JPS58112751A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To high-efficiently remove air bubbles and a solid matter in a pressure chamber by applying a mechanical vibration to a nozzle of a print head and ink in the pressure chamber at a non-recording operation time. CONSTITUTION:In case no ink drop is jetted through a nozzle 5 and 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 forcibly discharge ink through the nozzle 5. At a point of time when ink starts to overflow from the nozzle 5, an electric pulse is applied to a piezo-electric element 4 from a pulse generator 10' by changing over a switch S. A flexible wall 2 vibrates in a direction of a pressure chamber 3 side togetherwith an element 4. This operation causes air bubbles and a solid matter in the pressure chamber 3 and the nozzle 5 to flow to the outside of the nozzle 5 togetherwith the discharged ink, and the head 1 returns back to its normal recording operation again.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inkjet recording device, and is capable of highly efficiently eliminating factors that impede the normal ejection or flight of ink droplets, such as air bubbles or solid objects that have occurred or entered into a nozzle or pressure chamber. It is designed to be eliminated.

Several systems have been devised and put into practical use for print heads of inkjet recording devices. For example, FIG. 1 shows an example of the so-called drop-on-demand method. Now, consider a situation in which the nozzle 5 and the pressure chamber 3 are filled with ink introduced from the ink storage chamber 7 through the conduit 9. . Here, if the pulse generator 1o applies a stain pulse to the piezoelectric transducer 4, the flexible wall 2
is bent toward the pressure chamber 3 due to the piezoelectric transducer 4 and the mutual piezoelectric effect, and the volume of the pressure chamber 3 is rapidly reduced. This rapid decrease in volume generates a hydraulic pressure in the pressure chamber 3, and this hydraulic pressure causes the ink in the pressure chamber 3 to become ink droplets 6 through the nozzle 5 and to be ejected to the outside. Ink 8 stored in the ink storage chamber 7 flows into the pressure chamber 3 through the conduit 9 to compensate for the decrease in ink in the pressure chamber 3.

By the way, there are various factors that impede the normal ejection and flight of ink droplets, but among them, air bubbles and solid particles that are present in the nozzle 5 and pressure chamber 3 are among the factors that often occur during normal use. In other words, if there are air bubbles in the nozzle 5 or the pressure chamber 3, all or part of the specific pressure generated in the pressure chamber 3 will be absorbed by the air bubbles, making it impossible to eject ink droplets. Although the ink is ejected, abnormalities occur such as the flying speed fluctuates, the ink does not fly straight, or the ink droplets separate into many small droplets and scatter. Also,
If solid objects exist in the nozzle 5, the normal ejection of ink will be hindered, and in extreme cases, the nozzle will become clogged.
No ink droplets can be ejected at all. If a solid object 5 exists in the pressure chamber 3, K will not become abnormal immediately, but
Eventually, clogging will occur and the problems described above will occur.

Bubbles and solid objects that cause these abnormalities are thought to occur for the following reasons. In other words, an abnormal impact is applied to the print head 1 during the recording operation of the recording device (not shown) or during standby. When air bubbles are sucked in from the nozzle 5, if noise is superimposed on the electrical signal applied from the pulse generator 10 to the piezoelectric transducer 4 during the recording operation, the meniscus e[& vibration of the ink in the nozzle 5] If the air is disturbed and air bubbles are sucked in from the nozzle 5, if the air dissolved in the ink precipitates, or if the ambient temperature changes while the recording device is not operating, the ink thermally expands and contracts and the nozzle There are many reasons why air bubbles may be sucked in from the nozzle 5. In addition, solid objects may become trapped inside the nozzle 5 when the print head 1 is left unused for a long time or when the ambient temperature is abnormally low. The dust that is generated when the ink dries and solidifies, and the dust that floats in the air, and the paper powder that is generated from the recording paper, are
It can also be caused by entering the inside of the body. - In addition, it is necessary to eliminate air bubbles and solid objects that hinder the normal ejection and flight of ink from the nozzles 5 of the print head l, such as those that are originally contained in the ink. A method has been adopted in which a cleaning liquid pressure of a certain pressure or more is applied to the ink (the method of applying cleaning liquid pressure is not shown) to form a forced ink flow in the pressure chamber 3 and the nozzle 5.

(For example, Japanese Patent Laid-Open No. 52-150030) However, simply applying cleaning liquid pressure to form a forced ink flow was not sufficiently effective in eliminating air bubbles and solid objects. In other words, if air bubbles or solid objects are attached to the wall inside the nozzle 5 or the pressure 113, or if they are present near the wall, the ink flow velocity at these locations may not be sufficient and they may not be removed. There were many. In particular, if the print head 1 is not held horizontally as shown in FIG.
If the nozzle 5 side is tilted and held, the bubbles tend to move in the opposite direction to the nozzle 5 due to their buoyancy, and in such a case it is almost impossible to eliminate them. Met.

In this way, air bubbles and solid objects form the pressure chamber 3. Conventionally, if the ink is not removed from the nozzle 5, it is necessary to repeat the operation of forming an ink flow, which causes the problem that expensive ink is wasted. If the print head 1 does not recover normally, the print head 1 is considered to be a defective product, and it is necessary to refill the ink after removing the print head 1 from the recording device. In extreme cases, the expensive print head may be replaced. Sometimes it was discarded as a good powder product.

The purpose of the present invention is to eliminate the air bubbles and solid objects that impede the normal ejection and flight of ink from the nozzles 5 of the print head 1, and to improve the ineffectiveness of the conventional technology. ．． We hope to provide a new method that is highly efficient, inexpensive, simple, and easy to implement.

The gist of the present invention is as follows: 1) Applying mechanical vibration to the ink flow path including the nozzles and pressure chambers of the print head during non-printing operation of the inkjet recording device 2) During or at the end of the time including the mechanical vibration operation 03) Use defined electro-mechanical conversion means in the print head as a means for generating mechanical vibrations which subsequently create a forced ink flow in the ink flow path. 4) As a means for generating mechanical vibrations, an electro-mechanical conversion means used for jetting droplets is used. 5) As a means for generating mechanical vibrations, an electro-mechanical transducer that contacts the print head only when generating mechanical vibrations is used.Hereinafter, the present invention will be described in detail based on illustrated embodiments. .

FIG. 2 shows an embodiment according to the present invention.

That is, the piezoelectric transducer used to generate ink droplets during normal recording operations is used as is as a means for generating mechanical vibrations within the ink flow path.

Here, the operation for eliminating air bubbles and solid objects will be specifically explained. First, during the recording operation of the recording device, ink droplets may not be ejected from the nozzle 5, or they may be ejected but the ejection direction or ejection speed is not normal. If an abnormality is discovered visually or by some kind of detection means, the recording device shifts to an operation K for eliminating air bubbles (hereinafter, this operation is referred to as a purge operation).

When the purge operation begins, first, pressure is applied to the ink storage chamber 7 by a pressure applying means (not shown) K to cause ink to flow into the print head 1, and an electric pulse is transmitted from the nozzle 5 to the piezoelectric generator lσ. When a voltage is applied to the conversion element 4, the flexible wall 2 and the piezoelectric conversion element vibrate toward the pressure chamber 3 due to the piezoelectric effect. At this time, the electric pulse applied to the piezoelectric transducer 4 during the recording operation is used as the electric pulse, but it may be of a different shape. This operation causes pressure chamber 3. Nozzle 5
Air bubbles and solid objects inside the nozzle 5 are removed together with the ejected ink.
The print head 1 can return to normal recording operation again.

After ejecting ink for 5 seconds using the conventional method for a print head in which air bubbles or foreign matter have entered the nozzle, the probability that the print head will recover normally is less than 10%.
Even if the ink ejection time was increased to 9 seconds, the recovery rate was only a low degree. However, it has been confirmed that when the present invention is used to eject ink for 5 seconds while mechanically vibrating the pressure chamber 3, about 50 of the defective nozzles are restored to a normal state. Also, if you repeat purging while vibrating the pressure chamber 3,
Therefore, the recovery rate is approximately 100-.

