JPH022457B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION 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 the engine rotational speed, and at transient times, the fuel injection amount is determined by increasing or decreasing the basic injection amount according to the engine operating condition. This invention relates to improvements in electronically controlled fuel injection methods for internal combustion engines.

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. This electronically controlled fuel injection system can be roughly divided into two types: one that calculates the basic injection amount according to the intake air amount and engine speed of the engine;
There are so-called intake air amount sensing type electronically controlled fuel injection devices and so-called intake pipe pressure sensing type electronically controlled fuel injection devices that calculate the basic injection amount according to the engine intake 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 with 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
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. 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 when idling, positive feedback occurs due to a phase lag in the input signals from each sensor, causing engine rotation to hunt. It was hot. In order to prevent this hunting, it may be possible to correct the air-fuel ratio at idle as shown in Figure 1A, which corrects the fuel injection amount to increase or decrease during idle according to the rate of change in intake pipe pressure and engine speed. However, when used in conjunction with a post-start increase as shown in Figure 1B, in which after the engine starts, the fuel injection amount is increased according to the engine warm-up state and then attenuated, as shown in Figure 1C. As such, there is a problem in that the air-fuel ratio becomes overrich, especially immediately after starting the engine, which not only makes the engine rotation unstable but also deteriorates startability. Such problems are especially
This is significant when the engine cooling water temperature is low and a warm-up increase, which corrects the fuel injection amount according to the engine warm-up condition, is also used.

The present invention has been made to eliminate the above-mentioned conventional drawbacks, and is capable of improving starting performance at low temperatures and idling stability after starting, in particular, in an electronically controlled fuel injection system that detects intake pipe pressure. An object of the present invention is to provide an electronically controlled fuel injection method for an internal combustion engine.

The present invention determines the basic injection amount according to the engine intake pipe pressure and engine speed, and during transient periods, adjusts the fuel injection amount by increasing or decreasing the basic injection amount according to the engine operating state. In the electronically controlled fuel injection method for an internal combustion engine, after the engine starts, an initial value of the increase value is determined according to the engine cooling water temperature, and then the initial value is increased by a predetermined value at every predetermined time or every predetermined rotation. In addition to increasing the amount after starting to attenuate the engine, and performing an idle air-fuel ratio correction that stabilizes the idle rotation by correcting the increase or decrease of the fuel injection amount according to the rate of change in intake pipe pressure and the rate of change in engine speed during idle,
The purpose is achieved by prohibiting the idling air-fuel ratio correction during the post-start fuel increase.

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. 2 and 3. 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; a bypass passage 24 that bypasses the throttle valve 18; An idle rotation control valve 26 for controlling the idle rotation speed by controlling the opening area of the passage 24, and an idle rotation control valve 26 for injecting fuel toward the intake port of the engine 10, which is disposed in the intake manifold 28. Injector 30 and exhaust manifold 32
an oxygen concentration sensor 34 disposed in the exhaust gas for detecting the air-fuel ratio from the residual oxygen concentration in the exhaust gas; and a three-way catalytic converter 38 disposed midway in the exhaust pipe 36 downstream of the exhaust manifold 32. , a distributor 40 having a distributor shaft that rotates in conjunction with the rotation of the crankshaft of the engine 10, and a top dead center signal built in the distributor 40 that responds to the rotation of the distributor shaft. 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 the engine cooling water temperature, and the rotational speed of the output shaft of the transmission 48. a vehicle speed sensor 50 for detecting the running speed of the vehicle; and the intake pipe pressure sensor 2.
3-output intake pipe pressure and crank angle sensor 44
The basic injection amount per engine stroke is determined from the map according to the engine rotational speed determined from the output of The fuel injection amount is determined by correcting the increase or decrease of the output according to the engine cooling water temperature, etc., and a valve opening time signal is output to the injector 30, and the ignition timing is determined according to the engine operating state. In the intake pipe pressure type electronically controlled fuel injection device for an automobile engine 10, which outputs an ignition signal to a coil 52 with an igniter, and further includes a digital control circuit 54 that controls the idle rotation control valve 26 during idling. Within the digital control circuit 54, after the engine starts, the fuel injection amount is increased and corrected according to the engine warm-up state detected from the engine cooling water temperature, and then the amount is increased after starting, which is attenuated, and when the engine is idling, the intake pipe pressure and engine rotation are adjusted. The idling air-fuel ratio correction is performed to increase or decrease the fuel injection amount in accordance with the rate of change of the fuel injection amount, and the idling air-fuel ratio correction is prohibited during the execution of the post-start increase.

As shown in detail in FIG. 3, 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 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 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 in the CPU 60 to the idle rotation control valve 26, injector 30, coil with igniter 52, etc. at a predetermined timing, and each of the above-mentioned components. and a common bus 74 that connects between the two.

The action 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 (RM, 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+FSE+FLL)*WL...(1) Here, FSE is the post-start increase correction coefficient, FLL
is the idle air-fuel ratio correction coefficient, and WL is the warm-up increase correction coefficient.

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.

In this example, the calculation of the post-start increase correction coefficient FSE and the idle air-fuel ratio correction coefficient FLL is performed using the fourth
This is done according to the program shown in the figure.

That is, first, in step 101, the engine coolant temperature THW is acquired. Then, in step 102,
The initial value of the post-start increase correction coefficient FSE corresponding to the engine coolant temperature THW is read from a table that is stored in advance in the ROM 66 and represents the relationship between the engine coolant temperature THW and the initial value of the post-start increase correction coefficient FSE. . Furthermore, the process proceeds to step 103, where it is determined whether a predetermined time or a predetermined number of rotations have elapsed since the previous damping. If the judgment result is positive,
Proceeding to step 104, the current post-start increase correction coefficient FSE is attenuated by a predetermined amount ΔFSE according to the following equation, and the result is set as a new post-start increase correction coefficient FSE.

FSE = FSE - ΔFSE ... (2) After the completion of step 104, or if the judgment result in step 103 is negative, the process proceeds to step 105, and the post-start increase correction coefficient FSE at that time has reached 0. Determine whether or not. If the determination result is negative, that is, if the amount is being increased after starting, the process proceeds to step 106, where the idle air-fuel ratio correction coefficient FLL is set to 0, this program is ended, and the idle air-fuel ratio correction is not performed. Do it like this.

On the other hand, if the determination result in step 105 is positive, that is, if the increase after starting has been completed, the process proceeds to step 107, where the amount of change ΔPM in intake pipe pressure per engine rotation is determined. Next, the process proceeds to step 108, in which an intake pipe pressure correction coefficient FPM is calculated from a table stored in the ROM 66 in accordance with the obtained intake pipe pressure change amount ΔPM according to the relationship shown in FIG. Read out.
Furthermore, the process proceeds to step 109, where the amount of change ΔNE in the engine rotational speed per engine rotation is determined. Next, the process proceeds to step 110, in which an engine speed correction coefficient is determined from a table stored in advance in the ROM 66 according to the relationship shown in FIG.
Read FNE. Further, proceed to step 111,
As shown in the following equation, the idle air-fuel ratio correction coefficient FLL is calculated from the intake pipe pressure correction coefficient FPM and the engine speed correction coefficient FNE, and this program ends.

FLL=FPM+FNE (3) An example of the final change state of the correction coefficient in this embodiment is shown in FIG.

As explained above, according to the present invention, in an electronically controlled fuel injection system that detects intake pipe pressure, an overflow of the air-fuel ratio immediately after engine startup occurs due to the combination of post-start increase and idling air-fuel ratio correction. It has the excellent effect of being able to prevent engine richness and, in particular, improving engine startability at low temperatures, where warm-up fuel consumption is also performed, and idling stability after startup.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating how the amount increases when the after-starting amount increase and the idling air-fuel ratio correction are used together in an electronically controlled fuel injection method for an internal combustion engine, and FIG. FIG. 3 is a block diagram showing the configuration of an embodiment of an intake pipe pressure sensing type electronically controlled fuel injection device for an automobile engine in which a controlled fuel injection method is adopted, and FIG. 3 is a digital control circuit used in the above embodiment. FIG. 4 is a block diagram showing the configuration of the engine, and FIG. 4 is a flowchart showing a program for calculating the post-start increase correction coefficient and the idle air-fuel ratio correction coefficient, which are also used in the above embodiment. , a diagram showing the relationship between the amount of change in intake pipe pressure per engine revolution and the intake pipe pressure correction coefficient, and FIG. FIG. 7 is a diagram showing the relationship, and is a diagram showing how the amount is increased after starting and the air-fuel ratio at idle is corrected in the embodiment. 10...Engine, 14...Intake temperature sensor, 18...
Throttle valve, 20... Throttle sensor, 23... Intake pipe pressure sensor, 30... Injector, 34... Oxygen concentration sensor, 40... Distributor, 42... Top dead center sensor, 44... Crank angle sensor, 46... Cooling water temperature sensor , 54...digital control circuit.

Claims (1)

[Scope of Claims] 1. The basic injection amount is determined according to the intake pipe pressure and engine speed of the engine, and during transient periods, the basic injection amount is corrected to increase or decrease depending on the engine operating condition, thereby controlling the fuel consumption. In an electronically controlled fuel injection method for an internal combustion engine in which the injection amount is determined, an initial value of the increase value is determined according to the engine cooling water temperature after the engine is started, and then the initial value is changed at predetermined intervals or at each predetermined rotation. A post-start increase that attenuates by a predetermined value, and an idle air-fuel ratio correction that stabilizes idle rotation by correcting the increase or decrease of the fuel injection amount according to the rate of change in intake pipe pressure and the rate of change in engine speed during idle. An electronically controlled fuel injection method for an internal combustion engine, characterized in that the idling air-fuel ratio correction is prohibited during the execution of the post-start fuel increase.