Internal-combustion engines – Charge forming device – Supercharger
Reexamination Certificate
2000-04-03
2001-08-28
Nguyen, Hoang (Department: 3748)
Internal-combustion engines
Charge forming device
Supercharger
C060S605200, C060S611000
Reexamination Certificate
active
06279551
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for controlling an internal combustion engine with a supercharging device, such as a supercharger or a turbosupercharger (simply, a turbocharger), and particularly to an electronically-controlled internal combustion engine with a supercharging device and an electronic fuel-injection system used to switch between at least a homogeneous combustion mode and a stratified combustion mode.
2. Description of the Prior Art
In recent years, there have been proposed and developed various internal combustion engines capable of operating at either one of at least two combustion modes, namely a homogeneous combustion mode where fuel-injection early in the intake stroke produces a homogeneous air-fuel mixture and a stratified combustion mode (a late injection combustion mode) where late fuel-injection delays the event until the end of the compression stroke to produce a stratified air-fuel mixture. When accelerating in an engine operating region of a lean or ultra-lean air/fuel mixture ratio leaner than a stoichiometric air/fuel mixture ratio (14.6:1), that is, during acceleration in a lean-burn mode or in a ultra-lean-burn mode), there are two ways to increase the engine power output. One way is to control or manage the air/fuel mixture ratio (A/F or AFR) toward a richer air/fuel ratio. In this case, there is a problem of increased nitrogen oxides (NOx) emissions. Another method is to increase the pressure on the air-fuel mixture by way of the supercharging device, without changing the A/F. According to the latter method, it is possible to increase the engine power output while reducing NOx emissions, when accelerating in the lean-burn mode or in the ultra-lean-burn mode. One such method has been disclosed in Japanese Patent Provisional Publication No. 7-158462.
SUMMARY OF THE INVENTION
Boost-pressure change characteristics obtained during an accelerating condition in an engine operating region at a stoichiometric air/fuel ratio, (which region will be hereinafter referred to as a “stoichiometric combustion mode” or a “stoichiometric combustion zone”), are somewhat different from those obtained during an accelerating condition in an engine operating region at a lean air/fuel ratio (which region will be hereinafter referred to as a “lean combustion mode” or a “lean combustion zone”). In comparison with the accelerating/decelerating condition in the stoichiometric combustion mode, there is a great boost-pressure change during accelerating/decelerating condition in the lean combustion mode. For example, during the accelerating condition in the lean combustion mode, there is a response delay in a boost-pressure rise. The response delay in boost-pressure rise results in a delay in an increase in a quantity of air entering engine cylinders. Similarly, during the decelerating condition in the lean combustion mode, there is a response delay in a boost-pressure drop. The response delay in boost-pressure drop results in a delay in a decrease in intake-air quantity. Due to the response delay in boost-pressure change, engine torque rise/fall characteristics given during acceleration/deceleration in the lean combustion mode are different from those given during acceleration/deceleration in the stoichiometric combustion mode. As set out above, in the presence of the response delay in boost-pressure change, the lean combustion mode is inferior to the stoichiometric combustion mode, in engine torque rise/fall characteristics and driveability.
Accordingly, it is an object of the invention to provide an apparatus for controlling an internal combustion engine with a supercharging device, which avoids the aforementioned disadvantages of the prior art.
It is another object of the invention to provide an apparatus for controlling an internal combustion engine with a supercharging device and an electronic fuel-injection system, which is capable of providing engine torque rise/fall characteristics substantially equivalent to an accelerating/decelerating condition in a stoichiometric combustion mode, even during an accelerating/decelerating condition in a lean combustion mode.
In order to accomplish the aforementioned and other objects of the present invention, an apparatus for controlling an internal combustion engine with a supercharging device operable to produce a desired boost pressure comprises a throttle control device which controls a throttle valve, a pressure sensor located in an induction system to detect an actual boost pressure, a control unit being configured to be connected to the throttle control device for arbitrarily controlling a throttle opening of the throttle valve depending on an operated amount of an accelerator, the control unit comprising an arithmetic-calculation section which calculates a target air quantity used in an engine operating region of a lean air/fuel ratio, based on at least the operated amount of the accelerator, an arithmetic-calculation section which calculates the desired boost pressure based on engine speed and engine load, an arithmetic-calculation section which calculates a boost-pressure correction factor responsively to a difference between the desired boost pressure and the actual boost pressure, in the engine operating region of the lean air/fuel ratio, and an arithmetic-calculation section which compensates for the target air quantity used in the engine operating region of the lean air/fuel ratio by the boost-pressure correction factor to generate a compensated target air quantity, and determines the compensated target air quantity as a virtual target air quantity, and a throttle actuator device which drives the throttle valve, so that the virtual target air quantity is drawn into the engine.
According to another aspect of the invention, an apparatus for controlling an internal combustion engine with a supercharging device operable to produce a desired boost pressure comprises a throttle control device which controls a throttle valve, a pressure sensor located in an induction system to detect an actual boost pressure, a control unit being configured to be connected to the throttle control device for arbitrarily controlling a throttle opening of the throttle valve depending on an operated amount of an accelerator, the control unit comprising an arithmetic-calculation section which calculates a target air quantity based on at least the operated amount of the accelerator, an arithmetic-calculation section which calculates the desired boost pressure based on engine speed and engine load, an arithmetic-calculation section which calculates a boost-pressure correction factor responsively to a difference between the desired boost pressure and the actual boost pressure, and a determination section which determines whether the engine is in an operating region of a lean air/fuel ratio or in an operating region of a stoichiometric air/fuel ratio, and an arithmetic-and-logic section which is responsive to a result determined by the determination section, for compensating for the target air quantity by the boost-pressure correction factor to generate a compensated target air quantity and determining the compensated target air quantity as a virtual target air quantity when the engine is in the operating region of the lean air/fuel ratio, and for determining the target air quantity itself as the virtual target air quantity when the engine is in the operating region of the stoichiometric air/fuel ratio, and a throttle actuator device which drives the throttle valve, so that the virtual target air quantity is drawn into the engine.
According to a further aspect of the invention, in a computed-controlled internal combustion engine with a supercharging device operable to produce a desired boost pressure, an electronic engine control system for compensating for a response delay in boost-pressure change comprises a throttle control means for controlling a throttle valve, a pressure sensing means located in an induction system for detecting an actual boost pressure, a control unit being c
Fuse Toru
Iwano Hiroshi
Kazama Isamu
Ooba Hiraku
Foley & Lardner
Nguyen Hoang
Nissan Motor Co,. Ltd.
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