozzle plate 52, the supply side flexible plate 53, and the recovery side flexible plate 54, a plurality of individual flow paths Pa, a first common liquid chamber R1, and a second. A common liquid chamber R2 is formed.

Each of the first common liquid chamber R1 and the second common liquid chamber R2 extends in the X-axis direction. The first common liquid chamber R1 supplies ink to each of the plurality of individual flow paths Pa in common. Ink is commonly supplied to the second common liquid chamber R2 from each of the plurality of individual flow paths Pa. Each of the plurality of individual flow paths Pa is arranged in the X-axis direction and communicates with each of the plurality of nozzles N. The plurality of individual flow paths Pa communicate with the first common liquid chamber R1 and the second common liquid chamber R2. As shown in FIG. 3, the individual flow path Pa includes a supply flow path 133, a pressure chamber C, a nozzle communication flow path 135, and a recovery flow path 134.

As shown in FIG. 3, the supply flow path 133 is a flow path that communicates with the first common liquid chamber R1 and the pressure chamber C. The nozzle communication flow path 135 is a through hole that penetrates the flow path forming substrate 30 in the Z-axis direction, and is a flow path that communicates with the pressure chamber C and the recovery flow path 134. The recovery flow path 134 is a flow path that communicates with the nozzle communication flow path 135 and the second common liquid chamber R2. The flow path forming substrate 30 is manufactured by processing a silicon single crystal substrate according to, for example, a general processing method for manufacturing a semiconductor.

The nozzle plate 52 is manufactured by processing a silicon single crystal substrate, for example, according to a general processing method for manufacturing a semiconductor. Examples of such a processing method include dry etching and wet etching. The nozzle plate 52 and the flow path forming substrate 30 are joined to each other by, for example, an adhesive.

The recovery flow path substrate 70 is a plate long in the X-axis direction, and an ink accommodating chamber 70a is provided inside. The ink storage chamber 70a is a concave groove that opens in the −Z direction and extends along the X-axis direction, and receives ink discharged from the second common liquid chamber R2. The recovery flow path substrate 70 is formed by, for example, injection molding a resin material or the like. The recovery flow path substrate 70 and the flow path forming substrate 30 are joined to each other by, for example, an adhesive.

In the recording head 32 of the present embodiment, the ink sucked from the storage container 263 by the second supply pump 262 flows into the first common liquid chamber R1 via the ink receiving chamber 60a and is stored in the first common liquid chamber R1. Be done. The ink stored in the first common liquid chamber R1 is extruded from the ink receiving chamber 60a into the ink continuously supplied to the first common liquid chamber R1 and supplied to the pressure chamber C via the supply flow path 133. .. The ink supplied to the pressure chamber C receives the vibration of the piezoelectric element PZ, flows into the nozzle communication flow path 135, and is discharged from the nozzle N. The ink not ejected from the nozzle N flows to the second common liquid chamber R2 via the collection flow path 134, and is collected in the ink storage chamber 70a. The ink collected in the ink storage chamber 70a is collected in the storage container 263 via the ink collection flow path 265.

As shown in FIG. 3, the recording head 32 according to the present embodiment has a discharge unit D. The discharge unit D includes a piezoelectric element PZ, a pressure chamber C in which ink is filled, a nozzle N communicating with the pressure chamber C, and a vibration unit 42. The ejection unit D ejects the ink in the pressure chamber C from the nozzle N by driving the piezoelectric element PZ by the supply drive signal Vin.

The nozzle N is a circular through hole for ejecting ink, and communicates with the nozzle communication flow path 135. The nozzle N is provided on the nozzle plate 52 as shown in FIG. The pressure chamber C is a space defined by the pressure chamber plate 40 and the flow path forming substrate 30. The piezoelectric element PZ has an upper electrode Zu, a lower electrode Zd, and a piezoelectric body Zm provided between the upper electrode Zu and the lower electrode Zd. The lower electrode Zd is electrically connected to the feeder line Ld set in the potential VBS. Then, when the supply drive signal Vin is supplied to the upper electrode Zu and a voltage is applied between the upper electrode Zu and the lower electrode Zd, the piezoelectric element PZ moves in the + Z direction or the −Z direction according to the applied voltage. As a result, the piezoelectric element PZ vibrates. Here, since the vibrating portion 42 is joined to the lower electrode Zd, when the piezoelectric element PZ is driven by the supply drive signal Vin and vibrates, the vibrating portion 42 also vibrates. Then, the volume of the pressure chamber C and the pressure in the pressure chamber C change due to the vibration of the vibrating portion 42, and the ink filled in the pressure chamber C is ejected from the nozzle N.

FIG. 4 shows an arrangement of four recording heads 32 of the head module 3 and a total of 4M nozzles N provided on the four recording heads 32 when the liquid discharge device 1 is viewed in a plan view in the + Z direction. It is explanatory drawing for demonstrating an example. As shown in FIG. 4, each recording head 32 provided in the head module 3 is provided with nozzle rows Ln1 to Ln4. Here, the nozzle row Ln is a plurality of nozzles N provided so as to extend in a row in a predetermined direction. In the present embodiment, it is assumed as an example that each nozzle row Ln is composed of M nozzles N arranged so as to extend in the X-axis direction. In the present embodiment, for example, the nozzle row Ln1, the nozzle row Ln2, the nozzle row Ln3, and the nozzle row Lv4 eject cyan, magenta, yellow, and black inks, respectively.

<3. Head unit configuration>
Hereinafter, the configuration of the head unit HU will be described with reference to FIG.

FIG. 5 is a block diagram showing an example of the configuration of the head unit HU. As described above, the head unit HU has a switch circuit 31, a recording head 32, and a detection circuit 33. Further, the head unit HU has a wiring La to which the drive signal Com-A is supplied from the drive signal generation circuit 4, a wiring Lb to which the drive signal Com-B is supplied from the drive signal generation circuit 4, and a detection potential signal Vout. The wiring Ls for supplying to the detection circuit 33 and the feeding line Ld to which the potential VBS is supplied are provided.

As shown in FIG. 5, in the switch circuit 31, M switches Ra [1] to Ra [M], M switches Rb [1] to Rb [M], and M switches Rs [1]. It has ~ Rs [M] and a connection state designation circuit 311 that designates the connection state of each switch.

The connection state designation circuit 311 turns on / off the switch Ra [m] based on at least a part of the print signal SI, the latch signal LAT, the change signal CH, and the period specification signal Tsig supplied from the control unit 2. The connection state specification signal Ga [m] that specifies the on / off of the switch Rb [m], and the connection state specification signal Gs [m] that specifies the on / off of the switch Rs [m]. ], And generate.

The switch Ra [m] is composed of the wiring La and the upper electrode Zu [m] of the piezoelectric element PZ [m] provided in the discharge portion D [m] based on the connection state designation signal Ga [m]. Switch between conduction and non-conduction. In the present embodiment, the switch Ra [m] is turned on when the connection state designation signal Ga [m] is at a high level and turned off when the connection state designation signal Ga [m] is at a low level. Further, the switch Rb [m] has a wiring Lb and an upper electrode Zu [m] of the piezoelectric element PZ [m] provided in the discharge portion D [m] based on the connection state designation signal Gb [m]. , Switching between conduction and non-conduction. In the present embodiment, the switch Rb [m] is turned on when the connection state designation signal Gb [m] is at a high level and turned off when the connection state designation signal Gb [m] is at a low level.

Further, the switch Rs [m] has the wiring Ls and the upper electrode Zu [m] of the piezoelectric element PZ [m] provided in the discharge portion D [m] based on the connection state designation signal Gs [m]. , Switching between conduction and non-conduction. In the present embodiment, the switch Rs [m] is turned on when the connection state designation signal Gs [m] is at a high level and turned off when the connection state designation signal Gs [m] is at a low level. As described above, the supply drive signal Vin [m] is the piezoelectric element of the discharge portion D [m] of the drive signals Com-A and Com-B via the switch Ra [m] or Rb [m]. It is a signal supplied to PZ [m].

A detection potential signal Vout [m] indicating the potential of the piezoelectric element PZ [m] of the discharge unit D [m] driven as the discharge unit Ds to be detected is supplied to the detection circuit 33 via the wiring Ls. The detection circuit 33 generates a residual vibration signal Vd [m] based on the detection potential signal Vout [m].

<4. Operation of head unit>
Hereinafter, the operation of each head unit HU will be described with reference to FIGS. 6 and 7.

In the present embodiment, the operating period of the liquid discharge device 1 includes one or a plurality of unit periods Tu. Further, the liquid discharge device 1 according to the present embodiment can drive each discharge unit D for printing processing in each unit period Tu. Further, the liquid discharge device 1 according to the present embodiment can drive the detection target discharge unit Ds and detect the detection potential signal Vout from the detection target discharge unit Ds in each unit period Tu.

FIG. 6 is a timing chart for showing the operation of the liquid discharge device 1 in the unit period Tu. As shown in FIG. 6, the control unit 2 outputs a latch signal LAT having a pulse PIsL. As a result, the control unit 2 defines the unit period Tu as the period from the rise of the pulse PIsL to the rise of the next pulse PIsL. Further, the control unit 2 outputs a change signal CH having a pulse PIsC in the unit period Tu. Then, the control unit 2 divides the unit period Tu into a control period Tu1 from the rise of the pulse PIsL to the rise of the pulse PIsC and a control period Tu2 from the rise of the pulse PIsC to the rise of the pulse PIsL. Further, the control unit 2 outputs a period-defined signal Tsig having the pulse PIsT1 and the pulse PIsT2 in the unit period Tu. Then, the control unit 2 sets the unit period Tu to the control period TSS1 from the rise of the pulse PIsL to the rise of the pulse PIsT1, the control period TSS2 from the rise of the pulse PIsT1 to the rise of the pulse PIsT2, and the pulse from the rise of the pulse PIsT2. It is divided into the control period TSS3 until the rise of PIsL.

The print signal SI according to the present embodiment includes individually designated signals Sd [1] to Sd [M] that specify the driving mode of the ejection units D [1] to D [M] in each unit period Tu. When the printing process or the like is executed in the unit period Tu, the control unit 2 has a print signal SI including the individually designated signals Sd [1] to Sd [M] prior to the unit period Tu, as shown in FIG. Is synchronized with the clock signal CL and supplied to the connection state designation circuit 311. Then, the connection state designation circuit 311 generates the connection state designation signals Ga [m], Gb [m], and Gs [m] based on the individual designation signal Sd [m] in the unit period Tu.

Here, in the present embodiment, it is assumed that the ejection portion D [m] can form a large dot, a medium dot smaller than the large dot, and a small dot smaller than the medium dot. Then, in the present embodiment, the individually designated signal Sd [m] designates driving in a mode of ejecting an amount of ink corresponding to a large dot to the ejection unit D [m] in each unit period Tu. With respect to the value "1" and the value "2" that specifies the drive in the mode of ejecting the amount of ink corresponding to the middle dot to the ejection unit D [m], and to the ejection unit D [m]. A value "3" that specifies driving in a mode in which an amount of ink corresponding to a small dot is ejected, and a value "4" that specifies driving in a mode in which ink is not ejected with respect to the ejection unit D [m]. It is assumed that any one of the five values, "5", which specifies the drive as the detection target discharge unit Ds, can be taken with respect to the discharge unit D [m].

As shown in FIG. 6, in the present embodiment, the drive signal Com-A has a waveform PX provided in the control period Tu1 and a waveform PY provided in the control period Tu2. In the present embodiment, the waveform PX and the waveform PY are defined so that the potential difference between the maximum potential VHx and the minimum potential VLx of the waveform PX is larger than the potential difference between the maximum potential VHy and the minimum potential VLy of the waveform PY. .. Specifically, when the drive signal Com-A having the waveform PX is supplied to the ejection unit D [m], the ejection unit D [m] is driven in such a manner that an amount of ink corresponding to the middle dot is ejected. As such, the waveform PX is determined. Further, when the drive signal Com-A having the waveform PY is supplied to the ejection unit D [m], the ejection unit D [m] is driven so as to eject an amount of ink corresponding to a small dot. , The waveform PY is determined. Further, in the present embodiment, the potentials at the start and end of the waveform PX and the waveform PY are set to the reference potential V0.

Here, in the present embodiment, as an example, when the potential of the supply drive signal Vin [m] supplied to the discharge unit D [m] is high, the discharge unit D [m] is compared with the case where the potential is low. It is assumed that the volume of the pressure chamber C possessed by [m] becomes small. Therefore, when the discharge unit D [m] is driven by the supply drive signal Vin [m] having the waveform PX, the potential of the supply drive signal Vin [m] changes from the lowest potential VLx to the highest potential VHx. The ink in the ejection portion D [m] is ejected from the nozzle N. Further, when the discharge unit D [m] is driven by the supply drive signal Vin [m] having the waveform PY, the potential of the supply drive signal Vin [m] changes from the lowest potential VLy to the highest potential VHy, thereby discharging. The ink in the portion D [m] is ejected from the nozzle N.

Further, in the present embodiment, the drive signal Com-B has a waveform PS. The waveform PS becomes the reference potential V0 at the start time of the control period TSS1, maintains the potential VS1 having a higher potential than the reference potential V0 in the period T1 of the control period TSS1, and is the period after the period T1 in the control period TSS1. In Tpl, the potential VS1 changes to a potential VS2 having a potential lower than the reference potential V0, the potential VS2 is maintained in the period T2 after the period Tpl in the control period TSS1, and the potential VS2 is maintained in the control period TSS2. It is a waveform that changes from the potential VS2 to the reference potential V0 in the control period TSS3.

Further, in the present embodiment, when the discharge unit D [m] is driven by the supply drive signal Vin [m] having the waveform PS, the discharge unit D when the potential of the supply drive signal Vin [m] is the potential VS1. The volume of the pressure chamber C possessed by [m] is smaller than the volume of the pressure chamber C possessed by the discharge portion D [m] when the potential of the supply drive signal Vin [m] is the potential VS2. In other words, in the present embodiment, when the discharge unit D [m] is driven by the supply drive signal Vin [m] having the waveform PS, the volume of the pressure chamber C of the discharge unit D [m] in the period Tpl. Is expanded, and in the period Tpl, the ink in the ejection portion D [m] is drawn in the + Z direction.

In addition, in the present embodiment, when the ejection unit D [m] is driven by the supply drive signal Vin [m] having the waveform PS, the waveform PS is determined so that the ink is not ejected from the ejection unit D [m]. Has been done. The control period TSS2 is an example of the “detection period”.

FIG. 7 is an explanatory diagram for explaining the relationship between the individual designated signal Sd [m] and the connection state designated signals Ga [m], Gb [m], and Gs [m]. As shown in FIG. 7, the individually designated signal Sd [m] sets a value "1" that specifies a drive for ejecting an amount of ink corresponding to a large dot to the ejection unit D [m] in the unit period Tu. When shown, the connection state designation circuit 311 sets the connection state designation signal Ga [m] to a high level over a unit period of Tu. In this case, since the switch Ra [m] is turned on for the unit period Tu, the discharge unit D [m] is driven by the supply drive signal Vin [m] having the waveform PX and the waveform PY in the unit period Tu. Discharges an amount of ink equivalent to a large dot.

Further, as shown in FIG. 7, the individually designated signal Sd [m] specifies a drive for ejecting an amount of ink corresponding to a medium dot to the ejection unit D [m] in the unit period Tu, “2”. , The connection state designation circuit 311 sets the connection state designation signal Ga [m] to a high level only during the control period Tu1. In this case, since the switch Ra [m] is turned on only during the control period Tu1, the discharge unit D [m] is driven by the supply drive signal Vin [m] having the waveform PX in the unit period Tu, and becomes a middle dot. Discharges a considerable amount of ink.

Further, as shown in FIG. 7, the individually designated signal Sd [m] specifies driving in a mode of ejecting an amount of ink corresponding to a small dot to the ejection unit D [m] in the unit period Tu. When the value "3" is shown, the connection state designation circuit 311 sets the connection state designation signal Ga [m] to a high level only during the control period Tu2. In this case, since the switch Ra [m] is turned on only during the control period Tu2, the discharge unit D [m] is driven by the supply drive signal Vin [m] having the waveform PY in the unit period Tu, and becomes a small dot. Discharges a considerable amount of ink.

In addition, as shown in FIG. 7, the individually designated signal Sd [m] indicates a value “4” that specifies driving in a mode in which ink is not ejected to the ejection unit D [m] in the unit period Tu. In this case, the connection state designation circuit 311 sets the connection state designation signals Ga [m], Gb [m], and Gs [m] to low levels over a unit period of Tu. In this case, the ejection unit D [m] is not driven by the drive signal Com and does not eject ink in the unit period Tu.

Further, as shown in FIG. 7, when the individual designation signal Sd [m] indicates a value “5” that designates the drive as the detection target discharge unit Ds with respect to the discharge unit D [m] in the unit period Tu. , The connection state designation circuit 311 sets the connection state designation signal Gb [m] to a high level in the control period TSS1 and the control period TSS3, and sets the connection state designation signal Gs [m] to a high level in the control period TSS2. do. In this case, the switch Rb [m] is turned on in the control period TSS1 and the control period TSS3, and the switch Rs [m] is turned on in the control period TSS2. That is, in this case, in the control period TSS1, the discharge unit D [m] is driven by the supply drive signal Vin [m] having the waveform PS, and in the control period TSS2, residual vibration occurs in the discharge unit D [m]. The state of being is created. That is, in this case, in the control period TSS2, the potential of the upper electrode Zu [m] of the discharge portion D [m] changes according to the residual vibration generated in the discharge portion D [m]. Therefore, in this case, in the control period TSS2, the detection circuit 33 detects the detection potential signal Vout [m] based on the residual vibration generated in the discharge unit D [m].

As described above, the detection circuit 33 generates the residual vibration signal Vd [m] based on the detection potential signal Vout [m]. Specifically, the detection circuit 33 amplifies the detection potential signal Vout [m] and removes the noise component, thereby shaping the residual vibration signal Vd [m] into a waveform suitable for the processing of the amplitude specifying circuit 6. To generate. That is, in the present embodiment, the residual vibration signal Vd [m] indicates the waveform of the residual vibration generated in the discharge portion D [m] during the control period TSS2.

<5. Operation of amplitude specific circuit>
The operation of the amplitude specifying circuit 6 will be described with reference to FIGS. 8 and 9. Note that FIG. 8 is a block diagram showing a configuration example of the amplitude specifying circuit 6. Further, FIG. 9 is a diagram for explaining the residual vibration signal Vd [m].

As shown in FIG. 8, the amplitude specifying circuit 6 has a comparison unit 610 and a comparison unit 610 that binarize the residual vibration signal Vd [m] by comparing the residual vibration signal Vd [m] with the threshold potential. Based on the comparison result, it has an amplitude information generation unit 620 that generates an amplitude information NSP indicating the amplitude of the residual vibration signal Vd [m].

As shown in FIG. 8, the comparison unit 610 compares the potential of the residual vibration signal Vd [m] with the threshold potential VthW, which is the potential of the amplitude center level of the residual vibration signal Vd [m], and compares the potential. A comparison signal showing the result of the comparison by comparing the potential of the residual vibration signal Vd [m] with the comparison circuit 611 that generates the comparison signal CPW showing the result and the threshold potential VthZ having a potential higher than the threshold potential VthW. It has a comparison circuit 612 that generates a CPZ. Specifically, as shown in FIG. 9, the comparison circuit 611 generates a comparison signal CPW that becomes a high level when the potential of the residual vibration signal Vd [m] is equal to or higher than the threshold potential VthW. Further, the comparison circuit 612 generates a comparison signal CPZ having a high level when the potential of the residual vibration signal Vd [m] is equal to or higher than the threshold potential VthZ.

As shown in FIG. 8, the amplitude information generation unit 620 has a time length specifying circuit 630 and an amplitude calculation circuit 640. The time length specifying circuit 630 includes a time length specifying circuit 631 that specifies the time length of the period during which the comparison signal CPW is at a high level, and a time length specifying circuit 632 that specifies the time length of the period during which the comparison signal CPZ is at a high level. , Have.

As shown in FIG. 9, the time length specifying circuit 631 specifies the time length TWq of the period Wq at which the comparison signal CPW becomes the qth highest level in the control period TSS2, and generates the time information NTW indicating the time length TWq. do. Here, the variable q is a natural number satisfying “q ≧ 1”. In the following description, the time at which the potential of the residual vibration signal Vd [m] coincides with the threshold potential VthW at the jth position in the control period TSS2 is referred to as time ts-j. Here, the variable j is a natural number satisfying "j ≧ 1". Then, in the present embodiment, the case where the period Wq is the period from the time ts− (2q-1) to the time ts-2q is assumed as an example.

In this way, the time length specifying circuit 631 specifies the Q time lengths TW1 to TWQ corresponding to the Q period W1 to WQ and the Q time lengths TW1 to 1 in the control period TSS2. Generates Q time information NTWs indicating TWQ. Here, the value Q is a natural number satisfying “Q ≧ 2”. The variable q described above satisfies "1 ≦ q ≦ Q".

Further, the time length specifying circuit 632 specifies the time length TZq of the period in which the comparison signal CPZ becomes the qth highest level in the control period TSS2, and generates the time information NTZ indicating the time length TZq. As shown in FIG. 9, the period in which the comparison signal CPZ reaches the qth highest level is a part of the period Wq. That is, the time length specifying circuit 632 specifies the time length of the period in which the comparison signal CPZ is at a high level in the period Wq as the time length TZq.

In this way, the time length specifying circuit 632 specifies the Q time lengths TZ1 to TZQ corresponding to the Q period W1 to WQ and the Q period TZ1 to TZQ in the control period TSS2, and the Q time lengths TZ1 to Generates Q time information NTZs indicating TZQ.

As shown in FIGS. 8 and 9, the amplitude calculation circuit 640 identifies the amplitude VMq of the residual vibration signal Vd [m] in the period Wq based on the time information NTW and the time information NTZ, and indicates the amplitude VMq. Generate information NSP. Specifically, the amplitude calculation circuit 640 specifies the amplitude VMq using the following equation (1) by approximating the residual vibration signal Vd [m] to a sine wave.

Further, when the variable q1 is a natural number satisfying "q1 ≧ 1" and the variable q2 is a natural number satisfying "q2> 1" and "q2> q1", the attenuation rate of the amplitude VMq2 with respect to the amplitude VMq1 is as follows. It is represented by the formula (2) shown.

(VMq1-VMq2) / VMq1 ... (2)

The attenuation factor calculation unit 24 calculates the attenuation factor by substituting the amplitude VMq1 and the amplitude VMq2 indicated by the two amplitude information NSPs corresponding to the period Wq1 and the period Wq2 into the equation (2).

When the control unit 2 outputs a print signal SI that specifies that the ejection unit D [m] is driven as the detection target ejection unit Ds, for example, the amplitude information NSP acquired from the amplitude specifying circuit 6 is output from the ejection unit D [. It is stored in the storage unit 5 in association with the number "m" of "m".

<6. Operation of liquid discharge device>
Generally, in a liquid ejection device such as an inkjet printer, the vicinity of the nozzle is affected by changes in the surrounding environment such as temperature and humidity, the distance between the nozzle and the medium, or the volatility and viscosity of ink. The ink in the ejection part may thicken, resulting in ejection failure. Therefore, in recent years, thickening of the ink in the ejection portion has been suppressed by circulating the ink in the individual flow paths. The thickening of the ink in the ejection section does not progress much when the flow rate of the ink circulating in the individual flow paths increases to some extent. On the other hand, if the flow rate of the ink circulating in the individual flow paths is set to the maximum value in order to suppress the thickening of the ink in the ejection section, the pressure fluctuates between the flow path on the upstream side and the flow path on the downstream side of the nozzle. The difference becomes large, and it becomes difficult to secure the discharge stability of the liquid discharge device. Further, if the flow rate of the ink circulating in the individual flow path is set to the maximum value, the joint portion of various silicon or resin parts constituting the liquid ejection device may be destroyed. Further, in order to set the flow rate of the ink circulating in the individual flow paths to the maximum value, for example, a high output pump must be used. However, if a high-power pump is used, not only the liquid discharge device becomes larger than necessary, but also the power consumption may become excessive. Therefore, it is desired that the flow rate does not impose a burden on the liquid ejection device in suppressing the thickening of the ink.

In view of the above circumstances, the liquid ejection device 1 according to the present embodiment is a liquid ejection device for circulating the ink in the individual flow path Pa in order to suppress the thickening of the ink in the ejection unit D. Determine the optimum flow rate for 1. In the following description, the flow rate will be referred to as "circulating flow rate". Here, the residual vibration generated by supplying the drive signal COM-B to the detection target ejection unit Ds affects the thickening state of the ink in the ejection unit D. Therefore, in the present embodiment, the residual vibration is used as an index in determining the circulating flow rate. Hereinafter, the operation of such a liquid discharge device 1 will be described with reference to FIG. 10 as appropriate. FIG. 10 is a flowchart showing an example of the operation of the liquid discharge device 1 according to the present embodiment.

The liquid discharge device 1 according to the present embodiment receives an input from a user, changes in the surrounding environment in which a sensor (not shown) is placed, a distance between the nozzle N and the medium P, and the like. Alternatively, steps S10 to S20, which will be described later, are executed by detecting changes in the volatility and viscosity of the ink.

First, the flow rate determining unit 23 sets the flow rate of the ink circulating in the individual flow path Pa (S10). In this embodiment, an example is a case where the flow rate determination unit 23 sets the flow rate of the ink circulating in the individual flow path Pa to the maximum value of the flow rate of the ink that can be circulated in the individual flow path Pa in step S10. Assumed as. Next, the circulation control unit 21 drives the first supply pump 261 and the second supply pump 262 so that the ink of the flow rate determined in step S10 or step S20 described later circulates in the individual flow path Pa. The circulation mechanism 26 is controlled (S11).

Next, the control unit 2 controls each unit of the liquid discharge device 1 so that the flushing process is executed. Specifically, the liquid ejection device 1 first moves the head module 3 and the ejected ink receiving unit 400 so as to overlap each other in the Z-axis direction based on the control of the control unit 2. Secondly, based on the control of the control unit 2, by driving the 4M ejection units D provided in the head module 3, the ink in the ejection unit D is ejected to the ejected ink receiving unit 400 by the nozzle N. (S12). In step S12, typically, the control unit 2 drives the piezoelectric element PZ to perform a flushing process in which the ink in the ejection unit D is discharged, but the method is not limited to this, and the pressure chamber C is pressurized or pressed. A cleaning process may be performed in which the ink in the ejection portion D is forcibly ejected from the nozzle N by reducing the pressure. Note that step S12 may be executed before step S10.

Subsequently, the circulation control unit 21 controls the circulation mechanism 26 so that the state in which the ink of the flow rate determined in step S10 or step S20 circulates in the individual flow path Pa continues for a predetermined time (S13). The pressure in the pressure chamber C may be changed so that the ink is not ejected from the nozzle N.

After that, the control unit 2 selects the detection target discharge unit Ds from the discharge units D [1] to D [M]. In the following description, a case where the discharge unit D [m] is selected as the detection target discharge unit Ds will be described as an example. Next, the control unit 2 sets the individually designated signal Sd [m] to “5” so that the discharge unit D [m] is driven by the supply drive signal Vin having the waveform PS in the control period TSS1 and the control period is controlled. The switch circuit 31 is controlled so that the switch Rs [m] is turned on in TSS2. The detection circuit 33 detects the detection potential signal Vout from the discharge unit D [m] in the control period TSS2 (S14), and generates the residual vibration signal Vd [m]. The detection circuit 33 outputs the residual vibration signal Vd [m] to the amplitude specifying circuit 6. Step S14 is an example of the “detection step”.

Subsequently, the attenuation factor calculation unit 24 determines the detection potential signal Vout detected in step S14.
Using the amplitude information NSP generated based on the above, the attenuation rate of the amplitude of the residual vibration signal Vd [m] is calculated (S15).

Next, the control unit 2 determines whether or not the detection circuit 33 has acquired the detection potential signal Vout from the discharge unit D [m] a predetermined number of times after the process of step S11 (S16). If the result of the determination in step S16 is negative, the control unit 2 advances the process to step S13. In this embodiment, it is assumed that the specified number of times is two or more.

In the following, of the two processes selected from the processes of step S14 executed a specified number of times after the process of step S11, the earlier process is referred to as a preceding detection process, and the subsequent process is referred to as a preceding detection process. This is called the trailing detection process. Further, by shortening the predetermined time for continuing the ink circulation in step S13 to a certain extent and increasing the specified number of times, an approximate curve of the change in the attenuation rate with the passage of time can be accurately obtained, and the approximate curve can be obtained. It is also possible to select a preceding detection process and a subsequent detection process based on the above.
In the present embodiment, the control period TSS2 corresponding to the preceding detection process is an example of the “first detection period”, and may be hereinafter referred to as the first detection period. The control period TSS1 corresponding to the advance detection process is an example of the “first drive period”. Further, the attenuation factor calculated in the process of step S15 following the advance detection process is referred to as a "first attenuation rate".
Further, in the present embodiment, the control period TSS2 corresponding to the subsequent detection process is an example of the “second detection period”, and may be hereinafter referred to as the second detection period. The control period TSS1 corresponding to the trailing detection process is an example of the “second drive period”. Further, the attenuation factor calculated in the process of step S15 following the subsequent detection process is referred to as a "second attenuation rate".

In the present embodiment, the time interval between the end time of the first detection period and the start time of the second detection period may or may not be constant. Alternatively, the time interval may be longer than the time required for the carriage transfer mechanism 71 to move the recording head 32 from one end of the medium P in the Y-axis direction to the other end of the medium P in the Y-axis direction. Further, the time interval between the end time of the first detection period and the start time of the second detection period is the time interval from the start time when the head module 3 executes the flushing process to the start time when the next flushing process is executed. It may be the above. The time interval between the end time of the first detection period and the start time of the second detection period is an example of the "first time".

Next, when the detection circuit 33 acquires the detection potential signal Vout from the discharge unit D [m] a specified number of times (YES in S16), the change amount calculation unit 25 determines the difference between the first attenuation factor and the second attenuation factor. A certain amount of change is calculated (S17). When the change amount is equal to or less than a predetermined threshold value (YES in S18), the flow rate determining unit 23 determines the flow rate of the ink circulating in the individual flow path Pa by the circulation mechanism 26 under the control of the circulation control unit 21 in step S11. The flow rate is set to be smaller than the flow rate of the circulating ink (S20), and the process proceeds to step S11. Step S20 is an example of the “setting process”. If the flow rate of the ink circulating in the individual flow path Pa is set to the maximum value before the process of step S20 is executed, the step S12 executed after step S20 may be omitted. However, if thickening of the ink in the ejection unit D [m] is confirmed in the process of acquiring the residual vibration from the ejection unit D [m] a plurality of times, step 12 after step S20 is not omitted. The above-mentioned "maximum value" is determined according to the flow path resistance of the individual flow path Pa, the mechanical strength of the recording head 32, or the performance of the circulation mechanism 26.

On the other hand, when the amount of change, which is the difference between the first attenuation factor and the second attenuation factor, is larger than a predetermined threshold value (NO in S18), the flow rate determining unit 23 is the flow rate immediately before changing to the flow rate corresponding to the change amount. Is determined as the circulating flow rate (S19). That is, the smallest flow rate among the flow rates in which the amount of change, which is the difference between the first damping rate and the second damping rate, is smaller than the predetermined threshold value is determined as the circulating flow rate. The above-mentioned "threshold value" is a boundary value at which the ejection stability of the recording head 32 is ensured, and is a value confirmed in advance by an experiment or the like.

In the present embodiment, in step S10, the flow rate of the ink circulating in the individual flow path Pa is set to the maximum flow rate of the ink circulating in the individual flow path Pa, but the present invention is limited to such an embodiment. It's not something. For example, in step S10, the flow rate determination unit 23 may set the flow rate of the ink circulating in the individual flow path Pa to an initial flow rate that is sufficiently smaller than the maximum flow rate. In this case, in step S17, it is determined whether or not the calculated change amount is equal to or more than a predetermined threshold value, and if it is equal to or more than a predetermined threshold value, the flow rate determining unit 23 in step S20 in the individual flow path Pa. The flow rate of the ink circulating in the above may be set to a flow rate higher than the flow rate of the ink circulated by the circulation mechanism 26 under the control of the circulation control unit 21 in step S11. When the amount of change calculated in step S17 is not equal to or greater than a predetermined threshold value, the flow rate corresponding to the amount of change can be determined as the circulating flow rate (S19).

<7. Conclusion of the first embodiment>
As described above, in the present embodiment, the amount of change, which is the difference between the damping rate of the residual vibration detected in the first detection period and the damping rate of the residual vibration detected in the second detection period, is calculated. Then, among the flow rates of the ink circulating in the individual flow path Pa, the change amount is smaller than the predetermined threshold value, and a smaller flow rate can be found. As a result, by setting the flow rate of the ink circulating in the individual flow path Pa to the found flow rate, problems caused by the excessive flow rate are suppressed, and the thickening of the ink in the ejection portion D is suppressed, so that the liquid is liquid. Discharge failure of the discharge device 1 is suppressed.

B. Second Embodiment Hereinafter, the second embodiment of the present invention will be described. For the elements whose actions and functions are the same as those of the first embodiment in the embodiments exemplified below, the reference numerals used in the description of the first embodiment are diverted, and detailed description of each is appropriately omitted or simplified.

<8. Operation of liquid discharge device>
FIG. 11 is a flowchart showing an example of the operation of the liquid discharge device 1 according to the second embodiment. Hereinafter, an example of the operation of the liquid discharge device of the second embodiment will be described with reference to FIG. 11 as appropriate. In the following description of the operation, the same steps as the operation of the liquid discharge device 1 according to the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 11, the control unit 2 first sets the variable n to “1” (S21). Here, the variable n is a natural number satisfying "n ≧ 1". Next, the control unit 2 executes the processes of steps S10 to S17 described above. In the present embodiment, the difference between the first attenuation factor and the second attenuation factor is referred to as a change amount ΔG (n). Next, the control unit 2 determines whether or not the amount of change ΔG (n) is larger than the predetermined threshold value Gth. Then, when the determination result in step S22 is affirmative (YES in S22), the control unit 2 adds 1 to the variable n (S23).

Next, the control unit 2 calculates the change amount dL (n) (S24). The amount of change dL (n) calculated in step S24 is calculated by the following equation (3). N in the equation (3) is a natural number satisfying “n ≧ 2”. Further, in the present embodiment, the value ΔdL (n) in the equation (3) is a real number larger than “0”. In the present embodiment, the change amount dL (1) is a predetermined initial flow rate Lini.

dL (n) = dL (n-1) -ΔdL ... (3)
Subsequently, under the control of the circulation control unit 21, the flow rate of the ink circulating in the individual flow path Pa by the circulation mechanism 26 is increased by the amount of change dL (n) with respect to the flow rate L (n-1) (S25). , The process proceeds to step S11.

On the other hand, when the result of the determination in step S22 is negative (NO in S22), the control unit 2 calculates the absolute value of the difference between the change amount ΔG (n) and the threshold value Gth. Then, the control unit 2 determines whether or not the absolute value is equal to or less than a predetermined value (S26). Then, when the determination result in step S26 is negative (NO in S26), the control unit 2 adds 1 to the variable n (step S28). Subsequently, the control unit 2 executes the same process as in step S24 to calculate the change amount dL (n) (S29), and the circulation mechanism 26 circulates the individual flow path Pa under the control of the circulation control unit 21. The flow rate of the ink being made is reduced by the amount of change dL (n) with respect to the flow rate L (n-1) (S30), and the process proceeds to step S11.

