JPS5831466B2 - Fuel supply device for carburetor idling - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an idling fuel (slow fuel) supply device for a gasoline engine carburetor, and more particularly to an improvement in a flow rate control device for fuel supplied from an idle port.

In the idling fuel supply system, when the engine is idling or at low speed, i.e. when the opening of the throttle valve is small, sufficient air does not flow to create enough negative pressure in the venturi part of the carburetor to suck out fuel from the main nozzle.
It is provided separately from the main fuel system.

Conventionally, the flow rate control in this type of idling fuel supply device has been carried out using a needle valve or an adjusting screw 2 having a conical portion 1 at the tip, as shown in FIGS. 1 and 2.
This was done by sliding the engine toward the circular idle port section 3.

According to this method, as shown by curve I in FIG. 3, as the opening area of the idle port section becomes smaller, the amount of change in the opening area of the idle port section with respect to the sliding amount of the needle valve or adjustment screw increases. Fuel flow control during idling in a region where the air-fuel mixture ratio is large, that is, a lean region, is particularly difficult to finely adjust, and the fuel flow rate may be affected by misalignment between the center axis of the idle port and the center axis of the needle valve or adjustment screw. The amount of change over time also becomes large.

The present invention solves these problems, and aims to provide an idling fuel supply device that facilitates fine adjustment of the fuel flow rate during idling and reduces the amount of change in the fuel flow rate over time.

Hereinafter, a detailed explanation will be given based on the embodiment of the present invention shown in FIG.

FIG. 4 is a cross-sectional view of a gasoline engine carburetor equipped with the idling fuel supply device of the present invention, in which 10 is an intake passage, 12 is a venturi section, 14 is a main nozzle, and 16 is a float chamber. , 18 is a throttle valve, and 20 is a choke valve.

The structure of the main system fuel supply system is exactly the same as that of the conventional system, so a description thereof will be omitted.

The structure of the slow-type fuel supply device uses a fuel supply passage 26 that communicates the slow port fuel supply passage 22 and the idle boat fuel supply passage 24, instead of the conventional idle port fuel flow control system. , the fuel supply passage 2 on the side communicating with the idle port fuel supply passage 24.
The opening 28 has a substantially triangular or substantially rectangular shape elongated in the axial direction of the fuel supply passage 24, and an idling adjustment screw 32 having a cylindrical tip 30 is provided so as to be slidable along the inner wall of the fuel supply passage 24. .

By rotating the idling adjustment screw 32, the tip cylindrical portion 30 of the idling adjustment screw 32 can be adjusted to form the triangular or rectangular opening 28.
The fuel flow rate supplied from the idle port 34 to the intake passage 10 is controlled.

According to this method, curves II, III and
As shown in FIG. 2, as the opening area of the idling fuel passage becomes smaller, the amount of change in the opening area with respect to the amount of slide of the adjusting screw 32 becomes smaller or remains constant.

In particular, when the opening 28 is formed into an elongated triangular shape whose width decreases in the advancing direction of the adjusting screw 32 as shown in FIG. 5, as the opening area becomes smaller, the sliding amount of the adjusting screw 32 The amount of change in opening area gradually decreases (curve ■ in Figure 3).

The curve ■ in FIG. 3 defines the opening 28 with a length of 7.85 mm and a width of 0.5 mm.
This is the case when it is made into a rectangle with 4 angles, and the curve ■ has a length of 10.4
This is an example of a rectangular shape with a width of 7 mm and a width of 0.3 mm.

As is clear from FIG. 3, the idling fuel supply device of the present invention can control the amount of change in the opening area of the fuel passage portion to be small in the area where the opening area is small, so that the air-fuel supply system in the lean region during idling can reduce the amount of change in the opening area of the fuel passage. The mixing ratio can be easily set and finely adjusted.

In addition, the change in opening area with respect to the sliding amount of the adjustment screw 32 is small, and the adjustment screw 32 is guided along the inner wall of the idle port fuel supply passage 24, so there is little axis misalignment, and the amount of fuel supplied due to axis misalignment is small. Since the influence of this is small, it is possible to eliminate changes over time in the idle port fuel flow rate.

[Brief explanation of the drawing]

Figure 1 shows a conventional gasoline engine carburetor, Figure 2 shows its idling fuel supply section, Figure 3 shows various fuel flow control methods during idling, and opening area characteristics depending on the opening shape. The figure shows a sectional view of a gasoline engine carburetor employing the idling fuel supply device of the present invention, and FIG. 5 shows an enlarged view of the opening shape as seen from arrow V in FIG. 4. 22... Slow port section fuel supply passage, 24...
...Idle port fuel supply passage, 26...
...Fuel supply passage, 28...Opening, 30...
... Tip, 32 ... Idling adjustment screw.

Claims (1)

[Claims] 1. In a fuel supply device for idling of a gasoline engine carburetor, a fuel supply passage 26 that communicates between a slow port fuel supply passage 22 and an idle port fuel supply passage 24 is connected to a side that communicates with the idle port fuel supply passage 24. The fuel supply passage 24 has an elongated substantially triangular or substantially rectangular opening 28 in the axial direction, and an idling adjustment screw 32 having a cylindrical raw end portion 30 is provided so as to be slidable along the inner wall of the fuel supply passage 24. A fuel supply device for idling of a carburetor, characterized in that the tip end portion 30 of the idling adjustment screw allows the opening area of the substantially triangular or substantially rectangular opening 28 to be changed.