JPS6319700B2 - - 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 method of reducing the amount of fuel supplied to an intake passage.

[Conventional technology]

By the way, the above-mentioned method of reducing the amount of fuel supplied to the intake passage is disclosed in Japanese Patent Publication No. 38-17506 or Japanese Patent Application Laid-Open No. 52-37632, which are prior art examples. According to this method, the amount of fuel supplied to the intake passage is reduced by guiding engine negative pressure caused by engine operation to the float chamber only within a predetermined opening range of the throttle valve. Communication with the atmosphere through the air vent is restricted throughout the entire opening range of the throttle valve.

[Problems to be solved by the invention]

However, in the method described above in the prior art example, the throttle valve opens within a predetermined opening range and the negative pressure of the engine is introduced into the float chamber due to sudden acceleration. When changing the operating range to the load range, it is not possible to bring the inside of the float chamber to atmospheric pressure without delay. As a result, there is a problem in that the fuel supplied from the float chamber to the intake passage becomes insufficient, causing the engine to run out of breath. An object of the present invention is to provide a method for reducing the amount of fuel supplied to the intake passage, which eliminates such problems.

[Means to solve the problem]

The present invention has the following technical means to achieve the above object. That is, the throttle valve is opened only within a predetermined opening range to guide the negative pressure of the engine accompanying engine operation into the float chamber, and the communication with the atmosphere through the air vent of the float chamber is restricted only within the above-mentioned predetermined opening range. In this method, the amount of fuel supplied to the intake passage is reduced by controlling the negative pressure in the float chamber.

