Force detector and acceleration detector

• US 6,158,291 A
• Filed: 08/16/1999
• Issued: 12/12/2000
• Est. Priority Date: 10/12/1990
• Status: Expired due to Fees

• Current Assignee: Wacoh Company
• Original Assignee: Kazuhiro Okada
• Inventors: Okada, Kazuhiro
• Primary Examiner(s): Noori, Max
• Assistant Examiner(s): THOMPSON, JEWEL VERGIE
• Application Number:
  US09/375,334
• Time in Patent Office: 484 Days
• Field of Search: 73/862.043, 73/862.048
• US Class Current: 73/862.043
• CPC Class Codes: G01L 1/144 with associated circuitry G01L1/146 and G01L1/148 take precedence
• CPC Class Codes: G01L 5/165 using variations in capacitance
• CPC Class Codes: G01L 5/167 using piezoelectric means
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/0922 of the bending or flexing mode type
• CPC Class Codes: G01P 15/105 by magnetically sensitive devices
• 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: Y10S 73/04 Piezoelectric
• CPC Class Codes: Y10T 29/43 Electric condenser making
• CPC Class Codes: Y10T 29/49005 Acoustic transducer
• CPC Class Codes: Y10T 29/49007 Indicating transducer

Abstract

An electrode layer is formed on the upper surface of a first substrate, and a processing for partially removing the substrate is carried out in order to allow the substrate to have flexibility. To the lower surface of the first substrate, a second substrate is connected. Then, by cutting the second substrate, a working body and a pedestal are formed. On the other hand, a groove is formed on a third substrate. An electrode layer is formed on the bottom surface of the groove. The third substrate is connected to the first substrate so that both the electrodes face to each other with a predetermined spacing therebetween. Finally, the first, second and third substrates are cut off every respective unit regions to form independent sensors, respectively. When an acceleration is exerted on the working body, the first substrate bends. As a result, the distance between both the electrodes changes. Thus, an acceleration exerted is detected by changes in an electrostatic capacitance between both the electrodes.

Claims

1. In a force detector for detecting force components along a first axis and a second axis independently, said first axis being perpendicular to said second axis and the improvements comprising:

a stable member fixed to a detector casing;

a central member locating adjacent to said stable member with a space;

an intermediate member locating around said central member and connected to said central member;

a peripheral member locating around said intermediate member and fixing said intermediate member to said stable member;

a first fixed electrode, a second fixed electrode, a third fixed electrode and a fourth fixed electrode operatively on said stable member; and

a first displacement electrode, a second displacement electrode, a third displacement electrode and a fourth displacement electrode operatively on said central member;

wherein said central member, said intermediate member and said peripheral member are made of semiconductor and said intermediate member has flexibility to resiliently support said central member so that said central member moves along said first axis when a force component along said first axis is applied and along said second axis when a force component along said second axis is applied;

wherein said first fixed electrode is opposite to said first displacement electrode so that a first capacitance element is constituted, said second fixed electrode is opposite to said second displacement electrode so that a second capacitance element is constituted, said third fixed electrode is opposite to said third displacement electrode so that a third capacitance element is constituted and said fourth electrode is opposite to said fourth displacement electrode so that a fourth capacitance element is constituted; and

wherein said fixed electrodes and displacement electrodes are arranged so that an electrode distance of said first capacitance element decreases while an electrode distance of said second capacitance element increases when said central member is moved with said component in a positive direction along said first axis, an electrode distance of said first capacitance element increases while an electrode distance of said second capacitance element decreases when said central member is moved with said component in a negative direction along said first axis, an, electrode distance of said third capacitance element decreases while an electrode distance of said fourth capacitance element increases when said central member is moved with said component in a positive direction along said second axis and an electrode distance of said third capacitance element increases while an electrode distance of said fourth capacitance element decreases when said central member is moved with said component in a negative direction along said second axis.

2. The force detector as set forth in claim 1, and further comprising:

a fifth fixed electrode operatively on said stable member and a fifth displacement electrode operatively on said central member, said fifth fixed electrode being opposite to said fifth displacement electrode so that a fifth capacitance element is constituted;

wherein said intermediate member supports said central member so that said central member moves along a third axis perpendicular to both said first axis and said second axis; and

wherein said fifth fixed electrode and said fifth displacement electrode are arranged so that an electrode distance of said fifth capacitance element decreases when said central member is moved with said component in a positive direction along said third axis and an electrode distance of said fifth capacitance element increases when said central member is moved with said component in a negative direction along said third axis.

3. The force detector as set forth in claim 1, and further comprising:

an auxiliary electrode operatively on the stable member opposite to one of said displacement electrodes for moving said central member by a Coulomb force when a voltage is applied between said auxiliary electrode and said one of said displacement electrodes.

4. The force detector as set forth in claim 1, and further comprising:

an auxiliary electrode operatively on said central member opposite to one of said fixed electrodes for moving said central member by a Coulomb force when a voltage is applied between said auxiliary electrode and said one of said fixed electrodes.

5. The force detector as set forth in claim 1:

wherein either a plurality of said displacement electrodes or a plurality of said fixed electrodes are physically unitary.

6. The force detector as set forth in claim 1:

wherein said force components are caused by acceleration of said force detector so that said force detector functions as an acceleration detector.