JPH05223011A - Method of controlling flow control valve during deceleration - Google Patents

Abstract

PURPOSE:To reduce the CO value in emission without engine stall upon recovery from fuel cut-off during deceleration, by carrying out idle feed-back control when an engine is operated at a speed higher than a predetermined rotational speed during the fuel cut-off upon deceleration. CONSTITUTION:A flow control valve 8 for opening and closing an air-bleed passage 7 in a carburetor 1 is controlled for adjusting the air-fuel ratio of mixture fed to an engine. During this control, the opening position of a throttle valve 4 is detected so as to know that the throttle valve 4 is closed. When the fuel cut-off during deceleration is carried out, the idle feed-back control is carried out during operation of the engine at a speed higher than a predetermined rotational speed. Accordingly, it is possible to prevent the step for controlling the flow control valve 8 from being extremely lowered. As a result, the flow control valve 8 is controlled with a stoichiometric air-fuel ratio in a short predetermined time. With this arrangement, it is possible to restrain the air-fuel ratio from increasing, thereby it is possible to reduce the CO value in exhaust gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a flow rate control valve during deceleration in a feedback carburetor mainly applied to an automobile.

[0002]

2. Description of the Related Art A conventional flow control valve control method during deceleration of this type is disclosed in Japanese Patent Laid-Open No. 57-99256.
It is known to control the air-fuel ratio so as to increase the air bleed amount and reduce the air-fuel ratio during deceleration. Further, as shown in FIG. 4, when the idle switch is opened during deceleration, energization of the solenoid valve is stopped to execute fuel cut F / C, and at the same time, the air bleed passage of the feedback carburetor is opened / closed. There is also known a method of controlling the flow rate control valve by holding a step for controlling the flow rate control valve at a step obtained by subtracting an arbitrary step from the idle feedback learning value as a countermeasure against a stall when the vehicle is stopped. In the LA # 4 mode, which is implemented in the United States and other countries by the exhaust gas regulation test method, such control is performed even during mode running because frequent acceleration / deceleration is performed.

[0003]

However, in the above, when the re-acceleration after deceleration, that is, when the fuel supply is restored, the control step at the time of deceleration is a value far from the stoichiometric air-fuel ratio. Therefore, since it starts from the portion A shown in FIG. 4, that is, the step held during the fuel cut, it takes time to control the air-fuel ratio by stoichiometry, and during that time, the air-fuel ratio becomes temporarily rich (Fig. (Indicated by middle B), therefore, the CO in the exhaust gas increased and the emission deteriorated.

An object of the present invention is to eliminate such a problem.

[0005]

The present invention takes the following means in order to achieve such an object. That is, the method for controlling the flow rate control valve during deceleration according to the present invention, when controlling the flow rate control valve that opens and closes the air bleed passage of the carburetor in order to adjust the air-fuel ratio of the air-fuel mixture supplied to the engine, Detecting the open / closed position, it is detected that the throttle valve is closed,
Further, when the fuel cut at the time of deceleration is executed, the idle feedback control is performed while the engine is rotating at a predetermined rotation speed or more.

[0006]

With this structure, the idle feedback control is performed if the engine is rotating at a predetermined speed or more while the deceleration fuel cut is being performed.
Even if the step for controlling the flow rate control valve does not become extremely low and the vehicle is accelerated again after a short time fuel cut, the flow rate control valve can be controlled stoichiometrically in a short required time. Therefore, the rich air-fuel ratio after the re-acceleration state is suppressed, and the CO in the exhaust gas can be reduced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a carburetor mounted on an intake manifold of an engine, 2 is a mixing chamber thereof, 3 is a main jet, 4 is a throttle valve, 5 is a float chamber, and 6 is an air bleed. Shows. A flow rate control valve (hereinafter referred to as ABCV) 8 is provided in the air bleed passage 7 that forms the starting end portion of the air bleed 6, and the suction port 8a of this ABCV 8 is open to the atmosphere. ABCV8 has a valve element 9 with a pointed shape and a valve seat 1
The flow rate of air is controlled by advancing and retracting with respect to 0 and changing the opening area of the air passage formed between the valve body 9 and the valve seat 10.
Is attached to the tip of the operating rod 12 of the stepper motor 11. Although not shown, a solenoid valve for fuel cut is provided in each of the main system passage 1a and the slow system passage 1b of the carburetor 1. The solenoid valve used in the following description refers to this.

An O ₂ sensor 15 is provided in the exhaust pipe 14 located upstream of the three-way catalytic converter 13. The O ₂ sensor 15 generates only a low output voltage when the air-fuel ratio of the air-fuel mixture is leaner than the conversion point existing near the stoichiometric air-fuel ratio and the oxygen concentration in the exhaust gas is high, and In addition, when the air-fuel ratio of the air-fuel mixture is on the rich side of the conversion point and the oxygen concentration in the exhaust gas is low, a high output voltage can be generated.

Reference numeral 16 denotes a microcomputer system for controlling the ABCV8, which is a central processing unit (C
PU) 17, storage device 18, input interface 1
9 and an output interface 20. The input interface 19 receives the voltage signal a from the O ₂ sensor 15, the LL signal b from the idle switch (IDSW) 21, the pulse signal c generated at the terminal of the ignition coil 22, and the like. The idle feedback control signal d, the normal feedback control signal e, or the like is output from the interface 20 to the ABCV 8.

The idle switch 21 is an ON / OFF switch for detecting whether the throttle valve 4 is in the open position or the closed position.

The microcomputer system 16 includes
A stepper motor 11 that drives the valve body 9 of the ABCV 8 using the voltage signal a output from the O ₂ sensor 15 and the LL signal b output from the idle switch 21 as main information.
Of the normal feedback (normal F / B) control and idle feedback (ID F /
B) A program for selecting and performing control in accordance with the operating condition of the engine is incorporated. In this embodiment, as a program for controlling the ABCV8 during deceleration, a program whose outline is shown in FIG. 2 is further incorporated.

After the warm-up operation is completed, it is assumed that the engine is in a normal operation state. First, in step 51, it is determined whether or not the idle switch 21 is opened. If not opened, the process proceeds to step 61, and if opened, the process proceeds to step 52. In step 61, normal feedback control is performed based on the voltage signal a from the O ₂ sensor 15 and A
The opening of the BCV 8 is increased or decreased in fine steps. In step 52, the current engine speed E / Grev. Is greater than or equal to the fuel cut F / C return rotational speed,
If it is less than the fuel cut F / C return rotational speed, step 71
If it is above, proceed to step 53. The fuel cut F / C return rotation speed is, for example, 2200 rpm. In step 71, idle feedback control in which the speed of the control step for increasing / decreasing the opening of the ABCV 8 is different from the normal feedback control is performed. A method known in the art may be used for the normal feedback control and the idle feedback control, and the normal feedback control controls the opening of the ABCV8 at a speed that changes 100 steps in, for example, 4.2 seconds, and idle control is performed. Feedback control is ABCV
For example, the opening degree of 8 may be controlled at a rate of changing 100 steps in 45 seconds. In step 53,
The energization to the solenoid valve is stopped (non-energized), and the fuel cut F / C is executed.

In step 53, the fuel cut F
/ C is started, in step 54, the engine speed E / Grev. Is greater than or equal to the predetermined number of revolutions N ₁ , and if it is greater than or equal to, it proceeds to step 55. The predetermined rotation speed N ₁ is, for example, 2600 r, which is a rotation speed higher than the fuel cut F / C return rotation speed and satisfies stall resistance when the vehicle is stopped.
pm is preferred. In step 55, idle feedback control is executed as in step 71. Step 81
Then, as in the past, idle feedback (IDF
B) A constant S _HLDFC, for example, 30 steps is subtracted from the learned value, and the value is held at a step
V8 is controlled to adjust the air-fuel ratio.

In the above structure, as shown in FIG.
Engine speed E / Grev. Is gradually changing at a predetermined rotation speed N ₁ or higher, the idle switch 2
1 is closed and the solenoid valve is energized.
When the throttle valve 4 is fully closed due to deceleration from such a running state, the engine speed E / Grev. L indicates that the idle switch 21 is open.
The L signal b is output. In this state, control proceeds to step 52 and engine speed E / Gre decreased due to deceleration.
v. Is determined to be equal to or higher than the fuel cut F / C return rotation speed, step 53 is executed to enter the fuel cut state. Next, the control proceeds to step 54, where the engine speed E / Grev. When the rotation speed is equal to or higher than the predetermined rotation speed N ₁ , step 55 is executed and the idle feedback control is performed instead of the normal feedback control. Since the fuel cut F / C is being executed during this period, the air-fuel ratio is lean and therefore the ABCV
In step 8, the number of steps is reduced at a slower speed than in the case of normal feedback control so that the opening degree becomes smaller based on the input voltage signal a from the O ₂ sensor 15.

When the deceleration state is changed to the acceleration state again, the idle switch 21 is closed, so that the solenoid valve is re-energized to resume the fuel supply and the normal feedback control in step 61 is performed. At this time, since the idle feedback control was being executed during the fuel cut F / C, ABCV8
Is not controlled in an extremely low step, and therefore, it takes a short time to reach a step in which the ABCV8 can be stoichiometrically controlled. Therefore, during this period, the air-fuel ratio is prevented from becoming extremely rich (part C in FIG. 3), and as a result, CO in the exhaust gas can be reduced.

The present invention is not limited to the embodiments described above, that is, the configuration of each part is not limited to the illustrated examples, and various modifications can be made without departing from the spirit of the present invention. is there.

[0018]

As described in detail above, according to the present invention, while the deceleration fuel cut is being performed, if the engine is rotating at a predetermined speed or more, idle feedback control is performed to gradually increase the flow rate control valve. If the step is not extremely low and the acceleration state re-accelerates after this, the flow control valve can be controlled stoichiometrically in a short required time, and therefore, after the re-acceleration state, it becomes empty. It is possible to suppress the fuel ratio from becoming extremely rich and reduce the CO value in the emission.

[Brief description of drawings]

FIG. 1 is a schematic configuration explanatory view showing an embodiment of the present invention.

FIG. 2 is a flowchart showing a control procedure of the embodiment.

FIG. 3 is an explanatory view of the operation of the same embodiment.

FIG. 4 is an operation explanatory view of a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vaporizer 4 ... Throttle valve 7 ... Air bleed passage 8 ... Flow control valve (ABCV) 15 ... O ₂ sensor 16 ... Microcomputer system 17 ... Central processing unit 18 ... Storage device 19 ... Input interface 20 ... Output interface 21 ... Idle switch

Claims (1)

[Claims] 1. When controlling a flow control valve that opens and closes an air bleed passage of a carburetor in order to adjust an air-fuel ratio of an air-fuel mixture supplied to an engine, the open / close position of the throttle valve is detected and the throttle valve is closed. Flow control valve control during deceleration, which is characterized by performing idle feedback control while the engine is rotating at a prescribed speed or higher when it is detected that fuel is being cut during deceleration. Method.