JPS6098143A - Air-fuel ratio control method of internal-combustion engine - Google Patents

Abstract

PURPOSE:To perform air-fuel ratio control of each cylinder by controlling the fuel supply on the basis of air-fuel ratio of combustion gas in each cylinder detected in accordance to the exhaustion timing of each cylinder while correcting the open/close time of an electromagnetic switch on the basis of rotation and suction air. CONSTITUTION:Suction Qa and rotation N indicating the operating condition of engine 1 are measured respectively by an air flow sensor 6 and a rotation sensor then provided to a control unit 11 to calculate the valve open times T1-T4 of injector 3 for feeding fuel to each cylider. Then the air-fuel ratio of such cylinder as assigned synchronously with the injection timing at the position of crank phase delay angle QB to be determined by the engine rotation N and suction per single rotation Qa/N is sampled by a sensor 10 and fed to the control unit 11. Consequently, the open-valve pulses T1-T4 of each cylinder to be produced next are corrected to T1'-T4' thus to control fuel supply to each cylinder.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an air-fuel ratio control method for an internal combustion engine, and more particularly to an air-fuel ratio control method for controlling each cylinder separately in a system that performs sequential injection of fuel.

[Background of the invention]

Conventionally, the amount of fuel supplied to the engine has been monitored as the air-fuel ratio (A/F) by an air-fuel ratio sensor installed in the exhaust pipe that detects the oxygen concentration in the exhaust gas and calculates the air-fuel ratio. Since only one exhaust pipe was provided at the gathering part of the exhaust pipes provided in each of the compound cylinders, it was impossible to measure the air-fuel ratio in each cylinder in detail.

Recently, it has been found that sequential injection, which sequentially injects fuel in synchronization with the intake timing of each cylinder, is effective as described in Japanese Patent Application Laid-open No. 58-48730 to fully bring out the engine's performance. As a result, there is an increasing demand for measuring the air-fuel ratio of each cylinder separately. However, attaching one air-fuel ratio sensor to each exhaust pipe poses a problem in terms of cost, so a method of detecting the air-fuel ratio of each cylinder using one sensor has become necessary.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide air-fuel ratio feedback control that allows easy and highly accurate fuel amount control for each cylinder of a multi-cylinder engine. We are here to provide you with a method.

[Summary of the invention]

The present invention includes a detector for detecting the intake flow rate or load of a multi-cylinder engine, a detector for detecting the rotational speed of the engine, and at least one detector for each cylinder for supplying fuel to the engine according to these detected amounts. = consists of installed electromagnetic switches, an electronic circuit that determines the opening/closing time and timing of these electromagnetic switches, and a measuring device installed in the engine exhaust pipe that measures the air-fuel ratio of combustion gas. , the exhaust timing is set by the fuel supply control device to the engine according to the rotation angle of each cylinder of the engine, and the air-fuel ratio of combustion gas is injected from each cylinder according to this exhaust timing,
Fuel is supplied according to the detected air-fuel ratio'[1(
The amount of fuel supplied is controlled by adjusting the opening/closing time of the magnetic switch, and also by the engine speed and intake air amount of each cylinder? [f. The intended purpose is achieved by modifying the opening/closing time of the magnetic switch.

[Embodiments of the invention]

An embodiment of the air-fuel ratio method for an internal combustion engine according to the present invention will be described below with reference to the drawings.

An embodiment of the present invention is shown in FIGS. 1 and 2. FIG.

In FIG. 1, an engine 1 is provided with intake pipes 2 corresponding to the number of intake pipes, and a fuel injection valve injector 3 is provided in each of the intake pipes 2.

These intake pipes 2 are combined into one at an upstream collector 4, and a throttle valve 5 for determining the intake air amount of the engine 1 is provided further upstream.

The intake air of the engine 1 is measured by an air flow sensor 6 provided further upstream of the throttle valve 5. The rotation li of the engine 1 is detected by a rotation sensor (not shown) built into a power distributor 7 provided in the engine 1, and the temperature of the engine 1 is similarly detected by a temperature sensor 8. Furthermore, an air-fuel ratio sensor 10 is provided in an exhaust pipe 9 that collectively exhausts exhaust gases from each cylinder of the engine 1 to detect a total combustion ratio of combustion gases. Signals from the throttle valve 5, airflow sensor 6, rotation sensor, temperature sensor 8, and air-fuel ratio sensor 1° are input to a control unit 11, respectively. Fuel is supplied from a fuel tank 12 to a fuel pump 13 and a regulator 14.
The fuel is pressurized and regulated and sent to the injector 3, which is opened and closed by a signal from the control unit 11, and the amount of fuel is measured by the valve opening time of the injector 3. The control operation according to an embodiment of the present invention will be described below. FIG. 2 is a block diagram showing the input/output relationship of the engine l shown in FIG. 1, with sensors on the left and actuators on the right with respect to the control unit 11. As mentioned above, the sensors include an opening sensor for the throttle valve 5, an air flow sensor 6, a rotation sensor, a temperature sensor 8,
There are air-fuel ratio sensors 10, sensors A, B, C, l).
,E.

It is shown as F. The actuators include injector 3 (shown as injectors A, B, C, and D).
, pump 13, etc. 15 is ■ding.

It is the source. Also, inside the control unit 11, there is a waveform shaping circuit 16 shown on the left side, an Ilo LSI section 17 that performs exchange calculation processing of an AD converter and input/output, and this l10LS.
A CPTJ unit 18 that issues a command to the I unit 17 is disposed, and further to the right side, an output actuator 19 for the injector 3 and an output actuator 207 for the pump 13 are arranged.

FIG. 3 is an explanatory diagram showing the relationship between the engine crank angle and the process for each cylinder in the case of an in-line four-cylinder engine. Figure 3 shows a case where the intake timing and injection timing of a four-stroke engine are completely synchronized, and since one cycle is 7203, the intake timing of the third cylinder which comes after the intake of the first cylinder is the same as that of the third cylinder. The angle between them is 180°, and fuel is injected sequentially.

Further, since the exhaust timing is shifted by 540 degrees from the intake timing, for example, the exhaust timing of the third cylinder is performed at the same time as the intake timing of the first cylinder.

FIG. 4 shows the detection results of the air-fuel ratio by the air-fuel ratio sensor 10 installed in the exhaust pipe 9. The third cylinder is Rich and the second cylinder is (
, ean. Fourth
The solid line in the figure indicates when the engine rotation speed is low;
When the engine rotates at high speed, the phase gradually becomes delayed as shown by the broken line. That is, when measuring the air-fuel ratio of the third cylinder, for example, sampling may be performed at the crank angle θ summer phase when the speed is low, and the phase may be delayed to the crank angle θ2 as the speed increases. For the other cylinders, the air-fuel ratio may be similarly sampled at a point where the phase is delayed from the reference crank angle, for example, 1805 in the case of the 4th gas oil by an angle of θ.

Figure 5 shows engine rotation speed N and intake air per unit rotation: I
The phase delay angle θ of the position to be sampled varies depending on Q, , /N. As shown in the figure, θ1 gradually increases as N increases and as Q and /N increase.

FIG. 6 is a map of the graph in FIG. 5, and shows the phase delay angle θ of the crank angle to be sampled, which is determined by the engine rotation speed N and the intake air amount Q, /N per unit rotation. , , is shown.

FIG. 7 shows fuel supply amount control according to an embodiment of the present invention.
- This is shown as a chart, in which the intake air amount Q, which indicates the operating conditions of the engine 1, and the engine rotation speed N are measured by the air flow controller 6 and the rotation sensor, respectively, and input into the control unit 11 to supply fuel to each cylinder. The valve opening times T1 to T4 of the injection valve injector 3 for supplying the fuel are calculated. The valve opening pulse Tl=T4 is the characteristic of each cylinder,
It may be possible to obtain individual values for each cylinder by multiplying by a certain constant determined by the distribution of nitrogen gas, variations in the injectors 3, etc. Next, as shown in the map of FIG. 6, the crank phase delay angle θ is determined by the rotational speed N of the engine 1 and the intake air MQ, /N per unit rotation. At the position of
The air-fuel ratio of the designated cylinder is sampled and measured by the air-fuel ratio sensor 10 in synchronization with the injection timing, and the air-fuel ratio data is input to the control unit 11 and stored in the memory. Based on this data, the valve opening pulse Ts''-□T4 of each cylinder to be outputted next is determined as Tl'
~T, / to output accurate valve opening times to the injectors one after another to accurately control the fuel supply for each portion individually.

Note that this modification of the valve opening pulse T is basically performed by storing the air-fuel ratio signal of each cylinder independently for each generous portion, but it may also be controlled in a manner that the cylinders are related to each other.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to control the air-fuel ratio for each cylinder of a multi-cylinder engine by time-division (angle-division) sampling of the output of the air-fuel ratio sensor, which is faster than conventional control. This makes it possible to accurately control the amount of fuel supplied. In addition, the adoption of sampling angles and knobs has improved air-fuel ratio detection accuracy, making cylinder control easier and more accurate, which has a significant effect.

[Brief explanation of drawings]

1 and 2 show an embodiment of the air-fuel ratio control method for an internal combustion engine according to the present invention. A system diagram, and FIG. 3 shows an example of the system shown in FIGS.
An explanatory diagram showing the relationship between the crank angle and the process in each cylinder in the case of cylinders, Figure 4 is an explanatory diagram showing the output of the air-fuel ratio sensor in the exhaust pipe, and Figures 5 and 6 show how the air-fuel ratio signal should be sampled. Explanatory diagram showing the crank angle of the position, 7th
1 is a flowchart showing fuel supply i-alternative control m11 according to an embodiment of the present invention.

Claims (1)

[Claims] 1. By detecting at least either the intake air amount or the load of the multi-cylinder engine, and detecting the rotation speed of the engine,
In an air-fuel ratio control method for an internal combustion engine, which controls the fuel injection timing and injection amount to each cylinder via a control device, and also detects components in exhaust gas to control the air-fuel ratio, A component in the exhaust gas is detected for each generous amount according to a determined exhaust timing of each cylinder, and the timing and amount of fuel supplied to each cylinder are controlled in accordance with this detection signal. An air-fuel ratio control method for an internal combustion engine.