JP2007237599A - Inkjet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an inkjet head which can facilitate control of jetting of ink liquid droplets in the inkjet head that carries out recording with a pigment-based ink and a dye-based ink. <P>SOLUTION: Throttling part sizes of throttling parts 34b are made the same at the pigment-based ink side and the dye-based ink side, thereby making passage resistances at the throttling parts 34b approximately the same. Even when a pressure chamber length and a nozzle diameter change between the pigment-based ink side and the dye-based ink side, variation of jetting characteristics can be made approximately the same, and control of jetting of both can be made common. A liquid droplet volume of the pigment-based ink can be increased more than that of the dye-based ink by making the pressure chamber length L1 of the pigment-based ink side longer than that of the dye-based ink side, and making the nozzle diameter D1 of the pigment-based ink side larger than the nozzle diameter D2 of the dye-based ink side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention includes a nozzle that ejects ink droplets, a pressure chamber that communicates with the nozzle, and an actuator that selectively applies ejection pressure to ink in the pressure chamber, and uses pigment-based ink and dye-based ink. The present invention relates to an inkjet head that performs recording.

In recent years, in order to meet the demand for higher recording quality, inkjet heads that perform recording with pigment-based inks and dye-based inks have been proposed. For example, in order to record high-quality images with outstanding contrast, inkjet heads that use pigment-based inks for black ink and dye-based inks with bright colors for color inks other than black are known. ing.
In this type of ink jet head, pigment-based inks are less likely to spread on the recording medium than dye-based inks. Therefore, when recording an image with the same resolution, the droplet volume of ink ejected from the nozzle per recording per dot As a result, the pigment-based ink requires a larger droplet volume than the dye-based ink. For example, as described in Patent Document 1, such an ink jet recording apparatus uses a driving voltage waveform having a different number of pulses when ejecting pigment-based ink and ejecting dye-based ink. It is known that the number of droplets of pigment-based ink ejected for recording per dot is larger than that of dye-based ink.
Also known is a method of expanding the droplet gradation range by making the flow path dimension from the pressure chamber to the nozzle different between black ink and color ink.

JP 2001-315324 A (paragraphs 44 to 45)

  However, the conventional method of changing the volume of ink droplets by using different drive voltage waveforms with different number of pulses requires the use of various types of drive voltage waveforms, which complicates ink droplet ejection control. is there. Further, in the method of making the flow path dimensions different between the black ink and the color ink, since the cycle in which the pressure wave generated in the pressure chamber fluctuates due to the pressure applied to the ink in the pressure chamber by the actuator is different, Separate drive voltage waveforms are required for the color inks, and the ejection control is complicated as described above.

  Accordingly, an object of the present invention is to realize an ink jet head capable of facilitating ink droplet ejection control in an ink jet head that performs recording with pigment-based ink and dye-based ink.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a plurality of first pressure chambers (31a) respectively connected to a plurality of first nozzles (39a) for ejecting pigment-based ink. A plurality of first pressure chambers (31a) for accommodating pigment-based inks, each of which is selectively applied with a spray pressure by the first actuator (41), and a plurality of second pressure chambers for ejecting dye-based inks. A plurality of second pressure chambers respectively connected to the nozzles (39b to 39d), each of the plurality of second pressure chambers containing dye-based inks that are selectively given ejection pressure by a second actuator; A first common ink chamber (35a) for containing ink to be supplied to the plurality of first pressure chambers; a second common ink chamber for containing ink to be supplied to the plurality of second pressure chambers; The first The ink flow chamber and the plurality of first pressure chambers are connected, and the first common ink chamber and the first pressure chamber have a larger flow path resistance than the first common ink chamber. A first throttle section (34b) for supplying ink to the first pressure chamber, the second common ink chamber and the plurality of second pressure chambers, and the second common ink chamber and A second throttle part having a flow path resistance larger than that of the second pressure chamber and supplying ink from the second common ink chamber to the plurality of second pressure chambers. The length (L1) in the longitudinal direction of the pressure chamber is longer than the length (L2) in the longitudinal direction of the second pressure chamber, and the flow path resistance of the first throttle portion and the second throttle portion is substantially equal. The technical means of the same inkjet head (30) is used.

