JPS59231144A - Method of fuel injection in internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent the jerking of engine operation, by injecting fuel at the rate just before a throttle valve is closed for a prescribed while at the time of decelerating an engine when fuel injection is not interrupted or when the fuel injecton period is not long. CONSTITUTION:At steps 50-55, deceleration when fuel supply is not interrupted or the state that the fuel injection period tau is shorter than a prescribed value tau1 is detected. In this case, fuel is supplied at the rate just before a throttle valve is closed for a certain while determined by T1. At a step 60, count of a timer is started, and the injection quantity of fuel is increased gradually after passing of the time T1. Thus, it is enabled to prevent the jerking of engine operation or degradation in the exhaust-gas characteristics due to over-rich air-fuel mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection method for an internal combustion engine, and more particularly to a fuel injection method for an internal combustion engine that controls a fuel injection amount based on an engine load and an engine speed.

Conventionally, a fuel injection valve has been provided for each cylinder so as to protrude into the intake manifold, or a fuel injection valve has been provided upstream of the throttle valve, and a microcomputer or other device processes signals input from various sensors to determine the engine operating status. A fuel injection method is known in which the amount of fuel is injected according to the operating state. In this fuel injection method, the basic fuel injection time is determined according to the engine load (intake pipe pressure or intake air amount per engine rotation, etc.) and engine speed, and the basic fuel injection time is determined according to the intake air temperature, engine cooling water temperature, etc. The fuel injection time is determined by correcting the fuel injection time, and the fuel injection valve is opened for a time corresponding to this fuel injection time at a predetermined period to control the fuel injection amount. The intake pipe pressure is detected by a pressure sensor disposed in the intake pipe downstream of the throttle valve, and the intake air amount is detected by an air flow sensor disposed upstream of the throttle valve.

However, in an internal combustion engine controlled by such a fuel injection method, the throttle valve is suddenly closed during deceleration during low-speed running, so the air remaining in the intake pipe or surge tank is supplied to the engine combustion chamber. Since the throttle valve is fully closed, the intake pipe pressure and the amount of air passing through the throttle valve decrease. Therefore, with the above fuel injection method, less fuel is injected than is sufficient for the amount of air being supplied to the combustion chamber, and the air-fuel ratio in the combustion chamber becomes lean, resulting in the required torque. is generated, becomes force, and negative torque is generated. This negative torque resonates with the vehicle's natural frequency, causing jerking and drive surges, giving the driver a sense of discomfort and anxiety. For this reason, conventionally, fuel has been injected in synchronization with the negative torque to reduce the negative torque, but because the natural frequencies of the vehicles are different, it is not possible to inject fuel in synchronization with the negative torque. However, there is a problem in that it is difficult to control the control timing, and if the control timing is shifted, the hiccup phenomenon is aggravated.

In order to solve the above problem, the fuel injection time immediately before the throttle valve is fully closed is maintained, and the fuel injection valve is opened during this fuel injection time when the throttle valve is fully closed to prevent the air-fuel ratio from becoming lean. It is possible to prevent such phenomena. However, when the fuel injection is cut off after a predetermined period of time (for example, 500 m5ec) has elapsed since the throttle valve is fully closed and when the engine speed is above a predetermined number of revolutions, no fuel is injected, so it is difficult to prevent sagging phenomena. There is no need to take any countermeasures, and if the above fuel injection is executed in driving conditions where the fuel injection time is long or during upshifts, more fuel will be injected than the amount of air remaining in the surge tank, etc. A problem arises in that the fuel ratio becomes overrich and exhaust gas characteristics deteriorate.

The present invention has been made to solve the above-mentioned problems, and is a fuel injection method for an internal combustion engine that injects fuel so as not to generate negative torque to prevent the sagging phenomenon, and also prevents deterioration of exhaust gas characteristics. The purpose is to provide

In order to achieve the above object, the present invention provides a method for closing the throttle valve when a predetermined period of time has elapsed since the throttle valve is closed, during deceleration when fuel injection is being performed, and when the vehicle speed is within a predetermined range and the fuel injection time is within a predetermined range. It is configured to hold the fuel injection time immediately before the state and inject fuel at the held fuel injection time for a predetermined period, and to inject fuel by gradually shortening the held fuel injection time after the elapse of the predetermined period. It is.

According to the configuration of the present invention, the fuel immediately before the throttle valve is closed is injected for a predetermined period during deceleration other than when fuel injection is cut or during deceleration when the fuel injection time is not long, so the air-fuel ratio becomes rich and exhaust gas characteristics deteriorate. The effect is that the hiccup phenomenon can be prevented without causing any problems.

Next, FIG. 1 shows an example of an internal combustion engine to which the present invention is applied. An air flow sensor 4 that detects the amount of intake air and outputs a voltage according to the amount of intake air is arranged downstream of the air cleaner 2, and an intake air temperature sensor 6 is arranged near the air flow sensor 4.

A throttle valve 8 is arranged downstream of the air flow sensor 4, and an idle switch 10 is attached to the throttle valve 8, which is closed when the throttle valve is fully closed. A surge tank 12 located downstream of the throttle valve 8 is connected to a combustion chamber 16 of the internal combustion engine via an intake manifold 14. Intake manifold 14
A fuel injection valve 18 is provided for each cylinder and is controlled to open and close to intermittently inject pressurized fuel sent from a fuel supply system. The combustion chamber 16 is connected to a catalytic converter (not shown) filled with a three-way catalyst via an exhaust manifold.

Further, a water temperature sensor 20 is attached to the engine block to detect the engine cooling water temperature.

An ignition plug 22 projects into the combustion chamber 16, and the ignition plug 22 is connected to a distributor 24. The distributor 24 is provided with a crank angle sensor 26 that includes a pickup fixed to the distributor housing and a signal rotor fixed to the distributor shaft. This crank angle sensor 26 outputs a top dead center signal and an engine rotation speed signal. Further, the distributor is connected to an igniter, and the igniter is connected to a control circuit 28 composed of a microcomputer or the like.

Note that 30 is 0 used for air-fuel ratio feedback control.
, and 31 is a vehicle speed sensor.

As shown in FIG. 2, the control circuit 28 includes a central processing unit (
CPU)32. Random access memory (RAM) 34
, read-only memory (it, OM) 36.38
, an input boat 40, an input/output boat 42, and buses such as a data bus and a control bus that connect these. The input boat 40 is equipped with an analog multiplexer function and an analog-to-digital conversion function, and sequentially converts the signals input from the near-flow atmosphere tubes 4, 11 [sensor 6, water temperature sensor 20.0, sensor 30, and vehicle speed sensor 31] into digital signals. Convert. A crank angle sensor 26 is connected to the input/output boat 42 via a waveform shaping circuit (not shown), and the idle switch 1
0 is connected. The input/output boat 42 is also connected to a fuel injection valve 18 provided for each cylinder via a drive circuit (not shown). The above ROM contains a main processing routine program, an interrupt processing routine program for calculating fuel injection time, and a minimum fuel injection program to prevent irregular injection in which the fuel injection amount becomes uncertain when the opening time of the fuel injection valve is short. The time τmin, the maximum value T1 of the minimum fuel injection time, etc. are stored in advance. This maximum value τ is, for example, 2m5eC.

Next, a processing routine in an embodiment of the present invention will be explained based on FIG. In this embodiment, a timer is used to count the period during which the fuel injection time immediately before the slot valve closes. executed.

In step 50, it is determined whether the idle switch 10 is on, that is, whether the throttle valve is closed and a deceleration state is entered. If the idle switch is on, it is determined whether the vehicle is decelerating with fuel injection cut in step 51, whether the vehicle speed is less than a predetermined value υ, (for example, 2.7 Km/h) in step 52, or whether the vehicle speed is lower than the predetermined value υ (for example, 2.7 Km/h) in step 53. exceeds a predetermined value υ, (for example, 20) (m/h), the engine speed exceeds the fuel injection cutoff speed in step 54, and the minimum fuel injection time τmin is determined in step 5ξ. It is determined whether the maximum value τ is exceeded.

If any of the conditions in steps 51 to 55 is affirmative, in step 61 the value of the minimum fuel injection time τmin is changed to the minimum fuel injection time control value τm1.
nG, and in step 62 for a predetermined time (for example, 4
The count value Ti of the timer counted every m5ec)
Let mer be O.

If all the conditions in steps 51 to 55 are negative, in step 56 the timer count value Time is
It is determined whether or not r is 0, and if the count value Timer is O, the previous fuel injection time τold is set as the minimum fuel injection time control value τm1nG in step 57, and in step 58, this control value τm1nG and the maximum value τ are Compare sizes. If the control value τmLr+G is larger than the maximum value τ, the value of the control value τm1nc is changed to the maximum value τ in step 59.
The timer starts counting at step 60. On the other hand, when the count value Timer is O, it is determined in step 63 whether or not the count value Timer is less than a predetermined value 'r+ (for example, 125), and if it is less than, the count is continued and the predetermined value T1 When the count exceeds the limit, the timer stops counting in step 64. As a result of the above, during deceleration other than idle switch on and fuel injection cut, υ2
When ≦vehicle speed≦υ1, the engine speed is less than or equal to the fuel injection cut rotation speed, and the fuel injection time τ is less than or equal to the maximum value τ of the minimum fuel injection time, the fuel injection time τold immediately before the idle switch is turned on is the minimum fuel injection time control. The value is set to τm1nG. In this case, when the fuel injection time τold is equal to or greater than the above maximum value 11, the maximum value τ is reached.

The value of is set as the value of the control value τm1nc.

In the next step 65, the basic fuel injection time is calculated by dividing the intake air amount per engine revolution by the engine speed, and the basic fuel injection time is corrected to calculate the fuel injection time τ. In the next step 66, the fuel injection time τ is compared with the minimum fuel injection time control value τm1nG, and if τ≧τm1nG, the value of the fuel injection time τ is used as is, and τ<1m1
If nG, in step 67, the minimum fuel injection time control value τm1nc is set as the fuel injection time τ. In step 68, it is determined whether or not it is the injection timing based on the top dead center signal, and if it is the injection timing, in step 69, a pulse signal with a pulse width corresponding to the fuel injection time τ is output to the fuel injection valve to inject fuel. Fuel is injected by opening the valve. In the next step 70, the fuel injection time τ is stored in a predetermined area of the RAM as the previous fuel injection time τold, and in step 71 it is determined whether the count value Timer has reached a predetermined value of 18 or more. Count value T
When ime r is greater than or equal to the predetermined value T1, in step 72, the value obtained by subtracting a predetermined value 4τ (for example, 100 μs) from the minimum fuel injection time control value τm1nG is set as the minimum fuel injection time control value mir+G. When τm1nG≧τmin Using the value of the minimum fuel injection time control value τmin for that 'df, 1m1nG (If τmin, the value of the minimum fuel injection time τmin is set as the minimum fuel injection time control value τm1nc; in step 74. As a result of the above, For a predetermined (11) time after the conditions of steps 51 to 55 are negative and the throttle valve is closed, the fuel injection valve is controlled for a time longer than the fuel injection time immediately before the throttle switch is turned on, and the fuel injection valve is controlled as described above. After the predetermined time has elapsed, the fuel injection valve is controlled for a time longer than the fuel injection time, which is attenuated by a predetermined amount.

Here, the reason why the above control is not executed during deceleration during fuel injection cut is because the sagging phenomenon does not occur when fuel injection is cut, and the reason why the above control is not executed when the vehicle speed is outside the specified range is because the vehicle speed is This is because the hiccup phenomenon is less likely to occur outside the specified range, and the air-fuel ratio may become overrich during acceleration during upshifting.

Also, the reason why the above control is not executed when the engine speed exceeds the fuel injection cut speed is because the fuel injection cut is performed after a predetermined period of time has elapsed since the throttle switch is turned on. This is to increase the lifespan of the fuel by injecting it and making the air-fuel ratio overrich. Furthermore, the reason why the above control is not executed when the fuel injection time exceeds the maximum value τ1 is to prevent the air-fuel ratio from becoming overrich.

(12) Figures 4 (1) to (3) show changes in drive shaft torque and fuel injection time when the fuel injection time is changed as described above. In the figure, line A is the conventional shaft torque, line B is the shaft torque of this embodiment, line C is the fuel injection time according to this embodiment, line is the calculated value of the fuel injection time, that is, the conventional fuel injection time, and line E is Each shows the minimum fuel injection time control value. In addition, Fig. 4 (3) shows the characteristics when τ〉τ1, and Fig. 4 (3) shows the characteristics when τ≦
This is the characteristic when τ. As can be understood from the figure, no negative torque is generated in this embodiment.

In addition, although the example in which the fuel injection period immediately before the throttle valve closed state is held for a predetermined period of time has been described above, the present invention is not limited to this, and the period to be held may be determined from the number of injections. . The number of injections in this case is, for example, 8 to 9 times.

Furthermore, in the above description, an internal combustion engine has been described in which the basic fuel injection time is determined based on the intake air amount per engine rotation and the engine speed, but the present invention determines the basic fuel injection time based on the intake pipe pressure and the engine speed. It can also be applied to internal combustion engines.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of an internal combustion engine to which the present invention is applied, FIG. 2 is a block diagram of the control circuit of FIG. 1, and FIG. 3 is a flowchart showing a processing routine of an embodiment of the present invention. FIG. 4 is a diagram showing changes in drive shaft torque and fuel injection time. 4... Near flow valve, 10... Idle switch, 18... Fuel injection valve, 28... Control circuit, 31... Vehicle speed sensor. Agent Tatsuyuki Karasunuma (IJ”・12))

Claims (1)

[Claims] (1) In a fuel injection method for an internal combustion engine, the fuel injection time is determined based on the engine load and the engine speed, and the fuel injection valve is opened for a time corresponding to the fuel injection time to inject fuel.
When a predetermined period of time has passed since the throttle valve was closed and the vehicle is decelerating while fuel injection is being performed, and the vehicle speed is within a predetermined range and the fuel injection time is within a predetermined range, the fuel is injected for a predetermined period using the fuel injection time immediately before the throttle valve is closed. Along with injecting
A fuel injection method for an internal combustion engine, characterized in that fuel is injected by gradually shortening the fuel injection time just before a predetermined period of time elapses and the rear limb throttle valve is closed.