| 摘要 |
PURPOSE:To obtain an optimum detection element protection hood suitable for a threshold current type air-fuel ratio measuring device having a diffusion resistor, by preventing positional overlap between an outer electrode of a detection element and an exhaust gas intake opening provided in the side wall of a protection hood. CONSTITUTION:A heating ceramic heater 2 is arranged inside a detection element 1 to be held in a housing 3. A heater flange 5 is fixed on the heater 2. The heater 2 is pressed securely with a spring 6 and a shroud 7 is cauked on the housing 3. A protection hood 4 is cauked on the housing 3 completely surrounding the detection element 1. An output electrode 1c exposed to an exhaust gas is formed in a ring with a proper width. On the other hand, an inner electrode 1b is formed simultaneously with the outer electrode 1c or the like by chemical platinum plating and a diffusion resistor 1d is formed by plasma spray coating. Then, the outer electrode 1c of the detection element 1 and an opening 4a provided in the side wall of the protection hood 4 are arranged at a deviated position to prevent an exhaust gas from directly hitting the outer electrode 1c. |
