JP2005156296A - Instrument for measuring exhaust gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct the flow rate of diluting air and the total flow rate in an exhaust passage with precision to accurately control the flow rate of an exhaust gas, in an exhaust gas measuring instrument constituted so as to introduce the exhaust gas discharged from an internal combustion engine, into a measuring passage for measuring the same. <P>SOLUTION: This exhaust gas measuring instrument 100 is constituted, so that a part of the exhaust gas discharged from the engine 1 is introduced into a microtunnel 104 and the exhaust gas is diluted by air in the microtunnel 104 to be measured. On the basis of the relation between an error calculated from the flow rate set to a flow rate control part 102 and the flow rate measured in a flow rate control part 103, errors calculated from the flow rate set to a flow rate control part 106 and the flow rate measured in a flow rate control part 107 and a dilution ratio, the flow rate control parts are corrected so as to minimize the errors in the flow rate of the exhaust gas. Since the correction for the flow rate control parts is performed so as to minimize the error itself for the flow rate of the exhaust gas, not by correcting corrections for which minimize the errors in the flow rate of the flow rate control parts 102 and 106, the flow rate of the exhaust gas can be controlled simply and precisely. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exhaust gas measuring device that guides a part of exhaust gas discharged from an internal combustion engine to a measurement passage and dilutes the exhaust gas with air in the measurement passage to measure substances in the exhaust gas. .

  A microtunnel (dilution tunnel) is used to measure exhaust gas discharged from an internal combustion engine. An exhaust gas measuring device using a microtunnel extracts a part of the exhaust gas with a sampling tube, etc., dilutes a part of the exhaust gas with air in the microtunnel, and the exhaust gas is released into the atmosphere. In this case, the particulate matter (PM) or the like in the exhaust gas is measured by reproducing the same state as in the above case.

  Since the exhaust gas measuring device using such a microtunnel does not need to dilute the entire exhaust gas, the tunnel becomes small, and the overall size of the exhaust gas measuring device can be made compact. become.

  By the way, the control of the flow rate of exhaust gas measured by the exhaust gas measuring device is generally controlled by the flow rate of air used for dilution (hereinafter referred to as “dilution air flow rate”) and the total flow rate of air in the microtunnel. (Hereinafter referred to as “total flow rate”). That is, the exhaust gas flow rate is changed by adjusting the total flow rate and the dilution air flow rate, respectively. This is because PM, which is a target component for measurement, is mixed in the exhaust gas, and if a flow rate control device or a measurement device is provided in the middle of the sampling pipe into which the exhaust gas is introduced, a problem occurs. is there.

  On the other hand, in order to perform an exhaust gas measurement experiment with high accuracy, it is necessary to obtain an accurate flow rate of the exhaust gas to be measured that has flowed into the microtunnel. However, since the exhaust gas flow rate cannot be directly controlled for the reasons described above, the dilution air flow rate and the total flow rate must be controlled with high accuracy.

  As a specific method for accurately controlling such dilution air flow rate or total flow rate, for example, Patent Document 1 uses a highly accurate reference flow meter for the total flow rate and dilution air flow rate in the microtunnel. A technique for improving the measurement accuracy of the exhaust gas flow rate by performing calibration is described. Furthermore, Patent Document 2 describes a technique for controlling an dilution air flow rate control valve by a combination of a fixed flow rate control valve having a stable flow rate and a variable flow rate control valve to reduce errors caused by the dilution air flow rate control. ing. In addition, Patent Literature 3 and Patent Literature 4 describe techniques for improving the measurement accuracy of the exhaust gas measurement device.

  However, as described above, the dilution air flow rate and the total flow rate in the microtunnel are calibrated separately or accurately, or only the dilution air flow rate is adjusted accurately, and the error in the dilution air flow rate or the total flow rate itself becomes small. However, an unexpectedly large error may occur in the flow rate of the exhaust gas. This is because the exhaust gas flow rate is the difference between the dilution air flow rate and the total flow rate in the microtunnel, and if the sign of the error between the dilution air flow rate and the total flow rate is opposite, the exhaust gas error will increase. Because it will end up. Furthermore, when the dilution ratio is large (when the exhaust gas flow rate is small with respect to the total flow rate), the error in the exhaust gas flow rate described above becomes even larger. This is because even if the error is small for the dilution air flow rate or the total flow rate, the exhaust gas flow rate itself is very small, so the above error can be a non-negligible magnitude for the exhaust gas flow rate. is there. That is, the exhaust gas flow rate is greatly influenced by the dilution ratio.

