JP2659762B2 - Ink jet recording head - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid jet recording head, and more specifically, to a liquid pressure in a pipe by an electromechanical transducer provided around a pipe leading to a discharge port. And ejecting a recording liquid (hereinafter referred to as ink) from an ejection port to perform recording.

[Conventional technology]

FIG. 3 shows an example of a conventional recording head of this type. 1
Is a pipe having a discharge port 2 of a tapered nozzle at the tip thereof and constituting a head main body formed of a cylindrical glass tube or the like, and 3 is an electric machine provided around the outer periphery of the pipe 1. It is a piezoelectric element as a conversion element. Reference numeral 4 denotes an ink tank for storing the ink 5, reference numeral 6 denotes a tube for guiding the ink 5 in the ink tank 4 to a conduit 7 in the pipe 1, and reference numeral 8 denotes a filter attached to an ink inlet of the tube 6.

In the liquid jet recording head configured as described above, when piezoelectric is applied to the piezoelectric element 3, the pipe 7 is rapidly contracted via the valve 1 due to the electrostriction effect, and pressure is applied to the ink 5 in the pipe 7. By being transmitted, the ink droplet 5A is formed from the ejection port 2 and ejected.

FIG. 4 shows another conventional example. In this example, the pipe 1 is directly connected to the ink tank 4 and the ink 5 is passed without passing through the tube 6.
Is directly guided to the pipe line 7 through the filter 8.

[Problems to be solved by the invention]

However, in the conventional liquid jet recording head as described above, a pressure wave generated by the piezoelectric element 3 and transmitted through the ink, which is a liquid, is transmitted to the pipe 1 and the pipe 7 to travel in the direction of the ejection port 2, and A droplet 5A (hereinafter, referred to as a main droplet for the sake of distinction from an ink droplet formed by a reflected wave described later) is ejected. And the reflected wave propagates again toward the discharge port 2.

Then, when the reflected wave reaches the discharge port 2, ink drops (sub-droplets) are discharged again, thereby not only deteriorating the recording quality of characters and images, but also sometimes causing bubbles from the discharge port 2 to pass through the pipe 7. There is a possibility that the next normal ink ejection may not be performed.

FIG. 5 shows a change state of the meniscus 10 formed at the ejection port 2 shown in FIGS. 3 and 4, that is, the retreat amount X μm of the meniscus surface on the center line of the ejection port 2 and the ejection of the ink main droplet 5A. This shows the relationship with the elapsed time tμs since the start. As shown in this figure, when the main ink droplet 5A is ejected, the meniscus 10 starts to recede immediately after that, and retreats most at a certain time A, and then again at the time B, the influence of the reflected wave described above is obtained. Receiving the meniscus 10 and discharge port 2
It is extruded to the vicinity. Therefore, when such a fluctuation tendency is remarkable, the ink is ejected as a sub-droplet at the time point B.

The above-mentioned pressure wave is a kind of sound wave that is propagated to the ink 5 and the pipe 1 in the pipe 7 when the piezoelectric element 3 is rapidly deformed, and the pipe 1 itself is a rigid body. The light is reflected by a sudden change in acoustic impedance at the rear end of the pipe as viewed from 7.
That is, the meniscus 10 is extruded toward the ejection port 2 at the time of the main droplet ejection or B at which such a pressure wave acts in the ink ejection direction, and at the time of A, the meniscus 10 retreats. This operation causes a vibrating movement of the meniscus 10, and such operation largely depends on the viscosity of the ink and the surface tension thereof, but is largely influenced by the structure of the recording head itself.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a liquid jet recording head capable of preventing the ejection of sub-droplets by eliminating the influence of a reflected wave in order to solve the above-described conventional problems and to solve the problems. It is in.

[Means for solving the problem]

In order to achieve the above object, the present invention provides an electric power supply in which a part of the tubular body is provided with ink guided from a supply port provided at one end of the cylindrical body to a conduit in the tubular body. In the ink jet recording head for discharging from the discharge port by the pressure generated by the mechanical conversion element and performing printing, the shape of the conduit near the supply port on the upstream side of the electromechanical conversion element is a trumpet shape, The cross-sectional area of the channel gradually increases toward the supply port, and the flared region where the cross-sectional area increases is arranged in the ink in the ink tank that holds the ink supplied into the channel. It is characterized by having.

