JPH08151960A - Air vent mechanism for circulating carburetor - Google Patents

Abstract

PURPOSE: To prevent a leak of fuel from an air vent when a circulating carburetor is placed in an inclined/inverted attitude, further to make an engine operation capable when placed in the inclined/inverted attitude. CONSTITUTION: In an upper end of a return passage 25, the other end communicates with an air vent port 31 provided in an opposite side to the return passage 25 relating to the center of an intake air passage. An air vent passage 30 is opened. The highest level 30a of the air vent passage 30 is formed in a prescribed height from an upper end opening of a main nozzle. On the other hand, an air vent 35 of a fuel tank is connected to the air vent 30 of a carburetor, to connected to the air vent port 31 a point end opening 34a in a side of the return passage 25 relating to the center of the air intake passage, further to connected an air vent pipe 34 arranged in an outer side from the return passage 25. Further, the point end opening 34a of the air vent pipe 34 and the air vent 35 of the fuel tank are arranged in an opposite side to the carburetor relating to the center of the fuel tank in a direction of the intake air passage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air vent mechanism for a circulating carburetor used in portable small engines such as brush cutters, chain saws, power sprayers and the like.

[0002]

2. Description of the Related Art A circulation type vaporizer sucks fuel from a fuel tank by a fuel pump and supplies it to a fuel chamber. When the oil level in the chamber reaches a predetermined height, the fuel overflows to form a constant oil level. Moreover, the fuel overflowing from the chamber is returned to the fuel tank through the return passage. An air vent for introducing the atmosphere is provided in each of the fuel chamber and the fuel tank of the vaporizer. Each of the air vents is independently opened to the atmosphere, or the air vent of the carburetor is connected to the fuel tank and communicated with the atmosphere via the air vent of the tank.

[0003]

2. Description of the Related Art In a circulation type carburetor, an air vent passage 61 and a fuel tank 62 of the carburetor are connected by a return passage 63 as shown in FIG. The fuel may flow back from the tank 62 to the vaporizer, and the fuel may flow out from the air vent port 64 of the vaporizer.

Further, when both the air vent 65 and the return passage 63 of the fuel tank 62 are submerged in the fuel at the time of tilting, the inside of the fuel tank 62 becomes a hermetically sealed state, so that the inside of the fuel tank 62 is sucked as the fuel is sucked by the fuel pump. There is a drawback that the pressure gradually decreases and the amount of fuel to be fed by the fuel pump decreases.

Further, as shown in FIG. 8, when the engine is inverted while the engine is in operation, the air vents 61 and 65 of the carburetor and the fuel tank are under the fuel. In this case, the air vent of the fuel tank is used. Since 65 is located above the air vent 61 of the carburetor, air is sucked from the air vent 65 of the fuel tank as the engine operates. In this case, since the air vent 65 of the tank is at atmospheric pressure, fuel gravity acts on the main nozzle 66 of the carburetor located a distance ht below this, and as a result, a large amount of fuel is discharged from the main nozzle. Ejected, causing engine malfunction or engine stall.

The present invention provides an air vent mechanism for a circulation type carburetor that does not leak fuel from the air vents in the tilted posture and the inverted posture, operates well in the tilted posture, and can operate the engine even in the inverted posture. The purpose is to provide.

[0007]

According to the present invention, an air vent passage is opened in the upper portion of the return passage, the other end of which communicates with an air vent opening provided on the side opposite to the return passage with respect to the center of the intake passage. Along with forming the highest level of the air vent passage at a predetermined height from the nozzle of the fuel nozzle of the carburetor, further connecting the air vent of the fuel tank to the air vent of the carburetor, the air vent port of the carburetor is An air vent pipe having a tip opening arranged on the return passage side with respect to the center of the intake passage and outside the return passage is connected.

The above technical means is effective for the inclination around the intake passage of the carburetor, but the inclination in the intake passage direction is not taken into consideration. In order to improve the inclination in the intake passage direction, further, the other end opening of the pipe connected to the air vent port of the carburetor and the air vent of the fuel tank are connected to the carburetor with respect to the center of the fuel tank in the intake passage direction. It is installed on the opposite side of the installation side.

[0009]

According to the above construction, when the circulation type carburetor is tilted around the intake passage, one of the air vent port of the carburetor or the tip opening of the air vent pipe connected to the air vent port is located above the oil surface. Therefore, the fuel that flows backward from the fuel tank through the return passage does not flow out from the air vent. At the time of this inclination, either the return passage of the carburetor or the fuel tank side opening of the fuel tank air vent will be on the oil level, so the ventilation of the fuel tank will not be blocked and the vaporization by the fuel pump will not occur. Fuel is smoothly supplied to the vessel.

Furthermore, the other end opening of the air vent pipe connected to the air vent port of the carburetor and the air vent of the fuel tank are arranged on the side opposite to the installation side of the carburetor with respect to the center of the fuel tank in the direction of the intake passage. By doing so, even when the carburetor is inclined in the intake passage direction, one of the return passage side opening of the air vent passage of the carburetor or the air vent pipe tip opening is on the oil surface, and the fuel is prevented from flowing out. it can. Even during this tilt, either the return passage or the air vent of the fuel tank is on the oil level, so the ventilation of the fuel tank is not interrupted, and the fuel supply to the carburetor by the fuel pump is smooth. It is carried out.

Further, during the inverted operation, both the air vent of the carburetor and the air vent of the fuel tank are blocked with fuel, but when the pressure in the tank becomes negative due to the operation of the engine, air flows in from the air vent of the carburetor, and Air intermittently flows into the tank from the highest part of the air vent passage. As a result, since the highest pressure portion becomes atmospheric pressure, an appropriate head difference is formed between the fuel nozzle and the fuel nozzle injection port of the carburetor, and the amount of fuel ejected from the main nozzle is maintained in an appropriate range even during the inverted operation. Therefore, the engine can be operated even in this inverted posture.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a system explanatory view showing an embodiment of the air vent mechanism of the present invention, FIG. 2 is a system explanatory view taken along the arrow A in FIG. 1, and FIG.
FIG. 4 is an explanatory view of the system viewed from the direction of arrow B, FIG. 4 is an explanatory view of the circulation type carburetor of the present invention, FIG. 5 is an explanatory view showing an inverted state of the air vent mechanism of the present invention, and FIG. 6 is another embodiment of the air vent mechanism of the present invention. It is explanatory drawing which shows an example.

Reference numeral 1 denotes an engine body, which is composed of a cylinder block 2 and a crankcase 3. An intake port (not shown) is provided on the side wall of the cylinder block 2, and a circulation type carburetor 6 is attached to the intake port. Reference numeral 4 is an insulator interposed between the cylinder block 2 and the circulation type vaporizer 6. A fuel tank 7 is attached to the lower part of the crankcase 3.

An intake passage 12 is provided in the body 11 of the circulation type carburetor 6, the upstream side of the intake passage 12 is connected to an air cleaner (not shown), and the downstream side is connected to the intake port. A throttle valve 13 is provided in the intake passage 12 so as to be movable back and forth in a substantially orthogonal direction, and the effective diameter of the intake passage 12 is controlled.

A fuel chamber 16 is formed below the intake passage 12 by the carburetor body 11 and the chamber case 15, and a main nozzle boss 17 is projected from the body 11 into the fuel chamber 16. A main nozzle accommodating hole 19 is formed in the main nozzle boss 17, and the main nozzle 20 is accommodated in the accommodating hole 19 and is fixed by a main jet 21 screwed to the lower end of the boss 17. The upper end opening of the main nozzle 20 faces the intake passage 12, and the lower end opening communicates with the main jet 21 below the oil level of the fuel chamber 16. A jet needle 23 is suspended from the throttle valve 13. The jet needle 23 is inserted into the main nozzle 20 and controls the opening area of the main nozzle 20 as the throttle valve 13 advances and retracts.

A return passage 25 is provided at a side portion of the fuel chamber 16, and a weir 26 having a prescribed oil surface height is provided between them. A wire 27 is disposed between the fuel chamber 16 and the return passage 25. The wire 27 constantly discharges a small amount of fuel from the fuel chamber 16 to the return passage 25, and the fuel chamber 16 is automatically discharged after the engine is stopped. To empty.

The return passage 25 is the return pipe 2
An air vent passage 30 for introducing atmospheric pressure is opened in the upper air layer of the return passage 25 while being connected to the fuel tank 7 via 8. The air vent passage 30
The uppermost opening 30a of the main nozzle 20
It is provided at a predetermined height h2 from a, and the other end of the intake passage 12
It communicates with an air vent port 31 provided on the side opposite to the return passage 25 with respect to the center. The highest position 30a of the air vent passage 30 with respect to the main nozzle 20 is selected to have a height such that the air-fuel ratio during engine inversion operation falls within an appropriate range. It is desirable to approximate the head difference h1. A joint 33 is provided at the air vent port 31, and an air vent pipe 34 is connected to the joint 33. A tip opening 34a of the air vent pipe 34 is arranged on the return passage 25 side with respect to the center of the intake passage and outside the return passage 25. In addition, the air vent pipe 34
It is desirable that the tip opening 34a of the above is arranged downward so as to prevent the inflow of rainwater.

On the other hand, the fuel tank 7 has the intake passage 1
An air vent 35 is provided on the opposite side of the center Q from the return passage 25. The air vent 35 is connected to the air vent passage 30 of the carburetor or the upper air layer of the return passage 25 by a pipe 36. The pipe 36 may be connected to any position in the upper air layer of the air vent passage 30 or the return passage 25, but connecting the pipe 36 near the air vent port 31 improves the inclination around the intake passage 12. For example, as shown in FIG. 6, the air vent port 31 is provided with a two-port joint 37, and the air vent pipe 34 and the air vent pipe 3 of the fuel tank are provided in the joint 37.
If 6 is connected, even if the circulation type carburetor inclines to the vicinity of the overturn so that the return passage 25 is located downward with the intake passage 12 as the center, the air vent 35 of the fuel tank has the oil level S
Since the air vent 35 is above S and the air vent 35 is not blocked by the fuel, the fuel tank is not sealed.

The distribution of the air vents of the circulation type carburetor 6 and the fuel tank 7 is effective for the inclination of the carburetor around the intake passage 12, but the inclination in the intake passage 12 direction, particularly There is a problem with the orientation of the carburetor pointing downwards. To solve this, an air vent pipe 34 connected to the air vent port 31 of the vaporizer is further provided.
The other end opening 34a and the air vent 35 of the fuel tank 7.
Is disposed on the side opposite to the installation side of the carburetor with respect to the center R of the fuel tank 7 in the intake passage 12 direction.

In order to prevent the fuel from flowing out of the air vent pipe 34 in the inverted state, the tip opening 34a or the intermediate portion 34b of the air vent pipe 34 is provided.
Is arranged above the highest oil level in the fuel tank 7 when inverted. That is, when the circulating vaporizer is in the upright state, the air vent pipe 34 has a tip opening 34a or an intermediate portion 34b.
May be arranged near the bottom of the fuel tank.

The circulation type carburetor 6 is equipped with a fuel pump 40 driven by the operating pressure of the engine. The fuel pump 40 is a conventionally well-known diaphragm pump including a pump diaphragm 41 and a pair of check valves 42 and 43. The fuel pump 40 applies an operating pressure of the engine to a pressure chamber 44 formed on one side of the pump diaphragm 41. By virtue of this, the pump diaphragm 41 is vibrated, and fuel is pumped from the fuel tank 7 through the one check valve 42 to the pump chamber 45 formed on the other side of the pump diaphragm 41.
To the fuel chamber 16 from the other check valve 43 through the fuel passage 46. When the oil level in the fuel chamber 16 reaches the height of the weir 26, the fuel in the fuel chamber 16 overflows into the return passage 25 and forms a constant oil level H.

A priming pump 47 which can be manually pressed is provided on the outer surface of the carburetor 6, and a pump chamber 48 of the pump is connected to a pump chamber 45 of a fuel pump 40. Therefore, if the priming pump 47 is repeatedly pressed before starting, the check valves 42 and 43 of the fuel pump 40 are
The fuel in the fuel tank 7 is supplied to the fuel chamber 16 in cooperation with. Reference numeral 50 denotes a fuel inlet of a carburetor which communicates with the fuel pump 40. A fuel supply pipe 51 for inserting the tip side into the fuel tank 7 is connected to the inlet 50, and the tip of the pipe 51 is charged with fuel by its own weight. A fuel filter 52 that can move to a low position in the tank 7 is provided.

The operation of the above embodiment will be described below. According to the above configuration, when the circulation type carburetor is inclined around the intake passage 12, one of the air vent port 31 of the carburetor or one of the tip end openings 34a of the air vent pipes 34 connected to the air vent port 31 has an oil level. Since it is on the LL or MM, the fuel that flows backward from the fuel tank 7 through the return passage 25 does not flow out of the air vent pipe 34. Further, at the time of this inclination, either the air vent passage 30 of the carburetor or the air vent 35 of the fuel tank is on the oil level, so that the ventilation of the fuel tank 7 is not blocked, and the carburetor by the fuel pump 7 is not blocked. The fuel is smoothly supplied to. This inclination is improved as the connecting portion of the air vent pipe 30 of the fuel tank on the air vent passage 30 side of the vaporizer is brought closer to the air vent port 31.

Further, by disposing the tip opening of the air vent pipe 34 and the air vent 35 of the fuel tank on the side opposite to the installation side of the carburetor 6 with respect to the center R of the fuel tank 7 in the direction of the intake passage 12, Even when the carburetor 6 is inclined toward the intake passage 12, either the return passage 25 side opening of the air vent passage 30 of the carburetor or the tip opening 34a of the air vent pipe 34 is on the oil level NN or PP, It is possible to prevent the fuel from flowing out. Further, even during this inclination, either the air vent passage 30 of the carburetor or the air vent 35 of the fuel tank is on the oil level NN or PP, so that the ventilation of the fuel tank 7 is not interrupted and the fuel pump 40 The fuel is smoothly supplied to the carburetor.

During the inverted operation, the fuel tank 7 is located above the circulation type carburetor 6 as shown in FIG. 5, so that both the air vent 30 of the carburetor and the air vent 35 of the fuel tank are blocked with fuel. When the pressure in the tank 7 becomes negative as the engine operates, air flows in from the air vent 30 of the carburetor, and intermittently flows in the tank 7 from the highest portion 30a of the air vent passage 30. As a result, the highest part 30a becomes atmospheric pressure, so that the fuel nozzle 20 of the vaporizer
An appropriate head difference h2 is formed between the nozzle hole 20a of
Even during the inverted operation, the amount of fuel ejected from the main nozzle 20 is kept within an appropriate range. Therefore, the engine can be operated even in this inverted posture.

[0026]

As described in detail above, according to the present invention, fuel does not leak from the air vent pipe of the carburetor in the tilted posture and the inverted posture, so that the engine equipped with the circulation type carburetor is tilted in any direction. Can be made.

Further, since the air vent of the fuel tank is not closed by the fuel in the tilted posture, the tank is not closed and the discharge performance of the fuel pump is not deteriorated. The engine can be operated satisfactorily.

Further, in the inverted posture, the highest part of the air vent passage of the carburetor becomes atmospheric pressure, and a proper head difference is formed between the nozzle of the main nozzle and the jet nozzle of the main nozzle. It will be possible.

[Brief description of drawings]

FIG. 1 is a system explanatory view showing an embodiment of an air vent mechanism of the present invention.

FIG. 2 is an explanatory diagram of a system in the direction of arrow A in FIG.

FIG. 3 is an explanatory diagram of a system as viewed in the direction of arrow B in FIG.

FIG. 4 is a vertical sectional view of a circulation type vaporizer of the present invention.

FIG. 5 is an explanatory view showing an inverted state of the air vent mechanism of the present invention.

FIG. 6 is an explanatory view showing another embodiment of the air vent mechanism of the present invention.

FIG. 7 is an explanatory view showing a tilted state of the conventional air vent mechanism in the intake passage direction.

FIG. 8 is an explanatory view showing an inverted state of a conventional air vent mechanism.

[Explanation of Codes] 6 Circulating Vaporizer 7 Fuel Tank 6 Circulating Vaporizer 16 Fuel Chamber 20 Main Nozzle 25 Return Passage 26 Weir 28 Return Pipe 30 Air Vent Passage 31 Air Vent Port 34 Air Vent Pipe 35 Fuel Tank Air Vent 36 Fuel Tank Air vent pipe

Claims (3)

[Claims] 1. A fuel tank is provided on the lower side, and the fuel in the fuel tank is supplied to a fuel chamber by a fuel pump. When the oil level in the chamber reaches a predetermined height, the fuel overflows to a constant oil level. In a circulatory carburetor that forms a surface and returns the fuel overflowing from the chamber to the fuel tank via a return passage provided at a side portion of the chamber, above the return passage,
The other end communicates with the air vent port provided on the side opposite to the return passage with respect to the center of the intake passage, opens the air vent passage, and sets the highest position of the air vent passage to a predetermined height from the upper end opening of the main nozzle of the carburetor. Formed, further connecting the air vent of the fuel tank to the air vent of the carburetor, the air vent port of the carburetor,
An air vent mechanism for a circulation type carburetor, characterized in that an air vent pipe having a tip opening located on the return passage side with respect to the center of the intake passage and outside the return passage is connected. 2. A tip end opening of an air vent pipe, one end of which is connected to an air vent opening of the carburetor, and an air vent of the fuel tank are opposite to a carburetor installation side with respect to a center of the fuel tank in the intake passage direction. The air vent mechanism of the circulating carburetor according to claim 1, wherein the air vent mechanism is provided in 3. The air vent mechanism for a circulating carburetor according to claim 1, wherein a tip opening or an intermediate portion of the air vent pipe is arranged near a bottom portion of the fuel tank.