FIELD OF THE INVENTION

The present invention relates to a rotary electric machine comprising a rotor, a stator disposed facing the rotor in a radial direction and having a stator core with a plurality of slots extending in a radial direction from an inner periphery of the stator core towards an outer periphery thereof, each slot extending in an axial direction from a first axial end of the stator core to a second axial end of the stator core, a stator winding provided in said slots, wherein opposite axial ends of the core extend out of the slots at said first and second axial ends of the stator core, a cooling arrangement, comprising a cooling medium guide arranged at at least one of said first and second end , said guide comprising a cylindric element provided in connection the inner periphery of the stator core at said first or second end.

The invention also relates to a vehicle provided with such a rotary electric machine for its propulsion.

BACKGROUND

Direct cooling of stator end-windings is used by several manufacturers today. Compared to only using a cooling jacket to cool the stator back it increases the cooling performance. Examples of oil guides have been seen, with the purpose of getting a better wetting of the end windings. These guides are attached to the housing or to an attachment member arranged at the end of the stator.

US2017/0063201 discloses a rotary electric machine in which a cooling medium guide comprises a sealing formed by a cylindric element which is coaxial with the stator and which is provided with fingers that extend axially into spacings between the ends of the windings that project out of the end of the stator core. The sealing is attached to and supported by the ends of the windings. SUMMARY

It is an object to provide a rotary electric machine having a cooling medium guide for guiding a cooling medium used for cooling the stator end windings, which cooling medium guide requires little space, is relatively easy to mount and is effective and reliable as a cooling medium guide. The object of the invention is achieved by means of the initially defined rotary electric machine, which is characterized in that a plurality of fingers are connected to the cylindric element and that each finger of the plurality of fingers extends radially inside the stator winding in an axial direction from said first or second end of the stator core into a respective slot of the stator core. Fingers may also be referred to as projections in this context. Preferably, the number of fingers corresponds to the number of slots, one for each slot. Preferably, the width of each finger corresponds to the width of the respective slot.“Radially inside” may be referred to as adjacent the radial inner periphery of the winding.

Accordingly, the fingers extend into the slots in the stator core that house the windings. No extra fitting or holding elements are needed for the mounting and holding of the cooling medium guide. The fingers may also have a locking function, preventing the winding from falling out of the slots in a radial direction. Preferably, the end of the cylindric element which is adjacent to the stator core and from which the fingers extend bears sealingly on the end of the stator core, such that an efficient sealing is obtained and cooling medium is prevented from leaking to the rotor. Preferably, the cylindric element is coaxial with the stator. The winding may be of concentrated or distributed type. According to one embodiment, the winding is of the distributed type. The cooling medium may comprise any electrically non-conducting liquid having physical properties making it suitable as a cooling medium, typically an oil. According to one embodiment, each finger is sealingly arranged in said slot, preventing a cooling medium from passing the finger in a radial direction. Thereby, cooling medium is effectively prevented from finding its way past the fingers in a radial direction in said slots.

According to one embodiment, each finger is interlocking ly arranged in its respective slot or attached to an impregnation element inside the slot, such that the finger is fixed in its position and prevented from falling out of the slot in a radial direction. Thereby, the fingers also effectively contribute in preventing the winding from falling out of the slots in a radial direction . The fingers may be both attached to an impregnation and be interlockingly arranged in the slot. The impregnation element is formed by a polymer such as a suitable resin that has been introduced into the slot after mounting of the winding and the fingers, and thereafter has been solidified, typically by curing. The impregnation element fills voids in the slot between the winding and the stator core.

According to one embodiment, the rotary electric machine is characterized in that, on opposite sides of each slot there is provided a heel, and that the finger extending into the slot bears on said heel from inside the slot.

According to one embodiment, the fingers comprises a dielectric material, at least on an outer peripheral layer of the fingers.

According to one embodiment, the fingers, at least in a core portion of the respective finger, comprises a material that has a magnetic reluctance which is lower than the magnetic reluctance of air. Preferably, the core portion is formed by iron. Thereby, any negative effect on the yield of the machine due to the presence of an air gap in the stator core slots is suppressed . According to one embodiment, the sides of the fingers that in a tangential direction of the stator core face the stator core have an outer surface of said finger core material (i.e. there is no layer of said dielectric material on those sides), wherein the core of the finger, in its longitudinal direction , comprises two parallel core parts subdivided by an intermediate layer of a material having higher magnetic reluctance than the core parts. Preferably the finger core is in direct contact with the stator core on said sides that face the stator core.

According to one embodiment, spaces in the slots that are not occupied by the winding are filled with a solid dielectric impregnation , and at least an outer peripheral layer of the fingers comprises a porous material which is at least partly filled with said solid dielectric impregnation . The porosity of the fingers thus enables a fixation of the fingers in the slots as a result of a filling of the slots with a resin which upon curing thereof forms the impregnation.

According to one embodiment, the rotary electric machine is characterized in that it comprises a housing , and that the cylindric element is sealingly connected to the housing at an end of the cylindric element which is distal with regard to the stator core. Thereby, a well-defined space aimed to be at least partially filled with a cooling medium is formed around the windings at the stator end.

According to one embodiment, the rotary electric machine is characterized in that, at an end of the stator core at which the cylindric element is provided, the housing , the end of the stator core, the cylindric element and said fingers define a closed space into which ends of the winding of the stator project from axial ends of the slots, and in that the housing is provided with an inlet for introduction of a cooling medium into said closed space and an outlet for evacuation of a cooling medium from said closed space. In contradiction to prior art solution , the use of closed space enables a free positioning of said inlet and said outlet, and a more even cooling than if the cooling medium is only flowing by action of the gravitational force from top to bottom of the stator end. Preferably, the rotary electric machine also comprises a cooling medium circuit connected to the inlet and to the outlet and provided with a pump and filled with a cooling medium, preferably oil, which, during operation of the machine, is pumped into and through said space for cooling of the stator end.

According to one embodiment, the fingers extending from the cylindric element at one axial end of the stator core extend along at least 10% of the total length of the stator core.

According to one embodiment, fingers extending from at least one cylindric element provided at an axial end of the stator core extend along at least 50%, preferably at least 90% of the total length of the stator core. Accordingly, the total length of the fingers, extending from one single or from two opposite cylindric elements (at each end of the stator), is at least 50% or at least 90% of the total length of the core. Such design provides for improved sealing against cooling medium leakage from said space to the rotor, and provides for improved locking of the windings in the stator slots.

According to one embodiment, the rotary electric machine is characterized in that it comprises a first cylindric element provided at a first axial end of the stator core and a second cylindric element provided at a second axial end of the stator core. Fingers extend from each of the cylindric elements into the stator slots as described hereinabove.

The present invention also relates to a vehicle, comprising a rotary electric machine for its propulsion, characterized in that the rotary electric machine is a rotary electric machine as defined hereinabove or hereinafter. The vehicle may comprise a truck, a car, a multi-passenger vehicle such as a bus, or any similar vehicle. Further features and advantages of the present invention will be presented in the following detailed description of embodiments. BRIEF DESCRIPTION OF THE DRAWING

Embodiments of the invention will be described by way of example with reference to the annexed drawing, on which:

Fig. 1 is a cross-section of an electric machine according to the invention,

Fig. 2 is a partially cut side view of a stator part of the electric machine shown in fig. 1 ,

Fig. 3 is an enlarged view of a detail in fig. 2,

Fig. 4 is an axial cross-section of a part of the stator according to a first embodiment,

Fig. 5 is an enlarged view of a detail in fig. 4,

Fig. 6 is an axial cross-section of a part of the stator according to a second embodiment,

Fig. 7 is an enlarged view of a detail in fig. 6,

Fig. 8 is a perspective view of a cooling medium guide according to the invention, and

Fig. 9 is a side view of the cooling medium guide shown in fig. 8. DETAILED DESCRIPTION

Fig. 1 shows a rotary electric machine comprising a rotor 1 , a stator 2 disposed facing the rotor in a radial direction and having a stator core 3 with a plurality of slots 4 extending in a radial direction from an inner periphery (indicated with 5 in fig 4) of the stator core 3 towards an outer periphery (indicated with 6 in fig. 4) thereof. Each slot 4 extends in an axial direction from a first axial 3. The rotary electric machine further comprises a stator winding 9 provided in said slots 4, wherein opposite axial ends of the winding 9 extend out of the slots 4 at said first and second axial ends 7, 8 of the stator core 3. At each of said first and second end 7, 8 the rotary electric machine further comprises a cooling arrangement, comprising a cooling medium guide 10 (more clearly shown in figs. 8 and 9), said cooling medium guide 10 comprising a cylindric element 1 1 provided in connection the inner periphery 5 of the stator core 3 at said end 7, 8 of the stator core 3. A plurality of fingers 12 (see figs. 3, 8 and 9) are connected to the cylindric element 1 1 , and each of the plurality of fingers 12 extends radially inside the stator winding 9 in an axial direction from said first and second end 7, 8 of the stator core 3 into a respective slot 4 of the stator core 3.

Reference is made to fig . 3. The end of the cylindric element 1 1 which is adjacent to the stator core 3, and from which the fingers 12 extend, bears sealingly on the end 7, 8 of the stator core 3, such that an efficient sealing is obtained and cooling medium sprayed onto the axial ends of the winding 9 is prevented from leaking to the rotor 1 . The cylindric element 1 1 is coaxial with the stator 2.

Figs. 4 and 5 show a first embodiment of the rotary electric machine. In each slot 4 there is provided a dielectric impregnation element 13 formed by a resin that has been introduced in a liquid state into the slot 4 after mounting of the winding 9 in the slot, whereinafter the resin has been enabled to solidify, normally by curing .

Prior to the introduction of the resin, the fingers 12 of a cooling medium guide 10 are inserted into the respective slots 4. The fingers 12 may be formed by a dielectric material such as a paper or a polymer. Preferably, the fingers 12 are porous or have a surface to which the resin may adhere upon curing thereof. As a result thereof, the fingers 12 are held in place through their adhesion to and/or interaction with the dielectric impregnation element 13. In the embodiment shown in figs. 4 and 5, on the sides forming a radial inside and a radial outside of the fingers as seen in the radial direction of the stator core, the fingers have an outer layer 14 of a material which is porous and to which the resin may adhere, and an iron core 15, 15’. The sides of the fingers 12 that in a tangential direction of the stator core face the stator core 3 have an outer surface of said finger core material, preferably iron, wherein the core of the finger, in its longitudinal direction, comprises two parallel core parts subdivided by an intermediate layer 14’ of a material having higher magnetic reluctance than the separated core parts 15, 15’, preferably the same material as said outer layer 14. Preferably the finger core parts 15, 15’ are in direct contact with the stator core 3 on said sides that face the stator core.

Figs. 6 and 7 show an alternative embodiment which differs from the embodiment shown in figs. 4 and 5 in that, on opposite sides of each slot 4, as seen in a tangential direction of the stator core 3, there is provided a respective heel 16, 17, and that the finger 12 extending into the slot 4 bears on said heel 16, 17 from inside the slot 4.

With reference to figs. 1 -3, the rotary electric device further comprises a housing 18, and the cylindric element 1 1 at each end 7, 8 of the stator core 3 is sealingly connected to the housing 18 at an end of the cylindric element 1 1 which is distal with regard to the stator core 3.

The housing 18, the end 7, 8 of the stator core 3, the cylindric element 1 1 and said fingers 12 define a closed space 19, 20 at each end of the stator, into which space 19, 20 ends of the winding 9 of the stator 2 project from axial ends of the slots 4. The housing 18 is provided with an inlet 21 , 23 for introduction of a cooling medium into said closed spaces 19, 20 and a respective outlet 22, 24 for evacuation of a cooling medium from said closed spaces 19, 20. The fingers 12 extending from the cylindric elements 1 1 provided at the axial ends 7, 8 of the stator core 3 extend along at least 50%, preferably at least 90% of the total length of the stator core 3. In the embodiments shown, the fingers extend along

approximately 75% (see fig. 3 for example) of the length of the stator core 3. The fingers 12 of the opposite cooling medium guides 10 are equally long in the embodiment shown. However, it should be understood that, depending on the context, they may be of different lengths.

The rotary electric machine preferably also comprises a cooling medium circuit (not shown) connected to the inlets 21 , 23 and the outlets 22, 24 and provided with a pump and filled with a cooling medium, preferably oil, which, during operation of the machine, is pumped into and through the spaces 19, 20 for cooling of the stator ends.

The rotary electric machine is preferably arranged in a vehicle for the propulsion of the latter. The vehicle comprises a cooling system comprising the above-mentioned circuit and pump.