JPH0846263A - Multilayered piezoelectric actuator element and its manufacture - Google Patents

Abstract

PURPOSE:To improve endurance of an element under a high humidity environment, by setting the thickness of an outer film in a specified range. CONSTITUTION:A multilayered piezoelectric actuator element 1a is set in a flask 6. In the flask 6, gaps 7 from four side surfaces of the element la, except the displacement surfaces 2 of a protective layer 3, are set to be 0.3mm-2.0mm, preferably, 0.5mm-1.5mm. The length 1 of the inner surface of the flask is made a little shorter than the height (h) of the element 1a, in order to fix the element la on the displacement surfaces 2. As the material, transparent silicone having elasticity is used. Since the transparent flask is used, the alignment of the element la can be easily confirmed by visual observation. Since the elastic flask is used, the displacement surfaces of the element 1a is surely fixed to the inside surface 6a of the flask, and the gaps 7 from the four side surfaces except the displacement surfaces 2 are set to be constant. Finally resin is injected in the gaps 7 and hardened. Thereby an other film having a sufficient thickness is formed, and the multilayered piezoelectric actuator element 1 is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric actuator element having high reliability in a high humidity environment and having lead wires firmly attached to the element, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In conventional laminated piezoelectric actuator elements, a dipping method or a powder coating technique has been used when forming an outer coating. However, with the dipping method, there is a large variation in thickness, and it is possible to form only a thickness of about 0.1 mm at a time. In order to have a sufficient thickness, multiple coatings must be applied, so the entire thickness is sufficient. If you try to do so, there will be a portion where the coating becomes extremely thick. Therefore, it is very difficult to form a thick coating. Although it is possible to form a coating of up to about 0.5 mm by the powder coating method, a large number of bubbles remain inside the coating and the coating becomes porous, so that water easily permeates the coating. Due to such problems, when the conventional laminated piezoelectric actuator element is driven in a high humidity environment, moisture intrudes from the interface between the element and the resin or the thin portion of the outer coating, and the insulation resistance of the element deteriorates. It has a drawback that the displacement characteristic of 1 cannot be obtained. There is also a method of sealing with a metal to prevent moisture from entering the inside of the element, but when encapsulating the laminated piezoelectric actuator element in a metal tube, a bellows or the like is used so as not to prevent displacement of the element. Since it is necessary to use a metal tube having a precise structure having a stretchable portion, the cost is high and the encapsulation process is complicated. Furthermore, since the outer coating is thin and fragile, the lead wire is easily separated from the element when an external force is applied to the lead wire mounting portion.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a laminated piezoelectric actuator element with a dense outer coating having a sufficient thickness so that the insulation resistance of the element deteriorates even when the element is driven in a high humidity environment. It is an object of the present invention to efficiently produce and provide at low cost a highly reliable element in which the lead wire does not separate from the element even when an external force is applied to the lead wire.

[0004]

In order to solve the above-mentioned problems, the laminated piezoelectric actuator element of the present invention is characterized in that the outer coating has a thickness of 0.3 mm or more, preferably 0.5 mm or more. In the method for manufacturing a laminated piezoelectric actuator element, a mold having a gap between the element and the element is 0.3 mm or more, preferably 0.5 mm or more is used, and resin is injected into the gap and cured to form an exterior coating. It is characterized by

[0005]

According to the above structure, since the outer coating film is dense and has a thickness of 0.3 mm or more, it is possible to prevent moisture from easily adhering to the element, and the lead wire mounting portion is strongly reinforced. It

Other objects, features and advantages of the present invention will be shown by the following detailed description in conjunction with the accompanying drawings.

[0007]

EXAMPLE A binder, a solvent, a dispersant, and a defoaming agent are added to a fine powder of PZT, dispersed by an attritor, and then degassed in vacuum to form a slurry. Next, with a doctor blade, thickness 1
A sheet of 00 μm was molded. As an internal electrode
The g / Pd paste was printed, 130 sheets were laminated and pressed together with the protective layer 3. These laminates were fired, after cutting, Ag was burned as the external electrode 4, the lead wire 5 was soldered, and polarization treatment was performed to obtain the laminated piezoelectric actuator element 1a before the exterior coating (see FIG. 1). .

The laminated piezoelectric actuator element 1a is set on the mold 6 as shown in FIGS. The mold 6 has a gap 7 between the four sides of the protective layer 3 of the element 1a excluding the displacement surface 2 of 0.3 mm or more, preferably 0.3 mm to 2.0 mm, more preferably 0.5 mm to 1.5 mm. The length l of the inner surface of the frame is slightly shorter (about 0.2 mm to 0.5 mm) than the height h of the element 1a in order to fix the element 1a on the displacement surface 2, and the material is a flexible transparent silicone. I'm using it. Since the transparent mold 6 is used, the alignment of the element 1a can be easily confirmed visually. By using such a resilient mold, the inner surface 6a of the mold and the displacement surface 2 of the element 1a are
Are securely fixed, and the gap 7 between the four side surfaces except the displacement surface 2 is set to be constant.

Next, the mold frame 6 on which the element 1a is set is set at 80 ° C.
Place in a constant temperature bath maintained at and heat. By preliminarily heating and holding the mold 6 and the element 1a, when the resin is injected into the gap 7, it is prevented that the resin is rapidly cooled and the flow in the mold is deteriorated. As the resin used, a thermosetting resin is used, and for example, a one-liquid type epoxy resin can be preferably used. Since the one-pack type epoxy resin has a strong adhesive force and hardens densely, it can be suitably used for an exterior coating. The temperature can be changed appropriately depending on the resin used.

Next, the resin is injected into the gap 7 between the mold 6 and the element 1a, and the resin is again placed in a constant temperature bath kept at 80 to 120 ° C. to be cured. It is desirable to use a syringe because the gap 7 is narrow for resin injection. After the exterior resin is cured, it is taken out from the mold 6, so that the laminated piezoelectric actuator element 1 having a dense exterior coating 8 having a sufficient thickness can be obtained as shown in FIG.

Element 1 of the present invention having an outer coating thickness of 0.8 mm
For comparison, 30 elements A each having an outer coating thickness of 0.2 mm and 30 elements B each having an outer coating formed by the conventional dipping method were prepared. Further, several elements having an exterior coating formed by resin injection without preheating were also prepared. In this device, since the flow of the resin in the mold was poor, many air bubbles remained in the exterior coating film 8 or the exterior coating film was chipped without the resin flowing into the edge portion.

The evaluation of the laminated piezoelectric actuator element was carried out until the insulation resistance of the element became 10 MΩ or less when the DC 150V was continuously applied under the environment of 40 ° C. and 90% RH when 150V was applied (durability). It was judged based on time (10 elements 1 of the present invention, 10 elements A, 10 elements B). As a result, as shown in FIG. 5, the element of the present invention exhibited durability 10 times or more that of the elements A and B.

The attachment strength of the lead wire was measured by a tensile tester (20 elements 1 of the present invention,
20 elements A and 20 elements B). As a result, as shown in Table 1, in the element 1 of the present invention, the lead wire was broken and was not separated at the mounting portion. The element A is improved as compared with the element B, but the variation is large.

[0014]

[Table 1]

[0015]

As described above, according to the method for manufacturing a laminated piezoelectric actuator element of the present invention, it becomes possible to form a dense outer coating having a sufficient thickness, and the durability of the element in a high humidity environment is improved. It has become possible to efficiently produce a device that is expensive and that does not easily separate even when an external force is applied to the lead wire.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic perspective view of a laminated piezoelectric actuator element.

FIG. 2 is a view showing a schematic cross-sectional view of a laminated piezoelectric actuator element fixed to a mold.

FIG. 3 is a view showing a schematic vertical sectional view of a laminated piezoelectric actuator element fixed to a mold.

FIG. 4 is a diagram showing a schematic perspective view of a laminated piezoelectric actuator element having an exterior coating.

FIG. 5 is a diagram showing the results of humidity resistance tests of various elements.

[Explanation of symbols]

1 Multilayer Piezoelectric Actuator Element 1a After Forming Exterior Coating 1a Multilayer Piezoelectric Actuator Element Before Forming Exterior Coating 2 Displacement Surface 3 Protective Layer 4 External Electrode 5 Lead Wire 6 Formwork 6a Inner Side of Formwork 7 Formwork and Element Gap 8 Exterior coating h Height of laminated piezoelectric actuator element l Length of inner surface of formwork

Claims (10)

[Claims] 1. A laminated piezoelectric actuator element, wherein the outer coating has a thickness of 0.3 mm or more, preferably 0.5 mm or more, in a laminated piezoelectric actuator element that expands and contracts when a voltage is applied. 2. The laminated piezoelectric actuator element according to claim 1, wherein the thickness of the outer coating is 0.3 mm to 2.0 mm, preferably 0.5 mm to 1.5 mm. 3. The laminated piezoelectric actuator element according to claim 1, wherein the outer coating is made of a thermosetting resin. 4. The laminated piezoelectric actuator element according to claim 3, wherein the exterior coating is formed of a one-component epoxy resin. 5. When forming an exterior coating on a laminated piezoelectric actuator element that expands and contracts by applying a voltage,
The element is fixed to the mold so that the gap formed between the mold and the element is 0.3 mm or more, preferably 0.5 mm or more,
A method for manufacturing a laminated piezoelectric actuator element, which comprises injecting a resin into a gap and curing the resin to form an exterior coating film having a sufficient thickness. 6. The gap between the mold and the element is 0.3 mm to 2.0 mm.
The method for producing a laminated piezoelectric actuator element according to claim 5, wherein a mold having a size of preferably 0.5 mm to 1.5 mm is used. 7. The method for manufacturing a laminated piezoelectric actuator element according to claim 5, wherein a thermosetting resin is used as the resin for forming the exterior coating. 8. The method for manufacturing a laminated piezoelectric actuator element according to claim 7, wherein a one-component epoxy resin is used as the resin for forming the exterior coating. 9. Prior to injecting the resin into the gap of the mold,
9. The method for manufacturing a laminated piezoelectric actuator element according to claim 5, wherein the mold, the element, and the resin are preheated and maintained at a predetermined temperature. 10. The method for manufacturing a laminated piezoelectric actuator element according to claim 5, wherein the mold is made of a transparent and stretchable material.