JP4792848B2 - Inkjet recording device - Google Patents

Description

  The present invention relates to an ink jet recording apparatus that ejects ink onto a recording medium.

  In an inkjet head in which a large number of individual ink flow paths including a nozzle having an ink discharge surface and an opening on the ink discharge surface and a pressure chamber communicating with the nozzle are formed, bubbles and deteriorated ink remain in the inkjet head. As a result, the ink ejection performance may deteriorate. Therefore, in order to recover the ink ejection performance, it is necessary to perform a so-called purge operation for forcibly discharging bubbles remaining inside or deteriorated ink to the outside. As one of such purge operations, there is a positive pressure purge operation for pressurizing ink supplied to the inkjet head. In order to realize this positive pressure purge operation, an air tank that stores air having a predetermined pressure by supplying air from an air pump is provided upstream of an ink tank that stores ink supplied to the inkjet head. An ink jet printer (ink jet recording apparatus) provided is known (for example, see Patent Document 1). In this ink jet printer, during the positive pressure purge operation, the air in the air tank is supplied to the ink tank to supply the ink in the ink tank to the ink jet head. The deteriorated ink is forcibly discharged from the nozzle.

JP 2004-58348 A (FIG. 1)

  The ink that is forcibly discharged from the nozzle by this positive pressure purge operation tends to spread out along the ink discharge surface. At this time, the forcibly discharged ink wets and spreads to the openings of the other nozzles on the ink ejection surface, and may be mixed into the ink in the individual ink flow path through the openings of the other nozzles. Accordingly, in an inkjet head configured to be able to eject ink droplets of a plurality of colors for color printing, inks of other colors are mixed into the ink in the individual ink flow paths. When ink of other colors is mixed, the color of the ink changes, so that it is necessary to further discharge the ink in the individual ink flow path in order to recover the color of the ink. At this time, the color of a low-lightness ink such as black does not change greatly even if a small amount of yellow or other high-lightness ink is mixed, but the high-lightness ink is mixed only with a small amount of low-lightness ink. The color changes greatly. For this reason, in the individual ink flow path related to the low-lightness ink, after the positive pressure purge operation, a large amount of ink has to be discharged in order to recover the color of the ink, and the ink is wasted.

  An object of the present invention is to provide an ink jet recording apparatus in which ink is not consumed wastefully in a positive pressure purge operation.

Means for Solving the Problems and Effects of the Invention

An inkjet recording apparatus of the present invention includes a plurality of nozzle groups arranged on an ink ejection surface, which is a flat surface on which nozzles that eject ink droplets are continuous, individual ink flow paths for supplying ink to the plurality of nozzle groups, and a plurality of An inkjet head having a plurality of actuators for selectively applying ejection energy to ink in the individual ink flow path. A plurality of ink supply channels connected to the inkjet head for supplying ink to the plurality of individual ink channels; and one or a plurality of the ink supply channels corresponding to the plurality of nozzle groups. A pressure mechanism capable of pressurizing ink in the ink supply flow path and the individual ink flow path in units of at least one ink supply flow path, and a plurality of the individual inks based on the operation of the pressure mechanism. When performing a purge operation for forcibly discharging the ink in the flow path and the ink supply flow path, a maintenance mechanism is provided that opposes the entire nozzle group and collects the ink discharged in the purge operation. Yes. Further, in front Kipa over di operation, the ink of the plurality of individual ink flow passage and the ink supply channel according to the nozzle group lightness discharge ink colors is the largest among the plurality of the nozzle groups And a purge control means for controlling the pressurizing mechanism to forcibly discharge the ink in the plurality of individual ink flow paths and the ink supply flow paths related to the other nozzle groups. Yes.

  As described above, the color of a low-lightness ink such as black does not change greatly even if a small amount of high-lightness ink such as yellow is mixed. However, the high-lightness ink includes only a small amount of low-lightness ink. The color changes greatly. Therefore, in the positive pressure purge operation, the other color ink having the lightness that has been forcibly discharged first wets and spreads on the ink ejection surface, and is applied to the ink in the individual ink flow path related to the nozzle group having the highest lightness of the ejected ink color. When mixed, the color of the ink in the individual ink flow path changes greatly. According to the present invention, the ink in the plurality of individual ink flow paths related to the nozzle group having the highest lightness of the discharged ink color is forcibly discharged after the ink in the plurality of individual ink flow paths related to the other nozzle group is forcibly discharged. Therefore, at the time of the positive pressure purge operation, most of the inks of other colors mixed in the ink in the plurality of individual ink flow paths related to the nozzle group having the highest lightness of the discharged ink color are forcibly discharged. Thereby, the color of the ink in the said individual ink flow path is recovered. At this time, inks of other colors are mixed in the ink in the individual ink flow paths related to the other nozzle groups, but the color is large even if a small amount of ink having a relatively high lightness is mixed in a relatively light light ink. Hard to change. In addition, even when inks having low lightness are mixed with each other with a small amount of ink, the color is hardly changed. Thus, after the positive pressure purge operation, the amount of ink to be discharged is further reduced by flushing for recovering the color, and the ink is not easily consumed wastefully.

