JPH0573907B2 - - 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, particularly for use in an automobile internal combustion engine equipped with an intake pipe pressure type electronically controlled fuel injection device. An electronically controlled fuel injection method for an internal combustion engine, which is suitable for determining the basic injection amount according to the engine intake pipe pressure and engine speed, and correcting the basic injection amount by decreasing it during deceleration operation of the engine. Regarding improvements.

<Prior Art> One of the methods of 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. In addition to increasing the accuracy of calculation in the digital control circuit at the subsequent stage, the bit length of the electrical signal becomes longer, requiring the use of an expensive computer as the digital control circuit. In addition, in order to measure the amount of intake air, it is necessary to use a measuring device such as an air flow meter having a very precise structure, 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
Since the dynamic range is small, about 3 times as much, it is not only easy to perform arithmetic processing in the digital control circuit at the subsequent stage, but also the pressure sensor for detecting the intake pipe pressure is inexpensive. 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 Temporarily becomes rich, 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 a three-way catalytic converter. 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 of the oxygen concentration sensor is slow.

Therefore, conventionally, it has been difficult to use intake pipe pressure sensing type electronically controlled fuel injection devices in automobile engines that require precise control of the air-fuel ratio and are equipped with exhaust gas purification measures. It was considered.

In order to eliminate the above-mentioned drawbacks, it is also conceivable to perform a reduction correction during deceleration, as described in Japanese Patent Laid-Open No. 52-133418.

〓Problem to be Solved by the Invention〓 However, if this reduction in deceleration is continued even when the speed approaches the idle speed, the engine speed will fall below the idle speed when the deceleration state shifts to the idling state, causing the vehicle to This may cause discomfort to the occupants or, in extreme cases, may cause the engine to stall.

The present invention has been made in order to solve the above-mentioned conventional problems, and maintains the air-fuel ratio near the stoichiometric air-fuel ratio by performing appropriate reduction correction during deceleration.
Without impairing the original effect of the reduction correction, it is possible to prevent a drop in engine speed (undershoot) and engine stall when transitioning from deceleration to idling, thereby improving deceleration 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 exhaust gas purification performance.

<Means for Solving the Problems> The present invention provides an internal combustion engine in which a basic injection amount is determined according to the intake pipe pressure of the engine and the engine speed, and the basic injection amount is corrected to reduce the amount during deceleration operation of the engine. In this electronically controlled fuel injection method, during deceleration, the throttle valve opening is decreased in accordance with the decreasing speed of the throttle valve opening, and then recovered at a predetermined recovery speed, and the throttle valve opening is decreased in accordance with the decreasing speed of the intake pipe pressure. Then, the intake pipe pressure reduction to be recovered at a predetermined recovery speed is calculated, and a reduction correction is performed using the minimum value among these reduction values, and during the execution of the reduction correction, the throttle valve is fully closed, and,
When the engine speed falls below the predetermined value, the reduction correction is stopped and normal fuel supply is performed, while the throttle valve opening is not fully closed or the engine speed is not below the predetermined value. In this case, the objective is achieved by continuing the weight loss correction.

<Effect> In the present invention, during deceleration, the throttle valve opening is reduced in accordance with the decreasing speed of the throttle valve opening and then recovered at a predetermined recovery speed, and the throttle valve opening is decreased in accordance with the decreasing speed of the intake pipe pressure. Then, the intake pipe pressure loss to be recovered at a predetermined recovery speed is calculated, and the weight loss correction is performed using the minimum value among these weight loss values. Therefore, at the beginning of deceleration, highly responsive reduction correction can be performed in response to changes in the throttle valve opening, which changes rapidly in conjunction with the driver's accelerator pedal operation. Further, after the middle stage of weight loss, highly accurate weight loss correction can be performed in accordance with changes in intake pipe pressure, which changes slowly but clearly represents the weight loss state. Furthermore, when the throttle valve opening degree reduction and the intake pipe pressure reduction overlap, the reduction is corrected using the smaller value, so even if the two overlap, an excessive amount does not occur.

Therefore, it is possible to achieve good responsiveness and high performance by performing appropriate and not excessive weight loss corrections in response to changes in both the way the accelerator pedal is released (i.e., throttle valve opening) and the intake pipe pressure, commensurate with deceleration. It is possible to achieve both accuracy.

Furthermore, when the throttle valve becomes fully closed and the engine speed falls below a predetermined value during execution of the reduction correction, the reduction correction is stopped and normal fuel supply is performed, while the throttle valve is closed. If the engine is not in a fully closed state or the engine speed is not below the predetermined value, the reduction correction is continued, so that the original effect of the reduction correction is not impaired.
When transitioning from deceleration state to idling state,
Engine speed undershoot and engine stall can be effectively prevented.

Embodiments 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, 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 degree of 8, a surge tank 22 for preventing intake interference, and a system for detecting intake pipe pressure from the pressure inside the surge tank 22. the intake pipe pressure sensor 23 and the throttle valve 18
a bypass passage 24 that bypasses the bypass passage 24;
an idle rotation control valve 26 for controlling the idle rotation speed by controlling the opening area of the
, an injector 30 disposed in the intake manifold 28 for injecting fuel toward the intake port of the engine 10, and an injector 30 disposed in the exhaust manifold 32 for calculating the air-fuel ratio from the residual oxygen concentration in the exhaust gas. An oxygen concentration sensor 34 for detection, a three-way catalytic converter 38 disposed midway in the exhaust pipe 36 downstream of the exhaust manifold 32, and the engine 1.
Distributor 40 having a distributor shaft that rotates in conjunction with the rotation of the crankshaft of
and a top dead center sensor 4 built into the distributor 40 that outputs a top dead center signal and a crank angle signal in accordance with the rotation of the distributor shaft.
2, a crank angle sensor 44, a cooling water temperature sensor 46 disposed in the engine block for detecting the engine cooling water temperature, and a vehicle speed for detecting the running speed of the vehicle from the rotational speed of the output shaft of the transmission 48. The basic injection amount per engine stroke is determined according to the engine rotation speed determined from the sensor 50, the intake pipe pressure output from the intake pipe pressure sensor 23, and the output from the crank angle sensor 44.
By correcting this according to the output of the throttle sensor 20, the air-fuel ratio of the output of the oxygen concentration sensor 34, the engine coolant temperature of the output of the coolant temperature sensor 46, etc., the fuel injection amount is determined. Outputs a valve opening time signal to the injector 30, and
The intake air of an automobile engine 10 includes a digital control circuit 54 that determines the ignition timing according to the engine operating state and outputs an ignition signal to the igniter-equipped coil 52, and further controls the idle rotation control valve 26 during idling. In the pipe pressure sensing type electronically controlled fuel injection system, the rate of decrease in the opening of the throttle valve detected from the potentiometer output of the throttle sensor 20 and the intake pipe pressure sensor 23 are controlled in the digital control circuit 54 . A reduction correction is performed during deceleration according to the rate of decrease in intake pipe pressure detected from the output, and during the execution of the reduction correction, the throttle valve is fully closed and the engine speed is
A predetermined value slightly higher than the idle speed (e.g.
1000 rpm) or less, the above-mentioned weight loss correction is stopped.

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 air 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 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 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 correction. It represents. Further, K is the correction coefficient F
It is a correction magnification to further correct the
It is said that

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 reduction correction during deceleration (referred to as 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, this TA reduction is performed by setting the correction coefficient F to a value (negative value) that is the sum of integrated 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 speed, which is fast up to a predetermined level and slow after reaching the predetermined level, at regular intervals.

Next, when the intake pipe pressure PM starts to decrease, from time _t2 , 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 B in FIG. 3D. (hereinafter referred to as PM reduction) is performed. Specifically, this PM reduction is as follows:
For example, the correction coefficient F
This is then performed by recovering to zero at a predetermined recovery speed, which is fast up to a predetermined level and slow after reaching the predetermined level, every engine rotation or every fixed period of time.

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, as shown by the thick solid line in FIG. 3D, the TA
Tracing the minimum value of weight loss and PM weight loss, from time t ₂ to _{t 3}
In this case, only TA reduction is performed, and from time _t2 to _t4 , only PM reduction is performed.

Further, when reducing the TA and PM, when the throttle valve 18 becomes fully closed while the deceleration reduction is being executed, and the engine speed reaches a predetermined value slightly higher than the idle speed, for example, 1000 rpm or less, , cancel the deceleration reduction. Specifically, as shown in FIG. 4, first, in step 101, it is determined whether the idle switch of the throttle sensor 20 is on. If the determination result is positive, that is, if the throttle valve 18 is fully closed, the process proceeds to step 102, where it is determined whether the engine speed is a predetermined value, for example 1000 rpm. If the determination result is positive, step 10
Proceed to step 3, during deceleration reduction, i.e. TA reduction or
Determine whether PM reduction is in progress. If the determination result is positive, proceed to step 104;
The value of the correction coefficient F is forcibly returned to 0, and the deceleration reduction is stopped. On the other hand, the above steps 101 to 103
If either of the judgment results is negative, that is, even if deceleration reduction is being executed, the idle switch is off or the engine speed is low.
When the speed exceeds 1000 rpm, the deceleration reduction continues without stopping.

Engine speed during deceleration and reduction in this example
An example of the relationship between NE and correction coefficient F is shown in FIG.
As is clear from the solid line C in FIG. 5, in this embodiment, the deceleration reduction is stopped at time t ₅ 〓 when the engine speed NE reaches 1000 rpm, and the correction coefficient F is forcibly returned to 0. As shown by the broken line D in Fig. 5, the engine speed NE drops below the idle speed, or
As shown by the dashed line E in the figure, the engine does not stall.

As described above, by performing deceleration reduction by combining fast-response TA reduction and highly accurate PM reduction, appropriate deceleration reduction can be achieved and the air-fuel ratio can be maintained near the stoichiometric air-fuel ratio. This makes it possible to achieve both deceleration performance and exhaust gas purification performance.

〓Effects of the Invention〓 As explained above, according to the present invention, it is possible to perform appropriate weight loss correction during deceleration, maintain the air-fuel ratio near the stoichiometric air-fuel ratio, and reduce , it is possible to achieve both good deceleration performance and exhaust gas purification performance by smoothing changes in engine rotation. Therefore, even when using an electronically controlled fuel injection device that senses intake pipe pressure, it is possible to perform precise air-fuel ratio control.
In particular, when the throttle valve is not fully closed and there is no possibility of engine stalling, the reduction correction is continued without being canceled, so it maintains excellent effects such as not impairing the original effect of the reduction correction. have

[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. A block diagram showing the configuration of the digital control circuit used in the embodiment, FIG. 3 is a diagram showing the deceleration reduction in the embodiment, and FIG. 4 is a program for canceling the deceleration reduction. Similarly, FIG. 5 is a diagram showing an example of changes in the engine speed and the correction coefficient when transitioning from the deceleration state to the idling state. 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. Electronically controlled fuel injection for an internal combustion engine in which a basic injection amount is determined according to the intake pipe pressure and engine speed of the engine, and the basic injection amount is corrected to decrease during deceleration operation of the engine. In the method, during deceleration, the throttle valve opening is decreased in accordance with the decreasing speed of the throttle valve opening and then recovered at a predetermined recovery speed; Calculate the intake pipe pressure reduction to be recovered at a recovery speed of becomes below a predetermined value, the reduction correction is stopped and normal fuel supply is carried out.On the other hand, if the throttle valve opening is not fully closed, or
An electronically controlled fuel injection method for an internal combustion engine, characterized in that the reduction correction is continued when the engine speed is not below the predetermined value.