Force detector and acceleration detector and method of manufacturing the same

• US 6,477,903 B2
• Filed: 07/17/2001
• Issued: 11/12/2002
• Est. Priority Date: 10/12/1990
• Status: Expired due to Term

• Current Assignee: Wacoh Company
• Original Assignee: Kazuhiro Okada
• Inventors: Okada, Kazuhiro
• Primary Examiner(s): Fuller, Benjamin R.
• Assistant Examiner(s): Thompson, Jewel V.
• Application Number:
  US09/907,444
• Publication Number:
  US 20020014126A1
• Time in Patent Office: 483 Days
• Field of Search: 738/620.43, 735/041.1, 738/620.42, 735/040.4, 738/62, 736/26
• 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 flexible substrate including a fixed portion fixed to a detector casing, a working portion to which a force to be detected is transmitted, and a flexible portion having flexibility formed between said fixed portion and said working portion,

a fixed substrate fixed on said detector casing so as to face such flexible substrate,

a working body to receive a force to be detected and to transmit said force to said working portion of said flexible substrate,

a displacement electrode formed on a surface, which faces to said fixed substrate, and

a fixed electrode formed on a surface, which faces to said flexible substrate, of said fixed substrate,

wherein any one or both of said displacement electrode and said fixed electrode are constituted by four localized electrodes to form four capacitance elements by using said four localized electrodes, respectively, a first localized electrode to form a first capacitance element being located in a positive area with respect to a first axis of coordinates, a second localized electrode to form a second capacitance element being located in a negative area with respect to said first axis, a third localized electrode to form a third capacitance element being located in a positive area with respect to a second axis of coordinates, a fourth localized electrode to form a fourth capacitance element being located in a negative area with respect to said second axis, said first axis and said second axis being perpendicular to each other on a surface where said localized electrodes are formed,

a first force component which makes an electrode distance of said first capacitance element smaller than an electrode distance of said second capacitance element and a second force component which makes said electrode distance of said second capacitance element smaller than said electrode distance of said first capacitance element being detected by a difference between electrostatic capacitance values of said first and second capacitance elements.

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

wherein a perpendicular force component perpendicular to the fixed substrate is detected by a sum of electrostatic capacitance values of said first to fourth capacitance elements.

3. A force detector as set forth in claim 1, further comprising a fifth capacitance element including an additional displacement electrode and an additional fixed electrode, said additional displacement electrode being formed on a surface, which faces to the fixed substrate, of the flexible substrate and said additional fixed electrode formed on a surface, which faces to the flexible substrate, of the fixed substrate, and a perpendicular force component perpendicular to the fixed substrate being detected by an electrostatic capacitance value of said fifth capacitance element.

4. A force detector as set forth in claim 1, wherein a working body receives a force caused by acceleration so that the detector functions as an acceleration sensor.

5. A force detector as set forth in claim 2, wherein a working body receives a force caused by acceleration so that the detector functions as an acceleration sensor.

6. A force detector as set forth in claim 3, wherein a working body receives a force caused by acceleration so that the detector functions as an acceleration sensor.