JPH0660753U - Diaphragm vaporizer - Google Patents

Abstract

(57) [Abstract] [Purpose] The throttle valve is fully opened, and the engine can be set to have a relatively large amount of fuel at low speed rotation to reduce harmful components in exhaust gas without impairing acceleration. In a diaphragm type carburetor in which the throttle valve 20 is fully opened and the amount of fuel when the engine is rotating at high speed is regulated by a fuel jet 51, a recess 52a near the fuel injection hole 39a of the fuel jet 51 has an outer diameter of a recess 52a. Pipe 4 with the same inner diameter but larger than the inner diameter of the fuel jet 51
0 is inserted into one end and the other end of the pipe 40 is connected to the fuel supply pipe 39.
Insert into.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention is mainly a diaphragm type carburetor for a two-stroke internal combustion engine mounted on a portable working machine such as a chain saw or a brush cutter, and in particular, a diaphragm type carburetor that regulates the fuel amount (flow rate) at high speed rotation of the engine by a fuel jet. It is about.

[0002]

[Prior art]

 Since the diaphragm type carburetor has a closed fuel system from the fuel tank to the carburetor body to enable tilting operation of the engine in all directions, the throttle valve corrects the fuel amount at full opening. Therefore, an air jet or air bleed structure cannot be used.

In the conventional diaphragm type carburetor as shown in FIG. 5, the fuel supply system from the constant pressure fuel chamber to the slot hole is configured as follows. The intermediate body 49, the diaphragm 25, and the gasket 54 are formed with a passage 55 communicating with a constant pressure fuel chamber provided with a check valve 36 (see FIG. 1), while accommodating a rotary throttle valve of the carburetor body 17. A cylindrical portion 23 communicating with the passage 55 is formed on the bottom wall of the cylindrical portion, and a lower end portion of a fuel supply pipe (fuel nozzle) 39 is fitted in the cylindrical portion 23 and is also a flange 39d integral with the fuel supply pipe 39. Are superposed on the bottom surface 19a. The fuel supply pipe 39 is provided with a small-diameter passage 39b at its upper end and a large-diameter passage 39c at its lower end, and the passage 39c communicates with the jet passage 52 of the fuel jet 51.

The fuel jet 51 is fitted with an O-ring 53 and is fitted on the lower end of the cylindrical portion 23, and the flange 51 a at the lower end of the fuel jet 51 is superposed on the gasket 54. The upper end of the jet passage 52 of the fuel jet 51 is formed with a large diameter recess 52a through a tapered portion, and the lower end is formed with a similar recess 52b.

In order to adjust the fuel amount characteristic curve when the throttle valve 20 is fully opened, there are limits such as the shape of the fuel supply pipe (fuel nozzle) 39, the position and direction of the fuel injection hole 39a (see FIG. 1), etc. Compensation according to the engine specifications is performed by the specified means, and the throttle valve 20 is fully opened and the engine can be freely set to obtain the optimum fuel amount over the entire operating range from low speed rotation to high speed rotation. I couldn't do it.

By the way, in the diaphragm type carburetor only provided with the conventional fuel jet 51, as shown by the solid line in FIG. 4, the fuel jet 51 is provided so that the fuel amount required by the engine can be obtained by the high speed rotation of the engine. When the inner diameter of the jet passage 52 is selected, there is a tendency that the throttle valve 20 is fully opened and the fuel amount is small (mixing ratio is thin) at low speed rotation of the engine. This is because there is no air bleed or air jet for correcting the fuel amount as described above. Therefore, the acceleration performance of the engine may be deteriorated. In order to satisfy the acceleration performance, the throttle valve 20 is fully opened and the fuel passage 51 of the fuel jet 51 has a slightly large amount of fuel at high speed rotation. Had selected the inner diameter of.

[0007]

[Problems to be solved by the device]

 However, in recent years, even in portable work equipment, due to the fact that exhaust gas regulations are being enforced, the throttle valve is fully opened, and the engine is set to a proper fuel amount (mixing ratio) at high speed, or slightly lower ( It has become necessary to reduce the harmful components CO and HC by setting a low mixing ratio. However, if the mixing ratio with respect to the engine speed is set as described above, the throttle valve will be fully opened, the amount of fuel at the low speed rotation of the engine will be small, and the fuel amount will be too small at the time of sudden acceleration of the engine (the mixing ratio will be too thin). There is a problem that the engine speed may be temporarily reduced (breathing) or the engine may be stopped, resulting in a significant decrease in work efficiency.

The purpose of the present invention is to reduce the harmful components of the exhaust gas without impairing the acceleration so that the throttle valve is fully opened and the engine is designed to increase the amount of fuel at a low speed to some extent (make the mixing ratio rich). It is to provide a diaphragm type vaporizer that can be used.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the structure of the present invention is a diaphragm type carburetor in which the throttle valve is fully opened and the engine regulates the fuel amount at high speed rotation by a fuel jet. In the recess on the outlet side, one end of a pipe whose outer diameter is the same as the inner diameter of the recess and whose inner diameter is larger than the inner diameter of the fuel jet is inserted, and the other end of the pipe is inserted into the fuel supply pipe.

[0010]

[Action]

 According to the present invention, when a pipe is connected to the fuel jet, the flow coefficient of the fuel passage is small (the fluid resistance of the fuel passage is large) when the amount of fuel (flow rate) is large, such as during high-speed operation of the engine, and when operating at low speed. When the amount of fuel is small, as described above, the flow coefficient of the fuel passage is increased (the fluid resistance of the fuel passage is decreased). As a result, it is possible to suppress an increase in the fuel amount in the high-speed operation of the engine (rich mixture ratio), reduce CO and HC in the exhaust gas, and obtain a sufficient fuel amount in the acceleration operation from low speed rotation (mixing). Ratio becomes thicker).

[0011]

【Example】

 As shown in FIG. 1, in the diaphragm type carburetor, a rotary type throttle valve 20 having a slot hole 22 is rotatably and vertically movable fitted in a cylindrical portion 19 of a carburetor body 17. The shaft portion 15 at the upper end of the throttle valve 20 is supported by a cover plate 16 that closes the cylindrical portion 19, and the cam surface 13 at the lower surface of the slot lever 12 connected to the shaft portion 15 is a ball 14 supported by the cover plate 16. Is urged by the force of the spring 18. A rod valve 21 screwably supported on the shaft portion 15 is projected into the slot hole 22 of the throttle valve 20 and fitted into the fuel supply pipe 39.

When the throttle lever 12 is remotely rotated by a trigger lever (not shown), the opening degree of the slot hole 22 with respect to the intake passage (not shown) is changed, and at the same time, the rod valve 21 is operated together with the throttle valve 20. By moving up and down, the opening area of the fuel injection hole 39a of the fuel supply pipe 39 is adjusted. The fuel supply pipe 39 is fitted and supported by the cylindrical portion 23 provided at the center of the bottom portion of the cylindrical portion 19. The fuel supply pipe 39 can communicate with the constant pressure fuel chamber 35 of the fuel supply mechanism B via the pipe 40, the fuel jet 51, and the check valve 36.

In the fuel supply mechanism B including the constant pressure fuel chamber 35, the diaphragm 41 is sandwiched between the intermediate body 49 and the cover 50 to divide the constant pressure fuel chamber 35 and the atmosphere chamber 42. The lever 34 is supported by the support shaft 33 in the constant pressure fuel chamber 35, one end of the lever 34 is biased by the spring force to the projecting piece of the diaphragm 41, while the other end of the lever 34 is supported by the needle valve type. A fuel inflow valve 10 is arranged at the end of the discharge passage 9 of the fuel pump A.

The constant pressure fuel chamber 35 includes a passage 43, a check valve 45 formed in a peripheral portion of the mushroom valve, an inner space of a void 48 of the primer pump 44, a check valve 46 formed in a shaft portion of the mushroom valve, It is possible to communicate with the fuel tank 2 via the passage 47. When the engine is started, the air in the constant pressure fuel chamber 35 is removed to the fuel tank 2 by the operation of the primer pump 44, and the fuel in the fuel tank 2 is sucked into the constant pressure fuel chamber 35 via the passage 3 and the fuel pump A.

The fuel pump A has a diaphragm 25 sandwiched between a carburetor main body 17 and an intermediate body 49, and is divided into a pulsating pressure introducing chamber 24 and a pump chamber 7 which communicate with a crank chamber of the engine. When the diaphragm 25 vibrates up and down, the fuel in the fuel tank 2 is sucked into the pump chamber 7 through the passage 3, the check valve 5 and the passage 6, and further from the pump chamber 7 to the check valve 8, the discharge passage 9 and the fuel. It is discharged to the constant pressure fuel chamber 35 through the inflow valve 10. When the constant pressure fuel chamber 35 is filled with the fuel, the diaphragm 41 descends, the fuel inflow valve 10 is pushed up by the lever 34, and the end of the discharge passage 9 is closed. In this way, the fuel at a constant pressure is reserved in the constant pressure fuel chamber 35.

As shown in FIG. 2, a passage 55 communicating with the constant pressure fuel chamber 35 having the check valve 36 is formed in the intermediate body 49, the diaphragm 25, and the gasket 54, while the cylinder of the carburetor body 17 is formed. A cylindrical portion 23 communicating with the passage 55 is formed on the bottom wall of the portion 19, a lower end portion of the fuel supply pipe 39 is fitted to the cylindrical portion 23, and a flange 39d integral with the fuel supply pipe 39 is attached to the bottom surface 19a. Overlaid. The fuel supply pipe 39 has a small diameter passage 39b at its upper end and a large diameter passage 39c at its lower end.

A fuel jet 51 having an O-ring 53 attached is fitted to the lower end of the cylindrical portion 23, and a flange 51 a at the lower end of the fuel jet 51 is superposed on the gasket 54. The fuel jet 51 is provided with a jet passage 52 having a predetermined inner diameter. The upper end of the jet passage 52 is formed with a large diameter recess 52a through a tapered portion, and the lower end is formed with a similar recess 52b.

In the present invention, in order to improve the fuel amount characteristic at high speed rotation of the engine, a pipe 40 is fitted inside the fuel supply pipe 39, and a passage 40 a of the pipe 40 is connected to a fuel jet 51. Specifically, the upper end of the pipe 40 is fitted into the passage 39b of the fuel supply pipe 39, and the lower end thereof is fitted into the recess 52a of the fuel jet 51. The inner diameter of the passage 40a is slightly larger than that of the jet passage 52, the length of the passage 40a is much longer than that of the jet passage 52, and the fuel amount characteristic at high speed rotation of the engine is adjusted depending on the length of the passage 40a. .

As a result, the amount of fuel when the throttle valve 20 is fully opened and the engine is rotating at a high speed increases the fluid resistance of the passage 40a in proportion to the flow velocity of the fuel. It can be suppressed more than anything. In other words, the gradient of the fuel amount characteristic curve when the throttle valve 20 is fully opened is gentler than that of the conventional example. Therefore, as shown by the broken line in FIG. 4, when the throttle valve 20 is fully opened and the fuel amount at high speed rotation of the engine is set to the same value as the conventional one (the inner diameter of the jet passage 52 is larger than that of the conventional one). A little larger), the throttle valve 20 is fully opened, the amount of fuel at the low speed rotation of the engine is larger than that of the conventional example, and the acceleration of the engine is improved. Therefore, in order to improve the acceleration of the engine as in the past, it is not necessary to fully open the throttle valve and increase the amount of fuel at high speed rotation of the engine (enrich the mixing ratio). HC can be reduced.

In the embodiment of FIGS. 1 and 2, since the pipe 40 is simply assembled to the fuel supply pipe 39 having the conventional fuel jet 51, it is easy to process and can be provided at a low cost. The optimum fuel amount characteristics for exhaust gas countermeasures can be obtained by simply changing the height.

As shown in FIG. 3, the pipe 40 may be integrated with the fuel jet 51. In the embodiment shown in FIG. 3, since the pipe 40 and the fuel jet 51 are integrated, the assembly man-hours and the processing man-hours are reduced, and there is no discontinuous portion in the fuel passage. The flow of is stable.

[0022]

[Effect of device]

 As described above, the present invention relates to a diaphragm type carburetor in which the throttle valve is fully opened and the amount of fuel at high speed rotation of the engine is controlled by the fuel jet. The same inner diameter is larger than the inner diameter of the fuel jet.One end of the pipe is inserted and the other end of the pipe is inserted into the fuel supply pipe.Therefore, the throttle valve is fully opened compared to the conventional fuel jet only. In addition, the amount of fuel at the low speed rotation of the engine is large (mixing ratio is rich), and the acceleration performance of the engine is improved. Since it is not necessary to increase the amount of fuel in the exhaust gas and can be set to the optimum amount or a little larger amount, it contributes to the reduction of CO and HC in the exhaust gas.

[Brief description of drawings]

FIG. 1 is a front sectional view of a diaphragm type carburetor according to the present invention.

FIG. 2 is a front cross-sectional view showing an enlarged main part of the same.

FIG. 3 is a front sectional view showing a modified embodiment of the same main part.

FIG. 4 is a diagram showing fuel quantity characteristics of a diaphragm type carburetor according to the present invention and a conventional one.

FIG. 5 is a front sectional view of a main part of a conventional diaphragm type vaporizer.

[Explanation of symbols]

20: Throttle valve 35: Constant pressure fuel chamber 39: Fuel supply pipe
39a: Fuel injection hole 40: Pipe 51: Fuel jet 52a: Recess

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Creator Tomohiro Sato 2-925 Shinmaruko Higashi, Nakahara-ku, Kawasaki-shi, Kanagawa Walbrofer East Co., Ltd.

Claims (2)

[Scope of utility model registration request] 1. A diaphragm type carburetor in which the throttle valve is fully opened and the engine regulates the amount of fuel at high speed rotation by a fuel jet, and the recess on the outlet side of the fuel jet has an outer diameter equal to the inner diameter of the recess and an inner diameter of the recess. A diaphragm type carburetor characterized in that one end of a pipe having a diameter larger than the inner diameter of a fuel jet is inserted and the other end of the pipe is inserted into a fuel supply pipe. 2. The diaphragm type carburetor according to claim 1, wherein the pipe is formed integrally with a fuel jet.