Accleration sensor

• US 20040025591A1
• Filed: 06/10/2003
• Published: 02/12/2004
• Est. Priority Date: 11/19/2001
• Status: Abandoned Application

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Konno, Nobuaki, Yoshikawa, Eiji, Tsugai, Masahiro
• Application Number:
  US10/450,054
• Publication Number:
  US 20040025591A1
• Time in Patent Office: Days
• US Class Current: 73/514.32
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions

Abstract

First and second fixed electrodes provided on a substrate, a movable electrode which is provided above the first and second fixed electrodes facing against them, and is elastically supported on the substrate by a first elastic supporting body and is swingable, a mass which is elastically supported on the substrate by a second elastically supporting body and is movable in response to an acceleration in a direction perpendicular to the substrate, and a linking portion for linking the movable electrode and the mass at a position away from a swing axis of the movable electrode by a predetermined distance are provided. An acceleration is measured based on changes in a first capacitance provided by the first fixed electrode and the movable electrode and a second capacitance provided by the second fixed electrode and the movable electrode. Thus, a high impact resistant and highly reliable acceleration sensor can be obtained.

Claims

1. An acceleration sensor, comprising:

first and second fixed electrodes provided on a substrate;

a movable electrode which is provided above the first and second fixed electrode by facing against them, and is elastically supported on the substrate by a first elastic supporting body and is swingable;

a mass which is elastically supported on the substrate by a second elastic supporting body and is movable in response to an acceleration in a direction perpendicular to the substrate; and

a linking portion for linking the movable electrode and the mass at a position away from a swing axis of the movable electrode by a predetermined distance,

wherein an acceleration is measured based on changes in a first capacitance provided by the first fixed electrode and the movable electrode and a second capacitance provided by the second fixed electrode and the movable electrode.

2. The acceleration sensor according to claim 1, wherein the movable electrode is surrounded by the mass such that the center of gravity of the movable electrode and the center of gravity of the mass coincide each other.

3. The acceleration sensor according to claim 1, further comprising a self-diagnosis electrode provided facing against the mass on the substrate for checking an operation of the acceleration sensor by applying a voltage between the self-diagnosis electrode and the mass.

4. The acceleration sensor according to claim 1, further comprising a driving electrode provided facing against the movable electrode on the substrate for driving the movable electrode to a predetermined position by applying a voltage between the driving electrode and the movable electrode.

5. The acceleration sensor according to claim 1, further comprising a correcting electrode provided facing against the mass on the substrate for correcting a capacitance provided by the first and second fixed electrodes and the movable electrode based on a capacitance provided between the correcting electrode and the mass.

6. The acceleration sensor according to claim 5, further comprising:

a first capacitance voltage transformer for transforming a capacitance provided between the first and second fixed electrodes and the movable electrode to a voltage;

a second capacitance voltage transformer for transforming a capacitance provided between the mass and the correcting electrode to a voltage; and

a processor for computing an output value from the first capacitance voltage transformer and an output value from the second capacitance voltage transformer.

7. The acceleration sensor according to any one of claims 1 to 6, further comprising a second and a third acceleration sensors each for measuring an acceleration in a direction inside the substrate, wherein the second acceleration sensor and the third acceleration sensor are arranged to respond to accelerations in directions orthogonal to each other.

8. The acceleration sensor according to claim 1, wherein at least the movable electrode, the mass, the first elastic supporting body, the second elastic supporting body and the linking portion are integrally formed by polysilicon.

9. The acceleration sensor according to claim 1, wherein at least the movable electrode, the mass, the first elastic supporting body, the second elastic supporting body and the linking portion are integrally formed by monocrystal silicon.