(Operation)

According to the present invention, the supply port side end disposed in the ink tank is formed as a trumpet type so that the cross-sectional area of the conduit gradually increases as approaching the supply port, so that the volume velocity in acoustic impedance is reduced to the supply port. Changes smoothly toward the ink tank, and the matching between the ink and the ink in the ink tank becomes good, so that the reflection of the pressure wave transmitted to the ink at the end of the supply port can be suppressed, and the ejection of the sub-droplet can be prevented. High-quality recording.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail and specifically with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. Here, reference numeral 11 denotes a pipe constituting the head main body. In this example, a heat-resistant Pyrex glass (trade name) is used for the pipe 11,
One end of the pipe 11 is tapered to provide a discharge port 2 at the end, and the other end is formed in a flared flared shape, and the divergent supply port 12 is immersed in the ink in the ink tank 4. To do. In order to obtain such a shape, for example, a mold formed in such a shape may be used. The other configuration is the same as the example shown in FIG. 4, and no filter is provided in this example. However, a filter may be provided if necessary.

In the liquid jet recording head thus configured, the pipe
The cross-sectional shape of 11 is a wrapper type that gradually increases as it approaches the supply port 12 on the upstream side of the mounting portion of the piezoelectric element 3, and since this wrapper type area is immersed in the ink, a voltage is applied to the piezoelectric element 3. Even when the ink main droplet 5A is ejected, the volume velocity of the acoustic impedance is smoothly changed when the pressure wave is simultaneously propagated to the upstream side and reflected at the end of the supply port 12, so that the ink tank 4 , A good matching can be obtained, and reflection is prevented.

That is, as a result, as shown in FIG. 2, the peak of the meniscus retreat amount X μm at the time A after the main droplet ejection becomes significantly lower than that in FIG. 5, and the meniscus extrusion at the time B is also observed. That is, the ejection of the sub-droplets is prevented.

[Effect of the Invention] As described above, according to the present invention, the electromechanical conversion element is provided in the shape of the pipe in the cylindrical pipe having the recording liquid discharge port at one end. On the more upstream side, a trumpet-like shape whose cross-sectional area gradually increases as it approaches the supply port, and since this trumpet-shaped portion is immersed in the ink of the ink tank, the volume velocity in acoustic impedance is determined by the supply port. The pressure drop reflected at the end of the supply port can be remarkably attenuated by maintaining appropriate matching with the ink tank, and the main droplet can be converted. The variation of the meniscus after ejection is suppressed, and stable ejection is obtained, so that high-quality printing can be performed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing an example of the configuration of the liquid jet recording head of the present invention, FIG. 2 is a characteristic curve diagram showing the variation of meniscus at the discharge port of the recording head of the present invention over time, FIG. And FIG. 4 is a cross-sectional view schematically showing two examples of the configuration of a conventional liquid jet recording head, and FIG. 5 is a characteristic curve diagram showing the variation of meniscus at the discharge port of the conventional recording head with time. is there. 1,11 pipe, 2 discharge port, 3 piezoelectric element, 4 ink tank, 5 ink, 5A ink drop (mainly suitable), 7 pipe line, 10 meniscus .

Claims (1)

(57) [Claims] 1. An ink jet printer according to claim 1, wherein said ink is supplied from a supply port provided at one end of said cylindrical tubular body to a conduit in said tubular body by an electromechanical transducer provided in a part of said tubular body. In an ink jet recording head that performs recording by discharging from the discharge port by pressure, the shape of the pipe near the supply port upstream of the electromechanical transducer is a trumpet shape, and the pipe is directed toward the supply port. The cross-sectional area of the passage is gradually increased, and the trumpet-shaped region where the cross-sectional area is increased is arranged in the ink in the ink tank that holds the ink supplied in the conduit. Ink jet recording head.