Liquid dispensing device

Abstract

To provide a liquid discharge device that can restore decreased pressure in a storage part caused by ejection of liquid from a nozzle, without being enlarged in size.SOLUTION: A controller 130 of a complex machine 10 counts a count value indicating a quantity of ink ejected from a nozzle 39 of a head 38, in a closed state of a valve unit 91 provided in a storage part 80 for ink, and brings the valve unit 91 into an opened state under the condition that the count value reaches an opening threshold value ΔV. When volumes of the storage part 80 are defined as Vtmax, the maximum quantities of ink that can be stored in the storage part 80 are defined as Vi, atmospheric pressure is defined as P, and pressure that meniscus of ink formed in the nozzle 39 can withstand is defined as Pm, the opening threshold value ΔV satisfies a relational expression of ΔV≤(Vtmax-Vi)×Pm / (P-Pm).SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a liquid ejection device having a head that ejects liquid supplied from a reservoir. [Background technology]

[0002] An inkjet pen is known as a device that ejects ink stored in a tank from a nozzle to record an image (see Patent Document 1). In this inkjet pen, the liquid level of the ink stored in the ink cartridge is above the nozzle opening. In the ink cartridge, the gas layer is not connected to the outside, or a valve is provided in a gas flow path that connects the gas layer to the outside. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 55-65560 Summary of the Invention [Problem to be solved by the invention]

[0004] If the gas layer in the ink cartridge is not connected to the outside, the pressure of the gas layer will drop as the ink is consumed, which may result in the meniscus formed at the nozzle opening being destroyed. The smaller the volume of the gas layer in the ink cartridge, the more likely the pressure of the gas layer in the ink cartridge to drop. However, if the volume of the gas layer in the ink cartridge is increased, the ink cartridge will become larger, and as a result, the device will also become larger.

[0005] The present invention has been made in consideration of the above circumstances, and its object is to provide a means for recovering the pressure drop in a storage section that occurs when liquid is discharged from a nozzle, without increasing the size of the device. [Means for solving the problem]

[0006] (1) A liquid ejection device according to the present invention includes a head having a nozzle for ejecting liquid, a storage section in which the liquid is stored forming a liquid level and the height of the liquid level of the maximum amount that can be stored is located above an opening of the nozzle, a gas flow path that communicates the gas layer in the storage section with the outside through an air-open port that opens to the outside, a valve unit that opens or closes the air-open port or the gas flow path, a memory, and a controller. The memory stores an opening threshold ΔV, and the controller counts a count value indicating the amount of liquid discharged from the nozzle in a closed state in which the valve unit closes the air-open port or the gas flow path, and, on condition that the count value reaches the opening threshold ΔV, sets the valve unit to an open state in which the air-open port or the gas flow path is opened, and the opening threshold ΔV satisfies the following formula (1). ΔV≦(Vtmax-Vi)×Pm / (P-Pm)...Equation (1) Here, Vtmax is the volume of the storage portion, Vi is the maximum amount of liquid that can be stored in the storage portion, P is the atmospheric pressure, and Pm is the meniscus pressure resistance of the liquid formed in the nozzle.

[0007] According to the liquid ejection device, the volume of the storage portion is reduced while the pressure of the gas in the storage portion is brought to atmospheric pressure at an appropriate timing, so that the liquid can be ejected from the nozzle stably.

[0008] (2) Preferably, the controller resets the count value to an initial value after the valve unit is set to the open state.

[0009] According to this configuration, the valve unit can be brought into an open state every time the count value reaches the opening threshold value ΔV.

[0010] (3) Preferably, after resetting the count value to an initial value, the controller obtains the remaining amount of liquid stored in the storage portion, and changes the opening threshold ΔV in accordance with the obtained remaining amount.

[0011] According to this configuration, the opening threshold ΔV is set to a level appropriate for the remaining amount in the reservoir.

[0012] (4) Preferably, the controller sets the valve unit to the open state on condition that liquid is not being discharged from the nozzle.

[0013] (5) Preferably, the Vtmax is 25 mL or less, the Vi is 4.2 mL or less, and the opening threshold ΔV is 0.53 mL or less.

[0014] (6) Preferably, the Vtmax is 25 mL or less, the Vi is 12.5 mL or less, and the opening threshold ΔV is 0.32 mL or less.

[0015] (7) Preferably, the opening threshold ΔV is 0.16 mL or more. Effect of the Invention

[0016] According to the present invention, the pressure drop in the reservoir caused by the discharge of liquid from the nozzle can be restored without increasing the size of the device. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view of a multifunction peripheral 10 according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a vertical cross-sectional view showing a schematic internal structure of the printer unit 11. As shown in FIG. [Diagram 3] FIG. 3 is a vertical cross-sectional view showing a cross section of the recording unit 24 taken along a plane perpendicular to the front-rear direction 8. As shown in FIG. [Figure 4] FIG. 4 is a functional block diagram of the multifunction device 10. [Diagram 5] FIG. 5 is a diagram for explaining the operation of the valve unit 91, where FIG. 5(A) is a diagram showing the valve unit 91 in a closed state, and FIG. 5(B) is a diagram showing the valve unit 91 in an open state. [Figure 6] FIG. 6 is a flowchart for explaining the image recording control and the pressure release control by the controller 130. [Figure 7] 7A and 7B are diagrams showing the state of the gas layer in storage section 80, with FIG. 7A showing the state before image recording and FIG. 7B showing the state after image recording. [Figure 8] FIG. 8 is a diagram showing the range of the opening threshold ΔV and the volume Vtmax of the storage section 80, where FIG. 8(A) is a diagram showing the range when the amount of ink 99 is 4.2 mL, and FIG. 8(B) is a diagram showing the range when the amount of ink 99 is 12.5 mL. [Figure 9] FIG. 9 is a vertical cross-sectional view showing a cross section of a storage section 80 according to a modified example taken along a plane perpendicular to the front-rear direction 8. As shown in FIG. [Figure 10] FIG. 10 is a vertical cross-sectional view showing a section of a storage section 80 according to another modified example taken along a plane perpendicular to the front-rear direction 8. As shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described. Note that the embodiment described below is merely one example of the present invention, and it goes without saying that the embodiment of the present invention can be appropriately modified within the scope of the present invention. In addition, in the following description, the progress from the starting point of the arrow to the end point is expressed as a direction, and the movement on the line connecting the starting point and the end point of the arrow is expressed as a direction. In addition, in the following description, the up-down direction 7 is defined based on the state in which the multifunction device 10 is installed so as to be usable (the state in FIG. 1), the front-rear direction 8 is defined with the surface in which the opening 13 is provided as the front surface 23, and the left-right direction 9 is defined when the multifunction device 10 is viewed from the front. The up-down direction 7, the front-rear direction 8, and the left-right direction 9 are mutually perpendicular.

