JPH059620B2 - - 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 suitable for use in an automobile internal combustion engine equipped with an electronically controlled fuel injection device. An electronically controlled fuel injection method for an internal combustion engine, which determines the fuel injection amount by determining the injection amount and, during transient periods, correcting the basic injection amount using a correction coefficient calculated according to the engine operating state. Regarding improvements.

[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 engine cylinders or one engine cylinder, and the valve opening time of the injector is adjusted depending on the operating state of the engine. By controlling this, an air-fuel mixture with a predetermined air-fuel ratio is supplied to the engine combustion chamber. These electronically controlled fuel injection devices can be roughly divided into so-called intake air amount sensing type electronically controlled fuel injection devices that calculate the basic injection amount according to the engine's intake air amount and engine speed, and There is a so-called intake pipe pressure sensing type electronically controlled fuel injection system that determines a basic injection amount according to pipe pressure and engine speed. 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. In this intake air sensing type electronically controlled fuel injection system, in order to ensure drivability and exhaust gas purification performance during acceleration, the correction coefficient is increased during acceleration, and then damped at a predetermined damping speed. Accelerated increase in dosage is performed. In this acceleration increase, the attenuation speed of the acceleration increase is switched to a low speed in the middle of decay in accordance with the required engine characteristics, but conventionally, the switching was performed after a predetermined period of time had elapsed after the end of acceleration. In particular, when the correction coefficient is further increased by a predetermined correction factor in order to improve acceleration performance during engine warm-up, the damping speed is switched too quickly to a low speed, resulting in an excessive increase in the amount after switching. As a result, the air-fuel ratio sometimes became overrich. On the other hand, the latter electronically controlled fuel injection system that detects intake pipe pressure has the advantage that it can be constructed at a lower cost than the former.

[Problem to be solved by the invention]

However, the control accuracy of the air-fuel ratio is low, and especially during acceleration, the fuel injection amount cannot be increased unless the intake pipe pressure increases, so the air-fuel ratio temporarily becomes lean, resulting in poor acceleration performance. It was hot. In order to solve these problems, conventionally the acceleration was increased according to the pulse train output from a comb-like sensor installed in the throttle valve, but in order to improve drivability, In this case, the amount of increase must be very large, and in that case, the air-fuel ratio becomes overrich, the amount of carbon monoxide in the exhaust gas increases abnormally, and the air-fuel ratio is changed to a three-way catalytic converter. could not be maintained within a suitable predetermined range. 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, in the past, it was thought that it would be difficult to use an electronically controlled fuel injection system that senses intake pipe pressure in an automobile engine that requires precise control of the air-fuel ratio and that takes measures to purify exhaust gas. It was getting worse. The present invention was made to solve the above-mentioned conventional problems, and it is possible to determine how the accelerator pedal is pressed (i.e., the state of the idle switch and the opening degree of the throttle valve) during acceleration.
It is possible to maintain the air-fuel ratio near the stoichiometric air-fuel ratio by making appropriate and not excessive increase corrections commensurate with both the intake pipe pressure and the change in engine required characteristics due to the engine warm-up state. Then,
An object of the present invention is to provide an electronically controlled fuel injection method for an internal combustion engine that can achieve both good transient response 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, the after-idle amount increase is performed by increasing a correction coefficient when an idle switch is turned off during acceleration, and then attenuating at a predetermined decay speed; By setting a value obtained by integrating values corresponding to the amount of change in the throttle valve opening for each predetermined period as a correction coefficient, the correction coefficient is increased according to the increasing speed of the throttle valve opening, and then at a predetermined damping speed. The correction coefficient is increased according to the rate of increase in the intake pipe pressure by using the sum of the values corresponding to the increase in the opening of the throttle valve to be damped and the amount of change in the intake pipe pressure every predetermined period as a correction coefficient. Next, an increase in intake pipe pressure to be attenuated at a predetermined attenuation speed is calculated, and among these increase values, the maximum value is used to perform an acceleration increase. When the attenuation reaches a predetermined level that changes accordingly, the attenuation speed is switched to a low speed,
The above objective has been achieved.

[Effect]

In the present invention, during acceleration, the after-idle amount increase is performed at the moment the accelerator pedal is pressed, and the after-idle amount increases with extremely quick response.The amount is also increased in accordance with the rate of increase in the throttle valve opening prior to the increase in intake pipe pressure. Since the increase correction is performed by combining the throttle valve opening increase with a quick response, which performs the Acceleration increase can be performed quickly and with high precision. In other words, although the after-idle increase has an extremely quick response, it is not possible to determine how much acceleration the engine is accelerating.
Only estimated corrections can be made, and it is not possible to increase the amount by a large amount in order to prevent over-richness. In addition, since the throttle valve opening is increased based on the throttle valve opening, it can be quickly increased depending on how the accelerator pedal is pressed, and the intake pipe pressure can be increased with high accuracy. The responsiveness of the intermediate acceleration portion can be improved. On the other hand, the intake pipe pressure increase is performed after the intake pipe pressure changes after the throttle valve opening changes. This intake pipe pressure increase is performed based on the amount of air actually taken into the engine combustion chamber, and is highly accurate. In the case of the intake air amount sensing type, when the throttle valve is opened during acceleration, the air flow sensor output upstream of the throttle valve immediately detects an increase in the amount of intake air, whereas Since the increase in the amount of air caused by the throttle valve is delayed by the amount of the surge tank downstream from the throttle valve, the amount of fuel calculated from the sensor output increases in advance, and this becomes an appropriate increase in acceleration. Therefore, there is no need to increase the throttle valve opening as in the present invention. In the present invention, the acceleration increase is further performed by following the maximum values of the after-idle increase, the throttle valve opening increase, and the intake pipe pressure increase.
Even in the area where these overlap, the amount will not be increased excessively. Furthermore, during the attenuation, when the correction coefficient attenuates to a predetermined level that changes depending on the engine warm-up state, the attenuation speed is switched to a low speed, so that changes in engine required characteristics due to the engine warm-up state are avoided. Appropriate acceleration increases commensurate with the

【Example】

Embodiments of the present invention will be described in detail below with reference to the drawings. An embodiment of the intake pipe pressure sensing type electronically controlled fuel injection device in which the electronically controlled fuel injection method for an internal combustion engine according to the present invention is adopted is as shown in FIGS. 1 and 2. 12 and
An intake temperature sensor 14 for detecting the temperature of the intake air taken in from the air cleaner 12 is disposed in the intake passage 16, and opens and closes in conjunction with an accelerator pedal (not shown) disposed in the driver's seat. A throttle valve 18 for controlling the flow rate of intake air, and an idle contact (switch) for detecting whether or not the throttle valve 18 is at an idle opening.
and a throttle sensor 2 including a potentiometer that generates a voltage output proportional to the opening degree of the throttle valve 18.
0, a surge tank 22 for preventing intake air interference between cylinders, and an intake pipe pressure sensor 2 for detecting intake pipe pressure from the pressure inside the surge tank 22.
3, a bypass passage 24 that bypasses the throttle valve 18, and an idler 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. Rotation control valve 26 and intake manifold 2
an injector 30 disposed at 8 for injecting fuel toward the intake port of the engine 10;
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 a three-way catalyst disposed midway in the exhaust pipe 36 on the downstream side of the exhaust manifold 32. a converter 38; a distributor 40 having a distributor shaft that rotates in conjunction with the rotation of the crankshaft of the engine 10; A top dead center sensor 42 and a crank angle sensor 44 that output a dead center signal and a crank angle signal, a cooling water temperature sensor 46 disposed in the engine block to detect the engine cooling water temperature, and an output shaft of the transmission 48. The vehicle speed sensor 50 detects the running speed of the vehicle based on the rotation speed of the engine, and the engine speed is determined based on the engine rotation speed determined from the intake pipe pressure output from the intake pipe pressure sensor 23 and the output of the crank angle sensor 44. By determining the basic injection amount per hour and correcting this according to the output of the throttle sensor 20, the air-fuel ratio of the output of the oxygen concentration sensor 34, the engine coolant temperature of the output of the coolant temperature sensor 46, etc. It determines the fuel injection amount and outputs a valve opening time signal to the injector 30, determines the ignition timing according to the engine operating state and outputs an ignition signal to the igniter-equipped coil 52, and further, In the intake pipe pressure sensing type electronically controlled fuel injection system for the automobile engine 10, which is equipped with a digital control circuit 54 that controls the rotation control valve 26, in the digital control circuit 54, changes in the idle switch of the throttle sensor 20 are performed. during acceleration, the throttle valve opening degree detected from the potentiometer output of the throttle sensor 20, and the intake pipe pressure detected from the output of the intake pipe pressure sensor 23. Acceleration is increased by increasing the correction coefficient and then damping it at a predetermined damping speed. The damping speed is switched to a low speed. 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 to the CPU 60; and an idle switch for the throttle sensor 20; Top dead center sensor 42, crank angle sensor 44, vehicle speed sensor 50
A digital input port 64 is used to input digital signals input from other devices into the CPU 60 at predetermined timing, and a read-only memory (hereinafter referred to as ROM) is used to store programs or various constants.
) 66, a random access memory (hereinafter referred to as RAM) 68 for temporarily storing calculation data etc. in the CPU 60, and a backup random access memory that can be supplied with power from an auxiliary power source and retain memory even when the engine is stopped. (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-mentioned components. and a common bus 74 that connects between the two. The effects 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.
Accordingly, the basic injection time TP (PM, NE) is read 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; if F is negative, Represents weight loss 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, 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 accelerated increase in amount in this embodiment is performed as follows. That is, as shown in FIG. 3, the accelerator pedal is depressed during acceleration, and the idle switch of the throttle sensor 20 is activated at time t ₁ as shown in FIG. 3A.
When it turns off, the throttle valve opening TA and intake pipe pressure
Prior to the increase in PM, after-idle power increase (hereinafter referred to as LL power increase) is performed, which performs extremely rapid power increase correction, as shown by the solid line A in FIG. 3D. Specifically, this LL increase is performed by, for example, first setting the correction coefficient F to a predetermined positive value, and then attenuating it to 0 at a predetermined damping speed every engine rotation or every fixed time. . Next, the throttle valve 18 is further opened, and when the throttle valve opening TA detected from the potentiometer output of the throttle sensor 20 starts to rise at time _t2 as shown in FIG. 3B, the intake pipe pressure increases. Prior to the increase in PM, as shown by the solid line B in Figure 3D, the throttle valve opening is increased (hereinafter referred to as TA increase), which performs a rapid increase correction according to the rate of increase in the throttle valve opening TA. It will be done. Specifically, this TA increase is performed by setting the correction coefficient F to a value (positive value) that is the sum of the values corresponding to the amount of change in the throttle valve opening TA every predetermined time, and The damping speed is set to 0 at predetermined damping speeds ΔF ₁ and ΔF ₂ (ΔF ₁ >ΔF ₂ ), which is fast until a predetermined level L that changes according to the engine cooling water temperature, and slow after reaching the predetermined level L. It is done by folding. Furthermore, when the intake pipe pressure PM begins to increase with a delay in the increase in the throttle valve opening TA, from time t ₃ , Fig. 3D
As shown by a solid line C, an intake pipe pressure increase (hereinafter referred to as PM increase) is performed that performs a highly accurate increase correction according to the rate of increase in intake pipe pressure PM. Specifically, this PM increase is performed, for example, by setting the correction coefficient F to a value (positive value) that is the sum of values corresponding to the amount of change in intake pipe pressure PM at each predetermined time interval, and By damping down to 0 at predetermined damping speeds ΔF ₁ and ΔF ₂ (ΔF ₁ >ΔF ₂ ), which are fast up to a predetermined level L that changes according to the engine cooling water temperature, and slow after reaching the predetermined level L. It is carried out with Correction coefficient F for the TA increase and PM increase
The switching of the damping speed is performed at a relatively low predetermined level L ₁ as shown by the solid line D in FIG.
When the engine is warming up and the engine cooling water temperature is low, as shown by the solid line E in Fig. 4, the control is performed at a relatively high predetermined level _L2 . Accelerated increase in dosage is carried out. A program for attenuating the correction coefficient F for this acceleration increase is shown in FIG. On the other hand, in the conventional electronically controlled fuel injection system that detects the amount of intake air, regardless of the warm-up state of the engine, the fuel injection device
Since the damping speed was switched to a low speed at _t5 ), the acceleration increase characteristics during engine warm-up were as follows.
The result is as shown by the broken line F in FIG. 4, where the shaded area represents an excessive increase in fuel consumption and the air-fuel ratio becomes overrich. Note that from time t ₂ to _{t 3} , the LL increase and TA increase overlap, from time t ₃ to _{t 4} , all the increases overlap, and furthermore, from time t ₄ to t ₆ , the TA increase and PM increase overlap. However, if all the increases are superimposed and the increase correction is performed, the response is fast but the accuracy is not good.
Due to the effects of increasing LL and TA, there is a risk of overdosing. Therefore, in the present invention, as shown by the thick solid line in FIG. 3D, the accelerated increase is performed by following the maximum values of the LL increase, TA increase, and PM increase. As mentioned above, LL increase with extremely quick response,
By combining a quick response TA increase and a highly accurate PM increase to increase acceleration, a large amount is increased when the accelerator pedal is applied early, while a large amount is increased when the accelerator pedal is gradually depressed. It is possible to realize an appropriate increase in fuel volume depending on how the accelerator pedal is pressed, such as a small increase in fuel volume, and maintain the air-fuel ratio near the stoichiometric air-fuel ratio, achieving both transient response performance and exhaust gas purification performance. be able to. In the above embodiment, the engine warm-up state is detected from the engine cooling water temperature, but the method for detecting the engine warm-up state is not limited to this. It is also possible to detect from the later elapsed time. In addition, in the above example, TA increase and PM
During the decay of the increase, when the same predetermined level is reached,
It was designed to switch the damping speed, but depending on the required characteristics of the engine, the switching level of the damping speed can be changed by increasing the TA amount and the PM amount, or even by increasing the LL amount. It is possible to do so.

