JPS5867941A - Method of adjusting engine basic air/fuel ratio - Google Patents

Abstract

PURPOSE:To make the scattering of adjusted values of a basic air/fuel ratio small, by holding the adjustment of an air/fuel ratio setting mechanism in the vicinity of a range where the output of an oxygen concentration detector displayed under specific conditions are abruptly changed. CONSTITUTION:An oxygen concentration detector 7 in an air/fuel ratio feedback controlled type engine 1 is electrically connected to a solenoid valve 9 through a control circuit 8, and an idle port 23 opened to the downstream of a Venturi part 4 disposed in an intake passage 2, is adjusted in its open degree through a mixture adjusting screw 22 for controlling the flow of fuel. At first, a stationary duty oscillator 29 is started to be actuated for carrying out stationary duty control of the valve 9 after the valve 9 is connected to the oscillator 29 and the detector 7 is connected to a display unit 30 under the condition of deenergization of the circuit 8, and then the open degree of the port 23 is adjusted by rotating the screw 22 while the display unit 30 is observed for holding a desired air/fuel ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for adjusting the basic air-fuel ratio of an air-fuel ratio feedback control type engine to a desired value.

Generally, a fixed air-fuel ratio (hereinafter referred to as the basic air-fuel ratio) is set by a mixture supply device (for example, a carburetor or a fuel injection device) installed in the engine's intake system, and an oxygen In an air-fuel ratio feedback control engine that operates an air-fuel ratio correction device to correct the air-fuel ratio using an air-fuel ratio correction signal based on an output signal from a concentration detector, it is extremely difficult to adjust the basic air-fuel ratio. known to be important.

As a method of adjusting the basic air-fuel ratio, for example, as shown in Japanese Patent Application Laid-Open No. 5-1977, while performing feedback control of the air-fuel ratio, the voltage value of the air-fuel ratio correction signal at that time is measured with a voltmeter. While measuring, set the desired basic air-fuel ratio (voltage value)
There is one that adjusts the basic air-fuel ratio setting mechanism so that

However, with this method, the air-fuel ratio fluctuates between lean and rich during feedback control, making engine rotation unstable and causing the voltmeter to fluctuate. In addition to the force required to observe and adjust the voltmeter needle, there are also forces that affect the desired value of the adjustment value. be.

The present invention has been made in view of the above points, and uses a 111-day feedback control type engine to easily and quickly adjust the basic air-fuel ratio on the production line. The main object of the present invention is to provide a basic air-fuel ratio adjustment method for an engine that can stabilize engine rotational force and reduce variation in adjustment values.

First, the overall configuration of an air-fuel ratio feedper controlled engine that is adjusted by the method of the present invention will be described.

In Figure 1, 1 is the engine and 2 is the intake passage.

6 is an exhaust passage. A bench part 4 is interposed in the middle of the intake passage 2, and a throttle valve 5 is provided downstream of the venturi part 4 to control the amount of air-fuel mixture supplied to the engine 1 in conjunction with an accelerator pedal (not shown). Rotatably supported. On the other hand, a three-way catalyst 6 (catalyst device) is interposed in the exhaust passage 3, and an 02 sensor 7 (oxygen concentration detector) is provided upstream of the three-way catalyst 6 (catalyst device). This 02 sensor 7 is electrically linked via an air-fuel ratio feedback control circuit 8 to a solenoid valve 9 (air-fuel ratio correction device) that performs duty control of the air-fuel ratio. The basic configuration of the air-fuel ratio feedback control circuit 8 includes, for example, a comparison circuit that outputs a deviation signal between the output of the 02 sensor 7 and a set value corresponding to the stoichiometric air-fuel ratio, and a proportional circuit that outputs a proportional signal of the deviation signal. , an integration circuit that outputs an integral signal of the deviation signal, an addition circuit that outputs an air-fuel ratio control signal obtained by adding the proportional signal and the integral signal, a duty ratio control circuit that controls the duty ratio according to the air-fuel ratio control signal,
A signal generating circuit outputs a signal to the duty ratio control circuit, and a solenoid valve operating circuit operates the solenoid valve 9 in accordance with the duty ratio from the duty ratio control circuit.

Further, the electromagnetic valve 9 includes a valve body 9e that moves within a coil 9b attached to the upper side of the main body 9a and has a first valve portion 9C and a second valve portion 9d.

One auxiliary jet 10 at the lower end of the main body 9a of this solenoid valve 9
is screwed on, and a spring 9f is interposed between the second valve part 9d of the valve body 9e and the auxiliary jet 10, so that the valve body 9e is directed upward (as seen in the drawing). In addition, the upstream fl11 portion of the auxiliary jet 10 (the space where the lower end of the second valve portion 9d is located) and the float chamber 11 are constantly energized.
G) is communicated with the trowel through the communication port 9ql. Reference numeral 12 denotes a cylindrical support member, which is disposed on the outside with a slight gap between it and the first valve part 9C of the valve body 9C, and on the inside of the upper part.
The disk portion 9h at the upper end of C (the cylindrical member 16 that comes into contact with it is screwed into G. It is connected to 14.

15 is a main air bleed that opens in the intake passage 2 on the upstream side of the venturi part 4, and 16 is a slow air bleed that opens in the intake passage 21 through an opening 17 on the upstream side of the rib. This is intended to promote fuel atomization and set the air-fuel ratio during load.The downstream portion of the slow air bleed 16 is communicated with the upstream space of the cylindrical member 13 through the communication passage 18, and
It communicates through a passage 20 with a slow port 19 that is opened near the throttle valve 5 when it is fully open.

A main nozzle 21 is supported so as to protrude from the center of the venturi section 4, and fuel is sucked out from the float chamber 11 by the negative pressure generated in the venturi section 4. 22 is a mixture adjustment screw, the tip of which adjusts the opening amount of the idle port 23, thereby controlling the outflow and containment of fuel and thus the air-fuel ratio.

24 is a main jet installed in the main fuel passage 25;
Its upstream side is connected to the float chamber 11 through a communication passage 26, while its downstream side is connected to the main air bleed 15.
The fuel is mixed with the air that is taken in, and the mixture is configured to flow out into the intake passage 2 through the main nozzle 21. Reference numeral 27 denotes an auxiliary fuel passage, and the downstream portion of the auxiliary jet 10 is communicated with the main fuel passage 25 downstream of the main jet 24 through a communication passage 28 .

Next, a method for adjusting the basic air-fuel ratio of the engine 1 will be explained. First, for example, on a production line, the air-fuel ratio feedback control circuit 8 is removed, or the air-fuel ratio feedback control circuit 8 is installed. In this case, the fixed duty oscillator 29 is connected to the solenoid valve 9 while the air-fuel ratio feedback control circuit 8 is stopped.
(For example, the fixed duty ratio is set to 3.5%)
and a display 30 equipped with a display lamp are electrically connected to the 02 sensor 7 (see FIG. 1). This display 3
The 0 indicator lamp indicates the 02 sensor 7 as shown in FIG.
Since the output voltage of the 02 sensor changes rapidly near the stoichiometric air-fuel ratio (/X7) and the output voltage of the 02 sensor approximately corresponds to θpv, the light turns on when the output voltage is θyv or higher, and θp
It is configured to turn off when the voltage is less than v. therefore,
By blinking the indicator lamp, it can be easily seen that the air-fuel ratio has been adjusted to the stoichiometric air-fuel ratio.

Thereafter, the fixed duty oscillator 29 is activated, and the operation of the electromagnetic valve 9 is controlled with a fixed duty by a constant control signal generated from the oscillator 29 corresponding to the fixed duty ratio 3j.

In this state, while detecting the output change of the 02 sensor 7 through the display 30, the mixture adjustment screw 22 is rotated to adjust the opening amount of the idle port 23, thereby bringing the air-fuel ratio to the desired value (the stoichiometric air-fuel ratio). When the corresponding basic air-fuel ratio is reached, the indicator lamp on the display 3o changes from lighting to turning off or from turning off to lighting, and during this change, the adjustment of the mixture adjustment screw 22 is maintained, and the basic air-fuel ratio in the idling operating state is maintained. Adjustment work is completed.

In the engine 1 whose basic air-fuel ratio has been adjusted, the fixed duty oscillator 29 and the display device 3o are disconnected, and the solenoid valve 9 is then controlled by the air-fuel ratio feedback control circuit 8. become.

In the above embodiment, an indicator equipped with an indicator lamp was used as the indicator, but a voltmeter itself could also be used, and the voltage of the stoichiometric air-fuel ratio (θ<tV) and the output voltage of the 02 sensor could be used. It is also possible to use an indicator that lights up an indicator lamp when the stoichiometric air-fuel ratio is reached during comparison and adjustment.

Further, in the above embodiment, the fixed duty ratio of the fixed duty oscillator 29 was set to 3j%, but if the fixed duty ratio is adjusted to the lean side, for example, 30 to θ%, the solenoid valve 9 Even when a failure occurs and the duty ratio is reduced to θ%, the degree of richness of the air-fuel ratio is small, which is advantageous in terms of fuel efficiency.

As described above, in the present invention, the operation of the air-fuel ratio feedback control is stopped and the air-fuel ratio correction device is operated with a fixed control signal, so that the engine rotation is stabilized and the adjusted value of the basic air-fuel ratio is The variation becomes smaller. In addition, since the output of the oxygen concentration detector takes advantage of the fact that the output changes rapidly near the stoichiometric air-fuel ratio, it is possible to easily and quickly adjust the basic air-fuel ratio on the production line, etc. It has excellent effects.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an air-fuel ratio feedback control type engine to which the present invention is applied, and FIGS. 2 and 2 are graphs showing the relationship between the air-fuel ratio and the output voltage of the 02 sensor. 1...Engine, 2...Intake passage, 3
......r11 air passage, 5...throttle valve, 7.
...0,1 sensor, 8...Air-fuel ratio feedback, 9...Solenoid valve, 22...Mixture adjustment screw, 23...Idle Baud l-, 29-...Fixed duty oscillator,
60... Display unit

Claims (1)

[Claims] (F) The basic air-fuel ratio is set by the air-fuel mixture supply device installed in the engine's intake system, and based on the output No. 1 from the oxygen concentration detector installed in the engine's ? In the method for adjusting the basic air-fuel ratio of an air-fuel ratio feedback control engine, which operates an air-fuel ratio correction device to correct and control the air-fuel ratio, the operation of the air-fuel ratio feedback control is stopped and the air-fuel ratio correction device is fixed. Displaying a change in the output of the oxygen concentration detector while activated by a control signal, and adjusting the air-fuel ratio setting mechanism of the air-fuel mixture supply device in the vicinity where the displayed output of the oxygen concentration detector suddenly changes. A basic air-fuel ratio adjustment method for an engine characterized by maintaining the following.