JP2857631B2 - Diaphragm vaporizer - Google Patents

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 amount and concentration of an air-fuel mixture supplied to an engine. In particular, the carburetor is divided into a regulator chamber and an air chamber by a diaphragm disposed in the carburetor body. And, in the regulator chamber, a valve for controlling the opening and closing of a valve seat arranged at the end of the fuel passage in accordance with the movement of the diaphragm is arranged,
The present invention relates to a diaphragm carburetor in which a main fuel passage leading to a venturi section and a low-speed fuel passage leading to an intake passage downstream of the venturi section are opened in a regulator chamber.

[0002]

2. Description of the Related Art A conventional diaphragm carburetor is disclosed in Japanese Utility Model Laid-Open Publication No. 3-83355. According to this, at the time of low-speed operation of the engine when the throttle valve is at a low opening degree, a large negative pressure generated in the intake passage acts on the low-speed fuel passage, whereby the fuel in the regulator chamber passes through the low-speed fuel passage. And supplied into the intake passage. At this time, the negative pressure generated in the venturi portion is small, and the check valve disposed in the main fuel passage holds the main fuel passage closed.
Prevents air from entering the regulator chamber from the main fuel passage. On the other hand, when the throttle valve is opened to a medium or high opening degree and the engine is operated at high speed in the engine, a large negative pressure is generated in the venturi section and acts on the main fuel passage. According to this, the check valve opens the main fuel passage by the negative pressure, and the fuel in the regulator chamber is supplied to the venturi section via the main fuel jet.

[0003]

According to such a conventional diaphragm carburetor, the amount of fuel supplied to the intake passage via the venturi portion in the engine and in the high-speed operation range of the engine acts on the main fuel jet. It is uniquely determined by the negative pressure. In particular, during middle-speed operation in the middle range of the throttle valve opening, fuel controllability is poor, and it has been difficult to obtain good fuel compatibility with the engine. According to the above,
It took a lot of time to test the carburetor for the engine, which hindered development efficiency. Also, it has been difficult to use a single vaporizer for a plurality of engines with versatility. Further, the negative pressure acting on the main fuel jet can be adjusted within a limited range by changing the hole diameter, shape, and position of the venturi portion. It is necessary to change the mold, which is not preferable in manufacturing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to provide a diaphragm carburetor having excellent fuel controllability particularly at a medium speed operation in an intermediate opening range of the throttle valve opening. I do.

[0005]

In order to achieve the above object, the diaphragm type vaporizer according to the present invention is divided into a regulator chamber and an atmosphere chamber by a diaphragm, and the regulator chamber has a fuel passage connected to a fuel source. A valve seat arranged at the end, a main fuel passage connected to the venturi section,
In a diaphragm type carburetor in which a low-speed fuel passage connected to an intake passage downstream of the venturi portion is opened, and a valve arranged in a valve seat controls opening and closing of the valve seat in accordance with movement of the diaphragm, the main fuel passage includes: A main fuel discharge passage opening to the venturi portion, a first main fuel suction passage having a downstream end connected to the main fuel discharge passage and an upstream end opening to the regulator chamber, and the first main fuel suction passage are formed independently of each other; A downstream end is connected to the main fuel discharge passage, and an upstream end is formed by a second main fuel intake passage opening to the regulator chamber.
A check valve and a first main fuel jet are arranged in series, and a normally closed second check valve and a second main fuel jet are arranged in series in a second main fuel intake passage. The first feature is that a difference is provided in the closing force between the first check valve and the second check valve.

Further, according to the present invention, a diaphragm is divided into a regulator chamber and an atmosphere chamber. The regulator chamber has a valve seat disposed at an end of a fuel passage connected to a fuel source, and a main fuel passage connected to a venturi section. And a low-speed fuel passage connected to an intake passage downstream of the venturi section, and a valve disposed in the valve seat controls opening and closing of the valve seat in accordance with movement of the diaphragm. A main fuel discharge passage opening to the venturi portion, a main fuel suction passage opening to the regulator chamber, a first bypass main fuel passage having a downstream end connected to the main fuel discharge passage, and an upstream end connected to the main fuel suction passage. , Formed independently of the first bypass main fuel passage, the downstream end is connected to the main fuel discharge passage, and the upstream end is connected to the main fuel intake passage. A first normally closed check valve and a first main fuel jet are arranged in series in the first bypass main fuel passage, and the second bypass main fuel passage is normally formed in the second bypass main fuel passage. A second check valve of a closed type is disposed, a main fuel jet is disposed in the main fuel intake passage, a closing force of the first check valve is made smaller than a closing force of the second check valve, and a first main fuel jet is further provided. The second characteristic is that the jet diameter of the main fuel jet is smaller than the jet diameter of the main fuel jet.

Further, according to the present invention, a diaphragm is divided into a regulator chamber and an atmosphere chamber. The regulator chamber has a valve seat disposed at an end of a fuel passage connected to a fuel source, and a main fuel passage connected to a venturi section. And a low-speed fuel passage connected to an intake passage downstream of the venturi section, and a valve disposed in the valve seat controls opening and closing of the valve seat in accordance with movement of the diaphragm. A first main fuel passage having a downstream end opened to the venturi portion, an upstream end opened to the regulator chamber, and a normally closed first check valve and a first main fuel jet arranged in series in the passage; The downstream end communicates with the first main fuel passage between the first check valve and the first main fuel jet, the upstream end opens to the regulator chamber, and the normally closed second passage is formed in the passage. A third feature is that the check valve is formed by a second main fuel passage in which a check valve and a second main fuel jet are arranged in series, and a closing force of the second check valve is larger than a closing force of the first check valve. And

[0008]

According to the first feature, in the intermediate opening range of the throttle valve, first, the first check valve having a weak closing force opens the first main fuel intake passage, and the venturi section through the first main fuel jet. Supply fuel to Next, when the rotation of the engine further increases and the negative pressure generated in the venturi section increases, the second check valve opens the second main fuel intake passage and the second check valve opens.
In the high opening range of the throttle valve, which additionally supplies fuel via the main fuel jet, the combined fuel of the first and second main fuel jets is supplied.

According to a second feature, in the intermediate opening range of the throttle valve, first, the first check valve having a weak closing force opens the first bypass main fuel passage, and releases the fuel restricted by the main fuel jet. Further, the fuel is supplied to the venturi section while being restricted by the first main fuel jet. Next, when the rotation of the engine further increases and the negative pressure generated in the venturi section increases, the second check valve opens the second bypass main fuel passage to add a part of the fuel restricted by the main fuel jet. To be supplied in an increased amount. In the high opening region of the throttle valve, the fuel restricted by the main fuel jet is supplied.

According to the third feature, in the intermediate opening range of the throttle valve, first, the first check valve having a weak closing force opens the first main fuel passage and connects to the venturi via the first main fuel jet. Supply fuel. Next, when the rotation of the engine further increases and the negative pressure generated in the venturi section increases, the second check valve opens the second main fuel passage to add the fuel restricted by the second main fuel jet. Supply via the first main fuel passage. In the high opening range of the throttle valve, the first,
The summed fuel of the second main fuel jet is supplied.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a diaphragm type vaporizer according to the present invention will be described below with reference to FIGS. Reference numeral 1 denotes a carburetor body through which an intake passage 2 penetrates.
The throttle valve 3 is controlled to be opened and closed by a throttle valve 3. The throttle valve 3 is attached to a throttle valve shaft 4 rotatably supported by the carburetor body 1. A concave portion 1A is formed upward on the lower side of the vaporizer main body 1, and a diaphragm 6 as a partition is disposed between the concave portion 1A and a bottomed cup-shaped cover 5 covering the lower end surface of the concave portion 1A. . According to the above, the diaphragm 6
And a concave portion 1A of the vaporizer main body 1, a regulator chamber 7 is formed, and a lower surface of the diaphragm 5 and the cover 5 form an air chamber 8 having an air hole 8A formed therein.

Reference numeral 9 denotes a shaft 1 in the regulator chamber 7.
The right end 9A of the arm 9 is arranged to face the upper surface of the diaphragm 6, and the left end 9B is arranged to be in contact with a valve to be described later. Reference numeral 11 denotes a spring for applying a clockwise rotational force to the arm 9 (in other words, a valve to be described later is a side for closing a valve seat). The arm 9 is locked on the right end 9A. Reference numeral 12 denotes an upstream side connected to a fuel tank (not shown), and a downstream side through a valve seat 13 to a regulator chamber 7.
A valve 14 for opening and closing the opening is movably disposed in the valve seat 13. Then, the diaphragm 6 moves upward in response to the negative pressure in the regulator chamber 7, and the arm 9
When the valve 14 rotates counterclockwise against the spring force of 1, the valve 14 opens the valve seat 13 and supplies the fuel in the fuel source into the regulator chamber 7 through the fuel passage 12 and the valve seat 13.

S is a low-speed fuel passage, the upstream of which opens into the regulator chamber 7 through the low-speed fuel jet 15, and the downstream thereof has an intake passage 2 corresponding to the end of the throttle valve 3 through the bypass hole 16. Open into.

The main fuel passage M is formed as follows. Reference numeral 20 denotes a main fuel discharge passage downstream of which opens into a venturi portion V formed in an intake passage upstream of the throttle valve 3. Reference numeral 21 denotes a main fuel discharge passage 20 downstream of which is open to the regulator chamber 7. Further, a second main fuel inlet passage 22 is formed independently of the first main fuel inlet passage 21, a downstream side is connected to the main fuel discharge passage 20, and an upstream side is opened to the regulator chamber 7. It is a suction passage. In the present embodiment, a main fuel discharge chamber 20A is formed upstream of the main fuel discharge passage 20, and a downstream end of the first main fuel suction passage 21 and a second main fuel discharge passage 20A are formed in the main fuel discharge chamber 20A. The downstream end of the suction passage 22 was independently opened.

In the first main fuel intake passage 21, a first check valve 23 and a first main fuel jet 24 are arranged in series, and the first check valve 23 has a negative pressure applied to the valve of a predetermined value or more. When the number has increased, the first main fuel suction passage 21 is opened to allow the fuel to flow from the regulator chamber 7 into the main fuel discharge passage 20.

In the second main fuel intake passage 22, a second check valve 25 and a second main fuel jet 26 are arranged in series, and the second check valve 25 has a negative pressure applied to the valve of a predetermined value or more. When the number increases, the second main fuel suction passage 22 is opened to allow the fuel to flow from the regulator chamber 7 into the main fuel discharge passage 20.

Then, a difference is provided in the closing force between the first check valve 23 and the second check valve 25. In this embodiment, the closing force of the first check valve 23 is smaller than the closing force of the second check valve 25. According to this, the first check valve 2
3 opens the first main fuel intake passage 21 with a small constant negative pressure, and the second check valve 25 opens the second main fuel intake passage 22 with a large constant negative pressure. That is, at a small constant negative pressure, the second check valve 25 still holds the second main fuel intake passage 22 closed.

The jet diameter of the first main fuel jet 24 and the second main fuel jet 26 is determined by the sum of the fuel amounts controlled by the first main fuel jet 24 and the second main fuel jet 26, It is set to match the required maximum open flow rate.

Next, the operation will be described. Throttle valve 3
In the low opening range, the throttle valve 3 narrows the intake passage 2 near the bypass hole 16 greatly.
Is greatly increased, while the venturi section V
Does not increase because the throttle valve 3 has a low opening. According to the above, the negative pressure applied to the bypass hole 16 acts on the low speed fuel passage S, the fuel in the regulator chamber 7 is controlled by the low speed fuel jet 15, and this fuel is supplied into the intake passage 2. Then, as the negative pressure applied to the bypass hole 16 gradually increases with the increase in the throttle valve opening, the fuel flow rate gradually increases, and the fuel flow rate gradually increases until the throttle valve opening A shown in FIG. The flow rate of fuel supplied from the low-speed fuel passage S increases. And the throttle valve opening is A
When the pressure exceeds the predetermined value, the end of the throttle valve 3 is separated from the bypass hole 16 and the opening of the intake passage 2 facing the bypass hole 16 increases, so that the negative pressure acting on the bypass hole 16 decreases. The low-speed fuel sucked into the intake passage 2 from the outlet gradually decreases. The decrease in the flow rate of fuel supplied from the low-speed fuel passage S when the flow rate exceeds A degrees is indicated by a dotted line in FIG.

In the low opening region of the throttle valve 3, a negative pressure equal to or higher than a predetermined value is generated through the main fuel discharge passage 20.
Since it does not act on the first check valve 23 and the second check valve 25, both the first main fuel suction passage 21 and the second main fuel suction passage 22 are closed and held, so that the venturi portion V enters the regulator chamber 7 from the venturi portion V. Does not flow in and does not adversely affect the dynamic characteristics of the diaphragm 6.

