JPH0942059A - After starting air-fuel ratio control method for feedback carburetor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rationalize air-fuel ratio relating to an operating condition at this time so as to improve derivability, by detecting an engine temperature and an inflow amount of air to an intake system after starting, and setting an opening of a flow control valve in an air bleed passage based on each detection value. SOLUTION: In a CPU 17 of inputting an output signal of an O2 sensor 15, throttle opening sensor 21 and a water temperature sensor 22 when an engine is operated, in the case of after starting, the CPU 17 reads a cooling water temperature in this point of time and decides whether at high load operation time or not. In the case at high load time, a flow control valve 8 is controlled to be opened, and air-fuel ratio is controlled rich to prevent an engine speed from being unstable. On the other hand, in the case that an operating condition after starting is at low load operating time, an opening in accordance with a cooling water temperature at this time is set, to control the flow control valve 8. Thus by supplying a large amount of air to an air bleed 6, moving the air-fuel ratio to a rich condition is suppressed, and spark plug smoking, speed fluctuation, etc., can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a post-start air-fuel ratio control method for a feedback carburetor mounted mainly in an internal combustion engine for automobiles.

[0002]

2. Description of the Related Art Conventionally, as a method for controlling the air-fuel ratio after starting in a carburetor capable of feedback control, there is a theoretical air-fuel ratio of the air-fuel ratio of an air-fuel mixture based on exhaust gas components, as disclosed in JP-A-56-23543. It is known that an actuator for feedback control is controlled based on the temperature of the engine up to the temperature at which the actuator is normally operated. Also, in a carburettor engine, the fuel in the intake manifold vaporizes immediately after the start due to a sudden change in the pressure in the intake manifold, and the air-fuel ratio becomes rich. The amount of intake air is controlled to optimize the air-fuel ratio.

By the way, as described above, if the opening degree of the choke valve is kept constant after the start, the air-fuel ratio may become rich as the cooling water temperature rises. In order to prevent such a point, a two-stage choke breaker system or the like has been devised in which the choke opening is further opened according to the rise of the cooling water temperature.

[0004]

However, just by controlling the intake air amount immediately after starting in two stages as in the two-stage choke breaker system, the air-fuel ratio characteristic during warm-up from a very low temperature condition to a high temperature condition can be obtained. It can be difficult to optimize. In other words, if the temperature setting from the opening of the choke valve in the first temperature condition to the opening in the next temperature condition is large, the intake air amount becomes excessive or insufficient at each opening. Sometimes there is. Therefore, as a result, the air-fuel ratio fluctuates according to the temperature at that time, and due to temperature changes during warm-up, poor starting, rotational fluctuation during warm-up, engine stall, and ignition due to enrichment of the air-fuel ratio Problems such as smoldering of the plug sometimes occurred.

[0005] An object of the present invention is to solve such a problem.

[0006]

In order to achieve the above object, the present invention takes the following measures. That is, the post-start air-fuel ratio control method of the feedback carburetor according to the present invention adjusts the opening degree of the flow control valve provided in the air bleed passage communicating with the air bleed of the feedback carburetor mounted in the intake system of the engine to start the engine. A method for controlling the air-fuel ratio of a feedback carburetor after starting, which controls the air-fuel ratio of the air-fuel mixture, detects the engine temperature after starting, detects the amount of air flowing into the intake system, and detects the detected engine temperature and air amount. The opening degree of the flow rate control valve is set based on and.

Examples of the engine temperature in the present invention include engine cooling water temperature, lubricating oil temperature, intake air temperature and the like.

With such a structure, since the opening of the flow control valve is set based on the engine temperature at that time and the amount of air flowing into the intake system, the air flow is controlled via the flow control valve after starting. The amount of air flowing into the bleed is controlled. That is, the flow rate control valve is opened based on the engine temperature and the amount of air to the intake system at that time. Therefore, the flow rate control valve is opened by reflecting the engine temperature and the operating state at that time. As a result, an appropriate air-fuel ratio can be obtained even when the operating state after the start is, for example, the idle operation or the high load operation. In this way, the air-fuel ratio becomes appropriate by reflecting the operating state at that time, so that drivability can be improved.

[0009]

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

In FIG. 1, reference numeral 1 denotes a feedback carburetor mounted on an intake manifold, which is an intake system of the engine, and 2 denotes a mixing chamber thereof.
3 is a main nozzle, 4 is a throttle valve, 5 is a float chamber, 6 is an air bleed, 7 is an air bleed passage, and 8 is a flow control valve. Reference numeral 1b is a slow passage, and downstream thereof, an idle port 2a and a mixture adjustment screw 1c for adjusting the amount of air-fuel mixture ejected from the idle port 2a are provided. As the feedback carburetor 1 itself, any one widely known in this field may be used as long as it has a structure capable of controlling the amount of air supplied to both the main system and the slow system by the flow control valve 8. You may

The flow control valve 8 is provided in the air bleed passage 7 forming the starting end portion of the air bleed 6, and the suction port 8a is open to the atmosphere. This flow control valve 8 is
The pointed valve body 9 is moved back and forth with respect to the valve seat 10 to move the valve body 9
The opening area of the air passage formed between the valve seat 10 and the valve seat 10 is changed.
It is attached to the tip of the working rod 12 of No. 1. And
The stepper motor 11 is controlled by the electronic control unit 13,
From the fully closed position (0 step) to the fully opened position (100 step) of the valve body 9, during air-fuel ratio feedback control, the valve body 9 is moved forward and backward around a predetermined position set near the theoretical air-fuel ratio, for example, 14.5. is there.

On the other hand, an O ₂ sensor 15 is arranged upstream of the three-way catalytic converter 13 provided in the exhaust system 14. 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 stoichiometric air-fuel ratio and the oxygen concentration in the exhaust gas is high, and in the opposite case, that is, on the rich side. In some cases, it is configured to generate a high output voltage.

Reference numeral 16 is a microcomputer system which is a control means for controlling the flow control valve 8 and has a central processing unit (CPU) 17, a storage device 18, an input interface 19 and an output interface 20. There is. The input interface 19 has a voltage signal a output from the O ₂ sensor 15, an opening signal b output from the throttle opening sensor 21, and a water temperature signal c output from a water temperature sensor 22 that detects the cooling water temperature of the engine.
Etc. are input. The opening interface control signal d is output from the output interface 20 toward the flow control valve 8. The storage device 18 opens the flow control valve 8 according to the cooling water temperature in response to a high load in which the amount of air flowing into the intake system increases and an idling operation in which an air amount near the minimum is flowing. A table in which degrees are set is stored. That is, in the case of this embodiment, the amount of air flowing into the intake system is
By setting the operating state at the time of high load with a large amount of air and other operating states in advance, and detecting the opening degree of the throttle valve 4 from the opening degree signal b output from the throttle opening degree sensor 21, It detects two driving states.

The microcomputer system 16 includes
Using the voltage signal a output from the O ₂ sensor 15 and the opening signal b output from the throttle opening sensor 21 as main information, the step of the stepper motor 11 that drives the valve body 9 of the flow control valve 8 is changed. Then, a program for selecting and performing the air-fuel ratio feedback control in accordance with the operating condition of the engine so that the calculated air-fuel ratio is achieved is installed. Further, in this program, the cooling water temperature which is the engine temperature after starting is detected, the amount of air flowing into the intake system is detected, and the flow control valve 8 is opened based on the detected cooling water temperature and the amount of air. Programmed to set degrees.

The flow chart shown in FIG. 2 is an outline of a program for post-start air-fuel ratio control. First, step S1
Then, it is determined whether or not it has been started, and if it has been started, the process proceeds to step S2, and if it is being started, another routine is performed. The determination after this start is made based on the engine speed N
It may be performed based on that E is equal to or higher than a predetermined rotation speed. In step S2, the cooling water temperature at this point is read. In step S3, it is determined whether or not the engine is under high load,
If the load is high, the process proceeds to step S4, and if not, the process proceeds to step S5. This determination at the time of high load is performed by the LL signal b which is the output signal of the idle switch 21.
When the throttle valve 4 is open, the LL signal b is not output, so it is determined that the load is high. In step S4, the opening degree of the flow rate control valve 8 is set according to the cooling water temperature when the air flow rate is high, that is, when the load is high and the throttle valve 4 is opened relatively large. In step S5, the opening degree of the flow control valve 8 is set when the amount of air is low according to the cooling water temperature, that is, in the operating state in which the throttle valve 4 is in the substantially closed state including the idle operating state. The opening is set by searching a table stored in the storage device 18. The opening for a typical cooling water temperature is set in this table, and the other cooling water temperatures are calculated by interpolation calculation.
In step S6, the flow control valve 8
Is opened and the opened state is maintained.

Normally, the feedback carburetor 1 is provided with an O ₂ sensor 15 when the feedback driving condition is satisfied.
The flow rate control valve 8 is opened and closed on the basis of the voltage signal a output from the control unit 8 and the intake air amount is adjusted so that the air-fuel ratio becomes close to the stoichiometric air-fuel ratio. In the embodiment, the opening degree of the flow control valve is controlled based on the cooling water temperature and the amount of air flowing into the intake system in a state where the feedback operation condition after starting is not satisfied. Now, when the engine is started and the operating state after the start is reached, the control proceeds to steps S1 → S2 → S3, and the operation is performed depending on the operating state at that time, that is, whether the throttle valve 4 is closed or wide open. If the state is judged to be high, then step S4 →
In S6, the flow control valve 8 is controlled to be opened. As a result, the flow rate control valve 8 is opened according to the cooling water temperature and the inflowing air amount even under a high load with a relatively large intake air amount, and as a result, the air-fuel ratio becomes rich and the engine rotation becomes unstable. This can be prevented, and drivability can be improved.

On the other hand, if the operating state after the start is, for example, the idle operating state, the control is performed in steps S1 → S2.
→ S3 → S5 → S6, and the flow rate control valve 8 is controlled by setting the opening for a low air amount according to the cooling water temperature at that time. During this low air flow rate operation, the intake air flow rate is smaller than during high load operation. Therefore, if the flow control valve 8 opening is set only based on the cooling water temperature, the air flow ratio will not be sufficient at low temperatures. Tend to be rich. However, since the opening degree of the flow control valve 8 is set based on the cooling water temperature and the opening degree of the throttle valve 4 indicating the amount of inflowing air, it is possible to set a sufficient opening degree even at a low temperature. is there. As a result, the flow control valve 8 is greatly opened according to the cooling water temperature, and a large amount of air is supplied to the air bleed 6 via the flow control valve 8. Therefore, the air-fuel ratio does not become rich and problems such as smoldering of the spark plug and fluctuations in rotation can be prevented.

The present invention is not limited to the embodiment described above. For example, in the above-described embodiment, the amount of air flowing into the intake system is substantially closed based on the opening of the throttle valve 4 when the amount of air is high and the engine is idling. Divided into states
There were two types of setting, large amount and small amount, but throttle valve 4
The amount of inflowing air may be converted from the opening of the engine and the engine speed at that time. Thus, by converting the air amount, the opening degree of the flow control valve can be finely controlled according to the operating state after the start. Further, the intake pressure in the intake system may be detected and the air amount may be calculated from the intake pressure.

In addition, the configuration of each section is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.

[Brief description of drawings]

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

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

[Explanation of symbols]

 1 ... Feedback carburetor 6 ... Air bleed 7 ... Air bleed passage 8 ... Flow control valve 16 ... Microcomputer system 21 ... Throttle opening sensor 22 ... Water temperature sensor

Claims (1)

[Claims] 1. A feedback carburetor for adjusting the opening degree of a flow control valve provided in an air bleed passage communicating with an air bleed of a feedback carburetor mounted on an intake system of an engine to control an air-fuel ratio of a mixture after starting. This is a post-start air-fuel ratio control method that detects the engine temperature after starting, detects the amount of air flowing into the intake system, and sets the opening of the flow control valve based on the detected engine temperature and air amount. A method for controlling an air-fuel ratio after starting a feedback carburetor, characterized by: