JPS5844850B2 - Internal combustion engine air-fuel ratio adjustment device - Google Patents

Description

[Detailed description of the invention] The present invention relates to a power system for a carburetor of an internal combustion engine.

In order to increase the effectiveness of an exhaust gas purification system for an internal combustion engine, it is necessary to bring the air-fuel ratio supplied to the internal combustion engine closer to the stoichiometric air-fuel ratio by feeding back the sensing signal from the air-fuel ratio detector installed in the exhaust pipe. be.

For this purpose, conventionally, the air-fuel ratio supplied to the carburetor is set slightly richer than the stoichiometric air-fuel ratio (for example, A/F = 12 to 14), and the amount of diluted air for this is feedback-controlled by the sensing signal of the air-fuel ratio detector. Was.

However, in this case, for a certain period after the cold start, the air-fuel ratio detector did not function sufficiently due to the low exhaust temperature, making it impossible to feedback the dilution air amount.

In addition, in this case, considering that the catalyst used does not reach its activation temperature and that a small amount of nitrogen oxide NOx is generated during this period, the supplied air-fuel ratio is slightly leaner than the stoichiometric air-fuel ratio (for example, A/F = 15 ~ 17) It was necessary to set.

For this purpose, a certain temperature of the engine cooling water (e.g. 40°C) is required.
The air-fuel ratio characteristics had to be changed.

On the other hand, in order to perform more precise air-fuel ratio control after warm-up, it is preferable that the supplied air-fuel ratio be on the rich side close to the stoichiometric air-fuel ratio.

Particularly in a low air amount region, the supply air-fuel ratio tends to become extremely "rough" due to the slow flow rate of exhaust gas, so setting as described above is advantageous in terms of feedback control.

The sensing port in this conventional device is always located downstream of the throttle valve, and the water temperature is 40°.
Below, the power piston of the carburetor and the sensing port are electrically connected, resulting in a lean air-fuel ratio as shown by the broken line in Figure 2.
At 40 degrees or more, the power piston is exposed to the atmosphere, resulting in a rich air-fuel ratio as shown by the solid line in the figure.

When setting the air-fuel ratio to be richer than the stoichiometric air-fuel ratio in this state, as you can see from the figure, the air-fuel ratio is the leanest around -100 miHg, so if you adjust to this, the air-fuel ratio will become quite rich in the light load range (
For example, A/F=12-13).

The present invention was proposed in view of the above-mentioned problems, and provides a mixture close to the desired stoichiometric air-fuel ratio even in different regions of engine operation, thereby ensuring normal operation of the engine and taking measures against exhaust gas. An object of the present invention is to provide an air-fuel ratio adjustment device for an internal combustion engine that is effective.

The internal combustion engine air-fuel ratio adjustment device of the present invention includes a first sensing port that is located downstream of the throttle valve when the load is light and further upstream of the throttle valve when the throttle valve is open; A second sensing port is located downstream of the throttle valve, and a second sensing port is located in a pipe connecting each of the first and second sensing ports to the power piston of the carburetor. It consists of a switching three-way valve that selectively connects the second sensing port to the actuating part of the power piston when the temperature is below the set temperature, and the first sensing port when the temperature is above the set temperature.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of a carburetor equipped with an internal combustion engine air-fuel ratio adjustment device according to an embodiment of the present invention, and FIG. 3 is a graph showing intake pipe negative pressure and air-fuel ratio in a carburetor equipped with an air-fuel ratio adjustment device of the present invention. FIG.

The air-fuel ratio adjusting device of the present invention uses a throttle valve for light load of a conventional carburetor intake pipe consisting of a power piston 1, a first spring 2, a stopper 3, a second spring 4, a power valve 5, and a power jet 6. A first sensing port 7 is located on the downstream side of the throttle valve 10, and a first sensing port 7 is located on the upstream side of the throttle valve 10 when the throttle valve 10 is opened, and a first sensing port 7 is located on the downstream side of the throttle valve 10 at all times. a second sensing port 8 arranged;
These sensing ports 7.8 are arranged in a conduit connecting each of them to the actuating part of the power piston 10 of the carburetor,
The switch is made in response to a predetermined temperature of the cooling water of the internal combustion engine (40°C in this embodiment), and the second sensing port 8 is switched when the cooling water is below 40°C, and when it is above 40°C. consists of a temperature-sensitive three-way switching valve 9 that connects the first sensing 7 to the actuating part of the power piston 10 of the carburetor.

Next, vehicle equipment? The operation will be explained.

When the intake pipe negative pressure acts on the power piston 1, the negative pressure
The power piston 1 rises by overcoming the force of the spring 2, the power valve 5 is pushed up by the second spring 4, and the fuel from the power jet 6 is cut off.

On the contrary, if the negative pressure drops, fuel flows out from the power jet 6.

During a certain period of time after a cold start when the temperature of the cooling water of the internal combustion engine is below 40°C, the second sensing port 8 is in communication with the power piston 1, so the air-fuel ratio characteristics with respect to the negative pressure in the intake pipe are similar to those of the conventional one (Fig. 2). ) is the same as

When the temperature of the cooling water is 40° C. or higher, the first sensing port 7 is electrically connected to the power piston 1.

The light load range of the internal combustion engine (approximately -32
0 mmHg or less), the opening degree of the throttle valve 10 is small (solid line in the diagram), and the first sensing port 7 is located downstream of the intake pipe with respect to the throttle valve 10, so the air-fuel ratio is as shown by the solid line in Figure 3. characteristics, and the conventional (second
The air-fuel ratio will be leaner than in Figure).

Furthermore, when the throttle valve 10 opens (two-dot chain line) and the first sensing port 7 is located upstream of the throttle pulse 7'10, the negative pressure action of the intake pipe stops, the power piston 1 descends, and the power jet 6 is opened and the air-fuel ratio becomes rich as before.

According to the experimental results according to the embodiment of the present invention, the temperature of the cooling water at which the switching operation of the three-way switching valve 9 is performed is preferably about 40°C, and when the temperature exceeds this temperature, the air-fuel ratio varies from 2 to 2.5 compared to the conventional device.
can be limited to 1 to 1.5 or less, and the accuracy of feedback control has been greatly improved.

As described above, the internal combustion engine air-fuel ratio adjusting device according to the present invention maintains the supplied air-fuel mixture close to the stoichiometric air-fuel ratio over a wide range of operating ranges from low engine loads to high engine loads, thereby ensuring normal operation. It can show remarkable effects on exhaust gas control.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a carburetor equipped with an internal combustion engine air-fuel ratio adjustment device according to an embodiment of the present invention, FIG. 2 is a sectional view of a conventional carburetor, and FIG. FIG. 3 is a diagram showing the relationship between the intake pipe negative pressure of the engine and the air-fuel ratio. 1...Power piston, 2...First spring, 3...Stock spring, 4...Second spring, 5...Power valve , 6... power jet, 7... first sensing port, 8...
...Second sensing port, 9... Three-way switching valve, 10... Throttle valve.

Claims (1)

[Claims] 1. In a power system of a carburetor of an internal combustion engine, a first sensing port disposed at a position downstream of a throttle valve when the load is light and further upstream of the throttle valve when the throttle valve is opened;
A second sensing port is located downstream of the throttle valve, and a second sensing port is located in a conduit that connects the first and second sensing ports to the power piston of the carburetor. a three-way switching valve that selectively connects the second sensing port to the operating portion of the power piston when the temperature of the cooling water is below a predetermined temperature, and the first sensing port when the temperature is above the predetermined temperature; An internal combustion engine air-fuel ratio adjustment device comprising: