Liquid ejection head and liquid ejection apparatus

Abstract

A liquid discharge head comprises: a discharge element configured to generate pressure for discharging a liquid; a supply path through which the liquid is supplied to a pressure chamber; a recovery path connected to the supply path through the pressure chamber and through which the liquid is recovered from the pressure chamber; a circulation pump capable of supplying the liquid from the supply path into the pressure chamber, recovering the liquid to the pressure chamber through the recovery path, and sending the liquid to the supply path; a first pressure regulating unit disposed between the outlet path of the circulation pump and the supply path and configured to adjust the pressure of the supply path; and a second pressure regulating unit disposed between the inlet path of the circulation pump and the recovery path and configured to adjust the pressure of the recovery path.

Description

Technology Field

[0001] The present disclosure relates to a liquid dispensing head and a liquid dispensing device including the liquid dispensing head. Background Technology

[0002] A circulating liquid dispensing device is known that discharges bubbles in the flow path and suppresses ink thickening near the dispensing port by circulating liquid between a liquid dispensing head and a liquid storage unit. The circulating liquid dispensing device includes circulating the liquid using a main body-side pump provided outside the liquid dispensing head and circulating the liquid using a pump provided inside the liquid dispensing head.

[0003] International Publication No. WO2012 / 054017 (hereinafter referred to as Document 1) describes a configuration for circulating liquid using a main body-side pump. Document 1 discloses a configuration for maintaining the flow rate of ink flowing through an ink discharge nozzle by placing an ink discharge nozzle between two pressure control units provided to a liquid discharge head and having different pressures.

[0004] Japanese Patent Publication No. 2014-195932 (hereinafter referred to as Document 2) discloses a liquid dispensing device equipped with a piezoelectric circulation pump within a liquid dispensing head to circulate ink within the liquid dispensing head. In the configuration of Document 2, ink supplied from the circulation pump to the pressure control mechanism is supplied to the liquid dispensing port through an ink supply path, and undispensed ink is recovered to the circulation pump through an ink recovery path.

[0005] As described in Reference 1, in a configuration where liquid is circulated using a pump on the main body side, when liquid is discharged while the liquid discharge head is being injected, the liquid discharge head is injected with two flow paths (e.g., soft tubes, etc.) for supply and recovery drawn out from the liquid discharge head to the main body side. As the liquid discharge head is injected, the two flow paths fluctuate, which may cause pressure fluctuations within the liquid discharge head. As a result, the pressure within the liquid discharge nozzle may become unstable.

[0006] Meanwhile, in a configuration where liquid is circulated using a pump within the liquid discharge head as described in Reference 2, ink circulation is completed within the liquid discharge head. For this reason, only one flow path of the ink supply system needs to be drawn from the liquid discharge head to the main body. Furthermore, the opening and closing of this flow path of the ink supply system is controlled by a valve. Therefore, pressure generated by the oscillation of the tube caused by the injection of the liquid discharge head is prevented from affecting the ink discharge nozzle. Here, as described in Reference 2, when a pump is mounted within the liquid discharge head, the path from the pump to the pressure chamber is shortened. Consequently, the liquid circulation path is shortened. Therefore, there is a possibility that pressure fluctuations within the liquid discharge head due to pump pulsation may increase. If pressure fluctuations within the liquid discharge head increase, this will cause vibratory movement of the liquid within each pressure chamber. This may lead to fluctuations in the discharge volume. In other words, there is a possibility that it may become difficult to perform stable discharge. means of solving the problem

[0007] A liquid discharge head according to one embodiment of the present disclosure is a liquid discharge head that discharges a liquid while being injected in a main injection direction, and the liquid discharge head comprises: a discharge element configured to generate pressure for discharging a liquid in a pressure chamber; a supply path through which the liquid is supplied to the pressure chamber; a recovery path connected to the supply path through the pressure chamber and through which the liquid is recovered from the pressure chamber; a circulation pump capable of supplying the liquid into the pressure chamber from the supply path, recovering the liquid in the pressure chamber through the recovery path, and sending the liquid to the supply path; a first pressure adjustment unit disposed between the outlet path of the circulation pump and the supply path and configured to adjust the pressure of the supply path; and a second pressure adjustment unit disposed between the inlet path of the circulation pump and the recovery path and configured to adjust the pressure of the recovery path.

[0008] Further features of the present invention will become clear from the following description of exemplary embodiments with reference to the accompanying drawings. Brief explanation of the drawing

[0009] FIGS. 1a and FIGS. 1b are a perspective view and a block view illustrating a liquid discharge device. Figure 2 is an exploded perspective view of a liquid discharge head. FIGS. 3A and FIGS. 3B are a longitudinal cross-sectional view of a liquid discharge head and an enlarged cross-sectional view of a discharge module. Figure 4 is a schematic external view of the circulation unit. Figure 5 is a longitudinal section illustrating a circular path. Figure 6 is a block diagram schematically illustrating a circulation path. FIGS. 7a to 7c are cross-sectional views showing examples of pressure adjustment units. Figures 8a and 8b are external perspective views of a circulation pump. Figure 9 is a cross-sectional view along line IX-IX of the circulation pump shown in Figure 8a. FIGS. 10a to 10e are drawings illustrating the flow of ink within a liquid discharge head. FIGS. 11a and FIGS. 11b are schematic diagrams illustrating the circulation path in the discharge unit. Figure 12 is a drawing illustrating an opening plate. Figure 13 is a drawing illustrating a discharge element substrate. FIGS. 14a to 14c are cross-sectional views illustrating the ink flow in a discharge unit. FIGS. 15a and FIGS. 15b are cross-sectional views illustrating the vicinity of the discharge port. FIGS. 16a and FIGS. 16b are cross-sectional views illustrating comparative examples near the discharge port. Figure 17 is a drawing illustrating a comparative example of a discharge element substrate. Figures 18a and 18b are drawings illustrating the flow path configuration of a liquid discharge head. FIG. 19 is a diagram illustrating the connection state between the main body unit of the liquid discharge device and the liquid discharge head. Specific details for implementing the invention

[0010] Preferred embodiments of the present disclosure are described in detail with reference to the attached drawings. It should be noted that the following embodiments are not intended to limit the scope of the present disclosure, and that not all combinations of features described in the embodiments are necessarily essential to the means of the solution of the present disclosure. It should be noted that identical components are indicated by the same reference numerals. The present embodiment is described using an example in which a thermal type dispensing element, which generates bubbles by an electric heat conversion element to dispense liquid, is employed as each dispensing element for dispensing liquid, but is not limited thereto. The present embodiment is applicable not only to liquid dispensing heads employing a dispensing method using a piezoelectric element to dispense liquid, but also to liquid dispensing heads employing other dispensing methods. Furthermore, the pump, pressure regulating unit, etc. described below are not limited to the configurations described in the embodiments and illustrated in the drawings. In the following description, the basic configuration of the present disclosure is first explained, and the feature parts of the present disclosure are explained.

[0011] Liquid Dispensing Device

[0012] FIG. 1a is a drawing for explaining a liquid dispensing device and is an enlarged view of the liquid dispensing head and its surroundings. First, the schematic configuration of the liquid dispensing device (50) in the present embodiment will be explained with reference to FIG. 1a and FIG. 1b. FIG. 1a is a perspective view schematically illustrating a liquid dispensing device using a liquid dispensing head (1). The liquid dispensing device (50) of the present embodiment is configured as a serial inkjet recording device that performs recording on a recording medium (P) by dispensing ink as a liquid while injecting the liquid dispensing head (1).

[0013] A liquid dispensing head (1) is mounted on a carriage (60). The carriage (60) reciprocates along a guide shaft (51) in a main scanning direction (X direction). A recording medium (P) is conveyed by conveying rollers (55, 56, 57, 58) in a secondary scanning direction (Y direction) that intersects (orthogonally in this example) the main scanning direction. Note that in the drawings referenced below, the Z direction represents a vertical direction and intersects (orthogonally in this example) the XY plane defined by the X direction and the Y direction. The liquid dispensing head (1) is configured to be attachable and detachable from the carriage (60) by a user.

[0014] The liquid discharge head (1) includes a circulation unit (54) and a discharge unit (3) described later (see FIG. 2a and FIG. 2b). Although the specific configuration will be described later, the discharge unit (3) includes a plurality of discharge ports and an energy generating element (hereinafter referred to as "discharge element") that generates discharge energy for discharging liquid from each discharge port.

[0015] Additionally, the liquid discharge device (50) includes an ink tank (2) which is an ink source and an external pump (21). The ink stored in the ink tank (2) is supplied to the circulation unit (54) through the ink supply tube (59) by the driving force of the external pump (21).

[0016] The liquid dispensing device (50) forms a predetermined image on a recording medium (P) by repeating a recording scan in which a liquid dispensing head (1) mounted on a carriage (60) moves in a main scanning direction to discharge ink and perform recording, and a return operation in which a recording medium (P) is returned in a secondary scanning direction. Note that the liquid dispensing head (1) in this embodiment is capable of dispensing four types of ink, namely black (B), cyan (C), magenta (M), and yellow (Y) ink, and that full-color images can be recorded using these inks. Here, the inks that can be discharged from the liquid dispensing head (1) are not limited to the above four types of inks. The present disclosure is also applicable to liquid dispensing heads for dispensing other types of ink. In summary, the types and number of inks discharged from the liquid dispensing head are not limited.

[0017] Additionally, the liquid dispensing device (50) is provided with a cap member (not shown) capable of covering a discharge port surface in which a discharge port of a liquid dispensing head (1) is formed at a position separated in the X direction from the return path of the recording medium (P). The cap member covers the discharge port surface of the liquid dispensing head (1) during non-recording operation and is used to prevent drying of the discharge port, protect the discharge port, and perform ink suction operations from the discharge port.

[0018] The liquid discharge head (1) shown in FIG. 1a illustrates an example in which four circulation units (54) corresponding to four types of ink are included in the liquid discharge head (1), but it should be noted that it is sufficient to include circulation units (54) corresponding to the type of liquid being discharged. Additionally, multiple circulation units (54) may be included for the same type of liquid. That is, the liquid discharge head (1) may have a configuration including one or more circulation units. The liquid discharge head (1) may be configured to circulate only at least one ink, rather than circulating all four types of ink.

[0019] FIG. 1b is a block diagram illustrating a control system of a liquid dispensing device (50). The CPU (103) functions as a control unit that controls the operation of each unit of the liquid dispensing device (50) based on a program such as a processing procedure stored in ROM (101). RAM (102) is used as a work area, etc., for the CPU (103) to execute processing. The CPU (103) receives image data from a host device (400) outside the liquid dispensing device (50) and controls the head driver (1A) to control the driving of the dispensing element provided to the dispensing unit (3). In addition, the CPU (103) controls the drivers of various actuators provided to the liquid dispensing device. For example, the CPU (103) controls the motor driver (105A) of the carriage motor (105) for moving the carriage (60), the motor driver (104A) of the transport motor (104) for transporting the recording medium (P), etc. Additionally, the CPU (103) controls the pump driver (500A) of the circulation pump (500) described later, the pump driver (21A) of the external pump (21), etc. FIG. 1b shows a configuration in which image data is received from the host device (400) and processing is performed, but it should be noted that the liquid discharge device (50) can perform processing regardless of whether data is provided from the host device (400).

[0020] <Basic Configuration of Liquid Dispensing Head>

[0021] FIG. 2 is an exploded perspective view and a plan view of the liquid discharge head (1) of the present embodiment. FIG. 3a and FIG. 3b are cross-sectional views along line IIIA-IIIA of the liquid discharge head (1) shown in FIG. 2. FIG. 3a is a longitudinal cross-sectional view of the entire liquid discharge head (1), and FIG. 3b is an enlarged view of the discharge module shown in FIG. 3a. Hereinafter, the basic configuration of the liquid discharge head (1) in the present embodiment will be explained by mainly referring to FIG. 2 to FIG. 3b and appropriately referring to FIG. 1a.

[0022] As shown in FIG. 2, the liquid dispensing head (1) includes a circulation unit (54) and a dispensing unit (3) for dispensing ink supplied from the circulation unit (54) onto a recording medium (P). The liquid dispensing head (1) of the present embodiment is fixedly supported on the carriage (60) by a positioning unit and an electrical contact (not shown) provided on the carriage (60) of the liquid dispensing device (50). The liquid dispensing head (1) performs recording on the recording medium (P) by dispensing ink while moving together with the carriage (60) in the main scanning direction (X direction) shown in FIG. 1a.

[0023] An external pump (21) connected to an ink tank (2), which is an ink source, includes an ink supply tube (59) (see FIG. 1a). A liquid connector (not shown) is provided at the tip of each of these ink supply tubes (59). With a liquid discharge head (1) mounted on a liquid discharge device (50), a liquid connector, which is an inlet for introducing liquid and is provided at the tip of the ink supply tube (59), is hermetically connected to a liquid connector insertion slot (53a) provided in the head housing (53) of the liquid discharge head (1). As a result, an ink supply path is formed extending from the ink tank (2) through the external pump (21) to the liquid discharge head (1). In this embodiment, four types of ink are used. Here, four sets, each including an ink tank (2), an external pump (21), an ink supply tube (59), and a circulation unit (54), are provided for each ink, and four ink supply paths corresponding to each ink are formed independently of each other. As described above, the liquid dispensing device (50) of the present embodiment includes an ink supply system in which ink is supplied from an ink tank (2) provided outside the liquid dispensing head (1). Note that the liquid dispensing device (50) of the present embodiment does not include an ink recovery system for recovering ink within the liquid dispensing head (1) to the ink tank (2). Accordingly, the liquid dispensing head (1) includes a liquid connector insertion slot (53a) for connecting an ink supply tube (59) of the ink tank (2), but does not include a connector insertion slot for connecting a tube for recovering ink from the liquid dispensing head (1) to the ink tank (2). Note that the liquid connector insertion slot (53a) is provided for each ink.

[0024] In FIG. 3a, reference numerals 54B, 54C, 54M, and 54Y represent circulation units for black, cyan, magenta, and yellow inks, respectively. The circulation units have substantially the same configuration, and unless otherwise distinguished in the present embodiment, each circulation unit is referred to as "circulation unit (54)".

[0025] In FIG. 2 and FIG. 3a, the discharge unit (3) comprises two discharge modules (300), a first support member (4), a second support member (7), an electrical wiring member (electrical wiring tape) (5), and an electrical contact substrate (6). As shown in FIG. 3b, each discharge module (300) comprises a silicon substrate (310) having a thickness of 0.5 mm to 1 mm and a plurality of discharge elements (15) provided on one surface of the silicon substrate (310). In this embodiment, the discharge elements (15) each comprise a heat conversion element (heater) that generates thermal energy as discharge energy for discharging liquid. Power is supplied to each discharge element (15) through electrical wiring formed on the silicon substrate (310) by film forming technology.

[0026] Additionally, an exhaust port forming member (320) is formed on the surface of the silicon substrate (310) (the lower surface in FIG. 3B). In the exhaust port forming member (320), a plurality of pressure chambers (12) corresponding to a plurality of exhaust elements (15) and a plurality of exhaust ports (13) for exhausting ink are formed by photolithography technology. Additionally, a common supply channel (18) and a common recovery channel (19) are formed in the silicon substrate (310). Additionally, a supply connection channel (323) in which the common supply channel (18) and the pressure chamber (12) communicate with each other, and a recovery connection channel (324) in which the common recovery channel (19) and the pressure chamber (12) communicate with each other are formed in the silicon substrate (310). In this embodiment, one exhaust module (300) is configured to exhaust two types of ink. Specifically, among the two discharge modules shown in FIG. 3a, the discharge module (300) located on the left side of FIG. 3a discharges black ink and cyan ink, and the discharge module (300) located on the right side of FIG. 3a discharges magenta ink and yellow ink. Note that this combination is merely an example and any combination of inks can be adopted. It is also possible to have a configuration in which one discharge module discharges one type of ink or discharges three or more types of ink. The two discharge modules (300) do not have to discharge the same number of types of ink. It is also possible to have a configuration in which only one discharge module (300) is included or in which three or more discharge modules (300) are included. Furthermore, in the example shown in FIG. 3a and FIG. 3b, two discharge port rows extending in the Y direction are formed for one color of ink. For each of the plurality of discharge ports (13) forming a row of discharge ports, a pressure chamber (12), a common supply path (18), and a common recovery path (19) are formed.

[0027] On the back side (upper side in FIG. 3b) of the silicon substrate (310), an ink supply port and an ink recovery port, which will be described later, are formed. Through the ink supply port, ink is supplied from the ink supply channel (48) to a plurality of common supply channels (18). Through the ink recovery port, ink is recovered from a plurality of common recovery channels (19) to an ink recovery channel (49).

[0028] Note that the ink supply port and the ink recovery port correspond to openings that supply and recover ink during the forward ink circulation described below. Specifically, during the forward ink circulation, ink is supplied from the ink supply port to the common supply path (18), and ink is recovered from the common recovery path (19) to the ink recovery port. Note that ink circulation that causes ink to flow in the opposite direction can also be performed. In this case, ink is supplied from the aforementioned ink recovery port to the common recovery path (19), and ink is recovered from the common supply path (18) to the ink supply port.

[0029] As shown in FIG. 3a, the back surface (upper surface in FIG. 3a) of the discharge module (300) is adhesively fixed to one side (lower surface in FIG. 3a) of the first support member (4). In the first support member (4), an ink supply channel (48) and an ink recovery channel (49) are formed, penetrating from one side of the first support member (4) to the opposite side of the first support member (4). An opening on one side of the ink supply channel (48) communicates with the aforementioned ink supply port in the silicon substrate (310). An opening on one side of the ink recovery channel (49) communicates with the aforementioned ink recovery port in the silicon substrate (310). Note that the ink supply channel (48) and the ink recovery channel (49) are provided independently for each type of ink.

[0030] Additionally, on one side (the lower side in FIG. 3a) of the first support member (4), a second support member (7) is adhesively fixed, having an opening (7a) (see FIG. 2) for inserting a discharge module (300). An electrical wiring member (5) electrically connected to the discharge module (300) is retained and supported on the second support member (7). The electrical wiring member (5) is a member for applying an electrical signal for ink discharge to the discharge module (300). The electrical connection portion between the discharge module (300) and the electrical wiring member (5) is sealed by a sealant (not shown) to protect against corrosion caused by ink and external impact.

[0031] Additionally, an electrical contact substrate (6) is bonded to the end portion (5a) (see FIG. 2) of an electrical wiring member (5) by heat pressing using an anisotropic conductive film (not shown), and the electrical wiring member (5) and the electrical contact substrate (6) are electrically connected to each other. The electrical contact substrate (6) has an external signal input terminal (not shown) to receive an electrical signal from a liquid discharge device (50).

[0032] Additionally, a joint member (8) (Fig. 3a) is provided between the first support member (4) and the circulation unit (54). In the joint member (8), a supply port (88) and a recovery port (89) are formed for each type of ink. Through the supply port (88) and the recovery port (89), the ink supply channel (48) and the ink recovery channel (49) of the first support member (4) communicate with each other with the channels formed in the circulation unit (54). Additionally, in Fig. 3a, the supply port (88B) and the recovery port (89B) are for black ink, and the supply port (88C) and the recovery port (89C) are for cyan ink. Additionally, the supply port (88M) and the recovery port (89M) are for magenta ink, and the supply port (88Y) and the recovery port (89Y) are for yellow ink.

[0033] Note that the opening at one end of the ink supply channel (48) and ink recovery channel (49) of the first support member (4) has a small opening area corresponding to the ink supply port and ink recovery port in the silicon substrate (310). Meanwhile, the opening at the other end of the ink supply channel (48) and ink recovery channel (49) of the first support member (4) has an enlarged shape having an opening area equal to the opening area formed in the joint member (8) to correspond to the channel of the circulation unit (54). By adopting this configuration, the increase in channel resistance for the ink recovered from each recovery channel can be suppressed. Note that the shape of the openings at one end and the other end of the ink supply channel (48) and ink recovery channel (49) is not limited to the above example.

[0034] In the liquid discharge head (1) having the above configuration, the ink supplied to the circulation unit (54) passes through the supply port (88) of the joint member (8) and the ink supply path (48) of the first support member (4), and flows into the common supply path (18) from the ink supply port of the discharge module (300). Then, the ink flows from the common supply path (18) into the pressure chamber (12) through the supply connection path (323). A portion of the ink flowing into the pressure chamber is discharged from the discharge port (13) as the discharge element (15) is driven. The remaining ink that is not discharged passes through the recovery connection path (324) and the common recovery path (19) from the pressure chamber (12) and flows into the ink recovery path (49) of the first support member (4) from the ink recovery port. Then, the ink flowing into the ink recovery path (49) flows into the circulation unit (54) through the recovery port (89) of the joint member (8) and is recovered.

