Liquid ejection device and wiping method

Abstract

To provide means for optimizing a condition for a wiping process.SOLUTION: A printer 10 includes: a wiper 72 which abuts on a nozzle surface 33A of a print head 34 and moves relatively with respect to the print head 34; and a controller 130. Based on an elapsed time t from execution of a wiping process, a wiper speed V, and a power Fwipe, the controller 130 executes an estimation process for estimating whether a droplet of ink remains on the nozzle surface 33A or not when the wiping process is executed. At least one of the elapsed time t, the wiper speed V, and an amount p of pressing is changed in response to the estimation that the droplet of ink remains on the nozzle surface 33A in the estimation process.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a liquid ejection device equipped with a wiper that wipes liquid off a nozzle surface. [Background technology]

[0002] For example, in the image forming device disclosed in Patent Document 1, the dryness of the nozzle is calculated based on the dot size of the ink ejected from the nozzle of the head during the final ejection and the non-ejection time since the final ejection, and a determination is made as to whether or not a preliminary ejection of ink is necessary from the head. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-94950 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, ink that adheres to the nozzle surface of the head due to purging or the like is wiped off by a wiping process using a wiper. However, when moisture evaporates from the ink that adheres to the nozzle surface, the viscosity and surface tension of the ink change. In addition, the pressure with which the wiper presses against the nozzle surface and the speed at which the wiper moves can also affect the wiping off of the ink. This has led to the problem that it is difficult to set optimal conditions for the wiping process.

[0005] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a means for determining optimal wiping conditions. [Means for solving the problem]

[0006] (1) A liquid ejection device according to the present invention includes a head having nozzles opening on a nozzle surface, a wiper that comes into contact with the nozzle surface and moves relative to the head, and a controller. The controller executes a viscosity determination process that determines the viscosity of liquid adhering to the nozzle surface, and a wiping process that brings the wiper into contact with the nozzle surface and moves relative to the head. If the determined viscosity is less than a first viscosity that indicates that the liquid has substantially solidified, the wiping process causes the pressing pressure of the wiper when it comes into contact with the nozzle surface to be greater than the stress caused by viscous friction of the liquid located on the nozzle surface.

[0007] Even if water evaporates from the liquid adhering to the nozzle surface and part of the liquid solidifies, the liquid can be wiped off from the nozzle surface by the wiper.

[0008] (2) The controller may execute an adhesion determination process to determine an adhesion force of the liquid adhered to the nozzle surface when the determined viscosity is equal to or greater than the first viscosity. When the determined adhesion force is less than a first adhesion force, the pressing pressure in the wiping process may be greater than the determined adhesion force.

[0009] Even if the water evaporates from the liquid adhering to the nozzle face and the liquid substantially solidifies, the liquid can be wiped off from the nozzle face by the wiper.

[0010] (3) The liquid ejection device may further include an alarm connected to the controller, and the controller may activate the alarm when the determined adhesive force is equal to or greater than the first adhesive force.

[0011] The user can be notified by the alarm that an abnormality has occurred in the head.

[0012] (4) The controller may determine an evaporation rate of the liquid adhering to the nozzle surface based on at least a time elapsed since the previous wiping process was performed, liquid information about the liquid ejected by the head, and environmental information about the environment of the head. The controller may determine a viscosity of the liquid adhering to the nozzle surface based on the determined evaporation rate.

[0013] The wiper can more reliably wipe the liquid off the nozzle face.

[0014] (5) The liquid ejection device may further include an alarm connected to the controller. The controller may determine a stress due to viscous friction of the liquid in a shear flow generated in the liquid by the relatively moving wiper based on the determined viscosity. The controller may activate the alarm when the determined stress due to viscous friction is equal to or greater than the pressing pressure.

[0015] The user can be notified by the alarm that an abnormality has occurred in the head.

[0016] (6) When the determined stress due to viscous friction is less than the pressing pressure, the controller may determine a maximum movement speed of the wiper at which a workload caused by the stress due to viscous friction and a workload caused by the surface tension of the liquid generated in the liquid by the relatively moving wiper are balanced. When the determined maximum movement speed is smaller than a planned movement speed at which the head and the wiper are moved relatively in the wiping process, an alarm may be activated.

[0017] The user can be notified by the alarm that an abnormality has occurred in the head.

[0018] (7) The controller may determine the pressing pressure based on wiper information related to the wiper.

[0019] The wiper can more reliably wipe the liquid off the nozzle face.

[0020] (8) The controller may determine the adhesion force based on the determined evaporation rate.

[0021] The wiper can more reliably wipe the liquid off the nozzle face.

[0022] (9) The controller may increase the pressing pressure as the elapsed time increases.

[0023] As the elapsed time increases, the viscosity of the liquid increases, so by increasing the pressing pressure, the wiper can more reliably wipe the liquid from the nozzle surface.

[0024] (10) The controller may change the pressing pressure by changing a position of the wiper with respect to the nozzle face in a vertical direction.

[0025] The pressing pressure can be easily changed.

[0026] (11) The liquid may be a water-based ink containing a pigment and a water-soluble organic solvent.

[0027] (12) The liquid may further contain a plurality of resin fine particles.

[0028] A film in which multiple resin particles are connected together is formed as a result of drying, making it difficult for the wiper to wipe the liquid from the nozzle surface, but this makes it possible to effectively wipe the liquid from the nozzle surface with the wiper.

[0029] (13) In the liquid, the mass ratio of the solid content including at least the pigment to the water-soluble organic solvent (water-soluble organic solvent / solid content) may be 1.0 or more. The water-soluble organic solvent may include one having a saturated vapor pressure of 20 Pa or less at 20° C.

[0030] Because the liquid is less likely to solidify, the liquid can be wiped off from the nozzle surface by the wiper more reliably.

[0031] (14) In the liquid, a mass ratio of a solid content including at least the pigment to the water-soluble organic solvent (water-soluble organic solvent / solid content) may be 2.0 or more. An aqueous solution having a solid content of 10 wt % may have a conductivity of 5 mS / cm or less.

[0032] Because the viscosity of the liquid is reduced, the wiper can more reliably wipe the liquid from the nozzle surface.

[0033] (15) In the liquid, the mass ratio (water-soluble organic solvent / solids) of the solids content including at least the pigment to the water-soluble organic solvent may be 2.0 or more. The water-soluble organic solvent may include one having a saturated vapor pressure of 20 Pa or less at 20° C. An aqueous solution having a solid content of 10 wt % may have a conductivity of 5 mS / cm or less.

[0034] Because the liquid is less likely to solidify and the viscosity of the liquid is lower, the liquid can be wiped off from the nozzle surface by the wiper more reliably.

[0035] (16) A wiping method according to the present invention includes a viscosity determining step of determining a viscosity of a liquid adhering to a nozzle surface of a head, and a wiping step of wiping off the liquid adhering to the nozzle surface with a wiper that moves relatively to the head while contacting the nozzle surface. If the determined viscosity is less than a first viscosity indicating that the liquid has substantially solidified, a pressing pressure when the wiper contacts the nozzle surface in the wiping step is greater than a stress due to viscous friction of the liquid located on the nozzle surface.

[0036] Even if water evaporates from the liquid adhering to the nozzle surface and part of the liquid solidifies, the liquid can be wiped off from the nozzle surface by the wiper.

[0037] (17) The wiping method may further include an adhesion force determination step of determining an adhesion force of the liquid adhered to the nozzle surface when the determined viscosity is equal to or greater than the first viscosity. When the determined adhesion force is less than a first adhesion force, the pressing pressure in the wiping step may be greater than the determined adhesion force.

[0038] Even if the water evaporates from the liquid adhering to the nozzle face and the liquid substantially solidifies, the liquid can be wiped off from the nozzle face by the wiper.

[0039] (18) When the determined adhesion is equal to or greater than the first adhesion, an alarm may be activated.

[0040] The user can be notified by the alarm that an abnormality has occurred in the head.

[0041] (19) An evaporation rate of the liquid adhering to the nozzle surface may be determined based on at least the elapsed time since the wiping step in which the wiper comes into contact with the nozzle surface and moves relative to the head, liquid information about the liquid ejected by the head, and environmental information about the environment of the head. A viscosity of the liquid adhering to the nozzle surface may be determined based on the determined evaporation rate.

[0042] The wiper can more reliably wipe the liquid off the nozzle face.

[0043] (20) A stress due to viscous friction of the liquid in a shear flow generated in the liquid by the relatively moving wiper may be determined based on the determined viscosity. When the determined stress due to viscous friction is greater than the pressing pressure, an alarm may be activated.

[0044] The user can be notified by the alarm that an abnormality has occurred in the head.

[0045] (21) When the determined stress due to viscous friction is less than the pressing pressure, a maximum movement speed of the wiper at which the work amount caused by the stress due to viscous friction and the work amount caused by the surface tension of the liquid caused by the relatively moving wiper are balanced may be determined. When the determined maximum movement speed is smaller than a planned movement speed at which the head and the wiper are moved relatively in the wiping process, an alarm may be activated.

[0046] The user can be notified by the alarm that an abnormality has occurred in the head.

[0047] (22) The pressing pressure may be determined based on wiper information relating to the wiper.

[0048] The wiper can more reliably wipe the liquid off the nozzle face.

