Liquid discharge device, control method, recording medium, and program

Abstract

To provide an art which can resolve deposition of solid components in a relatively short time while reducing a load of a circulation pump.SOLUTION: A liquid discharge device includes: a circulation pump which is provided in a flow passage for supplying a liquid to a nozzle configured to discharge the liquid in a circulation manner and generates circulation flow of the liquid; and control means which controls driving of the circulation pump. The control means switches driving conditions of the circulation pump so that a flow rate of the liquid changes in a liquid circulation period.SELECTED DRAWING: Figure 25

Description

[Technical field]

[0001] The present invention relates to a control technique for a liquid ejection device. [Background technology]

[0002] As an example of a liquid ejection device, a recording device that ejects ink to record an image on a recording medium is known. In a recording device, the volatile components of the ink evaporate from the ejection openings of the nozzles, which may cause phenomena such as an increase in ink concentration or thickening of the ink. Such phenomena affect the quality of the recorded image. Therefore, a technology has been proposed for circulating the ink to the nozzles (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-169224 A [Patent Document 2] JP 2017-140807 A Summary of the Invention [Problem to be solved by the invention]

[0004] Ink is circulated, for example, during a printing operation. If circulation is stopped for a long time, precipitation of solid components may progress, and the circulation time required to resolve the precipitation may become long. Therefore, it is possible to resolve the precipitation in a relatively short circulation time by increasing the flow rate of the ink during circulation. However, this increases the load on the circulation pump, which may shorten the life of the circulation pump and increase power consumption.

[0005] The present invention provides a technique capable of eliminating precipitation of solid components in a relatively short period of time while reducing the load on the circulation pump. [Means for solving the problem]

[0006] According to the present invention, a circulation pump provided in a flow path that circulates the liquid to the nozzle that ejects the liquid, and that generates a circulating flow of the liquid; A control means for controlling the operation of the circulation pump; A liquid ejection device comprising: The control means switching a drive condition of the circulation pump so as to change a flow rate of the liquid during a circulation period of the liquid; A liquid ejection device is provided. Effect of the Invention

[0007] According to the present invention, it is possible to provide a technique capable of eliminating precipitation of solid components in a relatively short time while reducing the load on the circulation pump. [Brief description of the drawings]

[0008] [Figure 1] FIG. [Diagram 2] FIG. 2 is an explanatory diagram of an internal mechanism of the liquid ejection device of FIG. [Diagram 3] FIG. 2 is a block diagram of a control unit of the liquid ejection device of FIG. [Figure 4] An explanatory diagram of a recovery unit. [Diagram 5] FIG. [Figure 6] (a) is a longitudinal cross-sectional view of the ejection head, and (b) is an enlarged cross-sectional view of the ejection module. [Figure 7] Schematic diagram of a circulation unit. [Figure 8] FIG. [Figure 9] Block diagram of the circulation path. [Figure 10] 4(a) to (c) are explanatory diagrams of the pressure adjustment mechanism. [Figure 11] 4A and 4B are external perspective views of a circulating pump. [Figure 12] IX-IX line cross-sectional view of the circulating pump shown in FIG. [Figure 13]4A and 4B are exploded perspective views of a circulating pump. [Figure 14] FIG. 4 is a perspective view of the electrical connection portion of the piezoelectric ceramic as seen from the drive circuit board side. [Figure 15] FIG. 4 is a diagram illustrating the flow of ink inside the ejection head. [Figure 16] 4(a) and (b) are schematic diagrams showing the circulation path in the discharge unit. [Figure 17] FIG. [Figure 18] FIG. [Figure 19] 4A to 4C are cross-sectional views of the ejection unit showing the ink flow. [Figure 20] FIG. [Figure 21] FIG. 11 is a cross-sectional view showing the vicinity of a discharge port of a comparative example. [Figure 22] FIG. 13 is a diagram showing a comparative example of a discharge element substrate. [Diagram 23] 4A and 4B are diagrams showing the flow path configuration of the ejection head. [Figure 24] 4A is a flowchart showing an example of a control process for a circulating pump, and FIG. 4B is a diagram showing an example of a selection table for a drive pattern. [Diagram 25] 4A and 4B are timing charts showing examples of drive patterns of a circulation pump. [Figure 26] 4(a) to 4(d) are explanatory diagrams showing examples of ink flow patterns. [Figure 27] 6(a) to 6(c) are timing charts showing examples of drive patterns of a circulation pump. [Figure 28] 6(a) to 6(c) are timing charts showing examples of drive patterns of a circulation pump. [Figure 29] 4A and 4B are timing charts showing examples of drive patterns of a circulation pump. [Diagram 30] 4A is a flowchart showing an example of a control process for a circulating pump, and FIG. 4B is a diagram showing an example of a drive pattern selection. [Diagram 31] 6(a) to 6(c) are timing charts showing examples of drive patterns of a circulation pump. [Diagram 32] FIG. 13 is a graph showing the relationship between driving time and effect. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0010] <Outline of the liquid ejection device> Fig. 1 is an external view of a liquid ejection device 50 according to one embodiment of the present invention. Fig. 2 is an explanatory diagram of the internal mechanism of the liquid ejection device 50. In each drawing, arrows X, Y, and Z indicate directions that intersect with each other, and in this embodiment, arrows X and Y are horizontal directions that are perpendicular to each other and indicate the width direction and depth direction of the liquid ejection device 50, and arrow Z indicates the up-down direction (height direction).

[0011] The liquid ejection device 50 of this embodiment is an inkjet recording device that ejects ink as a liquid onto a recording medium to record an image on the recording medium. In this embodiment, a case where the present invention is applied to a serial type inkjet recording device will be described. The X direction is the reciprocating direction (main scanning direction) of the carriage 60, and the Y direction is the transport direction (sub-scanning direction) of the recording medium P. However, the present invention can also be applied to other types of recording devices.

[0012] In this embodiment, an example will be described in which a thermal method is adopted as an ejection element for ejecting liquid by generating bubbles using an electrothermal conversion element, but the present invention is not limited to this. The present invention can also be applied to an ejection head that employs an ejection method that ejects liquid using a piezoelectric element (piezo) or another ejection method.

[0013] In addition, "recording" includes not only the formation of meaningful information such as characters and figures, but also the formation of images, patterns, designs, etc. on a recording medium, regardless of whether they are meaningful or insignificant, or the processing of the medium, regardless of whether they are manifested in a way that can be visually perceived by humans. In addition, although a sheet of paper is assumed as the "recording medium" in this embodiment, it may also be cloth, plastic film, etc.

[0014] The liquid ejection device 50 includes an ejection head 1 that ejects ink as a liquid. The ejection head 1 is mounted on a carriage 60. The ejection head 1 is configured so that it can be removed from and attached to the carriage 60 by a user. The carriage 60 moves in the X direction along a guide shaft 51. A recovery unit 410 (see FIG. 4), not shown in FIGS. 1 and 2, is provided within the movement range of the carriage 60. The recovery unit 410 maintains and recovers the liquid ejection performance of the ejection head 1.

[0015] During recording, the recording medium P is transported in the Y direction on a platen 57 by a transport roller pair 55 and a transport roller pair 56. One of the transport roller pair 55 is a drive roller, and the other is a driven roller (e.g., a pinch roller). Similarly, one of the transport roller pair 56 is a drive roller, and the other is a driven roller (e.g., a pinch roller).

[0016] The liquid ejection device 50 is provided with an ink tank 2, which is an ink supply source, and an external pump 21. The ink stored in the ink tank 2 is supplied to the ejection head 1 via an ink supply tube 59 by the driving force of the external pump 21. The ejection head 1 is capable of ejecting four types of ink, for example, black (K), cyan (C), magenta (M), and yellow (Y), and is capable of recording a full-color image using these inks. The ejection head 1 is controlled by receiving an electrical signal via an electrical cable (not shown).

[0017] The ejection head 1 is provided with a circulation unit 54. The circulation unit 54 is a unit that circulates ink. In the case of this embodiment, the ejection head 1 is provided with four circulation units 54 corresponding to the four types of ink. The circulation unit 54 may be provided according to the type of liquid to be ejected, and multiple circulation units 54 may be provided for the same type of liquid. In other words, the ejection head 1 can be configured to include one or more circulation units 54.

[0018] The recording operation of the liquid ejection device 50 is started when the recording medium P is fed from a spool 106 holding the recording medium P by a feeding mechanism (not shown). The recording operation is performed by alternately repeating an intermittent transport operation of the recording medium P and a recording scan operation. The intermittent transport operation is an operation in which the recording medium P is transported a predetermined amount and then stopped, and is performed by a pair of transport rollers 55 and 56. The recording scan operation is an operation in which, while the transport of the recording medium P is stopped, the ejection head 1 is moved in the width direction of the recording medium P by the movement of the carriage 60, and ink is ejected. In the recording scan operation, the position of the carriage 60 is identified by reading the encoder 107 with an encoder sensor (not shown) provided on the carriage 60. The recording of an image on the recording medium P proceeds through such a recording operation.

[0019] In this embodiment, a so-called serial type recording device is given as an example, but the recording device may also use a full-line type ejection head capable of ejecting ink over the entire width of the recording medium P.

[0020] <Control unit> 3 is a block diagram of a control unit of the liquid ejection device 50. The CPU 100 controls the operation of each part of the liquid ejection device 50 based on programs such as processing procedures stored in the ROM 101. The RAM 102 is used as a work area when the CPU 100 executes processing. The CPU 100 receives image data from a host device 400 external to the liquid ejection device 50, controls the head driver 1A, and controls the driving of the ejection elements provided in the ejection head 1.

[0021] The CPU 100 also controls drivers of various actuators provided in the liquid ejection device 50. For example, the CPU 100 controls a motor driver 103A of a carriage motor 103, which is a drive source for moving the carriage 60, and a motor driver 104A of a conveying motor 104 for conveying the recording medium P. For example, the CPU 100 also controls a motor driver 22A of a recovery unit motor 22, etc. The moving mechanism of the carriage 60 is, for example, a belt transmission mechanism, and the carriage 60 can be moved by fixing the carriage 60 to an endless belt that runs by the driving force of the carriage motor 103. The recovery unit motor 22 is a motor mounted on the recovery unit 410. Furthermore, the CPU 100 controls a pump driver 500A that drives a circulation pump 500 described later, a pump driver 21A of the external pump 21, etc.

[0022] The head temperature sensor 25 is provided in the ejection head 1 and detects the temperature of the ejection head 1. The temperature and humidity sensor 24 detects the temperature and humidity of the environment surrounding the liquid ejection device 50, that is, the air temperature and humidity of the installation space of the liquid ejection device 50. The timer 23 measures time.

[0023] <Recovery unit configuration> FIG. 4 is a schematic diagram of the recovery unit 410. The cap 411 is supported by a lifting mechanism (not shown) so that it can be raised and lowered, and moves between a raised position and a lowered position. At the raised position, the cap 411 comes into contact with the ejection head 1 and covers (caps) its nozzle surface (ink ejection surface). The cap 411 forms a substantially sealed space by covering the nozzle surface of the ejection head 1. This makes it possible to prevent the nozzles of the ejection head 1 from drying out and the ink from evaporating during non-printing operations. In addition, by driving a suction pump 413 (described later), it is possible to suck ink from the ejection head 1 through the cap 411.

[0024] During a recording operation, the cap 411 is located in a lowered position to avoid interference with the ejection head 1 that moves together with the carriage 60. With the cap 411 located in the lowered position, the ejection head 1 can perform preliminary ejection onto the cap 411 when it moves to a position opposite the cap 411.

[0025] The wipers (wiper blades) 421 and 422 are made of an elastic material such as rubber, etc. In this embodiment, two wipers 421 spaced apart in the X direction, and a wiper 422 that wipes the entire nozzle surface are provided.

[0026] The wipers 421 and 422 are fixed to a wiper holder 420. The wiper holder 420 is movable along a guide 423 in the front-rear direction (the arrangement direction of the nozzles in the ejection head 1) as shown by an arrow W in the figure. When the ejection head 1 is positioned above the recovery unit 410, the wiper holder 420 moves in the direction of the arrow W (one direction), whereby the wipers 421 and 422 can perform a wiping operation in which they come into contact with the nozzle face and wipe the nozzle face. When the wiping operation is completed, the carriage 60 is moved and retracted from the area where the wiping operation is performed, and then the wiper holder 420 is moved to return the wipers 421 and 422 to their original positions (the positions before the wiping operation).

[0027] In this embodiment, the wiper is made of an elastic material such as rubber, but may be made of a porous material that absorbs ink. A vacuum wiper configuration capable of sucking the nozzle surface may be used. Alternatively, a configuration in which a nonwoven fabric is pressed against the nozzle surface by a pressing member to wipe the nozzle surface may be used. In this embodiment, wiping is performed only when the wiper moves in one direction, but a configuration in which wiping is performed when the wiper moves back and forth in both directions may be used. In this embodiment, the wiping direction is the nozzle arrangement direction in the ejection head 1, but a configuration in which the wiper moves in a direction intersecting (orthogonal to) that direction (arrangement direction of the nozzle row) may be used. In this configuration, the wiper may be fixed and the carriage 60 may move in the scanning direction to wipe the nozzle surface.

[0028] The suction pump 413 is driven with the cap 411 covering the nozzle surface of the ejection head 1 to make the inside a substantially sealed space, and performs a suction operation to suck ink from the ejection head 1 by generating negative pressure inside the cap 411. This suction operation is performed when filling the ejection head 1 with ink from an ink tank (initial filling) and when sucking and removing dust, stuck matter, air bubbles, etc. from inside the nozzles (suction recovery). The cap 411 is connected to a waste ink absorber (not shown) via a flexible tube 412.

[0029] In this embodiment, a tube pump is used as the suction pump 413. The tube pump has a holding section formed with a curved surface section along which (at least a part of) the tube 412 is held, a roller capable of pressing the held tube 412, and a roller support section rotatably supporting the roller. The tube pump rotates the roller while squeezing the tube 412 by rotating the roller support section in a predetermined direction. This generates negative pressure inside the cap 411, and sucks ink from the ejection head 1. The sucked ink is discharged through the tube 412 to a waste ink absorber (not shown).

[0030] The suction operation is also performed when preliminary ejection is performed by the ejection head 1 onto the cap 411, and ink received in the cap 411 by the preliminary ejection is discharged. That is, by driving the suction pump 413 when the ink that has been preliminary ejected and held in the cap 411 reaches a predetermined amount, the ink held in the cap 411 can be discharged to the waste ink absorber via the tube 412.

[0031] <Discharge head structure> The structure of the discharge head 1 will be described with reference to Fig. 2 as well as Fig. 5, Fig. 6(a) and Fig. 6(b). Fig. 5 is an exploded perspective view of the discharge head 1. Fig. 6(a) and Fig. 6(b) are vertical cross-sectional views of the discharge head 1. Fig. 6(a) is an overall vertical cross-sectional view of the discharge head 1, and Fig. 6(b) is an enlarged view of a discharge module 300.

[0032] The ejection head 1 includes a circulation unit 54 and an ejection unit 3 for ejecting the ink supplied from the circulation unit 54 onto a recording medium P. An ink supply tube 59 is provided to an external pump 21 connected to an ink tank 2 serving as an ink supply source (see FIG. 2). A liquid connector (not shown) is provided at the tip of the ink supply tube 59. When the ejection head 1 is mounted on the liquid ejection device 50, the liquid connector provided at the tip of the ink supply tube 59 is airtightly connected to a liquid connector insertion port (not shown) provided in a head housing 53 of the ejection head 1.

[0033] This forms an ink supply path that runs from the ink tank 2 through the external pump 21 to the ejection head 1. In this embodiment, four types of ink are used. For this reason, four sets of ink tank 2, external pump 21, ink supply tube 59, and circulation unit 54 are provided, and four ink supply paths corresponding to each ink are independently formed.

[0034] In this manner, the liquid ejection device 50 of this embodiment is provided with an ink supply system to which ink is supplied from the ink tank 2 provided outside the ejection head 1. It should be noted that the liquid ejection device 50 of this embodiment is not provided with an ink recovery system to recover ink in the ejection head 1 into the ink tank 2.

[0035] 6(a), the circulation units 54 are distinguished by the type of ink. That is, the ejection head 1 is provided with a circulation unit 54B for black ink, a circulation unit 54C for cyan ink, a circulation unit 54M for magenta ink, and an ink circulation unit 54Y for yellow ink. The circulation units 54B, 54C, 54M, and 54Y have substantially the same configuration, and in this embodiment, when there is no particular need to distinguish between the circulation units 54B, 54C, 54M, and 54Y, they are referred to as circulation units 54.

[0036] The discharge unit 3 forms a plurality of nozzles for discharging ink. Each nozzle includes a pressure chamber 12, a discharge port 13, and a discharge element 15. The discharge unit 3 includes two discharge modules 300, a first support member 4, a second support member 7, an electric wiring member (electric wiring tape) 5, and an electric contact substrate 6. The discharge module 300 includes a silicon substrate 310 having a thickness of 0.5 to 1 mm, and a plurality of discharge elements 15 provided on one side of the silicon substrate 310. In this embodiment, the discharge element 15 is configured by an electrothermal conversion element (heater) that generates thermal energy as discharge energy for discharging liquid. Electric power is supplied to each discharge element 15 via an electric wiring formed on the silicon substrate 310 by a film forming technique. A discharge port forming member 320 is formed on the surface (the lower surface in FIG. 6(b)) of the silicon substrate 310. In the ejection port forming member 320, a plurality of pressure chambers 12 corresponding to the plurality of ejection elements 15, and a plurality of ejection ports 13 for ejecting ink are formed by photolithography.

[0037] In the silicon substrate 310, an individual supply flow path 18 and an individual recovery flow path 19 communicating with each pressure chamber 12 are formed. In this embodiment, one ejection module 300 is configured to eject two types of ink. That is, of the two ejection modules 300 shown in FIG. 6(a), the ejection module 300 located on the left side of the figure ejects black ink and cyan ink, and the ejection module 300 located on the right side of the figure ejects magenta ink and yellow ink. Furthermore, in the example shown in FIG. 6(a), two ejection port arrays extending in the Y direction are formed for one color of ink. For each of the multiple ejection ports 13 constituting each ejection port array, a pressure chamber 12, an individual supply flow path 18, and an individual recovery flow path 19 are formed.

[0038] An ink supply port and an ink recovery port, which will be described later, are formed on the back surface (upper surface in FIG. 6(b)) of the silicon substrate 310. The ink supply port supplies ink from an ink supply flow path 48 to the multiple individual supply flow paths 18, and the ink recovery port recovers ink from the multiple individual recovery flow paths 19 to an ink recovery flow path 49.

[0039] The ink supply port and ink recovery port referred to here refer to openings that supply and recover ink during forward ink circulation, which will be described later. That is, during forward ink circulation, ink is supplied from the ink supply port to each individual supply flow path 18, and ink is recovered from each individual recovery flow path 19 to the ink recovery port. However, during ink circulation in a direction opposite to the forward direction, ink is supplied from the ink recovery port described above to the individual recovery flow path 19, and ink is recovered from the individual supply flow path 18 to the ink supply port.

[0040] As shown in FIG. 6(a), the back surface (upper surface in FIG. 6(a)) of the ejection module 300 is adhesively fixed to one surface (lower surface in FIG. 6(a)) of the first support member 4. An ink supply flow path 48 and an ink recovery flow path 49 are formed in the first support member 4, penetrating from one surface to the other surface. One opening of the ink supply flow path 48 is connected to the aforementioned ink supply port in the silicon substrate 310, and one opening of the ink recovery flow path 49 is connected to the aforementioned ink recovery port in the silicon substrate 310. The ink supply flow path 48 and the ink recovery flow path 49 are provided independently for each type of ink.

[0041] A second support member 7 having an opening 7a (see FIG. 5) through which the ejection module 300 is inserted is adhesively fixed to the other surface (the upper surface in FIG. 6(a)) of the first support member 4. The second support member 7 holds an electrical wiring member 5 that is electrically connected to the ejection module 300. The electrical wiring member 5 is a member for applying an electrical signal to the ejection module 300 for ejecting ink. The electrical connection portion between the ejection module 300 and the electrical wiring member 5 is sealed with a sealant and is protected from corrosion by ink and external impacts.

[0042] Furthermore, an electrical contact board 6 is thermocompression bonded to an end 5a (see FIG. 5) of the electrical wiring member 5 using an anisotropic conductive film (not shown), and the electrical wiring member 5 and the electrical contact board 6 are electrically connected to each other. The electrical contact board 6 has an external signal input terminal (not shown) for receiving an electrical signal from the liquid ejection device 50.

[0043] Furthermore, a joint member 8 (FIG. 6(a)) is provided between the first support member 4 and the circulation unit 54. A supply port 88 and a recovery port 89 are formed in the joint member 8 for each type of ink. The supply port 88 and the recovery port 89 serve to communicate the ink supply flow path 48 and the ink recovery flow path 49 of the first support member 4 with the flow paths formed in the circulation unit 54. In FIG. 6(a), the supply port 88B and the recovery port 89B correspond to black ink, and the supply port 88C and the recovery port 89C correspond to cyan ink. Furthermore, the supply port 88M and the recovery port 89M correspond to magenta ink, and the supply port 88Y and the recovery port 89Y correspond to yellow ink.

[0044] The openings at one end of the ink supply flow path 48 and the ink recovery flow path 49 of the first support member 4 have a small opening area that matches the ink supply port and ink recovery port in the silicon substrate 310. In contrast, the opening areas of the openings at the other end of the ink supply flow path 48 and the ink recovery flow path 49 of the first support member 4 have a shape that is expanded to the same opening area as the large opening area of ​​the joint member 8 formed to match the flow path of the circulation unit 54. By adopting such a configuration, it is possible to suppress an increase in flow path resistance for the ink collected from each recovery flow path.

[0045] In the ejection head 1 having the above configuration, ink supplied to the circulation unit 54 passes through the supply port 88 of the joint member 8 and the ink supply flow path 48 of the first support member 4, and flows from the ink supply port of the ejection module 300 into the individual supply flow path 18. The ink then flows from the individual supply flow path 18 into the pressure chamber 12, and a portion of the ink that has flowed into the pressure chamber 12 is ejected from the ejection port 13 by driving the ejection element 15. The remaining ink that has not been ejected passes from the pressure chamber 12 through the individual recovery flow path 19 and flows from the ink recovery port into the ink recovery flow path 49 of the first support member 4. The ink that has flowed into the ink recovery flow path 49 then flows into the circulation unit 54 through the recovery port 89 of the joint member 8 and is recovered.

[0046] <Circulation unit structure> Fig. 7 is a schematic diagram of the circulation unit 54. The circulation unit 54 in Fig. 7 shows one circulation unit 54 corresponding to one type of ink, and each of the circulation units 54B, 54C, 54M, and 54Y has a similar structure to the circulation unit 54 in Fig. 7.

[0047] The circulation unit 54 includes a filter 110, a first pressure adjustment mechanism 120, a second pressure adjustment mechanism 150, and a circulation pump 500 that generates a circulating flow. These components are connected by respective flow paths as shown in Fig. 8 and Fig. 9, and form a circulation path (circulation flow path) in the ejection head 1 that supplies and recovers ink to and from the ejection module 300.

[0048] Fig. 8 is a vertical cross-sectional view that shows a schematic diagram of a circulation path for one type of ink (one color of ink) that is configured inside the ejection head 1. Fig. 9 is a block diagram that shows a schematic diagram of the circulation path shown in Fig. 8.

[0049] The first pressure adjustment mechanism 120 includes a first valve chamber 121 and a first pressure control chamber 122. The second pressure adjustment mechanism 150 includes a second valve chamber 151 and a second pressure control chamber 152. The first pressure adjustment mechanism 120 is configured to have a relatively higher control pressure than the second pressure adjustment mechanism 150. In this embodiment, by using these two pressure adjustment mechanisms 120 and 150, the circulation of ink in the circulation path is achieved within a certain pressure range.

[0050] The ink is configured to flow near the pressure chamber 12 (ejection element 15) at a flow rate according to the pressure difference between the first pressure adjustment mechanism 120 and the second pressure adjustment mechanism 150. Below, we will explain the circulation path in the ejection head 1 and the flow of ink within the circulation path. Note that the arrows in each figure indicate the direction of ink flow.

[0051] First, the connection state of each component in the ejection head 1 will be described. An external pump 21 that sends ink contained in an ink tank 2 provided outside the ejection head 1 to the ejection head 1 is connected to a circulation unit 54 via an ink supply tube 59 (FIG. 2). A filter 110 is provided in the ink flow path located upstream of the circulation unit 54. The ink flow path located downstream of the filter 110 is connected to a first valve chamber 121 of a first pressure adjustment mechanism 120. The first valve chamber 121 communicates with a first pressure control chamber 122 via a communication port 191A that is opened and closed by a valve 190A shown in FIG.

[0052] The first pressure control chamber 122 is connected to the supply flow path 130, the bypass flow path 160, and the pump outlet flow path 180 of the circulation pump 500. The supply flow path 130 is connected to the individual supply flow paths 18 via an ink supply port provided in the ejection module 300. In addition, the bypass flow path 160 is connected to a second valve chamber 151 provided in the second pressure adjustment mechanism 150. The second valve chamber 151 is connected to the second pressure control chamber 152 via a communication port 191B that is opened and closed by a valve 190B shown in FIG.

[0053] The second pressure control chamber 152 is connected to the recovery flow path 140. The recovery flow path 140 is connected to the individual recovery flow path 19 via an ink recovery port provided in the ejection module 300. Furthermore, the second pressure control chamber 152 is connected to the circulation pump 500 via a pump inlet flow path 170. In addition, in FIG. 8, an inlet 170a indicates the inlet of the pump inlet flow path 170.

[0054] Next, the flow of ink in the ejection head 1 will be described. As shown in Fig. 9, the ink stored in the ink tank 2 is pressurized by an external pump 21 provided in the liquid ejection device 50, and is supplied to a circulation unit 54 of the ejection head 1 as a positive pressure ink flow. The ink supplied to the circulation unit 54 passes through a filter 110 to remove foreign matter such as dust, and then flows into a first valve chamber 121 provided in a first pressure adjustment mechanism 120. At this time, the ink is depressurized from positive pressure to negative pressure.

[0055] Next, the flow of ink in the circulation path will be described. The circulation pump 500 operates to pump ink sucked from the pump inlet flow path 170 on the upstream side thereof to the pump outlet flow path 180 on the downstream side thereof. When the circulation pump 500 is driven, the ink supplied to the first pressure control chamber 122 flows into the supply flow path 130 and the bypass flow path 160 together with the ink sent from the pump outlet flow path 180.

[0056] Although details will be described later, in this embodiment, a piezoelectric diaphragm pump using a piezoelectric element attached to a diaphragm as a drive source is used as the circulation pump 500. The piezoelectric diaphragm pump is a pump that changes the volume of the pump chamber by inputting a drive voltage to the piezoelectric element, and delivers liquid by alternately moving two check valves due to pressure fluctuations.

[0057] The ink that has flowed into the supply flow path 130 flows from the ink supply port of the ejection module 300 through the individual supply flow path 18 into the pressure chamber 12, and some of the ink is supplied to the ejection port 13 and ejected from the ejection port 13 by driving (heat generation) the ejection element 15. The remaining ink that is not used for ejection flows through the pressure chamber 12, passes through the individual recovery flow path 19, and then flows into the recovery flow path 140 connected to the ejection module 300. The ink that has flowed into the recovery flow path 140 flows into the second pressure control chamber 152 of the second pressure adjustment mechanism 150.

[0058] On the other hand, the ink that has flowed into the bypass flow path 160 flows into the second valve chamber 151, and then passes through the communication port 191B and flows into the second pressure control chamber 152. The ink that has flowed into the second pressure control chamber 152 via the bypass flow path 160 and the ink recovered from the recovery flow path 140 are sucked into the circulation pump 500 via the pump inlet flow path 170 by the drive of the circulation pump 500.

[0059] Then, the ink sucked into the circulation pump 500 is sent to the pump outlet flow path 180 and flows again into the first pressure control chamber 122. Thereafter, the ink that flows from the first pressure control chamber 122 through the supply flow path 130 and the ejection module 300 into the second pressure control chamber 152, and the ink that flows into the second pressure control chamber 152 through the bypass flow path 160, flow into the circulation pump 500. Then, the ink is sent from the circulation pump 500 to the first pressure control chamber 122. In this manner, the ink circulates in the circulation path.

[0060] As described above, the circulation pump 500 provided in the circulation path can circulate the ink in the circulation path including the ejection module 300. This makes it possible to suppress thickening of the ink and accumulation of sedimentation components of the ink color material in the ejection module 300, and makes it possible to maintain good ink fluidity in the ejection module 300 and ejection characteristics at the ejection port.

[0061] In addition, since there is no need to circulate the ink outside the ejection head 1, a small pump can be used as the circulation pump 500, thereby making it possible to miniaturize the device. However, it is also possible to adopt a configuration in which the ink is circulated through a path also outside the ejection head 1.

[0062] <Pressure adjustment mechanism> 10(a) to 10(c), the configurations and operations of the first pressure adjustment mechanism 120 and the second pressure adjustment mechanism 150 will be described in more detail. Since the first pressure adjustment mechanism 120 and the second pressure adjustment mechanism 150 have the same configuration, the first pressure adjustment mechanism 120 will be described as an example below. For the second pressure adjustment mechanism 150, the same reference numerals are used for parts corresponding to the first pressure adjustment mechanism 120 in FIGS. 10(a) to 10(c). In the case of the second pressure adjustment mechanism 150, the first valve chamber 121 described below should be read as the second valve chamber 151, and the first pressure control chamber 122 should be read as the second pressure control chamber 152.

[0063] The first pressure adjustment mechanism 120 has a first valve chamber 121 and a first pressure control chamber 122 formed in a cylindrical casing 125. The first valve chamber 121 and the first pressure control chamber 122 are separated by a partition wall 123 provided in the cylindrical casing 125. However, the first valve chamber 121 communicates with the first pressure control chamber 122 via a communication port 191 formed in the partition wall 123.

[0064] The first valve chamber 121 is provided with a valve 190 that switches between communication and cut-off between the first valve chamber 121 and the first pressure control chamber 122 at a communication port 191. The valve 190 is held in a position facing the communication port 191 by a valve spring 200, and has a configuration that allows it to come into close contact with the partition wall 123 by the biasing force of the valve spring 200. When the valve 190 comes into close contact with the partition wall 123, the flow of ink through the communication port 191 is cut off.

[0065] In order to increase the close contact with the partition wall 123, the contact portion of the valve 190 with the partition wall 123 may be made of an elastic material.

[0066] A valve shaft 190a protrudes from the center of the valve 190 and is inserted into the communication port 191. By pressing this valve shaft 190a against the biasing force of a valve spring 200, the valve 190 moves away from the partition wall 123, allowing ink to flow through the communication port 191. Hereinafter, the state in which the valve 190 blocks the flow of ink through the communication port 191 is referred to as the "closed state," and the state in which ink can flow through the communication port 191 is referred to as the "open state."

[0067] The opening of the cylindrical housing 125 is closed by the flexible member 230 and the pressure plate 210. The first pressure control chamber 122 is formed by the flexible member 230, the pressure plate 210, the peripheral wall of the housing 125, and the partition wall 123. The pressure plate 210 is configured to be displaceable in accordance with the displacement of the flexible member 230. The materials of the pressure plate 210 and the flexible member 230 are not particularly limited, but for example, the pressure plate 210 can be configured from a resin molded part, and the flexible member 230 can be configured from a resin film. In this case, the pressure plate 210 can be fixed to the flexible member 230 by thermal welding.

[0068] A pressure adjustment spring 220 is provided between the pressure plate 210 and the partition wall 123. The pressure plate 210 and the flexible member 230 are biased by the biasing force of the pressure adjustment spring 220 in a direction in which the internal volume of the first pressure control chamber 122 expands. When the pressure in the first pressure control chamber 122 decreases, the pressure plate 210 and the flexible member 230 are displaced in a direction in which the internal volume of the first pressure control chamber 122 decreases against the pressure of the pressure adjustment spring 220. When the internal volume of the first pressure control chamber 122 decreases to a certain amount, the pressure plate 210 abuts against the valve shaft 190a of the valve 190. When the internal volume of the first pressure control chamber 122 further decreases thereafter, the valve 190 moves together with the valve shaft 190a against the biasing force of the valve spring 200 and moves away from the partition wall 123. As a result, the communication port 191 is opened.

[0069] In this embodiment, the pressure in the first valve chamber 121 when the communication port 191 is in the open state is designed to be higher than the pressure in the first pressure control chamber 122. As a result, when the communication port 191 is in the open state, ink flows from the first valve chamber 121 to the first pressure control chamber 122. This ink inflow displaces the flexible member 230 and the pressure plate 210 in a direction increasing the internal volume of the first pressure control chamber 122. As a result, the pressure plate 210 moves away from the valve shaft 190a of the valve 190, and the communication port 191 is brought into close contact with the partition wall 123 by the biasing force of the valve spring 200, and the communication port 191 is in a closed state.

[0070] In this way, in the first pressure adjustment mechanism 120 of this embodiment, when the pressure inside the first pressure control chamber 122 decreases to a certain pressure or below (for example, when the negative pressure becomes stronger), ink flows in from the first valve chamber 121 via the communication port 191. This prevents the pressure in the first pressure control chamber 122 from decreasing any further. Therefore, the pressure in the first pressure control chamber 122 is controlled to be kept within a certain range.

[0071] Next, the pressure in the first pressure control chamber 122 will be described in more detail. As described above, the flexible member 230 and the pressure plate 210 are displaced in response to the pressure in the first pressure control chamber 122, and the pressure plate 210 comes into contact with the valve shaft 190a, opening the communication port 191 (the state shown in FIG. 10(b)). At this time, the relationship of the forces acting on the pressure plate 210 is expressed by the following formula 1.

[0072] P2×S2+F2+(P1-P2)×S1+F1=0...Equation 1 Furthermore, rearranging Equation 1 for P2 gives P2=-(F1+F2+P1×S1) / (S2-S1)...Equation 2 It becomes. P1: Pressure (gauge pressure) of the first valve chamber 121 P2: Pressure (gauge pressure) of the first pressure control chamber 122 F1: Valve spring force 200 F2: Spring force of the pressure adjusting spring 220 S1: Pressure receiving area of ​​valve 190 S2: Pressure receiving area of ​​the pressure plate 210 Here, the spring force F1 of the valve spring 200 and the spring force F2 of the pressure adjustment spring 220 are positive (rightward in FIG. 10) in the direction pressing the valve 190 and the pressure plate 210. In addition, the pressure P1 in the first valve chamber 121 and the pressure P2 in the first pressure control chamber 122 are configured so that P1 satisfies the relationship P1≧P2.

[0073] The pressure P2 in the first pressure control chamber 122 when the communication port 191 is open is determined by formula 2, and when the communication port 191 is open, due to the relationship P1≧P2, ink flows from the first valve chamber 121 into the first pressure control chamber 122. As a result, the pressure P2 in the first pressure control chamber 122 does not decrease any further, and P2 is maintained within a certain pressure range.

[0074] On the other hand, as shown in FIG. 10(c), when the pressure plate 210 is not in contact with the valve shaft 190a and the communication port 191 is closed, the relationship of the forces acting on the pressure plate 210 is expressed by Equation 3.

[0075] P3×S3+F3=0...Equation 3 Now, rearrange Equation 3 for P3 as follows: P3 = -F3 / S3 Equation 4 F3: The spring force of the pressure adjusting spring 220 when the pressure plate 210 and the valve shaft 190a are not in contact with each other P3: pressure (gauge pressure) in the first pressure control chamber 122 when the pressure plate 210 and the valve shaft 190a are not in contact with each other S3: Pressure-receiving area of ​​the pressure plate 210 when the pressure plate 210 and the valve shaft 190a are not in contact with each other It becomes.

[0076] 10(c) shows a state in which the pressure plate 210 and the flexible member 230 have been displaced to the right to their limit. Depending on the amount of displacement of the pressure plate 210 and the flexible member 230 until they reach the state shown in FIG. 10(c), the pressure P3 in the first pressure control chamber 122, the spring force F3 of the pressure adjustment spring 220, and the pressure-receiving area S3 of the pressure plate 210 change.

[0077] 10(c), the pressure-receiving area S3 of the pressure plate 210 becomes smaller and the spring force F3 of the pressure adjustment spring 220 becomes larger. As a result, the pressure P3 in the first pressure control chamber 122 becomes smaller according to the relationship in formula 4.

[0078] Therefore, according to formulas 2 and 4, the pressure in the first pressure control chamber 122 gradually increases (i.e., the negative pressure weakens and approaches the positive pressure) from the state shown in Fig. 10(b) to the state shown in Fig. 10(c). That is, the pressure plate 210 and the flexible member 230 gradually displace to the right from the state in which the communication port 191 is open, and the pressure in the first pressure control chamber gradually increases until the internal volume of the first pressure control chamber 122 finally reaches the limit of possible displacement. In other words, the negative pressure weakens.

[0079] <Circulation pump> Next, the configuration and operation of the circulation pump 500 will be described in detail with reference to Figures 11(a), 11(b) and 12. Figures 11(a) and 11(b) are external perspective views of the circulation pump 500. Figure 11(a) is an external perspective view showing the front side of the circulation pump 500, and Figure 11(b) is an external perspective view showing the rear side of the circulation pump 500.

[0080] The outer shell of the circulation pump 500 is composed of a pump housing 505 and a cover 507 fixed to the pump housing 505. The pump housing 505 is composed of a housing part main body 505a and a flow path connecting member 505b adhesively fixed to the outer surface of the housing part main body 505a.

[0081] A pair of through holes communicating with each other is provided at two different positions in each of the housing main body 505a and the flow path connection member 505b. The pair of through holes provided at one position forms the pump supply hole 501, and the pair of through holes provided at the other position forms the pump discharge hole 502.

[0082] The pump supply hole 501 is connected to a pump inlet flow path 170 which is connected to the second pressure control chamber 152, and the pump discharge hole 502 is connected to a pump outlet flow path 180 which is connected to the first pressure control chamber 122. Ink supplied from the pump supply hole 501 passes through a pump chamber 503 which will be described later, and is discharged from the pump discharge hole 502.

[0083] Fig. 12 is a cross-sectional view of the circulating pump 500 shown in Fig. 11(a) taken along line IX-IX. A diaphragm 506 is joined to the inner surface of a pump housing 505, and a pump chamber 503 is formed between the diaphragm 506 and a recess formed in the inner surface of the pump housing 505.

[0084] Pump chamber 503 communicates with pump supply hole 501 and pump discharge hole 502 formed in pump housing 505. A check valve 504a is provided in the middle of pump supply hole 501, and a check valve 504b is provided in the middle of pump discharge hole 502.

[0085] Specifically, check valve 504a is disposed in space 512a formed in the middle of pump supply hole 501 such that a portion of check valve 504a can move leftward in the figure. Check valve 504b is disposed in space 512b formed in the middle of pump discharge hole 502 such that a portion of check valve 504b can move rightward in the figure.

[0086] When diaphragm 506 is displaced and the volume of pump chamber 503 increases, reducing the pressure in pump chamber 503, so that check valve 504a moves away from the opening of pump supply hole 501 in space 512a (i.e., moves to the left in the figure). Valve 504a moves away from the opening of pump supply hole 501 in space 512a, and thus opens to allow ink to flow through pump supply hole 501.

[0087] When diaphragm 506 is displaced and the volume of pump chamber 503 is reduced, thereby pressurizing pump chamber 503, check valve 504a comes into close contact with the wall surface surrounding the opening of pump supply hole 501, thereby closing the flow of ink through pump supply hole 501.

[0088] When the pump chamber 503 is depressurized, the check valve 504b comes into close contact with the wall surface surrounding the opening of the pump housing 505 and enters a closed state in which it blocks the flow of ink through the pump discharge hole 502. When the pump chamber 503 is pressurized, the check valve 504b moves away from the opening of the pump housing 505 toward the space 512b (i.e., moves to the right in the figure), allowing the flow of ink through the pump discharge hole 502.

[0089] The material of each of the check valves 504a and 504b may be any material that can deform in response to the pressure in the pump chamber 503, and may be, for example, an elastic material such as EPDM or elastomer, or a film or thin plate such as polypropylene, but is not limited to these.

[0090] The pump chamber 503 is formed by joining a pump housing 505 and a diaphragm 506. Therefore, the pressure in the pump chamber 503 changes when the diaphragm 506 is deformed.

[0091] For example, when diaphragm 506 is displaced toward pump housing 505 (displaced to the right in the figure) and the volume of pump chamber 503 decreases, the pressure inside pump chamber 503 increases. This causes check valve 504b arranged opposite pump discharge hole 502 to open, and ink is discharged from pump chamber 503. At this time, check valve 504a arranged opposite pump supply hole 501 is in close contact with the wall surface surrounding pump supply hole 501, so that backflow of ink from pump chamber 503 to pump supply hole 501 is suppressed.

[0092] Conversely, when diaphragm 506 is displaced in the direction in which pump chamber 503 expands, the pressure in pump chamber 503 decreases. As a result, check valve 504a arranged opposite pump supply hole 501 opens, and ink is supplied to pump chamber 503. At this time, check valve 504b arranged in pump discharge hole 502 comes into close contact with the wall surface surrounding an opening formed in pump housing 505 to close said opening, thereby suppressing the backflow of ink from pump discharge hole 502 to pump chamber 503.

[0093] In this way, in the circulation pump 500, the diaphragm 506 deforms, changing the pressure inside the pump chamber 503, thereby sucking in and discharging ink. At this time, if bubbles get into the pump chamber 503, even if the diaphragm 506 is displaced, the expansion and contraction of the bubbles reduces the change in pressure inside the pump chamber 503, and the amount of liquid delivered decreases.

[0094] Therefore, pump chamber 503 is arranged parallel to gravity to make it easier for bubbles mixed in pump chamber 503 to gather at the top of pump chamber 503, and pump discharge hole 502 is arranged above the center of pump chamber 503. This makes it possible to improve the discharge of bubbles from within the pump, and stabilize the flow rate.

[0095] Next, a drive unit for displacing the diaphragm 506 will be described with reference to FIGS. 13(a), 13(b) and 14. FIG.

[0096] 13(a) and 13(b) are exploded perspective views of a circulation pump 500. The circulation pump 500 is a piezoelectric pump that is driven by applying a voltage to a piezoelectric ceramic, and a vibration plate 509 is bonded to a diaphragm 506 with an adhesive 508, and a piezoelectric ceramic 510 is fixed to the vibration plate 509 by adhesion.

[0097] Diaphragm 506 can be made of injection moldable materials such as modified PPE+PS and polypropylene, but may also be made of a film or a punched resin plate, and is not limited to these. Diaphragm 509 can be made of brass, stainless steel, iron-nickel alloy, etc., but is not limited to these.

[0098] A drive circuit board 513 is provided on the surface facing the piezoelectric ceramic 510, and the drive circuit board 513 is supplied with power from the power supply of the liquid ejection device 50 to apply a voltage to the piezoelectric ceramic 510 and the diaphragm 509 to drive them. Fig. 14 is a see-through view of the electrical connection part of the piezoelectric ceramic 510 from the drive circuit board 513 side.

[0099] The drive circuit board 513, the piezoelectric ceramic 510, and the diaphragm 509 are each electrically connected by an electrical connection cable 518. The electrical connection cable 518 and the drive circuit board 513 are fixed and electrically connected by solder 521, and the electrical connection cable 518, the piezoelectric ceramic 510, and the diaphragm 509 are fixed and electrically connected by solder 520.

[0100] The diaphragm 509 is connected to the GND wiring of the drive circuit board 513 via an electrical connection cable 518 , and the piezoelectric ceramic 510 is connected to an AC voltage output section of the drive circuit board 513 via the electrical connection cable 518 .

[0101] The vibration plate 509 is connected to GND, and an AC voltage is applied to the piezoelectric ceramic 510 to expand and contract the piezoelectric ceramic 510 and deform the diaphragm, thereby changing the pressure inside the pump chamber and sucking and discharging ink.

[0102] The drive circuit board 513 is electrically connected to the electrical contact board 6 (FIG. 5) by a cable, and the electrical contact board 6 is provided with an electrical connection terminal for driving the pump. When the carriage 60 is attached, an electrical signal from the electrical contact section on the carriage 60 side is input to the pump drive connection terminal, and the electrical signal is input to the drive circuit board 513 via the electrical contact board 6. By providing the pump drive electrical connection terminal on the electrical contact board 6 in this way, it is possible to drive the circulation pump 500 by applying a predetermined voltage to the electrical connection terminal even when the circulation pump 500 is removed from the carriage.

[0103] <Ink flow inside the ejection head> The following describes the circulation of ink inside the ejection head 1. Figures 15(a) to 15(e) are diagrams illustrating the flow of ink inside the ejection head 1.

[0104] Fig. 15(a) is a schematic diagram showing the flow of ink when a recording operation is performed. The arrows in the figure indicate the flow of ink. In this embodiment, when a recording operation is performed, both the external pump 21 and the circulation pump 500 start to operate. Note that the external pump 21 and the circulation pump 500 may be operated regardless of the recording operation. Furthermore, the external pump 21 and the circulation pump 500 do not have to be driven in conjunction with each other, and may be driven independently.

[0105] During the recording operation, the circulation pump 500 is ON (driven), and the ink flowing out from the first pressure control chamber 122 flows into the supply flow path 130 and the bypass flow path 160. The ink that flows into the supply flow path 130 passes through the ejection module 300, then flows into the recovery flow path 140, and is then supplied to the second pressure control chamber 152.

[0106] Meanwhile, the ink that has flowed from the first pressure control chamber 122 into the bypass flow path 160 passes through the second valve chamber 151 and flows into the second pressure control chamber 152. The ink that has flowed into the second pressure control chamber 152 passes through the pump inlet flow path 170, the circulating pump 500, and the pump outlet flow path 180, and then flows into the first pressure control chamber 122 again.

[0107] At this time, the control pressure by the first valve chamber 121 is set higher than the control pressure of the first pressure control chamber 122 based on the relationship of the above-mentioned formula 2. Therefore, the ink in the first pressure control chamber 122 does not flow into the first valve chamber 121, but is supplied again to the ejection module 300 via the supply flow path 130. The ink that has flowed into the ejection module 300 flows through the recovery flow path 140, the second pressure control chamber 152, the pump inlet flow path 170, the circulation pump 500, and the pump outlet flow path 180, and then flows again into the first pressure control chamber 122.

[0108] In this way, ink circulation is completed within the ejection head 1. In the ink circulation, the amount of ink circulating (flow rate) within the ejection module 300 is determined by the differential pressure between the control pressures of the first pressure control chamber 122 and the second pressure control chamber 152. This differential pressure is set so as to provide an amount of ink circulation that can suppress thickening of the ink in the vicinity of the ejection ports within the ejection module 300.

[0109] Furthermore, the ink consumed during printing is supplied from the ink tank 2 to the first pressure control chamber 122 via the filter 110 and the first valve chamber 121 .

[0110] A mechanism for supplying consumed ink will be described in detail. The ink in the first pressure control chamber 122 also decreases as the ink in the circulation path decreases by the amount of ink consumed by recording. As the ink in the first pressure control chamber 122 decreases, the internal volume of the first pressure control chamber 122 decreases. This decrease in the internal volume of the first pressure control chamber 122 opens the communication port 191A, and ink is supplied from the first valve chamber 121 to the first pressure control chamber 122. When the ink supplied passes through the communication port 191A from the first valve chamber 121, a pressure loss occurs, and the ink flows into the first pressure control chamber 122, causing the positive pressure ink to switch to a negative pressure state. Then, as the ink flows into the first pressure control chamber 122 from the first valve chamber 121, the internal volume of the first pressure control chamber increases, and the communication port 191A closes. In this way, the communication port 191A repeats an open state and a closed state according to the consumption of ink. Furthermore, when ink is not consumed, the communication port 191A is maintained in a closed state.

[0111] 15(b) is a schematic diagram showing the flow of ink immediately after the recording operation is completed and the circulation pump 500 is turned off (stopped). When the recording operation is completed and the circulation pump 500 is turned off, the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152 are both at the control pressure during the recording operation.

[0112] 15B occurs depending on the pressure difference between the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152. Specifically, ink continues to flow from the first pressure control chamber 122 to the ejection module 300 via the supply flow path 130, and then to the second pressure control chamber 152 via the recovery flow path 140. In addition, ink also continues to flow from the first pressure control chamber 122 to the second pressure control chamber 152 via the bypass flow path 160 and the second valve chamber 151.

[0113] The amount of ink that has moved from the first pressure control chamber 122 to the second pressure control chamber 152 by these ink flows is supplied to the first pressure control chamber 122 from the ink tank 2 via the filter 110 and the first valve chamber 121. Therefore, the content volume in the first pressure control chamber 122 is kept constant. From the relationship of the above-mentioned formula 2, when the content volume in the first pressure control chamber 122 is constant, the spring force F1 of the valve spring 200, the spring force F2 of the pressure adjustment spring 220, the pressure receiving area S1 of the valve 190, and the pressure receiving area S2 of the pressure plate 210 are kept constant. Therefore, the pressure in the first pressure control chamber 122 is determined according to the change in the pressure (gauge pressure) P1 in the first valve chamber 121. Therefore, when there is no change in the pressure P1 in the first valve chamber 121, the pressure P2 in the first pressure control chamber 122 is kept at the same pressure as the control pressure during the recording operation.

[0114] On the other hand, the pressure in the second pressure control chamber 152 changes over time according to the change in the content volume caused by the inflow of ink from the first pressure control chamber 122. Specifically, from the state shown in Fig. 15(b) until the communication port 191 closes and the second valve chamber 151 and the second pressure control chamber 152 do not communicate with each other as shown in Fig. 15(c), the pressure in the second pressure control chamber 152 changes according to Equation 2. Thereafter, the pressure plate 210 and the valve shaft 190a do not contact each other and the communication port 191 closes.

[0115] 15(d), ink flows from the recovery passageway 140 into the second pressure control chamber 152. This ink flow causes the pressure plate 210 and the flexible member 230 to be displaced, and the pressure in the second pressure control chamber 152 changes according to Equation 4 until the internal volume of the second pressure control chamber 152 reaches its maximum. In other words, the pressure rises.

[0116] 15(c), no ink flow occurs from the first pressure control chamber 122 to the second pressure control chamber 152 via the bypass flow path 160 and the second valve chamber 151. Therefore, after the ink in the first pressure control chamber 122 is supplied to the ejection module 300 via the supply flow path 130, only a flow occurs to the second pressure control chamber 152 via the recovery flow path 140. As described above, the movement of ink from the first pressure control chamber 122 to the second pressure control chamber 152 occurs according to the pressure difference between the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152. Therefore, when the pressure in the second pressure control chamber 152 becomes equal to the pressure in the first pressure control chamber 122, the movement of ink stops.

[0117] When the pressure in the second pressure control chamber 152 becomes equal to the pressure in the first pressure control chamber 122, the second pressure control chamber 152 expands to the state shown in Fig. 15(d). When the second pressure control chamber 152 expands as shown in Fig. 15(d), a storage section capable of storing ink is formed in the second pressure control chamber 152. Note that the time from when the circulation pump 500 is stopped until the state of Fig. 15(d) is reached is approximately 1 to 2 minutes, although this time may vary depending on the shape and size of the flow path and the properties of the ink.

[0118] When the circulation pump 500 is driven from a state in which ink is stored in the storage portion (the state shown in FIG. 15(d)), the ink in the storage portion is supplied to the first pressure control chamber 122 by the circulation pump 500. This causes the amount of ink in the first pressure control chamber 122 to increase as shown in FIG. 15(e), and the flexible member 230 and the pressure plate 210 are displaced in the expansion direction. Then, when the circulation pump 500 continues to be driven, the state inside the circulation path changes as shown in FIG. 15(a).

[0119] 15(a) is an example of the ink circulation during the printing operation, but as described above, the ink may be circulated without the printing operation. Even in this case, the ink flows as shown in Fig. 15(a) to Fig. 15(e) according to the driving and stopping of the circulation pump 500.

[0120] As described above, in this embodiment, the communication port 191B in the second pressure adjustment mechanism 150 is in an open state when the circulation pump 500 is driven to circulate ink, and is in a closed state when the circulation of ink stops, but this is not limited to the above example. The control pressure may be set so that the communication port 191B in the second pressure adjustment mechanism 150 is in a closed state even when the circulation pump 500 is driven to circulate ink. This will be described in detail below.

[0121] The bypass flow path 160 connecting the first pressure adjustment mechanism 120 and the second pressure adjustment mechanism is provided to prevent, for example, when the negative pressure generated in the circulation path becomes stronger than a predetermined value, from being affected by the ejection module 300. When the ink characteristics (e.g., viscosity) change due to a change in the environmental temperature, the pressure loss in the circulation path also changes.

[0122] For example, when the viscosity of the ink decreases, the pressure loss in the circulation path decreases, and the negative pressure in the circulation path may become stronger than the default value. When the negative pressure in the ejection module 300 becomes stronger than the default value, external air is drawn into the circulation path from the ejection port 13, destroying the meniscus of the ejection port 13, and there is a risk that normal ejection may not be possible. For this reason, in this embodiment, a bypass flow path 160 is formed in the circulation path. By providing the bypass flow path 160, when the negative pressure becomes stronger than the default value, ink also flows through the bypass flow path 160, so that the pressure in the ejection module 300 can be kept constant.

[0123] Therefore, for example, the communication port 191 in the second pressure adjustment mechanism 150 may be configured with a control pressure that maintains the closed state even when the circulation pump 500 is being driven. Then, the control pressure in the second pressure adjustment mechanism may be set so that the communication port 191 in the second pressure adjustment mechanism 150 is in an open state when the negative pressure becomes stronger than a default value.

[0124] Furthermore, pressure fluctuations in the circulation path can also occur due to the ejection operation by the ejection element 15. This is because the ejection operation generates a force that draws ink into the pressure chamber. Therefore, for example, even if the communication port 191 in the second pressure adjustment mechanism 150 is configured to be in a closed state when the circulation pump 500 is being driven, the communication port 191 may be in an open state due to the ejection operation.

[0125] For example, when recording continues with a high recording duty, the negative pressure in the pressure chamber increases. When the negative pressure in the pressure chamber increases, ink also flows back into the pressure chamber (ejection port 13) from the recovery passage 140 side. This backflow reduces the ink in the second pressure control chamber 152, causing the second pressure control chamber 152 to shrink. As a result, the communication port 191 in the second pressure adjustment mechanism 150 opens. In this case, the pressure chamber is filled with ink in the supply passage 130 and ink in the recovery passage 140, and is ejected.

[0126] Incidentally, the backflow of ink that occurs when the printing duty is high is a phenomenon that occurs due to the provision of the bypass flow path 160. Also, in the above explanation, an example has been explained in which the communication port 191 in the second pressure adjustment mechanism is opened in response to the backflow of ink. However, backflow of ink may occur when the communication port 191 in the second pressure adjustment mechanism is open. Also, even in a configuration that does not include the second pressure adjustment mechanism, the provision of the bypass flow path 160 may cause the above-mentioned backflow of ink.

[0127] <Ink flow in the ejection unit> 16(a) and 16(b) are schematic diagrams showing the circulation path for one color of ink in the discharge unit 3. Fig. 16(a) is an exploded perspective view of the discharge unit 3 seen from the first support member 4 side, and Fig. 16(b) is an exploded perspective view of the discharge unit 3 seen from the discharge module 300 side.

[0128] The arrows indicated by IN and OUT in the figure indicate the flow of ink, and although the flow of ink for only one color will be described, the other colors have similar flows. For ease of viewing, the second support member 7 and the electrical wiring member 5 are omitted. They are also omitted in the following description.

[0129] The first support member 4 in Fig. 16(a) shows a cross section corresponding to the cross section taken along line XI-XI in Fig. 6(a). The discharge module 300 includes a discharge element substrate 340 and an aperture plate 330. Fig. 17 is a diagram showing the aperture plate 330, and Fig. 18 is a diagram showing the discharge element substrate 340.

[0130] Ink is supplied to the discharge unit 3 from the circulation unit 54 via a joint member 8 (see FIG. 6). The ink path from when the ink passes through the joint member 8 until when the ink returns to the joint member 8 will be described. Note that the joint member 8 will be omitted from the following drawings.

[0131] The ejection module 300 includes an ejection element substrate 340 and an aperture plate 330, which are overlapped and joined together so that the ink flow paths communicate with each other to form the ejection module 300, and are supported by a first support member 4. The ejection module 300 is supported by the first support member 4 to form an ejection unit 3. The ejection element substrate 340 includes an ejection port forming member 320, which includes a plurality of ejection port rows in which a plurality of ejection ports 13 are arranged in rows, and ejects a portion of the ink supplied via the ink flow path in the ejection module 300 from the ejection port 13. Ink that is not ejected is collected via the ink flow path in the ejection module 300.

[0132] As shown in Figs. 16 and 17, the opening plate 330 has a plurality of arranged ink supply ports 311 and a plurality of arranged ink recovery ports 312. As shown in Figs. 18 and 19, the ejection element substrate 340 has a plurality of arranged supply connection channels 323 and a plurality of arranged recovery connection channels 324. The ejection element substrate 340 further has an individual supply channel 18 communicating with the plurality of supply connection channels 323 and an individual recovery channel 19 communicating with the plurality of recovery connection channels 324. The ink flow channel in the ejection unit 3 is formed by communicating an ink supply channel 48 and an ink recovery channel 49 (see Fig. 6(a)) provided in the first support member 4 with a channel provided in the ejection module 300. The support member supply port 211 is a cross-sectional opening that forms the ink supply channel 48, and the support member recovery port 212 is a cross-sectional opening that forms the ink recovery channel 49.

[0133] Ink supplied to the ejection unit 3 is supplied from the circulation unit 54 (see FIG. 6(a)) side to the ink supply flow path 48 (see FIG. 6(a)) of the first support member 4. The ink that flows through the support member supply port 211 in the ink supply flow path 48 is supplied to the individual supply flow path 18 of the ejection element substrate 340 via the ink supply flow path 48 (see FIG. 6(a)) and the ink supply port 311 of the opening plate 330, and enters the supply connection flow path 323. This is the supply side flow path. After that, the ink flows through the pressure chamber 12 (see FIG. 6(b)) of the ejection port forming member 320 to the recovery connection flow path 324 of the recovery side flow path.

[0134] In the recovery side flow path, the ink that has entered the recovery connection flow path 324 flows into the individual recovery flow path 19. After that, the ink flows from the individual recovery flow path 19 through the ink recovery port 312 of the opening plate 330 to the ink recovery flow path 49 of the first support member 4, and is recovered into the circulation unit 54 via the support member recovery port 212.

[0135] The area of ​​the opening plate 330 without the ink supply port 311 or the ink recovery port 312 corresponds to the area for separating the support member supply port 211 and the support member recovery port 212 in the first support member 4. Moreover, this area does not have an opening in the first support member 4 either. Such an area is used as an adhesion area when the ejection module 300 and the first support member 4 are adhered to each other.

[0136] In FIG. 17, the opening plate 330 has multiple rows of openings arranged in the X direction, and multiple rows in the Y direction, with the supply (IN) openings and the recovery (OUT) openings arranged alternately in the Y direction so as to be shifted by half a pitch in the X direction.

[0137] 18, in the ejection element substrate 340, individual supply flow paths 18 communicating with a plurality of supply connection flow paths 323 arranged in the Y direction, and individual recovery flow paths 19 communicating with a plurality of recovery connection flow paths 324 arranged in the Y direction are arranged alternately in the X direction. The individual supply flow paths 18 and individual recovery flow paths 19 are separated for each type of ink, and further, the number of individual supply flow paths 18 and individual recovery flow paths 19 arranged is determined according to the number of ejection port rows for each color. In addition, the supply connection flow paths 323 and recovery connection flow paths 324 are also arranged in the same number as the ejection ports 13. Note that there does not necessarily have to be a one-to-one correspondence, and one supply connection flow path 323 and one recovery connection flow path 324 may correspond to one ejection port 13.

[0138] Such an opening plate 330 and an ejection element substrate 340 are overlapped and joined so that the flow paths of each ink are connected to form an ejection module 300, and by being supported by the first support member 4, an ink flow path is formed that has the above-mentioned supply flow path and recovery flow path.

[0139] Figures 19(a) to 19(c) are cross-sectional views showing ink flows in different parts of the discharge unit 3. Figure 19(a) shows a cross-section of a part in the discharge unit 3 where the ink supply flow path 48 and the ink supply port 311 communicate with each other, and Figure 19(b) shows a cross-section of a part in the discharge unit 3 where the ink recovery flow path 49 and the ink recovery port 312 communicate with each other. Also, Figure 19(c) shows a cross-section of a part where the ink supply port 311 and the ink recovery port 312 do not communicate with the flow path of the first support member 4.

[0140] In the supply flow path for supplying ink, as shown in FIG. 19(a), ink is supplied from a portion where the ink supply flow path 48 of the first support member 4 and the ink supply port 311 of the opening plate 330 overlap and communicate with each other. In the recovery flow path for recovering ink, as shown in FIG. 19(b), ink is recovered from a portion where the ink recovery flow path 49 of the first support member 4 and the ink recovery port 312 of the opening plate 330 overlap and communicate with each other. In addition, as shown in FIG. 19(c), the ejection unit 3 has some regions where no openings are provided in the opening plate 330. In such regions, ink is not supplied or recovered, but is supplied in the region where the ink supply port 311 is provided as shown in FIG. 19(a), and is recovered in the region where the ink recovery port 312 is provided as shown in FIG. 19(b).

[0141] In this embodiment, the configuration using the aperture plate 330 has been described as an example, but a configuration may be adopted in which the aperture plate 330 is not used. For example, a configuration may be adopted in which flow paths corresponding to the ink supply flow path 48 and the ink recovery flow path 49 are formed in the first support member 4, and the ejection element substrate 340 is joined to the first support member 4.

[0142] 20(a) and 20(b) are cross-sectional views showing the vicinity of the ejection port 13 in the ejection module 300, and FIG. 21 is a cross-sectional view showing an ejection module having an individual supply flow path 18 and an individual recovery flow path 19 expanded in the X direction as a comparative example. Note that the thick arrows shown in the individual supply flow path 18 and the individual recovery flow path 19 in FIG. 20 and FIG. 21 indicate the oscillation of ink in a configuration using a serial type liquid ejection device 50. The ink supplied to the pressure chamber 12 via the individual supply flow path 18 and the supply connection flow path 323 is ejected from the ejection port 13 by driving the ejection element 15. When the ejection element 15 is not driven, the ink is recovered from the pressure chamber 12 to the individual recovery flow path 19 via the recovery connection flow path 324, which is a recovery flow path.

[0143] In a configuration using the serial type liquid ejection device 50, when ejection is performed from circulating ink in this manner, the ejection of ink is affected to no small extent by the fluctuation of ink in the ink flow path caused by the scanning of the ejection head 1.

[0144] Specifically, the influence of the ink oscillation in the ink flow path may appear as a difference in the ink ejection amount or a deviation in the ejection direction. As shown in FIG. 21, when the individual supply flow path 18 and the individual recovery flow path 19 have a cross-sectional shape that is wide in the X direction, which is the scanning direction, the ink in the individual supply flow path 18 and the individual recovery flow path 19 is easily subjected to inertial forces in the scanning direction, causing the ink to oscillate significantly. As a result, there is a risk that the ink oscillation will affect the ejection of ink from the ejection port 13. Furthermore, if the individual supply flow path 18 and the individual recovery flow path 19 are widened in the X direction, the distance between the colors will increase, which may reduce printing efficiency.

[0145] Therefore, the individual supply flow paths 18 and the individual recovery flow paths 19 of this embodiment extend in the Y direction in the cross section shown in FIG. 20, but are also configured to extend in the Z direction perpendicular to the X direction, which is the scanning direction. With this configuration, the width of each of the individual supply flow paths 18 and the individual recovery flow paths 19 in the scanning direction can be reduced. By reducing the width of each of the individual supply flow paths 18 and the individual recovery flow paths 19 in the scanning direction, the ink oscillation caused by the inertial force (indicated by the thick black arrow in the figure) acting on the ink in the individual supply flow paths 18 and the individual recovery flow paths 19 in the opposite direction to the scanning direction during scanning is reduced. This makes it possible to suppress the effect of the ink oscillation on the ink ejection. Also, by extending the individual supply flow paths 18 and the individual recovery flow paths 19 in the Z direction, the cross-sectional area is increased, and the flow path pressure loss is reduced.

[0146] As described above, by reducing the width of each of the individual supply flow paths 18 and the individual recovery flow paths 19 in the scanning direction, the oscillation of ink in the individual supply flow paths 18 and the individual recovery flow paths 19 during scanning is reduced, but the oscillation is not eliminated. Therefore, in order to suppress differences in ejection for each ink type that may still occur even with the reduced oscillation, in this embodiment, the individual supply flow paths 18 and the individual recovery flow paths 19 are configured to be disposed at positions that overlap with each other in the X direction.

[0147] As described above, in this embodiment, the supply connection flow path 323 and the recovery connection flow path 324 are provided corresponding to the ejection port 13, and the supply connection flow path 323 and the recovery connection flow path 324 are arranged side by side in the X direction with the ejection port 13 in between. Therefore, there are portions where the individual supply flow paths 18 and the individual recovery flow paths 19 do not overlap in the X direction, and if the corresponding relationship in the X direction between the supply connection flow path 323 and the recovery connection flow path 324 is lost, it will affect the flow and ejection of ink in the X direction in the pressure chamber 12. If the influence of ink fluctuation is added to this, it may further affect the ejection of ink from each ejection port.

[0148] Therefore, by arranging the individual supply flow paths 18 and the individual recovery flow paths 19 at positions where they overlap in the X direction, the ink oscillation during scanning in the individual supply flow paths 18 and the individual recovery flow paths 19 becomes approximately equal at any position in the Y direction where the ejection ports 13 are arranged. As a result, the pressure difference between the individual supply flow path 18 side and the individual recovery flow path 19 side generated in the pressure chamber 12 does not vary greatly, and stable ejection can be performed.

[0149] In addition, in some ejection heads 1 that circulate ink, the flow path that supplies ink to the ejection head 1 and the flow path that recovers the ink are configured as the same flow path, but in this embodiment, the individual supply flow paths 18 and the individual recovery flow paths 19 are separate flow paths. The supply connection flow path 323 and the pressure chamber 12 communicate with each other, and the pressure chamber 12 and the recovery connection flow path 324 communicate with each other, and ink is ejected from the ejection port 13 of the pressure chamber 12.

[0150] In other words, the pressure chamber 12, which is a path connecting the supply connection flow path 323 and the recovery connection flow path 324, is configured to include the ejection port 13. Therefore, an ink flow is generated in the pressure chamber 12 from the supply connection flow path 323 side to the recovery connection flow path 324 side, and the ink in the pressure chamber 12 is circulated efficiently. By circulating the ink in the pressure chamber 12 efficiently, the ink in the pressure chamber 12, which is easily affected by the evaporation of ink from the ejection port 13, can be kept fresh.

[0151] Furthermore, since the two flow paths, the individual supply flow path 18 and the individual recovery flow path 19, are connected to the pressure chamber 12, if it becomes necessary to eject ink at a high flow rate, it is possible to supply ink from both flow paths. In other words, compared to a configuration in which ink supply and recovery are configured using only one flow path, the configuration of this embodiment has the advantage of not only being able to circulate ink efficiently, but also being able to handle ejection at a high flow rate.

[0152] Furthermore, the individual supply flow paths 18 and the individual recovery flow paths 19 are less susceptible to the influence of ink fluctuations when they are disposed close to each other in the X direction. It is preferable that the distance between the flow paths is 75 μm to 100 μm.

[0153] Fig. 22 is a diagram showing an ejection element substrate 340 as a comparative example. Note that in Fig. 22, the supply connection flow path 323 and the recovery connection flow path 324 are omitted. Since ink that has received thermal energy from the ejection elements 15 in the pressure chambers 12 flows into the individual recovery flow path 19, ink with a relatively high temperature flows compared to the temperature of the ink in the individual supply flow path 18. At this time, in the comparative example, there is a portion in the X direction of the ejection element substrate 340 where only the individual recovery flow path 19 exists, such as the α portion surrounded by the dashed line in Fig. 22. In this case, the temperature locally increases in that portion, causing temperature unevenness in the ejection module 300, which may affect ejection.

[0154] In the individual supply flow paths 18, ink flows that is at a relatively low temperature relative to the individual recovery flow paths 19. Therefore, when the individual supply flow paths 18 and the individual recovery flow paths 19 are adjacent to each other, the temperatures in the individual supply flow paths 18 and the individual recovery flow paths 19 are partially offset in the vicinity thereof, suppressing a temperature rise. Therefore, it is preferable that the individual supply flow paths 18 and the individual recovery flow paths 19 are adjacent to each other and have approximately the same length, and are positioned so as to overlap each other in the X direction.

[0155] 23(a) and 23(b) are diagrams showing the flow path configuration of the ejection head 1 corresponding to three colors of ink: cyan (C), magenta (M), and yellow (Y). As shown in FIG. 23(a), the ejection head 1 is provided with a circulation flow path for each type of ink. The pressure chambers 12 are provided along the X direction, which is the scanning direction of the ejection head 1. As shown in FIG. 23(b), the individual supply flow paths 18 and the individual recovery flow paths 19 are provided along the ejection port row in which the ejection ports 13 are arranged, and are provided extending in the Y direction so as to sandwich the ejection port row between the individual supply flow paths 18 and the individual recovery flow paths 19.

[0156] <Circulation pump drive control> An example of drive control of the circulation pump 500 will be described. The circulation pump 500 is driven during a circulation period in which the ink is circulated within the ejection head 1, and is stopped outside the circulation period. The circulation period starts when a start condition is satisfied, and ends when a termination condition is satisfied.

[0157] The start condition is, for example, receiving a recording job from the host device 400, and the end condition is, for example, completing recording related to the recording job. In such a case, the recording operation is included in the circulation period. The start condition is also when the liquid ejection device 50 is turned on, or when a predetermined time has passed since the power was turned on during which no recording operation has been performed, and the end condition is, for example, when a specified time has passed. The start condition is also when a start instruction is given by the user, and the end condition is, for example, when a specified time has passed or when a user instruction to end is given. In such a case, thickening of the ink in the ejection head 1 can be suppressed.

[0158] Driving the circulation pump 500 at high output during the circulation period can quickly eliminate precipitation of solid components in the ink. However, this increases the load on the circulation pump 500, shortening the life of the circulation pump and increasing power consumption. Therefore, in this embodiment, the driving conditions of the circulation pump 500 are switched during the circulation period so that the flow rate of the ink changes.

[0159] Driving the circulation pump 500 so that the ink flow velocity becomes relatively fast promotes the elimination of precipitation of solid components in the ink. Driving the circulation pump 500 so that the ink flow velocity becomes relatively slow suppresses the precipitation of solid components in the ink while reducing the load on the circulation pump 500. This type of control makes it possible to both quickly eliminate the precipitation of solid components and reduce the load on the circulation pump 500.

[0160] Figure 24(a) is a flowchart showing a processing example of the CPU 100 and illustrates a drive control example of the circulation pump 500. It is executed when the start condition is satisfied. In step S1, the circulation stop time (the stop time of the circulation pump 500) from the previous circulation period to the current circulation period is acquired. In the case of this embodiment, this time is measured by the timer 23. In step S2, the selection table stored in the ROM 101 is read out, and the drive pattern of the circulation pump 500 in the current circulation period is selected. Figure 24(b) shows an example of the selection pattern. When the stop time acquired in step S1 is less than the threshold time ta, pattern 1 is selected. When the stop time acquired in step S1 is equal to or greater than the threshold time ta, pattern 2 is selected.

[0161] Figure 25(a) shows the timing chart of the control of pattern 1, and Figure 25(b) shows the timing chart of the control of pattern 2. In the illustrated example, as an example of the drive condition of the circulation pump 500, its drive frequency is illustrated. If the drive frequency of the circulation pump 500 is high, the flow rate of the ink becomes fast, and if it is low, it becomes slow.

[0162] In pattern 1, the drive frequency is set to f1 at a certain time from the start of driving (drive start frequency), and then set to f0 (<f1) (drive steady frequency). Before the start of the circulation period, the precipitation of the solid component of the ink is progressing. Immediately after the start of the circulation period, the drive frequency is set high to increase the flow rate of the ink, thereby promoting the elimination of precipitation. After a certain time has elapsed, the circulation is performed with the drive frequency lowered and the flow rate of the ink lowered. The load on the circulation pump 500 can be suppressed.

[0163] Similarly, in pattern 2, the drive frequency is set to f2 at a certain time from the start of driving, and then set to f0 (<f2). Comparing with the drive frequency f1 of pattern 1, the drive frequency f2 of pattern 2 has the relationship of f2 > f1. When the stop time is long, the precipitation of the solid component of the ink progresses more than when the stop time is short. Therefore, in pattern 2, the drive frequency immediately after the start of the circulation period is set even higher to increase the flow rate of the ink, thereby promoting the elimination of precipitation.

[0164] Figures 26(a) to 26(d) are explanatory diagrams showing examples of ink flow patterns in the nozzle (around the ejection port 13). Figure 26(a) shows a state in which the ink is circulating. The ink circulates in the direction of arrow A, and while it is circulating, no settling of the solid components of the ink occurs. Figure 26(b) shows a state in which circulation has been stopped. If circulation is stopped and the device is left alone for a long time, the solid components of the ink will settle and appear as deposits D on the flat areas. The longer the stop time is, the greater the amount of deposits D will be.

[0165] Fig. 26(c) is a schematic diagram showing when ink circulation is started by setting the drive start frequency of the circulation pump 500 higher than the steady drive frequency. When the ink starts circulating in the direction of arrow A, a large force of arrow B acts instantaneously on the deposit D. The settled deposit D becomes suspended. Fig. 26(d) shows a state in which the drive conditions of the circulation pump 500 have been changed and the pump is driven at the steady drive frequency. The suspended deposit D is washed away by a relatively small force (arrow C) and the precipitation is eliminated.

[0166] Returning to Fig. 24(a), in step S3, the driving of the circulation pump 500 is started according to the driving pattern selected in step S2. This starts the circulation of ink inside the ejection head 1. When the end condition for the circulation period is met, the driving of the circulation pump 500 is ended in step S4. In step S5, the timer 23 is reset, and a new stop time is measured.

[0167] The selection table and drive pattern may be the same regardless of the type of ink, but the selection table and drive pattern may be set for each type of ink, thereby allowing the precipitation of solid components to be appropriately eliminated according to the characteristics of the type of ink.

[0168] <Relationship between operating time and effect> 32 shows the results of an experiment in which the control of pattern 1 was performed by varying the drive time T (seconds) at drive frequency f1. For each range of drive time T, the effect of eliminating sedimentation and the effect of reducing the load on the circulation pump 500 were evaluated on a four-level scale, A to D. A indicates high effect, B indicates moderate effect, C indicates low effect, and D indicates no effect. Drive frequency f0 is 20 Hz, and drive frequency f1 is 60 Hz.

[0169] When there is no drive at drive frequency f1 (T=0), there is no precipitation elimination effect and the load reduction effect is high. When the drive time T is greater than 0 (i.e., at least 1 / 60 second) and less than 5 seconds, the precipitation elimination effect is somewhat effective (rating B) and the load reduction effect is also high (rating A). In other words, the precipitation elimination effect is achieved by driving the circulation pump 500 for one pulse or more (1 / 60 second or more). The longer the drive time T, the greater the precipitation elimination effect, but the greater the load on the circulation pump 500. From the perspective of the load reduction effect, the drive time T should be 30 seconds or less, and in particular 15 seconds or less.

[0170] The drive time at drive frequency f2 in the control of pattern 2 is considered to have a similar tendency, and the drive time may be set similarly to the drive time T at drive frequency f1. For example, it is 1 / f2 or more and 30 seconds or less, particularly 15 seconds or less.

[0171] The duration of the circulation period is set to, for example, 1 / 30 or more of the threshold time ta. When the threshold time ta is, for example, 1 hour, the circulation period is 2 minutes or more. When the circulation period is 2 minutes and pattern 1 is selected, the drive time T of the drive frequency f1 is, for example, 1 / 60 seconds or more and 20 seconds or less, as described above. When the threshold time ta is, for example, 30 minutes, the circulation period is, for example, 1 minute or more. The upper limit of the circulation period is, for example, 5 minutes or less, particularly 3 minutes or less.

[0172] <Another example of driving pattern 1> In the examples of FIGS. 25(a) and 25(b), the driving frequency of the circulation pump 500 immediately after the start of the circulation period was set to the driving start frequency. However, it may be set to the steady driving frequency immediately after the start, then to the driving start frequency, and again to the steady driving frequency. FIG. 27(a) shows an example thereof. The driving conditions (driving frequency) of the circulation pump 500 are switched multiple times. The driving start frequency may be set in the time zone included in the first half of the circulation period, particularly in the first 1 / 4 period, or the first 1 / 8 period.

[0173] <Another example 2 of the driving pattern> In the examples of FIGS. 25(a) and 25(b), the driving frequency was exemplified as the driving condition of the circulation pump 500, but other conditions may also be used. FIGS. 27(b) and 27(c) show examples of switching the driving voltage as the driving condition. If the driving voltage of the circulation pump 500 is high, the flow rate of the ink becomes fast, and if it is low, the flow rate becomes slow.

[0174] FIG. 27(b) shows an example used as pattern 1 in the selection table of FIG. 24(b). In this example, the driving voltage is set to V1 at a certain time from the start of driving, and then to V0 (<V1). Immediately after the start of the circulation period, the driving voltage is set high to increase the flow rate of the ink, thereby promoting the elimination of precipitation. After a certain time has elapsed, the driving voltage is lowered and the circulation is performed with the flow rate of the ink lowered. The load on the circulation pump 500 can be suppressed.

[0175] FIG. 27(c) shows an example used as pattern 2 in the selection table of FIG. 24(b). Similarly in this example, the driving voltage is set to V2 at a certain time from the start of driving, and then to V0 (<V2). Comparing with the driving voltage V1 of pattern 1, the driving voltage V2 of pattern 2 has the relationship of V2 > V1. When the stop time is long, the precipitation of the solid component of the ink progresses more than when the stop time is short. Therefore, in pattern 2, the driving voltage immediately after the start of the circulation period is set even higher to increase the flow rate of the ink, thereby promoting the elimination of precipitation.

[0176] <Another example 3 of the driving pattern> As differences between the drive patterns, the examples of Figures 25(a) and 25(b) show differences in the height of the drive frequency, and the examples of Figures 27(b) and 27(c) show differences in the height of the drive voltage, but the height may be the same but the time may be different. Also, in the selection table of Figure 24(b), one drive pattern is selected from two types of drive patterns, but one drive pattern may be selected from three or more types of drive patterns.

[0177] Fig. 28(a) to Fig. 28(c) show three types of drive patterns, and it is assumed that one drive pattern is selected from these three types of drive patterns in each circulation period. The three types of drive patterns have the same drive start frequency (f1), but the length of the drive time of the circulation pump 500 at the drive start frequency is different. The length of the drive time is the shortest in the example of Fig. 28(a), and the longest in the example of Fig. 28(c). If the stop time is relatively short, the example of Fig. 28(a) is selected, if it is relatively long, the example of Fig. 28(c) is selected, and if it is intermediate, the example of Fig. 28(b) is selected.

[0178] Next, Figures 29(a) and 29(b) show two types of drive patterns, and it is assumed that one of these two drive patterns is selected during each circulation period. The two drive patterns have the same drive voltage at the start of driving (V1), but the length of drive time of the circulation pump 500 at that drive voltage is different. The length of drive time is short in the example of Figure 29(a) and long in the example of Figure 29(b). When the stop time is relatively short, the example of Figure 29(a) is selected, and when it is relatively long, the example of Figure 29(b) is selected.

[0179] <Another example of how to select a drive pattern> The selection table in Fig. 24(b) was in a form of selecting a drive pattern according to the stop time. However, in addition to the stop time, the drive pattern may be selected according to the ambient environment of the liquid ejection device 50. Fig. 30(b) shows an example thereof. The example in Fig. 30(b) is an example of selecting one drive pattern from three patterns 9 to 11 based on the stop time and the ambient temperature of the liquid ejection device 50 detected by the temperature and humidity sensor 24. The stop time is divided into three categories: less than 1 hour, 1 hour or more and less than 5 hours, and 5 hours or more. The ambient temperature is divided into three categories: less than 20°C, 20°C or more and less than 30°C, and 30°C or more. It is assumed that the precipitation of solid components progresses as the stop time becomes longer, and the sedimentation of solid components progresses as the ambient temperature becomes higher.

[0180] Figs. 31(a) to 31(c) show drive patterns corresponding to patterns 9 to 11 in Fig. 30(b). Any of the drive patterns is a pattern in which the drive frequency is switched a plurality of times between f1 and f0 (<f1) as the drive condition of the circulation pump 500. And, in pattern 9 of Fig. 31(a), the set time of one time of the drive frequency f1 is the shortest, and in pattern 11 of Fig. 31(c), the set time of one time of the drive frequency f1 is the longest. Therefore, the relationship of the ability to eliminate the precipitation of solid components in the ink and the load of the circulation pump 500 in patterns 9 to 11 is pattern 9 < pattern 10 < pattern 11.

[0181] Fig. 30(a) shows an example of drive control of the circulation pump 500 corresponding to the selection pattern in Fig. 30(b). It is executed when the start condition is satisfied. In step S11, the time from the previous circulation period to the current circulation period (the stop time of the circulation pump 500) is acquired from the timer 23. In step S12, the temperature detection result (ambient temperature) of the temperature and humidity sensor 24 is acquired.

[0182] In step S13, the selection table (Fig. 30(b)) stored in the ROM 101 is read out. From the combination of the stop time acquired in step S11 and the ambient temperature acquired in step S12, the drive pattern of the circulation pump 500 in the current circulation period is selected from among patterns 9 to 11.

[0183] In step S14, the circulation pump 500 starts to be driven according to the drive pattern selected in step S13. This starts the circulation of ink inside the ejection head 1. When the end condition for the circulation period is met, the drive of the circulation pump 500 ends in step S15. In step S16, the timer 23 is reset and a new stop time is measured.

[0184] In this example, the environmental temperature is taken into consideration when selecting the drive pattern, but the environmental humidity around the liquid ejection device 50 detected by the temperature and humidity sensor 24 may also be taken into consideration. Alternatively, both the environmental temperature and the environmental humidity may be taken into consideration. Alternatively, the temperature of the ejection head 1 detected by the head temperature sensor 25 may also be taken into consideration when selecting the drive pattern. The temperature of the ejection head 1 is approximately equal to the ink temperature, and the drive conditions of the circulation pump 500 may be set so that the higher the temperature, the faster the ink flow rate.

[0185] <Other embodiments> In the above embodiment, the circulation pump 500 using a diaphragm mechanism is exemplified, but a circulation pump using a different mechanism, such as a tube pump that physically squeezes a tube with a roller, may be used. Also, multiple circulation pumps may be used.

[0186] The present invention can also be realized by a process in which a program for realizing one or more functions of the above-mentioned embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) for realizing one or more functions.

[0187] <Summary of the embodiment> The above embodiment discloses at least the following inventions.

[0188] Item 1. a circulation pump provided in a flow path that circulates the liquid to the nozzle that ejects the liquid, and that generates a circulating flow of the liquid; A control means for controlling the operation of the circulation pump; A liquid ejection device comprising: The control means switching a drive condition of the circulation pump so as to change a flow rate of the liquid during a circulation period of the liquid; A liquid ejection device comprising:

[0189] Item 2. The liquid ejection device according to item 1, the drive conditions include a first drive condition and a second drive condition, the first drive condition is a drive condition in which the flow velocity is faster than that of the second drive condition; A liquid ejection device comprising:

[0190] Item 3. Item 2. The liquid ejection device according to item 2, the control means controls the drive of the circulation pump under the first drive condition at the start of the circulation period. A liquid ejection device comprising:

[0191] Item 4. A liquid ejection device according to any one of items 1 to 3, the control means switches the drive conditions a plurality of times during the circulation period; A liquid ejection device comprising:

[0192] Item 5. A liquid ejection device according to any one of items 1 to 4, the circulation pump includes a piezoelectric element as a drive source, The driving condition is a driving frequency of the piezoelectric element. A liquid ejection device comprising:

[0193] Item 6. Item 5. The liquid ejection device according to any one of items 1 to 5, the circulation pump includes a piezoelectric element as a drive source, The driving condition is a driving voltage of the piezoelectric element. A liquid ejection device comprising:

[0194] Item 7. The liquid ejection device according to item 1, The control means Driving the circulation pump during the circulation period according to a drive pattern selected from a plurality of drive patterns. A liquid ejection device comprising:

[0195] Item 8. Item 7. The liquid ejection device according to item 7, the control means selects the drive pattern based on a circulation stop time from the previous circulation period to the current circulation period. A liquid ejection device comprising:

[0196] Item 9. Item 8. The liquid ejection device according to item 8, Further comprising a temperature sensor, The control means selects the drive pattern based on the circulation stop time and the temperature detection result of the temperature sensor. A liquid ejection device comprising:

[0197] Item 10. Item 9. The liquid ejection device according to item 9, The temperature sensor detects an environmental temperature around the liquid ejection device. A liquid ejection device comprising:

[0198] Item 11. Item 9. The liquid ejection device according to item 9, The temperature sensor is provided in an ejection head having the nozzle. A liquid ejection device comprising:

[0199] Item 12. A liquid ejection device according to any one of items 7 to 11, the plurality of drive patterns include a first drive pattern and a second drive pattern, the drive conditions in the first drive pattern include a first drive condition and a second drive condition, the drive conditions in the second drive pattern include a third drive condition and a fourth drive condition, the first drive condition and the third drive condition are drive conditions under which the flow velocity is faster than the second drive condition and the fourth drive condition; A liquid ejection device comprising:

[0200] Item 13. Item 13. The liquid ejection device according to item 12, the third drive condition is a drive condition in which the flow velocity is faster than that of the first drive condition; A liquid ejection device comprising:

[0201] Item 14. Item 13. The liquid ejection device according to item 12, a time for which the circulation pump is driven under the third drive condition in the second drive pattern is longer than a time for which the circulation pump is driven under the first drive condition in the first drive pattern; A liquid ejection device comprising:

[0202] Item 15. A liquid ejection device according to any one of claims 1 to 14, the liquid ejection device is a recording device that ejects ink as the liquid from the nozzles onto a recording medium; A liquid ejection device comprising:

[0203] Item 16. Item 2. The liquid ejection device according to item 2, The time for driving the circulation pump under the first driving condition is 1 / 60 seconds or more and 30 seconds or less. A liquid ejection device comprising:

[0204] Item 17. The liquid ejection device according to item 1, The circulation period is 2 minutes or more. A liquid ejection device comprising:

[0205] Item 18. The liquid ejection device according to item 1, The control means selecting the driving condition depending on whether a predetermined time has elapsed since the previous circulation period; The circulation period is set to a time equal to or longer than 1 / 30 of the predetermined time. A liquid ejection device comprising:

[0206] Item 19. A method for controlling a liquid ejection device including a circulation pump that is provided in a flow path that circulates liquid to a nozzle that ejects the liquid and generates a circulating flow of the liquid, comprising the steps of: and switching a drive condition of the circulation pump so as to change a flow rate of the liquid during a circulation period of the liquid. A control method comprising:

[0207] Item 20. A storage medium storing a program for causing a computer to execute a control method for a liquid ejection device including a circulation pump that is provided in a flow path that circulates liquid to a nozzle that ejects the liquid and that generates a circulating flow of the liquid, the storage medium comprising: The control method includes: and switching a drive condition of the circulation pump so as to change a flow rate of the liquid during a circulation period of the liquid. A storage medium comprising:

[0208] Item 21. A program for causing a computer to execute a control method for a liquid ejection device including a circulation pump that is provided in a flow path that circulates liquid to a nozzle that ejects the liquid and that generates a circulating flow of the liquid, the program comprising: The control method includes: and switching a drive condition of the circulation pump so as to change a flow rate of the liquid during a circulation period of the liquid. A program characterized by:

[0209] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0210] 1 Discharge head, 50 Liquid discharge device, 500 Circulation pump

Claims

1. a circulation pump provided in a flow path that circulates the liquid to the nozzle that ejects the liquid, and that generates a circulating flow of the liquid; A control means for controlling the operation of the circulation pump; A liquid ejection device comprising: The control means switching a drive condition of the circulation pump so as to change a flow rate of the liquid during a circulation period of the liquid; A liquid ejection device comprising:

2. The liquid ejection device according to claim 1 , the drive conditions include a first drive condition and a second drive condition, the first drive condition is a drive condition in which the flow velocity is faster than that of the second drive condition; A liquid ejection device comprising:

3. The liquid ejection device according to claim 2, the control means controls the drive of the circulation pump under the first drive condition at the start of the circulation period. A liquid ejection device comprising:

4. The liquid ejection device according to claim 1 , the control means switches the drive conditions a plurality of times during the circulation period; A liquid ejection device comprising:

5. The liquid ejection device according to claim 1 , the circulation pump includes a piezoelectric element as a drive source, The driving condition is a driving frequency of the piezoelectric element. A liquid ejection device comprising:

6. The liquid ejection device according to claim 1 , the circulation pump includes a piezoelectric element as a drive source, The driving condition is a driving voltage of the piezoelectric element. A liquid ejection device comprising:

7. The liquid ejection device according to claim 1 , The control means Driving the circulation pump during the circulation period according to a drive pattern selected from a plurality of drive patterns. A liquid ejection device comprising:

8. The liquid ejection device according to claim 7, the control means selects the drive pattern based on a circulation stop time from the previous circulation period to the current circulation period. A liquid ejection device comprising:

9. The liquid ejection device according to claim 8, Further comprising a temperature sensor, The control means selects the drive pattern based on the circulation stop time and the temperature detection result of the temperature sensor. A liquid ejection device comprising:

10. The liquid ejection device according to claim 9 , The temperature sensor detects an environmental temperature around the liquid ejection device. A liquid ejection device comprising:

11. The liquid ejection device according to claim 9 , The temperature sensor is provided in an ejection head having the nozzle. A liquid ejection device comprising:

12. The liquid ejection device according to claim 7, the plurality of drive patterns include a first drive pattern and a second drive pattern, the drive conditions in the first drive pattern include a first drive condition and a second drive condition, the drive conditions in the second drive pattern include a third drive condition and a fourth drive condition, the first drive condition and the third drive condition are drive conditions under which the flow velocity is faster than the second drive condition and the fourth drive condition; A liquid ejection device comprising:

13. The liquid ejection device according to claim 12, the third drive condition is a drive condition in which the flow velocity is faster than that of the first drive condition; A liquid ejection device comprising:

14. The liquid ejection device according to claim 12, a time for which the circulation pump is driven under the third drive condition in the second drive pattern is longer than a time for which the circulation pump is driven under the first drive condition in the first drive pattern; A liquid ejection device comprising:

15. The liquid ejection device according to claim 1 , the liquid ejection device is a recording device that ejects ink as the liquid from the nozzles onto a recording medium; A liquid ejection device comprising:

16. The liquid ejection device according to claim 2, The time for driving the circulation pump under the first driving condition is 1 / 60 seconds or more and 30 seconds or less. A liquid ejection device comprising:

17. The liquid ejection device according to claim 1 , The circulation period is 2 minutes or more. A liquid ejection device comprising:

18. The liquid ejection device according to claim 1 , The control means selecting the driving condition depending on whether a predetermined time has elapsed since the previous circulation period; The circulation period is set to a time equal to or greater than 1 / 30 of the predetermined time. A liquid ejection device comprising:

19. A method for controlling a liquid ejection device including a circulation pump that is provided in a flow path that circulates liquid to a nozzle that ejects the liquid and generates a circulating flow of the liquid, comprising the steps of: and switching a drive condition of the circulation pump so as to change a flow rate of the liquid during a circulation period of the liquid. A control method comprising:

20. A storage medium storing a program for causing a computer to execute a control method for a liquid ejection device including a circulation pump that is provided in a flow path that circulates liquid to a nozzle that ejects the liquid and that generates a circulating flow of the liquid, the storage medium comprising: The control method includes: and switching a drive condition of the circulation pump so as to change a flow rate of the liquid during a circulation period of the liquid. A storage medium comprising:

21. A program for causing a computer to execute a control method for a liquid ejection device including a circulation pump that is provided in a flow path that circulates liquid to a nozzle that ejects the liquid and that generates a circulating flow of the liquid, the program comprising: The control method includes: and switching a drive condition of the circulation pump so as to change a flow rate of the liquid during a circulation period of the liquid. A program characterized by:

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