JPS6112099B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an air-fuel ratio correction device for an internal combustion engine that feeds back the air-fuel ratio of an air-fuel mixture and corrects the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine to an appropriate value according to engine operating conditions. In general, carburetors are manufactured and adjusted so that they can supply a mixture with an appropriate air-fuel ratio under all operating conditions of the internal combustion engine, but when atmospheric temperature and pressure change, the air-fuel ratio of the mixture changes. This not only results in the generation of harmful exhaust gas, but also causes problems such as a reduction in the purification rate of the catalyst installed for exhaust gas purification and accelerated deterioration of the catalyst itself. On the other hand, a device has been proposed that detects the air-fuel ratio of the air-fuel mixture based on the oxygen concentration in the exhaust gas, returns the feedback, and controls the air-fuel ratio of the air-fuel mixture to an appropriate value. As shown in FIG. 1, this device includes an auxiliary air passage 2 that opens into an intake pipe 41 downstream of a throttle valve 14.
2, and a bypass valve 2 is provided in the passage 22.
1 is disposed, and a control circuit 100 controls the rotational direction of the pulse motor 20 based on an electric signal from an air-fuel ratio detector 50 disposed in an exhaust pipe 42 of an internal combustion engine 40. Then, the air-fuel mixture with an air-fuel ratio slightly lower than the appropriate air-fuel ratio is fed to the internal combustion engine 40.
The carburetor 10 is adjusted so that air can be supplied to the air, and air is added from the auxiliary air passage 22 downstream of the throttle valve 14 to control the air-fuel mixture to an appropriate air-fuel ratio. The air-fuel ratio detected by the device 50 is fed back, the air flow path area is changed by the bypass valve 21, and an amount of air to achieve the appropriate air-fuel ratio is added to control the air-fuel mixture to the appropriate air-fuel ratio. However, since such a device constantly controls the air-fuel ratio to a value that is advantageous for exhaust gas purification regardless of the operating state, a problem arises in that the engine output is inevitably insufficient when the engine is under high load. The present invention was made in view of the above-mentioned problems.
Normally, feedback correction can be performed by adjusting the amount of auxiliary air that bypasses the throttle valve so that the air-fuel ratio of the mixture supplied to the internal combustion engine with a carburetor becomes the set air-fuel ratio, and the internal combustion engine is under high load. By forcibly decreasing the amount of auxiliary air and increasing the amount of fuel supplied to the carburetor, the air-fuel ratio of the air-fuel mixture can be made sufficiently small, thereby effectively increasing the engine output. An object of the present invention is to provide an air-fuel ratio correction device for an internal combustion engine that can perform the following steps. Therefore, the present invention provides a carburetor and a throttle valve provided on the intake pipe side of an internal combustion engine, an auxiliary air passage that bypasses these carburetor and throttle valve and supplies auxiliary air to the internal combustion engine, and an auxiliary air passage that supplies auxiliary air to the internal combustion engine. an air-fuel ratio detector for detecting the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine; an operating means for controlling the amount of fuel supplied to the carburetor; load detection means for detecting the load state of the engine; first control means for controlling the bypass valve and adjusting the amount of auxiliary air according to the detection signal of the air-fuel ratio detector; When it is detected that the internal combustion engine is in a high load state, the adjustment operation by the first control means is disabled to reduce the opening degree of the bypass valve, and the operation means is driven to supply fuel to the carburetor. A second control means for controlling the amount to increase. The present invention will be described below with reference to a first embodiment shown in FIGS. 2 and 3. In FIG. 2, 10 is a carburetor, 11 is a main nozzle, 12 is a float chamber, 13 is a float, 14 is a throttle valve, 15 is an exciting coil,
16 is a needle valve, 17 is a spring, 18 is an auxiliary jet, and 19 is a main jet. When the needle valve 16 closes the auxiliary jet 18 by the pressing force of the spring 17, the carburetor 10 maintains the proper air-fuel ratio (A /F=14.8), and when the needle valve 16 opens the auxiliary jet 18, the fuel flow passage area becomes large, and the carburetor 10 has an air-fuel ratio slightly lower than the appropriate air-fuel ratio. It is adjusted to supply a mixture of 20 is a reversibly rotatable pulse motor;
The bypass valve 21 driven by the auxiliary air passage 22
The auxiliary air passage 22 is installed in the element 31.
It communicates with an air cleaner 30 that is installed inside. 40 is an internal combustion engine; 41 is an intake pipe that communicates with the auxiliary air passage 22 downstream of the throttle valve 14 and guides the air-fuel mixture to the internal combustion engine 40; 42 is an exhaust pipe that leads exhaust gas to the catalyst 60; An air-fuel ratio detector 50 and an operating state detector 80 for detecting whether the air-fuel ratio detector is in an operating state are provided. As the air-fuel ratio detector 50, a metal oxide of Zro ₂ is used so that a higher voltage can be obtained as the air-fuel ratio is smaller (the oxygen concentration in the exhaust gas is lower). As the operating state detector 80, a thermistor (negative resistance) is used so that a higher voltage is obtained as the temperature of the exhaust pipe 42 (approximately equal to the temperature of the air-fuel ratio detector 80 itself) is higher. 7
0 is an intake pressure detector which serves as a load detector, and includes a normally open switch 71, a diaphragm 72, and a spring 7.
3. Consists of a plunger 74 and an introduction pipe 75,
When the opening degree of the throttle valve 14 is increased when increasing the engine output, the pressure (absolute pressure) in the intake pipe 41 increases, so the plunger 74 closes the switch 71 by the pressing force of the spring 73. . Reference numeral 100 denotes a control circuit that determines the engine operating state based on electrical signals from the air-fuel ratio detector 50, the operating state detector 80, and the intake pressure detector 70, and generates electrical signals for driving the excitation coil 15 and the pulse motor 20. Its detailed configuration will be explained with reference to FIG. 81 is a fully closed detection switch that closes only when the bypass valve 21 shown in FIG. 2 is fully closed; 82 is a key switch; 83 is a power source; 101 to 107 are NAND gates;
127 is an inverter, 130 and 131 are comparators,
132, 133, 134 are transistors, 140
are known reversible shift registers, 141-157 are resistors, 161-165 are capacitors, 171-1
75 is a diode. Reversible shift register 1
40 is wired so that when a pulse signal is input to input p ₁ , the pulse motor 20 increases the opening degree of the bypass valve 21, and when a pulse signal is input to input p ₂ , the pulse motor 20 is wired to reverse rotation. There is.
Note that in FIG. 3, 110 is an oscillation circuit. In the above configuration, the operation of the control circuit 100 will be described first, and the electrical signals of each part will be simply referred to as "H" level (high level) or "L" level (low level) as logic signals. The voltage generated by the air-fuel ratio detector 50 is
0, it is compared with the specified voltage (voltage corresponding to the appropriate air-fuel ratio) by the resistors 143 and 144,
As mentioned above, the air-fuel ratio detector 50 generates a higher voltage as the air-fuel ratio is smaller, so when the air-fuel ratio is larger than the appropriate air-fuel ratio, the signal is "L" level, and when it is smaller, the signal is "H" level. occurs on line A. A pulse signal from an oscillation circuit 110 is generated on line F. The voltage generated by the operating state detector 80 is the voltage generated by the comparator 1.
31, the operating state detector 8
As mentioned above, the higher the temperature, the higher the voltage will be generated, so if the exhaust pipe temperature is below the specified temperature, it will be "L".
If the level temperature is higher than the specified temperature, an "H" level signal is generated on line C. Further, the switch 71 of the intake pressure detector 70 is normally open and therefore at the "H" level, and when the engine output is increased, it is closed as described above to produce a "L" level signal. The fully closed detection switch 81 is the second
It closes only when the bypass valve 21 shown in the figure is fully closed, and a signal of "L" level is generated on line E. Normally, a signal of "H" level is generated on line E. Therefore, the logical formula for the signal generated on line G is G=A・C・D・F, and the logical formula for the signal generated on line J is J=(・C++)・E・
It becomes F. Here, when J=K・E, the logical formula G
The truth tables of =A・C・D・F and K=(・C++)・F are shown in Tables 1 and 2, respectively.

