Force sensor, force detection system and force detection program

• US 7,395,721 B2
• Filed: 12/23/2004
• Issued: 07/08/2008
• Est. Priority Date: 05/14/2004
• Status: Expired due to Fees

• Current Assignee: Appside Co., Ltd.
• Original Assignee: Appside Co., Ltd.
• Inventors: Taniguchi, Nobumitsu
• Primary Examiner(s): NOORI, MASOUD H
• Application Number:
  US11/020,415
• Publication Number:
  US 20050252303A1
• Time in Patent Office: 1,293 Days
• Field of Search: 737/80
• US Class Current: 73/780
• CPC Class Codes: G01L 1/142 using capacitors
• CPC Class Codes: G01L 5/165 using variations in capacitance
• CPC Class Codes: G06F 3/0338 with detection of limited linear or angular displacement of an operating part of the device from a neutral position, e.g. isotonic or isometric joysticks
• CPC Class Codes: H01H 2025/004 the operating member being depressable perpendicular to the other directions
• CPC Class Codes: H01H 2239/006 Containing a capacitive switch or usable as such
• CPC Class Codes: H01H 25/041 having a generally flat operating member depressible at different locations to operate different controls
• CPC Class Codes: H03K 17/9625 using a force resistance transducer

Abstract

A force sensor converts a force into capacitance and makes it possible to generate a plurality of outputs with different output characteristics, force detection system, and a digital force detection program for it. The force sensor 20 has a displacement unit 24 for generating a displacement when a force is applied; a single or a plurality of first sensor units (36, 36A, 36B, 36C, and 36D) for generating a first output C₁ from said displacement of the displacement unit; and a second sensor unit 44, which is annexed to the first sensor unit, for generating a second output C₂ from the displacement of said displacement unit. The force detection system enhances the output accuracy by means of the first and second outputs of such a force sensor. The force detection program is used in the force detection system for executing the output process.

Claims

1. A force sensor comprising:

a displacement unit that displaces when a force is applied;

at least one first sensor unit that generates a first output by detecting the displacement of said displacement unit as change of capacitance; and

a second sensor unit that is annexed to said first sensor unit and generates a second output which is independent of said first output and rises steeply from said first output and shifts to a saturated state ahead of said first output by detecting the displacement of said displacement unit of the same direction that said first sensor unit detects as change of capacitance.

2. The force sensor of claim 1, wherein the displacement of said displacement unit includes either a deformation of said displacement unit or a movement of said displacement unit by force or both thereof.

3. The force sensor of claim 1, wherein said second sensor unit comprises a pair of second detection electrodes provided in the center of said displacement unit, while said first sensor unit comprises a single or a plurality of pair of first detection electrodes that surround said second detection electrode separated by an insulation distance.

4. A force detection system comprising:

a force sensor equipped with a displacement unit that displaces when a force is applied, at least one first sensor unit that generates a first output by detecting the displacement of said displacement unit as change of capacitance; and

a second sensor unit that is annexed to said first sensor unit and generates a second output which is independent of said first output and rises steeply from said first output and shifts to a saturated state ahead of said first output by detecting the displacement of said displacement unit of the same direction that said first sensor unit detects as change of capacitance; and

a processing unit that obtains said first output using said second output of said force sensor as a reference information for said first output.

5. The force detection system of claim 4, further comprising, a time information extracting unit for extracting time information representing level periods that exceed a specified level from said second output, wherein said processing unit obtains said first output referencing said time information extracted by said time information extracting unit.

7. The force detection system of claim 4 wherein said reference information is zero point information of said first output.

6. A force detection system comprising:

a force sensor equipped with first and second sensor units in a displacement unit that displaces when a force is applied and generates first and second outputs that are independent to each other and represent the displacement of said displace unit; and

a processing unit that obtains said first output using said second output of said force sensor as a reference information for said first output, wherein said second sensor unit of said force sensor shifts said second output to a saturated condition after said displacement unit starts to displace.

8. A method for detecting a force comprises the following steps:

obtaining a first output from a first sensor unit provided in a displacement unit that displaces in response to the application of the force;

obtaining a second output which is independent of said first output and rises steeply from said first output and shifts to a saturated state ahead of said first output as change of capacitance from a second sensor unit provided in said displacement unit and detecting the displacement of said displacement unit of the same direction that said first sensor unit detects as change of capacitance;

extracting time information representing a level period that exceeds a specified level from said second output; and

obtaining said first output referencing said time information.