Measuring and testing – Gas analysis – Detector detail
Reexamination Certificate
2001-04-27
2003-12-09
Lefkowitz, Edward (Department: 2855)
Measuring and testing
Gas analysis
Detector detail
C073S023310, C204S424000
Reexamination Certificate
active
06658918
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates generally to an improvement on a gas sensor which is employed, for example, in an oxygen measuring device of an air-fuel ratio control system to measure an oxygen content in exhaust gasses of an internal combustion engine for automotive vehicles, and more particularly to an improved structure of such a gas sensor which provides for ease of installation of an insulation porcelain.
2. Background Art
It is known in the art that burning control of fuel in internal combustion engines based on an oxygen content in exhaust gasses as a parameter indicating an air-fuel ratio is effective in energy saving and emission control. As gas sensors measuring the concentration of oxygen in exhaust gasses, gas sensors equipped with a sensing element made of a solid electrolyte such as zirconia are known.
FIG. 25
shows one example of conventional gas sensors.
The gas sensor
9
consists of a sensing element
910
, a housing
94
, and a protective cover
92
. The sensing element
910
has a portion
911
exposed to a gas to be measured and is retained within the housing
94
. The protective cover
92
is installed on the housing
94
and surrounds the gas-exposed portion
911
of the sensing element
910
. A packing or sealing member
918
is disposed between the housing
94
and the sensing element
910
.
The sensing element
910
is of a cup-shape and has defined therein a reference gas chamber
912
leading to the atmosphere. A gas chamber
913
into which the gas to be measured is admitted is defined in the protective cover
92
around the sensing element
910
. The sensing element
910
has a reference electrode exposed to the reference gas chamber
912
and a measuring electrode exposed to the gas chamber
913
. The sensing element
910
also has a heater
915
disposed therein.
The sensing element
910
is electrically connected to leads
981
and
991
through coupling terminals
982
and
992
and metallic terminals
983
and
993
, respectively. The metallic terminals
983
and
993
are in contact with terminals formed on the sensing element
910
leading to the reference and measuring electrodes, respectively. A lead
971
is connected to the heater
915
for supplying the power thereto.
Bases of the leads
981
and
991
connected to the coupling terminals
982
and
992
are retained within an insulation porcelain
95
. The insulation porcelain
95
is held by an inner cover
931
and an outer cover
932
of an air cover assembly. Specifically, the inner cover
931
supports at an end thereof a lower portion of the insulation porcelain
95
, while the outer cover
932
presses at a shoulder thereof the insulation porcelain
95
downward against the end of the inner cover
931
. A disc spring
956
is disposed between the shoulder of the outer cover
932
and the insulation porcelain
95
.
An air cover
933
surrounds an upper portion of the outer cover
932
through a cylindrical water-repellent filter
938
An elastic insulator
945
is fitted within an open end portion of the air cover
933
which holds the leads
971
,
981
, and
991
therein.
The air cover
933
and the outer cover
932
have first air vents
936
and second air vents
937
, respectively, which lead to the reference gas chamber
912
through the water-repellent filter
938
for inducting the air into the reference gas chamber
912
.
The elastic insulator
945
, the outer cover
932
of the air cover assembly, and the air cover
933
are joined together by crimping.
The gas sensor
9
produces at the sensing element
910
an electromotive force as a function of a difference in concentration between the air in the reference gas chamber
912
and the gas in the gas chamber
913
to be measured and outputs it through the leads
981
and
991
.
The above described structure of the gas sensor
9
contributes to the improvement of control ability in automotive internal combustion engines, however, it is being still required for decreasing the overall size and manufacturing costs, and improving the durability of the gas sensor
9
.
SUMMARY OF THE INVENTION
It is therefore a principal object of the invention to avoid the disadvantages of the prior art.
It is another object of the invention to provide an improved structure of a gas sensor which is compact in size, but possesses high durability and may be manufactured at low costs.
According to one aspect of the invention, there is provided an improved structure of a gas sensor designed to measure a given component content in a gas. The gas sensor comprises: (a) a housing having a first end and a second end; (b) a sensing element disposed in the housing, the sensing element having a base portion and a gas-sensing portion, the base portion projecting from the first end of the housing, the gas-sensing portion projecting from the second end of the housing; (c) a first cover installed on the first end of the housing to cover the base portion of the sensing element; (d) a plurality of electric terminals connected to the sensing element for establishing electric communication between the sensing element and an external device; (e) an insulator in which the electric terminals are disposed, the insulator including a body and a flange, the flange having an groove formed in a peripheral wall thereof; (f) a second cover installed on the second end of the housing to cover the gas-sensing portion of the sensing element and retain the insulator therein, the second cover including a small-diameter portion, a large-diameter portion, and a shoulder connecting between the small-diameter portion and the large-diameter portion, the small-diameter portion being greater in diameter than the body of the insulator and smaller in diameter than the flange of the insulator, the large-diameter portion being greater in diameter than the flange of the insulator; and (g) an elastic holding mechanism disposed between the groove of the flange of the insulator and an inner wall of the large-diameter portion of the second cover to be deformable elastically in a radius direction of the second cover to hold the insulator within the second cover firmly.
In the preferred mode of the invention, the elastic holding mechanism includes a plurality of springs disposed in the groove of the flange at regular intervals away from each other.
Each of the springs is made of a corrugated plate which is disposed between the groove of the flange and the inner wall of the large-diameter portion of the second cover so as to urge the flange of the insulator elastically inwardly of the second cover, thereby holding the insulator within the second cover.
Each of the corrugated plate may have an extension wall which is placed in surface contact with the inner wall of the second cover and welded at a portion thereof to the inner wall of the second cover.
The elastic holding mechanism may alternatively be made of a spring ring disposed in the groove of the flange of the insulator.
The spring ring has disposed on a periphery wall thereof a plurality of members which are so folded as to produce elastic pressure between the flange of the insulator and the inner wall of the second cover for holding the insulator within the second cover firmly.
According to the second aspect of the invention, there is provided a gas sensor measuring a given component content in a gas which comprises: (a) a housing having a first end and a second end; (b) a sensing element disposed in the housing, the sensing element having a base portion and a gas-sensing portion, the base portion projecting from the first end of the housing, the gas-sensing portion projecting from the second end of the housing; (c) a first cover installed on the first end of the housing to cover the base portion of the sensing element; (d) a plurality of electric terminals connected to the sensing element for establishing electric communication between the sensing element and an external device; (e) an insulator in which the electric terminals are disposed, the insulator including a body and
Hibino Hideki
Miyamoto Toshimi
Cygan Michael
Denso Corporation
Lefkowitz Edward
Nixon & Vanderhye PC
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