Electric motor for a motor vehicle

Abstract

To provide an electric motor for an automobile.SOLUTION: An electric motor for a motor vehicle includes a stator fixed to a shaft, a rotor capable of rotating about an axis A relative to the stator, a casing housing the rotor and the stator, and a cooling circuit through which a heat-transfer fluid can flow and which is thermally coupled to the stator to remove heat from the stator, the stator being pressed against the casing, the cooling circuit including a first branch passing through the heat-transfer fluid having a first temperature and a second branch passed through by the heat-transfer fluid having a second temperature higher than the first temperature, the cooling circuit including a first branch passing from the inlet towards the outlet and a second branch defined by at least one groove delimited radially relative to the axis between the stator and the casing.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This patent application claims priority from Italian Patent Application No. 102024000016768, filed July 19, 2024, the entire disclosure of which is incorporated herein by reference.

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

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

[0004] Quite simply, a permanent magnet electric motor: - a casing; a stator provided with electrical windings capable of being supplied with power to create a rotating magnetic field; a rotor mounted for rotation relative to the stator about its own axis and provided with permanent magnets, the rotor being subjected to a driving torque about said axis after energizing an electrical winding with alternating current; Includes:

[0005] The stator and rotor are housed within a casing.

[0006] In a known manner, the stator and the rotor are coaxial with one another, the stator coaxially receiving the rotor and further comprising a plurality of radial teeth mounted by interference in abutment against the radially inner surface of the casing.

[0007] There is a need in the field to cool electric motors while reducing their overall weight and reducing their overall size.

[0008] There is also a need in the area to increase / enhance the torque and power density, i.e., torque / power to weight ratio, of electric motors.

[0009] There is also a need in the field to reduce the number of components in an electric motor as much as possible to further limit its overall weight and size.

[0010] There is also a need in the art for cooling electric motors with as few modifications made to the rotor, to the casing, and to the stator as possible.

[0011] Finally, there is a need in the field of cooling electric motors that facilitates, as far as possible, the installation method on the associated axle of the motor vehicle. Summary of the Invention [Problem to be solved by the invention]

[0012] The object of the present invention is to obtain an electric motor for a motor vehicle, which allows at least one of the above-mentioned needs to be met. [Means for solving the problem]

[0013] The aforementioned object is achieved by the present invention, as it relates to an electric motor according to what is defined by claim 1.

[0014] For a better understanding of the invention, preferred embodiments are described below, by way of non-limiting example, and with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view of an electric motor constructed in accordance with the teachings of the present invention; [Figure 2] FIG. 2 is a perspective view of the electric motor of FIG. 1 with parts removed for clarity. [Figure 3] FIG. 3 is a front view of the electric motor of FIGS. 1 and 2. [Figure 4] FIG. 3 is a perspective view, particularly on an enlarged scale, of some details of the electric motor of FIG. 2; DETAILED DESCRIPTION OF THE INVENTION

[0016] With reference to FIG. 1, the number 1 indicates a motor vehicle 1 having electric or hybrid propulsion.

[0017] The diagram of the vehicle 1 is limited to only the electric motor 2, in the illustrated case, and the axle 7 which includes the permanent magnet electric motor.

[0018] It is envisaged that the electric motor 2 may be operatively connected to a pair of wheels, preferably the front or rear wheels of a motor vehicle (not shown in the accompanying drawings), preferably by means of an associated transmission unit.

[0019] Alternatively, it is contemplated that the axle 7 may include two electric motors 2, each operably connected to an associated front or rear wheel (not shown), preferably by a transmission unit.

[0020] More specifically, the electric motor 2 is a stator 3 fixed relative to the axis A; a rotor 4 rotatable relative to said stator 3 about an axis A; Essentially includes:

[0021] In known manner, the stator 3 is provided with electrical windings 5 ​​which are powered by alternating current and are capable of creating a rotating magnetic field.

[0022] The rotor 4 is provided with permanent magnets (not shown in FIG. 1) and is subjected to a driving torque about the axis A after energizing the electrical windings with alternating current.

[0023] In the illustrated case, the stator 3 is tubular, with the shaft A and the rotor 4 housed coaxially inside the stator 3 .

[0024] Stator 3 is a pair of rings 10, 11, respectively radially outer and radially inner relative to the axis A; a pair of head faces 12, 13 shaped as circular crowns and defining the opposite axial ends of the stator 3 itself; Includes:

[0025] The ring 10 is axially delimited between a head surface 12 and a head surface 13 .

[0026] Ring 11 is a portion 14 defined between the faces 12 and 13; a pair of opposite axial end portions 15, 16 between which the portion 14 extends and which project axially from the corresponding head faces 12, 13, respectively; Includes:

[0027] The rotor 4 is housed coaxially inside the stator 3 .

[0028] Rotor 4 is a tubular body 20; a shaft 21 housed inside said body 20 and provided with a pair of appendages 22, 23 arranged at respective axial ends of the shaft 21 itself; Further includes:

[0029] The appendage 23 defines a power take-off 25 for a transmission unit (not shown) and is operatively connected to one or more wheels of the vehicle 1 .

[0030] Appendages 22, 23 project axially from body 20.

[0031] The electric motor 2 is - a casing 30 of the axis A; a cover 35 connected to the casing 30 and also fixed relative to the axis A; a rolling bearing 40 inserted radially between the appendage 22 of the shaft 21 and the cover 35; a rolling bearing 41 inserted between the appendage 23 of the shaft 21 and the casing 30; Further includes:

[0032] The casing 30 includes: a tubular wall 31 having a mainly axial extent; - an axial end flange 38 traversed by the appendage 22; Essentially includes:

[0033] The bearing 41 is in particular inserted radially between the appendage 22 and the flange 38 .

[0034] A cover 35 is arranged axially opposite the flange 38 to close the casing 30 and is traversed by the appendage 22 of the shaft 21 .

[0035] The casing 30 and the cover 35 accommodate the rotor 4 coaxially.

[0036] The stator 3 is mounted inside the casing 30 by interference to deliver a reaction torque to the casing 30 itself.

[0037] The electric motor 2 advantageously includes a cooling circuit 50 through which a heat transfer fluid can flow and which is thermally coupled to the stator 3 to remove heat from said stator, The stator 3 is pressed against the casing 30 by interference, The cooling circuit 50 includes: an inlet 51 defined by the casing 30 and traversed in use by the heat transfer fluid having a first temperature; an outlet 52 defined by the casing 30 and traversed in use by said heat transfer fluid having a second temperature higher than said first temperature; Including, The cooling circuit 50 proceeds from the inlet 51 to the outlet 52, - a branch 55 passing through the stator 3; - a branch 56 defined by a plurality of grooves 65 radially relative to the axis A and delimited between the stator 3 and said casing 30; Further includes:

[0038] More particularly, and with particular reference to FIG. 4, the stator 3 includes a plurality of teeth 9 equally spaced angularly about an axis A and extending parallel thereto.

[0039] More specifically, the teeth 9 are pressed against a plate 31 of a casing 30 to prevent rotation of the stator 3 about the axis A.

[0040] The teeth 9 are inserted between the rings 10 and 11 and extend radially.

[0041] The teeth 9 have a substantially T-shaped cross section in a plane perpendicular to the axis A, each having: a respective radially inner part 18, on which the associated electrical winding 5 is fixed; - a respective pair of radially outer appendages 19 pressed against the casing 30; Includes:

[0042] An appendage 19 projects from a portion 18 of each tooth 9 in a circumferential direction relative to the axis A.

[0043] The appendage 19 of each tooth 9 further has a respective radially outer surface 26 opposite the respective portion 18 and which is pressed by interference onto a plate 31 of the casing 30 .

[0044] The face 26 of each tooth 9 is shaped as a respective cylindrical surface portion of the axis A.

[0045] The appendages 19 of each tooth 9 are circumferentially opposite one another and are spaced apart from one another by respective recesses 66 extending parallel to the axis A.

[0046] Each recess 66 is specifically a bottom surface 67 radially inward relative to the surface 26 and radially spaced apart from the casing 30; a pair of surfaces 68, each in a radial plane relative to the axis A, facing each other at a distance and extending radially between the respective surfaces 26 and 67; The scope is defined by.

[0047] The recess 66 is adapted to allow angular timing of the rotor 4 relative to the stator 3 about the axis A.

[0048] The recesses 66 and the wall 31 of the casing 30 define respective grooves 65 (FIG. 1) that extend parallel to the axis A and are equally angularly spaced about the axis A.

[0049] Each recess 66 further includes an axial end 72 disposed on the surface of cover 35 and an axial end 73 opposite axial end 72 disposed on the surface of flange 38 .

[0050] Thus, by interference, the coupling between the faces 26 of the teeth 9 and the wall 31 of the casing 30 not only ensures the locking of the stator 3 about the axis A, but also the fluid-tightness of the branches 55 of the circuit 30.

[0051] The cooling circuit 50 includes: an axial conduit 60 traversing the cover 35 and delimited by an inlet 51 on the outside of the casing 30; an axial conduit 61 traversing the cover 35 and delimited by an outlet 52 outside the casing 30; Further includes:

[0052] The conduit 60 follows the forward direction of the heat transfer fluid from the inlet 51 to the outlet 52 and is inserted between the inlet 51 and the branch 55 so that the fluid can flow therethrough.

[0053] The conduit 61 follows the forward direction of the heat transfer fluid from the inlet 51 to the outlet 52 and is inserted between the branch 56 and the outlet 52 so that the fluid can flow therethrough.

[0054] The conduits 60, 61 are arranged eccentrically with respect to the axis A.

[0055] In particular, the conduit 61 is radially outward of the conduit 60 and is disposed at a radially intermediate position between the conduit 60 and the plate 31 of the casing 30 .

[0056] Cooling circuit 50 further includes a branch 57 fluidly interposed between branches 55 and 56, along which the heat transfer fluid describes a substantially U-shaped path.

[0057] More specifically, the wall 31 of the casing 30 is, in particular, a radially outer surface 32; a radially inner surface 33 opposite said surface 32 and radially spaced apart from the ring 11; Includes:

[0058] Face 33 is a pair of axial end portions 46, 48 spaced radially from the respective portions 14, 15 of the ring 11, facing the respective portions 14, 15 without the interposition of any external element and axially offset by the teeth 9 of the stator 3; a main portion 47 diametrically opposed to the tooth 9 and axially inserted between the end portions 46 and 48, against which the face 26 of the portion 18 of the tooth 9 is pressed by interference; Includes:

[0059] The casing 30 further includes an annular portion 120 axially interposed between the cover 35 and the end 72 of the recess 66 located on the face of the cover 35 .

[0060] Specifically, the partition wall 120 extends from the cover 35 toward the head surface 12 of the stator 3, a conical section 121 tapering parallel to the axis A towards the cover 35; a cylindrical portion 122 radially arranged at the end 72 of the recess 66; Includes:

[0061] The electric motor 2 is an annular chamber 130 delimited at a radially inner position by the cover 35 and by the portion 15 of the ring 10, and at a radially outer position by the partition wall 120; an annular chamber 131 delimited at a radially inner position by the partition 120 and at a radially outer position by the end portion 46 of the face 33, the annular chamber 131 being fluidly connected to the groove 65; It further includes (Figure 1).

[0062] The branch 55 proceeds from the conduit 60 towards the branch 57 and is bounded by the chamber 130 and by the portion 18 of the tooth 9 .

[0063] The branch 56 includes an inlet portion I defined by the face 13 of the stator 3 .

[0064] The branch 56 proceeds from the inlet portion I towards the conduit 61 according to the forward direction of the heat transfer fluid and is bounded by the groove 65 and the chamber 131 as follows: - by the groove 65, and - by chamber 131, It is defined.

[0065] Chamber 131 is in fluid communication with conduit 61 .

[0066] The chamber 130 is in fluid communication with the conduit 60 .

[0067] The electric motor 2 further includes a chamber 58 defining a branch 57 of the cooling circuit 50 .

[0068] The chamber 58 is bounded axially between the flange 38 and the head face 12 of the stator 3, and radially between the end portion 16 of the ring 11 at its inner position and the axial end portion 48 of the plate 31 at its outer position.

[0069] Preferably, the heat transfer fluid is a dielectric oil.

[0070] The electric motor 2 is a gasket 80 inserted axially between the cover 35 and the axial end 125 of the ring 11, which is located on the face of the cover 35 itself; a gasket 81 axially inserted between an end 126 of the ring 11 axially opposite said end 125 and the flange 38; Further includes:

[0071] The electric motor 2 is a gasket 85 inserted between the axial end 140 of the partition 120 located on the face of the cover 35 and the cover 35 itself; a gasket 86 inserted between the axial end 141 of the bulkhead 120 opposite the end 140 and the head face 12; Further includes:

[0072] Quite simply, the cover 35 is: a body 90 fixed to the plate 31 of the casing 30 itself and arranged to close the casing 30 axially, and traversed axially by the conduit 61; an appendage 91, having a diameter smaller than that of the body 90, cantilevering from the body 90 inside the plate 31 and the ring 11 and radially spaced from the ring 11 itself; Includes:

[0073] The cooling circuit 50 is shown only diagrammatically in FIG. - a pump 100; - a radiator 102; Includes:

[0074] The pump 100 includes a suction port 103 and a delivery port 104 and can be operated to create the head necessary to advance the heat transfer fluid along the cooling circuit 50 .

[0075] The cooling circuit 50 follows the forward direction of the heat transfer fluid from the delivery port 104 to the suction port 103, a branch 105 outside the electric motor 2 and along which the heat transfer fluid flows at a first temperature value; - branches 55, 57, 56 obtained inside the electric motor 2, along which a heat transfer fluid removes heat from the stator 3 until a second temperature value higher than said first temperature value is reached; - the outer branch 107 of the electric motor 2; Includes:

[0076] A radiator 102 is inserted along branch 107 to change the temperature of the heat transfer fluid from the second value back to the first value by heat exchange with a cold source.

[0077] The pump 100 and the radiator 102 are carried by the vehicle 1 externally of the electric motor 2 .

[0078] During use, operation of the electric motor 2 causes heat production in the rotor 4 and stator 3 .

[0079] Rotation of the rotor 4 about axis A makes certain torque and power values ​​available to the power take-off 25 .

[0080] The heat transfer fluid flows within the cooling circuit 50 and removes heat from the stator 3 .

[0081] More specifically, the pump 100 causes the advancement of the heat transfer fluid within the cooling circuit 50 according to a direction directed from the suction port 103 to the delivery port 104 .

[0082] The heat transfer fluid flows along branch 105 outside the electric motor 2 at a first temperature value, reaches inlet 51, flows inside the electric motor 2 along branches 55, 57, 56, removing heat from the stator 3 until a second temperature value higher than the first temperature value is reached, leaves the electric motor 2 through outlet 52 and returns to the pump 100 outside the electric motor 2 by branch 107.

[0083] More specifically, the heat transfer fluid flows axially inside the conduit 60 and the chamber 130, along the branch 55 of the cooling circuit 50, and around the portion 18 of the tooth 9. The heat transfer fluid, in particular as it circumnavigates the portion 18 of the tooth 9, gradually increases its own temperature and cools the tooth 9 itself.

[0084] The heat transfer fluid then flows along a U-shaped path inside chamber 58 along branch 57 and along branch 56 of cooling circuit 50 inside groove 65 and chamber 131 .

[0085] In particular, the heat transfer fluid, as it circumnavigates the appendage 19 of the tooth 9, further increases its own temperature and cools the appendage 19 itself.

[0086] The heat transfer fluid then traverses the conduit 61 and exits the electric motor 2 along the outlet 52 at a second temperature value.

[0087] The heat transfer fluid then traverses the radiator 102 and cools until it returns to the first temperature value.

[0088] The advantages that may be obtained are apparent from an examination of an electric motor manufactured in accordance with the present invention.

[0089] In particular, branch 55 of cooling circuit 50 extends through stator 3, and branch 56 is defined by a groove 65 radially delimited on axis A between teeth 19 of stator 3 and flange 31 of casing 30.

[0090] Thus, the recesses 66 in the teeth 9 are used not only to enable angular timing between the rotor 3 and the stator 4, but also to define the extent of the grooves 65 that define the branches 56 of the cooling circuit 50.

[0091] The tooth appendages 19 can also be used, by interference, to mount the stator 3 to the casing 30 and prevent its rotation about the axis A, as well as to obtain a liquid-tight seal for the branches 56 of the cooling circuit 50.

[0092] In this way, the need for additional parts such as further gaskets to ensure the liquid tightness of branch 57 of circuit 30 is reduced, thus reducing the overall weight and size of electric motor 2 .

[0093] This leads to a corresponding increase in torque and power density of the electric motor, further reducing its overall weight and size.

[0094] The inlet 51 and outlet 52 are on axially opposite sides of the power take-off 25 .

[0095] In this way, the installation of the electric motor 2 on the axle 7 is facilitated.

[0096] The partition 120 allows for a fluid-tight separation of the branches 55 , 56 of the cooling circuit 30 .

[0097] The heat transfer fluid being insulating oil does not create a risk of short circuits for the electrical components of the stator 3 .

[0098] In conclusion, it is clear that modifications and variations can be made to the electric motor 2 made in accordance with the invention without departing from the scope of protection defined by the claims.

[0099] In particular, it is envisaged that the branch 56 may be delimited between a further component of the stator 3 and a further surface of the casing 30 . [Explanation of symbols]

[0100] 1. Automobiles 2 electric motors 3 Stator 4 rotors 5 Electrical Winding 7 axles 9 teeth 10 Rings 11 Ring, first radially inner end ring 12 Head surface 13 head surface, second axial end surface 14 (ring) parts 15, 16 Axial end portion (of the ring) 18 (of a tooth) radially inner part, radially inner root part 19 (of a tooth) radially outer appendage, radially outer end portion 20 Tubular body 21 Shaft 22, 23 (shaft) attachments 25 Power Take-Off 26 Radial outer surface, radial outer end surface 30 Casing 31 (casing) tubular wall, plate 32 (of the casing wall) radial outer surface 33 (of the casing wall) radial inner surface 35 Cover 38 Axial end flange 40, 41 Rolling bearings 46, 48 Axial end portions (of surface 33) 47 (Surface 33) Main part 50 Cooling circuit 51 Entrance 52 Exit 55 Branch (of cooling circuit), first branch 56 Branch (of cooling circuit), second branch 57 Branch (of cooling circuit), third branch 58 Chamber, annular chamber 60, 61 Axial conduit 65 Groove 66 Depression 67 (of a recess) bottom, first bottom 68 (concave) surface 72, 73 Axial end 80 Gasket, first gasket 81 Gasket, second gasket 85, 86 Gaskets 90 (Cover) Body 91 (Cover) Accessories 100 (cooling circuit) pump 102 Radiators, heat exchangers 103 (pump) suction port, suction part 104 (pump) delivery port, delivery portion 105, 107 (cooling circuit) branches 120 (casing) annular part, bulkhead 121 (of a bulkhead) conical part, second conical part 122 (of the partition) cylindrical portion, first cylindrical portion 125 (of ring 11) axial end 126 (Ring 11) End 130, 131 Annular chamber 140 (of partition wall) axial end, first axial end 141 (of the partition wall) axial end, second axial end I entrance part A-axis

Claims

1. An electric motor (2) for a motor vehicle (1), a stator (3) fixed relative to the axis (A); a rotor (4) capable of rotating about said axis (A) relative to said stator (3); a casing (30) containing said rotor (4) and said stator (3); Including, the electric motor (2) includes a cooling circuit (50) through which a heat transfer fluid can flow and which is thermally coupled to at least the stator (3) to remove heat from the stator (3); The stator (3) is pressed against the casing (30) by interference, The cooling circuit (50) an inlet (51) defined by said casing (30) and traversed in use by said heat transfer fluid having a first temperature; an outlet (52) defined by said casing (30) and traversed, in use, by said heat transfer fluid having a second temperature higher than said first temperature; Including, The cooling circuit (50) proceeds from the inlet (51) to the outlet (52), a first branch (55) passing through said stator (3); a second branch (56) defined by at least one groove (65) radially relative to said axis (A) and delimited between said stator (3) and said casing (30); An electric motor (2) for a motor vehicle (1), characterized in that it further comprises:

2. The stator (3) a first radially inner end ring (11) delimiting said first branch (55) at a radially inner position; a partition (120) connected to the first bottom surface (67) of each of the grooves (65) on the diametrically opposite side of the casing (30) and fixed to the casing (30); Including, the first branch (55) is at least partially bounded by the first ring (11) at a radially inner position and by the partition wall (120) at a radially outer position; the second branch (56) is bounded at a radially inner position by the partition wall (120) and at a radially outer position by the casing (30); 2. An electric motor according to claim 1, characterized in that:

3. The partition (120) extends axially from the first bottom surface (67) to the inlet and the outlet, a first cylindrical portion (122) connected to said tooth (9); a second conical portion (121) tapering from said first portion (122) to said inlet (51) and said outlet (52); 3. The electric motor of claim 2, comprising:

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

5. the electric motor includes an annular chamber (58) axially delimited between the casing (30) and a second axial end face (13) of the stator (3) opposite the inlet (51) and the outlet (52) and radially delimited between the casing (30) and the first ring (11); the cooling circuit (50) includes a third branch (57) fluidly interposed between the first branch (55) and the second branch (56) and defined by the chamber (58); 2. An electric motor according to claim 1, characterized in that:

6. 2. Electric motor according to claim 1, characterized in that the inlet (51) and / or the outlet (52) are arranged axially.

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

8. The stator (3) includes a plurality of teeth (9) extending along and spaced apart about the axis (A); Each tooth (9) is pressed against said casing (30) by interference and includes an associated recess (66) extending along said axis (A) and radially spaced from said casing (30); Each said recess (66) defines, together with said casing (30), an associated groove (65) extending parallel to said axis (A); 2. An electric motor according to claim 1, characterized in that:

9. Each tooth (9) a radially inner root portion (18) fixed to said first ring (11) and on which a plurality of electrical windings (5) are wound; a radially outer end portion (19) having a dimension, circumferentially relative to said axis (A), greater than said root portion (18); Including, said first branch (55) extending through said root portion (18); the end portion (19) of each tooth (9) includes a respective pair of radially outer end faces (26) circumferentially opposed to one another and spaced apart by the grooves (65), the radially outer end faces (26) being pressed against the casing (30); 9. An electric motor according to claim 8, characterized in that

10. The casing (30) a flange (38) defining a first axial end of said electric motor (2); - the cover (35) fixed to the casing (30) axially opposite the flange (38) and defining a second axial end of the electric motor (2) opposite the first end; Including, The rotor (4) includes a power take-off (25) coaxial with the shaft (A) and passing through the flange (38); the outlet (52) and the inlet (51) pass through the cover (35) and are on axially opposite sides of the flange (38). and / or the cooling fluid is oil, 2. The electric motor according to claim 1.

11. A motor vehicle, - an electric motor (2) according to claim 1; a pump (100) comprising a delivery portion (104) fluidly connected to said first branch (55) and a suction portion (103) fluidly connected to said second branch (56); a heat exchanger (102) fluidly inserted between said second branch (56) and said suction part (103); Including, the heat exchanger (102) receiving, in use, the heat transfer fluid at the second temperature and delivering, in use, the heat transfer fluid at the first temperature; The pump (100) and the heat exchanger (102) are arranged outside the electric motor (2). car.

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