JPH0423098B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Industrial Application] The present invention relates to an electronically controlled fuel injection method for an internal combustion engine, and particularly to an engine suitable for use in an automobile internal combustion engine equipped with an electronically controlled fuel injection device that senses intake pipe pressure. The basic injection amount is determined according to the intake pipe pressure and engine speed, and during transient periods, the basic injection amount is corrected using a correction coefficient calculated according to the engine operating condition to adjust the fuel injection amount. The present invention relates to an improvement in an electronically controlled fuel injection method for an internal combustion engine.

[Conventional technology]

2. Description of the Related Art One of the methods for supplying an air-fuel mixture at a predetermined air-fuel ratio to the combustion chamber of an internal combustion engine such as an automobile engine uses an electronically controlled fuel injection device. In this method, an injector for injecting fuel into the engine is installed in the intake manifold or throttle body of the engine, for example, in several or one engine cylinder, and the valve opening time of the injector is adjusted depending on the operating state of the engine. By controlling the air-fuel mixture, a mixture having a predetermined air-fuel ratio is supplied to the engine combustion chamber. 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 measure the amount of intake air, it is necessary to use a measuring device 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 device that senses the amount of intake air, the control accuracy of the air-fuel ratio is lower, and especially during deceleration, the amount of fuel injected does not decrease unless the intake pipe pressure decreases, so the air-fuel ratio becomes temporarily overrich, which not only reduces deceleration performance but also increases the amount of carbon monoxide in the exhaust gas, making it difficult to maintain the air-fuel ratio within a predetermined range suitable for the three-way catalytic converter. It was difficult. This is the same even when the fuel injection amount is feedback-controlled in accordance with the output signal of the oxygen concentration sensor disposed downstream of the exhaust gas because the response speed 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 in order to eliminate the above-mentioned drawbacks of the conventional technology.The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional technology. It is an object of the present invention to provide an electronically controlled fuel injection method for an internal combustion engine that can maintain an air-fuel ratio near the stoichiometric air-fuel ratio, thereby achieving both good deceleration performance and exhaust gas purification performance. .

[Means to solve the problem]

The present invention calculates the basic injection amount according to the engine intake pipe pressure and engine rotation speed, and during transient periods, corrects the basic injection amount using a correction coefficient calculated according to the engine operating state. In an electronically controlled fuel injection method for an internal combustion engine that determines the amount of fuel to be injected, during deceleration, a correction coefficient is reduced in accordance with the rate of decrease in throttle valve opening, and then the correction coefficient is restored at a predetermined recovery rate. Performing a reduction correction that combines a reduction in the throttle valve opening to reduce the intake pipe pressure, and a reduction in the intake pipe pressure in which the correction coefficient is reduced in accordance with the reduction rate of the intake pipe pressure, and then the correction coefficient is restored at a predetermined recovery speed, The deceleration reduction is performed by following the minimum value of the correction coefficient for each reduction, and during the recovery, when the correction coefficient has recovered to a predetermined level that becomes low when the engine is low temperature, the recovery speed is switched to a low speed, The above objective has been achieved.

[Effect]

In the present invention, during deceleration, the reduction in throttle valve opening is corrected in accordance with the rate of decrease in the throttle valve opening prior to the decrease in intake pipe pressure, and the reduction in throttle valve opening is performed in accordance with the rate of decrease in intake pipe pressure. Since the reduction correction is performed in combination with the intake pipe pressure reduction with high precision, which performs the reduction correction, the response is quick and the deceleration reduction can be performed with high precision. That is, since the reduction in the throttle valve opening is performed based on the throttle valve opening, the reduction can be quickly performed in accordance with how the accelerator pedal is depressed, and the amount of time needed to reduce the intake pipe pressure with high accuracy is achieved. The responsiveness of the intermediate deceleration portion can be improved. On the other hand, the intake pipe pressure reduction is performed after the intake pipe pressure changes after the throttle valve opening changes. This intake pipe pressure reduction is performed based on the amount of air actually taken into the combustion chamber, and is highly accurate. In addition, in the case of the intake air amount sensing type, when the throttle valve is closed during deceleration, the sensor output upstream of the throttle valve immediately detects a decrease in the amount of intake air; Since the amount of air is reduced by the amount of the surge tank downstream of the throttle valve, the amount of fuel calculated by the sensor output decreases in advance, and this results in an appropriate reduction in deceleration. There is no need to reduce the throttle valve opening as in the present invention. In the present invention, the deceleration reduction is further performed by following the minimum value of the correction coefficient for the throttle valve opening reduction and the intake pipe pressure reduction, so that even in a region where the two overlap, an excessive reduction does not occur. Furthermore, as the engine temperature is lower, the amount of fuel adhering to the intake pipe wall increases, so the deceleration loss needs to be increased compared to when the engine temperature is high. Therefore, even if the minimum value of the deceleration loss is made smaller as the engine temperature decreases, if the predetermined level at which the recovery speed is switched is constant regardless of the engine temperature, overrichness will occur in the latter half of the deceleration period. In contrast, in the present invention, during recovery from weight loss,
When the correction coefficient recovers to a predetermined level that is low when the engine temperature is low, the recovery speed is switched to a low speed, so that it is possible to perform an appropriate weight loss correction commensurate with changes in engine required characteristics due to engine temperature. .

【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 employing the electronically controlled fuel injection method for an internal combustion engine according to the present invention is as shown in FIGS. 1 and 2. 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, an idle contact and a throttle valve 1 for detecting whether or not the throttle valve 18 is at an idle opening degree.
A throttle sensor 20 including a potentiometer that generates a voltage output proportional to the opening of the cylinder 8, and a surge tank 22 for preventing intake air interference between cylinders.
, an intake pipe pressure sensor 23 for detecting intake pipe pressure from the pressure in the surge tank 22, and a bypass passage 24 that bypasses the throttle valve 18.
an idle rotation control valve 26 disposed in the middle of the bypass passage 24 to control the idle rotation speed by controlling the opening area of the bypass passage 24; and an idle rotation control valve 26 disposed in the intake manifold 28. An injector 30 for injecting fuel toward the intake port of the engine 10, and an oxygen concentration sensor 34 disposed in the exhaust manifold 32 for detecting the air-fuel ratio from the residual oxygen concentration in the exhaust gas.
and an exhaust pipe 36 downstream of the exhaust manifold 32.
a three-way catalytic converter 38 disposed in the middle of the
A distributor 40 has a distributor shaft that rotates in conjunction with the rotation of the crankshaft of the engine 10, and a top dead center signal and A top dead center sensor 42 and a crank angle sensor 44 that output a crank angle signal, a cooling water temperature sensor 46 disposed in the engine block for detecting engine cooling water temperature, and a transmission 4
A vehicle speed sensor 50 for detecting the running speed of the vehicle from the rotation speed of the output shaft of No. 8; The basic injection amount per engine stroke is determined, and this is calculated as the output of the throttle sensor 20,
Determine the fuel injection amount by correcting it according to the air-fuel ratio output from the oxygen concentration sensor 34, the engine cooling water temperature output from the cooling water temperature sensor 46, etc., and output a valve opening time signal to the injector 30;
Further, it determines the ignition timing according to the engine operating state and outputs an ignition signal to the igniter-equipped coil 52,
Furthermore, during idle, the idle rotation control valve 26
In the intake pipe pressure sensing type electronically controlled fuel injection device for an automobile engine 10, the digital control circuit 54 is configured to control a digital control circuit 54.
During deceleration, the correction coefficient is decreased in accordance with the decreasing speed of the throttle valve opening detected from the potentiometer output of the throttle sensor 20, and then,
Reducing the throttle valve opening to recover the correction coefficient at a predetermined recovery speed, decreasing the correction coefficient in accordance with the rate of decrease in intake pipe pressure detected from the output of the intake pipe pressure sensor 23, and then recovering the correction coefficient at a predetermined speed. A reduction correction is performed in combination with an intake pipe pressure reduction that restores the correction coefficient at speed, and the deceleration reduction is performed by following the minimum value of the correction coefficient for each reduction. When the recovery speed reaches a predetermined level, which sometimes becomes low, the recovery 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 temperature absorption sensor 14, the potentiometer of the throttle sensor 20, and the intake pipe pressure sensor 2.
3. An analog input port 62 with a multiplexer for converting analog signals input from the oxygen concentration sensor 34, cooling water temperature sensor 46, etc. into digital signals and sequentially inputting them into the CPU 60; and an idle contact point of the throttle sensor 20; Top dead center sensor 4
2. A digital input port 64 for inputting digital signals input from the crank angle sensor 44, vehicle speed sensor 50, etc. to the CPU 60 at a predetermined timing, and a read-only memory (hereinafter referred to as "read-only memory" for storing programs or various constants, etc.). Random access memory (hereinafter referred to as RAM) 68 for temporarily storing calculation data etc. in the CPU 60, and random access memory (hereinafter referred to as RAM) 68 for backup that can maintain memory by being supplied with power from the auxiliary power supply even when the engine is stopped. A memory (hereinafter referred to as backup RAM) 70, a digital output port 72 for outputting the calculation results of the CPU 60 to the idle rotation control valve 26, injector 30, coil with igniter 52, etc. at a predetermined timing, and each of the above components. It is composed of a common bus 74 that connects devices. The effects of the embodiment will be explained below. First, the digital control circuit 54 controls the engine rotational speed calculated from the intake pipe pressure PM output from the intake pipe pressure sensor 23 and the output from the crank angle sensor 44.
The basic injection time TP (PM, NE) is determined by NE from data previously stored 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, and when F is positive, it represents an increase correction, and when F is negative, it represents a decrease correction. Further, K is a correction magnification for further correcting the correction coefficient F, and is normally set to 1. Fuel injection time TAU determined in this way
A fuel injection signal corresponding to this is output to the injector 30, and the injector 30 is opened for the fuel injection time TAU in synchronization with the engine rotation, and fuel is injected into the intake manifold 28 of the engine 10. The deceleration reduction in this embodiment is performed as follows. That is, as shown in FIG. 3, when the throttle valve 18 begins to close at time _t1 during deceleration, the intake pipe pressure PM
Prior to the decrease in the throttle valve opening, a reduction in the throttle valve opening (hereinafter referred to as TA reduction) is carried out, which is a rapid reduction correction according to the rate of decrease in the throttle valve opening TA, as shown by the solid line A in FIG. 3D. be exposed. Specifically, for this TA reduction, for example, a value (negative value) obtained by integrating values corresponding to the amount of change in the throttle valve opening TA every predetermined time is set as a (reduction) correction coefficient F, and then Alternatively, a predetermined rotation recovery speed ΔF1, ΔF2 (ΔF1>ΔF2) that is high speed until a predetermined level L that changes depending on the engine cooling water temperature and low speed after reaching the predetermined level L is determined at regular intervals.
This is done by restoring it to 0. Next, when the intake pipe pressure PM starts to decrease, from time _t2 , the intake pipe pressure decrease is performed to perform a highly accurate reduction correction according to the decreasing rate of the intake pipe pressure PM, as shown by the solid line B in FIG. 3D. (hereinafter referred to as PM reduction) is performed. Specifically, for this PM reduction, for example, a value (negative value) that is the sum of values corresponding to the amount of change in intake pipe pressure PM for each predetermined time is set as a (reduction) correction coefficient F, and then The predetermined level L changes depending on the engine cooling water temperature at regular intervals.
The predetermined recovery speed ΔF1, ΔF2 (ΔF1>ΔF2) is fast until the predetermined level L is reached and is slow after reaching the predetermined level L.
This is done by restoring it to 0. In this embodiment, when the correction coefficient F is restored at the time of the TA reduction and PM reduction, as shown in detail in FIG. , the recovery speed is switched to a low speed. That is, in a state after warm-up where the engine cooling water temperature is high, the recovery speed is switched at a relatively high (small absolute value) predetermined level L1, as shown by solid line C in FIG. Similarly, when the water temperature is low and the engine is warming up, the solid line D is shown in Figure 4.
As shown, switching is performed at a relatively low (large absolute value) predetermined level L2 (<L2; however, |L2|>|L1|). FIG. 5 shows a program for recovering the deceleration loss in this embodiment. In this program, we will start with step 100.
Then, it is determined whether a predetermined period of time has passed since the previous recovery process. When the determination result of step 100 is negative,
Exit this program without performing recovery processing. On the other hand, the determination result in step 100 is positive;
When it is determined that recovery processing should be performed,
Proceeding to step 102, it is determined whether the engine cooling water temperature is equal to or higher than a predetermined value indicating the end of engine warm-up. If the determination result in step 102 is positive and it is determined that the warmed-up engine is sufficiently warm, the process advances to step 104, where the correction coefficient F is
It is determined whether or not the level is below the predetermined level L1 suitable for switching the recovery speed after the end of warm-up. When the judgment result in step 104 is positive and the value of the correction coefficient F is small (the absolute value is large), it is judged that high speed recovery is necessary, the process proceeds to step 106, and as shown in the following equation, large increment ΔF1
The correction coefficient F is incremented by . F=F+ΔF1...(2) Next, the process proceeds to step 108, where it is determined whether or not the incremented correction coefficient F has exceeded 0. If it has exceeded 0, it is forcibly set to 0 at step 110. Finish the current recovery process. On the other hand, the determination result in step 104 is negative;
Since the correction coefficient F is approaching 0, when it is determined that recovery should be performed at a low speed, step 120 is performed.
, and increment the correction coefficient F by an increment ΔF2 smaller than the increment ΔF1, as shown in the following formula,
Proceed to step 108. F=F+ΔF2...(3) Also, if the determination result in step 102 is negative,
When it is determined that the engine is not warmed up during warm-up, the process proceeds to step 130, and the correction coefficient F is set at the predetermined level suitable for switching the recovery speed during warm-up.
It is determined whether it is equal to or less than L2 (<L1). When the determination result in step 130 is positive and it is determined that high-speed recovery is required, step 130 is performed.
132, the correction coefficient F is incremented by a large increment ΔF1 according to equation (2) above, and the correction coefficient F is incremented by a large increment ΔF1.
Proceed to 108. On the other hand, the determination result in step 130 is negative;
When it is determined that recovery should be performed at a low speed, the process proceeds to step 134, where the correction coefficient F is incremented by a small increment ΔF2 according to equation (3), and the process proceeds to step 108. Therefore, regardless of the engine warm-up condition, over-richness that may occur when the recovery speed is set to a single high speed, or over-lean that may occur when the recovery speed is set to a single low speed, can be avoided. This ensures that the reduction in deceleration is properly prevented and that the amount of deceleration is reduced in accordance with the required characteristics of the engine. In addition, if TA weight loss and PM weight loss overlap,
If both are used together, there is a risk of excessive weight loss.
Therefore, in the present invention, as shown by the thick solid line in FIG. 3D, only the TA reduction is performed from time t ₂ to _{t 3} by tracing the minimum value of the correction coefficient F for the TA reduction and PM reduction, and From time _t3 to time _t4 , only PM reduction is performed. As described above, by performing deceleration weight loss by combining fast-response TA weight loss and highly accurate PM weight loss, appropriate weight loss can be achieved.
By maintaining the air-fuel ratio near the stoichiometric air-fuel ratio, it is possible to achieve both deceleration performance and exhaust gas purification performance. Furthermore, in the present invention, the recovery speed can be switched by
Since the correction is performed when the correction coefficient F has recovered to a predetermined level that changes depending on the warm-up state of the engine, the reduction in deceleration is performed that closely matches the required characteristics of the engine, regardless of the warm-up state of the engine. In the above embodiment, the engine temperature was detected from the engine cooling water temperature, but the method for detecting the engine temperature is not limited to this, and for example, the engine temperature may be estimated from the elapsed time after starting the engine. It is possible.

[Effects of the Invention] As explained above, according to the present invention, during deceleration, it is possible to perform an appropriate weight loss correction that does not become excessive, commensurate with changes in engine required characteristics due to the way the accelerator pedal is pressed and the engine temperature. By maintaining the air-fuel ratio near the stoichiometric air-fuel ratio, it is possible to achieve both good deceleration performance and exhaust gas purification performance. Therefore, even when using an 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 the deceleration loss in the embodiment, and FIG. 4 is a diagram showing the recovery of the deceleration loss. The diagram illustrating FIG. 5 is also a flowchart illustrating a program for recovery of deceleration loss. 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 fuel injection amount is determined by A reduction correction that combines the following: reducing the throttle valve opening to restore the coefficient; and reducing the intake pipe pressure in accordance with the rate of decrease in intake pipe pressure, and then recovering the correction coefficient at a predetermined recovery rate. and performing deceleration reduction by following the minimum value of each reduction correction coefficient, and switching the recovery speed to a low speed when the correction coefficient has recovered to a predetermined level that becomes low when the engine is low during the recovery. An electronically controlled fuel injection method for an internal combustion engine, characterized by: