JP3496068B2 - 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 in an internal combustion engine (hereinafter referred to simply as "engine") of a portable working machine such as a power saw or 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 carburetor of the Chiyoke valve type, it is structurally difficult to consider warm-up operation after starting the engine. The concentration of the air-fuel mixture during warm-up operation differs depending on operating conditions such as the outside air temperature, the operating location (especially in highlands), and the engine condition. In the case of a carburetor of the Chioke valve type, the Chioke valve must be manually operated in response to the warming-up operating conditions to continuously supply an air-fuel mixture having an appropriate concentration. The engine will stop if the chiyoke valve is operated delicately and the fuel is sucked too much to make the mixture too rich, or conversely, if the amount of fuel is too little and the mixture becomes too thin.

That is, the engine stops when the opening of the chain yoke valve is too large or too small. Therefore, it requires a great deal of skill to keep the opening of the chain yoke valve at an appropriate value. In particular, when starting in a cold region like a power saw or when starting in a state where fuel is not sufficiently contained in the constant pressure fuel chamber, it is difficult to continue the warm-up operation after starting the engine.

JP-B-47-26744 and JP-A-60-204951
In the starting fuel supply device for a membrane carburetor equipped with a by-starter disclosed in Japanese Patent Publication, the operation of the by-starter and the starting operation of the engine have to be performed independently and simultaneously, which makes the operation troublesome, and the starting fuel The feeder becomes large,
It is difficult to adopt it for equipment with limited space such as portable work machines.

[0005]

SUMMARY OF THE INVENTION In view of the above problems, the object of the present invention is to provide a safe engine start-up and a subsequent warm-up operation even for those who are not familiar with the start-up operation by the chioke valve. It is to provide a starting fuel supply device for a carburetor that can be reliably performed.

Another object of the present invention is to provide a starting fuel supply device for a carburetor, which can be arranged in a narrow mounting space such as a portable working machine and can be easily started.

[0007]

In order to achieve the above object, the structure of the present invention supplies a starting air-fuel mixture to a portion of the intake passage downstream of the throttle valve by a plunger provided in the middle of the starting fuel passage. In a carburetor by-starter starting fuel supply system, a starter shaft is rotatably supported parallel to the throttle valve shaft at an upstream portion of the carburetor body, and a notch cover formed on the starter shaft.
The plunger that is reciprocated by the
The starter plate with a cam on the outer end of the starting shaft.
Supports the holding plate, and the holding plate is rotated by the starting plate during the starting operation.
Starting position to engage the lock plate connected to the throttle valve shaft
When the starter plate is reversely operated, the starter plate holding plate
Rotation of the holding plate is caused by the cam of the starting plate.
It is characterized by being released .

[0008]

To operate the by-starter, when the start button is pulled by a predetermined amount, it is pushed by the starting plate of the starting shaft and the holding plate rotates, rotating the locking plate of the throttle valve shaft while rotating the locking plate. Pass through. Simultaneously with the release of the start button, the holding plate stops against the edge of the locking plate by the force of the spring.
At this time, the starting fuel passage and the air passage are opened, and the starting mixture is supplied to the intake passage through the mixture passage.

In order to stop the operation of the by-starter, when the start button is pushed back, the holding plate is pushed in the axial direction by the cam of the starting plate, the engagement with the locking plate is released, and the holding plate and the starting plate are spring-loaded. Is returned to the stop position by the force of.

[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 comprises a carburetor main body 15 having an intake passage 31 and a pair of left and right air purifiers. It is attached to the intake port of the engine by a bolt penetrating the bolt hole 15a. The cover 9 is joined to the upper end wall of the main 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. This constitutes the fuel pump D. 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 connects the bottom cover 52 to the lower end wall of the main body 15 with the gasket 49 and the membrane 54 interposed therebetween, the constant pressure fuel chamber 47 above the membrane 54 and the atmosphere chamber 51 below the membrane 54. Each is divided. The lever 50 is supported by the support shaft 57 on the wall of the constant pressure fuel chamber 47,
One end of 0 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. Conversely, when the constant pressure fuel chamber 47 is filled with 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.

Fuel in the constant pressure fuel chamber 47 is sucked from the high speed fuel injection hole 17 into the intake passage 31 penetrating the main body 15 through the passage 48, the high speed fuel adjusting needle valve 53 and the check valve 55, and as shown in FIG. Similarly, a plurality of low-speed fuel injection holes 17a
Is sucked into the intake passage 31. 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). By repeatedly pressing the spoid 44a, the constant pressure fuel chamber 47
Air and fuel vapor push the pipe 42 and the umbrella portion of the composite check valve 43 open, and are sucked into the inside of the spoid 44a, and further open the axial center portion of the composite check valve 43, and open the fuel tank 4 through the pipe 45.
It is discharged to 6. 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.

During the acceleration of the engine, in order to increase the fuel quantity,
A piston type acceleration pump B is arranged inside the main body 15. That is, the acceleration pump B is configured by fitting the piston 2 into the cylinder 3 that traverses the shaft hole of the throttle valve shaft 14. By the spring 4 interposed between the inner end of the cylinder 3 and the piston 2,
The piston 2 is brought into contact with the cutout cam 14 a of the throttle valve shaft 14. During low speed operation of the engine, the fuel in the constant pressure fuel chamber 47 is in the passage 4
8, the high-speed fuel adjustment needle valve 53, the annular groove 56 of the fitting portion of the check valve 55, and the suction fuel passage 5 are sucked into the cylinder 3 by the notch cam 14a of the throttle valve shaft 14 during engine acceleration. When the piston 2 is pushed, the fuel in the cylinder 3 causes the fuel in the acceleration fuel passage 5, the annular groove 56, the check valve 55, the high-speed fuel injection hole 1
It is supplied to the intake passage 31 via 7.

The by-starter A includes a check valve 24 disposed inside the main body 15 and a plunger 6 fitted in the cylinder 22.
And a starting shaft 21 having a notch cam 21a for driving the plunger 6. 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 and the check valve 24 and then enters the mixing chamber 49a composed of the holes provided in the gasket 49, and at the same time. As shown in FIG. 2, the air in the intake passage 31 enters the mixing chamber 49a through the air passage 18, the internal passage 20 of the starting shaft 21, and the air passage 20a (FIG. 3) of the main body 15, and both are mixed while being mixed. The mixture enters from the chamber 49a into the cylinder 22 through the mixture passage 75, the mixture passage 33 inside the main body 15, the chamber 49b formed of a hole provided in the gasket 49, and the mixture passage 33a.
And is supplied to a portion of the intake passage 31 on the downstream side of the throttle valve 32. As shown in FIG. 2, one end of the internal passage 20 opens to the end surface of the starting shaft 21. The other end of the internal passage 20 opens on the peripheral surface of the starting shaft 21 and is opened and closed by the rotation of the starting shaft 21. A jet 27 (FIG. 3) is provided integrally with the check valve 24 to regulate the starting fuel amount.

As shown in FIG. 2, the throttle valve shaft 14 is connected to the valve lever 12 at the left end, and the valve lever 12 and the main body 15 are connected together.
By means of the spring 13 that is locked between and, the throttle valve 32 is rotationally biased so as to return to the closed position. 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 throttle valve shaft 14 has a notch cam 14 a formed inside the main body 15.

The by-starter A is provided with a starting shaft 21 supported inside the main body 15 in parallel with the throttle valve shaft 14, and a plunger 6 driven by the rotation of the starting shaft 21. A cylinder 22 orthogonal to the starting shaft 21 is formed inside the main body 15, and the plunger 6 fitted in the cylinder 22 has a spring 72.
The force of (FIG. 3) engages the notch cam 21a of the starting shaft 21. As shown in FIG. 6, the annular groove 21 of the starting shaft 21.
The starting shaft 21 is prevented from moving in the axial direction by engaging with b a pin integral with the plug 69 fitted to the outer end of the cylinder 22.

As shown in FIG. 3, the spring 72 is interposed between the plunger 6 and the annular spring seat 71a, and the spring seat 71a.
Holds an O-ring 71 at the inner end of the cylinder 22. Plunger 6 is integrally provided with a valve body 6a to the end, the valve member 6a at the backward position of the plunger 6 is engaged with the O-ring 71, it is closed between the mixture passage 75 and the air-fuel mixture passage 33.
As shown in FIG. 2, the operating mechanism of the by-starter A includes a starting plate 66 rotatably supported on the starting shaft 21 and a starting shaft 21.
A holding plate 64 supported axially movable and non-rotatably
And a lock plate 62 connected to the throttle valve shaft 14. The spring 77 wound around the starting shaft 21 is interposed between the spring seat 68 and the holding plate 64, one end 77a is locked to the pin 78 (FIG. 4) of the main body 15, and the other end 77b is held on the holding plate 64. The starter plate 66 is locked to the projecting piece 64c, and the starter plate 66 shown in FIG.
Energize to 8

As shown in FIG. 4, the starting plate 66 has a rod-shaped starting button 59 connected to the hole a or the hole b, and a notched edge portion 66c that abuts against the pin 78 and an end portion 64b of the holding plate 64. The protruding piece 66b contacting with the end 64 of the holding plate 64
and a cam 66a that abuts the plate surface of a. When the notched edge portion 66c of the starting plate 66 hits the pin 78,
Clockwise rotation about the starting shaft 21 is blocked. As shown in FIG. 2, the cam 66a of the starting plate 66 does not come into contact with the end edge of the locking plate 62 at the idle position of the throttle valve shaft 14, and the cam 66a is curved toward the holding plate 64. Form a surface.

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 contacts the end 64b of the holding plate 64, and the starting shaft 21 is rotated counterclockwise against the force of the spring 77. The end 64a of the holding plate 64 hits the locking plate 62 of the throttle valve shaft 14, and the locking plate 62 is rotated clockwise (the opening direction of the throttle valve 32) in FIG. When disengaged from the lock plate 62, the lock plate 62 is returned to the idle position by the force of the spring 13.

When the start button 59 is released, the end 66a of the start plate 66 is rotated clockwise by the force of the spring 77.
Therefore, the end 64a of the holding plate 64 is also rotated clockwise.
Then, the end portion 64a engages with the end edge of the locking plate 62, whereby the starting shaft 21 is locked at the position shown in FIG. In this way, when the starting shaft 21 is rotated by a predetermined angle, the internal passage 20 of the starting shaft 21 communicates with the air passage 20a, the plunger 6 receives the force of the spring 72, and the notch cam 2 of the starting shaft 21.
1a, 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), the negative pressure of the intake passage 31 causes the fuel in the constant pressure fuel chamber 47 to be sucked into the mixing chamber 49a via the start fuel passage 25 and the check valve 24, so that the intake passage 31 is evacuated. Air is air passage 18, internal passage 2
0, and is sucked into the mixing chamber 49a through the air passage 20a.
The starting fuel and air are mixed in the mixing chamber 49a, the starting mixture is sucked into the cylinder 22 through the mixture passage 75, and further into the intake passage 31 through the mixture passage 33, the chamber 49b, and the mixture passage 33a. It In this way, even when the throttle valve 32 is at the idle position, a rich starting mixture of starting fuel and air is supplied to the portion of the intake passage 31 on the downstream side of the throttle valve 32, so that the engine is smoothly started. .

After the engine is started, the rich mixture for starting is still supplied, but when the warm-up is obtained, the valve lever 1
When the throttle valve shaft 14 is rotated in the accelerating direction (clockwise in FIG. 5) by 2, the locking between the locking plate 62 of the throttle valve shaft 14 and the end 64a of the holding plate 64 of the starting shaft 21 is released and held. The plate 64, the starting shaft 21, and the starting plate 66 are provided with a spring 77.
Is rotated clockwise by the force of, and stops when the notched edge portion 66c of the starting plate 66 hits the pin 78 as shown in FIG. At this time, the internal passage 20 and the air passage 20a are shut off, the plunger 6 is pushed up by the peripheral surface of the starting shaft 21, the valve body 6a engages with the O-ring 71, and the mixture passage 75 and the mixture passage are formed. It cuts off between 33.

After the engine is started, the operation of opening the throttle valve is continued.
When releasing the operating state of the bi-starter without moving it
When the start button 59 is pushed back, only the start plate 66 rotates clockwise about the start shaft 21 in FIG.
By the cam 66a of the starting plate 66, the end 64a of the holding plate 64
6 is pushed to the right as shown in FIG. 6, the locking between the holding plate 64 and the locking plate 62 is released, and the holding plate 64 is spring 77.
Is rotated in the clockwise direction by the force of, and the notched edge portion 66c of the starting plate 66 contacts the pin 78.

In the above embodiment, the cam 66a is used.
May be provided on the holding plate 64 instead of being provided on the starting plate 66.

[0026]

As described above, according to the present invention, by the starter fuel supply for the carburetor, the starter air-fuel mixture is supplied to the portion of the intake passage on the downstream side of the throttle valve by the plunger provided in the start-up fuel passage. In the device, a starter shaft is rotatably supported at the end of the carburetor main body in parallel with the throttle valve shaft, and the plunger is disposed inside the carburetor main body orthogonal to the starter shaft.
Since the plunger is reciprocated by the cam formed on the starting shaft, the following effects can be obtained.

The lock of the holding plate is made by a lock plate connected to the throttle valve shaft, and the lock release of the holding plate is made by the axial movement of the holding plate by the cam of the starting plate, and the axial movement amount of the holding plate is made by the locking plate. Since it is a slight amount corresponding to the plate thickness, there is no difficulty in operation.

The starting plate and the holding plate are arranged in the carburetor body, the return spring is provided at the outer end of the starting shaft, the jet of the starting fuel passage and the check valve are integrally formed, and the mixing chamber is constituted by the bottom cover. Since the closed gasket is formed as a hole, it is easy to process.

Since the holding plate and the starting plate are provided on the starting shaft , the overall size can be reduced. Since the holding plate is locked by coming into contact with the locking plate, it is sufficient to open the throttle valve a little when releasing the locking, and at this time the engine does not reach the high speed rotation range, which is safe.

In the present invention based on the by-starter method
Restricts the warm-up and warm-up cancellation mechanism of the engine after the engine is started.
Since it is installed on the shaft and the starting shaft, opening and starting the throttle valve after warm-up
The warm-up of the engine can be released by operating the operation buttons.
It can be easily performed by any operation of the engine operator.
It can be done.

[0031]

[0032]

[0033]

When the operation of the by-starter is stopped, the starting fuel passage is closed by the return movement of the plunger accompanying the rotation of the starting shaft, so that fuel and air are transferred from the by-starter to the intake passage during full load operation of the engine. It never leaks.

Since the starting shaft can be arranged at substantially the same position as the conventional chain yoke valve shaft so as to operate at the same operating angle, it can be mounted on a working machine having the same specifications as the chain yoke system without making structural changes.

[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 main part of the vaporizer before a starting operation.

FIG. 5 is a side view showing a main part at the time of starting operation of the vaporizer.

FIG. 6 is a cross-sectional plan view showing a main part of the vaporizer at the end of the starting operation.

[Explanation of symbols]

A: By-starter 6: Plunger 14: Throttle valve shaft
15: carburetor main body 18, 20a: air passage 21: starting shaft 24: check valve 25: starting fuel passage 27: jet 31: intake passage 32: throttle valve 33, 33a,
75: Mixture passage 47: Constant pressure fuel chamber 49: Gasket 49a: Mixing chamber 52: Bottom cover 59: Start button 62: Lock plate 64: Holding plate 6
6: Starter plate 66a: Cam 77: Spring 78: Pin

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-15749 (JP, A) JP-A-60-20495 (JP, A) Actually open 3-19457 (JP, U) Actually open-62- 74159 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F02M 1/06 F02M 17/04 F02M 19/00

Claims (5)

(57) [Claims] 1. A starter-type starter fuel supply device for a carburetor, which supplies a starter air-fuel mixture to a portion of a intake passage downstream of a throttle valve by a plunger provided in the starter fuel passage, upstream of a carburetor main body. The starter shaft is rotatably supported in parallel with the throttle valve shaft, and a notch cam formed on the starter shaft
The plunger, which is reciprocated, is placed inside the carburetor body.
And a starting plate having a cam on the outer end of the starting shaft and a holding plate.
And the holding plate is rotated by the starting plate during the starting operation.
The locking position is set to the starting position where it engages with the locking plate connected to the throttle valve shaft.
When the starter plate is operated in reverse, the starter plate is
The rotation of the holding plate is released by the cam of the starting plate.
A starting fuel supply device for a carburetor, characterized in that it is removed . 2. A starter plate for connecting a starter button to said starter shaft is supported, and when the starter plate rotates the starter shaft to the forward position of the plunger, the holding plate is locked to the lock plate of the throttle valve shaft.
Are, when rotated in the opening direction of the throttle valve shaft throttle valve, locking of the holding plate is released, the carburetor of the starting fuel supply system according to claim 1. 3. A starting plate is rotatably supported on the starting shaft, and a holding plate is rotatably and axially movable.
When the starting plate rotates the starting shaft to the forward movement position, the holding plate is rotated by the starting plate to be locked by the locking plate of the throttle valve shaft, and when the starting plate rotates the starting shaft to the backward movement position, the holding plate moves. The starting fuel supply device for a carburetor according to any one of claims 1 and 2, wherein the starting fuel supply device slides in the axial direction and is disengaged from the rotational trajectory of the locking plate of the throttle valve shaft. 4. The cam is formed on a plate surface of a starting plate, and
When rotating the starting shaft to the return position by the starting plate, hold the holding plate.
The starting fuel supply device for a carburetor according to claim 1, wherein the starting fuel supply device is slid in the axial direction . 5. A check valve is provided in the starting fuel passage to prevent air in the starting fuel passage from flowing back to the constant pressure fuel chamber during operation of the suction pump, and the amount of starting fuel is regulated adjacent to the check valve. The starting fuel supply device for a carburetor according to claim 1, further comprising a jet.