Liquid ejection device and control method thereof

Abstract

The present invention provides a liquid ejection device and a control method for the liquid ejection device. The problem is that when the head unit is detached from the mounting portion, the gas-liquid interface of the nozzle may collapse, resulting in ink leakage. The liquid ejection device (500) includes: a head unit (200) having a plurality of nozzles (N) for ejecting liquid, and including a filter (16) provided with holes (16H) through which ink can pass, a nozzle row (12a) formed by the plurality of nozzles (N), and a nozzle row (12e) formed by the plurality of nozzles (N); a mounting portion (40) detachably mounting the head unit (200), wherein the nozzles (N) forming the nozzle row (12e) communicate with the nozzles (N) forming the nozzle row (12a) via the filter (16). Before the head unit (200) is detached from the mounting portion (40), a pre-action of forming a gas-liquid interface in the holes (16H) provided in the filter (16) is performed.

Description

Technical Field

[0001] The present invention relates to a liquid ejection device and a control method for a liquid ejection device. Background Art

[0002] In Patent Document 1, an inkjet printer as an example of a liquid ejection device that performs printing by ejecting ink as an example of a liquid onto a medium is disclosed. The printer includes a liquid ejection head as an example of a head unit, and a mounting portion on which the liquid ejection head is detachably mounted. The liquid ejection head has a plurality of nozzle rows as an example of a nozzle group formed by a plurality of nozzles that eject ink. In addition, the plurality of nozzle rows communicate with each other via a flow path in the liquid ejection head.

[0003] However, in the liquid ejection device described in Patent Document 1, for example, there is a case where the attitude of the head unit changes by detaching the head unit from the mounting portion, and a height difference is generated between the plurality of nozzles. At this time, the pressure of the ink in the head unit generated by the height difference between the plurality of nozzles acts on the gas-liquid interface formed in the nozzles by the ink, and there is a possibility that the gas-liquid interface of the nozzles collapses and ink leakage occurs.

[0004] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2019-10860 Summary of the Invention

[0005] In the liquid ejection device of the present invention, there are provided: a head unit having a plurality of nozzles that eject a liquid, and having a filter chamber, a first nozzle group formed by the plurality of nozzles, and a second nozzle group formed by the plurality of nozzles, wherein the filter chamber includes a filter provided with holes through which the liquid can pass, and an upstream chamber and a downstream chamber partitioned by the filter; a mounting portion on which the head unit is detachably mounted; a gas introduction portion capable of introducing gas into the filter chamber; and a control portion. The nozzles forming the second nozzle group communicate with the nozzles forming the first nozzle group via the filter of the filter chamber. When the pressure difference between the pressure on the gas side and the pressure on the liquid side that can maintain the gas-liquid interface formed in the holes of the filter is defined as a withstand pressure Pf, and the pressure difference between the pressure on the gas side and the pressure on the liquid side that can maintain the gas-liquid interface formed in the nozzles is defined as a withstand pressure Pn, the withstand pressure Pf is greater than the withstand pressure Pn. Before the head unit is detached from the mounting portion, the control portion performs the following preliminary operation: by controlling the gas introduction portion to introduce gas into the filter chamber, a gas-liquid interface is formed in the holes provided in the filter.

[0006] In a control method of a liquid ejection device, the liquid ejection device includes: a head unit having a plurality of nozzles for ejecting a liquid, and having a filter provided with holes through which the liquid can pass, a first nozzle group formed by the plurality of nozzles, and a second nozzle group formed by the plurality of nozzles; a mounting portion on which the head unit is detachably mounted, and the nozzles forming the second nozzle group communicate with the nozzles forming the first nozzle group via the filter. When a pressure difference between the pressure on the gas side and the pressure on the liquid side capable of maintaining a gas-liquid interface formed in the holes of the filter is defined as a pressure resistance Pf, and a pressure difference between the pressure on the gas side and the pressure on the liquid side capable of maintaining a gas-liquid interface formed in the nozzles is defined as a pressure resistance Pn, the pressure resistance Pf is greater than the pressure resistance Pn. In the control method of the liquid ejection device, before the head unit is detached from the mounting portion, a pre-action is performed, that is, a gas-liquid interface is formed in the holes provided in the filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A block diagram showing a schematic structure of a liquid ejection device including a head unit as one embodiment of the present disclosure.

[0008] Figure 2 A view showing a structure around the head unit.

[0009] Figure 3A A cross-sectional view showing a detailed structure of the liquid ejection device.

[0010] Figure 3B A main part cross-sectional view showing a detailed structure of the head unit.

[0011] Figure 4 A flowchart showing an example of a control method of the liquid ejection device including a pre-action.

[0012] Figure 5A A cross-sectional view showing a state where gas flows into the head unit during the pre-action.

[0013] Figure 5B A cross-sectional view showing a state where gas flows into an upstream chamber of a filter chamber during the pre-action.

[0014] Figure 5C A cross-sectional view showing a state where gas flows into a downstream chamber of a filter chamber during the pre-action.

[0015] Figure 5D A cross-sectional view showing a maintenance action.

[0016] Figure 6A A cross-sectional view showing the state in which gas flows into the upstream chamber of the filter chamber during the preliminary operation in Embodiment 2.

[0017] Figure 6B A cross-sectional view showing the state in which gas flows into the downstream chamber of the filter chamber during the preliminary operation in Embodiment 2.

[0018] Figure 7 A cross-sectional view showing a liquid ejection device according to another embodiment in which a part of the fluid flow portion is changed.

[0019] Figure 8 A cross-sectional view showing a liquid ejection device according to another embodiment in which a part of the fluid flow portion and the head unit are changed. Detailed Embodiment

[0020] Hereinafter, the present invention will be described based on the embodiments. In the respective drawings, the same reference numerals are assigned to the same components, and redundant descriptions are omitted.

[0021] In addition, in the respective drawings, X, Y, and Z represent three mutually orthogonal spatial axes. In the present specification, the directions along these axes are set as the X-axis direction, the Y-axis direction, and the Z-axis direction. When determining the orientation, the positive direction is set as "+", the negative direction is set as "-", and the positive and negative signs are used together in the direction notations, so that the direction toward which the arrow mark in each drawing faces is the + direction, and the opposite direction of the arrow mark is the - direction for description. In addition, the Z direction represents the vertical direction, the +Z direction represents vertically downward, and the -Z direction represents vertically upward. Further, for the three spatial axes of X, Y, and Z for which the positive and negative directions are not limited, they are described as the X-axis, the Y-axis, and the Z-axis.

[0022] 1. Embodiment 1

[0023] In the present embodiment, the liquid ejection device 500 is configured as an inkjet printer, and forms an image by ejecting ink onto the printing paper P. Ink is an example of a liquid. In addition, any type of medium such as a resin film or a cloth can be set as the ejection target of the ink instead of the printing paper P.

[0024] As Figure 1 shown, the liquid ejection device 500 includes: a head unit 200, a fluid flow portion 20, a conveyance mechanism 30, a mounting portion 40, a maintenance portion 50, an input / output portion 80, and a control portion 90.

[0025] As Figures 1 to 3BAs shown, the head unit 200 has a flow path portion 211 and a liquid ejection head 10. A common flow path 224 and a second common flow path 225 are provided in the flow path portion 211. The common flow path 224 is a flow path that can supply the ink supplied from the liquid flow path 24 of the fluid flow portion 20 described later to the liquid ejection head 10 by mounting the head unit 200 on the mounting portion 40. The second common flow path 225 is a flow path that can discharge the ink discharged from the liquid ejection head 10 to the fluid flow path 25. The common flow path 224 has a common flow path side connection portion 224C that can communicate with the liquid flow path side connection portion 24C of the liquid flow path 24.

[0026] An opening and closing valve is provided on the common flow path side connection portion 224C. By mounting the head unit 200 on the mounting portion 40, the common flow path 224 is set in a communicating state with the liquid flow path 24, and by removing the head unit 200 from the mounting portion 40, the communication between the common flow path side connection portion 224C and the outside is cut off. The second common flow path 225 has a second common flow path side connection portion 225C that can communicate with the fluid flow path side connection portion 25C of the fluid flow path 25. An opening and closing valve is provided on the second common flow path side connection portion 225C. By mounting the head unit 200 on the mounting portion 40, the second common flow path 225 is set in a communicating state with the fluid flow path 25, and by removing the head unit 200 from the mounting portion 40, the communication between the second common flow path side connection portion 225C and the outside is cut off.

[0027] The liquid ejection head 10 has a plurality of nozzles N for ejecting ink. The plurality of nozzles N are arranged at equal intervals in one direction to form a nozzle row 12. In a state where the head unit 200 is mounted on the mounting portion 40 described later, the nozzle row 12 extends along the X-axis direction, and the dimension between the nozzles N at both ends in the X-axis direction among the plurality of nozzles N forming the nozzle row 12 is longer than the width dimension of the printing paper P. The nozzle row 12 is an example of a nozzle group.

[0028] The head unit 200 of the present embodiment is a so-called line head that forms an image on the printing paper P by ejecting ink from the plurality of nozzles N constituting the nozzle row 12 in the +Z direction. Although in the head unit 200 of the present embodiment, for example, black ink is used as the ink for ejection, four nozzle rows 12 can also be provided at intervals along the Y-axis direction on the head unit 200, and different inks, such as a total of four colors of black, cyan, magenta, and yellow, can be ejected from the respective nozzle rows 12.

[0029] The liquid ejection head 10 in the present embodiment is composed of a plurality of liquid ejection heads 10a, 10b, 10c, 10d, and 10e. The liquid ejection head 10 has a nozzle surface 11. The nozzle surface 11 is composed of nozzle surfaces 11a, 11b, 11c, 11d, and 11e. Each of the liquid ejection heads 10a, 10b, 10c, 10d, and 10e has a nozzle surface 11a, 11b, 11c, 11d, and 11e, respectively. On each of the nozzle surfaces 11a, 11b, 11c, 11d, and 11e, nozzle rows 12a, 12b, 12c, 12d, and 12e are respectively provided, which are formed by arranging a plurality of nozzles N in each of them in one direction. The nozzle row 12 in the present embodiment is composed of nozzle rows 12a, 12b, 12c, 12d, and 12e. The nozzle row 12a is an example of a first nozzle group, the nozzle row 12e is an example of a second nozzle group, and the nozzle row 12c is an example of a third nozzle group.

[0030] Although in the present embodiment, a plurality of liquid ejection heads 10a, 10b, 10c, 10d, and 10e are mounted on the flow path portion 211 in such a way that a plurality of nozzle rows 12a, 12b, 12c, 12d, and 12e form a single nozzle row 12, thereby forming the head unit 200, it is also possible to form the head unit 200 by mounting a single liquid ejection head 10 having a single nozzle row 12 formed by a plurality of nozzle rows 12a, 12b, 12c, 12d, and 12e on the flow path portion 211. Alternatively, the head unit 200 can also be configured in such a way that a single liquid ejection head 10 having a single nozzle row 12 formed by a plurality of nozzle rows 12a, 12b, 12c, 12d, and 12e integrally includes the flow path portion 211.

[0031] The liquid ejection head 10 has a filter chamber 17. The filter chamber 17 includes a filter 16 capable of filtering ink, and an upstream chamber 17U and a downstream chamber 17D partitioned by the filter 16. The filter 16 is provided with a plurality of holes 16H through which a fluid including ink can pass. In the upstream chamber 17U, a first filter flow path 18 that communicates the upstream chamber 17U with the common flow path 224 and a second filter flow path 19 that communicates the upstream chamber 17U with the second common flow path 225 are provided. The filter chamber 17 includes a plurality of filter chambers 17a, 17b, 17c, 17d, and 17e. In the present embodiment, the liquid ejection head 10a has a filter chamber 17a, the liquid ejection head 10b has a filter chamber 17b, the liquid ejection head 10c has a filter chamber 17c, the liquid ejection head 10d has a filter chamber 17d, and the liquid ejection head 10e has a filter chamber 17e.

[0032] The filter chamber 17a is an example of the first filter chamber. The upstream chamber 17U included in the filter chamber 17a is an example of the first upstream chamber, and the downstream chamber 17D included in the filter chamber 17a is an example of the first downstream chamber. The filter chamber 17e is an example of the second filter chamber. The upstream chamber 17U included in the filter chamber 17e is an example of the second upstream chamber, and the downstream chamber 17D included in the filter chamber 17e is an example of the second downstream chamber. The filter chamber 17c is an example of the third filter chamber. The upstream chamber 17U included in the filter chamber 17c is an example of the third upstream chamber, and the downstream chamber 17D included in the filter chamber 17c is an example of the third downstream chamber.

[0033] In the filter 16, for example, a mesh-like body, a porous body, a porous plate formed with fine through-holes, etc. can be used. As the filter of the mesh-like body, there are a metal mesh, a resin-made mesh, a mesh filter, metal fibers, etc. As the filter of the metal fibers, there are a felt filter in which fine stainless steel wires are made into a felt shape, a metal sintered filter obtained by compression-sintering fine stainless steel wires, etc. As the filter of the porous plate, there are an electroformed metal filter, a metal filter processed by electron beam, a metal filter processed by laser beam, etc.

[0034] The filter 16 traps foreign matters by providing a plurality of holes 16H through which a fluid can pass. The filtration particle size indicating the size of the foreign matters that the filter 16 can trap is preferably smaller than the minimum size of the nozzle N. For example, it is preferably smaller than the size of the nozzle opening formed on the nozzle surface 11 of the nozzle N. Thereby, it becomes difficult for the foreign matters in the ink to reach the nozzle N. When the nozzle opening is circular, the minimum size of the nozzle opening refers to the diameter of the nozzle opening.

[0035] Here, the gas-liquid interface formed by air and ink in the hole 16H of the filter 16 in the present embodiment is compared with the gas-liquid interface formed by air and ink in the nozzle N included in the head unit 200. When the pressure difference between the pressure on the ink side and the pressure on the air side that can maintain the gas-liquid interface formed on the hole 16H of the filter 16 is defined as the pressure resistance Pf, and the pressure difference between the pressure on the ink side and the pressure on the air side that can maintain the gas-liquid interface formed on the nozzle N is defined as the pressure resistance Pn, the pressure resistance Pf is greater than the pressure resistance Pn. That is, the specifications of the hole 16H of the filter 16 in the present embodiment are set such that the pressure resistance Pf becomes greater than the pressure resistance Pn. In addition, air is an example of a gas and refers to the air of the earth. The pressure resistance Pf in the present embodiment is, for example, 5.5 kPa, and the pressure resistance Pn is, for example, 3.5 kPa.

[0036] In addition, when the maximum pressure among the pressures of the ink in the head unit 200 acting on the gas-liquid interface formed in the nozzles N due to the height difference between the multiple nozzles N of the head unit 200 is set as the pressure Ph1, the specifications of the holes 16H of the filter 16 are set such that the pressure resistance Pf becomes greater than the pressure Ph1. For example, when the head unit 200 is removed from the mounting portion 40, so that the attitude of the head unit 200 is tilted with respect to the Figures 1 to 3A attitude shown, a height difference will be generated among the multiple nozzles N constituting the nozzle row 12. At this time, for the gas-liquid interface formed in the nozzles N through the ink, the following pressure acts, that is, the pressure of the ink in the head unit 200 caused by the height difference between the multiple nozzles N of the head unit 200.

[0037] In the present embodiment, when the attitude of the head unit 200 becomes the attitude in which the direction in which the multiple nozzles N constituting the nozzle row 12 are arranged is the vertical direction, that is, the Z-axis direction, the pressure of the ink in the head unit 200 acting on each nozzle N becomes the maximum. As Figure 2 , Figure 3A shown, the multiple nozzles N forming each of the nozzle rows 12a, 12b, 12c, 12d, 12e of the liquid ejection head 10 are sequentially set as the #1 nozzle, #2 nozzle, #3 nozzle, #4 nozzle, #5 nozzle, #6 nozzle starting from the -X direction side. That is to say, the #1 nozzle is the nozzle N located at the most -X direction side among the multiple nozzles N forming the nozzle group, and the #6 nozzle is the nozzle N located at the most +X direction side among the multiple nozzles N forming the nozzle group. Moreover, when the attitude of the head unit 200 becomes the attitude in which the direction in which the multiple nozzles N constituting the nozzle row 12 are arranged, or the direction in which the multiple liquid ejection heads 10 are arranged is the vertical direction, that is, the Z-axis direction, the pressure of the ink in the head unit 200 acting on each nozzle N becomes the maximum.

[0038] At this time, in nozzle row 12a, the nozzle N where the pressure of the ink that acts becomes the maximum is the #1 nozzle, and the pressure of the ink with the dimension Dha as the water level difference acts. The dimension Dha is the distance from the #1 nozzle of nozzle row 12a to the #6 nozzle of nozzle row 12e, which is the farthest from the #1 nozzle of nozzle row 12a in the Z-axis direction as the vertical direction when the attitude of the head unit 200 is the attitude in which the direction in which the plurality of nozzles N constituting nozzle row 12 or the direction in which the plurality of liquid ejection heads 10 are arranged is the vertical direction, i.e., the Z-axis direction. Further, in nozzle row 12b, the nozzle N where the pressure of the ink that acts becomes the maximum is the #1 nozzle, and the pressure of the ink with the dimension Dhb as the water level difference acts on this nozzle. The dimension Dhb is the distance from the #1 nozzle of nozzle row 12b to the #6 nozzle of nozzle row 12e, which is the farthest from the #1 nozzle of nozzle row 12b in the Z-axis direction as the vertical direction when the attitude of the head unit 200 is the attitude in which the direction in which the plurality of nozzles N constituting nozzle row 12 or the direction in which the plurality of liquid ejection heads 10 are arranged is the vertical direction, i.e., the Z-axis direction. Further, in nozzle row 12c, the nozzles N where the pressure of the ink that acts becomes the maximum are the #1 nozzle and the #6 nozzle, and the pressure of the ink with the dimension Dhc as the water level difference acts. The dimension Dhc is the distance from the #1 nozzle of nozzle row 12c to the #6 nozzle of nozzle row 12e, which is the farthest from the #1 nozzle of nozzle row 12c in the Z-axis direction as the vertical direction when the attitude of the head unit 200 is the attitude in which the direction in which the plurality of nozzles N constituting nozzle row 12 or the direction in which the plurality of liquid ejection heads 10 are arranged is the vertical direction, i.e., the Z-axis direction. Further, the dimension Dhc is the distance from the #6 nozzle of nozzle row 12c to the #1 nozzle of nozzle row 12a, which is the farthest from the #6 nozzle of nozzle row 12c in the Z-axis direction as the vertical direction when the attitude of the head unit 200 is the attitude in which the direction in which the plurality of nozzles N constituting nozzle row 12 or the direction in which the plurality of liquid ejection heads 10 are arranged is the vertical direction, i.e., the Z-axis direction. Further, in nozzle row 12d, the nozzle N where the pressure of the ink that acts becomes the maximum is the #6 nozzle, and the pressure of the ink with the dimension Dhb as the water level difference acts. The dimension Dhb is the distance from the #6 nozzle of nozzle row 12d to the #1 nozzle of nozzle row 12a, which is the farthest from the #6 nozzle of nozzle row 12d in the Z-axis direction as the vertical direction when the attitude of the head unit 200 is the attitude in which the direction in which the plurality of nozzles N constituting nozzle row 12 or the direction in which the plurality of liquid ejection heads 10 are arranged is the vertical direction, i.e., the Z-axis direction. Further, in nozzle row 12e, the nozzle N where the pressure of the ink that acts becomes the maximum is the #6 nozzle, and the pressure of the ink with the dimension Dha as the water level difference acts.The dimension Dha is the distance from the #6 nozzle of the nozzle row 12e to the #1 nozzle of the nozzle row 12a, which is the farthest from the #6 nozzle of the nozzle row 12e in the Z-axis direction (vertical direction), when the attitude of the head unit 200 is such that the direction in which the multiple nozzles N constituting the nozzle row 12 or the multiple liquid ejection heads 10 are arranged is the vertical direction, i.e., the Z-axis direction.

[0039] Thus, in the present embodiment, the maximum pressure of the ink in the head unit 200 that acts on the gas-liquid interface formed in the nozzle N due to the attitude of the head unit 200 is the pressure of the ink with the dimension Dha as the water level difference. Therefore, in the present embodiment, it is possible to maintain that the pressure difference, i.e., the withstand voltage Pn, between the pressure on the ink side and the atmospheric pressure of the gas-liquid interface formed on the nozzle N is less than the pressure Ph1 of the ink with the dimension Dha as the water level difference. In addition, the withstand voltage Pn in the present embodiment is less than the pressure of the ink with the dimension Dhb as the water level difference and greater than the pressure of the ink with the dimensions Dhc, Dhd, Dhg as shown in Figure 2 、 Figure 3A as the water level difference. In the present embodiment, Dhg is 0.09 m, Dhd is 0.19 m, Dhc is 0.29 m, DHb is 0.4 m, Dha is 0.5 m, and when the specific weight of the ink is set to 10 kN / m 3 , the pressure of the ink with the dimension Dhg as the water level difference becomes 0.9 kPa, the pressure of the ink with the dimension Dhd as the water level difference becomes 1.9 kPa, the pressure of the ink with the dimension Dhc as the water level difference becomes 2.9 kPa, the pressure of the ink with the dimension Dhb as the water level difference becomes 4 kPa, and the pressure of the ink with the dimension Dha as the water level difference becomes 5 kPa. That is, in the present embodiment, the pressure Ph1 is 5 kPa.

[0040] When a mesh filter is used as the filter 16, a twill-woven filter can be set. A mesh filter formed by weaving stainless steel wires is provided with mesh openings as the gaps between the wires. At this time, the mesh openings as the gaps between the wires are referred to as holes 16H.

[0041] When a perforated plate filter is used as the filter 16, it is preferable that the minimum size of the holes 16H is smaller than the minimum size of the nozzle openings. In the perforated plate filter, a plurality of holes 16H penetrating the stainless steel plate are formed. In the case where the holes 16H are circular, the minimum size of the holes 16H refers to the diameter (inner diameter) of the holes 16H. The shape of the holes 16H is not limited to circular, and can also be set to polygons such as squares and hexagons, ellipses, etc.

[0042] As Figure 3BAs shown, the liquid ejection head 10 has a common liquid chamber 13. The common liquid chamber 13 communicates with a filter chamber 17. Each of the liquid ejection heads 10a, 10b, 10c, 10d, and 10e has a common liquid chamber 13. In the present embodiment, the common liquid chamber 13 of the liquid ejection head 10a communicates with the filter chamber 17a, the common liquid chamber 13 of the liquid ejection head 10b communicates with the filter chamber 17b, the common liquid chamber 13 of the liquid ejection head 10c communicates with the filter chamber 17c, the common liquid chamber 13 of the liquid ejection head 10d communicates with the filter chamber 17d, and the common liquid chamber 13 of the liquid ejection head 10e communicates with the filter chamber 17e.

[0043] The liquid ejection head 10 has a plurality of independent liquid chambers 15 that communicate with one nozzle N and independent communication channels 14 that communicate with one independent liquid chamber 15 corresponding to a plurality of nozzles N. An ejection element ACT is provided in the independent liquid chamber 15. By being driven, the ejection element ACT can eject the ink in the independent liquid chamber 15 as droplets from the nozzle N. The ejection element ACT of the present embodiment is constituted by a piezoelectric element that contracts when a drive voltage is applied. By applying and then removing the drive voltage to the piezoelectric element, the ink in the independent liquid chamber 15 with a changed volume can be ejected as droplets from the nozzle N.

[0044] As Figure 3A shown, in the present embodiment, the independent liquid chamber 15 that communicates with the nozzle N of the liquid ejection head 10a communicates with the common liquid chamber 13 of the liquid ejection head 10a via the independent communication channel 14. The independent liquid chamber 15 that communicates with the nozzle N of the liquid ejection head 10b communicates with the common liquid chamber 13 of the liquid ejection head 10b via the independent communication channel 14. The independent liquid chamber 15 that communicates with the nozzle N of the liquid ejection head 10c communicates with the common liquid chamber 13 of the liquid ejection head 10c via the independent communication channel 14. The independent liquid chamber 15 that communicates with the nozzle N of the liquid ejection head 10d communicates with the common liquid chamber 13 of the liquid ejection head 10d via the independent communication channel 14. The independent liquid chamber 15 that communicates with the nozzle N of the liquid ejection head 10e communicates with the common liquid chamber 13 of the liquid ejection head 10e via the independent communication channel 14.

[0045] Therefore, in the present embodiment, the nozzles N constituting one of the nozzle rows 12a, 12b, 12c, 12d, and 12e and the nozzles N constituting the other nozzle rows communicate with each other via at least one filter 16. For example, the No. 1 nozzle to No. 6 nozzle constituting the nozzle row 12a and the No. 1 nozzle to No. 6 nozzle constituting the nozzle row 12e communicate with each other via the filter 16 in the filter chamber 17a and the filter 16 in the filter chamber 17e. In addition, for example, the No. 1 nozzle to No. 6 nozzle constituting the nozzle row 12c and the No. 1 nozzle to No. 6 nozzle constituting the nozzle row 12a communicate with each other via the filter 16 in the filter chamber 17c and the filter 16 in the filter chamber 17a. In addition, for example, the No. 1 nozzle to No. 6 nozzle constituting the nozzle row 12c and the No. 1 nozzle to No. 6 nozzle constituting the nozzle row 12e communicate with each other via the filter 16 in the filter chamber 17c and the filter 16 in the filter chamber 17e.

[0046] As Figures 1 to 3A shown, the fluid flow portion 20 has a connection flow path 22, a liquid storage portion 23, a liquid flow path 24, a fluid flow path 25, and an air passage 26. The connection flow path 22 is installed through the liquid storage portion 21, so that the ink in the liquid storage portion 21 can be supplied to the liquid storage portion 23. The liquid storage portion 23 stores the ink supplied from the liquid storage portion 21. An air opening hole 23AH is provided on the upper surface of the liquid storage portion 23. Through the air opening hole 23AH, the internal space of the liquid storage portion 23 for storing the ink communicates with the atmosphere that is the external space. The liquid level of the ink stored in the liquid storage portion 23 is adjusted to a position in the +Z direction with respect to the nozzle surface 11 of the head unit 200.

[0047] The liquid flow path 24 is connected to the common flow path 224 of the head unit 200, so that the upstream chamber 17U of the filter chamber 17 and the liquid storage portion 23 can be communicated. The liquid flow path 24 is an example of a first passage that can communicate the upstream chamber 17U and the liquid storage portion 23. The liquid flow path 24 and the liquid storage portion 23 are connected together at the side of the liquid storage portion 23. The connection position between the liquid flow path 24 and the liquid storage portion 23 is located in the +Z direction with respect to the air opening hole 23AH of the liquid storage portion 23. On the liquid flow path 24, a first pump 24P, a first on-off valve 24V, and the above-mentioned liquid flow path side connection portion 24C are provided. The first pump 24P can make the ink flow between the liquid storage portion 23 and the head unit 200. By driving the first pump 24P, for example, the ink in the liquid flow path 24 flows in the supply direction as shown by the arrow mark in Figure 3A the figure. The first on-off valve 24V can be switched between an open state that allows the ink in the liquid flow path 24 to flow and a closed state that cuts off the flow of the ink.

[0048] The fluid flow path 25 is connected together through the second common flow path 225 of the head unit 200, so that the liquid storage portion 23 and the upstream chamber 17U of the filter chamber 17 can communicate. The fluid flow path 25 is an example of a second passage that can communicate the liquid storage portion 23 and the upstream chamber 17U. The fluid flow path 25 and the liquid storage portion 23 are connected together at the side of the liquid storage portion 23. The connection position between the fluid flow path 25 and the liquid storage portion 23 is located in the +Z direction with respect to the atmospheric opening hole 23AH of the liquid storage portion 23, and is located in the -Z direction with respect to the connection position between the fluid flow path 24 and the liquid storage portion 23. On the fluid flow path 25, a second pump 25P, a switching valve 27, and the above-mentioned fluid flow path side connection portion 25C are provided. The second pump 25P can make the liquid flow between the liquid storage portion 23 and the head unit 200, and by driving the second pump 25P, for example, the ink in the fluid flow path 25 flows along the return direction as shown by the arrow mark in Figure 3A the figure. The second pump 25P is an example of an introduction pump.

[0049] The switching valve 27 is provided on the fluid flow path 25 at a position closer to the liquid storage portion 23 than the second pump 25P. That is, the switching valve 27 is arranged on the fluid flow path 25 between the second pump 25P and the liquid storage portion 23. The atmosphere passage 26 is connected to the fluid flow path 25 via the switching valve 27. The atmosphere passage 26 is an example of a gas introduction portion that can introduce gas into the filter chamber 17 of the liquid ejection head 10 by communicating the fluid flow path 25 with the atmosphere. By driving the switching valve 27, the state of the fluid flow path 25 can be switched to an open state in which the fluid flow path 25 and the liquid storage portion 23 communicate, a closed state in which the flow of the fluid in the fluid flow path 25 is cut off, and a communication state in which the fluid flow path 25 and the atmosphere passage 26 communicate. In addition, since the fluid flow path 25 and the atmosphere passage 26 do not communicate in the open state and the closed state, the open state and the closed state are non-communication states in which the fluid flow path 25 and the atmosphere passage 26 do not communicate. In other words, the switching valve 27 can switch between a communication state in which the fluid flow path 25 and the atmosphere passage 26 communicate and a non-communication state in which the fluid flow path 25 and the atmosphere passage 26 do not communicate.

[0050] The conveying mechanism 30 conveys the printing paper P along the conveying direction. As Figure 1As shown, the conveying directions in this embodiment are the +Y direction and the -Y direction. The conveying mechanism 30 includes a conveying rod 34 on which three conveying rollers 32 are installed, and a conveying motor 36 that rotationally drives the conveying rod 34. By rotationally driving the conveying rod 34 with the conveying motor 36, the plurality of conveying rollers 32 are rotated, so that the printing paper P is conveyed in the +Y direction of the conveying direction. In addition, the number of the conveying rollers 32 is not limited to three, and may be any number. Furthermore, it may be configured to include a plurality of conveying mechanisms 30.

[0051] As Figures 1 to 3A shown, the mounting portion 40 detachably mounts the head unit 200. The detaching and attaching direction in this embodiment is the X-axis direction. The mounting direction of the head unit 200 to the mounting portion 40 is the -X direction, and the detaching direction of the head unit 200 from the mounting portion 40 is the +X direction. By mounting the head unit 200 on the mounting portion 40, the common flow path 224 of the head unit 200 and the liquid flow path 24 are communicated, and the second common flow path 225 and the fluid flow path 25 are communicated. In addition, by mounting the head unit 200 on the mounting portion 40, electrical connection between the head unit 200 and the main body side is implemented, and thus ink ejection from the nozzle N can be achieved by the drive control of the ejection element ACT performed by the control unit 90 described later.

[0052] The maintenance unit 50 performs maintenance on the head unit 200. The maintenance unit 50 includes a maintenance unit holding portion 51, a maintenance unit driving portion 52, a cover 61, a cover valve 62, a suction pump 63, a waste liquid pipe 64, a waste liquid collection portion 66, and a wiper 71.

[0053] The cover 61 performs maintenance on the head unit 200 by discharging ink from the nozzle N of the head unit 200. The cover 61 forms a suction space in which a plurality of nozzles N are opened by contacting the nozzle surface 11 of the head unit 200. The cover 61 is held on the maintenance unit holding portion 51. The maintenance unit holding portion 51 that holds the cover 61 moves in any direction in the Y-axis direction and the Z-axis direction by driving the maintenance unit driving portion 52. The cover 61 moves to a non-covering position where it does not contact the nozzle surface 11 and a suctionable position where it contacts the nozzle surface 11 by driving the maintenance unit driving portion 52.

[0054] The cover 61 communicates with a waste liquid collection unit 66 that collects waste liquid via a waste liquid pipe 64. A suction pump 63 is provided on the waste liquid pipe 64, and the suction pump 63 is used to suction the suction space formed by the cover 61. In addition, a cover valve 62 is provided at a position in the waste liquid pipe 64 that is between the cover 61 and the suction pump 63, and the cover valve 62 can switch the connection state between the cover 61 and the suction pump 63 to an open state in which the cover 61 and the suction pump 63 are in communication and a closed state in which the cover 61 and the suction pump 63 are not in communication.

[0055] The cover 61 includes: a cover 61a that forms a suction space for opening a plurality of nozzles N that can form a nozzle row 12a by contacting a nozzle surface 11a of the head unit 200; a cover 61b that forms a suction space for opening a plurality of nozzles N that can form a nozzle row 12b by contacting the nozzle surface 11b; a cover 61c that forms a suction space for opening a plurality of nozzles N that can form a nozzle row 12c by contacting the nozzle surface 11c; a cover 61d that forms a suction space for opening a plurality of nozzles N that can form a nozzle row 12d by contacting the nozzle surface 11d; and a cover 61e that forms a suction space for opening a plurality of nozzles N that can form a nozzle row 12e by contacting the nozzle surface 11e.

[0056] The cover valve 62 includes: a cover valve 62a that can switch the connection state between the cover 61a and the suction pump 63; a cover valve 62b that can switch the connection state between the cover 61b and the suction pump 63; a cover valve 62c that can switch the connection state between the cover 61c and the suction pump 63; a cover valve 62d that can switch the connection state between the cover 61d and the suction pump 63; and a cover valve 62e that can switch the connection state between the cover 61e and the suction pump 63.

[0057] The cover 61 of the present embodiment performs maintenance of the head unit 200 by discharging ink from a plurality of nozzles N that constitute any one of the plurality of nozzle rows 12a, 12b, 12c, 12d, 12e. For example, when performing maintenance on the nozzle row 12a, by moving the covers 61a, 61b, 61c, 61d, 61e to the suctionable position, a plurality of suction spaces for opening a plurality of nozzles N that constitute the respective nozzle rows 12a, 12b, 12c, 12d, 12e are formed.

[0058] Moreover, by setting the cover valve 62a to the open state, setting the other cover valves 62b, 62c, 62d, 62e to the closed state, and driving the suction pump 63, ink can be discharged from the plurality of nozzles N constituting the nozzle row 12a into the suction space. The ink discharged into the suction space is collected in the waste liquid collection unit 66 via the waste liquid pipe 64. In addition, when maintaining the nozzle rows 12a, 12b, 12c, 12d, 12e, by setting the cover valves 62a, 62b, 62c, 62d, 62e to the open state and driving the suction pump 63, ink can be discharged from the plurality of nozzles N constituting the nozzle rows 12a, 12b, 12c, 12d, 12e into the suction space.

[0059] The wiper 71 performs maintenance of the head unit 200 by wiping the nozzle surface 11 of the head unit 200. The wiper 71 is held on the maintenance unit holding portion 51. The wiper 71 moves between a standby position where it does not contact the nozzle surface 11 and a wiping position where it can contact the nozzle surface 11 along the Z-axis direction by driving the maintenance unit driving portion 52. In the present embodiment, by driving the maintenance unit driving portion 52 in a state where the wiper 71 is in the wiping position, the maintenance unit holding portion 51 that holds the wiper 71 moves along the Y-axis direction to perform wiping of the nozzle surfaces 11a, 11b, 11c, 11d, 11e that constitute the nozzle surface 11.

[0060] The input / output unit 80 includes a display unit 81 and an operation unit 82. The display unit 81 is an example of an informing unit that performs guiding display of the operation of the liquid ejection device 500 or informs information related to the liquid ejection device 500. The user can perform various operations in the liquid ejection device 500 by operating the operation unit 82 while referring to the content displayed on the display unit 81. In addition, the display unit 81 is constituted by a liquid crystal display module having a touch panel function, and when it has a function as an operation unit for performing various settings on the liquid ejection device 500, the operation unit 82 may not be provided.

[0061] The control unit 90 controls the entirety of the liquid ejection device 500. For example, the control unit 90 controls the flow operation of the fluid between the liquid storage unit 23 determined by the fluid flow unit 20 and the head unit 200, the conveyance operation along the conveyance direction of the printing paper P, the ejection operation of the ink from the nozzles N of the head unit 200, the maintenance operation of the head unit 200 determined by the maintenance unit 50, the control of the liquid ejection device 500 based on a user instruction determined by the input / output unit 80, and the notification to the user, etc. The control unit 90 can be constituted, for example, by a processing circuit such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array), and a storage circuit such as a semiconductor memory.

[0062] The head unit 200 of the present embodiment is detachably provided on the mounting unit 40. For example, when the head unit 200 is detached from the mounting unit 40 so that the attitude of the head unit 200 is inclined with respect to the attitude as Figures 1 to 3A shown, a height difference is generated between the plurality of nozzles N constituting the nozzle row 12. At this time, for the gas-liquid interface formed in the nozzle N by the ink, the pressure of the ink in the head unit 200 generated by the height difference between the plurality of nozzles N acts. When the pressure of the ink in the head unit 200 acting on the gas-liquid interface formed in the nozzle N by the ink is greater than the pressure difference between the pressure on the ink side and the pressure on the atmosphere side that can maintain the gas-liquid interface formed in the nozzle N, that is, the pressure resistance Pn, there is a possibility that the gas-liquid interface formed in the nozzle N collapses, and ink leakage from the nozzle N occurs.

[0063] In the head unit 200 of the present embodiment, the nozzles N constituting one of the nozzle rows 12a, 12b, 12c, 12d, 12e and the nozzles N constituting the other nozzle rows communicate with each other via at least one filter 16. Further, when the pressure difference between the pressure on the ink side and the pressure on the atmosphere side that can maintain the gas-liquid interface formed in the hole 16H of the filter 16 is defined as the pressure resistance Pf, the pressure resistance Pf is greater than the pressure resistance Pn. That is, the specification of the hole 16H of the filter 16 in the present embodiment is set so that the pressure resistance Pf becomes greater than the pressure resistance Pn.

[0064] Thus, when a pressure of the ink in the head unit 200 caused by a height difference between a plurality of nozzles N acts on the gas-liquid interface formed in the nozzle N, according to the head unit 200 of the present embodiment, ink leakage from the nozzle N can be suppressed by forming a gas-liquid interface in the holes 16H of the filter 16. Further, since the gas-liquid interface can be formed in the holes 16H of the filter 16 by replacing the ink in the filter chamber 17 with the atmosphere, for example, compared with the case where all the ink in the head unit 200 is discharged in the preliminary operation performed before removing the head unit 200, effects such as shortening the time of the preliminary operation, reducing wasted ink, and reducing the usage amount of the waste liquid collection unit 66 can be achieved.

[0065] Therefore, before removing the head unit 200 from the mounting unit 40, the control unit 90 performs the following preliminary operation: by driving and controlling the switching valve 27, the atmosphere can be introduced into the filter chamber 17, and by introducing the atmosphere into the filter chamber 17, a gas-liquid interface is formed in the holes 16H of the filter 16. Here, with reference to the Figure 4 flowchart shown as follows, the flow of the process executed by the control unit 90 when implementing the control including the preliminary operation in the present embodiment will be described. In the present embodiment, the flow of the process executed by the control unit 90 when implementing the control including the preliminary operation corresponds to the control method of the liquid ejection device 500.

[0066] In the input / output unit 80, when an operation for removing the head unit 200 is performed by the user, in step S11, the control unit 90 determines whether the ink has been filled into the head unit 200. In step S11, when the ink has not been filled into the head unit 200, step S11 becomes NO. When step S11 is NO, the control unit 90 transfers the process to step S15 and displays a message indicating that the head unit 200 can be removed on the display unit 81. When executing the process of step S15, the control unit 90 ends the process executed when implementing the control including the preliminary operation.

[0067] In step S11, when the ink has been filled into the head unit 200, step S11 becomes YES. The control unit 90 transfers the process to step S12. In step S12, the control unit 90 displays a message indicating preparation before removing the head unit 200 on the display unit 81.

[0068] In step S13, the control unit 90 performs a pre-action. For the pre-action, the control unit 90 drives and controls the switching valve 27 to set the switching valve 27 to the connected state. Thereby, the fluid flow path 25 communicates with the atmosphere passage 26, and it becomes a state in which the atmosphere from the atmosphere passage 26 can be introduced into the filter chambers 17a, 17b, 17c, 17d, and 17e via the fluid flow path 25, the second common flow path 225, and the second filter flow path 19. The control unit 90 sets the first on-off valve 24V to the open state in the connected state, and drives and controls the second pump 25P and the first pump 24P so that the flow of the fluid in the atmosphere passage 26, the fluid flow path 25, and the liquid flow path 24 becomes Figure 5A the orientation of the arrow mark shown. Thereby, as Figure 5A shown, the atmosphere flows into the fluid flow path 25, the second common flow path 225, and each second filter flow path 19 via the atmosphere passage 26.

[0069] The ink in the fluid flow path 25, the second common flow path 225, and each second filter flow path 19 flows toward the liquid reservoir portion 23 in each first filter flow path 18, the common flow path 224, and the liquid flow path 24 via the filter chambers 17a, 17b, 17c, 17d, and 17e. In addition, considering the possibility of ink dripping from the nozzle N during the execution of the pre-action, the control unit 90 may also drive and control the maintenance unit drive unit 52 as Figure 5A shown before driving and controlling the switching valve 27 to move the cover 61 to the aspirable position.

[0070] When further continuing to drive the second pump 25P and the first pump 24P from the state as Figure 5A shown, as Figure 5B shown, the atmosphere flows into the upstream chambers 17U of the filter chambers 17a, 17b, 17c, 17d, and 17e, and the ink in each upstream chamber 17U is replaced by the atmosphere. Thereby, a gas-liquid interface can be formed on the upstream chamber 17U side of the holes 16H of the filters 16 in the filter chambers 17a, 17b, 17c, 17d, and 17e. By the inflow of the atmosphere into each upstream chamber 17U, the ink in each upstream chamber 17U, each first filter flow path 18, and the common flow path 224 flows toward the liquid reservoir portion 23.

[0071] When it is difficult to replace the ink in the upstream chamber 17U with the atmosphere, the control unit 90 can also control the driving of the second pump 25P so that the pressure in the upstream chamber 17U becomes higher than the atmospheric pressure. For example, the control unit 90 can also control the driving of the second pump 25P so that the flow rate of the fluid determined by the second pump 25P increases compared to the flow rate of the fluid determined by the driving of the first pump 24P. In addition, at this time, the control unit 90 can also control the driving of the second pump 25P so that the pressure in the upstream chamber 17U becomes higher than the pressure in the downstream chamber 17D, and the difference between the pressure in the upstream chamber 17U and the pressure in the downstream chamber 17D becomes greater than the withstand voltage Pf.

[0072] Although the control unit 90 can also end the pre-operation after forming a gas-liquid interface on the upstream chamber 17U side of the holes 16H in the filter 16, in the present embodiment, during the pre-operation, the atmosphere also flows into the downstream chamber 17D of the filter chamber 17. When the control unit 90 further continues to drive the second pump 25P and the first pump 24P, as Figure 5C shown, the atmosphere flows into the downstream chamber 17D of the filter chambers 17a, 17b, 17c, 17d, 17e, so that the ink in each downstream chamber 17D is replaced with the atmosphere. At this time, the ink in the holes 16H of each filter 16 is not replaced with the atmosphere but remains in the holes 16H, so that in the holes 16H, a gas-liquid interface is formed on both the upstream chamber 17U side and the downstream chamber 17D side by the retained ink.

[0073] In the case where it is difficult for the atmosphere to flow into the downstream chamber 17D, for example, the control unit 90 can also be controlled to drive the second pump 25P so that the pressure in the upstream chamber 17U becomes higher than the pressure in the downstream chamber 17D, and the difference between the pressure in the upstream chamber 17U and the pressure in the downstream chamber 17D becomes greater than the withstand voltage Pf. At this time, even when a part of the ink in the head unit 200 drips from the nozzle N, as Figure 5C shown, by previously moving the cover 61 to the suction position, the ink can be collected by the cover 61.

[0074] In step S13, when the pre-operation ends, the control unit 90 transfers the process to step S14. In step S14, the control unit 90 performs a maintenance operation. As the maintenance operation, the control unit 90, as Figure 5D shown, drives and controls the maintenance unit driving unit 52, so that the maintenance unit holding unit 51 that holds the wiper 71 moves along the Y-axis direction, thereby performing wiping of the nozzle surface 11a, 11b, 11c, 11d, 11e that constitutes the nozzle surface 11. In addition, in the present embodiment, as Figure 5DAs shown, after performing the preliminary operation, ink is still stored in the head unit 200. At this time, after wiping, the control unit 90 can also drive the ejection element ACT to eject the ink from the nozzle N, thereby performing a flushing operation to adjust the state of the ink in the nozzle N.

[0075] In step S14, when the maintenance operation ends, the control unit 90 transfers the process to step S15. In step S15, the control unit 90 displays information indicating that the head unit 200 can be disassembled on the display unit 81. When the process of step S15 is executed, the control unit 90 ends the process executed when performing the control including the preliminary operation.

[0076] As described above, according to the liquid ejection device 500 according to Embodiment 1 and the control method of the liquid ejection device 500, the following effects can be obtained.

[0077] The liquid ejection device 500 includes: a head unit 200 having a plurality of nozzles N that eject ink, and having a filter chamber 17a, a nozzle row 12a formed by the plurality of nozzles N, and a nozzle row 12e formed by the plurality of nozzles N. The filter chamber 17a includes a filter 16 provided with holes 16H through which ink can pass, and an upstream chamber 17U and a downstream chamber 17D partitioned by the filter 16; a mounting portion 40 that detachably mounts the head unit 200; a switching valve 27 that can introduce gas into the filter chamber 17a; a control unit 90. The nozzles N forming the nozzle row 12e communicate with the nozzles N forming the nozzle row 12a via the filter 16 of the filter chamber 17a. When the pressure difference between the pressure on the atmosphere side and the pressure on the ink side that can maintain the gas-liquid interface formed in the holes 16H of the filter 16 is defined as the pressure resistance Pf, and the pressure difference between the pressure on the atmosphere side and the pressure on the ink side that can maintain the gas-liquid interface formed in the nozzles N is defined as the pressure resistance Pn, the pressure resistance Pf is greater than the pressure resistance Pn. Before the head unit 200 is detached from the mounting portion 40, the control unit 90 performs the following preliminary operation: by controlling the switching valve 27 and introducing the atmosphere into the filter chamber 17a, the gas-liquid interface is formed in the holes 16H provided in the filter 16.

[0078] Due to the disassembly of the head unit 200 or other reasons, the attitude of the head unit 200 changes, resulting in the following pressure acting on the gas-liquid interface formed in the nozzle N, that is, the pressure of the ink in the head unit 200 generated by the height difference between the multiple nozzles N due to the attitude change of the head unit 200. At this time, since the nozzles N forming the nozzle row 12e communicate with the nozzles N forming the nozzle row 12a via the filter 16 in the filter chamber 17a, the pressure resistance Pf of the gas-liquid interface formed in the holes 16H of the filter 16 can suppress the leakage of ink from the nozzle N.

