JPS6237947Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a starting device for a carburetor that supplies a rich air-fuel mixture to an engine when the engine is started. The starting air mixture is mixed with the starting fuel controlled by the engine to form a starting air-fuel mixture, and a starting air passage that communicates the starting air-fuel mixture from a throttle valve to an intake duct on the engine side is opened by a starting on-off valve. The present invention therefore relates to a starting device for a carburetor that supplies this starting air-fuel mixture to an engine via an intake passage. According to such a conventional starting device, when the engine is started, the negative pressure generated in the intake passage on the side of the engine from the throttle valve acts on the starting fuel jet and the starting air jet through the starting mixture passage, thereby distributing the starting fuel and air. is sucked out and mixed to form a starting air-fuel mixture, and this starting air-fuel mixture is supplied into the intake tract. The concentration of this starting air-fuel mixture is determined by the negative pressure generated in the intake tract on the engine side from the throttle valve, and the greater the negative pressure, the more fuel and air will be sucked out, and the concentration of the air-fuel mixture will decrease. becomes richer, and on the other hand, if the negative pressure is small, the mixture concentration becomes thinner. Considering the relationship between the negative pressure in the intake tract downstream of the throttle valve and the engine ambient temperature when starting the engine, it can be seen that as the engine ambient temperature decreases, the viscosity of engine oil, etc. increases. Resistance inside the engine increases, and the cranking rotational speed of the engine in response to a starting operation decreases, and as a result, the negative pressure generated in the intake passage decreases as the engine ambient temperature decreases.
Due to this decrease in negative pressure in the intake tract, the concentration of the starting air-fuel mixture becomes thinner as described above, and even though it is desirable to supply a rich starting air-fuel mixture as the engine ambient temperature decreases, starting The concentration of the air-fuel mixture tends to be thinner, making it difficult to obtain good starting performance. The carburetor starting device of the present invention has been developed in view of the above points, and is capable of appropriately changing the starting mixture concentration according to changes in the engine ambient temperature, thereby achieving excellent starting performance. The goal is to provide equipment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a starting device for a carburetor according to the present invention will be described below with reference to the drawings. Reference numeral 1 denotes a carburetor main body through which an intake passage 2 passes, and a throttle valve 4 rotatably supported on a shaft 3 is disposed in the intake passage 2. A float chamber main body 5 is disposed at the lower end of the carburetor main body 1, thereby forming a float chamber 6. Inside this float chamber 6, a float 7, a float valve seat (not shown), and a float valve are constantly provided. A constant liquid level XX is formed.
A cylindrical valve chamber 8 is formed in the carburetor body 1, and a first starting air passage 9 that connects to the atmosphere opens laterally from the left side wall of the valve chamber 8, and the starting air-fuel mixture flows laterally from the right side wall. A passage 10 is opened, and the end of this starting mixture passage 10 is opened into the intake passage 2 downstream from the throttle valve 4 (on the right side in the figure). A series of starting fuel nozzles 12 are opened, and the starting fuel passage 11 is immersed below the constant liquid level of the starting fuel chamber 13 that communicates with the constant liquid level XX of the float chamber 6. A normally closed starting on/off valve 14 is arranged in the valve chamber 8 to open or close the starting fuel nozzle 12, the first starting air passage 9, and the starting mixture passage 10 that open into the valve chamber 8. The cylindrical side of the on-off valve controls the opening and closing of the first starting air passage 9 and the starting mixture passage 10, and the lower end of the starting on-off valve 14 controls the opening and closing of the starting fuel nozzle 12. In addition, 15 is a starting on-off valve 14
A spring is disposed above the starting on-off valve 14 and always presses the starting on-off valve 14 downward to keep the starting fuel nozzle 12, the first starting air passage 9, and the starting mixture passage 10 in a closed state. This is the operating lever that applies the opening force to the. The above is a conventionally known starting device for a carburetor, and the present invention adds the following structure to achieve the above object. That is, 20 is a second starting air passage whose one end branches from the first starting air passage 9 and whose other end opens into the starting fuel chamber 13;
A switching valve 21 is disposed in a branch path between the first and second starting air passages 9 and 20, and when the atmospheric opening 9A and the first starting air passage 9 communicate with each other, the switching valve 21 connects the atmospheric opening 9A and the second starting air passage 9. Shut off the starting air passage 20,
On the other hand, when the atmospheric opening 9A and the first starting air passage 9 are shut off, the atmospheric opening 9A and the second starting air passage 2
It communicates 0.

Next, its effect will be explained.

First, when the engine ambient temperature is at room temperature (for example, 10°C) or above, there is no need to supply a starting air-fuel mixture to start the engine, so the starting on-off valve 14 only needs to be in an inoperative state; The valve 14 is held in the state shown in the figure by the spring force of the spring 15, and the openings of the first starting air passage 9, starting fuel injection port 12, and starting mixture passage 10 to the valve chamber 8 are kept closed. It is something that Therefore, even if the negative pressure in the intake passage 2 on the downstream side of the throttle valve 4 acts on the starting mixture passage 10 in response to the engine starting operation, no starting mixture is sucked out, and the engine is not used normally. A suitable air-fuel mixture is supplied from a low-speed fuel system (not shown) to enable starting. Next, the engine ambient temperature is slightly low (for example -5℃)
To explain how to start the engine in a state where the temperature has decreased, first, when starting the engine, the starting on-off valve 14 is moved upward against the spring force of the spring 15, thereby opening the first starting air passage 9 to the valve chamber 8 and the starting fuel nozzle. 12. Maintaining the opening of the starting air mixture passage 10 in an open state and using the switching valve 21 to bring the first starting air passage 9 into communication with the atmosphere and keeping the second starting air passage 20 in a closed state. It is. When the engine is started in such a state, the negative pressure generated in the intake passage 2 on the downstream side of the throttle valve 4 is introduced into the valve chamber 8 through the starting mixture passage 10, and this negative pressure causes Then, starting air is taken in through the first starting air passage 9, and starting fuel is taken in from the starting fuel passage 11, and these are mixed in the valve chamber 8 to form a starting air-fuel mixture.
This is sucked out into the intake passage 2 through the starting air-fuel mixture passage 10, thereby supplying a starting air-fuel mixture commensurate with the low-temperature start and making it possible to start the engine.

Next, to explain about starting at an extremely low temperature (for example, -15°C) when the engine ambient temperature has further decreased, the starting on-off valve 14 is moved upward in the same way as described above, and each opening to the valve chamber 8 is opened. The switching valve 21 is held at 90 degrees counterclockwise to close the first starting air passage 9 to the atmosphere and to bring the second starting air passage 20 into communication with the atmosphere. When the engine is started in such a state, the negative pressure in the intake passage 2 on the downstream side of the throttle valve 4 is introduced into the valve chamber 8, as described above, but the first starting air passage 9 is connected to the switching valve 21. Since the valve chamber 8 is isolated from the atmosphere at the starting fuel nozzle 12, all of the negative pressure in the valve chamber 8 is introduced into the starting fuel chamber 13 through the starting fuel nozzle 12. According to this, while air is taken in from the second starting air passage 20, the fuel in the starting fuel chamber 8 is sucked out from the starting fuel passage 11 through the starting fuel nozzle 12 into the valve chamber 8. Since all the negative pressure acting inside has the effect of sucking out fuel from the starting fuel chamber 13, it is possible to supply a richer starting air-fuel mixture to the engine compared to the above-mentioned weak low temperature starting. This makes it possible to improve cryogenic startability.

Incidentally, after the engine has been started and the warm-up operation has been completed, it is sufficient to return the starting on-off valve 14 to its original position as in the conventional case. Further, in this embodiment, the second starting air passage 20 is branched from the first starting air passage 9, and the switching valve 21 is disposed in the branched path, but the first and second starting air passages are provided separately. A switching valve may be provided to open and close the passage. In addition, the first one by the switching valve 21,
By automatically controlling the opening and closing operations of the second starting air passages 9 and 20 using a thermally expandable material such as bimetal or wax, the starting operation can be automated.

As described above, the carburetor starting device according to the present invention has a valve chamber provided in the carburetor body, a first starting air passage whose one end is connected to the atmosphere, and a constant liquid level formed at one end in the float chamber. Opening a starting fuel passage that immerses into the starting fuel chamber connected below, and a starting mixture passage that has one end connected to the intake passage downstream of the throttle valve,
In a carburetor starting device that controls the supply of starting air-fuel mixture into the intake passage by opening and closing the opening of each passage to the valve chamber with a starting on-off valve disposed inside the valve chamber,
Opening a second starting air passage whose one end is connected to the atmosphere into the starting fuel chamber, opening one of the first and second starting air passages, and closing the other starting air passage. Since a switching valve is provided, when the engine is started, the engine ambient temperature is sensed and the opening/closing valve is controlled to open one of the first and second starting air passages and close the other passage. Therefore, the concentration of the starting mixture supplied into the intake passage through the starting mixture passage is increased at extremely low temperatures.
Since a relatively thin starting air-fuel mixture can be provided at slightly low temperatures, all starts from extremely low temperatures to slightly low temperatures can be performed extremely easily.

[Brief explanation of the drawing]

The figure is a longitudinal sectional view showing an embodiment of the carburetor starting device according to the present invention. 8... Valve chamber, 9... First starting air passage, 10...
...Starting mixture passage, 11...Starting fuel passage, 13
... Starting fuel chamber, 20 ... Second starting air passage, 2
1...Switching valve.

Claims (1)

[Claims for Utility Model Registration] A valve chamber 8 provided in the carburetor body 1 has a first starting air passage 9 connected to the atmosphere at one end, and a float chamber 6 at one end.
A starting fuel passage 11 that immerses into a starting fuel chamber 13 that is connected below a constant liquid level formed inside the engine, and a starting mixture passage 10 that is connected to the intake passage 2 downstream of the throttle valve 4 at one end. The passages 9, 10,
In a starting device for a carburetor that controls the supply of starting air-fuel mixture into the intake passage 2 by opening and closing an opening to the valve chamber 8 of 11 with a starting on-off valve 14 disposed in the valve chamber 8; A second starting air passage 20 into the starting fuel chamber 13 on the outer periphery of 11, one end of which is connected to the atmosphere.
at the same time as opening one of the first and second starting air passages 9 and 20,
A carburetor starting device comprising a switching valve 21 that closes the other starting air passage.