【Example】

An embodiment of an apparatus for carrying out the method of the present invention will be described below with reference to the drawings. In FIG. 1, numeral 1 is the carburetor main body;
An intake passage 2 is formed in this carburetor main body 1,
In the float chamber wall 3 fixed to the carburetor main body 1,
A float chamber 4 is formed. This float chamber 4 has a built-in float (not shown), and is configured to be supplied with fuel 5 so as to maintain a predetermined fuel level 6. 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 1 , 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 later, 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.
An arcuate groove 15 extending in the circumferential direction is formed on the outer peripheral surface of one end fitted to the carburetor main body 1, and the crankcase side portion 13a and the float chamber side portion of the negative pressure passage 13 are connected through the arcuate groove 15. 13 are configured to communicate with each other only in the normal opening range α of the throttle valve 9. Furthermore, one end of an air vent 16 is opened in the upper part of the float chamber 4, and this air vent 16 is
It is opened to the atmosphere via a diaphragm mechanism 17, which will be described later. This aperture mechanism 17 has an arcuate groove 18 along the circumferential direction formed in a portion of the outer peripheral surface of the throttle shaft 10 opposite to the arcuate groove 15, and a protrusion 19 provided in the center of the groove 18 to reduce the aperture. 20 is formed, and in the normal opening range α of the throttle valve 9, the air vent 1
6, the float chamber side portion 16a and the atmospheric pressure side portion 16
b are communicated via the aperture 20, and the normal opening range α
Other than that, communication is made without going through the diaphragm 20. In the device configured as described above, in the normal opening range α of the throttle valve 9, as shown in FIG. As shown in Figure 5, during one cycle of engine operation, the positive pressure period is shorter and the pressure value is smaller than the negative pressure period, so the pressure becomes negative on average. The pulsation of the negative pressure in the intake passage 2 is attenuated by the damper action of the lubricating oil, which acts on the upper part of the fuel surface 6 of the float chamber 4, and this part becomes negative pressure.Therefore, the negative pressure in the intake passage 2 and the float The difference with the negative pressure in the upper part of the fuel surface 6 of the chamber 4 becomes smaller. Therefore, the amount of fuel discharged from the main nozzle 7 to the bench lily portion 2a of the intake passage 2 is
The upper part of the fuel surface in the conventional float chamber is at atmospheric pressure, which is reduced compared to that of the conventional float chamber, resulting in a lean mixture and reduced fuel consumption. In this case, the air vent 16 has a float chamber side portion 16a and an atmosphere side portion 16b that are connected to the aperture 20.
The air introduced into the float chamber 4 from the air vent 16 is throttled by the throttle 20, thereby promoting 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 not aligned with the float chamber side portion 16a. Since the atmosphere side portion 16b is communicated with the air vent 16 on the other side of the throttle 20 through the groove 18, the atmosphere is introduced into the float chamber 4 through the air vent 16 without being throttled by the throttle 20. The upper part of the fuel surface 6 is at atmospheric pressure. Furthermore, even when the throttle valve 9 is fully open, which is higher than the normal opening range α, both parts 13 of the negative pressure passage 13
a, 13b are removed from the arcuate groove 15, no negative pressure is applied to the float chamber 4, and both parts 16a, 16b of the air vent 16 are communicated through the concave groove 18 on the other side of the throttle 20, so the float Air is introduced into the chamber 4 without being throttled by the throttle 20, and the portion above the fuel surface 6 in the float chamber 4 becomes atmospheric pressure. Therefore, the throttle valve 9 is within the normal opening range α and the negative pressure in the crankcase 11 is acting on the upper part of the fuel surface 6 in the float chamber 4, from the normal operating range to the high load operating range due to sudden acceleration. When the operating state changes to , the pressure inside the float chamber 4 reaches atmospheric pressure without delay, so sufficient fuel is supplied from the float chamber 4 to the bench lily portion 2a, and therefore,
This prevents the engine from suffocating. Therefore, the air-fuel mixture is not diluted when the throttle valve 9 is not in the normal opening range α. That is, according to the method of reducing the amount of fuel supplied to the intake passage of the present invention according to this embodiment, as shown by line a in FIG. 4, the float chamber becomes negative pressure only in the normal opening range α of the throttle valve. , other than this, the pressure is atmospheric pressure, and the amount of fuel supplied is reduced only in the normal opening range α of the throttle valve. In addition, since the air-fuel mixture does not become diluted outside the normal opening range α of the throttle valve, there may be problems such as deterioration of no-load operability at low openings, decrease in output during high-opening or high-load operation, and The breathing of the engine when changing operation from α to high-load operation area due to sudden acceleration,
This eliminates the problem of high temperatures of engine parts and lubricating oil during high opening and high load operation in air-cooled engines. In the present invention, the negative pressure applied to the float chamber is not necessarily the negative pressure within the crankcase, but may be any appropriate engine negative pressure associated with engine operation, such as suction negative pressure. Furthermore, the present invention is not limited to air-cooled general-purpose engines;
Widely applicable to other engine carburetors.

【Effect of the invention】

As explained above, according to the present invention, the throttle valve is opened only within a predetermined opening range to guide the negative pressure of the engine due to engine operation to the float chamber.
This is a method of reducing the amount of fuel supplied to the intake passage by controlling the communication with the atmosphere through the air vent of the float chamber only within the predetermined opening range and adjusting the negative pressure in the float chamber. In the normal valve opening range and normal operation range, the air-fuel mixture supplied to the intake passage can be diluted and the amount of fuel supplied can be reduced. Since the air-fuel mixture is not diluted during high-load operation, the problem of diluting the air-fuel mixture during these operations can be resolved, and the throttle valve can be moved from the predetermined opening range to the high-load operation area due to sudden acceleration. This has the effect of preventing the engine from breathing when changing the operating range.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of the throttle valve at the normal opening along line A-A in FIG. 1, and FIG. Fig. 4 is an enlarged cross-sectional view at low opening; Fig. 4 is a diagram showing the relationship between the throttle opening of the present invention and the pressure in the float chamber; and Fig. 5 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. 5 is the pressure generated in the crankcase. FIG. 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 The throttle valve is opened only within a predetermined opening range to guide the negative pressure of the engine accompanying engine operation to the float chamber, and the communication with the atmosphere through the air vent of the float chamber is throttled and controlled only within the above-mentioned predetermined opening range. and a method for reducing the amount of fuel supplied to the intake passage, which adjusts the negative pressure in the float chamber.