JP-A-11-326161 JP 2000-35822 A JP 2002-340754 A JP-A-10-104037

  The present invention has been made to solve such problems, and an object of the present invention is to measure exhaust gas by introducing exhaust gas discharged from an internal combustion engine into a measurement passage. It is an object of the present invention to provide an exhaust gas measuring device capable of accurately controlling the flow rate of exhaust gas by accurately correcting the flow rate of dilution air and the total flow rate in the exhaust passage.

  In one aspect of the present invention, an exhaust gas measuring device that dilutes exhaust gas discharged from an internal combustion engine with air and measures in the measurement passage is an error between the flow rate of diluted air and the total flow rate in the measurement passage. The flow rate of the dilution air based on the relationship between the error calculation means for calculating the flow rate, the error in the flow rate of the dilution air, the error in the total flow rate, and the dilution ratio between the flow rate of the exhaust gas and the flow rate of the air Correction means for correcting the total flow rate.

  The above exhaust gas measuring device is a device that guides a part of exhaust gas discharged from an internal combustion engine to a measurement passage, and measures the substance in the exhaust gas by diluting the exhaust gas with air in the measurement passage. It is. A microtunnel or the like can be used as the measurement exhaust passage. The exhaust gas flow rate is the difference between the total flow rate in the microtunnel (ie, “total flow rate”) and the dilution air flow rate (ie, “dilution air flow rate”). The error of the exhaust gas may become large, and the error of the exhaust gas is greatly influenced by the dilution ratio DF. Therefore, the dilution air flow rate or the total flow rate is corrected in consideration of the dilution air flow rate, the total flow rate, and the dilution ratio. Since the dilution air flow rate or the total flow rate is corrected so that the error of the exhaust gas flow rate itself becomes small, the flow rate of the exhaust gas can be easily controlled with high accuracy.

  In one aspect of the exhaust gas measuring apparatus, the apparatus includes a dilution air flow rate measuring unit that measures the flow rate of the dilution air, and a total flow rate measuring unit that measures the total flow rate, and the error calculation unit is measured An error in the flow rate of the dilution air is calculated based on the flow rate of the dilution air, and an error in the total flow rate is calculated based on the measured total flow rate. The exhaust gas measuring device can include a flow rate measuring device capable of measuring the flow rate of the gas flowing through the measurement passage. As the flow rate measuring device, a highly accurate flow meter such as a venturi flow meter can be used. As a result, the air flow rate and the total flow rate can be corrected with high accuracy, and the exhaust gas flow rate can be accurately controlled.

  In another aspect of the exhaust gas measuring device, the correction means may control the flow rate of the dilution air based on the error in the total flow rate and the dilution ratio so that the error in the flow rate of the exhaust gas is minimized. to correct. The error in the flow rate of the exhaust gas can be expressed by the error in the dilution air flow rate, the error in the total flow rate, and the dilution ratio. Therefore, when the dilution ratio is fixed and the total flow rate is fixed (that is, the dilution ratio and the total flow rate are treated as constants), the dilution air flow rate can be corrected to minimize the error in the exhaust gas flow rate. .

  In another aspect of the above exhaust gas measuring device, the correction means may be configured such that the flow rate of the dilution air is such that the error in the flow rate of the dilution air = (error in the total flow rate × dilution ratio) / (dilution ratio−1). Correct. In the equation expressing the error of the exhaust gas flow rate by the error of the dilution air flow rate, the error of the total flow rate, and the dilution ratio, if the error of the exhaust gas flow rate is zero, the error of the dilution air flow rate, The relationship between the error of the total flow rate and the dilution ratio is expressed by the above formula. By calculating the error of the dilution air flow rate according to the above equation and correcting the dilution air flow rate, the exhaust gas flow rate can be reduced to zero.

  In another aspect of the exhaust gas measuring device, the correction means may adjust the total flow rate based on the dilution flow rate error and the dilution ratio so that the exhaust flow rate error is minimized. to correct. The error in the flow rate of the exhaust gas can be expressed by the error in the dilution air flow rate, the error in the total flow rate, and the dilution ratio. Therefore, when the dilution ratio is fixed and the error in the dilution air flow rate is fixed (that is, the dilution ratio and the dilution air flow rate are treated as constants), the total flow rate is corrected to minimize the error in the exhaust gas flow rate. be able to.

[Configuration of exhaust gas measuring device]
Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an exhaust gas measuring device according to an embodiment of the present invention. FIG. 1 shows an exhaust gas measurement experiment.

  In FIG. 1, an exhaust gas measuring device 100 measures exhaust gas discharged from an engine 1 such as a vehicle. Exhaust gas discharged from the engine 1 flows through the exhaust passage 2, and the exhaust gas 122 is introduced into the exhaust gas measuring device 100 through the sampling tube 101 connected to the exhaust passage 2.

  The exhaust gas measuring device 100 includes a sampling tube 101, a flow rate control unit 102, a flow rate measurement unit 103, a microtunnel 104, a PM collection filter 105, a flow rate control unit 106, a flow rate measurement unit 107, and a control. And a computer 110.

  The sampling tube 101 is an introduction tube that introduces a part of the exhaust gas discharged from the engine 1 into the exhaust gas measuring device 100 as described above. The sampling tube 101 is connected to the microtunnel 104 from an exhaust passage 2 such as a vehicle (not shown).

  The flow controller 102 adjusts the flow rate of the dilution air 120 introduced into the microtunnel 104 to dilute the exhaust gas 122 (hereinafter, the dilution air flow rate is expressed as “Qd”). The flow rate control unit 106 adjusts the flow rate of all the gases 124 in the microtunnel 104 (hereinafter, the total flow rate is expressed as “Qt”). The flow rate control unit 102 and the flow rate control unit 106 can be, for example, valves whose opening degree varies depending on the applied voltages V 1 and V 2, and the applied voltages V 1 and V 2 are supplied from the control computer 110.

  The flow rate measurement unit 103 measures the dilution air flow rate Qd of the dilution air 120 and supplies the measurement result value D1 to the control computer 110. The flow rate measuring unit 103 theoretically measures the flow rate set by the flow rate control unit 102. On the other hand, the flow rate measuring unit 107 measures the total flow rate Qt. The flow rate measurement unit 107 also theoretically measures the flow rate set by the flow rate control unit 106, and supplies the measurement result value D2 to the control computer 110. The flow rate measurement by the flow rate measurement unit 103 and the flow rate measurement unit 107 is performed mainly during correction processing of the flow rate control units 102 and 106 before an exhaust gas measurement experiment described later. In addition, it is suitable for these flow measurement parts 103 and 107 to use a highly accurate flow meter like a venturi flow meter etc., for example.

  The PM collection filter 105 is a filter that can collect PM (particulate matter) in the exhaust gas. The collected PM can be analyzed by the control computer 110, for example.

  The control computer 110 includes a correction calculation unit 111 and a difference calculation unit 112. Details of the processing in these arithmetic units will be described later. The control computer 110 includes a CPU, a ROM, a RAM, an A / D converter, an input / output interface, and the like (not shown). The control computer controls each component based on the measurement result values D1, D2 and the like output from the measurement unit and the like of the exhaust gas measurement device 100, and in the exhaust gas collected by the PM collection filter 105. Analysis of PM and the like can also be performed.

  In FIG. 1, the flow rate control unit is provided on the upstream side of the flow rate measurement unit, but the flow rate control unit may be provided on the downstream side of the flow rate measurement unit.

  In general, the flow rate of the exhaust gas 122 flowing into the micro tunnel 104 (hereinafter, the exhaust gas flow rate is expressed as “Qe”) is adjusted by adjusting the flow rates of the flow rate control unit 102 and the flow rate control unit 106. Is going. That is, the exhaust gas flow rate is changed by adjusting the total flow rate Qt and the dilution air flow rate Qd, respectively. The exhaust gas flow rate Qe is calculated as the difference between the dilution air flow rate Qd and the total flow rate Qt (Qe = Qt−Qd). This is because PM and the like are mixed in the exhaust gas, so that a problem occurs if a flow rate control device, a flow rate measurement device, or the like is provided in the middle of the sampling tube 101 for introducing the exhaust gas.

  On the other hand, even if the flow rate control unit 102 is set to flow the flow rate Qd, the flow rate Qd cannot be flowed accurately, and an error (hereinafter referred to as “[Qd] error”) may occur. . Similarly, the flow rate control unit 106 may not be able to accurately flow Qt, and an error (hereinafter referred to as “[Qt] error”) may occur. Therefore, in general, the flow rate set in the flow rate control unit 102 (hereinafter referred to as “Qd1”) and the output value (hereinafter referred to as “Qd2”) in the flow rate measurement unit 103 are compared to control the flow rate. The opening degree of the valve of the flow rate control unit 102 is adjusted so that the unit 102 accurately flows the flow rate Qd1. In other words, the flow rate control unit 102 is set so that the flow rate Qd1 ± α is allowed to flow, and the valve opening is set so that the actual flow rate becomes Qd1. The flow rate control unit 106 is also compared with the set flow rate (hereinafter referred to as “Qt1”) and the output value of the flow rate measurement unit 107 (hereinafter referred to as “Qt2”). The valve opening and the like are corrected so that the actual flow rate becomes Qt1.

  The correction processing described above can be performed by the correction calculation unit 111 in the control computer 110. Further, the difference calculation unit 112 of the control computer 110 calculates the flow rate Qe of the exhaust gas 122 by taking the difference between the dilution air flow rate Qd and the total flow rate Qt. Note that such correction processing in the control computer 110 is performed before an exhaust gas measurement experiment.

  However, even if the dilution air flow rate Qd and the total flow rate Qt set as described above are corrected to minimize the error, the exhaust gas flow rate Qe is the difference between the dilution air flow rate Qd and the total flow rate Qt in the microtunnel. Therefore, an error in the exhaust gas flow rate Qe (hereinafter referred to as “[Qe] error”) may become unexpectedly large.

  For example, when the dilution air flow rate of the flow rate control unit 102 is set as Qd1 = 95 and the total flow rate of the flow rate control unit 106 is set as Qt1 = 100, the output of the flow rate measurement unit 103 is Qd2 = 94.525, and the flow rate measurement unit 107 Output Qt2 = 100.5. At this time, the flow control unit 102 has an error in the dilution air flow rate [Qd] error = −0.5%, and the flow control unit 106 has an error in the total flow rate [Qt] error = 0.5%. That is, both the two flow control units have an error of less than ± 1%. On the other hand, regarding the exhaust gas flow rate, the exhaust gas flow rate calculated from the flow rates set by the flow rate control units 102 and 106 is Qe1 = 5 (Qe1 = Qt1−Qd1), and the output values of the flow rate measurement units 103 and 107 are the same. Since the exhaust gas flow rate calculated from Qe2 = 5.975 (Qe2 = Qt2-Qd2), the error in the exhaust gas flow rate is [Qe] error = 19.5%. The reason why the exhaust gas flow rate error [Qe] error becomes unexpectedly large is that the signs of the dilution air flow rate error [Qd] error and the total flow rate error [Qt] error in the microtunnel are reversed. Is the case.

  Further, since the dilution ratio DF (= Qt1 / Qe1) is large (that is, the exhaust gas flow rate Qe1 is smaller than the total flow rate Qt1), the exhaust gas flow rate error [Qe] error is unexpectedly large. It may become. This is because even if the error is small for the dilution air flow rate Qd1 or the total flow rate Qt1, the exhaust gas flow rate Qe1 itself is a small amount, and thus becomes large for the exhaust gas flow rate Qe1. That is, the exhaust gas flow rate error [Qe] error is greatly influenced by the dilution ratio DF.

  Therefore, in this embodiment, the error [Qd] error of the dilution air flow, the error [Qt] error of the total flow in the microtunnel, and the dilution so that the error [Qe] error of the exhaust gas flow is minimized. The flow rate control unit 102 and the flow rate control unit 106 are corrected based on the relationship with the ratio DF.

[Correction processing of flow control unit]
Hereinafter, correction processing of the flow control unit 102 and the flow control unit 106 according to the present embodiment will be described with reference to the flowchart of FIG. In summary, Steps S11 to S13 are processing related to correction of the flow rate control unit 102, and Steps S14 to S16 are processing related to correction of the flow rate control unit 106, and the dilution ratio DF is acquired in Step S17. In step S18, the flow rate control unit 102 is further corrected based on the difference between the dilution ratio DF and the flow rate control unit 106.

  Note that the flow rate correction processing of the flow rate control unit 102 and the flow rate control unit 106 is performed before the start of the exhaust gas measurement experiment. Therefore, this correction process is performed without connecting the exhaust gas measuring device 100 to a vehicle or the like (that is, not connecting the exhaust passage 2 and the microtunnel 104). These processes are mainly performed by the control computer 110 in the exhaust gas measuring device 100. Further, the calculation related to the correction of the flow rate control unit or the like can be performed by the correction calculation unit 111 in the control computer 110.

  First, in step S11, the control computer 110 compares the flow rate Qd1 set by the flow rate control unit 102 and the flow rate Qd2 measured by the flow rate measurement unit 103 as described above. Specifically, an air flow is generated in the microtunnel 104 by a suction pump or the like (not shown), and the flow rate control unit 102 sets the valve opening degree so that the predetermined flow rate Qd1 flows. The actual flow rate Qd2 is measured by the flow rate measuring unit 103. One specific example is shown in FIG. FIG. 2 shows the flow rate Qd1 set in the flow rate control unit 102 on the horizontal axis, and the flow rate Qd2 measured by the flow rate measurement unit 103w on the vertical axis. As shown in FIG. 2, measurement is performed for a plurality of flow rates. If the flow rate control unit 102 is completely accurate, the flow rate Qd1 matches the flow rate Qd2 measured by the flow rate measurement unit 103. When the above process ends, the process proceeds to step S12.

  In step S <b> 12, the control computer 110 calculates a correction coefficient for the flow rate control unit 102 based on the flow rate Qd <b> 1 set by the flow rate control unit 102 and the flow rate Qd <b> 2 measured by the flow rate measurement unit 103. As shown in FIG. 2, the optimum correction coefficient is calculated based on the plurality of flow rates Qd1 set by the flow rate control unit 102 and the flow rates Qd2 measured by the flow rate measurement unit 103. This correction coefficient is calculated based on the least square method. Specifically, as shown in FIG. 2, the distance D to an arbitrary straight line L is calculated for all measured points, the squares of these calculated distances D are taken, and all of them are added (ie, , Take "sum of squares"). In the least square method, a straight line L that minimizes the sum of squares is determined. By calculating the correction coefficient in this way, for example, when there is a predetermined flow rate that should flow through the microtunnel 104, how much the valve opening degree of the flow rate control unit 102 is set to flow the predetermined flow rate. You can ask for it immediately. As a result, the flow rate control unit 102 can cause air with an accurate flow rate to flow into the microtunnel 104. When the above process ends, the process proceeds to step S13.

  In step S13, when the arbitrarily selected flow rate Qd1 is set in the flow rate control unit 102 and air is flown and measured by the flow rate measurement unit 107, the measured flow rate Qd2 is calculated from the correction coefficient determined in step S12. Check whether the calculated value is the same. Specifically, referring to FIG. 2, when the opening of the valve of the flow rate control unit 102 is set to flow an arbitrary flow rate A1 and the flow rate measurement unit 103 measures the flow rate, the measured flow rate is It is checked whether or not it matches the flow rate A2 obtained from the straight line L. Similarly, in order to cause the flow rate A2 to flow through the microtunnel 104, the opening degree of the valve to be set by the flow rate control unit 102 is calculated backward from the straight line L (in this case, A1), and air is flowed at this value. At this time, it may be checked whether the flow rate measured by the flow rate measurement unit 103 matches A2. As described above, when the check is performed in step S13, if the difference between the corrected flow rate from the flow rate control unit 102 and the measured flow rate is large, the process can be performed again by returning to step S11. Note that the processing in step S13 can also be performed mainly by the control computer 110. When the above process ends, the process proceeds to step S14.

  In step S14 to step S16, the correction coefficient of the flow rate control unit 106 is calculated for the flow rate control unit 106 by the same process as described above.

  First, in step S14, the control computer 110 compares the flow rate Qt1 set by the flow rate control unit 106 with the flow rate Qt2 measured by the flow rate measurement unit 107 as described above. Specifically, as shown in FIG. 2, an air flow is generated in the microtunnel 104 by a suction pump (not shown), and the flow rate control unit 106 opens the valve so that the air flows at a predetermined flow rate Qt1. Etc., and the flow rate measurement unit 107 measures the actual flow rate Qt2 at that time. As shown in FIG. 2, measurement is performed for a plurality of flow rates. If the flow rate control unit 106 is completely accurate, the flow rate Qt1 matches the flow rate Qt2 measured by the flow rate measurement unit 107. When the above process ends, the process proceeds to step S15.

  In step S <b> 15, the control computer 110 calculates a correction coefficient for the flow rate control unit 106 based on the flow rate Qt <b> 1 set by the flow rate control unit 106 and the flow rate Qt <b> 2 measured by the flow rate measurement unit 107. That is, an optimal correction coefficient is calculated by the least square method based on the plurality of flow rates Qt1 set by the flow rate control unit 106 and the actual flow rate Qt2 measured by the flow rate measurement unit 107. Specifically, as shown in FIG. 2, first, a distance D from an arbitrary straight line L is calculated at all measurement points, and a sum of squares is obtained from the calculated distance D. Then, a straight line L that minimizes the sum of squares is determined. By calculating the correction coefficient in this way, for example, when there is a flow rate that should actually flow through the microtunnel 104, how much the valve opening of the flow rate control unit 106 should be set to flow that flow rate. You can immediately ask for it. As a result, the flow rate control unit 106 can cause air or exhaust gas at an accurate flow rate to flow into the microtunnel 104. When the above process ends, the process proceeds to step S16.

  In step S16, when the arbitrarily selected flow rate Qt1 is set in the flow rate control unit 106 and air is allowed to flow, and the flow rate measurement unit 107 measures the flow rate Qt2, the measured flow rate Qt2 is determined in step S15. It is checked whether the value is the same as the value calculated from the correction coefficient. Specifically, referring to FIG. 2, when the opening of the valve of the flow rate control unit 106 is set to flow an arbitrary flow rate A1, and the flow rate measurement unit 107 measures the flow rate, the measured flow rate is It is checked whether or not it matches the flow rate A2 obtained from the straight line L. Similarly, in order to cause the flow rate A2 to flow through the microtunnel 104, the opening degree of the valve to be set by the flow rate control unit 106 is calculated back from the straight line L (in this case, A1), and air is flowed at this value. At this time, it may be checked whether the flow rate measured by the flow rate measuring unit 107 matches A2. As described above, when the check is performed in step S16, if the difference between the corrected flow rate from the flow rate control unit 106 and the measured flow rate is large, the process can be returned to step S14 to perform the process again. Note that the control computer 110 can also perform the processing in step S16. When the above process ends, the process proceeds to step S17.

  In step S <b> 17, the control computer 110 obtains from the outside a dilution ratio used when the exhaust gas measurement device performs measurement. For example, the control computer 110 can acquire the dilution ratio from the input of an experimenter who performs measurement.

Next, in step S <b> 18, the control computer 110 further performs a process of correcting the correction coefficient of the flow rate control unit 102. In the present invention, as described above, since the exhaust gas flow rate Qe is a difference value between the total flow rate Qt and the dilution air amount Qd, the error [Qe] error may become large even if it is separately separately corrected. In other words, further correction processing is performed by paying attention to the fact that the exhaust gas error [Qe] error is also affected by the dilution ratio DF. Therefore, in this embodiment, the error [Qd] error of the dilution air flow, the error [Qt] error of the total flow in the microtunnel, and the dilution so that the error [Qe] error of the exhaust gas flow is minimized. Further correction is performed based on the relationship with the ratio DF. First, an exhaust gas flow rate error [Qe] error is expressed using a dilution air flow rate error [Qd] error, a total flow rate error [Qt] error, and a dilution ratio DF.
[Qe] error = ([Qt] error × DF) − {[Qd] error × (DF−1)} (Formula 1)
Can be shown. The error [Qd] error of the dilution air flow rate, the error [Qt] error of the total flow rate, and the dilution ratio DF are:
[Qt] error = (Qt2−Qt1) / Qt1 (Formula 2)
[Qd] error = (Qd2-Qd1) / Qd1 (Formula 3)
DF = Qt1 / Qe1 (Formula 4)
It is. Here, as the flow rate Qd1 set in the flow rate control unit 102 and the total flow rate Qt1 set in the flow rate control unit 106, the flow rates corrected by the above processing are used.

  In this embodiment, in order to minimize the error [Qe] error in the flow rate of the exhaust gas, the flow rate control unit 102 is corrected so that [Qe] error = 0 in Equation 1. Therefore, the error [Qd] error2 of the diluted air flow rate after correction in step S18 needs to satisfy Expression 5.

[Qd] error2 = ([Qt] error × DF) / (DF-1) (Formula 5)
That is, the correction coefficient of the flow control unit 102 is calculated again so that the error in the diluted air flow after correction becomes [Qd] error2. In other words, based on the correction coefficient calculated in steps S11 to S13, a correction coefficient is calculated in step S18 such that the error is [Qd] error2. As described above, the correction is performed so that the error [Qe] error itself of the exhaust gas is minimized, not the correction of the flow rate control unit so that the error becomes small. Can be accurately controlled.

  When the above processing is completed, the flow rate control unit 102 adjusts the valve opening and the like based on the correction coefficient calculated in step S18, and the flow rate control unit 106 calculates the correction coefficient calculated in steps S14 to S16. The valve opening and the like are adjusted based on the above. Then, an exhaust gas measurement experiment is started at the set dilution ratio DF. These processes can be performed mainly by the control computer 110.

  As described above, the dilution air flow rate error [Qd] error, the total flow rate error [Qt] error, and the dilution ratio DF so that the exhaust gas flow rate error [Qe] error is minimized. By performing the correction based on the relationship, the flow rate of the exhaust gas can be controlled more easily and accurately than using a method such as individually correcting the flow rate control unit.

  In the correction process described above, only the flow rate control unit 102 is further corrected based on the total flow rate error [Qt] error and the dilution ratio DF so that the exhaust gas flow rate error [Qe] error is minimized. However, the flow rate control unit 102 does not correct again, and the flow rate control unit so that the error [Qe] error of the exhaust gas flow is minimized based on the error [Qd] error of the dilution air flow and the dilution ratio DF. Only 106 may be corrected.

1 is a schematic configuration diagram illustrating an exhaust gas measurement device according to an embodiment of the present invention. It is a figure shown about the method of calculating the correction coefficient of a flow control part. It is a flowchart which shows the correction process of the flow control part which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Exhaust passage 100 Exhaust gas measuring device 101 Sampling pipe 102,106 Flow control part 103,107 Flow measurement part 104 Microtunnel 110 Control computer 111 Correction | amendment calculating part 112 Difference calculating part

Claims (5)

An exhaust gas measurement device that dilutes exhaust gas discharged from an internal combustion engine with air and performs measurement in a measurement passage,
An error calculating means for calculating an error in the flow rate of the dilution air and an error in the total flow rate in the measurement passage;
Correction for correcting the flow rate of the dilution air or the total flow rate based on the relationship between the error in the flow rate of the dilution air, the error in the total flow rate, and the dilution ratio between the flow rate of the exhaust gas and the flow rate of the dilution air And an exhaust gas measuring device. Dilution air flow rate measuring means for measuring the flow rate of the dilution air;
A total flow rate measuring means for measuring the total flow rate,
The error calculating means calculates an error in the flow rate of the dilution air based on the measured flow rate of the diluted air, and calculates an error in the total flow rate based on the measured total flow rate. The exhaust gas measuring device according to 1. The correction means corrects the flow rate of the dilution air based on the error of the total flow rate and the dilution ratio so that the error of the flow rate of the exhaust gas is minimized. The exhaust gas measuring device described. The correction means includes
Error of dilution air flow rate = (error of total flow rate × dilution ratio) / (dilution ratio−1)
The exhaust gas measuring device according to any one of claims 1 to 3, wherein the flow rate of the dilution air is corrected so that The correction means corrects the total flow rate based on the flow rate error of the dilution air and the dilution ratio so that the flow rate error of the exhaust gas is minimized. The exhaust gas measuring device described.

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