JP3013541B2 - Air-fuel ratio control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control device for feedback-controlling the air-fuel ratio when a specific operating state of an internal combustion engine, such as idling, according to the oxygen concentration in exhaust gas.

[0002]

2. Description of the Related Art Conventionally, an exhaust gas purifying device (three-way catalyst) is provided in the exhaust passage of an internal combustion engine, and an O2 sensor for detecting the oxygen concentration in exhaust gas is arranged. The amount of fuel supplied to the engine is adjusted according to the concentration, and the air-fuel ratio is feedback-controlled near a predetermined air-fuel ratio (for example, a stoichiometric air-fuel ratio), so that nitrogen oxides, carbon monoxide, unburned An air-fuel ratio control device for purifying harmful substances such as hydrocarbons is known. More specifically, when injecting and supplying fuel to an internal combustion engine, the fuel injection amount Qf depends on the intake air amount in a so-called L-jetronics engine, and according to the intake pipe negative pressure in a D-jetronics engine. The basic amount is determined, and the basic amount is feedback-corrected by a rich / lean signal of an O2 sensor provided in the exhaust system.

[0003] The feedback correction of the fuel amount is such that even if the fuel injection amount changes, there is a response delay before this change is detected as a change in the oxygen concentration in the exhaust gas.
The output of the O2 sensor changes on and off in accordance with the residual oxygen concentration in the exhaust gas, and the like, so that the air-fuel ratio is repeatedly switched between a rich region and a lean region at a predetermined cycle (limit cycle). The air-fuel ratio of the air-fuel mixture supplied to the fuel cell fluctuates across the stoichiometric air-fuel ratio.

[0004]

There is no problem when the above-mentioned limit cycle is short, but there is a limit in setting this short limit cycle. This causes a problem that the engine speed fluctuates and idle performance such as driving feeling deteriorates. The change in the engine speed is caused by the change in the amount of fuel supplied to the engine, in other words, the change in the amount of energy applied to the engine. You do it.

The present invention has been made to solve such a problem, and changes the air-fuel ratio in the vicinity of the stoichiometric air-fuel ratio in accordance with the oxygen concentration in the exhaust gas to improve the purification efficiency of the catalyst. It is an object of the present invention to provide an air-fuel ratio control device for an internal combustion engine, which minimizes fluctuations in the engine speed and improves the driving feeling during idling or the like.

[0006]

According to the present invention, there is provided a fuel injection device for injecting a required amount of fuel into an internal combustion engine, and an oxygen sensor for detecting an oxygen concentration in exhaust gas. In an air-fuel ratio control device including a concentration detection unit and a control unit that feedback-controls an air-fuel ratio of an air-fuel mixture supplied to an internal combustion engine to a vicinity of a target air-fuel ratio according to an oxygen concentration in exhaust gas, An air amount increasing / decreasing means for increasing / decreasing the intake flow rate regardless of the accelerator operation is provided.
The control means controls whether the internal combustion engine is in a specific operating state.
The torque generated by the internal combustion engine
When there is no fuel, the amount of fuel injected and supplied to the fuel injection device
While held in a constant a, according to the oxygen concentration in the exhaust gas,
Activating the air amount increasing / decreasing means to increase / decrease the intake air flow rate,
Thus, there is provided an air-fuel ratio control device for an internal combustion engine, wherein the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine is feedback-controlled near the target air-fuel ratio.

The air-fuel ratio control device for an internal combustion engine according to the present invention further comprises a rotation speed detecting means for detecting the engine speed as required, wherein the specific operation state is an idle operation state. The control means increases or decreases the torque generated in the internal combustion engine in accordance with the deviation between the engine speed detected by the speed detection means and the target idle speed.
Calculated fuel increase value corresponding to the fuel injection device, thereby injection-supply the corrected fuel amount by the fuel increase value determined.

[0008]

FIG. 1 shows the conventional air-fuel ratio feedback control. The air-fuel ratio supplied to the engine fluctuates around the stoichiometric air-fuel ratio by increasing or decreasing the fuel injection amount Qfl. At this time, when the generated torque at the time of the stoichiometric air-fuel ratio is considered as a reference, the generated torque increases and decreases in accordance with the increase and decrease of the fuel injection amount Qfl. On the other hand, as shown in FIG. 2, when the amount of air Qa supplied to the engine is increased or decreased while the fuel injection amount Qfl is kept constant, the amount of energy applied to the engine is constant, so that the generated torque is equal to the stoichiometric air-fuel ratio. It does not change in the vicinity and can be kept substantially constant.

The air-fuel ratio control apparatus for an internal combustion engine according to the present invention is based on the above findings, and the control means controls the internal combustion engine in a specific operating state such as idling.
The torque generated by the internal combustion engine
When there is no fuel supply, the fuel supply amount is kept constant, and the air-fuel ratio is feedback-controlled to near the target air-fuel ratio by increasing / decreasing the intake air flow rate by the air amount increasing / decreasing means. Also, during idling operation, the fuel supply amount is generated in the internal combustion engine according to the deviation between the engine speed and the target idle speed.
The engine speed is increased / decreased in accordance with the increase / decrease of the applied torque, and the engine speed is feedback-controlled near the target idle speed.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 3 shows a schematic configuration of an air-fuel ratio control device for an internal combustion engine according to the present invention. The control device is, for example, a four-cylinder gasoline engine (hereinafter simply referred to as “engine”) 1.
2 is applied. In each of the intake manifolds 14 connected to each cylinder of the engine 12, an electromagnetic fuel injection valve 16 is arranged adjacent to each intake port.
One end of an intake pipe 20 is connected to the intake manifold 14 via a surge tank 18, and an air cleaner 22 is attached to the other end (atmosphere open end) of the intake pipe 20. A throttle valve 24 is provided in the intake pipe 20. Each of the fuel injection valves 16 is supplied with fuel whose fuel pressure is adjusted to be constant by a fuel pressure regulator 26 through a fuel passage 25 from a fuel pump (not shown).

The intake pipe 20 is provided with a bypass passage 21 for bypassing the throttle valve 24, and a bypass valve 28 is provided in the bypass passage 21. This bypass valve 28 is, for example, a pulse motor 2
8a to change the valve opening by being driven by
It is connected to an electronic control unit (ECU) 40, which will be described later. The valve opening is controlled by a drive signal from the electronic control unit 40, and the amount of auxiliary air supplied to the engine 12 via the bypass passage 21 is adjusted. The bypass passage 21 and the bypass valve 28 constitute an air amount increasing / decreasing means for increasing / decreasing the intake air flow regardless of the accelerator operation by the driver.

On the other hand, an exhaust manifold 30 is connected to the exhaust side of each cylinder of the engine 12, and an atmospheric end of the exhaust manifold 30 is connected to an exhaust pipe 34. A three-way catalyst type catalytic converter (catalytic exhaust gas post-treatment device) 36 is provided in the exhaust pipe 34.
An O2 sensor 44 for detecting the amount of oxygen in the exhaust gas is attached to the exhaust manifold 30. The O2 sensor 44 is electrically connected to the input side of the electronic control unit 40, and supplies an oxygen concentration detection signal to the electronic control unit 40.

An ignition plug 13 is provided in each cylinder, and each ignition plug 13 is connected to an electronic control unit 40 via a distributor 38 and an ignition coil (not shown). When the current supplied from the drive circuit (not shown) of the electronic control unit 40 to the primary coil of the ignition coil is cut off, a high voltage is generated in the secondary coil, and the high voltage causes a spark in the spark plug 13. Ignites the mixture supplied to the combustion chamber of each cylinder. The timing (ignition timing) for igniting this mixture is controlled according to the operating state.

The electronic control unit 40 includes a central processing unit (not shown), a control program for executing idle speed feedback control, air-fuel ratio feedback control, and the like, a storage device for storing various program variables and the like, It is composed of devices and the like. The storage device includes, in addition to the ROM and the RAM, a non-volatile battery backup RAM or the like that does not lose its stored contents even after the engine 12 is stopped.

