Liquid ejection head and liquid ejection apparatus

Abstract

A liquid discharge head includes a pressure chamber communicating with a discharge port, a discharge element for discharging liquid from the discharge port, and a circulation path for liquid including the pressure chamber. The circulation path includes a supply path for supplying liquid to the pressure chamber, a recovery path for recovering liquid from the pressure chamber, a circulation pump for supplying the recovered liquid to the supply path, and a pressure regulating unit configured to regulate the pressure of the liquid supplied to the supply path. The pressure of the liquid supplied to the pressure chamber while the pump is stopped (P21), the pressure of the liquid supplied to the pressure chamber while the pump is running (P22), and the pressure loss (△P) from the regulating unit to the pressure chamber while the pump is running satisfy P22 > P21 and P22 - △P < 0.

Description

Technology Field

[0001] The present disclosure relates to a liquid dispensing head having a circulation path for liquid, and a liquid dispensing device having such a liquid dispensing head. Background Technology

[0002] Some liquid dispensing devices circulate liquid for purposes such as preventing the sedimentation of colorants or the thickening of ink. Japanese Patent Publication No. 2019-64254 discloses a liquid dispensing device that circulates liquid between a liquid dispensing head that dispenses liquid and a liquid receiving unit that receives liquid supplied to the liquid dispensing head. In such a liquid dispensing device, ink within the liquid receiving unit is supplied to the liquid dispensing head through a supply channel, and a circulation path is formed so that liquid not discharged from the liquid dispensing head is returned to the liquid receiving unit through a recovery channel and recovered.

[0003] In a liquid dispensing device, when performing a liquid dispensing operation, it is desirable to redisperse sedimentation components, such as colorants and ink aggregates settled within the path, and to suppress ink thickening. Accordingly, a liquid dispensing device equipped with a liquid circulation path circulates the liquid prior to the dispensing operation. Here, in the liquid dispensing device disclosed in Japanese Patent Publication No. 2019-64254, a long circulation path is formed that extends from a liquid receiving unit to a liquid dispensing head and then returns to the liquid receiving unit. For this reason, when performing redispersion of sedimentation components and suppression of ink thickening, it is necessary to circulate the liquid through the long circulation path prior to the dispensing operation. This results in long downtime and thus reduces productivity. The problem to be solved

[0004] The objective of the present invention is to provide a liquid dispensing head and a liquid dispensing device capable of reducing downtime by performing short-term circulation, thereby enabling redispersion of sedimentation components and inhibition of ink thickening. means of solving the problem

[0005] In a first aspect of the present disclosure, a liquid discharge head is provided, wherein the liquid discharge head comprises a discharge port through which liquid is discharged, a pressure chamber communicating with the discharge port, a discharge element configured to discharge liquid supplied to the pressure chamber from the discharge port, and a circulation path through which liquid circulates, wherein the circulation path comprises a supply path through which liquid is supplied to the pressure chamber, a recovery path through which liquid is recovered from the pressure chamber, a circulation pump that supplies the liquid recovered through the recovery path to the supply path, and a pressure regulating unit configured to adjust the pressure of the liquid supplied to the supply path, wherein the pressure of the liquid supplied to the pressure chamber through the supply path from the pressure regulating unit when the circulation pump is stopped (P21), the pressure of the liquid supplied to the pressure chamber through the supply path from the pressure regulating unit when the circulation pump is driven (P22), and the pressure loss (△P) from the pressure regulating unit to the pressure chamber when the circulation pump is driven have the relationship P22 > P21 and P22 - △P < 0.

[0006] In a second aspect of the present disclosure, a liquid dispensing device is provided, wherein the liquid dispensing device comprises a liquid dispensing head, a liquid source for supplying liquid to the liquid dispensing head, and a conveying unit configured to convey a recording medium to a position opposite the discharge port of the liquid dispensing head, and the liquid dispensing head comprises a discharge port through which liquid is discharged, a pressure chamber communicating with the discharge port, a discharge element configured to discharge liquid supplied to the pressure chamber from the discharge port, and a circulation path through which liquid circulates, wherein the circulation path comprises a supply path through which liquid is supplied to the pressure chamber, a recovery path through which liquid is recovered from the pressure chamber, a circulation pump for supplying liquid recovered through the recovery path to the supply path, and a pressure regulating unit configured to adjust the pressure of the liquid supplied to the supply path, wherein the pressure of the liquid supplied to the pressure chamber through the supply path from the pressure regulating unit when the circulation pump is stopped (P21), the pressure of the liquid supplied to the pressure chamber through the supply path from the pressure regulating unit when the circulation pump is driven (P22), and the pressure from the pressure regulating unit to the pressure chamber when the circulation pump is driven The loss (△P) has the relationship P22 > P21 and P22 - △P < 0.

[0007] 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

[0008] FIGS. 1a and FIGS. 1b are a perspective view and a block view illustrating a liquid discharge device. FIG. 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 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. Figures 7a and 7c are cross-sectional views illustrating examples of pressure regulating 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. Figures 10a and 10b are exploded perspective views of a circulation pump. Figure 11 is a drawing illustrating the electrical connection portion of a piezoelectric ceramic. FIGS. 12a to 12e are drawings illustrating the flow of ink inside a liquid discharge head. FIGS. 13a and FIGS. 13b are schematic diagrams illustrating the circulation path in the discharge unit. Figure 14 is a drawing illustrating an opening plate. Figure 15 is a drawing illustrating a discharge element substrate. FIGS. 16a to 16c are cross-sectional views illustrating the ink flow in a discharge unit. FIGS. 17a and FIGS. 17b are cross-sectional views illustrating the vicinity of the discharge port. FIGS. 18a and FIGS. 18b are cross-sectional views illustrating comparative examples near the discharge port. FIG. 19 is a drawing illustrating a comparative example of a discharge element substrate. Figures 20a and 20b are drawings illustrating the flow path configuration of a liquid discharge head. FIG. 21 is a drawing showing the state in which the main body unit and the liquid discharge head of the liquid discharge device are connected. FIG. 22 is a cross-sectional view of a liquid discharge head in a second embodiment. Specific details for implementing the invention

[0009] Preferred embodiments of the present disclosure are described in detail with reference to the accompanying 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 these 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.

[0010] (First embodiment)

[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) of the present embodiment will be described 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 the main scanning direction (X direction). The recording medium (P) is conveyed by conveying rollers (conveying units) (55, 56, 57, and 58) in the secondary scanning direction (Y direction) which intersects (orthogonally in the present example) the main scanning direction. Note that in the drawings referenced below, the Z direction represents the vertical direction and intersects (orthogonally in the present 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 the 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) is provided with an ink tank (2) and an external pump (21) that function as an ink source (liquid source). 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 the 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 the liquid dispensing head (1) is formed, at a position spaced apart 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). The 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 (50). 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 processed, 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 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. The basic configuration of the liquid discharge head (1) in the present embodiment will be described below, with reference to FIG. 1a, focusing on FIG. 2 to FIG. 3b.

[0022] As illustrated 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). In this embodiment, the liquid dispensing head (1) is fixedly supported on the carriage (60) of the liquid dispensing device (50) by means of a positioning unit and an electrical contact (not shown) provided on the carriage (60). 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) that functions as an ink source includes an ink supply tube (59) (see FIG. 1a). A liquid connector (59a) (see FIG. 21), described later, 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), the liquid connector (59a) provided at the tip of the ink supply tube (59) is provided to the head housing (53) of the liquid discharge head (1) and is hermetically connected to a liquid connector insertion slot (53a), which is an inlet through which ink is introduced. 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. Accordingly, four sets, each comprising 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 from 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 the ink supply tube (59) of the ink tank (2), but does not include a connector insertion slot for connecting an ink recovery tube for recovering ink from within the liquid dispensing head (1) into 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, a discharge port forming member (320) is formed on the surface of the silicon substrate (310) (the lower surface in FIG. 3B). In the discharge port forming member (320), a plurality of pressure chambers (12) corresponding to a plurality of discharge elements (15) and a plurality of discharge ports (13) for discharging 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 discharge module (300) is configured to discharge two types of ink. Specifically, in the two discharge modules (300) illustrated 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 may be adopted. The configuration may be such that 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 that includes only one discharge module (300) or three or more discharge modules (300). Furthermore, in the example illustrated in FIG. 3a and FIG. 3b, for one color of ink, two rows of discharge ports extending in the Y direction are formed. 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 each correspond to an opening that supplies and recovers 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, a second support member (7) is adhesively fixed to one side (the lower side in FIG. 3a) of the first support member (4), having an opening (7a) (see FIG. 2a) into which a discharge module (300) is inserted. An electrical wiring member (5) that is 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 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, the electric contact substrate (6) is bonded to the end portion (5a) of the electric wiring member (5) (see FIG. 2a) by heat-press bonding using an anisotropic conductive film (not shown), and the electric wiring member (5) and the electric contact substrate (6) are electrically connected to each other. The electric contact substrate (6) has an external signal input terminal (not shown) to receive an electric signal from a liquid dispensing 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. As shown in FIG. 5 and FIG. 6, these components are connected by a flow path to form a circulation path for supplying and recovering ink to and from the discharge module (300) within the liquid discharge head (1).

[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. 21, 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). 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 described. Note that the arrows in FIGS. 5 and 6 indicate the direction of ink flow.

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

[0040] An external pump (21) that sends ink contained 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) via a communication port (191A) (first communication port) that can be opened and closed by a valve (190A) (first valve) 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) via a communication port (191B) (second communication port) which is opened and closed by the second 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 contained 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 made 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 through 7c are drawings illustrating examples of pressure regulating units. With reference to FIGS. 7a through 7c, the configuration and operation of pressure regulating units (first pressure regulating unit (120) and second pressure regulating unit (150)) included in the aforementioned liquid discharge head (1) will be described in more detail. It should be noted that the first pressure regulating unit (120) and the second pressure regulating unit (150) have substantially the same configuration. Accordingly, the first pressure regulating unit (120) will be described below as an example. For the second pressure regulating unit (150), only the reference numeral of the part corresponding to the first pressure regulating unit is provided in FIGS. 7a through 7c. In the case of the second pressure regulating unit (150), the first valve chamber (121) and the first pressure control chamber (122) described below are 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 adjustment spring (220) (deflection unit) is provided between the pressure plate (210) and the partition (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 adjustment spring (220). Additionally, when the pressure inside the first pressure control chamber (122) decreases, the pressure plate (210) and the flexible member (230) are displaced in a direction that decreases the internal volume of the first pressure control chamber (122) by resisting the pressure from the pressure adjustment spring (220). And 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 to a certain pressure or lower (for example, 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. Accordingly, the pressure in the first pressure control room (122) is controlled to be maintained within a certain range.

[0058] As described above, the first pressure adjustment unit (120) has a first pressure control chamber (first liquid chamber) (122) that receives liquid supplied from a liquid source (ink tank (2)) and a circulation pump (500), and a first adjustment mechanism that adjusts the liquid pressure within the first pressure control chamber (122). Furthermore, the first adjustment mechanism includes the aforementioned pressure plate (210), pressure adjustment spring (220), valve (190), valve spring (200), and first valve chamber (121), and is configured to adjust the pressure of the liquid received in the first pressure control chamber (122) according to the volume of the first pressure control chamber (122). Additionally, the second pressure adjustment unit (150) has a second pressure control chamber (second liquid chamber) (152) connected to a pump inlet path (170), and a second adjustment mechanism that adjusts the pressure of the liquid received within the second pressure control chamber (152). The second adjustment mechanism comprises the aforementioned pressure plate (210), pressure adjustment spring (220), second valve (190B), second valve spring (200), and second valve chamber (151), and is configured to adjust the pressure of the liquid contained in the second pressure control chamber (152) according to the volume of the second pressure control chamber (152).

[0059] Next, the pressure of the first pressure control room (122) will be explained in more detail.

[0060] 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 Equation (1).

[0061] P2×S2 + F2 + (P1 - P2)×S1 + F1 = 0 Equation (1)

[0062] Furthermore, Equation (1) is rearranged as follows for P2.

[0063] P2 = -(F1 + F2 + P1×S1) / (S2 - S1) Equation (2)

[0064] P1: Pressure (gauge pressure) of the first valve chamber (121)

[0065] P2: Pressure (gauge pressure) of the first pressure control room (122)

[0066] F1: Spring force of the valve spring (200)

[0067] F2: Spring force of the pressure adjustment spring (220)

[0068] S1: Water pressure area of ​​valve (190)

[0069] S2: Water pressure area of ​​the pressure plate (210)

[0070] Here, the spring force (F1) of the valve spring (200) and the spring force (F2) of the pressure adjustment spring (220) are set so that the direction of pressing the valve (190) and the pressure plate (210) is forward (left direction in FIGS. 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.

[0071] 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 as the relationship P1 ≥ P2 is satisfied when the communication port (191) is in an open state, ink flows from the first valve room (121) to 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.

[0072] 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 the following equation (3).

[0073] P3 × S3 + F3 = 0 Equation (3)

[0074] Here, Equation (3) is rearranged as follows for P3.

[0075] P3 = -F3 / S3 Equation (4)

[0076] F3: Spring force of the pressure adjustment spring (220) when the pressure plate (210) is not in contact with the valve shaft (190a)

[0077] 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)

[0078] S3: Hydrostatic pressure area of ​​the pressure plate (210) when the pressure plate (210) is not in contact with the valve shaft (190a)

[0079] 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 up 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 FIG. 7c, the hydraulic pressure area (S3) of the pressure plate (210) decreases, and the spring force (F3) of the pressure adjustment spring (220) increases. Accordingly, the pressure (P3) of the first pressure control chamber (122) decreases according to the relationship of Equation (4). Accordingly, according to Equations (2) and (4), when moving from the state of Fig. 7b to the state of Fig. 7c, the pressure inside the first pressure control room (122) gradually increases (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 in the first pressure control room (122) gradually rises. That is, the negative pressure weakens.

[0080] Circulation pump

[0081] Next, with reference to FIGS. 8a, FIGS. 8b and FIGS. 9, the configuration and operation of each circulation pump (500) included in the liquid discharge head (1) will be described in detail.

[0082] 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 outer shell 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. The pair of through holes provided at one location forms a pump supply hole (501). The other 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).

[0083] 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 (504a) 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).

[0084] 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).

[0085] 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).

[0086] 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.

[0087] 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).

[0088] 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).

[0089] 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.

[0090] Now, with reference to FIGS. 10a, FIGS. 10b, and FIGS. 11, the specific configuration of the components of the circulation pump (500) will be described. FIGS. 10a and FIGS. 10b are exploded perspective views of the circulation pump (500). FIGS. 10a is an exploded perspective view of each component of the circulation pump (500) viewed from the rear side. FIGS. 10b is an exploded perspective view of each component of the circulation pump (500) viewed from the front side. The circulation pump (500) in this embodiment is a piezoelectric pump driven by applying voltage to a piezoelectric ceramic. As shown in FIGS. 10a and FIGS. 10b, a circular diaphragm (509) is bonded to a diaphragm (506) by an adhesive (508). A circular piezoelectric ceramic (510) is bonded to the diaphragm (509). For the diaphragm (506), an injection-moldable material such as modified polyphenylene ether (PPE+PS) or polypropylene is used. Alternatively, a member cut from a film or resin plate may also be used. The material is not limited to these. For the diaphragm (509), brass, stainless steel, iron-nickel alloy, etc. are used, but the material is not limited to these.

[0091] A driving circuit board (513) is placed on a surface facing the piezoelectric ceramic (510). The driving circuit board (513) is connected to a power unit placed in the main body of the liquid discharge device (50) and applies a predetermined driving voltage (AC voltage) to the piezoelectric ceramic (510) and the diaphragm (509).

[0092] FIG. 11 is a diagram of the electrical connection portion of the piezoelectric ceramic (510) observed through the driving circuit board (513) from the side of the cover (507). The driving circuit board (513) and the piezoelectric ceramic (510) are connected by an electrical connection cable (518a), and the driving circuit board (513) and the diaphragm (509) are electrically connected by an electrical connection cable (518b). Solder (520) electrically connects the electrical connection cable (518a) to the driving circuit board (513) and electrically connects the electrical connection cable (518b) to the driving circuit board (513). Solder (521) electrically connects the electrical connection cable (518a) to the piezoelectric ceramic (510) and also electrically connects the electrical connection cable (518b) to the diaphragm (509).

[0093] The diaphragm (509) is connected to the GND wiring of the driving circuit board (513) by an electrical connection cable (518b). The piezoelectric ceramic (510) is connected to the AC voltage output unit of the driving circuit board (513) by an electrical connection cable (518a). By connecting the diaphragm (509) to GND and applying an AC voltage with a phase difference to the piezoelectric ceramic (510), the piezoelectric ceramic (510) expands and contracts, thereby deforming the diaphragm. As a result, the pressure inside the pump chamber changes, causing ink to be sucked in or discharged.

[0094] The driving circuit board (513) is electrically connected to the electrical contact board (6) via a cable, and the electrical contact board (6) is provided with an electrical connection terminal for driving the pump. With the circulation unit (54) attached to the carriage (60), an electrical signal output from the electrical contact on the carriage (60) side (not shown, first electrical connection) is input to the driving circuit board (513) through the corresponding electrical connection terminal of the electrical contact board (6) (not shown, second electrical connection).

[0095] As described above, by providing an electrical connection terminal for pump driving on the electrical contact board (6), the circulation pump (500) can be driven by applying a driving voltage (AC voltage) to the corresponding electrical connection terminal even when separated from the carriage (60).

[0096] Ink flow within the liquid ejection head

[0097] FIGS. 12a through 12e are drawings illustrating the flow of ink within a liquid discharge head. With reference to FIGS. 12a through 12e, the circulation of ink performed within the liquid discharge head (1) will be described. The relative positions of the components of FIGS. 12a through 12e, such as the first pressure regulating unit (120), the second pressure regulating unit (150), and the circulation pump (500), are simplified for a brief description of the ink circulation path. Accordingly, the relative positions of the components differ from those of FIGS. 2a and 4 and FIGS. 21a and 21b described later. FIG. 12a schematically illustrates the ink flow when performing a recording operation in which ink is discharged from the discharge port (13) to perform a recording. Note that the arrows in FIG. 12a 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.

[0098] During the recording operation, the circulation pump (500) is turned ON (operated) so that ink flowing out from the first pressure control room (122) (first liquid room) 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). Afterward, the ink is supplied to the second pressure control room (152).

[0099] 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 the aforementioned equation (2). 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) 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).

[0100] 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 to less than a predetermined volume, the communication port (191A) (first communication port) 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) to 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 above a predetermined volume, the communication port (191A) is closed. As described above, the communication port (191A) repeatedly switches between the open and closed states depending on the ink consumption. Additionally, if the ink is not consumed, the communication port (191A) remains closed.

[0101] FIG. 12b 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. 12b. 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.

[0102] 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 the aforementioned equation (2), 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) (deflection unit), 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.

[0103] 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) is closed, as shown in FIG. 12c, from the state of FIG. 12b until it does not allow communication between the second valve chamber (151) and the second pressure control chamber (152). After that, the pressure plate (210) is not in contact with the valve shaft (190a), and the communication port (191) is closed. Then, as shown in FIG. 12d, 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.

[0104] Note that once the state of FIG. 12c 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.

[0105] Additionally, when the pressure inside the second pressure control chamber (152) becomes equal to the pressure inside the first pressure control chamber (122), the second pressure control chamber (152) expands to the state shown in FIG. 12d. When the second pressure control chamber (152) expands as shown in FIG. 12d, a reservoir capable of holding ink is formed in the second pressure control chamber (152). Note that the transition to the state shown in FIG. 12d 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. 12d, the ink in the reservoir is supplied to the first pressure control chamber (122) by the circulation pump (500). Accordingly, as shown in FIG. 12e, 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. 12a.

[0106] In this embodiment, during the liquid circulation operation, a characteristic pressure relationship as shown in the following inequality (5) and equation (6) is maintained.

[0107] P22 > P21 Equation (5)

[0108] P21: Pressure (gauge pressure) of the first pressure control room (122) when the circulation pump (500) is stopped

[0109] P22: Pressure (gauge pressure) of the first pressure control room (122) when the circulation pump (500) is driven

[0110] Additionally, the pressure of the first pressure control room (122) is reduced when the circulation pump (500) is driven, but the following is satisfied.

[0111] P22 - △P < 0 Equation (6)

[0112] △P: Pressure loss from the first pressure control room (122) to the pressure room (12) when the circulation pump is driven

[0113] By satisfying the above conditions, ink is prevented from leaking from the discharge port (13) when the circulation pump (500) is driven.

[0114] With the above configuration, the ink is circulated through a circulation path completed within the liquid discharge head (1). Therefore, even if ink concentration or color settling temporarily occurs in the pressure chamber (12), the circulation of the ink through the circulation path resolves the color settling and ink thickening. This reduces downtime during recording.

[0115] In addition, in this embodiment, the configuration is such that a filter (110) is provided outside the ink circulation path, and once the ink passes through the filter (110), the ink circulates through the circulation path without passing through the filter. This prevents the filter (110) from becoming clogged with ink aggregates or the like due to the repeated circulation of the ink. Additionally, a relatively short circulation path is formed that is completed within the liquid discharge head (1). Furthermore, providing the filter outside the circulation path reduces pressure loss in the circulation path. This allows circulation to be performed by the relatively small circulation pump (500) described in this embodiment. Additionally, the pressure of the liquid supplied from the external pump through the filter (110) can be appropriately controlled on the supply path (130) by the first pressure adjustment unit (120). This allows the ink to be supplied to the filter (110) by pressurization by the external pump. Thus, the filtration area of ​​the filter can be set small, and the liquid discharge head can be miniaturized.

[0116] In addition, in this embodiment, as shown in FIGS. 12a to 12e, the filtration surface of the filter (110) is positioned along the direction of gravity and, more preferably, parallel to the direction of gravity, and the flow paths (270 and 290) on the inlet and outlet sides of the filter (110) are positioned at the bottom of the filter. This facilitates the flow of settled colorant downstream. Accordingly, clogging of the filter (110) can be prevented.

[0117] Additionally, in the first pressure control chamber (122) and the second pressure control chamber (152), a liquid outlet (250, 240) for discharging the liquid contained in each pressure control chamber (122 and 152) is provided at the lower part of the pressure control chamber in the direction of gravity (a part lower than the middle part of the pressure control chamber in the direction of gravity). By doing so, even if the composition of the ink, etc., settles, the settled material is more easily discharged from the pressure control chamber (122, 152). This shortens the ink stirring time by circulation.

[0118] In addition, when using ink in which the color material settles at a rapid rate, such as white ink, the ink needs to be stirred to perform circulation even when recording is not being performed. However, in this embodiment, ink can be circulated within the liquid discharge head (1) even when the circulation unit (54) is not mounted on the main body unit of the liquid discharge device (50), such as a carriage. That is, even when the liquid discharge head (1) is separated from the carriage (60) provided on the main body of the liquid discharge device (50), ink can be circulated by driving the circulation pump (500) by applying an alternating voltage to the electrical connection terminal of the electrical contact board (6). In this way, it is possible to resolve the settling of the ink color material within the liquid discharge head (1) in advance before use, and thus efficiently start the recording operation. In addition, when ink circulation is performed with the liquid discharge head (1) not mounted on the main body of the liquid discharge device, power consumption is reduced compared to when circulation is performed with the liquid discharge head (1) mounted on the main body of the liquid discharge device.

[0119] Note that in the above description, FIG. 12a 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. 12a to FIG. 12e in response to the driving and stopping of the circulation pump (500).

[0120] 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).

[0121] 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).

[0122] First, an example is described in which negative pressure that becomes 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.

[0123] 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, provided that the flow rate of the pump changes due to viscosity changes caused by environmental changes, etc., but the meniscus does not collapse or a predetermined negative pressure is maintained.

[0124] 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.

[0125] 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.

[0126] When recording at a high duty level, the amount of ink flowing into the second pressure control room (152) from the pressure room (12) through the recovery path (140) is reduced. 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 level. 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).

[0127] Additionally, as the high duty record continues, the amount of ink flowing from the pressure chamber (12) into the second pressure control chamber (152) through the recovery path (140) decreases, and conversely, the amount flowing from the communication port (191B) into 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) into 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) into 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.

[0128] 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).

[0129] <Composition of the Discharge Unit>

[0130] FIGS. 13a and 13b are schematic diagrams illustrating the circulation path of one color of ink in the discharge unit (3) of the present embodiment. FIG. 13a is an exploded perspective view of the discharge unit (3) from the side of the first support member (4). FIG. 13b is an exploded perspective view of the discharge unit (3) from the side of the discharge module (300). In FIGS. 13a and 13b, 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. 13a and 13b, 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. 13a, a cross-section along line XIII-XIII of FIG. 3a is shown. Each discharge module (300) includes a discharge element substrate (340) and an opening plate (330). FIG. 14 is a drawing illustrating the opening plate (330). FIG. 15 is a drawing illustrating the discharge element substrate (340).

[0131] 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.

[0132] 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).

[0133] As shown in FIGS. 13a, 13b, and 14, 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. 15 and FIGS. 16a through 16c, 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 the plurality of supply connection channels (323) and a common recovery channel (19) communicating with the plurality of recovery connection channels (324). The ink supply channels (48) and ink recovery channels (49) (see FIG. 3a) disposed on the first support member (4) 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).

[0134] 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.

[0135] 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).

[0136] 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.

[0137] In FIG. 14, 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. 15, 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).

[0138] 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.

[0139] FIGS. 16a to 16c are cross-sectional views showing ink flow in different parts of the discharge unit (3). FIG. 16a is a cross-section taken along the XVIA-XVIA line of FIG. 13a 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. 16b is a cross-section taken along the XVIB-XVIB line of FIG. 13a 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. 16c is a cross-section taken along the XVIC-XVIC line of FIG. 13a 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).

[0140] As illustrated in FIG. 16a, 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. 16b, 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. 16c, 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. 16a, ink is supplied in the region where the ink supply port (311) is provided. As shown in FIG. 16b, 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).

[0141] FIGS. 17a and 17b are cross-sectional views showing the vicinity of the discharge port (13) in the discharge module (300). FIGS. 18a and 18b 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. 17a and 17b and FIGS. 18a and 18b 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.

[0142] 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. 18a and 18b, 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.

[0143] Accordingly, each common supply channel (18) and each common recovery channel (19) of the present embodiment, whose cross-sections are illustrated in FIGS. 17a and 17b, 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. 17a and 17b) 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.

[0144] 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] FIG. 19 is a drawing illustrating a discharge element substrate (340) as a comparative example. Note that in FIG. 19, 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. 19, 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.

[0151] 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.

[0152] FIGS. 20a and 20b 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. 20a. 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. 20b, 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.

[0153] <Connection of the main unit and the liquid dispensing head>

[0154] FIG. 21 is a schematic diagram showing in more detail the arrangement of the ink tank (2), external pump (21), and liquid discharge head (1) connected as the main body unit of the liquid discharge device (50) of the present embodiment, and the circulation pump (500). 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 each ink supply tube (59) is connected to each external pump (21), and the liquid discharge heads (1) 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).

[0155] 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. 21, 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 positioned 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.

[0156] As described above, the liquid discharge head (1) shown in FIG. 21 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.

[0157] <Arrangement of circulation pumps, etc.>

[0158] As shown in FIG. 21, 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.

[0159] 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 electrical problems caused by ink leaking from the liquid connection part (700) can be reduced.

[0160] Additionally, in this embodiment, a wall portion (53b) of the head housing (53) is provided. Accordingly, 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 ink reaching the circulation pump (500) or the electrical connection portion (515).

[0161] (Second embodiment)

[0162] Next, a second embodiment of the present invention will be described. FIG. 22 is a cross-sectional view of a liquid discharge head in the second embodiment. In this embodiment, a second supply channel (600) is provided to communicate with the first pressure control chamber (122) of the first pressure regulating unit (120) in the first embodiment and the supply channel (130). The second supply channel (600) communicates with the upper end of the first pressure control chamber (122) in the direction of gravity at one end and communicates with the upper end of the supply channel (130) in the direction of gravity at the other end. By providing this second supply channel (600), bubbles introduced from the upstream side of the first pressure regulating unit (120) or bubbles generated within the circulation channel are efficiently discharged to the outside.

