JPH04219460A - Fuel injection device for two-cycle engine - Google Patents

Abstract

PURPOSE:To simplify construction and increase atomization of fuel by eliminating necessity of increasing fuel pressure and providing an counterflow prevention valve on an injection nozzle. CONSTITUTION:Scavenging ports 44 and 46 and exhaust port 50 are provided in a cylinder side-wall, and a small hole 52 is also formed in it. The small hole 52 is connected to a pressure supply source 32 through a fresh air supply line 40. Then a fuel injection nozzle is faced toward a portion 54 in the fresh air supply line 40 with a line cross-section larger than that of the small hole 52.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection system for a two-stroke engine.

0002

BACKGROUND OF THE INVENTION Conventional fuel injection systems for internal combustion engines, particularly two-stroke internal combustion engines, can be roughly divided into two types: those that directly inject fuel or a mixture of fuel and air into a cylinder;
There are two types: one injects fuel into the intake pipe in front of the cylinder, and the other into the scavenging passage.

Among the former, a diesel engine is an example of a case where only fuel is injected, but it is necessary to maintain the fuel at a high pressure, and when gasoline is injected, there are problems with lubrication of pumps and the like. Also, JP-A-62-25392
As described in No. 0, there are some that attach a fuel injection nozzle to the cylinder side wall and inject fuel during the compression process,
There is a problem that fuel atomization is not sufficient. Furthermore, in these cases, since the tip of the injection nozzle is exposed to high pressure at the early stage of combustion, it is necessary to attach a check valve to the nozzle.

In the former case, when a mixture of fuel and air is injected, it is usual to first inject the fuel into a high-pressure air chamber, and then inject the mixture of fuel and high-pressure air into the fuel chamber. . Therefore, when injecting fuel into the high-pressure air chamber, it is necessary to maintain the fuel pressure higher than the air chamber pressure.
Increasing the fuel pressure here causes the problem of fuel leakage from fuel piping and the like. Further, as described above, since the air chamber pressure is lower than the pressure during combustion, a flashback prevention valve is required. Furthermore, it is necessary to separately develop an injector for injecting fuel and air, and a regulator to adjust the differential pressure between the air chamber pressure and the fuel pressure. In addition, since the injection of both fuel and air must be controlled, there is also the problem that the control program becomes complicated.

[0005]

[Problems to be Solved by the Invention] Therefore, it has been considered to inject fuel into the intake pipe and scavenging passage, which is the latter of the fuel injection methods, and an example of this is disclosed in Japanese Patent Application Laid-Open No. 62-876.
There is one described in No. 34. Although this method injects fuel into the scavenging passage, there is still a problem that sufficient atomization of the fuel cannot be achieved.

The present invention was developed in view of the problems of the prior art, and its purpose is to simplify the structure by eliminating the need to increase fuel pressure or provide a check valve in the injection nozzle. An object of the present invention is to provide a fuel injection device for a two-stroke engine, which is designed to improve fuel atomization and fuel atomization.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a scavenging port and an exhaust port on the cylinder side wall, communicates the scavenging port with a fresh air supply source for scavenging, and A small hole is formed in the fresh air supply path, the small hole is communicated with a fresh air supply source for conveying the injected fuel through a fresh air supply path, and a fuel injection nozzle is provided in a portion of the fresh air supply path having a passage cross-sectional area larger than that of the small hole. It has a configuration that allows you to see

The present invention also provides a scavenging port on the side wall of the cylinder.
In a two-stroke engine equipped with an exhaust port and in which the scavenging port communicates with a fresh air pressure supply source, a small hole is formed in the cylinder side wall, and the small hole is communicated with the pressure source through a fresh air supply path. , the fuel injection nozzle is configured to face a portion of the fresh air supply path having a passage cross-sectional area larger than the small hole.

In the above structure, a chamber is provided in the fresh air supply path between the pressure supply source and the fuel injection nozzle, a chamber is provided in the pressure supply path and the pressure supply path is provided between the chamber and the pressure supply source. A check valve may be provided that only allows air to flow from the source to the chamber.

0010

[Operation] According to this configuration, when the fuel is atomized by the fresh air passing through the fresh air supply path and the fuel is supplied into the cylinder by the flow of fresh air, the flow velocity is increased by the small hole in the cylinder side wall, and the cylinder Atomization of the fuel within the tank is promoted. here,
The fresh air supply source for scavenging and the fresh air supply source for conveying the injected fuel may be separate, or they may be shared by one pressure supply source. Furthermore, even if the pressure of the pressure supply source fluctuates, high pressure can be stored in the chamber, thereby facilitating atomization of the fuel.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on embodiments shown in the drawings.

In the first embodiment of the present invention shown in FIG.
Reference numeral 10 denotes a crankshaft, and this crankshaft 10 is arranged within a crank chamber 14 formed by a cylinder body 12. A cylinder bore 18 is formed by the cylinder body 12 and a cylinder sleeve 16 disposed on the inner peripheral surface of the cylinder body.
A piston 20 sliding on the inner circumference is connected to the crankshaft 10 via a connecting rod 22. A combustion chamber 26 is defined by the top of the piston and the cylinder head 24;
A spark plug 28 is arranged so as to face this combustion chamber 26. A scavenging pump 32 is provided as a pressure supply source of fresh air, and this scavenging pump 32 is mechanically driven by the power of the crankshaft 10 via a belt (not shown) or the like. This scavenging pump 32 is a roots pump type blower,
By rotating the two rotors 34 that are in contact with each other, air introduced through the throttle valve 36 is forced into the intake passage 38 on the discharge side.

The upstream end of the intake passage 38 is connected to the cylinder body 1.
2, and communicates here with a scavenging passage 42 and a fresh air supply passage 40, which will be described later. The scavenging passage 42 extends in the cylinder body 12 in a loop shape that goes around the cylinder body 18 . In this embodiment, two substantially opposing scavenging ports 44 (only one is shown in FIG. 1),
A third scavenging port 46 is provided between both scavenging ports 44 and at a position opposite to the connection end of the intake passage 38, and each scavenging port 44
, 46 correspond to the scavenging passage 42, respectively.
It communicates with the cylinder head 24 through a rising passage 48 that rises from the cylinder head 24 toward the cylinder head 24. Therefore, fresh air is directed toward the cylinder head from each scavenging port and has a directivity toward the center of the cylinder bore. Note that the reference numeral 50 is an exhaust port, and the third scavenging port 4 is connected to the cylinder central axis as a boundary.
It is arranged to face 6. The crank chamber 14 contains lubricating oil like a normal 4-stroke engine,
This makes it possible to lubricate the large and small end bearings of the connecting rod 22 and the piston skirt.

A fresh air supply passage 4 communicating with the intake passage 38
Similarly to the scavenging passage 42, the scavenging passage 42 also extends in a loop shape around the cylinder bore 18 in the cylinder body 12, and rises from a part of the cylinder bore 18 to a position closer to the top dead center than the third scavenging passage 46. extends up to This rising end communicates with the cylinder bore 18 through a small hole 52 formed in the cylinder sleeve 16 at approximately the same position as the top dead center side end of the exhaust port. This small hole 52 has a directivity that allows fresh air and a mixture of fuel and fresh air to be injected toward the combustion chamber 26, has a passage cross-sectional area according to necessity, and has one in number. Or more than one can be provided. A subchamber 54 is formed immediately upstream of the small hole 52 of the fresh air supply path 40, and an injector 56 for fuel injection is formed in the subchamber 54.
is placed. This subchamber 54 has a passage cross-sectional area that is at least larger than the passage cross-sectional area of the small hole 52. The upstream side of the subchamber 54 communicates with a main chamber 58 via a throttle 57, and a check valve 60 is disposed upstream of the main chamber 58 to prevent air from flowing toward the intake passage 38.

Next, the operation of the above embodiment will be explained. As the crankshaft 10 rotates, fresh air is supplied from the intake passage 38 to the fresh air supply passage 40 together with the scavenging passage 42.
After passing through the check valve 60, the fresh air supplied to the main chamber 58 is stored in the main chamber 58. The small hole 52 is opened and closed by the piston 2.
During the scavenging and exhausting process, the piston 20 passes through the small hole 52 and the small hole 52 is opened, and almost at the same time, the exhaust port 50 is opened and the combustion gas is discharged. Air within chamber 58 is forced into cylinder bore 18 . At this time, only air is injected. When the piston 20 further descends, air is also sent into the cylinder bore 18 from the scavenging port 46. Next, during the compression process, a predetermined fuel flow rate is injected from the injector 56 into the subchamber 54 at a predetermined injection start time until the piston 20 rises and closes the small hole 52. The injected fuel mixes with the air flowing through the subchamber 54 and is injected from the small hole 52 toward the combustion chamber 26 .

According to this embodiment, the opening/closing timing of the small hole 52 by the piston, the inner diameter, and the number of holes are appropriately determined depending on the fuel flow rate and the atomization condition, thereby reducing the amount of fuel blow-through, especially in a two-stroke engine. This makes it possible to improve fuel efficiency. Also, compared to conventional in-cylinder injection,
Overall, the structure is simplified, reliability is improved, and costs are reduced. Further, since only fuel is injected from the injector 56, the control program is simplified, and there is no need to increase the fuel pressure as in the conventional case. Since the small hole 52, which is the injection port for the fuel-air mixture, is opened and closed by the piston, there is no need for a small-sized injection valve, which is required in conventional in-cylinder injection. Also, the scavenging port 44
Since only air is supplied from , 46, fuel filling efficiency is improved. In particular, in this embodiment, since the small hole 52 is arranged above the third scavenging port 46, and only air is injected at high speed immediately after the small hole 52 opens during the scavenging stroke, the directivity of the third scavenging air can be improved. This also leads to an improvement in the scavenging effect as a whole. Furthermore, in a device equipped with a scavenging pump 32 as in this embodiment, even if the intake ratio is increased to reduce residual gas as much as possible, the amount of fuel blow-through can be kept lower than in the case of the conventional fuel injection type in the scavenging passage. becomes possible. Furthermore, in this example,
Compared to direct injection into the combustion chamber, the pressure inside the cylinder is low, so there is no need to increase the air pressure to assist fuel injection, and the amount of air is small, so it can be used as a pressure source for fresh air. Not limited to the supercharger of the above-mentioned embodiment,
Various types can be adopted.

Another example is a second example shown in FIGS. 2 and 3. The second embodiment differs from the first embodiment in that, in addition to the scavenging pump 32 of the first embodiment, exhaust pressure is used as a pressure supply source. That is, the exhaust port 5
An exhaust intake port 62 is formed in the cylinder sleeve 16 separately from the exhaust intake port 62 , and this exhaust intake port 62 is communicated with the main chamber 58 via an exhaust supply passage 64 . Note that a check valve 65 is provided at the entrance to the main chamber 58 to prevent backflow of exhaust gas.
is necessary.

Although the small hole 52 in the above embodiment functions as an injection port for mixing, it does not have to be a sleeve-shaped hole, and a cartridge 68 having an aperture as in the third embodiment shown in FIG. By attaching it to the fresh air supply path 40, the small hole 52 described above may be replaced. This makes it possible to freely select the aperture diameter of the injection port according to the specifications of the engine, and as in the above embodiment, the subchamber 5 has a small hole 52 and a passage cross-sectional area larger than the small diameter.
4 is not required to be formed integrally.

FIG. 5 shows a fourth embodiment of the present invention, and this embodiment differs from the first embodiment in that there is a separate injector 56 in the position of the third scavenging passage 42. This is where the sub-injector 70 is placed. According to this embodiment, it is possible to further improve the responsiveness during sudden acceleration or during a transitional period of acceleration/deceleration. The fresh air supply passage 40 extends closer to the cylinder head than the scavenging passage 42.

Next, FIG. 6 shows a fifth embodiment of the present invention, and this embodiment differs from the first embodiment in that crank chamber pressure is used as the pressure supply source. The structure of this embodiment is similar to a general crank chamber compression type two-stroke engine, and the fresh air supply path 40 opens into the crank chamber 14. In addition, the reference numeral 72 is a check valve, 73 is a lubricating oil pump, and 74 is a lubricating oil nozzle that opens on the downstream side of the check valve 72.

Next, as shown in the sixth embodiment shown in FIG.
The source of fresh air for scavenging and the source of fresh air for conveying the injected fuel may be different. In FIG. 7, the scavenging port 46 communicates with the crank chamber 14 via a rising passage 48, and the crank chamber 14 serves as a fresh air supply path for scavenging. The blower or scavenging pump 32 communicates only with the main chamber 58 as a source of fresh air for conveying the injected fuel, so the capacity of this blower may be small. code 102
103 is a lubricating oil supply pump, and 104 is a lubricating oil nozzle that is connected to the crankshaft. It supplies lubricating oil into the chamber 14.

[0020]

[Effect] As explained above, according to the present invention, a small hole is formed in the side wall of the cylinder, the small hole is connected to a pressure supply source, and a portion of the fresh air supply path has a passage cross-sectional area larger than the small hole. Since the fuel injection nozzle is placed in front of the fuel chamber, it is possible to avoid the complication of the structure and increase in cost, which were problems when injecting a mixture of fuel and air directly into the fuel chamber, and also to prevent fuel atomization. It has a great effect of improving.

Furthermore, since a chamber is provided between the pressure supply source and the fuel injection nozzle and a check valve is disposed in this chamber, various pressure supply sources can be used, and even if the pressure supply source is Even if the pressure fluctuates, it is possible to store high pressure in the chamber, which has the excellent effect of promoting fuel atomization.

[0022]

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a first embodiment of a fuel injection device for a two-stroke engine according to the present invention.

FIG. 2 is a sectional view of a main part showing a second embodiment of the present invention.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a sectional view of a main part showing a third embodiment of the present invention.

FIG. 5 is a sectional view of a main part showing a fourth embodiment of the present invention.

FIG. 6 is a sectional view showing a fifth embodiment of the present invention.

FIG. 7 is a schematic diagram showing a sixth embodiment of the present invention.

[Explanation of symbols]

32　Scavenging pump 38 Intake passage 40 Fresh air supply path 52 Small hole 56 Injector 58 Chamber 60 Check valve

Claims (3)

[Claims] Claim 1: A cylinder side wall is provided with a scavenging port and an exhaust port, the scavenging port is communicated with a fresh air supply source for scavenging, and a small hole is formed in the cylinder side wall, and the small hole is used to inject fresh air through the fresh air supply path. A fuel injection device for a two-cycle engine, wherein a fuel injection nozzle is communicated with a fresh air supply source for fuel conveyance and faces a portion of the fresh air supply path having a passage cross-sectional area larger than the small hole. Claim 2: In a two-stroke engine that has a scavenging port and an exhaust port on the cylinder side wall, and the scavenging port communicates with a fresh air pressure supply source, a small hole is formed in the cylinder side wall, and the small hole is used to supply fresh air. A fuel injection device for a two-cycle engine, wherein a fuel injection nozzle is communicated with the pressure supply source through a passageway, and a fuel injection nozzle faces a portion of the fresh air supply passageway having a passage cross-sectional area larger than the small hole. 3. A chamber is provided in the fresh air supply path between the pressure supply source and the fuel injection nozzle, and a reverse air gap is provided between the chamber and the pressure supply source that allows air to flow only from the pressure supply source toward the chamber. 3. The fuel injection system for a two-stroke engine according to claim 2, further comprising a stop valve.