JP2000027706A - Acceleration device for membrane type carburetor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain smooth accelerating operation of an engine by gradually increasing pressure in a constant pressure fuel chamber and increasing a fuel amount at the time of abrupt acceleration of the engine. SOLUTION: The inner space of a membrane type carburetor is divided into a constant pressure fuel chamber 25 and an atmospheric pressure chamber 30 by means of a membrane 29. the membrane 29 is energized to the side of the atmospheric pressure chamber by the force of a spring 24. Fuel in the constant pressure fuel chamber 25 is sucked into an intake passage 16 through a fuel nozzle 56. In such a membrane type carburetor, the atmospheric pressure chamber 30 is opened to atmosphere through a throttle 39, and connected with a pump chamber 73 of an acceleration pump 70. A negative pressure operation chamber 77 of an acceleration pump 70 is connected to a downstream side portion 15c of a throttle valve 47 on the intake passage 16 through a pressure regulator 42.

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 of an engine mounted on a portable working machine such as a power saw, a brush cutter, etc., and in particular, when the engine is rapidly accelerated, the fuel amount becomes too small (the mixture is lean). To)
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an accelerator for a film-type carburetor, which prevents normal operation from being interrupted by stopping an engine.

[0002]

2. Description of the Related Art Small-sized, light-weight, high-output, and film-type vaporizers that can be operated in all postures are used in engines of portable working machines such as power saws and brush cutters. The engine of the portable work machine is normally operated at full load due to the nature of the work, and when the work is interrupted, the throttle valve lever (acceleration lever) is returned to switch to idle operation.

However, when the throttle valve lever is suddenly operated from the idling position to the fully open direction when the operation is resumed, the fuel amount becomes too small, that is, the air-fuel mixture becomes too thin, and the engine may stop. This is because if the throttle valve lever is suddenly operated in the fully open direction, the intake negative pressure acting from the intake passage to the constant pressure fuel chamber suddenly weakens, and the membrane that partitions the constant pressure fuel chamber is pushed down by the force of the spring, and the constant pressure fuel is released. This is because the pressure in the chamber suddenly decreases, and the amount of fuel flowing from the constant pressure fuel chamber through the fuel nozzle to the intake passage decreases.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to increase the amount of fuel by gradually increasing the pressure in the constant-pressure fuel chamber during a rapid acceleration operation of the engine, thereby enabling a smooth operation of the engine. An object of the present invention is to provide an accelerator for a film-type carburetor capable of obtaining an accelerated operation.

[0005]

In order to solve the above problems, according to the present invention, a constant pressure fuel chamber and an atmosphere chamber are defined by a membrane, and the membrane is urged toward the atmosphere chamber by a spring force. In a film-type carburetor in which fuel in the constant-pressure fuel chamber is sucked into an intake passage through a fuel nozzle, the atmospheric chamber is opened to the atmosphere through a throttle and connected to a pump chamber of an acceleration pump. The working chamber is connected to a portion of the intake passage downstream of the throttle valve via a pressure regulator.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a throttle for opening the atmosphere chamber to the atmosphere is connected to an atmosphere chamber partitioned by a membrane on a side opposite to the constant pressure fuel chamber. The atmosphere chamber is connected to the pump chamber of the membrane acceleration pump, either directly or via a check valve that allows air flow from the acceleration pump to the atmosphere chamber. The negative pressure working chamber of the acceleration pump is connected via a pressure regulator to a portion of the intake passage downstream of the throttle valve.

When the throttle valve lever is suddenly operated in the fully open direction during the acceleration operation of the engine, the negative pressure of the intake air acting from the intake passage to the constant-pressure fuel chamber suddenly weakens, and the membrane that separates the constant-pressure fuel chamber exerts a spring force. Is about to be pushed down. At the same time, the intake negative pressure acting from the intake passage to the negative pressure working chamber becomes weaker. Since a pressure regulator is connected to the passage connecting the intake path and the negative pressure working chamber, the negative pressure in the negative pressure working chamber gradually weakens, the membrane of the acceleration pump is pushed back by the force of the spring, and the air in the pump chamber is released. Is sent to the atmosphere chamber. The volume of the atmosphere chamber expands slowly,
The membrane is pushed up, and the amount of fuel supplied from the constant pressure fuel chamber to the intake path via the fuel nozzle increases. Therefore, even if the throttle valve lever is suddenly operated in the fully open direction, the amount of fuel sucked into the intake passage suddenly decreases (the mixture becomes thin) and the engine does not stop. .

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a main body 15 of a film-type carburetor is connected to an intake port (not shown) of an engine via a heat insulating pipe 63 and a gasket 62. The illustrated carburetor is of a known rotary throttle valve type. A valve chamber or a cylindrical portion 57 orthogonal to the intake passage 16 is formed in the main body 15, and a throttle valve 47 having a throttle hole 47 b in the cylindrical portion 57 is provided. It is rotatably and vertically inserted. A valve shaft 47a protruding upward from the throttle valve 47 through the cover plate 53 closing the cylindrical portion 57.
Is connected to the throttle valve lever 51. A cam mechanism is constituted by the lower cam surface 51a of the throttle valve lever 51 and the follower 52 of the cover plate 53. Throttle valve 4 by throttle valve lever 51
7 rotates in the acceleration direction against the force of the return spring 54,
The opening degree at which the throttle hole 47b communicates with the intake passage 16 increases, and at the same time, the needle valve 55 that projects from the shaft portion 47a of the throttle valve 47 into the throttle hole 47b and is inserted into the fuel nozzle 56,
Ascending from the injection hole 56a of the fuel nozzle 56, the opening degree of the injection hole 56a increases. The stationary fuel nozzle 56 is fitted and supported in a hole 58 at the bottom of the main body 15, and has a jet 59, a check valve 66.
Through the constant pressure fuel chamber 25 of the fuel metering mechanism A.

A fuel pump 11 and a fuel metering mechanism A are formed below the carburetor body 15. That is, the fuel pump 1
Reference numeral 1 denotes a pulsating pressure chamber 8 in which an intermediate wall 49 is connected to the lower end surface of the main body 15 with the membrane 10 interposed therebetween, and a spring 8a is accommodated above the membrane 10.
And a pump chamber 9 is defined below the membrane 10.
In a four-stroke engine, the fuel pump 11 is connected to the intake passage 6 of the heat insulating pipe 63.
The pulsating intake negative pressure of 3a is introduced into the pulsating pressure chamber 8 through the inlet 61a and the passage 61, and the pulsating pressure of the crank chamber is introduced into the pulsating pressure chamber 8 in the two-stroke engine, whereby the fuel in the fuel tank 37 is released. The liquid is sucked into the pump chamber 9 through the passage 38, the inlet 13, the check valve 12, and the passage 12a, and is discharged into the passage 7a through the passage 12a and the check valve 7.

The fuel metering mechanism A has a cover 30a connected to a lower end surface of an intermediate wall 49 with a membrane 29 interposed therebetween, and a constant pressure fuel chamber 25.
And the atmosphere chamber 30. A lever 28 is rotatably supported by a shaft 27 inside the constant pressure fuel chamber 25. Lever 2
8 is engaged with the inflow valve 2, and the inflow valve 2 is
Is applied to the valve seat at the end of the passage 7a. The other end of the lever 28 can be brought into contact with the membrane 29, and the force of the atmospheric pressure and the negative suction pressure acting on the membrane 29 is applied to the spring 24.
When the force exceeds the pressure, the lever 28 rotates clockwise, the inflow valve 2 opens, and fuel flows from the passage 7a into the constant-pressure fuel chamber 2.
5, the constant pressure fuel chamber 25 holds a predetermined amount of fuel at a predetermined pressure. The fuel in the constant pressure fuel chamber 25 is supplied to the intake passage 16 through the check valve 66, the jet 59, the injection hole 56a of the fuel nozzle 56, and the throttle hole 47b. In the illustrated embodiment, in order to prevent stagnation of fuel, the inner diameter is smaller than that of the heat insulating pipe 63 having the intake passage 63a connected between the intake port of the engine and the carburetor body 15, and the heat conductivity of aluminum or the like is large. The ring member 26 made of metal is
Is located at the exit.

The above-mentioned film-type vaporizer is disclosed in, for example,
No. 20551, the fuel sent to the constant-pressure fuel chamber 25 by the fuel pump 11 in any attitude of the engine (for example, in the state of being rolled over) is injected into the injection hole 56a of the fuel nozzle 56 by the suction negative pressure of the engine. Is sucked into the intake passage 16 from the suction port.

According to the present invention, the throttle 39 for opening the atmosphere chamber 30 to the atmosphere is connected to the atmosphere chamber 30 defined on the opposite side of the constant pressure fuel chamber 25 by the membrane 29. Atmospheric chamber 3
0 is a pump chamber 7 of a membrane type acceleration pump 70 through a passage 40.
3 is connected. The negative pressure working chamber 77 of the acceleration pump 70 passes through the passage 41 and the pressure regulator 42,
7 is connected to the downstream portion 15c. Acceleration pump 7
Reference numeral 0 denotes a film 7 between a pair of upper and lower cup-shaped cases 76 and 78.
The pump chamber 7 is connected to the upper side of the membrane 71 through the periphery of the pump chamber 7.
3 and a negative pressure working chamber 77 below the membrane 71. A spring 72 is interposed between a case plate 78 and a seat plate 74 connected to the center of the membrane 71.

Next, the operation of the accelerator for a film type vaporizer according to the present invention will be described. During normal operation of the engine, the intake air sucked into the intake passage 16 sucks fuel from the injection hole 56a of the fuel nozzle 56 when passing through the throttle hole 47b of the throttle valve 47, and the throttle hole 47b, the intake passage 16, It is supplied to the engine via the heat insulating pipe 63. At this time, the negative pressure of the intake
3. Acting on the negative pressure working chamber 77 via the pressure regulator 42 and the passage 41, the membrane 71 is sucked against the force of the spring 72, and the air in the atmosphere chamber 30 is sucked into the pump chamber 73.

When the throttle valve lever 51 is suddenly operated in the fully opening direction of the throttle valve during the acceleration operation of the engine, the intake negative pressure acting on the constant pressure fuel chamber 25 from the intake passage 16 suddenly weakens, and the intake passage 16 is sucked. As the amount of fuel to be supplied suddenly decreases, the membrane 29 defining the constant-pressure fuel chamber 25 tends to be pushed down by the force of the spring 24. However, since the atmosphere chamber 30 is open to the atmosphere via the throttle 39, a sudden reduction in the volume of the atmosphere chamber 30 can be suppressed. At the same time, the negative pressure of the intake air acting on the negative pressure working chamber 77 of the acceleration pump 70 from the intake passage 16 is alleviated by the pressure regulator 42 and becomes weaker and weaker. 73
Is sent to the atmosphere chamber 30 through the passage 40. Membrane 29
, And the amount of fuel sent from the constant-pressure fuel chamber 25 to the intake passage 16 through the fuel nozzle 56 gradually increases, and a smooth acceleration operation of the engine is achieved. Therefore, even if the throttle valve lever 51 is suddenly operated in the direction in which the throttle valve is fully opened, the amount of fuel sucked from the constant-pressure fuel chamber 25 into the intake passage 16 suddenly decreases (the air-fuel mixture becomes thin). Conversely, the amount of fuel sucked from the constant-pressure fuel chamber 25 into the intake passage 16 by the action of the acceleration pump 70 suddenly increases (the mixture becomes thicker),
The institution will not go wrong.

In the embodiment shown in FIG. 2, a throttle 39 for opening the atmosphere chamber 30 to the atmosphere is connected to the atmosphere chamber 30, and a pump chamber 73 of an acceleration pump 70 is connected to the atmosphere chamber 30 through a passage 40.
Is connected. The acceleration pump 70 is coupled between a pair of upper and lower cup-shaped cases 76 and 78 with a peripheral portion of the membrane 71 interposed therebetween, and a pump chamber 73 is provided above the membrane 71 and a negative pressure operation chamber 77 is provided below the membrane 71. Are each partitioned. A spring 72 is interposed between a case plate 78 and a seat plate 74 connected to the center of the membrane 71. The negative pressure working chamber 77 of the acceleration pump 70 is connected to a portion 15 c of the intake passage 16 downstream of the throttle valve 47 via the passage 41 and the pressure regulator 42. A check valve 46 that allows air to flow from the intake passage 16 to the negative pressure working chamber 77 is connected to a part of the passage 45 that connects the inlet and the outlet of the pressure regulator 42.

During the operation of accelerating the engine, the intake negative pressure acting on the constant pressure fuel chamber 25 from the intake passage 16 suddenly decreases, but at the same time, the negative pressure of the acceleration pump 70 from the intake passage 16 via the check valve 46. The intake negative pressure acting on the working chamber 77 is weakened, the membrane 71 is pushed up by the force of the spring 72, and the air in the pump chamber 73 is sent to the atmosphere chamber 30 via the passage 40.
The sudden pressure increase in the negative pressure working chamber 77 is mitigated by the pressure regulator 42. The membrane 29 is pushed up in accordance with the amount of air sent from the acceleration pump 70 to the atmosphere chamber 29, and the constant pressure fuel chamber 25
, The amount of fuel sent to the intake passage 16 via the fuel nozzle 56 gradually increases, and a smooth acceleration operation of the engine is achieved.
Therefore, even if the throttle valve lever 51 is suddenly operated in the direction in which the throttle valve 47 is fully opened, the amount of fuel sucked from the constant-pressure fuel chamber 25 into the intake passage 16 suddenly decreases, and conversely, the acceleration pump 7
By the action of 0, the amount of fuel sucked from the constant-pressure fuel chamber 25 into the intake passage 16 suddenly increases, and the engine does not malfunction.

In the embodiment shown in FIG. 3, a throttle 39 for opening the atmosphere chamber 30 to the atmosphere is connected to the atmosphere chamber 30, and the acceleration chamber 70 is connected to the atmosphere chamber 30 via a passage 40, a pressure regulator 42a, and a passage 43a. The pump chamber 73 is connected, and the pressure regulator 4
A check valve 46a that allows the flow of air from the pump chamber 73 to the atmosphere chamber 30 in the middle of the passage 45 connecting the inlet and the outlet of 2a.
Are connected. Other configurations are the same as those of the embodiment of FIG.

During the acceleration operation of the engine, the intake negative pressure acting on the negative pressure working chamber 77 of the acceleration pump 70 from the intake passage 16 via the pressure regulator 42a is weakened.
Is pushed up, and the air in the pump chamber 73 is sent to the atmosphere chamber 30 via the passage 43a, the check valve 46a, and the passage 45. Sudden pressure rise and pressure fluctuation in the negative pressure working chamber 77 are controlled by the pressure regulator 4.
2a. Pump chamber 73 of acceleration pump 70
The membrane 29 is pushed up according to the amount of air sent to the atmosphere chamber 30 via the check valve 46a from the valve, and the amount of fuel sent from the constant-pressure fuel chamber 25 to the intake passage 16 via the fuel nozzle 56 gradually increases, so that the engine smoothly runs. High acceleration operation is achieved.

In the embodiment shown in FIG. 4, a throttle 39 for opening the atmosphere chamber 30 to the atmosphere is connected to the atmosphere chamber 30.
0, a check valve 46a that allows air to flow from the pump chamber 73 of the acceleration pump 70 to the atmosphere chamber 30, a passage 43a.
The pump chamber 73 is connected to the pump chamber 73 through a valve, and a throttle 69 is provided at an end of the passage 43a to open the pump chamber 73 to the atmosphere. The passage 41, the pressure regulator 42,
It is connected to a portion 15c of the intake passage 16 downstream of the throttle valve 47 via the passage 43.

During the acceleration operation of the engine, the intake negative pressure acting on the negative pressure working chamber 77 of the acceleration pump 70 from the intake passage 16 via the pressure regulator 42 becomes weak, and the membrane 71 is pushed up by the force of the spring 72, and the pump 71 The air in the chamber 73 is sent to the atmosphere chamber 30 through the passage 43a, the check valve 46a, and the passage 40. Sudden pressure rise and pressure fluctuation in the atmosphere chamber 30 are mitigated by the throttle 69. Accordingly, the pump chamber 73 of the acceleration pump 70
The membrane 29 is pushed up in accordance with the amount of air sent to the atmosphere chamber 30 through the check valve 46a from above, and the amount of fuel sent from the constant-pressure fuel chamber 25 to the intake passage 16 gradually increases, so that a smooth acceleration operation of the engine is achieved. Can be

In the above embodiment, the pressure regulator 42 may be an ordinary container, but it is more effective to use a container having shrinkage and resilience. In addition, the present invention is not limited to a rotary throttle valve type film vaporizer, but is applicable to a butterfly valve type film vaporizer, a piston valve type film vaporizer, a float type vaporizer, and the like. The effect is obtained.

[0022]

As described above, according to the present invention, the constant pressure fuel chamber and the atmosphere chamber are partitioned by the membrane, and the membrane is urged toward the atmosphere chamber by the force of the spring, and the fuel in the constant pressure fuel chamber is supplied to the fuel nozzle. In the film-type vaporizer that is sucked into the intake passage through the air passage, the atmosphere chamber is opened to the atmosphere through a throttle and connected to the pump chamber of the acceleration pump, and the negative pressure working chamber of the acceleration pump is suctioned through the pressure regulator. Since it is connected to the downstream side of the throttle valve of the passage, even if the intake negative pressure acting from the intake passage to the constant-pressure fuel chamber suddenly decreases during acceleration operation of the engine, the reduction of the volume of the atmosphere chamber is suppressed by the throttle. Then, the intake negative pressure acting on the negative pressure working chamber of the acceleration pump from the intake path is weakened, the membrane is pushed by the force of the spring, and the air in the pump chamber is sent to the atmosphere chamber. The membrane is pushed up in accordance with the amount of air sent from the acceleration pump to the atmosphere chamber, the amount of fuel sent from the constant pressure fuel chamber to the intake passage increases, and a smooth acceleration operation of the engine is achieved.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a film-type vaporizer according to a first embodiment of the present invention.

FIG. 2 is a side sectional view showing a main part of a film type vaporizer according to a second embodiment of the present invention.

FIG. 3 is a side sectional view showing a main part of a film type vaporizer according to a third embodiment of the present invention.

FIG. 4 is a side sectional view showing a main part of a film type vaporizer according to a fourth embodiment of the present invention.

[Explanation of symbols]

A: Fuel metering mechanism 2: Inflow valve 8: Pulsating pressure chamber 9: Pump chamber 10: Membrane 11: Fuel pump 15: Vaporizer body 15c: Downstream portion 16: Intake path 25: Constant pressure fuel chamber 28: Lever 29: Membrane 30: Atmosphere chamber 30
a: Cover 37: Fuel tank 39: Restrictor 40, 41:
Passages 42, 42a: pressure regulators 43, 43a, 4
5: passage 46, 46a: check valve 47: throttle valve 4
9: Intermediate wall 51: Throttle valve lever 51a: Cam surface
52: follower 53: lid plate 55: needle valve 5
6: Fuel nozzle 57: Cylindrical part 59: Jet 6
3: Insulated pipe 66: Check valve 69: Restrictor 70: Acceleration pump 71: Membrane 72: Spring 73: Pump chamber 76,
78: Case 77: Negative pressure working chamber

Claims (4)

[Claims] 1. A constant pressure fuel chamber and an atmosphere chamber are defined by a membrane.
The membrane is urged toward the atmosphere chamber by the force of a spring, and the fuel in the constant-pressure fuel chamber is sucked into a suction passage through a fuel nozzle, and the atmosphere chamber is opened to the atmosphere through a throttle. A vacuum chamber of the acceleration pump connected to a pump chamber of the acceleration pump, and a negative pressure working chamber of the acceleration pump is connected to a portion of the intake passage downstream of the throttle valve via a pressure regulator. 2. A check valve according to claim 1, further comprising a check valve for allowing air to flow from an intake passage to a negative pressure working chamber of the acceleration pump in a passage connecting the inlet and the outlet of the pressure regulator. An accelerator for a film-type vaporizer according to the above. 3. A second pressure regulator is connected between the atmosphere chamber and a pump chamber of the acceleration pump, and the acceleration pump is provided in a passage connecting an inlet and an outlet of the second pressure regulator. The acceleration device for a film-type vaporizer according to any one of claims 1 and 2, further comprising a check valve connected to allow a flow of air from the air to the atmosphere chamber. 4. The pump chamber of the acceleration pump is connected to the atmosphere chamber through a check valve that allows air to flow from the acceleration pump to the atmosphere chamber, and the pump chamber of the acceleration pump is opened to the atmosphere through a throttle. An acceleration device for a film-type vaporizer according to claim 1.