JPS59206626A - Method of electronically controlled fuel injection in internal-combustion engine - Google Patents

Abstract

PURPOSE:To dispense with a linear throttle sensor, by determining a fuel increase value depending on the quantity of the change in the load upon an engine from the time of opening of an entirely closed throttle valve to the lapse of a prescribed period. CONSTITUTION:A throttle sensor 6 detects the time of opening of a throttle valve entirely closed. The quantity of the change in the negative pressure in an intake pipe from said time to the lapse of a prescribed period is detected by using the signal of a pressure sensor 10. A fuel increase value is determined depending on the quantity of the change in the negative pressure in the intake pipe. This constitution dispenses with a linear throttle sensor. The construction of a controller is thus simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronically controlled fuel injection method for an internal combustion engine, and particularly relates to a synchronous injection method in which fuel is injected at a predetermined period according to the crank angle, and an asynchronous injection method in which fuel is injected asynchronously to the crank angle during acceleration. This invention relates to an electronically controlled fuel injection method for an internal combustion engine.

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,
Synchronous injection in which fuel is injected to all cylinders simultaneously or to each specific cylinder at a predetermined period, and asynchronous injection in which fuel is injected during acceleration regardless of the synchronous injection are performed. Synchronous injection uses engine load (
The basic fuel injection pulse width is calculated according to the intake pipe pressure or the amount of intake air per engine revolution) and the engine speed, and this basic fuel injection pulse width is used to calculate the partial lean correction coefficient, feedback correction coefficient, cooling water temperature, etc. The fuel injection pulse width is determined by correcting the fuel injection pulse width using another correction coefficient determined according to the fuel injection pulse width, and the fuel injection valve is opened to inject fuel at a time when the fuel injection pulse width is adjusted to the fuel injection pulse width at a predetermined crank angle. In addition, asynchronous injection during acceleration is performed to improve engine response during acceleration, etc.A linear throttle sensor that outputs a voltage that is a linear function of the throttle opening is installed, and the output voltage The system injects fuel independently of synchronous injection according to the rate of change in engine load and the rate of change in engine load. According to this asynchronous injection, the air-fuel ratio that occurs during a transient period at the beginning of acceleration is corrected, so drivability and exhaust gas purification rate are improved.

However, with such conventional fuel injection methods, when accelerating from a light load range, the intake pipe pressure and intake air cap increase significantly in response to a slight increase in throttle opening, causing the air-fuel ratio to accelerate during acceleration. cannot be properly controlled depending on the situation,
There was a problem.

The present invention has been made to solve the above problems, and is an internal combustion engine that improves drivability during acceleration and exhaust gas purification rate by appropriately controlling the air-fuel ratio during acceleration according to the acceleration state. The purpose is to provide an electronically controlled fuel injection method.

To achieve the above object, the present invention provides an electronically controlled fuel injection method for an internal combustion engine in which fuel is injected asynchronously with the crank angle when the throttle valve is opened and the rate of change in engine load is a positive value. A first amount of fuel is injected when the rate of change in the engine load is equal to or greater than a first reference value until a predetermined time elapses from the time when the throttle valve in the closed state is opened, and when the predetermined time elapses, the engine The rate of change in the load change rate is the second
A second amount of fuel is injected when the amount is equal to or greater than a reference value. The engine load can be detected from intake pipe pressure, intake air amount per engine rotation, throttle rotation, fuel injection pulse width, etc. Further, in the above configuration, it is preferable that the first amount is a predetermined amount, and the second amount is increased in accordance with the rate of change of the rate of change of the engine load.

According to the configuration of the present invention, the acceleration state is detected based on the rate of change of the engine load, and the fuel injection amount is different between the initial stage of acceleration and after the initial stage of acceleration, so that the acceleration state can be accurately determined. (Not only can it be detected, but it also has the unique effect of being able to obtain an appropriate air-fuel ratio depending on the acceleration state.

An example of an internal combustion engine to which the present invention is applied will be explained in detail with reference to FIG. 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 to the throttle valve 4, which is turned off when the throttle valve is opened. A surge tank 8 is provided downstream of the throttle valve 4, and a pressure sensor 10 is attached to the surge tank 8 to detect the intake pipe pressure downstream of the throttle valve and output 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 engine cooling chamber 14 is connected to a catalytic converter (not shown) filled with a three-way catalyst via an exhaust manifold.The engine block also detects the engine cooling water temperature and outputs a water temperature signal. A water temperature sensor 2o is attached to the combustion chamber 14 of the engine.The tip of a spark plug 22 protrudes into the combustion chamber 14 of the engine.
A distributor 24 is connected to the spark plug 22 . The distributor 24 includes a pickup and a distributor fixed to the distributor housing.
A cylinder discrimination sensor 26 and an engine rotation speed sensor 28, each constituted by a signal rotor fixed to the heat engine 7, are provided. The cylinder discrimination sensor 26 is configured with a microcomputer or the like and outputs a cylinder discrimination signal to the control circuit 30 every 720'CA, for example, and the engine rotation speed sensor 28 outputs a crank angle signal to the control circuit 30 every 300CA, for example. Further, the distributor 24 is connected to the igniter 32. In addition, 3
4 is an O2 sensor that detects residual acidity in exhaust gas and outputs an air-fuel ratio signal.

As shown in FIG. 2, the control circuit 3o is connected to a central processing unit (C
PU) 36, read-only memory (rt.

M) 38.2 Quantum 7 ri*sume% li (RAM)
40° backup RAM (BU-RAM) 42, input/output capo) (l10) 44, analog-digital converter (
ADC) 46 and buses such as a data bus and a control bus that connect them. l10
44 receives a cylinder discrimination signal, a crank angle signal, an air-fuel ratio signal, and a throttle signal output from the throttle switch 6.
The fuel injection signal and igniter 3 that control the opening/closing time of
An ignition signal is output that controls the on/off time of 2.

Further, an intake pipe pressure signal, an intake air temperature signal, and a water temperature signal are input to the ADC 46 and converted into digital signals.

The above crank angle signal is passed through a waveform shaping circuit to l104.
4, and a digital signal representing the engine speed is formed from this crank angle signal. The cylinder discrimination signal is input to l1044 and converted into a digital signal in the same manner as above. This cylinder discrimination signal, together with the crank angle signal, serves as an interrupt request signal for basic fuel injection pulse width calculation.
The on/off signal for fuel injection throttle switch 6 is l.
1044 and is sent to a predetermined bit position and temporarily stored. Also, in l1044, there are presettable counters, V registers, etc. A well-known fuel+fR injection control circuit 46 is provided, which forms an injection pulse signal having the pulse width from binary data regarding the injection pulse width sent from the CPU 36, and transmits this injection pulse signal to the fuel injection valve. 16 sequentially or simultaneously to energize the injection valves. 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 the fuel injection N/< Luz width, an interrupt processing routine program for calculating coefficients such as the partial lean correction coefficient, other programs, and the above-mentioned calculation processing. Various necessary data are stored in advance. Also, R
The OM38 includes a first quantity and a second quantity for asynchronous fuel injection.
Data regarding the amount of L1, a first reference value L1, and a second reference value 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. Figure 3 tt
This shows the main routine, and 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 flag XLL is reset in step S3 and then the routine proceeds to the next step. If the throttle switch is off, it is determined whether the flag XLL set when the throttle switch is on has been reset. If flag XLL is set, proceed to the next routine; if flag XLL is reset,
That is, if the throttle switch was turned on last time, the counter is cleared in step S6, and the counter is cleared in step S8.
Set the flag XLLi. Therefore, the counter is constantly 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 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, step 81
2, the color is incremented by 4 every m5ec. 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 SL4.

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 AD conversion of the intake pipe pressure PM is completed. In addition, the intake pipe pressure P
The AD conversion of M is set to be executed every 12m5.

In step S16, the current intake pipe pressure PMn and the intake pipe pressure PMn-
2, and calculate the change f in the intake pipe pressure during 24 m5ec, that is, the rate of change ΔP M n. 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 ΔP M n and the previous rate of change ΔPMn-1, i.e., l 2' m5ec ago, is calculated, and the amount of change in the rate of change during 12 m5ec, that is, the change in intake pipe pressure is calculated. rate of change △
Calculate ΔP M n. This rate of change ΔΔP M n is equivalent to a second-order differential with respect to time.

Therefore, the rates of change ΔPMn and ΔΔP M n will be described below as first-order differential values and second-order differential values, respectively.

In step S20, it is determined whether or not the throttle switch is on, and in step S22, the first differential value ΔP of the intake pipe pressure is determined.
It is determined whether M n is negative or not, and the following steps are executed only when the throttle switch is off and the first-order differential value ΔP M n is 0 or more. Accordingly, it is determined whether the count value C exceeds 6), and if the count value C is 6 or less, step S26
If the count value C exceeds 6, proceed to step 83.
Proceed to 0.

In step S26, the second differential value △△P of the intake pipe pressure
It is determined whether or not Mn is greater than or equal to the first reference value Lt (positive value), and only when it is greater than or equal to the first reference value L1, the asynchronous injection pulse @TAUy is set to a predetermined value (for example, 2m5ec) in step 828.
). As a result, injection is performed asynchronously in a fully closed state.

Further, in step S30, the second-order differential value △ of the intake pipe pressure
Determine whether ΔP M n is greater than or equal to the second reference value L2 (positive value), and only when the second reference value is greater than or equal to 2, proceed to step 8.
At step 32, the asynchronous injection pulse width TAU is determined according to the following two.

Note that the coefficients 0.51 and 24 were determined through experiments, and the coefficient 1000 is a constant for converting into time in units of msec. As a result, the reference value above, L! is set to a positive value, so Δ△
Asynchronous injection is not performed during steady driving when PM is O (ΔPM-〇-) or during slow acceleration (ΔPM-constant).

Figure 6 shows the throttle opening during acceleration and the actual intake pipe pressure P.
, the intake pipe pressure PM detected by the pressure sensor, the first differential value ΔPM of the intake pipe pressure PM, the second differential value ΔΔPM of the intake pipe pressure PM, and the driving voltage of the fuel injection valve over time. 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 t, the throttle opening increases from 00. Accordingly, 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 1b indicates synchronous injection that is injected in synchronization with the crank angle, and corresponds to an amount obtained by correcting the basic injection amount determined according to the intake pipe pressure PM and the engine rotational speed based on the engine cooling water temperature and the like. The pulse Ic is an asynchronous accelerated fuel injection performed in conjunction with the execution of step 828, and when ΔΔP M n becomes equal to or greater than the first reference value L1 ↓ until a predetermined time has elapsed after the throttle valve in the fully closed state is opened. injecting a first amount of fuel; The pulse Id is an asynchronous accelerated fuel injection performed in conjunction with the execution of step S30, and a second amount of fuel is injected as soon as Δmm PMn reaches a second reference value of 3 or more after the asynchronous injection by the pulse Ic. △ΔP M n is ΔP M
Since the downward rise at the start of acceleration is larger than n, the start of acceleration can be quickly and accurately detected and asynchronous acceleration fuel injection can be performed. Therefore, 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 was calculated based on the intake pipe pressure and the engine rotation speed, but the present invention is based on the intake air amount Q per engine rotation.
It is also possible to apply this method to an engine in which the basic fuel injection amount is calculated based on the engine speed and the engine speed. In this case, PMn△PMn and △△PMn in Fig. 5 are each h Qn
, △Qn, △△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 linear throttle sensor is not used (a contact type throttle sensor is used, so the structure is simple and costs are reduced).

[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, and FIG.
The figure is a flowchart showing the main routine, Figure 4 is 4 m5e
FIG. 5 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, 1
6...Fuel injection valve. Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] (1) In an electronically controlled fuel injection method for an internal combustion engine in which fuel is injected asynchronously with the crank angle when the throttle valve is opened and the rate of change in engine load is a positive value, A first amount of fuel is injected when the rate of change in the engine load is equal to or greater than a first reference value from the time when the valve is opened until a predetermined time elapses, and the rate of change in the engine load is injected after the predetermined time elapses. An electronically controlled fuel injection method for an internal combustion engine, characterized in that a second amount of fuel is injected when a rate of change in the engine load is equal to or higher than a second reference value. (2) The second amount is a rate of change in the engine load. 2. The electronically controlled fuel injection method for an internal combustion engine according to claim 1, wherein the fuel injection rate is increased according to the rate of change of .