JP4383724B2 - Inkjet recording device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet recording apparatus, and more particularly to an ink jet recording apparatus that vibrates a meniscus of an ink jet head and a technique for preventing clogging of nozzle openings.
[0002]
[Prior art]
The on-demand type ink jet recording head includes a plurality of nozzle openings and a pressurizing chamber communicating with each nozzle opening, and is configured to generate ink droplets by expanding and contracting the pressurizing chamber in response to a print signal. Has been. In such a recording head, new ink is sequentially supplied to the nozzle openings where the printing operation is performed, so there is almost no clogging, but the chance of ink droplet ejection is extremely low, for example, nozzle openings such as upper and lower ends. Clogging is likely to occur if the product is placed in a resting state.
[0003]
For this reason, when the printing operation is continued for a certain period of time, the recording head is retracted to the capping means in the non-printing area, where a drive signal is applied to the piezoelectric vibrator to drop ink droplets from all nozzle openings toward the cap. It has been proposed to perform a so-called flushing operation for forcibly ejecting water.
[0004]
[Problems to be solved by the invention]
However, if such measures are taken, the printing operation is interrupted, resulting in a decrease in printing speed and consumption of ink. Therefore, it is provided in a pressurizing chamber that communicates with a nozzle opening that does not generate ink droplets during the printing operation. Many techniques have been proposed to prevent clogging by applying a minute driving signal that does not cause ink droplets to be ejected to a piezoelectric vibrator and causing the meniscus in the vicinity of the nozzle opening to vibrate slightly (Japanese Patent Laid-Open No. 55-123476). JP, 57-61576, U.S. Pat. No. 4,350,989).
[0005]
According to these, although the number of flushing operations can be reduced to prevent a decrease in printing speed and ink consumption, a relatively large pressure is applied to the ink, so that annoying noise is generated.
[0006]
In addition, when pressure is simply applied, meniscus vibrations remain, adversely affect ink droplet formation during ejection, and cause unstable ink ejection.
In order to prevent this, when applying the pressure, a pressure application timing and a complicated pressure application sequence that are sufficiently considered so that the residual vibration of the meniscus does not affect ink ejection are required. There is.
[0007]
The present invention has been made in view of such problems, and the object of the present invention is to vibrate the meniscus in a simple manner without generating noise, and to reliably prevent clogging of the nozzle opening. It is another object of the present invention to provide an ink jet recording apparatus that can prevent unstable ejection of ink that can be performed or that occurs even in a state where clogging is not reached.
[0008]
[Means for Solving the Problems]
In order to solve such a problem, the present invention provides a plurality of nozzle openings for ejecting ink droplets, a plurality of ink pressurizing chambers respectively communicating with the plurality of nozzle openings, and the plurality of ink pressurizing chambers. A plurality of ejection pressurizing means provided to eject ink from the nozzle openings, a common liquid chamber communicating in common with the plurality of ink pressurization chambers, and the nozzle openings provided in the common liquid chamber An ink jet recording head used to vibrate the ink meniscus to such an extent that no ink droplets are ejected from the nozzle openings, and each ejection pressure means at each ink ejection timing It controls the discharge pressure unit controller, the meniscus the meniscus at the nozzle openings co in a state in which a new ink is filled in the vicinity of Higher than the frequency a predetermined frequency, a said vibrating pressure means for controlling the vibration pressurizing means control unit as the meniscus in each of said nozzle openings is vibrated continuously over time from the state The vibration pressurization means control section for controlling the vibration pressurization means so that the resonance frequency of the meniscus at the nozzle opening does not exceed the predetermined frequency. An inkjet recording apparatus characterized by the above.
[0009]
(Function)
Applying vibration to the meniscus at a frequency close to the resonance frequency of the meniscus in the non-printing meniscus state than the resonance frequency of the meniscus in the continuous printing state, By applying, for example, the applied vibration becomes a resonance state with respect to a nozzle having a low opportunity for ink droplet discharge or a meniscus that is progressing to a clogged state of the nozzle opening such as when in a resting state, It is possible to effectively generate meniscus vibration, stir the ink in the vicinity of the meniscus and the ink in the pressure chamber, and replace the vicinity of the meniscus with fresh ink.
[0010]
On the other hand, a nozzle in which fresh ink is filled in the vicinity of the meniscus does not enter a resonance state, and thus the meniscus is stable without greatly vibrating.
[0011]
In this way, printing can be performed stably.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Therefore, the principle of the present invention will be described below based on the illustrated embodiment.
[0013]
FIG. 1 shows a main configuration of the present invention. In FIG. 1, reference numeral 1 conceptually shows the structure of an ink jet head. The ink jet head 1 is provided with a plurality of nozzle openings 2 on the outer surface to add ink. The pressure chamber 3, the common liquid chamber 4, and the ink supply port 5 communicate with each other.
[0014]
Each ink pressurizing chamber 3 is provided with a discharge ink pressurizing means 6.
The common liquid chamber 4 is provided with a meniscus microvibration pressurizing means 7.
[0015]
An ink tank 8, a discharge ink pressurizing unit control unit 9, and a minute vibration ink pressurizing unit control unit 10 are arranged and connected to the outside of the inkjet head 1.
[0016]
Ink is supplied from the ink tank 8 to the inkjet head 1 via the ink supply port 5.
[0017]
The discharge ink pressurizing unit 6 is connected to the discharge ink pressurizing unit control unit 9 and controls the discharge ink pressurizing unit 6 of the corresponding nozzle at the time of printing to discharge ink from the nozzle opening 2.
[0018]
The discharge ink pressurizing means controller 9 generates the pressure shown in FIG. 2 in the discharge ink pressurization chamber 3 in order to discharge ink in accordance with the image from each nozzle opening 2 at each discharge timing. In addition, the ejection ink pressurizing means 6 corresponding to each nozzle is controlled. FIG. 2 illustrates the generated pressure of each ejection ink pressurizing means 6. The pressure shown in FIG. 2 is large enough to cause the meniscus to be greatly displaced and ink to be ejected from the nozzle openings 2 by a single pressure fluctuation.
[0019]
The meniscus micro-vibration pressurizing means 7 is connected to the micro-vibration ink pressurizing means control unit 10 and in preparation for printing, the meniscus micro-vibration pressurizing means 7 is prevented from drying locally in the vicinity of each nozzle opening 2. Is controlled to vibrate the meniscus and stir the ink near the nozzle opening 2.
[0020]
The micro-vibration ink pressurizing unit controller 10 controls the meniscus micro-vibration pressurizing unit 7 so that the pressure shown in FIG. 3 is generated in the common liquid chamber 4 regardless of whether or not ejection is performed. The pressure shown in FIG. 3 propagates to each nozzle opening 2 while the pressure wave generated here is so small as to hardly displace the meniscus with a single pressure fluctuation. When discharging, it has almost no effect. However, when the period of the pressure fluctuation coincides with the resonance frequency of the meniscus vibration, vibration of a displacement that is large enough to stir the ink near each nozzle opening 2 can be given to the meniscus.
[0021]
FIG. 4 shows changes in the resonance frequency of meniscus vibration over time. The resonance frequency f shown in FIG. 4 is a value used to make it easy to understand a value representing ink physical properties, and does not indicate a value measured while applying meniscus vibration. As shown in “change in normal resonance frequency” in FIG. 4, the resonance frequency f of the meniscus vibration is shifted to a high frequency as time passes from a state where the ink near the nozzle opening 2 is fresh. This is considered to be caused by the local drying of the ink near the nozzle opening 2.
[0022]
The “change in the resonance frequency in the present invention” in FIG. 4 is the time elapsed when the meniscus microvibration pressurizing means 7 causes the common liquid chamber 4 to generate the pressure fluctuation with the period 1 / fc shown in FIG. The change of the resonance frequency of the meniscus vibration in FIG. As shown in FIG. 4 , the resonance frequency f of the meniscus vibration shifts from a fresh state f0 in the vicinity of the nozzle opening 2 to a high frequency over time, but when the resonance frequency f approaches fc, the meniscus vibration frequency is changed. Since the vibration displacement becomes large due to resonance and the ink is agitated and the local drying of the ink near the nozzle opening 2 is alleviated, the resonance frequency f of the meniscus vibration does not change greatly beyond fc.
[0023]
That is, simply applying a weak pressure fluctuation simply means that the physical properties of the ink near the nozzle opening 2 do not change greatly from the fresh state.
[0024]
FIG. 5 shows the structure around the printing mechanism of the printer of the present invention. In FIG. 5, reference numeral 101 denotes a carriage, which is connected to the pulse motor 103 via the timing belt 102 and guided to the guide member 104. Thus, the recording paper 105 is configured to reciprocate in the paper width direction.
[0025]
An ink jet recording head 106, which will be described later, is attached to the carriage 101 on the surface facing the recording paper 105, in this embodiment the lower surface. The ink jet recording head 106 receives ink replenishment from the ink cartridge 107 mounted on the upper portion of the carriage 101 and ejects ink droplets onto the recording paper 105 in accordance with the movement of the carriage 101 to form dots. Print images and text on recording paper.
[0026]
A capping device 108 is provided in a non-printing area, and seals the nozzle openings of the recording head 106 during a pause, while receiving ink droplets from the recording head 106 by a flushing operation performed during a printing operation. It is. In the figure, reference numeral 109 denotes a cleaning means.
[0027]
When the viscosity of the nozzle opening increases during printing, flushing is performed by this cleaning mechanism. In the present invention, the local increase in viscosity in the vicinity of the nozzle opening is mitigated by the slight vibration of the meniscus, but this flushing operation is performed when the entire viscosity increases during a long-time printing operation.
[0028]
【The invention's effect】
Above in the present invention as described, the application timing and the sufficient consideration pressure, it or the use of application sequence of complex pressure, without generating noise, vibrating the meniscus in a simple way, the nozzle openings Can be surely eliminated . Alternatively, the ink in the vicinity of the nozzle opening is replaced with the ink in the pressurizing chamber having a low viscosity so that the ink can be prevented from being unstablely ejected even when the ink is not clogged , and stable printing operation can be prevented. The work can be guaranteed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional block diagram illustrating a main configuration of the present invention of an ink jet recording head to which the present invention is applied.
FIG. 2 is a generated pressure of each ejection ink pressurizing unit.
FIG. 3 shows a pressure generated by a pressurizing means for meniscus microvibration.
FIG. 4 shows a change in resonance frequency of meniscus vibration over time.
FIG. 5 is a diagram showing an embodiment of an ink jet recording apparatus to which the present invention is applied.
FIG. 6 is a diagram showing an embodiment of an ink jet recording head in which the vibration means to which the present invention is applied is foaming by a heating element.
FIG. 7 is a diagram showing an embodiment of an ink jet recording head in which the vibrating means to which the present invention is applied is pressurization by deformation of a pressure chamber using electrostatic force.
FIG. 8 is a diagram showing an embodiment of an ink jet recording head in which the vibration means to which the present invention is applied is a mechanical vibrator.
[Explanation of symbols]
106 Inkjet recording head 108 Capping device 109 Cleaning device 3 Pressure chambers 6 and 7 Piezoelectric vibrator 2 Nozzle opening 4 Common liquid chamber

Claims (2)

A plurality of nozzle openings for ejecting ink droplets, a plurality of ink pressurizing chambers communicating with the plurality of nozzle openings, respectively, and provided for ejecting ink from the nozzle openings provided in the plurality of ink pressurizing chambers, respectively. A plurality of ejection pressurizing means, a common liquid chamber communicating with the plurality of ink pressurizing chambers in common, and an ink droplet ejecting an ink meniscus in the nozzle opening from the nozzle opening. An ink jet recording head having vibration pressing means used to vibrate to such an extent that
A discharge pressurization means control section for controlling each of the discharge pressurization means at each ink discharge timing;
The vibration pressurizing means is arranged so that the meniscus in each nozzle opening continuously vibrates at a predetermined frequency higher than the resonance frequency of the meniscus in the nozzle opening in a state where new ink is filled in the vicinity of the meniscus. A vibration pressurizing means controller that controls the vibration so that the resonance frequency of the meniscus at the nozzle opening does not exceed the predetermined frequency that shifts to a higher frequency as time elapses from the state. The pressurizing means controller for vibration for controlling the pressurizing means,
An ink jet recording apparatus comprising:   2. The ink jet recording apparatus according to claim 1, wherein the vibration of the meniscus by the vibration pressing unit is continuously applied to the meniscus of all the nozzle openings regardless of printing or non-printing.

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