Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Means for analyzing gas sample
Reexamination Certificate
1999-11-30
2002-02-05
Warden, Jill (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Means for analyzing gas sample
C422S098000, C436S143000, C436S137000
Reexamination Certificate
active
06344173
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the technology of measuring the non-methane hydrocarbon concentration in the emissions of an automotive internal combustion engine, and more particularly to the use of a catalytic differential calorimetric sensor, having a thin film selective catalyst layer, to monitor the non-methane oxidation efficiency of an exhaust system's catalytic converter.
2. Description of the Related Art
Catalytic converters have been used on gasoline-fueled automobiles produced in the United States since the mid-1970's for the purpose of promoting the oxidation of unburned hydrocarbons (HCs) and of carbon monoxide (CO). Soon after their introduction, the converters were adapted to promote the chemical reduction of oxides of nitrogen (NO
x
). At the present time these converters typically employ small amounts of platinum, palladium and rhodium dispersed over a high surface area particulate carrier vehicle which, in turn, is distributed as a thin, porous coating (sometimes called a washcoat) on the wall of a ceramic monolith substrate. The substrate is typically formed by an extrusion process providing hundreds of thin wall, longitudinal parallel open cells per square inch of cross section. These flow-through catalytic devices are housed in a suitable stainless steel container and placed in the exhaust stream under the vehicle downstream from the engine's exhaust manifold.
Under warm, steady-state engine conditions, this conventional catalytic converter containing the precious metal based three-way catalyst (TWC), so called because it simultaneously affects the oxidation of CO and unburned HC's and the reduction of NO
x
, effectively and efficiently removes most of the automotive emissions. However, the catalyst system may become malfunctioning after experiencing thermal aging at an unusually high temperature, due to high exposure to poisoning gases like SO
2
, Si and Pb, etc. Furthermore, new emissions regulations require an extended durability of the catalytic converter from 50,000 miles to 100,000 miles. The California Air Resource Board (CARB), has recently enacted the On-Board Diagnostics-II (OBD-II) regulation which ensures that vehicles meet the certified emission standards throughout the vehicle's operation life. Specifically, the regulation requires that any monitoring system should be able to indicate when the catalyst system is malfunctioning and its conversion capability has decreased to the point where either of the following occurs: (1) HC emissions exceed the applicable emission threshold of 1.5 times the applicable Federal Test Procedure (FTP) HC standard for the vehicle; and (2) the average FTP Non-methane Hydrocarbon (NMHC) conversion efficiency of the monitored portion of the catalyst system falls below 50 percent.
Automotive emissions prior to the catalyst system reaching its operational temperature, namely, cold start emissions, make up the majority of pollution from automobiles. Various approaches for reducing these emissions have been shown to be effective, including, for example, close-coupled catalytic converters, electrically heated catalytic converters and in-line adsorbers which temporarily store unburned hydrocarbons until the catalytic converter lights off Again, OBD-II regulations require that systems be installed in the exhaust system to directly monitor the functional status of any of these “cold-start” devices during the lifetime of the car (100,000 miles).
A direct result of this OBD-II legislation, is that the use of gas sensors, namely hydrocarbon sensors, for use as on-board catalytic efficiency monitors, although technologically new, has gained increasing popularity in the auto industry. Generally, the use of a catalytic calorimetric sensor, which measures the effect of the exotherm of the catalyzed oxidation of the hydrocarbons over supported precious metal catalysts on the resistance of a coil conductor is known.
U.S. Pat. No. 5,444,974 (Beck et al.) discloses a method of diagnosing the performance of the catalytic converter for the oxidation of CO and HC involving producing an electrical signal from a calorimetric sensor located in the exhaust stream downstream of the catalytic converter. The calorimetric sensor is comprised of a first portion bearing an oxidized catalyst for CO, H
2
and HC and an adjacent second portion that is oxidation catalyst-free.
A shortcoming of Beck, a reduced ability to accurately measure the HC concentration, is due to the fact that it does not compensate or account for the interference of CO, the concentration of which is typically an order of magnitude or greater than the concentration of the HC species.
U.S. patent application Ser. No. 08/980,925 (Faber et al.), a recent innovation, describes a system for measuring the non-methane HC concentration of automotive exhaust gas, that overcomes this sensitivity problem. The Faber system includes a selective sensor catalyst having an oxidation catalyst capable of selectively oxidizing the combination of CO+H
2
+alkene hydrocarbons and a catalytic differential calorimetric sensor, located downstream of the sensor catalyst, that is capable of producing a output signal representative of the exothennic effect of the remaining aromatic and alkane hydrocarbons species in the exhaust gas sample. This output signal is analyzed and converted into measure that is representative of the concentration of the total non-methane hydrocarbon species.
Although the system of Faber represents an improvement over those calorimetric sensors of the prior art, the systems disclosed therein are unnecessarily complex in their design. As such, there still exists a need for a simpler system for measuring the non-methane HC concentration.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed at a sensor having a simpler design for selectively and directly measuring the non-methane hydrocarbon concentration in a gas sample; e.g., the exhaust gases produced by an internal combustion engine. This simple hydrocarbon sensor is capable of detecting, under a variety of engine and fuel conditions, including cold start conditions, low (ppm) concentrations of non-methane hydrocarbons in exhaust gases, containing a variety of gaseous components, in addition to hydrocarbons.
Simply stated, the sensor has the capability of selectively oxidizing the combination of CO+H
2
+alkene hydrocarbons in a gas sample prior to measurement. Specifically, the sensor is provided with a porous, thin film oxidation catalyst layer capable of selectively oxidizing CO+H
2
+alkene hydrocarbon combination while leaving the aromatic and alkane hydrocarbons unoxidized. The sensor is further provided with a sensor base having, supported thereon or embedded therein, a pair of resistance temperature devices which are collectively capable of producing a signal representative of the concentration of unoxidized aromatic and alkane hydrocarbons in the exhaust gas to thereby enable the determination of the concentration of the total non-methane hydrocarbon species.
REFERENCES:
patent: 2980743 (1961-04-01), Toft
patent: 3560160 (1971-02-01), Lanneau
patent: 3898181 (1975-08-01), Barker
patent: 3906721 (1975-09-01), Micheli et al.
patent: 3914376 (1975-10-01), Barker
patent: 4006103 (1977-02-01), Meguerian et al.
patent: 4012485 (1977-03-01), Meguerian et al.
patent: 4036592 (1977-07-01), Brown et al.
patent: 4128506 (1978-12-01), Hegedus et al.
patent: 4171287 (1979-10-01), Keith
patent: 4256985 (1981-03-01), Goodson et al.
patent: 4289737 (1981-09-01), Acres et al.
patent: 4624940 (1986-11-01), Wan et al.
patent: 4863691 (1989-09-01), Noguchi et al.
patent: 4975406 (1990-12-01), Frestad et al.
patent: 4976929 (1990-12-01), Cornelison et al.
patent: 5157204 (1992-10-01), Brown et al.
patent: 5177464 (1993-01-01), Hamburg
patent: 5255511 (1993-10-01), Maus et al.
patent: 5265417 (1993-11-01), Visser et al.
patent: 5314828 (1994-05-01), Dalla Betta et al.
patent: 5408215 (1995-04-01), Hambu
Faber Margaret K.
Xie Yuming
Zhou Zhigang
Corning Incorporated
Schaeberle Timothy M.
Siefke Samuel P.
Sterre Kees van der
Warden Jill
LandOfFree
Automotive hydrocarbon sensor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Automotive hydrocarbon sensor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Automotive hydrocarbon sensor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2969934