JPS63622B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable ventilator carburetor comprising a piston valve.

Currently, a method of making the air-fuel mixture lean is used as one of the measures against exhaust gas, but when setting the air-fuel mixture lean, it is necessary that the mixture and atomization of fuel and air be good.

Fig. 1 is a cross-sectional conceptual diagram of a conventional variable ventilate type carburetor, in which 1 is a piston valve, 1a is a negative pressure outlet hole, 2 is a piston valve return spring, 3 is an upper negative pressure chamber, 4 is a diaphragm, and 5 is a The lower negative pressure chamber, 6 is an air hole, 7 is a jet needle, and 8 is a throttle valve. The piston valve 1 has a pressure difference between an upper negative pressure chamber 3 through which negative pressure of a ventilary part 9 is communicated through a negative pressure outlet hole 1a and a lower negative pressure chamber 5 which communicates with an air hole 6, and a return spring 2. It is constructed so that it moves up and down as a result of the action, and the ventilate area A changes.

In the case of such a variable ventilee type carburetor, when the intake air amount is small (low speed), the smaller the ventilate area A is, the higher the flow velocity is, which improves the mixing of fuel and air.
Atomization is improved and meets the above requirements. Therefore, in order to reduce the amount of rise of the piston valve 1, it is preferable to use a return spring 2 with a large spring constant. However, when the intake air amount is large (high speed), the output will be reduced unless the ventilary area A is increased, so it is not preferable to use a return spring 2 with a large spring constant.

In other words, in the case of a variable ventilate type carburetor, when the amount of intake air is small, the ventilary area A is reduced as much as possible.
It is desirable to make it small and make it sufficiently large when the intake air amount is large, but if you try to do this with the conventional piston valve stroke control using a return spring, when the intake air amount is small, the spring constant is large, When the amount of intake air is large, a spring with a small spring constant must be used, and in reality, it is almost impossible to manufacture such a spring.

In view of the above-mentioned circumstances, an object of the present invention is to change the opening area of the negative pressure outlet hole of the piston valve in accordance with the vertical movement of the piston valve, thereby making the ventilary area smaller than before when the amount of intake air is small. The object of the present invention is to provide a variable ventilate type carburetor which allows the ventilary area to be made sufficiently large as before when a large amount of intake air is used.
The gist is that, in a variable ventilator carburetor equipped with a piston valve having a negative pressure outlet hole, the negative pressure outlet hole is formed along the axial direction of the piston valve, and the negative pressure outlet hole is formed in the direction of the extension line of the negative pressure outlet hole. A needle valve whose distal end is the thinnest and gradually becomes thicker toward the proximal end is erected on the inner wall of the ventilate part, and as the piston valve moves in the closing direction, the needle valve enters the negative pressure outlet hole. The needle valve is inserted so that the opening area of the negative pressure outlet hole decreases in accordance with the decrease in the ventilary area, and the fuel is inserted into the surface of the needle valve at an intermediate portion between the proximal end and the distal end of the needle valve. A variable ventilee type carburetor is characterized in that a fuel injection port is formed, and a fuel supply passage is connected to the fuel injection port.

Hereinafter, the present invention will be explained in detail with reference to embodiments shown in the drawings.

FIG. 2 is a conceptual cross-sectional view showing the main parts of the carburetor which is the premise of the present invention. The configuration other than the main parts shown in the figure is the same as that in FIG. 1. The illustrated carburetor is a variable ventilator type carburetor equipped with a piston valve 1 having a negative pressure outlet hole 1a at the bottom, and has a needle valve 11 erected in the lower part of the ventilate part 9, that is, in the mixing body 10, with the needle valve 11 facing upward. , the needle valve 11 faces the negative pressure outlet hole 1a. The needle valve 11 is formed so that the cross-sectional area gradually decreases from the base end to the distal end, and the needle valve 11 is positioned directly below the negative pressure outlet hole 1a, that is, on the vertical movement trajectory of the hole 1a, and the negative pressure is Extraction hole 1
It is designed to be inserted into a. Therefore, the opening area of the negative pressure outlet hole 1a changes according to the vertical movement of the piston valve 1. When the intake air amount is small, the opening area is small, and as the intake air amount increases and the piston valve rises, the opening area changes. becomes larger. Note that the diameter of the negative pressure outlet hole 1a is slightly larger than that of the conventional one.

The relationship between the piston valve stroke and the intake air amount when the opening area of the negative pressure outlet hole 1a is changed is as shown in FIG. 4. That is, when the opening area is small, the piston valve stroke becomes small as shown by line B, and when the opening area is large, it becomes large as shown by line C. Line D shows the case of the conventional opening area. Therefore, by changing the opening area as described above, the relationship between the piston valve stroke and the intake air amount becomes as shown by line E in Figure 5, and when the intake air amount is small, the piston valve stroke is smaller than before. When the amount of intake air is large, it becomes larger than before. Note that line F shows the case of the conventional opening area.

As described above, according to the present invention, when the amount of intake air is small, the amount of rise of the piston valve can be reduced, and the ventilate area is therefore small and the air flow rate is increased, so that the mixing and atomization of fuel and air are improved. Carburetor setting becomes easier. At the same time, when the amount of intake air is large, the area of the ventilate can be made sufficiently large, and there is no risk of a decrease in output.

FIG. 3 is a conceptual sectional view showing only the essential parts of an embodiment of the present invention based on the carburetor shown in FIG. 2, and the structure other than the essential parts is the same as that in FIG. 1.
The illustrated vaporizer is provided with a needle valve 11 as shown in FIG.
In a variable ventule type carburetor in which the opening area of the negative pressure outlet hole 1a is changed by the needle valve 11, an auxiliary fuel supply passage 12 is provided in the needle valve 11, and the passage 12 is connected to the needle jet 13. A spout 14 communicating with the passage 12 is provided at an appropriate position on the side of the needle valve 11, and the fuel metered by the main jet (not shown) is transferred to the spout 1.
It is configured to eject from 4.

That is, the fuel supply corresponding to the vertical movement of the piston valve is currently metered only between the jet needle 7 and the needle jet 13, but this is because there are restrictions on the shape of the jet needle 7, such as its diameter and taper. It may not be possible to meet the demands of the engine. For example, if the air-fuel mixture is set to be lean to prevent exhaust gases, good fuel supply will occur from the pilot system and main system at low and high speeds, respectively, but in the middle, fuel supply from the pilot system will decrease due to a decrease in intake negative pressure. Since the piston valve is not raised very much, there is less fuel supplied from the main system, and a speed range appears where the air-fuel mixture becomes too lean, making setting difficult. FIG. 6 is a graph showing this state, and shows the relationship between CO concentration and vehicle speed. Line G in the figure is the CO curve.
Line H is the main system CO curve, line I is the pilot system CO curve.
Curve J indicates the over-lean region of the air-fuel mixture.

In this embodiment, a separate fuel supply passage 12 is provided in the needle valve 11 as described above, and fuel is jetted out through the passage 12 from the spout 14 provided at an appropriate position in the needle valve. be. Therefore, by appropriately determining the position of the ejection port 14, for example by providing the ejection port 14 at a position that receives high negative pressure at a desired piston valve position, it is possible to supply fuel corresponding to the vertical movement of the piston valve. It is possible to correct the above-mentioned overthin region at medium speed. Of course, since this embodiment has the configuration shown in FIG. 2, it is possible to correct the above-mentioned excessively thin region and the like, and also achieve the effect of changing the opening area of the above-mentioned negative pressure outlet hole 1a.

As mentioned above, the carburetor according to the present invention is configured to change the opening area of the piston valve negative pressure outlet hole using the needle valve in accordance with the vertical movement of the piston valve, so when the intake air amount is small, it is possible to The ventilator area can be made small and sufficiently large when a large amount of intake air is used, and even when the mixture is set to be lean, it is possible to obtain good mixing of fuel and air and atomization, while also reducing the power output. It is possible to perform carburetor setting that better corresponds to the engine's requirements without any risk. Also, since it is only necessary to install the needle valve upright on the inner wall of the ventilate part,
It is extremely simple in structure and can be easily attached to conventional vaporizers.

Furthermore, by providing a separate fuel supply passage within the needle valve and injecting fuel from the needle valve, it is possible to further correct the excessively lean region at medium speeds.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional conceptual diagram showing an example of a conventional variable ventilee type carburetor, Fig. 2 is a cross-sectional conceptual diagram of the essential parts of the carburetor that is the premise of the present invention, and Fig. 3 is a variable ventilary type carburetor according to the present invention. A cross-sectional conceptual diagram showing the main parts of an embodiment of the carburetor, Fig. 4 is a diagram showing the relationship between the piston valve stroke and the intake air amount when the opening area of the piston valve negative pressure outlet hole is different, and Fig. 5 is the main part of the carburetor. FIG. 6 is a diagram showing the relationship between the piston valve stroke and intake air amount of the carburetor according to the invention, and FIG. 6 is a diagram showing the excessively lean region at medium speed. 1...Piston valve, 1a...Negative pressure outlet hole, 9...
Bench turret part, 11... Needle valve, 12... Fuel supply passage, 14... Fuel spout.

Claims (1)

[Claims] 1. In a variable ventule type carburetor equipped with a piston valve having a negative pressure outlet hole, the negative pressure outlet hole is formed along the axial direction of the piston valve, and the ventilate portion is formed in the direction of the extension of the negative pressure outlet hole. A needle valve is erected on the inner wall of the piston valve, and the needle valve is thinnest at the distal end and gradually thickens toward the proximal end, and as the piston valve moves in the closing direction, the needle valve is inserted into the negative pressure outlet hole, The opening area of the negative pressure outlet hole is configured to decrease in accordance with the decrease in the ventilate area, and a fuel injection port is provided on the surface of the needle valve at an intermediate portion between the base end and the tip of the needle valve. 1. A variable ventilee type carburetor, characterized in that a fuel supply passage is connected to the fuel injection port.