JP2001241325A - Cooling structure of forced-air-cooled four cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling structure of a forced-air-cooled four cycle engine capable of contracting the width of the engine, reducing noise, and improving a cooling performance. SOLUTION: In this cooling structure of a forced-air-cooled four cycle engine wherein the whole of the engine is covered with an air shroud 24 and each part of the engine is forcibly cooled by cooling wind which is led from a cooling wind leading inlet 24a opened to the air shroud 24 into the air shroud 24 by a cooling fin 21 rotated coaxially with a crankshaft 7, the cooling wind leading inlet 24a opened to the air shroud 24 is bent to a diameter direction inner side of blades 21a of the cooling fan 21 so as to form it in a funnel shape, and the cooling wind leading inlet 24a and the blades 21a of the cooling fan 21 are overlapped in an axial direction. Since the cooling wind leading inlet 24a and the blades 21a of the cooling fan 21 are overlapped in the axial direction while employing the funnel shape for the cooling wind leading inlet 24a opened to the air shroud 24, the above purpose is achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling structure for a forced air-cooled four-cycle engine in which each part of the engine is forcibly cooled by cooling air introduced into an air shroud by a cooling fan.

[0002]

2. Description of the Related Art FIGS. 4 and 5 show a conventional example of a cooling structure of such a forced air-cooled four-cycle engine.

FIGS. 4 and 5 are cross-sectional views of a cooling air introduction portion of an engine. In the cooling structure shown in FIG. 4, a sirocco fan is used as a cooling fan 121 to cool an air shroud 124 covering the entire engine. Fan 1
Circular cooling air inlet 1 opening at a portion facing 21
24a is laid out at a predetermined distance (about 10 mm) from the cooling fan 121, and a funnel shape is not adopted for the air inlet 124a in order to reduce the width of the engine.

[0004] In the cooling structure shown in FIG.
A turbo fan is used as the fan 21. The blades 22 of the cooling fan 221 are used to efficiently send cooling air to various parts of the engine.
1a, a cylindrical ring 240 is attached to the distal end, and a cooling air inlet 22 opening to an air shroud 224.
The labyrinth structure is formed by making the cooling air inlet 224a a relief to avoid interference with the ring 240 at the funnel shape 4a.

[0005]

However, in the conventional cooling structure shown in FIG.
Because the funnel shape is not adopted for the cooling air inlet 124a that opens into the cooling air, the cooling air is not smoothly introduced from the cooling air inlet 124a, which causes problems such as an increase in noise and a decrease in cooling efficiency. there were.

In the conventional cooling structure shown in FIG. 5, a ring 240 projecting in the engine width direction is attached to the tip of a blade 221 a of a cooling fan 221, and a ring 240 is provided at a cooling air inlet 224 of an air shroud 224. There is a problem that the provision of the escape to avoid interference with the engine results in an increase in the engine width, which hinders downsizing of the engine.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a cooling structure of a forced air-cooled four-cycle engine capable of reducing the engine width, reducing noise, and improving the cooling performance. Is to provide.

[0008]

In order to achieve the above object, the present invention covers an entire engine with an air shroud and a cooling air inlet opening to the air shroud by a cooling fan rotating coaxially with a crankshaft. In a cooling structure of a forced air-cooled four-cycle engine forcibly cooling each part of the engine with cooling air introduced into an air shroud, a cooling air inlet opening to the air shroud is bent radially inward of the blades of the cooling fan. The cooling air introduction port and the blades of the cooling fan are overlapped in the axial direction.

Therefore, according to the present invention, while adopting a funnel shape for the cooling air inlet opening to the air shroud, the cooling air inlet and the blade of the cooling fan are overlapped in the axial direction. The engine width can be reduced to make the engine smaller and more compact, and the cooling air can be smoothly introduced from the cooling air inlet to reduce noise and improve the cooling performance.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a plan sectional view of a unit swing type engine, FIG. 2 is a plan sectional view of a four-cycle engine portion of the unit swing type engine, and FIG. 3 is a diagram showing a cooling structure according to the present invention. It is sectional drawing of a part.

Unit swing type engine 1 shown in FIG.
Numeral 0 is mounted on a scooter-type motorcycle (not shown), which is a forced air-cooled four-stroke engine equipped with a cooling structure according to the present invention (hereinafter simply referred to as engine).
1, a transmission mechanism including a V-belt type automatic transmission 2 is compactly incorporated in a crankcase 3 to constitute a unit.

Here, a schematic configuration of the engine 1 will be described.

The engine 1 is a single-cylinder engine. A single cylinder 5 is formed in a cylinder body 4 which is disposed substantially horizontally toward the front of the body of the scooter type motorcycle. Are slidably fitted. The piston 6 is connected via a connecting rod 8 to a rotatable crankshaft 7 arranged in the vehicle width direction.

The cylinder head 9 attached to the cylinder body 4 is formed with an intake port and an exhaust port (not shown), and the intake port and the exhaust port are formed by a valve mechanism including a cam shaft 11. The valve is opened and closed at an appropriate timing by an intake valve and an exhaust valve (not shown) driven by the actuator, thereby performing a required gas exchange in the cylinder 5. A chain sprocket 12 is attached to one end of the camshaft 11, and an endless cam chain 14 is wound between the chain sprocket 12 and a chain sprocket 13 attached to an intermediate portion of the crankshaft 7. The rotation of the crankshaft 7 is transmitted to the camshaft 11 through the chain sprocket 13, the cam chain 14, and the chain sprocket 12, and the camshaft 11 is rotated at a predetermined speed (1/2 of the crankshaft 7).
Speed).

As shown in FIG. 1, an ignition plug 19 is screwed to the cylinder head 9 and an electrode portion of the ignition plug 19 faces a combustion chamber S formed in the cylinder head 9. .

On the other hand, as shown in detail in FIG. 2, the crankshaft 7 is rotatably supported by a pair of left and right bearings 20, and one end (right end) of the cooling fan 2 is provided.
1 is attached by a nut 37, inside which the generator 22 is provided. A drive pulley 23 constituting the V-belt type automatic transmission 2 is attached to the other end (left end) of the crankshaft 7. As shown in detail in FIG. 3, a rotor 22a of a generator 22 is attached to the cooling fan 21, and a stator 22b is fixed inside the rotor 22a.

The entire engine 1 having the above configuration is covered with an air shroud 24 made of resin, and a portion of the air shroud 24 facing the cooling fan 21 has a circular cooling air flow. The inlet 24 a is formed coaxially with the crankshaft 7. Also, as shown in FIG.
At the front end of the air shroud 24, a plug hole 24b that opens diagonally laterally is formed, and behind the plug hole 24c, a circular hole 24c for confirming the top dead center is formed. And the plug hole 24b
As shown in FIG. 1, the ignition plug 19 is passed through. The ignition plug 19 is covered by a plug cap 25 fitted from the outside into a plug hole 24b, and is inserted into the circular hole 24c for confirming the top dead center. Has a rubber cap 26 detachably fitted therein. In addition, the air shroud 24 is attached to the crankcase 3 by screws 27 at a plurality of locations on the periphery.

Here, the characteristic structure of the cooling structure according to the present invention will be described with reference to FIG.

As shown in FIG. 3, the cooling air inlet 24a opening in the air shroud 24 has a peripheral edge 24a-1.
Is bent radially inward of the plurality of blades 21a of the cooling fan 21 to form a funnel shape. The cooling air inlet 24a and the blades 21a of the cooling fan 21 are axially (in the engine width direction). As shown, they overlap by δ. Therefore, a labyrinth structure as a seal structure is formed between the blade 21a of the cooling fan 21 and the cooling air inlet 24a of the air shroud 24. still,
The cooling air inlet 24a of the air shroud 24 is provided with concentric ribs 24a-2.

Next, the structure of the transmission mechanism of the unit swing type engine 10 will be described.

As shown in FIG. 1, a driven shaft 28, an intermediate shaft (not shown) and an output shaft (axle) are provided at the rear of the crankcase 3.
A driven pulley 30 and a centrifugal clutch 31 are attached to a driven shaft 28, and an endless V-belt 32 is wound between the driven pulley 30 and the driving pulley 23. The V-belt type automatic transmission 2 is configured to be mounted. A small-diameter drive gear 33 is integrally formed at one end (right end) of the driven shaft 28.

A drive gear and a driven gear (not shown) of large and small diameters are attached to the intermediate shaft. The drive gear 33 meshes with the driven gear of the intermediate shaft. The drive gear meshes with a large-diameter driven gear 34 attached to the output shaft 29. A rear wheel 35 of a scooter-type motorcycle is attached to an end of the output shaft 29 protruding outward from the crankcase 3. In FIG. 1, reference numeral 36 denotes a kick lever for a kick starter.

Next, the operation of the unit swing type engine 10 having the above configuration will be described.

In the unit swing type engine 10, when the engine 1 is started by operating the kick lever 36 and the crankshaft 7 is driven to rotate, the cooling fan 21 and the generator 22 coaxially mounted on the crankshaft 7 are mounted. And the rotation of the crankshaft 7 is automatically shifted by the V-belt type automatic transmission 2 and transmitted to the centrifugal clutch 31. Here, when the rotation speed of the centrifugal clutch 31 reaches a certain value or more, the centrifugal clutch 31 is turned ON to transmit the rotation to the driven shaft 28, and the rotation of the driven shaft 28 is transmitted to the drive gear 33 and a driven gear (not shown) provided on the intermediate shaft. And is transmitted to the intermediate shaft. The rotation of the intermediate shaft is further reduced through a drive gear and a driven gear 34 (not shown) and transmitted to the output shaft 29. The output shaft 29 and the rear wheel 35 attached to the output shaft 29 are driven to rotate, and the scooter type is rotated. A motorcycle is driven.

On the other hand, in the engine 1, when the cooling fan 21 is driven to rotate as described above, cooling air is introduced into the air shroud 24 from a cooling air inlet 24a opened on the side surface of the air shroud 24. The cooling air flows through the air shroud 24 to cool the respective parts of the engine 1 including the cylinder body 4 and the cylinder head 9.

In this embodiment, the cooling air inlet 24a and the blades 21a of the cooling fan 21 are used while adopting the funnel shape for the cooling air inlet 24a opening to the air shroud 24 as described above. Are overlapped in the axial direction, so that the engine width can be reduced and the size and size of the engine 1 can be reduced, and the cooling air can be smoothly introduced into the air shroud 24 from the cooling air inlet 24a. To realize low noise and improved cooling performance.

[0028]

As is apparent from the above description, according to the present invention, the entire engine is covered with the air shroud, and the cooling fan is rotated coaxially with the crankshaft. In a cooling structure of a forced air-cooled four-cycle engine forcibly cooling each part of the engine with cooling air introduced into an air shroud, a cooling air inlet opening to the air shroud is bent radially inward of the blades of the cooling fan. The cooling air inlet and the blades of the cooling fan are axially overlapped with each other in the axial direction, so that the effect of reducing the engine width, reducing noise, and improving the cooling performance can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan sectional view of a unit swing type engine.

FIG. 2 is a plan sectional view of a forced air-cooled four-stroke engine provided with a cooling structure according to the present invention.

FIG. 3 is a cross-sectional view of a cooling air introduction portion of a forced air-cooled four-stroke engine having a cooling structure according to the present invention.

FIG. 4 is a cross-sectional view of a cooling air introduction part of a forced air-cooled four-cycle engine showing a conventional cooling structure.

FIG. 5 is a cross-sectional view of a cooling air introduction part of a forced air-cooled four-cycle engine showing a conventional cooling structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Forced air-cooled 4-cycle engine 7 Crankshaft 21 Cooling fan 21a Blade 24 Air shroud 24a Cooling air inlet

Claims (1)

[Claims] An engine is covered with an air shroud and each part of the engine is forcibly forced by cooling air introduced into the air shroud from a cooling air inlet opening in the air shroud by a cooling fan rotating coaxially with a crankshaft. In a cooling structure of a forced air-cooled four-cycle engine for cooling, a cooling air inlet opening to the air shroud is bent inward in a radial direction of a blade of the cooling fan into a funnel shape,
A cooling structure for a forced air-cooled four-stroke engine, characterized in that the cooling air inlet and the blades of the cooling fan overlap in the axial direction.