Apparatus for detecting acceleration and method for testing this apparatus

• US 5,295,386 A
• Filed: 08/14/1991
• Issued: 03/22/1994
• Est. Priority Date: 12/28/1989
• Status: Expired due to Term

• Current Assignee: Kazuhiro Okada
• Original Assignee: Kazuhiro Okada
• Inventors: Okada, Kazuhiro
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US07/761,771
• Time in Patent Office: 951 Days
• Field of Search: 73/1 D, 73/517 R, 73/517 B
• US Class Current: 73/1.07
• 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 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
• CPC Class Codes: Y10T 29/49103 Strain gauge making

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 a detector (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 (E2, E9-E12) 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.

Claims

1. An acceleration sensor to detect a first component along an X-axis and a second component along a Y-axis of an acceleration in an XYZ three-dimensional coordinate system, the sensor comprising:

a first substrate having a first plane surface which is parallel with an XY-plane of said coordinate system, said first substrate including a working portion to which a force is applied, a fixed portion fixed to a sensor body, and a flexible portion having flexibility formed between said working portion and said fixed portion;

a second substrate having a second plane surface which is opposite to said first plane surface with a predetermined distance and is fixed to said fixed portion;

a weight body attached to said working portion to transmit a force produced by an acceleration to said working portion so that said first substrate produces a mechanical deformation;

eight resistance elements formed on said first plane surface, said elements having a property that a resistance value varies in dependency upon a mechanical deformation in said first substrate, wherein four of said resistance elements are arranged along X-axis of said coordinate system and four of said resistance elements are arranged along Y-axis of said coordinate system;

a first set of four electrode layers formed on said first plane surface, wherein a first layer is located in a positive field of the X-axis and substantially has a symmetrical shape with respect to the X-axis, a second layer is located in a negative field of the X-axis and substantially has a symmetrical shape with respect to the X-axis, a third layer is located in a positive field of the Y-axis and substantially has a symmetrical shape with respect to the Y-axis, and a fourth layer is located in a negative field of the Y-axis and substantially has a symmetrical shape with respect to the Y-axis;

a second set of four electrode layers formed on said second plane surface, wherein first to fourth layers of the second set are opposite to said first to fourth layers of the first set, respectively;

detecting means for detecting said first component of the acceleration applied to said weight body based on the resistance values of the resistance elements arranged along the X-axis, and detecting said second component of the acceleration applied to said weight body based on the resistance values of the resistance elements arranged along the Y-axis; and

testing means for applying predetermined voltages to said first set of electrodes and said second set of electrodes to exert a coulomb force therebetween, thereby permitting said first substrate to produce a mechanical deformation even in a state where no acceleration is applied.

4. An acceleration sensor as set forth in claim 1, wherein the working portion of the first substrate and the weight body are integrated.

7. An acceleration sensor as set forth in claim 1, wherein, in one of said first set and said second set of four electrode layers, said four electrode layers are electrically interconnected.

2. An acceleration sensor to detect a first component along an X-axis and a second component along a Z-axis of an acceleration in an XYZ three-dimensional coordinate system, the sensor comprising:

a first substrate having a first plane surface which is parallel with an XY-plane of said coordinate system, said first substrate including a working portion to which a force is applied, a fixed portion fixed to a sensor body, and a flexible portion having flexibility formed between said working portion and said fixed portion;

a second substrate having a second plane surface which is opposite to said first plane surface with a predetermined distance and is fixed to said fixed portion;

a weight body attached to said working portion to transmit a force produced by an acceleration to said working portion so that said first substrate produces a mechanical deformation;

eight resistance elements formed on said first plane surface, said elements having a property that a resistance value varies in dependency upon a mechanical deformation produced in said first substrate, wherein four of said resistance elements are arranged along X-axis of said coordinate system and four of said resistance elements are arranged along W-axis which is any axis on the XY-plane;

a first set of four electrode layers formed on said first plane surface, wherein a first layer is located in a positive field of the X-axis and substantially has a symmetrical shape with respect to the X-axis, a second layer is located in a negative field of the X-axis and substantially has a symmetrical shape with respect to the X-axis, a third layer is located in a positive field of the Y-axis and substantially has a symmetrical shape with respect to the Y-axis, and a fourth layer is located in a negative field of the Y-axis and substantially has a symmetrical shape with respect to the Y-axis;

a second set of four electrode layers formed on said second plane surface, wherein first to fourth layers of the second set are opposite to said first to fourth layers of the first set, respectively;

detecting means for detecting said first component of the acceleration applied to said weight body based on the resistance values of the resistance elements arranged along the X-axis, and detecting said second component of the acceleration applied to said weight body based on the resistance values of the resistance elements arranged along the W-axis; and

testing means for applying predetermined voltages of said first set of electrodes and said second set of electrodes to exert a coulomb force therebetween, thereby permitting said first substrate to produce a mechanical deformation even in a state where no acceleration is applied.

5. An acceleration sensor as set forth in claim 2, wherein the working portion of the first substrate and the weight body are integrated.

8. An acceleration sensor as set forth in claim 2, wherein, in one of said first set and said second set of four electrode layers, said four electrode layers are electrically interconnected.

3. An acceleration sensor to detect a first component along an X-axis, a second component along a Y-axis and a third component along a Z-axis of an acceleration in an XYZ three-dimensional coordinate system, the sensor comprising:

a first substrate having a first plane surface which is parallel with an XY-plane of said coordinate system, said first substrate including a working portion to which a force is applied, a fixed portion fixed to a sensor body, and a flexible portion having flexibility formed between said working portion and said fixed portion;

a second substrate having a second plane surface which is opposite to said first plane surface with a predetermined distance and is fixed to said fixed portion;

a weight body attached to said working portion to transmit a force produced by an acceleration to said working portion so that said first substrate produces a mechanical deformation;

twelve resistance elements formed on said first plane surface, said elements having a property that a resistance value varies in dependency upon a mechanical deformation produced in said first substrate, wherein four of said resistance elements are arranged along X-axis of said coordinate system, four of said resistance elements are arranged along Y-axis of said coordinate system and four of said resistance elements are arranged along W-axis which is any axis on the XY-plane;

a first set of four electrode layers formed on said first plane surface, wherein a first layer is located in a positive field of the X-axis and substantially has a symmetrical shape with respect to the X-axis, a second layer is located in a negative field of the X-axis and substantially has a symmetrical shape with respect to the X-axis, a third layer is located in a positive field of the Y-axis and substantially has a symmetrical shape with respect to the Y-axis, and a fourth layer is located in a negative field of the Y-axis and substantially has a symmetrical shape with respect to the Y-axis;

a second set of four electrode layers formed on said second plane surface, wherein first to fourth layers of the second set are opposite to said first to fourth layers of the first'"'"' set, respectively;

detecting means for detecting said first component of the acceleration applied to said weight body based on the resistance values of the resistance elements arranged along the X-axis, detecting said second component of the acceleration applied to said weight body based on the resistance values of the resistance elements arranged along the Y-axis, and detecting said third component of the acceleration applied to said weight body based on the resistance values of the resistance elements arranged along the W-axis; and

testing means for applying predetermined voltages to said first set of electrodes and said second set of electrodes to exert a coulomb force therebetween, thereby permitting said first substrate to produce a mechanical deformation even in a state where no acceleration is applied.

6. An acceleration sensor as set forth in claim 3, wherein the working portion of the first substrate and the weight body are integrated.

9. An acceleration sensor as set forth in claim 3, wherein, in one of said first set and said second set of four electrode layers, said four electrode layers are electrically interconnected.