Exhaust emission analysis method

Abstract

Method of analyzing the exhaust from an internal combustion engine that is fitted with a conventional exhaust pipe. The method utilizes an analyzer capable of indicating the concentration of at least one component of the exhaust which is transmitted to the analyzer through a conduit. The preferred form of the method includes the steps of heating the air inside the conduit while the conduit is not being used for exhaust analysis and transmitting the heated air into the analyzer. When engine exhaust is to be analyzed, the conduit is placed adjacent the exhaust pipe and the exhaust is transmitted from the tail pipe through the conduit into the analyzer so that the concentration of at least one component of the exhaust is indicated. The heating of the air inside the conduit prevents condensation of moisture in the conduit and the transfer of moisture to the analyzer, thereby enhancing the accuracy of the analysis.

Description

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to exhaust emission analyzers and more particularly relates to exhaust emission analyzers capable of being used in cold climates.

A variety of exhaust emission analyzers capable of indicating the concentration of at least one component of exhaust from an internal combustion engine have been designed in the past. These analyzers typically provide for the optical scanning of exhaust gases which are transmitted to the analyzer through a conduit from the tail pipe of the engine being tested.

Serious problems have arisen when such analyzers are used out of doors in temperatures below 32.degree. F. In such an environment, the accuracy of the analyzer becomes erratic and unreliable. The applicant has discovered that this condition can be corrected by preheating the air in the conduit while it is not being used for exhaust analysis. Heated air inside the conduit is transmitted to the analyzer, thereby maintaining the volume and moisture content of the air in proper balance. When an engine is to be analyzed, the conduit is placed adjacent the exhaust pipe, and the exhaust gases are transmitted through the conduit into the analyzer.

By preheating the air inside the conduit and transmitting the preheated air into the analyzer, the applicant has been able to maintain accurate and reliable exhaust pollutant concentration readings in below freezing weather, thereby increasing the environmental conditions under which the analyzer can be used to advantage.

DESCRIPTION OF THE DRAWING

These and other advantages and features of the present invention will appear in connection with the accompanying drawing wherein:

FIG. 1 is a schematic illustration of a preferred form of the present invention used in connection with a conventional vehicle; and

FIG. 2 is an enlarged, fragmentary, isometric view of the heater assembly shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a preferred embodiment of the present invention can be used in connection with a conventional motor vehicle 10 having an internal combustion engine 12 fitted with a tail pipe 14. The exhaust created by the engine and expelled by the tail pipe can be analyzed by a conventional analyzer, such as an exhaust emission analyzer 16 sold by Sun Electric Corporation, Chicago, Illinois.

Exhaust from engine 12 is transmitted to the analyzer through a conduit 18 comprising a hollow cylindrical metal probe 20 that is connected to a hollow hose 22. A stop member 23 prevents probe 20 from being pushed too far into tail pipe 14.

A suction pump 24 pulls exhaust gases or air through conduit 18 and a filter assembly 25 into analyzer 16. The filter assembly comprises a two-step filter which removes excess moisture and particles from the gases transmitted through hose 22. By well known optical techniques, analyzer 16 indicates the concentration of one or more pollutants in the exhaust gases, such as hydrocarbons or nitrogen oxides. The concentration is indicated on meters 26 and 27.

In order to allow the use of analyzer 16 in sub-freezing weather, a heater assembly 30 is provided. Referring to FIG. 2, assembly 30 comprises a base 31 that is supported by metal feet 33 and 34. Probe 20 is adapted to fit inside a duct assembly 36 comprising an inner duct 38 that is separated from an outer duct 42 by a layer of high temperature refractory insulation 40.

Air is admitted to inner duct 38 through a cover assembly 44 comprising an outer cover 46 and an inner panel 48 that are separated by another layer of high temperature refractory insulation 50. Air is admitted to cover assembly 44 through a perforated rear panel 52. When probe 20 is in place, it lies above a conventional strip heating element 54 that is positioned below a heat sink 56. The heat sink evenly distributes the heat generated by element 54 over the entire length of probe 20. Heating element 54 is a strip type heater rated at 300-550 watts that receives electrical power through an AC power cord 58 from a source (not shown).

In order to use the apparatus to advantage, probe 20 is placed inside duct assembly 36 at all times when the probe is not positioned inside tail pipe 14. As shown in the drawing, probe 20 is placed inside inner duct 38 and above heat sink 56 so that the heat from element 54 heats the air inside probe 20. Suction pump 24 pulls the heated air through hose 22 into the analyzer, thereby preventing the formation of moisture inside the entire length of probe 20 and hose 22. Preferably, the heat supplied by element 54 is sufficient to prevent the condensation of moisture inside probe 20 and hose 22, or to evaporate any moisture or ice which has condensed inside the conduit.

When the exhaust from vehicle 10 is analyzed, probe 20 is removed from heater assembly 30 and is placed into tail pipe 14 in the manner shown in phantom in FIG. 1. At this point in time, suction pump 24 pulls exhaust gases from tail pipe 14 through hose 22 into analyzer 16 so that the concentration of one or more pollutants in the exhaust gases is indicated on meters 26 and 27.

Those skilled in the art will recognize that the embodiment shown herein is merely exemplary of the preferred practice of the invention and may be modified and altered without departing from the true spirit and scope of the invention as defined in the appended claims.

Claims

What is claimed is:

1. A method of analyzing the exhaust flowing through an exhaust pipe connected to an internal combustion engine by means of an analyzer capable of indicating the concentration of at least one component of the exhaust transmitted to the analyzer through a conduit comprising a probe adapted to fit into the exhaust pipe and a hose connected between the probe and the analyzer, said method comprising the steps of:

heating the air inside the probe;

transmitting the heated air through the hose into the analyzer, so that the entire length of the conduit is exposed to the heated air;

placing the probe adjacent the exhaust pipe; and

transmitting the exhaust from the tail pipe through the conduit into the analyzer, whereby the heating of the air inside the entire length of the conduit prevents the condensation of moisture in the conduit, thereby increasing the accuracy of the analyzer.

2. A method, as claimed in claim 1, wherein the step of heating the air inside the probe comprises the step of heating the probe so that the temperature of the air inside the probe increases.

3. A method, as claimed in claim 1, wherein the step of heating the air inside the probe comprises the step of evaporating any moisture condensed on the probe.

4. A method of analyzing the exhaust flowing through an exhaust pipe connected to an internal combustion engine by means of an analyzer located adjacent a heater unit and capable of indicating the concentration of at least one component of exhaust transmitted to the analyzer through a conduit comprising a probe adapted to fit into the exhaust pipe and a hose connected between the prbe and the analyzer, said method comprising the steps of:

placing the probe adjacent the heater unit so that the air inside the probe is raised to at least a predetermined temperature;

transmitting the heated air through the hose into the analyzer so that the entire length of the conduit is exposed to the heated air;

removing the probe from the heater unit;

placing the probe adjacent the exhaust pipe; and

transmitting the exhaust from the tail pipe through the conduit into the analyzer, whereby the heating of the entire length of the conduit prevents condensation of moisture in the conduit, thereby increasing the accuracy of the analyzer.

5. A method, as claimed in claim 4, wherein the predetermined temperature is sufficiently great to evaporate condensed vapor in the entire length of the conduit.