JP2008243924A - Laminated type piezoelectric actuator element and laminated type piezoelectric actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated type piezoelectric actuator element capable of making its reliability better than that of conventional devices, without causing enlarging of the element, and to provide a laminated type piezoelectric actuator. <P>SOLUTION: A plurality of armored electrodes 6 and 6 and ones 7 and 7, each serving as a pole, are fitted so as to be connected at least at two places or more which are separated from internal electrodes 3 and 4 in a single layer at each conductive location, and external electrodes 10 and 11 are connected so that the plurality of electrodes 6 and 6 and outer-sheath electrodes 7 and 7 have the same polarity by the external electrodes 10 and 11, configured of a single member for the outer-sheath electrodes 6 and 6 and the electrodes 7 and 7, each serving as a pole. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a multilayer piezoelectric actuator element and a multilayer piezoelectric actuator, and more particularly to a multilayer piezoelectric actuator element and a multilayer piezoelectric actuator suitable as a drive source for a fuel injection injector or the like.

  2. Description of the Related Art In recent years, a stacked piezoelectric actuator element using a stacked body in which a plurality of piezoelectric layers that expand in response to an applied voltage and internal electrodes for supplying an applied voltage are alternately stacked has been developed and put into practical use. In such a multilayer piezoelectric actuator element, it is necessary to provide an external electrode electrically connected to each internal electrode, and even if the multilayer piezoelectric actuator element is repeatedly expanded and contracted, the external electrode and the internal electrode The structure must be able to maintain electrical connection.

For this reason, the laminated body of the structure which formed the exterior electrode (base electrode) formed from the electrically conductive paste etc. in the side surface of the laminated body, and connected this exterior electrode and the extensible external electrode formed in the metal mesh form A type piezoelectric actuator element is known (see, for example, Patent Document 1). A multilayer piezoelectric actuator element having a configuration in which a plurality of external electrodes having the same polarity are provided and lead wires are respectively connected to the external electrodes is also known (see, for example, Patent Document 2).
JP 2002-261339 A JP-A-5-226721

  In the multilayer piezoelectric actuator element using the above-described exterior electrode and the external electrode formed in a metal mesh shape, when repeated driving, damage such as a crack occurs in a part of the exterior electrode, and the internal electrode and the exterior electrode The electrical connection may be lost. In such a state, there is a problem that a voltage is not applied to a part of the piezoelectric layer and the displacement amount during driving is reduced. In addition, a discharge may occur between the internal electrode that has lost its electrical connection and the exterior electrode or the external electrode. This discharge may cause malfunction or radio wave noise due to the discharge. It was.

  Further, in the laminated piezoelectric actuator element having a configuration in which a plurality of external electrodes are provided and lead wires are connected to these external electrodes, if the connection portion between the external electrode and the lead electrode is provided on the exterior electrode, the lead wire Since it is easy to peel off, in order to ensure the reliability of the connection between the external electrode and the lead wire, the external electrode is intentionally enlarged or the element is lengthened so that the connection point between the external electrode and the lead wire is on the exterior electrode. It is necessary to provide it so as not to be arranged in the area. In such a case, there is a problem that the element becomes large.

  The present invention has been made in response to such a conventional situation, and provides a multilayer piezoelectric actuator element and a multilayer piezoelectric actuator capable of improving reliability as compared with the conventional one without causing an increase in size of the element. It is something to try.

    The laminated piezoelectric actuator element of the present invention includes a laminated body in which a plurality of piezoelectric layers and internal electrodes are alternately laminated, a side surface of the laminated body that is electrically connected to the internal electrode, and a positive electrode. In a stacked piezoelectric actuator element comprising an exterior electrode having a negative electrode and an external electrode electrically connected to the exterior electrode, each exterior electrode serving as each pole is a single layer of the internal electrode as a conduction destination A plurality of such electrodes are connected to each other at least at two or more positions apart from each other, and the plurality of electrodes have the same polarity by the external electrode configured as a single member with respect to the exterior electrode serving as each pole. Further, the external electrode is connected.

  In the multilayer piezoelectric actuator element of the present invention having the above-described configuration, a plurality of the exterior electrodes serving as the respective poles are provided so as to be connected at least at two or more locations separated from the internal electrode of one layer of the conduction destination, The external electrodes are connected so that a plurality of the electrodes have the same polarity by the external electrodes configured by a single member with respect to the exterior electrodes serving as the respective electrodes. Thus, by providing a plurality of same-polarity exterior electrodes with respect to one layer of the internal electrode, even if one exterior electrode is damaged and electrical connection with the internal electrode is lost, The electrical connection to the internal electrode can be maintained by the other exterior electrode, and the reliability can be improved. Moreover, since the external electrode comprised by the single member is connected with respect to the some same exterior electrode, the enlargement of an element is not caused.

  In the multilayer piezoelectric actuator element described above, it is possible to arrange an external connection terminal electrically connected to the external electrode between the plurality of same-polarity exterior electrodes. For this reason, the reliability of the connection between the external electrode and the external connection terminal can be ensured without enlarging the exterior electrode or the element. Furthermore, when the laminated body is viewed in a cross section perpendicular to the laminating direction, the external connection terminal can be disposed near the approximate center of the side face of the laminated body. As a result, it is possible to reduce the size as compared with the case where the external connection terminals are arranged in the vicinity of the end of the side surface of the laminate. Furthermore, if the external connection terminal is arranged between the external electrode and the laminated body, the size can be further reduced.

  In the above laminate, the cross-sectional shape perpendicular to the stacking direction can be a polygonal shape, for example, a quadrangular shape. In this case, a plurality of same-polarity exterior electrodes can be formed on the same side surface of the laminate. . Moreover, when the cross-sectional shape of such a laminated body is a shape having more corners such as an octagonal shape, a plurality of same-polarity exterior electrodes can be formed on different side surfaces of the laminated body.

  The multilayer piezoelectric actuator of the present invention described above can be housed in a case and configured as a multilayer piezoelectric actuator.

  ADVANTAGE OF THE INVENTION According to this invention, the laminated piezoelectric actuator element and laminated piezoelectric actuator which can aim at the improvement of reliability compared with the past can be provided, without causing the enlargement of an element.

  Hereinafter, details of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view schematically showing an overall schematic configuration of a multilayer piezoelectric actuator element according to an embodiment of the present invention. As shown in FIG. 1, a multilayer piezoelectric actuator element 1 is formed by alternately laminating a plurality of piezoelectric layers 2 made of piezoelectric ceramic such as lead zirconate titanate (PZT) and conductive internal electrodes 3 and 4. The structured laminate 5 is provided. In FIG. 1 and the like, the number of stacked layers of the stacked body 5 is omitted and reduced. However, in the actual stacked piezoelectric actuator element 1, for example, a large number of stacked layers such as several tens to several hundred layers are used. It has become.

  The internal electrodes 3 and 4 are alternately arranged in the stacking direction, and the piezoelectric layer 2 is sandwiched between the internal electrode 3 and the internal electrode 4. These internal electrodes 3 are used as electrodes having the same polarity (for example, positive electrode), and the internal electrodes 4 are used as electrodes having the same polarity (for example, negative electrode).

  The internal electrode 3 is formed up to its end so that one side is exposed on one side surface (the left side surface in FIG. 1) of the multilayer body 5, and the other side of the internal electrode 3 is the multilayer body. 5 is formed up to a predetermined distance from the other side surface (right side surface in FIG. 1) so as not to be exposed on the other side surface of the laminate 5. On the other hand, the internal electrode 4 is formed up to its end so that the other side is exposed on the other side surface (the right side surface in FIG. 1) of the multilayer body 5. The laminated body 5 is formed up to a predetermined distance from one side surface (the left side surface in FIG. 1) and is configured not to be exposed on one side surface of the laminated body 5. By configuring the internal electrodes 3 and 4 in this way, the internal electrodes 3 and 4 having different polarities are not electrically short-circuited.

  Exterior electrodes 6 and 7 having a positive electrode and a negative electrode are formed on the side surfaces on both sides of the laminate 5. As will be described later, these exterior electrodes 6 and 7 are formed by patterning a conductive paste by screen printing or the like, for example. As shown in FIGS. 2 and 3, the same-polarity exterior electrodes 6 and 7 are connected to the internal electrode 3 or the internal electrode 4 of the conduction layer at least at two or more locations separated from each other. A plurality of (in the example shown in FIGS. 2 and 3, two exterior electrodes 6 and 6 (for example, positive electrode) and exterior electrodes 7 and 7 (for example, negative electrode)) are provided.

  As shown in FIG. 3, (one) external electrode 10 composed of a single member is electrically connected to one of the plurality of same-polarity exterior electrodes 6, 6, and the other plurality of The external electrodes 11 made of a single member are electrically connected to the same-polarity exterior electrodes 7, 7. The external electrode 10 is connected to the exterior electrodes 6 and 6 by the solder layer 8, and the external electrode 11 is connected to the exterior electrodes 7 and 7 by the solder layer 9. In this way, the external electrode 10 is electrically connected to the internal electrode 3, and the external electrode 11 is electrically connected to the internal electrode 4. The external electrodes 10 and 11 are formed from a conductive member, for example, in a mesh shape, and can be deformed according to the expansion and contraction of the multilayer body 5. For example, it is composed of a metal mesh, expanded metal, or the like. These external electrodes 10 and 11 are provided with, for example, lead wires 12 and 13 as external connection terminals for electrical connection with the outside. The lead wire 13 is disposed between the outer electrodes 7 and 7 so that the lead wire 12 is positioned between the outer electrodes 6 and 6. In the present embodiment, the cross-sectional shape perpendicular to the stacking direction of the stacked body 5 is a square shape, the exterior electrodes 6 and 6 are formed on the same side surface, and the exterior electrodes 7 and 7 are also on the opposite side. It is formed on the same side.

  As described above, in the present embodiment, the exterior electrodes 6, 6 and the exterior electrodes 7, 7 serving as the respective poles are at least two locations that are separated from the internal electrodes 3, 4 in one conduction destination. A plurality are provided to connect. And the external electrode 10 comprised by the single member is connected so that these may become the same polarity with respect to the exterior electrodes 6 and 6, and these may become the same polarity with respect to the exterior electrodes 7 and 7. The external electrode 11 made of a single member is connected. In this way, by providing a plurality of same-polarity exterior electrodes 6, 6 and exterior electrodes 7, 7 with respect to one layer of the internal electrodes 3, 4, damage occurs to one exterior electrode 6, exterior electrode 7. Even when the electrical connection with the internal electrodes 3 and 4 is lost, the electrical connection to the internal electrodes 3 and 4 can be maintained by the other exterior electrode 6 and exterior electrode 7, and reliability is improved. Can be improved. In addition, external electrodes 10 and 11 made of a single member are connected to a plurality of same-polarity exterior electrodes 6 and 6 and exterior electrodes 7 and 7, and lead wires 12 and the like as external connection terminals are also included. Since only one is required for each pole, the size of the element is not increased.

  Further, as shown in FIG. 3, the external connection terminals composed of the lead wires 12 and 13 and the like are positioned between the exterior electrodes 6 and 6 and between the exterior electrodes 7 and 7, that is, a cross section perpendicular to the stacking direction. In FIG. 4, the laminated body 5 is disposed near the center of the side surface. On the other hand, for example, as shown in FIG. 7, in a conventional multilayer piezoelectric actuator element having one exterior electrode 6 and one exterior electrode 7, external connection terminals composed of lead wires 12, 13, etc. Must be located near the edge of the side. That is, since the exterior electrode 6 and the external electrode 10 and the exterior electrode 7 and the external electrode 11 are connected by solder, in order to ensure the reliability of the connection between the lead wires 12 and 13 and the external electrodes 10 and 11. This is because it is necessary to solder the lead wires 12 and 13 to the external electrodes 10 and 11 except for these connection portions (on the exterior electrodes 6 and 7).

  Then, as shown in FIG. 3, the lead wires 12 and 13 are arranged in the vicinity of the center of the side surface of the multilayer body 5, and as shown in FIG. Comparing with the case, for example, when the multilayer piezoelectric actuator 1 is accommodated in a case or resin-molded so that the outer shape is cylindrical, the lead wires 12 and 13 are arranged at substantially the center of the side surface of the multilayer body 5. In the case of being arranged in the vicinity, the diameter can be made smaller and the size can be reduced. This is advantageous particularly when the multilayer piezoelectric actuator 1 is housed in a cylindrical cylindrical body, such as when the multilayer piezoelectric actuator 1 is used as a drive source such as a fuel injection injector. Further, in the conventional multilayer piezoelectric actuator element, the external electrodes 10 and 11 may extend from the exterior electrodes 6 and 7 in the stacking direction, and the lead wires 12 and 13 may be soldered to the external electrodes 10 and 11 at the portions. However, even in that case, the element becomes longer and larger. On the other hand, in the multilayer piezoelectric actuator element 1 of the present invention, it is possible to ensure the reliability of connection between the lead wires 12 and 13 and the external electrodes 10 and 11 without lengthening the element.

  FIG. 3 shows a case where the cross-sectional shape perpendicular to the stacking direction of the laminate 5 is a square shape. For example, as shown in FIG. 4, the cross-sectional shape perpendicular to the stacking direction of the laminate 5 is Furthermore, it is good also as a polygonal shape with many corners. In the example illustrated in FIG. 4, the cross-sectional shape is substantially an octagonal shape such that the four corners of the quadrangular shape are chamfered. In the example shown in FIG. 4, the exterior electrodes 6, 6 and the exterior electrodes 7, 7 are arranged on different side surfaces instead of the same side surface of the laminate 5, and these exterior electrodes 6, 6, In addition, external electrodes 10 and 11 having a circular cross-sectional shape are provided so as to connect the exterior electrodes 7 and 7. That is, the plurality of exterior electrodes 6, 6 and the exterior electrodes 7, 7 having the same polarity are connected to the inner electrodes 3, 4 of the conduction destination on different (at least two or more) side surfaces. The lead wires 12 and 13 as external connection terminals are near the center of the side surface (side surface where the exterior electrodes 6 and 7 are not formed) of the multilayer body 5, and the multilayer body 5 and the external electrodes 10 and 11. It is arranged between. With such a configuration, when the multilayer piezoelectric actuator 1 is housed in a case or resin-molded so that the outer shape is a cylindrical shape, the diameter can be reduced and the size can be reduced. Become. In addition, since the plurality of same-polarity exterior electrodes 6 and 6 and exterior electrodes 7 and 7 are formed on different side surfaces, the connection reliability between the internal electrodes 3 and 4 and the exterior electrodes 6 and 7 can be further improved. Can be improved.

  As described above, in the multilayer piezoelectric actuator element 1 of the present embodiment, the reliability can be improved as compared with the conventional one without causing an increase in the size of the element. In the present invention, the plurality of exterior electrodes 6, 6 and the exterior electrodes 7, 7 may be formed so as to be connected to at least two separated positions with respect to the single-layer internal electrodes 3, 4. . The reason for this is that if the connection points to the internal electrodes 3 and 4 are separated, even if a crack or the like occurs in one connection point, the crack does not propagate to the other connection point. This is because the possibility that the crack propagates to the whole and the connection is lost increases. Therefore, for example, as shown in FIG. 5, the exterior electrodes 6, 6 and the exterior electrodes 7, 7 may be connected by an inactive region (region that does not contribute to expansion and contraction) at the end of the stacked body 5. . Further, the number of exterior electrodes is not limited to two with respect to the same polarity, and may be three or more.

  Next, an example of a method for manufacturing the multilayer piezoelectric actuator element 1 will be described. First, the prepared composition PZT mixed powder is heat-treated at a temperature of 600 to 1000 ° C. for about 1 to 10 hours to prepare a calcined powder.

  Next, calcined powder, polyvinyl butyral resin, and DOP (di-2-ethylhexyl phthalate) are mixed and pulverized, a sheet is produced by a doctor blade method, and cut into a predetermined size suitable for processing.

  In addition, ethyl cellulose, butyl carbitol or terpineol is added and mixed in advance with AgPd powder to prepare a conductive paste.

  The conductive paste is patterned on the obtained sheet by screen printing to form internal electrodes.

  Next, a plurality of the above sheets are appropriately laminated so as to have a desired structure to form a columnar body, and then degreased and fired.

  Next, a silver-based paste is printed on the side surface of the columnar body and baked at 600 to 800 ° C., and the exterior electrodes that become the respective electrodes after forming the external electrodes as shown in FIG. A plurality of exterior electrodes are formed so as to be connected to at least two positions separated from each other. After that, a solder paste is applied on the outer electrode to be each electrode, and a metal mesh external electrode composed of a single member is placed on the outer electrode so that the outer electrode has the same polarity. The solder is dissolved by reflow to connect the exterior electrode and the external electrode. Then, as shown in FIG. 3, an external connection terminal such as a lead wire is soldered near the center of the external electrode.

  The multilayer piezoelectric actuator element 1 is manufactured by the manufacturing process as described above. FIG. 6 shows a configuration of a multilayer piezoelectric actuator 100 including the multilayer piezoelectric actuator element 1 having the above configuration. The multilayer piezoelectric actuator 100 includes a multilayer piezoelectric actuator element 1 and a case 101 that houses the multilayer piezoelectric actuator element 1.

  One end face (upper end face in FIG. 6) of the multilayer piezoelectric actuator element 1 in the expansion / contraction direction (stacking direction of the multilayer body 5) is engaged with the back cover 102 of the case 101. Further, a push rod 103 is connected to the other end surface (lower end surface in FIG. 6) in the expansion / contraction direction of the multilayer piezoelectric actuator element 1, and this push rod 103 is connected to the case 101 via a leaf spring 104. The front lid 105 is locked. The tip of the push rod 103 is disposed so as to protrude from an opening 106 provided in the front lid 105. Further, the lead wires 12 and 13 of the multilayer piezoelectric actuator element 1 are fixed to the case 101 and the back cover 102 via a sleeve 107.

  In the multilayer actuator 100 having the above-described configuration, a high voltage is applied from a drive circuit (not shown) via the lead wires 12 and 13, whereby the multilayer piezoelectric actuator element 1 expands and contracts in the vertical direction on the order of, for example, several tens of micrometers. . This expansion and contraction is transmitted as a displacement to an injector valve (not shown) or the like via the push rod 103.

  While the present invention has been described in detail based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made without departing from the scope of the present invention.

The figure which shows typically the structure of the longitudinal cross-section direction of the lamination type piezoelectric actuator element of one Embodiment of this invention. FIG. 2 is a diagram showing a configuration of an exterior electrode of the multilayer piezoelectric actuator element of FIG. The figure which shows typically the structure of the cross-sectional direction of the lamination type piezoelectric actuator element of FIG. The figure which shows typically the structure of the cross-sectional direction of the laminated piezoelectric actuator element of other embodiment. The figure which shows the structure of the modification of an exterior electrode. The figure which shows typically the structure of the longitudinal cross-section direction of the lamination type piezoelectric actuator of one Embodiment of this invention. The figure which shows the structure of the conventional lamination type piezoelectric actuator element.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Laminated piezoelectric actuator element, 2 ... Piezoelectric layer, 3, 4 ... Internal electrode, 5 ... Laminated body, 6, 7 ... Exterior electrode, 8, 9 ... Solder layer, 10, 11 ... External electrode 12, 13, ... Lead wire.

Claims (6)

A laminate formed by alternately laminating a plurality of piezoelectric layers and internal electrodes; an exterior electrode formed on a side surface of the laminate and electrically connected to the internal electrode; and having a positive electrode and a negative electrode; and the exterior In a laminated piezoelectric actuator element comprising an external electrode electrically connected to an electrode,
A plurality of the exterior electrodes serving as the respective poles are provided so as to be connected at least at two or more locations separated from the internal electrode of the first layer of conduction,
A laminated piezoelectric device characterized in that the external electrodes are connected to each other so that a plurality of the electrodes have the same polarity by the external electrodes configured by a single member with respect to the exterior electrode serving as each electrode Actuator element. The multilayer piezoelectric actuator element according to claim 1,
A laminated piezoelectric actuator element comprising an external connection terminal positioned between a plurality of the same-polarity exterior electrodes and electrically connected to the external electrode. The multilayer piezoelectric actuator element according to claim 2,
The multilayer piezoelectric actuator element, wherein the external connection terminal is disposed between the external electrode and the multilayer body. It is a lamination type piezoelectric actuator element given in any 1 paragraph of Claims 1-3,
The multilayer piezoelectric actuator is characterized in that a cross-sectional shape perpendicular to the stacking direction is a polygonal shape, and a plurality of the same-polarity exterior electrodes are formed on the same side surface of the multilayer body. element. It is a lamination type piezoelectric actuator element given in any 1 paragraph of Claims 1-3,
The laminated body has a polygonal cross-sectional shape perpendicular to the laminating direction, and a plurality of the same-polarity exterior electrodes are formed on different side surfaces of the laminated body. . The laminated piezoelectric actuator element according to any one of claims 1 to 5,
A multilayer piezoelectric actuator comprising a case for housing the multilayer piezoelectric actuator element.

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