JP3144782B2 - Cylinder direct injection two-stroke engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cylinder direct injection two-stroke engine.

[0002]

2. Description of the Related Art As a well-known two-stroke engine, there are a crankcase precompression two-stroke engine and a cylinder direct injection two-stroke engine. The former is a mixture of air and fuel in a crank chamber due to reciprocation of a piston. Is compressed in a crank chamber, the above-mentioned mixture is transferred to a cylinder working chamber and a combustion chamber in a scavenging stroke, and ignited in the combustion chamber. Oil) is sucked into a crank chamber, and the mixture is transferred from the crank chamber to a cylinder working chamber in a scavenging stroke, and mixed with fuel injected into a combustion chamber and a cylinder working chamber by a fuel injector in the cylinder working chamber. In this method, a mixture of air, fuel, and oil is formed, and the mixture is ignited and burned.

[0003]

In the former pre-compression type crankcase, scavenging is performed by using a mixture of air and fuel supplied from the crankcase. It is difficult to raise the above, and it is not easy to improve fuel efficiency.

On the other hand, in the latter cylinder direct injection type, fuel is injected at right angles to the combustion chamber separately from air, so that the fuel utilization efficiency is high, the output is improved, and the fuel consumption is also improved. However, since the back side of the piston (crank chamber side) only contacts the mixture of air and oil sucked into the crank chamber, even if the output is improved as a cylinder direct injection type, it is difficult to increase the output. The cooling inside the piston cannot keep up. That is, since oil is less likely to evaporate than fuel, efficient cooling by heat of vaporization cannot be expected.

[0005] As a prior art document of a two-stroke engine in which an annular sub-chamber is formed by forming a stepped inner peripheral surface of a piston and a cylinder, there is, for example, Japanese Patent Application Laid-Open No. 5-79338. However, the two-stroke engine described in this publication relates to a two-stroke engine having two cylinders having a phase difference of 180 °, in which air is once sucked into an annular sub-chamber by reciprocation of a piston. In this structure, air is supplied as air for combustion in the cylinder working chamber of the other cylinder.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the cooling performance and lubrication performance of a piston in a cylinder direct injection two-stroke engine and to increase the power accordingly.

[0007]

According to the first aspect of the present invention, a mixture of air and oil is sucked into a crank chamber by a reciprocating motion of a piston, and the mixture is swept from the crank chamber. In a cylinder direct injection two-cycle engine in which fuel is transferred to a cylinder working chamber through a pore and fuel is directly injected into a combustion chamber and a cylinder working chamber by a fuel injector, a piston has a stepped shape having a small diameter portion and a large diameter portion. The inner peripheral surface of the cylinder also has a stepped shape having a small-diameter inner peripheral surface and a large-diameter inner peripheral surface corresponding to the stepped piston, and an annular auxiliary is provided between the large-diameter inner peripheral surface of the cylinder and the small-diameter portion of the piston. A chamber is formed, and a cylinder is provided with a fluid inlet and a fluid outlet that open to the sub-chamber, and a piston reciprocates to suck a mixture of air and oil into the sub-chamber from the fluid inlet and from the fluid outlet. It is characterized in that it is to be out. As a result, during the rotation of the engine, the sub-chamber around the piston is filled with new air and oil which are exchanged every time the piston reciprocates, thereby directly cooling the piston and improving the cooling effect, and at the same time, the oil lubrication effect of the piston. Can also be expected.

[0008]

[0009]

[0010]

First Embodiment FIGS. 1 and 2 show a structure in which only air is supplied to a sub-chamber to be used for cooling a piston. Before describing the present invention, first, FIGS.
2, the basic structure of a cylinder direct injection two-cycle engine and the structure and operation when only air is used for cooling a piston will be described. An intake port 16 having a reed valve 17 is formed in the crankcase 1.
An exhaust hole 11 and a scavenging hole 14 that open to the cylinder working chamber 5 are formed in the exhaust hole 11, and an exhaust pipe 13 is connected to the exhaust hole 11,
The scavenging hole 14 communicates with the crank chamber 6 through a scavenging passage,
Both holes 11 and 14 open and close with respect to the cylinder working chamber 5 by raising and lowering the piston 30. A fuel injector 7 facing the combustion chamber 4 is attached to the cylinder head 3, and a spark plug 8 projecting into the combustion chamber 4 is attached to the cylinder head 3. Reference numeral 9 denotes a cooling water jacket, which is formed on each of the cylinder head 3, the cylinder 2, and the exhaust pipe 13. Reference numeral 39 denotes a connecting rod, 40 denotes a center of a crankshaft, and 41 denotes a crank web.

The intake port 16 of the crankcase 1 is connected with an intake pipe 20 and a throttle valve 21 which are curved upward, and an intake device 22 is connected above the throttle valve 21. The intake device 22 has a function of separating air and water and passing only air, and also has a function as an intake resonator. An oil ejection nozzle 25 faces in the middle of the intake pipe 21, and the oil ejection nozzle 25 is connected to an oil tank 27 via an oil pump 26.

A piston 30 arranged in the cylinder 2
Is formed in a stepped shape having a small-diameter portion 31 and a large-diameter portion 32 at the lower end. Correspondingly, the cylinder inner peripheral surface has a small-diameter inner peripheral surface 34 into which the small-diameter portion 31 fits. And a large-diameter inner peripheral surface 35 with which the large-diameter portion 32 fits, and has a stepped shape. An annular sub-chamber 37 is formed between the small-diameter portion 31 and the large-diameter inner peripheral surface 35. . It is sufficient that the large-diameter portion 32 has a length in the up-down direction that basically serves to close the lower end of the sub-chamber 37. A piston ring 18 for sealing the cylinder working chamber 5 and the like are fitted on the outer peripheral surface of the upper end portion of the small diameter portion 31, and a seal ring 19 for sealing the sub-chamber 37 is fitted on the outer peripheral surface of the large diameter portion 32. I have.

A structure for forcibly flowing air through the sub chamber 37 will be described. At the upper end of the large-diameter inner peripheral surface 35 of the cylinder 2, a fluid inlet 43 and a fluid outlet 4 opening to the annular sub-chamber 37 are provided.
6, the fluid inlet 43 is arranged on the same side as the intake port 16, and the fluid outlet 46 is arranged on the same side as the exhaust hole 13. A sub chamber suction pipe 44 having a check valve 45 is connected to the fluid inlet 43, and the sub chamber suction pipe 44 is connected to the throttle valve 21.
It communicates with the intake device 22 on the more upstream side. The check valve 45 is a reed valve, and is configured to block the flow of air from the sub-chamber 37 to the suction device 22 and to flow air from the suction device 22 to the sub-chamber 37.

A sub-chamber discharge pipe 48 having a check valve 47 is connected to the fluid outlet 46, and the sub-chamber discharge pipe 48 communicates with the exhaust hole 11. The check valve 47 is a reed valve, and is configured to block the flow of air from the sub chamber 37 to the exhaust hole 11 and to flow air from the exhaust hole 11 to the sub chamber 37.

The operation will be described. FIG. 1 shows a state where the piston 30 has been lowered to the bottom dead center position. The crank chamber 6 is compressed by the lowering of the piston 30, and the mixture of air and oil sucked into the crank chamber 6 passes through the scavenging holes 14. As a result, the combustion gas in the cylinder working chamber 5 is discharged to the exhaust holes 11 and the cylinder working chamber 5 is filled with fresh air and oil. At this time, since the sub-chamber 37 is in a negative pressure state, air is sucked into the sub-chamber 37 from the intake device 22 through the sub-chamber suction pipe 44 and the check valve 45. The check valve 47 on the sub chamber discharge pipe 48 side is closed. The outer peripheral surface of the piston 30 is forcibly cooled directly by the new air sucked into the annular sub-chamber 37, and the rise of the piston temperature is suppressed. The back side (lower side) of the piston 30 is also cooled by the mixture of oil and air in the crank chamber 6 as in the related art.

FIG. 2 shows a state in which the piston 30 has moved to the top dead center from the state shown in FIG. 1. The crank chamber 6 is in a negative pressure state due to the rise of the piston. The air sucked into the intake pipe 20 through the intake pipe 20 mixes with the oil from the oil injection nozzle 25 in the intake pipe 20, and is sucked into the crank chamber 6 via the reed valve 17. On the other hand, the sub-chamber 3
The air 7 is compressed, and the air sucked into the sub chamber 37 is discharged into the exhaust pipe 13 through the sub chamber discharge pipe 48 and the check valve 47. The air discharged into the exhaust pipe 13 also serves to cool and purify the exhaust gas. At this time, the check valve 45 in the sub chamber suction pipe 44 is closed.

In FIG. 1, the sub-chamber discharge pipe 48 is communicated with the exhaust pipe 13. However, the sub-chamber discharge pipe 48 may be communicated with the atmosphere instead, or may be returned to the intake device 22.

FIG. 3 is a longitudinal sectional view of a cylinder direct injection two-cycle engine to which the present invention is applied, based on the cylinder direct injection two-cycle engine as shown in FIGS. The structure other than the sub-chamber discharge pipe 48 and the intake pipe 20 is the same as that of FIG. 1, and the same components are denoted by the same reference numerals and overlapping description will be omitted. The sub chamber suction pipe 44 is
The fluid inlet 43 of the sub chamber 37 communicates with the crank chamber 6, while the sub chamber discharge pipe 48 is connected to the fluid outlet 46 of the sub chamber 37.
And the oil discharge port 49 of the intake pipe 20 are communicated via the extension pipe 48a. The oil discharge port 49 opens into the intake pipe 20 slightly downstream of the oil injection nozzle 25.

The operation will be described. FIG. 3 shows a state in which the piston 30 has been lowered to the bottom dead center position. When the piston descends, most of the mixture of air and oil in the crank chamber 6 is transferred to the cylinder working chamber 5 through the scavenging holes 14. ,
A part passes through the sub-chamber suction pipe 44 and the check valve 45, and the sub-chamber 37
To directly cool the outer peripheral surface of the piston and lubricate the piston 30. The check valve 47 of the sub chamber discharge pipe 48 is closed by the negative pressure in the sub chamber 37.

In the piston rising stroke shown in FIG. 4, the mixture of air and oil in the sub-chamber 37 is discharged to the sub-chamber discharge pipe 48, the check valve 47, the extension pipe 48a and the discharge nozzle 49.
And is returned into the intake pipe 20 via the intake pipe 20. In the intake pipe 20, fresh air and oil
The oil is mixed with the oil from the cylinder 5 and is sucked into the crank chamber 6 again via the reed valve 17. At this time, the check valve 45 of the fluid inlet 43 is closed.

In FIG. 3, a part or all of the mixture of air and oil discharged from the sub chamber discharge pipe 48 may be returned to the oil tank 27 as shown by a virtual line pipe 48b.

[0022]

Embodiment 2 FIG. 5 is a longitudinal sectional view of another cylinder direct injection type two-cycle engine to which the present invention is applied. FIG. 1 shows a sub chamber suction pipe 44, a sub chamber discharge pipe 48, and an intake pipe. 20 are different, and the other structures are the same. Therefore, the same parts are denoted by the same reference numerals, and redundant description is omitted.

The sub-chamber suction pipe 44 has the same structure as that shown in FIG. 3, and communicates the fluid inlet 43 of the sub-chamber 37 with the crank chamber 6 (near the suction port). Is
The fluid outlet 46 of the sub-chamber 37 and the oil tank 27 communicate with each other via an oil-gas separator 50. The oil-gas separation device 5
0 also has a cooler function.

The operation will be described. In the piston up stroke shown in FIG. 5, the mixture of air and oil in the sub-chamber 37 is supplied to the oil-gas separation device 50 via the sub-chamber discharge pipe 48, the check valve 47 and the extension pipe 48a. Gas separation device 50
After being separated into oil and air inside, the oil is cooled,
The oil is returned to the oil tank 27, and the air is discharged. At this time, the check valve 45 of the fluid inlet 43 is closed.

Although not shown, in the descending stroke, FIG.
When the piston descends, the mixture of air and oil in the crank chamber 6 is mostly transferred to the cylinder working chamber 5 through the scavenging holes 14, and a part of the mixture is supplied to the sub chamber suction pipe 44 and the check valve. The air is sucked into the sub-chamber 37 through 45 and cools the outer peripheral surface of the piston and lubricates the piston 30. At this time, the check valve 47 of the sub chamber discharge pipe 48 is closed by the negative pressure in the sub chamber 37.

[0026]

Reference Example FIGS. 6 and 7 show a reference example, in which the sub-chamber 37 is configured to suck a mixture of fuel and air. The structure other than the sub-chamber suction pipe 44 and the sub-chamber discharge pipe 48 is the same as that in FIG.

A sub-chamber suction pipe 44 connected to the fluid inlet 43 of the sub-chamber 37 is connected to an air and fuel supply device 52, and a sub-chamber discharge pipe 48 connected to the fluid outlet 46 is connected to a gas-liquid separation device. It is connected to a fuel tank 56 via 54 and a cooler 55. The fuel tank 56 and the intake device 22 are connected to the fuel and air supply device 52, respectively.

The operation will be described. FIG. 6 shows a state in which the piston 30 has been lowered to the bottom dead center position, and a mixture of fresh air and fuel is sucked into the sub chamber 37 from the air and fuel supply device 52. The check valve 47 on the sub chamber discharge pipe 48 side is closed. Since the fuel sucked into the sub-chamber 37 is not used for combustion, a small quantity is sufficient. The mixture of air and fuel cools the outer peripheral surface of the piston and
Lubricate 0. In this case, since the fuel is easily vaporized as compared with the oil, the piston 30 can be cooled using the heat of vaporization of the fuel, and the cooling effect is larger than that of the oil.

In the piston rising stroke shown in FIG.
7 is compressed, the air and fuel in the sub-chamber 37 flow through the sub-chamber discharge pipe 48 and the check valve 47 to the gas-liquid separation device 5.
The fuel discharged to the fuel tank 4 and separated is cooled by the cooler 55 and then returned to the fuel tank 56. Sub chamber suction pipe 44
Check valve 45 is closed.

[0030]

[Other Embodiments] (1) It is also possible to adopt a structure in which a mixture of air, oil and fuel is sucked into the sub-chamber 37. That is, the mixture of the above three is sucked into the crank chamber 6 from the intake pipe 20 during the piston up stroke, and from the crank chamber 6 to the sub chamber suction pipe 4 during the piston down stroke.
The air is sucked into the sub chamber 37 through the check valve 4 and the check valve 45.

(2) The check valves 45 and 47 disposed on the sub-chamber suction pipe 44 and the sub-chamber discharge pipe 48 include, in addition to the reed valve,
It is also possible to use various check valves such as a ball valve.

As described above, according to the present invention, the piston and the cylinder inner peripheral surface are each formed in a stepped shape, and an annular sub-chamber is formed between the small-diameter portion of the piston and the large-diameter inner peripheral surface of the cylinder. In the descending stroke, the mixture of air and oil is sucked into the sub chamber from the fluid inlet, the piston outer peripheral surface is directly forcibly cooled, and discharged from the fluid outlet in the piston ascending stroke. A piston cooling effect can be obtained, and a cooling effect and a lubrication effect by oil can be obtained, so that the output of the engine is improved.

[0033]

[0034]

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a cylinder direct injection two-cycle engine.

FIG. 2 is a longitudinal sectional view of the same cylinder direct injection two-cycle engine as in FIG. 1 shown in a top dead center state.

FIG. 3 is a longitudinal sectional view of a cylinder direct injection two-cycle engine to which the present invention is applied.

FIG. 4 is a longitudinal sectional view of the same cylinder direct injection type two-stroke engine as in FIG. 3 shown in a top dead center state.

FIG. 5 is a longitudinal sectional view of another cylinder direct injection two-cycle engine to which the present invention is applied.

FIG. 6 is a longitudinal sectional view of a cylinder direct injection two-cycle engine showing a reference example.

FIG. 7 is a longitudinal sectional view of the same cylinder direct injection two-cycle engine as in FIG. 6 shown in a top dead center state.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crankcase 2 Cylinder 3 Cylinder head 4 Combustion chamber 5 Cylinder working chamber 6 Crank chamber 7 Fuel injector 8 Ignition plug 11 Exhaust hole 13 Exhaust pipe 14 Scavenging hole 16 Intake port 20 Intake pipe 22 Intake device 25 Oil injection nozzle 26 Oil pump 27 Oil tank 30 Piston 31 Small diameter part 32 Large diameter part 34 Small diameter inner peripheral surface 35 Large diameter inner peripheral surface 37 Annular sub chamber 43 Fluid inlet 44 Sub chamber suction pipe 45 Check valve 46 Fluid outlet 47 Check valve 48 Sub chamber discharge tube

Continuation of front page (56) References JP-A-1-301936 (JP, A) JP-A-58-143120 (JP, A) JP-A-5-106456 (JP, A) JP-A-5-79338 (JP, A) , A) Japanese Utility Model Showa 62-26524 (JP, U) Japanese Utility Model Showa 58-1729 (JP, U) Japanese Patent Publication No. 29-4857 (JP, B1) Japanese Patent Publication No. 51-44249 (JP, B2) 60-9365 (JP, Y2) (58) Fields investigated (Int. Cl. ⁷ , DB name) F01M 3/00 F02B 23/10 F02B 25/16 F02F 1/20

Claims (1)

(57) [Claims] 1. A reciprocating motion of a piston draws a mixture of air and oil into a crank chamber, transfers the mixture from the crank chamber to a cylinder working chamber via a scavenging hole, and uses a fuel injector to transfer fuel to the combustion chamber and the fuel chamber. In a cylinder direct injection two-cycle engine that directly injects into a cylinder working chamber, the piston has a stepped shape having a small-diameter portion and a large-diameter portion, and the inner peripheral surface of the cylinder is larger than the small-diameter inner peripheral surface corresponding to the stepped piston. A stepped shape with a radial inner peripheral surface, an annular sub-chamber is formed between the large-diameter inner peripheral surface of the cylinder and the small-diameter portion of the piston, and the cylinder is provided with a fluid inlet and a fluid outlet that open to the sub-chamber. A cylinder direct injection two-cycle engine, wherein a mixture of air and oil is sucked into the sub-chamber from a fluid inlet by a reciprocating motion of a piston and discharged from a fluid outlet. gin.