JPS6312865A - Air quantity detecting device for internal combustion engine - Google Patents

Abstract

PURPOSE:To enable accurate detection of air flow to a cylinder under transient condition, by detecting an air flow under steady state on the basis of an opening of throttle valve and an engine rotation then correcting said air flow with a lagging coefficient corresponding to the operating condition. CONSTITUTION:During operation of an engine, a control unit 18 obtains an open area of a throttle valve on the basis of an output signal from a throttle valve opening sensor 12 while simultaneously obtains an open area of a bypath 19 detouring a throttle valve 14 on the basis of a drive control signal for commanding an idle control valve 20. Then an air flow QH under steady state is obtained on the basis of a value obtained by dividing the sum of the throttle valve open area and the bypath open area, i.e. total flow path area, by an engine rotary speed obtained on the basis of an output from a crank angle sensor 15, and an engine rotation. Thereafter, a predetermined lagging coefficient is obtained on the basis of the total flow path area and the engine rotary speed, so as to calculate an air flow Qc to a cylinder on the basis of said lagging coefficient and the air flow QH and employ said air flow Qc in the control of air-fuel ratio.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an air amount detection device for an internal combustion engine.

(Prior art) In a fuel-injected internal combustion engine, it is important to accurately detect the amount of air taken into the engine. There are those that detect the engine directly, and those that indirectly detect the intake pipe pressure and engine rotation speed measured by a pressure sensor.

In addition to the pressure sensor, there is also a throttle valve opening sensor that detects the amount of air based on the throttle valve opening and the pressure in the intake pipe (see Japanese Patent Publication No. 4981/1981).

(Problems to be Solved by the Invention) However, in the detection device using a flow rate sensor or a pressure sensor, the detected value fluctuates greatly due to intake pulsation, and the injection of the fuel injector is controlled based on this. Since the amount fluctuates, engine torque fluctuations become large.

Further, since the response of flow rate sensors and pressure sensors is not so good, there are problems in that detection errors during transient periods are large and costs are high.

On the other hand, since these detection devices detect the air flow rate at the sensor position, the detected value and the amount of air flowing into the cylinder do not match during transient periods, and therefore vary depending on the position of the fuel injector. However, there is a problem in that the air-fuel ratio becomes rich or lean during acceleration or deceleration.

It is an object of the present invention to solve this problem, α, and to provide an air amount detection device with good transient response.

(Means for Solving the Problem) As shown in FIG. A steady air flow rate calculation means 3 that calculates the flow rate, a delay coefficient operator stage 4 that also calculates the delay coefficient of air flow from the rain detection value, and a lag coefficient operator stage 4 that calculates the air flow rate flowing into the shilling from the steady air flow rate and the delay coefficient. It consists of a correction means 5.

(Function) Therefore, from the throttle valve opening a and the engine speed N, the air flow fiQ)I
is accurately detected, and based on the air flow rate QH, the valve opening a and the engine rotational speed N (corrected by the delay coefficient K, the response is deteriorated even during transient times). The air flow rate Qc to the shilling can be detected accurately without having to do so.

(Embodiment) FIG. 2 shows the mechanical configuration of an embodiment in which the present invention is applied to a multi-point injection type engine in which each intake boat 10 is provided with a fuel injection valve 11.

12 is a throttle valve opening sensor that detects the opening degree α of the throttle valve 14 in the intake passage 13, 15 is a crank angle sensor that detects the engine rotation speed N, and these detection signals are sent to a water temperature sensor 161 that detects the engine cooling water temperature. , an intake air temperature sensor (not shown) that detects the temperature of intake air, an air-fuel ratio sensor 17 that detects the air-fuel ratio, etc., are input to the control unit 18.

Further, one is a passage that bypasses the throttle valve 14, and 20 is an idle control valve that makes the opening area Ab of the bypass passage 19 variable.

The control unit 18 includes CPU, RAM
.

It is composed of a microcomputer consisting of a ROM, an I10 device, etc., and has a total of 8 units of each means 1 to 4 shown in the fj41 diagram. It detects the air flow rate and controls the fuel injection of the fuel injection valve 11. In addition, the control unit 18
For example, the idle control valve 20 is driven and controlled so as to maintain a predetermined engine speed during idle.

Next, the contents executed in the control unit 18 will be explained based on the chart 70 in FIGS. 3 and 4.

FIG. 3 shows a calculation routine for the air flow tqc flowing into the cylinder. First, in step 10, the throttle valve opening area Aα is determined from the signal α of the throttle valve opening sensor 12 by table search. A characteristic diagram representing the contents of the table is shown in PIS5 diagram, and the opening area Aα changes in proportion to the throttle valve opening a.

In step 11, the opening area Ab of the passage 19 that bypasses the throttle valve 14 is determined by table search from the drive control signal (duty signal) ISCD that instructs the idle control valve 20.
is required. FIG. 6 shows a characteristic diagram representing the contents of the table. The opening degree of the idle control valve 20 increases as the duty value increases, and the opening area Ah also increases accordingly.

Then, in step 12, the total flow path surface feLA is calculated from the sum of the throttle valve opening area Aα and the bypass passage opening area Ab.

Next, in step 13, the steady air flow rate Q)l for the total flow path area A is determined, but in this case, the air flow i Q 1
1 is the value A/N obtained by dividing the total flow path area A by the engine rotation speed N from the crank angle sensor 15 and the engine rotation speed N
It is determined from the three-dimensional table assigned to 7th
The figure is a characteristic line diagram showing the contents of the table, and the equal air flow rate line has a characteristic that increases approximately according to A/N. This is because, assuming that the rotation speed N is constant, the A/N changes depending on the throttle valve opening degree α, and α becomes thicker (as the air flow rate increases).

In step 14, a delay coefficient K (K
<1) is determined from the total flow path area A and the engine rotational speed N by table search.

This search is performed using a three-dimensional table, and FIG. tpJ8 shows a characteristic diagram representing the contents of the table. Note that the delay coefficient changes approximately depending on the total flow path area A.

Then, in step 15, the air flow rate Qc to the Schilling is calculated from the air flow rate Q■ and the delay coefficient, Qc=Q Co
It is calculated using the formula 10K (Q HQ co).

Qco is the previously calculated air flow rate Qc, and in steady state Q
c,=QH.

FIG. 4 shows a calculation routine for the fuel injection amount Ti of the fuel injection valve 11. In step 2o, the basic injection amount Tp is
It is obtained by multiplying the air flow rate Qc by an atmospheric pressure correction coefficient Kp, an intake temperature correction coefficient Kt, and a constant Ka.

Then, in step 21, the basic injection amount Tp is multiplied by the conventionally used various correction coefficients C0EF and the feedback correction coefficient LA from the air-fuel ratio sensor 17, and the invalid pulse width (voltage correction portion) Ts is added to calculate the fuel injection amount. Ti is required.

Note that each routine is executed at predetermined time intervals or in synchronization with engine rotation.

In this way, since the airflow ff1Q)I is calculated based on the opening degree α of the throttle valve 14 (and the opening degree of the bypass passage 19 of the throttle valve 14) and the engine rotational speed N, it is possible to use a hot wire type flow sensor or Unlike when using a pressure sensor, it is not affected by intake pulsation, and good responsiveness can be maintained during transients when engine operating conditions change, making it possible to accurately detect the air flow rate QH. can get.

On the other hand, the air flow rate Q)I does not match the air flow rate QC flowing into the silling due to the air flow delay except in steady state, but the air flow delay corresponds to the throttle valve opening α and the engine speed N. By correcting the air flow rate Q11 using the delay coefficient K based on α and N, the air flow rate Q c to the Schilling during the transient period can be accurately determined.

Therefore, by calculating the fuel injection amount based on the air flow rate Qc detected in this way, it is possible to prevent the fuel injection amount Ti from the fuel injection valve 11 from becoming excessive or insufficient even during acceleration or deceleration. This makes it possible to control fuel injection according to the air flow rate Qc.
The proper air-fuel ratio can be maintained even during acceleration and deceleration.

Fig. 9 shows the operating characteristics during acceleration.While the air flow rate Q11 corresponds to the sudden opening of the throttle valve 14, the air flow rate Qc to the shilling gradually increases, and at this time the air flow rate QH If fuel is injected into the intake boat in accordance with be. In this case, the air-fuel ratio becomes lean, but this is an error caused by the amount of fuel adhering to the intake pipe increasing during acceleration.

Note that the ignition timing of the ennon may be controlled based on the air flow rate Qc, and in this way, optimal ignition timing control can be performed even during transient conditions.

(Effects of the Invention) As described above, according to the present invention, the steady air flow rate can be accurately detected from the throttle valve opening degree and the engine rotation speed, and this can be corrected using a delay coefficient according to the operating condition. By doing so, the air flow rate to the Schilling during transient times can be accurately detected, and therefore accurate air-fuel ratio control is always possible.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the present invention, Fig. 2 is a mechanical block diagram showing an embodiment of the present invention, and Figs. 3 and 4 are diagrams showing the contents of each calculation.
0-chart, FIGS. 5 to 8 are characteristic diagrams showing the contents of each table used for calculation, and FIG. 9 is an explanatory diagram showing operating characteristics during acceleration. DESCRIPTION OF SYMBOLS 1... Throttle valve opening detection means, 2... Engine rotation speed detection means, 3... Steady air flow rate detection means, 4... Delay coefficient calculation means, 5... Correction means. Figure 5 Figure 6 l5CD (X) Figure 7 Figure 8 A (Cm')

Claims (1)

[Claims] A means for detecting the throttle valve opening, a means for detecting the engine rotation speed, a steady air flow rate calculation means for calculating the steady air flow rate from both detected values, and an air flow delay coefficient calculated from both detected values. An air amount detecting device for an internal combustion engine, comprising a delay coefficient calculation means for calculating the flow rate of air flowing into the cylinder from the steady air flow rate and the delay coefficient.