JPH0459460B2 - - 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 engine operating state 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 engine revolution, 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. In addition, the applicant has devised a method for performing asynchronous injection when the rate of change (second-order differential value) of the rate of change in intake air amount exceeds a predetermined value, in order to quickly detect the acceleration state and perform asynchronous injection with good responsiveness. I am proposing it first. (Special application 1987-
149203) [Problem to be solved by the invention]
The technology described in No. 134718 has no choice but to use an acceleration judgment value that takes noise into account during the early stages of acceleration when particularly responsive asynchronous injection is required, which delays asynchronous injection and does not provide sufficient compensation. There's a problem. Furthermore, even if asynchronous injection could be executed with good responsiveness, the change in engine load from the beginning to the end of acceleration is not sufficiently taken into consideration, so the amount of asynchronous injection may not be appropriate, and the There was a problem that the stability and exhaust gas purification rate deteriorated.

Therefore, an object of the present invention is to solve the above problem by varying the amount of fuel injected asynchronously depending on the elapsed time from the time when acceleration operation is started.

[Means to solve the problem]

In order to achieve the above object, the present invention detects the load of the engine, injects fuel according to the load in synchronization with the crank angle, and maintains the rate of change of the detected engine load at a predetermined rate. When the value is greater than or equal to
In the electronically controlled fuel injection method for an internal combustion engine in which a predetermined amount of fuel is injected asynchronously with the crank angle, the elapsed time from the time when acceleration operation is started is determined, and if the elapsed time is within the predetermined time, the elapsed time is determined. The predetermined amount of fuel is set to a predetermined amount, and when the time period exceeds the predetermined time period, the predetermined amount of fuel is set to an amount corresponding to the rate of change of the rate of change of the engine load.

[Effect]

To determine whether it is necessary to increase the acceleration amount when the engine accelerates,
It is desirable to detect it as quickly and accurately as possible, and if it is detected, to increase the amount in a timely and appropriate manner. To this end, it is best to determine the acceleration increase based on the rate of change in the engine load (second-order differential value), but the rate of change in the rate of change in the engine load is small at the beginning of acceleration and continues to increase thereafter. It is unclear whether
It cannot be used to accurately determine the amount of asynchronous injection. Therefore, in the present invention, a fixed amount of fuel is injected asynchronously at the initial stage of acceleration, that is, within a predetermined time from the start of acceleration, so that after a predetermined time has elapsed, the rate of change in engine load reflects the degree of acceleration well. Therefore, asynchronous injection is performed in an amount corresponding to the rate of change in engine load. Thus,
The appropriate amount of fuel can be injected depending on the acceleration state.

〔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 can be 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 fuel 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 rotation 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 sends a cylinder discrimination signal every 720° CA to a control circuit 3 composed of a microcomputer or the like.
0, and the engine rotation speed sensor 28 outputs, for example,
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 and a read-on memory (ROM).
38, random access memory (RAM) 40,
It is configured to include 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. The I/O 44 includes a cylinder discrimination signal, a crank angle signal, an air-fuel ratio signal, and a throttle switch 6.
At the same time, a fuel injection signal that controls the opening/closing time of the fuel injection valve 16 and an ignition signal that controls the on/off time of the igniter 32 are outputted via the drive circuit.
Further, the ADC 46 receives an intake pipe pressure signal, an intake air temperature signal, and a water temperature signal and converts them 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 data regarding the first amount and second amount for asynchronous fuel injection and the first reference value _L1.
and a second reference value _L2 are stored.

Next, the asynchronous injection routine of the present invention will be explained using FIGS. 3 to 5. Note that the synchronous injection routine and the like are the same as the conventional ones, so the explanation will be omitted. FIG. 3 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, 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 is set, the routine proceeds to the next routine, and if the flag XLL is reset, that is, if the throttle switch was turned on last time, the counter is cleared in step S6, and the flag XLL is set in step S8. do. Therefore, the counter is always counting and is cleared when the throttle switch changes from on to off. That is, the counter counts the time based on the time when the throttle switch changes from on to off, and therefore the time when acceleration starts when the throttle valve is opened from the fully closed state.

FIG. 4 shows a routine for incrementing a counter at predetermined time intervals; in this embodiment, the count value C is incremented every 4 msec in step S12.
is incremented. In addition, step S10
In step S14, the count value C of the counter is limited to the maximum value MAX to prevent the counter from overflowing.

FIG. 5 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 12ms.
I try to run it every time. In step S16, the current intake pipe pressure PMn and the previous time, that is,
Calculate the difference from the intake pipe pressure PM _o-2 24msec ago,
Calculate the amount of change in intake pipe pressure during 24 msec, that is, the rate of change △PMn. This rate of change ΔPMn 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 △PMn and the previous rate of change △PMn _-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 in the rate of change of intake pipe pressure △△ Calculate PMn. This rate of change ΔΔPMn is equivalent to a second-order differential with respect to time.

Therefore, hereinafter, the rates of change ΔPMn and ΔΔPMn will be explained 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. In step S22, it is determined whether the first differential value △PMn of the intake pipe pressure is negative or not. Execute the following steps only when is greater than or equal to 0. Therefore,
When the first-order differential value ΔPMn is negative, that is, during deceleration, asynchronous injection is not performed. next step
In S24, it is determined whether or not the count value C of the counter exceeds a predetermined value (for example, 6). If the count value C is 6 or less, the process proceeds to step S26, and if the count value C exceeds 6, the process proceeds to step S30. Proceed to.

In step S26, it is determined whether the second order differential value △△PMn of the intake pipe pressure is greater than or equal to the first reference value _L1 (positive value), and only when it is greater than or equal to the first reference value _L1 , it is determined in step S28. The asynchronous injection pulse width TAU is set to a predetermined value (for example, 2 msec). As a result, the first amount of fuel corresponding to the asynchronous injection pulse width (2 msec) is asynchronously injected during acceleration until a predetermined time (24 msec) has elapsed from the time when the fully closed throttle valve was opened.

Further, in step S30, it is determined whether the second order differential value △△PMn of the intake pipe pressure is greater than or equal to the second reference value _L2 (positive value), and the step is executed only when it is greater than or equal to the second reference value _L2 . In S32, the asynchronous injection pulse width TAU is determined according to the following formula.

TAU=0.51+24・△△PMn/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 milliseconds. As a result, after the predetermined time has elapsed, a second amount of fuel is injected corresponding to the asynchronous injection pulse width TAU that is proportional to the second differential value ΔΔPMn of the intake pipe pressure.

In addition, since the reference values L ₁ and L ₂ are set to positive values, during steady driving when △△PMn is 0 (△PM
= 0) or during slow acceleration (△PM = constant), asynchronous injection is not performed.

Figure 6 shows the throttle opening during acceleration, the actual intake pipe pressure P, the intake pipe pressure PM detected by the pressure sensor, the first differential value △PM of the intake pipe pressure PM, and the second differential value of the intake pipe pressure PM. It shows the temporal changes in the drive voltage of △△PM and the fuel injection valve. 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,
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 Ib indicates synchronous injection that is injected in synchronization with the crank angle, and is an injection that corresponds to the basic injection amount determined according to intake pipe pressure PM and engine speed, corrected by engine cooling water temperature, etc. be. Pulse Ic is an asynchronous accelerated fuel injection performed in conjunction with the execution of step S28, and △△PMn remains at the first level until a predetermined time elapses after the fully closed throttle valve is opened, that is, after acceleration has started. When the reference value L1 or _more is reached, a first amount of fuel is injected. Pulse Id is an asynchronous accelerated fuel injection performed in conjunction with the execution of step S30, and
After asynchronous injection by Ic, △△PMn is the second reference value
When L ₂ or more is reached, a second amount of fuel is injected. △
Since △PMn increases more than △PMn at the start of acceleration, it is possible to quickly and accurately detect the start of acceleration and perform asynchronous acceleration fuel injection.
Furthermore, since the increase in ΔΔPMn closely reflects the increase in the throttle opening, asynchronous accelerated fuel injection can be performed depending on the acceleration state.

In the above embodiment, an engine was described 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
PMn△PMn, △△PMn are respectively Qn, △Qn, △△
Replaced by Qn. 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, asynchronous injection can be performed with good response during acceleration, and asynchronous injection can be performed thereafter depending on the acceleration state, so that the air-fuel ratio during acceleration can be made appropriate. As a result, drivability during acceleration and exhaust gas purification rate can be improved.

[Brief explanation of the drawing]

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 flow chart showing the main routine, and Fig. 4 is a 4 msec routine. Flow diagram shown, No. 5
The figure is a flowchart showing the asynchronous injection routine, and FIG. 6 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. Detecting the load of the engine, injecting fuel according to the load in synchronization with the crank angle, and when the detected rate of change of the engine load is equal to or higher than a predetermined value. , in the electronically controlled fuel injection method for an internal combustion engine that injects a predetermined amount of fuel asynchronously with the crank angle, the elapsed time from the time when acceleration operation is started is determined, and if the elapsed time is within the predetermined time, The predetermined amount of fuel is a predetermined amount, and when the time period exceeds the predetermined time period, the predetermined fuel amount is set to an amount corresponding to a rate of change in the rate of change of the engine load. Electronically controlled fuel injection method for internal combustion engines.