JPS6045763A - Membrane type carbureter - Google Patents

Abstract

PURPOSE:To supply an optimum amount of fuel over the entire running range of an engine, by changing the jet opening area of a membrane type carbureter in accordance with the opening degree of the throttle valve. CONSTITUTION:Fuel fed into a chamber 16 from a diaphragm pump 10 through a valve 15, flows from a chamber for a jet needle 37 through a jet 34 around the jet needle 37, and through a passage 27 and an adjusting screw 29, and then is mixed with bleed air 30. Then, the fuel is fed into the engine through nozzle ports 26a, 26b. A plunger 41 against which the lower end of the jet needle 37 abuts, is abutted by means of a spring 39 against the cam surface of a cam section 40 formed in the end part of the shaft 25 of a throttle valve 24. When the opening degree of the throttle valve 24 is small, the plunger 41 is lowered by the cam to decrease the opening area of the jet 34. Meanwhile the opening area of the jet 34 increases as the opening degree of the throttle valve 24 increases, so that a large amount of fuel is fed into the engine.

Description

DETAILED DESCRIPTION OF THE INVENTION The invention relates to a model carburetor used primarily in small general-purpose engines such as agricultural or horticultural machinery and small vehicles.

The type of carburetor that opens and closes the fuel valve according to the pressure received by the membrane and maintains the fuel pressure in the fuel chamber almost constant is significantly smaller and has a simpler structure than the float type carburetor of an automobile engine. It has the characteristic that it can be used not only in one position but also in any position.

By the way, such a model C-engine usually has a main system and a low-speed system in its fuel system, but it is only necessary to supply fuel that allows the engine to operate in the entire range from low to high speeds.
There is no fuel control means in the main fuel passage from the fuel chamber to the main nozzle, the idle boat, the low-speed fuel passage, or other parts due to reasons such as the lack of a 5-degree space like the float type carburetor. It's normal. Therefore, it is not possible to deal with issues such as the fuel connection when switching between the low-speed system and the main system, the fuel economy at a partial load, the increase in fuel amount during acceleration or high output, etc., and the driving performance expected from the engine. This method has the disadvantage that not only is it not possible to obtain the desired results, but also that the discharged scum is worsened.

The present invention is intended to solve these problems, and includes a jet provided in a fuel passage leading from a fuel chamber to a nozzle opening in an intake passage, which maintains fuel pressure almost constant, and a jet inserted into this jet. and a cam provided on the throttle valve shaft, the jet needle following the cam and reciprocating as the throttle valve shaft rotates to change the effective area of the jet. It is said that

Next, a specific example of the invention will be explained based on the drawings. A fuel pump 3 is provided on one side of a body 2 having an intake passage l extending vertically, and a pressure regulating part 4 is provided on the opposite side.
is provided.

The fuel pump 3 is connected to an inlet check valve 6 from a fuel inlet 5 connected to a fuel tank (not shown). a pump chamber 8 into which fuel is fed via an inlet passage 7;

It comprises a pulse chamber 9 into which the pulsating pressure of the engine crankcase is introduced, and a membrane ]O that partitions these two chambers 8 and 9,
The membrane 10 is pressed and fixed to the side surface of the body 2 by a side cover 11. The pulsating pressure generated in the crankcase due to engine operation is introduced into the pulse chamber 9, causing the membrane 10 to reciprocate, opening the inlet check valve 6, pressurizing the fuel sucked into the pump chamber 8, and exiting from the outlet passage 12. Check valve 13. Sending passage 1
4. The fuel is fed into the fuel chamber J6 of the pressure regulating section 4 through the fuel valve 5.

The pressure regulating MS 4 contacts and engages the fuel chamber ]6, the atmospheric chamber 17 opened to the atmosphere, #18 that partitions these compartments 16-7, and the center of this membrane ]8, and is connected to the fuel chamber 16. The fuel valve 1 is mounted on an arm 20 that is rotatably supported on a built-in support shaft 9.
A spring 21 acting on the arm 20 acts in the direction of contacting and engaging the fuel valve 5 and closing the fuel valve 5, and the membrane 8
is fixed to the body 2 by a side cover 22. Fuel chamber]
6 becomes a negative pressure when the fuel decreases, so the membrane 18 becomes a fuel chamber]
6, rotates the arm 2o, opens the fuel valve 15, and sends the fuel to the fuel chamber 16 of the fuel pump 3. When the fuel reaches a certain level, the membrane 18 is moved by the fuel pressure to the atmospheric chamber]7
The fuel valve [5] is bent toward the valve [5] and the fuel pressure in the fuel chamber [6] is maintained almost constant.
Formula % The body 2 and the two side lids 11. ,l! 2 constitutes a gas pump body 23, in which a throttle valve shaft 25 to which a disk-shaped throttle valve 24 is fixed is rotatably supported by the body 2, and two fuel nozzle ports 26m and 26b are connected. is the throttle valve 24 in the closed position.
It opens toward the intake passage 1 on the side of and slightly upstream of. Fuel is delivered from these nozzle ports 26a and 26b over the entire operating range of the engine, and the intake passage 1 does not have a venturi, but instead has an axial valve-shaped throttle valve 24 similar to the cylindrical throttle valve of the Amar carburetor. Has a variable venturi function.

The fuel in the fuel chamber J6 passes through the fuel passage 27 to the nozzle 026.
a, 26b, the fuel amount is adjusted from the outside of the carburetor body 23 by the needle 29 at the tip of the adjustment screw 28, and the fuel amount is controlled from the outside of the carburetor body 23 through the bleed air passage 30.
Similarly, the amount of bleed air introduced at 7 is adjusted from the outside using a needle 32 at the tip of an adjusting screw 31.

A tube 35 having an adjustment screw 33 at its base end and a jet 34 at its tip is inserted into a portion of the fuel passage 27 between the fuel chamber 16 and the fuel adjustment needle 29, and the adjustment screw 33 is screwed into the body 2. The position of the jet 34 is adjustable and fixed by the trap. The fuel that has passed through the jet 34 and entered the pipe 35 passes through the hole 36 of the pipe 35 and flows out into the annular gap between the fuel passage 27 and the pipe 35, and first passes around the needle 290 and enters the nozzle ports 26a and 26b. reach.

A jet needle 37 is inserted into the jet 34, and a base 38 inside the tube 35 has both opposing sides cut off flatly to form a gap 38a through which fuel passes. Further, a return spring 39 is inserted between the adjustment screw 33 and the base 38 and acts to push the jet needle 37 out of the jet 34. A notch is formed at the shaft end of the throttle valve shaft 25, and the notch surface 40a and the arc-shaped shaft peripheral surface 40b constitute a cam 4o. A plunger 41 is inserted between the cam 40 and the jet needle 37.

In the unspecified example configured in this manner, when the throttle valve 24 is in the closed position, the plunger 41 contacts the substantially horizontal notch surface 40a of the cam 40, and is returned to the four opposite surfaces of the plunger 41 by the action of the spring 390. The large diameter portion of the proximal end of the jet needle 37 in contact with the jet needle 37 minimizes the effective area of the jet 34 (see Fig. 1.2). Throttle valve 24
When the plunger 4 is opened, the plunger 4 is pushed by the notch surface 40a and the shaft peripheral surface 40b, and the jet needle 37 is pushed into the tube 3.
5 and the throttle valve 24 is fully opened, the small diameter portion at the tip maximizes the effective impulse of the jet 34 (see Fig. 3).

The jet needle 37, which reciprocates following the cam 40 that rotates together with the throttle valve shaft 25, is placed at a constant position with a constant opening of the throttle valve 24, so the position of the jet 34 can be finely adjusted using the adjustment screw 33. allows fine adjustment of fuel flow rate.

The jet needle 37 may have a shape having a substantially uniform taper over its entire length, and when the throttle valve 24 is half open, fuel economy is increased, and when the throttle valve 24 is fully open, fuel for high output is supplied. It may be formed into a stepped rod shape consisting of portions with different diameters, or may have a shape with different tapers depending on the portion so as to obtain the desired engine performance.

Incidentally, the cam 40 may be formed separately from the throttle valve shaft 25 and may come into direct contact with the jet needle 37, and due to the arrangement of each component and the fuel passage 27, a part of the carburetor valve 23 may be expanded outward. A jet 34. A space may be created to house the jet needle 37 and cam 40.

As described above, according to the present invention, a jet is provided in the fuel passage leading from the fuel chamber to the nozzle port, and the jet is driven by a jet needle that follows a cam provided on the throttle valve shaft and reciprocates as the throttle valve shaft rotates. Since the effective area is changed, by appropriately selecting the shape of the jet needle, it is possible to measure fuel economy at partial loads, increase in fuel amount during acceleration and high output, etc., as shown in the example shown in the figure. If the configuration is such that the nozzle opening is opened near the throttle valve in the closed position and the fuel for the entire operating range is supplied from this point, problems can occur with the connection of fuel when switching between low-speed fuel and main fuel. This means that the expected operating performance of the engine can be obtained, and the inconvenience of worsening exhaust gas emissions is eliminated.

In addition, the cam that drives the jet needle is installed inside the carburetor body, and the interlocking mechanism between the throttle valve shaft and jet needle is not exposed to the outside, so the membrane type gas ratio is small and has a simple structure. It does not impair the characteristics of

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of a specific example of the present invention, FIGS.
The figure explains the operation of the jet needle (it is a pHWT side view. J... Intake path, 3... Fuel pump, 4
...Pressure regulating section, 16...Fuel chamber, 23...
...The vaporizer is out of service. 24... Throttle valve, 25... Throttle valve shaft,
26a, 26b...Nozzle 0.27...
...Fuel passage, 33...Adjustment screw, 34...
...Jet, 35...Tube, 37...Jet needle, 39...Return spring, 40...
····cam.

Claims (3)

[Claims] (1) A jet provided in a fuel passage leading from a fuel chamber to a nozzle opening in an intake passage, which maintains fuel pressure almost constant, and a jet needle inserted into this jet;
and a cam provided on the throttle valve shaft, and the jet needle follows the cam and reciprocates with rotation of the throttle valve shaft to change the effective area of the jet. vessel,. (2) The scope of the patent claim (
The model vaporizer described in 1). (3) The membrane type pneumatic blower according to claim 1, wherein the cam is constituted by a cutout surface formed on the throttle valve shaft and an arcuate peripheral surface of the shaft.