JPH0533706A - Air-fuel ratio control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce the generation of harmful exhaust components by attenuating the correction coefficient toward a reference coefficient value with a specified gradient in corresponding relation to the temperature of the cooling water before commencement of the air-fuel feedback control, and converging, when the feedback control is started, the correction coefficient to the reference coefficient value with a particular gradient larger than said specified gradient. CONSTITUTION:When cooling the engine, warm-up increment correction for fuel is performed using a warm-up increment correction coefficient K1, which is a correction coefficient larger than a reference coefficient, up to the commencement (position A) of the feedback control owing to reach of the cooling-water temperature to a specified value. In addition, the correction coefficient is attenuated toward the reference coefficient value with a specified gradient L3, i.e., at an angle theta3 as defined between the gradient L3 and a vertical line VL3, in corresponding relation to the temperature of the cooling water. When the feedback control is started (position A), the warm-up increment coefficient K1 is converged to the reference coefficient value at a position B where a specified time length has lapsed from the start of the feedback control, at an angle theta2 with a particular gradient L2 larger than said specified gradient L3. At this time, a feedback correction coefficient L1 operates at an angle theta1 with respect to a vertical line VL1.

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 system for an internal combustion engine, and more particularly to an air-fuel ratio control system for an internal combustion engine capable of reducing the generation of exhaust harmful components when feedback control of the air-fuel ratio is started.

[0002]

2. Description of the Related Art In an internal combustion engine of a vehicle, there is a vehicle equipped with a fuel injection control type air-fuel ratio control device as a countermeasure against problems such as exhaust harmful components and combustion consumption rate.

In this fuel injection control type air-fuel ratio control device, the fuel injection amount (injection time) is based on the basic control (basic injection time) determined by the engine speed and the intake air amount.
To determine the fuel injection amount by incorporating correction control (correction time) that is determined based on information such as cooling water temperature and throttle valve opening into the basic control. Further, the air-fuel ratio is feedback-controlled (air-fuel ratio correction) (closed loop) with a feedback control correction coefficient by a detection signal from an O ₂ sensor which is an exhaust sensor.

Further, in the fuel injection control type air-fuel ratio control device, as shown in FIGS. 7 and 8, when the internal combustion engine is at a low temperature,
That is, at the time of cooling, warm-up increase correction is performed to increase the amount of fuel based on the detection signal from the water temperature sensor that detects the cooling water temperature and the engine speed.

As shown in FIG. 9, in the warm-up increase correction, the fuel amount is adjusted by the warm-up correction coefficient, which is a correction coefficient larger than the reference coefficient value (1.0), before the feedback control is started in the cold state. The temperature is increased to a predetermined value, and as the cooling water temperature rises, the warm-up correction coefficient is attenuated toward the reference coefficient value (1.0) at a predetermined inclination to increase the amount of fuel.

That is, the final injection time to the fuel injection valve is calculated by the following formula: final injection time = basic injection time × warm-up correction coefficient × intake air temperature correction coefficient × feedback (F / B) correction coefficient.

By the way, recently, with the tightening of exhaust regulations,
The set value of the cooling water temperature for starting the feedback control is low. Particularly, in the case of the fuel injection system in which the heater is attached to the O ₂ sensor, the feedback control is started before the cooling water temperature reaches 30 ° C.

The air-fuel ratio control in the fuel injection control device is disclosed, for example, in Japanese Patent Laid-Open No. 60-1341. The one described in this publication determines whether or not the O ₂ sensor is activated by determining the activation start point Vx ₁ of the O ₂ sensor.
In addition to the determination by the operating range of the engine, the O ₂ sensor completes the activation when the cooling water temperature becomes higher than a predetermined temperature or after a predetermined time elapses after detecting that it is in the feedback region. Thus, the feedback control is started to prevent the delay of the feedback start timing and to reduce the emission. Further, when the feedback control becomes possible after a lapse of a predetermined time after the activation of the O ₂ sensor is completed and the correction coefficients such as the engine water temperature correction coefficient and the post-start fuel increase coefficient are 1 or more, FIG. As shown in, the value of these coefficients is forcibly set to 1 to start the feedback control and reduce the emission.

[0009]

By the way, conventionally, in the fuel injection control type air-fuel ratio control device, since the warm-up increase correction is performed until the cooling water temperature reaches about 60 ° C.,
The feedback control was started in the state where the warm-up correction coefficient was the reference coefficient value (1.0) or more.

However, the warm-up correction coefficient is the reference coefficient value (1.
When acceleration / deceleration is performed above 0), the air-fuel ratio shifts to the rich side for the warm-up correction, and the deceleration / reduction amount that was matched to the complete warm-up is misaligned. The air-fuel ratio cannot be maintained properly. That is, in FIG. 10, the movement of the normal feedback correction coefficient responding to the vehicle speed after warming up is shown in FIG.
As shown in, when the feedback control is started in a state where the warm-up correction coefficient is larger than the reference coefficient value (1.0), the feedback control becomes significantly longer than the original feedback control cycle during acceleration / deceleration. A part is generated, and in this part, the air-fuel ratio does not exactly match the theoretical air-fuel ratio (14.6), that is, the feedback control cannot be completely executed, and the uncontrolled state occurs.
Exhaust gas harmful components such as O, HC, and NOx are frequently generated.

In more detail, referring to FIG. 11, when the feedback control is started when the warm-up correction coefficient is equal to or higher than the reference coefficient value (1.0), the feedback correction coefficient becomes negative (-) especially when decelerating. When making a large shift and then trying to accelerate, the air-fuel ratio becomes lean, so the feedback correction coefficient will return to the original position at the end when trying to shift to the rich side. A large amount of exhaust harmful components will be generated in the portion moving to the negative side.

Further, as shown in FIG. 9, when the warm-up correction hair number is set to the reference coefficient value (1.0) in accordance with the start timing of the feedback control,
In reality, the cooling water temperature at the time of starting the feedback control may be changed depending on the cooling water temperature state at the time of starting, so that the above setting has a problem that it is actually difficult.

[0013]

Therefore, in order to eliminate the above-mentioned inconvenience, the present invention performs the warm-up increase correction of the fuel by the correction coefficient larger than the reference coefficient value at the time of low temperature of the internal combustion engine and the internal combustion engine. In the air-fuel ratio control device of the internal combustion engine for performing feedback control of the air-fuel ratio to the target value by the detection signal from the exhaust sensor after warming up when the engine cooling water temperature reaches the set value, before the feedback control of the air-fuel ratio is started. The correction coefficient is attenuated toward the reference coefficient value at a predetermined gradient according to the cooling water temperature, and when the feedback control of the air-fuel ratio is started, the correction coefficient is set to the reference at a specific gradient larger than the predetermined gradient. It is characterized in that a control means for controlling so as to converge the coefficient value is provided.

[0014]

According to the structure of the present invention, the control means attenuates the correction coefficient toward the reference coefficient value with a predetermined inclination according to the cooling water temperature before starting the feedback control of the air-fuel ratio, and at the same time, performs the feedback control of the air-fuel ratio. When is started, the correction coefficient is converged to the reference coefficient value with a specific inclination larger than a predetermined inclination. As a result, after the feedback control is started, the feedback correction coefficient is finely operated, and the non-control time due to the normal long cycle is eliminated, so that the generation of the exhaust harmful component can be reduced.

[0015]

Embodiments of the present invention will now be described in detail and specifically with reference to the drawings. 1 to 6 show an embodiment of the present invention. In FIG. 1, 2 is an internal combustion engine of a vehicle, 4 is a fuel injection control type air-fuel ratio control device, 6 is control means, and 8 is a fuel injection valve. The control means 6 includes a basic injection time (basic injection amount) circuit 10 and a correction time (correction amount).
It is composed of a circuit 12 and an injection time (injection amount) circuit 14 connected to the fuel injection valve 8.

The basic injection time circuit 10 is connected to a crank angle sensor 16 which outputs a detection signal of an engine speed and an air flow meter 18 which outputs a detection signal of an intake air amount. As a result, the basic injection time circuit 10 determines the basic injection amount of fuel based on the engine speed and the intake air amount.

The correction time circuit 12 outputs a vehicle speed sensor 20 for outputting a vehicle speed detection signal, a water temperature sensor 22 for outputting a cooling water temperature detection signal for the internal combustion engine 2, and a throttle valve opening detection signal. Throttle sensor 24,
A battery 26 that supplies a voltage, an A / T controller 28 that detects each range signal of "R", "D", "2", and "L" of an automatic transmission (not shown), and oxygen in exhaust gas O ₂ sensor 30, which is an exhaust sensor that outputs a concentration detection signal
And an intake air temperature sensor 3 that outputs a detection signal of the intake air temperature
2 has been contacted. The correction time circuit 12 determines the correction time (correction amount) of fuel based on these signals.

The basic injection time circuit 10 and the correction time circuit 12 are connected to an injection time circuit 14. The injection time circuit 14 calculates the basic injection time from the basic injection time circuit 10 and the correction time from the correction time circuit 12,
The final injection time to the fuel injection valve 8 is determined.

In the control means 6, when the internal combustion engine 2 is at a low temperature, that is, when it is cold, as shown in FIG. 3, a warm-up correction coefficient which is a correction coefficient larger than the reference coefficient value (1.0). (K ₁ ) is used to correct the fuel warm-up increase.
This warm-up increase correction is performed until the cooling water temperature reaches the set value and the feedback control (F / B) is started (position A), and the reference coefficient value (1. It is attenuated at a predetermined inclination L ₃ toward the 0) side, that is, at an angle θ ₃ with respect to the vertical line VL ₃ (see FIG. 6).

As shown in FIG. 3, the control means 6 specifies the warm-up correction coefficient (K ₁ ) larger than the predetermined slope L ₃ when the feedback control is started (position A). With respect to the inclination L ₂ , the angle θ ₂ is converged to the reference coefficient value (1.0) (see FIG. 5). That is, the warm-up correction coefficient (K ₁ ) is set to the reference coefficient value (1.0) at the position B after a predetermined time t has elapsed from the start of the feedback control (position A). At this time, the feedback correction coefficient (L ₁ ) operates at an angle θ ₁ with respect to the vertical line VL.

