JPH0372824B2 - - 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 is converted into an electrical signal representing the amount of intake air. 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 monooxygen carbon 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. In addition, in an electronically controlled fuel injection system that detects intake pipe pressure, during deceleration, unless the intake pipe pressure decreases, the amount of fuel injected will not decrease, so the air-fuel ratio will temporarily become rich and the exhaust gas will be purified. Performance was also low. Furthermore, in the conventional system, transient fuel correction based on the rate of change in engine load, etc. was performed using a single parameter. It was not possible to improve the exhaust gas purification performance by maintaining the air-fuel ratio near the air-fuel ratio. The present invention was made in order to solve the above-mentioned conventional problems, and it is necessary to adjust both the accelerator pedal depression method (i.e., the idle switch state and the throttle valve opening) and the intake pipe pressure, respectively, during acceleration and deceleration. It is possible to maintain the air-fuel ratio near the stoichiometric air-fuel ratio by making appropriate and not excessive increase/decrease corrections in response to changes in engine temperature and warm-up state of the engine. An object of the present invention is to provide an electronically controlled fuel injection method for an internal combustion engine that can achieve both transient response performance and exhaust gas purification performance.

[Means to achieve the task]

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 amount of fuel to be injected, there is an after-idle amount increase that corrects the increase when the idle switch is turned off during acceleration, and an after-idle amount increase that corrects the increase in amount when the idle switch is turned off during acceleration. Calculate the increase in throttle valve opening that is increased and then attenuated at a predetermined damping speed, and the increase in intake pipe pressure that is increased in accordance with the increase speed of intake pipe pressure and then attenuated at a predetermined damping speed. Among the increase values, the correction coefficient is calculated from the maximum value to increase the acceleration, and during deceleration, the throttle valve opening is decreased according to the decreasing speed of the throttle valve opening, and then the throttle valve opening is recovered at a predetermined recovery speed. and the intake pipe pressure reduction, which is reduced according to the reduction rate of the intake pipe pressure and then recovered at a predetermined recovery speed, and the correction coefficient is calculated from the minimum value of these reduction values to determine the deceleration reduction. In addition, when warming up the engine,
The above objective is achieved by further correcting the correction coefficient using different correction magnifications during acceleration and deceleration depending on the warm-up state of the engine.

[Effect]

In the present invention, during acceleration and deceleration, the after-idle amount increase is performed at the moment the accelerator pedal is pressed, and the after-idle amount is increased with extremely quick response (only during acceleration).
and a fast-response throttle valve opening increase or decrease, in which an increase or decrease in throttle valve opening is corrected in accordance with the rate of increase or decrease in throttle valve opening prior to an increase or decrease in intake pipe pressure, and an increase or decrease in intake pipe pressure. Since the increase or decrease correction is performed in combination with highly accurate intake pipe pressure increase or decrease, which performs increase or decrease correction according to the decrease, the response is quick and the acceleration increase is highly accurate. and deceleration reduction. 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. Furthermore, since the throttle valve opening amount is increased or decreased based on the throttle valve opening degree, the amount can be quickly increased or decreased depending on how the accelerator pedal is depressed, and the intake pipe pressure can be increased or decreased with high precision. It is possible to improve the responsiveness of the intermediate acceleration or deceleration portion until weight reduction is performed. On the other hand, the intake pipe pressure increase or decrease is performed after the intake pipe pressure changes after the throttle valve opening changes. This intake pipe pressure increase or decrease is performed based on the amount of air actually taken into the engine combustion chamber, and is highly accurate. In addition, in the case of the intake air amount sensing type, when the throttle valve is opened during acceleration or closed during deceleration, the air flow sensor output upstream of the throttle valve immediately detects an increase or decrease in the intake air amount. However, the amount of air actually drawn into the combustion chamber is
Since the increase or decrease is delayed by the amount of the surge tank downstream from the throttle valve, the fuel amount calculated by the sensor output increases or decreases in advance, and this is determined by the appropriate acceleration increase or deceleration decrease. Therefore, there is no need to increase or decrease the throttle valve opening as in the present invention. In the present invention, the acceleration increase or deceleration decrease is further performed by following the maximum or minimum value of the after-idle increase, the throttle valve opening increase/decrease, and the intake pipe pressure increase/decrease, so that the acceleration increase or deceleration decrease is performed in the area where these overlap. However, there is no possibility of over-increase or under-dose. In addition, the correction magnification for further correcting the correction coefficient according to the engine warm-up state is different during acceleration and deceleration, so that acceleration and deceleration during engine warm-up are adjusted to match each acceleration and deceleration. Increase/decrease correction can be performed.

【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 idle rotation valve 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. 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 applied to 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 sent to the igniter-equipped coil 52. a digital control circuit 5 that outputs an output and further controls the idle rotation control valve 26 during idle;
In the intake pipe pressure sensing type electronically controlled fuel injection device for an automobile engine 10 comprising:
After-idle increase is performed by increasing the amount by a predetermined amount when the idle switch of 0 is turned off, and the increase/decrease correction is performed according to the rate of increase or decrease in the throttle valve opening detected from the output of the potentiometer of the throttle sensor 20. The acceleration increase is performed by combining the throttle valve opening increase/decrease that performs and deceleration reduction, and when warming up the engine when the engine cooling water temperature output from the cooling water temperature sensor 46 is below a predetermined temperature, the acceleration amount increase and deceleration amount are increased and The correction coefficient for deceleration reduction is further corrected. 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 sensors 44, vehicle speed sensor 50
A digital input port 64 for inputting digital signals input from etc. into the CPU 60 at a predetermined timing, a read-only memory (hereinafter referred to as ROM) 66 for storing programs or various constants, etc., and calculation data in the CPU 60. Random access memory (hereinafter referred to as RAM) 68 for temporarily storing information such as the engine, etc., and Backup random access memory (hereinafter referred to as backup RAM) 70 that can be supplied with power from an auxiliary power source and retain memory even when the engine is stopped. It is composed of a digital output port 72 for outputting the calculation results in the CPU 60 to the idle rotation control valve 26, injector 30, coil with igniter 52, etc. at a predetermined timing, and a common bus 74 that connects each of the above components. ing. The effects of the embodiment will be explained below. First, the digital control circuit 54 controls 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 basic injection time TAU is calculated 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 an increase correction. represents the 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 acceleration increase and deceleration decrease in this embodiment are 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, for example, by setting a value (positive value) that is the sum of the values corresponding to the amount of change in the throttle valve opening at each predetermined time period as a correction coefficient F, and then increasing the amount at each engine revolution or at a certain time period. 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, this PM increase is performed by setting a correction coefficient F to a value (positive value) that is the sum of values corresponding to the amount of change in intake pipe pressure every predetermined time, and then , by decaying to zero at a predetermined decay rate. In addition, at this time, from time t ₂ to t ₃ , LL increase and TA
The increases overlap, and from time t ₃ to _{t 4} all increases overlap, and furthermore, from time t ₄ to t ₅ , the TA increase and PM increase overlap, but all increases are superimposed to correct the increase. If you go too far, there is a risk of over-dosing due to the influence of LL and TA increases, which have a quick response but are not accurate. 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. Next, during deceleration, when the throttle valve 18 begins to close at time _t6 , the throttle valve opening increases as shown by the solid line D in FIG.
Throttle valve opening reduction (hereinafter referred to as TA reduction) is performed to perform rapid reduction correction according to the rate of reduction of TA. Specifically, for this TA reduction, for example, a value (negative value) that is the sum of the values corresponding to the amount of change in the throttle valve opening TA every predetermined time is set as the correction coefficient F, and then This is done by recovering to 0 at a predetermined recovery speed each time. Next, when the intake pipe pressure PM starts to decrease, from time _t7 , the intake pipe pressure is reduced by performing a highly accurate reduction correction according to the decreasing rate of the intake pipe pressure PM, as shown by the solid line E in FIG. 3D. (hereinafter referred to as PM reduction) is performed. Specifically, this PM reduction is achieved by using, for example, a value (negative value) that is the sum of values corresponding to the amount of change in intake pipe pressure PM at each predetermined time as a correction coefficient, and then This is done by recovering to 0 at a predetermined recovery speed. At this time, if TA weight loss and PM weight loss overlap, there is a risk that excessive weight loss will occur if both are performed together. Therefore, in the present invention, as shown by the thick solid line in FIG. 3D, only the TA reduction is performed from time t ₇ to t ₈ by following the minimum values of the TA reduction and PM reduction, and
From time _t8 to time _t9 , only PM reduction is performed. On the other hand, during acceleration during engine warm-up when the engine cooling water temperature is below a predetermined temperature, the lower the engine cooling water temperature, the greater the leanness of the air-fuel ratio, so the acceleration amount needs to be further increased.
Furthermore, during deceleration, the lower the engine cooling water temperature, the greater the degree of enrichment of the air-fuel ratio, so it is necessary to further increase the degree of reduction in the deceleration amount. Therefore, in the present invention, the correction magnification K in equation (1) above is set as shown in FIG. 4 (K1
...During acceleration, K2...During deceleration, K1>K2), before warming up, correction magnification according to engine cooling water temperature
K1 and K2 are used to further correct the correction coefficient F for the acceleration increase and deceleration decrease. Therefore, the increase in acceleration during engine warm-up is the fifth
As shown by the broken line G in the figure, the amount is increased compared to the increase in acceleration after the end of warm-up (solid line F), and the deceleration loss during engine warm-up is also shown by the broken line I in FIG. It is further reduced compared to the subsequent deceleration reduction (solid line H). Therefore, it is possible to perform good air-fuel ratio control not only after the engine has warmed up, but also during the engine warm-up. The accelerated dose increase program in this example is the sixth one.
Similarly, FIG. 7 shows a deceleration reduction program. As described above, LL dose increase with extremely quick response,
By combining fast-response TA increase/decrease and highly accurate PM increase/decrease to increase acceleration and deceleration, a large amount of increase is achieved when the accelerator pedal is pressed early, while a large amount is increased when the accelerator pedal is depressed. It is possible to achieve an appropriate increase in acceleration or decrease in deceleration depending on how the accelerator pedal is pressed, such as a small increase in the amount when the accelerator pedal is depressed gradually, and maintain the air-fuel ratio near the stoichiometric air-fuel ratio and It is possible to achieve both response performance and exhaust gas purification performance. In the present invention, since the correction magnification according to the engine cooling water temperature is different during acceleration and deceleration, it is possible to perform air-fuel ratio control closer to the required characteristics of the engine. In the above embodiment, the engine warm-up state was detected from the engine cooling water temperature, but the method for detecting the engine warm-up state is not limited to this. Of course, it is also possible to detect the engine warm-up state from the elapsed time and the like.

