Cleaning method for liquid jet head, and liquid jet device

Abstract

To provide: a cleaning method for a liquid jet head that can extend the life of the liquid jet head by cleaning a filter; and a liquid jet device.SOLUTION: Provided is a cleaning method for a liquid jet head H including: common liquid chamber portions 401, 402 communicating with a plurality of nozzles N; first flow passages 120, 243 allowing communication between the common liquid chamber portion 401 and first openings 111a, 111b which are flow passage connections 11a, 11c with outside; second flow passages 121, 244 allowing communication between the common liquid chamber portion 402 and second openings 111b, 111d which are flow passage connections 11b, 11d with outside; and filters F each provided at a certain point in the first flow passage. The method includes: a cleaning step of causing a liquid to flow from the second flow passages 121, 244 toward the first flow passages 120, 243. Therein, in the cleaning step, air is not drawn from the nozzles N for a first period after the cleaning step is started.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a liquid ejection head cleaning method for cleaning the inside of a flow path of a liquid ejection head that ejects liquid from a nozzle, and a liquid ejection apparatus. [Background technology]

[0002] 2. Description of the Related Art A liquid ejecting apparatus, typified by an ink jet recording apparatus such as an ink jet printer, is equipped with a liquid ejecting head capable of ejecting liquid, such as ink, stored in a cartridge, a tank, or the like, in the form of droplets.

[0003] A filter is provided inside the flow path of the liquid jet head to capture foreign matter such as dust and air bubbles contained in the ink. By capturing the foreign matter with the filter, poor droplet jetting is suppressed (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2021-194881 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, if foreign matter is trapped in the filter and the filter becomes clogged, the ink supply pressure decreases and droplet ejection failure occurs, necessitating the replacement of the liquid ejection head. [Means for solving the problem]

[0006] An aspect of the present invention that solves the above problem is a method for cleaning a liquid jet head having a common liquid chamber that communicates with a plurality of nozzles that eject liquid, a first flow path that connects the common liquid chamber with a first opening that is a flow path connection with the outside, a second flow path that is a flow path different from the first flow path that connects the common liquid chamber with a second opening that is a flow path connection with the outside, and a filter provided midway through the first flow path, the method including a cleaning step of flowing liquid from the second flow path toward the first flow path, characterized in that the cleaning step does not draw air from the nozzles for a first period of time after the start of the cleaning step.

[0007] Another aspect of the present invention is a liquid ejection head comprising: a common liquid chamber connected to a plurality of nozzles that eject liquid; a first flow path that connects the common liquid chamber with a first opening that is a flow path connection with the outside; a second flow path that is a flow path different from the first flow path that connects the common liquid chamber with a second opening that is a flow path connection with the outside; and a filter provided midway through the first flow path; and a circulation mechanism that circulates liquid within a circulation flow path that includes the first flow path, the common liquid chamber, and the second flow path, wherein the circulation mechanism is capable of performing a cleaning operation that causes liquid to flow in the order of the second flow path, the common liquid chamber, and the first flow path, and the cleaning operation does not draw air from the nozzles for a first period after the start of the cleaning operation. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a schematic configuration of a liquid ejecting apparatus according to a first embodiment of the present invention. [Diagram 2] 1 is an exploded perspective view of a liquid jet head according to a first embodiment of the present invention. [Diagram 3] 1 is a plan view of a flow path member according to a first embodiment of the present invention. [Figure 4] 1 is a cross-sectional view of a flow path member according to a first embodiment of the present invention. [Diagram 5]1 is a plan view of a head chip according to a first embodiment of the present invention. [Figure 6] 1 is a cross-sectional view of a head chip according to a first embodiment of the present invention. [Figure 7] 1 is a block diagram of a liquid circulation system according to a first embodiment of the present invention. [Figure 8] 4 is a table showing pressure settings according to the first embodiment of the present invention. [Figure 9] FIG. 5 is a block diagram of a liquid circulation system according to a second embodiment of the present invention. [Figure 10] FIG. 11 is a block diagram of a liquid circulation system according to a third embodiment of the present invention. [Figure 11] FIG. 11 is a block diagram of a cleaning device according to a fourth embodiment of the present invention. [Figure 12] FIG. 11 is a cross-sectional view showing a modified example of the head chip of the present invention. [Figure 13] FIG. 11 is a cross-sectional view showing a modified example of the head chip of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention will be described in detail below based on an embodiment. However, the following description shows one aspect of the present invention and can be arbitrarily modified within the scope of the present invention. In each drawing, the same reference numerals indicate the same members, and the description is omitted as appropriate. In each drawing, X, Y, and Z represent three spatial axes that are mutually orthogonal. In this specification, the directions along these axes are defined as the X direction, the Y direction, and the Z direction. The direction in which the arrow in each drawing points is defined as the positive (+) direction, and the opposite direction to the arrow is defined as the negative (-) direction. In addition, the directions of the three spatial axes that are not limited to the positive and negative directions are defined as the X-axis direction, the Y-axis direction, and the Z-axis direction.

[0010] (Embodiment 1) FIG. 1 is a diagram showing a schematic configuration of a liquid ejecting apparatus 1 according to a first embodiment of the present invention.

[0011] 1 is an inkjet printing device that ejects ink, a type of "liquid," as droplets onto a medium S. The liquid ejection device 1 is a so-called line-type printing device in which a plurality of nozzles N that eject ink are distributed across the Y-axis direction, which is the width direction of the medium S, and the medium S is transported in the X-axis direction while ejecting ink from the nozzles N to perform a printing operation. The medium S can be made of any material, such as recording paper, resin film, or cloth.

[0012] As shown in the figure, the liquid ejection device 1 is equipped with a main tank 5 that stores ink, which is a liquid. Examples of the main tank 5 include a cartridge that is detachable from the liquid ejection device 1, a bag-shaped ink pack formed of a flexible film, and an ink tank that can be refilled with ink. Note that the main tank 5 stores, for example, multiple types of ink with different colors, ingredients, etc. Also, while FIG. 1 illustrates one main tank 5, multiple main tanks 5 may be provided depending on the type of ink.

[0013] The liquid ejection device 1 includes a control unit 2, a transport mechanism 3, a liquid ejection module M, and a circulation mechanism 4.

[0014] The control unit 2 controls the operation of each element of the liquid ejection device 1. The control unit 2 includes, for example, a control device such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array), and a storage device such as a semiconductor memory. The control unit 2 also includes a power supply device that supplies power supplied from an external power source such as a commercial power source to each element of the liquid ejection device 1. The control unit 2 is electrically connected to the liquid ejection module M via external wiring (not shown). The control unit 2 comprehensively controls each element of the liquid ejection device 1 by the control device executing a program stored in the storage device.

[0015] The transport mechanism 3 transports the medium S in the X-axis direction under the control of the control unit 2. The transport mechanism 3 includes a transport roller 3a and a motor (not shown) that rotates the transport roller 3a, and transports the medium S in the X-axis direction as the transport roller 3a rotates. Note that the transport mechanism 3 that transports the medium S is not limited to one that includes the transport roller 3a, and may transport the medium S by, for example, a belt or a drum.

[0016] The liquid ejection module M includes a plurality of liquid ejection heads H and a support 6 that supports the plurality of liquid ejection heads H. The liquid ejection module M ejects ink supplied from a main tank 5 via a circulation mechanism 4 from each of a plurality of nozzles N in the +Z direction under the control of a control unit 2. The liquid ejection module M has a shape in which the Y-axis direction is the longitudinal direction and the X-axis direction is the transverse direction when viewed in the Z-axis direction, and is a line head having a plurality of liquid ejection heads H that are arranged such that the plurality of nozzles N are distributed over the entire range of the medium S in the Y-axis direction.

[0017] The main tank 5 is connected to the liquid ejection module M via a circulation mechanism 4. The circulation mechanism 4 is a mechanism that supplies ink to the liquid ejection module M and recovers ink discharged from the liquid ejection module M to be re-supplied to the liquid ejection module M. The circulation mechanism 4 includes a supply side sub-tank 500 that stores ink, a first circulation flow path 600 that supplies ink from the supply side sub-tank 500 to the liquid ejection module M, a second circulation flow path 601 that recovers ink from the liquid ejection module M to the recovery side sub-tank 501, a third circulation flow path 602 that connects the supply side sub-tank 500 and the recovery side sub-tank 501, and a pump for moving the ink. The circulation mechanism 4 also includes a waste liquid tank 503 that discards the liquid, in this embodiment, ink, when a cleaning operation is performed, which will be described in detail later. These are provided for each type of color. By circulating the ink between the supply side sub-tank 500 and the recovery side sub-tank 501 and the liquid ejection module M using the circulation mechanism 4, it is possible to suppress an increase in the viscosity of the ink and reduce the retention of air bubbles in the ink.

[0018] The liquid ejection device 1 may have a maintenance mechanism used for maintenance operations of the liquid ejection module M. The maintenance operations include, for example, a flushing operation and a nozzle cleaning operation. The flushing operation is an operation for forcibly ejecting ink that does not directly contribute to image formation from the multiple nozzles N. The nozzle cleaning operation is an operation for forcibly discharging ink inside the liquid ejection module M from the multiple nozzles N by pressurizing the ink in a flow path upstream of a pressure chamber 212 described later, or by sucking the ink in the nozzles N from the outside of the liquid ejection head H. The maintenance mechanism has, for example, a flushing box that receives ink ejected from each nozzle N by the flushing operation, and a cap that covers the multiple nozzles N when the nozzle cleaning operation is performed.

[0019] Fig. 2 is an exploded perspective view of the liquid jet head H. Fig. 3 is a plan view of the flow path member 11 as viewed in the +Z direction. Fig. 4 is a cross-sectional view taken along line AA' in Fig. 3. Note that each direction of the liquid jet head H will be described based on the directions when it is mounted on the liquid jet device 1, i.e., the X-axis direction, Y-axis direction, and Z-axis direction.

