Liquid ejection device and liquid ejection head

Abstract

To suppress occurrence of defects of a circulation pump by leaked ink.SOLUTION: A liquid discharge device 50 has a liquid storage part 2, a liquid discharge head 1, a liquid commutation path 59 for communicating the liquid storage part with the liquid discharge head, and liquid pressurization means 21 for pressurizing and supplying liquid of the liquid storage part to the liquid discharge head through the liquid communication path. The liquid discharge head includes an introduction port 53a for introducing liquid from the liquid storage part, a pressure chamber 12 to which the liquid introduced from the introduction port is supplied, a discharge port 13 for discharging the liquid in the pressure chamber, and a circulation path for circulating the liquid supplied from the liquid communication path. The circulation path includes a supply flow passage 130, a pressure chamber 12, a recovery flow passage 140, a circulation pump 500, and pressure adjustment means 120. The circulation pump is above in a gravity direction the liquid introduction port provided on a liquid flow passage from the liquid storage part to the pressure adjustment means, and is arranged at a position which is brought into non contact with the introduction port.SELECTED DRAWING: Figure 21

Description

[Technical Field]

[0001] The present disclosure relates to a liquid ejection device having a liquid circulation path, and a liquid ejection head used in the liquid ejection device. [Background technology]

[0002] Some liquid ejection devices circulate liquid to prevent the settling of coloring materials and thickening of ink. Patent Document 1 discloses a configuration in which a piezoelectric circulation pump is installed inside a liquid ejection head unit to circulate ink inside the liquid ejection head. In this configuration, ink supplied from the circulation pump to a pressure control unit is supplied to the liquid ejection orifices via an ink supply flow path, and ink that is not ejected is recovered by the circulation pump via an ink recovery flow path. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-195932 Summary of the Invention [Problem to be solved by the invention]

[0004] In a liquid ejection device that circulates liquid as in Patent Document 1, in order to compensate for pressure loss in the ink supply path, filter, etc., an ink pressurizing means is sometimes provided in the ink storage section or ink supply flow path, and pressurized ink is supplied to the liquid ejection head.

[0005] However, if a connection is provided in a path where ink is kept under pressure (positive pressure), there is a risk of ink leaking from the connection. In this case, if the ink connection is provided above the circulation pump as in Patent Document 1, the leaked ink can easily reach the circulation pump and come into contact with the electrical contacts of the circulation pump, potentially causing a malfunction in the circulation pump.

[0006] The present disclosure aims to provide a technology that can prevent malfunctions of a circulation pump caused by leaked ink. [Means for solving the problem]

[0007] The present disclosure provides a liquid ejection device having a liquid storage section that stores liquid, an inlet for introducing liquid from the liquid storage section, a pressure chamber to which the liquid introduced from the inlet is supplied, and an ejection port for ejecting the liquid in the pressure chamber, a liquid communication passage for connecting the liquid storage section with the inlet of the liquid ejection head, and a liquid pressurizing means for pressurizing and supplying the liquid from the liquid storage section to the liquid ejection head via the liquid communication passage, wherein the liquid ejection head has a circulation path for circulating the liquid supplied from the liquid communication passage within the liquid ejection head, and the circulation path has a supply flow path that supplies liquid to the pressure chamber, a recovery flow path that recovers liquid from the pressure chamber, a circulation pump that supplies the liquid recovered from the recovery flow path to the supply flow path, and a pressure adjustment means for adjusting the pressure of the liquid supplied to the supply flow path, and the circulation pump is positioned above the inlet in the direction of gravity and in a position that is not in contact with the inlet. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to prevent malfunctions of the circulation pump caused by leaked ink. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a liquid ejection device. [Figure 2] FIG. 1 is an exploded perspective view of a liquid ejection head; [Figure 3] 2A and 2B are longitudinal cross-sectional views of a liquid ejection head and an enlarged cross-sectional view of an ejection module. [Figure 4] FIG. 1 is a schematic view of the appearance of a circulation unit; [Figure 5] FIG. [Figure 6]FIG. 2 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 circulation pump shown in FIG. 8(a) taken along line IX-IX. [Figure 10] FIG. [Figure 11] FIG. 1 shows electrical connections to a piezoelectric ceramic. [Figure 12] 3A and 3B are diagrams illustrating the flow of ink inside a liquid ejection head. [Figure 13] FIG. 4 is a schematic diagram showing a circulation path in the discharge unit. [Figure 14] FIG. 10 is a diagram showing an aperture plate 330. [Figure 15] FIG. 2 is a diagram showing a discharge element substrate. [Figure 16] FIG. 4 is a cross-sectional view showing the flow of ink in the ejection unit. [Figure 17] FIG. 3 is a cross-sectional view showing the vicinity of a discharge port. [Figure 18] FIG. 10 is a cross-sectional view showing a comparative example of the vicinity of the ejection port. [Figure 19] FIG. 10 is a diagram showing a comparative example of a discharge element substrate. [Figure 20] FIG. 2 is a diagram showing a flow path configuration of a liquid ejection head. [Figure 21] 3 is a schematic diagram showing in more detail the connection state between the main body and the liquid ejection head of the liquid ejection device, and the arrangement of the circulation pump and the like. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. The following embodiments do not limit the scope of the present disclosure, and not all combinations of features described in the present embodiments are necessarily essential to the solutions of the present disclosure. The same reference numerals are used to designate the same components. In the present embodiments, an example is described in which a thermal method is used as an ejection element for ejecting liquid, in which an electrothermal conversion element generates bubbles to eject the liquid. However, this is not limited to this. The present invention can also be applied to liquid ejection heads that use an ejection method that ejects liquid using a piezoelectric element (piezo) or other ejection methods. Furthermore, the pump and pressure adjustment means described below are not limited to the configurations shown in the embodiments and drawings. In the following description, the basic configuration of the present disclosure will be described first, followed by a description of the characteristic features of the present disclosure.

[0011] <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, the 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 schematically shows a liquid ejection device that uses a liquid ejection head 1. The liquid ejection device 50 of 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.

[0012] The liquid ejection head 1 is mounted on a carriage 60. The carriage 60 moves back and forth along a guide shaft 51 in the main scanning direction (X direction). The recording medium P is transported in a sub-scanning direction (Y direction) that intersects (in this example, orthogonal to) the main scanning direction by transport rollers (transport means) 55, 56, 57, and 58. In each of the figures referred to below, the Z direction indicates the vertical direction, and intersects (in this example, orthogonal to) the XY plane defined by the X and Y directions. The liquid ejection head 1 is configured so that it can be removed from and attached to the carriage 60 by the user.

[0013] The liquid ejection head 1 is configured to include 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 of the ejection ports.

[0014] The liquid ejection device 50 is also provided with an ink tank (liquid storage section) 2, which is an ink supply source, and an external pump 21 (liquid pressurizing means). The ink stored in the ink tank 2 is pressurized and supplied to a circulation unit 54 via an ink supply tube (liquid communication path) 59 by the driving force of the external pump 21.

[0015] The liquid ejection device 50 forms a predetermined image on the recording medium P by repeating a printing scan in which the liquid ejection head 1 mounted on the carriage 60 moves in the main scanning direction while ejecting ink to perform printing, and a transport operation in which the recording medium P is transported in the sub-scanning direction. The liquid ejection head 1 in this embodiment is capable of ejecting four types of ink: 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.

[0016] 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 when not performing recording, and is used to prevent the ejection ports from drying out, protect the ejection ports, and perform ink suction operations from the ejection ports.

[0017] 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 configure the liquid ejection head 1 to circulate at least one ink rather than circulating all four types of ink.

[0018] FIG. 1B is a block diagram showing a control system of the liquid ejection device 50. The CPU 103 functions as a control unit that controls the operation of each component of the liquid ejection device 50 based on programs, such as processing procedures, stored in the ROM 101. The RAM 102 is used as a work area when the CPU 103 executes processing. The CPU 103 receives image data from a host device 400 external to the liquid ejection device 50, controls the head driver 1A, and controls the driving of the ejection elements provided in the ejection 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 that moves the carriage 60 and a motor driver 104A of a conveyance motor 104 that conveys the recording medium P. The CPU 103 also controls a pump driver 500A that drives a circulation pump 500 (described later) and a pump driver 21A of an external pump 21. 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 without relying on data from the host device 400.

[0019] <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(a) taken along line IIIa-IIIa. Fig. 3(a) is an overall longitudinal 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 configuration of the liquid ejection head 1 of this embodiment will be described below, focusing on Figs. 2 and 3, and also referring to Fig. 1 as appropriate.

[0020] 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.

[0021] An ink supply tube 59 is provided to the external pump 21 connected to the ink tank 2, which serves as an ink supply source (see FIG. 1). A liquid connector 59a (see FIG. 21), which will be described later, is provided at the end of the ink supply tube 59. When the liquid ejection head 1 is mounted on the liquid ejection device 50, the liquid connector 59a (described later) provided at the end of the ink supply tube 59 is airtightly connected to a liquid connector insertion port 53a, which is an inlet for introducing liquid, provided in 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, four types of ink are used, so four sets of ink tanks 2, external pumps 21, ink supply tubes 59, and circulation units 54 are provided, one for each ink, and four independent ink supply paths are formed corresponding to each ink. 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. The liquid ejection device 50 of this embodiment is not provided with an ink recovery system that recovers 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 an ink supply tube for recovering ink from the liquid ejection head 1 to the ink tank 2. The liquid connector insertion port 53a is provided for each ink.

[0022] 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 a substantially similar configuration, and in this embodiment, when there is no need to particularly distinguish between the circulation units, they will all be referred to as circulation unit 54.

[0023] 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. Power is supplied to each discharge element 15 via electric wiring formed on the silicon substrate 310 by a film formation technique.

[0024] Furthermore, an ejection port forming member 320 is formed on the surface (the lower surface in FIG. 3(b)) of the silicon substrate 310. A plurality of pressure chambers 12 corresponding to the plurality of ejection elements 15 and a plurality of ejection ports 13 for ejecting ink are formed in the ejection port forming member 320 by photolithography. Furthermore, a common supply flow path 18 and a common recovery flow path 19 are formed in the silicon substrate 310. Furthermore, a supply connection flow path 323 that connects the common supply flow path 18 to each pressure chamber 12, and a recovery connection flow path 324 that connects the common recovery flow path 19 to each pressure chamber 12 are formed in the silicon substrate 310. 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 in the figure ejects black ink and cyan ink, and the ejection module 300 located on the right side in the figure ejects magenta ink and yellow ink. Note that this combination is just an example, and any combination of inks is acceptable. A configuration in which one ejection module ejects one type of ink may be used, or a configuration in which one ejection module ejects three or more types of ink. The two ejection modules 300 do not have to eject the same number of types of ink. A configuration in which one ejection module 300 is provided, or a configuration in which three or more ejection modules 300 are provided. 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 make up each ejection port array.

[0025] An ink supply port and an ink recovery port, which will be described later, are formed on the back surface (top 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.

[0026] 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.

[0027] 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 channel 48 and an ink recovery channel 49 are formed in the first support member 4, penetrating from one surface to the other. One opening of the ink supply channel 48 is connected to the ink supply port in the silicon substrate 310, and one opening of the ink recovery channel 49 is connected to the ink recovery port in the silicon substrate 310. The ink supply channel 48 and the ink recovery channel 49 are provided independently for each type of ink.

[0028] Furthermore, 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 (the upper surface in FIG. 3(a)) of the first support member 4. The second support member 7 holds an electrical wiring member 5 that is electrically connected to the ejection module 300. The electrical wiring member 5 is a member for applying an electrical signal to the ejection module 300 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) to protect it from corrosion by ink and external impacts.

[0029] An electrical contact substrate 6 is thermocompression bonded to an end portion 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 substrate 6 are electrically connected. The electrical contact substrate 6 has an external signal input terminal (not shown) for receiving an electrical signal from the liquid ejection device 50.

[0030] 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 connect the ink supply flow path 48 and the ink recovery flow path 49 of the first support member 4 to 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.

[0031] The openings at one end of each of the ink supply channel 48 and the ink recovery channel 49 of the first support member 4 have a small opening area that matches the ink supply port and ink recovery port in the silicon substrate 310. In contrast, the openings at the other end of each of the ink supply channel 48 and the ink recovery channel 49 of the first support member 4 have a shape that is enlarged to the same opening area as the large opening area of ​​the joint member 8 that is formed to match the flow channels of the circulation unit 54. By adopting this configuration, it is possible to suppress an increase in flow channel resistance for ink collected from each recovery channel. However, the shapes of the openings at one end and the other end of each of the ink supply channel 48 and the ink recovery channel 49 are not limited to the above example.

[0032] 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 channel 48 of the first support member 4, and then flows into the common supply channel 18 from the ink supply port of the ejection module 300. The ink then flows from the common supply channel 18 through the supply connection channel 323 into the pressure chamber 12, and some 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 channel 324 and the common recovery channel 19, and flows into the ink recovery channel 49 of the first support member 4 from the ink recovery port. The ink that has flowed into the ink recovery channel 49 then flows into the circulation unit 54 through the recovery port 89 of the joint member 8, and is recovered.

[0033] <Components of the circulation unit> 4 is a schematic diagram showing the appearance 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 form a circulation path within the liquid ejection head 1 that supplies and recovers ink to and from the ejection module 300.

[0034] <Circulation path inside the liquid ejection head> Fig. 5 is a vertical cross-sectional view showing a schematic diagram of a circulation path for one type of ink (one color of ink) configured within the liquid ejection head 1. 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 have been simplified. Therefore, the relative positions of each component differ from those in Figs. 2 and 4 described above and Fig. 21 described below. Fig. 6 is a block diagram showing a schematic diagram of the circulation path shown in Fig. 5.

[0035] As shown in FIGS. 5 and 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, by using these two pressure adjustment means 120, 150, circulation within a constant pressure range is achieved within the circulation path. Furthermore, the ink is configured to flow through the pressure chamber 12 (ejection element 15) at a flow rate corresponding 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 FIGS. 5 and 6. Note that the arrows in each figure indicate the direction of ink flow.

[0036] First, the connection state of each component in the liquid ejection head 1 will be described. An external pump 21, which sends ink stored 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 (first communication port) that can be opened and closed by a valve 190A (first valve) shown in FIG.

[0037] The first pressure control chamber 122 is connected to the supply flow path 130, the bypass flow path 160, and the pump outlet flow path 180 of the circulation pump 500. The supply flow path 130 is connected to the 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 (second communication port) that is opened and closed by a second 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.

[0038] 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 FIG. 5, 170a denotes the inlet of the pump inlet flow path 170.

[0039] Next, we will explain the flow of ink in the liquid ejection head 1 having the above configuration. As shown in Figure 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.

[0040] 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 in a positive pressure state. After that, the ink that has flowed into the first valve chamber 121 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.

[0041] Next, the flow of ink within the circulation path will be described. The circulation pump 500 operates to suck ink from the pump inlet flow path 170, which is located upstream, and deliver it to the pump outlet flow path 180, which is located downstream. Therefore, when the pump is driven, ink supplied to the first pressure control chamber 122 flows into the supply flow path 130 and the bypass flow path 160 together with ink delivered from the pump outlet flow path 180. As will be described in detail later, this embodiment uses a piezoelectric diaphragm pump, driven by a piezoelectric element attached to a diaphragm, as the circulation pump capable of delivering liquid. A piezoelectric diaphragm pump changes the volume of the pump chamber by inputting a drive voltage to the piezoelectric element, and delivers liquid by alternately moving two check valves due to pressure fluctuations.

[0042] 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.

[0043] Meanwhile, ink that flows from the first pressure control chamber 122 into the bypass flow path 160 flows into the second valve chamber 151, then passes through the communication port 191B and flows into the second pressure control chamber 152. The ink that flows into the second pressure control chamber 152 via the bypass flow path 160 and the ink recovered from the recovery flow path 140 are sucked into the circulation pump 500 via the pump inlet flow path 170 by the operation of the circulation pump 500. The ink sucked into the circulation pump 500 is then sent to the pump outlet flow path 180 and flows back into the first pressure control chamber 122. Subsequently, the ink that flows from the first pressure control chamber 122 into the second pressure control chamber 152 via the supply flow path 130 and the ejection module 300, and the ink that flows into the second pressure control chamber 152 via the bypass flow path 160, both flow into the circulation pump 500. The ink is then sent from the circulation pump 500 to the first pressure control chamber 122. In this manner, ink circulates within the circulation path.

[0044] As described above, in this embodiment, the circulation pump 500 can circulate the liquid along the circulation path formed inside the liquid ejection head 1. This makes it possible to suppress thickening of the ink inside the ejection module 300 and accumulation of sedimentary components of the ink colorant, and it is possible to maintain good ink fluidity in the ejection module 300 and ejection characteristics at the ejection ports.

[0045] Furthermore, 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 reduced 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 using a small circulation pump.

[0046] 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, this configuration eliminates the need for a flow path for recovering ink from the liquid ejection head 1 to the ink tank 2. Therefore, only an ink supply tube is required to connect the ink tank 2 to the liquid ejection head 1, and no ink recovery tube is required. This allows the liquid ejection device 50 to have a simpler configuration with fewer tubes, thereby achieving a more compact overall device. Furthermore, reducing the number of tubes reduces ink pressure fluctuations caused by tube oscillations associated with the main scanning of the liquid ejection head 1. Furthermore, the oscillations of the tubes during the main scanning of the liquid ejection head 1 impose a driving load on the carriage motor that drives the carriage 60. Therefore, reducing the number of tubes reduces the driving load on the carriage motor, enabling the simplification of the main scanning mechanism, including the carriage motor. Furthermore, since it is no longer necessary to recover ink from the liquid ejection head to the ink tank, the external pump 21 can also be made more compact. As described above, according to this embodiment, the liquid ejection device 50 can be made smaller and less expensive.

[0047] <Pressure adjustment means> FIG. 7 is a diagram showing an example of a 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. Therefore, the following description will be given taking the first pressure adjustment means 120 as an example, and the second pressure adjustment means 150 will only be illustrated with the reference numerals of the parts corresponding to those of 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.

[0048] 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 via 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 in a position facing the communication port 191 by a valve spring 200, and is configured to be able 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 wall 123, it is preferable that the portion of the valve 190 that comes into contact with the partition wall 123 be made of an elastic material. Furthermore, a valve shaft 190a that is inserted into the communication port 191 protrudes from the center of the valve 190. By pressing this valve shaft 190a against the biasing force of a valve spring 200, the valve 190 moves away from the partition wall 123, allowing ink to flow through the communication port 191. Hereinafter, the state in which the valve 190 blocks the flow of ink through the communication port 191 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."

