KR19990002226A - Transient operation of gasoline vehicle direct injection engine Fuel compensation control method - Google Patents

Abstract

In a conventional engine for injecting fuel into an intake port, the throttle opening degree, the engine speed, and the amount of fuel adhering to the port are considered in a transient acceleration operation. Thereby performing fuel injection control.

However, since the injected fuel does not adhere to the inner wall of the port as in the case of the direct injection type fuel injection system, there is no need to compensate the fuel in consideration of the attachment of the fuel, and the injection angle of the throttle valve, Precise control can not be performed in transient operation in the engine.

3 and 4, a manifold predicted pressure value is obtained from a flow velocity-density algorithm using a pressure sensor based on the amount of air inflow in a throttle valve, and a predicted value of inflow and outflow in the manifold is obtained And when the rate of change of these is high, it is determined that the engine is in the transient state, and the basis of the fuel injection control according to the determination is provided.

Description

Transient operation of gasoline vehicle direct injection engine Fuel compensation control method

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a transient fuel compensation control method for a direct injection engine of a gasoline vehicle, and more particularly, And more particularly, to a fuel compensation control method for a transient operation of an engine.

[0003] It is well known that a fueling device of a vehicle is a device which supplies a mixer necessary for an engine under all operating conditions in a state in which it is most easily combusted, and its function is an important mechanism that greatly influences the performance of an engine,

The main part of such a fuel system is a fuel injection system where fuel and air are appropriately mixed and supplied to the engine. In recent years, an electronically controlled fuel injection system has been mainly employed in consideration of exhaust gas countermeasures and improvement of engine output.

1 is a schematic diagram showing such an electronically controlled fuel injection device. The structure is largely divided into three systems, namely, an intake system for supplying air to the engine combustion chamber, a fuel system for supplying fuel, and an engine And a control system composed of various sensors and an ECU (Electronic Control Unit) for determining and directing the amount of injection.

The double intake system includes an air cleaner 1 for filtering intake air, a surge tank 2 for preventing intake pulsation, an intake manifold 3 for distributing intake air to each cylinder, and the like.

An air flow meter 4 or a pressure sensor (not shown) is mounted on the intake system to measure the intake air flow rate, and the pressure of the intake manifold 3 is measured to send information on the intake air flow rate to the ECU It has been widely used to measure the flow rate to the throttle valve by using the air flow meter 4 because there is an error due to the influence of the disturbance in the low load region although it is accurate in the high load region using the pressure sensor.

The intake flow rate measured by the air flow meter 4 is sent to the ECU 5, where the injector is controlled so that the fuel is injected at an appropriate air-fuel ratio.

On the other hand, the ECU 5 performs the fuel compensation control according to various driving conditions to overcome the limitation of the mechanical control.

Examples thereof include intake air temperature increase compensation, water temperature increase compensation, start increase compensation, increase after start, compensation of full contact increase of throttle valve 6, increase after idle compensation, and compensation in transient operation.

In the double transient operation, when the vehicle is rapidly accelerated, a predetermined fuel injection amount is added to the basic injection amount in accordance with the acceleration. At this time, in addition to the opening degree of the throttle valve 6 and the number of revolutions of the engine, The ECU controls the fuel injection amount in consideration of the amount of fuel to be attached.

As described above, the ECU controls the fuel injection amount so that the proper air-fuel ratio is controlled based on the intake air flow rate measured by the air flow meter, and based on this, fuel compensation control suitable for various driving conditions is performed.

On the other hand, with the development of such electronically controlled fuel injection, a lean combustion engine which is capable of reducing various kinds of exhaust gas and further improving the output of the engine is being actively developed.

That is, the three emission characteristics such as nitrogen oxides, hydrocarbons, and carbon monoxide, which are main emissions in the gasoline engine, depend strongly on the equivalence ratio in the combustion or the air-fuel ratio.

From the relationship between the combustion temperature and the oxygen concentration, the nitrogen oxide has the highest concentration at an equivalence ratio of about 0.9, and the excess fuel having an equivalence ratio of 1 or more is an incomplete combustion component, which increases the hydrocarbon and carbon monoxide, thereby deteriorating the combustion consumption rate. Method is advantageous both in terms of improvement of thermal efficiency and reduction of nitrogen oxide.

