Hydrocarbon gas sensor

摘要

Provided is a gas sensor capable of accurately obtaining a hydrocarbon gas concentration even if a measurement gas contains water vapor. A main pumping cell adjusts an oxygen partial pressure of a first internal space such that a hydrocarbon gas in a measurement gas is not substantially burned in the first internal space. An auxiliary pumping cell adjusts an oxygen partial pressure of a second internal space such that inflammable gas components except for hydrocarbon are selectively burned. Then, the measurement gas is introduced into a third internal space through a third diffusion control part. With oxygen concentration equilibrium kept in the third internal space, hydrocarbon existing in the measurement gas that has reached the third internal space is all burned. Then, the concentration of the hydrocarbon gas component existing in the measurement gas is identified based on the magnitude of a current flowing between the measuring electrode and the main pumping electrode at that time.

主权项

1. A hydrocarbon gas sensor that has a sensor element formed of an oxygen-ion conductive solid electrolyte and identifies a concentration of a hydrocarbon gas component of a measurement gas based on a current flowing through said solid electrolyte when said hydrocarbon gas component is burned, said hydrocarbon gas sensor comprising:
a first diffusion control part that is in communication with the outside and applies a first diffusion resistance to said measurement gas; a first internal space that is in communication with said first diffusion control part, into which the measurement gas is introduced with said first diffusion resistance from said outside; a second diffusion control part that is in communication with said first internal space and applies a second diffusion resistance to said measurement gas; a second internal space that is in communication with said second diffusion control part, into which the measurement gas is introduced with said second diffusion resistance from said first internal space; a third diffusion control part that applies a third diffusion resistance to said measurement gas introduced into said second internal space; a third internal space that is in communication with said third diffusion control part, into which the measurement gas is introduced with said third diffusion resistance from said second internal space; a first electrochemical pumping cell formed of a first internal electrode formed to face said first internal space, a first external electrode formed on an outer surface of said sensor element, and said solid electrolyte located between said first internal electrode and said first external electrode; a second electrochemical pumping cell formed of a second internal electrode formed to face said second internal space, a second external electrode formed on the outer surface of said sensor element, and said solid electrolyte located between said second internal electrode and said second external electrode; a measuring pumping cell formed of a measuring electrode formed to face said third internal space, a third external electrode formed on the outer surface of said sensor element, and said solid electrolyte located between said measuring electrode and said third external electrode; a reference gas space into which a reference gas is introduced; and a reference electrode formed to face said reference gas space, means for causing said first electrochemical pumping cell to adjust an oxygen partial pressure of said first internal space such that a hydrocarbon gas in said measurement gas is not substantially burned in said first internal space, means for causing said second electrochemical pumping cell, based on said third diffusion resistance, to adjust an oxygen partial pressure of said second internal space such that an oxygen concentration gradient in said third internal space keeps an equilibrium state, and means for causing said hydrocarbon gas sensor to burn, on the surface of said measuring electrode, all of said hydrocarbon existing in said third internal space, by supplying oxygen to said third internal space by said measuring pumping cell, to thereby identify the concentration of said hydrocarbon gas component existing in said measurement gas based on the magnitude of a current flowing between said measuring electrode and said third external electrode or between said measuring electrode and said reference electrode.