Alternator

Abstract

The alternator comprises a casing (2), inside which a shaft (3) designed to be caused to rotate is mounted in a rotary manner; a rotor (5) associated with said shaft (3), said rotor (5) comprising an inductor assembly configured to generate, when said shaft (3) is caused to rotate, a rotating magnetic field. The alternator further comprises a stator (7) mounted coaxial to said rotor (5) inside said casing (2), said stator (7) comprising a core, with which windings are associated, on which, in use, electromotive forces are induced by said rotating magnetic field.

Description

DescriptionALTERNATORTechnical field

[0001] The invention relates to a dynamo-electric machine, in particular a synchronous alternating current generator, which is generally referred to as alternator.Prior art

[0002] The use of alternators in numerous applications has long been known, as they allow for the transformation of mechanical energy into alternating current electrical energy. By way of example, alternators are used in power plants or for the production of electrical energy in cars and, in general, in motor vehicles.

[0003] An alternator comprises an outer casing, which houses, on the inside, a rotating part, the rotor, which is integral to a rotation shaft, which can be caused to rotate by actuator means, for example an internal combustion engine, a hydraulic motor, an electric motor. A stator, which represents the static part, is mounted coaxially to the rotor inside the casing. The rotor is provided with an inductor assembly, while the stator comprises an induced assembly. In particular, the rotor can be made of permanent magnets or can comprise a substantially cylindrical core provided with two or more poles, on which windings powered by a direct current are arranged. The stator comprises a core, on which windings are mounted, and electromagnetic forces induced by the rotating magnetic field of the rotor are generated in said windings, according to the principles of magnetic induction.

[0004] A problem arising from alternators is the high amount of heat that is produced during their operation. Therefore, some solutions have been developed to ensure a correct cooling of the alternators.

[0005] International patent application W02004106749 discloses an alternator comprising a cooling device consisting of a ventilation member, which is mounted around a rotation shaft of the rotor of the alternator. The ventilation member is provided with a plurality of blades and comprises suction openings made on the blades to suck an air flow according to a substantially axial path inside the alternator. Outlet openings are also made on the blades in order to allow the air flow to flow outwards along a substantially radial path. The ventilation member also comprises deflector means for guiding the air flow from the axial path to the radial path.

[0006] A problem that can arise with a type of air cooling lies in the fact that, for high-capacity machines, bulky ventilation members are required, which need a significant power.

[0007] A further type of cooling used is cooling with a cooling liquid.

[0008] Patent FR 2667738 discloses an alternator cooled with a cooling liquid. The alternator comprises a first outer casing and a second casing, which is arranged inside the outer casing and is designed to house the alternator. The first casing comprises at least onecooling liquid supply duct and at least one cooling liquid outlet duct. The second casing comprises a series of grooves on an outer surface, which cooperate with the ducts of the first casing to constitute flowing passages for the cooling liquid.

[0009] Patent US 6,617,715 discloses an alternator comprising a first casing, which internally houses the components of the alternator. In particular, a shaft is arranged inside the first casing and is supported, in a rotary manner, by a pair of bearings. A two-pole rotor with inductor windings is mounted on the shaft and, at one end, there is also mounted a pair of excitation rings, which are configured to be coupled to 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 cooling liquid. The first casing is provided with a plurality of fins, which radially extend on an outer surface and are in contact with an inner surface of the outer casing to form respective axial flowing channels for the cooling liquid. The chamber comprises an inlet duct and an outlet duct to let the liquid into the chamber and to let the liquid out of the chamber, respectively. The cooling liquid is distributed to the alternator by a cooling circuit of an engine of a vehicle, which comprises a pump, a heater and a radiator.

[0010] A problem arising from the aforementioned type of alternator cooled with a cooling liquid is the structural complexity caused by the presence of a chamber on the outside of the casing of the alternator and of an outer circuit for the circulation of the cooling liquid supplied to the chamber. In addition, the alternator is less sturdy, for it has a larger number of components that are subject to wear and can be damaged, thus compromising the correct operation thereof. Finally, maintenance operations are more expensive, since the circuit and its components also require maintenance.

