JPS62178738A - Air-fuel ratio control method for engine - Google Patents

Abstract

PURPOSE:To improve the economical efficiency of fuel without spoiling operating properties, by a method wherein an air-fuel ratio switching delay time after transfer of a low speed operation region to a high speed operation region is set according to a rotation speed during shifting to the high speed side. CONSTITUTION:In a control unit 16, in a high speed operation region where a suction negative pressure is below a specified value or a rotation speed exceeds a specified value, feedback control based on an electric signal from an oxygen sensor 22 is released to operate a control valve 15 by means of a low duty value or hold the control valve in a closed state. With this constitution, fuel in a fundamental feed amount weighed mainly by a jet 3 is fed to a mixer 5 to feed air-fuel mixture, having a lean air-fuel ratio, to an engine 11 to improve the economical efficiency of fuel. In which case, a delay time, by which acceleration operation is effected in a theoretical air-fuel ratio even after an engine is transferred from a low speed operation region to a high speed operation region, is increased when a rotation speed, shifted to the high speed side in the low speed operation region, is decreased, and is decreased when the rotation speed is increased.

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 relates to a method for controlling the air-fuel ratio of an engine. ! It can be used to control the air-fuel ratio of engines used as power sources for Ig, work vehicles, industrial machinery, etc.

The technology that detects the operating state of the engine and controls the air-fuel ratio using a feedback method is widely known. The air-fuel ratio is adjusted to a predetermined air-fuel ratio by making corrections corresponding to engine operating conditions in consideration of exhaust gas countermeasures, etc.The air-fuel ratio is determined by adjusting whether there is fuel or low air (either of which is determined by a pulse waveform drive signal). It is controlled by the driven KakuJ Misaki valve, and the drive signal is normally output from an electronic control unit that receives the engine's operating record and calculates optimal conditions based on that information.

Here, excluding the high output range (below the rotational speed or above the suction negative pressure in the normal operating range, the engine is operated at a low-speed, air-to-air ratio to reduce emissions, but above the rotational speed or below the suction negative pressure) If you create a control system that operates at a lean air-fuel ratio and measures fuel economy as a king.

The boundary between the two operating regions is one foot, and as soon as this boundary is crossed, air-to-silver ratio correction is performed. Therefore, it is possible to improve fuel economy by setting the low-speed operating range based on the stoichiometric air-fuel ratio small.

There is a drawback that when accelerating across two operating ranges, the engine immediately shifts to a low-speed operating range due to a lean air-to-air ratio, impairing acceleration performance. For this reason, it has been considered to delay the air-fuel ratio switching so that the stoichiometric air-fuel ratio is maintained for the time that continues after the operating range is exceeded, but setting a fixed delay time is not possible because it depends on the acceleration situation. In some cases, fuel economy and drivability may be compromised.

The present invention solves the above problems and 7i.

It is an object of the present invention to provide an air-fuel ratio control method that can measure fuel economy without impairing drivability by appropriately changing the delay time depending on the degree of acceleration at high speeds.

A method for controlling the air-fuel ratio of an engine according to the present invention is as follows.

The engine's normal operating range is divided into a low-speed operating range based on the stoichiometric air-fuel ratio and a high-speed operating range based on the lean air-fuel ratio, and the stoichiometric air-fuel ratio is maintained even after the boundary is crossed when transitioning from the low-speed operating range to the high-speed operating range. In delaying the air-fuel ratio switching during operation, when the transmission position is shifted to the high speed side, the delay time is set according to the rotational speed at the time of this shift.

Example Embodiments of the present invention will be described based on the drawings.

Fig. 1 shows the case where the present invention is implemented in an engine using gaseous fuel such as LPG. 3, enters the annular chamber 7 formed along the venturi 6 of the mixer 5, is sucked out from the slit-shaped main nozzle 8 into the intake passage 9, mixes with air, and is sent to the engine 11 from the intake manifold lO. supplied to The exhaust gas is purified by the three-way catalytic converter 13 of the exhaust gas W12 and released into the atmosphere.

A correction feed 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. This passage 14 is provided with an electromagnetically driven control valve 15. According to the duty value of the pulse waveform drive signal sent from the control unit 16, the manual control valve 15 is opened and closed to control the corrected fuel so that the required air-fuel ratio is achieved.

Here, the position of the throttle valve 17 installed in the mixer 5 is 18. Pressure case/slot 19 installed in the intake manifold lO
．． Engine 11 rotational speed sensor 20 and temperature sensor 21. Acid X sensor 22 installed in the exhaust pipe 12
．． A position switch 23 that emits an electrical signal depending on the shift position of the transmission. In addition, intake air temperature, ignition switch, brake solenoid, etc. (not shown)
Sensors for detecting the operating conditions of the motors are provided as necessary, and electrical signals from these sensors are sent to the control unit 16, which calculates optimal conditions based on this information. A drive signal is generated to open and close the control valve 15 at a predetermined duty ratio, or the control valve 15 is kept in the closed or open state, and the duty value of the I drive signal is changed.

In addition, as shown in the control map in Fig. 2, the engine 110 rotational speed is constant at 1 [N
divided into a sluggish operation region (B) where the rotational speed is below a certain value Pa and the suction negative pressure is above a certain value Pa, Low speed 1
The transition area (A) is a mixture with a stoichiometric air-fuel ratio of 14. The high speed operation region (B) is set to operate with a mixture having a lean air-fuel ratio, and the high output operation region (q is set to be operated with a mixture having an output air-fuel ratio).

In this embodiment with such a configuration, during idle link, it is detected that the throttle valve 17 is at the idle position by the electric signal from the opening sensor 18, so that the air-fuel mixture at the stoichiometric air-fuel ratio or the temperature control valve 21 is detected. When the electric signal detects that the engine temperature is low, the control valve 15 is actuated to supply an air-fuel mixture slightly richer than the air-fuel ratio.

When the idle link ends and the throttle valve 17 opens,
In a low-speed operating region (A) where it is determined that the intake negative pressure of the engine 11 is at least a certain value p, ) or the rotational speed is at least a certain value Pa, based on electrical signals from the pressure sensor 19 and the rotational speed sensor 20, Based on the electrical signal from the sensor 22, the control valve 15 is electrically operated so that the air-fuel mixture at the stoichiometric air-fuel ratio is supplied. For this reason, for example, in a car, by setting the low-speed quadrature range (N) so that feedback control is performed to the stoichiometric air-fuel ratio in the normal city driving speed range, the exhaust purification efficiency by the three-way converter 13 is maximized. You can run on it.

It is determined that the suction negative pressure is constant 1:MPa or less or the rotational speed is constant 1:MPa or higher.In the high-speed operation region (B), the feedback control based on the electric signal from the oxygen sensor 22 is canceled and control 91.5 is activated. The valve is opened and closed at a small duty value or kept in a closed state, and the basic supply amount of fuel, which is mainly measured by the jet 3, is sent to the mixer 5.14 A mixture with a lean air-fuel ratio is supplied to the engine 11, and the fuel is supplied to the engine 11. @Measuring dominance.

Position/? High output operation range (
For example, when it is detected that the opening degree of the throttle valve 17 has reached 60 degrees or more, a mixture with a high concentration output air-fuel ratio is supplied.

The control valve 15 is driven at a large duty value or held at the open position so that the control valve 15 is opened.

Low speed operation 'liI region (When accelerating operation is started in the prisoner, it is assumed that the caro speed straddles the high speed operation region (B) as shown by the arrow (If the transmission position is shifted to the high speed side! curve 4th or 5th speed within N, and this shift is performed at low rotational speed N1 within this area fA), delay time T1 is Longer setting 11. Also, if the delay time T2 is set after high rotational speed N2, set the delay time T2 shorter. Transmission position switch 23
emits an electrical signal that is turned on at high speeds and turned off at other times, and is the same as that generally used for ignition timing control. This position switch 23 is turned on, and l! ! Extension of time I
J] When Tt~T2 is set, the delay time T1 is set from this
Continuous rotation is performed at the stoichiometric air-fuel ratio until T2 has elapsed.

7111 speed 4 rotation is carried out at the stoichiometric air-fuel ratio even after the high-speed operation region (B) is set, and after the delay time T1 to T2 has elapsed, the operation is switched to the 4-speed air-fuel ratio operation. Therefore, when the transmission shifts to high speed, 1
．． ! ! The extension area CD is the delay time T1 when crossing the boundary between the two preset operating areas (A) and (B).
Change the range to be determined by the remaining time of T2. here.

The delay time, which is set by the rotational speed at the time of shifting of the transmission, can be varied linearly according to the rotational speed as shown by the solid line in Figure 3, or it can be changed in a curved or stepwise manner as shown by the broken line in the same figure. and engine performance.

Select appropriate characteristics according to the gear ratio of the transmission, etc.

Note that 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. The injection valve constitutes a control valve.

Effects of the Invention According to the present invention, the normal operating range of the engine is divided into a low-speed operating range based on the stoichiometric air-fuel ratio and a high-speed operating range based on the lean air-fuel ratio, so that emission measures, drivability, and fuel economy can be adjusted according to the operating range. Not only can you measure each, but you can also adjust the degree of acceleration by controlling the speed of the transmission, especially if you want to operate at the stoichiometric air-fuel ratio for a certain period of time when accelerating from a low-speed transfer range to a high-speed range. The system detects the position and sets a delay time according to the rotational speed at the time of shifting when sudden acceleration shifts to the high speed side, so it can quickly achieve lean air-fuel ratio operation in response to the rapid increase in rotational speed during sudden acceleration. It becomes possible to switch. For this reason, a simple control system with 7 stems can control the air-fuel ratio f[tlllgl during acceleration without impairing fuel economy or drivability.

Furthermore, it is possible to increase fuel economy while ensuring good acceleration performance by setting a small low-speed operating region based on the stoichiometric air-fuel ratio.

[Brief explanation of drawings]

FIG. 1 is a layout diagram of an embodiment of the present invention, FIG. 2 is a control map diagram, and FIG. 3 is a diagram explaining delay time setting. 11...Engine, 14...Correction fuel passage, 15...Control rabbit, 16...ii
i control unit, 18...opening sensor, 19.
...Pressure sensor, 20 ... Rotation speed sensor, 22 ... Oxygen sensor, 23 ... Position switch.

Claims (2)

[Claims] (1) The engine's normal operating range is divided into a low-speed operating range based on the stoichiometric air-fuel ratio and a high-speed operating range based on the lean air-fuel ratio, and when the engine transitions from the low-speed operating range to the high-speed operating range, even after the boundary is crossed, A method for controlling an air-fuel ratio of an engine, characterized in that, in delaying air-fuel ratio switching to perform air-fuel ratio operation, a delay time is set according to the rotational speed at the time of shifting when the transmission position is shifted to a high speed side. (2) The air-fuel ratio control method according to claim (1), wherein the delay time is set long when the rotational speed at the time of shifting is low, and the delay time is gradually set short as the rotational speed increases.