JPS61101636A - Method of controlling fuel supply to internal-combustion engine at the time of its deceleration - Google Patents

Abstract

PURPOSE:To improve the properties of exhaust gas at the time of decelerating an engine, by making the air-fuel ratio lean according to the detected values of concentration of exhaust gas components when the engine is under deceleration and the engine speed is in a prescribed range where the engine speed is lowered. CONSTITUTION:In an apparatus in which the air-fuel ratio of mixture supplied to an internal-combustion engine 1 is feedback controlled on the basis of the output signal of an O2-sensor 13, judgement is made by an ECU5, during operation of the engine, whether the opening of a throttle valve 3' detected from the output of a throttle-valve opening sensor 4 is smaller than a predetermined reference value or not. In case that the judgement is YES, that is, when the engine is under deceleration, judgement is made whether the air-fuel ratio is in a lean region or not during the while when the engine speed Ne detected by an engine-speed sensor 10 is lowered from a value greater than a first reference value (for instance, 1,250rpm) to a second reference value (for instance, 900rpm). In case that the judgement is YES, the air-fuel ratio is controlled to be lean by setting a deceleration correction factor, for instance, at 0.95.

Description

TECHNICAL FIELD The present invention relates to a fuel supply control method for an internal combustion engine, and more particularly to a fuel supply control method for improving exhaust gas characteristics during deceleration during feedback control operation of the engine.

(Technical background of the invention and its problems) In order to reduce harmful components such as carbon oxide (CO) and unburned hydrocarbons (UHC) in the exhaust gas of internal combustion engines, a three-way catalyst or the like is installed in the exhaust passage. An exhaust purification device is installed, and an oxygen concentration detector (hereinafter referred to as "02 sesan") detects the concentration of exhaust gas components in the exhaust gas, such as oxygen, and the 02 concentration detection value signal output from this 0□ sensor is used. A fuel supply control method is conventionally known in which the air-fuel ratio of the air-fuel mixture supplied to the engine is feedback-controlled (hereinafter referred to as "02 feedback control") to a predetermined air-fuel ratio, for example, the stoichiometric air-fuel ratio. In order to maintain the purification rate of the exhaust gas purification device at the optimum value during such 0□ feedback control, it is important to accurately control the air-fuel ratio to the predetermined air-fuel ratio. is closed, the pressure in the intake pipe downstream of the throttle valve decreases,
Fuel adhering to the inner wall of the intake pipe may be supplied into the combustion chamber. As a result, during deceleration in the O2 feedback control operating state, the air-fuel mixture supplied into the combustion chamber becomes overrich, and even if O2 feedback control is performed, Co and UHC are emitted as unburned exhaust gas components.
It was not possible to sufficiently reduce the amount of emissions. Especially when decelerating from a high engine speed operating state, Co, UH
There was a strong tendency for the amount of C emissions to increase.

(Objective of the Invention) The present invention was made to solve the above problems, and an object of the present invention is to provide a fuel supply control method that improves the exhaust gas characteristics of an engine during deceleration.

(Structure of the Invention) For this purpose, according to the present invention, a mixture is supplied to the internal combustion engine based on a detected value signal from the exhaust gas component concentration detection means disposed in the exhaust passage of the internal combustion engine. In a fuel supply control method that performs feedback control of an air-fuel ratio of air, the engine rotation speed is detected to determine whether or not the internal combustion engine is in a decelerated operating state, and the internal combustion engine is in a decelerated operating state and the engine is in a decelerated operating state. During the period when the detected engine speed value decreases from a value larger than the first predetermined engine speed value to a second predetermined engine speed value smaller than the first predetermined engine speed value, the exhaust gas component concentration detection means There is provided a fuel supply control method during deceleration of an internal combustion engine, characterized in that the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine is made lean in accordance with a detected value.

(Example of the invention) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of a fuel supply control device to which the method of the present invention is applied. Reference numeral 1 indicates, for example, a four-cylinder internal combustion engine, and an intake pipe 2 is connected to the engine 1. A throttle body 3 is provided in the middle of the intake pipe 2, and a throttle valve 3' is provided inside. Throttle valve 3
A throttle valve opening (θth) sensor 4 is connected to ', which converts the valve opening of the throttle valve 3' into an electrical signal and sends it to an electronic control unit (hereinafter referred to as "ECU") 5. There is.

A fuel injection valve 6 is provided in the intake pipe 2 between the engine 1 and the throttle body 3 for each cylinder, slightly upstream of the intake valve (not shown) of each cylinder.

The fuel injection valve 6 is connected to a fuel pump (not shown) and is electrically connected to the ECU 3, EC: U5.
The valve opening time of the fuel injection valve 6 is controlled by a signal from the fuel injection valve 6.

On the other hand, an absolute pressure (CPBA) sensor 8 is provided downstream of the throttle valve 3' of the throttle body 3 via a pipe 7, and the absolute pressure signal converted into an electrical signal by the absolute pressure sensor 8 is transmitted to the Sent to ECU3.

The engine cooling water temperature sensor (rT) is installed on the engine 1 body.
Tw sensor 9 (referred to as "W sensor") 9 is provided, and Tw sensor 9 is made of a thermistor or the like, and is installed in the circumferential wall of the engine cylinder filled with cooling water, and supplies its detected water temperature signal to ECU 3. An engine rotation speed sensor (hereinafter referred to as "rNe sensor") 10 is attached around the camshaft or crankshaft (not shown) of the engine, and the Ne sensor 10 is mounted at a predetermined crank angle position every 180° rotation of the engine crankshaft. In other words, the top dead center (T D
Regarding C), a crank angle position signal (hereinafter referred to as "rTDc signal") is output at a crank angle position before a predetermined crank angle, and this TDC signal is sent to the ECU 3.
sent to.

A three-way catalyst 12 is disposed in the exhaust pipe 11 of the engine 1 to purify U HC, G O, and NOx components in the exhaust gas. On the upstream side of this three-way catalyst 12 is an 02 sensor 13.
is inserted into the exhaust pipe 11, and this sensor 13 detects the oxygen concentration in the exhaust gas and supplies a 02 concentration signal to the ECU 3.

Furthermore, other parameter sensors 14 such as an atmospheric pressure sensor are connected to the ECU 3, and the other parameter sensors 14 supply their detected value signals to the ECU 3.

The ECU 3 includes an input circuit 5a having functions such as shaping input signal waveforms from various sensors, correcting voltage levels to predetermined levels, and converting analog signal values into digital signal values.
Central processing circuit (hereinafter referred to as rCPUJ) 5b, CP
It is composed of a storage means 5c for storing various calculation programs and calculation results executed by the U5b, an output circuit 5d for supplying a drive signal to the fuel injection valve 6, and the like.

The CPU 5b calculates the fuel injection time TOuT of the fuel injection valve 6 given by a quintic equation based on engine parameter signals from the various sensors described above supplied via the input circuit 5a.

ToUT=TiXK+t+LXKo2XKLsXKt+
2...(1) Here, T1 indicates the basic fuel injection time of the fuel injection valve 6, and this basic injection time is stored in the storage means 5c in the ECUS based on, for example, the intake pipe absolute pressure PBA and the engine rotation speed Ne.
is read from. KID is a deceleration correction coefficient according to the present invention, and its value is set by the KIDLID function described later.

Ko, is a 02 feedback correction coefficient, and its value is a Ko2 feedback correction coefficient, which will be described later, and is set by the Ko2 subroutine, which will be described later. K
L5 is a lean correction coefficient.

This is a correction coefficient that is set to lean the air-fuel mixture when the engine is in a lean operation region where the load on the engine is low, as shown in region I in FIG. 2, which will be described later. K
1 and 2 are correction coefficients and correction variables that are respectively calculated according to various engine parameter signals, and are required values to optimize various characteristics such as fuel consumption characteristics and exhaust gas characteristics according to engine operating conditions. is set to

The CPU 5b calculates the fuel injection time To obtained as described above.
A drive signal for opening the fuel injection valve 6 based on uT is supplied to the fuel injection valve 6 via the output circuit 5d.

