JPS6314177B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel supply system for an engine that uses a mixed fuel made by mixing alcohol and gasoline at a predetermined ratio.

Recently, due to the fuel situation such as soaring oil prices,
In many countries around the world, alcohol such as ethanol and methanol is added to gasoline at a specified ratio, e.g. 10 to 20%.
Consideration is being given to using the mixed fuel as automobile fuel (for example, see pages 787 and 788 of "Internal Combustion Engine Lectures" by Fujio Nagao, May 20, 1960, published by Yokendo Co., Ltd.) has been done, and in the future,
It is expected that the use of this mixed fuel will increase rapidly.

However, this type of mixed fuel has a problem in that gasoline and alcohol separate under certain conditions. In other words, a gasoline layer containing a large amount of gasoline and an alcohol layer containing a large amount of alcohol form an upper layer (gasoline layer) due to the difference in specific gravity of each layer.
There is a problem in that the mixture ratio of gasoline and alcohol is different between the upper layer and the lower layer.

Various factors can be considered to cause this separation of the mixed fuel, but it is mainly due to the moisture content or temperature of the mixed fuel.For example, alcohol, which is a part of the mixed fuel, has the property of absorbing moisture in the atmosphere. It is known that separation occurs when a certain amount of water is mixed into the mixed fuel, and the lower the temperature of the mixed fuel, the easier the separation is. The degree of separation also changes depending on the type of alcohol and gasoline and the mixing ratio of alcohol and gasoline. For example, regarding the type of alcohol, methanol is easier to separate than ethanol, and regarding the type of gasoline, aromatic Gasoline with fewer components is easier to separate, and with regard to the mixing ratio of alcohol and gasoline, the higher the mixing ratio of alcohol to the total mixed fuel, the easier it is to separate, and separation of this mixed fuel is unavoidable. It is something.

Separation of such a mixed fuel of alcohol and gasoline causes various problems in engine drivability.
In particular, if separation occurs in the float chamber of the carburetor, the mixing ratio of alcohol and gasoline supplied to the engine becomes uneven, making it difficult to operate the engine stably. In other words, when a separation phenomenon occurs in the mixed fuel in the float chamber of the carburetor, an alcohol layer with high specific gravity is formed below the float chamber, and a gasoline layer with low specific gravity is formed above. According to a conventional carburetor configured to open a supply port and supply fuel from the supply port to the intake passage via the fuel passage, the mixed fuel in the alcohol layer that is separated and forms the lower layer is separated. It is mainly supplied to the intake passage, that is, to the engine. Basically, alcohol has significantly different characteristics from gasoline in terms of calorific value, latent heat of vaporization, stoichiometric air-fuel ratio, etc., so if the alcohol ratio of the mixed fuel changes, the required air-fuel ratio will change accordingly. . Therefore, in a carburetor that is appropriately set for a mixed fuel made by mixing alcohol and gasoline at a certain predetermined ratio, the mixed fuel is separated in the float chamber as described above, and the alcohol component is lower than the predetermined ratio. If a mixed fuel with a significantly high alcohol content is supplied to the engine, the engine becomes unstable, and this deterioration becomes particularly noticeable during startup and in low-speed operating ranges.

The present invention aims to solve the above-mentioned problems, and therefore focuses on the fact that the driving range where the drivability deteriorates significantly due to the separation of the mixed fuel is when the engine is started and in the low rotational speed range. , so that the mixed fuel in the gasoline layer is supplied to the engine, and in a stable operating range that is not significantly affected by slight changes in fuel composition.
It is designed to supply mixed fuel of alcohol layer.

That is, since the above two operating ranges almost correspond to the operating ranges of the primary vaporizer and the secondary vaporizer of the multiple carburetor, the present invention provides the following:
A dual carburetor has a primary vaporizer and a secondary vaporizer, and operates the primary vaporizer during light loads, while operating the secondary vaporizer in addition to the primary vaporizer during high loads. The engine is equipped with a fuel mixture made by mixing alcohol and gasoline at a predetermined ratio, and is configured to supply a mixed fuel made by mixing alcohol and gasoline at a predetermined ratio from the same float chamber to a primary intake passage and a secondary intake passage through a primary fuel passage and a secondary fuel passage, respectively. In this fuel supply system, the float chamber side opening of the primary fuel passage is provided slightly above where the alcohol layer in the float chamber is located, and the float chamber side opening of the secondary fuel passage is provided at 1.
It is characterized in that it is provided near the bottom of the float chamber below the secondary fuel passage opening.

The present invention will be described in detail below based on embodiments shown in the drawings.

In the figure, 1 is a multiple vaporizer having a primary vaporizer 2 and a secondary vaporizer 3, and the primary vaporizer 2 is 1
It is formed from a secondary fuel passage 4 and a primary intake passage 5,
Similarly, the secondary vaporization device 3 is formed from a secondary fuel passage 6 and a secondary intake passage 7. Primary fuel passage 4
branches in the middle, and includes a primary main system fuel passage 10 consisting of a primary main air bleed 8 and a primary main nozzle 9, and a slow system fuel passage consisting of a slow jet 11, a slow air bleed 12, a slow port 13, and an idle port 14. The mixed fuel 17 of alcohol and gasoline in the float chamber 16 is supplied into the primary intake passage 5 through the respective passages. Similarly, the secondary fuel passage 6 also branches in the middle, and is connected to a secondary main system fuel passage 20 consisting of a secondary main air bleed 18 and a secondary main nozzle 19, and a step jet 21, a step air bleed 22, and a step port 23. The fuel mixture 17 in the float chamber 16 is divided into two step system fuel passages 24 through each passage.
It is supplied into the secondary intake passage 7. A primary main jet 25 and a secondary main jet 26 are provided at the openings of the primary fuel passages 4 and the secondary fuel passages 6 on the float chamber 16 side, that is, at the fuel supply ports of the two fuel passages, respectively. As is clear from the figure, the primary main jet 25 is located slightly above the alcohol layer 17a in the float chamber 16, while the secondary main jet 26 is located below the primary main jet 25 in the float chamber. It is provided near the bottom of 16. Note that 27 and 28 are a primary throttle valve, a choke valve, and
Reference numeral 29 denotes a secondary throttle valve installed in the secondary intake passage 7. This secondary throttle valve 29 is opened when the ventilator negative pressure generated in the intake passage is equal to or higher than a predetermined value, and is operated in a high-load operating range. This controls the amount of air-fuel mixture flowing in the secondary intake passage 7.

The operation of the above configuration will be explained. When the mixed fuel separates due to the above-mentioned factors such as when the vehicle is stopped at night, the mixed fuel 17 in the float chamber 16 is separated into a lower alcohol layer 17a and an upper gasoline layer 17b. Since the fuel supplied to the engine at the time of starting the engine or in the low rotational speed range is supplied from the primary intake passage 4 of the primary vaporizer 2, that is, the primary main jet 2 of the primary fuel passage 4
In this operating range, the mixed fuel 17 in the gasoline layer 17b containing a large amount of gasoline is supplied to the engine from the primary main jet 25 provided at the upper part of the float chamber 16, resulting in good startability. , driving performance in the low-speed operating range is achieved. On the other hand, the mixed fuel 17 in the alcohol layer 17a at the bottom of the float chamber 16 is transferred to the secondary main jet 26.
The fuel is supplied to the secondary intake passage 7 via the secondary fuel passage 6. In this case, the operating range in which fuel (air mixture) is supplied to the engine from this secondary intake passage 7 is a high-load operating range, and the engine rotation is relatively stable.
Even if the mixed fuel 17 of 7a is supplied, there is no major adverse effect on drivability (driving performance). Furthermore, if the alcohol layer 17a in the float chamber 16 is left alone, its level will gradually rise, and the
Although it reaches the next main jet 25 position, since the mixed fuel 17 of this alcohol layer 17a is supplied to the engine by the secondary vaporizer 3 in each operating range of the secondary vaporizer 3, it accumulates in the lower part of the float chamber 16. There is no need to provide a separate device for removing the mixed fuel 17 from the alcohol layer 17a. In this way, the fuel supplied to the engine at startup or in the low-speed operating range can always be the gasoline layer 17b containing a large amount of gasoline or the mixed fuel 17 at a predetermined ratio (when not separated).

The present invention can be better achieved by appropriately selecting the positions of the primary main jet 25 and the secondary main jet 26, taking into consideration the separation status of the mixed fuel 17 within the float chamber 16. Can be done.

As described above, the present invention provides a dual carburetor having a primary vaporizer and a secondary vaporizer, and supplies a mixed fuel of alcohol and gasoline.
By simply changing the opening position of the fuel passage on the float chamber side of each vaporizer, stable engine operability can be achieved when using mixed fuel, which is extremely effective.

[Brief explanation of the drawing]

The drawing is a sectional view of a main part showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Double carburetor, 2...Primary vaporizer, 3...Secondary vaporizer, 4...Primary fuel passage, 5...Primary intake passage, 6...Secondary fuel passage, 7...Secondary intake passage, 16
...Float chamber, 17...Mixed fuel, 17a...Alcohol layer, 17b...Gasoline layer, 25...Primary main jet, 26...Secondary main jet.

Claims (1)

[Claims] 1. A multiple carburetor that has a primary vaporizer and a secondary vaporizer, and operates the primary vaporizer during light loads, while operating the secondary vaporizer in addition to the primary vaporizer during high loads. A mixed fuel made by mixing alcohol and gasoline at a predetermined ratio is supplied from the same float chamber to the primary intake passage and the secondary intake passage through the primary fuel passage and the secondary fuel passage, respectively. In the engine fuel supply system, the float chamber side opening of the primary fuel passage is provided slightly above where the alcohol layer in the float chamber is located, and the float chamber side opening of the secondary fuel passage is provided in the primary fuel passage. A fuel supply device for an engine, characterized in that it is provided near the bottom of a float chamber below an opening.