JPH01100355A - Carburettor with variable venturi - Google Patents

Abstract

PURPOSE:To prevent a metering needle from slipping off by mounting a metering needle, which has undergone anode oxidation upon fitting the needle base in a through hole of a flange, to the tip of a suction piston in the condition that the flange is pressurized by a compression spring. CONSTITUTION:A throttle valve 2 is mounted in a suction passage 1a of a carburettor body 1, and in its upstream, a main nozzle 4 is installed in communication to a float chamber 3. The foremost surface 5a of a suction piston 5 faces this main nozzle 4, and a venturi 6 is formed. In this structure, a metering needle 15 fitted in the main nozzle 4 is formed by subjecting its whole surfaces to hard anode oxidation after the base 16a of needle body 16 made of aluminum alloy is pressure fitted in a through hole 18 bored in a flange 17 made of aluminum alloy. The metering needle 15 is mounted to the tip of the suction piston 5 in the condition that the flange 17 is pressurized by a spring 22.

Description

[Detailed description of the invention] (Industrial application field) This invention relates to a carburetor for a gasoline engine.

(Prior art) Recently, as a carburetor for an engine of a car or a motorcycle, there are many
As shown in Japanese Patent No. 58758, a variable venturi type carburetor equipped with a suction piston that changes the area of the venturi portion according to the air flow rate in the intake passage has become widely used. As shown in the latter of the above-mentioned publications, the metering needle for adjusting the gasoline discharge amount of the main jet disposed opposite to the suction piston is
A widely used needle has a collar fixed to the base of the needle, and the collar is pressurized by a compression spring and attached to a suction piston.

(Problem to be solved by the invention) However, since the conventional metering needle was simply a steel needle base press-fitted into a 14-piece collar, it was difficult to use the metering needle with the carburetor mounted on the vehicle. Furthermore, repeated engine vibrations and temperature rises, or the vertical movement of the suction piston, may cause the needle to come off the flange, and mishandling the needle may make it impossible to measure fuel and cause an accident that may prevent normal operation. there were.

This invention solves the above-mentioned conventional problems, and aims to provide a highly reliable variable venturi type carburetor that can prevent the needle of the metering needle from being handled from the collar.

(Means for Solving the Problems) However, the carburetor of the present invention is a variable venturi type carburetor equipped with a suction piston that changes the area of the venturi portion according to the air flow rate in the intake passage. A metering needle, which is made by manually anodizing the base of an aluminum needle, is inserted into the through hole in which the metering needle is placed, with the collar being pressurized by a compression spring in a direction toward the distal end surface of the suction piston. This is a variable venturi type carburetor that is attached to the tip of the suction piston.

In this invention, aluminum or an aluminum alloy can be used as the aluminum material forming the needle. Further, as the material of the brim, aluminum may be used, or steel or other materials other than aluminum may be used.

In this invention, the fitting between the through hole of the collar and the outer diameter of the base of the needle may be a tight fit, but as a tight fit,
Most preferably, the base of the needle is press fit into the collar.

In addition, various anodizing methods can be applied to the anodizing treatment in this invention, but in particular, hard anodizing treatment in which a hard film is formed by using an aqueous sulfuric acid solution at a low temperature, etc.
It is preferable because it has excellent wear resistance.

(Function) In the variable venturi type vaporizer of the present invention, the base of the needle is anodized after the through hole bored in the brim, so there is a small gap between the through hole and the outside diameter of the needle base. The electrolyte for anodizing treatment enters the gap, causing damage to the outer periphery of the needle base in the above-mentioned insertion part and the inner periphery of the through hole in the collar (
However, when the brim is made of aluminum, an anodic oxide film is formed and grows and fills the above gap, so this anodic oxide film tightly and firmly connects the brim and the needle, making it difficult for the needle to come out from the brim. prevent. Further, the anodized film formed on the needle portion by anodizing treatment improves the wear resistance against sliding contact with the main nozzle.

(Example) An example of the present invention will be described below with reference to FIGS. 1 and 2.

In the figure, 1 is a carburetor main body, which is attached to an engine (not shown) via an intake pipe. A throttle valve 2 is rotatably attached to the intake path 1a of the carburetor main body 1, and a main nozzle 4 communicating with a float chamber 3 is provided upstream of the throttle valve 2. A suction piston 5 whose tip end face 5a faces the main nozzle 4
is in sliding contact with the piston bore 1b of the carburetor main body and can move up and down, and the suction piston 5 and the carburetor main body 1 constitute a venturi section 6. The suction piston 5 is constructed by press-fitting a bottomed cylindrical inner cylinder 8, which is slightly shorter than the piston main body 7, into a bottomed cylindrical piston body 7. A diaphragm 9 is inserted between the flanges of the piston body 7 and the inner cylinder 8. The inner periphery is clamped. This diaphragm 9
The outer periphery of the carburetor is held under pressure by the carburetor main body 1 and the cover 10, 11 is a suction chamber surrounded by the cover 10, the diaphragm 9, and the inner cylinder 8, and 12 is a suction chamber installed between the cover 10 and the inner cylinder 8. This is a suction spring. 13 is a lower suction hole formed in the piston body 7, and 14 is an upper suction hole formed in the inner cylinder 8. 15 is a metering needle that fits into the main nozzle 4, and the base 16a of the needle 16 made of aluminum alloy is
After being press-fitted into a through hole 18 formed in a stepped short cylindrical collar 17 made of aluminum alloy, the entire surface is hard anodized. Reference numeral 19 indicates an anodized film formed on the outer surface of the press-fitted portion, and reference numeral 20 indicates an anodized film formed within the gap between the through hole 18 and the base portion 16a. This metering needle 15 is constructed by fitting a collar 17 into a short cylindrical guide tube 21 protruding from the inner surface of the piston body 7 with a gap, and a compression spring 22 inserted between the collar 17 and the inner tube 8. The collar 17 is attached to the tip of the suction piston 5 with the spring force pressurizing the collar 17 in the direction toward the tip 5a of the suction piston.

In the variable venturi carburetor 23 having the above configuration, when the throttle valve 2 is opened, the amount of air taken into the engine increases, and a negative pressure is generated in the venturi portion 6 according to the amount of air flowing, and this negative pressure causes the float The fuel in the chamber 3 is metered by the main nozzle 4 and the metering needle 15 and sucked out to the venturi section 6. On the other hand, suction chamber 1
1 communicates with the venturi section 6 through the upper suction hole '14 and the lower suction hole 13, and its internal pressure is equal to the negative pressure generated in the venturi section 6.

When the suction chamber 11 becomes negative pressure, an upward force is generated on the suction piston 5 due to the pressure difference between the upper and lower sides of the diaphragm 9, and this force and the downward force of the suction spring 12
The suction piston 5 stops at the position where the urging forces of are balanced. When the amount of intake air is large, the negative pressure generated in the venturi section 6 becomes high, the air in the suction chamber 11 flows out to the venturi section 6 through both suction holes 13 and 14, and the suction piston 5 moves upward. Conversely, when the amount of intake air decreases, the negative pressure generated in the venturi section 6 decreases, the internal pressure of the suction chamber 11 decreases, and the suction piston 5 moves downward. The metering needle 15 held by the suction piston 5, which repeats the above-described vertical movement, measures the fuel from the main nozzle 4 while moving up and down together with the suction piston 5. The collar 17 is held in pressure contact with the bottom of the guide cylinder 21 by the spring force of the compression spring 22, and the needle 1
6 has a base 16a supported by this collar 17, but in addition to the fixing force due to the press fit between the collar 17 and the base 16a,
Anodic oxide film 20 formed in the gap inside the through hole 18
Due to the adhesion force, the needle 16 and the flange 17 are integrated with a strong force, and the needle 16 is able to maintain the flange 1 even against external forces caused by vibrations, repeated temperature rises, and contact with the main nozzle 4.
This prevents it from falling off from 7. Also, in this example,
The anodic oxide film 19 formed on the portion of the base 16a that protrudes from the flange 17 also has the function of preventing the needle 16 from falling off from the flange 17.

Metering needle 15 with the above configuration (however, diameter of needle base 16a: 2.5 as+, total thickness of collar 17: 2
．． When the pulling force required to pull out the needle 16 from the collar 17 was actually measured at 7 m, the film thickness of the anodized skin GL19: 15 mm), the pulling force was 11001 (showing,
On the other hand, the pull-out force of a conventional product that was only press-fitted and not anodized was 40KI.

The present invention is not limited to the above-mentioned embodiment. For example, the suction piston 5 may have a structure without the inner cylinder 8. In this case, the upper end of the compression spring 22 is connected to the guide cylinder 2.
It may be held by a cap etc. screwed into 1. Further, the collar 17 may be in the shape of a single perforated disk without a stepped portion, and the base 16a of the needle 16 is connected to the collar 17.
It may be structured so that it does not protrude upward.

The present invention can also be applied to a variable venturi type carburetor that does not use a diaphragm.

(Effects of the Invention) As explained above, according to the present invention, it is possible to prevent the needle of the metering nozzle from coming off from the flange portion, and a highly reliable variable venturi type carburetor can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a variable venturi type carburetor showing an embodiment of the present invention, and FIG. 2 is a partially enlarged vertical cross-sectional view of the metering nozzle shown in FIG. 1. DESCRIPTION OF SYMBOLS 1... Carburetor body, 1a... Intake path, 4... Main nozzle, 5... Suction piston, 5a... Tip surface, 6... Venturi part, 15... Metering needle , 16... Needle, 16a... Base, 1
7...Brim, 18...Through hole, 19...Anodized film, 20...Anodized film, 22...Compression spring,
23...Variable venturi type carburetor.

Claims (1)

[Claims] In a variable bench lily type carburetor equipped with a suction piston that changes the area of the bench lily part according to the air flow rate in the intake passage, the base of an aluminum needle is inserted into a through hole drilled in the brim and then anodized. A variable bench lily type carburetor, characterized in that the metering needle is attached to the tip of the suction piston with the collar being pressurized by a compression spring in a direction toward the tip surface of the suction piston.