JP2007085243A - Forcedly air-cooled engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a forcedly air-cooled engine capable of suppressing noise caused by cooling air. <P>SOLUTION: In the forcedly air-cooled engine 10, a cooling fan 13 is covered with a fan-cover 15 so as to form a cooling-air guide path 60 along the external periphery 13a of the cooling fan 13. An outlet port 62 is formed in communication with an outlet 60b of the cooling-air guide path 60. An opening 16 in communication with each of the outlet port 62 and the cooling-air guide-path 60 is provided in the fan cover 15. In the forcedly air-cooled engine 10, the noise caused by the cooling air is suppressed by providing at the opening 16 a leakage-inhibiting shield part 70, and a suction-suppressing shield part 71 which partly cover the cooling fan 13. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a forced air cooling engine that cools a cylinder block or the like by sending out outside air sucked by a cooling fan as cooling air.

The general-purpose forced air-cooled engine includes a cooling fan that is rotated by power of the engine, and cools a cylinder and the like by sending cooling air with the cooling fan.
This general-purpose forced air-cooled engine is provided with a cooling air guide path along the outer periphery of the cooling fan, and an air outlet between the inlet side and the outlet side of the cooling air guide path. ing.

According to the forced air cooling engine, the cooling fan rotates when the forced air cooling engine is driven, and the cooling air is guided to the cooling air guide path as the cooling fan rotates.
The guided cooling air is guided along the cooling air guide path from the inlet side to the outlet side of the cooling air guide path. The cooling air that has reached the outlet side of the cooling air guide path is sent out from the outlet toward the cylinder side to cool the cylinder and the like.

  By the way, when the cooling fan is rotated, the cooling air is guided over the entire area of the cooling air guide path from the outer peripheral side of the cooling fan. For this reason, the amount of cooling air gradually increases as it approaches the outlet from the inlet of the cooling air guide path.

Therefore, the forced air cooling engine is formed so that the cross-sectional area (cross-sectional shape) of the cooling air guide path gradually increases from the inlet to the outlet of the cooling air guide path in response to an increase in the amount of cooling air.
By gradually increasing the cross-sectional area of the cooling air guide path from the inlet toward the outlet, the cooling air having an increased air volume can be guided well to the outlet (see, for example, Patent Document 1).
No. 2-29224

However, it is conceivable that the amount of increase in cooling air also changes with changes in environmental conditions. Therefore, it is relatively difficult to determine the cross-sectional area of the cooling air guide path so that the cooling air flows favorably in consideration of the increase in the amount of cooling air guided to the cooling air guide path.
For this reason, for example, when a large amount of cooling air is guided to the cooling air guide path, the cooling air leaks out from the inside of the cooling air guide path, and at that time, noise due to the leakage may be generated.

On the other hand, the air outlet provided between the inlet and the outlet of the cooling air guide path is disposed so as to face the cooling fan. Therefore, when the cooling fan rotates, the cooling air is directly sent out from the portion of the cooling fan that faces the outlet to the outlet.
For this reason, it is conceivable that the amount of outside air sucked from the portion facing the air outlet increases, and noise is generated due to the suction of outside air.

  This invention makes it a subject to provide the forced air cooling engine which can suppress generation | occurrence | production of the noise by cooling air.

  The invention according to claim 1 includes a cooling fan that rotates with the power of the engine, and covers the cooling fan with a fan cover, thereby forming a cooling air guide path along the outer periphery of the cooling fan and cooling air guidance. A fan outlet is formed by communicating with the outlet of the road, and an opening that communicates with the outlet and the cooling air guide path is provided in the fan cover, and outside air sucked from the opening is guided to the cooling air guide path as cooling air. A forced air cooling engine that sends the guided cooling air from the outlet of the cooling air guide path to the air outlet and blows out the sent cooling air from the air outlet toward the required cooling part of the engine. The present invention is characterized in that noise generated by the cooling air is suppressed by providing a shielding portion that covers a part.

  According to a second aspect of the present invention, the shielding portion is a suction suppression shielding portion provided at a portion on the outlet side of the opening, and the outside air sucked from the portion on the outlet side by the suction suppression shielding portion. It is configured to suppress the suction amount.

Here, the opening communicates with the outlet. Therefore, the outside air sucked from the portion on the outlet side in the opening is directly sent out to the outlet as cooling air, and blown out from the outlet toward the cooling required portion of the engine.
For this reason, it is conceivable that the amount of outside air sucked from the part on the outlet side increases more than necessary.
Therefore, in claim 2, a suction suppressing shielding portion is provided in a portion of the opening on the outlet side.

  According to a third aspect of the present invention, the shielding portion is a leakage preventing shielding portion provided in a portion of the opening near the outlet of the cooling air guide path, and the leakage preventing shielding portion is provided near the outlet. The cooling air in the cooling air guide path is prevented from leaking from the part.

Here, when the outside air sucked from the opening is guided to the cooling air guide path as the cooling air, the cooling air is guided over the entire area of the cooling air guide path from the outer peripheral side of the cooling fan.
For this reason, it is conceivable that the amount of cooling air gradually increases as it approaches the outlet from the inlet of the cooling air guide passage, and the cooling air leaks out of the cooling air guide passage.
In view of this, in the third aspect of the present invention, the leakage preventing shielding portion is provided in a portion of the opening portion near the outlet of the cooling air guide path.

  According to a fourth aspect of the present invention, the shielding portion includes a suction-suppressing shielding portion provided at a portion on the outlet side of the opening, and a portion near the outlet of the cooling air guide path among the openings. The leakage prevention shielding portion provided in the air intake, the suction suppression shielding portion suppresses the amount of outside air sucked from the portion on the outlet side, and the leakage prevention shielding portion guides the cooling air from the portion near the outlet. It is configured to prevent the cooling air in the road from leaking out.

In the invention according to claim 1, the opening is provided with a shielding portion, and the shielding portion covers a part of the cooling fan.
By covering a part of the cooling fan with the shielding part, it is possible to suppress the cooling air in the cooling air guide path from leaking outside through the part of the cooling fan by the shielding part.
By suppressing the leakage of the cooling air at the shielding part, it is possible to suppress the generation of noise due to the cooling air.

In addition, by covering a part of the cooling fan with the shielding part, it is possible to suppress the outside air from being unnecessarily sucked from a part of the cooling fan by the shielding part.
By suppressing the outside air from being sucked more than necessary at the shielding part, it is possible to suppress the generation of noise due to cooling air.

In the invention which concerns on Claim 2, the shielding part for suction suppression was provided in the site | part by the side of a blower outlet among opening parts.
As a result, the suction suppression shielding part can suppress the amount of outside air sucked from the portion on the outlet side, and an appropriate amount of outside air can be sucked from the portion on the outlet side.
By sucking in an appropriate amount of outside air from the part on the outlet side, it is possible to suppress the generation of noise due to outside air suction.

In the invention which concerns on Claim 3, the shielding part for leak prevention was provided in the site | part by the side of the exit of a cooling wind guide path among opening parts.
Thereby, it is possible to prevent the cooling air in the cooling air guide path from leaking out from the vicinity of the exit at the leakage preventing shielding portion.
By preventing the cooling air from leaking from the portion near the outlet, it is possible to suppress the generation of noise due to the cooling air leakage.

In the invention which concerns on Claim 4, the shielding part for suction suppression was provided in the site | part by the side of a blower outlet among opening parts.
As a result, the suction suppression shielding part can suppress the amount of outside air sucked from the portion on the outlet side, and an appropriate amount of outside air can be sucked from the portion on the outlet side.
By sucking in an appropriate amount of outside air from the part on the outlet side, it is possible to suppress the generation of noise due to outside air suction.

In addition, a leakage prevention shielding portion is provided in a portion of the opening near the exit of the cooling air guide path.
Thereby, it is possible to prevent the cooling air in the cooling air guide path from leaking out from the vicinity of the exit at the leakage preventing shielding portion.
By preventing the cooling air from leaking from the portion near the outlet, it is possible to suppress the generation of noise due to the cooling air leakage.

The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is an exploded perspective view showing a forced air-cooled engine (first embodiment) according to the present invention.
In the forced air cooling engine 10, a cooling fan 13 is coaxially provided on the crankshaft 12 of the engine 11, the cooling fan 13 is covered with a fan cover 15, an opening 16 is formed in the fan cover 15, and the opening 16 is faced. In this engine, a recoil starter 18 is provided, the recoil starter 18 is coaxially connected to the crankshaft 12, and the recoil starter 18 is covered with a starter cover 19.
In FIG. 1, the recoil starter 18 is removed from the crankshaft 12 for easy understanding of the configuration.

The engine 11 includes a casing 21 that houses a crankshaft 12, a cylinder (not shown), and the like, and a cylinder head 22 that is bolted to the casing 21.
The casing 21 includes a crankcase 24 that houses the crankshaft 12, and a cylinder block (an engine-required cooling unit) 25 that is provided at the left end of the crankcase 24.
The cylinder is built in the cylinder block 25.

The cooling fan 13 is disposed on the side portion 24a side of the crankcase 24, and the cooling fan 13 is coaxially connected to the crankshaft 12.
The cooling fan 13 is provided coaxially with the crankshaft 12, and a plurality of blades 27 are provided along the fan outer periphery 13a (see FIG. 3).
The fan outer periphery 13 a refers to an arc along the outer edges 27 a of the plurality of blades 27, that is, the outer periphery of the cooling fan 13.
The cooling fan 13 rotates integrally with the crankshaft 12 by driving the forced air cooling engine 10 and rotating the crankshaft 12. That is, the cooling fan 13 is configured to rotate with the power of the engine.

By rotating the cooling fan 13, the outside air is sucked from the outside air introduction holes 42a,. The sucked outside air is sucked from the opening 16 of the fan cover 15 as indicated by an arrow B.
The outside air sucked from the opening 16 is blown as cooling air as indicated by an arrow C from the fan outer periphery 13a side of the cooling fan 13 toward the outside.

Of the side portion 24a of the crankcase 24, around the cooling fan 13, first to third fixed bosses 31 (the third fixed boss 31 is not shown) are clockwise from the cylinder block 25 side, etc. Three are provided at intervals, and first to third screw holes 31a are formed in the first to third fixed bosses 31 respectively.
A fourth fixed boss 32 is provided at the lower end 24 b of the crankcase 24 in the side portion 24 a of the crankcase 24, and a screw hole 32 a is formed in the fourth fixed boss 32.

The fan cover 15 is attached to the first to third fixed bosses 31 via studs 34, and the fan cover 15 is attached to the fourth fixed boss 32 via bolts 35.
Accordingly, the fan cover 15 is attached to the side portion 24a of the crankcase 24.

The fan cover 15 has an outer peripheral wall 37 disposed so as to rise from the side portion 24 a of the casing 21, a ceiling portion 38 is provided on the top of the outer peripheral wall 37, and an opening portion 16 is formed in the approximate center of the ceiling portion 38. The cover is provided with an inner peripheral wall 39 along the portion 16.
The starter cover 19 is attached to the ceiling portion 38 of the fan cover 15 with three studs 34 and bolts 41.
The starter cover 19 includes a peripheral wall 42 that is slightly larger than the opening 16, and includes a disc-shaped cover portion 43 on the top of the peripheral wall 42.

The peripheral wall 42 includes a plurality of outside air introduction holes 42 a. The cover portion 43 includes a plurality of outside air introduction holes 43a.
The outside air introduction holes 42a, 43a, ... are holes for introducing outside air into the starter cover 19. The grip holding part 45 holds the grip 46 of the recoil starter 18 in a raised state so that it can be easily gripped.

FIG. 2 is a cross-sectional view showing the forced air cooling engine according to the first embodiment.
A flywheel 51 is coaxially provided on the crankshaft 12, and a threaded portion 12 a of the crankshaft 12 protrudes from a central opening of the flywheel 51, and a connecting member 52 is attached to the flywheel 51 with the threaded portion 12 a and a nut 53. It has been.
The base 13 a of the cooling fan 13 is sandwiched between the connecting member 52 and the flywheel 51.

A pulley 57 of the recoil starter 18 is connected to the connecting member 52 via a ratchet 58. The ratchet 58 is connected to the connecting member 52 when the engine 10 is started by the recoil starter 18.
The recoil starter 18 is housed in a starter cover 19, and a non-rotating support portion (not shown) of the recoil starter 18 is attached to the cover portion 43.
A starting rope 59 is wound around the pulley 57, and a grip 46 (see FIG. 1) is attached to the tip of the starting rope 59.

The starter cover 19 is attached to the fan cover 15 with three studs 34 (only one is shown) and bolts 41.
The fan cover 15 is attached to the side portion 24 a of the crankcase 24 with three studs 34 (only one is shown) and a bolt 35.

When the forced air cooling engine 10 is driven and the crankshaft 12 rotates, the cooling fan 13 rotates together with the crankshaft 12.
As the cooling fan 13 rotates, the outside air is sucked from the outside air introduction holes 42a... 43a. The sucked outside air is guided to the cooling fan 13 as indicated by an arrow B through the opening 16. The guided outside air is guided from the outer peripheral side of the cooling fan 13 toward the cooling air guide path 60 as cooling air as indicated by an arrow.

3 is a cross-sectional view taken along line 3-3 of FIG.
Here, in order to facilitate understanding of the configuration of the forced air-cooled engine 10, the first to third studs 34 are described as a first stud 34A, a second stud 34B, and a third stud 34C.

First to third studs 34A to 34C are erected in the vicinity of the fan outer periphery 13a of the cooling fan 13 at an interval of approximately 90 ° in the clockwise direction, and a bolt is provided between the first stud 34A and the third stud 34C. 35 is attached.
From the first stud 34A to the third stud 34C through the second stud 34B, the inner peripheral wall 39 of the fan cover 15 extends in a substantially arc shape along the fan outer periphery 13a.

Furthermore, from the third stud 34 </ b> C to the bolt 35, a lower portion (hereinafter referred to as a lower outer peripheral wall) 37 a of the outer peripheral wall 37 of the fan cover 15 extends in a substantially arc shape.
The inner peripheral wall 39 and the lower outer peripheral wall 37a form a curved wall 40 that extends from the first stud 34A to the bolt 35 through the second and third studs 34B and 34C.

The curved wall 40 is formed so as to gradually move away from the fan outer periphery 13a from the vicinity 40a of the first stud 34A toward the vicinity 40b of the bolt 35.
The curved wall 40 and the cooling fan 13 form a cooling air guide path 60. The cooling air guide path 60 is provided along the fan outer periphery 13a. The vicinity 40 a of the first stud 34 </ b> A is used as the inlet 60 a of the cooling air guide path 60. The vicinity 40 b of the bolt 35 is set as the outlet 60 b of the cooling air guide path 60.
Therefore, the cooling air guide path 60 is formed so that the guide path width W gradually increases from the inlet 60a toward the outlet 60b.

An air outlet 62 is formed between the inlet 60 a and the outlet 60 b of the cooling air guide path 60.
The air outlet 62 communicates with the inlet 60a and the outlet 60b, respectively, and is provided at a position facing the cylinder block 25 of the engine 11.

Here, the reason why the cooling air guide path 60 is formed so that the guide path width W gradually increases from the inlet 60a to the outlet 60b will be described.
That is, by rotating the cooling fan 13 with the crankshaft 12 as shown by the arrow, the outside air sucked from the opening 16 (see FIG. 1) is guided to the cooling air guide path 60 as the cooling air by the blades 27 as shown by the arrow C.

The cooling air guided to the cooling air guide path 60 is guided along the cooling air guide path 60 from the inlet 60a side to the outlet 60b side as indicated by an arrow D. At this time, the cooling air is guided as indicated by an arrow C from the fan outer periphery 13 a side over the entire area of the cooling air guide path 60.
Therefore, the air volume of the cooling air gradually increases as it approaches the outlet 60b from the inlet 60a of the cooling air guide path 60.

Therefore, the cooling air guide path 60 is formed so that the guide path width W gradually increases from the inlet 60a toward the outlet 60b.
Thereby, the cross-sectional area (cross-sectional shape) of the cooling air guide path 60 gradually increases from the inlet 60a toward the outlet 60b, and the cooling air with the increased air volume can be guided well to the outlet 60b side.

Then, the cooling air guided to the outlet 60 b of the cooling air guide path 60 is sent from the outlet 60 b to the outlet 62.
The cooling air sent to the blower outlet 62 is blown out from the blower outlet 62 toward the cylinder block (cooling required part of the engine) 25, and the cylinder block 25 is cooled with the cooling air.

By the way, the blower outlet 62 is arrange | positioned so that the area | region 64 between the inlet 60a and the outlet 60b may be faced among the fan outer periphery 13a.
Therefore, when the cooling fan 13 rotates as indicated by the arrow, the outside air sucked from the portion corresponding to the region 64 of the cooling fan 13 is directly sent out as cooling air to the outlet 62 as indicated by the arrow E.

4 is a cross-sectional view taken along line 4-4 of FIG.
The fan cover 15 is provided with openings 16 communicating with the air outlet 62 and the cooling air guide path 60, respectively. The opening 16 is arranged coaxially with the cooling fan 13.
The opening 16 is formed by forming an arc periphery 66c between the upper position 66a and the right lateral position 66b of the periphery 66 in an arc.
The radius R1 of the arc peripheral edge 66c is slightly smaller than the radius R2 of the fan outer periphery 13a. The arc peripheral edge 66c is disposed at a position slightly closer to the center (crankshaft 12) side than the fan outer periphery 13a.

A leakage preventing shielding part (shielding part) 70 is provided between the right lateral position 66b and the lower position 66d in the peripheral edge 66 of the opening 16, and a suction suppressing shielding part (shielding part) is provided between the lower position 66d and the upper position 66a. ) 71 is provided.
Hereinafter, the portion between the right lateral position 66b and the lower position 66d is referred to as a portion 66e in the vicinity of the outlet 60b.
A portion between the lower position 66d and the upper position 66a is referred to as a portion 66f on the outlet 62 side.

The leakage preventing shielding part 70 is a crescent-shaped projecting part that is provided in a portion 66e in the vicinity of the outlet 60b and projects from the arc 68 (indicated by an imaginary line) 68 extending toward the crankshaft 12 from the arc peripheral edge 66c.
The arc 68 is an arc having a radius R1 with the crankshaft 12 as the center, like the arc periphery 66c.

The curved peripheral edge 70a of the leakage preventing shielding part 70 is formed in a curved shape.
This leakage prevention shielding part 70 covers a part of the cooling fan 13 (blade 27...).
The part of the cooling fan 13 refers to a part (blade 27...) Of the cooling fan 13 that is located in the part 66e near the outlet 60b.

The suction-inhibiting shielding part 71 is a crescent-shaped projecting part that is provided in a portion 66f on the air outlet 62 side and projects from an arc (shown by an imaginary line) 68 to the crankshaft 12 side.
The curved peripheral edge 71a of the suction suppressing shielding part 71 is formed in a curved shape.
A part (blade 27...) Of the cooling fan 13 is covered with the suction suppressing shielding part 71 (see also FIG. 2).
The part of the cooling fan 13 refers to a part (blade 27...) Of the cooling fan 13 that is located in the part 66 f on the outlet 62 side.

The opening 16 is an opening formed in a substantially circular shape by an arc peripheral edge 66 c, a curved peripheral edge 70 a of the leakage preventing shielding part 70, and a curved peripheral edge 71 a of the suction suppressing shielding part 71.
By making the leakage preventing shielding part 70 and the suction suppressing shielding part 71 into a crescent shape, the opening area of the opening part 16 is ensured satisfactorily.
By securing the opening area of the opening 16 in a satisfactory manner, the amount of outside air sucked in is favorably secured.

Here, the reason why the suction suppressing shielding part 71 is provided in the part 66f on the outlet 62 side will be described.
That is, when the cooling fan 13 rotates as shown by the arrow, the outside air sucked from the portion 66 f on the outlet 62 side in the opening 16 is directly sent out as cooling air from the portion corresponding to the region 64 to the outlet 62.
For this reason, in the cooling fan 13, the amount of outside air sucked from the portion 66f on the air outlet 62 side is increased more than necessary, and at that time, noise due to the suction of outside air may be generated.

Therefore, the suction suppressing shielding portion 71 is projected from the arc 68 toward the crankshaft 12 so as to cover the blades 27 of the cooling fan 13 corresponding to the portion 66f on the outlet 62 side.
Thereby, the suction | inhalation amount of the external air from the site | part 66f by the side of the blower outlet 62 is suppressed. Therefore, the cooling fan 13 can suck an appropriate amount of outside air from the portion 66f on the air outlet 62 side, and can suppress noise generated when the outside air is sucked.

5 is a cross-sectional view taken along line 5-5 of FIG.
The leakage preventing shielding part 70 is projected from the arc 68 (see FIG. 4) to the crankshaft 12 side. By projecting the leakage prevention shielding part 70, the leakage prevention shielding part 70 reliably partitions the part of the cooling air guide path 60 that is located in the part 66 e near the outlet 60 b.
Thereby, the cooling air in the cooling air guide path 60 is prevented from leaking to the outside from the part located in the part 66e in the vicinity of the outlet 60b in the cooling air guide path 60.

Returning to FIG. 4, the reason why the leakage prevention shielding part 70 is provided in the portion 66 e in the vicinity of the outlet 60 b of the cooling air guide path 60 will be described.
That is, the cooling air is guided over the entire area of the cooling air guide path 60 from the fan outer periphery 13a side when the cooling fan 13 is rotated as indicated by an arrow.
The cooling air flowing through the cooling air guide path 60 increases in air volume as it approaches the outlet 60b side from the inlet 60a side of the cooling air guide path 60.
On the other hand, the cooling air guided to the vicinity of the outlet 60 b side of the cooling air guide path 60 is sent out from the outlet 60 b to the outlet 62.

For this reason, the cooling air in the cooling air guide path 60 is at a portion 66e in the vicinity of the outlet 60b of the cooling air guide path 60 (that is, between the right lateral position 66b and the lower position 66d in the peripheral edge 66 of the opening 16). The air volume is increased.
Therefore, the leakage prevention shielding part 70 is provided in the part 66e in the vicinity of the outlet 60b of the cooling air guide path 60, and the part located in the part 66e in the vicinity of the outlet 60b is surely partitioned by the leakage prevention shielding part 70. did.
This prevents the cooling air from leaking out of the cooling air guide path 60 and suppresses the generation of noise due to the leakage of the cooling air.

In addition, by preventing the cooling air from leaking out of the cooling air guide path 60, the cooling air is efficiently guided to the outlet 60b.
Thereby, the cylinder block 25 (refer FIG. 3) is favorably cooled with the cooling air sent to the blower outlet 62 from the exit 60b.

Next, the operation of the forced air cooling engine 10 will be described with reference to FIGS.
First, the effect | action of the shielding part 70 for leakage prevention is demonstrated based on FIGS.
FIGS. 6A and 6B are diagrams illustrating an example in which outside air is sucked by the cooling fan of the forced air cooling engine according to the first embodiment.
In (a), the cooling fan 13 rotates as indicated by an arrow F, so that the outside air is sucked from the outside air introduction holes 42a,.
The sucked outside air is guided to the cooling fan 13 as indicated by an arrow H through the opening 16.

In (b), the outside air guided to the cooling fan 13 is guided toward the cooling air guide path 60 by the blades 27 as shown by an arrow I. This cooling air is guided over the entire area of the cooling air guide path 60 from the fan outer periphery 13 a side of the cooling fan 13.
The guided cooling air flows in the cooling air guide path 60 as indicated by an arrow J. The cooling air flowing through the cooling air guide path 60 increases in air volume as it approaches the outlet 60b side from the inlet 60a side of the cooling air guide path 60.

FIGS. 7A and 7B are diagrams illustrating an example in which cooling air leakage is prevented by the leakage prevention shielding portion of the forced air cooling engine according to the first embodiment.
In (a), the cooling air in the cooling air guide path 60 is in a state in which the air volume is increased at the portion 66e in the vicinity of the outlet 60b of the cooling air guide path 60.

In (b), the leakage prevention shielding part 70 projects from the arc 68 (see FIG. 4) toward the crankshaft 12, so that the cooling wind guide path 60 is reliably partitioned by the leakage prevention shielding part 70.
Thereby, the cooling air in the cooling air guide path 60 is prevented from leaking outside from the cooling air guide path 60, and the generation of noise due to the leakage of the cooling air is suppressed.

FIG. 8 is a diagram illustrating an example in which cooling air is blown out to the cylinder block of the forced air cooling engine according to the first embodiment.
By preventing the cooling air from leaking out of the cooling air guide path 60, the cooling air is efficiently guided to the outlet 60b as indicated by the arrow J.
As a result, the cooling air is sent from the outlet 60b to the outlet 62 as shown by the arrow K. The cooling air sent to the blowout port 62 is blown out to the cylinder block 25, and the cylinder block 25 is cooled well by the blown-out cooling air.

Next, the operation of the suction suppressing shielding part 71 will be described with reference to FIGS.
FIGS. 9A and 9B are diagrams illustrating an example in which outside air is sucked by the cooling fan of the forced air cooling engine according to the first embodiment.
In (a), the cooling fan 13 rotates as indicated by an arrow F, so that the outside air is sucked in as indicated by an arrow L from the outside air introduction holes 42a.
The sucked outside air is guided to the cooling fan 13 as indicated by an arrow M through the opening 16.

In (b), the outside air sucked in from the portion 66 f on the outlet 62 side in the opening 16 is guided to the region 64. The guided outside air is sent directly from the region 64 to the outlet 62 as cooling air as indicated by an arrow N.
For this reason, it is conceivable that the amount of outside air in the opening 16 from the portion 66f on the air outlet 62 side increases more than necessary.

Returning to (a), the suction suppressing shielding part 71 projects from the arc 68 (see FIG. 4) toward the crankshaft 12 side. Of the opening 16, a portion 66 f (blade 27...) On the outlet 62 side is covered with a suction suppressing shielding portion 71.
Therefore, the amount of outside air sucked from the portion 66f on the outlet 62 side in the opening 16 can be suppressed.

FIG. 10 is a view for explaining an example in which outside air is sucked by the cooling fan of the forced air cooling engine according to the first embodiment.
An appropriate amount of outside air can be sucked from the portion 66f on the outlet 62 side of the opening 16, and noise generated when sucking outside air can be suppressed.

  Next, forced air-cooled engines according to second to fourth embodiments will be described with reference to FIGS. In the second to fourth embodiments, the same members as those in the forced air cooling engine of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

Second Embodiment FIG. 11 is a cross-sectional view showing a forced air cooling engine (second embodiment) according to the present invention.
The forced air-cooled engine 90 of the second embodiment is provided with only the suction suppressing shielding part 71 (part indicated by the stitch) as the shielding part in the opening part 16 of the fan cover 15, and the other configuration is the first embodiment. It is the same as the forced air cooling engine 10 of a form.

According to the forced air cooling engine 90, the suction amount of the outside air from the portion 66f on the outlet 62 side in the opening portion 16 can be suppressed by the suction suppression shielding portion 71 as in the first embodiment.
An appropriate amount of outside air can be sucked from the portion 66f on the outlet 62 side of the opening 16, and noise generated when sucking outside air can be suppressed.

Third Embodiment FIG. 12 is a cross-sectional view showing a forced air-cooled engine (third embodiment) according to the present invention.
The forced air-cooled engine 100 of the third embodiment is such that the center 101a of the opening 101 is knitted from the axis 102 of the crankshaft 12, and the opening 101 is formed in an arc shape. Other configurations are the same as those of the first embodiment. It is the same as the forced air cooling engine 10 of a form.

The opening 101 is an opening formed in an arc shape having a radius R1. The radius R1 is the same size as the radius of the arc 68 shown in FIG.
The opening 101 is formed by knitting the center 101a to the right from the axis 102 of the crankshaft 12 by an L dimension.

Thereby, in the part 66f on the air outlet 62 side, the part 103 indicated by the stitch in the ceiling part 38 is projected in a crescent shape on the crankshaft 12 side.
A portion 103 indicated by the stitch is a suction suppressing shielding portion. Part of the cooling fan 13 (blade 27...) Is covered with the suction suppressing shielding part 103.
The part of the cooling fan 13 refers to a part (blade 27...) Of the cooling fan 13 that is located in the part 66 f on the outlet 62 side.
Therefore, the suction suppression shielding part 103 plays the same role as the suction suppression shielding part 71.

According to the forced air-cooled engine 100, the intake amount of the outside air from the portion 66f on the outlet 62 side in the opening 101 can be suppressed by the suction suppressing shielding portion 103, as in the first embodiment.
Thereby, it becomes possible to suck in an appropriate amount of outside air from the portion 66f on the outlet 62 side of the opening 101, and noise generated when sucking in outside air can be suppressed.

In addition, according to the forced air cooling engine 100, since the opening 101 is knitted to form the suction suppressing shielding part 103, the size of the opening 101 can be ensured.
Thereby, sufficient external air can be sucked from the opening 101 and a cooling effect can be secured.

Fourth Embodiment FIG. 13 is a cross-sectional view showing a forced air cooling engine (fourth embodiment) according to the present invention.
The forced air-cooled engine 110 of the fourth embodiment is provided with only the leakage prevention shielding part 70 (part indicated by the stitch) as the shielding part in the opening part 16 of the fan cover 15, and the other configuration is the first embodiment. It is the same as the forced air cooling engine 10 of a form.

According to the forced air cooling engine 110, as in the first embodiment, the cooling air in the cooling air guide path 60 is prevented from leaking outside from the portion 66 e in the vicinity of the outlet 60 b in the opening 16. This can be prevented by the shielding part 70 for use.
Thereby, it is possible to prevent the cooling air in the cooling air guide path 60 from leaking out from the cooling air guide path 60 and to suppress the generation of noise due to the leakage of the cooling air.

In addition, by preventing the cooling air from leaking out of the cooling air guide path 60, the cooling air can be efficiently guided to the outlet 60b.
Thereby, the cylinder block 25 can be favorably cooled by the cooling air sent from the outlet 60b to the outlet 62.

In the above-described embodiment, the example in which the leakage prevention shielding part 70 is integrally formed with the ceiling part 38 of the fan cover 15 has been described. However, the present invention is not limited to this, and the leakage prevention shielding part 70 is the ceiling part 38. It is also possible to configure with a separate member.
When the leakage prevention shielding part 70 is a separate member from the ceiling part 38, for example, the leakage prevention shielding part 70 is attached to the ceiling part 38 with a fastening member such as a bolt or a clip, or is adhered with an adhesive. Is possible.

Moreover, although the said embodiment demonstrated the example which integrally formed the suction suppression shielding part 71 in the ceiling part 38 of the fan cover 15, it is not restricted to this, What is the suction suppression shielding part 71 with the ceiling part 38? It is also possible to configure with a separate member.
When the suction suppression shielding part 71 is a separate member from the ceiling part 38, for example, the suction suppression shielding part 71 is attached to the ceiling part 38 with a fastening member such as a bolt or a clip, or is adhered with an adhesive. Is possible.

  INDUSTRIAL APPLICABILITY The present invention is suitable for application to a forced air cooling engine that cools a cylinder block or the like by sending outside air sucked by a cooling fan as cooling air.

1 is an exploded perspective view showing a forced air-cooled engine (first embodiment) according to the present invention. It is sectional drawing which shows the forced air cooling engine which concerns on 1st Embodiment. FIG. 3 is a sectional view taken along line 3-3 in FIG. 2. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. FIG. 5 is a sectional view taken along line 5-5 of FIG. It is a figure explaining the example which sucks in external air with the cooling fan of the forced air cooling engine which concerns on 1st Embodiment. It is a figure explaining the example which prevents the leakage of a cooling wind in the shielding part for leakage prevention of the forced air cooling engine which concerns on 1st Embodiment. It is a figure explaining the example which blows off cooling air to the cylinder block of the forced air cooling engine which concerns on 1st Embodiment. It is a figure explaining the example which sucks in external air with the cooling fan of the forced air cooling engine which concerns on 1st Embodiment. It is a figure explaining the example which sucks in external air with the cooling fan of the forced air cooling engine which concerns on 1st Embodiment. It is sectional drawing which shows the forced air cooling engine (2nd Embodiment) which concerns on this invention. It is sectional drawing which shows the forced air cooling engine (3rd Embodiment) which concerns on this invention. It is sectional drawing which shows the forced air cooling engine (4th Embodiment) which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Forced air cooling engine, 11 ... Engine, 13 ... Cooling fan, 13a ... Fan outer periphery (cooling fan outer periphery), 15 ... Fan cover, 16, 101 ... Opening part, 25 ... Cylinder block (engine cooling required part), 60 ... Cooling air guideway, 60b ... Outlet of cooling air guideway, 62 ... Air outlet, 66e ... Site near outlet, 66f ... Site on air outlet, 70 ... Leakage prevention shielding part (shielding part), 71 , 103... Suction suppression shielding part (shielding part).

Claims (4)

A cooling fan that rotates with the power of the engine is provided, and the cooling fan is covered with a fan cover to form a cooling air guide path along the outer periphery of the cooling fan, and to communicate with the outlet of the cooling air guide path. The fan cover is provided with an opening that forms an outlet and communicates with the air outlet and the cooling air guide path. The outside air sucked from the opening is guided to the cooling air guide path as cooling air, and the guided cooling air is supplied to the cooling air. A forced air cooling engine that sends out the cooling air sent from the exit of the guideway to the outlet and blows out the sent cooling air from the outlet toward the cooling part of the engine,
A forced air-cooling engine configured to suppress noise generated by the cooling air by providing a shielding portion that covers a part of the cooling fan in the opening. The shielding part is a suction suppressing shielding part provided at a part on the outlet side of the opening,
The forced air-cooled engine according to claim 1, wherein the suction suppression shielding portion is configured to suppress an intake amount of outside air sucked from a portion on the outlet side. The shielding portion is a leakage preventing shielding portion provided in a portion of the opening near the exit of the cooling air guide path.
2. The forced air cooling engine according to claim 1, wherein the leakage prevention shielding portion is configured to prevent cooling air in the cooling air guide path from leaking from a portion near the outlet. The shielding part includes a suction suppression shielding part provided in a part on the outlet side in the opening part, and a leakage provided in a part in the vicinity of the outlet of the cooling air guide path in the opening part. It consists of a shielding part for prevention,
The suction suppression shielding part suppresses the amount of outside air sucked in from the part on the outlet side, and the leakage prevention shielding part prevents the cooling air in the cooling air guide path from leaking from the part near the outlet. The forced air cooling engine according to claim 1, wherein the forced air cooling engine is configured as follows.

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