[0049] (23) The adhesive force of the liquid adhering to the nozzle surface may be determined based on the determined evaporation rate.

[0050] The wiper can more reliably wipe the liquid off the nozzle face.

[0051] (24) The pressing pressure may be increased as the elapsed time increases.

[0052] As the elapsed time increases, the viscosity of the liquid increases, so by increasing the pressing pressure, the wiper can more reliably wipe the liquid from the nozzle surface.

[0053] (25) The pressing pressure may be changed by changing the position of the wiper with respect to the nozzle face in the vertical direction.

[0054] The pressing pressure can be easily changed.

[0055] (26) The liquid may be a water-based ink containing a pigment and a water-soluble organic solvent.

[0056] (27) A wiping method according to the present invention is a liquid containing a pigment and a water-soluble organic solvent, and the liquid attached to the nozzle surface of a head has a mass ratio (water-soluble organic solvent / solids) of 2.0 or more between a solid content containing at least the pigment and the water-soluble organic solvent. The water-soluble organic solvent includes a solvent having a saturated vapor pressure of 20 Pa or less at 20° C. In a wiping step in which the liquid, in which a 10% aqueous solution of the solid content has a conductivity of 5 mS / cm or less, is wiped away by a wiper that moves relatively to the head while contacting the nozzle surface, a pressing pressure when the wiper contacts the nozzle surface is greater than a stress due to viscous friction of the liquid that is located on the nozzle surface and has a viscosity less than a first viscosity indicating that the liquid has substantially solidified.

[0057] Even if water evaporates from the liquid adhering to the nozzle surface and part of the liquid solidifies, the liquid can be wiped off from the nozzle surface by the wiper. Effect of the Invention

[0058] According to the present invention, the optimum wiping conditions are determined. [Brief description of the drawings]

[0059] [Figure 1] FIG. 1 is a perspective view of a printer 10. [Diagram 2] FIG. 2 is a schematic diagram showing the internal configuration of the printer 10. As shown in FIG. [Diagram 3] FIG. 3 is a schematic diagram showing the print head 34, the cap 71, the wiper 72, and the wet wiper 76. [Figure 4] FIG. 4 is a functional block diagram of the printer 10. [Diagram 5] FIG. 5 is a flowchart showing the determination process. [Figure 6] FIG. 6 is a flowchart showing the estimation process. [Figure 7] FIG. 7 is a schematic diagram showing a state in which wiper blade 73 comes into contact with ink droplets in a solid state adhering to nozzle face 33A. [Figure 8]FIG. 8 is a schematic diagram showing a state in which wiper blade 73 comes into contact with ink droplets in a liquid state adhering to nozzle face 33A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0060] The printer 10 according to the embodiment of the present invention will be described in detail below. Note that the embodiment described below is merely an example of the present invention, and it goes without saying that the embodiment can be modified as appropriate without departing from the gist of the present invention.

[0061] In the embodiment, the direction is expressed as the progress from the start point of the arrow to the end point, and the direction is expressed as the movement on the line connecting the start point and end point of the arrow. An up-down direction 1 is defined based on the state in which the printer 10 is installed and ready for use (the state in FIG. 1). A front-rear direction 2 is defined based on the side in the printer 10 where the paper feed tray 23 is pulled out being the front. A left-right direction 3 is defined when the printer 10 is viewed from the front side (front side).

[0062] [Appearance of Printer 10] 1 and 4, a printer 10 (an example of a liquid ejection device) includes a housing 20, an operation unit 21, a cover 22, a paper feed tray 23, a paper discharge tray 24, a controller 130, and a memory 140, which are held by the housing 20. The printer 10 records an image on a sheet 6 (see FIG. 2).

[0063] The sheet 6 may be a recording medium cut to a predetermined size, may be one pulled out from a roll wound into a cylindrical shape, or may be of a fanfold type.

[0064] The operation unit 21 includes a display and a plurality of operation switches. The operation unit 21 accepts operations by the user. The operation unit 21 may be a touch panel. The operation unit 21 is an example of an alarm device.

[0065] 1, the paper feed tray 23 is located at the bottom of the housing 20. The paper discharge tray 24 is located at the bottom of the housing 20, above the paper feed tray 23. The cover 22 is located at the right part of the front surface of the housing 20. The bottom end of the cover 22 is rotatable relative to the housing 20. When the cover 22 is opened, the cartridge 70 that stores ink is accessible.

[0066] In this embodiment, the cartridge 70 is not limited to one that stores ink of one color such as black, and may be, for example, four cartridges 70 each storing four inks of black, yellow, cyan, and magenta. As shown in Fig. 2, the cartridge is equipped with an IC board 79, and liquid information that specifies the type of ink stored in the cartridge 70 is stored therein.

[0067] [Print Engine 50] As shown in FIG. 2, the housing 20 holds the print engine 50 therein. The print engine 50 mainly includes a feed roller 25, a transport roller 26, a discharge roller 27, a platen 28, and a print head 34 (an example of a head). The feed roller 25 is rotatably supported by an arm 29. The arm 29 is rotatably supported by a frame (not shown) provided in the housing 20. The feed roller 25 abuts against the sheet 6 placed on the paper feed tray 23. When the drive of the feed motor 102 (see FIG. 4) is transmitted to the feed roller 25 to rotate, the sheet 6 is fed from the paper feed tray 23 to the transport path 37. The transport path 37 is a space partitioned by a guide member (not shown). In this embodiment, the transport path 37 extends from the rear end of the paper feed tray 23 while curving upward, and then extends forward.

[0068] The conveying roller 26 and the driven roller 35 are located downstream of the paper feed tray 23 in the conveying direction 4 of the sheet 6. The driven roller 35 is biased by a spring toward the conveying roller 26. The driven roller 35 sandwiches the sheet 6 between itself and the conveying roller 26. When the drive of the conveying motor 101 (see FIG. 4) is transmitted to the conveying roller 26 to rotate, the sheet 6 sandwiched between itself and the driven roller 35 is conveyed in the conveying direction 4.

[0069] The discharge roller 27 and the driven roller 36 are located downstream of the conveying roller 26 in the conveying direction 4. The driven roller 36 is biased by a spring toward the discharge roller 27. The driven roller 36 sandwiches the sheet 6 between itself and the discharge roller 27. When the drive of the conveying motor 101 (see FIG. 4) is transmitted to the discharge roller 27 to rotate, the sheet 6 sandwiched between itself and the driven roller 36 is conveyed in the conveying direction 4.

[0070] The conveying roller 26 is provided with a rotary encoder 75 (see FIG. 4) that detects the amount of rotation of the shaft of the conveying roller 26. The rotary encoder 75 has an encoder disk (not shown) that rotates together with the shaft of the conveying roller 26, and an optical sensor (not shown). The encoder disk is formed with a pattern in which transmissive portions through which light is transmitted and non-transmissive portions through which light is not transmitted are alternately arranged at equal pitches in the circumferential direction. When the encoder disk rotates, a pulse signal is generated every time the optical sensor detects a transmissive portion and a non-transmissive portion. The generated pulse signal is output to the controller 130 (see FIG. 4). The controller 130 calculates the amount of rotation of the conveying roller 26 based on the received pulse signal.

[0071] The platen 28 is located between the transport roller 26 and the discharge roller 27 in the front-rear direction 2. The platen 28 supports the sheet 6 on its upper surface.

[0072] The print head 34 is located between the transport roller 26 and the discharge roller 27 in the front-rear direction 2. The print head 34 is located above the platen 28 in the up-down direction 1. The print head 34 is mounted on a carriage 40 (see FIG. 4). The carriage 40 is movably supported by a guide rail (not shown) extending along the left-right direction 3. When the drive of a carriage drive motor 103 (see FIG. 4) is transmitted, the carriage 40 moves in the left-right direction 3. As the carriage 40 moves, the print head 34 moves along the left-right direction 3.

[0073] The print head 34 has an internal flow path through which ink flows. The flow path is connected to the cartridge 70 by a tube 31. Ink is supplied from the cartridge 70 to the print head 34 through the tube 31. The bottom surface of the print head 34 is the nozzle surface 33A. A plurality of nozzles 33 are opened in the nozzle surface 33A. When a piezoelectric element 45 (see FIG. 4) corresponding to each nozzle 33 is driven, ink droplets are ejected from each nozzle 33. Note that the print head 34 may be a line head instead of a serial head. In the case of a line head, a wiper 72 and a wet wiper 76 (see FIG. 3), which will be described later, move relatively to the line head to wipe the nozzle surface 33A.

[0074] An encoder 38 (see FIG. 4) is disposed on the guide rail. The encoder 38 includes an encoder strip extending along the guide rail, and an optical sensor mounted on the carriage 40. The encoder strip has a pattern in which light-transmitting sections that transmit light and light-blocking sections that block light are alternately arranged at equal pitches in the left-right direction 3. A pulse signal is detected by the optical sensor detecting the light-transmitting sections and the light-blocking sections. The pulse signal is a signal that corresponds to the position of the carriage 40 in the left-right direction 3. The pulse signal is output to the controller 130. The controller 130 calculates the position and speed of the carriage 40 in the left-right direction 3 based on the received pulse signal.

[0075] [Cap 71, Wiper 72, Wet Wiper 76] As shown in Figure 3, the cap 71 is made of an elastic material such as rubber. The cap 71 is located below the print head 34 in the maintenance position. The cap 71 is cup-shaped and opens upward. The cap 71 can be moved in the vertical direction 1 by a cap drive motor 104. As shown by the dashed line in Figure 3, the cap 71 comes into close contact with the nozzle surface 33A of the print head 34 in the maintenance position, covering the openings of all of the nozzles 33.

[0076] A waste ink tube 71A is connected to the cap 71. A discharge port 80 is formed at the bottom of the cap 71. One end of the waste ink tube 71A is connected to the discharge port 80. Fluid can flow through the internal space of the waste ink tube 71A. The other end of the waste ink tube 71A is connected to a waste ink tank (not shown).

[0077] When the pump 77 is driven with the cap 71 in close contact with the nozzle surface 33A of the print head 34, the internal space of the cap 71 is depressurized and ink is discharged from the nozzles 33 of the print head 34. The ink discharged from the print head 34 flows from the internal space of the cap 71 through the waste ink tube 71A into the waste ink tank.

[0078] The wiper 72 is located to the right of the cap 71, and can move in the vertical direction 1 as shown by the dashed line in FIG. 3. The wiper 72 has a wiper blade 73 made of an elastic material such as rubber, and a holder 74. The holder 74 supports the wiper blade 73. The wiper blade 73 extends upward from the holder 74. A tip 72A of the wiper blade 73 faces upward. The pressing pressure when the wiper blade 73 abuts against the nozzle surface 33A is determined by the overlapping length (push-in amount p) of the upper wiper blade 73 and the nozzle surface 33A in the vertical direction 1. In the wiper 72, the push-in amount p of the wiper blade 73 can be changed by, for example, changing the position of the holder 74 in the vertical direction 1. When the print head 34 moves to the right from the maintenance position with the wiper 72 in the upper position (as indicated by the dashed line in FIG. 3), the tip 72A of the wiper blade 73 comes into contact with the nozzle face 33A and wipes the nozzle face 33A. As a result, the wiper 72 wipes off the ink droplets adhering to the nozzle face 33A of the print head 34.

[0079] The wet wiper 76 is located to the right of the cap 71 and to the left of the wiper 72, and can move in the vertical direction 1 as shown by the dashed line in FIG. 3. The wet wiper 76 is made of a material capable of holding a cleaning liquid, such as a sponge. Specifically, the wet wiper 76 has a sponge wiper 76A and a holder 76B. The holder 76B supports the sponge wiper 76A. The sponge wiper 76A has a rectangular parallelepiped shape that is longer in the vertical direction 1 than in the horizontal direction 3. When the print head 34 moves to the right from the maintenance position in a state in which the wet wiper 76 is located at the top (the state shown by the dashed line in FIG. 3), the wet wiper 76 comes into contact with the nozzle surface 33A. As a result, the cleaning liquid is applied to the nozzle surface 33A of the print head 34. The cleaning liquid includes, for example, a water-soluble organic solvent, a surfactant, water, and the like.

[0080] [Controller 130 and Memory 140] The controller 130 controls various operations of the printer 10. As shown in Fig. 4, the controller 130 includes a CPU 131 and an ASIC 135. The memory 140 includes a ROM 132, a RAM 133, and an EEPROM 134. The CPU 131, the ASIC 135, the ROM 132, the RAM 133, and the EEPROM 134 are connected to each other via an internal bus 137.

[0081] The ROM 132 stores programs for the CPU 131 to control various operations. The RAM 133 is used as a storage area for temporarily recording data and signals used when the CPU 131 executes the programs, or as a working area for data processing. The EEPROM 134 stores settings and flags that should be retained even after the power is turned off.

[0082] The ASIC 135 is connected to the conveying motor 101, the feeding motor 102, the carriage driving motor 103, the cap driving motor 104, and the first wiper driving motor 105. The ASIC 135 incorporates a driving circuit for controlling each motor. The CPU 131 outputs a driving signal for rotating each motor to the driving circuit corresponding to each motor. The driving circuit outputs a driving current corresponding to the driving signal acquired from the CPU 131 to the corresponding motor. This causes the corresponding motor to rotate. That is, the controller 130 controls the feeding motor 102 to feed the sheet 6 to the conveying path 37. The controller 130 also controls the conveying motor 101 to drive the conveying roller 26 and the discharge roller 27 to convey the sheet 6. The controller 130 also controls the carriage driving motor 103 to move the carriage 40. The controller 130 also controls the cap driving motor 104 to move the cap 71 in the up-down direction 1. The controller 130 also controls the first wiper drive motor 105 to move the wiper 72 in the vertical direction 1. The controller 130 also controls the second wiper drive motor 106 to move the wet wiper 76 in the vertical direction 1.

[0083] The optical sensor of the rotary encoder 75 is connected to the ASIC 135. The controller 130 calculates the amount of rotation of the conveyor motor 101 based on the electrical signal received from the optical sensor of the rotary encoder 75.

[0084] The ASIC 135 is connected to an encoder 38. The controller 130 recognizes the position of the carriage 40 and whether or not it has moved, based on the pulse signal received from the encoder 38.

[0085] A piezoelectric element 45 is connected to the ASIC 135. The piezoelectric element 45 is operated by being supplied with power by the controller 130 via an IC (not shown). The controller 130 controls the supply of power to the piezoelectric element 45, and causes ink droplets to be selectively ejected from the multiple nozzles 33.

[0086] The ASIC 135 is connected to an environmental sensor 78. The environmental sensor 78 detects temperature and humidity and outputs a signal. The controller 130 determines the temperature and humidity of the environment in which the printer 10 is placed based on the signal output by the environmental sensor 78.

[0087] The ASIC 135 is connected to the IC board 79 of the cartridge 70 via, for example, a contact (not shown). The controller 130 writes electronic information to the IC board 79 and reads liquid information and the like stored in the IC board 79.

[0088] The operation unit 21 is connected to the ASIC 135. The ASIC 135 receives a signal from the operation unit 21 indicating that a button has been pressed. The ASIC 135 outputs display data indicating the content to be displayed on a display to the operation unit 21. For example, the ASIC 135 causes the display of the operation unit 21 to display messages such as "an abnormality has occurred in the head", "wiping operation cannot be performed properly", and "head maintenance cannot be performed properly". A pump 77 is also connected to the ASIC 35.

[0089] The IC substrate 79 stores liquid information related to the ink stored in the cartridge 70. The liquid information includes, for example, the ink density ρ, the initial concentration W0 of water, the maximum adhesive force A per unit area, the surface tension γ of the ink, the receding contact angle θD of the ink, and the equilibrium contact angle θE of the ink. The liquid information may be stored in the EEPROM 134 according to the type of ink. The controller 130 may read out the liquid information from the EEPROM 134 according to the type of ink read out from the IC substrate 79.

[0090] The EEPROM 134 stores wiper information about the wiper 72. The wiper information includes, for example, the Young's modulus E, thickness t, length L in the vertical direction 1, and depth b of the wiper blade 73, the pressing amount p of the wiper blade 73 against the nozzle surface 33A, and the wiper speed V.

[0091] The EEPROM 134 stores general constants such as the gas constant R, the molar mass M of water, the size a of one water molecule, the diffusion coefficient Dwa of water vapor, the saturated vapor pressure Ps of water, the diameter d of an ink droplet on the nozzle surface 33A, and other constants.

[0092] When recording an image on the sheet 6, the controller 130 alternately executes a transport process and a printing process. The transport process is a process for transporting the sheet 6 by a predetermined line feed amount by driving the transport rollers 26 and the discharge rollers 27. The controller 130 executes the transport process by controlling the transport motor 101. The printing process is a process for causing the print head 34 to eject ink droplets from the nozzles 33 by controlling the power supply to the piezoelectric elements 45 while moving the carriage 40 in the left-right direction 3.

[0093] After the conveying process is performed, the controller 130 stops the sheet 6. The controller 130 performs the printing process while the sheet 6 is stopped. That is, in the printing process, the controller 130 performs one pass in which ink droplets are ejected from the nozzles 33 while moving the carriage 40 rightward or leftward. In this way, one pass of image recording is performed on the sheet 6. The controller 130 can record images on the entire image recordable area of ​​the sheet 6 by alternately and repeatedly performing the conveying process and the printing process. That is, the controller 130 causes images to be recorded on one sheet 6 in multiple passes.

[0094] The controller 130 is not limited to the above, and may be one in which only the CPU 131 performs various processes, or one in which only the ASIC 135 performs various processes, or one in which the CPU 131 and the ASIC 135 work together to perform various processes. The controller 130 may be one in which one CPU 131 performs processes independently, or one in which multiple CPUs 131 share the processes. The controller 130 may be one in which one ASIC 135 performs processes independently, or one in which multiple ASICs 135 share the processes.

[0095] The controller 130 executes maintenance processes including a purging process, a wiping process, a wet wiping process, and a flushing process. The maintenance process is executed, for example, when the elapsed time t since the previous wiping process was executed reaches an initial elapsed time t0 stored in the EEPROM 134. The maintenance process may also be executed at other times, such as when the printer 10 is turned on or when the cartridge 70 is replaced.

[0096] The purging process is a process in which the pump 77 sucks ink from the nozzles 33 while the nozzles 33 are covered by the cap 71. In the purging process, the inside of the cap 71 is driven to create a negative pressure, and foreign matter is sucked out of the nozzles 33 together with the ink. The wiping process is a process in which the wiper 72 wipes the nozzle surface 33A of the print head 34. The wet wiping process is a process in which the wet wiper 76 applies cleaning liquid to the nozzle surface 33A of the print head 34. The flushing process is a process in which ink is ejected toward a flushing form (not shown).

[0097] [Ink composition] The ink is described in detail below. The ink is a water-based ink, and contains resin particles, a coloring material, a water-soluble organic solvent, a surfactant, and water.

[0098] The ink has wettability to hydrophobic recording media such as coated paper, plastic, film, and OHP sheets, but is not limited thereto, and may be suitable for image recording on recording media other than hydrophobic recording media such as plain paper, glossy paper, matte paper, etc. "Coated paper" refers to plain paper made mainly of pulp, such as high-grade printing paper or medium-grade printing paper, to which a coating agent has been applied for the purpose of improving smoothness, whiteness, gloss, etc., and specific examples include high-grade coated paper and medium-grade coated paper.

[0099] As the resin fine particles, for example, those containing at least one of methacrylic acid and acrylic acid as a monomer can be used, and for example, commercially available products may be used. The resin fine particles may further contain, for example, styrene, vinyl chloride, etc. as a monomer. The resin fine particles may be, for example, those contained in an emulsion. The emulsion is, for example, composed of resin fine particles and a dispersion medium (for example, water, etc.). The resin fine particles are not dissolved in the dispersion medium, but are dispersed within a specific particle size range. Examples of the resin fine particles include acrylic acid resins, maleic acid ester resins, vinyl acetate resins, carbonate type resins, polycarbonate type resins, styrene type resins, ethylene type resins, polyethylene type resins, propylene type resins, polypropylene type resins, urethane type resins, polyurethane type resins, polyester type resins, and copolymer resins thereof, and the like, but acrylic resins are preferable.

[0100] The resin particles used may have a glass transition temperature (Tg) in the range of 0° C. to 200° C. More preferably, the glass transition temperature (Tg) is 20° C. to 180° C., and even more preferably, 30° C. to 150° C.

[0101] As the emulsion, for example, commercially available products may be used. Examples of commercially available products include "Superflex (registered trademark) 870" (Tg: 71°C) and "Superflex (registered trademark) 150" (Tg: 40°C) manufactured by Daiichi Kogyo Seiyaku Co., Ltd., "Mobinyl (registered trademark) 6760" (Tg: -28°C) and "Mobinyl (registered trademark) DM774" (Tg: 33°C) manufactured by Japan Coating Resins Co., Ltd., "Polysol (registered trademark) AP-3270N" (Tg: 27°C) manufactured by Showa Denko K.K., "Hi-Loss-X (registered trademark) KE-1062" (Tg: 112°C) and "Hi-Loss-X (registered trademark) QE-1042" (Tg: 69°C) manufactured by Seiko PMC Co., Ltd.

[0102] The average particle diameter of the resin fine particles is, for example, in the range of 30 nm to 200 nm. The average particle diameter can be measured as an arithmetic mean diameter using, for example, a dynamic light scattering particle size distribution measuring device "LB-550" manufactured by Horiba, Ltd.

[0103] The content (R) of the resin particles in the total amount of the ink is, for example, preferably in the range of 0.1 wt% to 30 wt%, more preferably in the range of 0.5 wt% to 20 wt%, and particularly preferably in the range of 1.0 wt% to 15.0 wt%. One type of resin particles may be used alone, or two or more types may be used in combination.

[0104] The coloring material is, for example, a pigment that can be dispersed in water by a pigment dispersion resin (resin dispersant). Examples of the coloring material include carbon black, inorganic pigments, and organic pigments. Examples of carbon black include furnace black, lamp black, acetylene black, and channel black. Examples of inorganic pigments include titanium oxide, iron oxide inorganic pigments, and carbon black inorganic pigments. Examples of organic pigments include azo pigments such as azo lake, insoluble azo pigment, condensed azo pigment, and chelate azo pigment; polycyclic pigments such as phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments; dye lake pigments such as basic dye lake pigments and acid dye lake pigments; nitro pigments; nitroso pigments; aniline black daylight fluorescent pigments; and the like.

[0105] The solid content of the coloring material in the total amount of ink is not particularly limited and can be appropriately determined, for example, depending on the desired optical density or saturation. The solid content of the coloring material is, for example, preferably in the range of 0.1 wt% to 20.0 wt%, more preferably in the range of 1.0 wt% to 15.0 wt%. The solid content of the coloring material is the weight of the pigment only, and does not include the weight of the resin particles. The coloring material may be used alone or in combination of two or more types.

[0106] The water-soluble organic solvent is not particularly limited, and any one can be used. Examples of the water-soluble organic solvent include propylene glycol, ethylene glycol, 1,2-butanediol, propylene glycol monobutyl ether, dipropylene glycol monopropyl ether, triethylene glycol monobutyl ether, 1,2-hexanediol, 1,6-hexanediol, and the like, and glycol ethers having a propylene oxide group are preferred. Examples of other organic solvents include alkyl alcohols having 1 to 4 carbon atoms, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, and tert-butyl alcohol; alkylene glycols having an alkylene group containing 2 to 6 carbon atoms, such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, and diethylene glycol; glycerin, ethylene glycol monomethyl (or ethyl, propyl, or butyl) ether, diethylene glycol monomethyl (or ethyl, propyl, or butyric acid) ether, and the like. lower alkyl ethers of alkylene glycols such as triethylene glycol monomethyl (or ethyl, propyl, butyl, hexyl) ether, triethylene glycol monomethyl (or ethyl, propyl, butyl, hexyl) ether, tetraethylene glycol monomethyl (or ethyl, propyl, butyl, hexyl) ether, propylene glycol monomethyl (or ethyl, propyl, butyl) ether, dipropylene glycol monomethyl (or ethyl, propyl, butyl) ether, tripropylene glycol monomethyl (or ethyl, propyl, butyl) ether, and tetrapropylene glycol monomethyl (or ethyl) ether; N-methyl-2-pyrrolidone, 2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone.

[0107] The content of the water-soluble organic solvent in the total amount of ink is preferably 50 wt% or less, more preferably 40 wt% or less, of the organic solvent that exists as a liquid by itself at 25°C. The mass ratio of the water-soluble organic solvent to the solid content in the ink (water-soluble organic solvent / solid content) is preferably 1.0 or more in order to avoid contact between particles constituting the solid content. More preferably, the mass ratio of the water-soluble organic solvent to the solid content in the ink (water-soluble organic solvent / solid content) is 2.0 or more. The solid content includes at least a pigment. In this embodiment, the solid content includes a pigment and a resin microquantum. The water-soluble organic solvent is preferably a solvent whose evaporation rate at 20°C is equal to or less than the evaporation rate of water. For example, the saturated vapor pressure of water at 20°C is about 2300 Pa, so from the viewpoint of suppressing the evaporation rate of the ink to 1 / 10 of the evaporation rate of water, the saturated vapor pressure of the water-soluble organic solvent is preferably 230 Pa or less. Moreover, from the viewpoint of suppressing the evaporation rate of the ink to 1 / 100 of the evaporation rate of water, it is more preferable that the saturated vapor pressure of the water-soluble organic solvent is 20 Pa or less.

[0108] In order to facilitate the wiper 72 wiping off the ink adhering to the nozzle surface 33A, it is preferable that the viscosity of the ink is low. When the viscosity of the ink is low, the maximum wiper speed Vmax calculated from the formula (11) described later increases, and the adhesive force Fink of the ink to the nozzle surface 33A described later decreases, so that the ink adhering to the nozzle surface 33A is easily wiped off by the wiper 72. In general, the more the polymers on the particle surfaces constituting the solid content are entangled, the higher the viscosity of the ink. However, in order for the entanglement of the hydrated polymers to occur in a water-soluble organic solvent containing water, it is necessary that the polymer structure contains an ionic functional group. For this reason, there is an approximate correlation between the viscosity of the ink, the amount of ionic functional groups in the polymer structure, and the electrical conductivity associated therewith. From the viewpoint of keeping the viscosity of the ink low, it is preferable that the electrical conductivity is low. For example, the concentration, that is, the conductivity of the aqueous solution when solids at least including the pigment are added to water so that the aqueous solution has a solid content of 10 wt %, is preferably 5 mS / cm or less.

[0109] On the other hand, if the electrical conductivity is too low, the repulsive force between the particles constituting the solid content is reduced, and the particles are more likely to aggregate with each other. As a result, the storage stability of the ink may be impaired. From the viewpoint of ensuring the storage stability of the ink, it is preferable that the electrical conductivity is at least a certain level. For example, when a solid content containing at least a pigment is added to water so that the concentration of the aqueous solution becomes 10 wt%, the electrical conductivity of the aqueous solution is preferably 0.1 mS / cm or more.

[0110] The water is preferably ion-exchanged water or pure water. The content of water in the total amount of ink is, for example, preferably in the range of 15 wt% to 95 wt%, more preferably in the range of 25 wt% to 85 wt%. The content of water may be, for example, the balance of other components.

