JPH0520356U - Multilayer piezoelectric - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent the voltage-displacement characteristics of the laminated piezoelectric material 1 from being changed by heat. [Structure] A plurality of piezoelectric plates 2 and electrode plates 3 are alternately laminated, and an ear portion of each electrode plate 3 protruding to the outer peripheral side surface of the laminated body.
In the multilayer piezoelectric body 1 provided with the external electrode 4 connected to 31, the external electrode 4 is hollow and the cooling medium 5 is circulated in the external electrode 4. Since the electrode plate 3 in contact with the piezoelectric plate 2 absorbs heat, cooling efficiency is good.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a laminated piezoelectric material used for various sensors and actuators.

[0002]

[Prior Art]

 Piezoelectric materials made of materials that generate dielectric polarization (voltage) when they are deformed by applying an external force and that distort (distort) when voltage is applied to them are often used in speakers, microphones, mechanical filters, etc. However, in recent years, it has also come to be used in automobiles. For example, it may be a knocking sensor, an actuator of a fuel injection control device, or the like. Commonly used piezoelectric materials are lead zirconate titanate (PZT), barium titanate, and the like, which are ceramics showing high piezoelectricity.

The minimum constitutional unit of the piezoelectric body is one in which electrodes are provided on both surfaces of a piezoelectric plate (plate-shaped piezoelectric material; also called pellet). When the piezoelectric body is used as an actuator, in order to fully exhibit its function, a large number of piezoelectric bodies may be laminated to increase the displacement amount of the entire body. The so-called laminated piezoelectric body was created based on this idea. As shown in FIG. 4, the multi-layer piezoelectric body 1 is generally composed of a large number of piezoelectric plates 2, 2, ... And a large number of electrode plates 3, 3 ... External electrodes 4, 4 for connecting the ears 31, 31, ... Of the homopolar electrode plates are provided on the outer peripheral side surface of the laminated body (stack).

In the laminated piezoelectric body, a change in external temperature and self-heating (heat generation of the piezoelectric body itself when a voltage is applied to displace it as desired) become problems. Since the voltage-displacement characteristics of the laminated piezoelectric material are affected by heat, it becomes difficult to function accurately as an actuator (or sensor) under conditions where the temperature changes drastically. Also, self-heating depends on the usage conditions, such as frequency, magnitude of displacement, response speed, etc., and if the conditions become stricter, heat generation also increases. This may lead to deterioration of the insulation tube on the outer periphery, causing insulation breakdown, which may render it unusable. .

[0005]

[Problems to be solved by the device]

 Therefore, depending on the operating environment and conditions, it is necessary to cool the laminated piezoelectric material to a constant temperature as much as possible. Therefore, as shown in FIG. 6, the laminated piezoelectric body 1 is blown with air by a fan 8 or the like, or as shown in FIG. It has been attempted to circulate the cooling medium 5 having a conductive property around the piezoelectric body 1. However, in general, the outer circumference of the laminated piezoelectric body is covered with a heat-shrinkable tube for insulation protection and for ease of handling, so it is necessary to cool from the outer circumference of the tube cover 6 for cooling. is there. In the structure in which the cooling means cools from the outer periphery of the cover, the cooling capacity is limited. Moreover, since a space for circulating a cooling medium of gas or liquid is required around the laminated piezoelectric body, the advantage of a small actuator is lost.

The present invention has been made for the purpose of solving the above-mentioned problems, and the problem to be solved is to provide a mechanism capable of reliably and efficiently cooling the laminated piezoelectric body, requiring almost no cooling space. Another object is to provide a laminated piezoelectric body having the same.

[0007]

[Means for Solving the Problems]

 The laminated piezoelectric body of the present invention comprises a laminated piezoelectric body in which a plurality of piezoelectric plates and electrode plates are alternately laminated, and external electrodes for connecting the ears of each electrode plate protruding to the side surface of the laminated body are provided. In the above, the external electrode is hollow and the cooling medium is circulated in the external electrode.

The external electrode means one that electrically connects the electrode plates on the same polarity side of the laminated piezoelectric body (also referred to as side electrode). In the present invention, the external electrode is a metal pipe. Something like that is used. The shape and area of the cross section of the cavity are appropriately selected depending on the size of the laminated piezoelectric material, the required accuracy of function, usage conditions and the like.

Considering only electrical connection, each of the above electrode plates has one ear for connecting to an external electrode, and two external electrodes (one for cathode and one for anode) are sufficient. .. However, in order to improve the cooling capacity, it is preferable to provide a large number of ears on the periphery of the electrode plate and connect the electrode plate to a large number of external electrodes through which the cooling medium flows.

Each of the electrode plates alternately laminated with the piezoelectric plate is connected to each of the outer electrodes on the anode side and the cathode side alternately. Therefore, if an electrode plate having, for example, two ears is used as the electrode plate, two external electrodes are provided, two on the cathode side and two on the anode side. In that case, the cooling medium may flow through an independent path for each external electrode, but the ends of each external electrode are connected with an insulating hose to form one continuous flow path for all external electrodes. Is preferred.

The cooling medium is not particularly limited as long as it is a non-conductive fluid, and may be a gas such as air or freon, or a liquid such as methylene chloride, trichlorobenzene or oils and fats. Insulating oil used for electrical insulation, removal of generated heat, and cooling in electrical products such as transformers, capacitors, and circuit breakers is preferable. For example, conventionally used petroleum-based mineral oils and recently used alkylbenzene-based, polybutene-based, alkylnaphthalene-based, alkyldiphenylethane-based, and silicone oil-based insulating oils can be mentioned.

[0012]

[Action]

 In the laminated piezoelectric material having the above-described structure, when the cooling medium is circulated in the external electrode, the electrode plate connected to the external electrode is cooled. This cooled electrode plate prevents the temperature rise of the piezoelectric plate due to self-heating or the external environment temperature. Compared with the conventional structure in which the insulation protection tube covering the laminated piezoelectric body is cooled from the outer circumference, the structure in which the piezoelectric plate is directly cooled by the electrode plates alternately stacked with the piezoelectric plate has a higher cooling efficiency. The configuration in which the cooling medium is further increased and the cooling medium is circulated in the hollow external electrode enables downsizing of the device of the laminated piezoelectric body.

[0013]

【Example】

 An embodiment of the laminated piezoelectric material of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2, the laminated piezoelectric body of the present embodiment is a stack (laminated body) in which a large number of piezoelectric plates 2, 2 ... And a large number of electrode plates (internal electrodes) 3, 3 are alternately stacked. ) And six external electrodes 4, 4 ... (41, 42, 43, 44, 45, 46) provided in parallel on the outer peripheral side surface of the stack at equal intervals.

The piezoelectric plate 2 is prepared by mixing PbO, ZrO ₂ and TiO ₂ in a predetermined ratio according to a conventional method, calcining, press-molding, firing, polishing, forming a silver electrode film on the surface, and polarization. A PZT piezoelectric plate in the form of pellets (a disk having a diameter of about 15 mm and a thickness of about 0.5 mm) manufactured by the treatment, which expands and contracts in the thickness direction by the increase and decrease of the applied voltage.

The electrode plate 3 is made of stainless steel (SUS), and has disc-shaped body portions with ears 31, 31, 31 protruding in three directions. The diameter of the disk-shaped main body of the electrode plate 3 is almost the same as the size of the silver electrode film 21 (see FIG. 3) formed on the surface of the piezoelectric body, and the ears 31, 31, ... The electrode plates 3, 3 ... Are welded to the external electrodes 41, 43, 45 or 42, 44, 46 so as to have the same potential. The laminated electrode plates 3, 3, ... Are arranged such that one connected to the external electrodes 41, 43, 45 and one connected to the counter electrodes external electrodes 42, 44, 46 are arranged every other sheet. Become .

The external electrode 4 is not a simple rod-shaped electrode, but is made of a metal pipe having an elliptical cross section. One end of each of two adjacent pipes (external electrodes) serves as an inlet and an outlet for the cooling medium, and an insulating resin hose (for example, vinyl pipe) is provided at the end of the other adjacent pipe (external electrode 4). A cooling medium flow path is formed by the six external electrodes 41 to 46, which are connected and connected to each other.

The laminated piezoelectric body configured as described above is attached to the inside of the actuator assembly case by being coated with a heat-shrinkable tube on the outer periphery and connected to a pipe from a cooling medium circulation pump. When it is operated as an actuator, as shown in FIG. 3, silicone oil of a predetermined temperature flows as a cooling medium 5 at an appropriate flow rate in the external electrodes 4, 4, ... Of the laminated piezoelectric body. To be done. When a voltage is applied to the piezoelectric plates 2, 2 by the electrode plates 3, 3, ..., The piezoelectric plates 2, 2, ... Self-heat, but the heat is generated from the electrode plates 3, 3 ,. Since it escapes to 5, the piezoelectric body is kept at a substantially constant temperature.

[0018]

[Effect of the device]

 As is clear from the above description, the laminated piezoelectric body of the present invention has a structure that absorbs heat from the electrode plate that is in contact with the piezoelectric plate that is the source of heat generation. The cooling efficiency is much better than that of the cooling structure. That is, the heat of the piezoelectric body is quickly and reliably absorbed by the cooling medium, and the temperature change of the piezoelectric body becomes small. Therefore, the laminated piezoelectric body functions more accurately in relation to the voltage-displacement amount. In addition, since the cooling medium is circulated in the external electrode to cool it, a cooling space and a cooling medium flow path are provided on the side where the laminated piezoelectric body is installed, and the cooling medium flow method is devised. There is no need to do it. Therefore, the design can be simplified, and the actuator can function as a further downsized actuator, sensor, or the like.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a laminated piezoelectric material of the present invention.

FIG. 2 is a horizontal sectional view of the piezoelectric body shown in FIG.

FIG. 3 is a partially enlarged sectional view of the piezoelectric body.

FIG. 4 is a sectional view showing a basic structure of a conventional laminated piezoelectric material.

FIG. 5 is a cross-sectional view for explaining an example of a conventional piezoelectric body cooling method.

FIG. 6 is a sectional view for explaining another example of a conventional method for cooling a piezoelectric body.

[Explanation of symbols]

 1 Laminated Piezoelectric Body 2 Piezoelectric Plate 3 Electrode Plate 31 Ear 4 (41, 42, 43, 44, 45, 46) External Electrode 5 Cooling Medium

Claims (1)

[Scope of utility model registration request] 1. A laminated piezoelectric body comprising a plurality of piezoelectric plates and electrode plates, which are alternately laminated, and external electrodes for connecting the ears of the respective electrode plates protruding to the side surface of the laminated body are provided. A laminated piezoelectric body having a hollow structure in which a cooling medium is circulated in an external electrode.