JPH0615848B2 - Air-fuel ratio controller for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention is directed to an improvement in an air-fuel ratio control device for an internal combustion engine, which feedback-controls the air-fuel ratio of an intake air-fuel mixture of an internal combustion engine by detecting the exhaust gas concentration of an exhaust system. In particular, the present invention relates to an air-fuel ratio control device for an internal combustion engine, which stabilizes an air-fuel ratio and prevents engine stall and deterioration of an exhaust gas value in a warm-up operation during cold weather.

[Technical Background of the Invention] In a conventional mechanism for controlling the air-fuel ratio of a carburetor,
During the warm-up operation during cooling, the air-fuel ratio correction value is finely divided and controlled by open control based on the engine rotation input, the air temperature sensor input, and the highland sensor input until the water temperature of the engine exceeds a predetermined value. For example, at an extremely low temperature, the air-fuel ratio correction value is maintained at 10% by the air temperature sensor. If the engine speed increases, the correction value of the air-fuel ratio is maintained at 40%, and if there is a high-altitude input to these, the correction value of each of the above is changed to thereby secure an appropriate air-fuel ratio.

[Problems of background art] However, since the correction of the air-fuel ratio in the warm-up operation at the time of cooling is performed by the open control as described above, it is difficult to appropriately maintain the correction of the air-fuel ratio. In open control, this is all corrected depending on the reference air-fuel ratio of the carburetor, but when the production of the carburetor is taken into consideration, there are variations in the production, so the effect is that the reference air-fuel ratio of each carburetor is unique. This is because it is difficult to keep constant. If the corrected air-fuel ratio based on the open control is too rich due to variations in the carburetor and the lean spot, the CO value in the exhaust gas increases and the fuel efficiency deteriorates. There was an inconvenience such as engine stall.

In addition, many sensors are required to perform extremely fine control in the above-mentioned open control, which causes a problem of high cost.

[Object of the Invention] Therefore, an object of the present invention is to eliminate the above-mentioned inconveniences, to avoid the influence of the manufacturing error of the carburetor, and to use a large number of expensive sensors, in the warm-up operation at the time of cooling. An object of the present invention is to realize an air-fuel ratio control device for an internal combustion engine that can maintain the fuel ratio optimally.

In order to achieve this object, the present invention has an air-fuel ratio of an internal combustion engine having a control means for adjusting the air-fuel ratio by determining a correction amount of the air-fuel ratio of a carburetor based on an input signal from an exhaust sensor. In the control device, a water temperature detection sensor for detecting the temperature of the cooling water is provided, and it is judged from the input signal of the water temperature detection sensor that the water temperature is lower than the predetermined water temperature, and the exhaust sensor activates the second and subsequent exhaust sensor activities after starting the engine. When the air-fuel ratio rich signal is input, the air-fuel ratio correction amount is moved to the lean side by one predetermined value, and when the air-fuel ratio lean signal is input from the exhaust sensor, the air-fuel ratio correction amount is changed by another predetermined value. Is provided to the rich side, and a control means for controlling the carburetor to the optimum air-fuel ratio by the air-fuel ratio correction amount after the movement is provided.

Embodiments of the Invention Embodiments of the present invention will be described in detail and specifically with reference to the drawings.

FIG. 1 shows a schematic system diagram of the present invention, in which 2 is a carburetor, 4 is a control unit, and the control unit 4 is a central part when feedback controlling the air-fuel ratio of the carburetor 2. The control unit 4 receives an input signal from the water temperature detection sensor, determines that the water temperature is below the predetermined water temperature, and inputs the air-fuel ratio rich signal from the exhaust sensor for the second time and after the activation of the exhaust sensor after the engine is started. When the air-fuel ratio correction amount is moved from the exhaust sensor to the lean side and the air-fuel ratio lean signal is input from the exhaust sensor, the air-fuel ratio correction amount is moved to the rich side by another predetermined value and the air-fuel ratio correction amount after the movement is moved. The control unit 4 is configured so as to operate along the flow of the flowchart shown in FIG. 4 by including control means for controlling the carburetor to an optimum air-fuel ratio. Reference numeral 6 is a control valve for adjusting the air-fuel ratio in the intake passage 8, and the control valve 6 is started based on a control signal from the control section 4. Reference numeral 10 is an O ₂ sensor which is a kind of exhaust sensor provided in the exhaust passage 12, and the O ₂ sensor 10 has a function of detecting the ratio of O ₂ contained in the exhaust gas, and the information thereof is the above-mentioned control unit. 4 is transmitted. Reference numeral 14 is a rotation speed detection sensor for detecting the engine rotation speed of the engine 16, and the information detected here is transmitted to the control unit 4. Reference numeral 18 denotes a water temperature detection sensor that detects the engine temperature from the water temperature of the cooling water of the engine 16. The information detected here is transmitted to the control unit 4. Then, the control unit 4 determines whether or not there is a cold machine immediately after the start of operation based on the information from the water temperature detection sensor 18. The water temperature sensor 1
8 can be turned on / off by the control unit 4 and the switch mechanism.

FIG. 2 is a block diagram of the control unit 4, in which the control unit 4 compares the O ₂ sensor signal transmitted from the O ₂ sensor 10 with a reference value, and receives information from a plurality of locations as inputs. It comprises an input circuit 22 to be inserted, a computer 24 for judging the input taken in from the input circuit 22, and a drive circuit 26 for sending a control signal to the control valve 6 based on the judgment of the computer 24, and as shown in FIG. It is configured to operate according to the flow of the flowchart shown.

FIG. 3 is a schematic sectional view of the air-fuel ratio correction mechanism of the carburetor 2, and the control valve 6 uses a duty solenoid 28. Reference numeral 30 is a slow system air-fuel ratio adjusting air bleed passage, 32 is a main system air-fuel ratio adjusting air bleed passage, 34 is a float chamber, and 36 is a throttle valve.

Next, the operation of the above embodiment will be described.

Exhaust gas flows through the exhaust passage 12 when the engine is started during warm-up operation during cold weather. Thus, after the O ₂ sensor 10 in the exhaust passage 12 is activated, the O ₂ sensor 10 detects the amount of O _{2 in} the exhaust gas and sends the result to the control unit 4 as an input signal (see FIG. 5 ( A)). Further, information about the engine temperature is input to the control unit 4 from the water temperature detection sensor 18, and if it is less than the predetermined water temperature T ° C., for example, it is determined that the engine is cold. When it is determined that the engine is cold, the first air-fuel ratio rich signal is input to the control unit 4 from the activated O ₂ sensor 10, and when the rich signal continues for T ₁ seconds, that is, the same input signal continues for a predetermined engine, The control unit 4 skips or moves the air-fuel ratio correction value to the lean side by one predetermined value mo, and maintains the air-fuel ratio correction value at that position. If the rich signal continues after T ₁ second, the air-fuel ratio correction value is maintained at that position by further skipping to the lean side by mo. By repeating this, the optimum correction value of the air-fuel ratio peculiar to each carburetor is searched while changing the air-fuel ratio correction value stepwise from the rich side to the lean side by small mo at intervals of T ₁ second. This is because the optimum correction value peculiar to each vaporizer is considered to be within the range in which the input signal from the O ₂ sensor 10 shifts from the rich side to the lean side or the opposite state. Therefore, after the input signal from the O ₂ center 10 is inverted to the lean signal, when the lean signal continues for T ₁ seconds, the air-fuel ratio correction value is skipped to the rich side by another predetermined value m1 and the O ₂ sensor 10 outputs. When the input signal of is set to the rich side for the second time, it corresponds to the optimum optimum air-fuel ratio correction value of the carburetor at that time. Therefore, when the rich signal is generated for the second time, the air-fuel ratio correction value is maintained at that value (FIG. 5 (B)). By doing so, the air-fuel ratio during the disconnection becomes an idling ratio suitable for warm-up operation without being affected by the manufacturing error of the carburetor, and good warm-up at the time of cooling can be performed (FIG. 5 (D)).
Since the optimum air-fuel ratio correction value changes depending on the state of the engine, the optimum air-fuel ratio correction value may become the optimum air-fuel ratio correction value even on the second rich side. As a result, unlike the conventional open control, the engine stall (Fig. 5 (C)) and the exhaust gas are not affected by the manufacturing error of the carburetor. As described above, according to the present invention, even when the engine is cold, the O
After the activation of the ₂ sensor 10, the O ₂ sensor signal is input to partially perform the feedback control to achieve smooth warm-up during cooling. In FIGS. 5A to 5D, the solid line represents the present invention and the broken line represents the case of the open control of the conventional example, and the carburetor has a manufacturing error, and its peculiar air-fuel ratio tendency is lean. Is a vaporizer having. Therefore, engine stall occurs.

On the other hand, when the engine temperature is equal to or higher than T ° C., that is, when the engine is not cold, the feedback operation according to the normal O ₂ sensor input signal is started.

[Effects of the Invention] As will be apparent from the detailed description below, according to the configuration of the present invention, a water temperature detection sensor for detecting the cooling water temperature is provided,
When the input signal of the water temperature detection sensor determines that the water temperature is lower than the predetermined value, and when the air-fuel ratio rich signal after the second activation of the exhaust sensor after the engine is started is input from the exhaust sensor, the air-fuel ratio is increased by one predetermined value. When the correction amount is moved to the lean side and the air-fuel ratio lean signal is input from the exhaust sensor, the air-fuel ratio correction amount is moved to the rich side by another predetermined value and the carburetor is optimized by the air-fuel ratio correction amount after the movement. Since the control means for controlling the air-fuel ratio is provided, even if the unique air-fuel ratio correction amount of each carburetor is different due to the manufacturing error of the carburetor, the optimum air-fuel ratio correction amount unique to each carburetor can be obtained. Can be found. As a result, it is possible to prevent an increase in CO in exhaust gas and engine stall during warm-up operation during cooling. In this way, even if there is an error in the manufacture of each carburetor, it is possible to easily eliminate the effect and maintain the optimum air-fuel ratio during the warm-up operation of the cold equipment. In addition, since it is not necessary to use a large number of sensors, the above effect can be achieved without increasing the cost.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is a schematic system diagram, FIG. 2 is a block diagram, FIG. 3 is a schematic sectional view of an air-fuel ratio correction mechanism, FIG. 4 is a flow chart, and FIG. The figure is a diagram for explaining the operation. In the figure, 2 is a vaporizer, 4 is a control unit, 6 is a control valve, and 10 is O.
_Two sensors and 18 are water temperature detection sensors.

Claims (1)

[Claims] 1. An air-fuel ratio control system for an internal combustion engine, comprising: a control means for adjusting a correction amount of an air-fuel ratio of a carburetor based on an input signal from an exhaust sensor to adjust the air-fuel ratio. A detection sensor is provided, and when an input signal from the water temperature detection sensor determines that the water temperature is lower than the predetermined water temperature, and when an air-fuel ratio rich signal after the second activation of the exhaust sensor after engine start is input from the exhaust sensor, one When the air-fuel ratio lean signal is input from the exhaust sensor, the air-fuel ratio correction amount is moved to the rich side by another predetermined value and the air-fuel ratio correction amount is moved to the rich side by another predetermined value. An air-fuel ratio control device for an internal combustion engine, comprising control means for controlling the carburetor to an optimum air-fuel ratio based on the amount.