Sensor using a resistance element

• US 5,744,718 A
• Filed: 04/26/1996
• Issued: 04/28/1998
• 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): RAEVIS, ROBERT R
• Application Number:
  US08/641,078
• Time in Patent Office: 732 Days
• Field of Search: 73/652, 73/654, 73/514.38, 73/514.24, 73/862.044, 73/862.043, 73/862.632, 73/862.629, 73/514.33
• US Class Current: 73/514.33
• 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

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 sensor for detecting a physical quantity acting as an external force comprising:

a substrate having first and second opposite surfaces and including a working portion located at a center of said substrate, a flexible portion located around said working portion and a fixed portion located around said flexible portion, said flexible portion including a groove into said substrate from one of said surfaces of said substrate so that a thickness of said substrate at said groove of said flexible portion is less than that of said substrate in said working portion and said fixed portion;

a working body connected at one end to said second surface of said working portion for transmitting an external force to said working portion, whereby mechanical deformation of said flexible portion of said substrate is produced, the working body having an outside side surface;

a pedestal connected at one end to said second surface of said fixed portion of said substrate for supporting said fixed portion of said substrate fixedly relative to said flexible and working portions of said substrate, the pedestal having an inside side surface opposite said outside side surface of said working body at a space therefrom; and

detection elements on one of said surfaces of said flexible portion of said substrate each for providing an electric characteristic that changes on the basis of said mechanical deformation, whereby said external force is detected;

wherein said detection elements comprise a first detection element located on a first axis and a second detection element located on a second-axis, said first axis and said second axis being on said one of said surfaces of said flexible portion of said substrate with said detection elements and perpendicular to each other;

wherein a first component along said first axis of said external force is detected on the basis of said electric characteristic of said first detection element and a second component along said second axis of said external force is detected on the basis of said electric characteristic of said second detection element; and

wherein said space of said inside side surface of said pedestal from said outside side surface of said working body is set so that said outside side surface of said working body contacts with said inside side surface of said pedestal when said components of said external force exceed a predetermined intensity.

2. The sensor for detecting a physical quantity as set forth in claim 1, and further comprising:

a third axis perpendicular to said first surface of said substrate; and

a third detection element of said detection elements so that a third component along said third axis of said external force is detected based on an electric characteristic of said third detection element;

wherein a first portion and a second portion are defined on said second surface of said fixed portion of said substrate so that said first portion is located around said second portion, said pedestal being connected to said first portion; and

wherein a portion of an opposite end of said working body is opposite said second portion of said fixed portion of said substrate and spaced therefrom at a space that is set so that said portion of said working body contacts with said second portion of said fixed portion of said substrate when said third component of said external force in one direction exceeds a predetermined intensity.

3. The sensor for detecting a physical quantity as set forth in claim 2:

wherein the detection elements are resistance elements having electric resistances that vary on the basis of said mechanical deformation.

4. The sensor for detecting a physical quantity as set forth in claim 3:

wherein when a perpendicular drawn from a center of gravity of said working body to the first surface of said substrate satisfies the relationship L<

r2, wherein L is a length of said perpendicular and r2 a distance from said perpendicular to an outside of said groove.

5. The sensor for detecting a physical quantity as set forth in claim 1, and further comprising:

a third axis perpendicular to said first surface of said substrate;

a third detection element of said detection elements so that a third component along said third axis of said external force is detected based on an electric characteristic of said third detection element; and

a control surface fixed to said pedestal so that an opposite end portion of said working body and said control surface are opposite each other at a spacing therebetween so that said opposite end portion of said working body contacts said control surface when said third component of said external force in one direction exceeds a predetermined intensity.

6. The sensor for detecting a physical quantity as set forth in claim 5:

wherein the detection elements are resistance elements having electric resistances that vary on the basis of said mechanical deformation.

7. The sensor for detecting a physical quantity as set forth in claim 6:

wherein when a perpendicular drawn from a center of gravity of said working body to the first surface of said substrate satisfies the relationship L<

r2, wherein L is a length of said perpendicular and r2 a distance from said perpendicular to an outside of said groove.

8. The sensor for detecting a physical quantity as set forth in claim 5:

wherein when a perpendicular drawn from a center of gravity of said working body to the first surface of said substrate satisfies the relationship L<

r2, wherein L is a length of said perpendicular and r2 a distance from said perpendicular to an outside of said groove.

9. The sensor for detecting a physical quantity as set forth in claim 1:

wherein the detection elements are resistance elements having electric resistances that vary on the basis of said mechanical deformation.

10. The sensor for detecting a physical quantity as set forth in claim 9:

wherein when a perpendicular drawn from a center of gravity of said working body to the first surface of said substrate satisfies the relationship L<

r2, wherein L is a length of said perpendicular and r2 a distance from said perpendicular to an outside of said groove.

11. The sensor for detecting a physical quantity as set forth in claim 1:

wherein when a perpendicular drawn from a center of gravity of said working body to the first surface of said substrate satisfies the relationship L<

r2, wherein L is a length of said perpendicular and r2 a distance from said perpendicular to an outside of said groove.

12. The sensor for detecting a physical quantity as set forth in claim 1:

wherein when a perpendicular drawn from a center of gravity of said working body to the first surface of said substrate satisfies the relationship L<

r2, wherein L is a length of said perpendicular and r2 a distance from said perpendicular to an outside of said groove.