Liquid ejecting apparatus and maintenance method of liquid ejecting head

Abstract

To reduce an amount of a liquid consumed wastefully in discharge processing.SOLUTION: A liquid ejecting apparatus includes: a liquid ejecting head having a first nozzle row which jets a first liquid, a first tank for storing the first liquid; a first supply flow path for supplying the first liquid to the first nozzle row from the first tank; a first on-off valve provided in an intermediate portion of the first supply flow path and configured to open and close the first supply flow path; and a first pressurizing mechanism configured to pressurize an inside of the first tank. A pressure inside the first tank is set to a predetermined positive pressure by driving the first pressurizing mechanism in a closed state of the first on-off valve. Thereafter, discharge processing in which the first liquid from the first nozzle row is discharged can be performed by bringing the first on-off valve into an open state. In the discharge processing, the first on-off valve is switched from the open state to the closed state at a timing at which the first liquid is being discharged from the first nozzle row.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a liquid ejection apparatus and a maintenance method for a liquid ejection head. [Background technology]

[0002] Liquid ejection devices, such as inkjet printers, generally include a liquid ejection head having a plurality of nozzles for ejecting liquid such as ink. In such liquid ejection devices, as disclosed in Patent Document 1, for example, when the liquid ejection head is not filled with liquid or an abnormality occurs in the liquid ejection head, a filling process or a cleaning process may be performed in which a pressure mechanism is driven to pressurize the supply flow path and supply liquid from a tank to the liquid ejection head. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-231773 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the filling process or cleaning process is performed by pressurizing the supply flow path as in Patent Document 1, there is a risk that the liquid will be wasted. [Means for solving the problem]

[0005] In order to solve the above problems, one aspect of the liquid ejection device disclosed herein includes a liquid ejection head having a first nozzle row that ejects a first liquid, a first tank that stores the first liquid to be supplied to the first nozzle row, a first supply flow path that supplies the first liquid from the first tank to the first nozzle row, a first on-off valve that is provided midway through the first supply flow path and is capable of opening and closing the first supply flow path, and a first pressurization mechanism that is capable of pressurizing the inside of the first tank, wherein the first on-off valve is in a closed state and the first pressurization mechanism is driven to set the pressure in the first tank to a predetermined positive pressure, and then the first on-off valve is opened to execute a discharge process that discharges the first liquid from the first nozzle row, and the discharge process switches the first on-off valve from an open state to a closed state at a timing when the first liquid is being discharged from the first nozzle row.

[0006] One aspect of the maintenance method for a liquid jet head disclosed herein is a maintenance method for a liquid jet head having a first nozzle row that ejects a first liquid, and includes a pressurizing step of pressurizing the inside of a first tank while blocking a first supply flow path that stores the first liquid to be supplied to the first nozzle row from the first tank, an opening step of discharging the first liquid from the first nozzle row by opening the first supply flow path after the pressurizing step, and a closing step of blocking the first supply flow path at a timing when the first liquid is being discharged from the first nozzle row by the opening step. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram illustrating an example of the configuration of a liquid ejecting apparatus according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view of a head chip of the liquid jet head. [Figure 3] FIG. 2 is a schematic diagram of a liquid supply mechanism according to the first embodiment. [Figure 4] 4 is a flowchart of a maintenance method for the liquid jet head according to the first embodiment. [Figure 5]4 is a timing chart of the maintenance method for the liquid jet head according to the first embodiment. [Figure 6] FIG. 10 is a schematic diagram of a liquid supply mechanism according to a second embodiment. [Figure 7] FIG. 2 is a cross-sectional view showing an example of a pressure regulating valve. DETAILED DESCRIPTION OF THE INVENTION

[0008] Preferred embodiments of the present disclosure will be described below with reference to the accompanying drawings. Note that the dimensions and scale of each part in the drawings may differ from the actual dimensions and are shown schematically to facilitate understanding. Furthermore, the scope of the present disclosure is not limited to these embodiments unless otherwise specified in the following description to the effect that the present disclosure is limited.

[0009] For ease of explanation, the mutually intersecting X-axis, Y-axis, and Z-axis will be used as appropriate below. Also, hereinafter, one direction along the X-axis is the X1 direction, and the direction opposite the X1 direction is the X2 direction. Similarly, the opposite directions along the Y-axis are the Y1 direction and the Y2 direction. Also, the opposite directions along the Z-axis are the Z1 direction and the Z2 direction.

[0010] Typically, the Z axis is a vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. However, the Z axis does not have to be a vertical axis. Furthermore, the X axis, Y axis, and Z axis are typically perpendicular to each other, but are not limited to this. For example, they may intersect at an angle between 80° and 100°.

[0011] 1. First embodiment 1-1. Schematic configuration of the liquid ejection device FIG. 1 is a schematic diagram showing an example of the configuration of a liquid ejection apparatus 100 according to a first embodiment. The liquid ejection apparatus 100 is an inkjet printing apparatus that ejects ink, which is an example of a "liquid," as droplets onto a medium M. The medium M is typically printing paper. However, the medium M is not limited to printing paper, and may be a printing target made of any material, such as a resin film or fabric.

[0012] 1, the liquid ejecting device 100 includes a liquid supply mechanism 10, a control unit 20, a transport mechanism 30, a movement mechanism 40, a liquid ejecting head 50, and a maintenance mechanism 60. These will be briefly described below in order based on FIG.

[0013] 1, the liquid supply mechanism 10 supplies a first liquid as ink to the liquid jet head 50 via a first supply flow path SJ_1, and also supplies a second liquid, which is a different type from the first liquid, as ink to the liquid jet head 50 via a second supply flow path SJ_2. Each of the first supply flow path SJ_1 and the second supply flow path SJ_2 is formed of, for example, a flexible tube.

[0014] The liquid supply mechanism 10 has a first tank 11_1 that stores a first liquid and a second tank 11_2 that stores a second liquid. Specific embodiments of the first tank 11_1 and the second tank 11_2 include, for example, a cartridge that is detachable from the liquid ejection device 100, a bag-shaped ink pack made of flexible film, and an ink tank that can be refilled with ink. Details of the liquid supply mechanism 10 will be described later with reference to FIG. 3.

[0015] Each of the first tank 11_1 and the second tank 11_2 may be a sub-tank that receives ink from the main tank. In this case, for example, an on-off valve is provided between the main tank and the sub-tank, and it is preferable to keep the on-off valve closed during the discharge process described below.

[0016] The first liquid and the second liquid are not particularly limited and may be, for example, a bio-based ink in which a biomaterial or biocompatible material is dissolved in a solvent or dispersed in a dispersion medium, an aqueous ink in which a colorant such as a dye or pigment is dissolved in an aqueous solvent, a solvent-based ink in which a colorant is dissolved in an organic solvent, a UV-curable ink, a clear ink, a white ink, or a treatment liquid. Bio-based ink is, for example, a liquid containing at least one of cells, DNA, and proteins as a biomaterial or biocompatible material. Clear ink does not contain colorant and is used as an overcoat on a printed surface printed with colorant to improve the abrasion resistance of the printed surface or reduce unevenness caused by pigment components, thereby reducing color shift due to diffuse reflection. White ink contains a white pigment or the like and is used to reduce non-whiteness caused by stains on the medium M. The treatment liquid is an ink that is reactive with the components contained in the colorant ink and improves the fixation of the colorant ink by contacting the colorant ink on the medium M. In the following description, the first liquid and the second liquid may each be referred to as ink.

[0017] The control unit 20 includes a processing circuit such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array) and a storage circuit such as a semiconductor memory, and controls the operation of each element of the liquid ejection device 100.

[0018] The transport mechanism 30 transports the medium M in the Y1 direction under the control of the control unit 20. The movement mechanism 40 reciprocates the multiple liquid jet heads 50 in the X1 direction and the X2 direction under the control of the control unit 20. In the example shown in FIG. 1 , the movement mechanism 40 has a substantially box-shaped transport body 41 called a carriage that houses the liquid jet heads 50, and a transport belt 42 to which the transport body 41 is fixed. Note that, in addition to the multiple liquid jet heads 50, a part of the liquid supply mechanism 10 may be mounted on the transport body 41.

[0019] The liquid ejection head 50 ejects ink supplied from the liquid supply mechanism 10 from each of the multiple nozzles N onto the medium M in the Z2 direction under the control of the control unit 20. This ejection is performed in parallel with the transport of the medium M by the transport mechanism 30 and the reciprocating movement of the liquid ejection head 50 by the movement mechanism 40, thereby forming an ink image on the surface of the medium M.

[0020] Here, the liquid jet head 50 is supplied with a drive signal Com for driving the liquid jet head 50 and a control signal SI for controlling the driving of the liquid jet head 50 from the control unit 20. The control signal SI is a signal for specifying whether or not to supply the drive signal Com to a drive element 51f (described later) of the liquid jet head 50, and is generated based on image data Img. The image data Img is information representing an image, and is supplied to the control unit 20 from a host computer such as a personal computer or a digital camera.

[0021] 1, the liquid jet head 50 has a plurality of head chips 51. Each of the plurality of head chips 51 is connected to the liquid supply mechanism 10 via a first supply flow path SJ_1 and a second supply flow path SJ_2. Details of the head chips 51 will be described later with reference to FIG. 2. Note that the number of head chips 51 included in the liquid jet head 50 is not limited to the example shown in FIG. 1, and may be any number, and may be a single number.

[0022] The maintenance mechanism 60 is a mechanism for performing maintenance on the liquid ejecting head 50. In the example shown in FIG.

[0023] The wiping member 61 is a member for wiping the ejection surface FN of the liquid ejection head 50. The wiping member 61 is, for example, a blade-shaped elastic member made of rubber or the like, or a porous member made of a fiber material such as woven or nonwoven fabric, or a sponge or the like. From the viewpoint of suitably reducing ink contamination inside the nozzles N, it is preferable that the wiping member 61 be a porous member.

[0024] The wiping member 61 is disposed at a position offset from the transport path of the medium M in the width direction (X2 direction) of the medium M. With the wiping member 61 in contact with the ejection surface FN of the liquid ejection head 50, the wiping member 61 is moved relative to the ejection surface FN in the direction along the X axis, thereby causing the wiping member 61 to wipe away any deposits on the ejection surface FN. This offset position is, for example, one end point of the reciprocating motion of the liquid ejection head 50, and is also referred to as the home position. Typical examples of such deposits include ink and paper dust.

[0025] 1, the movement mechanism 40 moves the liquid ejection head 50 in the direction along the X-axis, causing the wiping member 61 to move relatively to the ejection surface FN in the direction along the X-axis. Note that it is only necessary that the wiping member 61 can be moved relatively to the ejection surface FN in the direction along the X-axis, and for example, the wiping member 61 may be configured to be movable in the direction along the X-axis. Alternatively, the wiping member 61 may be configured to be movable in the direction along the Z-axis.

[0026] The liquid receiving member 62 receives, as waste liquid, the liquid ejected from the liquid ejection head 50 positioned at the home position. The liquid receiving member 62 may be made of, for example, a fiber material or an absorbent such as a sponge that can absorb liquid, or may be a recessed container that opens toward the ejection surface FN.

[0027] 1, the maintenance mechanism 60 may have a configuration other than the wiping member 61 and the liquid receiving member 62. For example, the maintenance mechanism 60 may have a cap mechanism that covers the ejection surface FN.

[0028] 1-2.Head chip configuration FIG. 2 is a cross-sectional view of the head chip 51 of the liquid jet head 50. As shown in FIG. 2, the head chip 51 has a plurality of nozzles N arranged in a direction along the Y axis. The plurality of nozzles N are divided into a first nozzle row LN1 and a second nozzle row LN2 that are arranged at intervals in a direction along the X axis. Each of the first nozzle row LN1 and the second nozzle row LN2 is a collection of a plurality of nozzles N that are linearly arranged in a direction along the Y axis. However, the first nozzle row LN1 ejects a first liquid, while the second nozzle row LN2 ejects a second liquid. Note that, hereinafter, each of the first nozzle row LN1 and the second nozzle row LN2 may be referred to as the nozzle row LN.

[0029] The head chips 51 are configured to be approximately symmetrical with respect to each other in the direction along the X-axis. However, the positions of the multiple nozzles N of the first nozzle row LN1 and the multiple nozzles N of the second nozzle row LN2 in the direction along the Y-axis may or may not match. Figure 2 illustrates a configuration in which the positions of the multiple nozzles N of the first nozzle row LN1 and the multiple nozzles N of the second nozzle row LN2 in the direction along the Y-axis match each other.

[0030] As shown in FIG. 2, the head chip 51 has a flow path substrate 51a, a pressure chamber substrate 51b, a nozzle plate 51c, a vibration absorber 51d, a diaphragm 51e, a plurality of drive elements 51f, a protective plate 51g, a case 51h, and a wiring substrate 51i.

[0031] The flow path substrate 51a and the pressure chamber substrate 51b are stacked in this order in the Z1 direction to form a flow path for supplying ink to the multiple nozzles N. A diaphragm 51e, multiple drive elements 51f, a protective plate 51g, a case 51h, and a wiring substrate 51i are provided in an area positioned in the Z1 direction from the stack of the flow path substrate 51a and the pressure chamber substrate 51b. On the other hand, a nozzle plate 51c and a vibration absorber 51d are provided in an area positioned in the Z2 direction from the stack. Each element of the head chip 51 is roughly a plate-like member that is elongated in the Y direction, and is joined to one another by, for example, an adhesive. Each element of the head chip 51 will be described in order below.

[0032] The nozzle plate 51c is a plate-like member provided with a plurality of nozzles N of each of the first nozzle row LN1 and the second nozzle row LN2. Each of the plurality of nozzles N is a through-hole that allows ink to pass through. The surface of the nozzle plate 51c facing the Z2 direction is the ejection surface FN. The nozzle plate 51c is manufactured by processing a silicon single crystal substrate using semiconductor manufacturing techniques such as dry etching or wet etching. However, other known methods and materials may also be used as appropriate to manufacture the nozzle plate 51c. Furthermore, the cross-sectional shape of the nozzle is typically circular, but is not limited thereto and may be a non-circular shape such as a polygonal or elliptical shape.

[0033] The flow path substrate 51a is provided with a space R1, a plurality of individual flow paths Ra, and a plurality of communicating flow paths Na for each of the first nozzle row LN1 and the second nozzle row LN2. The space R1 is an elongated opening extending in the direction along the Y axis in a plan view seen in the direction along the Z axis. Each of the individual flow paths Ra and the communicating flow paths Na is a through hole formed for each nozzle N. Each individual flow path Ra communicates with the space R1.

[0034] The pressure chamber substrate 51b is a plate-like member in which a plurality of pressure chambers C, called cavities, are provided for each of the first nozzle row LN1 and the second nozzle row LN2. The plurality of pressure chambers C are arranged in a direction along the Y axis. Each pressure chamber C is formed for each nozzle N and is an elongated space extending in a direction along the X axis in a plan view. Like the nozzle plate 51c described above, the flow path substrate 51a and the pressure chamber substrate 51b are each manufactured by processing a silicon single crystal substrate using semiconductor manufacturing technology, for example. However, other known methods and materials may also be used as appropriate to manufacture the flow path substrate 51a and the pressure chamber substrate 51b.

[0035] The pressure chambers C are spaces located between the flow path substrate 51a and the vibration plate 51e. A plurality of pressure chambers C are arranged in the direction along the Y axis for each of the first nozzle row LN1 and the second nozzle row LN2. The pressure chambers C are also connected to the communication flow paths Na and the individual flow paths Ra. Therefore, the pressure chambers C are connected to the nozzles N via the communication flow paths Na and to the space R1 via the individual flow paths Ra.

[0036] A diaphragm 51e is disposed on the surface of the pressure chamber substrate 51b facing the Z1 direction. The diaphragm 51e is a plate-shaped member that can vibrate elastically. The diaphragm 51e has, for example, an elastic film made of silicon oxide (SiO2) and an insulating film made of zirconium oxide (ZrO2), which are laminated in this order in the Z1 direction. The elastic film is formed, for example, by thermally oxidizing one surface of a silicon single crystal substrate. The insulating film is formed, for example, by forming a zirconium layer by sputtering and then thermally oxidizing the layer. Note that the diaphragm 51e is not limited to the configuration of a laminate of the elastic film and insulating film described above, and may be, for example, a single layer or three or more layers.

[0037] On the surface of the vibration plate 51e facing the Z1 direction, a plurality of drive elements 51f corresponding to the nozzles N of each of the first nozzle row LN1 and the second nozzle row LN2 are arranged. Each drive element 51f is a passive element that deforms when a drive signal is supplied. Each drive element 51f has an elongated shape extending in the direction along the X axis in a plan view. The plurality of drive elements 51f are arranged in the direction along the Y axis so as to correspond to the plurality of pressure chambers C. The drive elements 51f overlap the pressure chambers C in a plan view.

[0038] Each drive element 51f is a piezoelectric element and includes a first electrode, a piezoelectric layer, and a second electrode (not shown), which are stacked in this order in the Z1 direction. One of the first and second electrodes is an individual electrode spaced apart from one another for each drive element 51f, and a drive signal Com is supplied to the one electrode. The other of the first and second electrodes is a strip-shaped common electrode extending continuously along the Y-axis across the plurality of drive elements 51f, and a constant potential is supplied to the other electrode. Examples of metal materials for these electrodes include platinum (Pt), aluminum (Al), nickel (Ni), gold (Au), and copper (Cu). These metals can be used singly or in combination of two or more in the form of an alloy or a laminate. The piezoelectric layer is made of a piezoelectric material such as lead zirconate titanate (Pb(Zr,Ti)O3) and has, for example, a strip shape extending continuously along the Y-axis across the plurality of drive elements 51f. However, the piezoelectric layer may be integral across the plurality of drive elements 51f. In this case, through-holes are provided in the piezoelectric layer extending along the X-axis in areas corresponding in plan view to the gaps between adjacent pressure chambers C. When the vibration plate 51e vibrates in conjunction with the deformation of the drive elements 51f, the pressure in the pressure chambers C fluctuates, causing ink to be ejected from the nozzles N.

[0039] The protective plate 51g is a plate-like member installed on the surface of the diaphragm 51e facing the Z1 direction, and protects the multiple drive elements 51f and reinforces the mechanical strength of the diaphragm 51e. The multiple drive elements 51f are housed between the protective plate 51g and the diaphragm 51e. The protective plate 51g is made of, for example, a resin material.

[0040] The case 51h is a member for storing ink to be supplied to the multiple pressure chambers C. The case 51h is made of, for example, a resin material. A space R2 is provided in the case 51h for each of the first nozzle row LN1 and the second nozzle row LN2. The space R2 is a space that communicates with the above-mentioned space R1, and together with the space R1, functions as a reservoir R that stores ink to be supplied to the multiple pressure chambers C. The case 51h is provided with an inlet IH for supplying ink to each reservoir R. The ink in each reservoir R is supplied to the pressure chamber C via each individual flow path Ra.

[0041] Here, the inlet IH corresponding to the first nozzle row LN1 communicates with the first supply flow path SJ_1. Therefore, the first liquid is supplied as ink to the first nozzle row LN1. On the other hand, the inlet IH corresponding to the second nozzle row LN2 communicates with the second supply flow path SJ_2. Therefore, the second liquid is supplied as ink to the second nozzle row LN2. Note that a portion of each of the first supply flow path SJ_1 and the second supply flow path SJ_2 may be configured as a portion of the liquid jet head 50. Specifically, each of the first supply flow path SJ_1 and the second supply flow path SJ_2 may include the inlet IH and the reservoir R of the liquid jet head 50. In other words, the first supply flow path SJ_1 may be configured as a flow path from the first tank 11_1 to the multiple individual flow paths Ra. Similarly, the second supply flow path SJ_2 may be configured as a flow path from the second tank 11_2 to the multiple individual flow paths Ra.

[0042] The vibration absorber 51d is also called a compliance substrate and is a flexible resin film that forms the wall surface of the reservoir R, and absorbs pressure fluctuations of the ink inside the reservoir R. The vibration absorber 51d may also be a flexible thin metal plate. The surface of the vibration absorber 51d facing the Z1 direction is bonded to the flow path substrate 51a with an adhesive or the like.

[0043] The wiring board 51i is mounted on the surface of the diaphragm 51e facing the Z1 direction and is a mounting component for electrically connecting the head chip 51 with the drive circuit 51j and the control unit 20. The wiring board 51i is a flexible wiring board such as a COF (Chip On Film), an FPC (Flexible Printed Circuit), or an FFC (Flexible Flat Cable). The wiring board 51i of this embodiment has the drive circuit 51j mounted on it. The drive circuit 51j is a circuit including a switching element that switches whether or not to supply at least a part of the waveform included in the drive signal Com as a drive pulse to the drive element 51f based on the control signal SI.

[0044] In the head chip 51 described above, when the drive elements 51f are driven by the drive signal Com, the pressure in the pressure chambers C fluctuates, and in response to this fluctuation, ink is ejected from the nozzles N. Here, a first liquid is ejected from the first nozzle row LN1, while a second liquid of a different type from the first liquid is ejected from the second nozzle row LN2.

[0045] Here, the shortest distance Dn between the nozzles of the first nozzle row LN1 and the second nozzle row LN2 is not particularly limited, but is, for example, 1.5 mm or less. Note that the shortest distance Dn between the nozzles of the first nozzle row LN1 and the second nozzle row LN2 is the distance between the first nozzle row LN1 and the second nozzle row LN2 in the arrangement direction of the first nozzle row LN1 and the second nozzle row LN2 (the X direction in this embodiment).

[0046] 1-3.Configuration of liquid supply mechanism Figure 3 is a schematic diagram of the liquid supply mechanism 10 of the first embodiment. Figure 3 schematically shows, among the components of the liquid supply mechanism 10, those corresponding to an arbitrary pair of the first nozzle array LN1 and the second nozzle array LN2. Note that the components corresponding to other pairs of the first nozzle array LN1 and the second nozzle array LN2 are configured in the same manner as the components corresponding to the arbitrary pair of the first nozzle array LN1 and the second nozzle array LN2. The operation of these components may be controlled simultaneously or independently.

[0047] As shown in FIG. 3, the liquid supply mechanism 10 includes, in addition to the first tank 11_1 and second tank 11_2 described above, a first opening / closing valve 12_1, a second opening / closing valve 12_2, a first pressurizing mechanism 13_1, a second pressurizing mechanism 13_2, a first pressure sensor 14_1, a second pressure sensor 14_2, a first atmosphere release valve 15_1, and a second atmosphere release valve 15_2.

[0048] The first on-off valve 12_1 is a valve mechanism provided in the first supply flow path SJ_1 and capable of opening and closing the first supply flow path SJ_1 under the control of the control unit 20. On the other hand, the second on-off valve 12_2 is a valve mechanism provided in the second supply flow path SJ_2 and capable of opening and closing the second supply flow path SJ_2 under the control of the control unit 20. Each of the first on-off valve 12_1 and the second on-off valve 12_2 is, for example, a solenoid valve, a diaphragm valve, a needle valve, or the like.

[0049] Here, the first supply flow path SJ_1 is a flow path for supplying the first liquid from the first tank 11_1 to the first nozzle row LN1. Therefore, when the first on-off valve 12_1 is in an open state, the first supply flow path SJ_1 is in an open state, and the supply of the first liquid from the first tank 11_1 to the first nozzle row LN1 is permitted. On the other hand, when the first on-off valve 12_1 is in a closed state, the first supply flow path SJ_1 is in a closed state, and the supply of the first liquid from the first tank 11_1 to the first nozzle row LN1 is not permitted.

[0050] Similarly, the second supply flow path SJ_2 is a flow path for supplying the second liquid from the second tank 11_2 to the second nozzle row LN2. Therefore, when the second on-off valve 12_2 is in an open state, the second supply flow path SJ_2 is in an open state, and the supply of the second liquid from the second tank 11_2 to the second nozzle row LN2 is permitted. On the other hand, when the second on-off valve 12_2 is in a closed state, the second supply flow path SJ_2 is in a closed state, and the supply of the second liquid from the second tank 11_2 to the second nozzle row LN2 is not permitted.

[0051] The first pressurizing mechanism 13_1 is a mechanism capable of pressurizing the inside of the first tank 11_1 under the control of the control unit 20. On the other hand, the second pressurizing mechanism 13_2 is a mechanism capable of pressurizing the inside of the second tank 11_2 under the control of the control unit 20. Each of the first pressurizing mechanism 13_1 and the second pressurizing mechanism 13_2 is, for example, a syringe pump, a diaphragm pump, a tube pump, or a compressor, and generates a positive pressure higher than atmospheric pressure. Note that each of the first pressurizing mechanism 13_1 and the second pressurizing mechanism 13_2 may have a regulator for adjusting the pressure. Furthermore, one of the first pressurizing mechanism 13_1 and the second pressurizing mechanism 13_2 may also serve as the other. That is, a single pressurizing mechanism serving as both the first pressurizing mechanism 13_1 and the second pressurizing mechanism 13_2 may be provided in common to the first tank 11_1 and the second tank 11_2.

[0052] The first pressure sensor 14_1 measures the pressure in the first tank 11_1. Meanwhile, the second pressure sensor 14_2 measures the pressure in the second tank 11_2. There are no particular limitations on the first pressure sensor 14_1 and the second pressure sensor 14_2, and for example, a known diaphragm-type pressure sensor can be used.

[0053] Information indicating the measurement results of the first pressure sensor 14_1 and the second pressure sensor 14_2 is input to the control unit 20. For example, the control unit 20 controls the operation of the first pressurizing mechanism 13_1 based on the measurement result of the first pressure sensor 14_1 so that the pressure in the first tank 11_1 becomes a predetermined pressure. Similarly, for example, the control unit 20 controls the operation of the second pressurizing mechanism 13_2 based on the measurement result of the second pressure sensor 14_2 so that the pressure in the second tank 11_2 becomes a predetermined pressure.

[0054] The first atmosphere release valve 15_1 is a valve mechanism that can be opened and closed to open the inside of the first tank 11_1 to the atmosphere under the control of the control unit 20, and opens and closes between the inside of the first tank 11_1 and the external space. That is, the first atmosphere release valve 15_1 is controlled by the control unit 20 to be switchable between an open state in which the inside of the first tank 11_1 is opened to the atmosphere and a closed state in which the inside of the first tank 11_1 is not opened to the atmosphere. On the other hand, the second atmosphere release valve 15_2 is a valve mechanism that can be opened and closed to open the inside of the second tank 11_2 to the atmosphere under the control of the control unit 20, and opens and closes between the inside of the second tank 11_2 and the external space. That is, the second atmosphere release valve 15_2 is controlled by the control unit 20 to be switchable between an open state in which the inside of the second tank 11_2 is opened to the atmosphere and a closed state in which the inside of the second tank 11_2 is not opened to the atmosphere. Each of the first atmosphere release valve 15_1 and the second atmosphere release valve 15_2 may be a valve that can be controlled by a device such as the control unit 20, and may be, for example, a diaphragm valve, a solenoid valve, or an electric valve. Note that one of the first atmosphere release valve 15_1 and the second atmosphere release valve 15_2 may also serve as the other. That is, a single atmosphere release valve that serves as both the first atmosphere release valve 15_1 and the second atmosphere release valve 15_2 may be provided in common to the first tank 11_1 and the second tank 11_2.

[0055] The liquid supply mechanism 10 described above supplies the first liquid in the first tank 11_1 to the liquid jet head 50, and also supplies the second liquid in the second tank 11_2 to the liquid jet head 50 under the control of the control unit 20.

[0056] Here, the liquid ejection device 100 can perform an ejection process SD to eject ink from the first nozzle row LN1 and the second nozzle row LN2 as maintenance of the liquid ejection head 50 by operating the liquid supply mechanism 10 under the control of the control unit 20.

[0057] More specifically, the liquid ejection device 100 is capable of executing one or both of a filling process, which starts the discharge process SD when the liquid ejection head 50 is not filled with ink, and a cleaning process, which starts the discharge process SD when the liquid ejection head 50 is filled with ink. Details of the discharge process SD will be described later with reference to Figures 4 and 5. The liquid ejection device 100 of this embodiment is capable of executing both the discharge process SD as a filling process and the discharge process SD as a cleaning process.

[0058] 1-4. Operation of the liquid injection device 4 is a flowchart of a maintenance method for the liquid jet head 50 according to the first embodiment. Hereinafter, the maintenance method will be described with reference to FIG. 4. Note that, hereinafter, each of the first supply flow path SJ_1 and the second supply flow path SJ_2 may be referred to as a supply flow path SJ, each of the first tank 11_1 and the second tank 11_2 may be referred to as a tank 11, each of the first on-off valve 12_1 and the second on-off valve 12_2 may be referred to as an on-off valve 12, each of the first pressurizing mechanism 13_1 and the second pressurizing mechanism 13_2 may be referred to as a pressurizing mechanism 13, each of the first pressure sensor 14_1 and the second pressure sensor 14_2 may be referred to as a pressure sensor 14, and each of the first atmosphere release valve 15_1 and the second atmosphere release valve 15_2 may be referred to as an atmosphere release valve 15.

[0059] In this maintenance method, the control unit 20 executes steps S11 to S18 in this order, as shown in Fig. 4. Here, a discharge process SD is executed in steps S11 to S14. Each step will be explained below in order.

[0060] First, in step S11, the control unit 20 closes the on-off valve 12 and the atmosphere release valve 15. Note that step S11 is omitted if the on-off valve 12 and the atmosphere release valve 15 are already in the closed state.

[0061] After step S11 described above, in step S12, the control unit 20 executes a pressurizing step SP. In the pressurizing step SP, a predetermined positive pressure is created by pressurizing the inside of the tank 11 while the supply flow path SJ is closed. Here, in the pressurizing step SP, the pressurizing mechanism 13 is driven with the on-off valve 12 in a closed state to pressurize the inside of the tank 11. At this time, since the supply flow path SJ is closed, ink is not supplied to the liquid ejection head 50.

[0062] In the pressurizing step SP of this embodiment, the pressurizing mechanism 13 is driven with the atmosphere release valve 15 in a closed state. This allows the inside of the tank 11 to be efficiently pressurized. The transition of the pressure inside the tank 11 will be described later with reference to FIG. 5.

[0063] After step S12, the control unit 20 executes the opening process SO in step S13. In the opening process SO, the supply flow path SJ is opened after the pressurizing process SP, thereby discharging ink from the nozzle row LN. Here, in the opening process SO, the pressure in the tank 11 is set to a predetermined positive pressure, and the on-off valve 12 is opened, so that the ink in the tank 11 is supplied to the liquid ejection head 50 via the supply flow path SJ due to the pressure in the tank 11.

[0064] The opening step SO of this embodiment is executed after the pressurizing mechanism 13 is stopped in the pressurizing step SP. That is, the pressurizing mechanism 13 is stopped before the on-off valve 12 is switched from the closed state to the open state in the opening step SO.

[0065] After step S13, the control unit 20 executes the closing process SC in step S14. The closing process SC closes the supply flow path SJ at a timing when ink is being discharged from the nozzle row LN in the opening process SO. Here, the closing process SC closes the supply flow path SJ by switching the on-off valve 12 from an open state to a closed state. This stops the supply of ink from the tank 11 to the liquid ejection head 50 via the supply flow path SJ.

[0066] Furthermore, from the viewpoint of improving the efficiency of the discharge process SD or reducing ink contamination in the nozzle row LN, it is preferable that in the opening process SO, at least a portion of the period during which the first supply flow path SJ_1 is maintained in an open state and a portion of the period during which the second supply flow path SJ_2 is maintained in an open state overlap with each other, and it is more preferable that these periods coincide.

[0067] Here, the period during which the first supply flow path SJ_1 is kept open is the period during which the first on-off valve 12_1 is kept open, and the period during which the second supply flow path SJ_2 is kept open is the period during which the second on-off valve 12_2 is kept open.

[0068] Furthermore, when the period during which the first supply flow path SJ_1 is maintained in an open state and the period during which the second supply flow path SJ_2 is maintained in an open state are made to coincide with each other, the timing at which the first opening / closing valve 12_1 is switched from a closed state to an open state and the timing at which the second opening / closing valve 12_2 is switched from a closed state to an open state are the same as each other, and the timing at which the first opening / closing valve 12_1 is switched from an open state to a closed state and the timing at which the second opening / closing valve 12_2 is switched from an open state to a closed state are the same as each other.

[0069] After step S14 described above, in step S15, the control unit 20 executes the wiping process SW. The wiping process SW is performed after the closing process SC, i.e., after the discharge process SD, and involves performing a wiping operation in which the wiping member 61 wipes the ejection surface FN while the supply flow path SJ is closed. From the perspective of reducing ink contamination of the nozzle row LN, the wiping process SW is preferably performed while both the first supply flow path SJ_1 and the second supply flow path SJ_2 are closed. In other words, the wiping process SW is preferably performed during a period in which both the first on-off valve 12_1 and the second on-off valve 12_2 are closed.

[0070] After step S15, in step S16, the control unit 20 switches the atmosphere release valve 15 from the closed state to the open state, thereby setting the pressure inside the tank 11 to atmospheric pressure. Note that step S16 may be executed during or before the wiping process SW, as long as it is executed after the discharge process SD.

[0071] After step S16, in step S17, the control unit 20 switches the on-off valve 12 from the closed state to the open state. As a result, the pressure of the ink in the nozzle row LN is reduced because the pressure inside the tank 11 is atmospheric pressure. Specifically, the pressure of the ink in the nozzle row LN is reduced to a pressure corresponding to the ink head difference between the tank 11 and the liquid ejection head 50.

[0072] In this way, the atmosphere release valve 15 is switched from the closed state to the open state at a timing after the on-off valve 12 is closed in the closing step SC and before the on-off valve 12 is opened after the wiping operation is performed. Here, the timing at which the atmosphere release valve 15 is switched from the closed state to the open state may be a timing before at least one of the first on-off valve 12_1 and the second on-off valve 12_2 is opened after the wiping operation is performed. Here, if the timing at which the first on-off valve 12_1 is opened after the wiping operation is performed and the timing at which the second on-off valve 12_2 is opened are the same, "the timing before at least one of the first on-off valve 12_1 and the second on-off valve 12_2 is opened after the wiping operation is performed" refers to a timing before both the first on-off valve 12_1 and the second on-off valve 12_2 are opened. Furthermore, if the timing at which the first opening / closing valve 12_1 is opened after the wiping operation is performed is different from the timing at which the second opening / closing valve 12_2 is opened, the "timing before at least one of the first opening / closing valve 12_1 and the second opening / closing valve 12_2 is opened after the wiping operation is performed" is the timing before the timing at which the opening / closing valve 12, whichever of the first opening / closing valve 12_1 and the second opening / closing valve 12_2 is opened first after the wiping operation is performed, is opened.

[0073] After step S17, in step S18, the control unit 20 executes a flushing process SF. In the flushing process SF, a flushing operation is executed after the wiping operation is executed. In the flushing operation, ink is ejected from the nozzles N toward the liquid receiving member 62 with the liquid ejection head 50 positioned at the home position. Here, ink is ejected from the nozzles N by driving the drive elements 51f of the liquid ejection head 50.

[0074] During the flushing operation, from the viewpoint of effectively removing contamination of the ink in the nozzle N, it is preferable that the total amount of ink ejected from one of the multiple nozzles N is less than the volume of the pressure chamber C connected to that nozzle, more preferably less than the volume of the communicating flow path Na, which is a flow path downstream of the pressure chamber C, and the nozzle N, and even more preferably less than the volume of the nozzle N.

[0075] In this manner, maintenance is performed on the liquid jet head 50. By performing this maintenance, the liquid jet head 50 is ready for printing. Note that the flushing step SF in step S18 is performed as needed, and may be omitted.

[0076] FIG. 5 is a timing chart of a maintenance method (maintenance process) for the liquid jet head 50 according to the first embodiment. FIG. 5 shows the operating states of the on-off valve 12, the pressurizing mechanism 13, the atmosphere release valve 15, and the wiping operation, as well as changes in the pressure in the tank 11 and the nozzle N, over a period from timing t0 to timing t10. The timing chart for the pressurizing mechanism 13 indicates that the pressurizing mechanism 13 is in an activated state when it is at a high level, and that the pressurizing mechanism 13 is in a deactivated state when it is at a low level. The timing chart for the on-off valve 12 indicates that the on-off valve 12 is in an open state when it is at a high level, and that the on-off valve 12 is in a closed state when it is at a low level. The timing chart for the atmosphere release valve 15 indicates that the atmosphere release valve 15 is in an open state when it is at a high level, and that the atmosphere release valve 15 is in a closed state when it is at a low level. In the timing chart of the wiping operation, a high level indicates that the wiping member 61 is wiping the ejection surface FN, and a low level indicates that the wiping member 61 is not wiping the ejection surface FN. Depending on the configuration of the on-off valve 12, the on-off valve 12 may be closed when the signal is high and open when the signal is low. The same applies to the atmosphere release valve 15.

[0077] First, a maintenance method including a discharge process SD as a filling process will be mainly described with reference to Fig. 5. In Fig. 5, the transition of the pressure inside the tank 11 during a maintenance method including a discharge process SD as a filling process is shown by a solid line.

[0078] 5, if the on-off valve 12 and the atmosphere release valve 15 are in an open state at timing t0 when the maintenance process is started, then at timing t1 after timing t0, the on-off valve 12 and the atmosphere release valve 15 are each closed (step S11). At this time, the pressurizing mechanism 13 and the wiping operation are both stopped. Also, the pressure inside the tank 11 and the nozzle N is 0 kPa. Note that the description of pressure in this specification is based on gauge pressure, where atmospheric pressure is 0 kPa.

[0079] At timing t2, which follows timing t1, the pressurizing mechanism 13 begins to operate. At timing t3, which follows timing t2, the pressurizing mechanism 13 stops operating. That is, the pressurizing mechanism 13 operates from timing t2 to timing t3 (step S12). This causes the pressurizing process SP to be performed, increasing the pressure in the tank 11 to a predetermined positive pressure, a first pressure P1. Note that in FIG. 5, the predetermined positive pressure in the tank 11 after the pressurizing process SP is performed as the filling process is referred to as the first pressure P1a, and the predetermined positive pressure in the tank 11 after the pressurizing process SP is performed as the cleaning process is referred to as the first pressure P1b. However, when there is no need to distinguish between the first pressure P1a and the first pressure P1b, they are simply referred to as the first pressure P1. In the example shown in FIG. 5, the first pressure P1a is 41 kPa. Note that if the liquid supply mechanism 10 includes a regulator connected to the tank 11, the pressurizing mechanism 13 does not need to be stopped at timing t3.

[0080] At timing t4 after timing t3, the on-off valve 12 is switched from the closed state to the open state (step S13). This performs the opening step SO, which causes the pressure in the tank 11 to decrease and the pressure in the nozzle N to rise sharply. Note that during the period from timing t3 to timing t4, the pressure in the tank 11 is maintained at the first pressure P1.

[0081] At timing t5 after timing t4, the on-off valve 12 is switched from the open state to the closed state. This performs the closing process SC (step S14). In this way, the on-off valve 12 is in the open state from timing t4 to timing t5. During this period, ink is discharged from the nozzle N. Ink is also discharged from the nozzle N from timing t5 to timing 21, which is after timing t5. As shown in FIG. 5, timing t21 is the timing at which the pressure inside the nozzle N reaches the meniscus withstand pressure Pm. In other words, the pressure inside the nozzle N at timing t5 is greater than the meniscus withstand pressure Pm of the nozzle N, and therefore timing t5 is the timing at which ink is being discharged from the nozzle N. In the example shown in FIG. 5, the meniscus withstand pressure Pm is 1 kPa.

[0082] In the example shown in FIG. 5, timing t5 is the timing when the pressure in tank 11 reaches third pressure P3. Third pressure P3 is a pressure between first pressure P1 and second pressure P2. Here, second pressure P2 is the pressure in tank 11 when, after the pressure in tank 11 reaches first pressure P1, the on-off valve 12 is kept open until the pressure in tank 11 becomes substantially constant; in other words, when the on-off valve 12 is not changed from the open state to the closed state at timing t5 (hereinafter referred to as the discharge process of Comparative Example 1). Here, "substantially constant" means that the pressure in tank 11 reaches an equilibrium state, more specifically, that a state in which the maximum amplitude of the pressure is 1 kPa or less continues for 3 seconds or more. In FIG. 5, the transition of pressure in tank 11 during the discharge process as the filling process of Comparative Example 1 is indicated by a two-dot chain line. That is, in the example shown in FIG. 5, the third pressure P3 is a pressure between the first pressure P1a and the second pressure P2, the second pressure P2 is 3 kPa, and the third pressure P3 is 19 kPa.

[0083] Furthermore, in Comparative Example 1, the length of time required from timing t4 to timing t11 when the pressure in the tank 11 becomes substantially constant is defined as a first time length T1, and the length of the period from timing t4 to timing t5 is defined as a second time length T2. From the viewpoint of reducing waste of ink ejected from the nozzle N, the second time length T2 is shorter than the first time length T1, preferably equal to or less than half the first time length T1, more preferably equal to or less than one-third the first time length T1, and even more preferably equal to or less than one-fifth the first time length T1. In the example shown in FIG. 5, the second time length T2 is 2 seconds, and the first time length T1 is approximately 5 to 10 seconds. Although not shown, in Comparative Example 1, during the period from timing t4 when the pressure in the nozzle N exceeds the meniscus withstand pressure Pm by opening the on-off valve 12 until timing t11 when the pressure in the nozzle N reaches the meniscus withstand pressure Pm, the pressure in the nozzle N is greater than the meniscus withstand pressure Pm, and therefore ink is ejected from the nozzle N.

[0084] During the period from timing t6 to timing t7 after timing t5, a wiping operation is performed (step S15). Timing t6 is preferably after timing t21 when the pressure inside the nozzle N reaches the meniscus withstand pressure Pm.

[0085] At timing t8 after timing t7, the atmosphere release valve 15 is switched from the closed state to the open state (step S16). This causes the pressure inside the tank 11 to drop to atmospheric pressure. From the viewpoint of shortening the processing time of the maintenance process, this switching may be performed during the execution of the wiping operation, i.e., the period from timing t6 to timing t7, or before the execution of the wiping operation, i.e., before timing t6.

[0086] At timing t9 after timing t8, the on-off valve 12 is switched from the closed state to the open state, thereby allowing ink to be supplied from the tank 11 to the liquid ejection head 50 via the supply flow path SJ. Thereafter, a flushing process SF is executed as necessary (step S18).

[0087] Next, a maintenance method including a discharge process SD as a cleaning process will be described with reference to FIG. 5. In this embodiment, the maintenance method including a discharge process SD as a filling process and the maintenance method including a discharge process SD as a cleaning process are substantially the same except for the first pressure P1 generated in the tank 11 by the pressurization step SP. Therefore, only the differences will be described. In FIG. 5, the transition of pressure in the tank 11 during the maintenance method including a discharge process SD as a cleaning process is indicated by a dashed line. Note that in FIG. 5, the transition of pressure in the nozzle N, the second pressure P2, the third pressure P3, the two-dot dashed line representing the transition of pressure in the tank 11 during the discharge process of Comparative Example 1, the timing t11, and the first time length T1 are shown for the maintenance process including a discharge process SD as a filling process. However, these are not shown for the maintenance process including a discharge process SD as a cleaning process.

[0088] When the liquid ejection device 100 is capable of performing both the filling process and the cleaning process, as shown in FIG. 5, it is preferable that the first pressure P1b in the cleaning process be lower than the first pressure P1a in the filling process. In the example shown in FIG. 5, the first pressure P1b in the cleaning process is 15 kPa, which is lower than the first pressure P1a in the filling process. This allows the filling process to be performed without excess or deficiency of ink and reduces the amount of ink wasted in the cleaning process. As can be seen from FIG. 5, in this embodiment, the period during which the pressurizing mechanism 13 is driven in the pressurizing step SP of the filling process and the period during which the pressurizing mechanism 13 is driven in the pressurizing step SP of the cleaning process are the same period from timing t2 to timing t3. Therefore, in the pressurizing step SP of the cleaning process, the output of the pressurizing mechanism 13 per unit time is set lower than that in the pressurizing step SP of the filling process, thereby making the first pressure P1b lower than the first pressure P1a. However, the first pressure P1b may be made smaller than the first pressure P1a by making the period during which the pressure mechanism 13 is driven in the pressure step SP of the cleaning process shorter than the period during which the pressure mechanism 13 is driven in the pressure step SP of the filling process. In this case, the output per unit time of the pressure mechanism 13 in the pressure step SP may be the same for the cleaning process and the filling process, or may be smaller for the cleaning process than for the filling process.

[0089] The discharge process of Comparative Example 2 will now be described. The change in pressure inside the tank 11 indicated by the dashed line in FIG. 5 represents the change in pressure inside the tank 11 during the discharge process of Comparative Example 2, which is a filling process. The filling process of Comparative Example 2 differs from the filling process of this embodiment in that the first pressure P1c, which is a predetermined positive pressure generated inside the tank 11 by the pressurizing step SP, is lower than the first pressure P1a generated inside the tank 11 by the pressurizing step SP of the filling process of this embodiment, and that the on-off valve 12 is opened at timing t4 after the pressurizing step SP and remains open until timing t12 when the pressure inside the tank 11 becomes substantially constant. In other words, the on-off valve 12 is not closed while ink is being discharged from the nozzles N. The first pressure P1c is set to a magnitude that allows ink to be filled into all of the nozzles N constituting the nozzle row LN by keeping the on-off valve 12 open from timing t4 to timing t12. In the example shown in FIG. 5, the first pressure P1c is 25 kPa.

[0090] The supply flow path SJ communicates with the multiple nozzles N that make up the nozzle row LN, and because there is variation in the flow path resistance from the inlet IH to each nozzle, there is variation in the time from when the on-off valve 12 is opened at timing t4 until ink is filled into each nozzle N. As a result, in Comparative Example 2, of the multiple nozzles N that make up the nozzle row LN, ink is wasted from the nozzles N that are filled with ink before the timing when all of the nozzles N are filled with ink.

[0091] On the other hand, the slope of the pressure change inside the tank 11 during the period from timing t4 to timing t5 in this embodiment is greater than the slope of the pressure change inside the tank 11 during the period from timing t4 to timing t5 in Comparative Example 2. Therefore, all of the nozzles N that make up the nozzle row LN can be instantly filled with ink, and the amount of ink that is wasted from the nozzles N can be reduced compared to Comparative Example 2.

[0092] The above describes a comparison between Comparative Example 2 and the present embodiment regarding the filling process. However, the relationship between the filling process of Comparative Example 2 and the filling process of the present embodiment is similar to the relationship between the cleaning process of Comparative Example 2 and the cleaning process of the present embodiment. Specifically, in the cleaning process of Comparative Example 2, there is variation in the time from when the on-off valve 12 is opened at timing t4 until a predetermined amount of ink required for cleaning is discharged from each nozzle N. Therefore, in the cleaning process of Comparative Example 2, ink is wasted from a nozzle N that discharges a predetermined amount of ink before the predetermined amount of ink is discharged from all nozzles N, among the multiple nozzles N that make up the nozzle row LN. On the other hand, the cleaning process of the present embodiment can reduce the amount of ink wasted from the nozzle N compared to Comparative Example 2 for the same reason as the filling process of the present embodiment.

[0093] As in the filling process of Comparative Example 1 described above, it is conceivable that the plurality of nozzles N constituting the nozzle row LN could be instantly filled with ink by increasing the predetermined positive pressure generated in the tank 11 by the pressurizing step SP to the same extent as in this embodiment. However, in the filling process of Comparative Example 1, the on-off valve 12 is not closed at timing t5, and therefore a positive pressure in the tank 11 that is excessive relative to the pressure required to fill all of the nozzles N constituting the nozzle row LN with ink acts on the liquid ejection head 50. As a result, the filling process of Comparative Example 1 unnecessarily discharges ink from the nozzles N compared to the filling process of this embodiment. The same is true for the cleaning process of Comparative Example 1, in that more ink is unnecessarily discharged from the nozzles N compared to the cleaning process of this embodiment.

[0094] As described above, the liquid ejection device 100 includes the liquid ejection head 50, the first tank 11_1, the first supply flow path SJ_1, the first on-off valve 12_1, and the first pressurizing mechanism 13_1. The liquid ejection head 50 includes a first nozzle row LN1 that ejects a first liquid. The first tank 11_1 stores the first liquid to be supplied to the first nozzle row LN1. The first supply flow path SJ_1 is a flow path for supplying the first liquid from the first tank 11_1 to the first nozzle row LN1. The first on-off valve 12_1 is provided midway along the first supply flow path SJ_1 and is capable of opening and closing the first supply flow path SJ_1. The first pressurizing mechanism 13_1 is capable of pressurizing the inside of the first tank 11_1.

[0095] Then, the liquid ejection device 100 can execute a discharge process SD. The discharge process SD sets the pressure in the first tank 11_1 to a predetermined positive pressure by driving the first pressurizing mechanism 13_1 with the first on-off valve 12_1 in a closed state, and then discharges the first liquid from the first nozzle row LN1 by opening the first on-off valve 12_1. Here, the discharge process SD switches the first on-off valve 12_1 from the open state to the closed state at a timing when the first liquid is being discharged from the first nozzle row LN1.

[0096] In the liquid jet head 50 described above, during the discharge process SD, the first pressure mechanism 13_1 is driven with the first on-off valve 12_1 in a closed state to set the pressure in the first tank 11_1 to a predetermined positive pressure, and then the first on-off valve 12_1 is opened. This allows the pressure for supplying the first liquid to the first nozzle row LN1 to be supplied to the liquid jet head 50 with a steep rise. This allows the liquid to be instantly distributed to all of the nozzles N constituting the first nozzle row LN1. Furthermore, during the discharge process SD, the first on-off valve 12_1 is switched from the open state to the closed state at a timing when the first liquid is being discharged from the first nozzle row LN1. This shortens the period during which the first liquid is unnecessarily discharged from the first nozzle row LN1. This prevents the first liquid from being unnecessarily discharged from the first nozzle row LN1.

[0097] As described above, the discharge process SD switches the first on-off valve 12_1 from the open state to the closed state at timing t5 when the pressure in the first tank 11_1 reaches the third pressure P3. Here, the third pressure P3 is a pressure between the first pressure P1 and the second pressure P2. The first pressure P1 is the predetermined positive pressure. The second pressure P2 is the pressure in the first tank 11_1 when the first on-off valve 12_1 is kept open until the pressure in the first tank 11_1 becomes approximately constant after the pressure in the first tank 11_1 reaches the first pressure P1. In this discharge process SD, the amount of the first liquid that is wasted can be reduced.

[0098] As described above, the timing t5 is the timing at which the second time length T2 has elapsed since the first on-off valve 12_1 was opened in the discharge process SD. That is, the discharge process SD switches the first on-off valve 12_1 from the open state to the closed state at the timing t5, which is the time length T2 since the first on-off valve 12_1 was opened. Here, the second time length T2 is a time length shorter than the first time length T1. The first time length T1 is the time length required from the time the first on-off valve 12_1 is opened until the pressure in the first tank 11_1 becomes substantially constant, in the case where the pressure in the first tank 11_1 is set to the first pressure P1 and then the first on-off valve 12_1 is opened until the pressure in the first tank 11_1 becomes substantially constant. This reduces the amount of the first liquid wasted.

[0099] Furthermore, as mentioned above, the second time length T2 is preferably equal to or less than half the first time length T1, which makes it possible to suitably reduce the amount of first liquid that is wasted in the discharge process SD.

[0100] Furthermore, as described above, the liquid ejection device 100 can perform one or both of the filling process, which starts the discharge process SD when the liquid ejection head 50 is not filled with the first liquid, and the cleaning process, which starts the discharge process SD when the liquid ejection head 50 is filled with the first liquid. Therefore, it is possible to reduce the amount of first liquid that is wasted in one or both of the filling process and the cleaning process.

[0101] Furthermore, as described above, when the liquid ejection device 100 is capable of performing both the filling process and the cleaning process, the predetermined positive pressure in the cleaning process is lower than the predetermined positive pressure in the filling process. In the filling process, the pressure in the first tank 11_1 needs to be higher than that in the cleaning process in order to replace the air in the liquid ejection head 50 with liquid. In addition, if a filter (not shown) is disposed midway along the first supply flow path SJ_1, the pressure in the first tank 11_1 needs to be higher than that in the cleaning process in order to exceed the bubble point of the filter. Therefore, by making the pressure in the first tank 11_1 in the cleaning process lower than the pressure in the first tank 11_1 in the filling process, the filling process can be performed without excess or deficiency of liquid, and the amount of liquid wasted in the cleaning process can be reduced.

[0102] Furthermore, as described above, the liquid ejection device 100 includes a first atmosphere release valve 15_1 that can be opened and closed to open the inside of the first tank 11_1 to the atmosphere. The discharge process SD pressurizes the inside of the first tank 11_1 to a predetermined positive pressure by driving the first pressurizing mechanism 13_1 with the first atmosphere release valve 15_1 in a closed state. Therefore, by driving the first pressurizing mechanism 13_1 with the first atmosphere release valve 15_1 in a closed state, the inside of the first tank 11_1 can be efficiently pressurized to a predetermined positive pressure. Furthermore, by opening the inside of the first tank 11_1 to the atmosphere when necessary, the inside of the first tank 11_1 can be set to atmospheric pressure. This allows, for example, a pressure corresponding to the head difference between the first tank 11_1 and the liquid ejection head 50 to be applied to the ink in the nozzles N.

[0103] As described above, the discharge process SD stops the first pressurizing mechanism 13_1 before switching the first on-off valve 12_1 from the closed state to the open state. Therefore, even if the first pressurizing mechanism 13_1 is stopped, the pressure in the first tank 11_1 can be maintained at a predetermined positive pressure. As a result, power saving can be achieved.

[0104] Furthermore, as described above, the liquid ejection head 50 has an ejection surface FN including the first nozzle array LN1 and the second nozzle array LN2 that ejects a second liquid different from the first liquid. The liquid ejection device 100 includes a second tank 11_2, a second supply flow path SJ_2, a second on-off valve 12_2, and a second pressurizing mechanism 13_2. The second tank 11_2 stores the second liquid to be supplied to the second nozzle array LN2. The second supply flow path SJ_2 is a flow path for supplying the second liquid from the second tank 11_2 to the second nozzle array LN2. The second on-off valve 12_2 is provided midway along the second supply flow path SJ_2 and is capable of opening and closing the second supply flow path SJ_2. The second pressurizing mechanism 13_2 is capable of pressurizing the second tank 11_2.

[0105] Then, in the discharge process SD, the second pressurizing mechanism 13_2 is driven with the second on-off valve 12_2 in a closed state to set the pressure in the second tank 11_2 to a predetermined positive pressure, and then the second on-off valve 12_2 is opened to discharge the second liquid from the second nozzle row LN2. In this process SD, the second on-off valve 12_2 is switched from the open state to the closed state while the second liquid is being discharged from the second nozzle row LN2. Furthermore, in the discharge process SD, at least a portion of the period during which the first on-off valve 12_1 is maintained in the open state and the period during which the second on-off valve 12_2 is maintained in the open state overlap with each other. In other words, at least a portion of the period from timing t4 to timing t5 in the discharge process SD corresponding to the first nozzle row LN1 overlaps with that from timing t4 to timing t5 in the discharge process SD corresponding to the second nozzle row LN2. Therefore, when discharging liquid from the plurality of nozzle arrays LN that eject different types of liquid in the discharge process SD, the internal pressure of each of the plurality of nozzle arrays LN can be made positive, which reduces the risk of the first liquid in the nozzles N of the first nozzle array LN1 being contaminated by the second liquid entering the nozzles N of the first nozzle array LN1, and the risk of the second liquid in the nozzles N of the second nozzle array LN2 being contaminated by the first liquid entering the nozzles N of the second nozzle array LN2.

[0106] Furthermore, as described above, in the discharge process SD, the timing at which the first on-off valve 12_1 is switched from the closed state to the open state and the timing at which the second on-off valve 12_2 is switched from the closed state to the open state are the same, and the timing at which the first on-off valve 12_1 is switched from the open state to the closed state and the timing at which the second on-off valve 12_2 is switched from the open state to the closed state are the same, thereby further reducing contamination of the liquid in the first nozzle row LN1 and the second nozzle row LN2.

[0107] Furthermore, as described above, the liquid ejecting device 100 further includes a wiping member 61 that wipes the ejection surface FN. After the discharge process SD, the liquid ejecting device 100 performs a wiping operation in which the wiping member 61 wipes the ejection surface FN while both the first on-off valve 12_1 and the second on-off valve 12_2 are closed. Therefore, the wiping operation is performed while the internal pressure of each of the first nozzle row LN1 and the second nozzle row LN2 is positive, thereby making it possible to suitably reduce contamination of the liquid in the first nozzle row LN1 and the second nozzle row LN2.

[0108] As described above, the liquid ejection device 100 further includes an openable first atmosphere release valve 15_1 for opening the inside of the first tank 11_1 to the atmosphere and an openable second atmosphere release valve 15_2 for opening the inside of the second tank 11_2 to the atmosphere. The liquid ejection device 100 switches both the first atmosphere release valve 15_1 and the second atmosphere release valve 15_2 from the closed state to the open state after closing both the first on-off valve 12_1 and the second on-off valve 12_2 in the discharge process SD and before opening at least one of the first on-off valve 12_1 and the second on-off valve 12_2 after performing the wiping operation. This prevents ink from being unnecessarily discharged from the nozzles N due to the positive pressure remaining in the tank 11 acting on the first nozzle row LN1 and the second nozzle row LN2 when the first on-off valve 12_1 and the second on-off valve 12_2 are opened.

[0109] Furthermore, as described above, the liquid ejecting device 100 may switch the first atmosphere release valve 15_1 and the second atmosphere release valve 15_2 from the closed state to the open state during or before the wiping operation, which can shorten the time required for printing preparation, including the filling process, or the time required for the cleaning process.

[0110] As described above, the first nozzle row LN1 is composed of a plurality of nozzles N. The liquid ejection head 50 has a plurality of pressure chambers C that communicate with each of the plurality of nozzles N. The liquid ejection device 100 performs a flushing operation after performing a wiping operation. Here, the total amount of the first liquid ejected by the flushing operation from one of the plurality of nozzles N is equal to or less than the volume of the pressure chamber C that communicates with that one of the plurality of pressure chambers C. Because the liquid in the nozzle N is only slightly contaminated by the discharging process SD and wiping process SW described above, it is sufficient to discharge only the vicinity of the surface of the meniscus of the liquid in the nozzle N by the flushing operation. Therefore, contamination of the meniscus surface of the first liquid in the nozzle N can be removed with a small amount of ink.

[0111] Furthermore, as described above, it is preferable that each of the first liquid ejected from the first nozzle row LN1 and the second liquid ejected from the second nozzle row LN2 is a liquid containing at least one of cells, DNA, and proteins. Such biological liquids are generally expensive. Furthermore, such biological liquids are easily contaminated by mixing with each other, which can impair the functionality of the liquid. Therefore, it is extremely useful to reduce wasteful consumption of such liquids and to reduce contamination of the liquids.

[0112] Furthermore, as described above, the first nozzle row LN1 and the second nozzle row LN2 are provided on the same nozzle plate 51c, which is a significant advantage in reducing contamination of the liquid in the nozzle row LN.

[0113] Furthermore, as mentioned above, it is preferable that the shortest distance between the nozzles of the first nozzle row LN1 and the second nozzle row LN2 is 1.5 mm or less. In such a configuration where the shortest distance Dn is relatively short, liquid discharged from one of the first nozzle row LN1 and the second nozzle row LN2 moves to the other nozzle row LN, which makes it easy for the liquid in the nozzles N to become contaminated. Therefore, in this case, the discharging process SD and wiping process SW are significantly effective in reducing liquid contamination in the nozzle rows LN.

[0114] As described above, the maintenance method for the liquid jet head 50 includes a pressurizing process SP, an opening process SO, and a closing process SC. The pressurizing process SP pressurizes the inside of the first tank 11_1 while closing the first supply flow path SJ_1, which supplies the first liquid to the first nozzle row LN1 from the first tank 11_1 that stores the first liquid to be supplied to the first nozzle row LN1. The opening process SO discharges the first liquid from the first nozzle row LN1 by opening the first supply flow path SJ_1 after the pressurizing process SP. The closing process SC closes the first supply flow path SJ_1 at a timing when the first liquid is being discharged from the first nozzle row LN1 by the opening process SO.

[0115] In the above-described maintenance method for the liquid ejection head 50, the aforementioned discharge process SD is performed, thereby preventing the first liquid from being unnecessarily discharged from the first nozzle row LN1 and allowing the liquid to be distributed to all nozzles N that make up the first nozzle row LN1 in a short period of time.

[0116] As described above, the pressurization process SP pressurizes the second tank 11_2 while closing the second supply flow path SJ_2, which supplies the second liquid from the second tank 11_2 that stores the second liquid to be supplied to the second nozzle array LN2. The opening process SO discharges the second liquid from the second nozzle array LN2 by opening the second supply flow path SJ_2. The closing process SC closes the second supply flow path SJ_2 while the second liquid is being discharged from the second nozzle array LN2 in the opening process SO. Moreover, in the opening process SO, at least a portion of the period during which the first supply flow path SJ_1 is kept open and a portion of the period during which the second supply flow path SJ_2 is kept open overlap with each other. Therefore, when liquid is discharged from the multiple nozzle arrays LN that eject different types of liquid in the discharge process SD, the internal pressure of each of the multiple nozzle arrays LN can be made positive. As a result, contamination of the liquid in the first nozzle row LN1 and the second nozzle row LN2 can be suitably reduced.

[0117] Furthermore, as described above, the maintenance method for the liquid ejection head 50 further includes, after the closing step SC, a wiping step SW in which the ejection surface FN is wiped with the wiping member 61 while both the first supply flow path SJ_1 and the second supply flow path SJ_2 are closed. Therefore, the wiping step SW is performed while the internal pressure of each of the first nozzle row LN1 and the second nozzle row LN2 is positive, and therefore contamination of the liquid in the first nozzle row LN1 and the second nozzle row LN2 can be suitably reduced.

[0118] 2. Modification of the First Embodiment In the first embodiment, as shown in FIG. 5, the second time length T2, which is the length of the period for performing the opening process SO included in the filling process, and the second time length T2, which is the length of the period for performing the opening process SO included in the cleaning process, are the same length, but this configuration is not limited to this. In a modification of the first embodiment, the time length T2b (not shown), which is the length of the period during which the opening step SO included in the cleaning process is performed, may be shorter than the time length T2a (not shown), which is the length of the period during which the opening step SO included in the filling process is performed. By doing so, similar to the first embodiment, it is possible to perform the filling process without excess or deficiency of ink and reduce the amount of ink wasted in the cleaning process. In the first embodiment, the first pressure P1b, which is the predetermined positive pressure in the tank 11 after the pressurizing step SP as the cleaning process, is set to be lower than the first pressure P1a, which is the predetermined positive pressure in the tank 11 after the pressurizing step SP as the filling process. However, in a modification of the first embodiment, the first pressure P1b may be set to be lower than the first pressure P1a, similar to the first embodiment, or the first pressure P1b and the first pressure P1a may be set to be the same.

[0119] As described above, when the liquid ejecting device 100 is capable of performing both the filling process and the cleaning process, the time length T2b from when the first on-off valve 12_1 is opened to when it is closed during the cleaning process is shorter than the time length T2a from when the first on-off valve 12_1 is opened to when it is closed during the filling process. This allows the filling process to be performed without excess or deficiency of liquid, and reduces the amount of liquid wasted during the cleaning process.

[0120] 3. Second embodiment A second embodiment of the present disclosure will be described below. In the following exemplary embodiment, for elements whose actions and functions are similar to those of the first embodiment, the reference numerals used in the description of the first embodiment will be used, and detailed descriptions of each element will be omitted as appropriate.

[0121] 6 is a schematic diagram of a liquid supply mechanism 10A according to the second embodiment. This embodiment is similar to the first embodiment described above, except that a liquid supply mechanism 10A is used instead of the liquid supply mechanism 10.

[0122] The liquid supply mechanism 10A is configured in the same manner as the liquid supply mechanism 10 of the first embodiment, except that pressure adjustment valves 16_1 and 16_2 are added.

[0123] The pressure regulation valve 16_1 is provided between the first on-off valve 12_1 of the first supply flow path SJ_1 and the liquid jet head 50, and opens and closes in accordance with the pressure of ink inside the liquid jet head 50. On the other hand, the pressure regulation valve 16_2 is provided between the second on-off valve 12_2 of the second supply flow path SJ_2 and the liquid jet head 50, and opens and closes in accordance with the pressure of ink inside the liquid jet head 50. Each of the pressure regulation valves 16_1 and 16_2 is configured to be able to be forcibly opened regardless of the pressure inside the liquid jet head 50.

[0124] 7 is a cross-sectional view showing an example of the pressure regulating valve 16. As shown in FIG. 7, the pressure regulating valve 16 has an upstream flow path RJ1 and a downstream flow path RJ2, which form part of the supply flow path SJ. An ink inlet DI is provided in the upstream flow path RJ1, and an ink outlet DO is provided in the downstream flow path RJ2. Ink flows in from the tank 11 into the inlet DI. The outlet DO discharges ink to be supplied to the liquid ejection head 50.

[0125] The pressure regulating valve 16 includes a valve element 16a, a valve seat 16b, and springs 16c and 16d. The valve element 16a moves toward or away from the valve seat 16b in the direction W in the figure or in the opposite direction to open or close the upstream flow path RJ1.

[0126] The valve seat 16b is a portion of the support body 16e located between the upstream flow path RJ1 and the downstream flow path RJ2, and faces a portion of the flexible membrane 16f that seals the downstream flow path RJ2 with a gap therebetween. A through-hole K that penetrates the support body 16e is provided at approximately the center of the valve seat 16b. The upstream flow path RJ1 and the downstream flow path RJ2 communicate with each other via the through-hole K.

[0127] The valve element 16a is installed in the upstream flow path RJ1. The valve element 16a has a base 16a1, a sealing portion 16a2, and a valve stem 16a3. The base 16a1 is a circular flat plate with an outer diameter greater than the inner diameter of the through-hole K. The valve stem 16a3 protrudes coaxially and perpendicularly from the surface of the base 16a1, and the annular sealing portion 16a2 is installed to surround the valve stem 16a3 in a plan view. The axis O of the valve stem 16a3 is parallel to the W direction, and when the valve stem 16a3 is inserted into the through-hole K of the valve seat 16b, the base 16a1 and the sealing portion 16a2 are located in the upstream flow path RJ1. A gap is formed between the inner circumferential surface of the through-hole K of the valve seat 16b and the outer circumferential surface of the valve stem 16a3. Spring 16c is installed in upstream flow path RJ1 between the surface of support body 16e facing valve seat 16b and base 16a1 of valve element 16a, and urges valve element 16a toward valve seat 16b. On the other hand, spring 16d is installed in downstream flow path RJ2 between valve seat 16b and pressure plate 16g. Sealing portion 16a2 of valve element 16a is located between base 16a1 and valve seat 16b, and functions as a seal that closes through-hole K by contacting sealing surface FS of valve seat 16b.

[0128] An atmospheric pressure chamber RC, which communicates with an external space under atmospheric pressure, is adjacent to the downstream flow path RJ2 via a flexible membrane 16f. The flexible membrane 16f is a flexible, elastic membrane made of, for example, film, rubber, or fiber. As shown in FIG. 7 , when the pressure in the downstream flow path RJ2 is maintained within a predetermined range, the biasing force of the spring 16d presses the sealing portion 16a2 of the valve element 16a against the sealing surface FS of the valve seat 16b, thereby isolating the upstream flow path RJ1 from the downstream flow path RJ2. On the other hand, when the pressure in the downstream flow path RJ2 falls below a predetermined negative pressure, the sealing portion 16a2 of the valve element 16a moves away from the sealing surface FS of the valve seat 16b against the biasing forces of the springs 16c and 16d, thereby connecting the upstream flow path RJ1 to the downstream flow path RJ2. In other words, the pressure adjustment valve 16 is configured to set the pressure of the ink inside the liquid ejection head 50 to a predetermined negative pressure so that an ink meniscus that enables ink to be ejected from the nozzle N is formed inside the nozzle N.

[0129] In the pressure regulation valve 16, the pressure regulation chamber RV is adjacent to the atmospheric pressure chamber RC via an elastic member 16h. The elastic member 16h is a flexible plate-like member made of an elastic material such as rubber. The pressure regulation chamber RV communicates with a gas flow path port DA. A pump (not shown) is connected to the gas flow path port DA. The pump is capable of pressurizing the pressure regulation chamber RV under the control of the control unit 20. When the pump pressurizes the pressure regulation chamber RV, the elastic member 16h is deflected and deformed so as to press against the flexible membrane 16f. As a result, the sealing portion 16a2 of the valve element 16a can be separated from the sealing surface FS of the valve seat 16b against the biasing forces of the springs 16c and 16d. In this way, the upstream flow path RJ1 and the downstream flow path RJ2 can be connected to each other by the operation of the pump, regardless of the pressure in the downstream flow path RJ2.

[0130] The pressure adjustment valve 16 is forcibly kept open throughout the duration of the aforementioned discharge process SD. This allows the same discharge process SD as in the first embodiment to be performed. It is also preferable to forcibly keep the pressure adjustment valve 16 open during the period from the end of the discharge process SD until the end of the wiping process SW. This reduces contamination of the liquid in the nozzles N during the wiping operation. By stopping the forcible open state of the pressure adjustment valve 16 after the end of the wiping process SW and before the timing t9 at which the on-off valve 12 is switched from the closed state to the open state in step S17, ink can be appropriately supplied from the tank 11 to the liquid ejection head 50 in accordance with the pressure within the liquid ejection head 50.

[0131] According to the second embodiment described above, the amount of liquid wasted during the discharge process SD can also be reduced. The configuration of the pressure regulating valve 16 is not limited to the example shown in Fig. 7, and may be configured to forcibly open the valve by, for example, using a mechanism such as a cam to flexibly deform the elastic member 16h.

[0132] 4. Variations The above-described embodiments can be modified in various ways. Specific modifications are exemplified below. Two or more embodiments selected from the following examples can be combined as long as they are not mutually contradictory.

[0133] 4-1. Variation 1 In the above-described embodiment, a first liquid and a second liquid of different types are used, but the present invention is not limited to this embodiment. For example, one type of liquid or three or more types of liquid may be used. When one type of liquid is used, the one type of liquid corresponds to the "first liquid." When three or more types of liquid are used, one of two types of liquids arbitrarily selected from the three types of liquid corresponds to the "first liquid" and the other corresponds to the "second liquid." Furthermore, the type of liquid may differ for each head chip 51.

[0134] 4-2. Variation 2 In the above-described embodiment, an example is given in which the pressurizing mechanism 13 is directly connected to the tank 11, but this is not limited to this embodiment, and for example, the pressurizing mechanism 13 may be connected to a portion of the supply flow path SJ between the tank 11 and the on-off valve 12.

[0135] 4-3. Variation 3 In the above-described embodiment, an example is given in which the pressurizing mechanism 13 pressurizes the inside of the tank 11 by introducing gas into the tank 11, but this is not limited to this embodiment. For example, if the tank 11 is a flexible bag body, the pressurizing mechanism 13 may be configured to pressurize the inside of the tank 11 by pressing the tank 11 from the outside.

[0136] 4-4. Variation 4 The liquid ejection device may be configured to circulate the first liquid or the second liquid inside and outside the liquid ejection head 50. However, in cases where the first liquid or the second liquid is expensive, from the viewpoint of minimizing the amount of liquid used, it is preferable that such circulation not be performed.

[0137] 4-5. Variation 5 In the above-described embodiment, the pressure of the ink inside the liquid jet head 50 is adjusted to a predetermined negative pressure by either the head difference between the tank 11 and the liquid jet head 50 or the pressure adjustment valve 16, but the configuration for adjusting the pressure of the ink inside the liquid jet head 50 is not limited to these configurations. For example, the pressure of the ink inside the liquid jet head 50 may be adjusted by driving the pressurizing mechanism 13 based on information about the pressure inside the tank 11 measured by the pressure sensor 14.

[0138] 4-6. Variation 6 In the embodiment described above, the on-off valve 12 is disposed midway through the supply flow path SJ that is disposed outside the liquid jet head 50. However, this is not limiting. The on-off valve 12 may be disposed inside the liquid jet head 50, i.e., midway through the supply flow path SJ that is formed inside the liquid jet head 50.

[0139] 4-7. Variation 7 The liquid ejection apparatus 100 exemplified in each of the above embodiments can be employed in various devices, such as facsimile machines and copiers, as well as devices dedicated to printing. However, the use of the liquid ejection apparatus of the present invention is not limited to printing. For example, a liquid ejection apparatus that ejects a solution or dispersion of a color material as the first liquid or the second liquid is used as a manufacturing apparatus for forming color filters for liquid crystal display devices. Furthermore, a liquid ejection apparatus that ejects a solution or dispersion of a conductive material as the first liquid or the second liquid is used as a manufacturing apparatus for forming wiring and electrodes on a wiring substrate. [Explanation of symbols]

[0140] 10...liquid supply mechanism, 10A...liquid supply mechanism, 11...tank, 11_1...first tank, 11_2...second tank, 12...on-off valve, 12_1...first on-off valve, 12_2...second on-off valve, 13...pressurizing mechanism, 13_1...first pressurizing mechanism, 13_2...second pressurizing mechanism, 14...pressure sensor, 14_1...first pressure sensor, 14_2...second pressure sensor, 15...atmospheric release valve, 15_1...first atmosphere release valve, 15_2...second atmosphere release valve, 16...pressure adjustment valve, 16_1...pressure adjustment valve, 16_2...pressure adjustment valve, 16a...valve body, 16a1...base, 16a2...sealing portion, 16a3...valve stem , 16b...valve seat, 16c...spring, 16d...spring, 16e...support, 16f...flexible membrane, 16g...pressure receiving plate, 16h...elastic member, 20...control unit, 30...transport mechanism, 40...movement mechanism, 41...transport body, 42...transport belt, 50...liquid ejection head, 51...head chip, 51a...flow path substrate, 51b...pressure chamber substrate, 51c...nozzle plate, 51d...vibration absorber, 51e...vibration plate, 51f...driving element, 51g...protective plate, 51h...case, 51i...wiring board, 51j...driving circuit, 60...maintenance mechanism, 61...wiping member, 62...liquid receiving member, 100...liquid ejection Device, C...pressure chamber, Com...driving signal, DA...gas flow path port, DI...inlet, DO...outlet, Dn...shortest distance, FN...ejection surface, FS...sealing surface, IH...inlet, Img...image data, K...through hole, LN...nozzle row, LN1...first nozzle row, LN2...second nozzle row, M...medium, N...nozzle, Na...communicating flow path, O...axis, P1...first pressure, P2...second pressure, P3...third pressure, R...reservoir, R1...space, R2...space, RC...atmospheric pressure chamber, RJ1...upstream flow path, RJ2...downstream flow path, RV...pressure adjustment chamber, Ra...individual flow path, S11...step, S12...step , S13...step, S14...step, S15...step, S16...step, S17...step, S18...step, SC...closing process, SD...discharge process, SF...flushing process, SI...control signal, SJ...supply flow path, SJ_1...first supply flow path, SJ_2...second supply flow path, SO...opening process, SP...pressurizing process, SW...wiping process, t0...timing, t1...timing, t2...timing, t3...timing, t4...timing, t5...timing, t6...timing, t7...timing, t8...timing, t9...timing, t10...timing.

Claims

1. A liquid injection head having a first nozzle row for injecting a first liquid, a first tank for storing the first liquid supplied to the first nozzle row, a first supply channel for supplying the first liquid from the first tank to the first nozzle row, a first on-off valve provided in the middle of the first supply channel and capable of opening and closing the first supply channel, and a first pressurizing mechanism capable of pressurizing the inside of the first tank, by driving the first pressurizing mechanism with the first on-off valve in a closed state, after setting the pressure in the first tank to a predetermined positive pressure, and then setting the first on-off valve to an open state, it is possible to execute a discharge process for discharging the first liquid from the first nozzle row, the discharge process switches the first on-off valve from an open state to a closed state at the timing when the first liquid is being discharged from the first nozzle row, A liquid injection device characterized by the above.

2. Let the predetermined positive pressure be the first pressure, when the pressure in the first tank is set to the first pressure and then the first on-off valve is kept open until the pressure in the first tank becomes substantially constant, let the pressure in the first tank be the second pressure, when the pressure between the first pressure and the second pressure is the third pressure, the discharge process switches the first on-off valve from an open state to a closed state at the timing when the pressure in the first tank becomes the third pressure, The liquid injection device according to claim 1, characterized by the above.

3. Let the predetermined positive pressure be the first pressure, when the pressure in the first tank is set to the first pressure and then the first on-off valve is kept open until the pressure in the first tank becomes substantially constant, let the time length required from when the first on-off valve is opened until the pressure in the first tank becomes substantially constant be the first time length, when a time length shorter than the first time length is the second time length, the discharge process switches the first on-off valve from an open state to a closed state at the timing when the second time length has elapsed since the first on-off valve was opened, The liquid injection device according to claim 1, characterized by the above.

4. The second time length is half or less of the first time length, The liquid injection device according to claim 3, characterized by the above.

5. A filling process for starting the execution of the discharge process in a state where the liquid injection head is not filled with the first liquid, and / or a cleaning process for starting the execution of the discharge process in a state where the liquid injection head is filled with the first liquid, One or both of them can be executed. ​ ​ ​ ​ ​ ​ ​ The liquid ejecting apparatus according to claim 1, characterized in that...

6. Both the filling process and the cleaning process can be executed, wherein the predetermined positive pressure in the cleaning process is less than the predetermined positive pressure in the filling process. The liquid ejecting apparatus according to claim 5, characterized in that...

7. Both the filling process and the cleaning process can be executed, wherein the time length from when the first on-off valve in the cleaning process is opened until it is closed is shorter than the time length from when the first on-off valve in the filling process is opened until it is closed. The liquid ejecting apparatus according to claim 5, characterized in that...

8. It includes a first atmosphere release valve that can be opened and closed to release the inside of the first tank to the atmosphere, wherein in the discharging process, the inside of the first tank is pressurized to the predetermined positive pressure by driving the first pressurizing mechanism with the first atmosphere release valve in a closed state. The liquid ejecting apparatus according to claim 1, characterized in that...

9. In the discharging process, before switching the first on-off valve from the closed state to the open state, the first pressurizing mechanism is stopped. The liquid ejecting apparatus according to claim 8, characterized in that...

10. The liquid ejecting head has an ejection surface including a first nozzle row and a second nozzle row that ejects a second liquid of a type different from the first liquid. The liquid ejecting apparatus includes a second tank that stores the second liquid supplied to the second nozzle row, a second supply channel for supplying the second liquid from the second tank to the second nozzle row, a second on-off valve provided in the middle of the second supply channel and capable of opening and closing the second supply channel, and a second pressurizing mechanism capable of pressurizing the inside of the second tank. In the discharging process, after pressurizing the pressure inside the second tank to a predetermined positive pressure by driving the second pressurizing mechanism with the second on-off valve in a closed state, the second liquid is discharged from the second nozzle row by opening the second on-off valve. In the discharging process, at the timing when the second liquid is being discharged from the second nozzle row, the second on-off valve is switched from the open state to the closed state. In the discharging process, at least a part of the period during which the first on-off valve is maintained in the open state and the period during which the second on-off valve is maintained in the open state overlap with each other. The liquid ejecting apparatus according to claim 1, characterized in that...

11. In the discharging process, the timing of switching the first on-off valve from the closed state to the open state and The timing for switching the second on-off valve from the closed state to the open state is the same timing as each other and, the timing for switching the first on-off valve from the open state to the closed state and the timing for switching the second on-off valve from the open state to the closed state are the same timing as each other. The liquid injection device according to claim 10, characterized in that.

12. Further comprising a wiping member for wiping the injection surface, During the period in which both the first on-off valve and the second on-off valve are in the closed state after the discharge process Execute a wiping operation for wiping the injection surface with the wiping member. The liquid injection device according to claim 10, characterized in that.

13. A first atmosphere release valve that can be opened and closed to release the inside of the first tank to the atmosphere, A second atmosphere release valve that can be opened and closed to release the inside of the second tank to the atmosphere, further comprising 、 After both the first on-off valve and the second on-off valve are closed in the discharge process, And, at the timing before at least one of the first on-off valve and the second on-off valve is set to the open state after the execution of the wiping operation, both of the first atmosphere release valve and the second atmosphere release valve Are switched from the closed state to the open state. The liquid injection device according to claim 12, characterized in that.

14. During the execution period of the wiping operation, or before the execution of the wiping operation, the first atmosphere release valve and The second atmosphere release valve is switched from the closed state to the open state. The liquid injection device according to claim 13, characterized in that.

15. The first nozzle row is composed of a plurality of nozzles, The liquid injection head has a plurality of pressure chambers communicating with each of the plurality of nozzles for each nozzle After the execution of the wiping operation, a flushing operation is executed, 、 The total amount of the first liquid injected by the flushing operation from one of the plurality of nozzles Is less than or equal to the volume of the pressure chamber communicating with the one nozzle among the plurality of pressure chambers. The liquid injection device according to claim 12, characterized in that.

16. Each of the first liquid injected from the first nozzle row and the second liquid injected from the second nozzle row Is a liquid containing at least one of cells, DNA and proteins. The liquid injection device according to claim 11, characterized in that.

17. The first nozzle row and the second nozzle row are provided on the same nozzle plate as each other. The liquid injection device according to claim 16, characterized in that.

18.

18. 、

18.

18. The shortest distance between the nozzles of the first nozzle row and the second nozzle row is 1.5 mm or less. The liquid ejecting apparatus according to claim 17, characterized in that. [

19. ] A method for maintaining a liquid ejecting head having a first nozzle row for ejecting a first liquid, comprising: A pressurizing step of pressurizing the inside of the first tank while closing a first supply passage for supplying the first liquid from the first tank storing the first liquid supplied to the first nozzle row to the first nozzle row; 、 An opening step of discharging the first liquid from the first nozzle row by opening the first supply passage after the pressurizing step; A closing step of closing the first supply passage at a timing when the first liquid is being discharged from the first nozzle row by the opening step, Characterized in that it includes. A method for maintaining a liquid ejecting head, characterized in that. [

20. ] The liquid ejecting head has an ejection surface including the first nozzle row and a second nozzle row for ejecting a second liquid of a type different from the first liquid. In the pressurizing step, the inside of the second tank is pressurized while closing a second supply passage for supplying the second liquid from the second tank storing the second liquid supplied to the second nozzle row to the second nozzle row. In the opening step, the second liquid is discharged from the second nozzle row by opening the second supply passage. In the closing step, the second supply passage is closed at a timing when the second liquid is being discharged from the second nozzle row by the opening step. In the opening step, at least a part of the period during which the first supply passage is kept open and the period during which the second supply passage is kept open overlap each other. The method for maintaining a liquid ejecting head according to claim 19, characterized in that. [

21. ] After the closing step, the method further includes a wiping step of wiping the ejection surface with a wiping member while both the first supply passage and the second supply passage are closed. The method for maintaining a liquid ejecting head according to claim 20, characterized in that. [

22. ] The second time length is 1 / 5 or less of the first time length. The liquid ejecting apparatus according to claim 4, characterized in that. [

23. ] In the discharging process, during the period from the timing when the driving of the first pressurizing mechanism is stopped to the timing when the first on-off valve is switched from the closed state to the open state, the driving of the first pressurizing mechanism is stopped. ​ ​ ​ The liquid ejecting apparatus according to claim 9, characterized in that

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