  According to a second aspect of the present invention, in the inkjet head (30) according to the first aspect, the diameter (D1) of the first nozzle (39a) is the diameter (D2) of the second nozzle (39b to 39d). ) And the dimension in the direction intersecting the ink flow direction is defined as the width, the length (L2), the width (H2), and the depth (H1) of the first aperture portion (34b). However, the technical means that the length, width and depth of the second throttle part are the same are used.

  According to a third aspect of the present invention, in the inkjet head (30) according to the first or second aspect, the cavity plate (31) in which the plurality of first and second pressure chambers are formed, and the first A manifold plate (35, 36) in which the first and second common ink chambers are formed, and a supply plate (between the cavity plate and the manifold plate) in which the first and second throttle portions are formed. 34), and the first and second throttle portions are respectively formed along the flat plate surface of the supply plate, and the first throttle portion is the first common at both ends thereof. The second throttle part is connected to the second common ink chamber and the second pressure chamber at both ends thereof, respectively connected to the ink chamber and the first pressure chamber. Using technical means that are.

  According to a fourth aspect of the present invention, in the inkjet head (30) according to the third aspect, the manifold plate (35, 36) is located on the opposite side of the supply plate (34), A nozzle plate (39) in which first and second nozzles are formed, and a longitudinally open surface of the first and second throttle portions formed in a groove shape in the supply plate, are positioned so as to cover the first plate A first communication hole (32a) for connecting one end of one throttle part to the first pressure chamber or the first common ink chamber; and one end of the second throttle part to the second pressure chamber or A technical means is used in which a base plate (32) having a second communication hole connected to the second common ink chamber is laminated with the respective plates.

According to a fifth aspect of the present invention, in the inkjet head (30) according to any one of the first to fourth aspects, the pigment-based ink is a black ink and the dye-based ink is a color ink. The technical means is used.
In addition, the code | symbol in the said parenthesis shows a corresponding relationship with the specific means as described in each embodiment mentioned later.

  As described in the embodiments of the invention described later, according to experiments conducted by the inventors of the present application, the pressure chamber is set so that the volume of the ejected ink droplet is larger than that of the dye-based ink in the pigment-based ink. Even if the length of the ink is changed, the flow path resistance of the throttle portion is made substantially the same on the side for ejecting the pigment-based ink and the side for ejecting the dye-based ink, so that the pigment-based ink and the dye-based ink The variation in ejection characteristics between inks can be made substantially the same, and the ejection control of both can be made common.

  Furthermore, even if the nozzle diameter is changed so that the volume of the ink droplets to be ejected is larger than that of the dye-based ink in the pigment-based ink, the flow of the restricting portion determined by the length, width, and depth of the restricting portion. By making the road resistance substantially the same on the side that ejects the pigment-based ink and the side that ejects the dye-based ink, the variation in ejection characteristics can be made substantially the same between the pigment-based ink and the dye-based ink, Both injection control can be made common.

  Further, as in the invention according to claim 3, by forming the throttle portion along the flat plate surface of the supply plate, the flow path resistance value of the throttle portion can be easily set to a desired value.

  Further, as in the invention according to claim 4, the structure in which the plates are stacked allows the nozzle, the common ink chamber, the throttle portion, and the pressure chamber to be easily manufactured, and in particular, the throttle portion having a desired flow path resistance. Can be easily formed.

Embodiments of the present invention will be described with reference to the drawings.
[Main configuration]
First, the main configuration of the ink jet recording apparatus will be described with reference to FIG. FIG. 1 is an explanatory plan view showing the main configuration of the inkjet recording apparatus.
Two guide shafts 6 and 7 are provided inside the ink jet recording apparatus 1, and a head holder 9 that also serves as a carriage is attached to the guide shafts 6 and 7. The head holder 9 holds an inkjet head 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 respectively connected to flexible ink supply tubes 14a, 14b, 14c, and 14d, and the inks supplied from the ink supply tubes are extended forward from the head holder 9. It is introduced into the inkjet head 30 through the tube joint 20. As each ink, a pigment-based ink or a dye-based ink can be used.

[Inkjet head structure]
Next, the structure of the inkjet head 30 will be described with reference to FIGS.
FIG. 2 is a plan view of the head holder 9 as seen from the nozzle surface. 3A is an explanatory plan view of the pressure chamber inside the inkjet head held by the head holder 9 shown in FIG. 2 as viewed from above, and FIG. 3B is one of the pressure chambers described in FIG. FIG. In the following description, the direction of ejecting ink droplets is assumed to be downward.

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

  As shown in FIG. 3A, the cavity plate 31 constituting the inkjet head 30 has a relative movement direction of the inkjet head 30 with respect to the recording medium (hereinafter referred to as a main scanning direction) and a direction orthogonal to the direction (hereinafter referred to as the main scanning direction). A plurality of pressure chambers 31a to 31d are arranged in a matrix in the sub-scanning direction). A total of eight pressure chambers are arranged in the main scanning direction of the ink jet head 30, and each of the pressure chambers is arranged in the sub scanning direction of the ink jet head 30. Each of the pressure chambers.

  Each of the pressure chambers 31a constituting the two left columns accommodates pigment-based black ink supplied from the ink supply port 30e. The pressure chambers 31b constituting the third and fourth rows from the left accommodate the dye-based yellow ink supplied from the ink supply port 30f, respectively. The pressure chambers 31c constituting the fifth and sixth rows from the left accommodate dye-based cyan ink supplied from the ink supply port 30g, respectively. Each of the pressure chambers 31d constituting the two right columns accommodates dye-based magenta ink supplied from the ink supply port 30h.

  In each row, nozzles 39a to 39d for ejecting ink contained in the pressure chamber as ink droplets are arranged so that the nozzles for ejecting ink droplets of the same color are staggered. The arrangement interval corresponding to the sub-scanning direction of each nozzle is determined corresponding to the resolution set in the specification of the ink jet head.

Next, the vertical cross-sectional structure of the inkjet head 30 will be described by taking a portion corresponding to the pressure chamber 31a for ejecting black ink as an example.
FIG. 4A is a cross-sectional view taken along the line AA in FIG. 3B, and the inkjet head 30 is cut longitudinally along the longitudinal direction at the portion of the pressure chamber 31a that ejects black ink droplets. A part of the cross section of the case is shown. (B) is an explanatory plan view of the pressure chamber and the throttle part, (c) is an explanatory longitudinal sectional view of the throttle part, and (d) is an explanatory diagram of the nozzle diameter.

  As shown in FIG. 4A, the inkjet head 30 is configured by bonding a piezoelectric actuator 40 to the upper surface of a cavity unit 50. The cavity unit 50 has a structure in which a total of eight thin plates including a nozzle plate 39, a spacer plate 38, a damper plate 37, manifold plates 36 and 35, a supply plate 34, a base plate 32, and a cavity plate 31 are stacked and joined in order from the bottom. It is. Bonding means such as an adhesive can be applied to the bonding between the plates and the bonding between the cavity unit 50 and the piezoelectric actuator 40.

  In the cavity plate 31, a plurality of pressure chambers 31a are formed in a groove shape with the upper surface opened. The manifold plates 36 and 35 are formed with a common ink chamber 35a for storing black ink to be supplied to each pressure chamber 31a. The supply plate 34 is formed with a throttle portion 34b. The restrictor 34b communicates with the common ink chamber 35a through a communication hole 34a formed through the supply plate 34. On the supply plate 34, a base plate 32 is laminated so as to cover the open surface in the longitudinal direction of each throttle portion 34b. A communication hole 32 a communicating with the pressure chamber 31 a is formed through the base plate 32, and the communication hole 32 a communicates with a throttle portion 34 b formed on the supply plate 34. That is, the pressure chamber 31a is connected to the common ink chamber 35a via the throttle portion 34b.

  The vertical cross-sectional area of each throttle portion 34b is formed smaller than the vertical cross-sectional area of the pressure chambers communicating with each other, and the flow path resistance is set larger than that of the common ink chamber and the pressure chamber. For this reason, each throttle part 34b plays the role which relieve | moderates the component which goes to a common ink chamber among the pressure fluctuations which generate | occur | produced in the pressure chamber which connects. Thereby, when the pressure is applied to the ink in the pressure chamber 31a by the piezoelectric actuator 40, the flow of the black ink toward the nozzle 39a can be efficiently generated.

  A damper chamber 37a is formed on the lower surface of the damper plate 37 disposed under each common ink chamber. Each damper chamber 37 a has an opening formed downward on the lower surface of the damper plate 37, and the cross-sectional shape of each damper chamber 37 a is the same as the cross-sectional shape of the lower surface of each common ink chamber adjacent to the damper plate 37. It is formed into a shape.

  The damper plate 37 is made of a material such as an elastically deformable metal, and the thin plate-like bottom plate portion 37b above the damper chamber 37a freely vibrates both in the common ink chamber 35a side and in the damper chamber 37a side. can do. Even when the pressure fluctuation generated in the pressure chamber 31a propagates to the common ink chamber when the black ink droplet is ejected, the bottom plate portion elastically deforms and vibrates, thereby absorbing and damping the pressure fluctuation. It has the effect of preventing crosstalk that the pressure fluctuation propagates to other pressure chambers.

Through holes 30a for guiding the black ink in the pressure chamber 31a to the nozzles 39a are formed in the plates 32 to 38 between the cavity plate 31 and the nozzle plate 39 so as to communicate with each other in the vertical direction. .
The piezoelectric actuator 40 is configured by alternately laminating sheet-like piezoelectric materials 41a and sheet-like electrodes 41b and 41c, and a portion of the piezoelectric material sandwiched between the electrodes 41b and 41c is used as an active portion 41a, and the electrode 41b , 41c, the active portion 41a is extended in the stacking direction by applying a voltage between them, and jetting pressure is applied to the ink in the pressure chamber 31a. The active portion is provided corresponding to the upper side of each pressure chamber 31a and has a plane area smaller than the plane area of each pressure chamber 31a in plan view. However, as the active portion 41a expands, the surrounding piezoelectric material Since the portion also extends, the portion where pressure is applied to the pressure chamber 31a is the same as the flat area of the pressure chamber 31a, that is, the area of the opening on the upper surface of the pressure chamber. The pressure chamber length L1 to be described later is the length of the pressure chamber of the portion to which this pressure is applied in the ink flow direction.

The longitudinal cross-sectional structure of the pressure chamber for storing the color ink is the same as that of the black ink pressure chamber described above, but the size of the pressure chamber, the throttle portion and the nozzle is different. The difference will be described by taking a pressure chamber for accommodating yellow ink as an example. The pressure chamber length L1 is longer in the pressure chamber 31a containing black ink than in the pressure chamber 31b containing yellow ink. Further, as shown in FIGS. 4B and 4C, the length L2 of the diaphragm portion 34b corresponding to the ink flowing direction (hereinafter referred to as the diaphragm portion length) L2 is smaller in the diaphragm portion 34b on the black ink side. Longer than the yellow ink side. Further, as shown in FIG. 4D, the nozzle diameter of the nozzle 39a that ejects black ink droplets is larger than the diameter D2 of the nozzle 39b that ejects yellow ink droplets.
That is, the volume of ink droplets ejected from the nozzles has a structure in which the black ink is larger than the color ink.

  The head holder 9 is provided with a relay tank (not shown) having a relay ink chamber for storing bubbles contained in ink supplied from the ink tanks 5a to 5d (FIG. 1). Ink is supplied from each of the ink tanks 5a to 5d via a relay tank to each ink supply port (not shown) for supplying ink to the ink chamber.

[Experiment 1]
Next, Experiment 1 conducted by the inventors will be described.
The inventors of the present application provide a value of the natural period of the pressure wave generated in the ink in the pressure chamber by the operation of the actuator (hereinafter, 1/2 of this value will be described as an AL value), a nozzle diameter D, and a pressure chamber length L. An experiment was conducted to find the correlation that exists between

The target value of the AL value is set to 4.2 (μs), the nozzle diameter D is changed in the range of 16.0 μm to 21.5 μm, and the pressure chamber length L is changed in the range of 1.12 mm to 1.42 mm. While measuring the AL value. In addition, the same measurement was performed on a plurality of heads having the same specifications, and manufacturing variations existing between the heads were converged.
Note that the pressure chamber 31a has a width (width in a direction perpendicular to the length L in plan view) of 270 μm, a depth (thickness of the cavity plate 30) of 50 μm, a throttling portion 34b having a length of 700 μm, a width of 80 μm, and a depth. Each was fixed at 30 μm.

FIG. 5 is a chart summarizing some results extracted from the measurement results. For example, from the chart, in order to make the AL value 4.2 μs when the nozzle diameter D is formed to the minimum of 16.0 μm, the pressure chamber may be formed so that the pressure chamber length L is 1.12 mm. I understood that. Further, it is understood that when the nozzle diameter D is formed to the maximum of 21.5 μm, the pressure chamber should be formed so that the pressure chamber length L is 1.42 mm in order to make the AL value the same 4.2 μs. It was.
From these measurement results, between the AL value, the nozzle diameter D and the pressure chamber length L, when the AL value is 4.2 μs,

  4.2≈−0.09D + 0.83L + 4.73 (Formula 1)

It was found that there is a correlation represented by the equation. FIG. 6 is a graph showing the relationship between the AL measured value and the AL predicted value, which are values obtained by actually measuring the AL value. The predicted AL value was calculated by substituting the nozzle diameter D and the active length L using the following equation with the AL value 4.2 in Equation 1 as an unknown.

  AL≈−0.09D + 0.83L + 4.73 (Expression 2)

  The graph shown by a solid line is a graph showing the above-mentioned formula 2, and the two graphs shown by broken lines are 95% confidence curves, respectively. As can be seen from this graph, the AL prediction value almost coincides with the AL actual measurement value. In other words, it can be seen that the above formula 2 is very reliable.

  Here, if the coefficients 0.09 and 0.83 of the nozzle diameter D and the active length L in the expression 2 are replaced with the coefficients x and y, respectively, and the constant 4.73 is the constant z, the following expression 3 is obtained.

  AL≈−xD + yL + z (Formula 3)

  That is, when the AL value is a constant value and the nozzle diameter D is changed, the pressure chamber length L to be set can be obtained by substituting the AL value and the nozzle diameter D into the above formula.

  Even if the nozzle diameter D and the active length L are the same, it is estimated that the AL value is slightly different between the pigment-based ink and the dye-based ink due to the difference in the properties of the ink. Since it is considered that it is within the range, the above formula 3 can be applied when jetting either pigment-based ink droplets or dye-based ink droplets.

  Therefore, a group consisting of a nozzle, a pressure chamber and an actuator using pigment-based ink is a first group, and a group consisting of a nozzle, a pressure chamber and an actuator using a dye-based ink is a second group, When the nozzle diameter and pressure chamber length of the first set are D1 and L1, respectively, and those of the second set are D2 and L2, the following equation 4 is established.

  AL≈−xD1 + yL1 + z≈−xD2 + yL2 + z (Formula 4)

  When the constant z is subtracted from the above equation 4, the following equation 5 is obtained.

  -XD1 + yL1≈-xD2 + yL2 (Formula 5)

  That is, by adjusting the pressure chamber lengths L1 and L2, the nozzle diameters D1 and D2 can be made different (D1 ≠ D2), so the first set of nozzle diameters D1 for ejecting pigment-based ink droplets is changed to the dye system. It can be made larger than the nozzle diameter D2 of the second set for ejecting ink.

  The drive voltage waveform used in the above-described ink jet head is, for example, the one that displaces the active portion by a so-called striking method. After the pressure chamber is expanded and the pressure wave is generated in the ink, the pressure increases. By reducing the volume of the pressure chamber at the timing, ink can be ejected efficiently. From the above experiment, even a set having different nozzle diameters and pressure chamber lengths can be driven with the same drive voltage waveform if the fluctuation period of the pressure wave is substantially the same. That is, in the case where the nozzle diameter D1 of the black ink is made larger than the nozzle diameter D2 of the color ink and the droplet volumes ejected from both are made different, the drive voltage waveforms used for both can be made common.

