JP2019214169A - Inkjet head and image forming device - Google Patents

Abstract

To provide an inkjet head and an image forming device which can more effectively suppress deterioration in image quality.SOLUTION: The inkjet head comprises: a plurality of nozzles; a plurality of supply passages through which ink is supplied to the nozzles respectively; individual discharge passages 214 whose one ends are connected to the plurality of supply passages respectively, through which ink in the supply passages is discharged; and common discharge passages 222 connected with the other ends at the opposite sides to the one ends of the individual discharge passages. With respect to an ink discharge direction of the common discharge passages, between third end parts at the most upstream side and the other ends closest to the third end parts are provided openings 226a into which ink flows. The plurality of other ends are arranged along rows, sectioned into two ranges for each row and connected to second discharge passages different from each other in the two ranges. In the two common discharge passages, either end parts of the third end parts and fourth end parts at the other side to the third end parts are adjacent to each other, and the other end parts are both ends.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an inkjet head and an image forming apparatus.

  2. Description of the Related Art There is an image forming apparatus (inkjet recording apparatus) that discharges ink from a nozzle and lands on a medium to record an image or the like. In this image forming apparatus, by applying pressure fluctuation to ink in an ink flow path communicating with each nozzle, a droplet having an ink amount and speed corresponding to the pressure fluctuation is ejected from the nozzle.

  However, if air bubbles or foreign substances are mixed in the ink, there is a problem that an appropriate pressure fluctuation is not applied to the ink, or these air bubbles or foreign substances are clogged in the nozzle, thereby causing a discharge failure. In addition, if the ink is not discharged in the ink flow path, the ink components are separated from the ink or the water evaporates from the nozzle openings. There's a problem. On the other hand, there is a technique in which a discharge flow path for discharging ink separately from the nozzle from an ink flow path through which ink supplied to the nozzle flows is provided to effectively discharge ink, bubbles, and foreign substances. As the discharge flow path, a first discharge flow path branched from each of the ink flow paths and a second discharge flow path to which the downstream side of the discharge ink flow of the plurality of first discharge flow paths is respectively connected are combined to form a second discharge flow path. By making the cross-sectional area of the flow path sufficiently larger than that of the first discharge flow path, it is possible to reduce the arrangement space of the discharge flow path and improve the discharge efficiency (Patent Documents 1 and 2).

  Further, in Patent Document 3, by providing a bypass flow path through which a part of the ink supplied to the nozzle is provided at the most upstream end of the second discharge flow path, the discharged ink (that is, the bubble A technique is disclosed in which ink does not stagnate due to the flow of foreign matter or accumulated ink, thereby appropriately discharging ink from each first discharge channel to the second discharge channel.

JP 2010-241120 A JP-T-2015-509454A JP 2015-36238 A

  However, as the number and arrangement density of the nozzles increase in response to the demand for higher resolution and higher speed of the image forming apparatus, the conventional discharge flow path has a longer second discharge flow path, and each of the first discharge flow paths has a longer length. The difference in the distance from the connection position with the second discharge flow path, that is, each inflow position into the second discharge flow path, to the outlet of the second discharge flow path, that is, the outlet from the second discharge flow path increases. As a result, a pressure distribution is generated in accordance with the pressure loss of the discharged ink flow in the second discharge flow path, and the outflow characteristics of the discharged ink in the first discharge flow path are different, which eventually leads to a reduction in image quality. is there.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet head and an image forming apparatus that can more effectively suppress a decrease in image quality.

In order to achieve the above object, the invention according to claim 1 is:
A plurality of nozzles for discharging ink,
A plurality of supply channels for supplying ink to the nozzles,
A first discharge channel connected to the plurality of supply channels at a first end to discharge ink in the supply channel;
A second discharge flow path to which a second end of the plurality of first discharge flow paths opposite to the first end is connected,
With
The supply is provided between a third end on the most upstream side in the ink discharge direction of the second discharge flow path and the second end closest to the third end in the ink discharge direction. An ink inlet for ink supplied without passing through the flow path is provided,
The plurality of second end portions are arranged along one or more rows, are divided into two ranges different from each other in a direction along the row for each row, and are different from each other in the two ranges. Connected to the second discharge channel,
The second discharge passage is connected to the third end and the third end of the two second discharge passages connected to the second ends of the two ranges. An ink jet head characterized in that one of the fourth ends is adjacent and the other is both ends.

According to a second aspect of the present invention, in the inkjet head according to the first aspect,
A plurality of the inflow ports are provided for one of the second discharge channels.

According to a third aspect of the present invention, in the inkjet head according to the first or second aspect,
The two second discharge passages respectively connected to the second ends of the two ranges are characterized in that the third ends are arranged adjacent to each other.

According to a fourth aspect of the present invention, in the inkjet head according to any one of the first to third aspects,
A first ink storage unit that stores the ink to be supplied to the plurality of supply channels,
A bypass flow path connecting the first ink reservoir and the inflow port,
It is characterized by providing.

According to a fifth aspect of the present invention, in the inkjet head according to the fourth aspect,
One of the bypass passages is connected to a plurality of the inlets.

According to a sixth aspect of the present invention, in the inkjet head according to the fourth or fifth aspect,
The two second discharge flow paths respectively connected to the second ends of the two ranges are arranged such that the third ends are adjacent to each other,
The bypass channel is provided between the third ends adjacent to each other.

According to a seventh aspect of the present invention, in the inkjet head according to any one of the fourth to sixth aspects,
The bypass flow path connected to the one second discharge flow path is a composite flow path of the bypass flow path that is smaller than the composite flow path resistance of the first discharge flow path connected to the one second discharge flow path. It is characterized in that it is provided in a number and a shape that increases the road resistance.

According to an eighth aspect of the present invention, in the ink jet head according to any one of the first to seventh aspects,
A predetermined range from the third end of the inner wall surface of the second discharge channel has a shape in which a cross-sectional area perpendicular to the ink discharge direction is monotonically non-decreasing toward the downstream in the ink discharge direction. It is characterized by the following.

According to a ninth aspect of the present invention, in the inkjet head according to the eighth aspect,
The inner wall surface in the predetermined range includes a curved surface shape.

According to a tenth aspect of the present invention, in the inkjet head according to any one of the first to ninth aspects,
The lengths of the second discharge passages provided in the two ranges are equal to each other.

The invention according to claim 11 is
An image forming apparatus comprising the inkjet head according to any one of claims 1 to 10.

According to a twelfth aspect of the present invention, in the image forming apparatus according to the eleventh aspect,
A second ink storage unit that stores ink to be supplied to the second discharge channel via the plurality of supply channels and the inflow port;
A circulation unit that returns the ink discharged from the second discharge flow path to the second ink storage unit;
It is characterized by providing.

  ADVANTAGE OF THE INVENTION According to this invention, there exists an effect that degradation of image quality can be suppressed more effectively.

FIG. 2 is a perspective view illustrating a schematic configuration of an inkjet recording apparatus. FIG. 3 is a bottom view of the head unit as viewed from an ink ejection surface side. FIG. 2 is a perspective view illustrating an appearance of the inkjet head. FIG. 2 is a schematic diagram illustrating the entire ink flow path configuration. FIG. 3 is a diagram showing a part of a cross section of a head chip. FIG. 3 is a diagram illustrating a structure of an ink discharge channel in a head chip. FIG. 3 is a diagram illustrating a structure of an ink discharge channel in a head chip. It is sectional drawing of a head chip. It is a figure explaining the modification 1 of a bypass passage. It is a figure explaining the modification 2 of a bypass passage. It is a figure explaining the modification 3 of a bypass passage. It is a figure explaining the modification 4 of a bypass passage. FIG. 9 is a schematic diagram illustrating the entire configuration of an ink flow path including an inkjet head according to a second embodiment. FIG. 4 is a diagram for describing discharge of ink from a common discharge channel.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a perspective view showing a schematic configuration of an ink jet recording apparatus 1 which is a first embodiment of the image forming apparatus of the present invention. The ink jet recording apparatus 1 includes a transport unit 2 and a head unit 3.

  The transport unit 2 includes two transport rollers 2a and 2b, a ring-shaped transport belt 2c, and the like. The transport rollers 2a and 2b are arranged in parallel with the direction in which the rotation axis extends in the X direction. The transport belt 2c is stretched between the transport rollers 2a and 2b, and moves around when the transport roller 2a rotates according to the operation of a transport motor (not shown). The transport roller 2b rotates according to the orbital movement of the transport belt 2c. In a section in which the outer peripheral surface (conveying surface) of the conveying belt 2c is oriented in the Z direction (upward), the recording medium M placed on the outer peripheral surface is conveyed in the Y direction according to the orbital movement of the conveying belt 2c. .

  The head unit 3 records an image on the recording medium M conveyed by the conveyance unit 2 by discharging ink at an appropriate timing based on the image data. The head unit 3 is arranged so that the ink can be ejected in the direction of the transport surface within a range where the recording medium M is placed on the transport surface, and here, the transport surface and the ink ejection surface face each other. . In the ink jet recording apparatus 1, a plurality of, for example, four head units 3 for ejecting four color inks of yellow (Y), magenta (M), cyan (C), and black (K) respectively include, for example, a recording medium. The colors are arranged at predetermined intervals in the order of Y, M, C, and K from the upstream side in the transport direction of M. The number of head units 3 need not be four, and ink of the number of colors corresponding to the number of head units 3 can be ejected. Further, in addition to the colored ink, a transparent ink for forming a film or the like may be included.

  FIG. 2 is a bottom view of the head unit 3 as viewed from the ink ejection surface side. Each of the head units 3 has a plurality of, here eight, ink jet heads 100, and these ink jet heads 100 are fixedly held on a support member. In each of the inkjet heads 100, openings N of a plurality of nozzles are arranged on a surface (nozzle surface) on the ejection surface side of the head chip 101. Here, the openings N are provided on nozzle rows extending in the X direction (direction perpendicular to the transport direction) at four positions in the Y direction (transport direction). The openings N are arranged at predetermined intervals (nozzle intervals) continuously over the width in which images can be recorded on the recording medium M in the X direction as a whole.

  The recording medium M is not particularly limited, but may be a sheet cut to a certain size. The recording medium M is supplied onto a transport belt 2c from a medium supply unit (not shown), and ink ejected from the head unit 3 lands to record an image (may include drying and fixing operations as necessary). After that, the sheet is sent from the transport section 2 to the medium discharge section. Alternatively, roll paper may be used as the recording medium M. Further, as the recording medium M, in addition to paper such as plain paper or coated paper, various media such as cloth or sheet-like resin that can fix ink that has landed on the surface may be used.

  FIG. 3 is a perspective view illustrating an appearance of the inkjet head 100 included in the head unit 3. The inkjet head 100 according to the present embodiment includes a head chip 101, a holding unit 102, a common ink chamber 103, and the like. The inkjet head 100 is held by the head unit 3 in a direction in which the head chip 101 faces the transport belt 2c.

As described above, the openings N of the nozzles are two-dimensionally arranged in the head chip 101, and ink is ejected from the openings N of the nozzles. Note that the arrangement of the openings N in FIG. 3B is for explanation, and does not reflect the actual nozzle spacing, the number of openings N, and the like.
The holding unit 102 is joined to the upper surface of the head chip 101 (the side opposite to the nozzle surface side, + Z side), and supports the common ink chamber 103.

  As shown in FIG. 3A, the common ink chamber 103 is provided with a common supply ink chamber 1031 (first ink storage unit) for storing ink to be supplied to the opening N, and is collected (discharged) without being discharged from the opening N. 2) and two common discharge ink chambers 1032 for storing the collected ink. In each ink chamber, ink of a color (here, any of YMCK) ejected from each head unit 3 is stored. Here, the common supply ink chamber 1031 is provided at the center of the common ink chamber 103, and the common discharge ink chamber 1032 is provided on both sides in the X direction of the common supply ink chamber 1031 in plan view from above.

  At a substantially center of the common ink chamber 103 (common supply ink chamber 1031), a space is provided through which a flexible printed board (FPC 111) connected to the head chip 101 penetrates. Ink is supplied to the common supply ink chamber 1031 via a supply port 1033 (inlet). Ink is discharged from the common discharge ink chamber 1032 through a discharge port 1034 (outlet).

  FIG. 4 is a schematic diagram showing the entire ink flow path configuration. The inkjet recording apparatus 1 includes a main tank 91, a supply sub-tank 92 (second ink storage section), a reflux sub-tank 93, and the like.

  The main tank 91 stores the ink supplied to the supply sub-tank 92. The main tank 91 is connected to a supply sub-tank 92 by an ink flow path 71 via a liquid feed pump 81. By the operation of the liquid sending pump 81, the ink is sent from the main tank 91 to the supply sub-tank 92.

  The supply sub-tank 92 stores ink supplied to the common supply ink chamber 1031 of the inkjet head 100. The supply sub-tank 92 is connected to the supply port 1033 by the ink flow path 72.

  The reflux sub-tank 93 stores the ink discharged from the common discharge ink chamber 1032. The reflux sub-tank 93 is connected to two discharge ports 1034 by an ink flow path 73.

The supply sub-tank 92 and the reflux sub-tank 93 are connected by an ink flow path 74 via a liquid feed pump 82. By the operation of the liquid supply pump 82, the ink in the reflux sub-tank 93 is returned to the supply sub-tank 92.
The ink flow paths 73 and 74, the reflux sub-tank 93, and the liquid feed pump 82 constitute a circulating unit in the image forming apparatus (inkjet recording apparatus 1) of the present embodiment.

  The supply sub-tank 92 is provided at a position higher than the ink ejection surface of the head chip 101 in the vertical direction, and the reflux sub-tank 93 is provided at a position lower than the ink ejection surface in the vertical direction. Therefore, the ink at the supply port 1033 depends on the pressure P1 due to the head difference between the liquid surface of the supply sub-tank 92 and the ink discharge surface, and the pressure P2 due to the head difference between the ink discharge surface and the reflux sub-tank 93. Is higher than the pressure of the ink at the discharge port 1034. The height (that is, the pressure P2) of the supply sub-tank 92 and the reflux sub-tank 93 in the vertical direction may be changeable.

  FIG. 5 is a diagram showing a part of a cross section of the head chip 101. Here, a cross section taken along a cross section line AA in FIG. 3 including one nozzle 211 and the connection portion 35 is shown.

  The head chip 101 has a nozzle substrate 21, an intermediate substrate 22, an actuator substrate 23, a protection substrate 24, and the like. The nozzle substrate 21, the intermediate substrate 22, the actuator substrate 23, and the protection substrate 24 are sequentially stacked.

  The nozzle substrate 21 is, for example, an SOI substrate (Silicon on Insulator) having an oxide film layer 21b interposed between a nozzle layer 21a of a Si layer and a nozzle support layer 21c. Alternatively, the nozzle substrate 21 may be formed of a resin material such as polyimide or a metal material such as SUS.

  The nozzle layer 21a is provided with a plurality of nozzles 211 for discharging ink droplets. The thickness of the nozzle layer 21a in the Z direction is, for example, 10 to 20 μm. Here, for example, a plurality of rows (for example, four rows) of nozzles 211 arranged at predetermined intervals in the X direction (nozzle rows) are provided at positions different from each other in the Y direction (transport direction).

  The nozzle support layer 21c has a thickness of, for example, 100 to 300 μm. The nozzle support layer 21c is provided with a through hole 213 serving as an ink flow path, an individual discharge flow path 214 (first discharge flow path), and the like. One end (first end) of the individual discharge channel 214 is connected to the through hole 213 (that is, a supply channel described later), and the other end (second end) is on the + Z side of the nozzle support layer 21c. Is connected to the common discharge channel 222 (second discharge channel). Here, the individual discharge channel 214 is open to the -Z side (bottom surface) of the nozzle support layer 21c, and the oxide film layer 21b forms an inner wall surface on the bottom surface side. Alternatively, the portion of the oxide film layer 21b facing the individual discharge channel 214 may be removed, and the upper surface of the nozzle layer 21a may form the inner wall surface on the bottom side of the individual discharge channel 214. Further, an individual discharge channel 214 may be provided over the nozzle layer 21a as long as the strength of the nozzle substrate 21 can be obtained.

The oxide film layer 21b is, for example, a SiO ₂ layer having a thickness of 0.3 to 1.0 μm. The oxide film layer 21b is provided with a through hole 212 for communicating between the nozzle 211 of the nozzle layer 21a and the through hole 213 of the nozzle support layer 21c. The through holes 212 and 213 are concentric with the nozzle 211 in a plan view, and the inner diameter of the through holes 212 and 213 is larger than the inner diameter of the nozzle 211. The nozzle 211 has an inverted tapered shape, and the inner diameter is smaller as it is closer to the opening N.

  The intermediate substrate 22 is made of, for example, a Si substrate having a thickness of 100 to 300 μm. The intermediate substrate 22 is provided with a through hole 221, a common discharge channel 222, a pressure buffer 223 (damper), and the like.

  The through hole 221 penetrates the intermediate substrate 22 in the Z direction and is connected to the through hole 213. The shape of the through hole 221 is not limited to a simple columnar shape. The diameter (cross-sectional area) of the through-hole 221 may be made non-uniform or the like, so that the magnitude of the pressure loss, that is, the kinetic energy at the time of ink ejection may be adjusted to an appropriate magnitude. .

  As described above, the other end of the individual discharge channel 214 (the end opposite to the side connected to the through hole 213) is connected to the common discharge channel 222. The common discharge channel 222 is connected to the common discharge ink chamber 1032 (not shown). Note that the individual discharge channel 214 may be provided in the intermediate substrate 22, and the through hole 221 and the common discharge channel 222 may be connected inside the intermediate substrate 22.

