JPS60240839A - Control device of air-fuel ratio in engine - Google Patents

Abstract

PURPOSE:To eliminate the influence of an increase in a wall surface flow of fuel caused by deterioration of an engine and continually maintain a good combustion condition of the engine over a long period, by correcting a fuel supply characteristic so that air-fuel ratio may be controlled to a rich state in accordance with the deterioration of the engine. CONSTITUTION:A control unit 18 controls an injector 12 by receiving an output signal from a speed sensor 13, opening sensor 14 of a throttle valve 11, intake air temperature sensor 15 and a cooling water temperature sensor 16 in an engine 1. And the control unit 18 is constituted of a fuel setting means 19 setting a supply quantity of fuel in every operational range of the engine 1 and a fuel control means 20 supplying the fuel in accordance with the operational range. The above control unit additionally provides a negative pressure sensor 21 as a means detecting deterioration of the engine 1. And the control unit 18 additionally provides a deterioration correcting control means 22 which controls the fuel control means 20 to be corrected so as to change air-fuel ratio into a rich state in accordance with the deterioration of the engine 1 by receiving an output signal of the negative pressure sensor 21.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine that controls the air-fuel ratio by supplying a fuel amount set for each operating range to the engine according to the operating state of the engine. The present invention relates to an air-fuel ratio control device, and particularly to a measure for correcting an air-fuel ratio in response to engine deterioration.

(Prior art) Conventionally, as an air-fuel ratio control device for this type of engine,
For example, as shown in Japanese Utility Model Publication No. 56-613,
Detecting the operating state of the engine based on the amount of intake air and engine speed, comparing this engine operating state with a preset operating range, and supplying the fuel amount set in the operating range bIi,@ to the engine. It is known that the air-fuel ratio of the engine is controlled by the following.

However, in the above-mentioned conventional system, the fuel supply amount is set constant for each engine operating range, so as the engine deteriorates, its intake capacity becomes weaker, and fuel ends up on the passage wall in the middle of the intake passage. If this occurs, even if fuel is being supplied normally, the air-fuel ratio will become over-lean due to fuel shortage until the wall flow is taken into the engine, leading to engine stalling. .

If you anticipate this engine deterioration and set the fuel supply characteristics so that the air-fuel ratio is a little rich, when the engine is new and the deterioration is small, it will become overrich, and the ignition plug will get wet and the ignition will be impaired. Problems such as a decrease in performance occur.

(Problems to be Solved by the Invention) The present invention has been made in view of the above points, and its purpose is to adjust the fuel supply characteristics to enrich the air-fuel ratio in response to engine deterioration. By correcting
The purpose of the present invention is to eliminate the influence of an increase in fuel wall flow due to engine deterioration and to achieve a consistently good engine combustion state over a long period of time.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention is as shown in FIG. Output signals 1 from the fuel setting means 19 for setting the fuel supply amount for each operating region and the operating state detecting means 17; 1, the air-fuel ratio control device for an engine is equipped with a fuel control means 20 for supplying fuel in accordance with the operating range determined by the fuel setting means 19. A deterioration correction control means 22 is provided which receives an output signal from the deterioration detection means 21 and corrects and controls the fuel control means 20 so as to enrich the air-fuel ratio in accordance with the deterioration of the engine.

(Function) Accordingly, in the present invention, the operating state of the engine detected by the operating state detection means 17 is compared with a preset operating range, and fuel is supplied based on the operating range, and if the engine has deteriorated, Deterioration detection means 2
1 detects the degree of deterioration, and depending on the deterioration of the engine, increases the amount of fuel supplied to the engine by the increase in fuel wall flow due to engine deterioration and enriches the air-fuel ratio, thereby reducing engine deterioration. This prevents the air-fuel ratio from becoming over-lean due to the influence of the wall flow of fuel.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings from FIG. 2 onwards.

FIG. 2 shows the overall configuration of an embodiment of the present invention, where 1 is an engine equipped with a combustion chamber 5 surrounded by a cylinder 2, a cylinder head 3, and a piston 4, and 6 is an engine that supplies intake air to the combustion chamber 5. 7 is an exhaust passage for discharging exhaust gas from the combustion chamber 5, 8 is an intake valve, and 9 is an exhaust valve. an air flow meter 10 that detects the amount of intake air taken into the combustion chamber 5 of the engine 1; a throttle valve 11 that controls the amount of intake air that is supplied to the combustion chamber 5; and an injector 12 that injects fuel into the engine 1. is installed.

To explain the control system for controlling the operation of the injector 12, 13 is a rotation sensor that detects the rotation speed of the engine 1, and 14 is the throttle valve 1.
1 is a throttle opening sensor that detects the load condition of the engine 1 based on the opening; 15 is an intake air amount sensor that detects the temperature of intake air taken into the engine 1; and 16 is a water temperature sensor that detects the temperature of the engine cooling water. The above-mentioned sensors 13 to 16 constitute an operating state detection means 17 that detects the actual operating state of the engine 1.

In addition, 18 receives output signals from each of the sensors 13 to 16 (operating state detection means 17) and operates the injector 12.
A control unit for controlling the operation of the engine 1], which controls the operation of the engine 1 in each operating range as shown in FIG. One fuel setting means sets the amount of fuel supplied to the engine, and in response to output signals from each of the sensors 13 to 16 (operating state detection means 17), fuel is supplied to the engine according to the operating range determined by the fuel setting means 19. 1
It also constitutes a fuel control means 20 for supplying fuel to the fuel.

That is, the operating range map set by the fuel setting means 19 of the control unit 18 is, for example, as shown in FIG. A low rotation high load region Z1 in which the engine performs idling operation, an idle region Z2 in which the engine performs idling operation, a high rotation high load region Z3 in which the engine performs high rotation high load operation, and the oxygen concentration in the exhaust gas measured by the O2 sensor 23, that is, the engine Feedback region tli that performs feedback control of fuel supply amount based on the air-fuel ratio of 1
Z a and light load area Z where the engine is operated under light load.
5, a fuel cut region Z6 in which the fuel supply is cut when the engine decelerates, and an idle return increase region Z7 in which the fuel is returned and increased during transition from the fuel cut region Z6 to the idle region Z2. has been done.

Further, as a feature of the present invention, a negative pressure sensor 21 is disposed in the intake passage 6 to detect the intake negative pressure at a position directly downstream of the throttle valve 11 during engine idling. constitutes a deterioration detection means for detecting deterioration of the .

The control unit 18 also controls the negative pressure sensor 21 (
The fuel control means 2 inputs the output signal of the deterioration detection means) and enriches the air-fuel ratio according to the deterioration of the engine.
It constitutes a deterioration correction control means 22 that performs correction control of 0. The operation of this deterioration correction control means 22 will be explained with reference to the flowchart shown in FIG. Based on the throttle opening signal, it is determined whether the engine operating state is in the idle region 72 or not. If this determination is YES based on the idle region Z2 of the engine operating state, a second step S2 determines whether the engine has warmed up sufficiently, that is, the cooling water temperature detected by the water temperature sensor 16 is, for example, 70°. If the determination is YES because the coolant temperature is 70'C or higher, the process proceeds to a third step S3, and the engine rotation speed detected by the rotation sensor 13 is determined, for example It is determined whether or not the speed has settled down to a range of 600±10 rpm. If this determination is YES because the engine speed is within the above range, a fourth step S4 is performed.
Then, it is determined whether or not the engine is igniting at the initially set regular ignition timing. If this determination is YES due to the normal state of the ignition timing, the intake negative pressure input from the intake negative pressure sensor 21 is measured in the fifth step S5, and the process moves to the sixth step. As shown in FIG. 5, a fuel map in which the cooling water temperature and fuel injection pulse width at engine startup are stored as parameters is corrected in accordance with the degree of engine deterioration indicated by the intake negative pressure. In other words, when the intake negative pressure decreases as the engine deteriorates, by shifting the fuel injection pulse width relative to the cooling water temperature on the map to the increasing side, fuel injection is performed when the engine starts, when the fuel supply tends to be insufficient due to wall flow. Increase the amount compared to when the deterioration is small.

In other words, the air-fuel ratio is enriched to perform correction control to prevent engine stalling caused by an increase in fuel wall flow due to engine deterioration.

On the other hand, if any of the first to fourth steps $1 to S4 is No, that is, the operating state of the engine is not in the idle region Z2, the cooling water temperature is less than 70'C, and the engine rotational speed is If the rotational speed is outside the range of 600±10rl)m, or if the ignition timing of the engine has changed from the normal ignition timing, the routine ends without performing deterioration correction.

Therefore, according to the above embodiment, when the engine becomes old and deteriorates, the degree of deterioration is detected by the negative pressure sensor 21 as a deterioration detection means, and the cooling water temperature in the fuel map is determined according to the degree of deterioration. The fuel injection pulse width at engine startup is corrected to the increasing side to increase the amount of fuel supplied at startup compared to a new engine. Even if the fuel flow increases, the fuel shortage to the engine is compensated for by the increased fuel supply until the wall flow is sucked into the engine, and the air-fuel ratio similar to that of a new engine can be ensured. Startability during deterioration can be improved.

Note that if the engine is new and has not deteriorated, the value of the intake negative pressure detected by the negative pressure sensor 21 will be large. This prevents the spark plug from getting wet due to the supply and does not cause deterioration in engine startability.

In the above embodiment, the amount of fuel supplied to the cooling water temperature at the time of engine startup is corrected in accordance with the deterioration of the engine. The amount of fuel supplied may be corrected, or the amount of fuel increased during warm-up or after startup may be corrected.

(Effects of the Invention) As described above, according to the engine air-fuel ratio control device of the present invention, deterioration of the engine is detected and the air-fuel ratio is corrected to become rich according to the degree of deterioration. )L'Th'
7) Even if the r″・1>′ engine deteriorates, the air-fuel ratio can be properly controlled just like a new engine by compensating for the insufficient fuel supply due to the accompanying increase in fuel wall flow even if the suction capacity is reduced.
! Therefore, good combustion conditions of the engine can be stably maintained over a long period of time.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of the present invention, Figs. 2 to 5 show an embodiment of the present invention, Fig. 2 is a general schematic diagram, and Fig. 3 shows the standard operating range of the engine. Explanatory diagram,
FIG. 4 is a flowchart of the control system, and FIG. 5 is an explanatory diagram of a fuel map storing fuel supply characteristics at engine startup. 1...Engine, 10...Air 70-meter, 1
2... Injector, 13... Rotation sensor, 14.
... Throttle opening sensor, 15... Intake air temperature sensor, 16... Water temperature sensor, 17... Operating state detection means, 18... Control unit, 19... Fuel setting means, 20... -Fuel control means, 21... deterioration detection means,
22...Deterioration correction control means. Fig. 1 Fig. 2 Fig. 3 Artwork〉Jin Kaishin No. 5B-Z! :) 15 (J Water bath (・C) Figure 4

Claims (1)

[Claims] (1) Operating state detection means for detecting the operating state of the engine; fuel setting means for setting the fuel supply amount for each engine operating range; and receiving an output signal from the operating state detection means, the fuel setting means In an air-fuel ratio control device for an engine, the engine air-fuel ratio control device is equipped with a fuel control means for supplying fuel according to a desired operating region, and a deterioration detection means for detecting engine deterioration, and a signal from the deterioration detection means is inputted to control the engine. An air-fuel ratio control device for an engine, comprising: deterioration correction control means for correcting and controlling the fuel control means so as to enrich the air-fuel ratio in accordance with deterioration.