JPH09209803A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control device having, for example, an extensive linearity region by carrying out fuel injection control to provide desired injection characteristics of a fuel injection valve. SOLUTION: A linearity correction coefficient KLN to provide linearity as desired injection characteristics of a fuel injection valve is computed (S2) by computing fuel injection quantity Tio by Tio=Tp×COEF×α+Ts in accordance with basic fuel injection quantity Tp, various weighting coefficients COEF, an air-fuel ratio feedback correction coefficient α and voltage correction Ts (S1) and referring a map in accordance with this fuel injection quantity Tio. Thereafter, fuel injection is carried out (S4) by computing final fuel injection quantity Ti by Ti=Tio×KLN (S3) in accordance with the computed fuel injection quantity Tio and the linearity correction coefficient KLN and supplying pulse width of an injection pulse signal equivalent to this final fuel injection quantity Ti.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to a fuel injection control technique for obtaining a desired injection characteristic of a fuel injection valve.

[0002]

2. Description of the Related Art Conventionally, as a fuel injection control device for an internal combustion engine, for example, a basic fuel injection amount is calculated from an intake air flow rate and an engine rotation speed, and the basic fuel injection amount is determined by the engine cooling water temperature or the like. The final fuel injection amount is calculated by performing the correction, and the injection pulse width (energization time) of the injection pulse signal corresponding to this fuel injection amount is supplied to the electromagnetic fuel injection valve to inject fuel into the engine. The amount is being controlled.

Further, when performing such fuel injection control, in the region where the injection pulse width supplied to the fuel injection valve is small, the injection pulse is, as shown in FIG. 6, due to the mechanical characteristics of the fuel injection valve. The relationship between the width and the fuel injection amount does not have a proportional relationship (hereinafter referred to as a linear region), and the fuel injection amount control in this region may be inappropriate.

Therefore, for example, as disclosed in Japanese Utility Model Laid-Open No. 3-52459, there has been devised a control for setting a lower limit value of the fuel injection amount.

[0005]

However, in the case where the lower limit value of the fuel injection amount is set in this way, the characteristic of the fuel injection valve, that is, the relationship between the injection pulse width and the fuel injection amount is actually used. Since the linearity region shown is not expanded, for internal combustion engines that require a wide linearity region, such as, for example, lean burn engines, direct injection gasoline engines or low friction high power engines, always: Since the fuel injection amount cannot be controlled appropriately, the drivability and the exhaust property may be deteriorated particularly in a region where the fuel injection amount is small (see FIG. 6).

In view of the conventional problems as described above, the present invention performs fuel injection control to obtain desired injection characteristics of the fuel injection valve, and thus, for example, a fuel injection control device having a wide linear range. The purpose is to provide.

[0007]

Therefore, according to the invention described in claim 1, as shown in FIG. 1, an operating state detecting means A for detecting an operating state of the engine and an engine operating state detecting means for detecting the operating state of the engine are transmitted to the engine. Fuel injection amount setting means B for setting the fuel injection amount of
And a fuel injection control means D for performing fuel injection control via the fuel injection valve C based on the set fuel injection amount, in a fuel injection control device comprising: Correction amount setting means E for setting a correction amount for correcting the amount to have a desired injection characteristic, and fuel injection for correcting the fuel injection amount set by the fuel injection amount setting means B based on the set correction amount. Quantity correction means F,
It was comprised including.

With this configuration, the fuel injection amount correction unit corrects the fuel injection amount to the engine based on the correction amount set by the correction amount setting unit to obtain the desired injection characteristic of the fuel injection valve. The desired fuel injection characteristic is the fuel injection characteristic of the intake system of the engine. According to a second aspect of the invention, the correction amount setting means sets the correction amount based on the fuel injection amount set by the fuel injection amount setting means.

With this configuration, the correction amount for correcting the injection characteristic of the fuel injection valve is set based on the fuel injection amount set by the fuel injection amount setting means, so that it is appropriate for the engine operating state. The correction amount is set. According to the third aspect of the present invention, the desired injection characteristic is a linear characteristic in which the relationship between the drive signal to the fuel injection valve and the fuel injection amount is substantially over the entire range and has a substantially constant inclination.

With this configuration, for example, the non-linear region existing in the injection characteristic of the fuel injection valve also becomes linear and the linear region is expanded, so that the control accuracy of the fuel injection amount is further improved. To do.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. In FIG. 2, which shows a system diagram of an embodiment of a fuel injection control device according to the present invention, an internal combustion engine 1
Air is introduced into the exhaust gas through the air cleaner 2, the intake duct 3, and the intake manifold 4. The intake duct 3 is provided with a throttle valve 5 that opens and closes in conjunction with an accelerator pedal (not shown).
The intake air flow rate Q to the internal combustion engine 1 is controlled by.

Further, an idle control valve 7 is provided in an auxiliary air passage 6 provided by bypassing the throttle valve 5. The opening of the idle control valve 7 is controlled by a drive pulse signal (opening control signal) from a control unit 8 including a microcomputer, and the intake air flow rate Q during idle operation is controlled by this opening. The engine speed is controlled so as to reach a predetermined value.

Further, the intake manifold 4 is provided with an electromagnetic fuel injection valve 9 for each cylinder. The fuel injection valve 9 supplies the fuel whose pressure is adjusted to a predetermined pressure by a pressure regulator (not shown) to the control unit 8
The valve is intermittently driven to open by synchronizing with the engine rotation by the injection pulse signal from the fuel, the fuel is mixed with the intake air and is sucked into the cylinder.

The control unit 8 is supplied with signals from various sensors for detecting the engine operating state in order to determine the pulse width of the injection pulse signal of the fuel injection valve 9. As these various sensors, an air flow meter 20 arranged upstream of the throttle valve 5 for detecting the intake air flow rate Q, a rotation speed sensor 21 for extracting a rotation signal from a crankshaft and detecting an engine rotation speed Ne,
An idle switch 22 attached to the throttle valve 5 and turned on at the idle position (fully closed position) of the throttle valve 5,
A water temperature sensor 23 provided in the water jacket of the internal combustion engine 1 for detecting a cooling water temperature Tw representative of the engine temperature, a voltage sensor 24 for detecting a terminal voltage V _B of a battery (not shown), and the like are provided. Further, the exhaust manifold 10 of the internal combustion engine 1 is provided with an air-fuel ratio sensor (hereinafter referred to as an O ₂ sensor) 25 that detects the air-fuel ratio of the intake air-fuel mixture by detecting the oxygen concentration in the exhaust gas.

The operating state detecting means includes an air flow meter 20, a rotation speed sensor 21, and an idle switch 2.
2, water temperature sensor 23, voltage sensor 24 and O ₂ sensor 2
5, including a control unit 8
Has a function as a fuel injection amount setting means, a fuel injection control means, a correction amount setting means, and a fuel injection amount correcting means.

Here, the outline of the conventional fuel injection control will be described. The control unit 8 calculates the basic fuel injection amount Tp based on the detected intake air flow rate Q and the engine rotation speed Ne, and the cooling water temperature Tw. And the like, and based on the air-fuel ratio signal from the O ₂ sensor 25, the final fuel injection amount Ti is calculated while performing the air-fuel ratio feedback control such that the air-fuel ratio of the intake air-fuel mixture approaches the stoichiometric air-fuel ratio. , The pulse width of the injection pulse signal corresponding to the fuel injection amount Ti is supplied to the fuel injection valve 9.

However, as described above, since the injection amount control accuracy is poor in a region where the fuel injection amount is small due to the mechanical characteristics of the fuel injection valve, a wide linear region such as a lean bang engine is required. It couldn't cope enough with the internal combustion engine. Therefore, the present invention solves this problem by performing the process of the flowchart shown in FIG. 3 so that the conventional fuel injection valve can be easily applied to, for example, an internal combustion engine that requires a wide linear region. Settled. Hereinafter, the fuel injection control according to the present invention will be described with reference to the flowchart of FIG. The routine shown in this flowchart is executed every time fuel injection is performed.

