Internal-combustion engines – Combustion chamber means having fuel injection only – Combustible mixture stratification means
Reexamination Certificate
2000-01-11
2001-06-12
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Combustible mixture stratification means
C123S305000, C123S406450
Reexamination Certificate
active
06244244
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an internal combustion engine that changes combustion modes. More particularly, the present invention pertains to a controller for reducing the torque of such an engine.
To improve fuel economy and to increase engine power at the same time, engines that change combustion mode according to current running conditions have been introduced. Japanese Unexamined Patent Publication No. 5-288098 discloses such an engine.
In that publication, the engine includes a fuel injector to supply fuel to each combustion chamber. When receiving a relatively great load, the engine must increase its power to increase the speed to a relatively high speed range. In this state, the engine performs homogeneous combustion, that is, it distributes and burns homogeneously mixed air-fuel mixture. Specifically, homogeneous combustion is performed by homogeneously mixing fuel injected during an intake stroke of a piston and igniting the mixture in the combustion chamber.
When the load applied to the engine is relatively small and the engine speed is low, the engine does not need to increase its power. In this state, the engine performs stratified combustion to enrich the air-fuel mixture near the spark plug. As a result, the mixture is easier to ignite. At the same time, the overall air-fuel ratio is adjusted to be slightly greater than the theoretical, or stoichiometric, air-fuel ratio, which improves the fuel economy. During stratified combustion, fuel is injected toward a recess formed on the head of a piston in the combustion chamber during a compression stroke, which concentrates fuel in the vicinity of the plug. The mixture of the concentrated fuel and the air in the combustion chamber is ignited by the spark plug.
Switching the combustion modes of an engine between homogenous charge combustion and stratified combustion improves the fuel economy and provides sufficient engine power when required.
The output torque of a vehicle internal combustion engine sometimes needs to be reduced in accordance with the current running conditions. For example, the output torque must be reduced when an automatic transmission coupled to the engine shaft is shifted. Shifting an automatic transmission produces shift shock. The shift shock is reduced by decreasing the engine output torque when the transmission is shifted.
Several methods of decreasing the output torque of engines are known. These include decreasing the amount of intake air, delaying the ignition timing and decreasing the amount of injected fuel. These methods may be applied to the above described engine, which switches the combustion modes. However, a given method of reducing the torque is not necessarily suitable for each combustion mode.
Delaying the phase of the ignition timing during stratified combustion destabilizes fuel combustion, which may lead to misfires. During stratified combustion, ignition must be executed when relatively a rich air-fuel mixture is in the vicinity of the spark plug. However, if the ignition timing is delayed, ignition is executed when the richer mixture is not near the spark plug.
During homogeneous combustion, decreasing the amount of injected fuel by a significant amount will lead to misfires if the amount of intake air is constant. Thus, the output torque cannot be significantly reduced by decreasing the injected fuel amount. That is, the output torque can be reduced only by a small amount by decreasing the injected fuel amount. As a result, the output torque cannot be reduced to the required level.
The above drawbacks are present not only when shifting an automatic transmission but also when a traction control apparatus commands the engine to decrease the output torque to keep a wheel from spinning and also when the engine output torque is reduced to reduce the shock caused by abrupt depression of the accelerator.
SUMMARY OF THE INVENTION
Accordingly, it is an objective of the present invention to provide a controller that properly decreases the output torque of an engine that switches combustion modes.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a controller of an engine having a plurality of combustion modes is provided. One of the combustion modes is selected depending on the running conditions of the engine. The controller reduces the output torque of the engine according to one of a plurality of predetermined torque reduction methods when a torque reduction requirement is in effect. The controller includes control means, setting means and converting means. The control means controls the engine to decrease the output torque according to a first torque reduction method when the engine is in a first combustion mode. The control means also controls the engine to decrease the output torque according to a second torque reduction method when the engine is in a second combustion mode, which is different from the first combustion mode. The setting means sets a first control amount that corresponds to the torque reduction requirement according to the first torque reduction method. The converting means converts the first control amount to a second control amount according to the second torque reduction method. The control means controls the engine according to the first control amount when the control means reduces the output torque by the first torque reduction method. The control means controls the engine according to the second control amount when the control means reduces the output torque by the second torque reduction method.
One of the first and second torque reduction methods is selected in accordance with the combustion mode of the engine and the output torque of the engine is reduced by the selected method. That is, the torque of the engine is reduced by a method that is suitable for the current combustion mode. Therefore, in an engine that switches the combustion mode, the engine torque can be properly reduced. Once the control amount of one of the first and second torque reduction methods is set, the other control amount is calculated by converting the first control amount. Such conversion shortens the time required for computing required torque reduction control amount, which is determined in accordance with the purpose of the torque reduction. The method also reduces the storage capacity required for storing maps, which are used for computing the required torque reduction amount.
REFERENCES:
patent: 5947079 (1999-09-01), Sivashankar et al.
patent: 6050238 (2000-04-01), Suzuki et al.
patent: 5288098 (1993-11-01), None
Fuwa Naohide
Mizuno Hiroyuki
Takagi Noboru
Argenbright Tony M.
Kenyon & Kenyon
Toyota Jidosha & Kabushiki Kaisha
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