Description

The present invention relates to a cooling system of an engine, e.g. an air-cooled engine, for example of a scooter, wherein a cooling fan is controlled by a shaft, put in rotation by the crankshaft or by the crankshaft itself, and it directs an air flow to touch an engine block through a duct .

The axis of the internal combustion engine generally is transversal with respect to the longitudinal development of the motorcycle and then it is horizontal with respect to a ground plane, as well as perpendicular to a vertical plane which is substantially defined by the rotation plane of the fixed, i.e. not steering, rear wheel, when the motorcycle moves forward according to a straight line.

Conveniently, the fan which provides for cooling the engine can be directly keyed to an end of the crankshaft which drags it in rotation, or to another axle adjacent and parallel to the crankshaft, actuated in rotation thereby.

The positioning of the protection guard, therethrough the air flow is drawn, makes that it is not hit by the air flow frontally, but tangentially . The air required for cooling is then drawn by the fan the axis thereof is substantially perpendicular to the air flow deriving from the forward motion of the motorcycle.

In the known examples, wherein the fan is not actuated independently from the rotation of the crankshaft, for example by means of a service electric motor, the rotation regime of the fan does not depend directly upon cooling needs, but it is determined by the rotation regime of the engine .

However, it is apparent that the engine could have cooling needs which do not depend upon the rotation regime of the crankshaft, for example in a starting phase, or with a particularly cold climate.

Nevertheless, this involves that the fan does not stop rotating: it continues to drawn air with a certain head depending upon the rotation regime of the crankshaft and this slows down the rise in temperature in the engine, which then hardly starts the regime operation.

This involves a not correct operation of the engine, a higher energy consumption due to higher inertia and due to the operation of the oil pump which works on a less fluid liquid.

The technical problem underlying the present invention is to provide a cooling system for engines allowing to obviate the drawbacks mentioned with reference to the known art.

Such problem is solved by a cooling system as specified in appended claim 1.

In a preferred solution, the fluid inside the engine is the lubricating oil circulating in the engine block, and the activation means includes a thermoexpansible material which increases its own volumetry when the temperature increases and directly acts on the partition by rotating it. In particular, this material preferably can be a wax and the activation then takes place by means of a wax actuator.

Said wax actuator can be placed at a direct contact with the portion of the engine block to be cooled down. As shown in the appended drawings, said wax actuator is placed directly on the finned wall of the cylinder block wherein the piston slides .

The main advantage of the cooling system according to the present invention lies in the fact of preventing the unwished cooling down of the engine when it is still cool, with a wholly mechanical solution which does not alter the structure of the fan and of the engine. This solution further allows a faster response time of the cooling system, since the actuation means is directly linked to the temperature of the engine portin to be cooled.

Moreover, since the partition is directly placed within the duct downstream to the fan, the partition is protected by accidental shocks, which could hinder the operation thereof, and by the damages derivable from an excessive heating of the engine block.

The present invention will be described hereinafter according to a preferred embodiment thereof, provided by way of example and not for limitative purposes with reference to the enclosed drawings wherein:

* figures 1A and IB show partial views of respective longitudinal sections of an air-cooled engine and of the fan thereof, incorporating a cooling system according to the invention;

* figures 2A and 2B show partial views of respective longitudinal sections of an air-cooled engine and of the fan thereof, illustrating the operation of the cooling system of figures 1A and IB;

* figure 3 shows a perspective top view of the cooling system of the previous figures, in partial section; and

* figure 4 shows a perspective view of a detail of the system of figure 3.

By referring to figures, a propulsion unit 1 is partially represented. It comprises an air-cooled single-cylinder internal combustion engine, the engine block thereof is represented wherein the cylinder is formed, with a finned outer surface.

The propulsion unit 1 even comprises a crankshaft 2 which transmits the motion to not represented transmission elements. The crankshaft 2 extends in opposite direction with respect to the transmission elements, and it is connected to an electric motor 3 comprising respective stator windings 4.

It is to be noted that the crankshaft 2 is transversal with respect to the longitudinal development of the motorcycle and then it is horizontal with respect to a ground plane, as well perpendicular to a vertical plane which is substantially defined by the rotation plane of the fixed, i.e. not steering, rear wheel, when the motorcycle moves forward according to straight line.

The motor 3 can be a simple current generator which provides for supplying electric energy to the combustion engine and to possible services and/or for feeding a battery.

In the present example, the propulsion unit 1 comprises a cooling system having a cooling fan 5 keyed directly on the crankshaft 2 which then acts as shaft for actuating the fan.

It is to be meant that the fan could be keyed on a different driving shaft with respect to the crankshaft, in case dragged thereby to offset the fan with respect to the crankshaft.

The fan 5 is included in a casing 6 which has an intake aperture 7 in case equipped with a protective guard. The fan 5 is keyed on an end of the crankshaft 2 by means of a simple fixed connection. It then rotates continuously at the regime of the crankshaft 2, and it directs a cooling air flow through a duct 8 formed by an extension 9 of the casing 6, so that the air flow touches the finned surface of the engine block by cooling it down. The duct 8 extends downstream, according to the discharge direction of the air flow from the fan 5.

A partition 10 is revolvingly fastened near the fan 5, inside the duct 8, to an axis 11 acting as fulcrum. At the ends of the axis 11, respective preloaded springs are provided: a first preloaded spring 12 which tends to keep the partition 10 in a starting configuration wherein it obstructs the duct 8 (figures IB and 2B) ; and a second preloaded spring 13 which tends to keep the partition 10 in a second configuration at regime wherein the duct 8 is free (figures 1A and 2A) .

Both springs are of helical type, wound around the axis 11 of the partition 10, and they transmit opposed twisting forces on the partition 10. The force exerted by the first spring 12 on the partition 10 is higher than the one exerted by the second spring 13.

The herein described cooling system comprises means for activating the partition 10, which is sensible to the temperature of a fluid circulating in the propulsion unit 1.

In this example, the fluid is the lubricating oil circulating in the engine block, forced in circulation by the oil pump of unit 1.

The oil then touches the above-mentioned activation means which, in the present case, is constituted by a wax actuator 14 having inside a tank 15 full of thermoexpansible material, preferably a wax.

The expansion of this material determines the translation of a control rod 17 which directly presses, without the interposition of mechanical members or rods, on the partition 10 by accompanying the opening thereof. The partition 10, through the opening, is displaced substantially parallel to the disharge direction of the air flow, in opposition to the twisting force of the first spring 12 (figure 1A) , that is overcoming the difference in the forces exerted by the first spring 12 with respect to the second spring 13.

The partition 10 comprises a proximal edge 18, near the axis 11, and a farer distal edge 19.

In the starting configuration, the distal edge 19 of the partition 10 rests upon a second abutting element 21, the partition 10 then is raised by obstructing the air duct 8 (figure IB) .

By increasing the temperature, the rod 17 extends by rotating the second spring 13 and the partition 10 towards said regime configuration. As the oil temperature increases, the partition rotates gradually, due to the effect of the combined force of the two springs 12 and 13 and of the pressure exerted by the rod 17, as far as the proximal edge 18 is resting upon a first abutting element 20, pushed by the first spring 12. The first abutment element prevents the partition 10 from rotating excessively.

When the rod 17 continues to extend, it acts only on the second spring 13. In this way, the position of the partition 10, related to a given temperature, is always the same.

In this way, an adjustment of the air flow is obtained which is partialised when the engine is not yet at its maximum temperature .

When the operation of the propulsion unit 1 stops, the engine block cools down and the partition returns to its starting position, that is to the first configuration.

It is meant however that the activation means can assume other shapes, for example be based upon thermoexpansible stiff elements or even other.

To the above-described cooling system a person skilled in the art, with the purpose of satisfying additional and contingent needs, could introduce several additional modifications and variants, however all comprised within the protective scope of the present invention, as defined by the enclosed claims.