JPS6341648A - Fuel flow rate regulating device for carburetor - Google Patents

Abstract

PURPOSE:To prevent mixture from suddenly becoming excessively rich by providing, in a pilot air passage, a normally-opened type control valve which gradually decreases the passage sectional area while interlocking with engine speed so as to gradually increase the fuel from a pilot system. CONSTITUTION:A bleed hole in a pilot fuel passage formed in a carburetor body is communicated with a pilot air passage 33, and further on this passage 33 a normally-opened type control valve 35 is arranged. In this case, in the control valve 36 a valve body 36 which partitions the pilot air passage 33 into an upstream side 33a and an downstream side 33b is provided, and further on the circumferential surface of the valve body 36 a communicating hole 37 penetrating in the diametral direction is formed. In addition, to the end part of the valve body 35 an operating wire 40 is connected, and further the operating wire 40 is connected to a wire 13 on the open side of an exhaust valve 11 via a wire connector 39. Thus, when the exhaust valve 11 is opened as the engine speed reaches a prescribed value, it is so arranged that the valve body 35 is moved so that the communicating hole 37 is gradually moved away from the pilot air passage 33.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel flow rate adjustment device for a carburetor used in a vehicle such as a motorcycle.

[Prior art]

Conventionally, in carburetors for vehicles such as motorcycles, in order to supply a mixture suitable for the operating conditions of the engine, the mixture ratio and supply amount are controlled based on the throttle valve opening and the engine's intake negative pressure at that time. automatically based on the

However, when actually driving on a road, the engine load changes from moment to moment depending on road conditions, weather conditions, etc., so the mixture ratio is not always appropriate for the engine load.

That is, for example, when the vehicle is traveling down a long downhill slope on a highway with a tailwind, the throttle valve is almost closed and the vehicle is operating at a high rotation speed with a low load. During this low load operation, the carburetor is operated by the pilot (
Since the slow) system is activated and the fuel mixture ratio is controlled to the lowest fuel consumption, the amount of fuel supplied to the engine is reduced and the air-fuel mixture becomes lean. Therefore, even though the engine speed is high, the cooling effect inside the engine due to the heat of vaporization is reduced, and the combustion temperature also becomes high, causing problems such as overheating of the piston and abnormal combustion.

For this reason, conventionally, in the pilot air passage,
A normally open solenoid valve is provided to open and close this passage, and by closing this solenoid valve when the engine speed reaches a certain value, the air flow guided to the pilot jet is reduced and the mixture is There are known methods that control the concentration to an excessively high concentration.

[Problem that the invention seeks to solve]

However, when the pilot air passage is opened and closed by a solenoid valve as in this prior art, the amount of air dedicated to the pilot jet decreases at once, so as shown by curve A in Figure 5, the amount of fuel jetted out from the idle port decreases. This results in the (air-fuel mixture) flow rate increasing rapidly after a certain rotation speed.

Therefore, the air-fuel mixture supplied to the combustion chamber suddenly becomes rich, causing problems such as a reduction in engine output and fouling of the spark plug.

[Means for solving problems]

Therefore, in the present invention, one end is opened to the atmosphere,
The pilot air passage, the other end of which is connected to the pilot jet, is provided with a normally open control valve that gradually reduces the cross-sectional area of the pilot air passage in conjunction with the engine speed.

[Effect]

With this configuration, the closing operation of the control valve is performed gradually as the engine speed increases, so the cross-sectional area of the pilot air passage gradually decreases.
It is possible to delicately control the increase in fuel from the pilot system. Therefore, the air-fuel mixture does not suddenly become too rich, and it is possible to prevent a decrease in engine output, fouling of the spark plug, etc.

[Embodiments of the invention]

An embodiment of the present invention will be described below based on drawings in which the present invention is applied to a two-stroke engine.

In the drawing, reference numeral 1 indicates a cylinder body, 2 indicates a cylinder head, and 3 indicates a piston. Between the top surface of the piston 3 and the cylinder head 2, a combustion chamber 5 is formed where a spark plug 4 faces. An intake lower which is opened and closed by a piston 3, an exhaust port 8, and a scavenging port 9 are formed on the inner surface of the cylinder body L, and an exhaust passage 1 is connected to the exhaust port 8.
An exhaust valve 11 for changing the exhaust timing is attached to the -1- side of the 0. This exhaust valve 11
As shown in the figure, it has a roughly hourglass shape, and a notch 12 matching the opening shape of the exhaust port 8 is formed on its outer peripheral surface facing the exhaust passage 10 . The exhaust valve 11 is connected to a servo motor 15 via an opening wire 3 and a closing wire 14.
5 is controlled by a microcomputer 17 which operates in response to ignition pulses from a CDI unit 16.

That is, the microcomputer 17 detects the engine speed from the ignition pulse of the CDI unit 16, and when the engine speed reaches N1, the servo motor 15 is activated.
In the low speed range where the engine speed does not reach N1, a part of the circumferential surface of the exhaust valve 12 extends to the edge of the opening of the exhaust port 8. Therefore, the position of the opening of the exhaust port 8 is lower than the first edge, and the exhaust timing is delayed accordingly.

When the engine speed reaches N1, the servo motor 15 is driven to rotate at a certain angle by a command from the microcomputer 17, and the opening wire I3 is pulled, causing the exhaust valve 11 to gradually begin to rotate. Its peripheral surface recedes from one edge of the opening of the exhaust port 8. Therefore, as the engine speed approaches the high speed range, the position of the opening edge of the exhaust port 8 becomes higher, and the exhaust timing becomes earlier.

A forced open/close type carburetor 19 is connected to the intake lower portion of the cylinder 6 via a reed valve 18 .

This carburetor 19 has a horizontally ventilated intake passage 21 inside a body 20, and a piston-shaped throttle valve 22 that is interlocked with a throttle is provided in this intake passage 21. The throttle valve 22 is moved up and down in a direction intersecting the intake passage 21, and a needle valve 24 is connected to the end face of the intake passage 21 facing the venturi portion 23. The needle valve 24 is inserted into a needle jet 25 that opens into the venturi portion 23 , and the lower end of the needle jet 25 opens into the fuel in the float chamber 29 via a main jet 26 . needle jet 2
A main air passage 27 for supplying air is connected to the bleed hole 5, and the upstream end of this main air passage 27 is open to the atmosphere, and a main air jet 28 is provided at the open end. It is being

On the other hand, a pilot fuel passage 30 that opens into the float chamber 29 is formed inside the body 20, and the upper end of this fuel passage 30 communicates with an idle port 31 that opens downstream of the throttle valve 22. At the same time, the upper end is opened into the fuel in the float chamber 29 via the pilot jet 32. In addition, the pilot fuel passage 30
A pilot air passage 33 for supplying air is communicated with the bleed hole.

As shown in FIG. 3, the upstream end of the pilot air passage 33 is opened to the atmosphere along with the main air passage 27, and the pilot air jet 3 is provided at the open end.
4 are provided.

In the middle of this pilot air passage 33, as shown in FIG.
or is incorporated. The control valve 35 has a rod-shaped valve body 36 that partitions the pilot air passage 33 into a first stream side 33a and a downstream side 33b, and a communication hole 37 that penetrates in the radial direction is formed in the circumferential surface of the valve body 36. has been done.

Then, the valve body 36 is moved by the return spring 38.
The communication hole 37 is always held in an open position in which it opens into the pilot air passage 33, and communicates between the downstream side 33a and the downstream side 33b of the pilot air passage 33.

Further, an operating wire 40 is connected to the tip of the valve body 36, and this operating wire 40 is connected to the opening side wire 1 for opening the exhaust valve 11 via a wire coupler 39.
It is connected to 3.

Therefore, when the engine speed reaches N1 and the exhaust valve 11 begins to open, the valve body 36 is slidably displaced in the axial direction in conjunction with this, so that the communication hole 37 is gradually removed from the pilot air passage 33. It has become.

In such a configuration, when the engine speed reaches N1, the opening side wire 13 is pulled by the servo motor 15, and the exhaust valve 11 gradually begins to open as the engine speed increases, and the exhaust timing becomes earlier. .

On the other hand, -1- the opening side wire 13 is connected to the wire coupler 39
Since the valve body 36 is interlocked with the operation wire 40 of the valve body 36 via the valve body 36, when the engine speed reaches N1, the valve body 36 slides and begins to gradually come out of the communication hole 37 or the pilot air passage 33.

That is, since the closing operation of the control valve 35 is performed gradually as the engine speed increases, the passage cross-sectional area of the pilot air passage 33 is successively narrowed, and the air is supplied to the bleed hole of the pilot fuel passage 30. Air volume gradually decreases. For this reason, the concentration of the air-fuel mixture supplied from the idle port 31 gradually increases, causing curve B in FIG.
As shown in , the amount of fuel is gradually increased.

In addition, the curve X in FIG. 5 shows the upper limit of the fuel flow rate necessary to prevent abnormal combustion and damage to the piston 3, the curve Y shows the lower limit of the fuel flow rate, and the curve Z shows the fuel flow rate when the economy is M and the combined ratio. The fuel flow rates are shown respectively.

According to such an embodiment of the present invention, the fuel flow rate from the pilot system is increased little by little in conjunction with the engine speed.
Even if the fuel-air mixture reaches 1, the air-fuel mixture does not suddenly become too rich, and irregular combustion and abnormal combustion are reduced, and a decrease in engine output and fouling of the spark plug 4 can be prevented.

Furthermore, in the case of this embodiment, since the existing exhaust valve 11 is used to control the opening and closing of the control valve 35, there is no need for a dedicated control system for the control valve, and the structure is simple and can be provided at low cost.

In addition, in the embodiment described above, the opening and closing of the control valve is controlled using the exhaust valve control system, but the present invention is not limited to this. For example, the control valve may be operated in conjunction with the engine speed. The opening/closing operation may be performed using another servo motor.

〔Effect of the invention〕

According to the present invention described in detail above, the amount of fuel from the pilot system is increased little by little in conjunction with the engine speed, so the air-fuel mixture does not suddenly become too rich as in the past. , irregular combustion and abnormal combustion are reduced,
This has the advantage of preventing low engine output and fouling of the spark plug.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; FIG. 1 is a cross-sectional view of the engine around the carburetor, FIG. 2 is a cross-sectional view showing the control system of the control valve, and FIG. 4 is a block diagram showing the control system of the exhaust valve, and FIG. 5 is a characteristic diagram of the fuel flow rate. 19... Carburetor, 32... Pilot shell, 3
3... Pilot air passage, 35... Control valve. Applicant's agent Patent attorney Takehiko Suzue No. 3L; Figure 4

Claims (1)

[Claims] The pilot air passage, which has one end open to the atmosphere and the other end connected to the pilot jet, is equipped with a normally open control valve that gradually reduces the cross-sectional area of the pilot air passage in conjunction with the engine speed. A fuel flow rate adjustment device for a carburetor.