JPH0964431A - Bimorph-type actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a bimorph-type actuator by which a displacement amount can be increased under a load by a method wherein the actuator is composed of the laminated structure of a plurality of bimorph elements whose length is different and the respective bimorph elements are arranged in such a way that the tip of the short bimporph elements is situated near the bending point of the long bimorph elements. SOLUTION: The size of respective bimorph elements is changed, and the bimroph elements which are provided with at least two kinds of sizes are used. Then, the respective bimporph elements are arranged and bonded in such a way that the tip of the short bimorph elements is situated near the bending point of the long bimorph elements 1. When the length of the laminated bimorph elements is different and the tip of the short bimorph elements 2 is arranged near the bending point of the long bimorph elements 1, the restraint of a part in which the long bimorph elements are displaced is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bimorph type actuator.

[0002]

2. Description of the Related Art Generally, when an electric field is applied to a piezoelectric material, its length changes. Bimorph elements are widely used as means for magnifying this displacement. As shown in FIG. 6, this bimorph element is a thin plate of two piezoelectric elements 4 and 5 having a metal elastic plate as a center electrode 3, and one piezoelectric element 4 expands when an electric field is applied. By causing a displacement and causing the other element 5 to contract, a bending displacement is exhibited as a whole (for example, the publication "Piezoelectric / electrostrictive actuator", pp. 82-84, Morikita Publishing Co., 1986. Please refer to the annual publication). This bimorph displacement element has low power consumption, good high-speed response,
It is compact and lightweight, has little heat generation, and is applied to piezoelectric fans, VTR heads, pressure control valves, printer heads, etc.

[0003]

The bimorph type actuator described above utilizes expansion and contraction of the piezoelectric element in a direction perpendicular to the electric field application direction. A laminated actuator in which a large number of piezoelectric elements are laminated by utilizing expansion and contraction is known.
This laminated actuator has a large generation force, but has a problem that the displacement amount of one piezoelectric element is small. However, since the displacement amount of the laminated actuator increases in proportion to the number of laminated piezoelectric elements, the problem that the amount of displacement is small can be solved by increasing the number of laminated layers. On the other hand, the bimorph type actuator has a problem that the displacement amount is large but the displacement force is low. Therefore, the bimorph type actuator cannot be used for a part requiring a large force. Further, when a load is applied to the bimorph type actuator, the displacement amount is greatly reduced. further,
When this bimorph type actuator is laminated, the piezoelectric element that causes the contraction displacement and the actuator that causes the extension displacement come into contact with each other, and as a result, the displacement amount becomes small.

[0004]

In order to solve the above problems, a bimorph type actuator of the present invention has a laminated structure of a plurality of bimorph elements having different lengths, and a short bimorph element has a long tip end. Each bimorph element is arranged so as to be located near the bending point.

When a load is applied to the bimorph type actuator, the amount of displacement greatly decreases because the applied load extends in the length direction of the bimorph element and a bending force acts in the direction opposite to the displacement direction due to the moment. This is because In the bimorph type actuator of the present invention,
Since the bending action due to the load applied to one bimorph element is suppressed in the displacement direction by the other bimorph element laminated with this bimorph element, the force acting in the direction opposite to the displacement is suppressed and the decrease in the displacement amount is suppressed.

Further, merely laminating bimorph elements of the same size does not improve the displacement amount because one bimorph element joined as described above restrains the displacement of the other bimorph element, but the bimorph element according to the present invention. -Type actuator has a short bimorph element whose tip is located near the bending point of a long bimorph element, so that the long bimorph element can be bent by bending displacement of a short bimorph element without restraining the displacement part of the long bimorph element. Since the points are bent in the displacement direction, the displacement amount is improved as a result.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The bimorph element used in the bimorph type actuator of the present invention is manufactured by a usual method. That is, it is manufactured by sandwiching and joining a metal plate called a shim between two piezoelectric elements.
In order to increase the displacement amount of the bimorph element, for example, a shim having an increased elastic modulus by mixing carbon fiber or the like may be used.

The piezoelectric element is also manufactured by an ordinary method. That is, PbO, ZrO ₂ , T as raw materials
After mixing io _{2 and the} like in a composition ratio that gives a desired piezoelectric material, and performing respective steps of calcination, crushing, molding, and calcination, it is processed into a target size and shape, and finally the electrode is baked.
A bimorph element is obtained by laminating the thus-produced piezoelectric elements via shims.

The bimorph type actuator of the present invention can be obtained by stacking a plurality of the bimorph elements thus manufactured. At this time, the size of each bimorph element is changed, and a bimorph element having at least two sizes is used. Each bimorph element is positioned so that the tip of the shorter bimorph element is located near the bending point of the longer bimorph element. The elements are arranged and bonded. As described above, the lengths of the laminated bimorph elements are different, and by arranging the tip of the shorter bimorph element near the bending point of the longer bimorph element, the displacement of the long bimorph element is restrained. Suppressed. In this way, the length of the laminated bimorph element is changed in order not to constrain the displacing portion of the bimorph element, and therefore, the tip of the shorter bimorph element is not necessarily the bending point of the longer bimorph element. It does not have to be placed exactly, and if it is placed near its inflection point, it achieves this purpose.

The bending point of the bimorph element exists at the center if it is an ordinary uniform one. Therefore, as shown in FIG. 1, in a general case where a bimorph type actuator is used for supporting one end, by using a shorter bimorph element 2 having a half length of the longer bimorph element 1, The tip of the shorter bimorph element is arranged at the center of the longer bimorph element, that is, the bending point.
In addition, the bending point may be provided at a portion other than the center depending on the manufacturing conditions of the piezoelectric element, and in this case,
The length of the bimorph element may be adjusted so that the tip of the shorter bimorph element is located near the bending point. Further, as shown in FIG. 2, the bimorph type actuator of the present invention can be similarly manufactured by using bimorph elements having three or more kinds of lengths.

[0011]

EXAMPLES PbO, TiO ₂ , ZrO ₂ , S as raw materials
rCO ₃ and Nb ₂ O were added to Pb _0.89 Sr _0.11 (Ti _0.44 Z
r _0.55 Nb _0.01 ) O ₃ was used in such a ratio as to give a piezoelectric body, which was granulated, formed into a rectangular shape using a mold, fired and then ground. A metal plate was sandwiched between these two piezoelectric bodies, and the piezoelectric bodies were bonded so that their displacement states were reversed, to obtain a bimorph element. In this way, a bimorph element 1 having a length of 48 mm and a thickness of 0.5 mm and a bimorph element 2 having a length of 24 mm and a thickness of 0.5 mm were manufactured, and one side was aligned with an epoxy resin adhesive as shown in FIG. Then, an electric wire for voltage application was connected to manufacture the bimorph type actuator of the present invention.

A voltage of 1 is applied to this bimorph actuator.
The amount of displacement when applying a load of 00 V was measured. The result is shown in FIG. Further, the displacement retention rate when a load was applied was measured, and the result is shown in FIG. For comparison, the displacement amount was similarly measured using the above bimorph element having a length of 48 mm.

As is clear from FIGS. 2 and 3, the laminated bimorph type actuator of the present invention has a larger displacement amount than one bimorph element even when no load is applied, and when a load is applied. A large amount of displacement was shown.

Further, the displacement amount with respect to the driving frequency was measured for one bimorph element, one in which two bimorph elements of the same size were laminated, and the bimorph type actuator of the present invention. The result is shown in FIG. In the case where one bimorph element or a bimorph element having the same size is laminated, mechanical vibration cannot catch up and the displacement amount decreases when the driving frequency increases. However, in the bimorph type actuator of the present invention, the displacement amount is high even at high frequencies. No decline was seen.

[0015]

The bimorph type actuator of the present invention exhibits a large displacement amount even under a load, and the displacement amount is improved as compared with one bimorph element. Further, it shows a large displacement even at a high driving frequency.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a bimorph actuator of the present invention consisting of two bimorph elements.

FIG. 2 is a schematic diagram of a bimorph actuator of the present invention consisting of three bimorph elements.

FIG. 3 is a graph showing a change in displacement amount when a load is applied.

FIG. 4 is a graph showing a change in displacement retention rate when a load is applied.

FIG. 5 is a graph showing a change in displacement amount with respect to a driving frequency.

FIG. 6 is a schematic diagram showing bending displacement of a bimorph element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Long bimorph element 2 ... Short bimorph element 3 ... Center electrode 4 ... Piezoelectric element 5 ... Piezoelectric element

Claims (1)

[Claims] 1. A bimorph element having a laminated structure of a plurality of bimorph elements having different lengths, wherein each bimorph element is arranged so that a tip of a short bimorph element is located near a bending point of a long bimorph element. Type actuator.