JPH0343461B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the operation of a suction piston in a variable bench lily carburetor.

A variable bench lily type carburetor changes the area of the vent lily by moving a suction piston forward and backward into the intake passage, so that the speed of air flowing through the vent lily remains approximately constant regardless of the amount of intake air. An important element governing the operation of the suction piston is the spring force that biases it. That is, when the spring force is strengthened, the amount of movement of the suction piston becomes relatively small, the flow velocity in the bench lily portion increases, and the negative pressure in the bench lily increases. Conversely, when the spring force is weakened, the amount of movement of the suction piston becomes relatively large, and the negative pressure in the bench lily becomes small. Therefore, in order to promote atomization of the fuel, it is preferable to increase the negative pressure in the vent by increasing the spring force, but if this is done, the amount of movement of the suction piston becomes smaller. For this reason, if the spring force is set to be optimal at light loads, the movement of the suction piston will be very small at idle, etc., especially when the needle has a notch for increasing the starting amount. Another problem was that even when the engine was idling, the needle could not completely come out of its starting position, resulting in overrichness. Also, at full throttle, the greater the amount of movement of the suction piston, the greater the output. Therefore, it is desired that the spring force be weakened to increase the amount of movement, ie, the amount of opening, of the suction piston at idle and at full throttle. However, in this case, there was a problem in that the fuel was not atomized sufficiently because the negative pressure in the vent lily was low during light loads.

The present invention was made in view of the above problem, and the amount of opening of the suction piston becomes large during idle and throttle, and the amount of opening becomes relatively small during light load, thereby promoting atomization of fuel. The purpose of the present invention is to provide a variable bench lily type vaporizer.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of an embodiment of a variable bench lily type carburetor according to the present invention. 1 is a carburetor main body, and an intake passage is formed in a vertical direction. Reference numeral 2 denotes a suction piston, which is attached to the intake passage so as to be horizontally movable.A bench lily 4 is formed between its tip and a raised portion 3 of the carburetor body 1 (closed in the figure). 5 is a throttle valve, and the passage between this and the suction piston 2 is called a mixing chamber 6 in which fuel and air are mixed.
The rear side of the suction piston 2 is housed in a suction piston casing 7. The diameter of the rear end 8 of the suction piston 2 is increased, and a labyrinth seal 9 is provided on the outer periphery thereof. A suction chamber 10 is formed within the casing 7 by the back surface of the suction piston 2, and communicates with the bench lily 4 through a suction hole 11. Further, an atmospheric pressure chamber 12 is formed outside the suction piston 2 and between the expanded diameter portion 8 and the casing 7, and this chamber 12 communicates with the upstream side of the vent lily of the intake passage through a port 13.

A piston rod 14 is crimped to the center of the suction piston 2 and supported by a bearing 15 fixed to the casing 7. The suction piston 2 is urged by a spring 16 toward its front side, that is, toward the intake passage.

The casing 7 has a first hole 17 passing through it toward the suction chamber 10 at the end remote from the suction piston 2 and a second hole 18 passing through it toward the atmospheric pressure chamber 12 at the end thereof. They are each provided near the end opposite to the hole 17. A pipe 19 connecting these holes is fitted into these holes 17 and 18. A negative pressure control valve 20 is disposed in the pipe 19, and consists of two chambers 22a and 22b separated by a diaphragm 21.
A valve body 23 is supported on the first chamber 22a side of 1 and is biased by a spring 24 on the second chamber 22b side. The second chamber 22b is connected via a pipe 25 to a port 26 that opens into the mixing chamber 6. The port 26 is located slightly upstream of the throttle valve 5, and receives a small negative pressure on the upstream side of the throttle valve 5 during idling, causing the throttle valve 5 to rotate and operate at a light load position. It directly faces the edge of the throttle valve 5, and receives negative pressure from the manifold downstream of the throttle valve at rotational positions beyond this point, and the negative pressure received becomes smaller when the throttle valve is near full opening. An example of the negative pressure experienced by port 26 is shown in FIG.

A fuel metering needle 27 is attached to the tip of the suction piston 2 and extends coaxially therewith. The shape of the needle 27 becomes narrower toward the tip, and is provided with a notch 28 (FIG. 3) for increasing the starting charge. The needle 27 enters a well 29 provided approximately coaxially therewith, and the well 29 is provided with a fuel metering jet 30. 31 is a fuel discharge nozzle, 32 is from the float chamber 33 to the well 29
It is a pipe connected to.

Next, the operation of the variable bench lily type carburetor having the above configuration will be explained.

When the engine is stopped, the suction piston 2
The area of the bench lily 4 becomes zero as it is pushed to the right by the spring 16, and at this time the notch 28 of the needle 27 is in a position where it overlaps the measuring jet 30.

When the engine is started, the needle 27 is in the above position, so the notch 28 and the fuel metering jet 3
Since the annular space between the engine and the engine is wide, a lot of fuel can be discharged, and the engine starts easily. Manifold negative pressure is generated when the engine starts, and this negative pressure is introduced from the mixing chamber 6 to the suction chamber 10 through the suction hole 11, and is applied to the suction chamber 2. The suction chamber negative pressure and atmospheric pressure When the differential pressure with the chamber 12 pressure overcomes the spring force of the spring 16, the suction piston moves to the left in the figure and the bench lily 4 is opened, air flows from here and a negative pressure is generated in the bench lily. .
As is well known, the amount of movement or opening of the suction piston 2 is determined so that the flow rate of air flowing through the bench lily 4 is approximately constant depending on the amount of intake air corresponding to the operating state of the engine, that is, it depends on the amount of intake air. The bench lily negative pressure changes so that it remains constant.
This opening amount is determined so that the above-mentioned differential pressure and the spring force of the spring 16 are balanced, so as mentioned above,
If the spring force of the spring 16 is strengthened, the amount of opening becomes relatively small, and conversely, if the spring force of the spring 16 is weakened, it becomes relatively large.

The discharged fuel is metered by the annular space between the outer circumference of the needle 27 and the inner circumference of the metering jet 30. Therefore, at the time of starting, the notch 28 is at the position of the jet 30, so a large amount of fuel is discharged. Since the diameter of the needle 27 decreases toward the tip, the more the suction piston 2 moves to the left, that is, the greater the amount of incoming air and the higher the load, the greater the amount of fuel discharged.

The present invention stabilizes idle rotation, and in particular, when the needle 27 is provided with a notch 28 for increasing the starting amount and the idle equivalent position of the needle 27 is adjacent to the notch 28, the starting position and the idle position can be clearly distinguished. In order to increase the amount of movement of the suction piston 2 and needle 27 in the idle state, and to reduce the flow resistance in the full throttle state, the suction piston 2 is also
The aim is to increase the amount of movement. For this reason, as described above, it is preferable to weaken the spring force of the spring 16. In such a case, the vent lily negative pressure becomes relatively small, and fuel atomization during light loads becomes a problem, especially when the air-fuel ratio is set low. It will be understood that one solution to this problem is to increase the movement of the suction piston 2 during idle and high loads, and to reduce the amount of movement during light loads, thereby increasing the bench lily negative pressure.

The variable bench lily type carburetor having the configuration shown in FIG. 1 controls the operation of a negative pressure control valve 20 by the negative pressure effect of a port 26 provided upstream of a throttle valve 5. When the spring force of the spring 24 of the negative pressure control valve 20 is balanced with the negative pressure of the port 26 in an appropriate state (see broken line A in FIG. 2), the valve body 2
3 is a suction chamber 1 consisting of a pipe 19 at port 26 when the negative pressure is low at idle and at high load.
The bypass air passage to 0 is shut off, and the pipe 19 from the atmospheric pressure chamber 12 is closed during light loads with large negative pressure at the port.
Atmospheric pressure is introduced into the suction chamber 10 through the suction chamber 10, and the negative pressure inside the suction chamber 10 becomes small. The pressure at this time is appropriately adjusted by a jet 34 provided in the pipe 19. Therefore,
The amount of movement of the suction piston 2 is made relatively small when the load is light, and the negative pressure in the vent lily at this time increases to promote atomization of the diluted fuel.

As explained above, according to the present invention, the amount of movement of the suction piston becomes large during idle and high load, and the amount of movement of the suction piston becomes relatively small during light load. Therefore,
Since atomization is promoted, the air-fuel ratio can be set low, resulting in an engine with excellent performance.

The present invention relates to a variable bench lily type carburetor having a notch for increasing the amount of fuel at start-up in the needle, and in this carburetor, there is no need to provide a separate fuel system for increasing the amount of fuel at the time of starting. Although it has the great advantage of being able to achieve its purpose with an extremely simple configuration of simply forming a notch in the needle, it also has the problem of unnecessary increase in fuel even during idling, resulting in over-richness. According to the invention, this problem is solved by making the amount of movement of the suction piston relatively large during idling, and with a simple configuration, it is possible to achieve both an increase in starting amount and stabilization of idling operation. I can do it.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of an embodiment of the variable bench lily type carburetor according to the present invention, Fig. 2 is a graph of port negative pressure against throttle valve opening, and Fig. 3 is a detailed view of the circled part in Fig. 1. . 1... Carburetor body, 2... Suction piston, 4
... bench lily, 7... suction piston casing, 9... labyrinth seal, 10... suction chamber, 11... suction hole, 12... atmospheric pressure chamber,
16... Spring, 17, 18... Hole, 19... Pipe, 2
0... Negative pressure control valve, 26... Port, 27... Needle, 28... Notch, 30... Fuel metering jet.

Claims (1)

[Claims] 1. The negative pressure from the bench lily on the front side of the suction piston is guided to the suction chamber formed by the suction piston casing and the back side of the suction piston, which can move forward and backward into the intake passage formed in the carburetor body. The suction piston is moved by the balance between the negative pressure inside the chamber and the spring force of the spring that urges the suction piston in the front direction, and the area of the bench lily is changed.
In a variable bench lily type carburetor that changes the width between the fuel metering needle attached to the tip of the suction piston and the fuel metering jet, the suction chamber and the upstream of the bench lily portion of the intake passage An air passage is provided that communicates with the intake passage, and the air passage opens and closes in response to the negative pressure generated in a port that opens opposite the throttle valve at a position slightly upstream of the throttle valve on the wall forming the intake passage. A negative pressure control valve is provided to introduce atmospheric pressure into the suction chamber during light loads, thereby making the amount of movement of the suction piston relatively small. In addition to prohibiting the introduction of fuel so that the amount of movement of the suction piston does not become relatively small, a notch for increasing the starting amount is provided in the fuel metering needle, so that a relatively large amount of fuel is discharged at the time of starting. A variable bench lily type vaporizer characterized by: