Method and apparatus for measuring evaporative vehicle emissions
First Claim
1. A leak-tolerant apparatus for use in cooperation with an absolute fluid pressure sensor for measuring evaporative emissions from motor vehicles in accordance with prescribed fluid-temperature profiles, comprising:
- a housing having an interior portion defining a fluid-fillable test chamber and an exterior portion;
a fluid-temperature sensor in thermal communication with said test chamber fluid;
fluid-conditioning means in fluid communication with said test chamber for controlling the temperature of said fluid disposed in said test chamber;
volume compensation means in fluid communication with said housing exterior portion for compensating for changes in said test chamber fluid volume; and
control means in electrical communication with said fluid temperature sensor, said fluid pressure sensor and said volume compensation means for determining the quantity of fluid required to be provided to or evacuated from said volume compensation means in accordance with the Ideal Gas Law (PV=nRT).
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Accused Products
Abstract
Provided is a method and apparatus for measuring evaporative vehicle emissions. In accordance with the invention, there is provided a leak-tolerant apparatus for use in cooperation with an absolute fluid pressure sensor for measuring evaporative emissions for motor vehicles in accordance with prescribed fluid-temperature profiles. The apparatus includes control means in electrical communication with fluid temperature sensor, a fluid pressure sensor and a volume compensation device for determining the quantity of fluid required to be provided to or evacuated from the volume compensation device in accordance with the ideal gas law. In operation, the control means compares the mass flow, volumetric flow, total mass or total volume with the rate or total change in temperature and pressure and corrects a flow metering device so as to allow more or less fluid into or out of the volume compensation device to achieve the desired test chamber volume compensation.
31 Citations
12 Claims
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1. A leak-tolerant apparatus for use in cooperation with an absolute fluid pressure sensor for measuring evaporative emissions from motor vehicles in accordance with prescribed fluid-temperature profiles, comprising:
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a housing having an interior portion defining a fluid-fillable test chamber and an exterior portion; a fluid-temperature sensor in thermal communication with said test chamber fluid; fluid-conditioning means in fluid communication with said test chamber for controlling the temperature of said fluid disposed in said test chamber; volume compensation means in fluid communication with said housing exterior portion for compensating for changes in said test chamber fluid volume; and control means in electrical communication with said fluid temperature sensor, said fluid pressure sensor and said volume compensation means for determining the quantity of fluid required to be provided to or evacuated from said volume compensation means in accordance with the Ideal Gas Law (PV=nRT). - View Dependent Claims (2, 3, 4, 5)
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6. A leak-tolerant apparatus for use in cooperation with a barometric air pressure sensor for measuring evaporative hydrocarbon emissions from motor vehicles in accordance with prescribed air-temperature profiles, comprising:
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a housing having an interior portion defining an air-fillable test chamber and an exterior portion; an air-temperature sensor disposed in said test chamber; air-conditioning means in fluid communication with said test chamber for controlling the temperature of said air disposed in said test chamber; volume compensation means in fluid communication with said housing exterior portion for compensating for changes in said test chamber fluid volume; and control means in electrical communication with said air temperature sensor, said air pressure sensor and said volume compensation means for determining the quantity of air required to be provided to or evacuated from said volume compensation means in accordance with the Ideal Gas Law (PV=nRT) so as to compensate for changes is said test chamber air volume.
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7. A leak-tolerant method of controlling the volume of a test chamber filled with a fluid having a predetermined mass, volume, temperature and pressure at time to and used to measure evaporative emissions from motor vehicles in accordance with prescribed fluid-temperature profiles, the method comprising the steps of:
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measuring the temperature of said test chamber fluid at a selected sample time tn, where n is a positive integer; measuring the absolute fluid pressure outside of said test chamber at said sample time tn ; determining the volume of said test chamber fluid at said sample time tn in accordance with the Ideal Gas Law (PV=nRT); providing volume compensation means in fluid communication with said fluid outside of said test chamber for compensating for changes in said test chamber fluid volume; and determining the volume of fluid required to be provided to or evacuated from said volume compensation means at time tn. - View Dependent Claims (8, 9)
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10. A leak-tolerant method of controlling the volume of a test chamber filled with a fluid having a predetermined mass, temperature and pressure at a first selected sample time t.sub.(n-y), (where n and y are both positive integers) and used to measure evaporative emissions from motor vehicles in accordance with prescribed fluid-temperature profiles, the method comprising the steps of:
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measuring the temperature of said test chamber fluid at a second selected sample time tn ; measuring the absolute fluid pressure outside of said test chamber at said sample time tn ; determining the volume of said test chamber fluid at said sample time tn in accordance with the Ideal Gas Law (PV=nRT); providing volume compensation means in fluid communication with said fluid outside of said test chamber for compensating for changes in said test chamber fluid volume; and determining the volume of fluid required to be provided to or evacuated from said volume compensation means at said sample time tn. - View Dependent Claims (11, 12)
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Specification