JPS58150037A - Electronically controlled fuel injection method of internal-combustion engine - Google Patents

Abstract

PURPOSE:To aim at improvement in starting characteristics at the time of low temperature, by carrying out an increase in quantity after engine starting and an air-fuel ratio compensation in time of idling, while stopping the air-fuel ratio compensation when cooling water temperature is below the specified value, in case of a method to properly compensate for the basic injection quantity accordance with a state of engine rotation. CONSTITUTION:In a digital control circuit 54, the basic injection time is read out of a read-only memory on a basis of both the suction pipe pressure by a suction pipe pressure sensor 23 and the engine speed by a crank angle sensor 44 whereby injection 30 is controlled. In this case, after engine starting, a fuel increment compensation is carried out in accordance with a coefficient of compensation read out according to the warm-up state by a water temperature sensor 46 and then the compensation is attenuated after the lapse of the specified time. Likewise, at the time of idling, the increase and decrease compensation of fuel is carried out according to the coefficient of compensation being varied with the suction pipe pressure and the engine speed change. And, at this time, this method makes the latter so as not to carry out the air-fuel ratio compensation in time of idling when the cooling water temperature is below the specified value.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronically controlled fuel injection method for an internal combustion engine, and is particularly suitable for use in an automobile internal combustion engine equipped with an intake pipe pressure type electronically controlled fuel injection device.

The basic injection amount is determined according to the engine 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. Improvement of electronically controlled fuel injection method for internal combustion engine [19].

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 several or one engine cylinder, and the valve opening time of the injector is adjusted depending on the engine operating state. By controlling accordingly, a mixture having a predetermined air-fuel ratio is supplied to the engine combustion chamber. This electronically controlled fuel injection system.

Broadly speaking, there are so-called intake air amount type electronically controlled fuel injection devices, which calculate the basic injection amount according to the engine's intake air amount and engine speed, and those that calculate the basic injection amount according to the engine's intake pipe pressure and engine speed. The basic injection amount is now calculated. There is a so-called intake pipe pressure type electronically controlled fuel injection device.

Of these, the former allows for precise control of the air-fuel ratio, and is now widely used in automobile engines equipped with exhaust gas purification measures. In a device, the amount of intake air changes by about 50 times between idle and high load, and F
Since the dynamic range is wide, the accuracy when converting the intake air tt to an electrical signal will be low (but if you try to increase the calculation accuracy in the digital control circuit at the subsequent stage, the bit length of the electrical signal will become longer, It is necessary to use an expensive computer as a digital control circuit.

In addition, in order to measure the intake air jll, 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 VK's intake pipe pressure type electronically controlled fuel injection system, the amount of change in intake pipe pressure is about 2 to 3 times smaller, and the dynamic range is narrower.

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 intake air volume type electronically controlled fuel injection system, the control accuracy of the air-fuel ratio is lower, and at %K and idle, positive feedback occurs due to the phase delay of the input signal of each sensor, causing engine rotation hunting. was there. To prevent this hunting, during idling, the fuel injection amount is corrected to increase or decrease according to the amount of change in intake pipe pressure and engine speed. Although it is possible to perform the air-fuel ratio correction at idle as shown in FIG. 1(A), after engine start #b, the fuel injection amount is corrected to increase in accordance with the engine warm-up state, and then is attenuated. If used in conjunction with the post-start condition shown in Figure 1 (OK-), the air-fuel ratio will become overrich, especially immediately after the engine starts, and the engine rotation will become unstable, as shown in Figure 1 (OK-). There was a problem that starting performance deteriorated.This problem is especially caused when the engine cooling water temperature is low and the warm-up increase that corrects the fuel injection amount according to the engine warm-up condition is not effective. Furthermore, it is large when used together.

The present invention has been made to eliminate the above-mentioned conventional drawbacks, and in particular, it is an object of the present invention to provide an electronically controlled fuel injection method for an internal combustion engine that can improve starting performance at low temperatures and idling stability after starting. purpose.

In the present invention, the basic injection amount is determined according to the engine intake pipe pressure and the engine rotation speed, and at transient times, the fuel injection amount is determined by correcting the basic injection amount to increase or decrease according to the engine operating state. In the electronically controlled fuel injection method for an internal combustion engine, after the engine starts, the fuel injection amount is increased according to the engine warm-up condition, and then the after-starting amount is attenuated, and the intake pipe pressure and the engine are adjusted at idle. The idling air-fuel ratio correction is performed to increase or decrease the fuel injection amount according to the rate of change of the rotational speed, and if the engine cooling water temperature is below a predetermined temperature, the idling air-fuel ratio correction is not performed. has been achieved.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described in detail below with reference to the drawings.

A solid line example of an intake pipe pressure 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 follows:
As shown in Figures 2 and 3, there is an air cleaner 12 for taking in outside air, and an intake air temperature sensor 14 for detecting the temperature 41 of the intake air taken in from the air cleaner 12.
A throttle valve 18 is disposed in the intake passage 16 and is opened and closed in conjunction with an accelerator pedal (not shown) disposed on the driver's seat. ,
A throttle sensor 2o including an idle contact for detecting whether or not the throttle valve 18 is in the idle open position and a potentiometer that generates a voltage output proportional to the open position of the throttle valve 18, a surge tank 22, and the surge tank 22. An intake pipe pressure sensor 23 for detecting the intake pipe pressure from the pressure in the tank 22, a bypass passage 24 that bypasses the throttle valve 18, and an intermediate part of the bypass passage 24 are provided.

An idle rotation control valve 26 for controlling the idle rotation speed by controlling the opening area of the bypass passage 24, and an engine 1 disposed in the intake manifold 28.
an injector 30 for injecting fuel toward the intake boat of 0; an oxygen concentration sensor 34 disposed in the exhaust manifold 32 for detecting the air-fuel ratio from residual oxygen am in the exhaust gas; A three-way catalytic converter 38 is disposed in the middle of the exhaust pipe 36 on the downstream side of the manifold 32, and a distributor 40 has a distributor shaft that rotates in conjunction with the rotation of the crankshaft of the engine IO.
It was built into the Resoist Repeater 40. A top dead center sensor 42 and a crank angle sensor 44 output a top dead center signal and a crank angle signal in accordance with the rotation of the distributor shaft.

installed in the engine block. A cooling water temperature sensor 46 for detecting the engine cooling water temperature, a ninth vehicle speed sensor 50 for detecting the running speed of the vehicle from the rotational speed of the output shaft of the variable speed 1m4B, and the intake pipe pressure.

The intake pipe pressure output from the sensor 23 and the crank angle sensor 4
The basic injection amount per engine stroke is determined from the map according to the engine rotation speed determined from the output of step 4, and this is calculated from the output of the throttle sensor 20, the air-fuel ratio of the oxygen concentration sensor 34 output, and the cooling water temperature sensor 46. The fuel injection amount is determined by correcting the increase or decrease in output according to the engine cooling water temperature, etc., and a valve opening time signal is output to the injector 30. Also, the ignition timing is determined according to the engine operating condition and the igniter is activated. An intake pipe pressure type electronically controlled fuel injection system for an automatic heavy-duty engine 10, which is equipped with a digital control circuit 54 that outputs an ignition signal to an attached coil 52 and further controls the idle rotation control valve 26 during idle. Within the circuit 54, after the engine is started, there is a post-start device that corrects the increase in fuel injection amount according to the engine warm-up state detected from the engine cooling water temperature, and then attenuates it, and a change in the intake pipe pressure and the engine rotational speed during idling. The idling air-fuel ratio correction is performed to increase or decrease the commercial injection amount according to the speed, and the idling air-fuel ratio correction is not performed when the engine cooling water temperature is less than a predetermined temperature.

As shown in detail in FIG. 3, the digital control circuit 54 includes a central processing unit (hereinafter referred to as CPU) 6 (1:, the intake temperature sensor 14, the throttle sensor 20) consisting of a microprocessor that performs various calculation processes. an analog input port 2 with a multiplexer for converting analog signals inputted from the potentiometer, the intake pipe pressure sensor 23, the oxygen concentration sensor 34, the cooling water temperature sensor 46, etc. into digital signals and sequentially inputting them into the CPU 60; A digital input port 4 for inputting digital signals inputted from the idle contact of the sensor 20, the top dead center sensor 42, the crank angle sensor 44, the vehicle speed sensor 50, etc. to the CPU 6oVc at a predetermined timing, and a program or various constants. A read-only memory (hereinafter referred to as ROM) 66 for storing data, a random access memory (hereinafter referred to as RAM) 68 for temporarily storing calculation data etc. in the CPU 60, and a read-only memory (hereinafter referred to as RAM) 68 for temporarily storing calculation data etc. in the CPU 60, and a (Random access memory for pick-up (hereinafter referred to as "tup-up RA")
M) 70 and the CPU 60 & CPU 60 & 70 output the calculation results to the idle rotation control valve 26. at a predetermined timing. It is comprised of a digital output port door 2 for outputting to the injector 30, the igniter-equipped coil 52, etc., and a common bus 74 that connects each of the above-mentioned components.

The action will be explained below.

First, the digital control circuit 54 uses 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 to perform basic injection from a map stored in advance in the ROM 66. Time TP
(RM, NE) Read k.

Furthermore, the fuel injection time TAUk is calculated by correcting the basic injection time TP (PM, NE) t using the following equation according to the signals from each sensor.

TAU=TP (PM, NE l * (1+FsE+
FLL l umbrella Wt.

(Here, FSEf'i is a post-shining heat increase correction coefficient, FLL is an idling air-fuel ratio correction coefficient, and WL is a slow heat increase correction coefficient.

A solvent injection signal corresponding to the fuel injection time TAU determined in this manner is output to the injector 30, and the injector 30 is activated for the fuel injection time TAU in synchronization with the engine rotation.
Only AU is opened, engine lO intake manifold 28
Fuel is injected inside.

Book 1! In this embodiment, the post-start increase correction coefficient PSE and the idle air-fuel ratio correction coefficient FLL are calculated according to a program as shown in Fig. 1.

That is, first in step 101, the engine cooling water temperature THW
t-take in; Next, the process proceeds to step 102, in which the relationship between the engine cooling water temperature THW and the initial value of the post-start increase correction coefficient PSE, which is stored in advance in the ROM 66, is determined according to the engine cooling water temperature THW read out in step 101. The initial value of the post-start increase correction coefficient PSE is read from the Table 9. 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 determination result is positive, step 104
Then, according to the following formula, the starting advantage increase correction coefficient PSE at that time is
1e The value attenuated by the shield quantity ΔFEE is set as the new post-start increase correction coefficient FEE.

F 8 E=F S E−△FSE ・・・・・・・・・
(2) After step 104 is completed, or if the determination result in step 103 is negative,
Proceeding to step 105, the engine coolant temperature TH at the time of i
' It is determined whether or not W has become equal to or higher than the PA constant value THWA (for example, 40 to 50°C). If the judgment result is negative,
That is, if the engine cooling water temperature has not yet risen sufficiently, the process proceeds to step 106, where the idling air-fuel ratio correction coefficient F L L t O is set, and this program is terminated, so that the idling air-fuel ratio correction is not performed. .

On the other hand, if the determination result at the x and f knobs 105 is positive, that is, if the engine cooling water temperature has risen to the predetermined value THWA, the process proceeds to KU step 1107, where the amount of change ΔPM in the intake pipe pressure per engine revolution 9 is calculated. demand. Next, proceed to step 108.

In accordance with the obtained intake pipe pressure change amount ΔPM, the intake pipe pressure correction coefficient PPMk is read out from a table stored in advance in the ROM 66 according to the relationship shown in FIG. Furthermore, the process proceeds to step 109, where the amount of change ΔNE in the engine speed per engine rotation is determined. Next, the process proceeds to step 110, in which the engine speed correction coefficient FNEt is read out from a table stored in advance in the ROM 66 according to the relationship shown in FIG. Further, the program proceeds to step ill, where an idling air-fuel ratio correction coefficient FLLk is calculated from the intake pipe pressure correction coefficient PPM and the engine speed correction coefficient FNE as shown in the following equation, and this program ends.

FLL=FPM+FNE ・・・・・・・・・・・・
(3) An example of the final change state of the correction coefficient in this example is shown in Figure @7.

As explained above, according to the present invention, it is possible to prevent over-richness of the air-fuel ratio immediately after starting the engine, which is caused by the combination of post-start increase and idle air-fuel ratio correction. This has the excellent effect of improving performance and idling stability after startup.

[Brief explanation of drawings]

Figure 1 is inside? In an electronically controlled fuel injection method for an engine,
Figure 2 is a graph showing how the amount increases when t is used in combination with the increase after starting and the air-fuel ratio correction at idle. A block diagram showing the configuration of an embodiment of an intake pipe pressure type electronically controlled fuel injection device for a private 11+ engine in which the electronically controlled fuel injection force method for an internal combustion engine according to the present invention is adopted, #E3
The figure shows the configuration of the digital control circuit used in the previous I[8] embodiment. *4 The diagram is also used in the above embodiment. A flowchart showing a program for calculating the post-start increase correction coefficient and the idle air ratio correction Sa, *5' Figure C also shows the relationship between the amount of change in intake pipe pressure per engine revolution and the intake pipe pressure correction coefficient. Similarly, the diagram shown in FIG. 6 is a diagram showing the relationship between the amount of change in the engine rotation speed per engine revolution and the engine rotation speed correction coefficient in the example described above. It is a line drawing showing an example of the relationship between engine cooling water temperature, increase after starting, and correction of air-fuel ratio at idle. 10...Engine, 14...Intake temperature sensor. 58... 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 center, 54...Digital control circuit. Agent Takaya Ron (and 1 other person)

Claims (1)

[Claims] (1) Calculate the basic injection amount according to the engine intake pipe pressure and engine speed, and at transient times, etc. In an electronically controlled fuel injection method for an internal combustion engine, in which the fuel injection amount is determined by increasing or decreasing the basic injection amount according to the engine operating state, after the engine is started, the fuel injection amount is determined according to the engine warm-up state. A post-start increase is performed in which the fuel injection amount is increased and then attenuated, and an idling air-fuel ratio correction is performed in which the fuel injection amount is increased or decreased during idle according to the rate of change in intake pipe pressure and engine speed. An electronically controlled fuel injection method for an internal combustion engine, in which an idling air-fuel ratio correction is not performed when an engine cooling water temperature is less than a predetermined temperature.