JP2850030B2 - Forced air-cooled engine - Google Patents

Description

Description: TECHNICAL FIELD [0001] The present invention relates to a forced air-cooled engine, and more particularly to a forced air-cooled engine for a motorcycle that enables efficient cooling of a generator together with a cylinder.

(Prior art)

A cooling fan attached to a forced air-cooled engine of a motorcycle is generally fixed to a top surface of a generator rotor fixed to a crankshaft end. Naturally, the cooling air generated by this cooling fan is used exclusively for cooling the outer circumference of the cylinder.However, if a part of the cooling air is also used for cooling the generator, the air flow increases. Therefore, the size of the cooling fan must be increased.

Increasing the size of the cooling fan increases the width of the engine in the crankshaft direction and the width in the front-rear direction, resulting in an increase in the size of the engine.

[Problems to be solved by the invention]

An object of the present invention is to provide a forced air-cooled engine that can be achieved without increasing the size of the engine due to the increase in the size of the cooling fan when increasing the blowing amount of the cooling fan to the generator without sacrificing the cylinder cooling function. To provide.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a generator rotor fixed to one end of a crankshaft, a cooling fan fixed to a top surface of the rotor, and cooling air generated by the cooling fan being cooled by cooling fins on the outer periphery of a cylinder body. In a forced air-cooled engine in which a shroud having an intake port provided at a position facing the cooling fan is mounted on an engine body, the cooling fan is fixed to the rotor and has a smaller outer diameter than the rotor. A plurality of blades extending radially outward from the rotor on the outer periphery of the base and arranged in a direction standing on the top surface of the rotor; and An annular plate fixed to the provided top and formed concentrically with the crankshaft;
A circular cone in which the outer peripheral edge of the annular plate is positioned substantially the same as the outer peripheral end of the blade, while the inner diameter is substantially the same as the diameter of the intake port, and the inner peripheral portion of the annular plate gradually expands from the inner peripheral side. The rotor is surrounded by a cover, an outer periphery of the rotor is surrounded by a cover, and an annular ventilation gap for introducing cooling air is formed between the outer periphery of the rotor and the cover. The cylinder body having a shape extending in the ventilation gap along with the blade, and a ventilation hole provided on the top surface of the rotor so as to penetrate between the blades in and out, and provided closest to the cover and the cover. The cooling air guide wall portion is formed between the cooling fins.

〔Example〕

1 to 4 show an example of the air-cooled engine according to the present invention, and FIG. 5 shows a motorcycle equipped with the air-cooled engine.

In the motorcycle shown in FIG. 5, 1 is a body frame, 2 is a front wheel, 3 is a rear wheel, 4 is an engine, and 5 is a cowl provided at a front portion of the body as a wind shield. An air cleaner 6 and a carburetor 7 are connected to the intake side of the engine 4, and an exhaust pipe 8 is connected to the exhaust side. Engine 4
The rear wheel 3 is driven via a chain 10 from a sprocket 9 provided at the rear.

In the air-cooled engine 4 shown in FIGS. 1 to 4, 11 is a cylinder body, 12 is a cylinder head, and 13 is a crankcase, which constitutes an engine body. The cylinder body 11 and the cylinder head 12 are connected by bolts (not shown) at four places on the outer periphery thereof.
And the crankcase 13 are similarly connected by bolts (not shown) at four locations on the outer periphery. Needless to say, this connection may be achieved by fixing the cylinder head 12 and the cylinder body 11 to the crankcase 13 by one through bolt, instead of using the above-described separation bolt.

A large number of cooling fins 11f are provided on the outer circumference of the cylinder body 11.
Are provided in multiple stages. Of these, the cooling fin 11f provided closest to the crankcase 13 has a larger shape than the other fins. On the other hand, a large number of cooling fins 12f are also provided on the upper surface of the cylinder head 12 so as to be erected, and a cooling base fin 12b is provided on the outer periphery of the cylinder body so as to extend in a direction orthogonal to the cylinder axis direction. Have been. This cylinder head 12 has a concave-convex cooling fin 12m with a low height on the back (bottom) as well.
Are arranged in multiple rows.

14 is a piston and 15 is a crankshaft. Crankshaft 15
The centrifugal clutch 16 (only the outer shape is indicated by a dashed line) is connected to one end (right end) thereof, and a multi-plate clutch 17 is operatively connected to the centrifugal clutch 16. The power is further transmitted from the multi-plate clutch 17 to the sprocket 9.

At the other end (left end) of the crankshaft 15 is a rotor 20 of the generator 18.
Are connected, and a cooling fan 19 is fixed to the top surface of the rotor 20. In the generator 18, an outer periphery of the rotor 20 is surrounded by a cover 21 made of aluminum casting, and an annular ventilation gap 22 for introducing cooling air into the generator 18 is formed between the outer peripheral edge of the rotor and the cover 21. ing. The partition-like cover 21 partially extends to the sprocket 9 and covers the outside of the sprocket 9.

The cooling fan 19 includes a conical bulging base 19 a fixed to the top surface of the rotor 20, a plurality of blades 23 radially provided on an outer periphery of the base 19, and an annular shape fixed to the blade 23. It is composed of a plate 23p. The outer diameter of the base 19a is a rotor
It is smaller than the outer diameter of 20. Radially extending wings 23
Are disposed so as to face a direction in which they are erected substantially vertically on the top surface of the rotor 20. The annular plate 23p is formed concentrically with the crankshaft 15, and is fixed to the top where the blades 23 are provided upright. The outer peripheral edge of the annular plate 23p is located at substantially the same position as the outer peripheral end of the blade 23, and the diameter (inner diameter) of the inner peripheral edge of the annular plate 23p is substantially the same as the diameter of an intake port described later. I have. The inner peripheral portion of the annular plate 23p is formed as a conical inclined portion that gradually expands from the inner peripheral edge side. On the top surface of the rotor 20,
A ventilation hole 24 penetrating between the blades 23 in and out is provided. The outer peripheral end of the blade 23 is
From the top surface to the ventilation gap 22 along the outer peripheral surface, and further into the ventilation gap 22.

The cooling fan 19 increases the amount of cooling air generated by the blade 23 having the above-described shape. In addition, since the cooling fan itself does not expand outward in the crankshaft direction, the amount of cooling air can be increased without particularly widening the width of the entire engine. Most of the cooling air thus increased is sent to the cylinder body 11 side, but the remaining part is forcibly supplied to the ventilation gap 22 side, and
Inside to cool the generator 18. The cooling air after cooling the generator 18 is exhausted again outside through the ventilation hole 24 on the top surface,
Since the position of the ventilation hole 24 is between the blades 23 and the place where the flow of the cooling air is the largest, a large amount of the cooling air is efficiently sucked from the inside of the rotor.

Also, on the outside of the cooling fan 19 and the cylinder body 11,
A resin shroud 25 is provided. Shroud 25
Sends the cooling air generated by the cooling fan 19 to the cylinder body 11
Further, a guide path leading to the back surface of the base fin 12b of the cylinder head 12 is formed. The shroud 25 includes a left shroud portion 25a and a right shroud portion 25b which are divided into two. The left shroud portion 25a is provided with three annular through-holes 28 for intake formed in a position facing the cooling fan 19 concentrically, and constitutes an intake port. The diameter of the intake port is substantially the same as the inner diameter of the annular plate 23p. An exhaust port 29 is provided in the right shroud portion 25b.

Right shroud part 2 of both left and right shroud parts 25a, 25b
5b is through a rubber grommet 32 with a bolt 30,
Together with the crankcase cover 31, it is fixed to the crankcase 13 at a plurality of locations. The left shroud portion 25a is connected to the right shroud portion 25b fixed as described above via the connecting portions 26 and 27 provided on the mating surface of the two, and the power is generated at a location indicated by Z in FIG. It is fixed to the machine cover 21 and forms a shroud 25.

The left and right shroud portions 25a, 25b have rubber seals 33, 34 attached to their peripheral edges, respectively.
The cylinder head 22 and the generator cover 21 are brought into contact with each other via 3, 34. Among these, the portion of the sealing material 33 that comes into contact with the base fin 12b in an annular shape is divided into two parts,
Each is independently mounted on the left shroud portion 25a and the right shroud portion 25b. Also, of the cooling fins of the cylinder body 11, the cooling fin provided closest to the crankcase
A sealing material 37 is attached to the inner surface of the shroud 25 so as to surround the cooling fin 11f so as to abut the outer periphery of the cooling fin 11f. Another sealing member 38 attached to the end of the generator cover 21 is in contact with the outer peripheral portion of the cooling fin 11f other than the contact of the sealing member 37. This cover 21
Extends to the cooling fins 11f of the cylinder body 11 provided closest to the cylinder case (closer to the cover), thereby forming a cooling air guide wall portion X between the cover 21 and the cooling fins 11f. ing. These sealing materials 3
Since the cooling air does not leak from the middle of the cooling air passage by providing the cooling air passages 3, 34, 37, and 38, cooling is efficiently performed. Also, by providing the guide wall portion X between the cover 21 and the cooling fin 11f closest to the cylinder case,
Since a cooling air introduction passage can be formed between the guide wall portion X and the shroud 25 facing the guide wall portion X, the cooling air can be easily sent to the cylinder body 11 side, and is adjacent to the upstream side of the guide wall portion X. The cooling air is also easily guided to the ventilation gap 22.

When the motorcycle equipped with the air-cooled engine having such a configuration travels, the front cylinder head 12 is cooled by the traveling wind. Cooling at this time is performed very efficiently because the cylinder head 12 has the base fins 12b and the cooling surface of the base fins 12b faces the traveling wind.

On the other hand, the cooling fan 19 sucks outside air through the through hole 28 of the shroud 25, and then forcibly blows air to the cylinder body 11 side. Here, the cooling air exchanges heat with the cooling fins 11f, and also contacts the back surface of the base fins 12b of the cylinder head 12 to perform heat exchange.

Further, since the cooling fan 19 has such a shape that its blades 23 are directed from the top surface of the rotor 20 to the ventilation gap 22 along the side circumference, as described above, a part of the cooling air is The generator 18 is forcibly supplied to cool the generator 18. The cooling of the generator 18 is performed by providing ventilation holes 24 provided on the top surface of the rotor 20 so as to penetrate between the blades 23, so that the cooling air in the rotor 20 is sucked out. It is very efficient to promote. Moreover, since the amount of air blown by the cooling fan 19 is increased by the blade shape, the cooling fan 19 can be implemented without sacrificing the cooling effect on the cylinder side and without increasing the size of the engine.

Further, since the cooling fan 19 forms an outside air introduction passage obliquely between the conical base 19a and the inner peripheral portion of the annular plate 23p formed in the conical slope, the passage is pressure-fed by the blades 23. Since the flow of outside air becomes a diagonal flow that tilts obliquely backward with respect to the radial direction, it is possible to obtain high suction efficiency in a motorcycle engine that rotates at a relatively high rotational speed, thereby improving cooling efficiency Can be.

A guide wall X is provided between the cover 21 and the cooling fin 11f closest to the cylinder case.
To form a cooling air introduction passage between the shroud 25 and the facing shroud 25, so that the cooling air is easily sent to the cylinder body 11 side, and the cooling air is introduced into the ventilation gap 22 adjacent to the upstream side of the guide wall portion X. Since the cooling air can be easily guided, the cooling effect of both can be further enhanced.

In addition, the projection wall 35 provided on the blowing side of the cooling air is
This is for preventing the cooling air blown out by the cooling fan 19 from returning to the cooling fan side again, and includes a wall integrally formed on the cover 21 and a wall formed on the left shroud portion 25a side in the same shape. Are formed by matching them.

〔The invention's effect〕

As described above, the forced air-cooled engine of the present invention is configured such that the outer periphery of the rotor is surrounded by the cover via the ventilation gap, and the blades of the cooling fan are extended along the outer periphery of the rotor toward the ventilation gap, In addition, since a ventilation hole is provided on the top surface of the rotor so as to penetrate between the blades inside and outside the blades, it is possible to increase the blowing amount of the cooling fan with a simple configuration without increasing the size of the engine. Moreover, it enables good cooling of the generator.

Further, the cooling fan is provided with a plurality of blades arranged radially on the outer periphery of a conical base fixed to the rotor, and an annular plate concentric with the crankshaft is fixed to the top of the blades. The inner diameter of the annular plate is made substantially the same as the diameter of the intake port, and the inner peripheral portion of the annular plate is formed as a conical inclined portion that gradually expands from the inner peripheral edge side. An oblique outside air introduction passage can be formed between the inclined portion and the inclined portion, so that the flow of the outside air pumped through the introduction passage by the blade becomes a diagonal flow inclined obliquely rearward with respect to the radial direction. Since high external air suction efficiency can be obtained in an engine such as a motorcycle that rotates at a rotational speed, the cooling capacity can be further improved.

Further, by providing a cooling air guide wall between the cover and the cooling fin of the cylinder body closest to the cover, a cooling air introduction passage to the cylinder body side is provided between the guide wall and the shroud facing the cooling wall. The cooling air can be easily blown to the cylinder body side and can be easily guided to the ventilation gap adjacent to the upstream side of the guide wall, so that the cooling effect of both can be further enhanced. Wear.

[Brief description of the drawings]

1 is a cross-sectional view of a forced air-cooled engine according to an embodiment of the present invention, FIG. 2 is a side view of the engine, FIG. 3 is a view taken in the direction of the arrow III in FIG. 2, and FIG. FIG. 5 is a side view of a motorcycle equipped with the engine, as viewed from arrows IV-IV. 4 ... Engine, 11 ... Cylinder body, 11f ... Cooling fin, 12 ... Cylinder head, 15 ... Crankshaft, 18
…… Generator, 19 …… Cooling fan, 19a …… Base, 20 ……
Rotor, 22 ventilation gap, 23 blade, 23p annular plate, 24 ventilation hole, 25 shroud, 28 through-hole (inlet), X guide wall.

Claims (1)

(57) [Claims] 1. A generator rotor is fixed to one end of a crankshaft, a cooling fan is fixed to a top surface of the rotor, and cooling air generated by the cooling fan is guided to cooling fins on the outer periphery of a cylinder body. In a forced air cooling engine in which a shroud provided with an intake port at a position facing the cooling fan is attached to an engine body, the cooling fan is bulged in a conical shape fixed to the rotor and having a smaller outer diameter than the rotor. A base, a plurality of blades extending radially outward from the rotor on the outer periphery of the base and arranged in a direction to be erected on the top surface of the rotor; and a ridged top of the blades And an annular plate formed concentrically with the crankshaft, and the outer peripheral edge of the annular plate is positioned substantially the same as the outer peripheral end of the blade, while the inner diameter is the diameter of the intake port. The inner peripheral portion of the annular plate is formed as a conical inclined portion that gradually expands from the inner peripheral edge side, the outer periphery of the rotor is surrounded by a cover, and cooling air flows between the outer peripheral edge of the rotor and the cover. To form a circular ventilation gap to introduce the, the outer peripheral end of the blade is extended into the ventilation gap along the outer periphery of the rotor,
A ventilation hole is provided on the top surface of the rotor so as to penetrate in and out between the blades, and the guide wall of the cooling air extends between the cover and a cooling fin of the cylinder body provided closest to the cover. Forced cooling engine with formed part.