Measuring and testing – Gas analysis – Gas of combustion
Reexamination Certificate
2001-04-17
2002-06-18
Larkin, Daniel S. (Department: 2856)
Measuring and testing
Gas analysis
Gas of combustion
C073S863030, C073S863110, C073S863210, C073S863310, C073S861530, C073S861630
Reexamination Certificate
active
06405577
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flow rate detector mechanism with a variable venturi therein for changing the value of constant flow rate with continuity, being suitable to be applied to a constant volume sampler (CVS) for diluting and sampling the exhaust gas discharged from an automobile, and further to an exhaust gas sampling method, in which the exhaust gas is diluted corresponding to the traveling mode patterns for evaluation test, using such the CVS as mentioned above wherein the variable venturi flow rate detector mechanism is applied, so as to sample the exhaust gas in a sampling bag.
2. Description of Related Art
For measuring weight of components in the exhaust gas emitted from an automobile, a sampling apparatus called a “constant volume sampler (CVS)” is used as shown, for example, in Japanese Laid-Open Patent No. Sho 54-71689 (1979) and Japanese Laid-Open Patent No. Sho 54-127388 (1979).
Further, in Japanese Laid-Open Patent No. Sho 55-65133 (1980) is described the CVS for sampling a portion of diluted gas to be analyzed, being formed at a constant flow rate, by diluting a target gas such as the exhaust gas from the automobile with fresh air, in which a constant volume pump is driven by a synchronous motor so as to form a constant flow rate of the diluted gas.
In Japanese Laid-Open Patent No. Sho 62-157547 (1987), there is described a modal mass analysis method, according to air dilution of exhaust gas from the automobile, for increasing the accuracy in analyzing the emitted amounts of components in each mode of travel, in which the flow rate of exhaust gas obtained through the air dilution method is compensated by concentration of the target components corresponding to the same phase, being obtained through interpolation. Further, in the
FIG. 1
of the publication thereof is described the CVS in which the constant volume venturi and a constant volume blower are connected in series.
In Japanese Laid-Open Patent No. Hei 4-216435 (1992), there is described an exhaust gas sampling apparatus for an internal combustion engine, in particular applying the CVS (Constant Volume Sampler) method thereto for improving the accuracy and also the response in the measurement. This exhaust gas sampling apparatus for an internal combustion engine is constructed in the following manner. Within a conduit, in which flows the diluted exhaust gas being formed by mixing the exhaust gas discharged from the internal combustion engine with fresh air, is positioned a sampling conduit for sampling a portion of the diluted exhaust gas. Connected to the sampling conduit are provided a suction pump, a critical venturi, an exhaust gas analyzer, and a throttle valve, in a sequence from the downstream side of the diluted exhaust gas. Further, between the critical venturi and the exhaust gas analyzer, there is provided a passage for introducing atmospheric air into the sampling conduit. With the provision of the passage for introducing the atmospheric air into the sampling conduit, fluctuation of the pressure in an exhaust gas analyzer is suppressed to be minute or very small even when the pressure rises in the conduit in which the diluted exhaust gas flows, thereby improving the response characteristic thereof. Further, the amount of change in the pressure within the exhaust gas analyzer is small even when a large volume of the diluted exhaust gas is introduced into the conduit, thereby having no influence on the accuracy in the measurement thereof.
Further, in Japanese Laid-Open Patent No. Hei 4-216435 (1992), with provision of an flow rate integrator in an air supply conduit, there is described an exhaust gas analyzer in which a standard total passage volume at a moment can be calculated in a calculation unit by taking into consideration the pressure and temperature of gas. This exhaust gas analyzer is constructed in the following manner. A sample-taking conduit is provided, into which the mixture of the exhaust gas and fresh air is supplied through a gas intake conduit, and a gas supply pump is positioned after the gas intake conduit. The gas supply pump is constructed with a rotation pump having a constant suction capacity, for example, and a critical nozzle is positioned before the rotation pump. In the air supply conduit is provided the flow rate integrator which is constructed with a vortex flow meter (a mass flow meter based on a principle such as Karman's vortex). The output of the flow rate integrator is provided to the calculation unit. The calculation unit obtains the standard total passage volume at a moment by taking into the consideration the pressure and temperature of gas from the flow rate in the air supply conduit.
In the analysis of components in the exhaust gas with use of the CVS method in this manner, there is a necessity to alter the flow rate of the diluted gas depending upon the test modes. For example, in a cold transient (CT) phase starting from a time point when engine is started to a time point 505 seconds later, the flow rate of the diluted gas is determined to be 15 m
3
/min, and in a cold stabilizing (CS) phase from 505 sec to 1374 sec to be 3 m
3
/min. Further, after being stopped for ten (10) minutes from the time point at 1374 sec, the engine is re-started, and in a hot transient (HT) phase the flow rate of the diluted gas is determined to be at 3 m
3
/min.
For altering or exchanging the flow volume of diluted gas depending upon the test modes, according to the CVS of the conventional art, a plurality of systems are provided in parallel, in each of which valves for opening and closing and a fixed venturi are connected in series, wherein the one fixed venturi of the desired flow rate is selectively used. Thus, the plurality of systems of the fixed venturis through which the diluted gas flows are switched between based on the flow rates thereof.
FIG. 16
shows problems arising when the flow rate of the diluted gas is altered in the CVS device of the conventional art. As shown in FIG.
16
(
a
), when the flow rate of the diluted gas is altered from 15 m
3
/min to 3 m
3
/min by, for example, turning from a condition where the first open/close valve
102
connected to the fixed venturi
101
in series is turned OPEN thereby conducting the diluted gas at the flow rate of 15 m
3
/min into a condition where the second open/close valve
104
of the flow rate of 3 m
3
/min, connected to the second venturi
103
in series, is turned OPEN while turning the first open/close valve
102
CLOSED, as shown in FIG.
16
(
b
), time delay (i.e., a region with hatching lines) occurs in the time sequence during which the flow rate of the diluted gas is altered from 15 m
3
/min to 3 m
3
/min, and disturbance in the flow rate occurs.
In the portion (in the hatched area) of the time delay in the flow rate, the flow rate of the diluted gas is larger than the desired one, i.e., 3 m
3
/min, however in the conventional exhaust gas analysis with use of the CVS device, since the decreased volume of the exhaust gas in the flow rate during the time delay portion (the hatched area) is not reflected upon the analysis data, an error occurs in the result of analysis of the exhaust gas components, for example, in the degree of 0.3%. Further, since the disturbance occurs after the exchange of the flow rate, it sometimes also results in decrease in accuracy of the analyzed result.
Then, with provision of a flow meter in the passage for the diluted gas for measuring the flow rate thereof continuously, it can be considered that the measured flow rate of the diluted gas is reflected in the analyzed result thereof, thereby preventing any error therein from occurring. However, the provision of the flow meter in the passage for the diluted gas not only makes the apparatus itself large in size and expensive in cost thereof, but also increases the resistance in the passage for the diluted gas. Thus, the capacity of the blower must be larger for sucking the diluted gas, and therefore this is not a wise plan or design.
Therefore, a first object of t
Hanashiro Noriyuki
Shibata Atsushi
Yamawaki Shuta
Yanagihara Shigeru
Birch, Stewart, Kolasch and Birch LLP
Honda Giken Kogyo Kabushiki Kaisha and Kabushiki Kaisha Tsukasa
Larkin Daniel S.
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