Therefore, since the size per dot recorded on the recording paper P can be made uniform between black and color, the recording quality can be improved. In addition, since the AL value can be the same in both sets, the drive voltage waveform can be used in common.
In this embodiment, for example, the nozzle diameter D1 for ejecting black ink is 20 μm, the pressure chamber length L1 is 1.42 mm, the nozzle diameter D2 for ejecting color ink is 16 μm, and the pressure chamber length L2 is 1.12 mm.

[Experiment 2]
In addition, the inventors of the present application experimented on the size of the throttle portion, that is, the flow path resistance in the sets having different nozzle diameters and pressure chamber lengths as described above. In this experiment, in the pressure chamber length L1 = 1.42 mm and the pressure chamber length L2 = 1.12 mm (width and depth are as described above), the nozzle diameter, the length L3 of the throttle portion, the aspect ratio of the throttle portion, and the drive voltage waveform The recording quality of each was evaluated.

FIG. 7 is an explanatory diagram showing drive voltage waveforms applied to the piezoelectric actuator. The main pulse is a main driving voltage waveform applied to the piezoelectric actuator in order to eject ink droplets, and the cancel pulse is piezoelectric in order to cancel the residual pressure fluctuation generated in the pressure chamber when ink droplets are ejected. It is the drive voltage waveform applied to the actuator.
In the waveform of FIG. 7, a voltage (22V) is applied during non-injection to expand the active part, the volume of the pressure chamber is kept in a reduced state, and application of the voltage is selectively stopped during injection (main pulse is applied). The pressure chamber is expanded, the volume of the pressure chamber is increased, and a voltage is applied again after a predetermined time (the main pulse is raised) to give the ejection pressure to the ink in the pressure chamber. The pulse width from the fall of the main pulse to the rise is selected from ½ of the natural period of the ink in the pressure chamber, that is, near the AL value.

In this experiment, the pulse width B of the main pulse at AL = 4.2 μs in Experiment 1 is set to 4.0 μs, the pulse width B of the cancel pulse is 0.5 to 2.0 μs, and the interval A between the main pulse and the cancel pulse is A. The experiment was conducted while changing the value in the range of 2.4 to 3.5 μs.
The diaphragm portion has a length L3 = 700 μm, the width H2 is changed in the range of 82 μm, 86 μm, and 90 μm, the aspect ratio (width H2 / depth H1) is fixed to 2.7, and the depth H1 is set to the width H2. Changed accordingly.

  The change range of the nozzle diameter D is 16 to 21.5 μm. In addition, the environmental temperature when the experiment was performed was 25 ° C., the viscosity of the ink used in the experiment was 2 to 5 cps, the driving frequency of the inkjet head was 20 to 40 kHz, and the ejection speed of the ink droplets was 5 to 5. 15 m / s.

  8 and 9 are tables summarizing the experimental results. FIG. 8 shows the experimental results when the pressure chamber length L1 is 1.42 mm, and FIG. 9 shows the experimental results when the pressure chamber length L2 is 1.12 mm. In the chart, “diaphragm” represents the throttle width H2, “φ” represents the nozzle diameter, and numerical values such as 24 and 22 described in the upper left corner of the chart represent the total number of evaluations ◯. In the figure, 2.4, 2.8, 3.1, and 3.5 described on the right side of B / A are values of A, and 0.5 to 2.0 described below are values of B. Indicates.

  The recording quality was evaluated by recording a specific pattern on a recording sheet and performing sensory evaluation on the recorded portion. In the chart, ○ indicates the evaluation when it can be estimated that the ink droplet landing position was not displaced and the spray was not sprayed, and normal ejection was possible, and all of those that did not satisfy the evaluation condition of ○ X.

  As shown in FIG. 8, as the aperture width H2 is increased to 82 μm, 86 μm, and 90 μm, the number of ◯ in the region where the values of A and B are large decreases. This phenomenon is substantially the same when the nozzle diameter is 19.5 μm, 20.5 μm, and 21.5 μm. In addition, as shown in FIG. 9, when the pressure chamber length is 1.12 mm, the number of ◯ in the region where the values of A and B are large decreases as the throttle width H2 increases. The same is true when the nozzle diameter is 16.0 μm, 17.0 μm, and 18.0 μm.

  That is, a combination of the pressure chamber length L1 = 1.42 mm and the nozzle diameter D = 19.5 μm to 21.5 μm, and a combination of the pressure chamber length L2 = 1.12 mm and the nozzle diameter D = 16.0 μm to 18.0 μm. In any of the sets, the same drive voltage waveform is used, and the same narrowing portion width H2 shows the same variation in injection characteristics. In both the above sets, the size of the throttle portion, that is, the flow path resistance can be made common by using the common ◯ portion of FIGS.

[Effect of the embodiment]
(1) As described above, when the ink jet head 30 of the above embodiment is used, the flow path resistance of the narrowed portion 34b is set to be substantially the same on the side ejecting the pigment-based ink and the side ejecting the dye-based ink. If the active length L1 is longer on the side for ejecting the pigment-based ink than on the side for ejecting the dye-based ink, the ejection control of the ink droplets does not become complicated, and the pigment-based ink liquid ejected from the nozzle Drop volume can be larger than dye-based ink droplets.

(2) The diameter of the nozzle is determined by the length L2, the width H2, and the depth H1 of the narrowed portion 34b so that the side that ejects the pigment-based ink is larger than the side that ejects the dye-based ink. If the flow path resistance of the restrictor is set to be the same for the pigment-based ink ejection side and the dye-based ink ejection side, in addition to increasing the actuator length, the nozzle diameter will increase. As a result, it is possible to further increase the droplet volume of the pigment-based ink ejected from the nozzle.

(3) Furthermore, since the throttle part 34b is formed along the flat plate surface of the supply plate 34, the flow path resistance value of the throttle part 34b can be easily set to a desired value.
(4) Due to the structure in which the plates are stacked, the nozzle, the common ink chamber, the throttle portion, and the pressure chamber can be easily manufactured, and in particular, the throttle portion 34b having a desired flow path resistance can be easily formed. .

(5) If the nozzle diameter and pressure chamber length of the group for ejecting the pigment-based ink are D1 and L1, respectively, and those of the group for ejecting the dye-based ink are D2 and L2, the approximate expression -xD1 + yL1≈-xD2 + yL2 holds. Therefore, the nozzle diameter D1 can be made larger than the nozzle diameter D2 by adjusting the pressure chamber lengths L1, L2.
Therefore, when the pigment-based ink is a black ink and the dye-based ink is a color ink, the maximum volume of ink droplets of the black ink can be made larger than that of the color ink. Since the size per dot can be made uniform between black and color, the recording quality can be improved.

(6) Since the AL value can be set to the same value in both the group for ejecting the pigment-based ink and the group for ejecting the dye-based ink, it is not necessary to use many types of drive waveforms. Is not complicated.
(7) AL = −xD1 + yL1 + z≈−xD2 + yL2 + z (where x and y are predetermined coefficients and z is a predetermined constant) between the AL value, the nozzle diameters D1 and D2, and the pressure chamber lengths L1 and L2. ), The pressure chamber length L to be set is obtained by substituting the AL value and the nozzle diameter D into the above formula when the AL value is constant and the nozzle diameter D is changed. be able to.

<Other embodiments>
(1) In the above embodiment, the ink jet head according to the present invention has been described in which the pigment-based ink is used only for the black ink, but the present invention is also applied to an ink-jet head that uses the pigment-based ink as part of the color ink. Can be applied.
(2) In the inkjet head 30 of the above-described embodiment, a configuration in which both the throttle portion 34b and the communication hole 34a are formed inside the supply plate 34 is adopted. However, only the throttle portion 34b is formed in the supply plate 34 to communicate with the supply plate 34. The spacer plate in which only the hole 34a is formed may be arranged below the supply plate 34.
In addition, it is also possible to form a throttle portion in the shape of a groove on the lower surface of the base plate 32 and form only the communication hole 34a in the supply plate.

(3) In the inkjet head 30 of the above embodiment, the piezoelectric element is used as the actuator. However, a configuration in which the diaphragm is displaced by static electricity and an injection pressure is applied to the pressure chamber may be used.

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 9 from the nozzle surface. 3A is an explanatory plan view of the pressure chamber inside the inkjet head held by the head holder 9 shown in FIG. 2 as viewed from above, and FIG. 3B is one of the pressure chambers described in FIG. FIG. FIG. 4A is a cross-sectional view taken along the line AA in FIG. 3B, and the inkjet head 30 is cut longitudinally along the longitudinal direction at the portion of the pressure chamber 31a that ejects black ink droplets. A part of the cross section of the case is shown. (B) is an explanatory plan view of the pressure chamber and the throttle part, (c) is an explanatory longitudinal sectional view of the throttle part, and (d) is an explanatory diagram of the nozzle diameter. It is the table | surface which put together the measurement result. It is a graph which shows the relationship between AL actual value which is a value which actually measured AL value, and AL prediction value. It is explanatory drawing which shows the drive voltage waveform applied to a piezoelectric actuator. It is the chart which summarized the experimental result. It is the chart which summarized the experimental result.

Explanation of symbols

1 .. Inkjet recording device, 30 .. Inkjet head,
31a .. pressure chamber, 34b .. throttling part, 39a .. nozzle
41a ... Piezoelectric element, 41b, 41c ... Electrode, D1, D2 ... Nozzle diameter,
L1 .. Active length, L2.

Claims (5)

A plurality of first pressure chambers respectively connected to a plurality of first nozzles for ejecting pigment-based ink, each of which accommodates a plurality of pigment-based inks to which a spray pressure is selectively applied by a first actuator. A first pressure chamber;
A plurality of second pressure chambers respectively connected to a plurality of second nozzles for ejecting dye-based ink, each of which contains a plurality of dye-based inks that are selectively given ejection pressure by a second actuator. A second pressure chamber;
A first common ink chamber for containing ink to be supplied to the plurality of first pressure chambers;
A second common ink chamber containing ink to be supplied to the plurality of second pressure chambers;
The first common ink chamber is connected to the plurality of first pressure chambers and has a larger flow resistance than the first common ink chamber and the first pressure chamber. A first throttle portion for supplying ink from a chamber to the plurality of first pressure chambers;
The second common ink chamber is connected to the plurality of second pressure chambers and has a larger flow resistance than the second common ink chamber and the second pressure chamber, and the second common ink A second throttle portion for supplying ink from a chamber to the plurality of second pressure chambers,
The length in the longitudinal direction of the first pressure chamber is longer than the length in the longitudinal direction of the second pressure chamber, and the flow path resistances of the first throttle portion and the second throttle portion are substantially the same. An inkjet head characterized by that.   When the diameter of the first nozzle is larger than the diameter of the second nozzle and the dimension in the direction intersecting the ink flow direction is the width, the length, width, and The inkjet head according to claim 1, wherein the depth is the same as the length, width, and depth of the second aperture portion. A cavity plate in which the plurality of first and second pressure chambers are formed;
A manifold plate in which the first and second common ink chambers are formed;
A supply plate located between the cavity plate and the manifold plate and having the first and second throttle portions formed thereon is laminated,
The first and second throttle portions are respectively formed along a flat plate surface of the supply plate, and the first throttle portion has the first common ink chamber and the first pressure chamber at both ends thereof. 3. The second throttle portion is connected to the second common ink chamber and the second pressure chamber at both ends thereof, respectively. The inkjet head as described. A nozzle plate that is located on the opposite side of the supply plate with respect to the manifold plate, and in which the first and second nozzles are formed;
The supply plate is positioned so as to cover longitudinally open surfaces of the first and second throttle portions formed in a groove shape on the supply plate, and one end of the first throttle portion is connected to the first pressure chamber or the first A base plate having a first communication hole connected to a common ink chamber, and a second communication hole connecting one end of the second throttle portion to the second pressure chamber or the second common ink chamber; The inkjet head according to claim 3, wherein each of the plates is laminated with each of the plates.   The inkjet head according to any one of claims 1 to 4, wherein the pigment-based ink is a black ink, and the dye-based ink is a color ink.

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