  The pressure buffer section 223 includes a thin plate 223a having a thickness (thickness) enough to have flexibility, and an air chamber 223b. Here, the thin plate 223a forms at least a part of the upper wall surface of the common discharge channel 222. The air chamber 223b is provided on the opposite side of the thin plate 223a from the common discharge channel 222 (here, above the thin plate 223a). The thickness of the air chamber 223b in the height direction is at least such that the deformation of the thin plate 223a is not hindered (for example, 1 to 100 μm). The volume of the air chamber 223b is smaller than the volume of the common discharge channel 222. The air chamber 223b may be connected to the atmosphere or may be closed. Further, a cover member or the like for opening and closing the hole for communicating with the atmosphere may be provided.

  When the ink pressure in the common discharge channel 222 changes, or when a pressure wave is transmitted through the ink, the pressure buffer 223 controls the thin plate 223a according to the difference between the ink pressure and the air pressure in the air chamber 223b. Deforms and vibrates to mitigate and attenuate pressure changes. Further, the thin plate 223a may be elastically (expanded or contracted) deformed according to the difference between the ink pressure and the air pressure in the air chamber 223b, or the elastically deformed member may be formed on the surface of the thin plate 223a (the common discharge channel). 222 side).

  The intermediate substrate 22 may be configured by a separate substrate including a portion including the common discharge channel 222 and the thin plate 223a and a portion including the air chamber 223b, and may be stacked.

  The actuator substrate 23 includes a pressure chamber layer 23a and a vibration layer 23b. The pressure chamber layer 23a is made of, for example, a Si substrate of about 100 to 300 μm. The pressure chamber layer 23a is provided with an ink flow path including a pressure chamber 231 for applying pressure fluctuation to the ink. One end of the ink flow path is connected to the through hole 221 of the intermediate substrate 22. Here, the ink flow path is provided vertically penetrating the pressure chamber layer 23a, the upper surface of the intermediate substrate 22 becomes a lower wall surface, and the vibration layer 23b becomes an upper wall surface.

  The vibration layer 23b is, for example, a thin elastically deformable Si substrate having a thickness of about 1 to 10 μm, and is provided in contact with the upper surface of the pressure chamber layer 23a. The vibration layer 23b is provided with a through hole 232 for communicating the other end of the ink flow path of the pressure chamber layer 23a (the end opposite to the side connected to the through hole 221) with the common supply ink chamber 1031. Have been.

  On the upper surface of the vibration layer 23b (on the surface opposite to the pressure chamber layer 23a), the pressurizing portion 31 is provided in accordance with the position of the pressure chamber 231 in plan view when viewed from above. The pressing unit 31 has a lower electrode 311, a piezoelectric layer 312, and an upper electrode 313, which are sequentially laminated and fixed. The lower electrode 311 is fixed on the upper surface of the vibration layer 23b, and the vibration layer 23b is distorted by the expansion and contraction of the piezoelectric layer 312 according to the voltage difference applied between the upper electrode 313 and the lower electrode 311. By periodically changing the voltage between the upper electrode 313 and the lower electrode 311, the strain pattern of the vibrating layer 23 b is periodically changed, and the volume of the pressure chamber 231 is changed according to the strain. A pressure change is applied to the ink inside 231.

  The lower electrode 311 is a thin film layer of, for example, titanium (Ti) or platinum (Pt). The piezoelectric layer 312 is, for example, lead zirconate titanate (PZT). The upper electrode 313 is a thin film of, for example, chromium (Cr) or gold (Au). These may be formed by sequentially forming films on the upper surface of the vibration layer 23b.

On the upper surface of the actuator substrate 23, a signal wire 36 for supplying a drive voltage signal to the lower electrode 311 and the upper electrode 313, and a connection portion 35 for connecting the signal wire 36 to a wire connecting the drive portion are provided. Is provided. Here, the connection part 35 is, for example, a connection part of the FPC 111 provided with the drive IC to the actuator board 23. As described above, the FPC 111 is drawn upward from the substantially central portion of the common supply ink chamber 1031. The circuit wiring of the FPC 111 and the signal wiring 36 on the actuator board 23 are thermocompression-bonded at the connection part 35 via, for example, an anisotropic conductive film (ACF) interposed therebetween. Alternatively, the connection may be made using an anisotropic conductive paste (ACP) or a silver paste. The signal wiring 36 and the vibration layer 23b are appropriately insulated from each other by an insulating layer (for example, an SiO ₂ film). Here, a common potential (for example, a ground potential) is supplied to the lower electrode 311, and individual drive voltage signals are sent to the upper electrode 313 by individual wiring.

  The protection substrate 24 is, for example, a substrate made of a 42 alloy, and a space for accommodating the pressurizing portion 31 and the like is formed on the contact surface side with the actuator substrate 23. Further, a through-hole 241 is formed in the protection substrate 24 in the up-down direction. The through hole 241 connects between the common supply ink chamber 1031 and the through hole 232.

  That is, the ink supplied from the supply sub-tank 92 to the common supply ink chamber 1031 via the supply port 1033 passes through the through-holes 241 and 232, the ink flow path including the pressure chamber 231 and the through-holes 221 and 213, respectively. Sent to 211. That is, from the entrance to the through hole 241 in the common supply ink chamber 1031 to the boundary of the through hole 213 with the nozzle 211 is a supply flow path for supplying ink to each nozzle. The ink that is not ejected from the nozzle 211 among the inks sent to the through holes 213 flows into the common ejection ink chamber 1032 through the individual ejection channel 214 and the common ejection channel 222, and further flows from the ejection port 1034 to the sub-tank 93 for reflux. Is returned to. This ink is circulated by being sent from the reflux sub-tank 93 to the supply sub-tank 92 again through a filter or the like that removes foreign matter and the like as appropriate.

  FIGS. 6 and 7 are diagrams illustrating the structure of the ink discharge channel in the head chip 101. FIG. FIG. 6A is a view of the ink discharge passage viewed from above. FIG. 6B is an enlarged view showing the vicinity of an end adjacent to the common discharge channel 222 at substantially the center in the X direction. FIG. 7A is a cross-sectional view taken along a cross-sectional line BB of FIG. FIG. 7B is a cross-sectional view taken along a cross-sectional line CC in FIG. FIG. 8 is a sectional view taken along section line DD in FIG.

  The common discharge flow path 222 to which the plurality of individual discharge flow paths 214 are connected at the second end is provided for each nozzle row (the row of the second end along the nozzle row) in the nozzle row direction (X direction). In the vicinity of the center, two sections are provided, each of which is divided into two different areas and extends in the ± X direction. The common discharge channel 222 is connected to ink discharge chambers 225 provided near both ends in the ± X direction of the head chip 101 at both ends (here, the fourth end; the other end with respect to the third end). Have been.

  Ends near the center (third end in this case) of the common discharge channel 222 are arranged adjacent to each other with a wall surface interposed therebetween, and near the third end, an opening 226a (inlet) is provided. Is provided. The wall only needs to separate the two common discharge channels 222 and may be sufficiently thin. The opening 226a connects the common supply ink chamber 1031 and the common discharge channel 222 via a bypass channel formed by through holes 226, 233, and 242. That is, a part of the ink in the common supply ink chamber 1031 can flow into the vicinity of the third end of the common discharge channel 222 from the opening 226a via the bypass channel. As the length of the common discharge channel 222 separated by the wall surface is equal, the difference in the pressure distribution by the longer common discharge channel 222 is reduced, but the two common discharge channels 222 depend on the arrangement of the nozzle 211 and the like. May be slightly different (that is, for example, within a range of several times the nozzle interval).

  The diameters of the through holes 226, 233, and 242 (the cross-sectional area in a plane perpendicular to the direction in which the flow path extends) may or may not be the same, and the diameters may be partially or wholly continuous. For example, it may have a tapered shape so as to change. The aperture (shape) and the length of the bypass channel may be determined so that the channel resistance (pressure loss of the flowing ink) has an appropriate value. In particular, the combined flow path resistance of the plurality of individual discharge flow paths 214 connected to one common discharge flow path 222 is equal to the flow path resistance of the bypass flow path (when a plurality of bypass flow paths are connected as described below). Is smaller than the combined flow path resistance), the shape and length of the bypass flow path (in the case of a plurality of paths, the number in addition to these) may be determined. Accordingly, in the inkjet head 100, the ink discharged from the individual discharge flow path 214 flows back to the bypass flow path, and the inflow of the ink in the individual discharge flow path 214 is prevented by a large amount of ink flowing from the bypass flow path. Can be suppressed.

  The ink flowing from the opening 226 a forms an ink flow in the common discharge channel 222 that is sent to the ink discharge chamber 225 without stagnation of the ink, bubbles, foreign matter, and the like flowing from the individual discharge channel 214. That is, the third end is the most upstream side in the ink discharge direction. The discharge side end (second end) of the individual discharge flow path 214 is provided between the opening 226a (the most upstream of the ink flow) and the ink discharge chamber 225a (the most downstream of the ink flow). (In other words, since the opening 226a is provided between the third end and the second end closest to the third end in the ink discharge direction), the individual discharge flow path 214 Does not stop until the ink discharged from the ink is discharged to the ink discharge chamber 225.

  Since the common discharge channel 222 is divided in the X direction, the difference in the distance from the connection position with each individual discharge channel 214 to the ink discharge chamber 225 can be reduced. Thereby, a difference in ink pressure (ie, a difference in pressure loss) from the branch position (first end) of each individual discharge flow path 214 from the ink flow path to the ink discharge chamber 225 (fourth end). Is kept small, and the difference in outflow characteristics is reduced.

  A discharge communication port 228a is provided above the ink discharge chamber 225 (on the + Z side). The discharge communication port 228a connects the common discharge ink chamber 1032 and the ink discharge chamber 225 via the through holes 228, 234, and 243 (collectively, bypass paths) without passing through the supply flow path. The ink flowing from the common discharge channel 222 into the ink discharge chamber 225 flows out from the discharge communication port 228a to the common discharge ink chamber 1032.

  FIG. 9 is a diagram illustrating a first modification of the bypass passage. The same reference numerals are used for the same configurations (including those whose locations have been changed) that are the same as those shown by the reference numerals in FIGS. 6 to 8.

  One common bypass channel (through holes 226, 233, 242) is provided for a plurality (two) of openings 226a provided at the first end of each of the adjacent common discharge channels 222 (see FIGS. Connected). As shown in FIG. 9B, here, the positions of the through holes 233 and 242 are not at the center of the two openings 226a in the X direction, but may be provided at the center. Further, similarly to the above-described embodiment, the diameter of the through holes 233 and 242 may be changed in the middle in the extending direction (Z direction). The positions of the through holes 233 and 242 may be appropriately determined so as to avoid a positional relationship with other components, for example, electrical wiring provided on the actuator substrate 23.

  FIG. 10 is a diagram illustrating a second modification of the bypass passage. The same reference numerals are used for the same configurations (including those whose locations have been changed) that are the same as those shown by the reference numerals in FIGS. 6 to 8.

  Here, two (plural) openings 226 a are provided for each common discharge channel 222. When a bypass channel having a sufficient diameter cannot be formed due to a configuration between the common discharge channel 222 and the common supply ink chamber 1031, for example, a positional relationship with an electrical wiring or the like, a plurality of bypass channels are required. Is connected to one common discharge channel 222, the combined flow channel resistance is reduced, and the ink can flow into the common discharge channel 222 at an appropriate pressure.

  Here, the openings 226 a are provided near both ends in the Y direction near the third end of each common discharge channel 222, however, the discharge ports (second The opening 226a may be provided at a different position in the X direction as long as the opening is located on the upstream side of the second end of the individual discharge channel 214 having the opening.

  In this case, similarly to the first modification, the common discharge flow from one bypass flow path via the opening 226a at the same position (not necessarily strictly equal) in the Y direction in the adjacent common discharge flow path 222. The ink may flow into the passage 222.

  FIG. 11 is a diagram illustrating a third modification of the bypass flow path. The same reference numerals are used for the same configurations (including those whose locations have been changed) that are the same as those shown by the reference numerals in FIGS. 6 to 8.

  Here, instead of being provided on the upper surface (the surface on the + Z side) of the common discharge channel 222, the opening 226a is provided on the side surface (the surface on the + Y side, that is, the individual discharge channel 214 connected to the common discharge channel 222). On the side opposite to the side provided). If there is no empty space just above the common discharge channel 222 due to another configuration, for example, electric wiring or the like, the opening 226a is provided on the side surface as described above, and the inside of the bypass channel from above (+ Z side) is formed. The ink flow may flow into the common discharge channel 222 while changing its direction in the −Y direction at the hole 2261.

  Further, here, the common discharge channel 222 is not in the shape of a rectangular parallelepiped, but has a curved shape at the −Y side of the third end, that is, the corner in the inflow direction of the ink flowing from the opening 226a. This curved surface shape is determined such that the cross-sectional area perpendicular to the ink discharge direction increases toward the downstream in the discharge direction (monotonic non-decreasing). Accordingly, it is possible to prevent the ink that has flowed into the common discharge channel 222 from easily stagnating near the third end or the second end of the individual discharge channel 214 on the upstream side. Here, only the side surface is rounded, but in addition to or instead of this, the connection portion between the side surface and the top surface (+ Z side) or the bottom surface (−Z side) may be rounded. Further, it may be rounded at a connection portion between the bottom surface of the hole 2261 and the facing surface (+ Y side) of the opening 226a.

  FIG. 12 is a diagram illustrating a fourth modification of the bypass passage. The same reference numerals are used for the same configurations (including those whose locations have been changed) that are the same as those shown by the reference numerals in FIGS. 6 to 8.

  Here, the opening 226a is provided on the side surface between the third ends of the common discharge channel 222. Accordingly, the thickness of the wall between the two common discharge channels 222 adjacent to each other at the third end is set to a thickness sufficient to provide two holes 2262 therebetween. On the other hand, since the arrangement of the opening N of the nozzle 211 and the corresponding through holes 221 and 213 is determined in advance in accordance with the nozzle interval and the arrangement interval of the pressurizing section 31, the individual discharge flow path 214 is 213 and the common discharge channel 222 extend obliquely with respect to the Y direction.

  In this case, the ink flow from the bypass flow path to the common discharge flow path 222 through the opening 226a flows from the third end in the common discharge flow path 222 in the ± X direction, and flows out to the ink discharge chamber 225. I do. As in the above-described embodiment and each of the modifications, the number of openings 226a provided for one common discharge channel 222, the opening area, and the opening position with respect to the wall surface are different from each other, such as the positional relationship with the electric wiring. May be determined as appropriate.

As described above, the inkjet head 100 according to the first embodiment includes a plurality of nozzles 211 for discharging ink, a plurality of supply channels for supplying ink to the nozzles 211, and the first supply channel for each of the plurality of supply channels. The individual discharge flow path 214 connected at the end to discharge the ink in the supply flow path, and the second end opposite to the first end of the plurality of individual discharge flow paths 214 are connected respectively. A common discharge channel 222. The common discharge flow path 222 does not pass through the supply flow path between the third end on the most upstream side in the ink discharge direction and the second end closest to the third end in the ink discharge direction. An opening 226a serving as an inflow port for the ink supplied to the printer is provided. The plurality of second ends are arranged along one or a plurality of columns, are divided into two ranges different from each other in a direction (X direction) along the column, and are mutually separated in the two ranges. They are connected to different common discharge channels 222. The common discharge channel 222 is a third end of the two common discharge channels 222 connected to the second ends of the two ranges, and a fourth end opposite to the third end. Are adjacent to each other, and the other ends are both ends.
In this manner, by dividing the common discharge flow path conventionally formed as one connection for each nozzle row into two, the increase in the pressure difference in the direction along the common discharge flow path is suppressed, and each individual discharge flow The unevenness of the inflow of ink from the path 214 is suppressed. Thereby, in the inkjet head 100, the non-uniformity of the influence on the ink ejection operation can be reduced. In addition, by connecting the vicinity of one side to the bypass flow path and connecting the other side to the ink discharge chamber 225, an ink flow is appropriately generated, and the ink flow is appropriately generated in the common discharge flow path 222 (further back to the individual discharge flow path 214). Ink or in the supply flow path). That is, in the ink jet head 100, bubbles and foreign substances in the supply flow path can be properly eliminated, and unevenness of ink components, changes in viscosity, temperature, and the like in the supply flow path can be appropriately suppressed. By arranging either the inflow side or the discharge side to be adjacent to each other, the configurations of the bypass flow path and the ink discharge flow path can be appropriately separated, and the common configuration can be appropriately used. The structure of the head is not complicated, and the head can be efficiently arranged to suppress the increase in size. Therefore, in the inkjet head 100, it is possible to more effectively suppress the deterioration of the image quality.

  In the inkjet head 100, a plurality of openings 226a are provided for one common discharge channel 222. That is, when a bypass channel having a required thickness cannot be formed due to a positional relationship with another configuration such as electric wiring, the shape is divided into a plurality of lines to supply ink to the common discharge channel 222. Thus, the ink in the common discharge channel 222 can be properly discharged.

  The two common discharge channels 222 connected to the second ends of the two ranges of the individual discharge channels 214 arranged in a row, respectively, have their third ends adjacent to each other. ing. As described above, in particular, by providing the inflow side at the center side of the head chip 101, it is easy to discharge and discharge the ink to the common discharge ink chamber 1032 by unifying and discharging the ink discharge channels using the space at the peripheral portion of the head chip 101. Become. Therefore, it is possible to efficiently discharge the ink by effectively using the space, and to suppress the deterioration of the image quality.

  Further, the inkjet head 100 includes a common supply ink chamber 1031 for storing ink to be supplied to the plurality of supply flow paths, and a bypass flow path connecting the common supply ink chamber 1031 and the opening 226a. The configuration in which ink is supplied directly from the common supply ink chamber 1031 for supplying ink to the nozzles to the common discharge flow path 222 by bypassing the supply flow path makes it possible to easily and properly discharge foreign matter and bubbles near the nozzles. It is possible to stably suppress a decrease in image quality.

  In the example of the second modification, one bypass passage is connected to the plurality of openings 226a. In particular, when the openings 226a are provided adjacent to each other near the center of the head chip 101, by flowing ink from the common bypass channel to the common discharge channel 222 through these openings 226a, a simpler structure and more appropriate Foreign matter, bubbles, and the like can be discharged to perform an image forming operation with stable image quality.

  Further, in the example of Modification 4, the bypass flow path is provided between the adjacent third ends. Accordingly, the ink can flow more uniformly and smoothly from the uppermost stream side of the common discharge channel 222, and a stable ink flow can be generated inside the common discharge channel 222. This makes it possible to discharge foreign substances and bubbles more reliably, and to reduce the influence on the ink ejection characteristics from each nozzle 211.

  In addition, the bypass flow path connected to the one common discharge flow path 222 is smaller than the composite flow path resistance of the individual discharge flow path 214 connected to the one common discharge flow path 222 in the combined flow path of the bypass flow path. They are provided in numbers and shapes that increase the resistance. Accordingly, the flow of ink from the individual discharge flow path 214 to the common discharge flow path 222 and the flow of ink from the common discharge flow path 222 to the ink discharge chamber 225 are not hindered. Foreign matter and the like can be discharged.

  Further, in a predetermined range from the third end of the inner wall surface of the common discharge channel 222, the cross-sectional area perpendicular to the ink discharge direction gradually increases toward the downstream in the ink discharge direction (monotonic non-uniformity). Decrease). Accordingly, it is possible to generate a more stable ink flow without the ink flowing from the opening 226a staying in the common discharge channel 222.

  Further, the inner wall surface in the above-mentioned predetermined range includes a curved surface shape. That is, it is possible to more effectively suppress stagnation of ink at a corner or the like due to a combination of planes.

  In addition, the lengths of the common discharge channels 222 provided in the two ranges according to the arrangement of the second end of the individual discharge channel 214 are equal. Here, the term “equal” may include a slight deviation in manufacturing from the design. As described above, by making the common discharge channel 222 have a uniform length, the maximum pressure difference in the common discharge channel 222 can be minimized. Thereby, the unevenness of the ink ejection characteristics can be reduced as much as possible.

  Further, the ink jet recording apparatus 1 of the present embodiment includes the above ink jet head. In such an ink jet recording apparatus 1, a high quality image with less unevenness can be formed stably.

  Further, a supply sub-tank 92 for storing the ink to be supplied to the common discharge channel 222 through the plurality of supply channels and the opening 226a, and the ink discharged from the common discharge channel 222 to the second ink storage section. A return circulation section (ink flow paths 73 and 74, a reflux sub-tank 93, and a liquid feed pump 82) is provided. In this way, by appropriately circulating the ink to remove bubbles and foreign substances and to enable the uniformly returned ink to be ejected, the ink jet recording apparatus 1 can minimize wasteful consumption of ink while minimizing wasteful consumption of ink. It is possible to perform stable ink ejection and suppress a decrease in image quality.

[Second embodiment]
Next, an inkjet head 100a according to a second embodiment will be described.
FIG. 13 is a schematic diagram illustrating the entire configuration of the ink flow path including the inkjet head 100a of the present embodiment.

  In the inkjet head 100a, the arrangement of the common supply ink chamber 1031 and the common discharge ink chamber 1032 is interchanged, and the supply port 1033 and the discharge port 1034 are interchanged accordingly. That is, for the ink, the common discharge ink chamber 1032 is located at the center of the common ink chamber 103 in the X direction, and two common supply ink chambers 1031 are provided on both sides thereof. Other arrangements of the configuration are the same as those of the flow path configuration including the inkjet head 100 of the first embodiment shown in FIG. 4, and are denoted by the same reference numerals.

FIG. 14 is a diagram illustrating the discharge of ink from the common discharge channel 222.
FIG. 14A is a view of the ink discharge passage viewed from above. FIG. 14B is an enlarged view showing the vicinity of an end adjacent to the common discharge channel 222 at substantially the center in the X direction.

  The two common discharge channels 222 located at the same position (the same Y coordinate position) in the transport direction are provided with a discharge communication port 228a at an end portion adjacent in the X direction, and each has a common discharge ink chamber 1032. Is in communication with Openings 226a are provided at opposite ends of the two common discharge channels 222, respectively, so that ink can flow from the common supply ink chambers 1031 on both sides via the bypass channel.

  Also in this case, the interval between the common discharge channels 222 has a width sufficient to provide two discharge communication ports 228a. Since the arrangement of the nozzle 211 (opening N) and the corresponding through-holes 221 and 213 is determined in advance in accordance with the nozzle interval and the arrangement interval of the pressurizing unit 31, the individual discharge flow path 214 is It extends obliquely with respect to the Y direction between the common discharge channel 222.

  In addition, instead of providing a discharge communication port 228a (such as a through hole 228) separately from each of the plurality of common discharge channels 222, an ink discharge chamber 225 that connects the ends of the plurality of common discharge channels 222 is provided. The ink may be discharged from the common discharge communication port 228a to the common discharge ink chamber 1032.

  As described above, as in the ink jet head 100a of the second embodiment, the positional relationship between the opening 226a to the common discharge channel 222 and the discharge communication port 228a at the discharge side end is opposite to that in the first embodiment. May be done. Even in this case, in the inkjet head 100a, it is possible to suppress the increase in the pressure difference in the direction along the common discharge flow path, and reduce the non-uniformity of the influence on the ink discharge operation. In addition, by connecting the vicinity of one side to the bypass flow path and connecting the other side to the ink discharge chamber 225, an appropriate ink flow is generated, so that ink does not stay in the common discharge path 222. Can be. In addition, the structure of the ink jet head is not complicated, and the ink jet head can be efficiently arranged to suppress an increase in size. Therefore, in the inkjet head 100a, it is possible to more effectively suppress the deterioration of the image quality.

It should be noted that the present invention is not limited to the above embodiment, and various modifications are possible.
For example, in the above-described embodiment, two adjacent common discharge channels 222 are arranged on the same straight line. However, a direction perpendicular to the straight line including a single common discharge channel 222 is described. The other common discharge channel 222 may be slightly shifted. Further, the extending directions of the two common discharge channels 222 may be slightly inclined (different).

  In the above embodiment, the second ends of the individual discharge channels 214 are arranged at equal intervals in the direction perpendicular to the ink discharge direction of the common discharge channel 222, but the present invention is not limited to this. Not something. They may be appropriately arranged at different positions in a direction perpendicular to the ink discharge direction.

  Further, the positions, shapes, sizes, and the like of the openings 226a provided in the plurality of common discharge channels 222 need not be the same. For example, when the lengths and shapes of a plurality of bypass channels cannot be the same, appropriate openings 226a different from each other may be provided according to the individual bypass channels. Further, the bypass flow path does not need to be linear from the common supply ink chamber 1031.

  Further, in the above-described embodiment, the shape of the third end side is a rectangular parallelepiped or a curved surface. Or, a more complicated shape may be used. Further, a partial protrusion or concave portion for guiding the flow of the flowing ink may be provided.

  Further, in the above embodiment, the ink is circulated by returning the ink from the reflux sub-tank 93 to the supply sub-tank 92, but the invention is not limited to such a configuration related to the circulation. It may be configured to return to the direct supply sub-tank 92. It does not exclude configurations that do not circulate.

In the above embodiment, the individual discharge flow path 214 is provided on the nozzle substrate, and the common discharge flow path 222 is provided on the intermediate substrate. However, the individual discharge flow path 214 may be provided on another substrate or may be provided across a plurality of substrates. It may be.
In addition, specific details such as the configuration, structure, positional relationship, size, and shape described in the above embodiment can be appropriately changed without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Ink-jet recording apparatus 2 Conveying part 2a Conveying roller 2b Conveying roller 2c Conveying belt 3 Head unit 21 Nozzle substrate 21a Nozzle layer 21b Oxide film layer 21c Nozzle supporting layer 211 Nozzle 212, 213 Through hole 214 Individual discharge flow path 22 Intermediate substrate 221, 226, 228 Through-hole 222 Common discharge flow path 223 Pressure buffer 223a Thin plate 223b Air chamber 225 Ink discharge chamber 225a Ink discharge chamber 226a Opening 2261, 2262 Hole 228a Discharge communication port 23 Actuator substrate 23a Pressure chamber layer 23b Vibration layer 231 Pressure Chambers 232 and 233 Through holes 24 Protective substrate 241 Through holes 31 Pressurizing section 311 Lower electrode 312 Piezoelectric layer 313 Upper electrode 35 Connection section 36 Signal wiring 71 to 74 Ink channels 81 and 82 Liquid supply pump 91 Main tank 92 Supply Subtank 93 wheeling subtank 100,100a inkjet head 101 head chip 102 holding section 103 common ink chamber 1031 common ink supply chamber 1032 common discharge ink chamber 1033 supply port 1034 outlet N openings

Claims (12)

A plurality of nozzles for discharging ink,
A plurality of supply channels for supplying ink to the nozzles,
A first discharge channel connected to the plurality of supply channels at a first end to discharge ink in the supply channel;
A second discharge flow path to which a second end of the plurality of first discharge flow paths opposite to the first end is connected,
With
The supply is provided between a third end on the most upstream side in the ink discharge direction of the second discharge flow path and the second end closest to the third end in the ink discharge direction. An ink inlet for ink supplied without passing through the flow path is provided,
The plurality of second end portions are arranged along one or more rows, are divided into two ranges different from each other in a direction along the row for each row, and are different from each other in the two ranges. Connected to the second discharge channel,
The second discharge passage is connected to the third end and the third end of the two second discharge passages connected to the second ends of the two ranges. An ink jet head, wherein one of the fourth ends is adjacent and the other is both ends.   The ink jet head according to claim 1, wherein a plurality of the inflow ports are provided for one of the second discharge channels.   The said two 2nd discharge flow paths respectively connected to the said 2nd end part of the said 2 area | regions, The said 3rd end part is arrange | positioned next to each other, The Claim 1 or 2 characterized by the above-mentioned. The inkjet head as described in the above. A first ink storage unit that stores the ink to be supplied to the plurality of supply channels,
A bypass flow path connecting the first ink reservoir and the inflow port,
The inkjet head according to any one of claims 1 to 3, further comprising:   The ink jet head according to claim 4, wherein one of the bypass passages is connected to a plurality of the inlets. The two second discharge flow paths respectively connected to the second ends of the two ranges are arranged such that the third ends are adjacent to each other,
The inkjet head according to claim 4, wherein the bypass flow path is provided between the third ends adjacent to each other.   The bypass flow path connected to the one second discharge flow path is a composite flow path of the bypass flow path that is smaller than the composite flow path resistance of the first discharge flow path connected to the one second discharge flow path. The ink jet head according to any one of claims 4 to 6, wherein the ink jet head is provided in such a number and shape that a path resistance increases.   A predetermined range from the third end of the inner wall surface of the second discharge channel has a shape in which a cross-sectional area perpendicular to the ink discharge direction becomes monotonically non-decreasing toward the downstream in the ink discharge direction. The inkjet head according to any one of claims 1 to 7, wherein:   The ink jet head according to claim 8, wherein the inner wall surface in the predetermined range includes a curved shape.   The inkjet head according to any one of claims 1 to 9, wherein the lengths of the second discharge channels provided in the two ranges are equal.   An image forming apparatus comprising the inkjet head according to claim 1. A second ink storage unit that stores ink to be supplied to the second discharge channel via the plurality of supply channels and the inflow port;
A circulation unit that returns the ink discharged from the second discharge flow path to the second ink storage unit;
The image forming apparatus according to claim 11, further comprising:

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