JP2005161745A - Method of driving inkjet recording head and inkjet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of driving an inkjet recording head wherein controlling of vibration is carried out, residual vibration is suppressed, an ink droplet is stably ejected by maintaining the ejection speed of the ink droplet and the volume of the ink droplet in an adequate level, thereby preventing quality of an image from being lowered, and to provide an inkjet recorder. <P>SOLUTION: In this method of driving the inkjet recording head, variation in a pressure is generated in a pressure generating chamber filled with ink by a pressure generating element and an ink droplet is ejected from a nozzle communicating with the pressure generating chamber. The method includes at least a first signal A for ejecting the ink droplet by contracting the pressure generating chamber, a second signal B for maintaining the contracting condition of the pressure generating chamber and a third signal C for suppressing residual vibration of a meniscus after the ejection of the ink droplet by contracting or expanding the pressure generating chamber. When a natural vibration cycle of the pressure generating chamber is represented by Tc, the time period of the third signal C is set to be not greater than Tc/2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ink jet recording head driving method and an ink jet recording apparatus in which a diaphragm is displaced by a pressure generating element (mainly a piezoelectric element) to eject ink droplets from nozzle openings.

  An inkjet head in an inkjet recording apparatus used as an image forming apparatus (image recording apparatus) such as a printer, a facsimile machine, a copying apparatus, or a plotter has a nozzle that ejects ink droplets and a pressure generation chamber (pressure chamber, pressure chamber) that communicates with the nozzle. Pressure chamber, liquid chamber, ink chamber, ink flow path, etc.) and actuator means (energy generating means) for generating energy to pressurize the ink in the pressure generating chamber. By driving, the ink in the pressure generating chamber is pressurized and ink droplets are ejected from the nozzle openings, and the ink-on-demand type in which ink droplets are ejected only when recording is necessary is the mainstream.

  Depending on the type of actuator means for ejecting ink droplets (recording liquid), there are roughly divided into several methods. A part of the wall of the pressure generating chamber is a thin diaphragm, and a piezoelectric element as a pressure generating element is arranged corresponding to this, and the diaphragm is deformed by the deformation of the piezoelectric element generated by voltage application. Piezo-type that discharges ink droplets by changing the pressure in the generation chamber. A heating element is placed inside the liquid chamber, bubbles are generated by heating the heating element by energization, and ink droplets are discharged by the pressure of the bubbles. The bubble jet (R) type is generally well known.

  In addition, a vibration plate that forms a wall surface of the pressure generation chamber and an individual electrode outside the pressure generation chamber that is disposed to face the vibration plate are generated by applying an electric field between the vibration plate and the electrode. There has also been proposed an electrostatic type in which an ink droplet is ejected from a nozzle by changing the pressure / volume in the pressure generating chamber by deforming the diaphragm by an electrostatic force.

In Patent Document 1, the yield of the actuator device is improved, and the sum of the signal time for contracting the pressure generating chamber and ejecting ink droplets and the time for maintaining the contraction of the pressure generating chamber is matched with the natural vibration period of the pressure generating chamber. Techniques for doing so are disclosed.
JP 2001-270092 A

  However, in any of the above-described methods, after ink droplets are ejected, mist is generated due to residual vibration, and image quality abnormality problems such as jet bending occur.

  In Patent Document 1, it is difficult to immediately suppress the residual vibration, and particularly when ejecting small ink droplets, the residual vibration may cause a problem in image quality abnormality such as ejection bending, mist generation, and striped image.

  Therefore, in the present invention, vibration is suppressed, residual vibration is suppressed, and ink droplets are stably ejected while maintaining Vj (ejection speed) and Mj (ink droplet volume) of ink droplets at appropriate values, thereby reducing image quality. Do not.

  In order to achieve the above object, the present invention drives an ink jet recording head that causes a pressure change in a pressure generating chamber filled with ink by a pressure generating element and ejects ink droplets from nozzles communicating with the pressure generating chamber. In the method, the first signal for causing the pressure generating chamber to contract and ejecting the ink droplet, the second signal for maintaining the contraction of the pressure generating chamber, and the ink after discharging the ink droplet by contracting or expanding the pressure generating chamber. And the third signal time is set to Tc / 2 or less, where Tc is the natural vibration period of the pressure generating chamber. .

