JPS58211543A - Control system of air-fuel ratio of internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent a misfire positively by setting a diluted air-fuel ratio on the basis of the load of the engine and correcting said ratio in response to the number of revolutions of the engine in the system in which the air-fuel ratio is changed over to a theoretical air-fuel ratio or the dilution air-fuel ratio in response to the state of operation of the engine and controlled. CONSTITUTION:When the engine is operated, the fundamental quantity of fuel injected is calculated on the basis of the quantity of air sucked from an airflow meter 15 in a controller 50. Whether or not the quantity of injection extends over an air-fuel ratio feedback control region is decided on the basis of data such as the temperature of cooling water from a water-temperature sensor 59, and whether or not the quantity of injection satisfies a condition of which the air-fuel ratio can be controlled by the dillution air-fuel ratio is decided when the quantity of injection extends over said region. A fuel injection valve 20 is controlled on the basis of an output from an O2 sensor 60 so that the air-fuel ratio is used as the theoretical air-fuel ratio when the quantity of injectin does not satisfy said condition. When the quantity of injection satisfies said condition, on the other hand, the value of the diluted air-fuel ratio is set on the basis of load value obtained from outputs from the airflow meter 15 and a revolution-number sensor 29, and the air-fuel ratio is controlled according to the value.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control system for an internal combustion engine, particularly an air-fuel ratio control system that controls the air-fuel ratio by switching to either the stoichiometric air-fuel ratio or the lean air-fuel ratio depending on the operating state of the engine. This is related to the improvement of.

In recent years, with the deterioration of the energy situation and the tightening of exhaust gas regulations to prevent popular pollution, the thermal efficiency of internal combustion engines has been improved.
Hiff, a 6-type model that makes exhaust gas cleaner
are studied, illuminated, and captured and offered in mountainous areas.

In addition, the air-fuel ratio (Δ'1), the weight ratio of air and fuel in the mixture sent to the engine is controlled, and the IJ
The deficiency of h-yellow components in IHX should be kept low.IJ
There are six known types of thermal effects. .

Dad, the air fuel ratio is 1III! The air-fuel ratio is not only controlled to the theoretically determined stoichiometric air-fuel ratio, but also when the negative part of the engine and the rotational speed are within a predetermined range. , the thermal efficiency is better than the stoichiometric air-fuel ratio, but Ml
) f) (Switch to a lean air-fuel ratio with fewer harmful components (
A method for controlling the air-fuel ratio has been proposed.

In addition, in such a 6-type, the lean air-fuel ratio is set as a unique value, for example, 20, within a range that does not cause the engine to misfire, or is known as engine L'! 65 (for example, Q/N), it is simply defined as a key that changes by C.

However, when the engine is controlled at a lean air-fuel ratio, the misfire range is as shown in Figures 1 and 2.
It is known that only N changes from 4 to 4 depending on engine speed N, and engine #! Jsen Q/N, rotation speed N
The air-fuel ratio is controlled according to the misfire range determined by the partner of
This makes it possible to increase thermal efficiency and reduce the amount of 4:i-basic components in the exhaust gas.

The present invention was completed based on this knowledge, and therefore,
In the operating range of the engine controlled by the lean air-fuel ratio, which is the objective of (a), the objective is to more precisely control the lean air-fuel ratio according to the operating state of the engine within a range that does not cause a misfire.

This purpose is to detect the residual oxygen in the exhaust gas, adjust the air-fuel ratio, and adjust the air-fuel ratio to either the stoichiometric air-fuel ratio or the lean air-fuel ratio depending on the operating state of the internal combustion engine. In the air-fuel ratio control method for an internal combustion engine, the lean air-fuel ratio is set based on the engine load, and the set value is corrected according to the engine speed. This is achieved by a fuel ratio control method.

The present invention will be described below with reference to examples and drawings.

FIG. 3 is a schematic configuration diagram showing an embodiment of an engine (one engine) to which the air-fuel ratio control method 11h according to the present invention is applied.

In the figure, reference numeral 1 represents one engine, and the engine 1 has a cylinder cock 2 and a cylinder head 3. Receive piston 4,
An intake boat 6 and an exhaust port 7 are formed in the 1° cylinder head 3, which forms a combustion chamber 5) with the cylinder head above the screws 1 to 4, and each boat is connected to an intake valve. 8 and exhaust valve 9 are opened and closed. Ma I
, the spark plug 19 is attached to the cylinder head 3 ()
It is being The spark plug 19 is supplied with the current generated in the ignition coil 26 through the distributor 27.
Sparks are generated by electric discharge in the combustion chamber 5.

The intake boat 6 includes an intake manifold 11, a surge tank 12, a throttle body 13, an intake tip 14,
Afrometer 15.1. The Acleaner 16 is connected in sequence. Also, the J engine intake system is provided with a single bypass passage 30 that bypasses the throttle body 13 and connects the intake channel J-'714 and the surge tank 12. This 1-7 bypass passage 30 is controlled by an electromagnetic bypass flow control valve 31 to control the opening degree of the frontage 1 and all sides.
1Ill is now available.

Further, an exhaust manifold 17 and an exhaust pipe 18 are connected to the exhaust port 7 in this order.

A fuel injection valve 20 is installed near the connection end of the intake manifold 11 to each intake boat. The fuel is now supplied through the fuel supply pipe 23.

The amount of intake air is ll1Ill for the throat 1 and the body 13.
A throttle valve 24 is provided, which
The first torque valve 24 is driven in response to depression of the accelerator pedal 25, and the fill of the valve 24 is □ so that it is detected by the throttle sensor 70.

■The AF meter 15 detects the flow of air flowing through the engine intake system and outputs a corresponding signal to the control device 50.
It's like tJ.

Distributor 27 is provided with 11 rotations and rotational phase of shaft 28 to which the rotation of the crankshaft is transmitted.
If so, a rotation speed sensor 29 for detecting the engine rotation speed N and the kufunk angle is incorporated (and this is R4, tj (c
No. 1 is controlled by the control device 550. The bleed gas i-galk'i ring ([GR) passage 34 connects the exhaust branch pipe 35 and the surge tank 12, and
The control type 11 air circulation valve 32 changes the EGR passage area in response to electric pulses. Then, the exhaust gas +Ijti ring valve 32 is controlled by the control I'& 50.

The control device 50 may be a microcombi coater, an example of which is shown in FIG.
51, a read-on memory 52 in which programs such as the air-fuel ratio control described later and data necessary for the Engine & II/III are stored, a random access memory 53, and a battery backup (memory is retained even after power is stopped). 54, an A/D converter 55 for providing a multiplexer, and an I710 device 56 having a buffer, which are connected to each other by a -17 link 57. .This little C1
The starter is supplied with a current supplied by a separate power supply 48 as shown in FIG. 3, and becomes operative.

The A/D converter 55 receives an intake air JiQ signal generated by the airfometer 15, an intake air temperature a signal generated by the intake air temperature sensor 58, and an engine cooling water temperature -r signal generated by the water temperature sensor 59. w signal and manually, each data is A
7.'1] is converted and output to the CP Ll 51 and the random access memory 53 or 54 at a predetermined time according to the instruction of the CP tJ 51. In addition, the r10H position 56 receives the engine rotational speed signal 3 generated by the rotational speed sensor 29, the air-fuel ratio signal generated by the crank angle sensor 60, and the like.
According to instructions from the PU 51, the CPU 51 and the random access memory 53 or 54 Δ are output to a predetermined Ill.

(The CPll 51 calculates the fuel injection 1i)j!13 based on the i''-ta detected by each hinge, and calculates the signal based on it.
The output is set to 4. In this case, the basic injection mTp obtained from the intake air amount Q detected by the fuel supply amount [)7 norometer 5) and the engine rotation speed N detected by the rotation speed control 29 is calculated by calculating the intake air temperature. It will be done.

Further, the CPU 51 outputs a bypass air amount signal to the bypass flow rate control valve 31 via I10% & 1156 in accordance with the intake air temperature detected by the intake air temperature sensor 58 and the water temperature detected by the water temperature sensor 59. There are 41. The bypass flow control valve 31 is opened and closed in response to the bypass air signal provided by the 110 device 56, and is opened and closed during this period.

Further, the CPU 51 generates an optimum ignition timing signal based on the basic fuel Tp calculated by the CPU 51, the engine rotation speed N and crank angle detected by the rotation speed sensor 29, and the intake air temperature detected by the intake air temperature sensor 58. 7ri 52
This is then output from the /Q device 56 to the ignition coil 26.

Next, FIG. 5 shows the control program applied to the air-fuel ratio &lj control method according to the first embodiment of the present invention. The operation of this embodiment will be described below along this flowchart 1-.

This program is part of the main program for engine 1 control, and is interrupted as a subroutine prior to predetermined fuel injection control processing.

When the processing of this program starts, in step 101, the process is performed via the I10 device 5G and the A/D converter 55).
Intake air IQ from meter 15, rotation speed sensor 29
The engine rotational speed N, engine cooling fJl water temperature TWW necessary data are input from the water temperature sensor 59, these data are stored in a predetermined area in the random access memory 53, and the process moves to the next step f102.

In step 102, the excess air ratio λ-1 is determined based on the intake air IQ. ! The basic fuel injection control Tp for the stoichiometric fuel ratio is calculated and stored in a predetermined register in the random access memory 53, and the process moves to the next step.

In the next step' 103, C performs the step 10
Based on the data such as engine cooling water temperature Tw read in step 1, check whether engine 1 is under conditions suitable for controlling the air-fuel ratio by feedback (hereinafter simply referred to as 17/B). is determined, and if the error is determined not to be in a suitable article f'tT-, then it is shown in step 104? # Processing is performed.

In step 104, the basic injection amount Tp calculated in step 102 is multiplied by the correction coefficient Ko for when BtIII control is not performed (set to 1 in normal operating conditions) to obtain the actual injection IN 'T' A LJ. After the calculation, the processing of this program ends.

On the other hand, in step 103, the engine, engine 1, is F/
If it is determined that the conditions are suitable for performing B I control, the process moves to step 105 and it is determined whether the conditions for controlling the air-fuel ratio at a lean air-fuel ratio (lean air-fuel ratio) are satisfied. If the result of the determination is rNOJ, the process moves to step 106.

In step 106, since the conditions for controlling the air-fuel ratio in the lean tl: state are not satisfied, a correction coefficient f111#5F is applied to maintain the air-fuel ratio at the stoichiometric air-fuel ratio.
/B111llll coefficient FAF & is calculated based on the output of the 02 sensor 60 read in step 101, and the process moves to the next step 107.

In step 107, the previous step 106 (-Basic injection ITI stored in a predetermined register in random access method 53 for the locked out F/8 control coefficient FA)
Actual injection I1. After asking for TAU, do you want to use this program? 4 Ru.

On the other hand, in step 105, the lean air-fuel ratio is controlled (・
If it is determined that the conditions that allow the processing to be performed are satisfied, the process proceeds to step 108.

In step 108, the open number t as shown in FIG.
A value (hereinafter referred to as engine load) Q indicating the engine load excluded from the intake air IQ and the engine rotation speed N read in step 101 and stored in a predetermined area in the random access memory 53. , 'N closes out the set value KL1 of the lean air-fuel ratio l+1011.

Now, FIG. 6 will be explained. In Figure 6, the vertical axis shows the air-fuel ratio (A, /F), and the horizontal axis shows the negative MQ/N ratio (1. : Therefore, the lean air-fuel ratio is determined as the numerical value f according to the negative Q/N of the engine1.In addition, the stoichiometric air-fuel ratio shown in 13 in the figure indicates the stoichiometric air-fuel ratio. To prevent hunting of the air-fuel ratio switch 84 in the restricted area, a hiss 7 lysis is installed to prevent hunting of the air-fuel ratio switch 84.

ybC, after locking out the set value Kl-1 in step 108, the engine rotation speed N and
Engine 1iiJ rotation speed A (normal rotation speed in the middle of the lean air-fuel ratio RIjilt range), which is the reference for changing the set value correction coefficient
If I N > A and 1, the determination is rNOJ and the process moves to step 110.

In step 110, the setting 46 obtained in step 108 is multiplied by 11 by the setting value correction coefficient KLB determined by the region to which the engine speed N belongs, and the product is set to the final setting value -L, and then the process moves to step 112. do.

Move on to processing.

S) In Tsubu 111, K L is the same as in Suftsuno 110.
, B. Multiply the set value K11 by the set value correction coefficient KL,A, which is smaller than B, and make the product the final setting of 16KL.

The process moves to the subsequent step 112.

In step 112, the U book in the register is
Multiply p by the final setting value KL and calculate the product by the actual value T' A U
Then exit this program.

In this way, according to the above program, if the engine speed N is greater than △, then if the engine speed is controlled by the lean air-fuel ratio, then The air-fuel ratio will be as shown by the chain line, and if the engine speed N is below A, the air-fuel ratio will be as shown by the solid line in the figure.

In other words, the engine load Q/
In this embodiment W4, the air-fuel ratio, which was determined based on the misfire range of the air-fuel ratio that changes depending on the magnitude of
Supplement the set value of lean air-fuel ratio control by
KL, A, KLB (however, K 1.A
, =: K L B >.

As a result, it is possible to control the lean air-fuel ratio 4 more precisely than in the past, and it becomes possible to achieve leaner air-fuel ratio 4 than the range C where misfire does not occur.

In addition, when the injection valve 20 is opened at 11]2 and the injection valve 20 is opened in the main routine, for example, the injection valve 20 is opened ↑II! In
! 1 is determined, and fuel proportional to the valve opening time, that is, the fuel required to maintain the desired air-fuel ratio, is injected into the intake boat 6.

In the first embodiment described below, two set value correction coefficients, KLA and KLB, are provided according to the engine speed N, but in order to perform even more precise lean air-fuel ratio control, the set value correction coefficient is set. may be a function determined by the engine speed. In the second embodiment described below, the set value correction coefficient is a value that changes depending on the number of engine revolutions N.

FIG. 8 shows a second embodiment of the present invention. The steps shown in blocks 101 to 107 are the same as those of the first embodiment, so the description will be given for approximately 1 degree. If the 1:/B condition is satisfied and it is determined in the subsequent step 105 that the lζth condition for performing lean air-fuel ratio control is satisfied, the process moves to the process shown in the snop 201 (4).

In step 201, similar to the first embodiment, the lean air-fuel ratio 1.IIN setting value K11 corresponding to τ current engine negative MQ, -'N is determined based on the function shown in FIG. Move on to processing.

Stella 7202-(: is the function Q1(N
), the set value correction coefficient KLC corresponding to the current engine speed N is calculated, and the set value K obtained in step 201 is calculated.
Multiply by L1 and set Yuzu to the final setting of 16K.

In the following step 203, the basic injection ITp stored in the register is multiplied by the final setting VUKI obtained in the previous step 202 to obtain the actual vI4 injection amount TAU, and the processing of this program is completed.

Note that the function g (N>) shown in Fig. 9 is expressed as the following function approximating the curve representing the misfire region !+9; It may be written as a quadratic function 02 (N) that further approximates the curve.

Set auxiliary 1 "coefficient KIC to misfire fJta"
By finding a function that approximates the expression curve, it is possible to set a lean air-fuel ratio near the limit of misfire (4).
I can do it.

Next, FIG. 10 shows a control program of the third embodiment of the present invention.

Book! 45 in 111 grams, and the processing shown in the tubes 101 to 107 is the same as in the first and second embodiments, so the explanation will be omitted.

Now, if the F/8 condition is satisfied in step 103 and the condition for performing control with a lean air-fuel ratio is satisfied in the subsequent step 105, the process moves to step 301.

In step 301, as shown in FIG. 11, is the engine negative or negative? aQ/N, 1- is searched (saw 1-) directly from the engine rotational speed N to the final set value.

In the following step 302, the basic jet DI collapse Tp in the register is added to the final setting value retrieved in the previous step 1301.
And was put on top of it, and the turret was a big blowout Q-11i! The processing of this program ends with r8U.

Here, we will explain about FIG. 11. The data map shown in this figure is a two-dimensional gate map whose data is determined from the engine rotation speed N and the engine rotation speed Q/N. Therefore, it is necessary to obtain the setting llf+ as in the above-mentioned embodiment, and each data of the map is stored as data corresponding to the final stage ffa corrected by the setting value correction coefficient.

Further, according to this embodiment, it becomes possible to more precisely control the lean air-fuel ratio, almost similarly to the second embodiment.

In the embodiments described below, the engine load is explained as a value expressed as Q/N, but the engine load is also expressed as a value (such as the aforementioned basic injection MTp or volumetric efficiency ηV, etc.). You may also use

In addition, in each embodiment, an engine using a fuel injection method using electronic I11 m will be described (although there are
Using a solenoid valve at I-Y, D1--JE ratio control, etc.
The present invention can be easily applied to a carburetor type engine that controls the air-fuel ratio by changing part of the fuel system.

1. As mentioned above, the air-fuel ratio &1 of the internal combustion engine of the present invention
The NIll method detects the residual oxygen in the exhaust gas and controls the air-fuel ratio to either the stoichiometric air-fuel ratio or the lean air-fuel ratio depending on the operating condition of the internal combustion engine. In the air-fuel ratio control method for an internal combustion engine, the lean air-fuel ratio is set based on the engine load, and the set value is corrected according to the engine speed. .

Therefore, according to the present invention, when the engine is operated at a lean air-fuel ratio, it is possible to operate the engine at a lean air-fuel ratio closer to the misfire region than in the past, which improves thermal efficiency and improves fuel efficiency. is improved. Furthermore, the amount of harmful components in the exhaust gas is reduced, making it possible to achieve the effect of reducing the burden on the exhaust gas purification device.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the correlation between engine load and air-fuel ratio misfire range, Figure 2 is an explanatory diagram showing the correlation between engine speed and air-fuel ratio misfire range, and Figure 3 is an explanatory diagram showing the correlation between misfire range of engine speed and air-fuel ratio. What about the internal combustion engine and its peripheral equipment? , Figure 4 is a block diagram showing the control system w50, Figure 5 is a diagram showing the air-fuel ratio aIIl/b11g of the first embodiment of the present invention, Figure 6 is is a function that determines the set feed for the 8 air-fuel ratio control [is shown in 1 graph), FIG. 7 is a graph explaining the operation of the first embodiment, and FIG. [Flowchart 1 showing J-gram, FIG. 9 shows the function Q+ (N) that determines the set value supplementary if coefficient in the second embodiment,
g2 (N), FIG. 10 is a graph showing the air-fuel ratio control program of the third embodiment of the present invention, and FIG. 11 is an explanatory diagram showing the data map used in the third embodiment. It is. 1... Engine (internal combustion engine) 14... I aphrometer 20... Fuel sniffer valve 27... Distributor 29... Rotation speed sensor 50... m control device 51... CPU 52. ...Read-on memory 53...Random access memory 55...A/DI converter 56...I10 installation 59...Water temperature sensor 60...02 sensor-227- Fig. 6 Q/N No. Figure 9 Figure 11

Claims (1)

[Claims] Detects the residual acid system in the exhaust gas and performs normal control of the C air-fuel ratio ()), and switches the air-fuel ratio to either the stoichiometric air-fuel ratio or the lean air-fuel ratio depending on the operating condition of the inner wA engine. 45 in the air-fuel ratio control system of the internal combustion engine, which is controlled by
In addition to setting the lean air fuel ratio 4 Iso 0 Taro J Suzuki,
An η' fuel ratio control method for an internal combustion engine, characterized in that the set value is supplemented according to the engine speed.