JPH0526026B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a slow system fuel device for guiding fuel to an idle port and a slow port at a throttle valve in a carburetor.

[Conventional technology]

Conventionally, this type of slow system fuel system has been generally constructed such that it communicates with the float chamber via a main jet, as described in, for example, Japanese Utility Model Application No. 58-27556 and Japanese Utility Model Application Publication No. 60-122560. A hollow slow jet tube with a slow jet at the lower end is provided in the vertical passage connecting the horizontally extending fuel passage and the second slow passage to the idle port and the slow port, and the slow jet at the lower end is connected to the fuel passage. The slow jet tube is inserted so as to be open, and the slow jet tube is configured to regulate the amount of slow system fuel.

[Problem to be solved by the invention]

However, in this conventional slow system fuel system, when the temperature of the carburetor becomes high, evaporative fuel vapor is generated in the fuel passage that extends substantially horizontally so as to communicate with the float chamber via the main jet. When this vapor gathers and grows into large bubbles, and these large bubbles communicate with the slow jet at the lower end of the slow jet tube, the flow of fuel from the fuel passage to the slow system fuel passage temporarily ceases. As a result, the air-fuel ratio during idling between the internal combustion engines fluctuates, which in turn causes uneven rotation during idling between the internal combustion engines.

The present invention aims to solve this problem.

The inventors of the present invention have found that in order to solve the above problem, the amount of vapor that flows into the slow jet in the slow jet tube from the sideways fuel passage is as small as possible, and the vapor is made as fine as possible to pass through the slow jet. As a result of various researches, we have completed the present invention.

[Means to solve the problem]

That is, the present invention provides a hollow slow jet tube with a slow jet inside thereof in a vertical passage extending upward from a substantially horizontal fuel passage that communicates with the float chamber via a main jet. In the carburetor, the lower end of the slow jet tube is inserted into the slow system fuel passage leading to the idle port and the slow port, and the lower end thereof is inserted into the fuel passage so that the inside communicates with the fuel passage. Stand out,
This protruding portion is composed of a downwardly tapered conical portion and a small diameter portion extending downward from the conical portion.

[Effect]

Since the vapor generated in the fuel passage extending laterally collects on the ceiling part of the fuel passage, by protruding the lower end of the slow jet tube into the fuel passage as described above, the vapor can be removed from the fuel passage. Therefore, the amount of vapor flowing into the slow jet inside the slow jet tube can be reduced.

Further, according to experiments, when the protruding portion of the slow jet tube into the fuel passage is configured with a downwardly tapered conical portion and a small diameter portion extending downward from the conical portion, the fuel passage It is possible to make the vapor flowing into the slow jet in the slow jet tube finer, and to prevent the protrusion from obstructing the flow of fuel in the fuel passage. By protruding the lower end of the fuel passage, it was possible to avoid increasing the cross-sectional area of the fuel passage.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, reference numeral 1 indicates a carburetor main body, and the carburetor main body 1 is formed with an intake passage 2 and a float chamber 3. is provided with a throttle valve 4.

Reference numeral 5 designates a fuel passage extending substantially laterally so as to communicate with the float chamber 3 via the main jet 6. It communicates with a main nozzle 10 in the ventilate 9 in the passage 2.

Reference numeral 11 indicates a vertical passage extending upward from the fuel passage 5, and at the upper end of this vertical passage 11 there is a slow port 1 at the location of the throttle valve 4.
2 and the idle port 13, and a hollow slow jet tube 15 having a slow jet 16 inside is inserted into the vertical passage 11. The inside of the upper end of the tube 15 is connected to the slow system fuel passage 14, and the inside of the lower end is connected to the fuel passage 5.
are connected to each other.

A protrusion 17 into the fuel passage 5 is integrally formed at the lower end of the slow jet tube 15, and the protrusion 17 is tapered downward as shown in FIG. It is composed of a conical portion 17a and a small diameter portion 17b extending downward from the conical portion 17a.

The outer periphery of the slow jet tube 15 is covered with a tube 18 made of a heat-shrinkable synthetic resin that contracts with heat, a soft synthetic resin, a paper material, a rubber material, or the like. It is fitted. Further, reference numeral 19 indicates an air bleed to the slow type fuel passage 14.

Since the vapor generated in the fuel passage 5 extending laterally from the float chamber 3 gathers at the ceiling part of the fuel passage 5, as described above,
By integrally forming the protrusion 17 into the fuel passage 5 at the lower end of the slow jet tube 15, the amount of vapor flowing into the inside of the slow jet tube 15 can be reduced.
The lower end of fuel passage 5 can be made smaller than that in the case where the lower end of fuel passage 5 does not protrude into fuel passage 5.

In this case, a part of the vapor generated in the fuel passage 5 flows into the slow jet tube 15 and passes through the slow jet 16 in the slow jet tube 15, but according to experiments, The protruding portion 17 into the fuel passage 5 at the lower end of the slow jet tube 15 is a conical portion 17 that is tapered downward as described above.
a and a small diameter portion 17b extending downward from the conical portion 17a, vapor flowing into the slow jet tube 15 from within the fuel passage 5 can be prevented without inhibiting fuel leakage within the fuel passage 5. It was possible to make it finer and eliminate uneven rotation during idling operation in a high temperature range.

That is, according to experiments, even when the lower end of the slow jet tube 15 protrudes into the fuel passage 5, the protrusion into the fuel passage 5 is smaller than the cross-sectional area of the fuel passage 5 due to the protrusion. In order to avoid shrinkage, as shown in FIG.
As shown in Figure 5,
In the case where the conical portion 17d was used only, it was not possible to make the vapor fitting into the slow jet tube 15 finer, and uneven rotation occurred during idling operation in a high temperature range. A protrusion 17 formed on the lower end of 15
As described above, when the conical part 17a is tapered downward and the small diameter part 17b extends downward from the conical part 17a, the cross-sectional area of the fuel passage 5 due to the protruding part 17 is In a state where shrinkage is avoided, the vapor flowing into the slow jet tube 15 can be made finer, and uneven rotation during idling operation in a high temperature range can be reliably prevented.

Note that it is effective that the protrusion dimension H of the protruding portion 17 into the fuel passage 5 is 1/3 to 2/3 of the inner diameter D of the fuel passage 5, and the diameter d1 of the small diameter portion 17b is , slow jet tube 1
It was effective to set the diameter to 1/1.8 to 1/2.2 of the diameter d0 of 5.

〔Effect of the invention〕

Therefore, according to the present invention, it is possible to reliably prevent uneven rotation during idling operation at high temperatures, and at the same time, only a conical portion and a small diameter portion that protrude into the fuel passage are formed at the lower end of the slow jet tube. Since the structure is simple and there is no need to increase the cross-sectional area of the fuel passage, it can be provided at low cost and has the advantage of being applicable to existing carburetors.

[Brief explanation of the drawing]

1 to 3 show embodiments of the present invention;
The figure is a vertical sectional view of the main parts of the vaporizer, FIG. 2 is a sectional view taken from the side of FIG. FIG. DESCRIPTION OF SYMBOLS 1... Carburetor body, 2... Intake passage, 3... Float chamber, 4... Throttle valve, 5... Fuel passage, 6... Main jet, 11... Vertical passage, 1
2...Slow port, 13...Idle port,
14...Slow system fuel passage, 15...Slow jet tube, 16...Slow jet, 17...
...Protrusion part, 17a... Conical part, 17b... Small diameter part.

Claims (1)

[Claims] 1. A hollow slow jet tube with a slow jet inside is installed in a vertical passage extending upward from a substantially horizontal fuel passage that communicates with the float chamber via the main jet. In a carburetor that is inserted into a slow system fuel passage leading to a port and a slow port so that the inside of the lower end communicates with the fuel passage, the lower end of the slow jet tube protrudes into the fuel passage, and the lower end of the slow jet tube protrudes into the fuel passage. 1. A slow system fuel device in a carburetor, characterized in that the section is comprised of a downwardly tapered conical section and a small diameter section extending downward from the conical section.