In step 1 (abbreviated as S1 in the drawing; the same applies hereinafter), the fuel injection amount Ti ₀ before correction of the injection characteristic of the fuel injection valve according to the present invention is calculated by the following process. (1) Based on the intake air flow rate Q detected by the air flow meter 20 and the rotation speed sensor 21 and the engine rotation speed Ne, the basic fuel injection amount Tp is calculated by the following equation.

Tp = K × Q / Ne (K: constant) (2) Engine rotation speed Ne detected by the rotation speed sensor 21, idle switch 22, water temperature sensor 23, idle signal, cooling water temperature Tw and calculated basic fuel Injection amount Tp
Based on the above, various increase factors COEF are calculated by the following equations, for example. COEF = K _TW (Water temperature increase correction) + K _AS (Start and post-start increase correction) + K _AI (Idle increase correction) + K _MR (Mixing ratio correction coefficient) where K _TW (Water temperature increase correction) is the cooling water temperature Tw correction based on, K _aS (starting and post-start increase correction) is corrected based on the coolant temperature Tw for the improvement of the engine rotational stability of the engine startability and after starting, K _AI (idle after increasing correction) is smooth A correction based on the idle signal and the cooling water temperature Tw for enabling the vehicle to start, K _MR (mixing ratio correction coefficient) is an engine rotation speed Ne for performing control more suitable for the engine operating state.
And the basic fuel injection amount Tp. The various increase factors COEF are not limited to the above calculation formulas, and various calculation formulas are known.

(3) When performing air-fuel ratio feedback control so that the three-way catalyst (not shown in FIG. 2) interposed in the exhaust passage works effectively based on the air-fuel ratio detected by the O ₂ sensor 25. The air-fuel ratio feedback correction coefficient α is calculated. (4) The voltage correction T _S is calculated based on the battery terminal voltage V _B detected by the voltage sensor 24.

(5) Basic fuel injection amount Tp calculated above, various increase factors COEF, air-fuel ratio feedback correction factor α
The fuel injection amount Ti ₀ is calculated by the following equation based on the voltage correction T _S and the voltage correction T _S. Ti ₀ = Tp × COEF × α + T _S The process of step 1 described above corresponds to the fuel injection amount setting means.

In step 2, the linearity correction coefficient K _LN for obtaining the linearity as the desired injection characteristic of the fuel injection valve according to the present invention is calculated by referring to the map shown in FIG. As the linearity correction coefficient K _LN , for example, a value obtained by an experiment in advance is set in a map from the single characteristic of the fuel injection valve used. The map referred to here does not always have linearity as shown in FIG. 4, and may have random values depending on the single characteristics of the fuel injection valve used. The process of step 2 corresponds to the correction amount setting means.

In step 3, the final fuel injection amount Ti is calculated by the following equation based on the fuel injection amount Ti ₀ and the linearity correction coefficient K _LN . Ti = Ti ₀ × K _LN The process of step 3 corresponds to the fuel injection amount correction means. In step 4, the pulse width of the injection pulse signal corresponding to the calculated final fuel injection amount Ti is supplied to the fuel injection valve 9 to perform fuel injection. The process of step 4 corresponds to the fuel injection control means.

In the fuel injection control shown in this embodiment, the basic fuel injection amount Tp is calculated on the basis of the intake air flow rate Q and the engine rotation speed Ne. However, the present invention is not limited to this method. The present invention is also applicable to a so-called D-Jetro internal combustion engine that calculates the basic fuel injection amount Tp based on the intake negative pressure. If the fuel injection control described above is performed, for example, by correcting the fuel injection valve having the injection characteristics of the fuel injection valve shown in FIG. 6, the straight-ahead region is expanded and the lean burn is performed as shown in FIG. It becomes possible to cope with an internal combustion engine that requires a wide linear range such as an engine.

Further, for example, even in a region where the fuel injection amount is small, which could not be properly controlled in the past, the fuel injection amount can be appropriately controlled. The fuel ratio can be brought close to, and the engine operability and the exhaust property can be improved. Further, since the correction amount for obtaining the desired injection characteristic is set based on the single characteristic of the fuel injection valve, the vehicle adaptation experiment of the fuel injection valve is not required, and the application man-hour is reduced, that is, the cost is reduced. You can also

[0026]

As described above, according to the invention described in claim 1, the fuel injection amount injected into the intake system of the engine is corrected based on the correction amount for obtaining the desired injection characteristic of the fuel injection valve. Therefore, it becomes possible to perform appropriate control even in the fuel injection amount region where the conventional cannot perform appropriate control.
For example, it becomes extremely easy to cope with an internal combustion engine that requires a wide linear region such as a lean van engine that has been difficult to adapt. Further, for example, even in the region where the fuel injection amount is small, the air-fuel ratio of the intake air-fuel mixture can be brought close to the stoichiometric air-fuel ratio, and the engine drivability and the exhaust property can be improved. Further, since the correction amount for obtaining the desired injection characteristic is set based on the single characteristic of the fuel injection valve, the vehicle adaptation experiment of the fuel injection valve is not required, and the application man-hour is reduced, that is, the cost is reduced. You can also

According to the second aspect of the present invention, the correction amount for correcting the injection characteristic of the fuel injection valve is set based on the fuel injection amount set by the fuel injection amount setting means, that is, the engine operating state. Therefore, an appropriate correction amount can be set according to the engine operating state, and as a result, the engine operability and the exhaust property can be further improved. According to the third aspect of the present invention, for example, the non-linear region existing in the injection characteristic of the fuel injection valve also becomes linear, so that a wider linear region is obtained and the fuel injection is performed. The amount control accuracy is further improved.

In addition to the above effects, the present invention can be easily realized only by changing the program for fuel injection control, so that it is possible to improve fuel efficiency without increasing costs.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to claims of the present invention.

FIG. 2 is a system diagram showing an embodiment of a fuel injection control device according to the present invention.

FIG. 3 is a flowchart showing a fuel injection control of the above.

FIG. 4 is a diagram showing an example of a linear correction coefficient for obtaining linearity as a desired injection characteristic of the fuel injection valve of the above.

FIG. 5 is a diagram showing the effect of the linear correction coefficient of the above.

FIG. 6 is a diagram showing an injection characteristic of a fuel injection valve.

[Explanation of symbols]

1 Internal Combustion Engine 8 Control Unit 9 Fuel Injection Valve 20 Air Flow Meter 21 Rotational Speed Sensor 22 Idle Switch 23 Water Temperature Sensor 24 Voltage Sensor 25 O ₂ Sensor

Claims (3)

[Claims] 1. An operating state detecting means for detecting an engine operating state, a fuel injection amount setting means for setting a fuel injection amount to the engine based on the detected engine operating state, and a fuel based on the set fuel injection amount. In a fuel injection control device including fuel injection control means for performing fuel injection control via an injection valve, a correction amount for correcting the fuel injection amount from the fuel injection valve to have a desired injection characteristic. And a fuel injection amount correction unit for correcting the fuel injection amount set by the fuel injection amount setting unit based on the set correction amount. Fuel injection control device for internal combustion engine. 2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the correction amount setting means sets the correction amount based on the fuel injection amount set by the fuel injection amount setting means. . 3. The desired injection characteristic is a linear characteristic in which a relationship between a drive signal to the fuel injection valve and a fuel injection amount is substantially over the entire range and has a substantially constant inclination. A fuel injection control device for an internal combustion engine according to claim 1 or 2.