【Effect of the invention】

As explained above, according to the present invention, it is possible to perform an appropriate and not excessive increase correction commensurate with changes in engine required characteristics due to both the way the accelerator pedal is depressed and the intake pipe pressure, and the engine warm-up state. The air-fuel ratio can be maintained near the stoichiometric air-fuel ratio,
It is possible to achieve both good transient response performance and exhaust gas purification performance. Therefore, even when using an electronically controlled fuel injection device that senses intake pipe pressure, there is an excellent effect in that precise air-fuel ratio control can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an intake pipe pressure sensing 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 embodiment, FIG. 3 is a diagram showing the acceleration increase in the embodiment, and FIG. 4 is a diagram showing the attenuation of the acceleration increase. FIG. 5 is also a flowchart showing the program for the attenuation of the acceleration increase. 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. The basic injection amount is determined according to the engine intake pipe pressure and the engine speed, and during transient periods, the basic injection amount is corrected using a correction coefficient calculated according to the engine operating state. In an electronically controlled fuel injection method for an internal combustion engine in which the amount of fuel injection is determined by The correction coefficient is increased according to the rate of increase in the throttle valve opening, and then the correction coefficient is increased according to the rate of increase in the throttle valve opening, and then the correction coefficient is increased according to the rate of increase in the throttle valve opening. By setting the correction coefficient as a value that is the sum of the increase in throttle valve opening that is attenuated by the damping speed and the amount of change in intake pipe pressure for each predetermined period, the correction coefficient can be adjusted according to the rate of increase in intake pipe pressure. The intake pipe pressure is increased, and then the intake pipe pressure is attenuated at a predetermined attenuation speed. Among these increase values, the maximum value is used to increase the intake pipe pressure during acceleration. An electronically controlled fuel injection method for an internal combustion engine, characterized in that the attenuation speed is switched to a low speed when the attenuation reaches a predetermined level that changes depending on the machine state.