JP2008069640A - All-purpose carburetor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure an excellent engine operation state without deteriorating exhaust gas, by uniformly maintaining a state of an air-fuel mixture supplied to an engine even in low speed operation, in a side draft type all-purpose carburetor. <P>SOLUTION: The side draft type all-purpose carburetor 1A is formed by suspending a main well 3A of arranging a main fuel passage 4A and a low speed fuel passage 5A in parallel in a constant fuel chamber 20A. A slow jet 52A of the low speed fuel passage 5A and a confluent part of a slow air bleed passage 11A and the low speed fuel passage 5A, are arranged in the main well 3A under an oil level L of the constant fuel chamber 20A. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a general carburetor disposed in an engine fuel supply system, and more particularly to a side draft type general carburetor having a sideways intake passage.

  A side draft type (horizontal type) general-purpose carburetor arranged in a fuel supply system such as a small gasoline engine has a configuration as shown in the longitudinal sectional view of FIG. 5, and includes a main body and a main well (columnar portion). In general, a die-cast metal such as aluminum is used for 3B. However, in the case of a metal die-cast molded product, a cast hole may be generated at the time of casting, and the passages may communicate with each other. Since aluminum and the like have high thermal conductivity, the main well 3B is heated when the engine is hot and the internal well 3B is heated. Vapor is generated in the fuel passage and the uniformity of the air-fuel mixture is lost, which adversely affects engine performance. For this reason, as described in Japanese Patent Application Laid-Open No. 2001-27156 and the like, a synthetic resin molded product having a low thermal conductivity and hardly causing a cast hole may be used for each component including the main well 3B.

  By the way, in such a general-purpose carburetor 1B, the flow rate of the fuel flowing into the vertical passage 51B from the constant fuel chamber 20B during low speed operation is adjusted by the slow jet 52B disposed on the upper side, and then the slow air bleed passage 11B merges with the air from 11B, is mixed in the lateral mixing passage 53B, and is sucked into the intake passage 2B through the slow port 54B disposed in proximity to the throttle valve 21a. A fuel passage 5B is formed.

  The mixing passage 53B of the low-speed fuel passage 5B is a mixture passage (mixing passage) because the slow port 54B and the slow air bleed passage 11B are disposed inside the intake pipe wall forming the intake passage 2B. ) Is very short, and is often supplied to the engine before the gas-liquid separation state is sufficiently resolved. Therefore, fuel atomization tends to be insufficient, and as shown in the graph of FIG. 4 showing the relationship between the CO concentration and the engine rotational speed during low-speed engine operation in a general-purpose carburetor formed similarly to the general-purpose carburetor 1B. When the engine speed is adjusted from the low rotation side to the high rotation side during low-speed operation, etc., a hysteris in the mixture state occurs between the return from the high rotation side to the low rotation side and the return Since the air-fuel mixture becomes lean on the side, the uniformity of the air-fuel mixture is difficult to be ensured, and the engine operation tends to malfunction.

In order to cope with this problem, it is common to set the base air-fuel mixture richly in consideration of this hysteris component. However, it is desirable to set it as lean as possible from the aspect of exhaust countermeasures corresponding to emission regulations and the like, and it is difficult to achieve both engine operability and exhaust countermeasures during low-speed operation.
JP 2001-27156 A

  The present invention is intended to solve the problems as described above, and for the side draft type general-purpose carburetor, so that the state of the air-fuel mixture supplied to the engine can be maintained even during low-speed operation, It is an object of the present invention to ensure a good engine operating state without causing deterioration of exhaust.

  In a side draft type general-purpose carburetor in which a main well provided with a main fuel passage and a low speed fuel passage in parallel is suspended in a constant fuel chamber, a slow jet and slow air bleed passage of the low speed fuel passage and the low speed fuel passage A junction with the fuel passage was provided in the main well below the oil level of the constant fuel chamber.

  In this way, by combining the slow jet / slow air bleed passage and the low-speed fuel passage at the joining portion below the oil level, the low-speed fuel passage has a long mixing passage leading to the slow air bleed passage and the slow port after joining. A sufficient distance for mixing the air and the air can be ensured, and sufficient atomization of the fuel can be realized, so that a good gas-liquid mixing state can be easily ensured even during low-speed operation.

  Also, this slow jet is provided in a tubular member with a fuel passage therethrough, an emulsion hole is drilled above the slow jet of the tubular member, and the air and fuel from the slow air bleed passage are mixed through this emulsion hole. If it does, it will become a thing which produces | generates a uniform air-fuel | gaseous mixture easily.

  Further, in the general-purpose carburetor described above, if at least the main well is made of a resin molded part, in addition to making it difficult to form a cast hole, it becomes difficult to be affected by engine heating, It becomes easy to avoid the generation of vapor.

  According to the present invention in which the junction of the slow jet / slow air bleed passage and the low speed fuel passage is arranged at the oil level of the constant fuel chamber, the state of the air-fuel mixture can be maintained in a uniform and good state even during low speed operation. Therefore, it is not necessary to make the base air-fuel mixture rich, and a good engine operating state can be secured without deteriorating exhaust.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a longitudinal sectional view of a general-purpose carburetor 1A according to the present embodiment. In the general-purpose carburetor 1A, an intake passage 2A arranged in a fuel supply system such as a small general-purpose engine has a sideways (side draft) type. A choke valve 20c, a main nozzle 20b, and a throttle valve 20a are arranged in the intake passage 2A penetrating the main body in the lateral direction from the inlet to the outlet, and the constant fuel chamber 20A is located below the main body. It has.

  The general-purpose carburetor 1A is provided with a low-speed fuel passage 5A that supplies fuel to the intake passage 2A during low-speed operation. The low-speed fuel passage 5A is arranged in parallel with the main nozzle 20b that constitutes the main fuel passage 4A. The vertical passage 51A for raising the fuel in the constant fuel chamber 20A to the main body, the mixing passage 53A formed by joining the vertical passage 51A to the slow air bleed passage (see FIG. 2), and the mixing passage 53A are connected to each other and the intake passage. And a slow port 54A that opens into 2A.

  In the present embodiment, the main well 3A provided with the main fuel passage 4A and the low speed fuel passage 5A is made of a resin molded part, and the low speed fuel passage viewed from the left side of the main well 3A in FIG. As shown in FIG. 2 which is an enlarged view of the 5A section, the slow jet 52A and the starting point of the mixing passage 53A formed by the combination of the slow air bleed passage 11A and the low speed fuel passage 5A are fixed in the main well 3A. It is characterized by being located below the oil level L of the fuel chamber 20A.

  That is, the columnar main well 3A suspended in the constant fuel chamber 20A is made of a resin molded product, so that the problem of the cast hole and the generation of fuel vapor that are likely to occur in the metal die cast molded product in the conventional example. In addition to this, in addition to this, in the vertical passage 51A of the low-speed fuel passage 5A provided in the main well 3A, a slow jet 52A is provided below the tubular member 55 through which the fuel passage has passed, The emulsion holes 55b, 55b penetrating from the outer surface of the tubular member 55 to the inside are drilled, and the slow air bleed passage 11A is connected to the vertical passage 51A on the side thereof, so that the mixing passage 54A is formed above this. This portion was positioned below the oil level L.

  As a result, the mixing passage 54A, which is a process of mixing fuel and air up to the slow port 54A, is greatly extended as compared with the conventional example, and fuel atomization is promoted to make the gas-liquid mixing state uniform and good. It becomes easy to maintain the state. Therefore, as shown in the graph of FIG. 3 showing the relationship between the CO concentration at the time of engine low speed operation and the engine speed by the general purpose carburetor having the same configuration as the general purpose carburetor 1A of the present embodiment, the mixing at the time of low speed operation is seen. Qi hysteris is reduced, and it is easy to ensure good engine operation.

  And since it is possible to maintain the uniformity of the air-fuel mixture supplied from the slow port 54A to the intake passage 2A by eliminating the hysteresis that is likely to occur during low speed operation, it becomes possible to set the base air-fuel mixture thinly. In addition to ensuring good engine drivability, it is extremely advantageous in terms of exhaust countermeasures.

  As described above, in the side draft type general-purpose carburetor, the present invention in which the mixing passage is significantly longer than the conventional one makes the state of the air-fuel mixture supplied to the engine even during low speed operation uniform. Thus, it is possible to maintain a good engine operating state without deteriorating exhaust.

The longitudinal cross-sectional view which shows embodiment of this invention. The expanded longitudinal cross-sectional view seen from the left side of the main well of the general purpose vaporizer of FIG. The graph which shows the relationship between the engine speed and CO density | concentration in the general purpose vaporizer of the structure similar to the general purpose vaporizer of FIG. The graph which shows the relationship between the engine speed and CO density | concentration in the general purpose vaporizer of the structure similar to the conventional general purpose vaporizer of FIG. The longitudinal cross-sectional view which shows a prior art example.

Explanation of symbols

1A General-purpose carburetor, 2A intake passage, 4A main fuel passage, 5A low speed fuel passage, 11A slow air bleed passage, 20A constant fuel chamber, 51A vertical passage, 52A slow jet, 53A mixing passage, 54A slow port, 55 tubular member, 55b Emulsion Hall

Claims (3)

  In a side draft type general-purpose carburetor in which a main well provided with a main fuel passage and a low speed fuel passage in parallel is suspended in a constant fuel chamber, a slow jet and slow air bleed passage of the low speed fuel passage and the low speed fuel passage A general-purpose carburetor characterized in that a junction with the fuel passage is provided in the main well below the oil level of the constant fuel chamber.   The slow jet is provided in a tubular member through which a fuel passage passes, and air and fuel from the slow air bleed passage are mixed through an emulsion hole formed above the slow jet of the tubular member. The general-purpose vaporizer according to claim 1. The general-purpose vaporizer according to claim 1, wherein at least the main well is a resin molded part.

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