KR840000831B1 - Apparatus for controlling air-fuel ratio for internal combustion engine - Google Patents

Abstract

An air-fuel ratio control apparatus for an internal combustion engine has a carburetor to control the air-fuel ratio of the fuel-air mixture supplied to the engine; a thermal reactor that causes the exhaust gas from the engine with secondary air supplied to the reactor; an oxygen sensor located in an exhaust gas passage between the reactor and three-way catalyst.

Description

Air-fuel ratio control device of internal combustion engine

1 is an overall schematic diagram of an air-fuel ratio control device according to an embodiment of the present invention.

FIG. 2 is a graph showing the characteristics of the negative pressure generator in the embodiment shown in FIG.

3 is a graph showing the characteristics of each actuator in the embodiment shown in FIG.

4 is a graph showing the characteristics of the internal combustion engine suitable for the air-fuel ratio control device of the present invention.

FIG. 5 is a graph showing the temporal change of the negative pressure at point A shown in FIG.

FIG. 6 is a graph showing the supply state of the air-fuel ratio of the mixer supplied to the internal combustion engine and the supply state of the secondary air amount from the air pump.

FIG. 7 is a graph showing the relationship between the rate of air detected by the O ₂ sensor and the amount of intake air in the embodiment of FIG. 1. FIG.

FIG. 8 is a block diagram showing details of the control circuit of the embodiment circuit shown in FIG.

FIG. 9 is a signal waveform diagram for explaining the operation of the circuit of FIG.

The present invention relates to an air-fuel ratio control apparatus for an internal combustion engine with a reactor for use in automobiles.

In order to purify the exhaust gas of an automobile engine, the engine provided with the reactor which adds air to the gas discharged from an engine and recombusts is used conventionally.

The engine to which the reactor is attached is designed to deepen the mixer supplied to the engine to a certain extent in the low speed rotation area of the engine to improve engine operation performance and to purify and reduce the final exhaust gas. However, this type of conventional device has not reached the extent to which the expected characteristics can be obtained. In particular, from the viewpoint of exhaust gas purification, it has a problem that it is difficult to operate stably at low intake volume. As such, there is a rotary engine as an engine for driving the mixer in the low speed rotation region of the engine.

The air-fuel ratio control method disclosed in U.S. Patent No. 3,827,237 controls the amount of secondary air at the reactor temperature and controls the amount of fuel supplied to the output of the O ₂ sensor, but the amount of secondary air controls the amount of fuel supplied. O without being controlled by the output of the _second sensor O ₂ sensor and the most suitable state according to the performance operation of the non-engine according to because it is controlled by the output of the sensor for detecting the temperature in a separate reactor, the intake side of the engine There is no guarantee that it will remain.

According to the present invention, by supplying a mixer having a higher concentration than the theoretical air-fuel ratio in the low speed rotation region, a reactor is provided to enable stable operation of the engine rotation in all the operating regions from low speed to high speed, and to exhaust the exhaust gas at all times. It is to provide an air-fuel ratio control device of an internal combustion engine. Its features include a vaporizer for controlling the air-fuel ratio of the mixer supplied to the engine, a reactor for mixing and reacting secondary air to the exhaust of the engine, and an exhaust path between the reactor and the three-way catalyst tube. An exhaust composition detector, a means for controlling the low speed fuel system and the main fuel system of the carburetor and a means for controlling the secondary air volume in response to the output signal of the exhaust composition detector, and the like to constantly control the exhaust composition flowing through the three-way catalyst pipe It is configured to

In FIG. 1, the engine 1 is operated by a mixer supplied from the vaporizer 2, but the air-fuel ratio of the mixer is controlled as follows. The carburetor 2 is provided with a low speed fuel system and a main fuel system, and the low speed fuel system has a low speed air bleed 15 and a low speed bleed (bypass) at the low speed injector 13. 14) is mixed with the air sucked in, the low-speed port 20 is supplied into the intake air. The fuel amount of this mixer is controlled by adjusting the opening area of the bypass low speed air bleed 14 by the low speed actuator 8 (AC ₁ ).

On the other hand, the main fuel system mixes the fuel improved in the main injector 11 and the bypass main injector 12 with the air sucked from the main air bleed 16 and supplies it to the intake air from the main nozzle 17. . The amount of fuel introduced from the main fuel system is controlled by adjusting the opening area of the bypass main injector 12 with the main actuator 10 (AC ₂ ). By changing the operating conditions of the engine 1, that is, the opening degree of the throttle valve 18, the air fuel ratio of the mixer which cooperates with the said main fuel system and the low speed fuel system to supply to the engine 1 is controlled.

The mixer supplied in this way is combusted in the engine 1 and then discharged to the thermal reactor 3.

The dewatering air of the air pump 19 which has passed through the secondary air actuator 9 (AC ₃ ) is supplied to the thermal reactor ₃ .

Therefore, by adjusting the opening area of the secondary air actuator 9, the amount of air supplied to the reactor 3 is controlled.

The composition of the exhaust gas reburned in the reactor 3 is detected by the O ₂ sensor 4 installed in the exhaust manifold 22 and discharged into the atmosphere via the three-way catalyst pipe 5.

The ternary catalyst tube 5 is filled with a ternary catalyst. This catalyst has a characteristic that the exhaust gas is best purified when the air-fuel ratio A / F of the mixer supplied to the engine 1 is a constant value (generally 14.7).

In other words, if the air-fuel ratio is controlled to make the exhaust composition in which the three-way catalyst exhibits the maximum efficiency, the harmful substances in the exhaust emitted can be minimized.

Therefore, by controlling the low speed actuator 8, the main actuator 10 and the secondary air actuator 9 of the vaporizer 2, the final exhaust composition can be made the most purified state in the low speed and high speed operation range. have. Next, the operation of these actuators will be described.

The signal of the O ₂ sensor 4 is input to and processed by the control circuit 6 to be described later, and the air-fuel ratio of the mixer supplied to the engine 1 is detected by detecting the oxygen concentration in the exhaust contacting the O ₂ sensor 4. The control signal is output to the negative pressure generator 7 so as to approach the target value. The negative pressure generator 7 generates negative pressure in proportion to the signal to operate the low speed actuator 8, the main actuator 10 and the secondary air actuator 9 to feed back the exhaust composition contacted with the O ₂ sensor 4. Doing. And the control circuit 6 is electrically connected with the throttle switch 21 which operates in the predetermined position of the throttle valve, and inputs the opening degree signal of the throttle valve 18, and responds to the change of an operation state. It is supposed to be.

2 is a diagram showing the characteristics of the negative pressure generator, the horizontal axis represents the ratio between the opening time t and the period T, and the vertical axis represents the generated negative pressure value as V _c .

The negative pressure generator 7 has an on / off valve 7A connected to a negative pressure source controlled to a constant negative pressure value.

The negative pressure source is known and is usually connected to the intake manifold old. By changing the ratio t / T (modification time ratio) between the opening time t and the period T of the on / off valve 7A, the low speed actuator 8, the main actuator 10 and the secondary are as described above. The negative pressure V _c supplied to the air actuator 9 is determined. The relationship between t / T and the negative pressure (V _c) as shown in Figure 2 is in inverse proportion relationship, in accordance with t / T grows V _c is reduced. That is, by controlling the opening / closing valve 7A of the negative pressure generator 7 according to the opening time ratio, an output matching signal in inverse proportion thereto is obtained. This negative pressure generator 7 is usually called a three-way solenoid valve device.

3 is a characteristic diagram of each actuator, in which the yellow axis represents the negative pressure V _c , and the vertical axis represents the opening area of each actuator. The right side on the horizontal axis shows a negative pressure close to vacuum.

AC ₁ is a characteristic of the low speed actuator 8, and as the negative pressure increases, that is, close to the vacuum direction, the opening displacement of the bypass low speed air bleed 14 is reduced in inverse proportion to the negative pressure. This works to increase the amount of fuel supplied from the low speed fuel system. AC ₂ is a characteristic of the main actuator 10, and when the negative pressure V _c becomes large, it acts to increase the opening area of the bi-cas main injector 12 to increase the amount of fuel supplied from the main fuel system.

AC ₃ is a characteristic of the secondary air actuator 9, which reduces the amount of air supplied to the reactor 3 in inverse proportion to the negative pressure up to a certain value of the negative pressure. That is, the actuators are diaphragm valves, but they vary the control direction depending on the direction.

It is known that such characteristics of each actuator are obtained by insulating the shape of the valve and the design of the elastic characteristics of the spring for pressing the valve. The fourth figure shows the operating characteristics of the engine of FIG. 1, where the horizontal axis represents the intake air amount Qair of the engine 1, and the vertical axis represents the excess air ratio? Of the mixer.

The engine 1 is in good operating condition when the air intake amount Qair is A or more when A is λ = 1 (14.7 in the air fuel ratio A / F). In the case of λ = 0.8, it has a property of being in a good operating state. Such engines include, for example, rotary engines.

In other words, this type of engine has been described as having a characteristic that the engine 1 will be in a proper operating state if the mixer is made to some extent at low speed.

The area where the air intake amount Qair is small is the area where the low speed actuator 8 predominantly changes the air-fuel ratio. In this case, as shown in FIG. 3, the low speed actuator 8 causes the bypass low speed air bleed 14 to The opening area is large. Therefore, considering the characteristics of FIG. 3, the amount of fuel supplied from the low-low fuel system can be thought of as small, but the opening area of AC ₁ at the negative pressure (V _cλ = 1) when λ = 1 is evaporated. The desired air-fuel ratio (e.g., lambda = 0.8) at this low speed is set. Therefore, a thick mixer can be supplied.

That is, the characteristic of the engine of FIG. 4 can be satisfied.

On the other hand, since the secondary air actuator 9 actually operates in the low negative pressure region as shown in FIG. 3, the amount of secondary air supplied to the reactor 3 is varied so that the O ₂ sensor ( The exhaust composition passing through 4) can be controlled so that λ = 1. In the state in which the air intake Qair of the engine 1 is large, the negative pressure V _c supplied from the negative pressure generator 7 is greater than or equal to V _b , so that the engine (by the low speed actuator AC ₁ and the main actuator AC ₂ ) The air-fuel ratio of the mixer supplied to 1) is controlled.

5 and 6 show temporal changes of the negative pressure V _{c at} point A of FIG.

The point A is detected by the throttle switch 21 of FIG. That is, since the throttle switch 21 is ON in the area | region whose air intake amount is less than A point, and it turns OFF in the big area | region, it turns ON and OFF at A point. Therefore, when the negative pressure changes instantaneously from the value of V _b , the air-fuel ratio of the mixer supplied to the engine 1 changes rapidly. This sudden change in air-fuel ratio deteriorates the riding comfort of the vehicle, so that there is a time delay to prevent this. This delay is obtained by aggravating the responsiveness of the negative pressure generator 7. That is, even if the on-off valve 7A changes abruptly, the change in the negative pressure V _c is alleviated.

The solid line of FIG. 5 is a case where the intake air quantity Qair increases from the point A of FIG. 4 to the point A or more, and the broken line has shown the opposite case.

It can be seen from the figure that the change in the negative pressure is gentle.

6A and 6B show the supply state of the air-fuel ratio of the mixer supplied to the engine and the supply state of the secondary intake air amount Qair from the air pump.

That is, when the low speed and the high speed driving state are changed, both the air-fuel ratio and the secondary air amount also have a time delay, i.e., change slowly.

FIG. 7 is a graph showing the relationship between the excess air detected by the O ₂ sensor (λ) and the intake air amount (Qair). As apparent from the figure, λ is substantially 1 in all the operating regions from low speed to high speed. It is being controlled back. Therefore, in this state, the three-way catalyst works most efficiently. As a result, the purification of the exhaust gas is optimal.

In the low speed region below the A point, as shown in FIG. 4, the fuel concentration of the mixer supplied to the engine is high. Therefore, the excess air ratio of the exhaust gas decreases, but in this case, since the secondary air amount is supplied in a large amount, the seventh downstream of the reactor Likewise, λ = 1 is maintained even below the A point.

8 is a view showing the details of the control circuit 6 shown in FIG. 1, in which the control circuit 6 for controlling the solenoid valve 7A of the negative pressure generator 7 has an output of the O ₂ sensor 4; An amplifier 30 for amplifying the amplifier, a comparator 32 for comparing the amplified output with a reference voltage, a proportional / integral control amplifier 34 for modulating the output of the comparator 32, When the oscillator 36 for generating a triangular wave of a predetermined frequency and the pulse generator 38 and the throttle switch 21 for generating a square wave of the same period T as the triangular wave are turned on, the output of the PI control amplifier 34 is predetermined. And an adder (i.e., level transfer) 40 for applying a voltage, an amplifier 42 for amplifying the output of the pulse generator 38, and the like.

The operation of the trout circuit 6 having such a configuration will be described below with reference to the waveform diagram of FIG.

As is well known, the output of the O ₂ sensor 4 installed in the exhaust manifold 22 is well known, and the output greatly differs around the theoretical performance ratio (i.e., about 14.7). Big and small in the above.

Therefore, it is possible to easily and accurately detected by comparing the actual performance output voltage and reference voltage of the non-theoretical air-fuel ratio greater than jakeunga the O ₂ sensor 4 is generated in the vaporizer (2) from the comparator 32. For example, when the actual air-fuel ratio is less than or equal to the theoretical air-fuel ratio, that is, when the output voltage of the O ₂ sensor 4 is equal to or greater than the reference voltage at the output shown by the solid line in FIG. As schematically shown by the dashed-dotted line in Fig. C, the amplitude is amplified continuously. When the throttle switch 21 is in the ON state, a predetermined voltage VD is applied by the adder (level converter) 40 so that the output of the PI control amplifier 34 is as shown by the solid line in Fig. 9B. do. The oscillator 36 generates a triangular wave (see FIG. 9D) that is continuous and of constant amplitude at a constant frequency to determine the period of the pulse generated by the pulse generator 38, but the angle of the burner to the pulse generator 38 The pulse width increases as shown in Fig. 9D while increasing the output amplitude of the adder 40, and decreases when the amplitude decreases. When each pulse as shown in FIG. 9E is applied to the excitation coil 7B for the magnetic valve via the amplifier 42, the solenoid valve 7A is close to the orifice 25. Therefore, as the opening time ratio t / T increases, the negative pressure V _c changes to become close to atmospheric pressure as shown in FIG.

When the O ₂ sensor fluctuates in a short period as shown by the dotted line in FIG. 9A (in this case, feedback control by the output of the O ₂ sensor is ideally operated) FIG. 9 (B As indicated by the dotted line, the voltage fluctuates with a very small amplitude centering on the output voltage Vλ = 1 (when the throttle switch 21 is ON) of the PI control amplifier 34 when λ = 1. . Similarly, when the throttle switch 21 is OFF, the voltage fluctuates small around the output voltage (V′λ = 1).

For example, now, when the detection signal of the O ₂ sensor 4 is close to the early air-fuel ratio (λ = 1), if the _stroke switch 21 is ON, that is, in the low speed region, the negative pressure is V _cλ as shown in FIG. It becomes a value of = 1, and when switch 21 is OFF, it becomes a value of _V'c ( _lambda) = 1.

The opening degree of the valve of the actuator at those negative pressures is as shown in FIG.

For example, in the low speed region in which the throttle switch 21 is ON, when the O ₂ sensor 4 issues a LEAN signal, the opening time ratio t / T decreases, so that the negative pressure V _c becomes large and AC ₁ , AC _3. The opening area of is small. On the other hand, the opening area of AC ₂ becomes large. As a result, the detection signal RICH of the O ₂ sensor 4 is obtained.

On the contrary, when the O ₂ sensor 4 issues a RICH signal, the opening areas of AC ₁ and AC ₃ become large and AC ₂ becomes small so that the detection signal of the O ₂ sensor 4 moves the air-fuel ratio (A / F) in the direction of LEAN. do. That is, normal feedback by the O ₂ sensor is operated to perform the air-fuel ratio control.

On the other hand, when the throttle switch 21 is OFF, the negative pressure value at the time of λ = 1 is V = _cλ 1~V 'standing merely be moved to _cλ = 1 its operation shall be determined by a third-degree characteristic.

The valves of the actuator AC ₃ are almost all closed at this time. The fluctuation range of the negative pressure is shown in FIG. 3 as ΔV (when the switch is ON) and ΔV ′ (when the switch is OFF). The values of ΔV and ΔV 'are ranges in which the output voltage of the PI control amplifier 34 changes. (See also FIGS. 9 (B) and (C).) In the low speed region in which the throttle switch 21 is ON, the opening displacements of AC ₁ and AC ₃ are turned on as compared with the case where the throttle switch 21 is OFF. That is, the low speed air bleed is in the LEAN state, and the secondary air is in a state in which there is a lot of supply. Therefore, it is thought that the fuel supply of the heavy furnace degree below the point A shown in FIG. 4 cannot be realized, but as described above, by setting the carburetor as follows, the engine of the dark engine in the low speed region as shown in FIG. It becomes possible to supply. That is, the opening area SAC ₁ of the actuator AC _{1 at the} negative pressure V _cλ = 1 provides a desired air-fuel ratio (eg, lambda = 0.8) at low speed.

In this case, when the throttle switch 21 is turned off, the opening area of AC ₁ is small, and the air-fuel ratio is small. Since the main fuel system (AC ₂ ) is dominant rather than the fuel system (AC ₁ ), even if the low speed fuel system is thickened, there is no significant effect, and the desired air-fuel ratio (λ = 1) can be maintained by setting the main fuel system as follows. have. That is, the actuator AC _{2 at the} negative pressure V _c lambda = 1 provides the desired air-fuel ratio (eg, lambda = 1) in the high speed region of the opening area SAC ₂ .

Since the control as described above, O ₂ sensor to the exhaust composition (4) the contact is able to be controlled constant without regard to the amount of intake air of the engine. The exhaust composition at this time can be controlled to be λ = 1. Also in the exhaust composition, the mixer supplied to the vaporizer 1 is dense in the low speed region of the low intake volume, and in the high speed region exceeding the A point, and has a standard air-fuel ratio. Proper condition is maintained. Secondary air is not supplied in the high speed region, and the low speed fuel system and the main fuel system operate together with a time delay near the point A.

As described above, the air-fuel ratio control device of the present embodiment controls the three diaphragm valves by the negative pressure generated in response to the signal of the O ₂ sensor which detects the exhaust composition after the thermal reactor 3. By controlling the amount of air, it is possible to purify the exhaust by adjusting the exhaust composition to fully demonstrate the capability of the three-way catalyst without deteriorating the operating state of the engine.

Claims (1)

A carburetor for controlling the air-fuel ratio of the mixer to be supplied to the internal combustion engine, including a low-speed fuel system and a main fuel system, a thermal reactor for supplying and reacting secondary air to the exhaust of the engine, and three sources connected to the thermal reactor An exhaust composition detector provided as exhaust between the catalyst tube and the thermal reactor and the three-way catalyst tube, a control circuit for outputting a control signal in response to an output signal from the detector, and a control signal from the control circuit Means for controlling the low-speed fuel system and the main fuel system, respectively, in response to the control signal; means for controlling the amount of secondary air in response to a control signal from the control circuit; and an output signal for changing the level of the control signal. An air-fuel ratio control apparatus for an internal combustion engine, comprising a detector for detecting a low speed and a high speed rotation area of the engine applied to the control circuit.

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