JPS6345952B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ink droplet ejecting device that ejects minute ink droplets.

The ink droplet ejecting device is mainly incorporated into an inkjet printer that ejects minute ink droplets and selectively adheres them to a recording medium such as plain paper to record images such as characters and figures.

The present invention provides an ink droplet ejecting device incorporated into such an inkjet printer.
On-demand patent application filed as No. 55-84264
This invention relates to an improvement in an ink droplet ejecting device called a diaphragm type.

First, the ink droplet ejecting device described in the above patent application specification, which is the basis of the present invention, will be explained with reference to FIG.

Reference numeral 1 denotes a piezoelectric vibrator as a pressure change means that vibrates in a curved manner in response to electrical signals such as sinusoidal, rectangular, or sawtooth waves; 2, the piezoelectric vibrator 1 forms one side wall of the long diameter end, and a small diameter is formed at the opposite location. 4 is a propagation medium that fills the pressure chamber 2 and propagates the bending vibration of the piezoelectric vibrator 1. The propagation medium 4 has a high propagation rate of the bending vibration and causes residual vibration. On the other hand, liquids having a damping effect such as water, ink, silicone oil, mercury, etc., viscoelastic substances such as silicone grease, and magnetic fluids in which powder is mixed in colloidal form are used as appropriate. 5 is a horn-shaped pressure chamber 2 filled with the propagation medium 4;
This is a diaphragm which closes the aperture 3 of the pressure vibrator 1 and vibrates in a curved manner by receiving the curved vibration of the pressure vibrator 1 via the propagation medium 4, and its entire contact surface is fixed to the wall surface with adhesive or the like. Reference numeral 6 denotes a front plate which is placed in front of the diaphragm 5 with a small gap therebetween and holds an ink layer 7 of a constant thickness in the gap; 8 is a diaphragm 5 located approximately in the center of the front plate 6;
A small-diameter orifice 9 bored in an opposing position is a capillary tube that supplies ink to the ink layer 7 from the outside.

When an electrical signal is applied to the piezoelectric vibrator 1 of such an ink droplet ejecting device to cause it to vibrate in a curved manner, the vibrating vibration causes a pressure change in the pressure chamber 2 . When the pressure increases, since the shape of the pressure chamber 1 is horn-shaped, the pressure is gradually amplified and applied to the diaphragm 5, causing the diaphragm 5 to curve toward the ink layer 7 as shown in FIG. On the other hand, when the pressure decreases, the pressure chamber 2 side is caused to vibrate in a curved manner. When the diaphragm 5 bends toward the ink layer 7, ink is projected from the orifice 8 in a columnar shape, and then the columnar ink becomes an ink droplet 10 and flies due to its own kinetic energy and surface tension.

In order to stably obtain the ink droplets 10 ejected in this manner, it is necessary to vibrate the diaphragm 5 with an appropriate amplitude. The appropriate amplitude depends on the dimensional conditions unique to the ink drop ejecting device, such as the aperture diameter of the orifice 8, the thickness of the ink layer 7, and the vibration diameter of the diaphragm 5, as well as physical conditions such as the viscosity, surface tension, and specific gravity of the ink. It depends, but in any case, at least the following two
One condition must be met.

(i) The amplitude should be large enough to allow the ink droplet 10 to be ejected; (ii) The amplitude should be such that air is not drawn in from the orifice 8 after the ink droplet 10 is ejected.

However, of the above two conditions (i) and (ii), for (i) it is sufficient to increase the amplitude, and for (ii), the amplitude should be decreased by doing the opposite of (i). Since these conditions are contradictory to each other, the amplitude that satisfies both conditions at the same time has been limited to an extremely narrow range. Along with this, the electric signal applied to the piezoelectric vibrator 1, which is the driving source of the diaphragm 5, is also restricted.
Even the droplet diameter control range of the ink droplet 10, which is proportional to the applied voltage, which is a feature of the on-demand diaphragm type, has been limited to a narrow range.

The ink droplet ejecting apparatus of the present invention has been developed in view of this point, and embodiments of the present invention will be described in detail below with reference to FIG. 3 and subsequent figures.

FIG. 3 shows an ink droplet ejecting device according to the present invention. In the same figure, the same parts as in FIG. 4 is a propagation medium, 5 is a diaphragm, 6 is a front plate, 7 is an ink layer, 8 is an orifice, and 9 is a capillary tube.The difference lies in the method of fixing the diaphragm 5. That is, in the conventional device shown in FIG. 1, the diaphragm 5 is arranged so as to close the aperture 3, and the entire contact surface that contacts the inner wall of the ink layer 7 is fixed with an adhesive or the like. However, in the present invention, as shown in FIG. 4, the diaphragm 5 is annularly supported around its periphery by an adhesive 11.

When the diaphragm 5 is supported by its periphery in this manner, when the diaphragm 5 vibrates toward the ink layer 7 as shown by the broken line in FIG. 4, the diameter of the vibration becomes the support diameter of the diaphragm 5. On the other hand, when the diaphragm 5 vibrates toward the pressure chamber 2, the vibration is regulated by the aperture 3 of the pressure chamber 2, as shown by the dashed line in FIG. That is, the vibration diameter of the diaphragm 5 is different between the vibration diameter toward the ink layer 7 side and the vibration diameter toward the pressure chamber 2 side, and the relationship is larger toward the ink layer 7 side.
Therefore, the diaphragm 5 has different diameters of reciprocating vibration during one vibration, and the diameter that contributes to the ejection of the ink droplet 10 is the large diameter, and the diameter after the ejection of the ink droplet 10 is the small diameter, which are contradictory to each other. Conditions (i) and (ii) can be satisfied simultaneously without limiting them to a narrow range.

In the above embodiment, the periphery of the diaphragm 5 is annularly supported by bonding it with the adhesive 11, but other methods may also be used, such as fitting and supporting with an annular cap, or using a laser beam. Possible methods include seam welding the outer periphery by welding or the like. In particular, since the seam welding described above integrally supports the diaphragm 5, the diaphragm 5 does not separate and has a structure that is resistant to changes over time.

As is clear from the above description, the present invention includes supporting a diaphragm around the periphery of the diaphragm, which closes the apertures of the pressure chambers and vibrates in response to pressure changes in the pressure chambers to eject ink droplets. Therefore, since the diameter of vibration in one round trip is made larger on the ink layer side than on the pressure chamber side, the contradictory conditions (i) required for the amplitude of the diaphragm are satisfied. ii) can be satisfied without being limited to an extremely narrow range, and the control range of the droplet diameter of ink droplets can be expanded. Therefore, it is possible to obtain a large number of intermediate tones, and especially when recording a color image using four such ink droplet ejecting devices, it is possible to accurately control the mixing ratio of each color.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional device which is the basis of the present invention, Fig. 2 is an enlarged sectional view of the main part thereof, Fig. 3 is a sectional view of the ink droplet ejecting device of the present invention, and Fig. 4 is an enlarged sectional view of the main part. In the figure, 1 is a piezoelectric vibrator, 2 is a pressure chamber, and 5
7 indicates a diaphragm, 7 indicates an ink layer, and 11 indicates an adhesive.

Claims (1)

[Claims] 1 A pressure change means is associated with a pressure chamber filled with a propagation medium, and the pressure change caused by the pressure change means is concentrated on a small-area diaphragm formed on a part of the side wall of the pressure chamber via the propagation medium. and apply
In an ink droplet ejecting device that ejects ink from an ink layer held on the front side of the diaphragm as ink droplets from an orifice provided at an opposing location,
Ink droplet jetting characterized in that the diaphragm is supported at its periphery, the support diameter is set as a vibration diameter when the diaphragm vibrates toward the ink layer side, and the vibration diameter is made larger than that toward the pressure chamber side. Device.