JPH11324802A - Rotary throttle valve carburetor - Google Patents

Abstract

(57) [Problem] To provide a fuel nozzle by making a passage area of a portion downstream of a valve chamber of a throttle valve of an intake passage at the time of engine start larger than a passage area of an upstream portion of a valve chamber. So as to increase the intake negative pressure acting on the intake air. A throttle valve (47) having a throttle hole (47a) aligned with the intake path (16) is rotatably fitted in a cylindrical valve chamber (57) crossing the intake path (16) of the carburetor. A central portion 50a of the valve chamber 57 and a portion 50b of the intake passage 16 downstream of the valve chamber 57.
Is provided in the vaporizer main body 15. Passage 50
An opening / closing valve 52 that opens when the engine is started is provided halfway.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane type carburetor for an engine mounted on a portable working machine such as a power saw, a brush cutter, etc. The present invention relates to a rotary throttle valve type carburetor.

[0002]

2. Description of the Related Art A rotary throttle valve carburetor has a high intake negative pressure acting on a fuel nozzle. However, even if a rotary valve is provided with a chiyoke valve, the effect of further increasing the intake negative pressure acting on the fuel nozzle is small. It is difficult to start the engine by the method in which the intake path of the carburetor is restricted by the chi-yoke valve, and other measures need to be taken.

[0003]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to reduce the passage area of a portion downstream of a valve chamber of a throttle valve of an intake passage at the time of starting an engine by reducing the passage area of a portion upstream of the valve chamber. It is an object of the present invention to provide a rotary throttle valve type carburetor in which the intake air pressure acting on the fuel nozzle is increased by increasing the passage area.

[0004]

According to the present invention, a throttle valve having a throttle hole aligned with an intake passage is rotated in a cylindrical valve chamber crossing the intake passage of a carburetor. In a rotary throttle valve carburetor that is inserted as possible, a passage connecting the central portion of the valve chamber and the downstream portion of the intake passage with respect to the valve chamber is provided in the carburetor main body. An open / close valve is provided.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A passage connecting a central portion of a valve chamber of a throttle valve to a portion downstream of an intake passage from a valve chamber is provided in a carburetor body, and an opening / closing valve provided in the middle of the passage is connected to an engine. Open when starting. At this time, the passage area of the portion of the intake passage downstream of the valve chamber is larger than the passage area of the portion upstream of the valve chamber,
There is no change in the amount of air flowing through the intake passage, but the intake negative pressure acting on the fuel nozzle increases and the amount of fuel increases, so a rich air-fuel mixture is supplied to the engine, improving the startability of the engine. I do.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a main body 15 of a rotary throttle valve type carburetor is connected to an intake port (not shown) of an engine via a heat insulating pipe 63 and a gasket 62. Intake path 16
Is formed in the carburetor main body 15, and a throttle valve 47 having a throttle hole 47b is rotatably and vertically inserted into the valve chamber 57. Throttle valve 47 to valve chamber 5
The throttle valve operating lever 51 is coupled to a shaft portion 47a that penetrates the lid plate 53 closing the valve 7 and protrudes upward, from the lower cam surface 51a of the throttle valve operating lever 51 and the follower 52 of the lid plate 53. A cam mechanism is configured. Throttle valve operating lever 5
When the throttle valve 47 is rotated in the acceleration direction against the force of the spring 54 by 1, the opening degree at which the throttle hole 47 b communicates with the intake passage 16 increases, and the throttle hole 47 b extends from the shaft portion 47 a of the throttle valve 47.
The needle valve 55 projecting to 7b and inserted into the fuel nozzle 56 rises from the injection hole 56a of the fuel nozzle 56, and the opening of the injection hole 56a increases. The stationary fuel nozzle 56 is fitted and supported in a hole 58 at the bottom of the carburetor body 15, passes through a jet 59 and a check valve 66, and receives a constant pressure fuel chamber 2 of the fuel metering mechanism A.
It is communicated to 5.

A fuel pump 11 and a fuel metering mechanism A are formed below the carburetor body 15. That is, the fuel pump 1
Reference numeral 1 denotes an intermediate wall 49 connected to the lower end surface of the vaporizer main body 15 with the membrane 10 interposed therebetween, and a pulsating pressure chamber 8 containing a spring 8a above the membrane 10 and a pump chamber 9 below the membrane 10 respectively. Be partitioned. In a four-stroke engine, the fuel pump 11 applies the pulsating intake negative pressure in the intake passage 63a of the heat insulating pipe 63 to the inlet 61a and the passage 6a.
In the two-stroke engine, the fuel in the fuel tank 37 is introduced into the passage 38, the inlet 13, the check valve 12, and the passage 1 by introducing the pulsating pressure of the crank chamber into the pulsating pressure chamber 8.
2a, suction into the pump chamber 9 and the passage 12a, the check valve 7
Through the passage 7a.

The fuel metering mechanism A has a cover 30a connected to the lower end surface of the intermediate wall 49 with a membrane 29 interposed therebetween.
And the atmosphere chamber 30. A lever 28 is rotatably supported by a shaft 27 inside the constant pressure fuel chamber 25. Lever 2
8 is engaged with the inflow valve 2, and the inflow valve 2 is
Is applied to the valve seat at the end of the passage 7a. The other end of the lever 28 can be brought into contact with the membrane 29. When the force of the atmospheric pressure and the suction pressure acting on the membrane 29 becomes larger than the force of the spring 24, the lever 28 turns clockwise to rotate the inflow valve. 2 is opened, and fuel is supplied from the passage 7a to the constant-pressure fuel chamber 25.
Thus, the constant-pressure fuel chamber 25 holds a predetermined amount of fuel at a predetermined pressure. The fuel in the constant pressure fuel chamber 25 is the check valve 6
6. The air is supplied to the intake passage 16 through the jet 59, the injection hole 56a of the fuel nozzle 56, and the throttle hole 47b. In the illustrated embodiment, in order to prevent stagnation of fuel, the inner diameter is smaller than that of the heat insulating pipe 63 having the intake passage 63a connected between the intake port of the engine and the carburetor body 15, and the heat conductivity of aluminum or the like is large. A ring member 26 made of metal is disposed at the outlet of the intake passage 16 of the carburetor.

The above-mentioned film type vaporizer is disclosed in, for example,
No. 20551, the fuel sent to the constant-pressure fuel chamber 25 by the fuel pump 11 in any attitude of the engine (for example, in the state of being rolled over) is injected into the injection hole 56a of the fuel nozzle 56 by the suction negative pressure of the engine. Is sucked into the intake passage 16 from the suction port.

As shown in FIG. 2, according to the present invention, an intake passage 1 is provided in a cylindrical valve chamber 57 which crosses the intake passage 16 of the carburetor.
A throttle valve 47 having a throttle hole 47b aligned with the valve 6 is rotatably inserted, and the central portion 50a of the valve chamber 57 and the intake passage 16 are
A passage 50 is provided in the carburetor main body 15 to connect to a portion 50 b downstream of the valve chamber 57. An on-off valve 45 that opens when the engine is started is provided in the middle of the passage 50. In the illustrated embodiment, a cylindrical portion 42 orthogonal to the passage portion is provided in a portion of the passage 50 parallel to the intake passage 16, and a valve body 41 having an operating rod 41 a is slidably fitted in the cylindrical portion 42. Inserted. The valve element 41 is biased to the closed position by the force of the spring 43 interposed between the lid 44 closing the cylindrical portion 42 and the valve element 41.

Preferably, when the engine is started, the valve body 41 is opened in conjunction with the operation of opening the throttle valve operating lever 51 to a predetermined opening degree, and when the warm-up operation is completed, the throttle valve operating lever is opened. The valve element 41 is configured to be closed by receiving the force of the spring 43 when the valve 51 is operated in a direction to open it to a predetermined opening degree or more.

Next, the operation of the rotary throttle valve type carburetor according to the present invention will be described. When the engine is started, the intake path 16
When the suctioned air passes through the throttle hole 47b from the inlet portion 67 of the throttle valve 47, the injection hole 56a of the fuel nozzle 56
The fuel is supplied to the engine through the outlet portion 67a of the throttle hole 47b, the intake passage 16, and the heat insulating pipe 63.

When the on-off valve 45 is opened, the throttle valve 4 of the intake passage 16 is opened.
Since the passage area downstream of the passage 7 is larger than the passage area upstream, the negative pressure of the intake air acting on the fuel nozzle 56 increases, and the fuel amount increases. The amount of air at this time is
Since b is determined by the degree of opening of the inlet portion 67 that communicates with the portion of the intake passage 16 upstream of the valve chamber 57, it is almost the same as when the valve body 41 is in the closed position. Accordingly, the mixture becomes rich, so that the startability of the engine is improved.

[0014]

As described above, the present invention provides a rotary throttle valve in which a throttle valve having a throttle hole aligned with an intake path is rotatably inserted into a cylindrical valve chamber that crosses the intake path of a carburetor. In the carburetor, a passage connecting the central portion of the valve chamber and the downstream portion of the intake passage with respect to the valve chamber is provided in the carburetor main body. When the on-off valve is opened at the start, the passage area on the downstream side of the throttle valve in the intake passage is larger than the passage area on the upstream side, so that the air amount does not change, but the intake negative pressure acting on the fuel nozzle And the amount of fuel increases. In other words, since the mixture becomes rich, the startability of the engine is improved.

[0015] Compared to the arrangement in which the chi-yoke valve is disposed upstream of the throttle valve in the intake path, the flow rate of the entire intake path is smaller, so that the amount of air increases.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a rotary throttle valve carburetor according to the present invention.

FIG. 2 is a plan sectional view of the rotary throttle valve type carburetor.

[Explanation of symbols]

A: Fuel metering mechanism 2: Inflow valve 7: Check valve 8: Pulsating pressure chamber 9: Pump chamber 10: Membrane 11: Fuel pump 1
2: check valve 15: carburetor body 16: intake path 25: constant pressure fuel chamber 28: lever 29: membrane 30: atmosphere chamber 37: fuel tank 41: valve body 41a: operating rod 4
2: cylindrical part 43: spring 44: lid 45: on-off valve 4
7: throttle valve 47b: throttle hole 49: intermediate wall body 50:
Passage 50a: Central part 50b: Downstream part 51:
Throttle valve operating lever 51a: cam surface 52: follower
53: cover plate 54: spring 55: needle valve 56: fuel nozzle 56a: injection hole 57: valve chamber 61: passage 66: check valve 67: inlet portion 67b: outlet portion

Claims (2)

[Claims] 1. A cylindrical valve chamber that crosses an intake passage of a carburetor,
In a rotary throttle valve carburetor in which a throttle valve having a throttle hole aligned with an intake passage is rotatably inserted, a passage connecting a central portion of the valve chamber and a downstream portion of the intake passage with respect to the valve chamber. A rotary throttle valve type carburetor characterized in that a valve is provided in the carburetor body, and an opening / closing valve that opens at the time of starting is provided in the middle of the passage. 2. The rotary throttle valve carburetor according to claim 1, wherein said on-off valve opens in conjunction with a start operation of a throttle valve operating lever.