【table】

【table】

[Table] From Table 1, all lines A, C, and D are “H”
It is clear that a pulse signal is generated on line G only when a level signal is generated, and based on the above-described configuration, pulse motor 20 rotates in a direction that increases the opening degree of bypass valve 21. In other words, the air-fuel ratio detector 50 is at a temperature sufficient to start operating, the air-fuel ratio of the air-fuel mixture being supplied to the internal combustion engine is lower than the appropriate air-fuel ratio, and the intake pipe pressure is at a temperature at which the engine output is increased. The opening degree of the bypass valve 21 is increased only when the pressure is not so high. Conversely, from Table 2, unless an "H" level signal is generated on all lines A, C, and D, if an "H" level signal is generated on line E, a pulse signal is generated on line J. It is clear that this occurs, and the pulse motor 20 rotates in a direction that reduces the opening degree of the bypass valve 21. That is, the air-fuel ratio detector 50 is in a state where the temperature is not sufficiently high as at the time of engine startup, a state in which the air-fuel ratio of the air-fuel mixture is higher than the appropriate air-fuel ratio, or a state in which the intake pipe pressure becomes high when the engine output is increased. If one of these conditions exists, the opening degree of the bypass valve 21 is reduced. However, when the bypass valve 21 is fully closed, an "L" level signal is generated on the line E, so it is clear that the bypass valve 21 is not driven. On the other hand, in FIG. 3, if an "H" level signal is generated on line C or an "L" level signal is generated on line D, the carburetor 10 shown in FIG.
The excitation coil 15 is energized. That is, if the air-fuel ratio detector 50 is in an operating state or when the engine output is being increased, the excitation coil 15 is energized. Next, the overall operation of the present invention will be described based on the operation of the control circuit 100 described above. When the internal combustion engine 40 is warmed up after starting, if the air-fuel ratio detector 50 has not reached the specified temperature at which the air-fuel ratio can be detected, the control circuit 100 does not energize the excitation coil 15, so the needle valve 16 is activated by the spring 17. is pressed to close the auxiliary jet 18. Therefore, the main nozzle 1 of the vaporizer 10
The fuel flowing out from the main jet 19 is measured only by the main jet 19, and the air-fuel mixture having an air-fuel ratio higher than the proper air-fuel ratio is supplied to the intake pipe 41. At this time, since the control circuit 100 drives the pulse motor 20 to fully close the bypass valve 21, no air is added from the auxiliary air passage 22. Therefore, since the internal combustion engine 40 is supplied with an air-fuel mixture with a relatively high air-fuel ratio, less harmful exhaust gas is emitted. As mentioned above, when an internal combustion engine is operated with a mixture with a high air-fuel ratio, a large engine output cannot be obtained, but if the opening of the throttle valve 14 is increased to increase the intake pipe pressure, Since the switch 71 of the barometric pressure detector 70 is closed, the control circuit 100 energizes the excitation coil 15 of the carburetor 10, causing the needle valve 16 to open the auxiliary jet 18.
Since the fuel flow path area of the carburetor 10 is increased, the internal combustion engine 40 is supplied with an air-fuel mixture having an air-fuel ratio slightly lower than the appropriate air-fuel ratio, and the engine output can be increased. By the way, when the temperature at which the air-fuel ratio detector 50 operates is reached after the engine is started, the control circuit 100 energizes the excitation coil 15 of the carburetor 10 in response to a signal from the operating state detector 80, so that the needle valve 16 is switched to the auxiliary jet. 18 is opened, the carburetor 10 adjusts the air-fuel ratio of fuel through the main jet 19 and the auxiliary jet 18, and supplies a mixture having an air-fuel ratio lower than the proper air-fuel ratio to the downstream side of the throttle valve 14. at the same time,
The control circuit 100 controls the rotational direction of the pulse motor 20 and changes the opening degree of the bypass valve 21 in accordance with the signal from the air-fuel ratio detector 50. To explain this operation in detail, when the control circuit 100 determines that the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine 40 is smaller than the appropriate air-fuel ratio, the air flow area of the auxiliary air passage 21 is increased; intake pipe 4
If the detected air-fuel ratio is larger than the appropriate air-fuel ratio, the amount of air added to the carburetor 10 becomes smaller, and the air-fuel mixture from the carburetor 10 with a relatively low air-fuel ratio increases. is controlled to an appropriate air-fuel ratio by adding an appropriate amount of air downstream of the throttle valve 14. In this way, by controlling the air-fuel mixture to a proper air-fuel ratio, harmful exhaust gases generated by the internal combustion engine 40 are reduced. Note that even when air is added to control the air-fuel mixture to a proper air-fuel ratio, if the opening degree of the throttle valve 14 is increased to increase engine output, the switch 71 of the intake pressure detector 70 will close. Therefore, the control circuit 100 drives the pulse motor 20 to reduce the opening degree of the bypass valve 21. Therefore, the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine 40 becomes smaller than the appropriate air-fuel ratio, and an increase in engine output can be achieved. Next, a second embodiment of the present invention will be described, focusing on the differences from the above-described first embodiment. In FIG. 4, 91 indicates the intake pipe 41 and the carburetor 1.
0, 92 is an excitation coil,
93 is an on-off valve, 94, 95, 98 are springs,
96 is a power piston, 97 is an on-off valve, and the fuel flow path area of the carburetor 10 is changed by changing the pressure introduced into the carburetor 10.
That is, when the excitation coil 92 is not energized,
Since intake pipe pressure is introduced into the carburetor 10 via the pressure passage 91, the on-off valve 97 is connected to the auxiliary jet 18.
is closed. On the other hand, when the excitation coil 92 is energized, the on-off valve 93 cuts off the intake pipe pressure and atmospheric pressure is introduced into the carburetor 10, so the power piston 96 presses the on-off valve 97 and turns off the auxiliary jet. Open 18. Therefore, if the excitation coil 92 is energized by the control circuit as in the first embodiment described above, the same operation as in the first embodiment can be achieved. Although the present invention has been described above with reference to embodiments, a thermocouple or a temperature switch may be used as the operating state detector 80, and the voltage generated by the air-fuel ratio detector 50 is compared with a set voltage to detect the air-fuel ratio. It is also possible to use a means for directly determining the operating state of the device 50 or a timer circuit instead. Further, in order to change the fuel flow path area of the carburetor 10, a bimetallic on-off valve, a wax expansion type on-off valve, or the like may be operated in accordance with the exhaust gas temperature. As described above, in the present invention, feedback correction is performed by adjusting the amount of auxiliary air that bypasses the throttle valve so that the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine with a normal carburetor becomes the set air-fuel ratio. In addition, when the internal combustion engine is under high load, the air-fuel ratio of the air-fuel mixture can be made sufficiently small by forcibly reducing the amount of auxiliary air and increasing the amount of fuel supplied to the carburetor. An excellent effect can be obtained in that the engine output can be effectively increased.

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram showing an example of a conventional air-fuel ratio correction device, FIG. 2 is a system configuration diagram showing a first embodiment of the present invention, and FIG. 3 is a system configuration diagram showing an example of a conventional air-fuel ratio correction device. FIG. 4 is a partial configuration diagram showing a second embodiment of the present invention. 10... Carburetor, 14... Throttle valve, 40... Internal combustion engine, 41... Intake pipe, 50... Air-fuel ratio detector, 7
0...Intake pressure detector forming a load detector, 100...Control circuit.

Claims (1)

[Claims] 1. A carburetor and a throttle valve provided on the intake pipe side of an internal combustion engine, an auxiliary air passage that bypasses these carburetors and throttle valves and supplies auxiliary air to the internal combustion engine, and an auxiliary air passage provided within this auxiliary air passage. a bypass valve that adjusts the amount of air passing therethrough; an air-fuel ratio detector that detects the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine; an operating means that operates the amount of fuel supplied to the carburetor; and a load condition of the internal combustion engine. a first control means that controls the bypass valve and adjusts the amount of auxiliary air according to the detection signal of the air-fuel ratio detector; When a load condition is detected, the adjustment operation by the first control means is invalidated to reduce the opening degree of the bypass valve, and
an air-fuel ratio auxiliary device for an internal combustion engine, comprising: second control means for controlling an increase in the amount of fuel supplied to the carburetor by driving the operating means;