[0111] The ink may further contain conventionally known additives as necessary. Examples of additives include surfactants, pH adjusters, viscosity adjusters, surface tension adjusters, preservatives, antifungal agents, leveling agents, defoamers, light stabilizers, antioxidants, nozzle drying inhibitors, polymer components such as emulsions, dyes, and the like. The surfactant may further contain a cationic surfactant, an anionic surfactant, or a nonionic surfactant. For example, commercially available products may be used as these surfactants. Examples of commercially available products include "Olfine (registered trademark) E1010", "Olfine (registered trademark) E1006", "Olfine (registered trademark) E1004", "Silface SAG503A", and "Silface SAG002" manufactured by Nissin Chemical Industry Co., Ltd. The content of the surfactant in the total amount of the ink is, for example, 5 wt% or less, 3 wt% or less, or 0.1 wt% to 2 wt%. Examples of viscosity adjusters include polyvinyl alcohol, cellulose, water-soluble resins, and the like.

[0112] The ink can be prepared, for example, by uniformly mixing resin fine particles, a coloring material, an organic solvent, water, and, if necessary, other additives, using a conventionally known method, and removing any insoluble matter using a filter or the like.

[0113] [Judgment of wiping process results] When the controller 130 executes the wiping process, it executes a determination process for determining the result of the wiping process. In the wiping process, default conditions are set in advance. As the default conditions, for example, an initial wiper speed V0, an initial pushing amount p0, and an initial elapsed time t0 are stored in the EEPROM 134.

[0114] The determination process is shown in FIG. 5 and FIG. 6. As shown in FIG. 5, the controller 130 assumes a wiping process under default conditions (step S1) and executes an estimation process (step S2). The estimation process will be described later. The controller 130 determines whether the result of the wiping process is good (OK) or bad (NG) based on the determination result recorded in the EEPROM 134 in the estimation process (step S3). If the result of the wiping process is good (step S3; Yes), the controller 130 determines the default conditions as the conditions for the wiping process (step S4). When the conditions for the wiping process are determined, the controller 130 executes the wiping process under the determined conditions.

[0115] If the result of the wiping process is poor (step S3; No), the controller 130 changes the initial wiper speed V0 to the minimum wiper speed Vmin (step S5). The minimum wiper speed Vmin refers to the slowest wiper speed within the range of wiper speeds or among multiple wiper speeds that can be set in the printer 10.

[0116] The controller 130 changes the initial wiper speed V0 of the default conditions to the minimum wiper speed Vmin, and then executes the estimation process again (step S6). The controller 130 determines whether the result of the wiping process is good (OK) or bad (NG) based on the determination result recorded in the EEPROM 134 in the estimation process (step S7). If the result of the wiping process is good (step S7; Yes), the controller 130 confirms the minimum wiper speed Vmin as the condition for the wiping process (step S8). When the condition for the wiping process is confirmed, the controller 130 executes the wiping process according to the confirmed condition.

[0117] If the result of the wiping process is not good (step S7; No), the controller 130 changes the initial push-in amount p0 to the maximum push-in amount pmax (step S9). The maximum push-in amount pmax corresponds to the maximum length that can be set among the lengths of overlap between the upper wiper blade 73 and the nozzle surface 33A in the up-down direction 1. As a result, the conditions of the wiping process are changed from the default conditions, with the initial wiper speed V0 being changed to the minimum wiper speed Vmin, and the initial push-in amount p0 being changed to the maximum push-in amount pmax. Note that as the push-in amount p increases, the displacement amount δ(m) and the deformation angle θ increase.

[0118] The controller 130 changes the initial push-in amount p0 to the maximum push-in amount pmax, and then executes the estimation process again (step S10). The controller 130 judges whether the result of the wiping process is good (OK) or bad (NG) based on the judgment result recorded in the EEPROM 134 in the estimation process (step S11). If the result of the wiping process is good (step S11; Yes), the controller 130 determines the condition with the push-in amount pmax as the condition of the wiping process (step S12). When the condition of the wiping process is determined, the controller 130 executes the wiping process according to the determined condition.

[0119] If the result of the wiping process is poor (step S11; No), the controller 130 changes the initial elapsed time t0 to the minimum elapsed time tmin (step S13). The controller 130 determines the conditions of the wiping process and executes the wiping process (step S14). As a result, the conditions of the wiping process are changed from the default conditions to the initial wiper speed V0 to the minimum wiper speed Vmin, the initial push-in amount p0 to the maximum push-in amount pmax, and the initial elapsed time t0 to the minimum elapsed time tmin. The initial wiper speed V0 and the minimum wiper speed Vmin are examples of the movement speeds that are intended to move the head and the wiper relative to each other in the wiping process.

[0120] [Inference Processing] The controller 130 executes the estimation process according to the procedure shown in Fig. 6. The controller 130 calculates the evaporation rate E (step S21). The evaporation rate E is calculated by multiplying the initial concentration W0 (kg / m 3 ), the water concentration W (kg / m 3 ), ink density ρ(kg / m 3 ) is calculated using the following formula (1).

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[0121] The initial water concentration W0 and the ink density ρ are read from the EEPROM 134 and the IC board 79. The elapsed time t is obtained based on an internal clock or an external clock and is the time that has elapsed since the previous wiping process was executed.

[0122] The concentration of water W (kg / m) after the passage of time t 3 ) is the initial concentration of water W0 (kg / m 3 ), saturated vapor pressure of water Ps (Pa), molar mass of water M (kg / mol), diffusion coefficient of water vapor Dwa (m 2 / s), relative humidity H0, gas constant R (Pa m 3The water concentration W (kg / m mol), the ambient temperature T (k), and the droplet diameter d (m) are calculated using the following formula (2). 3 ) may be calculated, for example, by a formula obtained from another viewpoint.

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[0123] The value obtained by differentiating the above (Equation 2) with respect to time represents the evaporation rate of water. The equation obtained by differentiating the above (Equation 2) with respect to time includes the saturated vapor pressure of water as a coefficient, which indicates that the evaporation rate of water is roughly proportional to the saturated vapor pressure of water. The evaporation rate of the water-soluble organic solvent can be calculated by replacing the saturated vapor pressure Ps of water in the above (Equation 2) with the saturated vapor pressure Ps of the water-soluble organic solvent.

[0124] The initial water concentration W0, the saturated vapor pressure Ps of water, the molar mass M of water, the diffusion coefficient Dwa of water vapor, the gas constant R, and the droplet diameter d are read from the EEPROM 134 and the IC board 79. The relative humidity H0 and the environmental temperature T are calculated based on the output value of the environmental sensor 78.

[0125] The controller 130 calculates the ink viscosity η (mPa s) based on the calculated evaporation rate E (step S22). The ink viscosity η is calculated by measuring the relationship between the evaporation rate E and the ink viscosity η for each type of ink in advance, and linearly interpolating between the measured values ​​from the measurement results with a slope α and an intercept β, using η=αE+β (Equation 3) for each interval between the measured values. Equation 3 may be stored in advance in the EEPROM 134 or in the IC board 79, for example, depending on the type of ink. The processes in steps S21 and S22 are an example of a viscosity determination process and a viscosity determination step.

[0126] The controller 130 determines whether the calculated ink viscosity η is less than a first viscosity (step S23). The first viscosity is, for example, 30,000 mPa·s and is stored in advance in the EEPROM 134. When the ink viscosity η is equal to or greater than the first viscosity, the ink is in a state where it has substantially solidified and has almost lost its fluidity as a liquid. In other words, when the ink viscosity η is equal to or greater than the first viscosity, the ink is in a solidified state.

[0127] When the controller 130 determines that the ink viscosity η is equal to or greater than the first viscosity (step S23; No), it determines whether the adhesive force Fink of the ink on the nozzle surface 33A is less than the first adhesive force (step S24). The first adhesive force is the same value as the maximum Fwipe calculated by the formula 4 described later. In other words, the first adhesive force is an adhesive force at which the ink that has substantially solidified on the nozzle surface 33A adheres to the nozzle surface 33A so firmly that it cannot be wiped away by the wiper blade 73. According to the formula 4 described later, Fwipe is maximum when θ=45°, so the first adhesive force is calculated according to the formula 4 with θ=45° using various parameters of the device. For example, the first adhesive force is 0.3 N. The first adhesive force is stored in advance in the EEPROM 134. Fink is calculated by the formula 7 described later.

[0128] When Fink is equal to or greater than the first adhesion (step S24; No), the controller 130 displays a message on the display of the operation unit 21 stating that "head maintenance cannot be performed properly" (step S25). The controller 130 ends the determination process of Fig. 5. When Fink is less than the first adhesion (step S24; Yes), the controller 130 determines whether the force Fwipe (an example of the pressing pressure) applied to the ink from the wiper blade 73 exceeds Fink (step S26).

[0129] Fwipe is the Young's modulus E (Pa) of the wiper blade 73, the second moment of area I (m 4), the displacement δ (m) of the wiper blade 73, the length L (m) of the wiper blade 73, and the deformation angle θ of the wiper blade 73, according to the following (Equation 4). Note that Fwipe in (Equation 4) may be calculated, for example, by a formula obtained from another viewpoint.

