JP2008061344A - Ultrasonic motor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic motor element with high productivity, where large power can be obtained with low voltage driving and feeding terminal electrodes can be collectively formed on one side. <P>SOLUTION: The ultrasonic motor element 10 is provided with a laminated body where piezoelectric boards 12 and internal electrodes are alternately laminated. The internal electrode has a driving electrode and a ground electrode 18. The driving electrode is provided with a first driving electrode 14 formed of first electrode parts 14a to 14d of two rows and two columns and a first electrode connection part 14e connecting the first electrode parts 14b and 14c which are diagonally positioned, and with a second driving electrode 16 formed of second electrode parts 16a to 16d of two rows and two columns and a second electrode connection part 16e connecting the second electrode parts 16a and 16d which are diagonally positioned. A first external electrode 24 connecting the ground electrodes 18, second external electrodes 26a and 26b connecting the conductive first electrode parts 14b and 14c and the isolated second electrode parts 16b and 16c and third external electrodes 28a and 28b connecting the isolated first electrode parts 14a and 14c and the conductive second electrode parts 16a and 16d are installed on a side of the laminated body. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ultrasonic motor element using a piezoelectric element suitable for a linear motor, an XY stage, or the like.

  An ultrasonic motor element that drives a piezoelectric element in the L1B2 resonance mode is known, and has recently been applied to a drive mechanism such as an XY stage, a linear motor, a rotary stage, and an autofocus mechanism of a camera (for example, (See Patent Documents 1 and 2).

  FIG. 3 shows an explanatory diagram of the L1B2 resonance mode in the piezoelectric element 90. The L1B2 resonance mode is generated by superposition (degeneration) of the expansion / contraction primary resonance (L1) mode in the longitudinal direction shown in the upper side of FIG. 3 and the bending secondary resonance (B2) mode in the width direction shown in the lower side of FIG. This is a resonance in which the belly part of the body performs an elliptical motion.

  In the ultrasonic motor element driven in the L1B2 resonance mode, two rows and two columns of electrode portions are formed on one main surface of the piezoelectric plate, and the two electrode portions positioned diagonally are connected by lead wires, A ground (earth) electrode is provided on the other main surface, and a sliding member that is in contact with the driven object is provided on the side surface of the piezoelectric plate. Voltages with phases shifted by 90 degrees are applied to the two sets of electrode portions. Apply and drive.

  As shown in FIG. 4A, when the sliding members 92 that are in contact with the driven body 94A are provided on both ends of the long side of the piezoelectric element 90, an ellipse whose phase is shifted by 180 degrees in each sliding member 92. A motion is generated, and a frictional force acts alternately on the driven body 94A to move the driven body 94A. The movement of the piezoelectric element 90 shown in FIG. 4B is the same as that of the piezoelectric element 90 shown in FIG. 4A. However, as shown in FIG. 4B, a sliding member 92 is provided at the center of the short side of the piezoelectric element 90. Also in this case, the sliding member 92 can be caused to have an elliptical motion. The driven body 94B shown in FIG. 4B is a rotating disk, and FIG. 4B shows a form that rotates counterclockwise.

  In the ultrasonic motor element disclosed in Patent Document 1, a single plate is used as the piezoelectric plate, and therefore, a certain thickness is required for the piezoelectric plate in order to provide a sliding portion on the side surface of the piezoelectric plate. As a result, the drive voltage increases. Further, there is a problem that it is difficult to reduce the size during integration because of the lead wire attached to the main surface of the piezoelectric plate.

  Patent Document 2 discloses an ultrasonic motor element having a laminated structure including a through-hole electrode as an ultrasonic motor element having a laminated structure of the ultrasonic motor element disclosed in Patent Document 1. It is possible to reduce the size and drive voltage. However, many piezoelectric plates (green sheets) with different electrode patterns must be manufactured, and in order to ensure conduction of the through-hole electrodes in the stacking direction, it is necessary to reliably apply the electrodes to the inner surface of the through-holes. There is a demerit that it takes time and effort to manufacture. In addition, a wide piezoelectric inactive non-driving region is formed at the central portion of the piezoelectric plate, and this portion is considered to suppress displacement. Furthermore, since the through-hole electrode is formed, the electrode must be taken out from the end face in the stacking direction because of the structure.

Patent Document 2 discloses a laminated ultrasonic motor element that is further characterized by the routing of the external electrode. However, the number of external terminals increases, and it takes time to connect the ultrasonic motor element. There is a problem that it becomes complicated.
JP-A-7-184382 (FIG. 1, paragraphs [0029] to [0031], etc.) Japanese Unexamined Patent Publication No. 2006-94A597 (FIGS. 1, 3, 7, etc.)

  The present invention is an ultrasonic motor element using a piezoelectric element, has high productivity, can obtain a large power by low-voltage driving, and can be formed by concentrating power supply terminal electrodes on one side surface. An object is to provide an ultrasonic motor element.

  The ultrasonic motor element according to the present invention includes a laminated body in which piezoelectric plates and internal electrodes are alternately stacked, and the internal electrodes include drive electrodes and ground electrodes provided in every other layer. The drive electrode includes a first drive electrode having four first electrode portions arranged in two rows and two columns, and four first electrodes arranged in two rows and two columns so as to correspond to the four first electrode portions. The second drive electrode has two electrode portions, and the first drive electrode and the second drive electrode are alternately arranged in the stacking direction. The first drive electrode further includes a first electrode communication portion that connects two first electrode portions located at one diagonal of the four first electrode portions in the electrode plane, and the second drive electrode Among the four second electrode parts, two second electrode parts located at diagonal opposite to the diagonals of the two first electrode parts that are conductive in the electrode surface of the first drive electrode are electrode surfaces. It further has the 2nd electrode communication part made to conduct in. The ground electrode is formed so as to include regions corresponding to the four first electrode portions. And on the side surface of the laminate, there are two isolated first electrodes that are connected to each other by the ground electrode, the two first electrode portions that are connected by the first electrode communication portion, and the second electrode communication portion that are not connected by the second electrode communication portion. A second external electrode that connects the two second electrode portions, two isolated first electrode portions that are not connected by the first electrode communication portion, and two second electrode portions that are connected by the second electrode communication portion, A third external electrode is provided to connect the two. Preferably, the first electrode communication portion and the second electrode communication portion are formed in regions that overlap each other when viewed from the stacking direction.

  In the ultrasonic motor element of the present invention, the power supply terminal electrode for applying the drive voltage to the internal electrode can be constituted by three of the first to third external electrodes. The second and third external electrodes are formed on the two side surfaces of the ultrasonic motor element, respectively, but one formed on one of the side surfaces may be used as the power supply terminal electrode, so that power can be supplied from one side surface. .

  Further, by forming the first electrode communication portion and the second electrode communication portion in a region overlapping each other when viewed from the stacking direction, the L1 resonance can be amplified in the central portion of the ultrasonic motor element, and a large displacement is obtained. be able to.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. A schematic plan view of the ultrasonic motor element 10 is shown in FIG. 1A, and schematic side views thereof are shown in FIGS. 1B and 1C. As shown in FIGS. 1A to 1C, the length direction of the ultrasonic motor element 10 is defined as the Y direction, the width direction is defined as the X direction, and the thickness direction is defined as the Z direction.

  The ultrasonic motor element 10 includes a laminate 20 in which piezoelectric plates 12 and internal electrodes (including first drive electrodes 14, second drive electrodes 16, and ground electrodes 18 described later) are alternately laminated. . This internal electrode includes drive electrodes (including the first drive electrode 14 and the second drive electrode 16) and the ground electrode 18 provided in every other layer. 1B and 1C, only the portion of the internal electrode exposed on the side surface is shown, and the shape of the internal electrode will be described in detail later with reference to FIG.

  Sliding members 22 are attached to both ends of the long side surface of the laminate 20, and the sliding members 22 are brought into contact with the driven body 50. The driven body 50 is slidably held in the length direction of the guide rail 52.

  As the sliding member 22, a wear-resistant material (for example, an alloy material such as stainless steel or a ceramic material such as silicon carbide) is preferably used, and is attached to the laminate 20 with an epoxy resin or the like.

  The configuration of the laminate 20 will be described in detail. FIG. 2 shows the structure of the piezoelectric plate and the internal electrodes constituting the ultrasonic motor element 10. From the lowermost layer of the ultrasonic motor element 10 to the uppermost layer, in FIG. Further, in FIG. 2, the internal electrode patterns immediately above the piezoelectric plates 12a to 12j are shown. For example, it can be seen that a ground electrode 18 is formed between the piezoelectric plates 12a and 12b as shown by the piezoelectric plate 12a.

  Between the piezoelectric plates 12b and 12c, as shown in the piezoelectric plate 12b, the first drive electrode 14 is disposed. The first drive electrode 14 includes four first electrode portions 14a to 14d arranged in two rows and two columns, and two first electrode portions 14a to 14d located at one diagonal of the four first electrode portions 14a to 14d. It has the 1st electrode communication part 14e which makes the electrode parts 14b and 14c conduct | electrically_connect in an electrode surface.

  Each of the first electrode portions 14 a to 14 d has a convex portion extending to the side surface of the piezoelectric plate 12 b, and this convex portion is exposed on the side surface of the multilayer body 20. The exposed portion is shown in FIGS. 1B and 1C.

  Between the piezoelectric plates 12d and 12e, the second drive electrode 16 is disposed as shown in the piezoelectric plate 12d. The second drive electrode 16 includes four second electrode portions 16a to 16d6 arranged in two rows and two columns so as to correspond to the four first electrode portions 14a to 14d, and the four second electrode portions 16a to 16d. 16d, two second electrode portions 16a and 16d that are located opposite to the diagonal of the two first electrode portions 14b and 14c that are conductive in the electrode surface of the first drive electrode 14 are electrode surfaces. It has the 2nd electrode communication part 16e connected inside.

  Each of the second electrode portions 16 a to 16 d also has a convex portion extending to the side surface of the piezoelectric plate 12 d, and such convex portion is exposed on the side surface of the multilayer body 20. The exposed portion is shown in FIGS. 1B and 1C.

  The first electrode communication portion 14e and the second electrode communication portion 16e are formed in a region where most of the portions overlap each other when viewed from the stacking direction.

  A ground electrode 18 is provided between the piezoelectric plates 12a and 12b. The ground electrode 18 includes a region corresponding to the four first electrode portions 14 a to 14 d (this region does not include a convex portion for exposure to the side surface of the ultrasonic motor element 10). The ground electrode 18 is also provided with a convex portion extending to the side surface of the piezoelectric plate 12 a, and such a convex portion is exposed on the side surface of the laminate 20. The exposed portion is shown in FIGS. 1B and 1C.

  In the ultrasonic motor element 10, the structure portion from the piezoelectric plate 12a to the piezoelectric plate 12e and the structure portion from the piezoelectric plate 12e to the piezoelectric plate 12i are apparent when the piezoelectric plate 12e overlaps the piezoelectric plate 12a. Have the same structure. The piezoelectric plate 12j is provided to protect the ground electrode 18 provided between the piezoelectric plate 12i and the piezoelectric plate 12j.

  As shown in FIG. 1B, a portion of the side surface of the stacked body 20 where the ground electrode 18 is exposed is provided with a first external electrode 24 for connecting them. Further, a second external electrode 26a for connecting the first electrode portion 14b and the second electrode portion 16b on the same side surface of the multilayer body 20 is provided. Further, a third external electrode 28a for connecting the first electrode portion 14d and the second electrode portion 16d on the same side surface of the stacked body 20 is provided.

  As shown in FIG. 1C, on the side surface opposite to the side surface on which the first external electrode 24 is provided, the first electrode portion 14c and the second electrode portion 16c are exposed to the exposed portions. The second external electrode 26b is provided. A third external electrode 28b for connecting the first electrode portion 14a and the second electrode portion 16a on the same side surface of the stacked body 20 is provided.

  That is, the second external electrodes 26a and 26b include two first electrode portions 14b and 14c connected by the first electrode communication portion 14e, and two isolated second electrodes not connected by the second electrode communication portion 16e. The parts 16b and 16c are connected. The third external electrodes 28a and 28b include two isolated first electrode portions 14a and 14d that are not connected by the first electrode communication portion 14e, and two second electrode portions 16a that are connected by the second electrode communication portion 16e.・ 16d is connected.

  The ultrasonic motor element 10 has a structure in which a lead wire 32 is attached to the first external electrode 24, a lead wire 34 is attached to the second external electrode 26a, and a lead wire 36 is attached to the third external electrode 28a for power supply. . As described above, in the ultrasonic motor element 10, power can be supplied from one side surface of the stacked body 20 in this way. In this case, it is not necessary to attach lead wires to the second external electrode 26b and the third external electrode 28b. That is, a lead wire may be attached to either one of the second external electrodes 26a and 26b, and a lead wire may be attached to any one of the third external electrodes 28a and 28b.

  Note that if a jig or container for fixing and holding the ultrasonic motor element 10 is provided with a power supply terminal that comes into contact with these external electrodes, it is not necessary to attach a lead wire to each external electrode.

  The ultrasonic motor element 10 having the above-described structure can be preferably manufactured by the following process. Piezoelectric ceramic powders such as lead zirconate titanate (PZT) -based piezoelectric ceramics are formed into a sheet using sheet forming techniques such as the doctor blade method and extrusion molding method, and the resulting green sheet is considered for firing shrinkage Then, it is punched into a rectangular shape of the piezoelectric plate.

  An electrode pattern of a ground electrode printed on a rectangular green sheet by a screen printing method using an internal electrode material paste (for example, Ag / Pd paste, Pd paste, Pt paste, etc.) suitable for the firing temperature of piezoelectric ceramics A predetermined number of sheets (hereinafter referred to as “sheet A”) are produced. Similarly, a rectangular green sheet printed with an electrode pattern of a first drive electrode (hereinafter referred to as “sheet B”) is prepared, and a rectangular green sheet printed with an electrode pattern of a second drive electrode (hereinafter referred to as “sheet B”). A predetermined number of sheets C) are prepared. The produced sheets A, B, and C are stacked in the order of the sheets A, B, A, C, A, B, A, C, and A, and the rectangular green on which no electrode paste is printed. The sheets are further stacked and integrated (thermocompression bonding) using a hot press or the like.

  By firing this pressure-bonded body at a predetermined temperature, the rectangular green sheet portion changes into a piezoelectric plate, and the printed electrode paste changes into respective internal electrodes. A laminated body is obtained by polishing the side surfaces and end surfaces of the obtained fired body as necessary, and adjusting the shape. In order to form the first to third external electrodes, an Ag paste or the like is applied to a predetermined position on the side surface of the laminate, and this is baked and baked.

  Next, lead wires are attached to the first to third external electrodes by soldering or the like. The piezoelectric plate is polarized by applying a predetermined DC voltage between the first external electrode and the second and third external electrodes. In this way, an ultrasonic motor element can be obtained.

  The driving method of the ultrasonic motor element 10 is performed by shifting the phase of the AC voltage V1 applied between the lead wires 32 and 34 and the AC voltage V2 applied between the lead wires 32 and 36 by 90 degrees. As AC voltage V1 * V2, a sine wave or a triangular wave is suitable.

  As described above with reference to FIG. 4A, when the ultrasonic motor element 10 is caused to vibrate in the L1B2 resonance mode, the sliding member 22 is in a plane parallel to the internal electrode surface (X-- in FIG. 1A). Since the elliptical motion occurs in the Y plane), the driven body 50 can be moved in the X direction, which is the length direction of the guide rail 52. Control of the traveling direction of the driven body 50 can be determined by which phase of the AC voltages V1 and V2 is advanced by 90 degrees.

  In the ultrasonic motor element 10, since the sliding member 22 is attached to the side surface on the long side of the laminate 20, the displacement amount of the sliding member 22 in the Y direction increases. Therefore, it is suitable for the purpose of moving the driven body 50 at a high speed. Further, since the ultrasonic motor element 10 can reduce the thickness of the piezoelectric plate 12 by the laminated structure, it can be driven at a low voltage. Further, since most portions of the first electrode communication portion 14e and the second electrode communication portion 16e are formed in regions that overlap each other when viewed from the stacking direction, L1 resonance is amplified in the central portion of the ultrasonic motor element 10. be able to. As a result, a large displacement can be obtained (in other words, the diameter of the elliptical orbit of the sliding member 22 is increased and the linear velocity of the sliding member 22 is increased), so that the driven body 50 can be moved at a high speed. it can. In addition, the fact that a large displacement is obtained also means that the torque for driving the driven body 50 is increased. As a result, the driven body 50 that requires a large torque for driving can be moved.

  In the above description, the configuration in which the sliding member 22 is provided in the vicinity of both ends of the side surface on the long side of the laminate 20 has been described. However, as described above with reference to FIG. You may provide in the center part of the side surface of the short side of the body 20. FIG. In this case, the amount of displacement in the direction in which the sliding member 22 presses the driven body 50 becomes large, which is suitable when a large torque is required to move the driven body 50. Moreover, although the form which picked up the to-be-driven body 50 which carries out a linear motion was demonstrated, the to-be-driven body is not restricted to this, For example, the sliding member 22 is provided in the side surface of the disc hold | maintained rotatably. This disk can be rotated by abutting in the radial direction.

The schematic plan view of an ultrasonic motor element. The schematic side view of an ultrasonic motor element. Another schematic side view of an ultrasonic motor element. The top view which shows the structure of the piezoelectric plate and electrode which comprise an ultrasonic motor element. Explanatory drawing of L1B2 resonance mode. The figure which shows the drive aspect of the to-be-driven body by L1B2 resonance mode of an ultrasonic motor element. The figure which shows another drive aspect of the to-be-driven body by L1B2 resonance mode of an ultrasonic motor element.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Ultrasonic motor element, 12 * 12a-12j ... Piezoelectric plate, 14 ... 1st drive electrode, 14a-14d ... 1st electrode part, 14e ... 1st electrode communication part, 16 ... 2nd drive electrode, 16a-16d 2nd electrode part, 16e ... 2nd electrode communication part, 18 ... Ground electrode, 20 ... Laminated body, 22 ... Sliding member, 24 ... 1st external electrode, 26a, 26b ... 2nd external electrode, 28a, 28b ... Third external electrode 32, 34, 36 ... lead wire, 50 ... driven body, 52 ... guide rail, 90 ... piezoelectric element, 92 ... sliding member, 94A / 94B ... driven body.

Claims (3)

An ultrasonic motor element comprising a laminate in which piezoelectric plates and internal electrodes are alternately laminated,
The internal electrode includes a drive electrode and a ground electrode provided every other layer,
The drive electrodes are arranged in two rows so as to correspond to the first drive electrodes having four first electrode portions arranged in two rows and two columns arranged alternately in the stacking direction, and the four first electrode portions. A second drive electrode having four second electrode portions arranged in two rows,
The first drive electrode further includes a first electrode communication portion that allows two first electrode portions located at one diagonal of the four first electrode portions to conduct in an electrode plane,
The second drive electrode includes two of the four second electrode portions that are located at diagonal opposite to the diagonal of the two first electrode portions that are conductive in the electrode plane in the first drive electrode. A second electrode communication portion for conducting the second electrode portion in the electrode plane;
The ground electrode includes a region corresponding to the four first electrode portions,
On the side surface of the laminate, the first external electrode that connects the ground electrodes, the two first electrode portions that are connected by the first electrode communication portion, and the isolation that is not connected by the second electrode communication portion A second external electrode that connects the two second electrode portions, two isolated first electrode portions that are not connected by the first electrode communication portion, and two second electrodes that are connected by the second electrode communication portion. An ultrasonic motor element comprising a third external electrode for connecting the two electrode portions.   2. The ultrasonic motor element according to claim 1, wherein the first electrode communication portion and the second electrode communication portion are formed in regions that overlap each other when viewed in the stacking direction.   The piezoelectric plate has a rectangular shape, and a sliding member that comes into contact with the driven body is provided on a side surface of the multilayer body corresponding to a short side central portion or both ends of the long side of the piezoelectric plate. The ultrasonic motor element according to claim 1, wherein:

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