Apparatus and method for determining evaporative emissions
First Claim
1. A system for testing motor vehicle evaporative emissions comprising:
- a substantially air-tight testing structure adapted for enclosing a motor vehicle to be placed under test, the testing structure containing a known volume of ambient interior air;
a sampling mechanism for periodically measuring and analyzing total hydrocarbon content and component parts of the total hydrocarbon content in a sample of the ambient interior air;
a pressure measuring mechanism for indicating a pressure differential between the ambient interior air and atmosphere outside of the testing structure;
an injector element for injecting air containing substantially zero hydrocarbons into the testing structure whenever the pressure of the atmosphere outside of the testing structure is higher than the pressure of the ambient interior air by a preselected differential;
an exhaling element for withdrawing interior ambient air from the testing structure whenever the pressure of the ambient interior air is higher than the pressure of the atmosphere outside of the testing structure by a predetermined differential; and
a flow measuring and calculation element for determining, in conjunction with a most recent sample from the sampling mechanism, an amount of hydrocarbons exhaled from the testing structure whenever the exhaling element is withdrawing interior ambient air from the testing structure.
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Abstract
A sealed housing evaporative determination (SHED) apparatus and method for practically zero emission vehicles (PZEV) provides periodic sampling of ambient air within a substantially air-tight testing structure enclosing a vehicle under test. Pressure drops within the testing structure are compensated by injecting air substantially free of hydrocarbons into the testing structure. Pressure increases within the testing structure are reduced by withdrawing ambient air from the testing structure. Hydrocarbon content of any withdrawn ambient air is determined from the latest sample, and cumulative evaporative emissions are adjusted accordingly.
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Citations
16 Claims
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1. A system for testing motor vehicle evaporative emissions comprising:
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a substantially air-tight testing structure adapted for enclosing a motor vehicle to be placed under test, the testing structure containing a known volume of ambient interior air;
a sampling mechanism for periodically measuring and analyzing total hydrocarbon content and component parts of the total hydrocarbon content in a sample of the ambient interior air;
a pressure measuring mechanism for indicating a pressure differential between the ambient interior air and atmosphere outside of the testing structure;
an injector element for injecting air containing substantially zero hydrocarbons into the testing structure whenever the pressure of the atmosphere outside of the testing structure is higher than the pressure of the ambient interior air by a preselected differential;
an exhaling element for withdrawing interior ambient air from the testing structure whenever the pressure of the ambient interior air is higher than the pressure of the atmosphere outside of the testing structure by a predetermined differential; and
a flow measuring and calculation element for determining, in conjunction with a most recent sample from the sampling mechanism, an amount of hydrocarbons exhaled from the testing structure whenever the exhaling element is withdrawing interior ambient air from the testing structure. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for determining evaporative emissions of a motor vehicle over a predetermined test time interval, the method comprising:
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enclosing a subject motor vehicle in a substantially air-tight testing structure containing a known volume of ambient interior air;
periodically sampling during the test time interval the ambient interior air for hydrocarbon content and maintaining a running count of the hydrocarbon content;
monitoring a pressure differential between the ambient interior air and atmosphere outside of the testing structure;
injecting air containing substantially zero hydrocarbons into the testing structure whenever the pressure differential indicates atmospheric pressure outside the testing structure exceed internal ambient air pressure by a preselected amount;
withdrawing interior ambient air from the testing structure whenever the pressure differential indicates interior ambient air pressure exceeds atmospheric pressure outside the testing structure by a preselected amount; and
determining an amount of hydrocarbons withdrawn from the testing structure for any withdrawal of interior ambient air and adjusting the running count accordingly. - View Dependent Claims (12, 13, 14, 15, 16)
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Specification