JPH01178759A - Starter for carburetor - Google Patents

Abstract

PURPOSE:To make a rich mixture suitable for a start-up feedable in abundance at the time of engine starting by installing a starting fuel pump and also such a mechanism that opens a throttle valve as longer as the specified opening than that of idling. CONSTITUTION:A starting fuel pump room 7 is installed adjacently in a float chamber 4 of a carburetor body 1. After pulling an operating lever 20 to the left, if this pulling force is released, the operating lever 20 is reset to the extent of an intermediate position by dint of a spring 23, and starting fuel in the starting fuel pump room 7 is sprayed to the inside of a suction passage via a starting fuel discharge passage 14. On the other hand, when ambient temperature in an engine is low, atmospheric pressure is led into a pressure chamber 37 of a throttle valve actuator 34 by a heat sensitive selector valve 40, so that a spring 39 inside the pressure chamber 37 presses an operating lever 38 upward, turning a throttle valve lever 31 clockwise, and opens a throttle valve 5 as longer as the specified opening than that of idling.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a carburetor that controls the concentration and amount of a mixture supplied to an engine, and particularly relates to a carburetor that supplies a rich mixture when starting an engine. The invention relates to a starting device.

[Prior Art] A starting device for a carburetor for a two-stroke engine, which has been commonly used in the past, will be explained with reference to FIG.

1, an intake passage 2 passes through the interior, a float basic body 3 is arranged on the side of the carburetor main body l, and a float chamber 4 is formed by the lower four parts of the carburetor main body l and the float basic body 3. Ru.

A constant liquid level XX is formed in the float chamber 4 by a float, a float valve, and a help sheet (not shown).

Further, 5 is a throttle valve that opens and closes the intake passage 2.

Reference numeral 6 denotes a partitioning body such as a diaphragm that is separated from the float chamber 4 and divides the inside into a starting fuel pump chamber 7 and an atmospheric chamber 8. Specifically, the starting fuel pump chamber 7 is divided into the partitioning body 6 and the float basic body. The atmospheric chamber 8 is formed by the concave portion of the partition body 6.
and cover 9. Note that J is an air hole that communicates the air chamber 8 with the atmosphere.

The following passages are opened in this starting fuel pump chamber 7. That is, 10 is a starting fuel inflow path which is provided with a suction side check valve 11 inside and communicates with the lower constant liquid level of the float chamber 4. A suction valve seat 12 is formed, and the suction side check valve 11 is pressed against the suction valve seat 12 by a spring 13.

Reference numeral 14 denotes a starting fuel discharge passage whose one end opens approximately in the center of the starting fuel pump chamber 7 and the other end opens into the intake passage 2 on the engine side (left side in the figure) from the throttle valve 5; In the passage, there is a discharge valve seat 15 and a spring 16 on the discharge valve seat 15.
A discharge side check valve 17 that is closed by being pressed is disposed.

Further, a valve seat 18 is formed at the opening end of the starting fuel discharge passage to the starting fuel pump chamber 7 .

Further, 18 is an on-off valve part provided integrally with the partition body 6,
This opening/closing valve section 18 is located at the valve seat 1 at the end of the starting fuel discharge passage 14.
The valve seat 18 is opened and closed in accordance with the movement of the partition body 6, thereby controlling the opening and closing of the starting fuel discharge passage 14. Further, an operating rod 20 is integrally disposed on the partitioning body 6, and by moving this operating rod 20, the partitioning body 6 and the on-off valve portion 18 are moved synchronously.

N is the first state (state shown in Fig. 1) in which the operating rod 20 (including the compartment body 6 and on-off valve part 18) is fully suppressed toward the starting fuel pump chamber 7 side, and the first state in which it is fully suppressed toward the atmospheric chamber 8 side. This is an intermediate position regulating member for holding the operating rod 20 approximately in the middle of the second pulled state (pulled all the way to the left in the figure). It consists of a pawl 21 and a spring 22 which apply a pressing force orthogonally to the operating rod 20 with elastic force to the groove 2OA when the operating rod 20 is operated to an intermediate position.

Further, 23 is contracted in the atmospheric chamber 8 and has one end attached to the cover 9.
It is a spring whose other end is locked to the partition body 6 and presses the one partition body 6 toward the starting fuel pump chamber 7 side.

Incidentally, when operating the intermediate position regulating member N described above, the pressing force exerted by the ball 21 by the spring 22 against the groove 2OA of the operating rod 20 in a direction perpendicular to the longitudinal axis direction Y-Y of the operating rod 20 is This is greater than the pressing force of the spring 23 in the longitudinal axis direction Y-Y of the operating rod 20 when the operating rod 20 is in the intermediate position, and thereby the operating rod 20 can be held at the intermediate position.

Regarding starting the engine in a state where the ambient temperature is low, before starting the engine, first press the operating lever 20.
is pulled all the way to the left in the figure against the spring force of the spring 23. By this operation, the partition body 6 and the on-off valve section 18 also move to the left in synchronization with the operating rod 20, and the on-off valve The portion 18 opens the valve seat 18 and increases the volume of the starting fuel pump chamber 7.

According to this, the suction side check valve 11 opens the suction valve seat 12, and the discharge side check valve 17 closes the discharge valve seat 15.

Therefore, by such an operation, the fuel stored in the float chamber 4 is sucked into the starting fuel pump chamber 7.

Next, the leftward cutting force on the operating rod 20 is released. According to this, the operating rod 20 is automatically moved toward the starting fuel pump chamber 7 (to the right) in the figure by the spring force of the spring 23. It moves, and the operating rod 20 is in the groove 2.
The OA is stopped in a state where it is engaged with the ball 21 as the intermediate position regulating member N.

The fact that the operating rod 20 stops at the intermediate position appropriately increases the pressing force of the spring 22 of the pawl 21 acting perpendicularly to the pressing force of the spring 23 in the longitudinal axis direction Y-Y of the operating rod 20. This can be achieved by

When the operating rod 20 is moved to the intermediate position, the starting fuel pump chamber 7 is compressed and the chamber volume is reduced.
The discharge side check valve 17 opens the discharge valve seat 15, and the starting fuel is injected and supplied from the starting fuel discharge passage 14 into the intake passage 2, thereby preparing the engine for the first complete explosion. After the process of pulling the rod 20 to the left all at once and the return process of releasing the attractive force on the operating rod to return it to the intermediate position, a cranking operation for starting the engine begins.

Then, since the fuel in the starting fuel pump chamber 7 has already been injected into the intake pipe from the starting fuel discharge passage 14,
A sufficiently rich air-fuel mixture can be supplied to the engine, ensuring the initial and complete explosion of the engine.

When the engine enters a warm-up state after a complete explosion, the operating rod 20 is held at an intermediate position and the valve seat 18 is held open by the opening/closing valve part 18, so that the engine is not generated in the intake pipe. Negative pressure acts on the discharge side check valve 17 from the starting fuel discharge passage 14, opens the discharge side check valve 17 from the discharge valve seat 15 against the spring force of the spring 16, and the fuel in the starting fuel pump chamber 7 is opened. The starting fuel is supplied from the starting fuel discharge passage 14 to the intake passage 2 to satisfy warm-up operation.

Next, when the warm-up of the engine is completed, the operating rod 20 is returned from the intermediate position to the original position shown in FIG. According to this, since the on-off valve section 19 closes the valve seat 18,
Fuel does not flow out from the starting fuel pump chamber 7 to the starting fuel discharge passage 14.

[Problems to be Solved by the Invention] According to the conventional starting device, it is possible to increase the amount of starting fuel, but it is not possible to increase the amount of air, so the starting test time for determining starting performance is reduced. It takes a lot of time and development efficiency is poor.

[Means for solving the problems] In view of the above-mentioned problems, the carburetor starting device according to the present invention has the following features:
It is an object of the present invention to provide a device with good starting performance, which allows easy setting work for improving starting performance, and can supply optimal starting fuel for initial explosion, complete explosion, and warm-up operation of the engine, and achieves the above-mentioned purpose. For this reason, the interior is divided into a starting fuel pump chamber and an atmospheric chamber by a partition, and a suction control 1F valve is placed inside the starting fuel pump chamber, which is connected to a constant liquid level below the float chamber. A starting fuel inlet passage and a starting fuel discharge passage in which a discharge side check valve is disposed are opened, and the starting fuel discharge passage is opened in a partition body that is pressed toward the starting fuel pump chamber by a spring. An on-off valve section capable of opening/closing control and an operating rod capable of applying a pump operating force to the partition body are integrally provided, and the operating rod has a starting fuel discharge passage which is blocked by the on-off valve section of the partition body. Providing an intermediate position regulating member N that can hold the partition at a substantially intermediate position between the first state and the second state in which the partition body is pulled toward the atmospheric chamber,
When the attractive force on the operating rod is released from the second state, the partition body is automatically returned to the approximately intermediate position by the spring force of the spring, and the fuel in the starting fuel pump chamber is discharged through the starting fuel discharge passage. In the starting device, the tire flam is divided into an atmospheric chamber and a pressure chamber, and the throttle valve lever, which is formed integrally with the tire plum and penetrates the atmospheric chamber and rotates synchronously with the throttle valve, is arranged to correspond to the tire flam. The operating rod is contracted in the pressure chamber, and when the pressure in the pressure chamber is at atmospheric pressure, the throttle valve returns to a tin rank 1 throttle valve.
A first idle spring that overcomes the biasing force in the throttle valve closing direction and presses the operating rod against the throttle valve lever to open the throttle valve to a constant opening compared to the idling opening, and a throttle valve actuating device comprising: an engine atmosphere; A vaporizer comprising a heat-sensitive switching valve that communicates the pressure chamber with the atmosphere when the temperature is low, and communicates the pressure chamber with the intake passage on the engine side of the throttle valve when the engine ambient temperature is high. This is the starting device for the device.

[According to this, when the gravitational force on the operating rod is released from the first state in which the operating rod is pulled all the way toward the atmospheric chamber, the operating rod automatically returns to the intermediate position due to the spring force; The starting fuel is injected and supplied into the intake passage through the starting fuel discharge passage.

On the other hand, when the ambient temperature of the engine is low, atmospheric pressure is introduced into the pressure chamber by the heat-sensitive switching valve, so the spring placed in the pressure chamber acts as an operating rod to rotate the throttle valve lever. This opens the throttle valve to a fixed opening compared to the idling opening.

Therefore, it is possible to supply the engine with a rich air-fuel mixture suitable for starting and an increased amount of air.

[Embodiment] The starting device for a carburetor of the present invention will be explained below with reference to FIGS. 2, 3, 4, and 5.

Components having the same structure as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

A throttle valve shaft 30 is rotatably supported by the carburetor main body 1 and has a throttle valve 5 attached thereto, and a throttle valve lever 31 is attached to an end of the throttle valve shaft 30.

The throttle valve lever 31 is provided with a first bent portion 31A and a second bent portion 31B, and a biasing force in the closing direction of the throttle valve 5 is applied by a throttle valve return spring 32.

A screw 33 for adjusting the minimum opening degree of the throttle valve 5 is screwed onto the carburetor body 1 in correspondence with the first bent portion 31A of the throttle valve lever 31.

Reference numeral 34 denotes a throttle valve operating device, the interior of which is divided into an atmospheric chamber 36 and a pressure chamber 37 by a diaphragm 35.

