JPH02184443A - Ink jet head - Google Patents

Abstract

PURPOSE:To enable a finer control of ejecting positions for liquid droplets by arranging vibrators and a liquid chamber so as to ensure self-convergence of waves into a surface perpendicular to the longitudinal direction of a nozzle, and disposing a plurality of the vibrators separated mechanically and electrically from each other in the longitudinal direction and a controller for the vibrators. CONSTITUTION:When an RF voltage is applied to an electrode 4 by a driver 5, a vibrator 3 is oscillated to excite a sound wave in a liquid chamber. An intersection of a cross-section perpendicular to a longitudinal direction with the vibrator is a circular arc with a center at a point A (convergence point) near a liquid surface. Therefore, the sound wave is converged into the point A to excite a capillary wave at the liquid surface, thereby forming a liquid droplet 10. Since the liquid surface can be located at a substantially fixed position in the vicinity of a slit nozzle 1 by a surface tension, there is no need for a special control of the positions of the liquid surface and the vibrator, and a head can be disposed in any direction, without any considerable effects of gravity. When the phases of vibrators 3a-3e are controlled precisely by appropriate driving of drivers 5a-5e, the convergence points A can be controlled with intervals not more than the pitch P of the vibrators.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an infusiera 1 head, and more particularly to an inkjet inkjet printer that utilizes the acoustic mode of an acoustic printer.

Conventional summer Prior art related to the present invention includes the following publications.

(])] Japanese Unexamined Patent Publication No. 62-66943 Planar 5AWI
- Regarding a nozzle-less droplet ejector using a transducer), (2) Japanese Patent Application Laid-Open No. 62-264962 (a nozzle-less droplet ejector having a means for emitting pressure waves and a surface tension wave emitting controller) , (3) Japanese Patent Application Laid-Open No. 63-162253 (in an acoustic lens array, the lens array solid substrate is considerably faster than the sound speed of ink), (4) Japanese Patent Application Laid-Open No. 63-166545 (in an acoustic printer, the speed of sound is much higher than that of the ink). (changes droplet size by signal modulation)
, (5) Japanese Patent Application Laid-Open No. 166546/1983 (In an acoustic printer, the distance between droplet ejectors is 1 from the center distance of pixels.
(6)
JP-A-63-166547 (acoustic print head with a concave surface, the concave surface is filled with a solid filler whose acoustic impedance and sound speed are between those of the ink and the head), (7) JP-A-63-166548 (In an acoustic print head, in a solid substrate that is much faster than the sound speed of the ink, the wavelength within the substrate is 1 greater than the aperture of the acoustic lens.
/1c or more), (8) U.S. Patent No. 4,719,476 (addressing changing the local surface properties of a liquid in means of forming peaks and troughs of surface tension waves) ), (9) U.S. Patent No. 4,719,480 (Means for stabilizing surface tension waves that periodically change wave propagation)
.

Conventionally, several mechanisms have been devised to excite pressure within ink, converge it near the surface, excite surface waves, and eject droplets. Among them, one that uses acoustic beams is IBM Teck Disclosure.
Bulletin, 16. no4 (1973) 116
8-1170 is the oldest. Subsequently, U.S. Pat. No. 4,308,547 (Loveladyl, 9
81/12/29) is an acoustic beam, it indicates the possibility of nozzleless.

The above-mentioned prior art (1) and (2) relate to a completely nozzle-less system in which a planar vibrator is used as a liquid reservoir.

However, this type has a major problem in that it is necessary to maintain a constant distance between the liquid level and the vibrator.

In the present invention, while ensuring ease of maintenance, which is an advantage of a nozzle-less system, by using the ridge-shaped nozzle of Surin 1, and by controlling the liquid level with Surin 1, it has been possible to obtain great ease of handling.

The above (3) to (7) have a concave acoustic beam forming surface,
This invention relates to the improvement of a printer head for acoustic printing, and as in the present invention, the acoustic beam self-converges near the liquid surface in the plane perpendicular to the longitudinal direction of the slit-shaped nozzle, and mechanical and electrical There is no disclosure of positioning using a plurality of separate vibrators and a control device.

The above (8) to (9) are similar to the present invention in that they are slit-shaped nozzles, but are completely different from the present invention in terms of positioning. The present invention enables finer position control than the pitch of the vibrator arranged in the longitudinal direction of the slit-shaped nozzle, and this point is explained in (8) above.
~ (9) cannot be done.

■--Momme The present invention was made to solve the above-mentioned drawbacks, and in order to effectively utilize the directivity of the acoustic beam, it is necessary to A vibrator and a liquid chamber are arranged so as to self-converge on a plane perpendicular to the longitudinal direction of the nozzle, and a plurality of vibrators and a control device are mechanically and electrically separated in the longitudinal direction. Positioning, easy maintenance and high dot
To provide an inkjet head using an acoustic mode that ensures perinch controllability, and in particular, by appropriately driving a control device, it is possible to control the ejection position of droplets below the pitch in the longitudinal direction of a vibrator. It was done for that purpose.

Proverb - One.

In order to achieve the above object, the present invention provides an inkjet head that excites pressure waves within an ink liquid chamber and uses the energy to eject droplets from the ink liquid surface. A plurality of slit-like nozzles are arranged on a circular arc with the position of the slit-like nozzle as the center on a plane perpendicular to the direction, and are mechanically and electrically controllable independently in the longitudinal direction of the slit-like nozzle. a piezoelectric or electrostrictive vibrator, and a controllable drive capable of concentrating acoustic energy on a single point on the liquid surface in the slit-shaped nozzle by changing the phase of the vibrator in the longitudinal direction of the slit-shaped nozzle. means, further comprising: a vertical cross section in the longitudinal direction of the slit-shaped nozzle of the ink liquid chamber;
It is characterized by having an ink chamber formed into a fan-shaped or circular arc shape that approaches the nozzle exponentially, and by using a piezoelectric or electrostrictive polymer as a piezoelectric or electrostrictive vibrator. Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a vertical cross-sectional view in the longitudinal direction of a slit-shaped nozzle of the printer head, and FIG. 2 is a perspective view thereof, for explaining an embodiment of an inkjet head according to the present invention. In the figure, 1 is a slit-shaped nozzle, 2 is an ink chamber, 3 is a piezoelectric or electrostrictive vibrator, 4 is an electrode, 5 is a driving device, 7 is a flow path, 9 is printing paper, and 10 is a droplet. .

When an RF lightning voltage is applied to the electrode 4 by the driving device 5 (58 to 5e in FIG. 2), the vibrator 3, which is poled in the normal direction of the electrode surface, vibrates and excites sound waves into the liquid chamber.

As shown in Figure 1, the tangent line between the cross section perpendicular to the longitudinal direction and the vibrator is a circular arc centered at point A (convergence point) near the liquid level, and since the vibrations occur in phase on this circular arc, point A The sound waves converge and have a large amplitude l', which excites surface tension waves on the liquid surface and forms droplets 10 if the amplitude is sufficiently large. At this time, the liquid level is 0 at slit-shaped nozzle III.
．． If it is 5 nn or less, it can be placed at a nearly constant position near the slit nozzle 1 due to surface tension.
There is no need to specially control the liquid level and the position of the vibrator, and the head can be placed in any direction without being affected by gravity.

In the two-dimensional convergence of sound waves described above, the sound wave energy density at the convergence point A cannot be made very large. In order to obtain high energy density and controllability of the ink droplet ejection position in the longitudinal direction of the slit-shaped nozzle 1, as shown in FIG.
By appropriately controlling the phases of a to 5e, the
Change the position of 8-3e. In order to show the situation, FIG. 3 shows a cut through the slit-shaped nozzle 1 of FIG. 2 along a plane parallel to the longitudinal direction of the nozzle. Convergence point A and oscillator 3
The distance between a and the center of the ink chamber side surface is Qa, and the distance from the vibrators 3b to 3e is similarly Rb-Qe. When the phase of the vibrator 3a is set to φ=φa at time t=ta, the phase of the vibrator 3b is controlled in exactly the same way as t=t a+ where φ=φ・at “a-fib”. Then, the phases of all the waves match at the convergence point A, and a large energy density is obtained. 11a to 11e in FIG. 12 is its envelope surface. 13 is the liquid level in the slit-shaped nozzle. As is clear from FIG. It can be seen that the convergence point A can be controlled, and as a result, the number of oscillators and drive circuits can be reduced.In fact, the drive frequency can be reduced by approximately 10
MHz, when the distance between the vibrator and the convergence point A shown in Fig. 1 is 2 strokes, and the opening width of the slit-shaped nozzle 1 is 100 μm, even if the pitch P is 200 μm, the control interval of the ejected droplets is set to 100 μm. We were able to.

As the vibrator 3, a piezoelectric polymer such as PZT is used.
V DF (T r −F E ), etc. can be used.

The latter has an acoustic impedance close to that of water, and can efficiently input energy. Furthermore, since the dielectric constant is small, it is suitable for high-frequency driving.

FIG. 4 shows another embodiment of the invention. Generally, it is difficult to make PZT or the like into a cylindrical shape as shown in FIG. Therefore, as shown in FIG. 4, an acoustic plastic lens 14 is bonded to a planar structure of PZT to produce an effect similar to that shown in FIG. 1. This makes it possible to significantly reduce costs.

Effects--As is clear from the above description, according to the present invention, the slit nozzle vibrates on a plane perpendicular to the longitudinal direction of the slit nozzle on an arc where the slit nozzle is the center of the arc. Since the child is arranged, the liquid level and the position of the vibrator are fixed, and the energy of the vibrator can be concentrated near the liquid surface stretched by the slit-shaped nozzle. Further, by using a plurality of mechanically and electrically independent vibrators in the longitudinal direction of the slit-shaped nozzle and their driving means, it is possible to concentrate energy near the liquid surface in the longitudinal direction as well as to control its position.

Both of the above energy concentrations excite surface tension waves,
You can eject ink droplets and control their position. In addition, by phase control, the discharge position can be controlled to be less than the pitch in the longitudinal direction of the vibrators, and the number of vibrators in the control device can be reduced. Furthermore, since it is a slit-shaped nozzle, there is less clogging and maintenance is easy.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view perpendicular to the longitudinal direction of a slit-shaped nozzle of the printer head, FIG. 2 is a perspective view thereof, and FIG. , Diagram showing the energy density of sound waves, 4th
The figure shows another embodiment of the invention. 1...Slit-shaped nozzle, 2...Ink liquid chamber, 3...
・Piezoelectric or electrostrictive vibrator, 4...electrode, 5...driver. Patent applicant Rico Co., Ltd.

Claims (1)

[Claims] 1. In an inkjet head that excites pressure waves in an ink liquid chamber and uses the energy to eject droplets from the ink liquid surface, there is a slit-shaped nozzle; A plurality of piezoelectric or electrostrictive vibrators are disposed on an arc whose center is at the position of the slit-shaped nozzle, and are mechanically and electrically controllable independently in the longitudinal direction of the slit-shaped nozzle. A controllable driving means that can concentrate acoustic energy at a point on the liquid surface in the slit-shaped nozzle by changing the phase of the slit-shaped nozzle in the longitudinal direction of the slit-shaped nozzle. inkjet head.