JP4282862B2 - Downdraft type constant vacuum vaporizer - Google Patents

Description

[0001]
[Industrial application fields]
TECHNICAL FIELD The present invention relates to a carburetor that adjusts and controls the concentration and amount of an air-fuel mixture supplied to an engine, and in particular, an intake passage that penetrates the carburetor body is disposed downwardly toward the engine and restricts the intake passage. The present invention relates to a downdraft type constant vacuum carburetor provided with a negative pressure operation valve that variably controls the area of a venturi section in accordance with a negative pressure generated in an intake passage upstream from the valve.
[0002]
[Prior art]
A conventional downdraft type constant vacuum vaporizer is shown in FIG. Reference numeral 1 denotes a carburetor main body formed by penetrating the downstream side of the intake passage 2 downward in the direction of gravity. The intake passage 2 is opened and closed by a throttle valve 4 attached to a throttle valve shaft 3. At the upstream side of the throttle valve 4, a negative pressure operating valve 5 that variably controls the area of the venturi portion V according to the negative pressure in the intake passage 2 is disposed so as to be movable substantially orthogonal to the intake passage 2. The lower mounting end 1A of the vaporizer body 1 is brought into contact with the upper mounting end 6A of the float chamber body 6 and is fixed by screwing with screws 7 to form a float chamber 8. Note that the longitudinal axis B-B of the screw 7 is inclined by Z degrees with respect to the longitudinal axis YY of the intake passage (2). A constant fuel liquid level PP is formed in the float chamber 8 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 operating valve 10 along the opening / closing movement direction of the negative pressure operating 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. A main fuel jet 13 that controls fuel directed to the needle jet holder 12 is screwed to the lower end of the needle jet holder 12. The needle jet holder is disposed so as to intersect the longitudinal axis AA of the jet needle 10. Reference numeral 13 denotes a main air passage having one end connected to the atmosphere and the other end connected to the annular groove 11A and including a main air jet 13A. Reference numeral 14 denotes an annular well 15 formed on the outer periphery of the needle jet holder 12 to the nozzle 11. It is a fuel flow path communicating toward 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 12 . Further, a guide hole 17 is provided at the lower bottom of the float chamber main body 6 so that the upstream 17A communicates with the float chamber 8 and the downstream 17B communicates with 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 prevents fuel in the downstream 17 </ b> B of the guide hole 17 from leaking directly into the float chamber 8.
[0003]
Here, the longitudinal axis BB of the screw 7 and the longitudinal axis C-C of the needle jet holder 12 are arranged in parallel, and the longitudinal axis of the tip opening 17C of the guide hole is a needle. It is arranged on the longitudinal axis CC of the jet holder 12.
Reference numeral 1B denotes a positioning protrusion that protrudes downward from the lower mounting end 1A of the vaporizer body 1, and 6B denotes a positioning recess that is recessed in the upper mounting end 6B of the float chamber body 6. By inserting the portion 1B into the positioning recess 6B, the floating chamber main body 6 can be accurately screwed to the vaporizer main body 1 with the screw 7. The floating chamber body 6 is assembled to the carburetor body 1 in the state where the component parts such as the needle jet holder 12 are attached to the carburetor body 1. At this time, the longitudinal axis direction B- The floating chamber body 6 is moved along B, and the upper mounting end 6A of the floating chamber body 6 is brought into contact with the lower mounting end 1A of the vaporizer body 1. According to the above, the positioning projection 1B is inserted and disposed in the positioning recess 6B, while the annular packing 16 disposed on the outer periphery of the lower end of the needle jet holder 12 is inserted into the tip opening 17C of the guide hole 17 of the float chamber body 6. In this state, the float chamber main body 6 is screwed and fixed to the vaporizer main body 1 with the screw 7. Therefore, when assembling the floating chamber body 6 to the vaporizer body 1, the floating chamber body 6 only needs to move directly in the longitudinal axis direction of the screw 7, so that a good assembling property can be obtained. Note that the longitudinal axis YY of the intake passage 2 of the downdraft type constant vacuum type carburetor is attached to the engine with a forward tilt of D degrees with respect to the horizontal line XX.
[0004]
[Problems to be solved by the invention]
Such a conventional downdraft type constant vacuum type vaporizer has the following problems. In the downdraft type constant vacuum carburetor, the forward tilt angle with respect to the engine requires different tilt angles depending on the engine. The longitudinal axis YY of the intake passage 2 is set to the forward tilt angle D shown in FIG. For example, when the longitudinal axis YY of the intake passage 2 is arranged in a direction substantially perpendicular to the horizontal line XX, the longitudinal axis CC of the needle jet holder 12 is further tilted forward. Is disposed parallel to the longitudinal axis BB of the screw 7. This is because the needle jet holder 12 including the main fuel jet 13 is greatly separated from the center of the fuel liquid level PP in the float chamber 8 at the time of such a steep forward inclination, thereby causing the influence of a large fuel liquid level change. This is because the tilt performance is hindered. In order to solve the problem, the longitudinal axis C-C of the needle jet holder 16 is changed to the longitudinal axis B- of the screw 7 so that the needle jet holder 16 including the main fuel jet 13 approaches the center of the fuel liquid level. It is considered to intersect with B at an angle of 45 degrees or less in the lower position. However, according to the above, since the longitudinal axis B-B of the screw 7 and the longitudinal axis C-C of the needle jet holder 16 are crossed and not arranged in parallel, the fastening operation of the screw 7 and the needle jet holder 16 are not performed. It is impossible to simultaneously insert the annular packing 16 on the outer periphery of the guide hole 17 into the tip opening 17C of the guide hole 17 from one direction. In the above operation, first, the annular packing 16 is inserted into the distal end opening 17C of the guide hole 17, and then the float chamber body 6 is rotated around the longitudinal axis CC of the needle jet holder 16 and screwed. However, according to this, it is necessary to rotate the floating chamber main body 6. For example, the positioning protrusion 1B provided on the vaporizer main body 1 or other fuel bosses, the float 9 and the like are configured. It may not be able to rotate due to interference with parts.
[0005]
The downdraft type constant-vacuum carburetor according to the present invention is made in view of the above problems, and is a screw tightening operation for fastening the floating chamber body to the carburetor body even if the forward inclination angle of the intake passage with respect to the engine changes. Another object of the present invention is to provide a downdraft type constant vacuum type vaporizer capable of simultaneously performing an insertion operation for inserting an annular packing into a tip opening of a guide hole from one direction.
[0006]
[Means for solving the problems]
In order to achieve the above object, the downdraft type constant vacuum carburetor according to the present invention has an intake passage penetrating the carburetor body downwardly directed toward the engine, upstream of a throttle valve that opens and closes the intake passage. A negative pressure valve that variably controls the area of the venturi section according to the negative pressure in the intake passage is arranged, and the upper mounting end of the float chamber body is screwed to the lower mounting end of the carburetor body with screws. Is placed on the outer periphery of the lower end of a needle jet holder that includes a main fuel jet that protrudes into the float chamber from the vaporizer body and communicates with the nozzle through an annular groove. In the downdraft type constant vacuum type vaporizer that seals the annular packing at the bottom of the floating chamber body at the side wall of the opening of the guide hole, the upstream of which is communicated with the floating chamber. The longitudinal axis of the screw for fixing the mounting end to the lower mounting end of the carburetor body and the longitudinal axis of the needle jet holder with the main fuel jet are narrowed by 45 degrees or less at the lower position. The guide hole has a conical hole at the tip opening of the guide hole, and a conical side surface facing the screw of the conical hole is formed in parallel with the longitudinal axis of the screw and has a conical angle. To do.
[0007]
【Example】
An embodiment of a downdraft type constant vacuum vaporizer according to the present invention will be described below with reference to FIG. In addition, the same structure part as FIG. 2 uses the same code | symbol, and abbreviate | omits description. In FIG. 1, the horizontal line XX and the longitudinal axis YY of the intake passage 2 intersect with each other with an inclination of E degrees, and this angle (E degrees) is larger than the angle (D degrees) in FIG. And has a large angle substantially perpendicular to the horizontal line XX. 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 with an included angle of 45 degrees or less, and even if the longitudinal axis YY of the intake passage 2 is arranged substantially orthogonal to the horizontal line XX, the needle The jet holder 16 can be disposed near the center of the fuel liquid level PP. The guide hole 20 is formed at the bottom of the float chamber main body 6, the upstream 20 </ b> A is connected to the float chamber 8 to open, and the downstream 20 </ b> B is positioned facing the annular packing 16 with the tip opening 20 </ b> C. The tip opening 20C of the guide hole 20 is formed as a conical hole, and the conical side surface 20Ca (the conical side surface on the left side in FIG. 1) facing the screw 7 is the longitudinal axis of the screw 7. It is formed parallel to the line BB and formed at a cone angle G.
[0008]
And each structure is assembled | attached similarly to the past, and especially the floating chamber main body 6 is assembled | attached to the vaporizer | carburetor main body 1 by the following. That is, the floating chamber main body 6 is moved to the carburetor main body 1 along the longitudinal axis BB of the screw 7, and the upper mounting end 6 A of the floating chamber main body 6 is moved to the lower mounting end 1 A of the carburetor main body 1. Abuttingly arranged. According to the above, the annular packing 16 disposed on the outer periphery of the needle jet holder 12 is inserted and disposed in the distal end opening 20C forming the conical hole of the guide hole 20, and the positioning protrusion 1B is inserted and disposed in the positioning recess 6B. In this state, the float chamber main body 6 is screwed and fixed to the vaporizer main body with screws 7.
[0009]
【The invention's effect】
As described above, according to the downdraft type constant vacuum carburetor according to the present invention, the intake passage penetrating the carburetor body is disposed downward toward the engine, and upstream 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 upper mounting end of the float chamber body is screwed and fixed to the lower mounting end of the carburetor body with a screw. Is arranged on the outer periphery of the lower end of a needle jet holder having a main fuel jet that protrudes from the carburetor body into the float chamber and communicates with the nozzle through an annular groove. In a downdraft type constant vacuum type vaporizer that seals the annular packing at the bottom of the floating chamber body at the side wall of the tip opening of the guide hole that communicates with the floating chamber in the upstream, The longitudinal axis of the screw for fixing the mounting end to the lower mounting end of the carburetor body and the longitudinal axis of the needle jet holder with the main fuel jet are narrowed by 45 degrees or less at the lower position. Since the front end opening of the guide hole is a conical hole and the conical side surface facing the screw of the conical hole is formed in parallel with the longitudinal axis of the screw and has a conical angle, the air intake passage The needle jet holder including the main jet can be disposed near the center of the fuel level in the float chamber and the tilt performance is maintained well even if the longitudinal axis of the nozzle is arranged in a direction substantially perpendicular to the horizontal line. On the other hand, when assembling the float chamber body to the vaporizer body, the guide hole is moved by moving the float chamber body in one direction along the longitudinal axis of the screw. Since the annular packing which is disposed at the distal end opening to the outer periphery of the needle jet holder can be inserted arrangement, it is possible to maintain good assembling operability.
[Brief description of the drawings]
FIG. 1 is a longitudinal 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 type vaporizer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Vaporizer main body 1A Lower attachment end part 6 Float chamber main body 6A Upper attachment end part 7 Screw 12 Needle jet holder BB Longitudinal axis CC of a needle Jet Longitudinal axis 20 of a needle jet holder Guide hole

Claims (1)

A negative pressure that variably controls the area of the venturi section according to the negative pressure in the intake passage, upstream of the throttle valve that opens and closes the intake passage, the intake passage that penetrates the carburetor body is arranged downward toward the engine the actuated valve arranged, carburetor and float chamber forming holding the fuel level made constant inside by the upper attachment end portion of the float chamber body lower mounting end of the body for screwing fixed by screws, the vaporizer An annular packing disposed on the outer periphery of the lower end of the needle jet holder provided with a main fuel jet that projects from the main body into the float chamber and communicates with the nozzle via an annular groove is located at the bottom of the float chamber main body, and its upstream is located in the float chamber In the downdraft type constant vacuum type carburetor that seals at the side wall of the tip opening of the guide hole communicated with the upper attachment end (6A) of the float chamber body (6), the lower attachment end of the carburetor body (1) Part (1 ) And the longitudinal axis (C)-(C) of the needle jet holder (12) including the main fuel jet (13). And a conical side surface on the side facing the screw (7) of the conical hole, with the tip opening (20C) of the guide hole (20) serving as a conical hole at a narrow angle F of 45 degrees or less in the lower position. A downdraft type constant vacuum vaporizer characterized in that (20Ca) is formed in parallel with the longitudinal axis (B)-(B) of the screw (7) and at a conical angle (G).

Images