JP2001212958A - Ink-jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive and highly reliable ink-jet head capable of obtaining a sufficient deflection amount even in the case the pressure area in pressure generating chamber is small. SOLUTION: The ink-jet head comprises a pressure generating chamber 12 for introducing an ink, for ejecting ink droplets from a nozzle opening part 13 by pressuring the INK by deforming the pressure generating chamber 12. The head is provided with a bimetal element 15 including a first metal plate 151 constitutions a part of the pressure generating chamber 12 for deforming the pressure generating chamber 12 and a second metal plate 152 to be attached to the first metal plate and having a thermal expansion ratio higher than that of the first metal plate, a mechanism for providing the electric current to the bimetal element 15 by applying a power source V, and a second metal plate deflection clearance space 17 provided on the second metal plate 152 side of the bimetal element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink-jet head which discharges ink droplets from a nozzle opening by bending a part of a pressure generating chamber communicating with the nozzle opening.

[0002]

2. Description of the Related Art As one mechanism of an ink jet head, there is a piezoelectric vibration type in which a pressure generating chamber containing ink is mechanically deformed to pressurize the ink. In a piezoelectric vibration type ink jet head, an ink pressing mechanism using a piezoelectric vibrator is incorporated in an actuator unit configured by etching a silicon substrate, for example. Further, a nozzle plate is fixed to the actuator unit so that pressurized ink is ejected as ink droplets.

Conventionally, the ink pressurizing mechanism has been constituted by a vibrating plate that flexes a part of a pressure generating chamber of an actuator unit by a piezoelectric film. That is, in the pressure generating chamber, a diaphragm made of zirconium oxide or the like, which is covered with a thin protective film, is disposed on the side facing the nozzle opening. A piezoelectric film containing PZT (lead zirconate titanate) is provided on the diaphragm outside the pressure generating chamber. The piezoelectric film is connected to the upper and lower electrodes, and causes distortion (expansion and contraction displacement) due to an applied electric field. The diaphragm converts this distortion into a deflection displacement. This displacement generates a predetermined pressure in the pressure generating chamber, and causes the ink in the pressure generating chamber to be ejected from the nozzle opening as ink droplets.

[0004]

SUMMARY OF THE INVENTION However, PZT
A piezoelectric vibrator (piezo element) including a piezoelectric film requires a large number of man-hours including production of upper and lower electrodes and a diaphragm, thereby increasing the production cost. In addition, due to the recent miniaturization and high-density arrangement of the nozzle openings, the pressurized area in the pressure generating chamber is reduced, so that a sufficient amount of deflection may not be obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a highly reliable ink jet head which is inexpensive and can obtain a sufficient amount of deflection even if the pressurized area in the pressure generating chamber is small. is there.

[0006]

According to the present invention, there is provided an ink jet head having a pressure generating chamber into which ink enters, wherein the pressure generating chamber is deformed to pressurize the ink to discharge ink droplets from an opening. A bimetal including a first metal plate constituting a part of the pressure generating chamber provided to deform the chamber and a second metal plate bonded to the first metal plate and having a higher coefficient of thermal expansion than the first metal plate An element, a mechanism for applying a current to the bimetal element, and a second metal plate deflection allowance space provided on the second metal plate side of the bimetal element.

According to the ink jet head of the present invention,
A current flows by applying a predetermined voltage to the bimetal element, and the second metal plate bends due to a difference in coefficient of thermal expansion during electrothermal conversion. Thereby, the volume of the pressure generating chamber increases and ink is introduced. If the current is stopped and heat is dissipated, the deformation of the bimetal element is restored. Thereby, the ink in the pressure generating chamber is pressurized, and the ink droplet is ejected to the outside.

[0008]

FIG. 1 is a sectional view showing a main part of an ink jet head according to an embodiment of the present invention. A pressure generating chamber 12 for storing the ink INK is formed in the ink flow path forming substrate 11. The pressure generating chamber 12 is provided with the ink IN
It is connected to the nozzle opening 13 from which K is discharged. The nozzle opening 13 is provided on a nozzle plate 14 that normally closes the pressure generating chamber.

A bimetal element 15 is arranged to face the nozzle opening 13 and forms a part of the pressure generating chamber 12. The bimetal element 15 is provided with a first metal plate 151 on the pressure generating chamber side via a thin protective elastic film 16. The first metal plate 151 includes the first metal plate 151.
A second metal plate 152 having a higher coefficient of thermal expansion is attached. That is, the first metal plate 151 has a low coefficient of thermal expansion, and the second metal plate 152 serves as the bimetal element 15 having a high coefficient of thermal expansion.

In the bimetal element 15, the second metal plate 152 expands more than the first metal plate 151 when heat is transmitted, so that the second metal plate 152 bends outside the pressure generating chamber 12. For this reason, a flexible room 17 is formed outside the pressure generating chamber 12. The formation portion of the deflection allowance space 17 is composed of, for example, a cap member 18 fixed on the ink flow path formation substrate 11. When a current is applied to the bimetal element 15 by applying the power supply V, the pressure generation chamber 12
To transform.

FIGS. 2A and 2B are cross-sectional views sequentially showing the ink discharging operation of the ink jet head of FIG. The same parts as those in FIG. 1 are described with the same reference numerals. First, as shown in FIG.
5, the second metal plate 152 having a higher coefficient of thermal expansion than the first metal plate 151 during electrothermal conversion
2 flexes (curves) outside. Thereby, the entire bimetal element 15 is deformed so as to increase the volume of the pressure generating chamber 12. Accordingly, the ink INK is further introduced into the pressure generating chamber 12 by that amount (arrow A).

Next, as shown in FIG. 2B, the current to the bimetal element 15 is cut off. Thereby, the bimetal element 15 returns to its original shape with heat radiation. As a result, the ink INK in the pressure generating chamber 12 is pressurized and ink droplets are ejected to the outside through the nozzle openings 13.

According to the above configuration, the ink INK in the pressure generating chamber 12 can be pressurized by the inexpensive bimetal element 15, and a sufficient amount of deflection can be obtained even if the pressure area in the pressure generating chamber 12 is small.

FIG. 3 is a sectional view showing a more specific structure of an ink jet head using the present invention. In an ink flow path forming substrate 31 formed by etching a silicon single crystal substrate, a first metal plate 351 is provided on one wall surface of a pressure generating chamber 32 via a thin protective elastic film 36. The first metal plate 351 is provided such that a second metal plate 352 having a higher coefficient of thermal expansion than the first metal plate 351 is attached. The first metal plate 351 is, for example, an alloy containing Ni and Fe (such as Invar), and the second metal plate 352 is, for example, an alloy containing Cu and Sn.

The other wall surface of the pressure generating chamber 32 facing the bimetal element 35 is, for example, a thin plate made of stainless steel, and serves as a nozzle plate 34 provided with a nozzle opening 33. The ink supply path 41 is also provided in the counter substrate 42 and extends on the opposite side of the nozzle plate 34. A cap member 38 is fixed to a region surrounded by the counter substrate 42. Each terminal of the bimetal element 35 is formed integrally with the cap member 38 and is connected to a flexible cable 43 from which an electrode is drawn through a via hole VIA.

The bimetal element 35 is given a current through the flexible cable 43 and is deformed during electrothermal conversion. Flexural space 37 provided in cap member 38
Forms a space not to hinder the bending (curving) of the second metal plate 352 of the bimetal element 35. The ink inlets 44 are provided on both sides of the flexible cable 43,
They are provided in the opposite substrate 42 so as not to interfere with each other. The ink supply path 41 connects the ink introduction port 44 and the pressure generating chamber 32, and although not shown, an ink reservoir may be provided in the middle of the flow path.

Next, with reference to FIG. 3, an operation when printing is performed by the ink jet head will be described.
Ink is introduced from the ink introduction port 44 and the ink supply path 4
The pressure IN of the pressure generating chamber 32 is filled with the ink INK. An electric field is applied between the terminals of the bimetal element 35 via the flexible cable 43 under the control of a driver IC (not shown). Thereby, the bimetal element 35 is bent in the direction of the arrow B with the electrothermal conversion. Therefore, the pressure generating chamber 32
And the ink INK is further introduced into the pressure generating chamber 32 by that amount.

Next, under the control of a driver IC (not shown), the current through the flexible cable 43 is cut off, and the bimetal element 35 is quickly radiated. Thereby, the deformation of the bimetal element 35 is returned to the original state as shown in the figure. As a result, the volume of the pressure generating chamber 32 decreases (returns to the original state), so that the ink INK is pressurized, and the ink droplet is discharged to the outside through the nozzle opening 33. Printing is performed with the ink thus ejected.

According to the above-described embodiment, the pressure generating chamber can be deformed by the bending of the bimetal element accompanying the electrothermal conversion. Thereby, the intake of the ink into the pressure generating chamber is increased, and the ink is ejected from the nozzle opening due to the recoil of the bimetal element radiating heat and returning to the original state. Bimetal elements can be configured at a lower cost than piezoelectric films. In addition, a sufficient amount of deflection can be expected even if the pressurized area in the pressure generating chamber is reduced due to the high density of the nozzle opening arrangement.

[0020]

As described above, according to the ink jet head of the present invention, an ink pressurizing mode in the pressure generating chamber is realized by a bimetal element utilizing electrothermal conversion. Thus, it is possible to provide a highly reliable ink jet head which can be configured at a low cost and can obtain a sufficient amount of deflection even if the pressure area in the pressure generating chamber is small.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a main part of an inkjet head according to an embodiment of the present invention.

FIGS. 2A and 2B are cross-sectional views sequentially showing the ink ejection operation of the inkjet head of FIG. 1;

FIG. 3 is a cross-sectional view showing a more specific configuration of an ink jet head using the present invention.

[Explanation of symbols]

 11, 31 ... ink flow path forming substrate 12, 32 ... pressure generating chamber 13, 33 ... nozzle opening 14, 34 ... nozzle plate 15, 35 ... bimetal element 151, 351 ... first metal plate 152, 352 ... second metal Plates 16, 36 ... Elastic films 17, 37 ... Room for flexure 18, 38 ... Cap member 41 ... Ink supply path 42 ... Counter substrate 43 ... Flexible cable 44 ... Ink inlet

Claims (1)

[Claims] 1. An ink jet head comprising: a pressure generating chamber into which ink enters; and an ink jet head configured to deform the pressure generating chamber and pressurize the ink to discharge ink droplets from an opening. A bimetal element including a first metal plate constituting a part of the pressure generating chamber provided, a second metal plate attached to the first metal plate and having a higher coefficient of thermal expansion than the first metal plate; An ink jet head, comprising: a mechanism for applying a current to the second metal plate; and a second metal plate deflection allowance space provided on the second metal plate side of the bimetal element.