JPH0238052A - Liquid jet recording head - Google Patents

Abstract

PURPOSE:To prevent the emission of a sub-droplet by eliminating the effect of a reflected wave by forming the shape of a supply port so that the length from an electrochemical converter element to the supply port along a tube body becomes different according to the position in the peripheral direction of the tube body. CONSTITUTION:The leading end of a pipe 11 on the side provided with an emitting orifice 2 is throttled into a tapered shape so as to obtain the emitting orifice 2 having a predetermined diameter and the other end part thereof is cut obliquely. When voltage is applied to a piezoelectric element 3, a main ink droplet 5A is emitted from the emitting orifice 2 and the generation pressure wave thereof is propagated rearwardly but, since the end part of the pipe 11 at the supply port 12 is formed obliquely, the time required until the pressure wave propagated rearwardly along the pipe 11 reaches the end part of the pipe 11 is different according to the circumferential position of the supply port 12 and, therefore, the energy of said pressure wave is dispersed until the said wave reflected at the supply port reaches the emitting orifice 12 and not concentrated to the emitting orifice. Further, since acoustic impedance is smoothly matched at the position of the supply port 12 in a state transferring from a pipeline 7 to an ink tank 4, the generation of a reflected wave at the end part of the supply port is suppressed. Therefore, the generation of a sub-droplet is prevented and ink can be stably emitted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a liquid jet recording head, and more specifically, the present invention relates to a liquid jet recording head. The present invention relates to a liquid jet recording head that performs recording by ejecting recording liquid (hereinafter referred to as ink) from ejection ports by varying pressure.

(Prior Art) FIG. 4 shows an example of a conventional recording head of this type. 1 is a pipe that has a tapered nozzle discharge port 2 at its tip and constitutes the head main body portion formed of a cylindrical glass tube, etc.; This is a piezoelectric element as a mechanical transducer. 4 is an ink tank that stores ink 5; 6 is ink 5 in ink tank 4;
8 is the tube 6 that guides the
This is a filter attached to the ink intake port of the printer.

In the liquid jet recording head configured as described above, when a voltage is applied to the piezoelectric element 3, the conduit 7 is rapidly contracted through the pipe 1 due to the electrostrictive effect, and pressure is applied to the ink 5 in the conduit 7. As a result of the transmission, ink droplets 5A are formed and ejected from the ejection port 2.

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

[Problem to be solved by the invention]

However, in the conventional liquid jet recording head as described above, the pressure waves generated by the piezoelectric element 3 are transmitted to the pipe 1 and the conduit 7, and proceed toward the ejection port 2, causing ink droplets (formed by reflected waves, which will be described later). 5A (hereinafter referred to as main droplets) is ejected in order to distinguish it from the ink droplets that are generated, but at the same time, it advances upstream from the piezoelectric element 3, that is, to the ink supply side, is reflected at the rear end of the pipe 1, and its reflected wave is ejected. It propagates in the direction of the discharge port 2 again.

Therefore, when this reflected wave reaches the ejection port 2, ink droplets (sub-droplets) are ejected again, which not only deteriorates the recording quality of characters and images, but also sometimes
This may cause air bubbles to be taken into the pipe line 7, and there is a possibility that the next normal ink ejection may not be performed.

FIG. 6 shows how the meniscus 10 formed at the ejection port 2 shown in FIGS. Elapsed time tμs since the
Indicates the relationship between As shown in this figure, the meniscus 1O begins to retreat immediately after the ink mass 58 is ejected, and reaches its maximum retreat at a certain point A, but then returns to 120~
At time B of 140 μs, the meniscus 10 is pushed out to the vicinity of the ejection port 2 under the influence of the reflected wave described above.

Therefore, when such a tendency of fluctuation is significant, ink is ejected as a sub-droplet at time B.

Note that the above-mentioned pressure wave is a type of sound wave that is propagated to the ink 5 and the pipe 1 in the conduit 7 by the sudden deformation of the piezoelectric element 3, and since the vibrator 1 itself is a rigid body, the conduit It is reflected by a sudden change in acoustic impedance at the rear end of the vibrator when viewed from 7. That is, at the time of main ejection or time B when such a pressure wave acts as Φ with respect to the ink ejection direction, the meniscus 10 is pushed toward the ejection port 2, and at the time A where it acts as e, the meniscus lO retreats. This type of oscillatory fluctuation movement of the meniscus lO is generated, and although this movement largely depends on the viscosity of the ink and its surface tension, it is also greatly affected by the structure of the recording head itself.

SUMMARY OF THE INVENTION An object of the present invention is to focus on the above-mentioned conventional problems, and to solve the problems, it is an object of the present invention to provide a liquid jet recording head that can prevent the ejection of sub-droplets by eliminating the influence of reflected waves. It is in.

[Means to solve the problem]

In order to achieve such an object, the present invention has a discharge port for discharging recording liquid at one end of a cylindrical tube, and the recording liquid is guided into the tube from a supply port provided at the other end. In a liquid jet recording head where recording is performed, the recording liquid is ejected from the ejection port by pressure waves generated by an electromechanical transducer provided in a part of the tube, and the liquid is ejected from the tube from the electromechanical transducer to the supply port. The supply port is characterized in that the shape of the supply port is formed so that the length thereof varies depending on the position in the circumferential direction of the tube.

[For production]

According to the present invention, the shape of the supply port provided at the end of the tube is formed such that the length along the tube from the electromechanical transducer element to the supply port varies depending on the position in the circumferential direction. The time it takes for the pressure waves generated by the electromechanical transducer to reach the supply port varies slightly depending on the circumferential direction, and the relationship between the timing of the pressure waves reaching the ink ejection port at the end of the supply port and the matching of acoustic impedance This prevents discharge of secondary resection.

(Example) Examples of the present invention will be described below in detail and specifically based on the drawings.

FIG. 1 shows an embodiment of the invention. Here, 11 is a pipe constituting the main body of the head part. In this example, heat-resistant glass is used for the pipe 11, and the tip on the side where the discharge port 2 is provided is tapered to a predetermined diameter. The other end is cut diagonally, for example at an angle of about 45°, so that a discharge opening 2 is obtained, and a beveled cut feed opening 12 is obtained.

In this example, the pipe 11 is directly attached to the ink tank 4 and no filter is provided, but a filter may be provided if necessary.

In the liquid jet recording head configured as described above, when a voltage is applied to the piezoelectric element 3, the main ink 5A is ejected from the ejection port 2, and the generated pressure wave is simultaneously propagated backward, that is, upstream. Due to the oblique formation of the end at the mouth 12, the time for the pressure waves propagating backwards along the pipe 11 to reach the end varies depending on the position around the supply mouth 12 and is therefore reflected here. The energy is dispersed before being transmitted to the discharge port 2 and is not concentrated at the discharge port 2.

Also, the acoustic impedance is lowered from the pipe line 7 to the ink tank 4.
Since it is smoothly matched at the position of the supply port 12 at the transition stage, the generation of reflected waves at the end of the supply port is suppressed,
For these reasons, the occurrence of side removal can be prevented and stable ink ejection can be performed.

FIG. 3 shows another embodiment of the invention. In this example, pipe 21
The shape of the end of the supply port 22 is not diagonal, but irregularly uneven in the length direction of the pipe.It is difficult to process if the pipe 21 is made of glass, etc., but if the pipe 21 is made of plastic. It can be easily formed into such a shape if it is made of metal or metal material. Alternatively, the ink discharge port 2 and the supply port 22 may be made separately from the pipe 21 and then connected and integrated.

In the liquid jet recording head configured in this manner, the generation of sublayers can be prevented for the same reason as explained above. Note that the shape of the end of the supply port 22 is not limited to the shape shown in FIGS. Any shape may be used as long as it differs depending on the position in the direction.

Therefore, in order to improve the acoustic impedance matching between the pipe and the ink tank 4, the upstream side of the pipe from the piezoelectric element 3 is formed into a trumpet shape (not shown) so that the pipe line 7 becomes wider as it approaches the supply port. Otherwise, the shape of the supply port may be formed as shown in FIG. 1 or 3.

Furthermore, the upstream side of the pipe from the piezoelectric element 3 may be curved, and the end of the supply port may be shaped as shown in FIG. 1 or 3.

(Effects of the Invention) As described above, according to the present invention, the other end of the cylindrical tube has an ink ejection port at one end and an electromechanical transducer around the ejection port. The shape of the supply port provided in the section is formed so that the length along the tube from the electromechanical conversion element to the supply port differs depending on the position in the circumferential direction of the tube. The time taken for the pressure waves to reach the end of the supply port can be varied depending on the position in the circumferential direction of the tube body, and the sound impedance can be matched at the boundary between the pipe line and the ink tank. The generation of reflected waves from the ink toward the ink ejection ports is suppressed, the occurrence of side droplets can be prevented, and good ink ejection can be performed.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view schematically showing an example of the structure of the liquid jet recording head of the present invention, FIG. 2 is a characteristic curve diagram showing the variation of the meniscus at the ejection port over time in the recording head of the present invention, and FIG. 3 4 and 5 are sectional views schematically showing two sides of the structure of a conventional liquid jet recording head, and FIG. 6 is a sectional view schematically showing the structure of another embodiment of the present invention. FIG. 3 is a characteristic curve diagram showing the variation of the meniscus at the ejection port in a conventional recording head over time. 4S evening 5B month θ-Souinuike Idari to 4 pods 1; Hosumura face map Figure 1 1, 11. 21...pipe, 2...discharge port, 3...piezoelectric element, 4... Ink tank, 5... Ink, 5A... Ink droplet (1 drop) 7... Pipe line, 10... Meniscus, 12, 22... Supply port. t (JJs) Nerimo Akira Otsu Roku Het I = Chi 1 Stone Meniscus Q Thing 2 I Kigasusu Odd Pillar Curved Figure 2 Heater Grasp 0 I Thought 0 Great Death I Column [Schematically Figure 3 Front view showing the row of rows of A and I (JJS) Figure 4 of Figure 4 (I) Fig. 6

Claims (1)

[Scope of Claims] 1) One end of a cylindrical tube has a discharge port for discharging recording liquid, and the recording liquid is introduced into the tube from a supply port provided at the other end. In a liquid jet recording head in which recording is performed by ejecting liquid from the ejection port using pressure waves generated by an electromechanical transducer provided in a part of the pipe, the pipe from the electromechanical transducer to the supply port A liquid jet recording head characterized in that the shape of the supply port is formed so that the length along the body varies depending on the position in the circumferential direction of the tube body.