[0079] When the maximum pressure of the ink pressure in the head unit 200 acting on the gas-liquid interface formed on the nozzle N due to the height difference between the multiple nozzles N of the head unit 200 is set as the pressure Ph1, the pressure resistance Pf is greater than the pressure Ph1. In this way, the pressure resistance Pf of the gas-liquid interface formed in the holes 16H of the filter 16 can further suppress the leakage of ink from the nozzle N caused by the attitude change of the head unit 200.

[0080] The liquid ejection device 500 includes: a liquid storage unit 23 that stores ink; a liquid flow path 24 that is configured to communicate the upstream chamber 17U and the liquid storage unit 23; a fluid flow path 25 that is configured to communicate the liquid storage unit 23 and the upstream chamber 17U; an air passage 26 that communicates with the fluid flow path 25; a switching valve that, as a gas introduction unit, can switch between a communication state in which the air passage 26 communicates with the fluid flow path 25 and a non-communication state in which the air passage 26 does not communicate with the fluid flow path 25; a second pump 25P that is provided on the fluid flow path 25. The control unit 90 performs the following pre-action, that is, by controlling the switching valve 27 to set the communication state, and by driving the second pump 25P, air is introduced into the upstream chamber 17U from the air passage 26 via the fluid flow path 25, and the ink in the upstream chamber 17U is returned to the liquid storage unit 23 via the liquid flow path 24, thereby forming the gas-liquid interface in the holes 16H of the filter 16. In this way, it is easy to form a gas-liquid interface in the holes 16H of the filter 16.

[0081] The control unit 90 drives the second pump 25P in such a way that the pressure in the upstream chamber 17U becomes higher than the pressure in the downstream chamber 17D, and the pressure difference between the pressure in the upstream chamber 17U and the pressure in the downstream chamber 17D becomes greater than the pressure resistance Pf. In this way, it is easy to form a gas-liquid interface in the holes 16H of the filter 16.

[0082] The head unit 200 has a filter chamber 17e and a common flow path 224. The filter chamber 17e includes a filter 16, an upstream chamber 17U and a downstream chamber 17D divided by the filter 16. The common flow path 224 connects the upstream chamber 17U of the filter chamber 17a and the upstream chamber 17U of the filter chamber 17e. The plurality of nozzles N forming the nozzle row 12a and the plurality of nozzles N forming the nozzle row 12e jet the ink supplied via the common flow path 224. The nozzles N forming the nozzle row 12e communicate with the nozzles N forming the nozzle row 12a via the filter 16 of the filter chamber 17e, the common flow path 224, and the filter 16 of the filter chamber 17a. The switching valve 27 is configured to be able to introduce the atmosphere into the filter chamber 17a and the filter chamber 17e. The control unit 90 forms the gas-liquid interface in the holes 16H provided in the filter 16 provided in the filter chamber 17a and the holes 16H provided in the filter 16 provided in the filter chamber 17e by introducing the atmosphere into the filter chamber 17a and the filter chamber 17e during the pre-operation.

[0083] According to this method, since the nozzles N forming the nozzle row 12e communicate with the nozzles N forming the nozzle row 12a via the filter 16 of the filter chamber 17e and the filter 16 of the filter chamber 17a, the pressure resistance Pf of the gas-liquid interface formed in the holes 16H of the filter 16 can further suppress the leakage of the ink from the nozzles N.

[0084] In the control method of the liquid ejection device 500, the liquid ejection device 500 includes: a head unit 200 having a plurality of nozzles N for ejecting ink, and having a filter 16 provided with holes 16H through which the ink can pass, a nozzle row 12a formed by the plurality of nozzles N, and a nozzle row 12e formed by the plurality of nozzles N; a mounting portion 40 detachably mounting the head unit 200. The nozzles N forming the nozzle row 12e communicate with the nozzles N forming the nozzle row 12a via the filter 16. When the pressure difference between the pressure on the atmosphere side and the pressure on the ink side that can maintain the gas-liquid interface formed in the holes 16H of the filter 16 is set as the pressure resistance Pf, and the pressure difference between the pressure on the atmosphere side and the pressure on the ink side that can maintain the gas-liquid interface formed on the nozzles N is set as the pressure resistance Pn, the pressure resistance Pf is greater than the pressure resistance Pn. In the control method of the liquid ejection device 500, before the head unit 200 is detached from the mounting portion 40, the following pre-operation is performed, that is, the gas-liquid interface is formed in the holes 16H provided in the filter 16.

[0085] According to this method, when the following pressure acts on the gas-liquid interface formed on the nozzle N, that is, the pressure of the ink in the head unit 200 caused by a change in the attitude of the head unit 200 due to the removal of the head unit 200 or the like, leakage of the ink from the nozzle N can be suppressed.

[0086] 2. Embodiment 2

[0087] Next, a liquid ejecting apparatus 500 according to Embodiment 2 as one embodiment of the present disclosure, and a control method of the liquid ejecting apparatus 500 will be described. In addition, parts common to the liquid ejecting apparatus 500 and the control method of the liquid ejecting apparatus 500 according to Embodiment 1 are denoted by the same reference numerals and their description will be omitted.

[0088] The specifications of the liquid ejecting apparatus 500 and the head unit 200 of the present embodiment are the same as those of the liquid ejecting apparatus 500 and the head unit 200 of Embodiment 1. Therefore, due to the attitude of the head unit 200, the pressure of the ink with the dimension Dha acting on the nozzle N in the nozzle row 12a as the water level difference, the pressure of the ink with the dimension Dhb acting on the nozzle N in the nozzle row 12b as the water level difference, the pressure of the ink with the dimension Dhb acting on the nozzle N in the nozzle row 12d as the water level difference, and the pressure of the ink with the dimension Dha acting on the nozzle N in the nozzle row 12e as the water level difference are greater than the pressure resistance Pn of the gas-liquid interface formed in the nozzle N. In addition, due to the attitude of the head unit 200, the pressure of the ink with the dimension Dhc acting on the nozzle N in the nozzle row 12c is greater than the pressure resistance Pn. Therefore, when the pressure of the ink with the dimension Dhc as the water level difference acts on the nozzle N in the nozzle row 12c, even if a gas-liquid interface is not formed in the holes 16H of the filter 16 in the filter chamber 17c, the gas-liquid interface of the nozzle N in the nozzle row 12c will not collapse.

[0089] In the preliminary operation executed by the control unit 90 in Embodiment 1, as Figures 5A to 5C shown, a gas-liquid interface is also formed in the holes 16H of the filter 16 in the filter chamber 17c. In contrast, although the control unit 90 in the present embodiment is as Figure 6A , Figure 6B shown, a gas-liquid interface is formed in the holes 16H of the filter 16 in the filter chambers 17a, 17b, 17d, and 17e in the preliminary operation, but a gas-liquid interface may not be formed in the holes 16H of the filter 16 in the filter chamber 17c.

[0090] Next, the process of the processing executed by the control unit 90 when implementing control including the pre-action in the present embodiment will be described. In addition, in the present embodiment, the process of the processing executed by the control unit 90 when implementing control including the pre-action is the same as the rest except that step S13 in the flowchart shown as Figure 4 is different from that in Embodiment 1. Therefore, the process of the processing in step S13 in the flowchart shown as Figure 4 will be described here.

[0091] In step S13, the control unit 90 executes the pre-action. In the pre-action, the control unit 90 moves the lid 61 to the suctionable position. In addition, the control unit 90 sets the first on-off valve 24V to the closed state. In addition, the control unit 90 sets the switching valve 27 to the connected state. In addition, the lid valves 62a, 62b, 62d, 62e are set to the open state, and the lid valve 62c is set to the closed state. Moreover, the control unit 90 drives the suction pump 63. At this time, the control unit 90 drives the suction pump 63 so that the pressure in the downstream chambers 17D of the filter chambers 17a, 17b, 17d, 17e becomes lower than the pressure in the upstream chambers 17U, and the pressure difference between the pressure in the downstream chambers 17D and the pressure in the upstream chambers 17U becomes greater than the withstand voltage Pn. Thus, as Figure 6A shown, the ink discharged from the nozzles N of the nozzle arrays 12a, 12b, 12d, 12e will flow toward the waste liquid collection unit 66 as indicated by the arrow marks via the lids 61a, 61b, 61d, 61e, and the waste liquid pipe 64.

[0092] Accompanying this, as indicated by the arrow marks, the atmosphere flows into the fluid flow path 25, the second common flow path 225, the second filter flow path 19 communicating with the filter chambers 17a, 17b, 17d, 17e, and the upstream chambers 17U of the filter chambers 17a, 17b, 17d, 17e through the atmosphere passage 26, thereby replacing the ink in the upstream chambers 17U of the filter chambers 17a, 17b, 17d, 17e with the atmosphere. Thus, a gas-liquid interface is formed on the upstream chamber 17U side of each of the holes 16H of the filter 16 in the filter chambers 17a, 17b, 17d, 17e. On the other hand, since the atmosphere does not flow into the second filter flow path 19 and the filter chamber 17c communicating with the filter chamber 17c, a gas-liquid interface is not formed in the holes 16H of the filter 16 in the filter chamber 17c.

[0093] Although the control unit 90 can end the pre-action after a gas-liquid interface is formed on the upstream chamber 17U side of the holes 16H of the filter 16 in the filter chambers 17a, 17b, 17d, 17e, as Figure 6BWhen a gas-liquid interface is formed on both the upstream chamber 17U side and the downstream chamber 17D side of the holes 16H in each of the filters 16 in the filter chambers 17a, 17b, 17d, 17e as shown, the driving of the suction pump 63 will continue. When it is difficult for the atmosphere to flow into the downstream chamber 17D of the filter chambers 17a, 17b, 17d, 17e, for example, the control unit 90 can drive the suction pump 63 in such a way that the pressure in the downstream chamber 17D of the filter chambers 17a, 17b, 17d, 17e becomes lower than the pressure in the upstream chamber 17U, and the pressure difference between the pressure in the downstream chamber 17D and the pressure in the upstream chamber 17U becomes greater than the withstand pressure Pf.

[0094] As described above, according to the liquid ejection device 500 according to the second embodiment, the following effects can be obtained.

[0095] The head unit 200 includes a filter chamber 17c and a nozzle row 12c. The filter chamber 17c includes a filter 16, an upstream chamber 17U and a downstream chamber 17D partitioned by the filter 16. The nozzle row 12c has a plurality of nozzles N that eject ink supplied through a common flow path 224 communicating with the upstream chamber 17U of the filter chamber 17c. The nozzles N forming the nozzle row 12c communicate with the nozzles N forming the nozzle row 12a through the filter 16 of the filter chamber 17c, the common flow path 224, and the filter 16 of the filter chamber 17a, and communicate with the nozzles N forming the nozzle row 12e through the filter 16 of the filter chamber 17c, the common flow path 224, and the filter 16 of the filter chamber 17e. When the maximum pressure among the pressures of the ink in the head unit 200 acting on the gas-liquid interface formed on the nozzles N in the nozzle row 12c due to the height difference between the plurality of nozzles N of the head unit 200 is set as the pressure Ph2, when the withstand pressure Pn is greater than the pressure Ph2, the control unit 90 does not form a gas-liquid interface in the holes 16H on the filter 16 provided in the filter chamber 17c during the pre-operation.

[0096] According to this method, when a pressure such as the pressure of the ink in the head unit 200 caused by a change in the attitude of the head unit 200 due to the removal of the head unit 200 or the like acts on the gas-liquid interface formed on the nozzles N, it is possible to reduce the replacement amount of the ink and the atmosphere in the filter chamber 17 while suppressing the leakage of the ink from the nozzles N.

[0097] Although the liquid ejection device 500 according to the above-described embodiment of the present invention is based on having the structure as described above, of course, partial structural changes or omissions, etc. can also be implemented without departing from the gist of the invention of the present application. In addition, the above-described embodiment and other embodiments described below can be implemented in a combined manner within a range where there is no technical contradiction. Hereinafter, other embodiments will be described.

[0098] In the preliminary operation in the above-described Embodiment 2, the control unit 90 may also form a gas-liquid interface in the hole 16H of any one of the filters 16 provided in the filter chambers 17a, 17b, 17c, 17d, 17e, so that the maximum pressure among the pressures of the ink in the head unit 200 acting on the gas-liquid interface formed on the nozzle N due to the height difference between the plurality of nozzles N provided in the head unit 200 becomes less than the withstand voltage Pn of the gas-liquid interface formed on the nozzle N. Since when the head unit 200 of the above-described embodiment is adopted, the pressure of the ink with the dimension Dhc as the water level difference is less than the withstand voltage Pn of the gas-liquid interface provided on the nozzle N, for example, a gas-liquid interface is formed in the hole 16H of the filter 16 provided in the filter chambers 17a, 17e. At this time, in the preliminary operation, the control unit 90 sets the first on-off valve 24V to the closed state, sets the switching valve 27 to the communicating state, sets the lid valves 62a, 62e to the open state, sets the lid valves 62b, 62c, 62d to the closed state, and drives the suction pump 63. In this preliminary operation, a gas-liquid interface is not formed in the hole 16H of the filter 16 provided in the filter chambers 17b, 17c, 17d. In addition, since when the head unit 200 of the above-described embodiment is adopted, the pressure of the ink with the dimension Dhc as the water level difference is less than the withstand voltage of the gas-liquid interface formed on the nozzle N, for example, a gas-liquid interface may also be formed in the hole 16H of the filter 16 provided in the filter chambers 17a, 17b, and a gas-liquid interface is not formed in the hole 16H of the filter 16 provided in the filter chambers 17c, 17d, 17e. In addition, for example, a gas-liquid interface may also be formed in the hole 16H of the filter 16 provided in the filter chambers 17d, 17e, and a gas-liquid interface is not formed in the hole 16H of the filter 16 provided in the filter chambers 17a, 17b, 17c.

[0099] In the preliminary operation in the above-described Embodiment 1, the control unit 90 may also, in the communicating state, set the first on-off valve 24V to the open state and drive and control either the second pump 25P or the first pump 24P so that the flow of the fluid in the atmosphere passage 26, the fluid passage 25, and the liquid passage 24 becomes as Figure 5A indicated by the arrow marks.

[0100] In the preliminary operation in the above-described Embodiment 1, the control unit 90 may also set the first on-off valve 24V to the closed state in the connected state and drive and control the second pump 25P so that the flow of the fluid in the atmosphere passage 26 and the fluid passage 25 becomes as shown in Figure 5A the arrow marks, so that the atmosphere flows into the filter chamber 17, and thus a gas-liquid interface is formed in the holes 16H of the filter 16. In this case, although the ink in the filter chamber 17 is discharged from the nozzle N, as shown in Figure 5C shown, by previously moving the lid 61 to the position where suction is possible, collection can be performed by the lid 61.

[0101] In the above-described embodiment, it may also be configured such that the liquid ejecting device 500 can introduce the atmosphere into the filter chamber 17 of the liquid ejecting head 10 via the liquid passage 24. In this case, for example, the switching valve 27 may be provided at a position between the first pump 24P and the liquid reservoir 23 in the liquid passage 24, and the atmosphere passage 26 may be connected to the liquid passage 24 via the switching valve 27. Further, in this case, in the preliminary operation, the control unit 90 can introduce the atmosphere from the atmosphere passage 26 into the filter chamber 17 via the liquid passage 24, the common passage 224, and the first filter passage 18 by setting the switching valve 27 to the connected state, and drive the first pump 24P in the direction in which the atmosphere flows from the atmosphere passage 26 toward the filter chamber 17.

[0102] In the above-described embodiment, the liquid ejecting device 500 may also include an air tank for storing the atmosphere introduced into the filter chamber 17. In this case, the atmosphere passage 26 may also be connected to the air tank and the fluid passage 25 via the switching valve 27.

[0103] In the above-described embodiment, the liquid ejecting device 500 may also be configured such that by connecting the fluid passage 25 to the space above the ink in the liquid reservoir 23, the gas in the liquid reservoir 23 can be introduced into the filter chamber 17 of the liquid ejecting head 10. In this case, as shown in Figure 7 shown, the fluid flow unit 20 may also have a gas passage 626 instead of the atmosphere passage 26.

[0104] In the above-described embodiment, the liquid ejecting device 500 may also not introduce the atmosphere from the atmosphere passage 26 into the filter chamber 17. For example, by setting the first on-off valve 24V to the open state, setting the switching valve 27 to the open state, and driving the second pump 25P, as shown in Figure 3AAs shown, with the ink in the liquid flow path 24 flowing in the supply direction and the ink in the fluid flow path 25 flowing in the return direction, the first on-off valve 24V is set to the closed state. Thereby, air enters from the nozzle N into the head unit 200, and the air can be introduced into the filter chamber 17 via the common liquid chamber 13. In this case, the first on-off valve 24V functions as a gas introduction part that can introduce gas into the filter chamber 17 of the head unit 200.

[0105] In the above-described embodiment, the liquid ejection device 500 may also introduce air from the air passage 26 into the filter chamber 17 without passing through the fluid flow path 25, the second common flow path 225, and the second filter flow path 19. At this time, for example, as Figure 8 shown, the fluid flow part 20 has a gas flow path 28, a third pump 28P, a gas flow path on-off valve 28V as an example of a gas introduction part, and a gas flow path side connection part 28C, instead of the air passage 26 and the switching valve 27. An on-off valve is provided on the gas flow path side connection part 28C, which makes the gas flow path 28 and the third common flow path 228 in a communicating state by mounting the head unit 200 on the mounting part 40, and cuts off the communication between the gas flow path side connection part 28C and the outside by removing the head unit 200 from the mounting part 40. The head unit 200 has a third common flow path 228 and a third common flow path side connection part 228C. The third common flow path 228 communicates with a third filter flow path 328 provided on each upstream chamber 17U of the filter chambers 17a, 17b, 17c, 17d, 17e in the flow path part 211. An on-off valve is provided on the third common flow path side connection part 228C, which makes the third common flow path 228 and the gas flow path 28 in a communicating state by mounting the head unit 200 on the mounting part 40, and cuts off the communication between the third common flow path side connection part 228C and the outside by removing the head unit 200 from the mounting part 40. In addition, in this case, during the pre-operation, the control unit 90 can introduce air from the gas flow path 28 into the filter chamber 17 via the third common flow path 228 and the third filter flow path 328 and drive the third pump 28P by opening the gas flow path on-off valve 28V. Thereby, as marked by the arrow in Figure 8 shown, air will flow from the gas flow path 28 toward the filter chamber 17.

[0106] It is also possible to make air flow from Figure 8The gas flow path 28 shown is selectively introduced into any one of the filter chambers 17a, 17b, 17c, 17d, 17e, and on each branch flow path of the third common flow path 228 connected to each third filter flow path 328 provided on the filter chambers 17a, 17b, 17c, 17d, 17e, an on-off valve is provided. Alternatively, the gas flow path 28 provided with the third pump 28P and the gas flow path on-off valve 28V as an example of the gas introduction portion may be connected in a manner corresponding to each third filter flow path 328 provided on the filter chambers 17a, 17b, 17c, 17d, 17e.

[0107] In the above-described embodiment, each of the plurality of nozzles N forming the nozzle rows 12a, 12b, 12c, 12d, 12e in a manner communicating with the plurality of common liquid chambers 13 of the head unit 200 may also form a plurality of nozzle rows on the condition that the maximum pressure among the pressures of the ink acting on the gas-liquid interface formed in the nozzle N is less than the pressure resistance Pn of the gas-liquid interface formed in the nozzle N due to the height difference between the plurality of nozzles N communicating with one common liquid chamber 13. In this case, the plurality of nozzle rows communicating with one common liquid chamber 13 form one nozzle group.

[0108] In the above-described embodiment, the nozzle rows 12a, 12b, 12c, 12d, 12e of the head unit 200 may not form a single row of nozzle rows. For example, the nozzle rows 12a, 12b, 12c, 12d, 12e may be arranged in a staggered manner.

[0109] Although in the above-described embodiment, as an example of the nozzle group of each liquid ejection head 10 of the head unit 200, the nozzle row 12 formed by arranging a plurality of nozzles N in a row along the X-axis direction is shown, it is not limited to this manner. As long as the nozzle group provided in each liquid ejection head 10 is composed of a plurality of nozzles N communicating with the downstream chamber 17D without passing through the filter 16, it may have other structures. In this case, for example, another structure of the nozzle group provided in each liquid ejection head 10 may be, for example, a nozzle group formed by arranging a plurality of nozzle rows formed by arranging a plurality of nozzles N in a row in a direction intersecting the X-axis direction along the X-axis direction.

[0110] In the above-described embodiment, the head unit 200 may not be a line head. For example, when an image is formed on the printing paper P while the head unit 200 moves in the X-axis direction, each of the nozzle rows 12a, 12b, 12c, 12d, 12e of the head unit 200 is arranged along the Y-axis direction such that the nozzle rows 12a, 12b, 12c, 12d, 12e are spaced apart from each other in the X-axis direction.

[0111] Symbolic Explanation

[0112] 10, 10a, 10b, 10c, 10d, 10e... liquid ejection heads; 11, 11a, 11b, 11c, 11d, 11e... nozzle surfaces; 12, 12a, 12b, 12c, 12d, 12e... nozzle rows; 13... common liquid chamber; 14... independent communication channel; 15... independent liquid chamber; 16... filter; 16H... hole; 17, 17a, 17b, 17c, 17d, 17e... filter chambers; 17D... downstream chamber; 17U... upstream chamber; 18... first filter flow path; 19... second filter flow path; 20... fluid flow portion; 21... liquid storage portion; 22... connecting flow path; 23... liquid retention portion; 23AH... air opening hole; 24... liquid flow path; 24C... liquid flow path side connection portion; 24P... first pump; 24V... first on-off valve; 25... fluid flow path; 25C... fluid flow path side connection portion; 25P... second pump; 26... air channel; 27... switching valve; 28... gas flow path; 28C... gas flow path side connection portion; 28P... third pump; 28V... gas flow path on-off valve; 30... conveying mechanism; 32... conveying rollers; 34... conveying rods; 36... conveying motor; 40... mounting portion; 50... maintenance portion; 51... maintenance unit holding portion; 52... maintenance unit driving portion; 61, 61a, 61b, 61c, 61d, 61e... covers; 62, 62a, 62b, 62c, 62d, 62e... cover valves; 63... suction pump; 64... waste liquid pipe; 66... waste liquid collection portion; 71... wiper; 80... input / output portion; 81... display portion; 82... operation portion; 90... control portion; 200... head unit; 211... flow path portion; 224... common flow path; 224C... common flow path side connection portion; 225... second common flow path; 225C... second common flow path side connection portion; 228... third common flow path; 228C... third common flow path side connection portion; 328... third filter flow path; 500... liquid ejection device; 626... gas channel.

Claims

1. A liquid ejection device, characterized in that, Comprising: A head unit having a plurality of nozzles for ejecting a liquid, and having a filter chamber, a first nozzle group formed by a plurality of the nozzles, and a second nozzle group formed by a plurality of the nozzles, wherein the filter chamber includes a filter provided with holes through which the liquid can pass, and an upstream chamber and a downstream chamber partitioned by the filter; A mounting portion that detachably mounts the head unit; A gas introduction portion that can introduce gas into the filter chamber; A control portion The nozzles forming the second nozzle group communicate with the nozzles forming the first nozzle group via the filter of the filter chamber. When the pressure difference between the pressure on the gas side and the pressure on the liquid side that can maintain the gas-liquid interface formed in the holes of the filter is defined as the pressure resistance Pf, and the pressure difference between the pressure on the gas side and the pressure on the liquid side that can maintain the gas-liquid interface formed in the nozzles is defined as the pressure resistance Pn, the pressure resistance Pf is greater than the pressure resistance Pn. Before the head unit is detached from the mounting portion, the control portion performs the following preliminary operation, that is, by controlling the gas introduction portion to introduce the gas into the filter chamber, thereby forming the gas-liquid interface in the holes provided in the filter.

2. The liquid ejection device according to claim 1, characterized in that, When the maximum pressure in the liquid in the head unit, which acts on the gas-liquid interface formed in the nozzles due to the height difference between the plurality of nozzles of the head unit, is defined as the pressure Ph1, the pressure resistance Pf is greater than the pressure Ph1.

3. The liquid ejection device according to claim 1 or 2, characterized in that, Comprising: A liquid storage portion that stores the liquid; A first passage provided to communicate the upstream chamber and the liquid storage portion; A second passage provided to communicate the liquid storage portion and the upstream chamber; An atmosphere passage that communicates with the second passage; A switching valve, which serves as the gas introduction portion, and can switch between a connected state in which the atmosphere passage communicates with the second passage and a non-connected state in which the atmosphere passage does not communicate with the second passage; An introduction pump provided on the second passage; The control portion performs the following preliminary operation, that is, by controlling the switching valve to be in the connected state and driving the introduction pump, thereby introducing the gas from the atmosphere passage through the second passage into the upstream chamber, and returning the liquid in the upstream chamber to the liquid storage portion through the first passage, thereby forming the gas-liquid interface in the holes of the filter.

4. The liquid ejection device according to claim 3, characterized in that, The control portion drives the introduction pump in such a manner that the pressure in the upstream chamber becomes higher than the pressure in the downstream chamber, and the pressure difference between the pressure in the upstream chamber and the pressure in the downstream chamber becomes greater than the pressure resistance Pf.

5. The liquid ejection device according to claim 1, characterized in that, When the filter chamber is set as the first filter chamber, the upstream chamber is set as the first upstream chamber, and the downstream chamber is set as the first downstream chamber, the head unit has a second filter chamber and a common flow path, wherein the second filter chamber includes the filter, and a second upstream chamber and a second downstream chamber divided by the filter, and the common flow path communicates the first upstream chamber and the second upstream chamber. The nozzles forming the first nozzle group and the nozzles forming the second nozzle group jet the liquid supplied via the common flow path, and the nozzles forming the second nozzle group communicate with the nozzles forming the first nozzle group via the filter of the second filter chamber, the common flow path, and the filter of the first filter chamber. The gas introduction part is configured to be able to introduce the gas into the first filter chamber and the second filter chamber. The control part forms a gas-liquid interface in the holes in the filter provided in the first filter chamber and the holes in the filter provided in the second filter chamber by introducing the gas into the first filter chamber and the second filter chamber during the pre-operation.

6. The liquid ejection device according to claim 5, characterized in that, The head unit has a third filter chamber and a third nozzle group, the third filter chamber includes the filter, and a third upstream chamber and a third downstream chamber divided by the filter, and the third nozzle group has a plurality of nozzles that jet the liquid supplied via the common flow path communicating with the third upstream chamber. The nozzles forming the third nozzle group communicate with the nozzles forming the first nozzle group via the filter of the third filter chamber, the common flow path, and the filter of the first filter chamber, and also communicate with the nozzles forming the second nozzle group via the filter of the third filter chamber, the common flow path, and the filter of the second filter chamber. When the maximum pressure of the liquid in the head unit acting on the gas-liquid interface in the nozzles forming the third nozzle group due to the height difference between the plurality of nozzles of the head unit is set as pressure Ph2, when the pressure resistance Pn is greater than the pressure Ph2. The control part does not form a gas-liquid interface in the holes in the filter provided in the third filter chamber during the pre-operation.

7. A control method for a liquid ejection device, characterized in that, The liquid ejection device includes: A head unit that has a plurality of nozzles for ejecting liquid, and has a filter provided with holes through which the liquid can pass, a first nozzle group formed by the plurality of nozzles, and a second nozzle group formed by the plurality of nozzles; A mounting part that detachably mounts the head unit; The nozzles forming the second nozzle group communicate with the nozzles forming the first nozzle group via the filter. When the pressure difference between the pressure on the gas side and the pressure on the liquid side that can maintain the gas-liquid interface formed in the holes of the filter is set as the pressure resistance Pf, and the pressure difference between the pressure on the gas side and the pressure on the liquid side that can maintain the gas-liquid interface formed in the nozzle is set as the pressure resistance Pn, the pressure resistance Pf is greater than the pressure resistance Pn. In the control method of the liquid ejection device, Before the head unit is detached from the mounting portion, a pre-action is performed as follows: a gas-liquid interface is formed in the holes provided in the filter.

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