JP2002113875A - Ink jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a nozzle plate from being deformed and correctly discharge ink drops from nozzles. SOLUTION: A recess 3 having a larger diameter than a diameter of a nozzle orifice is formed by electrocasting to a rear face of the nozzle plate 1 having a thickness of a level whereby the nozzle plate is prevented from being deformed by pressures and vibrations. Ink drops are efficiently discharged by acting the pressure only to the required nozzle 2 with the utilization of the formed recess pressed open to an arc-shaped section.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head for forming a dot image by causing ink in an ink chamber to fly as droplets on recording paper by the kinetic energy of electromechanical conversion means. It relates to the shape of the nozzle.

[0002]

2. Description of the Related Art In general, an ink jet recording head that forms characters and figures by a collection of dots by causing ink to fly as droplets on recording paper is provided with a thin nozzle plate so as to cover a pressure chamber. The required number of nozzles are formed.

[0003] The use of such a thin nozzle plate facilitates the formation of the nozzle and suppresses the axial length of the nozzle with respect to the diameter of the orifice within a predetermined range, thereby improving the ink ejection efficiency. The idea is to make it even higher.

However, when the diameter of the orifice is made smaller in order to fly smaller ink droplets in order to further improve the printing quality, it is necessary to make the nozzle plate thinner, and the rigidity of the nozzle plate becomes higher. Comes into question.

[0005] This is a problem particularly in the case where a piezoelectric vibrator is used as a means for ejecting ink droplets.
When a repetitive load of about 5 kg / cm @ 2 is applied, the nozzle plate is easily deformed and the flying direction of the ink droplet is disturbed.

In order to solve such a problem, as described in US Pat. No. 4,282,533, a nozzle plate having a sufficient thickness to withstand pressure and vibration is known.
A groove is provided on the back surface of the nozzle, and a required number of nozzles are arranged at the bottom of the groove. However, in such a configuration, one selected piezoelectric element is provided. Even when the vibrator is operated, the pressure acts as a stress concentration in the axial direction of the groove, resulting in a large deflection of the nozzle plate, or the applied pressure propagates along the groove, resulting in crosstalk. Another problem arises that may cause

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem.
An object of the present invention is to provide an ink jet recording head provided with a new nozzle plate capable of efficiently and accurately flying an ink liquid without being deformed by a pressurizing action at the time of discharging an ink droplet.

[0008]

That is, according to the present invention, as an ink jet recording head for achieving the above object, ink in an ink pressurizing chamber is moved from a nozzle onto a recording medium by a pressurizing action of electromechanical conversion means. An ink jet recording head of a type that discharges, a concave portion having a diameter larger than the nozzle orifice diameter is formed on the back surface of a nozzle plate having a thickness that is not deformed by pressure and vibration.
It is formed by electroforming for each nozzle.

[0009]

1 to 3 show an embodiment of the present invention. The nozzle plate denoted by reference numeral 1 in the figure is formed of a nickel plate material having a sufficient plate thickness T capable of withstanding pressure and vibration.

The plate thickness T of the nozzle plate 1 is represented by an ideal axial length with respect to the diameter d of the nozzle orifice t1, t1.
When the depth of the concave portion 3 is t2, it is set so that T = t1 + t2. For example, t1 = 30 .mu.m and t2 = 50 .mu.m.
m, T = 80 μm.

A large-diameter concave portion 3 having a depth t2 and an inner diameter D is formed on the back surface of the nozzle plate 1 by electroforming, and the inner bottom surface 4 has a ring-shaped large width. A flat surface having W is formed, and a funnel-shaped nozzle 2 having an orifice diameter d of, for example, 30 μm is formed coaxially with the concave portion 3 at the center thereof by electroforming.

As shown in FIGS. 2 and 3, a low partition wall 5 for partitioning the nozzles 2 and 2 is integrally formed on the back surface of the nozzle plate 1 so as to project therefrom. An ink pressurizing chamber 7 is formed inside the pressurizing plate 5 and a pressurizing plate 6 placed on the top thereof.

The above-mentioned partition 5 is provided with individual ink pressurizing chambers 7.
In order to prevent the pressure acting on the nozzles from reaching the other adjacent ink pressurizing chambers 7, as described above, these nozzles 2 are formed inside the recesses 3 via the recesses 3. In relation to these, it is sufficient that these partition walls 5 only imperfectly define the nozzle 2 part, and by forming gaps at both ends thereof, they can be used as ink flow paths 8.

In FIG. 1, reference numeral 9 denotes a support plate for pressing the other surface of the pressure plate 6, reference numeral 10 denotes an ink supply path communicating with an ink tank (not shown), reference numeral 11 denotes a piezoelectric vibrator,
Reference numeral 2 denotes each pressure plate.

In the ink jet recording head constructed as described above, the plate thickness T of the nozzle plate 1 can be made sufficiently large, and the axial length of the nozzle 2 is set to an ideal size by providing the concave portion 3 on the back surface. Because you can
Ink droplets can be stably ejected onto recording paper without deformation due to pressure or the like.

In addition, since the concave portion 3 reaches a flat portion having a large width through a curved surface which is smoothly expanded toward the pressurizing chamber 7 by electroforming, the concave portion 3 communicates with the nozzle 2. 7 has an effect of safely ejecting ink droplets from the nozzles 2 equally to the instantaneous pressure applied to the nozzles 7.

Moreover, the recess 3 is formed by electroforming in the pressure chamber 7.
It is formed as a curved surface that smoothly expands to the side and reaches a flat portion having a large width W through the concave portion 3 and communicates with the nozzle 2, so that the instantaneous pressure applied to the ink is equalized here. An effect of stably ejecting ink droplets from the nozzle 2 is provided.

FIG. 4 shows a second embodiment of the present invention. In this embodiment, two large and middle recesses 23A and 23B are formed on the back surface of the nozzle plate 21 so as to coincide with the axis of the nozzle 22.

These recesses 23A and 23B are formed by applying two electroforming processes from the back surface. Therefore, the inner peripheral surfaces of these recesses are stepped and open in an arc-shaped cross section. The arc-shaped inner peripheral surface simultaneously acts to effectively prevent bubbles in the ink from being caught and prevent defective ejection of ink droplets.

The recess 23 may be formed in one step, but if it is formed in two steps, the thickness of the remaining plate is more accurately controlled to a dimension corresponding to the axial length of the nozzle 22 in the process of forming the recess 23B in the second step. In addition, in this embodiment, in particular, by applying an ink-repellent fluorine resin co-fold plating to the back surface of the nozzle 22, wetting of the peripheral surface of the opening of the nozzle 22 can be eliminated.

[0021]

As described above, according to the present invention, a recess having a diameter much larger than the diameter of the orifice of the nozzle is formed on the back surface of the nozzle plate having a sufficient thickness by electroforming. Not only can the part be formed as a concave part which is greatly expanded in an arc shape on the side of the pressurizing chamber, but particularly in the case of an ink jet recording head in which a nozzle is arranged opposite to the electromechanical conversion means, the necessary concave part is provided. The ink droplet can be efficiently ejected from the nozzle at the center thereof while suppressing the occurrence of crosstalk.

[Brief description of the drawings]

FIG. 1 is a sectional view of a nozzle plate according to an embodiment of the present invention.

FIG. 2 is a side view showing a cross section of a part of an ink jet recording head provided with the nozzle plate.

FIG. 3 is a front view showing a part of the device in a cross section.

FIG. 4 is a sectional view of a nozzle plate according to a second embodiment of the present invention.

[Explanation of symbols]

 1, 21, nozzle plate 2, 22, nozzle 3, 23, concave portion 5, partition wall 7, ink pressurizing chamber 11, piezoelectric vibrator

Claims (2)

[Claims] An ink jet recording head of a type in which ink in an ink pressurizing chamber is ejected from a nozzle onto a recording medium by receiving a pressurizing action of an electromechanical converting means, and is of such a degree that it is not deformed by pressure and vibration. An ink jet recording head, wherein a concave portion having a diameter larger than the orifice diameter of a nozzle is formed by electroforming for each nozzle on the back surface of a thick nozzle plate. 2. The ink jet recording head according to claim 1, wherein said recess is formed in two steps by electroforming.