Liquid discharge head

Abstract

To enable circulating liquid between a plurality of pressure chamber channels and a common channel, and suppress reduction in absorption of pressure fluctuations by a damper.SOLUTION: A head 1 includes: a plurality of pressure chamber channels 20; and a common channel 12 including an upper common channel 12A and a lower common channel 12B which are positioned on top of each other in a vertical direction D3. A first damper 28A and a second damper 28B are disposed between the upper common channel 12A and the lower common channel 12B. Between the common channel 12 and the plurality of pressure chamber channels 20, for each of the pressure chamber channels 20, there are disposed a supply channel 18 positioned above the upper common channel 12A and supplying ink from the upper common channel 12A to the pressure chamber channel 20, and a circulation channel 19 positioned below the lower common channel 12B and returning ink from the pressure chamber channel 20 to the lower common channel 12B.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection head that ejects liquid. [Background technology]

[0002] Patent Document 1 describes a liquid ejection head including a plurality of pressure chambers (pressure chamber flow paths) that respectively communicate with a plurality of nozzles, and a common flow path that communicates with the plurality of pressure chambers. Between the common flow path and the plurality of pressure chambers of this liquid ejection head, an ink circulation flow path is arranged for each pressure chamber, returning ink from the pressure chamber to the common flow path. This allows ink to circulate between each pressure chamber and the common flow path. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-200902 Summary of the Invention [Problem to be solved by the invention]

[0004] In the liquid ejection head described in Patent Document 1, the ink circulation port of the ink circulation channel opens to the bottom surface of the common channel, connecting the common channel to the pressure chamber. Therefore, when a damper is provided on the bottom surface of the common channel to absorb pressure fluctuations of the ink in the common channel, the damper must be positioned to avoid overlapping with the ink circulation channel of the common channel. As a result, the movable area of ​​the damper becomes smaller, and its ability to absorb pressure fluctuations of the liquid in the common channel decreases.

[0005] Therefore, an object of the present invention is to provide a liquid ejection head that is capable of circulating liquid between multiple pressure chamber flow paths and a common flow path, and that is capable of suppressing a decrease in the absorption of pressure fluctuations by the damper. [Means for solving the problem]

[0006] The liquid ejection head of the present invention comprises a plurality of nozzles arranged in a first direction perpendicular to the vertical direction, a plurality of pressure chamber flow paths arranged in the first direction and each communicating with the plurality of nozzles, and a common flow path communicating with the plurality of pressure chamber flow paths, wherein the common flow path is an upper common flow path and a lower common flow path arranged one on top of the other in the vertical direction, the upper common flow path and the lower common flow path each extending in the first direction and communicating with each other at both ends in the first direction, a damper is arranged between the upper common flow path and the lower common flow path in the vertical direction to absorb pressure fluctuations of liquid in at least one of the upper common flow path and the lower common flow path, and between the common flow path and the plurality of pressure chamber flow paths there are arranged, for each of the pressure chamber flow paths, a supply flow path located above the upper common flow path and supplying liquid from the upper common flow path to the pressure chamber flow path, and a circulation flow path located below the lower common flow path and returning liquid from the pressure chamber flow path to the lower common flow path. [Effects of the Invention]

[0007] According to the liquid ejection head of the present invention, it is possible to supply liquid from the upper common flow path to each pressure chamber flow path and return the liquid from each pressure chamber flow path to the lower common flow path. In other words, it is possible to circulate liquid between multiple pressure chamber flow paths and the common flow path. Furthermore, a damper is disposed between the upper common flow path and the lower common flow path, with the supply flow path disposed above the upper common flow path and the circulation flow path disposed below the lower common flow path. Therefore, it is not necessary to position the damper to avoid the supply flow path or the circulation flow path, and the movable range of the damper is not limited, making it possible to suppress a decrease in the damper's ability to absorb pressure fluctuations. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a plan view of a printer including a head according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the electrical configuration of the printer. [Figure 3] FIG. [Figure 4]4 is an enlarged view of a region IV shown in FIG. 3 on the upper surface of the flow path member. [Figure 5] 4(a) is a cross-sectional view of the head taken along line VV shown in FIG. 3, and is a view in which the circulation flow paths included in the individual flow paths are added. FIG. [Figure 6] FIG. 4 is a cross-sectional view of the head taken along line VI-VI shown in FIG. 3. [Figure 7] FIG. 10 is a plan view of a head according to a second embodiment of the present invention. [Figure 8] FIG. 8 is a cross-sectional view of the head taken along line VIII-VIII shown in FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0009] First Embodiment First, referring to Figure 1, the overall configuration of a printer 100 equipped with a head 1 according to a first embodiment of the present invention will be described. In the following description, the first direction D1 and the second direction D2 are horizontal directions that are perpendicular to the up-down direction D3. In this embodiment, the up-down direction D3 is aligned with the vertical direction, but it may also be a vertical direction that intersects with the vertical and horizontal directions. The first direction D1 is perpendicular to the second direction D2.

[0010] <Overall printer configuration> The printer 100 includes a housing 100A, a head unit 1X, a platen 3, a transport mechanism 4, and a control unit 5. The head unit 1X, the platen 3, the transport mechanism 4, and the control unit 5 are arranged inside the housing 100A.

[0011] The length of the head unit 1X in a first direction D1 is longer than the length of the head unit 1X in the transport direction along a second direction D2. The first direction D1 is a direction along the width of the paper 9. The head unit 1X is fixed to a housing 100A. The head unit 1X is a line type.

[0012] The head unit 1X includes four heads 1. The four heads 1 are arranged in a staggered pattern in the first direction D1. The length of the heads 1 in the first direction D1 is longer than the length of the heads 1 in the second direction D2.

