U.S. patent application number 09/835353 was filed with the patent office on 2001-08-16 for flow rate detector mechanism with variable venturi and exhaust gas sampling method using the same.
This patent application is currently assigned to Honda Giken Kogyo Kabushiki Kaisha. Invention is credited to Hanashiro, Noriyuki, Shibata, Atsushi, Yamawaki, Shuta, Yanagihara, Shigeru.
Application Number | 20010013245 09/835353 |
Document ID | / |
Family ID | 26360780 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010013245 |
Kind Code |
A1 |
Hanashiro, Noriyuki ; et
al. |
August 16, 2001 |
Flow rate detector mechanism with variable venturi and exhaust gas
sampling method using the same
Abstract
A flow rate detector mechanism using variable Venturi therein,
comprising: a variable flow rate generator, comprising: a core 11;
and a variable Venturi 12; wherein a throat (flow passage)
cross-sectional area defined between the core and the venturi is
able to be changed by shifting relative positions of the core and
the venturi in a direction of axes thereof, and further comprising
a flow rate calculation processing portion 30 for calculating a
flow rate based on the relative positions in the direction of the
axes thereof and for outputting the calculated flow rate, thereby
continuously changing the constant flow rate, without occurrence of
any disturbance therein. Further, with an exhaust gas sampling
method applying the flow rate detector mechanism using variable
Venturi, CVS flow rate is changed within the range of the phases of
measure modes, so as to make small the difference between the peak
dew point in the bag and the final dew point in the bag, as well as
to causethe final dew point to approach the temperature at which
the bag is kept. Therefore, the dilution ratio of the final dew
point is decreased, so as to improve the accuracy in analysis.
Inventors: |
Hanashiro, Noriyuki; (Mie,
JP) ; Shibata, Atsushi; (Mie, JP) ;
Yanagihara, Shigeru; (Tokyo, JP) ; Yamawaki,
Shuta; (Tokyo, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
Honda Giken Kogyo Kabushiki
Kaisha
|
Family ID: |
26360780 |
Appl. No.: |
09/835353 |
Filed: |
April 17, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09835353 |
Apr 17, 2001 |
|
|
|
09349926 |
Jul 8, 1999 |
|
|
|
Current U.S.
Class: |
73/23.31 |
Current CPC
Class: |
G01F 7/005 20130101;
G01F 1/44 20130101; G01N 33/0016 20130101 |
Class at
Publication: |
73/23.31 |
International
Class: |
G01L 001/22; G01N
007/00; G01N 033/497 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 9, 1998 |
JP |
10-194,149 |
Feb 1, 1999 |
JP |
11-023,422 |
Claims
What is claimed is:
1. An exhaust gas sampling method for analyzing exhaust gas of an
automobile, using a flow rate detector mechanism using variable
Venturi therein, comprising the following steps: diluting the
exhaust gas from the automobile with fresh air from outside;
sampling a portion of the diluted exhaust gas into a sampling bag
at a certain ratio; and analyzing the diluted exhaust gas being
sampled, wherein a flow rate through said flow rate detector
mechanism is changed in a phase of mode for measurement, so that at
least a final dew point in the sampling bag approaches a
predetermined temperature within a predetermined range of
temperature.
2. An exhaust gas sampling method as defined in claim 1, wherein
the flow rate through said flow rate detector mechanism is changed
in the phase of mode for measurement, so that the dew points in the
sampling bag are averaged.
3. An exhaust gas sampling method as defined in claim 1, wherein
the flow rate through said flow rate detector mechanism is changed
in the phase of mode for measurement, so that at least the flow
rate through said flow rate detector mechanism does not exceed the
flow rate of the exhaust gas during the measurement.
4. An exhaust gas sampling method as defined in claim 1, wherein
the flow rate of the sampling is changed depending upon the change
in the flow rate through said flow rate detector mechanism.
Description
[0001] This application is a divisional of co-pending application
Ser. No. 09/349,926, filed on Jul. 8, 1999, the entire contents of
which are hereby incorporated by reference and for which priority
is claimed under 35 U.S.C. .sctn. 120; and this application claims
priority of Application No. 10-194149 and 11-023422 filed in Japan
on Jul. 9, 1998 and Feb. 1, 1999, respectively under 35 U.S.C.
119.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] 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.
[0004] 2. Description of Related Art
[0005] 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).
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] 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.sup.3/min, and in
a cold stabilizing (CS) phase from 505 sec to 1374 sec to be 3
m.sup.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.sup.3/min.
[0011] 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.
[0012] 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.sup.3/min to 3 m.sup.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.sup.3/min into
a condition where the second open/close valve 104 of the flow rate
of 3 m.sup.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.sup.3/min to 3 m.sup.3/min,
and disturbance in the flow rate occurs.
[0013] 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.sup.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.
[0014] 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.
[0015] Therefore, an first object of the present invention, for
dissolving such the problems as mentioned above, is to provide a
flow rate detector mechanism using variable Venturi therein, being
able to alter or exchange the flow rate with continuity by changing
the cross-sectional area of a throat, so as to eliminate the
disturbance occurring upon the change in the flow rate of the
diluted gas, and also to enable output the flow rate data with high
accuracy even when the flow rate is altered but without provision
of a flow meter as described above.
[0016] Japanese Laid-Open Patent No. Sho 54-127388 (1979) discloses
the following, in connection with the measurement of components of
the exhaust gas.
[0017] In general, the measurement of components in the exhaust gas
is practiced by measuring the concentration of the gas components
in the exhaust gas that is sampled in a bag within a predetermined
time period, by means of the CVS device. As a method for measuring
the gas concentration of components in the exhaust gas sampled in
the bag, there is known a continuous measure method for diluted
gas, by which the gas concentration of the components can be
obtained as an average concentration of the gas sampled as a whole
and can be measured in a moment. In this continuous measure method
for diluted gas, the gas concentration of specific component(s) in
sampling gas, being sampled from the exhaust gas which is diluted
with the air continuously, is measured by a continuous detector,
and instantaneous weight of the gas components is calculated by
computation using the measured concentration and the flow rate of
the sampled gas. However, the dilution ratio comes to be one per
several tens (1/several tens) depending upon the operating
condition of a car (in particular, in an idling operation). In
explanation, with this method the concentration of the sample gas
is decreased too much, therefore, the detector for measuring the
concentrations is required to be one which has high sensitivity.
Furthermore, since the concentration of the sample gas come to be
low (or lean), it is impossible to measure it/them with high
accuracy, due to error and so on being caused by changes in the
concentration of the target components to be measured, which are
contained in the air for use in dilution thereof.
[0018] In Japanese Laid-Open Patent No. Hei 4-268440 (1992) is
described an analyzer for exhaust gas of automobiles, in which the
exhaust gas discharged from the engine of an automobile is diluted
with a gas for dilution, at the gas being diluted at a constant
rate and such that the dilution ratio provides that no dew is
condensed therein, to the diluted gas then being supplied to an
analyzer portion as the sampling gas.
[0019] Further, in particular in the section describing the
conventional arts in Japanese Laid-Open Patent No. Hei 4-268440
(1992), it is described that, for quantitative analysis of the
components contained within the exhaust gas, the exhaust gas is
sampled as the sample gas with use of the CVS, during which the
automobile is operated on a chassis dynamo in accordance with a
driving mode, such as a 10 mode, a LA-4C/H mode, etc., to be
supplied to an analyzer portion of FTIR (Fourier Transform Infrared
Spectrometer).
[0020] Further, in the section describing the conventional arts in
Japanese Laid-Open Patent No. Hei 4-268440 (1992), it is described
that the components and the average value of concentration thereof
in the diluted gas can be obtained during a certain time period, by
supplying the diluted gas into an analyzer portion, which is
sampled in the bags for sampling dilute gas. Further, it is also
described that the result of analysis can be obtained more
correctly by having measured background values in advance through
analysis of the air which was sampled in the air sampling bag.
[0021] Moreover, in the description of the problems to be dissolved
by the invention of Japanese Laid-Open Patent No. Hei 4-268440
(1992), it is described that since the exhaust gas is obtained
through burning of organic compounds including gasoline, carbon and
hydrogen, the exhaust gas contains water vapor therein, and when
the water vapor is condensed into dew, the components of the gas
are reduced because they dissolve into the water condensed from the
vapor. Consequently, as a means for avoiding such the situations,
it is described that (1) the temperature of tunnels for dilution
and gas passages are maintained to be higher than a certain value,
so as to prevent the exhaust from being decreased in temperature
thereof, and (2) the dilution rate (multiplying factor) of the
diluted gas is increased by means of the air for dilution, so as to
increase the dew point.
[0022] Also, in Japanese Laid-Open Patent No. Hei 8-226879 (1996),
there is described a gas sampling apparatus wherein for diluting
the exhaust gas discharged from a source of exhaust gas to be
sucked in by the CVS, a sampling bag device is provided in a gas
sampling flow passage divided from the CVS through a suction pump
and a flow rate controller device, and wherein the gas sampling
flow passage is heated in the region reaching up to the sampling
bags in such a degree that the moisture in gas passing
there-through is not condensed, so as to provide for measurement of
components included within the exhaust gas with high accuracy,
while sampling the exhaust gas being diluted at the minimum
limit.
[0023] However, in the exhaust gas sampling method for analyzing
the components of the diluted gas being sampled in a sampling bag,
the diluted gas must be set at such a dilution ratio that no
condensation of moisture occurs in the diluted gas. By increasing
the flow rate of the CVS (i.e., setting the dilution ratio at a
high value), it is possible to protect the diluted gas from the
condensation of moisture therein. However, if the dilution ratio is
increased, the influences of CO, HC, NO.sub.x and so on contained
in the fresh air from outside become large, and therefore it is
difficult to obtain the analysis data correctly.
[0024] Turning attention to the discharged volume of the exhaust
gas in each of phases within the traveling modes, the dilution rate
is decreased by making the CVS different in the flow rate thereof
in each of the phases, so as to obtain the correct analysis
data.
[0025] FIG. 12 and FIG. 13 are graphs showing the results of
measurements in a case where the CVS flow rate is changed for each
of the phases wherein, in particular, FIG. 12 shows a relationship
between the flow rate of the exhaust gas in the LA4 mode, while
FIG. 13 shows the dew point in the gas sampling bag. The LA4 mode
comprises the CT phase from start of the measurement up to 505 sec,
the CS phase from 505 sec up to 1,374 sec, and the HT phase starts
after a 600 sec pause up to 505 sec thereafter (note that the HT
phase is similar to the CT phase, and therefore is eliminated in
FIGS. 8, 9, 10, 12, 13, 14 and 15). The traveling patterns,
including operation states such as acceleration, constant speed,
deceleration, etc. (speed patterns of automobiles), are set up
corresponding to the development of time. In FIGS. 12 and 13, the
traveling pattern indicates the speed (vehicle speed) of the
automobile running on the chassis dynamo equipment, for testing. In
FIG. 12, the flow rate of exhaust gas indicates the measured value
of exhaust gas of the automobile running on the chassis dynamo
equipment. The test condition shown in FIG. 12 is that the CVS flow
rate in the CS phase is set at 2.4 m.sup.3/min, while the CVS flow
rate is set at 1.6 m.sup.3/min. The sampling bags are heated at
40.degree. C. in temperature thereof.
[0026] For such a condition, the change in the dew point within the
gas sampling bag is shown in FIG. 13 in particular, using the case
of a gasoline car as an example, when a portion of the exhaust gas
(the diluted gas) which is diluted by means of the CVS is sampled
in the gas sampling bags. In the CT phase in which the CVS flow
rate is set at 2.4 m.sup.3/min, the peak value of the dew point
within the bag is 34.6.degree. C. (at the dilution ratio of 3.34),
however, the dew point within the bag is decreased to 32.6.degree.
C. (at the dilution ratio of 3.95) in the final stage of the CT
phase. In the same manner, in the CS phase in which the CVS flow
rate is set at 1.6 m.sup.3/min, the peak value of the dew point
within the bag is 36.0.degree. C. (at the dilution ratio of 2.29),
however, the dew point within the bags is decreased to 31.5.degree.
C. (at the dilution ratio of 4.34) in the final stage of the CS
phase.
[0027] Under the condition mentioned in the above, since the
sampling bag is heated to 40.degree. C. in temperature thereof, no
dew is condensed as long as the dew point within the sampling bag
(BAG) is less than 40.degree. C. In the measured results of the dew
points within the bag shown in FIG. 13, because there still remains
a margin up to 40.degree. C., it can be considered that the diluted
gas may be sampled in the sampling bag by changing the CVS flow
rate down to a lesser value (i.e., by decreasing the dilution
ratio), so as to sample in the sampling bag the diluted gas which
is higher or richer in the exhaust gas condensation.
[0028] FIGS. 14 and 15 show the measured results of the CVS flow
rates in a case where the condition is lower than those shown in
FIGS. 12 and 13. In particular, FIG. 14 shows a relationship
between the flow rate of exhaust gas and the CVS flow rate, and
FIG. 15 shows the dew point within the sampling bag. As shown in
FIG. 14, when the VCS flow rate is set at 1.84 m.sup.3/min in the
CT phase and the flow rate is set at 1.35 m.sup.3/min in the CS
phase, the peak values of the dew point within the bag come to be
38.degree. C. in both the CT phase and the CS phase, and the final
dew point within the bag to be 35.8 C in the CT phase and
33.3.degree. C. in the CS phase, as shown in FIG. 15, thereby
enabling bringing them closer to the heating temperature of the
sampling bag. However, as shown in FIG. 14, the flow rate of
exhaust gas sometimes exceeds the CVS flow rate in the case where
the VCS flow rate is set at 1.84 m.sup.3/min in the CT phase and
the flow rate at 1.35 m.sup.3/min in the CS phase, and therefore it
is impossible to perform the measurement correctly.
[0029] Therefore, another object according to the present
invention, for dissolving such problems as mentioned above, is to
provide an exhaust gas sampling method in which the diluted gas at
a low dilution ratio can be sampled in the sampling bag while
preventing the condensation of moisture therein, by changing the
CVS flow rate corresponding to the traveling mode patterns for
evaluation testing of the exhaust gas, and the diluted gas of the
low dilution ratio (the diluted gas in a condition of high exhaust
gas concentration) can be sampled in the sampling bag by bringing
the peak value of the dew point in the bag and the final dew point
in the bag towards the peripheral temperature of the bags, thereby
increasing the accuracy in analysis of the exhaust gas
components.
SUMMARY OF THE INVENTION
[0030] According to the present invention, for achieving the first
object of the invention mentioned above, there is provided a flow
rate detector mechanism using variable Venturi therein,
comprising:
[0031] a variable flow rate generator, comprising:
[0032] a core; and
[0033] a variable critical flow Venturi;
[0034] wherein a throat cross-sectional area defined between the
core and the variable critical flow Venturi may be changed by
shifting relative positions of the core and the variable critical
flow Venturi in a direction of axes thereof;
[0035] the flow rate detector mechanism further comprising a flow
rate calculation processing portion for calculating a flow rate on
basis of the relative positions in the direction of the axes
thereof and for outputting the calculated flow rate.
[0036] With the flow rate detector mechanism using variable Venturi
therein, since it is possible to change the value of constant flow
rate continuously, no disturbance occurs in the value thereof when
the flow rate is altered. Further, with the flow rate detector
mechanism using variable Venturi therein, according to the present
invention, it is possible to output the flow rate value even when
the flow rate is altered. Accordingly, upon analyzing the exhaust
gas components, it is possible to reflect the change in the flow
rate, occurring when the flow rate is altered, in the analysis
data, thereby outputting the result of analyzing correctly.
Accordingly, with using the flow rate detector mechanism using
variable Venturi therein, according to the present invention, no
error is contained in the result of analysis even when the flow
rate of the diluted gas is altered corresponding to the test modes,
thereby the results of analysis may be obtained with high
accuracy.
[0037] Next, according to the present invention, for achieving the
second abject mentioned above, there is provided an exhaust gas
sampling method for analyzing exhaust gas of an automobile, using a
flow rate detector mechanism using variable Venturi therein,
comprising the following steps:
[0038] diluting the exhaust gas from the automobile with fresh air
from outside;
[0039] sampling a portion of the diluted exhaust gas into a
sampling bag at a certain ratio; and
[0040] analyzing the diluted exhaust gas being sampled, wherein a
flow rate through said flow rate detector mechanism is changed in a
phase of mode for measurement, so that at least a final dew point
in the sampling bag approaches a predetermined temperature within a
predetermined temperature range.
[0041] Further, according to the present invention, it is
preferable that the flow rate through said flow rate detector
mechanism is changed in the phase of mode for measurement, so that
the dew point in the sampling bag is averaged. Also, the flow rate
through said flow rate detector mechanism is changed in the phase
of mode for measurement, so that at least the flow rate through
said flow rate detector mechanism does not exceed the flow rate of
the exhaust gas during the measurement. Furthermore, it is
preferable to change the flow rate of the sampling gas depending
upon a change in the flow rate through said flow rate detector
mechanism.
[0042] Applying the exhaust gas sampling method according to the
present invention, it is possible to make small the difference
between the peak value in the dew point within the bag and the
final dew point within the bag, as well as to cause the final dew
point to approach the temperature at which the bag is maintained.
Accordingly, it is possible to lower the dilution ratio at the
final dew point within the bag, as well as to improve the accuracy
of the analysis.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] FIG. 1 is a structural view of a flow rate detector
mechanism using variable Venturi therein according to the present
invention;
[0044] FIG. 2 is a graph showing a relationship between shift
distance (position) of the variable Venturi and flow rate
coefficient;
[0045] FIG. 3 is a flow chart showing processing in a CPU unit;
[0046] FIG. 4 is a graph showing an output characteristic of flow
rate when the flow rate is changed;
[0047] FIG. 5 is a structural view of a constant volume sampler
(CVS) applying the flow rate detector mechanism with variable
Venturi therein, according to the present invention;
[0048] FIG. 6 is a graph showing a measurement result of exhaust
gas in a cold transient (CT) phase and a cold stabilize (CS) phase
(LA-4 mode), as well as a traveling pattern (i.e., car speed) on a
chassis dynamo;
[0049] FIG. 7 is a graph showing a measurement result of exhaust
gas in US06 mode (high speed/high load), as well as a traveling
pattern (i.e., car speed) on a chassis dynamo;
[0050] FIG. 8 is an explanatory view of a sequence for changing
diluted gas flow rate in the LA-4 mode;
[0051] FIG. 9 is a graph showing a relationship between the exhaust
gas flow rate and CVS flow rate when applying an exhaust gas
sampling method according to the present invention;
[0052] FIG. 10 is a graph showing measurement result of dew point
within a sampling bag when applying the exhaust gas sampling method
according to the present invention;
[0053] FIG. 11 is an explanatory view showing another structure of
an altering mechanism of sampling gas flow, according to the
present invention;
[0054] FIG. 12 is a graph showing a relationship between the
exhaust gas flow rate and CVS flow rate in the LA-4 mode;
[0055] FIG. 13 is a graph showing dew point within the sampling bag
when sampling the diluted gas with the CVS flow rate shown in FIG.
12;
[0056] FIG. 14 is a graph showing a relationship between the
exhaust gas flow rate and CVS flow rate in the LA-4 mode in a case
where the CVS flow rate is lower than the condition shown in FIG.
12;
[0057] FIG. 15 is a graph showing dew point within the sampling bag
when sampling the diluted gas with the CVS flow rate shown in FIG.
14; and
[0058] FIGS. 16(a) and (b) are explanatory views showing problems
in a prior-art CVS apparatus when altering the flow rate of exhaust
gas therewith.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0059] Hereinafter, detailed explanation of the embodiments
according to the present invention will be given by referring to
the attached drawings. FIG. 1 shows the construction of a flow rate
detector mechanism with variable Venturi according to the present
invention, wherein the flow rate detector mechanism 1 with the
variable Venturi comprises a VCFV (Variable Critical Flow Venturi)
10 which can change the value of constant (critical) flow with
continuity, an actuator unit 20, and a processing unit 30 for
controlling the position of the variable Venturi and for
calculating the flow rate.
[0060] As the variable critical flow Venturi (VCFV) is used the
so-called sonic-type Venturi. This variable critical flow Venturi
(VCFV) comprises a fixed core 11 and a variable (or movable)
Venturi 12. The fixed core 11 is fixed at a central position of a
Venturi conduit. The variable Venturi 12 is so constructed that it
can be shifted in an axial direction of the Venturi conduit. The
cross-sectional area (the cross sectional area of the flow passage)
of a throat (flow passage) portion 13 between the fixed core 11 and
the variable Venturi 12 is changed continuously by shifting the
variable Venturi 12 in the axial direction thereof, thereby
obtaining the construction for changing the value of flow rate
continuously.
[0061] Though in FIG. 1 is shown a construction wherein the core is
fixed while the Venturi at an outside thereof can be shifted, it
may however also be constructed so that the Venturi at an outside
is fixed while the core can be shifted.
[0062] At an inflow side of the variable critical flow Venturi
(VCFV) 10 is connected a sampling conduit 2 for sampling the sample
gas. At the tip of the sampling conduit 2 is provided a sampling
Venturi 3 for the purpose of maintaining the sampling flow rate at
a predetermined flow rate. Further, at the inflow side of the
variable critical flow Venturi (VCFV) 10, there are provided a
pressure sensor 4 for detecting the pressure of the diluted gas as
well as a temperature sensor 5 for detecting the temperature of the
diluted gas, respectively.
[0063] An actuator unit 20 comprises a pulse motor 21, a ball screw
22 which is rotated upon the rotation of an output shaft of the
pulse motor 21, a driving fix sheet 23 which can be shifted in the
direction of the axis of the ball screw 22 following the rotation
thereof, and a rotary encoder 24 which detects the rotation angle
of the ball screw 22 and outputs pulse signals for plural systems
responding to each predetermined rotation angle of the ball screw
22.
[0064] The fix sheet 23 and the variable Venturi 12 at the side of
the VCFV 10 are connected to each other through a connector rod 25.
Therefore, the variable Venturi 12 is shifted following the shift
of the driving fix sheet 23 in the axial direction thereof, when
the ball screw 22 is rotated by driving the pulse motor 21.
Thereby, it is possible to vary the value of flow rate of the
variable critical flow Venturi (VCFV) 10 continuously.
[0065] A processing unit 30 for controlling the position of the
variable Venturi and for calculating the flow rate comprises an A/D
converter 31, a pulse counter unit 32, a pulse generating unit 33,
a motor driver unit 34, a D/A converter unit 35, a console unit 36,
a clock generating unit 37, a CUP unit 38 and a system bus 39. The
A/D converter 31, the pulse counter unit 32, the pulse generating
unit 33, the D/A converter unit 35 and the console unit 36 are
connected to the CUP unit 38 through the system bus 39 being, for
example, an address/data/control bus.
[0066] An output signal 4a of the pressure sensor 4 (the pressure
at the inflow portion of the variable Venturi) and an output signal
5a of the temperature sensor 5 (the temperature at the inflow
portion of the variable Venturi) are provided to the A/D converter
31 having a multiple type A/D converter therein, respectively. The
A/D converter 31 converts the voltage signals into digital data
corresponding to the pressure and the temperature, so as to output
them as such. The digital data relating to the pressure and the
temperature are provided to the CPU unit 38 through the system bus
39.
[0067] An output signal 24a of the rotary encoder 24 (pulse signal
corresponding to the shift distance of the variable Venturi) is
provided to the pulse counter unit 32. The pulse counter unit 32
decides the direction in shifting of the variable Venturi 12 on the
basis of the output signal 24a of the rotary encoder 24, and also
calculates the data of shift distance (position) of the variable
Venturi 12 on the basis of the result of counting the number of
pulses so as to output the data of shift distance (position) being
calculated therewith. The data of shifting distance (position) is
also provided to the CPU unit 38 through the system bus 39.
[0068] The pulse generating unit 33 produces a motor driving pulse
signal corresponding to the direction in rotation of the pulse
motor, being designated on the basis of a pulse motor driving
command when the pulse motor driving command is provided from the
CPU unit 38 through the system bus 39, so as to provide the motor
driving unit 34 with the motor driving pulse signal being
generated.
[0069] The D/A converter unit 35 produces a voltage signal (flow
rate output signal) corresponding to the flow rate on the basis of
the data of flow rate which is provided from the CPU unit 38
through the system bus 39 to be outputted therefrom. Although there
is disclosed the structure wherein the voltage signal (analog
signal) is outputted as the flow rate output signal corresponding
to the flow rate outputted in the present embodiment, it can
however be so constructed that the data of flow rate output (the
value of flow rate) is directly outputted therefrom. Also, it can
be structured so that not only the flow rate (instantaneous flow
rate), but also an integrated value of the flow rate, which is
integrally calculated with the CPU unit 38, may be outputted.
[0070] The console unit 36 comprises an input operating portion for
inputting information such as the flow rate, a condition for
changing the flow rate and parameter(s) for calculating the flow
rate, and a display portion on which are indicated the flow rate
and the condition for changing the flow rate which are determined,
as well as the present value of flow rate (instantaneous flow rate)
and the integrated value of flow rate, etc.
[0071] The clock generating unit 37 provides a system clock as the
basis for operation of the CPU unit 38. Also, the clock generating
unit 37 provides the CPU unit 38 with a signal of a predetermined
period (for example, 10 msec in the period) which is obtained by
dividing the system clock output as, for example, an interruption
signal for initiating the calculation of flow rate.
[0072] The CPU unit 38 comprises a table indicating correspondence
between the shift distance (position) of the variable Venturi 12
and flow rate coefficient Kv of the variable critical flow Venturi
(VCFV) 10. FIG. 2 shows one example of a relationship between the
shift distance (position) of the variable Venturi and the flow rate
coefficient Kv. In the present embodiment, the fixed core 11 and
the variable Venturi 12 are configured in the shapes thereof so
that the shift distance (position) of the variable Venturi is
proportional to the flow rate coefficient Kv.
[0073] However, rather than providing the correspondence table
which was prepared in the CPU unit 38 in advance, it also can be so
structured that an equation is provided therein, through which the
flow rate coefficient Kv of the variable critical flow Venturi
(VCFV) 10 is obtained on the basis of the shift amount (position)
of the variable Venturi 12. Further, regarding the data of the
correspondence table and the equation, they can be inputted and/or
altered through the console unit 36.
[0074] FIG. 3 is a flow chart showing processing in the CPU unit.
The CPU unit 38, by repeating a series of steps shown in FIG. 3 at
every cycle of the predetermined period (for example, a period of
10 msec.), performs the calculation of the flow rate, as well as
the calculation of integration of the flow rate. Also, the CPU unit
38 controls the position of the variable Venturi 12, so as to
obtain the flow rate which is set through the console unit 36,
through a feedback control, and controls that position of the
variable Venturi 12 so as to alter it when the set up flow rate is
altered.
[0075] Namely, the CPU unit 38 reads the shift distance (position)
of the variable Venturi 12 through the pulse counter unit 32
therein (step S1). Next, the CPU unit 38 reads the absolute
pressure P at the inlet of the variable critical flow Venturi
(VCFV) 10 and the absolute temperature at the inlet thereof through
the A/D converter unit 31 (step S2). The CPU unit 38 obtains the
flow rate coefficient Kv at the present shift distance (position)
of the variable Venturi 12, by referring to the correspondence
table between the shift distance of the variable Venturi 12 and the
flow rate coefficient of the variable critical flow Venturi (VCFV)
10 (step S3).The CPU unit 38 obtains the flow rate Q of the
variable critical flow Venturi (VCFV) 10 on the basis of the flow
rate coefficient Kv, the inlet absolute pressure P and the inlet
absolute temperature of the variable critical flow Venturi (VCFV)
10, by conducting the calculation indicated by the following
equation (1) (step S4). 1 Q = ( Kv + Kvs ) .times. P T ( Eq . 1
)
[0076] where, Q: instantaneous flow rate of VCFV [m.sup.3/min], Kv:
flow rate coefficient of VCFV, Kvs: flow rate coefficient of
sampling Venturi, P: inlet absolute pressure of VCFV [kPa], and T:
inlet absolute temperature of VCFV [K].
[0077] The CPU unit 38 displays the flow rate Q obtained in the
step S4 on the display portion of the console unit 36 for the flow
volume, as well as providing the flow rate output signal to an
external equipment (for example, a controller device 90 shown in
FIG. 5) through the D/A converter unit 35. Further, the CPU unit 38
conducts the integration of the flow rate on the basis of the flow
rate Q so as to display the integrated flow rate on the display
portion of the console 36 for the integrated flow rate (step S5).
However, the CPU unit 38 can be so constructed that it outputs the
integrated flow rate to the external equipment (such as the
controller device 90 shown in FIG. 5).
[0078] The CPU unit 38 obtains the deviation of the flow rate Q
obtained in step S4 from a target flow rate (for example, a CVS
flow rate which is designated with the controller device 90 shown
in FIG. 5), and drives the actuator unit 20 through the pulse
generator unit 33 and the motor driver unit 34 in such a direction
that the deviation approaches zero (0) when the deviation is formed
to exceed a permissible value which is determined in advance.
Thereby, the feedback control of the shift distance (position) of
the variable Venturi can be performed (step S6).
[0079] As shown in step S7, the CPU unit 38 repeats the above steps
S1 through S6 every time when the predetermined time period
elapses. Assuming that the repetitive time period (the
predetermined time period) of those steps is 10 msec, for example,
the calculation of the flow rate and the feedback control of the
shift distance of the variable Venturi are performed every 10 msec.
In the present embodiment, the series of processing of those steps
is conducted upon the interruption signal supplied from the clock
generating unit 37. Note that rather than supplying the
interruption signal from outside, the elapse of the predetermined
time period can be decided using an internal timer or the like
within the CPU unit 38. Further, though the example is shown
wherein the flow rate is outputted in step S5 after conducting the
flow rate calculation shown in step S4, as in FIG. 3, the
processing of steps S1 through S4 can, however, also be conducted
to calculate out the flow rate after outputting the flow rate being
obtained previously, at the time point when the predetermined time
elapses. With outputting the flow rate output at the beginning of
the series of steps, it is possible to correctly synchronize the
timing of outputting the flow rate with the predetermined
period.
[0080] In the present embodiment, as shown by the equation (i.e.,
Eq. (1)) for calculating the flow rate, obtaining a sum of the flow
rate coefficient of the variable critical flow Venturi (VCFV) 10
(the flow amount coefficient obtained corresponding to the shift
distance (position) of the variable Venturi) and the flow rate
coefficient of the sampling Venturi 3, the instantaneous flow rate
Q is obtained from it taking the temperature T and the pressure P
into the consideration. Accordingly, even in the condition where
the sampling gas is sampled through the sampling Venturi 3, it is
possible to obtain a total flow rate, adding the flow rates of
sampling gas. However, when no sampling gas is sampled from the
sampling Venturi 3, as shown in FIG. 1, information indicative of
non-sampling of the sampling gas (gas sampling/non-sampling
information) is provided to the CPU unit 38. The CPU unit 38, when
acknowledging the gas non-sampling condition on the basis of the
gas sampling/non-sampling information, turns the flow rate
coefficient of the sampling Venturi 3 to zero (0) and conducts the
calculation of the instantaneous flow rate Q using only the flow
rate coefficient of the variable critical flow Venturi (VCFV)
10.
[0081] With the construction mentioned above of the flow rate
detector mechanism 1 with the variable Venturi shown in FIG. 1, it
is possible to change or alter the flow rate of the diluted gas or
the like, on the basis of the flow rate or the flow rate changing
program set up in advance. Also, it is possible to calculate the
instantaneous flow rate so as to display it on the display portion
of the console unit 36, as well as to provide it to external
equipment (such as the controller device 90 shown in FIG. 5). With
the construction wherein the ball screw 22 is driven by the pulse
motor 21 so as to shift the position of the variable Venturi 12, it
is possible to control the shift distance (position) of the
variable Venturi 12 within the accuracy of 10 .mu.m, for example.
Therefore, it is possible to control the flow rate correctly, as
well as to alter or change the flow rate continuously without a
disturbance in the flow rate value occurring even when the flow
rate is changed.
[0082] However, in order to alter or change the flow rate quickly,
when changing the phase under which it is measured, it can be
controlled in the following manner ((1) through (4)):
[0083] (1) When the established flow rate is changed first in FIG.
1, the change of flow rate is sent by the console unit 36 to the
CPU unit 38.
[0084] (2) In the console unit 36, the pulse motor 21 is driven to
move the variable Venturi 12 by the shift distance (position)
thereof depending upon the flow rate, according to "the flow rate
and the shift distance (position) of the variable Venturi 12" (in
the proportional relationship) which was set up in advance, through
the pulse generator unit 33 and the motor driver unit 34.
[0085] (3) The driving fix sheet 23, which is moved by the pulse
motor, is monitored as for whether it shifts out of the
predetermined position or not, by means of the rotary encoder 24,
the pulse counter unit 32, and the CPU unit 38, and an alarm is
generated when it shifts out of the predetermined position.
[0086] (4) At the same time of the above (1) to (3), the flow rate
Q is obtained periodically (for example, at the time period of 10
msec) from the value Kv, which can be obtained from the values of
the pressure sensor 4 and the temperature sensor 5, and the shift
distance of the variable Venturi 12.
[0087] FIG. 4 is a graph showing an output characteristic of flow
rate when altering or exchanging the flow rate. In FIG. 4, modeled
on the manner of changing from the cold transient (CT) phase (for
example, at flow rate of 15 m.sup.3/min) to the cold stabilize (CS)
phase (for example, at flow rate of 3 m.sup.3/min), there is shown
an example of the output of flow rate in a case where it is changed
within the time period of about 1 sec. With the flow rate detector
mechanism 1 using a variable Venturi therein, since it calculates
to output the flow rate in the period (for example, 10 msec) being
sufficiently shorter than the time necessary for change of the flow
rate, it is possible to determine a degree in change of the flow
rate correctly, and there is no large error contained in the
integrated value of flow rate with integrating the instantaneous
flow rate Q which is outputted at the period being sufficiently
short (for example, 10 msec), thereby obtaining the integrated
value of flow rate with high accuracy is possible.
[0088] FIG. 5 is a view showing the structure of the constant
volume sampler (CVS) using the flow rate detector mechanism with
the variable Venturi mentioned above, according to the present
invention. The constant volume sampler (CVS) 50 shown in FIG. 5 is
able to analyze the components in the exhaust gas simultaneously
(in real-time), continuously analyzing the components of the
diluted gas which is obtained by mixing the exhaust gas and
external fresh air together, or to analyze the components of the
diluted gas which is sampled after being sampled in the sampling
bag.
[0089] The exhaust gas, from the automobile installed on a chassis
dynamo not shown in the figure, is supplied to an intake 51 for
exhaust gas through a flexible pipe and so on, which are not shown
in the figure. The exhaust gas is mixed with the external fresh
air, which is taken from an air intake 52 and is purified through a
filter unit 53, so as to form the diluted gas, and this diluted gas
is supplied to the variable critical flow Venturi (VCFV) 10, after
being removed and divided from dust and mist contained therein
through a cyclone unit 54. In a later stage of the variable
critical flow Venturi (VCFV) 10 is connected a blower 55 of a
constant capacity. The constant capacity blower 55 being used here
has an emitting capacity being sufficiently larger than the maximum
value of flow rate of the variable critical flow Venturi (VCFV) 10.
Through using the constant capacity blower 55 having such a large
emitting capacity, the flow rate of the diluted gas can be preset
through the variable critical flow Venturi (VCFV) 10. The diluted
gas emitted from the constant capacity blower 55 is discharged into
the air, or is discharged through a purifying apparatus not shown
in the figure and then into the air.
[0090] In a side up-stream from the exhaust gas intake 51, there is
provided an air flow detector 56 for detecting the flow rate of the
external fresh air and a Venturi 57 for sampling the fresh air
sample. The output of the detected flow rate of the air flow
detector 56 (not shown in the figure) is provided to the controller
90. The fresh air sampled through the Venturi 57 for sampling the
fresh air sample is supplied through a filter unit 58 to a pump 59
for sampling the fresh air. The filter unit 58 is provided for
preventing suction of foreign materials into the pump 59. An output
of the pump 59 is supplied through a flow rate detector 60 for the
sampled fresh air to one end of each of the respective
electromagnetic valves 61, 62 and 63. The other ends of the
electromagnetic valves 61, 62 and 63 are connected to the air
sampling bags (sampling bags) 64, 65 and 66, respectively. There is
used the pump 9 having a capacity being larger than the flow rate
of the fresh air sampling Venturi 57.
[0091] Accordingly, by turning the first electromagnetic valve 61
OPEN under the condition of driving the fresh air sampling pump 59,
it is possible to sample the fresh air into the first air sampling
bag 64. In the same manner, by turning the second electromagnetic
valve 62 OPEN, the fresh air can be sampled into the second air
sampling bag 65, and by turning the third electromagnetic valve 63
OPEN, into the third air sampling bag 66. An output of the detected
flow rate (not shown in the figure) from the flow rate detector 60
for the sampled fresh air is provided to the controller 90. The
controller 90 adjusts the volume of sampling the fresh air into the
air sampling bag, by integrating the flow rate on the basis of the
output of the detected flow rate from the flow rate detector 60.
Also, the controller 90 performs the selection of the air sampling
bags as well as the adjustment of the sampling volume thereof, by
controlling OPEN/CLOSE of the electromagnetic valves 61 to 63, via
signal lines for controlling the electromagnetic valves which are
not shown in the figure.
[0092] It is also possible to provide a heat exchanger 67 in the
upper stream side of the variable critical flow Venturi (VCFV) 10,
so as to heat or cool the diluted gas, thereby keeping the
temperature thereof within a predetermined temperature range. With
the control of temperature of the diluted gas, it is possible to
prevent the condensation of moisture therein. Further, relief from
fluctuation in temperature of the diluted gas makes the flow rate
control stable, thereby improving the accuracy of measurement.
[0093] The diluted gas, which is sampled through the sampling
Venturi 3 provided at the inlet side of the variable critical flow
Venturi (VCFV) 10, is supplied to one end of an electromagnetic
valve 68 for continuous gas analysis, and further to one end of an
electromagnetic valve 69 for sampling the diluted gas. When the
electromagnetic valve 68 for continuous gas analysis is controlled
to be OPEN, the diluted gas being sampled through the sampling
Venturi 3 is supplied to an analyzer 70 for continuous gas
analysis. Thereby, the analysis of gas is conducted
continuously.
[0094] When the electromagnetic valve 69 for sampling the diluted
gas is controlled to be OPEN, the diluted gas sampled through the
sampling Venturi 3 is supplied through a filter 71 to a pump 72 for
sampling the diluted gas. An output of the pump 72 is supplied
through a flow rate detector 73 of the diluted gas to one end of
each of respective electromagnetic valves 74, 75 and 76. The other
ends of the electromagnetic valves 74, 75 and 76 are connected to
sampling bags for the diluted gas 77, 78 and 79, respectively. The
pump 73 having a capacity being larger than the flow rate of the
sampling Venturi 3 is utilized.
[0095] Accordingly, under the condition where the electromagnetic
valve 69 for sampling the diluted gas is OPEN and the pump 72 for
the sampling is driven, the diluted gas can be sampled in the first
sampling bag 77 by turning the first electromagnetic valve 74 to
OPEN. In the same manner, the diluted gas can be sampled in the
second sampling bag 78 by turning the second electromagnetic valve
75 to OPEN, and in the third sampling bag 79 by turning the third
electromagnetic valve 76 to OPEN. An output of the detected flow
rate (not shown in the figure) from the flow rate detector 73 for
the diluted gas is provided to the controller 90. The controller 90
adjusts the volume of sampling the sample gas into the sampling
bag, by integrating the flow rate on the basis of the output of the
detected flow rate from the flow rate detector 73 for the diluted
gas. Also, the controller 90 performs the selection of the sampling
bags as well as the adjustment of the sampling volume thereof, by
controlling OPEN/CLOSE of the electromagnetic valves 74 to 76, via
signal lines for controlling the electromagnetic valves which are
not shown in the figure.
[0096] By turning to OPEN an electromagnetic valve 80 and an
electromagnetic valve 86 for analyzing the sampled gas, the fresh
air sampled in the first air sampling bag 64 is supplied to an
analyzer 87 of the sampled gas, so as to analyze the components of
the fresh air which is sampled in the first air sampling bag 64.
However, the analyzer 87 for the sampled gas comprises a pump (not
shown in the figure), thereby sucking the fresh air or the sample
gas (the diluted gas) into the bag to supply it to the analyzing
portion of components (not shown in the figure). The fresh air or
the sample gas (the diluted gas), being completed in component
analysis thereof, is discharged into the air, or is discharged
through the purifying apparatus not shown in the figure then into
the air.
[0097] In the same manner, the fresh air sampled in the second air
sampling bag 65 can be supplied to the analyzer 87 of the sampling
gas by turning the electromagnetic valve 81 and the electromagnetic
valve 86 for analysis of the sampling gas to OPEN, and the fresh
air sampled in the third air sampling bag 66 can be supplied to the
analyzer 87 of the sampled gas by turning the electromagnetic valve
82 and the electromagnetic valve 86 for analysis of the sampled gas
to OPEN. Further, the diluted gas (the sampling gas) sampled in the
first sampling bag 77 can be supplied to the analyzer 87 for the
sampled gas, by turning the electromagnetic valve 83 and the
electromagnetic valve 86 for analysis of the sampled gas to OPEN.
In the same manner, the sampling gas (the diluted gas) sampled in
the second sampling bag 78, by turning the electromagnetic valve 83
and the electromagnetic valve 86 for analysis of the sampled gas
into OPEN condition, or the diluted gas (the sampling gas) sampled
in the third sampling bag 79, by turning the electromagnetic valve
85 and the electromagnetic valve 86 for analysis of the sampled gas
into OPEN condition, can be supplied to the analyzer 87.
[0098] In the present embodiment, the circumference temperature
around each of the diluted gas sampling bags (sampling bags) 77 to
79 is maintained at 40.degree. C., by heating with a heater not
shown in the figure, or by positioning it within a thermostatic
chamber not shown in the figure.
[0099] Also, the inside of the first air sampling bag 64 can be
cleaned by repeating the process of supplying the cleaning air or
cleaning gas into the first air sampling bag 64 by operating a
reversible pump 89 under the condition that an electromagnetic
valve 88 for cleaning bag as well as the electromagnetic valve 80
are OPEN, then discharging to the outside the cleaning air or the
cleaning gas therein. Cleaning each of the bags 64 to 66 and 77 to
79 can be conducted by treating each respectively by the same
process.
[0100] The controller 90 provided for controlling total operation
of the CVS 50 is constructed with a computer system. The controller
90 controls the OPEN/CLOSE condition of each electromagnetic valve,
each of the pumps, and the blower, etc. through an output interface
unit not shown in the figure. Also, the controller 90 provides the
data relating to the values of flow rates, which are produced by
the variable critical flow Venturi (VCFV) 10, to the detector 1
with the variable Venturi, so as to control the value of the
constant flow rate of the diluted gas. Further, the controller 90
also can be so constructed that operating conditions (start/stop of
engine, revolution number of engine, etc.) of the engine for the
automobile is controlled therewith, i.e., a target to be measured
in the exhaust gas therefrom. In this instance, the controller 90
controls the operation conditions in the engine of the automobile,
which is installed on the chassis dynamo not shown in the figure,
on the basis of operation information supplied from an automatic
engine operation controller not shown in the figure, i.e., the
controller 90 acknowledges the traveling mode of the automobile.
Then, the controller 90 alters the flow rate through the variable
Venturi 1 (i.e., control of flow rate of the diluted gas) depending
upon the traveling mode of the automobile, and also alters the flow
rate of the variable Venturi 3 for sampling in synchronism with the
change in flow rate of the variable Venturi 1 (i.e., control in
sampling flow rate).
[0101] Further, the controller 90 obtains the flow rate of the
exhaust gas discharged from the automobile by subtracting the flow
rate of the external fresh air, detected by the air flow rate
detector 56, from the instantaneous flow rate Q which is outputted
from the flow rate detector mechanism 1 using the variable Venturi
therein. Under the condition of analyzing the gas continuously, the
controller 90 calculates the concentration of the exhaust gas and
the weight of each component thereof on the basis the analysis data
for each component outputted from the continuous gas analyzer 70
and the flow rate of the exhaust gas discharged from the
automobile, so as to display the calculated results (analysis
results) on a screen of an image display apparatus not shown in the
figure, or to print it out via a printer not shown in the figure.
Moreover, the controller 90 can provide the calculated results
(analysis results) to equipment of a higher rank. Also, the
controller 90 can obtain the concentration of the exhaust gas and
the weight of each component thereof with compensation of the
contents of the fresh air for use in dilution, when the analysis of
the sampled gas is completed so that the components of the dilution
air are known. In the analyzing mode for the sampling gas, the
controller 90 conducts the analysis of the sampling gas through the
sampling gas analyzer 87, so as to output the concentration of the
exhaust gas and the weight of each component thereof with
compensation for the contents of the fresh air.
[0102] The CVS 50 shown in FIG. 5 can control the flow rate with
high accuracy since it can alter or exchange the flow rate
continuously and also uses the flow rate detector mechanism 1 with
the variable Venturi, with which the instantaneous flow rate can be
obtained correctly. At the same time, since no disturbance occurs
during changing of the flow rate thereof, the CVS 50 enables the
measurement of the exhaust gas with high accuracy.
[0103] FIG. 6 shows the measurement result of the flow rate of
exhaust gas and the detected result of the specific components
therein, in the cold transient (CT) phase and the cold stabilize
(CS) phase (LA-4 mode). In FIG. 6, the vertical axis indicates the
time (in seconds), i.e., elapsed time from the time point of
starting of the engine. In an upper part is indicated the flow rate
of the exhaust gas. In a lower part thereof is indicated the
traveling pattern (i.e., the car speed) on the chassis dynamo.
[0104] FIG. 7 is a graph showing the measured result of the flow
rate of exhaust gas and the detected result of the specific
components therein, in the US06 mode (high speed/high load mode).
In FIG. 7, the vertical axis also indicates the time (in seconds),
and in an upper part is indicated the flow rate of the exhaust gas,
while in a lower part thereof the traveling pattern (i.e., the car
speed) on the chassis dynamo is indicated.
[0105] In this manner, with use of the flow rate detector mechanism
1 with the variable Venturi shown in FIG. 1, it is possible to
obtain the instantaneous flow rate over a short time period in
sequence such as, for example, 10 msec, therefore the change in
flow rate of the diluted gas can be determined correctly.
Accordingly, it is possible to perform the measurement of exhaust
gas and the analysis of contents thereof with higher accuracy.
[0106] Next, explanation will be given of a method according to the
present invention for sampling exhaust gas, wherein the exhaust gas
is diluted to be sampled in the sampling bags, corresponding to the
traveling mode pattern for evaluation test and using the flow rate
detector mechanism 1 with the variable Venturi mentioned in the
above.
1TABLE 1 Relationship CVS Flow Rate v. Sampling Flow Rate CVS Flow
Rate Sampling Flow Rate 0.6 m.sup.3/min (600 liter/min) 3 liter/min
1.0 m.sup.3/min (1,000 liter/min) 5 liter/min 1.8 m.sup.3/min
(1,800 liter/min) 9 liter/min 2.4 m.sup.3/min (2,400 liter/min) 12
liter/min
[0107] The above TABLE 1 shows a relationship between the CVS flow
rate (flow rate of the diluted gas) and the sampling flow rate, and
FIG. 8 shows a sequences for changing the flow rate of the diluted
gas in the LA-4 mode. In this embodiment, as shown in TABLE 1, the
flow rate of diluted gas and the sampling flow rate are changed or
altered in four (4) stages. Under the condition where the
discharged amount of the exhaust gas is very small in volume, for
example when traveling in idling condition or the like, the flow
rate of the diluted gas is set at 0.6 m.sup.3/min (600 l/min), and
the sampling flow rate (sampling flow volume into the diluted gas
sampling bag) is set at 3 liter/min, this being equal to
one-two-hundredth ({fraction (1/200)}) of the flow rate of diluted
gas. Under the condition where the discharged amount of the exhaust
gas is small in volume, for example when traveling at a constant
speed condition, the flow rate of the diluted gas is set at 1.0
m.sup.3/min (1,000l/min), and the sampling flow rate (sampling flow
volume into the diluted gas sampling bag) is set at 5 liter/min,
this being equal to one-two-hundredth ({fraction (1/200)}) of the
flow rate of diluted gas. Under the condition where the discharged
amount of the exhaust gas is large in volume, for example when
traveling in a high speed condition or accelerating/decelerating
condition, the flow rate of the diluted gas is set at 1.8
m.sup.3/min (1,800 l/min), and the sampling flow rate (sampling
flow volume into the diluted gas sampling bag) is set at 9
liter/min, this being equal to one-two-hundredth ({fraction
(1/200)}) of the flow rate of diluted gas. Under the condition
where the discharged amount of the exhaust gas is larger still in
volume, for example when traveling in a high speed condition or
accelerating/decelerating condition, the flow rate of the diluted
gas is set at 2.4 m.sup.3/min (2,400 l/min), and the sampling flow
rate (sampling flow volume into the diluted gas sampling bag) is
set at 12 liter/min, this being equal to one-two-hundredth
({fraction (1/200)}) of the flow rate of diluted gas.
[0108] In a traveling mode such as the LA-4 mode, etc., the time
schedules are determined corresponding to the time periods,
including idling time period, acceleration time period, traveling
time period of a predetermined constant speed, and so on, as shown
in FIG. 8, therefore, the sequence for changing the flow rate of
the diluted gas and the sampling flow rate is prepared in advance,
corresponding to the time schedule from the time point of starting
the test traveling, and the controller 90 controls the flow rates
in the variable Venturi 1 and the sampling Venturi 3 on the basis
of this sequence for changing the flow rates.
[0109] FIG. 9 is a graph showing the relationship between the flow
rate of exhaust gas and the flow rate of CVS, in a case of applying
the exhaust gas sampling method according to the present invention
therein, and FIG. 10 shows the results of dew points measured in
the bag in a case of applying the exhaust gas sampling method
according to the present invention. As shown in FIG. 9, the CVS
flow rate is altered or exchanged in four (4) stages with respect
to the traveling mode (car speed), therefore, there is no case
where the flow rate of the exhaust gas exceeds that of the CVS. In
the LA-4 mode, the minimum dilution ratio of 1.1% can be maintained
by altering the CVS flow rate in accordance with the sequence for
changing thereof shown in FIG. 8. Since the CVS flow rate is
changed within the phase of the measuring mode, as shown in FIG.
10, it is possible to cancel the difference between the peak of dew
point in the bag and the final dew point in the bag, as well as to
cause the final dew point to approach the temperature at which the
bag is kept.
[0110] In the case of applying the exhaust gas sampling method
according to the present invention, the final dilution ratio in the
bag is 2.57 in the CT phase, and the final dilution ratio in the
bag is 2.58 in the CS phase. On the other hand, according to the
conventional exhaust gas sampling method (i.e., the method of
changing the flow rate of CVS for each phase) shown in FIG. 12, the
final dilution ratio in the bag is 3.95 in the CT phase and the
final dilution ratio in the bag is 4.34 in the CS phase, therefore
it can be seen that the concentration can be rich in the diluted
gas which is sampled in the sampling bag.
[0111] However, the ratio between the CVS flow rate and the
sampling flow rate is always the same because the CVS flow rate
being based on the phases according to the conventional exhaust gas
sampling method (i.e., the CVS flow rate is changed when the phase
is exchanged, but at that time the sampling bag is exchanged,
therefore the ratio between the CVS flow rate and the sampling flow
rate is the same). On the contrary, with the exhaust gas sampling
method according to the present invention, since the CVS flow rate
is changed among the phases, the sampling volume must be changed by
the same ratio with respect to the change in the CVS flow rate.
[0112] In FIG. 5, though it is so constructed that the CVS flow
rate and the sampling flow rate come to a predetermined ratio (for
example, 200:1), as shown in FIG. 2, by changing the flow rate
through the variable Venturi 1 for setting the CVS flow rate and,
at the same time, the flow rate through the sampling variable
Venturi 3, it is also possible to make both the CVS flow rate and
the sampling flow rate variable, by combining the plurality of
orifices each having a different flow rate.
[0113] FIG. 11 is a view for explaining another structure for the
sampling flow rate altering mechanism. The sampling flow rate
altering mechanism shown in FIG. 11 comprises an orifice 101 of 1
liter/min in flow rate, an orifice 102 of 2 liter/min in flow rate,
an orifice 103 of 4 liter/min in flow rate, and an orifice 104 of 8
liter/min in flow rate, wherein electromagnetic valves 105 to 108
are connected in series to the orifices 101 to 104, respectively.
The reference numeral 109 indicates a pump for sampling the diluted
gas. The selection among the orifices 101 to 104 is conducted by
controlling OPEN/CLOSE of the electromagnetic valves 105 to 108.
When all of the orifices 101 to 104 are used, the sampling flow
rate comes to be 15 liter/min (the maximum value). This altering
mechanism for the sampling flow rate is able to change by a unit of
1 liter/min within a range from 1 liter/min to 15 liter/min.
[0114] In FIG. 5, though there is disclosed the structure for
altering the CVS flow rate by using the variable Venturi 1 therein,
it is also possible however to make the CVS flow rate variable, by
exchanging the fixed Venturis, each having different flow rate,
which are provided in plural in the number thereof, or by selecting
the combination of the fixed Venturis to be used at the same
time.
[0115] In the present embodiment, there is disclosed the LA-4 mode
as one example of the traveling mode, wherein the CVS flow rate and
the sampling flow rate are exchanged in four (4) stages in the CT
phase and the CS phase, however the exhaust gas sampling method
according to the present invention can be applied to other various
traveling modes as well. However, in such instances, the CVS flow
rate must be setup appropriately depending upon the displacement of
the car (engine) to be measured. Further, the exchange timing of
the CVS flow rate must be setup appropriately depending upon the
traveling modes.
[0116] In the present embodiment, there is disclosed the
construction wherein the sequence for changing the CVS flow rate
and the sampling flow rate, as shown in FIG. 8, is prepared in
advance, and the controller 90 controls the CVS flow rate and the
sampling flow rate on the basis of the sequence for changing.
However, it is also possible to construct it so that information
designating the sampling flow rate is outputted from the automatic
engine controller which controls the operation of the automobile on
the chassis dynamo, so as to control the CVS flow rate and the
sampling flow rate on the basis thereof. Further, supplying the
operation information relating to the car speed, the
acceleration/declaration, etc., from the chassis dynamo to the
controller 90, the controller 90 can change the CVS flow rate and
the sampling flow rate on the basis thereof.
[0117] As is fully explained in the above, according to the present
invention, the flow rate detector mechanism using the variable
Venturi therein, comprises: a variable flow rate generator,
comprising: a core; and a variable Venturi; wherein a throat (flow
passage) cross-sectional area defined between the core and the
venturi is able to be changed by shifting relative positions of the
core and the venturi in a direction of axes thereof, and further
comprising a flow rate calculation processing portion for
calculating a flow rate based on the relative positions in the
direction of the axes thereof and for outputting the calculated
flow rate, thereby enabling continuous change of the constant flow
rate, without any disturbance in the flow rate value occurring when
the flow rate is changed. Further, the flow rate detector mechanism
using the variable Venturi, according to the present invention, is
able to output the output even during the flow rate being altered
or exchanged. Therefore, by using the flow rate detector mechanism
with the variable Venturi according to the present invention, no
error is contained in the result of analysis even when the diluted
gas is changed in flow rate depending upon the test modes, thereby
obtaining the result of analysis with high accuracy.
[0118] Also, as is fully explained in the above, with the exhaust
gas sampling method according to the present invention, since the
CVS flow rate is changed within the range of the phases of measure
modes, it is possible to make small the difference between the peak
of the dew point in the bag and the final dew point in the bag, as
to cause the final dew point to approach the temperature at which
the bag is kept. Therefore, the dilution ration of the final dew
point in to bag can be decreased, so as to improve the accuracy of
analysis.
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