Pressure sensor having baffling means

• US 4,920,805 A
• Filed: 11/07/1988
• Issued: 05/01/1990
• Est. Priority Date: 11/27/1987
• Status: Expired due to Term

• Current Assignee: NGK Insulators Limited
• Original Assignee: NGK Insulators Limited
• Inventors: Watanabe, Yasushi, Shibata, Kazuyoshi, Yajima, Yasuhito
• Primary Examiner(s): Woodiel, Donald O.
• Application Number:
  US07/268,278
• Time in Patent Office: 540 Days
• Field of Search: 73/706, 73/707, 73/708, 73/756, 73/718, 73/720, 73/721, 73/724, 73/726, 73/727, 73/115, 338/4, 361/283
• US Class Current: 73/706
• CPC Class Codes: G01L 19/04 Means for compensating for effects of changes of temperature , i.e. other than electric compensation
• CPC Class Codes: G01L 19/0681 Protection against excessive heat
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass

Abstract

The invention relates to a pressure sensor having a ceramic diaphragm which is exposed at one of opposite surfaces thereof to a measurement fluid in an external space and deformable in response to a pressure of the measurement fluid, and a strain detector for producing an electrical output representative of an amount of deformation of the ceramic diaphragm. The ceramic diaphragm is fixedly supported at an outer portion thereof, so that a central working portion of the diaphragm is deformable in response to the pressure of the measurement fluid applied thereto. The sensor includes a baffling structure disposed adjacent the above-indicated one surface of the ceramic diaphragm. The baffling structure has portions which partially define a chamber to which the above-indicated one surface of the ceramic diaphragm is exposed. The baffling structure has at least one communication hole for communication between the chamber and the external space, such that the central working portion of the ceramic diaphragm is protected against direct exposure to a straightforward flow of the measurement fluid from the external space toward the central working portion of the diaphragm.

Claims

1. A pressure sensor having a ceramic diaphragm which is exposed at one of opposite surfaces thereof to a measurement fluid in an external space and deformable in response to a pressure of said measurement fluid, and strain detector means for producing an electrical output representative of an amount of deformation of the ceramic diaphragm, said pressure sensor comprising:

a support member for fixedly supporting said ceramic diaphragm at a peripheral portion of said diaphragm, so as to allow a central working portion of said diaphragm to be deformed in response to the pressure of said measurement fluid applied thereto; and

a baffling structure disposed adjacent said one surface of said ceramic diaphragm, and including portions which cooperate with said one surface to define a chamber to which said one surface of the ceramic diaphragm is exposed, said baffling structure having at least one communication hole for communication between said chamber and said external space, said at least one communication hole including at least one aperture formed through a portion of said baffling structure which faces said one surface of the ceramic diaphragm, said at least one aperture being substantially aligned with said support member such that said one surface of said central working portion of said ceramic diaphragm is protected against direct exposure to a straightforward flow of said measurement fluid from said external space toward said central working portion of the diaphragm.

2. The pressure sensor of claim 1, wherein said baffling structure comprises a plurality of baffleplate members which are spaced apart from each other and from said one surface of said ceramic diaphragm, in a direction substantially perpendicular to said one surface, said at least one communication hole consisting of at least one communication hole formed through a thickness of each of said plurality of baffleplate members, such that said at least one communication hole formed through one of said baffleplate members is spaced from said at least one communication hole formed through another of said baffleplate members, in a direction substantially parallel to said one surface of said ceramic diaphragm.

3. The pressure sensor of claim 2, wherein said plurality of baffleplate members consist of two baffleplate members.

4. The pressure sensor of claim 3, wherein one of said two baffleplate members consists of a bottom wall of a housing in which said support member, said ceramic diaphragm and the other baffleplate member are accommodated, said other baffleplate member dividing said chamber into two spaces which communicate with each other through said at least one communication hole formed through said other baffleplate member.

5. The pressure sensor of claim 1, wherein said baffling structure comprises a single baffleplate member which is spaced apart from said one surface of said ceramic diaphragm, in a direction substantially perpendicular to said one surface, said at least one communication hole being aligned with a portion of said ceramic diaphragm near said outer portion.

6. The pressure sensor of claim 5, wherein said single baffleplate member consists of a bottom wall of a housing in which said support member and said ceramic diaphragm are accommodated.

7. The pressure sensor of claim 1, wherein said said strain detector means comprises at least one resistor formed on another of said opposite surfaces of said ceramic diaphragm, a resistance value of said at least one resistor varying depending upon an amount of deformation of said ceramic diaphragm caused by said pressure of the measurement fluid, whereby said pressure is measured by said resistance value.

8. The pressure sensor of claim 1, wherein said strain detector means comprises a first electrode formed on another of said opposite surfaces of said ceramic diaphragm, and a second electrode fixedly positioned in spaced-apart relationship with said first electrode and electrically insulated from said first electrode, a static capacity between said first and second electrodes varying depending upon an amount of deformation of said ceramic diaphragm caused by said pressure of the measurement fluid, whereby said pressure is measured by said static capacity.