JPS62178746A - Air-fuel ratio control device - Google Patents

Abstract

PURPOSE:To prevent an over rich state caused by a choke, by controlling air- fuel ratio, when an engine temperature is in a predetermined value or less, while returning an air-fuel ratio correction value, when it reaches an upper limit value, to the fixed correction value when the engine temperature increases to the predetermined value or more, in the case of an engine having an automatic choke mechanism. CONSTITUTION:An output from an O2 sensor 18 is input to a control part 14, comprising a reference voltage comparator circuit 20, input circuit 26, CPU28 and an output circuit 30, and a valve 16 in a carburetor 6 is controlled through the output circuit 30, regulating air-fuel ratio. The control part 14, which performs an air-fuel ratio feedback control by the O2 sensor 18 when an engine water temperature is less than a preset value, controls an air-fuel ratio correction value to be directed to an upper limit value in a 100% side. When the engine water temperature increases to the preset value or more further when the air-fuel ratio correction value reaches the upper limit value, the air-fuel ratio correction value is repeatedly controlled so as to be forcedly returned to the fixed correction value by an optional speed thereafter to a lean side.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an air-fuel ratio control device, and particularly to a feedbank control system in which information of a value darker than the actual air-fuel ratio is erroneously input. In addition to avoiding engine troubles caused by
The present invention relates to an air-fuel ratio control device that purifies harmful exhaust gas such as HC.

[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 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.

[Problem that the invention seeks to solve]

By the way, conventional air-fuel ratio control devices include, for example,
No. 0-88834, and this application claims that when information on a concentration value that is higher than the actual air-fuel ratio is erroneously input to the feed hack control system and the air-fuel ratio correction value reaches a predetermined concentration limit setting value, It has a configuration that forcibly returns the air-fuel ratio correction value to a fixed correction value to avoid engine trouble.

However, in the above-mentioned air-fuel ratio control device, even if the normal air-fuel ratio value is input, when the air-fuel ratio correction value reaches a predetermined concentration limit setting value, the air-fuel ratio correction value is adjusted to a certain level. Forced back to the value.

As a result, in a carburetor that has an automatic choke mechanism in which the choke valve opening is set depending on the engine water temperature, the choke effect occurs particularly immediately after the engine temperature, for example, the engine water temperature rises and air-fuel ratio feedback control is started. As a result, the air-fuel ratio supplied from the carburetor becomes extremely rich. And at this time,
As shown by the broken line in Fig. 4, by forcibly returning the air-fuel ratio correction value to a certain correction value, the already enriched air-fuel ratio is forcibly enriched further by the air-fuel ratio control device, causing an emergency. However, there is a disadvantage that exhaust gas consisting of highly concentrated CO2 THC etc. is discharged. Furthermore, in highlands and the like, the air density is low and the air-fuel ratio supplied from the carburetor is richer than in lowlands, making the above-mentioned disadvantages more severe.

[Purpose of the invention]

Therefore, an object of the present invention is to perform feedbank control using the exhaust sensor when the engine temperature is lower than a set temperature, and when the engine temperature becomes higher than the set temperature and the air-fuel ratio correction value is set to a predetermined value. By providing a control unit that repeatedly controls the air-fuel ratio correction value to forcefully return it to a certain correction value when the upper limit value is reached, information on the air-fuel ratio value can be input incorrectly. The object of the present invention is to realize an air-fuel ratio control device that can avoid engine troubles caused by the engine troubles, perform effective air-fuel ratio control, and purify harmful exhaust gases such as Co and THC.

[Means for solving problems]

To achieve this objective, the present invention provides an air-fuel ratio control device that corrects and controls the air-fuel ratio by inputting a signal from an exhaust sensor and has an automatic choke mechanism that is operated depending on the engine temperature. In this case, feedback control is performed by the exhaust sensor, and when the engine temperature exceeds the set temperature and the air-fuel ratio correction value reaches a predetermined upper limit, the air-fuel ratio correction value is forced to a certain correction value. The present invention is characterized in that it is provided with a control section that performs repeated control to return to .

[Effect]

With the above configuration, when the engine temperature is less than the set temperature, feedback control is performed by the exhaust sensor, and when the engine temperature exceeds the set temperature and the air-fuel ratio correction value reaches the predetermined upper limit value. In order to do so, the air-fuel ratio correction value is forcibly returned to a certain correction value to avoid engine troubles caused by incorrect input of the air-fuel ratio value, and to purify harmful exhaust gases such as CO1 THC. There is.

〔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 the opening end of this carburetor 6 is connected to a combustion chamber (not shown) of an 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 02 sensor 18, which is an exhaust sensor for detecting 02'1H degree, is installed in the exhaust pipe 10.

A control section 14 is provided which receives the detection signal of the 02 sensor 18, and the control section 14 performs feedback control of the air-fuel ratio by the 02 sensor 18 according to the engine temperature. The configuration is such that the air-fuel ratio is controlled to an appropriate value. More specifically, as shown in FIG. 4, when the engine temperature, for example, the engine water temperature, is lower than the set temperature (1+ position) after the engine is started (tq position), the feed hack system by the exhaust sensor 18 is activated. Direct the air-fuel ratio correction value to the upper limit value on the 100% side by J The value should be forcibly returned to a fixed correction value at an arbitrary speed (the control unit 14 that repeatedly controls
Configure. Further, after the air-fuel ratio correction value is forcibly returned to a certain correction value at an arbitrary speed, the control unit 14 controls the air-fuel ratio correction value to be on the lean side. At this time, as a measure to forcibly return the air-fuel ratio correction value to a fixed correction value at an arbitrary speed, the control section 14 is configured to perform on/off control of the slow cut valve 46, for example.

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 manually inputting the respective output signals from the . Further, there is a computer 28 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 46 which will be described later. 30. In addition, the code|symbol 32 is an ignition switch, and 34 is a battery.

Furthermore, as shown in FIG. 3, the carburetor 6 has the valve 16, an intake passage 36, a throttle valve 38, a float chamber 40, a main system fuel passage 42, and a slow system 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 in an embodiment of the present invention will be explained along the flowchart of FIG.

First, start the engine (102) from start (lOO).
), it is determined whether the engine has started (104), and if NO, the process returns to starting the engine (102), and if YES, the engine water temperature is detected by a water temperature sensor (not shown) (106). . Then, it is determined whether or not the engine water temperature is equal to or higher than the set temperature (108).
In the case of 02 sensor 18, feedback control of the air-fuel ratio according to the human power (110) is performed, and the process returns to the detection of the engine water temperature (106), and in the case of YES, the air-fuel ratio correction value is set to the upper limit on the 100% side. Correction control (112)L is performed to bring the air-fuel ratio correction value closer to the upper limit value.Next, it is determined whether the air-fuel ratio correction value has reached the upper limit value (114). If this judgment is No, the feedback control of the air-fuel ratio according to the 02 sensor 18 human power is performed (116), and the process returns to the correction control of the air-fuel ratio correction value (112), and if the judgment is YES, the air-fuel ratio is corrected. (118) forcibly returning the value to a certain correction value at an arbitrary speed, and correction control (118) of the air-fuel ratio correction value.
This returns to 12).

As a result, when the engine temperature between positions t, This method is economically advantageous because it can purify exhaust gas and improve fuel efficiency.

Furthermore, poor combustion due to overrichness can be prevented, which is advantageous in practice.

Furthermore, on the other hand, when the engine temperature after the t1 position becomes equal to or higher than the set temperature and the air-fuel ratio correction value reaches a predetermined upper limit value, the air-fuel ratio correction value is forcibly returned to a certain correction value,
This can prevent engine troubles caused by incorrect input.

Note that the present invention is not limited to the above-described embodiments, and various modifications can be made.

For example, in the embodiment of the present invention, the engine water temperature, for example, is detected as the engine temperature, and the air-fuel ratio is feedback-controlled according to the engine water temperature, or the air-fuel ratio correction value is repeatedly controlled to forcefully return it to a certain correction value. However, a timer is used instead of engine water temperature,
It is also possible to set a predetermined time for the engine temperature to reach a set temperature in advance, and perform air-fuel ratio control according to the set time.

Furthermore, as shown by the dashed line in FIG. 5, if a high altitude switch is provided in the embodiment of the present invention, this high altitude switch
) to determine whether or not it is a high area (202), and if NO, the correction side '+111(112)L is set to bring the air-fuel ratio correction value closer to the upper limit value on the 100% side, and if YES, 02 While performing feedbank control (204) of the air-fuel ratio according to the sensor 18 manual power, the high altitude switch (200
). This can prevent the air-fuel ratio from becoming undesirably rich at high altitudes.

〔Effect of the invention〕

As explained in detail above, according to the present invention, when the engine temperature is less than the set temperature, feedback control is performed by the exhaust sensor, and when the engine temperature becomes equal to or higher than the set temperature, the air-fuel ratio correction value reaches the predetermined upper limit value. A control unit is provided that repeatedly controls the air-fuel ratio correction value to be forcibly returned to a certain correction value when the air-fuel ratio correction value is reached. At the same time, effective air-fuel ratio control is performed to prevent CO2THC
It is possible to purify harmful exhaust gas such as

Moreover, it is possible to avoid combustion defects due to over-reaction. Furthermore, it can be realized by changing only the program of the control part of the conventional air-fuel pressure control device, and since the conventional carburetor can be used, the cost can be kept low and it is economically advantageous. There is no need to carry out work such as reliability testing of the device (it can shorten the development schedule and reduce development costs).

[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 cross-sectional view showing the operating states of various parts in various operating states of the internal combustion engine, and FIG. 5 is a flowchart showing air-fuel ratio control 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 valve, 18 is an 02 sensor, and 20 is a reference. Voltage comparator circuit, 22 is an idle switch,
24 is an engine speed sensor, 26 is an input circuit, 28 is a computer, 30 is an output 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 fuel aisle, 44
4 is a slow system fuel passage, and 46 is a slow cut valve. Patent Applicant Suzuki Motor Co., Ltd. Agent
Patent attorney Yoshida Saigo! Figure 2 Figure 3 Figure 4

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 operated according to engine temperature, feedback control is performed by the exhaust sensor when the engine temperature is lower than a set temperature. A controller is provided for repeatedly controlling the air-fuel ratio correction value to forcibly return it to a certain correction value when the engine temperature becomes equal to or higher than a set temperature and the air-fuel ratio correction value reaches a predetermined upper limit value. An air-fuel ratio control device characterized by: