JPS62157244A - Air-fuel ratio control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To improve transient operating characteristics by predicting an intake air rate or a pressure within an intake pipe using present and at least one previous values detected at each specified crank angle and by operating an injection amount based on the predicted value. CONSTITUTION:A control circuit 10 predicts a next value of a pressure in an intake pipe or an intake air amount to be detected with a pressure sensor 3 at each crank angle specified by signals from crank angle sensors 5 and 6 based on a present value and at least one previous value stored in a RAM (random access memory) 105. And operating a fuel consumption based on the predicted pressure in the intake pipe or the intake air rate, a fuel injection valve 7 is driven at the next fuel supply according to the operated fuel consump tion. Thus, required rate of fuel can be supplied accurately without variance, leading to considerable improvements in transient operating characteristics and in emission constituents.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an air-fuel ratio control device for an internal combustion engine, and in particular, the present invention relates to an air-fuel ratio control device for an internal combustion engine, and particularly to an air-fuel ratio control device for controlling the intake air amount or intake pipe internal pressure when injected fuel is actually supplied into the combustion chamber. The present invention relates to an air-fuel ratio control device for an internal combustion engine that can predict the amount of fuel and inject an amount of fuel corresponding to the predicted value.

[Conventional technology]

In an engine that detects operating state parameters of the engine, such as intake pipe internal pressure and rotational speed, calculates the amount of fuel to be injected according to the detected parameters, and performs fuel injection according to the calculated value, the operating state parameters Due to the time lag between the time of detection and the time when the fuel based on the detection is actually introduced into the combustion chamber, the amount of fuel truly required by the engine may not be supplied.

For example, as shown in FIG. 5, at a predetermined crank angle position A before fuel injection, a fuel injection pulse width is calculated from the intake pipe internal pressure and rotational speed at that time, and the injector is driven to open for a period B using this pulse width. Perform injection. The intake valve opens for a period of time C, thereby supplying fuel to the combustion chamber. in this case,
The fuel actually enters the combustion chamber near the position D,
The amount of air introduced into the combustion chamber at this time is different from the amount of air calculated from the intake pipe internal pressure and rotational speed detected immediately before injection.

If there is a difference between the detected value of the air amount used for calculation and the amount of air actually entering the combustion chamber, there will be a significant excess or deficiency in the amount of fuel, especially when the engine is in a transient operating state. Conventionally, in order to compensate for this excess or deficiency, fuel amount increase or decrease was controlled according to the throttle valve opening signal, etc.
It is difficult to provide sufficient compensation, leading to deterioration in driving characteristics and emissions.

Therefore, before fuel injection, the intake pressure value (
The present inventor has already proposed a method of performing approximate calculation using the PM value, calculating the fuel injection amount from the PM value and the feedback rotation speed, and executing fuel injection using this value (Japanese Patent Application No. 1983-
22962).

[Problem that the invention seeks to solve]

However, even during steady driving, the PM value pulsates depending on the engine crank angle, whereas the method already proposed by the present inventor detects the PM value during injection by e.g.
Although it is performed at a time of 2 m5 and the detected value closest to jtll is used when calculating the fuel injection amount,
Because the detection cycle of the PM value does not match the pulsation cycle of the intake air, the phase of the pulsation of the intake air when calculating the injection amount differs each time, resulting in variations in the detected value and the next intake pressure value based on past and current PM value data. could not be accurately predicted. That is,
The data obtained by A/D converting the PM values detected at time periods has large variations, and this value is used to estimate the predicted P
There is a problem that the M value also varies and is not accurate, and as a result, the air-fuel ratio fluctuates due to the variation in the predicted PM value, resulting in poor drivability, poor emission, etc.

In addition, in this proposed device, if the detection period is shortened and high-speed A/D conversion is performed, the variation in the obtained data will be reduced, but in this case, an expensive high-speed A/D conversion device is required. There is a problem.

An object of the present invention is to solve the problems of the above-mentioned fuel injection control method for an internal combustion engine proposed by the present inventor, and to set the PM value detection timing to always be in the same phase regardless of fluctuations in the intake pulsation cycle. By performing this at a time near the intake bottom dead center, which is the optimum value for the intake pipe internal pressure representing the amount of air actually introduced into the combustion chamber, it is possible to obtain an accurate predicted PM value. The purpose is to provide a fuel ratio control device.

[Means for solving problems]

The air-fuel ratio control of the internal combustion engine of the present invention that achieves the above object? 11
1 device includes a crank angle detection means, an intake pipe internal pressure or intake air amount detection means, and a means for storing a detected value of the intake pipe internal pressure or intake air amount at a predetermined crank phase based on the crank angle detection output. , means for predicting the next detected value based on at least the stored previous detected value and the latest detected value, and means for calculating the fuel amount based on the predicted intake pipe internal pressure or intake air amount. It is characterized by

[For production]

According to the air-fuel ratio control device for an internal combustion engine of the present invention configured as described above, based on the current value and at least the previous value of the intake pipe internal pressure or intake air amount detected at each predetermined crank angle. The same detected value for the next time is predicted, and the amount of fuel calculated based on this predicted detected value is supplied at the next fuel supply time.

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

〔Example〕

FIG. 1 schematically shows an electronically controlled fuel injection type internal combustion engine equipped with an embodiment of the air-fuel ratio control device for an internal combustion engine according to the present invention. In this figure, an intake passage 2 of an engine (2) is provided with a pressure sensor 3 for detecting the internal pressure of the intake pipe. This pressure sensor 3 uses, for example, an SA using a surface acoustic wave that causes a propagation phase delay due to strain proportional to pressure.
A W-type sensor or the like is used, and a pressure signal is extracted at an oscillation frequency that is inversely proportional to this phase delay time.

This pressure signal is transmitted to the multiplexer built-in A/
The signal is supplied to the D converter 101. The distributor 4 has a crank angle sensor 5 whose axis generates a pulse signal for detecting a reference position every 3606 degrees in terms of crank angle (CA), and a pulse signal for detecting a reference position every 30 degrees in terms of crank angle (CA). Crank angle sensor 6 that generates a signal
is provided. The pulse signals of these crank angle sensors 5 and 6 are sent to the human output interface 102 of the control circuit 10.
Of these, the output of the crank angle sensor 6 is C
It is supplied to the interrupt terminal of PU 103.

Further, the intake passage 2 is provided with a fuel injection valve 7 for supplying pressurized fuel from a fuel supply system to the intake boat for each cylinder.

Furthermore, a water temperature sensor 11 is provided in the cooling water passage W of the cylinder block of the engine 1 to detect the temperature of the cooling water. The water temperature sensor 11 generates an analog voltage electrical signal according to the temperature THW of the cooling water. This output is also supplied to the A/D converter 101.

The control circuit 10 is configured as a microcomputer, for example, and includes the above-mentioned A/D converter 101, input/output interface 102, CPU 103, ROM 104, R
AM 105 , a backup RAM 109 that retains information even after the ignition switch is turned off, and the like are provided, and these are connected by a bus 110 . In this control circuit 10, a down counter 106, a flip-flop 107, and a drive circuit 108 are connected to the fuel injection valve 7.
The purpose is to control the i.e. fuel injection @TAU
is calculated, the fuel injection ITAU becomes the down counter 1.
06 and the flip-flop 107
Also cents. As a result, the drive circuit 108 starts energizing the fuel injection valve 7. On the other hand, the down counter 106
counts a clock signal (not shown) and finally when its carrier terminal reaches the 'l' level, the flip-flop 107 is reset and the drive circuit 108 stops energizing the fuel injection valve 7. In other words, the aforementioned fuel injection 1T
The fuel injection valve 7 is energized by the amount of fuel AU, so that fuel corresponding to the fuel injection amount TAU is sent into the combustion chamber of the engine 1.

The control circuit 10 also includes an intake air temperature sensor (not shown),
Detection signals from a throttle switch 13 that detects the opening of the throttle valve 12, an opening sensor 14 of the throttle valve 12, an oxygen concentration sensor 9, a vehicle speed sensor 17 attached to a speedometer cable from the transmission 16, etc. Noteri's terminal voltage, starter signal, near conditioner switch signal, etc. are sent to it. Also,
The control section unit 10 outputs an ignition signal to the igniter built into the distributor 4, thereby controlling the energization of the spark plug 15, but since these are not directly related to the present invention, their explanation will be omitted.

The detection signal of the pressure sensor 3 is converted into a 2-digit signal by A/D conversion executed at every predetermined crank angle.
RAM each time as data representing the intake pipe internal pressure PMO
105. A signal from the crank angle sensor 6 in the distributor 4 at every crank angle of 30' is taken into the control circuit IO via the input/output interface 102, and a 30' CA interrupt request signal is generated to calculate the rotational speed Ne and fuel injection -1TAU. becomes.

Next, the operation of the aforementioned control circuit will be explained using the flowchart shown in FIG.

FIG. 2 is a flowchart showing the operating procedure of the air-fuel ratio control device for an internal combustion engine according to the present invention, which is performed every 30' CA. In step 201, it is first determined whether or not this crank angle is the timing for detecting an intake pressure value (PM value). In this embodiment, this detection timing is 306 after the bottom dead center of the intake air every 360° CA. The reason why the PM value is detected near the intake bottom dead center in this manner is that PM4fL near the intake bottom dead center best represents the amount of intake air at that time. If YES in step 201, that is, it is the detection time, the process proceeds to step 202, where the detected value by the pressure sensor 3 is A/D converted and this value is stored in the RAM 105 as PMO.
The process proceeds to step 203 after being stored in step 2.
If No in 01, that is, it is not the detection time, step 202
The process is skipped and proceeds to step 203.

In step 203, it is determined whether the crank angle is at the calculation timing for the fuel injection amount TAU. This injection timing is also 360°C
Visit every A. If it is the calculation time (YES), the process proceeds to step 204 and reads out from the RAM 105 the latest intake pressure value PMO1, the intake pressure value PM1 at the time of the previous interruption, and the intake pressure value P M2 at the time of the previous interruption of υ1.

Next, in step 205, the optimum intake pressure value PMCAL at the time when the injected fuel actually reaches the combustion chamber is predicted according to the injection pulse width calculated this time. As described above, this value is the value of the intake pipe internal pressure near the next intake F dead center.

Generally, polynomials such as Macrolin expansion are used to predict future values from data up to the present. Macro
The general formula for phosphorus expansion is shown below.

In this example, f (x) is the pressure inside the intake pipe,
X is the crank angle, and m is;
, f''(x) as follows.

=1/m (f(x)-2f(x-m)+f(x-
2m)) ・=■ Considering the approximation up to the second order and substituting the 0th equation into the 0th equation, we get the following.

f(x+m) #2.5f(x)-2f(x-m)+0.
5f (x-2m) -... ■In the formula ■, f
Considering that (x) is the current intake pipe pressure value PMO, f (x-m) is PMI, f (x-2m) is PM2
Then, the predicted value PMCAL after 360° CA is f (x
+m).

That is, in step 205, P M OlPMI, PM2
The predicted value PMCAL is calculated from the following equation.

P M CAL=2.5P M O-2,0P M l
+0.5P M In the second step 206, the contents of PMI are converted to PM2 in order to prepare for calculating the predicted value for the next interrupt.
RAM to transfer the contents of PMO to PMI respectively.
105. Next, in step 207, the predicted intake pipe internal pressure PMCAL is determined from the rotational speed Ne at that time, and the basic injection pulse width TP is determined by a well-known method, such as a method using a table of TP=g(Ne, P MCAL). Furthermore, in step 208, corrections are made using detection signals from the cooling water temperature sensor 11, intake temperature sensor (not shown), throttle switch 13, opening sensor 14, oxygen concentration sensor 9, etc., battery voltage, etc., and the final injection pulse is determined. The width is determined and temporarily stored in the RAM 105, and the process proceeds to step 209.

On the other hand, if it is determined in step 203 that it is not the time to calculate fuel injection 1 TALJ (NO), the above-mentioned steps 204 to 208 are omitted and the process returns to step 2.
Proceed to 09.

Step 209 is for determining whether or not the fuel injection time is 1/1. If YES is determined here, step 21 is performed.
0, and the CPU 103 starts fuel injection. Thereafter, in step 211, the CPU 103 sets the injection Fft end time in the down counter 106 according to the injection pulse width calculated as described above. If it is determined in step 209 that it is not the fuel injection time, the injection strokes in steps 210 and 211 are omitted. This injection timing also occurs every 360° CA.

The intake pressure value P in the operation of the control circuit 10 as described above
The mutual relationship among the MO detection timing, the fuel injection 1iTAU calculation timing, and the fuel injection timing will be explained next with reference to FIGS. 3 to 5.

Symbols a-β in FIG. 3 are given every 30° CA, and the crank angle position indicated by symbol a indicates the intake bottom dead center. Then, even if an interrupt is made to 30'C shown in FIG. 2 at the crank angle indicated by symbol a, step 201 is not executed.
, 203.209 are all NO, so nothing is actually executed, but when the crank angle shown by the symbol is 30
When the ° interrupt is performed, the answer is YES in step 201, and the value of the intake pressure value PM is stored in the PMO (the part shown in range b in FIG. 2 is executed). Similarly, when the crank angle reaches the position shown by symbol C, YES is determined in steps 203 and 209 respectively when the crank angle comes to the position shown by symbol C, and when the crank angle reaches the position shown by symbol C, the fuel injection 1 TAU is calculated, symbol e Fuel injection is performed at the time indicated by (respectively indicated by ranges c and e in FIG. 2).

Air-fuel ratio control g of the internal combustion engine of the present invention that operates as described above
For example, when the intake pressure value PM changes as shown in FIG.
2 and the next intake pressure value PMC based on the current detected value PMO.
AL is predicted, and the current fuel injection amount TAU (injection pulse width) is calculated based on this predicted A1ηPMCAL.

Since this predicted value PMCAL corresponds to the amount of intake air at the time when the currently injected fuel reaches the combustion chamber, when the intake pipe internal pressure rises due to accelerated operation as shown in this figure, It is possible to supply the amount of fuel correctly commensurate with the climb. Therefore, acceleration response is greatly improved.

In the above embodiment, predicted values after 360′ CA were shown, but it is also possible to predict other crank angles using a similar method. Further, other polynomials may be used as the expression for calculating the predicted value. Of course, the order is not limited to the second order either.

Further, although the above-mentioned embodiment uses the intake pipe internal pressure, the device of the present invention can also be used when calculating the fuel injection amount using the intake air amount using a mechanical or hot wire air flow meter. It is.

〔Effect of the invention〕

In the device of the present invention, the intake air amount or intake pipe internal pressure at the time when the injected fuel reaches the combustion chamber is predicted using the current and small values detected at every predetermined crank angle (both are the same value from one past time). Since the injection amount is calculated and controlled using the predicted value, the amount of fuel that the engine truly requires can be supplied accurately and without variation even during transient operating conditions. It is possible to significantly improve the operating characteristics of the engine and to improve the eminocicin.

Further, in the present invention, since the intake air amount or the intake pipe internal pressure value is measured in synchronization with the crank angle, a high-speed A/D converter is not required, resulting in low cost. In addition, the logic of prediction calculation is simple and prediction accuracy can be improved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an engine showing the configuration of an air-fuel ratio control device for an internal combustion engine according to the present invention, FIG. 2 is a flowchart showing the operation of the control device in FIG. 1, and FIG. 3 is an operation of the flowchart in FIG. 2. FIG. 4 is an explanatory diagram showing the operation of the embodiment, and FIG. 5 is an explanatory diagram showing the timing of fuel injection, injection amount, etc. 2...Intake passage, 3...Pressure sensor, 4
...Distributor, 5.6...Crank angle sensor, 7...Fuel injection valve, 10...Control circuit. 30'CA Detection point Young cow cow cow ↑ cow ↑ cow cow cow beef now --- obcdefghilkAab --- Memory of PM value Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] A means for detecting a crank angle of an internal combustion engine; a means for detecting an intake pipe internal pressure or an intake air amount; and a detected value of the intake pipe internal pressure or intake air amount at a predetermined crank phase based on the crank angle detection output. means for predicting the next detected value based on the stored at least the previous detected value and the latest detected value; and means for calculating the fuel amount based on the predicted intake pipe internal pressure or intake air amount; An air-fuel ratio control device for an internal combustion engine.