JPH06226983A - Ink jet nozzle - Google Patents

Abstract

PURPOSE:To provide an ink jet nozzle which can make ink drops most appropriately by forming the inner structure of an ink jet nozzle so that the pressure wave distortion caused by its asymmetric element can be corrected or eliminated. CONSTITUTION:In an ink jet nozzle, a contraction R is formed between an asymmetric part and an orifice 0 to separate them. If the diameter of the contraction is shorter than the wave length of ink vibration, the end part from the contraction is in an equivalent state in which the vibration is given at the point on the central axis to shut off the asymmetric element. The inertial mass of ink is similar to that of ink of the orifice volume, effecting the reduction of a satellite. When a taper is formed only on the pressure chamber side of the contraction, the taper acts as a guide so that ink flows easily from the pressure chamber side to the orifice to prevent the flow from the orifice to an ink chamber. In this way, ink can hardly flow from the orifice to the ink chamber, preventing the mixing of bubbles from the orifice.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet nozzle of an inkjet printer.

[0002]

2. Description of the Related Art As one of the factors that affect the formation of ink particles in an ink jet printer, there is the structure of an ink jet nozzle.

In the conventional ink jet nozzle, the piezoelectric element (PZT), which is a driving element, and the tip of the nozzle orifice are connected straight without any obstacle for transmitting the pressure wave of the piezoelectric element. That is, due to the structure of the inkjet nozzle, there is no structure for correcting the transmission of the piezoelectric pressure wave, for example, unevenness. Therefore, the structural non-target element in front of the orifice affects the tip of the orifice. The non-target elements in this case are the pressure chamber,
A filter part is included.

[0004]

In an ink jet nozzle in which the inner shape of the nozzle is not symmetrical with respect to the central axis of the nozzle, that is, in the case of an asymmetrical structure, the influence of the non-symmetrical elements extends to the tip of the orifice. Also, the shape of the pressure wave generated inside the nozzle is not uniform.

As shown in FIG. 4, there is a vertical difference in the distance from the orifice to the filter portion, and P
Since ZT is also oscillated only from the lower part of the figure, the pressure wave reaches the orifice, but there is a difference between the top and bottom of the orifice tip. This has a great influence on the particle formation of the ink.

Further, in an ink jet nozzle having an asymmetrical structure, the inertial weight of the ink becomes large, which causes a decrease in satellite ejection and the like. That is, when the piezo is first pulled, ink flow occurs in the nozzle, and when the piezo pull is stopped, it cannot be stopped immediately due to the inertia of the ink itself, and as a result, high pressure is generated in the nozzle. Occurred, which is the cause of the preceding satellite. Similarly, in the case of a low speed satellite, the influence of inertia is large. In this case, after the main droplet is ejected, it tries to return in the direction opposite to the ink ejection due to the pressure vibration in the nozzle, but because the inertial weight of the ink in the nozzle is large, the flow cannot be stopped immediately and the main droplet is ejected. A long tail is drawn, which separates from the main droplet on the way to the printing surface, forming a low-speed satellite.

As described above, the shape of the ejected ink droplets becomes distorted or the low-speed satellite is generated, which causes the deterioration of print quality (FIG. 6, FIG. 6).
(See FIG. 7).

Therefore, an object of the present invention is to provide an ink jet nozzle capable of optimizing the particle formation of ink.

[0009]

In order to achieve the above object, in the present invention, in an ink jet nozzle having an asymmetrical structure, the structure inside the nozzle is corrected or the distortion of the pressure wave generated from the asymmetrical element is corrected or It has a structure that can be erased.

Specifically, an asymmetrical depression or protrusion or a diaphragm is provided in the nozzle to perform correction or separation from the asymmetrical element.

[0011]

With the above configuration, the shape inside the ink jet nozzle can be optimized from the viewpoint of pressure wave propagation, the distortion of the pressure wave caused by the non-target element is corrected, and the shape from the aperture ( In the direction of the orifice), the pressure wave can be optimized by the diffraction phenomenon.

[0012]

【Example】

Example 1 In FIG. 1, by providing a protrusion (P) in the nozzle, the orifice (O) generated above and below the central axis (A) of the nozzle.
The inkjet nozzle (B) in which the correction (1) of the distance difference from the filter unit to the filter unit (FS) is performed is shown.

Embodiment 2 FIG. 2 shows an ink jet nozzle in which a diaphragm (R) is provided between an asymmetric portion in the nozzle and the orifice (O) to separate the two.

In this case, if the diameter of the diaphragm is made shorter than the vibration wavelength of the ink, it will be equivalent to that from the point on the central axis after the diaphragm is vibrated (the pressure wave is optimized by diffraction). The target element can be blocked. Further, in this case, the inertial weight of the ink is about the volume of the orifice, which is effective in reducing satellites.

Furthermore, by providing a taper only on the pressure chamber side of the throttle, the taper serves as a guide, and ink easily flows from the pressure chamber side to the orifice (FIG. 3 (a)), and conversely flows from the orifice to the pressure chamber. Can be prevented (when the PZT contracts) (FIG. 3 (b)). This makes it difficult for the ink to flow from the orifice to the ink chamber, and as a result, the effect of preventing the inclusion of air bubbles from the orifice is produced.

With the ink jet nozzle having the structure as shown in the above embodiment, it is possible to form ideal droplet shapes without leading and low speed satellites.

[0017]

INDUSTRIAL APPLICABILITY In an ink jet nozzle having an asymmetrical structure, the pressure wave generated inside the nozzle is formed by making the structure inside the nozzle a structure capable of correcting or eliminating the distortion of the pressure wave generated from the asymmetrical element. It was possible to make the shape of the ink uniform and to optimize the particle formation of the ink.

[Brief description of drawings]

FIG. 1 illustrates an inkjet nozzle according to an exemplary embodiment of the present invention.

FIG. 2 is a view showing an inkjet nozzle according to another embodiment of the present invention.

FIG. 3 is a diagram showing a state where ink flows in the inkjet nozzle shown in FIG.

FIG. 4 is a diagram showing a propagation state of a piezoelectric pressure wave in a conventional inkjet nozzle.

5 is an X in the inkjet nozzle shown in FIG.
It is a figure which shows -X and YY sectional drawing.

FIG. 6 is a diagram showing a printing state associated with a low-speed satellite generated by a conventional inkjet nozzle.

FIG. 7 is a diagram showing a printing state associated with a shape-defective ink droplet ejected from a conventional inkjet nozzle.

[Explanation of symbols]

 A central axis of inkjet nozzle B inkjet nozzle FS filter slit O nozzle orifice PZT piezo P protrusion provided on inkjet nozzle l corrected distance difference R diaphragm provided on inkjet nozzle

Claims (3)

[Claims] 1. An inkjet nozzle having an asymmetrical structure, wherein the structure inside the nozzle is a structure capable of correcting or eliminating distortion of a pressure wave generated from the asymmetrical element. 2. As a structure capable of correcting or eliminating the distortion of the pressure wave generated from the non-target element, by providing a protrusion or a depression in the nozzle, from the orifice generated above and below the central axis of the nozzle to the filter section. The inkjet nozzle according to claim 1, wherein the distance difference is corrected. 3. As a structure capable of correcting or eliminating the distortion of the pressure wave generated from the non-target element, a restriction is provided between the non-target portion in the nozzle and the orifice to separate the two. The inkjet nozzle according to claim 1.