JPH0681717A - Carburetor of engine - Google Patents

Abstract

PURPOSE:To accurately increase or decrease output of an engine in accordance with driving operation of automobiles, motorcycles or the like. CONSTITUTION:A step portion 11 is formed on a jet needle 6 so that this step portion 11 may come in contact with a needle jet 3 when a piston 7 is lowered, and also a choke valve 9 is arranged near the piston 7. When the choke valve 9 is fully opened, the tip of the choke valve 9 comes in contact with the piston 7 so as to restrain the piston 7 from descending more than the fixed amount. Since the step portion 11 is pressed onto the end surface of the needle jet 3 when the jet needle 6 is lowered, the hole of the needle jet 3 can be reliably blocked. And the increase of fuel can be quickly performed when the piston 7 is lifted. Moreover, the hole of the needle jet 3 can be opened by pushing OP the piston 7 by the tip of the valve body of the choke valve 9 by the operation of the choke.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a carburetor used in engines of automobiles, motorcycles, etc., and more particularly to a variable venturi type carburetor.

[0002]

2. Description of the Related Art An intake system of an automobile, a motorcycle or the like is connected to an intake manifold which branches a passage from an air cleaner to each cylinder, and a carburetor is arranged in the middle of the intake manifold. For example, Japanese Patent Laid-Open No. 63-272956 discloses a variable venturi type vaporizer. In this carburetor, a sliding throttle valve is movably projected inside an intake passage, a needle-shaped jet needle is provided integrally with the sliding throttle valve, and a cylindrical main jet and a jet needle are inserted so as to pass through the jet needle. Needle jets are connected. This structure is intended to facilitate the manufacture of the hole for accommodating the jet needle.

On the other hand, the vaporizer 1 shown in FIG. 3 has a cylindrical main jet 2 and a needle jet 3 which are used.
Are projectingly provided inside the intake pipe 4, and their bases are opened to the fuel supply chamber 5. The conical jet needle 6 is attached to the piston 7 so as to face the hole of the needle jet 3.
The tip of the jet needle 6 can be moved into and out of the hole of the needle jet 3 via the piston 7. Reference numeral 8 is an air guide attached to the tip of the main jet 2. A choke valve 9 is installed on the upstream side of the carburetor 1, and a throttle valve 10 is installed on the downstream side.

When the piston 7 enters the inside of the intake pipe 4 and blocks the hole of the needle jet 3 by the jet needle 6, fuel is sprayed from the main jet 2 and adjusted by the throttle valve 10. Further, when the piston 7 is operated, the jet needle 6 is moved to the needle jet 3
Away from the jet needle 6 and needle jet 3
The fuel passes through the gap between and, the mixing ratio becomes high, and the output becomes high. Further, when the engine is started, the choke valve 9 is closed and the piston 7 is operated, so that the starting can be facilitated.

[0005]

However, the jet needle 6 and the needle jet 3 close the hole of the needle jet 3 by contacting the outer peripheral surface of the jet needle 6 only with the inner edge of the end of the hole of the needle jet 3. Therefore, at this abutting portion, the opening / closing piston 7 presses with an appropriate force to bring the outer periphery of the jet needle 6 into sliding contact with the inner edge of the end of the needle jet 3, which makes adjustment of this pressing force difficult. There is.

Therefore, when the choke is fully closed, fuel may leak from the hole of the needle jet 3, which makes setting the choke difficult. Therefore, the carburetor setting may be misaligned. Further, when the piston 7 is lifted, first, the sliding contact surface between the jet needle 6 and the needle jet 3 is slightly deviated from each other, so that the initial fuel increase may be small and the acceleration may be slow. .

It is an object of the present invention to provide a carburetor for an engine, which can appropriately increase or decrease the output of the engine by following the driving operation of an automobile or a motorcycle.

[0008]

In order to achieve the above-mentioned object, the present invention is a variable venturi type carburetor which moves a piston up and down by a variable throttle operation to move a jet needle attached to the piston back and forth into a needle jet. A step portion is formed in the jet needle so that the step portion contacts the needle jet when the piston descends, and a choke valve is arranged near the piston, and the choke valve is opened when the choke valve is fully opened. The tip of the piston comes into contact with the piston to prevent the piston from descending by a predetermined amount or more.

[0009]

Since the present invention is configured as described above, the step portion is pressed against the end surface of the needle jet when the jet needle is advanced into the needle jet due to the pressing force of the piston, so that the needle is securely brought into contact. Can block the holes of jets. Further, when the piston is lifted, it is possible to quickly increase the amount of fuel. When the choke valve is operated while the needle jet hole is closed, the choke valve valve body rotates, and when it is further rotated, the tip of the choke valve valve body pushes up the piston and supplies fuel from the needle jet hole. Therefore, the engine can be started easily.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The carburetor 1 shown in FIG. 1 is provided at an intermediate portion of an intake pipe 4 of an engine intake system. A cylindrical main jet 2 and a needle jet 3 used in the carburetor 1 project inside the intake pipe 4, and are fixed to the wall surface of the intake pipe 4. The base portions of the cylindrical main jet 2 and the needle jet 3 are inserted and opened inside the fuel supply chamber 5 provided along the wall surface of the intake pipe 4, and the intake pipe 4 is opened.
And the inside of the fuel supply chamber 5 are communicated with each other.

A conical jet needle 6 is fixed to a piston 7 facing the hole of the needle jet 3, and the piston 7 is provided so as to slide on the wall surface of the intake pipe 4 along the axis of the hole. . Further, a step 11 is formed on the peripheral surface of the jet needle 6 so as to face the end surface of the hole of the needle jet 3.
Are formed. A cylindrical air guide 8 having a wide inlet and an outlet is provided along the axial direction of the intake pipe 4 at the tip of the main jet 2 so as to assist the gasification of fuel. A choke valve 9 is installed on the upstream side of the carburetor 1 and a throttle valve 10 is installed on the downstream side of the intake pipe 4.

The piston 7 has a recess at the tip of its upstream side edge.
The choke valve 9 is installed at a position where the tip of the choke valve 9 engages with the recess 12 when the choke valve 9 is operated.

When the piston 7 is inserted into the intake pipe 4, the tip of the jet needle 6 is inserted into the hole of the needle jet 3, and the step portion 11 is pressed against the end surface of the needle jet 3, so that the needle jet is securely carried out. The hole of No. 3 can be closed, and the leakage of fuel can be prevented. Therefore, it becomes easy to set the choke and the carburetor when only the main jet 2 is used.

When the piston 7 is lifted, the amount of fuel can be increased quickly and the acceleration performance is improved. In addition, the power system fuel can be slightly leaked when the choke is fully opened. This operation activates the choke valve 9 when the hole of the needle jet 3 is closed, and rotates the valve body of the choke valve 9. Then, when the valve body is further rotated so that the choke is fully opened, the tip of the valve body surely engages with the recess 12 of the piston 7 and pushes up the piston 7 slightly. As a result, a gap is created between the jet needle 6 and the needle jet 3, and fuel is also supplied from the needle jet 3.

[0015]

Since the present invention is configured as described above, the fuel supplied from the needle jet can be adjusted accurately, so that choke setting and carburetor setting can be easily performed. The working time can be shortened. In addition, since the adjustment between the needle jet and the main jet is stable, the operability is good, and the response at the time of acceleration is good. Further, since the needle jet follows the choke operation, it is easy to start the engine. With such a configuration, the system can be simplified and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a carburetor of an intake system of an engine according to an embodiment of the present invention.

FIG. 2 is a side sectional view showing a state in which a choke valve is operated on the vaporizer shown in FIG.

FIG. 3 is a side sectional view showing a carburetor attached to a conventional intake system.

[Explanation of symbols]

 1 Vaporizer 2 Main jet 3 Needle jet 4 Intake pipe 6 Jet needle 7 Piston 9 Choke valve 11 Step part

Claims (1)

[Claims] 1. A variable venturi-type carburetor that moves a piston up and down by a variable throttle operation to move a jet needle attached to the piston back and forth into a needle jet, wherein a step portion is formed on the jet needle.
When the piston descends, the step portion is brought into contact with the needle jet, and a choke valve is arranged in the vicinity of the piston. When the choke valve is fully opened, the tip of the choke valve comes into contact with the piston so that the piston An carburetor for an engine, characterized in that it is configured to suppress a descent of a predetermined amount or more.