JPH0720364Y2 - Vaporizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a carburetor for an internal combustion engine, and more particularly to a carburetor equipped with a starter and an acceleration pump.

[Conventional technology]

A carburetor having a starter and an acceleration pump is, for example,
It is disclosed in Japanese Patent No. 63-21709. The starter guides the air-fuel mixture to the downstream side of the substantially fully closed throttle valve at the time of cold start, and connects the float chamber of the carburetor to the bypass passage that connects the upstream side and the downstream side of the throttle valve. The opening degree of the bypass passage is adjusted by the plunger to control the supply amount of the air-fuel mixture.
On the other hand, the acceleration pump is provided to prevent the fuel supplied to the engine from being relatively insufficient due to a sudden accelerator operation at the time of engine acceleration, resulting in a lean mixture and impairing acceleration performance. It is configured to supply fuel to the upstream side of the throttle valve during sudden acceleration.

In addition, Japanese Patent Publication No. 19-19542 discloses a configuration in which the opening degree of the leak passage connected to the discharge side of the acceleration pump is controlled according to the engine temperature. It does not suggest the configuration of the present invention that changes according to the opening degree of the starter.

[Problems to be solved by the device]

In the conventional carburetor as described above, when the throttle valve is opened to start immediately after the engine is started by using the starter when cold, the intake pipe negative pressure is not small, which acts on the starter. There is a problem that the negative pressure decreases, the fuel supply amount decreases, the air-fuel ratio becomes lean, and the startability is impaired.

The present invention supplies sufficient fuel to the downstream side of the throttle valve at the time of starting at the time of cold engine to improve the immediate startability at the time of cold engine, and at the time of warming up, the acceleration pump operates efficiently and is sufficient. The purpose of the invention is to provide a carburetor capable of obtaining acceleration performance.

[Means for Solving the Problems]

The carburetor according to the present invention includes a starter capable of supplying a fuel-air mixture to the intake passage of the carburetor by opening the starting fuel supply passage at the time of engine start, and fuel to the intake passage in association with opening / closing operation of the throttle valve. It has a dischargeable acceleration pump and a leak passage connected to the discharge side of the acceleration pump, and changes the opening of the leak passage according to the opening of the starter to control the fuel discharge amount of the acceleration pump. And means are provided.

[Action]

The larger the opening of the starter, the smaller the opening of the leak passage and the larger the amount of fuel discharged from the acceleration pump. When the starter is closed after warming up, the opening degree of the leak passage becomes small and the fuel discharge amount of the acceleration pump becomes small. During cold and warm-up, the pump stroke of the acceleration pump does not change, and only the fuel discharge amount changes.

〔Example〕

 The present invention will be described below with reference to illustrated embodiments.

FIG. 2 shows a schematic structure of a carburetor equipped with a starter and an acceleration pump, and this carburetor is mounted on, for example, a motorcycle.

In this figure, a throttle valve provided in the intake passage 11
Reference numeral 12 is pivotally supported on the carburetor main body 10 via a valve shaft 13 and is opened / closed by an accelerator mechanism (not shown). Throttle valve 12
The bypass passage 14 connecting the upstream side (left side in the figure) and the downstream side (right side in the figure) of is connected to the float chamber 16 via the fuel pipe 15. The bypass passage 14 and the fuel pipe 15 form a starting fuel supply passage. A plunger 17 is provided at a connecting portion between the bypass passage 14 and the fuel pipe 15, and these components constitute a starter. The plunger 17 has a needle valve 17a at its tip, and the flow passage areas of the bypass passage 14 and the fuel pipe 15 change according to the protrusion amount of the needle valve 17a into the bypass passage 14. The plunger 17 is connected to a knob (not shown) provided in the driver's seat and is constantly urged by a spring in a direction to close the bypass passage 14. A nozzle 21 of an acceleration pump described later is provided on the upstream side of the throttle valve 12.

During normal operation after warming up, the plunger 17 closes the bypass passage 14 and the fuel pipe 15 with a spring. On the other hand, when the engine is started when the engine is cold, when the knob is pulled against the spring, the plunger 17 opens the bypass passage 14 and connects the fuel pipe 15 to the bypass passage 14. Therefore, the negative pressure generated on the downstream side of the throttle valve 12 supplies the air-fuel mixture to the downstream side of the throttle valve 12 via the bypass passage 14 and the fuel pipe 15, so that the engine startability is improved.

FIG. 1 shows the structure of the acceleration pump. In this figure, the plunger 22 is slidably supported in a plunger hole 23 formed in the wall portion 20 of the float chamber 16. A pump chamber 24 is formed by the lower end portion of the plunger 22 and the plunger hole 23,
This pump chamber 24 is connected to the inside of the float chamber 16 via an inlet passage 25, and a nozzle in the intake passage via an outlet passage 26.
Connected to 21. The inlet passage 25 is provided with a check valve 27 for flowing the fuel in the float chamber 16 only to the pump chamber 25 side. Similarly, the outlet passage 26 is provided with the fuel in the pump chamber 22 on the nozzle 21 side. A non-return valve 26a is provided to allow the flow to flow only. A spring 28 is provided in the pump chamber 24 and
22 is always urged upward by this spring 28. The upper portion of the plunger 22 projects upward from a cap 29 that closes the upper opening of the plunger hole 23, and the projecting end portion engages with a plunger drive lever (not shown). The plunger drive lever rotates in conjunction with the opening / closing operation of the throttle valve. That is, the plunger 22 moves up and down together with the throttle valve, and its lifting stroke is proportional to the opening of the throttle valve.

When the throttle valve is fully closed, the plunger 22 is pressed by the spring 28 and is in the highest position, and when the throttle valve is opened here, the plunger 20 descends with this opening operation,
The fuel in the pump chamber 24 is supplied from the nozzle 21 into the intake passage. Then, when the throttle valve rotates in the closing direction,
The plunger 22 is lifted by the elastic force of the spring 28, and the fuel F in the float chamber 16 is supplied to the pump chamber 24 through the check valve 27. Then, as the throttle valve opens and closes,
Fuel is supplied into the intake passage by the pumping action of the acceleration pump, a predetermined air-fuel ratio is obtained, and the acceleration of the engine is compensated.

A leak passage 31 is connected between the check valve 27 and the pump chamber 24 of the inlet passage 25, that is, on the discharge side of the acceleration pump. The leak passage 31 extends vertically from the inlet passage 25 and communicates with the inside of the float chamber 16. The support hole 32 is provided on the side opposite to the leak passage 31 with respect to the inlet passage 25, extends coaxially with the leak passage 31, and the needle valve 33 is slidably supported in the support hole 32. . A tip portion 34 of the needle valve 33 is formed in a tapered shape, and the tip portion 34 extends through the inlet passage 25 and faces the leak passage 31. Base of needle valve 33
35 has a larger diameter than the other parts, and the end of the base 35 projects from the wall 20. Further, the needle valve 33, by the spring 36 provided between the base 35 and the edge of the leak passage 31,
It is constantly urged in the direction of opening the leak passage 31.

A diaphragm 41 is provided at the projecting end of the base portion 35 of the needle valve, and the inner peripheral edge portion of the diaphragm 41 is fixed to the base portion 35 by a pair of dish-shaped members 42. The outer peripheral edge portion of the diaphragm 41 is fixed between the annular ridge 43 formed on the outer surface of the wall portion 20 and the cover 44, whereby a fuel reservoir for holding the fuel leaked from the support hole 32 is provided inside the diaphragm 41. Chamber 45
Are sectioned. On the other hand, a bell 47 is pivotally supported by opening a pivot 47 on a flange 46 formed on the outer surface of the wall 20, and one end of the bell crank 48 passes through a slit 49 formed in the cover 44. Engage with the protruding end of the needle valve 22. A connecting rod 52 is connected to the other end of the bell crank 48 via a pin 51. The connecting rod 52 is connected to a starter lever (not shown) connected to the upper end of the starter plunger 17 (FIG. 1).

When the starter plunger 17 is fully opened, the connecting rod 52 is at the most displaced position in the direction of arrow A. Therefore, the bell crank 48 pushes the needle valve 33 to the right in the drawing, and the leak passage 31 is closed. That is, when the plunger 22 of the acceleration pump descends, all the fuel pumped from the pump chamber 24 is guided to the outlet passage 26 and discharged to the intake passage 11 (FIG. 1). On the other hand, when the plunger 17 of the starter is displaced to the closed side, the connecting rod 52 is displaced in the direction of arrow B, and the bell crank 48 weakens the pressing force of the needle valve 33 to the right, whereby the needle valve 33 Is retracted by the elastic force of the spring 36, and the leak passage 31 is opened. As a result, when the plunger 22 of the acceleration pump descends, a part of the fuel pumped from the pump chamber 24 flows back from the leak passage 31 into the float chamber 16, and the amount of fuel discharged to the intake passage decreases.

Therefore, the needle valve 33 decreases the opening degree of the leak passage 31 as the opening degree of the starter increases, and thus the fuel discharge amount of the acceleration pump increases. Therefore, in the cold state, the fuel discharge amount by the acceleration pump is increased with the opening of the starter, and a good prompt startability is obtained. On the other hand, after the warm-up, the opening degree of the starter is made small or made zero, which reduces the fuel discharge amount of the acceleration pump.

Here, the stroke of the plunger 22 of the acceleration pump is always proportional to the opening degree of the throttle valve and has no direct relation to the fuel discharge amount to the intake passage. That is, the amount of fuel discharged from the pump chamber 24 by the plunger 22 is determined by the opening of the throttle valve, and the amount of fuel discharged into the intake passage is determined by the opening of the leak passage 31, that is, the opening of the starter. As described above, the fuel discharge amount of the acceleration pump is determined not by changing the stroke of the plunger but by the opening degree of the leak passage 31, and the stroke of the acceleration pump is always changed in proportion to the opening degree of the throttle valve. There is.
Therefore, the effective stroke of the acceleration pump (the pump chamber 24
It is possible to secure a large stroke for sucking and discharging the fuel), and high pump efficiency can be obtained.

The opening of the starter does not necessarily have to be adjusted by the driver of the vehicle, but may be adjusted by a temperature sensitive actuator such as wax that expands and contracts according to the engine temperature. In this case, the temperature sensitive actuator may be configured to displace the needle valve 33 and increase the opening degree of the leak passage 31 as the engine temperature increases.

[Effect of device]

As described above, according to the present invention, it is possible to supply sufficient fuel to the downstream side of the throttle valve at the time of starting at the time of cold engine to improve the immediate startability at the time of cold engine, and after warming up,
It is possible to obtain a carburetor in which the acceleration pump operates efficiently and sufficient acceleration performance can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a side view showing a carburetor with a portion near a throttle valve cut away. 11 …… Intake passage 14 …… Bypass passage 15 …… Fuel pipe 17 …… Starter plunger 22 …… Accelerating pump plunger 31 …… Leak passage 33 …… Needle valve 48 …… Bell crank 52 …… Connecting rod

Claims (2)

[Scope of utility model registration request] 1. A starter capable of supplying a mixture to an intake passage of a carburetor by opening a starting fuel supply passage when starting an engine, and a fuel capable of discharging fuel to the intake passage in association with opening / closing operation of a throttle valve. An acceleration pump and a leak passage connected to the discharge side of the acceleration pump, the opening of the leak passage being changed according to the opening of the starter, and means for controlling the fuel discharge amount of the acceleration pump. A vaporizer characterized by having. 2. A practical use characterized in that the control means has a needle valve facing the leak passage, and the needle valve is displaced according to the opening degree of the starter to change the opening degree of the leak passage. A carburetor according to claim 1 of a new model registration claim.