JPH03117616A - Forcedly air-cooled engine - Google Patents

Abstract

PURPOSE:To restrain the occurrence of turbulence in a shroud by consecutively providing a stripe of projection on a centrifugal fan along the circumferential direction, and integrally providing an annular wall confronting with the peripheral surface of the stripe of projection, on the shroud. CONSTITUTION:A stripe of projection 20d extended to the upstream side of an air flow is provided consecutively along the circumferential direction on an open edge portion of a suction port in a turbofan 20. An annular wall 24c confronting with the peripheral surface of the projection 20d is integrally provided on a shroud 23. Thus, substantially a labyrinth seal is formed by the projection 20d and the annular wall 24c, so that an air flow discharged from the turbofan 20 is hard to be returned to the suction port side. Accordingly, it is possible to restrain the occurrence of a turbulence in the shroud 23.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a forced air-cooled engine employed in a scooter or the like, and particularly relates to the structure of an engine cooling fan and shroud.

[Conventional technology]

BACKGROUND ART Conventionally, unit swing type engines in which a transmission case supporting a rear wheel is integrally extended to one side of a crankcase have been widely used as engines for scooters. Many conventional unit swing engines are of the forced air cooling type, in which the engine body is cooled by airflow from a centrifugal fan that rotates together with the crankshaft. As this type of forced air cooling engine, for example,
There is one disclosed in Japanese Patent No. 237115. this is,
A centrifugal fan is fixed to the end of the crankshaft, and a shroud is attached to the engine body to cover the centrifugal fan and form a cooling air passage to the engine body. The shroud of this forced air-cooled engine is provided with an outside air intake port for introducing outside air at a location corresponding to the suction portion of the centrifugal fan. A so-called sirocco fan was used in which the fins were tilted forward in the direction of rotation.

[Problem to be solved by the invention]

However, in the conventional forced air-cooled engine configured as described above, most of the outside air discharged from the centrifugal fan is not blown onto the inner surface of the shroud, but is blown toward the front in the direction of rotation of the fan within the shroud. However,
A portion of the outside air blown onto the inner surface of the shroud is flown along a portion of the inner surface of the shroud located on the side of the centrifugal fan and returned to the suction port. Because this airflow is returned to the intake port side, in conventional forced air-cooled engines, not only does the air blowing efficiency become low, but also the turbulence caused by the above-mentioned airflow being stirred within the shroud increases wind noise. There was a problem. It is also possible to use a turbo fan, which has less noise than a sirofco fan, but in general, a turbo fan discharges a smaller amount of air per the same number of revolutions than a sirofco fan. For this reason, if a turbo fan is used, the air blowing efficiency will be lower than if a Shirofuco fan is used.

[Means to solve the problem]

In the forced air-cooled engine according to the present invention, a protrusion extending toward the upstream side of the air flow is provided in a series along the circumferential direction at the opening edge of the suction port of the centrifugal fan, and the protrusion is provided on the shroud. An annular wall facing the circumferential surface is integrally provided.

[For production]

Since a labyrinth seal is essentially formed between the annular wall of the shroud and the protrusion of the centrifugal fan, the air flow discharged from the centrifugal fan is difficult to return to the suction port, and turbulence is created within the shroud. can be prevented from occurring.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS. 1 to 4.

FIG. 1 is a side view showing a scooter equipped with a forced air-cooled engine according to the present invention, FIG. 2 is a cross-sectional view showing a main part of the forced air-cooled engine according to the present invention, and FIG. FIG. 1 is a diagram showing a turbo fan used in a forced air-cooled engine according to the invention, in which FIG. 1A is a front view and FIG. 1B is a rear view. FIG. 4 is a front view showing a shroud body used in a forced air-cooled engine according to the present invention. In these figures, 1 indicates a scooter, and this scooter 1 has a low-floor footrest 4 between a handle 2 and a seat 3.
A vehicle body cover 5 that covers the lower part of the seat 3 is provided at the rear. Reference numeral 6 denotes a body frame extending between the front and rear of the scooter 1, which includes a front frame 6a made of one tube, and two tubes branched left and right from the rear end of the front frame 6a. It is composed of a rear frame 6b and the like. 7 is a front wheel, 8 is a rear wheel, and 9 is a unit swing type engine for driving the rear wheel 8. This unit swing type engine 9 includes a forced air-cooled engine body 10, a V-belt type automatic transmission power transmission device 12 equipped with a belt 11 that transmits the power of this engine body 1o to the rear, and this V-belt type automatic transmission A transmission case 13 that accommodates a power transmission device 12 and supports the rear wheel 8 is provided, with the engine main body 10 facing inward of the vehicle body cover 5,
It is pivotably supported on the rear frame 6b of the frame 6 via a bracket 9a. The transmission case 13 of this unit swing type engine 9 also has a shock absorber 14.
It is connected to the rear frame 6b via. The engine main body 10 includes a cylinder 15 having a piston 10a.
and a crank case 1 connected to the transmission case 13.
6, and this crankcase 16 has a piston 10
Crankshaft 1 connected to a via a connecting rod 17
8 is rotatably supported. The left end of the crankshaft 18 is provided with the V-belt type automatic speed change power transmission device 12.
is attached, and a generator 19 is disposed at the right end. Further, the engine main body 10 is configured such that the crankshaft 18 is rotated clockwise when viewed from the right side of the vehicle body when the engine is driven. The generator 19 is composed of a rotor 19a fixed to the end of the crankshaft 18, and a stator 19b facing inside the rotor 19a and fixed to the crankcase 16.

Reference numeral 20 denotes a turbo fan serving as a cooling fan that sends outside air for cooling to the engine body 10, and this turbo fan 20 is fixed to the shaft end of the rotor 19a of the generator 19 with a mounting screw 21. That is, when the engine body 10 is driven and the crankshaft 18 is rotated, the turbo fan 20 is rotated by the rotor 19 of the generator 19.
Along with a, the vehicle is rotated clockwise when viewed from the right side of the vehicle. Moreover, this turbo fan 20 is shown in FIG. 3(a),
As shown in (b), a main plate 20a fixed to the rotor 19a, a plurality of fins 20b arranged in parallel along the circumferential direction on the main plate 20a, and an annular side plate connecting the upper portions of each fin 20b to each other. 20c, and is integrally molded from synthetic resin. A collar 22 into which a mounting screw 21 is inserted is press-fitted into the main plate 20a, and each of the fins 20b is inclined toward the rear side in the rotational direction. The inner peripheral portion of the side plate 20c protrudes outward in the axial direction of the turbo fan 20, in other words, toward the upstream side of the air flow sucked in by the turbo fan 20. That is, this protruding portion creates a series of protrusions 20d along the circumferential direction at the suction port of the turbo fan 20.
will be formed.

23 is a shroud for guiding the wind discharged from the turbo fan 20 to the engine body 10; this shroud 23 is connected to a shroud body 24 that covers the turbo fan 20;
and an engine cover 25 that covers the cylinder 15 of the engine main body 10, and are attached to the engine main body 10 by a screw (not shown). The shroud main body 24 is entirely integrally molded from synthetic resin, and has a suction nozzle 24 having an outside air intake port 24a in a portion facing the suction port of the turbo fan 20.
b is provided so as to face the inside of the protrusion 20d of the turbo fan 20, and the portion surrounding the suction nozzle 24b is recessed so that it approaches the side plate 20c of the turbo fan 20. turbo fan 2
An annular wall 24c facing the outer peripheral surface of the protrusion 20d at 0
is provided. Further, a portion of the shroud main body 24 corresponding to the outer peripheral edge of the turbo fan 20 is rounded and bulges out toward the opposite side from the crankcase 16 to have a substantially arcuate cross section. As shown in FIGS. 2 and 4, this bulging portion is formed so that the arc size gradually increases from the lower side of the shroud main body 24 toward the rear in the rotational direction of the turbo fan 20. That is, as the arc becomes larger, the distance between the inner circumferential surface of the shroud main body 24 and the outer circumferential edge of the turbo fan 20 gradually increases, and the air is discharged from the turbo fan 20 into this portion, in other words, inside the bulged portion. A cooling air passage is formed to collect the outside air and guide it to the engine cover 25.

In a forced air-cooled engine configured in this way,
When the engine body 10 is driven and the crankshaft is rotated, the turbo fan 20 together with the crankshaft 18 is rotated clockwise when viewed from the right side of the vehicle body, and outside air is sucked in from the intake nozzle 24b of the shroud body 24. will be included. Then, a part of the outside air is supplied to the shroud body 2 by the turbo fan 20 for cooling the generator 19.
4 and is blown into the engine cover 25, whereby the engine body 10 is forcedly cooled. Further, the outside air discharged from the turbo fan 20 is blown while being blown against the inner surface of the shroud main body 24, and a part of the outside air blown onto the inner surface of the shroud main body 24 flows along the inner surface of the shroud main body 24 to the suction nozzle 24b. However, the annular wall 24c of the shroud body 24 and the protrusion 2 of the turbo fan 20
0d narrows the flow path, thereby forming a substantial labyrinth seal, making it difficult for the outside air discharged from the turbofan 20 to be returned to the suction nozzle 24C.

Therefore, according to the present invention, generation of turbulent flow within the shroud can be suppressed.

In the above embodiment, a turbo fan was used as the centrifugal fan for cooling the engine, but it goes without saying that a sirocco fan may be used instead of the turbo fan.

Further, in the embodiment, the annular wall 24 of the shroud body 24
Although an example is shown in which the annular wall is provided on the radially outer side of the protrusion 20d of the turbo fan 20, the annular wall may also be provided on the inside of the protrusion 20d. Effects can be obtained. Furthermore, in the above embodiment, the annular wall 24c was formed by recessing the shroud body 24 toward the turbo fan 20, but the annular wall
It can also be formed by a protrusion as shown in the figure.

FIG. 5 is a sectional view showing another embodiment of the shroud body 24. In FIG. 5, numeral 31 indicates a shroud side protrusion as an annular wall according to the present invention, and this shroud side protrusion 31 is connected to the suction nozzle 24b in the shroud main body 24.
It is disposed radially outward from the protrusion 20d of the turbo fan 20, and is formed continuously along the circumferential direction of the turbo fan 2o. Even if the shroud side protrusion 31 is formed on the shroud main body 24 in this manner, the same effect as in the embodiment described above can be obtained.

Further, in each of the above-described embodiments, a part of the outside air discharged from the turbo fan 20 is used to cool the generator 19, but as shown in FIG.
A generator cover may be interposed between the shroud body 24 and the crankcase 16 to cover the outer peripheral portion of the generator and form a ventilation path.

FIG. 6 is a sectional view showing another embodiment in which a generator cover is attached to a forced air-cooled engine according to the present invention. In the same figure, 32 indicates a generator cover, and this generator cover 32 has a flange portion 32a attached to the crankcase 16 with a mounting screw 33, and a rotor 1 of the generator 19.
A cover main body 32b that covers the shroud 9a with a slight gap from the outer peripheral surface thereof, and a baffle plate 32c that extends radially outward of the rotor 19a and is connected to the edge of the shroud main body 24. The whole is integrally formed of synthetic resin or the like. Further, a portion of the air guide plate 32c of the generator cover 32 that corresponds to the outer peripheral portion of the turbo fan 2o is rounded and bulged toward the crankcase 16 side.

When the generator cover 32 configured in this way is attached,
The outside air discharged from the turbo fan 20 is difficult to flow to the generator 19 side (therefore, the amount of air blown to the engine body 10 side can be increased).Furthermore, the air guide plate 32c is provided with a rounded bulge. Therefore, the cooling air passage surrounded by the generator cover 32 and the shroud body 24 is formed round on both sides.Therefore, when the generator cover 32 is attached, air can be blown with high rectification efficiency. In addition, in the above-mentioned Figs. 5 and 6, the above-mentioned second
The same or equivalent members as those explained in the figures are given the same reference numerals, and detailed explanations are omitted here.

[Effects of the Invention] As explained above, the forced air-cooled engine according to the present invention has a series of protrusions extending toward the upstream side of the wind flow along the circumferential direction at the opening edge of the suction port of the centrifugal fan. and since the shroud is integrally provided with an annular wall facing the peripheral surface of the protrusion, a labyrinth seal is substantially formed by the annular wall of the shroud and the protrusion of the centrifugal fan; The air flow discharged from the centrifugal fan is less likely to be returned to the suction port side, and generation of turbulent flow within the shroud can be suppressed. Therefore, wind noise can be reduced and a low-noise forced air-cooled engine can be obtained. Furthermore, according to the present invention, the air flow discharged from the centrifugal fan is less likely to be returned to the suction port side, so that not only the air blowing efficiency can be improved, but also a turbo fan with less noise can be used. Furthermore, if a bulge with a substantially arcuate cross section is provided at a portion of the shroud corresponding to the outer peripheral edge of the centrifugal fan, the air flow blown onto the inner surface of the shroud and directed toward the suction port along the inner surface of the shroud can be Since the flow direction is reversed at the bulging portion having a substantially arcuate cross section and the flow is easily returned to the centrifugal fan side, the amount of air flow returned to the suction port side can be further reduced.

[Brief explanation of drawings]

FIG. 1 is a side view showing a scooter equipped with a forced air-cooled engine according to the present invention, FIG. 2 is a cross-sectional view showing a main part of the forced air-cooled engine according to the present invention, and FIG. FIG. 1 is a diagram showing a turbo fan used in a forced air-cooled engine according to the invention, in which FIG. 1A is a front view and FIG. 1B is a rear view. FIG. 4 is a front view showing a shroud body used in a forced air-cooled engine according to the present invention, FIG. 5 is a cross-sectional view showing another embodiment of the shroud body 24, and FIG. 6 is a forced air cooling according to the present invention. FIG. 4 is a cross-sectional view showing another embodiment in which a generator cover is attached to the engine. 9... Unit swing type engine, 10...
Engine body, 18...0. crankshaft, 20.・0.
Turbo fan, 20c...Side plate, 20d...Protrusion, 24...Shroud body, 24c...Annular wall, 31...Shroud side protrusion, 32...Power generation Machine cover 32c... Air guide plate.

Claims (1)

[Claims] In a forced air-cooled engine equipped with a centrifugal fan fixed to the end of the crankshaft, and a shroud that covers the centrifugal fan and guides the airflow to the engine body, a shroud that covers the centrifugal fan and guides the airflow to the engine body has a structure in which the upstream side of the airflow 1. A forced air-cooled engine characterized in that a series of protrusions extending to the side are provided along the circumferential direction, and the shroud is integrally provided with an annular wall facing the circumferential surface of the protrusions.