JPS61229964A - Fuel control device of carburetor - Google Patents

Abstract

PURPOSE:To supply a proper quantity of acceleration fuel by setting the discharge quantity from the acceleration pump of an air-fuel ratio feedback type carburetor so as to be large when feedback is interrupted to fix in a lean condition and to be small at the time of feedback. CONSTITUTION:A control unit 12 operates a solenoid valve 2 which opens or closes the fuel jet 5 and air bleeder 6 of a carburetor by a signal from an O2 sensor 11, and carries out O2 feedback control. An acceleration pump 3 provided in this carburetor discharges fuel taken from the suction passage 17 through a nozzle 15 via a discharge passage 14 when the piston 13 operates. Although a part of fuel returnsto a float chamber 16 through a bypass passage 19, the quantity of return fuel is reduced to increase acceleration fuel at the time of control in which feedback is interrupted at the time of acceleration to fix in a lean condition, and the quantity of return fuel is increased to reduce acceleration fuel in the case of acceleration at the time of feedback control.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a so-called feedback control type carburetor that includes a fuel control actuator that is driven in accordance with the output of an air-fuel ratio sensor.

[Prior Art] Conventionally, drive control has been performed so that the air-fuel ratio of the air-fuel mixture supplied to the engine becomes a predetermined target air-fuel ratio based on the output of an air-fuel ratio sensor such as an air-fuel ratio sensor installed in the exhaust passage of the engine. A carburetor equipped with a fuel control actuator has been proposed (see Japanese Patent Laid-Open No. 148254/1983).

This type of carburetor adjusts the air-fuel ratio to the target air-fuel ratio (a
Although there is an advantage in being able to accurately control the air-fuel ratio to a constant target air-fuel ratio (normally the stoichiometric air-fuel ratio), it is not necessarily a good idea to control the air-fuel ratio to a constant target air-fuel ratio from the viewpoint of improving the fuel efficiency of the engine.

For example, during feedback control based on the output of the air-fuel ratio sensor, when the engine operating state has reached a steady state, very high engine output is not required, so the air-fuel ratio is set to the lean side to reduce fuel consumption. It is possible to improve the

However, when accelerating from a state where the air-fuel ratio is set to the lean side, increasing the amount of fuel using the normal accelerator pump built into the carburetor does not provide enough fuel, and the air-fuel ratio becomes over-lean at the beginning of acceleration. , there is a risk that acceleration performance will be significantly deteriorated.

[Object of the Invention] An object of the present invention is to improve fuel efficiency by enabling lean control of the air-fuel ratio in a fuel feedback control operation region based on the output of an air-fuel ratio sensor, and to improve fuel efficiency in accordance with the lean control of the air-fuel ratio. It is an object of the present invention to provide a fuel control device for a carburetor that can effectively avoid deterioration in acceleration performance that may occur due to the above.

[Configuration of the Invention] Therefore, in the present invention, even during fuel feedback control based on the output of the air-fuel ratio sensor, when the operating state of the engine reaches a steady state, the feedback control is stopped and the air-fuel ratio is adjusted. is fixedly set on the lean side, and a discharge control means is provided for the acceleration pump built in the carburetor to control the discharge capacity of the acceleration pump in at least two stages, "large" and "small", to control the air-fuel ratio. The system is characterized in that the discharge capacity of the acceleration pump is set to the "large" side during steady lean operation, and the discharge capacity of the acceleration pump is set to the "small" side during feedback indexing.

[Effects of the Invention] According to the present invention, even during fuel feedback control, feedback can be stopped during steady operation and the air-fuel ratio can be fixed on the lean side, so fuel efficiency can be improved and the lean side can be fixed. When shifting from fixed to accelerated operation, the discharge capacity of the acceleration pump has been increased in advance, so that sufficient fuel can be supplied from the acceleration pump at the start of acceleration, without deteriorating acceleration performance.

[Example] Examples of the present invention will be described in detail below.

As shown in the system configuration in FIG. 3, the carburetor I includes a feedback solenoid valve 2 and an acceleration pump 3. As shown in the figure, the feedback solenoid valve 2 controls the fuel orifice 5 and air orifice 6 provided in the fuel passage 4 of the carburetor 1 simultaneously and reciprocally. (downward), the air-fuel ratio is corrected to the lean side,
Conversely, when it is driven in the direction of closing the air orifice 6 (upward), it is configured as a duty solenoid valve that corrects the air-fuel ratio to the rich side, and its duty ratio detects the engine rotation speed. The output of the rotation sensor 7, the output of the negative pressure sensor lO that detects the intake negative pressure downstream of the throttle valve 9 in the intake passage 8, and the exhaust passage (not shown)
Its drive is controlled by a control unit 12 which receives as inputs the output of a sensor (air-fuel ratio sensor) 11 provided in the air conditioner.

In addition, in the above-mentioned acceleration pump 3, when the throttle valve 9 is opened to a predetermined opening degree or more and the engine is accelerated, the piston 13 is pushed downward in the figure, and the fuel in the pump is transferred to the intake passage 8 through the outlet valve 14. The basic structure is that fuel is discharged from a pump injector 15 opened in a venturi portion of the engine to increase the amount of fuel during acceleration.

In this embodiment, a leak passage 19 that communicates with the fuel passage between the inlet valve 18 and the outlet valve 14 provided for the fuel passage 17 that leads fuel from the carburetor float chamber 16 to the acceleration pump 3 is used for vaporization. A discharge amount control valve 20 is provided in communication with the bottom of the float chamber 1G and opens and closes the leak passage 19 in the middle.
has been established.

Like the feedback solenoid valve 2, this control valve 20 is controlled by the control unit 12, and when it is driven open, a portion of the fuel to be discharged from this leak passage 19 during acceleration is released into the float chamber. Because of this, the discharge capacity of the acceleration pump 3 is set to "small". On the other hand, when the acceleration pump 3 is driven closed, the leak passage 19 is closed.
The entire amount of fuel discharged by this is discharged into the intake passage 8. In other words, the fuel discharge capacity of the acceleration pump 3 is set to "large".

Next, control by the control unit 12 will be explained.

The control unit 12 is basically constituted by a microcomputer, and controls the feedback solenoid valve 2 and the discharge amount control valve 20 according to a flowchart described below.

As shown in FIG. 2, when control by the control unit 12 is started, in step 101, engine cooling water temperature, engine speed, engine load, O,
Read the rich and lean signals from the sensor. Based on these input data, in step 102, it is determined whether the current operating state is in the fuel feedback control region based on the output of the O sensor. If it is determined that the vehicle is currently in the feedback control region, the process proceeds to step 103 where it is determined whether or not the current operating state is steady operation. This determination of whether or not the operation is steady can be made by detecting, for example, the rate of change in intake negative pressure. If it is not in a steady state, the process proceeds to step 104 and so-called feedback control of the air-fuel ratio is performed. For this reason, step 104
Well then, O.

Sensor output λ and preset target air-fuel ratio λ. The detected air-fuel ratio λ is the target air-fuel ratio λ. If the air-fuel ratio is higher than the target air-fuel ratio, the duty ratio of the feedback solenoid valve 2 is decreased by a predetermined value in step 105.
In step 06, the duty ratio of the feedback solenoid valve 2 is increased by a predetermined value.

Next, when it is determined in step 103 that the current operating state is a steady state, the process proceeds to step 107, where a lean control map (built in the ROM of the microcomputer) in which the air-fuel ratio is preset to the lean side is used. ), the duty ratio according to the corresponding operating state is read, and based on this duty ratio, step 10 is performed.
8, the feedback solenoid valve 2 is driven on duty.

Further, when it is determined in step 102 that the operating state of the engine is not in the feedback control region, in step 109, the duty ratio corresponding to the current operating state is read from the enrichment map in which the air-fuel ratio is set to the rich side in advance, Based on the duty ratio, the feedback solenoid valve 2 is duty-driven in step 11O.

As mentioned above, even if the engine operating state is in the feedback control region, when the feedback solenoid valve 2 is operating in a steady state, normal feedback control is stopped and the air-fuel ratio is adjusted to the preset lean side. Based on this, fuel control will be executed.

On the other hand, as shown in FIG.
executes the following control on the acceleration pump 3.

That is, in step 201, the intake negative pressure is read,
In step 202, it is determined whether the current operating state is in the feedback control region. And step 203
In step 204, it is determined whether the operating state in the feedback control region is a steady state, and if the operating state is a steady state, the discharge amount control valve 20 provided for the leak passage 19 is closed in step 204. In other words, during operation in this steady state, the discharge capacity of the acceleration pump is set to "large".

On the other hand, when it is not in a steady state, in step 205, the discharge amount control valve 20 is opened, the leak passage 19 is opened, and the discharge capacity of the acceleration pump 3 is set to the "small" side.

Therefore, as a result of the execution of the control shown in FIG. 2 and the control shown in FIG. Feedback control based on the output of the sensor is discontinued, the air-fuel ratio is set lean, and the operation is shifted to a so-called lean fixed operation, and the discharge capacity of the acceleration pump 3 is set to "large".

Therefore, when the engine shifts from a steady state to accelerated operation, a large amount of fuel is supplied from the acceleration pump with good responsiveness, making it possible to increase the amount of fuel required for acceleration. On the other hand, in the feedback control region, which is not in a steady state, the air-fuel ratio is controlled around the target air-fuel ratio, so there is no sudden shortage of fuel even when transitioning to acceleration operation, so the accelerator pump supplies a small amount of fuel. of fuel will be discharged.

[Brief explanation of drawings]

1 and 2 are flowcharts of control programs executed by the control unit for the feedback solenoid valve and the acceleration pump, respectively, and FIG. 3 is a system configuration diagram of the present invention. ■...Carburizer, 2...Feedback solenoid valve, 3...Acceleration pump, 11...0
．． Sensor, 12... Control unit, 19
...Leak passage, 20...Discharge rate control valve.

Claims (1)

[Claims] (1) It is equipped with a fuel control actuator that is driven according to the output of the air-fuel ratio sensor, and when the engine accelerates,
In a carburetor equipped with an accelerator pump that increases the amount of fuel, a discharge control means is provided to control the discharge capacity of the accelerator pump in multiple stages, and during steady operation, feedback control of fuel based on the output of an air-fuel ratio sensor is stopped and air is increased. A carburetor characterized in that it is provided with a fuel control means that fixes the fuel ratio lean, sets the discharge capacity of the accelerator pump to "large", and sets the discharge capacity of the accelerator pump to "small" during feedback control. Fuel control device.