Each of the above-described fuel injection valves 16 is electrically connected to the output side of an electronic control unit 40.
The valve is opened by a drive signal from 0, and a required amount of fuel is injected and supplied to each cylinder as described in detail later. On the input side of the electronic control unit 40, in addition to various sensors for detecting the operating state of the engine 12, for example, the above-mentioned O2 sensor 44, the sensor is attached near the open end of the intake pipe 20 to detect Karman vortices. An air flow sensor 42 that outputs a pulse proportional to the amount of intake air; an intake air temperature sensor 4 that is provided in the air cleaner 22 and detects the intake air temperature Ta
6. A throttle opening sensor 48 for detecting the opening of the throttle valve 24, which is provided in the distributor 38 connected to the camshaft, and which is pulsed every time a predetermined crank angle position at or near the top dead center is detected. A crank angle sensor 50 that outputs a signal (TDC signal), which is also provided in the distributor 38, and a specific cylinder (for example, the first cylinder) is positioned at a predetermined crank angle position (for example,
A cylinder discriminating sensor 52 for detecting that it is at the compression top dead center or an angular position just before it, a water temperature sensor 54 for detecting the cooling water temperature TW of the engine 12, an idle switch 56 for detecting a fully closed position of the throttle valve 24, Atmospheric pressure Pa
, An air conditioner switch (not shown) for detecting the operation state of the air conditioner, and a battery sensor for detecting the battery voltage. These sensors send detection signals to the electronic control unit 40. To supply.

The electronic control unit 40 detects operating states such as a predetermined idling speed feedback control operating state and an air-fuel ratio feedback control operating state based on detection signals of the various sensors described above, as will be described in detail later. Calculate the fuel injection amount Qfl according to the detected engine operating state,
A drive signal is supplied to each fuel injection valve 16 over a valve opening time corresponding to the calculated fuel injection amount Qfl to open it,
The required amount of fuel is injected and supplied to each cylinder. Further, when a specific operation state (idle operation state) is detected, the valve opening degree (position value of the pulse motor 28a) Pobj (t) of the bypass valve 28 is calculated, as will be described in detail later. The idle air-fuel ratio feedback control is executed, and the idle speed feedback control is executed.

Since the crank angle sensor 50 outputs a TDC signal every 180 ° of the crank angle, the electronic control unit 40 detects the engine speed Ne from the reciprocal of the pulse generation interval (stroke cycle) of the TDC signal. can do. Further, the electronic control unit 40 stores the ignition order of the cylinders, that is, the fuel supply order to each cylinder, and the above-described cylinder determination sensor 52 detects the predetermined crank angle position of the specific cylinder, thereby Next, it is possible to determine to which cylinder the fuel should be injected and supplied.

FIGS. 4 to 6 show a flowchart of an idle air-fuel ratio control routine executed by the electronic control unit 40. This routine is executed at a predetermined cycle, for example, every time the crank angle sensor 50 outputs the above-described TDC signal. Is done. First, the electronic control unit 40 inputs the operating state of the engine 12 detected by the various sensors described above (step S10). Then, it is determined from the detected operating state whether the engine 12 is in an operating state in which the air-fuel ratio feedback control may be performed (step S1).
2). For this determination, for example, it is determined whether a predetermined time has elapsed since the start of the engine 12 and whether the cooling water temperature TW is equal to or higher than a predetermined value. It is determined that the air-fuel ratio feedback control may be started.

The result of the determination in step S12 is negative (No).
In the case of, the feedback correction coefficient K _FB used for calculating the fuel injection amount Qfl (described later) is set to a value of 1 (step S14), and the integral term value K _I of the feedback correction coefficient K _FB is reset to a value of 0. Then (step S16), the process proceeds to step S30 in FIG. In step S30, it is determined whether or not the engine 12 is in an operating state in which it is possible to execute the idle speed feedback control. For this determination,
For example, that the idle switch 56 outputs an ON signal, that the engine speed Ne is equal to or less than a predetermined value,
It is determined whether conditions such as that the cooling water temperature TW is equal to or higher than a predetermined value are satisfied, and when all of these conditions are satisfied, it is determined that the idle speed feedback control may be executed.

If the result of the determination in step S30 is negative,
That is, when the engine 12 is not in the operating state in which the air-fuel ratio feedback control is possible and is not in the operating state in which the idle speed feedback control is performed, the engine 12 is determined according to the operating state from the map previously stored in the storage device described above. Then, the position value Pobj (t) of the bypass valve 28 is read, and the pulse motor 28a is driven to a position corresponding to the read position value Pobj (t) (step S3).
2). The map for obtaining the position value Pobj (t) stores, for example, a value corresponding to the engine speed Ne.
Auxiliary air according to the engine operating state is supplied to the bypass passage 21.
The supply of the auxiliary air prevents a rapid decrease in the engine speed Ne when the throttle valve 24 is rapidly closed.

Then, the process proceeds to a step S44, wherein a fuel injection amount Qfl supplied to the engine 12 is calculated. The electronic control unit 40 calculates the fuel injection amount Qfl according to the following equation (A1). Qfl = (A / N) ÷ (A / F) × K × K _FB (A1) where A / N is the amount of intake air taken into the cylinder in one intake stroke. It is determined according to the output Karman vortex generation cycle and the engine speed Ne. A / F is a target air-fuel ratio, and is set to a constant value 14.7, which is a stoichiometric air-fuel ratio, for example. K is various correction coefficients. The correction coefficient includes a water temperature correction coefficient set according to the engine cooling water temperature TW, an intake air temperature Ta, an atmospheric correction coefficient set according to the atmospheric pressure Pa, and a throttle valve 24. It includes an acceleration increase correction coefficient set according to the valve opening speed, a fuel increase correction after fuel cut, an engine start increase correction, and the like.
K _FB is the O ₂ feedback correction coefficient described above.

Then, the electronic control unit 40 operates the fuel injection valve 1 for a valve opening time corresponding to the calculated fuel injection amount Qfl.
A drive signal for opening the valve 6 is supplied to the injection valve 16 to inject the fuel of the injection amount Qfl, and the routine ends. Next, when the determination result of step S30 is affirmative (Yes), the subsequent steps S34 to S42 are executed, and the idle speed feedback control according to the conventional method is executed. First, the process proceeds to step S34, and it is determined whether or not the position value Pobj (t) of the bypass valve 28 may be updated, that is, whether or not the update cycle has elapsed. Large-capacity surge tank 1 in the intake system of engine 12
8 is arranged, and even if the auxiliary air amount is changed, a time delay occurs for the effect to appear. If the next position value Pobj (t) is calculated and executed before this effect is not determined, the engine control may become unstable. Therefore, the update period is set, and the position value Pobj (t) is set for each update period.

If the determination result in step S34 is affirmative, the current engine speed Ne and the target idle speed N
A deviation ΔN from tg is calculated (step S36). ΔN = Ne−Ntg (A2) Then, a correction value ΔP of the position value Pobj (t) is calculated according to the deviation ΔN (step S38). The method of calculating the correction value ΔP is not particularly limited.
Various conventionally known methods such as PID control can be applied. When the calculation of the correction value ΔP is completed, the correction value ΔP is added to the previous position value Pobj (t-1) to obtain the current value Pobj (t), and the position corresponding to the obtained position value Pobj (t) is obtained. The pulse motor 28a is driven (Step S40).

Pobj (t) = Pobj (t−1) + ΔP (A3) If it is determined in step S34 that the update period has not yet elapsed, the current value Pobj (t) of the position value of the pulse motor 28a Is held at the previous value Pobj (t-1) (expression (A
4)), the pulse motor 28a is driven to a position corresponding to the same position value as the previous time (step S42).

Pobj (t) = Pobj (t−1) (A4) When the current engine speed Ne is lower than the target idle speed Ntg, the correction value ΔP increases the auxiliary air amount. The value is set to a value to be decreased, and to a value to be decreased if the value is high. After the feedback control of the auxiliary air amount is performed, the fuel injection amount Qfl is calculated in step S44 described above, and the required amount of fuel is supplied to the engine 1.
2 and is subjected to feedback control so that the engine speed Ne is stabilized near the target idle speed Ntg.

Returning to FIG. 4, when the engine 12 is in an operating state in which the air-fuel ratio feedback control may be performed and the determination result in step S12 is affirmative, step S18 is performed.
Then, the output value of the O2 sensor 44 is compared with a predetermined value to determine whether or not the value is on the fuel rich side (rich), that is, whether or not a rich signal is being output. If the rich signal has been output, steps S20 and S22 are executed, and the feedback correction coefficient K _FB and the integral term value K _{FB are} calculated.
_I is calculated by the following equations (A5) and (A6).

K _FB = 1− (K _P / 2) + K _I (A5) K _I = K _I −ΔI (A6) where K _P is a proportional term value and is set to a constant value. It is. ΔI is a predetermined minute value for gradually decreasing the integral term value K _I. Therefore, the feedback correction coefficient K _FB is
By executing step S20, the value is set to a value smaller than the value 1 by (K _P / 2), and thereafter, every time step S20 is executed, the value is set to a value smaller by ΔI.

On the other hand, if the result of the determination in step S18 is negative, that is, if the air-fuel ratio of the air-fuel mixture supplied to the engine 12 is larger than the stoichiometric air-fuel ratio (value on the fuel lean side), steps S24 and S26. And the feedback correction coefficient K _FB and the integral term value K _I are calculated by the following equation (A
7), calculated by (A8). K _FB = 1 + (K _P / 2) + K _I (A7) K _I = K _I + ΔI (A8) By executing step S24, the feedback correction coefficient K _FB becomes greater than the value 1 (K _P / 2). After that, every time this step S24 is executed, the value is set to a value larger by ΔI.

When the setting of the feedback correction coefficient K _FB is completed, step S50 in FIG. 6 is executed. In this step, similarly to step S30 described above, it is determined whether or not the engine 12 is in an operating state in which the idle speed feedback control can be executed. If the determination result is negative, that is, if the engine 12 may execute the air-fuel ratio feedback control, but is not in the operating state in which the idle speed feedback control should be executed, the above-described steps S32 and S32 in FIG. Step S44 is executed. In this case, the fuel amount Q supplied to the engine 12
fl becomes to be corrected by the feedback correction coefficient K _FB, the air-fuel ratio is to be O2 feedback control by increasing or decreasing the amount of fuel supplied to the engine 12.

On the other hand, when the engine 12 is in an operating state in which it is possible to execute the idle speed feedback control, and the determination result of step S50 is affirmative, the air-fuel ratio feedback control and idle control according to the present invention of steps S52 to S60 are performed. Rotation speed feedback control is executed. First, the electronic control unit 40 determines the current engine speed Ne and the target idle speed Ntg based on the above-described equation (A2).
Is calculated (step S52). And
A fuel increase Q _Ne is obtained according to the calculated deviation ΔN (step S54). FIG. 7 shows a fuel increase map previously stored in the storage device described above. If the deviation ΔN is larger than 0, that is, if the engine speed Ne is larger than the target idle speed Ntg, the fuel increase Q _Ne is negative. Is set to a positive value if it is small, and this fuel increase Q _Ne is added to the fuel injection amount Qfl obtained by the equation (A1). That is, the fuel injection amount Qfl is calculated by the following equation (A9) (step S5).
6).

Qfl = (A / N) ÷ (A / F) × K × K _FB + Q _Ne (A9) Then, the electronic control unit 40 calculates the calculated fuel injection amount Qfl
Is supplied to the injection valve 16 over the valve opening time corresponding to the injection time, and the fuel of the injection amount Qfl is injected. Next, the process proceeds to a step S58 to calculate a correction value ΔP of the position value Pobj (t) according to the feedback correction coefficient K _FB . Method of calculating the correction value ΔP in this case is not particularly limited also, but for example, reads out the correction value ΔP according to the correction coefficient K _FB from the map shown in FIG.
When the calculation of the correction value ΔP is completed, the correction value ΔP is added to the previous position value Pobj (t-1) using the above-described equation (A3) to obtain the current value Pobj (t), and the obtained position value Pobj The pulse motor 28a is driven to a position corresponding to (t) (step S60).

If it is determined from the oxygen concentration in the exhaust gas that the air-fuel ratio supplied to the engine 12 is larger than the stoichiometric air-fuel ratio (the value on the fuel lean side), the feedback correction coefficient K _FB becomes larger than the value 1. The value is set to a large value, and the correction value ΔP is set to a negative value. Therefore, the amount of auxiliary air supplied to the engine 12 via the bypass passage 21 decreases, and the intake flow rate of the engine 12 decreases. On the other hand, if the fluctuation of the engine speed Ne is not taken into account, the feedback correction coefficient term K _FB in the equation (A9) contributes to increasing the fuel injection amount Qfl since its value is larger than the value 1. However, since the value of the (A / N) term is reduced by the correction value ΔP, the calculated fuel injection amount Qfl is eventually kept substantially constant. Therefore, in this case, the air-fuel ratio is corrected to a smaller value (to the rich side) by the decrease in the intake air flow rate. Conversely, when it is determined that the air-fuel ratio supplied to the engine 12 is smaller than the stoichiometric air-fuel ratio (a value on the fuel rich side), the feedback correction coefficient K _FB is set to a value smaller than the value 1, and the correction is performed. The value ΔP is set to a positive value, the auxiliary air supplied to the engine 12 via the bypass passage 21 increases, and the intake flow rate of the engine 12 increases. On the other hand, the feedback correction coefficient term K _FB in the equation (A9) is smaller than the value 1 and therefore contributes to the reduction of the fuel injection amount Qfl, but the value of the (A / N) term increases. As a result, the calculated fuel injection amount Qfl is kept substantially constant. Therefore, when a rich signal is output from the O2 sensor 44, the air-fuel ratio is corrected to a larger value (toward the lean side) by an increase in the intake air flow rate.

As described above, in the air-fuel ratio feedback control of the present invention, the fuel injection amount supplied to the engine 12 is kept substantially constant, and the air-fuel ratio is fed back near the stoichiometric air-fuel ratio by increasing or decreasing the intake air flow rate. Will be in control. Since the amount of fuel supplied to the engine 12 is kept substantially constant, the amount of energy applied to the engine 12 does not change, and therefore, the amount of generated engine torque does not change, and the engine speed does not change even when the air-fuel ratio changes. There is no need to worry about changing Ne. On the other hand, with respect to the fluctuation of the engine speed Ne, feedback control is performed by increasing or decreasing the fuel injection amount (increase or decrease with the fuel increase Q _Ne ) according to the deviation ΔN from the target idle speed Ntg. The responsiveness of the numerical feedback control also improves.

[0034] The fuel injection amount Qfl calculated by the formula (A9) described above, are held at a constant value by multiplying the feedback correction coefficient K _FB, in such a calculation method, always at a constant value It is conceivable that the engine speed may not be maintained, but it is sufficient if the engine speed does not change beyond an allowable range due to a change in the amount of energy applied to the engine 12.
In such a case, it can be considered that the engine speed Ne is kept substantially constant.

The air-fuel ratio control apparatus for an internal combustion engine according to the present invention is particularly effective for the air-fuel ratio control in an operation state in which the engine speed during idling is feedback-controlled as in the above embodiment. When only the feedback control of the air-fuel ratio is performed, the specific operation state of the present invention need not be particularly limited to the idle operation state. Furthermore,
The air amount increasing / decreasing means for increasing / decreasing the intake air flow rate irrespective of the accelerator operation by the driver is not limited to the air amount adjusting means for opening and closing the bypass valve 28 to adjust the intake air amount as in the present embodiment. In addition, a device that adjusts the amount of intake air by forcibly opening and closing the throttle valve near its fully closed position regardless of the amount of depression of the accelerator petal may be used.

