EXHAUST-GAS ANALYZING DEVICE

Abstract: In a low-pressure testing room for analyzing a gas exhaust­ ed from cars (4) under the condition that the air pressure is low, an exhaust-gas analyzing device is provided with a dilution tunnel (6) for diluting the exhaust gas from a car with air which is under decompressed condition and an ex­ haust-gas analyzer (l8) connected with said dilution tunnel (6) at a supply port side thereof, arranged in said low-­ pressure testing room (l), and provided with an exhaust in-­ take open to air outside of the low-pressure testing room by the use of an airtight piping. The influence of pressure fluctuation within the low-pres­ sure testing room upon the accuracy of analysis is elimi­ nated.

Description: The present invention relates to an analyzing device of a gas exhausted from cars. In order to reduce the distance (ℓ in the conventional device Fig. 3) from an exhaust-gas analyzer to a sample-inlet of a dilution tunnel for diluting an exhaust gas from cars with air within a sub-atmospheric pressure testing room, the exhaust-gas analyzer has been arranged in the low-pressure testing room. That is to say, a construction as shown in Fig. 3 has been used. In this Fig. 3, the reference numerals shown designate the following elements and features: 1 = a sub-atmospheric pressure testing room, 2 = atmospheric pressure, 3 = a decompression blower, 4 = a car, 5 = a chassis dynamometer, 6 = a dilution tunnel, 7 = air, 8 = an analyzer, 9 = an overflow line, 10 = a zero gas passage, 11 = a span gas passage, 12 = a bag sample passage, and 13 = a valve. In the case where HC (hydrocarbon) is measured, if the temperature is reduced, certain kinds of HC change their state of aggregation to other than gas, so that it is necessary to maintain the temperature high and therefore, ℓ has been reduced. For example, this is the case where a HC analyzer is used as an exhaust-gas analyzer. The analytical sensitivity of an exhaust-gas analyzer for use in a car is influenced by pressure, i.e. in the device of Fig.3, the sensitivity depends on the actual pressure within the testing room 1. With conventional analyzers, this problem has not been realized and no measures have been taken for overcoming the above described problem. With measuring methods of this type measurement is carried out only under conditions in which the accuracy is reduced in dependence of the degree of the pressure setting in the low-pressure testing room, or a method has been used, in which the atmospheric pressure is calibrated and then data are read. However, the step of calibrating is difficult, troublesome and time consuming. It is an object of the present invention to provide an exhaust-gas analyzing device whose sensitivity is influenced by fluctuation of the pressure within a low-pressure testing room less than in conventional devices. The exhaust-gas analyzing device of the present invention comprises: a dilution tunnel for diluting an exhaust-gas from cars with air of sub-atmospheric pressure, an exhaust-gas analyzer, a pump pumping air from said dilution tunnel into said exhaust-gas analyzer, and an exhaust-pipe, opening to atmospheric pressure, through which the analyzed gas is output from said exhaust-gas analyzer. With this arrangement the exhaust-gas analyzer always works under atmospheric pressure. In consequence, the sensitivity of the analyzer is less strongly influenced by the pressure fluctuations within the sub-atmospheric pressure testing room. According to a preferred embodiment, the exhaust-gas analyzer and the pump at its input side are commonly arranged in an analyzing portion. The inventive concept and embodiments of the invention will be described in the following with reference to the accompanying drawings in which Fig. 1 is a diagram showing a device according to one preferred embodiment of the present invention, Fig. 2 is a diagram showing a device according to another preferred embodiment of the present invention, and Fig. 3 is a diagram showing a conventional device. Referring to Fig. l, reference numerals l, 2, 4 to l3 designate the same members as in Fig. 3 showing the conventional example. Reference numeral l4 designates an opening of an air side of an exhaust-pipe l6 connected to the analyzer and reference numeral l5 designates a pressure pump provided between the dilution tunnel 6 and the analyzer 8. The exhaust-pipe 16 is guided to the outside of the testing room 1 in an air tight manner. The operation of the above described construction is described in the following. According to the present invention, since the analyzer 8 works under atmospheric pressure by opening the exhaust-pipe 16 of the analyzer 8 to the atmospheric pressure, the influence of the fluctuation of pressure within the sub-atmospheric pressure testing room upon the accuracy of the analyzer 8 is reduced. The apparatus of another preferred embodiment of the present invention depicted in Fig. 2 is different from the apparatus of Fig. l merely in that the pressure pump l5 is included in an analyzing portion l8. The operation and effects are the same.

Claims: An exhaust-gas analyzing device in a sub-atmospheric pressure testing room (1) for analyzing gas exhausted from cars (4), said device comprising: a dilution-tunnel (6) for diluting an exhaust gas from cars with air (7) of sub-atmospheric pressure, an exhaust-gas analyzer (8) receiving gas from said dilution-tunnel and outputting the analyzed gas through an exhaust-pipe (16), and a pump, wherein said exhaust-pipe (16) opens to air of atmospheric pressure, and said pump (15) is arranged at the inlet side of said exhaust-gas analyzer (8) to pump the diluted gas through the analyzer against the atmospheric pressure within the exhaust-pipe (16) and with this within the analyzer. A device as set forth in claim 1, characterized in that said pump (15) and said exhaust-gas analyzer (8) are commonly arranged within an analyzing portion (18).

Inventors: KOHSAKA, HIROJI, KOJIMA, MITOKU, MATSUI, HISAO
Applicants: HORIBA, LTD.
Application year: 1987
Main classification: G01N1
IPC codes: G01N1, G01N33, G01M15