Liquid ejection head and liquid ejection device

Abstract

To attenuate pressure vibration generated in a common channel.SOLUTION: A head 1 includes a common channel 12 and a plurality of individual channels each of which communicates with the common channel 12. The common channel 12 has: inflow ports 12A1, 12A2 disposed at both ends of the common channel in a first direction D1; a first passage portion 113; a second passage portion 115; and a common portion 114 disposed between both the passage portions 113, 115. The first passage portion 113 is disposed between the inflow port 12A2 and a connection port of the individual channel disposed at a position closest to the inflow port 12A2 in the first direction D1. The second passage portion 115 is disposed between the inflow port 12A1 and a connection port of the individual channel disposed at a position closest to the inflow port 12A1 in the first direction D1. A cross-sectional area S1 of the first passage portion 113 orthogonal to the first direction D1 is smaller than cross-sectional areas S2, S3 of the second passage portion 115 and the common portion 114 orthogonal to the first direction D1.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection head and a liquid ejection apparatus that are provided with a common flow path that communicates with a plurality of individual flow paths. [Background technology]

[0002] Patent Document 1 describes an inkjet head (liquid ejection head) that includes a plurality of individual flow paths, each of which includes a nozzle and a pressure chamber communicating with the nozzle, a manifold (common flow path) that communicates with the plurality of individual flow paths, and a damper provided in the manifold. The manifold is provided with a damper, which can absorb and suppress pressure vibrations of the ink inside the manifold. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-273193 Summary of the Invention [Problem to be solved by the invention]

[0004] To improve the image quality of printed materials, nozzle density can be increased. To increase nozzle density without changing the flat size of the head, one possible solution is to reduce the width of the manifold to ensure sufficient nozzle placement area. In this case, the number of individual flow paths increases as the nozzle density increases, increasing the amount of ink flowing from the manifold to the multiple individual flow paths. This can cause pressure vibrations within the manifold to become too large for the damper to absorb, making it necessary to use other mechanisms to attenuate the pressure vibrations.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a liquid ejection head and a liquid ejection apparatus that are capable of attenuating pressure vibrations that occur within a common flow path. [Means for solving the problem]

[0006] A liquid ejection head according to the present invention comprises a common flow path extending in a first direction perpendicular to a vertical direction, a nozzle, and a plurality of individual flow paths each including a pressure chamber communicating with the nozzle, the plurality of individual flow paths being arranged in the first direction and each communicating with the common flow path, the common flow path comprising a first supply port disposed at one end in the first direction and through which liquid is supplied, a second supply port disposed at the other end in the first direction and through which liquid is supplied, and a nozzle disposed at a position in the first direction closest to the first end among the plurality of individual flow paths. and a first passage portion disposed between the individual flow paths arranged at a position closest to the other end of the plurality of individual flow paths and a first connection portion which is a connection point between the individual flow paths and the common flow path, and a second passage portion disposed in the first direction between the second supply port and a second connection portion which is a connection point between the individual flow path arranged at a position closest to the other end of the plurality of individual flow paths and the common flow path, wherein the first passage portion has a smaller cross-sectional area perpendicular to the first direction than the second passage portion and a portion of the common flow path between the first connection portion and the second connection portion.

[0007] A liquid ejection device of the present invention includes a liquid ejection head including a common flow path extending in a first direction perpendicular to a vertical direction, and a plurality of individual flow paths each including a nozzle and a pressure chamber communicating with the nozzle, the plurality of individual flow paths being arranged in the first direction and each communicating with the common flow path; a supply unit; and a control unit, wherein the common flow path includes a first supply port arranged at one end in the first direction and through which liquid is supplied, and a second supply port arranged at the other end in the first direction and through which liquid is supplied, and a liquid ejection head including a liquid ejection head and a liquid ejection head, the liquid ejection head including a common flow path extending in a first direction perpendicular to a vertical direction, and a plurality of individual flow paths each including a nozzle and a pressure chamber communicating with the nozzle, the plurality of individual flow paths being arranged in the first direction and communicating with the common flow path; and a first passage portion disposed in the first direction between the second supply port and a first connection portion which is a connection point between the individual flow path and the common flow path, the individual flow path being disposed at a position closest to the other end of the plurality of individual flow paths, the second passage portion having a cross-sectional area perpendicular to the first direction smaller than that of the second passage portion in the common flow path and that of a portion of the common flow path between the first connection portion and the second connection portion, and the control unit controls the supply unit so that liquid is supplied to the first supply port and the second supply port at the same pressure. [Effects of the Invention]

[0008] According to the liquid ejection head of the present invention, liquid is supplied to the common flow path from both ends, and the liquid in the common flow path flows into the multiple individual flow paths. At this time, pressure waves generated in the common flow path are attenuated as they pass through the first passage portion, which has a high flow path resistance. This makes it possible to attenuate pressure vibrations generated in the common flow path. According to the liquid ejection device of the present invention, liquid is supplied to the common flow path from both ends, and the liquid in the common flow path flows into the multiple individual flow paths. At this time, pressure waves generated in the common flow path are attenuated as they pass through the first passage section, which has a high flow path resistance. This makes it possible to attenuate pressure vibrations generated in the common flow path. In addition, the pressure difference between the individual flow paths close to the first supply port and the individual flow paths close to the second supply port is suppressed. This stabilizes the ejection characteristics from the multiple nozzles. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a plan view of a printer including a head according to an 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] FIG. 4 is a cross-sectional view of the head taken along line IV-IV in FIG. 3. [Figure 5] FIG. 4 is a cross-sectional view of the head taken along line VV in FIG. [Figure 6] FIG. 6 is a cross-sectional view of the head taken along line VI-VI in FIG. [Figure 7] 7(a) is a plan view of the analytical model, and (b) is a cross-sectional view taken along line VII-VII in FIG. 7(a). [Figure 8] FIG. 10 is a diagram showing measurement positions P1 to P5 in a common flow path in an analytical model. [Figure 9] (a) is a diagram showing the change in pressure over time at each of measurement positions P1 to P5 when the vertical length of the first passage portion is 20 μm, (b) is a diagram showing the change in pressure over time at each of measurement positions P1 to P5 when the vertical length of the first passage portion is 50 μm, and (c) is a diagram showing the change in pressure over time at each of measurement positions P1 to P5 when the vertical length of the first passage portion is 80 μm. [Figure 10] FIG. 10 is a diagram showing the relationship between the vertical length of the first passage portion and the magnitude of pressure vibration. [Figure 11] FIG. 10 is a diagram showing the relationship between flow path resistance and the magnitude of pressure vibration. [Figure 12] (a) is a diagram showing an image solid-printed by a head in which the first passage portions of two common flow paths are arranged on the other end side in the first direction, and (b) is a diagram showing an image solid-printed by a head in which the first passage portions of two common flow paths are arranged on opposite sides of each other in the first direction. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Embodiment> First, with reference to Figure 1, the overall configuration of a printer 100 equipped with a head 1 according to one 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 head 1 corresponds to the "liquid ejection head" of the present invention, and the printer 100 corresponds to the "liquid ejection device" of the present invention.

[0011] <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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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).

[0017] 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.

[0018] <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.

[0019] As shown in Fig. 3, two supply ports 105, 106 open in the upper surface (surface) 21A of the flow path member 21. The supply port 105 is disposed at one end of the flow path member 21 in the first direction D1. The supply port 106 is disposed at the other end of the flow path member 21 in the first direction D1. These two supply ports 105, 106 extend in the second direction D2. Each of the supply ports 105, 106 communicates with an ink tank via a tube. The flow path member 21 has two common flow paths 12, a plurality of individual flow paths 13, and two damper chambers 28.

[0020] The two common flow paths 12 are aligned in the second direction D2 and extend in the first direction D1. Each common flow path 12 has a supply port 105 connected to one end (the upper end in FIG. 3) in the first direction D1 and a supply port 106 connected to the other end (the lower end in FIG. 3). Each common flow path 12 communicates with an ink tank via these two supply ports 105, 106, and also communicates with a plurality of individual flow paths 13.

[0021] As shown in Fig. 3, the two common flow paths 12 are arranged point-symmetrically with respect to the center point G of the flow path member 21. In other words, of the two common flow paths 12, one common flow path 12 (on the left in Fig. 3) is equivalent to the other common flow path 12 (on the right in Fig. 3) rotated 180° with respect to the center point G. Therefore, the detailed configuration of one common flow path 12 will be described below. Regarding the other common flow path 12, components similar to those of the one common flow path 12 are designated by the same reference numerals, and detailed description thereof will be omitted.

[0022] 5, one common flow channel 12 has two inlets 12A1 and 12A2 that open to an upper surface 12A of the common flow channel 12. The inlet 12A1 is a portion that overlaps with the supply port 105 of one common flow channel 12 in the vertical direction D3, and ink flows in from the supply port 105. The inlet 12A2 is a portion that overlaps with the supply port 106 of the other common flow channel 12 in the vertical direction D3, and ink flows in from the supply port 106. The inlet 12A1 corresponds to the "second supply port" of the present invention, and the inlet 12A2 corresponds to the "first supply port" of the present invention.

[0023] One common flow path 12 has a first supply section 111, a second supply section 112, a first passage section 113, a common section 114, and a second passage section 115. The first supply section 111 is disposed at the other end of the common flow path 12 in the first direction D1 (the right end section in FIG. 5), and has an inlet 12A2 opening upward. The first supply section 111 communicates with the first passage section 113. The second supply section 112 is disposed at one end of the common flow path 12 in the first direction D1 (the left end section in FIG. 5), and has an inlet 12A1 opening upward. The second supply section 112 communicates with the second passage section 115.

[0024] As shown in Fig. 3, the first passage portion 113 is disposed in the first direction D1 between the inlet 12A2 and a connection port 18B1 of an individual flow path 13 that is located closest to the inlet 12A2 among the multiple individual flow paths 13 that communicate with one of the common flow paths 12. The second passage portion 115 is disposed in the first direction D1 between the inlet 12A1 and a connection port 18A1 of an individual flow path 13 that is located closest to the inlet 12A1 among the multiple individual flow paths 13 that communicate with one of the common flow paths 12. As shown in Fig. 5, the common portion 114 is disposed between both passage portions 113 and 115, and the first passage portion 113 is connected to the other end (right end in Fig. 5) in the first direction D1, and the second passage portion 115 is connected to one end (left end in Fig. 5) in the first direction D1. The connection port 18A1 corresponds to the "second connection portion" of the present invention, and the connection port 18B1 corresponds to the "first connection portion" of the present invention.

[0025] As shown in FIG. 3, the first passage portion 113, the common portion 114, and the second passage portion 115 all have the same length in the second direction D2. The first passage portion 113 and the second passage portion 115 also have the same length in the first direction D1. The common portion 114 is longer in the first direction D1 than the first passage portion 113 and the second passage portion 115. The first passage portion 113 is shorter in the vertical direction D3 than the common portion 114 and the second passage portion 115. The common portion 114 and the second passage portion 115 have the same length in the vertical direction D3. As shown in FIG. 5, the cross-sectional area S1 of the first passage portion 113 perpendicular to the first direction D1 is smaller than the cross-sectional areas S2 and S3 of the common portion 114 and the second passage portion 115 perpendicular to the first direction D1. Furthermore, the cross-sectional area S3 of the common portion 114 perpendicular to the first direction D1 is the same as the cross-sectional area S2 of the second passage portion 115 perpendicular to the first direction D1.

[0026] 6, the other common flow path 12 is arranged point-symmetrically with respect to the center point G, and therefore the arrangement order in the first direction D1 of the first supply section 111, the second supply section 112, the first passage section 113, the common section 114, and the second passage section 115 that constitute the other common flow path 12 is reversed from that of the one common flow path 12. That is, ink flows into the inlet 12A1 from the supply port 106, and ink flows into the inlet 12A2 from the supply port 105. The inlet 12A1 is a portion that overlaps with the supply port 106 of the other common flow path 12 in the vertical direction D3, and the inlet 12A2 is a portion that overlaps with the supply port 105 of the other common flow path 12 in the vertical direction D3.

[0027] 3, the first passage portion 113 is disposed in the first direction D1 between the inlet 12A2 and a connection port 18A1 of an individual flow path 13 that is closest to the inlet 12A2 among the plurality of individual flow paths 13 that communicate with the other common flow path 12. The second passage portion 115 is disposed in the first direction D1 between the inlet 12A1 and a connection port 18B1 of an individual flow path 13 that is closest to the inlet 12A1 among the plurality of individual flow paths 13 that communicate with the other common flow path 12. In this manner, the first passage portions 113 of the two common flow paths 12 are disposed on opposite sides of each other in the first direction D1, sandwiching a common portion 114 of the common flow path 12 therebetween. The common portion 114 includes a region between the connection port 18A1 or 18B1 of the individual flow path 13 that is closest to the inlet 12A2 and the connection port 18B1 or 18A1 of the individual flow path 13 that is closest to the inlet 12A1. The end of the common flow path 12 where the inlet 12A1 is arranged corresponds to the "one end in the first direction" of the present invention, and the end of the common flow path 12 where the inlet 12A2 is arranged corresponds to the "other end in the first direction" of the present invention.

[0028] The two damper chambers 28 are each disposed below 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.

[0029] 3 and 4, the individual flow path 13 includes a nozzle 15, a pressure chamber 16, a communication flow path 17, and a supply flow path 18. One end of the communication flow path 17 communicates with the nozzle 15, and the other end communicates with the pressure chamber 16. One end of the supply flow path 18 communicates with the common flow path 12, and the other end communicates with the pressure chamber 16.

[0030] 4, the flow path member 21 includes eight plates 121 to 128. The flow path member 21 may be configured with nine or more or seven or fewer plates. Of the eight plates 121 to 128, the uppermost plate 121 has a plurality of pressure chambers 16 formed therein, and the lowermost plate 128 has a plurality of nozzles 15 formed therein. The plurality of pressure chambers 16 are located above the common flow path 12.

[0031] 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 128. In this manner, the plurality of nozzles 15 are arranged on a nozzle surface 128A, which is the lower surface of the plate 128. 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. 4, the nozzles 15 have a shape that tapers downward.

[0032] 5 and 6, two supply ports 105 and 106 are formed on the upper surface 21A of the plate 121. These supply ports 105 and 106 are formed by connecting holes formed in the three plates 121 to 123, respectively.

[0033] As shown in Figures 4 to 6, the common flow path 12 is formed by interconnecting holes formed in each of the three plates 124 to 126. A first passage section 113 included in the common flow path 12 is configured by some of the holes formed in the plate 124, and is disposed along the upper surface 12A of the common flow path 12. The first supply section 111, the second supply section 112, the common section 114, and the second passage section 115 included in the common flow path 12 other than the first passage section 113 are formed by interconnecting holes formed in each of the three plates 124 to 126. Each common flow path 12 overlaps in the up-down direction D3 with all of the pressure chambers 16 communicating with that common flow path 12.

[0034] Each damper chamber 28 is formed by blocking a recess formed in the plate 127 with the plate 128. The portion of the plate 127 above the damper chamber 28, which is sandwiched between the damper chamber 28 and the common flow path 12, functions as a damper 28A that absorbs pressure vibrations of the ink in the common flow path 12. In other words, the damper 28A is arranged along the bottom surface 12B of the common flow path 12, and even if pressure generated in the pressure chamber 16 when ink is ejected from the nozzle 15 is propagated to the common flow path 12, the damper 28A attenuates the pressure by elastic deformation, thereby preventing the pressure from propagating to other pressure chambers 16 (so-called crosstalk). The damper 28A also absorbs to some extent pressure vibrations caused by ink flowing from the common flow path 12 to the individual flow paths 13 due to ink ejection from the nozzle 15.

[0035] 3, the multiple individual flow paths 13 are arranged in a 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. These individual flow path rows 14R are aligned in a second direction D2. The individual flow paths 13 belonging to two individual flow path rows 14R adjacent to each other in the second direction D2 are arranged with a shift in the first direction D1. 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 order from upstream to downstream in the transport direction.

[0036] The first individual flow path array 14R1 and the third individual flow path array 14R3 each include a plurality of individual flow paths 13A aligned in the first direction D1. The second individual flow path array 14R2 and the fourth individual flow path array 14R4 each include a plurality of individual flow paths 13B aligned in the first direction D1. The individual flow paths 13A and 13B 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 13B included in the second individual flow path array 14R2 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. The individual flow paths 13A included in the third individual flow path array 14R3 and the individual flow paths 13B included in the fourth individual flow path array 14R4 are also 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.

[0037] The detailed configuration of the individual flow path 13A will be described below, and the detailed configuration of the individual flow path 13B will be omitted.

[0038] As shown in Fig. 4, the individual flow path 13A includes a nozzle 15A, a pressure chamber 16A, a communication flow path 17A, and a supply flow path 18A. As shown in Fig. 3, the individual flow path 13B also includes a nozzle 15B, a pressure chamber 16B, a communication flow path 17B, and a supply flow path 18B, and is disposed at the same height level as the individual flow path 13A.

[0039] 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 six plates 122 to 127, and has a diameter larger than that of the nozzle 15A.

[0040] 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.

[0041] 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).

[0042] 3 and 4, the supply flow path 18A is connected to the individual flow path 13A via a connection port 18A1 that is a connection point between the individual flow path 13A and the common flow path 12 and opens into the common flow path 12. Note that the supply flow path 18B of the individual flow path 13B is connected to the individual flow path 13B via a connection port 18B1 that is a connection point between the individual flow path 13B and the common flow path 12 and opens into the common flow path 12, as shown in FIG.

[0043] 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 (first direction D1) is smaller than the opening area of ​​connection port 18A1.

[0044] 3, in each individual flow path array 14R, the plurality of 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 plurality of 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 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.

[0045] During printing, the control unit 5 controls the two pressure pumps 10 and 11 shown in FIG. 2 to be driven, whereby the ink in the ink tank is supplied to each common flow path 12 via two supply ports 105 and 106, and then 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 and 11. More specifically, the pressure pump 10 is connected to the supply port 105 and is controlled by the control unit 5 so that a predetermined pressure (negative pressure) is applied to the ink in the supply port 105. The pressure pump 11 is connected to the supply port 106 and is controlled by the control unit 5 so that a predetermined pressure (negative pressure) of the same magnitude as that of the ink in the supply port 105 is applied to the ink in the supply port 106. When ink is ejected from the nozzle 15 during printing, the ink is supplied from the common flow path 12 to the individual flow paths 13. 5 and 6, ink is supplied from two supply ports 105 and 106 through two inlets 12A1 and 12A2 to the common flow path 12. The pressure pumps 10 and 11 correspond to the "supply unit" of the present invention.

[0046] Furthermore, when ink in the ink tank is initially introduced into the head 1, the two pressure pumps 10 and 11 apply different pressures to the ink in the supply ports 105 and 106 under the control of the control unit 5. That is, the pressure pump 10 is controlled by the control unit 5 to apply a first pressure (negative pressure) to the ink in the supply port 105, and the pressure pump 11 is controlled by the control unit 5 to apply a second pressure (negative pressure) lower than the first pressure to the ink in the supply port 106. Due to this pressure difference, the ink supplied from the supply port 105 moves from the inlet 12A1 through the common flow path 12 from one end to the other in the first direction D1, and reaches the supply port 106 from the inlet 12A2. The ink that reaches the supply port 106 is returned to the ink tank via a tube. In this way, the ink is initially introduced into the head 1. At this time, the first passage portion 113 is arranged along the upper surface 12A of the common flow path 12. This makes it easier to expel air bubbles in the common flow path 12. If the first passage portion 113 were disposed away from the upper surface 12A, air bubbles would easily accumulate in the vertical direction D3 between the upper surface 12A and the first passage portion 113. However, in this configuration, air bubbles are easily discharged and are less likely to accumulate in the common flow path 12.

[0047] When ink is ejected from the nozzle 15 and the ink in the common flow path 12 flows into the individual flow paths 13, a pressure wave is generated in the common flow path 12. The pressure wave propagates in the common flow path 12 in the first direction D1, causing pressure vibrations in the common flow path 12. Because the cross-sectional area S1 of the first passage portion 113 is smaller than the cross-sectional areas S2, S3 of the common portion 114 and the second passage portion 115, the flow path resistance of the first passage portion 113 is larger than the flow path resistances of the common portion 114 and the second passage portion 115. Therefore, the pressure wave generated in the common flow path 12 is attenuated when passing through the first passage portion 113. This makes it possible to attenuate the pressure vibrations generated in the common flow path 12.

[0048] 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.

[0049] 3 to 6, the actuator member 22 is fixed to the upper surface 21A of the flow path member 21. The actuator member 22 includes a metallic vibration plate 31, a piezoelectric layer 32, and a plurality of individual electrodes 33, as shown in FIG.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] Here, the flow path resistance of the first passage portion 113 included in the common flow path 12 in this embodiment will be described. The flow path resistance of the first passage portion 113 is 1.3×10 10 ~1.9×10 11 Pa·s / m 3 This is set to be in the range of 1.3 × 10 10 ~1.9×10 11 Pa·s / m 3 The range was derived based on the analysis shown below.

[0056] First, two common flow paths 12 formed in the flow path member 21 in this embodiment were set as a simplified analytical model as shown in FIG. 7 . This analytical model was configured with two common flow paths 12 and four nozzle rows, two rows of which were connected to the bottom surfaces of each of the two common flow paths 12. The length of the common flow path 12 in the second direction D2 was 1500 μm. The length of the common flow path 12 in the up-down direction D3 was 415 μm. That is, the length of the common portion 114 and the second passage portion 115 in the up-down direction D3 was 415 μm. The length of the first passage portion 113 and the second passage portion 115 in the first direction D1 was 1000 μm, and the length of the common portion 114 in the first direction D1 was 38576 μm. The nozzle row was configured by arranging a plurality of nozzles 15 along the first direction D1, and was positioned 1000 μm away from each of the passage portions 113 and 115 in the common portion 114. All dimensions in FIG. 7 are in μm.

[0057] Then, by changing the length of the first passage portion 113 in the vertical direction D3 of the above-mentioned analysis model, the flow path resistance of the first passage portion 113 that can most effectively attenuate the pressure vibrations in the common flow path 12 is derived. The ink discharge conditions at this time were such that ink was discharged simultaneously from all nozzles 15 in each nozzle row, and ink was discharged at 0.4 pl / μs from one nozzle 15, i.e., one individual flow path 13. Furthermore, each nozzle row was composed of 70 nozzles 15, and the same pressure was applied to ink from the two supply ports 105, 106 that supplied ink to each common flow path 12.

[0058] After starting to discharge ink under the above ink discharge conditions, the internal pressure was measured at measurement positions P1 to P5 of each common flow path 12 shown in Fig. 8. The measurement positions P1 to P5 correspond to five divided positions in a length region of the common portion 114 of each common flow path 12 corresponding to the nozzle row.

[0059] 9(a) shows the change in pressure over time at measurement positions P1 to P5 when the length of first passage portion 113 in the vertical direction D3 is 20 μm, FIG. 9(b) shows the change in pressure over time at measurement positions P1 to P5 when the length of first passage portion 113 in the vertical direction D3 is 50 μm, and FIG. 9(c) shows the change in pressure over time at measurement positions P1 to P5 when the length of first passage portion 113 in the vertical direction is 80 μm. In FIG. 9, the solid line indicates the change in pressure over time in one common flow path 12 (left in FIGS. 7 and 8), and the dashed line indicates the change in pressure over time in the other common flow path 12 (right in FIGS. 7 and 8). In FIG. 9, the vertical axis of the graph at measurement positions P1 to P5 indicates the magnitude of pressure, and the horizontal axis indicates time.

[0060] 9(a) to 9(c), in one common flow path 12, the pressure value until the vibration attenuates increases from measurement position P1 to measurement position P5. On the other hand, in the other common flow path 12, the pressure value until the vibration attenuates decreases from measurement position P1 to measurement position P5. At measurement position P3, the pressure values ​​are approximately the same in each common flow path 12.

[0061] When the length of the first passage portion 113 in the up-down direction D3 is 20 μm, the initial pressure values ​​at the measurement positions P1 to P5 are larger and it takes longer for the vibration to dampen than when the length is 50 μm or 80 μm. When the length of the first passage portion 113 in the up-down direction D3 is 80 μm, the initial pressure values ​​at the measurement positions P1 to P5 are slightly smaller than when the length is 50 μm, but it takes longer for the vibration to dampen. In other words, it can be seen from FIG. 9 that of the three lengths of the first passage portion 113 mentioned above, the time required for the vibration to dampen is shortest when the length is 50 μm.

[0062] Next, a range in which pressure vibration can be effectively attenuated is determined. The pressure vibration in each common flow path 12 is quantified. This quantification method uses a value obtained by integrating the absolute value of the pressure in the time direction. For example, when the pressure at measurement position j is Pj(t), the value Sj obtained by integrating the absolute value of the pressure in each common flow path 12 is given by

number

[0063] From the above, the absolute value of the pressure at each measurement position P1 to P5 is integrated in the time direction, S P1 , S P2 , S P3 , S P4 , S P5 is derived, and their average value is defined as the magnitude of the pressure vibration in the common flow path 12. The magnitude of the pressure vibration is derived when the length of the first passage portion 113 in the vertical direction D3 is set to a range of 20 μm to 200 μm. FIG. 10 shows the derived relationship between the length of the first passage portion 113 in the vertical direction D3 and the magnitude of the pressure vibration. The vertical axis of FIG. 10 represents the magnitude of the pressure vibration, and the horizontal axis represents the length of the first passage portion 113 in the vertical direction D3. As shown in FIG. 10, the magnitude of the pressure vibration in the common flow path 12 is greatest when the length of the first passage portion 113 in the vertical direction D3 is 20 μm. On the other hand, the magnitude of the pressure vibration in the common flow path 12 is smallest when the length of the first passage portion 113 in the vertical direction D3 is set to a range of 50 μm to 60 μm.

[0064] Here, the length of the first passage portion 113 in the up-down direction D3 is normalized by the flow path resistance of the first passage portion 113. Since the planar flow path shape of the first passage portion 113 is rectangular, the following formula for the flow path resistance R of a rectangular flow path is used. The flow resistance R is

number

number

[0065] The relationship between the value derived from the above formula for flow path resistance R and the magnitude of pressure vibration is shown in Figure 11. The vertical axis of Figure 11 shows the magnitude of pressure vibration, and the horizontal axis shows flow path resistance. Figure 11 shows that when the magnitude of pressure vibration is 4000 or less, the flow path resistance R is 1.3 x 10 10 ~1.9×10 11 Pa·s / m 3 When the magnitude of the pressure vibration is 4000 or less, it is possible to more effectively attenuate the pressure vibration in the common flow path 12. As a result, the flow path resistance of the first passage portion 113 in this embodiment is in the range of 1.3×10 10 ~1.9×10 11 Pa·s / m 3 It is set to be in the range of

[0066] As described above, according to the head 1 of this embodiment, ink is supplied to the common flow path 12 from both ends in the first direction D1, and the ink in the common flow path 12 flows into the multiple individual flow paths 13. At this time, the pressure wave generated in the common flow path 12 is attenuated when passing through the first passage portion 113, which has a large flow path resistance. Therefore, it is possible to attenuate the pressure vibration generated in the common flow path 12.

[0067] The flow resistance of the first passage portion 113 is 1.3×10 10 ~1.9×10 11 Pa·s / m 3 Since this range is satisfied, the pressure wave generated in the common flow path 12 can be effectively attenuated when passing through the first passage portion 113.

[0068] Furthermore, the cross-sectional area S2 of the second passage portion 115 is the same as the cross-sectional area S3 of the common portion 114. This allows ink to be smoothly supplied from the second passage portion 115 to the common portion 114. Therefore, while the pressure wave is attenuated in the first passage portion 113, poor ink supply to the multiple individual flow paths 13 is less likely to occur.

[0069] Furthermore, a damper 28A is disposed along the bottom surface 12B of the common flow path 12. This improves the effect of damping pressure waves generated in the common flow path 12.

[0070] Furthermore, the first passage portions 113 of the two common flow paths 12 are arranged on opposite sides of the common portion 114 of the common flow paths 12 in the first direction D1. As a result, even if the amount of ink ejected from the nozzles 15 at the other end (lower end side in FIG. 3) in the first direction D1 that communicates with one common flow path 12 (left side in FIG. 3) is less than the amount of ink ejected from the nozzles 15 at one end (upper end side in FIG. 3), the amount of ink ejected from the nozzles 15 at the other end in the first direction D1 that communicates with the other common flow path 12 (right side in FIG. 3) adjacent to the one common flow path 12 is greater than the amount of ink ejected from the nozzles 15 at one end. Therefore, in the head 1, bias in the amount of ink ejected from the nozzles 15 in the first direction D1 is suppressed.

[0071] If the first passage portions 113 of the two common flow paths 12 are arranged on the other end side in the first direction D1, the pressure vibrations in both of the two common flow paths 12 become larger as they approach the first passage portions 113. The amount of ink ejected from the nozzles 15 communicating with a location with large pressure vibrations is easily affected by the pressure vibrations. For example, if the amount of ink ejected from the nozzles 15 decreases as the pressure vibration increases, the amount of ink ejected from the nozzles 15 on the other end side of the two common flow paths 12 decreases. FIG. 12(a) shows an image printed in a solid state by ejecting ink from all nozzles of a head arranged on the other end side in the first direction D1 of the two common flow paths 12. FIG. 12(b) shows an image printed in a solid state by ejecting ink from all nozzles of the head 1 in this embodiment. In this case, as shown in FIG. 12(a), the amount of ink decreases as you approach the other end side of the common flow path 12, resulting in noticeable stripes. In this configuration, the first passage portions 113 of the two common flow paths 12 are arranged on opposite sides of each other in the first direction D1. This prevents the ink ejection amount from the nozzles 15 from being biased in the first direction D1, as described above. This makes the striped pattern less noticeable, as shown in FIG. 12(b).

[0072] In the printer 100 of this embodiment, the control unit 5 controls the two pressure pumps 10 and 11 during printing so that ink is supplied at the same pressure to the inlets 12A1 and 12A2 of the common flow path 12. This reduces the pressure difference between the individual flow paths 13 close to the inlet 12A1 and the individual flow paths 13 close to the inlet 12A2 in the head 1. This stabilizes the ejection characteristics from the multiple nozzles 15.

[0073] 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.

[0074] In the above-described embodiment, if the cross-sectional area S1 of the first passage portion 113 is smaller than the cross-sectional areas S2 and S3 of the common portion 114 and the second passage portion 115, the flow path resistance is 1.3×10 10 ~1.9×10 11 Pa·s / m 3 The cross-sectional area S3 of the common portion 114 and the cross-sectional area S2 of the second passage portion 115 may be different from each other.

[0075] In the above-described embodiment, the damper 28A is provided along the bottom surface 12B of the common flow path 12 of the head 1, but the damper 28A does not have to be provided. The first passage portion 113 may be disposed below and spaced apart from the top surface 12A of the common flow path 12.

[0076] The head 1 may be provided with one or more common flow paths 12. When the head 1 has a plurality of common flow paths 12, the first passage portion 113 may be provided on one side of each common flow path 12 in the first direction D1.

[0077] Also, there may be provided only one pressure pump 10, 11. Furthermore, when three or more common flow paths 12 are provided, three or more pressure pumps may be provided corresponding to the respective common flow paths 12.

[0078] In the above-described embodiment, 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.

[0079] The type of liquid ejection head of the present invention is not limited to the line type, but may also be a serial type.

[0080] The object onto which the liquid is ejected is not limited to paper, but may be, for example, a cloth, a substrate, or plastic.

[0081] 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 ink.

[0082] The liquid ejection apparatus of 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 and liquid ejection apparatuses used for purposes other than image recording. For example, the present invention can be applied to liquid ejection heads and liquid ejection apparatuses that eject conductive liquid onto a substrate to form a conductive pattern. [Explanation of symbols]

[0083] 1 head 10,11 Pressure pump 12 Common flow path 12A top 12A1,12A2 Inlet 12B Bottom 13 Individual flow path 15 nozzles 16 Pressure Chamber 18A1, 18B1 connection port 28A Damper 113 1st passage section 115 2nd passage section D1 1st direction D2 2nd direction D3 up and down direction S1~S3 cross-sectional area

Claims

1. a common flow path extending in a first direction perpendicular to the up-down direction; a plurality of individual flow paths each including a nozzle and a pressure chamber communicating with the nozzle, the individual flow paths being arranged in the first direction and each communicating with the common flow path; The common flow path is a first supply port that is disposed at one end in the first direction and through which a liquid is supplied; a second supply port disposed at the other end in the first direction and through which the liquid is supplied; a first passage portion disposed in the first direction between the first supply port and a first connection portion that is a connection point between the common flow path and the individual flow path that is disposed at a position closest to the one end of the plurality of individual flow paths; a second passage portion disposed in the first direction between the second supply port and a second connection portion that is a connection point between the common flow path and the individual flow path that is disposed at a position closest to the other end of the plurality of individual flow paths, A liquid ejection head characterized in that the first passage portion has a smaller cross-sectional area perpendicular to the first direction than the second passage portion in the common flow path and the portion of the common flow path between the first connection portion and the second connection portion.

2. The flow resistance of the first passage portion is 1.3×10 10 ~1.9 x 10 11 Pa·s / m 3 2. The liquid ejection head according to claim 1, wherein the range is:

3. A liquid ejection head according to claim 1, characterized in that the cross-sectional area of ​​the second passage portion perpendicular to the first direction is the same as the cross-sectional area of ​​the common flow path perpendicular to the first direction between the first connection portion and the second connection portion.

4. The liquid ejection head according to claim 1 , wherein the first passage portion is disposed along an upper surface of the common flow path.

5. 2. The liquid ejection head according to claim 1, further comprising a damper disposed along the bottom surface of the common flow path, for absorbing pressure vibrations of the liquid within the common flow path.

6. a plurality of the common flow channels are arranged side by side in a second direction perpendicular to both the first direction and the up-down direction, A liquid ejection head as described in claim 1, characterized in that the first passage portions of two of the common flow paths adjacent in the second direction are arranged on opposite sides of each other in the first direction, sandwiching an area between the first connection portion and the second connection portion of the common flow path.

7. a liquid ejection head including a common flow path extending in a first direction perpendicular to a vertical direction, and a plurality of individual flow paths each including a nozzle and a pressure chamber communicating with the nozzle, the individual flow paths being arranged in the first direction and each communicating with the common flow path; a supply unit; a control unit, The common flow path is a first supply port that is disposed at one end in the first direction and through which a liquid is supplied; a second supply port disposed at the other end in the first direction and through which the liquid is supplied; a first passage portion disposed in the first direction between the first supply port and a first connection portion that is a connection point between the common flow path and the individual flow path that is disposed at a position closest to the one end of the plurality of individual flow paths; a second passage portion disposed in the first direction between the second supply port and a second connection portion that is a connection point between the common flow path and the individual flow path that is disposed at a position closest to the other end of the plurality of individual flow paths, the first passage portion has a smaller cross-sectional area perpendicular to the first direction than the second passage portion and a portion of the common flow path between the first connection portion and the second connection portion, The liquid ejection device, wherein the control unit controls the supply unit so that the liquid is supplied to the first supply port and the second supply port at the same pressure.

Images