Gas sensor and casing for containing sensor element
A gas sensor includes: a sensor element including a sensing part on a side of one end portion thereof; a casing; and a connector disposed in the casing to electrically connect the sensor element to an outside, wherein the casing includes: an outer tube including a main portion in which a reference gas is included and a sealing portion being an end portion having a smaller diameter than the main portion, another end portion of the sensor element protruding to the main portion, a rubber seal member fitted into the sealing portion to seal the outer tube, and a spacer intervening between the seal member and the connector in the outer tube. The spacer includes a concave portion in an end surface on a side having contact with the connector, and has contact with the connector in the end surface except for the concave portion.
1 . A gas sensor for sensing a predetermined gas component contained in a measurement gas, the gas sensor comprising:
a sensor element including a sensing part on a side of one end portion thereof;
a casing in which the sensor element is contained and secured; and
a connector disposed in the casing to electrically connect the sensor element to an outside, wherein
the casing includes:
an outer tube including a main portion in which a reference gas is included and a sealing portion being an end portion having a smaller diameter than the main portion, another end portion of the sensor element protruding to the main portion,
a rubber seal member fitted into the sealing portion to seal the outer tube, and
a ceramic spacer intervening between the seal member and the connector in the outer tube,
the ceramic spacer includes a concave portion in an end surface on a side having contact with the connector, and has contact with the connector in the end surface except for the concave portion, and
when a smaller one of an area of a contact surface of the connector having contact with the ceramic spacer and an area of the whole end surface including the concave portion of the ceramic spacer is S0, and a contact area between the connector and the ceramic spacer is S. satisfied for a contact portion area ratio S/S0 is:
0.2≤ S/S 0≤0.7.
2 . The gas sensor according to claim 1 , wherein
when a height of the ceramic spacer is a and a depth of the concave portion is b, satisfied for a depth ratio b/a is:
0.08≤ b/a≤ 0.6.
3 . The gas sensor according to claim 1 , wherein
the concave portion has a linear shape, a cross-like shape, or a circular shape in a plan view from a side of the end surface of the ceramic spacer.
4 . The gas sensor according to claim 1 , wherein
a thermal conductivity of the ceramic spacer is equal to or smaller than 32 W/m·K.
5 . A sensor element containment casing for containing a sensor element and a connector while securing the sensor element therein, the sensor element including, on a side of one end portion thereof, a sensing part for sensing a predetermined gas component contained in a measurement gas, the connector electrically connecting the sensor element to an outside, the sensor element containment casing comprising:
an outer tube including a main portion in which a reference gas is included and a sealing portion being an end portion having a smaller diameter than the main portion, another end portion of the sensor element protruding to the main portion;
a rubber seal member fitted into the sealing portion to seal the outer tube; and
a ceramic spacer intervening between the seal member and the connector in the outer tube, wherein
the ceramic spacer includes a concave portion in an end surface on a side having contact with the connector, and has contact with the connector in the end surface except for the concave portion, and
when a smaller one of an area of a contact surface of the connector having contact with the ceramic spacer and an area of the whole end surface including the concave portion of the spacer is S0, and a contact area between the connector and the ceramic spacer is S. satisfied for a contact portion area ratio S/S0 is:
0.2≤ S/S 0≤0.7.
6 . The sensor element containment casing according to claim 5 , wherein
when a height of the ceramic spacer is a and a depth of the concave portion is b, satisfied for a depth ratio b/a is:
0.08≤ b/a≤ 0.6.
7 . The sensor element containment casing according to claim 5 , wherein
the concave portion has a linear shape, a cross-like shape, or a circular shape in a plan view from a side of the end surface of the ceramic spacer.
8 . The sensor element containment casing according to claim 5 , wherein
a thermal conductivity of the ceramic spacer is equal to or smaller than 32 W/m·K.
9 . The gas sensor according to claim 2 , wherein
the concave portion has a linear shape, a cross-like shape, or a circular shape in a plan view from a side of the end surface of the ceramic spacer.
10 . The gas sensor according to claim 2 , wherein
a thermal conductivity of the ceramic spacer is equal to or smaller than 32 W/m·K.
11 . The sensor element containment casing according to claim 6 , wherein
the concave portion has a linear shape, a cross-like shape, or a circular shape in a plan view from a side of the end surface of the ceramic spacer.
12 . The sensor element containment casing according to claim 6 , wherein
a thermal conductivity of the ceramic spacer is equal to or smaller than 32 W/m·K.