TUNING-FORK-TYPE BIMORPH PIEZOELECTRIC VIBRATOR, VIBRATING GYROSCOPE MODULE INCLUDING THE VIBRATOR, AND METHOD FOR MANUFACTURING THE TUNING-FORK-TYPE BIMORPH PIEZOELECTRIC VIBRATOR

• US 20090007665A1
• Filed: 09/18/2008
• Published: 01/08/2009
• Est. Priority Date: 04/26/2006
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: KURAKAWA, Haruyoshi
• Granted Patent: US 7,900,514 B2
• Time in Patent Office: Days
• US Class Current: 73/504.160
• CPC Class Codes: G01C 19/5607 using vibrating tuning forks double-ended tuning forks using planar vibrating masses suspended at opposite ends G01C19/5719
• CPC Class Codes: H03H 9/21 Crystal tuning forks
• CPC Class Codes: H03H 9/583 comprising a plurality of piezoelectric layers acoustically coupled
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

A tuning-fork-type bimorph piezoelectric vibrator includes two piezoelectric bodies that are bonded together and have opposite polarization directions. An intermediate metal layer is disposed between bonding surfaces of the piezoelectric bodies. A first slit is arranged to define legs and a base of the tuning fork structure. Second slits are provided in a first principal surface having a front metal layer to define driving/detecting electrodes. The tuning-fork-type bimorph piezoelectric vibrator provides improved temperature characteristics of a detuning frequency by not including a back metal layer on a second principal surface at least in an area in which greater than a predetermined level of stress is applied during operation.

Claims

1. A tuning-fork-type bimorph piezoelectric vibrator comprising:

at least two piezoelectric bodies having opposite polarization directions and being bonded together to define a tuning fork structure;

driving/detecting electrodes provided on a first principal surface defined by a surface of one of the at least two piezoelectric bodies;

an intermediate metal layer disposed between bonding surfaces of the at least two piezoelectric bodies;

wherein no metal layer is provided on a second principal surface defined by a surface of the other of the at least two piezoelectric bodies bonded together.

2. The tuning-fork-type bimorph piezoelectric vibrator according to claim 1, wherein

a first slit extending in a longitudinal direction of the at least two piezoelectric bodies is provided and partially divides the vibrator into right and left substantially symmetric portions in a width direction of the vibrator, to thereby define legs of the tuning fork structure;

and

second slits extending in the longitudinal direction of the at least two piezoelectric bodies are arranged to divide a metal layer disposed on the first principal surface into the driving/detecting electrodes.

3. A vibrating gyroscope module comprising the tuning-fork-type bimorph piezoelectric vibrator according to claim 1 arranged to detect a rotational angular velocity, the vibrating gyroscope module comprising:

a supporting substrate including a driving/detecting circuit arranged to drive the tuning-fork-type bimorph piezoelectric vibrator to detect a rotational angular velocity and a wiring electrode arranged to be connected to the driving/detecting electrodes of the tuning-fork-type bimorph piezoelectric vibrator; and

a support arranged to support a vibration actuator of the tuning-fork-type bimorph piezoelectric vibrator so as to be spaced away from the supporting substrate.

4. The vibrating gyroscope module according to claim 3, wherein the wiring electrode on the supporting substrate is disposed opposite the driving/detecting electrodes in the base of the tuning-fork-type bimorph piezoelectric vibrator.

5. The vibrating gyroscope module according to claim 4, wherein the support bonds the driving/detecting electrodes of the tuning-fork-type bimorph piezoelectric vibrator to the wiring electrode on the supporting substrate via a conductive material, to thereby support the vibration actuator of the tuning-fork-type bimorph piezoelectric vibrator so as to be spaced away from the supporting substrate and to provide an electrical connection between the driving/detecting electrodes and the wiring electrode.

6. A tuning-fork-type bimorph piezoelectric vibrator comprising:

at least two piezoelectric bodies having opposite polarization directions and being bonded together to define a tuning fork structure;

driving/detecting electrodes provided on a first principal surface defined by a surface of one of the at least two piezoelectric bodies;

an intermediate metal layer disposed between bonding surfaces of the at least two piezoelectric bodies; and

a back metal layer arranged on only a portion of a second principal surface defined by a surface of the other of the at least two piezoelectric bodies, the portion not being subjected to greater than a predetermined level of stress during operation.

7. The tuning-fork-type bimorph piezoelectric vibrator according to claim 6, wherein the tuning fork structure includes legs and a base, the back metal layer is arranged on at least one of an end portion of the legs of the tuning fork structure and an end portion of the base of the tuning fork structure.

8. The tuning-fork-type bimorph piezoelectric vibrator according to claim 6, wherein

a first slit extending in a longitudinal direction of the at least two piezoelectric bodies is provided and partially divides the vibrator into right and left substantially symmetric portions in a width direction of the vibrator, to thereby define legs of the tuning fork structure;

and

second slits extending in the longitudinal direction of the at least two piezoelectric bodies are arranged to divide a metal layer disposed on the first principal surface into the driving/detecting electrodes.

9. A vibrating gyroscope module comprising the tuning-fork-type bimorph piezoelectric vibrator according to claim 6 arranged to detect a rotational angular velocity, the vibrating gyroscope module comprising:

a supporting substrate including a driving/detecting circuit arranged to drive the tuning-fork-type bimorph piezoelectric vibrator to detect a rotational angular velocity and a wiring electrode arranged to be connected to the driving/detecting electrodes of the tuning-fork-type bimorph piezoelectric vibrator; and

a support arranged to support a vibration actuator of the tuning-fork-type bimorph piezoelectric vibrator so as to be spaced from the supporting substrate.

10. The vibrating gyroscope module according to claim 9, wherein the wiring electrode on the supporting substrate is disposed opposite to the driving/detecting electrodes in the base of the tuning-fork-type bimorph piezoelectric vibrator.

11. The vibrating gyroscope module according to claim 10, wherein the support bonds the driving/detecting electrodes of the tuning-fork-type bimorph piezoelectric vibrator to the wiring electrode on the supporting substrate via a conductive material, to thereby support the vibration actuator of the tuning-fork-type bimorph piezoelectric vibrator so as to be spaced from the supporting substrate and to provide an electrical connection between the driving/detecting electrodes and the wiring electrode.

12. A method for manufacturing a tuning-fork-type bimorph piezoelectric vibrator, the method comprising steps of:

bonding a first piezoelectric body polarized in a thickness direction thereof and having a metal layer formed on a front surface thereof and a second piezoelectric body polarized in a thickness direction thereof and having a metal layer formed on a back surface thereof together such that the polarization directions of the two piezoelectric bodies are opposite to each other, thereby producing a master substrate in which an intermediate metal layer is disposed between bonding surfaces of the two piezoelectric bodies and a front metal layer is arranged on a first principal surface defined by a surface of one of the two piezoelectric bodies bonded together;

cutting the master substrate at predetermined intervals to form cutout blocks;

forming first slits at predetermined intervals in the cutout blocks, each first slit extending in a longitudinal direction of a respective one of the cutout blocks and partially dividing the cutout blocks into right and left substantially symmetrical portions in a width direction of the cutout block, thereby forming a tuning fork structure including legs;

forming second slits along the longitudinal direction and in the first principal surface of each of the cutout blocks in which the legs of the tuning fork structure are formed, the second slits having a depth less than a thickness of the one piezoelectric body on which the front metal layer is formed, thereby dividing the front metal layer into driving/detecting electrodes; and

separating the cutout blocks by cutting along lines, each line being located substantially at a center between adjacent first slits and being substantially parallel to the first slits.

13. A method for manufacturing a tuning-fork-type bimorph piezoelectric vibrator, the method comprising steps of:

bonding a first piezoelectric body polarized in a thickness direction thereof and having metal layers formed on both of a front surface and a back surface thereof and a second piezoelectric body polarized in a thickness direction thereof together such that the polarization directions of the two piezoelectric bodies are opposite to each other, thereby producing a master substrate in which an intermediate metal layer is disposed between bonding surfaces of the two piezoelectric bodies and a front metal layer is arranged on a first principal surface defined by a surface of one of the two piezoelectric bodies bonded together;

cutting the master substrate at predetermined intervals to form cutout blocks;

forming first slits at predetermined intervals in the cutout blocks, each first slit extending in a longitudinal direction of a respective one of the cutout blocks and partially dividing the cutout blocks into right and left substantially symmetrical portions in a width direction of the cutout blocks, thereby forming a tuning fork structure including legs;

forming second slits along the longitudinal direction and in the first principal surface of each of the cutout blocks in which the legs of the tuning fork structure are formed, the second slits having a depth less than a thickness of the one piezoelectric body on which the front metal layer is formed, thereby dividing the front metal layer into driving/detecting electrodes; and

separating the cutout blocks by cutting along lines, each line being located substantially at the center between adjacent first slits and being substantially parallel to the first slits.

14. A method for manufacturing a tuning-fork-type bimorph piezoelectric vibrator, the method comprising steps of:

bonding a first piezoelectric body polarized in a thickness direction thereof and having metal layers formed on both of a front surface and a back surface thereof and a second piezoelectric body polarized in a thickness direction thereof and having a metal layer formed on a back surface thereof together such that the polarization directions of the two piezoelectric bodies are opposite to each other, thereby producing a master substrate in which an intermediate metal layer is disposed between bonding surfaces of the two piezoelectric bodies, a front metal layer is arranged on a first principal surface defined by a surface of one of the two piezoelectric bodies, and a back metal layer is arranged on a second principal surface defined by a surface of the other of the two piezoelectric bodies bonded together;

removing a portion of the back metal layer from the second principal surface of the master substrate, the portion being subjected to greater than a predetermined level of stress during operation;

cutting the master substrate at predetermined intervals to form cutout blocks;

forming first slits at predetermined intervals in the cutout blocks, each first slit extending in a longitudinal direction of the cutout blocks and partially dividing the cutout blocks into right and left substantially symmetrical portions in a width direction of the cutout blocks, thereby forming a tuning fork structure including legs;

forming second slits along the longitudinal direction and in the first principal surface of each of cutout blocks in which the legs of the tuning fork structure are formed, the second slits having a depth less than a thickness of the one piezoelectric body on which the front metal layer is formed, thereby dividing the front metal layer into driving/detecting electrodes; and

separating the cutout blocks by cutting along lines, each line being located substantially at the center between adjacent first slits and being substantially parallel to the first slits.

15. The method for manufacturing the tuning-fork-type bimorph piezoelectric vibrator according to claim 14, wherein in the step of removing, the portion of the back metal layer is removed by grinding.

16. The method for manufacturing the tuning-fork-type bimorph piezoelectric vibrator according to claim 14, wherein in the step of removing, the portion of the back metal layer is removed by etching.