JPS6158939A - Control method for fuel injection amount of internal-combustion engine - Google Patents

Abstract

PURPOSE:To eliminate generation of decelerative shock by controlling the decrease in the amount of fuel injection during deceleration so as to be over a lower limit, which is in response to the decreasing rate of the actually inhaled air amount by the cylinder, thereby preventing overlean at the time of deceleration. CONSTITUTION:In this system the amount of fuel injection is determined on the basis of the revolving speed of an engine and the amount of suction air sensed upstream the throttle valve, and if the decreasing rate of the amount of fuel injection under deceleration is larger than the max. decreasing ate in correspondence to the max. decreasing speed of the actual inhalation amount of air by the cylinder while deceleration is made with the throttle valve fully closed, the previous amount of fuel injection subtracted by the above-mentioned max. decreasing rate is used as the amount of fuel injection at this time. According to this arrangement an amount of fuel in correspondence to the change of the actual inhalation amount of air is supplied at the time of deceleration, which can well eliminate occurrence of decelerative shocks.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a fuel injection method for an internal combustion engine,
Particularly suitable for use in an automobile engine equipped with an electronically controlled fuel injection device that senses the amount of intake air, the fuel injection amount is based on the intake air flow rate and engine speed detected at least upstream of the throttle valve. The present invention relates to an improvement in a fuel injection amount control method for an internal combustion engine, which determines the amount of fuel injected into an internal combustion engine.

[Conventional technology]

One of the methods for supplying an air-fuel mixture at a predetermined air-fuel ratio to the fuel of an internal combustion engine such as an engine for a self-help vehicle uses an electronic till fuel injection device. This means that, for example, 11 [1i1 or 2 injectors (in the case of a single point injection type),
Alternatively, by arranging several engine cylinders (in the case of a multi-point injection type) in the intake manifold and controlling the valve opening time of the injectors according to the operating state of the engine, a mixture with a predetermined air-fuel ratio can be delivered to the engine. This is to ensure that it is supplied at will. In this electronically controlled wholesale fuel injection system, the basic injection amount is normally determined according to the basic operating condition of the engine such as the engine load and engine speed detected from the engine intake air amount or intake pipe pressure. The actual injection amount is determined by adding various increases and decreases based on signals input from sensors disposed in various parts of the engine, and fuel injection is executed. Such an electronic system'a punishment spout! ) fll device, especially in an engine equipped with an intake air amount sensing type electronically controlled injection device that senses the engine load from the intake air amount of the engine, the throttle valve is adjusted based on the running condition of the vehicle in which the engine is installed. If you suddenly decelerate at full throttle,
The output signal of the air flow meter, which measures the intake air flow upstream of the fully open throttle valve, undershoots the actual intake air amount of the cylinder that sucks the air remaining between the fully open throttle valve and the intake valve. As a result, the air-fuel ratio within the cylinder becomes larger than the ideal air-fuel ratio, resulting in a sudden drop in engine torque due to lean misfire, which may result in deceleration shock. Therefore, conventionally, so-called deceleration increase processing has been carried out in which the air flow meter output signal, which changes completely differently from the actual intake air amount during deceleration with the throttle valve fully closed, is increased by a certain percentage within the electronic control unit (hereinafter referred to as ECU). It is being done.

[Problems to be solved by the invention]

However, when this deceleration and increase processing is performed, the breakdown I! is shown in FIG. As shown in G, the jet during steady driving! )1
There are some parts where the value is larger than fi, which may cause problems such as deterioration of exhaust gas. In FIG. 6, the dashed line H is the injection amount calculated directly from the output signal of the air flow meter. On the other hand, as something similar to the present invention, the applicant has already set in advance a minimum fuel injection amount that regulates the lower limit of the first shift of the fuel injection amount in Japanese Patent Application No. 56-172953, and the fuel injection amount is the minimum fuel injection amount. In the fuel injection control device, the minimum fuel injection amount is increased to a predetermined set value when the brake pedal is in an open state and the vehicle speed is within a predetermined speed range. We are proposing a fuel Ill copper control device for internal combustion. However, the minimum fuel injection m guard in this fuel injection control device does not correspond to the rate of decrease of the cylinder's actual intake air amount, and therefore it is not possible to inject fuel commensurate with the cylinder's actual intake air amount. Ta. [Object of the Invention] The present invention has been made to solve the above-mentioned conventional problems, and can supply fuel commensurate with changes in cylinder actual intake air amount during deceleration, thereby eliminating deceleration shock. Another object of the present invention is to provide a fuel injection amount control method for a self-destructing engine that does not cause adverse effects such as deterioration of exhaust gas.

