JPH0353886Y2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Industrial Application The present invention relates to an inkjet head that ejects minute ink droplets.

(b) Prior art An inkjet printer equipped with an inkjet head that ejects minute ink droplets is a non-impact type printer that produces low noise, can use plain paper as a recording medium, and can easily print in color. It has excellent features such as being able to be realized.

FIG. 1 shows an ink jet head disclosed in Japanese Patent Application Laid-Open No. 57-8163, etc., in which numeral 1 denotes a piezoelectric vibrator as a pressure changing means that bends and vibrates in response to an image signal;
2 is a horn-shaped pressure chamber in which the piezoelectric vibrator 1 is disposed at the opening on the long diameter side; 3 is a thin plate-shaped pressure chamber provided in the short diameter side of the pressure chamber 2, which vibrates in response to pressure changes caused by the piezoelectric vibrator 1; A diaphragm, 4 is an ink layer held on the front side of the diaphragm 3, 5 is a front plate facing the diaphragm 3 with the ink layer 4 in between, and 6 is an ink layer held on the front side of the diaphragm 3 on the front plate 5. This is a micro-diameter orifice drilled in a location opposite the center of vibration.

In such a configuration, when an image signal is applied to the piezoelectric vibrating body 1, the piezoelectric vibrating body 1 vibrates in a curved manner in its thickness direction to pressurize the pressure chamber 2. This pressurization (pressure change) propagates into the horn-shaped pressure chamber 2 and causes the small-diameter diaphragm 3 to suddenly and greatly bend. Therefore,
The ink in the ink layer 4 located on the front side of the diaphragm 3 is extruded as an ink column 7 from an orifice 6 bored at the opposite location, and is then affected by the reaction and surface tension caused by the vibration of the diaphragm 3 in the opposite direction. Therefore, the ink drops become minute ink droplets 7', 7' and fly.

However, as the thin diaphragm 3 is attached to the head body 8, which forms the pressure chamber 2 together with the piezoelectric vibrator 1, via the adhesive 9, as shown in an enlarged view in FIG. 9'... seeps out from the interface between the head body 8 and the diaphragm 3 in the outer and inner periphery directions, and in particular, the excess adhesive 9' that seeps out on the inner periphery also damages the vibrating part 3a of the diaphragm 3. Outer circumference 3
Attempts to bond from b to 3a reduce the vibration diameter d of the vibrating portion 3a, resulting in variations between installations in the vibration characteristics that contribute to the ejection of ink droplets. That is, the amount of excess adhesive 9' that seeps out differs from one ink jet head to another, leading to variations in vibration characteristics, and such vibrations cause the size of ink droplets ejected from the orifice 6 to become non-uniform. It had drawbacks.

(c) Purpose of the invention The present invention was made with the aim of preventing such variations in vibration characteristics and ejecting ink droplets of uniform particle size.

(d) Structure of the invention The inkjet head of the invention includes a head body having a pressure chamber associated with a pressure change means, and a central vibrating part bonded to the head body so as to vibrate in response to intensive pressure changes in the pressure chamber. The diaphragm has a diaphragm bonded to the diaphragm through an agent, an ink layer held on the front surface of the diaphragm, and an orifice placed at a position facing the diaphragm across the ink layer. The vibrating portion is configured to be offset toward the orifice side from the adhesive surface of the base portion that is adhered to the head body.

(e) Embodiment FIG. 3 shows an embodiment of the present invention, which differs from the conventional one in the bonding structure of the diaphragm 3 to the head body 8. That is, the vibrating portion 3a is located at the center of the diaphragm 3 and is biased toward the orifice 6 from the adhesive surface of the base portion 3c that is adhered to the head body 8 so that the ink droplets 7' are ejected from the orifice 6. Therefore, in the diaphragm 3, the central vibrating portion 3a is biased toward the orifice 6, thereby moving away from the adhesive surface and causing the head body 8 and the base 3 to deviate.
Even if excess adhesive 9' seeps out from the interface with the adhesive surface of c, it hardly adheres to the central vibrating section 3a.

For example, when the diaphragm 3 has a concave shape in which the central vibrating part 3a is concave with reference to the adhesive surface of the base 3c as in this embodiment, a thick diaphragm material is prepared and the central part is removed or etched. Etching is preferred from the viewpoint of processing accuracy, since it can be easily formed by removing. Alternatively, a thin diaphragm material may be prepared and a thick base 3c may be grown using electrohoming technology.

More specifically, we prepared a disk-shaped diaphragm material made of stainless steel with a diameter (D) of 3 mm and a thickness (t) of about 150 microns, and removed the central part from one side using photo etching to remove the deviation from the bonding surface. A depression with a depth (t ₁ ) of 100 microns corresponding to the length is formed.
The vibrating portion 3a formed at this time had a vibration diameter (d) of 1 mm and a thickness (t ₂ ) of 50 microns.

Note that it is preferable that the vibration diameter of the piezoelectric vibrating body 1 for the vibration diameter (d) is about 5 mm.

FIG. 4 shows another embodiment of the present invention, which differs from the previous embodiment in the shape of the diaphragm 3. That is, the diaphragm 3 is made of a thin disc-shaped material by pressing or the like so that only the central portion thereof protrudes, thereby biasing the oscillating portion 3a toward the orifice 6 with respect to the adhesive surface of the base 3c'.

(f) Effects of the invention As is clear from the above explanation, the vibration part of the diaphragm whose base is bonded to the head body via an adhesive is biased toward the orifice side from the adhesive surface of the base. Even if the adhesive seeps out from the interface, it hardly adheres to the biased vibrating part, and therefore it does not cause variations between devices in the vibration characteristics that contribute to the ejection of ink droplets. Ejection of ink droplets with uniform particle size can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a conventional ink jet head, FIG. 2 is an enlarged sectional view of the main part thereof, FIG. 3 is an enlarged sectional view of the main part of an embodiment of the ink jet head of the present invention, and FIG. 4 is an enlarged sectional view of the main part of the ink jet head of the present invention. FIG. 7 shows enlarged sectional views of main parts of other embodiments. DESCRIPTION OF SYMBOLS 1... Piezoelectric vibrating body, 2... Pressure chamber, 3... Vibration plate, 3a... Vibrating part, 3c... Base, 4... Ink layer, 6... Orifice, 8... Head body,
9...Adhesive.

Claims (1)

[Scope of utility model registration request] a head body having a pressure chamber associated with a pressure change means; a diaphragm bonded to the head body via an adhesive so that a central vibrating section vibrates by intensively receiving pressure changes in the pressure chamber; The vibrating portion of the diaphragm includes an ink layer held on the front surface of the diaphragm, and an orifice placed opposite the diaphragm across the ink layer. An inkjet head characterized by being biased more toward the orifice side.