Circulation unit, liquid discharge head, and liquid discharge device

Abstract

To improve discharge stability.SOLUTION: During a period after an operating circulation pump stops until the pressure in a first pressure control chamber of a first pressure control mechanism becomes equal to the pressure in a second pressure control chamber of a second pressure control mechanism, when the volume of fluid passing through a communication port between the first pressure control chamber and a fourth flow path in the direction toward the fourth flow path that communicates to the circulation pump and the first pressure control chamber from the first pressure control chamber is VV, and the volume of the fourth flow path is V2, the relation of VV<V2 is satisfied.SELECTED DRAWING: Figure 19

Description

[Technical field]

[0001] The present disclosure relates to a circulation unit, a liquid ejection head, and a liquid ejection apparatus. [Background technology]

[0002] A circulation type liquid ejection device is known that circulates liquid between a liquid ejection head and a liquid storage unit to suppress the discharge of air bubbles in a flow path and the thickening of ink near an ejection port. Some circulation type liquid ejection devices use a pump on the main body side outside the liquid ejection head to circulate liquid between the liquid ejection head and the main body, while others use a pump inside the liquid ejection head to circulate liquid inside the liquid ejection head. Patent Document 1 discloses a liquid ejection device that circulates ink inside the head by a circulation pump mounted on the main body side. In the configuration of Patent Document 1, ink supplied from the circulation pump to a first tank is supplied to the liquid ejection head through a primary circulation path, and ink that is not ejected is collected by the circulation pump through a secondary circulation path and a second tank. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-59046 A Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, the ink amount in the upstream tank and the downstream tank is read by two float-type liquid level sensors, and ink is replenished by a refill pump based on the ink level detected by the two sensors. However, depending on the configuration, the float part of the two float-type liquid level sensors may malfunction due to ink bubbling, etc., so there is a possibility that the ink level in at least the downstream tank may drop. If the ink level drops, the inlet and outlet of the flow path communicating with the circulation pump may be exposed to air, and air may enter the circulation pump. If air flows into the pump chamber of a small piezoelectric pump as a circulation pump as in Patent Document 1, depending on the configuration, the flow of air may act as a damper and the desired pressure may not be generated, reducing the flow rate and decreasing the ejection stability.

[0005] An object of the present disclosure is to improve ejection stability. [Means for solving the problem]

[0006] One embodiment of the present disclosure is a first pressure adjustment means for adjusting the pressure of a liquid, comprising a first valve chamber, a first pressure control chamber, a first communication port for communicating the first valve chamber and the first pressure control chamber, a first valve for opening and closing the first communication port, a first flexible member that forms a part of the surface of the first pressure control chamber and is configured to be displaceable, and a first pressure plate that forms another part of the surface of the first pressure control chamber and is configured to be displaceable in conjunction with the first flexible member; a second pressure adjustment means for adjusting the pressure of a liquid, comprising a second valve chamber, a second pressure control chamber, a second communication port for communicating the second valve chamber and the second pressure control chamber, a second valve for opening and closing the second communication port, a second flexible member that forms a part of the surface of the second pressure control chamber and is configured to be displaceable, and a second pressure plate that forms another part of the surface of the second pressure control chamber and is configured to be displaceable in conjunction with the second flexible member; a first flow path for communicating the pressure chamber and the first pressure control chamber, a second flow path for communicating the pressure chamber and the second pressure control chamber, a third flow path for communicating the second pressure control chamber and a circulation pump for circulating a liquid, and a fourth flow path for communicating the circulation pump and the first pressure control chamber. During the period from when the operating circulation pump stops until the pressures in the first pressure control chamber and the second pressure control chamber become equal, when the volume of the fluid passing through the communication port between the first pressure control chamber and the fourth flow path in the direction from the first pressure control chamber toward the fourth flow path is VV and the volume of the fourth flow path is V2, VV < V2. The circulation unit is provided.

Advantages of the Invention

[0007] According to the present disclosure, the discharge stability can be improved.

Brief Description of the Drawings

[0008] [Figure 1] It is a perspective view and a functional block diagram of a liquid discharge device. [Diagram 2] It is an exploded perspective view of a liquid discharge head [Diagram 3] It is a longitudinal section of a liquid discharge head and an enlarged cross-sectional view of a discharge module. [Figure 4] FIG. 1 is a perspective view showing the outline of an external appearance of a circulation unit; [Diagram 5] FIG. [Figure 6] FIG. 4 is a block diagram showing a schematic diagram of a circulation path. [Figure 7] FIG. 4 is a cross-sectional view showing an example of a pressure adjusting means. [Figure 8] FIG. 2 is an external perspective view of a circulation pump. [Figure 9] 9 is a cross-sectional view of the circulating pump shown in FIG. 8(a) taken along line IX-IX. [Figure 10] 3A and 3B are diagrams illustrating the flow of ink in a liquid ejection head. [Figure 11] FIG. 4 is a schematic diagram showing a circulation path in the discharge unit. [Figure 12] FIG. 2 is a diagram showing an aperture plate. [Figure 13] FIG. 2 is a diagram showing a discharge element substrate. [Figure 14] 5A and 5B are cross-sectional views showing the ink flow in the ejection unit. [Figure 15] FIG. 4 is a cross-sectional view showing the vicinity of a discharge port. [Figure 16] FIG. 11 is a cross-sectional view showing a comparative example near the ejection port. [Figure 17] 11A and 11B are diagrams showing a comparative example of a discharge element substrate. [Figure 18] FIG. 2 is a diagram showing a flow path configuration of a liquid ejection head. [Figure 19] 11 is a diagram showing a flow path of the liquid ejection device after the ink circulation has been stopped. FIG. [Figure 20] 4 shows the state change of the second pressure control mechanism. [Figure 21] 4 shows the relationship between pressure and volume of the second pressure control mechanism. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A preferred embodiment of the present disclosure will be described in detail below with reference to the accompanying drawings. The following embodiment does not limit the disclosed matters, and not all combinations of features described in the present embodiment are necessarily essential to the solving means of the present disclosure. The same components are given the same reference numbers. In the present embodiment, an example is described in which a thermal method is adopted in which an electrothermal conversion element generates bubbles to eject liquid as an ejection element for ejecting liquid, but this is not limited thereto. The present invention can also be applied to an ejection method in which a piezoelectric element (piezo) is used to eject liquid, or to a liquid ejection head in which another ejection method is adopted. Furthermore, the pump and pressure adjustment means described below are not limited to the configurations themselves described in the embodiments and drawings. In the following description, the basic configuration of the present disclosure will be described first, and then the characteristic parts of the present disclosure will be described.

[0010] <Liquid discharge device> Fig. 1 is a diagram for explaining a liquid ejection device, and is an enlarged view of a liquid ejection head of the liquid ejection device and its surroundings. First, a schematic configuration of a liquid ejection device 50 in this embodiment will be described with reference to Fig. 1. Fig. 1(a) is a perspective view that shows a liquid ejection device that uses a liquid ejection head 1. The liquid ejection device 50 in this embodiment constitutes a serial type inkjet recording device that performs recording on a recording medium P by ejecting ink as a liquid while scanning the liquid ejection head 1.

[0011] The liquid ejection head 1 is mounted on a carriage 60. The carriage 60 reciprocates along a guide shaft 51 in a main scanning direction (X direction). The recording medium P is transported by transport rollers 55, 56, 57, and 58 in a sub-scanning direction (Y direction) that intersects (orthogonal in this example) the main scanning direction. In each of the figures referred to below, the Z direction indicates the vertical direction, and intersects (orthogonal in this example) the XY plane defined by the X and Y directions. The liquid ejection head 1 is configured to be removable and attachable to the carriage 60 by the user.

[0012] The liquid ejection head 1 includes a circulation unit 54 and an ejection unit 3 (see FIG. 2) described later. The specific configuration will be described later, but the ejection unit 3 is provided with a plurality of ejection ports and energy generating elements (hereinafter referred to as ejection elements) that generate ejection energy for ejecting liquid from each ejection port.

[0013] The liquid ejection device 50 is also provided with an ink tank 2, which is an ink supply source, and an external pump 21, and the ink stored in the ink tank 2 is supplied to the circulation unit 54 via an ink supply tube 59 by the driving force of the external pump 21.

[0014] The liquid ejection device 50 repeats a recording scan in which the liquid ejection head 1 mounted on the carriage 60 moves in the main scanning direction while ejecting ink to perform recording, and a transport operation in which the recording medium P is transported in the sub-scanning direction, thereby forming a predetermined image on the recording medium P. The liquid ejection head 1 in this embodiment is capable of ejecting four types of ink, namely black (K), cyan (C), magenta (M), and yellow (Y), and is capable of recording a full-color image using these inks. However, the inks that can be ejected from the liquid ejection head 1 are not limited to the above four types of ink. The present disclosure is also applicable to liquid ejection heads for ejecting other types of ink. In other words, the types and number of inks ejected from the liquid ejection head are not limited.

[0015] Furthermore, the liquid ejection device 50 is provided with a cap member (not shown) capable of covering the ejection port surface on which the ejection ports of the liquid ejection head are formed, at a position offset in the X direction from the transport path of the recording medium P. The cap member covers the ejection port surface of the liquid ejection head 1 during non-recording operations, and is used to prevent and protect the ejection ports from drying, and to suck ink from the ejection ports, etc.

[0016] 1(a) shows an example in which the liquid ejection head 1 is provided with four circulation units 54 corresponding to the four types of ink, but it is sufficient that the liquid ejection head 1 is provided with a circulation unit 54 corresponding to the type of liquid to be ejected. Also, multiple circulation units 54 may be provided for the same type of liquid. In other words, the liquid ejection head 1 can be configured to include one or more circulation units. It is also possible to have a configuration in which at least one ink is circulated rather than circulating all four types of ink.

[0017] FIG. 1B is a block diagram showing a control system of the liquid ejection device 50. The CPU 103 functions as a control means for controlling the operation of each part of the liquid ejection device 50 based on a program such as a processing procedure stored in the ROM 101. The RAM 102 is used as a work area when the CPU 103 executes processing. The CPU 103 receives image data from a host device 400 outside the liquid ejection device 50, controls the head driver 1A, and controls the driving of the ejection elements provided in the ejection unit 3. The CPU 103 also controls the drivers of various actuators provided in the liquid ejection device. For example, the CPU 103 controls a motor driver 105A of a carriage motor 105 for moving the carriage 60, a motor driver 104A of a conveying motor 104 for conveying the recording medium P, and the like. The CPU 103 also controls a pump driver 500A for driving a circulation pump 500 described later, a pump driver 21A of an external pump 21, and the like. Although FIG. 1B shows a form in which processing is performed upon receiving image data from the host device 400, processing may be performed by the liquid ejection device 50 independently of data from the host device 400.

[0018] <Basic configuration of liquid ejection head> Fig. 2 is an exploded perspective view of the liquid ejection head 1 of this embodiment. Fig. 3 is a cross-sectional view of the liquid ejection head 1 shown in Fig. 2 taken along line IIIA-IIIA. Fig. 3(a) is an overall vertical cross-sectional view of the liquid ejection head 1, and Fig. 3(b) is an enlarged view of the ejection module shown in Fig. 3(a). The basic structure of the liquid ejection head 1 of this embodiment will be described below, mainly with reference to Fig. 2 and Fig. 3, and also with reference to Fig. 1 as appropriate.

[0019] 2, the liquid ejection head 1 includes a circulation unit 54 and an ejection unit 3 for ejecting ink supplied from the circulation unit 54 onto a recording medium P. The liquid ejection head 1 in this embodiment is fixedly supported on a carriage 60 of the liquid ejection device 50 by positioning means and electrical contacts (not shown) provided on the carriage 60. The liquid ejection head 1 ejects ink while moving together with the carriage 60 in the main scanning direction (X direction) shown in FIG. 1, and performs recording on the recording medium P.

[0020] An ink supply tube 59 is provided on the external pump 21 connected to the ink tank 2 serving as the ink supply source (see FIG. 1). A liquid connector (not shown) is provided on the tip of the ink supply tube 59. When the liquid ejection head 1 is mounted on the liquid ejection device 50, the liquid connector provided on the tip of the ink supply tube 59 is airtightly connected to a liquid connector insertion port 53a, which is a liquid inlet port provided on a head housing 53 of the liquid ejection head 1. This forms an ink supply path from the ink tank 2 to the liquid ejection head 1 via the external pump 21. In this embodiment, since four types of ink are used, four sets of the ink tank 2, the external pump 21, the ink supply tube 59, and the circulation unit 54 are provided corresponding to each ink, and four ink supply paths corresponding to each ink are independently formed. In this way, 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 liquid ejection head 1. Note that the liquid ejection device 50 of this embodiment is not provided with an ink recovery system that recovers the ink in the liquid ejection head 1 to the ink tank 2. Therefore, the liquid ejection head 1 is provided with a liquid connector insertion port 53a for connecting an ink supply tube 59 of the ink tank 2, but is not provided with a connector insertion port for connecting a tube for recovering ink from the liquid ejection head 1 to the ink tank 2. A liquid connector insertion port 53a is provided for each ink.

[0021] 3, 54B indicates a circulation unit for black ink, 54C indicates a circulation unit for cyan ink, 54M indicates a circulation unit for magenta ink, and 54Y indicates an ink circulation unit for yellow ink. Each circulation unit has substantially the same configuration, and in this embodiment, when there is no need to distinguish between the circulation units, they are all referred to as circulation unit 54.

[0022] 2 and 3(a), 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. As shown in FIG. 3(b), 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 elements 15 are configured by electrothermal conversion elements (heaters) that generate thermal energy as discharge energy for discharging liquid. Electric power is supplied to each discharge element 15 via electric wiring formed on the silicon substrate 310 by a film formation technique.

[0023] Further, an ejection port forming member 320 is formed on the surface (lower surface in FIG. 3(b)) of the silicon substrate 310. In the ejection port forming member 320, a plurality of pressure chambers 12 corresponding to a plurality of ejection elements 15 and a plurality of ejection ports 13 for ejecting ink are formed by photolithography. Furthermore, a common supply flow path 18 and a common recovery flow path 19 are formed in the silicon substrate 310. Further, in the silicon substrate 310, a supply connection flow path 323 that communicates the common supply flow path 18 with each pressure chamber 12, and a recovery connection flow path 324 that communicates the common recovery flow path 19 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 shown in FIG. 3(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. Note that this combination is an example, and any combination of inks may be used. One ejection module may be configured to eject one type of ink, or may be configured to eject three or more types of ink. The two ejection modules 300 do not have to eject the same number of types of ink. One ejection module 300 may be provided, or may be configured to include three or more ejection modules 300. Furthermore, in the example shown in FIG. 3, two ejection port arrays extending in the Y direction are formed for one color of ink. A pressure chamber 12, a common supply flow path 18, and a common recovery flow path 19 are formed for each of the multiple ejection ports 13 that constitute each ejection port array.

[0024] An ink supply port and an ink recovery port, which will be described later, are formed on the back surface (upper surface in FIG. 3(b)) of the silicon substrate 310. The ink supply port supplies ink from an ink supply flow path 48 to the multiple common supply flow paths 18, and the ink recovery port recovers ink from the multiple common recovery flow paths 19 to an ink recovery flow path 49.

[0025] 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 common supply flow path 18, and ink is recovered from each common recovery flow path 19 to the ink recovery port. However, ink may also be circulated in the reverse direction. In this case, ink is supplied from the ink recovery port described above to the common recovery flow path 19, and ink is recovered from the common supply flow path 18 to the ink supply port.

[0026] As shown in FIG. 3(a), the back surface (upper surface in FIG. 3(a)) of the ejection module 300 is adhesively fixed to one surface (lower surface in FIG. 3(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.

[0027] A second support member 7 having an opening 7a (see FIG. 2) through which the ejection module 300 is inserted is adhesively fixed to one surface of the first support member 4 (the upper surface in FIG. 3(a)). 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 to eject ink. The electrical connection portion between the ejection module 300 and the electrical wiring member 5 is sealed with a sealant (not shown) and is protected from corrosion by ink and external impacts.

[0028] Furthermore, an electrical contact board 6 is thermocompression bonded to an end 5a (see FIG. 2) 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. The electrical contact board 6 has an external signal input terminal (not shown) for receiving an electrical signal from the liquid ejection device 50.

[0029] Furthermore, a joint member 8 (FIG. 3(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 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. 3(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.

[0030] The openings at one end of each of the ink supply flow passage 48 and the ink recovery flow passage 49 of the first support member 4 have a small opening area that matches the ink supply port and the ink recovery port in the silicon substrate 310. In contrast, the openings at the other end of each of the ink supply flow passage 48 and the ink recovery flow passage 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 passage of the circulation unit 54. By adopting such a configuration, it is possible to suppress an increase in flow passage resistance to the ink collected from each recovery flow passage. However, the shapes of the openings at one end and the other end of each of the ink supply flow passage 48 and the ink recovery flow passage 49 are not limited to the above example.

[0031] In the liquid 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 common supply flow path 18. The ink then flows from the common supply flow path 18 into the pressure chamber 12 via the supply connection flow path 323, and a portion of the ink that has flowed into the pressure chamber 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 recovery connection flow path 324 and the common 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 via the recovery port 89 of the joint member 8, and is recovered.

[0032] <Components of the circulation unit> 4 is a schematic external view of one circulation unit 54 corresponding to one type of ink applied to the recording apparatus of this embodiment. The circulation unit 54 is provided with a filter 110, a first pressure adjustment means 120, a second pressure adjustment means 150, and a circulation pump 500. These components are connected by respective flow paths as shown in FIGS. 5 and 6, and constitute a circulation path that supplies and recovers ink to and from the ejection module 300 in the liquid ejection head 1.

[0033] <Circulation path inside the liquid ejection head> FIG. 5 is a vertical cross-sectional view showing a circulation path of one type of ink (one color ink) in the liquid ejection head 1. In order to explain the circulation path more clearly, the relative positions of each component (first pressure adjustment means 120, second pressure adjustment means 150, circulation pump 500, etc.) in FIG. 5 are simplified. Therefore, the relative positions of each component are different from the configuration in FIG. 19 described later. FIG. 6 is a block diagram showing the circulation path shown in FIG. 5. As shown in FIG. 5 and FIG. 6, the first pressure adjustment means 120 includes a first valve chamber 121 and a first pressure control chamber 122. The second pressure adjustment means 150 includes a second valve chamber 151 and a second pressure control chamber 152. The first pressure adjustment means 120 is configured to have a relatively higher control pressure than the second pressure adjustment means 150. In this embodiment, the two pressure adjustment means 120 and 150 are used to achieve circulation within a certain pressure range in the circulation path.

[0034] Also, the ink is configured to flow through the pressure chamber 12 (ejection element 15) at a flow rate according to the pressure difference between the first pressure adjustment means 120 and the second pressure adjustment means 150. Below, the circulation path in the liquid ejection head 1 and the flow of ink within the circulation path will be described with reference to Figures 5 and 6. Note that the arrows in each figure indicate the direction of ink flow.

[0035] First, the connection state of each component of the liquid ejection head 1 will be described. An external pump 21 that sends ink contained in an ink tank 2 (FIG. 6) provided outside the liquid ejection head 1 to the liquid ejection head 1 is connected to a circulation unit 54 via an ink supply tube 59 (FIG. 1). A filter 110 is provided in the ink flow path located upstream of the circulation unit 54. An ink supply path located downstream of the filter 110 is connected to a first valve chamber 121 of a first pressure adjustment means 120. The first valve chamber 121 communicates with a first pressure control chamber 122 via a communication port 191A that can be opened and closed by a valve 190A shown in FIG.

[0036] The first pressure control chamber 122 is connected to the supply flow path 130, the bypass flow path 160, and the circulation pump 500. The supply flow path 130 is connected to the common supply flow path 18 via the ink supply port provided in the ejection module 300. The bypass flow path 160 is connected to a second valve chamber 151 provided in the second pressure adjustment means 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. 5. Note that FIGS. 5 and 6 show an example in which one end of the bypass flow path 160 is connected to the first pressure control chamber 122 of the first pressure adjustment means 120, and the other end of the bypass flow path 160 is connected to the second valve chamber 151 of the second pressure adjustment means 150. However, one end of the bypass flow path 160 may be connected to the supply flow path 130, and the other end of the bypass flow path may be connected to the second valve chamber 151.

[0037] The second pressure control chamber 152 is connected to the recovery flow path 140. The recovery flow path 140 is connected to the common recovery flow path 19 via the 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. 5, 170a indicates the inlet of the pump inlet flow path 170.

[0038] Next, a description will be given of the flow of ink in the liquid ejection head 1 having the above configuration. As shown in Fig. 6, 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 the circulation unit 54 of the liquid ejection head 1 as a positive pressure ink flow.

[0039] The ink supplied to the circulation unit 54 passes through the filter 110 to remove foreign matter such as dust and air bubbles, and then flows into the first valve chamber 121 provided in the first pressure adjustment means 120. The ink pressure decreases due to pressure loss when passing through the filter 110, but the ink pressure at this stage is positive. The ink that has flowed into the first valve chamber 121 then passes through the communication port 191A and flows into the first pressure control chamber 122 when the valve 190A is in the open state. Due to the pressure loss when passing through the communication port 191A, the ink that has flowed into the first pressure control chamber 122 switches from positive pressure to negative pressure.

[0040] 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 to the pump outlet flow path 180 on the downstream side. Therefore, the ink supplied from the first valve chamber 121 to the first pressure control chamber 122 by driving the supply pump (not shown) 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. Note that, although details will be described later, in this embodiment, a piezoelectric diaphragm pump using a piezoelectric element attached to a diaphragm as a driving source is used as a circulation pump capable of sending liquid. The piezoelectric diaphragm pump is a pump that changes the volume of the pump chamber by inputting a driving voltage to the piezoelectric element, and sends liquid by alternately moving two check valves due to pressure fluctuations.

[0041] When air flows into the piezoelectric diaphragm pump, the pump capacity may decrease due to the damping effect of the air, and if the pump capacity decreases, the necessary circulation flow rate may not be achieved, and ejection stability may decrease. To prevent this, it is preferable that the pump inlet 170a of the pump inlet flow path 170 is located as low as possible in the second pressure control chamber 152 and not exposed from the ink, as shown in FIG.

[0042] 5, it is preferable that the pump outlet 180a of the pump outlet flow path 180 is provided on the upper side of the first pressure control chamber 122. This allows an ink flow from top to bottom inside the first pressure control chamber 122, thereby making it possible to suppress settling due to ink stagnation.

[0043] Furthermore, if sedimentation has progressed to a certain extent while circulation is stopped, when the circulation pump 500 is operated, the thick ink that has accumulated below the first pressure control chamber 122 is transported to the second pressure chamber 152 and sucked out from the pump inlet 170a located below the second pressure control chamber 152.

[0044] By ejecting the relatively thick ink onto the relatively thin portion at the top of the first pressure control chamber 122, it is possible to make the density closer to uniform.

[0045] The ink that has flowed into the supply flow channel 130 flows from the ink supply port of the ejection module 300 through the common supply flow channel 18 into the pressure chamber 12, and some of the ink is ejected from the ejection port 13 by driving (heat generation) the ejection element 15. The remaining ink that has not been used for ejection flows through the pressure chamber 12, passes through the common recovery flow channel 19, and then flows into the recovery flow channel 140 connected to the ejection module 300. The ink that has flowed into the recovery flow channel 140 flows into the second pressure control chamber 152 of the second pressure adjustment means 150.

[0046] On the other hand, the ink that has flowed from the first pressure control chamber 122 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 that has been recovered from the recovery flow path 140 are sucked into the circulation pump 500 through the pump inlet flow path 170 by the operation of the circulation pump 500. Then, the ink that has been sucked into the circulation pump 500 is sent to the pump outlet flow path 180 and flows into the first pressure control chamber 122 again. Thereafter, the ink that has flowed into the second pressure control chamber 152 from the first pressure control chamber 122 via the supply flow path 130 and the ejection module 300, and the ink that has flowed into the second pressure control chamber 152 via 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 is circulated in the circulation path.

[0047] Here, the flow path that communicates the first pressure adjustment means 120 and the pressure chamber 12 is referred to as the upstream flow path, and the flow path that communicates the pressure chamber 12 and the circulation pump 500 is referred to as the downstream flow path. That is, the supply flow path 130 is referred to as the upstream flow path, and the recovery flow path 140, the second pressure adjustment means 150, and the pump inlet flow path 170 are collectively referred to as the downstream flow path. Note that the downstream flow path does not necessarily have to have the second pressure adjustment means 150 and the pump inlet flow path 170. The pump outlet flow path 180 is also referred to as the intermediate flow path. Therefore, in this embodiment, the liquid flows through the circulation path of the circulation pump 500, the intermediate flow path, the first pressure adjustment means 120, the upstream flow path, the pressure chamber 12, the downstream flow path, and the circulation pump 500 in this order. The supply flow path 130 is also referred to as the first flow path, the recovery flow path 140 is also referred to as the second flow path, the pump inlet flow path 170 is also referred to as the third flow path, and the pump outlet flow path 180 is also referred to as the fourth flow path.

[0048] As described above, in this embodiment, the circulation pump 500 can circulate the liquid along the circulation path formed in the liquid ejection head 1. This makes it possible to suppress thickening of the ink in the ejection module 300 and accumulation of sedimentation components of the ink color material, and makes it possible to maintain good ink fluidity in the ejection module 300 and ejection characteristics at the ejection ports.

[0049] In addition, since the circulation path in this embodiment is configured to be completed within the liquid ejection head 1, the length of the circulation path can be significantly shortened compared to when ink is circulated between the ink tank 2 provided outside the liquid ejection head and the liquid ejection head 1. This makes it possible to circulate the ink with a small circulation pump.

[0050] Furthermore, the connection flow path between the liquid ejection head 1 and the ink tank 2 is configured to include only a flow path for supplying ink. In other words, a configuration is adopted in which a flow path for recovering ink from the liquid ejection head 1 to the ink tank 2 is not required. Therefore, only a tube for supplying ink is required to connect the ink tank 2 and the liquid ejection head 1, and no tube for recovering ink is required. Therefore, the inside of the liquid ejection device 50 can be simplified with a reduced number of tubes, and the entire device can be made compact. Furthermore, by reducing the number of tubes, it is possible to reduce the pressure fluctuation of the ink caused by the oscillation of the tubes accompanying the main scanning of the liquid ejection head 1. In addition, the oscillation of the tubes during the main scanning of the liquid ejection head 1 becomes a driving load of the carriage motor that drives the carriage 60. Therefore, by reducing the number of tubes, the driving load of the carriage motor is reduced, and it is possible to simplify the main scanning mechanism including the carriage motor and the like. Furthermore, since it is not necessary to recover ink from the liquid ejection head to the ink tank, the external pump 21 can also be made compact. In this way, according to this embodiment, the liquid ejection device 50 can be made smaller and its costs reduced.

[0051] <Pressure Adjustment Means> FIG. 7 is a diagram showing an example of pressure adjustment means. The configuration and operation of the pressure adjustment means (first pressure adjustment means 120, second pressure adjustment means 150) built into the liquid ejection head 1 described above will be described in more detail with reference to FIG. 7. The first pressure adjustment means 120 and the second pressure adjustment means 150 have substantially the same configuration. For this reason, the first pressure adjustment means 120 will be described below as an example, and the second pressure adjustment means 150 will only be described with the reference numerals of the parts corresponding to the first pressure adjustment means in FIG. 7. In the case of the second pressure adjustment means 150, the first valve chamber 121 described below will be read as the second valve chamber 151, and the first pressure control chamber 122 will be read as the second pressure control chamber 152.

[0052] The first pressure adjustment means 120 has a first valve chamber 121 and a first pressure control chamber 122 formed in a cylindrical housing 125. The first valve chamber 121 and the first pressure control chamber 122 are separated by a partition wall 123 provided in the cylindrical housing 125. However, the first valve chamber 121 communicates with the first pressure control chamber 122 through a communication port 191 formed in the partition wall 123. The first valve chamber 121 is provided with a valve 190 that switches between communication and blocking between the first valve chamber 121 and the first pressure control chamber 122 at the communication port 191. The valve 190 is held at 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 blocked. In order to increase the close contact with the partition 123, it is preferable that the portion of the valve 190 that comes into contact with the partition 123 is made of an elastic material. A valve shaft 193A that is inserted into the communication port 191 protrudes from the center of the valve 190. By pressing this valve shaft 193A against the biasing force of a valve spring 200, the valve 190 moves away from the partition 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 will be referred to as the "closed state", and the state in which ink can flow through the communication port 191 will be referred to as the "open state".

[0053] 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.

[0054] A pressure adjustment spring 220 (biasing member) 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, as shown in FIG. 7(a). 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 193A 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 193A pushed by the pressure plate 210 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 in an open state (the state shown in FIG. 7(b)).

[0055] In this embodiment, the connection in the circulation path is set so that the pressure in the first valve chamber 121 when the communication port 191 is in the open state is 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 in which the internal volume of the first pressure control chamber 122 increases. As a result, the pressure plate 210 moves away from the valve shaft 193A of the valve 190, and the valve 190 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 the closed state (the state of FIG. 7(c)).

[0056] In this manner, in the first pressure adjustment means 120 of this embodiment, when the pressure in 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.

[0057] Next, the pressure in the first pressure control chamber 122 will be described in more detail. Consider a state in which the flexible member 230 and the pressure plate 210 are displaced in response to the pressure in the first pressure control chamber 122 as described above, and the pressure plate 210 comes into contact with the valve shaft 193A, opening the communication port 191 (the state shown in FIG. 7(b)). At this time, the relationship of the forces acting on the pressure plate 210 is expressed by the following equation 1.

[0058] 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.

[0059] 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. 7) 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.

[0060] 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.

[0061] On the other hand, as shown in FIG. 7(c), when the pressure plate 210 is not in contact with the valve shaft 193A and the communication port 191 is closed, the relationship of the forces acting on the pressure plate 210 is expressed by Equation 3.

[0062] P3×S3+F3=0...Equation 3 Now, rearrange Equation 3 for P3 as follows: P3 = -F3 / S3 Equation 4 It becomes.

[0063] F3: The spring force of the pressure adjusting spring 220 when the pressure plate 210 and the valve shaft 193A 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 193A are not in contact with each other S3: The pressure-receiving area of ​​the pressure plate 210 when the pressure plate 210 and the valve 190 are not in contact with each other Here, Fig. 7(c) shows a state in which the pressure plate 210 and the flexible member 230 are displaced to the left in the figure to their limit of displacement. 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 according to the amount of displacement while the pressure plate 210 and the flexible member 230 are displaced to the state of Fig. 7(c). Specifically, when the pressure plate 210 and the flexible member 230 are in the right direction in Fig. 7 compared to Fig. 7(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 (it becomes stronger as a negative pressure) according to the relationship of Equation 4. 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. 7(b) to the state shown in Fig. 7(c). That is, the pressure plate 210 and the flexible member 230 gradually displace to the left 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.

[0064] In this embodiment, the first pressure adjustment means 120 adjusts the pressure of the liquid in the upstream flow channel, and the second pressure adjustment means 150 adjusts the pressure of the liquid in the pump inlet flow channel 170 (in the inlet flow channel).

[0065] <Circulation pump> Next, the configuration and operation of the circulation pump 500 built into the above-mentioned liquid ejection head 1 will be described in detail with reference to FIGS.

[0066] 8(a) and 8(b) are external perspective views of the circulation pump 500. FIG. 8(a) is an external perspective view showing the front side of the circulation pump 500, and FIG. 8(b) is an external perspective view showing the rear side of the circulation pump 500. 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 body 505a and a flow path connecting member 505b adhesively fixed to the outer surface of the housing body 505a. The housing body 505a and the flow path connecting member 505b each have a pair of through holes communicating with each other provided at two different positions. 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. 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 (see FIG. 9) which will be described later, and is discharged from the pump discharge hole 502.

[0067] FIG. 9 is a cross-sectional view of the circulating pump 500 shown in FIG. 8(a) taken along line IX-IX. A diaphragm 506 is joined to the inner surface of the pump housing 505, and a pump chamber 503 is formed between the diaphragm 506 and a recess formed on the inner surface of the pump housing 505. The pump chamber 503 communicates with a pump supply hole 501 and a pump discharge hole 502 formed in the pump housing 505. A check valve 504a is provided in the middle part of the pump supply hole 501, and a check valve 504b is provided in the middle part of the pump discharge hole 502. That is, the circulating pump 500 is provided with a check valve in a flow path that communicates the downstream flow path and the intermediate flow path. Specifically, the check valve 504a is arranged so that a part of the check valve 504a can move to the left in the figure in a space 512a formed in the middle part of the pump supply hole 501. Also, the check valve 504b is disposed in a space 512b, a part of which is formed in the middle portion of the pump discharge hole 502, so as to be movable to the right in the figure.

[0068] When diaphragm 506 is displaced to increase the volume of pump chamber 503 and reduce the pressure in pump chamber 503, 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). When check valve 504a moves away from the opening of pump supply hole 501 in space 512a, the check valve 504a enters an open state that allows the flow of ink through pump supply hole 501. When diaphragm 506 is displaced to decrease the volume of pump chamber 503 and reduce the pressure in pump chamber 503, check valve 504a comes into close contact with the wall surface surrounding the opening of pump supply hole 501. As a result, the check valve 504a enters a closed state that blocks the flow of ink through pump supply hole 501.

[0069] On the other hand, 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.

[0070] 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.

[0071] As described above, pump chamber 503 is formed by joining pump housing 505 and diaphragm 506. Therefore, the pressure in pump chamber 503 changes as diaphragm 506 deforms. 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 in pump chamber 503 increases. As a result, check valve 504b arranged opposite pump discharge hole 502 opens, and ink in pump chamber 503 is discharged. 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 the backflow of ink from pump chamber 503 to pump supply hole 501 is suppressed.

[0072] Conversely, when the diaphragm 506 is displaced in the direction in which the pump chamber 503 expands, the pressure in the pump chamber 503 decreases. As a result, the check valve 504a arranged opposite the pump supply hole 501 opens, and ink is supplied to the pump chamber 503. At this time, the check valve 504b arranged at the pump discharge hole 502 comes into close contact with the wall surface surrounding the opening formed in the pump housing 505 and closes the opening. As a result, the backflow of ink from the pump discharge hole 502 to the pump chamber 503 is suppressed.

[0073] In this way, in the circulation pump 500, the diaphragm 506 deforms, changing the pressure in 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 bubbles expand and contract, reducing the pressure change in the pump chamber 503 and decreasing the amount of liquid delivered. Therefore, the pump chamber 503 is arranged parallel to gravity to make it easier for bubbles that get into the pump chamber 503 to gather above the pump chamber 503, and the pump discharge hole 502 is arranged above the center of the pump chamber 503. This makes it possible to improve the discharge of bubbles in the pump and stabilize the flow rate.

[0074] <Ink flow inside the liquid ejection head> FIG. 10 is a diagram for explaining the flow of ink in the liquid ejection head. The circulation of ink in the liquid ejection head 1 will be explained with reference to FIG. 10. In order to more clearly explain the ink circulation path, the relative positions of each component (first pressure adjustment means 120, second pressure adjustment means 150, circulation pump 500, etc.) in FIG. 10 are simplified. Therefore, the relative positions of each component are different from the configuration in FIG. 19 described later. FIG. 10(a) is a schematic diagram showing the flow of ink when a recording operation is performed in which ink is ejected from the ejection port 13 to perform recording. 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 be driven. The external pump 21 and the circulation pump 500 may be driven regardless of the recording operation. The external pump 21 and the circulation pump 500 may not be driven in conjunction with each other, and may be driven independently.

[0075] 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.

[0076] On the other hand, the ink that has flowed from the first pressure control chamber 122 into the bypass flow path 160 flows into the second pressure control chamber 152 via the second valve chamber 151. The ink that has flowed into the second pressure control chamber 152 passes through the pump inlet flow path 170, the circulation pump 500, and the pump outlet flow path 180, and then flows into the first pressure control chamber 122 again. At this time, based on the relationship of the above-mentioned formula 2, the pressure of the first valve chamber 121 is set to be higher than the control pressure of the first pressure control chamber 122. Therefore, the ink in the first pressure control chamber 122 is supplied to the ejection module 300 again via the supply flow path 130 without flowing into the first valve chamber 121. The ink that has flowed into the ejection module 300 flows into the first pressure control chamber 122 again via 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. Moreover, the remaining ink in the first pressure control chamber 122A flows back into the first pressure control chamber 122A via the bypass flow path 160, the second valve chamber 121B, the second pressure control chamber 122B, the pump inlet flow path 170, the circulation pump 500, and the pump outlet flow path 180. In this manner, the ink circulation is completed within the liquid ejection head 1.

[0077] In the above ink circulation, the amount of ink circulating (flow rate) in the ejection module 300 is determined by the difference in the control pressure between the first pressure control chamber 122 and the second pressure control chamber 152. This pressure difference is set so as to be a circulation amount capable of suppressing thickening of ink near the ejection port in the ejection module 300. In addition, the ink consumed by recording is supplied from the ink tank 2 to the first pressure control chamber 122 via the filter 110 and the first valve chamber 121. The mechanism by which the consumed ink is supplied will be described in detail. By reducing the ink from the circulation path by the amount of ink consumed by recording, the pressure in the first pressure control chamber is reduced, and as a result, the ink in the first pressure control chamber 122 is also reduced. As the ink in the first pressure control chamber 122 is reduced, the internal volume of the first pressure control chamber 122 is reduced. Due to this reduction in the internal volume of the first pressure control chamber 122, the communication port 191A is opened, and ink is supplied from the first valve chamber 121 to the first pressure control chamber 122. A pressure loss occurs in this supplied ink as it passes from the first valve chamber 121 to the communication port 191A. Then, as the ink flows into the first pressure control chamber 122, the positive pressure ink switches to a negative pressure state. As the ink flows from the first valve chamber 121 into the first pressure control chamber 122, the pressure inside the first pressure control chamber 122 increases, increasing the internal volume of the first pressure control chamber 122 and closing the communication port 191A. In this way, the communication port 191A alternates between an open state and a closed state depending on the consumption of ink. Furthermore, if no ink is consumed, the communication port 191A is maintained in a closed state.

[0078] FIG. 10B 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 pressures of the first pressure control chamber 122 and the second pressure control chamber 152 are both at the control pressure during the recording operation. Therefore, the ink moves as shown in FIG. 10B according to the pressure difference between the pressures of the first pressure control chamber 122 and the second pressure control chamber 152. Specifically, the 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. The 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.

[0079] The same amount of ink as that which 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. In the state shown in FIG. 10(b), the second communication port 191B is in an open state, and the second pressure plate 210B and the second valve 190B are in contact with each other, so that the pressure in the second pressure control chamber 122B changes according to formula 2.

[0080] On the other hand, the pressure of 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 of FIG. 10(b) until the communication port 191B is closed and the second valve chamber 151 and the second pressure control chamber 152 are not in communication with each other as shown in FIG. 10(c), the pressure of the second pressure control chamber 152 changes according to the formula 2. Thereafter, the pressure plate 210 and the valve shaft 193A are not in contact with each other and the communication port 191B is closed. Then, as shown in FIG. 10(d), ink flows from the recovery passage 140 into the second pressure control chamber 152. This ink inflow displaces the pressure plate 210 and the flexible member 230, and the pressure of the second pressure control chamber 152 changes according to the formula 4 until the internal volume of the second pressure control chamber 152 reaches its maximum. That is, it rises.

[0081] 10(c), no ink flow occurs from the first pressure control chamber 122 through the bypass flow path 160 and the second valve chamber 151 to the second pressure control chamber 152. Therefore, after the ink in the first pressure control chamber 122 is supplied to the ejection module 300 through the supply flow path 130, only a flow occurs through the recovery flow path 140 to the second pressure control chamber 152.

[0082] 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. For this reason, 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.

[0083] In addition, in a state where the pressure in the second pressure control chamber 152 is equal to the pressure in the first pressure control chamber 122, the second pressure control chamber 152 expands to the state shown in FIG. 10(d). When the second pressure control chamber 152 expands as shown in FIG. 10(d), a storage portion capable of storing ink is formed in the second pressure control chamber 152. The time required from stopping the circulation pump 500 to transition to the state shown in FIG. 10(d) is approximately 1 to 2 minutes, which may vary depending on the shape and size of the flow path and the properties of the ink. When the circulation pump 500 is driven from the state shown in FIG. 10(d) where ink is stored in the storage portion, the ink in the storage portion formed in the second pressure control chamber 152 is supplied to the first pressure control chamber 122 by the circulation pump 500. As a result, the amount of ink in the first pressure control chamber 122 increases, and the flexible member 230 and the pressure plate 210 of the first pressure control mechanism 120 are displaced in the expansion direction, as shown in Fig. 10(e). If the circulation pump 500 continues to be driven, the state in the circulation path changes until it becomes as shown in Fig. 10(a).

[0084] In the above description, Fig. 10(a) is an example during a recording operation, but as described above, ink may be circulated without a recording operation. Even in this case, the ink circulation path transitions from Fig. 10(a) to Fig. 10(e) in response to the driving and stopping of the circulation pump 500.

[0085] As described above, in this embodiment, the communication port 191B in the second pressure adjustment means 150 is in an open state when the circulation pump 500 is driven to circulate the ink, and is in a closed state when the circulation of the 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 means 150 is in a closed state even when the circulation pump 500 is driven to circulate the ink. Hereinafter, the role of the bypass flow path 160 will be specifically described.

[0086] The bypass flow path 160 connecting the first pressure adjustment means 120 and the second pressure adjustment means 150 is provided to prevent the negative pressure generated in the circulation path from being affected by the discharge module 300 when the negative pressure exceeds a predetermined value. The bypass flow path 160 is also provided to supply ink to the pressure chamber 12 from both sides of the supply flow path 130 and the recovery flow path 140.

[0087] First, an example will be described in which the bypass flow path 160 is provided to prevent the negative pressure from being influenced by the discharge module 300 when the negative pressure becomes stronger than a preset value. For example, the ink characteristics (e.g., viscosity) may change due to a change in the environmental temperature. When the ink viscosity changes, the pressure loss in the circulation path also changes. For example, when the ink viscosity decreases, the pressure loss in the circulation path decreases. As a result, the flow rate of the circulation pump 500 driven at a constant drive amount increases, and the flow rate through the discharge module 300 increases. On the other hand, since the discharge module 300 is kept at a constant temperature by a temperature adjustment mechanism (not shown), the viscosity of the ink in the discharge module 300 is maintained constant even if the environmental temperature changes. While the viscosity of the ink in the discharge module 300 does not change, the flow rate of the ink flowing through the discharge module 300 increases, and the negative pressure in the discharge module 300 is strengthened due to flow resistance. In this way, if the negative pressure in the discharge module 300 becomes stronger than the default value, the meniscus of the discharge port 13 may be destroyed, and external air may be drawn into the circulation path, preventing normal discharge. Even if the meniscus is not destroyed, the negative pressure in the pressure chamber 12 may become stronger than the default value, affecting discharge.

[0088] For this reason, in this embodiment, the bypass flow path 160 is formed in the circulation path. By providing the bypass flow path 160, when the negative pressure becomes stronger than a preset value, ink also flows through the bypass flow path 160, so that the pressure of the ejection module 300 can be kept constant. Therefore, for example, the communication port 191B in the second pressure adjustment means 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 means may be set so that the communication port 191 in the second pressure adjustment means 150 is in an open state when the negative pressure becomes stronger than a preset value. In other words, if the meniscus does not collapse even when the flow rate of the pump is changed due to a viscosity change such as an environmental change, or if a predetermined negative pressure is maintained, the communication port 191B may be in a closed state when the circulation pump 500 is driven.

[0089] Next, an example will be described in which the bypass flow path 160 is provided to supply ink to the pressure chamber 12 from both the supply flow path 130 and the recovery flow path 140. Pressure fluctuations in the circulation path can also be caused by the ejection operation of the ejection element 15. This is because a force that draws ink into the pressure chamber is generated by the ejection operation.

[0090] Below, it will be explained that when high duty recording continues, the ink supplied to the pressure chamber 12 is supplied to both the supply flow path 130 side and the recovery flow path 140 side. Note that the definition of duty can change depending on various conditions, but here, the state in which one 4pl ink droplet is recorded on a 1200dpi grid is treated as 100%. High duty recording means, for example, recording at a duty of 100%.

[0091] If recording at a high duty continues, the amount of ink flowing from the pressure chamber 12 into the second pressure control chamber 152 through the recovery flow path 140 decreases. On the other hand, since the circulation pump 500 causes a constant amount of ink to flow out, the balance between the inflow and outflow in the second pressure control chamber 152 is lost, the ink in the second pressure control chamber 152 decreases, the negative pressure in the second pressure control chamber 152 becomes stronger, and the second pressure control chamber 152 shrinks. Then, as the negative pressure in the second pressure control chamber 152 becomes stronger, the inflow amount of ink flowing into the second pressure control chamber 152 through the bypass flow path 160 increases, and the second pressure control chamber 152 becomes stable with the outflow and inflow balanced. As a result, the negative pressure in the second pressure control chamber 152 becomes stronger according to the duty. Furthermore, as described above, when the circulation pump 500 is driven, in a configuration in which the communication port 191B is in a closed state, the communication port 191B opens depending on the duty, and ink flows from the bypass flow path 160 into the second pressure control chamber 152.

[0092] Then, when recording at an even higher duty is continued, the amount of ink flowing from the pressure chamber 12 into the second pressure control chamber 152 through the recovery flow passage 140 decreases, and instead the amount of ink flowing into the second pressure control chamber 152 from the communication port 191B via the bypass flow passage 160 increases. If this state progresses further, the amount of ink flowing from the pressure chamber 12 into the second pressure control chamber 152 through the recovery flow passage 140 becomes zero, and all ink flowing out to the circulation pump 500 becomes ink flowing in from the communication port 191B. If this state progresses further, ink now flows back from the second pressure control chamber 152 into the pressure chamber 12 through the recovery flow passage 140. In this state, the ink flowing out from the second pressure control chamber 152 to the circulation pump 500 and the ink flowing out to the pressure chamber 12 flow into the second pressure control chamber 152 from the communication port 191B through the bypass flow passage 160. In this case, the pressure chamber 12 is filled with ink from the supply flow passage 130 and ink from the recovery flow passage 140, and is ejected.

[0093] Incidentally, the backflow of ink that occurs when the recording duty is high is a phenomenon that occurs due to the provision of the bypass flow path 160. In addition, in the above, an example has been described in which the communication port 191B in the second pressure adjustment means 150 is opened in response to the backflow of ink, but the backflow of ink may occur when the communication port 191B in the second pressure adjustment means 150 is in the open state. Even in a configuration that does not include the second pressure adjustment means 150, the backflow of ink may occur due to the provision of the bypass flow path 160. Incidentally, it is sufficient that the bypass flow path 160 communicates at least one of the upstream flow path and the first pressure adjustment means 120 with the downstream flow path without passing through the pressure chamber 12.

[0094] <Configuration of the discharge unit> FIG. 11 is a schematic diagram showing a circulation path for one color of ink in the discharge unit 3 of this embodiment. FIG. 11(a) is an exploded perspective view of the discharge unit 3 seen from the first support member 4 side, and FIG. 11(b) is an exploded perspective view of the discharge unit 3 seen from the discharge module 300 side. The arrows indicated by IN and OUT in the figure indicate the flow of ink, and the flow of ink for only one color will be described, but the other colors flow in the same manner. Also, the second support member 7 and the electric wiring member 5 are omitted in FIG. 11, and are also omitted in the following description of the configuration of the discharge unit. Also, the first support member 4 in FIG. 11(a) shows a cross section taken along line XI-XI in FIG. 3. The discharge module 300 includes a discharge element substrate 340, an aperture plate 330, and a discharge port forming member 320. FIG. 12 is a diagram showing the aperture plate 330, and FIG. 13 is a diagram showing the discharge element substrate 340.

[0095] Ink is supplied to the discharge unit 3 from the circulation unit 54 via a joint member 8 (see FIG. 3). 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.

[0096] As described above, the ejection module 300 includes an ejection element substrate 340, an aperture plate 330, and an ejection port forming member 320. The ejection element substrate 340 and the aperture plate are formed of a silicon substrate 310 that is integrated with or separate from each other. The ejection element substrate 340, the aperture plate 330, and the ejection port forming member 320 are overlapped and joined together so that the ink flow paths communicate with each other to form the ejection module 300, which is supported by the 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 a row, and ejects a portion of the ink supplied through the ink flow path in the ejection module 300 from the ejection port 13. Ink that is not ejected is collected through the ink flow path in the ejection module 300.

[0097] 11 and 12, the aperture plate 330 has a plurality of arranged ink supply ports 311 and a plurality of arranged ink recovery ports 312. As shown in FIGS. 13 and 14, 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 a common supply channel 18 communicating with the plurality of supply connection channels 323, and a common recovery channel 19 communicating with the plurality of recovery connection channels 324. The ink flow channels in the ejection unit 3 are formed by communicating an ink supply channel 48 and an ink recovery channel 49 (see FIG. 3) provided in the first support member 4 with channels provided in the ejection module 300. The support member supply port 211 (see Figures 11(a) and 14(a)) is a cross-sectional opening that forms the ink supply flow path 48, and the support member recovery port 212 (see Figures 11(a) and 14(b)) is a cross-sectional opening that forms the ink recovery flow path 49.

[0098] Ink supplied to the ejection unit 3 is supplied from the circulation unit 54 (see FIG. 3(a)) side to the ink supply flow path 48 (see FIG. 3(a)) of the first support member 4. The ink flowing through the support member supply port 211 in the ink supply flow path 48 is supplied to the common supply flow path 18 of the ejection element substrate 340 via the ink supply flow path 48 (see FIG. 3(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. 3(b)) of the ejection port forming member 320 to the recovery connection flow path 324 of the recovery side flow path. The flow of ink in the pressure chamber 12 will be described in detail later.

[0099] In the recovery side flow path, the ink that has entered the recovery connection flow path 324 flows into the common recovery flow path 19. Thereafter, the ink flows from the common 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 then through the support member recovery port 212 to be recovered in the circulation unit 54.

[0100] 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.

[0101] In FIG. 12, the aperture plate 330 has a plurality of rows of apertures arranged in the X direction, and the supply (IN) apertures and the recovery (OUT) apertures are arranged alternately in the Y direction so as to be shifted by half a pitch in the X direction. In FIG. 13, the ejection element substrate 340 has a common supply flow path 18 communicating with a plurality of supply connection flow paths 323 arranged in the Y direction, and a common recovery flow path 19 communicating with a plurality of recovery connection flow paths 324 arranged in the Y direction, arranged alternately in the X direction. The common supply flow paths 18 and the common recovery flow path 19 are separated for each type of ink, and further, the number of common supply flow paths 18 and common recovery flow paths 19 is determined according to the number of ejection port rows of each color. In addition, the supply connection flow paths 323 and the recovery connection flow paths 324 are also arranged in the number corresponding to the ejection ports 13. It is not necessarily required that they correspond one-to-one, and one supply connection flow path 323 and one recovery connection flow path 324 may correspond to a plurality of ejection ports 13.

[0102] 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 having a supply flow path and a recovery flow path as described above is formed.

[0103] Fig. 14(a) to Fig. 14(c) are cross-sectional views showing ink flows in different parts of the discharge unit 3. Fig. 14(a) is a cross-section shown by XIVa-XIVa in Fig. 11(a) and shows a cross-section of a part where the ink supply flow path 48 and the ink supply port 311 in the discharge unit 3 communicate with each other. Fig. 14(b) is a cross-section shown by XIVb-XIVb in Fig. 11(a) and shows a cross-section of a part where the ink recovery flow path 49 and the ink recovery port 312 in the discharge unit 3 communicate with each other. Fig. 14(c) is a cross-section shown by XIVc-XIVc in Fig. 11(a) and 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.

[0104] In the supply flow path for supplying ink, as shown in FIG. 14(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. 14(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. 14(c), in the ejection unit 3, there is also a region where the opening plate 330 does not have an opening. In such a region, ink is not supplied or recovered between the ejection element substrate 340 and the first support member 4. As shown in FIG. 14(a), ink is supplied in a region where the ink supply port 311 is provided, and as shown in FIG. 14(b), ink is recovered in a region where the ink recovery port 312 is provided. In the present embodiment, the configuration using the opening plate 330 has been described as an example, but the opening plate 330 may not be used. For example, a configuration may be used 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.

[0105] 15(a) and 15(b) are cross-sectional views showing the vicinity of the ejection port 13 in the ejection module 300, and FIG. 16 is a cross-sectional view showing an ejection module having a configuration in which the common supply flow path 18 and the common recovery flow path 19 are expanded in the X direction as a comparative example. Note that the thick arrows shown in the common supply flow path 18 and the common recovery flow path 19 in FIG. 15 and FIG. 16 indicate the oscillation of ink in a configuration in which a serial type liquid ejection device 50 is used. The ink supplied to the pressure chamber 12 via the common 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 common recovery flow path 19 via the recovery connection flow path 324, which is a recovery flow path.

[0106] In the case of using the serial type liquid ejection device 50, when ejecting ink from the circulating ink, the ejection of the ink is influenced by the ink oscillation in the ink flow path caused by the main scanning of the liquid ejection head 1. Specifically, the influence of the ink oscillation in the ink flow path may appear as a difference in the amount of ink ejected or a deviation in the ejection direction. As shown in FIG. 16, when the common supply flow path 18 and the common recovery flow path 19 have a cross-sectional shape that is wide in the X direction, which is the main scanning direction, the ink in the common supply flow path 18 and the common recovery flow path 19 is easily subjected to an inertial force in the main scanning direction, and the ink is greatly oscillated. As a result, there is a risk that the ink oscillation will affect the ejection of the ink from the ejection port 13. In addition, if the common supply flow path 18 and the common recovery flow path 19 are widened in the X direction, the distance between the colors will be increased, which may reduce the printing efficiency.

[0107] Therefore, the common supply flow path 18 and the common recovery flow path 19 of this embodiment extend in the Y direction in the cross section shown in FIG. 15, but are also configured to extend in the Z direction perpendicular to the X direction, which is the main scanning direction. With this configuration, the width of each flow path in the main scanning direction of the common supply flow path 18 and the common recovery flow path 19 can be reduced. By reducing the width of each flow path in the main scanning direction of the common supply flow path 18 and the common recovery flow path 19, the ink oscillation caused by the inertial force (indicated by the thick black arrow in the figure) acting on the ink in the common supply flow path 18 and the common recovery flow path 19 in the opposite direction to the main scanning direction during the main scanning is reduced. This makes it possible to suppress the effect of the ink oscillation on the ink ejection. In addition, the cross-sectional area is increased by extending the common supply flow path 18 and the common recovery flow path 19 in the Z direction, thereby reducing the flow path pressure loss.

[0108] As described above, by reducing the width of each of the common supply flow path 18 and the common recovery flow path 19 in the main scanning direction, the oscillation of ink in the common supply flow path 18 and the common recovery flow path 19 during main scanning is reduced, but the oscillation is not eliminated. Therefore, in order to suppress the occurrence of differences in ejection for each ink type that may still occur even with the reduced oscillation, in this embodiment, the common supply flow path 18 and the common recovery flow path 19 are configured to be disposed at positions that overlap with each other in the X direction.

[0109] 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 common supply flow path 18 and the common recovery flow path 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.

[0110] Therefore, by arranging the common supply flow path 18 and the common recovery flow path 19 at positions where they overlap in the X direction, the ink oscillation during main scanning in the common supply flow path 18 and the common recovery flow path 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 common supply flow path 18 side and the common recovery flow path 19 side generated in the pressure chamber 12 does not vary greatly, and stable ejection can be performed.

[0111] In addition, in some liquid ejection heads that circulate ink, the flow path that supplies ink to the liquid ejection head and the flow path that recovers ink are configured as the same flow path, but in this embodiment, the common supply flow path 18 and the common recovery flow path 19 are configured as separate flow paths. The supply connection flow path 323 and the pressure chamber 12 are connected to each other, and the pressure chamber 12 and the recovery connection flow path 324 are connected to each other, and ink is ejected from the ejection port 13 of the pressure chamber 12. In other words, the pressure chamber 12, which is a path that connects the supply connection flow path 323 and the recovery connection flow path 324, is configured to have the ejection port 13. Therefore, an ink flow that flows from the supply connection flow path 323 side to the recovery connection flow path 324 side is generated in the pressure chamber 12, and the ink in the pressure chamber 12 is efficiently circulated. By efficiently circulating the ink in the pressure chamber 12, 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.

[0112] Furthermore, since the two flow paths, the common supply flow path 18 and the common 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.

[0113] Furthermore, the common supply flow path 18 and the common recovery flow path 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.

[0114] Fig. 17 is a diagram showing an ejection element substrate 340 as a comparative example. Note that in Fig. 17, 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 common recovery flow path 19, ink with a relatively high temperature flows compared to the temperature of the ink in the common 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 common recovery flow path 19 exists, such as the α portion surrounded by the dashed line in Fig. 17. In this case, the temperature locally increases in that portion, causing temperature unevenness in the ejection module 300, which may affect ejection.

[0115] In the common supply flow path 18, ink flows that is at a relatively low temperature relative to the common recovery flow path 19. Therefore, when the common supply flow path 18 and the common recovery flow path 19 are adjacent to each other, the temperatures in the common supply flow path 18 and the common recovery flow path 19 are partially offset in the vicinity thereof, suppressing a temperature rise. Therefore, it is preferable that the common supply flow path 18 and the common recovery flow path 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.

[0116] 18(a) and 18(b) are diagrams showing the flow path configuration of the liquid ejection head 1 corresponding to three colors of ink: cyan (C), magenta (M), and yellow (Y). As shown in FIG. 18(a), the liquid 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 main scanning direction of the liquid ejection head 1. As shown in FIG. 18(b), the common supply flow path 18 and the common recovery flow path 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 common supply flow path 18 and the common recovery flow path 19.

[0117] <Connection between the main body and the liquid ejection head> 19 is a schematic diagram showing in more detail the connection state between the ink tank 2 and external pump 21 provided in the main body of the liquid ejection device 50 of this embodiment and the liquid ejection head 1, and the arrangement of the circulation pump, etc. The liquid ejection device 50 of this embodiment has a configuration that allows the liquid ejection head 1 alone to be easily replaced when a malfunction occurs in the liquid ejection head 1. Specifically, it has a liquid connection part 700 that allows the ink supply tube 59 connected to the external pump 21 to be easily connected and disconnected from the liquid ejection head 1. This makes it possible to easily attach and detach only the liquid ejection head 1 to and from the liquid ejection device 50.

[0118] 19, the liquid connection part 700 has a liquid connector insertion port 53a protruding from the head housing 53 of the liquid ejection head 1, and a cylindrical liquid connector 59a into which the liquid connector insertion port 53a can be inserted. The liquid connector insertion port 53a is fluidly connected to an ink supply flow path formed in the liquid ejection head 1, and is connected to the first pressure adjustment means 120 via the above-mentioned filter 110. In addition, the liquid connector 59a is provided at the tip of an ink supply tube 59 connected to an external pump 21 that pressurizes and supplies ink from the ink tank 2 to the liquid ejection head 1.

[0119] 19, the liquid ejection head 1 can be easily attached, detached, and replaced by the liquid connection part 700. However, if the sealing performance between the liquid connector insertion port 53a and the liquid connector 59a is reduced, there is a risk that ink supplied under pressure by the external pump 21 will leak from the liquid connection part 700. If the leaked ink adheres to the circulation pump 500 or the like, a malfunction may occur in the electrical system. Therefore, in this embodiment, the circulation pump and the like are arranged as follows.

[0120] 19 and 20 are diagrams illustrating the characteristic features of this embodiment. Fig. 20(a) is a schematic cross-sectional view of the second pressure control mechanism 150 during a period in which ink is circulating (i.e., a circulation period) due to operation of the circulation pump 500. Note that in Fig. 20(a), the dashed line 1230 indicates the pressure plate 210, flexible member 230, and shaft 193A of the first pressure control mechanism 120 during this period.

[0121] 20(a), the lengths of the shafts 193A, 193B are determined so that the shaft 193B of the second pressure control chamber 152 is shorter than the shaft 193A of the first pressure control chamber 122. By doing so, during the recording operation, the pressure plate 210 of the first pressure control chamber 122 is located at the position indicated by the dashed line 1230, and the pressure plate 210 of the second pressure control chamber 152 is located at the position indicated by the solid line. Therefore, during the recording operation, the pressure in the second pressure control chamber 152 is lower than the pressure in the first pressure control chamber 122.

[0122] However, the configuration for making the pressure in the second pressure control chamber 152 lower than the pressure in the first pressure control chamber 122 is not limited to this.

[0123] Although not described in detail as it is not an essential part of the present disclosure, it is also possible to make the pressure in the second pressure control chamber 152 lower than the pressure in the first pressure control chamber 152 by changing other parts that configure the second pressure control chamber 152. It is also possible to make the pressure in the second pressure control chamber 152 lower than the pressure in the first pressure control chamber 152 by adjusting the positional relationship between the first pressure control chamber 122 and the second pressure control chamber 152 in the gravity direction, etc.

[0124] Arrows X to Z in FIG. 19 indicate three flow paths that communicate between the first pressure control chamber 122 and the second pressure control chamber 152, and the flow directions after the circulation pump 500 is stopped.

[0125] 19, the flow paths connecting the first pressure control chamber 122 and the second pressure control chamber 152 include a flow path X passing through the circulation pump 500, a flow path Y passing through the discharge unit 300, and a flow path Z passing through neither of these. Here, the flow path X includes a pump outlet flow path 180, the circulation pump 500, and a pump inlet flow path 170. The flow path Y includes a supply flow path 130, the pressure chamber 12, and a recovery flow path 140. The flow path Z includes a bypass flow path 160.

[0126] As described with reference to FIG. 10, when the circulation pump 500 that has been operating is stopped, the fluid in the first pressure control chamber 122 moves to the second pressure control chamber 152 until the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152 become equal. The fluid here includes ink and air, as will be described later. Normally, the fluid moves mainly through flow paths Y and Z. Although flow path X includes the circulation pump 500, the circulation pump 500 has a check valve therein, so normally, very little fluid flows through flow path X.

[0127] However, although the check valves 504a, 504b of the circulation pump 500 are placed in the intermediate portions between the pump supply hole 501 and the pump discharge hole 502 and the pump chamber 503, they are not biased against the wall surfaces that they are in close contact with.

[0128] This is because if a configuration is adopted in which each check valve 504a, 504b is biased by a spring or the like to be normally closed, extra force is required to release the biasing force, and this leads to an increase in size and cost in order to improve the pump capacity.

[0129] Therefore, when the circulation pump 500 is stopped, each of the non-actuated check valves 504a, 504b leaks a small amount of fluid. Therefore, depending on the size of the valve chamber and the state of the check valve, there is a possibility that fluid may flow from the first pressure control chamber 122 to the second pressure control chamber 152 via the flow path X.

[0130] Therefore, when the circulation pump 500 is stopped, if the flow resistance of flow path Y increases significantly due to some cause (e.g., bubbles) and exceeds the flow resistance of flow path X, the fluid that should flow from the first pressure control chamber 122 to flow path Y may flow to flow path X.

[0131] At this time, there is no problem if the fluid flowing out from the first pressure control chamber 122 to the flow path X is liquid. However, in a configuration like this example where there is no ink outlet to the ejection module 300 at the top of the first pressure control chamber 122, there is a risk that air remaining at the time of initial ink filling or air flowing in from upstream may remain at the top of the first pressure control chamber 122.

[0132] That is, when the pump outlet 180a is provided above the first pressure control chamber 122 to prevent settling as in this example, the fluid flowing out from the first pressure control chamber 122 to the flow path X may be air.

[0133] As described above, the circulation pump 500 of this example is a small piezoelectric diaphragm pump, and if air flows into the inside, the pump capacity may decrease due to the damping effect of the air, etc. Therefore, it is necessary to prevent air from flowing into the circulation pump 500.

[0134] For this purpose, it is sufficient that the volume V2 of the pump outlet flow path 180 satisfies the following relationship with the volume VV. VV <V2 Where: Volume VV: Volume of fluid passing through the pump outlet 180a in the direction from the first pressure control chamber toward the pump outlet flow passage 180 during the period from when the operating circulation pump 500 stops until the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152 become equal It is. The pump outlet port 180 a is a communication port between the first pressure control chamber 122 and the pump outlet flow path 180 .

[0135] However, the volume VV generally fluctuates. Therefore, a volume VT, which is the maximum estimated value of the volume VV, may be used instead of the volume VV. Here, the volume VT is the volume of the fluid that flows from the first pressure control chamber 122 to the second pressure control chamber 152 during the period from when the operating circulation pump 500 stops until the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152 become equal. In other words, VV <V2 The conditions are as follows: VT <V2 It may be changed to: VV≦VT Since the relationship is satisfied, VT <V2 If the relationship is satisfied, the above VV <V2 The relationship is also satisfied.

[0136] The volume VT can be calculated in advance based on the pressure characteristics of the second pressure control mechanism 150 and the set pressure of the first pressure control chamber 122.

[0137] Figures 20(a) to 20(c) show the state transition of the second pressure control chamber 152 after the circulation pump is stopped. Also, Figure 21 shows a graph of the volume vs. pressure characteristics of the second pressure control chamber 152. Figure 20(a) corresponds to point Qa (Va, Pa) in the graph of Figure 21, Figure 20(b) corresponds to point Qb (Vb, Pb) in the graph of Figure 21, and Figure 20(c) corresponds to point Qc (Vc, Pc) in the graph of Figure 21.

[0138] The solid line in FIG. 20(a) indicates the shape of the second pressure control mechanism 150 during the circulation period.

[0139] 20(a), as described above, indicates the pressure plate 210, flexible member 230, and shaft 193A of the first pressure control mechanism 120 during the circulation period. If the pressure in the first pressure control chamber 122 is always constant, then when the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152 match, the pressure plate 21 and flexible member 230 of the first pressure control mechanism 150 will also be located at the position indicated by the dashed line 1230.

[0140] Fig. 20(b) shows the shape of the second pressure control mechanism 150 when the communication port 191B is closed by the valve 190B in the second pressure control mechanism 150. Also, Fig. 20(c) shows the shape of the second pressure control mechanism 150 when the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152 are equal.

[0141] 21, during the circulation period, the volume and pressure of the second pressure control chamber 152 are at point Qa (Va, Pa). The pressure Pa is smaller than the pressure Pc of the first pressure control chamber 122.

[0142] When the pressure in the second pressure control chamber 152 becomes equal to the pressure in the first pressure control chamber 122, the volume and pressure of the second pressure control chamber 152 are at the position of point Qc (Vc, Pc).

[0143] Therefore, in a configuration without flow path Z (bypass flow path 160), the difference obtained by subtracting the volume Va from the volume Vc becomes the inflow amount V1a of the fluid flowing from the first pressure control chamber 122 to the second pressure control chamber 152 via flow path X or flow path Y (V1a = Vc - Va).

[0144] In particular, if flow path Y is closed in this configuration, the difference obtained by subtracting the volume Va from the volume Vc becomes the inflow amount V1a of the fluid flowing from the first pressure control chamber 122 to the second pressure control chamber 152 via flow path X (V1a=Vc-Va). Alternatively, if the flow resistance of flow path Y is much larger than the flow resistance of flow path X, this difference becomes approximately equal to the inflow amount V1a of the fluid flowing from the first pressure control chamber 122 to the second pressure control chamber 152 via flow path X (V1a≈Vc-Va).

[0145] Therefore, Vc-Va <V2 If the volume V2 of the pump outlet flow path 180 is set so that the volume V2 of the pump outlet flow path 180 is equal to or greater than the volume V2 of the pump outlet flow path 180, then even in a configuration that does not have either flow path Y or flow path Z (bypass flow path 160), it is possible to prevent the air present in the first pressure control chamber 122 from reaching the circulation pump 500 via the pump outlet flow path 180. In other words, even in a configuration that does not have either flow path Y or flow path Z (bypass flow path 160) immediately after the circulation pump 500 is stopped, it is possible to prevent the air present in the first pressure control chamber 122 from reaching the circulation pump 500 via the pump outlet flow path 180.

[0146] Needless to say, in a configuration in which there is a flow path Y in addition to the flow path X, in a configuration in which there is a flow path Z in addition to the flow path X, and in a configuration in which there are flow paths Y and Z in addition to the flow path X, Vc-Va <V2 By setting the volume V2 of the pump outlet flow path 180 so that the volume V2 is equal to or greater than the volume V1 of the pump outlet flow path 180, it is possible to prevent the air present in the first pressure control chamber 122 from reaching the circulation pump 500 via the pump outlet flow path 180, even in a configuration that does not have both flow path Y and flow path Z (bypass flow path 160).

[0147] Here, as shown in FIG. 20(a), there is also a configuration in which the communication port 191B is not closed by the valve 190 in the second pressure control mechanism 150 on average during the circulation period, not limited to the period during which a predetermined amount or more of ink is discharged from the discharge port 13. In such a configuration, the flow path Z (bypass flow path 160) is closed (disappears) after a certain amount of time has elapsed since the circulation pump 500 was stopped. During the period from when the flow path Z is closed until the pressure in the second pressure control chamber 152 becomes equal to the pressure in the first pressure control chamber 122, liquid flows from the first pressure control chamber 122 to the second pressure control chamber 152 via the flow path X or the flow path Y. Therefore, the lower limit value of the volume V2 is specified on the assumption that the liquid flows from the first pressure control chamber 122 to the second pressure control chamber 152 only via the flow path X during the period from when the flow path Z is closed until the pressure in the second pressure control chamber 152 becomes equal to the pressure in the first pressure control chamber 122. This makes it possible to prevent the air present in the first pressure control chamber 122 from reaching the circulation pump 500 via the pump outlet flow path 180. Note that it is assumed here that the fluid flowing into flow path X during the period from when the circulation pump 500 is stopped until when flow path Z is closed can be ignored.

[0148] After the circulation pump 500 is stopped, the fluid flows from the first pressure control chamber 122 into the second pressure control chamber 152, so that the communication port 191B in the second pressure adjustment means 150 is closed by the valve 190B after a certain time has elapsed since the circulation pump 500 was stopped. At this time, the flow path Z (bypass flow path 160) is closed. At this time, the pressure plate 210 is in contact with the valve shaft 193B. In the graph of FIG. 21, the volume and pressure of the second pressure control chamber 152 are at the point Qb (Vb, Pb). After that, as the fluid further flows into the second pressure control chamber 152, the second pressure adjustment means 150 takes the shape shown in FIG. 20(c). In this shape, the communication port 191B remains closed by the valve 190B, and the pressure plate 210 is separated from the valve shaft 193B. At this time, the volume and pressure of the second pressure control chamber 152 are at the position of point Qc (Vc, Pc).

[0149] In the section from point Qb to point Qc, there is no bypass flow path 160, which is the flow path Z. Therefore, the difference obtained by subtracting the volume Vb from the volume Vc becomes the inflow amount V1 of the fluid flowing from the first pressure control chamber 122 to the second pressure control chamber 152 via the flow path X or the flow path Y (V1=Vc-Vb).

[0150] In particular, in a configuration in which neither flow path Z nor flow path Y is present, the difference obtained by subtracting the volume Vb from the volume Vc becomes the inflow amount V1 of the fluid flowing from the first pressure control chamber 122 to the second pressure control chamber 152 via the flow path X (V1=Vc-Vb).

[0151] Therefore, Vc-Vb <V2 If the volume V2 of the pump outlet flow path 180 is set so that the volume V2 of the pump outlet flow path 180 is equal to or greater than the volume V2 of the pump outlet flow path 180, the air present in the first pressure control chamber 122 can be prevented from reaching the circulation pump 500 via the pump outlet flow path 180 in any of the following configurations. That is, even in a configuration in which there is no flow path Y and flow path Z disappears halfway through, the air present in the first pressure control chamber 122 can be prevented from reaching the circulation pump 500 via the pump outlet flow path 180. Also, even in a configuration in which there are no flow paths Y and Z immediately after the circulation pump 500 is stopped, the air present in the first pressure control chamber 122 can be prevented from reaching the circulation pump 500 via the pump outlet flow path 180.

[0152] In addition, even if there is a flow path Y and the flow path Z disappears halfway through, Vc-Vb <V2 If the volume V2 of the pump outlet flow path 180 is set so that the volume V2 of the pump outlet flow path 180 is equal to or greater than the volume V1 of the pump outlet flow path 180, the air present in the first pressure control chamber 122 can be prevented from reaching the circulation pump 500 via the pump outlet flow path 180.

[0153] In addition, even in a configuration in which there is a flow path Y and there is no flow path Z immediately after the circulation pump 500 is stopped (for example, a configuration in which the bypass flow path 160, which is a flow path, is not provided), Vc-Vb <V2 If the volume V2 of the pump outlet flow path 180 is set so that ... Vc-Va <V2 It becomes the same as:

[0154] Furthermore, Vc-Vb <V2 If so, Vc-Va <V2 Therefore, even if the flow path Z is present, Vc-Va <V2 may be set as a condition.

[0155] Although some of the explanation will be repeated, the following explanation will be given with reference to FIG. 21. During the period from when the operating circulation pump 500 is stopped until the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152 become equal, the volume V1a of the fluid flowing from the first pressure control chamber 122 to the second pressure control chamber 152 is V1a = Vc - Va Here, during this period, the fluid flows through one to three flow paths selected from the flow path X, the flow path Y, and the flow path Z.

[0156] Therefore, even if the flow passes through any one to three flow paths selected from the flow paths X, Y, and Z, V1a = Vc - Va <V2 If the above condition is met, the air in the first pressure control chamber 122 can be prevented from reaching the circulation pump 500.

[0157] Therefore, whether the bypass flow path 160, which is the flow path Z, is provided or not, V1a = Vc - Va <V2 If the above condition is met, the air in the first pressure control chamber 122 can be prevented from reaching the circulation pump 500.

[0158] As shown in FIG. 21, during the period from when the circulation pump 500 is stopped and the flow path Z is closed until the pressure in the first pressure control chamber 122 becomes equal to the pressure in the second pressure control chamber 152, the volume V1 of the fluid flowing from the first pressure control chamber 122 to the second pressure control chamber 152 is V1=Vc-Vb Here, during this period, the fluid flows through one or two flow paths selected from the flow path X and the flow path Y.

[0159] Therefore, even if the liquid passes through one or two of the flow paths X and Y, V1=Vc-Vb <V2 If the above condition is met, the air in the first pressure control chamber 122 can be prevented from reaching the circulation pump 500.

[0160] Similarly, as shown in Fig. 21, in a configuration without the bypass flow path 160, which is the flow path Z, the following occurs. During the period from when the circulation pump 500 is stopped until the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152 become equal, the volume V1 of the fluid flowing from the first pressure control chamber 122 to the second pressure control chamber 152 is V1=Vc-Vb Here, during this period, the fluid flows through one or two flow paths selected from the flow path X and the flow path Y. In addition, in a configuration without the bypass flow path 160, which is the flow path Z, Va=Vb.

[0161] Therefore, even if the liquid passes through one or two of the flow paths X and Y, V1=Vc-Vb <V2 If the above condition is met, the air in the first pressure control chamber 122 can be prevented from reaching the circulation pump 500.

[0162] In order to reduce the size of the pump, if it is desired to reduce the volume V2 of the pump outlet flow path 180 as much as possible, Vc-Va <V2 Instead of the condition, Vc-Vb <V2 In other words, it is also possible to reduce the lower limit of the allowable range of the volume V2 of the pump outlet flow path 180.

[0163] In that case, as shown in FIG. 19, it is desirable to provide an inlet 260 of the bypass flow passage 160 at the lowest part of the first pressure control chamber 122 so that the bypass flow passage 160 is not blocked by bubbles.

[0164] As a result, even if the flow resistance of flow path Y increases and the air accumulated in the upper part of the first pressure control chamber 122 flows out into flow path X, the air will not reach the circulation pump 500. Therefore, the circulation pump will not malfunction due to air, and the discharge stability can be improved.

[0165] <Other embodiments> In the above embodiment, when the pressure in the second pressure control chamber 152 becomes equal to the pressure in the first pressure control chamber 122 after the circulation pump 500 is stopped, the communication port 191B remains closed by the valve 190B as shown in FIG. 20(c). Also, the pressure plate 210 is separated from the valve shaft 193B. However, at this time, there is also a configuration in which the communication port 191B remains closed by the valve 190B and the pressure plate 210 abuts against the valve shaft 193B. Even in such a configuration, Vc and Pc at the point Qc can be applied as they are as the volume and pressure of the second pressure control chamber 152 when the pressure in the second pressure control chamber 152 becomes equal to the pressure in the first pressure control chamber 122. In the above embodiment, the circulation pump 500 is installed inside the circulation unit as shown in FIG. 4, but this is not limiting, and the circulation pump 500 may be installed outside the circulation unit .

[0166] <Technical Features of the Present Disclosure> The present disclosure includes the following configurations, methods, and programs. [Configuration 1] a first pressure adjustment means for adjusting a pressure of a liquid, the first pressure adjustment means comprising: a first valve chamber, a first pressure control chamber, a first communication port that communicates the first valve chamber and the first pressure control chamber, a first valve that opens and closes the first communication port, a first flexible member that constitutes a portion of a surface of the first pressure control chamber and is configured to be displaceable, and a first pressure plate that constitutes another portion of a surface of the first pressure control chamber and is configured to be displaceable in conjunction with the first flexible member; a second pressure adjustment means for adjusting a pressure of a liquid, the second pressure adjustment means comprising: a second valve chamber, a second pressure control chamber, a second communication port that communicates the second valve chamber with the second pressure control chamber, a second valve that opens and closes the second communication port, a second flexible member that constitutes a portion of a surface of the second pressure control chamber and is configured to be displaceable, and a second pressure plate that constitutes another portion of a surface of the second pressure control chamber and is configured to be displaceable in conjunction with the second flexible member; a first flow passage that communicates a pressure chamber and the first pressure control chamber; a second flow passage communicating the pressure chamber with the second pressure control chamber; a third flow path communicating the second pressure control chamber with a circulation pump for circulating liquid; a fourth flow path communicating the circulation pump and the first pressure control chamber; Equipped with During a period from when the operating circulation pump is stopped until the pressure in the first pressure control chamber and the pressure in the second pressure control chamber become equal, when the volume of the fluid passing through the communication port between the first pressure control chamber and the fourth flow path in a direction from the first pressure control chamber toward the fourth flow path is VV and the volume of the fourth flow path is V2, VV <V2 That is, Circulation unit.

[0167] [Configuration 2] When the volume of fluid flowing from the first pressure control chamber to the second pressure control chamber during the period from when the circulating pump stops operating until the pressure in the first pressure control chamber becomes equal to the pressure in the second pressure control chamber is VT, VT <V2 That is, 2. The circulation unit according to configuration 1.

[0168] [Configuration 3] When the volume of the second pressure control chamber during the period when the circulation pump is operating is Va, and the volume of the second pressure control chamber when the pressure in the first pressure control chamber and the pressure in the second pressure control chamber become equal after the circulation pump is stopped is Vc, Vc-Va <V2 That is, 2. The circulation unit according to configuration 1.

[0169] [Configuration 4] a bypass flow passage communicating between the first pressure control chamber and the second valve chamber, The bypass flow path is opened and closed in response to the second communication port being opened and closed by the second valve. 2. The circulation unit according to configuration 1.

[0170] [Configuration 5] When the volume of fluid flowing from the first pressure control chamber to the second pressure control chamber during the period from when the circulating pump stops operating until the pressure in the first pressure control chamber becomes equal to the pressure in the second pressure control chamber is VT, VT <V2 That is, 5. The circulation unit according to configuration 4.

[0171] [Configuration 6] When the volume of the second pressure control chamber during the period when the circulation pump is operating is Va, and the volume of the second pressure control chamber when the pressure in the first pressure control chamber and the pressure in the second pressure control chamber become equal after the circulation pump is stopped is Vc, Vc-Va <V2 That is, 5. The circulation unit according to configuration 4.

[0172] [Configuration 7] When the volume of the second pressure control chamber when the bypass flow path is closed after the circulation pump in operation is stopped is Vb, and the volume of the second pressure control chamber when the pressure in the first pressure control chamber and the pressure in the second pressure control chamber become equal after the circulation pump in operation is stopped is Vc, Vc-Vb <V2 That is, 5. The circulation unit according to configuration 4.

[0173] [Configuration 8] The bypass flow path communicates with the first pressure control chamber at a lowermost portion of the first pressure control chamber. A circulation unit according to any one of configurations 4 to 7.

[0174] [Configuration 9] The third flow path is in communication with the second pressure control chamber at a lower portion of the second pressure control chamber. A circulation unit according to any one of configurations 1 to 8.

[0175] [Configuration 10] The fourth flow path communicates with the first pressure control chamber at an upper side of the first pressure control chamber. 10. A circulation unit according to any one of configurations 1 to 9.

[0176] [Configuration 11] A circulation unit according to any one of configurations 1 to 10, The circulation pump; A dispensing module; Equipped with The dispensing module includes: A discharge port for discharging a liquid; The pressure chamber communicated with the discharge port; an ejection element for ejecting liquid from the ejection port via the pressure chamber; Equipped with Liquid ejection head.

[0177] [Configuration 12] The circulation pump is installed inside the circulation unit. A liquid ejection head according to configuration 11.

[0178] [Configuration 13] A liquid ejection head according to aspect 11 or 12, a carriage for scanning the liquid ejection head in a main scanning direction; A conveying means for conveying the recording medium in a sub-scanning direction; A liquid ejection device comprising: [Explanation of symbols]

[0179] 1 Liquid ejection head 12 Pressure Chamber 15 Discharge element 120 First pressure control mechanism 130 Supply Channel 140 Recovery channel 150 Second pressure control mechanism 160 Bypass flow path 170 Pump inlet passage 180 Pump outlet flow path 500 Circulation Pump

Claims

1. a first pressure adjustment means for adjusting a pressure of a liquid, the first pressure adjustment means comprising: a first valve chamber, a first pressure control chamber, a first communication port that communicates the first valve chamber and the first pressure control chamber, a first valve that opens and closes the first communication port, a first flexible member that constitutes a portion of a surface of the first pressure control chamber and is configured to be displaceable, and a first pressure plate that constitutes another portion of a surface of the first pressure control chamber and is configured to be displaceable in conjunction with the first flexible member; a second pressure adjustment means for adjusting a pressure of a liquid, the second pressure adjustment means comprising: a second valve chamber, a second pressure control chamber, a second communication port that communicates the second valve chamber with the second pressure control chamber, a second valve that opens and closes the second communication port, a second flexible member that constitutes a portion of a surface of the second pressure control chamber and is configured to be displaceable, and a second pressure plate that constitutes another portion of a surface of the second pressure control chamber and is configured to be displaceable in conjunction with the second flexible member; a first flow passage that communicates a pressure chamber and the first pressure control chamber; a second flow passage communicating the pressure chamber with the second pressure control chamber; a third flow path communicating the second pressure control chamber with a circulation pump for circulating liquid; a fourth flow path communicating the circulation pump and the first pressure control chamber; Equipped with During a period from when the operating circulation pump is stopped until the pressure in the first pressure control chamber and the pressure in the second pressure control chamber become equal, a volume of fluid passing through the communication port between the first pressure control chamber and the fourth flow path in a direction from the first pressure control chamber toward the fourth flow path is defined as VV, and a volume of the fourth flow path is defined as V2, VV<V2 That is, Circulation unit.

2. When a volume of fluid flowing from the first pressure control chamber to the second pressure control chamber during a period from when the circulating pump is stopped until the pressure in the first pressure control chamber becomes equal to the pressure in the second pressure control chamber is VT, VT<V2 That is, 2. The circulation unit according to claim 1.

3. When the volume of the second pressure control chamber during the period when the circulation pump is operating is Va, and the volume of the second pressure control chamber when the pressure in the first pressure control chamber and the pressure in the second pressure control chamber become equal after the circulation pump is stopped is Vc, Vc-Va<V2 That is, 2. The circulation unit according to claim 1.

4. a bypass flow passage communicating between the first pressure control chamber and the second valve chamber, The bypass flow path is opened and closed in response to the second communication port being opened and closed by the second valve.

2. The circulation unit according to claim 1.

5. When a volume of fluid flowing from the first pressure control chamber to the second pressure control chamber during a period from when the circulating pump is stopped until the pressure in the first pressure control chamber becomes equal to the pressure in the second pressure control chamber is VT, VT<V2 That is, 5. A circulation unit according to claim 4.

6. When the volume of the second pressure control chamber during the period when the circulation pump is operating is Va, and the volume of the second pressure control chamber when the pressure in the first pressure control chamber and the pressure in the second pressure control chamber become equal after the circulation pump is stopped is Vc, Vc-Va<V2 That is, 5. A circulation unit according to claim 4.

7. When the volume of the second pressure control chamber when the bypass flow path is closed after the circulation pump in operation is stopped is Vb, and the volume of the second pressure control chamber when the pressure in the first pressure control chamber and the pressure in the second pressure control chamber become equal after the circulation pump in operation is stopped is Vc, Vc-Vb<V2 That is, 5. A circulation unit according to claim 4.

8. The bypass flow path communicates with the first pressure control chamber at a lowermost portion of the first pressure control chamber.

5. A circulation unit according to claim 4.

9. The third flow path is in communication with the second pressure control chamber at a lower portion of the second pressure control chamber.

2. The circulation unit according to claim 1.

10. The fourth flow path communicates with the first pressure control chamber at an upper side of the first pressure control chamber.

2. The circulation unit according to claim 1.

11. A circulation unit according to any one of claims 1 to 10; The circulation pump; A dispensing module; Equipped with The dispensing module includes: A discharge port for discharging a liquid; The pressure chamber communicated with the discharge port; an ejection element for ejecting liquid from the ejection port via the pressure chamber; Equipped with Liquid ejection head.

12. The circulation pump is installed inside the circulation unit. The liquid ejection head according to claim 11.

13. The liquid ejection head according to claim 11, a carriage for scanning the liquid ejection head in a main scanning direction; A conveying means for conveying the recording medium in a sub-scanning direction; A liquid ejection device comprising:

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