JPS58197056A - Ink jet head for charge-deflection type ink jet printer - Google Patents

Abstract

PURPOSE:To obtain always a constant granulating characteristic for an ink head even when temperature is varied by a method in which a tiered portion is provided on the outside of an ink jet head structure and a drive frequency for a variator is set up between two or more resonance points. CONSTITUTION:A tiered portion 3 is provided on the outside of an ink jet head structure. If the distance from the front of a vibrating plate 6 to the rear step of the orifice of a nozzle 7 is l1, ink 1 in a liquid chamber 4 is vibrated by a vibrator and resonated by the vibration in terms of a connection of the distance l1 and sound velocity in the liquid at a resonance frequency f1 to the distance l1. Also, the ink 1 is resonated at a given resonance frequency f2 on the basis of a resonance principle for a columnar body even to the distance l2. The pressure of ink in the nozzle portion becomes almost constant in the frequency region between the frequency f1 and the frequency f2. Thus, the vibrator 5 is driven at a frequency corresponding to a fixed pressure section.

Description

[Detailed description of the invention] This invention relates to an improved ink jet head.

Conventional charge deflection type ink jet heads apply alternating current to an ultrasonic vibrator to vibrate the vibrator, transmit this vibration to the ink in the liquid chamber through a diaphragm, and adjust the ink flowing out from the nozzle to the frequency of this pressure vibration. The cut droplets are charged and deflected to be printed on a desired position on printing paper. In such an ink jet head, the resonant frequency can be determined from the relationship between the length of the liquid chamber from the diaphragm to the nozzle and the sound speed in the liquid.If this resonant frequency is used, efficient ink particleization is possible. . However, this resonant frequency is affected by the bending rigidity of the diaphragm, and may shift slightly due to temperature changes, deterioration of I/R, etc. Furthermore, since the customization of ink particle formation changes rapidly near the resonance frequency, there is a drawback that the ink particle formation becomes unstable.

In order to eliminate the adverse effects of the above-mentioned resonance and stabilize the formation of ink particles, the nozzle's 0. An elastomer member such as a butyl coat is installed in the closing part of the chamber in the shape of a tube or rod that is approximately equal to the length of the liquid chamber and occupies approximately half of the cross-sectional area of the liquid chamber. Some have a buffering means that absorbs the skin and suppresses the resonance of the liquid column. However, in this conventional technique, the efficiency of atomizing the ink decreases due to the fact that it absorbs the mechanical energy.

Therefore, the present invention provides general charge deflection type ink,
By making the outside of the structure of Tohe and Do step-shaped, the resonance point of the liquid F- and the resonance due to the stepped part of the structure are generated, and by using the frequency between these close resonance points. , eliminates the negative effects of resonance caused by changes in environmental conditions without sacrificing efficiency, and enables the stable formation of beautiful ink particles. 'It's what we offer. Hereinafter, the present invention 7) Friendly fitting 11 will be explained in detail with reference to the drawings.

C3) FIG. 1 is a sectional view of an embodiment of the present invention. Ink] is filled from the ink supply inlet 2 into a liquid chamber 4 inside the structure, which has a step 3 outside the structure. The vibrator 5 is the diaphragm 6
It is installed at the rear of the liquid chamber 4 across from the diaphragm 6, vibrates in response to a sine wave input, and adds pressure to the ink 1 in the liquid chamber 4 by adding a diaphragm 6, causing it to vibrate.The ink flow caused by this vibration pressure Ink 1 is ejected from the nozzle 7 at the tip of the liquid chamber 4, and is separated into individual ink droplets and granulated by the period of vibration in the ink stream.

In the ink jet head having the above structure, if the distance from the front surface of the diaphragm 6 to the rear surface of the orifice of the nozzle 7 is tl, and the distance from the rear surface of the diaphragm 3 to the step 3 is t2, then the liquid The ink 1 is vibrated by a vibrator in the chamber 4, and due to the vibration, at the resonance frequency ft for the distance 1, it exhibits a resonant state in relation to the distance t1 and the sound speed in the liquid, and also for the distance t2. Due to the principle of cylindrical resonance, the cylinder also exhibits a resonant state at a predetermined resonance frequency f2.
, I) 1st and 2nd have two resonance points.

FIG. 2 is a schematic diagram of frequency characteristics of an embodiment of the present invention. The vertical axis is the nozzle pressure amplitude P, and the horizontal axis is the frequency f.

Since this example has two resonance points at frequencies 11 and 12, the frequency characteristics of this example are a composite of two curves each having these resonance points.
Since the peak of the curve at frequency 1 and the peak of the curve at frequency 12 are close to each other, the peaks of the curve are connected to each other, and the curve between resonance frequencies f1 and f2 is smooth.
The slope becomes flat, and the ink pressure in the nozzle portion between frequencies f1 and 12 has little variation and is almost constant.

The most distinctive feature of the present invention is the frequency fl.

The idea is to use a frequency between the two resonance points of f2. In other words, when the vibrator drive frequency fa is set between the resonance frequencies f+ and f2, the ink pressure at the nozzle section changes in the frequency range between frequencies 11 and 12 because the curve between frequencies 11 and 12 is sloped or gentle. It becomes very constant.

Therefore, if the vibrator is moved by γ at a frequency corresponding to the constant pressure part, the sound speed in the liquid will change due to environmental temperature changes and ink deterioration during circulation, and the resonance point will change. However, constant ink particle formation can be obtained. However, using a frequency relatively close to the resonance point is also very efficient and economical.

In the above embodiment, the case where there are two resonance points has been described, but it is clear that the same applies to the case where there are three or more resonance points.

As explained above, the present invention provides step-like steps outside the structure of the inkjet head.
There are two or more resonance points, and the vibrator drive frequency is set between these resonance points, so even if the resonance points move due to temperature changes or ink deterioration, the particleization characteristics remain constant. It has effects such as stable image quality and excellent excitation efficiency.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of an embodiment of the present invention, and Fig. 2 is a schematic diagram of frequency characteristics of an embodiment of the present invention. Part, 4 liquid chamber, 5
Vibrator, (5 diaphragm, 7-・nozzle. , □□' (7) Fig. 1↑ Fig. 2 f, fa f2f

Claims (2)

[Claims] (1) In an ink jet head that has a structure in which the liquid chamber has two resonance points, and the vibrator drive frequency is set between the adjacent resonance frequencies, a step is provided outside the structure of the liquid chamber, and the step is An ink jet head characterized by generating resonance in response to certain parts of the ink jet head. (2) In an ink tsherad with a structure in which the liquid chamber has two or more resonance points and the vibrator 1 drive frequency is set between the resonance frequencies at both ends, the distance from the front of the vibrator to the rear surface of the orifice of the nozzle A first resonance occurs with respect to the liquid chamber length, and a second resonance occurs with respect to the distance from the rear surface of the vibrator to the stepped portion. Inokutsufu tohe, de, which is characterized by producing third-order resonance.