Internal-combustion engines – Combustion chamber means having fuel injection only – Combustible mixture stratification means
Reexamination Certificate
1999-08-26
2001-01-23
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Combustible mixture stratification means
C123S520000
Reexamination Certificate
active
06176217
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a fuel vapor processing apparatus and method of an internal combustion engine, and particularly to a fuel vapor processing apparatus and method where the combustion method is switched between homogeneous combustion and stratified combustion according to operating conditions of the engine.
(2) Related Art of the Invention
The conventional fuel vapor processing apparatus of an internal combustion engine for vehicles are equipped with a canister for adsorbing the fuel vapor generated in a fuel tank, and a purge control valve mounted in a purge passage extending from the canister to an intake system of the engine for controlling the purging quantity of the fuel vapor (refer to Japanese Unexamined Patent Publication No. 7-42588).
On the other hand, a direct injection-spark ignition internal combustion engine where fuel is directly injected to the combustion chamber is being widely noticed recently. In this type of engine, it is common to switchingly control the combustion method in accordance with the operating conditions of the engine. The combustion method is switchingly controlled between a homogeneous combustion where fuel is injected during the intake stroke so as to diffuse the fuel in the combustion chamber to form a homogeneous mixture, and a stratified combustion where fuel is injected during the compression stroke so as to form a stratified mixture centralizing around the ignition plug (refer to Japanese Unexamined Patent Publication No. 59-37236).
When the combustion method is switchingly controlled, if purging of the fuel vapor is performed during the stratified combustion in the same manner as during the homogeneous combustion, the introduction of the fuel vapor generates a very rich air-fuel ratio condition for stratified combustion, since the target air-fuel ratio during the stratified combustion is set to a very lean level. This exerts undesirable influence on the operating performance and exhaust air. Therefore, during the stratified combustion, the purging of the fuel vapor is either reduced or prohibited.
However, when the stratified combustion is continuously performed, if the purging of the fuel vapor is reduced or prohibited during the stratified combustion mode, the canister may overflow and the vapor may be discharged to the atmosphere. In order to prevent such overflow, there is a need to increase the capacity of the canister, which leads to increase of the manufacturing cost.
Therefore, during stratified combustion, the combustion method is forced to be switched temporarily to the homogeneous combustion by a predetermined cycle, so as to perform the purging of the fuel vapor. The cycle is set in accordance with the vehicle speed, which is set to be shorter as the speed increases.
However, the trend in the vehicle speed and the generation quantity of the fuel vapor may vary, and there are cases where the stratified combustion may not be switched to the homogeneous combustion by the best cycle. In some cases, the forced switching cycle is too long, which leads to overflow of the canister and discharge of the vapor to the atmosphere, or too short in other cases, which leads to deterioration of the fuel economy.
Accordingly, the present invention aims at switching the stratified combustion to the homogeneous combustion by the best cycle, so as to prevent the overflow of the canister, and at the same time, improve fuel economy.
SUMMARY OF THE INVENTION
The present invention premises that a fuel vapor processing apparatus and method of an internal combustion engine comprises a combustion method switching device for switching the combustion method between homogeneous combustion and stratified combustion according to the operating conditions of the engine, and a purge control device for controlling, according to said combustion method, a purge control valve equipped in a purge passage extending from a canister for adsorbing the fuel vapor generated in a fuel tank to an intake system of the engine, so that purging of the fuel vapor is performed during the homogeneous combustion and purging of the fuel vapor is either reduced or prohibited during the stratified combustion.
The fuel vapor processing apparatus according to the present invention comprises a forced switching device for forcedly switching the combustion method to the homogeneous combustion temporarily according to predetermined cycles while performing the stratified combustion by said combustion method switching device so that purging of the fuel vapor is performed, a fuel temperature detecting device for detecting the fuel temperature, and a forced switching cycle setting device for variably setting said cycle for forcedly switching the combustion method from the stratified combustion to the homogeneous combustion according to the fuel temperature, so that said cycle is set shorter when the fuel temperature is higher.
According to the above-mentioned constitution, since the fuel temperature which is highly correlated with the amount of generated fuel vapor may be detected, and according to the detected fuel temperature, the cycle for forcedly switching the combustion method from the stratified combustion to the homogeneous combustion may be set variably, the combustion method can be switched by the most suitable cycle, to improve the purge balance, and to achieve prevention of overflow of the canister and improvement of the fuel economy.
Further, it is preferred that the fuel temperature detecting device detects the fuel temperature inside the fuel tank. The temperature of the fuel inside the fuel tank which is most closely related with the amount of generated fuel vapor is detected, thus achieving the further improvement.
Moreover, it is preferred that the forced switching cycle setting device varies said cycle continuously according to the fuel temperature. This enables the control with even higher accuracy.
Even further, it is preferred that the forced switching cycle setting device sets said cycle to a maximum value when the fuel temperature is equal to or lower than a predetermined value. This enables to substantially prohibit the periodical switching of the combustion method to the homogeneous combustion while the fuel temperature is low which means that there is no need to consider the generation of the fuel vapor, which leads to the further improvement of the fuel economy.
Moreover, the period of time for performing the forcedly switched homogeneous combustion by said forced switching device may simply be set to a fixed time, but it may preferably be varied according to the fuel temperature. However, when the fuel temperature is higher, more fuel vapor is generated, therefore the time for forcedly performing the homogeneous combustion is preferably set longer.
The characteristic structure of the present invention and the functions and effects based on such structure will become apparent by the following explanation on the preferred embodiment of the invention in connection with the accompanied drawings.
REFERENCES:
patent: 6079397 (2000-06-01), Matsumoto et al.
patent: 59-37236 (1984-02-01), None
patent: 7-42588 (1995-02-01), None
patent: 11-36921 (1999-02-01), None
Furushou Masaya
Ohkuma Shigeo
Argenbright Tony M.
McDermott & Will & Emery
Unisia Jecs Corporation
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