JPS6318022B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention controls the amount of fuel supplied to the intake passage only within a predetermined opening range of the throttle valve.
The present invention relates to a device that reduces engine fuel consumption.

[Conventional technology]

In a conventional carburetor, simply selecting the jets, main nozzle, throttle valve, and various passages does not allow the mixture to be diluted only within a predetermined opening range, such as the engine's normal opening range, that is, the throttle valve's normal opening range. It is difficult to reduce fuel consumption.

[Problem that the invention attempts to solve]

By the way, if we try to reduce fuel consumption over the entire throttle valve opening range, the no-load drivability at low throttle valve openings deteriorates, and at the same time, output decreases when the throttle valve is operated at high openings and under high load. Particularly in air-cooled engines, if the air-fuel mixture is diluted, there will be no fuel cooling, causing problems such as the temperature of various parts of the engine and the temperature of the lubricating oil becoming high.

[Means for Solving the Problems] The present invention applies negative pressure from below the lubricating oil level in the crankcase to above the fuel level in the float chamber only within a predetermined opening range of the throttle valve, such as the normal engine range. By doing so, it is possible to reduce the pressure difference between the intake passage and the float chamber, control the amount of fuel supplied to the intake passage, dilute the air-fuel mixture, reduce fuel consumption, and eliminate the above-mentioned problems. The purpose of the present invention is to provide a fuel consumption reduction device for a carburetor that can be expected to operate stably by using the negative pressure below the surface of the lubricating oil in the crankcase, which has less pulsation and less negative pressure. be.

【Example】

Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings. In FIG. 1, numeral 1 is the carburetor main body;
An intake passage 2 is formed in this carburetor body 1, and a float chamber 4 is formed in a float chamber wall 3 fixed to the carburetor body 1. This float chamber 4
1 has a built-in float (not shown) and is configured to replenish fuel 5 so as to maintain a fuel level 6 at a predetermined height. A main nozzle 7 is opened in the bench lily portion 2a of the intake passage 2, and this nozzle 7 is communicated with the lower part of the float chamber 4 via a main jet 8. A throttle valve 9 is provided in the intake passage 2, and a throttle shaft 10 fixed to the throttle valve 9 is rotatably supported by the carburetor body 1. Further, in FIG. 1, reference numeral 11 is a crank case of an air-cooled general-purpose engine, and this case 1
One end of a negative pressure passage 13 is opened below the lubricating oil level 12 in the float chamber 4 , and the other end of this negative pressure passage 13 is opened above the fuel surface 6 above the float chamber 4 .
An opening/closing means 14, which will be described below, is provided in the middle. This opening/closing means 14 opens the negative pressure passage 13 only in the normal opening range of the throttle valve 9, and as shown in FIGS.
On the outer peripheral surface of one end fitted to the carburetor main body 1,
An arcuate groove 15 is formed along the circumferential direction, and the crankcase side portion 13a and the float chamber side portion 13b of the negative pressure passage 13 are connected via the arcuate groove 15 only in the normal opening range α of the throttle valve 9. configured to communicate. Furthermore, an air vent 1 is provided at the top of the float chamber 4.
One end of the air vent 16 is opened, and the air vent 16 is opened to the atmosphere via a diaphragm mechanism 17, which will be described later. The aperture mechanism 17 has an arcuate groove 18 along the circumferential direction formed on the outer peripheral surface of the throttle shaft 10 on the opposite side to the arcuate groove 15, and a protrusion 19 provided in the center of the groove 18 to form the aperture 20. is formed, and the float chamber side portion 16a and atmospheric pressure side portion 16b of the air vent 16 are in the normal opening range α of the throttle valve 9.
In this case, the openings are communicated through the throttle 20, and the openings are communicated without going through the throttle 20 outside the normal opening range α. In the device configured as described above, in the normal opening range α of the throttle valve 9, the crankcase side portion 13a and the float chamber side portion 13b of the negative pressure passage 13 are connected through the arcuate groove 15, as shown in FIG. Since the positive pressure period is shorter and the pressure value is smaller than the negative pressure period during one cycle of engine operation, as shown in FIG. 5, the negative pressure of the crankcase 11 becomes negative on average. The pulsation of the pressure is attenuated by the damper action of the lubricating oil, and the pressure always acts on the upper part of the fuel surface 6 of the float chamber 4. Therefore, this part becomes a negative pressure and the fuel in the intake passage 2 and the float chamber 4 is reduced. The negative pressure and the difference with the upper part of surface 6 become smaller. Therefore, in the normal opening range α of the throttle valve 9, the amount of fuel discharged from the main mezzle 7 to the bench lily portion 2a of the intake passage 2 is smaller than that of a conventional float chamber where the upper part of the fuel surface is at atmospheric pressure. The air-fuel mixture decreases, making the air-fuel mixture leaner and reducing fuel consumption. In this case, since the float chamber side portion 16a and the atmosphere side portion 16b of the air vent 16 communicate with each other via the throttle 20, the air introduced from the air vent 16 into the float chamber 4 is throttled by the throttle 20. This facilitates the effect of reducing the amount of fuel discharged to the bench lily portion 2a described above. Further, when the throttle valve 9 is opened at a lower opening than the normal opening range α, as shown in FIG. 3, the negative pressure passage 1
3, the crankcase side portion 13a and the float chamber side portion 13b are shifted from the arcuate groove 15, so that the negative pressure inside the crankcase 11 does not act on the float chamber 4, and the air vent 16 is aligned with the float chamber side portion 16a. Since the atmosphere side portion 16b is communicated with the other side of the throttle 20 through the groove 18, air is introduced into the float chamber 4 without being throttled by the throttle 20, and therefore the fuel level in the float chamber 4 is reduced. 6 The upper part is at atmospheric pressure. Furthermore, the throttle valve 9
Since both parts 13a and 13b of the negative pressure passage 13 are removed from the arcuate groove 15 even when the valve is fully opened, which is higher than the normal opening range α, the crankcase 1 is not placed in the float chamber 4.
Since the negative pressure inside the air vent 16 does not act and both parts 16a and 16b of the air vent 16 communicate with each other through the groove 18 on the other side of the throttle 20, air can flow into the float chamber 4 without being throttled by the throttle 20. has been introduced,
The portion above the fuel surface 6 in the float chamber 4 is at atmospheric pressure. Therefore, the air-fuel mixture is not diluted when the throttle valve 9 is not in the normal opening range α. That is, in this example, line a in FIG.
As shown in Figure 2, the float chamber is at negative pressure only in the throttle valve's normal opening range α, and is at atmospheric pressure at other times, and the float chamber is at atmospheric pressure in the throttle valve's full opening range. Compared to this, as shown by line b, the fuel consumption of this embodiment is reduced only in the normal opening range α of the throttle valve. Since the air-fuel mixture is not diluted outside the normal opening range α of the throttle valve, unlike the case where the air-fuel mixture is diluted in the full throttle valve opening range, there is a risk of deterioration of no-load operability at low openings or There are no problems such as a decrease in opening degree or output during high-load operation, or an increase in the temperature of various parts of the engine or lubricating oil temperature during high-opening or high-load operation in an air-cooled engine. Furthermore, the lubricating oil surface 12 inside the crankcase 11
By opening the negative pressure passage 13 downward, the pulsation of the negative pressure inside the crankcase 11 is reduced due to the damper action of the lubricating oil. It can act reliably above the surface 6, and therefore, stable operation can be achieved with a simple configuration that does not require a restriction in the negative pressure passage or a negative pressure adjustment means such as a surge tank.

[Effect of the idea]

As explained above, according to the present invention, by opening the negative pressure passage with an opening/closing means that opens only within a predetermined opening range of the throttle valve, negative pressure is guided from below the lubricating oil level in the crankcase to the float chamber. This creates a negative pressure in the float chamber and dilutes the mixture.
Fuel consumption can be reduced, and on the other hand, the air-fuel mixture is not diluted during no-load operation with a low opening of the throttle valve, or during high-load operation with a high opening, so the air-fuel mixture is diluted even during these operations. This eliminates the problems of the conventional type, and also allows the relatively small negative pressure with less pulsation under the lubricating oil surface in the crankcase to be guided to the float chamber, resulting in stable operation with a simple configuration. There is an effect that can be expected.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view showing one embodiment of the present invention, Fig. 2 is an enlarged cross-sectional view of the throttle valve at the normal opening along the line AA in Fig. 1, and Fig. 3 is an enlarged cross-sectional view of the throttle valve at its normal opening. Fig. 4 is an enlarged cross-sectional view at a low opening, and Fig. 4 is a diagram showing the relationship between the throttle opening of the present invention and the pressure in the float chamber, as well as the relationship in fuel efficiency compared to the conventional example. FIG. 3 is a diagram showing pressure fluctuations. 1... Carburetor body, 2... Intake passage, 2a...
Bench lily part, 3... Float chamber wall, 4... Float chamber, 5... Fuel, 6... Fuel surface, 7... Main nozzle, 8... Main jet, 9... Throttle valve, 10... Throttle shaft, 11...Crankcase, 12...Lubricating oil surface, 13...Negative pressure passage, 13a...Crankcase side portion, 13b...
...Float chamber side portion, 14...Opening/closing means, 15...
...Arc-shaped groove, 16...Air vent, 16a...Float chamber side part, 16b...Atmospheric side part, 17...
Aperture mechanism, 18...concave groove, 19...protrusion, 20...
...Aperture.

Claims (1)

[Claims] 1. A negative pressure passage that opens below the lubricating oil level in the crankcase is communicated with above the fuel level of the float chamber,
The negative pressure passage is provided with an opening/closing means that opens the negative pressure passage only within a predetermined opening range of the throttle valve, and the amount of fuel supplied to the intake passage is controlled when the throttle valve is within a predetermined opening range. A fuel consumption reduction device for a carburetor, which is characterized by: