Electric motor for motor vehicle

Abstract

Described is an electric motor for a motor vehicle, comprising: a stator fixed relative to an axis (A); a rotor rotatable about an axis (A) with respect to the stator; a housing accommodating the rotor and the stator; a cooling circuit through which a heat transfer fluid can flow, and which is thermally coupled with at least the stator to remove heat from the stator; the stator is pressed on the shell through interference fit; the cooling circuit comprises, in order: an inlet nozzle defined by the housing and traversed by a heat transfer fluid having a first temperature in use; and an outlet nozzle defined by the housing and traversed by a heat transfer fluid having a second temperature higher than the first temperature in use; an outlet nozzle defined by the housing and traversed by a heat transfer fluid having a second temperature higher than the first temperature in use; from the inlet nozzle toward the outlet nozzle, the cooling circuit further comprises: a first branch passing through the stator; a second branch defined by at least one groove defined radially relative to the axis (A) between the stator and the housing.

Description

Cross Reference to Related Applications

[0001] This application claims priority to Italian Patent Application No. 102024000016768, filed on July 19, 2024, the entire disclosure of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present invention relates to an electric motor for a motor vehicle. BACKGROUND

[0003] Vehicles are known with electric or hybrid propulsion, comprising permanent magnet electric motors.

[0004] Briefly, a permanent magnet electric motor comprises, in turn:

[0005] - a housing;

[0006] - a stator provided with electric windings, which can be powered to create a rotating magnetic field; and

[0007] - a rotor rotatably mounted with respect to the stator about its own axis, and provided with permanent magnets, and subjected to a driving torque about said axis after the electric windings are powered with an alternating current.

[0008] The stator and the rotor are housed inside the housing.

[0009] In a known manner, the stator and the rotor are coaxial to each other. The stator coaxially houses the rotor and also comprises a plurality of radial teeth mounted by interference against a radially inner surface of the housing.

[0010] There is a need in the industry to cool the electric motor, thus reducing its overall weight and size.

[0011] There is also a need in the industry to increase the torque and power density (i.e. torque / power and weight ratio) of the electric motor.

[0012] There is also a need in the industry to reduce as much as possible the number of components of the electric motor, in order to further limit its overall weight and size.

[0013] There is also a need in the industry to cool the electric motor, minimizing as much as possible the changes made to the rotor, the housing and the stator.

[0014] Finally, there is a need in the industry to cool the electric motor, thus favoring as much as possible the installation method on the opposite axles of the motor vehicle. SUMMARY

[0015] The aim of the present invention is to obtain an electric motor for a motor vehicle which allows to meet at least one of the above needs.

[0016] The electric motor can comprise:

[0017] - a stator fixed with respect to the axis;

[0018] - a rotor rotatable with respect to the stator about the axis A;

[0019] - a housing accommodating the rotor and the stator;

[0020] The electric motor comprises a cooling circuit through which a heat transfer fluid is flowable, and the cooling circuit is at least thermally coupled with the stator to remove heat from the stator;

[0021] The stator is press-fitted onto the housing by an interference fit;

[0022] The cooling circuit comprises in sequence:

[0023] - an inlet mouth defined by the housing and traversed by the heat transfer fluid having, in use, a first temperature; and

[0024] - an outlet mouth defined by the housing and traversed by the heat transfer fluid having, in use, a second temperature higher than the first temperature;

[0025] Along a direction from the inlet mouth towards the outlet mouth, the cooling circuit further comprises:

[0026] - a first branch traversing the stator;

[0027] - a second branch defined by at least one recess delimited radially between the stator and the housing with respect to the axis A.

[0028] Further, the stator can comprise in sequence:

[0029] - a first radially inner end ring delimiting the first branch in a radially inner position;

[0030] - a partition connected to a first bottom surface of the respective recess radially opposite the housing, and the partition being fixed to the housing;

[0031] The first branch is at least partially delimited by the first radially inner end ring in the radially inner position and by the partition in the radially outer position;

[0032] The second branch is delimited by the partition in the radially inner position and by the housing in the radially outer position.

[0033] From the first bottom surface axially to the inlet mouth and to the outlet mouth, the partition can comprise in sequence:

[0034] - a first cylindrical section connected to the teeth; and

[0035] - a second conical section tapering from the first cylindrical section to the inlet mouth and to the outlet mouth.

[0036] Further, the electric motor can comprise:

[0037] - a cover arranged to close the housing;

[0038] - a first gasket interposed between the first axial end of the partition and the cover; and

[0039] - a second gasket interposed between the second axial end of the partition, opposite the first axial end, and the stator.

[0040] Further, the electric motor can further comprise an annular chamber axially delimited between the housing and a second axial end surface of the stator, opposite the inlet mouth and the outlet mouth, and radially delimited between the housing and the first radially inner end ring;

[0041] The cooling circuit comprises a third branch fluidically interposed between the first branch and the second branch and delimited by the chamber.

[0042] Further, the inlet mouth and / or the outlet mouth can be axially arranged.

[0043] The first branch and the second branch can be coaxial to each other, and the first branch can be radially arranged on the outside of the second branch.

[0044] The stator can in turn comprise a plurality of teeth elongated along the axis A and spaced apart around the axis A;

[0045] Each tooth is press-fitted onto the housing by interference fit and in turn comprises an opposite recess elongated along the axis A and radially spaced apart from the housing; each recess, together with the housing, defines an opposite groove elongated parallel to the axis A.

[0046] Further, each tooth can in turn comprise:

[0047] - a radially inner portion fixed to the first radially inner end ring, and on which a plurality of electrical windings are wound; and

[0048] - a radially outer appendix having a greater size than the radially inner portion in the circumferential direction with respect to the axis A;

[0049] The first branch extends through the radially inner portion;

[0050] The radially outer appendix of each tooth in turn comprises a respective pair of radially outer end faces press-fitted onto the housing, circumferentially facing each other, and separated from each other by the groove.

[0051] Further, the housing can in turn comprise:

[0052] - a flange defining a first axial end of the electric motor; and

[0053] - a cover fixed to the casing on a side axially opposite to the flange and defining a second axial end opposite to the first end of the electric motor;

[0054] The rotor comprises a power take-off coaxial to the axis A and passing through the flange;

[0055] The outlet mouth and the inlet mouth pass through the cover and are axially opposite to the flange;

[0056] Further, the cooling fluid can be oil.

[0057] There is also provided a motor vehicle comprising:

[0058] - an electric motor as described above;

[0059] - a pump comprising in turn a delivery section fluidically connected to the first branch and a suction section fluidically connected to the second branch;

[0060] - a heat exchanger fluidically interposed between the second branch and the suction section;

[0061] The heat exchanger receives in use a heat transfer fluid at a second temperature and delivers in use a heat transfer fluid at a first temperature;

[0062] The pump and the heat exchanger are arranged outside the electric motor.

[0063] The aforementioned objects are achieved by the present application since it relates to an electric motor as described above. BRIEF DESCRIPTION OF DRAWINGS

[0064] For a better understanding of the present application, preferred embodiments thereof will be described below, by way of non-limiting example, and with reference to the accompanying drawings, in which:

[0065] - Figure 1 is a cross section of an electric motor made in accordance with the present application;

[0066] - Figure 2 is a perspective view of the electric motor of Figure 1 , with some parts removed for the sake of clarity;

[0067] - Figure 3 is a front view of the electric motor of Figure 1 and Figure 2 ; and

[0068] - Figure 4 is a perspective view of some details of the electric motor of Figure 2 , at a particularly enlarged scale. DETAILED DESCRIPTION

[0069] refer to Figure 1 The number 1 indicates a motor vehicle 1 with electric propulsion or hybrid propulsion.

[0070] The illustration of motor vehicle 1 is limited to axle 7, which includes electric motor 2 (in the case shown, a permanent magnet motor).

[0071] The electric motor 2 can preferably be operatively connected to a pair of wheels (not shown in the figures) via a plurality of associated transmission units, preferably the front or rear wheels of a motor vehicle.

[0072] Alternatively, the axle 7 may include two electric motors 2, each preferably being operatively connected to the associated front or rear wheel (not shown) via a transmission unit.

[0073] More specifically, the electric motor 2 basically includes:

[0074] - Stator 3, which is fixed relative to axis A; and

[0075] - Rotor 4, which can rotate about axis A relative to stator 3.

[0076] In a known manner, the stator 3 is provided with an electric winding 5, which can be powered by alternating current to form a rotating magnetic field.

[0077] Rotor 4 is equipped with a permanent magnet ( Figure 1 (not shown in the figure), and after the winding is powered by alternating current, it is subjected to a driving torque around axis A.

[0078] In the case shown, the stator 3 is tubular with axis A, and the rotor 4 is coaxially housed within the stator 3.

[0079] Stator 3 includes, in sequence:

[0080] - A pair of rings 10 and 11, located radially outer and radially inner relative to axis A, respectively; and

[0081] - A pair of head surfaces 12, 13, which are shaped as circular crowns and define the respective axial ends of the stator 3 itself that are opposite to each other;

[0082] Ring 10 is axially defined between head surfaces 12 and 13.

[0083] Ring 11 includes, in sequence:

[0084] -The portion 14 defined between the head surfaces 12 and 13; and

[0085] - a pair of axial end portions 15, 16 opposite each other, the portion 14 extending between the pair of axial end portions 15, 16 and projecting in the axial direction from the corresponding head surface 12, 13, respectively.

[0086] The rotor 4 is housed coaxially within the stator 3.

[0087] The rotor 4 in turn comprises:

[0088] - a tubular body 20; and

[0089] - a shaft 21 housed within the body 20 and provided with a pair of appendages 22, 23 arranged to define respective axial ends of the shaft 21 itself.

[0090] The appendage 23 defines a power output device 25 for a transmission unit (not shown) and operatively connected to one or more wheels of the motor vehicle 1.

[0091] The appendages 22, 23 axially protrude from the body 20.

[0092] The electric motor 2 further comprises:

[0093] - a housing 30 of the axis A;

[0094] - a cover 35 connected to the housing 30 and also fixed with respect to the axis A;

[0095] - a rolling bearing 40 radially interposed between the appendage 22 of the shaft 21 and the cover 35; and

[0096] - a rolling bearing 41 interposed between the appendage 23 of the shaft 21 and the housing 30.

[0097] The housing 30 substantially comprises:

[0098] - a tubular wall 31 having a prevailing axial extension; and

[0099] - an axial end flange 38 crossed by the appendage 22.

[0100] In particular, the bearing 41 is radially interposed between the appendage 22 and the flange 38.

[0101] The cover 35 is arranged to close the housing 30 in a position axially opposite the flange 38 and is crossed by the appendage 22 of the shaft 21.

[0102] The housing 30 and the cover 35 coaxially house the rotor 4.

[0103] The stator 3 is mounted within the housing 30 by means of an interference fit so as to transmit the reaction torque to the housing 30 itself.

[0104] Advantageously, the electric motor 2 comprises a cooling circuit 50 through which a heat transfer fluid can flow and which is thermally coupled with the stator 3 to remove heat therefrom;

[0105] The stator 3 is forced onto the housing 30 by means of an interference fit;

[0106] The cooling circuit 50 comprises, in turn:

[0107] - an inlet mouth 51 defined by the housing 30 and crossed by the heat transfer fluid which, in use, has a first temperature; and

[0108] - an outlet mouth 52 defined by the housing 30 and crossed by the heat transfer fluid which, in use, has a second temperature higher than the first temperature;

[0109] Proceeding from the inlet mouth 51 towards the outlet mouth 52, the cooling circuit 50 further comprises:

[0110] - a first branch 55 which crosses the stator 3; and

[0111] - a second branch 56 defined by a plurality of grooves 65 which are radially delimited between the stator 3 and the housing 30 with respect to the axis A.

[0112] With more detail and with particular reference to Figure 4 The stator 3 comprises a plurality of teeth 9 which are equally spaced apart about the axis A and which are elongated parallel to the axis A.

[0113] More specifically, the teeth 9 are forced onto the plate 31 of the housing 30 so as to prevent the stator 3 from rotating about the axis A.

[0114] The teeth 9 extend radially between the rings 10 and 11.

[0115] The teeth 9 have a substantially T-shaped cross section on a plane orthogonal to the axis A and each tooth 9 comprises:

[0116] - a respective radially inner portion 18 and on which the relative electric winding 5 is fixed; and

[0117] - a respective pair of radially outer appendices 19 which are forced onto the housing 30.

[0118] The radially outer appendices 19 project from the radially inner portion 18 of the respective tooth 9 circumferentially with respect to the axis A.

[0119] The radially outer appendix 19 of each tooth 9 further has a respective radially outer surface 26, which is opposite the respective radially inner portion 18 and is press-fitted onto the plate 31 of the casing 30 by interference fit.

[0120] The surface 26 of each tooth 9 is shaped as a respective cylindrical surface portion of the axis A.

[0121] The radially outer appendix 19 of each tooth 9 is circumferentially facing each other and is spaced apart from each other by a respective recess 66 elongated parallel to the axis A.

[0122] Each recess 66 is in particular delimited by:

[0123] - a first bottom surface 67, which is radially inner with respect to the surface 26 and is radially spaced apart from the casing 30; and

[0124] - a pair of surfaces 68, which are on respective radial planes with respect to the axis A, facing each other at a distance, and radially extend between the respective surface 26 and the first bottom surface 67.

[0125] The recess 66 is adapted to allow the angular timing of the rotor 4 with respect to the stator 3 around the axis A.

[0126] The recess 66 and the wall 31 of the casing 30 define a respective groove 65 ( Figure 1 ) elongated parallel to the axis A and equally angularly spaced around the axis A.

[0127] Each recess 66 further comprises an axial end 72 arranged on one side of the cover 35 and an axial end 73, opposite the axial end 72, arranged on one side of the flange 38.

[0128] The coupling by interference fit between the surface 26 of the tooth 9 and the wall 31 of the casing 30 therefore ensures not only the locking of the stator 3 around the axis A, but also the fluid tightness of the first branch 55 of the circuit 30.

[0129] The cooling circuit 50 further comprises:

[0130] - an axial duct 60, which passes through the cover 35 and is delimited by the inlet mouth 51 outside the casing 30; and

[0131] - an axial duct 61, which passes through the cover 35 and is delimited by the outlet mouth 52 outside the casing 30.

[0132] Along the direction of travel of the heat transfer fluid from the inlet mouth 51 to the outlet mouth 52, the duct 60 is fluidically interposed between the inlet mouth 51 and the first branch 55.

[0133] Along the direction of travel of the heat transfer fluid from the inlet mouth 51 to the outlet mouth 52, the conduit 61 is fluidically interposed between the second branch 56 and the outlet mouth 52.

[0134] The conduits 60, 61 are arranged eccentrically with respect to the axis A.

[0135] In particular, the conduit 61 is radially external to the conduit 60 and is arranged in a radially intermediate position between the conduit 60 and the plate 31 of the housing 30.

[0136] The cooling circuit 50 also comprises a third branch 57 fluidically interposed between the first branch 55 and the second branch 56, and along which the heat transfer fluid substantially assumes a U-shaped path.

[0137] More in detail, the wall 31 of the housing 30 comprises, in particular:

[0138] - a radially external surface 32; and

[0139] - a radially internal surface 33, opposite the surface 32 and radially spaced from the ring 11.

[0140] The surface 33 comprises, in turn:

[0141] - a pair of axial end portions 46, 48, radially spaced from the respective portions 14, 15 of the ring 11, facing the respective portions 14, 15 without interposition of external elements, and axially staggered by the teeth 9 of the stator 3; and

[0142] - a main portion 47, axially interposed between the end portions 46, 48, radially facing the teeth 9, and on which the surface 26 of the radially internal portion 18 of the teeth 9 is press-fitted by interference.

[0143] The housing 30 also comprises an annular partition 120 axially interposed between the cover 35 and the end 72 of the recess 66 arranged on one side of the cover 35.

[0144] Advancing from the cover 35 towards the head surface 12 of the stator 3, the partition 120 comprises, in particular:

[0145] - a conical section 121 tapered towards the cover 35 extending parallel to the axis A; and

[0146] - a cylindrical section 122 arranged radially at the end 72 of the recess 66.

[0147] The electric motor 2 also comprises (not shown): Figure 1 ):

[0148] - an annular chamber 130, whose radially inner position is delimited by the cover 35 and by the portion 15 of the ring 11, and whose radially outer position is delimited by the partition 120; and

[0149] - an annular chamber 131, whose radially inner position is delimited by the partition 120, and whose radially outer position is delimited by the end portion 46 of the surface 33, and which is fluidically connected with the recess 65.

[0150] From the conduit 60 towards the third branch 57, the first branch 55 is delimited by the chamber 130 and by the radially inner portion 18 of the tooth 9.

[0151] The second branch 56 comprises, in turn, an inlet section I delimited by the surface 13 of the stator 3.

[0152] From the inlet section I towards the duct 61, according to the direction of travel of the heat transfer fluid, the second branch 56 is delimited by:

[0153] - the recess 65; and

[0154] - the chamber 131.

[0155] The chamber 131 is fluidically connected with the conduit 61.

[0156] The chamber 130 is fluidically connected with the conduit 60.

[0157] The electric motor 2 also comprises a chamber 58 which delimits the third branch 57 of the cooling circuit 50.

[0158] The chamber 58 is axially delimited between the flange 38 and the head surface 12 of the stator 3, and is radially delimited between the end portion 16 of the ring 11 in the inner position and the axial end portion 48 of the plate 31 in the outer position.

[0159] Preferably, the heat transfer fluid is a dielectric oil.

[0160] The electric motor 2 also comprises:

[0161] - a gasket 80 axially interposed between the cover 35 and the axial end 125 of the ring 11, which is arranged on one side of the cover 35 itself; and

[0162] - a gasket 81 axially interposed between the end 126 of the ring 11, which is axially opposite to the end 125, and the flange 38.

[0163] The electric motor 2 also comprises:

[0164] - a gasket 85 interposed between the axial end 140 of the partition 120 arranged on one side of the cover 35 and the cover 35 itself; and

[0165] - a gasket 86, which intervenes between the axial end 141 of the partition 120 opposite the end 140 and the head surface 12.

[0166] Briefly, the cover 35 comprises, in turn:

[0167] - a body 90, which is arranged to axially close the casing 30, is fixed to the plate 31 of the casing 30 itself, and is axially crossed by the duct 61; and

[0168] - an appendix 91, which has a smaller diameter than the body 90, projects cantilevered from the body 90 inside the plate 31 and the ring 11, and is radially spaced from the ring 11 itself.

[0169] In Figure 1 only schematically shown, the cooling circuit 50 comprises, in turn:

[0170] - a pump 100; and

[0171] - a radiator 102.

[0172] The pump 100 comprises a suction mouth 103 and a delivery mouth 104, and is operable to generate the head required to advance the heat transfer fluid along the cooling circuit 50.

[0173] According to the direction of advancement of the heat transfer fluid, along from the delivery mouth 104 to the suction mouth 103, the cooling circuit 50 comprises, in turn:

[0174] - a branch 105, external to the electric motor 2, along which the heat transfer fluid flows at a first temperature value;

[0175] - a first branch 55, a third branch 57, a second branch 56, obtained inside the electric motor 2, along which the heat transfer fluid removes heat from the stator 3 until reaching a second temperature value higher than the first temperature value; and

[0176] - a branch 107, external to the electric motor 2.

[0177] The radiator 102 intervenes along the branch 107, and returns the temperature of the heat transfer fluid from the second value to the first value by exchanging heat with a cold source.

[0178] The pump 100 and the radiator 102 are external to the electric motor 2, and are carried by the motor vehicle 1.

[0179] In use, the operation of the electric motor 2 causes heat to be generated at the rotor 4 and the stator 3.

[0180] The rotation of the rotor 4 around the axis A makes a specific torque and power value available to the power take-off device 25.

[0181] The heat transfer fluid flows within the cooling circuit 50, removing heat from the stator 3.

[0182] In greater detail, the pump 100 causes the heat transfer fluid to advance within the cooling circuit 50 according to a direction oriented from the suction mouth 103 to the delivery mouth 104.

[0183] The heat transfer fluid flows along the branch 105 outside the electric motor 2 at a first temperature value, reaches the inlet mouth 51, flows within the electric motor 2 along the first branch 55, the third branch 57, the second branch 56, and removes heat from the stator 3 until reaching a second temperature value higher than the first temperature value, exits from the electric motor 2 through the outlet mouth 52, and returns to the pump 100 through the branch 107 outside the electric motor 2.

[0184] In greater detail, the heat transfer fluid flows axially within the duct 60 and the chamber 130, and laps the portion 18 of the tooth 9 along the first branch 55 of the cooling circuit 50. In particular, as the heat transfer fluid laps the portion 18 of the tooth 9, it gradually increases its own temperature and cools the tooth 9 itself.

[0185] Subsequently, the heat transfer fluid flows within the chamber 58 along a U-shaped path along the third branch 57, and flows within the recess 65 and the chamber 131 along the second branch 56 of the cooling circuit 50.

[0186] In particular, as the heat transfer fluid laps the radially outer appendix 19 of the tooth 9, the heat transfer fluid itself temperature further increases and cools the radially outer appendix 19 itself.

[0187] Subsequently, the heat transfer fluid passes through the duct 61 and exits from the electric motor 2 along the outlet mouth 52 at the second temperature value.

[0188] The heat transfer fluid then passes through the radiator 102 and cools until it has returned to the first temperature value.

[0189] The advantages that can be obtained through the examination of the electric motor manufactured according to the present application are evident.

[0190] In particular, the first branch 55 of the cooling circuit 50 extends through the stator 3 and the second branch 56, and is defined by the recess 65 radially delimited at the axis A between the tooth 9 of the stator 3 and the flange 31 of the housing 30.

[0191] Therefore, the recess 66 of the tooth 9 can be used, not only allowing the angular positioning between the rotor 3 and the stator 4, but also defining the recess 65 that defines the second branch 56 of the cooling circuit 50.

[0192] The radial outer appendix 19 of the tooth can also be used not only to mount the stator 3 on the housing 30 by interference fit and to prevent the stator 3 from rotating about the axis A, but also to obtain fluid tightness of the second branch 56 of the cooling circuit 50.

[0193] In this way, the need for additional components, such as further gaskets, to ensure the fluid tightness of the third branch 57 of the circuit 30 is reduced, thus reducing the overall weight and size of the electric motor 2.

[0194] This leads to a corresponding increase in the torque and power density of the electric motor and further reduces its overall weight and size.

[0195] The inlet mouth 51 and the outlet mouth 52 are axially opposite the power take-off 25.

[0196] In this way, it is facilitated to mount the electric motor 2 on the axle 7.

[0197] The partition 120 allows a fluid-tight separation of the first branch 55 and the second branch 56 of the cooling circuit 30.

[0198] Since the heat transfer fluid is an insulating oil, there is no risk of short-circuiting with the electrical components of the stator 3.

[0199] In any case, it is clear that changes and variants can be made to the electric motor 2 manufactured according to the present application without thereby departing from the scope of protection defined by the technical solution.

[0200] In particular, the second branch 56 can be delimited between other components of the stator 3 and other surfaces of the housing 30.

Claims

1. An electric motor (2) for a motor vehicle (1), comprising: - a stator (3) fixed with respect to an axis (A); - a rotor (4) rotatable with respect to the stator (3) about the axis (A); - a housing (30) which houses the rotor (4) and the stator (3); characterized in that the electric motor (2) comprises a cooling circuit (50) through which a heat transfer fluid can flow and which is at least thermally coupled with the stator (3) to remove heat therefrom; the stator (3) being press-fitted onto the housing (30) by interference fit; the cooling circuit (50) comprising in succession: - an inlet mouth (51) defined by the housing (30) and traversed by the heat transfer fluid which, in use, has a first temperature; and - an outlet mouth (52) defined by the housing (30) and traversed by the heat transfer fluid which, in use, has a second temperature higher than the first temperature; along a direction from the inlet mouth (51) towards the outlet mouth (52), the cooling circuit (50) further comprises: - a first branch (55) which traverses the stator (3); - a second branch (56) defined by at least one recess (65) delimited radially between the stator (3) and the housing (30) with respect to the axis (A).

2. The electric motor of claim 1, wherein the stator (3) comprising in succession: - a first radially inner end ring (11) which delimits the first branch (55) in a radially inner position; - a partition (120) connected to a first bottom surface (67) of the respective recess (65) diametrically opposite the housing (30) and fixed to the housing (30); the first branch (55) being at least partially delimited by the first radially inner end ring (11) in a radially inner position and by the partition (120) in a radially outer position; the second branch (56) being delimited by the partition (120) in a radially inner position and by the housing (30) in a radially outer position.

3. The electric motor of claim 2, wherein from the first bottom surface (67) axially to the inlet mouth and to the outlet mouth, the partition (120) comprises in succession: - a first cylindrical section (122) connected to the teeth (9); and - a second conical section (121) tapering from the first cylindrical section (122) to the inlet mouth (51) and to the outlet mouth (52).

4. The electric motor of claim 3, wherein the electric motor comprising: - a cover (35) arranged to close the housing (30); - a first gasket (80) interposed between a first axial end (140) of the partition (120) and the cover (35); and - a second gasket (81) interposed between a second axial end (141) of the partition (120), opposite the first axial end (140), and the stator (3).

5. The electric motor of claim 1, wherein The electric motor comprises an annular chamber (58) axially delimited between the casing (30) and a second axial end surface (13) of the stator (3), opposite the inlet mouth (51) and the outlet mouth (52), and radially delimited between the casing (30) and the first radial inner end ring (11); The cooling circuit (50) comprises a third branch (57) fluidically interposed between the first branch (55) and the second branch (56) and delimited by the chamber (58).

6. The electric motor of claim 1, wherein The inlet mouth (51) and / or the outlet mouth (52) are axially arranged.

7. The electric motor of claim 1, wherein The first branch (55) and the second branch (56) are coaxial to each other, and the first branch (55) is radially arranged on the outside of the second branch (56).

8. The electric motor of claim 1, wherein The stator (3) in turn comprises a plurality of teeth (9) elongated along the axis (A) and spaced around the axis (A); Each tooth (9) is press-fitted to the casing (30) by interference fit and in turn comprises an opposite recess (66) elongated along the axis (A) and radially spaced from the casing (30); each recess (66) defines, with the casing (30), an opposite groove (65) elongated parallel to the axis (A).

9. The electric motor of claim 8, wherein, Each tooth (9) in turn comprises: - a radially inner portion (18) fixed to the first radial inner end ring (11) and on which a plurality of electric windings (5) are wound; and - a radially outer appendix (19) having a greater size than the radially inner portion (18) in a circumferential direction with respect to the axis (A); The first branch (55) extends through the radially inner portion (18); The radially outer appendix (19) of each tooth (9) in turn comprises a respective pair of radially outer end faces (26) press-fitted to the casing (30), circumferentially facing each other and separated from each other by the groove (65).

10. The electric motor of claim 1, wherein The casing (30) in turn comprises: - a flange (38) defining a first axial end of the electric motor (2); and - the cover (35) fixed to the casing (30) on a side axially opposite the flange (38) and defining a second axial end opposite the first end of the electric motor (2); The rotor (4) comprises a power take-off device (25) coaxial to the axis (A) and passing through the flange (38); The outlet mouth (52) and the inlet mouth (51) pass through the cover (35) and are axially opposite the flange (38); and / or it is characterized in that the cooling fluid is oil.

11. A motor vehicle comprising: - an electric motor (2) according to claim 1; - a pump (100) comprising in sequence a delivery section (104) fluidically connected to said first branch (55) and a suction section (103) fluidically connected to said second branch (56); - a heat exchanger (102) fluidically interposed between said second branch (56) and said suction section (103); said heat exchanger (102) receiving in use said heat transfer fluid at said second temperature and delivering in use said heat transfer fluid at said first temperature; said pump (100) and said heat exchanger (102) being arranged outside said electric motor (2).

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