JP2789443B2 - 2 cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-stroke engine (two-stroke cycle engine) having a cooling mechanism such as a piston, and more particularly to a high-power type two-stroke engine fuel supply device.

[0002]

2. Description of the Related Art An example of this type of two-stroke engine is the engine described in Japanese Utility Model Laid-Open No. 60-194149. In this engine, although not shown, a cooling fin is provided on the inner surface of the piston head, and a through hole extending from the inside of the piston to the outer periphery of the piston is provided between the piston head and the boss of the piston pin hole. And a mixture passage for communicating the through hole with the crank chamber. According to this structure, a large amount of air-fuel mixture flows between the crank chamber and the inside of the piston through the scavenging passage with the through-hole facing the outlet of the scavenging passage during operation of the engine. Flows into the piston and contacts the cooling fins, thereby cooling the piston head.

[0003]

However, the two-stroke engine described in the above publication has room for improvement in the following points.

[0004] Since the piston is cooled by using the air-fuel mixture which flows into the crankcase (crank chamber) and has a slightly increased temperature, the cooling efficiency is poor.

To increase the output of a two-cycle engine, it is effective to increase the opening width of the exhaust port. However, if the opening width is too large, the piston ring and the piston may protrude outward from the exhaust port. There is. As a countermeasure, there is a method of providing a rib at the center of the exhaust port.In this case, the surface pressure of the contact area between the piston ring and the piston and the rib increases, and the rib is easily worn, and the rib is heated at a high temperature. Exposed to the exhaust gas, the ribs may be deformed.

A two-cycle engine generally has the following problems. In other words, when the engine output is promoted, the number of explosions is twice as large as that of a four-cycle engine (one explosion per engine revolution), and the heat load on the piston is high, resulting in insufficient cooling. If so, the piston may be seized.

In order to lean (lean) the air-fuel mixture in order to achieve low fuel consumption, the temperature of the air-fuel mixture gradually increases under normal conditions (leaning when the air / fuel concentration is higher than the stoichiometric mixture ratio). As the frequency increases, it is difficult to reduce fuel consumption because the frequency of occurrence of the above increases.

The present invention has been made in view of the above points, and 1) to improve the durability and reliability of a piston, particularly in a high-power two-stroke engine, and 2) to make the air-fuel mixture lean. The objectives are to achieve low fuel consumption and 3) to improve the lubricity of the ribs and prevent thermal deformation in a two-stroke engine with ribs at the exhaust port.

[0009]

Means for Solving the Problems] 2-cycle engine of the present invention to solve the aforementioned problem, the central portion of the exhaust port
In a two-stroke engine with vertical ribs,
Piston with a vertical slit narrower than the width of the rib
Formed at a position corresponding to the rib on the side peripheral surface of the piston head, an injection nozzle penetrates from the outside to the inside of the cylinder portion , and the injection nozzle is provided at an inner surface of the piston head at or near the top dead center of the piston. is inclined upwardly toward Rutotomoni, said pin
With the stone moved near the top dead center, the injection nozzle
So as to face the inside of the piston through the slit ,
A part of the fuel or a part of the air-fuel mixture supplied to the crankcase is injected from the injection nozzle to the inner surface of the piston head and the slit without passing through the crankcase.
The piston and the slit are cooled by radiating .

According to a second aspect of the present invention, a fuel injection device is provided in an intake pipe connected to the crankcase via a check valve, and a fuel supply unit of the fuel injection device is connected to the injection nozzle. Is preferred.

According to a third aspect of the present invention, the fuel injection device is provided.
Fuel supply unit and the injection nozzle are connected via a check valve
More preferably,

According to the two-stroke engine having the above structure, when the piston moves to or near the top dead center, the suction force generated during the movement or the injection force of the fuel injection device. , A part of the fuel or a part of the mixture immediately before being supplied to the crankcase
Fuel or mixture from the injection nozzle through the slit in the piston
Aiki is injected into the inner surface of the piston,
It is also injected toward the rib near the lit and the exhaust port.
You. Therefore, the fuel injected to the inner surface of the piston head is vaporized and cooled around the piston head, thereby suppressing the temperature rise of the entire piston. Ma
Not only the piston cools, but also the rib cools
Thermal deformation is suppressed and the fuel injected into the ribs
Lubrication between piston and piston ring
And the wear of the ribs is reduced. In the present invention, fuel or air-fuel mixture before being supplied to the crankcase is injected. However, since their temperature is considerably lower than that supplied to the crankcase, the cooling effect of the piston is high and the piston is effectively Cooled. On the other hand, during exhaust, the piston
It descends to the bottom dead center, but the injection nozzle is on the side wall of the piston
Fuel is injected from the injection nozzle
Never.

[0013] In the two-cycle engine according to the second aspect,
Since the fuel is forcibly injected into the inner surface of the piston head by the injection force of the fuel injection device without depending on the suction force (suction force) when the piston moves to the vicinity of the top dead center, the piston can be efficiently cooled.

[0014] In the two-stroke engine according to the third aspect,
While the piston descends, the air-fuel mixture is reversed from the injection nozzle.
Even if you try to flow, the check valve
Flow is blocked.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a two-stroke engine according to the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view schematically showing a main part of a two-cycle engine according to the present embodiment, in which a piston is raised near a top dead center. FIG. It is sectional drawing which shows roughly the state which fell to the vicinity of a bottom dead center. FIG. 3 is a sectional view taken along line III-III in FIG. 2, and FIG. 4 is a perspective view showing a piston.

As shown in FIGS. 1 and 2, the two-stroke engine 1 has a cylinder head 2a at the upper end of a cylinder 2.
Are integrally fastened with bolts 2b, and the crankcase 3 is integrally formed at the lower end of the cylinder 2 with a general structure.
A crank 4 is rotatably supported by a crankshaft 4 a in the crankcase 3, and a piston pin 5 a of a piston 5 slidably disposed in the cylinder 2 and the crankshaft 4 a are connected via a connecting rod 6. Are linked. The inside of the cylinder 2 and the inside of the crankcase 3 are communicated by a plurality of scavenging passages 7, and a scavenging port 7 a at the upper end of each scavenging passage 7 (FIG. 2) faces the inside of the cylinder 2.

An exhaust port 8 is formed at a position slightly higher than each of the scavenging ports 7a of the cylinder 2, and a rib 9 is formed vertically at the center of the exhaust port 8. A cylinder liner 10 is mounted on the inner peripheral wall of the cylinder 2 and the inner wall of the rib 9. One end of an intake pipe 11 is connected to the crankcase 3, and a reed valve 12 is provided at an inlet (intake port) thereof.
Is interposed. A fuel injection device 13 is provided in the intake pipe 11. In this example, air sucked and supplied into the intake pipe 11 through an air cleaner (not shown) connected to the downstream side of the intake pipe 11 and a fuel injection device 13 of the fuel injection device 13. Fuel injected from a fuel supply unit (not shown) is mixed in the intake pipe 11 and injected into the crankcase 3 as an air-fuel mixture.

The two-stroke engine according to the present invention has the following characteristic configuration. That is, as shown in FIG. 4, the skirt portion 5 'of the piston 5 is formed with a vertically oriented slit 15 therethrough. This slit 15
As can be seen from FIG. 3, the rib 9 is disposed at a position smaller than the width of the rib 9 and corresponding to the rib 9. For this reason, when the piston 5 is located above the exhaust port 8, the slit 1
The exhaust port 8 is closed by the piston 5 because the rib 5 is covered with the rib 9.

Also, as shown in FIG.
Immediately below the position, the fuel injection nozzle 16 penetrates the lower peripheral wall 2 c of the cylinder 2, and is disposed obliquely upward with the nozzle tip 16 a facing the inside of the cylinder 2.
As shown in FIG. 1, the direction of the injection nozzle 16 is set so that the injection is substantially uniformly performed on the cooling fins 5c formed on the inner surface of the piston head 5b when the piston 5 reaches the vicinity of the top dead center. I have. The base end of the injection nozzle 16 is connected to a fuel supply unit (not shown) of the fuel injection device 13 by a fuel supply pipe 17, and a check valve 18 is provided between the fuel supply pipe 17 and the injection nozzle 16. Is interposed. Then, a part (for example, 10 to 20%) of the fuel injected from the fuel injection device 13 is injected through the injection nozzle 16 to the inner surface of the piston head 5b and its periphery. Also,
In this example, the inner surface of the rib 9 (the liner 1
Fuel is also injected to 0).

In this embodiment, the fuel is supplied from the fuel injection device 13 to the injection nozzle 16. Alternatively, the fuel is injected into the intake pipe 11 from the fuel supply section of the fuel injection device 13.
A part (for example, 15%) of a so-called air-fuel mixture mixed with air may be supplied to the injection nozzle 16 by the fuel supply pipe 17 and injected to the inner surface of the head 5b of the piston 5. 1 and FIG.
Denotes a spark plug, 22 denotes a water jacket of the cylinder 2, and 23 denotes a water jacket of the cylinder head 2a. Reference numeral 24 in FIG. 4 indicates a piston pin hole.

Next, the operation of the two-stroke engine 1 according to the present embodiment configured as described above will be described.

As shown in FIG. 1, when the piston 5 rises in the cylinder 2 from near the bottom dead center (FIG. 2), fuel is injected from the fuel injection device 13 into the intake pipe 11 and mixed with air. , The reed valve 12 opened as an air-fuel mixture
From the crankcase 3. At the same time, a part of the fuel is sent from the fuel injection device 13 to the injection nozzle 16 through the fuel supply pipe 17, and from the injection nozzle 16, the cooling fins 5 c and the ribs on the inner surface of the piston head 5 b pass through the slit 15 of the piston 5. 9 (Liner 1
0). As a result, the piston head 5b and the rib 9 are cooled by the latent heat effect when the fuel is vaporized. Further, since the fuel injected to the inner surface of the rib 9 also functions as a lubricant, the friction between the rib 5 and the piston 5 or a piston ring (not shown) is reduced.

During this time, the air-fuel mixture that has flowed into the crankcase 3 flows from the scavenging passage 7 above the piston 5 in the cylinder 2 and is gradually compressed by the rising piston 5 so that the piston 5 reaches the top dead center. Spark plug 21
Is ignited and explodes.

When the piston 5 starts descending and the exhaust port 8 opens, exhaust gas is discharged from the exhaust port 8. Then, the piston 5 descends to the bottom dead center. In this state, the injection nozzle 16 is closed by the piston 5 as shown in FIG. Even if the air-fuel mixture or the like tries to flow backward from the injection nozzle 16 while the nozzle 5 moves downward, the check valve 18 prevents the fuel mixture 13 from flowing back.

The injection timing and the injection amount of the fuel injected from (the fuel supply unit of) the fuel injection device 13 are controlled based on an injection map created for each engine. That is, the injection timing and the injection amount of the fuel or air-fuel mixture injected from the injection nozzle 16 via the fuel injection device 13 are controlled based on, for example, the throttle valve, the engine speed, and the engine temperature. Thereby, the cooling of the piston 5 is performed more efficiently.

Although one embodiment of the two-stroke engine of the present invention has been described above, the present invention can be implemented as follows.

A) A carburetor (not shown) is connected to the intake pipe 11 without the fuel injection device 13, and
A part of the air-fuel mixture introduced into the inside can be injected from the injection nozzle 16 toward the inner surface of the piston head 5b by using the suction force generated when the piston 5 moves up in the cylinder 2.

B) An engine having a structure in which the exhaust port 8 is not provided with the rib 9, and
The same can be applied to the case where no is provided. In this case, for example, the injection nozzle 16 is displaced in the circumferential direction from the exhaust port 8 to form a semicircular cutout (reference numeral 5 ″ in FIG. 1) formed below the skirt 5 ′ of the piston 5. ), And the direction of the injection nozzle 16 is directed toward the inner surface of the piston head 5b.

C) The direction of the injection nozzle 16 is not necessarily limited to the inner surface of the piston head 5b at the top dead center of the piston 5 but before the piston 5 reaches the top dead center (however, the cylinder is shifted from the middle position of the stroke of the piston 5 to the cylinder). Head 2a
It may be directed to the inner surface of the piston head 5b at the position (close). Note that, in claim 1, "the top dead center of the piston or its vicinity" is expressed, but "the vicinity" corresponds to this example.

[0031]

As is apparent from the above description,
The two-stroke engine of the present invention has the following effects.

(1) The cooling efficiency of the piston is higher than in the prior art, and the rise in the temperature of the piston is effectively suppressed.
The durability of the piston is improved, the reliability is improved, and the mixture is easily made lean, so that low fuel consumption is easily achieved. Ma
Not only the piston cools, but also the rib cools
Thermal deformation is suppressed and the fuel injected into the ribs
Lubrication between piston and piston ring depending on material
Performance and rib wear is reduced.

(2) In the two-stroke engine according to the second aspect, since the fuel or the air-fuel mixture is forcibly injected toward the inner surface of the piston head by the injection force of the fuel injection device, the piston is efficiently cooled. .

(3) In the two- cycle engine according to the third aspect, while the piston descends, the air-fuel mixture or the like is injected from the injection nozzle.
To the fuel injection device by the check valve
Backflow is prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a main part of a two-stroke engine according to one embodiment of the present invention, showing a state where a piston has risen to a position near a top dead center.

FIG. 2 is a cross-sectional view schematically showing a state where a piston of the two-stroke engine of FIG. 1 is lowered to a position near a bottom dead center.

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

FIG. 4 is a perspective view showing a piston used in the two-stroke engine of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 2 cycle engine 2 Cylinder 3 Crankcase 5 Piston 5b Piston head 8 Exhaust port 9 Rib 11 Intake pipe 13 Fuel injection device 15 Slit 16 Injection nozzle 17 Fuel supply pipe 18 Check valve

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02B 25/16 F02B 25/16 R F02F 1/22 F02F 1/22 C 3/22 3/22 Z F02M 61/14 310 F02M 61 / 14 310Z 69/00 63/00 P // F02M 63/00 69/00 320F (56) Reference JP-A-62-111161 (JP, A) JP-A-3-260373 (JP, A) JP-A 2-140460 (JP, A) JP-A-5-256229 (JP, A) JP-A-3-57876 (JP, A) JP-A-2-123278 (JP, A) A) (58) Field surveyed (Int. Cl. ⁶ , DB name) F02M 69/10 F02M 69/00 320 F02M 61/14 F02M 63/00 F01P 3/08 F02F 3/22 F02F 1/22 F02B 23 / 08 F02B 25/16

Claims (3)

(57) [Claims] 1. A vertical rib is provided at a central portion of an exhaust port.
In a two-cycle engine, a vertical slit narrower than the width of the rib
Formed at a position corresponding to the rib on the side peripheral surface of the cylinder , and an injection nozzle penetrates from the outside to the inside of the cylinder portion.
When the elevation nozzle Ru is inclined upward toward the inner surface of the piston head in the dead center or near the top of the piston
In both cases, with the piston moved near TDC,
The injection nozzle is inserted into the piston through the slit.
So as to face, injection a part of some or mixture of the fuel supplied to the crankcase, from the injection nozzle without passing through the crankcase to the inner surface and the slit portion of the piston head
A two-stroke engine characterized in that the piston and the slit are cooled by radiating . 2. A fuel injection device is provided in an intake pipe connected to the crankcase via a check valve, and a fuel supply unit of the fuel injection device and the injection nozzle are connected.
A two-stroke engine as described. 3. A fuel supply unit of the fuel injection device and the fuel injection unit.
The injection nozzle is connected via a check valve to the injection nozzle.
On-board two-stroke engine.