KR101339221B1 - Control method of exhaust-gas recirculation rate according to combustion pressure for internal combustion engine - Google Patents

Abstract

The present invention relates to a method for controlling the exhaust gas recirculation amount of an internal combustion engine, and more particularly, to a method for controlling the exhaust gas recirculation amount according to the combustion pressure in a cylinder.

To this end, the present invention comprises the steps of: a) detecting the combustion pressure inside the cylinder mounted to the internal combustion engine;

b) calculating the maximum slope of the combustion pressure with respect to the crank angle; And,

c) calculating a standard deviation of the maximum slope;

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When the standard deviation is smaller than the preset standard value, steps a), b) and c) are repeatedly performed, and when the standard deviation is larger than the preset standard value, the exhaust gas recycle amount is reduced. It provides a method for controlling the exhaust gas recirculation amount according to the combustion pressure of the engine.

Exhaust gas recirculation, combustion pressure, internal combustion engine

Description

CONTROL METHOD OF EXHAUST-GAS RECIRCULATION RATE ACCORDING TO COMBUSTION PRESSURE FOR INTERNAL COMBUSTION ENGINE}

The present invention relates to a method for controlling the exhaust gas recirculation amount of an internal combustion engine, and more particularly, to a method for controlling the exhaust gas recirculation amount according to the combustion pressure in a cylinder.

In general, as an apparatus applied to an internal combustion engine, an Exhaust-Gas Recirculation (EGR) apparatus that recycles a part of the exhaust gas to an intake machine in order to suppress generation of NOx in the exhaust gas is well known.

The internal combustion engine provided with such an EGR device adjusts the amount of EGR according to the engine operation state through the opening degree control of the EGR valve provided in the EGR path.

Such an exhaust gas recirculation apparatus includes an exhaust gas circulation passage for sending a part of the exhaust of an internal combustion engine having a throttle valve in the intake system to the intake machine, and an intake negative pressure downstream of the throttle valve provided as a driving source provided in the exhaust gas circulation passage. The exhaust gas circulation valve for controlling the exhaust gas circulation amount and the exhaust gas pressure applied to the valve element of the exhaust gas circulation valve, and when the exhaust gas pressure is less than or equal to a predetermined value, the intake negative pressure is applied to the exhaust gas circulation valve. It is provided with a back pressure control valve for communicating a part of the leading passage to the atmosphere to open and close to block the communication to the atmosphere when the exhaust gas pressure exceeds a predetermined value to constantly control the back pressure applied to the exhaust circulation valve.

That is, this is a back pressure control type exhaust circulation control device. When the pressure in the pressure operating chamber of the back pressure control valve is low, and the valve body is spaced from the opening, the atmosphere is introduced into the pressure operating chamber of the exhaust gas circulation valve and the valve body drops to exhaust gas. The circulation valve is closed, but when the pressure in the pressure operating chamber of the back pressure control valve rises and the valve body closes the opening, the negative pressure in the intake manifold passes through the negative pressure introducing pipe into the pressure operating chamber of the exhaust gas circulation valve. And the valve body is raised to make the exhaust circulation valve closed, so that a part of the exhaust gas is introduced into the intake machine with an exhaust circulation passage.

By the way, in the conventional internal combustion engine provided with the conventional exhaust gas recirculation apparatus, even if it is in the predetermined | prescribed operation area | region which does not perform exhaust gas circulation by an exhaust gas recirculation valve, for example, a deceleration operation area | region, the exhaust gas recirculation valve is opened and closed. Since a predetermined exhaust gas pressure acts on the back pressure control valve upstream of the back pressure control valve to be controlled, there is a problem that the diaphragm in the back pressure control valve vibrates and noise is generated by this pressure.

In addition, increasing exhaust gas recirculation deteriorates combustion stability, increases HC emission levels, reduces fuel economy, and delays intake air volume such as turbo-lag in transient mode. This causes excessive EGR to flow into the engine, resulting in unstable combustion.

In addition, as the flow rate of the EGR increases, pressure pulsation occurs in the EGR gas flowing through the EGR passage.

If the EGR gas having this pressure pulsation flows into the EGR cooler having a case, the high pressure pressure wave of the EGR gas may act on the EGR cooler, vibrate the EGr cooler, and generate noise.

Therefore, it is necessary to control the EGR flow rate in a range of the exhaust gas recirculation amount in which the target emission level of NOx and the combustion stability of the engine are compatible.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to reduce the exhaust gas recirculation amount according to the pressure inside the cylinder, And controlling the exhaust gas recirculation amount based on the combustion pressure of the internal combustion engine.

Exhaust gas recirculation amount control method according to the combustion pressure of the internal combustion engine according to an embodiment of the present invention for achieving this object,

a) detecting the combustion pressure inside the cylinder mounted to the internal combustion engine;

b) calculating the maximum slope of the combustion pressure with respect to the crank angle; And,

c) calculating a standard deviation of the maximum slope;

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When the standard deviation is smaller than the preset standard value, steps a), b) and c) are repeatedly performed. When the standard deviation is larger than the preset standard value, the exhaust gas recirculation amount is reduced.

In addition, the standard deviation is calculated from immediately after the ignition until the end of the explosion pressure drop.

In addition, the combustion pressure is characterized in that detected by the pressure sensor mounted inside the cylinder.

As described above, according to the exhaust gas recirculation amount control method according to the combustion pressure of the internal combustion engine according to the present invention, it is expected that the quality of the engine can be improved by reducing the exhaust gas recirculation amount until the noise and vibration are optimized according to the pressure inside the cylinder .

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The engine applied to the method for controlling the exhaust gas recirculation amount according to the combustion pressure of the internal combustion engine according to an embodiment of the present invention will be described in brief with reference to a basic configuration not shown for the purpose of the present invention.

The engine has a combustion chamber composed of a piston and a cylinder, and the combustion chamber is equipped with an intake valve and an exhaust valve.

A fuel injection device is mounted inside the combustion chamber and typically injects fuel into the compression stroke of the engine.

The mixer in the combustion chamber is also ignited by a spark plug.

The cylinder is provided with a pressure sensor for detecting the pressure, in the multi-cylinder engine may be provided in each cylinder to detect the pressure for each cylinder.

The crankshaft may be equipped with a rotation sensor for measuring the engine speed.

Part of the exhaust flowing from the combustion chamber to the exhaust pipe is returned to the intake pipe through the annular flow passage.

In this way, the combustion speed and the combustion temperature are reduced, so that NOx emissions can be suppressed.

The ratio between the air passing through the throttle valve and the reflux gas, that is, the exhaust gas recirculation amount, is controlled by the EGR valve.

Signals of the pressure sensor inside the cylinder and the rotation sensor mounted on the crankshaft are input to the computing device, which sends commands to the ignition control circuit, the EGR control circuit, and the injector control circuit based on these signals.

Referring to the exhaust gas recirculation amount control method according to the combustion pressure of the internal combustion engine according to an embodiment of the present invention having the configuration as described above in detail as follows.

First, the pressure is detected from the pressure sensor inside the cylinder. (S100)

Then, the maximum value of the pressure signal rising slope is calculated using the pressure value received from the pressure sensor. (S110)

At this time, the output of the pressure sensor is sampled synchronously with the crank angle from immediately after ignition (θ ₁ ) to when the pressure is lowered after the explosion (θ _n ), so that the pressure ratio P (θ ₁ ) and P ( θ ₂ ),. , P (θ _n ) can be obtained.

That is, differential calculation is performed with respect to the above pressure ratio.

In addition, according to the judgment of those skilled in the art, n may be set from 1 to 100 and θ _n may be set to 60 degrees after ignition.

Then, the standard deviation of the pressure for the crank angle from 1 to 100 is calculated. (S120)

Then, a standard value having a good noise and stability is set in advance through experiments, and it is determined whether the standard value is larger than the standard deviation. (S130)

If the standard value is greater than the standard deviation in the above step, it is executed again to calculate the maximum value of the rising slope of the pressure signal (S110). If the standard value is less than the standard deviation, the EGR control is performed to reduce the exhaust gas recirculation amount by 10%. do. (S140)

All the above-described processes can be repeatedly performed while the ignition switch is turned on, thereby controlling the exhaust gas recirculation amount not excessively increased according to the pressure in the cylinder, thereby reducing noise and vibration and improving engine stability.

Next, experimental data using the exhaust gas recirculation amount control method according to an embodiment of the present invention will be described.

Figure 2a shows the standard deviation with respect to the pressure represented by the prior art, it can be seen that the standard deviation is large, Figure 2b is the exhaust gas recirculation amount according to the exhaust gas recirculation amount control method according to an embodiment of the present invention As the state is reduced, it can be seen that the standard deviation becomes small.

In addition, Figure 3a shows a standard deviation with respect to the crank angle shown by the prior art, it can be seen that the standard deviation is large as described above, Figure 3b is the combustion pressure of the internal combustion engine according to an embodiment of the present invention As a standard deviation with respect to the pressure exhibited by the exhaust gas recirculation amount control method according to the present invention, it can be seen that the standard deviation is small.

That is, according to Figures 2a to 3b it can be seen that the noise and vibration is improved because the fluctuation range of the pressure is reduced.

In addition, Figure 4a shows a noise measurement of the conventional exhaust gas recirculation amount, it can be seen that the amplitude of the sound wave is large, Figure 4b is a noise measurement diagram showing a state of reducing the exhaust gas recirculation amount by 50% Figure 4a In comparison with, it can be seen that the amplitude of the sound wave is reduced.

That is, according to Figures 4a and 4b it can be seen that the overall running noise is improved by about 5dB by reducing the amount of EGR.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, And all changes to the scope that are deemed to be valid.

1 is a flow chart showing a method for controlling the exhaust gas recirculation amount according to the combustion pressure of the internal combustion engine according to an embodiment of the present invention.

Figure 2a is a standard deviation for the pressure represented by the prior art.

Figure 2b is a standard deviation of the pressure represented by the exhaust gas recirculation control method according to the combustion pressure of the internal combustion engine according to an embodiment of the present invention.

Figure 3a is a standard deviation for the crank angle shown by the prior art.

Figure 3b is a standard deviation of the pressure represented by the exhaust gas recirculation control method according to the combustion pressure of the internal combustion engine according to an embodiment of the present invention.

Figure 4a is a noise measurement of the conventional exhaust gas recycle amount.

4B is a noise measurement diagram showing a state in which the exhaust gas recirculation amount is reduced by 50%.

Claims (3)

a) detecting the combustion pressure inside the cylinder mounted to the internal combustion engine; b) calculating the maximum slope of the combustion pressure with respect to the crank angle; And, c) calculating a standard deviation of the maximum slope; , ≪ / RTI & When the standard deviation is smaller than the preset standard value, steps a), b) and c) are repeatedly performed, and when the standard deviation is larger than the preset standard value, the exhaust gas recycle amount is reduced. A method for controlling the exhaust gas recirculation amount according to the combustion pressure of the engine. The method of claim 1, The standard deviation is calculated from the end of the explosion immediately after the ignition until the pressure is lowered, the exhaust gas recirculation amount control method according to the combustion pressure of the internal combustion engine. The method of claim 1, The combustion pressure is exhaust gas recirculation control method according to the combustion pressure of the internal combustion engine, characterized in that detected by the pressure sensor mounted inside the cylinder.

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