JP2002309937A - Cooling system for accessories of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling system for accessories of an engine to lower an atmospheric temperature around the accessories such as an igniter or the like. SOLUTION: In the engine, a crankshaft 10 is vertically arranged in the engine, a flywheel 37 is disposed at an upper end of the crankshaft projecting upward from the engine, and the accessory 38 is disposed to neighbor the flywheel 37. A cover member 41 covers the flywheel 37, and an extending portion 45 covering an upper face and side faces of the accessory 38 is formed to the cover member 41. On the other hand, a ventilation mechanism 42 is disposed to the flywheel 37. After rotations of flywheels 37 make the ventilation mechanism 42 introduce air into the cover member 41, the air is introduced to the accessory 38 as cooling air through the extending portion 45 and is discharged from an exhaust port 47.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auxiliary cooling system for an engine, and more particularly to an auxiliary cooling system for a vertical crank engine having a manual starting device.

[0002]

2. Description of the Related Art A crankshaft is arranged vertically.
For example, there is an engine mounted on an outboard motor or the like that has a flywheel magneto device at the upper end of a crankshaft protruding above the engine.

[0003] When the magneto device is an external magnet type,
An igniter, which is an auxiliary device of an engine having a built-in ignition system drive unit, is disposed adjacent to the outer peripheral surface of the flywheel.

[0004]

However, in the case of an outboard motor in which the intake port is provided not at the upper part but at the lower part of the engine cover for the purpose of preventing seawater or the like from entering the engine cover, the outboard motor is heated to a high temperature by the engine. The air in the engine cover is trapped in the upper portion of the engine cover, that is, around the igniter.

The igniter is attached to an engine body, for example, a cylinder block, so as to be disposed adjacent to the flywheel. The igniter receives conduction heat of the engine body and is exposed to the above-mentioned high-temperature air.

[0006] Since the electronic equipment including the igniter is vulnerable to high temperatures, the above-mentioned surrounding environment is not preferable.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above circumstances, and has as its object to provide an engine accessory cooling device for reducing the ambient temperature around an engine accessory such as an igniter.

[0008]

According to a first aspect of the present invention, there is provided an auxiliary cooling device for an engine, wherein a crankshaft is disposed in a vertical direction inside the auxiliary cooling device. A flywheel is provided at the upper end of the crankshaft protruding above the engine, and in an engine in which an auxiliary device is arranged adjacent to the flywheel, the flywheel is covered with a cover member, and the upper surface and side surfaces of the auxiliary device are covered. While forming the extending portion to be covered on the cover member, a ventilation mechanism is provided on the flywheel, and the ventilation mechanism guides air into the cover member by rotation of the flywheel, and then cools the air by cooling air. The auxiliary device is guided to the auxiliary device through the extension portion, and is discharged from the air outlet of the extension portion.

In order to solve the above-mentioned problems, an exhaust duct is provided in the extending portion, and the exhaust duct is formed on an engine cover formed on an engine cover for covering the engine. The exhaust duct extends to the outlet, and an exhaust port is provided at the downstream end of the exhaust duct.

In order to solve the above-mentioned problem, the heat radiating plate is fastened together with the auxiliary device with the auxiliary device fixing bolt.

Further, in order to solve the above-mentioned problems,
As described in claim 4, a boss for fixing the auxiliary device is protruded from the upper surface of the engine, and a rib is formed integrally with the boss, and the rib is formed in the same direction as a side wall of the extending portion. It was extended toward.

Further, in order to solve the above-mentioned problem, a manual engine starting device is provided on the cover member, and the cover member is provided on an upper surface of the flywheel when the engine starting device is operated. An annular driving projection with which the engaging portion engages is integrally formed upward and concentrically with the flywheel, and a plurality of fins are arranged on a side surface of the driving projection.

[0013] In order to solve the above-mentioned problems,
As described in claim 6, an intake port is formed on the front side in the traveling direction of the cover member.

In order to solve the above-mentioned problem, a fuel tank is arranged in the engine cover adjacent to the engine, and the cover member is connected to the auxiliary device. And a structure for guiding cooling air to both the fuel tank.

In order to solve the above-mentioned problem, a fuel tank is disposed in the engine cover adjacent to the engine, and an intake air is supplied to the engine cover below the fuel tank. While forming the mouth,
An air inlet is formed in the cover member near the fuel tank, and the auxiliary device is cooled after the air is led into the cover member through the periphery of the fuel tank by rotation of the flywheel. It was done.

[0016]

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

FIG. 1 is a right side view showing an example of an outboard motor according to the present invention. As shown in FIG. 1, the outboard motor 1 has a box-shaped engine cover 2 at the top, and a vertical (vertical) engine 3 is housed inside. A steering handle 4 extends forward from a lower front part of the engine 3 (right side in FIG. 1), and a throttle grip 5 for adjusting an engine output is provided at a tip end thereof.

The engine cover 2 is formed so as to be vertically splittable, and includes an upper upper cover 2a and a lower lower cover 2b. A drive shaft housing 6 is provided below the lower cover 2b, and a gear case 7 is provided below the drive shaft housing 6. A propeller shaft 8 is rotatably supported inside the gear case 7, and a propeller 9 is provided at a rear end thereof.

FIG. 2 is a longitudinal sectional view of the engine 3 of the outboard motor 1 according to the first embodiment of the present invention, and FIG. 3 is a plan view of the engine 3. As shown in FIGS. 1 and 2, a crankshaft 10 is provided vertically (vertically) in the engine 3 so as to face a substantially vertical direction.

The drive shaft 1 connected to the lower end of the crankshaft 10 is provided in the drive shaft housing 6.
1 extends downward, and the lower end of the drive shaft 11 is connected to the propeller shaft 8 via the bevel gear 12. The output of the engine 3, that is, the crankshaft 1
The rotation of 0 is applied to the drive shaft 11 and the bevel gear 12.
And is transmitted to the propeller shaft 8 to rotate the propeller 9.

The upper portion of the drive shaft housing 6 is rotatably supported by a rotation support portion 13a of a clamp bracket 13, and the clamp bracket 13 is fixed to a transom 14a of the boat 14. That is, the outboard motor 1 is provided so as to be rotatable about 360 ° with respect to the boat 14, and the steering of the boat 14 is performed by changing the direction of the entire outboard motor 1 by swinging the steering handle 4 in the horizontal direction. It is configured to be able to.

On the other hand, the engine 3 used in this embodiment
Is a four-stroke single-cylinder engine, for example. As shown in FIGS. 2 and 3, the engine 3 includes a vertically split crankcase 15 disposed on the front side (right side in the drawing) of the outboard motor 1, A cylinder block 16 is arranged on the rear side (left side in the figure) of the case 15 and is formed integrally with the upper part of the crankcase 15, and a cylinder head 17 is arranged on the rear side (left side in the figure) of the cylinder block 16. It is composed of The engine 3 is fixed on an extension case 18 provided at the upper end of the drive shaft housing 6.

The cylinder block 16 has a cylindrical cylinder sleeve 19 extending rearward (to the left in the drawing) in a direction perpendicular to the crankshaft 10, and a rear portion of the cylinder head 17 is opened to move into the interior. A valve chamber 20 is formed, and is closed by a cylinder head cover 21. A combustion chamber 22 is formed in the cylinder head 17 so as to match the cylinder sleeve 19. Although not shown in detail, a spark plug 23 (see FIG. 3) is connected to the combustion chamber 22 from outside.

A piston 24 is provided in the cylinder sleeve 19.
Are slidably inserted. The piston 24 and the crankshaft 10 are connected by a connecting rod 25, whereby the piston 24 in the cylinder sleeve 19 is
Of the crankshaft 10 is converted into a rotational movement of the crankshaft 10. At the upper end of the crankshaft 10, a flywheel magneto device 26 for power generation and a rope-recoil type manual engine starting device 27 are provided.

In the cylinder head 17, an intake port 28 and an exhaust port 29 connected to the combustion chamber 22 are formed.
Further, an intake valve 30 and an exhaust valve 31 for opening and closing both ports are arranged in the cylinder head 17.

The exhaust port 29 extends downward in the cylinder head 17 toward the extension case 18, and exhausts exhaust gas from the exhaust passage 32 formed in the extension case 18 through the drive shaft housing 6 to the outside of the machine. It is configured as follows. A carburetor 34 constituting an intake device 33 is disposed above the cylinder block 16, and a carburetor 34 is provided downstream of the carburetor 34.
5, and connected to an intake port 28 opened on the upper surface of the cylinder head 17, and a silencer 36 is connected to the upstream side of the carburetor 34.

The flywheel magneto device 26 is, for example, of an external magnet type, and comprises a disk-shaped flywheel 37 provided integrally with the upper end of a crankshaft 10 protruding above the engine 3 and a flywheel 37. An igniter 38 which is an auxiliary device of the engine 3 and has a built-in ignition system drive unit disposed adjacent to the outer peripheral surface of the engine 37.

The igniter 38 includes the cylinder block 16
The flywheel magneto device 26 is covered from above by a recoil cover 41 which is a cover member integrally provided with the engine starting device 27, for example, and is fixed to a boss 39 projecting from the upper surface of the device by bolts 40, for example.

FIG. 4 shows a flywheel magneto device 2
6 is an enlarged plan view, and FIG. 5 is a sectional view taken along line VV in FIG. FIG. 6 is an enlarged vertical sectional view of the flywheel magneto device 26 and the engine starting device 27.

As shown in FIGS. 4 to 6, for example, a ventilation mechanism 42 is provided on the upper surface of the flywheel 37. The ventilation mechanism 42 is a pair of holes formed, for example, with the center of the flywheel 37 interposed therebetween.
Numeral 3 denotes an inclined shape which is inclined downward in the rotational direction of the flywheel, in this embodiment, clockwise, and the lower portion of the flywheel 37 is formed by the rotation of the flywheel 37 as shown by arrows in FIGS. The air is guided above the flywheel 37. Note that the ventilation mechanism 42 may use another well-known technique.

The recoil cover 41 is connected to the flywheel 37
Is formed along the periphery thereof, and a space 44 is formed above the flywheel 37. The recoil cover 41 is formed integrally with an extension 45 that covers the top and side surfaces of the igniter 38. further,
A part of the wall portion of the extension portion 45 that covers the side surface of the igniter 38 extends in a tangential direction of the outer peripheral surface of the flywheel 37 to form a wind guide wall 46. The side of the extension 45 opposite to the flywheel 37 is opened to form an air outlet 47.

On the other hand, the operating section 48 of the engine starting device 27
Is arranged on the upper front portion of the upper cover 2a, and an operation cable 49 extends from the operation section 48 toward the main body of the engine starting device 27. The recoil cover 41 has an extension 50 covering the upper and side surfaces of the operation cable 49.
Are integrally formed. The end of the extension portion 50 extends outside the upper cover 2a toward the front of the outboard motor 1, and forms an intake port 51.

When the flywheel 37 rotates, the air in the engine cover 2 is released by the ventilation mechanism 42 from the gap between the upper surface of the crankcase 15 and the lower surface of the recoil cover 41 inside the recoil cover 41 formed above the flywheel 37. It is led to the space 44. This air rotates along the rotation direction of the flywheel 37, becomes cooling air, is guided to the wind guide wall 46 of the extension 45, passes around the igniter 38, and is discharged from the air outlet 47 into the engine cover 2. Is done.

By these actions, the air around the igniter 38 is reliably circulated, and the igniter 38 is forcibly cooled to improve its function, reliability and life. Further, the extension portion 45 can prevent the igniter 38 from being splashed with water.

When the marine vessel 14 travels forward, fresh outside air is forcibly guided into the recoil cover 41 from the intake port 51 provided in the extension 50 of the recoil cover 41, and the cooling efficiency of the igniter 38 is reduced. Can be improved.

7 and 8 show a second embodiment of the present invention. FIG. 7 is a right side view of the engine 3 of the outboard motor 1, and FIG. 8 is a plan view of the engine 3. As shown in FIG. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

As shown in FIGS. 7 and 8, in the second embodiment, an exhaust duct 54 is provided in the extending portion 53 of the recoil cover 52, and the exhaust duct 54 is connected to an exhaust port formed in the lower cover 2b. 55, and an exhaust port 56 is provided at the downstream end. With this configuration, the cooling air that has cooled the igniter 38 does not stay in the engine cover 2 but is discharged to the outside of the engine cover 2 to prevent the ambient temperature in the engine cover 2 from rising.

FIGS. 9 and 10 show a third embodiment of the present invention. FIG. 9 is an enlarged vertical sectional view of a flywheel magneto device 26 and an engine starting device 27, and FIG. FIG. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

As shown in FIGS. 9 and 10, the igniter 38 has a radiator plate 57 such as an aluminum plate fastened together with the igniter 38 by fixing bolts 40 of the igniter 38. Heat sink 57 is igniter 38
, The cooling efficiency of the igniter 38 can be improved. Further, the number of components can be reduced by fastening the heat sink 57 together with the igniter 38.
Note that an exhaust duct may be provided on the recoil cover 41 shown in this embodiment as in the second embodiment.

FIGS. 11 and 12 show a fourth embodiment of the present invention. FIG. 11 is a plan view of a crankcase 15 and a cylinder block 16 formed integrally with an upper portion of the crankcase 15. Is XII in FIG.
It is an arrow view. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. The recoil cover is indicated by an imaginary line (two-dot chain line).

As shown in FIGS. 11 and 12, a plate-shaped rib 58 extending in the vertical direction is integrally formed on a fixing boss 39 of the igniter 38 protruding from the upper surface of the cylinder block 16. The rib 58 extends in the same direction as the wind guide wall 46 of the extension 45. This rib 58
The air flow can be created below the igniter 38 by providing the igniter 38, and the cooling efficiency of the igniter 38 can be improved.

The surface area of the boss 39 is increased by the rib 58, and the temperature of the boss 39 itself is lowered by the cooling air generated by the flywheel 37. As a result, conduction heat from the engine 3 to the igniter 38 decreases. Further, the provision of the ribs 58 on the boss 39 increases the strength of the boss 39.

FIGS. 13 and 14 show a fifth embodiment of the present invention. FIG. 13 is a plan view of the flywheel magneto device 26, and FIG. 14 is a view taken in the direction of the arrow XIV in FIG. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

As shown in FIGS. 13 and 14, on the upper surface of the flywheel 59, an annular recoil driving projection 61 with which the engaging portion 60 (for example, see FIG. 6) is engaged when the engine starting device 27 is operated is provided. It is formed integrally upward with the wheel 59 concentrically. A plurality of fins 62 are arranged at equal intervals on the side surface of the recoil driving projection 61.

The air guided above the flywheel 59 is supplied to the fins 6 which rotate as the flywheel 59 rotates.
The cooling air is accelerated by 2 and is led to the igniter 38 to improve the cooling efficiency of the igniter 38.

FIGS. 15 to 18 show a sixth embodiment of the present invention. FIG. 15 is a longitudinal sectional view of the engine 3 of the outboard motor 1, and FIG. FIG. 17 is an enlarged plan view of the flywheel magneto device 26 in which the recoil cover is indicated by an imaginary line (two-dot chain line). FIG. 18 is an enlarged vertical sectional view of the flywheel magneto device 26 and the engine starting device 27. It is. In addition,
The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

As shown in FIGS. 15 to 18, the outboard motor 1 is provided with a fuel tank 63 in the space inside the engine cover 2 in front of the engine 3 and the fuel filler port 64 protrudes above the upper cover 2a to extend the fuel cap. It is closed by 65.

The recoil cover 41 which covers the upper and side surfaces of the operation cable 49, that is, has an open lower surface.
Is disposed above the fuel tank 63, and the space 44 above the flywheel 37 and the space 66
And communicate.

When the flywheel 37 rotates, the air below the flywheel 37 is guided by the ventilation mechanism 42 to the space 44 in the recoil cover 41 formed above the flywheel 37, and becomes a cooling wind, and a part of the air is cooled. The air is discharged from the exhaust port 47 into the engine cover 2 through the periphery of the igniter 38, and the other part is discharged from the lower surface of the extension 50 of the recoil cover 41 toward the fuel tank 63. The fuel (not shown) is cooled.

FIGS. 19 to 21 show a seventh embodiment of the present invention. FIG. 19 is a longitudinal sectional view of the engine 3 of the outboard motor 1. FIG. 20 is an enlarged plan view of the flywheel magneto device 26 showing the recoil cover by imaginary lines (two-dot chain line), and FIG. 21 is an enlarged vertical sectional view of the flywheel magneto device 26 and the engine starting device 27. It is. Note that the seventh embodiment is a modification of the above-described sixth embodiment, and the same components as those in the sixth embodiment are denoted by the same reference numerals and description thereof is omitted.

As shown in FIGS. 19 to 21, the outboard motor 1 also has a fuel tank 63 in the space inside the engine cover 2 in front of the engine 3, and its fuel filler port 64 projects above the upper cover 2a to extend the fuel cap. It is closed by 65.

A rising wall 69 is formed on the upper surface of the crankcase 65 so as to coincide with the lower edge of the recoil cover 68, thereby eliminating a gap between the upper surface of the crankcase 65 and the lower surface of the recoil cover 68. An air inlet 70 is formed in the recoil cover 68 immediately after the fuel tank 63.
An intake port 71 is provided directly below the fuel tank 63 in the lower case 2b.

Since the gap between the upper surface of the crankcase 65 and the lower surface of the recoil cover 68 is eliminated, the air is guided into the recoil cover 68 from the air inlet 70 immediately after the fuel tank 63 by the rotation of the flywheel 37.
In addition, since the intake port 71 is provided in the lower case 2b immediately below the fuel tank 63, the air introduced from the air inlet port 70 into the recoil cover 68 is inevitably supplied to the fuel tank 63.
Pass around. Thus, the fuel tank 63 and the fuel therein are sufficiently cooled, and the air guided into the recoil cover 68 cools the igniter 38.

In any of the embodiments, the rotation of the flywheel 37 guides the air around the igniter 38 and the fuel tank 63, which are auxiliary parts of the engine 3, so that the engine cover heated to a high temperature by the engine 3 The air inside the igniter 38 does not accumulate in the upper portion of the engine cover 2, that is, around the igniter 38, and the ambient temperature around the igniter 38 can be reduced.

In each of the above-described embodiments, the flywheel / magnet device 26 is covered with the recoil cover 41 integrally provided with the engine start device 27. A cover (not shown) may be used.

[0056]

As described above, according to the auxiliary cooling device for an engine according to the present invention, the crankshaft is vertically disposed inside, and the flywheel is provided at the upper end of the crankshaft protruding above the engine. In the engine provided with the auxiliary device adjacent to the flywheel, the flywheel is covered with a cover member, and the extended portion for covering the upper surface and the side surface of the auxiliary device is formed in the cover member. A ventilation mechanism is provided on the flywheel, and after the ventilation mechanism guides air into the cover member by rotation of the flywheel, the air is guided to the auxiliary device through the extension as cooling air, Air that accumulates around the auxiliary device without increasing the number of parts because it is configured to be exhausted from the exhaust port of the extension Circulation can, it becomes possible to auxiliary equipment cooling may prevent water from being applied to the auxiliary unit by the extended portion.

An exhaust duct is provided in the extending portion, and the exhaust duct is extended to an exhaust port formed in an engine cover covering the engine, and an exhaust port is provided at a downstream end of the exhaust duct. Therefore, the air after cooling the auxiliary device is discharged to the outside of the engine cover to prevent the ambient temperature in the engine cover from rising.

Further, since the radiator plate is fastened together with the auxiliary device with the auxiliary device fixing bolt, the cooling efficiency of the auxiliary device is improved.

A boss for fixing the auxiliary device is protruded from the upper surface of the engine, and a rib is formed integrally with the boss, and the rib extends in the same direction as the side wall of the extending portion. As a result, air flow can be created at the lower part of the auxiliary device, improving the cooling efficiency of the auxiliary device, increasing the surface area of the boss by the rib, and lowering the temperature of the boss itself by the cooling air generated by the flywheel. As a result, the heat transmitted from the engine to the auxiliary device is reduced, while the ribs increase the strength of the boss.

Further, a manual engine starting device is provided on the cover member, and an annular driving projection with which the engaging portion engages when the engine starting device is operated is provided on the upper surface of the flywheel with the flywheel. Since the plurality of fins are formed concentrically and upward, and a plurality of fins are arranged on the side surface of the driving projection, the cooling air speed is increased and the cooling efficiency of the auxiliary device is improved.

Since the air inlet is formed on the front side of the cover member in the traveling direction, the cooling efficiency of the auxiliary device is improved by the outside air guided into the cover member.

Further, since the fuel tank is arranged in the engine cover adjacent to the engine and the cover member is structured to guide the cooling air to both the auxiliary device and the fuel tank, The fuel tank and the fuel inside it can be cooled in the same manner.

A fuel tank is disposed in the engine cover adjacent to the engine, and an intake port is formed in the engine cover below the fuel tank, while an air inlet is formed in the cover member near the fuel tank. To form
Since the auxiliary device is cooled after the air is led into the cover member through the periphery of the fuel tank by the rotation of the flywheel, the auxiliary device, the fuel tank, and the fuel therein are made the same. Can be cooled.

[Brief description of the drawings]

FIG. 1 is a right side view of an outboard motor showing one embodiment of an engine accessory cooling device according to the present invention.

FIG. 2 is a longitudinal sectional view of an engine part of the outboard motor showing the first embodiment of the present invention.

FIG. 3 is a plan view of the engine shown in FIG. 2;

FIG. 4 is an enlarged plan view of the flywheel magneto device (first embodiment).

FIG. 5 is a sectional view taken along the line VV of FIG. 4 (first embodiment).

FIG. 6 is an enlarged vertical sectional view of a flywheel magneto device and an engine starting device (first embodiment).

FIG. 7 is a right side view of an engine portion of the outboard motor (second embodiment).

FIG. 8 is a plan view of the engine shown in FIG. 7 (second embodiment).

FIG. 9 is an enlarged vertical sectional view of a flywheel magneto device and an engine starting device (third embodiment).

FIG. 10 is a view taken in the direction of the arrow X in FIG. 9 (third embodiment).

FIG. 11 is a plan view of a crankcase and a cylinder block (fourth embodiment).

FIG. 12 is a view taken in the direction of the arrow XII in FIG. 11 (fourth embodiment).

FIG. 13 is a plan view of a flywheel magneto device (fifth embodiment).

FIG. 14 is a view taken in the direction of the arrow XIV in FIG. 13 (fifth embodiment).

FIG. 15 is a longitudinal sectional view of an engine part of an outboard motor (sixth embodiment).

FIG. 16 is a plan view of the engine shown in FIG. 15 (sixth embodiment).

FIG. 17 is an enlarged plan view of a flywheel magneto device (sixth embodiment).

FIG. 18 is an enlarged vertical sectional view of a flywheel magneto device and an engine starting device (sixth embodiment).

FIG. 19 is a longitudinal sectional view of an engine part of an outboard motor (seventh embodiment).

FIG. 20 is an enlarged plan view of a flywheel magneto device (seventh embodiment).

FIG. 21 is an enlarged longitudinal sectional view of a flywheel magneto device and an engine start device (seventh embodiment).

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 outboard motor 2 engine cover 3 engine 10 crankshaft 26 flywheel / magnet device 27 manual engine starter 37, 59 flywheel 38 igniter (auxiliary device) 39 boss for fixing igniter (auxiliary device) 40 igniter (auxiliary device) ) Fixing bolts 41, 52, 68 Recoil cover (cover member) 42 Ventilation mechanism 45, 53 Extension 47, 56 Exhaust port 51, 71 Inlet port 54 Exhaust duct 55 Exhaust port 57 Radiator plate 58 Rib 60 Engine Engaging part of starting device 61 Driving projection 62 Fin 63 Fuel tank 70 Air inlet

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02B 67/00 F02B 67/00 H F02N 3/02 N F02N 3/02 P B63H 21/26 D

Claims (8)

[Claims] 1. An engine in which a crankshaft is vertically disposed inside, an flywheel is provided at an upper end of the crankshaft protruding above the engine, and an auxiliary device is arranged adjacent to the flywheel. Along with covering the wheel with a cover member, an extended portion covering the top and side surfaces of the auxiliary device is formed on the cover member, while a ventilation mechanism is provided on the flywheel, and the rotation of the flywheel causes the ventilation mechanism to rotate. An engine configured to guide air into the cover member, guide the air as cooling air to the auxiliary device through the extended portion, and discharge the cooled air from an exhaust port of the extended portion. Accessory cooling system. 2. An exhaust duct is provided in the extending portion, the exhaust duct is extended to an exhaust port formed in an engine cover covering the engine, and an exhaust port is provided at a downstream end of the exhaust duct. The cooling device for an auxiliary device of an engine according to claim 1, wherein 3. An auxiliary cooling system for an engine according to claim 1, wherein the radiator plate is fastened together with the auxiliary device with the auxiliary device fixing bolt. 4. A boss for fixing the auxiliary device protrudes from an upper surface of the engine, and a rib is formed integrally with the boss, and the rib extends in the same direction as a side wall of the extending portion. An engine accessory cooling device according to claim 1, 2 or 3. 5. A manual engine starting device is provided on the cover member, and an annular driving projection which is engaged with the engaging portion when the engine starting device is operated is concentric with the flywheel on the upper surface of the flywheel. 5. The cooling device for an auxiliary device of an engine according to claim 1, wherein the fin is integrally formed upward and a plurality of fins are arranged on a side surface of the driving projection. 6. An auxiliary cooling device for an engine according to claim 1, wherein an intake port is formed at a front side of the cover member in a traveling direction. 7. A fuel tank according to claim 1, wherein a fuel tank is disposed adjacent to said engine in said engine cover, and said cover member is structured to guide cooling air to both said auxiliary device and said fuel tank. An auxiliary cooling device for an engine according to any one of the preceding claims. 8. A fuel tank is arranged in the engine cover adjacent to the engine, an intake port is formed in the engine cover below the fuel tank, and an air inlet is provided in the cover member near the fuel tank. 7. The auxiliary device according to claim 1, wherein the auxiliary device is cooled after the air is led into the cover member through the periphery of the fuel tank by the rotation of the flywheel. 8. Engine accessory cooling system.