Force detector

• US 6,779,408 B2
• Filed: 09/19/2002
• Issued: 08/24/2004
• 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): Lefkowitz, Edward
• Assistant Examiner(s): THOMPSON, JEWEL VERGIE
• Application Number:
  US10/247,772
• Publication Number:
  US 20030015043A1
• Time in Patent Office: 705 Days
• Field of Search: 738/620.43, 738/620.44, 738/620.45, 738/620.46
• US Class Current: 73/862.043
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 3/0021 Transducers for transforming electrical into mechanical energy or vice versa dynamo-electric machines H02K99/00; electrostatic machines H02N1/00; piezoelectric devices H10N30/00
• 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 1/023 for acceleration measuring devices
• 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

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. A force detector comprising:

a stable member fixed to a detector casing and extending along a first plane;

a central member locating on a second plane parallel to said first plane;

an intermediate member locating around said central member on said second plane and connected to said central member;

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

a fixed electrode operatively on said stable member; and

a displacement electrode operatively on said central member;

wherein said intermediate member has flexibility to resiliently support said central member so that said central member moves when force having a component parallel to said first or second plane is applied; and

wherein said fixed electrode is opposite to said displacement electrode to constitute a capacitance element so that said component is detected based on a capacitance value of said capacitance element.

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

wherein a first fixed electrode and a first displacement electrode are provided to constitute a first capacitance element, and a second fixed electrode and a second displacement electrode are provided to constitute a second capacitance element, said first capacitance element and said second capacitance element being used to detect a force component along a detection axis parallel to the first or second plane; 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 a force component in a positive direction along said detection axis, and 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 a force component in a negative direction along said detection axis.

3. The force detector as set forth in claim 2, 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 2, 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 2:

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 2:

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