| 摘要 |
PURPOSE:To enable rapid start-up of a sensor by respectively specifying ratios between an outer diameter of a heater unit, an inner diameter of a solid electrolyte unit, and the axial length of a heat generating body, and a distance from the lower end of the heat generating body to the tip of the solid electrolyte unit/an inner diameter of the heater unit. CONSTITUTION:A solid electrolyte unit 1 comprises metal oxide having oxygen ion conductivity in this oxygen sensor, while a pair of electrodes are provided on inner and outer surfaces and a ceramic insulating body 25 and a ceramic heater 2 having a surface heat generating body 26 are housed in an inner cavity. At this time a ratio of an outer diameter Rh of the heater 2 to an inner diameter Rs of the electrolyte unit 1 is specified to be 0.8 or larger as activation time is suddenly extended if it is 0.8 or less, while a ratio of a length L of the heat generating body 26 to the outer diameter Rh is specified to 2 or less since the activation time is the shorter and stable when the ratio if 2 or less. A distance l between the tips of the heater 2 and the electrolyte unit 1 to the inner diameter Rs is specified to be 3/5 or less since activation time suddenly increases when it exceeds 3/5. By thus specifying a shape and positioning of the heater within a constant range, the tip of the electrolyte unit can be rapidly heated. |
