JPH10138471A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet head in which the ink jet quantity can be increased or the residual pressures can be canceled without requiring an expensive circuit. SOLUTION: A common electrode 16 and an individual electrode 20 of a first planar body 6 made of a piezoelectric material are arranged while being shifted to the manifold plate 12 side. A common electrode 18 and an individual electrode 22 of a second planar body 8 made of a piezoelectric material are arranged while being shifted to a nozzle plate 10 side. Consequently, deformable parts A, B or piezoelectric elements in first and second planar bodies 6, 8 are arranged while being shifted in the direction of ink flow in an ink pressure chamber. When the first and second planar bodies 6, 8 are driven to be deformed at different timing, a first peak of ink pressure is superposed by a second peak of ink pressure and the ink pressure is doubled in the ink pressure chamber.

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, and more particularly, to a method in which a piezoelectric element is provided on a wall surface of an ink pressure chamber, and the piezoelectric element is deformed by applying a driving voltage to deform the wall surface. The present invention relates to an ink jet head that applies pressure fluctuation to ink in the ink pressure chamber and discharges the ink from nozzles connected to the ink pressure chamber to the outside.

[0002]

2. Description of the Related Art Conventionally, in an ink jet head used in an ink jet printer, a side wall of an ink pressure chamber is deformed by deformation of a piezoelectric element, thereby causing a pressure fluctuation in ink inside the ink pressure chamber and continuously changing the pressure in the ink pressure chamber. A type in which ink is ejected from a nozzle that emits ink has been known.

In such an ink jet head, in order to increase the ejection amount, two piezoelectric elements are attached to the same position on the opposite side wall in one ink pressure chamber, and the driving voltage is simultaneously increased. Is applied to both the piezoelectric elements, so that a large deformation of the side wall of the pressure chamber as a whole is realized at once.

Further, even when the side wall of the ink pressure chamber is deformed by one piezoelectric element, the deformation vibration of the side wall remains, so that the side wall interferes with the next pressure generation for ink discharge, When ink is continuously ejected, the next ejection amount becomes excessively large, or conversely, becomes too small, which may cause a problem in print quality. For this reason, conventionally, a drive voltage waveform is set to a special waveform to cancel the ink pressure remaining immediately after ink ejection.

[0005]

However, when the piezoelectric elements are simultaneously driven, as in the former case, the drive current increases in proportion to the number of piezoelectric elements, and a circuit for generating such a large drive current is required. It has become expensive.

Further, as in the latter case, a circuit for outputting a drive voltage waveform satisfying both functions of pressure generation and pressure cancellation is more complicated than a circuit for outputting a simple drive voltage waveform. This had to be done, resulting in higher costs. SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet head capable of increasing the ejection amount or canceling out the residual pressure without using a circuit that increases the cost.

[0007]

Means for Solving the Problems and Effects of the Invention Here, one or more inventions are described, each having the structure and effect described below. A piezoelectric element is provided on the wall surface of the ink pressure chamber, and the piezoelectric element is deformed by application of a driving voltage to deform the wall surface,
An ink jet head that applies pressure fluctuation to ink in the ink pressure chamber and discharges the ink to the outside from a nozzle that is continuous with the ink pressure chamber, wherein a plurality of piezoelectric element deforming sections and each of the piezoelectric element deforming sections are provided. And a drive voltage applying section for deforming at different timings.

As described above, the drive voltage applying section deforms the plurality of piezoelectric element deforming sections at different timings. As this different timing, for example, the timing at which each of the piezoelectric element deforming sections is driven by the drive voltage applying section is a timing at which the ink pressure generated by each of the piezoelectric element deforming sections overlaps, thereby amplifying the ink pressure. be able to.

[0009] The ink pressure generated by the second and subsequent piezoelectric element deforming portions is successively superimposed on the ink pressure generated by one piezoelectric element at a different timing, not at the same time. Then, the ink pressure gradually increases, and the ejection amount can be increased.
In addition, since it is not necessary to simultaneously apply a drive voltage to each piezoelectric element deforming section, a large drive current is not required at a time, and a circuit for that purpose does not increase in cost.

The different timings described above include, for example, the timing at which each of the piezoelectric element deforming sections is driven by the drive voltage applying section is determined by the deviation of the ink pressure generated by each of the piezoelectric element deforming sections. The timing at which the ink pressure is canceled can be set.

[0011] The generation of ink pressure by the second and subsequent piezoelectric element deformers at the timing different from the ink pressure generated by one piezoelectric element, not at the same time, coincides with the timing of canceling the ink pressure generated last time. If this is the case, the ink pressure is immediately canceled and the residual ink pressure can be eliminated. Therefore, since the piezoelectric element deforming section does not need to apply a drive voltage having a complicated waveform, the cost of a circuit therefor does not increase.

It is to be noted that the plurality of piezoelectric element deforming portions are arranged at different positions in the ink flow direction, so that even when the ink pressure is amplified or canceled at a shifted timing, the amplification and cancellation can be performed quickly. It is preferred. The different position means that the piezoelectric element deformed portions may not be completely opposed to each other and may be present at positions completely separated from each other, or even if they partially overlap each other, the ink pressure generated by the piezoelectric element deformed portion may be different. The position where the peak is shifted may be used.

Further, since the plurality of piezoelectric element deforming portions are provided on different wall surfaces with respect to the ink pressure chambers, respectively, the piezoelectric element deforming portions can be formed large, so that a large ink pressure can be generated and generated. It is preferable from the viewpoint of its amplification or cancellation.

The ink pressure chamber is formed in the cavity plate and has two open surfaces opposed to each other. The ink pressure chamber is formed so as to close a hole continuous with the nozzle and each open surface of the hole. A first and a second piezoelectric element fixed to the cavity plate and having the two piezoelectric element deformation parts formed by polarization, respectively, and applying a voltage to the first piezoelectric element to cause the one piezoelectric element deformation part to A configuration may be provided including a first electrode for deforming and a second electrode for applying a voltage to the second piezoelectric element to piezoelectrically deform the other piezoelectric element deforming portion.

Since the piezoelectric element itself is formed as the side wall of the ink pressure chamber, the amount of deformation of the side wall can be increased. In the first and second piezoelectric elements, some of the layers are polarized in their own thickness direction, and the first and second electrodes are respectively oriented in the same direction as the polarization direction or in the opposite direction to the polarization direction. , A structure in which an electric field can be generated in some of the layers. For this reason, some of the layers can be expanded and contracted, and the other layers do not expand and contract to serve as a restraint plate, so that bimorph-type deformation can be performed, and a large amount of deformation can be achieved. And a large ink pressure can be obtained.

Further, it is possible to provide an auxiliary electrode capable of generating an electric field in a direction orthogonal to the polarization direction of the first and second piezoelectric elements. By adding such a configuration that performs the shear mode deformation to the piezoelectric element that performs the bimorph type deformation, a larger deformation amount and ink pressure can be obtained.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment FIG. 1 shows an inkjet head 2 according to a first embodiment to which some of the above-described inventions are applied.
FIG. 3 is an exploded perspective view illustrating a schematic configuration of FIG. FIG. 2 is a schematic longitudinal sectional view of the ink jet head 2.

The ink jet head 2 includes a cavity plate 4, two plate-like members 6, 8 made of a piezoelectric material, a nozzle plate 10, and a manifold plate 12. In addition, as a piezoelectric material, lead zirconate titanate (PZT), lead magnesium niobate, lead nickel niobate, lead zinc niobate, lead manganese niobate,
Materials mainly containing lead antimony stannate, lead titanate, and the like can be given.

An ink pressure chamber 14 is provided in the cavity plate 4 in a long hole shape, and upper and lower surfaces of the ink pressure chamber 14 are formed as open surfaces. 1st to upper open surface
The plate-shaped members 6 are stacked, and the second plate-shaped member 8 is stacked on the lower open surface to close the ink pressure chamber 14.

At the end of the first plate 6, the ink pressure chamber 1 is provided.
4 is provided with a continuous through-hole 6a, and the nozzles 10 of the nozzle plate 10 stacked so as to cover the portion of the through-hole 6a.
a and the ink pressure chamber 14 are continuous. At the end of the second plate 8 opposite to the nozzle plate 10, a through hole 8 a that is continuous with the ink pressure chamber 14 is provided, and the inside of the manifold plate 12 that is laminated so as to cover the through hole 8 a is provided. The ink reservoir 12a and the ink pressure chamber 14 are continuous. When the ink jet head 2 is installed in a printer, ink is supplied to the ink reservoir 12a from a cartridge (not shown).

The first plate-shaped member 6 and the second plate-shaped member 8 are each composed of two layers 7a, 7b, 9a, 9b made of a piezoelectric material.
, Each of which has a total ink pressure chamber 1
Each one of the common electrodes 16 and 18 common to 4 is formed of a conductive paste. In addition, individual electrodes 20 and 22 are provided for each of the ink pressure chambers 14 at the lamination interface of the piezoelectric material.

The common electrodes 16 and the individual electrodes 20 of the first plate-like body 6 are arranged so as to be biased toward the manifold plate 12. Further, the common electrode 18 and the individual electrode 22 of the second plate-shaped body 8 are arranged to be biased toward the nozzle plate 10. Therefore, as shown in FIG.
Piezoelectric element deformable portion A deformable in the second plate-shaped body 8
Is displaced from the piezoelectric element deformable portion B in the ink flow direction of the ink in the ink pressure chamber 14 and is arranged at a different position.

FIG. 3 is a block diagram showing a circuit for outputting a drive voltage for the electrodes 16, 18, 20, and 22. The electrodes 16 and 18 are connected to the ground side. On the other hand, the voltage waveform generated by the first voltage generation circuit 40 is provided on the individual electrode 20 side, and the voltage waveform generated by the second voltage generation circuit 42 is provided on the individual electrode 21 side, and the switching circuits 26, 28, 30, and
32, 34, and 36. The drive control circuit 38 controls these switching circuits 26 to 36 based on print data. Further, the voltage control circuit 4
4 is a first voltage generation circuit 40 and a second voltage generation circuit 42
And the magnitude of the generated voltage.

The first plate 6 is polarized in the thickness direction and in the direction opposite to the cavity plate 4 as shown by an arrow A in FIG. The second plate 8 is polarized in the thickness direction as shown by the arrow B and in the direction opposite to the cavity plate 4.

Under the control of the voltage control circuit 44, the first
The voltage generation circuit 40 outputs the drive voltage E in the pattern shown in FIG. Time t0 is the time when the control is started, and time t1 is the time when the drive voltage E reaches a peak.
By applying the driving voltage E in this manner, the upper layer 7a of the first plate-shaped body 6 contracts in a plane direction perpendicular to the ink flowing direction. Since the lower layer 7b of the first plate 6 does not shrink, it functions as a restraining plate, and the first plate 6 is deformed so as to protrude toward the ink pressure chamber 14 as shown in the center of FIG. As a result, the ink pressure in the ink pressure chamber 14 increases.

Subsequently, the voltage control circuit 44 controls the second voltage generation circuit 42 to output a voltage at a timing delayed by Δt from the voltage output from the first voltage generation circuit 40. Therefore, as shown in the left portion or the right portion of FIG. 4, the second plate-like body 8 is deformed so as to be convex toward the ink pressure chamber 14. As a result, the ink pressure in the ink pressure chamber 14 increases. The waveform of the drive voltage E is the same as that output by the first voltage generation circuit 40.

At time t0, the distribution of the ink pressure generated by the switching control of the first plate-like body 6 moves from the state of FIG. The state shown in FIG. That is, this Δt
In the meantime, the peak of the ink pressure generated first is almost at the center of the piezoelectric element deforming portion A, but moves to almost the center of the piezoelectric element deforming portion B. At this time, FIG.
As shown in (e), the second plate-like body 8 generates a second ink pressure. Therefore, the peak of the second ink pressure overlaps the peak of the first ink pressure,
The ink pressure will be amplified almost twice. Thereafter, the ink is ejected, so that the ink ejection amount is almost doubled.

The ink jet head 2 according to the first embodiment
When the ink pressure is amplified by the deformation of the two plate-like members 6 and 8 in this manner, the positions of the piezoelectric element deformed portions A and B are shifted in the ink flowing direction, and the ink pressure is changed. The deformation timings (drive voltage application timings) of the plate-shaped members 6 and 8 are shifted by Δt, and the ink pressures generated by the plate-shaped members 6 and 8 are superposed so as to be amplified.

Therefore, in the amplification of the ink pressure by the two plate-like members 6, 8, it is not necessary to apply a drive voltage to both at the same time, so that a large drive current is not required at one time, and the circuit therefor is also cost-effective. Does not go high. Further, since the piezoelectric element deforming portions A and B are formed on different wall surfaces with respect to the ink pressure chamber 14, the respective areas can be large, and a large ink pressure can be generated.

[Second Embodiment] A second embodiment differs from the first embodiment only in the timing of the voltage generated by the first voltage generation circuit 40 and the second voltage generation circuit 42 by the voltage control circuit 44. And the others have the same configuration.

FIG. 6 shows the application timing. Under the control of the voltage control circuit 44, the first voltage generation circuit 40 outputs the drive voltage E in the pattern shown in FIG. Time t1 is the time when the drive voltage E reaches a peak. This is the same as the first embodiment. Accordingly, the first plate-like body 6 is deformed by the above-described mechanism so as to protrude toward the ink pressure chamber 14 as shown in the central portion of FIG.
As a result, the ink pressure in the ink pressure chamber 14 increases.

Subsequently, the voltage control circuit 44 controls the second voltage generation circuit 42 to output a voltage at a timing delayed by ΔT from the voltage output from the first voltage generation circuit 40. Therefore, as shown in the left portion or the right portion of FIG. 4, the second plate-like body 8 is deformed so as to be convex toward the ink pressure chamber 14. As a result, the ink pressure in the ink pressure chamber 14 increases. Here, in consideration of the later-described cancellation, the waveform of the drive voltage E is set slightly lower than the switching control of the first plate-shaped body 6 side.

During ΔT, the distribution of the ink pressure generated by the switching control of the first plate-shaped body 6 is such that the distribution of the ink pressure from the state of FIG.
The state moves from (d) to FIG. 6 (e), and ink is ejected from the nozzle 10a in the state between FIGS. 6 (d) and (e).

After ΔT, the state shown in FIG. That is, during the time ΔT, the peak of the ink pressure generated first, whose peak was almost at the center of the piezoelectric element deformed portion A, moved to the nozzle 10a side to discharge the ink, and then FIG. As a result, a state in which a negative pressure having a peak substantially at the active center B is generated.

At this time, as shown in FIG. 6G, a second ink pressure is generated by the second plate 8.
Therefore, the peak of the negative pressure caused by the first ink pressure and the peak of the second ink pressure are substantially at the same position. Since the absolute value of the ink pressure on the negative pressure side is smaller by attenuation than the absolute value of the ink pressure at the time of occurrence, the negative pressure in FIG. 6F can be canceled.

In the ink jet head according to the second embodiment, the ink pressure is changed by the deformation of the first plate-shaped body 6 as described above.
After the ink is ejected, the second plate-shaped body 8 is driven by shifting the deformation timing (driving voltage application timing) by ΔT,
Since the ink pressure generated by the first plate-shaped body 6 is canceled, the residual ink pressure which adversely affects the next ejection can be immediately eliminated.

Therefore, conventionally, in the case where only the first plate member 6 is used, the residual ink pressure cannot be canceled without applying a voltage having a complicated shape to the first plate member 6.
You can cancel with a simple waveform. This eliminates the need for using a complicated drive voltage application circuit,
The cost does not increase.

[Embodiment 3] This embodiment 3 is different from FIG.
The control is applicable to any of the first and second embodiments, but the configuration of the first plate 50 and the second plate 52 is four The difference is that sheets of material are stacked. All layers 50a, 5
0b, 50c, 50d, 52a, 52b, 52c, 52
d is polarized in the direction of arrow A or arrow B as shown. The first plate-like body 50 and the second
The hatching of the plate member 52 is omitted.

With respect to the first plate-like body 50, the first layer 50 a and the second layer 50
b, a third layer 50c and a fourth layer 50d. The second plate-shaped body 52 includes a first layer 52a, a second layer 52b, a third layer 52c, and a fourth layer 52d from the side opposite to the cavity plate 54.

The grounded common electrodes 56 and 58 are provided on the first layers 50a and 52a, and individual electrodes 60a, 60b, 60c, 62a and 62 are provided between the layers.
b, 62c, which are controlled by a drive control circuit 63 to switch circuits 64, 66, 68, 70,
A drive voltage is applied from a power supply 76 via 72 and 74.

The common electrodes 56 and 58 are driven by the driving voltage.
And the individual electrodes 60a, 60b, 60c, 62a, 62b,
62c, in particular, the portions of the first layers 50a, 52a shrink and the other layers 50b, 50c, 50d, 52b, 52c, 5c.
2d plays the role of a restraint plate and is deformed in the same direction as in the first and second embodiments.

However, each layer 50a, 50b, 50c, 5
The individual electrodes 60a, 60b, 60c, 62a, 62b, 62 are provided at the interfaces of 0d, 52a, 52b, 52c, 52d.
c, the auxiliary electrodes 78a, 78b, 78c,
80a, 80b, and 80c are arranged, and have the same potential as the common electrodes 56 and 58, respectively.

Therefore, the individual electrodes 60a, 60b, 6
0c, 62a, 62b, 62c and auxiliary electrodes 78a, 78
b, 78c, 80a, 80b, 80c
1, P1, S2, and P2 also have individual electrodes 60a, 60b,
60c, 62a, 62b, 62c to auxiliary electrodes 78a,
An electric field is generated toward 78b, 78c, 80a, 80b, 80c, and the common electrodes 56, 58 and the individual electrodes 60 described above are generated.
a, 60b, 60c, 62a, 62b, 62c, and a shear mode deformation in a direction to further increase the deformation. Therefore, the amount of deformation of the first plate-shaped body 50 and the second plate-shaped body 52 is increased, and a larger ink discharge amount can be obtained.

[Others] In the second embodiment, similarly to the first embodiment, the piezoelectric element deforming section B is replaced with the piezoelectric element deforming section A.
Is shifted in the direction of the nozzle 10a, but this is for canceling the negative pressure generated after the ink is ejected. Therefore, the piezoelectric element deforming section B faces the piezoelectric element deforming section A at the same position to cancel the negative pressure. You may do it.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view illustrating a schematic configuration of an inkjet head according to a first embodiment.

FIG. 2 is a schematic longitudinal sectional view of the inkjet head according to the first embodiment.

FIG. 3 is a block diagram showing a circuit for generating a drive voltage according to the first embodiment;

FIG. 4 is a diagram illustrating a deformation state of the ink jet head according to the first embodiment.

FIG. 5 is a graph showing a temporal change of a driving voltage and a positional change of an ink pressure according to the first embodiment.

FIG. 6 is a graph showing a temporal change of a driving voltage and a positional change of an ink pressure according to the second embodiment.

FIG. 7 is a block diagram illustrating a circuit that generates a drive voltage according to a third embodiment;

[Explanation of symbols]

2: Inkjet head 4: Cavity plate 6: First plate 6a: Through hole 7a: Upper layer
7b Lower layer 8 Second plate 8a Through hole 10 Nozzle plate 10a Nozzle 12 Manifold plate 1
2a: ink reservoir 14: ink pressure chamber 16, 18, common electrode 2
0, 22 ... individual electrode 24 ... power supply 26, 28, 30, 32, 34, 36 ...
Switching circuit 38 Drive control circuit 40 First voltage generation circuit 42 Second voltage generation circuit 44 Voltage control circuit 5
0: first plate-shaped body 50a, 50b, 50c, 50d, 52a, 52b, 5
2c, 52d: each layer 52: second plate-like body 54: cavity plate 5
6, 58 ... common electrodes 60a, 60b, 60c, 62a, 62b, 62c ... individual electrodes 63 ... drive control circuits 64, 66, 68, 70, 72, 74 ... switching circuits 76 ... power supplies 78a, 78b, 78c, 80a, 80b, 80c: auxiliary electrode

Claims (8)

[Claims] A piezoelectric element provided on a wall surface of the ink pressure chamber, wherein the piezoelectric element is deformed by applying a driving voltage,
An ink jet head that deforms the wall surface to apply pressure fluctuation to ink in the ink pressure chamber, and discharges the ink from nozzles connected to the ink pressure chamber to the outside, wherein a plurality of piezoelectric element deforming units; And a drive voltage applying section for deforming each piezoelectric element deforming section at a different timing. 2. The method according to claim 1, wherein the driving voltage applying section drives the piezoelectric element deforming sections at a timing at which the ink pressures generated by the piezoelectric element deforming sections overlap to amplify the ink pressure. The ink-jet head according to claim 1, wherein: 3. A timing at which each of the piezoelectric element deforming sections is driven by the drive voltage applying section is a timing at which a residual ink pressure is canceled out due to a shift in ink pressure generated by each piezoelectric element deforming section. The ink jet head according to claim 1, wherein: 4. The ink jet head according to claim 1, wherein said plurality of piezoelectric element deforming portions are arranged at different positions in a direction in which said ink flows. 5. The ink jet head according to claim 1, wherein said plurality of piezoelectric element deforming portions are provided on different wall surfaces with respect to said ink pressure chamber. 6. The ink pressure chamber is formed in a cavity plate, has two open surfaces facing each other, and closes a hole connected to the nozzle and each open surface of the hole. A first and a second piezoelectric element fixed to the cavity plate and having the two piezoelectric element deforming parts formed by polarization, respectively; and applying a voltage to the first piezoelectric element to deform the one piezoelectric element deforming part. And a second electrode for applying a voltage to the second piezoelectric element to deform the other piezoelectric element deforming portion. 6. The inkjet head according to any one of 1 to 5. 7. The first and second piezoelectric elements have some layers polarized in their own thickness direction, and the first and second piezoelectric elements have different polarities.
7. The ink jet head according to claim 6, wherein the electrodes are arranged so as to generate an electric field in the partial layer in the same direction as the polarization direction or in the direction opposite to the polarization direction. 8. An ink jet head according to claim 6, further comprising an auxiliary electrode capable of generating an electric field in a direction orthogonal to a polarization direction of said first and second piezoelectric elements.