  In the present invention, the purge control means includes a plurality of the individual ink flow paths and the ink supply flow paths related to the nozzle group having the smallest lightness of the discharge ink color among the plurality of nozzle groups. It is preferable to control the pressurizing mechanism so that the ink in the plurality of individual ink flow paths and the ink supply flow paths related to the other nozzle groups is forcibly discharged before the ink is forcibly discharged. According to this, in the positive pressure purge operation, the ink with the smallest lightness is wet and spreads on the ink ejection surface and is mixed into the ink in the individual ink flow path related to the nozzle group with the large lightness of the ejected ink color. Although the color of the ink in the flow path changes greatly, the ink in the plurality of individual ink flow paths related to the nozzle group having a large lightness of the discharge ink color is related to the nozzle group having the lightness of the discharge ink color. Since the ink in the plurality of individual ink flow paths is forcibly discharged and then forcibly discharged, most of the ink having the smallest brightness mixed during the positive pressure purge operation is forcibly discharged. Thereby, the color of the ink in the said individual ink flow path is recovered. At this time, ink of another color having a high lightness is mixed in the individual ink flow path related to the nozzle group having the lightness of the discharged ink color. However, a small amount of ink having a high lightness is mixed in the ink having the lowest lightness. Even so, the color does not change significantly.

  At this time, the purge control means performs the addition so that the ink in the plurality of individual ink flow paths and the ink supply flow path is forcibly discharged in order from the nozzle group having the lightness of the discharged ink color. More preferably, the pressure mechanism is controlled. According to this, in the positive pressure purge operation, the ink in the plurality of individual ink flow paths related to the nozzle group having a high lightness of the discharged ink color is changed in the plurality of individual ink flow paths related to the nozzle group having a low lightness of the discharge ink color. Since the ink is forcibly discharged after being forcibly discharged, most of the low-lightness ink mixed during the positive pressure purge operation is forcibly discharged. Thereby, the color of the ink in each individual ink flow path is recovered. At this time, ink of another color having a high lightness is mixed in each individual ink flow path. However, even if a small amount of ink having a high lightness is mixed in an ink having a low lightness, the color does not change greatly.

  Further, at this time, the purge control means, in the nozzle groups having the same lightness of the discharge ink color, in the plurality of individual ink flow paths and the ink in order from the nozzle group having the small saturation of the discharge ink color. It is even more preferable to control the pressure mechanism so that the ink in the supply flow path is forcibly discharged. According to this, in the positive pressure purge operation, the ink in the plurality of individual ink flow paths related to the nozzle group having a high saturation of the discharge ink color is changed to the plurality of individual ink flows related to the nozzle group having a low saturation of the discharge ink color. Since the ink in the path is forcibly discharged after being forcibly discharged, most of the low-saturated ink mixed during the purge operation is forcibly discharged. Thereby, the color of the ink in each individual ink flow path is recovered. At this time, other color inks with high saturation are mixed in each individual ink flow path. However, even if a small amount of ink with high saturation is mixed in ink with low saturation, the color does not change greatly. .

  In the present invention, the ink having the highest brightness may be a yellow ink. According to this, most of the inks of other colors mixed in the individual ink flow paths related to the yellow nozzle group during the positive pressure purge operation are forcibly discharged.

  In the present invention, the ink having the smallest brightness may be a black ink. According to this, most of the black ink mixed in the individual ink flow path during the positive pressure purge operation is forcibly discharged.

  Further, in the present invention, the purge control means controls the pressurizing mechanism to forcibly discharge the ink in the plurality of individual ink flow paths and the ink supply flow path, and then drives the plurality of actuators. And a flushing control means for controlling the plurality of actuators so as to discharge the ink in the plurality of individual ink flow paths. According to this, the inks of other colors mixed during the positive pressure purge operation can be surely discharged from the individual ink flow paths.

  In addition, in the present invention, it is preferable that the pressurizing mechanism includes a pump disposed outside the inkjet head. According to this, the pressurizing mechanism can be configured with a simple configuration.

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

  FIG. 1 is a schematic configuration diagram of an ink jet recording apparatus according to a preferred embodiment of the present invention. As shown in FIG. 1, the ink jet recording apparatus 101 of the present embodiment is mounted on a carriage 17 and the carriage 17, and ink droplets of four colors (yellow, cyan, magenta, and black) are applied to the recording paper P. It has a dischargeable inkjet head 1, a purge mechanism (pressure mechanism) 90, and a control device 83 that controls the operation of the inkjet recording apparatus 101. In addition, a platen 85 is provided in the main body frame 2, and the recording paper P is conveyed forward (frontward in FIG. 1) on the platen 85. Further, a purge position in which the inkjet head 1 performs a purge operation is provided in the main body frame 2 on one side in the scanning direction (right side in FIG. 1) with respect to the platen 85 that is a conveyance path of the recording paper P. A base 95 having a waste liquid foam 94 is installed at the purge position. In addition, a retreat position for retreating when the inkjet head 1 does not perform recording on the recording paper P is provided on the other side in the scanning direction (left side in FIG. 1). At this retracted position, a cap (not shown) that covers the nozzle surface is provided.

  The carriage 17 is movable along the two guide shafts 15 and 16 provided in the main body frame 2 in a direction (left and right direction in the figure) perpendicular to the conveyance direction of the recording paper P. The ink-jet head 1 is connected with four ink cartridges 53 for storing inks of four colors (yellow, cyan, magenta, and black) through tubes (ink supply channels) 40 (see FIG. 2). As indicated by a two-dot chain line in FIG. 1, the inkjet head 1 is conveyed forward while reciprocating in the main scanning direction (left and right direction in FIG. 1) integrally with the carriage 17 above the platen 85. A desired color image is recorded on the recording paper P by ejecting four color ink droplets onto the recording paper P. That is, the inkjet head 1 is a serial head.

  Next, the inkjet head 1 will be described in detail with reference to FIGS. FIG. 2 is an external perspective view of the inkjet head 1. 3 is a cross-sectional view taken along line III-III in FIG. 4 is a perspective view showing a state in which a reinforcing plate is bonded to the head main body shown in FIG. As shown in FIGS. 2 and 3, the inkjet head 1 includes an ink tank 71 in which four ink chambers 3 for storing four colors of ink are formed, and a head main body 70 disposed below the ink tank 71. And a flexible printed circuit board (FPC) 50 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 yellow, cyan, magenta, and black inks are sequentially stored from the left ink chamber 3 in FIG. . These four ink chambers 3 are connected to ink cartridges 53 for storing corresponding color inks via tubes 40 (see FIG. 1), and ink of each color is supplied from the ink cartridges 53 to the ink chambers 3. It is like that. Further, as shown in FIGS. 3 and 4, 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. Furthermore, an opening 42 having a rectangular planar shape is formed in the reinforcing plate 41. The head main body 70 is bonded and fixed to the lower surface (right side of FIG. 2) of the reinforcing plate 41 so that an actuator unit 21 described later is disposed in the opening 42. At the lower end of the ink tank 71, four ink outlets 3a communicating with the ink chambers 3 are formed. On the other hand, the reinforcing plate 41 is formed with four through holes 41a that are continuous with the four ink outlets 3a and have an elliptical planar shape.

  The head body 70 includes a flow path unit 4 in which a plurality of ink flow paths are formed for each color, and a pressure chamber (described later) that is bonded to the upper surface of the flow path unit 4 and is formed in the flow path unit 4. 10 (see FIG. 7) and an actuator unit 21 that applies pressure (discharge energy) to ink. On the upper surface of the flow path unit 4, four ink supply ports 4a (see FIG. 5) having an elliptical planar shape are formed. The lower surface of the flow path unit 4 is an ink discharge surface 70a in which a large number of nozzles 8 (see FIG. 7) are opened. Further, the flow path unit 4 is bonded to the reinforcing plate 41 so that the through hole 41a and the ink supply port 4a formed in the flow path unit 4 are connected to each other. With this configuration, the ink of each color in the ink tank 71 is supplied into the flow path unit 4 via the ink outlet 3a, the through hole 41a, and the ink supply port 4a.

  Further, as shown in FIG. 3, the reinforcing plate 41 is attached to a stepped opening 72 a formed on the lower surface of the holder 72. 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. 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 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.

  FIG. 5 is a plan view of the head body 70. As shown in FIG. 5, the head main body 70 has a rectangular planar shape extending in the longitudinal direction (sub-scanning direction) of the flow path unit 4. In the flow path unit 4, four manifold flow paths 5 extending in parallel with each other along the longitudinal direction of the flow path unit 4 are formed. Ink is supplied to the manifold channel 5 from the ink chamber 3 of the ink tank 71 through the ink supply port 4a. In the present embodiment, manifold channels 5A, 5B, 5C, and 5D corresponding to yellow, cyan, magenta, and black are formed in order from the manifold channel 5 shown in the upper part of FIG. 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 in the ink supplied from the ink tank 71 into the flow path unit 4 is captured by the filter 45a of the filter member 45.

  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. A large number of pressure chambers 10 (see FIG. 7) and voids 60 (see FIG. 6) arranged in a matrix are formed in the adhesion region of the flow path unit 4 facing the actuator unit 21.

  FIG. 6 is an enlarged view of a region surrounded by a one-dot chain line drawn in FIG. As shown in FIG. 6, in the flow path unit 4, four manifold flow paths 5A, 5B, 5C, and 5D each branch into two sub-manifold flow paths 5a. 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. 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 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 communicates with the nozzle 8 via the descender hole 14, and the other end communicates with the protrusion 80 of the sub-manifold channel 5a via the aperture 13 and the communication hole 68 (FIG. 7). reference). In FIG. 6, the pressure chamber 10, the gap 60, the aperture 13, the nozzle 8, and the like that are in the flow path unit 4 and should be drawn by broken lines are drawn by solid lines for easy understanding of the drawing.

  As will be described later, on the actuator unit 21, individual electrodes 35 (see FIG. 8) 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. In FIG. 6, only one of the plurality of individual electrodes 35 is drawn to simplify the drawing.

  FIG. 7 is a cross-sectional view showing the individual ink flow path 7 along the line VII-VII shown in FIG. As shown in FIG. 7, the sub-manifold flow path 5a has a rectangular cross-sectional shape and a protruding portion 80 that protrudes substantially horizontally from the side wall. Each nozzle 8 communicates with the protruding 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 8. In this way, a large number of individual ink channels 7 communicate with each sub-manifold channel 5a.

  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. 7, 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.

  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 a metal in which 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 8 is provided for one pressure chamber 10 of the cavity plate 22. It is a 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 67 is a metal plate provided with a recess that becomes a part of the lower damper chamber 82 and a hole that becomes the descender hole 14. The bottom of the recess that becomes the lower damper chamber 82 becomes the lower thin film portion 82a. The nozzle plate 30 is a metal plate in which the nozzles 8 are respectively provided for one pressure chamber 10 of the cavity plate 22.

  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. 7 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 diagonally downward in a direction away from the aperture 13 for a while and then heads downward toward the nozzle 8 vertically.

  Returning to FIG. 6, 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 such that 11a → 11c → 11b → 11d → 11a → 11c → 11b from one side to the other side in the width direction of the actuator unit 21 (from the bottom to the top in FIG. 6). 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. The pressure chambers 10 of each pressure chamber group 12 communicate with each manifold channel 5 via an aperture 13. In FIG. 6, 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 designated as pressure chamber groups 12A (yellow) and 12B (cyan), respectively. , 12C (magenta), 12D (black). A plurality of nozzles 8 corresponding to each pressure group 12 forms a nozzle group 18. That is, the four nozzle groups 18 are different from each other in ejected ink colors (yellow, cyan, magenta, and black).

  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. 7).

  FIG. 8 shows the actuator unit 21. FIG. 8A is an enlarged view of a portion surrounded by a one-dot chain line in FIG. 7, and FIG. 8B is a plan view of an individual electrode. In FIG. 8, in order to make the drawing easier to understand, the terminal portion 48a, the wiring 48b, and the like that are in the FPC 50 and should be drawn with broken lines are drawn with solid lines. As shown in FIGS. 8A and 8B, 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.

  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.

  The main electrode region 35 a 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. A sharp corner portion on the left side in FIG. 8B in the substantially rhomboid main electrode region 35a extends to a region overlapping with the sharp corner 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. The land portion 36 faces 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. 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.

  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.

  The FPC 50 includes a base film 46 and a conductor pattern 47 formed on the lower surface of the base film 46. 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 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 the ejection of ink droplets 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. Accordingly, 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 piezoelectric transverse effect.

  In the present embodiment, the portion sandwiched between the individual electrode 35 and the common electrode 37 in the piezoelectric sheet 31 functions as an active portion that generates distortion due to the piezoelectric effect when an electric field is applied. 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. Therefore, a portion of the piezoelectric sheet 31 sandwiched mainly between the main electrode region 35a and the common electrode 37 contracts in a direction perpendicular to the polarization direction due to the piezoelectric lateral effect.

  On the other hand, the piezoelectric sheets 32 to 34 are not spontaneously displaced because they are not affected by the electric field, so that the piezoelectric sheets 32 to 34 are not displaced in the direction perpendicular to the polarization direction between the upper piezoelectric sheet 31 and the lower piezoelectric sheets 32 to 34. A difference is caused in the distortion, and the whole piezoelectric sheets 31 to 34 try to be deformed so as to protrude toward the non-active side (unimorph deformation). At this time, as shown in FIG. 8A, 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. Specifically, the piezoelectric sheets 31 to 34 are deformed so as to protrude toward the pressure chamber. For this reason, the volume of the pressure chamber 10 is reduced, the pressure of the ink is increased, and ink droplets are ejected from the nozzles 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. .

  Returning to FIG. 1, the purge mechanism 90 is deteriorated by foreign matters such as air and dust mixed in the ink in the tube 40, the ink chamber 3, the manifold channel 5 (sub-manifold channel 5 a), and the individual ink channel 7. This is a maintenance mechanism for forcibly discharging ink and the like together with ink. The purge mechanism 90 selectively selects the air pump 91, the surge tank 92 that temporarily stores the pressurized air pressurized by the air pump 91, and the pressurized air in the surge tank 92 to the four ink cartridges 53. And a switching unit 93 to be supplied. The purge mechanism 90 selectively supplies the pressurized air stored in the surge tank 92 to a predetermined ink cartridge 53 via the switching unit 93 based on an instruction from the control device 83. As a result, the air in the ink cartridge 53 is pressurized, and the ink in the ink cartridge 53 is forcibly supplied to the inkjet head 1 via the corresponding tube 40 at this pressure. At this time, the ink from the ink cartridge 53 spreads in the order of the tube 40 corresponding to each ink cartridge 53, the ink chamber 3, the manifold flow path 5, and the individual ink flow path 7, and is forced from the nozzle group 18 corresponding thereto simultaneously. Discharged. That is, the purge mechanism 90 is configured to perform a so-called positive pressure purge operation. Further, since the ink cartridge 53 that supplies the pressurized air can be switched by the switching unit 93, the tube 40, the ink chamber 3, the manifold channel 5, and the individual ink channel 7 in each nozzle group 18 are switched. A single-color purge operation in which ink is forcibly discharged individually is possible.

  In the positive pressure purge operation, the purge pressure can be increased compared to the suction purge operation in which the ink in the tube 40 and the inkjet head 1 is forcibly discharged by sucking ink directly from the nozzle 8. For this reason, the positive pressure purge operation has a high effect of discharging foreign matters such as air and dust mixed in each ink flow path and thickened ink clogged in the nozzle 8, and as a result, the ink consumed (discharged) is discharged. The advantage is that the amount is small.

  A wipe member 96 extending in the vertical direction is installed on the left side (platen 85 side) of the base 95. The wipe member 96 is made of a flexible material such as rubber. The wipe member 96 can be moved in the vertical direction by a drive mechanism (not shown). When the inkjet head 1 moves from above the platen 85 to the purge position, the wipe member 96 is moved downward so that the tip portion thereof does not contact the ink ejection surface 70a. Further, as will be described later, after the inkjet head 1 is moved to the purge position and the positive pressure purge operation is performed, the wipe member 96 is moved upward so that the tip portion thereof contacts the ink ejection surface 70a. In this state, when the inkjet head 1 moves to the left from the purge position, the tip of the wipe member 96 moves while being in contact with the ink discharge surface 70a, and the ink attached to the ink discharge surface 70a is wiped off. (Wiping operation).

  Next, the control device 83 will be described with reference to FIG. FIG. 9 is a functional block diagram of the control device 83. As described above, the control device 83 controls the entire inkjet recording apparatus 101 including the inkjet head 1, the purge mechanism 90, and a transport mechanism (not shown). As shown in FIG. 9, the control device 83 includes a print control unit 83a, a purge control unit (purge control unit) 83b, and a flushing control unit (flushing control unit) 83c.

  The print control unit 83a controls a recording operation on the recording paper P in the inkjet recording apparatus 101. More specifically, the carriage 17 is driven so that the inkjet head 1 moves in the main scanning direction above the recording paper P while controlling the conveyance mechanism (not shown) to convey the recording paper P onto the platen 85, and as desired. The actuator unit 21 is driven so that the ink droplets of the colors are ejected from the nozzles 8 onto the recording paper P. As a result, a desired color image is recorded on the recording paper P.

  The purge controller 83b performs a positive pressure purge operation by controlling the purge mechanism 90. Specifically, the inkjet head 1 is moved to the purge position by driving the carriage 17. Then, the purge mechanism 90 is controlled so that the ink in the tube 40, the ink chamber 3, the manifold channel 5, and the individual ink channel 7 related to the nozzle group 18 is forcibly discharged from the nozzle group 18 (single color purge operation). To do. The purge control unit 83b executes this single color purge operation for each nozzle group 18, in other words, for each ink color.

At this time, the purge control unit 83b, the discharge ink color lightness (e.g., L ^* a ^* b ^* color system (L ^* value in CIE1976)) tube 40 from those of the small nozzle group 18 in this order, an ink chamber 3. The purge mechanism 90 is controlled so that the ink in the manifold channel 5 and the individual ink channel 7 is forcibly discharged. For example, in the present embodiment, the purge control unit 83b determines that black (L ^* = 0) → magenta (L ^* = 40 to 60) → cyan (L ^* = 50 to 65) → yellow (L ^* = 85). The purge mechanism 90 is controlled so that the ink is forcibly discharged from each nozzle group 18 in the order of the colors 90). That is, the ink with the smallest brightness is the black ink, and the ink with the greatest brightness is the yellow ink. For example, since the lightness difference between magenta ink and cyan ink is small, the lightness of magenta ink and cyan ink may be the same depending on the type of ink. In this case, the purge control unit 83b determines the saturation of the ejected ink color (for example, C ^* = ((a ^* ) ² + (b ^* ) ² ) in the L ^* a ^* b ^* color system (CIE1976)) ^{1 / The} purge mechanism 90 is controlled so that the ink in the tube 40, the ink chamber 3, the manifold channel 5, and the individual ink channel 7 is forcibly discharged in order from the nozzle group 18 having the smallest value ( ² ). The ink that is forcibly discharged by each single color purge operation is collected by a waste liquid form 94 installed on the base 95.

  Then, the purge control unit 83b executes the wiping operation after all the single color purge operations are completed. As a result, the ink that has spread on the ink discharge surface 70a in each single color purge operation is wiped off.

  The flushing control unit 83c performs a flushing operation for ejecting a predetermined amount of ink from all the nozzles 8 by driving the actuator unit 21 after the positive pressure purge operation and the wiping operation are completed. The ink discharge amount by the flushing operation may be determined for each nozzle group 18. As described above, when the positive pressure purge operation is performed, a part of the forcibly ejected ink spreads wet on the ink ejection surface 70a. At this time, since each individual ink channel has a negative pressure, ink of other colors may be mixed into the ink in the individual ink channel through the opening of the nozzle 8. In order to reliably discharge the mixed ink, a flushing operation is performed.

  Based on the above, the processing procedure of the control device 83 when performing the purge operation will be described with reference to FIG. FIG. 10 is a flowchart showing a processing procedure when the purge operation is executed. As shown in FIG. 10, when the purge operation is started, the purge control unit 83b moves the inkjet head 1 to the purge position so that the ink is forcibly discharged from the nozzle group 18 whose discharge ink color is black. The purge mechanism 90 is controlled (step S101: hereinafter abbreviated as S101. The same applies to other steps). Next, the purge mechanism 90 is controlled so that the ink is forcibly discharged from the magenta nozzle group 18 (S102). Further, the purge mechanism 90 is controlled so that the ink is forcibly discharged from the nozzle group 18 whose discharge ink color is cyan (S103). Then, the purge mechanism 90 is controlled so that the ink is forcibly discharged from the nozzle group 18 whose discharge ink color is yellow (S104). When all the single color purge operations are completed, a wiping operation for wiping the ink ejection surface 70a is performed (S105). When the wiping operation is completed, the flushing control unit 83c performs a flushing operation for ejecting ink droplets from the nozzles 8 (S106). The purge operation is completed as described above, and the standby state is entered.

