Structure of gas sensor designed to ensure stability of waterproofing and airventilation

Abstract

A gas sensor designed to ensure waterproofing and air ventilation is provided which includes a rubber bush fitted in an end of an air cover joined to a housing. The rubber bush has formed in a base portion thereof lead-pass holes and in a top portion thereof an air flow path through which air is introduced into an air chamber in the gas sensor. The air cover is crimped circumferentially to provide an elastic nip only to the base portion of the rubber bush, thereby ensuring tight fits of the leads in the lead-pass holes without deforming the air flow path undesirably. An ventilation filter is fit on a neck of the rubber bush between the base portion and the top portion in communication with the air flow path, thus ensuring the stability of entrance of the air into the air flow path through the ventilation filter.

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 longitudinal sectional view, as taken along the line E-E in FIG. 6, which shows a ventilation filer and a rubber bush installed in the gas sensor of FIG. 1;

FIG. 3 is a partially enlarged longitudinal sectional view, as taken along the line F-F in FIG. 6, which shows a ventilation filer and a rubber bush installed in the gas sensor of FIG. 1;

FIG. 4 is an exploded view which shows a rubber bush and a ventilation filter to be fitted on the rubber bush in the gas sensor of FIG. 1;

FIG. 5 is a transverse sectional view, as taken along the line B-B in FIG. 2;

FIG. 6 is a transverse sectional view, as taken along the line C-C in FIG. 2;

FIG. 7 is a transverse sectional view, as taken along the line D-D in FIG. 2;

FIG. 8 is a transverse sectional view, as taken along the line A-A in FIG. 1;

FIG. 9 is a longitudinal sectional view which shows an internal structure of a gas sensor according to the second embodiment of the invention;

FIG. 10 is a partially enlarged longitudinal sectional view, as taken along the line J-J in FIG. 14, which shows a ventilation filer and a rubber bush installed in the gas sensor of FIG. 9;

FIG. 11 is a partially enlarged longitudinal sectional view, as taken along the line K-K in FIG. 14, which shows a ventilation filer and a rubber bush installed in the gas sensor of FIG. 9;

FIG. 12 is an exploded view which shows a rubber bush and a ventilation filter to be fitted on the rubber bush in the gas sensor of FIG. 9;

FIG. 13 is a transverse sectional view, as taken along the line G-G in FIG. 10;

FIG. 14 is a transverse sectional view, as taken along the line H-H in FIG. 10;

FIG. 15 is a transverse sectional view, as taken along the line I-I in FIG. 10;

FIG. 16 is a partially enlarged longitudinal sectional view which shows an internal structure of a base end portion of a gas sensor according to the third embodiment of the invention;

FIG. 17 is a transverse sectional view, as taken along the line L-L in FIG. 16;

FIG. 18 is a longitudinal sectional view which shows an internal structure of a conventional gas sensor; and

FIG. 19 is a partially enlarged longitudinal sectional view which shows a base end portion of another type of a conventional gas sensor.

Claims

1. A gas sensor having a length with a top end and a base end opposite the top end comprising: a sensor element sensitive to a gas to produce a signal as a function of concentration of the gas;a housing in which said sensor element is retained, said housing having a top end and a base end opposite the top end;an elastic block having holes through which leads pass to connect electrically with said sensor element, said elastic block being made up of a top portion closer to the top end of the gas sensor, a base portion closer to the base end of the gas sensor, and a neck formed between the top portion and the base portion, the base portion having a first shoulder surface, the top portion having a second shoulder surface facing the first shoulder surface in a lengthwise direction of the gas sensor;an air flow path extending within the top portion of said elastic block, said air flow path having an air inlet and an air outlet, the air inlet opening on an outer surface of the neck of said elastic block, the air outlet opening on a surface of the top portion of said elastic block exposed to an air chamber leading to said sensor element;an annular ventilation filter fitted on the neck of said elastic block in communication with the air inlet of said air flow path to permit air to enter said air flow path from outside said elastic block through said ventilation filter, said ventilation being nipped between the first and second shoulder surfaces of said elastic block;an air cover joined to said housing to extend away from the base end of the gas sensor to define therein the air chamber to which the air outlet of said air flow path is exposed, said air cover being crimped to provide a lateral elastic nip to the base portion of said elastic block in a direction perpendicular to the lengthwise direction of the gas sensor and also crimped to provide a longitudinal elastic nip to said elastic block in the lengthwise direction of the gas sensor; andan air inlet hole formed in said air cover through which the air is admitted to said ventilation filter.

2. A gas sensor as set forth in claim 1, wherein the top portion and the base portion of said elastic block are greater in diameter than the neck, and wherein said ventilation filter is fitted around a periphery of the neck.

3. A gas sensor as set forth in claim 1, wherein the top portion and the base portion of said elastic block are made of discrete parts, the top portion and the base portion being arranged to provide a longitudinal elastic nip to said ventilation filter in the lengthwise direction of the gas sensor.

4. A gas sensor as set forth in claim 3, wherein the base portion has a small-diameter portion, and wherein the top portion is made of a ring member with an opening fit on the small-diameter portion of the base portion to define the neck of said elastic block.

5. A gas sensor as set forth in claim 1, wherein said air cover is made of an assembly of a protective cover and a support cover, the protective cover having a base end and a top end opposite the base end and surrounding said elastic block, the support cover having a base end and a top end opposite the base end, the protective cover being fitted on the support cover to elastically nip said elastic block between the base ends of the protective cover and the support cover in the lengthwise direction of the gas sensor.

6. A gas sensor as set forth in claim 5, wherein the protective cover is fitted on the support cover through crimped joints which are located away from each other circumferentially of said air cover to define air gaps, each between adjacent two of the crimped joints, and wherein the air inlet hole is formed in a portion of the protective cover closer to the top end thereof than the crimped joints.

7. A gas sensor as set forth in claim 1, wherein said ventilation filter is made of a porous PTFE.

8. A gas sensor as set forth in claim 1, wherein said ventilation filter is made of a sintered metal.