JPH0730351U - Air vent mechanism of circulating carburetor - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a circulation type carburetor capable of operating an engine even in a tilted posture and an inverted posture. [Structure] Fuel is sucked from a fuel tank 7 by a fuel pump 35 and supplied to a fuel chamber 16. When the oil level of the chamber reaches a predetermined height, the fuel overflows to form a constant oil level, and further from the chamber. In the circulation type vaporizer in which the overflowed fuel is returned to the fuel tank through the return passage 25, the fuel tank is communicated with the atmosphere only through the air vent passage 30 of the vaporizer.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an air vent mechanism for a circulation type carburetor used in portable small engines such as brush cutters, chain saws, and power sprayers.

[0002]

[Prior art]

 The circulating carburetor sucks fuel from the fuel tank by the fuel pump and supplies it to the fuel chamber, and when the oil level in the chamber reaches a predetermined height, the fuel overflows to form a constant oil level. The fuel that overflows from the tank is returned to the fuel tank through the return passage. The fuel chamber and fuel tank of the carburetor are equipped with air vents for introducing the atmosphere.

[0003]

[Problems of conventional technology]

 In general, a vaporizer is provided with the main nozzle nozzle at a certain distance above the oil level in the fuel chamber (hereinafter referred to as the head difference), and the intake negative pressure acting on the nozzle nozzle and the atmospheric pressure acting on the fuel chamber are The fuel is ejected from the nozzle by the pressure difference. However, in the above circulation type carburetor, when the engine is operated in the inverted posture as shown in FIG. 5, the carburetor and the air vent of the fuel tank 7 are blocked by the fuel. In this state, since the air vent Tb of the fuel tank is located above the air vent 30 of the carburetor, air is taken in from the air vent Tb side of this tank as the engine operates. In this case, since the air vent portion of the tank is at atmospheric pressure, a large amount of fuel pressure acts on the injection port of the main nozzle 20 of the carburetor located below by a head difference ht, and as a result, the main nozzle A large amount of fuel is ejected from the engine, causing engine malfunction or engine stall.

An object of the present invention is to provide an air vent mechanism of a circulation type carburetor capable of operating an engine even in an inclined posture and an inverted posture.

[0005]

[Technical means for solving problems]

 The present invention is characterized in that the fuel tank is connected to the atmosphere only through the air vent passage of the carburetor.

[0006]

[Action]

 According to the above configuration, the atmosphere acts only on the carburetor chamber and the fuel tank from the air vent passage of the carburetor, which has a small head difference from the main nozzle injection port, so the fuel jetted from the main nozzle even during the inverted operation. The amount is kept in the proper range. Therefore, the engine can be operated even in the inverted posture. Further, if the air vent passage of the carburetor is provided at a predetermined height from the injection port of the main nozzle, the injection port of the main nozzle is located above the action part of atmospheric pressure by a predetermined height during the inverted operation, so that it is more empty. The fuel ratio can be made close to that at the erecting.

[0007]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. 1 is a vertical cross-sectional view showing an embodiment of the air vent mechanism of the present invention, FIG. 2 is an explanatory view of a circulation type carburetor of the present invention, and FIG. 3 is a vertical cross-sectional view showing an inverted state of the air vent mechanism of the present invention. is there.

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 capable of advancing and retracting 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 a carburetor body 11 and a chamber case 15, and a main nozzle boss 17 is projected from the body 11 into the fuel chamber 16. . The main nozzle boss 17 is provided with a main nozzle accommodating hole 19, 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 lower surface of the fuel chamber 16 via the main jet 21. A jet needle 23 is suspended from the throttle valve 13, and the jet needle 23 is inserted into the main nozzle 20 to control the opening area of the main nozzle 20 as the throttle valve 13 moves back and forth.

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 automatically after the engine is stopped. Empty the fuel chamber 16.

The return passage 25 is connected to the fuel tank 7 via a return pipe 28, and an air vent passage 30 for introducing atmospheric pressure is opened in an upper air layer of the return passage 25. The air vent passage 30 is provided at a position higher by a distance h2 from the upper end opening of the main nozzle. The air vent passage 30 does not need to be provided above the main nozzle 20 injection port. If the air-fuel ratio during engine inversion operation falls within an appropriate range, it does not matter if it is located below, but basically it is not It is desirable that the head difference h2 be approximated to the head difference h1 in the upright state, and a better effect is expected by providing it above. An air vent pipe 31 is connected to the outer end of the air vent passage 30, and a tip opening thereof is arranged at the bottom of the fuel tank 7 so that fuel does not flow out from the air vent 30 when the engine is upside down.

The circulation type carburetor 6 is provided with a fuel pump 35 which is driven by the operating pressure of the engine. The fuel pump 35 is a conventionally well-known diaphragm pump composed of a pump diaphragm 36 and a pair of check valves 37 and 38. The fuel pump 35 applies an operating pressure of the engine to a pressure chamber 39 formed on one side of the pump diaphragm 36. By virtue of this, the pump diaphragm 36 is vibrated, and fuel is sucked from the fuel tank 7 through one check valve 37 into the pump chamber 40 formed on the other side of the pump diaphragm 36, and the other check valve 38. Is sent to the fuel chamber 16 via the fuel passage 41. 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 to form a constant oil level H.

A priming pump 43 that can be manually pressed is provided on the outer surface of the carburetor 6, and a pump chamber 44 of the pump is connected to a pump chamber 40 of a fuel pump 35. Therefore, when the priming pump 43 is repeatedly pressed, the fuel in the fuel tank 7 is supplied to the fuel chamber 16 in cooperation with the check valves 37 and 38 of the fuel pump 35.

The operation of the above embodiment will be described below. According to the above configuration, in the upright posture, the head difference h1 is formed between the defined oil surface H formed in the fuel chamber 16 and the injection port of the main nozzle 20, so that proper fuel is supplied. On the other hand, in the inverted posture, the distance h2 between the air vent 30 and the nozzle of the main nozzle is the head difference, and proper fuel is supplied even in the inverted posture. Further, by changing the height of the air vent, it is possible to adjust the head difference h2 when the head is inverted.

Further, when the return passage 25 is also used as the air vent of the fuel tank 7 and the introduction of the atmosphere into the tank becomes unstable, as shown in FIG. 4, the fuel tank 7 and the air vent passage 30 of the carburetor are shown. By installing the breather pipe 32 that communicates with, it is possible to stabilize the introduction of the atmosphere.

[0017]

[Effect of device]

 As described above in detail, according to the present invention, the fuel tank is configured to communicate with the atmosphere only through the air vent passage of the carburetor, so that the main nozzle injection port is provided in the carburetor chamber and the fuel tank. Since the atmosphere acts only from the air vent passage of the carburetor, which has a small head difference from the above, the amount of fuel ejected from the main nozzles is maintained in an appropriate range even during inverted operation, and the engine can be operated even in the inverted position.

Further, if the air vent passage of the carburetor is provided at a predetermined height from the injection port of the main nozzle, the injection port of the main nozzle is above the action part of atmospheric pressure by a predetermined height during the inverted operation. , Which is more effective because it can bring the air-fuel ratio closer to that at the upright position.

[Brief description of drawings]

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

FIG. 2 is an explanatory view showing a circulation type vaporizer of the present invention.

FIG. 3 is a vertical cross-sectional view showing an inverted state of the air vent mechanism of the present invention. .

FIG. 4 is a vertical cross-sectional view showing another embodiment of the air vent mechanism of the present invention.

FIG. 5 is a vertical cross-sectional view showing a conventional air vent mechanism.

[Explanation of symbols]

 6 Circulating Vaporizer 7 Fuel Tank 16 Fuel Chamber 20 Main Nozzle 25 Return Passage 26 Weir 30 Air Vent Passage

Claims (2)

[Scope of utility model registration request] 1. A fuel pump sucks fuel from a fuel tank and supplies it to a fuel chamber, and when the oil level in the chamber reaches a predetermined height, the fuel overflows to form a constant oil level, and further overflows from the chamber. In the circulation type vaporizer for returning the fuel to the fuel tank through the return passage, the fuel tank is communicated with the atmosphere only through the air vent passage of the vaporizer, and the air vent mechanism of the circulation type vaporizer. . 2. The air vent mechanism for a circulation type carburetor according to claim 1, wherein the air vent passage of the carburetor is provided at a predetermined height from the injection port of the main nozzle.