Anti-corrosion structure of gas sensor

Abstract

An anti-corrosion structure of a gas sensor is provided. The gas sensor includes a hollow cylindrical air cover assembly made up of an inner and an outer cover. The air cover assembly has formed therein air inlets through which air is admitted into the gas sensor. The inner and outer covers are joined together through at least one crimped portion which defines a water drain path extending from the air inlets to outside the air cover assembly, thereby draining the water entering at the air inlets out of the gas sensor. This avoids staying of the water between the inner and outer covers to minimize gap corrosion therebetween.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detailed description given hereinbelow and from the accompanying drawings of the preferred embodiments of the invention, which, however, should not be taken to limit the invention to the specific embodiments but are for the purpose of explanation and understanding only.

In the drawings:

FIG. 1 is a longitudinal sectional view which shows an internal structure of a gas sensor according to the first embodiment of the invention;

FIG. 2 is a partially enlarged sectional view, as circled by a broken line B in FIG. 1, which shows an inner and an outer cover of an air cover assembly of the gas sensor, as illustrated in FIG. 1;

FIG. 3 is a transverse sectional view, as taken along the line A-A in FIG. 1;

FIG. 4 is a longitudinal sectional view which shows an internal structure of a gas sensor according to the second embodiment of the invention;

FIG. 5 is a partially enlarged sectional view, as circled by a broken line C in FIG. 4, which shows an inner and an outer cover of an air cover assembly of the gas sensor, as illustrated in FIG. 4;

FIG. 6 is a partially side view which shows an air cover assembly of the gas sensor of FIG. 4;

FIG. 7 is a graph which shows results of corrosion tests;

FIG. 8 is a partially longitudinal sectional view which shows an internal structure of a conventional gas sensor; and

FIG. 9 is a partially enlarged sectional view, as circled by a broken line D in FIG. 8, which shows an inner and an outer cover of an air cover assembly of the gas sensor, as illustrated in FIG. 8.

Claims

1. A gas sensor comprising: a sensor element sensitive to a gas to produce a signal as a function of concentration of the gas, said sensor element having a length with a top end and a base end opposite the top end;a housing in which said sensor element is retained, said housing having a top end and a base end opposite the top end;an air cover assembly having a top end and a base end opposite the top end, said air cover assembly being made up of an inner cover and an outer cover, the inner cover being secured to the base end of said housing, the outer cover surrounding the inner cover and being joined to the inner cover through at least one crimped portion;an air inlet formed in a portion of said air cover assembly which is closer to the base end of said air cover assembly than the crimped portion, the air inlet being designed to admit air into said air cover assembly; andan air chamber defined by the crimped portion between the inner and outer covers of said air cover assembly from the crimped portion circumferentially of said air cover assembly, said air chamber being exposed outside said air cover assembly at a side opposite said air inlet across the crimped portion to define a water drain path establishing fluid communication between said air inlet and outside said air cover assembly.

2. A gas sensor comprising: a sensor element sensitive to a gas to produce a signal as a function of concentration of the gas, said sensor element having a length with a top end and a base end opposite the top end;a housing in which said sensor element is retained, said housing having a top end and a base end opposite the top end;an air cover assembly having a top end and a base end opposite the top end, said air cover assembly being made up of an inner cover and an outer cover, the inner cover being secured to the base end of said housing, the outer cover surrounding the inner cover and being joined to the inner cover through a crimped portion which extends over the whole of a periphery of said air cover assembly;an air inlet formed in a portion of said air cover assembly which is closer to the base end of said air cover assembly than the crimped portion, the air inlet being designed to admit air into said air cover assembly; anda water drain hole formed in said air cover assembly to establish fluid communication of outside said air cover assembly with a clearance extending from the crimped portion to said air inlet between the inner and outer covers of said air cover assembly.

3. A gas sensor as set forth in claim 2, wherein said drain hole is formed in the outer cover of said air cover assembly to extend from an edge of the crimped portion toward said air inlet.