JPH09158782A - Motorcycle carburetor starter - Google Patents

Abstract

(57) An object of the present invention is to provide a starter for a carburetor for a motorcycle, which can reduce the dependence on mechanical accuracy and can supply an accurate mixing ratio. SOLUTION: The ratio of the amount of air passing through a passage cross section of a starting passage 20 which is variable by a piston valve 18 and the amount of fuel from a fuel nozzle between a needle 16 and a needle jet 22 The needle 16 is set so that it is always constant even if the number is increased or decreased. The starting passage 20 communicates with an intake passage 34 on the downstream side of the carburetor 32. An air-fuel mixture control means 12 for controlling the opening of the cross-sectional area of the starting passage 20 when the temperature is low and closing the starting passage 20 when the temperature is high is provided in the middle of the starting passage 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a starting device used in a two-wheel carburetor.

[0002]

2. Description of the Related Art Conventionally, a plunger type starting device shown in FIG. 3 is known as a starting device used in a two-wheel carburetor. The starting device 50 includes a body 52, a starting passage formed in the body 52, a slide valve 54 for varying a cross section (the portion is referred to as a "venturi portion") in the middle of the starting passage, and It has a needle 56 provided at the tip of the sliding valve 54, and a needle jet 58 with which the needle 56 is fitted to form a fuel nozzle. The starting passage opened / closed by the slide valve 54 is an upstream starting passage 6 arranged in an offset shape and having a relatively large diameter.
0 and a downstream starting passage 62 having a relatively small diameter. In this starting device 50, the amount of air introduced from the upstream starting passage 60 to the downstream starting passage 62 is adjusted by the movement of the slide valve 54, and between the needle 56 and the needle jet 60 fitted thereto. The fuel discharge amount is changed by changing the cross-sectional area of the fuel nozzle, and the air-fuel ratio of the starting mixture is made constant.

In FIG. 3, it is assumed that the upstream side starting passage 60 is provided.
Assuming that the downstream start passage 62 and the downstream start passage 62 have the same cross section and the same central axis, the amount of air flowing through the downstream start passage 62 decreases when the slide valve 54 narrows the start passage cross section. . Therefore, in order to keep the air-fuel ratio constant, it is necessary to reduce the negative pressure applied to the fuel nozzle of the needle jet 60 and reduce the amount of fuel discharged from the fuel nozzle. However, when the cross section of the starting passage is narrowed by the sliding valve 54, the cross section of the connecting portion between the venturi portion and the upstream starting passage 60 is also narrowed, and the amount of air reaching the fuel nozzle is reduced. As a result, the negative pressure applied to the fuel nozzle does not decrease, and more fuel than necessary is discharged from the fuel nozzle, resulting in a high mixing ratio. In order to solve this problem, it is required to finely control the shape of the needle 56 to adjust the cross-sectional area of the fuel nozzle, but there is a limit to the fine control of the shape of the needle 56. .

As a solution to this drawback, in the starting device 50 shown in FIG. 3, the cross section of the upstream starting passage 60 is made larger than the cross section of the downstream starting passage 62, and as a result, the centers of these passages are It is arranged in an offset shape.
In this way, by increasing the cross-sectional area of the upstream side starting passage 60, the passage area that connects the venturi portion formed by the slide valve 54 and the upstream side starting passage 60 can be made relatively large. (For a large diameter and a small diameter of the passage, the larger diameter communicates with the venturi portion in a wider area), and introduces a relatively large amount of air from the upstream side starting passage 60 to the fuel nozzle. be able to. As a result, even when the amount of air flowing through the downstream side starting passage 62 is reduced by narrowing the passage cross section by the slide valve 54, the negative pressure applied to the fuel nozzle can be reduced, and more fuel than necessary is prevented from being discharged. Thus, it is possible to prevent the problem that the mixing ratio becomes high. As another method for preventing the mixture ratio from becoming high, as shown in FIG. 4, a notch 68 is provided at the lower end on the upstream side of the slide valve 54, and the notch 68 causes an air amount from the upstream side to the fuel nozzle. There are some that are designed to increase.

[0005]

In the conventional starting device 50, the control of the air-fuel ratio depends on the mechanical precision such as the offset machining of the starting passage and the precise machining of the needle 56 for adjusting the mixing ratio. Therefore, it is difficult to obtain the optimum air-fuel ratio, and the processing man-hours are required.

[0006] The present invention has been made in view of this point,
An object of the present invention is to provide a starter for a two-wheel carburetor that can supply a highly accurate mixing ratio by reducing the dependence on mechanical accuracy.

[0007]

In order to achieve the above object, the present invention is to open a fuel nozzle in a starting passage, and to mix a starting mixture with fuel discharged from the fuel nozzle and air passing therethrough. In the starting device of the carburetor for two wheels that forms the starting air-fuel mixture into the intake passage to change the passage cross section of the starting passage by being displaced according to the negative pressure applied to the starting passage at that position. A piston valve, which is attached to the piston valve and which is for varying the cross-sectional area of the fuel nozzle, discharges a fuel amount proportional to the amount of air passing through the starting passage from the fuel nozzle. The formed needle and the air-fuel mixture control for adjusting the amount of the air-fuel mixture for starting that is provided in the middle of the starting passage on the downstream side of the piston valve position. It is obtained by such a means.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of a two-wheel carburetor starting device according to the present invention. The two-wheel carburetor starting device of the present invention comprises a constant negative pressure fuel supply means 10 and an air-fuel mixture control means 12. The constant negative pressure type fuel supply means 10 is
A body 14, a piston valve 18 having a needle 16 for adjusting the fuel amount at the tip, and a starting passage 20 whose cross section can be varied by the piston valve 18 (where the cross section can be varied is referred to as a "venturi section"). ), A needle jet 22 that fits the needle 16 into its internal space to form a fuel nozzle, a diaphragm 24 attached to the piston valve 18, and a negative pressure chamber 26 defined by the diaphragm 24. A spring 28 that is provided in the negative pressure chamber 26 and biases the piston valve 18 in the direction in which the needle 16 is provided. Further, inside the piston valve 18, a negative pressure introducing passage 30 for connecting the negative pressure chamber 26 and the venturi portion of the starting passage 20 is provided.

The constant negative pressure type fuel supply means 10 has a function similar to that of a so-called constant negative pressure type carburetor, and the negative pressure applied to the venturi portion causes the piston valve 18 to move and the venturi portion of the starting passage 20 to move. Change the cross-sectional area. With the movement of the piston valve 18, the amount of starting air passing through the venturi portion changes. Further, since the needle 16 attached to the piston valve 18 is displaced with respect to the fuel nozzle, the amount of fuel discharged from the fuel nozzle changes according to the cross-sectional shape of the needle 16. The shape of the needle 16 is such that, regardless of the position of the piston valve 18, the amount of air passing through the venturi portion of the starting passage 20 and the starting passage 20 from the fuel nozzle.
It is set so that the ratio with the amount of fuel discharged to is the same. For example, the cross-sectional area of the venturi portion of the starting passage 20 is set to be proportional to the cross-sectional area of the fuel nozzle.

A starting passage 2 of the constant negative pressure fuel supply means 10.
The downstream side of 0 is connected to the intake passage 34 of the carburetor 32 via the mixture amount control means 12. The air-fuel mixture control means 12 adjusts the amount of air-fuel mixture for start-up that passes through the starting passage 20 at low temperatures, and closes the starting passage 20 at high temperatures. The air-fuel mixture control means 12 shown in FIG. 1 is attached to the body 36 having the inside thereof as the passage 20 for starting, a bimetal 38 as a temperature operating means provided inside the body 36, and the bimetal 38. And a valve body 42 for opening and closing the communication port 40 as the starting passage 20 of the body 36. The body 36 may be installed so as to be in direct contact with the engine 44, for example. The bimetal 38 adjusts the amount of the air-fuel mixture for starting through the communication port 40 according to the temperature change when the temperature is low, and operates so that the valve body 42 closes the communication port 40 when the temperature is high.

With the above-described structure, the constant negative pressure fuel supply means 10 has the needle 16 and the needle jet 2 as the amount of air passing through the starting passage 20 changes.
The amount of fuel from the gap between 2 and 2 is changed so that a mixture of starting gas having a constant mixing ratio can be introduced into the intake passage 34 from the starting passage 20 regardless of the amount of air. The air-fuel mixture control means 12 controls the amount of the air-fuel mixture for start-up produced by the negative pressure type fuel supply means 10 at the time of low temperature start to control the intake passage 3.
No. 4 in the intake passage 34 at high temperature.

According to the present invention, the constant negative pressure type fuel supply means 1
At 0, the shape of the needle 16 is set so that the ratio of the amount of air passing through the venturi portion of the starting passage 20 and the amount of fuel discharged from the fuel nozzle is constant. The needle 16 can be easily manufactured as long as the cross-sectional area of the venturi portion and the cross-sectional area of the fuel nozzle have a constant proportional relationship. Further, according to the present invention, the needle 1
Since the shape of 6 may be related to the amount of air passing through the venturi portion, it is not necessary to bias the starting passage 20 at the front and rear positions of the piston valve 18 or change the diameter.

The air-fuel mixture control means 12 has been described as a controllable opening / closing of the starting passage 20 by means of a bimetal 38, but another example is shown in FIG. A wax 46 as a temperature operating means is fixed to the body 36, and a valve body 48 is attached to the wax 46. When the temperature is low, the valve body 48 has the starting passage 2
The amount of air-fuel mixture passing through 0 is controlled, and the valve body 48
(One-dot chain line) is set so that the starting passage 20 is closed. The mixture amount control means 12 is not limited to this configuration, and may be a manual one. Mixture amount control means 1
Since 2 is for opening and closing the starting passage 20, the installation location can be freely selected apart from the constant negative pressure type fuel supply means 10. At that time, the starting passage 20
May be formed by a hose or the like.

A cutout may be provided at the lower end on the upstream side of the piston valve 18, as in the case shown in FIG. Although not shown, the body of the carburetor 32 is also used as the body 14 of the constant negative pressure type fuel supply means 10, and the air passing through the same air cleaner (not shown) is fixed to the intake passage 34 of the carburetor 32. It may be introduced into the starting passage 20 of the negative pressure type fuel supply means 10.

[0015]

As described above, according to the two-wheel carburetor starter according to the present invention, the needle has a shape that is easy to manufacture, and it is necessary to form a needle or a bias that must meet a complicated mixing ratio requirement. Compared with the conventional one having a starting passage, the dependency of mechanical precision is significantly reduced. As a result, the present invention can improve the accuracy of the mixing ratio more than the conventional starter for a two-wheel carburetor.
Further, since the accuracy of the mixing ratio is higher, it can be used as an automatic starter for a multiple vaporizer.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a starting device for a two-wheel carburetor according to the present invention.

FIG. 2 is a configuration diagram showing another mixture amount control means used in the present invention.

FIG. 3 is a sectional view of a main part of a conventional starting device for a two-wheel carburetor.

FIG. 4 is a front view showing a conventionally known sliding valve.

[Explanation of symbols]

 10 Constant Negative Pressure Fuel Supply Means 12 Mixture Amount Controlling Means 16 Needle 18 Piston Valve 20 Starting Passage 22 Needle Jet 32 Vaporizer 34 Intake Passage 38 Bimetal 42 Valve Body 46 Wax 48 Valve Body

Claims (2)

[Claims] 1. A fuel nozzle is opened in a starting passage,
In the starting device of the carburetor for two wheels, which forms the starting mixture by the fuel discharged from the fuel nozzle and the air passing therethrough, the starting passage at that position A piston valve that is displaced according to the negative pressure applied to the passage to change the passage cross section of the starting passage,
A needle attached to the piston valve for varying the cross-sectional area of the fuel nozzle and configured to discharge from the fuel nozzle a fuel amount proportional to the amount of air passing through the starting passage; And a mixture amount control means for adjusting a mixture amount for starting, which is provided in the middle of the starting passage on the downstream side of the piston valve position and which passes therethrough. Vaporizer starter. 2. The air-fuel mixture control means comprises a valve body that opens and closes a cross section of the starting passage and a temperature actuating means that displaces the valve body according to a temperature change. A two-wheeled carburetor starter.