Gas component detection apparatus

• US 4,322,383 A
• Filed: 08/18/1980
• Issued: 03/30/1982
• Est. Priority Date: 12/23/1975
• Status: Expired due to Term

• Current Assignee: Nippon Soken, Inc., Toyota Jidosha Kogyo Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Nippon Soken, Inc., Toyota Jidosha Kogyo Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Sato, Susumu, Hattori, Tadashi, Yasuda, Eturo, Aoki, Keiji, Segawa, Yoshihiro
• Primary Examiner(s): Turk, Arnold
• Application Number:
  US06/179,222
• Time in Patent Office: 589 Days
• Field of Search: 422/94, 422/95, 422/96, 422/97, 422/98, 338/34, 73/23, 73/27 R, 324/71 SN, 324/65 R, 324/65 P, 204/195 S
• US Class Current: 422/95
• CPC Class Codes: G01N 27/12 of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid , for detecting components in the fluid
• CPC Class Codes: G01N 27/16 caused by burning or catalytic oxidation of surrounding material to be tested, e.g. of gas
• CPC Class Codes: G01N 33/0031 comprising two or more sensors, e.g. a sensor array electrochemical electrode arrays G01N27/27
• CPC Class Codes: H01C 13/00 Resistors not provided for elsewhere

Abstract

A gas component detection apparatus comprises a first and a second gas sensing elements each composed of a metal oxide which exhibits variable electric resistances according to gaseous components and temperatures of gases to be detected. A catalyst is carried at least by the first sensing element for promoting oxidation reactions of the gaseous components of the gases. A first pair of electrodes are inserted into those portions of the first sensing element which are subjected to catalytic action of the catalyst. Into the portions of the second sensing element which are not subjected to catalytic action are inserted a second pair of electrodes. The first pair of electrodes sense a variation in electric resistances resulting from the gaseous components and temperatures of the gases, while the second pair of electrodes detect an electric resistance variation related mainly upon the gas temperatures. Consequently, an output signal reflecting substantially only the gaseous components of the gases is produced by offsetting both of the electric resistances separately sensed utilizing a suitable electric circuit.

Claims

1. A gas component detection apparatus comprising:

first and second gas sensing elements each including a metal oxide which exhibits variable electric resistance according to gaseous components and temperatures of gases to be detected, each element additionally carrying a catalyst for promoting oxidation reactions of the gaseous components of the gases,

a first pair of electrodes inserted into said first sensing element for sensing a variation in electric resistance exhibited at a portion of said first sensing element subjected to catalytic action of the catalyst carried thereon,

a second pair of electrodes inserted into said second sensing element for sensing a variation in electric resistance exhibited at a portion of said second sensing element at which the electric resistance sensed across the second pair of electrodes is not affected by the catalytic action of the catalyst carried thereon, and

circuit means adapted to be joined to said pairs of electrodes for producing an output signal in a manner whereby the variations in resistance of the sensing elements resulting from gas temperatures offset one another and said output is representative of variations in resistance of the first sensing element resulting from the gaseous components.

2. A gas component detection apparatus as set forth in claim 1, wherein the metal oxide of each of said first and second sensing elements includes a plurality of different metal oxides exhibiting substantially same resistance variation for the same temperature variation.

3. A gas component detection apparatus as set forth in claim 1 or 2, wherein said first sensing element has a porous structure, while said second sensing element has a dense structure.

4. A gas component detection apparatus as set forth in claim 3, wherein said second sensing element includes chromium oxide.

5. A gas component detection apparatus as set forth in claim 3, wherein said second sensing element includes manganese oxides.

6. A gas component detection apparatus as set forth in claim 1 wherein said second sensing element carries said catalyst in a region spaced apart from at least one of said second pair of electrodes.

7. A gas component detection apparatus as set forth in claim 6, wherein said region is spaced apart from both of said second pair of electrodes.

8. A gas component detection apparatus as set forth in claim 6, wherein the region in which said catalyst is carried is adjacent a surface of the second sensing element, a portion of one of said second pair of electrodes extending within said region.

9. A gas component detection apparatus as set forth in claim 6, wherein the region in which said catalyst is carried surrounds one of the second pair of electrodes inserted within said second sensing element.