Internal-combustion engines – Engine speed regulator – Open loop condition responsive
Reexamination Certificate
2002-03-28
2003-09-30
Solis, Erick (Department: 3747)
Internal-combustion engines
Engine speed regulator
Open loop condition responsive
C123S406520, C123S090150
Reexamination Certificate
active
06626144
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a device for controlling an internal combustion engine. More specifically, the invention relates to a device for controlling an internal combustion engine which estimates a future value of a degree of opening of the engine throttle valve after a predetermined time lapses by delaying the start of operation for controlling a degree of opening of the engine throttle valve to a target value and, based on this estimated value of the degree of opening of the throttle valve, precisely estimating the amount of the intake air taken into the engine in the future.
BACKGROUND ART
There has been known a device for controlling an internal combustion engine including a so-called electronically controlled throttle valve of which the opening degree can be controlled independently of the amount of accelerator pedal operation by the driver and precisely estimating the amount of the air that will be taken in by the engine by delaying the start of the operation for controlling the throttle valve opening degree to a target value determined from the amount of accelerator pedal operation by a predetermined delay time.
In general, there has been employed a so-called air amount-based fuel amount control system in which the amount of the air taken in by the internal combustion engine is first measured, and the amount of fuel injection is controlled based on the measured air amount so that the engine air-fuel ratio becomes an optimum value. In such an engine, it is important to precisely measure the amount of the air taken in by the engine. In a state where the amount of the air taken in by the engine is varying due to changes in the throttle valve opening degree and in the rotational speed as a result of transient operation condition, however, it often becomes difficult to precisely measure the amount of the air taken in by the engine. The amount of the air actually taken in by the cylinders of the engine is determined at the time when the intake valves of the respective cylinders close. In order to precisely set the amount of fuel injection, therefore, the amount of fuel injection must be set based upon the amount of the air taken in by the engine at a moment when the intake valve of the cylinder closes. Generally, however, the timing for calculating the amount of fuel injection for each cylinder precedes the timing at which the intake valve closes. In order to precisely set the amount of fuel injection based on the amount of the air actually taken in by the cylinder, therefore, it is necessary to precisely estimate the amount of the air taken in by the engine at a moment when the intake valve will be closed in the future at a moment of calculating the amount of fuel injection.
The amount of the air taken in by the engine varies depending upon the throttle valve opening degree and the rotational speed of the engine. Since the rate of change in the throttle valve opening degree is relatively larger than a rate of change in the engine rotational speed during the transient operation, if the throttle valve opening degree at the time when the intake valve is closed could be precisely estimated, then, the amount of the air taken in by the engine at the time when the intake valve is closed can be estimated. In an engine equipped with an electronically controlled throttle valve which can be operated independently of the acceleration pedal operation by the driver, there has been proposed a so-called phase-advanced inverse calculation method in which the future throttle valve opening degree is precisely estimated by delaying the operation of opening or closing of the throttle valve by a predetermined period of time and the amount of the air that will be taken in by the engine in the future (amount of the air taken in by the engine when the intake valve closes in the cylinder) is precisely estimated based on the estimated throttle valve opening degree.
A device for controlling an internal combustion engine by estimating the intake air amount of this kind has been disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 10-169469.
According to the device of this publication, the target opening degree of the electronically controlled throttle valve is set based upon the present amount of accelerator pedal operation (amount of depression). However, the throttle valve is not driven to a target opening degree immediately after the target opening degree is set. Instead, the throttle valve is driven after a predetermined delaying time elapses. In general, the electronically controlled throttle valve involves a lag in operation due to the delay in the control operation or due to the delay in the activation of the mechanism. Even when the target opening degree has rapidly (e.g., stepwise) changed, therefore, there occurs a delaying time determined from the operation characteristics of the throttle valve until the throttle valve opening degree actually arrives at the target opening degree. Therefore, if the operating characteristics of the throttle valve are precisely known, it becomes possible to calculate the throttle valve opening degree at each moment until the throttle valve actually arrives at a target opening degree even when the target opening degree of the throttle valve varies stepwise. In theory, it is possible to estimate the throttle valve opening degree at each moment based on the operating characteristics of the throttle valve at a moment when the target opening degree has changed stepwise.
In actual operation, however, when the accelerator pedal is moved a large amount by the driver and the target opening degree changes continuously, a change in the target opening degree after the, moment of estimation is not reflected on the estimated value even when the future throttle valve opening degree is estimated at each moment based on the throttle valve operation characteristics at a given moment. Therefore, the estimated throttle valve opening degree loses precision.
According to the device of the above publication, after the target opening degree has been set, the start of the operation for driving the throttle valve depending upon the target opening degree is delayed by a predetermined delay time (a period of the delay time is so short that the driver does not actually feel the delay), so that a change in the target opening degree is completely reflected on the estimated throttle valve opening degree. Namely, in the device of the above publication, the actual operation of the throttle valve is delayed by the above delay time to after the change in the target opening degree. This, in other words, makes it possible to know exactly, at a moment when the throttle valve actually starts operating, how the target throttle valve opening degree will change thereafter. It is, therefore, made possible to completely reflect a change in the target opening degree on the estimated throttle valve opening degree and, hence, to precisely estimate an actual change in the throttle valve opening degree. According to the device of the above publication, the throttle valve opening degree at a moment when the intake valve closes is precisely estimated at a moment when the amount of fuel injection is calculated, and the amount of the air taken in by the engine at a moment when the intake valve closes is calculated based on this estimated throttle valve opening degree.
When applied to a fixed-valve-timing engine in which the intake and exhaust valves have fixed opening/closing timings, the device of the above publication makes it possible to precisely estimate the amount of the air taken in by the engine. However, when applied to a variable-valve-timing engine in which the timings for opening and closing the intake and exhaust valves are varied depending upon the engine operating conditions, the device of the above publication is not capable of precisely estimating the amount of the air taken in by the engine.
In the variable-valve-timing engine, the target valve timing is set depending upon the engine load (amount of the air taken in by the engine and the rotational
Solis Erick
Toyota Jidosha & Kabushiki Kaisha
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