JP2007185953A - Droplet discharge apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an ink-jet recording apparatus capable of increasing the recording speed using a pigment ink and improving the recording quality using a colorant ink. <P>SOLUTION: The diameter of a nozzle 39a for jetting out the pigment ink is larger than the diameter of each of nozzles 39b to 39d for jetting out the colorant ink. The area S1 of an activation portion 41 for jetting out the pigment ink is larger than the area S2 of each of activation portions 42 to 44 for jetting out the colorant ink. The electrostatic capacitance C1 of the activation portion 41 is larger than the electrostatic capacitance C2 of each of the activation portions 42 to 44. The rise time T1 of a drive waveform for generating a piezoelectric effect in the activation portion 41 is longer than the rise time T2 of each of the drive waveforms for generating piezoelectric effects in the activation portions 42 to 44. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus including a first nozzle group that ejects pigment ink and a second nozzle group that ejects dye ink.

In general, pigment inks are less likely to spread on paper than dye inks. Therefore, in the conventional ink jet recording apparatus, when images of the same resolution are recorded, the droplet volume of the pigment ink ejected to form one dot is made larger than the droplet volume of the dye ink. For example, in the inkjet recording apparatus described in Patent Document 1 (Japanese Patent Laid-Open No. 2001-315324), by using different numbers of driving waveforms when ejecting pigment ink and ejecting dye ink, The number of droplets of pigment ink ejected to form one dot is larger than the number of droplets of dye ink.
JP 2001-315324 A (paragraphs 44 to 45)

  However, the conventional method of changing the ink droplet volume depending on the number of drive waveforms has a limit on the ink droplet volume that can be controlled, and thus cannot meet the demand for further improving the recording speed and recording quality. There is a problem. For example, in order to record a high-quality image with outstanding contrast, an ink jet recording apparatus using a pigment ink as a black ink and a dye ink as a color ink other than black is known. Here, in the case of recording a solid area (area to be recorded without a gap), the method of changing the droplet volume according to the number of driving waveforms described above requires black ink rather than color ink to form one dot. The number of drive waveforms becomes larger. In order to output many drive waveforms, the drive cycle must be lengthened, and the recording time is lengthened. In addition, in high-resolution recording, a smaller droplet volume is required. However, it is difficult to improve the quality of the color ink of the dye ink with respect to the black ink of the pigment ink because the dot diameter tends to expand on the paper surface. there were.

  A first object of the present invention is to realize an ink jet recording apparatus capable of further speeding up recording with pigment ink. The second object of the present invention is to realize an ink jet recording apparatus capable of further improving the quality of recording with dye ink. In addition, the code | symbol with the parenthesis attached | subjected to each element shown below is only the illustration of the element, and does not limit each element.

Means for Solving the Problems and Effects of the Invention

  According to a first aspect of the present invention, there is provided an ink jet recording apparatus (1) that performs recording by ejecting pigment ink and dye ink, and includes a first nozzle group (39a) that ejects the pigment ink; The second nozzle group (39b, 39c, 39d) for ejecting the dye ink, the first pressure chamber group (31a) provided corresponding to the first nozzle group (39a), and the second nozzle The second pressure chamber group (31b, 31c, 31d) provided corresponding to the group (39b, 39c, 39d) and the pigment ink in the first pressure chamber group (31a) are ejected by the piezoelectric effect. The first active part group (41) for applying the pressure of the second active part and the second active part for applying the pressure for jetting to the dye ink in the second pressure chamber group (31b, 31c, 31d) by the piezoelectric effect A group (42, 43, 44), and a first nozzle The diameter (Φ1) of the nozzle belonging to the group (39a) is larger than the diameter (Φ2) of the nozzle belonging to the second nozzle group (39b, 39c, 39d), and the active part belonging to the first active part group (41) The area (S1) facing the pressure chambers belonging to the first pressure chamber group (31a) of the active portion belonging to the second active portion group (42, 43, 44) is the second pressure chamber group (31b, An ink jet recording apparatus (1) larger than the area (S2) facing the pressure chambers belonging to 31c, 31d) is provided.

  In the ink jet recording apparatus (1) of the present invention, the area facing the pressure chamber belonging to the first pressure chamber group (31a) of the active portion belonging to the first active portion group (41) for ejecting the pigment ink (S1). From the area (S2) facing the pressure chambers belonging to the second pressure chamber group (31b, 31c, 31d) of the active part belonging to the second active part group (42, 43, 44) ejecting the dye ink Therefore, even if the same voltage is applied to the first active part group (41) and the second active part group (42, 43, 44), the active parts belonging to the first active part group (41) Can generate larger energy than the active parts belonging to the second active part group (42, 43, 44). That is, when recording with pigment ink, a larger droplet volume is obtained than when recording with dye ink. Therefore, it is not necessary to increase the number of drive waveforms when forming one dot of black ink than the number of drive waveforms when forming one dot of color ink. As a result, the cycle for forming one dot of black ink can be shortened, and the recording speed of the pigment ink can be increased. Furthermore, the diameter (Φ1) of the nozzle belonging to the first nozzle group (39a) connected to the first pressure chamber group (31a) is set to the second nozzle group (39b, 39c, 39d connected to the second pressure chamber group). ) Is larger than the diameter (Φ2) of the nozzles belonging to (2), it is possible to eject pigment ink and dye ink droplets having different energies at substantially the same speed. Therefore, the droplet can be landed at a predetermined position and recorded with high quality. Further, since the volume of the dye ink droplet can be reduced, the recording quality of the dye ink can be improved.

  In the inkjet recording apparatus (1) of the present invention, the nozzle diameter (Φ1) belonging to the first nozzle group (39a) may be 20 μm, and the nozzle belonging to the second nozzle group (39b, 39c, 39d). The diameter (Φ2) may be 17 μm.

  In the ink jet recording apparatus (1) of the present invention, the active part capacitance (C1) belonging to the first active part group (41) is the active part belonging to the second active part group (42, 43, 44). It may be larger than the electrostatic capacity (C2). Specifically, the capacitance (C1) of the active part belonging to the first active part group (41) may be 1500 pF, and the active part belonging to the second active part group (42, 43, 44). May have a capacitance (C2) of 1000 pF. In an ink jet recording apparatus that applies pressure for ejection to ink in a pressure chamber using the piezoelectric effect, energy increases and the volume of ink droplets increases when the capacitance of the active portion increases. There are characteristics. Therefore, the capacitance (C1) of the active part belonging to the first active part group (41) is larger than the capacitance (C2) of the active part belonging to the second active part group (42, 43, 44). Thus, a large droplet volume can be obtained when recording with pigment ink, and a small droplet volume can be obtained when recording with dye ink. Thereby, it is possible to increase the recording speed with the pigment ink and to improve the recording quality with the dye ink.

  In the ink jet recording apparatus (1) of the present invention, the rise time or fall time (T1) of the drive waveform for generating the piezoelectric effect in the active part belonging to the first active part group (41) is the second active part. It may be longer than the rise time or fall time (T2) of the drive waveform for generating the piezoelectric effect in the active part belonging to the group (42, 43, 44). Specifically, the rise time or fall time (T1) of the drive waveform for generating the piezoelectric effect in the active part belonging to the first active part group (41) may be 1.5 μs, and the second The rise time or fall time (T2) of the drive waveform for generating the piezoelectric effect in the active portions belonging to the active portion group (42, 43, 44) may be 1.0 μs. In an ink jet recording apparatus that applies a jetting pressure to ink in a pressure chamber using the piezoelectric effect, the volume of ink droplets increases as the rise time or fall time of the drive waveform increases. There is a characteristic. Therefore, the rise time or fall time (T1) of the drive waveform for generating the piezoelectric effect in the active part for pigment ink ejection is the drive waveform for generating the piezoelectric effect in the active part for dye ink ejection. In the case of recording with pigment ink, a large droplet volume is obtained, and in the case of recording with dye ink, a small droplet volume is obtained. can get. Thereby, it is possible to increase the recording speed with the pigment ink and to improve the recording quality with the dye ink.

  In the inkjet recording apparatus (1) of the present invention, the diameter (Φ1) of the nozzles belonging to the first nozzle group, and the second so that the ejection speed of the pigment ink and the ejection speed of the dye ink are the same. The diameter (Φ2) of the nozzles belonging to the nozzle group can be selected.

  In the inkjet recording apparatus (1) of the present invention, the pigment ink may be a black ink, and the dye ink may be a color ink. In this case, since a droplet of black ink having a large volume is obtained, a recording area where a large amount of black ink is used, such as solid coating with black ink, can be recorded at high speed. In addition, by recording the color ink droplets having a small droplet volume in an overlapping manner, small-diameter dots and large-diameter dots can be freely obtained, so that high-quality color recording can be performed.

  According to the second aspect of the present invention, an inkjet recording apparatus (1) that performs recording by ejecting pigment ink and dye ink, the first nozzle group (39a) that ejects the pigment ink; The second nozzle group (39b, 39c, 39d) for ejecting the dye ink, the first pressure chamber group (31a) provided corresponding to the first nozzle group (39a), and the second nozzle The second pressure chamber group (31b, 31c, 31d) provided corresponding to the group (39b, 39c, 39d) and the pigment ink in the first pressure chamber group (31a) are ejected by the piezoelectric effect. The first active part group (41) for applying the pressure of the second active part and the second active part for applying the pressure for jetting to the dye ink in the second pressure chamber group (31b, 31c, 31d) by the piezoelectric effect A group (42, 43, 44), and a first nozzle The diameter (Φ1) of the nozzle belonging to the group (39a) is larger than the diameter (Φ2) of the nozzle belonging to the second nozzle group (39b, 39c, 39d), and the active part belonging to the first active part group (41) The area (S1) facing the pressure chambers belonging to the first pressure chamber group (31a) of the active portion belonging to the second active portion group (42, 43, 44) is the second pressure chamber group (31b, 31c, 31d) is larger than the area (S2) facing the pressure chamber, and the drive waveform rise time or fall time (in order to generate a piezoelectric effect in the active part belonging to the first active part group (41)) ( T1) is longer than the rise time or fall time (T2) of the drive waveform for generating the piezoelectric effect in the active parts belonging to the second active part group (42, 43, 44), and the first active part Capacitance (C1) of the active part belonging to the group (41) The ratio (C1 / C2) of the active part belonging to the second active part group (42, 43, 44) and the capacitance (C2) of the active part belongs to the active part belonging to the first active part group (41). Drive waveform rise time or fall time (T1) for generating the effect and drive waveform rise time for generating the piezoelectric effect in the active part belonging to the second active part group (42, 43, 44) or An ink jet recording apparatus (1) equal to the ratio (T1 / T2) to the fall time (T2) is provided.

  In the ink jet recording apparatus (1) of the present invention, the area facing the pressure chamber belonging to the first pressure chamber group (31a) of the active portion belonging to the first active portion group (41) for ejecting the pigment ink (S1). From the area (S2) facing the pressure chambers belonging to the second pressure chamber group (31b, 31c, 31d) of the active part belonging to the second active part group (42, 43, 44) ejecting the dye ink Therefore, even if the same voltage is applied to the first active part group (41) and the second active part group (42, 43, 44), the active parts belonging to the first active part group (41) Can generate larger energy than the active parts belonging to the second active part group (42, 43, 44). Therefore, when recording with pigment ink, a large droplet volume is obtained, and when recording with dye ink, a small droplet volume is obtained. Furthermore, the diameter (Φ1) of the nozzle belonging to the first nozzle group (39a) connected to the first pressure chamber group (31a) is the second nozzle connected to the second pressure chamber group (31b, 31c, 31d). By being larger than the diameter (Φ2) of the nozzles belonging to the group (39b, 39c, 39d), it is possible to eject droplets of pigment ink and dye ink given different energy at substantially the same speed. Accordingly, it is possible to record the liquid droplets at a predetermined position and with high recording quality. In an ink jet recording apparatus that applies a jetting pressure to ink in a pressure chamber using the piezoelectric effect, the volume of ink droplets increases as the rise time or fall time of the drive waveform increases. There is a characteristic. The rise time or fall time of the drive waveform is proportional to the product of the capacitance of the active portion and the internal resistance value in the drive circuit for supplying the drive waveform to the active portion. Therefore, the ratio (C1 / C2) between the electrostatic capacity (C1) of the active part for pigment ink ejection and the electrostatic capacity (C2) of the active part for dye ink ejection is defined as the activity for pigment ink ejection. Drive waveform rise time or fall time (T1) for generating a piezoelectric effect in a portion and drive waveform rise time or fall time (T2) for generating a piezoelectric effect in an active portion for dye ink ejection The internal resistance value in the drive circuit for supplying drive waveforms to both active portions can be made the same. This facilitates the design of the drive circuit. In addition, the quality control of the drive circuit is not complicated, and the manufacturing cost of the ink jet recording apparatus can be reduced.

  In the inkjet recording apparatus (1) of the present invention, the nozzle diameter (Φ1) belonging to the first nozzle group (39a) may be 20 μm, and the nozzle belonging to the second nozzle group (39b, 39c, 39d). The diameter (Φ2) may be 17 μm.

  In the inkjet recording apparatus (1) of the present invention, the rise time or fall time (T1) of the drive waveform for generating the piezoelectric effect in the active portions belonging to the first active portion group (41) is 1.5 μs. The rise time or fall time (T2) of the drive waveform for generating the piezoelectric effect in the active portions belonging to the second active portion group (42, 43, 44) may be 1.0 μs. .

In the ink jet recording apparatus (1) of the present invention, the capacitance (C1) of the active part belonging to the first active part group (41) and the active part belonging to the second active part group (42, 43, 44) The ratio to the electrostatic capacity (C2) may be 1.5.
In the inkjet recording apparatus (1) of the present invention, the circuit resistance in the output circuit for driving the active part belonging to the first active part group (41) and the second active part group (42, 43, 44) May be equal to the circuit resistance in the output circuit for driving the active part belonging to. In this case, the design of the drive IC (80) for driving the first active part group (41) and the second active part group (42, 43, 44) is facilitated, and the quality control of the drive IC (80) is also facilitated. It becomes easy.

  Embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, two guide shafts 6 and 7 are provided inside the ink jet recording apparatus 1. A head holder 9 also serving as a carriage is attached to the guide shafts 6 and 7. The head holder 9 holds a head unit 30 that performs recording by ejecting ink onto the recording paper P. The head holder 9 is attached to an endless belt 11 that is rotated by a carriage motor 10, and moves along the guide shafts 6 and 7 by driving the carriage motor 10.

  The inkjet recording apparatus 1 also includes an ink tank 5a containing yellow ink, an ink tank 5b containing magenta ink, an ink tank 5c containing cyan ink, and an ink tank containing black ink. 5d. The ink tanks 5a to 5d are connected to flexible ink supply tubes 14a, 14b, 14c, and 14d, respectively. Each ink supplied from each ink supply tube is introduced into the head unit 30 via a tube joint 20 extending forward from the head holder 9.

  In this embodiment, the black ink is a pigment ink, and each color ink other than black is a dye ink.

  Next, the structure of the head unit 30 will be described with reference to FIGS. In the following description, the direction of ejecting ink is assumed to be downward.

