JP2001073879A - Starter for diaphragm type carburetor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish possibility of adding a starter to a diaphragm type carburetor by making it possible to start a mowing machine, etc., in its rotating range in which blades refrain from rotation for the sake of safety, i.e., idle starting, and suppressing low the rise of the costs of carburetor. SOLUTION: A fuel passage 45 for starting leading to an intake passage 3 downstream of a throttle valve is connected in a position between a check valve 34 in a main fuel passage 6 and a throttle part 18 of a fuel nozzle 5 or a main jet 31 and is furnished with a start valve 46 so that it is opened and closed. When the engine is started by opening the start valve 46, the intake negative pressure downstream of the throttle valve 4 is fed to the fuel passage 45, and a fuel for starting is sucked out from the main fuel passage 6 to the intake passage 3 while the air measured by the throttle part 18 or main jet 31 flows in from the fuel nozzle 5 and is mixed with the fuel to be supplied to the engine, where a certain minor quantity of air is increased, and a mowing machine, etc., can be started at a revolving speed at which blades refrain from rotation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a starting device for a diaphragm carburetor mounted on a small portable engine such as a brush cutter.

[0002]

2. Description of the Related Art Generally, in an internal combustion engine, it is desired to increase the concentration of an air-fuel mixture sent to an engine when the outside air temperature at the time of starting is low or the engine is not sufficiently warmed up. Conventionally, a starter such as a choke valve or a starter is provided in a carburetor, and the starting air-fuel mixture is generated by operating the starter and supplied to an engine.

[0003]

In recent years, however, the necessity of a so-called idle start in a rotation range in which the blade does not rotate has been increasing for safety in a brush cutter or the like. In order to apply a sufficient negative pressure to the throttle valve, the throttle valve is widely opened, so that the rotation of the engine at the time of start-up becomes high. In the starter system, the throttle valve bypasses the throttle valve in an idle opening state. Although the air-fuel mixture is supplied from the intake passage, the amount of air flowing through the starting intake passage and the amount of the air-fuel mixture are relatively large, so that the rotation of the engine becomes high, and both have difficulty in idling start.

[0004]

SUMMARY OF THE INVENTION The present invention controls the area of a throttle portion of a fuel nozzle by a jet needle interlocking with a throttle valve, and further comprises a main fuel passage connecting a diaphragm chamber and the fuel nozzle. In the diaphragm type carburetor provided with a check valve that allows only a flow in a direction of flowing into the main fuel passage, a check valve is provided between the check valve of the main fuel passage and the throttle portion of the fuel nozzle and communicates with an intake passage downstream of the throttle valve. A starting fuel passage is connected, and a starting valve for opening and closing the passage is provided in the starting fuel passage. Thus, when the throttle valve is at the idle opening degree and the engine is started by opening the start valve, the intake negative pressure downstream of the throttle valve is introduced into the auxiliary fuel passage, and the starting fuel is sucked from the main fuel passage into the intake passage. . At this time, air measured by the gap between the jet needle and the throttle portion of the fuel nozzle flows from the fuel nozzle, mixes with the fuel and is supplied to the engine, and a slight increase in air is performed. Fast idle at a rotation speed at which the blade does not rotate becomes possible.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described based on one embodiment of the present invention illustrated in the accompanying drawings. 1 and 2, reference numeral 1 denotes a diaphragm type carburetor, and an intake passage 3 is provided through the body 2,
The upstream side of the intake passage 3 is connected to an air cleaner (not shown), and the downstream side is connected to an intake port of an engine (not shown). In addition, the intake passage 3
The throttle valve 4 for making the effective diameter of the aperture variable is arranged to be able to advance and retreat. A fuel nozzle 5 is opened in the intake passage wall below the throttle valve 4, and the fuel nozzle 5 is connected to a diaphragm chamber 7 by a main fuel passage 6. An atmosphere chamber 15 is formed on the back surface of the diaphragm 19 that is stretched in the diaphragm chamber 7. A jet needle 16 hangs down from the bottom wall of the throttle valve 4, and its tip is inserted into the fuel nozzle 5. A throttle 18 is provided in the fuel nozzle 5.
The amount of fuel supplied to the intake passage 3 is controlled by a gap formed between the intake passage 6 and the intake passage 6.

[0006] A fuel pump 10 driven by the operating pressure of the engine is connected to a fuel inlet 8 of the diaphragm chamber 7 through a fuel supply passage 9. The fuel pump 10 includes a pump diaphragm 11 and a pair of check valves 1.
A well-known diaphragm pump composed of a pump diaphragm 2 and a pump chamber 11. The pressure chamber 14 is formed on one side of the pump diaphragm 11.
The pump diaphragm 11 is vibrated to suck fuel from a fuel tank (not shown) through one check valve 12 into a pump chamber 17 formed on the other side of the pump diaphragm 11, and the fuel is supplied from the other check valve 13 to the fuel supply passage 9. And is fed to the diaphragm chamber 7 by pressure.

The inlet 8 of the diaphragm chamber 7 is provided with a fuel valve 20 which operates in order to open and close the inlet 8 in relation to the diaphragm 19, that is, to open and close the communication between the fuel pump 10 and the diaphragm chamber 7. Have been. A shaft 21 is provided between the fuel valve 20 and the diaphragm 19.
, A lever 22 is disposed, one side of which is connected to the fuel valve 20 and the other side of which is connected to the diaphragm 19. The lever is urged by a spring 23 in a direction to always close the needle valve 20. Therefore, when an intake negative pressure acts on the diaphragm chamber 7 via the fuel nozzle 5, the diaphragm 19 causes the fuel valve 2 through the lever 22 to introduce fuel into the diaphragm chamber 7.
0 is held at the open position of the fuel inlet 8. The fuel valve 2
0 changes the opening area of the fuel inlet 8 in accordance with the displacement amount of the diaphragm 19, that is, the magnitude of the intake negative pressure, so that the inside of the diaphragm chamber 7 is always adjusted to a constant pressure.

A suction passage 27 of a starting pump 25 is connected to the diaphragm chamber 7. This pump 2
By repeatedly operating 5, a negative pressure acts on the diaphragm chamber 7, and the fuel in the fuel tank 15 is sucked into the chamber 7 via the fuel pump 10. The fuel that has flowed into the diaphragm chamber 7 is returned to the fuel tank 7 through the discharge passage 28 with the subsequent operation of the starting pump 25. 26 is a combination valve integrally forming an umbrella type check valve 26a as a suction valve and a duckbill type check valve 26b as a discharge valve.

In the main fuel passage 6, the main jet 3 whose throttle diameter is adjusted by a fuel adjusting needle 30 is provided.
1 is formed. The fuel adjustment needle 30 is screwed into a screw hole 32 which is substantially orthogonal to the fuel nozzle 5 and in which the main jet 31 communicating with the fuel nozzle 5 is formed at the back. The needle portion 33 provided is connected to the main jet 31.
Has been inserted. Therefore, by rotating the fuel adjustment needle 30, the fuel adjustment needle 30 advances and retreats, and the throttle diameter of the main jet 31 is adjusted.

The main fuel passage 6 is provided with a check valve 34 at the diaphragm chamber side entrance, which allows only a flow from the diaphragm chamber 7 toward the fuel nozzle 5, and the other is connected to the screw hole 32. Accordingly, the needle chamber 38 substantially forms a part of the main fuel passage 6. A large-diameter chamber 40 for housing the head 39 of the fuel adjustment needle 30 is formed on the outer opening side of the screw hole 32, and a sealing material for sealing the screw hole 32 is provided in the head 39 of the fuel adjustment needle. 41 are provided. A compression spring 43 is disposed between a shoulder 42 formed at the back of the large-diameter chamber 40 and the head 39 of the fuel adjustment needle in order to prevent the needle 30 from loosening.

The screw hole 32 is connected to a starting fuel passage 45 that connects the other end to the intake passage 3 downstream of the throttle valve 4. A starting valve 46 for controlling the opening and closing of the passage 45 is provided in the middle of the starting fuel passage 45. This starting valve 46
Is slidably accommodated in a starting valve chamber 47 provided orthogonally to the starting fuel passage 45, and an operating rod 48 having the other end protruding outside the carburetor is provided on the back surface, and the starting valve 46 is provided. A return spring 50 for urging the starting valve 46 to the closing side is disposed between the first spring 50 and the lid 49. Upstream of the starting fuel passage 45 is not only the screw hole 32 but also the main fuel passage 6.
May be connected anywhere between the check valve 34 and the throttle portion 18 of the fuel nozzle 5.

Next, the operation of the above embodiment will be described. If the starting pump 25 is repeatedly operated prior to starting, a negative pressure acts in the diaphragm chamber 7, and fuel is sucked into the chamber 7 from a fuel tank (not shown) via the fuel pump 10. The fuel that has flowed into the diaphragm chamber 7 is returned to the fuel tank via the discharge passage 28 with the subsequent operation of the starting pump 25.

Next, when the start valve 46 is opened to start the engine, the intake negative pressure generated in the intake passage 3 downstream of the throttle valve 4 is introduced into the starting fuel passage 45, and the start-up fuel is introduced into the intake passage 3 from the screw hole 32. Drain the fuel. At this time, the air measured in the gap between the throttle portion 18 of the fuel nozzle 5 and the jet needle 16 flows in at the same time, and a slight increase in the amount of air is performed. It is possible to perform a start operation at a first idle without rotating. Further, since the fuel is filled up to the main jet 31 in the main fuel passage 6 by the start operation, the supply of the fuel from the fuel nozzle 5 can be smoothly performed when the start valve is closed after the warm-up.

In the above embodiment, the starting valve 46 is manually operated to open and close the starting fuel passage 45. However, the starting valve 46 is automatically opened and closed by a temperature-sensitive member such as wax or bimetal. It is also possible.

In the above embodiment, the amount of air supplied to the starting fuel passage 45 is controlled by the gap between the throttle portion 18 in the fuel nozzle 5 and the jet needle 16. In a carburetor not provided with the above, the amount of air can be controlled by the main jet 31 as shown in FIG.

[0016]

As described above in detail, according to the present invention, between the check valve of the main fuel passage and the throttle portion or the main jet of the fuel nozzle, the starting fuel passage communicating with the intake passage downstream of the throttle valve. The starting fuel passage is provided with a starting valve for opening and closing the passage, so that at the time of starting, the measured air flows from the fuel nozzle into the throttle portion of the fuel nozzle or the main jet, and mixes with the starting fuel. Since the air is supplied to the engine and the amount of air is slightly increased, the idling rotation of the engine slightly increases, so that a brush cutter or the like can perform a start-up operation at a first idle in which the blade does not rotate.

Further, since the fuel is filled up to the main fuel passage by this starting operation, it is possible to smoothly shift to the supply of fuel from the fuel nozzle when the starting valve is closed after warming up.

A starting fuel passage communicating with an intake passage downstream of the throttle valve is connected between a check valve of the main fuel passage and a throttle portion of the fuel nozzle, and the starting fuel passage is opened and closed. With a simple configuration that only requires the provision of a start valve, the throttle portion of the fuel nozzle is used to measure the air for the first idling and the supply of the air-fuel mixture for the start is enabled, so that an increase in the cost of the carburetor is suppressed. Thus, a starter can be added.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view of a main part showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diaphragm type carburetor 3 Intake passage 4 Throttle valve 5 Fuel nozzle 6 Main fuel passage 7 Diaphragm chamber 16 Jet needle 18 Throttle section 30 Fuel adjustment needle 31 Main jet 32 Screw hole 34 Check valve 45 Starting fuel passage 46 Start valve

Claims (2)

[Claims] A jet needle interlocking with a throttle valve controls an area of a throttle portion of a fuel nozzle, and restricts only a flow in a direction flowing into the main fuel passage into a main fuel passage connecting a diaphragm chamber and the fuel nozzle. In a diaphragm type carburetor having an allowable check valve, a starting fuel passage communicating with an intake passage downstream of a throttle valve is connected between a check valve of the main fuel passage and a throttle portion of the fuel nozzle, A starting device for a diaphragm type carburetor, wherein a starting valve for opening and closing the passage is provided in the starting fuel passage. 2. A non-return valve, wherein a main jet is formed in the middle of a main fuel passage connecting the diaphragm chamber and the fuel nozzle, and a check valve is provided upstream of the main jet to allow only a flow in a direction flowing into the main fuel passage. In the diaphragm type carburetor, a starting fuel passage communicating with an intake passage downstream of a throttle valve is connected between the check valve and the main jet in the main fuel passage, and the starting fuel passage is opened and closed. A starting device for a diaphragm type carburetor, comprising a starting valve.