US-12618800-B2 - Gas sensor element and gas sensor

Abstract

A gas sensor element ( 10 ) which includes an element body portion ( 100 ); a pump cell ( 110 ) which is configured to adjust a concentration of oxygen in a gas to be measured which is introduced into the element body portion ( 100 ); a detection chamber ( 160 ) which is formed inside the element body portion ( 100 ) and into which the gas to be measured in which the concentration of oxygen has been adjusted is introduced; and a layer-shaped cathode electrode ( 133 ) which is housed in the detection chamber ( 160 ) and configured to decompose NO. A relationship between a volume V 1 of the detection chamber ( 160 ) and a volume V 2 of the cathode electrode ( 133 ) in the gas sensor element ( 10 ) satisfies either one of conditions (A) and (B) as defined herein.

Inventors

• Hitoshi Furuta
• Akinori Kojima
• Kentaro Kamada
• Yosuke Suzuki

Assignees

• NGK SPARK PLUG CO., LTD.

Dates

Publication Date

20260505

Application Date

20221220

Priority Date

20211221

Claims (4)

1. 1 . A gas sensor element comprising: an element body portion which includes a plurality of laminated ceramic sheets; a pump cell which is configured to adjust a concentration of oxygen in a gas to be measured which is introduced into the element body portion; a detection chamber which is formed inside the element body portion and into which the gas to be measured in which the concentration of oxygen has been adjusted is introduced; and a layer-shaped cathode electrode which is housed in the detection chamber and configured to decompose NO, wherein a relationship between a volume V 1 of the detection chamber and a volume V 2 of the cathode electrode satisfies either a condition (A) or a condition (B) described below, Condition (A): the volume V 1 is not less than 0.047 mm 3 and not greater than 0.057 mm 3 and the volume V 2 is not less than 0.031 mm 3 and not greater than 0.047 mm 3 , and Condition (B): the volume V 1 is not less than 0.057 mm 3 and not greater than 0.117 mm 3 and the volume V 2 is not less than 0.047 mm 3 and not greater than 0.059 mm 3 .
2. 2 . The gas sensor element as claimed in claim 1 , wherein the detection chamber penetrates at least one ceramic sheet among the plurality of ceramic sheets, in a thickness direction, and in a region where the detection chamber penetrates the at least one ceramic sheet, a cross-sectional area of the detection chamber in a plane direction of the at least one ceramic sheet is not less than 0.05 mm 2 and not greater than 0.35 mm 2 .
3. 3 . The gas sensor element as claimed in claim 1 , further comprising: a solid electrolyte layer which forms a part of the element body portion and has a front surface on which the cathode electrode is formed; and an anode electrode which is disposed on the front surface of the solid electrolyte layer and configured to receive oxygen ions that are generated at the cathode electrode in accordance with decomposition of NO and move in the solid electrolyte layer.
4. 4 . A gas sensor comprising the gas sensor element as claimed in claim 1 .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present disclosure relates to a gas sensor element and a gas sensor. 2. Description of the Related Art A gas sensor that detects the concentration of NOx contained in exhaust gas of an internal combustion engine is known. Such a type of gas sensor utilizes the oxygen ion conductivity of zirconia (ZrO2) heated to high temperatures, and in an equilibrium reaction of NO with N2 and O2. Further, while the decomposition of NO is accelerated by removing oxygen (O2), oxygen generated by the decomposition is measured, whereby an NOx concentration is obtained. As such a gas sensor, for example, a gas sensor that includes a gas sensor element including a first pump cell, a detection cell, a second pump cell, a first measurement chamber, a second measurement chamber, etc., is known (see, for example, Patent Document 1). The first pump cell performs pumping-out and pumping-in (so called “pumping”) of oxygen in exhaust gas between the first measurement chamber and the outside, and adjusts the concentration of oxygen in the exhaust gas. The concentration of oxygen in the first measurement chamber is controlled to a low level by the action of the first pump cell. The detection cell measures the concentration of oxygen in the exhaust gas on which pumping-out and pumping-in of oxygen has been performed by the first pump cell, and acts to apply a current (first pump current) to the first pump cell such that an output voltage (electromotive force) corresponding to the concentration of oxygen is constant. The exhaust gas in the first measurement chamber in which the concentration of oxygen is controlled as described above is introduced into the second measurement chamber through a predetermined path in the gas sensor element. The second pump cell detects an NOx concentration from the exhaust gas introduced into the second measurement chamber. The second pump cell includes a pair of electrodes, and one electrode (cathode electrode, Ip2− electrode) of these electrodes is housed in the second measurement chamber. NO in the exhaust gas introduced into the second measurement chamber is decomposed into N2 and O2 at the electrode in the second measurement chamber. A second pump current for pumping out the oxygen generated by the decomposition to the other electrode (anode electrode) flows through the second pump cell. The second pump current is proportional to the NO concentration, so that the concentration of NOx (NO) in the exhaust gas is obtained by measuring the second pump current. [Patent Document 1] Japanese Patent Application Laid-Open (kokai) No. 2017-207466 3. Problems to be Solved by the Disclosure In a conventional gas sensor, improved responsiveness to NO is required by shortening the rise time of the output waveform of the second pump current described above. SUMMARY OF THE DISCLOSURE It is therefore an object of the present disclosure to provide a gas sensor element and a gas sensor having excellent NO responsiveness. The means for solving the above problems are as follows. <1> A gas sensor element including: an element body portion which includes a plurality of laminated ceramic sheets; a pump cell which is configured to adjust a concentration of oxygen in a gas to be measured which is introduced into the element body portion; a detection chamber which is formed inside the element body portion and into which the gas to be measured in which the concentration of oxygen has been adjusted is introduced; and a layer-shaped cathode electrode which is housed in the detection chamber and configured to decompose NO, wherein a relationship between a volume V1 of the detection chamber and a volume V2 of the cathode electrode satisfies either one of a condition (A) and a condition (B) described below, Condition (A): the volume V1 is not less than 0.047 mm3 and not greater than 0.065 mm3 and the volume V2 is not less than 0.030 mm3 and not greater than 0.059 mm3, andCondition (B): the volume V1 is not less than 0.047 mm3 and not greater than 0.125 mm3 and the volume V2 is not less than 0.044 mm3 and not greater than 0.059 mm3. <2> The gas sensor element according to the above <1>, wherein the detection chamber penetrates at least one ceramic sheet among the plurality of ceramic sheets, in a thickness direction, and in a region where the detection chamber penetrates the ceramic sheet, a cross-sectional area of the detection chamber in a plane direction of the ceramic sheet is not less than 0.05 mm2 and not greater than 0.35 mm2. <3> The gas sensor element according to the above <1> or <2>, further including: a solid electrolyte layer which forms a part of the element body portion and has a front surface on which the cathode electrode is formed; and an anode electrode which is disposed on the front surface of the solid electrolyte layer and configured to receive oxygen ions that are generated at the cathode electrode in accordance with decomposition of NO and move in the soli