[0011] Therefore, there is a need to devise an improving solution for the cooling of the alternators.Disclosure of the invention

[0012] The object of the invention is to solve the problems mentioned above, by devising an alternator that allows the cooling of its components to be carried out in an optimal manner.

[0013] Within the scope of this task, a further object of the invention is to provide a reliable and compact alternator.

[0014] A further object of the invention is to provide an alternator having an optimal performance level.

[0015] A further object of the invention is to provide an alternator with a simple constructive and functional design, featuring a reliable operation, a versatile use as well as a relatively economic cost.

[0016] The aforesaid objects are achieved, according to the invention, by the alternator according to claim 1 .

[0017] The alternator comprises a casing, inside which a shaft designed to be caused to rotate is mounted in a rotary manner; a rotor arranged inside said casing, said rotor being associated with said shaft, said rotor comprising an inductor assembly configured to generate, when said shaft is caused to rotate, a rotating magnetic field; a stator mounted coaxial to said rotor inside said casing, said stator comprising a core, which is associated with windings, on which electromotive forces are induced, in use, by said rotating magnetic field.

[0018] The stator is arranged on the outside of said rotor.

[0019] Advantageously, said casing internally defines a hermetically closed space region comprising a predetermined quantity of a cooling liquid designed to perform a cooling of said alternator, in particular of said rotor and of said stator.

[0020] Preferably, said rotor and said stator are at least partly immersed in said cooling liquid.

[0021] Said space region substantially corresponds to the volume internally defined by the free casing, namely the volume that is not occupied by the components of the alternator.

[0022] Preferably, said cooling liquid occupies a volume ranging from 25% to 40% of the free volume inside said casing.

[0023] The rotor advantageously comprises at least one groove made on an outer surface, which extends in a longitudinal direction, designed to facilitate the movement of the cooling liquid, in a use phase.

[0024] Said rotor preferably has a substantially cylindrical shape.

[0025] Said groove is preferably made on a side surface of said rotor.

[0026] Said groove preferably extends along a longitudinal direction inclined with respect to said shaft. Alternatively, said groove extends along a longitudinal direction parallel to said shaft.

[0027] The alternator allows for an optimal cooling thanks to the presence of a hermetically closed space region defined by the casing, in which there is a predetermined quantity of liquid, and thanks to the presence of at least one groove on an outer surface of the rotor, which fulfils the function of facilitating the movement of the cooling liquid when, in use, the rotor is caused to rotate. Therefore, in use, the liquid is distributed by the rotor so as to effectively come into contact with the inner components of the alternator and, hence, promote the exchange of heat towards the outside of the casing.

[0028] A further advantage of the invention lies in that the alternator has a compact layout thanks to the very use of a cooling by means of a liquid hermetically contained inside the casing, since no recirculation circuit for the cooling liquid on the outside of the casing is necessary. This also leads to greater reliability, as the number of components used is smaller compared to alternators provided with an outer cooling liquid recirculation circuit.

[0029] Advantageously, said space region defines a closed circuit for the circulation of saidcooling liquid inside said casing.

[0030] Preferably, said alternator does not comprise an inlet opening for letting said cooling liquid into said space region.

[0031] Preferably, said alternator does not comprise an outlet opening for allowing said cooling liquid to flow from said space region towards the outside of said casing.

[0032] Basically, the alternator permits neither the entry of a cooling liquid nor the release of the liquid and, therefore, it does not require an outer circuit for the cooling liquid. This gives the alternator versatility, since it does not need to make use of an outer cooling circuit, for example the cooling circuit of an internal combustion engine in the case of application in a motor vehicle.

[0033] Said cooling liquid preferably is oil.

[0034] Advantageously, said rotor comprises moving means for moving said cooling liquid associated with at least one surface of said rotor, at an end of said rotor. Experiments have shown that the combination of the groove and the moving means has the effect of significantly increasing the cooling capacity of the alternator, as the groove and the moving means have a synergistic effect, helping the liquid get mixed during the rotation of the rotor.

[0035] Said moving means are preferably associated with a base surface of the rotor.

[0036] Said rotor preferably comprises a pair of closing members, mounted on relative opposite end surfaces of said rotor. Basically, the closing members are mounted on respective base surfaces of said rotor.

[0037] Preferably, at least one of said closing members is associated with said moving means for moving said cooling liquid.

[0038] In particular, at least one of said closing members carries said moving means.

[0039] Said moving means preferably comprise at least one moving element having an oblong shape protruding from a base surface of the rotor.

[0040] Said moving element preferably projects towards the outside of said rotor.

[0041] Said at least one moving element preferably has an oblong protruding shape and extends from a closing member towards the outside of said rotor.

[0042] At least one moving element preferably extends along a longitudinal direction, preferably parallel to said shaft.

[0043] Preferably, at least one moving element defines a cavity designed to facilitate the mixing of said cooling liquid, in a use phase.

[0044] Preferably, said moving means preferably comprise at least one pair of moving elements having an oblong shape and protruding from a base surface of the rotor, in particular from a closing member.

[0045] Preferably, a channel is defined between said windings of said stator and said casing soas to allow for the passage of said cooling liquid, in a use phase. The channel helps facilitate the distribution of the liquid and, hence, also increases the effectiveness of the cooling.

[0046] Said shaft is preferably designed to be caused to rotate by an actuator member.

[0047] Said shaft is preferably connected, at a first end, to transmission means associated with said actuator member designed to transmit, in use, a rotational motion to said shaft.

[0048] Said shaft is preferably connected, at a second end, opposite said first end, to a ventilation device.

[0049] Said ventilation device is preferably arranged on the outside of said casing and is protected by a cover mounted in front of said ventilation device.

[0050] Alternatively, said ventilation device is arranged inside said casing. This layout is advantageous in that it reduces the noise produced during the operation of the alternator.

[0051] Said ventilation device preferably consists of a fan.

[0052] Said casing preferably comprises a first substantially central portion designed to contain said stator, said first portion being integral, at one end, to a second portion and, at the opposite end, to a third portion.

[0053] Said first portion preferably constitutes the case of said stator.

[0054] Said first portion preferably is substantially cylindrical.

[0055] Preferably, said first portion, said second portion and said third portion internally define respective volumes, which are filled, at least in part, with said cooling liquid. It should be pointed out that the cooling liquid is inserted rather evenly inside the casing and this allows the liquid to come into contact with components of the alternator other than the rotor and the stator, with a consequent better cooling of the alternator.

[0056] Preferably, sealing means are arranged between said first portion and said second portion.

[0057] Preferably, relative sealing means are arranged between said first portion and said third portion.

[0058] Said sealing means preferably comprise an O-ring.

[0059] Said alternator preferably comprises a first sealing ring mounted on said rotation shaft, at said first end of said shaft.

[0060] Said first sealing ring is preferably interposed between said shaft and said casing to prevent said cooling liquid from leaking out of said casing.

[0061] Said alternator preferably comprises a second sealing ring mounted on said rotation shaft, at said second end of said shaft.

[0062] Said second sealing ring is preferably interposed between said shaft and said casing to prevent said cooling liquid from leaking out of said casing.

[0063] It should be pointed out that the presence of a casing that defines a hermetically sealedregion, in particular thanks to the aforementioned sealing means and to the sealing rings, makes the alternator more protected from external agents, such as, for example, dust or water, thus increasing its life.

[0064] Advantageously, said casing advantageously forms, on an inner surface, a seat for housing said first sealing ring.

[0065] Advantageously, said casing also forms, on a relative inner surface, a further seat for housing said second sealing ring.

[0066] Said alternator preferably comprises rolling means designed to support said shaft within said casing, said rolling means being arranged at opposite ends of said shaft, between said shaft and said casing.

[0067] Preferably, said inductor assembly comprises permanent magnets or said inductor assembly comprises a core provided with two or more poles, on which windings designed to be electrically powered to generate said magnetic field are arranged.

[0068] In case of a wound rotor, the alternator also comprises an excitation assembly designed to supply an excitation current to the windings of said rotor.

[0069] Preferably, said excitation assembly is of the brushless type.

[0070] Advantageously, said excitation assembly is at least partly immersed in said cooling liquid.

[0071] In case of a brushless excitation assembly, the assembly comprises a rotor exciter, mounted on said shaft, and a stator exciter, coaxial to the rotor exciter.

[0072] Preferably, said stator exciter is arranged on the outside of the rotor exciter.

[0073] Preferably, the rotor exciter comprises, on an outer surface, at least one pair of further moving elements, which are designed to facilitate the movement of the cooling liquid, in use.

[0074] Preferably, said further moving elements extend from a side surface of the rotor exciter along a longitudinal direction, preferably parallel to the shaft.

[0075] Preferably, said moving elements of each pair of said rotor exciter are aligned along the longitudinal direction and develop from the side surface in opposite directions.

[0076] Preferably, the rotor exciter comprises a plurality of pairs of moving elements distributed along the periphery of the rotor exciter at regular distances.Brief description of the drawings

[0077] The details of the invention will be best understood upon perusal of the following detailed description of a preferred embodiment of the alternator according to the invention, shown by way of example in the drawing, wherein: figure 1 shows a longitudinal section view of the alternator according to the invention; figure 2 shows a longitudinal section view of the alternator in question according to a different embodiment; figure 3 shows an axonometric view of the alternator, in which some components wereremoved; figure 4 shows an axonometric view of a component of the alternator; figure 5 shows an axonometric view of a longitudinal section of the alternator; figure 6 shows a front view of the alternator, in which part of the casing was removed Description of embodiments of the invention

[0078] With particular reference to these figures, number 1 indicates, as a whole, the alternator according to the invention.

[0079] The alternator 1 comprises an outer casing 2 housing, on the inside, a shaft 3 designed to be caused to rotate by an actuator member, which is not shown. By way of example, the actuator member can be an electric motor or an internal combustion engine or a hydraulic motor or a hydraulic turbine.

[0080] The shaft 3 extends along a direction that is transverse to the casing 2. The shaft 3 is mounted in a rotary manner inside the casing 2 and is supported by rolling means 4 arranged at opposite ends of the shaft 3. More in particular, 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, which are arranged between the shaft 3 and the casing 2 at a second end 3b of the shaft 3, which is opposite the first end 3a.

[0081] Each rolling means 4 preferably is a ball bearing.

[0082] Preferably, the first end 3a of the shaft 3 is designed to be connected to transmission means, not visible in the figures, associated with the actuator member to transmit, in use, a rotational motion to the shaft 3.

[0083] Preferably, the second end 3b of the shaft 3 is connected to a ventilation device 100, such as a fan, which is caused to rotate by the shaft 3. The fan 100 is located on the outside of the casing 2 and is protected by a cover 101 arranged in front of the fan 100. The cover 101 is connected to the casing 2.

[0084] Alternatively, the fan 100 can be mounted at an end of the shaft 3 inside the casing 2. This layout is advantageous in that it reduces the noise produced by the fan 100 during the operation of the alternator.

[0085] A rotor 5 is associated with the shaft 3 and rotates with the shaft 3 in an integral manner, in a use configuration. The rotor 5 is arranged inside the casing 2.

[0086] The rotor 5 comprises an inductor assembly configured to generate, when the shaft 3 is caused to rotate, a rotating magnetic field.

[0087] According to an embodiment, the rotor 5 is of the wound type and entails an inductor assembly comprising a core provided with two or more poles 50, on which windings 51 designed to be electrically powered to generate a magnetic field are positioned.

[0088] Each winding 51 consists of coils of conductor elements connected to one another, preferably coils of copper elements. The core, on the other hand, has a substantiallycircular crown shape and is made of a ferromagnetic material.

[0089] The wound rotor 5 can be a salient-pole rotor or an isotropic rotor.

[0090] In case of a wound rotor 5, the alternator 1 also comprises an excitation assembly 6 designed to supply an excitation current to the windings of the rotor 5.

[0091] The embodiment shown in figures 1-6 shows a wound rotor 5, whose windings are powered by a brushless excitation assembly 6 comprising a rotor exciter 60, mounted on the shaft 3, and a stator exciter 61 , coaxial to the rotor exciter 3 and arranged externally to the rotor exciter 60. The excitation assembly 6 is not further described as it is known per se.

[0092] It is possible to envisage that, as an alternative to the brushless excitation assembly, an excitation assembly can be used, which comprises an excitation circuit connected to a pair of rings splined on the shaft 3, on which respective brushes slide.

[0093] As an alternative to the wound rotor 5, the rotor 5 can be a permanent magnet rotor, so that, in this case, the use of an excitation assembly 6 is not necessary.

[0094] The rotor 5 comprises at least one groove 52 obtained on an outer surface, which extends along a longitudinal direction, preferably along the entire length of the rotor 5. The groove 52 fulfils the function of facilitating the movement of a cooling liquid 200, in a use phase.

[0095] The groove 52 is obtained on a side surface of the rotor 5.

[0096] In case of a wound rotor 5, the groove 52 can extend between the poles 50 along a longitudinal direction, as shown in figures 3 and 4.

[0097] The rotor 5 also comprises cooling liquid moving means 53 designed to facilitate, in a use phase, the mixing of the cooling liquid 200.

[0098] The moving means 53 are associated with a surface of the rotor 5, at an end of the rotor 5.

[0099] More in particular, the moving means 53 are associated with at least one base surface of the rotor 5, preferably with both base surfaces of the rotor 5. Indeed, the rotor 5 has a substantially cylindrical shape.

[0100] In particular, the rotor 5 is associated, in the area of opposite end surfaces, namely of the opposite base surfaces, with respective closing members 54, which carry the moving means 53. Each closing member 54 constitutes the head of the rotor 5.

[0101] The moving means 53 preferably comprise at least one pair of moving elements having an oblong shape and protruding from a base surface of the rotor 5, in particular from a relative head member 54. In the embodiment shown in figures 2-6, the rotor 5 comprises a pair of moving elements 53 on each head member 54.

[0102] Each moving element 53 forms a cavity 55, which facilitates the mixing of the liquid 200.

[0103] The configuration of the rotor 5, provided with the groove 52, is particularly advantageous for it facilitates the movement of the cooling liquid 200 in the casing 2 and, therefore,facilitates the cooling of the components inside the casing 2.

[0104] Furthermore, experiments have shown that the combination of the groove 52 and the moving means 53 has the effect of significantly increasing cooling capacity, as the groove 52 and the moving means 53 have a synergistic effect, helping the liquid get mixed during the rotation of the rotor 5.

[0105] In the case of a wound rotor 5, whose windings are powered by a brushless excitation assembly 6, the rotor exciter 60 comprises, on an outer surface, at least one pair of further moving elements 62, which are designed to facilitate the movement of the cooling liquid 200 inserted inside the casing 2, in use (see figure 4).

[0106] The moving elements 62 extend from a side surface of the rotor exciter 60 along a longitudinal direction, preferably parallel to the shaft 3. The moving elements 62 of each pair are aligned along the longitudinal direction and develop from the side surface in opposite directions.

[0107] Preferably, the rotor exciter 60 comprises a plurality of pairs of moving elements 62 distributed along the periphery of the rotor exciter 60 at regular distances.

[0108] Preferably, the rotor exciter 60 has a substantially circular crown shape.

[0109] Each moving element 62 has an oblong shape and forms a sort of peg.

[0110] Inside the casing 3, a stator 7 is mounted coaxial to the rotor 5. A circular crown-shaped space is defined between the rotor 5 and the stator 7 and is generally referred to as air gap. The stator 7 is mounted on the outside of the rotor 5.

[0111] The stator 7 comprises a relative core, with which windings 70 are associated, on which, in use, electromotive forces are induced by the rotating magnetic field generated by the rotor 5 according to the principles of magnetic induction. Each winding 70 preferably consists of coils of conductor elements connected to one another, in particular coils of copper elements.

[0112] The core and the windings 70 of the stator 7 are surrounded by a relative case 20, which is created by the casing 2 itself. According to a preferred embodiment, a space forming a passage channel 71 for the cooling liquid 200 is defined between the windings 70 and the case 20.

[0113] The casing 2 of the alternator 1 internally defines a hermetically closed space region 8, which comprises a predetermined quantity of a cooling liquid 200 designed to perform a cooling of the alternator 1. More specifically, the cooling liquid 200 contained inside the casing 2 allows the alternator components, such as, for example, the rotor 5 and the stator 7, to be cooled.

[0114] Said space region 8 basically is the volume internally defined by the “free” casing 2, namely the volume that is not occupied by the components of the alternator 1.

[0115] The space region 8 comprises a predetermined amount of cooling liquid 200 and air.

[0116] Advantageously, the cooling liquid 200 is oil. In the following description, oil will be indicated as the preferred cooling liquid 200, but it is possible that a different cooling liquid is used.

[0117] The rotor 5 and the stator 7 are at least partly immersed in the oil 200. In case the excitation assembly 6 is present, said excitation assembly 6 also is at least partly immersed in the oil 200.

[0118] Said space region 8 defines a closed circuit for the circulation of the oil 200 inside the casing 2, since oil can only circulate inside the casing 2 without the possibility letting oil flow out of the casing 2 or of letting oil flow, from the outside, into the casing 2.

[0119] In fact, the alternator 1 does not comprise an opening for letting oil into the space region 8 or an outlet opening for letting oil out of the space region 8 towards the outside of the casing 2. Experimental tests have been carried out on the amount of oil 200 to be inserted into the casing 2 in order to obtain an optimal operation of the alternator. It has been experimentally observed that, when oil occupies a volume ranging from 25% to 40% of the free volume inside the casing 2, an ideal heat removal occurs.

[0120] The casing 2 preferably comprises a first substantially central portion 20 designed to contain the stator 7, which represents the case of the stator 7. The first portion 20 has a substantially cylindrical shape. The first portion 20 is integral, at one end, to a second portion 21 and, at the opposite end, to a third portion 22. The second portion 21 and the third portion 22 substantially are the shields of the alternator 1 .

[0121] The first portion 20, the second portion 21 and the third portion 22 define respective volumes, which are filled, at least in part, with the oil 200. It should be pointed out that the free volumes of the portions 20, 21 and 22, namely the volumes not occupied by the components, obviously are at least partly filled with oil 200. The sum of the free volumes defined by the portions 20, 21 and 22 represents the free volume 8 defined by the casing 2.

[0122] Between the first portion 20 and the second portion 21 there are sealing means 9 and, in the same way, between the first portion 20 and the third portion 22 there are relative sealing means 9, such as, for example, an O-ring, so as to ensure the sealing of the casing 2.

[0123] The casing 2 forms, on an inner surface, at the first end 3a of the shaft 3, a seat 10 for housing a first sealing ring 11 designed to prevent oil from leaking out of the casing 2.

[0124] The first sealing ring 11 is interposed 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.

[0125] At the second end of the shaft 3b, the casing 2 forms, on an inner surface, a further seat 10’ for a second sealing ring 1 T, which fulfils the function of preventing oil from leaking out.

[0126] The second sealing ring 1 T is interposed between the shaft 3 and the casing 2, at the second end 3b of the shaft 3, and is housed in the aforementioned seat 10’.

[0127] At each end of the shaft 3a, 3b, the casing 2 also forms a seat 40 concentric to the seat 10, 10’ for the respective sealing ring 11 , 11 ’, which is designed to house a relative rolling means 4.

[0128] The second portion 21 and the third portion 22 form, in the area of the rolling means 4, relative channels 400, which allow the oil 200 contained in the casing 2 to flow through in order to lubricate the rolling means 4. In this way, the rolling means 4 can be continuously lubricated.

[0129] The alternator 1 also comprises a compartment 12 designed to house electronic components needed for the operation of the alternator. The compartment 12 is defined by a box-shaped body 13, which is externally associated with the casing 2. Taking into account the fact that the casing 2 defines a hermetically sealed region, which prevents the cooling liquid 200 from flowing out, the compartment 12 does not comprise the cooling liquid.

[0130] Said electronic components comprise an electronic voltage regulator 14, designed to carry out a control on the output voltage of the alternator 1 , and a terminal block 15. The terminal block 15 is isolated from the region inside the casing 2 by means of a plurality of cable glands 16.

[0131] The operation of the alternator can easily be understood from the description above.

[0132] In a starting phase, the shaft 3 caused to rotate by the actuator member, by means of the transmission means, and the rotor 5 rotates with the shaft 3 in an integral manner. In phase relationship with the activation of the rotation of the rotor 5, the excitation assembly 6 is activated so as to electrically power the windings of the rotor 5 and, by so going, a rotating magnetic field is generated by the rotor 5.

[0133] The rotating magnetic field induces electromotive forces in the windings of the stator 7 and, by so doing, an alternating current is generated.

[0134] During the operation of the alternator 1 , the oil 200 contained in the space region 8 is distributed by the rotor 5 so that it effectively comes into contact with the inner components of the alternator. Hence, the oil 200 is sprayed in the space region 8, thus increasing the exchange of heat towards the outside of the casing 2.

[0135] The groove 52 made on an outer surface of the rotor 5, during the rotation of the rotor 5, conveys the oil 200, thus improving its movement with an advantage in terms of effectiveness of the cooling of the alternator.

[0136] In addition, the moving means 53 cooperate with the groove 52 and help move the oil 200.

[0137] If the rotor is of the wound type, the further moving means 62 of the rotor exciter 60 also help move the oil, so as to facilitate the cooling.

[0138] The alternator disclosed herein achieves the aforesaid object of carrying out the cooling in an optimal way thanks to the presence of a hermetically closed space region internally defined by the casing, which comprises a predetermined amount of liquid, and to the presence of a groove made on an outer surface of the rotor, which helps move the liquid. The liquid distributed in the inner region significantly increases the heat exchange, with a consequent increase in the efficiency of the alternator in terms of power delivered. More in particular, given the same overall dimensions, the use of a cooling liquid hermetically contained in the casing increases the power delivered by the alternator.

[0139] A further advantage of the invention lies in that the alternator has a compact layout thanks to the very use of a cooling by means of a liquid hermetically contained inside the casing, since no recirculation circuit for the cooling liquid on the outside of the casing is necessary. This also leads to greater reliability, as the number of components used is smaller compared to alternators provided with an outer cooling liquid recirculation circuit.

[0140] The alternator also is more versatile since it does not need to make use of an external cooling circuit, for example the cooling circuit of an internal combustion engine in the case of application in a motor vehicle.

[0141] Finally, a further advantage of the alternator lies in that the presence of a casing that defines a hermetically sealed region, in particular thanks to the sealing means and to the sealing rings, makes the alternator more protected from external agents, such as, for example, dust or water, thus increasing its life.

[0142] The alternator described herein by way of example can be subject to numerous changes and variations depending on the different needs.

[0143] In the actual use of the invention, the materials used as well as the shape and the dimensions can be of any kind depending on the needs.

[0144] If 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, as a consequence, they do not have any limiting value regarding the purpose of each element identified by way of example by such reference signs.

Claims

Claims1. An alternator comprising a casing (2), where, on the inside, a shaft (3) is mounted, which is designed to be caused to rotate; a rotor (5) arranged inside said casing (2), said rotor (5) being associated with said shaft (3) and comprising an inductor assembly configured to generate, when said shaft (3) is caused to rotate, a rotating magnetic field; a stator (7) mounted coaxial to said rotor (5) inside said casing (2), said stator (7) being external to said rotor (5), said stator (7) comprising a core, with which windings (70) are associated, on which, in use, electromotive forces are induced by said rotating magnetic field, characterized in that said casing (2) internally defines a hermetically closed space region (8) comprising a predetermined amount of a cooling liquid (200) designed to perform a cooling of said rotor (5) and of said stator (7), said rotor (5) and said stator (7) being at least partly immersed in said cooling liquid (200), and in that said rotor (5) comprises at least one groove (52) made on an outer surface, which extends in a longitudinal direction, designed to facilitate the movement of the cooling liquid (200), in a use phase.

2. The alternator of claim 1 , wherein said casing (2) comprises a first substantially central portion (20) designed to contain said stator (7), said first portion (20) being integral, at one end, to a second portion (21) and, at the opposite end, to a third portion (22).

3. The alternator of claim 2, wherein said first portion (20), said second portion (21 ) and said third portion (22) internally define respective volumes, which are filled, at least in part, with said cooling liquid (200).

4. The alternator of any one of claims 1-3, wherein said rotor (5) comprises moving means(53) for moving said cooling liquid (200) associated with at least one surface of said rotor (5), at an end of said rotor (5).

5. The alternator of claim 4, wherein said moving means (53) are associated with at least one base surface of said rotor (5).

6. The alternator of claim 4 or 5, wherein said rotor (5) comprises a pair of closing members(54), mounted on relative opposite end surfaces of said rotor (5), in particular on relative base surfaces of said rotor (5), at least one of said closing members (54) being associated with said moving means (53) for said cooling liquid (200).

7. The alternator of claim 4, 5 or 6, wherein said moving means (53) comprise at least one moving element having an oblong shape protruding from a base surface of said rotor (5).

8. The alternator of claim 7, wherein said moving element defines a cavity (55) designed to facilitate the mixing of said cooling liquid (200), in a use phase.

9. The alternator of any one of the preceding claims, wherein a channel (71) is defined between said windings (70) of said stator (7) and said casing (2) so as to allow for the passage of said cooling liquid (200), in a use phase.

10. The alternator of any one of the preceding claims, wherein said cooling liquid (200) is oil.

11. The alternator of any one of the preceding claims, wherein said space region (8) defines a closed circuit for the circulation of said cooling liquid (200) inside said casing (2).

12. The alternator of claim 2 or 3, wherein relative sealing means (9) are arranged between said first portion (20) and, respectively, said second portion (21 ) and said third portion (22), for example of the O-ring type.

13. The alternator of any one of the preceding claims, wherein it comprises a first sealing ring (11) mounted on said rotation shaft (3), at a first end (3a) of said shaft (3) designed to be connected to an actuator member for causing said shaft (3) to rotate, said first sealing ring (11) being interposed between said shaft (3) and said casing (2) to prevent said cooling liquid (200) from leaking out of said casing (2).

14. The alternator of claim 13, wherein it comprises a second sealing ring (1 T) mounted on said rotation shaft (3) at a second end (3b), opposite said first end (3a), said second sealing ring (1 T) being interposed between said shaft (3) and said casing (2) to prevent said cooling liquid (200) from leaking out of said casing (2).

15. The alternator of claim 14, wherein said casing (2) forms, on an inner surface, a seat (10) for housing said first sealing ring (11) and also forms, on a relative inner surface, a further seat (10’) for housing said second sealing ring (1 T).

16. The alternator of any one of the preceding claims, wherein it comprises rolling means (4) designed to support said shaft (3) within said casing (2), said rolling means (4) being arranged at opposite ends of said shaft (3), between said shaft (3) and said casing (2).

17. The alternator of any one of the preceding claims, wherein said inductor assembly comprises permanent magnets or said inductor assembly comprises a core provided with two or more poles (50), on which windings (51) designed to be electrically powered to generate said magnetic field are arranged.

18. The alternator of any one of the preceding claims, wherein said inductor assembly comprises a core provided with two or more poles (50), on which windings (51) are arranged, and comprises an excitation assembly (6) designed to supply an excitation current to said windings (51), said excitation assembly (6) being at least partly immersed in said cooling liquid (200).

19. The alternator of any one of the preceding claims, wherein said cooling liquid (200) occupies a volume ranging from 25% to 40% of the free volume inside said casing (2).

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