JP4810908B2 - Inkjet head - Google Patents

Description

  The present invention relates to an ink jet head having nozzle holes for ejecting ink.

  An ink jet head used in an ink jet printer or the like includes a nozzle plate in which a large number of nozzles are formed, and a flow path unit in which a large number of individual ink flow paths are formed from each nozzle to a common ink chamber through a pressure chamber. Have been known (see Patent Document 1). According to this ink jet head, the ink supplied from the ink tank flows into the pressure chambers of the individual ink flow paths via the common ink chamber. Then, by selectively applying a pulsed pressure to the pressure chamber, ink droplets are ejected from the nozzles communicating with the pressure chamber.

JP 2002-036539 A (FIG. 2)

  As such an ink jet head, there are a color type capable of ejecting ink droplets of a plurality of colors from one ink jet head, and a monochrome type capable of ejecting single color ink droplets with high resolution. . If these plural types of inkjet heads are individually designed and manufactured according to the application, the manufacturing cost of the inkjet heads increases.

  On the other hand, for example, a color ink jet head and a monochrome ink jet head have substantially the same other flow path configurations although the positions of the discharge ports of the nozzle holes are different. Therefore, it is conceivable to manufacture color and monochrome ink jet heads by changing only the nozzle plate in which the nozzle holes are formed. That is, the flow path unit is divided into a nozzle plate in which nozzle holes are formed and a main flow path portion in which flow paths other than the nozzle holes are formed, and the main flow path portion is formed as a common component. FIG. 11 shows an example in which this concept is applied to a conventional color inkjet head. FIG. 11 is a schematic diagram showing the positional relationship between the nozzle holes of the nozzle plate and the connection ports of the main flow path portion to which the nozzle plate is fixed. For convenience of explanation, the basic part of the range where the difference in the positional relationship can be understood is shown. Here, the discharge ports of the four nozzle holes (opening on the ink discharge surface side) and the inflow port (opening on the side opposite to the ink discharge surface), and the connection port of the main flow channel portion connected to this inflow port (the descender in the individual ink flow channel) Respective projection images obtained by projecting the opening of the hole) onto a virtual plane parallel to the ink ejection surface along the direction perpendicular to the ink ejection surface are illustrated. FIG. 11A shows projection images of a color inkjet head using four colors (M: magenta, Y: yellow, C: cyan, K: black), and FIG. Each projection image when the nozzle plate is changed to monochrome from the color ink-jet head is shown.

  In the case of color printing, since it is necessary to superimpose color inks, the ejection openings for ejecting ink droplets of different colors are arranged linearly in a predetermined direction (for example, the paper transport direction). On the other hand, in the case of monochrome printing, there is no overlap of the discharge ports in a predetermined direction in order to cope with higher printing resolution. In this case, the discharge ports are arranged at equal intervals corresponding to the resolution in a direction orthogonal to the discharge ports.

  Therefore, when a color nozzle plate is used, as shown in FIG. 11A, the projection contour (projection image of the connection port) 92 of each connection port corresponds to the projection contour (discharge) of the corresponding discharge port. It is arranged concentrically with the projected image 91a of the outlet and the projected contour line 91b of the inlet (projected image of the inlet). That is, the projection image at the center of the connection port: the projection connection port point and the projection image at the center of the corresponding discharge port: the projection discharge port point coincide with each other, and a straight projection image drawn in a predetermined direction: virtual line Located on X. It can also be said that the projection contour 92 of the connection port completely includes the projection contour 91a of the discharge port and the projection contour 91b of the inflow port. On the other hand, when the monochrome nozzle plate is used, as shown in FIG. 11B, the positional relationship of the projection contour 92 of the connection port with respect to the virtual line X is the same as that in the case of the color. The projected contour lines 91a ′ are located one by one on the four virtual lines Y1 to Y4 drawn in parallel with respect to the virtual line X. In any connection port, the projection connection port point and the projection discharge port point do not coincide. In particular, in the direction orthogonal to the imaginary line X, the two projected contour lines 91a ′ located at both ends are close to the projected contour line 92 of the connection port. When forming nozzle holes in the nozzle plate, the diameter may decrease from the inlet to the outlet in accordance with the required discharge characteristics (speed, amount, directionality, etc.). At this time, depending on the degree of proximity between the connection port and the discharge port and the degree of diameter reduction of the nozzle hole, if a slight deviation occurs in the manufacturing process, the projection contour 92b of the inflow port is projected from the projection contour 92 of the connection port. 'May protrude. In this figure, the projected contour lines 91b and 91b 'at the inlet are shown by broken lines. In this case, the ink flow from the connection port to the nozzle hole is disturbed, and the ink ejection performance is deteriorated. Therefore, it is difficult to realize a color inkjet head and a monochrome inkjet head that differ only in the nozzle plate.

  The main object of the present invention is to share a member other than the nozzle plate as a constituent member of the flow path unit, and in the nozzle plate, the centers of the plurality of discharge ports are arranged in a straight line along a direction orthogonal to one direction. Ink jet heads that are less likely to disturb ink flow and have excellent ink ejection performance regardless of whether the center of the plurality of nozzles and the centers of the plurality of ejection ports are separated from each other in the one direction are provided. It is to be.

Means for Solving the Problems and Effects of the Invention

In the inkjet head of the present invention, a plurality of individual ink flow paths are formed from an outlet of a common ink chamber to a discharge port through which a droplet is discharged via a pressure chamber, and a plurality of discharge ports having a plurality of discharge ports on an ink discharge surface. It is an inkjet head including a flow path unit to which a nozzle plate in which nozzle holes are formed is fixed. In the flow path unit, a plurality of ejection port arrays that extend in the first direction by the plurality of ejection ports and are arranged to face each other are formed on the ink ejection surface, and the nozzle plate On the fixed surface, connection ports of the plurality of individual ink flow paths are formed corresponding to the plurality of nozzle holes, respectively. The center of n (n is a natural number) of the ejection ports adjacent to each other in an arbitrary point on the ink ejection surface, a second direction that belongs to different ejection port arrays and intersects the first direction. And when the centers of the n connection ports corresponding to the n discharge ports are projected on a virtual plane parallel to the ink discharge surface along a direction perpendicular to the ink discharge surface, In the individual ink flow path group composed of the n individual ink flow paths related to the n discharge ports, the arbitrary point is projected to project a common origin formed on the virtual plane with respect to the common origin. The projection connection port point formed on the virtual plane by projecting the center of the connection port is a coordinate component in one direction in the virtual plane, and the projection port corresponding to each projection connection port point The center is projected The individual ink passage both are different from each other at least two of the coordinate components relating to said one direction projection discharge opening points formed on the virtual plane is present by. For each of the pair of projection connection port points that are most distant from each other among the n projection connection port points, the positional relationship in the one direction with the corresponding projection discharge port point is n. In contrast, when the projected discharge port points are arranged at different positions with respect to the one direction, and when the n projected discharge port points are arranged in a straight line along a direction orthogonal to the one direction. It has become.

  According to the present invention, a plurality of individual ink flow paths in which both the coordinate component related to the one direction of the projection connection port point with respect to the common origin and the coordinate component related to the one direction of the projection discharge port point relative to each projection connection port point are different from each other. In the case where the centers of the plurality of discharge ports are arranged on a straight line along a direction orthogonal to the one direction, and the centers of the plurality of discharge ports are separated from each other in the one direction In either case, even if a slight misalignment occurs in the manufacturing process, the projected contour of the inlet of the nozzle hole is easily included in the projected contour of the connection port. Therefore, as the nozzle plate, the center of the discharge ports of the plurality of nozzle holes is arranged in a straight line along the direction orthogonal to the one direction, and the center of the discharge ports of the plurality of nozzle holes is related to the one direction. Regardless of which one is used, the ink flow is hardly disturbed between the plurality of individual ink flow paths, and excellent ink ejection performance can be obtained.

  In the present invention, both the coordinate component related to the one direction of the projection connection port point relative to the common origin and the coordinate component related to the one direction of the corresponding projection discharge port point relative to the projection connection port point are n pieces. It is preferable that all the individual ink flow paths are different. According to this, the range in which the nozzle hole can be connected to the connection port without protruding in a plan view is further widened. Thereby, n individual ink flow paths in which both the coordinate component in the one direction of the projection connection port point with respect to the common origin and the coordinate component in the one direction of the projection discharge port point with respect to each projection connection port point are different from each other. In the case where the centers of the plurality of discharge ports are arranged in a straight line along a direction orthogonal to the one direction, and the centers of the plurality of discharge ports are separated from each other in the one direction. In any case, even if a slight misalignment occurs in the manufacturing process, the projected contour of the inlet of the nozzle hole is more easily included in the projected contour of the connection port. Accordingly, as the nozzle plate, the center positions of the discharge ports of the plurality of nozzle holes are arranged in a straight line along the direction orthogonal to the one direction, and the center positions of the discharge ports of the plurality of nozzle holes are the one position. Regardless of which of those separated from each other in the direction is used, the ink flow is hardly disturbed among these n individual ink flow paths, and excellent ink ejection performance is obtained.

  In the present invention, it is preferable that the n projecting connection points are equally spaced with respect to the one direction.

  Alternatively, n distances in the one direction between the n projection connection port points and the n projection discharge port points corresponding thereto may be changed at equal intervals.

  Alternatively, the n projection connection port points are separated by a first interval in the one direction, and between the n projection connection port points and the n projection discharge port points corresponding to the projection connection port points. The n distances in the one direction may change by the second interval. According to these, the structure of the individual ink channel set can be simplified.

  At this time, it is preferable that the n projecting discharge outlet points are spaced at equal intervals in the one direction. According to this, a high-resolution monochrome image can be printed.

  Further, at this time, it is more preferable that the first interval is smaller than the second interval. According to this, the projected contour of the inlet of the nozzle hole is more easily included in the projected contour of the connection port.

  In addition, at this time, the larger the coordinate component related to the one direction of the projection connection point with respect to the common origin, the larger the coordinate component related to the one direction of the projection discharge port point corresponding to the projection connection point. Even more preferred. According to this, the projected contour of the inlet of the nozzle hole is surely included in the projected contour of the connection port.

  In the present invention, it is preferable that the n projection discharge port points are arranged on a straight line along a direction orthogonal to the one direction. According to this, a good color image can be printed.

  In the present invention, when the n projection connection port points and the n projection discharge port points are arranged at equal intervals in the second direction on the virtual plane, the n projection connection port points are provided. Are present on the first straight line, and the n projection discharge port points are preferably present on the second straight line extending in a direction intersecting the first straight line. According to this, the structure of the individual ink flow path set can be simplified.

  In addition, in the present invention, when the contour line of the connection port is projected onto the virtual plane along a direction perpendicular to the ink discharge surface, the projection discharge port point corresponding to the connection port is projected. By doing so, it is preferable that the projected outline of the connection port formed in the virtual plane is included. According to this, the ink discharge performance can be further improved.

  Further, when the contour line of the ejection port is projected onto the virtual plane along a direction perpendicular to the ink ejection surface, the projected contour line of the ejection port formed on the virtual plane by being projected Is more preferably included in the projected outline of the connection port. According to this, the ink ejection performance can be further improved.

  In the present invention, the plurality of common ink chambers may be arranged so as to face each other while extending in the first direction. Each common ink chamber may communicate with m (m: natural number) individual ink flow paths related to the common ejection port array. At this time, m projection discharge port points corresponding to the m individual ink flow paths communicating with the same common ink chamber are spaced apart at equal intervals in the one plane on the virtual plane. It is preferable that m individual ink flow path groups each including n individual ink flow paths communicating with different common ink chambers are formed. According to this, the above-described effect can be obtained over the entire head.

  At this time, n common ink chambers are formed, and each of the n common ink chambers has two sub-common ink chambers, and the two sub-common chambers belonging to each common ink chamber. It is preferable that m projection discharge port points corresponding to the m individual ink flow paths communicating with the ink chamber are spaced apart at equal intervals in the one direction on the virtual plane. According to this, color printing using the same number of ink colors as that of the common ink chamber and color printing using the same number of ink colors as that of the sub-common ink chamber twice that of the common ink chamber can be realized by one inkjet head.

  Moreover, in these, it is more preferable that the n × m pressure chambers and the individual electrodes arranged to face the pressure chambers are arranged in a staggered manner with respect to the one direction. According to this, since the pressure chambers can be arranged with high density, high-resolution printing can be performed.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an external perspective view of an ink jet head according to a preferred embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1 and shows a state in which the head body is assembled to a holder constituting the inkjet head. FIG. 3 is a perspective view showing a state in which a reinforcing plate is bonded to the head body shown in FIG. The ink-jet head 1 is used in a serial-type ink-jet printer (not shown) and records by ejecting ink of four colors, magenta, yellow, cyan and black, onto a sheet conveyed in parallel in the sub-scanning direction. To do. The inkjet head 1 is detachably mounted on a carriage (not shown), reciprocated in the main scanning direction, and ejects ink droplets every time it crosses the paper. As shown in FIGS. 1 and 2, the inkjet head 1 includes an ink tank 71 in which four ink chambers 3 for storing four color inks are formed, and a head body 70 disposed below the ink tank 71. And a flexible printed circuit board (FPC) 50 that is a signal transmission board attached to the head body 70.

  Inside the ink tank 71, four ink chambers 3 are formed side by side in the main scanning direction, and magenta, yellow, cyan, and black inks are sequentially stored from the left ink chamber 3 in FIG. . These four ink chambers 3 are respectively connected to corresponding ink cartridges (not shown) by tubes 40 (see FIG. 1), and ink of each color is supplied from the ink cartridges to the ink chambers 3. Yes. Further, as shown in FIGS. 2 and 3, the ink tank 71 is assembled to a reinforcing plate 41 having a planar rectangular shape. The reinforcing plate 41 is fixed to a holder 72 having a substantially rectangular parallelepiped shape with an ultraviolet curing agent 43. Further, as shown in FIG. 3, the reinforcing plate 41 has an opening 42 having a rectangular planar shape, and an actuator unit (piezoelectric actuator) 21 to be described later is disposed in the opening 42. Thus, the head main body 70 is bonded and fixed. At the lower end of the ink tank 71, four ink outlets 3a communicating with the four ink chambers 3 are formed. On the other hand, as shown in FIG. 3, the reinforcing plate 41 is formed with four through-holes 41a each having an elliptical planar shape connected to the four ink outlets 3a.

  The head main body 70 includes a flow path unit 4 in which a plurality of ink flow paths are formed for each color, and an actuator unit 21 bonded to the upper surface of the flow path unit 4 with an epoxy-based thermosetting adhesive. It is out. The flow path unit 4 and the actuator unit 21 are configured by laminating a plurality of thin plates and bonding them together. The flow path unit 4 and the actuator unit 21 are disposed below the ink tank 71. On the upper surface of the flow path unit 4, four ink supply ports 4a (see FIG. 4) having an elliptical planar shape are formed. Further, as shown in FIG. 3, the flow path unit 4 is bonded to the reinforcing plate 41 so that the through holes 41 a formed in the reinforcing plate 41 and the ink supply ports 4 a formed in the flow path unit 4 are connected to each other. Has been. With this configuration, four types of ink in the ink tank 71 pass through the four ink outlets 3a formed in the ink tank 71 and the four through holes 41a formed in the reinforcing plate 41, respectively. The ink is supplied from the four ink supply ports 4 a of the unit 4 into the flow path unit 4.

  As shown in FIG. 2, the head main body 70 has a stepped opening 72 a formed on the lower surface of the holder 72 with the ink ejection surface 70 a of the flow path unit 4 exposed to the outside. The holder 72 and the flow path unit 4 are sealed with a sealant 73. Further, the bottom surface of the head body 70 is an ink ejection surface 70a in which ejection ports 8a (see FIG. 6) of a large number of nozzle holes 8 having a minute diameter are arranged. Further, the FPC 50 is fixed to the upper surface of the actuator unit 21 by a thermosetting adhesive, pulled out in one of the main scanning directions, and pulled out upward while being bent. Further, a protective plate 44 for protecting the FPC 50 and the actuator unit 21 is attached to the upper surface of the FPC 50. Further, the protective plate 44 functions to make the temperature distribution generated in the actuator unit 21 uniform and to align the ink ejection characteristics.

  The FPC 50 fixed to the actuator unit 21 is pulled out along the side surface of the ink tank 71 through an elastic member 74 such as a sponge, and a driver IC 75 is installed on the FPC 50. The FPC 50 is electrically connected to the actuator unit 21 so as to transmit the drive signal output from the driver IC 75 to the actuator unit 21 (described later in detail) of the head main body 70.

  An opening 72b for dissipating the heat of the driver IC 75 to the outside is formed on the side wall of the holder 72 facing the driver IC 75. Further, a heat sink 76 made of an approximately rectangular parallelepiped aluminum plate is disposed between the driver IC 75 and the opening 72 b of the holder 72 so as to be in close contact with the driver IC 75. The heat generated by the driver IC 75 can be efficiently dissipated by the heat sink 76 and the opening 72b. In addition, a sealant 77 for filling a gap between the side wall of the holder 72 and the heat sink 76 is disposed in the opening 72b to prevent dust and ink from entering the main body of the inkjet head 1.

  FIG. 4 is a plan view of the head body 70. As shown in FIG. 4, the head body 70 has a rectangular planar shape. In FIG. 4, four (n) manifold channels 5 extending in parallel with each other along the longitudinal direction (sub-scanning direction) of the channel unit 4 are formed in the channel unit 4. . Ink is supplied to the manifold channels 5 from the ink chamber 3 of the ink tank 71 through the four ink supply ports 4 a of the channel unit 4. In the present embodiment, manifold channels 5A, 5B, 5C, and 5D corresponding to magenta, yellow, cyan, and black are formed in order from the manifold channel 5 shown in the upper part of FIG. 4 to the lower side. A filter member 45 is disposed at a position on the upper surface of the flow path unit 4 so as to cover the four ink supply ports 4a. The filter member 45 has a filter 45a in which a plurality of minute holes are formed at positions overlapping with the ink supply ports 4a. Thus, dust or the like in the ink supplied from the ink tank 71 into the flow path unit 4 is captured by the filter 45a.

  On the upper surface of the flow path unit 4, an actuator unit 21 having a rectangular planar shape is bonded to a substantially central portion avoiding the ink supply port 4a. The lower surface of the flow path unit 4 corresponding to the adhesion region between the actuator unit 21 and the flow path unit 4 is an ink discharge surface 70a on which a large number of nozzle holes 8 (see FIG. 6) are arranged. A large number of pressure chambers 10 (see FIG. 6) and gaps 60 (see FIG. 5) arranged in a matrix are formed in the adhesion region of the flow path unit 4 facing the actuator unit 21. In other words, the actuator unit 21 has dimensions over all the pressure chambers 10 and the gaps 60.

  FIG. 5 is an enlarged view of a region surrounded by a one-dot chain line drawn in FIG. As shown in FIG. 5, in the flow path unit 4, four manifold flow paths (common ink chambers) 5A, 5B, 5C, and 5D each branch into two sub-manifold flow paths (sub-common ink chambers) 5a. is doing. In other words, a total of eight sub-manifold channels 5a are formed. The sub-manifold flow path 5a protrudes outward from both side walls in the width direction in plan view and includes a large number of protrusions 80 arranged in a staggered manner along the extending direction (FIG. 6). reference). Further, the flow path unit 4 includes 16 pressure chamber rows 11 in which a plurality of pressure chambers 10 are arranged in parallel to the manifold flow passage 5 (sub-manifold flow passage 5a), and a large number of gaps 60. And four gap rows 61 arranged in parallel with each other. The 16 pressure chamber rows 11 are divided into 12 groups and 4 groups by a group of four gap rows 61 formed adjacent to each other. The pressure chamber 10 and the gap 60 have the same planar shape and size. The large number of pressure chambers 10 and the gaps 60 are regularly arranged so that one arrangement pattern is formed in the flow path unit 4 when the two are considered to be indistinguishable.

  The pressure chamber 10 formed in the flow path unit 4 has a substantially rhombic planar shape with rounded corners, and the longer diagonal line is the width direction (main scanning direction) of the flow path unit 4. Parallel to One end of each pressure chamber 10 is formed in a nozzle hole (a nozzle plate 30) via a descender hole (a hole formed across the plates 23, 24, 25, 66, 26, 27, 28, 29, and 67) 14. The other end communicates with the protruding portion 80 of the sub-manifold channel 5a through the aperture 13 and the communication hole 68 (see FIG. 6). In FIG. 5, in order to make the drawing easy to understand, the pressure chamber 10, the gap 60, the aperture 13, the nozzle hole 8, and the like that are in the flow path unit 4 and should be drawn by broken lines are drawn by solid lines.

  As will be described later, on the actuator unit 21, individual electrodes 35 (see FIG. 9) whose planar shape is substantially rhombus and slightly smaller than the pressure chamber 10 are arranged in a matrix so as to face the pressure chamber 10. Yes. FIG. 5 shows only one of the plurality of individual electrodes 35 in order to simplify the drawing.

  FIG. 6 is a cross-sectional view showing the individual ink flow path 7 along the line VI-VI shown in FIG. As shown in FIG. 6, the sub-manifold channel 5a has a rectangular cross-sectional shape and has a protruding portion 80 that protrudes substantially horizontally from the side wall. Each nozzle hole 8 communicates with the projecting portion 80 of the sub-manifold channel 5 a via the descender hole 14, the pressure chamber 10, the aperture (that is, the throttle) 13, and the communication hole 68. At this time, one individual ink flow path 7 is formed including the communication hole 68, the aperture 13, the pressure chamber 10, the descender hole 14, and the nozzle hole 8. Thus, a large number (m / 2 in this embodiment) of individual ink flow paths 7 communicate with each sub-manifold flow path 5a (see FIG. 5). That is, m individual ink channels 7 communicate with each manifold channel 5.

  Further, an upper damper chamber 81 is formed so as to be adjacent to the sub-manifold channel 5a through an upper thin film portion 81a constituting a part of the inner wall surface of the sub-manifold channel 5a. Further, a lower damper chamber 82 is formed so as to be adjacent to the sub-manifold channel 5a via a lower thin film portion 82a that constitutes a part of the inner wall surface facing the upper thin film portion 81a. Therefore, the upper damper chamber 81 and the lower damper chamber 82 are disposed so as to face each other with the sub manifold channel 5a interposed therebetween.

  As shown in FIG. 6, the head main body 70 includes, from above, the actuator unit 21, the cavity plate 22, the base plate 23, the aperture plate 24, the supply plate 25, the upper damper plate 66, the manifold plates 26 to 29, the lower damper plate 67, In addition, the nozzle plate 30 has a laminated structure in which a total of 12 sheet materials are laminated. Among these, the flow path unit 4 is composed of 11 plates excluding the actuator unit 21.

  As will be described later, the actuator unit 21 includes a laminated body of four piezoelectric sheets 31 to 34 (see FIG. 9). Of these, only the uppermost layer is a layer having a portion that becomes an active portion when an electric field is applied (hereinafter simply referred to as “a layer having an active portion”), and the remaining three layers are an inactive layer having no active portion. It has been done. The cavity plate 22 is a metal plate in which a large number of diamond-shaped holes constituting the pressure chamber 10 and the gap 60 are provided in the pasting range (adhesion region) of the actuator unit 21. The base plate 23 is provided with a hole serving as a communicating hole between the pressure chamber 10 and the aperture 13 and a descender hole 14 serving as a communicating hole from the pressure chamber 10 to the nozzle hole 8 with respect to one pressure chamber 10 of the cavity plate 22. It is a metal plate.

  The aperture plate 24 is a metal plate provided with holes serving as descender holes 14 in addition to holes serving as the apertures 13 for one pressure chamber 10 of the cavity plate 22. The supply plate 25 is a metal plate provided with a hole serving as a part of the communication hole 68 communicating with the aperture 13 and a hole serving as the descender hole 14 for one pressure chamber 10 of the cavity plate 22.

  The upper damper plate 66 has, for one pressure chamber 10 of the cavity plate 22, a hole that becomes a part of the communication hole 68 that communicates with the aperture 13, a hole that becomes the descender hole 14, and a recess that becomes a part of the upper damper chamber 81. Each is a metal plate. That is, the communication hole 68 is formed by the holes of the supply plate 25 and the upper damper plate 66. In addition, the bottom of the concave portion that becomes a part of the upper damper chamber 81 becomes the upper thin film portion 81a.

  The manifold plates 26 to 29 are metal plates provided with a hole that becomes a part of the sub-manifold channel 5 a and a hole that becomes the descender hole 14 for one pressure chamber 10 of the cavity plate 22. Note that a hole that becomes a part of the sub-manifold flow path 5 a of the manifold plate 26 includes a portion that becomes the protruding portion 80. The lower damper plate (a plate adjacent to the nozzle plate 30) 67 is a metal plate provided with a recess serving as a part of the lower damper chamber 82 and a hole serving as the descender hole 14. The bottom of the recess that becomes the lower damper chamber 82 becomes the lower thin film portion 82a. In addition, the opening of the hole serving as the descender hole 14 on the surface in contact with the nozzle plate 30 is a connection port 67 a connected to the nozzle hole 8. The nozzle plate 30 is a metal plate in which the nozzle holes 8 are provided for one pressure chamber 10 of the cavity plate 22. The opening located on the ink discharge surface 70a of the nozzle hole 8 is the discharge opening 8a, and the opening connected to the connection opening 67a of the lower damper plate 67 is the upper opening (inlet) 8b.

  These twelve sheets 21 to 30, 66, and 67 are stacked in alignment with each other so that the individual ink flow paths 7 as shown in FIG. 6 are formed. The individual ink channel 7 extends upward from the sub-manifold channel 5 a through the communication hole 68, extends horizontally at the aperture 13, then further upwards, extends horizontally again at the pressure chamber 10, Then, it heads for a while away from the aperture 13 obliquely downward and then vertically downward toward the nozzle hole 8.

  As is clear from FIG. 6, the pressure chamber 10 and the aperture 13 are provided at different levels in the stacking direction of the plates. Accordingly, as shown in FIG. 5, the aperture 13 communicating with one pressure chamber 10 is arranged in the flow path unit 4 so as to overlap with another pressure chamber 10 adjacent to the pressure chamber in a plan view. Is possible. As a result, the pressure chambers 10 are in close contact with each other and are arranged at high density, so that high-resolution image printing is realized by the inkjet head 1 having a relatively small occupation area.

  The plurality of gaps 60 formed in the cavity plate 22 are defined by holes having the same shape and the same size as the pressure chambers 10 formed in the cavity plate 22 being closed by the actuator unit 21 and the base plate 23. ing. Therefore, no ink flow path is connected to the gap 60, and the plurality of gaps 60 are not filled with ink. The plurality of gaps 60 are adjacently arranged in a matrix in a staggered arrangement pattern in two directions of the arrangement direction A (sub-scanning direction) and the arrangement direction B. The plurality of gaps 60 form four gap rows 61 parallel to each other, and the four gap rows 61 constitute a gap group 62. A plurality of pressure chambers 10 are formed in the flow path unit 4 so as to sandwich the gap group 62.

  As described above, the large number of pressure chambers 10 arranged in a matrix form 16 pressure chamber rows 11 along the arrangement direction A. These sixteen pressure chamber rows 11 have a first pressure chamber row 11a, a second pressure chamber row 11b, and a third pressure chamber row 11c according to the relative position to each manifold channel 5 in plan view. And the fourth pressure chamber row 11d. These first to fourth pressure chamber rows 11a to 11d are arranged from one side in the width direction of the actuator unit 21 to the other side (from the lower side to the upper side in FIG. 5), 11a → 11c → 11b → 11d → 11a → 11c → 11b. 4 pieces are periodically arranged in the order of 11d →. In addition, four pressure chamber groups 12 are formed for each of the first to fourth pressure chamber rows that are periodically arranged by four, and the pressure chambers 10 of each pressure chamber group 12 are connected to each manifold channel 5. And communicate with each other via an aperture 13. That is, since each pressure chamber group 12 is formed for each manifold flow path 5, the pressure chamber groups 12 corresponding to the four color inks are changed to pressure chamber groups 12A (magenta), 12B (yellow), and 12C (cyan), respectively. , 12D (black).

  The pressure chamber group 12 will be described with further reference to FIG. FIG. 7 is an enlarged view of a region surrounded by a one-dot chain line drawn in FIG. In FIG. 7, only the sub-manifold flow path 5a, the aperture 13, the pressure chamber 10, the connection port 67a, and the nozzle hole 8 are drawn with solid lines for easy understanding of the drawing. As shown in FIG. 7, in each pressure chamber group 12, the pressure chamber 10a constituting the pressure chamber row 11a and the pressure chamber 10c constituting the pressure chamber row 11c communicate with the same sub-manifold channel 5a. . Further, the pressure chamber 10b constituting the pressure chamber row 11b and the pressure chamber 10d constituting the pressure chamber row 11d communicate with the same sub-manifold channel 5a. Further, in each pressure chamber group 12, a large number of virtual lines Z passing through the center of the discharge port 8a of each nozzle hole 8 and parallel to the main scanning direction do not overlap each other. That is, the centers of the discharge ports 8a of the nozzle holes 8 are separated by equal distances in the sub-scanning direction. For example, in the present embodiment, in order to enable printing with a resolution of 150 dpi, two adjacent virtual lines Z are separated by 150 dpi. Further, when only the imaginary line Z passing through the center of the discharge port 8a of the nozzle hole 8 related to the pressure chambers 10a, 10c or the pressure chambers 10b, 10d communicating with the one sub-manifold channel 5a is taken out, the adjacent two The virtual lines Z of the books are separated by 75 dpi. Further, when only the virtual line Z passing through the center of the discharge port 8a of the nozzle hole 8 related to the pressure chamber (for example, the pressure chamber 10a) belonging to any one of the four pressure chamber rows 11 is taken out, two adjacent two The virtual lines Z are separated by 37.5 dpi. And when only the virtual line Z passing through the center of the discharge port 8a of the nozzle hole 8 related to the pressure chamber (for example, the pressure chamber 10a) belonging to one pressure chamber row 11 is taken out, it is between two adjacent virtual lines Z. Each has one imaginary line Z passing through the center of the discharge port 8a of the nozzle hole 8 associated with the pressure chambers (for example, the pressure chambers 10c, 10b, 10d) belonging to the other three pressure chamber rows 11. Yes. When only one pressure chamber group 12 is considered, only one center of the discharge port 8a of the nozzle hole 8 exists on each virtual line Z. Further, when considering the four pressure chamber groups 12A, 12B, 12C, and 12D, there are four centers of the discharge ports 8a of the nozzle holes 8 on each virtual line Z. The centers of these four discharge ports 8a are each selected from those belonging to the four pressure chamber groups 12A, 12B, 12C, and 12D.

  At this time, on the ink discharge surface 70a, a plurality of discharge ports 8a are formed in a plurality of discharge port arrays 18 that extend in the sub-scanning direction (first direction) and are arranged to face each other. (See FIG. 5). In the flow path unit 4, four individual ink flow paths 7 including nozzle holes 8 corresponding to different pressure chamber groups 12 having the center of the discharge port 8 a on the same imaginary line Z are provided as one individual ink. It constitutes a channel set. As described above, in the present embodiment, the pressure chamber group 12 is configured for each ink color, and the positions of the pressure chambers 10, the sub-manifold 5 a, the aperture 13, the connection port 67 a, and the nozzle hole 8 belonging to this group. The relationship is the same between the pressure chamber groups 12. Therefore, also for the pressure chambers 10 belonging to one individual ink flow path set, the positional relationship between each flow path component (sub-manifold 5a, aperture 13 and the like) and each pressure chamber 10 is the same.

  Next, the positional relationship between the discharge port 8a and the upper opening 8b of the nozzle hole 8 and the connection port 67a connected to the nozzle hole 8 in one individual ink channel set will be described with reference to FIG. FIG. 8 shows an arbitrary point set on the ink discharge surface 70a, four discharge ports 8a, an upper opening 8b, and a connection port 67a related to one individual ink flow path set along a direction perpendicular to the ink discharge surface 70a. FIG. 6 is a diagram projected onto a virtual plane parallel to the ink ejection surface 70a. That is, in FIG. 8, the positional relationship between the four nozzle holes 8 and the connection ports 67a corresponding to the pressure chamber groups 12A, 12B, 12C, and 12D existing on the virtual line Z is shown. Hereinafter, on the virtual plane, the projection of an arbitrary point set on the ink ejection surface 70a is the common origin O, the projection of the ejection port 8a is the projection contour 8a 'of the ejection port, and the upper opening 8b is the projection. The projected outline 8b 'of the upper opening and the projection of the connection port 67a are referred to as the projection outline 67a' of the connection port. The center point of the projection contour line 8a 'of the discharge port is referred to as a projection discharge port point 8c, and the center point of the projection contour line 67a' of the connection port is referred to as a projection connection port point 67b. In FIG. 8, the projected outline 8b ′ of the upper opening is indicated by a broken line. Further, in FIG. 8, the projection outlines 67a ′ and the like of the four connection ports are drawn so that the separation distance in the main scanning direction is shorter than the distance when the scale in the sub scanning direction is considered as a reference. Specifically, the separation distance in the main scanning direction, such as the projected contour lines 67a ′ of the four connection ports, is drawn at a position further reduced by the same ratio when the distance when considered on the basis of the scale in the sub scanning direction is used. Yes. Furthermore, in order to make the positional relationship easy to understand, the projection outline 67a ′ of the connection port and the like are drawn so as to be arranged at equal intervals in the main scanning direction.

  As shown in FIG. 8, on the virtual plane, four projected discharge port points 8c are arranged on a straight line A (second straight line) along the main scanning direction. The four projection connection points 67b are arranged on a straight line B (first straight line) intersecting with the straight line A while being separated by a fixed interval l (1200 dpi) in the sub-scanning direction. At this time, considering the direction, the distance (LA, LB, LC, LD) in the sub-scanning direction of the corresponding projection discharge port point 8c with respect to the projection connection port point 67b is 1.5l, 0.5l, -0. The interval changes by 5 l and -1.5 l. Thus, both the coordinate component related to the sub-scanning direction of the projection connection port point 67b with respect to the common origin O and the coordinate component related to the sub-scanning direction of the corresponding projection discharge port point 8c with respect to the projection connection port point 67b are one individual. All four individual ink channels 7 belonging to the ink channel group are different. Further, at this time, in the virtual plane, the projection discharge port point 8c, the projection contour 8a ′ of the discharge port, and the projection contour 8b ′ of the upper opening are completely included in the projection contour 67a ′ of the connection port. Thereby, in each individual ink flow path 7, the ink from the pressure chamber 10 flows smoothly into the nozzle hole 8 via the connection port 67a.

  Next, the configuration of the actuator unit 21 and the FPC 50 will be described. On the actuator unit 21, a large number of individual electrodes 35 are arranged in a matrix with the same arrangement pattern as the pressure chambers 10. Each individual electrode 35 is disposed at a position facing the pressure chamber 10 in plan view (see FIG. 5).

  FIG. 9 shows the actuator unit. FIG. 9A is an enlarged view of a portion surrounded by a dashed line in FIG. 6, and FIG. 9B is a plan view of an individual electrode. In FIG. 9, in order to make the drawing easy to understand, the terminal portion 48 a and the wiring 48 b that are to be drawn with broken lines in the FPC 50 are drawn with solid lines. As shown in FIGS. 9A and 9B, the individual electrode 35 is disposed at a position facing the pressure chamber 10, and is a main electrode region formed in the planar region of the pressure chamber 10 in plan view. 35 a and an auxiliary electrode region 35 b connected to the main electrode region 35 a and formed outside the plane region of the pressure chamber 10.

  As shown in FIG. 9A, the actuator unit 21 includes four piezoelectric sheets 31 to 34 each having a thickness of about 15 μm. The piezoelectric sheets 31 to 34 are formed into a continuous layered flat plate (continuous flat plate layer) so as to be disposed across a large number of pressure chambers 10 and gaps 60 formed in the ink discharge region in the head main body 70. Yes. The piezoelectric sheets 31 to 34 are made of a lead zirconate titanate (PZT) ceramic material having ferroelectricity.

  As shown in FIG. 9B, the main electrode region 35a of the individual electrode 35 formed on the uppermost piezoelectric sheet 31 has a substantially rhombic planar shape that is substantially similar to the pressure chamber 10. An acute angle portion on the left side in FIG. 9B in the substantially rhomboid main electrode region 35a extends to a region overlapping with the acute angle portion of the pressure chamber 10, and is connected to the auxiliary electrode region 35b. A circular land portion 36 electrically connected to the individual electrode 35 is provided at the tip of the auxiliary electrode region 35b. The land portion 36 is a terminal that is electrically connected to a terminal portion 48a that becomes a joint portion described later. As shown in FIG. 9B, the land portion 36 is opposed to a region of the cavity plate 22 where the pressure chamber 10 is not formed, and has a diameter of about 0.3 mm and a thickness of about 10 μm. Yes. The land portion 36 is made of, for example, gold containing glass frit, and is formed on the surface of the auxiliary electrode region 35b as shown in FIG.

  A common electrode 37 having the same outer shape as the piezoelectric sheet 31 and a thickness of about 2 μm is interposed between the uppermost piezoelectric sheet 31 and the lower piezoelectric sheet 32. Both the individual electrode 35 and the common electrode 37 are made of, for example, a metal material such as Ag—Pd.

  The common electrode 37 is grounded in a region not shown. Thereby, the common electrode 37 is kept at an equally constant potential in the region corresponding to all the pressure chambers 10, that is, the ground potential in the present embodiment.

  As shown in FIG. 9A, the FPC 50 includes a base film (flexible layer) 46 and a conductor pattern 47 formed on the lower surface of the base film 46 (a surface facing the head body 70). The base film 46 is made of a polyimide resin film having flexibility and insulation. The conductor pattern 47 is made of copper foil.