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[0130] FIG. 7 shows the wiper blade 73 in contact with the nozzle surface 33A of the print head 34. When the wiper blade 73 is in contact with the nozzle surface 33A, it tilts in the direction of movement of the print head 34 (to the right in FIG. 7). The length L of the wiper blade 73 is the length from the upper surface of the holder 74 to the tip of the wiper blade 73 when the wiper blade 73 is extended upward without tilting. The second moment of area I of the wiper blade 73 is calculated from the thickness t (m), length L (m), and depth b (m) of the wiper blade 73. When the length L and the pushing amount p of the wiper blade 73 are determined, the displacement amount δ and deformation angle θ of the wiper blade 73 are calculated according to the following (Equation 5) and (Equation 6).

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[0131] Fink uses the depth b (m) of the wiper blade 73, the droplet diameter d (m), and the maximum adhesion force A (N / m 2 ) is calculated based on the following (Equation 7). Note that Fink in (Equation 7) may be calculated, for example, by a formula obtained from another viewpoint. The calculation based on the following (Equation 7) is an example of the adhesion determination process and adhesion determination step.

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[0132] When Fwipe is greater than Fink, the controller 130 determines that ink droplets on the nozzle surface 33A are peeled off by the wiper blade 73 (Decision 1) (Step S26; Yes). The controller 130 records the determination result in the EEPROM 134 (Step S27). When Fwipe is equal to or less than Fink, the controller 130 determines that ink that has substantially solidified on the nozzle surface 33A remains without being peeled off by the wiper blade 73 (Decision 2) (Step S26; No). The controller 130 records the determination result in the EEPROM 134 (Step S28).

[0133] When the controller 130 determines that the ink viscosity η is less than the first viscosity (step S23; Yes), it determines whether Fwipe applied to the ink from the wiper 72 exceeds the stress Fink due to the viscous friction of the ink (step S29). When the ink viscosity η is less than the first viscosity, the ink is in a state where it flows as a liquid. In a state where the ink flows as a liquid, the stress Fink due to the viscous friction of the ink becomes much higher than the adhesive force Fink of the ink to the nozzle surface 33A, so that the stress Fink due to the viscous friction of the ink becomes dominant. In other words, in a state where the ink flows as a liquid, the adhesive force Fink of the ink to the nozzle surface 33A is negligibly small compared to the stress Fink due to the viscous friction of the ink. In other words, Fink is calculated and compared using different formulas depending on whether the ink is liquid or solid. When the ink viscosity η is less than the first viscosity, Fink is calculated based on (Formula 8) described later. Fwipe is calculated based on (Formula 4) described above.

[0134] FIG. 8 shows a state in which the wiper blade 73 comes into contact with the ink droplet L1 adhering to the nozzle surface 33A and viscous friction is generated from the shear flow 51 of the ink droplet L1. The viscous friction of the ink droplet L1 is calculated as Fink. Specifically, Fink is calculated based on the ink viscosity η (Pa·s), the depth (m) of the wiper blade 73, the wiper speed V (m / s), and the deformation angle θ of the wiper blade 73, according to the following (Equation 8). Note that Fink in (Equation 8) may be calculated, for example, by a formula obtained from another viewpoint. The wiper speed V is the planned moving speed at which the head and the wiper are to be moved relative to each other in the wiping process. The wiper speed V is the initial wiper speed V0 under default conditions.

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[0135] Here, l is calculated based on the size of a single water molecule, a (m), and the diameter of the droplet, d (m), as l = ln(d / a). Also, tan(π / 2-θ) = cosθ / sinθ.

[0136] When Fwipe is equal to or less than Fink, the controller 130 determines that the wiper blade 73 is overpowered by the ink droplets on the nozzle surface 33A (step S29; No). In this case, the controller 130 causes the display of the operation unit 21 to display a message stating that "head maintenance cannot be performed appropriately" (step S30). The controller ends the determination process of FIG. 5.

[0137] When Fwipe exceeds Fink, the controller 130 determines that the wiper blade 73 is not overpowered by the ink droplets on the nozzle surface 33A (step S29; Yes). In this case, the controller 130 determines whether the ink droplets on the nozzle surface 33A move along the nozzle surface 33A following the wiper blade 73 (step S31). Specifically, as described below, it is determined whether the wiper speed V is equal to or less than the maximum wiper speed Vmax.

[0138] 8 shows a state in which ink droplets L1 adhering to the nozzle face 33A are wiped away by the wiper blade 73. In FIG. 8, the print head 34 moves rightward relative to the wiper blade 73.

[0139] The tip 72A of the wiper blade 73 abuts against the nozzle surface 33A, but since the tip 72A has slight unevenness in the front-rear direction 2 (the direction perpendicular to the paper surface in FIG. 8), the entire tip 72A does not abut against the nozzle surface 33A evenly, and there are some parts of the tip 72A that abut against the nozzle surface 33A and some parts that do not. FIG. 8 shows the parts of the tip 72A that do not abut against the nozzle surface 33A. At the parts of the tip 72A that do not abut against the nozzle surface 33A, there is a gap 111 in the up-down direction 1 between the tip 72A and the nozzle surface 33A.

[0140] When the tip 72A comes into contact with the right side of an ink droplet attached to the nozzle face 33A, part of the ink droplet flows through the gap 111 between the tip 72A and the nozzle face 33A and moves to the right of the tip 72A. To the right of the tip 72A, viscous friction of the ink against the nozzle face 33A and surface tension of the ink occur. If the workload dQ due to the viscous friction of the ink is smaller than the workload F·V due to the surface tension of the ink, the ink droplet follows the wiper blade 73 and is wiped off the nozzle face 33A. If the workload dQ due to the viscous friction of the ink is greater than the workload F·V due to the surface tension of the ink, the ink droplet does not follow the wiper blade 73 and remains on the nozzle face 33A.

[0141] The work load dQ due to the viscous friction of the ink is calculated based on the following (Equation 9).

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[0142] The work load F·V due to the surface tension of the ink is calculated based on the following formula (10): Note that the work load F·V in formula (8) may be calculated by a formula obtained from another viewpoint.

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[0143] The contact angle on the right side of the ink droplet in FIG. 8 is the receding contact angle θ D The contact angle on the left side of the ink droplet is the advancing contact angle θ A In FIG. 8, the equilibrium contact angle θ of the ink droplet before contact with the wiper blade 73 is E is equal on both the left and right sides.

[0144] The work load dQ due to the viscous friction of the ink and the work load F·V due to the surface tension of the ink both increase in proportion to the wiper speed V. The wiper speed V at which the work load dQ due to the viscous friction of the ink and the work load F·V due to the surface tension of the ink are equal is the maximum wiper speed Vmax at which the wiper blade 73 can wipe the ink droplets from the nozzle surface 33A.

[0145] By solving (Equation 9) and (Equation 10) for the wiper speed V, the following (Equation 11) for calculating the maximum wiper speed Vmax is derived.

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[0146] If the wiper speed V is equal to or less than the maximum wiper speed Vmax (V≦Vmax, step S31; Yes), the controller 130 determines that the ink droplets will follow the wiper blade 73 and be wiped off from the nozzle surface 33A (Determination 3). The controller 130 records the determination result in the EEPROM 134 (step S32). If the wiper speed V is greater than the maximum wiper speed Vmax (V>Vmax, step S31; No), the controller 130 determines that the ink droplets will not follow the wiper blade 73 and will remain on the nozzle surface 33A. In this case, the controller 130 causes the display of the operation unit 21 to display a message indicating that "head maintenance cannot be performed appropriately" (step S33). The controller ends the determination process of FIG. 5.

[0147] In the estimation process described above, judgment 1, in which ink that has adhered to the nozzle surface 33A and has substantially solidified is peeled off by the wiper blade 73, and judgment 3, in which ink droplets that have adhered to the nozzle surface 33A are wiped away from the nozzle surface 33A by following the wiper blade 73, are judgments that the result of the wiping process is good (OK). Judgment 2 is a judgment that the result of the wiping process is bad (NG). After determining in step S26 that the result of the wiping process is bad (NG), the controller 130 changes the default condition assumed in step S1 to any one of the minimum wiper speed Vmin, the maximum push amount Pmax, and the minimum elapsed time tmin.

[0148] For example, when the initial wiper speed V0 is changed to the minimum wiper speed Vmin in step S5, the wiper speed V may become equal to or less than the maximum wiper speed Vmax. As a result, in step S29 of the estimation process, it may be determined that ink droplets follow the wiper blade 73 and are wiped off from the nozzle surface 33A. Also, when the initial push-in amount p0 is changed to the maximum push-in amount pmax in step S9, the displacement amount δ(m) of the wiper blade 73 and the deformation angle θ of the wiper blade 73 change in (Equation 4), and Fwipe becomes larger. As a result, in step S26 of the estimation process, it may be determined that the ink that has substantially solidified on the nozzle surface 33A is peeled off by the wiper blade 73.

[0149] In addition, when the initial elapsed time t0 is changed to the minimum elapsed time tmin, the interval between wiping processes is shortened. As a result, in (Equation 2), the water concentration W (kg / m 3) becomes smaller, and as a result, the evaporation rate E becomes smaller in (Equation 1). When the evaporation rate E becomes smaller, the ink viscosity η becomes smaller in (Equation 3). When the ink viscosity η becomes smaller, Fink becomes smaller in (Equation 8), and the work load dQ due to viscous friction of the ink becomes smaller in (Equation 9). As a result, the maximum wiper speed Vmax becomes larger, and in step S29 of the estimation process, it can be determined that the ink droplets are wiped away from the nozzle surface 33A by following the wiper blade 73 (Decision 3).

[0150] In addition, when the controller 130 determines in step S23 of the estimation process that the ink viscosity η is equal to or greater than the first viscosity, it may perform a wet wiping process in which the wet wiper 76 is brought into contact with the nozzle surface 33A and the print head 34 is moved, in addition to the wiping process.

[0151] Furthermore, after it is determined in step S26 of the estimation process that the ink that has substantially solidified on the nozzle surface 33A remains without being peeled off by the wiper blade 73 (judgment 2), even if the conditions for the wiping process are changed to the minimum wiper speed Vmin and the maximum depression amount pmax, the wet wiping process may be performed if judgment 2 is reached.

[0152] [Effects of this embodiment] In the printer 10, the controller 130 executes an estimation process, and changes at least one of the wiper speed V, the push amount p, and the elapsed time t depending on whether the estimation process determines that ink droplets remain on the nozzle surface 33A, thereby optimizing the conditions for the wiping process.

[0153] In the printer 10, the controller 130, in response to an estimation process inferring that ink droplets remain on the nozzle surface 33A, changes the wiper speed V, the push-in amount p, and the elapsed time t in that order and re-executes the estimation process, thereby optimizing the conditions for the wiping process while reducing the frequency of the wiping process.

[0154] In the printer 10, when the ink viscosity η is less than the first viscosity in the estimation process, the controller 130 determines that the ink droplets will be wiped off the nozzle surface 33A by following the wiper blade 73, provided that Fwipe when the wiper blade 73 contacts the nozzle surface 33A is greater than the stress Fink due to the viscous friction of the ink. This provides high determination accuracy for the controller 130. Therefore, even if moisture evaporates from the ink adhering to the nozzle surface 33A and part of the ink solidifies, the ink is wiped off the nozzle surface 33A by the wiper blade 73 in the wiping process.

[0155] In the printer 10, when the ink viscosity η is less than the first viscosity in the estimation process, the controller 130 determines that the ink droplets will be wiped away from the nozzle surface 33A by following the wiper blade 73, provided that Fwipe when the wiper blade 73 contacts the nozzle surface 33A is greater than Fink and the wiper speed V is equal to or less than the maximum wiper speed Vmax. This provides high determination accuracy for the controller 130.

[0156] In the printer 10, when the ink viscosity η is equal to or greater than the first viscosity in the estimation process, the controller 130 determines that the ink droplets on the nozzle surface 33A will be peeled off by the wiper blade 73, provided that Fink is less than the first adhesive force and Fwipe is greater than Fink. This provides high determination accuracy. Therefore, even if moisture evaporates from the ink adhering to the nozzle surface 33A and the ink is substantially solidified, the ink is wiped off from the nozzle surface 33A by the wiper blade 73 in the wiping process.

[0157] In the printer 10, if Fink is equal to or greater than the first adhesion in the estimation process, the controller 130 displays a message on the display of the operation unit 21 stating that "head maintenance cannot be performed properly." This allows the user to know that an abnormality has occurred in the print head 34, and the user can resolve the malfunction of the print head 34 by, for example, replacing or cleaning the print head 34.

[0158] In the printer 10, the controller 130 calculates the ink viscosity η based on the evaporation rate E calculated based on the above formula 1 in the estimation process, and therefore the determination accuracy of the controller 130 is high. As a result, ink is more reliably wiped off from the nozzle surface 33A by the wiper blade 73 in the wiping process.

[0159] In the printer 10, the controller 130 displays a message on the display of the operation unit 21 stating that "head maintenance cannot be performed properly" on the condition that the calculated stress Fink due to viscous friction in the estimation process is equal to or greater than Fwipe. This allows the user to know that an abnormality has occurred in the print head 34, and therefore allows the user to resolve the malfunction of the print head 34 by, for example, replacing or cleaning the print head 34.

[0160] In the printer 10, if the calculated stress Fink due to viscous friction is less than Fwipe in the estimation process, the controller 130 displays a message on the display of the operation unit 21 stating that "head maintenance cannot be performed properly," provided that the calculated maximum wiper speed Vmax is less than the wiper speed V. This allows the user to know that an abnormality has occurred in the print head 34, and the malfunction of the print head 34 can be resolved by, for example, replacing or cleaning the print head 34.

[0161] In the printer 10, the controller 130 calculates Fwipe based on wiper information related to the wiper 72, so that the wiper blade 73 more reliably wipes ink from the nozzle surface 33A.

[0162] In the printer 10, the controller 130 calculates the stress Fink due to viscous friction of the ink located on the nozzle surface 33A based on the ink viscosity η in step S27 of the estimation process. The ink viscosity η is then calculated based on the evaporation rate E calculated in step S21 of the estimation process. In other words, Fink is calculated based on the calculated evaporation rate E. As a result, the wiper blade 73 can more reliably wipe the ink from the nozzle surface 33A in the wiping process.

[0163] In the printer 10, the push amount p can be changed by changing the position of the wiper blade 73 with respect to the nozzle face 33A in the vertical direction 1. For this reason, it is easy to change Fwipe.

[0164] In the printer 10, the ink contains multiple resin particles, and therefore a film in which multiple resin particles are connected together is likely to form when the ink dries. This can make it difficult to wipe the ink from the nozzle surface 33A with the wiper blade 73. However, in the printer 10, the conditions for the wiping process are optimized, so that the wiper blade 73 can effectively wipe the ink from the nozzle surface 33A.

[0165] Here, when the ink that has adhered to the nozzle surface 33A and has not yet substantially solidified is wiped away by the wiper blade 73, the stress Fink due to viscous friction of the ink is taken into consideration. The stress Fink due to viscous friction of the ink is proportional to the ink viscosity η, as can be seen from equation (8). Therefore, when the ink viscosity η is unlikely to increase, the stress Fink due to viscous friction of the ink is also unlikely to increase, so that the ink that has adhered to the nozzle surface 33A is easily wiped away by the wiper blade 73.

[0166] In order to prevent the ink viscosity η from becoming too high, it is possible to consider: (a) containing an organic solvent whose vapor pressure at 20°C is smaller than that of water, (b) increasing the mass ratio (water-soluble organic solvent / solids), and (c) reducing the electrical conductivity of the aqueous solution when solids, including at least the pigment contained in the ink, are added to water.

[0167] In the printer 10, the mass ratio of the water-soluble organic solvent to the solid content in the ink containing at least a pigment (water-soluble organic solvent / solid content) is 1.0 or more to avoid contact between particles constituting the solid content containing at least a pigment. More preferably, the mass ratio of the water-soluble organic solvent to the solid content in the ink (water-soluble organic solvent / solid content) is 2.0 or more. Therefore, even after water evaporates from the ink, the ink can maintain a state in which the water-soluble organic solvent is contained in a large amount, so the ink viscosity η is less likely to increase compared to when the ink contains a small amount of water-soluble organic solvent. In addition, the water-soluble organic solvent has a vapor pressure of 20 Pa or less at 20° C. Therefore, the ink contains a water-soluble organic solvent that is less likely to volatilize than water, so the ink is less likely to solidify. Therefore, the ink viscosity η is less likely to increase, so the wiper blade 73 can easily wipe the ink from the nozzle surface 33A.

[0168] In the printer 10, when the solid content of the ink containing at least the pigment is added to water to form a 10% aqueous solution, the conductivity of the aqueous solution is 5 mS / cm or less. Therefore, the amount of ionic functional groups is small, and the polymers on the particle surfaces that make up the solid content containing at least the pigment are less likely to be entangled with each other. As a result, the viscosity of the ink is less likely to increase, making it easier for the wiper blade 73 to wipe the ink from the nozzle surface 33A.

[0169] [Variations] In the embodiment described above, the wiper speed V, the depression amount p, and the elapsed time t are changed in this order in the determination process, but the order may be reversed. Also, in the determination process, it is not necessary to change all of the wiper speed V, the depression amount p, and the elapsed time t, and only some of them may be changed.

[0170] Furthermore, while the wiper 72 moves upward in the up-down direction 1, the print head 34 moves in the left-right direction 3 to perform the wiping process, but the wiping process is not limited to this. For example, the wiping process may be performed by moving the wiper 72 in the left-right direction 3 relative to the print head 34 that is stationary.

[0171] In the above embodiment, the controller 130 displays a message on the display of the operation unit 21 in steps S25, S30, and S33 of the estimation process, stating that "head maintenance cannot be performed appropriately." However, a message urging the user to perform a wet wiping process may be displayed together with this message. In this way, the user can cause the controller 130 to perform a wet wiping process. As a result, the cleaning liquid comes into contact with the ink adhering to the nozzle surface 33A, so that the adhesive force Fink of the ink to the nozzle surface 33A decreases, and the ink can be removed from the nozzle surface 33A.

[0172] Furthermore, the liquid information does not have to be stored in the IC board 79 of the cartridge 70 or in the EEPROM 134. For example, the liquid information may be stored in the memory of a server with which the printer 10 can communicate via the Internet. Furthermore, the liquid information may be input by the user from the operation unit 21 and stored in the EEPROM 134.

