JPH02219655A - Ink jet head - Google Patents

Abstract

PURPOSE:To obtain an ink jet head capable of jetting ink drops with enough jet force by a method wherein a vibration wall of a pressure chamber is displaced by Lorentz's force by making a record signal current flow through a current part to jet the ink drop from a nozzle. CONSTITUTION:An ink jet head equipped with a pressure chamber block 11a. When a current i is made to flow according to a recording signal, a thin wall 15a of a pressure chamber 12a receives Lorentz's force to be distorted in a direction of reducing volume, and an ink drop is jetted from a nozzle 17a. However, since the current is made to flow through a conductor 14a outside the pressure chamber 12a, the current neither electrolyzes ink nor generates any bubble due to Joule heat. Further, since jetting force of the ink drop can be intensified by increasing any one of a magnetic flux density B, the number of the conductors, the current i, and a length of the thin wall 15a, enough jetting force of the ink drop can be obtained. Therefore, the ink drop can be jetted with enough force according to the recording signal neither by electrolyzing the ink nor by generating any bubble in the ink due to Joule heat.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet head in an inkjet recording apparatus, and particularly relates to an improvement of an ink-on-demand type inkjet head.

[Prior Art] FIG. 3A is a schematic cross-sectional view showing an inkjet head disclosed in Japanese Patent Application Laid-Open No. 58-208070,
FIG. 3B is a cross-sectional view taken along line 3B-3B in FIG. 3A. Referring to these figures, conductive ink 2 is supplied into an ink tube 1 having a nozzle at its tip.

The ink tube 1 is sandwiched between an upper magnet 3a and a lower magnet 3b. Arrows X represent the directions of magnetic lines of force generated by these magnets. Furthermore, a pair of electrodes 4a and 4b are provided inside the ink tube 1, which face each other in the horizontal direction. Arrow Y represents the direction of current flowing in the conductive ink 2 between these electrodes. a pair of electrodes 4a,
4b is connected to an amplifier 5, and a pulsed recording signal is input to an input terminal 6 of the amplifier 5.

In the conventional inkjet head configured as described above, when a pulsed recording signal is input to the input terminal 6, the recording signal amplified by the amplifier 5 is applied to the pair of electrodes 4a, 4b, and the conductive A current Y flows across the ink 2. At this time, since the current Y is substantially orthogonal to the magnetic lines of force X, the conductive ink 2 receives a force in the direction of arrow F according to Fleming's left-hand rule. Therefore, ink droplets are ejected from the nozzle 7 at the tip of the ink tube 1.

[Problem to be solved by the invention] In the conventional inkjet head as described above,
Since a current is passed directly into the conductive ink, the ink may electrolyze and change in quality or generate gas. Furthermore, it is difficult to impart sufficient conductivity to the liquid ink 2, and therefore it is difficult to flow a sufficient current Y to obtain a sufficient Lorentz force F. If a large current Y is caused to flow through the ink having low conductivity, bubbles may be generated in the ink 2 due to the sudden generation of Joule heat. When gas or bubbles are generated in the ink 2, ink droplets are ejected or leaked from the nozzle 7 due to the volume expansion. Such ejection or leakage of ink droplets due to gas or bubbles is not synchronized with the recording signal, resulting in unusable prints.

In view of these problems of the prior art, an object of the present invention is to provide an inkjet head that can eject ink droplets with sufficient ejection force without changing the quality of the ink or generating gas or bubbles in the ink. That's true.

[Means for Solving the Problems] An inkjet head according to the present invention includes a pressure chamber having an ink supply hole and an ink ejection nozzle, and includes a vibrating wall in which at least a portion of the wall of the pressure chamber is thinned. The vibrating wall of the pressure chamber is equipped with a pressure chamber block, a current path provided in the vibrating wall, and a magnet for generating a magnetic field having lines of magnetic force that are substantially perpendicular to the current path. is displaced by Lorentz force, thereby ejecting ink droplets from the nozzle.

[Function] According to the inkjet head of the present invention, the pressure chamber having the nozzle is provided with a thinned vibrating wall, and the vibrating wall is provided with a current path substantially orthogonal to the lines of magnetic force. Therefore, by passing a recording signal current through the current path, the vibrating wall can be displaced by the Lorentz force, thereby ejecting ink droplets from the nozzle with sufficient ejection force in synchronization with the recording signal without changing the quality of the ink. can do.

[Example] FIG. 1 is a cross-sectional perspective view of an inkjet head according to an example of the present invention. This inkjet head is
It is equipped with a pressure chamber block 11a, and a pressure chamber block l.
la includes a pressure chamber 12a. The pressure chamber block 11a also includes an ink supply hole 16a for supplying ink from an ink source (not shown) to the pressure chamber 12a, and further includes a nozzle 17a for ejecting ink droplets from the pressure chamber 12a. Contains. The wall surrounding the pressure chamber 12a includes a thin section 15a. pressure chamber block l
A conducting wire 14 is provided as a current path along a thin wall 15a.
A is provided. Arrow i indicates the direction of the current flowing through the conducting wire 14a.

The pressure chamber block lla is sandwiched between an upper magnet 13a and a lower magnet 13b1. The direction of the magnetic lines of force of the magnetic field generated by these two magnets is represented by arrow B, and is approximately perpendicular to the direction of current i.

In the inkjet head constructed in this way,
If the current i is applied in response to the recording signal, the pressure chamber 12a
The thin wall 15a of is subjected to the Lorentz force in the direction of arrow F, and is bent in a direction that reduces the volume of the pressure chamber 12a. As a result, ink droplets are ejected from the nozzle 17a. At this time, the entire thin wall 15a receives a Lorentz force of 11-i ml during F-B. Here, F is the Lorentz force, B is the magnetic flux density, n is the number of conductive wires 14a along the thin wall 15a, i is the current, and gun is the length of the thin El 15a along the conductive wire 14a.

In the inkjet head shown in FIG. 1, the current is passed through the conductor 14a outside the pressure chamber 12a.
It will also be appreciated that there is no electrolysis of the ink within, nor does it create bubbles due to Joule heating. Also,
The ejection force of the ink droplet is the magnetic flux density B, the number of conductors n, and the current i
, can be strengthened by increasing either the length of the thin wall 15a. In particular, in the inkjet head of FIG. 1, since there is no need to pass current through the ink, the current i can be easily increased and a sufficient ink droplet ejection force can be obtained.

FIG. 2 is a schematic perspective view of an inkjet head according to another embodiment of the present invention. In this inkjet head, a pressure chamber block llb is sandwiched between a pair of magnets 13a2 and 13b2. The pressure chamber block 11b includes an ink supply hole 16b for supplying ink from an ink source (not shown), and a nozzle 17b for ejecting ink droplets. Nozzle 17b
The magnet 13b2 facing the magnet 13b2 includes an opening 20 for passing an ink droplet. Approximately hexahedral pressure chamber block l
Of the six outer walls of lb, the four outer walls are almost parallel to the magnetic field line B! ! 15b are thinned and their thin outer walls 15
A conducting wire 14b is wound around b. On the other hand, among the outer walls of the pressure chamber block 11b, the remaining two that are almost perpendicular to the lines of magnetic force B
The two outer walls 18 are thickened.

In such an inkjet head, when a current is applied to the conductive wire 14b in the direction of the arrow 1 in accordance with a recording signal, each portion of the conductive wire 14b receives a Lorentz force F directed toward the inside of the pressure chamber block llb. That is, the four thin outer walls 15b substantially parallel to the lines of magnetic force B are bent toward the inside of the pressure chamber block 11b, and ink droplets are ejected from the nozzle 17b. It will be understood that the inkjet head of FIG. 2 can easily obtain a larger change in the volume of the pressure chamber than the inkjet head of FIG. 1, that is, a greater ejection force of ink droplets.

[Effects of the Invention] As described above, according to the present invention, ink droplets can be ejected with sufficient force in response to recording signals without electrolyzing the ink or generating bubbles in the ink due to Joule heat. It is possible to provide an inkjet head that can perform

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional perspective view schematically showing an inkjet head according to an embodiment of the present invention. FIG. 2 is a schematic perspective view showing an inkjet head according to another embodiment of the present invention. FIG. 3A is a sectional view showing an example of a conventional inkjet head. FIG. 3B is a cross-sectional view taken along line 3B-3B in FIG. 38. In the figure, lla and llb are pressure chamber blocks, 12a
, 12b is a pressure chamber, 13a+, i3b+. 13a2, 13b2 are magnets, 14a, 14b are conductive wires, 1
5a and 15b are thin walls, 16a and 16b are ink supply holes, 17a and 17b are nozzles, 18 is a thick wall, arrow B is the direction of magnetic field lines, arrow i is the direction of current, arrow F is the direction of Lorentz force, and 20 represents an opening. Note that in FIG. 3A and FIG. 3B, the same reference numerals indicate the same or equivalent contents.

Claims (1)

[Scope of Claims] A pressure chamber block including a pressure chamber having an ink supply hole and an ink ejection nozzle, and including a vibrating wall in which at least a portion of the wall of the pressure chamber is thinned; a current path provided therein, and a magnet for generating a magnetic field having lines of magnetic force substantially orthogonal to the current path, and by passing a recording signal current through the current path, the vibrating wall of the pressure chamber is moved by a Lorentz force. An inkjet head characterized in that the head is displaced, thereby ejecting ink droplets from the nozzle.