JPS62174546A - Air-fuel ratio control for engine - Google Patents

Abstract

PURPOSE:To improve the fuel economic efficiency by dividing the normal operation region of an engine into the theoretical air-fuel ratio operation region having a relatively low speed and the lean air-fuel ratio operation region having a relatively high speed, thus securing the superior acceleration performance. CONSTITUTION:A control valve 15 is driven so that the mixed gas in the theoretical air-fuel ratio is supplied on the basis of the electric signal supplied from an oxygen sensor 22 in the theoretical air-fuel ratio operation region. In the lean air-fuel ratio operation region, the control valve 15 is opened and closed with a small duty value or kept in the valve closed state, and the fuel in the fundamental feed quantity metered mainly by a jet 3 is sent into a mixer 5, and the mixed gas in the lean air-fuel ratio is supplied into an engine 11, and thus the fuel economic efficiency is improved. Thus, the fuel economic efficiency can be improved, securing the superior acceleration performance.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for controlling the air-fuel ratio of an engine, and the present invention relates to a method for controlling the air-fuel ratio of an engine, which is used as a power source for automobiles, work vehicles, industrial machinery, etc. used for.

The technology to control the air-fuel ratio using a feedback method by detecting the operating state of the engine is widely used (as mentioned above).The basic supply amount of fuel is set according to the amount of intake air, and this is used to improve operating performance and fuel economy. The air-fuel ratio is set to a predetermined air-fuel ratio by making corrections corresponding to the operating conditions of the engine in consideration of exhaust countermeasures, etc. tA is controlled by a control valve, and is output from an electronic control unit that manually calculates the operating state of the #A dynamic signal engine and calculates optimal conditions based on that information.

Here, we exclude the high output range (in the normal operating range, below a certain rotational speed or above the suction negative pressure, we operate at the stoichiometric window/fuel ratio to mainly reduce emissions, but above a certain rotational speed or below the suction negative pressure) If you create a control system that operates at a lean air-fuel ratio and measures the fuel efficiency as a king.

The boundary between the two operating ranges is constant, and as soon as this boundary is crossed, air-fuel ratio correction is performed. Therefore, if you aim to improve fuel efficiency by setting the stoichiometric air-fuel ratio operating range small, there is a drawback that when accelerating across two operating ranges, you will gradually shift to the lean full-fuel ratio operating range, impairing acceleration performance. . For this reason, it has been considered to delay the air-fuel ratio switching so that acceleration is performed at the stoichiometric air-fuel ratio for a certain period of time even after the operating range is exceeded, but it is possible to set a constant delay time regardless of the degree of acceleration. Therefore, during rapid acceleration, stoichiometric air-fuel ratio operation may be performed even after the end of acceleration, or during slow acceleration, air-fuel ratio switching may occur at the beginning. There's a problem.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide an air-fuel ratio control method that improves fuel economy and drivability by changing the delay time depending on the degree of acceleration.

Composition of the invention An engine air-fuel ratio control method according to the present invention.

The normal operating range of the engine is divided into a stoichiometric air-fuel ratio operating range below a certain rotational speed and a lean air-fuel ratio operating range above a certain rotational speed, and even after the boundary is crossed during acceleration across the two operating ranges. In order to delay air-fuel ratio switching so as to perform stoichiometric air-fuel ratio operation, a delay time is set according to the degree of acceleration, the rotational speed at the time the delay time elapses is calculated, and if the rotational speed is changed to the above-mentioned rotational speed within the delay time. is set to 1, which switches to lean air-fuel ratio operation.

Example Embodiments of the present invention will be explained with reference to the drawings.

Figure 1 shows the case where the present invention is implemented in an engine using gaseous fuel such as LPG, in which the gaseous fuel in a pressure vessel 1 is reduced to about atmospheric pressure in a vaporizer 2, and a jet is used to set the basic flow rate. The fuel enters the annular chamber 7 formed along the venturi 6 of the mixer 5 through the fuel passage 4 (3), is sucked out from the slit-shaped main nozzle 8 into the intake passage 9, mixes with air, and is passed through the intake manifold 10. /Shiff 11. The exhaust gas is purified by a three-way catalytic converter 13 in an exhaust pipe 12 and released into the atmosphere.

A correction fuel passage 14 is provided which branches from the upstream side of the jet 3 of the fuel passage 4 and is connected to the annular chamber 7, and this passage 14 is provided with a control valve 15 of t-occupying motion. The control valve 15 is opened and closed in accordance with the duty value of the pulse waveform drive signal sent from the control valve 16 to control the correction fuel so that the required air-fuel ratio is achieved.

Here, the opening sensor 18. Pressure sensor 1 provided in intake manifold 10
9. Rotational speed sensor 20 and temperature sensor 21 of engine/engine 11. Oxygen sensor 22 provided in the exhaust pipe 12. Furthermore, sensors (not shown) for detecting the intake air temperature, ignition switch, brake, and other operating conditions of the engine 11 are provided as necessary, and electrical signals from these sensors are sent to the control unit 16 to control the control unit 16. Tsu H6
The optimum conditions are calculated based on this information and a drive signal is generated to open and close the control valve 15 at a predetermined duty ratio, or the valve is kept in the closed or open state, and the duty value of the drive signal is set in the center. change.

In addition, as shown in the control map in Fig. 2, in the normal operating range excluding the high output operating range, the engine IIQ rotation speed is set to a constant value NQ.
In the operating range where the suction negative pressure is equal to or higher than the constant value pg (N and 1), the rotational speed is equal to or higher than the constant MNa and the suction negative pressure is constant 1[
It is divided into the operating region below Po (B) and the former operating region (B).
A) is operated at the stoichiometric air-fuel ratio mixture 2, and the latter operating region (B
) is set to operate with a lean air/fuel mixture.

Further, the high output operating range (C) is set to operate with a mixture having an output air-fuel ratio.

In this embodiment having such a configuration, during idling, the throttle valve 1 is activated by the tILz signal from the opening sensor 18.
7 is in the idle position, the air-fuel mixture at the stoichiometric air-fuel ratio or the electric signal from the temperature sensor 21 is used to detect the
When it is detected that the engine temperature is low, the control valve 15 is actuated to supply a mixture slightly richer than the stoichiometric air-fuel ratio.

When the throttle valve 17 opens after idling, does the pressure rise? In the stoichiometric air-fuel ratio operating region (A) where it is determined that the intake negative pressure of the engine 11 is above a certain value PQ or the rotation speed is below a certain value N, based on electrical signals from the engine 19 and the rotational speed sensor 20. So that the air-fuel mixture at the stoichiometric air-fuel ratio is supplied based on the electrical signal from the sensor 22: i
? II IIQI valve 15 valve part 5. For this reason, for example, in a car, by setting the driving range (shu) so that the feedback control is performed to the stoichiometric air-fuel ratio within the normal city driving speed range, the vehicle runs in a state where the exhaust purification efficiency by the three-way catalytic converter 13 is maximized. Be able to do that.

Suction negative pressure is below a certain value PQ or rotation speed is a certain value NQ
In the lean air-fuel ratio operating region (B) identified as above, the feedback control based on the ML electric signal from the oxygen sensor 22 should be canceled and the control valve 15 should be opened and closed at a small duty value, or the control valve 15 should be kept in the closed state and the control valve 15 should be kept closed. The basic supply amount of fuel metered by the jet 3 is sent to the mixer 5, and a mixture with a lean air-fuel ratio is supplied to the engine 11 to measure fuel economy.

The high output operating range (
Shifting to C) 9 For example, when it is detected that the throttle valve 17 has opened at 60 degrees or more, the control valve 15 is driven at a large duty value so that a high concentration output air-fuel mixture is supplied. Or keep it in an open position.

Stoichiometric air-fuel ratio operating region (from high to lean air-fuel ratio operating region (B)
The opening speed of the throttle valve 17 is detected by the opening sensor 18, and the control unit 16 identifies the opening speed of the throttle valve 17 based on the electric signal.

Here, when acceleration operation is performed across two operating ranges (A) and CB), the air-fuel ratio is switched so that the stoichiometric air-fuel ratio operation continues for a certain period of time even after shifting to the operating range (Bl). This delay time and the rotational speed N1 at the end of the delay time are calculated and set in advance based on, for example, an average or small degree of acceleration.

The area below this delay release rotational speed N1 is defined as the maximum delay area (DI) during acceleration.

When the delay release rotation speed N1 is reached within the set delay time during sudden acceleration with a large degree of acceleration, 9 rotation speed sen?
The electric signal from 20 switches to lean air-fuel ratio operation. During slow acceleration where the caro speed is small, the delay time elapses before the delay release rotational speed N1 is reached, and at that time the operation is switched to lean air-fuel ratio operation. Therefore, it is preferable to set the delay time as long as possible based on a small acceleration degree.

2. The present invention is applicable not only to gaseous fuel but also to those that supply liquid fuel by a vaporizer method or an injection method. In this method, the injection valve consists of a control piece or groove.

According to the present invention, since the normal operating range of the engine is divided into a relatively low-speed stoichiometric air-fuel ratio operating range and a relatively high-speed lean air-fuel ratio operating range, anti-wandering measures and drivability can be improved depending on the operating range. Isn't it just possible to measure the positive and positive fuel meridians?

In particular, during acceleration when transitioning from the stoichiometric air-fuel ratio operation region to the lean air-fuel ratio operation region, the stoichiometric air-fuel ratio operation is performed for a certain period of time even after the boundary is crossed, and when the set delay release rotational speed is reached, the set Since the system switches to lean air-fuel ratio operation even within the delay time, a simple control system can switch the air-fuel ratio appropriately even during sudden acceleration, and the flow rate can be maintained without impairing fuel economy or drivability. In addition, by setting the stoichiometric air-fuel ratio operating range small, it is possible to improve fuel@adjacency while ensuring good acceleration performance.

[Brief explanation of drawings]

FIG. 1 is a layout diagram of an embodiment of the present invention, and FIG. 2 is a control map diagram. 11...Engine, 14...Correction fuel passage, 15...Control outlet valve, 16...I
III control unit...Opening sensor, 19
......Pressure sensor, 20...Rotation speed sensor? 122...Oxygen ce/su. Figure 1

Claims (1)

[Scope of Claims] The normal operating range of the engine is divided into a stoichiometric air-fuel ratio operating range below a certain rotational speed and a lean air-fuel ratio operating range above a certain rotating speed, and when accelerating across the two operating ranges, In order to delay air-fuel ratio switching so that stoichiometric air-fuel ratio operation is performed even after the boundary has been crossed, a delay time and a delay release rotational speed are set, and the delay release rotational speed is reached within the delay time depending on the degree of acceleration. An engine air-fuel ratio control method characterized by switching to lean air-fuel ratio operation when this occurs.