Patent Description:
As is known, an alternator is a rotating electrical machine that converts rotation mechanical energy provided by a primary motor into electrical energy that is transferred to a user in the form of alternating current.

Prior art alternators with a cooling system are disclosed for example by <CIT>, <CIT> or <CIT>.

Constructively, an alternator of the prior art is represented in schematic form in <FIG>, where it is indicated overall with A and where it can be observed that it comprises a stator case B which contains the stator C and the rotor D with which the rotation shaft E is associated.

The stator case B is axially comprised between the rear shield, not represented, and the front shield H from which the end L of the rotation shaft E protrudes to which the cooling fan M that is housed in the front shield H is keyed.

It can be observed that the outer diameter of the fan M is smaller than the inner diameter of the stator case B and the assembly of the alternator A takes place by performing the following operations:.

When the assembly is completed, the alternator A then assumes the configuration represented in <FIG>.

The alternators A of the prior art of the type now described have the advantage of mounting simplicity since the front shield H is made as a single body and is easily fixed to the stator case B after the fan M has been fixed to the rotation shaft E.

However, these alternators have the drawback that the outer diameter of the fan M cannot exceed the inner diameter of the stator case B and must be significantly smaller than it since, otherwise, this would prevent the mounting of the front shield H and the fixing thereof to the stator case B.

Fans of this type could result in insufficient cooling of the alternator and the impossibility of increasing the electrical power that it could deliver.

To overcome these drawbacks and limitations, alternators are made, one of which is schematically represented in <FIG> where it is indicated overall with N, which differ from the alternator A just described in that the front shield <NUM> is made of two parts S1 and S2 which can be conjugated to each other by means of flanges F or similar means and which allows to accommodate a fan P whose outer diameter is greater than the outer diameter of the stator case B.

Alternators of this type have the advantage that the fan P with increased diameter than the outer diameter of the stator case improve cooling and this allows to increase the power that the alternator is able to deliver.

Mounting the alternators of this type involves the execution of the following operations:.

It is understood that this embodiment involves first of all a higher cost for making the front shield <NUM> which must be made up of two parts provided with flanges F and with fixing means for their mutual connection.

In addition, this embodiment also has a higher mounting cost due to the longer assembly times for the connection of the two parts S1 and S2 that make up the front shield <NUM>.

The present invention is intended to overcome the drawbacks of the prior art which have been described hereinabove.

Specifically, the present invention aims to realize an alternator provided with a cooling fan whose outer diameter is greater than the outer diameter of the stator case that is housed in a front shield made as a single monoblock body. The present invention also aims to realize a method that, in an alternator provided with a cooling fan with outer diameter greater than the outer diameter of the stator case and with a front shield made as a single monoblock body, allows to assemble the cooling fan to the rotor shaft before mounting the front shield on the stator case.

The aim listed are achieved by the alternator having the characteristics according to claim <NUM> to which reference will be made and by the mounting method according to claim <NUM>.

In the alternator of the invention, the advantages deriving from the simplicity of construction and mounting that can be found in alternators with cooling fan with a diameter smaller than the outer diameter of the stator case are combined with the advantages deriving from the use of a cooling fan with an increased diameter than the outer diameter of the stator case. Advantageously, in fact, the use of the cooling fan with increased diameter improves the cooling of the alternator allowing to increase the deliverable power thereof.

In addition, advantageously, the use of a front shield in a single monoblock body and therefore with simpler and more economical construction also facilitates the mounting operations of the alternator.

The aims and advantages listed, and any others, will be better highlighted below during the description of a preferred, but not exclusive, embodiment of the alternator of the invention, which is given below for indicative and not exclusive purposes only with reference to the appended drawing tables, in which:.

The alternator object of the invention is represented in different views in <FIG> where it is indicated overall with <NUM>.

It can be observed that the alternator <NUM> comprises a stator case <NUM> which houses a stator winding <NUM> and a rotor <NUM>, the latter inserted coaxially inside the stator winding <NUM>.

A rear shield <NUM> and a front shield <NUM> axially delimit the stator case <NUM>, both being removably fixed to the ends of the same stator case <NUM> by means of removable connection means of known type, preferably but not exclusively bolts.

The rotor <NUM> is associated with a rotation shaft <NUM> which identifies a longitudinal axis X of rotation and which has a first end 7a protruding from the front shield <NUM>.

There is also a cooling fan <NUM> that protrudes from the stator case <NUM> and is keyed to the first end 7a of the rotation shaft <NUM>.

The fan <NUM> is peripherally provided with a plurality of blades <NUM> and has the outer diameter greater than the outer diameter of the stator case <NUM>.

It can also be observed that the front shield <NUM> has a box shape and according to the invention in it there is a plurality of slits <NUM> which are configured to allow the passage of the blades <NUM> of the fan <NUM>.

This occurs when the front shield <NUM> is first positioned as it can be observed in particular in <FIG>, so that each slit <NUM> is aligned with a corresponding blade <NUM> of the fan <NUM>, and then shifted axially towards the fan <NUM> according to the direction defined by the longitudinal axis X of the rotation shaft <NUM>.

In this way, each blade <NUM> passes through a respective slit <NUM>, as it can be observed in <FIG>, until the front shield <NUM> receives the fan <NUM> and is arranged close to the stator case <NUM> to which it is finally fixed at the flange ring 2a visible in <FIG> by means of the removable connection means.

As far as the front shield <NUM> is concerned, it can be observed that its box shape is defined by a rear plane <NUM> in which the slits <NUM> are made, by a front plane 11a facing and spaced from the rear plane <NUM> and by a lateral surface 11b peripherally fixed to the rear <NUM> and front 11a planes.

The front plane 11a could be substantially closed, apart from the first end 7a of the rotation shaft <NUM> coming out, for complete protection against accidental contact by the operator with the blades <NUM>, or, according to the preferred embodiment of the invention, as represented in <FIG>, it could be centrally drilled so as to define a first annular abutment zone <NUM> for the coupling of an outer main motor, not represented in the figures, the latter acting to rotate the aforementioned rotation shaft <NUM>.

According to the invention, the outer diameter of the plurality of blades <NUM> of the fan <NUM> is greater than the diameter of such first annular abutment zone <NUM>.

In any case, the front shield <NUM> also acts as a protective casing against accidental contact by the operator with the blades <NUM> of the fan <NUM>.

Preferably, the front shield <NUM> is made as a single body.

Furthermore, in the embodiment being described, the front shield <NUM> has a cylindrical box shape, but this is only one of the many possible embodiments in which it can be made.

Referring also to the detailed <FIG>, it can be observed that, according to the preferred embodiment of the invention, in the rear plane <NUM> of the front shield <NUM> in which the slits <NUM> are made, there is also a second annular abutment zone <NUM> which is configured to couple with the stator case <NUM> when the front shield <NUM> is arranged close to the stator case <NUM>, as can be observed particularly in <FIG> and <FIG>.

The fixing of the front shield <NUM> to the stator case <NUM> takes place by means of removable connection means which, as it has been said, preferably but not exclusively comprise bolts, which are inserted into through holes <NUM> present in the second annular abutment zone <NUM> of the rear plane <NUM> and in the profile of the stator case <NUM>.

According to the preferred embodiment of the invention, the profiles of the blades <NUM> of the fan <NUM> develop according to a plane orthogonal to the longitudinal axis X defined by the rotation shaft <NUM> and parallel to the rear plane <NUM> of the front shield <NUM>.

Furthermore, preferably but not necessarily, the slits <NUM> and the blades <NUM> have straight profiles that develop in a radial direction with respect to the rotation shaft <NUM>.

With reference to <FIG>, it can be observed that each of the through holes <NUM> belongs to a first angular zone 14a of the rear plane <NUM> which is comprised between two slits <NUM> which are consecutive to each other that define a first angle α between them.

In addition, in the rear plane <NUM> there can be also identified second angular zones 14b each of which is comprised between two slits <NUM> which are consecutive to each other, of which at least one external to the aforementioned first angular zone <NUM>, which define between them a second angle β whose width is less than the width of the first angle α.

Since the presence of the slits <NUM> creates a structural weakening of the rear plane <NUM>, according to the preferred embodiment of the invention, this weakening is overcome by delimiting each slit <NUM> with two lateral ribs <NUM>, one arranged at one edge and another arranged at the opposite edge of the same slit <NUM>.

Furthermore, still preferably but not necessarily, each first angular zone <NUM> of the rear plane <NUM> is also stiffened by arranging in it central ribs <NUM> which are comprised between the lateral ribs <NUM> of the two slits <NUM> that delimit the angular zone <NUM>.

In the embodiment described, in each angular zone <NUM> there are five stiffening bodies which comprise two lateral ribs <NUM> each arranged at the side of a respective slit <NUM> and three central ribs <NUM> comprised between the two aforementioned lateral ribs <NUM>.

Obviously, in other embodiments the number of ribs may be different. Preferably but not necessarily, the lateral ribs <NUM> and the central ribs <NUM> are projecting from the rear plane <NUM> and facing towards the stator case <NUM> and develop in a radial direction with respect to the rotation shaft <NUM>.

The described embodiment therefore achieves the aim of the invention to realize an alternator <NUM> provided with a cooling fan whose outer diameter is greater than the outer diameter of the stator case, said fan being housed in a front shield made as a single monoblock body.

In fact, it has been seen that the presence of the slits <NUM> made in the front shield <NUM> allows the passage of the blades <NUM> of the fan <NUM> and therefore allows the front shield <NUM> to be made as a single body and to couple it to the stator case <NUM>.

In addition, the use of a front shield <NUM> in single body makes the mounting operations of the alternator <NUM> simpler, faster and less expensive.

Operationally, for assembling the alternator <NUM> it is first necessary to provide: the stator case <NUM>, the rotor <NUM>, the rotation shaft <NUM>, the fan <NUM>, the rear shield <NUM> and the front shield <NUM> together with other auxiliary materials such as the removable connection means of the rear <NUM> and front <NUM> shields to the stator case <NUM>.

The rotation shaft <NUM> is then coupled to the rotor <NUM> and the rear shield <NUM> is then fixed to the stator case <NUM>.

With particular reference to <FIG> and <FIG>, according to the preferred embodiment of the invention, the rotor <NUM> with the rotation shaft <NUM> is inserted inside the stator case <NUM>.

The fan <NUM> is then assembled to the first end 7a of the rotation shaft <NUM> that protrudes from the stator case <NUM> from the opposite side of the rear shield <NUM>.

It is not excluded, however, that according to different embodiments of the invention the series of operating steps described so far can be performed in a different order.

For example, the fan <NUM> could be assembled at the first end 7a of the rotation shaft <NUM> prior to the insertion of the rotor <NUM> with the same rotation shaft <NUM> inside the stator case <NUM>.

At this point the front shield <NUM> is arranged coaxial to the first end 7a of the rotation shaft <NUM> positioning each of the slit <NUM> thereof aligned with a corresponding blade <NUM> of the fan <NUM>.

According to the preferred embodiment of the invention, then the front shield <NUM> is axially shifted towards the stator case <NUM> making sure that each blade <NUM> passes through a corresponding slit <NUM> until the front shield <NUM> receives the fan <NUM> and its second annular abutment zone <NUM> abuts against the stator case <NUM>.

It is also not excluded that according to different embodiments of the method of the invention the aforementioned steps of coupling the front shield <NUM> with the fan <NUM> can be performed prior to the insertion of the rotor <NUM> with the rotation shaft <NUM> inside the stator case <NUM>.

In any case, the front shield <NUM> is then fixed to the stator case <NUM> by means of the removable connection means and the assembly of the alternator <NUM> is thus completed.

The description highlights that the assembly of the alternator <NUM> of the invention, with respect to equivalent alternators of the prior art provided with a fan with diameter greater than the outer diameter of the stator case and also greater than the diameter of the first annular abutment zone <NUM> for the coupling of the main motor, is made easier and faster since it uses the front shield <NUM> made as a single monoblock body but provided with slits <NUM> for the passage of the blades <NUM> of the cooling fan <NUM>.

In fact, the mounting steps of the alternator <NUM> of the invention are the same as those that have been briefly listed in the introductory part to describe the assembly of any alternator of the prior art having the cooling fan with outer diameter smaller than the outer diameter of the stator case.

Furthermore, the assembly of the alternator of the invention is also faster and therefore less expensive than equivalent alternators of the prior art that fit a front shield made up of two parts that need to be coupled together by means of connection members, for example flanges with screws or bolts.

Claim 1:
Alternator (<NUM>) comprising:
- a stator case (<NUM>) containing a stator winding (<NUM>) and a rotor (<NUM>), the latter inserted coaxially inside said stator winding (<NUM>);
- a rear shield (<NUM>) and a front shield (<NUM>) both removably fixed to said stator case (<NUM>) by means of removable connection means;
- a rotation shaft (<NUM>) identifying a longitudinal axis (X), coaxially associated with said rotor (<NUM>);
- a cooling fan (<NUM>) provided with a plurality of blades (<NUM>) and keyed to a first end (7a) of said rotation shaft (<NUM>), said fan (<NUM>) having the outer diameter greater than the outer diameter of said stator case (<NUM>) and being protruding from said stator case (<NUM>),
characterized in that in said front shield (<NUM>) there is a plurality of slits (<NUM>) which are configured to allow the passage of said blades (<NUM>) of said fan (<NUM>) when said front shield (<NUM>) is first positioned so that each slit (<NUM>) is aligned with a corresponding blade (<NUM>) and then shifted axially towards said fan (<NUM>) according to said longitudinal direction (X) so that each blade (<NUM>) passes through the corresponding slit (<NUM>) so that said fan (<NUM>) is received in said front shield (<NUM>) and that said front shield (<NUM>) is finally fixed to said stator case (<NUM>) by means of said removable connection means.