JPH03237338A - Exhaust gas measuring instrument - Google Patents

Abstract

PURPOSE:To absorb the pulsation of the output of an exhaust gas flowmeter by bringing a pump for sampling under feedback control by using the value obtained by averaging the output of the exhaust gas flowmeter. CONSTITUTION:The exhaust gas of an engine is guided by an exhaust pipe 12 to a dilution tunnel 13 and diluted with air admitted from an intake part 14 by an air blower 15. The gas is sucked by a pump 20 and the amount of particulates sticking on a filter 19 is measured. A film type gas meter 21 is used for the gas amount measurement. This meter converts the reciprocation of a rubber film into the rotation of a pointer to display the flow rate. A shaft encoder is fitted on the pointer and the flow rate is transduced into an electric signal to generate 1,000-2,000 pulses in one rotation of the pointer. This meter is a reciprocal motion type, so the rotation of the pointer pulsates. The detection output of the flowmeter 21 is averaged by an averaging circuit 22 and a control circuit 23 performs the feedback control over the sampling pump. Consequently, the flow rate becomes constant and the exhaust gas is accurately measured.

Description

[Detailed description of the invention]

[Industrial Application Field 1] The present invention relates to an engine exhaust gas measuring device, and in particular, it dilutes the exhaust gas emitted from the engine with a dilution tunnel. When measuring the particulates contained in the exhaust gas, the exhaust gas is diluted in a dilution tunnel to achieve the same conditions as when it is released into the atmosphere. Then, the diluted exhaust gas is sampled, and particulates contained therein are captured by a particulate filter and the amount thereof is measured.

[Problem to be solved by the invention Σ In measuring such a particulate filter,
As particulates accumulate on the surface of the particulate filter due to sampling of the diluent gas, the flow resistance in the sampling pipe increases, and the flow rate decreases as shown in FIG. Conventionally, the sampling flow rate is measured by a flow meter, and the output signal of the flow meter is fed back to the sampling pump, thereby controlling the flow rate so as to maintain a constant flow rate as shown in FIG. However, if a diaphragm-type reciprocating flowmeter is used as the flowmeter, the output signal of the flowmeter will pulsate even if the flow rate is constant. Therefore, even if feedback is applied using such a signal, the sampling pump will instead cause hunting, and there is a problem that good IIItl cannot be performed. The present invention has been made in view of these problems, and it is an exhaust gas measuring device that uses a model reciprocating flowmeter to maintain a constant flow rate even if the output signal of the flowmeter pulsates. It is an object of the present invention to provide an exhaust gas measuring device that can perform the following steps. [Means for Solving the Problems] The present invention provides an apparatus for diluting exhaust gas discharged from an engine in a dilution tunnel and sampling the diluted exhaust gas for measurement. Means for averaging the output of the flow meter for detecting the flow rate is provided, and the sampling pump is feedback-controlled using the averaged value by the means. K effect l Therefore, even when a sampled flow rate is detected using a model reciprocating type intermittent flowmeter, the output of the flowmeter is averaged by the averaging means, and for this reason, this averaging By feeding back the sampling pump υ1w based on the detected value, it becomes possible to make the flow rate constant.

Embodiment 1 FIG. 1 shows an outline of an exhaust gas measuring device according to an embodiment of the present invention, and this device relates to a device for measuring exhaust gas discharged from a diesel engine 10. An exhaust manifold 11 is attached to the side surface of the cylinder block of the engine 10, and an exhaust pipe 12 is connected to the exhaust manifold 11. The distal end side of the exhaust pipe 12 is opened into the dilution tunnel 13. The dilution tunnel 13 introduces atmospheric air through an air introduction part 14 provided on the upstream side thereof, and the dilution tunnel 13 is The atmosphere is made to flow from upstream to downstream within the engine, and the exhaust gas is diluted by this atmosphere. A sampling tube 18 is installed in the dilution tunnel 13.
is now inserted. A particulate filter 19 is connected to the sampling pipe 18, and a suction pump 20 is connected downstream of this filter 19. A flow meter 21 is connected downstream of the suction pump 20 to detect the sampling flow rate. The detection output of the flowmeter 21 is averaged by an averaging circuit 22, and the averaged value is supplied to an 1lli11 circuit 23, which controls the suction pump 20 in feedback. FIGS. 2 and 3 show a schematic reciprocating type flowmeter for measuring the sampling flow rate, and this flowmeter has an upper chamber 26, an intermediate chamber 27 arranged below it,
It is composed of a lower front chamber 28 located at the lower front and a lower rear chamber 29 located at the lower rear side. The intermediate chamber 27 includes valves 31, 32 and a crank mechanism 33.
is provided. On the other hand, the upper chamber 26 is provided with a linkage mechanism 34 that interlocks with the crank mechanism 33 and the valves 31, 32. The link mechanism 34 is connected to a wing shaft 35 arranged to extend vertically from the upper chamber 26 to the lower front chamber 28. Further, the crank mechanism 33 is connected to a gear transmission device 36 in the upper chamber 26, as shown in FIG. In contrast, two rubber membranes 37, 38 are accommodated in the lower front chamber 28 and the lower rear chamber 29. Further, an inlet 39 is provided so as to communicate with the intermediate chamber 27, and an outlet 40 is provided so as to communicate with the lower rear chamber 29. In the above configuration, exhaust gas generated by the operation of the diesel engine 10 passes through the exhaust manifold 11 and the exhaust pipe 12 to the dilution tunnel 13.
Become guided by. Dilution tunnel 13
Air is introduced from the air introduction part 14 by the feeder fill 15, and the exhaust gas is diluted by this air. By driving the sampling pump 20, the diluted exhaust gas is sucked by the sampling tube 18, and the sucked gas passes through the particulate filter 19. At this time, particulates in the exhaust gas are captured by the filter 19. Therefore, by measuring the amount of particulates adhering to the filter 19, it is possible to measure the crushing of particulates in the exhaust gas. The sampling flow rate is connected by a flow meter 21 connected to the sampling tube 18. This flowmeter 21 has a structure as shown in FIGS. 2 and 3, and gas taken in through an inlet 39 is introduced into an intermediate chamber 27.
Through the valves 31, 32 it enters the rubber g137 or 38 and the lower rear chamber 29 or the lower front chamber 28. The movement of the rubber tables 37 and 38 at this time is transmitted to the crank mechanism 33 by the wing shaft 35 via the link mechanism 34, and the valves 31 and 32 are actuated alternately. Membrane 37.38
Since the amount of gas discharged due to the reciprocating motion is constant, this movement is connected to the pointer board through the gear transmission device 36 by the crank mechanism 33, and the amount of exhaust gas is integrated. Generally, to measure the amount of gas passing through the filter 19, a second
A model gas meter 21 as shown in FIGS. and 3 is used. This is because this type of gas meter is inexpensive and can determine the integrated flow rate with high accuracy. As described above, the model gas meter 21 converts the reciprocating motion of the rubber membranes 37 and 38 into the rotation of the pointer to display the flow rate. In order to read this flow rate, a shaft encoder is usually attached to the pointer and the flow rate is converted into an electrical signal.
I am trying to transmit 0 pulse. In measuring such particulates, correct chains cannot be measured unless exhaust gas is sucked in at a constant flow rate from the start of collection to the end of collection. However, when particulates accumulate on the filter 19, the flow rate gradually decreases as shown in FIG. 5 when the rotational speed of the suction pump 20 is constant. Moreover, since the flow meter 21 is a reciprocating type meter, pulsation occurs in the rotation of the pointer. Therefore, if feedback is applied to the sampling pump 20 using the indicated value of the flow meter 21 as it is, the pump 20 will instead cause hunting. Therefore, in this embodiment, the detection output of the flowmeter 21 is averaged by the averaging circuit 22, and the averaged value is used by the MIg circuit 23 to control the sampling pump 20.
Feedback control is performed. The averaging circuit 22 may be configured, for example, by a filter provided in a circuit for converting the signal of the shaft encoder of the flowmeter 21, or alternatively may be a time constant circuit or an integrating circuit that obtains an integral representation of a constant time condition. It may also be done by By providing such an averaging circuit 22, the fourth
As shown in the figure, it becomes possible to accurately maintain the actual flow rate at a constant value, thereby making it possible to improve particulate measurement accuracy. [Effects of the Invention] As described above, the present invention provides an I
Means for averaging the output of the I meter is provided, and the sampling pump is feedback-controlled using the averaged value by this means. Therefore, with such a configuration, even if a model reciprocating flowmeter is used, the pulsations in the detection output are averaged, thereby preventing hunting from occurring in the sampled flow rate and keeping the flow rate constant. This makes it possible to perform accurate exhaust gas measurements.

[Brief explanation of drawings]

FIG. 1 is a piping diagram showing an exhaust gas measuring device according to an embodiment of the present invention, FIG. 2 is a front view of the internal structure of a schematic reciprocating flowmeter, and FIG. 3 is a sectional view of the same essential parts. FIG. 4 is a graph showing changes in the sampling flow rate, and FIG. 5 is a graph showing changes in the flow rate when feedback control of the sampling pump is not performed. The names of the main parts in the drawings are as follows. 10... Diesel engine 11... Exhaust manifold 12... Exhaust pipe 13... Dilution tunnel 18... Sampling pipe 19... Particulate filter 20... Suction pump 21... Flow rate Total 22...Averaging circuit 23...$111i11 circuit

Claims (1)

[Claims] 1. In a device that dilutes the exhaust gas emitted from the engine in a dilution tunnel and samples and measures the diluted exhaust gas, the output of the flowmeter that detects the sampling flow rate is averaged. 1. An exhaust gas measuring device characterized in that a means is provided, and a sampling pump is feedback-controlled using a value averaged by the means.