JP2001018384A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive ink jet head having ink grooves defined by barrier walls made of a piezoelectric material in which the driving voltage being applied to the barrier wall is lowered. SOLUTION: A plurality of grooves 21, 22 separated by barrier walls 24 of a polarized piezoelectric material are made in an actuators substrate and electrodes 26a, 26b generation a field orthogonal to the direction of polarization are formed on the barrier walls 24. A cover plate 30 is bonded to the barrier walls 24 while covering the open face of the grooves 21, 22. The cover plate 30 is composed of an inexpensive material having a higher Young's modulus than the piezoelectric material composing the barrier walls 24, e.g. forsterite (2MgO.SiO2), beryllia (BeO), magnesia (MgO), alumina (Al2O3) or zirconia (ZrO2). Deformation of the cover plate 30 is reduced when the barrier walls 24 is deformed by shearing and the barrier walls 24 are deformed by an expended amount with a low voltage.

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 for recording an image by discharging ink droplets on a recording medium.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 63-247051 and Japanese Patent Application Laid-Open No.
There are those described in JP-A-52750 and JP-A-2-150355. This is generally a configuration in which a plurality of grooves are formed in a piezoelectric ceramic plate, and a cover plate is adhered so as to cover the upper surface of the grooves. An electric field is generated in an orthogonal direction to shear the partition walls, apply pressure to the ink in the grooves, and eject the ink from the nozzle holes.

[0003]

In this type of construction, the partition wall is deformed in the width direction of the groove so as to increase or decrease the volume of the groove, so that a reaction force acts on the cover plate. However, when the cover plate is deformed as a result, the amount of deformation of the partition wall is reduced, and a sufficient pressure for ejecting ink cannot be obtained.

For this reason, conventionally, it has been practiced to increase the drive voltage so as to sufficiently deform the partition walls, or to form the cover plate from a piezoelectric ceramic plate or a material having a rigidity equivalent thereto. When the driving voltage is increased, not only power consumption is increased, but also components related to the related circuits must have high withstand voltage performance. Also, the use of a piezoceramic plate or equivalent material for the cover plate is very expensive.

SUMMARY OF THE INVENTION An object of the present invention is to solve these drawbacks and to provide an inexpensive ink jet head having a low driving voltage.

[0006]

In order to achieve the above object, an ink jet head of the present invention has a plurality of grooves at least partially separated by a partition made of a piezoelectric material which is polarized. An actuator substrate having a longitudinal side surface of the groove opened, and a partition wall formed on the partition wall in a plane parallel to the polarization direction, and orthogonal to the partition wall direction so as to deform the partition wall in the width direction of the groove. An electrode for generating an electric field, and a cover plate covering the open surface of the groove and fixed to the partition, wherein the cover plate is made of a material having a higher Young's modulus than the partition.

Thus, when a voltage is applied to the electrodes of the partition, an electric field is generated in the partition perpendicular to the direction of polarization, the partition is deformed in the width direction of the groove, the volume of the groove is increased or decreased, and ink droplets are ejected. . When the partition wall is deformed in the width direction of the groove, a reaction force acts on the cover plate, but by forming the cover plate with a material having a higher Young's modulus than the piezoelectric material forming the partition wall, the cover plate is deformed by the reaction. The amount is small, and the desired ink ejection pressure can be reliably obtained. In addition, in order to obtain the desired ink ejection pressure, a lower drive voltage is required as compared with the conventional one, and the configuration related to the electric can be configured at low cost.

The cover plate preferably uses forsterite (2MgO.SiO ₂ ), beryllia (BeO), magnesia (MgO), alumina (Al ₂ O ₃ ) or zirconia (ZrO ₂ ). These are piezoelectric materials constituting the partition walls, for example, lead zirconate titanate (PZT),
Since the Young's modulus is higher and inexpensive than lead titanate (PT) or the like, an inkjet head can be provided at low cost. Further, since forsterite and alumina are lightweight, they can contribute to the weight reduction of the ink jet head.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail.

The ink jet head according to the present embodiment is
As shown in FIG. 1, an actuator substrate 10 having a plurality of ink grooves 21 and dummy grooves 22 on both sides thereof, a cover plate 30 covering the upper surface of each groove, a manifold 31 for distributing ink to the ink grooves 21, A nozzle plate 32 having a nozzle hole 33 corresponding to the groove 21.

The actuator substrate 10 is made of two rigid lead zirconate titanate (PZ) adhered to each other.
T) and substrates 11 and 12 made of a piezoelectric ceramic material such as lead titanate (PT). The two substrates are polarized in opposite directions in the thickness direction. In addition,
It is also possible to configure only one of the substrates 11 and 12 with a piezoelectric material. A large number of parallel grooves serving as the ink grooves 21 and the dummy grooves 22 are cut in the thickness directions of the base materials 11 and 12 by a diamond blade or the like. As a result, the partition wall 24 that separates the ink groove 21 and the dummy groove 22 has a configuration in which a piezoelectric material having an opposite polarization direction is stacked in the height direction.

As shown in FIG. 1, the ink groove 21 is formed by opening the front and rear ends in the longitudinal direction (that is, the ink ejection direction) to the front and rear ends of the actuator substrate, and the dummy groove 22 is opened to the front end face 10a. Are formed leaving the rising portions 23 so as to close at the rear end face 10b. As shown in FIG. 3, a first electrode 26 a is formed on the side surface of the partition wall 24 in the ink groove 21, and a second electrode 26 b is formed on the side surface of the partition wall 24 in the dummy groove 22. On the upper surface 10c of the actuator substrate 10, a cover plate 30 that covers an open surface of the ink groove 21 and the dummy groove 22 along the longitudinal direction is fixed by bonding.

A nozzle plate 32 having a nozzle hole 33 corresponding to the ink groove 21 is bonded and fixed to a front end face 10a of the actuator substrate 10 and a front end face 30a of the cover plate 30, and a manifold 31 is provided to the rear end face thereof. Is fixedly adhered.

The ink introduced from the ink supply source into the manifold 31 is supplied to the ink groove 21 and is not supplied to the dummy groove 22 by the rising portion 23. The first electrode 26a in each ink groove is connected to a common potential, for example, the ground, and the second electrodes 26b, 26b on the dummy groove 22 side of the partition walls 24, 24 sandwiching the ink groove 21 from which ink is to be ejected. When a voltage is applied, the first and second
An electric field E is generated between the electrodes 26a and 26b in a direction perpendicular to the polarization direction P of the piezoelectric material. As shown in FIG. 3, the piezoelectric materials at the upper and lower portions of the partition wall 24 are sheared in the opposite directions, that is, deformed into diamond shapes. In addition, the volume in the ink groove 21 is enlarged.
When the application of the voltage is stopped, pressure is applied to the ink in the ink groove when the partition wall 24 returns, and the ink is ejected from the nozzle holes 33.

When the partition walls 24 are deformed as described above, the joining portions of the piezoelectric material at the upper and lower portions of the partition walls 24 move outward with respect to the ink grooves 21 (arrow F1). At the upper end, a force F2 heading toward the ink groove 21 is likely to spread. At this time, if the rigidity of the cover plate 30 is low, the cover plate 30 will be buckled and deformed, and the amount of deformation of the partition wall 24 will be reduced, so that sufficient pressure for ejecting ink cannot be obtained.

In the present embodiment, the cover plate 30 is
4, a material having a higher Young's modulus than the piezoelectric material
Stellite (2MgO ・ SiO_Two), Beryllia (Be
O), magnesia (MgO), alumina (Al_TwoO_Three)
Or zirconia (ZrO_Two). Forstera
The Young's modulus of the kit is 1.5 × 10⁶kg / cm^Two, Berylia
Has a Young's modulus of 3.5 × 10⁶kg / cm^Two, Magnesia
Young's modulus is 3.15 × 10 ⁶kg / cm^Two, Alumina ya
3.85 × 10⁶kg / cm^Two, Zirconia ya
Ing rate is 1.61 × 10⁶kg / cm^TwoWhereas
Lead zirconate titanate (PZ) constituting the partition wall 24
T) and lead titanate (PT) have a Young's modulus of about 0.1.
0546 × 10⁶kg / cm^TwoIt is. This allows the hippo
-The deformation of the plate 30 is almost eliminated, and the partition 24 is
Can be sufficiently deformed.

As a result of the experiment, the partition wall 24 and the cover plate 30 were formed with lead zirconate titanate (PZT) or lead titanate (PZT).
T) and the like, a voltage of 16 V was required to obtain the expected volume change of the ink groove 21, but when the cover plate 30 was changed to forsterite as described above, the same volume was obtained. It has been found that 14.7 V is sufficient to obtain the change. It was also confirmed that the thickness of the cover plate 30 should be substantially equal to or greater than the width (about 50 μm) of the partition wall 24.

Also, lead zirconate titanate (PZT)
And lead titanate (PT) have a specific gravity of 8, while forsterite has a specific gravity of 2.8, which is also effective in reducing the weight of the ink jet head. Alumina is also lightweight. Moreover, the above materials such as forsterite are less expensive than lead zirconate titanate (PZT) and lead titanate (PT).

Although the partition 24 is made of two piezoelectric materials, only the upper half or the lower half may be made of a piezoelectric material.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an inkjet head to which the present invention is applied.

FIG. 2 is a partial horizontal sectional view of the inkjet head.

FIG. 3 is an enlarged sectional view of the inkjet head cut at right angles to a groove.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Actuator board 21 and 22 Ink groove, dummy groove 30 Cover plate 32 Nozzle plate

Claims (2)

[Claims] 1. An actuator substrate having a plurality of grooves separated by a partition made of a piezoelectric material at least partially polarized, and having an open longitudinal side surface of the groove, wherein the partition is parallel to the polarization direction. An electrode that generates an electric field perpendicular to the direction of polarization in the partition so as to deform the partition in the width direction of the groove; and a cover plate fixed to the partition covering the open surface of the groove. Wherein the cover plate is made of a material having a higher Young's modulus than the partition walls. 2. The ink jet head according to claim 1, wherein the cover plate is made of forsterite, beryllia, magnesia, alumina, or zirconia.