JPH0219583Y2 - - 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 has a diaphragm that separates a metering chamber that communicates with the fuel nozzle, a fuel pump that is driven by the pulsating pressure of the engine, and a metering chamber that pumps fuel from the fuel tank by the fuel pump. It is equipped with an inflow valve for introducing the water into the tank.

During normal operation, fuel in the metering chamber is drawn into the engine through the fuel nozzle and intake passage, and when the amount of fuel in the metering chamber decreases, the inlet valve opens due to negative intake pressure acting on the diaphragm, allowing fuel to flow from the fuel pump to the engine. is supplied intermittently. 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 stored in the metering chamber when starting the engine, making it difficult to start 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, atmospheric heat, and radiant heat from sunlight, and the metering chamber is filled with fuel gas. . In this case, 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, resulting in a temporary fuel shortage.
The engine may stop immediately or have poor acceleration after starting, making it difficult to maintain smooth operation.

In order to solve this problem, the present applicant has proposed a method for connecting a suction pump between the passage connecting the metering chamber of the carburetor and the fuel tank, and the driving rod of the suction pump as disclosed in Utility Model Application No. 61-128377. A recoil device is proposed in which the drive rod is disposed in the rope guide portion of the recoil device so as to engage with the rope, and the drive rod is operated against a spring by the tensile force of the rope.

However, in the above-mentioned engine, since the rope is hung around the roller provided at the tip of the drive rod, the local load on the rope is large, and conventional ropes cannot be said to have sufficient strength. Higher strength is required. That is, since the rope is extremely bent at the engagement portion between the roller or groove wheel of the drive rod and the rope, the rope is likely to wear out and break during long-term use. In addition, as the rope is pulled and becomes closer to a straight line, the stroke of the suction pump becomes smaller, so the stroke of the suction pump cannot be used effectively against the tension of the rope, and it is difficult to obtain the required amount of suction. requires a large suction pump.

[Problems to be solved by the invention] In view of the above-mentioned problems, the purpose of the invention is to bring the rope into frictional contact with the drive rod of the suction pump in a gently curved state, until the rope is pulled in a straight line. An object of the present invention is to provide an engine with a diaphragm type carburetor, in which a sufficient stroke can be given to a suction pump during this period.

[Means for Solving the Problems] In order to achieve the above object, the present invention has a structure in which a suction pump is installed in the rope pull-out portion of the recoil device to suck and discharge fuel gas from the metering chamber of the diaphragm type carburetor into the fuel tank. , an eccentric cam with a circumferential surface that makes frictional contact with the rope is supported on the housing of the suction pump by a shaft, and fuel is placed on the cam surface of the eccentric cam whose distance from the shaft gradually decreases in accordance with the rotation angle. A roller supported by the drive rod of the pump is biased and engaged by a spring.

[Operation] When the rope is pulled, the engine crankshaft is rotated, and at the same time, the eccentric cam that is in frictional contact with the rope is rotated, and the drive rod of the suction pump, which is in contact with the cam surface of the eccentric cam, resists the spring. It is driven by Therefore, the fuel gas and air in the metering chamber are discharged to the fuel tank 1 by the fuel pump,
At the same time, fuel is supplied from the fuel tank to the metering room. Therefore, the fuel shortage in the metering room is eliminated and the engine can be started smoothly.

Since the rope is in frictional contact with the circumferential surface of the eccentric cam, the movement of the rope is easy, and the eccentric cam is rotated simultaneously with the rope pulling operation.

Since the cam surface of the eccentric cam is formed so that the distance from the shaft gradually decreases as the eccentric cam is rotated, the stroke movement of the drive rod of the suction pump is reliably achieved by the rotation of the eccentric cam.

[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 reinforced through the inlet closed by 4. A filter 8 is housed inside the fuel tank 1 , and a fuel pipe 9 connected to the filter 8 is connected to an inlet 7 of the carburetor 2 .

A recoil device 30 is connected to the end of a crankshaft 34 of the engine 27 via a known one-way clutch. This recoil device 30 has a handle 31 connected to the end of a rope 51 wound around a pulley, and when the rope 51 is pulled by the handle 31 against a spring, the crankshaft 34 is rotated via a one-way clutch. It is becoming more and more like this.

According to the present invention, the rope 5 of the recoil device 30
A suction pump 33 is attached to the drawer part of 1,
As shown in FIG. 2, when the rope 51 is pulled,
The drive rod 35 of the suction pump 33 is pulled against the force of the spring 37, and the suction pump 33 is driven. Housing 5 of suction pump 33
A driving rod 35 is slidably supported on the middle partition wall 52a of the roller 43, and a roller 43 is supported axially by a bifurcated fork at the tip of the driving rod 35.

As shown in FIG. 2, an eccentric cam 56 is rotatably supported by a support shaft 54 in a portion above the partition wall 52a (the right half in the figure). The rope 51 is in frictional contact with a groove provided on the circumferential surface of the eccentric cam 56 in a curved state. An opening is provided in the eccentric cam 56, and a cam surface 55 is formed at the edge of this opening. A roller 43 supported by a drive rod 35 is rotatably abutted on this cam surface 55.

A diaphragm 36 is supported in the lower half of the housing 52 (the left half in FIG. 2), thereby dividing the pump chamber 53 and the atmospheric chamber. The proximal end of the drive rod 35 is connected to the diaphragm 36, and a spring 37 is interposed between the diaphragm 36 and the partition wall 52a. Pump chamber 53 in pump chamber 53
A suction valve 38 that allows inflow into the pump chamber 53 and a discharge valve 39 that allows outflow from the pump chamber 53 are provided. As shown in FIG. 1, the suction valve 38 is connected to a suction port 40 of the vaporizer 2, which will be described later, via a suction pipe 41. The discharge valve 39 is connected to the inside of the fuel tank 1 via a reflux pipe 42 .

Note that, in reality, the upper half of the suction pump 33 is formed separately from the partition wall 52a, and is connected by appropriate means. A mounting screw 52b is integrally formed in this upper half portion, and this mounting screw 52b is screwed and fixed to the rope pull-out portion of the recoil device 30 shown in FIG.

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. A pulsating pressure inlet 5 is provided in the cover 4 and is connected to a crank chamber of a two-stroke engine, so that pulsating pressure in the crank chamber acts on a diaphragm 6 constituting a fuel pump 50. 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 is connected to the metering chamber 16 via the check valve 48, the passage 60, and the 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 opened and closed by a lever 13. 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 includes a check valve 26 and a high speed fuel metering needle valve 25.
It is connected to the high speed fuel nozzle 24 through the. Further, the metering chamber 16 is connected to the low-speed fuel injection port 21 via a check valve 23 and a low-speed fuel metering needle valve 22 .

An intake passage 18 with a bench lily 17 in the main body 3
is provided, and a throttle valve 20 is disposed thereon via a valve shaft 19. The air cleaner 28 shown in FIG. 1 is connected to the left end of the main body 3, and the engine 2 is connected to the right end.
Connected to 7.

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 drive rod 35 of the suction pump 33 is pushed back downward by the force of the spring 37 (FIG. 2).
The rope 51 is in a relaxed state. When the handle 31 is pulled upward to start the engine 27, the rope 51 is pulled, and the profile of the cam surface is such that the distance from the support shaft 54 gradually decreases in accordance with the rotation angle. , the drive rod 35 is connected to the spring 37 via the roller 43 that engages the cam surface 55.
is pulled against the force of , and the volume of the pump chamber 53 increases. Therefore, the pump chamber 53 becomes negative pressure,
The suction valve 38 is opened, and the air and fuel gas in the metering chamber 16 are sucked into the pump chamber 53 from the suction port 40 through the suction pipe 41, and the drive rod 35 is moved by the spring 3.
7, the fuel is discharged into the fuel tank 1 via the discharge valve 39 and the reflux pipe 42.

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 acts on the filter 8 through the inlet 7 and the fuel pipe 9, and the fuel in the fuel tank 1 flows into the metering chamber 1.
It is attracted to 6.

In this way, the air and fuel gas in the metering chamber 16 are discharged to the fuel tank 1, and when the metering chamber 16 is filled with fuel, the check valve 23 is opened by the negative intake pressure of the bench lily 17, and the metering chamber 16 fuel passes through the check valve 23 and the low-speed fuel metering needle valve 22, is sucked into the intake passage 18 from the low-speed fuel nozzle 21, is mixed with air, and is supplied to the engine 27, making it possible to start the engine. .

On the other hand, when the metering chamber 16 is filled with fuel, the diaphragm 11 is pushed down, and in response to the expansion of the diaphragm 11, the lever 13 is rotated clockwise about the support shaft 12 by the force of the spring 14. The inlet valve 10 is pressed against a valve seat formed at the end of the passageway 60, closing the passageway 60.
In this way, excess fuel is prevented from being pumped into the metering chamber 16 by the fuel pump 50. Conversely, when the fuel in the metering chamber 16 becomes low and the pressure decreases, the lever 13 is pushed up together with the diaphragm 11 by atmospheric pressure, and the inflow valve 10 is opened.

When the pulley around which the rope 51 is wound is rotated in accordance with the recoil operation, and the engine crankshaft 34 (FIG. 1) is rotated via a one-way clutch (not shown), the crank chamber of the two-cycle engine is rotated. Pulsating pressure flows from the inlet 5 to the fuel pump 50
act on the diaphragm 6 to move it up and down. When the diaphragm 6 is sucked up, the fuel in the fuel tank 1 shown in FIG. 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.

By the way, in chainsaws and the like, it is common for all the small engines to be used for load operation, and the carburetor itself is exposed to a considerable high temperature due to the exhaust heat of 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 pushes open the check valve 23 due to the internal pressure of the metering chamber 16, flows out to the low-speed fuel nozzle 21 through the low-speed fuel metering needle valve 22, and flows out into the intake passage 18. The fuel stagnates inside the metering chamber 16, the fuel concentration becomes abnormally high, and the fuel inside the metering chamber 16 becomes insufficient. 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 insufficient fuel in the metering chamber 16. Therefore, fuel does not flow sufficiently to the low-speed fuel injection port 21 through the low-speed fuel metering needle valve 22, and the engine stops.

As described above, according to the present invention, when the rope 51 of the recoil device 30 is pulled when restarting the engine, the crankshaft 34 of the engine is rotated and at the same time, the eccentricity that frictionally engages with the rope 51 is rotated. Since the suction pump 33 is driven as the cam 56 rotates, the metering chamber 1 is
6 is discharged into the fuel tank 1, and the fuel in the fuel tank 1 is replenished into the metering chamber 16. Therefore, the fuel shortage in the metering chamber 16 is resolved, and the rich mixture in the intake passage is first supplied to the engine and exhausted from the engine with incomplete combustion, and then new fuel is supplied from the metering chamber. The mixture is drawn into the intake passage and supplied to the engine as a proper air-fuel mixture, so that the engine can be restarted smoothly.

[Effects of the invention] As described above, the present invention has a suction pump that sucks and discharges fuel gas from the metering chamber of the diaphragm carburetor into the fuel tank, and attaches the rope to the rope pull-out part of the recoil device, and attaches the rope to the housing of the suction pump. An eccentric cam with a circumferential surface that comes into frictional contact is supported by a shaft, and a roller supported by the drive rod of the suction pump is attached to the cam surface of the eccentric cam whose distance from the shaft gradually decreases in accordance with the rotation angle. Therefore, when the recoil device is operated, the suction pump is activated, and the air and fuel gas in the metering chamber are discharged to the fuel tank. At this time, the metering chamber becomes negative pressure, and the recoil device is operated. The fuel pump is driven based on the pulsating pressure in the crank chamber of the engine, which is rotated by As a result, the engine can be started smoothly and quickly, and stable continued operation can be achieved even after starting.

Since the rope and the eccentric cam come into frictional contact with each other on a gentle circumferential surface and are not bent at an acute angle as in the conventional case, the durable life of the rope is improved.

The cam surface of the eccentric cam is formed so that the distance from the spindle that supports the eccentric cam gradually decreases in accordance with the rotation angle, so when the eccentric cam is rotated, the distance from it to the spindle that supports the eccentric cam is approximately proportional to the rotation angle of the eccentric cam. As a result, the operating stroke of the suction pump increases, and a sufficient amount of suction can be obtained even with a smaller suction pump compared to the conventional example.

Since the suction pump is disposed in the rope pull-out part of the recoil device, which is located away from the high temperature part of the engine, the temperature rise is small and the generation of fuel gas inside the suction pump is suppressed.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of an engine with a diaphragm type carburetor according to the present invention, Fig. 2 is a side sectional view showing an enlarged main part of the engine, and Fig. 3 is a side sectional view of the diaphragm type carburetor. It is. 1: Fuel tank, 2: Diaphragm type carburetor,
16: Metering chamber, 21: Low speed fuel nozzle, 2
4: High-speed fuel nozzle, 27: Engine, 30: Recoil device, 31: Handle, 33: Suction pump,
34: Crankshaft, 35: Drive rod, 37: Spring, 43: Roller, 50: Fuel pump, 51: Rope, 52: Housing, 53: Pump chamber, 5
5: Cam surface, 56: Cam.

Claims (1)

[Scope of utility model registration request] A suction pump that sucks and discharges fuel gas from the metering chamber of the diaphragm carburetor into the fuel tank is attached to the rope pull-out part of the recoil device, and an eccentric cam with a circumferential surface that makes frictional contact with the rope is attached to the housing of the suction pump. A diaphragm type characterized in that a roller supported by a drive rod of a suction pump is biased and engaged by a spring to the cam surface of an eccentric cam whose distance from the shaft gradually decreases in accordance with the rotation angle. Engine with carburetor.