JPH03258550A - Ink jet recording head - Google Patents

Abstract

PURPOSE:To avoid an unnecessary deformation of a vibration plate and enhance energy conversion efficiency by providing a piezoelectric actuator having the vibration plate joined to a cover block and a plurality of joint faces, all of which are pressed simultaneously. CONSTITUTION:Signal voltage is applied from a driving circuit to signal electrodes 25a and 25b and, due to the resulting vertical piezoelectric effect, each of the projections 21a and 21b of a piezoelectric actuator 21 is displaced in the direction of the arrow, whereby the corresponding positions of a vibration plate 22 are forced up. Because of this, the volume of an ink chamber 28 corresponding to the upwardly displaced position is reduced and, with the resulting pressure, ink in the ink chamber 28 is pressed and injected through a nozzle against paper for printing thereon. Since, in this way, the projections 21a and 21b are equally polarized upon the signal voltage application, their displacement length becomes equal. Therefore, the vibration plate 22 is free from a wavy form and kept flat and smooth and its unnecessary deformation is avoidable.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an inkjet recording head.

[Prior Art] Printers are often used as output devices for electronic devices such as word processors and personal computers. One of the heads of this printer is an inkjet recording head.

FIG. 4 shows an exploded perspective view of a conventional inkjet recording head of this type.

In the figure, a comb-shaped piezoelectric actuator 12 is provided on a substrate 11. A common electrode 13 is provided on the upper surface of the portion corresponding to the teeth of the piezoelectric actuator 12, and although a portion is hidden in the figure, a signal electrode 13 is provided on the lower surface of the common electrode 13.
4 is provided. Each electrode 13 and 14 is connected to the drive circuit 1
5.

A cover block 17 is joined onto the piezoelectric actuator 12 with a diaphragm 16 interposed therebetween. This cover block 1
7 has an ink chamber 18 and a nozzle 19 integrally formed between it and the diaphragm I6.

A voltage is applied to one of the signal electrodes 13 via the drive circuit 15 from an external control circuit (not shown).

Therefore, the teeth 12a of the corresponding piezoelectric actuator 12
is displaced by the piezoelectric effect, and the corresponding portion of the diaphragm 16 is pushed up. As a result, the volume of the ink chamber I8 contracts, ink is ejected from the nozzle 19, and printing is performed on paper or the like.

[Problems to be Solved by the Invention] In the conventional inkjet recording head described above, the teeth 12
The structure is such that a signal voltage is applied to a portion a, and only that portion is polarized. For this reason, the teeth 12b do not deform, but the teeth 12a extend upward (FIG. 5), and the diaphragm 16 moves upward as shown in the sectional view taken along line A--A in FIG.
As shown in the figure, it is deformed into a wavy shape.

Furthermore, such deformation of the diaphragm 16 requires extra injection energy. That is, since a pressing force due to deformation is constantly acting on the tooth 12a from the diaphragm 16, the amount of deformation response of the tooth 12a to the signal voltage is smaller than when no load is applied, and the amount of change in the volume of the ink chamber 18 is small. Become. Therefore, higher electrical energy must be applied to the ink in order to obtain extra pressurizing force, that is, ejection energy.

Therefore, an object of the present invention is to provide an inkjet recording head that can avoid such unnecessary deformation of the diaphragm and can improve energy conversion efficiency.

[Means for Solving the Problems] According to the present invention, the above-mentioned object includes: a cover block forming an ink chamber; a diaphragm joined to the cover block;
This is achieved by including a diaphragm and a piezoelectric actuator that has a plurality of bonding surfaces and presses all of the plurality of bonding surfaces simultaneously.

[Operation] A signal voltage is applied to the electrodes of all the convex portions of the piezoelectric actuator. As a result, the piezoelectric bodies of all the convex portions are simultaneously displaced in the vertical direction, that is, in the direction of pushing the diaphragm, due to the piezoelectric effect.

This presses the diaphragm, reducing the volume of the ink chamber, increasing the pressure, and ink is ejected from the nozzle to print on paper or the like.

[Example 7] The inkjet recording head according to the present invention will be explained in detail with reference to Examples below.

FIG. 2 is a perspective view of a recording head for an inkjet printer as an embodiment of the present invention.

As shown in the figure, a diaphragm 2 is attached to a piezoelectric actuator 21.
2 are joined together, and a cover block 24 having a plurality of nozzles 23 is joined to this diaphragm 22, thereby constructing an inkjet recording head.

FIG. 1 is a partial sectional view taken along the line A--A in FIG. 2.

In the figure, a convex portion 21a of a piezoelectric actuator 21 is provided with a signal electrode 25a and a common electrode 26a.

Similarly, the convex portion 21b also has a signal electrode 25b and a common electrode 26b.
is provided.

The signal electrode 25a and the signal electrode 25b are commonly connected to each other and connected to a drive circuit (not shown). The common electrode 26a and the common electrode 26b are also commonly connected to each other and to a drive circuit.

That is, each convex portion 21a and 21b of the piezoelectric actuator 21
are connected in parallel.

A diaphragm 22 is bonded onto each convex portion 21a and 21b of the piezoelectric actuator 21.

A cover block 24 in which a plurality of recesses or grooves are formed is bonded onto the diaphragm 22 . The convex portion 27 of the cover block 24 is the convex portion 21b of the piezoelectric actuator 21.
are joined to face each other.

The piezoelectric actuator 21 has a plurality of recesses, that is, a plurality of grooves formed on one side thereof. These grooves are processed using, for example, a dicing saw or a laser, but pressure such as pressing or injection molding may also be applied before firing the piezoelectric body.

Note that PZT (lead zirconium titanate) is preferably used as the material of the piezoelectric body of the piezoelectric actuator 21.

Furthermore, the convex portions 21a and 21b of the piezoelectric actuator 21
is shown as a single layer structure in the figure, but may have a multilayer structure.

The electrodes 25a, 25b, 26a and 26b are formed by electroless plating the piezoelectric actuator 21, but may also be formed by photoetching.

Furthermore, the signal electrodes 25a and 25b are connected to the piezoelectric actuator 2.
It may be provided on the surface of 1 (lower side in the figure). However, the displacement directions of the convex portions 21a and 21b of the piezoelectric actuator 21 are assumed to press the diaphragm 22 in the same direction (upward in the figure).

The cover block 24 is integrally formed with a plurality of grooves and a diaphragm 22, and a plurality of ink chambers 28 and a nozzle (not shown) communicating with the ink chambers 28. The cover block 24 is formed, for example, by photo-etching photosensitive glass.

Next, the operation of the recording head of this embodiment will be explained.

A signal voltage is applied to the signal electrodes 25a and 25b from a drive circuit (not shown), and the convex portions 21a and 21b of the piezoelectric actuator 21 are displaced in the direction of the arrow in the figure due to the piezoelectric longitudinal effect.

As a result, the corresponding portion of the diaphragm 22 is pushed up. Therefore, the ink chamber 2 corresponding to the pushed up part
The volume of the ink chamber 2 contracts due to the pressure of the contraction.
The ink in 8 is ejected from the nozzle and printed on paper or the like.

In this way, the protrusions 21a and 21b are polarized equally when a signal voltage is applied, so that the lengths of displacement are the same. Therefore, the diaphragm 22 is kept flat without becoming wavy.

FIG. 3 is a reaction force characteristic diagram showing the relationship between the reaction force of the diaphragm 22 of the inkjet recording head shown in FIG. 1 and the amount of deformation of the diaphragm 22.

In the same figure (A), when the diaphragm is flat, the reaction force is proportional to the amount of deformation of the diaphragm (ultimately, the external force applied to the diaphragm is proportional to the amount of deformation of the diaphragm). shows.

The final force required to vibrate a flat diaphragm is
This is the reaction force of the diaphragm when the diaphragm deformation is completed.

Furthermore, what is necessary to eject ink from the nozzle is a change in the volume of the ink chamber due to deformation of the diaphragm.

For example, suppose that a volume change Δ■ is required to vibrate a flat diaphragm and eject ink from an ink chamber, and a deformation L1 of the diaphragm is required. At this time, the force finally applied to the diaphragm is Fl ((B) in the same figure).

On the other hand, when vibrating a wave-shaped diaphragm, the initial displacement is by R, so in order to obtain the volume change Δ■, it is necessary to displace it from this state to L2 (generally, L1≠
L2). At this time, the force finally applied to the diaphragm is F2 ((C) in the same figure).

Since the reaction force from the diaphragm is Fl<F2, when a wavy-deformed diaphragm is vibrated, a larger electrical energy must be applied to PzT, resulting in a decrease in efficiency. Note that (A) to (C) of the same figure all show the relationship in the final state of the diaphragm.

Therefore, since the inkjet recording head of the present invention does not unnecessarily deform the diaphragm, no extra electrical energy is required to vibrate the deformed diaphragm.

Therefore, energy conversion efficiency can be increased.

[Effects of the Invention] As described in detail above, according to the present invention, a cover block forming an ink chamber, a diaphragm joined to the cover block, and a diaphragm having a plurality of bonding surfaces and a plurality of Since it is equipped with a piezoelectric actuator that presses all joint surfaces simultaneously, unnecessary deformation of the diaphragm can be prevented. Moreover, since extra electrical energy for vibrating the deformed diaphragm can be omitted, energy conversion efficiency can be improved.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of an embodiment of the inkjet recording head of the present invention, FIG. 2 is an external perspective view of the same embodiment, and FIG. 3 is a reaction force and vibration of the diaphragm of the inkjet recording head shown in FIG. 1. A reaction force characteristic diagram showing the relationship with the amount of deformation of the plate; FIG. 4 is an exploded perspective view showing a conventional example of an inkjet recording head;
FIG. 5 is a sectional view taken along the line A--A shown in FIG. 4. 21...Piezoelectric actuator, 21a, 2
1b, 27... Convex portion, 22... Vibration plate, 23... Nozzle, 24... Cover block, 25a125b... Signal electrode ,2
6a126b... Common electrode, 28...
ink chamber. soil O

Claims (1)

[Claims] A cover block forming an ink chamber, a diaphragm joined to the cover block, and a piezoelectric actuator having a plurality of joint surfaces with the diaphragm and pressing all of the plurality of joint surfaces simultaneously. Characteristic inkjet recording head.