In the feedback control, the feedback correction coefficient operates on the plus side (+) and the minus side (-) according to the detection signal of the O ₂ sensor 30 to determine the fuel injection amount, and the air-fuel ratio is the target. Theoretical air-fuel ratio (1
Control to 4.6).

[0022] In the this embodiment, the feedback correction coefficient L ₁ angle theta ₁ and the feedback control start after the warm-up correction factor L ₂ of the warm-up correction factor angle theta ₂ and the feedback control before the control movement of the movement the relationship between the angle theta ₃ motion L ₃ and _{θ 3> θ 2> θ 1} .

Next, the operation of this embodiment will be described with reference to the flowchart of FIG.

In the control means 6, when the program starts (step 102), first the O ₂ sensor 30
It is determined whether or not the feedback control condition is satisfied and the feedback control is started (step 10).
4). That is, it is determined whether or not the cooling water temperature has reached the set value for the feedback control by the O ₂ sensor 30. If NO in this step 104, this judgment is continued.

On the other hand, if YES at step 104, the warm-up correction coefficient (K ₁ ) is the reference coefficient value (1.0).
It is determined whether or not the above (step 106). At this time,
The warm-up correction coefficient (K ₁ ) is attenuated with a predetermined slope L ₁ according to the cooling water temperature.

If YES in step 106, the reduction amount of the warm-up correction coefficient (K ₁ ) is reduced by the O ₂ sensor 30.
Is larger than that before the feedback control is started (before the position A), that is, the warm-up correction coefficient (K ₁ ) is a reference coefficient value (1.0) with a specific slope L ₂ larger than the predetermined slope L _1.
Converge to. The warm-up correction coefficient K ₁ is converged to the reference coefficient value (1.0) at the predetermined time t from the start of the feedback control (position A) (position B).

At this time, the relationship between the angle θ ₁ of movement of the feedback correction coefficient, the angle θ ₂ of the warm-up correction coefficient after starting the feedback control, and the angle θ ₃ of the warm-up correction coefficient before starting the feedback control is θ ₃ > Θ ₂ > θ ₁ .

On the other hand, if NO in step 106, normal feedback control (F / B) is performed.

As a result, even if the deceleration / acceleration is performed after the feedback control is started, the feedback correction coefficient can be finely operated to eliminate the non-control time due to the long cycle, and exhaust harmful components (CO, HC, NOx) can be eliminated. Occurrence can be reduced.

[0030]

As is apparent from the above detailed description, according to the present invention, before the feedback control of the air-fuel ratio is started, the correction coefficient is attenuated toward the reference coefficient value with a predetermined inclination according to the cooling water temperature, and the air-fuel ratio is reduced. When the feedback control of the fuel ratio is started, by providing the control means for controlling the correction coefficient to converge to the reference coefficient value with a specific inclination larger than the predetermined inclination, after the feedback control is started,
It is possible to reduce the generation of exhaust harmful components by finely operating the feedback correction coefficient and eliminating the non-control time due to the normal long cycle.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an air-fuel ratio control device.

FIG. 2 is a flowchart of air-fuel ratio control.

FIG. 3 is a time chart of air-fuel ratio control.

FIG. 4 is an enlarged view of arrow 〓 in FIG.

5 is an enlarged view of arrow V in FIG.

6 is an enlarged view of arrow 〓 in FIG.

FIG. 7 is a diagram showing the relationship between cooling water temperature and fuel increase ratio.

FIG. 8 is a diagram showing a relationship between an engine speed and a fuel increase ratio.

FIG. 9 is a diagram showing an operating state of a conventional warm-up correction coefficient.

FIG. 10 is an explanatory diagram showing a movement of a normal feedback correction coefficient after warming up.

FIG. 11 is an explanatory diagram showing the movement of the feedback correction coefficient when the feedback control is started when the warm-up correction coefficient is the reference coefficient value (1.0) or more.

[Explanation of symbols]

2 internal combustion engine 4 air-fuel ratio control device 6 control means 10 basic injection time circuit 12 correction time circuit 14 injection time circuit 30 O ₂ sensor

Claims (1)

Claim: What is claimed is: 1. When the internal combustion engine is at a low temperature, a correction coefficient larger than a reference coefficient value is used to perform a warm-up increase correction of fuel, and the temperature of the cooling water of the internal combustion engine reaches a set value. After that, in the air-fuel ratio control device of the internal combustion engine that feedback-controls the air-fuel ratio to the target value by the detection signal from the exhaust sensor, the correction coefficient before the feedback control of the air-fuel ratio starts at a predetermined inclination according to the cooling water temperature. A control means is provided for controlling the correction coefficient to converge to the reference coefficient value at a specific inclination larger than the predetermined inclination when feedback control of the air-fuel ratio is started while damping toward the reference coefficient value. An air-fuel ratio control device for an internal combustion engine, comprising: