Axial fan for a cooling fan module

An axial fan for a cooling fan module has a cup-shaped central hub with a front wall intended to be connected to the rotor of an electric motor at connection points and with a side wall from which a plurality of outer blades extend. At least one transverse opening is provided in the front wall of the hub, between each of the connection points and the side wall, the opening extending in the circumferential direction, relative to the axis of the hub, beyond the associated connection point in both directions, so that the vibrations transmitted during operation from the motor to the front wall of the hub are propagated towards the side wall of the hub following a path which is longer than a radial path.

CROSS REFERENCE TO RELATED APPLICATIONS

This non-provisional patent application claims priority under 35 U.S.C. § 119(a) from Patent Application No. TO2014A000340, filed in Italy on Apr. 23, 2014, the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to an electric fan for a cooling fan module, in particular for a heat exchanger (such as a radiator) of a motor vehicle.

BACKGROUND OF THE INVENTION

More specifically, the present invention relates to an axial fan for use in such a module, comprising an essentially cup-shaped central hub with a front wall intended to be connected to the rotor of an electric motor at/in a plurality of connection points or areas, and a side wall from which a plurality of outer blades extend.

These fans are generally fixed to the rotor of the drive motor by means of screws or bolts.

During operation the motor generates considerable vibrations which are transmitted to the fan and cause the generation of an acoustic noise which is somewhat bothersome for the human ear, in particular at the low and middle range speeds.

SUMMARY OF THE INVENTION

Hence there is a desire for a fan of this type designed so as to overcome the abovementioned drawback of fans according to the prior art.

Accordingly, in one aspect thereof, the present invention provides an axial fan for a cooling fan module, comprising an essentially cup-shaped central hub with a front wall configured to be connected to the rotor of an electric motor at a plurality of connection points and with a side wall from which a plurality of outer blades extend, the fan having an axis about which the fan rotates in use; wherein at least one essentially transverse opening is provided in the front wall of the hub, between each of the connection points and the side wall, the opening extending in the circumferential direction, relative to the axis of the hub, beyond the associated connection point in both directions, so that vibrations transmitted during operation from the motor to the front wall of the hub are propagated towards the side wall of the hub following a path which is longer than a radial path.

Preferably, the transverse opening in the front wall of the hub, associated with each connection point, is in the form of an arc, i.e. a part of a circumference of a circle.

Preferably, at each connection point the front wall of the hub of the fan has a through-hole for receiving a fixing member for fixing the hub to the rotor of the motor, and wherein the extension in the circumferential direction of the opening is at least equal to three times the diameter of the corresponding through-hole.

Optionally, the extension in the circumferential direction of the opening is about five times the diameter of the corresponding through-hole in each direction.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the drawings1denotes overall an axial fan according to the preferred embodiment of the present invention. In the example embodiment shown the fan1comprises an essentially cup-shaped central hub2. The hub2has a front wall2aintended to be connected to the rotor R of an electric motor M (FIG. 3) at a plurality of connection points3. It should be realized that the term connection point may not be necessarily a single point and may include a connection area, in accordance with the type of fixing member or fastener used.

In the embodiment shown each connection point3comprises an essentially circular through-hole4for receiving a corresponding screw5for fixing the hub2to the rotor R (seeFIG. 3).

As shown inFIG. 1, the front wall2aof the hub2of the fan has three connection points3in positions offset with respect to the axis X of the hub2and the fan and angularly equidistant.

The hub2also has an at least approximately cylindrical side wall2bfrom which a plurality of curved outer blades6extend.

Preferably, as shown, the outer ends of the blades6are connected to a peripheral ring7coaxial with the hub2.

An essentially transverse opening10is formed in the front wall2aof the hub2, between each connection point3and the side wall2b. This opening extends in the circumferential direction, relative to the axis X of the hub2, beyond the associated through-hole4in both directions.

The arrangement is such that, during operation, the vibrations transmitted from the rotor R of the motor M to the front wall2aof the hub at the connection points3are propagated in the front wall2atowards the side wall2bfollowing a path which has to go around the openings10and which is therefore considerably longer than an essentially radial path which would instead exist in the absence of these openings10. As a result, the vibrations are significantly dampened in the front wall2aof the fan hub, before they reach the side wall2bof this hub and then the blades6and the peripheral ring7. The acoustic noise level generated during operation of the fan as a result of the vibrations transmitted from the electric motor is thus drastically reduced.

In the embodiment shown the transverse openings10associated with each connection point3are in the form of arcs or parts of circles.

Conveniently, although not necessarily, the extension, in each circumferential direction, of the openings10is at least equal to about 3 times, and preferably about 5 times, the diameter of the corresponding through-holes4.

The fan1may be conveniently made of molded plastic and the openings10in the front wall2aof its hub2are conveniently formed during the fan molding operation.

In the description and claims of the present application, each of the verbs “comprise”, “include”, “contain” and “have”, and variations thereof, are used in an inclusive sense, to specify the presence of the stated item or feature but do not preclude the presence of additional items or features.

The embodiments described above are provided by way of example only, and various other modifications will be apparent to persons skilled in the field without departing from the scope of the invention as defined by the appended claims.