Oxygen sensor for internal combustion engine, has protective device including upper end area, where ratio of product of external diameter and size of device to cross-sectional area of passage is less than or equal to specific percentage

摘要

The sensor (10) has a sensor unit (11) that detects an oxygen concentration in an exhaust gas that is to be measured and that is flowed into an exhaust pipe (1). A protective device (12) covers an outer side of the sensor unit and includes an upper end area that is projected to an inner side of the pipe. An external diameter (D) of the device and a projection size (L) of the device in an interior of the pipe are determined such that a ratio of a product of the diameter and projection size to a cross-sectional area of a flow passage of the pipe is less than or equal to 2.5 percentage.