Differential pressure sensor

• US 20060169048A1
• Filed: 12/08/2005
• Published: 08/03/2006
• Est. Priority Date: 01/28/2005
• Status: Active Grant

• Current Assignee: MKS Japan, Inc. (MKS Instruments Incorporated)
• Original Assignee: MKS Japan, Inc. (MKS Instruments Incorporated)
• Inventors: Suzuki, Isao
• Granted Patent: US 7,219,551 B2
• Time in Patent Office: Days
• US Class Current: 73/716
• CPC Class Codes: G01L 13/025 using diaphragms
• CPC Class Codes: G01L 9/0072 using variations in capacitance

Abstract

According to the present invention, there is provided a high-precision differential pressure sensor which is not affected by a considerable change in baseline pressure. A differential pressure sensor of the present invention comprises: a pair of diaphragms, each including a diaphragm portion capable of being deformed due to application of a pressure and a support portion for holding an outer peripheral edge of the diaphragm portion; a pair of fixed electrodes in disk-like form fixed to the support portions of the diaphragms; and a movable electrode including a disk-like electrode portion and shaft-like projections extending in opposite directions from a central portion of the electrode portion. The shaft-like projections extend at a right angle relative to the electrode portion, and the movable electrode is secured to central portions of the diaphragms through the shaft-like projections so that the electrode portion faces each of the fixed electrodes in a predetermined spaced relationship. The movable electrode is capable of moving so as to allow a distance between the electrode portion and each of the fixed electrodes to vary according to a difference between fluid pressures acting on the respective diaphragm portions of the diaphragms. A capacitance generated between the electrode portion and each of the fixed electrode changes due to a variance in the distance between the electrode portion and each of the fixed electrode, and a differential pressure is detected, based on this change in capacitance.

Claims

1. A differential pressure sensor comprising:

a pair of diaphragms each capable of being deformed according to a pressure applied, each of said pair of diaphragms being at least partially made of a metal and having a common center axis;

a disk-like movable electrode provided between said pair of diaphragms and located on said common center axis, said movable electrode being at least partially made of a metal, each of opposing surfaces of said movable electrode including a shaft-like projection formed at a central portion thereof, said shaft-like projection being secured to a central portion of an associated one of said diaphragms; and

fixed electrodes held by outer peripheral portions of said pair of diaphragms, so as to face said opposing surfaces of the movable electrode,

wherein a change in capacitance between said movable electrode and each of said fixed electrodes is detected to determine a differential pressure.

2. A differential pressure sensor according to claim 1, wherein said fixed electrodes are formed by a pair of fixed electrodes respectively provided on surfaces of electrically insulated disk-like members, said electrically insulated disk-like members being secured to said outer peripheral portions of the pair of diaphragms.

3. A differential pressure sensor according to claim 2, wherein another fixed electrode is provided on a surface of each of said electrically insulated disk-like members, which surface is in opposing relation to the surface on which one of said pair of fixed electrodes is provided.

4. A differential pressure sensor according to claim 2, wherein a hole is formed at a central portion of each of said pair of fixed electrodes so as to allow said shaft-like projection of the movable electrode to extend therethrough, and a hole is also formed at a central portion of each of said electrically insulated disk-like members so as to allow said shaft-like projection of the movable electrode to extend therethrough.

5. A differential pressure sensor according to claim 3, wherein said differential pressure sensor is capable of correcting an output value of the differential pressure, based on a change in capacitance between said another fixed electrode and the diaphragm facing said another fixed electrode.

6. A differential pressure sensor according to claim 1, wherein a surface of each of said pair of diaphragms that makes contact with an object to be detected is at least partially covered by a fluorine-type polymer resin.

7. A differential pressure sensor according to claim 2, wherein a surface of each of said pair of diaphragms that makes contact with an object to be detected is at least partially covered by a fluorine-type polymer resin.

8. A differential pressure sensor according to claim 3, wherein a surface of each of said pair of diaphragms that makes contact with an object to be detected is at least partially covered by a fluorine-type polymer resin.

9. A differential pressure sensor according to claim 4, wherein a surface of each of said pair of diaphragms that makes contact with an object to be detected is at least partially covered by a fluorine-type polymer resin.

10. A differential pressure sensor according to claim 5, wherein a surface of each of said pair of diaphragms that makes contact with an object to be detected is at least partially covered by a fluorine-type polymer resin.