[0049] The opening of the cylindrical housing 125 is closed by a flexible member 230 and a pressure plate 210. The first pressure control chamber 122 is formed by this 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 as a molded resin part, and the flexible member 230 can be configured as a resin film. In this case, the pressure plate 210 can be fixed to the flexible member 230 by thermal welding.

[0050] A pressure adjustment spring 220 (biasing means) is provided between the pressure plate 210 and the partition wall 123. The biasing force of the pressure adjustment spring 220 biases the pressure plate 210 and the flexible member 230 in a direction in which the internal volume of the first pressure control chamber 122 increases, as shown in FIG. 7( a). Furthermore, when the pressure in the first pressure control chamber 122 decreases, the pressure plate 210 and the flexible member 230 displace 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 190 a of the valve 190. Thereafter, when the internal volume of the first pressure control chamber 122 further decreases, the valve 190 moves together with the valve shaft 190 a against the biasing force of the valve spring 220 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)).

[0051] In this embodiment, the connections within the circulation path are 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 into the first pressure control chamber 122. This ink inflow displaces the flexible member 230 and the pressure plate 210 in a direction that increases the internal volume of the first pressure control chamber 122. As a result, the pressure plate 210 moves away from the valve shaft 190a of the valve 190, and the 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 becomes closed (the state shown in FIG. 7(c)).

[0052] In this way, in the first pressure adjustment means 120 of this embodiment, when the pressure inside the first pressure control chamber 122 decreases below a certain pressure (for example, when the negative pressure becomes strong), 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.

[0053] As described above, the first pressure adjustment means 120 has a first pressure control chamber (first liquid chamber) 122 that contains liquid supplied from the liquid supply source (ink tank 2) and the circulation pump 500, and a first adjustment mechanism that adjusts the pressure of the liquid in the first pressure control chamber 122. The first adjustment mechanism includes the pressure plate 210, pressure adjustment spring 220, valve 190, valve spring 200, and first valve chamber 121 described above, and is configured to adjust the pressure of the liquid contained in the first pressure control chamber 122 in conjunction with the volume of the first pressure control chamber 122. The second pressure adjustment means 150 has a second pressure control chamber (second liquid chamber) 152 connected to the pump inlet flow path 170, and a second adjustment mechanism that adjusts the pressure of the liquid contained in the second pressure control chamber 152. The second adjustment mechanism includes the pressure plate 210, the pressure adjustment spring 220, the second valve 190B, the second valve spring 200, and the second valve chamber 151, and is configured to adjust the pressure of the liquid contained in the second pressure control chamber 152 in conjunction with the volume of the second pressure control chamber 152.

[0054] Next, the pressure in the first pressure control chamber 122 will be described in more detail. As described above, 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, causing the pressure plate 210 to come into contact with the valve shaft 190a and open the communication port 191 (the state shown in FIG. 7(b)). At this time, the relationship between the forces acting on the pressure plate 210 is expressed by the following equation 1.

[0055] 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 This becomes: P1: Pressure (gauge pressure) of the first valve chamber 121 P2: Pressure (gauge pressure) of the first pressure control chamber 122 F1: Valve spring force 200 F2: Spring force of pressure adjusting spring 220 S1: Pressure-receiving area of ​​valve 190 S2: Pressure receiving area of ​​pressure plate 210

[0056] Here, the spring force F1 of the valve spring 200 and the spring force F2 of the pressure adjustment spring 220 are positive (to the right in FIG. 7) in the direction in which they press the valve 190 and the pressure plate 210. Furthermore, with regard to the pressure P1 in the first valve chamber 121 and the pressure P2 in the first pressure control chamber 122, P1 is configured to satisfy the relationship P1≧P2.

[0057] The pressure P2 in the first pressure control chamber 122 when the communication port 191 is in the open state is determined by Equation 2, and when the communication port 191 is in the open state, 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.

[0058] On the other hand, as shown in FIG. 7(c), when the pressure plate 210 is not in contact with the valve shaft 190a and the communication port 191 is closed, the relationship of the forces acting on the pressure plate 210 is expressed by Equation 3.

[0059] P3×S3+F3=0...Equation 3

[0060] Now, rearranging Equation 3 for P3 gives P3=-F3 / S3 Equation 4 This becomes: F3: The spring force of the pressure adjusting spring 220 when the pressure plate 210 and the valve shaft 190a are not in contact with each other P3: Pressure (gauge pressure) in the first pressure control chamber 122 when the pressure plate 210 and the valve shaft 190a are not in contact with each other S3: Pressure-receiving area of ​​the pressure plate 210 when the pressure plate 210 and the valve 190 are not in contact with each other

[0061] FIG. 7(c) shows a state in which the pressure plate 210 and flexible member 230 have been displaced to the right to their limit. 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 depending on the amount of displacement of the pressure plate 210 and flexible member 230 as they move to the state shown in FIG. 7(c). Specifically, when the pressure plate 210 and flexible member 230 are positioned more leftward in FIG. 7 than in 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 decreases according to the relationship shown in Equation 4. Therefore, according to Equations 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) as the state changes from FIG. 7(b) to FIG. 7(c). That is, from the state in which the communication port 191 is open, the pressure plate 210 and the flexible member 230 gradually displace to the right, and the pressure in the first pressure control chamber 122 gradually increases until the internal volume of the first pressure control chamber 122 finally reaches its limit of displacement. In other words, the negative pressure weakens.

[0062] <Circulation pump> Next, the configuration and operation of the circulation pump 500 built into the liquid ejection head 1 described above will be described in detail with reference to FIGS.

[0063] FIG. 8 is an external perspective view 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 main body 505a and a flow path connecting member 505b adhesively fixed to the outer surface of the housing main body 505a. The housing main body 505a and the flow path connecting member 505b each have a pair of through holes that communicate with each other and are provided at two different positions. The pair of through holes provided at one position form pump supply holes 501, and the pair of through holes provided at the other position form pump discharge holes 502. The pump supply holes 501 are connected to the pump inlet flow path 170 connected to the second pressure control chamber 152, and the pump discharge holes 502 are connected to the pump outlet flow path 180 connected to the first pressure control chamber 122. Ink supplied from pump supply hole 501 passes through pump chamber 503 (see FIG. 9) to be described later and is discharged from pump discharge hole 502.

[0064] 9 is a cross-sectional view of the circulation pump 500 shown in FIG. 8(a) taken along line IX-IX. A diaphragm 506 is bonded to the inner surface of a pump housing 505, and a pump chamber 503 is formed between the diaphragm 506 and a recess formed in the inner surface of the pump housing 505. The pump chamber 503 is connected to 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 of the pump supply hole 501, and a check valve 504b is provided in the middle of the pump discharge hole 502. Specifically, the check valve 504a is arranged so that a portion of the check valve 504a can move leftward in the figure in a space 512a formed in the middle of the pump supply hole 501. The check valve 504b is arranged so that a portion of the check valve 504b can move rightward in the figure in a space 512b formed in the middle of the pump discharge hole 502.

[0065] When diaphragm 506 is displaced and the volume of pump chamber 503 increases, reducing 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, it enters an open state that allows ink to flow through pump supply hole 501. When diaphragm 506 is displaced and the volume of pump chamber 503 decreases, pressurizing 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, it enters a closed state that blocks the flow of ink through pump supply hole 501.

[0066] 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 and toward the space 512b (that is, moves to the right in the figure), thereby allowing the flow of ink through the pump discharge hole 502.

[0067] The material of each check valve 504a, 504b may be any material that can deform in response to the pressure in the pump chamber 503, and may be made of, 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.

[0068] As described above, pump chamber 503 is formed by the joining of 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. This causes check valve 504b, which is disposed opposite pump discharge hole 502, to open, and ink is discharged from pump chamber 503. At this time, check valve 504a, which is disposed opposite pump supply hole 501, is in close contact with the wall surface surrounding pump supply hole 501, and therefore backflow of ink from pump chamber 503 to pump supply hole 501 is suppressed.

[0069] Conversely, when diaphragm 506 is displaced in the direction in which pump chamber 503 expands, the pressure in pump chamber 503 decreases. As a result, check valve 504a arranged opposite pump supply hole 501 opens, and ink is supplied to pump chamber 503. At this time, check valve 504b arranged at pump discharge hole 502 comes into close contact with the wall surface surrounding an opening formed in pump casing 505, closing the opening. As a result, backflow of ink from pump discharge hole 502 to pump chamber 503 is suppressed.

[0070] In this way, in the circulation pump 500, the diaphragm 506 deforms, changing the pressure inside the pump chamber 503, thereby suctioning and discharging ink. At this time, if bubbles get into the pump chamber 503, even if the diaphragm 506 is displaced, the expansion and contraction of the bubbles will reduce the change in pressure inside the pump chamber 503, and the amount of liquid delivered will decrease. Therefore, the pump chamber 503 is arranged parallel to gravity to make it easier for bubbles that get into the pump chamber 503 to collect 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 ability to discharge bubbles inside the pump, and stabilize the flow rate.

[0071] Here, the specific configuration of the components of the circulation pump 500 will be described with reference to FIGS. 10 and 11 . FIG. 10 is an exploded perspective view of the circulation pump 500, with FIG. 10(a) being an exploded perspective view of the components of the circulation pump 500 viewed from the rear side, and FIG. 10(b) being an exploded perspective view of the components of the circulation pump 500 viewed from the front side. In this embodiment, the circulation pump 500 is a piezoelectric pump driven by applying a voltage to a piezoelectric ceramic. As shown in FIG. 10 , a circular diaphragm 509 is bonded to a diaphragm 506 with adhesive 508. A circular piezoelectric ceramic 510 is fixed to the diaphragm 509 by adhesive. The diaphragm 506 is made of an injection-moldable material such as PPE+PS (modified polyphenylene ether) or polypropylene, but a punched film or resin plate can also be used, and the material is not limited to these. The diaphragm 509 is made of brass, stainless steel, an iron-nickel alloy, or the like, but is not limited to these.

[0072] A drive circuit board 513 is provided on the surface facing the piezoelectric ceramic 510. The drive circuit board 513 is connected to a power supply unit provided in the main body of the liquid ejection device 50, and applies a predetermined drive voltage (AC voltage) to the piezoelectric ceramic 510 and the vibration plate 509.

[0073] 11 is a perspective view of the electrical connection portion of piezoelectric ceramic 510 seen from the cover 507 side, looking through drive circuit board 513. Drive circuit board 513 and piezoelectric ceramic 510 are connected by electrical connection cable 518a, and drive circuit board 513 and diaphragm 509 are electrically connected by electrical connection cable 518b. The electrical connection between electrical connection cable 518a and drive circuit board 513, and the electrical connection between electrical connection cable 518b and drive circuit board 513, are each made by solder 520. The electrical connection between electrical connection cable 518a and piezoelectric ceramic 510, and the electrical connection between electrical connection cable 518b and diaphragm 509 are each made by solder 521.

[0074] The diaphragm 509 is connected to the GND wiring of the drive circuit board 513 via an electrical connection cable 518b, and the piezoelectric ceramic 510 is connected to the AC voltage output section of the drive circuit board 513 via an electrical connection cable 518a. By connecting the diaphragm 509 to the GND and applying a shifted AC voltage to the piezoelectric ceramic 510, the piezoelectric ceramic 510 expands and contracts, deforming the diaphragm. This changes the pressure inside the pump chamber, allowing ink to be sucked in and expelled.

[0075] The drive circuit board 513 is electrically connected to the electrical contact board 6 by a cable, and an electrical connection terminal for driving the pump is provided on the electrical contact board 6. When the circulation unit 54 is attached to the carriage 60, an electrical signal output from an electrical contact section (first electrical connection section) (not shown) on the carriage 60 side is input to the drive circuit board 513 via an electrical connection terminal (second electrical connection section) (not shown) on the electrical contact board 6.

[0076] By providing the electrical contact substrate 6 with an electrical connection terminal for driving the pump in this manner, the circulation pump 500 can be driven by applying a driving voltage (AC voltage) to the electrical connection terminal even when the pump is removed from the carriage 60.

[0077] <Ink flow inside the liquid ejection head> FIG. 12 is a diagram illustrating the flow of ink within the liquid ejection head. The circulation of ink within the liquid ejection head 1 will be described with reference to FIG. 12. To more clearly illustrate the ink circulation path, the relative positions of the components (such as the first pressure adjustment unit 120, the second pressure adjustment unit 150, and the circulation pump 500) in FIG. 12 are simplified. Therefore, the relative positions of the components differ from those in FIGS. 2 and 4 and the later-described FIG. 21. FIG. 12(a) is a schematic diagram illustrating the flow of ink during a recording operation in which ink is ejected from the ejection ports 13 to record. The arrows in the figure indicate the flow of ink. In this embodiment, both the external pump 21 and the circulation pump 500 start operating during a recording operation. The external pump 21 and the circulation pump 500 may be operating regardless of the recording operation. The external pump 21 and the circulation pump 500 do not need to be driven in conjunction with each other, but may be driven independently.

[0078] During the recording operation, the circulation pump 500 is in an ON state (driving state), and the ink flowing out from the first pressure control chamber 122 (first liquid chamber) 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.

[0079] Meanwhile, ink that has flowed from the first pressure control chamber 122 into the bypass flow path 160 passes through the second valve chamber 151 and then flows into the second pressure control chamber 152. The ink that has flowed into the second pressure control chamber 152 passes through the pump inlet flow path 170, the circulation pump 500, and the pump outlet flow path 180, and then flows back into the first pressure control chamber 122. At this time, the control pressure of the first valve chamber 121 is set higher than the control pressure of the first pressure control chamber 122 based on the relationship of Equation 2 described above. Therefore, the ink in the first pressure control chamber 122 does not flow into the first valve chamber 121, but is instead supplied to the ejection module 300 again via the supply flow path 130. The ink that has flowed into the ejection module 300 passes through the recovery flow path 140, the second pressure control chamber 152, the pump inlet flow path 170, the circulation pump 500, and the pump outlet flow path 180, and then flows back into the first pressure control chamber 122. In this manner, ink circulation is completed within the liquid ejection head 1.

[0080] <Ink flow inside the liquid ejection head> FIG. 12 is a diagram illustrating the flow of ink within the liquid ejection head. The circulation of ink within the liquid ejection head 1 will be described with reference to FIG. 12. FIG. 12(a) is a schematic diagram illustrating the flow of ink during a recording operation in which ink is ejected from the ejection ports 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 operate. The external pump 21 and the circulation pump 500 may be operated regardless of the recording operation. The external pump 21 and the circulation pump 500 do not have to be driven in conjunction with each other, and may be driven independently.

[0081] During the recording operation, the circulation pump 500 is in an ON state (driving state), and the ink flowing out from the first pressure control chamber 122 (first liquid chamber) 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.

[0082] Meanwhile, ink that has flowed from the first pressure control chamber 122 into the bypass flow path 160 passes through the second valve chamber 151 and then flows into the second pressure control chamber 152. The ink that has flowed into the second pressure control chamber 152 passes through the pump inlet flow path 170, the circulation pump 500, and the pump outlet flow path 180, and then flows back into the first pressure control chamber 122. At this time, the control pressure of the first valve chamber 121 is set higher than the control pressure of the first pressure control chamber 122 based on the relationship of Equation 2 described above. Therefore, the ink in the first pressure control chamber 122 does not flow into the first valve chamber 121, but is instead supplied to the ejection module 300 again via the supply flow path 130. The ink that has flowed into the ejection module 300 passes through the recovery flow path 140, the second pressure control chamber 152, the pump inlet flow path 170, the circulation pump 500, and the pump outlet flow path 180, and then flows back into the first pressure control chamber 122. In this manner, ink circulation is completed within the liquid ejection head 1.

[0083] In the ink circulation described above, the amount of ink circulating (flow rate) within the ejection module 300 is determined by the difference in control pressure between the first pressure control chamber 122 and the second pressure control chamber 152. This pressure difference is set to a circulation amount that can suppress thickening of ink near the ejection ports within the ejection module 300. In addition, ink consumed during printing is supplied from the ink tank 2 to the first pressure control chamber 122 via the filter 110 and the first valve chamber 121. The mechanism by which the consumed ink is supplied will be described in detail. As ink is reduced from the circulation path by the amount of ink consumed during printing, the pressure within the first pressure control chamber decreases, and as a result, the ink within the first pressure control chamber 122 also decreases. As the ink within the first pressure control chamber 122 decreases, the internal volume of the first pressure control chamber 122 decreases. When the internal volume of the first pressure control chamber 122 decreases below a predetermined volume, the communication port 191A (first communication port) switches to an open state, and ink is supplied from the first valve chamber 121 to the first pressure control chamber 122. This supplied ink experiences a pressure loss as it passes from the first valve chamber 121 to the communication port 191A, and as it flows into the first pressure control chamber 122, the ink switches from a positive pressure state to a negative pressure state. Then, 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 increases, and when the internal volume of the first pressure control chamber increases to or exceeds a predetermined volume, the communication port 191A switches to a closed state. In this way, the communication port 191A alternates between an open state and a closed state depending on the consumption of ink. Furthermore, when ink is not consumed, the communication port 191A remains closed.

[0084] FIG. 12B is a schematic diagram showing the flow of ink immediately after the recording operation is completed and the circulation pump 500 is turned off (stopped). When the recording operation is completed and the circulation pump 500 is turned off, the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152 are both at the control pressures during the recording operation. Therefore, the ink moves as shown in FIG. 12B depending on the pressure difference between the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152. Specifically, ink continues to flow from the first pressure control chamber 122 to the ejection module 300 via the supply flow path 130, and then through the recovery flow path 140 to the second pressure control chamber 152. In addition, ink also continues to flow from the first pressure control chamber 122 to the second pressure control chamber 152 via the bypass flow path 160 and the second valve chamber 151.

[0085] The amount of ink that moves from the first pressure control chamber 122 to the second pressure control chamber 152 due to 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 internal volume of the first pressure control chamber 122 is maintained constant. From the relationship in Equation 2 above, when the internal volume of 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 (biasing means), the pressure-receiving area S1 of the valve 190, and the pressure-receiving area S2 of the pressure plate 210 are maintained constant. Therefore, the pressure in the first pressure control chamber 122 is determined according to changes 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 maintained at the same pressure as the control pressure during the recording operation.