In order to realize such a lean burn, it is known that the stratified combustion is most effective. In order to accomplish this lean combustion, direct injection of fuel into the combustion chamber to form an excess fuel mixture around the spark plug, The method is most likely.

In the direct injection type engine for achieving the lean burn, a more precise fuel injection amount control is required, and the same is true in the case of the compensation control.

On the other hand, in the direct injection type engine, the compensation control can not be appropriately performed in the compensation control, particularly in the transient operation.

That is, in the direct injection type fuel injected as in the case of the port injection type does not adhere to the inner wall of the port, fuel compensation considering the attachment of the fuel is not necessary.

In addition, precise control can not be performed during transient operation in the direct injection type engine only with the opening angle of the throttle valve and the number of revolutions of the engine.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a method for controlling over-driving fuel compensation of a direct injection engine of a gasoline vehicle, which performs fuel compensation control by predicting a pressure change of an intake manifold during an over- It is.

For this purpose, a manifold predicted pressure value is obtained through a flow velocity-density algorithm using a pressure sensor based on the amount of air inflow in a throttle valve to obtain a predicted value of inflow and outflow in the manifold, and when the rate of change of the manifold is rapid, And provides the basis of the fuel injection control according to the determination.

1 is an outline view of an electronically controlled fuel injection device,

2 is a schematic diagram showing an intake manifold pressure prediction cycle according to the present invention,

3 is a schematic diagram showing fuel compensation at the time of transient operation by the value calculated from the intake manifold pressure prediction cycle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the accompanying drawings.

(M, e) of the intake manifold with respect to the atmospheric pressure correction flow rate value, the intake air temperature correction flow rate value and the atmospheric pressure P (baro) to the maximum flow rate m '(max) at this point from the opening degree of the throttle valve, (M, e) and the measured pressure value P (m, m) of the manifold are calculated by multiplying the manifold predicted inflow value m '(i, e, t) (O, e) from the manifold predicted pressure values P (m, e) through a flow-density algorithm to obtain the manifold predicted inflow values m ' ), And obtains a manifold flow rate change rate m 'which is a difference between the manifold predicted inflow value m' (i, e) and the manifold predicted inflow value m '(i, e), and integrates the manifold flow rate change rate m' to obtain an intake mass m. The pressure predicting cycle of the intake manifold in which the pressure value P (m, e) is obtained is constituted, while in the throttle (M, e) of the manifold and the measured pressure value P (m, m) at the time of the difference between the predicted pressure value P (m, e) of the manifold and the absolute value of the predicted inflow value m ' A reference value for the absolute value of the rate of change of the intake manifold pressure is set and a reference value for the absolute value of the rate of change of the manifold measured pressure value P (m, m) with respect to time is set, (M, m) with respect to time with respect to the manifold predicted inflow value m '(i, e, t) in the throttle from the average value of the rate of change with respect to time with respect to the manifold- Fuel ratio control method of a direct injection engine of a gasoline vehicle which controls the fuel injection amount of the engine.

FIG. 2 is a schematic diagram showing an intake manifold pressure predicting cycle according to the present invention, and FIG. 3 is a schematic diagram showing fuel compensation at the time of an overdrive operation by a value calculated from this intake manifold pressure predicting cycle.

In the present invention, a manifold predicted pressure value P (m, e) is obtained through a flow velocity-density algorithm using a pressure sensor on the basis of an air inflow amount in a throttle valve to obtain predicted values of inflow and outflow in a manifold, If it is urgent, it is determined that the engine is in the transient state, and the basis of the fuel injection control corresponding thereto is provided.

The present invention is carried out by the ECU described above, and a reference value for comparing the pressure prediction cycle of the intake manifold with the value calculated therefrom is set.

First, the pressure prediction cycle of the intake manifold will be described as follows.

(M, e) at the manifold predicted inflow value m '(i, e, t) manifold and the measured pressure value P (m, m) at the throttle, Continue computing the difference.

That is, the maximum flow rate m '(max) in the throttle body is calculated based on the opening degree of the throttle valve on the basis of the geometric characteristic of the opening degree, and correction for the air flow rate is applied to the manifold predicted inflow value m' , e, t) are calculated, and t is the throttle valve, e is the predicted value, i is the inflow, o is the outflow, and m is the abbreviation for the manifold.

Here, the correction is greatly affected by pressure and temperature due to the characteristics of the intake air being a compressible fluid, so that correction by atmospheric pressure is multiplied by correction by intake air temperature, which is multiplied by correction by pressure ratio.

The correction value by the atmospheric pressure and the correction value by the intake air temperature are given by the ECU by the measuring sensor, and the pressure ratio correction value is calculated by the predicted pressure value P (m, e) of the manifold calculated through the flow velocity- ) Is divided by the atmospheric pressure P (baro).

The difference between the predicted pressure value P (m, e) of the manifold calculated at the manifold predicted inflow value m '(i, e, t) in this throttle and the pressure value P (m, m) Is fed back and multiplied to calculate the manifold predicted inflow value m '(i, e).

The difference between this and the manifold predicted effluent value m '(o, e) is the flow rate change rate and the manifold predicted effluent value m' (o, e) Algorithm.

In other words, N is the number of revolutions of the engine and is sensed by the sensor signal. Vd is determined by the amount of displacement. EV is the value that is tabulated in the ECU as volumetric efficiency, R is the gas constant, and Tm is the temperature in the manifold.

On the other hand, the manifold predicted pressure value P (m, e) is obtained by integrating the flow rate change rate to obtain an air mass m and substituting it into the ideal gas equation.

That is, PV = mRT .

The manifold predicted pressure value P (m, e) thus obtained is used to calculate the pressure ratio correction, the feedback calculation process for calculating the manifold inflow predicted value, and the manifold predicted output value m '(o, e) And it is transmitted to the calculation process of the flow velocity-density algorithm and is repeatedly performed.

Therefore, the rate of change of the difference between the predicted inflow value and the manifold predicted pressure value P (m, e) and the measured pressure value P (m, m) in the throttle from the pressure prediction cycle of this intake manifold, The rate of change of the value P (m, m) with respect to time can be continuously computed, and it is possible to determine the transient operation based on this and to perform the control accordingly.

That is, as shown in FIG. 3, each reference value corresponding to the normal operation is set to the absolute value of the value sent out from the pressure prediction cycle of the intake manifold, and when it is compared with the reference value,

Subsequently, the average value of the rate of change of the intake manifold pressure value P (m, m) is divided by the manifold predicted inflow value m '(i, e, t) in the throttle, Fuel injection.

As described above, according to the present invention, a manifold predicted pressure value is obtained through a flow velocity-density algorithm using a pressure sensor on the basis of an air inflow amount in a throttle valve to obtain predicted values of inflow and outflow in a manifold, When the engine is in a hurry, it is determined that the engine is in a transient state, and fuel injection control according to the determination is performed. Thus, precise fuel injection control is performed in the direct injection type engine, thereby improving the performance of the engine.

Claims (1)

(M, e) of the intake manifold with respect to the atmospheric pressure correction flow rate value, the intake air temperature correction flow rate value and the atmospheric pressure P (baro) at the maximum flow rate m '(max) at this point from the opening degree of the throttle valve (M, e) is multiplied by the difference between the predicted pressure value P (m, e) of the manifold and the measured pressure value P (m, m) by multiplying the manifold predicted inflow value m ' The manifold predicted effluent value m '(o, e) is obtained from the manifold predicted pressure value P (m, e) through the flow velocity-density algorithm, The manifold flow rate change rate m ', which is the difference between this and the manifold predicted inflow value m' (i, e), is integrated to obtain the intake mass m. Then, the predicted pressure value P (m, e) of the intake manifold, the pressure prediction cycle of the intake manifold constituting the intake manifold, (M, m) of the difference between the predicted pressure value P (m, e) of the manifold and the measured pressure value P (m, m) with respect to time is set as a reference value for the absolute value of the side inflow value m ' And sets a reference value for the absolute value of the rate of change of the manifold measurement pressure value P (m, m) with respect to time so that the value input from the pressure cycle of the intake manifold is equal to or greater than the reference value (M, m) with respect to time with respect to the manifold predicted inflow value m '(i, e, t) in the throttle from the average value of the rate of change of the manifold measured pressure value P A method of controlling over-running fuel compensation of a direct injection engine of a gasoline vehicle.