JPS601519A - Computing method of amount of intake air - Google Patents

Abstract

PURPOSE:To make it possible to compute the adequate amount of intake air regardless of the pulsating output of an air flowmeter, by providing the air flowmeter in the intake air path of an engine, and providing the maximum value of the amount of the detected intake air in the air flowmeter. CONSTITUTION:An air flowmeter 1 is provided in an intake air path 4 of an engine. The maximum value Qmax of the amount of detected intake air Q' during a period, which is longer than the pulsating period of an amount of the detected intake air Q' of an air flowmeter 1, is obtained. During the period the maximum value Qmax exceeds a limit value Qg, a specified value Qc is determined as the amount of the intake air Q. Therefore, the fact that pulsation in the output of the air flowmeter is increased is detected by the values of Qmax >=Qg. Even at a point where the output of the air flowmeter is largely pulsating, the adequate amount of the intake air can be computed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake air amount subtraction method for dividing the intake air amount of an engine using an air flow meter.

In a vane-type air flow meter, which detects the amount of intake air from the rotation angle of a measurement plate (vane) that rotates in relation to the amount of intake air, when the throttle valve is near full opening, the rotation angle of the measurement plate is the angle corresponding to the actual amount of intake air. Since the amount of fuel injection calculated based on the amount of intake air becomes excessive, a guard is set as an upper limit on the final amount of fuel injection to prevent such a situation. On the other hand, with high-response airflow meters such as the Karman eddy current type and heat wire type, the output changes greatly periodically in synchronization with the intake pulsation. Inhalation air supply c
, LI: becomes a smaller value, and it is difficult to improve the accuracy of air-fuel ratio control when the throttle valve is close to being fully open just by setting a guard on the detected amount.

An object of the present invention is to provide an intake air ifl' calculation method that can calculate an appropriate amount of intake air despite the pulsating output of an air flow meter.

In order to achieve this object, according to the intake air amount subtraction method of the present invention, an air cleaner is provided in the intake passage of the engine,
Maximum value Qma of detected intake air amount Q in a period longer than the pulsation period of intake air fJk Q' detected by the air flow meter
During the period in which the maximum value Qmax is equal to or greater than the limit value 08, a constant value Qc is determined as the intake air mQ.

Therefore, it is detected from the fact that Qmax≧Qg that the pulsation of the output of the air flow meter is increasing, and Qmax
≧ Qg, the constant value Qc is determined as the intake air amount Q, so even if the output of the air flow meter pulsates greatly and the detection timing corresponds to the peak or valley of the pulsating output, the appropriate intake air amount can be calculated. This makes it possible to avoid excesses and shortages of fuel injection 11 calculated based on the intake air f5IQ.

It is preferable that the constant value Qc be approximately the theoretical value of the amount of intake air when the throttle valve is fully open.

Since the period of the air flow meter's pulsating output and the approximate theoretical value of the amount of intake air when the throttle valve is fully open change in relation to the engine speed, the limit value Qg and constant value Qc should be made functions of the engine speed. is preferable.

The present invention is particularly effective when applied to a high response air flow meter such as a Karman vortex air flow meter.

The present invention will be described in detail with reference to the drawings.

In addition, in the calculation of the fuel injection time, the amount of intake air per engine rotation is the basis for subtraction, so in the example, the intake air detected by the air flow meter: fit Q': the maximum value Qmax corresponding to the peak value of the pulsation; Instead of the constant value Qc that should be determined as the intake air mQ when the limit value Qg1 as a guard of Qmax and Q' are deviated from the true value due to pulsation, Qn as a value divided by the engine speed N is used. ' +QnmaX+ Qng+ Q
This will be explained using nc.

1 and 2 show a Karman vortex type air flow meter 1, in which a pipe main body 2 forms an intake passage 4 and is provided between an air cleaner and a throttle valve. The intake air is rectified by first-stage and second-stage rectifier gratings 6 and 8. The vortex generator 10 is provided at the center of the intake passage 4,
The rectified intake air passes on both sides of the vortex generator 10.

The air pressure on both sides of the vortex generator 10 is guided to both sides in the width direction of the span band 14 through the pressure guiding holes 12a+12b. The span band 14 is fixed at one end and pressed by a spring 18 via a pusher 16 at the other end. The span band 14 has @20 at a position corresponding to the upper end of the pressure-conducting holes 12a, 12b.
12b is twisted in relation to the air pressure difference. The light from the light emitting diode 22 may or may not reach the phototransistor 24 due to the oscillation of the mirror 20, so the phototransistor 24 is turned on and off due to the Karman vortex flow, and the pulses generated accordingly. Karman vortex flow (■ intake air flow rate) can be detected by measuring the frequency of .

FIG. 3 shows the change over time of the intake air ff1Qn' per engine revolution calculated from the output of the air flow meter l when the throttle valve is fully open (WOT). Qn' is the detected intake air 1i detected from the output of the air flow meter 1
k It moves 1y1 due to the pulsation of Q'. Note that this engine is a 4-cylinder engine with an exhaust capacity of 2000 cc, and the pulsation period is 180° CA (CA: crank angle).

FIG. 4 shows the relationship between intake pipe pressure and intake air amount per engine revolution. The peak value and average value of the intake air amount qn' per engine revolution calculated based on the output of the air flow meter 1 are the theoretical value (the range where the intake pipe pressure is low) in the range where the throttle valve opening is small (= the range where the intake pipe pressure is low). However, when the throttle valve is fully opened, it pulsates and increases rapidly. In the present invention, it is determined that it is difficult to accurately detect the intake air amount due to the pulsating output of the air flow meter 1 during the period when the peak value Qnp of the detected value is equal to or higher than the guard limit value Qng, and when Qnp≧Qng, it is determined that the intake air amount remains constant during the period when Qnp≧Qng. Let the value Qnc be the intake air amount Qn. The limit value Qng is set as a value for determining that the detected value deviates significantly from the actual value due to the pulsating output of the air flow meter 1. For example, the limit value Qng is set as a value that is slightly larger than the theoretical value when the throttle valve is fully open (WOT). be done. The constant value Qnc is set as the actual value or a value estimated as a value close to it during a period in which the detected value deviates sharply from the actual value, and is, for example, a theoretical value at WOT.

FIG. 5 shows the relationship between the engine rotational speed N and the aforementioned limit value Qng and constant value Qnc. Qng and Qnc
is set as a function of N.

FIG. 6 is a flowchart of the maximum value subtraction routine for Qn'. The air flow meter 1 generates a pulse every time a Karman vortex is generated, and from the period T of this pulse and the engine rotation speed N, it is possible to calculate the amount of intake air ill per engine rotation.
Qn/ is calculated, and the maximum value Qnmax of Qn' is calculated as the peak value of the pulsation of Qn'. Note that this routine is an interrupt routine that is executed every time a pulse occurs, and Q
Since nmax is cleared in step 56 of FIG. 7, it becomes the maximum value of Qn' during one rotation of the engine.

Since the pulsation period of Qn' is equal to 180 degrees in crank angle, one revolution of the engine corresponds to twice the pulsation period of Qn'.

To explain each step in detail, in step 36, the time interval from the previous generation time of the output pulse of the air flow meter to the current generation time is detected as the period 1'' of the output pulse. Step 38 subtracts the amount of intake air Qt per unit time from the equation Qt = K・-, and calculates it by the function 1゛1
``Substitute the intake air amount Qt/N per rotation into Qn'.

However, N is the engine rotation speed, and 1( is a constant.

In step 40, Qn' is compared with Qnmax defined as the maximum value of Qn', and if Qn'≧Qnmax, the process proceeds to step 42, where Qn/ is substituted for Qnmax, and if Qn'<Q'nmax, then In this case, Qnmax is not updated.

FIG. 7 is a flowchart of the fuel injection routine. Since the same KjJ fuel injection from the fuel injection valve is performed every engine revolution in this embodiment, this routine is performed as an interrupt routine due to the generation of a crank pulse.
The fuel injection time is subtracted every time the crank angle changes by 3606.

If Qnmax exceeds the limit value Qng, it is determined that Qn has deviated greatly from the true value due to the pulsation of the output of the air flow meter 1, and a constant value Qnc is substituted for Qn, and q
If lmax is less than the limit value Qng, Qn' is substituted for Qn, the fuel injection time Tp is calculated as a function of Qn thus determined, and fuel injection is performed. To explain each step in detail, in step 46, it is determined whether the crank angle is 360' or not, and only if the determination is positive, the process proceeds to the following steps, and if not, this routine is ended. Step 48 converts the limit value Qng into a function f of the engine rotational speed N.
(N). At step 50, the constant value Qnc
is calculated as a function g(Nl) of the engine rotation speed N. In step 52, Qn old LX and Qng are compared, and Qnm
If ax≧Qng, proceed to step 60 via steps 54 and 56; if Qr++++ax < Qng, proceed to step 60 via step 54.
Then, substitute Qnc for Qn, and in step 56, Qnma
Clear x. In step 58, Qn' is substituted for Qn. In step 60, the fuel injection time '1p is expressed as a function b (Qn) of Qn.

In step 62, fuel injection is performed.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of the air flow meter, Fig. 2 is a tentative sectional view taken along the It-It line in Fig. 1, and Fig. 3 is a graph showing the pulsation of the intake air amount per engine revolution. Figure 4 is a graph showing the relationship between intake pipe pressure and intake air amount per engine rotation, and Figure 5 is a graph showing the relationship between engine rotation speed and the limit value and constant value of intake air amount per engine rotation. , Figure 6 is a flowchart of a routine that calculates the maximum amount of intake air per revolution of the engine, and Figure 7 is a flowchart of the fuel injection routine.1... Air flow meter, 4... Intake air Passage, 10... Vortex generator, 22
...Light emitting diode, 24...Phototransistor. Fig.2

Claims (1)

[Scope of Claims] l An air flow meter is provided in the intake passage of the engine, and the maximum value Qmax of the detected intake air fik Q' during a period longer than the pulsation period of the detected intake air amount Q' of the air flow meter is determined, and the maximum value Qmax is A method for calculating an intake air amount, characterized in that a constant value Qc is set as an intake air amount Q during a period in which the intake air amount is equal to or greater than a limit value of 0 g. 2. The method according to claim 1, characterized in that the limit value Qg and the constant value Qc are made functions of engine rotational speed. 3. The method according to claim 2, wherein the constant value Qc is approximately the theoretical value of the amount of intake air when the throttle valve is fully opened. 4. The method according to claim 2, wherein the air flow meter is of the Karman vortex type.