[0036]

As is apparent from the above description, according to the air-fuel ratio control apparatus for an internal combustion engine of the present invention, an air amount increasing / decreasing means for increasing / decreasing the intake air flow regardless of the accelerator operation by the driver is provided. Ri particular operating condition near such an engine there idle, to vary the torque which the internal combustion engine to generate
The amount of fuel injected and supplied to the fuel injector when not required
While held in a constant a, according to the oxygen concentration in the exhaust gas,
The air amount increasing / decreasing means is operated to increase / decrease the intake air flow rate, and thus the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine is feedback-controlled to, for example, near the target air-fuel ratio of the stoichiometric air-fuel ratio. The amount of energy applied to the internal combustion engine is kept substantially constant, and thus the engine generated torque is constant. As a result, the purification efficiency of the catalyst can be improved by changing the air-fuel ratio near the stoichiometric air-fuel ratio in accordance with the oxygen concentration in the exhaust gas without changing the engine speed. Further, during the engine speed feedback control during idling, in addition to the air-fuel ratio feedback control described above, the torque generated in the internal combustion engine is increased in accordance with the deviation between the engine speed and the target idle speed.
By increasing or decreasing the fuel supply amount in response to the decrease, the responsiveness of the engine speed feedback control can be improved, the fluctuation of the engine speed can be further suppressed, and the driving feeling during idling can be improved. Can be improved.

[Brief description of the drawings]

FIG. 1 is a graph illustrating a relationship between a change in an air-fuel ratio and a change in torque with respect to a change in a fuel amount supplied to an engine, for explaining a conventional air-fuel ratio control method.

FIG. 2 is a graph showing a relationship between a change in an air-fuel ratio and a change in torque with respect to a change in an amount of air supplied to an engine, for explaining an air-fuel ratio control method of the present invention.

FIG. 3 is a diagram showing a schematic configuration of an air-fuel ratio control device of the present invention.

FIG. 4 is a flowchart showing a control procedure of air-fuel ratio control executed by the air-fuel ratio control device of the present invention.

FIG. 5 is a flowchart showing a control procedure of air-fuel ratio control, following the flowchart shown in FIG. 4;

FIG. 6 is another flowchart showing the control procedure of the air-fuel ratio control, following the flowchart shown in FIG. 4;

FIG. 7 is a graph showing a relationship between an engine speed deviation ΔN and a fuel increase Q _Ne .

FIG. 8 is a graph showing a relationship between an O2 feedback correction coefficient K _FB used for calculating a fuel injection amount Qfl and a position correction value ΔP of a bypass valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Internal combustion engine 16 Fuel injection valve 24 Throttle valve 21 Bypass passage (Air amount increasing / decreasing unit) 28 Bypass valve (Air amount increasing / decreasing unit) 40 Electronic control unit (ECU) 44 O2 sensor 50 Crank angle sensor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02D 41/16

Claims (2)

(57) [Claims] 1. A fuel injection device for injecting a required amount of fuel into an internal combustion engine, an oxygen concentration detecting means for detecting an oxygen concentration in exhaust gas, and an air-fuel ratio of an air-fuel mixture supplied to the internal combustion engine. A control means for performing feedback control near the target air-fuel ratio in accordance with the oxygen concentration in the gas, the air-fuel ratio control apparatus comprising: an air amount increasing / decreasing means for increasing / decreasing an intake air flow rate regardless of a driver's accelerator operation; means, Ri particular operating condition near the internal combustion engine, an internal combustion et
Engine-out <br/> that there is no need to change the torque generated, while retaining the amount of fuel to be injected and supplied to the fuel injection device in a constant, depending on the oxygen concentration in the exhaust gas, the air quantity adjusting unit The air-fuel ratio control device for the internal combustion engine is characterized in that the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine is feedback-controlled near the target air-fuel ratio by operating the air-fuel ratio. 2. The vehicle according to claim 1, further comprising a rotation speed detection unit configured to detect an engine rotation speed, wherein the specific operation state is an idle operation state, and the control unit determines an engine rotation speed detected by the rotation speed detection unit. Corresponds to increase or decrease of torque generated in internal combustion engine according to deviation from target idle speed
2. A fuel increase value to be obtained is obtained, and the fuel injection device is caused to inject and supply a fuel amount corrected by the obtained fuel increase value.
An air-fuel ratio control device for an internal combustion engine according to claim 1.