JPS61201837A - Air-fuel ratio control device for engine - Google Patents

Abstract

PURPOSE:To prevent abnormal increase of the temperature of exhaust gas and to improve acceleration, by controlling an air-fuel ratio so that it is brought to a value closer to the lean side than an air-fuel ratio in a high load range and an output is controlled to the vicinity of a maximum for a specified time during acceleration. CONSTITUTION:By means of signals from an airflow meter 6, a throttle opening sensor 11, and an 0 sensor 9, a control unit 14 outputs a signal to a fuel injection valve 8 and an ignition plug 12 and controls an quantity of fuel injected and an ignition time. When the control unit 14 decides that an engine is during acceleration, a fuel correction value of a maximum output is read, and an air-fuel ratio is controlled so that it is adjusted to a value closer to the lean side than an air-fuel ratio in a high load range and an output is controlled to the vicinity of a maximum output for a specified time in which the temperature of exhaust gas is below an allowable temperature. This preents abnormal increase of an exhaust gas temperature and improves acceleration.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine air-fuel ratio control device that controls the air-fuel ratio in a high load range to be richer than the air-fuel ratio in a light load range.

(Prior art) In general, in an engine air-fuel ratio control device, as shown in Figure 5, the output is maximum at a slightly lean side of the stoichiometric air-fuel ratio R. There is a demand to control the air-fuel ratio to around that range, but if it is controlled around that range, the exhaust gas temperature will rise abnormally and exceed the allowable temperature (approximately 950°C), causing problems in terms of reliability. Therefore, in a high load range, it is necessary to control the air-fuel ratio to be richer than the constant air-fuel ratio R2 so that the exhaust gas temperature is below the allowable temperature. In reality, in consideration of engine manufacturing errors, etc., a certain ratio (7
At present, the air-fuel ratio is controlled so that it is richer than the set air-fuel ratio R3, which is richer by about 10%.

Therefore, when accelerating to a high load range, only a considerably smaller output than originally obtained is obtained, resulting in poor acceleration performance.

By the way, Japanese Patent Publication No. 54-27491 discloses that the amount of fuel is increased or decreased depending on the acceleration state.

iv of fuel at the time of acceleration as the engine speed increases
An electric fuel injection device for internal combustion engines that can increase the amount of fuel necessary for acceleration and prevent unnecessary increases in fuel by reducing the amount of fuel, thereby purifying exhaust gas and saving fuel. Although described, the air-fuel ratio is not taken into account and the above problem cannot be addressed.

(Objective of the Invention) The present invention provides the following advantages:
The object of the present invention is to provide an air-fuel ratio control device for an engine that has excellent acceleration performance.

(Structure of the Invention) The present invention relates to an air-fuel ratio control device for an engine that controls the air-fuel ratio in a high load range to be richer than the air-fuel ratio in a light load range.

In order to achieve the above object, the present invention provides a load detection means for detecting the load of an engine, an acceleration detection means for receiving the output of the load detection means and detecting acceleration to a high load range, and the acceleration detection means. and an air-fuel ratio correction means for correcting the air-fuel ratio to be leaner than the air-fuel ratio in the high load range and near the maximum output for a certain period of time based on the output of the exhaust gas temperature. Acceleration is achieved by controlling the air-fuel ratio to maximize output for a certain period of time not exceeding .

(Example) Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1 showing the overall configuration, l is an engine, and an intake passage 4 and an exhaust passage 5 are connected to intake and exhaust ports la and lb which are opened and closed by intake and exhaust valves 2 and 3.

In the intake passage 4, an air flow meter 6, a throttle valve 7, and a fuel injection valve 8 are arranged in order from the upstream side.
In the exhaust passage 5, an O2 sensor 9 and a catalyst device IO are arranged in this order from the upstream side.

11 is a throttle opening sensor that detects the opening of the throttle valve 7, 12 is a spark plug, and 13 is an engine rotation speed sensor.

14 is a control unit, air flow meter 6,
Signals from the throttle opening sensor 11 and O2 sensor 9 are used to output signals to the fuel injection valve 8 and spark plug 12 to control the fuel injection amount and ignition timing.

Specifically, the control unit 14 is configured as shown in FIG. 2. That is, an intake air amount calculation circuit 21 receives the output of the air flow meter (A, F, M,) 6 and calculates the intake air amount, and receives the output of the circuit 21 and calculates the basic fuel injection pulse. A basic injection pulse calculation circuit 22 is provided. Further, an acceleration detection circuit 23 receives the outputs of the air flow meter 6 and the throttle opening sensor 11 and detects whether or not the throttle valve 7 is fully open and is accelerating. The present invention includes a timer control circuit 24 that counts a certain period of time during which the temperature does not exceed the allowable temperature, and an output best fuel correction calculation circuit 25 that receives the output of the circuit 24 and calculates the correction amount of the fuel that provides the best output. Furthermore, an open operation region detection circuit 26 receives the outputs of the throttle opening sensor 11 and the engine rotation speed sensor 13 and detects whether or not there is a feedback (F/B) open operation region (see FIG. 4); A normal fuel correction amount calculation circuit 27 is provided which receives the outputs of the circuit 26 and the timer control circuit 24 and calculates the correction amount of normal fuel. It is equipped with an F/B operating range detection circuit 28 that detects whether or not it is in the operating range, and an F/B correction amount calculation circuit 29 that receives the outputs of the circuit 28 and the 02 sensor 9 and calculates a correction amount for feedback control. . Thus, the final fuel injection pulse is calculated by receiving the outputs of the basic injection pulse calculation circuit 22, the output best fuel correction calculation circuit 251, the normal fuel correction amount calculation circuit 27, and the F/B correction amount calculation circuit 29 to calculate the final fuel injection pulse. circuit 3
0, the final fuel injection pulse is output to the fuel injection valve 8.Next, the flow of processing of the control unit 14 will be explained with reference to FIG.

First, when you start, step S! The engine speed is read from the engine speed sensor 13 in step S2.
The throttle opening is read from the throttle opening sensor 11, and in step S3, it is determined whether the engine is in the feedback (F/B) operation region based on the engine speed and the throttle opening (see FIG. 4).

If YES, it is the F/B operation area, so it is detected by the F/B operation area detection circuit 28, and o is set in step S4.
In step S5, the F/B correction amount calculation circuit 29 calculates the F/B correction amount, and controls the air-fuel ratio to the target air-fuel ratio.
Move to G.

On the other hand, if NO, the F/B open operation region is detected, so the open operation region detection circuit 26 detects the F/B open operation region. Then, in step S8, it is determined whether the throttle valve 7 is in a fully open state, that is, an opening state of 90% or more. Y
In the case of ES, since it is a high load area, the output value V s of the air flow meter 6 (A, F, M,) is determined in step S7.
1, and in step Sa, read the output value Vs2 of the air flow meter 6 before Looms, and set the surface output values Vsl, V
Step S9) to calculate the difference A of s2, Step 81
G updates the output value V s 2 to Vsl. after that,
In step S11, a preset acceleration detection comparison level value B is read, and in step St2, it is determined whether the above-mentioned difference A is larger than the acceleration detection comparison level value B, and thereby it is determined whether or not it is during acceleration. Determine. Note that the determination of the throttle opening degree and acceleration is performed by the acceleration detection circuit 23.

If the determination in step S12 is YES, it means that the acceleration is being performed, so in step S13, it is determined whether A>B and this is the first time. If YES, the counter N is reset to the initial value a. Step 514) reads the counter N in step S15, while if NO, immediately reads the counter N in step S15, then sets the counter N to N-1 (step 5xs), and then reads L in step SIT. Determine whether the counter N is 0 or not. Note that the counting by the counter N is performed by the timer control circuit 24.

If YES in step S17, acceleration has ended, so in step Sla, the fuel correction value calculated by the 1 normal fuel correction amount calculation circuit 27 is read from the point of view of exhaust gas temperature countermeasures, and the fuel correction value calculated in the F/B operation area is read. The air-fuel ratio is controlled to be richer than the set air-fuel ratio in the open operating range where the exhaust gas temperature does not exceed the allowable temperature and the target air-fuel ratio is richer than the target air-fuel ratio, but if the answer is No, the output is set to the best since it is under acceleration. Output calculated by the fuel correction amount calculation circuit 25.

The fuel correction value is read in, and the air-fuel ratio is controlled to be leaner than the set air-fuel ratio for a certain period of time during which the exhaust gas temperature does not exceed the allowable temperature, thereby maximizing the output and achieving acceleration.

After that, in step 32G, the basic injection pulse calculation circuit 22
Calculate the basic injection pulse width corresponding to the basic injection amount,
In step S21, the final injection pulse calculation circuit 30 calculates the final injection pulse width, and in step S22, the fuel injection valve 8
The final injection pulse is output.

In addition, in the case of No in step S6+312.

Since not much output is required, the process moves to step SlB.

(Effects of the Invention) As described above, the present invention controls the air-fuel ratio so that the output is maximized for a certain period of time during acceleration, so the acceleration performance can be improved without abnormally increasing the exhaust gas temperature. You can improve your performance.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of an engine air-fuel ratio control device that is an embodiment of the present invention, Fig. 2 is a configuration diagram of a control unit, Fig. 3 is a flowchart showing the flow of processing of the control unit, and Fig. 4 is an explanatory diagram of the F/B operating region and the F/B open operating region, and FIG. 5 is an explanatory diagram showing the relationship between the air-fuel ratio, exhaust gas temperature, and output. l... Engine, 6... Air flow meter, 14... Control unit, 23...
... Acceleration detection circuit, 25 ... Output best fuel correction calculation circuit.

Claims (1)

[Claims] (1) In an engine in which the air-fuel ratio is controlled to be richer than the air-fuel ratio in the light load range in a high load range, there is a load detection means for detecting the engine load, and a load detection means for detecting the load in the high load range. and an air-fuel ratio correcting means that receives the output of the acceleration detecting means and corrects the air-fuel ratio to be leaner than the air-fuel ratio in the high load range for a certain period of time and near the maximum output. An engine air-fuel ratio control device characterized by: