JPS58126452A - Bistarter device of diaphragm carburetor - Google Patents

Abstract

PURPOSE:To improve startability in a carburetor for an all attitude operational engine used for a chain saw or the like, by providing a relief valve opened only at self powered rotation of the engine to an intake air passage in the front position of an opening and closing valve of a bistarter device. CONSTITUTION:Suction of fuel at least about 250mm. is ncessary in a diaphragm carburetor 1, at starting recoil, a relief valve 7 provided in an intake air passage 6 is closed to increase suction negative pressure, and only the fuel is sucked and jetted into a mixture passage, then initial explosion is promptly operated to also decrease a number of times of the recoil. Then at self powered operation after initial explosion, the valve 7 is opened to suck air into a bistarter, prevent overrichness of a mixture and smoothly continue a start. This starting mixture is directly introduced to a crank chamber 9 through a check valve 10 to enable the quick starting of a two-cycle engine. And if a bistarter opening and closing valve 5 is operated by an automatic valve of turning responsive valve or the like operated by pressure in a crank chamber, the starting can be automatically operated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a bistarter as a starting device for a diaphragm type carburetor.

Diaphragm type carburetors are widely used as carburetors for engines that operate in all positions, such as chainsaw brush cutters, but in order to support all-position operation, such engines use a fuel pump to vaporize from the bottom tank during operation. The fuel is pumped all the way to the
Maximum distance from tank to carburetor is approximately 150 in normal starting position.
There are suction heads before and after.

In addition, in order to prevent fuel from leaking from the fuel tank even during full-position operation, a check valve on the tank vent sets the pressure inside the tank to negative pressure, which is close to atmospheric pressure for operational performance. A desirable value is a negative pressure level.

Engines are designed to be lightweight and compact so that workers can easily operate the engine, so after the engine is stopped, the fuel in the fuel system, including the carburetor, is The fuel often evaporates into fuel vapor or bubbles, and the fuel tank often becomes empty and the engine stalls due to the focus on work.

In other words, the starting conditions are not only the temperature conditions such as air temperature and engine temperature as in a float type carburetor, but also the suction of a total of about 250 mm of negative pressure from the tank head and the tank interior, as described above, and the elimination of air bubbles on the way. There are also problems such as differences in suction performance due to various positions in which the carburetor is attached, and the starting position is not always correctly horizontal on slopes in mountains and forests.

In the case of a normal float type carburetor, the suction is about 20 mm head from the float chamber oil level to the fuel nozzle, and a diaphragm type carburetor needs to suck up about 10 times more fuel than a float type carburetor. Therein lies the problem of starting.

However, once the first explosion occurs (another word for the first starting explosion), the fuel pump also operates, so a starting mixture of the same level as a float type carburetor is required.

That is, it is desirable to suck up as much fuel as possible during starting recoil (usually below 1000 RPM), and after the first explosion, the mixture becomes the starting operation mixture.

Conventional bi-starter devices have been widely used in small float type carburetors such as motorcycles and general-purpose engines, but as mentioned above, the fuel suction of float type carburetors is small at about 20 millimeters, so starting recoil (or kick electric starter, etc.) is required. In this case, fuel and air are injected into the intake pipe as a mixture using a small carburetor. In order to prevent the engine from becoming too rich due to the high revolutions at the same time as the first explosion, the engine is equipped with a function to provide a proper starting operation air-fuel mixture through air bleed correction.

However, as mentioned above, a diaphragm type carburetor requires a suction of more than 250 millimeters, ten times as much as a float type carburetor, so during recoil, the intake air of the bistarter is shut off and the suction pressure is maintained high. If only the fuel is sucked up and ejected into the mixture passage, the initial explosion will be faster and the number of recoils will be reduced. Furthermore, during self-powered operation after the first explosion, the relief valve allows air to be sucked into the by-starter and prevents the mixture from becoming too rich, allowing smooth startup to continue.

In all-position operation engines, the 2-cycle engine is dedicated, and the crank chamber is also the mixture passage, so by providing a check valve that communicates with the bi-starter only when the crank chamber is under negative pressure, the starting mixture is converted to the bi-starter. It can be introduced more directly into the crank chamber, further speeding up the start.

In addition to the manual valve, the by-starter opening/closing valve can be operated automatically by using an automatic valve (for example, a rotary valve that converts the crank chamber pressure into pressure) to automate the start.

Referring to the drawings, 1 is a diaphragm type carburetor main body, 2 is a throttle valve, 3 is a metering diaphragm chamber, and 4 is a bistarter fuel nozzle which communicates with the metering diaphragm chamber 3. 5 is a by-starter on-off valve that automatically or manually opens and closes fuel and air. 6 is a by-starter intake passage, and 7 is a relief valve provided in the intake passage before and after the on-off valve 5, which is closed during recoil and opened when the engine runs on its own. 8 is a bistarter discharge passage, 9 is a crank chamber discharge port, and 10 is a check valve that opens only when the crank chamber is under negative pressure. Reference numeral 11 is an example where the outlet is not in the crank chamber but in the suction pipe.

This design is configured in this way to improve the starting performance of diaphragm carburetors, such as speeding up the initial explosion with fewer recoils, sustaining the initial explosion with an appropriate starting air-fuel mixture, ensuring reliable detection, and preventing swallowing due to erroneous operation. It can be greatly improved.

[Brief explanation of the drawing]

The drawings show the main parts of the invention■

Claims (1)

[Claims] Bi-starter device A bi-starter device for a diaphragm type carburetor characterized by providing a relief valve in the intake air passage before and after the on-off valve that opens only when the engine rotates under its own power.