[0086] Meanwhile, the pressure in the second pressure control chamber 152 changes over time in response to changes in the volume of ink contained in the second pressure control chamber 152 due to the inflow of ink from the first pressure control chamber 122. Specifically, from the state shown in FIG. 12(b) until the communication port 191 closes and the second valve chamber 151 and the second pressure control chamber 152 are not in communication with each other, as shown in FIG. 12(c), the pressure in the second pressure control chamber 152 changes according to Equation 2. Thereafter, the pressure plate 210 and the valve shaft 190a are no longer in contact with each other, and the communication port 191 is closed. Then, as shown in FIG. 12(d), ink flows from the recovery channel 140 into the second pressure control chamber 152. This ink inflow displaces the pressure plate 210 and the flexible member 230, and the pressure in the second pressure control chamber 152 changes according to Equation 4, i.e., increases, until the volume of the second pressure control chamber 152 reaches its maximum.

[0087] 12(c), no ink flows from the first pressure control chamber 122 to the second pressure control chamber 152 via the bypass flow path 160 and the second valve chamber 151. Therefore, after the ink in the first pressure control chamber 122 is supplied to the ejection module 300 via the supply flow path 130, only a flow occurs to reach the second pressure control chamber 152 via the recovery flow path 140. As described above, the movement of ink from the first pressure control chamber 122 to the second pressure control chamber 152 occurs according to the pressure difference between the pressure in the first pressure control chamber 122 and the pressure in the second pressure control chamber 152. Therefore, when the pressure in the second pressure control chamber 152 becomes equal to the pressure in the first pressure control chamber 122, the movement of ink stops.

[0088] Furthermore, when the pressure in the second pressure control chamber 152 becomes equal to the pressure in the first pressure control chamber 122, the second pressure control chamber 152 expands to the state shown in FIG. 12(d). When the second pressure control chamber 152 expands as shown in FIG. 12(d), a storage portion capable of storing ink is formed in the second pressure control chamber 152. Note that the time required from stopping the circulation pump 500 to transition to the state shown in FIG. 12(d) generally takes about one to two minutes, although this time 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. 12(d) in which ink is stored in the storage portion, the circulation pump 500 supplies the ink in the storage portion to the first pressure control chamber 122. As a result, the amount of ink in the first pressure control chamber 122 increases, as shown in FIG. 12(e), and the flexible member 230 and the pressure plate 210 are displaced in the expansion direction. Then, when the circulation pump 500 continues to be driven, the state inside the circulation path changes as shown in FIG. 12(a).

[0089] 12(a) has been described as an example during a printing operation, but as mentioned above, ink may be circulated without a printing operation. Even in this case, ink flows as shown in FIGS. 12(a) to 12(e) occur depending on whether the circulation pump 500 is driven or stopped.

[0090] 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 ink, and is in a closed state when the circulation of ink stops, but this is not limiting. 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 ink. Below, this will be described in detail together with the role of the bypass flow path 160.

[0091] 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 stronger than a predetermined value, for example, from affecting the ejection module 300. The bypass flow path 160 is also provided to supply ink to the pressure chamber 12 from both the supply flow path 130 and the recovery flow path 140.

[0092] First, an example will be described in which the bypass flow path 160 prevents the negative pressure from being stronger than a predetermined value and affecting the ejection module 300. For example, changes in the ambient temperature can change the ink characteristics (e.g., viscosity). 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, which is driven at a constant drive rate, increases, and the flow rate through the ejection module 300 also increases. Meanwhile, because the ejection module 300 is maintained at a constant temperature by a temperature adjustment mechanism (not shown), the viscosity of the ink in the ejection module 300 remains constant even when the ambient temperature changes. While the viscosity of the ink in the ejection module 300 remains unchanged, the flow rate of the ink flowing through the ejection module 300 increases, resulting in flow resistance and an increase in the negative pressure in the ejection module 300. In this way, if the negative pressure in the discharge module 300 becomes stronger than the predetermined 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 predetermined, which may affect discharge.

[0093] For this reason, in this embodiment, a bypass flow path 160 is formed in the circulation path. By providing the bypass flow path 160, when the negative pressure becomes stronger than a predetermined value, ink also flows through the bypass flow path 160, making it possible to maintain a constant pressure in the ejection module 300. Therefore, for example, the communication port 191B in the second pressure adjustment unit 150 may be configured with a control pressure that maintains the communication port 191B in a closed state even when the circulation pump 500 is being driven. The control pressure in the second pressure adjustment unit 150 may be set so that the communication port 191B in the second pressure adjustment unit 150 is opened when the negative pressure becomes stronger than a predetermined value. In other words, as long as the meniscus does not collapse even when the pump flow rate changes due to viscosity changes such as environmental changes, or as long as a predetermined negative pressure is maintained, the communication port 191B may be closed when the circulation pump 500 is being driven.

[0094] 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 within the circulation path can also occur due to the ejection operation of the ejection element 15. This is because the ejection operation generates a force that draws ink into the pressure chamber.

[0095] Below, we will explain how the negative pressure in the pressure chamber increases when high-duty printing continues, and how, as a result, ink is supplied to the pressure chamber 12 from 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 4 pL ink droplet is printed on a 1200 dpi grid is treated as 100%. High-duty printing means, for example, printing at 100% duty.

[0096] As 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. Meanwhile, because the circulation pump 500 discharges ink at a constant rate, the balance between inflow and outflow in the second pressure control chamber 152 is disrupted, the ink in the second pressure control chamber 152 decreases, the negative pressure in the second pressure control chamber 152 increases, and the second pressure control chamber 152 shrinks. As the negative pressure in the second pressure control chamber 152 increases, the amount of ink flowing into the second pressure control chamber 152 via the bypass flow path 160 increases, and the second pressure control chamber 152 stabilizes with the inflow and outflow balanced. As a result, the negative pressure in the second pressure control chamber 152 increases in accordance with 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.

[0097] Then, as recording at an even higher 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, and instead the amount flowing into the second pressure control chamber 152 from the communication port 191B via the bypass flow path 160 increases. As 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 path 140 becomes zero, and all of the ink flowing out to the circulation pump 500 becomes ink flowing in from the communication port 191B. As this state progresses further, ink now flows back from the second pressure control chamber 152 through the recovery flow path 140 into the pressure chamber 12. 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 via the bypass flow path 160. In this case, the pressure chamber 12 is filled with ink from the supply flow channel 130 and ink from the recovery flow channel 140, and is ejected.

[0098] Incidentally, this backflow of ink that occurs when the printing duty is high is a phenomenon that occurs due to the provision of the bypass flow path 160. Also, in the above, an example has been described in which the communication port 191B in the second pressure adjustment means is opened in response to the backflow of ink, but the backflow of ink can also occur when the communication port 191B in the second pressure adjustment means is opened. Also, even in a configuration that does not include the second pressure adjustment means, the provision of the bypass flow path 160 can cause the backflow of ink.

[0099] <Configuration of the discharge unit> FIG. 13 is a schematic diagram showing the circulation path for one color of ink in the ejection unit 3 of this embodiment. FIG. 13(a) is an exploded perspective view of the ejection unit 3 as seen from the first support member 4 side, and FIG. 13(b) is an exploded perspective view of the ejection unit 3 as seen from the ejection module 300 side. The arrows marked IN and OUT in the figure indicate the flow of ink. While only one color of ink will be described, the other colors have similar flows. The second support member 7 and the electrical wiring member 5 are omitted from FIG. 13 and will also be omitted in the following description of the ejection unit configuration. The first support member 4 in FIG. 13(a) shows a cross section taken along line XI-XI in FIG. 3. The ejection module 300 includes an ejection element substrate 340 and an aperture plate 330. FIG. 14 illustrates the aperture plate 330, and FIG. 15 illustrates the ejection element substrate 340.

[0100] Ink is supplied to the discharge unit 3 from the circulation unit 54 via a joint member 8 (see FIG. 3). The following describes the ink path from when the ink passes through the joint member 8 until it returns to the joint member 8. Note that the joint member 8 will not be shown in the following drawings.

[0101] The ejection module 300 includes an ejection element substrate 340, which is a silicon substrate 310, and an aperture plate 330, and further includes an ejection port forming member 320. 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 a first support member 4. The ejection module 300 is supported by the first support member 4 to form an ejection unit 3. The ejection element substrate 340 includes an ejection port forming member 320, which includes a plurality of ejection port arrays each including a plurality of ejection ports 13. A portion of the ink supplied via the ink flow path in the ejection module 300 is ejected from the ejection ports 13. Unejected ink is collected via the ink flow path in the ejection module 300.

[0102] As shown in FIGS. 13 and 14, 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. 15 and 16, 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 that communicates with the plurality of supply connection channels 323, and a common recovery channel 19 that communicates with the plurality of recovery connection channels 324. The ink channels in the ejection unit 3 are formed by connecting an ink supply channel 48 and an ink recovery channel 49 (see FIG. 3) provided in the first support member 4 to channels provided in the ejection module 300. The support member supply port 211 is a cross-sectional opening that forms the ink supply channel 48, and the support member recovery port 212 is a cross-sectional opening that forms the ink recovery channel 49.

[0103] 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 flows through the support member supply port 211 in the ink supply flow path 48, and 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 forms the supply side flow path. The ink then flows through the pressure chamber 12 (see FIG. 3(b)) of the ejection port forming member 320 to the recovery connection flow path 324, which is a recovery side flow path. The flow of ink in the pressure chamber 12 will be described in detail later.

[0104] In the recovery flow path, the ink that has entered the recovery connection flow path 324 flows into the common recovery flow path 19. The ink then 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 passes through the support member recovery port 212 to be recovered into the circulation unit 54.

[0105] The area of ​​the opening plate 330 that does not have the ink supply port 311 or the ink recovery port 312 corresponds to the area that separates the support member supply port 211 and the support member recovery port 212 in the first support member 4. The first support member 4 also does not have any openings in this area. 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.

[0106] In FIG. 14, the aperture plate 330 has multiple rows of apertures arranged in the X direction, and multiple rows of apertures arranged in the Y direction. The supply (IN) apertures and the recovery (OUT) apertures are alternately arranged in the Y direction so as to be offset by a half pitch in the X direction. In FIG. 15, the ejection element substrate 340 has common supply channels 18 communicating with multiple supply connection channels 323 arranged in the Y direction and common recovery channels 19 communicating with multiple recovery connection channels 324 arranged in the Y direction, arranged alternately in the X direction. The common supply channels 18 and the common recovery channels 19 are separated by ink type, and the number of common supply channels 18 and common recovery channels 19 is determined depending on the number of ejection port rows for each color. The supply connection channels 323 and recovery connection channels 324 are also arranged in the same number as the ejection ports 13. Note that a one-to-one correspondence is not necessarily required; one supply connection channel 323 and one recovery connection channel 324 may correspond to multiple ejection ports 13.

[0107] Such an opening plate 330 and an ejection element substrate 340 are overlapped and joined together so that the flow paths of each ink are connected to form an ejection module 300, and by being supported by the first support member 4, an ink flow path is formed that includes the supply flow path and recovery flow path as described above.

[0108] Figures 16(a) to 16(c) are cross-sectional views showing ink flow in different parts of the discharge unit 3. Figure 16(a) is a cross-section shown at XIVa-XIVa in Figure 13(a) and shows a cross-section of a part in the discharge unit 3 where the ink supply channel 48 and the ink supply port 311 communicate with each other. Figure 16(b) is a cross-section shown at XIVb-XIVb in Figure 13(a) and shows a cross-section of a part in the discharge unit 3 where the ink recovery channel 49 and the ink recovery port 312 communicate with each other. Figure 16(c) is a cross-section shown at XIVc-XIVc in Figure 13(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 channels in the first support member 4.

[0109] In the supply flow path for supplying ink, as shown in FIG. 16( 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 aperture plate 330 overlap and communicate with each other. In the recovery flow path for recovering ink, as shown in FIG. 16( 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 aperture plate 330 overlap and communicate with each other. As shown in FIG. 16( c), the ejection unit 3 has a partial region where no opening is provided in the aperture plate 330. 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. 16( a), ink is supplied in a region where the ink supply port 311 is provided, and as shown in FIG. 16( b), ink is recovered in a region where the ink recovery port 312 is provided. Note that, although the present embodiment has been described using an example of a configuration in which the aperture plate 330 is used, a configuration in which the aperture plate 330 is not used may also be used. For example, a configuration may be adopted in which flow paths corresponding to the ink supply flow path 48 and the ink recovery flow path 49 are formed in the first support member 4, and the ejection element substrate 340 is joined to the first support member 4.

[0110] 17(a) and 17(b) are cross-sectional views showing the vicinity of the ejection ports 13 in the ejection module 300, and FIG. 18 is a cross-sectional view showing, as a comparative example, an ejection module configured such that the common supply channel 18 and the common recovery channel 19 are widened in the X direction. Note that the thick arrows shown in the common supply channel 18 and the common recovery channel 19 in FIGS. 17 and 18 indicate the oscillation of ink in a configuration using a serial-type liquid ejection device 50. Ink supplied to the pressure chambers 12 via the common supply channel 18 and the supply connection channel 323 is ejected from the ejection ports 13 when the ejection elements 15 are driven. When the ejection elements 15 are not driven, ink is recovered from the pressure chambers 12 to the common recovery channel 19 via the recovery connection channel 324, which is a recovery channel.

[0111] In a configuration using a serial-type liquid ejection device 50, when ejecting ink from circulating ink in this manner, the ejection of ink is affected to a certain extent by the fluctuation of ink in the ink flow paths due to the scanning of the liquid ejection head 1. Specifically, the influence of the fluctuation of ink in the ink flow paths can manifest as differences in the amount of ink ejected or deviations in the ejection direction. As shown in FIG. 18 , if the common supply flow path 18 and the common recovery flow path 19 have cross-sectional shapes that are wide in the X direction, which is the scanning direction, the ink in the common supply flow path 18 and the common recovery flow path 19 is more susceptible to inertial forces in the scanning direction, causing the ink to fluctuate significantly. As a result, the fluctuation of ink may affect the ejection of ink from the ejection ports 13. Furthermore, widening the common supply flow path 18 and the common recovery flow path 19 in the X direction increases the distance between colors, which may reduce printing efficiency.

[0112] Therefore, in this embodiment, the common supply flow path 18 and the common recovery flow path 19 both extend in the Y direction in the cross section shown in FIG. 17, but are also configured to extend in the Z direction, which is perpendicular to the X direction, which is the main scanning direction. This configuration allows the width of each of the common supply flow path 18 and the common recovery flow path 19 in the scanning direction to be reduced. By reducing the width of each of the common supply flow path 18 and the common recovery flow path 19 in the scanning direction, ink fluctuation due to inertial force acting on the ink in the common supply flow path 18 and the common recovery flow path 19 in the direction opposite to the scanning direction (indicated by the thick black arrow in the figure) during scanning is reduced. This makes it possible to suppress the effect of ink fluctuation on ink ejection. Furthermore, extending the common supply flow path 18 and the common recovery flow path 19 in the Z direction increases the cross-sectional area, thereby reducing flow path pressure loss.

[0113] 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 scanning direction, the ink oscillation in the common supply flow path 18 and the common recovery flow path 19 during scanning is reduced, but this does not mean that the oscillation is eliminated. Therefore, in order to suppress differences in the ejection of each ink type that may still occur even with reduced oscillation, in this embodiment, the common supply flow path 18 and the common recovery flow path 19 are configured to be positioned so as to overlap in the X direction.

[0114] 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 sandwiched between them. 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 disrupted, this will affect the flow and ejection of ink in the X direction in the pressure chamber 12. When the influence of ink fluctuation is added to this, there is a risk that this will further affect the ejection of ink from each ejection port.

[0115] 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, ink fluctuation during scanning in the common supply flow path 18 and the common recovery flow path 19 becomes approximately the same 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 that occurs inside the pressure chamber 12 does not vary greatly, allowing for stable ejection.

[0116] Furthermore, 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 separate flow paths. The supply connection flow path 323 and the pressure chamber 12 are connected to each other, and the pressure chamber 12 is connected to the recovery connection flow path 324, 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 connecting 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 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 evaporation of ink from the ejection port 13, can be kept fresh.

[0117] 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 accommodate ejection at a high flow rate.

[0118] 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 positioned closer to each other in the X direction. Preferably, the distance between the flow paths is 75 μm to 100 μm.

[0119] FIG. 19 is a diagram showing an ejection element substrate 340 as a comparative example. Note that in FIG. 19, the supply connection channel 323 and the recovery connection channel 324 are not shown. Since ink that has received thermal energy from the ejection elements 15 in the pressure chambers 12 flows into the common recovery channel 19, ink with a relatively high temperature flows therethrough compared to the temperature of the ink in the common supply channel 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 channel 19 exists, such as the portion α surrounded by the dashed dotted line in FIG. 19. In this case, the temperature rises locally in that portion, causing temperature unevenness in the ejection module 300 and possibly affecting ejection.

[0120] 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, suppressing temperature increases in the vicinity thereof. 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.

[0121] 20(a) and (b) are diagrams showing the flow path configuration of a liquid ejection head 1 corresponding to three colors of ink: cyan (C), magenta (M), and yellow (Y). As shown in FIG. 20(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 scanning direction of the liquid ejection head 1. As shown in FIG. 20(b), the common supply flow path 18 and the common recovery flow path 19 are provided along the ejection port array in which the ejection ports 13 are arranged, and extend in the Y direction so that the ejection port array is sandwiched between the common supply flow path 18 and the common recovery flow path 19.

[0122] <Pressure fluctuations in the discharge module> Next, pressure fluctuations in the liquid ejection head 1 of this embodiment will be described with reference to Figure 21. In a liquid ejection device 50 that uses a serial type liquid ejection head 1 of this embodiment, ink is supplied to a circulation unit 54 of the liquid ejection head 1 using an ink supply tube 59. For this reason, when the liquid ejection head 1 is scanned during a recording operation or the like, the ink supply tube 59 vibrates, and there is a risk that pressure fluctuations will occur in the ink inside the ink supply tube 59.

[0123] As described above, the liquid ejection device 50 of this embodiment does not include an ink recovery path that recovers ink in the liquid ejection head 1 to the ink tank 2. Therefore, the only flow path connected to the circulation unit 54 is the ink supply tube 59 for supplying liquid to the liquid ejection head 1. In this embodiment, four circulation tubes 59 are connected (see FIG. 2). If the liquid ejection head 1 were provided with a recovery tube that recovers ink in the ink tank 2, there is a risk that pressure fluctuations would also propagate from the recovery tube side to the liquid ejection head 1. In this embodiment, since a circulation path that is completed within the liquid ejection head 1 is provided, the only flow path connected to the circulation unit 54 is the ink supply tube 59. Furthermore, the ink supplied from the ink supply tube 59 to the circulation unit 54 flows into the first valve chamber 121 of the first pressure adjustment means 120 (see FIG. 5). Then, the valve 190 controls the opening and closing of the communication port 191. This makes it possible to suppress the tube oscillation pressure generated when the liquid ejection head 1 is scanned from affecting the ejection module 300.

