JPH0647956B2 - Electronically controlled fuel injection method for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electronically controlled fuel injection method for an internal combustion engine that does not have a throttle opening sensor that can linearly detect a throttle valve opening, and particularly relates to a crank angle. The present invention relates to an electronically controlled fuel injection method for an internal combustion engine, which performs synchronous injection for injecting fuel at a predetermined cycle and asynchronous injection for injecting fuel asynchronously with a crank angle during acceleration.

[Conventional technology]

Conventionally, so that it projects into the intake manifold,
A fuel injection method is known in which a fuel injection valve is provided for each cylinder, a signal input from various sensors is processed by a microcomputer to determine an engine operating state, and an amount of fuel corresponding to the operating state is injected. . In this fuel injection method,
Synchronous injection in which fuel is injected simultaneously in all cylinders or in each specific cylinder in a predetermined cycle, and asynchronous injection in which fuel is injected at the time of acceleration regardless of synchronous injection are performed.

Asynchronous injection during acceleration is performed to improve engine responsiveness during acceleration, so conventionally, a linear throttle sensor (linear throttle sensor) that outputs a voltage that is a linear function with respect to the throttle opening is used. Installation,
Some of them perform asynchronous injection according to the rate of change of the output voltage.

As a method for detecting acceleration, it is the fastest method to detect a change in throttle opening. For this purpose, as described above, a voltage that is a linear function with respect to the throttle opening is output. That is, a linear throttle sensor that can detect the full throttle opening is essential.

However, since such a sensor is expensive, there is a demand for a technique capable of quickly executing asynchronous injection at the time of acceleration without using such a sensor. It has been previously proposed that the above-mentioned demand is achieved by using a detected value and performing an asynchronous injection by detecting acceleration when the second differential value of the detected value is equal to or greater than a predetermined reference value. (Japanese Patent Application No. 57-149203) [Problems to be Solved by the Invention] However, even with the above-mentioned prior art,
When the comparison reference value of the two-time differential value is set so that the asynchronous injection is performed early in the initial stage of acceleration, acceleration proceeds,
Even if the need for asynchronous injection is reduced, asynchronous injection is executed in the same manner as in the initial stage of acceleration, and as a result, the number of times asynchronous injection is executed increases, and conversely there is a problem of overrich.

Therefore, the present invention determines the time based on the time point when the acceleration operation is started, and performs the asynchronous injection when the change rate of the change rate of the intake air amount is equal to or greater than a predetermined reference value. It is an object to solve the above problem by increasing the predetermined reference value.

[Means for Solving the Problems]

In order to solve the above-mentioned object, the present invention detects the intake air amount of an engine, injects fuel in accordance with the intake air amount in synchronization with a crank angle, and changes the detection rate of the intake air amount. When the rate of change is equal to or greater than a predetermined reference value, in the electronically controlled fuel injection method for an internal combustion engine that injects fuel in a day-synchronous manner with the crank angle, the time is calculated based on the time point when acceleration operation is started, and the time The longer the length, the larger the predetermined reference value.

[Action]

According to the present invention, the intake air amount of the engine is detected, the fuel corresponding to the intake air amount is injected in synchronization with the crank angle, and the change rate of the change rate of the detected value of the intake air amount is set to a predetermined standard. When the value is equal to or more than the value, when injecting fuel asynchronously with the crank angle, a time based on the time point when the acceleration operation is started is determined, and the longer the time, the larger the predetermined reference value, As the acceleration progresses, the asynchronous injection execution condition becomes more severe.

As a result, it is possible to quickly execute the asynchronous injection at the time of acceleration without using the linear throttle sensor, and it is possible to prevent the overrich when the acceleration advances.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an example of an internal combustion engine (engine) to which the present invention is applied. An intake air temperature sensor 2 that detects the temperature of intake air and outputs an intake air temperature signal is attached downstream of an air cleaner (not shown). A throttle valve 4 is arranged downstream of the intake air temperature sensor.
A slot switch 6 which is interlocked with and is turned off when the throttle valve is fully closed is opened. A surge tank 8 is provided on the downstream side of the throttle valve 4, and a pressure sensor 10 for detecting the intake pipe pressure on the downstream side of the throttle valve and outputting an intake pipe pressure signal is attached to the surge tank 8. Surge tank 8
Are 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 with a catalytic converter (not shown) filled with a three-way catalyst via an exhaust manifold. Also, for the engine block,
A water temperature sensor 20 that detects a cooling water temperature of the engine and outputs a water temperature signal is attached. Engine combustion chamber 14
The tip of the spark plug 22 is projected into the
A distributor 32 is connected to 2. The distributor 24 is provided with a cylinder discriminating sensor 26 and an engine speed sensor 28, each of which is composed of a pick-up fixed to the distributor housing and a signal rotor fixed to the distributor shaft. The cylinder discrimination sensor 26 is, for example, 720 ° CA.
The cylinder discrimination signal is output to the control circuit 30 composed of a microcomputer for each time, and the engine speed sensor 28 outputs the crank angle signal to the control circuit 30 at every 30 ° CA, for example. The distributor 24 is connected to the igniter 32. Reference numeral 34 is an O ₂ sensor that detects the residual acidity in the exhaust gas and outputs an air-fuel ratio signal.

As shown in FIG. 2, the control circuit 30 includes a central processing unit (C
PU) 36, read only memory (ROM) 38, random access memory (RAM) 40, back up RAM (BU-RAM) 42, input / output port (I / O) 44,
It is configured to include an analog digital converter (ADC) 46 and buses such as a data bus and a control bus that connect these. The I / O 44 has a cylinder discrimination signal,
The crank angle signal, the air-fuel ratio signal, and the throttle signal output from the throttle switch 6 are input, and the fuel injection signal that controls the opening / closing time of the fuel injection valve 16 and the on / off time of the igniter 32 are controlled via a drive circuit. Ignition signal is output. Also, for the ADC 46. The intake pipe pressure signal, the intake temperature signal and the water temperature signal are input and converted into a digital signal.

The above crank angle signal is transmitted to the I / O4 via the waveform shaping circuit.
4 and a digital signal representing the engine 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 an interrupt request signal for basic fuel injection pulse width calculation together with a crank angle signal,
It is used to form a fuel injection start signal, a cylinder discrimination signal, and the like. The on / off signal from the slot switch 6 is I /
It is sent to a predetermined bit position of O44 and temporarily stored. A well-known fuel injection control circuit including a presettable counter, a register, and the like is provided in the I / O 44, and an injection having a pulse width based on binary data regarding the injection pulse width sent from the CPU 36 is provided. A pulse signal is formed, and this injection pulse signal is supplied to the fuel injection valve 1
Input to 6 sequentially or simultaneously to energize the injection valve. As a result, the amount of fuel corresponding to the pulse width of the injection pulse signal is injected synchronously or asynchronously. In the ROM 38, a main processing routine program, an interrupt processing routine program for calculating a fuel injection pulse width, an interrupt processing routine program for calculating a coefficient such as a partial lean correction coefficient,
Other programs and various data necessary for each of the above-mentioned arithmetic processes are stored in advance. Further, in the ROM 38, data relating to the first amount and the second amount for asynchronous fuel injection and the map shown in FIG. 3 are stored in advance. This map defines the reference value L for the count value C of the counter for counting the time based on the time when the throttle valve in the fully closed state as the start time of acceleration is opened, and the count value C The reference value L is set to increase stepwise as the value increases.

Next, the asynchronous injection routine of the present invention will be described with reference to FIGS. 4 to 7. Note that the synchronous injection routine and the like are the same as the conventional ones, and thus the description thereof is omitted. FIG. 4 shows a 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 slot switch is on, step S
After resetting the flag XLL in step 3, the routine proceeds to the next routine, and if the slot switch is off, it is judged whether or not the flag XLL set by the slot switch off is reset. If the flag XLL has been set, the routine proceeds to the next routine. If the flag XLL has been reset, that is, if the previous slot switch has been turned on, the counter is cleared in step S6, and the flag XLL is set in step S8. To do. Therefore, the counter is always counted and is cleared when the slot switch is changed 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 accordingly the time when the throttle valve is opened from the fully closed state, as the time from the start of acceleration.

FIG. 5 shows a routine for incrementing the counter every predetermined time, and in this embodiment, step S1.
In 2, the count value C of the counter is incremented every 4 msec. In addition, in step S10 and step S14, the count value C of the counter is set to the maximum value M.
By limiting to AX, overflow of the counter is prevented.

FIG. 6 shows a reference value processing routine for changing the reference value L according to the engine speed NE. Step S
9, the engine speed NE is a predetermined value (for example, 18
00r. p. m) or more, and only when the engine speed is less than the predetermined value, a positive predetermined value A is added to the reference value L in step S11 to increase the reference value L. This is because in the low engine speed region, the ripple of the intake pipe pressure due to the fluctuation of the engine speed is large even in the steady running state, not to mention the transient state, so that the asynchronous injection is not executed. As a result, the reference value L is increased from the time when the throttle switch changes from on to off, that is, the time from the start of acceleration, and is further increased in the low engine speed region, as shown in FIG. R
It is stored in a predetermined address of AM.

FIG. 7 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 interrupted when the AD conversion of the intake pipe pressure PM is completed. The intake pipe pressure P
The AD conversion of M is executed every 12 msec. In step S16, the difference between the intake pipe pressure PMn of this time and the intake pipe pressure PM _n-2 of the previous time, that is, 24 msec before is calculated, and the change amount of the intake pipe pressure during 24 msec, that is, the change rate ΔPM _n is calculated. This rate of change ΔPM _n is equivalent to the one-step differentiation of the intake pipe pressure PM with respect to time. In step S18, the difference between the change rate ΔPM _{n of} this time and the change rate ΔPM _{n−1 of} 12 msec before is calculated, and 1 is calculated.
The amount of change in the rate of change for 2 msec, that is, the rate of change in the rate of change in intake pipe pressure ΔΔPM _n is calculated. This rate of change ΔΔPM
_n is equivalent to the second derivative with respect to time.

Therefore, in the following, the change rates ΔPM _n and ΔΔPM _n are respectively 1
It will be described as a second derivative value.

In step S20, it is determined whether or not the throttle switch is turned on, and in step S22, the first-order differential value ΔPM of the intake pipe pressure.
_It is determined whether or not _n is negative, and the following steps are executed only when the slot switch is off and the first-order differential value ΔPM _n is 0 or more. Therefore, the asynchronous injection is not performed when the first-order differential value ΔPM _n is negative, that is, during deceleration. In the next step S24, it is determined whether or not the count value C of the counter exceeds a predetermined value (for example, 6). Depending on whether or not the count value exceeds the predetermined value, asynchronous injection is performed in the subsequent steps. The method of obtaining the asynchronous injection amount when judged is changed. That is, if the count value does not exceed the predetermined value, the asynchronous injection amount is determined in step S28, and if the count value exceeds the predetermined value, step S32.
The asynchronous injection amount is determined by. Next, if the count value C is 6 or less, the reference value L is read from the RAM in step S25 and then the process proceeds to step S26. If the count value exceeds 6, the reference value L is read from the RAM in step S27 and then step S30. Go to. This reference value L is obtained from the map shown in FIG. 3 based on the count value C counted in the routine of FIG. 5, and it is assumed that the count value C increases, that is, increases with the lapse of time from the start of acceleration. .

In step S26, the second-order differential value ΔΔPM of the intake pipe pressure
_It is determined whether _n is greater than or _equal to the first reference value L ₁ (positive value),
The asynchronous injection pulse width TAU is set to a predetermined value (for example, 2 msec) in step S28 only when the _first reference value L ₁ or more. As a result, the first amount of fuel corresponding to the asynchronous injection pulse width TAU is asynchronously injected during acceleration from the time when the throttle valve in the fully closed state is opened until a predetermined time (24 msec) elapses.

Further, in step S30, the second-order differential value Δ of the intake pipe pressure
It is determined whether ΔPM _n is greater than or _equal to the second reference value L ₂ (positive value), and only when the _second reference value L _{2 is} greater than or equal to step S32
Then, the asynchronous injection pulse width TAU is determined according to the following equation.

The coefficients 0.51 and 24 are determined by experiments, and the coefficient 1000 is a constant for converting the time into a unit of msec. As a result, after the lapse of the predetermined time, the second amount of fuel corresponding to the asynchronous injection pulse width proportional to the second-order differential value ΔΔPM _n of the intake pipe pressure is injected.

Since the reference values L ₁ and L ₂ are set to positive values,
Asynchronous injection is not performed during steady running (ΔPM _n = 0) when ΔΔPM _n is 0 or during relaxation speed (ΔPM _n = constant).

FIG. 8 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 the time variation of the drive voltage of the fuel injection valve. The fuel injection valve is maintained in the open state to inject fuel during the period when the drive voltage is at a low level. When acceleration starts at time t ₁ , the throttle opening increases from 0 °. Along with this, the actual intake pipe pressure P increases, and the intake pipe pressure PM as the detection value of the pressure sensor also increases.
Overshoot occurs in the intake pipe pressure PM. The pulse Ib indicates a synchronous injection that is injected in synchronization with the crank angle, and is an injection corresponding to an amount obtained by correcting the basic injection amount that is determined according to the intake pipe pressure PM and the engine speed with the engine cooling water temperature or the like. is there. The pulse Ic is step S28.
Asynchronous acceleration fuel injection performed with the execution of
When ΔΔPM _n becomes _equal to or larger than the first reference value L ₁ until a predetermined time elapses after the throttle valve in the fully closed state is opened, the first amount of fuel corresponding to the asynchronous injection pulse width (2 msec) is injected. The pulse Id is the asynchronous acceleration fuel injection performed in association with the execution of step S30, and the pulse Ic
When ΔΔPM _n after the asynchronous injection by becomes equal to or larger than the second reference value L ₂ , the second amount of fuel corresponding to the asynchronous injection pulse width obtained in step S32 is injected. ΔΔPM is ΔPM
Since the increase at the start of acceleration is large, the start of acceleration can be detected promptly and accurately to perform asynchronous acceleration fuel injection, and the increase in ΔΔPM well reflects the increase in the throttle opening. Asynchronous acceleration fuel injection can be performed depending on the acceleration state.

In the above embodiment, the engine in which the basic fuel injection amount is calculated based on the intake pipe pressure and the engine speed has been described, but the present invention is the intake air amount Q per engine revolution.
It can also be applied to an engine that calculates the basic fuel injection amount based on the engine speed. In this case, PM _n , ΔPM _n , and ΔΔPM _n in FIG. 5 are Q _n , ΔQ _n , and Δ, respectively.
Replaced by ΔQ _n . Further, the asynchronous injection timing can be determined from the differential value of the function having the fuel injection pulse width as a variable, as in the present embodiment.

As described above, in the present embodiment, since the contact type throttle sensor is used without using the linear throttle sensor, the structure is simple and the cost is reduced, and the reference value is increased in the low engine rotation range. As a result, the asynchronous injection is not performed and the driver's ability is improved.

〔The invention's effect〕

As described above, according to the present invention, it is possible to quickly execute the asynchronous injection at the time of acceleration without using the linear throttle sensor, and it is possible to prevent the overrich when the acceleration proceeds.

[Brief description 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.
FIG. 4 is a diagram showing a map of the reference value with respect to the count value, FIG. 4 is a flow chart showing the main routine, and FIG. 5 is 4 msec.
FIG. 6 is a flow chart showing a routine, FIG. 6 is a flow chart showing a routine for changing the reference value according to the engine speed, FIG. 7 is a flow chart showing an asynchronous injection routine, and FIG. 8 is a drive voltage of the fuel injection valve at the time of acceleration. It is a diagram showing the time change of. 6 ... Slot sensor, 10 ... Pressure sensor, 16 ...
… Fuel injection valve.

Claims (1)

[Claims] 1. An intake air amount of an engine is detected, fuel corresponding to the intake air amount is injected in synchronization with a crank angle, and
In the electronically controlled fuel injection method for an internal combustion engine that injects fuel asynchronously with the crank angle, when the rate of change in the rate of change in the detected value of the intake air is greater than or equal to a predetermined reference value, the time point at which acceleration operation is started An electronically controlled fuel injection method for an internal combustion engine, comprising: determining a reference time and increasing the predetermined reference value as the time is longer.