JP2000145459A - Cooling mechanism of air-cooled engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve air-cooling efficiency of an air-cooled engine. SOLUTION: This air-cooled engine has a cooling mechanism where a cooling- air path 17 is formed so that cooling air generated by a cooling fan 11 be guided into a cylinder 3 by a cylinder cover 14 covering the periphery and the upper side of the cylinder 3. A wind shield 20 is attached to the upper side of the cylinder 3. This wind shield 20 has an external shape in which the wind shield 20 is guided along the internal wall of the cylinder cover 14 by forming a small gap 22. Preferably, the wind shield 20 is a metal plate excellent in heat transfer action.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling structure of an air-cooled engine for guiding cooling air from a cooling fan of the air-cooled engine to cooling fins of a cylinder.

[0002]

2. Description of the Related Art An air-cooled engine such as a small two-stroke engine generally has a cooling fan, and a cooling air generated by the cooling fan covers a fan cover for covering the cooling fan and side and top surfaces of a cylinder. The cooling air passage formed by the cylinder cover guides the cooling fins provided in the cylinder, and the wind that has taken heat from the cylinder is discharged to the outside of the engine cover to cool the engine. Various means for improving the cooling efficiency of the engine have been conventionally proposed. One example is disclosed in Japanese Utility Model Publication No. 4-6527 and Utility Model Registration No. 2505755.

[0003] Japanese Unexamined Utility Model Publication No. 4-6527 discloses that a projection for changing the flow direction of cooling air flowing toward a cooling air outlet is formed on the inner surface of the recoil starter side above the cylinder cover of a two-cycle engine in the direction of cooling air flow. It is configured to intersect with each other. This changes the flow direction of the cooling air flowing between the upper part of the cylinder and the cylinder cover, and discharges it in a substantially horizontal direction from the cylinder cover outlet to prevent hot air from hitting the crankcase and prevent the temperature from rising, thereby improving cooling efficiency. Is being improved.

Japanese Utility Model Registration No. 2505755 discloses an obliquely upwardly facing upper wall of a cover body which covers a cylinder and forms a cooling air passage for guiding cooling air generated in a fan housing to an outer peripheral portion of the cylinder. At the inner surface of the plug cover portion which is formed by opening it, a baffle rib is vertically provided in a direction of blocking the flow of cooling air from the cooling air passage to the plug cover portion, and a small clearance is provided between the baffle rib and the cylinder upper surface. Is formed. Thereby, the cooling air flowing from the cooling air passage to the plug cover is turned to the cylinder side to increase the effective cooling air amount, thereby improving the cooling efficiency. In addition, when an external force is applied to the upper portion of the cover, the air guide rib contacts the upper surface of the cylinder to prevent deformation of the cover.

[0005]

However, in each of the above arrangements, a part of the cooling air flows on the upper surface of the cylinder, and the flow is disturbed by hitting the projections and the ribs. Therefore, there is a problem that the cooling air does not effectively contribute to the cooling, and the cooling efficiency is not good.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a cooling structure of an air-cooled engine that utilizes cooling air effectively and has high cooling efficiency.

[0007]

In order to achieve the above object, a first invention of a cooling structure for an air-cooled engine according to the present invention comprises a cylinder cover for covering the periphery and upper part of a cylinder. In a cooling structure of an air-cooled engine in which a cooling air passage for guiding cooling air generated by a cooling fan to a cylinder is provided, a windshield having an outer shape formed along a top surface of the cylinder with a small gap formed on an inner wall of a cylinder cover. The board is attached.

According to the above configuration, since the clearance between the cylinder cover and the baffle plate attached to the upper surface of the cylinder is small, the amount of cooling air leaking from here to the upper surface of the cylinder is small. Therefore, the cooling air flowing in through the cooling air passage hits the baffle plate on the upper surface of the cylinder, and substantially the entire amount flows along the baffle plate to the cooling fin side of the cylinder wall. Thereby, disturbance of the flow of the wind does not occur, and the entire amount of the cooling wind passes through the cooling fins, so that the engine can be efficiently cooled.

In a second aspect based on the configuration of the first aspect, the windshield is formed of a metal plate having a good heat transfer function.

According to the above configuration, since the windshield plate is formed of a metal plate having a good heat transfer function, the heat radiation area of the cylinder is increased, the cooling capacity is improved, and the cooling efficiency can be improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a cooling structure of an air-cooled engine according to the present invention will be described below in detail with reference to FIGS.

FIG. 1 is a side sectional view of the two-stroke engine 1, and FIG. 2 is a front sectional view taken along the line AA of FIG. A cylinder 3 having a cooling fin 4 is attached to an upper portion of the crankcase 2, and a piston 5 is provided in the cylinder 3 so as to be slidable in a vertical direction. A crankshaft 6 is rotatably mounted on the crankcase 2, and a piston 5
And the crankshaft 6 are connected by a connecting rod 7. A flywheel 10 having a cooling fan 11 is attached to one end of the crankshaft 6. The cooling fan 11 is covered with a fan cover 12 integrally formed with the crankcase 2.
A cylinder cover 14 for covering the side surface and the upper surface is mounted. The fan cover 12 has an air inlet 13.
Is provided. A cooling air discharge port 15 is provided on a side surface of the cylinder 3 opposite to the cooling fan 11 of the cylinder cover 14. As shown in FIG. 2, a pair of left and right air guide plates 16, 16 vertically extending from a cylinder cover 14 are provided on both left and right side surfaces of the cylinder 3 in the crankshaft direction. , 16 and a side surface of the cylinder 3, a cooling air passage 17 is formed. 1 and 2, reference numeral 30 denotes a fuel tank, in FIG. 2, 31 denotes a muffler, and 32 denotes a vaporizer.

As shown in FIGS. 1 and 2, a windshield plate 20 is fastened to the upper part of the cylinder 3 by screws 21.
The windshield plate 20 is made of a material having a good heat transfer function, such as aluminum, an iron plate, or a copper plate. FIG. 3 is a view taken in the direction of arrows BB in FIG. In FIG. 1, a baffle plate 20 and a cooling fan 11
Small gaps 22 are provided between the side cylinder cover 14 and between the windshield plate 20 and the left and right air guide plates 16, 16. The size of the small gap 22 depends on the size of the baffle plate 20, the cylinder cover 14, and the baffle plate 1 during assembly and operation.
This is a minimum gap for preventing interference with the light emitting elements 6 and 16, and is set to about 1 to 2 mm in the present embodiment. Cylinder cover 14 on the opposite side of wind shield 20 and cooling fan 11
Is provided with a predetermined gap 23. The gap 23 is set to be larger than the small gap 22, and is set to approximately 8 mm in this embodiment.

Next, the cooling operation and effect will be described. When the cooling fan 11 is rotated, the cooling air is sucked from the air inlet 13 as shown by the arrow in FIG. 1 and rises along the side of the crankcase 2 facing the cooling fan 11 to reach the upper part of the cylinder 3. The cooling air passes through the space between the cooling fins 4 to cool the cylinder 3, and is discharged from the cooling air outlet 15 to the outside of the cylinder cover 14. The cooling air that has risen to the upper part of the cylinder 3 hits the windshield 20 and passes through the lower surface thereof, and is discharged from the cooling air outlet 15. At this time, the windshield 20
Is a material having a good heat transfer function, so that the cooling air draws heat from its back surface. The cooling air leaking from the small gap 22 to the upper surface of the cylinder, though its amount is small, deprives the upper surface of the windshield plate 20 of heat and is discharged from the cooling air outlet 15 through the gap 23. As described above, the cooling air efficiently passes through the space between the cooling fins 4 to efficiently cool the cylinder 3 and also removes heat from the windshield plate 20 having a good heat transfer function attached to the upper surface of the cylinder. This means that the area has increased. Therefore,
The cooling efficiency of the two-cycle engine can be improved.

[Brief description of the drawings]

FIG. 1 is a side sectional view of an air-cooled engine according to the present invention.

FIG. 2 is a view taken along the line AA of FIG. 1;

FIG. 3 is a view taken in the direction of arrows BB in FIG. 1;

[Explanation of symbols]

 2 Crankcase 3 Cylinder 4 Cooling fin 11 Cooling fan 12 Fan cover 14 Cylinder cover 16 Wind guide plate 17 Cooling air passage 20 Wind shield plate 22 Small gap

Claims (2)

[Claims] An air cooling system having a cooling air passage (17) for guiding cooling air generated by a cooling fan (11) to the cylinder (3) by means of a cylinder cover (14) covering the periphery and the upper part of the cylinder (3). In the cooling structure of a type engine, a windshield plate (2) having an outer shape formed along the upper surface of the cylinder (3) with a small gap (22) formed along the inner wall of the cylinder cover (14)
0) A cooling structure of an air-cooled engine, characterized by being attached. 2. The cooling structure for an air-cooled engine according to claim 1, wherein the windshield plate (20) is a metal plate having a good heat transfer function.