US 12,135,307 B2
Sensor element of gas sensor
Ryo Onishi, Iwakura (JP); Yusuke Watanabe, Nagoya (JP); and Takashi Hino, Kasugai (JP)
Assigned to NGK INSULATORS, LTD., Nagoya (JP)
Filed by NGK INSULATORS, LTD., Nagoya (JP)
Filed on Aug. 30, 2021, as Appl. No. 17/460,752.
Application 17/460,752 is a continuation of application No. PCT/JP2020/009602, filed on Mar. 6, 2020.
Claims priority of application No. 2019-066768 (JP), filed on Mar. 29, 2019.
Prior Publication US 2021/0389268 A1, Dec. 16, 2021
Int. Cl. G01N 27/407 (2006.01); G01N 27/41 (2006.01)
CPC G01N 27/4077 (2013.01) [G01N 27/4072 (2013.01); G01N 27/41 (2013.01)] 2 Claims
OG exemplary drawing
 
1. A sensor element of a gas sensor, the sensor element comprising:
an element base being a ceramic structure having a gas inlet in one end portion thereof into which a measurement gas containing a gas component to be measured is introduced and including therein a gas distribution part communicating from said gas inlet in a longitudinal direction, and a sensing part for sensing said gas component to be measured disposed in said gas distribution part; and
a leading-end protective layer being a porous layer disposed around an outer periphery of said element base in a predetermined range from said one end portion, wherein
said leading-end protective layer includes:
an inner leading-end protective layer disposed to cover said end portion and four side surfaces of said element base contiguous with said end portion; and
an outer leading-end protective layer disposed to cover said inner leading-end protective layer, and having a lower porosity than said inner leading-end protective layer,
said sensor element further includes an underlying layer provided between said inner leading-end protective layer and said element base, having a porosity of 30% to 60% and a thickness of 15 μm to 50 μm, and
a total thickness representative value is 250 μm or more, and a film thickness variation degree is 20 or less,
where said total thickness representative value is defined as an average value of total thicknesses of said leading-end protective layer at a plurality of thickness evaluation positions, said plurality of thickness evaluation positions including at least:
a first position as a position of a starting point of said gas distribution part where said gas inlet is disposed;
a second position as an intermediate position of said gas distribution part; and
a third position as a position of an innermost end of said gas distribution part from said gas inlet, and
said film thickness variation degree is defined as a ratio of a difference between a maximum value and a minimum value of said total thicknesses of said leading-end protective layer at said plurality of thickness evaluation positions with respect to said total thickness representative value that is multiplied by 100.