JPH0220457Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an engine with a diaphragm type carburetor used in a portable working machine.

[Prior Art] Engines whose working posture changes, such as chainsaws and brush cutters, are equipped with a diaphragm type carburetor. This type of diaphragm type carburetor includes a diaphragm to define a metering chamber that communicates with a fuel nozzle that opens into the intake passage, a fuel pump that is driven by the pulsating pressure of the engine, and a fuel pump that pumps the fuel from the fuel tank. and an inflow valve for introducing fuel into the metering chamber.

During normal operation, when fuel in the metering chamber is drawn into the engine from the fuel nozzle through the intake passage, the inlet valve opens due to negative intake pressure acting on the diaphragm, and the fuel pump intermittently replenishes fuel in the fuel tank. be done. Therefore, while the engine is in operation, a predetermined amount of fuel is retained in the metering chamber regardless of its orientation, and an appropriate amount of fuel is supplied to the engine depending on the operating state of the engine.

However, it is often the case that sufficient fuel is not retained in the metering chamber when starting the engine. For example, when a chain saw finishes cutting down trees, it is common to stop the engine, move to the next work area, and then restart the engine. While the engine is stopped for just a few minutes, the fuel in the fuel nozzle and the metering chamber that communicates with it evaporates due to heat from the engine, ambient heat, and radiant heat from sunlight, and the metering chamber is filled with fuel gas. As a result, even if the engine is still at warm-up temperature, the mixture becomes too lean due to the fuel gas, making it difficult to restart the engine. In addition, even if the engine starts, the fuel nozzle and metering chamber are not filled with fuel, which may cause a temporary fuel shortage, causing the engine to stop immediately or cause poor acceleration after starting, resulting in smooth operation. It becomes impossible to maintain proper driving.

In order to solve such problems, the applicant has filed Utility Model Application No. 11667-1983 (Patent Application No. 128377-1987).
Accordingly, a suction pump is connected between the passage connecting the metering chamber of the carburetor and the fuel tank, and the driving body of the suction pump is arranged in the rope guide section of the recoil device so as to be in frictional contact with the rope. We have proposed an engine with a diaphragm type carburetor that is configured so that the driving body is operated by force against a spring. According to this engine, the suction pump operates in conjunction with the recoil operation, and the fuel gas and air in the metering chamber of the diaphragm carburetor are sucked and discharged into the fuel tank, and as a result, the metering chamber becomes under negative pressure. Fuel in the tank is replenished into the metering chamber via the inlet valve.

By the way, it is desirable to set this type of suction pump to a large capacity so that the metering chamber is filled with fuel with one recoil operation, but if the engine does not start after the first recoil operation, In this case, the suction pump operates in the same way during the second recoil operation and the pressure in the metering chamber decreases. The flow of fuel is obstructed, making it difficult to start the engine.

[Problems to be solved by the invention] Therefore, the purpose of the invention is to operate the suction pump during the first recoil operation and replenish sufficient fuel to the metering chamber, while the suction pump operates during the second recoil operation. An object of the present invention is to provide an engine with a diaphragm type carburetor in which the operation of the metering chamber is restricted and fuel in a metering chamber flows smoothly into an intake passage.

[Means for Solving the Problems] In order to achieve the above object, the configuration of the present invention is such that a suction pump is connected between the passage connecting the metering chamber of the carburetor and the fuel tank, and the suction pump driver is arranged in the rope guide part of the recoil device so as to frictionally engage with the rope, and the driving body is configured to move forward against the spring by the tensile force of the rope. A delay means is provided for delaying the backward movement of the driving body by the spring.

[Function] In the first recoil operation, the forward movement of the suction pump causes the fuel gas and air in the metering chamber to be sucked into the suction pump, and as a result, the pressure in the metering chamber decreases, causing the fuel in the fuel tank to reach the meter. The ring room is replenished. After the first recoil operation is completed, the return motion by the spring of the suction pump becomes slow due to the action of the delay means in the discharge side passage of the suction pump.

During this time, the rich air-fuel mixture in the intake passage is drawn into the engine as the engine rotates, and is exhausted from the engine with incomplete combustion, so that no rich air-fuel mixture remains in the intake passage.

In the subsequent second recoil operation, since the return operation of the suction pump is not completed, the substantial pumping action of the suction pump is limited, and the pressure drop in the metering chamber is suppressed. As a result, the negative pressure in the intake passage acts effectively on the metering chamber, and the fuel in the metering chamber is smoothly drawn into the intake passage.
The engine can be started smoothly.

[Embodiment of the invention] As shown in FIG. 1, an engine 27 has an air cleaner 28 and a diaphragm type carburetor 2 attached to one side of a main body including a cylinder, and an exhaust muffler 29 is attached to the other side. engine 27
A fuel tank 1 is attached to the lower end of the engine, that is, below the crank chamber. Fuel tank 1 and cap 4
Fuel is supplied through the inlet closed by 4. A filter 8 housed inside the fuel tank 1 is connected to an inlet 7 of the carburetor 2 via a fuel pipe 9.

A recoil device 30 is connected to the end of the crankshaft 34 of the engine 27 via a known one-way clutch. The recoil device 30 has a handle 31 connected to the end of a rope 51 wound around a pulley.
Pulling 1 rotates the crankshaft 34 via the one-way clutch.

A suction pump 33 is attached to the pull-out portion of the rope 51 of the recoil device 30, and when the rope 51 is pulled, the driver of the suction pump 33, that is, the rod 35 is pulled against the force of the spring 37, and the suction pump 33 is pulled. It is starting to be moved back and forth. Rod 35
is slidably supported on the middle partition wall of the housing 52 of the suction pump 33, and a roller 43 is axially supported by a bifurcated fork formed at the tip of the rod 35. It is passed over so that it does not occur.

A diaphragm 36 is attached to the lower half of the housing 52.
is supported, thereby dividing the pump chamber 53 and the atmospheric chamber. The proximal end of the rod 35 is connected to the diaphragm 36, and a spring 37 is interposed between the diaphragm 36 and the partition wall. A suction valve 38 that allows air to flow into the pump chamber 53;
3. A discharge valve 39 is provided to allow outflow from 3.
The suction valve 38 is connected to the vaporizer 2 which will be described later through the suction pipe 41.
It is connected to the suction port 40 of. The discharge valve 39 is connected to the inside of the fuel tank 1 via a reflux pipe 42 .

According to the present invention, in order to limit the operation of the suction pump 33, a restrictor 71 as a delay means is inserted and connected to the discharge port side passage of the suction pump 33, specifically, in the middle of the reflux pipe 42.

As shown in FIG.
A cover 4 is coupled to the upper wall of the main body 3 provided with 7 with a diaphragm 6 in between, and a cover 15 is coupled to the lower wall with a diaphragm 11 in between. The cover 4 is provided with a pulsating pressure inlet 5, which is connected to the crank chamber of the two-stroke engine, and the pulsating pressure in the crank chamber is connected to a diaphragm 6 that constitutes a fuel pump 50.
It has come to act on A passage leading to the fuel chamber 61 defined by the diaphragm 6 is connected to the inlet 7 via the check valve 47 . Further, a passage connected to the fuel chamber 61 includes a check valve 48, a passage 60,
It is connected to a metering chamber 16 via an inflow valve 10.

Diaphragm 1 that partitions metering chamber 16
1 is held at its peripheral edge by a cover 15 on the main body 3, and a chamber between the cover 15 and the diaphragm 11 is opened to the atmosphere through an atmosphere port 62. A needle-type inflow valve 10 is disposed at the end of the passage 60 and is connected to the lever 1.
3 to be opened and closed. That is, one end of the lever 13, which is rotatably supported on the wall of the metering chamber 16 by the support shaft 12, is urged into engagement with the end of the inflow valve 10 by the force of the spring 14. The other end of the lever 13 abuts against a protrusion connected to the approximate center of the diaphragm 11. The metering chamber 16 is connected to the high speed fuel injection port 24 via a check valve 26 and a high speed fuel metering needle valve 25. The metering chamber 16 also includes a check valve 23 and a low-speed fuel metering needle valve 2.
2 to the low-speed fuel nozzle 21.

An intake passage 18 having a bench lily 17 in the main body 3
is provided, and a throttle valve 20 is connected to the valve shaft 1 in the intake passage 18.
9. An air cleaner 28 shown in FIG. 1 is connected to the left end of the main body 3, and an engine 27 is connected to the right end of the main body 3.

FIG. 3 shows another example of the delay means. That is,
A pump chamber 5 is provided in the housing 52 of the suction pump 33.
The discharge valve 39 is constructed by pressing a ball 75 against a valve seat formed in the discharge port 74 by a spring 76. As a delay means, a spring seat supporting the spring 76 is constituted by a porous member 72 made of porous ceramics, for example, and is supported by a retaining ring 77. Discharge port 7
A threaded hole 78 is formed at the outer end of 4 to connect the reflux pipe 42.

According to this embodiment, the porous member 72 exerts a fluid resistance when the fuel gas in the pump chamber 53 flows into the fuel tank 1 through the discharge port 74, thereby inhibiting the backward motion of the diaphragm 36 and the rod 35 shown in FIG. delay.

Next, the operation of the engine with a diaphragm type carburetor according to the present invention will be explained. engine 27
While the suction pump 33 is stopped, the rod 35 serving as the driving body of the suction pump 33 is pushed back downward by the force of the spring 37, and the rope 51 is in a relaxed state. engine 2
7, when the rope 51 is pulled upwards by the handle 31, the rod 35 is moved forward via the roller 43 against the force of the spring 37. Therefore, the pump chamber 53 becomes negative pressure, and the suction valve 3
8 is opened, and the air and fuel gas in the metering chamber 16 flow from the suction port 40 through the suction pipe 41 to the pump chamber 5.
It is attracted to 3.

When the air and fuel gas in the metering chamber 16 are discharged from the suction port 40, the metering chamber 16 becomes negative pressure, the diaphragm 11 is pushed up by atmospheric pressure, and the lever 13 is moved counterclockwise around the support shaft 12. Since it is rotated, the inflow valve 10 is opened. Negative pressure in the metering chamber 16 is supplied to the passage 60, the check valve 48, the fuel chamber 61 of the fuel pump 50, and the check valve 4.
7, the fuel in the fuel tank 1 is replenished into the metering chamber 16 by acting on the filter 8 through the inlet 7 and the fuel pipe 9.

When the operating force on the handle 31 is released, the rope 51 is rewound by a return spring provided in the recoil device 30. At this time, the operating force of the rod 35 is released, and the force of the spring 37 causes the rod 35 to be
At the same time, the diaphragm 36 is moved back, and the fuel gas and air in the pump chamber 53 are sent to the fuel tank 1 through the discharge valve 39, the throttle 71 as a delay means, and the reflux pipe 42.
However, due to the throttle 71, the rod 3
The backward motion of No. 5 is slow.

If the engine does not start after the first recoil operation, if you perform the second recoil operation, the rod 35 and diaphragm 36 will not have returned completely, so even if you pull the rope 51, the stroke of the rod 35 will not continue. The suction pump 3
3 pump action is limited, metering chamber 16
pressure is mostly unaffected.

In this way, in the first recoil operation, the fuel gas and air in the metering chamber 16 are discharged to the pump chamber 53 of the suction pump 33, and the metering chamber 16 is filled with fuel from the fuel tank 1. Because the fuel gas and air are not immediately discharged to the fuel tank 1 due to the action of the throttle 71,
In the second recoil operation, the suction pump 33 hardly operates, and the pressure drop in the metering chamber 16 is suppressed. Therefore, the intake negative pressure of the bench lily 17 effectively acts on the metering chamber 16, and the fuel in the metering chamber 16 passes through the check valve 23, the low-speed fuel metering needle valve 22, and the low-speed fuel injection port 21 to the intake passage 18. It is sucked in and mixed with air to the engine 27.
The engine can be started.

Further, as the recoil operation is performed, the pulley around which the rope 51 is wound is rotated, and the engine crankshaft 3 is
When the fuel pump 50 is rotated four times, the pulsating pressure in the crank chamber of the two-stroke engine acts on the diaphragm 6 of the fuel pump 50 through the inlet 5, causing it to move up and down. When the diaphragm 6 is sucked up, the fuel in the fuel tank 1 shown in FIG.
1. Next, when the diaphragm 6 is pushed down, the fuel in the fuel chamber 61 opens the check valve 48 and is supplied to the metering chamber 16 through the passage 60.

When the metering chamber 16 is filled with fuel, the diaphragm 11 is pushed down and the diaphragm 1
The lever 13 is moved by the force of the spring 14 in response to the expansion of the lever 13.
is rotated clockwise about the support shaft 12, the inflow valve 10 is pressed against a valve seat formed at the end of the passage 60, and the passage 60 is closed. thus,
Excess fuel is prevented from being pumped into the metering chamber 16. Conversely, when the fuel in the metering chamber 16 decreases and the pressure in the metering chamber 16 decreases, the lever 13 is pushed up together with the diaphragm 11 by atmospheric pressure, so the inflow valve 10 is opened.

By the way, it is common for chainsaws and the like to use small engines under full load operation, and the carburetor itself is exposed to quite a high temperature due to exhaust heat from the engine, making it easy for the fuel in the metering chamber 16 to vaporize. There is. Therefore, once the engine is stopped, the fuel in the metering chamber 16 turns into gas, flows out to the low-speed fuel nozzle 21 via the low-speed fuel metering needle valve 22 due to the internal pressure of the metering chamber 16, and stagnates inside the intake passage 18. However, the fuel concentration in the intake passage 18 becomes abnormally high, and the metering chamber 16
This causes a fuel shortage inside the unit. If the engine is restarted in this condition, the rich mixture will be sucked into the cylinder, making it temporarily impossible to achieve good combustion, and even if the engine starts, there will be a lack of fuel in the metering chamber 16. Fuel does not flow sufficiently to the intake passage through the low-speed fuel metering needle valve 22 and the low-speed fuel injection port 21, and the engine stops.

However, as mentioned above, according to the present invention, 1
When the suction pump 33 is moved forward by the second recoil operation, fuel gas and air in the metering chamber 16 are sucked into the suction pump 33, and at the same time, the fuel pump is pumped based on the pulsating pressure in the crank chamber of the engine rotated by the recoil operation. 50 is driven, and the fuel in the fuel tank 1 is in a negative pressure state.
will be replenished to.

Furthermore, as the engine rotates, the rich air-fuel mixture in the intake passage 18 is sucked into the engine and is discharged from the engine with incomplete combustion, so that no rich air-fuel mixture remains in the intake passage 18.

The double action of the suction pump 33 by the spring 37 is as follows:
The forward movement (stroke) of the suction pump 33 is slowed down due to the action of delay means such as a throttle or porous member, so in the subsequent second recoil operation, the forward movement (stroke) of the suction pump 33 is delayed.
The pressure drop in the metering chamber 16 caused by the suction pump 33 is suppressed. Therefore, as the engine rotates due to the second recoil operation, the metering chamber 1 is removed from the intake passage 18.
6 works effectively, and the fuel in the metering chamber 16 is smoothly sucked into the intake passage 18 and supplied to the engine as a proper mixture, so that the engine can be started smoothly and quickly. It will be done.

In conventional devices of this type, the suction pump works in the same way no matter how many times the recoil operation is repeated.
Due to the pressure drop in the metering chamber due to the action of the suction pump, the suction force of fuel from the metering chamber due to the negative intake pressure in the intake passage was canceled out, impairing engine startability. For example, if you perform two recoil operations in succession, the pressure drop in the metering chamber due to the action of the suction pump will be suppressed the second time, and the flow of fuel from the metering chamber to the intake passage will improve, resulting in improved engine performance. Startability is improved.

[Effects of the invention] As described above, the invention connects a suction pump between the passage connecting the metering chamber of the carburetor and the fuel tank, and connects the driving body of the suction pump to the rope guide part of the recoil device. Since the arrangement is such that there is frictional engagement, when the rope is pulled by operating the recoil device and the suction pump is moved forward against the spring, the air and fuel gas in the metering chamber are transferred to the suction pump. At the same time, the metering chamber becomes negative pressure and the fuel in the fuel tank is replenished into the metering chamber.

In addition, the passageway on the discharge port side of the suction pump is equipped with a delay means for delaying the return movement of the suction pump's drive body by the spring, so that the metering can be stopped as the pressure in the metering chamber decreases due to the suction force of the suction pump. The flow of fuel from the chamber to the intake passage is obstructed, and 1
If the engine does not start after the first recoil operation, if the second recoil operation is performed, the operation of the suction pump will be restricted by the action of the delay means.
Pressure drop in the metering chamber is suppressed, negative intake pressure in the intake passage acts effectively on the metering chamber, and fuel in the metering chamber flows smoothly into the intake passage, resulting in smooth and quick engine startup. .

This invention installs a suction pump in the recoil device,
Since it has a simple configuration of just providing a delay means in the discharge port side passage of the suction pump, the cost burden is low.
Easy to operate and greatly improves engine starting performance.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of an engine with a diaphragm type carburetor according to a first embodiment of the present invention, Fig. 2 is a side sectional view of the same diaphragm type carburetor, and Fig. 3 is a side sectional view of an engine with a diaphragm type carburetor according to a first embodiment of the present invention. FIG. 2 is a side cross-sectional view showing the main parts of such a diaphragm-type carburetor-equipped engine. 1: fuel tank, 2: carburetor, 16: metering chamber, 21: low speed fuel nozzle, 24: high speed fuel nozzle, 27: engine, 30: recoil device, 3
1: Handle, 33: Suction pump, 35: Rod, 37: Spring, 39: Discharge port, 42: Reflux pipe,
50: fuel pump, 51: rope, 53: pump chamber, 71: throttle hole, 72: porous member.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A suction pump is connected between the passage connecting the metering chamber of the carburetor and the fuel tank, and the driving body of the suction pump is connected to the rope guide part of the recoil device by connecting the rope and the friction The driving body is configured to move forward against the spring by the tensile force of the rope, and the forward movement of the driving body by the spring is delayed in the passage on the discharge port side of the suction pump. An engine with a diaphragm type carburetor characterized by being equipped with a delay means. (2) The engine with a diaphragm type carburetor according to claim (1), wherein the delay means is a throttle hole. (3) The engine with a diaphragm type carburetor according to claim (1), wherein the delay means is made of a porous member.