JP2021146674A - Liquid discharge device - Google Patents

Abstract

To provide a liquid discharge device that can appropriately suppress poor discharging of dispersed liquid from a liquid discharge hole of a liquid discharge head.SOLUTION: In a recording device 1, a measuring part 731 measures a vibration of liquid surface LS of ink in an opening edge 535E of a liquid discharge hole 535. This enables the measuring part 731 to obtain a viscosity index value IV as an index of viscosity change caused by drying of the liquid surface LS. An analyzing part 74 performs analysis processing for determining change with time of the viscosity index value IV on the liquid surface LS in the liquid discharge hole 535, on the basis of a measured result by the measuring part 731. Analysis information AIF showing a result of the analysis processing by the analyzing part 74 is outputted toward a control part 90. The control part 90 determines a timing for executing increased-viscosity removal processing for removing a viscosity-increased portion caused by drying of the liquid surface LS, on the basis of the analysis information AIF, and enables the increased-viscosity removal processing to be executed at the timing for executing.SELECTED DRAWING: Figure 11

Description

The present invention relates to a liquid discharge device including a liquid discharge head that discharges a dispersion liquid in which particles are dispersed in an aqueous medium.

The inkjet recording device to which the liquid ejection device is applied is provided with a liquid ejection head that ejects ink (dispersion liquid) in which colored particles such as pigments and resin particles such as binder resin are dispersed in an aqueous medium. .. The liquid discharge head has a piezoelectric actuator (piezoelectric element) and a liquid discharge hole, and is configured to discharge ink from the liquid discharge hole according to the displacement of the piezoelectric actuator.

From the liquid surface of the ink at the open edge of the liquid discharge hole, the liquid component evaporates as the liquid surface dries due to contact with the outside air, and the viscosity of the ink may increase (thicken) in the vicinity of the liquid surface. be. In this case, ink may not be ejected from the liquid ejection holes, or ejection defects such as a decrease in the speed of ejected ink droplets may occur. In order to suppress such a phenomenon of discharge failure, it is necessary to remove the thickened portion due to the drying of the liquid surface.

Patent Document 1 discloses a technique for removing a thickened portion in the vicinity of the liquid level in the liquid discharge hole. In the prior art disclosed in Patent Document 1, the piezoelectric actuator is driven to slightly vibrate the liquid surface according to the detection temperature of the temperature sensor provided in the liquid discharge head to the extent that ink is not discharged from the liquid discharge hole. Vibration processing (empty drive operation) and forced ejection processing (preliminary ejection operation) for forcibly ejecting ink from the liquid ejection holes are performed.

International Publication No. 2010/106719

It is the temperature and humidity near the liquid surface where the evaporation of the liquid component occurs that affects the viscosity change due to the drying of the liquid surface in the liquid discharge hole. It is assumed that the temperature and humidity near the liquid surface are different from the detected values of the temperature sensor in the above-mentioned prior art, which are provided at positions that are not directly affected by the evaporation of the liquid component. That is, the detected value of the temperature sensor in the above-mentioned prior art is not an appropriate index showing the change in viscosity due to the drying of the liquid level in the liquid discharge hole. Therefore, in order to reliably remove the thickened portion near the liquid surface in the above-mentioned prior art, the execution timings of the vibration process and the forced discharge process must be set early with a margin. As a result, the vibration treatment and the forced ejection treatment are excessively performed, and not only the waiting time until the completion of these treatments becomes long, but also ink ejection failure may occur.

The present invention has been made in view of such circumstances, and an object of the present invention is a liquid discharge device capable of appropriately suppressing a defective discharge of a dispersed liquid from a liquid discharge hole of a liquid discharge head. Is to provide.

The liquid discharge device according to one aspect of the present invention has a pressurizing unit and a liquid discharge hole for discharging a dispersion liquid in which particles are dispersed in an aqueous medium according to the pressure applied by the pressurizing unit. By measuring the vibration of the liquid level of the liquid discharge head and the dispersion liquid at the open end edge of the liquid discharge hole according to the pressure applied by the pressurizing portion, an index of the change in viscosity due to the drying of the liquid level is performed. An analysis unit that acquires the viscosity index value to be obtained, and an analysis process that obtains a change with time of the viscosity index value based on the measurement result of the measurement unit, and outputs analysis information indicating the result of the analysis process. And a control unit that controls the liquid discharge head. When the analysis information is input, the control unit determines the execution timing of the thickening removal process by the liquid discharge head for removing the thickening portion due to the drying of the liquid level based on the analysis information. Then, the thickening removal process is executed at the execution timing.

According to this liquid discharge device, the measuring unit measures the vibration of the liquid level of the dispersion liquid at the open edge of the liquid discharge hole. As a result, the measuring unit can acquire a viscosity index value which is an appropriate index of the viscosity change on the liquid surface where the liquid component evaporates due to drying due to contact with the outside air.

The viscosity index value acquired by the measuring unit is output to the analysis unit. The analysis unit performs an analysis process for obtaining a change over time in the viscosity index value at the liquid level in the liquid discharge hole. The analysis information indicating the result of the analysis processing by the analysis unit is output to the control unit. Based on the input analysis information, the control unit determines the execution timing of the thickening removal process for removing the thickening portion due to the drying of the liquid surface, and executes the thickening removal process at the execution timing. .. Here, the analysis information used by the control unit is based on the measurement result of the measurement unit, and is information indicating the time-dependent change of the viscosity index value which is an appropriate index of the viscosity change at the liquid level in the liquid discharge hole. be. By using such analysis information, the control unit can execute the thickening removal process at an appropriate timing corresponding to the change in viscosity due to the drying of the liquid level in the liquid discharge hole. As a result, it is possible to prevent excessive execution of the thickening removal process. For this reason, it is possible to prevent the promotion of drying on the new liquid surface after the removal of the thickening portion due to the excessive execution of the thickening removal treatment as much as possible, and it is appropriate to prevent the dispersion liquid from being discharged from the liquid discharge hole. Can be suppressed.

In the above liquid discharge device, the measuring unit acquires the viscosity index values of three or more points having different drying times of the liquid surface, and the analysis unit acquires the viscosity index values of three or more points different from each other in the analysis process. Based on the viscosity index value above the point, an approximate curve showing the change with time of the viscosity index value is obtained as the analysis information, and the analysis process is terminated when the determination coefficient of the approximate curve becomes equal to or more than a predetermined threshold value. It may be configured to be.

In this aspect, the analysis unit can acquire the approximate curve as the analysis information by obtaining an approximate curve based on the viscosity index values of three or more points having different drying times acquired by the measurement unit. At this time, the analysis unit ends the analysis process when the coefficient of determination of the approximate curve becomes equal to or higher than a predetermined threshold value. That is, the analysis information is represented by an approximate curve in which the coefficient of determination is equal to or greater than a predetermined threshold value. As a result, the analysis information is represented by an approximate curve that accurately shows the change with time of the viscosity index value. By using such analysis information, the control unit can more accurately derive the execution timing of the thickening removal process corresponding to the change in viscosity due to the drying of the liquid surface in the liquid discharge hole.

In the above liquid discharge device, the analysis unit may have a configuration for obtaining the approximate curve by using an advection-diffusion equation capable of calculating the water concentration inside the liquid discharge hole.

There is a correlation between the water concentration of the dispersion liquid in the liquid discharge hole and the viscosity of the dispersion liquid near the liquid surface. In view of this fact, there is also a correlation between the viscosity index value on the liquid surface and the water concentration. Therefore, the analysis unit can obtain an approximate curve that accurately shows the change with time of the viscosity index value at a small number of measurement points of the viscosity index value by using the convection-diffusion equation that can calculate the water concentration in the analysis process. .. As a result, the time required for the measurement process of the measurement unit and the analysis process of the analysis unit can be shortened.

In the above liquid discharge device, when a liquid discharge request indicating a request for discharging the dispersion liquid from the liquid discharge hole is input, the control unit discharges the dispersion liquid from the liquid discharge hole in response to the liquid discharge request. The liquid discharge head is made to execute the liquid discharge process for driving the pressurizing unit so as to be discharged, and the measuring unit acquires the viscosity index value while the liquid discharge process is stopped by the liquid discharge head. It may be configured to be used.

In this aspect, the measuring unit performs a measurement process for acquiring a viscosity index value while the liquid discharge process is stopped in response to the liquid discharge request. As a result, it is possible to prevent a waiting time for waiting for the measurement process of the measuring unit from occurring during the execution of the liquid discharge process.

In the above liquid discharge device, the analysis unit may be configured to perform the analysis process while the liquid discharge process is stopped by the liquid discharge head.

In this aspect, the analysis unit performs an analysis process for obtaining a change with time of the viscosity index value while the liquid discharge process is stopped. As a result, it is possible to prevent a waiting time for waiting for the analysis process of the analysis unit from occurring during the execution of the liquid discharge process.

In the above liquid discharge device, the thickening removal treatment includes a vibration treatment that drives the pressurizing portion so that the liquid level vibrates within a range in which the discharge of the dispersion liquid from the liquid discharge hole can be regulated. The control unit includes a forced discharge process for forcibly discharging the dispersed liquid pressurized from the liquid discharge hole, and the control unit sets the execution timing of the forced discharge process later than the vibration process. You may.

In this aspect, the thickening removal process includes a vibration process and a forced discharge process. By vibrating the liquid level in the liquid discharge hole in the vibration treatment, the thickening portion near the liquid level can be diffused and the thickening portion can be removed. On the other hand, in the forced discharge process, the pressurized dispersion liquid is discharged from the liquid discharge hole, so that the thickened portion having a higher viscosity near the liquid surface can be forcibly discharged and removed.

As described above, according to the present invention, it is possible to provide a liquid discharge device capable of appropriately suppressing the discharge failure of the dispersed liquid from the liquid discharge hole of the liquid discharge head.

