Multilayer piezoelectric device and piezoelectric actuator formed using the same

• US 6,747,398 B2
• Filed: 06/26/2002
• Issued: 06/08/2004
• Est. Priority Date: 07/25/2001
• Status: Expired due to Term

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Nakatani, Hiroshi
• Primary Examiner(s): BUDD, MARK OSBORNE
• Application Number:
  US10/179,236
• Publication Number:
  US 20030020371A1
• Time in Patent Office: 713 Days
• Field of Search: 310/328, 310/330-332, 310/358, 310/359, 310/366, 347/68-72
• US Class Current: 310/328
• CPC Class Codes: H10N 30/50 having a stacked or multilayer structure
• CPC Class Codes: H10N 30/871 Single-layered electrodes of multilayer piezoelectric or electrostrictive devices, e.g. internal electrodes

Abstract

A multilayer piezoelectric device includes long internal electrodes and short internal electrodes which are arranged so as to extend from a pair of opposing side surfaces of a piezoelectric substrate towards the corresponding side surfaces opposite to the side surfaces from which they extend, and so as to be alternately stacked in the piezoelectric substrate. Active portions are located at portions where the long internal electrodes and the corresponding short internal electrodes are stacked. Further, a first external electrode, connected to the short internal electrodes, is electrically connected to the side surface near the active portions, and a second external electrode, connected to the long internal electrodes, is electrically connected to the side surface distant from the active portions. The first external electrode extends from the side surface of the piezoelectric substrate near the active portions, onto a main surface, and to a location adjacent to the side surface distant from the active portions, while the second external electrode extends onto the main surface so as to be disposed on left and right sides of locations at the first external electrode that are adjacent to the side surface of the piezoelectric substrate distant from the active portions.

Claims

1. A multilayer piezoelectric device comprising:

a piezoelectric substrate;

a plurality of longer internal electrodes;

a plurality of shorter internal electrodes wherein the longer internal electrodes and the shorter internal electrodes have different lengths, are arranged so that the longer internal electrodes and the shorter internal electrodes extend from a pair of opposing side surfaces of the piezoelectric substrate towards the corresponding side surfaces of the piezoelectric substrate opposite to the side surfaces from which the longer internal electrodes and the shorter internal electrodes extend, and are arranged so that the shorter internal electrodes and the longer internal electrodes are alternately stacked inside the piezoelectric substrate;

active portions disposed at locations where the longer internal electrodes and the corresponding shorter internal electrodes are stacked, the active portions being displaced in a direction that is substantially perpendicular to a direction in which the longer internal electrodes and the corresponding shorter internal electrodes are stacked;

a first external electrode which is electrically connected to the shorter internal electrodes at one of the side surfaces of the piezoelectric substrate; and

a second external electrode which is electrically connected to the longer internal electrodes at one of the side surfaces of the piezoelectric substrate;

wherein the first external electrode and the second external electrode are separately disposed on a surface of the piezoelectric substrate; and

the first external electrode extends from the side surface of the piezoelectric substrate near the active portions, extends onto a main surface of the piezoelectric substrate, and extends to a location adjacent to the side surface that is distant from the active portions where the longer internal electrodes are drawn out, and the second external electrode extends onto the main surface so as to be disposed on left and right sides of locations at the first external electrode that are adjacent to the side surface of the piezoelectric substrate that is distant from the active portions.

2. A multilayer piezoelectric device according to claim 1, wherein the piezoelectric substrate has a substantially rectangular shape.

3. A multilayer piezoelectric device according to claim 1, wherein the second external electrode is arranged so as to extend onto the main surface from the side surface of the piezoelectric substrate that is distant from the active portions.

4. A multilayer piezoelectric device according to claim 1, wherein the second external electrode is arranged so as to extend onto the main surface from a side surface of the piezoelectric substrate that is substantially perpendicular to the side surface of the piezoelectric substrate that is distant from the active portions.

5. A multilayer piezoelectric device according to claim 1, wherein the active portions include cuts formed therein to define slits.

6. A multilayer piezoelectric device according to claim 1, wherein the piezoelectric substrate vibrates in a direction that is substantially perpendicular to a thickness direction of the piezoelectric substrate.

7. A multilayer piezoelectric device according to claim 1, wherein the active portions vibrate in a direction that is substantially perpendicular to a thickness direction of the piezoelectric substrate.

8. A piezoelectric actuator comprising:

a multilayer piezoelectric device including;

a piezoelectric substrate;

a plurality of longer internal electrodes;

a plurality of shorter internal electrodes wherein the longer internal electrodes and the shorter internal electrodes have different lengths, are arranged so that the longer internal electrodes and the shorter internal electrodes extend from a pair of opposing side surfaces of the piezoelectric substrate towards the corresponding side surfaces of the piezoelectric substrate opposite to the side surfaces from which the longer internal electrodes and the shorter internal electrodes extend, and are arranged so that the shorter internal electrodes and the longer internal electrodes are alternately stacked inside the piezoelectric substrate;

active portions disposed at locations where the longer internal electrodes and the corresponding shorter internal electrodes are stacked, the active portions being displaced in a direction that is substantially perpendicular to a direction in which the longer internal electrodes and the corresponding shorter internal electrodes are stacked;

a first external electrode which is electrically connected to the shorter internal electrodes at one of the side surfaces of the piezoelectric substrate; and

a second external electrode which is electrically connected to the longer internal electrodes at one of the side surfaces of the piezoelectric substrate;

wherein the first external electrode and the second external electrode are separately disposed on a surface of the piezoelectric substrate;

the first external electrode extends from the side surface of the piezoelectric substrate near the active portions, extends onto a main surface of the piezoelectric substrate, and extends to a location adjacent to the side surface that is distant from the active portions where the longer internal electrodes are drawn out, and the second external electrode extends onto the main surface so as to be disposed on left and right sides of locations at the first external electrode that are adjacent to the side surface of the piezoelectric substrate that is distant from the active portions; and

slits are formed to extend from the side surface near the active portions towards the side surface opposite thereto, the slits being formed at a predetermined pitch along a direction that is substantially perpendicular to the direction of extension of the slits in order to provide separately drivable movable portions between the corresponding slits; and

an electrical conductor on a flexible printed circuit board is connected to the first external electrode, divided by the slits, and the second external electrode.

9. A piezoelectric actuator according to claim 8, wherein the piezoelectric substrate has a substantially rectangular shape.

10. A piezoelectric actuator according to claim 8, wherein the second external electrode is arranged so as to extend onto the main surface from the side surface of the piezoelectric substrate that is distant from the active portions.

11. A piezoelectric actuator according to claim 8, wherein the second external electrode is arranged so as to extend onto the main surface from a side surface of the piezoelectric substrate that is substantially perpendicular to the side surface of the piezoelectric substrate that is distant from the active portions.

12. A piezoelectric actuator according to claim 8, wherein the slits are formed by cuts in the active portions.

13. A piezoelectric actuator according to claim 8, wherein the piezoelectric substrate vibrates in a direction that is substantially perpendicular to a thickness direction of the piezoelectric substrate.

14. A piezoelectric actuator according to claim 8, wherein the active portions vibrate in a direction that is substantially perpendicular to a thickness direction of the piezoelectric substrate.