JPH03117677A - Two cycle internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent injection of quantities of compressed air due to deterioration of atomization of injection fuel and reduction in a pressure in a combustion chamber by a method wherein when fuel is injected in a combustion chamber from an air blast valve, the pressure of compressed air is increased with the increase in a pressure in the combustion chamber. CONSTITUTION:When a feed valve 5 is opened, the interior of a surge tank 12 is communicated with the interior of a combustion chamber 4, and a scavenging pressure in the surge tank 12 attains a value approximately equal to a pressure in the combustion chamber 4. In this period, a compressed air pressure fed to an air blast valve 21 is regulated to a value approximately 3kg/cm<2> higher than a pressure in the combustion chamber 4 by means of a pressure regulator 22. Thus, when, during this period, the nozzle of the air blast valve 21 is opened to inject fuel in the combustion chamber 4, since a compressed air pressure is always regulated to a value higher by a proper pressure than that in the combustion chamber 4, atomization of injection fuel is prevented from worsening due to an increase in a pressure in the combustion chamber 4, and quantities of compressed air is prevented from being injected in the combustion chamber 4 from the air blast valve 21 as a result of a pressure in the combustion chamber 4 being reduced.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a two-stroke internal combustion engine.

[Conventional technology]

Conventionally, internal combustion engines have been known in which a so-called air blast valve that blows out fuel using compressed air is placed facing into a combustion chamber, and the compressed air supplied to the air blast valve is adjusted to a constant pressure by a pressure regulator. ing.

On the other hand, Japanese Patent Publication No. 63-500324 discloses that the pressure of compressed air supplied to the air blast valve that injects fuel into the combustion chamber is adjusted so that it is always higher than the fuel pressure by a constant pressure, and An internal combustion engine is disclosed in which the fuel pressure is increased when the engine reaches a predetermined rotational speed.

[Problem to be solved by the invention]

However, in the former type of conventional internal combustion engine, for example, when the pressure of compressed air is adjusted to a relatively low constant pressure, when the pressure inside the combustion chamber increases during fuel injection,
There is a problem that the atomization of the injected fuel worsens because the pressure difference between the pressure of the compressed air for injecting the fuel and the pressure inside the combustion chamber becomes small. Furthermore, if the pressure of compressed air is adjusted to a relatively high constant pressure, the injected fuel can be atomized well even if the pressure inside the combustion chamber increases during fuel injection, but the When the pressure in the chamber becomes low, a large amount of compressed air is injected into the combustion chamber from the air blast valve, resulting in problems such as the need for a large-capacity near compressor as a compressed air supply source.

On the other hand, in the internal combustion engine disclosed in Japanese Patent Application Publication No. 63-500324, the pressure of compressed air supplied to the air blast valve is not increased in accordance with the increase in pressure in the combustion chamber during fuel injection. Therefore, problems similar to those of the conventional internal combustion engine described above occur.

[Means to solve the problem]

In order to solve the above-mentioned problems, according to the present invention, an air blast valve for injecting fuel with compressed air is arranged facing into the combustion chamber, and a pressure adjustment mechanism is provided to adjust the pressure of the compressed air supplied to the air blast valve. Scavenging pressure is introduced into the combustion chamber, and the pressure of compressed air is increased in accordance with the increase in scavenging pressure, so that when the air supply valve is open, fuel injection into the combustion chamber is started from the air blast valve.

[Operation] When the intake valve is open, the scavenging pressure is almost equal to the pressure inside the combustion chamber, so when injecting fuel into the combustion chamber from the air blast valve, the pressure of compressed air is equal to the pressure inside the combustion chamber. It can be adjusted to increase according to the increase.

〔Example〕

Referring to FIG. 1, 1 is a cylinder block, 2 is a piston, 3 is a cylinder head, 4 is a combustion chamber, 5 is an intake valve,
6 is an air supply boat, 7 is an exhaust valve, 8 is an exhaust hoard, 9 is a spark plug, 10 is a crankcase, 11 is an intake manifold, 12 is a surge tank, 13 is an air cleaner, 14
1 and 2 show air supply pipes connecting the surge tank 12 and the air cleaner 13, respectively. In the middle of the air supply pipe 14, an air flow meter 15, a throttle valve 16, and a mechanical supercharger 17 are sequentially provided from the upstream side. The supercharger 17 pressurizes and pumps air flowing in from the air cleaner 13 in order to feed air into the combustion chamber 4 . Therefore, so-called scavenging pressure is supplied by the supercharger 17 to the air supply pipe 14, surge tank 12, intake manifold 11, and air supply boat 6 downstream from the supercharger 17, and this scavenging pressure causes the charge to be combusted. This will flow into the chamber 4. Air cleaner 1
A suction passage 18 is branched from the air supply pipe 14 between the compressor 3 and the air flow meter 150, and this suction passage 18 is connected to the suction port 19a of the near compressor 19. - On the other hand, the discharge port 19b of the near compressor 19 is connected to an air blast valve 21 via a discharge passage 20.
supply compressed air. The near compressor 19 is a vane type near compressor, and is rotationally driven by an engine. A pressure regulator 22 is connected in the middle of the discharge passage 2o. The pressure regulator 22 is connected within the crankcase 10 via a release air pipe 23 and into the surge tank 12 via a scavenging pressure conduit 24.

FIG. 2 shows an enlarged sectional view of the pressure regulator 22.

Referring to FIG. 2, the pressure regulator 22 is connected to the diaphragm 2
The first chamber 26 has a first chamber 26 and a second chamber 27 separated by a diaphragm compression spring 28. The first chamber 26 is connected to the surge tank 12 via the scavenging pressure conduit 24 and thus this first chamber 26
Scavenging pressure is introduced inside. On the other hand, a side portion of the second chamber 27 is connected to the discharge passage 20, and compressed air is introduced into the second chamber 27. A +7-square air pipe 23 is projected into the second chamber 27, and a ball valve 30 that is integrally displaced with the diaphragm 25 is provided opposite the opening 29 of the release air pipe 23. The pressure of the compressed air in the second chamber 27 is
A predetermined pressure than the internal scavenging pressure, e.g. 3kg/c
When I11 becomes high, the ball valve 30 opens the opening 29, whereby a portion of the compressed air is released into the crankcase 10 through the release air pipe 23. Therefore, the pressure in the discharge passage 20 is adjusted to be higher than the scavenging pressure in the surge tank 12 by, for example, 3 kg/caf.

The engine upper space 31 is communicated with the inside of the crankcase 10,
It also communicates with the air supply pipe 14 at a position upstream of the throttle valve 16 and near the throttle valve 16 via a blow-by gas discharge passage 32 . The compressed air released into the crankcase 10 via the release air pipe 23 is released into the air supply pipe 14 via the engine upper space 31 and the blow-by gas discharge passage 32, so that the pressure inside the crankcase 10 becomes excessive. It won't get any higher. In addition, the blow-by gas discharge passage 3
Blow-by gas discharged into the intake pipe 14 from 2 is sent into the combustion chamber 4 by the mechanical supercharger 17.
It will not be released into the atmosphere.

The air flow meter 15 generates an output voltage proportional to the amount of intake air, and the output voltage is determined by the electronic control unit) (lEc
tl) is input to 40. In addition, the crank angle sensor 3
3 generates an output pulse proportional to the engine speed, and this output pulse is also input to the electronic control unit 40. The fuel injection amount and the like are calculated within the electronic control unit 40 from these input signals. Further, the electronic control unit 40 is connected to a solenoid 50 of the air blast valve 21 and a fuel injection valve 56 (see FIG. 3), and controls these according to the engine operating state.

FIG. 3 shows a partially sectional side view of the air blast valve 21.

Referring to FIG. 3, a straightly extending needle insertion hole 42 is formed in the housing 41 of the air blast valve 21.
A needle 43 with a smaller diameter is inserted. A nozzle port 44 is formed at one end of the needle insertion hole 42, and the opening and closing of the nozzle port 44 is controlled by a valve portion 45 formed at the tip of the needle 43. In the embodiment shown in FIG. 3, this nozzle opening 44 is arranged within the combustion chamber 4. In the embodiment shown in FIG. Further, a spring retainer 46 is fixed to the needle 43, and a compression spring 4 is connected between the spring retainer 46 and the housing 41.
7 is inserted. Due to the spring force of this compression spring 47, the nozzle port 44 is normally closed by the valve portion 45 of the needle 43. A movable core 48 is always brought into contact with the end of the needle 43 on the opposite side to the valve portion 45 by the spring force of a compression spring 49, and a solenoid 50 and a stator for suctioning the movable core 48 are provided in the housing 41. 51 are arranged.

When the solenoid 50 is energized, the movable core 48 moves toward the stator 51, and as a result, the needle 43 moves in the direction of the nozzle port 44 against the spring force of the compression spring 47, so that the nozzle port 44 is opened. It will be done.

On the other hand, inside the housing 41 is a cylindrical nozzle chamber 52.
is formed. One end 52a of the nozzle chamber 52 is communicated with the discharge passage 20 of the near compressor 19, and the other end 52b of the nozzle chamber 52 is communicated with the needle insertion hole 42 via a compressed air outflow passage 55. A nozzle 57 of the fuel injection valve 56 is disposed within the nozzle chamber 52, and the nozzle 57 is located between one end 52a and the other end 52b within the nozzle chamber 52. As shown in FIG. 3, the compressed air outlet passage 55 extends straight. The nozzle 57 is arranged on the axis of the compressed air outflow passage 55, and fuel with a small spreading angle is injected from the nozzle 57 along the axis of the compressed air outflow passage 55. The compressed air outflow passage 55 extends obliquely to the needle insertion hole 42 in the direction of the nozzle opening 44 and is connected obliquely to the needle insertion hole 42 at an angle of 20 to 45 degrees with respect to the needle insertion hole 42. .

The needle insertion hole 42, the nozzle chamber 52, and the compressed air outflow passage 55 are connected to the near compressor 19 via the discharge passage 20.
(See Figure 1). Therefore, these needle insertion hole 42, nozzle chamber 52 and compressed air outflow passage 55
The inside is filled with compressed air. Fuel is injected into this compressed air from the nozzle 57 along the axis of the compressed air outflow passage 55. As shown in FIG.
5 is obliquely connected to the needle insertion hole 42, most of the injected fuel reaches the needle insertion hole 42 around the needle 43 near the valve portion 45. At this time, some of the fuel adheres to the inner wall surface of the compressed air outflow passage 55 and the inner wall surface of the nozzle chamber 52. Next, when the solenoid 50 is energized, the needle 43 opens the nozzle port 44. At this time, since the injected fuel is gathered near the valve portion 45, as soon as the needle 43 opens the nozzle port 44, both fuel and compressed air are injected from the nozzle port 44 into the combustion chamber 4. Furthermore, when the needle 43 opens the nozzle port 44, compressed air flows into the discharge passage 2.
0 into the nozzle chamber 52 and then passes through the compressed air outlet passage 55 toward the nozzle port 44, so that the fuel deposited on the inner wall surface of the compressed air outlet passage 55 and the inner wall surface of the nozzle chamber 52 is caused by the compressed air flow. carried away, nozzle port 4
It is made to erupt from 4. Therefore, as soon as the needle 43 opens, all of the injected fuel is ejected from the nozzle port 44, and then, when all of the injected fuel has been ejected, only compressed air is ejected from the nozzle port 4. Then, the solenoid 50 is deenergized and the needle 43 moves to the nozzle port 4.
Close valve 4.

Referring again to FIG. 1, the fuel injection valve 56 is connected to the fuel tank 35 via the fuel supply passage 34, and the fuel supply pump 36 is disposed in the middle of the fuel supply passage 34. Further, the fuel supply passage 34 is connected to a pressure regulator 37. This pressure regulator 37 is similar to the pressure regulator 22 shown in FIG. compressed air is introduced. Fuel is introduced into the second chamber 27 via the fuel supply passage 34. Further, the second chamber 27 is connected to the fuel tank 35 via a fuel return passage 39, and excess fuel is returned to the fuel tank 35. Therefore, the pressure of the fuel supplied to the fuel injection valve 56 is controlled by the pressure regulator 3.
The pressure of the fuel is controlled by the pressure of the compressed air introduced into the injector 7, and the pressure of the fuel is controlled to a predetermined pressure higher than the pressure of the compressed air, e.g. 2.5 kg/cn (as a result of this, the fuel injection valve 56 and the pressure of the compressed air in the nozzle chamber 52 and the compressed air outlet passage 55 (FIG. 3) are approximately constant, so that the fuel injection calculated by the electronic control unit 40 The amount can be precisely metered by the fuel injection valve 56.

FIG. 4 shows the opening period of the supply/exhaust valve 5.7 and the air blast valve 21. When the air supply valve 5 opens, the surge tank 1
The inside of the surge tank 12 is communicated with the inside of the combustion chamber 4, and as a result, the scavenging pressure inside the surge tank 12 becomes almost equal to the pressure inside the combustion chamber 4. Therefore, during this period, the compressed air pressure supplied to the air blast valve 21 is adjusted by the pressure regulator 22 to be approximately 3 kg/cat higher than the pressure within the combustion chamber 4. Therefore, during this period, the nozzle port 4 of the air blast valve 21
When valve 4 is opened and fuel is injected into combustion chamber 4,
Since the compressed air pressure is adjusted so that it is always higher than the pressure in the combustion chamber 4 by an appropriate pressure, for example, 3 kg/caf, the atomization of the injected fuel may become worse due to the increase in the pressure in the combustion chamber 4. By lowering the pressure within the combustion chamber 4, it is possible to prevent a large amount of compressed air from being injected into the combustion chamber 4 from the air blast valve 21. In FIG. 4, the nozzle port 44 is opened to inject fuel immediately after the exhaust valve 7 is closed and for a while after the intake valve 5 is closed. During this period, the scavenging pressure inside the combustion chamber 4 is The pressure is closest to that of .

As mentioned above, the fuel pressure is also varied in accordance with the variation in the pressure of the compressed air supplied to the air blast valve 21, so that the pressure difference between them is kept constant, so the amount of injected fuel can be accurately controlled. Can be weighed.

〔Effect of the invention〕

When injecting fuel into the combustion chamber from the air blast valve, the pressure of compressed air is increased in accordance with the increase in pressure within the combustion chamber, so even if the pressure within the combustion chamber increases during fuel injection, the injected fuel will not be It is possible to prevent deterioration of atomization, and even if the pressure inside the combustion chamber decreases during fuel injection, a large amount of compressed air is not injected into the combustion chamber from the air blast valve.

[Brief explanation of drawings]

Figure 1 is an overall view of a two-stroke internal combustion engine, Figure 2 is an enlarged cross-sectional view of the pressure regulator, Figure 3 is a partial cross-sectional side view of the air blast valve, and Figure 4 is a diagram of the supply/exhaust valve and air blast valve. FIG. 3 is a diagram showing valve opening periods and the like. 4... Combustion chamber, 5... Air supply valve, 12...
- Surge tank, 20...Discharge passage, 21...Air blast valve, 22...Pressure regulator, 24...Scavenging pressure conduit. Figure 2 Funeral map

Claims (1)

[Claims] An air blast valve that injects fuel with compressed air is arranged facing into the combustion chamber, and scavenging pressure is introduced to a pressure regulator for adjusting the pressure of the compressed air supplied to the air blast valve to increase the scavenging pressure. The two-stroke internal combustion engine is configured to increase the pressure of the compressed air accordingly, and to start fuel injection from the air blast valve into the combustion chamber when the intake valve is open.