Apparatus for detecting a physical quantity acting as an external force and method for testing and manufacturing this apparatus

• US 20070256469A1
• Filed: 04/20/2007
• Published: 11/08/2007
• Est. Priority Date: 12/28/1989
• Status: Active Grant

• Current Assignee: Wacoh Company
• Original Assignee: Kazuhiro Okada
• Inventors: Okada, Kazuhiro
• Granted Patent: US 7,578,162 B2
• Time in Patent Office: Days
• US Class Current: 73/1.380
• CPC Class Codes: G01L 1/148 using semiconductive material, e.g. silicon
• CPC Class Codes: G01L 1/18 using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
• CPC Class Codes: G01L 25/00 Testing or calibrating of apparatus for measuring force, torque, work, mechanical power, or mechanical efficiency
• CPC Class Codes: G01L 5/162 of piezoresistors
• CPC Class Codes: G01P 1/023 for acceleration measuring devices
• CPC Class Codes: G01P 15/123 by piezo-resistive elements, e.g. semiconductor strain gauges
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/084 the mass being suspended at more than one of its sides, e.g. membrane-type suspension, so as to permit multi-axis movement of the mass
• CPC Class Codes: G01P 21/00 Testing or calibrating of apparatus or devices covered by the preceding groups

Abstract

A sensor comprises a semiconductor pellet (10) including a working portion (11) adapted to undergo action of a force, a fixed portion (13) fixed on the sensor body, and a flexible portion (13) having flexibility formed therebetween, a working body (20) for transmitting an exterted force to the working portion, and detector means (60-63) for transforming a mechanical deformation produced in the semiconductor pellet to an electric signal to thereby detect a force exerted on the working body as an electric signal. A signal processing circuit is applied to the sensor. This circuit uses analog multipliers (101-109) and analog adders/subtracters (111-113), and has a function to cancel interference produced in different directions. Within the sensor, two portions (E3, E4-E8) located at positions opposite to each other and producing a displacement therebetween by action of a force are determined. By exerting a coulomb force between both the portions, the test of the sensor is carried out. Further, a pedestal (21, 22) is provided around the working body (20). The working body and the pedestal are located with a predetermined gap or spacing therebetween. A displacement of the working body is caused to limitatively fall within a predetermined range corresponding to the spacing. The working body and the pedestal are provided by cutting a same common substrate (350, 350′).

Claims

1. A method of testing an acceleration sensor,

said acceleration sensor comprising:

a substrate arranged along an XY-plane of an XYZ three-dimensional coordinate system;

a working body receiving a force and located adjacent to said substrate with a predetermined distance;

a flexible member supporting said working body so that said working body is suspended and spatial deviation of said working body is produced by applying said force thereto;

a fixing member fixing said flexible member to said substrate; and

a transducer for transforming said spatial deviation into an electric signal that indicates said force;

said method comprising the steps of;

providing a deviation electrode and a fixed electrode, said deviation electrode being located on the working body at a position which deviates in an X-axis direction and said fixed electrode being fixed to said substrate so as to face a part of said deviation electrode;

applying a voltage between said deviation electrode and said fixed electrode so that Coulomb force is produced which causes spatial deviation of said working body in an X-axis direction of said XYZ three-dimensional coordinate system;

detecting an electric signal transformed by said transducer while said spatial deviation is caused by applying said voltage; and

testing an operation of said acceleration sensor with respect to said X-axis direction based on a relationship between said applied voltage and said detected electric signal.

2. The method of testing an acceleration sensor according to claim 1:

wherein a voltage is applied so that an attractive force or a repulsive force is exerted between the fixed electrode and the deviation electrode.

3. The method of testing an acceleration sensor according to claim 1:

wherein the substrate, the working body, the flexible member and the fixing member are made of silicon.

4. A method of testing an acceleration sensor,

said acceleration sensor comprising:

a substrate arranged along an XY-plane of an XYZ three-dimensional coordinate system;

a working body receiving a force and located adjacent to said substrate with a predetermined distance;

a flexible member supporting said working body so that said working body is suspended and spatial deviation of said working body is produced by applying said force thereto;

a fixing member fixing said flexible member to said substrate; and

a transducer for transforming said spatial deviation into an electric signal that indicates said force;

said method comprising the steps of;

providing a deviation electrode on the working body so as to deviate in an X-axis direction and in a Y-axis direction;

providing a first fixed electrode fixed to said substrate so as to face a part of said deviation electrode;

providing a second fixed electrode fixed to said substrate so as to face a part of said deviation electrode;

applying a first voltage between said deviation electrode and said first fixed electrode so that Coulomb force is produced which causes first spatial deviation of said working body in an X-axis direction of said XYZ three-dimensional coordinate system;

detecting a first electric signal transformed by said transducer while said first spatial deviation is caused by applying said first voltage;

testing a first operation of said acceleration sensor with respect to said X-axis direction based on a relationship between said applied first voltage and said detected first electric signal;

applying a second voltage between said deviation electrode and said second fixed electrode so that Coulomb force is produced which causes second spatial deviation of said working body in a Y-axis direction of said XYZ three-dimensional coordinate system;

detecting a second electric signal transformed by said transducer while said second spatial deviation is caused by applying said second voltage; and

testing a second operation of said acceleration sensor with respect to said Y-axis direction based on a relationship between said applied second voltage and said detected second electric signal.

5. The method of testing an acceleration sensor according to claim 4:

wherein the first voltage is applied so that an attractive force or a repulsive force is exerted between the first fixed electrode and the deviation electrode when the first operation is tested; and

wherein the second voltage is applied so that an attractive force or a repulsive force is exerted between the second fixed electrode and the deviation electrode when the second operation is tested.

6. The method of testing an acceleration sensor according to claim 4:

wherein the substrate, the working body, the flexible member and the fixing member are made of silicon.