  The conductor pattern 47 includes a plurality of terminal portions 48a formed at positions facing the land portions 36 of the base film 46, and wirings 48b drawn from the center of the lower ends of the terminal portions 48a toward the base end side of the FPC 50. Have. The terminal portion 48a is formed in a circular planar shape. The surface of the terminal portion 48a is plated with gold (not shown) in order to prevent oxidation of the terminal portion 48a and ensure reliable conduction to the land portion 36.

  The plurality of wirings 48 b are respectively connected to the driver IC 75 on the base end side of the FPC 50. In the base film 46, a part of the region facing the land portion 36 is formed with a convex portion 51 that protrudes toward the center of the land portion 36. A protruding portion 55 that protrudes from the central portion of the terminal portion 48 a toward the center of the land portion 36 is formed on the terminal portion 48 a so as to face the convex portion 51.

  An epoxy-based thermosetting adhesive 56 made of a non-conductive material is disposed around the protrusion 55, and the tip of the protrusion 55 is caused by the contraction force accompanying the curing of the thermosetting adhesive 56. The surface of the land 36 is crushed in contact with the surface. As a result, the terminal portion 48a and the land portion 36 are electrically connected. With such a configuration, the FPC 50 can transmit a drive signal from the driver IC 75 to the individual electrode 35 via the wiring 48b and the terminal portion 48a. That is, each of the plurality of individual electrodes 35 is connected to the driver IC 75 via the independent terminal portion 48 a and the wiring 48 b in the FPC 50. This makes it possible to control ink ejection for each pressure chamber 10.

  Next, a method for driving the actuator unit 21 will be described. The polarization direction of the piezoelectric sheet 31 in the actuator unit 21 is the thickness direction thereof. In other words, the actuator unit 21 includes the upper piezoelectric sheet 31 (that is, away from the pressure chamber 10) as the active portion layer and the lower piezoelectric element 10 (that is, close to the pressure chamber 10). It has a so-called unimorph type structure in which 32 to 34 are inactive layers. Therefore, when the individual electrode 35 is set to a predetermined potential that is positive or negative with respect to the ground potential, for example, if the electric field and the polarization are in the same direction, the electric field application portion sandwiched between the electrodes in the piezoelectric sheet 31 functions as an active portion. Shrink in the direction perpendicular to the polarization direction due to the electrostrictive effect.

  On the other hand, the three piezoelectric sheets 32 to 34 below the piezoelectric sheet 31 are not applied with an electric field from the outside, and therefore hardly function as active parts.

  That is, since the piezoelectric sheets 32 to 34 are not spontaneously displaced, there is a difference in distortion in the direction perpendicular to the polarization direction between the upper piezoelectric sheet 31 and the lower piezoelectric sheet 32 to 34. Then, the piezoelectric sheets 31 to 34 try to be deformed so as to be convex toward the non-active side (unimorph deformation). At this time, as shown in FIG. 9A, the lower surface of the actuator unit 21 constituted by the piezoelectric sheets 31 to 34 is fixed to the upper surface of the partition wall (cavity plate) 22 that partitions the pressure chamber. In particular, the piezoelectric sheets 31 to 34 reduce the volume of the pressure chamber. For this reason, the pressure of the ink rises and the ink is ejected from the nozzle hole 8. Thereafter, when the individual electrode 35 is returned to the same potential as that of the common electrode 37, the piezoelectric sheets 31 to 34 return to the original shape and the volume of the pressure chamber 10 returns to the original volume, so that ink is sucked from the manifold channel 5 side. .

  As another driving method, the individual electrode 35 is set to a potential different from that of the common electrode 37 in advance, and the individual electrode 35 is temporarily set to the same potential as the common electrode 37 (for example, a ground potential) every time there is an ejection request. The individual electrode 35 can be set to a potential different from that of the common electrode 37 again at the timing of In this case, when the individual electrode 35 and the common electrode 37 become the same potential, the piezoelectric sheets 31 to 34 return to the original shape, so that the volume of the pressure chamber 10 is in an initial state (a state where the potentials of the electrodes are different) ) And the ink is sucked into the pressure chamber 10 from the manifold channel 5 side. Thereafter, at the timing when the individual electrode 35 is set to a potential different from that of the common electrode 37 again, the piezoelectric sheets 31 to 34 are deformed so as to protrude toward the pressure chamber 10, and the pressure on the ink increases due to the volume reduction of the pressure chamber 10. Ink is ejected. In this way, ink is ejected from the nozzle holes 8 and the inkjet head 1 is appropriately moved in the main scanning direction to print a desired image on the paper.

  The ink jet head 1 described above functions as a color ink jet head capable of ejecting ink droplets of four colors. However, by changing the nozzle plate 30 to a monochrome nozzle plate 30A, a single color ink drop can be obtained. It can function as a monochrome inkjet head capable of discharging at narrow intervals. In this case, it is only necessary that the same color ink is stored in all of the four ink chambers 3. Hereinafter, the case where the nozzle plate 30 is changed to the monochrome nozzle plate 30A will be described. The nozzle plate 30 </ b> A is a metal plate provided with nozzle holes 8 </ b> A for one pressure chamber 10 of the cavity plate 22. An opening located on the ink ejection surface 70a of the nozzle hole 8A is an ejection opening 8Aa, and an opening connected to the connection opening 67a of the lower damper plate 67 is an upper opening 8Ab (see FIG. 6).

  In addition, when the four pressure chamber groups 12 are considered together, a large number of virtual lines Z ′ (see FIG. 10) that pass through the center of the discharge port 8Aa of each nozzle hole 8A and are parallel to the main scanning direction are in any two. Are not overlapped with each other. For example, in the present embodiment, in order to enable printing with a resolution of 600 dpi, two adjacent virtual lines Z ′ are separated by a distance corresponding to 600 dpi. At this time, 16 ejection port arrays 18A (see FIG. 5) are arranged on the ink ejection surface 70a so that a large number of ejection ports 8Aa extend in the sub-scanning direction (first direction) and face each other. ) Is formed. In the flow path unit 4, four individual ink flow paths 7 including nozzle holes 8A corresponding to different pressure chamber groups 12 existing on four virtual lines Z ′ adjacent to each other are provided as one individual ink flow path. It constitutes a set.

  Next, the positional relationship between the ejection port 8Aa of the nozzle hole 8A and the connection port 67Aa connected to the nozzle hole 8A in one individual ink channel set will be described with reference to FIG. FIG. 10 shows an arbitrary point set on the ink discharge surface 70a when the nozzle plate 30A is used, and four discharge ports 8Aa, an upper opening 8Ab, and a connection port 67a related to one individual ink flow path set. FIG. 6 is a diagram projected onto a virtual plane parallel to the ink ejection surface 70a along a direction perpendicular to the surface 70a. That is, FIG. 10 shows the positional relationship between the four nozzle holes 8A corresponding to the pressure chamber groups 12A, 12B, 12C, and 12D existing on the mutually adjacent virtual lines Z ′ and the connection ports 67a. . Hereinafter, in the virtual plane, the projection of the discharge port 8Aa is referred to as a projection contour 8Aa 'of the discharge port, and the projection of the upper opening 8Ab is referred to as a projection contour 8Ab' of the upper opening. Further, the center point of the projection outline 8Aa ′ of the discharge port is referred to as a projection discharge port point 8Ac. In FIG. 10, the projected outline 8Ab ′ of the upper opening is indicated by a broken line. In FIG. 10, the projected outlines 67 a ′ of the four connection ports are drawn so that the separation distance in the main scanning direction is shorter than the distance when the scale in the sub scanning direction is considered as a reference. Specifically, the separation distance in the main scanning direction, such as the projected contour lines 67a ′ of the four connection ports, is drawn at a position further reduced by the same ratio when the distance when considered on the basis of the scale in the sub scanning direction is used. Yes. Furthermore, in order to make the positional relationship easy to understand, the projection outline 67a ′ of the connection port and the like are drawn so as to be arranged at equal intervals in the main scanning direction.

  As shown in FIG. 10, in the virtual plane, the four projection connection points 67b are separated by a fixed interval l (first distance: 1200 dpi) with respect to the sub-scanning direction and inclined with respect to the main scanning direction. Are arranged on a straight line B. Further, the four projection discharge port points 8Ac are spaced apart from each other by a constant interval L (second distance: 600 dpi) in the sub-scanning direction, and are arranged on a straight line A ′ intersecting with the straight line B. Since the interval l is smaller than the interval L, the straight line A ′ is inclined more than the straight line B. At this time, considering the direction, the distance (LA ′, LB ′, LC ′, LD ′) in the sub-scanning direction of the corresponding projection discharge port point 8Ac with respect to the projection connection port point 67b is the interval L−the interval l (= 600 dpi). Further, the larger the coordinate component related to the sub-scanning direction of the projection connection port point 67b with respect to the common origin O, the larger the coordinate component related to the sub-scanning direction of the projection discharge port point 8Ac corresponding to the projection connection port point 67b. Thus, both the coordinate component related to the sub-scanning direction of the projection connection port point 67b with respect to the common origin O and the coordinate component related to the sub-scanning direction of the corresponding projection discharge port point 8Ac with respect to the projection connection port point 67b are one individual. All four individual ink channels 7 belonging to the ink channel group are different. Furthermore, at this time, the projection discharge port point 8Ac, the projection contour 8Aa ′ of the discharge port, and the projection contour 8Ab ′ of the upper opening are completely included in the projection contour 67a ′ of the connection port in the virtual plane. Thereby, in each individual ink flow path 7, the ink from the pressure chamber 10 flows smoothly into the nozzle hole 8A via the connection port 67a.

  According to the embodiment described above, even if any of the nozzle plates 30 and 30A where the positions of the discharge ports 8a and 8Aa are different from each other is used, it is assumed that a slight positional deviation occurs in the manufacturing process of the inkjet head 1. Also, the projected contours 8b ′ and 8Ab ′ of the upper opening are surely included in the projected contour 67a ′ of the connection port. Accordingly, in all the individual ink flow paths 7, the ink flow is hardly disturbed, and excellent ink ejection performance can be obtained. Further, the plates 21 to 29, 66 and 67 other than the nozzle plates 30 and 30A can be shared. Therefore, the color and monochrome ink jet heads 1 can be manufactured at low cost.

  Further, in the virtual plane, the coordinate component related to the sub-scanning direction of the projection connection point 67b with respect to the common origin O, and the coordinate component related to the sub-scanning direction of the corresponding projection discharge port point 8c and the projection discharge port point 8Ac with respect to the projection connection port point 67b. Are different for all four individual ink channels 7 belonging to one individual ink channel group. According to this, since the range of nozzles that can be connected to the connection port 67a is further widened, even when any of the nozzle plates 30, 30A having the nozzle holes 8, 8A having different positions of the discharge ports 8a, 8Aa is used. In all the individual ink flow paths 7, the ink flow is not easily disturbed reliably, and more excellent ink ejection performance can be obtained.

  Further, in the virtual plane, the four projection connection points 67b are separated by a fixed interval l with respect to the sub-scanning direction, and corresponding projections for the projection connection point 67b when the monochrome nozzle plate 30A is used. Since the distance (LA ′, LB ′, LC ′, LD ′) in the sub-scanning direction of the ejection port point 8Ac changes by the interval L−the interval 1 (= 600 dpi), the structure of the individual ink flow path set is simple. become.

  In addition, in the virtual plane, distances (LA, LB, LC, LD; LA ′, LB ′, LC ′, LD ′) in the sub-scanning direction of the corresponding projection discharge port points 8c, 8Ac with respect to the projection connection port point 67b. However, since the distance is changed by a certain distance, the difference in the ink ejection characteristics between the nozzle holes 8 and 8A in the individual ink flow path group is reduced. Thereby, especially when a monochrome inkjet head is configured using the nozzle plate 30A, it is possible to suppress a decrease in image quality of monochrome printing.

  In addition, by using the nozzle plate 30A, high-resolution monochrome printing is possible. At this time, in the virtual plane, the four projection discharge port points 8Ac are separated by a certain interval L with respect to the sub-scanning direction. Since the four projection connection port points 67b are arranged on the straight line A while being separated by a constant interval l smaller than the interval L in the sub-scanning direction, the structure of the individual ink flow path set is It becomes easier.

  Furthermore, by configuring so that different inks are supplied to each sub-manifold 5a and changing the nozzle plate, it is possible to configure an inkjet head capable of ejecting a maximum of eight colors of ink.

  In addition, since the pressure chambers 10 and the individual electrodes 35 are arranged in a staggered manner in the sub-scanning direction, the pressure chambers 10 can be arranged after high density, and high-resolution printing is possible.

  Further, the projection discharge port points 8c of the color nozzle plate 30 are arranged on a straight line A extending in the main scanning direction, and the monochrome nozzle plate 8Ac is arranged on a straight line A ′ intersecting the straight line A. On the other hand, the projection connection points 67b having a common arrangement for color and monochrome are arranged on a straight line B having an intermediate inclination between the two straight lines A and A ′. The difference in ink discharge characteristics between the nozzles 8 and 8A is easily reduced in the individual ink flow path group except that the ink droplet landing positions are different.

  The preferred embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and various design changes can be made as long as they are described in the claims. . For example, in the above-described embodiment, the four individual ink channels 7 form one individual ink channel group, but a plurality of individual ink channels other than four are one individual ink channel. The structure which forms a set may be sufficient.

  In the embodiment described above, one manifold channel 5 is branched into two sub-manifold channels 5a, but may be configured not to be branched into two sub-manifolds, or three or more sub-manifolds. The structure which branches to may be sufficient.

  Furthermore, in the above-described embodiment, the configuration has a large number of individual ink flow path sets. However, the number of individual ink flow path sets may be one.

  In the embodiment described above, in the virtual plane, the coordinate component related to the sub-scanning direction of the projection connection port point 67b with respect to the common origin O, and the corresponding projection discharge port point 8c and the projection discharge port point with respect to the projection connection port point 67b. Each individual ink flow path is configured so that both of the coordinate components of 8Ac in the sub-scanning direction are different for all four individual ink flow paths 7 belonging to one individual ink flow path set. Both of the coordinate component regarding the sub-scanning direction of the projection connection port point and the coordinate component regarding the sub-scanning direction of the corresponding projection discharge port point with respect to the projection connection port point are among the individual ink channels belonging to one individual ink channel group. It is sufficient that the individual ink flow paths are configured so that at least two of them are different.

  Furthermore, in the above-described embodiment, the connection port 67a is formed so that the four projection connection port points 67b are separated from each other by a predetermined interval l in the sub-scanning direction in the virtual plane. May be formed so as to be spaced apart at an arbitrary interval in the sub-scanning direction.

  In addition, in the above-described embodiment, each individual ink flow path is set so that the distance between the four projection discharge port points 8c and 8Ac and the corresponding projection connection port point 67b changes by a certain distance in the virtual plane. However, the individual ink flow paths may be formed such that the distance between the projection discharge port point and the projection connection port point corresponding to the projection discharge port point changes by an arbitrary distance on the virtual plane.

  In the above-described embodiment, the ejection port arrays 18 and 18A are configured to extend along the sub-scanning direction, but the ejection port arrays extend along directions other than the sub-scanning direction. It may be configured as follows.

  Further, in the above-described embodiment, in the virtual plane, the four projection discharge port points 8Ac are arranged on the straight line A ′ while being spaced apart by a constant interval L with respect to the sub-scanning direction. The individual ink flow paths 7 are formed such that 67b is arranged on the straight line B while being spaced apart by a constant interval l smaller than the interval L in the sub-scanning direction. The interval l is the same as the interval L. Alternatively, the individual ink flow paths may be formed so that the interval 1 is larger than the interval L. Further, the individual ink flow paths may be formed so that the projection connection port points are not arranged on a straight line.

  In addition, in the above-described embodiment, the inkjet head 1 has a configuration capable of four-color printing or monochrome printing by changing the nozzle plates 30 and 30A. For example, by changing the nozzle plate, it may be configured to be capable of color printing of two colors, three colors, or five colors or more, and part of the color printing is possible. In other words, the remaining portion may be configured to be capable of monochrome printing.

  Moreover, although the inkjet head 1 mentioned above is applied to a serial type inkjet printer, it is applicable also to the inkjet head applied to a line type inkjet head printer. The ink jet head is driven by a piezoelectric actuator unit, and ink is ejected from the nozzle. The ink in each pressure chamber is heated by a signal sent from the FPC to give ejection energy to the ink in the pressure chamber. Even an inkjet head of this type can be applied.

1 is an external perspective view of an inkjet head according to an embodiment of the present invention. It is sectional drawing in the II-II line of FIG. FIG. 3 is a perspective view showing a state where a reinforcing plate is bonded to the head body shown in FIG. 2. FIG. 3 is a plan view of the head main body shown in FIG. 2. It is an enlarged view of the area | region enclosed with the dashed-dotted line drawn in FIG. It is sectional drawing along the VI-VI line of FIG. FIG. 6 is an enlarged view of a region surrounded by an alternate long and short dash line drawn in FIG. 5. FIG. 7 is a diagram in which the ejection port, the upper aperture, and the connection port in the color nozzle plate depicted in FIG. 6 are projected onto a virtual plane parallel to the ink ejection surface. The actuator unit of FIG. 6 is shown, (a) is an enlarged view of a portion surrounded by a one-dot chain line in FIG. 6, and (b) is a plan view of an individual electrode. FIG. 7 is a diagram in which an ejection port, an upper aperture, and a connection port in the monochrome nozzle plate depicted in FIG. 6 are projected on a virtual plane parallel to the ink ejection surface. When the color nozzle plate and the monochrome nozzle plate are respectively used in the flow path configuration of the conventional color ink jet head, the nozzle hole discharge port, the inflow port formed on the side opposite to the discharge port, and this FIG. 6 is a diagram in which a connection port connected to an inflow port is projected onto a virtual plane parallel to the ink ejection surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet head 4 Flow path unit 5 Manifold flow path 5a Sub manifold 7 Individual ink flow path 8 Nozzle 8a Discharge port 8a 'Projection outline 8b of discharge port 8c Projection discharge port point 10 Pressure chamber 11 Pressure chamber row 12 Pressure chamber group 14 Descender hole 18 Discharge port array 21 Actuator unit 30 Nozzle plate 67a Connection port 67a 'Projection outline 67b of projection port Projection connection port point 70 Head body 70a Ink ejection surface

Claims (15)

A nozzle in which a plurality of individual ink flow paths are formed from an outlet of a common ink chamber to a discharge port through which a droplet is discharged through a pressure chamber, and a plurality of nozzle holes having the plurality of discharge ports are formed on an ink discharge surface An inkjet head including a flow path unit to which a plate is fixed,
In the flow path unit, a plurality of ejection port arrays that extend in the first direction by the plurality of ejection ports and are arranged to face each other are formed on the ink ejection surface, and the nozzle plate In the fixed surface, connection ports of the plurality of individual ink flow paths are respectively formed corresponding to the plurality of nozzle holes,
An arbitrary point in the ink ejection surface, the centers of n (n: natural number) ejection ports adjacent to each other in a second direction belonging to different ejection port arrays and intersecting the first direction, and When n centers of the n connection ports corresponding to the n discharge ports are projected onto a virtual plane parallel to the ink discharge surface along a direction perpendicular to the ink discharge surface, n The connection port with respect to a common origin formed on the virtual plane by projecting the arbitrary point in the individual ink flow channel group composed of the n individual ink flow channels related to the discharge port Of the projection connection port point formed in the virtual plane by projecting the center of the coordinate component in one direction in the virtual plane, and the center of the discharge port corresponding to each projection connection port point is By being projected Wherein the individual ink passage both differ at least two mutually between the coordinate components relating to said one direction projection discharge opening points formed on the virtual plane is present,
For each of the pair of projection connection port points that are most distant from each other among the n projection connection port points, the positional relationship in the one direction with the corresponding projection discharge port point is n. In contrast, when the projected discharge port points are arranged at different positions with respect to the one direction, and when the n projected discharge port points are arranged in a straight line along a direction orthogonal to the one direction. ink jet head, characterized in that it it.   Both the coordinate component related to the one direction of the projection connection port point with respect to the common origin and the coordinate component related to the one direction of the projection discharge port point corresponding to the projection connection port point are n individual ink flow paths. The inkjet head according to claim 1, wherein all are different.   The inkjet head according to claim 2, wherein the n projection connection port points are equally spaced with respect to the one direction.   3. The n distances in the one direction between the n projection connection port points and the n projection discharge port points corresponding to the projection connection port points change at equal intervals. The inkjet head described in 1.   The n projection connection port points are separated by a first interval with respect to the one direction, and the n projection connection port points and the n projection discharge port points corresponding to the n projection connection port points. The inkjet head according to claim 2, wherein n distances in one direction are changed every second interval.   The inkjet head according to claim 5, wherein the n projection discharge port points are spaced at equal intervals in the one direction.   The inkjet head according to claim 6, wherein the first interval is smaller than the second interval.   The coordinate component related to the one direction of the projection discharge port point corresponding to the projection connection port point is larger as the coordinate component related to the projection connection port point with respect to the common origin is larger. The inkjet head described in 1.   The inkjet head according to claim 5, wherein the n projection discharge port points are arranged on a straight line along a direction orthogonal to the one direction.   When n projection connection port points and n projection discharge port points are arranged at equal intervals in the second direction on the virtual plane, the n projection connection port points are a first straight line. 10. The n projection outlet points are present on a second straight line extending in a direction intersecting with the first straight line. The inkjet head of any one of these.   When the outline of the connection port is projected onto the virtual plane along a direction perpendicular to the ink discharge surface, the projection discharge port point corresponding to the connection port is projected onto the virtual plane. The inkjet head according to claim 1, wherein the inkjet head is included in a projected outline of the connection port formed.   When the contour of the ejection port is projected onto the virtual plane along a direction perpendicular to the ink ejection surface, the projected contour of the ejection port formed on the virtual plane by being projected is The inkjet head according to claim 11, wherein the inkjet head is included in a projected outline of the connection port. The plurality of common ink chambers are arranged so as to face each other while extending in the first direction,
Each common ink chamber communicates with m (m: natural number) of the individual ink flow paths related to the common ejection port array,
M projection discharge port points corresponding to the m individual ink flow paths communicating with the same common ink chamber are equally spaced with respect to the one direction on the virtual plane;
13. The m individual ink flow path groups each including the n individual ink flow paths communicating with the different common ink chambers are formed. Inkjet head. n common ink chambers are formed;
Each of these n common ink chambers has two sub-common ink chambers,
The m projection discharge port points corresponding to the m individual ink flow paths communicating with the two sub-common ink chambers belonging to each common ink chamber are equally spaced with respect to the one direction on the virtual plane. The inkjet head according to claim 13, wherein 15. The inkjet head according to claim 13, wherein the n × m pressure chambers and the individual electrodes arranged to face the pressure chambers are arranged in a staggered manner with respect to the one direction.

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