FIG. 3 shows a flowchart of the KO□ subroutine for setting the 02 feedback correction coefficient value KO2, which is executed in the CPUUSb of FIG.

First, in step 301, it is determined whether activation of the 02 sensor 13 in FIG. 1 has been completed. As a method for determining the activation of the 02 sensor, for example, there is an internal resistance detection method that allows a required current to flow through the 0□ sensor and diagnoses that activation has been completed when the output voltage of the 02 sensor drops across the reference voltage. It is being If the activation has been completed (the determination result in step 301 is affirmative (Yes)), the process proceeds to step 302.

In step 302, it is determined whether the engine water temperature value Tw is larger than a predetermined determination water temperature value TWO2 (for example, 70° C.). When the engine temperature becomes lower than the predetermined determination water temperature value T w o , the mixture becomes lean due to reasons such as some of the fuel supplied to the cylinders adhering to the inner walls of the cylinders or insufficient vaporization of the fuel. , engine operation tends to become unstable.

For this reason, the amount of fuel supplied is increased to enrich the air-fuel mixture. When increasing the amount of fuel, that is, enriching the mixture, 02
In order to stop the feedback control, it is determined based on the engine water temperature whether or not the engine is in an operating state that requires an increase in the amount of fuel. If the engine water temperature value Tw is larger than the predetermined determination water temperature value Two□, it is determined that there is no need to increase the amount of fuel, and the process proceeds to step 303.

On the other hand, only a few of the steps 301 and 302 are performed.

If at least one of them is negative (No), the engine is 0. It is determined that the operation state is such that feedback control should be stopped, and the process proceeds to step 305.

Performs open loop control, which will be described later.

In step 303, it is determined whether the engine is in the 02 feedback operation region. 0□Feedback operation area is the shaded area in Figure 2 (part of H and ■)
It is shown as. If the engine is in the 02 feedback operation region, the ○2 feedback correction coefficient Ko2 is calculated according to the 02a degree detection value signal from the 02 sensor 13, and 1DL is calculated as the deceleration correction coefficient according to the present invention by the program described later. , these calculated Ko,
The air-fuel ratio of the air-fuel mixture is feedback-controlled according to the value and the KIDL value.

If the determination result in step 303 is negative (No), that is, if the engine is in the open loop control operation region, the o2 feedback control is canceled and the correction coefficient Ko2 is set to the value 1.0 (step 305), and this program is executed. finish. The open-loop control operation region is, for example, the region ■ (lean operation region) shown in Fig. 2, a part of the region ■ (idle operation region) (the area not shaded), the region ■ (low-speed operation region), Area ■ (high load operation area) and area ■ (high rotation operation area) are included. The lean operating region ■ is a region where the intake pipe absolute pressure PBA is set to a large value as the engine speed Ne increases during engine deceleration, and is below the discriminant value P e ALJ, and the idle operating region ■ is a region where the engine speed Ne is the discriminant value NIDL. (For example 1000p
p m ) and the intake pipe absolute pressure PBA is lower than the discrimination value PBAIDL (for example, 360 mmt1g), and the low rotation operating region ■ is the region where the engine rotation speed Ne is lower than the discrimination value NLOP (for example, 600 rpm) and the intake pipe absolute pressure PBA is the discriminant value PBAIDL (for example, 360 mm
Hg) and the high load region discrimination value θWOT set according to the engine speed Ne, the high load operation region ■ is a region between the high load region discrimination value θWOT set according to the engine speed Ne, when the throttle valve opening θth is set to the above discrimination value θ at high load.
The region above WOT, the high-speed operation region (2), is a region where the engine speed Ne is above the discrimination value NHOP (for example, 3000 ppm).

Figure 4 shows the deceleration correction coefficient value KIDL which is executed in CPUUSb every time the TDC signal is generated by the Ne sensor 10 in Figure 1.
A flowchart of the KID subroutine for setting the KID is shown.

First, it is determined whether or not the engine is in the aforementioned lean operating region (region ■ in FIG. 2) (step 401), and if it is not in the lean operating region (determination result is negative (No)), the process proceeds to step 402. .

In step 402, it is determined whether the valve opening value θth of the throttle valve 3' shown in FIG. If it is smaller than the oFC value, the process proceeds to step 403, and if the answer is negative (NO), it is determined that the accelerator is in a normal accelerator depression state and therefore not in a deceleration driving state, and a flag NeFLG, which will be described later, is set to the value 0 (steps 411) and 412. Proceed to Step 403. In step 403, it is determined whether or not the engine speed value Ne exceeds a predetermined determination value No, LSH (for example, 1250 rpm). This determination is made when the engine is in a high rotation speed region (
It is determined whether or not deceleration has started from the shaded area H) in FIG. 5. If the result of determination 1 is affirmative (Yes), the flag NeFLG is set to the value 1 (step 404).
, it is memorized that the deceleration is from a high rotational speed region.

Next, it is determined whether the engine is under the aforementioned 02 feedback control (in other words, whether the engine is in the shaded area in FIG. 5) (step 405), and if this determination result is negative ( If No), the step 412;
In the case of affirmation (Yes), the process proceeds to step 406, respectively.

In step 406, it is determined whether the flag value NepLG is 1 or not, and if the deceleration is from a high rotational speed region (shaded region H in FIG. 5), this determination result is affirmative (Yes).
Proceed to step 407.

In step 407, the engine rotation value Ne is the discrimination value No.
, a predetermined discrimination value No. smaller than LSH (1250 rpm)
, LSL (for example, 900 rpm). If the determination result in step 403 of this loop is affirmative (Yes), naturally the determination result in step 407 is also positive (Yes), and the process proceeds to step 409. or,
If the NepLG value is 1, that is, deceleration from a high rotation speed region, and the Ne value of this loop is larger than the No2LSL value, that is, the engine rotation value Ne is equal to the No2LSH value and No.
The middle eye roll number area between the 2Ls value (the shaded area M in Figure 5)
) (engine operating line B in Figure 5).

In this case as well, the process proceeds to step 409.

On the other hand, although the NeFLG value is 1, the engine speed Ne
further decreases and enters a low rotational speed region (shaded region L in FIG. 5) smaller than the No. 2 LSL value (engine operating line C shown by a broken line in FIG. 5), the determination result in step 407 becomes negative (No), The flag value NepL (, is reset to the value O (step 408), and the process proceeds to step 412.

If the determination result in step 406 is negative (No), that is, the engine is in the shaded area in FIG.

In addition, if the flag value NepL (, is zero, it means that deceleration has started from a state where the engine speed Ne is less than the discrimination value NO□LSH (engine operating line A in Fig. 5), and in such a case, the mixture It is assumed that there is no concern about enrichment of Qi, and the process proceeds to step 412.

In step 409, it is determined whether the air-fuel mixture supplied to the engine has a predetermined air-fuel ratio 1, for example, a fuel richer state than the stoichiometric air-fuel ratio. This determination is made using the 02 sensor 1 in Figure 1.
The determination is made based on whether the output level of the detection value signal No. 3 is higher than a predetermined reference level indicating a rich state of the air-fuel mixture.

If the determination result in step 409 is affirmative (Yes), that is, if the air-fuel mixture is in a rich state, the process proceeds to step 410, and by closing the throttle valve 3', the fuel adhering to the inner wall of the intake pipe is removed from the combustion chamber. The deceleration correction coefficient KIDL is set to a value of 0.95 in order to prevent over-richness of the air-fuel mixture, that is, deterioration of exhaust gas characteristics due to the supply of the fuel to the engine. On the other hand, if the air-fuel mixture is not in a rich state, the deceleration correction coefficient KIDL is set to a value of 1.0 in order to prevent engine drivability from deteriorating due to excessive lean (step 412).

Here, the determination result in step 401 is determined (Ye).
In the case of s), that is, if the engine is in the lean operation region, the air-fuel mixture is made lean by the lean correction coefficient KLs of both equations (1), as described above.

In order to prevent double leanness, the process proceeds to step 412 via step 411, and the correction coefficients are set to a value of 1.0. If the determination result in step 402 is negative (No), that is, if the accelerator is depressed, the process proceeds to step 412 via step 411, and the correction coefficient is set to 1. ) The reason why L is set to a value of 1.0 is to prevent the re-engine output from becoming insufficient due to making the air-fuel mixture lean.

If the determination result in step 405 is negative (No),
That is, when the engine is not under 0□ feedback control, the deceleration correction coefficient KIDL is set to a value of 1.0 because the correction coefficient is appropriately set according to each specific operating state as described above.

Further, if the determination result in step 406 is negative (No),
That is, the engine speed Ne is the discrimination value No, Ls.

When deceleration is started from the following conditions, the effect on the air-fuel ratio of the air-fuel mixture due to the suction of fuel adhering to the inner wall of the intake pipe when the throttle valve is fully open is reduced, so the correction coefficient is adjusted accordingly. conversion is not performed.

It should be noted that the deceleration correction coefficient value KIt set as described above
+L is applied to both equations (1), and the fuel injection time TOIJT of the fuel injection valve 6 is set.

(Effects of the Invention) As detailed above, according to the fuel supply control method during deceleration of an internal combustion engine of the present invention, in the fuel supply control method for controlling the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine, detecting an engine rotation speed; detecting whether the internal combustion engine is in a deceleration operation state; the internal combustion engine is in a deceleration operation state, and the engine rotation speed detection value is greater than a first predetermined engine rotation value; from the value
The air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine is made lean in accordance with the detected value from the exhaust gas component concentration detection means, while the engine speed decreases to a second predetermined engine speed smaller than the predetermined engine speed. This makes it possible to prevent deterioration of engine exhaust gas characteristics during deceleration from a high engine speed.

[Brief explanation of drawings]

Fig. 1 is a fuel supply control system for an internal combustion engine to which the present invention is applied, Fig. 2 is an engine operating range diagram, Fig. 3 is a flowchart showing a subroutine for calculating the 02 feedback correction coefficient Ko, and Fig. 4 is a flowchart showing the subroutine for calculating the 02 feedback correction coefficient Ko. Deceleration correction coefficient K
Flowchart showing IDL calculation subroutine, No. 5
The figure shows the 02 footback driving range. 1... Internal combustion engine, 3'... Throttle valve, 4.
...Throttle valve opening sensor, 5...Electronic control unit (ECU), 6...Fuel injection valve, 8...
Absolute pressure sensor, 10...Engine speed sensor (Ne
sensor), 11...exhaust passage, 13...exhaust gas component concentration detection means (02 sensor).

Claims (1)

[Claims] 1. Fuel supply control that performs feedback control of the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine based on a detected value signal from an exhaust gas component concentration detection means disposed in the exhaust passage of the internal combustion engine. In the method, detecting engine rotation speed;
detecting whether or not the internal combustion engine is in a decelerating operating state; and detecting whether or not the internal combustion engine is in a decelerating operating state, and from a value in which the internal combustion engine is in a decelerating operating state and a detected engine rotational speed value is larger than a first predetermined engine rotational value, the first predetermined engine rotational speed value is Leaning the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine according to the detected value from the exhaust gas component concentration detection means during the period when the engine speed decreases to a second predetermined engine speed smaller than the engine speed. A method for controlling fuel supply during deceleration of an internal combustion engine, characterized by: 2. When the detection value signal from the exhaust gas component concentration detection means indicates a value at which the mixture should be made lean, the air-fuel ratio of the mixture is made leaner than the value set based on the detection value signal. A method for controlling fuel supply during deceleration of an internal combustion engine as claimed in claim 1.