JPS6136611B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an emission measurement device for measuring the emission amount of particulates (hereinafter referred to as particulates) contained in exhaust gas from a vehicle.

In recent years, the number of vehicles equipped with diesel engines has been increasing due to their good fuel efficiency, but diesel engines have the problem of emitting a larger amount of particulate matter than gasoline engines, so there are concerns about their negative impact on the environment. In the United States and other countries, there is a movement to measure the weight of particulate matter discharged from diesel vehicles and to regulate the amount of particulate matter discharged from vehicles. Under these circumstances, there has been a need for a highly accurate particulate discharge amount measuring device, and the present invention adds a sampling flow rate stabilization function to the sampling device section of the particulate discharge amount measuring device. Overall, it is possible to provide a highly accurate emissions measuring device.

The main components of particulate matter contained in the exhaust gas of diesel engines are carbon particles that have adsorbed unburned hydrocarbons, combustion-produced organic compounds, sulfates, etc. in their surroundings. In addition to containing thermally unstable organic compound components, the amount of particulate discharged in a state close to that released into the atmosphere is measured to avoid condensation of moisture in the sampling gas during sampling. To measure particulate emissions, the exhaust gas is mixed and diluted with a large amount of clean air, a portion of which is sampled, and particulates in the sampled gas are collected using a filter.The emissions are calculated from the weight of the collected particulates. A method called diluted sampling is used to find the

The operation and drawbacks of the conventionally used particulate discharge measuring device will be explained below with reference to FIG. Number 4 in the figure is called the dilution tunnel.
The vehicle exhaust gas supplied from the exhaust gas introduction pipe indicated by 2 and the diluted air that has passed through the filter indicated by 1 and has become clean are uniformly mixed. 3 is an orifice that gives appropriate turbulence to the mixed gas to promote mixing. 6 is the Roots Prower, which is responsible for sucking in and discharging diluted gas, and 7 is its drive motor. 8 and 9 are pressure gauges that measure the Roots blower inlet pressure and the Roots blower outlet and outlet differential pressure;
10 is a thermometer that measures the Roots blower inlet temperature and is used to calculate an accurate flow rate of diluent gas. 5 is a heat exchanger for keeping the temperature of the dilution gas constant. A part of the uniformly mixed diluent gas is led out of the tunnel by a sampling probe 11 and passes through a particulate collection filter 14.
pass through. At this time, the particulate in the diluent gas is collected on this filter 12 (the weight of the collected particulate is determined from the difference in weight between the filters before and after collection). 20 is a gas meter that measures the flow rate of sampling gas; 16
is a suction pump that sucks the sampling gas, 15
indicates a needle valve that adjusts the sampling gas flow rate. Valve 12 and 13 are opened only during the sampling operation, and serve to prevent unnecessary pressure fluctuations from being applied to the filter 14 at times other than the sampling operation. The valves 12 and 13 are opened and closed by pressurized air or the like, and 12a indicates a control valve thereof. Reference numerals 18 and 19 are a manometer and a thermometer for measuring gas meter inlet pressure and gas temperature within the gas meter, respectively, and are used to accurately calculate the sampling gas flow rate.

Of the above-mentioned components, 11 to 20 will be hereinafter referred to as a sampling device. To measure the particulate matter emissions of a vehicle, the sampling operation starts as soon as the vehicle starts driving in a specified driving mode, and the sampling action stops at the same time as the end of driving, and the particulate matter emissions are calculated from the weight of the particulate matter collected during this period. be done. Therefore, the sampling flow rate must be maintained at a constant flow rate during the sampling operation. Otherwise, each portion of the driving mode will be weighted in accordance with the variation in the sampling flow rate, making it impossible to calculate the true amount of emissions. However, in the conventional exhaust amount measuring device having the above-mentioned configuration, as particulate matter accumulates on the particulate collection filter 14, the ventilation resistance of the filter 14 increases, so that the sampling flow rate gradually decreases. Conventionally, as a means to avoid this decrease in flow rate, sampling was performed at a small flow rate to reduce the adhesion of particulate on the collection filter 14, thereby suppressing an increase in ventilation resistance, or a method was used to reduce the area by using a large-area filter. One of the methods used has been to reduce the per-sampling flow rate and reduce ventilation resistance. However, with these methods, it is unavoidable that the sampling flow rate slightly decreases due to the accumulation of particulate matter, and the amount of particulate matter collected per unit area of the filter decreases, so the weight of particulate matter collected relative to the weight of the filter cannot be avoided. This method has the serious drawback that the ratio becomes smaller and the measurement accuracy of the particulate weight becomes worse.

In view of these drawbacks of the conventional methods, the present invention provides a sampling flow rate control device that controls the sampling flow rate of the sampling device, so that a large amount of sampling can be obtained using a relatively small diameter filter without causing a decrease in the sampling flow rate. It is an object of the present invention to provide a particulate discharge amount measuring device that makes it possible to collect particulate matter and accurately measure the particulate discharge amount.

The structure and operation of the present invention will be explained below with reference to the embodiments shown in FIGS. 2 and 3. FIG. 2 is a configuration diagram showing one embodiment of the measuring device according to the present invention.
The same reference numerals as in the figures indicate the same components. 2 in the diagram
Reference numerals 1 to 29 constitute the main parts of the sampling flow rate control device of the present invention, and in particular, 21, 22, 23, and 24 indicate parts related to the sampling flow rate control mechanism. Reference numerals 28a and 28b are buffer tanks for reducing pulsation of the suction pump 16, and 22 is an orifice for measuring flow rate provided downstream of the suction pump 16, which measures the flow rate of the sampling gas at approximately atmospheric pressure. This differential pressure across the orifice 22 is converted into an electrical signal by a differential pressure converter 23, and this signal is sent to a control circuit 24. Reference numeral 21 denotes a flow rate regulating valve that is opened and closed by a small motor, and has one end connected to the suction port 16a of the suction pump 16, and the other end connected to the discharge port 16b, forming a bypass flow path. Therefore, when the flow rate regulating valve 21 is opened, the sampling flow rate decreases, and when it is closed, the flow rate increases. Note that 29 is a relay device that forms a closed circuit while the suction pump is in operation. 24a is a flow rate setting device;
A voltage signal corresponding to the set flow rate is supplied to the flow rate control circuit 24 by the potentiometer. The flow rate control circuit 24 compares the output voltage of the flow rate setter supplied via the signal line 24b and the output voltage of the differential pressure converter 23 supplied via the signal line 24c, and determines the output voltage of the differential pressure converter 23. is lower than the set voltage, that is, when the sampling flow rate is less than the set flow rate, the flow rate adjustment valve 21 is driven to increase the flow rate, and in the opposite case, the valve is driven to decrease the flow rate, and as a result, the set signal Control can be performed so that the sampling flow rate corresponds to the voltage. As particulate accumulates on the particulate collection filter 14, the pressure loss at the filter increases and the pressure upstream of the suction pump gradually decreases, but the flow rate measurement is performed in the flow path downstream of the suction pump 16, which is at almost atmospheric pressure. Therefore, accurate flow rate control can be performed regardless of the amount of filter pressure loss.

FIG. 3 shows another embodiment of the present invention, which differs from the above-described structure in that a flow rate regulating valve 21 is inserted in series on the suction pump inlet side. In this case, since the sampling flow rate decreases when the flow rate regulating valve 21 is closed, the output voltage characteristic of the flow rate control circuit 24 may have the opposite polarity to that shown in FIG.

Now, during the sampling operation, the flow rate adjustment valve 21 gradually changes the valve opening degree as the pressure drop of the particulate collection filter 14 increases, and at the end of sampling, the sampling flow rate is adjusted to be appropriate for the filter, which has a large pressure drop due to adhesion of particulate. However, for filters to which particulate does not adhere, the valve opening degree has changed to a point where an excessive flow rate occurs. If the particulate collection filter 14 is replaced with a new one in this state and the sampling operation is performed again, there is a risk that an excessive flow rate of sampling gas may temporarily flow at the start of sampling.

Therefore, an automatic return mechanism of the flow rate regulating valve 21 after the completion of the sampling operation to prevent this will be explained. 25 is a particulate collection filter 14
A filter of the same type or an element having the same ventilation resistance characteristics is connected downstream of the particulate collection filter 14 via an electromagnetic valve 26. This element 25 will be referred to as a simulating filter hereinafter. 27 is a control device that controls the movement of the sampling device, and at the same time as the sampling operation is completed, the valve 12,
13 is closed, and conversely, the electromagnetic valve 26 is opened for a certain period of time, and the suction pump 16 continues to be driven for the same period of time. 27a, 27b, 27c are valves 12, respectively.
26 and the power supply line that drives the suction pump 16. By performing such an operation, the opening degree of the flow rate regulating valve 21 changes until it becomes an appropriate valve opening degree for the set flow rate and the ventilation resistance of the simulated filter 25, and then becomes stable. Here, as described above, since the simulating filter 25 has the same ventilation resistance characteristics as the particulate collection filter 14, the flow rate regulating valve opening degree will eventually return to its initial state. After a certain period of time, the electromagnetic valve 26 closes, the suction pump 16 also stops, and the relay 29 opens, thereby fixing the opening degree of the flow rate regulating valve 21 and completing the return operation. Another method is to detect the opening degree of the flow rate adjustment valve 21 with a potentiometer or the like.
It is possible to return to the initial valve opening, but if the set flow rate is different, the initial valve opening will be different, and even if the set flow rate is the same, filter 1
If valves 4 with different ventilation resistances are used, the initial valve opening will be different, resulting in a rather complicated configuration. On the other hand, according to the above-described flow rate adjustment valve return mechanism, by using the same type of filter as the filter 14 or an element with the same ventilation resistance characteristics as the simulating filter 25, any set flow rate can be adjusted with a simple operation. It is possible to restore the valve opening even if the

Note that in the above two examples, an orifice was used to measure the sampling flow rate;
A nozzle, a bench lily, a laminar flow meter, a calorific mass flow meter, or the like may be used.

As explained in detail above, the present invention adds a sampling flow rate control device to the sampling device, thereby making it possible to collect a large amount of particulate matter with a relatively small-diameter particulate collection filter without reducing the sampling flow rate. As a result, it is possible to accurately measure the amount of particulate waste discharged, and the valve opening of the flow rate regulating valve can be automatically adjusted by using an element that has ventilation resistance characteristics equivalent to that of the particulate collection filter. Since the valve opening is restored to the original opening, it is possible to accurately restore the valve opening for any set flow rate, and the sampling flow rate at the start of the sampling operation can be properly controlled, which is an excellent effect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional particulate discharge amount measuring device, FIG. 2 is a block diagram of main parts of one embodiment of the present invention, and FIG. 3 is a block diagram of main parts of another embodiment of the present invention. 2... Exhaust gas introduction pipe, 4... Dilution tunnel,
14...Pateikureate collection filter, 16
... Suction pump, 16a, 16b ... Suction pump inlet and outlet, respectively, 21 ... Flow rate control valve, 2
2... Orifice, 23... Differential pressure converter, 24...
...Flow rate control circuit, 25...Simulation filter, 27
...Control device, 29...Relay.

Claims (1)

[Claims] 1. A sampling device that dilutes vehicle exhaust gas with a large amount of clean air and then sucks a part of this exhaust gas with a suction pump for sampling,
In a particulate emission measurement device that collects particulates contained in the sampled exhaust gas by a particulate collection filter, the sampling flow rate control device corrects a decrease in the sampling flow rate due to an increase in pressure drop of the particulate collection filter. The sampling flow rate control device measures the sampling flow rate by a flow rate measuring means provided downstream of the suction pump, and based on this measurement signal, the sampling flow rate is adjusted between the inlet and outlet of the suction pump or between the inlet and the inlet of the suction pump and the particulate collecting device. A particulate emission measurement device characterized in that a sampling flow rate is controlled by a flow rate adjustment valve provided between a filter and a flow rate adjustment valve. 2. Particulate emission measurement according to claim 1, wherein the sampling flow rate control device automatically returns the valve opening degree of the flow rate adjustment valve that changed during sampling to the valve opening degree before sampling after the sampling ends. Device. 3. The flow rate regulating valve automatically returns its valve opening to the valve opening before sampling based on the ventilation resistance of an element having ventilation resistance characteristics equivalent to that of the particulate filter. The particulate emission measurement device according to item 2.