JP2001214809A - Downdraft constant vacuum type carburetor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simultaneously conduct screwing work for fastening a float chamber body 6 to a carburetor body 1, and inserting work for inserting an annular packing 16 in a tip end opening 20C of a guide hole 20, from one direction, even if a forward inclination angle of an intake air passage 2 to an engine is changed, in a downdraft constant vacuum type carburetor. SOLUTION: A longitudinal axis line B-B of a screw 7 and a longitudinal axis line C-C of a needle jet holder 12 provided with a main fuel jet 13 are disposed to intersect at a lower position thereof with a narrow angle F not more than 45 degrees. A tip end opening 20C of the guide hole 20 is formed in a cone hole shape, and the cone hole has a cone angle G parallel with the longitudinal axis line B-B of the screw 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carburetor for adjusting and controlling the concentration and amount of an air-fuel mixture supplied to an engine, and in particular, an intake passage passing through the carburetor body is disposed downward toward the engine. The present invention also relates to a downdraft type constant vacuum carburetor provided with a negative pressure operated valve for variably controlling the area of a venturi section in accordance with a negative pressure generated in an intake path, upstream of a throttle valve for opening and closing the intake path.

[0002]

2. Description of the Related Art A conventional downdraft type constant vacuum vaporizer is shown in FIG. Reference numeral 1 denotes a carburetor body formed so that the downstream of the intake passage 2 penetrates downward in the direction of gravity, and the intake passage 2 is opened and closed by a throttle valve 4 attached to a throttle valve shaft 3. And the intake passage 2 upstream of the throttle valve 4.
A negative pressure actuated valve 5 for variably controlling the area of the venturi portion V in accordance with the negative pressure in the inside is movably disposed substantially orthogonal to the intake path 2. The lower mounting end 1A of the carburetor main body 1 is brought into contact with the upper mounting end 6A of the floating chamber main body 6 and is screwed and fixed with screws 7 to form a floating chamber 8. In the float chamber 8, a constant fuel liquid level PP is formed by the cooperative action of the valve seat 30, the float valve 31, and the float 9. Reference numeral 10 denotes a jet needle attached to the negative pressure operation valve 10 along the opening / closing movement direction of the negative pressure operation valve 5, and the jet needle 10 is inserted and arranged in a nozzle 11 opened in the intake passage 2. An annular groove 11A is formed on the outer periphery of the nozzle 11, and the needle jet holder 12 communicates with the annular groove 11A. The lower end of the needle jet holder 12 has a main fuel jet 13 for controlling fuel directed to the needle jet holder 12.
Are screwed and arranged. The needle jet holder is disposed to intersect the longitudinal axis AA of the jet needle 10. Reference numeral 13 denotes a main air passage having one end communicating with the atmosphere and the other end communicating with the annular groove 11A and having a main air jet 13A. Reference numeral 14 designates an annular well 15 formed on the outer periphery of the needle jet holder 12 for the nozzle 11. The fuel flow path communicates with the lower end opening. An annular packing 16 such as an O-ring is mounted on the outer periphery of the lower end of the needle jet holder 14. Further, a guide hole 17 is provided at the lower bottom of the float chamber main body 6 such that an upstream 17A is connected to the float chamber 8 and a downstream 17B is connected to the opening of the main fuel jet 13. The opening 17 </ b> C presses and holds the annular packing 16 on the outer periphery of the lower end of the needle jet holder 14, and
The fuel of B is prevented from leaking directly into the float chamber 8.

Here, the longitudinal axis B-
B and the longitudinal axis CC of the needle jet holder 12
And the tip opening 17C of the guide hole.
Is disposed on the longitudinal axis CC of the needle jet holder 12. 1B is a positioning projection projecting downward from the lower mounting end 1A of the vaporizer main body 1, and 6B is an upper mounting end 6 of the floating chamber main body 6.
B, and the positioning protrusion 1B is inserted into the positioning recess 6B.
Can be accurately screwed to the carburetor body 1 with the screw 7. The float chamber main body 6 is assembled to the vaporizer main body 1 in a state where the component parts such as the needle jet holder 12 are attached to the vaporizer main body 1. Move the float chamber body 6 along B,
The upper mounting end 6A of the float chamber main body 6 contacts the lower mounting end 1A of the vaporizer main body 1. According to the above, the positioning projection 1B is inserted and arranged in the positioning recess 6B.
An annular packing 16 arranged on the outer periphery of the lower end of the needle jet holder 12 is inserted and arranged in the distal end opening 17C of the guide hole 17 of the floating chamber main body 6, and in this state, the floating floating chamber main body 6 is screwed into the carburetor main body 1 by the screw 7. Put on and fix. Therefore, when assembling the float chamber main body 6 to the vaporizer main body 1, the float chamber main body 6 only needs to move directly in the longitudinal axis direction of the screw 7, so that good assemblability can be obtained. The longitudinal axis YY of the intake passage 2 of the down-draft type constant vacuum carburetor is mounted on the engine with a forward inclination of D degrees with respect to the horizontal line XX.

[0004]

The conventional downdraft type constant vacuum vaporizer has the following disadvantages. In the down-draft type constant vacuum carburetor, various leaning angles are required for the engine with respect to the engine, and the longitudinal axis YY of the intake passage 2 is changed to the forward leaning angle D shown in FIG. The needle jet holder 12 is tilted even more steeply. For example, when the longitudinal axis YY of the intake passage 2 is disposed in a direction substantially orthogonal to the horizontal line XX, the longitudinal axis CC of the needle jet holder 12 is Is arranged in parallel with the longitudinal axis BB of the screw 7. This is because the needle jet holder 12 including the main fuel jet 13 is farther outward than the center of the fuel liquid level PP in the float chamber 8 at the time of such a steep forward inclination, so that the influence of the large fuel liquid level change is reduced. This is because it hinders tilt performance. In order to solve the problem, the needle jet holder 16 including the main fuel jet 13 is moved closer to the center of the fuel level by changing the longitudinal axis CC of the needle jet holder 16 to the longitudinal axis B- of the screw 7. It is considered that B is intersected at a position below B at an included angle of 45 degrees or less. However, according to the above, since the longitudinal axis BB of the screw 7 and the longitudinal axis CC of the needle jet holder 16 intersect and are not arranged in parallel, the fastening operation of the screw 7 and the needle jet holder 1 are not performed.
6 cannot be simultaneously inserted from one direction into the distal end opening 17C of the guide hole 17. In the above operation, first, the annular packing 1
6 into the tip opening 17C of the guide hole 17, and then
It is possible to rotate the float chamber main body 6 around the longitudinal axis CC of the needle jet holder 16 and perform the fastening operation with the screw 7, but according to this, it is necessary to rotate the float chamber main body 6. For example, there is a case where rotation may not be possible due to interference with components such as the positioning protrusion 1B provided on the carburetor body 1 or other fuel bosses and the float 9.

The down-draft type constant vacuum carburetor according to the present invention has been made in view of the above-mentioned problems, and is used for fastening the float chamber main body to the carburetor main body even when the forward inclination angle of the intake passage with respect to the engine changes. An object of the present invention is to provide a down-draft type constant-vacuum vaporizer that can simultaneously perform a screw tightening operation and an insertion operation of inserting an annular packing into a distal end opening of a guide hole from one direction.

[0006]

In order to achieve the above object, a downdraft type constant vacuum carburetor according to the present invention has an intake passage penetrating through the carburetor body and is disposed downward toward the engine.
On the upstream side of the throttle valve that opens and closes the intake passage, a negative pressure operating valve that variably controls the area of the venturi section according to the negative pressure in the intake passage is arranged, and the floating chamber main body is mounted at the lower mounting end of the carburetor main body. A float chamber that forms and holds a constant fuel level inside by screwing and fixing the upper mounting end portion with a screw, and an annular packing that protrudes into the float chamber and is disposed on the outer periphery of a needle jet holder having a main fuel jet In the down-draft type constant vacuum type vaporizer which is located at the bottom of the float chamber main body and the upstream side is sealed by the side wall of the guide hole connected to the float chamber, the upper mounting end of the float chamber main body is connected to the vaporizer main body. The longitudinal axis of the screw to be screwed and fixed to the lower mounting end of the needle jet holder and the longitudinal axis of the needle jet holder provided with the main fuel jet have a narrow angle of 45 degrees or less at a position below the same. Crossed arrangement, characterized in that the guide hole has a conical angle which the conical hole is parallel to the longitudinal axis of the screw with a conical hole.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a downdraft type constant vacuum vaporizer according to the present invention will be described below with reference to FIG. The same components as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted. FIG.
In FIG. 2, the horizontal line XX and the longitudinal axis YY of the intake passage 2 intersect at an angle of E degrees while being inclined forward, and this angle (E degrees) is larger than the angle (D degrees) in FIG. Horizontal line X
It has a large angle substantially perpendicular to -X. At this time, the longitudinal axis CC of the needle jet holder 16 including the main fuel jet 13 has an angle (F degrees) with respect to the longitudinal axis BB of the screw 7 at a position below the screw 7. Intersect. This angle (F degrees) intersects at an included angle of 45 degrees or less, so that even if the longitudinal axis YY of the intake path 2 is disposed substantially orthogonal to the horizontal line XX, Move the jet holder 16 to the fuel level P
−P can be arranged near the center. The guide hole 20 is formed at the bottom of the float chamber main body 6, the upstream 20 A thereof is connected to the float chamber 8 and opened, and the downstream 20 B is located facing the annular packing 16 with the distal end opening 20 C. The distal end opening 20 </ b> C of the guide hole 20 is formed as a conical hole, and the conical surface is formed at a conical angle G parallel to the longitudinal axis BB of the screw 7.

Each of the components is assembled in the same manner as in the prior art. Among them, the float chamber main body 6 is particularly assembled to the carburetor main body 1 as follows. That is, the float chamber main body 6 moves along the longitudinal axis BB of the screw 7 along the vaporizer main body 1.
The upper mounting end 6A of the float chamber main body 6 is placed in contact with the lower mounting end 1A of the vaporizer main body 1. According to the above, the distal end opening 20C which forms the conical hole of the guide hole 20
An annular packing 16 arranged on the outer periphery of the needle jet holder 12 is inserted therein, and the positioning projection 1B is inserted and arranged in the positioning recess 6B. In this state, the float chamber main body 6 is screwed into the carburetor main body by the screw 7. It is fixed.

[0009]

As described above, according to the downdraft type constant vacuum vaporizer according to the present invention, the longitudinal axis of the screw for fixing the upper mounting end of the float chamber main body to the lower mounting end of the vaporizer main body. The core wire and the longitudinal axis of the needle jet holder provided with the main jet are arranged so as to intersect at a narrow angle of 45 degrees or less at a position below the core wire, and the guide hole is a conical hole and the conical hole is a longitudinal axis of a screw. Because the cone angle is parallel to the line, the needle jet holder including the main jet is placed near the center of the fuel level in the float chamber even if the longitudinal axis of the intake path is arranged in a direction substantially perpendicular to the horizontal line. It can be arranged and the inclination performance can be maintained satisfactorily. Since the annular packing which is disposed on the outer periphery of the needle jet holder front end opening of the guide hole by moving in the direction to insert arrangement, it is possible to maintain good assembling operability.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a downdraft type constant vacuum vaporizer according to the present invention.

FIG. 2 is a longitudinal sectional view of a conventional downdraft type constant vacuum vaporizer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vaporizer main body 1A Lower mounting end part 6 Float chamber main body 6A Upper mounting end part 7 Screw 12 Needle jet holder BB Longitudinal axis of screw CC Longitudinal axis of needle jet holder 20 Guide hole

Claims (1)

[Claims] 1. An intake passage penetrating a carburetor body is disposed downward toward an engine, and an area of a venturi portion is increased upstream of a throttle valve that opens and closes the intake passage in accordance with a negative pressure in the intake passage. A float for arranging a variable pressure controlled negative pressure valve and forming a fixed fuel level inside by fixing an upper mounting end of the float chamber body to a lower mounting end of the carburetor body with a screw. Chamber, the annular packing protruding into the float chamber and disposed on the outer periphery of the needle jet holder provided with the main fuel jet, at the bottom of the float chamber main body, the upstream of which is at the side wall of the guide hole connected to the float chamber. In the sealed down-draft type constant-vacuum vaporizer, the upper mounting end 6A of the floating chamber main body 6 is fixed to the lower mounting end 1A of the vaporizer main body 1 by screws.
And a longitudinal axis CC of the needle jet holder 12 provided with the main fuel jet 13 is arranged to intersect at a narrow angle F of 45 degrees or less at a position below the needle jet holder 12, so that the guide hole 20 is formed as a conical hole and the conical hole is formed. A down-draft type constant vacuum vaporizer characterized in that the hole has a conical angle G parallel to the longitudinal axis BB of the screw 7.