Acceleration sensor element and acceleration sensor

• US 7,565,840 B2
• Filed: 12/11/2006
• Issued: 07/28/2009
• Est. Priority Date: 12/13/2005
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Epson Toyocom Corporation (Seiko Group)
• Inventors: Watanabe, Jun
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US11/636,583
• Publication Number:
  US 20070151339A1
• Time in Patent Office: 960 Days
• Field of Search: 735/142.9, 734/93, 735/140.1, 735/143.6, 735/143.4
• US Class Current: 73/514.29
• CPC Class Codes: G01P 15/09 by piezoelectric pick-up
• CPC Class Codes: G01P 15/097 by vibratory elements
• CPC Class Codes: G01P 2015/0831 the mass being of the paddle type having the pivot axis between the longitudinal ends of the mass, e.g. see-saw configuration

Abstract

An objective is to provide an acceleration sensor element that has a high detection sensitivity and that realizes an accurate measurement of acceleration; and an acceleration sensor including this acceleration sensor element to realize a smaller size and a thinner thickness.

An acceleration sensor element comprises a quartz, has a thickness in a Z axis direction, and is formed in a quartz substrate developed in an orthogonal XY plane. A thin-walled section of a bottom section of a concave section of the quartz substrate has a double-ended vibrating reed in which a pair of vibration arms extend in a Y axis direction. When acceleration in a Z axis direction is applied while this double-ended vibrating reed having bending vibration, the acceleration is detected based on a change in a resonance frequency caused when the double-ended vibrating reed deflects in the Z axis direction.

Claims

1. An acceleration sensor element comprising piezoelectric material, that has a thickness in a Z axis direction, and that is formed at a substrate developed in an orthogonal XY plane, wherein

when acceleration in the Z axis direction is applied to the substrate while a double-ended vibrating reed in which a pair of vibration arms extend in a Y axis direction of the substrate having bending vibration, the acceleration is detected based on a change in a resonance frequency caused when the double-ended vibrating reed deflects in the Z axis direction,

both of top and back main surfaces of vibration arms of the double-ended vibrating reed include, in a longitudinal direction of the vibration arms, a groove that has a substantially “

H”

cross section, and

the groove is divided at an additional mass section provided at a center in the longitudinal direction of the vibration arms.

2. The acceleration sensor element according to claim 1, wherein

the double-ended vibrating reed is formed at a thin-walled section of a bottom section of a concave section provided in the substrate;

a cantilever arm structure includes;

a fixed section connected with end sections in a −

Y axis direction of the pair of vibration arms; and

a weight section connected with end sections in a +Y axis direction of the pair of vibration arms, and

when acceleration is applied, the double-ended vibrating reed deflects in the Z axis direction while the fixed section being as a base section.

3. The acceleration sensor element according to claim 1, wherein

the double-ended vibrating reed is formed closer to a +Z axis direction side or a −

Z axis direction side in a thickness direction.

4. The acceleration sensor element according to claim 1, wherein the substrate includes a fixed section side and a weight section side located opposite of the substrate to the fixed section side in the Y axis direction and the double-ended vibrating reed is formed closer to the fixed section side in the Y axis direction of the substrate than the weight section side.

5. The acceleration sensor element according to claim 1, wherein an excitation electrode provided at the double-ended vibrating reed is divided to three parts in a longitudinal direction of the vibration arms to provide reverse potentials of neighboring excitation electrodes.

6. An acceleration sensor, comprising:

the acceleration sensor element according to claim 1 that is stored in a chassis consisting of a case and a covering; and

a fixed section of an end section in a −

Y axis direction of the acceleration sensor element is fixed to an inner face of the case.

7. The acceleration sensor element according to claim 6, further comprising

a control circuit that controls excitation of the double-ended vibrating reed and is located in the chassis, and

the control circuit is provided in a space of a concave section in which the double-ended vibrating reed is formed.