Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Reexamination Certificate
2003-07-21
2004-11-16
Moulis, Thomas (Department: 3747)
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
C123S520000
Reexamination Certificate
active
06817346
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No.2002-215391 filed on Jul. 24, 2002, including the specification, drawings and abstract are incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to an evaporated fuel processing apparatus for an internal combustion engine, and more particularly to an evaporated fuel processing apparatus suitable for effectively prevent the evaporated fuel generated in a fuel tank from being released to atmosphere.
2. Description of Related Art
There is disclosed an apparatus for processing evaporated fuel or fuel vapor generated within a fuel tank using a canister that adsorbs the fuel vapor so as not to be released to atmosphere, for example, in JP-A-6-93932. In such a generally employed fuel vapor processing apparatus, the intake negative pressure is introduced into the canister during operation of the internal combustion engine such that the fuel adsorbed in the canister is purged with air into an intake passage. This makes it possible to restore the fuel adsorbing capability of the canister without releasing the fuel into atmosphere during operation of the internal combustion engine.
In the aforementioned fuel vapor processing apparatus, quantity of injected fuel is adjusted so as to offset the quantity for purging. This allows the fuel in the canister to be purged into the internal combustion engine without varying the air/fuel ratio of the internal combustion engine.
In order to correct the fuel injection quantity accurately upon purging of the fuel in the canister into the intake passage, it is necessary to accurately detect the quantity of the fuel supplied through purging. Accordingly it is preferable to detect the fuel adsorbing state in the canister appropriately so as to accurately detect the quantity of the fuel supplied through purging.
The aforementioned apparatus is structured to monitor the temperature inside the canister and the temperature change is time integrated, based on which the fuel adsorbing state of the canister is estimated. Adsorption of the fuel vapor in the canister may cause an exothermic reaction. On the contrary, desorption of the fuel from the canister may cause an endothermic reaction. The temperature inside the canister, therefore, varies as the fuel is adsorbed in or released from the canister. The time integral value of the inner temperature is correlated with the residual state of the fuel in the canister. In the aforementioned apparatus, the fuel adsorbing state in the canister can be estimated with accuracy to a certain degree.
The change in the temperature inside the canister depends on the increase or decrease in the fuel adsorbed in the canister. The time integration of the temperature change may be effective for detecting the relative change in the quantity of the fuel in the canister. The absolute quantity of the fuel adsorbed in the canister, however, cannot be obtained by the aforementioned apparatus.
It is necessary to detect the absolute quantity of the fuel adsorbed in the canister for accurately detecting the quantity of the fuel supplied through purging. The detection of the fuel adsorbing state of the canister performed in the aforementioned apparatus, thus, is not sufficient to allow accurate correction of the fuel injection quantity.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an evaporated fuel processing apparatus capable of detecting an absolute quantity of the fuel adsorbed in the canister accurately.
According to an embodiment of the invention, an evaporated fuel processing apparatus for an internal combustion engine includes a canister that adsorbs a fuel vapor generated within a fuel tank, a gas flow detecting mechanism that detects a flow of gas at least at a predetermined flow rate between the fuel tank and the canister. The predetermined flow rate is higher than a flow rate of gas normally flowing between the fuel tank and the canister which are communicated with each other. The apparatus further includes a canister temperature detector that detects a temperature of the canister, and a controller that detects one of an upper peak value and a lower peak value of the temperature of the canister caused in a continual state of the flow of gas at least at the predetermined flow rate detected by the gas flow detecting mechanism, and estimates a fuel adsorbing state within the canister on the basis of the canister temperature obtained subsequent to a detection of the one of the upper peak value and the lower peak value. According to an embodiment of the invention, the peak value of the canister temperature is detected in the condition where a large quantity of gas flows between the fuel tank and the canister. In the case where the fuel is adsorbed, the canister temperature reaches the peak temperature at a time when the canister no longer adsorbs the fuel. Meanwhile in the case where the fuel is desorbed, the canister temperature reaches the peak temperature at a time when the canister no longer desorbs the fuel. In the aforementioned cases, the absolute quantity of the fuel adsorbed in the canister is determined in accordance with the canister temperature, that is, the canister peak temperature. Accordingly, the fuel adsorbing state corresponding to the absolute quantity of the adsorbed fuel may be accurately estimated on the basis of the canister temperature subsequent to the peak temperature.
In the embodiment, the canister includes a purge port communicated with an intake passage of the internal combustion engine, and the canister temperature detector comprises a canister temperature sensor disposed around the purge port such that a temperature within the canister is detected. According to the embodiment, the canister temperature is detected around the purge port of the canister. The fuel adsorbing state around the purge port can be particularly detected with high accuracy. After the start of purging of the fuel, the fuel vapor concentration of the gas to be first purged is greatly influenced by the fuel adsorbing state of the canister around the purge port. If the fuel adsorbing state around the purge port can be accurately detected, the fuel vapor concentration of the purge gas may be accurately estimated immediately after the start of purging. This makes it possible to generate a large quantity of fuel to be purged.
In the embodiment, the controller obtains a fuel vapor concentration of the gas flowing between the fuel tank and the canister in the continual state of the flow of gas at least at the predetermined flow rate, and a flow rate of the gas flowing between the fuel tank and the canister in the continual state of the flow of gas at least at the predetermined flow rate. The controller further estimates the fuel adsorbing state on the basis of the canister temperature obtained subsequent to the detection of the one of the upper peak value and the lower peak value, the fuel vapor concentration, and the flow rate of the gas. According to the embodiment, the fuel adsorbing state can be estimated on the basis of the fuel vapor concentration of the gas that flows between the fuel tank and the canister, and the flow rate of the gas in addition to the canister temperature after reaching the peak temperature. This makes it possible to accurately estimate the fuel adsorbing state of the canister.
In the embodiment, the controller contains a map that stores the fuel adsorbing state within the canister defined by the canister temperature, the fuel vapor concentration, and the flow rate of the gas. The controller refers to the map so as to determine the fuel adsorbing state in accordance with the canister temperature obtained subsequent to the detection of the one of the upper peak value and the lower peak value, the fuel vapor concentration, and the flow rate of the gas. According to the embodiment, the fuel adsorbing state of the canister can be simply and yet accurately estimated by referring to the map of the fuel adsorbing state of the canister, which is defined
Kato Junji
Konishi Masaaki
Namura Yoshikazu
Yada Kazuyuki
Moulis Thomas
Toyota Jidosha & Kabushiki Kaisha
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