JPH01287977A - Piezoelectric actuator - Google Patents

Abstract

PURPOSE:To improve heat dissipation by employing epoxy resin composition in which sintered aluminium nitride powder is mixed as a filler as an electric insulator of the end face of the electrode of a piezoelectric actuator as the package of the actuator. CONSTITUTION:A sintered aluminum nitride(ALN) to be mixed as a package 4 with epoxy resin composition as a filler is formed by mixing ALN powder of high purity of 99% or more with 5wt.% of Y2O3 as an additive and organic binder, and then baking the mixture in a nonoxidative atmosphere. The sintered ALN is pulverized into powder containing 80mum or less of particle size, and mixed with epoxy resin as a filler. A laminated type piezoelectric actuator is formed by directly coating the four sides with the epoxy resin composition mixed with the ALN powder and curing it to form a package 4. Thus, the heat dissipation of the end face of an electrode can be improved.

Description

[Detailed Description of the Invention] [Overview of the Field] The present invention relates to a piezoelectric actuator that utilizes the piezoelectric effect to convert electrical input energy into mechanical energy in the form of displacement or force. This invention relates to a piezoelectric actuator whose surface is coated with a resin containing powder as a filler.

[Contents and problems of conventional technology]

Piezoelectric actuators are voltage-driven, whereas electromagnetic actuators are current-driven, and have advantages such as essentially low power consumption and excellent responsiveness.

Because of these advantages, it has been put to practical use in the head section of impact dot printers. The piezoelectric actuator used as the printer head is driven by a pulse voltage of I KHz or higher, and when driven for a long time, the piezoelectric actuator element generates heat and the temperature rises to about 100°C, as shown in Figure 5. As shown in FIG. 2, when the temperature of the piezoelectric actuator element increases, the amount of displacement, which is an important characteristic of the actuator, also decreases as the temperature increases. Furthermore, for applications in which the printer is continuously driven due to the heat generated by the piezoelectric actuator, countermeasures such as increasing the size of the piezoelectric actuator element or lowering the driving frequency are required, which limits the miniaturization of the device. There were problems such as the equipment becoming larger.

[Purpose of the invention]

In view of this, the present invention uses an epoxy resin containing sintered aluminum nitride powder as a filler as an exterior member of a piezoelectric actuator, instead of the resin applied to the electrode end surface exposed on the actuator surface. The purpose of this invention is to provide a piezoelectric actuator with improved electrical insulation and heat dissipation at the electrode end surface.

[Structure of the invention]

The present invention uses a resin mixed with powder obtained by crushing an aluminum nitride sintered body as a filler as an exterior material for the purpose of electrical insulation of the electrode end surface exposed on the surface of the piezoelectric actuator and heat dissipation. The aluminum nitride sintered body powder contains the well-known Y2 as a sintering aid to improve thermal conductivity.
It is desirable to add O3 or the like in an amount of 3% to 5% by weight.

In addition, the resin used to fill the aluminum nitride powder is black.
In order to increase the heat dissipation area of the coated resin surface, the surface has a fin shape or a structure in which numerous protrusions are attached to the coated surface.

That is, the present invention provides (1) a laminated piezoelectric actuator formed by laminating and sintering a plurality of piezoelectric bodies, in which the outer wall of the actuator is closely coated with a resin composition containing aluminum nitride powder; A piezoelectric actuator featuring:

2. For the epoxy resin composition filled with aluminum nitride powder, the amount of aluminum nitride powder is 50 to 80 w by weight.
2. The piezoelectric actuator according to claim 1, wherein t%.

3. The piezoelectric actuator according to claim 1.2, wherein the exterior material filled with aluminum nitride and closely coated on the outer wall of the piezoelectric actuator has a shape of a fin-like protrusion or a structure in which a protrusion is attached on the covered surface. It is an actuator.

[Explanation based on examples]

An embodiment of the present invention will be described in detail below with reference to the drawings.

First, a sintered body of aluminum nitride (hereinafter referred to as ALN) which is blended as a filler into an epoxy resin composition as an exterior material will be described.

The ALN sintered body was made by mixing high-purity ALN powder of 99% or more, 35 wt% of Y2O as an additive, and an organic binder, and then firing the mixture at 1900° C. for 2 hours in a non-oxidizing atmosphere.

The ALN sintered body produced in this manner has a thermal conductivity of 180 to 200 W/mk and a specific resistance of >10'3 Ωcm, making it a material with excellent thermal conductivity and electrical insulation.

This ALN sintered body was crushed into powder having a diameter of 80 μm or less, and the powder was blended into an epoxy resin as a filler. The thermal conductivity due to the combination of the epoxy resin and ALN powder used was 4th.
As shown in the figure, the thermal conductivity increases as the amount of ALN powder increases, and reaches 85 W/mk or more at 60% or more, showing almost the same characteristics as ordinary metal materials. In this example, the exterior material was made by blending 65% ALN powder.

FIG. 2 is a perspective view showing the structure of a laminated piezoelectric actuator measuring 1.4 mm x 3 mm x 9 mm before being packaged.

A negative voltage is applied to the internal electrode 1 connected to the external electrode 3 through the lead wire 2 . The internal electrode spacing is 100 μm (
(Exaggerated and widened in the figure) and exposed on all four sides. Figure 1 shows a laminated piezoelectric actuator whose surface is coated with a resin containing ALN powder according to the present invention.
An epoxy resin composition containing 65% LN powder was applied to the side surface 4.
The exterior member 4 is formed by applying it directly to the surface and curing it. The color of the epoxy resin used is preferably black to improve heat dissipation, and the shape of the exterior material made of ALN filler formed on the surface of the piezoelectric actuator is the fin shape shown in Fig. 5.
Alternatively, by forming countless protrusions on the covering surface, the heat dissipation characteristics are further improved and temperature rise of the piezoelectric actuator is suppressed during actual operation.

When the piezoelectric actuator constructed according to the present invention was incorporated into a printer head and driven by applying a pulse voltage of 150 V and IKHz, the surface temperature of the piezoelectric actuator during operation was approximately 90°C. This is 8 ~
It is 12 degrees Celsius lower.

Further, in the piezoelectric actuator shown in FIG. 3, in which the surface of the piezoelectric actuator was shaped into a fin shape using the ALN-filled resin of the present invention, a further temperature decrease of 5° C. on average was observed. This reduces the decrease in displacement due to temperature rise of the piezoelectric actuator and enables continuous pulse drive, while greatly contributing to the miniaturization of the device and the improvement of the characteristics and reliability of the piezoelectric actuator such as high-speed operation. It is something to do.

Furthermore, as shown in Figure 4, when the weight ratio of aluminum nitride in the epoxy resin filled with aluminum nitride powder that coats the piezoelectric actuator is small, the thermal conductivity value is low and the heat dissipation effect is 50%. On the other hand, when increasing the filling rate of ALN, the resin mixed with the filler is hard and does not mix well with the resin, so the amount of ALN mixed is 80wt%.
The extent is the limit.

〔Effect of the invention〕

As described above (according to the present invention), an epoxy resin composition containing aluminum nitride sintered powder as a filler is used as an exterior material of the piezoelectric actuator as an electrical insulating material for the electrode end surface of the piezoelectric actuator, and has excellent heat dissipation properties. This makes it possible to provide a piezoelectric actuator that operates at high speed, is compact, and has improved reliability, such as a printer.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a laminated piezoelectric actuator coated with an epoxy resin containing aluminum nitride according to the present invention. (a) is a front view, (b) is a side view. FIG. 2 is an external view of the laminated piezoelectric actuator. (a) is a perspective view of the electrode terminal side, and (b) is a front view of the electrode end side. FIG. 3 is a front view of a piezoelectric actuator in which an epoxy resin is filled with aluminum nitride powder according to the present invention, and an uneven surface is provided on the surface of the exterior material. FIG. 4 is a diagram showing the relationship between the weight ratio of ALN in the resin and the thermal conductivity of an exterior material in which an epoxy resin is filled with aluminum nitride powder (ALN). FIG. 5 is a diagram showing the relationship between displacement and temperature of a 2X3X9mm laminated piezoelectric actuator. 1...Piezoelectric actuator. 2... Lead wire. 3...External electrode. 4...Exterior member. 5...Internal electrode. Patent applicant: Tohoku Metal Industry Co., Ltd. Figure 1 (a) (b) Figure 2 (a) (b) Figure 3
(*l-4□) Buniiritsu, 11 and Noui'p)

Claims (1)

[Claims] 1. In a multilayer piezoelectric actuator formed by laminating and sintering a plurality of piezoelectric bodies, the outer wall of the actuator is closely coated with a resin composition containing aluminum nitride powder. A piezoelectric actuator characterized by: 2. For the epoxy resin composition filled with aluminum nitride powder, the amount of aluminum nitride powder is 50 to 80 w by weight.
2. The piezoelectric actuator according to claim 1, wherein t%. 3. The exterior material filled with aluminum nitride, which is closely coated on the outer wall of the piezoelectric actuator, has a shape of a fin-like protrusion or a structure in which a protrusion is attached to the covered surface. piezoelectric actuator.