JPH03253758A - Starting device for diaphragm type carburetor - Google Patents

Abstract

PURPOSE:To dispense with troublesome actions entirely in connection with the start of an engine and improve starting operability by filling fuel into a starting fuel holding chamber and the diaphragm chamber of a diaphragm type carburetor via negative pressure with the action of a starting pump. CONSTITUTION:When a starting pump 31 is operated prior to the start of an engine, negative pressure is applied to a starting fuel holding chamber 25, and fuel is sucked into a diaphragm chamber 5 applied with the negative pressure via a fuel pump 10. When fuel is filled into the diaphragm chamber 5, fuel is guided into the starting fuel holding chamber 25 by the action of the starting pump 31 and returned to a fuel tank 15 from a discharge port 35 via the pump chamber 45 of the starting pump 31. When the engine is cranked under this condition, the operating pressure generated in a crank chamber is guided into the inner chamber 39 of a bag body 37 to expand the bag body 37, and the fuel in the holding chamber 25 is pushed out to an intake path 3 via a passage 26 and fed to an engine together with the fuel from a main fuel injection port 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a diaphragm type carburetor used in engines such as brush cutters and chain saws.

[Conventional technology]

Diaphragm type carburetors generally used in engines such as brush cutters and chainsaws require the diaphragm chamber to be filled with fuel before starting.

Therefore, conventionally, as disclosed in Japanese Utility Model Publication No. 51-43315, a starter pump was used to supply the fuel in the fuel tank to the diaphragm chamber, and a fuel valve at the inlet of the diaphragm chamber was opened by pushing up the diaphragm of the diaphragm chamber. It is equipped with a tickler lever that opens the overflow valve at the same time. Before starting the engine, the starter pump and the tickler lever are operated simultaneously to introduce fuel into the diaphragm chamber and to check that the diaphragm chamber is filled with fuel from the fuel overflow. A detection mechanism is used.

Furthermore, although it is necessary to enrich the mixture concentration to start the engine, the setting is such that even if the diaphragm chamber is filled with fuel, the fuel supply from the fuel nozzle is adapted to the operating conditions after IkL+1 startup. Therefore, in order to supply the desired rich mixture to the engine, it is necessary to further limit the amount of intake air by closing the choke valve.

[Problems with conventional technology]

Moreover, with the above-mentioned device, it is necessary to operate both the starter pump and the daycler lever before starting 1i, which requires both hands and is cumbersome to handle.

Further, after the diaphragm chamber is filled with fuel, it is necessary to perform a choke operation in order to obtain a rich mixture for starting, and this operation is very troublesome.

SUMMARY OF THE INVENTION An object of the present invention is to provide a starting device for a diaphragm carburetor that does not require complicated starting operations and can be started easily and reliably.

[Technical means to solve problems]

The present invention provides a second passage that is connected to the intake passage through a first passage that is equipped with a check valve that allows flow in the direction of the intake passage, and that is equipped with a check valve that blocks flow in the direction of the diaphragm. a starting fuel storage chamber connected to the diaphragm chamber through the
A starter pump is provided with an inlet connected to the storage chamber and a discharge port connected to the fuel tank, and the storage chamber expands in response to positive pressure taken from the engine operating pressure, and the fuel in the storage chamber is expanded. The present invention is characterized in that the fuel is not pushed out toward the intake path and a bag body is provided.

[Effect]

When the starter pump is operated prior to starting the engine, negative pressure acts in the starter fuel storage chamber, and the negative pressure is led to the diaphragm chamber through the second passage, which causes fuel to flow through the fuel pump and into the diaphragm chamber. is attracted.

When the diaphragm chamber is filled with fuel, the fuel is guided to the starter fuel storage chamber by the subsequent operation of the starter pump, passes through the pump chamber of the starter pump, and is returned to the fuel tank from the discharge port. During this operation, the diaphragm chamber and the starting fuel storage chamber are filled with fuel.

After that, when the engine is cranked for starting, engine operating pressure is generated, and the positive pressure taken out from this operating pressure causes the bag to expand, and the fuel in the storage chamber passes through the first passage and enters the intake passage. It is pushed out and supplied to the engine along with the fuel sucked in from the main fuel jet. As a result, the mixture concentration is increased, and the engine can be reliably started when the engine is cold.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

Reference numeral 1 denotes a carburetor, and an intake passage 3 is provided through the carburetor body 2, and the downstream side of this intake passage 3 is connected to an intake boat of an engine (not shown). A throttle valve 4 for varying the effective diameter of the intake passage 3 is disposed in the intake passage 3, and a main fuel injection port 6 connected to a diaphragm chamber 5 is opened.

io, tt This fuel pump is driven by the operating pressure of the engine. By applying the operating pressure of the engine to the pressure chamber 14 formed on one side, the pump diaphragm 11 is vibrated, and the fuel in the fuel tank 15 is transferred from the fuel supply passage 16 through one check valve 12 to the pump diaphragm 11. The fuel is sucked into a pump chamber 17 formed on the other side, and the fuel is pumped from the other check valve 13 to the diaphragm chamber 5 via a fuel supply passage 18.

A fuel valve is provided at the diaphragm l of the fuel supply passage 18 and the air inlet thereof in association with the diaphragm 19 to disconnect the passage 18, that is, to disconnect the communication between the fuel pump 1o and the diaphragm chamber 5. 20 are provided. A lever 22 having a support shaft 21 is disposed between the fuel valve 2o and the diaphragm 19. The lever 22 is connected to the fuel valve 2o on one side about the support shaft 21, and connected to the diaphragm 19 on the other side. Therefore, when a strong intake negative pressure acts on the diaphragm chamber 5 through the main fuel injection port 6, the diaphragm 19 moves through the lever 22 to prevent the fuel from the fuel pump 10 from being introduced into the diaphragm chamber 5. The fuel valve 20
is held in the open position of the fuel supply passage 18. Further, when the strong negative pressure in the diaphragm chamber 5 disappears due to the introduction of fuel into the diaphragm chamber 5-, the diaphragm chamber 5- Preventing the introduction of fuel into the interior 4-・
Close off the passage 18.

Reference numeral 25 denotes a starting fuel storage chamber, which is connected to the intake passage 3 through a first passage 26 and connected to the diaphragm chamber 5 through a second passage 27.
It is connected to the. A check valve 28 is provided in the first passage 26 and opens from the storage chamber toward the intake path.
A check valve 29 that opens from the diaphragm chamber 5 toward the storage chamber 25 is provided in the passage 27 .

Reference numeral 31 designates a starting pump, the suction port 33 of which is connected to the storage chamber 25 via the suction side check valve 32, and the discharge side check valve 34.
A discharge port 35 is connected to the fuel tank 15 through the fuel tank 15 .

By operating this starting pump 31, the starting fuel storage chamber 25
Negative pressure acts within the diaphragm chamber 5, and the negative pressure is introduced into the diaphragm chamber 5 through the second passage 27, thereby causing the diaphragm 1
9, the fuel valve 20 is opened, and the fuel in the fuel tank 15 is transferred to the fuel pump 10, the diaphragm chamber 5, and the starting fuel storage chamber 2.
Aspirate through step 5. Further, excess fuel sucked by the starter pump 31 is returned to the fuel tank 15 via the discharge port 35.

Further, the starting fuel storage chamber 25 is expanded by positive pressure taken from the operating pressure of the engine, and pushes out the starting fuel stored in the starting fuel storage chamber 25 into the intake passage 3 through the first passage 26. A bellows-shaped bag body 3 made of an elastic material for
7 are arranged. The bag body 37 is urged in a contracting direction by a compression spring 38, and is normally held in a contracted state.

Further, a pressure passage 40 for introducing the positive pressure of the operating pressure is connected to the inner chamber 39 of the bag body 37, and the pressure passage 40 includes:
In order to take out only the positive pressure component of the operating pressure, a check valve 41 is provided that allows flow only in the direction of the inner chamber 39.

The operating pressure of the engine is, for example, the crank chamber pressure, and the other end of the pressure passage 40 is the crank chamber pressure of the engine.
(not shown) or the pressure chamber of the fuel pump 1.4. -;l:
Alternatively, it is connected to a passage 42 that communicates the crank chamber and the power chamber 14.

Further, on the discharge side advance 1F of the starting pump 31, the valve 34 is
', i'tjrA Appropriate valve opening pressure is applied by the elastic spring 44 so that the fuel pushed out by the bag body 37 does not flow out to the fuel tank 15 side. This valve opening pressure can also be applied to the suction side check valve 32 side or to both the suction side check valve 32 and the discharge side check valve 34.

Next, the operation of this embodiment will be explained.

When the starting pump 31 is operated prior to starting the engine, negative pressure acts in the starting fuel storage chamber 25, and this negative pressure is led to the diaphragm chamber 5 via the second passage 27, thereby causing the fuel pump 10 Fuel is drawn into the diaphragm chamber 5 through the diaphragm chamber 5.

Once the diaphragm chamber 5 is filled with fuel, the fuel is transferred to the starting fuel storage chamber 25 by the subsequent operation of the starting pump.
is guided to the discharge port 3 through the pump chamber 45 of the starting pump 31.
5 is returned to the fuel tank 15. This operation fills the diaphragm chamber 5 and the starting fuel storage chamber 25 with fuel.

Thereafter, when the engine is cranked, the operating pressure generated in the crank chamber is rectified to positive pressure by the check valve 41 and introduced into the inner chamber 39 of the bag body 37. This positive pressure causes the bag 37 to expand, and the fuel in the storage chamber 25 is pushed out into the intake passage 3 through the first passage 26, and is supplied to the engine together with the fuel sucked in from the main fuel injection port 6. As a result, the mixture concentration is increased, and the engine can be reliably started when the engine is cold.

FIG. 2 shows another embodiment of the present invention, in which a bag body 37
A valve portion 37a is provided at the tip of the bag body 37, and the valve portion 37a is inserted into the opening 26 of the first passage 26 when the bag body 37 is inflated.
By making pressure contact with the diaphragm chamber 5 and arranging the passage 26 to be a chamber, the first passage 26 is closed during engine operation in which the bag body 37 maintains an inflated state, and fuel is transferred from the diaphragm chamber 5 to the intake passage 3. This is to prevent it from being sucked in.

Note that the bag 37 is not limited to the bellows shape, but may have any other suitable shape.

〔Effect of the invention〕

As described in detail above, according to the present invention, the diaphragm chamber of the carburetor and the starting fuel storage chamber can be filled with fuel by operating the starting pump, and when the engine is subsequently started, the bag in the storage chamber is filled with fuel. is expanded by the operating pressure generated when the engine is cranked, and the fuel in the storage chamber is automatically supplied to the intake passage to increase the mixture concentration. This eliminates all the troublesome operations associated with starting the engine, even for beginners. Starting the engine is easy.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention, and FIG. 2 is a sectional view of essential parts showing another embodiment of the invention. DESCRIPTION OF SYMBOLS 1... Carburetor, 3... Intake path, 5... Diaphragm chamber, 10... Fuel pump, 25... Starting fuel storage chamber, 26... First passage, 27... 2nd aisle, 37・
...Bag body, 40...Pressure passage.

Claims (2)

[Claims] (1) In a diaphragm type carburetor that adjusts the pressure of fuel supplied by a fuel pump to a constant pressure in a diaphragm chamber and injects it into the intake passage, the first passage is equipped with a check valve that allows flow in the direction of the intake passage. a second air intake passage connected to the air intake passage through the air intake passage and provided with a check valve for blocking the flow toward the diaphragm chamber;
A starting fuel storage chamber connected to the diaphragm chamber via a passage, and a starting pump having an inlet connected to the storage chamber and a discharge port connected to the fuel tank, further comprising:
Expands in response to positive pressure taken from the engine operating pressure,
A starting device for a diaphragm type carburetor, characterized in that a bag body is disposed to push out fuel in the storage chamber toward an intake passage. (2) When the bag is inflated, a valve portion provided at the tip of the bag closes the opening of the first passage on the storage chamber side. ) A starting device for a diaphragm carburetor as described in paragraph 1.