Diagnosis apparatus for fuel vapor purge system
First Claim
1. A diagnosis apparatus for a fuel vapor purge system that includes a fuel tank for storing fuel and supplies fuel vapor from the rank to an air-intake passage of an engine, wherein the diagnosis apparatus determines whether the fuel vapor purge system has a malfunction, the apparatus comprising:
- a pressure sensor for detecting purge system pressure in the fuel vapor purge system;
a pressure changing means for changing the purge system pressure to a predetermined level; and
a diagnosis means for diagnosing the fuel vapor purge system, wherein the diagnosis means closes the fuel vapor purge system after the purge system pressure has been changed by using the pressure changing means, measuring a first rate of pressure change when the purge system pressure approaches a predetermined first reference pressure, and for measuring a second rate of pressure change when the purge system pressure approaches a predetermined second reference pressure, wherein the second reference pressure differs from the first reference pressure, and the second reference pressure value is closer to the purge system pressure before the purge system pressure was changed by the pressure changing means than the first reference pressure, and wherein the diagnosis means judges whether the fuel vapor purge system has a malfunction based on the ratio of the first rate to the second rate.
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Accused Products
Abstract
An improved diagnosis apparatus for detecting leakage of a fuel vapor purge system that purges fuel vapor from a fuel tank to an intake passage of an engine. The apparatus includes a pressure sensor and a purge valve. The pressure sensor detects the pressure in the purge system. The purge valve connects the purge system with the intake passage for lowering the purge system pressure to a predetermined pressure level. After the purge system pressure is lowered to the predetermined level, the purge system is sealed. The apparatus measures the rate of pressure change immediately after the purge system is sealed. The apparatus subsequently measures the rate of pressure change when the purge system pressure reaches a second reference pressure value and computes the ratio of the rates. The apparatus diagnoses whether there is a leak in the purge system based on the ratio and the rate of pressure change at the second reference pressure value.
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Citations
18 Claims
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1. A diagnosis apparatus for a fuel vapor purge system that includes a fuel tank for storing fuel and supplies fuel vapor from the rank to an air-intake passage of an engine, wherein the diagnosis apparatus determines whether the fuel vapor purge system has a malfunction, the apparatus comprising:
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a pressure sensor for detecting purge system pressure in the fuel vapor purge system;
a pressure changing means for changing the purge system pressure to a predetermined level; and
a diagnosis means for diagnosing the fuel vapor purge system, wherein the diagnosis means closes the fuel vapor purge system after the purge system pressure has been changed by using the pressure changing means, measuring a first rate of pressure change when the purge system pressure approaches a predetermined first reference pressure, and for measuring a second rate of pressure change when the purge system pressure approaches a predetermined second reference pressure, wherein the second reference pressure differs from the first reference pressure, and the second reference pressure value is closer to the purge system pressure before the purge system pressure was changed by the pressure changing means than the first reference pressure, and wherein the diagnosis means judges whether the fuel vapor purge system has a malfunction based on the ratio of the first rate to the second rate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method for diagnosing whether a fuel vapor purge system has a malfunction, wherein the purge system includes a fuel tank for storing fuel and supplies fuel vapor from the tank to an air-intake passage of an engine, the method including:
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changing purge system pressure in the fuel vapor purge system to a predetermined level;
closing the purge system after the purge system pressure reaches the first pressure value;
measuring a first rate of pressure change at a first reference pressure;
measuring a second rate of pressure change at a predetermined second reference pressure, wherein the second reference pressure differs from the first reference pressure, and wherein the second reference pressure is closer to the purge system pressure before the purge system pressure was changed to the predetermined level than the first reference pressure; and
calculating a ratio of the first rate of pressure change to the second rate of pressure change. - View Dependent Claims (16, 17)
measuring a fluctuation level of the purge system pressure while measuring the second rate of pressure change; and
judging whether the fuel vapor purge system has a malfunction based on the second rate of pressure change and the measured fluctuation level.
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18. A diagnosis apparatus for a fuel vapor purge system that includes a fuel tank for storing fuel and supplies fuel vapor from the tank to an air-intake passage of an engine, wherein the diagnosis apparatus determines whether the fuel vapor purge system has a malfunction, the apparatus comprising:
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a pressure sensor for detecting purge system pressure in the fuel vapor purge system;
a valve for changing the purge system pressure to a predetermined level; and
a computer for diagnosing the fuel vapor purge system, wherein the computer closes the fuel vapor purge system after the purge system pressure has been changed by using the valve, measuring a first rate of pressure change when the purge system pressure approaches a predetermined first reference pressure, and for measuring a second rate of pressure change when the purge system pressure approaches a predetermined second reference pressure, wherein the second reference pressure differs from the first reference pressure, and the second reference pressure value is closer to the purge system pressure before the purge system pressure was changed by using the valve than the first reference pressure, and wherein the computer judges whether the fuel vapor purge system has a malfunction based on the ratio of the first rate to the second rate.
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Specification