JPH0368221B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electronically controlled fuel injection method for an internal combustion engine, and is particularly applicable to an automobile internal combustion engine equipped with an intake pipe pressure type electronically controlled fuel injection device. In addition to determining the basic injection amount according to the engine intake pipe pressure and engine speed, which is suitable for The present invention relates to an improvement in an electronically controlled fuel injection method for an internal combustion engine, in which the fuel injection amount is determined based on the fuel injection amount.

[Conventional technology]

2. Description of the Related Art One of the methods for supplying an air-fuel mixture at a predetermined air-fuel ratio to the combustion chamber of an internal combustion engine such as an automobile engine uses an electronically controlled fuel injection device. In this method, an injector for injecting fuel into the engine is installed in the intake manifold or throttle body of the engine, for example, in several or one engine cylinder, and the valve opening time of the injector is adjusted depending on the operating state of the engine. By controlling the air-fuel mixture, a mixture having a predetermined air-fuel ratio is supplied to the engine combustion chamber. This electronically controlled fuel injection system can be roughly divided into two types: one that calculates the basic injection amount according to the intake air amount and engine speed of the engine;
The so-called intake air amount (sensing) type electronically controlled fuel injection device, and the so-called intake pipe pressure (sensing) type electronically controlled fuel injection that determines the basic injection amount according to the engine intake pipe pressure and engine speed. There is a device.

Among these, the former allows for precise control of the air-fuel ratio, and has come to be widely used in automobile engines equipped with exhaust gas purification measures. However, in this intake air volume type electronically controlled fuel injection system, the intake air volume changes by about 50 times between idle and high load, and the dynamic range is wide, so the intake air volume is converted into an electrical signal. Not only does this result in lower accuracy, but if you try to improve the calculation accuracy in the digital control circuit at the subsequent stage, the bit length of the electrical signal becomes longer, and it becomes necessary to use an expensive computer as the digital control circuit. Furthermore, in order to measure the amount of intake air, it is necessary to use a measuring device with a very precise structure, such as an air flow meter, resulting in problems such as high equipment costs.

On the other hand, in the latter type of intake pipe pressure type electronically controlled fuel injection system, the amount of change in intake pipe pressure is small, about 2 to 3 times, and the dynamic range is narrow.
Not only is the arithmetic processing in the subsequent digital control circuit easy, but the pressure sensor for detecting the intake pipe pressure is also inexpensive.

[Problem to be solved by the invention]

However, compared to electronically controlled fuel injection systems that use intake air flow, the control accuracy of the air-fuel ratio is lower, and especially during deceleration, the fuel injection amount does not decrease unless the intake pipe pressure decreases, so the air-fuel ratio Not only does this temporarily become rich, reducing deceleration performance, but the amount of carbon monoxide in the exhaust gas increases, making it difficult to maintain the air-fuel ratio within a predetermined range suitable for a three-way catalytic converter. It was difficult. This is the same even when the fuel injection amount is feedback-controlled in accordance with the output signal of the oxygen concentration sensor disposed downstream of the exhaust gas because the response of the oxygen concentration sensor is slow. Therefore, conventionally, it has been considered difficult to use intake pipe pressure type electronically controlled fuel injection devices in automobile engines that require precise control of the air-fuel ratio and are equipped with exhaust gas purification measures. It was getting worse.

The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional art, and, when decelerating, the amount of weight loss is corrected appropriately and not excessively according to the way the accelerator pedal is pressed, that is, both the throttle valve opening and the intake pipe pressure. go and
The air-fuel ratio can be maintained near the stoichiometric air-fuel ratio,
Therefore, it is an object of the present invention to provide an electronically controlled fuel injection method for an internal combustion engine that can achieve both good deceleration performance and exhaust gas purification performance.

[Means to solve the problem]

The present invention calculates the basic injection amount according to the engine intake pipe pressure and engine rotation speed, and during transient periods, corrects the basic injection amount using a correction coefficient calculated according to the engine operating state. In an electronically controlled fuel injection method for an internal combustion engine that determines the fuel injection amount, during deceleration, a value corresponding to the amount of change in the throttle valve opening for each predetermined period is used as a correction coefficient to adjust the rate of decrease in the throttle valve opening. Intake control that performs reduction correction according to the rate of decrease in intake pipe pressure, using a correction coefficient that is the sum of the throttle valve opening reduction and the amount of change in intake pipe pressure for each predetermined period. The above object is achieved by performing a reduction correction by combining pipe pressure reduction and deceleration reduction by following the minimum value of each reduction, and setting a lower limit on the correction coefficient for the throttle valve opening reduction. It is.

[Effect]

In the present invention, during deceleration, the reduction in throttle valve opening is corrected in accordance with the rate of decrease in the throttle valve opening prior to the decrease in intake pipe pressure, and the reduction in throttle valve opening is performed in accordance with the rate of decrease in intake pipe pressure. Since the reduction correction is performed in combination with the intake pipe pressure reduction with high precision, which performs the reduction correction, the response is quick and the deceleration reduction can be performed with high precision.

That is, since the reduction in the throttle valve opening is performed based on the throttle valve opening, the reduction can be quickly performed in accordance with how the accelerator pedal is depressed, and the amount of time needed to reduce the intake pipe pressure with high accuracy is achieved. The responsiveness of the intermediate deceleration portion can be improved.

On the other hand, the intake pipe pressure reduction is performed after the intake pipe pressure changes after the throttle valve opening changes. This intake pipe pressure reduction is performed based on the amount of air actually taken into the combustion chamber, and is highly accurate.

In addition, in the case of the intake air amount sensing type, when the throttle valve is closed during deceleration, the sensor output upstream of the throttle valve immediately detects a decrease in the amount of intake air; Since the amount of air is reduced by the amount of the surge tank downstream of the throttle valve, the amount of fuel calculated by the sensor output decreases in advance, and this results in an appropriate reduction in deceleration. There is no need to reduce the throttle valve opening as in the present invention.

Further, in the present invention, since the deceleration reduction is performed by following the minimum value of the throttle valve opening reduction and the intake pipe pressure reduction, an excessive reduction does not occur even in a region where the two overlap.

Furthermore, since the throttle valve opening reduction has a quick response but low precision, if the reduction is continued in accordance with the rate of reduction, there is a risk of an excessive amount. Therefore, in the present invention, a lower limit is set for the correction coefficient for reducing the throttle valve opening to prevent the throttle valve opening from being excessively reduced due to low accuracy.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

An embodiment of an intake pipe pressure type electronically controlled fuel injection device employing the electronically controlled fuel injection method for an internal combustion engine according to the present invention is as shown in FIGS. 1 and 2. , an intake temperature sensor 14 for detecting the temperature of intake air taken in from the air cleaner 12, and an intake passage 1.
a throttle valve 18 for controlling the flow rate of intake air, which is disposed in the interior of the vehicle and is opened and closed in conjunction with an accelerator pedal (not shown) disposed in the driver's seat;
, a throttle sensor 20 including an idle contact for detecting whether or not the throttle valve 18 is at an idle opening, and a potentiometer that generates a voltage output proportional to the opening of the throttle valve 18, and a surge tank. 22, an intake pipe pressure sensor 23 for detecting intake pipe pressure from the pressure inside the surge tank 22,
Bypass passage 24 that bypasses the throttle valve 18
an idle rotation control valve 26 disposed in the middle of the bypass passage 24 for controlling the idle rotation speed by controlling the opening area of the bypass passage 24; and an idle rotation control valve 26 disposed in the intake manifold 28. , an injector 30 for injecting fuel toward the intake port of the engine 10, and an oxygen concentration sensor 34 disposed in the exhaust manifold 32 for detecting the air-fuel ratio from the residual oxygen concentration in the exhaust gas.
and an exhaust pipe 36 downstream of the exhaust manifold 32.
a three-way catalytic converter 38 disposed in the middle of the
A distributor 40 has a distributor shaft that rotates in conjunction with the rotation of the crankshaft of the engine 10, and a top dead center signal and A top dead center sensor 42 and a crank angle sensor 44 that output a crank angle signal, a cooling water temperature sensor 46 disposed in the engine block for detecting engine cooling water temperature, and a transmission 4
A vehicle speed sensor 50 for detecting the running speed of the vehicle from the rotation speed of the output shaft of No. 8; The basic injection amount per engine stroke is determined from the map, and this is corrected according to the output of the throttle sensor 20, the air-fuel ratio of the output of the oxygen concentration sensor 34, the engine cooling water temperature of the output of the cooling water temperature sensor 46, etc. By doing so, the fuel injection amount is determined and a valve opening time signal is output to the injector 30, and the ignition timing is determined according to the engine operating condition and an ignition signal is output to the igniter-equipped coil 52. Furthermore, in the intake pipe pressure type electronically controlled fuel injection device for the automobile engine 10, which includes a digital control circuit 54 that controls the idle rotation control valve 26 during idle, the digital control circuit 54 controls the throttle speed during deceleration. A value obtained by integrating the values corresponding to the amount of change in the throttle valve opening detected from the potentiometer output of the torque sensor 20 every predetermined time is used as a correction coefficient, and a reduction correction is performed in accordance with the decreasing speed of the throttle valve opening. A value obtained by integrating the throttle valve opening reduction and the amount of change in the intake pipe pressure detected from the output of the intake pipe pressure sensor 23 every predetermined time is used as a correction coefficient, and the correction coefficient is adjusted according to the rate of decrease in the intake pipe pressure. A reduction correction is performed in combination with an intake pipe pressure reduction that performs a reduction correction, and a deceleration reduction is performed by tracing the minimum value of each reduction, and a lower limit is set for the correction coefficient for the throttle valve opening reduction.

As shown in detail in FIG. 2, the digital control circuit 54 is a central processing unit (hereinafter referred to as CPU) consisting of a microprocessor that performs various arithmetic operations.
60, the intake temperature sensor 14, the potentiometer of the throttle sensor 20, and the intake pipe pressure sensor 2.
3. An analog input port 62 with a multiplexer for converting analog signals input from the oxygen concentration sensor 34, cooling water temperature sensor 46, etc. into digital signals and sequentially inputting them into the CPU 60; and an idle contact point of the throttle sensor 20; Top dead center sensor 4
2. A digital input port 64 for inputting digital signals input from the crank angle sensor 44, vehicle speed sensor 50, etc. to the CPU 60 at predetermined timing, and a read-only memory (hereinafter referred to as "read-only memory" for storing programs or various constants, etc.). Random access memory (hereinafter referred to as RAM) 68 for temporarily storing calculation data etc. in the CPU 60, and random access memory (hereinafter referred to as RAM) 68 for backup that can maintain memory by being supplied with power from the auxiliary power supply even when the engine is stopped. A memory (hereinafter referred to as backup RAM) 70, a digital output port 72 for outputting the calculation results of the CPU 60 to the idle rotation control valve 26, injector 30, coil with igniter 52, etc. at a predetermined timing, and each of the above components. It is composed of a common bus 74 that connects devices.

The operation of the embodiment will be explained below.

First, the digital control circuit 54 calculates the intake pipe pressure PM output from the intake pipe pressure sensor 23 and the engine rotation speed NE calculated from the output of the crank angle sensor 44.
The basic injection time TP (PM, NE) is read out from the map stored in the ROM 66 in advance.

Furthermore, the fuel injection time TAU is calculated by correcting the basic injection time TP (PM, NE) using the following equation according to the signals from each sensor.

TAU=TP(PM,NE)*(1+K*F)...(1) Here, F is a correction coefficient; if F is positive, it represents an increase correction, and if F is negative, it represents a reduction. It represents a correction. Further, K is a correction magnification for further correcting the correction coefficient F, and is normally set to 1.

Fuel injection time TAU determined in this way
A fuel injection signal corresponding to this is output to the injector 30, and the injector 30 is opened for the fuel injection time TAU in synchronization with the engine rotation, and fuel is injected into the intake manifold 28 of the engine 10.

The deceleration reduction in this embodiment is performed as follows.

That is, as shown in FIG. 3, when the throttle valve 18 begins to close at time _t1 during deceleration, the intake pipe pressure PM
Prior to the decrease in the throttle valve opening, a reduction in the throttle valve opening (hereinafter referred to as TA reduction) is carried out, which is a rapid reduction correction according to the rate of decrease in the throttle valve opening TA, as shown by the solid line A in FIG. 3D. be exposed. Specifically, as shown in Fig. 4, this TA reduction is a value that is preset in accordance with the amount of change △TA in the throttle valve opening TA for each predetermined time. The value (negative value) obtained by integrating △F (solid line C in Figure 6) is the correction coefficient F,
Next, when the throttle valve opening TA becomes constant, the correction coefficient F is restored to 0 at a predetermined recovery speed ΔF' every engine rotation or every fixed period of time. Therefore, for example, the throttle valve opening TA
If becomes constant during deceleration, the state will be as shown by solid line D in Fig. 4, and on the other hand, the throttle valve opening
If the TA is closed all at once,
Similarly, a state as shown by the broken line E in FIG. 4 is reached, and the optimal weight reduction correction is performed in accordance with the rate of change and amount of change in the opening degree of the throttle valve.

In addition, in the case of sudden deceleration as shown by the broken line E in Fig. 4, the value obtained by integrating the value △F is directly used as the correction coefficient F.
If this happens, there is a possibility that the amount of fuel will be too low, resulting in over lean during deceleration. Therefore, in this embodiment, as shown by the dashed line G in FIG.
A lower limit is set for the value obtained by integrating the integrated value ΔF, so that the correction coefficient F does not fall below the lower limit value Fmin. This TA reduction program is shown in Figure 5.

Next, when the intake pipe pressure PM starts to decrease, from time _t2 , the intake pipe pressure decrease is performed to perform a highly accurate reduction correction according to the decreasing rate of the intake pipe pressure PM, as shown by the solid line B in FIG. 3D. (hereinafter referred to as PM reduction) is performed. Specifically, this PM reduction is as follows:
For example, the value (negative value) that is the sum of the values corresponding to the amount of change in intake pipe pressure PM for each predetermined time is set as the correction coefficient F, and then the correction coefficient is recovered to 0 at a predetermined recovery speed every engine rotation or every fixed time. It is done by letting

In addition, if TA weight loss and PM weight loss overlap,
If both are used together, there is a risk of excessive weight loss. Therefore, in this embodiment, as shown by the thick solid line in FIG. 3D, only the TA reduction is performed from time t ₂ to t ₃ by following the minimum values of the TA reduction and PM reduction, and
From time _t3 to time _t4 , only PM reduction is performed.

As described above, by performing deceleration weight loss by combining fast-response TA weight loss and highly accurate PM weight loss, appropriate weight loss can be achieved.
By maintaining the air-fuel ratio near the stoichiometric air-fuel ratio, it is possible to achieve both deceleration performance and exhaust gas purification performance.

In the above embodiment, the value △F, which is accumulated according to the amount of change △TA in the throttle valve opening degree TA every predetermined time, is equal to the amount of change △, as shown by the solid line C in FIG.
Although it was assumed to be a linear function of TA, the relationship between the amount of change △TA and the value △F is not limited to this, and can also be a quadratic function, as shown by the broken line H or the dashed-dotted line I in Figure 6. It is.

〔Effect of the invention〕

As explained above, according to the present invention, during deceleration, it is possible to perform an appropriate weight reduction correction that does not become excessive, depending on how the accelerator pedal is pressed, that is, both the throttle valve opening and the intake pipe pressure. By maintaining the air-fuel ratio near the stoichiometric air-fuel ratio, it is possible to achieve both good deceleration performance and exhaust gas purification performance. Therefore, even when using an intake pipe pressure type electronically controlled fuel injection device, it is possible to perform precise air-fuel ratio control. Furthermore, since the current richness degree (during deceleration) is affected by the history of deceleration, determining the reduction value based only on the current deceleration degree will not result in an appropriate value. Thus, by determining the current weight loss value in consideration of the history during deceleration, it has excellent effects such as optimal deceleration weight loss.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an intake pipe pressure type electronically controlled fuel injection device for an automobile engine in which the electronically controlled fuel injection method for an internal combustion engine according to the present invention is adopted, and FIG. FIG. 3 is a block diagram showing the configuration of the digital control circuit used in the example. FIG. 3 is a diagram showing how the reduction in deceleration occurs in the example. FIG. Diagram showing the state of deceleration loss, No. 5
FIG. 6 is a flowchart showing a program for reducing deceleration according to the rate of decrease in the throttle valve opening, and FIG. It is a diagram showing the relationship between values according to the amount of change. 10...Engine, 14...Intake temperature sensor, 1
8... Throttle valve, 20... Throttle sensor, 23
...Intake pipe pressure sensor, 30...Injector,
34... Oxygen concentration sensor, 40... Distributor, 42... Top dead center sensor, 44... Crank angle sensor, 46... Cooling water temperature sensor, 54...
Digital control circuit.

Claims (1)

[Scope of Claims] 1. A basic injection amount is determined according to the intake pipe pressure of the engine and the engine speed, and the basic injection amount is corrected during a transient period using a correction coefficient calculated according to the engine operating state. Therefore, in an electronically controlled fuel injection method for an internal combustion engine that determines the amount of fuel to be injected, during deceleration, the throttle valve opening is adjusted using a correction coefficient that is the sum of values corresponding to the amount of change in the throttle valve opening for each predetermined period. The throttle valve opening is adjusted according to the speed of decrease in the opening, and the correction coefficient is the sum of the values corresponding to the amount of change in intake pipe pressure for each predetermined period. A reduction in intake pipe pressure is performed to correct the reduction in intake pipe pressure, and a reduction correction is performed in combination with the following, and a reduction in deceleration is performed by tracing the minimum value of each reduction, and a lower limit is set for the correction coefficient for the reduction in throttle valve opening. An electronically controlled fuel injection method for internal combustion engines.