Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
2001-06-19
2004-02-17
Vo, Hieu T. (Department: 3747)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C073S118040, C123S690000, C060S274000, C060S285000
Reexamination Certificate
active
06694244
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to emission control devices, positioned within an exhaust treatment system for a vehicle's internal combustion engine, which store oxygen present in the engine-generated exhaust gas during certain engine operating conditions and which release previously-stored oxygen during other engine operating conditions.
2. Background Art
Generally, the operation of a vehicle's internal combustion engine produces engine exhaust that includes a variety of constituent gases, including carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NO
x
). The rates at which the engine generates these constituent gases are dependent upon a variety of factors, such as engine operating speed and load, engine temperature, spark timing, and EGR. Moreover, such engines often generate increased levels of one or more constituent gases, such as NO
x
, when the engine is operated in a lean-burn cycle, i.e., when engine operation includes engine operating conditions characterized by a ratio of intake air to injected fuel that is greater than the stoichiometric air-fuel ratio, for example, to achieve greater vehicle fuel economy.
In order to control vehicle tailpipe emissions, the prior art teaches vehicle exhaust treatment systems that employ one or more three-way catalysts, also referred to as emission control devices, in an exhaust passage to store and release select constituent gases, such as oxygen and NO
x
, depending upon engine operating conditions. For example, U.S. Pat. No. 5,437,153 teaches an emission control device which stores exhaust gas NO
x
when the exhaust gas is lean, and releases previously-stored NO
x
when the exhaust gas is either stoichiometric or “rich” of stoichiometric, i.e., when the ratio of intake air to injected fuel is at or below the stoichiometric air-fuel ratio.
Such systems often employ open-loop control of device storage and release times (also respectively known as device “fill” and “purge” times) with a view toward maximizing the benefits of increased fuel efficiency obtained through lean engine operation without concomitantly increasing tailpipe emissions as the device becomes “filled.” The timing of each purge event must be controlled so that the device does not otherwise exceed its NO
x
storage capacity, because NO
x
would then pass through the device and effect an increase in tailpipe NO
x
emissions. The frequency of the purge is preferably controlled to avoid the purging of only partially filled devices, due to the fuel penalty associated with the purge event's enriched air-fuel mixture.
The prior art has recognized that the storage capacity of a given emission control device as to both oxygen and selected constituent gases is itself a function of many variables, including device temperature, device history, sulfation level, and the presence of any thermal damage to the device. Moreover, as the device approaches its maximum capacity, the prior art teaches that the incremental rate at which the device continues to store the selected constituent gas may begin to fall.
Accordingly, U.S. Pat. No. 5,437,153 teaches use of a nominal NO
x
-storage capacity for its disclosed device which is significantly less than the actual NO
x
-storage capacity of the device, to thereby provide the device with a perfect instantaneous NO
x
-absorbing efficiency, that is, so that the device is able to store all engine-generated NO
x
as long as the cumulative stored NO
x
remains below this nominal capacity. A purge event is scheduled to rejuvenate the device whenever accumulated estimates of engine-generated NO
x
reach the device's nominal capacity. Unfortunately, however, the use of such a fixed device capacity necessarily requires a larger device, because this prior art approach relies upon a partial, e.g., fifty-percent NO
x
fill in order to ensure retention of all engine-generated NO
x
.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method and system for determining a value representative of a quantity of oxygen stored in a vehicle emission control device, as may be useful for optimizing open-loop control of the filling of the device with a selected constituent gas of the engine-generated exhaust gas during lean-burn engine operation.
Under the invention, a method and system are provided for quantifying oxygen stored in an emission control device used to reduce emission of a selected constituent gas of engine-generated exhaust gas, by periodically generating an open-loop first and second fill time during which the device is respectively filled with the selected constituent gas to respective, sub-optimal capacity levels; and filling and purging the device based on the generated first and second fill times within a predetermined number of successive fill and purge cycles. Then, for each sub-optimal fill, an output signal is detected from an oxygen concentration sensor positioned within the flow of exhaust gas passing through the device, and a first and second actual purge time respectively corresponding to the first and second fill times are generated based on the detected output signal. A value representative of the quantity of oxygen stored in the device is then generated as a function of both the first and second fill times, and the first and second actual purge times.
Thus, the present invention provides a method and system which periodically determines the amount of oxygen being stored in the device, which can be used along with a value for a total device capacity to determine the actual capacity of the device to store the selected constituent gas, such as NO
x
. In this manner, vehicle tailpipe emissions can be advantageously minimized while simultaneously minimizing the fuel consumption associated with purging of the device.
The above object and other objects, features, and advantages of the invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.
REFERENCES:
patent: 3696618 (1972-10-01), Boyd et al.
patent: 3969932 (1976-07-01), Rieger et al.
patent: 4033122 (1977-07-01), Masaki et al.
patent: 4036014 (1977-07-01), Ariga
patent: 4167924 (1979-09-01), Carlson et al.
patent: 4178883 (1979-12-01), Herth
patent: 4186296 (1980-01-01), Crump, Jr.
patent: 4251989 (1981-02-01), Norimatsu et al.
patent: 4533900 (1985-08-01), Muhlberger et al.
patent: 4622809 (1986-11-01), Abthoff et al.
patent: 4677955 (1987-07-01), Takao
patent: 4854123 (1989-08-01), Inoue et al.
patent: 4884066 (1989-11-01), Miyata et al.
patent: 4913122 (1990-04-01), Uchida et al.
patent: 4964272 (1990-10-01), Kayanuma
patent: 5009210 (1991-04-01), Nakagawa et al.
patent: 5088281 (1992-02-01), Izutani et al.
patent: 5097700 (1992-03-01), Nakane
patent: 5165230 (1992-11-01), Kayanuma et al.
patent: 5174111 (1992-12-01), Nomura et al.
patent: 5189876 (1993-03-01), Hirota et al.
patent: 5201802 (1993-04-01), Hirota et al.
patent: 5209061 (1993-05-01), Takeshima
patent: 5222471 (1993-06-01), Stueven
patent: 5233830 (1993-08-01), Takeshima et al.
patent: 5267439 (1993-12-01), Raff et al.
patent: 5267472 (1993-12-01), Schneider et al.
patent: 5270024 (1993-12-01), Kasahara et al.
patent: 5272871 (1993-12-01), Oshima et al.
patent: 5325664 (1994-07-01), Seki et al.
patent: 5331809 (1994-07-01), Takeshima et al.
patent: 5335538 (1994-08-01), Blischke et al.
patent: 5357750 (1994-10-01), Ito et al.
patent: 5359852 (1994-11-01), Curran et al.
patent: 5377484 (1995-01-01), Shimizu
patent: 5379591 (1995-01-01), Iwata et al.
patent: 5402641 (1995-04-01), Katoh et al.
patent: 5410873 (1995-05-01), Tashiro
patent: 5412945 (1995-05-01), Katoh et al.
patent: 5412946 (1995-05-01), Oshima et al.
patent: 5414994 (1995-05-01), Cullen et al.
patent: 5419122 (1995-05-01), Tabe et al.
patent: 5423181 (1995-06-01), Katoh et al.
patent: 5426934 (1995-06-01), Hunt et al.
patent: 5433074 (1995-07-01), Seto et al.
patent: 5437153 (1995-08-01), Takeshima et al.
patent: 5448886 (1995-09-01), Toyoda
p
Asik Joseph Richard
Meyer Garth Michael
Ford Global Technologies LLC
Kolisch Hartwell PC
Lippa Allan J.
Vo Hieu T.
LandOfFree
Method for quantifying oxygen stored in a vehicle emission... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for quantifying oxygen stored in a vehicle emission..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for quantifying oxygen stored in a vehicle emission... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3299030