VIBRATION GYRO ELEMENT, VIBRATION GYRO SENSOR, ELECTRONIC DEVICE, AND METHOD OF DETECTING PHYSICAL QUANTITY OF VIBRATION

• US 20110226057A1
• Filed: 03/08/2011
• Published: 09/22/2011
• Est. Priority Date: 03/19/2010
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: NISHIZAWA, Ryuta
• Granted Patent: US 8,783,104 B2
• Time in Patent Office: Days
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5642 using vibrating bars or beams

Abstract

A vibration gyro element includes: a base section; a detection arm extending from the base section in a first direction; a joint section disposed at an end portion of the base section; a first drive arm extending from the joint section in a second direction intersecting with the first direction in a plan view; a second drive arm extending from the joint section in a direction opposite to the extending direction of the first drive arm; a first set of drive electrodes provided to the first drive arm; a second set of drive electrodes provided to the second drive arm; and a set of detection electrodes provided to the detection arm, wherein the first drive arm vibrates in a third direction perpendicular to the first direction and the second direction, the second drive arm vibrates in a same direction as the first drive arm.

Claims

1. A vibration gyro element comprising:

a base section;

a detection arm extending from the base section in a first direction;

a joint section disposed at an end portion of the detection arm opposite to another end portion near to the base section;

a first drive arm extending from the joint section in a second direction intersecting with the first direction in a plan view;

a second drive arm extending from the joint section in a direction opposite to the extending direction of the first drive arm;

a first set of drive electrodes provided to the first drive arm;

a second set of drive electrodes provided to the second drive arm; and

a set of detection electrodes provided to the detection arm,

wherein the first drive arm vibrates in a third direction perpendicular to the first direction and the second direction,

the second drive arm vibrates in a same direction as the first drive arm,

thereby detecting a physical quantity acting around an axis in the first direction.

2. The vibration gyro element according to claim 1, wherein

the detection arm, the first drive arm, and the second drive arm are all made of a same piezoelectric material.

3. The vibration gyro element according to claim 1, wherein

the first drive arm, the second drive arm, and the detection arm each have a pair of principal surfaces opposed to each other and a pair of side surfaces coupling the principal surfaces to each other,

the first set of drive electrodes and the second set of drive electrodes are each disposed on at least one of the pair of principal surfaces, and each form an inter digital transducer having electrodes arranged in the second direction, and

the set of detection electrodes are disposed on the pair of principal surfaces and the pair of side surfaces in a solid manner.

4. The vibration gyro element according to claim 3, wherein

in the inter digital transducer, assuming that a distance between one of the electrodes and another of the electrodes adjacent on one side of the one of the electrodes is L1, and a distance between the one of the electrodes and another of the electrodes adjacent on the other side of the one of the electrodes is L2, L1<

L2 is true.

5. The vibration gyro element according to claim 4, wherein

the distance L2 in a vicinity of a tip of either of the first and second drive arms is larger than the distance L2 in a vicinity of the joint section.

8. A vibration gyro sensor comprising:

the vibration gyro element according to claim 1; and

a detection circuit adapted to detect a physical quantity acting around an axis in the first direction based on an electrical signal output from the set of detection electrodes.

9. An electronic device comprising:

a first sensor including the vibration gyro element according to claim 1; and

a second sensor including a detection element adapted to detect a physical quantity different from the physical quantity detected by the first sensor.

6. A vibration gyro element comprising:

a base section;

a first detection arm extending from the base section in a first direction;

a second detection arm extending from the base section in a direction opposite to the extending direction of the first detection arm;

a first joint section disposed at an end portion of the first detection arm opposite to another end portion near to the base section;

a second joint section disposed at an end portion of the second detection arm opposite to another end portion near to the base section;

a first drive arm extending from the first joint section in a second direction intersecting with the first direction in a plan view;

a second drive arm extending from the first joint section in a direction opposite to the extending direction of the first drive arm;

a third drive arm extending from the base section in the second direction;

a fourth drive arm extending from the base section in a direction opposite to the extending direction of the third drive arm;

a fifth drive arm extending from the second joint section in the second direction; and

a sixth drive arm extending from the second joint section in a direction opposite to the extending direction of the fifth drive arm,

wherein the first through sixth drive arms are each provided with a set of drive electrodes,

the first and second detection arms are each provided with a set of detection electrodes,

the first, second, fifth, and sixth drive arms vibrate in a third direction perpendicular to the first direction and the second direction,

the third and fourth drive arms vibrate in a direction opposite to the vibrating direction of the first, second, fifth, and sixth drive arms,

thereby detecting a physical quantity acting around an axis in the first direction.

7. The vibration gyro element according to claim 6, wherein

the first through sixth drive arms, the first detection arm, and the second detection arm each have a pair of principal surfaces opposed to each other and a pair of side surfaces coupling the principal surfaces to each other,

the sets of drive electrodes are each disposed on at least one of the pair of principal surfaces, and each form an inter digital transducer having electrodes arranged in the second direction, and

the set of detection electrodes are disposed on the pair of principal surfaces and the pair of side surfaces in a solid manner.

10. A method of detecting a physical quantity of a vibration gyro sensor, the method comprising:

providing a vibration gyro element including a base section, a detection arm extending from the base section in a first direction, a joint section disposed at an end portion of the detection arm opposite to another end portion near to the base section, a first drive arm extending from the joint section in a second direction intersecting with the first direction in a plan view, and a second drive arm extending from the joint section in a direction opposite to the extending direction of the first drive arm;

vibrating the first drive arm in a third direction perpendicular to the first direction and the second direction;

vibrating the second drive arm in the same direction as the first drive arm;

generating a Coriolis force in the first drive arm and the second drive arm in accordance with a physical quantity acting around an axis in the first direction, thereby generating a detection vibration in the second direction in the detection arm; and

detecting the physical quantity based on an electrical signal generated by a migration of a charge due to an electrical field generated by the detection vibration.