JP2017058173A - Exhaust gas measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the zero point adjustment of an exhaust gas measurement device to be carried out easily and accurately.SOLUTION: An exhaust gas measurement device comprises: a sample gas passageway 2 for drawing in a sample gas into a mixing unit 12; a dilution gas passageway 6 for introducing a dilution gas into the mixing unit 12; a measurement gas passageway 4 for introducing a measurement gas from the mixing unit 12 into a measurement unit 16; a measurement gas flow rate adjustment unit for adjusting the flow rate of the measurement gas; and a dilution gas flow rate adjustment unit for adjusting the flow rate of the dilution gas. The exhaust gas measurement device further has a zero point adjustment unit for executing the zero point adjustment of a detection signal obtained by the measurement unit 16, controlling the measurement gas flow rate adjustment unit and the dilution gas flow rate adjustment unit so that the flow rate of the dilution gas flowing in the dilution gas passageway is greater than or equal to the flow rate of a gas flowing in the measurement gas passageway.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an exhaust gas measuring apparatus that takes in exhaust gas from an automobile as a sample gas and measures the number of particles contained in the sample gas.

  In order to measure the number of particulate matter in the gas discharged from automobile engines, etc., the sample gas is diluted with a dilution gas such as air, and the mixed gas is introduced into the particle number measurement device. Thus, there is a system configured to measure the number of particles contained in exhaust gas. As the particle number measuring device of such a system, for example, a particle measuring device for classifying and measuring particles in a sample gas according to their size is used (see Patent Document 1).

WO2013-183652A1 JP 2012-127773 A

  In the exhaust gas measuring device, in order to accurately measure the number of particles, it is necessary to perform zero point adjustment and store the zero point of the detection signal in the device before measuring the exhaust gas. When adjusting the zero point, a gas that does not contain particles to be measured is introduced into the detector, so a filter is attached to the inlet that takes in the sample gas, and a gas that does not contain particles is introduced into the detector. The output value of the instrument was the zero point of the measurement.

  However, it is troublesome to attach a filter to the sample gas inlet only during zero point adjustment. In particular, when the exhaust gas measuring device is mounted on an automobile, remove the device from the exhaust gas outlet of the automobile and attach a filter. After the zero point adjustment is completed, remove the filter and attach the device to the automobile. The operation at the time of zero point adjustment becomes complicated.

  In addition, because the inner wall of the pipe that introduces the sample gas is contaminated, particles attached to the inner wall of the pipe are introduced into the detector even if a filter is attached to the sample gas inlet during the zero point adjustment. There is a possibility that the number of particles in the gas introduced into the detector at the time of adjustment does not become zero and an accurate baseline cannot be grasped.

  Accordingly, an object of the present invention is to enable easy and accurate zero point adjustment of an exhaust gas measuring device.

  One embodiment of the exhaust gas measuring apparatus according to the present invention includes a mixing unit that mixes a sample gas and a dilution gas to make a measurement gas, and a dilution gas that introduces a dilution gas that does not contain particles to be measured into the mixing unit A flow path, a measurement section that measures the measurement gas from the mixing section, a measurement gas flow path that introduces the measurement gas from the mixing section to the measurement section, and draws the measurement gas from the mixing section to the measurement gas flow path, A measurement gas flow rate adjustment unit that adjusts the flow rate of the measurement gas flowing through the measurement gas flow channel to a preset flow rate, and a dilution gas that is sent through the dilution gas flow channel to the mixing unit and the dilution gas flow through the dilution gas flow channel A dilution gas flow rate adjusting unit for adjusting the flow rate of the working gas to a preset flow rate, and a sample gas flow channel for taking the sample gas into the mixing unit, and the dilution gas from the flow rate of the measured gas flowing through the measurement gas flow channel For dilution through the flow path It has a sample gas flow path through which the sample gas flows at a flow rate minus the flow rate of the gas and a zero point adjustment unit that performs zero point adjustment of the detection signal obtained by the measurement unit. A control unit for controlling the measurement gas flow rate adjustment unit and the dilution gas flow rate adjustment unit so that the flow rate of the dilution gas flowing through the measurement gas flow channel is equal to or higher than the flow rate of the gas flowing through the measurement gas flow channel. It is.

  In one embodiment of the exhaust gas measuring apparatus according to the present invention, the flow rate of the gas flowing through the sample gas flow channel is the amount obtained by subtracting the flow rate of the dilution gas flowing through the dilution gas flow channel from the flow rate of the gas flowing through the measurement gas flow channel. Therefore, when adjusting the zero point, the flow rate of the dilution gas sent from the dilution gas flow rate to the mixing unit is set to be equal to or higher than the flow rate of the gas flowing through the measurement gas flow channel. It is possible to feed only the dilution gas into the tank. As a result, since the gas from the sample gas flow path is not introduced into the measurement unit during the zero point adjustment, the zero point adjustment is performed easily and accurately without attaching a filter to the sample gas flow path. be able to.

It is a channel lineblock diagram showing one example of an exhaust gas measuring device. It is a block diagram which shows the whole structure of the Example. It is a flowchart which shows an example of the operation | movement of zero point adjustment of the Example. It is sectional drawing which shows an example of a measurement part roughly.

  In the exhaust gas measuring apparatus according to the present invention, the control unit is configured to measure the measurement gas so that a part of the dilution gas sent from the dilution gas channel to the mixing unit flows through the sample gas channel when the zero point is adjusted. It is preferable that the flow rate of the dilution gas flowing through the dilution gas flow channel is made larger than the flow rate during sample measurement without changing the flow rate of the gas flowing through the flow channel from the flow rate during sample measurement. . This allows only the dilution gas to be introduced into the measurement unit while maintaining the same flow rate as that used during sample measurement during the zero point adjustment. Can be performed accurately. Furthermore, since a part of the dilution gas sent to the mixing section flows through the sample gas flow path, the sample gas flow path can be purged during zero point adjustment.

  Furthermore, it is preferable that a heater for heating the gas flowing through the sample gas channel is provided on the sample gas channel. Then, when the zero point is adjusted, the dilution gas heated by the heater flows through the sample gas channel, so that the removal efficiency of contaminants attached to the inner wall surface of the sample gas channel is improved and the measurement accuracy is improved. I can plan. Further, by heating the sample gas with such a heater, volatile substances such as moisture and oil adhering to the particles in the sample gas can be removed.

  A charging device for charging particles in the measurement gas is further provided on the measurement gas flow path, and as a measurement unit, a measurement flow path through which the measurement gas flows, a plate-like classification electrode provided along the inside of the measurement flow path, and A plurality of measurement electrodes arranged opposite to the classification electrode and along the measurement gas flow flowing through the measurement flow path and electrically insulated from each other, and a voltage is applied between the classification electrode and the measurement electrode to generate an electric field. By generating the particles, it is possible to use a particle classification measuring device that classifies charged particles for each particle size, captures them on each measurement electrode, and counts the number of the particles. Such a particle classification measurement apparatus is disclosed in, for example, Patent Document 1, and has a movable structure other than the air blowing mechanism and has a simple and robust structure, and is therefore portable. Therefore, by using such a particle classification measurement device, the exhaust gas measurement device can be further reduced in size, and a portable exhaust gas measurement device can be realized.

An embodiment of an exhaust gas measuring device will be described with reference to the drawings.
First, the flow path configuration of the embodiment will be described with reference to FIG.

  The exhaust gas measuring apparatus of this embodiment includes a sample gas channel 2, a measurement gas channel 4, and a dilution gas channel 6. These flow paths 2, 4, 6 are connected to the mixing unit 12. The mixing unit 12 mixes the sample gas taken in through the sample gas flow path 2 and the dilution gas sent from the dilution gas flow path 6, and these mixed gases pass through the measurement gas flow path 4 to measure gas. Is introduced into the measuring unit 16. The sample gas flow path 2 is a flow path for taking a sample gas such as automobile exhaust gas into the mixing unit 12. The dilution gas flow path 4 is a flow path for sending a dilution gas that does not contain particles to be measured to the mixing unit 12.

  A heater 8 and an impactor 10 are provided on the sample gas flow path 2. The heater 8 removes volatile substances such as moisture and oil adhering to the particles in the sample gas by heating the sample gas to about 300 ° C. Providing the heater 8 prevents the particles in the sample gas from condensing into large particles, reducing the number of particles, and preventing particles from adhering to the mixing unit 12, leading to improved measurement accuracy. The impactor 10 is adjusted so that the sample gas is sucked through the slit and particles having a certain size or larger are removed by colliding with a plate disposed immediately after the slit.

  A dilution gas pump 24, a dilution gas flow rate adjustment valve 26, a flow meter 28, and a filter 30 are provided on the dilution gas flow path 6 from the upstream side. The dilution gas pump 24 is driven constant, and the atmosphere is taken into the dilution gas flow path 6 by the dilution gas pump 24. Particles are removed from the air taken into the dilution gas flow path 6 by passing through the filter 30 and sent to the mixing unit 12 as a dilution gas.

  The dilution gas flow rate adjustment valve 26 adjusts the flow rate of the dilution gas sent into the mixing unit 12 according to the opening degree. The flow meter 28 measures the flow rate of the gas flowing through the dilution gas flow path 6. The opening of the dilution gas flow rate adjustment valve 26 is controlled based on the measured value of the flow meter 28 so that the flow rate of the gas flowing through the dilution gas flow path 6 becomes a preset flow rate (FIG. 2). Feedback control is performed. The dilution gas pump 24, the dilution gas flow rate adjustment valve 26, and the flow meter 28 form a dilution gas flow rate adjustment unit.

  On the measurement gas flow path 4, a charging device 14, a measurement unit 16, a flow meter 18, a measurement gas flow rate adjustment valve 20, and a measurement gas pump 22 are provided from the mixing unit 12 side. The charging device 14 and the measurement unit 16 will be described later. The measurement gas pump 22 is driven constantly. The flow rate of the measurement gas flowing through the measurement gas channel 4 is adjusted by the opening degree of the measurement gas flow rate adjustment valve 20. The flow meter 18 measures the flow rate of the measurement gas flowing through the measurement gas channel 4. The opening of the measurement gas flow rate adjusting valve 20 is controlled based on the measurement value of the flow meter 18 so that the flow rate of the measurement gas flowing through the measurement gas flow path 4 becomes a preset flow rate (see FIG. 2). ) Feedback control is performed. The flow meter 18, the measurement gas flow rate adjustment valve 20, and the measurement gas pump 22 form a measurement gas flow rate adjustment unit.

  The measurement unit 16 of this embodiment is a particle classification measurement device in which a plurality of measurement electrodes are arranged along the flow direction of the measurement gas, classified according to particle size, and counted. The charging device 14 provided on the upstream side of the measurement unit 16 charges particles in the measurement gas. Note that the measurement unit 16 does not necessarily need to be such a measurement device, and a particle number measurement device as disclosed in Patent Document 2 can also be used. In such a case, the charging device 14 is unnecessary.

  An example of the measurement unit 16 is shown in FIG.

  The measurement unit 16 has a measurement flow path 43 inside, and the measurement gas flowing in from the gas inlet 38 flows through the measurement flow path 43 and flows out from the gas outlet 40.

  A classification electrode 42, a trap electrode 44, measurement electrodes 46, 48, 50, 52, 54 and 56 are provided inside the measurement flow path 43. The classification electrode 42 is a flat plate electrode provided so as to extend from the upstream side to the downstream side along the measurement gas flow in the measurement flow path 43. The trap electrode 44 is disposed opposite to the classification electrode 42 on the upstream end side of the measurement channel 43. Each of the measurement electrodes 46, 48, 50, 52, 54, and 56 is opposed to the classification electrode 42 and is disposed along the measurement flow path 43 at a distance from each other. The trap electrode 44 and the measurement electrodes 46, 48, 50, 52, 54 and 56 are electrically insulated from each other.

  An electric field for classification is applied between the classification electrode 42 and the trap electrode 44 and each of the measurement electrodes 46, 48, 50, 52, 54 and 56, and charged particles in the measurement gas are classified for each particle diameter. Are captured by each measurement electrode 46, 48, 50, 52, 54 and 56, and the number thereof is counted.

  Returning to FIG. 1, the flow rate of the measurement gas flowing through the measurement gas channel 4 is the total flow rate of the sample gas taken into the mixing unit 12 and the dilution gas fed into the mixing unit 12. The flow rate of the sample gas taken into the mixing unit 12 through the sample gas flow channel 2 is a flow rate obtained by subtracting the flow rate of the dilution gas from the flow rate of the measurement gas. For example, when the flow rate of the measurement gas is set to 10 L / min and the flow rate of the dilution gas is set to 9 L / min, the sample gas is taken into the mixing unit 12 through the sample gas flow path 2 at a flow rate of 1 L / min. It will be.

  Here, by making the flow rate of the dilution gas flowing through the dilution gas flow channel 6 equal to or higher than the flow rate of the gas flowing through the measurement gas flow channel 4, the gas from the sample gas flow channel 2 is not taken into the mixing unit 12 and diluted. Only the working gas flows through the measurement gas flow path 4. Therefore, in this embodiment, when adjusting the zero point of the detection signal of the measurement unit 16, the flow rate of the dilution gas is adjusted to the normal exhaust gas measurement so that the gas from the sample gas channel 2 is not taken into the mixing unit 12. The control unit 32 controls the dilution gas flow rate adjustment valve 26 so as to increase the time.

  The overall configuration of this embodiment will be described with reference to FIG.

  The measurement unit 16, the flow meters 18 and 28, the measurement gas flow rate adjustment valve 20, the measurement gas pump 22, the dilution gas flow rate adjustment valve 26 and the dilution gas pump 28 are electrically connected to a common control unit 32. The control unit 32 is realized by a dedicated computer such as a system controller or a general-purpose personal computer. The control unit 32 includes a measurement gas flow rate control unit 33, a dilution gas flow rate control unit 34, an exhaust gas measurement unit 35, a zero point adjustment unit 36, and a flow rate set value holding unit 37.

  The measurement gas flow rate control unit 33, the dilution gas flow rate control unit 34, the exhaust gas measurement unit 35, and the zero point adjustment unit 36 are functions obtained by executing a program stored in the control unit 32. The flow rate set value holding unit 37 is a storage area for holding set values of the gas flow rate of the measurement gas flow channel 4 and the gas flow rate of the dilution gas flow channel 6. The flow rate set value holding unit 37 holds a flow rate set value during normal exhaust gas measurement and a flow rate set value during zero point adjustment as a gas flow rate set value for the dilution gas flow path 6. The flow rate during zero point adjustment is set larger than the flow rate during normal exhaust gas measurement.

  The measurement gas flow rate control unit 33 adjusts the measurement gas flow rate so that the flow rate of the measurement gas flowing through the measurement gas channel 4 becomes the set value held in the flow rate set value holding unit 37 based on the output signal of the flow meter 18. The valve 20 is configured to perform feedback control.

  The dilution gas flow rate control unit 34 is based on the output signal of the flow meter 28 so that the flow rate of the dilution gas flowing through the dilution gas flow path 6 becomes the set value held in the flow rate set value holding unit 37. The gas flow rate adjusting valve 26 is configured to perform feedback control.

  The exhaust gas measurement unit 35 is configured to perform exhaust gas measurement. When the exhaust gas measurement is performed, the detection signal obtained by the measurement unit 16 is taken into the control unit 32.

  The zero point adjustment unit 36 is configured to perform zero point adjustment for adjusting the zero point of the detection signal of the measurement unit 16. When the zero point adjustment is executed, the setting value (for example, 9 L / min) for measuring the flow rate of the dilution gas flowing through the dilution gas flow path 6 is changed to the setting value for the zero point adjustment (for example, 11 L / min). Then, the flow rate (for example, 11 L / min) of the dilution gas flowing through the dilution gas flow channel 6 becomes larger than the set value (for example, 10 L / min) of the flow rate of the measurement gas flowing through the measurement gas flow channel 4. As a result, the measurement gas composed only of the dilution gas flows through the measurement gas flow path 4, and a part of the dilution gas sent to the mixing unit 12 flows back through the sample gas flow path 2.

  At this time, the detection signal obtained by the measurement unit 16 is taken into the control unit 32 and stored as a zero point. At the same time, the inside of the sample gas flow path 2 is purged with the diluting gas flowing backward. The dilution gas flowing through the sample gas flow path 2 is heated to about 300 ° C. by passing through the heater 8, and the heated dilution gas flows through the sample gas flow path 2, so that it is applied to the inner wall surface of the sample gas flow path 2. Adhering contaminants are easily removed.

  An example of the operation at the time of zero point adjustment in this embodiment will be described using the flowchart of FIG. 3 together with FIGS.

  When the user inputs an instruction to start zero point adjustment to the control unit 32, the setting value of the flow rate of the dilution gas is changed to the set value for zero point adjustment, and the flow rate of the dilution gas flowing through the dilution gas flow path 6 The feedback control of the dilution gas flow rate adjustment valve 26 is performed so that becomes the set value. The control unit 32 monitors the signal from the flow meter 18 and confirms whether or not the flow rate of the measurement gas channel 4 is stable. Whether or not the flow rate of the measurement gas flow path 4 is stable depends on an allowable range in which the maximum value and the minimum value of the detection signal from the flow meter 18 are set based on the set value of the gas flow rate of the measurement gas flow path 4. Judgment is made based on whether or not (for example, set value ± 5%).

  After the flow rate of the measurement gas channel 4 is stabilized, the detection signal of the measurement unit 16 is read and stored as a zero point. The intensity of the signal stored as the zero point is, for example, an average value of the detection signal intensity of the measurement unit 16 during the measurement time. After storing the zero point, return the setting value of the dilution gas flow rate to the set value for normal exhaust gas measurement, and end the zero point adjustment.

2 Sample gas flow path 4 Measurement gas flow path 6 Dilution gas flow path 8 Heater 10 Impactor 12 Mixing unit 14 Charging device 16 Measurement unit 17 Charging device 18, 28 Flow meter 20 Measuring gas flow rate adjustment valve 22 Measuring gas pump 24 Dilution gas pump 26 Gas flow control valve for dilution 32 Control unit 33 Gas flow control unit for measurement 34 Gas flow control unit for dilution 35 Exhaust gas measurement unit 36 Zero point adjustment unit 38 Gas inlet 40 Gas outlet 42 Classification electrode 43 Measurement flow path 44 Trap electrode 46, 48, 50, 52, 54, 56 Measuring electrodes

Claims (4)

A mixing section that mixes the sample gas and the dilution gas into a measurement gas;
A dilution gas flow path for introducing a dilution gas that does not contain particles to be measured into the mixing section;
A measurement unit for measuring the measurement gas from the mixing unit;
A measurement gas flow path for introducing a measurement gas from the mixing unit into the measurement unit;
A measurement gas flow rate adjustment unit that draws the measurement gas from the mixing unit into the measurement gas flow channel and adjusts the flow rate of the measurement gas flowing through the measurement gas flow channel to a preset flow rate;
A dilution gas flow rate adjusting unit that feeds the dilution gas to the mixing unit through the dilution gas flow channel and adjusts the flow rate of the dilution gas flowing through the dilution gas flow channel to a preset flow rate;
A sample gas flow path for taking the sample gas into the mixing unit, and the sample gas at a flow rate obtained by subtracting the flow rate of the dilution gas flowing through the dilution gas flow path from the flow rate of the measurement gas flowing through the measurement gas flow path Sample gas flow path through which
A zero point adjustment unit that performs zero point adjustment of a detection signal obtained by the measurement unit, and the flow rate of the dilution gas flowing through the dilution gas channel during the zero point adjustment is the measurement gas channel; An exhaust gas measurement apparatus comprising: a control unit that controls the measurement gas flow rate adjustment unit and the dilution gas flow rate adjustment unit so as to be equal to or higher than a flow rate of the gas flowing through the gas.   The control unit adjusts the measurement gas flow path so that a part of the dilution gas sent from the dilution gas flow path to the mixing part flows through the sample gas flow path during the zero point adjustment. 2. The structure according to claim 1, wherein the flow rate of the dilution gas flowing through the dilution gas flow path is increased from the flow rate at the time of sample measurement without changing the flow rate of the flowing gas from the flow rate at the time of sample measurement. Exhaust gas measuring device.   The exhaust gas measuring apparatus according to claim 2, wherein a heater for heating the gas flowing through the sample gas channel is provided on the sample gas channel. A charging device for charging particles in the measurement gas on the measurement gas flow path;
The measurement unit includes a measurement channel through which a measurement gas flows, a plate-like classification electrode provided along the inside of the measurement channel, and a measurement gas flow that faces the classification electrode and flows through the measurement channel. Are arranged and electrically insulated from each other, and a voltage is applied between the classification electrode and the measurement electrode to generate an electric field. The exhaust gas measuring device according to any one of claims 1 to 3, wherein the exhaust gas measuring device is a particle classification measuring device that classifies and captures each measuring electrode and counts the number thereof.

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