JPH0428897B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electronically controlled fuel injection method during acceleration of an internal combustion engine, and particularly relates to synchronous injection in which fuel is injected in synchronization with the crank angle, and The present invention relates to an electronically controlled fuel injection method for an internal combustion engine that performs asynchronous injection in which fuel is injected asynchronously with the angle.

[Conventional technology]

Conventionally, a fuel injection valve is provided for each cylinder so as to protrude into the intake manifold, and a microcomputer processes signals input from various sensors to determine the operating state for a period of time, and injects the amount of fuel according to the operating state. A fuel injection method is known. In this fuel injection method, there is a synchronous injection in which fuel is injected according to the engine load (intake pipe pressure or intake air amount per revolution per period, etc.) at every predetermined crank angle, and a synchronous injection in which fuel is injected at a timing unrelated to this synchronous injection. Asynchronous injection is performed.

Of these, asynchronous injection performed during engine acceleration is
This is done to improve engine response during acceleration, etc., and various methods have been proposed. For example, the rate of change in the throttle opening of the engine is determined, and when this rate of change is greater than a predetermined value, asynchronous injection is performed. (Japanese Unexamined Patent Publication No. 58-48725), and one that performs asynchronous injection when the rate of change in intake air amount exceeds a predetermined value (Japanese Unexamined Patent Publication No. 58-48725).
-134718) is known.

However, it is necessary to perform asynchronous injection as soon as acceleration starts, and for this reason, the applicant has developed a method that first performs asynchronous injection when the rate of change in the load change rate (second-order differential value) exceeds a predetermined reference value. is proposed. (Japanese Patent Application No. 57-149203) [Problem to be Solved by the Invention] However, even in the technology described in Japanese Patent Application No. 57-149203, the above-mentioned 2. If a predetermined standard value of the floor differential value is set, even if acceleration progresses and the need for asynchronous injection becomes low, asynchronous injection will be executed in the same way as at the beginning of acceleration, and as a result, the number of asynchronous injection executions will increase. On the other hand, there was a problem that it became overrich.

Therefore, the present invention performs asynchronous injection when the rate of change of the engine load is equal to or higher than a predetermined reference value, and determines the time with reference to the point in time when acceleration is started. It is an object of the present invention to solve the above problem by increasing the reference value and further increasing the reference value when asynchronous injection is executed after the start of acceleration.

[Means to solve the problem]

According to the present invention, the load of the engine is detected, an amount of fuel corresponding to the load is injected in synchronization with the crank angle, and the rate of change of the detected engine load is equal to or higher than a predetermined reference value. Sometimes, in an electronically controlled fuel injection method for an internal combustion engine that injects fuel asynchronously with the crank angle, a time based on the time when acceleration operation is started is determined, and the longer the time, the larger the predetermined reference value is. In addition, when the asynchronous injection is executed, the predetermined reference value is further increased.

[Effect]

According to the present invention, the reference value for determining whether or not to perform asynchronous injection during acceleration is increased as the time from the start of acceleration operation becomes longer, and when asynchronous injection is performed, the reference value is increased. is also enlarged.

As a result, asynchronous injection is executed only during acceleration when asynchronous injection is really required, so overcorrection of the air-fuel ratio can be prevented when acceleration progresses.

〔Example〕

Embodiments of the present invention will be described below based on the drawings. FIG. 1 is a diagram showing an example of an internal combustion engine to which the present invention is applied. An intake temperature sensor 2 is installed downstream of an air cleaner (not shown) to detect the temperature of intake air and output an intake temperature signal. A throttle valve 4 is disposed downstream of the intake air temperature sensor, and a throttle switch 6 is attached which is interlocked with the throttle valve 4 and turns off when the on-throttle valve opens when the throttle valve is fully closed. A surge tank 8 is provided downstream of the throttle valve 4, and a pressure sensor 10 is attached to the surge tank 8 for detecting the intake pipe pressure downstream of the throttle valve and outputting an intake pipe pressure signal. The surge tank 8 is communicated with a combustion chamber 14 of the engine via an intake manifold 12. A fuel injection valve 16 is attached to the intake manifold 12 for each cylinder. The combustion chamber 14 of the engine is communicated via an exhaust manifold with a catalytic converter (not shown) filled with a three-way catalyst. Further, a water temperature sensor 20 is attached to the engine block to detect the engine cooling water temperature and output a water temperature signal. A tip of a spark plug 22 projects into the combustion chamber 14 of the engine, and a distributor 24 is connected to the spark plug 22. The distributor 24 is provided with a cylinder discrimination sensor 26 and an engine rotational speed sensor 28, each of which includes a pickup fixed to the distributor housing and a signal rotor fixed to the distributor shaft. The cylinder discrimination sensor 26 outputs a cylinder discrimination signal, for example, every 720° CA to the control circuit 30 composed of a microcomputer, etc.
A crank angle signal is output to the control circuit 30 every 30° CA. The distributor 24 is connected to the igniter 32. Furthermore, 34 detects the residual acidity in the exhaust gas and outputs an air-fuel ratio signal.
It is an _O2 sensor.

As shown in FIG. 2, the control circuit 30 includes a central processing unit (CPU) 36, a read-only memory (ROM) 38, a random access memory (RAM) 40, and a backup RAM (BU-RAM).
42, an input/output port (I/O) 44, an analog-to-digital converter (ADC) 46, and buses such as a data bus and a control bus that connect these. A cylinder discrimination signal, a crank angle signal, an air-fuel ratio signal, and a throttle signal output from the throttle switch 6 are input to the I/O 44, and the fuel injection valve 1 is also input via a drive circuit.
A fuel injection signal that controls the opening/closing time of the igniter 6 and an ignition signal that controls the on/off time of the igniter 32 are output. Further, an intake pipe pressure signal, an intake air temperature signal, and a water temperature signal are inputted to the ADC 46 and converted into digital signals.

The above crank angle signal is input to the I/O 44 via a waveform shaping circuit, and a digital signal representing the engine rotation speed is formed from this crank angle signal. The cylinder discrimination signal is input to the I/O 44 and converted into a digital signal in the same manner as above. This cylinder discrimination signal is used together with the crank angle signal to form an interrupt request signal, a fuel injection start signal, a cylinder discrimination signal, etc. for basic fuel injection pulse width calculation. The on/off signal from the throttle switch 6 is sent to a predetermined bit position of the I/O 44 and temporarily stored. Also, in I/O44,
A well-known fuel injection control circuit including a presettable counter and register is provided.
An injection pulse signal having the pulse width is formed from binary data regarding the injection pulse width sent from the CPU 36, and the injection pulse signals are input to the fuel injection valve 16 sequentially or simultaneously to energize the injection valve. As a result, an amount of fuel corresponding to the pulse width of the injection pulse signal is injected synchronously or asynchronously.
The ROM 38 contains a main processing routine program, an interrupt processing routine program for calculating fuel injection pulse width, an interrupt processing routine program for calculating coefficients such as partial lean correction coefficients, other programs, and other programs necessary for each of the above calculation processes. Various data are stored in advance. Also,
The ROM 38 stores in advance data regarding the first and second amounts for asynchronous fuel injection and the map shown in FIG. This map defines the reference value L for the count value C of the counter for calculating the time based on the time when the throttle valve in the fully closed state is opened as the start point of acceleration, and the reference value L for the count value C of the counter is determined. The reference value L is set to increase stepwise as the value increases.

Next, the asynchronous injection routine of the present invention will be explained using FIGS. 4 to 6. Note that the synchronous injection routine and the like are the same as the conventional ones, so the explanation will be omitted. FIG. 4 shows the main routine. In step S2, it is determined based on the throttle signal whether the throttle switch 6 is off, that is, whether the throttle valve is open. If the throttle switch is on, the step
After resetting the flag XLL in S3, proceed to the next routine, and if the throttle switch is off, the flag set by the throttle switch off
Determine whether XLL has been reset. If the flag XLL has been set, the routine advances to the next routine, and if the flag XLL has been reset, that is, if the throttle switch was last turned on, the counter is cleared in step S6, and the flag XLL is set in step S8. do. Therefore, the counter is constantly counted and is cleared when the throttle switch changes from on to off. That is, the counter counts the time with reference to the time when the throttle switch changes from on to off, that is, the time when the throttle valve is opened from the fully closed state, that is, the time when acceleration operation is started.

