JPS58112752A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To remove air bubbles and a solid matter, by a method wherein a magnitude of a mechanical vibration applied to a nozzle and ink in a pressure chamber at a non-recording time is set to smaller than that of a mechanical vibration applied to the inteior of the pressure chamber at a recording operation time. CONSTITUTION:In case no ink drop is jetted through a nozzle 5, and a jet direction or a jet speed is abnormal, through, firstly, application of a pressure to an ink storage chamber 7, ink is caused to flow into a print head 1 to compulsorily discharge ink through the nozzle 5. At a current point of time, a switch means 14 is brought to OFF, and simultaneously, a strobe pulse 17 is generated by a strobe pulse generator 16 to apply a drive to a piezo-element 4'. While ink is being discharged, a mechanical vibration smaller than that at a recording time is applied to the inside of a pressure chamber 3, whereby a flexible wall 2 vibrates in the direction of the pressure chamber 3 togetherwith an element 4' and air bubbles and a solid matter in the pressure chamber 3 and the nozzle 5 flow out togetherwith ink.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inkjet recording device, and is capable of highly efficiently eliminating factors that hinder the normal ejection and flight of ink droplets, such as air bubbles and solid objects generated or intruded into a nozzle or pressure chamber. It has been marked K so that it can be eliminated.

Conventionally, several systems have been devised and put into practical use for print heads of inkjet recording devices. For example, FIG. 1 is an example of a method called a drop-on-demand method. Now consider a situation in which the nozzle 5 and the pressure chamber 3 are filled with ink led from the ink reservoir 7 by the conduit 9. Here, if an electric pulse is applied from the pulse generator 10 to the piezoelectric transducer 4, the flexible wall 2 and the piezoelectric transducer 4 will be moved into the pressure chamber 3 by the piezoelectric effect.
The volume of the IJh1 pressure chamber 3 decreases rapidly. This rapid decrease in volume generates hydraulic pressure in the pressure chamber 3, and this hydraulic pressure causes the ink within the pressure 1!13 to pass through the nozzle 5, become ink droplets 6, and be jetted to the outside. The amount of ink reduced in the pressure chamber 3 is reduced by the amount of ink stored in the ink storage chamber 7.
flows into the pressure chamber 3 through the conduit 9 to supplement this.

By the way, there are various factors that impede the normal ejection and flight of ink droplets, and among them, bubbles and solid objects that often occur in the nozzle or pressure chamber are ones that often occur during normal use. In other words, if air bubbles exist in the nozzle 5 or the pressure island, all or part of the pressure generated in the pressure chamber 3 is absorbed by the air bubbles, so ink droplets may not be ejected, or they may be ejected but may not fly. Abnormalities occur such as speed fluctuations, ink droplets not flying straight, and ink droplets breaking up into multiple droplets and scattering. Furthermore, if solid matter is present in the nozzle 5, normal ejection of ink will be hindered, and in extreme cases, the nozzle 5 will become clogged, making it impossible to eject any ink droplets.

If the fixed object 5 is present in the pressure chamber 3, it will not cause any abnormality immediately, but it will eventually cause clogging and cause the following problems as described above.

The bubbles and solid objects that cause these abnormalities are thought to occur for the following reasons. That is, when the recording device (not shown) is in recording operation or on standby, the 71J y head 1
If an abnormal impact is applied to the nozzle 5 and air bubbles are sucked in from the nozzle 5, noise may be superimposed on the electrical signal applied from the Hals generator 10 to the piezoelectric transducer 4 during the recording operation, causing the ink meniscus in the nozzle 5 to If the normal vibration of the ink is disturbed and air bubbles are sucked in from the nozzle 5, if air dissolved in the ink is precipitated, or if the ambient temperature changes while the recording device is not operating, the ink may undergo thermal expansion and contraction. There are many reasons for this, such as air bubbles being sucked in from the nozzle 5 when the print head 1 is left unused for a long time, or when the environmental humidity is abnormally low. It is generated when the ink dries and solidifies, and it is also generated when dust floating in the air or paper dust generated from recording paper enters the nozzle 5. Furthermore, solid foreign matter may originally be contained in the ink.