【Effect of the invention】

As explained above, according to the present invention, an appropriate increase/decrease correction that does not result in temperature is made in accordance with changes in both the way the accelerator pedal is pressed and the intake pipe pressure, and the engine warm-up state, commensurate with each other during acceleration and deceleration. The air-fuel ratio can be maintained near the stoichiometric air-fuel ratio, and both good transient response performance and exhaust gas purification performance can be achieved regardless of the warm-up state of the engine. 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 drawings]

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 how the acceleration amount increases and deceleration decreases in the embodiment, and FIG. , a diagram showing an example of the relationship between the engine cooling water temperature and the correction magnification of acceleration increase and deceleration decrease; FIG. FIG. 6 is a flowchart showing a program for increasing acceleration and FIG. 7 is a flowchart showing a program for reducing deceleration. 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 to be injected is determined by Calculate the throttle valve opening increase that is increased according to the rate of increase in intake pipe pressure and then attenuated at a predetermined damping speed, and the intake pipe pressure increase that is increased according to the increase rate of intake pipe pressure and then attenuated at a predetermined damping speed. Then, among these increase values, the correction coefficient is determined from the maximum value, and the throttle valve is increased during acceleration, and during deceleration, the throttle valve opening is decreased according to the decreasing speed of the throttle valve opening, and then the throttle valve is restored at a predetermined recovery speed. Calculate the opening reduction and the intake pipe pressure reduction, which is reduced according to the reduction rate of the intake pipe pressure and then recovered at a predetermined recovery speed, and calculate the correction coefficient from the minimum value among these reduction values. The electronically controlled fuel for an internal combustion engine is characterized in that the correction coefficient is further corrected at a correction magnification that differs during acceleration and deceleration, depending on the engine warm-up state, when the engine is warmed up. Injection method.