JPH0512538B2 - - 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 detects 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 reaction 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 in response to changes in both the intake pipe pressure and the intake pipe pressure, resulting in good transient response performance and exhaust gas purification performance. An object of the present invention is to provide an electronically controlled fuel injection method for an internal combustion engine that can achieve both of the following.

[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 amount of fuel to be injected, there is an after-idle increase that performs an increase correction when the idle switch is turned off during acceleration, and an after-idle increase that performs an increase correction when the idle switch is turned off during acceleration. If the throttle valve opening is large, no increase correction is performed, and the value obtained by integrating the values according to the amount of change in the throttle valve opening at predetermined time intervals within the range of the specified opening is used as a correction coefficient to adjust the increase speed of the throttle valve opening. An intake system that performs an increase correction in accordance with the rate of increase in intake pipe pressure, using a correction coefficient that is the sum of the throttle valve opening increase and the amount of change in intake pipe pressure at each predetermined time interval. The above objective is achieved by calculating the pipe pressure increase and performing accelerated increase using the maximum value among these increase values.

[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 amount is determined based on the throttle valve opening degree, the amount can be quickly increased depending on how the accelerator pedal is depressed, and the intake pipe pressure can be increased quickly until the intake pipe pressure is increased with high precision. The responsiveness of the acceleration part 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 fuel calculated by the sensor output will increase in advance, and this will result in an appropriate increase in acceleration. , it is not necessary 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, since the throttle valve opening increase has a quick response but low accuracy, if the increase is continued in accordance with the speed of increase regardless of the throttle valve opening, there is a risk of an excessive increase. Therefore, in the present invention, in a region where the throttle valve opening exceeds a predetermined opening and the next increase in intake pipe pressure is considered to be starting, the accumulation of the correction coefficient for the throttle valve opening increase is prohibited to improve accuracy. This prevents an excessive increase in the amount due to a low throttle valve opening.

【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, and an intake air temperature sensor 14 disposed in the intake passage 16 so as to open and close 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, an idle contact (switch) for detecting whether or not the throttle valve 18 is at the idle opening, and a throttle valve 18 that is proportional to the opening of the throttle valve 18. a throttle sensor 20 including a potentiometer that produces a voltage output of
, a surge tank 22 for preventing intake air interference between cylinders, and an intake pipe pressure sensor 23 for detecting intake pipe pressure from the pressure inside the surge tank 22.
a bypass passage 24 that bypasses the throttle valve 18; and a bypass passage 24 disposed in the middle of the bypass passage 24;
By controlling the opening area of the bypass passage 24, fuel is injected toward the intake port of the engine 10, which is arranged in the idle rotation control valve 26 for controlling the idle rotation speed and the intake manifold 28. 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; a three-way catalytic converter 38 provided therein, a distributor 40 having a distributor shaft that rotates in conjunction with rotation of the crankshaft of the engine 10, and the distributor built into the distributor 40. A top dead center sensor 42 and a crank angle sensor 44 output a top dead center signal and a crank angle signal according to the rotation of the shaft, and a cooling water temperature sensor 46 disposed in the engine block to detect the engine cooling water temperature.
, 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 rotation 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 number of engine steps, and this is determined 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 correcting the amount, 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 sent to the igniter 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 system for an automobile engine 10, which is equipped with 4, in the digital control circuit 54, when the idle switch of the throttle sensor 20 is turned off during acceleration and deceleration, An after-idle increase that performs a predetermined increase correction, and a change in the throttle valve opening for each predetermined period within a range where the throttle valve opening detected from the potentiometer output of the throttle sensor 20 is less than or equal to the predetermined opening. The value obtained by integrating the corresponding values is used as the correction coefficient,
The throttle valve opening increase/decrease is corrected according to the speed of change of the throttle valve opening, and the intake pipe pressure sensor 23
The intake pipe pressure increase/decrease correction is performed according to the rate of change of the 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 of the Among these increase/decrease values, the maximum value is used during acceleration and the minimum value is used during deceleration to perform acceleration increase and deceleration decrease. 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 port for the throttle sensor 20. switch, top dead center sensor 42, crank angle sensor 44, vehicle speed sensor 5
A digital input port 64 is used to input digital signals input from 0, etc. to the CPU 60 at a predetermined timing, and a read-only memory (hereinafter referred to as "read-only memory") is used to store programs or various constants.
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. Memory (hereinafter referred to as backup RAM) 70 and CPU 6
0 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 pressure sensor 23 and the engine rotation coefficient NE calculated from the output from 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, 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 acceleration amount increase and deceleration amount increase 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 LL will be referred to as "power increase") is performed to perform 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 positive predetermined value, and then setting it to zero at a predetermined damping speed for each engine rotation or for a certain period of time.
This is done by attenuating the 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 rapid 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 at each predetermined time interval, and 0 at a predetermined deceleration speed.
Furthermore, when the intake pipe pressure PM starts to increase with a delay in the increase in the throttle valve opening TA, from time _t3 ,
Intake pipe pressure increase (hereinafter referred to as PM image amount) is performed to perform a highly accurate increase correction according to the rate of increase in intake pipe pressure M, as shown by a solid line C. 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 TA decreases as shown by the solid line D in FIG. 3D, prior to the decrease in the intake pipe pressure PM. Throttle valve opening reduction (hereinafter referred to as TA reduction) is performed to perform rapid reduction correction according to the speed. Specifically, this TA reduction is performed by setting a correction coefficient F to 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, and then This is performed by recovering to 0 at a predetermined recovery rate every 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 performed, for example, by setting the correction coefficient F to a value (negative value) that is the sum of values corresponding to the amount of change in the intake pipe pressure PM every predetermined time, and then This is done by recovering to 0 at a predetermined recovery speed. In addition, 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 this embodiment, as shown by the thick solid line in FIG. 3D, only the TA reduction is performed from time _t7 to _t8 , following the minimum values of the TA reduction and PM reduction, and
From time _t8 to time _t9 , only PM reduction is performed. In addition, when increasing or decreasing the TA, the opening of the throttle valve is adjusted as shown by the broken line G in Fig. 4.
Regardless of the size of TA, if the throttle valve opening is increased or decreased according to the speed of change in the throttle valve opening, if the throttle valve is at a predetermined opening, for example 45° or more, the throttle valve opening will change. (for example, from 45° to 90°), the engine operating condition (intake pipe pressure) remains almost the same.
Although the response is quick, due to the influence of TA increase/decrease with low accuracy, there is a risk of over-increasing or under-dosing, which may have the opposite effect. Therefore, in this embodiment, the solid line H in FIG.
As shown, the throttle valve opening TA is the predetermined opening TA1,
For example, if it exceeds 45°, the throttle valve is attenuated without integrating the correction coefficient according to the speed of change of the throttle valve opening, and the throttle valve is opened only when the throttle valve opening TA is 45° or less. The correction coefficient is integrated according to the rate of change in temperature. The TA increase program in this example is the fifth one.
As shown in the figure. This makes it possible to prevent over-richness during acceleration or over-lean during deceleration due to excessive increase or under-increase when fuel correction is performed in accordance with the rate of change of the throttle valve opening. 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/or decrease deceleration, if the accelerator pedal is pressed early, a large amount of increase will be implemented; It is possible to achieve an appropriate increase or decrease depending on how the accelerator pedal is pressed, such as a small amount of increase when the pedal is depressed gradually, and maintain the air-fuel ratio near the stoichiometric air-fuel ratio to prevent transient It is possible to achieve both response performance and exhaust gas purification performance. In the above embodiment, both the acceleration image amount and deceleration reduction are performed, but it is also possible to omit the deceleration reduction.

【Effect of the invention】

As explained above, according to the present invention, during acceleration, it is possible to perform an appropriate increase correction that does not result in concentration according to changes in both the way the accelerator pedal is pressed and the intake pipe pressure, and the air-fuel ratio is changed 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,
This has the excellent effect of making it possible to perform precise air-fuel proportional 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 increase in acceleration and decrease in deceleration in the embodiment, and FIG. Similarly, FIG.
It is a flowchart which shows the program of acceleration increase according to the rate of change of throttle valve opening. 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 If the value is larger than the specified opening degree, no increase correction is performed, and the value obtained by integrating the values corresponding to the amount of change in the throttle valve opening for each specified period within the range below the specified opening is used as a correction coefficient to adjust the throttle valve opening. The throttle valve opening is increased to perform an increase correction according to the increase speed, and the value obtained by integrating the value according to the amount of change in intake pipe pressure for each predetermined period is used as a correction coefficient to perform increase correction according to the increase rate of intake pipe pressure. An electronically controlled fuel injection method for an internal combustion engine, characterized in that the intake pipe pressure increase is calculated, and the maximum value among these increase values is used to perform the acceleration increase.