[0020] 2, the liquid jet head H has a flow path member 11, a wiring board 12, a holder 13, a plurality of head chips 14, and a fixed plate 15. These are arranged in the +Z direction in the following order: flow path member 11, wiring board 12, holder 13, a plurality of head chips 14, and fixed plate 15. Each part of the liquid jet head H will be described below in order.

[0021] 2 to 4, flow path member 11 is a structure in which a flow path is provided therein for causing ink to flow between circulation mechanism 4 and a plurality of head chips 14. Flow path member 11 includes a first member 111, a second member 112, and a third member 113, and first member 111, second member 112, and third member 113 are layered in this order in the +Z direction.

[0022] The surface of the first member 111 facing the -Z direction has a plurality of flow path connectors 11a to 11d, four in this embodiment, connected to the circulation mechanism 4. The flow path connectors 11a to 11d are tubular bodies protruding in the -Z direction and having flow paths provided therein. In this embodiment, the same ink is supplied to two head chips 14 located in the -X direction from the flow path connector 11a, and ink not ejected from these two head chips 14 is discharged from the flow path connector 11b to the outside of the liquid ejection head H. In addition, the same ink is supplied to two head chips 14 located in the +X direction from the flow path connector 11c, and ink not ejected from these two head chips 14 is discharged from the flow path connector 11d to the outside of the liquid ejection head H. That is, in this embodiment, the opening 111a in the -Z direction of the flow path connector 11a is an example of a "first opening", and the opening 111b in the -Z direction of the flow path connector 11b is an example of a "second opening".

[0023] The flow path member 11 is provided with a supply flow path 120 for supplying ink to the multiple head chips 14, and a discharge flow path 121 for discharging ink from the multiple head chips 14. The supply flow path 120 and the discharge flow path 121 are formed by providing grooves, holes, or the like in the first member 111, the second member 112, and the third member 113. In this embodiment, the flow path member 11 is provided with two supply flow paths 120 and two discharge flow paths 121. One end of each of the two supply flow paths 120 opens at an end in the -Z direction of either of the flow path connecting portions 11a, 11c and is connected to the circulation mechanism 4, and the other end is branched into two midway and connected to the two head chips 14. In this embodiment, one supply flow path 120 opening to the flow path connection portion 11a communicates with two head chips 14 located in the -X direction, and the other supply flow path 120 opening to the flow path connection portion 11c communicates with two head chips 14 located in the +X direction. In addition, a filter F that crosses the supply flow path 120 is provided at a portion before the branching of each supply flow path 120. The filter F is for capturing foreign matter such as air bubbles and dust contained in the ink flowing through the supply flow path 120, and for example, a sheet-like filter having multiple fine holes formed by finely weaving fibers such as metal or resin can be used. The filter F is disposed in a filter chamber CF that is a part of the supply flow path 120. The filter chamber CF is partitioned into a filter upstream chamber CF1 arranged upstream of the filter F and a filter downstream chamber CF2 arranged downstream of the filter F in the flow of ink during a printing operation. In addition, the filter F can be a plate-like member such as metal or resin with multiple fine through holes. Furthermore, the filter F may be made of nonwoven fabric or the like, and the material is not particularly limited. The filter F can be fixed to the flow path member 11 by, for example, adhesion with an adhesive, heat welding, or the like.

[0024] One end of each of the two discharge flow paths 121 opens to an end in the -Z direction of either of flow path connecting parts 11b or 11d and is connected to circulation mechanism 4, and the other end branches into two and is connected to two head chips 14. In this embodiment, one discharge flow path 121 opening to flow path connecting part 11b communicates with two head chips 14 located in the -X direction, and the other discharge flow path 121 opening to flow path connecting part 11d communicates with two head chips 14 located in the +X direction.

[0025] As shown in FIG. 2, the flow path member 11 is provided with a connector insertion hole 11e into which a connector 12c, which will be described later, is inserted.

[0026] The wiring board 12 is a relay board for electrically connecting the head chips 14 and external wiring for electrically connecting the control unit 2 and the liquid ejection head H. The wiring board 12 is, for example, a rigid board. The wiring board 12 is disposed between the flow path member 11 and the holder 13, and a connector 12c is provided on a surface of the wiring board 12 facing the flow path member 11. The connector 12c is a connection part that electrically connects the control unit 2 and the wiring board 12. In addition, the wiring board 12 is provided with a plurality of holes 12a and a plurality of openings 12b. Each hole 12a is a hole for allowing the connection between the flow path member 11 and the holder 13. A wiring member 14a that connects the head chip 14 and the wiring board 12 is inserted into each opening 12b. The wiring member 14a is connected to a surface of the wiring board 12 facing the -Z direction. The wiring member 14a is a member including wiring electrically connected to a piezoelectric actuator, which will be described later, and is, for example, an FPC (Flexible Printed Circuits) or a COF (Chip On Film).

[0027] The holder 13 is a structure that houses and supports a plurality of head chips 14. The holder 13 is provided with a plurality of ink holes 13a and a plurality of wiring holes 13b. Each ink hole 13a is an opening on the flow path member 11 side in a flow path that allows ink to flow between the head chip 14 and the flow path member 11. Each wiring hole 13b is a hole through which a wiring member 14a that connects the head chip 14 and the wiring board 12 is passed. Here, although not shown, the inside of the holder 13 has a supply communication path for feeding ink from the supply flow path 120 of the flow path member 11 to the head chip 14, and a discharge communication path for allowing ink to flow from the head chip 14 to the discharge flow path 121 of the flow path member 11. In addition, although not shown, a surface of the holder 13 facing the +Z direction is provided with a plurality of recesses that house a plurality of head chips 14. In addition, the flow path member 11 and the wiring board 12 are fixed to the holder 13 by screws or the like.

[0028] Each head chip 14, which will be described in detail later, is provided with a plurality of nozzles N that eject ink onto a surface facing the +Z direction.

[0029] Fixing plate 15 is a plate member for fixing multiple head chips 14 to holder 13. Fixing plate 15 is arranged with multiple head chips 14 sandwiched between holder 13 and fixing plate 15, and is fixed to holder 13 with an adhesive. Fixing plate 15 is made of, for example, a metal material. Fixing plate 15 is provided with multiple exposure openings 15a for exposing nozzles N of the multiple head chips 14. In the example shown in FIG. 2, multiple exposure openings 15a are provided individually for each head chip 14.

[0030] Fig. 5 is a plan view of head chip 14 of this embodiment as viewed in the -Z direction. Fig. 6 is a cross-sectional view of line BB' in Fig. 5. Each direction of head chip 14 will be described based on the direction when it is mounted on liquid jet head H, that is, the X-axis direction, the Y-axis direction, and the Z-axis direction. The direction in which multiple nozzles N are arranged side by side is defined as the Xa direction inclined with respect to the X-axis direction, and the direction perpendicular to both the Xa direction and the Z-axis direction is defined as the Ya direction.

[0031] As shown in the figure, the head chip 14 includes a plurality of members such as a flow path forming substrate 210 as a flow path substrate, a communication plate 215, a nozzle plate 220, a protective substrate 230, a case 240, and a compliance substrate 249.

[0032] The flow path forming substrate 210 is made of a silicon single crystal substrate, and on one surface thereof is formed a vibration plate 250. The vibration plate 250 is made of a single layer or a laminated layer selected from a silicon dioxide layer, a zirconium oxide layer, and the like.

[0033] The flow path forming substrate 210 is provided with a plurality of pressure chambers 212 that constitute individual flow paths 410, partitioned by a plurality of partition walls. The pressure chambers 212 are arranged in parallel at a predetermined pitch along the Xa axis direction in which a plurality of nozzles N that eject ink are arranged in parallel. In this embodiment, one row is provided in which the pressure chambers 212 are arranged in parallel in the Xa axis direction. The flow path forming substrate 210 is arranged such that the in-plane direction is a direction that includes the X axis direction and the Y axis direction.

[0034] In this embodiment, only the pressure chamber 212 is provided on the flow path forming substrate 210, but a flow path resistance imparting section having a narrower cross-sectional area across the flow path than the pressure chamber 212 may be provided so as to impart flow path resistance to the ink supplied to the pressure chamber 212.

[0035] A vibration plate 250 is formed on the surface of the flow channel forming substrate 210 facing the -Z direction, and a first electrode 260, a piezoelectric layer 270, and a second electrode 280 are laminated on the vibration plate 250 by film formation and lithography to form a piezoelectric actuator 300. In this embodiment, the piezoelectric actuator 300 is a driving element that generates a pressure change in the ink in the pressure chamber 212. Here, the piezoelectric actuator 300 is also called a piezoelectric element, and refers to a portion including the first electrode 260, the piezoelectric layer 270, and the second electrode 280. In general, one of the electrodes of the piezoelectric actuator 300 is a common electrode, and the other electrode and the piezoelectric layer 270 are patterned for each pressure chamber 212. In this embodiment, the first electrode 260 is a common electrode of the piezoelectric actuator 300, and the second electrode 280 is an individual electrode of the piezoelectric actuator 300, but there is no problem even if this is reversed due to convenience of the drive circuit and wiring. In the above example, the diaphragm 250 and the first electrode 260 act as a diaphragm, but of course the present invention is not limited to this, and for example, the diaphragm 250 may not be provided and only the first electrode 260 may act as a diaphragm. Also, the piezoelectric actuator 300 itself may essentially function as a diaphragm.

[0036] Further, a lead electrode 290 is connected to the second electrode 280 of each of the piezoelectric actuators 300 , and a voltage is selectively applied to each of the piezoelectric actuators 300 via the lead electrode 290 .

[0037] A protective substrate 230 is bonded to the surface of the flow path forming substrate 210 on the side of the piezoelectric actuator 300. A piezoelectric actuator holding portion 231 having a space that does not hinder the movement of the piezoelectric actuator 300 is provided in an area of ​​the protective substrate 230 facing the piezoelectric actuator 300. The piezoelectric actuator holding portion 231 only needs to have a space that does not hinder the movement of the piezoelectric actuator 300, and the space may be sealed or not sealed. In this embodiment, the piezoelectric actuator holding portion 231 is formed to a size that covers the row of the multiple piezoelectric actuators 300 arranged in parallel in the Xa axis direction as a whole. Of course, the piezoelectric actuator holding portion 231 is not particularly limited to this, and may cover the piezoelectric actuator 300 individually, or may cover each group consisting of two or more piezoelectric actuators 300 arranged in parallel in the Xa direction. As the protective substrate 230, it is preferable to use a material having a thermal expansion coefficient approximately the same as that of the flow path forming substrate 210, for example, a silicon single crystal substrate.

[0038] Further, the vicinity of the end of the lead electrode 290 drawn out from each piezoelectric actuator 300 is extended so as to be exposed inside a connection port 245 formed in the case 240, through which the wiring member 14a is inserted, and is electrically connected to the wiring member 14a inside the connection port 245. The wiring member 14a is a flexible wiring board, and in this embodiment, a driving circuit which is a semiconductor element is mounted thereon.

[0039] A case 240 is fixed to the surface of the protective substrate 230 facing the -Z direction. The case 240 is joined to the surface of the protective substrate 230 opposite to the flow passage forming substrate 210, and is also joined to a communication plate 215 described later. The case 240 is provided with a first liquid chamber portion 241 constituting a part of the first common liquid chamber 401 and a second liquid chamber portion 242 constituting a part of the second common liquid chamber 402. The first liquid chamber portion 241 and the second liquid chamber portion 242 are provided on both sides of a row of pressure chambers 212 in the Ya axis direction. Each of the first liquid chamber portion 241 and the second liquid chamber portion 242 has a concave shape that opens to a surface of the case 240 facing the +Z direction, and is provided continuously across the multiple pressure chambers 212 arranged side by side in the Ya axis direction. The case 240 is also provided with an inlet 243 that communicates with the first liquid chamber 241 to introduce ink into the first liquid chamber 241, and an outlet 244 that communicates with the second liquid chamber 242 to discharge ink from the second liquid chamber 242.

[0040] On the other hand, on the surface of the flow path forming substrate 210 facing the +Z direction, a communication plate 215, a nozzle plate 220, and a compliance substrate 249 are provided.

[0041] A plurality of nozzles N are formed in the nozzle plate 220, which communicate with the outside and with the pressure chambers 212. As shown in Fig. 5, the plurality of nozzles N are arranged along the Xa direction inclined with respect to both the X-axis direction and the Y-axis direction to form a nozzle row. In this embodiment, one nozzle row is provided for one head chip 14.

[0042] Such a nozzle plate 220 can be formed, for example, from a metal such as stainless steel (SUS), an organic material such as polyimide resin, or a flat plate material such as silicon.

[0043] In this embodiment, the communication plate 215 includes a first communication plate 215a and a second communication plate 215b. The first communication plate 215a and the second communication plate 215b are stacked in this order in the +Z direction.

[0044] The first communication plate 215a and the second communication plate 215b constituting the communication plate 215 can be manufactured from a silicon single crystal substrate, a metal such as stainless steel, glass, a ceramic material, etc. It is preferable that the communication plate 215 is made of a material having approximately the same thermal expansion coefficient as the flow path forming substrate 210.

[0045] The communicating plate 215 is provided with a first communicating portion 216 that communicates with the first liquid chamber portion 241 of the case 240 and constitutes part of the first common liquid chamber 401, and a second communicating portion 217 and a third communicating portion 218 that communicate with the second liquid chamber portion 242 of the case 240 and constitute part of the second common liquid chamber 402.

[0046] The first communication part 216 is provided at a position overlapping the first liquid chamber part 241 of the case 240 in the Z-axis direction, and is provided penetrating the communication plate 215 in the Z-axis direction. The first communication part 216 defines a first common liquid chamber 401 by communicating an end part in the -Z direction with the first liquid chamber part 241. That is, the first common liquid chamber 401 is defined by the first liquid chamber part 241 of the case 240 and the first communication part 216 of the communication plate 215. The first communication part 216 extends in the +Ya direction to a position where an end part in the +Z direction overlaps with the pressure chamber 212 in the Z-axis direction. The first common liquid chamber 401 may be defined by the first liquid chamber part 241 of the case 240 without providing the first communication part 216 in the communication plate 215.

[0047] The second communication portion 217 is provided at a position overlapping with the second liquid chamber portion 242 of the case 240 in the Z-axis direction, and opens on a surface of the first communication plate 215a facing the -Z direction. In addition, the second communication portion 217 is provided such that an end portion in the +Z direction is widened toward the nozzle N in the -Ya direction.

[0048] The third communication portion 218 is provided to penetrate the second communication plate 215b in the Z-axis direction. The opening of the third communication portion 218 on the +Z direction side is covered by the nozzle plate 220.

[0049] A second common liquid chamber 402 is formed by the second communicating portion 217 and the third communicating portion 218 provided in the communicating plate 215 and the second liquid chamber portion 242 provided in the case 240. The second common liquid chamber 402 may be formed by the second liquid chamber portion 242 of the case 240 without providing the second communicating portion 217 and the third communicating portion 218 in the communicating plate 215.

[0050] A compliance substrate 249 having a compliance portion 249a is provided on the surface of the communication plate 215 facing the +Z direction where the first communication portion 216 opens. This compliance substrate 249 seals the opening of the first common liquid chamber 401 on the nozzle surface 220a side.

[0051] In this embodiment, the compliance substrate 249 includes a sealing film 249b made of a flexible thin film, and a fixed substrate 249c made of a hard material such as metal and fixed to the surface of the fixed plate 15 facing the -Z direction. The region of the fixed substrate 249c facing the first common liquid chamber 401 is an opening that is completely removed in the thickness direction, and therefore a part of the wall surface of the first common liquid chamber 401 is a compliance portion 249a that is a flexible portion sealed only by the sealing film 249b having flexibility. By providing the compliance portion 249a on a part of the wall surface of the first common liquid chamber 401 in this manner, the pressure fluctuation of the ink in the first common liquid chamber 401 can be absorbed by the deformation of the compliance portion 249a.

[0052] Further, the flow path forming substrate 210, the communication plate 215, the nozzle plate 220, the compliance substrate 249, etc., which constitute the flow path substrate, are provided with a plurality of individual flow paths 410 which communicate with the first common liquid chamber 401 and the second common liquid chamber 402 and send ink from the first common liquid chamber 401 to the second common liquid chamber 402. Here, the individual flow paths 410 in this embodiment communicate with the first common liquid chamber 401 and the second common liquid chamber 402 and are provided for each nozzle N, and include the nozzle N. The plurality of individual flow paths 410 provided for each nozzle N are provided so as to communicate only with the first common liquid chamber 401 and the second common liquid chamber 402, respectively, and the plurality of individual flow paths 410 do not communicate with each other except with the first common liquid chamber 401 and the second common liquid chamber 402. That is, in this embodiment, a flow path in which one nozzle N and one pressure chamber 212 are provided is referred to as an individual flow path 410, and the individual flow paths 410 communicate with each other only via the first common liquid chamber 401 and the second common liquid chamber 402.

[0053] In this embodiment, the first common liquid chamber 401 and the second common liquid chamber 402 correspond to a "common liquid chamber portion." The inlet 243 and the supply flow path 120, which connect the first common liquid chamber 401 to the opening 111a of the flow path connection portion 11a with the outside, are an example of a "first flow path." The outlet 244 and the discharge flow path 121, which connect the second common liquid chamber 402 to the opening 111b of the flow path connection portion 11b with the outside, are an example of a "second flow path." As described above, a filter F is provided midway along the supply flow path 120.

[0054] As shown in FIG. 6, the individual flow path 410 includes a nozzle N, a pressure chamber 212, an individual recovery flow path 411, a nozzle communication path 412, and an individual supply flow path 413.

[0055] As described above, the pressure chamber 212 is provided in the flow path forming substrate 210, and extends along the Ya axis direction. That is, the pressure chamber 212 has an end in the -Ya direction connected to the individual supply flow path 413, and an end in the +Ya direction connected to the nozzle communication path 412.

[0056] The individual supply flow paths 413 connect the pressure chambers 212 and the first common liquid chamber 401, and are provided penetrating the first communication plate 215a in the Z-axis direction. That is, the individual supply flow paths 413 extend along the Z-axis direction, with one end in the +Z direction connected to the first common liquid chamber 401 and the other end in the -Z direction connected to the pressure chambers 212.

[0057] The individual recovery flow passages 411 extend in an in-plane direction of the nozzle plate 220, i.e., in an in-plane direction of the nozzle face 220a. In this embodiment, the individual recovery flow passages 411 extend in the Ya-axis direction among directions including the X-axis direction and the Y-axis direction which are in-plane directions of the nozzle face 220a. The individual recovery flow passages 411 are provided between the second communication plate 215b and the nozzle plate 220 along the Ya-axis direction. Specifically, the individual recovery flow passages 411 are formed by providing a recess in the second communication plate 215b and covering the opening of this recess with the nozzle plate 220.

[0058] The nozzle communication passages 412 are connected to the individual recovery passages 411 and extend in the Z axis direction. In this embodiment, the nozzle communication passages 412 are provided penetrating the communication plate 215 in the Z axis direction, and have one end in the -Z direction connected to the pressure chambers 212 and the other end in the +Z direction connected to the individual recovery passages 411, thereby communicating between the pressure chambers 212 and the individual recovery passages 411.

[0059] The nozzle N is disposed at a position overlapping the nozzle communication passage 412 when viewed in a plan view in the Z axis direction. Of course, the position of the nozzle N is not particularly limited to this, and the nozzle N may be disposed at a position not overlapping the nozzle communication passage 412 when viewed in a plan view in the Z axis direction, that is, so as to be in communication with the middle of the individual recovery passage 411.

[0060] In such an individual flow path 410, ink flows from the first common liquid chamber 401 through the individual flow path 410 to the second common liquid chamber 402 by a circulation operation, which will be described later, performed during a printing operation or normal cleaning. This makes it possible to suppress the sedimentation of the components contained in the ink, and also makes it possible to remove air bubbles contained in the ink to the outside of the liquid ejection head H. In addition, by driving the piezoelectric actuator 300, a pressure change is caused in the ink in the pressure chamber 212, and the pressure of the ink in the nozzle N is increased, so that the ink is ejected as droplets from the nozzle N to the outside. When a printing operation is performed during the circulation operation, the piezoelectric actuator 300 is driven when the ink flows from the first common liquid chamber 401 through the individual flow path 410 to the second common liquid chamber 402. Note that a flow of ink from the second common liquid chamber 402 to the first common liquid chamber 401 may temporarily occur due to a pressure change caused by driving the piezoelectric actuator 300.

[0061] 7 is a block diagram showing the liquid circulation system of the liquid ejection device 1 of this embodiment. The circulation flow paths communicating with the flow path connectors 11a and 11b and the circulation flow paths communicating with the flow path connectors 11c and 11d are separate flow paths independent of each other, but have almost the same functions and configurations. Therefore, to simplify the explanation, only the flow paths corresponding to the flow path connectors 11a and 11b will be illustrated and explained below.

[0062] As shown in the figure, the liquid circulation system includes a main tank 5, a liquid ejection head H, and a circulation mechanism 4. The liquid circulation system executes operations related to the flow of ink, such as a cleaning operation, a normal cleaning operation, and a circulation operation during a printing operation, based on the control of a control unit 2. The circulation mechanism 4 circulates ink within a circulation flow path that includes a first common liquid chamber 401, a second common liquid chamber 402, a supply flow path 120 and an opening 111a, and a discharge flow path 121 and an opening 111b. Specifically, the circulation flow path includes a supply side sub-tank 500, a first circulation flow path 600, an opening 111a, a supply flow path 120, an inlet 243, a first common liquid chamber 401, an individual flow path 410, a second common liquid chamber 402, an outlet 244, a discharge flow path 121, an opening 111b, a second circulation flow path 601, a recovery side sub-tank 501, and a third circulation flow path 602, and the ink circulates within the circulation flow path in this order by the circulation operation performed during printing operations and normal cleaning.

[0063] The circulation mechanism 4 includes a supply side sub-tank 500, a recovery side sub-tank 501, a waste liquid tank 503, a compressor 504, a first vacuum pump 505, a second vacuum pump 506, a first liquid supply pump 507, a second liquid supply pump 508, a first pressure sensor 509, a second pressure sensor 510, a first regulator 511, a second regulator 512, a third regulator 513, a first flow path switching unit 520, a second flow path switching unit 530, and the like.

[0064] The supply side sub-tank 500 is connected to an opening 111a of a flow path connection portion 11a of the liquid jet head H via a first circulation flow path 600. A first pressure sensor 509 is connected to the first circulation flow path 600 at a position between the liquid jet head H and the supply side sub-tank 500 close to the liquid jet head H. A compressor 504 is connected to the supply side sub-tank 500 via a first regulator 511, and the pressure of the supply side sub-tank 500 is controlled by the first regulator 511 so that a predetermined pressure is detected by the first pressure sensor 509.

[0065] The recovery side sub-tank 501 is connected to the opening 111b of the flow path connection portion 11b of the liquid jet head H via a second circulation flow path 601. The second pressure sensor 510 is connected to a position of the second circulation flow path 601 between the liquid jet head H and the recovery side sub-tank 501 close to the liquid jet head H. A first vacuum pump 505 is connected to the recovery side sub-tank 501 via a second regulator 512, and the pressure of the recovery side sub-tank 501 is controlled by the second regulator 512 so that a predetermined pressure is detected by the second pressure sensor 510.

[0066] By controlling the first regulator 511 and the second regulator 512 so that the first pressure sensor 509 detects a predetermined positive pressure and the second pressure sensor 510 detects a predetermined negative pressure, ink flows from the supply side subtank 500 through the first circulation flow path 600 into the liquid jet head H, and the ink that has flowed into the liquid jet head H is collected in the recovery side subtank 501 through the second circulation flow path 601. In addition, the recovery side subtank 501 is connected to the supply side subtank 500 through a third circulation flow path 602. A first liquid feed pump 507 is connected in the middle of the third circulation flow path 602, and the ink in the recovery side subtank 501 flows into the supply side subtank 500 through the third circulation flow path 602. As a result, ink flows from the supply side sub-tank 500 into the liquid ejection head H, the ink that flows into the liquid ejection head H is collected in the recovery side sub-tank 501, and the ink collected in the recovery side sub-tank 501 is sent to the supply side sub-tank 500, thereby circulating the ink.

[0067] The recovery side sub-tank 501 is connected to the main tank 5 via a refill passage 603. A second liquid feed pump 508 is provided in the middle of the refill passage 603, and ink consumed by ejecting ink from the liquid ejection head H is replenished from the main tank 5 via the refill passage 603 to the recovery side sub-tank 501.

[0068] In addition, the circulation mechanism 4 is capable of performing a cleaning operation to cause liquid ink to flow in the following order: the discharge flow path 121 and the discharge port 244, the first common liquid chamber 401 and the second common liquid chamber 402, and the supply flow path 120 and the inlet port 243.

[0069] Specifically, a first flow path switching unit 520 is provided between the first circulation flow path 600 and the second circulation flow path 601. Here, the supply side sub-tank 500 side of the first circulation flow path 600 from the first flow path switching unit 520 is referred to as a first portion 600a, and the liquid jet head H side is referred to as a second portion 600b. In addition, the recovery side sub-tank 501 side of the second circulation flow path 601 from the first flow path switching unit 520 is referred to as a third portion 601a, and the liquid jet head H side is referred to as a fourth portion 601b. The first flow path switching unit 520 connects the first portion 600a and the second portion 600b, and also connects the third portion 601a and the fourth portion 601b. This is referred to as a normal connection state. In the normal connection state, as shown by the solid line in FIG. 7, the ink supplied from the supply side sub-tank 500 is supplied to the liquid jet head H from the opening 111a of the flow path connection part 11a, and the ink is discharged to the outside of the liquid jet head H from the opening 111b of the flow path connection part 11b. In addition, the first flow path switching part 520 connects the first part 600a and the fourth part 601b, and also connects the third part 601a and the second part 600b. This is called a reverse connection state. In the reverse connection state, as shown by the dotted line in FIG. 7, the ink supplied from the supply side sub-tank 500 is supplied to the liquid jet head H from the opening 111b of the flow path connection part 11b, and the ink is discharged to the outside of the liquid jet head H from the opening 111a of the flow path connection part 11a.

[0070] That is, the first flow path switching unit 520 switches between a normal connection state and a reverse connection state. When the first flow path switching unit 520 is in the normal connection state, the above-mentioned circulation operation is performed during a printing operation or a normal cleaning operation. When the first flow path switching unit 520 is in the reverse connection state, the cleaning operation of this embodiment is performed.

[0071] Specifically, the first flow path switching unit 520 includes a first connection flow path 521 having one end connected to the first portion 600a, a first switching unit 522 having the other end connected to the first connection flow path 521, a second connection flow path 523 having one end connected to the first switching unit 522 and the other end connected to the second portion 600b, and a third connection flow path 524 having one end connected to the first switching unit 522 and the other end connected to the fourth portion 601b. The first switching unit 522 is configured as a three-way valve (also referred to as a three-way valve) and switches the connection between the first connection flow path 521 and the second connection flow path 523 and the connection between the first connection flow path 521 and the third connection flow path 524. That is, the first switching unit 522 switches the connection between the first portion 600a and the second portion 600b and the connection between the first portion 600a and the fourth portion 601b.

[0072] Similarly, the first flow path switching unit 520 includes a fourth connection flow path 525 having one end connected to the third portion 601a, a second switching unit 526 having the other end connected to the fourth connection flow path 525, a fifth connection flow path 527 having one end connected to the second switching unit 526 and the other end connected to the fourth portion 601b, and a sixth connection flow path 528 having one end connected to the second switching unit 526 and the other end connected to the second portion 600b. The second switching unit 526 is configured as a three-way valve (also referred to as a three-way valve) and switches the connection between the fourth connection flow path 525 and the fifth connection flow path 527 and the connection between the fourth connection flow path 525 and the sixth connection flow path 528. That is, the second switching unit 526 switches the connection between the third portion 601a and the fourth portion 601b and the connection between the third portion 601a and the second portion 600b.

[0073] As described above, the normal connection state and the reverse connection state can be switched by the first switching unit 522 and the second switching unit 526 of the first flow path switching unit 520. Note that the first switching unit 522 and the second switching unit 526 may be, for example, solenoid valves operated by electromagnets, and are controlled by the control unit 2 that controls the entire liquid ejection device 1.

[0074] In addition, the waste liquid tank 503 is connected to the middle of the third portion 601a of the second circulation flow path 601 between the first flow path switching unit 520 and the recovery side sub-tank 501 via the second flow path switching unit 530 and the waste liquid flow path 604. The second flow path switching unit 530 is configured with a three-way valve (also referred to as a three-way valve). The second flow path switching unit 530 switches so that the first flow path switching unit 520 connects the flow path connection unit 11b of the liquid jet head H to the recovery side sub-tank 501 when the first flow path switching unit 520 is in a normal connection state, and connects the flow path connection unit 11b of the liquid jet head H to the waste liquid tank 503 when the first flow path switching unit 520 is in a reverse connection state. In addition, the second vacuum pump 506 is connected to the waste liquid tank 503 via a third regulator 513, and the pressure of the waste liquid tank 503 is controlled by the third regulator 513 so that a predetermined negative pressure is detected by the second pressure sensor 510 when the reverse connection state is reached. A single vacuum pump may be used as both the first vacuum pump 505 and the second vacuum pump 506. This reduces the number of parts and the cost.

[0075] Here, the normal connection state by the first flow path switching unit 520 is established in a circulation operation that is performed during a printing operation or a normal cleaning operation.

[0076] Furthermore, if foreign matter adheres to the filter F of the liquid jet head H, a cleaning operation (also called a cleaning step) is performed in which the liquid, in this embodiment, the ink, flows backward in a reverse connection state by the first flow path switching unit 520. The cleaning operation may be performed periodically at regular intervals, or may be performed when foreign matter such as dust or air bubbles adheres to the filter F, causing a drop in the ink supply pressure and resulting in poor jetting of droplets from the nozzles N.

[0077] The cleaning operation of the liquid jet head H causes liquid, ink in this embodiment, to flow from the discharge flow path 121 and the discharge port 244 toward the supply flow path 120 and the inlet port 243. In this embodiment, the first flow path switching unit 520 is in a reverse connection state, so that ink is supplied from the supply side sub-tank 500 into the liquid jet head H through the opening 111b of the flow path connection unit 11b, and the ink in the liquid jet head H is discharged to the outside from the opening 111a of the flow path connection unit 11a. At this time, as described above, the ink discharged to the outside from the opening 111a of the flow path connection unit 11a is collected in the waste liquid tank 503 by the second flow path switching unit 530 together with the foreign matter removed by the filter F.

[0078] In such a cleaning process, air is not drawn from the nozzle N during a first period after the start of the cleaning process. Here, "not drawing air from the nozzle N" means that the pressure of the ink in the nozzle N is adjusted so as not to be smaller than the meniscus withstand pressure against the pressure from the atmosphere side to the ink side across the ink liquid surface formed in the nozzle N, that is, the meniscus. For example, when the meniscus withstand pressure (gauge pressure) is 0 kPa or less and -5 kPa or more, air is drawn from the nozzle N when the ink pressure in the nozzle N becomes smaller than -5 kPa. For this reason, during the first period, the pressure value acting on the nozzle N is controlled by controlling the circulation mechanism 4 so that the ink pressure in the nozzle N does not become smaller than -5 kPa, which is the minimum value of the meniscus withstand pressure. Note that when the ink pressure in the nozzle N is greater than 0 kPa, which is the maximum value of the meniscus withstand pressure, ink is discharged from the nozzle N to the outside, but air is not drawn from the nozzle N. In other words, "not drawing air from the nozzle N" also includes discharging liquid from the nozzle N to the outside.

[0079] Here, in the circulation operation during the printing operation, the circulation operation during the normal cleaning operation, and the cleaning operation for washing the filter F when the meniscus pressure resistance is 0 kPa or less and -5 kPa or more, examples of settings of the first pressure at the opening 111a, the second pressure which is the pressure of the liquid at the opening 111b, the differential pressure between the first pressure and the second pressure, the flow rate of the ink flowing into the liquid ejection head H through the opening 111a, and the pressure of the liquid in the nozzle N (also called the nozzle pressure) are shown in Table Ta1 of FIG. 8. The first pressure, the second pressure, and the nozzle pressure shown in Table Ta1 are gauge pressures obtained by subtracting the atmospheric pressure from the absolute pressure. In addition, since the opening 111a is disposed near the first pressure sensor 509, the first pressure is approximately equal to the pressure detected by the first pressure sensor 509. Similarly, since the opening 111b is disposed near the second pressure sensor 510, the second pressure is approximately equal to the pressure detected by the second pressure sensor 510.

[0080] 8, in the circulation operation during the printing operation, the first pressure for supplying ink to the opening 111a of the flow path connection portion 11a, i.e., the pressure detected by the first pressure sensor 509, is set to 10 kPa, and the second pressure for recovering ink from the opening 111b of the flow path connection portion 11b, i.e., the pressure detected by the second pressure sensor 510, is set to -5 kPa. As a result, the differential pressure between the openings 111a and 111b in the liquid ejection head H is set to 15 kPa, and the nozzle pressure is set to a negative pressure of -1 kPa. By setting in this manner, the nozzle pressure falls within the meniscus withstand pressure range of the nozzle N, so that air is not drawn from the nozzle N into the individual flow path 410, and ink is not discharged from the nozzle N.

[0081] In addition, in the normal cleaning operation, the differential pressure between the first pressure and the second pressure is made larger than in the circulation operation during the printing operation, thereby increasing the circulation flow rate of the ink circulating in the circulation flow path, which corresponds to the flow rate of the ink flowing into the liquid jet head H through the opening 111a. This allows air bubbles that have entered and remained in the filter upstream chamber CF1 to pass through the filter F, and the air bubbles can be discharged to the outside of the liquid jet head H. In this normal cleaning operation, the first pressure, i.e., the pressure detected by the first pressure sensor 509, is set to 30 kPa, and the second pressure, i.e., the pressure detected by the second pressure sensor 510, is set to -15 kPa, so that the differential pressure between the two is set to 45 kPa, and the nozzle pressure is set to a negative pressure of -1 kPa. This prevents air from being drawn into the nozzle N even in the normal cleaning operation.

[0082] In addition, in the first period of the cleaning operation of this embodiment, in the reverse connection state, the first pressure, i.e., the pressure detected by the first pressure sensor 509, is set to -30 kPa, and the second pressure, i.e., the pressure detected by the second pressure sensor 510, is set to 15 kPa. As a result, the differential pressure between the two is set to 45 kPa, and the nozzle pressure is set to -1 kPa. By performing the cleaning operation with such pressure settings, the ink passes through the filter F in a flow opposite to the above-mentioned circulation operation without drawing in air bubbles from the nozzle N, and the foreign matter captured in the mesh of the filter F can be discharged to the outside of the liquid ejection head H through the opening 111a, that is, the filter F can be cleaned. Therefore, by not drawing in air bubbles from the nozzle N when cleaning the filter F, it is possible to suppress poor cleaning of the filter F caused by air bubbles drawn in from the nozzle N entering the filter downstream chamber CF2 and blocking the mesh of the filter F. Furthermore, the cleaning operation can remove foreign matter adhering to the filter F and eliminate clogging of the filter F, thereby suppressing poor droplet ejection caused by clogging of the filter F and also suppressing the need to replace the liquid ejection head H caused by clogging of the filter F, thereby extending the life of the liquid ejection head H. Furthermore, since air bubbles are not retracted from the nozzles N during the first period when the filter F is cleaned, there is no need to eject ink together with the air bubbles from the nozzles N to form a meniscus in the nozzles N, and thus unnecessary consumption of ink can be suppressed.

[0083] In addition, when the ink in the liquid ejection head H is caused to flow in the opposite direction to that during the circulating operation during the cleaning operation, it is preferable that the pressure of the ink in the nozzle N is as close as possible to the maximum value of the meniscus withstand pressure, that is, a value close to 0 kPa. Here, the side close to the maximum value of the meniscus withstand pressure means that it is closer to the maximum value side than the intermediate value of the range of the meniscus withstand pressure. In other words, as described above, when the meniscus withstand pressure is 0 kPa or less and -5 kPa or more, it is preferable that the value is greater than -2.5 kPa. Of course, it is more preferable that the nozzle pressure is as close as possible to a value within the range of the meniscus withstand pressure. This makes it difficult for the pressure of the ink in the nozzle N to become smaller than the meniscus withstand pressure, and makes it difficult for air to be drawn in from the nozzle N, even when an unexpected fluctuation occurs in the pressure of the ink in the nozzle N. The pressure of the ink in the nozzle N is the same in each circulating operation of the printing operation and the normal cleaning operation.

[0084] Also, as shown in Table Ta1, the flow rate of ink flowing into the liquid jet head H during the normal cleaning operation is greater than the flow rate of ink flowing into the liquid jet head H. In other words, the circulation flow rate, which is the flow rate of ink flowing through the liquid jet head H during the printing operation, is 100 ml / min, whereas the circulation flow rate, which is the flow rate of ink flowing through the liquid jet head H during the normal cleaning operation, is 250 ml / min, which is greater than the circulation flow during the printing operation. That is, in this embodiment, the circulation operation during the printing operation corresponds to the "first circulation operation," and the normal cleaning operation corresponds to the "second circulation operation." Furthermore, while the absolute value of the negative pressure applied to the opening 111b during the normal cleaning operation is 15 kPa, the absolute value of the negative pressure applied to the opening 111a during the cleaning operation is 30 kPa, which is greater than that during the normal cleaning operation.

[0085] In this way, by making the absolute value of the negative pressure applied to the opening 111a in which the filter F is placed during the cleaning operation greater than the absolute value of the negative pressure applied to the opening 111b during the normal cleaning operation, it is possible to reliably apply negative pressure to the filter F, and to effectively remove foreign matter adhering to the filter F.

[0086] Also, as shown in table Ta1, the positive pressure applied to opening 111b during the cleaning operation is 15 kPa, while the positive pressure applied to opening 111a during the normal cleaning operation is 30 kPa, which is smaller during the cleaning operation than during the normal cleaning operation. In this way, by reducing the positive pressure applied to opening 111b, which does not have filter F that acts as a flow path resistance, during the cleaning operation, it is possible to suppress the discharge of ink from nozzle N and suppress unnecessary consumption of ink.

[0087] The first period of the cleaning process may include a second period in which liquid ink is discharged from the nozzle N. That is, in the second period, the first pressure and the second pressure are controlled so that the nozzle pressure is equal to or higher than the meniscus withstand pressure of the nozzle N, thereby discharging ink from the nozzle N. In this way, in the second period, ink is discharged from the nozzle N, and thus, in the early stage of the cleaning process, air is prevented from being drawn in from the nozzle N, and foreign matter can be reliably removed. The first period may include a third period after the second period in which ink is not discharged from the nozzle N. That is, in the second period, the pressure in the nozzle N becomes higher than the meniscus withstand pressure due to clogging of the filter F, and ink is discharged from the nozzle N to the outside. Thereafter, the filter F begins to be cleared by the backflow, and the negative pressure acting on the opening 111a becomes easily transmitted to the ink in the nozzle N, and a meniscus is formed in the nozzle N in the third period. That is, when the second period ends and the third period begins, it can be known that the clogging of the filter F has been cleared by the cleaning process. Furthermore, by providing the third period, a meniscus can be formed in the nozzle N, and therefore there is no need to subsequently form a meniscus by discharging ink from the nozzle N. Incidentally, if the third period is too long, the amount of ink wasted increases, and if it is too short, a meniscus cannot be formed, so for example, about 2 to 4 seconds is preferable.

[0088] The first period may be composed of only the second period. In other words, the pressure may be set so that ink is discharged from the nozzles N when the filter F is not clogged. By configuring the first period to consist of only the second period in this way, the amount of ink consumed increases relatively, but it is possible to reliably suppress the intake of air bubbles from the nozzles N.

[0089] Incidentally, the first period may also be composed of only the third period. For example, if no foreign matter is attached to the filter F when a periodic cleaning operation is performed, the second period in which ink is discharged from the nozzles N will not occur even if the cleaning operation is performed at the set pressure in Table Ta1.

[0090] (Embodiment 2) 9 is a block diagram showing a liquid circulation system of a liquid ejecting device 1 according to a second embodiment of the present invention. Note that the same members as those in the above-mentioned embodiment are given the same reference numerals and overlapping descriptions will be omitted.

[0091] As shown in FIG. 9, the liquid circulation system includes a main tank 5, a liquid ejecting head H, and a circulation mechanism 4.

[0092] The circulation mechanism 4 has a supply side sub-tank 500, a recovery side sub-tank 501, a compressor 504, a first vacuum pump 505, a first liquid delivery pump 507, a first pressure sensor 509, a second pressure sensor 510, a first regulator 511, a second regulator 512, a flow path switching unit 540, a first check valve 550, a second check valve 551, and a foreign matter capture filter 552.

[0093] The supply side sub-tank 500, the recovery side sub-tank 501, the compressor 504, the first vacuum pump 505, the first liquid supply pump 507, the first pressure sensor 509, the second pressure sensor 510, the first regulator 511, and the second regulator 512 are the same as those in the above-mentioned embodiment 1, so duplicated explanations will be omitted.

[0094] The flow path switching unit 540 is provided midway through the first circulation flow path 600 and the second circulation flow path 601. As in the above-described first embodiment, the first circulation flow path 600 has a first portion 600a and a second portion 600b with the flow path switching unit 540 in between, and the second circulation flow path 601 has a third portion 601a and a fourth portion 601b with the flow path switching unit 540 in between.

[0095] The flow path switching unit 540 of this embodiment is capable of switching between a normal connection state and a reverse connection state, similar to the first flow path switching unit 520 described above.

[0096] Specifically, the flow path switching unit 540 includes a tenth connection flow path 541 that communicates the first portion 600a and the second portion 600b, an eleventh connection flow path 542 that communicates the first portion 600a and the fourth portion 601b, a twelfth connection flow path 543 that communicates the third portion 601a and the fourth portion 601b, and a thirteenth connection flow path 544 that communicates the third portion 601a and the second portion 600b. In addition, a first valve 545, a second valve 546, a third valve 547, and a fourth valve 548 are provided in the middle of the tenth connection flow path 541, the eleventh connection flow path 542, the twelfth connection flow path 543, and the thirteenth connection flow path 544, respectively. The first valve 545 to the fourth valve 548 open and close the tenth connection flow path 541 to the thirteenth connection flow path 544, respectively.

[0097] The flow path switching unit 540 configured as above opens the tenth connection flow path 541 with the first valve 545, and closes the eleventh connection flow path 542 with the second valve 546. At the same time, the twelfth connection flow path 543 is opened with the third valve 547, and the thirteenth connection flow path 544 is closed with the fourth valve 548. This allows the first portion 600a and the second portion 600b to communicate with each other, and the third portion 601a and the fourth portion 601b to communicate with each other, thereby achieving a normal connection state.

[0098] Furthermore, the flow path switching unit 540 closes the tenth connection flow path 541 with the first valve 545, and opens the eleventh connection flow path 542 with the second valve 546. At the same time, the twelfth connection flow path 543 is closed with the third valve 547, and opens the thirteenth connection flow path 544 with the fourth valve 548. This allows the first portion 600a and the fourth portion 601b to communicate with each other, and also the third portion 601a and the second portion 600b to communicate with each other, creating a reverse connection state.

[0099] Further, a first check valve 550 is provided in the second portion 600b of the first circulation flow path 600. The first check valve 550 is a so-called check valve, and allows the ink to flow from the flow path switching unit 540 of the second portion 600b toward the liquid ejecting head H and prevents a backflow.

[0100] In second portion 600b, a communication passage 553 is provided that communicates with both sides of first check valve 550. In communication passage 553, a second check valve 551 and a foreign matter trapping filter 552 located closer to flow path switching unit 540 than second check valve 551 are provided.

[0101] The second check valve 551 is a so-called check valve, which allows the flow of ink from the liquid ejecting head H through the communication passage 553 toward the flow path switching unit 540 and prevents a backflow.

[0102] The foreign matter trapping filter 552 traps foreign matter such as dust and air bubbles flowing through the communication passage 553, and may be the same as the filter F provided in the liquid ejecting head H, for example.

[0103] 9, the first check valve 550 causes ink to flow through the second portion 600b from the flow path switching unit 540 toward the liquid ejection head H. At this time, the second check valve 551 prevents ink from flowing through the communication passage 553 from the flow path switching unit 540 toward the liquid ejection head H.

[0104] 9, the second check valve 551 causes ink to flow through the communication passage 553 from the liquid jet head H toward the flow passage switching unit 540. At this time, foreign matter captured in the filter F flows through the communication passage 553 and is captured by the foreign matter capture filter 552. Therefore, foreign matter generated by cleaning the filter F does not move to the supply side subtank 500, and when the printing operation is resumed in the normal connection state, clogging of the filter F due to foreign matter being resupplied to the liquid jet head H can be suppressed. Furthermore, in the reverse connection state, the first check valve 550 can suppress ink from returning to the supply side subtank 500 without passing through the foreign matter capture filter 552.

[0105] By performing the cleaning operation using such a liquid circulation system, the same effects as those of the first embodiment described above can be achieved.

[0106] (Embodiment 3) 10 is a block diagram showing a liquid circulation system according to a third embodiment of the present invention, in which the same members as those in the above-mentioned embodiments are given the same reference numerals and overlapping descriptions will be omitted.

[0107] As shown in FIG. 11, the liquid circulation system includes a liquid jet head H and a circulation mechanism 4.

[0108] The circulation mechanism 4 includes a main tank 5, a first circulation flow path 600, a second circulation flow path 601, a third liquid feed pump 560, a fourth liquid feed pump 561, a first pressure sensor 509, a second pressure sensor 510, a first check valve 550, a second check valve 551, a foreign matter capture filter 552, and a communicating passage 553.

[0109] The first circulation flow path 600 connects the main tank 5 and the flow path connection portion 11a of the liquid jet head H. A third liquid feed pump 560 and a first pressure sensor 509 are provided in the first circulation flow path 600. The first pressure sensor 509 is disposed on the liquid jet head H side with respect to the third liquid feed pump 560.

[0110] A first check valve 550 is provided between the third liquid feed pump 560 and the first pressure sensor 509 of the first circulation flow path 600. The first check valve 550 is a so-called check valve, and allows the flow of ink through the first circulation flow path 600 from the main tank 5 toward the liquid ejection head H and prevents backflow.

[0111] Further, the first circulation flow path 600 is provided with a communication passage 553 that communicates with both sides of the first check valve 550. The communication passage 553 is provided with a second check valve 551 and a foreign matter capture filter 552 that is located closer to the main tank 5 than the second check valve 551. The second check valve 551 is a so-called check valve, and allows the flow of ink through the communication passage 553 from the liquid ejection head H toward the main tank 5 and prevents backflow.

[0112] The foreign matter trapping filter 552 traps foreign matter such as dust flowing through the communication passage 553, and may be the same as the filter F provided in the liquid ejecting head H, for example.

[0113] The second circulation flow path 601 connects the main tank 5 and the flow path connection portion 11b of the liquid jet head H. A fourth liquid feed pump 561 and a second pressure sensor 510 are provided in the second circulation flow path 601. The second pressure sensor 510 is disposed on the liquid jet head H side with respect to the fourth liquid feed pump 561.

[0114] In the circulation mechanism 4 configured as above, during printing operation or normal cleaning operation, normal circulation is performed in which ink in the main tank 5 is supplied to the liquid jet head H via the first circulation flow path 600 and ink in the liquid jet head H is collected into the main tank 5 via the second circulation flow path 601, as shown by solid lines in FIG. 10. The supply of ink from the main tank 5 to the liquid jet head H is performed by controlling the third liquid feed pump 560 so that the first pressure sensor 509 is at a predetermined positive pressure. The collection of ink from the liquid jet head H to the main tank 5 is performed by controlling the fourth liquid feed pump 561 so that the second pressure sensor 510 is at a predetermined negative pressure. In normal circulation, ink does not flow through the communication path 553 and does not pass through the foreign matter capture filter 552.

[0115] During the cleaning operation, the third liquid feed pump 560 and the fourth liquid feed pump 561 are rotated in reverse, so that the ink in the main tank 5 is supplied to the liquid jet head H via the second circulation flow path 601, and the ink in the liquid jet head H is recovered to the main tank 5 via the first circulation flow path 600, as shown by the dotted line in Fig. 10, thereby performing reverse circulation. In the reverse circulation, the supply of ink from the main tank 5 to the liquid jet head H is performed by controlling the fourth liquid feed pump 561 so that the second pressure sensor 510 is at a predetermined positive pressure. In addition, the recovery of ink from the liquid jet head H to the main tank 5 is performed by controlling the third liquid feed pump 560 so that the first pressure sensor 509 is at a predetermined negative pressure.

[0116] Furthermore, in reverse circulation, the second check valve 551 causes ink to flow through the communication passage 553 from the liquid ejection head H toward the main tank 5. At this time, foreign matter captured in the filter F flows through the communication passage 553 and is captured by the foreign matter capture filter 552. Therefore, foreign matter generated by cleaning the filter F does not move to the main tank 5, and clogging of the filter F due to foreign matter being supplied to the liquid ejection head H during printing in normal circulation can be suppressed. Furthermore, in reverse circulation, the first check valve 550 can suppress ink from returning to the main tank 5 without passing through the foreign matter capture filter 552.

[0117] By performing the cleaning operation using such a liquid circulation system, the same effects as those of the first embodiment described above can be achieved.

[0118] In this embodiment, the circulation mechanism 4 circulates and reverse-circulates the ink between the main tank 5 and the liquid ejection head H, but the present invention is not particularly limited to this, and a sub-tank may be provided in the circulation mechanism 4, as in the above-described embodiment 1. In other words, the circulation mechanism 4 may circulate and reverse-circulate the ink between the sub-tank and the liquid ejection head H, and replenish the ink consumed by the liquid ejection head H from the main tank 5 to the sub-tank.

[0119] (Embodiment 4) 11 is a block diagram showing a cleaning device 610 for a liquid jet head H according to a fourth embodiment of the present invention. Note that the same members as those in the above-mentioned embodiments are given the same reference numerals and overlapping descriptions will be omitted.

[0120] As shown in FIG. 11, the cleaning device 610 includes a tank 611, a waste liquid tank 612, a first cleaning flow path 613, a second cleaning flow path 614, a compressor 615, a vacuum pump 616, a third pressure sensor 617, a fourth pressure sensor 618, a fourth regulator 619, and a fifth regulator 620.

[0121] The tank 611 stores a cleaning liquid for cleaning the inside of the flow path of the liquid jet head H. The cleaning liquid may be, for example, ink used for printing. If the inside of the flow path of the liquid jet head H is cleaned with a cleaning liquid other than ink, when printing is performed after cleaning, it becomes necessary to discard the ink together with the cleaning liquid so that the cleaning liquid in the liquid jet head H is replaced with ink. On the other hand, by using the ink used for printing as the cleaning liquid, it becomes unnecessary to discard the ink. Of course, the cleaning liquid may be a solvent or the like other than the ink. The tank 611 is connected to the flow path connection portion 11b of the liquid jet head H via a first cleaning flow path 613.

[0122] The third pressure sensor 617 is connected to the first cleaning flow path 613 at a position close to the liquid ejection head H. A compressor 615 is connected to the tank 611 via a fourth regulator 619, and the pressure of the tank 611 is controlled by the fourth regulator 619 so that the third pressure sensor 617 detects a predetermined positive pressure.

[0123] The waste liquid tank 612 recovers the cleaning liquid used to clean the inside of the flow passage of the liquid jet head H, and is connected to the liquid jet head H via a second cleaning flow passage 614.

[0124] The fourth pressure sensor 618 is connected to the second cleaning flow path 614 at a position close to the liquid ejecting head H. A vacuum pump 616 is connected to the waste liquid tank 612 via a fifth regulator 620, and the pressure in the waste liquid tank 612 is controlled by the fifth regulator 620 so that the fourth pressure sensor 618 detects a predetermined negative pressure.

[0125] To perform the cleaning process of the liquid jet head H using such a cleaning device 610, first, the first cleaning flow path 613 is connected to the flow path connection part 11b of the liquid jet head H in which the filter F is clogged, and the second cleaning flow path 614 is connected to the flow path connection part 11a. Then, as described above, the compressor 615 and the vacuum pump 616 supply the cleaning liquid from the tank 611 to the liquid jet head H, and the cleaning liquid of the liquid jet head H is collected in the waste liquid tank 612, so that the flow path in the liquid jet head H is made to flow in the opposite direction to the flow of ink during normal circulation operations such as during a printing operation or a normal cleaning operation, and foreign matter attached to the filter F can be collected together with the cleaning liquid. At this time, as in the above-mentioned embodiment 1, air is not drawn from the nozzle N during the first period after the start of the cleaning process. This makes it possible to suppress the air bubbles drawn from the nozzle N from adhering to the filter F and causing poor cleaning of the filter F.

[0126] Moreover, in the cleaning process of the liquid jet head H in the cleaning device 610, the first period preferably includes a second period in which ink is discharged from the nozzles N, similar to the first embodiment. Furthermore, in the cleaning process, the first period preferably includes a third period after the second period in which ink is not discharged from the nozzles N, similar to the first embodiment. Note that, in the cleaning process of the liquid jet head H in the cleaning device 610, the entire first period may be the second period in which ink is discharged from the nozzles N, similar to the first embodiment.

[0127] (Other embodiments) Although each embodiment of the present invention has been described above, the basic configuration of the present invention is not limited to the above.

[0128] For example, in the cleaning steps of the first to fourth embodiments described above, the filter F is cleaned by backflowing the ink, but the present invention is not limited to this, and a cleaning liquid other than the ink may be backflowed.

[0129] In addition, in each of the above-described embodiments, the liquid jet head H having the head chip 14 in which ink circulates through the individual flow paths 410 has been exemplified, but the present invention is not limited to this. Modified examples of the head chip 14 used in the liquid jet head H are shown in Figs. 12 and 13. Fig. 12 is a cross-sectional view of the flow path forming substrate 210 along the XY plane of the head chip 14. Fig. 13 is a cross-sectional view taken along line CC' in Fig. 12. The same reference numerals are used to designate the same members as in the above-described embodiments, and duplicated explanations will be omitted.

[0130] As shown in the figure, a flow path forming substrate 210 used in the head chip 14 has two rows of pressure chambers 212 arranged side by side along the Xa axis direction, the rows being aligned along the Ya axis direction.

[0131] The communication plate 215 is composed of a single plate-shaped member. In addition, the communication plate 215 is provided with an individual supply flow path 413 that connects the pressure chamber 212 with a common liquid chamber, and a nozzle communication path 412 that connects the nozzle N with the pressure chamber 212, for each pressure chamber 212.

[0132] The head chip 14 is provided with a common liquid chamber 400 on each side of the two rows of pressure chambers 212 sandwiched in the Ya axis direction. One common liquid chamber 400 is commonly connected to the pressure chambers 212 in one row, and the other common liquid chamber 400 is commonly connected to the pressure chambers 212 in the other row. In other words, the two common liquid chambers 400 are provided without communicating with each other. Note that each common liquid chamber 400 is similar to the first common liquid chamber 401 described above, and therefore a duplicated description will be omitted.

[0133] Each common liquid chamber 400 is provided with an inlet 243 at one end in the Ya axis direction and an outlet 244 at the other end in the Ya axis direction, and during printing, ink is supplied into the common liquid chamber 400 from the inlet 243, and the ink that moves inside the common liquid chamber 400 along the Xa axis direction is discharged to the outside from the outlet 244. Conversely, during cleaning, ink is supplied into the common liquid chamber 400 from the outlet 244, and ink is discharged to the outside from the inlet 243. That is, in the head chip 14 of this embodiment, the direction of ink flowing inside the common liquid chamber 400 is reversed between the cleaning operation and the circulation operation during the printing operation and normal cleaning operation.

[0134] The head chip 14 having such a configuration can perform the cleaning operation of each of the above-mentioned embodiments. In this modification, the “common liquid chamber portion” corresponds to the common liquid chamber 400.

[0135] In the above-described embodiments, the thin-film type piezoelectric actuator 300 has been used as the pressure generating means for generating a pressure change in the pressure chamber 212, but the present invention is not limited thereto. As the pressure generating means, for example, a thick-film type piezoelectric actuator formed by attaching a green sheet or a vertical vibration type piezoelectric actuator in which a piezoelectric material and an electrode forming material are alternately laminated and expanded and contracted in the axial direction can be used. As the pressure generating means, a device in which a heating element is disposed in the pressure chamber and droplets are ejected from a nozzle by bubbles generated by the heat generated by the heating element, or a so-called electrostatic actuator in which static electricity is generated between a vibration plate and an electrode, and the vibration plate is deformed by electrostatic force to eject droplets from a nozzle can be used.

[0136] Furthermore, the present invention is broadly intended for liquid ejection devices in general that are equipped with a liquid ejection head. Examples of the liquid ejection head include recording heads such as various ink jet recording heads used in image recording devices such as printers, and color material ejection heads used in manufacturing color filters for liquid crystal displays, etc. Examples of the liquid ejection head include electrode material ejection heads used in forming electrodes in organic EL displays, FEDs (field emission displays), etc., and bioorganic material ejection heads used in biochip manufacturing, and the present invention can be applied to liquid ejection devices equipped with these liquid ejection heads.

[0137] (Additional Note) From the above-described exemplary embodiments, the following configurations can be understood, for example.

[0138] A cleaning method for a liquid jet head according to embodiment 1, which is a preferred embodiment, is a cleaning method for a liquid jet head having a common liquid chamber communicating with a plurality of nozzles that eject liquid, a first flow path connecting the common liquid chamber with a first opening that is a flow path connection with the outside, a second flow path that is a flow path different from the first flow path and connects the common liquid chamber with a second opening that is a flow path connection with the outside, and a filter provided midway through the first flow path, the method including a cleaning step of causing liquid to flow from the second flow path toward the first flow path, and the cleaning step not drawing air from the nozzles for a first period of time after starting the cleaning step.

[0139] According to this, by performing a cleaning process in which liquid flows from the second flow path to the first flow path, foreign matter adhering to the filter can be removed. Therefore, it is possible to suppress liquid ejection failure, and to extend the replacement cycle of the liquid ejection head, thereby reducing costs. In addition, by preventing air drawn in from the nozzle from entering the filter chamber in the cleaning process, it is possible to efficiently create a cleaning effect for the filter by the backflow of ink.

[0140] In Aspect 2, which is a specific example of Aspect 1, the first period includes a second period in which the liquid is discharged from the nozzle. This increases the amount of liquid consumed, but suppresses the intake of air bubbles in the initial stage of the cleaning process, making it possible to more reliably remove foreign matter adhering to the filter.

[0141] In aspect 3, which is a specific example of aspect 2, the first period includes a third period that follows the second period and in which liquid is not discharged from the nozzle. According to this, foreign matter adhering to the filter is removed during the second period, and negative pressure acts on the nozzle, forming a meniscus. Therefore, the amount of liquid consumed can be reduced compared to when the first period is entirely the second period. Furthermore, the end of the second period allows the user to know that cleaning of the filter has been completed, and thus the timing for the end of maintenance can be known.

[0142] In Aspect 4, which is a specific example of Aspect 1, the entire first period is the second period in which liquid is discharged from the nozzle. This increases the amount of liquid consumed, but more reliably suppresses the intake of air bubbles in the cleaning process, and more reliably removes foreign matter adhering to the filter.

[0143] A liquid ejection device according to a preferred embodiment, aspect 5, includes a liquid ejection head having a common liquid chamber communicating with a plurality of nozzles that eject liquid, a first flow path that connects the common liquid chamber with a first opening that is a flow path connection with the outside, a second flow path that is a flow path different from the first flow path and connects the common liquid chamber with a second opening that is a flow path connection with the outside, and a filter provided midway through the first flow path, and a circulation mechanism that circulates liquid within a circulation flow path that includes the first flow path, the common liquid chamber, and the second flow path, wherein the circulation mechanism is capable of performing a cleaning operation that causes liquid to flow in the order of the second flow path, the common liquid chamber, and the first flow path, and the cleaning operation does not draw air from the nozzles for a first period after the start of the cleaning operation.

[0144] According to this, by performing a cleaning operation in which the liquid flows from the second flow path to the first flow path, foreign matter adhering to the filter can be removed. Therefore, it is possible to suppress liquid ejection failure, and to extend the replacement cycle of the liquid ejection head, thereby reducing costs. In addition, by preventing the air drawn in from the nozzle during the cleaning operation from entering the filter chamber, it is possible to efficiently create a cleaning effect for the filter by the backflow of the liquid.

[0145] In Aspect 6, which is a specific example of Aspect 5, the circulation mechanism is capable of performing a first circulation operation in which the liquid in the circulation flow path is circulated through the first flow path, the common liquid chamber, and the second flow path in that order during a printing operation of the liquid jet head, and a second circulation operation in which the liquid in the circulation flow path is circulated through the first flow path, the common liquid chamber, and the second flow path in that order so that a flow rate of the liquid flowing through the liquid jet head is greater than that in the first circulation operation, and an absolute value of the negative pressure applied to the first opening during the cleaning operation is greater than an absolute value of the negative pressure applied to the second opening during the second circulation operation. According to this, by making the absolute value of the negative pressure applied to the first flow path in which a filter is disposed during the cleaning operation greater than the absolute value of the negative pressure applied to the second flow path during the second circulation operation, it is possible to reliably apply negative pressure to the filter and effectively remove foreign matter adhering to the filter.

[0146] In Aspect 7, which is a specific example of Aspect 6, the positive pressure applied to the second opening during the cleaning operation is lower than the positive pressure applied to the first opening during the second circulation operation. This prevents excessive positive pressure from being applied to a filter provided in the first flow path, thereby preventing liquid from being wasted from the nozzle and reducing unnecessary consumption of liquid.

[0147] Furthermore, the ink jet recording apparatus I has been described as an example of a liquid ejecting apparatus, but the present invention can also be applied to liquid ejecting apparatuses using other liquid ejecting heads as described above. [Explanation of symbols]

[0148] 1...liquid ejection device, 2...control unit, 3...transport mechanism, 4...circulation mechanism, 5...main tank, 6...support, 11...flow path member, 11a to 11d...flow path connection portion, 111a to 111d...opening, 12...wiring board, 13...holder, 14...head chip, 14a...wiring member, 15...fixing plate, 120...supply flow path, 121...discharge flow path, 210...flow path forming board, 212...pressure chamber, 215...communicating plate, 220...nozzle plate, 220a...nozzle surface, 230...protective board, 240...case, 243...inlet, 244...discharge port, 249...comp 1. A piezoelectric substrate, 249a...compliance section, 250...diaphragm, 260...first electrode, 270...piezoelectric layer, 280...second electrode, 290...lead electrode, 300...piezoelectric actuator, 400...common liquid chamber, 401...first common liquid chamber, 402...second common liquid chamber, 410...individual flow paths, 411...individual recovery flow paths, 412...nozzle communication paths, 413...individual supply flow paths, 500...supply side sub-tank, 501...recovery side sub-tank, 503...waste liquid tank, 504...compressor, 505...first vacuum pump, 506...second vacuum pump, 507... First liquid supply pump, 508... second liquid supply pump, 509... first pressure sensor, 510... second pressure sensor, 511... first regulator, 512... second regulator, 513... third regulator, 520... first flow path switching unit, 522... first switching unit, 526... second switching unit, 530... second flow path switching unit, 540... flow path switching unit, 545... first valve, 546... second valve, 547... third valve, 548... fourth valve, 550... first check valve, 551... second check valve, 552... foreign matter capture filter, 553... connecting passage , 560...third liquid supply pump, 561...fourth liquid supply pump, 600...first circulation flow path, 601...second circulation flow path, 602...third circulation flow path, 603...replenishment flow path, 610...cleaning device, 611...tank, 612...waste liquid tank, 613...first cleaning flow path, 614...second cleaning flow path, 615...compressor, 616...vacuum pump, 617...third pressure sensor, 618...fourth pressure sensor, 619...fourth regulator, 620...fifth regulator, F...filter, H...liquid ejection head, M...liquid ejection module, N...nozzle, S...medium

Claims

1. A cleaning method for a liquid ejecting head including a common liquid chamber communicating with a plurality of nozzles ejecting liquid, a first flow path communicating the common liquid chamber with a first opening which is a flow path connecting portion with an outside, a second flow path which is a flow path different from the first flow path and communicating the common liquid chamber with a second opening which is a flow path connecting portion with an outside, and a filter provided midway through the first flow path, a cleaning step of causing a liquid to flow from the second flow path toward the first flow path, The cleaning step does not draw air through the nozzle for a first period of time from initiating the cleaning step. A method for cleaning a liquid ejection head.

2. the first period includes a second period during which liquid is ejected from the nozzle; 2. The method for cleaning a liquid jet head according to claim 1.

3. the first period of time includes a third period of time that follows the second period of time during which no liquid is ejected from the nozzles; The method for cleaning a liquid jet head according to claim 2 .

4. the entirety of the first period is a second period during which liquid is ejected from the nozzle; 2. The method for cleaning a liquid jet head according to claim 1.

5. a liquid ejection head including: a common liquid chamber communicating with a plurality of nozzles ejecting liquid; a first flow path communicating the common liquid chamber with a first opening which is a flow path connecting portion with the outside; a second flow path which is a flow path different from the first flow path and communicates the common liquid chamber with a second opening which is a flow path connecting portion with the outside; and a filter provided midway through the first flow path; a circulation mechanism that circulates liquid within a circulation flow path including the first flow path, the common liquid chamber, and the second flow path; Equipped with the circulation mechanism is capable of executing a cleaning operation of causing liquid to flow through the second flow path, the common liquid chamber, and the first flow path in this order; the cleaning operation does not draw air through the nozzles for a first period of time after initiating the cleaning operation; A liquid ejection apparatus comprising:

6. The circulation mechanism includes: a first circulation operation for circulating the liquid in the circulation flow path in the order of the first flow path, the common liquid chamber, and the second flow path during a printing operation of the liquid ejection head; a second circulation operation that circulates the liquid in the circulation flow path in the order of the first flow path, the common liquid chamber, and the second flow path so that a flow rate of the liquid flowing in the liquid jet head is greater than that in the first circulation operation, an absolute value of the negative pressure applied to the first opening during the cleaning operation is greater than an absolute value of the negative pressure applied to the second opening during the second circulation operation; The liquid ejecting apparatus according to claim 5 .

7. a positive pressure applied to the second opening during the cleaning operation is smaller than a positive pressure applied to the first opening during the second circulation operation; The liquid ejecting apparatus according to claim 6 .

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