[0019] [Overall structure of multifunction device 10] As shown in FIG. 1, the multifunction device 10 (an example of a liquid ejection device) has a housing 14 having a generally rectangular parallelepiped shape. A printer unit 11 is provided at the bottom of the housing 14. The multifunction device 10 has various functions such as a facsimile function and a print function. The multifunction device 10 has a function of recording an image on one side of a sheet of paper 12 (see FIG. 2) by an inkjet method as a print function. The multifunction device 10 may record an image on both sides of the sheet of paper 12. An operation unit 17 is provided at the top of the housing 14. The operation unit 17 is composed of buttons that are operated to instruct image recording and for various settings, a liquid crystal display that displays various information, and the like. In this embodiment, the operation unit 17 is composed of a touch panel having both the functions of a button and a liquid crystal display.

[0020] 2, the printer unit 11 includes a feed tray 20, a feed section 16, an outer guide member 18, an inner guide member 19, a pair of transport rollers 59, a pair of discharge rollers 44, a platen 42, a recording section 24, an encoder 35 (see FIG. 4), a rotary encoder 75 (see FIG. 4), a controller 130 (see FIG. 4), and a memory 140 (see FIG. 4). These are arranged inside the housing 14. Inside the housing 14, various status sensors (not shown) are arranged that detect the status of the multifunction device 10 and output signals according to the detection results.

[0021] [Feed Tray 20] As shown in Fig. 1, an opening 13 is formed in a front surface 23 of the printer unit 11. The feed tray 20 can be inserted into and removed from the housing 14 through the opening 13 by moving in the front-rear direction 8. The feed tray 20 can be moved between a feed position (position shown in Figs. 1 and 2) where it is attached to the housing 14, and a non-feed position where it is removed from the housing 14. The feed tray 20 moves to the feed position by being inserted backward into the housing 14, and moves to the non-feed position by being pulled forward into the housing 14.

[0022] The feed tray 20 is a box-shaped member that is open at the top and stores the papers 12. As shown in Fig. 2, the papers 12 are supported in a stacked state on a bottom plate 22 of the feed tray 20. The discharge tray 21 is disposed above the front part of the feed tray 20. The papers 12 that have been image-recorded by the recording unit 24 and discharged are supported on the upper surface of the discharge tray 21. When the feed tray 20 is in the feed position, the papers 12 supported by the feed tray 20 can be fed to the transport path 65.

[0023] [Feeding section 16] 2, the feeding unit 16 is disposed below the recording unit 24 and above the bottom plate 22 of the feeding tray 20. The feeding unit 16 includes a feeding roller 25, a feeding arm 26, a drive transmission mechanism 27, and a shaft 28. The feeding roller 25 is rotatably supported at the tip of the feeding arm 26. The feeding arm 26 rotates in the direction of the arrow 29 about the shaft 28 provided at the base end. This allows the feeding roller 25 to come into contact with and separate from the feeding tray 20 or the paper 12 supported by the feeding tray 20.

[0024] The feed roller 25 rotates by transmitting the driving force of the feed motor 102 (see FIG. 4) through a drive transmission mechanism 27 formed by meshing multiple gears. As a result, of the sheets 12 supported on the bottom plate 22 of the feed tray 20 at the feed position, the uppermost sheet 12 in contact with the feed roller 25 is fed to the conveying path 65. Note that the drive transmission mechanism 27 is not limited to a form in which multiple gears are meshed, and may be, for example, a belt stretched between the shaft 28 and the shaft of the feed roller 25.

[0025] [Transport Path 65] 2, a transport path 65 extends from the rear end of the feed tray 20. The transport path 65 includes a curved portion 33 and a straight portion 34. The curved portion 33 extends upward, making a U-turn from the rear to the front. The straight portion 34 extends generally along the front-rear direction 8.

[0026] The curved portion 33 is formed by an outer guide member 18 and an inner guide member 19 which face each other with a predetermined gap between them. The outer guide member 18 and the inner guide member 19 are provided to extend in the left-right direction 9. The straight portion 34 is formed by the recording unit 24 and a platen 42 which face each other with a predetermined gap between them at the position where the recording unit 24 is disposed.

[0027] The paper 12 supported on the feed tray 20 is transported along the curved portion 33 by the feed roller 25 and reaches the pair of transport rollers 59. The paper 12 held between the pair of transport rollers 59 is transported forward along the straight portion 34 toward the recording unit 24. The paper 12 that has reached directly below the recording unit 24 has an image recorded on it by the recording unit 24. The paper 12 with the image recorded on it is transported forward along the straight portion 34 and discharged onto the discharge tray 21. As a result, the paper 12 is transported along the transport direction 15 indicated by the dashed-dotted arrow in FIG. 2.

[0028] [Transport roller pair 59 and discharge roller pair 44] 2, a conveying roller pair 59 is disposed in the straight section 34. A discharge roller pair 44 is disposed downstream of the conveying roller pair 59 in the straight section 34 in the conveying direction 15.

[0029] The conveying roller pair 59 includes a conveying roller 60 and a pinch roller 61 disposed below the conveying roller 60 so as to face the conveying roller 60. The pinch roller 61 is pressed against the conveying roller 60 by an elastic member (not shown) such as a coil spring. The conveying roller pair 59 is capable of pinching the paper 12.

[0030] The discharge roller pair 44 includes a discharge roller 62 and a spur roller 63 disposed above the discharge roller 62 so as to face the discharge roller 62. The spur roller 63 is pressed toward the discharge roller 62 by an elastic member (not shown) such as a coil spring. The discharge roller pair 44 is capable of clamping the paper 12.

[0031] The conveying roller 60 and the discharge roller 62 are rotated by a driving force applied from a conveying motor 101 (see FIG. 4). When the conveying roller 60 rotates with the paper 12 sandwiched between the conveying roller pair 59, the paper 12 is conveyed in the conveying direction 15 by the conveying roller pair 59 and conveyed onto the platen 42. When the discharge roller 62 rotates with the paper 12 sandwiched between the discharge roller pair 44, the paper 12 is conveyed in the conveying direction 15 by the discharge roller pair 44 and discharged onto the discharge tray 21. Note that a common motor may be used as the conveying motor 101 and the feeding motor 102. In this case, the drive transmission path from the common motor to each roller is configured to be switchable.

[0032] It should be noted that the means for transporting the paper 12 is not limited to the above-mentioned roller pair. For example, instead of the transport roller pair 59 and the discharge roller pair 44, a transport belt may be provided.

[0033] [Platen 42] 2, the platen 42 is disposed in the straight section 34 of the transport path 65. The platen 42 faces the recording unit 24 in the up-down direction 7. The platen 42 supports the paper 12 transported along the transport path 65 from below. The paper 12 transported along the transport path 65 passes through an area between the right and left ends of the platen 42 in the left-right direction 9 (hereinafter referred to as the medium passing area).

[0034] [Record 24] 2, the recording unit 24 is disposed above the platen 42 so as to face the platen 42. The recording unit 24 includes a carriage 40, a head 38, and a storage unit 80.

[0035] The carriage 40 is supported by two guide rails 56, 57 spaced apart in the front-rear direction 8 so as to be movable along a left-right direction 9 perpendicular to the conveying direction 15. The carriage 40 is movable in the left-right direction 9 from the right of the medium passing area to the left of the medium passing area. The movement direction of the carriage 40 is not limited to the left-right direction 9, and may be any direction that intersects with the conveying direction 15.

[0036] Guide rail 56 is disposed upstream of head 38 in conveying direction 15. Guide rail 57 is disposed downstream of head 38 in conveying direction 15. Guide rails 56, 57 are supported by a pair of side frames (not shown) disposed outside straight portion 34 of conveying path 65 in left-right direction 9. Carriage 40 moves when a driving force is applied from a carriage drive motor 103 (see FIG. 4).

[0037] An encoder 35 (see FIG. 4) is disposed on guide rail 56 or guide rail 57. Encoder 35 includes an encoder strip extending in left-right direction 9, and an optical sensor provided at a location on carriage 40 facing the encoder strip. 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 left-right direction 9. 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 carriage 40 in left-right direction 9. The pulse signal is output to controller 130 (see FIG. 4).

[0038] The head 38 is supported by the carriage 40. A lower surface 68 of the head 38 is exposed downward and faces the platen 42. The head 38 includes a plurality of nozzles 39, an ink flow path 37, and a piezoelectric element 45 (see FIG. 4).

[0039] The multiple nozzles 39 are opened on the bottom surface 68 of the head 38. The ink flow path 37 connects the storage section 80 and the multiple nozzles 39. The piezoelectric element 45 (see FIG. 4) ejects ink droplets downward from the nozzles 39 by deforming a part of the ink flow path 37. The piezoelectric element 45 is operated by being supplied with power by the controller 130 (see FIG. 4). Thus, the head 38 has the nozzles 39 that eject ink (an example of liquid).

[0040] The storage unit 80 is supported by the carriage 40 in a state where it is attached to the carriage 40. The storage unit 80 has an internal space 81. Ink 99 is stored in the internal space 81. In this embodiment, the recording unit 24 has one storage unit 80. Black ink 99 is stored in this one storage unit 80. Note that the color of the ink 99 stored in the storage unit 80 is not limited to black.

[0041] The storage portion 80 is located above the head 38. In this embodiment, the entire storage portion 80 is located above the head 38, but a part of the storage portion 80 may be located above the head 38, and the other part of the storage portion 80 may be located at a height equal to or lower than the head 38. The internal space 81 of the storage portion 80 communicates with the multiple nozzles 39 via the ink flow path 37. As a result, ink 99 is supplied from the internal space 81 to the nozzles 39.

[0042] An inlet 83 for injecting ink 99 into the internal space 81 is provided in the upper wall 82 of the storage section 80. The inlet 83 penetrates the upper wall 82 in the thickness direction, and connects the internal space 81 to the outside of the storage section 80. A protruding wall 84 is provided around the inlet 83 on the upper surface of the upper wall 82 (see FIG. 3). The inlet 83 is closed by fitting a lid 85 to the protruding wall 84. When the lid 85 is removed from the protruding wall 84, the inlet 83 is exposed to the outside. In this state, a bottle (not shown) is inserted into the inlet 83, and ink 99 is injected from the bottle into the internal space 81 through the inlet 83. The inlet 83 may be provided in a position other than the upper wall 82 as long as it connects the upper part of the internal space 81 to the outside.

[0043] As shown in FIG. 3, an air vent 88 that opens to the outside of the storage unit 80 is provided in an upper portion of a side wall 87 of the storage unit 80. Air enters a portion of the internal space 81 of the storage unit 80 where no ink 99 is present. The portion of the internal space 81 of the storage unit 80 into which air has entered is referred to as a gas layer. A gas flow path 89 that passes through the air vent 88 is formed between the gas layer of the storage unit 80 and the outside. The gas flow path 89 communicates between the gas layer of the storage unit 80 and the outside through the air vent 88 that opens to the outside.

[0044] The storage section 80 is provided with a valve unit 91 that opens or closes the atmosphere open port 88. The valve unit 91 includes a valve 92 and a coil spring 93. The valve 92 is a member that abuts against or moves away from the atmosphere open port 88. The coil spring 93 is a member that urges the valve 92 to the right so that the valve 92 abuts against the atmosphere open port 88. A side surface 86 that faces the side wall 87 is formed at a position inside the storage section 80 corresponding to the coil spring 93. The left end of the coil spring 93 is connected to the side surface 86, and the right end is connected to the valve 92.

[0045] [Rotary Encoder 75] The rotary encoder 75 shown in FIG. 4 is composed of an encoder disk that is provided on the shaft of the conveyor motor 101 (see FIG. 4) and rotates together with the conveyor motor 101, and an optical sensor. The encoder disk is formed with a pattern in which light-transmitting portions and non-light-blocking portions are alternately arranged at equal pitches in the circumferential direction. When the encoder disk rotates, a pulse signal is generated each time the optical sensor detects a light-transmitting portion and a non-transmitting portion. The generated pulse signal is output to the controller 130 (see FIG. 4). The controller 130 calculates the amount of rotation of the conveyor motor 101 based on the pulse signal. The rotary encoder 75 may be provided on a portion other than the conveyor motor 101, such as the feed motor 102 or the conveyor roller 60.

[0046] [Controller 130 and Memory 140] The configurations of the controller 130 and the memory 140 will be described below with reference to Fig. 4. The controller 130 controls the overall operation of the multifunction device 10. 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 by an internal bus 137.

[0047] 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.

[0048] The ASIC 135 is connected to the conveying motor 101, the feeding motor 102, and the carriage driving motor 103. 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 cause the feeding unit 16 to feed the paper 12. The controller 130 also controls the conveying motor 101 to cause the conveying roller pair 59 and the discharge roller pair 44 to convey the paper 12. The controller 130 also controls the carriage driving motor 103 to move the carriage 40.

[0049] In addition, an 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. In addition, an encoder 35 is connected to the ASIC 135. Based on the pulse signal received from the encoder 35, the controller 130 recognizes the position of the carriage 40 and whether or not it is moving.

[0050] A piezoelectric element 45 is also connected to the ASIC 135. The piezoelectric element 45 operates when power is supplied from the controller 130 via a drive circuit (not shown). The controller 130 controls the power supply to the piezoelectric element 45 to selectively eject ink droplets from the multiple nozzles 39. A status sensor (not shown) is also connected to the ASIC 135. The controller 130 performs the image recording process and abnormality process described below based on a signal received from the status sensor.

[0051] When recording an image on the paper 12, the controller 130 alternately executes a transport process and a printing process. The transport process is a process in which the transport roller pair 59 and the discharge roller pair 44 transport the paper 12 by a predetermined line feed amount. The controller 130 controls the transport motor 101 to cause the transport roller pair 59 and the discharge roller pair 44 to execute the transport process. The printing process is a process in which the carriage 40 is moved in the left-right direction 9 while controlling the supply of power to the piezoelectric element 45 to cause the head 38 to eject ink droplets from the nozzle 39. During the printing process, the carriage 40 is located in a medium passing area (an area between the right and left ends of the platen 42) and faces the platen 42.

[0052] The controller 130 stops the paper 12 for a certain period between the current transport process and the next transport process. Then, while the paper 12 is stopped, the printing process is executed. That is, in the printing process, the controller 130 executes one pass in which ink droplets are ejected from the nozzles 39 while moving the carriage 40 rightward or leftward. In this way, one pass of image recording is executed on the paper 12.

[0053] The controller 130 alternately and repeatedly executes the transport process and the printing process, thereby making it possible to record an image in the entire image recordable area of ​​the paper 12. In other words, the controller 130 causes an image to be recorded on one sheet of paper 12 in multiple passes.

[0054] 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.

[0055] [Valve unit 91 operation] The state of the valve unit 91 changes between a closed state in which the atmospheric vent port 88 is closed, and an open state in which the atmospheric vent port 88 is open. The carriage 40 moves to a pressure release position set outside the medium passing area in accordance with control from the controller 130. In this embodiment, the pressure release position is a position to the right of the medium passing area. When the carriage 40 is within the medium passing area, the valve unit 91 is in a closed state. When the carriage 40 is in the pressure release position, the valve unit 91 is in an open state.

[0056] 5(A) is a member that extends in the up-down direction 7 and the front-rear direction 8 (not shown). The abutment portion 152 is a rod-shaped member that protrudes from the frame 151 and extends in the left-right direction 9. The position of the abutment portion 152 in the up-down direction 7 and the front-rear direction 8 is the same as the position of the atmosphere open port 88 in the up-down direction 7 and the left-right direction 9, respectively. The outer diameter of the abutment portion 152 is smaller than the inner diameter of the atmosphere open port 88.

[0057] 5(A), while an image is being recorded, the carriage 40 moves in the left-right direction 9 at a position away from the frame 151 and the contact portion 152. At this time, the coil spring 93 urges the valve 92 to the right so as to contact the atmosphere opening port 88. As a result, the valve unit 91 is in a closed state in which the atmosphere opening port 88 is closed.

[0058] 5(B), when the carriage 40 moves to the pressure release position, the contact portion 152 penetrates the atmosphere open port 88 from the right and pushes the valve 92 to the left. At this time, the valve 92 moves to the left against the biasing force of the coil spring 93 and moves away from the atmosphere open port 88. As a result, the valve unit 91 enters an open state in which the atmosphere open port 88 is open. When the valve unit 91 enters an open state, the pressure of the gas layer in the storage portion 80 becomes equal to atmospheric pressure.

[0059] When image recording is resumed, the carriage 40 moves away from the frame 151 and the abutment portion 152. At this time, the valve 92 moves rightward by the biasing force of the coil spring 93 and abuts against the atmosphere release port 88. Therefore, the valve unit 91 becomes closed again.

[0060] [Image recording control and pressure release control by controller 130] In the printer unit 11 configured as described above, the controller 130 executes image recording control to feed the paper 12 and record an image on the fed paper 12. In addition, the controller 130 executes pressure release control to open the valve unit 91 (open the atmosphere vent 88) at the required timing.

[0061] To perform pressure release control, the controller 130 counts a count value. This count value indicates the amount of ink discharged from the nozzles 39 while the valve unit 91 is in a closed state. The memory 140 stores an open threshold ΔV related to the count value. The open threshold ΔV is stored in, for example, the RAM 133 in the memory 140. The controller 130 sets the valve unit 91 to an open state on the condition that the count value reaches the open threshold ΔV.

[0062] Image recording control and pressure release control by the controller 130 will be described below with reference to the flowchart shown in Fig. 6. When the controller 130 receives a print command, it performs the control shown in Fig. 6. The print command is sent to the controller 130 from the operation unit 17 (see Fig. 1) of the multifunction device 10 or an external device connected to the multifunction device 10. The print command includes a command to start image recording control, information about the size of the paper 12, and print data to be image-recorded on the paper 12. When the print command is received, the valve unit 91 is in a closed state.

[0063] First, the controller 130 judges whether the ink tank 80 is empty (S110). In S110, it is judged whether the ink 99 stored in the storage unit 80 is empty using any method. The controller 130 may judge whether the ink tank 80 is empty using, for example, a method of detecting the position of a float (not shown) provided inside the storage unit 80, or a method of detecting light reflected by a prism (not shown) provided inside the storage unit 80. The amount of ink 99 that is judged to be empty is determined in advance. The controller 130 may judge the ink tank 80 to be empty when it is judged that the ink 99 is completely empty, or when it is judged that the ink 99 is less than a predetermined amount.

[0064] On the condition that it is determined in S110 that the ink is empty (S110: Yes), the controller 130 controls the carriage drive motor 103 to move the carriage 40 to the ink refill position (S120). While the carriage 40 is in the ink refill position, ink is refilled (S130). In S130, the lid 85 is removed from the protruding wall 84, and ink 99 is injected from a bottle (not shown) into the internal space 81 through the injection port 83. The ink refill position may be the same as the pressure release position, or may be different from the pressure release position. On the condition that it is determined in S110 that the ink is not empty (S110: No), the controller 130 proceeds to S140 without executing S120 and S130.

[0065] Next, the controller 130 flushes the nozzles 39 and feeds the paper 12 (S140). The controller 130 flushes the nozzles 39 by controlling the carriage drive motor 103 to move the carriage 40 to a flushing position, and then controls the piezoelectric element 45. The controller 130 feeds the paper 12 by controlling the feed motor 102. The flushing of the nozzles 39 and the feeding of the paper 12 are performed in parallel.

[0066] Next, the controller 130 judges again whether the ink is empty (S150). If it is judged that the ink is empty in S150 (S150: Yes), the controller 130 controls the carriage drive motor 103 to move the carriage 40 to the ink refill position (S160). While the carriage 40 is in the ink refill position, ink is refilled (S170). The processes of S160 and S170 are the same as the processes of S120 and S130, respectively. If it is judged that the ink is not empty in S150 (S150: No), the controller 130 proceeds to S180 without executing S160 and S170. The reason for executing S150 is that even if it is judged that the ink is not empty in S110, the ink may become empty due to the flushing in S140.

[0067] Next, the controller 130 judges whether the count value is equal to or greater than the release threshold value ΔV (S180). The process of S180 is an example of a process for judging whether the count value has reached the release threshold value ΔV. If it is judged in S180 that the count value is equal to or greater than the release threshold value ΔV (S180: Yes), the controller 130 releases the pressure and resets the count value to an initial value (S190). If it is judged in S180 that the count value is not equal to or greater than the release threshold value ΔV (S180: No), the controller 130 proceeds to S200 without executing S190.

[0068] In S190, the controller 130 controls the carriage drive motor 103 to move the carriage 40 to the pressure release position. When the carriage 40 moves to the pressure release position, the valve unit 91 enters an open state in which the air release port 88 is opened, and the pressure of the gas layer in the reservoir 80 becomes equal to atmospheric pressure. The pressure release is performed on the condition that ink is not discharged from the nozzles 39 while the carriage 40 is in the pressure release position. After the pressure release, the controller 130 controls the carriage drive motor 103 to move the carriage 40 to its original position. In parallel with the pressure release, the controller 130 resets the count value to an initial value. The initial value of the count value is, for example, 0.

[0069] Next, the controller 130 updates the count value while printing (S210). In S210, the controller 130 records an image on one sheet of paper 12. The controller 130 records an image on the entire image recordable area of ​​the paper 12 by alternately and repeatedly executing a transport process and a printing process. The controller 130 calculates the amount of ink discharged from the nozzles 39 when recording an image on one sheet of paper 12, based on, for example, the print data. The controller 130 adds this amount of ink to the count value.

[0070] Next, the controller 130 judges whether the count value is equal to or greater than the release threshold value ΔV (S210). As with the process of S180, the process of S210 is a process for judging whether the count value has reached the release threshold value ΔV. If it is judged in S210 that the count value is equal to or greater than the release threshold value ΔV (S210: Yes), the controller 130 releases the pressure and resets the count value to an initial value (S220). The process of S220 is the same as the process of S190. If it is judged in S210 that the count value is not equal to or greater than the release threshold value ΔV (S210: No), the controller 130 proceeds to S230 without executing S220.

[0071] Next, the controller 130 discharges the paper 12 (S230). In S230, the controller 130 causes the pair of conveying rollers 59 and the pair of discharging rollers 44 to convey the paper 12 in the conveying direction 15 and discharge the paper 12 onto the discharge tray 21.

[0072] Next, the controller 130 determines whether printing is completed (S240). In S240, the controller 130 determines whether all image data included in the print command has been recorded on the paper 12.

[0073] On the condition that it is determined in S240 that printing is not completed (S240: No), the controller 130 feeds the paper 12 (S250). The process of S250 is the same as the feeding of S140. Thereafter, the controller 130 proceeds to S150. Note that the feeding of the subsequent paper 12 may be performed in parallel with the ejection of the preceding paper 12 (S230).

[0074] If it is determined in S240 that printing has ended (S240: Yes), the controller 130 releases the pressure and resets the count value to the initial value (S260). The process of S260 is the same as the processes of S190 and S220. With this, the controller 130 ends the image recording control and the pressure release control.

[0075] In this way, the controller 130 counts the count value indicating the amount of ink discharged from the nozzles 39 while the valve unit 91 is in a closed state. The controller 130 sets the valve unit 91 to an open state on the condition that the count value reaches the open threshold value ΔV. After setting the valve unit 91 to an open state in S190, S220, and S260, the controller 130 resets the count value to an initial value. The controller 130 sets the valve unit 91 to an open state on the condition that ink is not being discharged from the nozzles 39.

[0076] Note that, although the case where controller 130 normally performs image recording has been described here, controller 130 may also execute a process for detecting an abnormality and a process when an abnormality is detected (neither of which are shown in the figures) while performing image recording.

[0077] [Open threshold ΔV] The release threshold ΔV used in the pressure release control will be described below. When the volume of the storage section 80 is Vtmax, the maximum amount of ink that can be stored in the storage section 80 is Vi, the atmospheric pressure is P, and the meniscus pressure resistance of the ink formed in the nozzle 39 is Pm, the release threshold ΔV satisfies the following formula (1). ΔV≦(Vtmax-Vi)×Pm / (P-Pm) Formula (1)

[0078] The process of deriving formula (1) will be described with reference to Figures 7(A) and 7(B). Figures 7(A) and 7(B) show schematic diagrams of the state of the gas layer in storage section 80 when valve unit 91 is in a closed state. Figure 7(A) shows the state before image recording, and Figure 7(B) shows the state after image recording. As shown in Figures 7(A) and 7(B), ink 99 is stored in storage section 80 forming a liquid surface. The height of the maximum amount of ink 99 that can be stored in storage section 80 is located above the opening of nozzle 39.

[0079] As shown in Fig. 7(A), before image recording, the pressure of the gas layer in storage section 80 is atmospheric pressure P, and the volume of the gas layer in storage section 80 is V. In the state shown in Fig. 7(A), assume that ΔV (ΔV is a positive value) of ink 99 is discharged due to image recording, resulting in a change to the state shown in Fig. 7(B). Assuming that storage section 80 is a rigid body that does not deform due to image recording, when ΔV of ink 99 is discharged, the volume of the gas layer in storage section 80 increases by ΔV to (V+ΔV). If the amount of decrease in pressure of the gas layer in storage section 80 at this time is ΔP (ΔP is a positive value), the following equation (2) is established. PV=(P-ΔP)(V+ΔV)...Equation (2) From equation (2), the following equation (3) is derived. ΔP=P×ΔV / (V+ΔV) Formula (3)

[0080] When the ink 99 stored in the storage section 80 is reduced by ΔV, if the pressure in the storage section 80 is released while the fluctuation (increase) in the pressure of the gas layer in the storage section 80 is below the meniscus withstand pressure Pm, the meniscus of the ink formed in the nozzle 39 will be maintained. On the other hand, the pressure of the gas layer in the storage section 80 is more likely to fluctuate the smaller the volume of the gas layer in the storage section 80 is (the greater the amount of ink 99 stored in the storage section 80 is). For this reason, when the ink 99 is reduced by ΔV, it can be said that maintaining the meniscus is most difficult when the maximum amount of ink 99 that can be stored in the storage section 80 is stored.

[0081] Therefore, if ΔV in equation (3) is the release threshold ΔV used in pressure release control, when the maximum amount of ink 99 that can be stored in the storage unit 80 is stored, if ΔP in equation (3) is equal to or less than the meniscus withstand pressure Pm, the meniscus of ink formed in the nozzle 39 will be maintained regardless of the amount of ink 99 stored in the storage unit 80. When the maximum amount of ink 99 that can be stored in the storage unit 80 is stored, V=Vtmax-Vi. By solving the inequality in which the result of substituting this equation into the right hand side of equation (3) is equal to or less than Pm, equation (1) is derived.

[0082] [Example of opening threshold ΔV] A specific example of the opening threshold ΔV will be described below. When evaluating the speed of a printer or the like, an ISO chart containing four color images is sometimes used. When the four color images included in the ISO chart are printed using four colors of ink (magenta, yellow, cyan, and black), black ink is consumed the most among the four colors of ink, and the average amount of black ink consumed per image is 0.020 mL. When this value is adopted as the amount of ink required to print one image, the amount of ink required to print 200 images is 4.2 mL, and the amount of ink required to print 600 images is 12.5 mL.

[0083] The atmospheric pressure is 101.3 kPa, and the meniscus pressure resistance of the ink 99 formed in the nozzle 39 is 2.5 kPa. The volume of the gas layer in the reservoir 80 changes according to the opening threshold ΔV as follows. Under the above assumptions, when the opening threshold ΔV is 0.2 mL, the volume of the gas layer is 7.90 mL or more. Under the same assumptions, when the opening threshold ΔV is 0.3 mL, the volume of the gas layer is 11.85 mL or more. Under the same assumptions, when the opening threshold ΔV is 0.4 mL, the volume of the gas layer is 15.82 mL. Under the same assumptions, when the opening threshold ΔV is 0.5 mL, the volume of the gas layer is 19.75 mL or more. Under the same assumptions, when the opening threshold ΔV is 0.6 mL, the volume of the gas layer is 23.70 mL or more.

[0084] When the number of printed sheets is 200 (corresponding to an ink amount of 4.2 mL) and the opening threshold ΔV is 0.2 mL, the volume of the storage section 80 that satisfies formula (1) is 12.07 mL or less. When the same number of printed sheets and the opening threshold ΔV is 0.3 mL, the volume of the storage section 80 that satisfies formula (1) is 16.02 mL or less. When the same number of printed sheets and the opening threshold ΔV is 0.4 mL, the volume of the storage section 80 that satisfies formula (1) is 19.99 mL or less. When the same number of printed sheets and the opening threshold ΔV is 0.5 mL, the volume of the storage section 80 that satisfies formula (1) is 23.92 mL or less. When the same number of printed sheets and the opening threshold ΔV is 0.6 mL, the volume of the storage section 80 that satisfies formula (1) is 27.87 mL or less.

[0085] When the number of printed sheets is 600 (corresponding to an ink amount of 12.5 mL) and the opening threshold ΔV is 0.2 mL, the volume of the storage section 80 that satisfies formula (1) is 20.40 mL or less. When the same number of printed sheets and the opening threshold ΔV is 0.3 mL, the volume of the storage section 80 that satisfies formula (1) is 24.35 mL or less. When the same number of printed sheets and the opening threshold ΔV is 0.4 mL, the volume of the storage section 80 that satisfies formula (1) is 28.32 mL or less. When the same number of printed sheets and the opening threshold ΔV is 0.5 mL, the volume of the storage section 80 that satisfies formula (1) is 32.25 mL or less. When the same number of printed sheets and the opening threshold ΔV is 0.6 mL, the volume of the storage section 80 that satisfies formula (1) is 36.20 mL or less.

[0086] It is preferable that the MFP 10 does not release the pressure in the reservoir 80 until the speed evaluation using the ISO chart is completed. For example, when the print speed of the MFP 10 is 6 ipm (Image Per Minute: the number of sides that can be output per minute), in the speed evaluation using the ISO chart, four color images included in one copy are printed in order, followed by images included in the minimum number of copies whose print time exceeds 30 seconds (here, four color images), so that a total of eight images are printed. The amount of ink required to print eight images is 0.16 mL. Taking this into consideration, the release threshold ΔV is set to 0.16 mL or more.

[0087] Furthermore, in order to reduce the size of the multifunction device 10, it is necessary to also reduce the size of the storage unit 80. In consideration of the size of the multifunction device 10, the volume Vtmax of the storage unit 80 is set to 25 mL or less.

[0088] When the number of printed sheets is 200 (corresponding to an ink amount of 4.2 mL), the range of the open threshold ΔV and the volume Vtmax of the storage section 80 where ΔV is 0.16 mL or more, Vtmax is 25 mL or less, and formula (1) is satisfied is the range indicated by the diagonal lines in FIG. 8(A). In the diagonal lines in FIG. 8(A), the open threshold ΔV is 0.53 mL or less. Therefore, when the volume Vtmax of the storage section 80 is 25 mL or less and the maximum amount Vi of ink 99 that can be stored in the storage section 80 is 4.2 mL or less, the open threshold ΔV is 0.53 mL or less.

[0089] When the number of printed sheets is 600 (corresponding to an ink amount of 12.5 mL), the range of the open threshold ΔV and the volume Vtmax of the storage section 80 where ΔV is 0.16 mL or more, Vtmax is 25 mL or less, and formula (1) is satisfied is the range indicated by the diagonal lines in FIG. 8(B). In the diagonal lines in FIG. 8(B), the open threshold ΔV is 0.32 mL or less. Therefore, when the volume Vtmax of the storage section 80 is 25 mL or less and the maximum amount Vi of ink 99 that can be stored in the storage section 80 is 12.5 mL or less, the open threshold ΔV is 0.32 mL or less.

[0090] [Control of opening threshold ΔV according to remaining ink amount] By setting the release threshold ΔV to a small value within a range that satisfies formula (1), the pressure of the gas layer in the storage unit 80 can be kept within a suitable range, and ink 99 can be stably ejected from the nozzle 39. On the other hand, by setting the release threshold ΔV to a large value within a range that satisfies formula (1), the frequency of pressure release can be reduced, and printing speed can be increased. Taking these points into consideration, the controller 130 may reset the count value to the initial value, and then obtain the remaining amount of ink 99 stored in the storage unit 80, and change the release threshold ΔV in accordance with the obtained remaining amount.

[0091] In order to control the opening threshold value ΔV according to the remaining amount of ink, the controller 130 counts, for example, a count value (hereinafter referred to as a full count value) different from the above count value. This full count value indicates the amount of ink 99 consumed from the point in time when the maximum amount of ink 99 is stored in the storage section 80 to that point in time. The controller 130 counts the full count value based on the print data.

[0092] The memory 140 stores a table in which the full count value (or the range of the full count value) is associated with the release threshold value ΔV. The smaller the full count value (i.e., the greater the remaining amount of ink 99), the smaller the release threshold value ΔV stored in this table. After resetting the count value to the initial value in S190, S220, and S250 shown in FIG. 6, the controller 130 reads out the release threshold value ΔV corresponding to the full count value at that time from the table, and uses the read-out release threshold value ΔV in the subsequent pressure release control. The full count value can be associated with the remaining amount of ink 99 stored in the storage section 80. In this manner, the controller 130 obtains the remaining amount of ink 99 stored in the storage section 80, and changes the release threshold value ΔV according to the obtained remaining amount.

[0093] When the remaining amount of ink 99 is large, the volume of the gas layer in the storage unit 80 is small. When ink 99 is discharged from the nozzle 39 in this state, the pressure of the gas layer in the storage unit 80 changes significantly. For this reason, the pressure of the gas layer in the storage unit 80 is likely to deviate from the desired range, making it difficult to stably eject the ink 99 from the nozzle 39. Therefore, when the remaining amount of ink 99 is large, a relatively small value is used as the opening threshold ΔV. This allows the pressure of the gas layer in the storage unit 80 to be kept within the desired range, and the ink 99 to be stably ejected from the nozzle 39.

[0094] On the other hand, when the remaining amount of ink 99 is small, the volume of the gas layer in the storage section 80 is large. Even if ink 99 is discharged from the nozzle 39 in this state, the pressure of the gas layer in the storage section 80 does not change significantly. Therefore, the pressure of the gas layer in the storage section 80 is unlikely to deviate from the preferred range, and ink 99 can be stably ejected from the nozzle 39. However, if the release threshold ΔV is smaller than necessary, the frequency of pressure release increases, and the printing speed decreases. Therefore, when the remaining amount of ink 99 is small, a relatively large value is used as the release threshold ΔV. This reduces the frequency of pressure release, and prevents a decrease in printing speed.

[0095] In this way, by changing the opening threshold ΔV according to the remaining amount of ink 99, an opening threshold ΔV suitable for the remaining amount in the storage section 80 is set. This makes it possible to stably eject ink 99 from the nozzles 39 and prevent a decrease in printing speed.

[0096] It should be noted that the controller 130 may obtain the remaining amount of ink 99 stored in the storage unit 80 by a method other than the above. The controller 130 obtains the remaining amount of ink 99 stored in the storage unit 80 by, for example, using a method of detecting the position of a float (not shown) provided inside the storage unit 80 or a method of detecting light reflected by a prism (not shown) provided inside the storage unit 80. The controller 130 may obtain the remaining amount of ink 99 by using the same method as in S110 and S150, or may obtain the remaining amount of ink 99 by using a method different from S110 and S150.

[0097] In this case, the controller 130 does not need to obtain an accurate value of the remaining amount of ink 99, but may obtain an approximate value of the remaining amount of ink 99. The controller 130 may obtain, for example, a two-level value (high level and low level) or a three-level value (high level, middle level, and low level) as the remaining amount of ink 99.

[0098] [Effects of the embodiment] According to the liquid ejection device, the volume of the storage section 80 is reduced while the pressure of the gas in the storage section 80 is brought to atmospheric pressure at an appropriate timing, so that the liquid can be ejected from the nozzle 39 stably.

[0099] Furthermore, since the controller 130 resets the count value to the initial value after opening the valve unit 91, the valve unit 91 can be opened every time the count value reaches the opening threshold value ΔV.

[0100] In addition, after the controller 130 resets the count value to the initial value, it obtains the remaining amount of ink 99 flowing into the storage section 80 and changes the opening threshold ΔV according to the obtained remaining amount, thereby setting the opening threshold ΔV appropriate for the remaining amount in the storage section 80.

[0101] [Variations] In the above embodiment, the valve unit 91 opens or closes the atmosphere open port 88, but the valve unit 91 may open or close the gas flow path 89. For example, in the storage section 80 shown in Fig. 9, the valve unit 91 is provided midway through the gas flow path 89 and opens or closes the gas flow path 89 rather than the atmosphere open port 88. In this way, the valve unit 91 may be any valve that opens or closes the atmosphere open port 88 or the gas flow path 89.

[0102] In the above embodiment, the recording unit 24 is provided with only one storage unit 80, but the recording unit 24 may be provided with multiple storage units 80. For example, as shown in Fig. 10, the recording unit 24 may be provided with four storage units 80C, 80M, 80Y, and 80B. In addition, in the above embodiment, the state of the valve unit 91 changes depending on the position of the carriage 40, but the state of the valve unit 91 may change regardless of the position of the carriage 40.

[0103] Cyan ink (not shown) is stored in the storage section 80C. Magenta ink (not shown) is stored in the storage section 80M. Yellow ink (not shown) is stored in the storage section 80Y. Black ink (not shown) is stored in the storage section 80B. The storage sections 80C, 80M, 80Y, and 80B are arranged side by side in the left-right direction 9. The storage sections 80C, 80M, 80Y, and 80B may be arranged side by side in a direction other than the left-right direction 9, for example, in the front-rear direction 8. The arrangement order of the storage sections 80C, 80M, 80Y, and 80B is not limited to the order shown in FIG. 10. The sizes of the storage sections 80C, 80M, 80Y, and 80B may be the same or different.

[0104] The air-opening port 88 is provided in each of the storage sections 80C, 80M, 80Y, and 80B. A valve unit 91 is provided corresponding to each air-opening port 88. Each valve unit 91 includes a valve 92 and a solenoid 94. Each valve 92 is supported by the corresponding solenoid 94 so as to be movable along the up-down direction 7. FIG. 10 shows the four valve units 91 in a closed state. In FIG. 10, the members supporting the solenoid 94 are omitted. When the controller 130 supplies electric current to the four solenoids 94, each valve 92 independently abuts against or separates from the air-opening port 88 at the upper end of the gas flow path 89. When the valve 92 abuts against the air-opening port 88, the corresponding valve unit 91 is in a closed state. When the valve 92 is separated from the air-opening port, the corresponding valve unit 91 is in an open state.

[0105] 10, four valve units 91 are provided corresponding to the four atmosphere open ports 88, but one valve unit 91 may be provided for the four atmosphere open ports 88. In this case, the valve unit includes four valves 92 and one solenoid 94. When a current is supplied from the controller 130 to the solenoid 94, the four valves 92 are simultaneously brought into contact with or separated from the atmosphere open port 88 at the upper end of the gas flow path 89.

[0106] In the above embodiment, the method in which the head 38 records an image on the paper 12 is a serial head type in which the head 38 moves by the carriage 40 to record an image on the paper 12, but the recording unit 24 may not have a carriage 40 and may be a line head type in which the head 38 records an image on the paper 12 without moving. In the case of the line head type, the head 38 is provided from the right end to the left end of the medium passing area. Also, the transport process and the printing process are performed in parallel and continuously. That is, ink droplets are continuously ejected from the nozzles 39 while the paper 12 is transported. Also, in the case of the line head type, the head 38 is supported by a frame of the housing 14. This frame corresponds to a support member.

[0107] In the above embodiment, the storage unit 80 is attached to the carriage 40, and ink is replenished by injecting ink from the inlet 83. However, the storage unit 80 is not limited to this configuration. For example, the storage unit 80 may be a cartridge that is detachable from the carriage 40. In this case, when the ink stored in the cartridge becomes low or runs out, the cartridge is replaced with a new cartridge.

[0108] In the above embodiment, the storage unit 80 is supported by the carriage 40, but it does not have to be supported by the carriage 40. For example, the storage unit 80 may be disposed at a location in the multifunction device 10 separate from the carriage 40. In this case, the storage unit 80 and the head 38 are connected by a tube or the like, and the ink stored in the storage unit 80 is supplied to the head 38 via the tube or the like. In this case as well, at least a portion of the storage unit 80 is located above the head 38. [Explanation of symbols]

[0109] 10...Multifunction device (liquid discharge device) 38 Head 39 Nozzle 80 Storage section 88 Atmospheric release port 89...Gas flow path 91 Valve unit 99...Ink (liquid) 130...Controller 140...Memory

Claims

1. A head having a nozzle for ejecting liquid; a storage section in which the liquid is stored and forms a liquid level, and the height of the liquid level of the maximum amount that can be stored is located above the opening of the nozzle; a gas flow path that communicates the gas layer of the storage unit with the outside through an air opening that opens to the outside; a valve unit that opens or closes the atmosphere opening or the gas flow path; Memory, A controller, The memory stores an opening threshold value ΔV, The above controller is counting a count value indicating an amount of liquid discharged from the nozzle in a closed state in which the valve unit closes the atmosphere release port or the gas flow path; On the condition that the count value has reached the opening threshold value ΔV, the valve unit is put into an open state in which the atmosphere opening port or the gas flow path is opened; the controller places the valve unit in the open state on condition that liquid is not being discharged from the nozzle; The liquid ejection device has an opening threshold value ΔV that satisfies the following formula (1). ΔV≦(Vtmax-Vi)×Pm / (P-Pm)...Formula (1) where Vtmax is the volume of the storage portion, Vi is the maximum amount of liquid that can be stored in the storage portion, P is the atmospheric pressure, and Pm is the meniscus pressure that the liquid forms in the nozzle.

2. 2. The liquid ejection device according to claim 1, wherein the controller resets the count value to an initial value after the valve unit is opened.

3. The liquid ejection device according to claim 2 , wherein the controller resets the count value to an initial value, obtains the remaining amount of liquid stored in the storage section, and changes the opening threshold ΔV in accordance with the obtained remaining amount.

4. The Vtmax is 25 mL or less, The V is 4.2 mL or less, The liquid ejection device according to claim 1 , wherein the opening threshold value ΔV is 0.53 mL or less.

5. The Vtmax is 25 mL or less, The V is 12.5 mL or less, The liquid ejection device according to claim 1 , wherein the opening threshold value ΔV is 0.32 mL or less.

6. 6. The liquid ejection device according to claim 4, wherein the opening threshold value ΔV is 0.16 mL or more.

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