In order to eliminate air bubbles and solid objects that may impede the normal ejection and flight of ink from the nozzles 5 of the print head 1, in the past, a cleaning liquid pressure higher than a certain pressure is applied to the ink to clean the pressure chambers 3 and nozzles. A method is adopted in which a forced ink flow is formed in the pressure chamber 3 and mechanical vibration is applied to the pressure chamber 3 by using a piezoelectric transducer 4' fixed to the print head IK, for example, in FIG. I came. By using such a method, the pressure chamber 3. Bubbles and solid matter adhering to the wall inside the nozzle 5 were also given separation energy and separated from the wall, and were discharged out of the nozzle 5 along with a turbulent ink flow.

However, by applying cleaning liquid pressure in this way to form a forced ink flow and applying mechanical vibrations to the pressure chamber 3, the efficiency of discharging bubbles and solid matter is not necessarily high. That is, as shown in FIG. 3, the ink in the pressure chamber 3 is pressurized or depressurized by one mechanical vibration, but...
If we apply mechanical vibrations of the same magnitude as those used during recording, the decompression will be too large, resulting in qi? '6+ increases both in volume and number, and the ejection of ink droplets becomes abnormal.

This phenomenon is generally called cavitation, but when solid objects are present in the ink, the air bubbles tend to proliferate because minute air bubbles are often attached to the solid object. , it will cause more trouble.

In this way, air bubbles and solid objects form the pressure chamber 3. If the ink is not removed from the nozzle 5, it has conventionally been necessary to repeat the operations of forming an ink flow and applying mechanical vibration over and over again, resulting in the problem that expensive ink is wasted. If the print head 1 does not recover normally on the recording device, the print head 1 is considered to be a defective product, and the print head 1 is removed from the recording device and then refilled with ink. In extreme cases, the expensive print head 1 was sometimes discarded as a defective product.

The purpose of the present invention is to prevent air bubbles from properly ejecting and flying ink from the nozzles 5 of the print head 1. The object of the present invention is to correct the extremely inefficient point in the conventional technology of eliminating solid objects, and to provide a new means that is highly efficient, inexpensive, simple, and easy to implement. The main point is that when the inkjet recording device is not recording, the nozzle of the printhead of the recording device,
Applying mechanical vibration to an ink flow path including a pressure chamber, and forming a forced ink flow within the ink flow path during a period including the mechanical vibration operation or after the end of the mechanical vibration operation. In the inkjet recording apparatus thus constructed, the magnitude of the mechanical vibration is made smaller than the magnitude of the mechanical vibration generated within the pressure chamber during the recording operation.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 4(a) shows a driving pulse applied to the piezoelectric element 4' during a recording operation of the recording apparatus, and FIG. 4(b) shows a driving pulse applied to the piezoelectric element 4' according to the present invention.
VO〉vl. Figure 5 shows the piezoelectric element 4' during recording operation.
This is an example of a circuit for switching between a drive pulse applied to an IC and a drive pulse applied to a piezoelectric element 4' according to the present invention. During the recording operation of the recording device, visually check for abnormalities such as ink droplets not being ejected from the nozzle 5, ink droplets being ejected but the ejecting direction and speed are not normal, or ink droplets splitting into many parts and being ejected. Or, if it is detected by some detection means, the recording device moves to an operation to eliminate the bubbles (hereinafter this operation is referred to as a purge operation). ), pressure is applied to cause ink to flow into the print head 1-, and the ink is forcibly ejected from the nozzle 5 and overflows. At the point when ink starts to overflow from the nozzle 5, the switch means 14 is turned off. At the same time, a strobe pulse 17 is generated in the strobe pulse generator 16, and as a result, a driving pulse shown in FIG. 4(b) is applied to the piezoelectric element 4'. At this time, the driving frequency is made to match the frequency of the electric pulse applied to the button piezoelectric transducer 4 during the recording operation, but a different value may be used depending on the case. The flexible wall 2 is a piezoelectric transducer 4'
At the same time, due to the piezoelectric effect, it vibrates in the direction of the pressure chamber 3, and as a result of this action, air bubbles and solid objects in the pressure chamber 3 and the nozzle 5 flow out of the nozzle 5 together with the ink. When the purge operation is completed, the switch means 14 is turned on, and when the next recording operation is started, the drive pulse shown in FIG. 4(a) is applied to the piezoelectric element 4', and normal recording operation is possible. be.

If a print head in which air bubbles or solid matter have entered the nozzle is ejected with ink for, for example, 5 seconds using a conventional method, the probability that the print head will return to normal is about 50%. However, it has been confirmed that when the method of the present invention is used to eject ink for 5 seconds while mechanically vibrating the pressure chamber 3, about 70% of the defective nozzles are restored to a normal state. Moreover, if purging is repeated while vibrating the pressure chamber 3, the recovery rate becomes approximately 1001.

The reason why the efficiency of removing air bubbles and solid objects becomes higher when a smaller mechanical vibration than during recording operation is applied to the pressure chamber 3 while ejecting ink is that the air bubbles and solid objects that adhere to the air bubbles and solid objects become more efficient. This is because the volume of the bubble does not increase or new bubbles are generated using the bubble as a core. That is, if mechanical vibrations of the same magnitude as during the recording operation are applied to the pressure chamber 3, the pressure chamber 3. Some of the air bubbles and solid matter adhering to the wall inside the nozzle 5 are given separation energy and detached from the wall, and are discharged out of the nozzle 5 along with the turbulent ink flow. However, in this case, because the mechanical vibration is too large, some of the bubbles multiply in volume and number during depressurization, causing the pressure chamber 3. It remains in the nozzle 5, and the overall removal efficiency is not very high.

By reducing the magnitude of mechanical vibration, the proliferation of such bubbles is eliminated, and as a result, the efficiency of removing bubbles and solid objects is increased. In this way, bubbles are generated in the liquid when the pressure is reduced, The phenomenon of multiplication is generally called cavitation, but 1. The occurrence of cavitation is influenced by the physical properties of the liquid (evaporation characteristics, surface strength, viscosity, etc.), substances dissolved in the liquid, substances floating in the liquid, etc. Therefore, according to the present invention, the maximum voltage V of the drive pulse (FIG. 4(b)) applied to the piezoelectric element 4' is determined in part by i.
Although it is difficult, the drive pulse during recording operation (Figure 4
(a) It has been confirmed that good results can be obtained by setting (■)≦Vo with respect to the maximum voltage VO in (a).

In the explanation so far, the piezoelectric transducer 4' has been used to generate mechanical vibrations within the pressure chamber 3, but as shown in FIG. It is able to eliminate air bubbles and solid objects generated or intruded into pressure chambers and nozzles with high efficiency.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the structure of a conventional print head. FIG. 2 is a diagram showing an embodiment of the present invention. FIG. 3(a) shows the driving pulse applied to the piezoelectric element, the third
Figure (b) is a diagram showing pressure fluctuations within the pressure chamber. FIG. 4(&) is a diagram showing a driving pulse applied to the piezoelectric element during a recording operation, and FIG. 4(b) is a diagram showing a driving pulse applied to the piezoelectric element according to the present invention. FIG. 5 is a diagram showing an example of a circuit for switching between a drive pulse applied to a piezoelectric element during a recording operation and a drive pulse applied to a piezoelectric element according to the present invention. FIG. 6 is a diagram showing another embodiment of the present invention. 1 is a print head, 2 is a flexible wall, 3 is a pressure chamber, 4.4
' is a piezoelectric transducer, 5 is a nozzle, 6 is an ink droplet, 7 is an ink storage chamber, 8 is ink, 9 is a conduit, 10, , 10
' is a pulse generator, 11 is a drive pulse waveform, 12 is a pressure fluctuation waveform, 13 is a high voltage power supply, 14 is a switch means, 15
is a low piezoelectric λ, 16 is a strobe pulse generator, and 17 is a strobe, pulse. Agent Yoshimi Kuwahara 0 2nd f! 1 v35 diagram (α) 5th flash (b) 41st! ] (α) Figure 4 (b) Evening 5th hour

Claims (1)

[Claims] (1) When the inkjet recording device is not recording, 1. Applying mechanical vibration to the nozzles of the print head of the recording device and the ink in the pressure chamber, and within the time period including the mechanical vibration operation or when the mechanical vibration operation ends. In an inkjet recording device configured to later form a forced ink flow within the ink flow path, the magnitude of the mechanical vibration is made smaller than the magnitude of mechanical vibration applied within the pressure chamber during recording operation. Inkjet recording device. (2. In the recording device according to claim 1, the magnitude of the armpit-like mechanical vibration applied during the non-recording operation is set to be one-third or less of the mechanical vibration applied during the recording operation. An inkjet recording device featuring: