JP3513544B2 - Starter fuel supply for carburetor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane type carburetor used for an internal combustion engine (hereinafter simply referred to as an engine) of a portable working machine such as a power saw and a brush cutter, and more particularly to a by-starter mechanism for easily starting the engine. The present invention relates to a starting fuel supply device for a carburetor.

[0002]

2. Description of the Related Art In a conventional carburetor starting fuel supply system,
Since the concentration of the air-fuel mixture for starting the engine is set to be constant, it is not possible to maintain good startability in a temperature range from low temperature to normal temperature and to obtain a sufficient warm-up time after starting.

As shown by the line A in FIG. 9, when the concentration of the air-fuel mixture for starting the engine is set to be low, the startability at room temperature is good and the warm-up time after starting can be made sufficiently long. Therefore, there is no particular problem, but the startability at low temperatures decreases as the outside air temperature or ambient temperature decreases. Therefore, as shown by the line B in FIG. 9, when the concentration of the mixture for starting is set to be high, the startability at low temperature is improved and the warm-up time after starting can be made sufficiently long, but at room temperature. A warm-up time cannot be taken enough by starting at. In other words, in the case of starting at room temperature, the concentration of the mixture for starting is too high, so even if the engine starts, it will stop immediately.

Even at the first start-up at room temperature, since fuel does not adhere to the inside of the intake passage of the carburetor, the crank chamber of the engine, the cylinder, etc., the starter is operated to improve the startability. Is preferred. At this time, if sufficient warm-up operation time for returning the starter cannot be taken, too much fuel may enter the engine, making restarting difficult.

[0005]

SUMMARY OF THE INVENTION In view of the above problems, the object of the present invention is to set the concentration of the starting air-fuel mixture to be different in the normal temperature region and the low temperature region, and to set the starting air-fuel mixture according to the ambient temperature condition. It is an object of the present invention to provide a starting fuel supply device for a carburetor, in which the concentration of the can be arbitrarily selected.

[0006]

In order to solve the above-mentioned problems, the structure of the present invention is a by-starter of a carburetor which supplies a mixture for starting to a portion of the intake passage downstream of a throttle valve. The starter shaft is rotatably supported in parallel with the throttle valve shaft on the main body of the carburetor, and the plunger orthogonal to the starter shaft arranged inside the carburetor main body is reciprocated by the notch cam formed on the starter shaft to mix for start. When the plunger is moved to the forward position by the starter plate supported by the starter shaft, the holding plate connected to the starting shaft is locked by the lock plate connected to the throttle valve shaft via the cam of the holding plate, When the valve shaft is rotated in the opening direction of the throttle valve, the locking of the holding plate by the locking plate is released .
A cam is provided so that the holding plate can be locked at multiple rotation positions of the starting plate.
Start provided on the starting shaft by being locked by the plate
Characteristic that the air passage can be switched between normal temperature and low temperature
It is what

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention enhances the startability over a wide range from low temperature to room temperature (for example, -20 ° C to 20 ° C) by setting the concentration of the starting mixture to two levels. In addition, the warm-up time is sufficient.

Therefore, by making the inner diameter of the passage on the inlet side of the mixing chamber where the starting fuel and the starting air are mixed smaller than that of the passage on the outlet side, the concentration of the starting mixture suitable for the ambient temperature can be obtained. To do so. Specifically, a starting shaft is provided with an air passage for low-temperature starting and an air passage for normal-temperature starting, which have mutually different inner diameters, and one of the air passages is selectively communicated with the air passage of the carburetor main body by rotation of the starting shaft. .

For example, in order to obtain the concentration of the air-fuel mixture suitable for the normal temperature range, the air passage having a large inner diameter is selected, and the optimum fuel jet for the normal temperature range is selected. On the other hand, in order to obtain the concentration of the starting air-fuel mixture that is suitable for the low temperature range, leave the fuel jet set in the normal temperature range as it is and select the air passage with the smaller inner diameter, and the starting effect will be achieved by the chioke effect on the mixing chamber. The negative pressure acting on the fuel passage becomes stronger, and the supply amount of starting fuel increases. On the contrary, a single air passage is provided in the starting shaft, an air passage for normal temperature starting and an air passage for cold starting with different inner diameters are provided in the carburetor body, and the air passage of the starting shaft is vaporized by rotating the starting shaft. It may be selectively communicated with one of the air passages of the container body.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a carburetor equipped with a starting fuel supply device according to the present invention is an air system in which a carburetor main body 15 having an intake passage 31 is butted against an upstream end 31a of the intake passage 31. Along with a purifier (not shown), it is attached to the intake port of the engine by bolts passing through a pair of left and right bolt holes 15a. A cover 9 is connected to the upper end wall of the carburetor body 15 with the membrane 10 interposed therebetween, and a chamber for introducing the pulsating pressure of the crank chamber of the two-stroke engine is defined above the membrane 10 and a pump chamber is defined below the membrane 10. Then, the fuel pump D is constituted by this. The fuel pump D supplies the fuel in the fuel tank 46 to the pipe 58,
Suction is performed through the inlet 58a and is supplied to the constant pressure fuel chamber 47 of the constant pressure fuel supply mechanism C through an inflow valve (not shown).

The constant pressure fuel supply mechanism C has a bottom cover 52 on the lower end wall of the carburetor main body 15 with a gasket 49 and a membrane 54 interposed therebetween.
And a constant pressure fuel chamber 47 is defined above the membrane 54, and an atmosphere chamber 51 is defined below the membrane 54. The lever 50 is supported by the support shaft 57 on the wall portion of the constant pressure fuel chamber 47, one end of the lever 50 is engaged with the membrane 54, and the other end of the lever 50 is engaged with an inflow valve (not shown). Therefore, when the fuel in the constant pressure fuel chamber 47 runs short and the membrane 54 rises, the inflow valve opens and the fuel is replenished. On the contrary, when the constant pressure fuel chamber 47 is filled with the fuel and the membrane 54 descends, the inflow valve is closed and the fuel supply is interrupted. Thus, the constant pressure fuel is always reserved in the constant pressure fuel chamber 47.

The fuel in the constant pressure fuel chamber 47 is sucked into the intake passage 31 penetrating the carburetor main body 15 through the passage 48, the high speed fuel adjusting needle valve 53, the check valve 55, and the high speed fuel injection hole 17, and FIG. As shown in FIG. 5, it is similarly sucked into the intake passage 31 through the plurality of low speed fuel injection holes 17a. A known throttle valve 32 is rotatably arranged in the intake passage 31 by the throttle valve shaft 14. The plurality of low-speed fuel injection holes 17a are arranged in the axial direction in the vicinity of the closed position of the throttle valve 32 in the intake passage 31 (more precisely, the idle position). The high-speed fuel injection hole 17 is arranged in the bench lily portion 16 on the upstream side of the throttle valve 32 in the intake passage 31.

Before starting the engine, a manual suction pump 41 is used to remove air and fuel vapor from the constant pressure fuel chamber 47 shown in FIG. 1 and replenish the fuel in the fuel tank 46 to the constant pressure fuel chamber 47. It is connected between the constant pressure fuel chamber 47 and the fuel tank 46. The suction pump 41 has a body 44 to which a spoid 44a is coupled, and a mushroom-shaped composite check valve 43 inside the spoid 44a.
(Incorporating a suction valve and a discharge valve integrally). When the void 44a is repeatedly crushed, the air or fuel vapor in the constant pressure fuel chamber 47 pushes open the pipe 42 and the umbrella portion of the composite check valve 43, and is sucked into the inside of the void 44a. Is opened and discharged to the fuel tank 46 through the pipe 45. Since the constant pressure fuel chamber 47 has a negative pressure, the fuel in the fuel tank 46 is sucked into the constant pressure fuel chamber 47 through the pipe 58, the inlet 58a, the suction valve and the discharge valve of the fuel pump D, and the inflow valve described above.

As shown in FIG. 2, a piston type acceleration pump B is provided inside the carburetor body 15 in order to increase the amount of fuel during acceleration of the engine. That is, the acceleration pump B
Is the piston 2 in the cylinder 3 that traverses the shaft hole of the throttle valve shaft 14.
It is fitted. The piston 2 is brought into contact with the notch cam 14 a of the throttle valve shaft 14 by the spring 4 interposed between the inner end of the cylinder 3 and the piston 2. During low speed operation of the engine, the fuel in the constant pressure fuel chamber 47 is supplied to the passage 48 and the high speed fuel adjusting needle valve 5.
3, annular groove 56 of the fitting portion of check valve 55, acceleration fuel passage 5
Is then sucked into the cylinder 3. When the piston 2 is pushed by the notch cam 14a of the throttle valve shaft 14 during the acceleration of the engine, the fuel in the cylinder 3 is accelerated in the acceleration fuel passage 5 and the annular groove 5.
6, the check valve 55, the high-speed fuel injection hole 17 and the intake passage 31
Is supplied to.

The by-starter A includes a check valve 24 arranged inside the carburetor main body 15, a plunger 6 fitted in a cylinder 22, and a notch cam 21 for driving the plunger 6.
and a starting shaft 21 having a. That is, as shown in FIGS. 1 and 3, when the engine is started, the fuel in the constant pressure fuel chamber 47 passes through the starting fuel passage 25, the fuel jet 27 which is integral with the check valve 24, the check valve 24, and then enters the gasket 49. At the same time, as shown in FIG. 2, the air at the upstream end 31a of the intake passage 31 beyond the throttle valve 32 is introduced into the mixing chamber 49a formed by the holes, and the air passage 18 and the air passage 19 inside the starting shaft 21 are supplied. , 20a and the air passage 20c of the carburetor main body 15 to enter the mixing chamber 49a shown in FIG. 3, and both are mixed and mixed from the mixing chamber 49a through the mixture passage 75 to the cylinder 22.
And the mixture passage 3 inside the carburetor body 15
3, the chamber 49b formed of a hole provided in the gasket 49, and the air-fuel mixture passage 33a, and is supplied to the portion of the intake passage 31 on the downstream side of the throttle valve 32.

As shown in FIG. 2, one end of the air passage 19 opens at the end face of the starting shaft 21. The other end of the air passage 19 is opened to the circumferential surface of the starting shaft 21 via a radial air passage 20a, and is connected to and blocked from the air passage 20c of the carburetor body 15 by the rotation of the starting shaft 21. As shown in FIG. 7, according to the present invention, in order to obtain the concentration of the starting air-fuel mixture suitable for the ambient temperature or the ambient temperature, the starting shaft 21 and the air passage 20a for cold-starting having different inner diameters and the cold-starting. And an air passage 20b for use in the carburetor main body 15 are selectively communicated with one of the air passages 20a and 20b by rotating the starting shaft 21.

As shown in FIG. 2, the throttle valve shaft 14 is connected to the valve lever 12 at the left end, and the throttle valve 32 is closed by a spring 13 locked between the valve lever 12 and the carburetor body 15. Rotation is urged to return to. The stop ring 61 is locked at the right end of the throttle valve shaft 14, and the axial movement of the throttle valve shaft 14 is blocked by the spring 13. A lock plate 62 is connected to the right end of the throttle valve shaft 14. The starting shaft 21 is the carburetor main body 15
Is supported in parallel with the throttle valve shaft 14. A cylinder 22 orthogonal to the starting shaft 21 is formed inside the carburetor main body 15,
The plunger 6 fitted in the cylinder 22 is engaged with the notch cam 21 a of the starting shaft 21 by the force of the spring 72. By engaging the annular groove 21b of the starting shaft 21 with a pin integrated with the plug 69 fitted to the outer end portion of the cylinder 22, the starting shaft 21 is prevented from moving in the axial direction. As shown in FIG. 3, the spring 72 is interposed between the plunger 6 and the annular spring seat 71 a, and the spring seat 71 a holds the O-ring 71 at the inner end of the cylinder 22. The plunger 6 is integrally provided with a valve body 6a at its end, and the valve body 6a is O when the plunger 6 is in the returning position.
The mixture passage 75 and the mixture passage 33 are separated from the ring 71.
Communicate between.

As shown in FIG. 2, the operating mechanism of the by-starter A has a starting plate 66 which is supported by the starting shaft 21 so as to be freely rotatable.
A holding plate 64 supported by the starting shaft 21 so as to be movable in the axial direction and non-rotatable, and a locking plate 6 connected to the throttle valve shaft 14.
2 and. The spring 77 wound around the starting shaft 21 is interposed between the spring seat 68 and the holding plate 64, and as shown in FIG. 4, the end portion 77a is locked to the pin 78 of the carburetor main body 15 and the end portion 77b. Is locked to the protrusion 64c of the holding plate 64. The holding plate 64 is urged to rotate in the clockwise direction by the force of the spring 77, and the edge 64 b of the holding plate 64 causes the protrusion 6 of the starting plate 66 to move.
6b, the starter plate 66 is rotated clockwise to move the starter plate 6
The notched edge portion 66c of 6 is brought into contact with the pin 78. As shown in FIG. 4, the holding plate 64 has cams 64A and 64B defined by V-shaped grooves on the periphery of the end 64a. The starting plate 66 has a hole a or a hole b for connecting the starting button 59 made of a rod, and a notched edge portion 66 that abuts on the pin 78.
c and a projecting piece 66b that abuts on the edge 64b of the holding plate 64.
And a cam 66 that contacts the plate surface of the end 64a of the holding plate 64.
and a. As shown in FIG. 2, the cam 66a of the starting plate 66 forms a cam surface curved toward the holding plate 64, and does not abut against the end edge of the locking plate 62 of the throttle valve shaft 14 in the idle position. .

Next, the operation of the starting fuel supply system according to the present invention will be described. Before starting the engine, the suction pump 41 is operated to remove the fuel vapor and air in the constant pressure fuel chamber 47 and replenish the fuel in the fuel tank 46 to the constant pressure fuel chamber 47. Then
When the starter button 59 is pulled to rotate the starter plate 66 from the position shown in FIG. 4 about the starter shaft 21 in the counterclockwise direction,
The projection 66b of the starting plate 66 pushes the edge 64b of the holding plate 64, and the starting shaft 21 is rotated counterclockwise against the force of the spring 77. As shown in FIG. 5, the cam 64A of the holding plate 64
Hits the lock plate 62 of the throttle valve shaft 14, and rotates the lock plate 62 in the clockwise direction (the opening direction of the throttle valve 32) in FIG.

[0020] Hakodate at the start of the engine at room temperature (for example 0 ℃)
When the start button 59 is released in this state, as shown in FIG.
The starting plate 66 is rotated clockwise by the force of the spring 77,
The V-groove-shaped cam 64A engages with the end edge of the locking plate 62 of the throttle valve shaft 14, whereby the starting shaft 21 is locked at the position shown in FIG. In this way, when the starting shaft 21 is rotated by the predetermined angle α, the air passage 20a of the starting shaft 21 communicates with the air passage 20c of the carburetor main body 15, and the plunger 6 receives the force of the spring 72, so that the starting shaft 21 moves. The valve body 6a is separated from the O-ring 71 by falling into the notch cam 21a, and the mixture passage 75
And the mixture passage 33 communicate with each other.

When the engine is recoiled (started) in such a state, the negative pressure action of the intake passage 31 causes the constant pressure fuel chamber 4
The fuel of No. 7 is sucked into the mixing chamber 49a through the starting fuel passage 25, the fuel jet 27, and the check valve 24, and at the same time, the air in the end portion 31a of the intake passage 31 upstream of the throttle valve 32 is
Mixing chamber 49 through air passages 18, 19, 20a, 20c
is aspirated to a. The starting fuel and the starting air are mixed in the mixing chamber 49a, and the starting air- fuel mixture is sucked into the cylinder 22 through the air- fuel mixture passage 75, and further passes through the air-fuel mixture passage 33, the chamber 49b, the air-fuel mixture passage 33a, and the intake passage 31. It is sucked to the downstream side of the throttle valve 32. In this way, even when the throttle valve 32 is in the idle position, a relatively rich mixture of starting fuel and starting air is supplied to the intake passage 31, so that the engine is smoothly started.

After the engine is started, a relatively rich starting air-fuel mixture is continuously supplied, but when warm-up is obtained, the throttle lever shaft 14 is rotated in the acceleration direction (clockwise in FIG. 5) by the valve lever 12. When moved, the locking plate 62 of the throttle valve shaft 14
And the cam 64A of the holding plate 64 of the starting shaft 21 are unlocked, and the holding plate 64, the starting shaft 21, and the starting plate 66 are rotated clockwise by the force of the spring 77, as shown in FIG. It stops when the notched edge portion 66c of the starting plate 66 hits the pin 78. At this time, the air passage 20a and the air passage 2
0c is cut off (state of FIG. 7), the plunger 6 is pushed by the peripheral surface of the starting shaft 21, and the valve body 6a is pushed by the O-ring 7.
1 and disconnects the mixture passage 75 and the mixture passage 33 from each other.

When the supply of the starting air-fuel mixture is interrupted immediately after the engine is started, when the start button 59 is pushed back, only the starting plate 66 in FIG. 5 rotates clockwise about the starting shaft 21 to start the engine. The holding plate 64 is held by the cam 66a of the plate 66.
End portion 64a is pushed in the axial direction (to the right in FIG. 2) to release the locking between the holding plate 64 and the locking plate 62,
The holding plate 64 is rotated in the clockwise direction in FIG. 5 by the force of the spring 77, and the edge portion 64b of the holding plate 64 contacts the projecting piece 66b of the starting plate 66.

When the engine is started at a low temperature (eg, -20.degree. C.), as shown in FIG. 6, when the cam 64B of the holding plate 64 pushes up the lock plate 62 of the throttle valve shaft 14 and passes by, the start button 59 is pushed. When released, the starting plate 66 is rotated clockwise by the force of the spring 77, and the cam 64B moves the locking plate 62.
Engaging the edge of the start shaft 21 to lock the starting shaft 21 to the position shown in FIG. At this time, the air passage 2 of the starting shaft 21
0b communicates with the air passage 20c, and the plunger 6 is connected to the spring 7
2 receives the force of 2, and falls into the notch cam 21a of the starting shaft 21, the valve body 6a separates from the O-ring 71, and the mixture passage 75
And the mixture passage 33 communicate with each other.

When the engine is recoiled (started) in this state, the negative pressure action of the intake passage 31 causes the constant pressure fuel chamber 4 to be operated.
7 is sucked into the mixing chamber 49a via the starting fuel passage 25, the fuel jet 27, and the check valve 24, and at the same time, the air in the intake passage 31 at the upstream end 31a of the throttle valve 32 is introduced into the air passages 18, 19. , 20b, 20c and then a mixing chamber 49a
Is sucked into. The starting fuel and the starting air are mixed in the mixing chamber 49a, and a richer starting air-fuel mixture is sucked into the cylinder 22 through the air-fuel mixture passage 75, and then the air-fuel mixture passage 33, the chamber 49.
b, the throttle valve 32 of the intake passage 31 through the mixture passage 33a
Is sucked to the downstream side.

As described above, according to the present invention, the intake passage 3
Since the concentration of the air-fuel mixture to be supplied to No. 1 is adjusted depending on the normal temperature range and the low temperature range, the engine is started more smoothly than the conventional example shown by the solid line, as shown by the broken lines in FIGS. .

In the embodiment shown in FIG. 8, the starting shaft 21 is provided with a single radial air passage 20a, and the carburetor main body 15 has an air passage 20c for starting at room temperature and an air passage 20d for starting at low temperature which have different inner diameters. And the air passage 20a of the starting shaft 21 is moved by the rotation of the starting shaft 21.
c and 20d are selectively communicated with each other.

[0028]

As described above, according to the present invention, it is possible to select the optimum concentration of the air-fuel mixture for start-up in accordance with the ambient temperature or the ambient temperature. You can secure a warm-up time.

Since the start button can be returned and the throttle valve lever can be operated remotely while the working machine is sufficiently held,
The operation after starting the engine can be made safe.

[0030]

[Brief description of drawings]

FIG. 1 is a front sectional view of a carburetor equipped with a starting fuel supply device according to the present invention.

2 is a plan sectional view taken along the line 2A-2A in FIG.

3 is a side sectional view taken along the line 3A-3A in FIG.

FIG. 4 is a side view showing a state before the start-up fuel supply device is started.

FIG. 5 is a side view showing a state of the starting fuel supply device at a room temperature start.

FIG. 6 is a side view showing a state of the starting fuel supply device at a low temperature start.

FIG. 7 is a side sectional view showing a switching portion of an air passage of the starting fuel supply system.

FIG. 8 is a side sectional view showing a switching portion of an air passage according to a modified embodiment of the present invention.

FIG. 9 is a diagram showing the starting characteristics of a carburetor equipped with the starting fuel supply device according to the present invention and a conventional example.

FIG. 10 is a diagram showing the starting characteristics of a carburetor equipped with a starting fuel supply device according to the present invention and a conventional example.

[Explanation of symbols]

A: By-starter 6: Plunger 14: Throttle valve shaft
15: Vaporizer main body 18, 19, 20a to 20d: Air passage 21: Starting shaft 24: Check valve 25: Starting fuel passage 27: Fuel jet 31: Intake passage 32: Throttle valve 33, 33a, 75: Mixture passage 47: Constant pressure fuel chamber 49: Gasket 49a: Mixing chamber 62: Lock plate 64: Holding plate 66: Starting plate 66
A, 66B: Cam 77: Spring 78: Pin

Front page continued (58) Fields surveyed (Int.Cl. ⁷ , DB name) F02M 1/04 F02M 1/08 F02M 1/10 F02M 1/12

Claims (4)

(57) [Claims] 1. A carburetor by-starter for supplying a starting air-fuel mixture to a downstream side portion of a throttle valve of an intake passage, wherein a carburetor main body rotates a starting shaft having a notch cam parallel to the throttle valve shaft. The plunger, which is supported inside the carburetor body and is orthogonal to the starting shaft, is reciprocated by the notched cam of the starting shaft to control the starting mixture, and the starting plate is free to rotate on the starting shaft.
When the starter plate supports the holding plate so that it cannot freely rotate and the plunger is moved to the forward position via the holding plate, the holding plate is connected to the throttle valve shaft via a cam provided on the holding plate. is lock by the plate, when rotated in the opening direction of the throttle valve shaft throttle valve, the starting fuel supply system for a carburetor locking by locking plate of the holding plate is released, a plurality a holding plate
The cam is provided so that the holding plate can be rotated at multiple rotation positions of the starting plate.
The starter installed on the starting shaft is locked by the locking plate.
The dynamic air passage can be switched between normal temperature and low temperature.
The starting fuel supply device for the carburetor. 2. A starter having a part of a starter air passage extending from the intake passage to a mixing chamber where a starter fuel passage and a starter air passage meet together at an axis of a starting shaft and extending from the axis of the starting shaft to an outer peripheral surface. The starting fuel supply device for a carburetor according to claim 1, wherein the air passage and the starting air passage of the carburetor main body are connected and disconnected by rotation of a starting shaft. 3. The starting air passage of the starting shaft has a single passage extending from the axial center of the starting shaft to the outer peripheral surface, and the starting air passage of the carburetor main body is selective to the starting air passage of the starting shaft. The starting fuel supply device for a carburetor according to claim 2, comprising a plurality of passages having different inner diameters and communicating with each other. 4. A starting air passage of the start axis have different passage inner diameters extending shaft center outer peripheral surface of the starting shaft, started
The starter fuel supply device for a carburetor according to claim 2, wherein one of the starter air passages of the starter shaft communicates with the starter air passage of the carburetor main body when the holding plate of the drive shaft is locked by the lock plate.