Pressure variable capacitor

• US 3,993,939 A
• Filed: 01/07/1975
• Issued: 11/23/1976
• Est. Priority Date: 01/07/1975
• Status: Expired due to Term

• Current Assignee: Siemens-Bendix Automotive Electronics LP (Siemens AG)
• Original Assignee: The Bendix Corporation (Honeywell International Inc.)
• Inventors: Slavin, Michael, Bata, George T., Carp, Ralph W.
• Primary Examiner(s): Goldberg, E. A.
• Application Number:
  US05/539,212
• Time in Patent Office: 686 Days
• Field of Search: 317/245, 317/246, 317/247, 317/248, 317/249 R, 317/398 C, 73/398 C
• US Class Current: 361/283.4
• CPC Class Codes: G01L 9/0072 using variations in capacitance
• CPC Class Codes: H01G 5/16 using variation of distance between electrodes

Abstract

A pressure responsive diaphragm is attached to a substrate carrying a thick film metallic coating covered by a dielectric glass coating so that the diaphragm and thick film coating comprise a pressure variable capacitor. Changes in pressure difference across the diaphragm force the diaphragm to roll against the glass to vary the area of diaphragm in contact with the glass, thus changing the capacity.

Claims

1. A fluid pressure variable capacitor comprising:

an electrically nonconductive substrate having a supporting surface;

an electrode comprising an electrically conductive film affixed to a portion of said supporting surface;

an electrically conductive diaphragm having a thin flexible active section which includes a central area;

said active section being least stiff to forces perpendicular to said active section at said central area, said active section being increasingly stiffer as the distance along said diaphragm from said central area increases, said active section being relatively fixed at the outer extremity thereof with respect to forces perpendicular thereto, the periphery of said diaphragm being hermetically sealed to said supporting surface so that said active section overlies said electrode, said diaphragm and said electrode comprising the plates of said pressure variable capacitor; and

,

a dielectric film disposed between said diaphragm and said electrode;

said capacitor being useful for producing a capacity related to difference of pressure across said diaphragm at least in a predetermined pressure difference range, said active section being in contact with said electrode through said dielectric film at said central area at the low end of said range and rolling into increasingly greater area of contact with said electrode through said dielectric film as the pressure difference across said diaphragm increases, the area of contact of said diaphragm with said electrode through said dielectric film at the high end of said range being at least several magnitudes greater than said central area and wherein said diaphragm, when flat, is relatively close to said electrode.

2. The fluid pressure variable capacitor of claim 1 with a cupshaped rigid structure hermetically sealed to the surface of said substrate opposite said diaphragm to form a closed space between the opposite surface of said substrate and said structure and with a passage through said substrate to permit equilization of pressure on both sides of said substrate.

3. The fluid pressure responsive capacitor of claim 1 wherein said dielectric film is affixed to and over said electrode.

4. The fluid pressure variable capacitor of claim 1 wherein the space enclosed by said diaphragm is at least partially evacuated and sealed.

5. The fluid pressure variable capacitor of claim 4 wherein said diaphragm is normally flat and secured at the periphery thereof.

6. The fluid pressure responsive capacitor of claim 4 wherein said diaphragm is relatively free to change size radially in response to temperature changes.

7. A fluid pressure variable capacitor comprising:

a first electrode;

a support member having an electrically nonconductive gas impervious surface upon which said first electrode is supported;

a gas impervious diaphragm means comprising a second electrode and having a flexible active section which includes a central area and including means supporting said active section to be relatively immovable at the outer extremity thereof in a direction perpendicular to the plane of said active section, said active section being increasingly less stiff as the distance from said outer extremity toward said central area increases, said diaphragm means being in hermetically sealed relationship with said gas impervious surface, said first and second electrodes forming plates of said pressure variable capacitor; and

,

a dielectric film interposed between said first and second electrodes, said second electrode being disposed at a relatively close distance to said first electrode so that at least a portion of said first and second electrodes are in increasingly greater area of contact with one another through said dielectric film from a relatively small area of contact to an area of contact several magnitudes greater as the pressure difference across said diaphragm means increases.

8. The fluid pressure variable capacitor of claim 7 wherein the area of contact of said first and second electrodes through said dielectric film is approximately circular.

9. The fluid pressure variable capacitor of claim 7 wherein the space between said diaphragm and said surface is evacuated.

10. The fluid pressure variable capacitor of claim 7 wherein said diaphragm includes an elastomer means for supporting said second electrode in said hermetically sealed relationship with said gas impervious surface.