[0013] The platen 3 is a plate along a plane perpendicular to the up-down direction D3, and is disposed below the head unit 1 X. A paper sheet 9 is supported on the upper surface of the platen 3.

[0014] The transport mechanism 4 has two roller pairs 4A and 4B arranged in the second direction D2 with the platen 3 sandwiched between them. When the transport motor 4C is driven under the control of the control unit 5, the roller pairs 4A and 4B rotate while sandwiching the paper 9, and the paper 9 is transported in the transport direction along the second direction D2.

[0015] 2, the control unit 5 includes a CPU 5A, a ROM 5B, and a RAM 5C. The CPU 5A executes various controls in accordance with programs and data stored in the ROM 5B and RAM 5C, based on data input from an external device. The external device is, for example, a personal computer (PC).

[0016] The ROM 5B stores programs and data for the CPU 5A to perform various controls. The RAM 5C temporarily stores data used when the CPU 5A executes the programs.

[0017] <head> 3, the head 1 has a flow path member 21 and an actuator member 22. Both the flow path member 21 and the actuator member 22 have a rectangular shape in which the length in the first direction D1 is longer than the length in the second direction D2 in a plane perpendicular to the up-down direction D3.

[0018] 3, two supply ports 111 and two return ports 112 are opened on the upper surface 21A of the flow path member 21. The two supply ports 111 are arranged at both ends of the flow path member 21 in the first direction D1. The two return ports 112 are also arranged at both ends of the flow path member 21 in the first direction D1. The supply ports 111 and the return ports 112 are connected to ink tanks via tubes. The flow path member 21 has two common flow paths 12, a plurality of individual flow paths 13, and two damper chambers 28.

[0019] The two common flow paths 12 are aligned in the second direction D2 and extend in the first direction D1. One of the two common flow paths 12 (on the left in FIG. 3) has a supply port 111 connected to one end (the upper end in FIG. 3) in the first direction D1 and a return port 112 connected to the other end (the lower end in FIG. 3), while the other common flow path 12 (on the right in FIG. 3) has a return port 112 connected to one end (the first direction D1) and a supply port 111 connected to the other end. The common flow path 12 communicates with an ink tank via the supply port 111 and the return port 112, and also communicates with a plurality of individual flow paths 13.

[0020] 5 and 6, the common flow path 12 has an upper common flow path 12A and a lower common flow path 12B that are arranged to overlap each other in the vertical direction D3. The upper common flow path 12A and the lower common flow path 12B each extend in a first direction D1 and communicate with each other via communication ports 12C and 12D at both ends in the first direction D1.

[0021] The two damper chambers 28 are respectively disposed between the upper common flow path 12A and the lower common flow path 12B of the common flow path 12. The two damper chambers 28 are also aligned in the second direction D2 and extend in the first direction D1.

[0022] 3 to 5, the individual flow path 13 includes a nozzle 15, a pressure chamber flow path 20, a supply flow path 18, and a circulation flow path 19. The pressure chamber flow path 20 has a pressure chamber 16 and a communication flow path 17. One end of the communication flow path 17 communicates with the nozzle 15, and the other end communicates with the pressure chamber 16.

[0023] The supply flow path 18 is located above the upper common flow path 12A, with one end communicating with the upper common flow path 12A and the other end communicating with the pressure chamber 16. The circulation flow path 19 is located below the lower common flow path 12B, with one end communicating with the communication flow path 17 and the other end communicating with the lower common flow path 12B.

[0024] 5, the flow path member 21 includes nine plates 121 to 129. The flow path member 21 may be configured with ten or more or eight or fewer plates. Of the nine plates 121 to 129, the uppermost plate 121 has a plurality of pressure chambers 16 formed therein, and the lowermost plate 129 has a plurality of nozzles 15 formed therein. The plurality of pressure chambers 16 are located above the common flow path 12.

[0025] A plurality of pressure chambers 16 open to the upper surface (upper surface 21A) of the plate 121, and a plurality of nozzles 15 open to the lower surface of the plate 129. In this manner, the plurality of nozzles 15 are arranged on a nozzle surface 129A, which is the lower surface of the plate 129. The openings of the nozzles 15 are circular, and the openings of the pressure chambers 16 are generally rectangular and slightly elongated in the second direction D2. In other words, the length (width) of the pressure chambers 16 in the first direction D1 is shorter than the length in the second direction D2. As shown in FIG. 5, the nozzles 15 have a shape that tapers downward.

[0026] 5 and 6, the upper common flow path 12A of the common flow path 12 is configured by a hole formed in the plate 124. As shown in FIG. 6, the upper common flow path 12A has an inlet 12A1 through which ink flows in from the supply port 111, and an outlet 12A2 through which ink flows out to the return port 112. The inlet 12A1 is located at one end (left in FIG. 6) of the upper common flow path 12A, and is arranged to overlap with the supply port 111 in the vertical direction D3. The outlet 12A2 is located at the other end (right in FIG. 6) of the upper common flow path 12A, and is arranged to overlap with the return port 112 in the vertical direction D3.

[0027] 3 and 6, the upper common flow path 12A is provided with an upper narrow section 12E where the flow path narrows. As shown in Fig. 3, the upper narrow section 12E is arranged on the other side of the first direction D1 than a connection port 18B1 (described later), which is arranged furthest in the other side of the first direction D1 (downstream in the liquid flow direction in Fig. 3 and to the right in Fig. 6) among the multiple supply flow paths 18 communicating with the upper common flow path 12A. Note that the liquid flow direction in the common flow path 12 is the direction in which ink flows from the supply port 111 toward the return port 112 along the extension direction of the common flow path 12.

[0028] As shown in FIGS. 5 and 6, the lower common flow path 12B of the common flow path 12 is formed by a hole formed in the plate 127. As shown in FIG. 6, the communication ports 12C and 12D are formed by connecting holes formed in two plates 125 and 126, respectively. The upper common flow path 12A and the lower common flow path 12B are connected to each other by the communication ports 12C and 12D at both ends in the first direction D1, thereby forming one common flow path 12. The communication port 12C is located at a position overlapping with the inlet 12A1 in the vertical direction D3. The communication port 12D is located at a position overlapping with the outlet 12A2 in the vertical direction D3. As shown in FIG. 3, each common flow path 12 overlaps with all pressure chambers 16 communicating with the common flow path 12 in the vertical direction D3. The inlet 12A1 corresponds to a "liquid supply port" in the present invention, and the outlet 12A2 corresponds to a "liquid discharge port" in the present invention. The communication port 12C corresponds to the "one communication port" of the present invention, and the communication port 12D corresponds to the "other communication port" of the present invention.

[0029] 3 and 6, the lower common flow path 12B is also provided with a lower narrow section 12F where the flow path narrows. As shown in Fig. 3, the lower narrow section 12F is arranged on one side in the first direction D1 of a connection port 19A1 (described later) that is arranged furthest in one side in the first direction D1 (upstream in the liquid flow direction in Fig. 3 and to the left in Fig. 6) among the multiple circulation flow paths 19 that communicate with the lower common flow path 12B.

[0030] As shown in Fig. 6, the opening area S1 of the communication port 12C and the opening area S2 of the communication port 12D are larger than the opening area S3 of the upper common flow path 12A, which is perpendicular to the first direction D1, excluding the upper narrow portion 12E, and the opening area S4 of the lower common flow path 12B, which is perpendicular to the first direction D1, excluding the lower narrow portion 12F. The opening area S3 of the upper common flow path 12A and the opening area S4 of the lower common flow path 12B are the same. The lengths in the vertical direction D3 and the second direction of the opening area S3 portion of the upper common flow path 12A and the opening area S4 portion of the lower common flow path 12B are also the same. The lengths in the first direction D1 of the upper common flow path 12A and the lower common flow path 12B are also the same.

[0031] 3, the opening area S3A of the upper narrow portion 12E is the smallest of the opening areas of the upper common flow path 12A perpendicular to the first direction D1. The opening area S4A of the lower narrow portion 12F is the smallest of the opening areas of the lower common flow path 12B perpendicular to the first direction D1. These opening areas S3A and S4A are also the same size.

[0032] As shown in FIG. 5 , each damper chamber 28 is formed by connecting the openings of recesses formed in the two plates 125 and 126. The upper portion of the damper chamber 28 in the plate 125, which is sandwiched between the damper chamber 28 and the upper common flow path 12A, functions as a first damper 28A that absorbs pressure fluctuations of the ink in the upper common flow path 12A. The lower portion of the damper chamber 28 in the plate 126, which is sandwiched between the damper chamber 28 and the lower common flow path 12B, functions as a second damper 28B that absorbs pressure fluctuations of the ink in the lower common flow path 12B. Even if pressure generated in the pressure chamber 16 when ink is ejected from the nozzle 15 is transmitted to the upper common flow path 12A and the lower common flow path 12B, these dampers 28A and 28B attenuate the pressure by elastic deformation, thereby preventing the pressure from being transmitted to other pressure chambers 16 (so-called crosstalk).

[0033] 3, the individual flow paths 13 are arranged in the first direction D1 to form four individual flow path rows, a first individual flow path row 14R1 to a fourth individual flow path row 14R4. That is, like the individual flow path row 14R, the pressure chamber flow paths 20 also form four pressure chamber flow path rows, a first pressure chamber flow path row 20R1 to a fourth pressure chamber flow path row 20R4. The pressure chamber flow path row 20R and the individual flow path row 14R are aligned in the second direction D2. Furthermore, the individual flow paths 13 belonging to two individual flow path rows 14R adjacent to each other in the second direction D2 are arranged so as to be shifted in the first direction D1.

[0034] Furthermore, two of the four individual flow path rows 14R correspond to one common flow path 12. The first individual flow path row 14R1 to the fourth individual flow path row 14R4 are arranged in this order from upstream to downstream in the transport direction.

[0035] The first individual flow path array 14R1 is configured with individual flow paths 13A aligned in the first direction D1. The second individual flow path array 14R2 is configured with individual flow paths 13B aligned in the first direction D1. The third individual flow path array 14R3 is configured with individual flow paths 13B aligned in the first direction D1, which are formed by rotating the individual flow paths 13B included in the second individual flow path array 14R2 by 180° around a rotation axis along the vertical direction D3. The fourth individual flow path array 14R4 is configured with individual flow paths 13A aligned in the first direction D1, which are formed by rotating the individual flow paths 13A included in the first individual flow path array 14R1 by 180° around a rotation axis along the vertical direction D3.

[0036] The first pressure chamber flow path array 20R1 and the fourth pressure chamber flow path array 20R4 are configured with their respective pressure chamber flow paths 20A aligned in the first direction D1, similar to the above-described first individual flow path array 14R1 and fourth individual flow path array 14R4. The second pressure chamber flow path array 20R2 and the third pressure chamber flow path array 20R3 are configured with their respective pressure chamber flow paths 20B aligned in the first direction D1, similar to the above-described second individual flow path array 14R2 and third individual flow path array 14R3.

[0037] The individual flow paths 13A included in the first individual flow path array 14R1 and the individual flow paths 13A included in the fourth individual flow path array 14R4 have the same flow path configuration, including flow path shape and size. More specifically, the individual flow paths 13A included in the first individual flow path array 14R1 and the individual flow paths 13A included in the fourth individual flow path array 14R4 are arranged symmetrically with respect to the midpoint of the line segment connecting the nozzles 15 in a plane perpendicular to the up-down direction D3.