Here, when the throttle valve 3 is opened to the opening degree A,
The negative pressure in the Venturi section V increases to a small constant negative pressure, and this negative pressure acts on the first check valve 23 via the main fuel discharge passage 20, whereby the first check valve 23 becomes the first check valve 23.
The main fuel intake passage 21 is opened. On the other hand, since the second check valve 25 has not been increased to a large constant negative pressure, the second main fuel suction passage 22 is still closed.

According to the above description, the fuel controlled by the first main fuel jet 24 from the first main fuel intake passage 21 is supplied to the venturi section V via the main fuel discharge passage 20. During the period from A to the full opening, the fuel is supplied in an increasing amount as indicated by a dashed line.

Accordingly, in the throttle valve opening from the opening A of the throttle valve 3 to the opening B of the throttle valve 3 in which the second check valve 25 described later opens the second main fuel intake passage 22, the low speed The fuel supplied from the fuel passage S is added to the first main fuel intake passage 21.
Is added and supplied. As shown in FIG. 3, a fuel flow rate of X (L / H) is obtained at the throttle valve opening A, and Y is increased at the throttle valve opening B.
A fuel flow rate of (L / H) is obtained.

When the throttle valve 3 is further opened to the opening degree B, the negative pressure of the venturi portion V further increases to a large constant negative pressure. Acts on the second check valve 25 through the second check valve 25.
This opens the second main fuel intake passage 22. On the other hand, a large constant negative pressure acts on the first check valve 23, so that the first main fuel intake passage 2
Release 1 to continue fuel supply.

According to the above description, the fuel controlled by the second main fuel jet 26 from the second main fuel intake passage 22 is supplied to the venturi V through the main fuel discharge passage 20. During the period from A to the full opening, fuel is supplied while being increased as indicated by a two-dot chain line.

Therefore, the throttle valve opening from the throttle valve opening B to the throttle valve fully open corresponds to the fuel supplied from the low-speed fuel passage S and the fuel supplied from the first main fuel intake passage 21.
The fuel supplied from the second main fuel intake passage 22 is additionally supplied. As shown in FIG. 3, a fuel flow rate of Y (L / H) is obtained at the throttle valve opening B, and a fuel flow rate of Z (L / H) is obtained when the throttle valve is fully opened.

The increasing change point of the fuel flow rate (corresponding to the throttle valve openings A and B in this example) is determined by adjusting the closing force of the first check valve 23 and the second check valve 25. It can be set arbitrarily. In other words, when the closing force is weakened, the increasing change point can be moved in the small direction of the throttle valve opening.

After the first check valve 23 opens the first main fuel intake passage 21, the throttle valve opening degree A to B until the second check valve 25 opens the second main fuel intake passage 22. The increase curve of the fuel flow rate between them can be easily performed by selecting the jet diameter of the first main fuel jet 24. That is, when the jet diameter is increased, the fuel flow rate curve can be raised, and when the jet diameter is reduced, the fuel flow rate curve can be degraded.

Further, after the second check valve 25 opens the second main fuel intake passage 22 and before it is fully opened, the increase curve of the fuel flow from the throttle valve opening degree B to the fully opened state is represented by the second curve. It can be performed by selecting the jet diameter of the two main fuel jets 26.

As described above, according to the first embodiment, the flow rate of the fuel supplied from the main fuel discharge passage 20 to the venturi V is controlled by the first check valve 23 and the first main fuel jet 24.
And the second check valve 25 and the second main fuel jet 26 can be optimally set by selecting the throttle valve 3. Particularly, good fuel compatibility with the engine in the intermediate opening range of the throttle valve 3 and the carburetor The development efficiency for the conformity test can be improved, and the versatility of the vaporizer can be improved. Among them, the fact that good fuel compatibility was obtained was a significant contribution to improving the performance of the engine.

A second embodiment of the present invention will be described with reference to FIGS. 1 and 2 are denoted by the same reference numerals and description thereof is omitted. The main fuel passage M is as follows. 3
Reference numeral 0 denotes a main fuel discharge passage whose downstream side opens to the venturi portion V, reference numeral 31 denotes a main fuel suction passage whose upstream side opens into the regulator chamber 7, and a main fuel jet 32 for controlling a fully open flow rate is disposed inside. You. 33, the downstream end is connected to the main fuel discharge passage 30, and the upstream end is connected to the main fuel intake passage 31.
Is a first bypass main fuel passage connected to the
, A normally closed first check valve 34 and a first main fuel jet 35 are arranged in series. Reference numeral 36 denotes a second bypass main fuel passage formed independently of the first bypass main fuel passage 33, the downstream end of which is connected to the main fuel discharge passage 30, and the upstream end of which is connected to the main fuel intake passage 31. A normally-closed second check valve 37 is disposed in the main fuel intake passage 31.

The closing force of the first check valve 34 is set smaller than the closing force of the second check valve 37. That is, the first check valve 34 opens the first bypass main fuel passage 33 with a small constant negative pressure, and the second check valve 37 opens the second bypass main fuel passage 36 with a large constant negative pressure. Further, the jet diameter of the first main fuel jet 35 is formed smaller than the jet diameter of the main fuel jet 32.

According to the second embodiment, when the negative pressure of the venturi portion V increases to a small negative pressure in the intermediate opening range of the throttle valve 3, the first check valve 34 causes the first bypass main fuel passage 33 to pass through. When opened, the fuel controlled by the first main fuel jet 35 is supplied to the venturi V through the first bypass main fuel passage 33 and the main fuel discharge passage 30. At this time, the jet diameter of the first main fuel jet 35 is set to be smaller than the jet diameter of the main fuel jet 32, so that the supplied fuel is appropriately suppressed.

When the opening degree of the throttle valve 3 further increases and the negative pressure in the venturi section V further increases and reaches a large negative pressure, the second check valve 37 causes the second bypass main fuel passage 36 to pass through. Open. According to the above, the main fuel intake passage 31
A part of the fuel controlled by the main fuel jet 32 of the second bypass main fuel passage 36 without passing through the first main fuel jet 35 of the first bypass main fuel passage 33,
The fuel is supplied to the venturi section V via the main fuel discharge passage 30. Therefore, the fuel flowing through the second bypass main fuel passage 36 could be added to the fuel supplied from the first bypass main fuel passage 33 to the main fuel discharge passage 30, so that the increase in the throttle valve opening was achieved. Fuel can be increased. When the throttle valve 3 is fully opened, the fuel restricted by the main fuel jet 32 is supplied to the venturi section V.

According to the second embodiment, in addition to the effects of the first embodiment, the maximum fuel flow rate at the time of full opening is controlled only by the main fuel jet 32. It is possible to control the full open flow rate more accurately than the control. or,
In the second bypass main fuel passage 36 on the upstream side of the second check valve 37, a first upstream side of the first main fuel jet 35 is provided.
Since the negative pressure in the bypass main fuel passage 33 is introduced, the opening timing of the second check valve 37 to the second bypass main fuel passage 36 can be delayed. According to this, the means for setting the fuel of the carburetor can be increased, and the compatibility with the actual machine can be further improved.

A third embodiment will be described with reference to FIGS. 1 and 2 are denoted by the same reference numerals and description thereof is omitted. The main fuel passage M includes the following. 40
Is a first main fuel passage having a downstream end opening to the venturi portion V and an upstream end opening to the regulator chamber 7. The first main fuel passage includes a normally-closed first check valve 41 and a first main fuel jet 42. Are arranged in series. Reference numeral 43 denotes a second main fuel passage whose downstream end is connected to the first main fuel passage 40 between the first check valve 41 and the first main fuel jet 42, and whose upstream end opens into the regulator chamber 7. . In the second main fuel passage 43, a normally closed second check valve 44 and a second main fuel jet 45 are arranged in series. And the second
The closing force of the check valve 44 is larger than the closing force of the first check valve 41.

According to the third embodiment, when the negative pressure of the venturi portion V increases to a small negative pressure in the intermediate opening range of the throttle valve 3, the first check valve 41 causes the first main fuel passage 40 to move through the first main fuel passage 40. When opened, the fuel controlled by the first main fuel jet 42 is supplied to the venturi section V via the first main fuel 40.

Then, the opening degree of the throttle valve 3 further increases, and the negative pressure in the venturi portion V increases, and this increased negative pressure is transmitted through the first check valve 41 to the upstream side of the first check valve 41. After reaching the first main fuel passage 40, the first main fuel passage 4
When the negative pressure in 0 reaches a large constant negative pressure, the second check valve 44 opens the second main fuel passage 43. According to the above, the fuel controlled by the second fuel control jet 45 is additionally supplied into the first main fuel passage 40 downstream of the first main fuel jet 42. Accordingly, since the fuel controlled by the second fuel control jet 45 can be added to the fuel controlled by the first main fuel jet 42, the amount of fuel can be increased in accordance with the increase in the throttle valve opening. When the throttle valve 3 is fully opened, the total fuel of the first main fuel jet 42 and the second main fuel jet 45 is supplied as a fully opened flow rate.

According to the third embodiment, in addition to the effects of the first embodiment, the downstream end of the second main fuel passage 43 is provided between the first check valve 41 and the first main fuel jet 42. 1 Venturi V
The negative pressure occurring in the first main fuel passage 40 between the first check valve 41 and the first main fuel jet 42 can be increased. According to the above, the second check valve 44
The opening timing of the second main fuel passage 43 can be accelerated. According to this, the means for setting the fuel of the carburetor can be increased, and the compatibility with the actual machine can be further improved.

[0040]

As described above, the main fuel discharge passage opening to the venturi portion, the first main fuel suction passage having a downstream end connected to the main fuel discharge passage and the upstream end opening to the regulator chamber, and the first main fuel suction passage. The main fuel passage is formed independently of the passage, the main fuel passage is formed by a second main fuel intake passage having a downstream end connected to the main fuel discharge passage and an upstream end opening to the regulator chamber. Arranges a normally closed first check valve and a first main fuel jet in series,
A normally-closed second check valve and a second
According to a first feature of arranging a main fuel jet in series and further providing a difference in closing force between the first check valve and the second check valve, the first check valve, the first main fuel jet, and the second By selecting the check valve and the second main fuel control jet, fuel compatibility with the engine and development efficiency can be improved, and the versatility of the carburetor can be expanded.

A main fuel discharge passage opening to the venturi portion, a main fuel suction passage opening to the regulator chamber,
A first bypass main fuel passage having a downstream end connected to the main fuel discharge passage, an upstream end connected to the main fuel suction passage, and the first bypass main fuel passage are formed independently, and a downstream end connected to the main fuel discharge passage. A main fuel passage is formed by a second bypass main fuel passage having an upstream end connected to the main fuel suction passage, and a normally closed first check valve and a first main fuel jet are provided in the first bypass main fuel passage. The second check valve is disposed in series, a normally closed second check valve is disposed in the second bypass main fuel passage, the main fuel jet is disposed in the main fuel suction passage, and the closing force of the first check valve is reduced by the second check valve. According to the second feature, which is smaller than the closing force of the first fuel jet and the jet diameter of the first main fuel jet is smaller than the jet diameter of the main fuel jet, in addition to the effect of the first feature, accurate control of the full open flow rate is achieved. Can be performed, and Charge setting means can be increased, the actual compliance can be improved, can and improving the development efficiency.

The downstream end is open to the venturi portion, the upstream end is open to the regulator chamber, and the first normally closed type is provided in the passage.
A first main fuel passage in which a check valve and a first main fuel jet are arranged in series; a downstream end connected to the first main fuel passage between the first check valve and the first main fuel jet; A main fuel passage formed by a normally closed second check valve and a second main fuel passage in which a second main fuel jet is arranged in series in the passage, and a closing force of the second check valve is formed. According to the third feature, which is larger than the closing force of the first check valve, in addition to the effect of the first feature, the fuel setting means of the carburetor can be increased, and the compatibility with the actual machine and the improvement of the development efficiency can be achieved. .

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of a diaphragm type vaporizer according to the present invention.

FIG. 2 is a system diagram of a main fuel passage according to the first embodiment.

FIG. 3 is a diagram showing a relationship between a throttle valve opening and a fuel flow rate according to the present invention.

FIG. 4 is a longitudinal sectional view showing a second embodiment of the diaphragm type vaporizer according to the present invention.

FIG. 5 is a system diagram of a main fuel passage according to a second embodiment.

FIG. 6 is a longitudinal sectional view showing a third embodiment of the diaphragm type carburetor according to the present invention.

FIG. 7 is a system diagram of a main fuel passage according to a third embodiment.

[Explanation of symbols]

 M Main fuel passage V Venturi section 7 Regulator chamber 20 Main fuel discharge passage 21 First main fuel suction passage 22 Second main fuel suction passage 23 First check valve 24 Main fuel jet 25 Second check valve 26 Second main fuel jet 30 Main fuel discharge passage 31 Main fuel suction passage 32 Main fuel jet 33 First bypass main fuel passage 34 First check valve 35 First main fuel jet 36 Second bypass main fuel passage 37 Second check valve 40 First main fuel passage 41 First check valve 42 First main fuel jet 43 Second main fuel passage 44 Second check valve 45 Second main fuel jet

Claims (3)

(57) [Claims] A diaphragm is divided into a regulator chamber and an atmosphere chamber. The regulator chamber has a valve seat disposed at an end of a fuel passage connected to a fuel source, a main fuel passage connected to a venturi section, and a venturi section. In a diaphragm carburetor in which a low-speed fuel passage communicating with an intake passage on the downstream side is opened, and a valve disposed in a valve seat controls opening and closing of the valve seat in accordance with movement of the diaphragm, a main fuel passage M is a venturi. A main fuel discharge passage 20 opening to a portion V, and a main fuel discharge passage 2
And a first main fuel intake passage 21 whose upstream end is open to the regulator chamber 7 and is formed independently of the first main fuel intake passage 21. A downstream end is connected to the main fuel discharge passage 20 and an upstream end is a regulator. The first main fuel intake passage 21 is formed by a second main fuel intake passage 22 opening into the chamber 7.
A first check valve 23 of a normally closed type and a first main fuel jet 24 are arranged in series, and a second main fuel intake passage 22
A normally-closed second check valve 25 and a second main fuel jet 26 are arranged in series, and the first check valve 23 and the second check valve 25 are provided with a difference in closing force. A diaphragm type vaporizer characterized by the following. 2. A diaphragm, which is divided into a regulator chamber and an atmosphere chamber by a diaphragm. The regulator chamber has a valve seat disposed at an end of a fuel passage connected to a fuel source, a main fuel passage connected to a venturi section, and a venturi section. In a diaphragm carburetor in which a low-speed fuel passage communicating with an intake passage on the downstream side is opened, and a valve disposed in a valve seat controls opening and closing of the valve seat in accordance with movement of the diaphragm, a main fuel passage M is a venturi. A main fuel discharge passage 30 opening to the portion V, a main fuel suction passage 31 opening to the regulator chamber 7, and a main fuel discharge passage 30 at the downstream end.
A first bypass main fuel passage 33 whose upstream end is connected to the main fuel suction passage 31;
And a second bypass main fuel passage 36 whose downstream end is connected to the main fuel discharge passage 30 and whose upstream end is connected to the main fuel suction passage 31. The normally closed first check valve 34 and the first main fuel jet 35 are arranged in series, the second bypass main fuel passage 36 is provided with a normally closed second check valve 37, and the main fuel intake The main fuel jet 32 is provided in the passage 31.
Are arranged, the closing force of the first check valve 34 is made smaller than the closing force of the second check valve 37, and the jet diameter of the first main fuel jet 35 is made smaller than the jet diameter of the main fuel jet 32. Characteristic diaphragm type vaporizer. 3. A diaphragm is divided into a regulator chamber and an atmosphere chamber by a diaphragm, wherein the regulator chamber has a valve seat disposed at an end of a fuel passage connected to a fuel source, a main fuel passage connected to a venturi section, and a venturi section. In a diaphragm-type carburetor in which a low-speed fuel passage communicating with an intake passage on the downstream side is opened, and a valve disposed in a valve seat controls opening and closing of the valve seat in accordance with movement of the diaphragm, the main fuel passage M is located downstream. The first main fuel passage 40 has an end opened to the venturi section V, an upstream end opened to the regulator chamber 7, and a normally closed first check valve 41 and a first main fuel jet 42 arranged in series in the passage. The downstream end communicates with the first main fuel passage 40 between the first check valve 41 and the first main fuel jet 42, and the upstream end opens into the regulator chamber 7, A second main fuel passage 43 in which a normally closed type second check valve 44 and a second main fuel jet 45 are arranged in series, and the closing force of the second check valve 44 is reduced by the first check valve 41 A diaphragm type vaporizer characterized by having a closing force greater than that of the diaphragm.