IT202300008178A1 - ALTERNATOR - Google Patents

Description

Description

ALTERNATOR

Technical field

The present invention relates to a dynamoelectric machine, in particular an alternating current synchronous generator, which is generally called an alternator.

Known art

The use of alternators has long been known in numerous applications because they allow the transformation of mechanical energy into alternating current electrical energy. For example, alternators are used in power plants or for the production of electrical energy in automobiles and, in general, in motor vehicles.

An alternator comprises an external casing which houses inside it a rotating part, the rotor, which is integral with a rotation shaft which can be rotated by actuator means, for example of the type of an internal combustion engine, hydraulic engine, electric engine. Coaxially to the rotor is mounted inside the casing a stator, which represents the static part. The rotor is equipped with an inductor group while the stator comprises an induced group. In particular, the rotor can be made with permanent magnets or it can comprise a substantially cylindrical core equipped with two or more poles on which are arranged windings powered by a direct current. The stator comprises a core on which windings are mounted and in these windings electromagnetic forces are generated induced by the rotating magnetic field of the rotor, according to the principles of magnetic induction.

One problem with alternators is the high amount of heat that is produced during their operation. Therefore, some solutions have been developed to ensure proper cooling of alternators.

International application WO2004106749 discloses an alternator comprising a cooling device consisting of a ventilation member which is mounted around a rotation shaft of the alternator rotor. The ventilation member is provided with a plurality of blades and includes intake openings formed on the blades to draw in a flow of air along a substantially axial path inside the alternator. Outlet openings are also formed on the blades to direct the flow of air outwards along a substantially radial path. The ventilation member also comprises deflector means to guide the flow of air from the axial path to the radial path. A problem that may arise with an air-cooling type is that for high capacity machines bulky ventilation members are necessary which require considerable power.

Another type of cooling used is liquid cooling.

Patent FR 2667738 illustrates an alternator cooled by a coolant. The alternator comprises a first outer casing and a second casing, arranged inside the outer casing, which is adapted to house the alternator. The first casing comprises at least one duct for supplying a coolant and at least one duct for the outlet of the coolant. The second casing comprises a series of grooves on an outer surface which cooperate with the ducts of the first casing to form circulation passages for the coolant.

U.S. Patent 6,617,715 describes an alternator comprising a first casing that internally houses the alternator components. In particular, a shaft is arranged inside the first casing and is rotatably supported by a pair of bearings. Mounted on the shaft is a two-pole rotor with inductor windings and also mounted at one end is a pair of excitation rings that are configured to mate with respective brushes. A stator is fixed to the first casing. A second outer casing is arranged around the first casing so as to define a chamber for the flow of a coolant. The first casing is provided with a plurality of fins that extend radially on an outer surface and are in contact with an inner surface of the outer casing to form respective axial channels for the flow of the coolant. The chamber includes an inlet duct and an outlet duct for the entry of the liquid into the chamber and for the exit of the liquid from the chamber, respectively. The coolant is distributed to the alternator from a vehicle engine cooling circuit that includes a pump, a heater and a radiator.

A problem complained about with the above-mentioned type of alternator cooled with a refrigerant is the structural complexity due to the provision of a chamber external to the alternator casing and an external circuit for the circulation of the refrigerant liquid fed to the chamber. Furthermore, the alternator is less robust because it has a greater number of components that are subject to wear and can be damaged, compromising its correct functioning. Finally, maintenance operations are more expensive since it is also necessary to provide for the maintenance of the circuit and its components.

? It was therefore felt necessary to devise an improved solution for alternator cooling.

Presentation of the invention

The aim of the present invention is to solve the above mentioned problems by devising an alternator which allows the cooling of its components to be carried out in an optimal way.

Within the scope of this task, a further aim of the present invention is to provide a reliable and compact alternator.

A further object of the invention is to provide an alternator which exhibits an optimum level of performance.

A further aim of the invention is to provide an alternator with a simple construction and functional concept, featuring definitely reliable operation, versatile use and a relatively low cost.

The above mentioned objects are achieved, according to the present invention, by the alternator according to claim 1.

The alternator comprises a casing within which is rotatably mounted a shaft capable of being driven into rotation; a rotor associated with said shaft, said rotor comprising an inductor assembly configured to generate, upon drive into rotation of said shaft, a rotating magnetic field; a stator mounted coaxially with said rotor within said casing, said stator comprising a core with which are associated windings upon which, in use, electromotive forces are induced by said rotating magnetic field.

Advantageously, said casing defines internally a hermetically sealed region of space comprising a predetermined quantity of a cooling liquid suitable for cooling said alternator, in particular said rotor and said stator.

The alternator allows for optimal cooling thanks to the provision of a hermetically sealed region of space defined by the casing in which a predetermined quantity of liquid is present. In use, the liquid is distributed by the rotor so as to come into effective contact with the internal components of the alternator and thus promote heat exchange towards the outside of the casing. A further advantage of the present invention is that the alternator has a compact configuration thanks precisely to the provision of cooling by means of a liquid contained hermetically inside the casing since no recirculation circuit of the coolant external to the casing is necessary. This also results in greater reliability since the number of components used is smaller than in alternators equipped with an external recirculation circuit of the coolant.

Advantageously, said region of space defines a closed circuit for the circulation of said coolant within said casing.

Preferably said alternator does not include an opening for the entry of said coolant into said space region.

Preferably, said alternator does not comprise an outlet opening for said coolant from said space region to the outside of said casing. In practice, the alternator does not allow either the inlet of a coolant or the outlet of the coolant and therefore does not require an external circuit for the coolant. This gives the alternator versatility since it is not necessary to exploit an external cooling circuit, for example the cooling circuit of an internal combustion engine in the case of application in a motor vehicle.

Preferably called coolant? oil.

Preferably said shaft is capable of being rotated by an actuator.

Preferably, said shaft is connected, at a first end, to transmission means associated with said actuator organ capable of transmitting, in use, a rotational motion to said shaft.

Preferably, said shaft is connected, at a second end, opposite to said first end, to a ventilation device.

Preferably, said ventilation device is arranged outside said casing and is protected by a casing mounted frontally with respect to said ventilation device.

Alternatively, said ventilation device is arranged inside said casing. This configuration is advantageous as it allows to reduce the noise produced during the operation of the alternator.

Preferably this ventilation device is realized by a fan.

Preferably, said casing comprises a first substantially central portion suitable for containing said stator, said first portion being integral, at one end, with a second portion and, at the opposite end, with a third portion.

Preferably, said first portion constitutes the case of said stator.

Preferably said first portion is substantially cylindrical.

Preferably, sealing means are arranged between said first portion and said second portion.

Preferably, relative sealing means are arranged between said first portion and said third portion.

Preferably said sealing means comprise an O-ring.

Preferably said alternator comprises a first sealing ring mounted on said rotation shaft, at said first end of said shaft.

Preferably, said first sealing ring is interposed between said shaft and said casing to prevent leakage of said coolant towards the outside of said casing.

Preferably said alternator comprises a second sealing ring mounted on said rotation shaft, at said second end of said shaft.

Preferably, said second sealing ring is interposed between said shaft and said casing to prevent leakage of said coolant towards the outside of said casing.

It is noted that the provision of a casing that defines a hermetically sealed region, in particular thanks to the aforementioned sealing means and sealing rings, makes the alternator more protected from external agents, such as, for example, dust or water, increasing its life.

Advantageously, said casing forms a seat on an internal surface for housing said first sealing ring.

Advantageously, said casing also forms on a relative internal surface a further seat for housing said second sealing ring. Preferably, said alternator comprises rolling means suitable for supporting said shaft inside said casing, said rolling means being arranged at opposite ends of said shaft, between said shaft and said casing.

Preferably said inductor group comprises permanent magnets or said inductor group comprises a core equipped with two or more poles on which windings are arranged which can be electrically powered to generate said magnetic field.

In the case of a wound rotor, the alternator also includes an excitation group capable of supplying an excitation current to the windings of said rotor.

Preferably said excitation group is of the brushless type.

Brief description of the drawings

The details of the invention will become more apparent from the detailed description of a preferred embodiment of the alternator according to the invention, illustrated for illustrative purposes in the drawing, in which:

Figure 1 shows a longitudinal sectional view of the alternator according to the present invention.

Embodiments of the invention

With particular reference to this figure, the alternator according to the present invention is indicated as a whole with 1.

The alternator 1 comprises an external casing 2 which houses inside it a shaft 3 capable of being driven into rotation by an actuator, not shown. By way of example, the actuator may be an electric or internal combustion or hydraulic motor or a hydraulic turbine.

The shaft 3 extends in a direction transverse to the casing 2. The shaft 3 is rotatably mounted inside the casing 2 and is supported by rolling means 4 arranged at opposite ends of the shaft 3. More specifically, the rolling means 4 comprise first rolling means which are arranged between the shaft 3 and the casing 2, at a first end 3a of the shaft 3, and second rolling means, arranged between the shaft 3 and the casing 2 at a second end 3b of the shaft 3, opposite the first end 3a.

Each rolling element 4 is preferably a ball bearing.

Preferably the first end 3a of the shaft 3 is suitable for being connected to transmission means, not visible in the figure, associated with the actuator member to transmit, in use, a rotational motion to the shaft 3.

Preferably the second end 3b of the shaft 3 is connected to a ventilation device 100, of the type of a fan which is driven into rotation by the shaft 3. The fan 100 is positioned outside the casing 2 and is protected by a casing 101 arranged frontally with respect to the fan 100. The casing 101 is connected to the casing 2.

Alternatively, it is possible to provide for the fan 100 to be mounted at one end of the shaft 3 inside the casing 2. This configuration is advantageous as it allows to reduce the noise produced by the fan 100, during the operation of the alternator.

Shaft 3 is associated with a rotor 5 that rotates in conjunction with shaft 3, in a configuration of use. Rotor 5 comprises an inductor assembly configured to generate, upon rotation of shaft 3, a rotating magnetic field. According to one embodiment, rotor 5 is of the wound type and comprises an inductor assembly comprising a core equipped with two or more poles on which windings are positioned that can be electrically powered to generate a magnetic field. The windings and poles are not visible in the figure.

Each winding is made of coils of conductive elements connected to each other, preferably coils of copper elements. The core instead has a substantially circular crown shape and is made of ferromagnetic material.

The wound rotor 5 can be salient pole or isotropic.

In the case of a wound rotor 5, the alternator 1 also comprises an excitation group 6 capable of supplying an excitation current to the windings of the rotor 5.

The embodiment illustrated in figure 1 shows a wound rotor 5 whose windings are powered by a brushless excitation group 6 comprising a rotor exciter 60, mounted on the shaft 3, and a stator exciter 61, coaxial with the rotor exciter 3. The excitation group 6 is not further described as it is known in itself.

It is possible to foresee that, as an alternative to the brushless excitation group, an excitation group comprising an excitation circuit connected to a pair of rings keyed onto shaft 3 on which respective brushes slide can be used.

As an alternative to the wound rotor 5, the rotor 5 can be permanent magnet, therefore, in this case, the use of an excitation group 6 is not necessary.

Inside the casing 3, a stator 7 is mounted coaxially with the rotor 5. Between the rotor 5 and the stator 7, a space in the shape of a circular crown is defined, which is generally called the air gap.

The stator 7 comprises a relative core with associated windings, not shown, on which, in use, electromotive forces are induced by the rotating magnetic field generated by the rotor, according to the principles of magnetic induction.

Preferably each winding is made up of coils of conductive elements connected to each other, in particular coils of copper elements.

The casing 2 of the alternator 1 internally defines a hermetically sealed region of space 8 which comprises a predetermined quantity of a coolant 200 suitable for cooling the alternator 1. More specifically, the coolant 200 contained within the casing 2 allows the cooling of the alternator components such as, for example, the rotor 5 and the stator 7.

In essence, this region of space 8 is the volume defined internally by the "free" casing 2, i.e. the volume that is not occupied by the components of the alternator 1. The region of space 8 includes a predetermined quantity of the coolant 200 and air.

Advantageously, the coolant 200 is oil. In the following description, oil will be indicated as the preferred coolant 200, but it is possible that a different coolant may be used.

This space region 8 defines a closed circuit for the circulation of the oil 200 inside the casing 2 since the oil can only circulate internally inside the casing 2 without the possibility of the oil leaking out towards the outside of the casing 2 or of the oil entering from the outside into the casing 2.

In fact, the alternator 1 does not include an opening for the oil to enter the space region 8, nor an outlet opening for the oil to exit from the space region 8 to the outside of the casing 2.

Preferably, the casing 2 comprises a first substantially central portion 20 suitable for containing the stator 7, which represents the stator case 7. The first portion 20 has a substantially cylindrical shape. The first portion 20 is integral, at one end, with a second portion 21 and, at the opposite end, with a third portion 22.

Sealing means 9 are arranged between the first portion 20 and the second portion 21 and, similarly, sealing means 9, such as an O-ring, are arranged between the first portion 20 and the third portion 22 in order to ensure the seal of the casing 2.

The casing 2 forms on an internal surface, in correspondence with the first end 3a of the shaft 3, a seat 10 for the housing of a first sealing ring 11, designed to prevent any oil leakage towards the outside of the casing 2.

The first sealing ring 11 is placed between the shaft 3 and the casing 2, at the first end 3a of the shaft 3, and is housed in the aforementioned seat 10.

At the second end of the shaft 3b, the casing 2 forms on an internal surface a further seat 10? for a second sealing ring 11? which has the function of preventing any oil leakage towards the outside.

The second sealing ring 11? is interposed between the shaft 3 and the casing 2, in correspondence with the second end 3b of the shaft 3, and is housed in the aforementioned seat 10?.

At each end of the shaft 3a, 3b, the casing 2 also forms a seat 40 concentric with the seat 10, 10? for the respective sealing ring 11, 11?, which is designed to house a relative rolling element 4.

The alternator 1 also includes a compartment 12 designed to house the electronic components necessary for the operation of the alternator. The compartment 12 is defined by a box-like body 13 externally associated with the casing 2. Considering that the casing 2 defines a hermetically sealed region, which prevents the escape of the coolant 200, the compartment 12 does not include the coolant.

These electronic components include an electronic voltage regulator 14, designed to control the output voltage of the alternator 1, and a terminal block 15. The terminal block 15 is isolated from the internal region of the casing 2 by means of a plurality of cable glands 16.

The operation of the alternator is easily understood from the preceding description.

In a start-up phase, the shaft 3 is driven into rotation by the actuator, by means of the transmission means, and the rotor 5 rotates in solidarity with the shaft 3. In phase relation with the drive into rotation of the rotor 5, the excitation group 6 is activated to electrically supply the windings of the rotor 5 and a rotating magnetic field is thus generated by the rotor 5.

The rotating magnetic field induces 7 electromotive forces in the stator windings and an alternating current is thus generated.

During operation of the alternator 1, the oil 200 contained in the space region 8 is distributed by the rotor 5 so that it effectively contacts the internal components of the alternator. The oil 200 is then sprayed into the space region 8, increasing the heat exchange towards the outside of the casing 2.

The described alternator allows the intended purpose of optimal cooling to be achieved thanks to the provision of a hermetically sealed space region defined internally by the casing which contains a predetermined quantity of liquid. The liquid distributed in the internal region significantly increases the heat exchange with a consequent increase in the efficiency of the alternator in terms of power output. More specifically, given the same overall dimensions, the use of a cooling liquid hermetically contained in the casing increases the power output of the alternator.

A further advantage of the present invention is that the alternator has a compact configuration thanks to the provision of cooling by means of a liquid contained hermetically inside the casing since no recirculation circuit of the coolant external to the casing is necessary. This also results in greater reliability since the number of components used is smaller than in alternators equipped with an external recirculation circuit of the coolant.

The alternator is also more versatile since it does not need to use an external cooling circuit, for example the cooling circuit of an internal combustion engine in the case of application in a motor vehicle.

Finally, a further advantage of the alternator is that the provision of a casing that defines a hermetically sealed region, in particular thanks to the sealing means and sealing rings, makes the alternator more protected from external agents, such as, for example, dust or water, increasing its life.

The alternator described as an example is susceptible to numerous modifications and variations depending on different needs.

In the practical implementation of the invention, the materials used, as well as the shape and dimensions, can be any according to the needs.

Where the technical features mentioned in each claim are followed by reference signs, such reference signs have been included for the sole purpose of increasing the understanding of the claims and consequently they have no limiting value on the purpose of each element identified by way of example by such reference signs.

Claims (10)

Claims 1) Alternator comprising a casing (2) inside which a shaft (3) is rotatably mounted, capable of being driven into rotation; a rotor (5) associated with said shaft (3), said rotor (5) comprising an inductor assembly configured to generate, upon rotational actuation of said shaft (3), a rotating magnetic field; a stator (7) mounted coaxially to said rotor (5) inside said casing (2), said stator (7) comprising a core with associated windings on which, in use, electromotive forces are induced by said rotating magnetic field, characterised in that said casing (2) internally defines a hermetically sealed region of space (8) comprising a predetermined quantity of a cooling liquid (200) suitable for carrying out cooling of said alternator, in particular of said rotor (5) and of said stator (7). 2) Alternator according to claim 1, characterised in that said cooling liquid (200) is oil. 3) Alternator according to claim 1 or 2, characterised in that said space region (8) defines a closed circuit for the circulation of said cooling liquid (200) inside said casing (2). 4) Alternator according to one of the preceding claims, characterised in that said casing (2) comprises a first substantially central portion (20) suitable for containing said stator (7), said first portion (20) being integral, at one end, with a second portion (21) and, at the opposite end, with a third portion (22). 5) Alternator according to claim 4, characterised in that between said first portion (20) and respectively said second portion (21) and said third portion (22) there are relative sealing means (9), for example of the type of an O-ring. 6) Alternator according to one of claims 1-5, characterised in that it comprises a first sealing ring (11) mounted on said rotation shaft (3), at a first end (3a) of said shaft (3) suitable for being connected to an actuator member for the rotational actuation of said shaft (3), said first sealing ring (11) being interposed between said shaft (3) and said casing (2) to prevent leakage of said cooling liquid (200) towards the outside of said casing (2). 7) Alternator according to claim 6, characterised in that it comprises a second sealing ring (11?) mounted on said rotation shaft (3) at a second end (3b), opposite to said first end (3a), said second sealing ring (11?) being interposed between said shaft (3) and said casing (2) to prevent leakage of said cooling liquid (200) towards the outside of said casing (2). 8) Alternator according to claim 7, characterised in that said casing (2) forms on an internal surface a seat (10) for housing said first sealing ring (11) and also forms on a relative internal surface a further seat (10?) for housing said second sealing ring (11?). 9) Alternator according to one of the preceding claims, characterised in that it comprises rolling means (4) suitable for supporting said shaft (3) inside said casing (2), said rolling means (4) being arranged at opposite ends of said shaft (3), between said shaft (3) and said casing (2). 10) Alternator according to one of the preceding claims, characterised in that said inductor group comprises permanent magnets or said inductor group comprises a core equipped with two or more poles on which windings are arranged which can be electrically powered to generate said magnetic field.