[0173] In printer 10, in step S29 of the estimation process, it is determined whether Fwipe exceeds Fink, thereby determining whether ink droplets on nozzle surface 33A move along nozzle surface 33A by following wiper blade 73, but the process of step S29 may be omitted. In this case, on the condition that it is determined in step S27 that Fwipe applied to the ink from wiper 72 exceeds stress Fink due to viscous friction of the ink, it may be determined that ink droplets will follow the wiper blade 73 and be wiped off nozzle surface 33A (Determination 3).

[0174] In the printer 10, the initial push-in amount p0 is set as the default condition for the wiping process, but the initial push-in amount p0 may be set to a larger value as the elapsed time t since the previous wiping process is performed increases. In this case, the elapsed time t is acquired based on an internal clock or an external clock, etc. As the elapsed time t increases, the evaporation rate E increases and the ink viscosity η increases. Therefore, by increasing the initial push-in amount p0 to increase Fwipe, the wiper blade 73 can more reliably wipe ink from the nozzle surface 33A.

[0175] In the printer 10, the ink viscosity η of the ink attached to the nozzle surface 33A is determined in steps S21 and S22, but the ink viscosity η does not have to be determined. That is, steps S21 to S23 may be omitted. In this case, the ink used has a mass ratio (water-soluble organic solvent / solids) of 2.0 or more between the solid content containing at least the pigment and the water-soluble organic solvent. The water-soluble organic solvent includes a solvent having a saturated vapor pressure of 20 Pa or less at 20°C. In addition, the ink used has a conductivity of 5 mS / cm or less when the solid content containing at least the pigment is added to water to form a 10% aqueous solution. Furthermore, since the ink attached to the nozzle surface 33A is difficult to solidify, steps S24 to S28 may be omitted. [Explanation of symbols]

[0176] 10 Printer (liquid ejection device) 21 Operation unit (alarm) 33 Nozzle 33A Nozzle surface 34 Print head (head) 72 Wiper 76 Wet wiper 130...Controller

Claims

1. a head having nozzles opening on a nozzle surface; a wiper that comes into contact with the nozzle face and moves relatively to the head; A controller, The above controller is a viscosity determination process for determining a viscosity of the liquid adhered to the nozzle surface; a wiping process in which the wiper comes into contact with the nozzle surface and moves relative to the head; A liquid ejection device, wherein when the determined viscosity is less than a first viscosity indicating that the liquid has substantially solidified, the pressing pressure when the wiper contacts the nozzle face during the wiping process is greater than the stress due to viscous friction of the liquid located on the nozzle face.

2. The above controller is executing an adhesion determination process for determining an adhesion of the liquid adhered to the nozzle surface when the determined viscosity is equal to or greater than the first viscosity; The liquid ejection device according to claim 1 , wherein, when the determined adhesive force is less than a first adhesive force, the pressing pressure in the wiping process is greater than the determined adhesive force.

3. The device further includes an alarm connected to the controller, The above controller is The liquid ejection device according to claim 2 , wherein the alarm is activated when the determined adhesive force is equal to or greater than the first adhesive force.

4. The above controller is determining an evaporation rate of the liquid adhering to the nozzle surface based on at least the elapsed time since the previous wiping process was performed, liquid information related to the liquid ejected by the head, and environmental information related to the environment of the head; The liquid ejection apparatus according to claim 2 , further comprising: a step of determining a viscosity of the liquid adhered to the nozzle surface based on the determined evaporation rate.

5. The apparatus further includes an alarm connected to the controller, The above controller is determining a stress due to viscous friction of the liquid in a shear flow caused by the relatively moving wiper based on the determined viscosity; The liquid ejection device according to claim 1 , wherein the alarm is activated when the determined stress due to the viscous friction is equal to or greater than the pressing pressure.

6. The above controller is determining a maximum moving speed of the wiper when a work load caused by the stress due to the viscous friction is balanced with a work load caused by a surface tension of the liquid generated in the liquid by the wiper moving relatively thereto, when the determined stress due to the viscous friction is less than the pressing pressure; 6. The liquid ejection device according to claim 5, further comprising: a warning device that activates an alarm when the determined maximum movement speed is lower than a planned movement speed at which the head and the wiper are to move relative to each other in the wiping process.

7. The liquid ejection device according to claim 1 , wherein the controller determines the pressing pressure based on wiper information relating to the wiper.

8. The liquid ejection device according to claim 4 , wherein the controller determines the adhesive force based on the determined evaporation rate.

9. The liquid ejection device according to claim 4 , wherein the controller increases the pressing pressure as the elapsed time increases.

10. The liquid ejection apparatus according to claim 9 , wherein the controller changes the pressing pressure by changing a position of the wiper with respect to the nozzle face in a vertical direction.

11. 11. The liquid ejection device according to claim 1, wherein the liquid is a water-based ink containing a pigment and a water-soluble organic solvent.

12. The liquid ejection device according to claim 11 , wherein the liquid further contains a plurality of resin fine particles.

13. a mass ratio of a solid content including at least the pigment to the water-soluble organic solvent in the liquid (water-soluble organic solvent / solid content) is 1.0 or more; The liquid ejection device according to claim 11 , wherein the water-soluble organic solvent includes a solvent having a saturated vapor pressure of 20 Pa or less at 20° C.

14. a mass ratio of a solid content including at least the pigment to the water-soluble organic solvent in the liquid (water-soluble organic solvent / solid content) is 2.0 or more; The liquid ejection device according to claim 11, wherein the aqueous solution having a solid content of 10 wt % has a conductivity of 5 mS / cm or less.

15. a mass ratio of a solid content including at least the pigment to the water-soluble organic solvent in the liquid (water-soluble organic solvent / solid content) is 2.0 or more; The water-soluble organic solvent includes a solvent having a saturated vapor pressure of 20 Pa or less at 20° C., The liquid ejection device according to claim 11, wherein the aqueous solution having a solid content of 10 wt % has a conductivity of 5 mS / cm or less.

16. a viscosity determining step of determining the viscosity of the liquid adhered to the nozzle surface of the head; a wiping step of wiping off the liquid adhering to the nozzle surface by a wiper that moves relatively to the head while contacting the nozzle surface, A wiping method, wherein, when the determined viscosity is less than a first viscosity indicating that the liquid has substantially solidified, in the wiping process, a pressing pressure when the wiper contacts the nozzle face is greater than a stress due to viscous friction of the liquid located on the nozzle face.

17. the method further includes an adhesion determining step of determining an adhesion of the liquid adhered to the nozzle surface when the determined viscosity is equal to or greater than the first viscosity, The wiping method according to claim 16 , further comprising the step of: when the determined adhesive force is less than a first adhesive force, the pressing pressure in the wiping step is made greater than the determined adhesive force.

18. The wiping method according to claim 17, further comprising activating an alarm when the determined adhesion is equal to or greater than the first adhesion.

19. determining an evaporation rate of the liquid adhering to the nozzle surface based on at least the elapsed time since the wiping step was performed in which the wiper comes into contact with the nozzle surface and moves relative to the head, liquid information related to the liquid ejected by the head, and environmental information related to the environment of the head; The wiping method according to claim 16 , further comprising determining a viscosity of the liquid adhered to the nozzle face based on the determined evaporation rate.

20. determining a stress due to viscous friction of the liquid in a shear flow caused by the relatively moving wiper based on the determined viscosity; The wiping method according to claim 16, further comprising activating an alarm when the determined stress due to viscous friction is greater than the pressing pressure.

21. determining a maximum moving speed of the wiper when a work load caused by the stress due to the viscous friction is balanced with a work load caused by a surface tension of the liquid generated in the liquid by the wiper moving relatively thereto, when the determined stress due to the viscous friction is less than the pressing pressure; The wiping method according to claim 20, further comprising activating an alarm when the determined maximum movement speed is lower than a planned movement speed at which the head and the wiper are to move relative to each other in the wiping step.

22. The wiping method according to claim 16, further comprising determining the pressing pressure based on wiper information relating to the wiper.

23. The wiping method according to claim 19 , further comprising determining an adhesive force of the liquid adhered to the nozzle face based on the determined evaporation rate.

24. The wiping method according to claim 19, further comprising increasing the pressing pressure as the elapsed time increases.

25. The wiping method according to claim 24, further comprising changing the pressing pressure by changing a position of the wiper with respect to the nozzle face in a vertical direction.

26. 26. The wiping method according to claim 16, wherein the liquid is a water-based ink containing a pigment and a water-soluble organic solvent.

27. a liquid containing a pigment and a water-soluble organic solvent, the liquid adhered to the nozzle surface of the head has a mass ratio of a solid content containing at least the pigment to the water-soluble organic solvent (water-soluble organic solvent / solid content) of 2.0 or more; The water-soluble organic solvent includes a solvent having a saturated vapor pressure of 20 Pa or less at 20° C., A wiping method in which the liquid, the electrical conductivity of a 10% aqueous solution of the solid content of which is 5 mS / cm or less, is wiped away by a wiper that moves relatively to the head while contacting the nozzle face, wherein the pressing pressure when the wiper contacts the nozzle face is greater than the stress due to viscous friction of the liquid, which is located on the nozzle face and has a first viscosity less than that which indicates that the liquid has substantially solidified.

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