Liquid ejection head

Abstract

To suppress variation in a recovery state among a plurality of nozzles.SOLUTION: The head 1 includes a plurality of nozzles 15, a plurality of pressure chamber channels 20, and two common channels 12. Between the common channel 12 and the plurality of pressure chamber channels 20, the supply channel 18 and the circulation channel 19 are arranged for each of the pressure chamber channels 20. The first distances L1A, L1B between the connection ports 18A1, 18B1 and the connection ports 19A1, 19B1 communicating with the same pressure chamber flow path 20, the first distances L1A, L1B along the liquid flow direction of the common flow path 12 are different from each other in the first pressure chamber flow path 20A and the second pressure chamber flow path among the plurality of pressure chamber flow paths 20. 20B.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection head having a plurality of nozzles for ejecting liquid. [Background technology]

[0002] Patent Document 1 describes a liquid ejection head including multiple pressure chambers (pressure chamber flow paths) each connected to a multiple nozzles, and a common flow path provided in common to the multiple pressure chambers. Between the common flow path and the multiple pressure chambers of this liquid ejection head, an ink supply flow path is arranged for each pressure chamber, supplying ink from the common flow path to the pressure chamber, and an ink circulation flow path is arranged for each pressure chamber, returning ink from the pressure chamber to the common flow path. The distance between the ink supply port (supply flow path connection port) and the ink circulation port (circulation flow path connection port), which open into the common flow path and connect to the same pressure chamber, along the liquid flow direction of the common flow path, is the same for all pressure chambers. This allows the flow rate of liquid flowing through each pressure chamber to be the same for all pressure chambers. [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] The dry state of the ink inside the nozzles differs depending on the position of the nozzle. In the liquid ejection head described in Patent Document 1, the flow rate of the liquid flowing through each pressure chamber is made equal for all pressure chambers, so even if the ink is circulated to restore the dry state of each nozzle, variations in the restored state occur among the multiple nozzles, resulting in variations in the ink ejection characteristics.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a liquid ejection head that is capable of suppressing variations in the recovery state among a plurality of nozzles. [Means for solving the problem]

[0006] The liquid ejection head of the present invention comprises a plurality of nozzles, a plurality of pressure chamber flow paths respectively communicating with the plurality of nozzles, and a common flow path communicating with the plurality of pressure chamber flow paths, 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 that supplies liquid from the common flow path to the pressure chamber flow path and a circulation flow path that returns liquid from the pressure chamber flow path to the common flow path, and the first distance between the connection port of the supply flow path and the connection port of the circulation flow path, which open into the common flow path and lead to the same pressure chamber flow path, is the first distance along the liquid flow direction of the common flow path, and is different between a first pressure chamber flow path and a second pressure chamber flow path among the plurality of pressure chamber flow paths. [Effects of the Invention]

[0007] According to the liquid ejection head of the present invention, the circulation flow rate of the liquid differs between the first pressure chamber flow path and the second pressure chamber flow path. This makes it possible to set the circulation flow rate for each pressure chamber flow path to a circulation flow rate appropriate for restoring the dried state of the liquid in the nozzles communicating with that pressure chamber flow path. As a result, it is possible to suppress variations in the restored state among multiple nozzles. [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]3A is a cross-sectional view of the head taken along line VA-VA in FIG. 3, with the circulation flow path included in individual flow path 13A added, and FIG. 3B is a cross-sectional view of the head taken along line VB-VB in FIG. 3, with the circulation flow path included in individual flow path 13B added. [Figure 6] FIG. 10 is a cross-sectional view of a main part of a head according to a third embodiment of the present invention, with a circulation flow path included in an individual flow path 13A added. [Figure 7] FIG. 10 is a plan view of a main part of a flow path member of a head according to a fourth embodiment of the present invention. 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 along 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. The first direction D1 corresponds to the "liquid flow direction of the common flow path" of the present invention, and the second direction D2 corresponds to the "orthogonal direction" of the present invention.

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

[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 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 each extend in the first direction D1. One of the two common flow paths 12 has a supply port 111 connected to one end in the first direction D1 and a return port 112 connected to the other end, while the other common flow path 12 has a return port 112 connected to one end in 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] The two damper chambers 28 are disposed below the two common flow paths 12. The two damper chambers 28 are also aligned in the second direction D2 and extend in the first direction D1.

[0021] 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.

[0022] The supply flow path 18 has one end communicating with the common flow path 12 and the other end communicating with the pressure chamber 16. The circulation flow path 19 has one end communicating with the communication flow path 17 and the other end communicating with the common flow path 12.

[0023] 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.

[0024] 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.

[0025] Each common flow channel 12 is formed by connecting holes formed in each of the four plates 124 to 127. Each common flow channel 12 overlaps with all of the pressure chambers 16 communicating with that common flow channel 12 in the up-down direction D3.

[0026] Each damper chamber 28 is formed by a recess formed in a plate 128 being blocked by a plate 129. The bottom of the damper chamber 28 of the plate 128, which is sandwiched between the damper chamber 28 and the common flow path 12, functions as a damper 28A that absorbs pressure fluctuations of the ink in the common flow path 12. In other words, even if pressure generated in a pressure chamber 16 when ink is ejected from a nozzle 15 is transmitted to the common flow path 12, the damper 28A attenuates the pressure by elastically deforming, and can prevent the phenomenon of the pressure being transmitted to other pressure chambers 16 (so-called crosstalk).

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] The detailed configurations of the individual flow paths 13A and 13B will be described below.

[0034] 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 pressure chamber flow path 20A corresponds to the "first pressure chamber flow path" of the present invention.

[0035] 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.

[0036] 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.

[0037] 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 common flow path 12, and the other end is connected to the lower end of the pressure chamber 16A (the end opposite to the communicating flow path 17A).

[0038] 4 and 5(a), the supply flow path 18A is connected via a connection port 18A1 that opens to the common flow path 12. As shown in Fig. 4, the connection port 18A1 opens to a portion 12W2 (a portion farther from the pressure chamber 16A) that is outside a central portion 12W1 of the common flow path 12 that is obtained by dividing the common flow path 12 into three equal parts in the second direction D2.

[0039] Supply flow path 18A also has throttle portion 18A2. Throttle portion 18A2 is formed by closing a recessed groove formed in plate 122 with plate 123. The cross-sectional area of ​​throttle portion 18A2 perpendicular to the liquid flow direction is smaller than the opening area of ​​connection port 18A1.

[0040] 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 common flow path 12, and the other end is connected to the lower end of the communication flow path 17A (the end on the nozzle 15A side).

[0041] 4 and 5(a), the circulation flow path 19A is connected via a connection port 19A1 that opens to the common flow path 12. As shown in FIG. 4, the connection port 19A1 opens to a portion 12W3 (a portion closer to the pressure chamber 16A) that is outside a central portion 12W1 of the common flow path 12 that is divided into three equal parts in the second direction D2.

[0042] Circulation flow path 19A has a throttle portion 19A2. Throttle portion 19A2 is formed by closing a recessed groove formed in plate 128 with plate 123. The cross-sectional area of ​​throttle portion 19A2 perpendicular to the liquid flow direction is smaller than the cross-sectional area of ​​communication flow path 17A perpendicular to the liquid flow direction.

[0043] 5(b), the individual flow path 13B includes a nozzle 15B, a pressure chamber flow path 20B, a supply flow path 18B, and a circulation flow path 19B. The pressure chamber flow path 20B has a pressure chamber 16B and a communication flow path 17B. The pressure chamber flow path 20B corresponds to the "second pressure chamber flow path" of the present invention.

[0044] The communication flow path 17B extends upward from the nozzle 15B in the vertical direction D3 and is connected to the lower end of the pressure chamber 16B. The communication flow path 17B 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 15B.

[0045] Further, nozzle 15B is disposed directly below communicating flow path 17B. Further, nozzle 15B overlaps with pressure chamber 16B in the up-down direction D3. Further, the plurality of nozzles 15B are disposed outward of the common flow path 12 with which they communicate in the second direction D2. More specifically, as shown in FIG. 4, nozzle 15A and nozzle 15B are disposed on opposite sides in the second direction D2, sandwiching the common flow path 12 with which they communicate.

[0046] 5(b), the supply flow path 18B is formed by connecting holes formed in the two plates 122 and 123. One end of the supply flow path 18B is connected to the upper end of the common flow path 12, and the other end is connected to the lower end of the pressure chamber 16B (the end opposite to the communicating flow path 17B).

[0047] 4 and 5(b), the supply flow path 18B is connected via a connection port 18B1 that opens to the common flow path 12. As shown in FIG. 4, the connection port 18B1 opens to a portion 12W3 (a portion farther from the pressure chamber 16B) that is outside a central portion 12W1 of the common flow path 12 that is obtained by dividing the common flow path 12 into three equal parts in the second direction D2.

[0048] Supply flow path 18B also has throttle portion 18B2. Throttle portion 18B2 is formed by closing a recessed groove formed in plate 122 with plate 123. The cross-sectional area of ​​throttle portion 18B2 perpendicular to the liquid flow direction is smaller than the opening area of ​​connection port 18B1.

[0049] 5(b), the circulation flow path 19B 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 19B is connected to the lower end of the common flow path 12, and the other end is connected to the lower end of the communication flow path 17B (the end on the nozzle 15B side).

[0050] 4 and 5(b), the circulation flow path 19B is connected via a connection port 19B1 that opens to the common flow path 12. As shown in FIG. 4, the connection port 19B1 opens to a portion 12W2 (a portion closer to the pressure chamber 16B) that is outside a central portion 12W1 of the common flow path 12, which is obtained by dividing the common flow path 12 into thirds in the second direction D2. Because the connection ports 19A1 and 19B1 of the circulation flow paths 19A and 19B open to portions outside the common flow path 12, the damper 28A can be disposed in the central portion of the bottom surface 12A of the common flow path 12. This makes it possible to maintain the effect of absorbing pressure fluctuations within the common flow path 12.

[0051] Circulation flow path 19B also has a throttle portion 19B2. The throttle portion 19B2 is formed by closing a recessed groove formed in plate 128 with plate 123. The cross-sectional area of ​​throttle portion 19B2 perpendicular to the liquid flow direction is smaller than the cross-sectional area of ​​communicating flow path 17B perpendicular to the liquid flow direction.

[0052] 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.

[0053] 2 are driven under the control of the control unit 5, whereby ink in the ink tank is supplied to the common flow path 12 via the supply port 111 and distributed from the common flow path 12 to the multiple individual flow paths 13. More specifically, the 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 pump 11 is connected to the 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. Due to this pressure difference, the ink supplied from the supply port 111 moves from one end to the other end in the first direction D1 within the common flow path 12 and reaches the return port 112. The ink that reaches the return port 112 is returned to the ink tank via a tube.

[0054] Furthermore, when ink flows through the common flow channel 12, for each individual flow channel 13, the ink flows from the common flow channel 12 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 common flow channel 12, and the ink circulates between the individual flow channels 13 and the common flow channel 12. More specifically, as shown in FIG. 4 , connection ports 18A1 and 18B1 of the supply flow channel 18 and 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.

[0055] In this embodiment, in the first direction D1 (liquid flow direction), a first distance L1A, which is the distance between connection port 18A1 and connection port 19A1 included in individual flow path 13A, is greater than a first distance L1B, which is the distance between connection port 18B1 and connection port 19B1 included in individual flow path 13B. Furthermore, the first distances L1A and L1B are greater than a second distance L2, which is the distance between two connection ports 18A1 and 18B1 included in two individual flow paths 13A and 13B adjacent to each other in the first direction D1.

[0056] 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 droplets from the nozzle 15.

[0057] 3 and 5, 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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 droplets to be ejected from the nozzle 15 through the communicating flow path 17.

[0063] As described above, in the head 1 of this embodiment, the first distance L1A is greater than the first distance L1B, and therefore the pressure difference between the connection ports 18A1 and 19A1 of the individual flow path 13A is greater than the pressure difference between the connection ports 18B1 and 19B1 of the individual flow path 13B. Therefore, the ink circulation flow rates differ between the pressure chamber flow paths 20A and 20B. That is, the ink circulation flow rate in the pressure chamber flow path 20A is greater than the ink circulation flow rate in the pressure chamber flow path 20B. This makes it possible to set the ink circulation flow rate for each pressure chamber flow path 20 to a circulation flow rate suitable for restoring the dried state of ink in the nozzles 15 connected to that pressure chamber flow path 20. As a result, variation in the restored state among the plurality of nozzles 15 can be suppressed.

[0064] Note that, in order to restore the ink drying state in all nozzles 15 in the same manner, it is also possible to set the first distance L1B between connection port 18B1 and connection port 19B1 to the same length as the first distance L1A. However, this would result in the circulating flow rate of ink in individual flow path 13B exceeding the flow rate required to restore nozzle 15B and becoming unnecessarily large. This would increase the temperature difference between the upstream and downstream of the ink flowing in common flow path 12, making it more likely that variations in ink ejection characteristics would occur among the multiple nozzles 15 aligned in the first direction D1.

[0065] Furthermore, the first distances L1A, L1B are greater than the second distance L2. By increasing the first distances L1A, L1B in this manner, the circulating flow rate of ink in each of the individual flow paths 13A, 13B also increases. This makes it possible to optimize the circulating flow rate for each pressure chamber flow path 20 while arranging the nozzles 15 and pressure chamber flow paths 20 at high density.

[0066] The first pressure chamber channel array 20R1 and the fourth pressure chamber channel array 20R4 are configured such that the pressure chamber channels 20A included in the individual channels 13A are aligned in the first direction D1. The second pressure chamber channel array 20R2 and the third pressure chamber channel array 20R3 are configured such that the pressure chamber channels 20B included in the individual channels 13B are aligned in the first direction D1. This makes it possible to vary the circulating flow rate of ink for each pressure chamber channel array 20R.

[0067] 3, the first pressure chamber channel array 20R1 is disposed upstream in the transport direction relative to the second pressure chamber channel array 20R2. The pressure chamber channels 20A constituting the first pressure chamber channel array 20R1 have a higher ink circulation flow rate than the pressure chamber channels 20B constituting the second pressure chamber channel array 20R2. When the head unit 1X is a line type, the nozzles located more upstream in the transport direction tend to dry out more easily due to the airflow generated when the paper 9 is transported. However, by increasing the ink circulation flow rate in the pressure chamber channels 20A constituting the first pressure chamber channel array 20R1 located upstream in the transport direction, it is possible to suppress variations in the recovery state between the nozzles 15A located upstream in the transport direction and the nozzles 15B located downstream in the transport direction.

[0068] Furthermore, the nozzles 15 arranged at the outermost positions in the transport direction of the head 1 (the direction parallel to the nozzle surface 129A) tend to dry out more easily. In this embodiment, of the four nozzles, the first pressure chamber channel array 20R1 to the fourth pressure chamber channel array 20R4, the first pressure chamber channel array 20R1 is arranged at the most upstream position in the transport direction, and the fourth pressure chamber channel array 20R4 is arranged at the most downstream position. The fourth pressure chamber channel array 20R4 is also composed of a plurality of pressure chamber channels 20A that have a higher ink circulation flow rate than the pressure chamber channels 20B that constitute the second pressure chamber channel array 20R2 and the third pressure chamber channel array 20R3. This makes it possible to suppress variations in the recovery state between the outermost nozzles 15A and the nozzles 15B that are located more inward than the nozzles 15A in the transport direction.

[0069] A heater may also be provided inside the printer 100 to warm the ink to be supplied to the head 1. In this case, the nozzles 15 located on the outermost side in the transport direction of the head 1 tend to dry out due to the air inside the printer 100 that has been heated by the heat of the heater, but these nozzles have a high ink circulation flow rate. This makes it possible to suppress variations in the recovery state between the nozzle 15A, which is on the outermost side in the transport direction, and the nozzle 15B, which is located inside the nozzle 15A.

[0070] 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 common flow path 12. By providing the communicating flow path 17 extending in the vertical direction D3, the length of the flow path member 21 in the vertical direction D3 is increased. Therefore, the length of the common flow path 12 in the vertical direction D3 can also be increased, and the flow rate of ink in the common flow path 12 can be increased. By increasing the flow rate of ink, it becomes easier to attenuate pressure waves propagating from each pressure chamber 16. As a result, crosstalk between multiple pressure chambers 16 can be suppressed.

[0071] Second Embodiment While the head 1 in the first embodiment is of a line type, the head 1 in the second embodiment may be of a serial type. That is, the printer 100 may be provided with a carriage that carries the head 1 and moves in a scanning direction perpendicular to the transport direction, and the carriage may be moved back and forth in the scanning direction above the platen 3 while ejecting ink from multiple nozzles 15 toward the paper 9 to print an image on the paper 9. In this case, the head 1 is mounted on the carriage so that its longitudinal direction (first direction D1) is parallel to the transport direction. The scanning direction is parallel to the second direction D2 and corresponds to the "relative movement direction" of the present invention.

[0072] In the head 1 of the second embodiment, the head 1 moves back and forth in the scanning direction by a carriage during printing, so the nozzles 15 located closer to the outside in the scanning direction tend to dry out. In this embodiment, of the four pressure chamber channel arrays (first to fourth pressure chamber channel arrays) 20R1 to 20R4, the first pressure chamber channel array 20R1 and the fourth pressure chamber channel array 20R4 are arranged on the outermost sides in the scanning direction (second direction). That is, the second pressure chamber channel array 20R2 and the third pressure chamber channel array 20R3 are located between the first pressure chamber channel array 20R1 and the fourth pressure chamber channel array 20R4. The first pressure chamber channel array 20R1 and the fourth pressure chamber channel array 20R4 are each composed of a plurality of pressure chamber channels 20A. This reduces variations in the recovery state between the outermost nozzle 15A and the nozzle 15B located more inward than the nozzle 15A in the scanning direction. The third pressure chamber channel array 20R3 in this embodiment corresponds to the "other pressure chamber channel array" of the present invention.

[0073] Third Embodiment Next, a head 1 according to a third embodiment of the present invention will be described with reference to FIG. 6. The head 1 according to this embodiment is similar to the first and second embodiments except that the connection ports 19A1 and 19B1 of the circulation flow path 19 open to the side surface 12B (the side surface on the communicating flow path 17 side) connected to the bottom surface 12A of the common flow path 12, and the lengths of the damper chamber 28 and the damper 28A in the second direction D2 are increased. Note that components similar to those in the first and second embodiments are denoted by the same reference numerals and will not be described again. Furthermore, while FIG. 6 shows only the connection port 19A1 of the connection ports 19A1 and 19B1 of the circulation flow path 19, the connection port 19B1 of the circulation flow path 19B is also formed on the side surface 12B of the common flow path 12.

[0074] Because the connection ports 19A1 and 19B1 of the circulation flow path 19 open to the side surface 12B of the common flow path 12, the damper 28A can be provided over a wide range of the bottom surface 12A of the common flow path 12. In other words, the length in the second direction D2 of the recessed groove that forms the damper chamber 28 is made close to the length in the second direction D2 of the common flow path 12. This makes it possible to arrange the damper 28A over a wide range of the bottom surface 12A, thereby improving the absorption effect of pressure fluctuations. Note that only one of the connection ports 19A1 and 19B1 of the circulation flow path 19 may open to the side surface 12B of the common flow path 12. In this case, the same effect as described above can be obtained.

[0075] <Fourth embodiment> Next, a head 1 according to a fourth embodiment of the present invention will be described with reference to Fig. 7. The flow path member 21 of the head 1 in this embodiment is the same as the first and second embodiments described above, except that the connection port 18A1 of the supply flow path 18A opens on one side closer to the pressure chamber flow path 20A than the center of the common flow path 12 in the second direction D2 (i.e., the center line C of the common flow path 12 in the second direction D2). Note that components similar to those in the first and second embodiments are denoted by the same reference numerals, and descriptions thereof will be omitted.

[0076] In this embodiment, the connection port 18A1 of the supply flow path 18A and the connection port 19A1 of the circulation flow path 19A open to one side of the common flow path 12. As a result, even if the lengths of the supply flow path and the circulation flow path are the same as in the first embodiment, the first distance L1A can be made longer than in the first embodiment, and the pressure difference between the connection port 18A1 and the connection port 19A1 can be made relatively large. This makes it possible to increase the circulation flow rate of ink in the individual flow paths 13A. Note that the individual flow paths 13B may also have a similar configuration. This makes it possible to increase the circulation flow rate of ink in each individual flow path 13.

[0077] 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.

[0078] In each of the above-described embodiments, in the second direction D2, the individual flow path 13A is arranged on the outside of the head 1 and the individual flow path 13B is arranged inside thereof, but for example, if the nozzles 15 on the inside of the head are drier than the nozzles 15 on the outside, the individual flow path 13B may be arranged on the outside and the individual flow path 13A may be arranged inside thereof. In short, it is sufficient that the head has individual flow paths 13A and 13B having different first distances L1A and L1B from each other.

[0079] The first pressure chamber channel array 20R1 (first individual channel array 14R1) and the second pressure chamber channel array 20R2 (second individual channel array 14R2) may be arranged alternately in the second direction D2.

[0080] The pressure chamber flow path row 20R may include one or more pressure chamber flow paths 20A and one or more pressure chamber flow paths 20B. In other words, when the dryness states of the plurality of nozzles 15 aligned in the first direction D1 differ in the first direction D1, it is possible to suppress variations in the recovery states among the plurality of nozzles 15.

[0081] The first distances L1A, L1B may be equal to or shorter than the second distance L2. Furthermore, one end of the circulation flow path 19 that is connected to the pressure chamber flow path 20 may be connected to any location on the pressure chamber flow path 20. In other words, one end of the circulation flow path 19 may be connected to a central or upper portion of the pressure chamber 16 or the communication flow path 17 rather than a lower portion in the up-down direction D3. Furthermore, the connection ports 19A1, 19B1 of the circulation flow path 19 may open to the upper surface of the common flow path 12.

[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] When the head has multiple pressure chamber channel arrays 20R, it is sufficient that it has a first pressure chamber channel array 20R1 and a second pressure chamber channel array 20R2. When the head has three or more pressure chamber channel arrays 20R, it is sufficient that it has a first pressure chamber channel array 20R1, a second pressure chamber channel array 20R2 or a third pressure chamber channel array 20R3, and a fourth pressure chamber channel array 20R4.

[0084] The head may not have the damper 28A.

[0085] 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.

[0086] The object onto which the droplets are ejected is not limited to paper, but may be, for example, a cloth, a substrate, or plastic.

[0087] The droplets ejected from the nozzles are not limited to ink droplets, but may be droplets of a treatment liquid that aggregates or precipitates components in the ink, for example.

[0088] 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]

[0089] 1 head (liquid ejection head) 12 Common flow path 12A bottom 12B Side 12W1 center part 12W2, 12W3 outer part 13, 13A, 13B Individual flow paths 15, 15A, 15B nozzles 16, 16A, 16B pressure chamber 17, 17A, 17B connecting flow path 18, 18A, 18B Supply channel 18A1, 18B1 connection port 19, 19A, 19B Circulation flow path 19A1, 19B1 connection port 20 Pressure chamber flow path 20A Pressure chamber flow path (first pressure chamber flow path) 20B pressure chamber flow path (second pressure chamber flow path) 20R pressure chamber channel array 20R1 First pressure chamber channel array 20R2 Second pressure chamber channel array 20R3 Third pressure chamber channel array 20R4 Fourth pressure chamber channel array 28A Damper 129A Nozzle surface D1 1st direction (liquid flow direction) D2 Second direction (orthogonal direction, relative movement direction) D3 Up and down direction L1A,L1B 1st distance L2 2nd distance

Claims

1. A plurality of nozzles; a plurality of pressure chamber flow paths respectively communicating with the plurality of nozzles; a common flow path communicating with the plurality of pressure chamber flow paths, a supply flow path for supplying liquid from the common flow path to the pressure chamber flow path, and a circulation flow path for returning liquid from the pressure chamber flow path to the common flow path, are disposed for each of the pressure chamber flow paths between the common flow path and the plurality of pressure chamber flow paths; a first distance between a connection port of the supply flow path and a connection port of the circulation flow path, the connection port opening into the common flow path and leading to the same pressure chamber flow path, the first distance along the liquid flow direction of the common flow path being different between a first pressure chamber flow path and a second pressure chamber flow path among the plurality of pressure chamber flow paths.

2. 2. A liquid ejection head according to claim 1, wherein the first distance is greater than a second distance between a connection port of the supply flow path that leads to the pressure chamber flow path and a connection port of the supply flow path that leads to a pressure chamber flow path that is adjacent to the pressure chamber flow path in the liquid flow direction among the plurality of pressure chamber flow paths.

3. 3. The liquid ejection head according to claim 1, further comprising: a first pressure chamber flow path array in which a plurality of the first pressure chamber flow paths are arranged in the liquid flow direction; and a second pressure chamber flow path array in which a plurality of the second pressure chamber flow paths are arranged in the liquid flow direction, the second pressure chamber flow path array being aligned with the first pressure chamber flow path array in a direction perpendicular to the liquid flow direction.

4. 4. The liquid ejection head according to claim 3, wherein when a transport direction of a recording medium relative to the liquid ejection head is the perpendicular direction and the first pressure chamber flow path array is located upstream of the second pressure chamber flow path array in the transport direction, the first distance in the first pressure chamber flow path array is greater than the first distance in the second pressure chamber flow path array.

5. three or more pressure chamber flow path rows including the first pressure chamber flow path row and the second pressure chamber flow path row are aligned in the orthogonal direction, In the three or more pressure chamber flow path arrays, the first pressure chamber flow path array is located at an end in the perpendicular direction, and the second pressure chamber flow path array is located at a position sandwiched between other pressure chamber flow path arrays in the perpendicular direction, 4. The liquid ejection head according to claim 3, wherein when a relative movement direction of a recording medium with respect to the liquid ejection head is the perpendicular direction, the first distance in the first pressure chamber flow path array is greater than the first distance in the second pressure chamber flow path array.

6. 2. A liquid ejection head according to claim 1, which has a nozzle surface on which the plurality of nozzles are arranged, and wherein when the first pressure chamber flow path is located outside the second pressure chamber flow path in a direction parallel to the nozzle surface, the first distance in the first pressure chamber flow path is greater than the first distance in the second pressure chamber flow path.

7. a damper disposed along a bottom surface of the common flow path for absorbing pressure fluctuations of the liquid in the common flow path; 2. The liquid ejection head according to claim 1, wherein the connection port of the circulation flow path is open to a portion outside the central portion of the bottom surface divided into three equal parts in a direction perpendicular to the liquid flow direction.

8. a damper disposed along a bottom surface of the common flow path for absorbing pressure fluctuations of the liquid in the common flow path; 2. The liquid ejection head according to claim 1, wherein the connection port of the circulation flow path is open to a side surface of the common flow path that is connected to the bottom surface.

9. 2. The liquid ejection head according to claim 1, wherein the connection port of the supply flow channel and the connection port of the circulation flow channel are open to one side of the center of the common flow channel in a direction perpendicular to the liquid flow direction.

10. the pressure chamber flow path includes a pressure chamber that communicates with the supply flow path, and a communication flow path that communicates with the nozzle at one end and the pressure chamber at the other end, 2. The liquid ejection head according to claim 1, wherein the circulation flow path communicates with the communication flow path and the common flow path.

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