JP2002206424A - Air-cooled two-stroke cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air-cooled two-stroke cycle engine capable of improving the cooling performance thereof, without enlarging the size of an engine proper. SOLUTION: An air introducing plate 15 is installed on the upper end part of a cylinder 1. The air introducing 15 has a clearance L in the clearance thereof from the inner surface of a cover 14, and is provided with a curved part 20, which is projected from the side part of the cylinder 1 to the outside of a cooling fan 8 and is curved downward, gradually toward the end of the engine proper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-cooled two-stroke engine used for brush cutters and the like.

[0002]

2. Description of the Related Art Conventionally, for example, in a two-stroke engine used for a working machine such as a brush cutter, a cooling air generated by a cooling fan attached to one end of a crankshaft and driven by rotation of the crankshaft is generated. A method of cooling a cylinder and a spark plug by using the same is adopted.

This air-cooled two-stroke engine has a cover attached to cover the upper part of the engine including the cylinder and the cooling fan. By sending the cooling air, the cylinder and the spark plug are cooled.

[0004]

However, in the above-mentioned conventional air-cooled two-cycle engine, since the cooling effect of the cylinder and the spark plug portion is not always sufficient, problems such as port blockage by a ring stick or carbon occur. In some cases, it is necessary to further improve the cooling effect.

For this reason, it has been studied to increase the diameter of the cooling fan or to improve the cooling performance by improving the muffler-side and carburetor-side air guide plates. This is a problem in that the size is increased, and sufficient improvement in cooling performance has not been achieved only by improving the air guide plates on the muffler side and the carburetor side.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide an air-cooled two-stroke engine that can improve the cooling performance of an engine without enlarging the engine body. I do.

[0007]

According to a first aspect of the present invention, there is provided an air-cooled two-stroke engine, comprising: a cooling fan (8) provided at an end of a crankshaft (6); (1) and the cooling fan (8)
And a cover (14) for covering the cooling fan (8).
An air-cooled two-stroke engine, which guides the cooling air sent by the engine to a discharge port (14a) through a cooling air passage formed by an inner surface of the cover (14) and an outer surface of the cylinder (1). A wind guide plate (15) is provided at the upper end of the cylinder (1), and the wind guide plate (15)
A protrusion (L) protrudes outward from the side of the cylinder (1) toward the cooling fan (8) so as to form a gap (L) with the inner surface of the cover (14), and gradually lowers toward the end. And a bending portion (20) that bends as described above.

According to the first aspect of the present invention, the engine is cooled by sending cooling air to a cooling air passage formed by the inner surface of the cover and the outer surface of the cylinder by a cooling fan. The distribution of the cooling air in the cooling air passage is controlled by the air guide plate to improve the cooling efficiency.

That is, the air guide plate according to the present invention has a curved portion that protrudes outward from the side of the cylinder toward the cooling fan and is gradually curved downward toward the end. A part of the cooling air sent upward by the fan is efficiently collected by the curved portion of the baffle plate, reaches the outlet through the upper end of the cylinder, and is discharged from the engine to the outside of the engine. Therefore, cooling of the upper end of the cylinder, that is, the vicinity of the combustion chamber and the vicinity of the spark plug is effectively performed.

Further, since the air guide plate protruding outward from the side of the cylinder acts as a resistance to the rising cooling air, the amount of air guided to the discharge port through the side of the cylinder increases. As a result, the cooling efficiency of the side portion of the cylinder is also improved.

Further, the air guide plate according to the present invention is
The cooling fan protrudes so as to form a sufficient gap with the inner surface of the cover to allow a part of the cooling air rising by the cooling fan to blow through the air guide plate. This gap can prevent the cooling air from stagnating due to a decrease in the cross-sectional area of the cooling air passage, so that the cooling air can be fully used.

According to a second aspect of the present invention, in the air-cooled two-stroke engine according to the first aspect, the wind guide plate (15) has a downwardly extending laterally extending lower portion on both sides thereof. 17, 17).

According to the second aspect of the present invention, since the air guide plate is provided with the downwardly extending lower portions on both sides thereof, the gap between the upper end of the cylinder and the air guide plate is reduced. The flowing cooling air can be prevented from diverting to the side, and the cooling effect of the upper end of the cylinder can be further improved.

According to a third aspect of the present invention, in the air-cooled two-stroke engine according to the second aspect, the air guide plate (15) is provided with a spark plug (10, 17) for each of the side hanging portions (17, 17). ) Side, is provided with a spark plug side hanging portion (18, 18) extending downward and inclined toward the spark plug (10).

According to the third aspect of the present invention, since the ignition plug side of each side hanging portion is provided with the ignition plug side hanging portion inclined toward the ignition plug, cooling air is directed to the ignition plug. It is possible to concentrate and cool the spark plug more effectively.

[0016] The reference numerals in parentheses in the above denote the corresponding elements in the drawings for convenience.
Therefore, the present invention is not limited to the description on the drawings. The same applies to the description in the column of “Claims”.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2, the air-cooled two-cycle engine according to the present embodiment includes a cylinder 1 having a multi-stage fin 1a formed on an outer peripheral portion. One side of this cylinder 1 in the left-right direction (inlet side)
, A carburetor 2 is attached, and on the other side (exhaust port side), a muffler 3 is attached. A crankshaft 6 extending in the front-rear direction of the engine is connected via a connecting rod 5 to a piston 4 fitted into the cylinder 1 from below. A recoil starter 7 is attached to one end of the crankshaft 6,
A cooling fan 8 and a power take-out unit 9 are attached to the other end.

Further, an ignition plug 10 is screwed obliquely into the upper portion of the cylinder 1 on the side of the recoil starter 7, and the ignition plug 10
It is electrically connected to an ignition coil 11 fixed to the side. Further, a fuel tank 13 is attached to a lower side of the crankcase 12 which is joined to a lower portion of the cylinder 1 and houses the crankshaft 6. The fuel in the fuel tank 13 is supplied to the cylinder 1 via the carburetor 2.

A cover 14 is attached to the crankcase 12 so as to cover the cylinder 1 and the cooling fan 8, and a cooling air from the cooling fan 8 is formed by a gap between an inner surface of the cover 14 and an outer surface of the cylinder 1. A cooling air passage that passes therethrough is formed. The cover 14 is provided with a plurality of cooling air outlets 14 a extending from a position facing the side of the cylinder 1 above the recoil starter 7 to a position obliquely above the cylinder 1.

On the side of the cooling fan 8 at the upper end of the cylinder 1,
A wind guide plate 15 made of a metal such as a cold rolled steel plate (SPCC) is attached. This wind guide plate 15
As shown in FIG. 3 and FIG. 4, the top plate 16 is formed in a dish-like shape in a prone state,
7 and a spark plug side hanging portion 18.

The top plate 16 has a shape in which the tip of a piece of the general shogi is cut off in a square shape in plan view. The top plate 16 will be described in more detail. The end of the top plate 16 on the side of the spark plug 10 has a central portion protruding toward the ignition plug 10 in a mountain shape. Are cut out in a square shape, whereby arm portions 19 and 19 are formed on both sides of the ignition plug 10 so as to sandwich the ignition plug 10. Each tip portion of each of the arms 19, 19 is formed so as to gradually project toward the end as approaching the spark plug 10.

A curved portion 20 is formed at an end of the top plate 16 opposite to the spark plug 10 so as to bend gradually downward toward the end. This curved portion 20
Protrudes outward from the side of the cylinder 1 toward the cooling fan 8. A gap L is provided between the upper surface of the curved portion 20 and the inner surface of the cover 14. The gap L is set to such a size that a part of the cooling air can be blown over the wind guide plate 15. Note that reference numeral 20a
Is a bulging portion formed at the end of the curved portion 20 so as to protrude upward. The bulging portion 20a is provided to avoid interference with the ignition coil 11 and the like.

The side hanging parts 17, 17 are respectively
6 extend vertically downward from both side edges and are shaped like a knife in a side view. Each of the spark plug side hanging portions 18, 18 extends vertically downward from the distal end edge of each arm of the top plate 16, and is connected to each side hanging portion 17, respectively. It is formed in a rectangular shape, whereby each of the spark plug side hanging portions 18, 18 is inclined toward the spark plug 10.

In the air guide plate 15, bolts 21 are inserted through through holes formed in the center of the top plate 16, and the bolts 21 are screwed into female screws 22 formed in the cylinder 1, so that the cylinder 1 Mounted on top.

In the air-cooled two-stroke engine constructed as described above, as shown by arrows in FIGS. 1, 3 and 4, the cooling fan 8 draws in the cooling air which is sucked from the outside of the engine and rises. A part is efficiently collected by the lower surface of the curved portion 20 of the top plate 16 of the wind guide plate 15, and the top plate 16 of the wind guide plate 15,
7 and 17 and the spark plug side hanging portions 18 and 18, and the space is filled with the discharge port 1 of the cover 14.
When the cooling air proceeds toward 4a, the upper end of the cylinder 1 is cooled. Thereafter, the cooling air is collected around the spark plug 10 by the spark plug side hanging portion 18 to cool the spark plug 10, and thereafter, the notch between the two arms 19 of the top plate 16 of the air guide plate 15. Through the outlet 14a of the cover 14 and is discharged from the engine through the outlet 14a. Therefore, cooling of the upper end portion of the cylinder 1, that is, the vicinity of the combustion chamber and the vicinity of the spark plug 10 can be effectively performed.

A part of the cooling air that has risen by the cooling fan 8 passes through the side of the cylinder 1 and is
a, the curved portion 20 of the top plate 16 of the air guide plate 15 provided to protrude laterally from the upper end of the cylinder 1 acts as a resistance to the rising cooling wind. The amount of cooling air guided to the discharge port 14a through the passage increases, and the cooling effect on the side of the cylinder 1 is improved.

Further, part of the cooling air that has been raised by the cooling fan 8 passes through the gap L between the upper surface of the curved portion 20 of the top plate 16 of the air guide plate 15 and the inner surface of the cover 14, and the outlet of the cover 14. It is led to 14a. The gap L allows a part of the cooling air rising by the cooling fan 8 to flow through the air guide plate, thereby preventing the cooling air from stagnating due to a decrease in the cross-sectional area of the cooling air passage. And the cooling air can be fully used.

[0028]

As described above, according to the present invention,
The amount of cooling air at the upper end of the cylinder can be increased without stagnation of the cooling air sent by the cooling fan, so that the upper end of the cylinder, that is, the vicinity of the combustion chamber and the vicinity of the ignition plug can be effectively cooled. it can. Therefore, the cooling performance of the engine can be improved without increasing the size of the engine body.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an air-cooled two-stroke engine according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a plan view of a portion including a wind guide plate according to the present invention.

FIG. 4 is a side view of a portion including a wind guide plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder 1a Fin 2 Carburetor 3 Muffler 4 Piston 5 Connecting rod 6 Crankshaft 7 Recoil starter 8 Cooling fan 9 Power take-out part 10 Ignition plug 11 Ignition coil 12 Crankcase 13 Fuel tank 14 Cover 15 Wind guide plate 16 Top plate 17 Side droop Part 18 Spark plug side hanging part 19 Arm part 20 Curved part 20a Swelling part 21 Bolt 22 Female screw

Claims (3)

[Claims] 1. A cooling fan (8) provided at an end of a crankshaft (6), and a cover (14) for covering the cylinder (1) and the cooling fan (8), wherein the cooling fan (8) is provided. (2) an air-cooled two-stroke engine that guides the cooling air sent by the cooling air passage to a discharge port (14a) through a cooling air passage formed by an inner surface of the cover (14) and an outer surface of the cylinder (1); A wind guide plate (15) is provided at the upper end of the cylinder (1), and the wind guide plate (15) is provided with a cover (14).
It protrudes outward from the side of the cylinder (1) to the side of the cooling fan (8) so as to form a gap (L) between the inner surface and the inner surface, and curves gradually downward toward the end. An air-cooled two-stroke engine comprising a curved portion (20). 2. The air guide plate (15) has a downwardly extending side portion (17, 1) extending downward on both sides thereof.
7. The air-cooled two-stroke engine according to claim 1, further comprising: (7). 3. The air guide plate (15) extends downwardly toward the spark plug (10) of each of the side hanging portions (17, 17), and the air guide plate (15) extends downward.
0), which is inclined toward the spark plug side (18,
The air-cooled two-stroke engine according to claim 2, further comprising (18).