[0038] The individual flow paths 13B included in the second individual flow path array 14R2 and the individual flow paths 13B included in the third individual flow path array 14R3 also have the same flow path configuration, including flow path shape and size. More specifically, the individual flow paths 13B included in the second individual flow path array 14R2 and the individual flow paths 13B included in the third individual flow path array 14R3 are arranged symmetrically with respect to the midpoint of the line segment connecting the nozzles 15 in a plane perpendicular to the up-down direction D3.

[0039] An individual flow path 13B is equivalent to an individual flow path 13A adjacent to the individual flow path 13B in the second direction D2 being arranged symmetrically with respect to a center line along the first direction D1 passing through the center of both the individual flow paths 13B and the second direction D2, and the symmetrically arranged individual flow paths 13A are arranged offset by a predetermined distance in the first direction D1. In other words, the individual flow paths 13A and the individual flow paths 13B are also substantially the same in flow path configuration, including the flow path shape and size. Therefore, a detailed description of the configuration of the individual flow path 13B will be omitted, and the detailed configuration of the individual flow path 13A will be described below.

[0040] 5(a), the individual flow path 13A includes a nozzle 15A, a pressure chamber flow path 20A, a supply flow path 18A, and a circulation flow path 19A. The pressure chamber flow path 20A has a pressure chamber 16A and a communication flow path 17A. The individual flow path 13B also includes a nozzle 15B, a pressure chamber flow path 20B, a supply flow path 18B, and a circulation flow path 19B, and is disposed at the same height level as the individual flow path 13A. The individual flow path 13B has a pressure chamber flow path 20B, a pressure chamber 16B, and a communication flow path 17B.

[0041] The communication flow path 17A extends upward from the nozzle 15A along the vertical direction D3 and is connected to the lower end of the pressure chamber 16A. The communication flow path 17A is formed by interconnecting holes formed in each of the seven plates 122 to 128, and has a diameter larger than that of the nozzle 15A.

[0042] The nozzles 15A are disposed directly below the communicating flow paths 17A. The nozzles 15A overlap the pressure chambers 16A in the up-down direction D3. The nozzles 15A are disposed outside the common flow paths 12 with which they communicate in the second direction D2.

[0043] The supply flow path 18A is formed by connecting holes formed in the two plates 122 and 123. One end of the supply flow path 18A is connected to the upper end of the upper common flow path 12A, and the other end is connected to the lower end of the pressure chamber 16A (the end opposite to the communicating flow path 17A).

[0044] 4 and 5(a), the supply flow path 18A is connected to the upper common flow path 12A via a connection port 18A1 that opens to the upper common flow path 12A. The supply flow path 18A also has a throttle portion 18A2. The throttle portion 18A2 is formed by closing a recessed groove formed in a plate 122 with a plate 123. The cross-sectional area of ​​the throttle portion 18A2 perpendicular to the liquid flow direction (first direction D1) is smaller than the opening area of ​​the connection port 18A1.

[0045] 5(a), the circulation flow path 19A is formed by a groove formed in the plate 128 and a hole at the end of the groove. One end of the circulation flow path 19A is connected to the lower end of the lower common flow path 12B, and the other end is connected to the lower end of the communication flow path 17A (the end on the nozzle 15A side).

[0046] 4 and 5(a), the circulation flow path 19A is connected to the lower common flow path 12B via a connection port 19A1 that opens to the lower common flow path 12B. The circulation flow path 19A has a throttle portion 19A2. The throttle portion 19A2 is formed by closing a recessed groove formed in a plate 128 with a plate 129. The cross-sectional area of ​​the throttle portion 19A2 perpendicular to the liquid flow direction is smaller than the cross-sectional area of ​​the communication flow path 17A perpendicular to the liquid flow direction (vertical direction D3).

[0047] In each individual flow path array 14R, as shown in Figures 3 and 4, the multiple nozzles 15 are arranged at a predetermined pitch P in the first direction D1. All of the nozzles 15 are arranged at different positions in the first direction D1. Of the multiple nozzles 15, two nozzles 15 adjacent to each other in the first direction D1 are arranged at a distance of ¼ of the pitch P in the first direction D1, as shown in Figure 4. As a result, when the printing resolution at the pitch P is 300 dpi, a printing resolution of 1200 dpi is achieved by all of the nozzles 15.

[0048] 2 is driven under the control of the control unit 5, whereby ink in the ink tank is supplied to each common flow path 12 via a supply port 111 and distributed from each common flow path 12 to multiple individual flow paths 13. In other words, both ends of each common flow path 12 in the first direction D1 are connected to different pressure pumps 10, 11. More specifically, the pressure pump 10 is connected to the supply port 111 and is controlled by the control unit 5 so that a first pressure (negative pressure) is applied to the ink in the supply port 111. On the other hand, the pressure pump 11 is connected to a return port 112 and is controlled by the control unit 5 so that a second pressure (negative pressure) smaller than the first pressure is applied to the return port 112. 6, the ink supplied from the supply port 111 moves from the inlet 12A1 through the common flow path 12 in the first direction D1 from one side (the supply port 111 side, upstream) to the other side (the return port 112 side, downstream), and reaches the return port 112 through the outlet 12A2. The ink that reaches the return port 112 is returned to the ink tank via a tube.

[0049] 6, the pressure of ink flowing from the inlet 12A1 into the upper common flow path 12A gradually decreases as the ink moves toward the outlet 12A2 due to the flow path resistance of the upper common flow path 12A. The ink then passes through the upper narrow portion 12E before reaching the outlet 12A2. At this time, the pressure of the ink drops significantly due to the flow path resistance of the upper narrow portion 12E.

[0050] In addition, the ink flowing in from the inlet 12A1 also flows into the lower common flow path 12B through the communication port 12C. The ink flowing into the lower common flow path 12B passes through the lower narrow portion 12F. At this time, the pressure of the ink drops significantly due to the flow path resistance of the lower narrow portion 12F. Thereafter, as the ink moves toward the outlet 12A2, the pressure gradually decreases due to the flow path resistance of the lower common flow path 12B, just like the upper common flow path 12A.

[0051] Between the upper common flow path 12A and the lower common flow path 12B, the ink pressure in the upper common flow path 12A is greater than the ink pressure in the lower common flow path 12B at the same position in the first direction D1. Furthermore, by significantly reducing the ink pressure once in the lower narrow portion 12F, it is possible to prevent a reversal of the pressure magnitude between the connection ports 18A1, 18B1 of the supply flow paths 18 of each individual flow path 13 and the connection ports 19A1, 19B1 of the circulation flow path 19. Similarly to the above, the opening area S2 of the communication port 12D is greater than the opening area S4 of the lower common flow path 12B, which also makes it possible to prevent a reversal of the pressure magnitude between the connection ports 18A1, 18B1 of the supply flow paths 18 of each individual flow path 13 and the connection ports 19A1, 19B1 of the circulation flow path 19.

[0052] Furthermore, when ink flows through the common flow channel 12, for each individual flow channel 13, the ink flows from the upper common flow channel 12A through the supply flow channel 18 into the pressure chamber flow channel 20, then returns from the pressure chamber flow channel 20 through the circulation flow channel 19 to the lower common flow channel 12B, and the ink circulates between the individual flow channels 13 and the common flow channel 12. More specifically, as shown in FIG. 4 , the connection ports 18A1 and 18B1 of the supply flow channel 18 and the connection ports 19A1 and 19B1 of the circulation flow channel 19, both of which are included in the same individual flow channel 13, are spaced apart in the ink liquid flow direction along the first direction D1. Because the connection ports 18A1 and 18B1 are located upstream of the connection ports 19A1 and 19B1 in the ink liquid flow direction of the common flow channel 12, the ink pressure at the connection ports 18A1 and 18B1 is greater than the ink pressure at the connection ports 19A1 and 19B1. Therefore, the ink circulates between the individual flow channels 13 and the common flow channel 12.

[0053] In this embodiment, the separation distance L between the connection ports 18A1, 18B1 and the connection ports 19A1, 19B1 included in each individual flow path 13 in the first direction D1 (liquid flow direction) is the same. In other words, the separation distance L along the first direction D1 between the connection ports 18A1, 18B1 of the supply flow path 18 and the connection ports 19A1, 19B1 of the circulation flow path 19, which communicate with the same pressure chamber flow path 20, is the same for all pressure chamber flow paths 20. This makes it possible to make the flow rate of ink flowing through each pressure chamber flow path 20 the same for all pressure chamber flow paths 20. This makes it possible to suppress variation in the recovery state of the dried state of each nozzle 15. This makes it possible to suppress variation in the ink ejection characteristics among multiple nozzles 15.

[0054] Within the individual flow path 13, the volume of the pressure chamber 16 is reduced by driving the actuator unit 35 described later, and pressure is applied to the ink within the pressure chamber 16, causing it to pass through the communicating flow path 17 and be ejected as ink from the nozzle 15.

[0055] 3, 5, and 6, the actuator member 22 is fixed to the upper surface 21A of the flow path member 21. As shown in FIG. 5, the actuator member 22 includes a metallic vibration plate 31, a piezoelectric layer 32, and a plurality of individual electrodes 33.

[0056] The portions of the actuator member 22 that overlap with the pressure chambers 16 in the up-down direction D3 function as actuator portions 35. The actuator portions 35 are capable of independently deforming in response to the potentials applied to the individual electrodes 33.

[0057] The actuator section 35 is a thin-film piezoelectric element. A thin-film piezoelectric element is a so-called micro electro mechanical system (MEMS). The actuator section 35 is formed by sequentially depositing a thin film that will become the piezoelectric layer 32 and a thin film that will become the individual electrodes 33 on the upper surface of the diaphragm 31.

[0058] The vibration plate 31 is disposed on the upper surface 21A of the flow path member 21 so as to cover the multiple pressure chambers 16. The piezoelectric layer 32 is disposed on the upper surface of the vibration plate 31. The individual electrodes 33 are disposed on the upper surface of the piezoelectric layer 32 so as to overlap the pressure chambers 16 in the up-down direction D3.

[0059] The diaphragm 31 and the individual electrodes 33 are electrically connected to a driver IC 6. The driver IC 6 maintains the potential of the diaphragm 31 at ground potential, while changing the potential of the individual electrodes 33. The diaphragm 31 functions as a common electrode that is a common electrode for the multiple actuator elements 35.

[0060] The driver IC 6 generates a drive pulse signal based on a control signal from the control unit 5 and supplies the drive pulse signal to the individual electrode 33. The drive pulse signal changes the potential of the individual electrode 33 between a predetermined drive potential and ground potential. In this way, the actuator unit 35 is driven, and pressure is applied to the ink in the pressure chamber 16, causing ink to pass through the communication flow path 17 and be ejected from the nozzle 15.

[0061] As described above, with the head 1 of this embodiment, it is possible to supply ink from the upper common flow path 12A to each pressure chamber flow path 20 and return the ink from each pressure chamber flow path 20 to the lower common flow path 12B. That is, it is possible to circulate ink between the multiple pressure chamber flow paths 20 and the common flow path 12. Furthermore, the first damper 28A and the second damper 28B are disposed between the upper common flow path 12A and the lower common flow path 12B, and the supply flow path 18 is disposed above the upper common flow path 12A and the circulation flow path 19 is disposed below the lower common flow path 12B. Therefore, it is not necessary to dispose the first damper 28A and the second damper 28B to avoid the supply flow path 18 and the circulation flow path 19, and the movable range of these dampers 28A, 28B is not limited, making it possible to suppress a decrease in the absorption of pressure fluctuations by these dampers 28A, 28B.

[0062] Furthermore, both ends of each common flow path 12 in the first direction D1 communicate with different pressure pumps 10, 11. This allows the pressure pumps 10, 11 to apply different pressures, and the pressure difference between the both ends of the common flow path 12 in the first direction D1 allows ink to flow from one side of the common flow path 12 to the other side in the first direction D1.

[0063] In addition, the communication port 12C is positioned so as to overlap with the inlet 12A1 in the up-down direction D3, thereby reducing the pressure loss from the inlet 12A1 to one end (left side in FIG. 6) of the lower common flow path 12B and reducing the ink pressure difference on the ink inflow side between the upper common flow path 12A and the lower common flow path 12B.

[0064] In addition, the communication port 12D is positioned so as to overlap with the outlet 12A2 in the up-down direction D3, thereby reducing the pressure loss from the other end (right in FIG. 6) of the lower common flow path 12B to the outlet 12A2 and making it possible to reduce the pressure difference of the ink on the ink outflow side between the upper common flow path 12A and the lower common flow path 12B.

[0065] Furthermore, the opening area S1 of the communication port 12C is larger than the opening area S3 of the upper common flow path 12A and the opening area S4 of the lower common flow path 12B. This makes the flow path resistance of the communication port 12C smaller than the flow path resistance of the upper common flow path 12A and the lower common flow path 12B, thereby reducing the effect of pressure loss at the communication port 12C. If the flow path resistance of the communication port 12C were higher than the flow path resistance of the upper common flow path 12A and the lower common flow path 12B, the ink pressure difference between the upper common flow path 12A and the lower common flow path 12B would likely increase. However, in this embodiment, it is possible to further reduce the ink pressure difference between the upper common flow path 12A and the lower common flow path 12B.

[0066] Furthermore, the opening area S2 of the communication port 12D is larger than the opening area S3 of the upper common flow path 12A and the opening area S4 of the lower common flow path 12B. This makes the flow path resistance at the communication port 12D smaller than the flow path resistances at the upper common flow path 12A and the lower common flow path 12B, thereby reducing the effect of pressure loss at the communication port 12D. If the flow path resistance at the communication port 12D were higher than the flow path resistances at the upper common flow path 12A and the lower common flow path 12B, the ink pressure difference between the upper common flow path 12A and the lower common flow path 12B would likely increase. However, in this embodiment, it is possible to further reduce the ink pressure difference between the upper common flow path 12A and the lower common flow path 12B.

[0067] Furthermore, the opening area S3 of the upper common flow path 12A and the opening area S4 of the lower common flow path 12B are the same. This makes it possible to suppress the difference in ink flow rate between the upper common flow path 12A and the lower common flow path 12B. This makes it possible to suppress a decrease in the circulation flow rate due to a difference in flow rate between the supply side and the return side.

[0068] Furthermore, an upper narrow portion 12E is provided in the upper common flow path 12A, and a lower narrow portion 12F is also provided in the lower common flow path 12B. This makes it possible to prevent backflow in each pressure chamber flow path 20, which would occur if the pressure at the connection ports 18A1 and 18B1 of the supply flow path 18 and the pressure at the connection ports 19A1 and 19B1 of the circulation flow path 19 were reversed. Furthermore, when ink flows into the upper common flow path 12A from the inlet 12A1, a pressure wave is generated in the upper common flow path 12A. This pressure wave propagates from the inlet side to the upper narrow portion 12E, passes through the upper narrow portion 12E, and propagates to another portion of the upper common flow path 12A that is closer to the outlet 12A2 than the upper narrow portion 12E, where it is attenuated. In other words, because the upper narrow portion 12E is a narrow flow path, the pressure wave propagated to the other portion is less likely to cross the upper narrow portion 12E again and propagate to the inlet 12A1 side of the upper common flow path 12A. As a result, it is possible to attenuate pressure fluctuations caused by pressure waves generated in the upper common flow path 12A. Similarly, when ink flows into the lower common flow path 12B from the communicating port 12C, a pressure wave is generated in the lower common flow path 12B. In this case, because the pressure wave is less likely to propagate from the communicating port 12C side across the lower narrow portion 12F, it is attenuated in one portion of the lower common flow path 12B closer to the communicating port 12C than the lower narrow portion 12F. As a result, it is possible to attenuate pressure fluctuations caused by pressure waves generated in the lower common flow path 12B. By attenuating pressure fluctuations in the upper common flow path 12A and the lower common flow path 12B in this way, it is possible to suppress crosstalk between the multiple pressure chamber flow paths 20.

[0069] The pressure chamber flow path 20 includes a pressure chamber 16 and a communicating flow path 17 extending in the vertical direction D3, and a circulation flow path 19 communicates with the communicating flow path 17 and the lower common flow path 12B. By providing the communicating flow path 17 extending in the vertical direction D3, the length of the common flow path 12 in the vertical direction D3 can be increased. This makes it possible to increase the flow rate of ink in the common flow path 12. Increasing the ink flow rate makes it easier to attenuate pressure waves propagating from each pressure chamber 16. As a result, it is possible to suppress crosstalk between multiple pressure chambers 16.

[0070] Second Embodiment Next, a head 1 according to a second embodiment of the present invention will be described with reference to FIGS. 7 and 8. The head 1 according to this embodiment has two common flow paths 12. One (left in FIG. 7) of the two common flow paths 12 does not have a return port 112 connected to the other end in the first direction D1, and the other (right in FIG. 7) of the two common flow paths 12 does not have a supply port 111 connected to the other end in the first direction D1. The head 1 has a connecting flow path 90 connecting the other ends of the two common flow paths 12. Components similar to those in the first embodiment are denoted by the same reference numerals, and descriptions thereof will be omitted. The common flow path 12 according to this embodiment corresponds to a "common flow path set including an upper common flow path and a lower common flow path" of the present invention, and the two common flow paths 12 correspond to a "common flow path" of the present invention. Furthermore, one common flow path 12 corresponds to a "one common flow path set" of the present invention, and the other common flow path 12 corresponds to a "other common flow path set" of the present invention. The other end of the common flow path 12 in the first direction D1 corresponds to the "other end of the common flow path set in the first direction" of the present invention.

[0071] As shown in Fig. 7, the connection flow path 90 extends in the second direction D2 at the other end of the flow path member 21 in the first direction D1. Also, as shown in Fig. 8, the connection flow path 90 is formed by interconnecting holes formed in the four plates 124 to 127. The connection flow path 90 interconnects the upper common flow path 12A and the lower common flow path 12B included in one common flow path 12 with the upper common flow path 12A and the lower common flow path 12B included in the other common flow path 12.

[0072] In this embodiment as well, the two pumps 10 and 11 are driven under the control of the control unit 5, whereby ink is supplied to the upper common flow path 12A and the lower common flow path 12B included in one common flow path 12 via the supply port 111. Then, ink flows from one common flow path 12 via the connection flow path 90 to the upper common flow path 12A and the lower common flow path 12B included in the other common flow path 12. Then, the ink that reaches the return port 112 from the other common flow path 12 is returned to the ink tank via a tube.

[0073] Ink flows through each common flow path 12 in this embodiment in the same manner as in the first embodiment, so that the same effects can be obtained in a configuration similar to that of the first embodiment described above.

[0074] Because one common flow path 12 and the other common flow path 12 are connected by the connection flow path 90, ink supplied from the supply port 111 flows to the other end of one common flow path 12 and then flows to one end of the other common flow path 12 via the connection flow path 90. In this embodiment, ink heated to a predetermined temperature by a heater may be supplied from an ink tank to the head 1. When heated ink is supplied to the common flow path 12, the cooled ink that flows through the common flow path 12 and is discharged from one end of the other common flow path 12. Because the ink that cools as it flows through the common flow path 12 is discharged from the end where the heated ink is supplied, the temperature difference between the ends of the head 1 in the first direction D1 is smaller than in a configuration in which ink is discharged from the other end. Therefore, the temperature difference between the ink flowing through the pressure chamber flow paths 20 at one end and the other end in the first direction D1 is also smaller. This makes it possible to suppress variations in ink ejection characteristics among the multiple nozzles 15.

[0075] The connection flow path 90 in this embodiment connects the upper common flow path 12A and the lower common flow path 12B included in one common flow path 12 to the upper common flow path 12A and the lower common flow path 12B included in the other common flow path 12. As a result, the connection flow path 90 almost eliminates the pressure difference between the other ends in the first direction D1 of the upper common flow path 12A and the lower common flow path 12B of one common flow path 12. This makes it possible to reduce the ink pressure difference between the other ends in the first direction D1 of the upper common flow path 12A and the lower common flow path 12B of the other common flow path 12. This makes it possible to reduce the difference between the ink pressure difference between the upper common flow path 12A and the lower common flow path 12B of one common flow path 12 and the ink pressure difference between the upper common flow path 12A and the lower common flow path 12B of the other common flow path 12.

[0076] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims.

[0077] In each of the above-described embodiments, the first damper 28A is provided in the upper common flow path 12A and the second damper 28B is provided in the lower common flow path 12B, but a damper may be provided between the upper common flow path 12A and the lower common flow path 12B only in either the upper common flow path 12A or the lower common flow path 12B.

[0078] In addition, both ends of the common flow path 12 in the first direction D1 in the first embodiment may be connected to the same pressure pump. Also, the inlet 12A1 and the communication port 12C may not overlap in the vertical direction D3. Also, the outlet 12A2 and the communication port 12D may not overlap in the vertical direction D3.

[0079] Furthermore, the opening area S1 of the communication port 12C and the opening area S2 of the communication port 12D may be equal to or smaller than the opening area S3 of the upper common flow path 12A and the opening area S4 of the lower common flow path 12B. The opening area S3 of the upper common flow path 12A and the opening area S4 of the lower common flow path 12B may be different. Furthermore, the common flow path 12 may not be provided with at least one of the upper narrow section 12E and the lower narrow section 12F.

[0080] The connection flow path 90 in the second embodiment described above may individually connect at least one of the upper common flow paths 12A of the two common flow paths 12 and the lower common flow paths 12B of the two common flow paths 12.

[0081] Furthermore, the separation distance L of the individual flow paths 13A may be different from the separation distance L of the individual flow paths 13B. Furthermore, the separation distances L of the individual flow paths 13 may be different from each other.

[0082] Furthermore, the pressure chamber flow path 20 may be formed from the pressure chamber 16. In other words, the pressure chamber 16 may be directly connected to the nozzle 15. In this case, it is desirable that the circulation flow path 19 communicates with the connection point between the pressure chamber 16 and the nozzle 15.

[0083] In each of the above-described embodiments, the electrodes constituting the actuator section 35 have a two-layer structure including an individual electrode and a common electrode, but may have a three-layer structure. For example, a three-layer structure is a structure including a drive electrode to which a high potential or a low potential is selectively applied, a high-potential electrode that is held at a high potential, and a low-potential electrode that is held at a low potential.

[0084] The type of liquid ejection head of the present invention is not limited to the line type, but may also be a serial type.

[0085] The object onto which the liquid is ejected is not limited to paper, but may be, for example, a cloth, a substrate, or plastic.

[0086] The liquid ejected from the nozzles is not limited to ink, but may be, for example, a treatment liquid that aggregates or precipitates components in the liquid or ink.

[0087] The present invention is not limited to printers, but can also be applied to facsimiles, copiers, and multifunction peripherals. The present invention can also be applied to liquid ejection heads used for purposes other than image recording. For example, the present invention can be applied to liquid ejection heads that eject conductive liquid onto a substrate to form a conductive pattern. [Explanation of symbols]

[0088] 1 head (liquid ejection head) 10,11 Pressure pump 12 Common flow path 12A Upper common flow path 12A1 Inlet 12A2 Outlet 12B Lower common flow path 12C communication port 12D communication port 12E Upper narrow part 12F Lower narrow area 13 Individual flow path 15 nozzles 16 Pressure Chamber 17 Connecting flow path 18 Supply channel 18A1, 18B1 connection port 19 Circulation flow path 19A1, 19B1 connection port 20 Pressure chamber flow path 28A First Damper 28B Second damper 90 connecting flow channel D1 1st direction D2 2nd direction D3 Up and down direction L distance S1~S4 opening area S3A,S4A opening area

Claims

1. a plurality of nozzles arranged in a first direction perpendicular to the up-down direction; a plurality of pressure chamber flow paths arranged in the first direction and communicating with the plurality of nozzles, respectively; a common flow path communicating with the plurality of pressure chamber flow paths, the common flow path includes an upper common flow path and a lower common flow path that are arranged to overlap in the vertical direction, the upper common flow path and the lower common flow path each extending in the first direction and communicating with each other at both ends in the first direction, a damper that absorbs pressure fluctuations of liquid in at least one of the upper common flow path and the lower common flow path is disposed between the upper common flow path and the lower common flow path in the vertical direction; A liquid ejection head characterized in that, between the common flow path and the plurality of pressure chamber flow paths, there are arranged, for each pressure chamber flow path, a supply flow path that is located above the upper common flow path and supplies liquid from the upper common flow path to the pressure chamber flow path, and a circulation flow path that is located below the lower common flow path and returns liquid from the pressure chamber flow path to the lower common flow path.

2. 2. The liquid ejection head according to claim 1, wherein both ends of the common flow path in the first direction communicate with different pressure pumps.

3. the upper common flow path has a liquid supply port disposed at one end in the first direction, 2. The liquid ejection head according to claim 1, wherein one of the communication ports, by which the upper common flow path and the lower common flow path communicate with each other at one end in the first direction, overlaps with the liquid supply port in the vertical direction.

4. the upper common flow path has a liquid outlet disposed at the other end in the first direction, 2. A liquid ejection head according to claim 1, wherein the other communication port through which the upper common flow path and the lower common flow path communicate with each other at the other end in the first direction overlaps with the liquid discharge port in the vertical direction.

5. The liquid ejection head according to claim 3, wherein the opening area of ​​one of the communication ports is larger than the opening area of ​​the upper common flow path in a direction perpendicular to the first direction and the opening area of ​​the lower common flow path in the direction perpendicular to the first direction.

6. A liquid ejection head according to claim 4, characterized in that the opening area of ​​the other communication port is larger than the opening area of ​​the upper common flow path in a direction perpendicular to the first direction and the opening area of ​​the lower common flow path in the direction perpendicular to the first direction.

7. 2. The liquid ejection head according to claim 1, wherein an opening area of ​​the upper common flow path in a direction perpendicular to the first direction and an opening area of ​​the lower common flow path in the direction perpendicular to the first direction are the same.

8. the plurality of supply flow paths and the plurality of circulation flow paths are aligned in the first direction, an upper narrow portion having a smallest opening area in a direction perpendicular to the first direction is provided in the upper common flow path on the other side of the first direction than a connection point with a supply flow path among the plurality of supply flow paths that is arranged furthest in the other side of the first direction, A liquid ejection head as described in claim 4, characterized in that in the lower common flow path, a lower narrow section having the smallest opening area in a direction perpendicular to the first direction is provided on one side of the first direction than the connection point with the circulation flow path that is positioned furthest toward the one side of the first direction among the multiple circulation flow paths.

9. the common flow path includes two common flow path sets each including the upper common flow path and the lower common flow path, and the two common flow path sets are aligned in a second direction perpendicular to both the first direction and the up-down direction, a liquid is supplied to one end in the first direction of one of the two common flow path sets, and a liquid is discharged from one end in the first direction of the other common flow path set; The liquid ejection head according to claim 1, characterized in that the common flow path has a connecting flow path that connects the other end of one common flow path set in the first direction to the other end of the other common flow path set in the first direction.

10. The liquid ejection head according to claim 9, wherein the connection flow path connects the upper common flow path and the lower common flow path included in one of the common flow paths with the upper common flow path and the lower common flow path included in the other common flow path.

11. 2. A liquid ejection head according to claim 1, wherein the distance between the connection port of the supply flow channel and the connection port of the circulation flow channel, which open into the common flow channel and lead to the same pressure chamber flow channel, along the liquid flow direction of the common flow channel, is equal for all of the pressure chamber flow channels.

12. the pressure chamber flow path includes a pressure chamber that communicates with the supply flow path, and a communication flow path that extends in the vertical direction and has one end that communicates with the nozzle and the other end that communicates with the pressure chamber, 2. The liquid ejection head according to claim 1, wherein the circulation flow path communicates with the communication flow path and the lower common flow path.

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