JPS58174142A - Feedback controller of air fuel ratio in internal-combustion engine - Google Patents

Abstract

PURPOSE:To optimize purifying efficiency of an exhaust gas purifier, by setting a target value to a prescribed frequency and amplitude generated with the theoretical air fuel ratio as the center when air fuel ratio is feedback controlled to the target value in accordance with an exhaust gas component. CONSTITUTION:A detecting value of an air fuel ratio detector 2A set to the upstream of an exhaust gas purifier 5 in an exhaust passage 6 of an internal- combustion engine 1 is input to a fuel device 3A, and the injection timing of a fuel control valve 4 is feedback controlled by the deviation between said detecting value and a target value. A fuel controller 3A is constituted by a microcomputer, when the target value of air fuel ratio is set in the vicinity of a theoretical air fuel ratio, the target value is programmably controlled to a ripple having prescribed amplitude L and prescribed period T.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio feedback control device for an internal combustion engine that controls the air-fuel ratio of an air-fuel mixture to achieve optimal purification conditions for an exhaust gas purification device.

Conventionally, in order to keep the exhaust gas emitted from an internal combustion engine clean, all components of the exhaust gas are detected and feedback control is performed based on the amount of fuel supplied, and the air-fuel ratio is controlled to almost reach the stoichiometric air-fuel ratio. A method was used to optimize the purification efficiency of an exhaust gas purification device using a catalyst.

The conventional example will be explained below along with all the drawings.

Figure 1 shows the technique described above. This is a conventional example using fuel injection.

In Fig. 1, 1 is an internal combustion engine, 2 is an air-fuel ratio detector, and 3 is an internal combustion engine.
4 is a fuel control device, 4 is a fuel control valve, and 5 is an exhaust gas purification device. 6 is an exhaust pipe.

The operation of the conventional device will be explained based on the above configuration.

As shown in FIG. 2, the purifying device 5 uses a well-known method to eliminate HC and CO only near the stoichiometric air-fuel ratio (approximately 14.7).

Optimum tl according to the characteristics of this engineered purification device 5, which provides optimal purification efficiency for the three harmful components of NOx! ,
In order to obtain the fuel ratio, the output of the air-fuel ratio detector 2 decreases at the stoichiometric air-fuel ratio as shown in FIG. As a result, the fuel control device 13 determines the % nitrous fuel ratio, that is, the internal combustion engine 1
As shown in FIG. 4, the amount of fuel supplied to the air-fuel ratio is responsive to the output pulse of the air-fuel ratio detector 2 to produce a ripple pattern with such a period and amplitude that the average value of the air-fuel ratio is approximately the stoichiometric air-fuel ratio. In the conventional air-fuel ratio feedback control device as described above, which drives and controls the fuel control valve 4' to Feedback control to air-fuel ratios other than those in the vicinity was impossible, and oven loop control was the only option. Therefore, when controlling an arbitrary air-fuel ratio as a target value using an open-loop control method, the fuel control device 3° fuel control valve 4. In addition, the intake nitrogen cover to the internal combustion engine 1.

It is affected by the difference in accuracy of the sensor that detects various operating meters such as the temperature of the nuclear engine 1, and as a result, variations in the Vc nitrous fuel ratio are unavoidable.

Conventionally, in order to eliminate such drawbacks, a fuel-fuel ratio detector 2A2 whose output changes continuously with respect to the air-fuel ratio as shown in FIG. 5 is used to return to an arbitrarily set air-fuel ratio. It has been experimentally confirmed that the purification efficiency of the purification device 5 decreases if the air-fuel ratio is maintained at a constant value over time when the fuel ratio is near the fuel ratio for which control is proposed. The reason for this is that the periodic presence of oxygen components in the exhaust gas causes HC, CO,
It is believed that this is to promote catalytic purification of NOx. This strange phenomenon, as shown in FIG. 6, means that when the amplitude of the fuel ratio becomes too small, the purification rate decreases. On the other hand, the amplitude of the air-fuel ratio fluctuation is too large and the second
Outside the shaded area in the figure, the purification rate also decreases.

This invention was made by focusing on the above points, and uses an air-fuel ratio detector whose output changes continuously with respect to the air-fuel ratio, and makes it possible to create a ripple in the air-fuel ratio near the stoichiometric air-fuel ratio. '&
K! 1f) Z for the purpose of providing an air-fuel ratio feedback control device 11111 for an internal combustion engine that can maximize the purification efficiency of a purification device that purifies exhaust gas.
'Ruru.

VC% An embodiment of the fuel injection system of the present invention will be described below with reference to FIG. Note that the same components as in FIG. 1 of the conventional example are indicated by the same reference numerals, and detailed explanation thereof will be omitted.

In FIG. 7, the two detectors are air-fuel ratio detectors whose output characteristics vary continuously with respect to the air-fuel ratio, as shown in FIG. Further, 3A is a fuel control device which is composed of a microcomputer, and when the set value of the air-fuel ratio is near the stoichiometric air-fuel ratio, a ripple having a predetermined amplitude and a predetermined period T-i is generated as shown in FIG. The process is completely program controlled.

Based on the above configuration, the operation of the embodiment of the present invention will be explained. The period T of the air-fuel ratio is set to a value corresponding to the responsiveness of the internal combustion engine 1, which is determined according to the rotational speed and load condition of the internal combustion engine 1.

First, the air-fuel ratio detector 2, which detects the air-fuel ratio of the exhaust pipe 6, continuously changes its output with respect to the air-fuel ratio, as shown in FIG. In response to such an output, the fuel control device 3 controls the fuel control valve 4 so as to cause an air-fuel ratio ripple in the vicinity of the stoichiometric air-fuel ratio as shown in FIG. As a result, so that the purification efficiency of the purification device 5 always reaches its maximum value,
The average value of the actual air-fuel ratio can be set and controlled to approximately the value of the stoichiometric air-fuel ratio. In this embodiment, the above-mentioned air-fuel ratio feedback control device has been fully described when applied to a fuel injection system, but the present invention can be applied to any type of fuel injection system as long as the fuel supply to an internal combustion engine is carried out by electronic control means. This can also be applied to control devices.

In addition to the intermittent injection method and continuous injection method of fuel injection, the present invention can also be applied to air-fuel ratio feedback control such as a fuel control device using a carburetor.

As explained above, the present invention is designed to perform feedback control of the Vc air-fuel ratio that maximizes the efficiency of the exhaust gas purification device, and is excellent in maintaining exhaust gas purity without reducing the engine efficiency of the internal combustion engine. Furthermore, they have a stable friendship effect.

[Brief explanation of the drawing]

Figure 1 is a block configuration diagram of a conventional desired fuel ratio feedback control device for an internal combustion engine, Figure 2 is a characteristic diagram of a purification device, Figure 3 is a characteristic diagram of the air-fuel ratio detector shown in Figure 1, and Figure 4 is t-th operation waveform diagram explained in the conventional control method, FIG. 5 is a characteristic diagram of the embodiment of the present invention and other air-fuel ratio detectors of the conventional example, and FIG. 6 is a characteristic diagram of the purification device shown in FIG. 7 is a block diagram of the air-fuel ratio feedback control device of the present invention, and FIG. 8 is an operational waveform diagram for explaining a control method in an embodiment of the present invention. 1... Internal combustion engine %2, 2A... Air-fuel ratio detector, 3° 3 people... Fuel control device, 4... Fuel control valve, 5...
・Exhaust gas purification device, 6...exhaust pipe. In the drawings, the same reference numerals indicate the same or corresponding parts. Agent Shin Kuzuno - Figure 1 Figure 2? A/F on the ground Figure 3 qP ratio A/F Figure 4 Figure 5 Air-heavy AJF Figure 6 Section 7 Figure 8

Claims (1)

[Scope of Claims] (An air-fuel ratio detector that generates an output that is substantially proportional to the air-fuel ratio based on exhaust gas components; a fuel control device that performs feedback control via the fuel supply amount total fuel control 5f11-;
In an air-fuel ratio feedback control device for a constant internal combustion engine, which comprises an exhaust gas purification device. A microcomputer is installed in the fuel control device, and the target value of the air-fuel ratio is set to be a lip having a frequency and amplitude of 90 degrees around the stoichiometric air-fuel ratio, thereby achieving optimal purification of the air-fuel ratio feedback control device. To control the process to meet the conditions.
Features: Air-fuel ratio feedback control device for internal combustion engines.