Method for controlling liquid ejection device, liquid ejection device

Abstract

To provide a control method for a liquid discharge device and a liquid discharge device that can suppress an increase in viscosity of liquid in nozzles.SOLUTION: Provided is a control method for a liquid discharge device which includes: a liquid discharge head 20 capable of discharging multiple kinds of liquids from multiple nozzles 19; a cap 25 capable of forming a closed space 33 to which the multiple nozzles 19 are open; and a cleaning part 24 which is capable of executing cleaning for draining liquid from the nozzles 19 to the cap 25 and for discharging the liquid from the cap 25 to the outside of the cap 25. In the control method for a liquid discharge device, cleaning is executed on the basis of a result of correcting a relationship between a moisture evaporation rate change and viscosity variation for multiple kinds of liquids by using a moisture content included in each of the multiple kinds of liquids before moisture evaporation, an amount of a humectant substance included in each of the multiple kinds of liquids, a moisture content included before moisture evaporation in a mixed liquid in which the multiple kinds of liquids are mixed, and an amount of a humectant substance included in the mixed liquid.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for controlling a liquid ejection device such as a printer, and to a liquid ejection device. [Background technology]

[0002] For example, as disclosed in Patent Document 1, there is a printer, which is an example of a liquid ejection device, that performs printing by ejecting ink, which is an example of a liquid, from multiple nozzles formed in a recording head, which is an example of a liquid ejection head. The printer is provided with a cap that caps the nozzles.

[0003] The ink contains a humectant to prevent the viscosity from increasing inside the nozzle. However, when the water in the ink evaporates, the humectant absorbs the surrounding water. Therefore, when the nozzle is capped with a cap that has ink on it, the humectant removes the water from the ink inside the nozzle. The printer in Patent Document 1 replenishes the ink in the cap to make up for the evaporated water with ink. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-44337 Summary of the Invention [Problem to be solved by the invention]

[0005] The printer in Patent Document 1 refills the cap with liquid so that the available moisture content in the cap, calculated by subtracting the moisture absorbed by the humectant from the moisture content of the liquid, returns to its initial value. However, the way in which the viscosity of liquid changes with changes in the moisture evaporation rate varies depending on the type of liquid. Therefore, in a liquid ejection device capable of ejecting multiple types of liquid, even if the cap is refilled with liquid to match one of the liquids, the viscosity of the liquid in the nozzle may increase more than expected. [Means for solving the problem]

[0006] A control method for a liquid ejection device that solves the above problem is a control method for a liquid ejection device that includes a liquid ejection head capable of ejecting multiple types of liquid from multiple nozzles, a cap capable of forming a closed space in which the multiple nozzles open, and a cleaning unit that discharges the liquid from the nozzles into the cap and performs cleaning by discharging the liquid from the cap to the outside, and performs the cleaning based on the results of correcting the relationship between the change in water evaporation rate and the change in viscosity of each of the multiple types of liquid using the amount of water that each of the multiple types of liquid has before water evaporation, the amount of moisturizing substance that each of the multiple types of liquid has, the amount of water that a mixed liquid obtained by mixing the multiple types of liquids has before water evaporation, and the amount of moisturizing substance that the mixed liquid has.

[0007] A liquid ejection device that solves the above problem comprises a liquid ejection head capable of ejecting multiple types of liquid from multiple nozzles, a cap capable of forming a closed space in which the multiple nozzles open, a cleaning unit that discharges the liquid from the nozzles into the cap and performs cleaning by discharging the liquid from the cap to the outside, and a control unit, wherein the control unit causes the cleaning unit to perform the cleaning based on the results of correcting the relationship between the change in water evaporation rate and the change in viscosity of each of the multiple types of liquid using the amount of water that each of the multiple types of liquid has before water evaporation, the amount of moisturizing substance that each of the multiple types of liquid has, the amount of water that a mixed liquid obtained by mixing the multiple types of liquids has before water evaporation, and the amount of moisturizing substance that the mixed liquid has. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of an embodiment of a liquid ejection device. [Figure 2] FIG. 2 is a schematic cross-sectional view of a cap. [Figure 3] 10 is a graph showing the relationship between a change in water evaporation rate and a change in viscosity before correction. [Figure 4]10 is a graph showing the relationship between the change in water evaporation rate and the change in viscosity after correction. [Figure 5] 10 is a flowchart showing a maintenance routine. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Embodiment] An embodiment of a liquid ejection device and a method for controlling the liquid ejection device will be described below with reference to the drawings. The liquid ejection device is an inkjet printer that prints by ejecting ink, which is an example of a liquid, onto a medium such as paper, fabric, vinyl, plastic parts, or metal parts.

[0010] In the drawings, the liquid ejection device 11 is placed on a horizontal plane, with the direction of gravity indicated by the Z axis, and directions along the horizontal plane indicated by the X and Y axes. The X, Y, and Z axes are perpendicular to one another. In this embodiment, an increase in the viscosity of the liquid is also referred to as thickening.

[0011] <Liquid discharge device> 1, the liquid ejection device 11 may include a housing 12, a guide shaft 13, and a printing unit 14. The liquid ejection device 11 may also include a medium support unit 16 that supports a medium 15, and a maintenance unit 17.

[0012] The guide shaft 13 may be supported by the housing 12 . The printing unit 14 may be provided so as to be movable along the guide shaft 13. The printing unit 14 includes a liquid ejection head 20 having a plurality of nozzles 19. The printing unit 14 may also include a carriage 21. The carriage 21 moves the liquid ejection head 20 back and forth along the guide shaft 13.

[0013] The carriage 21 may move with a plurality of liquid containers 22 mounted thereon. Each of the plurality of liquid containers 22 contains a different type of liquid. When one liquid container 22 can contain a plurality of types of liquid, the carriage 21 may move with a single liquid container 22 mounted thereon.

[0014] The multiple types of liquid are each supplied to a liquid ejection head 20. The liquid ejection head 20 is capable of ejecting multiple types of liquid from multiple nozzles 19. The different types of liquid are, for example, inks of different colors. The liquid ejection head 20 may eject, for example, cyan, magenta, yellow, and black ink.

[0015] Each nozzle 19 ejects a corresponding type of liquid. The number of nozzles 19 ejecting the same type of liquid may be the same or different for each type of liquid ejected. For example, the number of nozzles 19 ejecting black ink may be greater than the number of nozzles 19 ejecting cyan, magenta, and yellow inks, respectively. For example, the number of nozzles 19 ejecting cyan, magenta, and yellow inks may be the same for each color.

[0016] The maintenance unit 17 performs maintenance on the printing unit 14. The maintenance unit 17 may include a wiping unit 23. The maintenance unit 17 includes a cleaning unit 24. The cleaning unit 24 may include a cap 25, a suction mechanism 26, and a waste liquid storage unit 27. The suction mechanism 26 may include a discharge path 28 and a discharge pump 29.

[0017] The cap 25 is provided so as to be movable between a spaced position shown in Fig. 1 and a capping position shown in Fig. 2. The cap 25 receives the liquid discharged from the liquid ejection head 20.

[0018] Discharge path 28 connects cap 25 and waste liquid storage section 27. Discharge path 28 has an upstream end connected to cap 25 and a downstream end connected to waste liquid storage section 27. Discharge path 28 may be configured by a tube that deforms in accordance with the movement of cap 25.

[0019] The discharge pump 29 may be provided in the middle of the discharge path 28. The discharge pump 29 sends the liquid in the cap 25 to the waste liquid storage section 27. The waste liquid storage section 27 stores the liquid sent from the cap 25 as waste liquid.

[0020] As shown in FIG. 2, the cap 25 may include a lip portion 31 and an absorbent member 32 capable of absorbing liquid. The lip portion 31 is capable of coming into contact with the liquid ejection head 20. When the lip portion 31 of the cap 25 of this embodiment comes into contact with the liquid ejection head 20, a closed space 33 is formed between the cap 25 and the liquid ejection head 20, with a plurality of nozzles 19 opening therein. If the lip portion 31 is made of, for example, elastically deformable rubber or elastomer, the airtightness of the closed space 33 can be improved.

[0021] The absorbent member 32 is capable of absorbing liquid. The absorbent member 32 may be formed of, for example, a sponge having voids capable of holding liquid. The absorbent member 32 is positioned within the closed space 33 and keeps the closed space 33 moist with the liquid it holds.

[0022] <Maintenance> 1, the wiping unit 23 is provided so as to be movable between a wiping position where it can wipe the liquid ejection head 20 and a non-wiping position where it does not come into contact with the liquid ejection head 20. The wiping unit 23 positioned at the wiping position wipes the liquid ejection head 20 by coming into contact with the moving liquid ejection head 20. Maintenance in which the wiping unit 23 wipes the liquid ejection head 20 is also called wiping.

[0023] 2, maintenance in which the cap 25 forms a closed space 33 between itself and the liquid ejection head 20 is also called capping. The cap 25, which is positioned at the capping position, caps the liquid ejection head 20, which is positioned at the home position. The cap 25 opens the closed space 33 by moving from the capping position to the separated position.

[0024] The suction mechanism 26 sucks the liquid from the nozzle 19 through the closed space 33. Specifically, the suction mechanism 26 drives the discharge pump 29 to reduce the pressure inside the closed space 33 and forcibly discharge the liquid from the nozzle 19. The discharged liquid is stored as waste liquid in the waste liquid storage section 27 through the discharge path 28. Maintenance in which the pressure inside the closed space 33 is reduced and the liquid is forcibly discharged from the nozzle 19 is also called suction cleaning.

[0025] The suction mechanism 26 may drive the discharge pump 29 while the cap 25 is in the separated position to discharge the liquid from the cap 25. Maintenance in which the liquid in the cap 25 is forcibly discharged while the closed space 33 is open is also called empty suction.

[0026] Maintenance in which liquid is discharged from the nozzles 19 by discharge is also called blank discharge or flushing. The cap 25 may receive the liquid discharged by blank discharge from the liquid discharge head 20. In the blank discharge of this embodiment, the liquid discharge head 20, which is located at the home position, discharges liquid toward the cap 25, which is located at the separated position.

[0027] Suction cleaning, in which liquid is discharged from the nozzle 19 into the cap 25 and from the cap 25 to the outside of the cap 25, is an example of cleaning. Idle discharge, in which liquid is discharged from the nozzle 19 into the cap 25, and idle suction, in which liquid is discharged from the cap 25 to the outside of the cap 25, are also examples of cleaning. The cleaning unit 24 of this embodiment can perform suction cleaning, idle discharge, and idle suction as cleaning. The cleaning unit 24 may discharge liquid into the cap 25 and discharge liquid from the cap 25 simultaneously or separately.

[0028] During suction cleaning and idle ejection, multiple types of liquid are ejected from the liquid ejection head 20. The multiple types of ejected liquid are mixed together within one cap 25. In this embodiment, the liquid within the cap 25 is also referred to as a mixed liquid.

[0029] <Electrical configuration> 2, the liquid ejection device 11 includes a control unit 35. The control unit 35 controls various components of the liquid ejection device 11, such as the printing unit 14 and the cleaning unit 24.

[0030] The control unit 35 may be configured as a circuit including: α: one or more processors that execute various processes according to a computer program; β: one or more dedicated hardware circuits, such as application specific integrated circuits, that execute at least some of the various processes; or γ: a combination thereof. The processor includes a CPU and memory, such as RAM and ROM, that stores program code or instructions configured to cause the CPU to execute processes. The memory, i.e., computer-readable medium, includes any readable medium that can be accessed by a general-purpose or dedicated computer.

[0031] <Liquid> The liquid contains a humectant and water. The liquid may contain materials such as a coloring material. The humectant may be, for example, a polyhydric alcohol such as glycerin or diethylene glycol. The humectant is hygroscopic and retains the absorbed water. The humectant prevents the liquid from thickening, thereby preventing clogging of the nozzle 19.

[0032] In this embodiment, the amount of moisturizer contained in a unit amount of liquid is referred to as the moisturizer amount M (unit: mol / g). The moisturizer amount M varies depending on the type of liquid. In this embodiment, the amount of water contained in a liquid is referred to as the water content. Water evaporates from the liquid surface where the liquid comes into contact with the air. Therefore, the amount of liquid and the amount of water change. In this embodiment, the amount of water contained in a liquid per unit amount before evaporation is referred to as the initial water content. The initial water content of each of multiple types of liquid differs depending on the type of liquid. Therefore, the water ratio R, which is the ratio of water to liquid per unit amount, differs depending on the type of liquid.

[0033] As shown in Table 1, the control unit 35 may store the number of nozzles N, the water ratio R, and the amount of humectant substance M in association with each type of liquid. The liquid ejection head 20 of this embodiment is capable of ejecting four types of liquid. The number of types of liquid that the liquid ejection head 20 is capable of ejecting may be less than four or more than four.

[0034] [Table 1]

[0035] The control unit 35 may store the number of nozzles Nm, water ratio Rm, and amount of moisturizer substance Mm corresponding to the mixed liquid. The control unit 35 may calculate the number of nozzles Nm, water ratio Rm, and amount of moisturizer substance Mm based on the number of nozzles Ni for each liquid (i: type of liquid), or may store the calculated values. The proportion of each type of liquid in the mixed liquid is proportional to the number Ni of nozzles ejecting that liquid.

[0036] The control unit 35 may calculate the number of nozzles Nm based on equation (1).

[0037]

number

[0038] The number of nozzles Nm, which is the number of nozzles 19 corresponding to the mixed liquid, is the total number of nozzles 19 that eject each liquid. The number of nozzles Nm may be the total number of nozzles 19 that the liquid ejection head 20 has.

[0039] The control unit 35 may calculate the water ratio Rm based on the formula (2).

[0040]

number

[0041] The water ratio Rm of the mixed liquid is the ratio of water to the mixed liquid per unit amount. The control unit 35 may calculate the amount of moisturizer substance Mm based on equation (3).

[0042]

number

[0043] The amount of moisturizing agent substance Mm in the mixed liquid is the amount of moisturizing agent substance contained in the mixed liquid per unit amount. In this embodiment, the amount of water lost due to evaporation from the water contained in each liquid is also referred to as the evaporation amount. In this embodiment, the ratio of the evaporation amount to the water before evaporation is also referred to as the water evaporation rate.

[0044] 3, the multiple liquids have different water and moisturizer contents, and therefore the way in which viscosity changes with respect to the moisture evaporation rate differs. In this embodiment, the control unit 35 corrects the relationship between the moisture evaporation rate change and the viscosity change for each of the multiple liquids using the water ratios R1 to R4 of the liquid, the moisturizer substance amounts M1 to M4 of the liquid, the water ratio Rm of the mixed liquid, and the moisturizer substance amount Mm of the mixed liquid.

[0045] The water ratios R1 to R4 are the water ratios of each of the multiple liquids, and the moisturizer substance amounts M1 to M4 are the moisturizer substance amounts of each of the multiple liquids. The water ratio Rm is the water ratio of the mixed liquid, and the moisturizer substance amount Mm is the moisturizer substance amount of the mixed liquid.

[0046] The control unit 35 corrects the relationship between the change in water evaporation rate and the change in viscosity of each of the plurality of types of liquid based on equation (4).

[0047]

number

[0048] FIG. 4 shows the results of correcting the relationship between the change in water evaporation rate and the change in viscosity of each of multiple types of liquid based on equation (4). When the cap 25 forms the closed space 33, the water vapor pressure of the mixed liquid inside the cap 25 and the first to fourth liquids inside each nozzle 19 becomes equilibrium. The specified viscosity P is set to the viscosity of the liquid that can be ejected by the liquid ejection head 20. The specified viscosity P is set in advance based on the results of ejecting liquids of different viscosities using the liquid ejection head 20 in use. The specified viscosity P may be set to a limit viscosity that is the limit viscosity at which the liquid ejection head 20 can eject liquid, or may be set to a viscosity that is a predetermined amount lower than the limit viscosity to allow for a margin.

[0049] In this embodiment, the liquid among the multiple liquids that has the lowest water evaporation rate at which the specified viscosity P is reached as a result of the correction is set as the reference liquid. In this embodiment, the water evaporation rate at which the reference liquid reaches the specified viscosity P is set as the specified water evaporation rate. That is, in the case of FIG. 4, the first liquid is the reference liquid, and the specified water evaporation rate is approximately 25%. The control unit 35 may store, along with the specified water evaporation rate, a preliminary water evaporation rate that is lower than the specified water evaporation rate.

[0050] Next, a control method for the liquid ejection device 11 will be described with reference to the flowchart shown in Fig. 5. The control unit 35 may execute the maintenance routine shown in Fig. 5 when the power supply of the liquid ejection device 11 is turned on.

[0051] 5, in step S101, the control unit 35 determines whether the water evaporation rate of the mixed liquid is equal to or greater than the controlled water evaporation rate C. Here, the controlled water evaporation rate C may be set to a specified water evaporation rate, or may be set to a reserve water evaporation rate lower than the specified water evaporation rate in consideration of evaporation due to leaving the liquid standing, etc. If the water evaporation rate is equal to or greater than the controlled water evaporation rate C, step S101 becomes YES, and the control unit 35 proceeds to step S102.

[0052] In step S102, the control unit 35 executes cleaning. Thereafter, in step S103, the control unit 35 determines whether the water evaporation rate immediately before cleaning was equal to or less than the limit water evaporation rate X. The limit water evaporation rate X is the limit water evaporation rate at which the cumulative amount of water evaporated from the mixed liquid in the cap 25 can be returned to a value as close to zero as possible by the cleaning in step S102, and cleaning is usually set so that the limit water evaporation rate X is higher than the specified water evaporation rate. If the water evaporation rate immediately before cleaning is equal to or less than the limit water evaporation rate X, step S103 becomes YES, and the control unit 35 proceeds to step S104.

[0053] In step S104, the control unit 35 sets the cumulative value of the amount of water evaporated from the mixed liquid to 0, and in step S105, calculates an updated water evaporation rate. Thereafter, in step S106, the control unit 35 sets the water evaporation rate of the mixed liquid as the updated water evaporation rate, and ends the process. In step S101, if the water evaporation rate of the mixed liquid is less than the controlled water evaporation rate C, step S101 becomes NO, and the control unit 35 ends the process.

[0054] In step S103, if the water evaporation rate immediately before cleaning is greater than the limit water evaporation rate X, for example, if evaporation has progressed more than expected until cleaning is performed due to leaving the liquid unattended, step S103 is determined as NO, and the control unit 35 proceeds to step S107. In step S107, the control unit 35 calculates an updated water evaporation rate. In step S108, the control unit 35 sets the water evaporation rate of the mixed liquid as the updated water evaporation rate, and ends the process.

[0055] <Operation of the embodiment> The operation of this embodiment will be described. The control unit 35 performs cleaning based on the result of correction using the relationship between the change in water evaporation rate and the change in viscosity of each of the plurality of types of liquid.

[0056] Specifically, the control unit 35 sets the controlled evaporation rate C based on the result of correcting the relationship between the change in evaporation rate and the change in viscosity of each of the multiple types of liquid. The control unit 35 may perform cleaning based on the controlled evaporation rate C. The control unit 35 calculates the evaporation rate of the mixed liquid, and performs cleaning by comparing the calculated evaporation rate with the controlled evaporation rate C.

[0057] The control unit 35 may calculate an updated water evaporation rate based on the amount of water lost due to evaporation when the water evaporation rate is lower than the control water evaporation rate C. In the case of evaporation, the control unit 35 may calculate the updated water evaporation rate based on the following formula:

[0058] Updated water evaporation rate = Cumulative amount of water evaporated from the mixed liquid up to this calculation / Cumulative amount of mixed liquid replenished and drained up to this calculation Amount of mixed liquid in this calculation = Amount of mixed liquid in the previous calculation - Amount of water evaporated from the mixed liquid between the previous calculation and the current calculation Cumulative amount of water evaporated from the mixed liquid up to the current calculation = Cumulative amount of water evaporated from the mixed liquid up to the previous calculation + Amount of water evaporated from the mixed liquid from the previous calculation to the current calculation The cumulative amount of mixed liquid refilled and discharged up to this calculation = the cumulative amount of mixed liquid refilled and discharged up to the previous calculation Here, the cumulative value of the amount of mixed liquid is a value that is added by refilling, which will be described later, and is a value that is subtracted by discharge, such as by empty suction, which will be described later, and the cumulative value of the amount of water that has evaporated from the mixed liquid is a value that is normally added, but is a value that is subtracted by discharge, such as by empty suction, which will be described later.

[0059] When the water evaporation rate is lower than the control water evaporation rate C, the control unit 35 may calculate the updated water evaporation rate based on the amount of water increased by replenishment such as blank discharge. In the case of replenishment, the control unit 35 may calculate the updated water evaporation rate based on the following formula.

[0060] Updated water evaporation rate = Cumulative amount of water evaporated from the mixed liquid up to this calculation / Cumulative amount of mixed liquid replenished and drained up to this calculation Amount of mixed liquid in this calculation = Amount of mixed liquid in the previous calculation + Amount of mixed liquid replenished this time Cumulative amount of water evaporated from the mixed liquid up to the current calculation = Cumulative amount of water evaporated from the mixed liquid up to the previous calculation - Amount of mixed liquid replenished in this replenishment × Evaporation coefficient The cumulative amount of mixed liquid refilled and discharged up to this calculation = the cumulative amount of mixed liquid refilled and discharged up to the previous calculation + the amount of mixed liquid refilled in this refill Here, the cumulative value of the amount of mixed liquid is a value that is added by refilling and subtracted by discharge such as empty suction, which will be described later, and the cumulative value of the amount of water evaporated from the mixed liquid is a value that is normally added, but is a value that is subtracted by discharge such as empty suction, which will be described later.

[0061] When the water evaporation rate is smaller than the updated water evaporation rate, the control unit 35 may calculate the updated water evaporation rate based on the amount of water reduced by discharge such as empty suction. In the case of discharge, the control unit 35 may calculate the updated water evaporation rate based on the following formula:

[0062] Updated water evaporation rate = Cumulative amount of water evaporated from the mixed liquid up to this calculation / Cumulative amount of mixed liquid replenished and drained up to this calculation Amount of mixed liquid in this calculation = Initial amount of mixed liquid Cumulative amount of water evaporated from the mixed liquid up to the current calculation = Cumulative amount of water evaporated from the mixed liquid up to the previous calculation × Initial amount of mixed liquid / Amount of mixed liquid in the previous calculation Accumulative amount of mixed liquid replenished and discharged up to the current calculation = Accumulative amount of mixed liquid replenished and discharged up to the previous calculation × Initial amount of mixed liquid / Amount of mixed liquid at the previous calculation Here, the cumulative value of the amount of mixed liquid is a value that is added by refilling as already explained and is subtracted by discharge such as empty suction, and the cumulative value of the amount of water evaporated from the mixed liquid is a value that is usually added, but is a value that is subtracted by discharge such as empty suction.

[0063] The control unit 35 may perform cleaning when the evaporation rate inside the cap 25 reaches the controlled evaporation rate C. The evaporation rate inside the cap 25 is also the evaporation rate of the mixed liquid. The cleaning may be, for example, suction cleaning. When cleaning is performed when the evaporation rate is equal to or higher than the controlled evaporation rate C and equal to or lower than the limit evaporation rate X, the control unit 35 may calculate an updated evaporation rate based on the following formula:

[0064] Updated water evaporation rate = Cumulative amount of water evaporated from the mixed liquid up to this calculation / Cumulative amount of mixed liquid replenished and drained up to this calculation Amount of mixed liquid in this calculation = Initial amount of mixed liquid The cumulative amount of water evaporated from the mixed liquid up to this calculation = 0 The cumulative amount of mixed liquid that has been replenished and discharged up to this calculation = the initial amount of mixed liquid If cleaning is to be performed after the moisture evaporation rate has exceeded the control moisture evaporation rate C and the limit moisture evaporation rate X due to neglect or the like, the control unit 35 may calculate an updated moisture evaporation rate by combining the calculation based on the replenishment and the calculation based on the discharge.

[0065] <Effects of the embodiment> The effects of this embodiment will be described. (1) The relationship between the change in water evaporation rate and the change in viscosity of each of the multiple liquids is corrected using the amount of water and the amount of humectant substance M contained in each of the multiple liquids and the mixed liquid. The mixed liquid is a mixture of multiple liquids discharged from multiple nozzles 19 inside the cap 25. Therefore, by performing cleaning based on the correction results, cleaning can be performed taking into account the multiple liquids and the mixed liquid, and an increase in viscosity of the liquid inside the nozzle 19 can be suppressed.

[0066] (2) Cleaning is performed based on the specified water evaporation rate of the reference liquid, which is the liquid that is most likely to increase in viscosity among multiple liquids. In other words, cleaning is performed based on the liquid that is most likely to increase in viscosity, so that the increase in viscosity inside the nozzle 19 can be further suppressed.

[0067] (3) Since cleaning is performed when the water evaporation rate inside the cap 25 reaches a specified water evaporation rate, the risk of the viscosity of the liquid inside the nozzle 19 increasing and causing ejection defects can be reduced.

[0068] (4) Since cleaning is performed when the water evaporation rate in the cap 25 reaches a preliminary water evaporation rate that is lower than the specified water evaporation rate, the risk of the water evaporation rate in the cap 25 exceeding the specified water evaporation rate can be reduced.

[0069] (5) Since the cumulative amount of water evaporated from the mixed liquid in the cap 25 during cleaning is set to 0, the load on the control unit 35 can be reduced compared to when the water evaporation rate is calculated, for example.

[0070] (6) Since the water evaporation rate in the cap 25 after cleaning is set to the calculated updated water evaporation rate, the accuracy of the water evaporation rate in the cap 25 after cleaning can be improved.

[0071] [Example of change] This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0072] The control unit 35 may periodically execute blank ejection and update the water evaporation rate during printing. The liquid ejection device 11 may include a pressurizing mechanism that pressurizes the liquid inside the liquid ejection head 20. The liquid ejection device 11 may perform pressure cleaning, in which pressurized liquid is discharged from the nozzles 19, as cleaning.

[0073] The control unit 35 may perform at least one of suction cleaning, idle discharge, idle suction, and pressure cleaning in step S102 of Fig. 5. The control unit 35 may perform a combination of suction cleaning, idle discharge, idle suction, and pressure cleaning as cleaning.

[0074] The control unit 35 may perform cleaning by simultaneously discharging liquid from all nozzles 19. The control unit 35 may also perform cleaning by discharging liquid from some of the nozzles 19. For example, the control unit 35 may perform cleaning for each nozzle 19 that ejects the same type of liquid. The control unit 35 may calculate an updated water evaporation rate according to the type of liquid to be discharged. The control unit 35 may calculate an updated water evaporation rate and set the water evaporation rate in the cap 25 as the updated water evaporation rate even when cleaning is performed when the water evaporation rate in the cap 25 is equal to or higher than the control water evaporation rate C and equal to or lower than the limit water evaporation rate X.

[0075] The control unit 35 may set the cumulative amount of water evaporated from the mixed liquid up to the current calculation time to 0, regardless of the cleaning being performed or the water evaporation rate at that time. The control unit 35 may perform cleaning based on either the controlled water evaporation rate C or the preliminary water evaporation rate.

[0076] After performing cleaning, the control unit 35 may perform cleaning at a time interval shorter than the time interval required for the amount of water evaporation to exceed the controlled water evaporation rate C. The liquid container 22 may be a replaceable cartridge or a tank that can be replenished with liquid. The liquid container 22 may be provided at a position different from the carriage 21. The liquid ejection head 20 may eject liquid supplied from the liquid container 22 via a liquid supply flow path.

[0077] In the case of a liquid ejection device that uses a liquid container 22 with a small capacity, it may not be possible to set a sufficient amount of cleaning, and the limit evaporation rate X may become smaller than the specified evaporation rate. In such cases, the limit evaporation rate X may be set as the controlled evaporation rate C, or a moisture evaporation rate smaller than the limit evaporation rate X may be set.

[0078] The liquid ejection device 11 may be a liquid ejection device that ejects or discharges liquids other than ink. The liquid ejected as minute droplets from the liquid ejection device may be in the form of granules, tears, or strings. The liquid referred to here may be any material that can be ejected from the liquid ejection device. For example, the liquid may be in any liquid phase, including fluids such as high or low viscosity liquids, sols, gel water, other inorganic solvents, organic solvents, solutions, liquid resins, liquid metals, and metal melts. The liquid may refer not only to a single state of matter, but also to solid functional material particles, such as pigments and metal particles, dissolved, dispersed, or mixed in a solvent. Typical examples of liquids include inks and liquid crystals, as described in the above embodiments. Here, ink encompasses various liquid compositions, such as general water-based inks and oil-based inks, as well as gel inks and hot-melt inks. Specific examples of liquid ejection devices include devices that eject liquids containing dispersed or dissolved materials such as electrode materials and color materials used in the manufacture of liquid crystal displays, electroluminescent displays, surface-emitting displays, and color filters. The liquid ejection device may be a device that ejects bioorganic materials used in biochip manufacture, a device used as a precision pipette to eject sample liquids, a textile printing device, a microdispenser, or the like. The liquid ejection device may be a device that ejects lubricating oil with pinpoint accuracy onto precision machinery such as watches and cameras, or a device that ejects transparent resin liquids such as ultraviolet-curing resins onto substrates to form micro-hemispherical lenses, optical lenses, and the like used in optical communication elements. The liquid ejection device may also be a device that ejects etching liquids such as acids or alkalis to etch substrates, etc.

[0079] [Note] The technical concepts and effects that can be understood from the above-described embodiment and modified examples will be described below.

[0080] (A) A method for controlling a liquid ejection device includes a liquid ejection head capable of ejecting multiple types of liquid from multiple nozzles, a cap capable of forming a closed space in which the multiple nozzles are open, and a cleaning unit capable of performing cleaning by discharging the liquid from the nozzles into the cap and discharging the liquid from the cap to the outside, wherein the cleaning is performed based on the results of correcting the relationship between the change in water evaporation rate and the change in viscosity of each of the multiple types of liquid using the amount of water contained in each of the multiple types of liquid before water evaporation, the amount of moisturizing substance contained in each of the multiple types of liquid, the amount of water contained in a mixed liquid obtained by mixing the multiple types of liquid before water evaporation, and the amount of moisturizing substance contained in the mixed liquid.

[0081] According to this method, the relationship between the change in water evaporation rate and the change in viscosity of each of the multiple liquids is corrected using the amount of water and the amount of humectant substance contained in each of the multiple liquids and the mixed liquid. The mixed liquid is a mixture of multiple liquids discharged from multiple nozzles inside the cap. Therefore, by performing cleaning based on the correction results, cleaning can be performed taking into account the multiple liquids and the mixed liquid, and an increase in the viscosity of the liquid inside the nozzles can be suppressed.

[0082] (B) In the control method for a liquid ejection device, when the liquid having the lowest water evaporation rate at which the liquid reaches a specified viscosity P among the plurality of liquids is used as a reference liquid in the corrected result, and the water evaporation rate at which the reference liquid reaches the specified viscosity P is used as a specified water evaporation rate, the cleaning may be performed based on the specified water evaporation rate.

[0083] According to this method, cleaning is performed based on the specified water evaporation rate of the reference liquid, which is the liquid that is most likely to increase in viscosity among multiple liquids. In other words, cleaning is performed according to the liquid that is most likely to increase in viscosity, so the increase in viscosity inside the nozzle can be further suppressed.

[0084] (C) In the method for controlling a liquid ejection device, the cleaning may be performed when the water evaporation rate in the cap reaches the specified water evaporation rate. According to this method, cleaning is performed when the water evaporation rate inside the cap reaches a specified water evaporation rate, thereby reducing the risk of ejection defects occurring due to an increase in the viscosity of the liquid inside the nozzle.

[0085] (D) In ​​the method for controlling a liquid ejection device, the cleaning may be performed when the water evaporation rate in the cap reaches a preliminary water evaporation rate that is lower than the specified water evaporation rate. According to this method, cleaning is performed when the water evaporation rate inside the cap reaches a preliminary water evaporation rate that is lower than the specified water evaporation rate, thereby reducing the risk of the water evaporation rate inside the cap exceeding the specified water evaporation rate.

[0086] (E) In the method for controlling a liquid ejection device, the cumulative amount of water evaporated from the mixed liquid in the cap during the cleaning may be set to zero. According to this method, the load on the control unit can be reduced compared to when the water evaporation rate is calculated, for example.

[0087] (F) The control method for a liquid ejection device may further include calculating an updated water evaporation rate based on the amount of water contained in the liquid replenished in the cap by the cleaning and the water evaporation rate in the cap immediately before the cleaning, and setting the water evaporation rate in the cap to the updated water evaporation rate in conjunction with the cleaning.

[0088] According to this method, the water evaporation rate inside the cap after cleaning is set to the calculated updated water evaporation rate, so that the accuracy of the water evaporation rate inside the cap after cleaning can be improved.

[0089] (G) A liquid ejection device includes a liquid ejection head capable of ejecting multiple types of liquid from multiple nozzles, a cap capable of forming a closed space in which the multiple nozzles open, a cleaning unit capable of ejecting the liquid from the nozzles into the cap and performing cleaning to eject the liquid from the cap to the outside, and a control unit, wherein the control unit causes the cleaning unit to perform the cleaning based on the results of correcting the relationship between the change in water evaporation rate and the change in viscosity of each of the multiple types of liquid using the amount of water contained in each of the multiple types of liquid before water evaporation, the amount of moisturizing substance contained in each of the multiple types of liquid, the amount of water contained in a mixed liquid obtained by mixing the multiple types of liquid before water evaporation, and the amount of moisturizing substance contained in the mixed liquid.

[0090] According to this configuration, it is possible to achieve the same effects as the above-described method for controlling a liquid ejection device. [Explanation of symbols]

[0091] 11...liquid ejection device, 12...housing, 13...guide shaft, 14...printing unit, 15...medium, 16...medium support unit, 17...maintenance unit, 19...nozzle, 20...liquid ejection head, 21...carriage, 22...liquid container, 23...wiping unit, 24...cleaning unit, 25...cap, 26...suction mechanism, 27...waste liquid storage unit, 28...discharge path, 29...discharge pump, 31...lip unit, 32...absorbing member, 33...closed space, 35...control unit, C...controlled moisture evaporation rate, P...specified viscosity.

Claims

1. A method for controlling a liquid ejection device including a liquid ejection head capable of ejecting a plurality of types of liquid from a plurality of nozzles, a cap capable of forming a closed space in which the plurality of nozzles are open, and a cleaning unit capable of performing cleaning by discharging the liquid from the nozzles to the cap and discharging the liquid from the cap to the outside, comprising: The relationship between the change in water evaporation rate and the change in viscosity of each of the plurality of liquids is the amount of water contained in each of the plurality of liquids before evaporation of the water; the amount of moisturizing agent contained in each of the plurality of liquids; the amount of water contained in the mixed liquid obtained by mixing the plurality of liquids before water evaporation; the amount of moisturizing agent contained in the mixed liquid; and performing the cleaning based on the correction result using the correction result.

2. In the corrected results, when the liquid having the lowest water evaporation rate at which the specified viscosity is reached among the plurality of liquids is defined as a reference liquid, and the water evaporation rate at which the reference liquid reaches the specified viscosity is defined as a specified water evaporation rate, The method for controlling a liquid ejection device according to claim 1 , wherein the cleaning is performed based on the specified water evaporation rate.

3. 3. The method for controlling a liquid ejection device according to claim 2, wherein the cleaning is performed when the water evaporation rate in the cap reaches the specified water evaporation rate.

4. 3. The method for controlling a liquid ejection device according to claim 2, wherein the cleaning is performed when the water evaporation rate in the cap reaches a preliminary water evaporation rate that is lower than the specified water evaporation rate.

5. 5. The method for controlling a liquid ejection device according to claim 1, wherein a cumulative value of the amount of water evaporated from the mixed liquid in the cap during the cleaning is set to zero.

6. calculating an updated water evaporation rate based on the amount of water contained in the liquid replenished in the cap by the cleaning and the water evaporation rate in the cap immediately before the cleaning; setting the water evaporation rate in the cap to the updated water evaporation rate during the cleaning; 5. The method for controlling a liquid ejection device according to claim 1, further comprising:

7. a liquid ejection head capable of ejecting a plurality of types of liquid from a plurality of nozzles; a cap capable of forming a closed space in which the plurality of nozzles are open; a cleaning unit that discharges the liquid from the nozzle into the cap and performs cleaning by discharging the liquid from the cap to the outside of the cap; A control unit; Equipped with The control unit The relationship between the change in water evaporation rate and the change in viscosity of each of the plurality of liquids is the amount of water contained in each of the plurality of liquids before evaporation of the water; the amount of moisturizing agent contained in each of the plurality of liquids; the amount of water contained in the mixed liquid obtained by mixing the plurality of liquids before water evaporation; the amount of moisturizing agent contained in the mixed liquid; and causing the cleaning unit to perform the cleaning based on the correction result using the above formula.

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