JPS6088857A - Plastic diaphragm type carburetter - Google Patents

Abstract

PURPOSE:To prevent vapor from generating in a metering chamber in a diaphragm type carburetter provided with a rotary throttle valve made of synthetic resin, by disposing a metallic material between the metering chamber and a throttle valve hole. CONSTITUTION:Fuel is fed from a nozzle 17 formed in the center section of a rotary throttle valve 14 which is provided in the upper section of a metering chamber 12 in a carburetter made of synthetic resin and having a diaphragm 7. A metallic member 20 is embedded between a throttle valve hole surrounding the throttle valve and the upper section of the metering chamber 12. With this arrangement, fuel sprayed from the nozzle 17 transmits its evaporating heat to the metallic member 20 so that the metering chamber which is liable to be heated is cooled to prevent the generation of vapor.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to solving thermal problems during hot restart of a rotary throttle valve type diaphragm type carburetor whose main body is formed of a heat insulating material such as a plastic material.

Since the diaphragm type carburetor can be operated in all directions, it can be installed on a 2-stroke engine that can also be operated in all directions.
Hand-held or backpack-type portable working machines, such as chainsaws,
It is widely known that it is used in brush cutters, pest control machines, blowers, etc.

Second-class portable work machines are easy to work with and have high efficiency, but they have recently become widespread, and they are also being used by workers who are relatively powerless, such as women and the elderly. Due to strong demand, lightweight plastic materials are used for some engine functional parts, including covers for work equipment, and recently, carburetors with diaphragm-type carburetor bodies molded from plastic materials are also being used. became. The advantages of using a plastic material for the carburetor body, compared to metal materials, are that it is lightweight and has heat insulation properties.

A diaphragm type carburetor is generally attached to a cylinder or crank chamber of an engine through seven insulated runs with a plurality of attachment screws. The plastic carburetor body has higher insulation properties than metal materials, so it absorbs less heat from engine heat and sunlight radiant heat, and the vaporizer temperature rises less, so less fuel paper is generated inside the vaporizer. In the early stages of operation, its high heat insulation properties are an advantage in stabilizing the performance of the carburetor.

However, after 5 to 20 minutes of stopping high-load operation or high-temperature operation for a long period of time, the engine's conductive heat, radiant heat,
The temperature of the vaporizer rises to the fuel evaporation temperature of approximately 45℃ due to the ambient heat, and paper forms in the fuel pool and fuel passages inside the vaporizer, making it difficult to restart or causing major problems such as unstable operation after restart. is a well-known place. In such a so-called hot restart, a choke valve or a primer pump is generally used to remove the paper before restarting.

In the case of a metal vaporizer, after restarting, the metal in the carburetor body is rapidly cooled by the latent heat of vaporization due to the vaporization of the fuel mixture, and the heat drops below the fuel evaporation temperature in a short time, so there is no occurrence of fuel paper in a short time. It is possible to restore normal operating conditions.

On the other hand, plastic vaporizers have poor thermal conductivity due to their insulation properties, and the heat drop due to the latent heat of vaporization of the air-fuel mixture is significantly slower than that of metals, causing the fuel in the vaporizer to drop below the evaporation temperature and generate paper. It takes a long time for the machine to stop, and during that time the operating condition becomes unstable and work may become impossible.

The present invention aims to solve this problem during hot restart.
The inner surface of the metering chamber, which has a large fuel reservoir volume, and the inner surface of the rotary throttle valve hole on the metering chamber side are connected with a metal material, and the latent heat of vaporization of the injected fuel is utilized to reduce the fuel in the metering chamber to below the evaporation temperature by utilizing the high thermal conductivity of metal. The purpose is to quickly cool down the fuel, prevent the occurrence of fuel paper, and restore normal operation quickly.

To explain the drawings, Fig. 1 is a longitudinal sectional view of the main part of the embodiment of the carburetor of the present invention at an intermediate opening of the rotary throttle valve;
The figure is a sectional view taken along the line AA in FIG.

Reference numeral 1 denotes a carburetor body made of a heat insulating material such as plastic, and an air cleaner (not shown) is attached to the top surface of the carburetor body, through which intake air is introduced in the direction shown by the circular arrow in the figure.

2 is the front wooden lid.

Fuel is supplied from the fuel tank 3 to the fuel pump 4 as shown in the system diagram.
The fuel is sucked in by the engine, and is force-fed to the inflow valve 6 through the fuel inlet 5 of the carburetor body 1.

7 is a metering diaphragm, 8 is a metering lever shaft, 9 is a metering lever, 10 is a metering lever spring, and 11 is a metering cover that communicates with the outside air. The metering chamber 12 inside the metering diaphragm is maintained at a capacity pressure by the metering diaphragm function during operation.

Reference numeral 13 denotes an intake air hole that penetrates the carburetor main body 1 back and forth, and the intake air hole 13 is opened and closed by rotation of a horizontal through hole 15 of a rotary throttle valve 14 parallel to the metering chamber 12.

A low-speed fuel metering rod valve 16 is screwed and fixed to the axis of the rotary throttle valve 14, and is inserted into the center hole of a fuel jet 17, which is press-fitted into the carburetor body 1 and communicated with the fuel in the metering chamber 12. ing. A fuel nozzle groove 18 opens toward the metering chamber 12 on the outer periphery of the fuel jet 17 in the axial direction, and the low-speed fuel metering rod valve 16 opens in the center hole of the fuel jet 17 according to the throttle valve opening degree of the rotary throttle valve 14. The opening area of the fuel nozzle groove 18 is increased or decreased to adjust the appropriate low-speed and medium-speed mixture. When the opening degree is high, the high speed fuel metering needle valve 19 adjusts to an appropriate high speed air-fuel mixture.

In the rotary throttle valve diaphragm type carburetor parallel to the metering chamber 12 as described above, the inner surface of the metering chamber side of the throttle valve hole corresponding to the horizontal through air hole 15 of the rotary throttle valve 14 and the inner surface of the metering chamber 12 are connected to each other. The metal material 20 to be connected,
It is characterized by being built into the vaporizer main body 1 which is made of a heat insulating material such as plastic material.

Since the present invention is configured in this way, the metering chamber 12
When the rotary throttle valve 14 is at an intermediate opening position, the fuel jetted from the fuel nozzle groove 18 that opens in the direction is injected onto the inner surface of the metering chamber side of the throttle valve hole as shown by the dotted line in the figure, and the latent heat of vaporization is absorbed by the high heat of the metal material 20. Due to thermal conductivity, the inner surface of the metering chamber 12 is rapidly cooled, and the large amount of fuel stored in the metering chamber 12 is rapidly cooled to below the evaporation temperature, thereby preventing repeated occurrence of fuel paper and achieving early recovery to normal operation.

By incorporating a metal material into a part of the carburetor body 1, the increase in weight is minimal, eliminating the instability of operation caused by repeated occurrence of papers after a hot restart without compromising the lightness that is a feature of plastic materials. It is possible to do so and has great industrial effects.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a main part of a carburetor according to an embodiment of the present invention at an intermediate opening of a rotary throttle valve, and FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1. patent applicant

Claims (1)

[Claims] A diamond structure in which a metal material 20 connecting the metering chamber side inner surface of the throttle hole of the rotary throttle valve 14 parallel to the metering chamber 12 and the inner surface of the metering chamber 12 is built into the carburetor main body 1 molded from a heat insulating material such as plastic. Plum type vaporizer.