  As shown in FIG. 2, the nozzle surface 39e formed on the lower surface of the head unit 30 has nozzles 39a (first nozzle group) for ejecting black ink, nozzles 39b for ejecting yellow ink, and cyan ink. The nozzles 39c for ejecting, the nozzles 39d for ejecting magenta ink (second nozzle group) are arranged in two rows in a direction orthogonal to the moving direction (main scanning direction) of the head holder 9. Each nozzle is opened downward so as to face the upper surface of the recording paper P (FIG. 1).

  As shown in FIG. 5B, the head unit 30 is configured by bonding a piezoelectric actuator 40 to the upper surface of the cavity unit 50. The cavity unit 50 includes a total of nine thin plates, a nozzle plate 39, a spacer plate 38, a damper plate 37, manifold plates 36 and 35, a spacer plate 34, a supply plate 33, a base plate 32, and a cavity plate 31 in order from the bottom. It is a joined structure. Each plate, the cavity unit 50, and the piezoelectric actuator 40 are joined by an adhesive or the like.

  As shown in FIG. 3, the piezoelectric actuator 40 includes an active portion 41 (first active portion group) that generates energy for ejecting black ink and an active portion 42 that generates energy for ejecting yellow ink. And an active portion 43 that generates energy for ejecting cyan ink, and an active portion 44 that generates energy for ejecting magenta ink (second active portion group). Here, the active part is a part that acts to apply pressure for ejection to the ink in the pressure chamber disposed under the active part.

  The piezoelectric actuator 40 is configured by alternately stacking piezoelectric sheets formed of a piezoelectric material and film-like electrodes. As shown in FIG. 5B, the active part 41 is composed of a piezoelectric sheet portion 41a sandwiched between the electrodes 41b. The active part 42 includes a piezoelectric sheet portion 42a sandwiched between the electrodes 42b. The active parts 43 and 44 are similarly configured. Assuming that the active portion is the length in the longitudinal direction at the portion of the active portion facing the pressure chamber located below the active portion, as shown in FIG. 5A, the active portion 41 for ejecting black ink is used. The active length L1 (length in the longitudinal direction) is set longer than the active length L2 of the active portion 42 for ejecting yellow ink. The lengths of the active portions 41 and 42 in the short direction are set to the same D1. Although not shown, the active lengths of the active portions 43 and 44 are the same L2 as that of the active portion 42, and the length (width) in the short direction is D1. That is, the area S1 of the active part 41 for ejecting black ink is larger than the areas S2 of the active parts 42 to 44 for ejecting ink other than black. In this case, when the same voltage is applied to the active part 41 for ejecting black ink and the active parts 42 to 44 for ejecting ink other than black, the active part 41 is more active than the other active parts 42 to 44. Can generate large energy for ink ejection. Therefore, a large droplet volume can be obtained when recording with black ink, and a small droplet volume can be obtained when recording with color ink. Thereby, it is possible to increase the recording speed with the black ink and to improve the recording quality with the color ink.

  In addition, since the portion made of the piezoelectric material in each active portion has a positive characteristic that the capacitance increases as the area of the electrode increases, the capacitance C1 of the portion made of the piezoelectric material in the active portion 41 has another characteristic It is larger than each capacitance C2 in the active portions 42 to 44. Therefore, when the same drive waveform is applied to the electrodes, the active portion 41 can generate larger energy for ink ejection than the other active portions 42 to 44. Therefore, a large droplet volume can be obtained when recording with black ink, and a small droplet volume can be obtained when recording with color ink. Thereby, it is possible to increase the recording speed with the black ink and to improve the recording quality with the color ink.

  In this embodiment, the active portion 41 has an active length L1 of 1.2 mm, each of the active portions 42 to 44 has an active length L2 of 0.8 mm, and each of the active portions 41 to 44 has a width D1 of 0.16 mm. is there. That is, the area S1 of the active portion 41 is L1 × D1 = 1.2 mm × 0.16 mm = 0.192 mm2, and the areas S2 of the active portions 42 to 44 are L2 × D1 = 0.8 mm × 0.16 mm = 0. 128 mm 2. Further, the capacitance C1 of the portion made of the piezoelectric material in the active portion 41 is 1500 pF, and each capacitance C2 in the other active portions 42 to 44 is 1000 pF.

  A common ink chamber is formed below each active portion and inside the manifold plates 36 and 35. As shown in FIG. 5B, below the active portions 41 and 42, inside the manifold plates 36 and 35, a common ink chamber 35a for storing black ink and a common ink chamber for storing yellow ink. 35b is formed. The common ink chamber that stores cyan ink and magenta ink has the same volume as the yellow ink chamber. The common ink chamber 35a that stores black ink is formed to have a larger volume than the common ink chamber that stores ink of other colors.

  The head holder 9 is provided with a relay tank (not shown) having a relay ink chamber for storing bubbles contained in the ink supplied from the ink tanks 5a to 5d (FIG. 1). Ink is supplied from the ink tanks 5a to 5d to the ink supply ports 30e to 30h (FIG. 4) via the relay tank. The inks supplied to the ink supply ports 30e to 30h are supplied to the common ink chambers 35a to 35d communicating with the ink supply ports, respectively.

  In the supply plate 33 disposed above each common ink chamber, a throttle portion is formed. Each restricting portion communicates with each common ink chamber through a communication hole formed in the spacer plate 34 disposed between the manifold plate 35 and the supply plate 33 in the vertical direction. As shown in FIG. 5B, a throttle portion 33a is formed above the common ink chamber 35a that contains black ink, and the throttle portion 33a communicates with the common ink chamber 35a through the communication hole 34a. ing. A throttle portion 33b is formed above the common ink chamber 35b containing yellow ink, and the throttle portion 33b communicates with the common ink chamber 35b through the communication hole 34b.

  A pressure chamber is formed in a portion of the cavity plate 31 disposed above each throttle portion and facing the lower surface of each active portion. As shown in FIG. 4, when the surface of the cavity plate 31 is viewed from above, the pressure chambers are arranged in accordance with the arrangement of the nozzles. In this embodiment, each pressure chamber is arranged in two rows for each ink, and each of the two rows of pressure chambers is arranged in a staggered manner. Each pressure chamber extends in a direction perpendicular to the nozzle arrangement direction. Each of the pressure chambers has a length and a width that are slightly larger than the lengths L1 and L2 and the width D1 of the active portions 41, 42, 43, and 44 corresponding to the pressure chambers. Accordingly, the pressure chamber 31a (first pressure chamber group) for black ink is longer than the pressure chambers 31b, 31c, 31d (second pressure chamber group) for the other three colors of ink, but the width is the same. . The lengths of the pressure chambers 31b, 31c, 31d for the other three colors of ink are the same. FIG. 4 is drawn with the number of pressure chambers omitted. Actually, the number of pressure chambers included in one row is larger than the number shown in FIG. 4, for example, 64.

  Each pressure chamber communicates with each throttle portion through a communication hole formed in the base plate 32 disposed between the supply plate 33 and the cavity plate 31 so as to penetrate in the vertical direction. As shown in FIG. 5B, a pressure chamber 31a for accommodating black ink is formed at a portion facing the lower surface of the active portion 41 and above the throttle portion 33a through which the black ink flows. The chamber 31a communicates with the throttle portion 33a through the communication hole 32a. A pressure chamber 31b for accommodating yellow ink is formed in a portion facing the lower surface of the active portion 42 and above the throttle portion 33b through which yellow ink flows. The pressure chamber 31b is throttled through the communication hole 32b. It communicates with the portion 33b.

  Since the cross-sectional area in the vertical direction of each throttle part is formed smaller than the cross-sectional area in the vertical direction of the pressure chambers that communicate with each other, each throttle part has a larger flow path resistance than the pressure chambers that communicate with each other. In other words, the throttle portion serves to alleviate the pressure fluctuation generated in the communicating pressure chamber from reaching the common ink chamber.

  On the lower surface of the damper plate 37, damper chambers are formed below the respective common ink chambers. Each damper chamber has an opening formed downward on the lower surface of the damper plate 37. Each damper chamber is formed to have the same shape in plan view as the lower surface of each common ink chamber adjacent to the damper plate 37. As shown in FIG. 5B, a damper chamber 37a is formed below the black ink common ink chamber 35a, and a damper chamber 37b is formed below the yellow ink common ink chamber 35b. Yes.

  The damper plate 37 is made of a material such as an elastically deformable metal. The thin plate-like bottom plate portion at the top of the damper chamber can freely vibrate both on the common ink chamber side and on the damper chamber side. Even when the pressure fluctuation generated in the pressure chamber propagates to the common ink chamber when ink is ejected, the bottom plate portion elastically deforms and vibrates to absorb and attenuate the pressure fluctuation, and the pressure fluctuation is transferred to another pressure chamber. Prevent propagating crosstalk.

  In each of the plates 32 to 38 between the cavity plate 31 and the nozzle plate 39, through holes for guiding the ink in the pressure chamber to the nozzles are formed to communicate with each other in the vertical direction. Hereinafter, the ink flow path formed by each through hole is referred to as a descender. As shown in FIG. 5B, a descender 30a is vertically formed between the nozzle 39a that ejects black ink in the pressure chamber 31a and the pressure chamber 31a. A descender 30b is formed in a vertical direction between the nozzle 39b for ejecting yellow ink in the pressure chamber 31b and the pressure chamber 31b.

  The diameter Φ1 of the nozzle 39a that ejects black ink is formed larger than the diameter Φ2 of the nozzles 39b to 39d that eject other ink. Therefore, it is possible to eject the black ink and the color ink droplets having different energies at substantially the same speed. As a result, the liquid droplets can be landed at a predetermined position and recorded with high quality. Further, since the volume of the dye ink droplet can be reduced, the recording quality of the dye ink can be improved. In this embodiment, the diameter Φ1 of the nozzle 39a that ejects black ink is 20 μm, and the diameters Φ2 of the other nozzles 39b to 39d are 17 μm, respectively. Further, in this embodiment, the maximum amount of ink droplet volume that can be ejected from the nozzle when one drive signal is given to the active portion is 24 pl (picoliter) for black ink, and other color inks Is 16 pl. However, these volume capacities are merely examples, and are not limited to the above numerical values. The appropriate value varies depending on the components (surfactant, etc.) contained in the ink, the viscosity, the type of paper to be recorded, etc., but for the ink and recording paper (plain paper) that are commonly used at present, black The ratio of the ink droplet volume to the color ink droplet volume is preferably set in a range of 3: 2 to 2: 1.

  Further, as described above, the active portion 41 of the black ink generates larger energy than the active portions 42, 43, and 44 of the other inks. Further, since the pressure chamber 31a for black ink has a larger capacity than the pressure chambers 31b, 31c, 31d for other inks, the droplet volume of black ink ejected from the nozzle 39a is ejected from the nozzles 39b to 39d, respectively. It can be made larger than each droplet volume of yellow ink, cyan ink, and magenta ink.

  Next, the main configuration of the control system of the inkjet recording apparatus 1 will be described with reference to the block diagram of FIG. The ink jet recording apparatus 1 includes a microcomputer 70, a ROM 74, and a RAM 75. The microcomputer 70 includes an operation panel 12 for a user to give a recording instruction, a motor driver 17 for driving the carriage motor 10, a motor driver 18 for driving the LF motor 16, and a recording paper P. A paper sensor 76 for detecting the tip of the head holder 9, an origin sensor 77 for detecting the origin position of the head holder 9, and a temperature sensor 72 for detecting the temperature of the head unit 30 are connected. When the temperature detected by the temperature sensor 72 changes, the driving voltage for driving the head unit 30 is changed, so that the recording quality does not deteriorate with the change in the ink viscosity due to the temperature change.

  The head unit 30 is driven by a driving IC 80, and the driving IC 80 is controlled by a gate array (G / A) 73. Each electrode constituting each active part provided in the head unit 30 is connected to the drive IC 80. The drive IC 80 generates a drive signal suitable for each active part based on the control of the gate array 73 and applies it to each electrode.

  The microcomputer 70, the ROM 74, the RAM 75, and the gate array 73 are connected via an address bus 60 and a data bus 61. The microcomputer 70 generates a recording timing signal TS and a control signal RS according to a program stored in advance in the ROM 74 and transfers the signals TS and RS to the gate array 73. The gate array 73 is based on the recording data stored in the image memory 62 in accordance with the recording timing signal TS and the control signal RS, and transfer data DATA that is recording data for recording the recording data on the recording paper P. A transfer clock TCK synchronized with the transfer data DATA, a strobe signal STB, and a recording clock ICK are generated, and these signals DATA, TCK, STB, and ICK are transferred to the drive IC 80.

Further, the gate array 73 stores recording data transferred from an external device such as a host computer (host PC) 71 in the image memory 62. The gate array 73 generates a data reception interrupt signal WS based on the data transferred from the host computer 71 or the like, and transfers the signal WS to the microcomputer 70. The gate array 73 is connected to an encoder sensor 13 that detects the travel position of the head holder 9.

Next, the main configuration of the drive IC 80 will be described with reference to FIGS. Here, a drive IC 80 in the case of driving a 64-channel multi-nozzle head having 64 nozzles in one column for each ink will be described as an example.

  The drive IC 80 includes a serial-parallel conversion circuit 81, a latch circuit 82, an AND gate 83, and an output circuit 84. The serial-parallel conversion circuit 81 is composed of a 64-bit shift register, receives transfer data DATA transferred serially in synchronization with the transfer clock TCK from the gate array 73 (FIG. 6), and rises the transfer clock TCK. The transfer data DATA is converted into parallel data PD0 to PD63 according to the above. That is, serial-parallel conversion of the transfer data DATA is performed.

  The latch circuit 82 latches each of the parallel data PD0 to PD63 in accordance with the rising edge of the strobe signal STB transferred from the gate array 73. The 64 AND gates 83 logically AND each parallel data PD0 to PD63 output from the latch circuit 82 and the print clock ICK transferred from the gate array 73, respectively. Each drive data A0-A63 which is the result of the logical product is generated.

  8A and 8B, the capacitor C connected to the output side of the output circuit 84 is a capacitor as an equivalent circuit of a portion made of a piezoelectric material in the active portion. The resistance R in the output circuit 84 is an internal resistance of the output circuit 84. The output circuit 84 includes an N-type power MOSFET Q1 and a P-type power MOSFET Q2, and a drive voltage V is applied to the source terminal of the power MOSFET Q1. The drain terminal of the power MOSFET Q1 is connected to the capacitor C through the resistor R together with the drain terminal of the power MOSFET Q2. The output of the AND gate 83 is given to each gate terminal of the power MOSFETs Q1 and Q2.

  As shown in FIG. 8A, when a current flows from the AND gate 83 to the gate terminal of the power MOSFET Q1, the power MOSFET Q1 is turned on and the power MOSFET Q2 is turned off, a current flows between the source and drain of the power MOSFET Q1, and the capacitor C is charged. Thereby, the active part is displaced downward, and the volume of the pressure chamber is reduced. As shown in FIG. 8B, when the power MOSFET Q1 is turned off and the power MOSFET Q2 is turned on, a current flows between the drain and source of the power MOSFET Q2, and the capacitor C is discharged. As a result, the active part returns to the state before displacement, the volume of the pressure chamber increases, and a pressure wave is generated in the ink in the pressure chamber. When the power MOSFET Q1 is turned on again and the volume of the pressure chamber is decreased again almost in time with the timing when the pressure rises in the fluctuation cycle of the pressure wave, the pressure wave pressure and the pressure due to the displacement of the active part are superimposed, Ink in the pressure chamber is ejected from the nozzle through the descender. That is, the pressure chamber is normally reduced by the output from the AND gate 83, and the output is turned off and then turned on, so that ink is ejected by a so-called striking operation. In the normal state, the active portion is not displaced, and ink may be ejected by a pushing method in which the volume of the pressure chamber is reduced by turning on the voltage.

Here, the drive waveform applied to the electrodes of the active portions 41 to 44 has the charge / discharge characteristics of the capacitor C shown in FIG. In addition, the time required for the charging voltage to reach 90% from the start of charging of the capacitor C is the drive waveform rising time T, and the time required for the charging voltage to reach −90% is started from the fully charged state. Assuming that the waveform fall time T is between the rise time and fall time T, the capacitance C of the capacitor, and the internal resistance R,
T = −ln (0.1) CR Equation 1
The relationship is established.

Here, in this embodiment, as shown in FIG. 9A and FIG. 9B, the rise time and fall time T1 of the drive waveform applied to the active part 41 for black ink ejection are set to the color ink ejection. The rise time and fall time of the drive waveform applied to each of the active portions 42 to 44 are made longer than T2. In general, as the rise time or fall time of the drive waveform increases, the volume of the ink droplet increases. Therefore, a large droplet volume can be obtained when recording with black ink, and a small droplet volume can be obtained when recording with color ink. Thereby, it is possible to increase the recording speed with the black ink and to improve the recording quality with the color ink. Furthermore, in the inkjet recording apparatus 1 of this embodiment,
C1 / C2 = T1 / T2 Expression 2
The relationship is established. That is, since the internal resistance R in each output circuit 84 for driving each active part has the same value, the design of the drive IC 80 is facilitated. Therefore, the quality control of the drive IC 80 is not complicated, and the manufacturing cost of the ink jet recording apparatus 1 can be reduced. In this embodiment, T1 = 1.5 μs and T2 = 1.0 μs. As described above, since C1 = 1500 pF and C2 = 1000 pF, C1 / C2 = 1500/1000 = 1.5 and T1 / T2 = 1.5 / 1.0 = 1.5. C2 = T1 / T2. In this embodiment, the black ink drive waveform has a longer rise time and fall time than the color ink drive waveform, but only one of them may be controlled to be longer.

In this embodiment, the dimensions of the ink flow paths such as the respective areas S2 of the active portions 42 to 44, the pressure chambers corresponding to the active portions 42 to 44, the throttle portion, and the common ink chamber are smaller than those of the active portion 41. Regardless of the type of ink, it is possible to reduce the size of the head unit in which the area of the active portion and the volume of the ink flow path are the same. In addition, by reducing the size of the ink flow path, the fluctuation cycle of the pressure wave in the pressure chamber can be shortened. Therefore, since the drive frequency can be increased, the recording speed can be increased.
Although the present invention has been specifically described above, the present invention is not limited thereto, and can be improved and modified within the scope of the matters described in the claims. For example, the present invention can also be applied to an ink jet recording apparatus in which black ink is pigment ink and at least one kind of color ink other than black ink is pigment ink. In this case, the same effect as the above embodiment can be obtained. it can. The length D1 of the active portion in the short direction may be different between the active portion for jetting the pigment ink and the active portion for jetting the dye ink.

  The number of rows of nozzles that eject specific ink may be different from the number of rows of nozzles that eject other ink. For example, the nozzles that eject black ink may be in a plurality of rows, and the nozzles that eject other color inks may be in rows. The same effect can be obtained even when a MOSFET, FET, NPN type or PNP type transistor is used instead of the power MOSFET.

It is a plane explanatory view showing the main composition of the ink jet recording apparatus. It is the top view which looked at the head holder from the nozzle surface. It is an enlarged view of the AA arrow cross section of the head unit hold | maintained at the head holder shown in FIG. FIG. 4 is an explanatory plan view of a cavity unit constituting the head unit shown in FIG. 3. (A) is a top view of the head unit active part shown in FIG. 3, (b) is the elements on larger scale of the head unit shown in FIG. FIG. 2 is a block diagram of a main configuration of a control system of the ink jet recording apparatus shown in FIG. 1. It is a block diagram of the main components of a drive IC. 7A is an explanatory diagram at the time of charging when the portion made of the piezoelectric material of the active portion is replaced with a capacitor in the output circuit shown in FIG. 7, FIG. 7B is an explanatory diagram at the time of discharging, and FIG. It is a wave form diagram of a drive signal to be performed. (A) is a timing chart showing a drive waveform applied to the active part for black ink ejection, and (b) is a timing chart showing a drive waveform applied to the active part for color ink ejection.

Explanation of sign

1 .. Inkjet recording apparatus, 30 .. Head unit 39a .. Nozzle (nozzles belonging to the first nozzle group)
39b to 39d (nozzles belonging to the second nozzle group)
31a ... Pressure chamber (pressure chamber belonging to the first pressure chamber group)
31b .. Pressure chamber (pressure chamber belonging to the second pressure chamber group)
41 .. Active part (active part belonging to first active part group)
42 to 44 .. active part (active part belonging to second active part group)

Claims (15)

An inkjet recording apparatus that performs recording by ejecting pigment ink and dye ink,
A first nozzle group for ejecting the pigment ink;
A second nozzle group for ejecting the dye ink;
A first pressure chamber group provided corresponding to the first nozzle group;
A second pressure chamber group provided corresponding to the second nozzle group;
A first active portion group for applying pressure for jetting to the pigment ink in the first pressure chamber group by the piezoelectric effect;
A second active portion group for applying pressure for jetting to the dye ink in the second pressure chamber group by the piezoelectric effect;
With
The diameter of the nozzle belonging to the first nozzle group is larger than the diameter of the nozzle belonging to the second nozzle group;
The area facing the pressure chamber belonging to the first pressure chamber group of the active part belonging to the first active part group faces the pressure chamber belonging to the second pressure chamber group of the active part belonging to the second active part group. An ink jet recording apparatus having a larger area than that of the ink jet recording apparatus.   2. An ink jet recording apparatus according to claim 1, wherein the diameter of the nozzle belonging to the first nozzle group is 20 [mu] m and the diameter of the nozzle belonging to the second nozzle group is 17 [mu] m.   2. The ink jet recording apparatus according to claim 1, wherein the capacitance of the active part belonging to the first active part group is larger than the capacitance of the active part belonging to the second active part group.   4. The ink jet recording according to claim 3, wherein the capacitance of the active portion belonging to the first active portion group is 1500 pF, and the capacitance of the active portion belonging to the second active portion group is 1000 pF. apparatus.   The rise time or the fall time of the drive waveform for generating the piezoelectric effect in the active part belonging to the first active part group is the drive waveform for generating the piezoelectric effect in the active part belonging to the second active part group. 2. The ink jet recording apparatus according to claim 1, wherein the rise time or the fall time is longer.   The rise time or the fall time of the drive waveform for generating the piezoelectric effect in the active part belonging to the first active part group is 1.5 μs, and the piezoelectric effect is generated in the active part belonging to the second active part group 6. The ink jet recording apparatus according to claim 5, wherein a rising time or a falling time of the drive waveform for driving is 1.0 [mu] s.   The diameter of the nozzle belonging to the first nozzle group and the diameter of the nozzle belonging to the second nozzle group are selected so that the ejection speed of the pigment ink and the ejection speed of the dye ink are the same. The inkjet recording apparatus according to claim 1, wherein   The inkjet recording apparatus according to claim 1, wherein the pigment ink is a black ink, and the dye ink is a color ink. An inkjet recording apparatus that performs recording by ejecting pigment ink and dye ink,
A first nozzle group for ejecting the pigment ink;
A second nozzle group for ejecting the dye ink;
A first pressure chamber group provided corresponding to the first nozzle group;
A second pressure chamber group provided corresponding to the second nozzle group;
A first active portion group for applying pressure for jetting to the pigment ink in the first pressure chamber group by the piezoelectric effect;
A second active portion group for applying pressure for jetting to the dye ink in the second pressure chamber group by the piezoelectric effect;
With
The diameter of the nozzle belonging to the first nozzle group is larger than the diameter of the nozzle belonging to the second nozzle group;
The area facing the pressure chamber belonging to the first pressure chamber group of the active part belonging to the first active part group faces the pressure chamber belonging to the second pressure chamber group of the active part belonging to the second active part group. Larger than the area to be
The rise time or the fall time of the drive waveform for generating the piezoelectric effect in the active part belonging to the first active part group is the drive waveform for generating the piezoelectric effect in the active part belonging to the second active part group. Longer than the rise or fall time,
The ratio of the capacitance of the active part belonging to the first active part group and the capacitance of the active part belonging to the second active part group causes the active part belonging to the first active part group to generate a piezoelectric effect. An ink jet characterized by being equal to a ratio of a rise time or fall time of a drive waveform for generating a piezoelectric effect in an active portion belonging to the second active portion group to a rise time or fall time of the drive waveform Recording device.   10. The ink jet recording apparatus according to claim 9, wherein the diameter of the nozzle belonging to the first nozzle group is 20 μm, and the diameter of the nozzle belonging to the second nozzle group is 17 μm.   The rise time or the fall time of the drive waveform for generating the piezoelectric effect in the active part belonging to the first active part group is 1.5 μs, and the piezoelectric effect is generated in the active part belonging to the second active part group The ink jet recording apparatus according to claim 9, wherein a rise time or a fall time of the drive waveform for driving is 1.0 μs.   The inkjet according to claim 9, wherein a ratio of an electrostatic capacity of an active part belonging to the first active part group to an electrostatic capacity of an active part belonging to the second active part group is 1.5. Recording device.   The diameter of the nozzle belonging to the first nozzle group and the diameter of the nozzle belonging to the second nozzle group are selected so that the ejection speed of the pigment ink and the ejection speed of the dye ink are the same. The ink jet recording apparatus according to claim 9.   The circuit resistance in the output circuit for driving the active part belonging to the first active part group is equal to the circuit resistance in the output circuit for driving the active part belonging to the second active part group. An ink jet recording apparatus according to claim 9. The inkjet recording apparatus according to claim 9, wherein the pigment ink is a black ink, and the dye ink is a color ink.

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