An operating rod 38 is integrally attached to the diaphragm 35,
This operating rod 38 passes through the atmospheric chamber 36 and the throttle valve lever 3
This corresponds to the second bent portion 31B of No. 1.

Further, a first idle spring 38 is compressed in the pressure chamber 37 to press the diaphragm 35 toward the atmospheric chamber 36.
The opening force of the throttle valve 5 against the throttle valve lever 31 via the operating rod 38 is greater than the closing force of the throttle valve 5 of the throttle valve return spring 32 against the throttle valve lever 31 in the low opening range of the throttle valve 5. That is.

Reference numeral 40 denotes a heat-sensitive switching valve, which has the following configuration.

Reference numeral 41 denotes a valve body having a valve hole 42 penetrated therethrough, and inside the valve hole, there is a straight atmospheric air inlet passage 43 and a pressure passage extending substantially perpendicularly and parallel to the diameter of the valve hole. An introduction path 44 is bored.

One end 43A of this atmosphere introduction path 43 is connected to the pressure chamber 37, the other end 43B via the valve hole 42 is connected to the atmosphere, and one end 44A of the pressure introduction path 44 is connected to the pressure chamber 37, and the other end 43B through the valve hole 42 is connected to the atmosphere. The other end 44B is connected from the throttle valve 5 to the intake passage 2 on the engine side.

45 is movably arranged in the valve hole 42 and connects to the atmosphere introduction path 4.
3. A spool valve as a switching valve for connecting either one of the pressure introduction passages 44 to the pressure chamber, and a valve groove 45A having a diameter smaller than the outer diameter of the spool valve 45 is provided in the middle part of the spool valve 45. is bored, and when this valve groove 45A is located corresponding to the introduction path, the corresponding introduction path is connected to the pressure chamber 37, and the outer diameter of the spool valve 45 does not correspond to the other valve groove 45A. The introduction path corresponding to the pressure chamber 37 is cut off from the pressure chamber 37.

Further, 48 is a thermowax, for example, in which a hot W wire member such as paraffin is sealed, and the output 1: I+ 4 e A of the thermowax 46 is the -.
It is arranged opposite to the side end +1'4i (the right side of the spool valve 45). (Output 1: t + 4 e A increases its projection (L) as the ambient temperature increases.) 47 is the other end face of the spool valve 45 (the left side of the spool valve 45). The spring force of this spring 47 presses one end surface of the spool valve 45 against the output shaft 48A.

Next, its effect will be explained.

First, a case where the engine atmosphere temperature and the engine temperature are high will be explained. Since the temperature is high, there is no need to supply a rich air-fuel mixture to the engine.

Therefore, the operating lever 20 of the starting device is held in the inoperative state 4. This state is shown in FIG. 2, in which the partition 6 is pressed toward the starting fuel t'l pump chamber 7 by the spring 23, and the on-off valve section 19 provided integrally with the partition 6 is Starting fuel discharge passage 14 starting fuel 21 pump chamber 7
Since the valve seat 18 which is open to the engine is closed and held, the starting fuel will not be discharged. Also, in such a state, the thermal expansion/contraction member in the thermowax 46 expands and moves the output shaft 4eA to the left in the figure. 37, and the atmosphere introduction passage 43 is connected to the spool valve 4.
5 and is blocked off from the pressure chamber 37. Therefore, the pressure chamber 37 is connected to the intake passage 2 on the engine side via the pressure introduction passage 44 via the throttle valve 5.

The opening state of the throttle valve 5 of the carburetor before the engine starts is such that the pressure chamber 37 is maintained at atmospheric pressure since the engine has not yet started and no negative pressure is generated in the intake passage 2. , the operating rod 3 is operated by the spring force of the first idle spring 38.
8 is in one position in the figure, and the throttle valve 5 is kept open from the idling opening to a constant opening.

When the engine is started in such a state, starting fuel is not supplied from the starting fuel pump chamber 7 into the intake passage 2, so the starting air-fuel mixture does not exceed 7 m, and the air pressure is increased. With good fuel atomization, the engine can be started at a rotational speed fm that is 1 - more than the idling opening, thereby improving startability.

Then, when the engine goes through the initial explosion and complete explosion and returns to the normal operating state, the intake passage negative pressure generated in the intake passage 2 is introduced into the pressure chamber 37 of the throttle valve actuating device 34 through the pressure introduction passage 44. The diaphragm 35 is moved toward the pressure chamber 37 against the spring force of the first idle spring 39.

According to this, the rotation suppression force in the clockwise direction of the operating rod 38 with respect to the throttle valve lever 31 is released, so that the throttle valve /<-31 is rebounded by the spring force of the throttle valve return spring 32 until it comes into contact with the screw 33. By rotating clockwise, the desired idling opening degree of the throttle valve 5 can be obtained.

Therefore, it is possible to immediately return to idling rotation without impairing fuel economy or producing noise.

Next, we will talk about starting the engine in a state where the ambient temperature is low. Prior to starting the engine, the operating rod 20 is pulled all the way to the left in the figure against the spring force of the spring 23. This state is the first state. This is clearly shown in Figure 3. By this operation, the partition body 6 and the on-off valve section 19 are also moved to the left in synchronization with the operating rod 20, and the on-off valve section 19 is moved to the left side in synchronization with the operating rod 20.
8 is opened and the volume of the starting fuel pump chamber 7 is increased.

According to this, the suction side check valve 11 opens the suction valve seat 12, and the discharge side check valve i'T17 opens the suction valve seat 12.
occlude.

Therefore, by this operation, the fuel I'4 stored in the float chamber 4 is drawn into the starting fuel pump chamber 7.

Next, the leftward cutting force on the operating rod 20 is released. According to this, the operating rod 20 is moved toward the starting fuel I pump chamber 7 side (as shown in the figure) by the spring force of the spring 23.
(to the right), and the operating rod 20 stops when it is engaged with the groove 20A or the ball 21 as the intermediate position regulating member N. (This state is shown in FIG. 4.) The fact that the operating rod 20 is stopped at the intermediate position is that the operating rod 20 acts in a direction perpendicular to the pushing force of the spring 23 in the longitudinal axis direction Y-Y of the operating rod 20. This can be achieved by appropriately increasing the pressing force of the spring 22 of the ball 21.

When the operating rod 20 is moved to the intermediate position, the starting fuel pump chamber 7 is compressed and the chamber volume is reduced, so that the discharge side check valve 17 opens the discharge valve seat 15 and the starting fuel discharge passage 14 is opened. Starting fuel is injected and supplied into the intake passage 2 by the stroke of the partition body 6.

On the other hand, in the heat-sensitive switching valve 40, due to the low engine ambient temperature, the heat w1 in the thermowax 4B? The i member contracts, thereby reducing the projecting dimension (L) of the output shaft 46A, and the spool valve 45 moves to the right in the valve hole 42 by the spring force of the spring 47, and the valve of the spool valve 45 is moved to the right. The atmosphere introduction path 43 and the pressure chamber 37 are connected through the groove 45A, and the pressure introduction path and the pressure chamber 37 are isolated from each other by the outer periphery of the spool valve 47.

Therefore, the atmosphere is introduced into the pressure chamber 37 from the atmosphere introduction path 43. According to this, the diaphragm 35 and the operating rod 38 move upward in the figure due to the spring force of the fast idle spring 3θ, and the throttle valve lever 31 clockwise to keep the throttle valve 5 open to a certain degree from the idling opening.

After the process of pulling the operating rod 20 to the left all at once, and the return process of releasing the attractive force on the operating rod 20 to return it to the intermediate position, a cranking operation for starting the engine begins. Then, the fuel in the starting fuel pump chamber 7 is already injected into the intake pipe from the starting fuel discharge passage 14, and the throttle valve 5 is opened more than the idling opening, so a sufficiently rich mixture is supplied to the engine. It can be supplied in large quantities and ensures the initial and complete explosion of the engine.

When the engine enters a warm-up state after a complete explosion, the operating rod 20 is held at an intermediate position and the valve seat 18 is held open by the on-off valve part 19, so that the engine is not generated in the intake pipe. Negative pressure acts on the discharge side check valve 17 from the starting fuel discharge passage 14, opens the discharge side check valve 17 from the discharge valve seat 15 against the spring force of the spring 16, and the fuel in the starting fuel pump chamber 7 is opened. The starting fuel is supplied from the starting fuel discharge passage 14 to the intake passage 2, and an increased amount of air is supplied to the engine to satisfy warm-up operation.

In particular, since the rotational speed during the warm-up operation can be increased, the warm-up time can be shortened.

Next, when the warm-up operation of the engine is completed and the engine concentration increases, the operating rod 20 is returned from the intermediate position 1 in FIG. 4 to the original position in FIG. 2. According to this, since the on-off valve section 18 closes the valve seat 18, fuel does not flow out from the starting fuel pump chamber 7 to the starting fuel discharge passage 14.

On the other hand, in such a state, the thermowanx 46 senses the increase in engine concentration and extends the output shaft 48A to the right in the figure to increase its protrusion length (L). According to this, the valve of the spool valve 45 The groove 45A opens the pressure introduction path 44 and connects the pressure chamber 37 and the pressure introduction path 44,
The outer periphery of the spool valve 45 closes the atmospheric air introduction path 43.

Therefore, the intake passage negative pressure of the intake passage 2 is introduced into the pressure chamber 37 via the pressure introduction passage 44, and according to this,
Diaphragm 35 is first idle spring 39
It moves downward in the figure against the spring force of , thereby eliminating the clockwise rotational force exerted by the operating rod 38 on the throttle valve lever 31.

Therefore, the throttle valve lever 31 is connected to the throttle valve return spring 3.
The idling opening of the throttle valve 5 can be maintained automatically by rotating the throttle valve counterclockwise until the first bent portion 31A of <-31 comes into contact with the screw 33. .

During subsequent operation, the operating rod 38 will be connected to the throttle valve lever 31.
Since no rotational force is applied to the throttle valve 5, the idling opening degree of the throttle valve 5 set by the screw 33 can be maintained.

The operation of the diaphragm 35 and the operating rod 38 described above can be easily performed by selecting the intake road vehicle pressure generated in the intake path 2, the spring force of the fast idle spring 38 and the throttle valve return spring 32, or the pressure receiving diameter of the diaphragm 35. can be achieved.

Furthermore, the structure of the heat-sensitive switching valve 40 is such that the pressure chamber 37 and the pressure introduction passage 44 are connected to each other when the temperature is high, and the pressure chamber 37 and the atmosphere introduction passage 43 are cut off, and when the actual temperature is low, the pressure It is sufficient that the chamber 37 and the atmospheric air introduction path 43 are connected and the pressure chamber 37 and the pressure introduction path 44 are blocked, and the present invention is not limited to the examples not yet implemented.

[Effects of the Invention] According to the carburetor starting device of the present invention as described below,
It has the following effects.

■When starting the engine at a low ambient temperature,
Starting fuel pump The desired starting fuel suitable for initial and complete explosion of the engine is directly injected into the intake duct from the starting fuel discharge passage without relying on the negative pressure in the intake duct, and the throttle valve is opened at a constant rate from idling. By keeping the air-fuel mixture open, a large amount of the air-fuel mixture suitable for starting the engine can be supplied, which improves the engine's startability. The test efficiency of the starting performance test can be improved compared to a method that matches the starting performance using the same method.

Furthermore, when the engine warms up during warm-up operation, the throttle valve can be automatically returned to its idling opening due to the rise in temperature, making it possible to perform a good warm-up operation.

