JPS6142101B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel supply system for starting an internal combustion engine that uses a fuel containing few low boiling point components as the main fuel and mixes this main fuel with intake air using a vaporizer.

In internal combustion engines that use fuel with few low-boiling point components such as alcohol, kerosene, and diesel oil as the main fuel and mix this main fuel into the intake air using a vaporizer, not only does the main fuel adhere to the inner wall of the intake passage, but this Due to the poor evaporability of the main fuel, starting performance, especially at low temperatures, becomes poor. Therefore, in engines that use such fuel with a small amount of low-boiling point components, it has been considered to add a starting fuel such as gasoline that has a large amount of low-boiling point components at the time of starting.

Conventionally, at the time of starting, the main fuel and starting fuel are mixed in advance in the part of the carburetor that communicates with the main fuel float chamber, and this mixed fuel is sucked out through the slow system of the carburetor by intake negative pressure. Something is being considered. However, if the engine relies only on the intake negative pressure in this way, it is unavoidable that the responsiveness deteriorates, and there is a problem in that prompt starting is not possible due to a delay in the supply of starting fuel. Furthermore, at the beginning of the starting operation, a mixed fuel containing a large proportion of the main fuel is sucked out, resulting in poor starting performance. There is also the disadvantage that starting fuel diffuses into the main fuel float chamber of the carburetor, resulting in wasted starting fuel consumption.

This invention was made in view of the above circumstances, and it further improves starting performance and eliminates the diffusion of starting fuel into the main fuel float chamber of the carburetor.
Furthermore, it is an object of the present invention to provide a starting fuel supply device that can be used with almost no modification to conventional devices and is easy to operate. According to the present invention, the object is to provide a starting fuel tank for accommodating starting fuel containing many low boiling point components in an internal combustion engine whose main fuel is a fuel containing few low boiling point components, and a starting fuel tank for storing the starting fuel containing many low boiling point components, and a method for directing the main fuel into a main intake passage. a carburetor having a main fuel supply system and a starting system that supplies the main fuel into a starting intake passage that bypasses a throttle valve in the main intake passage; a plunger that opens and closes the starting intake passage; a starting fuel discharge port that opens at a position not downstream of the plunger in the intake passage;
This is achieved by a starting fuel supply device for an internal combustion engine, comprising a starting fuel pump that discharges the starting fuel to the discharge port when starting the internal combustion engine. The present invention will be explained in detail below based on the drawings.

FIG. 1 is a cross-sectional view showing a first embodiment of the invention, FIG. 2 is a cross-sectional view taken along the - line, and FIG.
It is a - line sectional view in a figure. In Fig. 1, reference numeral 1 indicates a crank chamber preload type two-stroke engine body, 2 a cylinder block, 3 a cylinder liner, 4 a cylinder head, 5 a crankcase, 6 a piston, 7 a crankshaft, and 8 a cylinder block. A combustion chamber, 9 an exhaust passage, 10 an intake passage, and 11 a spark plug. 15 is a piston type carburetor,
It is connected to the intake passage 10 of the cylinder block 2 via a heat insulating connecting member 16 and a reed valve holding member 17. Note that a reed 18 is attached to the reed valve holding member 17 to prevent backflow of intake air from the crank chamber toward the carburetor 15, and the intake passage 10 downstream of the reed valve is always in communication with the crank chamber. . 19 is a main body of the carburetor 15, in which a main intake passage 20 communicating with the intake passage 10 is formed;
Inside, a piston-shaped throttle valve 21 faces from above so as to be able to move forward and backward. That is, a guide cylinder part 22 is formed in the main body 19 in a direction perpendicular to the main intake passage 20, and a throttle valve 21 is slidably fitted into this guide cylinder part 22, and is mounted above the throttle valve 21 by a screw cap 23. is prevented from coming off. 24 is a compression coil spring interposed between the throttle valve 21 and the screw cap 23, and this spring 24 connects the throttle valve 21 to the main intake passage 2.
Force it to protrude into 0. The throttle valve 21 is
It is pulled upward by an inner Bowden wire 25 connected to an external accelerator operating mechanism (not shown) and moved out of the main intake passage 20 against the spring force of the spring 24. 26 is a raised portion formed on the inner surface of the main intake passage 20 below the throttle valve 21;
A bench lily part 27 is provided between the lower part of the throttle valve 21 and the lower part of the throttle valve 21.
is formed. Reference numeral 28 denotes a jet needle, whose upper end is held by the throttle valve 21, and whose lower part advances into the needle jet 29 opened in the raised portion 26, and which moves as the throttle valve 21 moves up and down. , the opening area of the needle jet 29 is increased or decreased. These jet needle 28, needle jet 29, etc. form a main fuel system. 30 is an idle port. It should be noted that from the needle jet 29 and the idle port 30, a main fuel such as alcohol containing few low-boiling components contained in a float chamber (not shown) is sucked into the main intake passage 20.

Reference numerals 35 and 36 are intake passages for starting, which cross the guide cylinder portion 22 and open into the main intake passage 20 on the upstream and downstream sides of the throttle valve 21. The starting intake passage 36 is provided with a starting system for main fuel, and the starting fuel is discharged into this passage 36 as described later. 37 is a starting intake passage 36 on the downstream side
A plunger chamber 37 is formed approximately horizontally in the middle of the plunger chamber 37, and one end of the plunger chamber 37 is open. The bottom of the plunger chamber 37 is slightly raised, and one end of a passage 38 communicating with the float chamber containing the main fuel is opened there. The starting intake passage 36 opens at a position close to the bottom of the inner peripheral surface of the plunger chamber 37.
A starting fuel passage 39 is also opened on the inner peripheral surface of the plunger chamber 37 near the bottom. A plunger 40 is inserted into the plunger chamber 37 with appropriate sliding resistance. The plunger 40 has a rod 4 that protrudes from the plunger chamber 37 to the outside through a lid member 41 and a rubber cap 42.
3 is integrally formed, and a knob 44 is fixed to the tip of this rod 43. 45 is plunger 4
A rubber member fixed at 0, 46 is a plunger 40
This spring 46 is a coil spring compressed between the opposing surfaces of the lid member 41, and this spring 46 has the function of pressing the rubber member 45 against the opening of the passage 38 to seal it when the knob 44 is pushed in.

Therefore, now plunger 40 and plunger chamber 37
If the plunger 40 is pulled outward against the sliding resistance and the spring force of the spring 46, the plunger 40 is fixed by the sliding resistance, and at this time, the starting intake passage 36, the passage 3
8 and 39 communicate. Therefore, the main fuel for starting is sucked up from the passage 38 by the negative pressure generated by the intake air flowing across the plunger chamber 37, and the air-fuel mixture flows out to the main intake passage downstream of the throttle valve 21. . If you push the knob 44 again,
Plunger 40 closes passages 36 and 39, and rubber member 45 is pressed against the opening of passage 38 to completely seal it.

50 is a diaphragm type pump as a starting fuel pump, which includes a diaphragm 53 that partitions an oil chamber 51 and an atmospheric pressure chamber 52, a coil spring 54 that presses this diaphragm 53 toward the oil chamber 51,
A knob 55 for pulling out the diaphragm 53 toward the atmospheric pressure chamber 51 and check valves 56 and 57 are provided. 58 is a starting fuel tank, and the pump 50 is attached to this tank 58. The check valve 56 is connected to this tank 5.
The check valve 57 is connected to guide the starting fuel from the oil chamber 51 to the passage 39 of the carburetor 15. In addition, the oil chamber 51 and check valve 57
A passage 59 communicating with the oil chamber 51 opens approximately at the center of the oil chamber 51.

53a is a valve body attached to the top surface of the diaphragm 53 on the oil chamber 51 side, and when the diaphragm 53 is pressed by the spring 54 on the back and moves forward to the maximum,
The opening of the passage 59 is completely blocked.

Therefore, when the knob 55 of the pump 50 is pulled now, starting fuel flows from the tank 58 through the check valve 56 into the oil chamber 51. Next, this knob 55
When released, the diaphragm 53 returns to the oil chamber 51 side by the spring 54, and at this time, the diaphragm 53 returns to the oil chamber 51 side.
The starting fuel in the check valve 57 and the passage 39
If the plunger 40 is pulled out, this fuel is discharged into the main intake passage 20 through the starting intake passage 36. By repeating the operation of pulling and releasing the knob 54, the amount of starting fuel discharged into the main intake passage 20 increases.

In this embodiment, the plunger 4 is
0 knob 44, then pull the pump 50 knob 55.
By pulling the button several times, the starting fuel flows out from the plunger chamber 37 into the main intake passage 20. When an engine starting operation is performed, the main fuel is sucked up from the passage 38 by the intake air flowing across the plunger chamber 37, and the air-fuel mixture flows out into the main intake passage 20. At the same time, almost at the same time as the engine starting operation, the starting fuel accumulated here is drawn into the intake air. It is also sucked into the engine body 1. Therefore, starting is quick and reliable. Also, try discharging a small amount of starting fuel before starting the engine, and if the engine continues to rotate smoothly, you can leave it as it is.
You can add a small amount of starting fuel by subtracting . Therefore, the amount of starting fuel used can be kept to the minimum necessary.

Although this embodiment is configured with a manual starting fuel pump (pump 50), the present invention can also be configured with an automatic pump that utilizes engine pulsation such as negative pressure in the crank chamber. . Fourth
The figure is a sectional view showing the second embodiment constructed in this manner, and FIG. 5 is a partially enlarged sectional view thereof. In these figures, the same parts as in the first embodiment are given the same reference numerals, so their description will not be repeated. This embodiment includes a diaphragm pump 60 fixed to the starting fuel tank 58 and a temperature-sensitive on-off valve 70 fixed to the cylinder head 4 to guide the pulsating pressure in the crank chamber to the pump 60 only when the engine is at low temperature. The temperature-sensitive on-off valve 70 is fixed to a recess 71 formed in the cylinder head 4 and includes a main body 73 in which a valve chamber 72 is formed. A disc-shaped bimetal 74 is housed within the valve chamber 72. It warps downward as shown in FIG. 4 when the temperature is below a certain temperature (for example, 20° C.), and warps upward as shown by the chain line when the temperature exceeds this temperature. At the center of this valve chamber 72 is an opening 75 connected to a communication pipe 75 that guides the pulsating pressure of the crank chamber.
A is formed, and an O-ring 76 is fixed so as to surround this opening 75a. The bimetal 74 comes into contact with this O-ring 76 when the temperature is above a certain level and closes the opening 75a. An opening 78 is formed on the outside of the O-ring 76 and is connected to a communication pipe 77 that introduces pulsating pressure to the pump 60. Furthermore, the communication pipe 7
Reference numeral 5 denotes a wall surface of the intake passage 10 of the engine 1, and extracts the crank chamber pulsation from a position on the downstream side of the reed valve holding member 17. Further, a diaphragm 79 is provided between the communication pipe 75 and the opening 75a. This throttle 79 buffers the pulsating pressure acting on the pump 60. Therefore, as the engine speed increases and the pulsation period becomes faster, the pulsation pressure is averaged out and the pump 60 becomes inoperable. In other words, since starting fuel is not required when the engine is operating at high speed, the fuel supply is automatically stopped.

The diaphragm pump 60 has a diaphragm 6
1 into an oil chamber 62 and a pressure chamber 63,
The diaphragm 61 is urged toward the oil chamber 62 by a compression coil spring 64. The communication pipe 77 is connected to the pressure chamber 63. Also, the discharge side of the check valve 57 of this pump 60 is the fourth one.
As shown in the figure, it is connected to a discharge port 65 on the upstream side of the plunger chamber 37 of the starting intake passage 36. Note that a passage 65 that communicates the oil chamber 62 and the check valve 57 opens approximately at the center of the oil chamber 72.

Reference numeral 61a denotes a valve body attached to the top surface of the diaphragm 61 on the oil chamber 62 side, which completely blocks the opening of the passage 65 when the diaphragm 61 is pressed by the spring 64 on the back and moves forward to the maximum. ing.

63a is an orifice with a very small opening area that communicates the pressure chamber 63 with the atmosphere. This orifice 63a introduces atmospheric air into the pressure chamber 63 while the engine is stopped, and seats the valve body 61a in the opening of the passage 65.

In this embodiment, when the temperature of the engine body 1 is below a certain temperature (for example, 20°C), the temperature-sensitive on-off valve 70
The bimetal 74 is in the solid line position in FIG. 5, and the temperature-sensitive on-off valve 70 is open. When the engine is started in this state, the positive and negative pulsating pressure in the crank chamber is guided to the pressure chamber 63 of the pump 60. Therefore, the diaphragm 61 pulses, and the starting fuel is discharged through the passage 65 and the check valve 57 into the starting intake passage 36 on the upstream side of the plunger chamber 37. At this point, if the plunger 40 is pulled out, the starting intake air flows into the starting intake passage 3.
5 and 36, the starting fuel flows into the main intake passage 20 downstream of the throttle valve 21 together with this intake air. At this time, it goes without saying that the main fuel is also sucked up from the passage 38 and flows out into the main intake passage 20 as an air-fuel mixture.

When the engine starts, the engine temperature rises, and when it exceeds a certain temperature, the bimetal 74 of the temperature-sensitive on-off valve 70 bends back to the chain line position in FIG. 5, opening 75.
occlude. Therefore, the pulsating pressure is blocked by the bimetal 74, and the operation of the pump 60 is stopped. That is, the discharge of starting fuel to the starting intake passage 36 is stopped. However, the main fuel continues to be supplied from the passage 38, and if the plunger 40 is pushed in to close the starting intake passage 36 when the engine is sufficiently warmed up, the supply of this main fuel is also stopped.

According to this embodiment, the starting fuel is supplied with good response in conjunction with the starting operation, which not only ensures reliable starting, but also the starting fuel is supplied and stopped automatically. Easy to operate,
Furthermore, starting fuel is not wasted.

In this embodiment, the pump 60 is operated by the negative pressure in the crank chamber, but it is of course possible to operate the pump 60 by pulsating pressure extracted from other places such as the intake pulsation upstream of the reed valve. be.

In the first embodiment, the starting fuel is discharged into the plunger chamber 37 of the starting intake passage 36, and in the second embodiment, the starting fuel is discharged to the upstream side of the plunger chamber 37. Since the valve bodies 53a and 61a completely block the openings of the passages 59 and 65, the pumps 50 and 6
The starting fuel accumulated in the communication pipe between the engine 0 and these discharge ports is not sucked out in the normal operating state after warm-up when the knob 44 of the plunger 40 is pushed in. Therefore, when the knob 44 is pulled to perform a starting operation, starting fuel is instantly discharged, resulting in even better starting performance.

Furthermore, in the first and second embodiments, the plunger 40 that connects and blocks the starting intake passage 36 is
Although the plunger 40 is configured to be operated manually, the plunger 40 may be operated automatically by detecting the engine temperature. In this case, for example, the plunger forms a normally open valve, and this valve is closed by engine pulsating pressure via a temperature-sensitive on-off valve and a negative pressure delay valve that open when the engine temperature exceeds a certain temperature (for example, 40°C). It can be configured as follows. Note that this negative pressure delay valve has the function of amplifying the negative pressure and suppressing the pulsation by allowing only the negative pressure of the pulsating pressure to pass through.For example, it is made up of a check valve and an orifice provided on the partition wall. can do.

In each of the above embodiments, a manual pump 50 and a pump 60 using crank chamber pulsating pressure are used, but the present invention can be applied to various pumps as long as they operate only at startup. It goes without saying that the present invention can also be applied to a four-stroke engine.

As described above, in an internal combustion engine whose main fuel is fuel with few low-boiling point components, the present invention is directed to a position other than the plunger which opens and closes the starting intake passage that bypasses the throttle valve in the main intake passage, that is, the plunger. A starting fuel discharge port is opened at a position where communication with the main intake passage on the downstream side of the throttle valve is interrupted by the throttle valve, and the starting fuel is supplied from this discharge port by the starting fuel pump that operates at the time of starting. Discharge.
Therefore, the starting fuel can be mixed into the intake air immediately after starting, and since the starting intake passage has a smaller diameter than the main intake passage, the intake air flow velocity in the starting intake passage increases and the starting fuel is atomized. promoted,
Engine startability, especially low-temperature startability, is improved. Particularly expensive starting fuel is not supplied to the main fuel float chamber, but only the required amount is directly discharged into the starting intake passage, so the amount of fuel used is small, and the plunger can be closed after the engine has started. It is economical because the starting fuel is not sucked out by the intake negative pressure. Furthermore, when converting a conventional gasoline carburetor to an internal combustion engine that uses main fuel with few low-boiling components by simply adjusting the air-fuel ratio (for example, the stoichiometric air-fuel ratio for ethanol is approximately 9), these conventional devices can be used in most cases. It can be used as is without any modification and is easy to operate.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a first embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the - line, and FIG.
- line sectional view in Fig. 2, Fig. 4 shows the
A sectional view showing the embodiment, FIG. 5 is a partially enlarged sectional view thereof. DESCRIPTION OF SYMBOLS 1... Engine body, 50... Diaphragm type pump as a starting fuel pump, 58... Starting fuel tank, 60... Diaphragm type pump as a starting fuel pump.

Claims (1)

[Scope of Claims] 1. In an internal combustion engine whose main fuel is fuel with a small amount of low-boiling point components, there is provided a starting fuel tank containing starting fuel with a large amount of low-boiling point components, and supplying the main fuel into the main intake passage. a carburetor having a main system and a starting system that supplies the main fuel into a starting intake passage that bypasses a throttle valve in the main intake passage; a plunger that opens and closes the starting intake passage; and a starting intake passage. A starting fuel pump for discharging the starting fuel to the outlet when starting the internal combustion engine; and a starting fuel pump for discharging the starting fuel to the outlet when starting the internal combustion engine. fuel supply device.