Diagnostic apparatus and method for fuel vapor purge system
First Claim
1. A diagnostic apparatus for a fuel vapor purge system in which fuel vapor generated in a fuel tank is trapped in a chamber, and the fuel vapor trapped in the chamber is purged into an intake passage of an internal combustion engine through a purge path that includes the fuel tank, the apparatus comprising:
- a controller that;
measures a first change in an internal pressure of the purge path after creating a pressure difference between an inside and an outside of the purge path and sealing the purge path;
measures a second change in the internal pressure that varies with an amount of fuel vapor generated in the fuel tank, which second change is measured while the purge path is sealed for a first predetermined period of time after an atmospheric pressure is introduced into the purge path in which the pressure difference was created;
performs leakage diagnosis to determine whether leakage is present in the purge path, based on the first change and the second change in the internal pressure of the purge path;
measures a third change in the internal pressure that varies with an amount of fuel vapor generated in the fuel tank, prior to measurement of the first change and measurement of the second change, the third change in the internal pressure being measured while the purge path is sealed for a second predetermined period of time after an atmospheric pressure is introduced into the purge path before the pressure difference is created; and
inhibits the leakage diagnosis when a result of measurement of the third change in the internal pressure is greater than a predetermined value, and permits the leakage diagnosis when the result of measurement of the third change is equal to or less than the predetermined value.
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Abstract
In a diagnostic apparatus and method for a fuel vapor purge system in which fuel vapor generated in a fuel tank trapped in a chamber is purged into an intake passage of an internal combustion engine through a purge path, a first change in a pressure of the purge path is measured after creating a pressure difference between the inside and outside of the purge path and sealing the purge path, and a second change in pressure that varies with an amount of fuel vapor generated in the fuel tank is measured while the purge path is sealed for a first period of time after an atmospheric pressure is introduced into the purge path. Then, it is determined whether leakage is present in the purge path, based on the first change and the second change in the pressure of the purge path. Before the measurement of the first and second pressure changes, a third change in the pressure that varies with an amount of fuel vapor generated in the fuel tank is measured while the purge path is sealed for a second period of time after the atmospheric pressure is introduced into the purge path before the pressure difference is created. The leakage diagnosis is inhibited when the third change in the internal pressure is greater than a predetermined value, and the leakage diagnosis is permitted when the third change is equal to or less than the predetermined value.
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Citations
8 Claims
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1. A diagnostic apparatus for a fuel vapor purge system in which fuel vapor generated in a fuel tank is trapped in a chamber, and the fuel vapor trapped in the chamber is purged into an intake passage of an internal combustion engine through a purge path that includes the fuel tank, the apparatus comprising:
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a controller that;
measures a first change in an internal pressure of the purge path after creating a pressure difference between an inside and an outside of the purge path and sealing the purge path;
measures a second change in the internal pressure that varies with an amount of fuel vapor generated in the fuel tank, which second change is measured while the purge path is sealed for a first predetermined period of time after an atmospheric pressure is introduced into the purge path in which the pressure difference was created;
performs leakage diagnosis to determine whether leakage is present in the purge path, based on the first change and the second change in the internal pressure of the purge path;
measures a third change in the internal pressure that varies with an amount of fuel vapor generated in the fuel tank, prior to measurement of the first change and measurement of the second change, the third change in the internal pressure being measured while the purge path is sealed for a second predetermined period of time after an atmospheric pressure is introduced into the purge path before the pressure difference is created; and
inhibits the leakage diagnosis when a result of measurement of the third change in the internal pressure is greater than a predetermined value, and permits the leakage diagnosis when the result of measurement of the third change is equal to or less than the predetermined value. - View Dependent Claims (2, 3, 4)
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5. A method of diagnosing a fuel vapor purge system in which fuel vapor generated in a fuel tank is trapped in a chamber, and the fuel vapor trapped in the chamber is purged into an intake passage of an internal combustion engine through a purge path that includes the fuel tank, the method comprising the steps of:
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measuring a first change in an internal pressure of the purge path after creating a pressure difference between an inside and an outside of the purge path and sealing the purge path;
measuring a second change in the internal pressure that varies with an amount of fuel vapor generated in the fuel tank, which second change is measured while the purge path is sealed for a first predetermined period of time after an atmospheric pressure is introduced into the purge path in which the pressure difference was created;
performing leakage diagnosis to determine whether leakage is present in the purge path, based on the first change and the second change in the internal pressure of the purge path;
measuring a third change in the internal pressure that varies with an amount of fuel vapor generated in the fuel tank, prior to measurement of the first change and measurement of the second change, the third change in the internal pressure being measured while the purge path is sealed for a second predetermined period of time after an atmospheric pressure is introduced into the purge path before the pressure difference is created; and
inhibiting the leakage diagnosis when a result of measurement of the third change in the internal pressure is greater than a predetermined value, and permitting the leakage diagnosis when the result of measurement of the third change is equal to or less than the predetermined value. - View Dependent Claims (6, 7, 8)
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Specification