JPH0221578Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an overrich prevention device for a compound type carburetor that prevents air vents from being blocked by fuel bubbles generated in a float chamber.

[Description of Prior Art] In the float chamber of a vaporizer, low boiling point components of fuel boil at high temperatures and bubbles are generated. When the fuel bubbles block the air vent, the pressure inside the float chamber increases, causing a large amount of bubbles to be discharged from the air vent or fuel to be discharged from the main nozzle. As a result, the air-fuel mixture became overrich, resulting in power loss or inoperability.

To overcome this drawback, for example, as shown in Utility Model Application Publication No. 59-76742, a scavenging passage is provided that communicates the ventilate part of the intake passage with the upper part of the float chamber, and air is flowed from the air vent via the float chamber. A scavenging flow of air is created from the scavenging passage to the ventilate, and this scavenging flow prevents the air vent from being blocked by fuel bubbles generated in the float chamber.It also takes low-temperature air into the float chamber from the air vent and uses it as the introduced air. Therefore, a configuration has been provided in which the inside of the float chamber is cooled to reduce the generation of fuel bubbles.

[Problems to be solved by the invention] However, this configuration is a single carburetor, and the air vent and the scavenging passage are always in communication with the float chamber, so no matter what operating conditions, there is no flow from the air vent to the float chamber. This causes a flow of scavenging air to reach the scavenging passage, and as a result, the air pressure in the float chamber becomes inconsistent. If the air pressure in the float chamber is not stable, there will be no problem in high-load operating ranges, but in low-load operating ranges where air/fuel efficiency adjustment is delicate, the desired air/fuel efficiency will not be obtained, and as a result, waste gas This resulted in a problem that the amount of nitrogen oxides inside increased.

In addition, in this configuration, the air vent and scavenging passage are always in communication with the float chamber, so when the engine is stopped at high temperatures, fuel vapor generated in the float chamber is discharged from the air vent and scavenging passage into the intake passage, resulting in fuel However, it is not possible to prevent the disadvantage that the engine starts after the engine starts.

[Purpose of the invention] The present invention has been made in view of the above points, and has the conventional advantage of preventing the air vent from being blocked by fuel bubbles by using the scavenging air flow introduced from the air vent, and also has the conventional advantage of preventing blockage of the air vent due to fuel bubbles. It is an object of the present invention to provide a compound type carburetor which eliminates the influence of scavenging air flow on waste gas by preventing the pressure in the float chamber from decreasing, and which also prevents fuel vapor from being discharged into the intake passage when the engine is stopped. It is something to do.

[Means for Solving the Problems] In order to achieve the above object, the present invention forms a communication chamber that communicates with the upper part of the float chamber in a compound type carburetor, and an air vent that communicates with the upstream side of the secondary intake passage. and a scavenging passage that opens to the ventilate of the secondary intake passage are communicated with the communication chamber,
The engine is equipped with a switching valve device that shuts off the float chamber and the communication chamber when the engine is stopped and communicates the float chamber and the communication chamber when the engine is running.

[First example] Next, the present invention will be explained based on the drawings.

The attached drawing is a sectional view showing an embodiment of the overrich prevention device for a compound type vaporizer according to the present invention. The compound type carburetor has a primary side intake passage, a secondary side intake passage 10, and a float chamber 12 (not shown). A ventilator 14 is formed in the middle of the secondary intake passage 10, and a throttle valve 16 is provided downstream of the ventilator 14. A communication chamber 18 communicating with the float chamber 12 is formed in the upper part of the float chamber 12, and an air vent 20 as an inner vent is formed in the communication chamber 18.
are being communicated. This communication chamber 18 also communicates with a scavenging passage 22 that opens into the ventilate 14 of the secondary intake passage 10 . A passage 26 serving as an outer vent communicating with the canister 24 is provided in the upper part of the float chamber 12 adjacent to the communication chamber 18 .

These communication rooms 18 and the float room 1 of the passage 26
2 is effected by a switching valve device 28 which is mainly operated by the manifold negative pressure in the primary intake passage. This switching valve device 28 communicates the float chamber 12 with the communication chamber 18 when the engine is operating, blocks off the float chamber 12 and the passage 26 during high-load operation, and communicates the float chamber 12 and the passage 26 when the engine is stopped. At the same time, the float chamber 12 and the communication chamber 18 are cut off. This switching valve device 28 includes a diaphragm 32 to which the valve body 30 is fixed to the tip of one side, a negative pressure chamber 34 and an atmospheric chamber 36 defined by the diaphragm 32, and a negative pressure chamber 34 of the diaphragm 32.
It consists of a magnetic body 38 fixed to the side, an electromagnetic coil 40 for attracting the magnetic body 38, and a spring 42 that always biases the diaphragm 32 toward the atmospheric chamber 36 side. The electromagnetic coil 40 is energized when the engine is operating and demagnetized when the engine is stopped. During high load operation, the diaphragm 32 closes to the negative pressure chamber 34.
The magnetic body 38 is set to be attracted to the electromagnetic coil 40 when the user approaches the side.

[Operation] In the above configuration, the electromagnetic coil 40 is excited during engine operation, and the negative pressure generated in the primary intake passage is introduced into the negative pressure chamber 34 of the switching valve device 28. When negative pressure is introduced into the negative pressure chamber 34, the diaphragm 32 is gradually drawn toward the negative pressure chamber 34, and the communication chamber 18, which had been blocked by the valve body 30, is communicated with the float chamber 12. . When the negative pressure increases in a high-load operating range, the diaphragm 32 approaches the electromagnetic coil 40, the magnetic body 38 is attracted to the electromagnetic coil 40, and the diaphragm 32 and the valve body 30 are kept at a fixed position, that is, in the communication chamber 18.
and the float chamber 12 are kept fully open. In this state, the float chamber 12 and the passage 26 are shut off by the valve body 30 (the state shown in the attached drawing). After the electromagnetic coil 40 attracts the magnetic body 38, even if the manifold negative pressure becomes small, such as when the engine is fully open and at low speed, the electromagnetic coil 40 will continue to attract the diaphragm 32 as long as the engine does not stop.
The valve body 30 is held at a fixed position, and the float chamber 12 and the communication chamber 18 are always kept fully open.

Next, when the engine is stopped, the electromagnetic coil 40 is demagnetized, the inside of the negative pressure chamber 34 becomes atmospheric pressure, the diaphragm 32 and the valve body 30 are moved to the right in the figure by the spring 42, and the valve body 30 , the float chamber 12 and the communication chamber 18 are separated from each other, while a passage 26 leading to the canister 24 is communicated with the float chamber 12 . That is, when the engine is stopped, the air vent 20 and the scavenging passage 22 are completely cut off from the float chamber 12.

As described above, in the present invention, when the engine is stopped, the air vent 20 and the scavenging passage 22 are completely cut off from the float chamber 12, and the upper part of the float chamber 12 is communicated with the canister 24, so that the high temperature condition is maintained. Fuel bubbles and fuel vapor generated in the float chamber 12 when the engine is stopped are absorbed by the canister 24. Therefore, fuel bubbles generated in the float chamber 12 may block the air vent 20 or cause the air vent 20 or the scavenging passage 2 to become clogged.
2, fuel vapor will not leak out into the intake passage. As a result, when the engine is restarted after being stopped at a high temperature, it is possible to prevent engine starting failure due to leakage of fuel vapor into the intake passage.

Furthermore, in the present invention, since the scavenging passage 22 is provided only in the secondary intake passage 10, negative pressure is not generated in the secondary intake passage 10 in a low load operating range where only the primary intake passage is used. , scavenging passage 22
No air flow occurs through the Therefore, in the low-load operating range, the air pressure in the float chamber 12 does not decrease or fluctuate, and problems such as those caused by an increase in nitrogen oxides in the exhaust gas do not occur as in the conventional system.

Thereafter, when the secondary side intake passage 10 operates in a high-load operation range, negative pressure is generated in the ventilator 14 and the negative pressure is introduced into the communication chamber 18. As a result, a scavenging air flow is generated from the air vent 20, passing through the communication chamber 18, passing through the scavenging passage 22, and reaching the vent uree 14 of the secondary intake passage 10.
This prevents blockage of the float chamber, and prevents overrichness that occurs when the internal pressure of the float chamber increases.

[Effect of the invention] As described above, according to the overrich prevention device for a compound type carburetor according to the invention, the communication chamber in which the air vent and the scavenging passage are opened and the upper part of the float chamber are communicated by the switching valve device. When the secondary intake passage is activated, the scavenging air flow prevents fuel bubbles from clogging the air vent and prevents overriching, and also blocks the air vent and scavenging passage from the float chamber when the engine is stopped. This prevents fuel from leaking into the intake passage, eliminating poor starting, and also prevents an increase in nitrogen oxides in the exhaust gas in a low-load operating range.

[Brief explanation of drawings]

The attached drawing is a sectional view showing an embodiment of the overrich prevention device for a compound type vaporizer according to the present invention. 10... Secondary intake passage, 12... Float chamber, 14... Bench lily, 18... Communication room, 2
0...Air vent, 22...Scavenging passage, 24...
Canister, 28... switching valve device, 30... valve body.

Claims (1)

[Scope of claim for utility model registration] (1) In a compound type carburetor having a primary side intake passage and a secondary side intake passage, a communication chamber communicating with the upper part of the float chamber is formed and communicates with the upstream side of the intake passage. A switching valve that communicates an air vent and a scavenging passage that opens to a ventilate of a secondary intake passage with the communication chamber, communicates the float chamber and the communication chamber when the engine is operating, and cuts off the communication chamber and the float chamber when the engine is stopped. An overrich prevention device for a compound type vaporizer, characterized in that it is equipped with a device. (2) A passage leading to the canister is provided in the upper part of the float chamber, and the switching valve device connects the float chamber and the canister passage when the engine is stopped, and blocks the float chamber and the canister passage when the engine is running. An overrich prevention device for a compound type vaporizer according to claim 1, which is a registered utility model.