JPS5924267B2 - Air-fuel ratio control device for internal combustion engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control device for an internal combustion engine that controls the air-fuel ratio of an air-fuel mixture by supplying additional air into an intake pipe of an internal combustion engine equipped with a carburetor.

In general, the load on the internal combustion engine and the air-fuel ratio A/F, which causes torque fluctuations due to improper combustion, misfires, etc., have a relationship as shown by curve a in Figure 1, and the rotational speed N of the internal combustion engine and the air-fuel ratio A/F, which causes torque fluctuations. The air-fuel ratio A/F has a relationship as shown in FIG.

Therefore, in order to prevent torque fluctuations, the air-fuel ratio of the mixture supplied from the carburetor is adjusted, for example, by the broken line b in FIG.
It is desirable to control as shown in y ct d.

However, with conventional carburetors, the air-fuel ratio of the air-fuel mixture can only be adjusted to a nearly constant level, so if, for example, the air-fuel ratio is set near point A in Figure 1 in consideration of fuel efficiency and exhaust gas purification, the load will increase. Torque fluctuations occur in light areas.

Therefore, the air-fuel ratio had to be set in a region near point B, which is inferior in terms of fuel efficiency and exhaust gas purification.

In this way, conventional carburetors are limited in the setting of the air-fuel ratio and cannot control the air-fuel ratio over a wide range of air-fuel ratios of 15 to 20. Furthermore, it is not possible to control the air-fuel ratio over a wide range of air-fuel ratios of 15 to 20. Setting was not possible.

The present invention has been made in view of the above points, and its purpose is to perform air-fuel ratio control using additional air, and use a comparison control valve to provide negative pressure representing the amount of intake air and negative pressure representing the amount of additional air. By controlling the amount of additional air while comparing the combined pressure of intake air and intake negative pressure, it is possible to control the air-fuel ratio with high precision over a wide range, and the air-fuel ratio can be corrected depending on the load and rotation speed. An object of the present invention is to provide an air-fuel ratio control device.

The present invention will be described below with reference to embodiments shown in the drawings.

In FIG. 3, reference numeral 1 denotes an ordinary four-stroke spark ignition internal combustion engine, and its intake system is provided with an intake pipe 2, and its exhaust system is provided with an exhaust pipe 3.

A carburetor 4 is connected to the intake pipe 2 and supplies air-fuel mixture to the engine 1.

This carburetor 4 is a normal one that mixes clean air from an air filter 5 with fuel, and includes a venturi 6, a fuel nozzle 7 that spouts fuel, and a throttle valve that can be operated arbitrarily to adjust the amount of intake air. It has 8.

The auxiliary intake pipe 10 is for supplying additional air to control the air-fuel ratio of the air-fuel mixture, and has one end connected to the air filter 5 and the other end connected to the intake pipe 2 downstream of the throttle valve 8.
It is provided so as to bypass the fuel nozzle 7 and throttle valve 8 of the carburetor 2.

This auxiliary intake pipe 10 is provided with a venturi 11 to measure the additional air flowing therethrough, and an additional air control valve 20 is provided downstream of the venturi to control the amount of additional air in accordance with a pressure signal. be.

This additional air control valve 20 swings a diaphragm in response to a pressure signal, thereby opening and closing the butterfly valve 21. Two pressure chambers 23 and 24 are formed by the cage jig and the diaphragm 22.

A pressure signal is guided to the pressure chamber 23, and the pressure chamber 24 is open to the atmosphere.

The butterfly valve 21 is rotatably provided in the sub-intake pipe 10 and is configured to form a variable throttle.

Further, the butterfly valve 21 is connected to the diaphragm 22 via a link mechanism 25 consisting of a shaft and a plate, and is driven to open and close in conjunction with the swinging of the diaphragm 22.

Note that a spring 26 is provided in the pressure chamber 23 so as to press the diaphragm 22, and urges the butterfly valve 21 in the valve closing direction.

The comparison control valve 30 is for generating a pressure signal to the additional air control valve 20, and has a housing 31 divided into three parts.
Two diaphragms 32 and 33 sandwiched between the housing 31 form three pressure chambers 34, 35, and 36.

The first pressure chamber 34 is connected to the aperture 11 through the pipe 51.
It is connected to the throat, from which a negative pressure signal, ie a pressure signal representing the additional air volume, is led.

Further, the pipe 51 is connected to the intake pipe 2 through pipes 52, 53 and a throttle 54, and the pressure signal to the first pressure chamber 34 is bleed and adjusted by the intake negative pressure downstream of the throttle valve 8.

The second pressure chamber 35 is connected to the venturi 6 of the carburetor 4 through a pipe 55, and a negative pressure signal therein, that is, a pressure signal representing the amount of intake air, is guided.

The third pressure chamber 36 includes an air hole 3 provided in the housing 31.
7 to open to the atmosphere.

The two diaphragms 32, 33 are connected to each other by a shaft 38, and a valve body 39 is provided at the end of the shaft 38.
is fixed.

This valve body 39 is connected to a passage 40 formed in the housing 31.
The communication hole 41 that communicates the third pressure chamber 36 with the third pressure chamber 36 is opened and closed.

The channel 40 is connected on one side through a pipe 56 to the pressure chamber 23 of the additional air control valve 20 and on the other side through a pipe 53 to the intake pipe 2 downstream of the throttle valve 8;
The intake negative pressure in the intake pipe 2 is adjusted by the atmosphere guided from the communication hole 41 according to the opening and closing of the valve body 39 to generate a control pressure signal, which is applied to the additional air control valve 20.

In addition, since the diaphragm 33 is for sealing,
The pressure receiving area is smaller than that of the diaphragm 32.

In the above configuration, the carburetor 4 is set to generate a mixture slightly richer than the mixture required by the engine 1, and the intake air adjusted by the throttle valve 8 is mixed with fuel in the carburetor 4. The mixture is supplied to the engine 1, burned in the combustion chamber, and then released into the atmosphere as exhaust gas.

At this time, a venturi negative pressure of a magnitude related to the main intake air amount of the engine 1 is generated in the venturi 6 of the carburetor 4, as shown by equation (1), and the same is generated in the throttle 11 of the auxiliary intake pipe 10. As shown in equation (2), a negative pressure related to the amount of additional air passing through the sub-intake pipe 10 is generated.

Q1=CI AI J△P1 ・・・・・・(1
) Q2-C2A25 `` ...... (2) (where, Ql: Intake air amount, Q2: Additional air amount A1: Venturi area, A2: Area of throttle 11, △P1: Absolute venturi negative pressure Value, △P2: Absolute value of negative pressure of throttle 11,
C1y C2: flow coefficient) Then, the venturi negative pressure of the carburetor 4 and the negative pressure of the throttle 11 are compared by the comparison control valve 30, and a pressure signal adjusted accordingly is sent from the comparison control valve 30 to the additional air control. The additional air control valve 20 controls the sub-intake pipe 100 passage area so that the venturi negative pressure and the throttle 11 negative pressure are substantially proportional.

That is, when the amount of intake air increases and the venturi negative pressure increases, the valve body 39 of the comparison control valve 30 moves downward due to the differential pressure between the first and second pressure chambers 34 and 35, and moves from the communication hole 41 to the passage 40. The intake air negative pressure (pressure signal) applied to the pressure chamber 23 of the additional air control valve 20 is increased, thereby opening the butterfly valve 21 and increasing the amount of additional air.

Conversely, when the amount of intake air decreases and the venturi negative pressure decreases, the valve body 39 of the comparison control valve 30 closes in the first and second pressure chambers 34.
．． 35 moves upward and increases the amount of air flowing from the communication hole 41 to the passage 40, reducing the negative intake pressure applied to the pressure chamber 23 of the additional air control valve 20, thereby closing the butterfly valve 21. direction to reduce the amount of additional air.

Further, when the amount of additional air increases and the negative pressure of the throttle 11 becomes too large, the valve body 39 of the comparison control valve 30 moves upward due to the differential pressure between the first and second pressure chambers 34 and 35, and the communication hole 41
The amount of air flowing from the air to the passage 40 is increased, and the intake negative pressure applied to the pressure chamber 23 is decreased, thereby operating the butterfly valve 21 in the direction of closing, thereby reducing the amount of additional air.

Conversely, when the amount of additional air decreases and the negative pressure of the throttle 11 becomes too small, the comparison control valve 30 increases the intake negative pressure applied to the pressure chamber 23 and opens the butterfly valve 21 to increase the amount of additional air.

In this way, basically the comparison control valve 30
0 and △P2 are controlled so that they are proportional, and the sub-intake pipe 10
The additional air supplied from the pump is basically proportional to the amount of intake air as shown in equation (3).

Q2 = C2A2 a = K1Cl A1 u, =
KQ1 Between songs (3) (Here, C2A2 = KICIA1 t△P2= 2△
P1 has 1 J K,=to, and K, , has 2. is a constant of proportionality.

) Here, the intake negative pressure downstream of the throttle valve 8 is guided to the pipe 51 via the pipes 52, 53 and the throttle 54, and this corrects ΔP2, so the additional air amount Q2 is (4)
It becomes as shown by the formula.

