Semiconductor device manufacturing: process – Making device or circuit responsive to nonelectrical signal – Chemically responsive
Reexamination Certificate
2000-03-07
2001-10-23
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Making device or circuit responsive to nonelectrical signal
Chemically responsive
C029S432000, C029S465000
Reexamination Certificate
active
06306677
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to exhaust gas sensors, and specifically to exhaust oxygen sensors.
Oxygen sensors are used in a variety of applications that require qualitative and quantitative analysis of gases. For example, oxygen sensors have been used for many years in automotive vehicles to sense the presence of oxygen in exhaust gases, for example, to sense when an exhaust gas content switches from rich to lean or lean to rich. In automotive applications, the direct relationship between oxygen concentration in the exhaust gas and the air-to-fuel ratios of the fuel mixture supplied to the engine allows the oxygen sensor to provide oxygen concentration measurements for determination of optimum combustion conditions, maximization of fuel economy, and the management of exhaust emissions.
A conventional stoichiometric oxygen sensor typically consists of an ionically conductive solid electrolyte material, a porous platinum electrode with a porous protective overcoat on the sensor's exterior exposed to the exhaust gases, and a porous electrode on the sensor's interior surface exposed to a known oxygen partial pressure. Sensors typically used in automotive applications use a yttria-stabilized, zirconia-based electrochemical galvanic cell operating in potentiometric mode, to detect the relative amounts of oxygen present in an automobile engine's exhaust. When opposite surfaces of this galvanic cell are exposed to different oxygen partial pressures, an electromotive force is developed between the electrodes on the opposite surfaces of the zirconia electrolyte, according to the Nernst equation:
E
=
(
RT
4
F
)
ln
(
P
O
2
ref
P
O
2
)
where:
E=electromotive force
R=universal gas constant
F=Faraday constant
T=absolute temperature of the gas
p
O
2
ref
=oxygen partial pressure of the reference gas
P
O
2
=oxygen partial pressure of the exhaust gas
Due to the large difference in oxygen partial pressures between fuel rich and fuel lean exhaust conditions, the electromotive force changes sharply at the stoichiometric point, giving rise to the characteristic switching behavior of these sensors. Consequently, these potentiometric oxygen sensors indicate qualitatively whether the engine is operating fuel rich or fuel lean, without quantifying the actual air to fuel ratio of the exhaust mixture.
Prior art exhaust sensors have utilized solid electrolytes that are disposed as layers independent from supporting materials. Such a configuration requires more raw material and fabrication. What is needed in the art is an apparatus and method for incorporating electrolytes directly into substrate layers in a process that is preferably amenable to automation.
BRIEF SUMMARY OF THE INVENTION
Herein is described a method of placing inserts into a substrate for a gas sensor, comprising punching a hole in a first layer, positioning a die over said first layer, positioning a second layer over said die opposite to said first layer, punching an insert out of said second layer, and, moving said insert through said die into said hole.
An apparatus is also described for doing the same. The apparatus comprises: a first support surface having an aperture; a punch, wherein said punch is aligned with said aperture and said aperture has a diameter equal to or greater than a cross-sectional diameter of said punch; a die having a diameter and cross-sectional geometry substantially similar to the cross-sectional geometry and diameter of said punch; and a second support surface disposed at a second end of said die, wherein when said punch is disposed at a first end of said die, said punch can move through said die toward said second support surface.
REFERENCES:
patent: 4805280 (1989-02-01), Elander et al.
patent: 4909922 (1990-03-01), Kato et al.
patent: 5239744 (1993-08-01), Fleming et al.
patent: 402148853-A (1990-06-01), None
Bloink Raymond Leo
Kechner Robert Gregory
Vargo James P.
Cichosz Vincent A.
Delphi Technologies Inc.
Niebling John F.
Simkovic Viktor
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