Gas detecting device for vehicle

摘要

A gas detecting device (1) for a vehicle includes a casing (8) which is formed therein with an air passage having an air inlet (15) and an air outlet (17) located above the air inlet (15). A filter (10) is provided in the air passage below and downstream of a gas sensor (11). The filter (10) has a lower end surface (10d) at a side of the air inlet and an upper end surface (10c) at a side of the gas sensor (11). The lower end surface (10d) of the filter works as an air-passing surface through which the air flows into the filter, while the upper end surface (10c) of the filter works as an air-passing surface through which the air flows out of the filter. A certain gap (32) is provided between a lower portion of a side surface of the filter (10) and an inner wall surface of the casing (14) defining the air passage so that this lower portion of the filter also works as an air-passing surface through which the air flows into the filter (10). A labyrinth structure (22) may be provided in the air passage between the air inlet and the filter for causing the air to meander at the labyrinth structure. Further, it may be arranged that the air passage has an opening area which is the greatest at the air inlet and then is gradually reduced as advancing toward the labyrinth structure.