JPS59167267A - Multi-nozzle printing head - Google Patents

Abstract

PURPOSE:To stably perform high-speed jetting of ink droplets at a rate of 3,000 dots/sec or more without intermixture of air by a multi-nozzle printing head by using a system in which a capacity chamber and a fluid resistor group are set and the equilibrated state of ink is kept only by the surface tension of ink in the nozzle hole. CONSTITUTION:A capacity chamber 11 leading to a nozzle hole 10 through which ink droplets are jetted and having a smaller capacity than a pressure generating chamber serves to prevent the intermixture of air bubbles from the nozzle hole 10 into the pressure-generating chamber 12 and also to stabilize the discharge of ink droplets. The other end of the pressure-generating chamber 12 leading to the capacity chamber 11 through a throttled portion A1 is led to an thin-layer ink supplier 13 through a throttled portion A2. The thin-layer ink supplier 13 is of a depth of 0.04-0.2mm. and supplies unformly ink to each jet channel by a capillary phenomenon. Ink supplied from an ink supply hole 15 is temporarily stored in an ink trap 14, and air is drawn out by an air vent 18.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to drop-on-demand printheads.

Conventionally, this type of print head is as shown in Fig. 1 (aL (b) (
Between the nozzle hole 101 and the ink reservoir 105 (
Then, a thin flat flexible upper plate 102 made of a material such as glass ceramics or stainless steel is bonded by some means to the channel substrate 100, which consists of a plurality of injection channel systems each having a pressure generating chamber 104. .

Electromechanical conversion means 103 made of zirconate lead titanate porcelain, barium titanate porcelain, etc. is the upper plate) 102
This is a print head that is configured to be glued at a position corresponding to the upper pressure generating chamber 104. Note that the upper plate 102 and the electromechanical transducer 103 are not shown in FIG. Each electromechanical conversion means 103 according to the recording signal
By applying an electric signal to the upper plate 102, the upper plate 102 is instantly and greatly deformed. As a result, the volume of the pressure generating chamber 104 instantly decreases, generating pressure waves. The injection principle is that one droplet of 9472 is ejected from the nozzle hole 101 using this pressure wave. Therefore, by moving the print head in which seven nozzles are arranged in the vertical direction as shown in FIG. )×5 (horizontal) dot matrix structure can be recorded and printed on a recording medium.

By the way, during non-recording, in the print head configured as shown in FIGS. 1(a) and 1(b), ink is pushed to the nozzle due to the force relationship between the ink static pressure in the ink reservoir 105 and the ink surface tension in the nozzle hole 101. The flow from the hole 101 keeps the ink in equilibrium. For example, in the print head shown in FIG. 1(a), the water head pressure difference H is at most several c1rLH2
It was about 0. However, as the number of nozzle holes 101 increases, this water head pressure difference (2) inevitably increases, and as a result, the water head pressure increases. However, when the water head pressure H becomes several centimeters or more than 0, the static pressure generated by this water head pressure becomes larger than the surface tension of the ink at the tip of the nozzle hole 101, causing a big problem in that the ink flows out from the nozzle hole 101. there were.

In addition, in the print head shown in FIG. 1(b), since the water head pressure difference is negative, the phenomenon of in> flowing out from the nozzle hole 101 does not occur, but this poses a geometrical problem when increasing the number of nozzles. There was a problem in that the number of Atp nozzles could not be increased.

Furthermore, with the means for keeping the ink in an equilibrium state using the static pressure of the ink in the ink reservoir 105 and the surface tension of the ink with the nozzle hole 101, if the static pressure of the ink reservoir 105 fluctuates due to some disturbance (for example, temperature change, shock, etc.), This equilibrium state cannot be maintained, and there is a problem that ink drips from the small drop hole 101.

On the other hand, when an electric signal is applied to the piezo vibrator 101, the internal pressure of the pressure generating chamber 103 increases instantaneously, and the nozzle hole 104
There is a major problem in that at the same time as more ink droplets are ejected, a backflow of ink occurs in the ink reservoir (not shown), causing an extra volume change in the pressure generating chamber 103 that does not contribute to the generation of ink droplets.

Therefore, in order to eject a predetermined ink droplet diameter, it is necessary to apply a high voltage so as to cause the piezoelectric vibrator 101 to become more distorted.

Furthermore, by greatly distorting and deforming the piezoelectric vibrator 101, the ink within the pressure generating chamber 103 causes a large amplitude vibration. Therefore, as the driving frequency increases, the next electrical signal is applied before the ink amplitude vibration is damped and stopped, causing fluctuations in the ejection speed of the ink droplets. Eventually, the state of ink droplet generation no longer follows the electrical signal, so air bubbles enter the pressure generation chamber 103 from the nozzle hole 104, resulting in a major drawback in that ink droplets no longer eject.

On the other hand, it is necessary to fill the flow rate of ink ejected from the nozzle hole 104 through the throttle 9 at the other end of the P1 pressure chamber 103, but the larger the backflow of ink, the longer the filling time. It takes time.

When operating at a drive frequency of 3,000 dots/see or higher, this filling time also becomes a problem, and is an obstacle to high-speed printing operations.

The purpose of the present invention is to provide high reliability with an ejection channel shape that prevents air from entering the pressure generation chamber from the nozzle hole and to reduce backflow of ink to the ink reservoir, and extremely practical use that allows a large number of nozzles to be arranged. The objective is to provide a versatile multi-nozzle print head.

According to the present invention, there is a capacity chamber between the nozzle hole and the pressure generation chamber, which has a volume p smaller than that of the pressure generation chamber, and a plurality of ejection channel systems consisting of the nozzle hole, the capacity chamber, and the pressure generation chamber, and a common ink a thin layer ink supply section between the reservoir and the reservoir that supplies ink to the pressure generation chamber by capillary action; an air hole in the upper part of the ink reservoir and an ink supply port in the lower part; A multi-nozzle print head is obtained in which a fluid resistance group having low-pass filter characteristics is disposed on the side of the thin layer ink supply section.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 2 is a partially cutaway diagram showing the principle of an embodiment of the present invention, and FIG. 3 is a schematic diagram of a multi-nozzle print head in which a large number of nozzles are arranged. FIG. 4 is an enlarged view of a fluid resistance group having a low-nox filter characteristic used in the present invention. In FIGS. 2 and 3, 10 is a nozzle hole for ejecting ink droplets, and 11 is a nozzle hole 10.
This is a capacity chamber that communicates with the pressure generating chamber 12 and has a smaller volume than the pressure generating chamber, and has the role of stabilizing the ejection of ink droplets and preventing air bubbles from entering the pressure generating chamber 12 from the nozzle hole 10. 12 is the capacity chamber 11 via the throttle part A1.
The other end of the pressure generating chamber 12 communicates with the thin layer ink supply section 13 via the constriction section A2. This thin layer ink supply section 13 is formed by etching technology or the like.
It is formed to a depth of about 0.4 to 0.2%. This thin layer allows ink to be uniformly supplied to each ejection channel by capillary action. 14 is an ink reservoir,
It is used to temporarily store ink supplied from the ink reservoir 16. 30 is a flexible upper plate;
31 is a piezo vibrator made of zirconium titanate-based porcelain, barium titanate porcelain, or the like. 15 is an ink supply port of the print head, and 16 is an ink reservoir to which constant pressure is applied, which supplies ink to the print head 1 via a vibrator 17. The maximum value of the pressurization of the ink reservoir 16 must be set so that the liquid level of the ink reservoir 14 is below level a. 18 is an air vent, and when filling the print head 1 with ink, a large external force is applied to the ink reservoir 16 to forcibly fill it with ink. At this time, the hole fm is simply for venting the air remaining in the ink reservoir 14.

FIG. 3 is a block diagram showing an embodiment in which a large number of nozzle holes 10 are arranged in a fan shape according to the present invention, and the constituent elements are the same print head as the principle shown in FIG.

Now, when a recording signal is applied to the piezo vibrator 31, the flexible plate 30 instantly expands and contracts, and one ink droplet is ejected from the nozzle hole 10. Ink from the ink reservoir 16 is supplied to the ink reservoir 14, and at the same time, since the thin layer ink supply portion 13 is formed of a thin layer with a culmency of 0°04 to 0.2·χ, the ink is absorbed by capillary action. It rises and is evenly supplied to each injection channel system. Therefore, after ink droplets are ejected from the nozzle holes 10 by the pump action of the pressure generating chamber 12, an ink flow rate corresponding to the ejected amount is supplied to the pressure generating chamber 12 via the thin layer ink supply section 13. In addition, the thin layer ink supply section 13 has a thickness of 0.04 to 0.2''
Since it is made up of a thin layer of about n thickness, a kind of squeezing effect is produced, and therefore, it is possible to supply ink without being affected by fluctuations in the static pressure of the ink generated in the ink reservoir 14. Therefore, the equilibrium state of the ink in the nozzle hole 10 is determined only by the ink surface tension, and it is necessary to maintain an accurate balance between the ink surface tension in the nozzle hole 10 and the static pressure in the ink reservoir 14, as in conventional print heads. Suddenly,
This has the advantage that the number of nozzles can be increased considerably. As a result, the ink reservoir 14 only needs to temporarily store ink, and precise control of the static pressure of the ink is no longer necessary.

On the other hand, as the repetition drive frequency of the recording signal increases, the ink pressure vibration in the pressure generating chamber 12 increases. In the conventional print head, air easily enters the pressure generating chamber 12 from the nozzle hole 10 due to this effect, and as a result, there is a problem in that the ejecting operation of ink droplets becomes impossible. On the other hand, by providing this canonical city chamber 11, air is mixed into the pressure generating chamber 12 so that K<<. As a result, the air that entered through the nozzle hole 10 accumulated in the canopy chamber 11 and did not enter the pressure generating chamber 12.

Therefore, since the pressure generation chamber 12 always generates normal pressure waves, the air accumulated in the capacity chamber 11 is easily pushed out by continuously repeating the discharge operation, and normal injection is quickly performed. I was able to get back to normal. As a result, it was possible to sufficiently follow high-speed repetitive motions of 3,000 dots per second or more. Regarding these, please refer to the specification of Japanese Patent Application No. 56-159945 and Japanese Patent Application No. 1983.
6-159,947 in detail.

By the way, when the piezo vibrator 31 is applied, an impulse wave generated in the pressure generating chamber 12 is propagated to the nozzle hole 10 through the constriction part A□, and ejects ink droplets. At the same time, ink flows back from the other end of the pressure generating chamber 12 toward the ink reservoir 14 through the constriction part A2 at high speed. By squeezing this throttle part A1, it is possible to reduce the backflow of ink. However, if the constriction section A2 is constricted too finely, fluid resistance becomes large, ink becomes difficult to flow, and ink filling time becomes longer. has created a limit. Therefore, as an aim of the present invention, it is not possible to tighten the drawing part A2 too much, and it is impossible to do so due to the above-mentioned problems.
This method has been realized to further reduce the backflow of ink. In other words, if a large number of semi-cylindrical fluid resistance groups 20 are arranged at regular intervals as shown in FIG. Since it is a pressure wave containing pressure waves, this fluid resistance 8P20 reaches the constriction part A from the reflection attenuation line. As a result, this pressure wave is propagated to the constriction section A2 with a slight attenuation, so that the amount of ink backflow can be significantly reduced compared to a mere change in the shape of the constriction section A. Also, Figure 4 (
As shown in b), since the ink filling operation is performed by capillary action, this fluid resistance group 20 does not become much resistance and the ink flows, and the ink filling time is equal to this fluid resistance group 2.
Placing 0 did not make it longer. This semi-cylindrical fluid resistance group 20 acts as a high fluid resistance against ink containing a high frequency component that flows backward when applied, and acts as a low fluid resistance against the movement of ink containing a low frequency component during filling. work. In other words, this fluid resistance group 20 serves as a filter with low-pass characteristics. As a result, the ink backflow during application can be minimized without squeezing the constriction part A, which has significant effects such as lowering the applied voltage, shortening the ink filling time, and enabling high-speed printing. It is.

Orange: The ink flow grooves and fluid resistance group of the print head can be manufactured at the same time by etching. Also, according to our experiments, the nozzle hole 10. The etching depth of the capacity chamber 11 and the pressure generation chamber 12 is 0.04 to 0.1%, the depth of the thin layer ink supply part is 0.04 to 0.2%, and the depth of the ink reservoir is 0.4 to 0.1%. The range of 3゛χ was suitable for practical use.

As described above, the multi-nozzle print head of the present invention can maintain the equilibrium state of the ink only by the ink surface tension of the nozzle holes, so a multi-nozzle print head with a large number of nozzles arranged is possible, and the capacity chamber The arrangement of the fluid resistance group and the fluid resistance group results in a print head that can achieve high-speed jetting of more than 3,000 doors per second, stable jetting conditions, and high reliability with no air contamination.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are partially cutaway schematic diagrams of examples of conventional multi-nozzle print heads, and FIG. 2 is a partially cutaway diagram showing the principle of the present invention. FIG. 3 is an enlarged view of a high-density group in which a large number of nozzles are arranged in a fan shape according to the present invention. In the figure, 10 is a nozzle hole, 11 is a capacity chamber,
12 is a pressure generation chamber, 13 is a thin layer ink supply section, 111 is an ink reservoir, 15 is an ink supply port, 16 is an ink reservoir, 18 is an air vent hole, 30° IC)'2! ri flexible upper plate, 31 and 103 are piezo vibrators, and 20 is a fluid resistance group. Hegakito? Uchihara Fu (1 ゝ(O 1 Flash/bθ O? Figure O U (θ) (b)

Claims (1)

[Claims] In a multi-nozzle print head in which a plurality of ejection channel systems each having a structure having a nozzle hole and a pressure generating chamber communicate with one common ink reservoir, the pressure is applied between the nozzle hole and the pressure generating chamber, respectively. a thin-layer ink supply section for disposing a capacity chamber having a smaller volume than the generation chamber, and supplying ink to each of the pressure generation chambers by capillary action between the plurality of ejection channel systems and the common ink reservoir; and an air hole in the upper part of the ink reservoir, an ink supply port in the lower part of the ink reservoir, and a fluid resistance group having low-pass filter characteristics on the thin layer ink supply part side of the pressure generation chamber. A multi-nozzle print head that features: