US 12,416,601 B2
Gas sensor
Takayuki Sekiya, Nissin (JP); and Yusuke Watanabe, Nagoya (JP)
Assigned to NGK INSULATORS, LTD., Nagoya (JP)
Filed by NGK INSULATORS, LTD., Aichi (JP)
Filed on Sep. 23, 2021, as Appl. No. 17/483,657.
Application 17/483,657 is a continuation of application No. PCT/JP2020/013415, filed on Mar. 25, 2020.
Claims priority of application No. 2019-064322 (JP), filed on Mar. 28, 2019.
Prior Publication US 2022/0011261 A1, Jan. 13, 2022
Int. Cl. G01N 27/41 (2006.01); G01N 27/30 (2006.01); G01N 27/407 (2006.01); G01N 33/00 (2006.01)
CPC G01N 27/41 (2013.01) [G01N 27/301 (2013.01); G01N 27/4071 (2013.01); G01N 27/4075 (2013.01); G01N 33/0037 (2013.01)] 2 Claims
OG exemplary drawing
 
1. A gas sensor that detects a specific gas concentration in a measurement-object gas, the gas sensor comprising:
an element body including an oxygen-ion-conductive solid electrolyte layer and provided with a measurement-object gas flow section therein, the measurement-object gas flow section receiving the measurement-object gas and allowing the measurement-object gas to flow therethrough;
a main pump cell having an inner main pump electrode and an outer main pump electrode, the inner main pump electrode being disposed in a first internal cavity in the measurement-object gas flow section and containing a catalytically-active noble metal, the outer main pump electrode being disposed in an area to be exposed to the measurement-object gas at an outer side of the element body, the main pump cell pumping out oxygen from the first internal cavity,
an auxiliary pump cell having an inner auxiliary pump electrode and an outer auxiliary pump electrode, the inner auxiliary pump electrode being disposed in a second internal cavity provided downstream of the first internal cavity in the measurement-object gas flow section and containing a catalytically-active noble metal, the outer auxiliary pump electrode being disposed in an area to be exposed to the measurement-object gas at an outer side of the element body, the auxiliary pump cell pumping out oxygen from the second internal cavity,
a measurement pump cell having an inner measurement electrode and an outer measurement electrode, the inner measurement electrode being disposed in a measurement chamber provided downstream of the second internal cavity in the measurement-object gas flow section and containing a catalytically-active noble metal, the outer measurement electrode being disposed in an area to be exposed to the measurement-object gas at an outer side of the element body, the measurement pump cell pumping out oxygen produced in the measurement chamber from the specific gas,
a CPU coupled to a memory storing instructions that when executed by the CPU configure the CPU to:
pump out oxygen from the measurement chamber by applying a measurement pump current repeatedly as an on-off controlled pump current between the inner measurement electrode and the outer measurement electrode; and
a reference electrode that is disposed inside the element body and that receives a reference gas serving as a reference for detection of the specific gas concentration;
wherein the CPU is configured to:
detect a measurement voltage between the reference electrode and the inner measurement electrode,
control the measurement pump current based on the measurement voltage during a second period among a first period and the second period so as to set an oxygen concentration in the measurement chamber to a predetermined low concentration, the first period being a period in which a change has occurred in the measurement voltage due to the measurement pump current being in an on mode, and the second period being a period in which the change in the measurement voltage has receded as compared with the first period due to the measurement pump current being in an off mode; and
detect the specific gas concentration in the measurement-object gas based on the measurement pump current.