  By the way, the color of a low-lightness ink such as black does not change greatly even if a small amount of high-lightness ink such as yellow is mixed. However, the color of a high-lightness ink is only mixed with a small amount of low-lightness ink. Changes significantly. Therefore, in the positive pressure purge operation, the other color ink having the lightness that has been forcibly discharged first wets and spreads on the ink discharge surface 70a, and the inside of the individual ink flow path 7 related to the nozzle group 18 having the highest lightness of the discharged ink color. When mixed in the ink, the color of the ink in the individual ink flow path 7 changes greatly. According to the ink jet recording apparatus 101 according to the present embodiment described above, in the positive pressure purge operation, the tube 40, the ink chamber 3, the manifold channel 5, Since the ink in the individual ink channel 7 is forcibly discharged, most of the ink having a smaller lightness mixed during the positive pressure purge operation is forcibly discharged from the individual ink channel 7 in each individual ink channel 7. . At this time, inks of other colors having a high lightness are mixed in the individual ink flow path 7, but even if a small amount of ink having a high lightness is mixed in an ink having a low lightness, the color does not change greatly.

  In particular, most of the mixed inks of other colors (black, magenta, and cyan) are forcibly discharged in the individual ink flow path 7 related to the nozzle group 18 whose discharge ink color is yellow having the highest brightness. As a result, the color of the ink in the individual ink flow path 7 is almost completely recovered. As a result, the amount of ink to be discharged in the flushing operation is reduced, and the ink is hardly consumed wastefully.

Further, when the lightness of the ejected ink color becomes the same value, it relates to the nozzle group 18 having a small saturation of the ejected ink color (for example, the value of C ^{* in} the L ^* a ^* b ^* color system (CIE1976)). Since the ink in the tube 40, the ink chamber 3, the manifold channel 5 and the individual ink channel 7 is forcibly discharged in order from the one in the order, the inside of the individual ink channel 7 related to the nozzle group 18 having the discharge ink color with high saturation In FIG. 5, most of the mixed ink with low saturation is forcibly discharged. Thereby, the color of the ink in each individual ink flow path 7 is further recovered. At this time, in the individual ink flow path 7 related to the nozzle group 18 having a low-saturated discharge ink color, ink of another color having high saturation is mixed, but the low-saturation ink has saturation. Even if a large amount of large ink is mixed, the color does not change greatly. Thereby, it becomes difficult to consume ink more wastefully.

  Further, since the flushing operation is performed after the positive pressure purge operation, the ink of other colors mixed in the individual ink flow path 7 can be completely discharged.

  In addition, since the purge mechanism 90 includes the air pump 91 disposed outside the inkjet head 1, the purge mechanism 90 can be easily configured.

  The preferred embodiment of the present invention has been described above, but 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, in the positive pressure purge operation, the ink is forcibly discharged from each nozzle group 18 in the order of black, magenta, cyan, and yellow in the order of decreasing ink brightness values. The configuration is not limited to such a configuration. If the yellow ink, which is the ink having the highest brightness, is configured to be forcibly discharged from the nozzle group 18 at the end, the other color inks are discharged from the nozzle group 18. The order of forced discharge may be arbitrary. For example, in the positive pressure purge operation, ink may be forcibly discharged from each nozzle group 18 in the order of black → cyan → magenta → yellow, or each nozzle group in the order of magenta → black → cyan → yellow. The ink may be forcibly discharged from 18.

  In the present embodiment, when inks having the same brightness value are forcibly discharged, each ink is forcibly discharged from the nozzle group 18 in the order of decreasing ink saturation value. Even when the same ink is forcibly ejected, the ink may be forcibly ejected from the nozzle group 18 in an order not related to the saturation value.

  Furthermore, in the present embodiment, the inkjet head 1 is configured to eject ink droplets of four colors of black, cyan, magenta, and yellow, but is configured to eject ink droplets of other colors. Alternatively, it may be configured to be able to eject ink droplets of five or more colors. For example, the ink jet head may be configured to eject ink droplets of seven colors of black, red, magenta, blue, cyan, green, and yellow. In this case, in the positive pressure purge operation, it is preferable that each ink is forcibly discharged in the order of the lightness value as in the present embodiment. However, as described above, the order of forced discharge is used. However, the order of forcibly discharging the inks of the other colors may be arbitrary as long as the ink having the highest brightness is forcibly discharged last. For example, each ink may be forcibly discharged in the order of black → red → magenta → blue → cyan → green → yellow, or each ink may be forcibly discharged in the order of black → red → magenta → blue → green → cyan → yellow. Alternatively, each ink may be forcibly discharged in the order of black → red → blue → magenta → cyan → green → yellow, or each ink may be forcibly discharged in the order of black → red → blue → magenta → green → cyan → yellow. Alternatively, each ink may be forcibly discharged in the order of black → red → blue → cyan → magenta → green → yellow.

  Further, in the present embodiment, the control device 83 is configured to perform the flushing operation after the positive pressure purge operation, but may be configured not to perform such a flushing operation.

  Furthermore, in this embodiment, the purge mechanism 90 is configured to include the air pump 91, but the purge mechanism may be configured by other mechanisms.

  In addition, in the present embodiment, the inkjet head 1 is configured as a serial head, but the inkjet head is configured as a line-type head as disclosed in Japanese Patent Application Laid-Open No. 2003-31955. May be.

1 is a schematic configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention. It is a perspective view of the inkjet head shown in FIG. FIG. 3 is a cross-sectional view of the ink jet head taken along line III-III in FIG. 2. FIG. 4 is a perspective view showing a state where a reinforcing plate is bonded to the head body shown in FIG. 3. FIG. 4 is a plan view of the head body shown in FIG. 3. It is an enlarged view of the area | region enclosed with the dashed-dotted line of FIG. It is a fragmentary sectional view in alignment with the VII-VII line of FIG. FIG. 6 is an enlarged view of the actuator unit shown in FIG. 5. It is a functional block diagram of the control apparatus shown in FIG. It is a flowchart which shows the process sequence of the purge operation | movement shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet head 2 Main body frame 3 Ink chamber 4 Flow path unit 5 Manifold flow path 5a Sub manifold flow path 7 Individual ink flow path 8 Nozzle 21 Actuator unit 40 Tube 53 Ink cartridge 70a Ink ejection surface 70 Head main body 83 Controller 83a Print control Unit 83b purge control unit 83c flushing control unit 90 purge mechanism 91 air pump 92 surge tank 93 switching unit 101 inkjet recording apparatus

Claims (8)

In a plurality of nozzle groups arranged on an ink ejection surface, which is a flat surface where nozzles that eject ink droplets are continuous, individual ink flow paths for supplying ink to the plurality of nozzle groups, and the plurality of individual ink flow paths An inkjet head having a plurality of actuators for selectively applying ejection energy to the ink;
A plurality of ink supply channels connected to the inkjet head to supply ink to the plurality of individual ink channels;
The ink in the ink supply channel and the individual ink channels can be pressurized in units of at least one of the ink supply channels corresponding to the plurality of nozzle groups. Pressure mechanism ,
When performing a purge operation for forcibly discharging the ink in the plurality of individual ink flow paths and the ink supply flow path based on the operation of the pressurizing mechanism, the plurality of nozzle groups are opposed to each other and the purge operation is performed. In an inkjet recording apparatus comprising a maintenance mechanism for collecting discharged ink ,
Before at Kipa over di operation, the ink of a plurality of said individual ink passage and the ink supply channel according to the highest said nozzle groups brightness of ejected ink color among the plurality of the nozzle groups, other Purge control means for controlling the pressurizing mechanism so as to forcibly discharge the ink in the plurality of individual ink flow paths and the ink supply flow path related to the nozzle group. An ink jet recording apparatus.   The purge control unit is configured such that the ink in the plurality of individual ink flow paths and the ink supply flow path related to the nozzle group having the smallest lightness of the discharge ink color is the other nozzles. 2. The pressurizing mechanism is controlled so as to forcibly discharge ink in the plurality of individual ink flow paths and the ink supply flow path related to the group before forcibly discharging the ink. Inkjet recording device.   The purge control means controls the pressurizing mechanism so that the ink in the plurality of individual ink flow paths and the ink supply flow paths are forcibly discharged in order from the nozzle group having the lightness of the discharged ink color. The inkjet recording apparatus according to claim 2, wherein the inkjet recording apparatus is controlled.   The purge control means includes a plurality of the individual ink flow paths and the ink supply flow paths in order from the nozzle group having the small saturation of the discharge ink color with respect to the nozzle groups having the same lightness of the discharge ink color. The inkjet recording apparatus according to claim 3, wherein the pressure mechanism is controlled so that the ink is forcibly discharged.   The ink jet recording apparatus according to claim 1, wherein the ink having the highest brightness is a yellow ink.   6. The ink jet recording apparatus according to claim 2, wherein the ink having the smallest brightness is a black ink.   After the purge control means forcibly discharges the ink in the plurality of individual ink flow paths and the ink supply flow path by controlling the pressurizing mechanism, a plurality of the plurality of the individual inks are driven based on driving of the plurality of actuators. The inkjet recording apparatus according to claim 1, further comprising a flushing control unit that controls the plurality of actuators so as to discharge ink in the ink flow path. The inkjet recording apparatus according to claim 1, wherein the pressurizing mechanism includes a pump disposed outside the inkjet head.

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