  Further, after the third signal, it includes a fourth signal time for contracting or expanding the pressure generating chamber to return to the initial state, and the fourth signal time is set to Tc / 2 or less. .

  Then, the vibration damping effect can be strengthened, the residual vibration can be suppressed quickly, and the image quality abnormality problems such as the occurrence of mist and ejection bend after ink droplet ejection can be reduced.

  Furthermore, it is possible to achieve desired Vj and Mj by including a fifth signal for maintaining the contraction or expansion state of the pressure generating chamber after the third signal.

  Furthermore, microdroplet formation is possible by including a sixth signal for expanding the pressure generating chamber and a seventh signal for maintaining the expanded state before the first signal.

  Further, in the present invention, in an ink jet recording apparatus having an ink jet recording head that causes a pressure change in a pressure generating chamber filled with ink by a pressure generating element and discharges ink droplets from a nozzle communicated with the pressure generating chamber. A first signal for contracting the pressure generating chamber to eject ink droplets, a second signal for maintaining contraction of the pressure generating chamber, and a meniscus of the meniscus after ejecting ink droplets by contracting or expanding the pressure generating chamber And the third signal time is set to Tc / 2 or less, where Tc is a natural vibration period of the pressure generating chamber.

  Further, after the third signal, it includes a fourth signal time for contracting or expanding the pressure generating chamber to return to the initial state, and the fourth signal time is set to Tc / 2 or less. .

  Then, the vibration damping effect can be strengthened, the residual vibration can be suppressed quickly, and the image quality abnormality problems such as the occurrence of mist and ejection bend after ink droplet ejection can be reduced.

  Furthermore, it is possible to achieve desired Vj and Mj by including a fifth signal for maintaining the contraction or expansion state of the pressure generating chamber after the third signal.

  Furthermore, microdroplet formation is possible by including a sixth signal for expanding the pressure generating chamber and a seventh signal for maintaining the expanded state before the first signal.

  According to the present invention, residual vibration can be suppressed and image quality can be prevented from being degraded.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an enlarged view of elements of an ink jet head to which the present invention is applied, FIG. 2 is an enlarged cross-sectional view of a main part in the direction between channels of the head, and FIG. 3 is a top view of a pressure generating chamber.

  This ink jet head has an ink supply port 1-1 and a frame 1 formed with a carving to be a common liquid chamber 1-2, a fluid resistance unit 2-1, a carving to be a pressure generating chamber 2-2, and a nozzle 3-1. A flow path plate 2 having a communication port 2-3 that communicates, a nozzle plate that forms a nozzle 3-1, a diaphragm 6 having a convex portion 6-1, a diaphragm portion 6-2, and an ink inlet 6-3. A laminated piezoelectric element 5 joined to the diaphragm via an adhesive layer 7, and a base 4 to which the laminated piezoelectric element 5 is fixed.

  The base 4 is made of a barium titanate ceramic, and the laminated piezoelectric elements 5 are arranged in two rows and joined.

  The laminated piezoelectric element 5 includes a lead zirconate titanate (PZT) piezoelectric layer 5-1 having a thickness of 10 to 50 μm / layer and an internal electrode layer made of silver and palladium (AgPd) having a thickness of several μm / layer. 5-2 are alternately laminated. The internal electrode layer 5-2 is connected to the external electrode 5-3 at both ends.

  The laminated piezoelectric element 5 is divided onto comb teeth by half-cut dicing and used as a drive unit 5-6 and a support unit 5-7 (non-drive unit) one by one. The outside of the external electrode 5-3 is limited in length by cutting or the like so as to be divided by half-cut dicing, and these become a plurality of individual electrodes 5-4. The other is not divided by dicing but is conductive and becomes the common electrode 5-5.

  The FPC 8 is soldered to the individual electrode 5-4 of the driving unit. Moreover, the common electrode 5-5 is provided with an electrode layer at the end of the laminated piezoelectric element and is wound around to join the Gnd electrode of the FPC 8. A driver IC (not shown) is mounted on the FPC 8 to control application of drive voltage to the drive unit 5-6.

  The diaphragm 6 has a thin film diaphragm 6-2 and an island-shaped convex portion (island portion) 6- 6 that is joined to the laminated piezoelectric element 5 serving as the driving unit 5-6 formed at the center of the diaphragm 6-2. 1, a thick film portion including a beam joined to the support portion 18, and an opening serving as an ink inflow port 6-3 are formed by stacking two Ni plating films by an electroforming method. The diaphragm portion has a thickness of 3 μm and a width of 35 μm (one side).

  The island-shaped convex part 6-1 of the diaphragm 6 and the movable part 5-6 of the laminated piezoelectric element 5 and the coupling of the diaphragm 5 and the frame 1 are bonded by patterning the adhesive layer 7 including a gap material. .

  The flow path plate 2 uses a silicon single crystal substrate, an etching method for engraving the fluid resistance portion 2-1, the pressure generation chamber 2-2, and the through-hole serving as the communication port 2-3 at a position relative to the nozzle 3-1. And patterned.

  The portion left by etching becomes the partition wall 2-4 of the pressure generating chamber 2-2. Moreover, in this head, the part which narrows an etching width | variety was provided and this was made into the fluid resistance part 2-1.

  The nozzle plate 3 is formed of a metal material, for example, an Ni plating film formed by an electroforming method, and has a large number of nozzles 3-1 that are fine discharge ports for flying ink droplets. The inner shape (inner shape) of the nozzle 3-1 is formed in a horn shape (may be a substantially cylindrical shape or a substantially frustum shape). The diameter of the nozzle 3-1 is about 20 to 35 μm on the ink droplet outlet side. The nozzle pitch of each row was 150 dpi.

  The ink ejection surface (nozzle surface side) of the nozzle plate 3 is provided with a water repellent treatment layer 3-2 that has been subjected to a water repellent surface treatment (not shown). Ink physical properties such as PTFE-Ni eutectoid plating, electrodeposition coating of fluororesin, vapor-deposited fluororesin (for example, fluorinated pitch), baking after solvent application of silicon resin / fluorine resin, etc. A water-repellent treatment film selected according to the above is provided to stabilize the ink droplet shape and flight characteristics so that high-quality image quality can be obtained.

  The frame 1 that forms the engraving that becomes the ink supply port 1-1 and the common liquid chamber 1-2 is manufactured by resin molding.

  In the ink jet head configured as described above, a driving waveform (pulse voltage of 10 to 50 V) is applied to the driving unit 5-6 according to the recording signal, thereby causing a displacement in the stacking direction in the driving unit 5-6. The pressure generating chamber 2-2 is pressurized through the vibration plate 3 to increase the pressure, and ink droplets are ejected from the nozzle 3-1.

  Thereafter, the ink pressure in the pressure generating chamber 2-2 decreases with the end of ink droplet ejection, and a negative pressure is generated in the pressure generating chamber 2-2 due to the inertia of the ink flow and the discharge process of the drive pulse. The process proceeds to the ink filling process. At this time, the ink supplied from the ink tank flows into the common liquid chamber 1-2, passes through the fluid resistance portion 2-1 from the common liquid chamber 1-2 through the ink inlet 6-3, and the pressure generating chamber 2- 2 is filled.

  The fluid resistance unit 2-1 is effective in damping the residual pressure vibration after ejection, but becomes resistant to the maximum filling (refill) due to surface tension. By appropriately selecting the fluid resistance portion, it is possible to balance the attenuation of the residual pressure and the refill time, and to shorten the time (drive cycle) until the transition to the next ink droplet ejection operation.

  Hereinafter, the drive signal driving method of the ink jet recording head will be described.

  As shown in the drive signal diagram of FIG. 4, the first signal A raises the voltage from the reference potential, contracts the pressure generating chamber to eject ink droplets, and holds the voltage by the second signal B to hold the pressure. The contraction of the generation chamber is held, and the voltage is increased by the third signal C to contract the pressure generation chamber to perform vibration suppression.

  In the method as described in Patent Document 1, the residual vibration of the meniscus may not be suppressed well as shown in the left diagram of FIG.

  By setting the signal time of the third signal C to Tc / 2 or less as in the present embodiment, the residual vibration of the meniscus can be quickly suppressed as shown in the right diagram of FIG. Thereby, it is possible to reduce image quality abnormality problems such as mist generation after ejection of ink droplets and ejection bending.

  As shown in the drive signal diagram of FIG. 4, the first signal A raises the voltage from the reference potential, contracts the pressure generating chamber to eject ink droplets, and holds the voltage by the second signal B to hold the pressure. The contraction of the generation chamber is maintained, the voltage is increased by the third signal C, the pressure generation chamber is contracted to control vibration, and then the voltage is held by the fifth signal E to reduce the contraction of the pressure generation chamber. The pressure is reduced by the fourth signal D to expand the pressure generating chamber, and the pressure is returned to the reference potential while applying vibration suppression.

  By reducing the signal time of the fourth signal D to Tc / 2 or less as in this embodiment, the residual vibration of the meniscus can be further suppressed as shown in the right diagram of FIG. Thereby, it is possible to reduce image quality abnormality problems such as mist generation after ejection of ink droplets and ejection bending.

  Further, as in the present embodiment, the time interval between the third signal C and the fourth signal D can be adjusted by inputting the fifth signal E.

  As shown in the drive signal diagram of FIG. 5, before the pressure generating chamber is contracted, the pressure generating chamber is expanded by the sixth and seventh signals (F, G), and then ink droplets are ejected to make a minute. Can be discharged.

  In addition, the said form is an example of a suitable thing of this invention, and it can change variously in the range which does not change the summary of this invention.

It is an element enlarged view of an inkjet head. It is a principal part enlarged view of the direction between channels of an inkjet head. It is a top view of a pressure generation chamber part. It is a drive signal diagram. It is a drive signal diagram. It is a figure showing the suppression state of the residual vibration of a meniscus.

Explanation of symbols

A 1st signal B 2nd signal C 3rd signal D 4th signal E 5th signal F 6th signal G 7th signal

Claims (8)

In a method for driving an ink jet recording head, a pressure change is generated in a pressure generating chamber filled with ink by a pressure generating element, and an ink droplet is ejected from a nozzle connected to the pressure generating chamber.
A first signal for causing the pressure generation chamber to contract and ejecting an ink droplet, a second signal for maintaining the contraction of the pressure generation chamber, and a meniscus of the meniscus after ink droplet ejection by contracting or expanding the pressure generation chamber At least a third signal for suppressing residual vibration,
3. A method for driving an ink jet recording head, wherein the third signal time is set to Tc / 2 or less, where Tc is a natural vibration period of the pressure generating chamber.   2. The method according to claim 1, further comprising: after the third signal, a fourth signal time for contracting or expanding the pressure generating chamber to return to the initial state, and setting the fourth signal time to Tc / 2 or less. A method for driving an inkjet recording head, which is characterized.   3. The method of driving an ink jet recording head according to claim 1, further comprising a fifth signal for maintaining a contracted or expanded state of the pressure generating chamber after the third signal.   4. The inkjet according to claim 1, further comprising: a sixth signal for expanding the pressure generating chamber and a seventh signal for maintaining the expanded state before the first signal. 5. Driving method of the recording head. In an ink jet recording apparatus having an ink jet recording head that causes a pressure change in a pressure generating chamber filled with ink by a pressure generating element and discharges ink droplets from a nozzle communicated with the pressure generating chamber.
A first signal for causing the pressure generation chamber to contract and ejecting an ink droplet, a second signal for maintaining the contraction of the pressure generation chamber, and a meniscus of the meniscus after ink droplet ejection by contracting or expanding the pressure generation chamber At least a third signal for suppressing residual vibration,
The third recording time is set to Tc / 2 or less, where Tc is a natural vibration period of the pressure generating chamber.   6. The method according to claim 5, further comprising a fourth signal time after the third signal for contracting or expanding the pressure generating chamber to return to an initial state, wherein the fourth signal time is set to Tc / 2 or less. An ink jet recording apparatus.   7. The ink jet recording apparatus according to claim 5, further comprising a fifth signal for maintaining a contracted or expanded state of the pressure generating chamber after the third signal.   8. The inkjet according to claim 5, further comprising: a sixth signal for expanding the pressure generating chamber and a seventh signal for maintaining the expanded state before the first signal. Recording device.