JPH07124103A - Piezoelectric actuator - Google Patents

Abstract

PURPOSE:To obtain a large displacement quantity with a very small shape applicable to an ultrasonic probe. CONSTITUTION:This piezoelectric type actuator is constituted by using a bimorph type actuator 101 for executing curvilinear deformation as a basic member and arranging plural pieces of the basic members E1 in directions which are orthogonal with the direction of the curvilinear deformation and where both ends AB of the basic members are respectively adjacent to each other. The respective basic members E1, E2, E3 are only connected with the other one adjacent basic member and either of the ends AB. The respectively unconnected two ends of the two basic members existing in the outermost part among the basic members arranged in plural pieces are formed as stationary ends of output ends. Further, the directions of the curvilinear deformation when a voltage is applied to the basic members are so set as to be reverse from each other between the adjacent basic members.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric actuator which is small in size and capable of operating with a large amount of displacement and large generated force.

[0002]

2. Description of the Related Art In recent years, a fine driving mechanism has been developed due to the progress of fine processing technology. Particularly in the field of medical devices, with the increasing need for minimally invasive treatment that significantly reduces the burden on patients, diagnostic and therapeutic devices that function in a narrow body (for example, in body cavities such as blood vessels and digestive tracts) are being developed. is there. An example is an ultrasonic endoscope. In an ultrasonic endoscope, an ultrasonic beam is sent to the patient's body (for example, inside a body cavity such as a blood vessel or digestive tract) and an ultrasonic transducer for capturing the reflected wave is arranged at the tip. In order to image as, the ultrasonic transducer must be mechanically rotated or deflected. Currently, most ultrasonic endoscopes employ a method in which the rotation of an external motor is transmitted to an ultrasonic transducer provided inside the tip of a catheter by a shaft passing through the catheter.

[0003]

[Problems of the Prior Art] However, in order to transmit such power, it is necessary to have a shaft which is highly flexible and has little twist (excellent torque transmission), and a mechanism for absorbing expansion and contraction of a long shaft. Etc. are required, and they are major barriers in terms of performance, reliability, and price. In addition, the volume occupied by the shaft in the catheter significantly limits the space required for other measurements and treatments, which is a major obstacle in realizing a smaller-diameter ultrasonic endoscope that can be used in blood vessels. It's a problem. To overcome such a problem, a drive mechanism may be arranged inside the distal end of the catheter, but at that time, a minute actuator having a diameter and a length of several millimeters or less is required.

At present, there is an electromagnetic motor having a diameter of about several millimeters as a minute actuator, but it is not practical because the torque is weak. As a scanning method of the ultrasonic beam, there is a method of deflecting a vibrator in addition to the rotation method.
In the case of this method, the use of a reciprocating piezoelectric actuator can be considered. Typical piezoelectric actuators include a laminated type and a bimorph type, but the laminated type has a large generated force but a significantly small displacement amount and is not practical. It can be said that the bimorph type is the most practical because it has a larger displacement than the laminated type and has a generating force. However, if the shape satisfies the above conditions, for example, if the total length is 5 mm or less, the displacement amount is about several tens of microns, which is not practically sufficient.

In view of the above problems, an object of the present invention is to realize a piezoelectric actuator capable of obtaining a large displacement with a minute shape.

[0006]

In order to achieve the above object, the present invention uses a bimorph type actuator that performs bending deformation as a basic member, the basic member being orthogonal to the direction of the bending deformation, A plurality of both end portions of the basic member are arranged in parallel in a direction in which they are adjacent to each other, and the basic member is connected to only one of the end portions and another adjacent basic member, Of the plurality of basic members arranged in parallel, the two non-connected ends of the two outermost basic members are fixed ends or output ends, and when a voltage is applied to the basic members, The present invention provides a piezoelectric actuator, characterized in that the directions of bending deformation are mutually opposite between the adjacent basic members.

[0007]

As shown in FIG. 1, one of the two outermost basic members is designated as E1 and its unconnected end is designated as the fixed end A1. When a voltage is applied, E1 bends in one direction (+ direction) orthogonal to the direction in which the basic element is arranged, and the end B1 on the opposite side of E1 is + Δy from the straight line with A1 as a contact point. Displace in distance. Since one end B2 of the basic element E2 adjacent to E1 is connected to B1, it is also displaced by the distance of + Δy. Here, considering the tangent line 1 having B1 as a contact point, as a result of the bending of E1, this tangent line is separated from the fixed end A1 by −Δy. E1
Simultaneously with the bending of E2, E2 bends in the direction opposite to the bending direction of E1 (negative direction), so that the end A2 on the opposite side of E2 is displaced from the tangent line 1 to the distance of −Δy. That is, A2 is A1
From -2 · Δy (here, Δy is sufficiently small with respect to the length A1B1 of the basic element). Similarly, since the displacements of the adjacent basic elements also sequentially increase, the displacement amount at the output end increases by the number of basic elements times the displacement amount Δy of one basic element. When the polarities of the applied voltages are reversed, the displacement directions of the respective basic elements are all reversed, so that the output end is displaced in the opposite direction.

[0008]

Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a plan view when the number of bimorph type actuator basic members is three. In FIG. 1A, E1, E2, and E3 are basic members, and a fixed member 101 is provided at the fixed end A1. An end B1 of the basic member E1 opposite to the fixed end A1 is an end B2 of the basic member E2.
Are connected to each other by a connecting member 102. Further, the other end A2 of E2 and the end A3 of E3 are similarly connected by the connecting member 103. The other end B3 of the basic member E3 is the output end (free end), and the output member 104 is provided.

FIG. 1 (b) is a side view of the bimorph type actuator of FIG. 1 (a). The piezoelectric element of the bimorph type actuator has a piezoelectric material sandwiching an intermediate electrode plate 111 (referred to as a shim material) and a piezoelectric material on both sides having the same polarization direction (parallel type) and the opposite direction (series type). There are two forms. Any of the above embodiments can be applied to the practice of the present invention, but a parallel type will be described in the present embodiment. In the parallel type, the electrodes 112 and 113 on the surface are connected so as to have the same potential, but in the present embodiment, the fixing member 101, the connecting members 102 and 103, and the output member 104 are made of metal,
It is electrically connected to the electrodes 112 and 113.

Both ends of the piezoelectric element are intermediate electrode plates 11
1 (hereinafter referred to as "shim material") is exposed and the shim terminal 11
4 is formed, and electrical connection is made inside the connecting members 102 and 103. Here, the intermediate electrode plate 111
The basic member E1 is composed of the electrodes 112 and 113 sandwiching the electrodes from both sides.

Wiring is drawn out from the fixing member 101 and the shim terminal 114 in the fixing member, and a voltage is applied between the surface electrode and the shim. In this embodiment, the wiring terminal T on the shim side
1 is a signal terminal, and the wiring terminal T2 on the surface electrode side is a ground (GND) terminal. The polarization directions of the piezoelectric element are E1 and E
3 is in the same direction (indicated by a symbol ◯), E2 is E1,
It is arranged so as to be opposite to E3 (indicated by a symbol ●).

When a voltage + V is applied to the terminal T1, E1 bends in one direction orthogonal to the direction in which the basic member is arranged. This direction is the plus direction. At the same time, the basic member E2 adjacent to and parallel to E1 is bent in the minus direction. Further, the basic element E3 which is substantially parallel to and adjacent to E2 is bent in the + direction. As a result, B1 end and B2
The edge is displaced from the original position to the position + Δy. The A2 end and the A3 end are displaced to the position of −2 · Δy. And B3
The edge is displaced to the position of + 3 · Δy (Fig. 1 (c)). To be precise, strictly speaking, the bending of the piezoelectric element is arcuate, so the locus of each end is also arcuate, but compared to the total length of the piezoelectric element,
Since the amount of displacement is about several tenths, the above approximation holds.

When the polarities of the applied voltages are reversed, the displacement directions of the respective basic elements are also reversed, so that the position of the output terminal B3 is displaced to the position of -3.Δy as compared with when no voltage is applied. (Fig. 1 (d)). That is, according to the present embodiment, it is possible to obtain a displacement amount about three times as large as that in the case of using one piezoelectric element.

As the material of the shim plate 111, a material having a high elasticity and a low electric resistance is preferable, and phosphor bronze, beryllium bronze or the like is particularly preferably used.

The material of the electrodes 112 and 113 is formed by printing silver paste (main component: Ag-Pt, Ag-Pd, etc.), carbon paste, etc. , after printing and firing.

The intermediate electrode plate 111 and the piezoelectric material are bonded with an anaerobic adhesive, and it is particularly preferable that the intermediate material is bonded with an ultraviolet curable adhesive.

Brass, silver, copper or the like is preferably used as the material of the connecting portions 101, 102, 103 and 104.

In this embodiment, the case where the number of bimorph type actuator basic members is three has been described.
It can be applied by expanding to an arbitrary plurality of two or more. FIG. 2 shows a second embodiment of the present invention. Figure 2 (a)
2B is a perspective view of the second embodiment, and FIG. 2B is a plan view of a piezoelectric element portion. In this embodiment, the piezoelectric element 201 is made of a single piece of piezoelectric material, and
It is cut into a shape as shown in FIG. The output member 202 has a symmetrical shape, and the fixing members 203 and 204 at both ends are fixed to a pedestal of a mechanical system (not shown). A cut line 219 is formed on the piezoelectric material by a diamond cutter, a laser, a high-pressure water stream processing, etc., and the cut line 219 divides the whole into seven elements. Each element is screen-printed with electrodes 211 to 217. And the like. These elements are polarized so that the polarization directions are opposite to each other (shown by ● or ○). After the polarization process, the electrodes 211 to 217 on the front and back are the wiring 2
21 to 226 are connected.

Since the shim member 231 is composed of one conductor in advance, it is continuous with each element. Therefore, the second book
Unlike the first embodiment, the second embodiment does not require a connecting member, and therefore has an advantage that the structure is simplified. Moreover, since it is composed of one piezoelectric material, the assembly process is also simplified. In the present embodiment, since the number of piezoelectric elements connected from the fixed member on one side to the output member 202 is four, the displacement amount is about four times that in the case of one element. The displacement amount can be further increased by increasing the number of connected piezoelectric elements.

Since the piezoelectric actuator of the present invention has a structure in which all the basic elements are arranged on the same plane, it is possible to stack and use a plurality of basic elements. FIG. 3 shows one example thereof. This embodiment (third embodiment) has a structure in which three actuators of the second embodiment shown above are stacked. However, although the fixing members 303 and 304 collectively fix the three actuators, the output members 302a, 302b and 302c of the respective layers are in contact with each other but not fixed.

A flexible output connecting member 310 (eg, silicone rubber) is provided at the tip of each of these output members.
The output member 311 is connected via. When a voltage is applied, the actuators in each layer are displaced in the same way,
Since they do not interfere with each other, in the output member 311 it is possible to obtain approximately three times the generated force with the same displacement amount as in the case of the second embodiment (FIGS. 3B and 3C).
(D)). It is possible to further increase the generated force by increasing the number of actuators to be overlapped.

In the above embodiment, one of the basic elements located at the outermost side is the fixed end, but both ends can be used as the output end.

FIG. 4 shows an example of application of the piezoelectric actuator of the present invention to a sector scanning ultrasonic catheter. In FIG. 4A, an ultrasonic transducer (not shown) is attached to the piezoelectric actuator 401. It is a perspective view which shows the mounted state. Reference numeral 401 is a piezoelectric actuator, 402 is an ultrasonic transducer holder, 403 is an ultrasonic transducer lead wire, 404
Is a lead wire for driving the piezoelectric actuator, and 405 is a frame material. FIG. 4B is a cross-sectional view of an ultrasonic catheter provided with a piezoelectric actuator at its tip. The ultrasonic transducer holder 40 is attached to the free end of the piezoelectric actuator 401.
2 is provided, and the ultrasonic transducer 407 is provided thereon. The piezoelectric actuator 401 is fixed inside the catheter 406 by a frame member 405. The piezoelectric actuator 401, the frame member 405, the ultrasonic transducer holder 402, the insulating oil (silicone oil, etc.) 409 are the partition walls 40.
It is sealed at the tip of the catheter by 8. Figure 4
(C) is a cross-sectional view when the catheter is rotated 90 ° in the axial direction.

[0024]

According to the present invention, a large displacement amount can be obtained even if the total length of the actuator is shortened, so that the tip of an ultrasonic catheter (endoscope) having a small diameter used in a blood vessel. A micro actuator that can be mounted on

Further, since all the basic elements are arranged on the same plane, it is possible to use a plurality of piezoelectric type actuators of the present invention in an overlapping manner, and it is possible to increase the generated force.

Further, since it is possible to manufacture the whole body from one piezoelectric material, the structure can be simplified and the manufacturing cost can be reduced.

[Brief description of drawings]

1 (a) is a plan view of a first embodiment of a piezoelectric actuator according to the present invention, and FIG. 1 (b) is a cross-sectional view of a first embodiment of a piezoelectric actuator according to the present invention. FIG. 1C and FIG. 1D are schematic diagrams for explaining the driving state of the piezoelectric actuator of the first embodiment.

2 (a) is a perspective view showing a second embodiment of the piezoelectric actuator according to the present invention, and FIG. 2 (b) is a second embodiment of the piezoelectric actuator according to the second embodiment of the present invention. It is a top view explaining the piezoelectric element in an example.

3 (a) is a perspective view showing a third embodiment of the piezoelectric actuator according to the present invention, FIG. 3 (b) and FIG.
FIG. 3C and FIG. 3D are schematic diagrams for explaining the driving state of the piezoelectric actuator of the third embodiment.

FIG. 4 is a diagram showing an application example of the piezoelectric actuator of the present invention to a sector scanning ultrasonic catheter.

[Explanation of symbols]

101, 203, 204, 303, 304 ... Fixing member 102, 103 ... Connecting member 104, 202, 302a 302b, 302c, 311
Output member E1, E2, E3 ... Actuator basic member 111 ... Intermediate electrode plate (shim material) 112, 113 ... Electrode 201, 401 ... Piezoelectric actuator 402 ... Ultrasonic transducer holder 403 ... Ultrasonic transducer lead wire 404 ... Piezoelectric actuator driving lead wire 405 ... Frame material 406 ... Catheter 407 ... Ultrasonic transducer 408 ... Partition wall 409 ... Insulating oil

Claims (1)

[Claims] 1. A bimorph type actuator that performs bending deformation is used as a basic member, and a plurality of the basic members are arranged in a direction orthogonal to the direction of the bending deformation, and both ends of the basic member are adjacent to each other. The basic members are arranged and connected to one other basic member adjacent to each other only at any one of the end portions, and the two outermost basic members of the plurality of basic members arranged in parallel are arranged. When the two non-connected ends of the basic members are fixed ends or output ends, and when a voltage is applied to the basic members, the bending deformation directions are opposite to each other between the adjacent basic members. A piezoelectric actuator characterized in that