JPH066223Y2 - Diaphragm carburetor starter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a starting device for a diaphragm type carburetor.

[Conventional technology]

2. Description of the Related Art Conventionally, in a diaphragm type carburetor used for an engine of a working machine such as a brush cutter, it is necessary to fill a sensing chamber (metaling chamber) with fuel before starting. Therefore, a priming pump is installed in the fuel supply passage leading to the fuel tank and the fuel valve (needle valve), and the fuel valve is opened manually by the taker and at the same time the air vent and fuel overflow valve is opened. The pump is operated to cause the fuel to flow into the sensing chamber, and the fact that the sensing chamber is full of fuel can be detected from the fuel flowing out of the vaporizer from the overflow portion. However, in this starting device, it is necessary to operate both the priming pump and the taker at the time of starting, which requires both hands and is inconvenient in operation. Further, the fuel in the fuel tank is discharged to the outside, which is uneconomical.

Therefore, in order to solve these problems, a starting device for the diaphragm type carburetor 31 disclosed in Japanese Patent Application Laid-Open No. 61-83474 having a fuel storage chamber 36 as shown in FIG. 2 has been proposed. According to this configuration, if the priming pump 32 is operated at the time of starting the engine, the fuel in the fuel tank 33 is pressure-fed from the suction pipe 34a to the carburetor 31 through the fuel supply passage 34. Valve 39
Is closed, the fuel is pumped into the fuel storage chamber 36. Since the air layer 36a is formed above the fuel storage chamber 36, this fuel compresses the air layer 36a and flows into the fuel storage chamber 36. When the fuel pressure in the fuel storage chamber 36 reaches a certain level or more, the check valve 37 communicating with the return passage 38 opens and the fuel is circulated into the fuel tank 33. When the engine is recoiled, the negative suction pressure of the engine acts on the sensing chamber 42 in conjunction with the rotation of the engine, pulls up the main diaphragm 41, and opens the fuel valve 39 through the operating rod 40. The fuel staying under pressure is sent into the sensing chamber 42, and the fuel is filled therein. In addition, 35 shows a pump diaphragm.

[Problems to be solved by the device]

In the prior art described in the above publication, the valve opening pressure (0.4 kg / cm ² ) of the fuel valve 39> the check valve 37 on the return passage side
Since the valve opening pressure is set to (0.3 kg / cm ² ), apparently, when the priming pump 32 is operated, the fuel is not supplied to the sensing chamber 42 but is recirculated to the fuel tank 33. However, in actuality, when the priming pump 32 is suddenly operated, a sudden pressure due to the operation of the priming pump 32 is applied to the fuel valve 39 due to the passage resistance of the check valve 37, which exceeds the opening pressure of the fuel valve 39.
May open and the sensing chamber 42 may be filled with fuel by some operations, the main nozzle may overflow and the spark plug may be fogged and the engine may not start. Further, if the priming pump 32 is operated when the sensing chamber 42 is full of fuel at the time of restart, the fuel may overflow and restart may be impossible as in the above case.

Therefore, an object of the present invention is to solve the conventional problems by providing an intake check valve and a supply passage fuel storage chamber leading to a fuel valve (hereinafter referred to as a needle valve) in a supply passage leading to a priming pump.

[Means for Solving the Problems]

In order to achieve the above object, a diaphragm type vaporizer starter of the present invention has a fuel suction line and a return line connecting the vaporizer and the fuel tank, and a fuel supply passage communicating with the fuel suction line and a metering chamber. In a carburetor provided with a needle valve for connecting and disconnecting the communication of, and a fuel supply pump operated by pulsation of the engine, a return passage communicating with the return line is provided in the carburetor,
An intake check valve is provided on the upstream side of the return passage, and a discharge check valve is provided on the downstream side of the return passage, and a priming pump is connected between the check valves, while the fuel in front of the needle valve is provided downstream of the fuel supply pump. A fuel storage chamber is formed on the supply passage, and the return passage is connected to the fuel storage chamber via the suction check valve.

[Action]

In the above configuration, when the priming pump is operated at engine start, the fuel in the fuel tank enters the carburetor through the suction line, stays in the fuel reservoir through the fuel supply pump, and the excess fuel remains on the return passage. It returns to the fuel tank through the return line through the intake check valve and the discharge check valve provided in the. On the other hand, when the engine is rotated by a recoil starter, etc., the negative suction pressure of the engine acts on the metering chamber (sensing chamber), pulls up the main diaphragm and simultaneously opens the needle valve, and pulsates the engine, causing the fuel supply pump. Is operated to stay in the fuel storage chamber immediately before the needle valve, and when the fuel is pumped to the metering chamber, the fuel is filled there.

Particularly in this case, by operating the priming pump, the fuel is supplied by the priming pump to the fuel storage chamber immediately before the needle valve.

Since the suction check valve is located on the upstream side of the return passage, the high pressure caused by pushing the priming pump is prevented from being directly applied to the needle valve.

By operating the priming pump, the fuel is temporarily stored in the fuel storage chamber provided in front of the needle valve and can be pumped to the metering chamber by the discharge pressure of the fuel supply pump, so that the startability is improved.

〔Example〕

FIG. 1 is a sectional view of a diaphragm type carburetor 1 including a fuel tank 14 according to the present invention. The carburetor 1 and the fuel tank are connected via an intake line 2 for sucking up the fuel in the fuel tank 14, and also connected via a return line 13 for returning the excess fuel to the fuel tank 14. There is.

A check valve 4, a pump diaphragm 5 constituting a fuel supply pump, and a check valve 7 are arranged in a fuel supply passage 3 communicating with the fuel inlet A of the carburetor 1, and then, on the upstream side thereof, in front of a needle valve 15 described below. A fuel storage chamber 8 is provided in the fuel supply passage. The lower part of the fuel storage chamber 8 is connected to the main diaphragm 19 via the needle valve 15.
It communicates with the inside of the metering chamber 20 defined by. On the other hand, a return passage 11 communicating with the return line 13 communicates with the upper portion of the fuel storage chamber 8, and an intake check valve 9 is arranged upstream of the return passage 11 and a discharge check valve 12 is arranged downstream thereof. There is. Further, a priming pump 10 for supplying fuel into the fuel storage chamber 8 at the time of starting the engine is connected to the return passage 11 between the intake check valve 9 and the discharge check valve 12. Thus, the suction check valve 9 is located upstream of the return passage 11, the priming pump 10 is located downstream thereof, and the discharge check valve 12 is located downstream thereof.

In the pump diaphragm chamber, an engine impulse passage 6 for introducing an operating pressure having an engine pulsation for operating the pump diaphragm 5, for example, a crank chamber pressure in a two-cycle engine, communicates with the pump diaphragm 5. Fuel supply pump P
Are configured.

A control lever 18 pivotally supported by a hinge pin 16 is provided in the metering chamber 20, one end of which abuts against a main diaphragm 19 and the other end of which is connected to a needle valve 15. Control lever 1
8 is provided with a control lever spring 17 for urging the needle valve 15 in the closing direction.
The lower surface of the main diaphragm 19 has the opening 2 of the cover 21.
It faces the atmosphere side through 1a. On the other hand, on the opposite (downstream) side of the needle valve 15 of the metering chamber 20, a fuel supply passage connected to the intake port of the engine in a direction perpendicular to the plane of the drawing through a passage formed in the tip of the adjusting screw 23 and the jet needle 25. 22 are formed in communication with each other. Reference numeral 28 is a body cap, 26 is a throttle valve, 27 is a throttle cable, and 24 is a slow stop screw.

In the above configuration, when the priming pump 10 is operated (pushed or pinched) at the time of starting the engine, the change in the pump internal volume and the suction and discharge check valves 4 and 7 and the seals provided on a part of the surface of the pump diaphragm 5 and the seals. By the action of the springs 4a and 7a for strengthening the property, the fuel is sucked up from the fuel tank 14 and is supplied from the supply passage 3 through the fuel supply pump P into the fuel storage chamber 8 and stays there, while the excess fuel is checked by suction. Valve 9 spring 9
The return passage 11 is opened by opening it against the biasing force P ₁ of a.
Into the discharge check valve 12 and the spring 12a.
The return passage 11 and the return line 13 side communicate with each other by opening this against the urging force P ₂ of the fuel cell P, and the fuel is returned to the fuel tank 14 through the return line 13. At this time, the needle valve 15 is closed by the urging force P ₃ by the control lever spring 17, and the pressure generated by the operation of the priming pump 10 is blocked by the suction check valve 9 to push the needle valve 15 open. Since there is no metering chamber 20
No fuel flows into it.

The above operation is performed because the suction check valve 9 is provided on the upstream side of the return passage 11. That is,
The pressure generated when the priming pump 10 is pinched or pushed acts on the suction check valve 9 so that the pressure is not transmitted to the needle valve 15, but conversely the discharge check valve on the return side. This is because it acts on 12 to open the spring 12a against the spring 12a, so that the return passage 11 and the return line 13 communicate with each other. Thus, the priming pump 1 at the time of starting
During the operation of 0, a fuel circulation line such as the fuel tank 14 → intake line 2 → carburetor 1 (fuel supply passage 3 and return passage 11) → return line 13 → fuel tank 14 is formed, and the fuel storage chamber 8 is also formed. Although the fuel will remain in the metering chamber, the fuel is not pushed into the metering chamber 20 by pushing the needle valve 15 open. Therefore, no matter how many times the priming pump 10 is operated at the time of engine start, the fuel does not flow into the engine side via the metering chamber 20.

Next, when the engine is recoiled, the negative pressure of the intake air of the engine is interlocked with the rotation of the engine and acts on the inside of the metering chamber 20 through the supply passage 22 to pull up the main diaphragm 19 and the needle valve 15 via the control lever 18.
Is opened to connect the fuel storage chamber 8 and the inside of the metering chamber 20. At the same time, the pulsation of the engine causes the fuel supply pump P to operate, whereby the fuel staying in the fuel storage chamber 8 is pressure-fed into the metering chamber 20 through the needle valve 15, and the fuel is filled therein.

[Effect of device]

According to the present invention described above, since the intake check valve is provided on the upstream side of the return passage leading to the return line,
No matter how many times the priming pump is operated, the fuel returns to the fuel tank via the return line except that the fuel stays in the fuel storage chamber.As a result, the needle valve is pushed open and the fuel passes through the metering chamber. It is possible to avoid a situation in which the engine flows into the engine side. Therefore, the sparg plug does not cover the fuel and causes difficulty in starting, and the startability is improved.

In addition, a fuel storage chamber is provided in front of the needle valve, and the fuel that has been temporarily stored here is operated by the operation of the priming pump to be pumped to the metering chamber by the discharge pressure of the fuel supply pump. Startability can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a diaphragm type carburetor including a fuel tank according to the present invention. FIG. 2 is a schematic explanatory view of a conventional diaphragm type vaporizer. 1 ... Vaporizer, 2 ... Suction line, 3 ... Fuel supply passage, 8 ... Fuel storage chamber, 9 ... Suction check valve, 10 ...
Priming pump, 11 ... Return passage, 12 ...
Discharge check valve, 13 ... Return line, 14 ... Fuel tank, 15 ... Needle valve, 16 ... Metalling chamber, P ... Fuel supply pump.

Claims (1)

[Scope of utility model registration request] 1. A needle valve having a fuel suction line and a return line connecting between a carburetor and a fuel tank, and connecting and disconnecting a fuel supply passage communicating with the fuel suction line and a metering chamber, and an engine pulsation. In a carburetor equipped with a fuel supply pump operated by the above, a return passage communicating with the return line is provided in the carburetor, an intake check valve is provided upstream of the return passage, and a discharge check valve is provided downstream thereof. While connecting a priming pump between the two check valves, a fuel reservoir is formed on the fuel supply passage in front of the needle valve on the downstream side of the fuel supply pump. A starter for a diaphragm type carburetor, characterized in that the return passage is connected via a starter.