JPS6120284Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a device for controlling the air-fuel ratio of the intake air mixture to the engine in a carburetor of an internal combustion engine without impairing the cold start performance of the engine. .

In modern carburetors, depending on the negative pressure of the sensing port provided in the air introduction passage to one air bleed port in the main air bleed, at a location slightly upstream of the throttle valve closed position in the carburetor, An air-fuel ratio control valve that operates is provided, and the air-fuel ratio control valve is opened in a partial load region where the negative pressure of the sensing port is large, and air from the atmospheric side such as an air cleaner is introduced into the air bleed port. While controlling the air-fuel ratio to an appropriate level, the air-fuel ratio control valve is closed in the idling range to ensure stable idling.
In the full load range, the air-fuel ratio control valve is closed to control the output air-fuel ratio. However, the throttle valve of the carburetor is related to the throttle valve so that when the throttle valve is closed, it opens slightly to reach the fast idle opening, so when the throttle valve is closed when the engine is cold started, When the throttle valve opens to the first idle opening degree, negative pressure is generated at the appropriate location at the sensing port, and this negative pressure causes the air-fuel ratio control valve to open. Therefore, in the conventional air-fuel ratio control device, air from the clean side of the air cleaner is guided to the air bleed port by closing the choke valve.
Since the air-fuel ratio of the intake air mixture becomes lean, the effect of yoking is reduced, resulting in poor engine startability or the engine sometimes stopping after starting.

The present invention provides an air-fuel ratio control device of this type.
The above-mentioned drawbacks of the conventional system are solved by configuring the system so that air does not enter the air bleed port even if the air-fuel ratio control valve opens when the choke valve is closed.

Hereinafter, the drawings of the embodiment will be described. In the drawings, reference numeral 1 indicates a carburetor attached to an intake manfold (not shown) of an internal combustion engine, and an air cleaner 2 is attached to the upstream side of the carburetor. The carburetor 1 is equipped with a choke valve 5 at the upstream side of the ventilate 4 having the main nozzle 3, and a throttle valve 6 at the downstream side, and a main air bleed 9 in the main passage 8 leading from the float chamber 7 to the main nozzle 3. is equipped with a plurality of air bleed ports 10, 11, and 12.

Reference numeral 13 indicates a pressure-operated air-fuel ratio control valve. Valve chamber 14 with spring 18 inside
The pressure chamber 15 is connected via a passage 21 to a sensing port 20 provided in a portion of the carburetor 1 slightly upstream of the closed position (idle opening degree) of the throttle valve 6. On the other hand, the port 19 is connected to at least one arbitrary air bleed 12 among the air bleed ports 10, 11, and 12 via the air introduction passage 22, and the valve chamber 14 is connected to the air bleed port 12 in the vaporizer 1. It is connected to an atmospheric port 23 provided between the choke valve 5 and the ventilator 4 via an air introduction passage 24.

In this configuration, in an operating state in which the engine has warmed up to a predetermined temperature (normal operating temperature) (thus, the throttle valve 5 is open), and in a partial load region with the throttle valve 6 partially open, The negative pressure in the sensing port 20 increases, and this negative pressure is transmitted to the pressure chamber 15 of the air-fuel ratio control valve 13, and the valve body 1
Since port 7 opens port 19, air is introduced into air bleed port 12 from air introduction passages 22 and 24. As a result, the amount of fuel supplied from the main nozzle 3 is reduced by the amount of air that enters one air bleed port 12, so the air-fuel ratio of the intake air-fuel mixture is controlled to be slightly leaner than during idling operation. . Furthermore, in the full load range where the throttle valve 6 is fully open or close to fully open, the negative pressure at the sensing port 20 decreases to approximately atmospheric pressure, so the air-fuel ratio control valve 13 is closed and the air bleed port 12 is closed. Since the introduction of air into the engine is cut, the air-fuel ratio of the intake air-fuel mixture is controlled to an output air-fuel ratio that is suitably richer than the air-fuel ratio in the partial load range.

and cold start of the engine
When the check valve 5 is closed and started,
The throttle valve 6 reaches the first idle opening, the negative pressure at the sensing port 20 increases, and the air-fuel ratio control valve 13 opens.

In this case, when the inlet end of the air introduction passage 24 to the air bleed port 12 is connected to the atmosphere on the upstream side of the choke valve 5, such as on the clean side of the air cleaner 2, as in the conventional air-fuel ratio control device, A pressure difference is created between the inlet end of the atmosphere and the main nozzle 13, which becomes a negative pressure in the ventilate section 3. Due to this pressure difference, air is introduced into the air bleed port 12, and the air-fuel ratio is changed. However, in the present invention, the inlet end of the air introduction passage 24 is connected to the atmospheric port 23 provided between the choke valve 5 and the ventilator 4 in the carburetor 1 as described above. The pressure specific to the atmospheric port 23 is approximately the same as the negative pressure of the ventilate 4 when the intake air volume is throttled by closing the choke valve 5, and the pressure between the main nozzle 3 and Since the difference is small, even if the air-fuel ratio control valve 13 is open, the introduction of air to the air bleed port 12 is cut off. That is, when the check valve 5 is closed, the air bleed port 12
No air is introduced into the engine, preventing the intake mixture from becoming lean and keeping it relatively rich.

Therefore, according to the present invention, it is possible to prevent the air-fuel ratio from becoming lean when the choke valve is closed during a cold start of the engine without impairing the air-fuel ratio control in the operating range of the engine at a predetermined temperature. The engine has a good cold startability and can be started reliably and quickly, and also has the effect of reliably preventing the engine from stopping immediately after a cold start.

In addition, in a normal carburetor, the dimension between the chiyoke valve 5 and the ventilator 4 is narrow, so providing the atmospheric port 23 between them means that the atmospheric port 23 is close to the chiyoke valve 5,
There is a possibility that the pressure in the atmospheric port 23 becomes lower than the pressure in the main nozzle 3 under the influence of the negative pressure generated by the opening/closing movement of the main nozzle 3, and the fuel flows backward toward the atmospheric port 23. This problem can be solved by providing a check valve 25 in the air introduction passage 24 as shown in the figure.

[Brief explanation of the drawing]

The drawings are diagrams showing embodiments of the present invention. 1... Carburetor, 5... Chiyoke valve, 6... Throttle valve, 4... Ventilation, 3... Main nozzle, 9... Nine air bleed, 10, 11,
12... Air bleed port, 20... Sensing port, 13... Air-fuel ratio control valve, 22, 24...
...Air introduction passage, 23...Atmospheric port.

Claims (1)

[Scope of utility model registration request] A pressure-operated air-fuel ratio control valve is provided in the air introduction passage connected to the air bleed port in the main air bleed of the carburetor, and the pressure chamber in the air-fuel ratio control valve is set at a position slightly below the closed position of the throttle valve in the carburetor. In the air-fuel ratio control device, the air-fuel ratio control valve is connected to a sensing port provided on the upstream side so that the air-fuel ratio control valve opens when the negative pressure of the sensing port is large, and the inlet end of the air introduction passage is connected to the carburetor. An air-fuel ratio control device for a carburetor, characterized in that the air-fuel ratio control device is connected to an atmospheric port provided between a chiyoke valve and a ventilator.