AIR FUEL RATIO SENSOR

• US 3,844,920 A
• Filed: 11/21/1973
• Issued: 10/29/1974
• Est. Priority Date: 11/21/1973
• Status: Expired due to Term

• Current Assignee: Bruce W. Holleboom, Richard R. Burgett
• Original Assignee: Bruce W. Holleboom, Richard R. Burgett
• Inventors: Holleboom, Bruce W., Burgett, Richard R.
• Primary Examiner(s): Tung, T.
• Application Number:
  US05/417,724
• Time in Patent Office: 342 Days
• Field of Search: 60/276,285,289 123/119R,119E 204/1T,195S
• US Class Current: 204/428
• CPC Class Codes: G01N 27/4077 Means for protecting the electrolyte or the electrodes

Abstract

This invention relates to a sensor that can be used in an exhaust system for sensing the relative presence of oxygen in the exhaust stream. The sensor includes a hollow zirconia element that is conical in shape, and is closed at one end with the zirconia element having platinum electrodes on the inside and outside surfaces. A mounting device that is constructed of easily assembled parts supports the zirconia element. The sensor is constructed and adapted to be mounted in the automobile exhaust stream so as to expose the outside of the zirconia element to the exhaust stream and the inside to atmosphere. A shield that protects the outside of the zirconia element is attached to the mounting device to prevent erosion of the electrode coating. Because of the diverse thermal expansion rates of the components that make up the sensor, a mica insulator is included as an essential element in the assembly to maintain a tight seal between the different component parts and assure electrical continuity.

Claims

1. An exhaust gas sensor for measuring the relative presence of oxygen in an exhaust system comprising:

a hollow metal shell having a shoulder therein, a first metal gasket on said shoulder, a conically shaped hollow zirconia element positioned within said hollow metal shell on said gasket having one end closed and thin walls tapering from the thinnest section that begins at the closed end and terminates in a thicker section at the opposite end, which end has an enlarged diameter that forms a top shoulder and a bottom shoulder, said zirconia element having a platinum coating on the inside and outside surfaces including the top and bottom shoulders to form inner and outer electrodes on said zirconia element with the enlarged diameter portion between the top and bottom shoulders being uncoated, said bottom shoulder of said zirconia element being in contact with said first metal gasket to form a first electrical contact means between said outer shell and said outer electrode, a second metal gasket on the top shoulder of said zirconia element that provides electrical contact with the inner electrode on said zirconia element and a metal body member placed thereon forming a second contact means with a terminal on said body member, said outer metal shell including clamping means to retain said zirconia body, said gaskets and said body member in a gas tight relationship, and mica means between said body member and clamping means to compensate for the different expansion and contraction rates of the different components assembled in gas tight relationship to maintain such relationship through the operating life of the sensor.

2. An exhaust gas sensor for measuring the relative presence of oxygen in an exhaust system comprising:

a hollow metal shell having a shoulder formed on the inner surface thereof intermediate its ends and being adapted to be mounted in an exhaust gas conduit, a first metal gasket on said shoulder, a conically shaped hollow zirconia element positioned within said hollow metal shell and having its small diameter end closed and adapted to be exposed to the exhaust gas, the large diameter open end of said zirconia element being joined with an enlarged diameter portion on the outer surface thereof to form a top shoulder and a bottom shoulder, a platinum coating provided on the inside and outside surfaces of said zirconia element including the top and bottom shoulders to form inner and outer electrodes thereon, the surface of said enlarged diameter portion between said shoulders being uncoated, the bottom shoulder of said zirconia element being positioned in contact with said first metal gasket to complete an electrical path between said metal shell and said outer electrode, a second metal gasket on the top shoulder of said zirconia element to complete an electrical path between the inner electrode and a metal body member positioned thereon, said body member having an electrical terminal provided thereon, the open end of said zirconia element being positioned within the end of said metal shell, clamping means provided on the end of said shell to retain said zirconia element in gas tight relationship with said shell, mica means between said metal body member and said clamping means to compensate for the different expansion and contraction rates of the differeNt components assembled in gas tight relationship within said shell and thus seal exhaust gas from the inner electrode, and a shield provided on the end of said shell and about the small diameter end of said zirconia element to protect the outer electrode from the direct impact of the exhaust gas.

3. An exhaust gas sensor for measuring the relative presence of oxygen in an exhaust system comprising:

a hollow metal shell having a shoulder formed on the inner surface thereof intermediate its ends and being adapted to be mounted in an exhaust gas conduit, a first metal gasket on said shoulder, a conically shaped hollow zirconia element positioned within said hollow metal shell and having its small diameter end closed and adapted to be exposed to the exhaust gas, the large diameter open end of said zirconia element being joined with an enlarged diameter portion on the outer surface to form a top shoulder and a bottom shoulder, a platinum coating provided on the inside and outside surfaces of said zirconia element including the top and bottom shoulders to form inner and outer electrodes thereon, the surface of said enlarged diameter portion between said shoulders being uncoated, the bottom shoulder of said zirconia element being positioned in contact with said first metal gasket to complete an electrical path between said metal shell and said outer electrode, a second metal gasket on the top shoulder of said zirconia element to complete an electrical path between the inner electrode and a metal body member positioned thereon, said body member having an electrical terminal provided thereon, the open end of said zirconia element being positioned on the shoulder formed on the inner surface of said metal shell to thereby position the top shoulder within the end of said metal shell below the end thereof, mica means positioned on a shoulder on said metal body member to compensate for the different expansion and contraction rates of the different components assembled within said shell, a nut threadably attached to said metal shell that is in contact with the mica means to retain said zirconia element in gas tight relationship with said shell and thus prevent exhaust gas from reaching the inner electrode, and a shield provided on the end of said shell that encircles the small diameter end of said zirconia element to protect the outer electrode from the direct impact of the exhaust gas.

4. An exhaust gas sensor for measuring the relative presence of oxygen in an exhaust system comprising:

a hollow metal shell having a shoulder formed on the inner surface thereof intermediate its ends and being adapted to be mounted in an exhaust gas conduit, a first metal gasket on said shoulder, a conically shaped hollow zirconia element positioned within said hollow metal shell and having its small diameter end closed and adapted to be exposed to the exhaust gas, the large diameter open end of said zirconia element being joined with an enlarged diameter portion on the outer surface to form a top shoulder and a bottom shoulder, a platinum coating provided on the inside and outside surfaces of said zirconia element including the top and bottom shoulders to form inner and outer electrodes thereon, the surface of said enlarged diameter portion between said shoulders being uncoated, the bottom shoulder of said zirconia element being positioned in contact with said first metal gasket to complete an electrical path between said metal shell and said outer electrode, a second metal gasket on the top shoulder of said zirconia element to complete an electrical path between the inner electrode and a metal body member positioned thereon, said body member having an electrical terminal provided thereon, the open end of said zirconia element being positioned within the end of said metal shell, mica means positioned on a shoulder on said metal body member to compensate for the different expansion and contraction rates of the different components assembled within said shell, a spacer means in contact with thE mica means and held in such position by said metal shell to retain said zirconia element in gas tight relationship with said shell and thus prevent exhaust gas from reaching the inner electrode, and a shield provided on the end of said shell that encircles the small diameter end of said zirconia element to protect the outer electrode from the direct impact of the exhaust gas.

5. An exhaust gas sensor as set forth in claim 4, wherein said spacer means is an insulator.

6. An exhaust gas sensor as set forth in claim 4, wherein said spacer means is a metal nut that is spaced from said body member and is attached to said outer shell.