[0124] In this embodiment, a piezoelectric diaphragm pump is used as the circulation pump 500. The circulation pump 500 changes the volume of the pump chamber by inputting a drive voltage to a piezoelectric element, and two check valves move alternately due to pressure fluctuations, thereby delivering ink. Therefore, the ink collected by the circulation pump 500 and delivered from the circulation pump 500 pulsates in accordance with the increase and decrease in the volume of the pump chamber 503.

[0125] In this embodiment, a configuration for suppressing the propagation of pulsation is provided on the inlet and outlet sides of the circulation pump 500, which is the source of ink pulsation in the circulation path. That is, a first pressure adjustment means 120 is connected to the pump outlet flow path 180, and a second pressure adjustment means 150 is connected to the pump inlet flow path 170. With this configuration, it is possible to suppress the transmission of pulsation generated by driving the circulation pump 500 to the ejection module 300 from both the inlet and outlet sides of the circulation pump 500.

[0126] As shown in FIG. 7, the pressure adjustment means preferably includes a pressure adjustment spring 220, a pressure plate 210, and a flexible member 230. A comparative example of the pressure adjustment means may be configured to detect pressure using a pressure sensor, process electrical signals, and then maintain a predetermined pressure using a pressure adjustment pump or the like. Because ink is ejected from the ejection elements 15 at a frequency of several tens of kilohertz, high-speed feedback control processing is required. However, with the configuration of this comparative example, there is a risk that high-speed feedback control processing may not be performed appropriately. As a result, ink pulsation may be transmitted to the ejection module 300.

[0127] In contrast to this, if the pressure adjustment means is configured with the pressure adjustment spring 220, pressure plate 210, and flexible member 230, as in the present embodiment, it is possible to appropriately suppress the transmission of ink pulsation to the ejection module 300. In other words, the pressure adjustment spring 220, pressure plate 210, and flexible member 230 mechanically absorb the ink pulsation generated by the circulation pump 500, so it is possible to suppress the transmission of ink pulsation to the ejection module 300.

[0128] As described above, it is preferable to supply ink from the ink tank 2 to the liquid ejection head 1 under pressure. Pressure fluctuations can be further suppressed by supplying ink under pressure. A specific explanation follows. As described above, the liquid ejection head 1 is scanned in the main scanning direction. Therefore, the ink supply tube 59, which supplies ink from the ink tank 2 to the liquid ejection head 1, also oscillates in the main scanning direction, causing the pressure P1 inside the ink supply tube 59 to fluctuate. Note that, as described above, the pressure P1 is the pressure inside the first valve chamber 121, and no pressure adjustment mechanism is provided between the first valve chamber 121 and the ink supply tube 59. Therefore, the pressure inside the ink supply tube 59 and the pressure inside the first valve chamber 121 are treated as being the same. As shown in Equation 2, the pressure P2 inside the first pressure control chamber 122 of the first pressure adjustment means 120 is proportional to the pressure P1. As shown in Equation 2, the proportionality constant is determined by the ratio between the pressure-receiving area S1 of the valve 190 and the pressure-receiving area S2 of the pressure plate 210 (see also FIG. 7). When ink is supplied under pressure, the pressure receiving area S1 of the valve 190 can be made smaller relative to the pressure receiving area S2 of the pressure plate 210, and as a result, fluctuations in pressure P2 due to fluctuations in pressure P1 can be made smaller. In other words, since the pressure P2 in the first pressure control chamber 122 caused by fluctuations in pressure P1 in the ink supply tube 59 due to scanning is reduced, pressure fluctuations in the circulation path can be suppressed, and pressure fluctuations in the pressure chamber 12 can also be suppressed.

[0129] In this way, supplying ink under pressure to the liquid ejection head 1 is effective in suppressing pressure fluctuations within the circulation path. However, when ink is supplied under pressure, the ink supply path from the external pump 21 to the first valve chamber 121 of the liquid ejection head 1 becomes a positive pressure region where the ink pressure is positive. For this reason, there is a concern that ink may leak from the connections between the components that make up the ink supply path and adhere to the conductive parts of the circulation pump 500, causing malfunctions in the electrical system. In this embodiment, a connection part (liquid connection part 700), which will be described later, that detachably connects the ink supply tube 59, which communicates with the external pump 21, to the liquid ejection head 1 is present within the ink supply path.

[0130] The configuration of the liquid connection part 700 in this embodiment and measures to be taken against ink leaking from the liquid connection part 700 will be described below.

[0131] <Liquid connection part> Figure 21 is a schematic diagram showing the connection state of the ink tank 2, external pump 21, and liquid ejection head 1 in the liquid ejection device 50 of this embodiment. Figure 21(a) is a cross-sectional view taken along line XXIa-XXIa in Figure 2(b). Figure 21(b) is a partial cross-sectional view of the connection state of the liquid connection part 700.

[0132] The liquid ejection device 50 of this embodiment is configured to allow for easy replacement of just the liquid ejection head 1 when a malfunction occurs in the liquid ejection head 1. Specifically, it has a liquid connection part 700 that allows for easy connection and disconnection between the ink supply tube 59 connected to the external pump 21 and the liquid ejection head 1. This makes it possible to easily attach and detach just the liquid ejection head 1 to and from the liquid ejection device 50.

[0133] 21(a), 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 filter 110 described above. The liquid connector 59a is also provided at the tip of an ink supply tube 59 that is connected to an external pump 21 (liquid pressurizing means) that pressurizes and supplies ink from the ink tank 2 to the liquid ejection head 1.

[0134] As shown in FIG. 21(b), an O-ring 59c is provided on the inner surface of the liquid connector 59a near the opening 59b. In this embodiment, the O-ring 59c is made of an elastic material such as rubber or elastomer. The O-ring 59c tightly contacts the outer peripheral surface of the liquid connector insertion port 53a inserted through the opening 59b of the liquid connector 59a, sealing the gap between the liquid connector 59a and the liquid connector insertion port 53a and maintaining liquid-tightness. Furthermore, when the liquid connector insertion port 53a is removed from the liquid connector 59a, a spring biasing force causes a valve member (not shown) to tightly contact the O-ring 59c, preventing ink leakage from the liquid connector 59a. In this embodiment, a connector-type configuration has been described for the liquid connection unit 700. However, this is not limited to this. For example, the tip of the ink supply tube 59 may be directly inserted into the liquid connector insertion port 53a, which is the inlet of the liquid ejection head 1.

[0135] As described above, the liquid ejection head of this embodiment allows for easy installation, removal, and replacement of the liquid ejection head 1 via the liquid connection part 700. However, during replacement of the liquid ejection head 1, dust or other foreign matter may adhere to the O-ring 59c or the liquid connector insertion port 53a, potentially reducing the sealing performance. Furthermore, because the external pump 21 supplies ink to the liquid ejection head 1 under pressure, the ink supply path in which the liquid connection part 700 is located is a positive pressure region where the flowing ink is under positive pressure. That is, the flow path (liquid flow path) from the external pump 21 through the ink supply tube 59, the liquid connection part 700, and the filter 110 to the first pressure adjustment unit 120 is a positive ink pressure region (positive liquid pressure region) where the ink is maintained at a positive pressure. Therefore, if the sealing performance of the liquid connection part 700 located in the positive ink pressure region is reduced as described above, there is a risk of ink leaking from the liquid connection part 700. Ink leaking from the liquid connection part 700 may cause malfunctions in the electrical system of the circulation pump 500. Therefore, in this embodiment, the following measures are taken against leaking ink.

[0136] The features of this invention will be described below.

[0137] <Measures against leaking ink> In this embodiment, the following configuration is provided as a measure against ink leaking from the liquid connection part 700 provided in the ink positive pressure region. In this embodiment, to prevent ink leaking from the liquid connection part 700 from adhering to the circulation pump 500, the circulation pump 500 is positioned above the liquid connection part 700 in the direction of gravity. In other words, the circulation pump 500 is positioned above the liquid connector insertion port 53a, which is the liquid inlet port of the liquid ejection head 1, in the direction of gravity. Furthermore, the circulation pump 500 is positioned so as not to come into contact with the components that make up the liquid connection part 700. As a result, even if ink leaks from the liquid connection part 700, the ink flows horizontally toward the opening of the liquid connector 59a or downward in the direction of gravity, thereby preventing the ink from reaching the circulation pump 500, which is located above in the direction of gravity. Furthermore, because the circulation pump 500 is positioned away from the liquid connection part 700, the possibility of ink reaching the circulation pump 500 by traveling along components is reduced. In addition, the circulation unit 54 is formed as a separate component from the head housing 53 in which the liquid connection part 700 is formed, and the circulation pump 500 is also unitized and placed inside the circulation unit 54, thereby preventing leaked ink from reaching the circulation pump 500.

[0138] In addition, the electrical connection part 515, which electrically connects the circulation pump 500 and the electrical contact board 6 via the flexible wiring member 514, is provided above the liquid connection part 700 in the direction of gravity. Therefore, even if ink leaks from the liquid connection part 700, the possibility of electrical problems caused by the ink can be reduced.

[0139] Furthermore, if the pressure loss between the liquid connection part 700 and the liquid flow path is large and the ink pressure must be increased by the external pump 21, the liquid may leak more easily from the liquid connection part 700, and in some cases, ink may even spurt from the liquid connection part 700. To prevent the adverse effects of ink leaking or spurting out and adhering to the circulation pump 500 or the electrical connection part 515, it is effective to provide an ink blocking part that blocks the leaking or spurting ink. In the example shown in FIG. 21(a), the wall part 53b of the head housing 53 is formed as the ink blocking part. By providing this wall part 53b, it is possible to prevent ink from moving or scattering into the area surrounded by the dashed line R connecting the opening 59b of the liquid connector 59a to the circulation pump 500 and the dashed line R' connecting the opening 59b of the liquid connector 59a to the electrical connection part 515. Therefore, even if pressurized ink is ejected from opening 59b of liquid connection part 700, the ink will hit wall 52b and bounce back in the opposite direction, reducing the possibility of the ink reaching circulation pump 500 or electrical connection part 515. The ink blocking part is not limited to wall part 53b of head housing 53, and a member separate from head housing 53 may be provided. Furthermore, in this embodiment, head housing 53 is box-shaped, with liquid connection part 700 provided on the outer surface of one side, and electrical contact substrate 6 provided on the outer surface of the other side, which is disposed on the back side of the one side. As a result, even if ink leaks from liquid connection part 700, it is possible to prevent the leaked ink from adhering to electrical contact substrate 6 and electrical connection part 515.

[0140] As described above, according to this embodiment, the effects of pulsation of the circulation pump 500 are suppressed by the pressure adjustment means, and ink is pressurized and supplied to the liquid ejection head 1, thereby improving ejection stability. That is, pressure fluctuations in the pressure chambers 12 are suppressed, and stable ejection can be achieved. Furthermore, even if ink leaks or sprays from the connection between the ink supply tube 59 and the liquid ejection head 1 due to pressurized supply, it is possible to suppress adhesion of ink to the circulation pump 500 and the electrical connection part 515. It is possible to suppress malfunctions in the electrical system of the liquid ejection head 1 over the long term, and a highly reliable liquid ejection head 1 can be obtained.

[0141] (Other embodiments) In the above embodiment, assuming ink leakage from the liquid connection part 700 provided in the ink positive pressure region, an example was shown in which the circulation pump 500 and the electrical connection part 515 were arranged above the liquid connection part 700 in the direction of gravity. However, if there is another part in the ink positive pressure region where liquid leakage may occur, the circulation pump 500 and the electrical connection part 515 may be arranged above that part in the direction of gravity.

[0142] In the above embodiment, an example was shown in which a bypass flow path was provided to prevent the pressure generated by the circulation pump 500 from exceeding a predetermined value from being affected by the discharge module 300. However, if the pressure fluctuation caused by the circulation pump 500 is small and the pressure is maintained within the predetermined value, it is possible to omit the bypass flow path 160 and the second pressure adjustment means 150. [Explanation of symbols]

[0143] 12 Pressure Chamber 13 Outlet 15 Discharge element 21 External Pump 50 Liquid dispensing device 53a Liquid connector insertion port 59 Ink supply tube 120 First pressure adjusting means 122 First Pressure Control Room 130 supply channel 140 Recovery channel 500 Circulation Pump 515 Electrical Connections 700 Liquid Connection

Claims

1. a liquid storage section that stores liquid; a liquid ejection head having an inlet for introducing liquid from the liquid storage portion, a pressure chamber to which the liquid introduced from the inlet is supplied, and an ejection port for ejecting the liquid in the pressure chamber; a liquid communication path for communicating the liquid storage portion with the inlet of the liquid ejection head; a liquid pressurizing means for pressurizing and supplying the liquid in the liquid storage portion to the liquid ejection head through the liquid communication path; A liquid ejection device having the liquid ejection head includes a circulation path that circulates the liquid supplied from the liquid communication path within the liquid ejection head; The circulation path is a supply flow channel for supplying liquid to the pressure chamber; a recovery flow path that recovers liquid from the pressure chamber; a circulation pump that supplies the liquid recovered from the recovery flow path to the supply flow path; a pressure adjusting means for adjusting the pressure of the liquid supplied to the supply flow path, The liquid ejection device is characterized in that the circulation pump is disposed above the inlet in the direction of gravity and at a position not in contact with the inlet.

2. The liquid ejection device according to claim 1 , wherein a liquid connector that is connected to the inlet is provided at an end of the liquid communication path.

3. 3. The liquid ejection device according to claim 1, wherein the flow path connecting the inlet and the pressure adjusting means is a positive pressure region in which the liquid is under positive pressure, and the circulation pump is disposed above the positive pressure region in the direction of gravity.

4. The liquid ejection device according to claim 1, wherein the liquid ejection head is provided with an electrical contact substrate for receiving electrical signals, and an electrical connection portion electrically connecting the circulation pump and the electrical contact substrate is positioned above the inlet in the direction of gravity.

5. The liquid ejection device according to claim 4 , wherein the liquid ejection head includes a wall portion that prevents the liquid leaking from the inlet from adhering to the circulation pump and the electrical connection portion.

6. The liquid ejection apparatus according to claim 1 , wherein the liquid ejection head ejects the liquid while scanning in a main scanning direction.

7. 7. The liquid ejection device according to claim 1, wherein the liquid communication path is formed by a flexible supply tube, and oscillates in accordance with main scanning of the liquid ejection head.

8. the pressure adjusting means includes a first pressure adjusting means connected between the liquid storage portion and the supply flow path, 8. A liquid ejection device according to claim 1, wherein the first pressure adjustment means comprises a first liquid chamber that accommodates the liquid supplied from the liquid storage section and the circulation pump, and a first adjustment mechanism that adjusts the pressure of the liquid supplied from the first liquid chamber to the supply flow path by switching from positive pressure to negative pressure.

9. the first liquid chamber has a volume that changes depending on the amount of liquid supplied from the liquid storage portion and the circulation pump; The liquid ejection device according to claim 8 , wherein the first adjustment mechanism adjusts the pressure of the liquid contained in the first liquid chamber in conjunction with the volume of the first liquid chamber.

10. The first adjustment mechanism includes: a first valve chamber that communicates with the first liquid chamber via a first communication port and that supplies liquid supplied from the liquid storage portion to the first liquid chamber via the first communication port; The liquid ejection device according to claim 8 , further comprising: a first valve that switches the first communication port between an open state and a closed state depending on the volume of the first liquid chamber.

11. 11. The liquid ejection device according to claim 10, wherein the first valve opens the first communication port when the volume of the first liquid chamber containing the liquid is less than a predetermined volume, and closes the first communication port when the volume of the first liquid chamber is equal to or greater than the predetermined volume.

12. The volume of the first liquid chamber changes due to displacement of a flexible member formed in at least a part of the first liquid chamber, The first adjustment mechanism includes: a biasing means for biasing the flexible member in a direction that increases the volume of the first liquid chamber; a first valve that is displaced in response to displacement of the flexible member, 12. A liquid ejection device as described in claim 10 or 11, wherein the first valve is displaced to a position that opens the first communication port when the flexible member is displaced to a position where the volume of the first liquid chamber is less than a predetermined volume, and opens the first communication port when the flexible member is displaced to a position where the volume of the first liquid chamber is equal to or greater than the predetermined volume.

13. the pressure adjusting means further includes a second pressure adjusting means connected to the first liquid chamber, the recovery flow path, and the circulation pump; 13. A liquid ejection device according to claim 8, wherein the second pressure adjustment means adjusts the pressure of a second liquid chamber that accommodates liquid supplied from the first liquid chamber and the recovery flow path, and the pressure of the liquid supplied to the second liquid chamber.

14. 14. The liquid ejection device according to claim 1, wherein the circulation pump is a piezoelectric pump having a pump chamber to which liquid is supplied and a piezoelectric element that displaces to change the volume of the pump chamber when a drive voltage is applied.

15. a conveying unit that conveys a recording medium at a position facing the ejection opening of the liquid ejection head; 15. A liquid ejection device according to claim 1, wherein the liquid ejection head is detachably mounted on a carriage that moves along a main scanning direction that intersects with the direction in which the recording medium is transported by the transport means, and performs recording by ejecting liquid from the ejection openings while moving in the main scanning direction together with the carriage.

16. A liquid ejection head comprising: an inlet for introducing pressurized liquid from the outside; a pressure chamber to which the liquid introduced from the inlet is supplied; and an ejection port for ejecting the liquid in the pressure chamber, and further comprising a circulation path for circulating the liquid introduced from the inlet within the liquid ejection head, The circulation path is a supply flow channel for supplying liquid to the pressure chamber; a recovery flow path that recovers liquid from the pressure chamber; a circulation pump that supplies the liquid recovered from the recovery flow path to the supply flow path; a pressure adjusting means for adjusting the pressure of the liquid supplied to the supply flow path, The liquid ejection head is characterized in that the circulation pump is disposed above the inlet in the direction of gravity and at a position not in contact with the inlet.

17. 17. The liquid ejection head according to claim 16, wherein the flow path connecting the inlet and the pressure adjusting means is a positive pressure region where the liquid is under positive pressure, and the circulation pump is disposed above the positive pressure region in the direction of gravity.

18. A liquid ejection head as described in claim 16 or claim 17, wherein the liquid ejection head is provided with an electrical contact substrate for receiving electrical signals, and an electrical connection portion electrically connecting the circulation pump and the electrical contact substrate is positioned above the inlet in the direction of gravity.

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