JPS608455A - Method of controlling air-fuel ratio in supercharged internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent an air-fuel ratio from becoming lean, by reducing air bleed upon acceleration in a supercharged engine provided with a three-way catalytic feedback controlled carburetor. CONSTITUTION:In the case that a supercharger is mounted to an engine for controlling an air bleed 16 of a carburetor 10 by means of a valve 18 according to an output from an exhaust gas sensor 19 upstream of a three-way catalyst 13, it is difficult to responsively supply much fuel as soon as intake air amount is increased upon acceleration. Accordingly, an acceleration condition is detected by a throttle sensor 21 with a normal feedback control stopped, and air bleed is reduced or stopped to enrich an air-fuel ratio thereby to prevent the same from becoming lean.

Description

[Detailed description of the invention] The present invention is a supercharger driven by exhaust gas.

In other words, an internal combustion engine 9 equipped with a supercharger such as an exhaust turbo supercharger
．． This invention relates to a method of controlling the air-fuel ratio of the intake air-fuel mixture.

No. 7 in the exhaust gas is used to purify the exhaust gas of an internal combustion engine.
An exhaust gas purification device is used that includes a three-way catalyst that purifies the kings of C%Co and HC at the same time. When purifying exhaust gas using this three-way catalyst, it is necessary to adjust the air-fuel ratio to the stoichiometric air-fuel ratio in order to increase the purification rate.

Therefore, JP-A-52-1245 as a prior art document
No. 41 discloses that an exhaust sensor such as 02 is installed in the exhaust system, and the air-fuel ratio is adjusted to stoichiometric by increasing or decreasing the amount of air supplied to the air bleed in the main nozzle of the carburetor according to the detection signal of the exhaust sensor. It is proposed that feedback control be applied to the fuel ratio.

Furthermore, recently, the exhaust purification device using the three-way catalyst and feedback control of the air-fuel ratio have been applied to internal combustion engines equipped with an exhaust turbo supercharger.

However, in an internal combustion engine equipped with a supercharger such as an exhaust turbo supercharger, the amount of intake air suddenly increases due to a sudden increase in supercharging pressure during acceleration, but it takes time for the amount of fuel supplied to the carburetor to increase. Because of the delay, in the feedback control of the air-fuel ratio, the air-fuel ratio of the intake air-fuel mixture to the engine tends to temporarily become leaner than the stoichiometric air-fuel ratio, and not only does the acceleration output decrease by this amount, but also the exhaust gas There is a tendency for the purification rate to decrease as well, for example, as shown in Japanese Patent Application Laid-open No. 57-14602 and Japanese Patent Publication No. 57-157017, the boost pressure is made higher than the normally set boost pressure during acceleration. In some cases, it was noticeable.

In a supercharged internal combustion engine equipped with an air-fuel ratio feedback control system, when the supercharging pressure increases, such as during acceleration, the present invention discontinues the feedback control by the exhaust sensor and stops the supply of air to the air bleed. By reducing or cutting the air-fuel ratio, the air-fuel ratio is prevented from becoming lean.

The drawings of an embodiment in which the present invention is applied to an exhaust turbocharged internal combustion engine will be explained below.
are intake manifold (2) and exhaust manifold (3)
a multi-cylinder internal combustion engine having (4) an exhaust turbine (5);
and a blower-compressor (6) are shown, and the discharge side of the blower-compressor (6) in the exhaust turbo-supercharger (4) is connected to the intake manifold (2). The supercharging passage (7) is provided with a surge tank (8) for eliminating pulsation and a carburetor 00 with a throttle valve (9) with the surge tank (8) on the upstream side, and a blower-compressor (6). An air cleaner 0υ is connected to the suction side of the exhaust turbine (5) in the exhaust turbocharger (4).
On the inlet side of the exhaust pipe, the exhaust makohold (3) is connected via the exhaust passage; 0→ are connected to each other.

An air supply passage 071 from the surge tank (8) is connected to the air bleed 00 of the main nozzle ON in the carburetor 00, and an actuator 08) for controlling the amount of supplied air is connected to the air supply passage α. On the other hand, the exhaust pipe 0 is provided with 02.0% in the exhaust gas. CO, CO2, H
An exhaust sensor 01 is provided to detect C or NOx concentration.

(B) is a control circuit that receives a signal from the exhaust sensor 00, and this control circuit (1) compares the output of the exhaust sensor (IG) with a control target value, and controls the actuator according to the output of the exhaust sensor (IG). 08). For example, if the exhaust sensor 0 is to detect the 02 concentration,
When the detected 02 concentration is the stoichiometric air-fuel ratio,
2 concentration, the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, so actuator 08) air bleed O.
Reduce the amount of air to e - and also detect 0 with the exhaust sensor.
When the 2 concentration is opposite to the above, the air-fuel ratio is richer than the stoichiometric air-fuel ratio, so actuator 08) increases the amount of air to the air bleed 0Q so that the air-fuel ratio becomes approximately the stoichiometric air-fuel ratio. It is designed to perform feedback control.

The control circuit (A) inputs a signal from the throttle opening sensor 01) for the throttle valve (9) of the carburetor 00, and controls the actuator 08 during acceleration by rapidly opening the throttle valve (9). ) to exhaust sensor 0
9), it is designed to close for an appropriate time regardless of the signal from 9).

Further, a signal from a supercharging pressure sensor (A) in a surge tank (8) or the like is input to the control circuit (A). An exhaust turbine (
The exhaust bypass (to) provided for 5) is equipped with a waste gate valve (c) that is opened and closed by a drive means (c) - the drive means (c) is connected to the control circuit (a). death,
When the boost pressure reaches the normally set boost pressure (for example, about 350 mmHg), the wastegate valve (c) is opened by its drive means (c) to control the boost pressure to the normally set boost pressure, while the throttle valve (9) is suddenly opened and the wastegate valve (c) is held closed for an appropriate period of time by its driving means (c) during acceleration.

In this configuration, in the operating range where the throttle valve (9) is not opened suddenly, the air-fuel ratio is feedback-controlled to approximately the stoichiometric air-fuel ratio, but when accelerating by opening the throttle valve (9) suddenly, air bleed occurs. The actuator 08) in the air supply passage 07 to (16+) is
Since the amount of air supplied to the air bleed 00 is reduced or cut regardless of the signal from the main nozzle 0, the amount of fuel supplied from the main nozzle 0 increases by this amount.

Therefore, even if the boost pressure increases rapidly when the engine accelerates, or if the boost pressure rises beyond the normally set boost pressure by keeping the wastegate valve (c) closed for an appropriate period of time, the intake air-fuel mixture to the engine The air-fuel ratio never becomes the same.

Although the above embodiment is applied to an exhaust turbocharged internal combustion engine, the present invention is not limited to this, but can be similarly applied to other supercharged internal combustion engines such as a mechanical supercharger. Needless to say, it is possible to reduce or cut the amount of air to the air bleed OQ when the boost pressure increases by connecting the actuator 08) to the boost pressure sensor (A) via the control circuit (A). You may also do this.

In summary, the present invention includes a supercharger and a carburetor in the intake system, and adjusts the air-fuel ratio by increasing or decreasing the air supplied to the air bleed of the carburetor in accordance with the output from the exhaust sensor provided in the exhaust system. A supercharged internal combustion engine that performs feedback control to a predetermined value, characterized in that when supercharging pressure from the supercharger increases, air supplied to the air bleed is reduced or cut. A method for controlling the air-fuel ratio in a supercharged internal combustion engine, in which the air-fuel ratio in a supercharged internal combustion engine is feedback-controlled to a predetermined value according to an exhaust sensor. Since it is possible to prevent the air-fuel ratio to the engine from becoming lean when the air-fuel ratio increases, there is an effect that acceleration performance does not decrease due to a lean air-fuel ratio, and the purification rate of exhaust gas does not decrease.

[Brief explanation of the drawing]

The drawings are diagrams showing embodiments of the invention. (1)...Engine-(4)...Exhaust turbo supercharger-0
0... Carburizer, (7)... Supercharging passage - 〇... Exhaust passage, α0... Air bleed - aη... Air supply passage - (1B+... Actuator for supply air control ,α
[Phase]...Exhaust sensor, (A)...Control circuit, (
b)...Supercharging pressure sensor.

Claims (1)

[Claims] (1) The intake system is equipped with a supercharger and a carburetor, and the air supplied to the air bleed of the carburetor is increased or decreased to a predetermined value according to the output from the exhaust sensor installed in the exhaust system. A supercharged internal combustion engine that performs feedback control of the supercharged internal combustion engine, characterized in that when supercharging pressure from the supercharger increases, air supplied to the air bleed is reduced or cut. A method for controlling the air-fuel ratio in an internal combustion engine.