JPH05318728A - Ink jet head - Google Patents

Abstract

PURPOSE:To remove shortage of an ink excluding amount caused by leak of ink by a method wherein an inactive part which does not exhibit a piezoelectricity reverse effect is arranged on an ink chamber side of a beam shaped pressure generating member consisting of a laminated piezoelectric element. CONSTITUTION:A shape of a pressure generating member 150 is a beam shape of which a root is fixed, and its inside is composed of an inner electrode 18, and a laminated piezoelectric element wherein a piezoelectric material and an inner electrode 19 are partially laminated. Then, since an inactive part 27 is arranged on an ink chamber 170 side, a difference in lamination of the inner electrode 18 and the inner electrode 19 does not appear on an end surface 29 facing the ink chamber 170. Consequently, an ink chamber wall 180 comes to stick fast to the end surface 29 without any gap, and ink is prevented from leaking. Further, the ink in the ink chamber 170 can be ejected perfectly, and an ink discharge amount and its discharge speed are improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-demand type ink jet head for ejecting ink droplets when receiving print data and forming dots on a recording sheet by the ink droplets.

[0002]

2. Description of the Related Art The following are known documents in which the prior art relating to the present invention is described. JP-A-3-197
In the 049 publication, an embodiment of an ink jet head using a laminated piezoelectric element having an active portion and an inactive portion is shown. FIG. 13 shows an example thereof. In this conventional technique, the active portion 26 is arranged in contact with the ink chamber 170 side.

[0003]

In such a conventional technique, it is very important to precisely control the surface accuracy of the end surface 29 of the pressure generating member 150. The reason is that by controlling the surface accuracy, the airtightness between the ink chamber wall 180 and the end surface 29 can be maintained, ink leakage from the ink chamber 170 can be prevented, and the ink in the ink chamber 170 can be removed without waste. Because it is equipped. However, with such a conventional technique, it is difficult to precisely control the surface accuracy of the end surface 29 of the pressure generating member 150. The reason is that the internal electrode 1
8 and the internal electrode 19 are arranged near the end face 29. That is, since the laminated thickness L1 of the active portion 26 is increased by the thickness of the internal electrode 18 and the internal electrode 19, there is a difference between the thickness L2 of the inactive portion 27. Therefore, a step is formed on the end surface 29. As a result, problems such as leakage of ink from the gap 290 between the cavity wall 180 and the end surface 29, head corrosion, and deterioration of ejection characteristics occur.

Further, the end surface 2 of the pressure generating member 150.
9 is difficult to correct. That is, as shown in FIG. 14, when processing is performed by a cutting machine 70 or the like for the purpose of correcting the end surface 29, the internal electrodes 18 and 19 may be damaged, which makes the correction of the end surface 29 difficult. Of.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the problem of ink leakage and the accompanying shortage of ink removal amount. Further, it is also an object to solve the damage of the internal electrodes caused by the correction of the end surface of the pressure generating member.

[0006]

A beam-shaped pressure generating member composed of laminated piezoelectric elements is provided, and inside the pressure generating member, an active portion that can be actively expanded and contracted by a piezoelectric inverse effect,
An inactive portion that does not exhibit the piezoelectric inverse effect is provided, and the pressure generating member is flexibly deformed by expanding and contracting the active portion, pressing at least one wall of the ink chamber, and removing ink in the ink chamber. In the ink jet head which ejects from the nozzle, the inactive portion is arranged on the ink chamber side of the pressure generating member.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a perspective view of an ink jet head showing a first embodiment of the present invention. In this figure, the overall configuration of the inkjet head of the present invention and its mechanism will be described. For the sake of explanation, a part is cut to show a cross section. The pressure generating member 150 has a beam shape with its root fixed, and the internal configuration is a laminated piezoelectric element in which the internal electrode 18, the piezoelectric material 23, and the internal electrode 19 are partially laminated. The active portion 26 refers to a portion where the internal electrode 18 and the internal electrode 19 are arranged so as to face each other. In addition, the inactive portion 27 refers to a portion where the internal electrode 18 and the internal electrode 19 are not opposed to each other. The active part 26 is
When a voltage is applied between the internal electrode 18 and the internal electrode 19, the piezoelectric material 23 contracts in the X direction due to internal strain caused by the d31 piezoelectric inverse effect. On the other hand, the inactive part 2
Internal strain due to the d31 piezoelectric inverse effect does not occur at 7, and as a result, the pressure generating member 150 undergoes flexural deformation in which the tip end portion is displaced in the Z minus direction. Pressure generating member 150
The arrangement is such that the inactive portion 27 is arranged on the ink chamber 170 side and is joined to the substrate 14. Pressure generating member 15
A mold material such as silicon having a low Young's modulus is filled between 0, and one wall of the ink chamber 170 is constituted by the end surface 29 of the pressure generating member 150 and the mold material end surface 310. A drive pulse is applied to the pressure generating member 150 by the drive circuit 43, and the ink in the ink chamber 170 is pressurized by the end surface 29 and ejected as an ink droplet 50 from the nozzle 190.

FIG. 2 is an enlarged sectional view of the pressure generating member 150 of this embodiment. In the present embodiment, since the inactive portion 27 is arranged on the ink chamber 170 side, the end surface 29 facing the ink chamber 170 does not show the step difference of the lamination of the internal electrode 18 and the internal electrode 19. As a result, the ink chamber wall 180 and the end surface 29 are brought into close contact with each other without a gap, and it becomes possible to prevent ink leakage. Therefore, the ink chamber 1 can be used without waste.
The ink in 70 can be eliminated, and the effect of improving the ink ejection amount and ejection speed is produced.

Further, as shown in FIG. 3, even when the end surface 29 of the inactive portion 27 has irregularities, a part of the inactive portion 27 is processed by the processing machine 70 to sacrifice the displacement characteristic. Instead, the surface accuracy of the end surface 29 can be corrected.

Further, by disposing the inactive portion 27 on the ink chamber 170 side, the ejection efficiency could be improved. The effect will be described with reference to FIGS. 4, 5, and 6.
The charge switch 41 is closed and the inner electrode 18 and the inner electrode 19 are closed.
When an electric field is applied between them, the active portion 26 contracts in the X direction due to the d31 piezoelectric inverse effect. Then, the pressure generating member 150 is flexibly deformed in the negative Z direction. When the charge switch 41 is opened and the discharge switch 42 is closed immediately after the time t1 as shown in FIG. 5, the strain generated inside the pressure generating member 150 is released, and the pressure generating member 150 is restored to the original strain. The shape returns to the original shape, and the pressure generating member 150 is displaced in the Z direction by the reaction. As shown in FIG. 6, the overshoot X1 can be obtained by matching t1 with the natural period of the flexural vibration of the pressure generating member 150. Therefore, the displacement X2 at the time of ink ejection is changed to the static displacement X0 and the overshoot X1.
It was possible to make a large displacement by adding only × 2.
As described above, by selecting the timing of the voltage applied to the pressure generating member 150, it becomes possible to obtain sufficient characteristics at a low voltage. Further, at the time when ink ejection is required, it is sufficient to energize for a period of time t1, so the duty ratio of voltage application is small, and the stress and strain time applied to the piezoelectric element is small, and the durability is improved.

FIG. 7 is a sectional view taken along line AA of FIG. When a voltage is applied to the pressure generating member 150, the width W of the active portion 26 contracts due to the d31 piezoelectric inverse effect. Then, tensile stress acts on the joint between the pressure generating member 150 and the molding material 300. However, in this embodiment, the active portion 26
Is separated from the ink chamber 170, and the inactive portion 27 is separated from the ink chamber 1
Since it was placed in contact with 70, peeling did not occur on the joint surface with the molding material 300. In this way, the molding material 3
This example was also effective for sealing ink using 00.

In addition, as shown in FIG.
Since the inactive portion 27 is sandwiched between the internal electrode 19 and the internal electrode 19 and separated by the distance L3, the ink is blocked by the inactive portion 27. Therefore, the internal electrodes 19 could be protected from corrosion due to ink moisture. As described above, the present embodiment was effective also in preventing the corrosion of the electrodes.

Further, as shown in FIG. 9, the displacement characteristics could be measured by irradiating the gold sputtered negative electrode external electrode 16 with laser light or the like from the back surface of the ink jet. Displacement can be measured at the same time as ink ejection, and dynamic analysis of motion was comprehensive and easy. It was also effective for inspection during manufacturing.

FIG. 10 shows the ink chamber 170 and the pressure generating member 1.
This is an example in which an elastic plate 30 formed by Ni electroforming or the like is arranged between 50. Since the ink is enclosed by the elastic plate 30, it is possible to prevent corrosion due to moisture. The elastic plate 30 and the pressure generating member 150 are bonded together with an adhesive or the like. Even in this bonding, the end surface 2 of the pressure generating member 150 is joined.
Since the surface accuracy of 9 was secured, the adhesive pressure, adhesive thickness,
And the adhesive properties such as adhesive strength could be controlled. 11 is a state diagram when the elastic plate 30 and the pressure generating member 150 are joined. For the purpose of bringing the elastic plate 30 and the pressure generating member 150 into close contact with each other, even if the bonding pressure P is applied to the nozzle forming substrate 33 and the pressure generating member 150 bends in the Z direction as shown by the broken line, the active portion 26 is compressed in the X direction. Stress works. In general,
Since a piezoelectric element such as lead zirconate titanate exhibits high resistance to compressive stress, it is possible to perform uniform bonding without damaging the active portion 26 and without impairing displacement characteristics. FIG. 12 shows an embodiment in which the pressure generating member 150 is cut out from a single-plate laminated piezoelectric element and processed into a comb tooth shape, and the number of parts is reduced. Since the fixed end portion 28 having no notch supports the position of each pressure generating member 150, the substrate 14 becomes unnecessary and the number of parts can be reduced. Further, since the elastic plate 30 is firmly supported by the fixed end portion 28, the displacement of the pressure generating member 150 is efficiently transmitted to the elastic plate 30. Also in this embodiment, the elastic plate 30 and the pressure generating member 150 are securely joined,
In order to securely support the elastic plate 30, it was effective to secure the surface accuracy of the end surface 29.

[0016]

As is apparent from the above description, the present invention has the following effects. (1) By arranging the inactive portion on the ink chamber side,
The surface accuracy of the end surface of the pressure generating member on the ink chamber side has been improved.
Therefore, the close contact with the ink chamber wall was ensured, and the ink leakage could be prevented. Also, in order to secure the adhesion,
It has become possible to eliminate ink without waste. Therefore, both the ink ejection amount and the ejection speed could be improved.

(2) The inactive portion can be additionally processed without impairing the displacement characteristics, and the end face can be easily corrected.

[Brief description of drawings]

FIG. 1 is a perspective view of an inkjet head according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of an arrangement of pressure generating members according to the first embodiment.

FIG. 3 is a diagram illustrating a processed state of the pressure generating member according to the first embodiment.

FIG. 4 is a diagram illustrating the operation of the pressure generating member according to the first embodiment.

FIG. 5 is a diagram illustrating the operation of the pressure generating member according to the first embodiment.

FIG. 6 is a diagram illustrating the operation of the pressure generating member according to the first embodiment.

FIG. 7 is a diagram illustrating an effect of preventing ink leakage according to the first embodiment.

FIG. 8 is a diagram illustrating the effect of protecting the internal electrodes according to the first embodiment.

FIG. 9 is a diagram illustrating a measurement effect of the first embodiment.

FIG. 10 is a perspective view showing a second embodiment of the present invention.

FIG. 11 is a diagram illustrating joining of the pressure generating member and the elastic plate according to the second embodiment.

FIG. 12 is a perspective view showing a third embodiment of the present invention.

FIG. 13 is a cross-sectional view of a conventional inkjet head.

FIG. 14 is a processing diagram of a conventional pressure generating member.

[Explanation of symbols]

 14. ． ． ． Substrate 16. ． ． ． Negative electrode external electrode 17. ． ． ． Positive electrode external electrode 18. ． ． ． Internal electrode 19. ． ． ． Internal electrode 26. ． ． ． Active part 27. ． ． ． Inactive part 28. ． ． ． Fixed end 29. ． ． ． End face 30. ． ． ． Elastic plate 33. ． ． ． Nozzle forming substrate 43. ． ． ． Drive circuit 50. ． ． ． Ink drop 70. ． ． ． Processing machine 150. ． ． ． Pressure generating member 170. ． ． ． Ink chamber 190. ． ． ． Nozzle 290. ． ． ． Gap 300. ． ． ． Mold material 310. ． ． ． Mold material end face

Claims (1)

[Claims] 1. A beam-shaped pressure-generating member composed of a laminated piezoelectric element, wherein the pressure-generating member has an active portion that is capable of actively expanding and contracting due to a piezoelectric inverse effect, and an inert portion that does not exhibit a piezoelectric inverse effect. And an ink jet head for ejecting the ink from the nozzle by bending and deforming the pressure generating member by expanding and contracting the active portion, pressing at least one wall of the ink chamber, and ejecting the ink in the ink chamber. In the inkjet head, the inactive portion is disposed on the ink chamber side of the pressure generating member.