JPS62129553A - Air-fuel ratio controller - Google Patents

Abstract

PURPOSE:To prevent an air-fuel ratio from going to the rich side as well as to improve a rate of fuel consumption, by letting a controller perform on-off control over a slow cut valve at a time when air-fuel ratio compensation value is approximated to a range of 100% and simultaneously engine speed and throttle opening both become more than the specified value. CONSTITUTION:At a control part 14 which controls the valve 16 installed in a carburetor for its opening or closing and also controls an air-fuel ratio for feedback, at the time of feedback control over the air-fuel ratio by an oxygen sensor 18, air-fuel compensation value is made to go up and simultaneously engine speed and throttle valve opening both are made to go up. And, when the air-fuel ratio compensation value is approximated to a range of 100% and simultaneously the engine speed and the throttle valve opening both become more than the specified value, a slow-cut valve is controlled for opening or closing at every T second interval. And, when any one of the air-fuel ratio compensation value, the engine speed and the throttle valve opening becomes less than the setting value, it is constituted so as to stop on-off control over the said slow-cut valve.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an air-fuel ratio control device, and in particular, it prevents the air-fuel ratio from becoming lynched, purifies exhaust gas such as C02 THC, and improves fuel efficiency. , relates to an air-fuel ratio control device that improves drivability.

[Conventional technology]

Internal combustion engines for vehicles have extremely large fluctuations in vehicle running speed, that is, engine rotational speed, and load, and are required to have performance such as low fuel consumption and low harmful exhaust gas under various operating conditions that combine these two variables. Therefore, it is necessary to keep the air-fuel ratio appropriate under various operating conditions.

In order to properly control the air-fuel ratio, an exhaust sensor is installed to detect components in the exhaust gas, and the output signal from this sensor operates a control valve that adjusts the amount of bleed air supplied to adjust the air-fuel ratio. A feedback type air-fuel ratio control device is used which controls the air-fuel ratio and adjusts the air-fuel ratio to always obtain the best combustion condition for each of the above-mentioned operating conditions.

[Problems to be Solved by the Invention] In the conventional air-fuel ratio control device, feedback control using an O2 sensor, which is an exhaust sensor, is started from open control after the engine is started. Immediately after starting this feedback control, the engine temperature has not completely risen.

As a result, in a carburetor having an automatic choke mechanism that operates depending on the engine temperature, the choke effect remains, and the base air-fuel ratio of the carburetor becomes extremely rich. Then, in order to make this richer air-fuel ratio leaner,
When attempting to control the air-fuel ratio to the stoichiometric air-fuel ratio by opening and closing the air-fuel ratio solenoid valve (duty control), as shown by the broken line in Figure 5, the air-fuel ratio correction value continues to maintain approximately 100%, so the air-fuel ratio is corrected. I couldn't. For this reason,
The increased air-fuel ratio increases the amount of harmful exhaust gases such as CO1THC, which is disadvantageous in that it worsens fuel efficiency. Furthermore, in highlands and the like, the air density is low and the base air-fuel ratio of the carburetor is richer than in lowlands, making the above-mentioned disadvantages more severe.

[Object of the Invention] Therefore, an object of the present invention is to eliminate the above-mentioned inconvenience by adjusting the air-fuel ratio correction value to approach 100% and the engine speed and throttle opening after starting air-fuel ratio feed-hack control by the exhaust sensor. When the air-fuel ratio correction value, engine speed, or throttle opening is less than the set value, the slow cut valve is controlled on and off. By providing a control unit that stops valve on/off control, it is possible to prevent the air-fuel ratio from becoming richer, purify harmful exhaust gases such as Co and THC, and improve fuel efficiency. The object of the present invention is to realize an air-fuel ratio control device that can improve drivability.

[Means for solving problems]

To achieve this object, the present invention provides an air-fuel ratio control device that corrects and controls an air-fuel ratio by inputting a signal from an exhaust sensor and has an automatic choke mechanism operated according to engine temperature. After starting the feedback control, when the air-fuel ratio correction value approaches 100% and the engine speed and throttle opening exceed the set values, the slow-cut valve is controlled on and off,
On the other hand, the present invention is characterized in that a control section is provided that stops the on/off control of the slow-cut valve when any one of the air-fuel ratio correction value, engine speed, and throttle opening becomes less than a set value. .

[Effect]

By configuring as described above, the air-fuel ratio correction value is set to 100 after the start of air-fuel ratio feedback control by the exhaust sensor.
% and when the engine speed and throttle opening exceed the set values, the slow cut valve is controlled on and off, and on the other hand, either the air-fuel ratio correction value, the engine speed or the throttle opening When one becomes less than the set value, the on/off control of the slow-cut valve is stopped and normal air-fuel ratio control is performed to prevent the air-fuel ratio from becoming richer and eliminate harmful emissions such as Co and THC. Cleans gas, improves fuel efficiency, and improves drivability.

〔Example〕

Embodiments of the present invention will be described in detail below based on the drawings.

1 to 5 show embodiments of this invention. 1st
．． In Figure 2, 2 is an air cleaner and 4 is an intake pipe. An electronically controlled venturi type carburetor 6 is provided midway through the intake pipe 4 on the downstream side of the air cleaner 2, and this carburetor 6 has an open end in a combustion chamber (not shown) of the engine 8. Also,
The combustion chamber has an exhaust pipe 10 at its opening end, and a catalytic converter 12 consisting of a three-way catalyst for performing post-exhaust processing is provided in the middle of the exhaust pipe 10.

The vaporizer 6 is provided with a valve 16 whose opening and closing are controlled by a control section 14, which will be described later.

In addition, in order to detect the engine operating status, exhaust gas concentration,
For example, an O2 sensor 18, which is an exhaust sensor that detects 02 fm degrees, is installed in the exhaust pipe 10.

A control section 14 is provided which receives a detection signal from the 02 sensor 18, and the control section 14 controls the air-fuel ratio to an appropriate value after the 02 sensor 18 starts feedback control of the air-fuel ratio. Specifically, as shown in FIG. 5, the engine is started (t (1 position)), running is started (1+ position), the engine speed is increased, and the air-fuel ratio is feedback-controlled by the 02 sensor 18. (t2 position).At this time, the air-fuel ratio correction value is increased by air-fuel ratio feedback control, and the engine speed and throttle opening are also increased, so that the air-fuel ratio correction value becomes 1.
00% and when the engine speed and throttle opening exceed the set value (t3 position), the slow cut valve, which will be described later, is controlled on and off every T seconds, while the air-fuel ratio correction is performed. value, engine speed, and throttle opening are less than the set value (t4th position K)
When this occurs, the control section 14 is configured to stop the on/off control of the slow cut valve.

Further, as shown in FIG. 1, the control section 14 controls the 02
It has a reference voltage comparison circuit 20 that inputs the detection signal from the sensor 18, and also includes an idle switch 22, an engine rotation speed sensor 24, and the reference voltage comparison circuit 20.
It has an input circuit 26 for inputting respective output signals from the . Furthermore, there is a computer 2 which inputs the output signal from this input circuit 26 and performs various control calculations, and an output circuit which inputs the output signal from this computer 28 and outputs it to the valve 16 and a slow-cut valve to be described later. 30
It also has The reference numeral 32 is an ignition switch, and the reference numeral 34 is an ignition switch.

Further, as shown in FIG. 3, the carburetor 6 includes the valve 16, an intake passage 36, a throttle valve 38, a float chamber 40, a main fuel passage 42, and a slow fuel passage 44. The control section 14 is connected to the system fuel passage 44.
A slow cut valve 46 is provided which is controlled to open and close by.

Next, air-fuel ratio control of an internal combustion engine in an embodiment of the present invention will be explained along the flowchart of FIG.

First, the internal combustion engine starts (100
), and then it is determined whether or not air-fuel ratio feedback control has been started (102), and if NO, it is repeatedly determined whether or not feedback control has been started.
If YES, the air-fuel ratio correction value is detected (104) and it is determined whether or not this air-fuel ratio correction value approaches 100% (104).
06). If the answer is No, the judgment is repeated as to whether the air-fuel ratio correction value approaches 100%, and if the answer is YES, the engine speed is detected (108) and the engine speed is determined to be equal to or higher than the set value. A judgment (110) is made. At this time, in the case of No, detection of the air-fuel ratio correction value (104)
Return to , and if YES, detect the throttle opening (11
2) Do. Furthermore, it is determined whether the throttle opening is greater than or equal to the set value (114), and if No, the process returns to detecting the air-fuel ratio correction value (104), and if YES, the slow cut valve 46 is operated (114). 116), and performs on/off control (118) every T seconds.

Then, the air-fuel ratio correction value is detected (120), and it is determined whether the air-fuel ratio correction value is greater than or equal to the set value (122), and if NO, on/off control of the slow-cut valve 46 is performed. is stopped (124), and in the case of YES, the engine speed is detected (126)L, and it is determined whether or not this engine speed is equal to or higher than a set value (128). If this judgment is No, the process moves to stopping the on/off control of the slow cut valve 46 (124), and if YES, the throttle opening is detected (130)L, and whether this throttle opening is equal to or greater than the set value. A determination is made as to whether or not it is true (132), and in the case of NO, the on/off control of the slow cut valve 46 is stopped (132).
24), if YES, detecting the air-fuel ratio correction value after on/off control of the slow cut valve 46 (12).
0).

As a result, when the air-fuel ratio correction value approaches 100% after the start of air-fuel ratio feedbank control by the exhaust sensor and the engine speed and throttle opening exceed the set values, the slow-cut valve is controlled to turn on and off. It is possible to prevent the air-fuel ratio from lynching, to purify harmful exhaust gases such as CO1THC, and to improve fuel efficiency, which is economically advantageous.

On the other hand, when any one of the air-fuel ratio correction value, engine speed, and throttle opening becomes less than the set value,
The on/off control of the slow cut valve can be stopped, and normal air-fuel ratio control can be performed after the continuous on/off control of the slow cut valve has been stopped, thereby improving drivability.

In addition, in the embodiment of the present invention, the slow cut valve is controlled on and off to prevent a sudden change in the air-fuel ratio due to the cut of slow system fuel when the slow cut valve is completely turned off, and to improve drivability. This is to prevent any negative impact on

In addition, by controlling the engine speed and throttle opening status as the stopping conditions for the on/off control of the slow cut valve, slow system fuel, which accounts for a large proportion of the total fuel in the low speed and low load range, can be reduced. This enables effective control and prevents problems such as poor drivability and engine stall.

〔Effect of the invention〕

As explained in detail above, according to the present invention, when the air-fuel ratio correction value approaches 100% after the start of feedback control of the air-fuel ratio by the exhaust sensor and the engine speed and throttle opening exceed the set values, the slowdown occurs. Control that controls the cut valve on and off, and stops the on and off control of the slow cut valve when any one of the air-fuel ratio correction value, engine speed, and throttle opening becomes less than a set value. Since the air-fuel ratio is provided with a section, it is possible to prevent the air-fuel ratio from becoming excessively high, and it is possible to purify harmful exhaust gases such as Co and THC, thereby improving fuel efficiency and drivability. In addition, this can be realized by changing only the program of the control section of the conventional air-fuel ratio control device, and by using the conventional carburetor, the cost can be kept low.
Economically advantageous.

[Brief explanation of drawings]

1 to 5 show embodiments of the present invention, FIG. 1 is a block diagram for air-fuel ratio control of an internal combustion engine, FIG. 2 is a schematic diagram of the internal combustion engine, and FIG. 3 is a schematic diagram of the carburetor of the internal combustion engine. 4 is a flowchart showing the air-fuel ratio control of the internal combustion engine, and FIG. 5 is a diagram showing the operating states of various parts in various operating states of the internal combustion engine. In the figure, 2 is an air cleaner, 4 is an intake pipe, 6 is a carburetor, 8 is an engine, 10 is an exhaust pipe, 12 is a catalytic converter, 14 is a control unit, 16 is a switching valve, 18 is an 02 sensor,
20 is a reference voltage comparison circuit, 22 is an idle switch, 2
4 is an engine speed sensor, 26 is an input circuit, 28 is a computer, 30 is a drive circuit, 32 is an ignition switch, 34 is a battery, 36 is an intake passage, 38 is a throttle valve, 40 is a float chamber, 42 is a main system A fuel passage, 44 is a slow system fuel passage, and 46 is a slow cut valve.

Claims (1)

[Claims] In an air-fuel ratio control device that corrects and controls an air-fuel ratio by inputting a signal from an exhaust sensor and has an automatic choke mechanism that is operated depending on engine temperature, the air-fuel ratio correction value is set to 100 after the exhaust sensor starts feedback control of the air-fuel ratio. % and when the engine speed and throttle opening exceed the set values, the slow cut valve is controlled on and off. An air-fuel ratio control device comprising: a control section that stops on/off control of the slow-cut valve when the ratio becomes less than a set value.