In this way, in eliminating air bubbles and solid objects in the pressure chamber and nozzle, we not only eject ink from the nozzle, but also
The reason why the efficiency of removing air bubbles and solid objects increases when mechanical vibration is applied to the pressure chamber 3 at the same time is that the flow of ink inside the pressure chamber 3 and nozzle 5 is caused by mechanical vibration inside the pressure chamber 3. This is thought to be because the ink flow is different from when no vibration is applied. In other words, when no mechanical vibration is applied to the pressure chamber 3, the flow of ink is laminar because the ink flow velocity is relatively slow. At this time, since the flow velocity near the walls in the pressure chamber 3 and nozzle 5 is approximately 0, bubbles and solid matter adhering to the walls cannot be removed. On the other hand, when mechanical vibrations are applied to the inside of the pressure chamber 3, the flow of ink becomes turbulent, and the flow velocity becomes considerable even near the walls of the pressure chamber 3 and the nozzle 5. In addition, pressure chamber 3.
When air bubbles and solid objects attached to the wall surface of the nozzle 5 are also given mechanical vibrations, they are given energy to break away and break away. Things can also be easily removed.

FIG. 3 shows another embodiment of the present invention in which mechanical vibrations are generated in a print head other than the electro-mechanical transducers used to generate ink droplets during normal marking operation. In this case as well, in which a fixed electro-mechanical conversion means 4' is used, if the purge operation is performed according to the procedure explained in FIG. 2, the same effect as in the case of FIG. 1 can be obtained.

FIG. 4 shows another embodiment of the invention, in which the print head 1 uses electro-mechanical transducers not on the print head 1 as the means for generating mechanical vibrations. In operation, the print head 1 and the electro-mechanical transducer 4' are in contact and the electro-mechanical transducer 4' produces an effect similar to the piezoelectric transducer 4 in FIG. - The method of bringing the mechanical conversion means 4' into contact with the print head 1 may be such that the print head 1 moves to the fixed electro-mechanical conversion means 4' and the contact is completed, or vice versa. It is also possible to adopt a method in which the electro-mechanical conversion means 4' moves to the fixed print head 1 to complete the contact. 3 and 84, the shape and magnitude of the electric pulse applied to the electro-mechanical conversion means 4' are selected so as to produce the same effect as the piezoelectric conversion element 4 in the embodiment 1 of FIG. 2. Should.

As the electro-mechanical conversion means 4' in FIGS. 2 and 3, a piezoelectric conversion element, a magnetostrictive vibrator, a horn, etc. can be used. As the piezoelectric conversion element, for example, PZT-5H manufactured by Beien Vernitron Co., Ltd. is effective. .

As described above, according to the present invention, in the print head of an inkjet recording device, pressure is generated in the pressure chamber and nozzle, and intruding air bubbles and solid objects are removed with high efficiency. be.

BRIEF DESCRIPTION OF THE DRAWINGS 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 is a diagram showing another embodiment of the present invention. FIG. 4 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 is a piezoelectric conversion element, 4' is an electro-mechanical conversion means, 5 is a nozzle,
6 is an ink droplet, 7 is an ink storage chamber, 8 is an ink, 9
is a conduit, and 10,1σ is a pulse generator. 1υ 10 1υ th + concave

Claims (1)

[Scope of Claims] 11) An inkjet recording device characterized in that, in the printhead of the inkjet recording device, mechanical vibration is applied to the nozzles of the printhead and the ink in the pressure chamber when the recording device is not in a recording operation. (2. In the recording device set forth in the claims, an ink flow may be formed in the inward flow path during the time including the mechanical vibration operation or after the wrinkle mechanical vibration operation is completed. An inkjet recording device characterized by: (3) In the recording device according to claim 1 or 2, an electromechanical transducer fixed to the print head is used as the means for generating the mechanical vibration. Inkjet recording device (4) characterized by (5) In the recording device according to claim 1 or 2, in which the means for generating mechanical vibrations is used, printing is performed only when mechanical vibrations are generated. An inkjet recording device 0 characterized by using an electro-mechanical conversion means that comes into contact with a head.