Measuring and testing – Gas analysis – Detector detail
Reexamination Certificate
2000-08-29
2002-11-12
Larkin, Daniel S. (Department: 2856)
Measuring and testing
Gas analysis
Detector detail
C073S023310, C204S424000, C204S426000, C204S431000
Reexamination Certificate
active
06477887
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention generally relates to a gas sensor. This invention relates to, for example, a gas sensor located in an exhaust system of an automotive internal combustion engine for measuring a specific-component concentration such as an oxygen concentration, in an exhaust gas produced by the engine.
2. Description of the Related Art
FIG. 1
shows a prior-art gas sensor which includes a sensor element
920
inserted into a housing. An atmosphere-side cover is provided on the housing. An insulator
93
is provided in the housing. The insulator
93
has terminal accommodation holes
930
and
931
. Two metal terminals
94
are placed in each of the terminal accommodation holes
930
and
931
.
As shown in
FIG. 2
, each of the metal terminals
94
has a connecting portion
941
and a resilient contact portion
940
. The resilient contact portion
940
is designed and formed as a leaf spring. The insulator
93
has ribs
91
providing insulation between the metal terminals
94
in the terminal accommodation hole
930
and the metal terminals
94
in the terminal accommodation hole
931
.
A base end of the sensor element
920
is disposed in an
25
element accommodation hole
92
formed among the metal terminals
94
. As the sensor element
920
is placed in position, the sensor element
920
meets and then resiliently deforms the resilient contact portions
940
of the metal terminals
94
. In this way, terminal electrodes of the sensor element
920
and the resilient contact portions
940
of the metal terminals
94
are brought into contact with each other. The deformation of the resilient contact portions
940
provides reliable electric contact between the metal terminals
94
and the terminal electrodes of the sensor element
920
.
As the prior-art gas sensor in
FIG. 1
is miniaturized, the size of the insulator
93
decreases and the element accommodation hole
92
among the metal terminals
94
narrows. In some cases, the metal terminals
94
are close to or in contact with each other before the sensor element
920
is placed in position.
With reference to
FIG. 3
, as the sensor element
920
is inserted into the insulator
93
, the sensor element
920
meets the resilient contact portions
940
of the metal terminals
94
. Then, the sensor element
920
is further pushed into the insulator
93
by a strong force, deforming and moving the resilient contact portions
940
of the metal terminals
94
away from each other along directions “a”. Thus, a sufficient gap is formed between the resilient contact portions
940
of the metal terminals
94
. The sensor element
920
moves through the region between the resilient contact portions
940
of the metal terminals
94
while sliding on and contacting with them.
The sensor element
920
is made of fragile material, such as ceramic. Thus, the sensor element
920
tends to be damaged when being pushed against the resilient contact portions
940
of the metal terminals
94
by the strong force.
It is conceivable to thicken the sensor element
920
to increase its stiffness. Also, it is conceivable to increase the original distance between the metal terminals
94
. In these cases, the body size of the prior-art gas sensor is large.
It is conceivable to reduce the spring performances of the resilient contact portions
940
of the metal terminals
94
. In this case, the sensor element
920
can be placed in position with a weaker force. On the other hand, wrong electric contact tends to occur between the sensor element
920
and the resilient contact portions
94
C of the metal terminals
94
.
Thus, it is difficult that the prior-art gas sensor in
FIG. 1
is miniaturized while reliable electric contact is provided between the sensor element
920
and the metal terminals
94
.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a small-sized gas sensor in which reliable electric contact is provided between a sensor element and a metal terminal (or metal terminals).
A first aspect of this invention provides a gas sensor comprising a housing having a base end; a sensor element inserted into the housing and fixed with respect to the housing, the sensor element having a base end; terminal electrodes provided on the base end of the sensor element; an atmosphere-side cover provided on the base end of the housing; an insulator provided in the atmosphere-side cover and having terminal accommodation holes, the insulator having an element accommodation hole in which the base end of the sensor element is placed, the element accommodation hole communicating with the terminal accommodation holes, the insulator having ribs forming inner surfaces defining the element accommodation hole, the ribs having a thickness smaller than a thickness of the base end of the sensor element; leads for electrical connection with an external; metal terminals at least partially placed in the terminal accommodation holes respectively and having connecting portions connected with the leads, the ribs being located between the metal terminals to form spaces between the metal terminals; wherein as the base end of the sensor element is placed in the element accommodation hole, the terminal electrodes on the base end of the sensor element come into contact with the metal terminals so that the terminal electrodes are electrically connected with the leads via the metal terminals.
A second aspect of this invention is based on the first aspect thereof, and provides a gas sensor wherein the metal terminals include the connecting portions connected with the leads, and resilient contact portions which are resiliently deformable, the resilient contract portions being in contact with the ribs while being resiliently deformed.
A third aspect of this invention is based on the first aspect thereof, and provides a gas sensor wherein the metal terminals have projections in contact with the terminal electrodes on the base end of the sensor element.
A fourth aspect of this invention is based on the first aspect thereof, and provides a gas sensor wherein the ribs include ribs for locating the metal terminals, and ribs for providing insulation between the metal terminals.
A fifth aspect of this invention is based on the second aspect thereof, and provides a gas sensor wherein the metal terminals have shoulders between the connecting portions and the resilient contact portions, the shoulders including bends at right angles.
A sixth aspect of this invention is based on the second aspect thereof, and provides a gas sensor wherein in each of the metal terminals, a central line of the connecting portion and a central line of the resilient contact portion are out of alignment.
A seventh aspect of this invention is based on the first aspect thereof, and provides a gas sensor wherein the base end of the sensor element has a taper portion.
An eighth aspect of this invention is based on the first aspect thereof, and provides a gas sensor wherein the ribs extend between the terminal accommodation holes.
A ninth aspect of this invention is based on the first aspect thereof, and provides a gas sensor wherein the insulator is fixed with respect to the atmosphere-side cover.
A tenth aspect of this invention provides a gas sensor comprising a housing having a base end; a sensor element inserted into the housing and fixed with respect to the housing, the sensor element having a base end; at least one terminal electrode provided on the base end of the sensor element; an atmosphere-side cover provided on the base end of the housing and having a base end and a front end; a resilient insulating member provided on the base end of the atmosphere-side cover and having at least one first insertion hole; an insulator provided in the front end of the atmosphere-side cover and having at least one second insertion hole; a lead placed in the first insertion hole; and a metal terminal placed in the second insertion hole and having a connecting portion electrically connected with the lead and a resilient contact portion electrically connected with
Nakano Syuichi
Ozawa Masato
LandOfFree
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