[Means to solve the problem]

The present invention provides a fuel injection amount control method for an internal combustion engine, in which the fuel injection amount is determined based on an intake air flow rate and engine rotation speed detected at least upstream of a throttle valve. As shown in the figure below, the procedure for detecting deceleration and the fuel injection when decelerating or speeding up! A procedure for comparing the reduction rate of the iFl amount with the maximum reduction rate corresponding to the maximum value of the reduction rate of the cylinder actual intake air amount during deceleration with the throttle valve fully closed; The above object is achieved by including a step of reducing the previous fuel injection amount by the maximum reduction rate and setting the current fuel injection amount when it is larger.

[Effect]

In the present invention, when determining the fuel injection amount based on the intake air flow rate and engine rotation speed detected at least upstream of the throttle valve, during deceleration, the reduction rate of the fuel injection amount is determined by the throttle valve fully open deceleration. Since guarding is performed at the maximum reduction rate corresponding to the maximum value of the reduction rate of the cylinder actual intake air amount at the time of deceleration, over lean during deceleration can be prevented and deceleration shock can be eliminated. Furthermore, since fuel is injected in an amount commensurate with the actual amount of intake air into the cylinder, there will be no adverse effects such as deterioration of exhaust gas. (Practical example 1) Referring to the drawings below, a motor vehicle equipped with a multi-point injection type intake air amount sensing type electronically controlled fuel injection device in which the fuel @ injection amount control method for an internal combustion engine according to the present invention is adopted. An embodiment of a car engine will be described in detail.As shown in FIG. 2, this embodiment includes an air flow meter 12 for detecting the flow rate of intake air and a , an intake air temperature sensor 14 for detecting the temperature of intake air, and a thrower i. Pressurized fuel is intermittently directed toward the throttle sensor 19 including the idle contact LL for detecting the opening of the valve 18 and the intake boat of each cylinder, which is disposed in the intake manifold 21 downstream of the surge tank 20. the cylinder block 10A of the engine 10; Fuel injection is performed according to the engine load determined from the output of the air flow meter 12 and the engine rotational speed determined from the output of the rotation angle sensor 28. It is composed of an electronic control unit (hereinafter referred to as ECU) 32 for calculating time and outputting a valve opening time signal to the injector 22. In the figure, 10B is an intake valve, 10G is a cylinder, 3
6 is a spark plug, 38 is an exhaust manifold, and 40 is an ignition coil with an igniter. As shown in detail in FIG. 3, the ECI 132 includes a central processing unit (hereinafter referred to as CPU) 32A consisting of, for example, a microprocessor for performing various arithmetic processing, and storing control programs, various data, etc. a read-only memory (hereinafter referred to as ROM) 32B, a random access memory (hereinafter referred to as RA IVI) 32C for temporarily storing calculation data etc. in the CPU 32A, and a board for generating various clock signals. The output of the air flow meter 12 inputted via the O-sock generation circuit 32D and the buffer 32E, and the buffer 32
A multiplexer (hereinafter referred to as IIV/+ (referred to as p x)321. Analog-to-digital converter (hereinafter referred to as A/D)
converter) 32J and the first input/output boat (referred to as
(hereinafter referred to as I10 boat) 32, and the shaping circuit 32L.
A second l710 port 32M for receiving the outputs of the cylinder discrimination sensor 26 and the rotation angle sensor 28, and the output of the throttle sensor 20, which are input via the CPU 32A. , an output port 32P for outputting a valve opening time signal to the injector 22 via a drive circuit 32N, and a common bus 32Q for connecting each of the component parts and transferring data and commands. has been done. The operation of the actual M example will be explained below. Guarding of the reduction rate of the fuel injection amount in this embodiment is executed according to the procedure shown in FIG. 4. That is, first, in step 110, the fuel injection amount (hereinafter referred to as AFM injection amount) T calculated based on the output signal of the air flow meter 12 is greater than the previous fuel injection amount (hereinafter referred to as previous injection amount) πi-1. Determine whether it is small. If the determination result is positive, that is, if it is determined that deceleration is occurring, the process proceeds to step 112, and the cylinder actual intake air amount at the time of deceleration with the throttle valve fully closed is added to the previous injection amount πi-l, as shown in the following equation. The value obtained by multiplying the smoothing coefficient K (0≦≦1) of the maximum reduction rate corresponding to the maximum value of the reduction speed of is set as the current fuel injection l)ijm<hereinafter referred to as the current injection amount)πi. πi←πi−+ If the determination result of step 114 is positive or the determination result of step 110 is negative, and it is determined that there is no need to guard the reduction rate of the fuel injection amount, step 11 is performed.
Proceeding to step 6, the AFM injection mT is set as the current injection amount πi. After the completion of step 116, or when the judgment result of step 114 is negative and it is judged that it is necessary to guard the decreasing rate of AFM injection IT, the process proceeds to step 118, and the current injection amount πi at that time is stored in the RAM 3.
Store on 2C. Next, the process proceeds to step 120, where fuel injection is performed using the current injection amount πi, and this routine ends. Therefore, AFL calculated from the air flow meter output signal
whether v+injection ff1T is greater than or equal to the previous injection amount πi-1;
Or, the value π obtained by multiplying the previous injection amount πi−1 by the smoothing coefficient K
When it is greater than =+, fuel injection is performed by AF~1 injection IT. On the other hand, when the AFM injection amount T is smaller than the value π1-lK obtained by multiplying the previous injection port π1-1 by the smoothing coefficient K, the fuel injection amount guarded by the smoothing coefficient K is set as the current injection port. The smoothing coefficient can be determined, for example, as follows. That is, it is assumed that when the throttle valve 18 is fully open, the air flow rate passing through the air flow meter 12 (throttle valve 18) is zero as shown by arrow E, and as shown in FIG. From the air in a constant volume ff1A up to 10B, each cylinder IO of volume IB
Assuming that C is the intake efficiency C and that air is taken in one cylinder at a time as shown by arrow F, the amount of air taken into the nth cylinder after the throttle valve 18 is fully closed [)n is the following formula % formula % Therefore, this BxC/ (A+B) is given by cylinder 10
This can be the maximum rate of decrease of the actual intake air amount of C per ignition. Therefore, in an electronically controlled fuel injection system in which the fuel injection period is every y point, the maximum rate of decrease for each injection at the actual intake air end of the cylinder 10C is expressed by the following equation. k-1-(1-BXC/(A+B)? ・ (3) Therefore, it is sufficient to set a guard on the reduction side for each sword by the maximum reduction speed k for each injection, and the smoothing coefficient is given by the following formula. K-1-k (4) In this example, the injection amount smoothing ratio on the decreasing side is set to 10'%.
/injection, the state of change in the fuel injection amount during deceleration with the throttle fully open is shown by the solid line J in FIG. 6 mentioned above. As is clear from the figure, the AFM injection IT calculated directly from the airflow meter output signal (broken line F) and the fuel injection amount when deceleration and increase (broken line F) correspond to the change in the actual cylinder intake air amount, which is between the Additional punishment will be provided. In addition, in the above embodiment, the present invention has a multi-point l111
However, the scope of application of the present invention is not limited thereto; It is clear that the present invention can be similarly applied to general engines equipped with a 1j controlled fuel injection device. [Effects of the Invention] As explained above, according to the present invention, it is possible to supply fuel commensurate with the change in the actual intake air amount during deceleration. Therefore, over lean during deceleration can be prevented, deceleration shock can be eliminated, and drivability can be improved. In addition, it has the advantageous effect of not causing harmful effects such as exhaust gas pollution.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the gist of the fuel mat amount control method for an internal combustion engine according to the present invention, and FIG. FIG. 3 is a cross-sectional view, including a partial block diagram, showing the overall configuration of an embodiment of an automobile engine equipped with an injection device; FIG. 3 is a block diagram showing the configuration of an electronic control unit used in the embodiment; FIG. , FIG. 4 is a flowchart showing the injection interrupt routine for guarding the rate of decrease in the fuel injection amount, and FIG. 5 is the principle of the method for determining the smoothness coefficient K used in the above embodiment. FIG. 6, which is a schematic diagram of the intake system for explaining the above, is a line section showing a comparison of changes in the throttle distance and fuel injection amount during full throttle deceleration in the embodiment and the conventional example. 10...Engine, 10C...Cylinder,
12... Air flow meter, 18... Throttle valve, 20... Surge tank, ? 1... Intake manifold, 22... Injector, 28... Rotation angle sensor, 32... Electronic control unit (ECU),
■...Fuel injection amount calculated from the air flow meter output, πGobi...Previous fuel injection amount, πi...Current fuel injection amount, K...Smoothing coefficient.

Claims (1)

[Claims] (1) In a fuel injection amount control method for an internal combustion engine that determines the fuel injection amount based on the intake air flow rate and engine rotation speed detected at least upstream of the throttle valve, detecting that deceleration is occurring. a step of comparing the reduction rate of the fuel injection amount during deceleration with a maximum reduction rate corresponding to the maximum value of the reduction rate of the cylinder actual intake air amount during deceleration with the throttle valve fully closed; When the reduction rate of is larger than the maximum reduction rate, the previous fuel injection amount is reduced by the maximum reduction rate and the current fuel injection amount is set. Injection amount control method.