Internal-combustion engines – Combustion chamber means having fuel injection only – Combustible mixture stratification means
Reexamination Certificate
1999-02-19
2001-05-22
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Combustible mixture stratification means
C123S568210, C701S104000
Reexamination Certificate
active
06234139
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an engine control system for controlling an engine to operate in different engine operation modes according to operating conditions.
2. Description of the Related Art
Typically, in order to secure engine output torque in an engine operating zone of higher engine loads and provide an improved fuel consumption in an engine operating zone of lower engine loads, it has been well known in the art to operate an engine in a plurality of engine operation modes different fuel injection form (injection timing, air-to-fuel ratio, etc.) according to operating conditions.
There have been known engine control systems which control engines of a type of injecting fuel directly into combustion chambers to operate in different combustion modies, namely a stratified charge combustion mode in which fuel injection is made in a compression stroke and stratified charge combustion is performed with a fuel mixture at a significantly higher air-to-fuel ratio, a homogeneous charge combustion mode in which fuel injection is made in an intake stroke and homogeneous charge combustion is performed with a fuel mixture it a relatively high air-to-fuel ratio, and a homogeneous charge combustion mode in which fuel injection is made in an intake stroke and homogeneous charge combustion is performed with a fuel mixture at a stoichiometric air-to-fuel ratio. Such an engine control system is known from, for example, Japanese Unexamined Patent Publication No. 8-312402. This engine control system determines a slow response group of control parameters, such as the amount of exhaust gas recirculation and a bypass intake air flow rate, on the basis of an engine load calculated based on an engine operating condition and determines a fast response group of control parameters, such as the amount of fuel injection, a fuel injection timing and an ignition timing, calculated based on a parameter related to the engine load after a correction in relation to a response delay, so as thereby to adjust control timing between the fast and slow response control parameters.
The engine control system described in the Japanese Unexamined Patent Publication No. 8-312402 is hard to have control timing for the control parameters completely adjusted. In particular, in the case where intake air flow control means such as a swirl control valve operative to regulate a swirl of intake air is employed to change an intake air flow, there is a problem that engine output torque fluctuates due to temporary aggravation of combustion during a shift between operation modes. Specifically, operation of the intake air flow control means, e.g. opening of a swirl control valve, changes according to the engine operation modes and, in consequence, during an operation mode shift, the intake air flow control means is accompanied by a delay in attaining an operated condition suitable for an engine operation mode into which the operation mode shift is made. An intake air flow condition is made contrary to a suitable condition for the engine operation mode into which the operation mode shift has been made due to the delay, which causes temporary aggravation of combustion and a change in engine output torque. Further, in the case where the engine is equipped with an exhaust gas recirculation system, exhaust gas recirculation control means such as an EGR valve is accompanied by a delay in attaining an operated condition suitable for an engine operation mode into which the operation mode shift is made, which possibly causes temporary aggravation of combustion and a change in engine output torque.
SUMMARY OF THE INVENTION
It is an objective of the invention to provide an engine control system which prevents an occurrence of aggravation of combustion and/or a change in engine output torque due to a delay in response of intake air flow control means and the like during an operation mode shift of an engine.
The foregoing object of the present invention is achieved by providing an engine control system for an engine which is operative in a plurality of engine operation modes different in fuel injection form according to engine operating conditions and has intake air flow control means for controlling an intake air flow introduced into a combustion chamber of the engine from an intake passage according to a control value thereof. The engine control system judges based on a change in the engine operating condition whether an operation mode shift to one of the engine operation modes to another of the engine operation modes is demanded, compares the control value with a limit value of the intake air flow control means permissible in the one engine operation mode when a specific engine operation mode shift between the engine operation modes is demanded, and controls the intake air flow control means so as to attain a target control value of the intake air flow control means for the one engine operation mode to which the specific mode shift is made while keeping the specific mode shift waiting until the control value reaches the limit value when the control value is judged to be out of the limit value.
According to the engine control system, while the intake air flow control means causes a change in control value to the target value for the demanded operation mode during an operation mode shift, the engine operation mode from which the operation mode shift is made lasts until the change reaches within the limit permissible in the demanded engine operation mode.
In the case where the engine is of a type injecting fuel directly into a combustion chamber and operative in a stratified charge combustion mode in which fuel injection is made in a compression stroke and stratified charge combustion is performed and a homogeneous charge combustion mode in which fuel injection is made in an intake stroke and homogeneous charge combustion is performed, the engine control system keeps an operation mode shift to the stratified charge combustion mode from the homogeneous charge combustion mode waiting until the control value reaches the limit value for the stratified combustion charge mode when the control value is judged to be out of the limit value. This prevents an insufficiency of intake air flow due to a delay in response of the intake air flow control means during an operation mode shift the stratified charge combustion mode from the homogeneous charge combustion mode.
The engine control system may desirably execute an operation mode shift to the homogeneous charge combustion mode from the stratified charge combustion mode when the control value is judged to be out of the limit value for the homogeneous charge combustion mode and continuously performs a correction of ignition timing until the control value reaches the limit value. In events where the control valve of the intake air flow control means is changed with a delay during the operation mode shift to the homogeneous charge combustion mode from the stratified charge combustion mode, it is easy to cause an over ignition timing advance due to unnecessarily strong intake air flow. in such an event, the over ignition timing advance can be redressed by a correction, the operation mode shift is executed without being retarded.
The engine control system may incorporate exhaust gas recirculation control means such as an EGR valve for controlling an amount of exhaust gas admitted into the intake air flow as the intake air control means. In this instance, the engine control system compares a control value of the exhaust gas recirculation control means with a limit value of the exhaust gas recirculation control means permissible in the one engine operation mode when a specific operation mode shift between the engine operation modes is demanded, and controls the exhaust gas recirculation control means so as to attain a target control value of the exhaust gas recirculation control means for the one engine operation mode to which the specific operation mode shift is made while keeping the specific mode shift waiting until the control value reaches the limit value
Imada Michihiro
Kuroki Masayuki
Mamiya Kiyotaka
Nishimura Hirofumi
Taga Junichi
Castro Arnold
Mazda Motor Corporation
Nixon & Peabody LLP
Studebaker Donald R.
Wolfe Willis R.
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