[0163] Specifically, the first pressure control chamber (122) of the first pressure adjustment unit (120) is positioned above the liquid discharge head (1) in the direction of gravity. Accordingly, bubbles (BL) introduced into the first pressure adjustment unit (120) along with ink from the upstream side of the liquid discharge head (1), or bubbles (BL) introduced into the upper part of the first pressure control chamber (122) from the circulation path, rise to the upper part of the first pressure control chamber (122) or the upper part of the second supply path (600), and are collected there. Additionally, it should be noted that the collected bubbles (BL) cannot move to the discharge module (300) at the flow rate of the liquid flowing through the supply path (130) and the second supply path (600) during the ink discharge operation.

[0164] Bubbles (BL) collected in the upper portion of the first pressure control chamber (122) and the second supply path (600) can be discharged along with ink by performing a suction process to forcibly draw ink from the discharge port while the discharge operation is not being performed. The suction process is performed by bringing a cap member into close contact with the discharge port surface of the liquid discharge head (1) in which the discharge port is formed, and applying negative pressure from a negative pressure source connected to the cap member to the discharge port to forcibly draw ink from the discharge port. During this suction, the flow rate of ink generated inside the path is greater than the flow rate of ink generated by a normal ink discharge operation. Therefore, bubbles (BL) collected in the upper portion of the first pressure control chamber (122) and the second supply path (600) move to the pressure chamber (12) through the second supply path (600) and the supply path (130) together with the ink, and are subsequently discharged along with the ink from the discharge port (13). In addition, this suction treatment is generally performed by a suction recovery treatment, which is carried out to restore discharge performance by discharging thickened ink, etc., appearing in the discharge port, pressure chamber, etc., from the discharge port, and an initial filling treatment, which fills the ink into the flow path.

[0165] As described above, by forming a second supply channel, bubbles contained in the ink within the liquid discharge head (1) can be collected and discharged all at once by suction treatment. Therefore, the discharge treatment of bubbles can be performed efficiently.

[0166] (Other embodiments)

[0167] In the above embodiment, an example is provided in which a bypass path (160) is provided to prevent the discharge module (300) from being affected when the pressure generated by the circulation pump (500) exceeds a specified value. However, when the pressure fluctuation by the circulation pump (500) is small and the pressure is maintained within a specified value, the bypass path (160) and the second pressure adjustment unit (150) may be omitted.

[0168] According to the present invention, by performing circulation for a short period of time, it is possible to suppress the redispersion of sedimentation components and the thickening of ink, thereby providing a liquid dispensing head and a liquid dispensing device that can reduce downtime.

[0169] 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 port through which a liquid is discharged, a pressure chamber communicating with the discharge port, a discharge element configured to discharge the liquid supplied to the pressure chamber from the discharge port, and a circulation path through which the liquid circulates, wherein the circulation path comprises a supply path through which the liquid is supplied to the pressure chamber, a recovery path through which the liquid is recovered from the pressure chamber, a circulation pump that supplies the liquid recovered through the recovery path to the supply path, and a pressure regulating unit configured to adjust the pressure on the liquid supplied to the supply path, wherein the pressure of the liquid in the pressure chamber (P21) set by the pressure regulating unit when the circulation pump is stopped, the pressure of the liquid in the pressure chamber (P22) set by the pressure regulating unit when the circulation pump is driven, and the pressure loss (△P) from the pressure regulating unit to the pressure chamber when the circulation pump is driven have the relationship P22 > P21 and P22 - △P < 0. Claim 2 A liquid discharge head according to claim 1, wherein the pressure regulating unit comprises a first pressure regulating unit connected between an inlet through which a liquid supplied from a liquid source is introduced and the supply path, and the first pressure regulating unit comprises a first liquid chamber receiving the liquid supplied from the liquid source and the circulation pump, and a first regulating mechanism for regulating the pressure on the liquid supplied from the first liquid chamber to the supply path. Claim 3 A liquid discharge head according to paragraph 2, wherein the volume of the first liquid chamber varies according to the amount of liquid supplied from the liquid source and the circulation pump, and the first adjusting mechanism adjusts the pressure of the liquid contained within the first liquid chamber according to the volume of the first liquid chamber. Claim 4 In paragraph 2, the first adjusting mechanism comprises a first valve chamber that communicates with the first liquid chamber through a first communication port and supplies the liquid supplied from the liquid source to the first liquid chamber through the first communication port, and a first valve that switches the first communication port between an open state and a closed state according to the volume of the first liquid chamber, a liquid discharge head. Claim 5 A liquid discharge head according to claim 4, wherein the first valve opens the first communication port when the volume of the first liquid chamber receiving the liquid is less than a predetermined volume, and closes the first communication port when the volume of the first liquid chamber is greater than or equal to the predetermined volume. Claim 6 A liquid discharge head according to claim 4, wherein the volume of the first liquid chamber changes by the displacement of a flexible member formed in at least a part of the first liquid chamber, and the first adjusting mechanism includes a deflection unit configured to deflect the flexible member in a direction in which the volume of the first liquid chamber increases, and a first valve that is displaced according to the displacement of the flexible member, wherein the first valve is displaced to a position in which the first communication port is opened when the flexible member is displaced to a position in which the volume of the first liquid chamber is less than a predetermined volume, and the first communication port is closed when the flexible member is displaced to a position in which the volume of the first liquid chamber is greater than or equal to the predetermined volume. Claim 7 In paragraph 2, the pressure regulating unit further comprises a second pressure regulating unit fluidically connected to the first liquid chamber, the recovery path, and the circulation pump, wherein the second pressure regulating unit has a second liquid chamber receiving the liquid supplied from the first liquid chamber and the recovery path, and a second regulating mechanism for regulating the pressure on the liquid supplied to the second liquid chamber, a liquid discharge head. Claim 8 A liquid discharge head according to claim 7, wherein the volume of the second liquid chamber varies according to the amount of liquid supplied from the liquid source and the circulation pump, and the second adjusting mechanism adjusts the pressure of the liquid contained in the second liquid chamber according to the volume of the second liquid chamber. Claim 9 In claim 8, the second adjusting mechanism comprises a second valve chamber communicating with the second liquid chamber through a second communication port and supplying the liquid supplied from the first liquid chamber and the recovery path to the second liquid chamber through the second communication port, and a second valve that switches the second communication port between an open state and a closed state according to the volume of the second liquid chamber, wherein the second valve opens the second communication port to the open state when the volume of the second liquid chamber receiving the liquid is less than a predetermined volume, and closes the second communication port to the closed state when the volume of the second liquid chamber is greater than or equal to the predetermined volume. Claim 10 A liquid discharge head according to claim 7, wherein a discharge port through which the liquid contained in the first liquid chamber and the second liquid chamber is discharged is provided in the lower portion of the first liquid chamber and the second liquid chamber in the direction of gravity. Claim 11 A liquid discharge head according to paragraph 2, further comprising an upper portion of the first liquid chamber and a second supply channel that communicates with each other through the supply channel. Claim 12 A liquid discharge head according to claim 1, further comprising an electrical connection terminal capable of applying at least a driving voltage for the circulation pump from an external power source. Claim 13 In claim 1, the circulation pump is a piezoelectric pump having a pump chamber to which liquid is supplied and a piezoelectric element, and the liquid discharge head is displaced to change the volume of the pump chamber in response to the application of a driving voltage to the piezoelectric element. Claim 14 A liquid discharge head according to claim 13, wherein an alternating current voltage having a phase difference is applied as a driving voltage to the piezoelectric element. Claim 15 A liquid discharge head according to claim 1, further comprising a filter provided between the circulation path and the liquid source and filtering the liquid supplied from the liquid source. Claim 16 In item 15, the filter is a liquid discharge head positioned along the direction of gravity. Claim 17 A liquid dispensing device comprises a liquid dispensing head, a liquid source for supplying liquid to the liquid dispensing head, and a return unit configured to return a recording medium to a location opposite the discharge port of the liquid dispensing head, wherein the liquid dispensing head comprises a discharge port through which liquid is discharged, a pressure chamber communicating with the discharge port, a discharge element configured to discharge the liquid supplied to the pressure chamber from the discharge port, and a circulation path through which the liquid circulates, wherein the circulation path comprises a supply path through which the liquid is supplied to the pressure chamber, a recovery path through which the liquid is recovered from the pressure chamber, a circulation pump for supplying the liquid recovered through the recovery path to the supply path, and a pressure adjustment unit configured to adjust the pressure on the liquid supplied to the supply path, wherein the pressure of the liquid in the pressure chamber (P21) set by the pressure adjustment unit when the circulation pump is stopped, the pressure of the liquid in the pressure chamber (P22) set by the pressure adjustment unit when the circulation pump is driven, and the circulation pump A liquid discharge device having a pressure loss (△P) from the pressure regulating unit to the pressure chamber in an operating state, such that P22 > P21 and P22 - △P < 0. Claim 18 A liquid dispensing device according to claim 17, wherein the liquid dispensing head is mounted in a manner that is removablely attachable on a carriage that moves in a main scanning direction across the direction in which the conveying unit conveys the recording medium, and performs recording by dispensing the liquid from the dispensing port while moving together with the carriage in the main scanning direction. Claim 19 A liquid dispensing device according to claim 18, wherein the carriage has a first electrical connection portion electrically connected to a power source, and the liquid dispensing head has a second electrical connection portion connected to the first electrical connection portion when the liquid dispensing head is attached to the carriage. Claim 20 A liquid discharge device according to claim 19, wherein the power for the discharge element generates energy to discharge the liquid, and the driving voltage for the circulation pump is supplied from the power source to the liquid discharge head through the first electrical connection and the second electrical connection.

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