Measuring and testing – Simulating operating condition – Marine
Reexamination Certificate
2002-07-25
2004-10-26
Lefkowitz, Edward (Department: 2855)
Measuring and testing
Simulating operating condition
Marine
C073S040000, C073S049700
Reexamination Certificate
active
06807851
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based on Japanese Patent Applications No. 2001-223764 filed on Jul. 25, 2001, No. 2001-226914 filed on Jul. 27, 2001, No. 2001-241509 filed on Aug. 9, 2001, No. 2001-249345 filed on Aug. 20, 2001, and No. 2001-266638 filed on Sep. 4, 2001 the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a leak-check apparatus of a fuel-vapor-processing system, a fuel-temperature estimation apparatus and a fuel-temperature-sensor diagnosis apparatus.
2. Description of Related Art
U.S. Pat. No. 6,082,337 (JP-A-11-101162) discloses an apparatus, which is used for checking a leak on a passage of a fuel-vapor-processing system during a running state of the engine. In a running state of the engine, however, the level of fuel in a fuel tank varies. It is thus difficult to check a leak with a high degree of precision during a running state of the engine.
On the other hand, JP-A-6-81727 (Japan Patent No. 2,745,991) discloses leak-check processing, which is carried out after the engine is stopped. However, leak-check processing, which is carried out after the engine is stopped, exhausts the battery.
U.S. Pat. No. 5,263,462 discloses an apparatus, which is used for detecting a pressure in the passage when the temperature of the fuel tank increases by a predetermined quantity, and used for checking a leak of the same system on the basis of this pressure. When the ambient temperature is low, however, the temperature of fuel in the fuel tank may not increase. Thus, the number of times the leak-check processing is carried out decreases.
In the leak-check processing, a leak is checked by hermetically sealing the passage of the system. Thus, when the passage of the system is opened after the leak-check processing, a flow is generated in the system due to a difference in pressure between the system and the atmosphere. If a flow is generated in a canister, for example, fuel vapor transits to an undesirable state in some cases.
In leak-check processing, detection of a small leak is also demanded. In the case of a small leak, however, it takes a long time to generate a detectable change in pressure. Thus, in order to detect a small leak, a long check time is required. During such a long check time, however, it is quite within the bounds of possibility that the operating condition of the engine changes. It is thus difficult to detect a small leak.
JP-A-6-81727 discloses a leak-check apparatus provided with a sensor for detecting a temperature of fuel in the fuel tank. This apparatus finds a difference in fuel temperature between a stopped state of the engine and a start of the engine. If the difference in fuel temperature is found greater than a predetermined value, a leak is checked on the basis of an internal pressure of the fuel tank. However, the fuel-temperature sensor increases the number of components and brings about an increase in assembly man-hour.
SUMMARY OF THE INVENTION
It is thus an object of the present invention to provide an improved fuel-vapor-processing system capable of solving the problems raised by the conventional technology.
It is another object of the present invention to provide a leak-check apparatus capable of detecting a leak in a fuel-vapor-processing system with a high degree of precision and reducing the amount of consumed power generated by the battery in a stopped state of the engine.
It is a further object of the present invention to provide the fuel-vapor-processing system with a leak-check apparatus capable of carrying out leak-check processing at a proper frequency.
It is a still further object of the present invention to provide the fuel-vapor-processing system with a leak-check apparatus capable of making it difficult for air to flow into the system after leak-check processing.
It is a still further object of the present invention to provide the fuel-vapor-processing system with a leak-check apparatus capable of executing a leak-check procedure over a long period of time.
It is a still further object of the present invention to provide a fuel-temperature estimation apparatus for estimating a temperature of fuel in the fuel tank.
It is a still further object of the present invention to provide the fuel-vapor-processing system with a leak-check apparatus for estimating a temperature of fuel in the fuel tank and checking a leak in the fuel-vapor-processing system on the basis of the estimated temperature of the fuel.
It is a still further object of the present invention to provide a diagnosis apparatus for diagnosing a fuel-temperature sensor for detecting a temperature of fuel in the fuel tank.
According to a first aspect of the present invention, only if a preliminary leak is determined to exist in the fuel-vapor-processing system by an engine-running-state leak-check function of an engine-running-state leak-check means, is an engine-stopped-state leak-check function of an engine-stopped-state leak-check means executed so that a leak in a fuel-vapor-processing system can be detected and the power consumption in a stopped state of the engine can be reduced.
A small leak detected by the engine-running-state leak-check means may be regarded as a preliminary leak in the fuel-vapor-processing system and, when the engine-running-state leak-check means detects a preliminary leaks, the engine-stopped-state leak-check means may then confirm the leak.
It is also possible to provide a configuration wherein, when the engine-stopped-state leak-check means detects a leak in the fuel-vapor-processing system, only the engine-running-state leak-check means determines whether a normal condition has been restored in the fuel-vapor-processing system.
Thus, once a leak has been determined to exist in the fuel-vapor-processing system, only the engine-running-state leak-check means carries out leak-check processing in the fuel-vapor-processing system so that it is possible to reduce the amount of power consumed by an ECU in a stopped state of the engine.
According to a second aspect of the present invention, in the above configuration, a pressure in the fuel-vapor-processing system is detected within a leak-check period following termination of the running state of the engine and leak-check processing is carried out on the basis of the detected pressure. Thus, even if the temperature of fuel in the fuel tank increases only slightly after the running state of the engine is stopped, a condition for execution of the leak-check processing becomes easier to satisfy. As a result, leak-check processing can be carried out if necessary after the running state of the engine is stopped so that the frequency of the leak-check processing can be increased.
According to a third aspect of the present invention, the pressure of the fuel-vapor-processing system is limited to values lower than a predetermined limit during a leak-check period. Thus, when an open-air opening/closing valve of the canister is opened to expose the fuel-vapor-processing system to the atmosphere after the leak-check processing is finished, gas can be prevented from forcibly flowing into the canister and the fuel component in the canister can thus be prevented from being blown to the atmosphere.
According to a fourth aspect of the present invention, when the running state of the engine is stopped in the course of leak-check processing, a leak-check means continues an operation to supply power to components required for continuing the leak-check processing so that the leak-check processing can be carried out to its end. By doing so, even if there are more chances that the running state of the engine is stopped in the course of leak-check processing due to the fact that a long leak-check period is required for detecting a small leak, the leak-check processing is continued even after the running state of the engine is stopped so that it is possible to determine whether a leak exists in the fuel-vapor-processing system. Thus, the number of times the leak-check processing is carried out can b
Maegawa Yoshinori
Miwa Makoto
Morinaga Syujiro
Wakahara Keiji
Denso Corporation
Jenkins Jermaine
Lefkowitz Edward
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