Internal-combustion engines – Charge forming device – Including exhaust gas condition responsive means
Reexamination Certificate
2002-08-28
2004-03-30
Gimie, Mahmoud (Department: 3747)
Internal-combustion engines
Charge forming device
Including exhaust gas condition responsive means
C123S688000, C123S698000, C123S703000, C123S568190, C060S285000
Reexamination Certificate
active
06712053
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based on Japanese Patent Applications No. 2001-55931 filed on Feb. 28, 2001, and No. 2001-389024 filed on Dec. 21, 2001 the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control system for an internal combustion engine.
2. Description of Related Art
In recent years, the regulations against the exhaust gas of a Diesel engine have been more and more strict to enhance the necessities for highly precise EGR controls and injection amount controls. In the EGR controls, for example, there has been mass-produced a method (for an airflow meter F/B control), in which the airflow to be sucked into a cylinder is feedback-controlled to a target value by measuring it with an airflow meter disposed in an intake line, so as to enhance the precision in the EGR ratio.
In a transient state for acceleration or deceleration, however, the actual airflow into the cylinder and the airflow measured by the airflow meter are different so that the so-called “model-based control” has been investigated in various manners considering the transmission delay of air. In this model-based control, the air to flow in the transient state into the cylinder is estimated by calculating a transmission delay in the air physically or in a transmission function on the basis of the airflow signal measured by the airflow meter.
However, the EGR amount recirculated from the EGR passage is highly varied with the back pressure on the EGR upstream side (i.e., on the exit side of the cylinder). Especially in the turbo engine, the back pressure changes highly transiently so that the EGR amount changes to cause an error in the EGR ratio. Especially in the variable turbo engine, the back pressure change is so seriously high that the EGR ratio cannot be precisely controlled by the airflow meter F/B control of the prior art or by the model-based control on the former thereby to fail to prevent the adverse effects such as the smoke emission.
In the case of the Diesel engine for the injection amount control, moreover, the injection amount is made different from a command value by the manufacture tolerance or aging of a fuel injection device so that the fuel becomes excessive or short to cause problems of the smoke emission or the torque shortage. In order to solve these problems, there has been investigated a method for feedback-controlling a fuel amount with an exhaust O
2
concentration by providing the exhaust line with an O
2
sensor for detecting the exhaust concentration. With the O
2
sensor in the exhaust line, however, a time delay occurs till the exhaust gas reaches the position of the O
2
sensor. With the delay in the chemical reaction of the O
2
sensor itself, moreover, the actual exhaust O
2
concentration and the exhaust O
2
concentration detected by the O
2
sensor have been different to cause a problem that the control precision especially at the transient time drastically drops.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an internal combustion engine control system that is capable of estimating an exhaust O
2
concentration precisely.
It is another object of the present invention to provide an internal combustion engine control system that is capable of performing an adequate EGR control and an injection amount control.
The present invention has been conceived on the basis of the background thus far described and has an object to realize an EGR control and an injection amount control, which are excellent in responsibility and highly precise.
According to the present invention, the exhaust O
2
concentration of each combustion in a cylinder is estimated by using an intake airflow signal outputted from the intake measuring means, an intake pressure signal outputted from the intake pressure sensor, and command injection amount information calculated by the command injection amount calculating means, and at least one of an EGR valve and the fuel injection amount is controlled in accordance with the estimated exhaust O
2
concentration.
By using the intake pressure signal, according to this construction, the total amount of air to enter the cylinder can be detected, and the fresh airflow (i.e., the airflow containing no EGR gas) of the intake passage can be highly precisely detected with the intake airflow signal and the intake pressure signal. From the total amount of air and the amount of fresh air into the intake passage, it is possible to determine the amount of EGR gas into the intake passage. By adding the command injection amount information, moreover, it is possible to estimate the exhaust O
2
concentration after each injection highly precisely. According to this method, the exhaust O
2
concentration can be estimated before it is actually detected by the sensor, so that the method can control in high responsibility when used for the injection amount control or the EGR control.
The exhaust O
2
concentration estimating means may include consumed O
2
amount calculating means for calculating the O
2
amount to be consumed in terms with the command injection amount.
In this case, the exhaust O
2
concentration after injection can be calculated highly precisely by calculating the O
2
amount to be consumed with the command injection amount.
The exhaust O
2
concentration estimating means may calculate the O
2
amount in the gas (containing an EGR gas) to flow into the cylinder, by using the O
2
amount in the fresh air sucked into the intake passage and the O
2
amount in the EGR gas.
As a result, the O
2
amount to flow into the cylinder can be calculated highly precisely to improve the estimating precision of the exhaust O
2
concentration.
The exhaust O
2
concentration estimating means may calculate the O
2
amount in the EGR gas by using the estimated value of the past exhaust O
2
concentration calculated beforehand.
In this case, the detection delay is less influenced than the case in which the O
2
concentration of the exhaust gas is actually detected by the sensor, so that the exhaust O
2
concentration can be estimated highly precisely.
The control system may further comprise: an O
2
sensor disposed in an exhaust passage for detecting the actual exhaust O
2
concentration; and learning means for controlling the estimated value of the exhaust O
2
concentration so that the estimated value may coincide with the output value of the O
2
sensor.
As a result, the error of the exhaust O
2
concentration estimating means can be reduced to improve the estimating precision of the exhaust O
2
concentration.
The control system may further comprise: an O
2
sensor disposed in an exhaust passage for detecting the actual exhaust O
2
concentration; filtering means for correcting a time delay till the exhaust O
2
concentration of the exhaust gas discharged from the cylinder is detected by the O
2
sensor; and learning means for calculating a learning correction so that the estimated value of the exhaust O
2
concentration may coincide with the output value of the O
2
sensor, after filtered by the filtering means, to correct the estimated value of the exhaust O
2
concentration with the learning correction.
By executing the filtering, according to this construction, it is possible to detect the difference between the estimated value of the exhaust O
2
concentration and the actually measured value (or the output value of the O
2
sensor) highly precisely. As a result, the highly precise learning control can also be realized even at the transient time.
The updating of the learning correction may be inhibited under the condition in which the changing rate of the estimated exhaust O
2
concentration is no less than a predetermined value.
Generally, the learning is done at a steady time, but the driving state for the steady time is limited in the ordinary drive so that the steady state is difficult especially in the region of a low speed and a high load. In the case of a learning to the transient time, therefore, it is important h
Haraguchi Hiroshi
Kobayashi Kazuo
Kohira Sumiko
Kondo Toshio
Denso Corporation
Gimie Mahmoud
Huynh Hai
Nixon & Vanderhye P.C.
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