1C1AIJ△P2- to Q2 = 3P = 1C1A1 JK2△P1- to 3P ... (4
) (Here, P is the intake negative pressure and K3 is the proportionality constant.

) In other words, the additional air amount Q2 is basically the intake air amount Q1.
, but is corrected by the intake negative pressure P downstream of the throttle valve 8.

The intake negative pressure P changes depending on the load and rotation speed of the internal combustion engine. For example, when the rotation speed is constant and the load is light, the intake negative pressure is large and the additional air amount Q2 is small, but as the load becomes heavier, the intake negative pressure increases. becomes smaller, and the additional air amount Q2 becomes larger.

In addition, when the load is constant, when the rotation speed is low, the intake negative pressure P is small and the additional air amount Q2 is small, and when the rotation speed is extremely high, the intake negative pressure becomes large and the additional air amount Q2 is large. Become.

Therefore, the ratio of the additional air amount Q2 to the intake air amount Q1 changes according to the intake negative pressure P, and the intake negative pressure P
When changing from 0 mmHg to -100 miHg, the air-fuel ratio A/F of the mixture supplied to the engine 1 changes from around 15 to around 20 using the rotation speed as a parameter.

When the intake negative pressure P changes from -1100m7XHg to atmospheric pressure, the intake air amount Q□ increases and the valve body 39 of the comparison control valve 30
However, since the intake negative pressure is also guided to the pressure chamber 23 of the additional air control valve 20, the valve 2 of the additional air control valve 20 closes.
5 is closed by the biasing force of the spring 26 as the intake negative pressure P becomes smaller, reducing the additional air amount Q2.

Therefore, the air-fuel ratio A/F of the air-fuel mixture changes from around 20 to around 15.

In this way, the air-fuel ratio A/F of the mixture is determined by the broken line in FIG.
The engine 1 is controlled as shown in c or d, and the engine 1 is operated with good fuel efficiency without causing torque fluctuation, and harmful components in the exhaust gas are also reduced.

Since the amount of additional air and the amount of intake air are kept in a proportional relationship, the air-fuel ratio A/F can be accurately controlled.

In the above embodiment, the negative pressure at the throat of the throttle 11 is used as a signal representing the amount of additional air, but the differential pressure across the throttle 110 may also be used.

In this case, since the pressure upstream of the throttle 11 is atmospheric pressure,
In particular, it is not necessary to introduce a negative pressure port 12 to the comparison control valve 30 downstream of the throttle 11, and connect this port 12 and the first pressure chamber 34 of the comparison control valve 30 with a pipe 55. .

As described above, according to the present invention, the air-fuel ratio of the air-fuel mixture supplied to the engine can be ideally controlled with a simple structure.
It has the excellent effects of preventing engine torque fluctuations, improving fuel efficiency, and reducing harmful exhaust gas components.

In addition, conventional carburetors require a large number of air passages such as a primary port, a secondary port, and an idle port, as well as a large number of fuel systems, but this can be simplified and has the effect of increasing productivity.

[Brief explanation of the drawing]

1 and 2 are graphs showing the relationship between load (intake negative pressure) rotational speed and air-fuel ratio, and FIG. 3 is a schematic diagram showing an embodiment of the present invention. 1... Internal combustion engine, 2... Intake pipe, 4... Carburetor,
6...Venturi, 10...Sub-intake pipe, 11...
Throttle, 20... Additional air control valve, 30... Comparison control valve, 54... Comparison.

Claims (1)

[Scope of Claims] 1. In an internal combustion engine in which an air-fuel mixture is supplied via an intake pipe by a carburetor, an auxiliary intake pipe for supplying additional air into the intake pipe, and a sub-intake pipe provided within the auxiliary intake pipe. an additional air control valve that is provided downstream of the throttle of the auxiliary intake pipe and controls the amount of additional air based on a pressure signal; and a venturi negative pressure of the carburetor that represents the amount of intake air taken in from the carburetor. Compares the negative pressure generated by the throttle representing the amount of additional air with the combined pressure of the negative pressure in the intake pipe led through other throttles, and adjusts the amount of air led from the intake pipe accordingly.Additional air control An internal combustion engine, comprising a comparison control valve for controlling negative pressure applied to the valve, and for controlling the air-fuel ratio of the air-fuel mixture with additional air controlled according to intake air amount, rotational speed, and load. air-fuel ratio control device. 2. The air-fuel ratio control device for an internal combustion engine according to claim 1, wherein the negative pressure representing the additional air amount is a negative pressure at a throat of the throttle.