Physical quantity sensor, electronic device, and moving object

• US 9,952,251 B2
• Filed: 08/05/2014
• Issued: 04/24/2018
• Est. Priority Date: 08/06/2013
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Tanaka, Satoru
• Primary Examiner(s): SCHMITT, BENJAMIN R
• Application Number:
  US14/451,816
• Publication Number:
  US 20150040667A1
• Time in Patent Office: 1,358 Days
• Field of Search: 7351432
• CPC Class Codes: B81B 2203/04 Electrodes
• CPC Class Codes: B81B 3/0008 Structures for avoiding electrostatic attraction, e.g. avoiding charge accumulation
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• 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

A physical quantity sensor according to the embodiment includes: a substrate; a movable body including a movable electrode portion; and a support which supports the movable body around a first shaft to be displaced, in which, when the movable body is divided into a first portion and a second portion with the first shaft as a boundary, the physical quantity sensor includes a first fixed electrode portion which is disposed on the substrate to oppose the first portion, and a second fixed electrode portion which is disposed on the substrate to oppose the second portion, and a guard portion which suppresses an electrostatic force generated between the movable body and the substrate is provided in an inter-electrode area between the first fixed electrode portion and the second fixed electrode portion, on the substrate.

Claims

1. A physical quantity sensor comprising:

a substrate including a recess;

a movable body including a movable electrode portion and disposed over the recess;

a support which supports the movable body around a first shaft to be displaced; and

a post provided on a bottom surface of the recess and protruding toward the movable body, wherein the post engages the support to support the movable body,

wherein the support is centered on an axis of the movable body, the axis extending through the first shaft, and includes a plurality of penetration holes disposed on the axis on opposing sides of a fixed portion, the fixed portion being connected to a post portion provided on the substrate and supporting the movable body for rotation about the first shaft,

wherein, when the movable body is divided into a first portion and a second portion with the first shaft as a boundary, the physical quantity sensor includes

a first fixed electrode portion which is disposed on the substrate to oppose the first portion, and

a second fixed electrode portion which is disposed on the substrate to oppose the second portion,

wherein a guard portion which suppresses an electrostatic force generated between the movable body and the substrate is provided in an inter-electrode area between the first fixed electrode portion and the second fixed electrode portion, on the substrate, an electrode configuring the guard portion being electrically connected to the movable body such that the electrode configuring the guard portion and the movable body are equipotential, and

wherein an exposed surface of the substrate between the substrate and the movable body is formed from insulating material, effectively reducing the electrostatic force that occurs between the substrate and the movable body.

2. The physical quantity sensor according to claim 1,

wherein the guard portion is provided in a position overlapped with the support on the substrate in a plan view.

3. The physical quantity sensor according to claim 1,

wherein the guard portion is provided in a position overlapped with the movable body in a plan view and outside the first fixed electrode portion, the second fixed electrode portion, and the inter-electrode area.

4. The physical quantity sensor according to claim 1,

wherein the guard portion is an electrode electrically connected to the movable body.

5. The physical quantity sensor according to claim 4,

wherein the electrode of the guard portion is provided in an inner bottom surface of a groove portion provided on the substrate.

6. The physical quantity sensor according to claim 4,

wherein groove portions are provided in an area between the electrode and the first fixed electrode portion of the substrate, and an area between the electrode and second fixed electrode portion of the substrate.

7. The physical quantity sensor according to claim 4,

wherein the number of the electrodes adjacent to the first fixed electrode portion and the number of the electrodes adjacent to the second fixed electrode portion are equivalent to each other.

8. The physical quantity sensor according to claim 4,

wherein a protrusion portion which is protruded to the movable body is provided on at least one of the electrode, the first fixed electrode portion and the second fixed electrode portion.

9. The physical quantity sensor according to claim 1,

wherein the guard portion is a groove portion.

10. A physical quantity sensor comprising:

a substrate including a recess;

a movable body including a movable electrode portion and disposed over the recess;

a support which supports the movable body around a first shaft to be displaced; and

a post provided on a bottom surface of the recess and protruding toward the movable body, wherein the post engages the support to support the movable body,

wherein, when the movable body is divided into a first portion and a second portion with the first shaft as a boundary, the physical quantity sensor includes

a first fixed electrode portion which is disposed on the substrate to oppose the first portion, and

a second fixed electrode portion which is disposed on the substrate to oppose the second portion,

wherein a guard portion which suppresses an electrostatic force generated between the movable body and the substrate is provided in an inter-electrode area between the first fixed electrode portion and the second fixed electrode portion, on the substrate, an electrode configuring the guard portion being electrically connected to the movable body such that the electrode configuring the guard portion and the movable body are equipotential, the guard portion extending along the recess and a wall of the post portion, and

wherein an exposed surface of the substrate between the substrate and the movable body is formed from insulating material, effectively reducing the electrostatic force that occurs between the substrate and the movable body.