JPH057546B2 - - 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 particularly to an engine intake pipe pressure and engine rotation method suitable for use in an automobile internal combustion engine equipped with an intake pipe pressure sensing type electronically controlled fuel injection device. In this internal combustion engine, the basic injection amount is determined according to the number of fuel injections, and the fuel injection amount is determined by correcting the basic injection amount using a correction coefficient calculated according to the engine operating state during transient times. This invention relates to improvements in electronically controlled fuel injection methods.

[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 the air-fuel mixture, a mixture having 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. However, in this electronically controlled fuel injection system that senses the amount of intake air, the amount of intake air changes by about 50 times between idle and high load, and has a wide dynamic range, so it converts the amount of intake air into an electrical signal. Not only does this result in lower accuracy when calculating, but if the calculation accuracy in the digital control circuit at the subsequent stage is to be increased, the bit length of the electrical signal becomes longer, requiring the use of an expensive computer as the digital control circuit. Furthermore, in order to detect the amount of intake air, it is necessary to use a sensor having 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 electronically controlled fuel injection device that detects intake pipe pressure, the amount of change in intake pipe pressure is 2 to 2.
Since the dynamic range is narrow, about 3 times as much, 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 an electronically controlled fuel injection system that senses the amount of intake air, the control accuracy of the air-fuel ratio is lower, and especially during acceleration, the amount of fuel injected does not increase unless the intake pipe pressure increases, so the air-fuel ratio was temporarily lean, resulting in poor acceleration performance. 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 has been made to solve the above-mentioned conventional problems, and the present invention performs an appropriate and not excessive increase correction in response to changes in both the way the accelerator pedal is pressed and the intake pipe pressure during acceleration. It is an object of the present invention to provide an electronically controlled fuel injection method for an internal combustion engine that can maintain a fuel ratio near the stoichiometric air-fuel ratio, thereby achieving 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 speed, and when excessive, corrects the basic injection amount using a correction coefficient calculated according to the engine operating condition. In an electronically controlled fuel injection method for an internal combustion engine that determines the amount of fuel to be injected, there is an after-idle amount increase that performs an increase correction when the idle switch is turned off during acceleration, and the amount of change in the throttle valve opening for each predetermined period. The value obtained by integrating the values according to is used as the correction coefficient,
The rate of increase in intake pipe pressure is calculated using the correction coefficient, which is the sum of the throttle valve opening increase, which performs an increase correction according to the increase rate of the throttle valve opening, and the amount of change in intake pipe pressure for each predetermined period. Calculate the intake pipe pressure increase to perform the increase correction according to the increase value, perform the acceleration increase using the maximum value among these increase values, and at least set an upper limit on the correction coefficient of the intake pipe pressure increase. , 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 a fast-response increase in the throttle valve opening, which performs the It is possible to quickly and accurately increase the amount of acceleration. 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, if the correction coefficient is accumulated as it is during full acceleration where acceleration continues, even if the intake pipe pressure is increased with high accuracy, there is a risk that the amount will be increased excessively. Therefore, in the present invention, at least an upper limit is set on the correction coefficient for the intake pipe pressure increase to prevent such an excessive increase during full acceleration.

【Example】

Embodiments of the present invention will be described in detail below with reference to the drawings. As shown in FIGS. 1 and 2, an embodiment of the intake pipe pressure sensing 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. Air cleaner 12,
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 28
an injector 30 for injecting fuel toward the intake port of the engine 10, and an oxygen concentration sensor for detecting the air-fuel ratio from the residual oxygen concentration in the exhaust gas, located in the exhaust manifold 32. A distributor having a sensor 34, a three-way catalytic converter 38 disposed in the middle of an exhaust pipe 36 downstream of the exhaust manifold 32, and a distributor shaft that rotates in conjunction with the rotation of the crankshaft of the engine 10. 40, a top dead center sensor 42 and a crank angle sensor 44, which are built in the distributor 40 and output a top dead center signal and a crank angle signal in accordance with the rotation of the distributor shaft, and a top dead center sensor 42 and a crank angle sensor 44, which are installed in the engine block. A cooling water temperature sensor 4 is installed to detect the engine cooling water temperature.
6, a vehicle speed sensor 50 for detecting the running speed of the vehicle from the rotation speed of the output shaft of the transmission 48, and an engine that is determined from the intake pipe pressure output from the intake pipe pressure sensor 23 and the output from the crank angle sensor 44. The basic injection amount per engine stroke is determined according to the rotational speed, and this is used as the output of the throttle sensor 20, the air-fuel ratio of the oxygen concentration sensor 34 output, the engine cooling water temperature of the cooling water temperature sensor 46 output, etc. The fuel injection amount is determined by correcting it accordingly, 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. , further comprising a digital control circuit 54 that controls the idle rotation control valve 26 during idle.
In the intake pipe pressure sensing type electronically controlled fuel injection system for an automobile engine 10, the digital control circuit 54 increases the amount by a predetermined amount when the idle switch of the throttle sensor 20 is turned off during acceleration. The throttle valve opening is determined using a correction coefficient that is the sum of the after-idle increase to be corrected and the amount of change in the throttle valve opening detected from the potentiometer output of the throttle sensor 20 for each predetermined period. and the intake pipe pressure sensor 23.
Calculates the intake pipe pressure increase amount, which performs an increase correction according to the rate of increase in intake pipe pressure, using the value obtained by integrating the values corresponding to the amount of change in the intake pipe pressure detected from the output at each predetermined time as a correction coefficient. Among these increase values, the maximum value is used to perform accelerated increase. 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 advance in the ROM 66. 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, 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 certain period of time. . Next, the throttle valve 18 is further opened, and the throttle valve opening degree TA detected from the potentiometer output of the throttle sensor 20 becomes as shown in FIG. 3B.
When the rise starts at time _t2 , the throttle valve performs a quick increase correction according to the rate of increase in the throttle valve opening TA, as shown by the solid line B in FIG. 3D, prior to the increase in the intake pipe pressure PM. Opening increase (hereinafter referred to as TA increase)
will be held. 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 then This is done by damping down to zero at a predetermined damping rate. 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, as shown in FIG.
According to the change amount ΔPM, a preset value ΔF (solid line D in Figure 6) is integrated, the value (positive value) is set as a correction coefficient F, and then the intake pipe pressure is
When PM becomes constant, the correction coefficient F is attenuated to 0 at a predetermined attenuation speed ΔF' every engine rotation or every fixed period of time. Therefore, for example, if the throttle valve opening TA becomes constant during acceleration, the state will be as shown by the solid line E in Fig. 4, but on the other hand, if the throttle valve opening TA becomes fully open all at once. In this case, a state as shown by the broken line F in FIG. 4 is reached, and an optimal increase correction is performed in accordance with the rate and amount of change in the intake pipe pressure. In addition, in the case of full acceleration where the acceleration continues as shown by the broken line F in Fig. 4, if the value obtained by integrating the value ΔF is used as the correction coefficient F, the amount will be increased excessively, resulting in overrichness during acceleration. there is a possibility. Therefore, in the present invention, as shown by the dashed line G in FIG. 4, an upper limit is set on the value of the integrated value ΔF,
The correction coefficient F is kept from exceeding the upper limit value Fmax. This PM increase program is shown in FIG. It should be noted 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 ₅ , 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 quick response TA increase and highly accurate PM increase to increase acceleration, a large amount of increase is achieved when the accelerator pedal is depressed quickly, while a large amount is increased when the accelerator pedal is depressed gradually. It is possible to perform an appropriate acceleration increase depending on how the accelerator pedal is pressed, such as a small amount increase, and maintain the air-fuel ratio near the stoichiometric air-fuel ratio, achieving both transient response performance and exhaust gas purification performance. can do. In addition, in the above embodiment, the intake pipe pressure PM
The value ΔF, which is accumulated according to the amount of change ΔPM for each predetermined time, was assumed to be a linear function of the amount of change ΔPM, as shown by the solid line D in FIG. 6, but the relationship between the amount of change ΔPM and the value ΔF is The function is not limited to this, and it is also possible to use a quadratic function as shown by the broken line H or the dashed-dotted line I in FIG.

【Effect of the invention】

As explained above, according to the present invention, during acceleration, it is possible to perform appropriate and not excessive increase correction according to changes in both the way the accelerator pedal is pressed and the intake pipe pressure, and the air-fuel ratio is adjusted to the stoichiometric air-fuel ratio. By maintaining it in the vicinity, 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,
It has excellent curing properties that enable precise air-fuel ratio control.

[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 rate of increase in intake pipe pressure. Figure 5 is a line diagram showing how the amount of acceleration increases depending on the rate of increase in intake pipe pressure, and Figure 6 is a flowchart showing a program of increasing amount of acceleration depending on the rate of increase in intake pipe pressure.
The figure is a diagram showing the relationship between the amount of change in intake pipe pressure every predetermined time and the integrated value, which is used in the embodiment. 10...Engine, 14...Intake temperature sensor, 18...
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 to be injected is determined by Throttle valve opening increase, which performs an increase correction according to the rate of increase in throttle valve opening, using the value obtained by integrating the values corresponding to the amount of change in the throttle valve opening as a correction coefficient; and The integrated value is used as a correction coefficient to calculate the intake pipe pressure increase that is corrected according to the rate of increase in intake pipe pressure, and among these increase values, the maximum value is used to perform accelerated increase, An electronically controlled fuel injection method for an internal combustion engine, characterized in that at least an upper limit is set for the correction coefficient for the intake pipe pressure increase.