JPH03115765A - Carburetor - Google Patents

Abstract

PURPOSE:To improve startability by providing a device, delivering fuel in a fuel provision chamber out to a starting combustion chamber by a displacing member in the carburetor of an engine for a moving machine or the like, with stoppers for regulating the stroke quantity of the displacing member in the decreasing direction as the temperature rise. CONSTITUTION:At the time of starting an engine, a primary pump 44 is hand- operated to lead fuel in a fuel tank into a metering chamber 38 from an inlet port 48. A starting valve 76 is then pushed in against a spring 90 to displace a diaphragm 80 until it is brought into contact with the upper wall part 82 of a diaphragm chamber 74 with the force of a spring 86 so as to deliver fuel in the diaphragm chamber 74 out to a wick 88 through the starting valve 76. The fuel at this wick 88 is led out through the connecting hole 24 of a throttle valve 22. When the engine is started and temperature rises, a spring seat 87 and a raised part 84 as stoppers are thermal-expanded, and their vertical thicknesses lx, ly are increased, so that the stroke quantity la of the diaphragm 80 is reduced, thereby reducing the fuel supply quantity.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a vaporizer that generates atomized fuel to be supplied to an engine installed in a brush cutter, a backpack-powered spreader, etc. The present invention relates to a carburetor that can improve engine startability by adjusting supplied fuel.

[Conventional technology]

A carburetor that generates atomized fuel to be supplied to a two-cycle engine installed in a brush cutter, backpack power spreader, etc. is equipped with a starting fuel chamber that communicates with the intake passage. By manually operating the valve, fuel is introduced into the starting fuel chamber, and the fuel in the starting fuel chamber is sent to the two-cycle engine, enriching the air-fuel mixture at startup to ensure smooth starting. .

In such conventional carburetors, the amount of fuel sent into the starting fuel chamber by operating the starting valve is fixed.

[Problem a that the invention attempts to solve]

FIG. 3 is a diagram showing the relationship between the temperature in a conventional carburetor and the number of times a two-cycle engine is attempted before starting, using the fuel ff1V introduced into the starting fuel chamber as a parameter. Since the vaporization of the fuel in the starting fuel chamber changes depending on the temperature, in conventional carburetors, if the amount of fuel introduced into the starting fuel chamber is set to be large (V =
0, 45cc), the startability at low temperatures is good, but the startability at high temperatures worsens, and conversely, when it is set to a lower value (V-0, 25cc), the startability at high temperatures deteriorates. Although this is good, there is a problem that starting performance at low temperatures deteriorates.

An object of the present invention is to provide a carburetor that can control the amount of fuel introduced into the starting fuel chamber and obtain good starting performance of the engine regardless of the temperature.

An object of the invention in claim 2 is to provide a preferred embodiment of claim 1.

[Means to solve the problem]

The invention will be described using reference numerals in the drawings that correspond to the embodiments.

The carburetor (10), which is the premise of claim 1, includes a starting fuel chamber (88) that communicates with the intake passage and stores fuel, and a starting fuel chamber (88) that stores fuel to be supplied to the starting fuel chamber (88). A starting valve (76) that opens and closes manually to control the connection between the starting fuel chamber (88) and the fuel preparation chamber (74); ) is biased in the direction of decreasing the volume of the starting valve (76), and moves when the starting valve (76) is opened, and moves the fuel in the fuel preparation chamber (74) to the starting valve (76).
The displacement member (8) delivers fuel to the starting fuel chamber (88) via the
0). And a vaporizer like this (10
), stoppers (84, 87) are provided for regulating the stroke amount of the displacement member (80) so as to reduce the stroke amount of the displacement member (80) as the temperature rises.

In the vaporizer (10) of claim 2, the stopper (84, 87
) is a member that increases or decreases the length of the displacement member (80) in the stroke direction in relation to temperature.

[Effect]

In the invention of claim 1, when starting the engine, the starting valve (76) is opened manually. Fuel preparation room (74)
Fuel is stored in advance in the fuel preparation chamber (74) and the starting fuel chamber (88) when the starting valve (76) is opened. The chamber (74) is displaced in the direction of decreasing volume.

The fuel in the fuel preparation chamber (74) is pushed out of the fuel preparation chamber (74) by the displacement member (80) and the fuel in the fuel preparation chamber (74) is pushed out of the fuel preparation chamber (74) by the displacement member (80).
) and is introduced into the starting fuel chamber (88). The fuel introduced into the starting fuel chamber (88) is supplied to the engine through the intake passage, enriching the air-fuel mixture at the time of starting.

When the displacement member (80) opens the starter valve (76), fuel corresponding to the amount of displacement is introduced into the starter fuel chamber (88) in a direction that reduces the volume of the fuel preparation chamber (74). Ru.

The stopper (84, 87) regulates the stroke amount of the displacement member (80) so that the stroke amount of the displacement member (80) accompanying the opening of the starter valve (76) decreases as the temperature rises. .

As a result, the amount of fuel introduced into the starting fuel chamber (88) is as follows.

It decreases as the temperature increases.

In the invention of claim 2, the stopper (84, 87) increases or decreases the length of the displacement member (80) in the stroke direction in relation to the temperature. A stopper (84,
87), the stroke amount of the displacement member (80) when the starting valve (76) opens increases or decreases, so the amount of fuel introduced into the starting fuel chamber (88) also increases or decreases.6 [Implementation] Example] The present invention will be described below with reference to embodiments of the drawings.

FIG. 2 is an overall structural diagram of the rotary throttle valve type carburetor 10. This rotary throttle valve type carburetor 10 is attached to a two-cycle engine (not shown) mounted on a working machine such as a brush cutter or a backpack-powered spreader. It communicates with the engine's crankcase. The body 12 includes portions 14, 16, 18, and 20 that are joined in a stacked manner in the vertical direction. The throttle valve 22 is a part 1 of the body 12.
It is slidably contacted in the inner hole of No. 4 so as to be freely rotatable around the vertical axis and freely movable in the vertical direction. The connecting hole 24 passes through the throttle valve 22 in the diametrical direction, and can freely connect both ends to the intake passage in the body 12, and increases or decreases the connection area with the intake passage as the throttle valve 22 rotates. The opening degree of the throttle valve 22 is increased or decreased by such an increase or decrease. Lid 26
closes the upper part of the inner hole of the body 12 to which the connection hole 24 is in sliding contact, and the compression coil spring 28 is compressed under the lid 26 to urge the throttle valve 22 downward. The rotary lever 30 is disposed above the body 12, is fixed to the throttle valve 22, and rotates and moves up and down integrally with the throttle valve 22. The rotating lever 30 connects to a throttle lever (not shown) via a throttle cable (not shown).
It rotates according to the operator's operation of the throttle lever, and its rotational range is limited by contact with the idle adjustment screw 31. The tip position of the idle adjustment screw 31,
In other words, the rotational position of the rotary lever 30 when the idle adjustment screw 31 comes into contact with the rotary lever 30 can be adjusted by rotating the idle adjustment screw 31, so that the idle opening degree of the throttle valve 22 can be adjusted appropriately. Ru. The slope 32 is formed on the lower surface of the rotary lever 30, and the protrusion 34 is
It is fixed to the upper surface side of the lid 26 and slides on a slope 32 as the rotary lever 30 rotates, and as a result, the one-turn lever 30 and the throttle valve 22 move up and down. The idle needle pin 36 is positioned on the center line of the throttle valve 22.
It is attached to the throttle valve 22 and moves up and down integrally with the throttle valve 22.

The metering chamber 38 is formed approximately in the center of the body 12, and is partitioned on the lower side by a metering diaphragm 40.
Primary pump 44 via combination valve 42
It communicates with the chamber 46. The combination valve 42 is
At the periphery, it functions as a check valve that only allows flow in the direction of introduction into the chamber 46, and at the center, it functions as a check valve that only allows flow in the direction of extraction from the chamber 46. The primary pump 44 is elastically compressible, and when the primary pump 44 returns to its original size after being compressed,
The check valve in the center of the combination valve 42 closes, creating a negative pressure in the chamber 46, which is transferred to the combination valve 42.
The metering chamber 3 is
8. In this way, fuel from a fuel tank (not shown) is sucked in through the inlet 48 and is cleared of foreign matter at the inlet screen 50 before the check valves 52,54
The surplus fuel passes through the metering chamber 38 and the inlet needle valve 56 in order, and is introduced into the metering chamber 38. Further, the excess fuel passes through the open check valve mechanism around the combination valve 42 from the metering chamber 38 to the chamber 46 of the primary pump 44. .

Conversely, when the primary pump 44 is elastically compressed,
The check valve mechanisms at the periphery and center of the combination valve 42 are closed and closed, respectively, and the fuel in the chamber 46 is discharged from the center of the combination valve 42.

The pump diaphragm 58 faces the intermediate passage of the check valve 52, 54 on its lower side and defines an engine pulse chamber 60 on its upper side. The engine pulse chamber 60 communicates with the crank chamber of the two-cycle engine, and is supplied with the pulsating pressure of the crank chamber due to the reciprocation of the piston of the two-cycle engine. During operation of the two-cycle engine after starting the two-cycle engine, the pump diaphragm 58 is displaced up and down due to the pulsating pressure in the engine pulse chamber 60, and the check valves 52 and 54 are alternately opened and closed as an intake valve and a discharge valve, respectively. The fuel sucked from the fuel tank is transferred to the metering chamber 38.
send to. The metering lever 62 is swingably supported within the metering chamber 38 and is connected to the inlet needle valve 56.
The metering lever spring 6 swings in the closing direction.
4, which fixes the lower end of the inlet needle valve 56 at one end and presses the metering diaphragm 40 toward the atmospheric chamber 66 at the other end. When the negative pressure in the metering chamber 38 increases, the metering diaphragm 40 rises against the metering lever blade 64 and the inlet needle valve 56 opens, allowing fuel to flow into the metering chamber 38 through the inlet needle valve 56. is introduced, and the negative pressure within the metering chamber 38 decreases. In this way, the metering diaphragm 40 and the metering lever spring 64 have the function of keeping the negative pressure in the metering chamber 38 constant.

The nozzle 68 protrudes from the center of the connection hole 24 of the throttle valve 22, and has the idle needle pin 36 inserted through its upper end. Metering chamber 38 communicates with nozzle 68 via main check valve 70 and jet valve 72 .

As the throttle valve 22 rotates, the idle needle pin 36 moves up and down within the nozzle 68.

The flow cross-sectional area of the nozzle 68 is increased or decreased to control the amount of fuel jetted from the nozzle 68 to the connection hole 24.

Due to the elastic compression and restoring movement of the primary pump 44 or due to a fuel surplus in the metering chamber 38, the combination valve 4 is removed from the chamber 46 of the primary pump 44.
The fuel that has been drawn out through the check valve mechanism in the center of 2 is
It is guided to the overflow lower outlet 8 through the diaphragm chamber 74 and the lower side of the starting valve 76.
is returned to the fuel tank.

The diaphragm 80 is connected to the diaphragm chamber 74 and the atmospheric chamber 81
is partitioned into upper and lower parts, the upward displacement is limited by contact with the upper wall part 82 of the diaphragm chamber 74, and the downward displacement is limited by contact with the raised part 84 raised at the center of the lower part of the atmospheric chamber 81. limited. The compression coil spring 86 is compressed between a spring seat 87 attached to the lower surface side of the diaphragm 80 and the lower surface of the atmospheric chamber 81.
is urged toward the diaphragm chamber 74.

Wick 88 is formed at the bottom of throttle valve 22 and communicates with starting valve 76 . The starting valve 76 is biased upward by a lower compression coil spring 90, and the starting valve 76 is normally
The lower side of the starter valve 76 is disconnected from the wick 88, and is manually pushed against the compression coil spring 90 to open the starter valve 76, thereby connecting the lower side of the starter valve 76 to the wick 88. The check ball 92 is disposed between the lower side of the starting valve 76 and the overflow lower part 8, and is connected to the compression coil spring 94.
is biased in the closing direction, and only allows flow from the compression coil spring 90 side to the overflow output lower 8 side. The spring force of the compression coil spring 94 is suitably larger than the spring force of the compression coil spring 86 in the atmospheric chamber 81, and the overflow output lower 8 is removed from the diaphragm chamber 74 by the urging force of the diaphragm 80 by the compression coil spring 86. The check ball 92 will not open in response to the force of sending fuel in that direction.

FIG. 1 is a detailed structural diagram of the area including the diaphragm chamber 74. The second limit of the stroke of the diaphragm 80 is the position where the diaphragm 80 abuts against the wall portion 82.

The lower limit of the stroke of the diaphragm 80 is the position when the spring seat 87 comes into contact with the upper surface of the raised portion 84, and the stroke amount of the diaphragm 80 is represented by Qa. Qx and Qy represent the vertical thickness of the spring seat 87 and the raised portion 84, respectively;
The stroke amount Qa decreases as Qx and Qy increase. The spring seat 87 and the raised portion 84 are made of gold 596.98 laminated with different coefficients of expansion with respect to temperature, that is, bimetallic. As the temperature rises, QX and Qy increase due to the difference in thermal expansion coefficient of the metal 96.98, and the amount of one stroke Qa decreases. The diaphragm chamber 74 when displaced toward the diaphragm chamber 74 by the action of the spring 86
This results in a decrease in the amount of fuel discharged from the start valve 76 toward the starting valve 76.

The operation of the embodiment will be explained.

When starting a two-cycle engine to start work using a brush cutter, backpack power implement, etc., there is no fuel in the metering chamber 38 of the rotary throttle valve type carburetor 10, so one worker , primary pump 44
The operation of manually compressing and restoring the fuel is repeated several times, which causes the pumping action of the primary pump 44 to introduce fuel from the fuel tank into the metering chamber 38 through the inlet 48. Further, surplus fuel is introduced from the metering chamber 38 into the chamber 46 of the primary pump 44,
Furthermore, the check ball 9 is connected to the combination valve 42.
2 and is returned to the fuel tank from the overflow lower outlet 8. Since the spring force of the compression coil spring 94 of the check ball 92 is suitably stronger than the spring force of the compression coil spring 86 of the diaphragm 80, the diaphragm 8
0 is held pressed against the raised portion 84 against the compression coil spring 86.

Next, when the starter valve 76 is pushed in against the compression coil spring 90, the starter valve 76 brings its lower side into communication with the wick 88. Along with this, the diaphragm 80 is displaced toward the diaphragm chamber 74 by the stroke amount Qa until it comes into contact with the upper wall portion 82 of the diaphragm chamber 74 due to the urging force of the compression coil spring 86, and the diaphragm 80 is displaced toward the diaphragm chamber 74 by a stroke amount Qa.
The fuel inside is sent out. This fuel is introduced into the wick 88 through the starting valve 76. When the pushing force of the starting valve 76 by the six workers is released, the starting valve 76 is returned to its original closed position by the compression coil spring 90, and the wick 88 is introduced into the wick 88. Fuel supply to 88 is canceled. While the operator is pushing in the starter valve 76, the diaphragm 80 is compressed by the compression coil spring 86.
As a result, an amount of fuel corresponding to the stroke amount Qa of the diaphragm 80 is introduced into the wick 88 by pushing the starting valve 76.

The fuel in the wick 88 flows through the connection hole 24 of the throttle valve 22.
The air-fuel mixture is guided to the two-cycle engine through the 2-cycle engine, enriching the air-fuel mixture supplied to the two-cycle engine.

Metal 96°9 forming the spring seat 87 and the raised portion 84
Due to the difference in the coefficient of thermal expansion of 8, as the ambient temperature increases,
Vertical thickness Qx, Qy of spring seat 87 and raised portion 84
increases, and the stroke amount Qa of the diaphragm 80 decreases as the starter valve 76 opens. therefore.

The amount of fuel introduced from the diaphragm chamber 74 into the wick 88 is large at low temperatures and small at high temperatures. On the other hand, the vaporization of the fuel supplied from the wick 88 to the two-cycle engine improves as the temperature rises. In this way, the decrease in the amount of fuel in the wick 88 and the increase in vaporization are offset, and the air-fuel ratio of the mixture at the time of starting the two-cycle engine remains approximately constant regardless of the temperature.

In the illustrated embodiment, changes in the thickness of the metal 96,98 with respect to the displacement and temperature of the diaphragm 80 are used to control the amount of fuel introduced from the diaphragm chamber 74 into the wick 88 when the starter valve 76 is pushed in. However, a piston may be used instead of the diaphragm 80, and a stopper for regulating the displacement of the piston may be applied to the free end side of the bimetal, so that the position of the stopper may change depending on the temperature.

〔Effect of the invention〕

In the invention of claim 1, the stroke amount of the displacement member that sends the fuel in the fuel preparation chamber to the starting fuel chamber is decreased by the stopper as the temperature rises, so that the amount of stroke of the displacement member that sends the fuel in the fuel preparation chamber to the starting fuel chamber is reduced as the temperature rises. The amount of fuel introduced is large at low temperatures and small at high temperatures, making it possible to improve engine startability despite temperature changes.

In the invention of claim 2, the stroke amount of the displacement member can be regulated by increasing or decreasing the length of the stopper in the stroke direction of the displacement member.

[Brief explanation of drawings]

1 and 2 relate to an embodiment of the invention. Figure 1 is a detailed structural diagram of the range including the diaphragm chamber, Figure 2 is an overall structural diagram of the rotary throttle valve type carburetor,
FIG. 3 is a diagram showing the relationship between the temperature in a conventional carburetor and the number of times a two-cycle engine is attempted before starting, using the amount of fuel introduced into the starting fuel chamber as a parameter. 10... rotary throttle valve type carburetor (carburetor),
74...Diaphragm chamber (fuel preparation chamber), 76...
Starting valve, 80... diaphragm (displacement member), 84...
...Protuberance (stopper), 87...Spring seat (stopper), 88...Wick (starting fuel chamber). Diagram

Claims (2)

[Claims] (1) Starting fuel chamber that communicates with the intake passage and stores fuel (
88), a fuel preparation chamber (74) that prepares and stores fuel to be supplied to the starting fuel chamber (88), and a fuel preparation chamber (74) that opens and closes manually to supply the starting fuel chamber (88) and the fuel. a starting valve (76) that controls connection with the preparation room (74);
It is biased in a direction to reduce the volume of the fuel preparation chamber (74) and moves when the starting valve (76) is opened, thereby discharging the fuel in the fuel preparation chamber (74) through the starting valve (76). a displacement member (80) that delivers to the starting fuel chamber (88);
A stopper (10) that regulates the stroke amount of the displacement member (80) so as to reduce the stroke amount of the displacement member (80) as the temperature rises.
84, 87). (2) The stoppers (84, 87) are arranged so that the displacement member (
8. The carburetor according to claim 1, wherein the length of step 80) in the stroke direction is increased or decreased in relation to temperature.