Gas sensor and method of manufacturing thereof

A gas sensor comprising:

• a sensing element with an axial direction which is set along a length direction thereof, a thickness direction perpendicular to the axial direction, and a width direction perpendicular to both the axial direction and the thickness direction when the gas sensor is assembled, and comprising (i) a base end portion located at one end of the sensing element in the axial direction, (ii) a cell composed of an oxygen ion conductive solid electrolyte member, (iii) a pair of electrode-mounted surfaces formed on both outer sides of the base end portion to be back to back in the thickness direction, to be parallel with each other, and to be perpendicular to the thickness direction, and (iv) a heater to heat the cell, the cell being integrally assembled with the heater;
• a first insulator through which the sensing element is inserted to be held;
• a housing fixedly containing the first insulator which is inserted through the housing;
• two pairs of electrode pads secured on the pair of electrode-mounted surfaces of the base end portion of the sensing element so as to allow the two pairs of electrode pads to provide electrical connections for heating the cell and for detecting a concentration of a specific gas to be measured, pair by pair, wherein the two electrode pads belonging to each of the two pairs of electrode pads are disposed on the pair of electrode-mounted surfaces respectively such that the two electrode pads are distanced from each other in the width direction;
• and
• a terminal unit comprising a pair of second insulators, each insulator of the pair of second insulators having an inner side flat surface and an outer side surface with securing recesses, the pair of second insulators being disposed to pinch and hold both the electrode-mounted surfaces of the base end portion of the sensing element, two pairs of plate-shaped metal terminals electrically contacting the electrode pads, pair by pair, respectively, and being disposed on the inner side surfaces of the pair of second insulators, the two pairs of metal terminals and the pair of second insulators being aligned via the sensing element in the thickness direction, and a spring member formed to have a plurality of spring contact portions and arranged such that the spring contact portions of the spring member press the securing recesses of the pair of second insulators mutually inward from the securing recesses in the thickness direction at one or more different positions on each of the electrode-mounted surfaces in the width direction, the one or more different positions including two different positions on, at least, one of the electrode-mounted surfaces on both sides of the sensing element in the thickness direction, the two different positions being separated larger than a distance between the two metal terminals in the width direction and located respectively on both outsides of the two metal terminals in the width direction.