[0035] Components of the Circulation Unit

[0036] FIG. 4 is a schematic view of one circulation unit (54) for one type of ink used in the recording device of the present embodiment. In the circulation unit (54), a filter (110), a first pressure regulating unit (120), a second pressure regulating unit (150), and a circulation pump (500) are disposed. These components are connected by a flow path to form a circulation path for supplying and recovering ink from the liquid discharge head (1) to the discharge module (300), as shown in FIG. 5 and FIG. 6.

[0037] <Circulation path within the liquid dispensing head>

[0038] FIG. 5 is a cross-sectional view schematically illustrating the circulation path of one type of ink (one color ink) formed within a liquid discharge head (1). For a clearer explanation of the circulation path, the relative positions of the components in FIG. 5 (the first pressure regulating unit (120), the second pressure regulating unit (150), and the circulation pump (500), etc.) are simplified. Accordingly, the relative positions of the components differ from those of FIG. 19, which will be described later. Also, FIG. 6 is a block diagram schematically illustrating the circulation path shown in FIG. 5. As shown in FIG. 5 and FIG. 6, the first pressure regulating unit (120) includes a first valve chamber (121) and a first pressure control chamber (122). The second pressure regulating unit (150) includes a second valve chamber (151) and a second pressure control chamber (152). The first pressure regulating unit (120) is configured such that the control pressure inside it is higher than that of the second pressure regulating unit (150). In this embodiment, circulation within a constant pressure range within the circulation path is realized by using these two pressure adjustment units (120, 150). Additionally, ink is configured to flow through the pressure chamber (12) (discharge element (15)) at a flow rate corresponding to the pressure difference between the first pressure adjustment unit (120) and the second pressure adjustment unit (150). Hereinafter, with reference to FIGS. 5 and 6, the circulation path in the liquid discharge head (1) and the flow of ink within the circulation path will be explained. Note that the arrows in FIGS. 5 and 6 indicate the direction in which the ink flows.

[0039] First, I will explain how the components in the liquid discharge head (1) are connected.

[0040] An external pump (21) that sends ink stored in an ink tank (2) (Fig. 6) located outside the liquid discharge head (1) to the liquid discharge head (1) is connected to a circulation unit (54) through an ink supply tube (59) (Fig. 1). A filter (110) is placed 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 regulating unit (120). The first valve chamber (121) communicates with a first pressure control chamber (122) through a communication port (191A) that can be opened and closed by a valve (190A) shown in Fig. 5.

[0041] The first pressure control room (122) is connected to the supply path (130), the bypass path (160), and the pump outlet path (180) of the circulation pump (500). The supply path (130) is connected to the common supply path (18) through the aforementioned ink supply port provided to the discharge module (300). Additionally, the bypass path (160) is connected to the second valve room (151) provided to the second pressure adjustment unit (150). The second valve room (151) communicates with the second pressure control room (152) through a communication port (191B) that is opened and closed by the valve (190B) shown in FIG. 5. Note that FIGS. 5 and 6 illustrate an example in which one end of the bypass path (160) is connected to the first pressure control room (122) of the first pressure regulating unit (120) and the other end of the bypass path (160) is connected to the second valve room (151) of the second pressure regulating unit (150). However, one end of the bypass path (160) may be connected to the supply path (130) and the other end of the bypass path may be connected to the second valve room (151).

[0042] The second pressure control room (152) is connected to the recovery path (140). The recovery path (140) is connected to the common recovery path (19) through the aforementioned ink recovery port provided in the discharge module (300). Additionally, the second pressure control room (152) is connected to the circulation pump (500) through the pump inlet path (170). Note that reference numeral 170a in FIG. 5 indicates the inlet port of the pump inlet path (170).

[0043] Next, the flow of ink in the liquid discharge head (1) having the above configuration will be described. As shown in FIG. 6, the ink stored in the ink tank (2) is pressurized by an external pump (21) provided to the liquid discharge device (50), becomes a constant pressure ink flow, and is supplied to the circulation unit (54) of the liquid discharge head (1).

[0044] Ink supplied to the circulation unit (54) passes through a filter (110) to remove foreign substances such as dust and bubbles. Afterward, the ink flows into the first valve chamber (121) provided to the first pressure adjustment unit (120). Due to the pressure loss when the ink passes through the filter (110), the pressure of the ink decreases, but at this point, the pressure of the ink is still in a positive pressure state. Afterward, when the valve (190A) is opened, the ink flowing into the first valve chamber (121) passes through the communication port (191A) and flows into the first pressure control chamber (122). Due to the pressure loss when the ink passes through the communication port (191A), the pressure of the ink flowing into the first pressure control chamber (122) is converted from positive pressure to negative pressure.

[0045] Next, the flow of ink within the circulation path is described. The circulation pump (500) operates such that ink sucked from the pump inlet path (170) located upstream of the circulation pump (500) is discharged to the pump outlet path (180) located downstream of the circulation pump (500). Accordingly, as the pump is driven, the ink supplied to the first pressure control chamber (122) flows into the supply path (130) and the bypass path (160) together with the ink discharged from the pump outlet path (180). Although details will be described later, in this embodiment, a piezoelectric diaphragm pump is used as a circulation pump capable of discharging liquid, using a piezoelectric element attached to a diaphragm as a driving source. The piezoelectric diaphragm pump is a pump that discharges liquid by changing the volume within the pump chamber by inputting a driving voltage to the piezoelectric element and by alternately moving two check valves in response to pressure fluctuations.

[0046] Ink flowing into the supply channel (130) flows into the pressure chamber (12) through the common supply channel (18) from the ink supply port of the discharge module (300). A portion of the ink is discharged from the discharge port (13) as the discharge element (15) is driven (heated). Additionally, the remaining ink not used for discharge flows through the pressure chamber (12) and passes through the common recovery channel (19). Afterward, the ink flows into the recovery channel (140) connected to the discharge module (300). The ink flowing into the recovery channel (140) flows into the second pressure control chamber (152) of the second pressure adjustment unit (150).

[0047] Meanwhile, the ink flowing into the bypass path (160) from the first pressure control room (122) flows into the second valve room (151), passes through the communication port (191B), and flows into the second pressure control room (152). The ink flowing into the second pressure control room (152) through the bypass path (160) and the ink recovered from the recovery path (140) are sucked into the circulation pump (500) through the pump inlet path (170) as the circulation pump (500) is driven. Then, the ink sucked into the circulation pump (500) is sent to the pump outlet path (180) and flows back into the first pressure control room (122). After that, the ink flowing into the second pressure control room (152) from the first pressure control room (122) through the supply path (130) and the discharge module (300), and the ink flowing into the second pressure control room (152) through the bypass path (160), are introduced into the circulation pump (500). Then, the ink is discharged from the circulation pump (500) to the first pressure control room (122). In this way, ink circulation is performed within the circulation path.

[0048] As described above, in this embodiment, liquid can be circulated through each circulation path formed within the liquid discharge head (1) by the circulation pump (500). Accordingly, it is possible to suppress the thickening of the ink within the discharge module (300) and the deposition of the ink sedimentation component of the colorant. Thus, excellent fluidity of the ink in the discharge module (300) and excellent discharge characteristics at the discharge port can be maintained.

[0049] In addition, the circulation path in this embodiment is configured to be completed within the liquid discharge head (1). Therefore, the length of the circulation path can be significantly shortened compared to the case where ink circulates between the liquid discharge head (1) and the ink tank (2) located outside the liquid discharge head (1). Thus, the ink can be circulated by a small circulation pump.

[0050] Additionally, a configuration is possible in which only a flow path for supplying ink is included as a flow path connecting the liquid discharge head (1) and the ink tank (2). That is, a configuration is adopted that does not require a flow path for recovering ink from the liquid discharge head (1) to the ink tank (2). Therefore, only an ink supply tube connecting the ink tank (2) and the liquid discharge head (1) is required, and an ink recovery tube is not required. Accordingly, the interior of the liquid discharge device (50) has a more concise configuration with fewer tubes. This allows the entire device to be miniaturized. Furthermore, the reduction in the number of tubes reduces fluctuations in ink pressure caused by the oscillation of the tubes resulting from the main injection of the liquid discharge head (1). Additionally, the oscillation of the tubes during the main injection of the liquid discharge head (1) increases the driving load of the carriage motor driving the carriage (60). Therefore, the reduction in the number of tubes reduces the driving load of the carriage motor, which allows the main injection mechanism including the carriage motor to be simplified. In addition, since there is no need for the ink to be recovered from the liquid discharge head (1) to the ink tank, the external pump (21) can also be miniaturized. As described above, according to this embodiment, the liquid discharge device (50) can be miniaturized and the cost reduced.

[0051] Pressure Adjustment Unit

[0052] FIGS. 7a to 7c are drawings illustrating examples of pressure adjustment units. With reference to FIGS. 7a to 7c, the configuration and operation of pressure adjustment units (first pressure adjustment unit (120) and second pressure adjustment unit (150)) embedded in the aforementioned liquid discharge head (1) will be described in more detail. Note that the first pressure adjustment unit (120) and the second pressure adjustment unit (150) have substantially the same configuration. Therefore, the first pressure adjustment unit (120) will be described below as an example. Regarding the second pressure adjustment unit (150), the reference numeral of the part corresponding to the first pressure adjustment unit in FIGS. 7a to 7c will be indicated together. In the case of the second pressure adjustment unit (150), the first valve chamber (121) and the first pressure control chamber (122) described below should be read as the second valve chamber (151) and the second pressure control chamber (152), respectively.

[0053] The first pressure regulating unit (120) has a first valve chamber (121) and a first pressure control chamber (122) formed within a cylindrical housing (125). The first valve chamber (121) and the first pressure control chamber (122) are separated by a partition (123) provided within the cylindrical housing (125). However, the first valve chamber (121) communicates with the first pressure control chamber (122) through a communication port (191) formed in the partition (123). The first valve chamber (121) is provided with a valve (190) that switches between allowing communication between the first valve chamber (121) and the first pressure control chamber (122) through the communication port (191) and blocking communication. The valve (190) is supported by the valve spring (200) in a position facing the communication port (191) and has a close contact configuration with the partition wall (123) by the deflection force from the valve spring (200). The valve (190) blocks the flow of ink through the communication port (191) by making close contact with the partition wall (123). It should be noted that in order to improve the close contact with the partition wall (123), the contact portion of the valve (190) with the partition wall (123) is preferably formed by an elastic member. Additionally, a valve shaft (190a) inserted through the communication port (191) is provided in a protruding manner in the central part of the valve (190). By applying pressure to this valve shaft (190a) against the deflection force from the valve spring (200), the valve (190) is separated from the partition wall (123), allowing ink to flow through the communication port (191). Hereinafter, the state in which the valve (190) blocks the flow of ink through the communication port (191) is referred to as the “closed state,” and the state in which ink can flow through the communication port (191) is referred to as the “open state.”

[0054] The opening of the cylindrical housing (125) is closed by a flexible member (230) and a pressure plate (210). The flexible member (230) and the pressure plate (210), the surrounding wall of the housing (125), and the partition (123) form a first pressure control chamber (122). The pressure plate (210) is configured to be displaceable according to 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) may be composed of a molded resin part, and the flexible member (230) may be composed of a resin film. In this case, the pressure plate (210) may be fixed to the flexible member (230) by heat welding.

[0055] A pressure adjusting spring (220) (deflection member) is provided between the pressure plate (210) and the partition wall (123). As shown in FIG. 7a, the pressure plate (210) and the flexible member (230) are deflected in a direction that increases the internal volume of the first pressure control chamber (122) by the deflection force from the pressure adjusting spring (220). Additionally, when the pressure inside the first pressure control chamber (122) decreases, the pressure plate (210) and the flexible member (230) resist the pressure from the pressure adjusting spring (220) and are displaced in a direction that decreases the internal volume of the first pressure control chamber (122). Then, when the internal volume of the first pressure control chamber (122) decreases to a certain volume, the pressure plate (210) comes into contact with the valve shaft (190a) of the valve (190). After that, when the internal volume of the first pressure control chamber (122) is further reduced, the valve (190) moves together with the valve shaft (190a) in resistance to the deflection force from the valve spring (200) and is separated from the bulkhead (123). As a result, the communication port (191) becomes open (state of FIG. 7b).

[0056] In this embodiment, a connection is established within the circulation path such that when the communication port (191) is in an open state, the pressure in the first valve chamber (121) becomes higher than the pressure in the first pressure control chamber (122). In this way, when the communication port (191) is in an open state, ink flows from the first valve chamber (121) into the first pressure control chamber (122). The inflow of ink causes the flexible member (230) and the pressure plate (210) to be displaced in the direction of increasing the internal volume of the first pressure control chamber (122). As a result, the pressure plate (210) is separated from the valve shaft (190a) of the valve (190), and the valve (190) comes into close contact with the partition wall (123) by the deflection force from the valve spring (200), so that the communication port (191) becomes closed (state of FIG. 7c).

[0057] As described above, in the first pressure adjustment unit (120) of the present embodiment, when the pressure in the first pressure control room (122) decreases below a certain pressure (e.g., when negative pressure increases), ink is introduced from the first valve room (121) through the communication port (191). This configuration limits the pressure in the first pressure control room (122) from decreasing further. Therefore, the pressure in the first pressure control room (122) is controlled to be maintained within a certain range. That is, since the first pressure control room (122) is connected to the supply path (130), it can be said that the first pressure adjustment unit (120) adjusts the pressure of the supply path (130).

[0058] Next, the pressure of the first pressure control room (122) will be explained in more detail.

[0059] As described above, the flexible member (230) and the pressure plate (210) are displaced according to the pressure of the first pressure control room (122), so that the pressure plate (210) comes into contact with the valve shaft (190a) and the communication port (191) is opened (state of FIG. 7b). At this time, the relationship between the forces acting on the pressure plate (210) is expressed by the following Equation 1.

[0060] P2 × S2 + F2 + (P1 - P2) × S1 + F1 = 0 ... Equation 1

[0061] In addition, Equation 1 is summarized for P2 as follows.

[0062] P2 = -(F1 + F2 + P1 × S1) / (S2 - S1) ... Equation 2

[0063] P1: Pressure (gauge pressure) of the first valve chamber (121)

[0064] P2: Pressure (gauge pressure) of the first pressure control room (122)

[0065] F1: Spring force of the valve spring (200)

[0066] F2: Spring force of the pressure adjustment spring (220)

[0067] S1: Water pressure area of ​​valve (190)

[0068] S2: Water pressure area of ​​the pressure plate (210)

[0069] Here, regarding the spring force (F1) of the valve spring (200) and the spring force (F2) of the pressure adjustment spring (220), the direction of pressing the valve (190) and the pressure plate (210) is defined as the forward direction (left direction in FIG. 7a to 7c). In addition, the pressure (P1) of the first valve chamber (121) and the pressure (P2) of the first pressure control chamber (122) are configured to satisfy the relationship P1≥P2.

[0070] The pressure (P2) of the first pressure control room (122) when the communication port (191) is in an open state is determined by Equation 2, and since the relationship P1 ≥ P2 is satisfied when the communication port (191) is in an open state, ink flows from the first valve room (121) into the first pressure control room (122). As a result, the pressure (P2) of the first pressure control room (122) does not decrease further, and the pressure (P2) is maintained at a pressure within a certain range.

[0071] Meanwhile, as shown in FIG. 7c, when the pressure plate (210) does not come into contact with the valve shaft (190a) and the communication port (191) is closed, the relationship between the forces acting on the pressure plate (210) is expressed by Equation 3 below.

[0072] P3 × S3 + F3 = 0 ... Equation 3

[0073] Here, Equation 3 is summarized for P3 as follows.

[0074] P3 = -F3 / S3 ... Equation 4

[0075] F3: Spring force of the pressure adjusting spring (220) when the pressure plate (210) is not in contact with the valve shaft (190a)

[0076] P3: Pressure (gauge pressure) of the first pressure control chamber (122) when the pressure plate (210) is not in contact with the valve shaft (190a)

[0077] S3: Hydrostatic pressure area of ​​the pressure plate (210) when the pressure plate (210) is not in contact with the valve shaft (190a)

[0078] Here, FIG. 7c shows a state in which the pressure plate (210) and the flexible member (230) are displaced to the left side of FIG. 7c to the limit of displacement. Depending on the amount of displacement when the pressure plate (210) and the flexible member (230) are displaced to the state of FIG. 7c, the pressure (P3) of the first pressure control chamber (122), the spring force (F3) of the pressure adjustment spring (220), and the hydraulic pressure area (S3) of the pressure plate (210) change. Specifically, when the pressure plate (210) and the flexible member (230) are positioned to the right side of FIG. 7c compared to the pressure plate (210) and the flexible member (230) in FIG. 7c, the hydraulic pressure area (S3) of the pressure plate (210) becomes smaller, and the spring force (F3) of the pressure adjustment spring (220) becomes larger. Accordingly, the pressure (P3) of the first pressure control room (122) decreases according to the relationship of Equation 4. Accordingly, according to Equations 2 and 4, the pressure of the first pressure control room (122) gradually increases from the state of Fig. 7b to the state of Fig. 7c (i.e., the negative pressure weakens toward a value approaching the positive pressure side). Specifically, while the pressure plate (210) and the flexible member (230) are gradually displaced to the left from the state where the communication port (191) is in an open state until the internal volume of the first pressure control room reaches a limit where the pressure plate (210) and the flexible member (230) can be displaced, the pressure of the first pressure control room (122) gradually increases. That is, the negative pressure weakens.

[0079] Circulation pump

[0080] Next, with reference to FIGS. 8a, FIGS. 8b, and FIGS. 9, the configuration and operation of each circulation pump (500) embedded in the liquid discharge head (1) will be described in detail.

[0081] FIGS. 8A and FIGS. 8B are external perspective views of a circulation pump (500). FIG. 8A is an external perspective view showing the front side of the circulation pump (500), and FIG. 8B is an external perspective view showing the rear side of the circulation pump (500). The exterior of the circulation pump (500) includes a pump housing (505) and a cover (507) fixed to the pump housing (505). The pump housing (505) includes a housing body (505a) and a flow path connecting member (505b) adhesively fixed to the outer surface of the housing body (505a). In each of the housing body (505a) and the flow path connecting member (505b), a pair of through holes communicating with each other is formed at two different locations. One pair of through holes provided at one location forms a pump supply hole (501). Another pair of through holes provided at the other location forms a pump discharge hole (502). The pump supply hole (501) is connected to the pump inlet path (170) connected to the second pressure control room (152). The pump discharge hole (502) is connected to the pump outlet path (180) connected to the first pressure control room (122). Ink supplied from the pump supply hole (501) passes through the pump room (503) (see FIG. 9) described later and is discharged from the pump discharge hole (502).

[0082] FIG. 9 is a cross-sectional view along line IX-IX of the circulation pump (500) shown in FIG. 8a. A diaphragm (506) is attached to the inner surface of the pump housing (505), and a pump chamber (503) is formed between the diaphragm (506) and the concave portion formed on the inner surface of the pump housing (505). The pump chamber (503) communicates with the pump supply hole (501) and the pump discharge hole (502) formed in the pump housing (505). Additionally, a check valve (504a) is provided in the middle portion of the pump supply hole (501). A check valve (504b) is provided in the middle portion of the pump discharge hole (502). Specifically, the check valve (504a) is positioned so that a part thereof can move in the left direction of FIG. 9 within a space (512a) formed in the middle portion of the pump supply hole (501). The check valve (504b) is positioned so as to be movable in the right direction of FIG. 9 within a space (512b) in which a part thereof is formed in the middle part of the pump discharge hole (502).

[0083] As the diaphragm (506) is displaced to increase the volume of the pump chamber (503), the pump chamber (503) is depressurized. In response to this displacement, the check valve (504a) is moved away from the opening of the pump supply hole (501) in the space (512a) (i.e., moves to the left in FIG. 9). By being moved away from the opening of the pump supply hole (501) in the space (512a), the check valve (504a) becomes open, allowing ink to flow through the pump supply hole (501). As the diaphragm (506) is displaced to decrease the volume of the pump chamber (503), the pump chamber (503) is pressurized. In response to this displacement, the check valve (504a) comes into close contact with the wall surface around the opening of the pump supply hole (501). Accordingly, the check valve (504a) becomes closed, blocking the flow of ink through the pump supply hole (501).

[0084] Meanwhile, as the pump chamber (503) is depressurized, the check valve (504b) comes into close contact with the wall around the opening of the pump housing (505), and the check valve (504b) becomes closed, blocking the flow of ink through the pump discharge hole (502). Additionally, as the pump chamber (503) is pressurized, the check valve (504b) moves away from the opening of the pump housing (505) and moves toward the space (512b) (i.e., moves to the right in FIG. 9), thereby allowing ink to flow through the pump discharge hole (502).

[0085] Note that the material of each check valve (504a, 504b) can be deformable according to the pressure in the pump chamber (503). For example, the material of each check valve (504a, 504b) may be composed of an elastic material such as ethylene-propylene-diene methylene linkage (EPDM) or an elastomer, or a film or sheet such as polypropylene. However, the material is not limited to these.

[0086] As described above, the pump chamber (503) is formed by joining the pump housing (505) and the diaphragm (506). Accordingly, as the diaphragm (506) deforms, the pressure in the pump chamber (503) changes. For example, when the diaphragm (506) is displaced toward the pump housing (505) (displaced toward the right side of FIG. 9) and the volume of the pump chamber (503) decreases, the pressure inside the pump chamber (503) increases. As a result, the check valve (504b) positioned to face the pump discharge hole (502) becomes open to discharge ink from the pump chamber (503). At this time, the check valve (504a) positioned to face the pump supply hole (501) is in close contact with the wall surface around the pump supply hole (501), thereby suppressing the backflow of ink from the pump chamber (503) to the pump supply hole (501).

[0087] Conversely, when the diaphragm (506) is displaced in a direction that widens the pump chamber (503), the pressure in the pump chamber (503) decreases. As a result, the check valve (504a) positioned to face the pump supply hole (501) becomes open to supply ink to the pump chamber (503). At this time, the check valve (504b) positioned at the pump discharge hole (502) closes the opening by making close contact with the wall surface around the opening formed in the pump housing (505). This prevents the backflow of ink from the pump discharge hole (502) to the pump chamber (503).

[0088] As described above, in the circulation pump (500), ink is sucked in and discharged as the diaphragm (506) deforms to change the pressure within the pump chamber (503). At this time, if air bubbles are mixed into the pump chamber (503), the displacement of the diaphragm (506) causes the pressure within the pump chamber (503) to change to a smaller range due to the expansion or contraction of the air bubbles. Consequently, the amount of liquid discharged is reduced. To resolve this phenomenon, the pump chamber (503) is positioned parallel to gravity so that air bubbles mixed into the pump chamber (503) can easily collect at the top of the pump chamber (503). Additionally, the pump discharge hole (502) is positioned higher than the center of the pump chamber (503). This improves the ease of discharging air bubbles within the pump and thus stabilizes the flow rate.

[0089] Ink flow within the liquid ejection head

[0090] FIGS. 10a to 10e are drawings illustrating the flow of ink within a liquid discharge head. Referring to FIGS. 10a to 10e, the circulation of ink within the liquid discharge head (1) is described. To make the description of the ink circulation path clearer, the relative positions of the components of FIGS. 10a to 10e, such as the first pressure adjustment unit (120), the second pressure adjustment unit (150), and the circulation pump (500), are simplified. Accordingly, the relative positions of the components differ from those of FIG. 19, which will be described later. FIG. 10a schematically illustrates the flow of ink when a recording operation is performed by discharging ink from the discharge port (13) to perform recording. Note that the arrows in FIG. 10a indicate the flow of ink. In this embodiment, to perform a recording operation, both the external pump (21) and the circulation pump (500) are started to operate. Additionally, the external pump (21) and the circulation pump (500) can be driven regardless of whether a recording operation is performed. The external pump (21) and the circulation pump (500) do not need to be driven in conjunction with each other and can be driven independently of each other.

[0091] During the recording operation, the circulation pump (500) is turned ON (operated) so that ink flowing out from the first pressure control room (122) flows into the supply path (130) and the bypass path (160). The ink flowing into the supply path (130) flows into the recovery path (140) after passing through the discharge module (300). After that, the ink is supplied to the second pressure control room (152).

[0092] Meanwhile, ink introduced into the bypass path (160) from the first pressure control room (122) is introduced into the second pressure control room (152) through the second valve room (151). The ink introduced into the second pressure control room (152) passes through the pump inlet path (170), the circulation pump (500), and the pump outlet path (180), and then is introduced back into the first pressure control room (122). At this time, the control pressure of the first valve room (121) is set higher than the control pressure of the first pressure control room (122) based on the relationship of Equation 2 described above. Accordingly, the ink in the first pressure control room (122) does not flow back into the first valve room (121) but is supplied to the discharge module (300) again through the supply path (130). The ink introduced into the discharge module (300) is introduced back into the first pressure control room (122) through the recovery path (140), the second pressure control room (152), the pump inlet path (170), the circulation pump (500), and the pump outlet path (180). As described above, ink circulation is performed within the liquid discharge head (1).

[0093] In the above ink circulation, the differential pressure between the control pressure of the first pressure control room (122) and the control pressure of the second pressure control room (152) determines the circulation amount (flow rate) of ink within the discharge module (300). Additionally, this differential pressure is set to obtain a circulation amount capable of suppressing the thickening of ink near the discharge port within the discharge module (300). Furthermore, the amount of ink consumed by recording is supplied from the ink tank (2) to the first pressure control room (122) through the filter (110) and the first valve room (121). The method of supplying the consumed ink is described in detail. The amount of ink in the circulation path is reduced by the amount of ink consumed by recording. Accordingly, the pressure within the first pressure control room (122) decreases, and as a result, the amount of ink within the first pressure control room decreases. As the amount of ink within the first pressure control room (122) decreases, the internal volume of the first pressure control room (122) decreases. As the internal volume of the first pressure control chamber (122) decreases, the communication port (191A) is opened to allow ink to be supplied from the first valve chamber (121) to the first pressure control chamber (122). As the ink supplied from the first valve chamber (121) passes through the communication port (191A), pressure loss occurs in the supplied ink. As the ink flows into the first pressure control chamber (122), the positive pressure of the ink is converted to negative pressure. 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 rises. When the internal volume of the first pressure control chamber increases, the communication port (191A) is closed. As described above, the communication port (191A) repeatedly switches between the open and closed states depending on ink consumption. Additionally, when ink is not consumed, the communication port (191A) remains in the closed state.

[0094] FIG. 10b schematically illustrates the flow of ink immediately after the recording operation is terminated and the circulation pump (500) is turned OFF (stopped). At the point when the recording operation is terminated and the circulation pump (500) is turned OFF, the pressure in the first pressure control room (122) and the pressure in the second pressure control room (152) are both control pressures used in the recording operation. Because of this, ink moves according to the differential pressure between the pressure in the first pressure control room (122) and the pressure in the second pressure control room (152), as shown in FIG. 10b. Specifically, an ink flow continues to occur from the first pressure control room (122) to the discharge module (300) through the supply path (130) and then to the second pressure control room (152) through the recovery path (140). In addition, the flow of ink from the first pressure control room (122) through the bypass path (160) and the second valve room (151) to the second pressure control room (152) also continues to occur.

[0095] The amount of ink that has moved from the first pressure control room (122) to the second pressure control room (152) by the flow of these inks is supplied from the ink tank (2) to the first pressure control room (122) via the filter (110) and the first valve room (121). Accordingly, the internal volume of the first pressure control room (122) is maintained at a constant level. According to the relationship of Equation 2 described above, when the internal volume of the first pressure control room (122) is constant, the spring force (F1) of the valve spring (200), the spring force (F2) of the pressure adjustment spring (220), the hydraulic pressure area (S1) of the valve (190), and the hydraulic pressure area (S2) of the pressure plate (210) are maintained at a constant level. Accordingly, the pressure of the first pressure control room (122) is determined according to the change in the pressure (gauge pressure) (P1) of the first valve room (121). In this way, when the pressure (P1) of the first valve chamber (121) does not change, the pressure (P2) of the first pressure control chamber (122) is maintained at the same pressure as the control pressure during the recording operation.

[0096] Meanwhile, the pressure of the second pressure control chamber (152) changes over time according to the change in internal volume caused by the inflow of ink from the first pressure control chamber (122). Specifically, the pressure of the second pressure control chamber (152) changes according to Equation 2 until the communication port (191) becomes closed, which does not allow communication between the second valve chamber (151) and the second pressure control chamber (152), as shown in FIG. 10c, from the state of FIG. 10b. After that, the pressure plate (210) does not come into contact with the valve shaft (190a), and the communication port (191) becomes closed. Then, as shown in FIG. 10d, ink flows from the recovery path (140) into the second pressure control chamber (152). This inflow of ink displaces the pressure plate (210) and the flexible member (230). The pressure in the second pressure control room (152) changes according to Equation 4. Specifically, the pressure rises until the internal volume of the second pressure control room (152) reaches its maximum.

[0097] Note that once the state of FIG. 10c is reached, ink no longer flows from the first pressure control room (122) to the second pressure control room (152) via the bypass path (160) and the second valve room (151). Therefore, only ink flow occurs in which ink in the first pressure control room (122) is supplied to the discharge module (300) through the supply path (130) and then passes through the recovery path (140) to the second pressure control room (152). As described above, ink moves from the first pressure control room (122) to the second pressure control room (152) according to the differential pressure between the pressure in the first pressure control room (122) and the pressure in the second pressure control room (152). Therefore, when the pressure in the second pressure control room (152) becomes equal to the pressure in the first pressure control room (122), the movement of ink stops.

[0098] Additionally, when the pressure inside the second pressure control room (152) becomes equal to the pressure inside the first pressure control room (122), the second pressure control room (152) expands to the state shown in FIG. 10d. When the second pressure control room (152) expands as shown in FIG. 10d, a reservoir capable of holding ink is formed in the second pressure control room (152). Note that the transition to the state shown in FIG. 10d after the circulation pump (500) stops takes about 1 to 2 minutes. The time may vary depending on the shape and size of the flow path and the properties of the ink. As the circulation pump (500) is driven while the ink is held in the reservoir as shown in FIG. 10d, the ink in the reservoir is supplied to the first pressure control room (122) by the circulation pump (500). Accordingly, as shown in FIG. 10e, the amount of ink in the first pressure control chamber (122) increases, and the flexible member (230) and the pressure plate (210) are displaced in the expansion direction. And, as the circulation pump (500) continues to operate, the state within the circulation path changes to the state shown in FIG. 10a.

[0099] Note that in the above description, FIG. 10a is described as an example of ink circulation during a recording operation. However, as previously mentioned, ink can be circulated without accompanying a recording operation. In this case as well, ink flows as shown in FIG. 10a to FIG. 10e in response to the driving and stopping of the circulation pump (500).

[0100] Additionally, as described above, in this embodiment, the communication port (191B) in the second pressure adjustment unit (150) is in an open state when ink is circulated by driving the circulation pump (500), and in a closed state when ink circulation is stopped. However, this embodiment is not limited to this example. The control pressure can be set so that the communication port (191B) in the second pressure adjustment unit (150) remains in a closed state even when ink is circulated by driving the circulation pump (500). This will be explained in detail below in accordance with the function of the bypass path (160).

[0101] A bypass channel (160) connecting the first pressure adjustment unit (120) and the second pressure adjustment unit (150) is provided to allow the discharge module (300) to avoid the influence of strong negative pressure, for example, when the negative pressure generated within the circulation path becomes stronger than a preset value. Additionally, the bypass channel (160) is also provided to supply ink to the pressure chamber (12) from both the supply channel (130) and the recovery channel (140).

[0102] First, an example is described in which negative pressure stronger than a preset value is avoided affecting the discharge module (300) by providing a bypass path (160). For example, changes in ambient temperature may change the characteristics of the ink (e.g., viscosity). As the viscosity of the ink changes, the pressure loss in the circulation path also changes. For example, as the viscosity of the ink decreases, the amount of pressure loss in the circulation path decreases. As a result, the flow rate of the circulation pump (500) driven at a constant amount increases, and the flow rate through the discharge module (300) increases. Here, the discharge module (300) is maintained at a constant temperature by a temperature control mechanism (not shown). Therefore, the viscosity of the ink in the discharge module (300) remains constant even when the ambient temperature changes. While the viscosity of the ink within the discharge module (300) remains unchanged, the flow rate of the ink flowing through the discharge module (300) increases; accordingly, the negative pressure in the discharge module (300) becomes stronger due to flow resistance. As described above, if the negative pressure in the discharge module (300) becomes stronger than a preset value, the meniscus of the discharge port (13) may be destroyed and ambient air may be drawn into the circulation path, potentially making it impossible to perform normal discharge. Furthermore, even if the meniscus is not destroyed, the negative pressure in the pressure chamber (12) may still become stronger than a preset level and affect the discharge.

[0103] For this reason, in this embodiment, a bypass channel (160) is formed within the circulation path. By providing the bypass channel (160), ink flows through the bypass channel (160) when the negative pressure becomes stronger than a preset value. Thus, the pressure of the discharge module (300) is maintained constant. Therefore, for example, the control pressure can be set so that the communication port (191B) in the second pressure adjustment unit (150) remains closed even when the circulation pump (500) is driven. Additionally, the control pressure in the second pressure adjustment unit (150) can be set so that the communication port (191B) in the second pressure adjustment unit (150) becomes open when the negative pressure becomes stronger than a preset value. That is, when the circulation pump (500) is driven, the communication port (191B) may be in a closed state, as long as the meniscus does not collapse or a predetermined negative pressure is maintained even when the flow rate of the pump changes due to a change in viscosity caused by environmental changes, etc.

[0104] Next, an example is described in which a bypass path (160) is provided to supply ink to the pressure chamber (12) from both the supply path (130) and the recovery path (140). The pressure in the circulation path may fluctuate due to the discharge operation of the discharge element (15). This is because the discharge operation generates a force that draws ink into the pressure chamber.

[0105] Below, it is explained that when high-duty recording is continued, the ink supplied to the pressure chamber (12) is supplied from both the supply path (130) side and the recovery path (140) side. Although the definition of "duty" may vary depending on various conditions, below, the state in which a 1200 dpi grid cell is recorded with one 4 pl ink droplet will be considered as 100%. "High-duty recording" is, for example, recording performed at 100% duty.

[0106] When recording a high duty cycle, the amount of ink flowing into the second pressure control room (152) from the pressure room (12) through the recovery path (140) decreases. Meanwhile, the circulation pump (500) causes the ink to flow out in a certain amount. This disrupts the balance between the inflow into the second pressure control room (152) and the outflow from it. Consequently, the ink in the second pressure control room (152) decreases, and the negative pressure in the second pressure control room (152) increases, causing the second pressure control room (152) to contract. As the negative pressure in the second pressure control room (152) increases, the amount of ink flowing into the second pressure control room (152) through the bypass path (160) increases, and the second pressure control room (152) stabilizes in a state where the outflow and inflow are balanced. In this way, the negative pressure in the second pressure control room (152) increases according to the duty cycle. Additionally, as described above, when the circulation pump (500) is driven, in a configuration where the communication port (191B) is in a closed state, the communication port (191B) becomes open according to the duty cycle, and ink flows from the bypass path (160) into the second pressure control room (152).

[0107] Additionally, as the high duty record continues, the amount of ink flowing from the pressure chamber (12) to the second pressure control chamber (152) through the recovery path (140) decreases, and conversely, the amount flowing from the communication port (191B) to the second pressure control chamber (152) through the bypass path (160) increases. As this condition progresses further, the amount of ink flowing from the pressure chamber (12) to the second pressure control chamber (152) through the recovery path (140) becomes zero, and the ink flowing from the communication port (191B) becomes the entire amount of ink flowing out to the circulation pump (500). As this condition progresses further, the ink flows back from the second pressure control chamber (152) to the pressure chamber (12) through the recovery path (140). In this state, the ink flowing from the second pressure control room (152) to the circulation pump (500) and the ink flowing from the second pressure control room (152) to the pressure room (12) flow from the communication port (191B) to the second pressure control room (152) through the bypass path (160). In this case, the ink from the supply path (130) and the ink from the recovery path (140) are filled into the pressure room (12) and discharged therefrom.

[0108] Note that the ink backflow occurring when the recording duty is high is a phenomenon caused by the installation of the bypass path (160). Additionally, as described above, an example was explained where the communication port (191B) in the second pressure adjustment unit is in an open state regarding the ink backflow. However, the ink backflow can occur even when the communication port (191B) in the second pressure adjustment unit is in an open state. Furthermore, the ink backflow can occur even in a configuration without a second pressure adjustment unit by installing the bypass path (160).

[0109] <Composition of the Discharge Unit>

[0110] FIGS. 11a and 11b are schematic diagrams illustrating the circulation path of one color ink in the discharge unit (3) of the present embodiment. FIG. 11a is an exploded perspective view of the discharge unit (3) from the side of the first support member (4). FIG. 11b is an exploded perspective view of the discharge unit (3) from the side of the discharge module (300). In FIGS. 11a and 11b, the arrows labeled "IN" and "OUT" indicate the ink flow, and while the ink flow is described only for one color, it should be noted that other colors of ink flow similarly. Furthermore, in FIGS. 11a and 11b, the illustration of the second support member (7) and the electrical wiring member (5) is omitted, and their description is also omitted in the following description of the configuration of the discharge unit. Additionally, regarding the first support member (4) in FIG. 11a, a cross-section along the line XI-XI of FIG. 3a is shown. Each discharge module (300) includes a discharge element substrate (340) and an opening plate (330). FIG. 12 is a drawing illustrating the opening plate (330). FIG. 13 is a drawing illustrating the discharge element substrate (340).

[0111] Ink is supplied to the discharge unit (3) from each circulation unit (54) through the joint member (8) (see FIG. 3a). The ink path from when the ink passes through the joint member (8) until it returns to the joint member (8) is described. Note that the joint member (8) is omitted from the drawings described below.

[0112] Each discharge module (300) comprises a discharge element substrate (340), which is a silicon substrate (310), and an opening plate (330), and further comprises a discharge port forming member (320). The discharge element substrate (340), the opening plate (330), and the discharge port forming member (320) are stacked and bonded so that the flow paths of each ink communicate with one another to form the discharge module (300). The discharge module (300) is supported on a first support member (4). The discharge unit (3) is formed by supporting each discharge module (300) on the first support member (4). The discharge element substrate (340) comprises a discharge port forming member (320), and the discharge port forming member (320) comprises a plurality of discharge port rows, each comprising a plurality of discharge ports (13) that form a single line. A portion of the ink supplied through the ink flow paths within the discharge module (300) is discharged from the discharge ports (13). The ink that is not discharged is recovered through the ink flow path within the discharge module (300).

[0113] As shown in FIGS. 11a, 11b, and 12, the opening plate (330) includes a plurality of arranged ink supply ports (311) and a plurality of arranged ink recovery ports (312). As shown in FIGS. 13 and FIGS. 14a through 14c, the discharge element substrate (340) includes a plurality of arranged supply connection channels (323) and a plurality of arranged recovery connection channels (324). The discharge element substrate (340) further includes a common supply channel (18) communicating with a plurality of supply connection channels (323) and a common recovery channel (19) communicating with a plurality of recovery connection channels (324). The ink supply channels (48) and ink recovery channels (49) disposed on the first support member (4) (see FIGS. 3a and 3b) and the channels disposed on each discharge module (300) communicate with each other to form ink channels within the discharge unit (3). The support member supply port (211) is a cross-sectional opening forming an ink supply channel (48). The support member recovery port (212) is a cross-sectional opening forming an ink recovery channel (49).

[0114] Ink supplied to the discharge unit (3) is supplied from the side of the circulation unit (54) (see FIG. 3a) to the ink supply channel (48) (see FIG. 3a) of the first support member (4). Ink flowing through the support member supply port (211) within the ink supply channel (48) is supplied to the common supply channel (18) of the discharge element substrate (340) through the ink supply channel (48) (see FIG. 3a) and the ink supply port (311) of the opening plate (330), and enters the supply connection channel (323). The channel up to this point is the supply side channel. After that, the ink passes through the pressure chamber (12) (see FIG. 3b) of the discharge port forming member (320) and flows into the recovery connection channel (324) of the recovery side channel. Details of the ink flow in the pressure chamber (12) will be described later.

[0115] In the recovery side path, the ink that enters the recovery connection path (324) flows into the common recovery path (19). Afterwards, the ink flows from the common recovery path (19) into the ink recovery path (49) of the first support member (4) through the ink recovery port (312) of the opening plate (330), and is recovered to the circulation unit (54) through the support member recovery port (212).

[0116] Among the opening plates (330), the area where the ink supply port (311) or ink recovery port (312) does not exist corresponds to the area for separating the support member supply port (211) and the support member recovery port (212) of the first support member (4). Additionally, the first support member (4) does not have an opening in these areas. Such an area is used as an adhesive area when the discharge module (300) and the first support member (4) are bonded together.

[0117] In FIG. 12, a row of multiple openings arranged along the X direction is provided in parallel in the Y direction on the opening plate (330), and the openings for supply (IN) and for recovery (OUT) are arranged alternately in the Y direction such that they are offset from each other by half a pitch in the X direction. In FIG. 13, on the discharge element substrate (340), a common supply channel (18) communicating with a plurality of supply connection channels (323) arranged in the Y direction, and a common recovery channel (19) communicating with a plurality of recovery connection channels (324) arranged in the Y direction are arranged alternately in the X direction. The common supply channels (18) and the common recovery channels (19) are divided by ink type. Additionally, the number of discharge port rows for each color determines the number of common supply channels (18) and common recovery channels (19) to be placed. Additionally, the number of supplied connection channels (323) and the number of distributed recovery connection channels (324) correspond to the number of discharge ports (13). Note that a one-to-one correspondence is not strictly necessary, and that one supply connection path (323) and one return connection path (324) may correspond to multiple discharge ports (13).

[0118] Each discharge module (300) is formed by stacking and bonding an opening plate (330) and a discharge element substrate (340) as described above so as to communicate with each other as a channel for each ink, and is supported on a first support member (4). As a result, an ink channel including a supply channel and a recovery channel is formed as described above.

[0119] FIGS. 14a to 14c are cross-sectional views showing ink flow in different parts of the discharge unit (3). FIG. 14a is a cross-section taken along the XIVA-XIVA line of FIG. 11a and shows a cross-section of the part of the discharge unit (3) where the ink supply channel (48) and the ink supply port (311) communicate with each other. FIG. 14b is a cross-section taken along the XIVB-XIVB line of FIG. 11a and shows a cross-section of the part of the discharge unit (3) where the ink recovery channel (49) and the ink recovery port (312) communicate with each other. FIG. 14c is a cross-section taken along the XIVC-XIVC line of FIG. 11a and shows a cross-section of the part where the ink supply port (311) and the ink recovery port (312) do not communicate with the channel of the first support member (4).

[0120] As illustrated in FIG. 14a, the ink supply channel supplies ink from a portion where the ink supply channel (48) of the first support member (4) and the ink supply port (311) of the opening plate (330) overlap and communicate with each other. Additionally, as illustrated in FIG. 14b, the ink recovery channel recovers ink from a portion where the ink recovery channel (49) of the first support member (4) and the ink recovery port (312) of the opening plate (330) overlap and communicate with each other. Additionally, as illustrated in FIG. 14c, the discharge unit (3) has a region where the opening plate (330) is not locally provided with an opening. In such a region, ink is neither supplied nor recovered between the discharge element substrate (340) and the first support member (4). As illustrated in FIG. 14a, ink is supplied in the region where the ink supply port (311) is provided. As shown in FIG. 14b, ink is recovered in an area where an ink recovery port (312) is provided. Although this embodiment has been described as an example using an opening plate (330), it should be noted that a configuration without an opening plate (330) may be adopted. For example, a configuration may be adopted in which a channel corresponding to an ink supply channel (48) and an ink recovery channel (49) is formed in the first support member (4), and a discharge element substrate (340) is bonded to the first support member (4).

[0121] FIGS. 15a and 15b are cross-sectional views showing the vicinity of the discharge port (13) in the discharge module (300). FIGS. 16a and 16b are cross-sectional views showing a discharge module having a configuration in which the common supply channel (18) and the common recovery channel (19) are extended in the X direction as a comparative example. Note that the bold arrows shown in FIGS. 15a and 15b and FIGS. 16a and 16b for the common supply channel (18) and the common recovery channel (19) indicate the vibrational movement of the ink occurring in a configuration using a serial liquid discharge device (50). Ink supplied to the pressure chamber (12) through the common supply channel (18) and the supply connection channel (323) is discharged from the discharge port (13) as the discharge element (15) is driven. When the discharge element (15) is not driven, the ink is recovered from the pressure chamber (12) to the common recovery path (19) through the recovery connection path (324), which is the recovery path.

[0122] In a configuration using a serial type liquid dispensing device (50), when dispensing circulating ink as described above, the ink dispensing is significantly affected by the vibrational movement of the ink within the ink flow path caused by the main injection of the liquid dispensing head (1). Specifically, the effect of the vibrational movement of the ink within the ink flow path manifests as a difference in the amount of ink dispensed and a deviation in the direction of dispensing. As shown in FIGS. 16a and 16b, when the common supply flow path (18) and the common recovery flow path (19) have a wide cross-sectional shape in the X direction, which is the main injection direction, the ink within the common supply flow path (18) and the common recovery flow path (19) is more susceptible to inertial force in the main injection direction, causing the ink to vibrate significantly. This results in the possibility that the vibrational movement of the ink may affect the dispensing of ink from the dispensing port (13). Additionally, if the common supply flow path (18) and the common recovery flow path (19) are extended in the X direction, the distance between colors is extended. This can reduce recording efficiency.

[0123] Accordingly, each common supply channel (18) and each common recovery channel (19) of the present embodiment, whose cross-sections are illustrated in FIGS. 15a and 15b, have a configuration in which each common supply channel (18) and each common recovery channel (19) extend in the Y direction and also extend in the Z direction, which is perpendicular to the X direction, which is the main injection direction. By this configuration, the common supply channel (18) and the common recovery channel (19) are given a small channel width in the main injection direction. By giving the common supply channel (18) and the common recovery channel (19) a small channel width in the main injection direction, the vibrational movement of the ink within the common supply channel (18) and the common recovery channel (19) caused by the inertial force (black thick arrow in FIGS. 15a and 15b) that acts on the ink during main injection and is applied in the opposite direction to the main injection direction is reduced. This reduces the influence of the vibrational movement of the ink during ink ejection. In addition, by extending the common supply channel (18) and the common recovery channel (19) in the Z direction, their cross-sectional area is increased. This reduces the pressure drop in the Euro.

[0124] As described above, each common supply channel (18) and each common recovery channel (19) is provided with a small channel width in the main injection direction. This configuration reduces the vibratory movement of ink within the common supply channel (18) and the common recovery channel (19) during main injection, but does not eliminate the vibratory movement. Therefore, in this embodiment, in order to reduce the ejection difference between ink types that may be caused by the reduced vibratory movement, the common supply channel (18) and the common recovery channel (19) are configured to be positioned so as to overlap each other in the X direction.

[0125] As described above, in this embodiment, the supply connection path (323) and the recovery connection path (324) are provided to correspond to the discharge port (13). Additionally, the correspondence between the supply connection path (323) and the recovery connection path (324) is formed such that the supply connection path (323) and the recovery connection path (324) are arranged in the X direction with the discharge port (13) interposed between them. Accordingly, if the common supply path (18) and the common recovery path (19) have parts that do not overlap with each other in the X direction, the correspondence between the supply connection path (323) and the recovery connection path (324) in the X direction is broken. This non-correspondence affects the ink flow and ink discharge of the pressure chamber (12) in the X direction. When this non-correspondence is combined with the effect of the vibrational movement of the ink, there is a possibility that it may further affect the ink discharge from each discharge port.

[0126] Accordingly, by arranging the common supply channel (18) and the common recovery channel (19) in positions that overlap each other in the X direction, the vibrational movement of the ink within the common supply channel (18) and the common recovery channel (19) during main injection is substantially the same at any position in the Y direction where the discharge port (13) is arranged. Therefore, the pressure difference between the common supply channel (18) side and the common recovery channel (19) side occurring in the pressure chamber (12) does not fluctuate significantly. This low pressure difference enables stable discharge.

[0127] Additionally, some liquid discharge heads that circulate ink internally are configured such that the flow path supplying ink to the liquid discharge head and the flow path recovering ink are the same flow path. However, in this embodiment, the common supply flow path (18) and the common recovery flow path (19) are different flow paths. Furthermore, the supply connection flow path (323) and the pressure chamber (12) are in communication with each other, and the pressure chamber (12) and the recovery connection flow path (324) are in communication with each other, and ink is discharged from the discharge port (13) of the pressure chamber (12). That is, a configuration is formed in which the pressure chamber (12), which is a path connecting the supply connection flow path (323) and the recovery connection flow path (324), includes the discharge port (13). Accordingly, in each pressure chamber (12), an ink flow occurs from the supply connection flow path (323) side to the recovery connection flow path (324) side, and the ink within 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 susceptible to the effects of evaporation of ink from the discharge port (13), is kept fresh.

[0128] In addition, since the two channels, namely the common supply channel (18) and the common recovery channel (19), are connected to the pressure chamber (12), ink can be supplied from both channels when it is necessary to discharge at a high flow rate. That is, compared to a configuration in which only one channel is formed for ink supply and recovery, the configuration of this embodiment has the advantage of being able to perform efficient circulation as well as handle discharge at a high flow rate.

[0129] Additionally, when the common supply channel (18) and the common recovery channel (19) are positioned close to each other in the X direction, the effect of vibrational movement of the ink is less. It is preferable that the common supply channel (18) and the common recovery channel (19) be positioned such that the gap between the channels is 75 μm to 100 μm.

[0130] FIG. 17 is a drawing illustrating a discharge element substrate (340) as a comparative example. Note that in FIG. 17, the supply connection channel (323) and the recovery connection channel (324) are omitted from the illustration. Ink that has received thermal energy from the discharge element (15) of the pressure chamber (12) flows into the common recovery channel (19). Therefore, the temperature of the ink flowing through the common recovery channel (19) is higher than the temperature of the ink in the common supply channel (18). Here, in the comparative example, as indicated by the α portion enclosed by the dashed line in FIG. 17, there is a portion in the X direction of the discharge element substrate (340) where only the common recovery channel (19) exists. In this case, the temperature may rise locally in that portion, causing temperature non-uniformity within the discharge module (300). This temperature non-uniformity may affect the discharge.

[0131] The temperature of the ink flowing through the common supply channel (18) is lower than that of the common recovery channel (19). Therefore, when the common supply channel (18) and the common recovery channel (19) are close to each other, the ink in the common supply channel (18), which has a relatively lower temperature, lowers the temperature of the ink in the common recovery channel (19) at the point where the two channels are close. This suppresses the rise in temperature. Therefore, it is desirable for the common supply channel (18) and the common recovery channel (19) to have substantially the same length, be located at an overlapping position in the X direction, and be close to each other.

[0132] FIGS. 18a and 18b are drawings illustrating the flow path configuration of a liquid dispensing head (1) for three colors of ink: cyan (C), magenta (M), and yellow (Y). In the liquid dispensing head (1), a circulation path is provided for each type of ink, as shown in FIG. 18a. A pressure chamber (12) is provided along the X direction, which is the main injection direction of the liquid dispensing head (1). Additionally, as shown in FIG. 18b, a common supply path (18) and a common recovery path (19) are provided along a column of discharge ports, which is a column of discharge ports (13). The common supply path (18) and the common recovery path (19) are provided to extend in the Y direction with the column of discharge ports between them.

[0133] <Connection of the main unit and the liquid dispensing head>

[0134] FIG. 19 is a schematic diagram showing in more detail the arrangement of the liquid discharge head (1) and the ink tank (2) and external pump (21) provided as the main body unit of the liquid discharge device (50) of the present embodiment, and the circulation pump. The liquid discharge device (50) in the present embodiment has a configuration in which only the liquid discharge head (1) can be easily replaced in the event that a problem occurs with the liquid discharge head (1). Specifically, the liquid discharge device (50) of the present embodiment has a liquid connection part (700) in which the liquid discharge head (1) and each ink supply tube (59) connected to each external pump (21) can be easily connected and disconnected from each other. By doing so, it becomes possible to easily attach and detach only the liquid discharge head (1) to the liquid discharge device (50).

[0135] Each liquid connection (700) has a liquid connector insertion slot (53a) provided in a protruding manner on the head housing (53) of the liquid discharge head (1), as shown in FIG. 19, and a cylindrical liquid connector (59a) into which the liquid connector insertion slot (53a) can be inserted. The liquid connector insertion slot (53a) is fluidically connected to an ink supply channel formed within the liquid discharge head (1) and is connected to a first pressure regulating unit (120) through the aforementioned filter (110). The liquid connector (59a) is provided at the tip of an ink supply tube (59) connected to an external pump (21) that supplies ink from the ink tank (2) to the liquid discharge head (1) by pressurization.

[0136] As described above, the liquid discharge head (1) shown in FIG. 19 has a liquid connection part (700). This facilitates the attachment, detachment, and replacement of the liquid discharge head (1). However, if the sealing performance between the liquid connector insertion slot (53a) and the liquid connector (59a) deteriorates, there is a possibility that ink supplied by pressurization by the external pump (21) may leak from the liquid connection part (700). For example, if the leaked ink adheres to the circulation pump (500), etc., it may cause problems in the electrical system. To solve this, in this embodiment, the circulation pump, etc. is arranged as follows.

[0137] <Arrangement of circulation pumps, etc.>

[0138] As shown in FIG. 19, in this embodiment, to prevent ink leaked from the liquid connection (700) from adhering to the circulation pump (500), the circulation pump (500) is positioned higher in the direction of gravity than the liquid connection (700). Specifically, the circulation pump (500) is positioned higher in the direction of gravity than the liquid connector insertion slot (53a), which is the liquid inlet of the liquid discharge head (1). Additionally, the circulation pump (500) is positioned so as not to come into contact with the components of the liquid connection (700). Thus, even if ink leaks from the liquid connection (700), the ink flows in the horizontal direction or downward in the direction of gravity, which is the opening direction of the opening of the liquid connector (59a). This prevents the ink from reaching the circulation pump (500), which is positioned higher in the direction of gravity. In addition, since the circulation pump (500) is positioned at a location spaced apart from the liquid connection part (700), the possibility of ink reaching the circulation pump (500) through the member is also reduced.

[0139] Additionally, an electrical connection part (515) that electrically connects the circulation pump (500) and the electrical contact substrate (6) through a flexible wiring member (514) is provided higher in the direction of gravity than the liquid connection part (700). Thus, the possibility of ink from the liquid connection part (700) causing electrical problems is reduced.

[0140] Additionally, in this embodiment, a wall portion (53b) of the head housing (53) is provided. Thus, even when ink is ejected from the opening (59b) of the liquid connection portion (700), the wall portion (53b) blocks the ink, thereby reducing the possibility of the ink reaching the circulation pump (500) or the electrical connection portion (515).

[0141] Pressure fluctuations in the discharge module

[0142] Next, pressure fluctuations in the liquid discharge head (1) in the present embodiment, which are related to the features of the present disclosure, will be explained. In the liquid discharge device (50) using the serial type liquid discharge head (1) in the present embodiment, ink is supplied to the circulation unit (54) of the liquid discharge head (1) using an ink supply tube (59). When the circulation pump (500) of the circulation unit (54) is mounted within the liquid discharge head (1), the path from the circulation pump (500) to the pressure chamber is shortened, and thus the circulation path of the liquid is shortened. As a result, there is a possibility that pressure fluctuations within the liquid discharge head due to pump pulsation may increase. Therefore, when the liquid discharge head (1) is injected during a recording operation, etc., the ink supply tube (59) oscillates. This causes the possibility that the pressure of the ink within the ink supply tube (59) may fluctuate.

[0143] In this embodiment, components for suppressing the propagation of ink pulsation within the circulation path are provided at the inlet and outlet sides of the circulation pump (500), which is the source of the pulsation. Specifically, a first pressure adjustment unit (120) is connected to the pump outlet path (180), and a second pressure adjustment unit (150) is connected to the pump inlet path (170). With this configuration, the propagation of pulsation generated from the operation of the circulation pump (500) to the discharge module (300) can be suppressed from both the inlet and outlet sides of the circulation pump (500). Two pressure adjustment units (a first pressure adjustment unit and a second pressure adjustment unit) are provided within the liquid discharge head (1), and pressure fluctuations are handled by the two pressure adjustment units. In this way, pressure fluctuations that could not be suppressed by only one pressure adjustment unit can be suppressed. More specifically, since the pressure adjusting spring (220), pressure plate (210), and flexible member (230) forming each pressure adjusting unit mechanically absorb the ink pulsation generated by the circulation pump (500), the propagation of ink pulsation to the discharge module (300) can be suppressed.

[0144] In addition, as described above, the liquid discharge device (50) of the present embodiment does not include an ink recovery system for recovering ink within the liquid discharge head (1) to the ink tank (2). Specifically, a flow path for recovering liquid from the circulation unit (54) is not provided. Therefore, each ink supply tube (59) is the only flow path connected to the corresponding circulation unit (54). If a recovery tube for recovering ink from the ink tank (2) is provided, there is a possibility that pressure fluctuations will be propagated to the liquid discharge head (1) from the recovery tube side as well. In the present embodiment, each ink supply tube (59) is the only flow path connected to the corresponding circulation unit (54). Furthermore, each 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 unit (120). Then, the opening and closing of the communication port (191) is controlled by the valve (190). In this way, the pressure generated by the shaking of the tube due to the injection of the liquid discharge head (1) is prevented from affecting the discharge module (300).

[0145] In addition, as previously described, it is preferable that the supply of ink from each ink tank (2) to the liquid discharge head (1) be supplied by pressurization. Supply by pressurization suppresses pressure fluctuations. This will be explained in detail below. As previously described, the liquid discharge head (1) is injected in the main injection direction. Accordingly, the ink supply tube (59) supplying ink from the ink tank (2) to the liquid discharge head (1) oscillates in the main injection direction, and thus the pressure (P1) within each ink supply tube (59) fluctuates. Note that the pressure (P1) is the pressure of the first valve chamber (121) as previously described, and that no pressure adjustment mechanism is provided between the first valve chamber (121) and the ink supply tube (59). Therefore, the pressure within the ink supply tube (59) and the pressure within the first valve chamber (121) are considered to be the same. Additionally, as described in Equation 2, the pressure (P2) of the first pressure control chamber (122) of the first pressure adjustment unit (120) is proportional to the pressure (P1) described above. Also, as described in Equation 2, the proportionality constant is determined by the ratio between the hydraulic pressure area (S1) of the valve (190) and the hydraulic pressure area (S2) of the pressure plate (210) (see FIGS. 7a to 7c). By supplying by pressurization, the ratio of the hydraulic pressure area (S1) of the valve (190) to the hydraulic pressure area (S2) of the pressure plate (210) can be reduced. In this way, the fluctuation of pressure (P2) caused by fluctuations in pressure (P1) can be reduced. Specifically, the fluctuation of pressure (P2) in the first pressure control chamber (122) caused by fluctuations in pressure (P1) within the ink supply tube (59) caused by injection is reduced. This suppresses pressure fluctuations within the circulation path.

[0146] As described above, according to the present embodiment, discharge safety can be improved. That is, pressure fluctuations in the pressure chamber (12) can be suppressed, and thus stable discharge can be realized.

[0147] Although the present invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims should be interpreted in the broadest sense to include structures and functions equivalent to all such variations.

Claims

Claim 1 A liquid discharge head comprising: a discharge element configured to generate pressure for discharging liquid while being injected in a main injection direction; a supply path through which the liquid is supplied to the pressure chamber; a recovery path connected to the supply path through the pressure chamber and through which the liquid is recovered from the pressure chamber; a circulation pump capable of supplying the liquid into the pressure chamber from the supply path, recovering the liquid within the pressure chamber through the recovery path, and sending the liquid to the supply path; a first pressure adjustment unit disposed between the outlet path of the circulation pump and the supply path and configured to adjust the pressure of the supply path; and a second pressure adjustment unit disposed between the inlet path of the circulation pump and the recovery path and configured to adjust the pressure of the recovery path. Claim 2 A liquid discharge head according to claim 1, wherein the first pressure regulating unit and the second pressure regulating unit each have a valve chamber, a pressure control chamber, an opening communicating with each other between the valve chamber and the pressure control chamber, and a valve configured to open and close the opening; one side of the pressure control chamber is formed by a flexible member configured to be displaceable; the pressure control chamber has a pressure plate displaceable in conjunction with the flexible member, and a deflection member that deflects the pressure plate in a direction in which the volume of the pressure control chamber increases; and the pressure control chamber is configured to open and close the valve according to the displacement of the pressure plate and the flexible member. Claim 3 In paragraph 2, the pressure control chamber of the first pressure regulating unit is a liquid discharge head connected to the outlet path and the supply path of the circulation pump. Claim 4 In paragraph 2 or 3, the pressure control chamber of the second pressure regulating unit is a liquid discharge head connected to the inlet path and the recovery path of the circulation pump. Claim 5 In paragraph 2 or 3, the valve chamber of the first pressure regulating unit is a liquid discharge head in communication with a supply tube through which the liquid is supplied from an ink tank located outside the liquid discharge head. Claim 6 In paragraph 5, the control pressure of the second pressure adjustment unit is lower than the control pressure of the first pressure adjustment unit, and the liquid from the ink tank is supplied by a liquid discharge head by pressurization. Claim 7 In paragraph 2 or 3, the first pressure regulating unit is a liquid discharge head connected to the second pressure regulating unit through the pressure chamber. Claim 8 In claim 7, the upstream side of the pressure chamber and the downstream side of the pressure chamber further include a bypass channel in communication with each other, and the first pressure regulating unit also includes a liquid discharge head connected to the second pressure regulating unit through the bypass channel. Claim 9 A liquid dispensing device comprising a liquid dispensing head, a dispensing element configured to generate pressure for dispensing a liquid in a pressure chamber, a supply path through which the liquid is supplied to the pressure chamber, a recovery path connected to the supply path through the pressure chamber and through which the liquid is recovered from the pressure chamber, a circulation pump capable of supplying the liquid into the pressure chamber from the supply path, recovering the liquid in the pressure chamber through the recovery path, and sending the liquid to the supply path, a first pressure adjustment unit disposed between the outlet path of the circulation pump and the supply path and configured to adjust the pressure of the supply path, and a second pressure adjustment unit disposed between the inlet path of the circulation pump and the recovery path and configured to adjust the pressure of the recovery path, wherein the liquid dispensing device causes the liquid dispensing head to discharge the liquid while injecting the liquid dispensing head.

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