FIG. 5 shows a routine for incrementing a counter at predetermined time intervals, and in this embodiment, the count value C of the counter is incremented every 4 msec in step S12. Note that the counter overflow is prevented by limiting the count value C of the counter to the maximum value MAX in step S10 and step S14.

FIG. 6 shows a routine for determining the acceleration state and calculating the pulse width TAU of the fuel injection signal in asynchronous injection. This routine is a routine that is interrupted when the AD conversion of the intake pipe pressure PM is completed. In addition, AD conversion of intake pipe pressure PM is
I am trying to run it every 12msec. step
In S16, the difference between the current intake pipe pressure PM _o and the intake pipe pressure PM _o-2 from the previous time, that is, 24 msec ago, is calculated, and the amount of change in the intake pipe pressure during 24 msec, that is, the rate of change ΔPM _o is calculated. This rate of change ΔPM _o is equivalent to the first-order differential of the intake pipe pressure PM with respect to time. In step S18, the difference between the current rate of change ΔPM _o and the previous rate of change ΔPM _o-1 12 msec ago is calculated, and the amount of change in the rate of change during 12 msec, that is, the rate of change ΔΔPM _o of the intake pipe pressure is calculated. Calculate. This rate of change ΔΔPM _o is equivalent to a second-order differential with respect to time.

Therefore, hereinafter, the rates of change ΔPM _o and ΔΔPM _o will be described as first-order differential values and second-order differential values, respectively.

In step S20, it is determined whether the throttle switch is on or not, and in step 22, it is determined whether the first differential value ΔPM _o of the intake pipe pressure is negative or not, and if the throttle switch is off and the first differential value ΔPM _o Execute the following steps only when is greater than or equal to 0. Therefore, asynchronous injection is not performed when the first-order differential value ΔPM _o is negative, that is, during deceleration. In the next step S24, it is determined whether the count value C of the counter exceeds a predetermined value (for example, 6). If the count value is 6 or less, the process proceeds to step S26, and if the count value exceeds 6, the process proceeds to step S26. Proceed to S30.

In step S26, it is determined whether the second-order differential value ΔΔPM _o of the intake pipe pressure is greater than or equal to the first reference value L ₁ (positive value) corresponding to the count value C of the counter read from the ROM, and the first Only when the reference value _L1 is greater than or equal to the reference value L1, the asynchronous injection pulse width TAU is set to a predetermined value (for example, 2 msec) in step S28. As a result, the first amount of fuel corresponding to the asynchronous injection pulse width TAU is asynchronously injected during acceleration until a predetermined time (24 msec) has elapsed from the start of acceleration when the fully closed throttle valve was opened.

Furthermore, in step S30, the second-order differential value ΔΔPM _o of the intake pipe pressure is determined as a second reference value L ₂ (positive value) corresponding to the count value C of the counter read from the ROM.
The asynchronous injection pulse width TAU is determined in step S32 only when it is equal to or greater than the second reference value _L2 .
is determined according to the following formula.

TAU=0.51+24・ΔΔPM _o /1000 (1) Note that the coefficients 0.51 and 24 were determined through experiments, and the coefficient 1000 is a constant for converting into time in msec. As a result, after the above predetermined time has elapsed, a second amount of fuel is injected corresponding to the asynchronous injection pulse width proportional to the second order differential value ΔΔPM _o of the intake pipe pressure.

In addition, since the reference values L ₁ and L ₂ corresponding to the count values are set to positive values, ΔΔPM _o becomes 0 during steady driving (ΔPM _o = 0) or during slow acceleration (ΔPM _o
= constant), asynchronous injection is not performed.

In the next step S34, a predetermined value (for example, 6) is added to the count value C of the counter, and in step S36 it is determined whether the count value C has reached the maximum value MAX.
Set the count value to the maximum value MAX in S38. In this way, after executing the asynchronous injection in step S28 and step S32, the count value C of the counter is incremented, and since the reference value is set to increase according to the count value C, as a result, the asynchronous injection The post-reference value will be increased, and the number of asynchronous injections will decrease over time.

Figure 7 shows the throttle opening during acceleration, the actual intake pipe pressure P, the intake pipe pressure PM detected by the pressure sensor, the first derivative ΔPM of the intake pipe pressure PM, and the second derivative ΔΔPM of the intake pipe pressure PM. and shows temporal changes in the driving voltage of the fuel injector. During the period when the driving voltage is at a low level, the fuel injection valve is maintained in an open state and injects fuel. When acceleration starts at time _t1 , the throttle opening increases from 0°. Along with this, the actual intake pipe pressure P increases, and the intake pipe pressure PM as a detected value of the pressure sensor also increases. An overshoot has occurred in the intake pipe pressure PM. Pulse b indicates synchronous injection that is injected in synchronization with the crank angle, and is an injection equivalent to the basic injection amount determined according to the intake pipe pressure PM and engine speed, corrected by engine cooling water temperature, etc. be. Pulse c is an asynchronous acceleration fuel injection performed in conjunction with the execution of step S28, and ΔΔPM _o remains at least the first reference value L ₁ until a predetermined period of time elapses from the start of acceleration when the fully closed throttle valve is opened. Then, the first amount of fuel corresponding to the asynchronous injection pulse width (2 msec) is injected. Pulse d is an asynchronous accelerated fuel injection performed in conjunction with the execution of step S30, and when ΔΔPM _o becomes equal to or greater than the second reference value _L2 after the asynchronous injection by pulse c, it corresponds to the asynchronous injection pulse width determined in step S32. A second amount of fuel is injected. Since ΔΔPM increases more than ΔPM at the start of acceleration, it is possible to quickly and accurately detect the start of acceleration and perform asynchronous acceleration fuel injection, and the increase in ΔΔPM reflects the increase in throttle opening. Because there are
Asynchronous acceleration fuel injection can be performed depending on the acceleration state.

In the above embodiment, an engine was explained in which the basic fuel injection amount is calculated based on the intake pipe pressure and the engine speed, but the present invention calculates the basic fuel injection amount based on the intake air amount Q per engine rotation and the engine speed. It can also be applied to engines that calculate quantities. In this case, in Figure 5
PM _o , ΔPM _o , ΔΔPM _o are Q _o , ΔQ _o , ΔΔQ _o respectively
replaced by Further, the asynchronous injection timing can also be determined from the differential value of a function using the throttle opening degree and the fuel injection pulse width as variables, as in the present embodiment.

As explained above, in this embodiment, a contact type throttle sensor is used without using a linear throttle sensor, so that the effect of simple structure and cost reduction can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, the asynchronous injection is executed immediately after the start of acceleration, and the next asynchronous injection is not executed unnecessarily when acceleration has progressed or immediately after the asynchronous injection. , it is possible to maintain an appropriate air-fuel ratio during the initial stage of acceleration and as the acceleration progresses.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of an engine to which the present invention is applied, FIG. 2 is a block diagram showing the control circuit of FIG. 1, FIG. 3 is a diagram showing a map of reference values to count values, and FIG. Figure 4 is a flowchart showing the main routine, Figure 5 is a flowchart showing the 4msec routine, Figure 6 is a flowchart showing the asynchronous injection routine,
FIG. 7 is a diagram showing temporal changes in the driving voltage of the fuel injection valve during acceleration. 6... Throttle sensor, 10... Pressure sensor, 16... Fuel injection valve.

Claims (1)

[Claims] 1. The engine load is detected, and an amount of fuel corresponding to the load is injected in synchronization with the crank angle, and the detected rate of change in the engine load is equal to or higher than a predetermined reference value. In the electronically controlled fuel injection method for an internal combustion engine in which fuel is injected asynchronously with the crank angle, a time is determined based on the time when acceleration operation is started, and the longer the time, the more the predetermined reference value is set. An electronically controlled fuel injection method for an internal combustion engine, characterized in that the predetermined reference value is further increased when the asynchronous injection is performed.