■When the engine is warmed up, the throttle valve is kept open from the idling opening, so the engine speed is -h R
According to this, the warm-up time could be shortened.

[Brief explanation of the drawing]

Figure 1 is a longitudinal sectional view showing a conventional carburetor starting device;
The figure is a longitudinal cross-sectional view showing a closed state of the starting fuel discharge passage of the starting device for a carburetor according to the present invention, and Fig. 3 is a longitudinal cross-sectional view showing a state in which the operating rods of Fig. 2 are applied to the atmospheric chamber side at the same time. 4 is a longitudinal cross-sectional view showing a state in which the operating rod has been returned to an intermediate position from the state shown in FIG. 83. 1... Carburetor body, 2... Intake path, 4...
...Float chamber, 5.. Throttle valve, 6.. Compartment body, 7.. Starting fuel pump chamber, 8.. Atmospheric chamber, 9.
...cover, 10...starting fuel inlet passage, 14...starting fuel discharge passage, 18...valve seat,
18... Opening/closing valve part, 23... Spring, 31... Throttle valve lever, 32... Throttle valve return spring, 34...
Throttle valve operating device, 35...Diaphragm, 36...Atmospheric chamber, 37...Pressure chamber, 38...Operation rod, 39...First idle spring, 40
...Thermal switching valve, 43...Atmosphere introduction path, 4
4...Pressure introduction path, 45...Spool valve,

Claims (2)

[Claims] (1) The interior is divided into a starting fuel pump chamber and an atmospheric chamber by a partition, and a suction side check valve is placed inside the starting fuel pump chamber, which is connected to a constant level below the liquid level in the float chamber. A starting fuel inflow passage and a starting fuel discharge passage in which a discharge side check valve is disposed are opened, and a partition body that is pressed toward the starting fuel pump chamber by a spring is provided with a starting fuel discharge passage that opens and closes. A controllable opening/closing valve part and an operating lever capable of applying a pump operating force to the partition body are integrally provided, and the operating lever includes:
An intermediate position regulating member N is provided which can hold the starting fuel discharge passage in a first state in which the opening/closing valve portion of the partition body is closed and a second state in which the partition body is pulled toward the atmospheric chamber. When the attractive force on the operating rod is released from the second state, the partition body is automatically returned to the approximately intermediate position by the spring force, and the fuel in the starting fuel pump chamber is discharged through the starting fuel discharge passage to start the carburetor. The device includes a diaphragm that divides into an atmospheric chamber and a pressure chamber, and an operating rod that is formed integrally with the diaphragm and is disposed corresponding to a throttle valve lever that passes through the atmospheric chamber and rotates synchronously with the throttle valve. is compressed in the pressure chamber, and when the pressure in the pressure chamber is at atmospheric pressure, it overcomes the force of the throttle valve return spring against the throttle valve lever in the direction of closing the throttle valve, presses the operating rod against the throttle valve lever, and closes the throttle valve. A first idle spring that opens the opening to a certain degree from the idling opening; and a throttle valve actuating device that communicates the pressure chamber with the atmosphere when the engine ambient temperature is low and reduces the pressure when the engine ambient temperature is high. A starting device for a carburetor comprising a heat-sensitive switching valve that communicates a chamber with an intake passage on the engine side of the throttle valve. (2) The heat-sensitive switching valve has a valve hole drilled in the valve body, a spool valve that is slidably arranged in the valve hole and has a valve groove bored in the middle part, and an opening in the valve hole. The air introduction path is opened and closed by the valve groove of the spool valve, and has one end connected to the pressure chamber and the other end connected to the atmosphere, and one end connected to the pressure chamber and the other end connected to the intake path on the engine side from the throttle valve. and,
The carburetor according to claim 1, comprising: a heat-sensitive expansion/contraction body disposed corresponding to the spool valve and controlling the movement of the spool valve in the valve hole according to changes in the engine ambient temperature. starting device.