JPS62348B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection control method for an automobile engine, and particularly to a method for calculating and outputting a fuel injection control pulse width.

In the electronic fuel injection control system using a microcomputer, various information such as engine speed, intake air amount, throttle opening, cooling water temperature, intake air temperature, battery voltage, oxygen concentration in exhaust gas, etc. is input, and this information is The optimum fuel injection amount (fuel injection control pulse width) for the engine operating conditions at that time.
is calculated and output, and this output drives a fuel injection device (injector) to perform fuel injection.

Here, in order to improve the responsiveness of the fuel injection control described above, (1) improving the responsiveness of the various sensors that output the various types of information, (2) importing and importing the various sensor outputs into the microcomputer; One possibility is to improve the calculation and output speed of later microcomputers.

The present invention relates to the latter.

The latter ideal state is to input various information necessary for calculating the width of the fuel injection control pulse within a very short period of time immediately before the output of the fuel injection control pulse is to be started, and to output the pulse based on the input information. This is to calculate the width and start outputting the pulse width as a result of the calculation.

However, when performing the above processing every time the crankshaft rotates by a certain angle, for example, the fuel injection control pulse is In reality, the output start timing is significantly delayed from the ideal timing.

The following will explain the fuel injection control device shown in FIG. 1 as an example.

In Fig. 1, 1 is a microcomputer;
2 is engine intake air amount information and intake air temperature information from the air flow sensor and intake temperature sensor installed in the intake pipe, throttle opening information from the throttle position sensor, cooling water temperature information from the cooling water temperature sensor, and an analog-to-digital converter (A/D converter) that converts analog information such as a divided voltage value of a battery voltage into a digital quantity based on instructions from the microcomputer 1 and outputs it to the microcomputer 1;
3 is attached to the crankshaft, and outputs a signal as shown in Fig. 2a every time the crankshaft rotates by a certain angle (θ°).It shapes the output of the crank angle sensor and generates a crank pulse as shown in Fig. 2b. 4 is a timer that measures the crank pulse period and outputs the measurement result to the microcomputer; 5 is a drive circuit that drives the fuel injection injector with an injector control signal that is the output of the microcomputer; It is.

FIG. 2 is an explanatory diagram of the conventional operation of the configuration example of FIG. 1. In FIG. 2, a shows the crank angle sensor output, b shows the crank pulse which is the output of the waveform shaping circuit 3, and c shows the time division of the calculation routine of the microcomputer. In addition, in Fig. 2c, T
_A is the crank pulse interrupt routine execution time, and T _B is the background routine execution time. FIG. 2d is a fuel injection control pulse.

In the fuel injection control device shown in Fig. 1, input information such as intake air amount, intake air temperature, throttle opening, cooling water temperature, battery voltage, and engine speed are conventionally input as (A) (B) Those with large fluctuation speeds (intake air amount, throttle opening, and engine speed) and (B) those with small fluctuation speeds (intake air temperature, cooling water temperature, and battery voltage), and the latter (analog・Digital conversion), and correction coefficients K _A (intake air temperature correction coefficient), K _W (cooling water temperature correction coefficient), K _A
The calculations of _W (K _A ×K _W ) and τ _V (injector invalid injection time...depends on battery voltage) are performed during the background routine (during time T _B in Figure 2 c), and the former (analog)
digital conversion and crank pulse period - engine rotation speed - measurement), the basic injection amount τ ₀ determined by the crank pulse period and intake air amount information, and the addition determined by the amount of change in throttle opening. Calculation of deceleration increase/decrease τ _AD and fuel injection control pulse width τ determined by the above τ ₀ , τ _AD , K _AW , τ _V = (τ ₀ + τ _AD )×K _AW
The calculation of +τ _V and the start of output are executed during the crank pulse interrupt routine (during time T _A in FIG. 3c) which is executed every time a crank pulse is input.

The flowchart of these operations is shown in Figure 3a and b.
Shown below. FIG. 3a is a flowchart of a background routine, and FIG. 3b is a flowchart of an interrupt routine using a crank pulse.

As mentioned above, conventionally, there are generally many processing items to be executed during _the time T _A shown in FIG.

The present invention provides a fuel injection control method that shortens the above-mentioned time T _A and improves the response performance of a fuel injection control device.

One way to shorten the above time T _A is to temporarily output the fuel injection control pulse immediately after the crank pulse is output, and then re-input the temporarily output pulse width once the calculation of the fuel injection control pulse width is completed. A method has been proposed to set the
Publication No. 1, “Method for controlling fuel injection device”).

This method determines whether fuel cut is not performed (failure to inject fuel at the timing when fuel injection should be performed under specific engine operating conditions) or whether fuel cut is performed (when engine operating conditions are This is effective when determining whether the cutting condition has been met or not using a routine other than the clamp pulse interrupt routine. However, fuel cut is effective from the point of view of fuel efficiency, and the judgment of whether or not fuel cut is effective from the point of view of engine response performance and fuel efficiency is based on the conditions necessary for the judgment just before the start of fuel injection. It is most effective to import the information and make decisions based on this.

The present invention takes these points into consideration.

Here, the relationship between the fuel injection amount Q of the injector and the fuel injection control pulse width τ is as follows: Q = (τ - τ _V )q Where, q: Fuel injection amount per unit time τ _V : Ineffective injection time of the injector [i.e. , when the fuel injection control pulse width is less than or equal to τ _V , the injector does not open and fuel injection is not performed. This invalid injection time τ _V depends on the injector drive power supply voltage (automobile battery voltage). ] It is.

Therefore, when the time T _{A from the start of the crank pulse interrupt routine to the start of fuel injection control pulse width calculation and output and the invalid injection time τ V are} τ _V T _A , immediately after the start of the crank pulse interrupt routine. (T _A
A fuel injection control pulse having a pulse width T that satisfies the relationship Tτ _V ) is temporarily output, and when the calculation of the fuel injection control pulse width is completed, the pulse width is reset to the pulse width based on the calculation result. Also, when τ _V < _TA , after starting the crank pulse interrupt routine ( _TA <
A fuel injection control pulse with a pulse width T″ (<τ _V ) is provisionally output after a time T′ that satisfies the relationship T′+T″), and when the calculation of the fuel injection control pulse width is completed, a pulse based on the calculation result is output. Reset to width.

A flow chart of the above process (in the case of τ _V T _A ) is shown in FIG. 4, and a time chart is shown in FIG. 5.

FIG. 6 shows the functional blocks of an apparatus implementing the method of one embodiment of the present invention.

In FIG. 6, the same parts as in FIG. 1 are given the same numbers.

In FIG. 6, 6 is an invalid injection time calculating means for calculating the invalid injection time (τ _V ) of the injector based on the battery voltage information from the A/D converter 2, and 7 is the invalid injection time calculating means 6 calculated by the invalid injection time calculating means 6. This is an invalid injection time setting means for setting the injection time (τ _V ) in the timer 8 at the rising timing of the crank pulse output from the waveform shaping circuit 3. The output of the timer 8 becomes "H" when the invalid injection time (τ _V ) is set, and is counted down by the clock pulse from the clock pulse generating means 9. When the timer 8 is counted down to zero, the output becomes "L". ” becomes. That is, the timer 8 outputs a pulse with a time width corresponding to the set value. Reference numeral 10 denotes a fuel cut necessity determining means for determining whether or not a fuel cut is to be performed, mainly based on the crank pulse cycle information output from the timer 4 and the intake air amount information from the A/D converter 2.
11 is crank pulse cycle information from timer 4;
Fuel injection time calculation means calculates the fuel injection time (τ) based on the intake air amount information, throttle opening information, etc. from the A/D converter 2, and 12 is a crankshaft control unit that calculates the fuel injection time (τ) obtained by the calculation. The (τ- _TA ) calculation means 13 subtracts the pulse interrupt routine processing time ( _TA ), and 13 resets (τ- _TA ) to the timer 8 at the timing when the (τ- _TA ) calculation is completed (τ -τ _A ) is a setting means.

In Fig. 6, the invalid injection time (τ _V ) is set in the timer 8 at the timing of the rise of the crank pulse output from the waveform shaping circuit 3 (Fig. 5 A), and the output of the timer 8 becomes "H" and the fuel is injected. As the temporary injection control pulse (FIG. 5C) rises, a down count is performed. In parallel with the rise of the fuel injection control provisional pulse (FIG. 5 c), it is determined whether or not to perform a fail cut. If it is determined that the fail cut is not possible, the calculation of the fuel injection time (τ) and the calculation of the fuel injection time (τ) are performed.
T _A ) is calculated, and (τ - T _A ) is reset in the timer 8 when the calculation is completed. This (τ
-T _A ), the fuel injection control pulse (FIG. 5 (c)) is "H", and (τ- _TA ) is reset, the fuel injection control pulse continues to be "H". The timer 8 starts counting down when (τ- _TA ) is set, and when the count value reaches zero, the output of the timer 8 becomes "L". In this way, timer 8
is (τ−T _A ) from the time of setting the invalid injection time (τ _V ).
A fuel injection control pulse (FIG. 5D) with a time width (τ) until the down count value of becomes zero is output. Note that when the fail cut determination means 10 determines that a fail cut is necessary, the fuel injection time (τ) and (τ− _TA ) are not calculated. Therefore, the timer 8 is not reset to (τ - T _A ), and the time width T shown in FIG.
(The temporary fuel injection control pulse of Tτ _V is only output, but no fuel injection is performed.

By outputting the fuel injection control pulse as described above, even if the fuel cut is found after temporarily outputting the fuel injection control pulse, the temporary output pulse width must be reset at the time of resetting. For example, since the temporary output pulse width is less than or equal to the invalid injection time τ _V , the fuel is cut.

In the above description, the output timing of the fuel injection pulse is set at the time of crank pulse input, but the method of the present invention can also be applied to every predetermined time period.

As described above, according to the method for calculating and outputting the fuel injection control pulse width according to the present invention, improvements in response performance of the fuel injection control device, improvement in fuel efficiency, and good timing for starting and ending fuel cut can be achieved. It is possible to obtain many effects such as improved driving performance.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a general fuel injection control device, Fig. 2 a to d are timing charts of a conventional device, and Fig. 3 a and b are a background routine and a crank pulse interrupt routine of a conventional device, respectively. 4 is a flowchart of a fuel injection control method according to an embodiment of the present invention, FIG. 5 is a timing chart of the fuel injection control method, and FIG. 6 is a flowchart of an apparatus for implementing the fuel injection control method. It is a diagram shown in functional blocks. 1...Microcomputer, 2...Analog-digital converter (A/D converter), 3
...Waveform shaping circuit, 4...Timer, 5...Drive circuit.

Claims (1)

[Claims] 1 Every time the crankshaft rotates by a certain angle or every predetermined time period, a fuel injection control pulse with a pulse width less than or equal to the injector's invalid injection time is temporarily output, and a determination is made as to whether or not a fuel cut is necessary. When it is determined that this is the case, the fuel injection control pulse width is calculated, and the previously temporarily set fuel injection control pulse width is reset to the fuel injection control pulse width obtained by the above calculation. Injection control method.