On the other hand, when the determination result in step S26 is affirmative (YES in S26), the control unit 2 determines the flow rate L (n) as the circulating flow rate (S27). N of the flow rate L (n) is a natural number satisfying “n ≧ 1”.

FIG. 12 is an explanatory diagram showing the relationship between the flow rate L (n) set for the nth time and the change amount ΔG (n) calculated in the process when the process shown in FIG. 11 is executed. Is.

As illustrated in FIG. 12, the control unit 2 sets the flow rate L (1) to the initial flow rate Lini, and sets the flow rate L (2) to a flow rate that is larger than the flow rate L (1) by the amount of change dL (2). Also, the flow rate L (3) is set to a flow rate that is larger than the flow rate L (2) by the amount of change dL (3). Here, the amount of change dL (1) and the amount of change dL (2) satisfy "dL (1)> dL (2)". In the example shown in FIG. 12, the change amount ΔG (3) corresponding to the flow rate L (3) is smaller than the threshold value Gth, and the absolute value of the difference between the change amount ΔG (3) and the threshold value Gth is a predetermined value. Imagine a case larger than. Therefore, in the example shown in FIG. 12, the control unit 2 sets the flow rate L (4) to a flow rate that is smaller than the flow rate L (3) by the amount of change dL (4). In the example shown in FIG. 12, it is assumed that the absolute value of the difference between the change amount ΔG (4) and the threshold value Gth is equal to or less than a predetermined value. Therefore, the control unit 2 determines the flow rate L (4) corresponding to the change amount ΔG (4) as the circulation flow rate. In this example, by setting ΔdL (n) so that dL (1)> dL (2)> dL (3)> dL (4), the amount of change ΔG (n) and the threshold value Gth are gradually set. It is possible to approach the flow rate in which the absolute value of the difference between the two is smaller than the predetermined value.

In the present embodiment, the change amount ΔG (n1) is equal to or less than the threshold Gth, the change amount ΔG (n2) is equal to or less than the threshold Gth, and the absolute value of the difference between the change amount ΔG (n2) and the threshold Gth is When it is smaller than the absolute value of the difference between the amount of change ΔG (n1) and the threshold Gth, the flow rate L (n2) may be determined as the circulating flow rate. Here, the value n1 is a natural number satisfying "n1 ≧ 1", and the value n2 is a natural number satisfying "n2> n1".

In the present embodiment, among the periods in which the change amount ΔG (n1) is calculated, the control period TSS2 corresponding to the advance detection process is an example of the “first detection period”, and the control period corresponding to the advance detection process. TSS1 is an example of the "first drive period". Further, the attenuation factor calculated in the process of step S15 following the advance detection process is an example of the “first attenuation rate”. Further, in the present embodiment, among the periods in which the change amount ΔG (n1) is calculated, the control period TSS2 corresponding to the trailing detection process is an example of the “second detection period”, and is used in the trailing detection process. The corresponding control period TSS1 is an example of a “second drive period”. Further, the attenuation factor calculated in the process of step S15 following the follow-on detection process is an example of the “second attenuation rate”.

Further, in the present embodiment, among the periods in which the change amount ΔG (n2) is calculated, the control period TSS2 corresponding to the advance detection process is an example of the “third detection period” and corresponds to the advance detection process. The control period TSS1 is an example of the “third drive period”. Further, the attenuation factor calculated in the process of step S15 following the advance detection process is another example of the “first attenuation rate”. Further, in the present embodiment, among the periods in which the change amount ΔG (n2) is calculated, the control period TSS2 corresponding to the trailing detection process is an example of the “fourth detection period”, and is used in the trailing detection process. The corresponding control period TSS1 is an example of the "fourth drive period". Further, the attenuation factor calculated in the process of step S15 following the follow-on detection process is another example of the “second attenuation rate”. Further, in the present embodiment, the flow rate L (n1) is an example of the "first flow rate", and the flow rate L (n2) is an example of the "second flow rate".

<9. Conclusion of the second embodiment>
As described above, in the second embodiment, the absolute value of the difference between the threshold value Gt and the change amount ΔG (n) is increased or decreased by increasing or decreasing the flow rate of the ink circulating in the individual flow path Pa using the threshold value Gth as an index. Search for a flow rate where is less than or equal to a predetermined value. Therefore, by setting the flow rate of the ink circulating in the individual flow path Pa to the flow rate obtained as the search result, the flow rate of the ink circulating in the individual flow path Pa is not increased more than necessary in the ejection unit D. The progress of thickening of the ink is reduced. Further, as described above, since it is possible to suppress the increase in the flow rate of the ink circulating in the individual flow path Pa more than necessary, the liquid ejection device 1 can be used without imposing an excessive load on the liquid ejection device 1. Discharge failure is suppressed.

C. Modification example Each of the above forms can be variously transformed. Specific embodiments will be illustrated below. Two or more embodiments arbitrarily selected from the following examples may be applied to each other to the extent that they do not contradict each other. In the modified examples exemplified below, for the elements whose actions and functions are equivalent to those of the embodiment, the reference numerals may be used and detailed description of each may be omitted as appropriate.

[Modification 1]
In the above-described embodiment, the liquid ejection device 1 is a serial type inkjet printer, but the present invention is not limited to such an aspect, and may be, for example, a line type inkjet printer. In this case, the time interval between the end time of the first detection period and the start time of the second detection period may be set to be longer than the period during which the liquid discharge device 1 prints an image on the medium P.

[Modification 2]
The liquid ejection device 1 of the above-described embodiment may have a different configuration from the piezoelectric element driven when detecting residual vibration and the piezoelectric element driven when ejecting ink from the nozzle N.

[Modification 3]
In the control unit 2 of the liquid ejection device 1 of the above-described embodiment, the head module 3 is sent to the discharged ink receiving unit 400 before the printing process, during the printing process, and after the printing process, based on the calculation result of the damping factor calculation unit 24. The predetermined time interval for executing the maintenance process for executing the flushing process and the cleaning process for ejecting ink may be changed.

[Modification 4]
In the above-described embodiment, the time interval between the end time of the first detection period and the start time of the second detection period is, for example, the next flushing process is executed from the start time when the head module 3 executes the flushing process. The present invention is not limited to such an embodiment, although it is equal to or longer than the time interval until the start time. Based on the print data Img acquired from the host computer, the control unit 2 has a nozzle having the longest ink ejection period among the plurality of nozzles N between the time when the flushing process is executed and the time when the flushing process is executed next. Identify N. The time interval between the end time of the first detection period and the start time of the second detection period may be longer than that period.

[Modification 5]
In step S14 of the above-described embodiment, ink is ejected from 50% or more of the nozzles N among the plurality of nozzles N within the same unit period Tu, and the drive signal COM-is sent to the piezoelectric element corresponding to the nozzle N for ejecting the ink. The drive signal COM-B may be supplied to the piezoelectric element corresponding to the nozzle N that supplies A and does not eject ink to detect the detection potential signal Vout. In this case, ink is ejected from 50% or more of the nozzles N among the plurality of nozzles N, and residual vibration is detected from the piezoelectric element corresponding to the nozzle N of less than 50% that does not eject ink, and is based on the detected residual vibration. The circulation flow rate can be determined.

[Modification 6]
The circulation control unit 21 of the above-described embodiment determines the flow rate of the ink circulating in the individual flow path Pa according to the number of nozzles in which the ink is ejected to the medium P in the same unit period Tu based on the print data Img. You may control it. In this case, for example, the storage unit 5 stores a table in which the number of nozzles ejecting ink within the same unit period Tu among the plurality of nozzles N and the corresponding flow rate are associated with each other, and the print data is stored. Based on Img, the circulation control unit 21 refers to the individual flow path Pa according to the average value or the maximum value of the number of nozzles ejected ink within the same unit period Tu with respect to the medium P. The flow rate circulating in the water may be controlled.

[Modification 7]
In the above-described embodiment, the amount of change is calculated from the difference between the damping rate of the residual vibration detected in the first detection period and the damping rate of the residual vibration detected in the second detection period after the first detection period. However, the aspect of the present invention is not limited to such an aspect, and the damping rate and the amount of change may be calculated from one residual vibration.
Specifically, for example, the amplitude calculation circuit 640 specifies the amplitude VMq1 to the amplitude VMq4 of the residual vibration signal Vd [m] of the residual vibration detected in the first detection period. The attenuation factor calculation unit 24 calculates the attenuation factor by substituting the amplitude VMq1 and the amplitude VMq2 indicated by the two amplitude information NSPs corresponding to the period Wq1 and the period Wq2 into the equation (2). Further, the attenuation factor calculation unit 24 calculates the attenuation factor by substituting the amplitude VMq3 and the amplitude VMq4 indicated by the two amplitude information NSPs corresponding to the period Wq3 and the period Wq4 into the following equation (4). Then, the change amount calculation unit 25 calculates the change amount which is the difference between the attenuation rate of the amplitude VMq2 with respect to the amplitude VMq1 and the attenuation rate of the amplitude VMq4 with respect to the amplitude VMq3. The variable q3 in the equation (4) is a natural number satisfying "q3>2" and "q3>q2", and the variable q4 is a natural number satisfying "q4>3" and "q4>q3".

(VMq3-VMq4) / VMq3 ... (4)

D: Supplement The liquid ejection device exemplified in the above-described embodiment may be adopted in various devices such as a facsimile machine and a copier, in addition to a device dedicated to printing, and the use of the present invention is not particularly limited. However, the application of the liquid discharge device is not limited to printing. For example, a liquid discharge device that discharges a solution of a coloring material is used as a manufacturing device for forming a color filter of a display device such as a liquid crystal display panel. Further, a liquid discharge device that injects a solution of a conductive material is used as a manufacturing device for forming wirings and electrodes of wiring members. Further, a liquid discharge device for injecting a solution of an organic substance related to a living body is used, for example, as a manufacturing device for manufacturing a biochip.

Moreover, the effects described herein are merely explanatory or exemplary and are not limiting. That is, the present invention may exhibit other effects apparent to those skilled in the art from the description herein, with or in place of the above effects.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person having ordinary knowledge in the technical field of the present invention can come up with various modifications or modifications within the scope of the technical ideas described in the claims. Of course, it is understood that the above also belongs to the technical scope of the present invention.

E: Addendum For example, the following configuration can be grasped from the above-exemplified forms.

The control method of the liquid discharge device according to the first aspect, which is one aspect of the present invention, is a control method of the liquid discharge device having a discharge portion for discharging the liquid in the pressure chamber from the nozzle according to the drive of the piezoelectric element. Based on the detection step of detecting the residual vibration generated in the discharge portion according to the drive of the piezoelectric element and the detection result of the residual vibration, the liquid in the pressure chamber is supplied from the supply flow path for supplying the liquid to the pressure chamber. It is provided with a setting step of setting the circulation flow rate of the liquid circulating in the recovery flow path for collecting the liquid.
According to this aspect, by controlling the flow rate of the liquid circulating from the supply flow path to the recovery flow path using the residual vibration generated in the discharge section as an index, the thickening of the liquid in the discharge section is suppressed and the liquid discharge device is used. It is possible to suppress the discharge failure of.

According to the second aspect, which is a specific example of the first aspect, in the detection step, the residual vibration generated in the discharge portion is detected in the first detection period, and in the second detection period after the first detection period. The residual vibration generated in the discharge portion is detected, and in the setting step, the damping rate of the residual vibration detected in the first detection period and the damping rate of the residual vibration detected in the second detection period are used. , The circulation flow rate is set.
According to this aspect, the damping rate of residual vibration is adopted as an index for controlling the flow rate of the liquid circulating from the supply flow path to the recovery flow path. As a result, the flow rate can be controlled after quantitatively grasping the degree of thickening of the liquid in the discharge portion.

According to the third aspect, which is a specific example of the second aspect, the circulation flow rate is set to the first flow rate from before the start of the first detection period to the end of the second detection period, and the detection is performed in the first detection period. After the end of the second detection period, when the first change amount, which is the difference between the decay rate of the residual vibration detected and the damping rate of the residual vibration detected in the second detection period, is smaller than a predetermined threshold value. In the setting step in the above, the circulation flow rate is set to the first flow rate.
According to this aspect, the amount of change, which is the difference between the damping rate of the residual vibration detected in the first detection period and the damping rate of the residual vibration detected in the second detection period, is calculated. Then, among the flow rates of the liquid circulating from the supply flow path to the recovery flow path, a flow rate whose change amount is smaller than a predetermined threshold value is found. As a result, by setting the flow rate of the liquid circulating from the supply flow path to the recovery flow path as the found flow rate, the thickening of the liquid in the discharge portion is suppressed, and the discharge failure of the liquid discharge device is suppressed.

According to the fourth aspect, which is a specific example of the second aspect or the third aspect, in the detection step, the piezoelectric element is driven in the first driving period, and the piezoelectric element is driven in the second driving period after the first driving period. The piezoelectric element is driven, the circulation flow rate is set to the first flow rate from before the start of the first drive period to the end of the second detection period, and the first detection period is the end of the first drive period. It is a period that is started later and ends before the start of the second drive period, and the second detection period may be characterized in that it starts after the end of the second drive period.

According to Aspect 5, which is a specific example of any one of Aspects 2 to 4, the liquid discharge device includes a recording head having the discharge portion and a medium in which an image is formed by the liquid discharged from the discharge portion. It has a transport mechanism for transporting and a moving mechanism for moving the recording head in a second direction intersecting the first direction in which the medium is transported, and the second detection period ends the first detection period. The first time is started at a time when the first time has elapsed from the time when the recording head is moved, and the first time is longer than the time required for the moving mechanism to move the recording head from one end to the other end of the medium in the second direction. It is characterized by being.
According to this aspect, the operation of moving the recording head from one end to the other end of the medium can be interposed between the end of the first detection step and the start of the second detection step. This makes it possible to detect residual vibration generated in the ejection portion while forming an image on the medium.

According to Aspect 6, which is a specific example of any one of Aspects 2 to 4, the liquid discharge device is subjected to a maintenance process for discharging the liquid in the pressure chamber from the nozzle at predetermined time intervals, and the first step is performed. The time interval from the end of one detection period to the start of the second detection period may be characterized by being equal to or longer than the predetermined time interval.

According to the seventh aspect, which is a specific example of any one of the second aspect to the sixth aspect, the discharge step of discharging the liquid in the pressure chamber from the nozzle is further provided, and the circulation flow rate is before the start of the first detection period. Is set to the first flow rate, and the discharge step may be characterized in that the liquid in the pressure chamber is discharged from the nozzle before the start of the first detection period.

According to the eighth aspect, which is a specific example of the third aspect, in the detection step, the residual vibration generated in the discharge portion is further detected in the third detection period after the second detection period, and the third detection is performed. In the fourth detection period after the period, the residual vibration generated in the discharge portion is detected, and the circulation flow rate is set to be higher than the first flow rate from before the start of the third detection period to the end of the fourth detection period. The second change amount, which is the difference between the attenuation rate of the residual vibration detected in the third detection period and the attenuation rate of the residual vibration detected in the fourth detection period, set to a small second flow rate, and the second change amount. When the amount of change is smaller than the threshold value, the setting step is characterized in that the circulating flow rate after the end of the fourth detection period is set to the second flow rate.
According to this aspect, the progress of thickening of the liquid in the discharge portion is reduced without increasing the flow rate of the liquid circulating from the supply flow path to the recovery flow path more than necessary. In addition, since it is possible to suppress an increase in the flow rate of the liquid circulating from the supply flow path to the recovery flow path more than necessary, the liquid discharge device may have a discharge failure without imposing an excessive load on the liquid discharge device. It is suppressed.

According to Aspect 9, which is a specific example of any one of Aspects 1 to 8, the liquid discharge device is subjected to a maintenance process for discharging the liquid in the pressure chamber from the nozzle at predetermined time intervals, and the piezoelectric is discharged. It is further characterized by further comprising a step of changing the predetermined time interval for executing the maintenance process based on the attenuation rate of the residual vibration detected in the detection period after the element is driven.
According to this aspect, the liquid in the pressure chamber can be discharged from the nozzle at an arbitrary timing when the thickening of the ink in the ejection portion is confirmed.

The liquid discharge device according to the tenth aspect, which is one aspect of the present invention, is generated in the discharge portion for discharging the liquid in the pressure chamber from the nozzle according to the drive of the piezoelectric element and in the discharge portion according to the drive of the piezoelectric element. Circulation of the liquid that circulates from the detection unit that detects the residual vibration and the supply flow path that supplies the liquid to the pressure chamber to the recovery flow path that collects the liquid in the pressure chamber based on the detection result of the residual vibration. It is provided with a setting unit for setting the flow rate.

1 ... Liquid discharge device, 2 ... Control unit, 3 ... Head module, 4 ... Drive signal generation circuit, 5 ... Storage unit, 6 ... Amplitude specification circuit, 7 ... Conveyance mechanism, 31 ... Switch circuit, 32 ... Recording head, 33 ... Detection circuit, D ... Discharge section, HU ... Head unit.

Claims (10)

It is a control method of a liquid discharge device having a discharge unit that discharges a liquid in a pressure chamber from a nozzle according to the drive of a piezoelectric element.
A detection step for detecting residual vibration generated in the discharge portion according to the drive of the piezoelectric element, and
Based on the detection result of the residual vibration, the setting step of setting the circulation flow rate of the liquid circulating from the supply flow path for supplying the liquid to the pressure chamber to the recovery flow path for collecting the liquid in the pressure chamber is provided. How to control the liquid discharge device. In the detection step,
In the first detection period, the residual vibration generated in the discharge part is detected, and the residual vibration is detected.
In the second detection period after the first detection period, the residual vibration generated in the discharge portion is detected.
In the setting process,
The damping rate of the residual vibration detected during the first detection period and
The control method for a liquid discharge device according to claim 1, wherein the circulation flow rate is set based on the damping rate of the residual vibration detected in the second detection period. From before the start of the first detection period to the end of the second detection period, the circulation flow rate is set to the first flow rate.
When the first change amount, which is the difference between the damping rate of the residual vibration detected in the first detection period and the damping rate of the residual vibration detected in the second detection period, is smaller than a predetermined threshold value, the said The control method for a liquid discharge device according to claim 2, wherein the circulation flow rate is set to the first flow rate in the setting step after the end of the second detection period. In the detection step, the piezoelectric element is driven in the first drive period, and the piezoelectric element is driven in the second drive period after the first drive period.
From before the start of the first drive period to the end of the second detection period, the circulation flow rate is set to the first flow rate.
The first detection period is a period that starts after the end of the first drive period and ends before the start of the second drive period.
The control method for a liquid discharge device according to claim 2 or 3, wherein the second detection period is started after the end of the second drive period. The liquid discharge device is
A recording head having the discharge portion and
A transport mechanism that transports a medium on which an image is formed by the liquid discharged from the discharge unit, and
It has a moving mechanism for moving the recording head in a second direction intersecting the first direction in which the medium is conveyed.
The second detection period is started at a time when the first time has elapsed from the time when the first detection period ends.
The first time is more than the time required for the moving mechanism to move the recording head from one end to the other end of the medium in the second direction, according to claims 2 to 4. The method for controlling a liquid discharge device according to any one of them. The liquid discharge device is subjected to maintenance processing for discharging the liquid in the pressure chamber from the nozzle at predetermined time intervals.
The time interval from the end of the first detection period to the start of the second detection period is
The control method for a liquid discharge device according to any one of claims 2 to 4, wherein the time interval is equal to or longer than the predetermined time interval. A discharge step for discharging the liquid in the pressure chamber from the nozzle is further provided.
Prior to the start of the first detection period, the circulating flow rate was set to the first flow rate.
In the discharge process,
The control method for a liquid discharge device according to any one of claims 2 to 6, wherein the liquid in the pressure chamber is discharged from the nozzle before the start of the first detection period. In the detection step, further
In the third detection period after the second detection period, the residual vibration generated in the discharge portion is detected.
In the fourth detection period after the third detection period, the residual vibration generated in the discharge portion was detected.
From before the start of the third detection period to the end of the fourth detection period, the circulation flow rate is set to a second flow rate smaller than the first flow rate.
The second change amount, which is the difference between the damping rate of the residual vibration detected in the third detection period and the damping rate of the residual vibration detected in the fourth detection period, and the first change amount are from the threshold value. The control method for the liquid discharge device according to claim 3, wherein in the setting step, the circulating flow rate after the end of the fourth detection period is set to the second flow rate. The liquid discharge device is subjected to maintenance processing for discharging the liquid in the pressure chamber from the nozzle at predetermined time intervals.
A claim is further comprising a step of changing the predetermined time interval for executing the maintenance process based on the damping rate of the residual vibration detected in the detection period after the piezoelectric element is driven. The control method for a liquid discharge device according to any one of claims 1 to 8. A discharge part that discharges the liquid in the pressure chamber from the nozzle according to the drive of the piezoelectric element,
A detection unit that detects residual vibration generated in the discharge unit in response to the drive of the piezoelectric element, and a detection unit.
A setting unit for setting the circulation flow rate of the liquid circulating from the supply flow path for supplying the liquid to the pressure chamber to the recovery flow path for collecting the liquid in the pressure chamber based on the detection result of the residual vibration is provided. Liquid discharge device.

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