Liquid ejection head

Abstract

To circulate a liquid between a plurality of pressure chamber flow passages and a common flow passage, and to suppress deterioration of absorption of pressure fluctuation by a damper.SOLUTION: The head 1 includes a plurality of nozzles 15, a plurality of pressure chamber channels 20, a common channel 12, a damper 28A, and a circulating channel 50. The circulating channel 50 is arranged at a position not overlapping with the common channel 12 on the D3 in the up-down direction, and allows the plurality of pressure chamber channels 20 aligned on the D1 in the first direction to communicate with each other.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

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

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

[0004] In the liquid ejection head described in Patent Document 1, the ink circulation port of the ink circulation channel opens to the bottom surface of the common channel, and the ink circulation channel and the common channel overlap in the vertical direction. When a damper is provided on the bottom surface of the common channel to absorb pressure fluctuations of the ink in the common channel, the damper is positioned to avoid the area of ​​the common channel that overlaps with the ink circulation channel. This reduces the movable area of ​​the damper, reducing its ability to absorb pressure fluctuations of the liquid in the common channel.

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

[0006] The liquid ejection head of the present invention comprises a plurality of nozzles arranged in a first direction perpendicular to the vertical direction, a plurality of pressure chamber flow paths arranged in the first direction and each communicating with one of the nozzles, a common flow path extending in the first direction and communicating with the plurality of pressure chamber flow paths, a damper arranged along the bottom surface of the common flow path and absorbing pressure fluctuations of the liquid in the common flow path, and a circulation flow path arranged in a position that does not overlap with the common flow path in the vertical direction and communicating two of the pressure chamber flow paths adjacent to each other in the first direction. [Effects of the Invention]

[0007] According to the liquid ejection head of the present invention, liquid in a common flow path can be circulated from one pressure chamber flow path to the other pressure chamber flow path via the circulation flow path, and then circulated from the other pressure chamber flow path to the common flow path. Furthermore, because the circulation flow path does not overlap the common flow path in the vertical direction, the movable area of ​​the damper on the bottom surface of the common flow path is not limited by the circulation flow path. This makes it possible to prevent a decrease in the damper's ability to absorb pressure fluctuations. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a plan view of a printer including a head according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the electrical configuration of the printer. [Figure 3] FIG. [Figure 4] 4 is an enlarged view of a region IV shown in FIG. 3 on the upper surface of the flow path member. [Figure 5] 4A is a cross-sectional view of the head taken along line VA-VA shown in FIG. 3, and FIG. 4B is a cross-sectional view of the head taken along line VB-VB shown in FIG. [Figure 6] FIG. 6 is a partial cross-sectional view of the head taken along line VI-VI shown in FIG. [Figure 7] FIG. 10 is a plan view of a main part of a flow path member of a head according to a second embodiment of the present invention. [Figure 8]FIG. 10 is a plan view of a main part of a flow path member of a head according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

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

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

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

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

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

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

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

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

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

[0018] 3, a supply port 111 and a return port 112 open on the upper surface 21A of the flow path member 21. The supply port 111 is disposed at one end of the flow path member 21 in the first direction D1. The return port 112 is disposed at the other end of the flow path member 21 in the first direction D1. The supply port 111 and the return port 112 communicate with ink tanks via tubes. The flow path member 21 has a common flow path 12, a plurality of individual flow paths 13, a plurality of dummy individual flow paths 53, a damper chamber 28, two circulation flow paths 50, and two connection paths 60.

[0019] The common flow path 12 extends in a first direction D1. One end of the common flow path 12 is connected to a supply port 111, and the other end is connected to a return port 112 in the first direction D1. 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 damper chamber 28 is disposed below the common flow path 12. The damper chamber 28 also extends in the first direction D1.

[0021] As shown in FIGS. 3 to 6, the individual flow paths 13 include a nozzle 15, a pressure chamber flow path 20, and a supply flow path 18. 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. The supply flow path 18 has one end communicated with the common flow path 12, and the other end communicated with the pressure chamber 16.

[0022] The dummy individual flow path 53 also includes a dummy nozzle 55, a dummy pressure chamber flow path 54, and a dummy supply flow path 58. The dummy pressure chamber flow path 54 has a dummy pressure chamber 56 and a dummy communication flow path 57. One end of the dummy communication flow path 57 communicates with the dummy nozzle 55, and the other end communicates with the dummy pressure chamber 56. The dummy supply flow path 58 has one end communicated with the common flow path 12, and the other end communicates with the dummy pressure chamber 56.

[0023] 3, the two circulation channels 50 are aligned in the second direction D2 and extend in the first direction D1. Of the two circulation channels 50, one circulation channel 50 is disposed on one outer side of the common channel 12 in the second direction D2, and the other circulation channel 50 is disposed on the other outer side of the common channel 12. In other words, each circulation channel 50 is disposed at a position that does not overlap with the common channel 12 in the up-down direction D3. Each circulation channel 50 communicates with the multiple individual channels 13 and the multiple dummy individual channels 53 aligned in the first direction D1.

[0024] The two connection paths 60 are aligned in the second direction D2 and each extend in the first direction D1. Of the two connection paths 60, one connection path 60 is arranged on one outer side of the common flow path 12 in the second direction D2, and the other connection path 60 is arranged on the other outer side of the common flow path 12. Each connection path 60 is arranged above the circulation flow path 50, and connects the multiple pressure chambers 16 and dummy pressure chambers 56 aligned in the first direction D1.

[0025] As shown in Fig. 5, the flow path member 21 includes ten plates 121 to 130. The flow path member 21 may be composed of eleven or more, or nine or fewer plates. Of the ten plates 121 to 130, the uppermost plate 121 has a plurality of pressure chambers 16 and a plurality of dummy pressure chambers 56 formed therein, and the lowermost plate 130 has a plurality of nozzles 15 and a plurality of dummy nozzles 55 formed therein. The pressure chambers 16 and the dummy pressure chambers 56 are located above the common flow path 12. The plate 130 corresponds to the "nozzle plate" of the present invention.

[0026] A plurality of pressure chambers 16 and a plurality of dummy pressure chambers 56 open to the upper surface (upper surface 21A) of the plate 121, and a plurality of nozzles 15 and a plurality of dummy nozzles 55 open to the lower surface of the plate 130. In this manner, the plurality of nozzles 15 and the plurality of dummy nozzles 55 are arranged on a nozzle surface 130A, which is the lower surface of the plate 130. The opening of the nozzle 15 is circular, and the opening of the pressure chamber 16 is generally rectangular and slightly elongated in the second direction D2. In other words, the length (width) of the pressure chamber 16 in the first direction D1 is shorter than its length in the second direction D2. As shown in FIG. 5 , the nozzle 15 has a shape that tapers downward. The dummy nozzle 55 and dummy pressure chamber 56 have the same shape and size as the nozzle 15 and pressure chamber 16.

[0027] Each connection path 60 also opens to the upper surface (upper surface 21A) of the plate 121. As shown in FIGS. 3 and 6, each connection path 60 extends in a first direction D1 so as to penetrate multiple pressure chambers 16, and both ends thereof communicate with two dummy pressure chambers 56. Furthermore, as shown in FIGS. 5 and 6, the height of each connection path 60 in the vertical direction D3 is approximately half the height of the pressure chamber 16 in the vertical direction D3. In this way, the cross-sectional area of ​​each connection path 60 perpendicular to the first direction D1 is smaller than the cross-sectional area of ​​the pressure chamber 16 perpendicular to the second direction D2. The first direction D1 corresponds to the "direction of liquid flow in the connection path 60" in this invention, and the second direction D2 corresponds to the "direction of liquid flow in the pressure chamber 16" in this invention.

[0028] The common flow path 12 is formed by interconnecting holes formed in each of the four plates 124 to 127. The common flow path 12 overlaps in the up-down direction D3 with all of the pressure chambers 16 and dummy pressure chambers 56 that communicate with the common flow path 12.

[0029] The damper chamber 28 is formed by blocking a recess formed in the plate 128 with the 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 the pressure chamber 16 when ink is ejected from the nozzle 15 is transmitted to the common flow path 12, the damper 28A attenuates the pressure by elastically deforming, thereby preventing the phenomenon of the pressure being transmitted to other pressure chambers 16 (so-called crosstalk). The plate 128 corresponds to the "damper plate" of the present invention.

[0030] As shown in FIGS. 5 and 6 , the two circulation channels 50 are each formed by a hole formed in the plate 129. The length of each circulation channel 50 in the up-down direction D3 is the same as the thickness of the plate 129. In other words, the circulation channels 50 can be formed by full etching of the plate 129, eliminating variations in depth dimension. This makes it possible to suppress variations in the channel resistance of the circulation channels 50. The plate 129 corresponds to the "return plate" of the present invention. Furthermore, each circulation channel 50 is disposed between the nozzle 15 and the communicating channel 17, and between the dummy nozzle 55 and the dummy communicating channel 57, connecting the nozzle 15 and the communicating channel 17, and connecting the dummy nozzle 55 and the dummy communicating channel 57.

[0031] 3, the multiple individual flow paths 13 are arranged in the first direction D1 and form two individual flow path arrays 14R. That is, the multiple pressure chamber flow paths 20 also form two pressure chamber flow path arrays 20R, similar to the individual flow path arrays 14R. The pressure chamber flow path arrays 20R and the individual flow path arrays 14R are aligned in the second direction D2. Furthermore, the individual flow paths 13 belonging to two individual flow path arrays 14R adjacent to each other in the second direction D2 are arranged so as to be shifted in the first direction D1.

[0032] Of the two individual flow path rows 14R, the individual flow paths 13 included in one individual flow path row 14R and the individual flow paths 13 included in the other individual flow path row 14R are arranged point-symmetrically with respect to the midpoint of the line segment connecting the nozzles 15 of each other in a plane perpendicular to the vertical direction D3.

[0033] The dummy individual flow paths 53 are arranged one by one outside the individual flow paths 13 located at both ends of each individual flow path array 14R in the first direction D1. The dummy individual flow paths 53 aligned in the first direction D1 of one individual flow path array 14R and the dummy individual flow paths 53 aligned in the first direction D1 of the other individual flow path array 14R are arranged symmetrically with respect to the midpoint of the line segment connecting the dummy nozzles 55 in a plane perpendicular to the up-down direction D3.

[0034] The detailed configurations of the individual flow paths 13 and the dummy individual flow paths 53 will be described below.

[0035] 5(a), the communication flow path 17 included in the individual flow path 13 extends upward from the circulation flow path 50 along the vertical direction D3 and is connected to the lower end of the pressure chamber 16. The communication flow path 17 is formed by connecting holes formed in each of the seven plates 122 to 128 to each other, and has a diameter larger than that of the nozzle 15.

[0036] The nozzles 15 are disposed below the communicating flow paths 17. The nozzles 15 overlap with the pressure chambers 16 in the up-down direction D3. The nozzles 15 are disposed outside the common flow paths 12 with which they communicate in the second direction D2.

[0037] The supply flow path 18 is formed by connecting holes formed in the two plates 122 and 123. One end of the supply flow path 18 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 16 (the end opposite to the communicating flow path 17).

[0038] 4 and 5(a), the supply flow paths 18 are connected to the common flow path 12 via connection ports 18A that open to the common flow path 12. The connection ports 18A open to an end of the common flow path 12 in the second direction D2, at an end that is distant in the second direction D2 from the pressure chambers 16 that are connected to the supply flow paths 18.

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

[0040] As shown in FIG. 5(b), the dummy communication channel 57 included in the dummy individual channel 53 extends upward from the circulation channel 50 in the vertical direction D3 and is connected to the lower end of the dummy pressure chamber 56. The dummy communication channel 57 is also formed by interconnecting holes formed in each of the seven plates 122 to 128, and has a diameter larger than that of the dummy nozzle 55. The diameter of the dummy communication channel 57 is also larger than the diameter of the communicating channel 17. In other words, the channel resistance of the dummy communication channel 57 is smaller than the channel resistance of the communicating channel 17. As a result, the channel resistance of the dummy pressure chamber channel 54 is smaller than the channel resistance of the pressure chamber channel 20. This makes it easier for ink to flow through the dummy pressure chamber channel 54.

[0041] The dummy nozzles 55 are also arranged below the dummy communicating channels 57. The dummy nozzles 55 overlap with the dummy pressure chambers 56 in the up-down direction D3. The dummy nozzles 55 are also arranged outside the common channels 12 with which they communicate in the second direction D2.

[0042] The dummy supply flow path 58 is formed by connecting holes formed in the two plates 122, 123. One end of the dummy supply flow path 58 is connected to the upper end of the common flow path 12, and the other end is connected to the lower end of the dummy pressure chamber 56 (the end opposite to the dummy communication flow path 57).

[0043] 4 and 5(b), the dummy supply flow paths 58 are connected via connection ports 58A that open to the common flow path 12. The connection ports 58A are at the end of the common flow path 12 in the second direction D2, and open to an end that is away from the dummy pressure chambers 56 connected to the dummy supply flow paths 58 in the second direction D2.

[0044] Furthermore, the dummy supply flow paths 58 are formed such that most of the holes formed in the plate 122 are blocked by the two plates 121, 123. The cross-sectional area of ​​the dummy supply flow paths 58 perpendicular to the liquid flow direction (a direction perpendicular to the up-down direction D3 and intersecting both the first direction D1 and the second direction D2) is larger than the cross-sectional area of ​​the throttle section 18B of the supply flow path 18 perpendicular to the liquid flow direction. In other words, the flow path resistance of the dummy supply flow paths 58 is smaller than the flow path resistance of the supply flow path 18. As a result, the flow path resistance from the connection port 58A of the dummy individual flow paths 53 to the dummy nozzle 55 is even smaller than the flow path resistance from the connection port 18A of the individual flow path 13 to the nozzle 15. This makes it easier for ink to flow through the dummy individual flow paths 53.

[0045] 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 half 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 600 dpi, a printing resolution of 1200 dpi is achieved by all of the nozzles 15.

[0046] 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 plurality of individual flow paths 13 and the plurality of dummy individual flow paths 53. More specifically, the pump 10 communicates with 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 communicates with 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.

[0047] When ink flows into the common flow path 12, it flows from the common flow path 12 through the connection ports 58A of the two dummy individual flow paths 53 on the supply port 111 side and the connection ports 18A of each individual flow path 13 into the two dummy pressure chamber flow paths 54 on the supply port 111 side and each pressure chamber flow path 20. The ink that has flowed into the two dummy pressure chamber flow paths 54 on the supply port 111 side and each pressure chamber flow path 20 then flows through each circulation flow path 50 into the two dummy pressure chamber flow paths 54 on the return port 112 side, and returns to the common flow path 12 through the connection ports 58A of the two dummy individual flow paths 53 on the return port 112 side. In this way, ink circulates between the dummy individual flow paths 53, the individual flow paths 13, and the common flow path 12.

[0048] 3 , the connection port 58A of the dummy individual flow path 53 connected to the end of the circulation flow path 50 on the supply port 111 side and the connection port 58A of the dummy individual flow path 53 connected to the end of the circulation flow path 50 on the return port 112 side are spaced apart in the ink liquid flow direction along the first direction D1. Because the connection port 58A of the dummy individual flow path 53 on the supply port 111 side is located upstream of the connection port 58A of the dummy individual flow path 53 on the return port 112 side in the liquid flow direction of the common flow path 12, the ink pressure at the connection port 58A of the dummy individual flow path 53 on the supply port 111 side is greater than the ink pressure at the connection port 58A of the dummy individual flow path 53 on the return port 112 side. Therefore, the ink flows in the circulation flow path 50 in the same direction as the ink flowing in the common flow path 12. Since the connection port 18A of each individual flow path 13 is also located closer to the supply port 111 than the connection port 58A of the dummy individual flow path 53 on the return port 112 side, ink flows from the common flow path 12 into each pressure chamber flow path 20 via each connection port 18A, and then returns to the common flow path 12 via the circulation flow path 50 and the dummy individual flow path 53 on the return port 112 side.

[0049] Furthermore, when ink flows into the common flow channel 12, the ink that has flowed from the common flow channel 12 into the two dummy pressure chamber flow channels 54 on the supply port 111 side and into each pressure chamber flow channel 20 also flows into each connection channel 60. As with the circulation flow channel 50, ink also flows in each connection channel 60 in the same direction as the flow of ink flowing in the common flow channel 12. In other words, the ink that has flowed into the two dummy pressure chamber flow channels 54 on the supply port 111 side and each pressure chamber flow channel 20 flows via each connection channel 60 into the two dummy pressure chamber flow channels 54 on the return port 112 side, and returns to the common flow channel 12 from the connection ports 58A of the two dummy individual flow channels 53 on the return port 112 side.

[0050] Air bubbles in the pressure chambers 16 are difficult to discharge via the communication flow path 17 located below the pressure chambers 16. In this regard, in this configuration, the connection path 60 connects multiple pressure chamber flow paths 20 aligned in the first direction D1 above the circulation flow path 50, so that air bubbles in one (upstream) pressure chamber 16 can be made to flow to the other (downstream) pressure chamber 16 via the connection path 60. Ultimately, the air bubbles can be made to flow to the dummy pressure chamber 56 on the return port 112 side. In this way, air bubbles can be effectively discharged from each pressure chamber 16.

[0051] Furthermore, because the cross-sectional area of ​​the connection path 60 perpendicular to the liquid flow direction is small, the flow rate itself flowing through the connection path 60 is small. However, because the cross-sectional area of ​​the connection path 60 is smaller than the cross-sectional area of ​​the pressure chamber 16 perpendicular to the second direction D2, the flow rate of ink in the connection path 60 is high. This makes it easier for air bubbles in one pressure chamber 16 to flow to the other pressure chamber 16, making it possible to more effectively discharge air bubbles from the pressure chambers 16.

[0052] In the individual flow paths 13, the volume of the pressure chambers 16 is reduced by driving the actuator units 35 described below, and pressure is applied to the ink in the pressure chambers 16, causing the ink to pass through the communicating flow paths 17 and be ejected as ink droplets from the nozzles 15. Note that, because no pressure is applied to the ink in the dummy pressure chambers 56 by the actuator units 35, ink is not ejected from the dummy nozzles 55. In other words, the dummy individual flow paths 53 in this embodiment constitute flow paths for circulating ink and do not contribute to ink ejection from the nozzles 55. Furthermore, although the dummy nozzles 55 are provided in this embodiment, the dummy nozzles 55 may not be provided.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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 and the multiple dummy pressure chambers 56. 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 vertical direction D3. In other words, the individual electrodes 33 are not disposed in positions that overlap the dummy pressure chambers 56 in the vertical direction D3.

[0057] 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.

[0058] 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.

[0059] As described above, with the head 1 of this embodiment, ink in the common flow path 12 can be made to flow from one pressure chamber flow path 20 (the supply port 111 side) to the other pressure chamber flow path 20 (the return port 112 side) via the circulation flow path 50. This makes it possible to prevent the ink in the pressure chamber flow paths 20 from becoming thicker, stabilizing the ink ejection characteristics from the nozzles 15. Furthermore, because the circulation flow path 50 does not overlap with the common flow path 12 in the up-down direction D3, the movable area of ​​the damper 28A on the bottom surface 12A of the common flow path 12 is not limited by the circulation flow path 50. This makes it possible to prevent a decrease in the absorption of pressure fluctuations by the damper 28A.

[0060] Plates 129 and 130 are disposed adjacent to each other. This allows ink near nozzles 15 to flow through circulation flow path 50, further suppressing the increase in viscosity of ink near nozzles 15.

[0061] Plates 128 and 129 are disposed at different positions in the up-down direction D3. As a result, damper 28A and circulation flow path 50 are formed on different plates 128 and 129, and therefore damper 28A and circulation flow path 50 are formed in processes suited to each. This reduces dimensional variation between damper 28A and circulation flow path 50.

[0062] The cross-sectional area of ​​the connection path 60 shown in Fig. 5 perpendicular to the liquid flow direction is smaller than the cross-sectional area of ​​the pressure chamber 16 perpendicular to the second direction D2 shown in Fig. 6. When ink is ejected from the nozzle 15, the pressure applied to the ink in one pressure chamber 16 is less likely to be transmitted to the ink in the other pressure chamber 16 via the connection path 60. As a result, the pressure for ejecting ink from the nozzle 15 is less likely to be lost.

[0063] The circulation flow path 50 connects three or more pressure chamber flow paths 20 arranged in the first direction D1, thereby making it possible to increase the flow rate through each pressure chamber flow path 20.

[0064] When the circulation channel 50 connects only three or more pressure chamber channels 20, in the pressure chamber channel 20 arranged on the outermost side (upstream side) in the first direction D1, the flow of ink flowing in from its own connection port 18A causes the ink in the pressure chamber channel 20 to flow into the circulation channel 50. On the other hand, in the pressure chamber channel 20 adjacent to the pressure chamber channel 20 on the supply port 111 side (upstream side) in the first direction D1, the flow of ink flowing in from its own connection port 18A and the flow of ink in the circulation channel 50 make it easier for the ink in the pressure chamber channel 20 to flow into the circulation channel 50. In other words, a difference in the flow of ink in the pressure chamber channel 20 occurs between the outermost pressure chamber channel 20 and another pressure chamber channel 20 adjacent to that pressure chamber channel 20. In this configuration, the circulation channel 50 connects three or more pressure chamber channels 20 and the dummy pressure chamber channel 54. This makes it difficult for differences to occur in the flow of ink in the pressure chamber flow paths 20 between the outermost pressure chamber flow path 20 and another pressure chamber flow path 20 adjacent to that pressure chamber flow path 20. Therefore, in the three or more pressure chamber flow paths 20, the flow of ink via the circulation flow path 50 tends to be equal, and the ink ejection characteristics are stabilized between the three or more nozzles 15 that are respectively connected to the three or more pressure chamber flow paths 20.

[0065] The resistance of the dummy pressure chamber flow path 54 is smaller than the resistance of the pressure chamber flow path 20. This makes it easier for ink to flow through the dummy pressure chamber flow path 54, and the flow rate flowing through each pressure chamber flow path 20 can be further increased.

[0066] The connecting path 60 connects the pressure chambers 16 and the dummy pressure chambers 56 to each other. This allows air bubbles in each pressure chamber 16 to flow into the dummy pressure chamber 56 via the connecting path 60. This makes it possible to effectively discharge air bubbles from the pressure chambers 16.

[0067] Second Embodiment Next, a head 1 according to a second embodiment of the present invention will be described with reference to Fig. 7. The head 1 in this embodiment is not provided with a dummy individual flow path 53, and only has a circulation flow path 250 and a connection path 260 that connects the pressure chamber flow paths 20 to each other for each pair of adjacent pressure chamber flow paths 20 in the first direction D1, and is otherwise the same as the first embodiment described above. Note that components similar to those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0068] The multiple circulation channels 250 and the multiple connection channels 260 extend in the first direction D1 and are aligned in the first direction D1. Each circulation channel 250 is formed by a hole formed in the plate 129, and connects the lower ends of two adjacent communication channels 17 in the first direction D1. Each connection channel 260 opens to the plate 121, and connects two adjacent pressure chambers 16 in the first direction D1. The circulation channels 250 and connection channels 260 in this embodiment have a configuration similar to that of the circulation channel 50 and connection channel 60 in the first embodiment, which are divided into two pressure chamber channels 20 adjacent in the first direction D1.

[0069] In this embodiment, when ink flows into the common flow channel 12, the ink flows from the common flow channel 12 via the connection port 18A into one of the pressure chamber flow channels 20 on the supply port 111 side of the two pressure chamber flow channels 20 that communicate with each other via the circulation flow channel 250 and the connection channel 260. Then, ink flows from one of the pressure chamber flow channels 20 into which the ink has flowed, via the circulation flow channel 250, into the other pressure chamber flow channel 20 on the return port 112 side, and returns to the common flow channel 12 via the connection port 18A. At this time, the ink in the circulation flow channel 250 flows in the same direction as the flow of ink flowing in the common flow channel 12. In this way, ink circulates between the pressure chamber flow channels 20 and the common flow channel 12.

[0070] Furthermore, when ink flows into the common flow path 12, the ink that has flowed from the common flow path 12 into one of the pressure chamber flow paths 20 passes through the connection path 260 and flows into the other pressure chamber flow path 20. In other words, in the connection path 260, as in the circulation flow path 250, the ink flows in the same direction as the ink flowing in the common flow path 12.

[0071] In the head of this embodiment as well, ink in the common flow path 12 can be circulated from one pressure chamber flow path 20 to the other pressure chamber flow path 20 via the circulation flow path 250, and then circulated from the other pressure chamber flow path 20 to the common flow path 12. This makes it possible to prevent the ink in each pressure chamber flow path 20 from becoming thicker, stabilizing the ink ejection characteristics from the nozzles 15. Furthermore, because the circulation flow path 250 does not overlap with the common flow path 12 in the up-down direction D3, the movable area of ​​the damper 28A on the bottom surface 12A of the common flow path 12 is not limited by the circulation flow path 250. This makes it possible to prevent a decrease in the absorption of pressure fluctuations by the damper 28A.

[0072] Furthermore, by providing the connection path 260, similar to the first embodiment described above, it is possible to allow air bubbles in one pressure chamber 16 to flow to the other pressure chamber 16 via the connection path 260. This makes it possible to effectively discharge air bubbles from each pressure chamber 16.

[0073] <Third embodiment> Next, a head 1 according to a third embodiment of the present invention will be described with reference to Fig. 8. The head 1 in this embodiment does not have a connection path 260, the shape of the circulation path 350 is different from that of the circulation path 250 in the second embodiment, and the position of the nozzle 15 is different from that in the second embodiment, but otherwise is the same as the second embodiment described above. Note that components similar to those in the second embodiment are designated by the same reference numerals and will not be described again.

[0074] The circulation flow path 350 in this embodiment has a pair of first portions 351 extending in the second direction D2 and a second portion 352 connecting the pair of first portions 351. The first portions 351 extend in a direction away from the common flow path 12 from the connection portions with the respective communicating flow paths 17. The second portion 352 extends in the first direction D1 and connects the ends of the first portions 351 that are farthest from the common flow path 12. The first portions 351 correspond to the "extending portion" of the present invention.

[0075] The nozzle 15 is disposed at a position in the up-down direction D3 that does not overlap the communication flow path 17 but overlaps with the first portion 351. The nozzles 15 are also disposed side by side in the first direction D1.

[0076] In this embodiment, when ink flows into the common flow channel 12, the ink flows from the common flow channel 12 via the connection port 18A into one of the pressure chamber flow channels 20 that is closer to the supply port 111, of the two pressure chamber flow channels 20 that are connected to each other by the circulation flow channel 350. Then, ink flows from one of the pressure chamber flow channels 20 into which the ink has flowed into the other pressure chamber flow channel 20 that is closer to the return port 112, via the circulation flow channel 350, and returns to the common flow channel 12 via the connection port 18A. At this time, the ink in the circulation flow channel 350 flows in the direction away from the common flow channel 12 along the second direction D2 in the first portion 351 that is connected to one of the pressure chamber flow channels 20, flows in the same direction as the ink flowing in the common flow channel 12 in the second portion 352, and flows in the direction toward the common flow channel 12 along the second direction D2 in the first portion 351 that is connected to the other pressure chamber flow channel 20. In this way, ink circulates between the pressure chamber flow channels 20 and the common flow channel 12.

[0077] When the circulation flow path has a portion extending in the first direction D1 and this extending portion is connected to the communicating flow path 17, the ink ejected from the nozzle 15 is influenced by the ink flow flowing through this extending portion and is likely to deviate in the first direction D1 from the desired landing position. If the landing position is deviated in the first direction D1, white streaks are likely to occur on the paper 9 (printed material). However, in this configuration, the portion of the circulation flow path 350 connected to the communicating flow path 17 is the first portion 351 extending in the second direction D2, so the ink ejected from the nozzle 15 is hardly affected by the ink flow in the first direction D1. As a result, the ink ejected from the nozzle 15 is less likely to deviate in the first direction D1 from the desired landing position. Therefore, white streaks are less likely to occur on the paper 9. Note that, as a modified example, the first portion 351 may extend in a direction perpendicular to the up-down direction D3 and intersects both the first direction D1 and the second direction D2. Even in this case, the ink flow in the first direction D1 has little effect on the ink ejected from the nozzle 15. As a result, the ink ejected from the nozzle 15 is less likely to deviate in the first direction D1 from the desired landing position.

[0078] Furthermore, the nozzle 15 communicates with the communicating flow path 17 via the first portion 351, and is disposed at a position that does not overlap with the communicating flow path 17 in the vertical direction D3. This causes a flow of ink along the first portion 351 near the nozzle 15. This makes it easier to expel air bubbles in the nozzle 15 along the flow of ink. As a modified example, a portion of the nozzle 15 may overlap with the communicating flow path 17 in the vertical direction D3. This also achieves the same effect as described above. As another modified example, the entire nozzle 15 may overlap with the communicating flow path 17 in the vertical direction D3.

[0079] 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.

[0080] In the first embodiment described above, one dummy individual flow path 53 is arranged outside each of the individual flow paths 13 located at both ends of the individual flow path row 14R in the first direction D1, but a dummy individual flow path 53 may be arranged only on one side. In this case, the same effects as those described above can be obtained for the dummy individual flow path 53 and the individual flow path 13 (pressure chamber flow path 20) adjacent to the first direction D1.

[0081] Furthermore, the dummy individual flow paths 53 do not have to be arranged outside the individual flow paths 13 located at both ends of the individual flow path array 14R. In other words, the dummy individual flow paths 53 do not have to be provided. Even in this case, the connection ports 18A of the individual flow paths 13 located at both ends are far apart in the first direction D1, so the amount of ink flowing through the circulation flow path 50 increases, and the flow rate flowing into each pressure chamber flow path 20 can be increased. In this case, if the number of individual flow paths 13 (pressure chamber flow paths 20) connected by the circulation flow path 50 is three or more, the same effect as described above can be obtained.

[0082] Furthermore, the flow path resistance of the dummy individual flow path 53 or the dummy pressure chamber flow path 54 may be equal to or greater than the flow path resistance of the individual flow path 13 or the pressure chamber flow path 20 .

[0083] Furthermore, although the circulation channels 50, 250, 350 communicate the lower ends of the communication channels 17, they may also communicate portions of the pressure chamber channels 20 other than the lower ends of the communication channels 17 (for example, the central portions or upper ends of the communication channels 17 in the vertical direction D3, or the pressure chambers 16). When the circulation channels 50, 250, 350 communicate the pressure chambers 16, the connection channels 60, 260 may not be provided.

[0084] The length of the circulation flow path 50, 250, 350 in the up-down direction D3 may be less than the thickness of the plate 129. Furthermore, the circulation flow path 50, 250, 350 may be formed in a plate other than the plate adjacent to the plate 130. Furthermore, the circulation flow path 50, 250, 350 and the damper 28A may be formed in the same plate.

[0085] Furthermore, the pressure chamber flow path 20 may be formed from the pressure chamber 16. In other words, the pressure chamber 16 and the nozzle 15 may be directly connected. In this case, it is desirable that the circulation flow paths 50, 250, 350 communicate with the connection point between the pressure chamber 16 and the nozzle 15. Furthermore, the pressure chamber 16 and the nozzle 15 may communicate with each other via the circulation flow paths 50, 250, 350.

[0086] Furthermore, the cross-sectional area of ​​the connection paths 60, 260 perpendicular to the first direction D1 (the ink flow direction in the connection paths) may be equal to or greater than the cross-sectional area of ​​the pressure chamber 16 perpendicular to the second direction D2 (the ink flow direction in the pressure chamber).

[0087] 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.

[0088] The type of liquid ejection head of the present invention is not limited to the line type, but may also be a serial type.

[0089] The object onto which the droplets are ejected is not limited to paper, but may be, for example, a cloth, a substrate, or plastic.

[0090] 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.

[0091] 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]

[0092] 1 head (liquid ejection head) 12 Common flow path 12A bottom 15 nozzles 16 Pressure Chamber 17 Connecting flow path 20 Pressure chamber flow path 28A Damper 50,250,350 Circulation flow path 54 Dummy pressure chamber flow path 56 Dummy pressure chamber 57 Dummy connecting passage 60,260 connecting roads 128 Plate (Damper Plate) 129 Plate (return plate) 130 Plate (Nozzle Plate) 351 Part 1 D1 1st direction D2 2nd direction D3 Up and down direction

Claims

1. a plurality of nozzles arranged in a first direction perpendicular to the up-down direction; a plurality of pressure chamber flow paths arranged in the first direction and communicating with the plurality of nozzles, respectively; a common flow path extending in the first direction and communicating with the plurality of pressure chamber flow paths; a damper disposed along a bottom surface of the common flow path to absorb pressure fluctuations of the liquid in the common flow path, a circulation flow path that is arranged at a position that does not overlap with the common flow path in the vertical direction and that connects two of the pressure chamber flow paths adjacent to each other in the first direction;

2. a return plate in which the circulation flow path is formed, The liquid ejection head according to claim 1 , wherein the length of the circulation flow path in the vertical direction is the same as the thickness of the return plate.

3. a nozzle plate having the plurality of nozzles formed therein; 3. The liquid ejection head according to claim 2, wherein the nozzle plate and the return plate are adjacent to each other in the vertical direction.

4. a damper plate on which the damper is formed, 3. The liquid ejection head according to claim 2, wherein the damper plate and the return plate are disposed at different positions in the vertical direction.

5. the pressure chamber flow path includes a pressure chamber disposed above the nozzle, and a communication flow path having one end communicating with the nozzle and the other end communicating with the pressure chamber, the circulation flow path connects the communication flow paths included in the two adjacent pressure chamber flow paths to each other; A liquid ejection head as described in any one of claims 1 to 4, further comprising a connection path that is arranged above the circulation flow path and connects the pressure chambers included in the two adjacent pressure chamber flow paths to each other.

6. 6. The liquid ejection head according to claim 5, wherein a cross-sectional area of ​​the connection path perpendicular to the direction of liquid flow is smaller than a cross-sectional area of ​​the pressure chamber perpendicular to the direction of liquid flow.

7. the pressure chamber flow path includes a pressure chamber disposed above the nozzle, and a communication flow path having one end communicating with the nozzle and the other end communicating with the pressure chamber, the circulation flow path connects the communication flow paths included in the two adjacent pressure chamber flow paths to each other; The liquid ejection head according to claim 1 , wherein the circulation flow path has a portion extending from a connection portion with each of the communication flow paths in a second direction intersecting both the first direction and the vertical direction.

8. The liquid ejection head according to claim 7, characterized in that the nozzle is connected to the communicating flow path via the extending portion, and is arranged in the vertical direction at a position overlapping a portion of the communicating flow path or at a position not overlapping the communicating flow path.

9. 2. The liquid ejection head according to claim 1, wherein the circulation flow path connects three or more of the pressure chamber flow paths arranged in the first direction.

10. a dummy pressure chamber flow path communicating with the common flow path is arranged in line with the three or more pressure chamber flow paths in the first direction on one side of the pressure chamber flow path located at one end in the first direction among the three or more pressure chamber flow paths, 10. The liquid ejection head according to claim 9, wherein the circulation flow path connects the three or more pressure chamber flow paths and the dummy pressure chamber flow path.

11. 11. The liquid ejection head according to claim 10, wherein the resistance of the dummy pressure chamber flow path is smaller than the resistance of the pressure chamber flow path.

12. the pressure chamber flow path includes a pressure chamber disposed above the nozzle, and a communication flow path having one end communicating with the nozzle and the other end communicating with the pressure chamber, the dummy pressure chamber flow path includes a dummy pressure chamber and a dummy communication flow path that communicates with the dummy pressure chamber, the circulation flow path interconnects the communication flow paths included in each of the three or more pressure chamber flow paths and the dummy communication flow paths included in the dummy pressure chamber flow paths; A liquid ejection head as described in claim 10, further comprising a connection path arranged above the circulation flow path and connecting the pressure chambers included in each of the three or more pressure chamber flow paths and the dummy pressure chambers included in the dummy pressure chamber flow path to each other.

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