Linkage with capacitive force sensor assembly

• US 6,279,407 B1
• Filed: 04/25/2000
• Issued: 08/28/2001
• Est. Priority Date: 04/25/2000
• Status: Expired due to Fees

• Current Assignee: Kavlico Corporation (Sensata Technologies Holding Plc)
• Original Assignee: Kavlico Corporation (Sensata Technologies Holding Plc)
• Inventors: Park, Kyong M., Nassar, Marcos A.
• Primary Examiner(s): Fuller, Benjamin R.
• Assistant Examiner(s): DAVIS, OCTAVIA L
• Application Number:
  US09/558,431
• Time in Patent Office: 490 Days
• Field of Search: 738/56, 737/74, 738/31, 738/66, 738/623.81, 738/623.91
• US Class Current: 73/862.391
• CPC Class Codes: G01L 1/142 using capacitors
• CPC Class Codes: G01L 5/103 using sensors fixed at one end of the flexible member

Abstract

A combined mechanical linkage and force-measuring assembly includes a central capacitive force sensor, in which force applied to the sensor causes the flexing of a diaphragm toward and away from a substrate, and a change in the capacitance between two conductive surfaces on the diaphragm and the substrate is sensed and processed to indicate the direction and magnitude of the force applied to the linkage. The linkage may have two parts coupled together by a flange which flexes under applied forces, to change the spacing of the conductive surfaces.

Claims

1. A combined mechanical linkage and force measurement assembly, comprising:

a first linkage member having a first coupling point;

a second linkage member having a second coupling point;

an intermediate coupling subassembly between said first and second linkage members, said subassembly including a force measurement transducer;

said first linkage member having a generally mushroom shaped end at said coupling sub-assembly, with a shaft extending from said first coupling point to said subassembly, and a peripheral flange extending outwardly from said shaft;

said second linkage member having an inner opening or bore making a close sliding fit with said shaft, and an outer portion secured to said peripheral flange, whereby said shaft can move linearly toward and away from said second linkage member in accordance with said outwardly extending flange, said flange being resilient to permit the linear movement of said shaft in said bore;

a capacitive transducer having a diaphragm mechanically coupled to said shaft to flex as said shaft shifts position, said diaphragm having a conductive layer thereon, in facing juxtaposition to a fixed conductive surface; and

electrical circuitry for measuring a change in capacitance between said conductive layer and said conductive surface to thereby indicate the force being applied to said linkage assembly between said first and second coupling points.

2. A combined mechanical linkage and force measurement assembly as defined in claim 1 wherein said opening or bore is cylindrical, and said shaft makes a close sliding fit within said bore.

3. A combined mechanical linkage and force measurement assembly as defined in claim 1 wherein said second linkage member has a generally circular outer portion firmly secured to said peripheral flange.

4. A combined mechanical linkage and force measurement assembly as defined in claim 1 wherein said diaphragm is formed of ceramic material.

5. A combined mechanical linkage and force measurement assembly as defined in claim 1 wherein said diaphragm, having a center, is bonded to said first linkage member at said center of said diaphragm.

6. A combined mechanical linkage and force measurement assembly, comprising:

a first linkage member having a first coupling point;

a second linkage member having a second coupling point;

an intermediate coupling subassembly between said first and second linkage members, said subassembly including a force measurement transducer;

said first linkage member having a shaft extending from said first coupling point to said subassembly, and a peripheral flange extending outwardly from said shaft at said subassembly;

said second linkage member having an inner opening or bore making a close sliding fit with said shaft, and an outer portion secured to said peripheral flange, whereby said shaft can move linearly toward and away from said second linkage member in accordance with said outwardly extending flange, said flange being resilient and flexing to permit the linear movement of said shaft in said bore;

a capacitive transducer having two spaced conductive surfaces, with the spacing of said surfaces varying with the relative movement of said two linkage members and the flexing of said flange; and

electrical circuitry for measuring a change in capacitance between said conductive surfaces to thereby indicate the force being applied to said linkage assembly between said first and second coupling points.

7. A combined mechanical linkage and force measurement assembly as defined in claim 6 wherein said opening or bore is cylindrical, and said shaft makes a close sliding fit within said bore.

8. A combined mechanical linkage and force measurement assembly as defined in claim 6 wherein said second linkage member is firmly secured to said peripheral flange.

9. A combined mechanical linkage and force measurement assembly as defined in claim 6 wherein one of said conductive surfaces is mounted on a diaphragm formed of ceramic material.

10. A combined mechanical linkage and force measurement assembly as defined in claim 6 wherein said capacitive transducer includes a thin diaphragm and a relatively thick substrate secured together and spaced apart by between 0.0005 inch and 0.020 inch, said diaphragm and substrate being formed of ceramic material and having facing surfaces and also having conductive layers on said diaphragm'"'"'s and said substrate'"'"'s facing surfaces.

14. A combined mechanical linkage and force measurement assembly as defined in claim 6 wherein said second linkage member is firmly secured to said outwardly extending portion of said first linkage member.

11. A combined mechanical linkage and force measurement assembly, comprising:

a first linkage member having a first coupling;

a second linkage member having a second coupling;

an intermediate coupling subassembly between said first and second linkage members, said subassembly including a force measurement transducer;

said first linkage member having a shaft extending from said first coupling point to said subassembly, said linkage member having at least a portion thereof being resilient and extending outwardly from said shaft at said sub-assembly;

said second linkage member making a guiding fit with said shaft, and having an outer portion secured to said outwardly extending portion of said first linkage member, whereby said shaft can move toward and away from said second linkage member in accordance with the resilience of said outwardly extending portion of said first linkage; and

a capacitive transducer included in said subassembly, said transducer having two spaced conductive surfaces, with the spacing of said surfaces varying with the movement of said two linkage members and the resilience of said outwardly extending portion of said first linkage member.

12. A combined mechanical linkage and force measurement assembly as defined in claim 11, further comprising electrical circuitry for measuring a change in capacitance between said conductive surfaces to thereby indicate the force being applied to said linkage assembly between said first and second coupling points.

13. A combined mechanical linkage and force measurement assembly as defined in claim 11 wherein said guiding fit utilizes a cylindrical opening or bore, and said shaft makes a close sliding fit within said bore.

15. A combined mechanical linkage and force measurement assembly as defined in claim 11 wherein one of said conductive surfaces is mounted on a diaphragm formed of ceramic material.

16. A combined mechanical linkage and force measurement assembly as defined in claim 15 wherein said diaphragm, having a center, is bonded to said first linkage member at said center of said diaphragm.

17. A combined mechanical linkage and force measurement assembly as defined in claim 11 wherein said capacitive transducer includes a thin diaphragm and a relatively thick substrate secured together and spaced apart by between 0.0005 inch and 0.020 inch, said diaphragm and substrate being formed of ceramic material and having facing surfaces and also having conductive layers on said diaphragm'"'"'s and said substrate'"'"'s facing surfaces.

18. A combined mechanical linkage and force measurement assembly as defined in claim 11 wherein said outwardly extending portion forms a peripheral flange.

19. A combined mechanical linkage and force measurement assembly as defined in claim 11 wherein a portion of said first linkage is formed of ceramic material having a conductive coating thereon forming part of said force measurement transducer.

20. A combined mechanical linkage and force measurement assembly as defined in claim 11 wherein said two linkage members are secured together by high strength metal-to-metal mechanical connections to maintain high overall mechanical strength of said combined mechanical linkage and force measurement assembly under high stress conditions.