It is a figure which shows typically the recording apparatus to which the liquid discharge apparatus which concerns on one Embodiment of this invention is applied. It is a block diagram of a recording device. It is a figure which enlarges and shows the periphery of the liquid discharge head provided in the recording apparatus. It is sectional drawing which shows the internal structure of a liquid discharge head. It is sectional drawing which shows the main part of the liquid discharge head in an enlarged manner. It is a figure for demonstrating the liquid discharge process performed by a recording apparatus. It is a figure for demonstrating the cap process performed by a recording apparatus. It is a figure for demonstrating the vibration processing performed by a recording apparatus. It is a figure for demonstrating the 1st flushing process executed by a recording apparatus. It is a figure for demonstrating the 2nd flushing process executed by a recording apparatus. It is a figure for demonstrating the measurement process performed by a recording apparatus. It is a figure which shows the measurement result of the measuring part provided in the recording apparatus. It is a figure for demonstrating the analysis process of the analysis part provided in the recording apparatus. It is a flowchart which shows the processing flow of a measurement process and an analysis process. It is a figure for demonstrating the processing of the control part when the analysis information from an analysis part is input. It is a flowchart which shows the processing flow of a recording apparatus. It is a flowchart which shows the processing flow of a recording apparatus. It is a figure which shows the result of the experiment which evaluated the relationship between the execution timing of vibration control and the liquid discharge speed from a liquid discharge head.

Hereinafter, an inkjet recording device to which the liquid discharge device according to the embodiment of the present invention is applied will be described with reference to the drawings. In the following, the directional relationship will be described using the XYZ orthogonal coordinate axes. The X direction corresponds to the front-back direction (+ X is the back, -X is the front), the Y direction is the left-right direction (+ Y is the left, -Y is the right), and the Z direction is the up-down direction (+ Z is up, -Z is down). do. Further, in the following description, the term "sheet" means copy paper, coated paper, transparency sheet, cardboard, postcard, tracing paper and other sheet materials to be printed.

FIG. 1 is a diagram schematically showing a recording device 1 to which the liquid discharge device according to the embodiment of the present invention is applied. FIG. 2 is a block diagram of the recording device 1. FIG. 3 is an enlarged view of the periphery of the liquid discharge head 51 provided in the recording device 1. The recording device 1 is a liquid ejection device that ejects ink as a dispersion liquid, and is an inkjet type image forming apparatus that forms (records) an image on a sheet S by ejecting the ink. The ink is a dispersion liquid in which colored particles such as pigments and resin particles such as binder resin are dispersed in an aqueous medium. The ink may be a dispersion liquid, and its constituent components are not particularly limited.

The recording device 1 includes an apparatus main body 10, a paper feeding unit 20, a sheet reversing unit 30, a sheet transport unit 40, and a recording unit 50.

The device main body 10 is a box-shaped housing that houses various devices for recording images on the sheet S. The apparatus main body 10 is formed with a first transport passage 11, a second transport passage 12, and a third transport passage 13 that serve as transport passages for the seat S.

The paper feeding unit 20 feeds the sheet S to the first transport path 11. The paper feed unit 20 includes a paper feed cassette 21 and a pickup roller 22. The paper cassette 21 is removable from the device main body 10 and houses the sheet S inside. The pickup roller 22 is arranged at the end on the −Y side and the + Z side of the paper feed cassette 21. The pickup roller 22 feeds out the uppermost sheet S of the sheet bundle housed in the paper feed cassette 21 one by one and sends it out to the first transport path 11.

The sheet S fed into the first transport path 11 is a sheet transport unit 40 arranged at the downstream end of the first transport path 11 by the first transport roller pair 111 provided in the first transport path 11. It is conveyed to the resist roller pair 44. Further, a paper feed tray 25 is arranged on the side surface of the apparatus main body 10 on the −Y side, and the sheet S can be placed on the upper surface portion of the paper feed tray 25. The sheet S placed on the paper feed tray 25 is fed by the paper feed roller 24 toward the resist roller pair 44.

The resist roller pair 44 is a transport roller pair arranged at the upstream end of the sheet transport unit 40. The resist roller pair 44 performs skew correction of the sheet S, and sends the sheet S toward the transport belt 41 via the sheet introduction guide unit 23 at the timing of the printing process by the recording unit 50. The sheet introduction guide unit 23 guides the sheet S delivered by the resist roller pair 44 toward the outer peripheral surface 411 of the transfer belt 41 in the sheet transfer unit 40.

When the tip of the sheet S guided by the sheet introduction guide unit 23 comes into contact with the outer peripheral surface 411 of the transfer belt 41, the sheet S is conveyed in the sheet transfer direction A while being held on the outer peripheral surface 411 by the drive of the transfer belt 41. Will be done. The sheet transport direction A is a direction from the −Y side to the + Y side in the Y direction.

The sheet transport unit 40 is arranged on the −Z side of the recording unit 50 so as to face the liquid discharge head 51. The sheet transfer unit 40 conveys the sheet S guided and introduced by the sheet introduction guide unit 23 in the sheet transfer direction A so that the sheet S passes through the −Z side of the recording unit 50. The sheet transfer unit 40 includes a transfer belt 41 and a suction unit 43 in addition to the resist roller pair 44.

The transport belt 41 is an endless belt having a width in the X direction and extending in the Y direction. The transport belt 41 is arranged so as to face the recording unit 50, and transports the sheet S in the sheet transport direction A on the outer peripheral surface 411.

The transport belt 41 is stretched on a first roller 421, a second roller 422, a third roller 423, and a pair of fourth rollers 424. Inside the stretched transport belt 41, a suction portion 43 is arranged so as to face the inner peripheral surface 412. The first roller 421 is rotationally driven by a drive motor (not shown) to orbit the transport belt 41 in a predetermined orbital direction. As the transport belt 41 goes around, the sheet S held on the outer peripheral surface 411 is transported in the sheet transport direction A.

The second roller 422 is a belt speed detection roller extending along the X direction, and is arranged on the upstream side of the suction portion 43 in the sheet transport direction A. Here, on the outer peripheral surface 411 of the transport belt 41, a region facing the liquid discharge head 51 and between the first roller 421 and the second roller 422 is for holding and transporting the sheet S. It becomes the predetermined transport area. The second roller 422 is driven to rotate in conjunction with the rotation of the transport belt 41. A pulse plate (not shown) is attached to the second roller 422, and the pulse plate rotates integrally with the second roller 422. By measuring the rotation speed of the pulse plate, the rotation speed of the transport belt 41 is detected.

The third roller 423 is a tension roller extending in the X direction, and applies tension to the transport belt 41 so that the transport belt 41 does not bend. The third roller 423 rotates drivenly in conjunction with the rotation of the transport belt 41. Each of the pair of fourth rollers 424 is a guide roller extending in the Y direction, and guides the transport belt 41 so that the transport belt 41 passes through the −Z side of the suction portion 43. The pair of fourth rollers 424 are driven to rotate in conjunction with the rotation of the transport belt 41.

The transport belt 41 has a plurality of suction holes penetrating in the thickness direction from the outer peripheral surface 411 to the inner peripheral surface 412.

The suction unit 43 is arranged so as to face the recording unit 50 via the transport belt 41. The suction unit 43 causes the sheet S to be brought into close contact with the outer peripheral surface 411 of the transport belt 41 by generating a negative pressure between the sheet S held on the outer peripheral surface 411 of the transport belt 41 and the transport belt 41. The suction unit 43 includes a belt guide member 431, a suction housing 432, a suction device 433, and an exhaust duct 434.

The belt guide member 431 is arranged to face the region between the first roller 421 and the second roller 422 on the inner peripheral surface 412 of the transport belt 41, and has a length in the width direction (Y direction) of the transport belt 41. It is a plate having substantially the same width dimension. The belt guide member 431 constitutes the upper surface portion of the suction housing 432 and has substantially the same shape as the suction housing 432 when viewed from the + Z side. The belt guide member 431 guides the orbital movement of the transport belt 41 linked to the rotation of the first roller 421 between the first roller 421 and the second roller 422.

Further, the belt guide member 431 has a plurality of grooves formed on the belt guide surface facing the inner peripheral surface 412 of the transport belt 41. Each groove is formed corresponding to the suction hole of the transport belt 41. Further, the belt guide member 431 has a through hole provided corresponding to each groove. The through hole is a hole that penetrates in each groove in the thickness direction of the belt guide member 431, and communicates with the suction hole of the transport belt 41 through each groove.

The suction portion 43 provided with the belt guide member 431 configured as described above is provided from the space on the + Z side of the transport belt 41 via the groove portion and the through hole of the belt guide member 431 and the suction hole of the transport belt 41. A suction force is generated by sucking air. Due to this suction force, an air flow (suction wind) toward the suction portion 43 is generated in the space above the transport belt 41. When the seat S is guided on the transport belt 41 by the seat introduction guide portion 23 and covers a part of the outer peripheral surface 411 of the transport belt 41, a suction force (negative pressure) acts on the sheet S, and the sheet S is transferred to the transport belt. It is in close contact with the outer peripheral surface 411 of 41.

The suction housing 432 constitutes a support frame that supports the belt guide member 431 from below. The suction housing 432 is a box-shaped housing having an opening on the + Z side, and is arranged on the −Z side of the transport belt 41 so that the opening on the + Z side is covered by the belt guide member 431. The suction housing 432 defines the suction space 432A in cooperation with the belt guide member 431 constituting the upper surface portion thereof. That is, the space surrounded by the suction housing 432 and the belt guide member 431 becomes the suction space 432A. The suction space 432A communicates with the suction hole of the transport belt 41 through the groove portion and the through hole of the belt guide member 431.

An opening 432B is formed in the bottom wall portion of the suction housing 432, and a suction device 433 is arranged corresponding to the opening 432B. An exhaust duct 434 is connected to the suction device 433. The exhaust duct 434 is connected to an exhaust port (not shown) provided in the apparatus main body 10.

A recording unit 50 is arranged on the + Z side of the sheet transport unit 40. Specifically, the recording unit 50 is arranged on the + Z side of the sheet transfer unit 40 so as to face the outer peripheral surface 411 of the transfer belt 41. The recording unit 50 performs a printing process on the sheet S that is conveyed in the sheet conveying direction A while being held on the outer peripheral surface 411 of the conveying belt 41, and records an image. In the present embodiment, the recording method for image formation is an inkjet method, and the recording unit 50 discharges ink as a dispersion liquid and records an image on the sheet S.

The recording unit 50 includes liquid discharge heads 51Bk, 51C, 51M, 51Y held in the head housing 55. The liquid discharge head 51Bk discharges black ink, the liquid discharge head 51C discharges cyan ink, the liquid discharge head 51M discharges magenta ink, and the liquid discharge head 51Y discharges yellow ink. do. The liquid discharge heads 51Bk, 51C, 51M, and 51Y are arranged side by side from the upstream side to the downstream side in the sheet transport direction A. Since the liquid ejection heads 51Bk, 51C, 51M, and 51Y have the same configuration except that the colors of the ejected inks are different, they may be collectively referred to as the liquid ejection head 51.

The liquid discharge head 51 discharges ink to the sheet S transported in the sheet transport direction A while being held on the outer peripheral surface 411 of the transport belt 41, and records an image on the sheet S. Specifically, the liquid discharge head 51 discharges ink toward the sheet S which is conveyed by the transfer belt 41 and passes through a position facing the liquid discharge head 51. As a result, the image is recorded on the sheet S. Details of the liquid discharge head 51 will be described later.

The sheet S on which the image is recorded is conveyed by the transfer belt 41 and is sent to the transfer unit 45 arranged on the downstream side of the sheet transfer direction A of the transfer belt 41. The transport unit 45 further transports the sheet S received from the sheet transport unit 40 to the downstream side in the sheet transport direction A. A decaler unit 46 is arranged on the downstream side of the transport unit 45. The decaler unit 46 further conveys the sheet S to the downstream side in the sheet transfer direction A while correcting the curl of the sheet S received from the transfer unit 45. The sheet S transported by the decara unit 46 is delivered to the second transport path 12.

The second transport path 12 extends along the + Y side side surface of the apparatus main body 10. The sheet S sent out to the second transport path 12 is conveyed toward the paper ejection port 12A formed on the + Y side of the apparatus main body 10 by the second transport roller pair 121 provided in the second transport path 12. , Is discharged onto the paper ejection section 47 from the paper ejection port 12A.

On the other hand, when the sheet S sent to the second transport path 12 is for double-sided printing in which the printing process of the first surface (front surface) is completed, the sheet S is sent to the sheet reversing section 30. .. The sheet reversing portion 30 is a transport path branched in the middle of the second transport path 12, and is a portion where the sheet S is reversed (switched back). The sheet S whose front and back sides have been inverted by the sheet inversion unit 30 is sent to the third transport path 13. The sheet S sent out to the third transport path 13 is back-fed by the third transport roller pair 131 provided in the third transport path 13, and the front and back sides are turned through the resist roller pair 44 and the sheet introduction guide portion 23. In the inverted state, it is supplied again on the outer peripheral surface 411 of the transport belt 41. The sheet S supplied on the outer peripheral surface 411 of the transport belt 41 in such a state that the front and back sides are reversed is conveyed by the recording unit 50 on the second surface (opposite the first surface) while being conveyed by the transfer belt 41. The back side) is printed. The sheet S for which double-sided printing has been completed passes through the second transport path 12 and is discharged from the paper ejection port 12A onto the paper ejection portion 47.

As shown in FIG. 3, a container mounting unit 60 is arranged above the + Z side of the liquid discharge head 51 of the recording unit 50. A plurality of ink containers 61Y, 61M, 61C, 61Bk containing inks of each color of yellow (Y), magenta (M), cyan (C), and black (Bk) are detachably mounted on the container mounting portion 60. ing. The ink containers 61Y, 61M, 61C, 61Bk are liquid storage containers capable of storing ink as a liquid, and the liquid ejection heads 51Y, 51M, 51C, respectively, via the ink supply tube 62 and the sub ink tank 64 of each color. It is connected to 51Bk. Since the ink containers 61Y, 61M, 61C, and 61Bk have the same configuration except that the colors of the inks contained in them are different, they may be collectively referred to as the ink containers 61.

A solenoid valve 63 for opening and closing the ink flow path in the ink supply tube 62 is provided on the upstream side of the ink supply tube 62 with respect to the sub ink tank 64. The sub ink tank 64 is arranged between the ink container 61 and the liquid ejection head 51, and is a liquid storage tank that temporarily stores the ink in the ink container 61 before being supplied to the liquid ejection head 51. Is. In the present embodiment, the ink stored in the sub-ink tank 64 is supplied to the liquid ejection head 51. The sub-ink tank 64 is provided with an ink sensor (not shown) that detects the amount of ink in the sub-ink tank 64, and the electromagnetic valve 63 is opened according to the amount of ink to be opened from the ink container 61 to the sub-ink tank 64. Ink is replenished to 64. The sub-ink tank 64 is arranged at a position lower than that of the ink container 61, and the ink of the corresponding color from the ink container 61 is discharged from the sub-ink tank by the ink pressure generated by the height difference between the sub-ink tank 64 and the ink container 61. It is replenished to 64.

The liquid discharge head 51 included in the recording unit 50 will be described in detail with reference to FIGS. 4 and 5. The liquid discharge head 51 has an elongated shape extending in the X direction. The liquid discharge head 51 includes a liquid relay flow path member 52, a liquid discharge flow path member 53, and a piezoelectric actuator substrate 54. In the liquid discharge head 51, the liquid discharge flow path member 53 and the piezoelectric actuator board 54 are joined, and the liquid relay flow path member 52 is laminated on the liquid relay flow path member 52 so as to sandwich the piezoelectric actuator board 54. And glued. However, the piezoelectric actuator substrate 54 and the liquid relay flow path member 52 are not adhered to each other, and a space 524 is appropriately formed.

The liquid relay flow path member 52 has a substantially rectangular parallelepiped shape extending in the X direction, and constitutes a portion on the + Z side of the liquid discharge head 51. The liquid relay flow path member 52 guides the liquid inflow port 521 connected to the sub ink tank 64, the liquid relay port 522 connected to the liquid discharge flow path member 53, and the ink flowing in from the liquid inflow port 521 to the liquid relay port 522. It has an internal liquid relay flow path 523.

The liquid discharge flow path member 53 has a substantially rectangular parallelepiped shape extending in the X direction, is located on the −Z side of the liquid relay flow path member 52, and constitutes a portion of the liquid discharge head 51 on the −Z side. The liquid discharge flow path member 53 includes a common flow path 531, a plurality of individual supply flow paths 532, a plurality of liquid pressurizing chambers 533, a plurality of individual discharge flow paths 534, and a plurality of liquid discharge holes 535. Have.

The common flow path 531 is a flow path formed inside the liquid discharge flow path member 53 and connected to the liquid relay port 522 of the liquid relay flow path member 52. The plurality of individual supply flow paths 532 are internal flow paths of the liquid discharge flow path member 53 that are connected to the common flow path 531 in a separated state. In the plurality of individual supply flow paths 532, the end opposite to the side connected to the common flow path 531 is connected to the corresponding liquid pressurizing chamber 533. The plurality of liquid pressurizing chambers 533 are hollow regions opened on the upper surface of the liquid discharge flow path member 53. Each opening of the plurality of liquid pressurizing chambers 533 is closed by adhering the piezoelectric actuator substrate 54 to the upper surface of the liquid discharge flow path member 53. The plurality of individual discharge flow paths 534 are internal flow paths of the liquid discharge flow path member 53 connected to the corresponding liquid pressurizing chamber 533 in a separated state. In each of the plurality of individual discharge flow paths 534, the end opposite to the side connected to the liquid pressurizing chamber 533 is connected to the liquid discharge hole 535. The plurality of liquid discharge holes 535 are connected to the corresponding individual discharge flow paths 534 in a separated state. The plurality of liquid discharge holes 535 are opened on the lower surface of the liquid discharge flow path member 53. That is, the lower surface of the liquid discharge flow path member 53 constitutes a liquid discharge surface 535S in which a plurality of liquid discharge holes 535 are formed.

In the liquid discharge flow path member 53 configured as described above, the plurality of liquid pressurizing chambers 533 are connected to the common flow path 531 connected to the liquid relay port 522 of the liquid relay flow path member 52 via the individual supply flow path 532. It is connected. Further, the plurality of liquid pressurizing chambers 533 and the plurality of liquid discharge holes 535 are connected to each other via individual discharge flow paths 534.

As shown in FIG. 5, the piezoelectric actuator substrate 54 has a laminated structure in which the first piezoelectric ceramic layer 541 and the second piezoelectric ceramic layer 542 are laminated. The piezoelectric actuator substrate 54 further has a common electrode 543 and an individual electrode 544. The individual electrode 544 is an electrode arranged at a position facing the liquid pressurizing chamber 533 on the upper surface of the piezoelectric actuator substrate 54.

When the discharge drive signal CS1 (FIG. 6 described later) is supplied from the control unit 90 to the individual electrodes 544, the first piezoelectric ceramic layer 541 is piezoelectrically deformed, and pressure is applied to the ink in the liquid pressurizing chamber 533. The pressure applied to the ink propagates through the ink in the individual discharge flow paths 534, and the ink is discharged from the liquid discharge hole 535. That is, the piezoelectric element composed of the second piezoelectric ceramic layer 542, the common electrode 543, the first piezoelectric ceramic layer 541, and the individual electrode 544 located directly above each liquid pressurizing chamber 533 applies pressure to eject ink. It is a pressure portion 545. The pressurizing unit 545 may be any one to which pressure can be applied, and may be one other than the above-mentioned piezoelectric method, for example, one using an electrostatic method or a thermal method.

When the amount of ink in the common flow path 531 decreases according to the discharge of ink from the liquid discharge hole 535, the ink in the sub ink tank 64 moves through the liquid inflow port 521, the liquid relay flow path 523, and the liquid relay port 522 in this order. The common flow path 531 is replenished through the above.

As shown in FIG. 3, the liquid discharge head 51 is provided with a temperature / humidity detection sensor 56 and a warmer 57. The temperature / humidity detection sensor 56 detects the temperature of the ink in the liquid discharge head 51 by detecting the temperature of the liquid discharge head 51, and also detects the humidity around the liquid discharge head 51. The temperature / humidity detection sensor 56 is not particularly limited in its arrangement position as long as it can detect the temperature of the liquid discharge head 51 and the humidity around it. In the present embodiment, the temperature / humidity detection sensor 56 is arranged on the liquid relay flow path member 52 that constitutes the + Z side portion of the liquid discharge head 51. The warmer 57 heats the ink in the liquid discharge head 51 by heating the liquid discharge head 51.

As shown in FIG. 2, the recording device 1 further includes a flushing mechanism 64P, a maintenance unit 70, an analysis unit 74, an operation unit 81, a communication unit 82, a timekeeping unit 83, a storage unit 84, and a control unit 90. The maintenance unit 70 includes a cap unit 71 and a cleaning unit 72. A measurement unit 73 having a measurement unit 731 is arranged in the maintenance unit 70.

The operation unit 81 is composed of various operation keys, a touch panel, and the like for performing various settings and operation requests of the recording device 1. The communication unit 82 has a function of transmitting and receiving various data such as image data used for printing processing to and from an external device such as a personal computer via a network such as LAN (Local Area Network). The image data is an example of a liquid ejection request indicating an ink ejection request from the liquid ejection hole 535 of the liquid ejection head 51. The image data is a signal indicating which size of the pixel is formed on the sheet S by each of the plurality of liquid ejection holes 535 in the liquid ejection head 51. The image data received by the communication unit 82 is input to the control unit 90.

The timing unit 83 measures the drying time of the ink in the liquid discharge hole 535 due to contact with the outside air in a state where the ink is not discharged from the liquid discharge hole 535 of the liquid discharge head 51. During the drying time, in a state where the cap unit 71 described later is arranged in the retracted position with respect to the liquid ejection head 51, the cap unit 71 is prepared and waits so that the ink can be ejected from the liquid ejection hole 535 immediately. Wait time is included. Further, when the ink is ejected a plurality of times from the liquid ejection hole 535 according to the image data, the time between one ink ejection and the next ink ejection is also included in the drying time.

The storage unit 84 stores various information acquired by each process executed by the measurement unit 731 and the analysis unit 74, which will be described later.

The control unit 90 is an arithmetic processing circuit of a microcomputer or the like equipped with a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. A control program for controlling the operation of the recording device 1 is stored in the ROM. The control unit 90 reads the control program stored in the ROM and expands the control program in the RAM to control the entire device including the liquid discharge head 51, the flushing mechanism 64P, and the maintenance unit 70.

When the image data is input via the communication unit 82, the control unit 90 causes the liquid discharge head 51 to execute the liquid discharge process. This liquid discharge process will be described with reference to FIG. The liquid ejection process is a process of driving the pressurizing unit 545 so that ink is ejected from the liquid ejection hole 535 according to the image data. The control unit 90 causes the liquid discharge head 51 to execute the liquid discharge process by performing the liquid discharge control CX1. Specifically, the control unit 90 supplies a discharge drive signal CS1 including a pulse for driving the pressurizing unit 545 to the individual electrodes 544 constituting the pressurizing unit 545. The discharge drive signal CS1 is a drive signal in which the potential and pulse width of the individual electrodes 544 are set so that ink can be discharged from the liquid discharge hole 535. There are a plurality of types of the discharge drive signal CS1 depending on how the pressurizing unit 545 is driven. For example, the corresponding discharge drive signal CS1 corresponds to each of the plurality of liquid discharge holes 535, depending on which size pixel each of the plurality of liquid discharge holes 535 discharges ink droplets forming a pixel on the sheet S. It is supplied to the individual electrode 544 of the pressurizing unit 545.

When the pressurizing unit 545 is driven by supplying the discharge drive signal CS1 to the individual electrode 544, the pressure in the liquid pressurizing chamber 533 changes accordingly, and the liquid corresponding to the liquid pressurizing chamber 533 changes. Ink is ejected from the ejection hole 535. As a result, the image corresponding to the image data is recorded on the sheet S transported by the sheet transport unit 40.

When the liquid discharge head 51 executes the liquid discharge process, the control unit 90 determines that the head temperature of the liquid discharge head 51 is suitable for discharging ink from the liquid discharge hole 535 based on the detection result of the temperature / humidity detection sensor 56. The warmer 57 is controlled so that the temperature changes within a predetermined allowable range centered on the reference temperature. As a result, the head temperature of the liquid discharge head 51 can be changed in the vicinity of the reference temperature during the execution of the liquid discharge process by the liquid discharge head 51.

Further, when the liquid discharge head 51 executes the liquid discharge process, the control unit 90 arranges the maintenance unit 70 at a retracted position retracted in the horizontal direction (Y direction) with respect to the liquid discharge head 51. The maintenance unit 70 includes a cap unit 71 and a cleaning unit 72, and is a unit used when maintenance processing is performed on the liquid discharge head 51. The maintenance process is a process for preventing defective ink ejection from the liquid ejection hole 535 of the liquid ejection head 51, and includes a cap process and a thickening removal process. The control unit 90 causes the cap unit 71 to execute the cap processing, and causes the liquid discharge head 51 or the flushing mechanism 64P to execute the thickening removal processing.

First, the cap treatment will be described with reference to FIG. 7. The control unit 90 causes the cap unit 71 to execute the cap processing by performing the cap control CC while the liquid discharge processing by the liquid discharge head 51 is stopped. The cap unit 71 is a unit for capping the liquid discharge surface 535S in which the liquid discharge hole 535 is formed in the liquid discharge head 51. The cap unit 71 has a flat plate-shaped cap tray 712 and a concave cap portion 711 arranged on the upper surface of the cap tray 712. On the upper surface of the cap tray 712, a number of cap portions 711 corresponding to the liquid discharge head 51 provided in the recording portion 50 are arranged. That is, four cap portions 711 are arranged on the cap tray 712 corresponding to each of the four liquid discharge heads 51 for each of the Y, M, C, and Bk colors. The cap portion 711 is a portion of the liquid discharge head 51 that covers the liquid discharge surface 535S on which the liquid discharge hole 535 is formed. The cap unit 71 executes the cap process by covering the liquid discharge surface 535S with the cap portion 711.

The cap unit 71 has a retracted position in which the cap portion 711 retracts in the horizontal direction (Y direction) with respect to the liquid discharge surface 535S of the liquid discharge head 51, and the cap portion 711 is −Z in the Z direction with respect to the liquid discharge surface 535S. It is movable to and from the cappable position located on the side. Further, the cap unit 71 can move up and down along the Z direction in a state where the cap unit 71 is arranged at the cappable position.

When causing the cap unit 71 to perform the cap processing, the control unit 90 moves the cap unit 71 from the retracted position to the cappable position in the Y direction. Before moving the cap unit 71 in the Y direction, the control unit 90 lowers the sheet transport unit 40 from the position directly below the liquid discharge head 51 to the −Z side in the Z direction. When the movement of the cap unit 71 to the cappable position is completed, the control unit 90 raises the cap unit 71 to the + Z side in the Z direction. As a result, the cap portion 711 is put on the liquid discharge surface 535S. The cap unit 71 prevents the liquid discharge hole 535 from being exposed to the outside air by the cap treatment in which the cap portion 711 is put on the liquid discharge surface 535S. As a result, it is possible to suppress a phenomenon in which the viscosity of the ink increases (thickens) in the vicinity of the liquid surface as the ink in the liquid discharge hole 535 dries due to contact with the outside air.

During the waiting period in which the liquid discharge head 51 prepares and waits so that the liquid discharge process can be immediately executed, or during the period in which the liquid discharge process is executed (printing process period), the control unit 90 retracts the cap unit 71. Executes the cap withdrawal process to be placed at the position. When the cap unit 71 is arranged at the retracted position, the liquid discharge hole 535 is exposed to the outside air. In this case, from the liquid surface of the ink in the liquid discharge hole 535, the liquid component evaporates as the liquid surface dries due to contact with the outside air, and a thickened portion in the vicinity of the liquid surface where the viscosity of the ink increases is generated. .. If a thickened portion is formed in the vicinity of the liquid surface, non-ejection of ink from the liquid ejection hole 535 or ejection failure such as a decrease in the speed of ejected ink droplets may occur. In order to suppress such a phenomenon of discharge failure, it is necessary to perform a thickening removal treatment for removing a thickening portion due to drying of the liquid surface.

Therefore, the control unit 90 causes the liquid discharge head 51 or the flushing mechanism 64P to execute the thickening removal process. The thickening removal treatment includes a vibration treatment, a first flushing treatment, and a second flushing treatment.

FIG. 8 is a diagram for explaining the vibration process. The control unit 90 applies vibration processing to the liquid discharge head 51 during the period from one ink discharge from the liquid discharge hole 535 to the next ink discharge while the liquid discharge process is being executed by the liquid discharge head 51. Let it run. The execution timing of the vibration process by the liquid discharge head 1 is determined by the control unit 90. The operation of determining the execution timing of the vibration process by the control unit 90 will be described later.

The vibration process is a process of driving the pressurizing unit 545 so that the liquid level of the ink in the liquid discharge hole 535 vibrates within a range in which the discharge of ink from the liquid discharge hole 535 can be regulated. The control unit 90 causes the liquid discharge head 51 to execute the vibration process by performing the vibration control CX2. Specifically, the control unit 90 supplies the vibration drive signal CS2 to the individual electrodes 544 constituting the pressurizing unit 545. The vibration drive signal CS2 is a drive signal changed to a pulse width that can regulate the ejection of ink from the liquid ejection hole 535 with respect to the ejection drive signal CS1 supplied to the individual electrodes 544 in the liquid ejection control CX1. Is. Further, the vibration drive signal CS2 may be a drive signal such that the difference in potential applied to the individual electrodes 544 is smaller than that of the discharge drive signal CS1.

By vibrating the liquid surface of the ink in the liquid discharge hole 535 in the vibration treatment, the thickening portion near the liquid surface is diffused to remove the thickening portion, or the degree of thickening is reduced to the extent that the ink can be ejected. can do.

FIG. 9 is a diagram for explaining the first flushing process. The control unit 90 is executing the liquid discharge process by the liquid discharge head 51, and during the period from one ink discharge from the liquid discharge hole 535 to the next ink discharge, the flushing mechanism 64P is subjected to the first flushing process. To execute. The execution timing of the first flushing process by the flushing mechanism 64P is determined by the control unit 90. The operation of determining the execution timing of the first flushing process by the control unit 90 will be described later.

The first flushing process is a forced ejection process for forcibly ejecting pressurized ink from the liquid ejection hole 535. The control unit 90 causes the flushing mechanism 64P to execute the first flushing process by performing the first flushing control CF1. As the first flushing control CF1, for example, the liquid discharge control CX3 is performed. In the liquid discharge control CX3, the flushing mechanism 64P supplies a liquid discharge signal CS3 including a pulse for driving the pressure unit 545 to the individual electrodes 544 constituting the pressure unit 545. The liquid discharge signal CS3 is a drive signal in which the potential and pulse width of the individual electrodes 544 are set so that ink can be discharged from the liquid discharge hole 535.

The liquid discharge signal CS3 may be the same as the discharge drive signal CS1, or may be a signal such that the total amount of ink discharged is larger than that of the discharge drive signal CS1. Here, the fact that the total amount of ejected ink increases is a result of comparison in the same environment where thickening or the like does not occur. As the signal that increases the total amount of ink to be ejected, for example, a plurality of the ejection drive signals CS1 may be included. Further, the pulse width and the potential difference may be changed so that the amount of one ink droplet ejected is larger than that of the ejection drive signal CS1. Even if the liquid discharge signal CS3 is the same as the discharge drive signal CS1, depending on the degree of thickening, ink can be discharged even if the amount and speed of the liquid can be used for printing. Is.

Further, as the first flushing control CF1, the flushing mechanism 64P pumps the ink in the sub-ink tank 64 toward the liquid ejection head 51. As a result, the pressurized ink is forcibly ejected from the liquid ejection hole 535. The structure of the flushing mechanism 64P is not particularly limited as long as the ink in the sub-ink tank 64 can be pumped, and the flushing mechanism 64P is configured by, for example, a pump. The flushing mechanism 64P may be configured to move the sub-ink tank 64 in the Z direction at a position higher than the liquid ejection head 51. In this case, the flushing mechanism 64P pumps the ink in the sub ink tank 64 toward the liquid ejection head 51 by the ink pressure generated by the height difference between the sub ink tank 64 and the liquid ejection head 51.

By ejecting the pressurized ink from the liquid ejection hole 535 in the first flushing treatment, a thicker portion having a higher viscosity near the liquid surface of the ink in the liquid ejection hole 535 is forcibly ejected and removed. be able to.

The ink discharged by the first flushing process is, for example, discharged toward the transport belt 41 at a specific position where the sheet S is not placed. The transport belt 41 at a specific position may be provided with an absorbing member for absorbing ink or provided with a through hole so that the ink that has passed through the through hole is collected in an ink receiver (not shown). Further, the sheet S may be ejected to an inconspicuous place, for example, an inconspicuous place in the printed image.

FIG. 10 is a diagram for explaining the second flushing process. The control unit 90 causes the flushing mechanism 64P to execute the second flushing process after the completion of one liquid discharge process by the liquid discharge head 51 and during the waiting period until the next liquid discharge process is executed. The execution timing of the second flushing process by the flushing mechanism 64P is determined by the control unit 90. The operation of determining the execution timing of the second flushing process by the control unit 90 will be described later.

The second flushing process is a forced ejection process for forcibly ejecting pressurized ink from the liquid ejection hole 535. The control unit 90 causes the flushing mechanism 64P to execute the second flushing process by performing the second flushing control CF2. The flushing mechanism 64P pumps the ink in the sub-ink tank 64 toward the liquid ejection head 51. As a result, the pressurized ink is forcibly ejected from the liquid ejection hole 535.

When the second flushing process by the flushing mechanism 64P is executed, the control unit 90 arranges the cleaning unit 72 at a cleaning position vertically below the liquid discharge head 51. The cleaning unit 72 has a wiper blade 721 and a waste liquid tray 722. The waste liquid tray 722 is a tray that receives the ink discharged from the liquid discharge hole 535 as waste liquid when the second flushing process by the flushing mechanism 64P is executed. The wiper blade 721 is a blade for performing a wiping process for wiping off ink droplets adhering to the liquid discharge surface 535S of the liquid discharge head 51 after the second flushing treatment by the flushing mechanism 64P. The control unit 90 causes the wiper blade 721 to execute the wiper process by performing the wiper control CW.

The cleaning unit 72 can move between the retracted position retracted in the horizontal direction (Y direction) with respect to the liquid discharge head 51 and the cleaning position. When the second flushing process by the flushing mechanism 64P is executed, the control unit 90 moves the cleaning unit 72 from the retracted position to the cleaning position in the Y direction. Before moving the cleaning unit 72 in the Y direction, the control unit 90 lowers the sheet transport unit 40 from the position directly below the liquid discharge head 51 to the −Z side in the Z direction. On the other hand, the cleaning unit 72 is arranged at the retracted position during the period other than the execution of the second flushing process by the flushing mechanism 64P.

By ejecting the pressurized ink from the liquid ejection hole 535 in the second flushing treatment, a thicker portion having a higher viscosity near the liquid surface of the ink in the liquid ejection hole 535 is forcibly ejected and removed. be able to.

As described above, the maintenance unit 70 is provided with a measurement unit 73 having a measurement unit 731. The measuring unit 731 is placed on the measuring table 732. The measuring unit 73 will be described with reference to FIG.

The measurement unit 73 can move between a retracted position retracted in the horizontal direction (Y direction) with respect to the liquid discharge head 51 and a measurement position vertically downward with respect to the liquid discharge head 51. The measurement unit 73 is arranged at the measurement position when the measurement unit 731 performs the measurement process, and is arranged at the retracted position during other periods.

The measuring unit 731 performs a measurement process for measuring the vibration of the liquid level LS of the ink at the opening edge 535E of the liquid discharge hole 535 according to the pressure applied by the pressure unit 545. When the measurement unit 731 performs the measurement process, the control unit 90 supplies the vibration drive signal CS2 to the individual electrodes 544 constituting the pressurizing unit 545 by performing the vibration control CX2. As a result, the pressurizing unit 545 is displaced so that the liquid level LS of the ink in the liquid discharge hole 535 vibrates within a range in which the discharge of ink from the liquid discharge hole 535 can be regulated.

The measuring unit 731 has a measuring instrument 73A and a reflection mirror 73B. The measuring instrument 73A is composed of, for example, a laser Doppler vibrometer (for example, LV-1800 manufactured by Ono Sokki). The measuring instrument 73A emits a laser beam. This laser light is reflected by the reflection mirror 73B and is incident on the liquid level LS in the liquid discharge hole 535 from the −Z side. The reflected light from the liquid level LS in response to the incident of the laser light is guided to the measuring instrument 73A via the reflection mirror 73B. The measuring instrument 73A measures the vibration of the liquid level LS based on the reflected light from the liquid level LS. The measuring unit 731 may be configured so that the laser light emitted from the measuring instrument 73A is directly incident on the liquid surface LS from the −Z side without passing through the reflection mirror 73B. Further, the measuring unit 731 may be provided corresponding to a specific (for example, one) specific liquid discharge hole 535 among the plurality of liquid discharge holes 535 in the liquid discharge head 51, or all liquids may be discharged. It may be provided corresponding to the hole 535.

The measuring unit 731 measures the vibration of the liquid level LS of the ink in the liquid ejection hole 535. As a result, the measuring unit 731 acquires the viscosity index value IV shown in FIG. 12, which is an appropriate index of the viscosity change in the liquid level LS in which the liquid component evaporates due to the drying due to the contact with the outside air. Can be done. The viscosity index value IV is a value that serves as an index of a change in viscosity of the liquid level LS due to drying due to contact with the outside air of the liquid level LS. The viscosity index value IV is the maximum vibration velocity indicating the maximum value of the vibration velocity of the liquid surface LS, the minimum vibration velocity indicating the minimum value of the vibration velocity, the damping coefficient indicating the degree of attenuation of the vibration velocity, and the high-speed Fourier conversion to the waveform of the vibration velocity. It is selected from the vibration strength required by processing. In the present embodiment, the measuring unit 731 acquires the maximum vibration velocity as the viscosity index value IV. The maximum vibration velocity as the viscosity index value IV has a correlation with the viscosity of the liquid level LS, and shows a smaller value as the viscosity of the liquid level LS increases as the liquid level LS dries.

While the liquid discharge process by the liquid discharge head 51 is stopped, the measurement unit 731 performs a measurement process for measuring the vibration of the liquid level LS to acquire the viscosity index value IV (maximum vibration velocity). As a result, it is possible to prevent a waiting time for waiting for the measurement process of the measuring unit 731 from occurring during the execution of the liquid discharge process. The timing at which the measurement unit 731 performs the measurement process is the timing before the product of the recording device 1 is shipped or when the power is turned on, the timing when a predetermined measurement condition is satisfied after the power is turned on, or the measurement request input via the operation unit 81. It is set at the specified timing specified by.

The measurement condition is that the predetermined observed value is equal to or higher than the predetermined threshold value. The observed values are based on the detection results of the temperature / humidity detection sensor 56, and include the temperature change width ΔT and the humidity change width ΔW within a predetermined time, the cumulative number of printed sheets ΔX from the previous measurement process, and the elapsed time. Δt and change in average printing rate ΔZ. The measuring unit 731 determines that the measurement condition is satisfied when at least one of the temperature change width ΔT, the humidity change width ΔW, the cumulative number of printed sheets ΔX, the elapsed time Δt, and the average printing rate change ΔZ becomes equal to or more than the corresponding threshold value. Then, the measurement process is performed at that timing.

The maximum vibration velocity as the viscosity index value IV acquired by the measuring unit 731 is input to the analysis unit 74. When the maximum vibration velocity is input, the analysis unit 74 performs an analysis process for obtaining a change with time of the maximum vibration velocity, and outputs analysis information indicating the result of the analysis process. The analysis process of the analysis unit 74 will be described with reference to FIG.

The measuring unit 731 acquires the maximum vibration velocities v1, v2, v3 of three or more points having different drying times t1, t2, t3 due to the contact of the liquid level LS with the outside air. At this time, when the measurement process for acquiring one maximum vibration velocity is performed and then the measurement process for acquiring the next maximum vibration velocity is performed, the flushing control of the control unit 90 is performed before that. The flushing process of the flushing mechanism 64P is executed. That is, when the measurement unit 731 performs the measurement process in which the drying time is changed, the flushing process of the flushing mechanism 64P is executed for each measurement process. As a result, the dry state of the liquid level LS can be kept constant for each measurement process. The drying times t1, t2, and t3 are timed by the time measuring unit 83.

The analysis unit 74 obtains an approximate curve showing the change with time of the maximum vibration velocity as the analysis information AIF based on the maximum vibration velocities v1, v2, v3 of three or more points acquired by the measurement unit 731. Specifically, the analysis unit 74 uses two theoretical formulas, the convection-diffusion equation represented by the following equation (1) and the evaporation mass rate equation represented by the following equation (2), to show an approximate curve showing the analysis information AIF. Ask for.

The left side of the formula (1) shows the water concentration (wt%) inside the liquid discharge hole 535. “V” in the formula (1) is the advection speed (m / s) when an amount of water corresponding to the water evaporated from the liquid level LS of the ink in the liquid discharge hole 535 is supplied to the liquid level LS. Is shown. “D” in the formula (1) indicates a mass diffusivity (m ² / s) due to the density gradient in the ink.

“M” in the formula (2) indicates the evaporation mass rate (kg / s) when water evaporates from the liquid level LS of the ink in the liquid ejection hole 535. “Dw” in the formula (2) indicates the mass diffusivity (m ² / s) of water in the air. “Cs” in the formula (2) indicates the mole fraction of water in the ink. “C∞” in the formula (2) indicates the relative humidity detected by the temperature / humidity detection sensor 56. “Pv” in the formula (2) indicates the vapor pressure (Pa) of water. "M" in the formula (2) represents the molar mass (kg / mol) of water. “R” in the formula (2) indicates the gas constant (Pa · m ³ / K · mol).

In the formula (2), the diffusion coefficient Dw can be experimentally determined as a fixed value, and the mole fraction Cs can be experimentally determined as a variable value that fluctuates according to the drying of the liquid surface LS. Further, in the formula (2), literature values can be used for the vapor pressure Pv of water, the molar mass M of water, and the gas constant R. That is, the evaporation mass velocity m can be calculated by using the evaporation mass velocity equation of the equation (2) with the relative humidity C∞ as a variable parameter.

In the formula (1), the diffusion coefficient D can be experimentally obtained as a fixed value. Further, in the formula (1), the transfer rate V uses the evaporation mass rate m of the formula (2), the cross-sectional area A (m ² ) of the liquid discharge hole 535, and the ink density ρ (kg / m ³ ). Therefore, it can be obtained according to V = m / (A × ρ). That is, the water concentration inside the liquid discharge hole 535 can be derived by the convection-diffusion equation of the formula (1) using the evaporation mass rate m calculated according to the evaporation mass rate equation of the formula (2).

The water concentration of the ink in the liquid discharge hole 535 correlates with the viscosity of the liquid level LS, and shows a smaller value as the viscosity of the liquid level LS increases as the liquid level LS dries. Further, as described above, the maximum vibration velocities v1, v2, v3 as the viscosity index value IV have a correlation with the viscosity of the liquid surface LS. In view of these facts, there is also a correlation between the maximum vibration velocities v1, v2, v3 at the liquid level LS and the water concentration. Therefore, the analysis unit 74 uses the advection-diffusion equation of the formula (1), which can calculate the water concentration, in the analysis process, so that the analysis shows the time-dependent change of the maximum vibration velocity accurately at a small measurement point of the maximum vibration velocity. An approximate curve as information AIF can be obtained. As a result, the time required for the measurement process of the measurement unit 731 and the analysis process of the analysis unit 74 can be shortened.

Analyzing unit 74, coefficient of determination R ² of the approximate curve as the analysis information AIF finishes analysis processing when a predetermined analysis threshold AT more. That is, the analysis information AIF is the coefficient of determination R ² is represented by the approximate curves and analysis threshold AT more. As a result, the analysis information AIF is represented by an approximate curve that accurately shows the time-dependent changes in the maximum vibration velocities v1, v2, and v3. Incidentally, the analysis unit 74 calculates the coefficient of determination R ² trendline according to the following equation (3).

“Yi” in the formula (3) indicates the measured values of the maximum vibration velocities v1, v2, v3 by the measuring unit 731. “Μy” in the formula (3) indicates the average value of yi. “F (xi)” in the equation (3) indicates an estimated value based on the approximate curve as the analysis information AIF. As the coefficient of determination R ² approaches "1", it becomes an approximate curve that accurately shows the time-dependent changes in the maximum vibration velocities v1, v2, and v3.

Similar to the measuring unit 731, the analysis unit 74 performs an analysis process for obtaining a time-dependent change in the maximum vibration speeds v1, v2, v3 while the liquid discharge process by the liquid discharge head 51 is stopped. As a result, it is possible to prevent a waiting time for waiting for the analysis process of the analysis unit 74 from occurring during the execution of the liquid discharge process.

The measurement process of the measurement unit 731 and the analysis process of the analysis unit 74 will be described in more detail with reference to the flowchart of FIG. 14 in addition to FIG.

The measurement unit 731 sets the number of measurements i to i = i + 1 with respect to the initial value i = 0 (step a1). When the setting of the number of measurements i is completed, the flushing process of the flushing mechanism 64P is executed by the flushing control of the control unit 90 (step a2). Next, the measuring unit 731 sets the drying time t to the initial value t = 0 (step a3). When the initialization of the drying time t is completed, the measuring unit 731 determines whether or not t ≧ t (i) is satisfied with respect to the drying time t (step a4). When t ≧ t (i) (YES in step a4), pressure is applied to the pressurizing unit 545 according to the vibration drive signal CS2 by the vibration control CX2 of the control unit 90 (step a5). As a result, the liquid level LS of the ink in the liquid discharge hole 535 vibrates. In this state, the measuring unit 731 performs a measurement process for measuring the vibration of the liquid level LS to acquire the maximum vibration speed v (i) corresponding to the drying time t (i) (step a6). The maximum vibration velocity v (i) acquired by the measuring unit 731 is stored in the storage unit 84 (step a7).

Next, the measurement unit 731 determines whether or not i ≧ 3 is satisfied with respect to the number of measurements i (step a8). That is, the measuring unit 731 determines whether or not the maximum vibration velocities at three or more points having different drying times have been acquired. When the maximum vibration velocities of three or more points are acquired (YES in step a8), the measurement unit 731 outputs those maximum vibration velocities to the analysis unit 74. On the other hand, when the maximum vibration velocities of 3 points or more have not been acquired (NO in step a8), the measuring unit 731 repeats the measurement process until the acquisition of the maximum vibration velocities of 3 points or more is completed.

When the maximum vibration velocities of three or more points are input, the analysis unit 74 obtains an approximate curve showing the change with time of the maximum vibration velocities as the analysis information AIF based on the maximum vibration velocities (step a9). Then, the analyzing unit 74, coefficient of determination ^{R 2} of the approximate curve as the analysis information AIF determines whether a parsing threshold AT more (step a10). When the coefficient of determination R ² of the approximate curve is equal to or greater than the analysis threshold AT (YES in step a10), the analysis unit 74 ends the analysis process. On the other hand, when the coefficient of determination R ² of the approximate curve is not equal to or greater than the analysis threshold AT (NO in step a10), a new measurement process is performed by the measurement unit 731. Each time a new measurement process is completed, the measurement unit 731 outputs a new maximum vibration velocity indicating the result of the measurement process to the analysis unit 74. Each time a new maximum vibration velocity is input, the analysis unit 74 adds the new maximum vibration velocity to obtain an approximate curve. Such measurement process of the measurement unit 731 and the analysis processing of analyzing unit 74, coefficient of determination R ² of the approximate curve is repeated until the analysis threshold AT more.

In the example shown in FIG. 13, the measuring unit 731 acquires the maximum vibration velocities v1, v2, v3 at three points corresponding to the drying times t1, t2, t3, respectively, and outputs the results to the analysis unit 74 at that time. .. Analysis unit 74 obtains the approximate curve as the analysis information AIF based on the maximum vibration speed v1, v2, v3 of the three points, and calculates a determination coefficient ^{R 2} of the approximate curve. Since the coefficient of determination R ² of the approximate curve of this time is less than the analysis threshold AT, measuring section 731 acquires the maximum vibration speed v4 of the new fourth point corresponding to the drying time t4, the analysis unit and the results Output to 74. Analysis unit 74 obtains an approximate curve based on the maximum vibration speed v1, v2, v3, v4 of four points by adding up vibration velocity v4 of the new fourth point, and calculates a determination coefficient R ² of the approximate curve .. Since the coefficient of determination R ² of the approximate curve of this time becomes the analysis threshold AT above, analysis unit 74 ends the analysis process.

The analysis unit 74 outputs analysis information AIF (approximate curve) indicating the result of the analysis process to the control unit 90. FIG. 15 is a diagram for explaining the processing of the control unit 90 when the analysis information AIF from the analysis unit 74 is input.

When the analysis information AIF is input, the control unit 90 determines the execution timing of the vibration process, the first flushing process, and the second flushing process described above as the thickening removal process based on the analysis information AIF. The control unit 90 sets the execution timing of the first flushing process and the second flushing process to be later than the vibration process. Specifically, the control unit 90 sets the execution timing of each process so that the execution timing is delayed in the order of the vibration process, the first flushing process, and the second flushing process.

The control unit 90 has a first velocity threshold value Tv1 for executing the vibration process, a second velocity threshold value Tv2 for executing the first flushing process, and a second velocity threshold value Tv2 for the maximum vibration velocity as the viscosity index value IV of the liquid level LS. A third speed threshold value Tv3 for executing the flushing process is set in advance. The first speed threshold value Tv1, the second speed threshold value Tv2, and the third speed speed threshold value Tv3 are set so as to show smaller values in this order.

In the analysis information AIF (approximate curve) indicating the time course of the maximum vibration velocity at the liquid level LS, the control unit 90 sets the drying time corresponding to the first velocity threshold value Tv1 to the first timing threshold value Tt1 indicating the execution timing of the vibration processing. To determine as. Similarly, the control unit 90 determines the drying time corresponding to the second speed threshold value Tv2 as the second timing threshold value Tt2 indicating the execution timing of the first flushing process. Further, the control unit 90 determines the drying time corresponding to the third speed threshold value Tv3 as the third timing threshold value Tt3 indicating the execution timing of the second flushing process.

When the control unit 90 determines the execution timing of each thickening removal processing of the vibration processing, the first flushing processing, and the second flushing processing, each thickening removal processing is executed at each execution timing. Specifically, the control unit 90 does not execute each thickening removal process when the drying time measured by the time measuring unit 83 is less than the first timing threshold value Tt1. The control unit 90 causes the liquid discharge head 51 to perform vibration processing by the vibration control CX2 at the timing when the drying time measured by the time measuring unit 83 has passed the first timing threshold value Tt1 (see FIG. 8). During the period in which the drying time measured by the time measuring unit 83 is equal to or greater than the first timing threshold value Tt1 and less than the second timing threshold value Tt2, the control unit 90 causes the vibration processing to be executed.

The control unit 90 causes the flushing mechanism 64P to execute the first flushing process by the first flushing control CF1 at the timing when the drying time measured by the timing unit 83 has passed the second timing threshold value Tt2 (see FIG. 9). During the period in which the drying time measured by the time measuring unit 83 is equal to or greater than the second timing threshold value Tt2 and less than the third timing threshold value Tt3, the control unit 90 causes the first flushing process to be executed.

The control unit 90 causes the flushing mechanism 64P to execute the second flushing process by the second flushing control CF2 at the timing when the drying time measured by the clocking unit 83 has passed the third timing threshold value Tt3 (see FIG. 10). During the period when the drying time measured by the time measuring unit 83 is equal to or greater than the third timing threshold value Tt3, the control unit 90 causes the second flushing process to be executed.

The analysis information AIF used by the control unit 90 to determine the execution timing of each thickening removal process is based on the measurement result of the measurement unit 731, and is appropriate for the change in viscosity at the liquid level LS in the liquid discharge hole 535. It is the information which shows the time-dependent change of the viscosity index value IV which becomes an index. By using such analysis information AIF, the control unit 90 can execute each thickening removal process at an appropriate timing corresponding to the change in viscosity of the liquid level LS in the liquid discharge hole 535 due to drying. As a result, it is possible to prevent excessive execution of each thickening removal process. For this reason, it is possible to prevent the promotion of drying on the new liquid level LS after the removal of the thickening portion due to the excessive execution of each thickening removal treatment as much as possible, and the ink ejection failure from the liquid ejection hole 535 is poor. Can be appropriately suppressed.

Next, the overall processing flow of the recording device 1 will be described with reference to the flowcharts of FIGS. 16A and 16B.

In the recording device 1, the power is turned off with the cap portion 711 of the cap unit 71 covered with the liquid discharge surface 535S of the liquid discharge head 51. When the power of the recording device 1 is turned on in this state (step b1), the control unit 90 determines whether or not the execution of the measurement process by the measuring unit 731 at the time of turning on the power is set (step b2). When the execution of the measurement process at the time of turning on the power is set (YES in step b2), the control unit 90 executes the cap retract process for arranging the cap unit 71 at the retracted position (step b3). When the cap unit 71 is arranged in the retracted position, the liquid discharge hole 535 is exposed to the outside air.

When the cap unit 71 is arranged in the retracted position, the measuring unit 73 is arranged in the measuring position. In this state, the measuring unit 731 performs a measurement process for measuring the vibration of the liquid level LS in the liquid discharge hole 535 to obtain the viscosity index value IV, and the analysis unit 74 obtains the change with time of the viscosity index value IV. The analysis process is performed to acquire the analysis information AIF (step b4). The analysis information AIF is stored in the storage unit 84. When the acquisition of the analysis information AIF by the analysis unit 74 is completed, the control unit 90 causes the cap unit 71 to execute the cap process (step b5). As a result, the cap portion 711 is put on the liquid discharge surface 535S.

Next, the control unit 90 determines whether or not the measurement request is input via the operation unit 81 and the execution of the measurement process by the measurement unit 731 is set at the designated timing specified by the measurement request (). Step b6). When the execution of the measurement process at the designated timing is set (YES in step b6), the control unit 90 executes the cap retract process for arranging the cap unit 71 at the retracted position (step b7). When the cap unit 71 is arranged in the retracted position, the liquid discharge hole 535 is exposed to the outside air.

When the cap unit 71 is arranged in the retracted position, the measuring unit 73 is arranged in the measuring position. In this state, the measuring unit 731 performs a measurement process for measuring the vibration of the liquid level LS in the liquid discharge hole 535 to obtain the viscosity index value IV, and the analysis unit 74 obtains the change with time of the viscosity index value IV. The analysis process is performed to acquire the analysis information AIF (step b8). The analysis information AIF is stored in the storage unit 84. When the acquisition of the analysis information AIF by the analysis unit 74 is completed, the control unit 90 causes the cap unit 71 to execute the cap process (step b9). As a result, the cap portion 711 is put on the liquid discharge surface 535S.

Next, the control unit 90 determines whether or not the image data has been input via the communication unit 82 (step b10). When the image data is input (YES in step b10), the control unit 90 executes a cap withdrawal process for arranging the cap unit 71 at the evacuation position (step b11).

When the cap unit 71 is arranged in the retracted position, the measuring unit 731 satisfies the measurement condition when at least one of the temperature change width ΔT, the humidity change width ΔW, and the elapsed time Δt becomes equal to or more than the corresponding threshold value. (Step b12). If the measurement condition is satisfied (YES in step b12), the measurement unit 73 is arranged at the measurement position. In this state, the measuring unit 731 performs a measurement process for measuring the vibration of the liquid level LS in the liquid discharge hole 535 to obtain the viscosity index value IV, and the analysis unit 74 obtains the change with time of the viscosity index value IV. The analysis process is performed to acquire the analysis information AIF (step b13). The analysis information AIF is stored in the storage unit 84.

When the acquisition of the analysis information AIF by the analysis unit 74 is completed, the control unit 90 determines the execution timing of each thickening removal processing of the vibration processing, the first flushing processing, and the second flushing processing based on the analysis information AIF ( Step b14). When the determination of the execution timing of each thickening removal process is completed, the control unit 90 causes the liquid discharge head 51 to start the liquid discharge process according to the image data (step b15). As a result, recording of the image on the sheet S is started. At this time, the time measuring unit 83 starts measuring the drying time indicating the time between one ink ejection and the next ink ejection with respect to the ink ejection from the liquid ejection hole 535 according to the image data.

The control unit 90 determines whether or not the drying time measured by the time measuring unit 83 has passed the first timing threshold value Tt1 (step b16). When the drying time from one ink ejection from the liquid ejection hole 535 to the next ink ejection becomes long, a thickening portion is formed on the liquid level LS of the ink in the liquid ejection hole 535. Therefore, when the drying time elapses from the first timing threshold value Tt1 (YES in step b16), the control unit 90 causes the liquid discharge head 51 to execute the vibration process by the vibration control CX2 (step b17). By vibrating the liquid level LS of the ink in the liquid discharge hole 535 in the vibration treatment, the thickening portion in the vicinity of the liquid level LS can be diffused and the thickening portion can be removed.

Further, the control unit 90 determines whether or not the drying time measured by the time measuring unit 83 has passed the second timing threshold value Tt2 (step b18). When the drying time from one ink ejection from the liquid ejection hole 535 to the next ink ejection becomes longer, a thickened portion having a high viscosity is generated due to the liquid level LS of the ink in the liquid ejection hole 535. Therefore, when the drying time elapses from the second timing threshold value Tt2 (YES in step b18), the control unit 90 causes the flushing mechanism 64P to execute the first flushing process by the first flushing control CF1 (step b19). By ejecting the pressurized ink from the liquid ejection hole 535 in the first flushing treatment, a thicker portion having a higher viscosity near the liquid level LS of the ink in the liquid ejection hole 535 is forcibly ejected and removed. can do.

When the printing process corresponding to the image data is completed, the control unit 90 stops the liquid discharging process of the liquid discharging head 51 (step b20). At this time, the time measuring unit 83 continues to measure the drying time, including a waiting time for preparing and waiting for the ink to be ejected from the liquid ejection hole 535 immediately according to the next image data. Become.

The control unit 90 determines whether or not the drying time measured by the time measuring unit 83 has passed the third timing threshold value Tt3 (step b21). When the drying time elapses from the third timing threshold value Tt3 (YES in step b21), the control unit 90 flushes the flushing mechanism 64P with the second flushing mechanism 64P by the second flushing control CF2 in a state where the cleaning unit 72 is arranged at the cleaning position. The process is executed (step b22). By ejecting the pressurized ink from the liquid ejection hole 535 in the second flushing treatment, a thicker portion having a higher viscosity near the liquid level LS of the ink in the liquid ejection hole 535 is forcibly ejected and removed. can do.

When the second flushing process of the flushing mechanism 64P is completed, the measuring unit 731 has a threshold value corresponding to at least one of the temperature change width ΔT, the humidity change width ΔW, the cumulative number of prints ΔX, the elapsed time Δt, and the average print rate change ΔZ. With the above, it is determined whether or not the measurement condition is satisfied (step b23). If the measurement condition is satisfied (YES in step b23), the measurement unit 73 is arranged at the measurement position. In this state, the measuring unit 731 performs a measurement process for measuring the vibration of the liquid level LS in the liquid discharge hole 535 to acquire the viscosity index value IV, and the analysis unit 74 obtains the change with time of the viscosity index value IV. The analysis process is performed to acquire the analysis information AIF (step b24). The analysis information AIF is stored in the storage unit 84. When the acquisition of the analysis information AIF by the analysis unit 74 is completed, the control unit 90 causes the cap unit 71 to execute the cap process (step b25). As a result, the cap portion 711 is put on the liquid discharge surface 535S.

In the above processing flow, during the period of the printing process from the start of the liquid discharge process by the liquid discharge head 51 (step b15) to the stop of the liquid discharge process (step b20), the measurement process and the analysis unit 74 of the measurement unit 731 Although the control that does not perform the analysis process has been described, the present invention is not limited to this. For example, when the detection result of the temperature / humidity detection sensor 56 shows a sudden change during the printing process, the measurement process of the measurement unit 731 and the analysis process of the analysis unit 74 may be performed. ..

Hereinafter, an experiment conducted using the recording device 1 according to the present embodiment will be described with reference to FIG. FIG. 17 is a diagram showing the results of an experiment evaluating the relationship between the execution timing of the vibration control CX2 and the ink ejection speed from the liquid ejection head 51.

(Experimental conditions)
Regarding the evaporation mass rate equation of the formula (2), the diffusion coefficient Dw uses Dw = 2.36 × ^10-5 (m ² / s) as the measured value, and the mole fraction Cs fluctuates according to the drying of the liquid level LS. The measured value to be used was used. Document values were used for the vapor pressure Pv of water, the molar mass M of water, and the gas constant R. For the convection-diffusion equation of equation (1), D = 0.79 × ^10-9 (m ² / s) was used as the measured value for the diffusion coefficient D. The transfer rate V is V = m / (A) using the evaporation mass rate m of the formula (2), the cross-sectional area A (m ² ) of the liquid discharge hole 535, and the ink density ρ (kg / m ^3). It was calculated according to × ρ). As the conditions for the liquid discharge head 51, the inner diameter of the opening of the liquid discharge hole 535 was set to 20 μm, the voltage applied to the pressurizing portion 545 was set to AC10 V (100 kHz), and the drive frequency was set to 10 Hz.

(experimental method)
The temperature / humidity environment in the room where the recording device 1 was installed was changed from 10 ° C. 10% RH to 25 ° C. 50% RH. This change in temperature and humidity is based on the assumption that the indoor heating equipment will start operating from a stopped state in winter. At this time, the temperature and humidity in the room are maintained at 10 ° C. and 10% RH during the first period, and then through the second period in which the temperature and humidity change according to the operation of the heating equipment, the third period During that time, the temperature changes to maintain 25 ° C. and 50% RH. The power of the recording device 1 was turned on within the first period.

(Example)
When the power of the recording device 1 is turned on within the first period, the measuring unit 731 performs the measurement process to acquire the viscosity index value IV, and the analysis unit 74 performs the analysis process to obtain the change with time of the viscosity index value IV. An example is a configuration in which analysis information AIF is acquired. In this embodiment, the control unit 90 determines the first timing threshold value Tt1 indicating the execution timing of the vibration processing by the liquid discharge head 51 based on the analysis information AIF.

(Comparison example)
A configuration in which the measurement unit 731 and the analysis unit 74 do not execute each process is used as a comparative example. In this comparative example, the control unit 90 determines the first timing threshold value Tt1 indicating the execution timing of the vibration process by the liquid discharge head 51 based on the detection result of the temperature / humidity detection sensor 56.

(Experimental result)
FIG. 17A shows the transition of the first timing threshold value Tt1 in each of the examples and the comparative examples. In the embodiment, the first timing threshold value Tt1 changes at a constant value in the first period and the second period, and starts to decrease from around the beginning of the third period. That is, in the embodiment, the first timing threshold value Tt1 does not change in the second period in which the temperature and humidity in the room change with the operation of the heating device. This is because the change in viscosity of the liquid level LS in the liquid discharge hole 535, which is a determination index of the first timing threshold value Tt1 in the embodiment, has a time lag with respect to the change in temperature and humidity in the room due to the operation of the heating equipment. Because. On the other hand, in the comparative example, the first timing threshold value Tt1 starts to decrease from around the beginning of the second period so as to synchronize with the change in the temperature and humidity in the room due to the operation of the heating equipment. As described above, the transition of the first timing threshold value Tt1 is clearly different between the example and the comparative example with respect to the change in indoor temperature and humidity.

FIG. 17B shows a timing chart of the vibration control CX2 when the liquid discharge head 51 is made to execute the vibration process according to the first timing threshold value Tt1 in each of the examples and the comparative examples. In the embodiment, the vibration control CX2 is not executed for the liquid discharge control CX1 in the first period and the second period, and the vibration control CX2 is executed for the liquid discharge control CX1 in the third period. As a result, the vibration process by the liquid discharge head 51 is executed at an appropriate timing corresponding to the change in viscosity of the liquid level LS in the liquid discharge hole 535 due to drying. On the other hand, in the comparative example, the vibration control CX2 is also executed for the liquid discharge control CX1 in the second period. That is, in the comparative example, the vibration control CX2 is executed earlier than in the embodiment.

FIG. 17C shows the transition of the speed (discharge speed) of the ink droplets discharged from the liquid discharge hole 535 according to the liquid discharge control CX1 in each of the examples and the comparative examples. In the embodiment, the ink droplet ejection speed changes within a range in which ejection defects can be prevented with respect to the liquid ejection control CX1 in any of the first period, the second period, and the third period. This is because, as described above, the vibration treatment by the liquid discharge head 51 is executed at an appropriate timing corresponding to the change in viscosity of the liquid level LS in the liquid discharge hole 535 due to drying. On the other hand, in the comparative example, the ejection speed of the ink droplet corresponding to the liquid ejection control CX1 in the second period is clearly lower than that in the embodiment. This is because, in the comparative example, the vibration control CX2 was executed earlier than in the embodiment in the second period in which the thickening due to the drying of the liquid level LS in the liquid discharge hole 535 was not so large. That is, in the comparative example, the excessive vibration control CX2 earlier than in the example promotes drying on the new liquid surface after the removal of the thickening portion in the vicinity of the liquid surface LS, resulting in an increase in viscosity. Therefore, in the comparative example, the ejection speed of the ink droplets decreases.

1 Recording device (liquid discharge device)
50 Recording unit 51 Liquid discharge head 535 Liquid discharge hole 535E Opening edge 545 Pressurization unit 73 Measurement unit 731 Measurement unit 74 Analysis unit 90 Control unit AIF analysis information AT analysis threshold CF1 1st flushing control CF2 2nd flushing control CX1 Liquid discharge Control CX2 Vibration control CX3 Liquid discharge control IV Viscosity index value Tv1 1st speed threshold Tv2 2nd speed threshold Tv3 3rd speed threshold Tt1 1st timing threshold Tt2 2nd timing threshold Tt3 3rd timing threshold

Claims (6)

A liquid discharge head having a pressurizing portion and a liquid discharge hole for discharging a dispersion liquid in which particles are dispersed in an aqueous medium according to the pressure applied by the pressurizing portion.
By measuring the vibration of the liquid level of the dispersion liquid at the open edge of the liquid discharge hole according to the pressure applied by the pressurized portion, a viscosity index value that is an index of the viscosity change due to the drying of the liquid level can be obtained. The measuring unit to be acquired and
An analysis unit that performs an analysis process for obtaining a change with time of the viscosity index value based on the measurement result of the measurement unit and outputs analysis information indicating the result of the analysis process.
A control unit that controls the liquid discharge head is provided.
When the analysis information is input, the control unit determines the execution timing of the thickening removal process by the liquid discharge head for removing the thickening portion due to the drying of the liquid level based on the analysis information. A liquid discharge device that executes the thickening removal process at the execution timing. The measuring unit acquires the viscosity index values of three or more points having different drying times on the liquid surface, and obtains the viscosity index values.
In the analysis process, the analysis unit obtains an approximate curve showing the change with time of the viscosity index value as the analysis information based on the three or more points of the viscosity index value acquired by the measurement unit, and obtains the approximate curve as the analysis information. The liquid discharge device according to claim 1, wherein the analysis process is terminated when the coefficient of determination of is equal to or higher than a predetermined threshold value. The liquid discharge device according to claim 2, wherein the analysis unit obtains the approximate curve by using an advection-diffusion equation capable of calculating the water concentration inside the liquid discharge hole. When a liquid discharge request indicating a request for discharging the dispersion liquid from the liquid discharge hole is input, the control unit adds the dispersion liquid so that the dispersion liquid is discharged from the liquid discharge hole in response to the liquid discharge request. The liquid discharge head is made to execute the liquid discharge process for driving the pressure unit.
The liquid discharge device according to any one of claims 1 to 3, wherein the measuring unit acquires the viscosity index value while the liquid discharge process is stopped by the liquid discharge head. The liquid discharge device according to claim 4, wherein the analysis unit performs the analysis process while the liquid discharge process is stopped by the liquid discharge head. The thickening removal treatment
Vibration processing that drives the pressurizing unit so that the liquid level vibrates within a range in which the discharge of the dispersed liquid from the liquid discharge hole can be regulated.
Includes a forced discharge process that forcibly discharges the dispersed liquid pressurized from the liquid discharge hole.
The liquid discharge device according to any one of claims 1 to 5, wherein the control unit sets the execution timing of the forced discharge process to a later timing than the vibration process.

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